Light guide plate for image display

Abstract

Provided of an image display light guide plate capable of displaying a clear image even when using a resin substrate. An image display light guide plate having a first resin substrate (1001) and a hologram layer (1002), wherein the first resin substrate (1001) has an MC value of 0.120 or less obtained from evaluation by shadow contrast, and the image display light guide plate (1004).

Description

Technology Field

[0001] The present invention relates to a light guide plate for displaying images.

[0002] The present application claims priority based on Japanese patent applications 2019-018943, 2019-018944, 2019-018945, and 2019-018946, filed in Japan on February 5, 2019, and incorporates the contents thereof herein. Background Technology

[0003] In display devices, a light guide plate for image display is used. For example, in display devices using VR (Virtual Reality) technology, AR (Extended Reality) technology, or MR (Mixed Reality), a light guide plate for image display in which a hologram layer is supported on a transparent substrate is used. A hologram having various optical functions, such as wave guiding, reflection, and diffraction, is formed in the hologram layer.

[0004] Glass substrates are often used as transparent substrates. However, from the perspective of processability, lightness, durability, and portability, it is more preferable to use resin substrates as transparent substrates.

[0005] Patent Document 1 discloses a holographic laminate used in a head-up display for vehicles. This holographic laminate comprises an acrylic resin substrate, an acrylic adhesive layer, a holographic layer composed of an acrylic photopolymer, an acrylic adhesive layer, and an acrylic resin substrate, which are laminated in this order.

[0006] Patent Document 1 describes that a change in the appearance of a hologram occurs due to the surface smoothness of an acrylic resin substrate. According to Patent Document 1, if the maximum height Rmax, which indicates the surface smoothness of a hologram laminate, exceeds 50 μm, the change in the appearance of the hologram becomes significant. If the maximum height Rmax is less than 25 μm, the change in the appearance of the hologram is within an acceptable range. However, Patent Document 1 does not specifically describe the necessity of nano-order surface smoothness with a maximum height Rmax of 1 μm or less. Patent Document 1 also does not describe any specific examples having nano-order surface smoothness.

[0007] Furthermore, holographic materials forming the holographic layer may erode the resin substrate due to temperature changes. It is also known that holographic materials deteriorate due to moisture absorption. For this reason, display devices that support the holographic layer with a resin substrate are prone to deterioration in high-temperature and high-humidity environments.

[0008] Patent Document 2 describes forming a photosensitive material layer that forms a hologram on an optically transparent resinous gaseous phase, and coating the photosensitive material layer with an aqueous polymer protective barrier. Patent Document 2 suggests that the aqueous polymer protective barrier is formed to withstand attacks caused by moisture.

[0009] Patent Document 3 describes a holographic laminate having a hologram embedded in a resin substrate via an optical adhesive, wherein the entire outer periphery is covered with a protective coating layer. Patent Document 3 also describes that the protective coating layer may be a coating that enhances airtightness and gas barrier properties. Prior art literature

[0010] Japanese Published Patent Application No. 2000-296583, Japanese Published Patent Application No. Hei 5-181400, Japanese Published Patent Application No. Hei 11-184363 The problem to be solved

[0011] However, the aforementioned related technology has the following problems.

[0012] The holographic laminate described in Patent Document 1 is primarily used in in-vehicle head-up displays viewed by the driver. For this reason, the image quality of the displayed image does not need to be particularly high. However, for example, in the case of wearable displays or head-mounted displays used for AR or MR, realistic images are often displayed across the user's entire field of vision, or fine characters appear. For such applications, further high image quality is required.

[0013] According to the inventors' review, when a hologram layer is embedded in a resin substrate in a light guide plate for image display, image quality degradation may be observed even if the maximum height Rmax is less than 25 μm. For example, if pitch curvature (gear mark) corresponding to the meshing pitch of the driving gear of the extrusion roller occurs on the surface of the extrusion-molded resin substrate, points where the image is unclear are likely to occur.

[0014] In the technology described in Patent Document 2, a resin-based gas is adhered to the surface opposite to the aqueous polymer protective barrier in the photosensitive material layer.

[0015] For this reason, there is a concern that the photosensitive material may corrode the resin gas under high-temperature environments.

[0016] Furthermore, since the interior of the resin gas contains moisture, the moisture diffuses into the photosensitive material layer through the contact surface with the photosensitive material layer. Additionally, because the gas is exposed to the outside, moisture from the outside continuously penetrates into the gas. As a result, since moisture penetrates into the photosensitive material layer via the resin gas, even if moisture is shielded by an aqueous polymer protective barrier, the time-dependent deterioration of the photosensitive material layer caused by moisture from the gas side cannot be prevented.

[0017] In the technology described in Patent Document 3, the entire outer periphery of a laminate containing a hologram is sealed by a protective coating layer. For this reason, moisture penetrating from the outside of the hologram laminate into the interior and causing the hologram to deteriorate is suppressed. However, moisture contained in the resin substrate during the formation of the protective coating layer is trapped inside the protective coating layer. As a result, there is a risk that moisture contained in the resin substrate will penetrate into the hologram, thereby causing the hologram to deteriorate over time. In particular, in high-temperature environments, the effect of moisture release from the resin substrate becomes significant.

[0018] The present invention is made in consideration of the above-mentioned problems and aims to provide a light guide plate for image display that can display a clear image even when a resin substrate is used.

[0019] In addition, the present invention aims to provide a light guide plate for image display that can suppress the degradation of the hologram layer even when a resin substrate is used. means of solving the problem

[0020] The inventors have conducted research and discovered that, in a resin substrate used for an image display light guide plate, a clear image can be displayed by improving the flatness corresponding to the size of the surface curvature changing to a pitch significantly larger than the pitch measured by surface roughness, thereby arriving at the present invention.

[0021] If the flatness of the resin substrate surface is degraded by curvature, variations in the thickness of the holographic layer laminated onto the resin substrate occur. When variations in the thickness of the holographic layer occur, deviations in the waveguide light result, causing minute distortions and deformations in the image, which makes the image unclear. In the case of color images, color differences and color bleeding caused by deviations in the waveguide light result in the image becoming unclear.

[0022] In this regard, if the surface smoothness of the resin substrate is reduced by fine irregularities, scattering of waveguide light occurs, resulting in an unclear image.

[0023] Furthermore, the inventors conducted research and discovered that by introducing a barrier layer into a resin substrate having a hologram layer used in a light guide plate for image display, the degradation of the hologram layer is suppressed, thereby enabling the display of a clear image, and thus arrived at the present invention.

[0024] To solve the above-mentioned problem, for example, the present invention has the following aspects.

[0025] [1] As a light guide plate for image display having a first resin substrate and a hologram layer,

[0026] The above-mentioned first resin substrate is a light guide plate for image display having an MC value of 0.120 or less obtained from evaluation by shadow contrast.

[0027] [2] A light guide plate for image display having a first resin substrate, a first barrier layer, and a hologram layer.

[0028] [3] The first resin substrate, the first barrier layer, and the hologram layer are arranged in this order in the thickness direction, as described in [2], for an image display light guide plate.

[0029] [4] Additionally, having a second resin substrate and a second barrier layer,

[0030] A light guide plate for image display described in [3], wherein the first resin substrate, the first barrier layer, the hologram layer, the second barrier layer, and the second resin substrate are arranged in this order in the thickness direction.

[0031] [5] A light guide plate for displaying images described in any one of [2] to [4], wherein the refractive index of the first barrier layer is higher than the refractive index of the first resin substrate.

[0032] [6] A light guide plate for displaying images described in any one of [2] to [5], wherein the refractive index of the first barrier layer is 1.48 or higher.

[0033] [7] The first barrier layer described above comprises an inorganic material, and is a light guide plate for image display as described in any one of [2] to [6].

[0034] [8] The first barrier layer comprises at least one inorganic material selected from the group consisting of silicon oxide, silicon nitrate oxide, diamond-like carbon, aluminum oxide and glass, [7] a light guide plate for image display.

[0035] [9] The first barrier layer above is a light guide plate for image display described in any one of [2] to [8], disposed on a resin film.

[0036]

[10] A light guide plate for image display described in any one of [2] to [9], wherein a water vapor barrier material is used as the material of the first barrier layer.

[0037]

[11] The first barrier layer is a light guide plate for image display described in any one of [2] to

[10] , which is disposed on the hologram layer.

[0038]

[12] A light guide plate for displaying images described in any one of [1] to

[11] , wherein the refractive index of the first resin substrate is 1.48 to 1.70.

[0039]

[13] A light guide plate for image display described in any one of [1] to

[12] , wherein the first resin substrate comprises at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin and polycarbonate.

[0040]

[14] A light guide plate for image display described in any one of [1] to

[13] , wherein the thermal shrinkage rate of the first resin material is less than 3% as measured in accordance with Annex A of JIS K 6718-1:2015.

[0041]

[15] A light guide plate for image display described in any one of [1] to

[14] , wherein the arithmetic mean roughness Ra of the surface of the first resin substrate is 10 nm or less. Effects of the invention

[0042] According to the present invention, a light guide plate for displaying images can be provided that can display a clear image even when a resin substrate is used.

[0043] In addition, according to the present invention, a light guide plate for image display can be provided that can suppress the degradation of the hologram layer even when a resin substrate is used. Brief explanation of the drawing

[0044] FIG. 1 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a first embodiment of the present invention. Figure 2 is a schematic front view illustrating the method of evaluating MC values. Figure 3 is a schematic plan view illustrating the method of evaluating MC values. Figure 4 is a schematic diagram showing an example of an image for evaluating MC values. Figure 5 is a schematic diagram showing an example of a digitized evaluation image of an MC value. Figure 6 is a schematic graph showing the method of calculating the MC value. FIG. 7 is a schematic cross-sectional view showing an example of a light guide plate for image display of a first variation of the first embodiment of the present invention. FIG. 8 is a schematic cross-sectional view showing an example of a manufacturing apparatus for a resin substrate of Example 1. FIG. 9 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a second embodiment of the present invention. FIG. 10 is a schematic front view illustrating the measurement method of luminance value and FOV. FIG. 11 is a schematic cross-sectional view showing an example of a light guide plate for image display of a first variation of a second embodiment of the present invention. FIG. 12 is a schematic cross-sectional view showing a light guide plate for image display of Example 5. FIG. 13 is a schematic cross-sectional view showing a light guide plate for image display of Example 6. FIG. 14 is a schematic diagram showing the layer configuration of a light guide plate for image display related to the third embodiment of the present invention. FIG. 15 is a schematic diagram showing the layer configuration of a light guide plate for image display related to a first variation of the third embodiment of the present invention. FIG. 16 is a drawing showing two overlapping hard coat films related to the third embodiment. FIG. 17 is a drawing showing two overlapping hard coat films related to the first variation of the third embodiment. FIG. 18 is a schematic cross-sectional view showing an example of a light guide plate for image display according to the fourth embodiment of the present invention. FIG. 19 is a schematic cross-sectional view showing an example of a display device including a light guide plate for image display according to the fourth embodiment of the present invention. FIG. 20 is a schematic cross-sectional view showing an example of a light guide plate for image display of a first variation of the fourth embodiment of the present invention. FIG. 21 is a schematic cross-sectional view showing an example of a light guide plate for image display of a second variation of the fourth embodiment of the present invention. FIG. 22 is a schematic cross-sectional view showing an example of a light guide plate for image display of a third variation of the fourth embodiment of the present invention. Specific details for implementing the invention

[0045] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all drawings, even if the embodiments differ, the same reference numerals are assigned to identical or equivalent components, and common descriptions are omitted.

[0046] A numerical range represented using "~" includes the values ​​at both ends of "~".

[0047] "UV" stands for ultraviolet rays.

[0048] "(Meth)acrylic" means either or both of acrylic and methacrylic.

[0049] "(Meth)acrylate" means either or both of acrylate and methacrylate.

[0050] [First Embodiment]

[0051] <Basic Example>

[0052] A light guide plate for image display according to the first embodiment of the present invention will be described.

[0053] The light guide plate for image display according to the first embodiment of the present invention has a first resin substrate and a hologram layer. The light guide plate for image display according to the present embodiment may additionally have a second resin substrate. In the present embodiment, the first resin substrate and the second resin substrate may be collectively referred to as "resin substrate" below. The resin substrate is transparent.

[0054] The above hologram layer is sandwiched between the first resin substrate and the second resin substrate, or between the first resin substrate and the glass substrate.

[0055] The light guide plate for image display described above has an incident portion for incident image light and a display image output portion for displaying an image using the image light. The hologram layer is disposed between the incident portion and the display image output portion. The hologram layer has a diffraction grating pattern formed therein for guiding image light incident from the incident portion to the display image output portion and emitting it from the display image output portion. The diffraction grating pattern in the display image output portion transmits at least a portion of external light incident from outside the light guide plate for image display. Additionally, the external light incident portion points to a side opposite to the display image output portion.

[0056] The image light incident on the above-mentioned incident portion is guided into the hologram layer and emitted to the outside from the display image emission portion. Meanwhile, as external light also passes through the resin substrate and the display image emission portion, an observer at the display image emission portion can observe both the image light and the external light within their field of view.

[0057] The light guide plate for image display according to the present embodiment is preferably used in a display device using AR technology or MR technology. For example, the light guide plate for image display according to the present embodiment may be used in devices such as AR glasses for head-mounted displays or head-up displays for automotive use.

[0058] The resin substrate used in the light guide plate for image display according to the present embodiment has an MC value of 0.120 or less obtained from evaluation by shadow contrast. The definition of the MC value and the specific evaluation method will be described later. The MC value is particularly effective for evaluating flatness among the surface characteristics of the resin substrate. That is, regarding irregularities with a spatial frequency lower than the spatial frequency of the surface roughness irregularity, the lower the MC value, the smaller the degree of irregularity. For this reason, the lower the MC value of the resin substrate, the better the flatness.

[0059] The material of the resin substrate above is not particularly limited as long as it is a transparent material.

[0060] The material used in the above resin substrate preferably comprises at least one resin selected from the group consisting of acrylic resin, cyclic polyolefin resin, and polycarbonate resin, and acrylic resin is more preferred.

[0061] The refractive index of the material used in the above resin substrate is preferably 1.48 to 1.70.

[0062] The thermal shrinkage rate of the material used in the above resin substrate is preferably less than 3%. Here, the thermal shrinkage rate is the rate of change in dimensions upon heating based on Annex A of JIS K 6718-1:2015, “Measurement of change in dimensions (shrinkage) upon heating”.

[0063] In addition, this "measurement of dimensional change (shrinkage) upon heating" is a standard for cast plates, but the thermal shrinkage rate in the present invention adopts a value based on this standard even when the resin substrate using the above material is an extruded plate or a continuous cast plate.

[0064] The smoothness of the resin substrate (indicated by surface roughness, such as arithmetic mean roughness Ra or maximum height Rmax) is preferably 10 nm or less, as the arithmetic mean roughness Ra of the surface of the resin substrate.

[0065] In addition, the light guide plate for image display according to the present embodiment may also introduce a barrier layer described later. By introducing a barrier layer, the degradation of the hologram layer is suppressed, thereby maintaining a clear image.

[0066] A resin substrate with excellent flatness, such as having the MC value described above, is manufactured by using a manufacturing method such as a casting method or an extrusion method, for example, or by performing post-processing such as cutting, polishing, or heat pressing on the resin substrate.

[0067] As the above casting method, a glass casting method may be used. In the above glass casting method, the raw material of the resin substrate is solidified by a polymerization process after the raw material of the resin substrate is flowed between glass plates having good flatness and smoothness. When the resin substrate is manufactured by the above glass casting method, the surface shape of the glass used in the glass casting method (hereinafter referred to as "casting glass") is transferred to the resin substrate. Therefore, if the flatness and smoothness of the surface of the casting glass are good, the flatness and smoothness of the surface of the resin substrate are also good.

[0068] As the internal distortion of the above-mentioned casting glass decreases, the flatness of the surface of the casting glass improves, thereby improving the flatness of the resin substrate. For example, non-tempered glass is preferred over tempered glass as the casting glass. However, even if it is tempered glass, if it is chemically tempered glass with less distortion than air-cooled tempered glass, the flatness of the resin substrate can be improved.

[0069] The thicker the thickness of the above-mentioned casting glass, the higher the rigidity of the above-mentioned casting glass and the suppression of deformation of the glass during manufacturing, so the flatness of the above-mentioned resin substrate can be improved.

[0070] When molding the resin substrate, if surface pressure is applied to the casting glass and pressed, the smoothness and flatness of the resin substrate can be improved.

[0071] The above casting method is not limited to the glass casting method described above.

[0072] For example, as a cast, opposing metal endless belts may be used. In this case, the resin substrate can be continuously manufactured by performing a polymerization process while rotating the endless belt. The shape of the surface of the endless belt is transferred to the resin substrate. Therefore, the smoothness of the resin substrate can be improved by performing mirror polishing on the surface of the endless belt. In addition, the flatness of the resin substrate can be improved by controlling the tension of the endless belt.

[0073] Other casting methods include using a metal plate instead of the glass for casting mentioned above.

[0074] In the polymerization process of the above-mentioned casting method, the lower the curing speed, the easier it is for the surface shape of the cast to be transferred to the resin substrate, thereby improving the flatness and smoothness of the resin substrate.

[0075] As means to reduce the above curing speed, for example, means such as reducing the amount of polymerization initiator or lowering the polymerization temperature may be used.

[0076] The lower the amount of crosslinking agent added to crosslink the material of the resin substrate, the lower the curing speed becomes, and the surface shape of the cast becomes easier to transfer to the resin substrate, thereby improving the flatness of the resin substrate. The amount of crosslinking agent added is preferably a small amount of 0.5 parts by mass or less per 100 parts by mass of the total of polymerizable monomer components or polymerizable oligomer components other than the crosslinking agent, which serve as raw materials for the resin substrate.

[0077] A release agent may be used in the above cast, but it is preferable to use less of it. By doing so, the surface shape of the above cast becomes easier to transfer to the resin substrate, thereby improving the flatness and smoothness of the resin substrate.

[0078] In the polymerization process of the above-mentioned casting method, the planarity and smoothness of the resin substrate can be improved by pre-polymerizing the monomer for forming the substrate.

[0079] In the polymerization process of the above-mentioned casting method, by using a raw material in which a polymer for forming a substrate is dissolved in a monomer for forming a substrate, the casting polymerization is performed, thereby reducing the curing shrinkage and making it easier to transfer the surface shape of the cast to the resin substrate, so that the flatness and smoothness of the resin substrate can be improved.

[0080] In the above casting method, each of the techniques described above may be used in combination of two or more. In this case, the planarity and smoothness of the resin substrate can be further improved by the synergistic effect of each technique.

[0081] When the above resin substrate is manufactured by an extrusion method, for example, a polishing roll method or an air knife method may be used.

[0082] Due to the processing precision of the die line of the extrusion die, there is a risk that the smoothness of the surface of the resin substrate may be reduced as fine irregularities of the die line are transferred. Therefore, the extrusion die is finished with high precision so that the die line becomes smooth.

[0083] For example, in the polishing roll method, molten resin is generally cooled by pressing it between a set of three polishing rolls. The pressure applied to the molten resin when pressing it between the polishing rolls is linear pressure. This linear pressure is susceptible to influences such as uneven rotation of the polishing rolls and deviations in the processing precision of the roll axis or the base. Consequently, the linear pressure becomes uneven, making it prone to thickness unevenness and a decrease in flatness, such as gear marks, on the resin substrate. The gear marks occur as a line extending in a direction perpendicular to the feed direction of the resin substrate.

[0084] If the surface temperature of the polishing roll is excessively high, the resin substrate is prone to deformation, so it is desirable that the surface temperature be low.

[0085] For the conveying mechanism of the polishing roll above, it is more preferable to use a configuration that minimizes driving non-uniformity. For example, in order to suppress the transmission of gear meshing vibrations, a planetary roller may be used instead of a gear transmission mechanism for the transmission mechanism, such as a reduction gear of the conveying mechanism. However, any gear transmission mechanism that does not easily cause meshing vibrations compared to spur gears, such as worm gears or helical gears, may be used as the transmission mechanism of the conveying mechanism.

[0086] Instead of the polishing rolls mentioned above, a configuration may be used in which a pair of seamless metal belts for cooling the molten resin are arranged facing each other at a predetermined distance at the molten resin outlet of the extruder. In this case, the molten resin is conveyed while being cooled by being caught in the pair of seamless metal belts. As a result, the pressure applied to the molten resin becomes surface pressure, thereby suppressing the reduction of flatness caused by linear pressure, such as in the polishing roll method described above.

[0087] A known resin material for forming a hologram is used in the above hologram layer. For example, a known material may be appropriately selected and used as the resin material for forming a hologram. A photosensitive material may be appropriately determined by considering the wavelength of the light guiding, or an acrylic photosensitive resin material for forming a hologram with excellent optical properties may be used.

[0088] The above hologram layer may be formed on the surface of the resin substrate, or it may be laminated onto the resin substrate with a suitable transparent layer in between. When the light guide plate for image display includes a glass substrate, the above hologram layer may be formed on the surface of the glass substrate, or it may be laminated onto the glass substrate with a suitable transparent layer in between.

[0089] The resin substrate may be disposed at the outermost part in the thickness direction of the light guide plate for image display, or may be disposed inside. When the light guide plate for image display includes the glass substrate, the glass substrate may be disposed at the outermost part in the thickness direction of the light guide plate for image display, or may be disposed inside.

[0090] In a light guide plate for image display, one or more suitable transparent layers may be disposed between the resin substrate and the hologram layer in the thickness direction, or between the glass substrate and the hologram layer in the case of including a glass substrate.

[0091] In a light guide plate for displaying images, at least one suitable transparent layer different from the resin substrate and the glass substrate may be disposed at the outermost part in the thickness direction.

[0092] For example, when a transparent layer is disposed on at least one surface of a resin substrate, the transparent layer may be a hard coat layer that protects the surface of the resin substrate.

[0093] Other examples of transparent layers include an absorption layer having an absorption peak in UV or a specific wavelength range, and an adhesive layer.

[0094] Hereinafter, based on the example shown in FIG. 1, the detailed configuration of an example of a light guide plate for image display according to the present embodiment will be described. FIG. 1 is a schematic cross-sectional view showing an example of a light guide plate for image display according to the first embodiment of the present invention.

[0095] In the light guide plate (1004) for image display shown in Fig. 1, a first resin substrate (1001), a hologram layer (1002), and a second resin substrate (1003) are arranged in this order in the thickness direction.

[0096] The shape of the image display light guide plate (1004) as seen from a planar view is not particularly limited. For example, the image display light guide plate (1004) may be shaped into a form that can be mounted on a display device used.

[0097] For example, the light guide plate (1004) for image display may be a rectangular plate larger than the shape mounted on the display device. In this case, the light guide plate (1004) for image display is shaped by being cut or shaped into a shape that can be mounted on the display device before being assembled on the display device.

[0098] The light guide plate (1004) for displaying images may be flat, or, if necessary, may be curved.

[0099] Below, an example is described in which the light guide plate (1004) for displaying images is formed as a flat plate in the shape of a rectangle when viewed from a flat plane.

[0100] The first resin substrate (1001) is disposed on the outermost portion in the thickness direction of the light guide plate (1004) for image display. The first resin substrate (1001) is disposed on the image display side surface of the light guide plate (1004) for image display.

[0101] The first resin substrate (1001) has the same shape as the external shape of the light guide plate (1004) for image display.

[0102] In the first resin substrate (1001), image light emitted from the hologram layer (1002) and external light passing through the second resin substrate (1003) and the hologram layer (1002) described later are transmitted.

[0103] The thickness of the first resin substrate (1001) is not particularly limited. For example, the thickness of the first resin substrate (1001) may be 0.05 to 2 mm. If the thickness of the first resin substrate (1001) is 0.05 mm or more, it is desirable because it is easy to maintain a stable shape and the measurement error of the MC value described later can be suppressed to a small size. If the thickness of the first resin substrate (1001) is 2 mm or less, it is desirable because the mass of the light guide plate (1004) for image display can be reduced, making it lightweight. The thickness of the first resin substrate (1001) is preferably 0.05 mm or more, more preferably 0.1 mm or more, and even more preferably 0.5 mm or more. Meanwhile, in terms of deformation or residual distortion of the substrate accompanying the absorbency of the substrate, the thickness of the first resin substrate (1001) is preferably 2 mm or less, more preferably 1.5 mm or less, and even more preferably 1 mm or less.

[0104] Materials that can be used for the first resin substrate (1001) include, for example, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluoropolymer film, polyvinyl chloride, polyethylene, polypropylene, cyclic polyolefin, cellulose, acetylcellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, poly(meth)acrylic resin, phenolic resin, epoxy resin, polyarylate, polynorbornene, styrene-isobutylene-styrene block copolymer (SIBS), allyl diglyglycol carbonate, etc., but it is preferable to include at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin, and polycarbonate.

[0105] From the perspective of transparency of the first resin substrate (1001), it is preferable to use polycarbonate or poly(meth)acrylic resin, and from the perspective of process resistance such as chemical resistance and processability of the first resin substrate (1001), it is preferable to use poly(meth)acrylic resin, epoxy resin, or cyclic polyolefin, but among them, poly(meth)acrylic resin is more preferable in that transparency and process resistance can be achieved together.

[0106] For the first resin substrate (1001), a plate material having an MC value of 0.120 or less obtained from evaluation by shadow contrast is used.

[0107] Here, the specific evaluation and calculation methods for the MC value are explained.

[0108] FIG. 2 is a schematic front view illustrating a method for evaluating MC values. FIG. 3 is a schematic plan view illustrating a method for evaluating MC values. FIG. 4 is a schematic diagram showing an example of an image for evaluating MC values. FIG. 5 is a schematic diagram showing an example of a digitized image for evaluating MC values. FIG. 6 is a schematic graph illustrating a method for calculating MC values.

[0109] (Shadow Contrast Evaluation)

[0110] Shadow contrast evaluation can be performed using the evaluation device (1200) shown in FIGS. 2 and FIGS. 3.

[0111] The evaluation device (1200) is equipped with a light source (1201), a screen (1202), a camera (1203) (see FIG. 3), and a computation processing unit (1204) (see FIG. 3).

[0112] The evaluation device (1200) forms a transmission projection image of the measurement sample (S) on a screen (1202) by irradiating the measurement sample (S) with measurement light emitted from a light source (1201), and calculates the MC value of the measurement sample (S) based on the brightness distribution of the transmission projection image.

[0113] The shape of the measurement sample (S) is identical to the external shape of the first resin substrate (1001). Below, an example is described in which the measurement sample (S) is a rectangular flat plate when viewed from a flat surface.

[0114] The type of light source (1201) is not particularly limited as long as it can form a transmission projection image of the measurement sample (S). For example, as the light source (1201), it is more preferable to use a point light source in that the transmission projection image projected onto the screen (1202) becomes clear. Examples of point light sources include, for instance, metal halide lamps, halogen lamps, and high-pressure mercury lamps. The wavelength of the light is preferably in the range of 280 to 780 nm. If the measurement sample (S) is a resin substrate, it is preferable to have a wavelength in the range of 400 nm to 780 nm.

[0115] Examples of screens (1202) include matte screens, bead screens, and pearl screens. The color of the screen (1202) is not particularly limited as long as it does not interfere with the brightness measurement of the projected image on the screen (1202). The color of the screen (1202) may be, for example, white or gray. The size of the screen (1202) is not particularly limited as long as it is large enough to include the transmitted projected image of the measurement sample (S) within the required measurement range. It is more preferable that the screen (1202) be larger than the size that includes the transmitted projected image of the entire measurement sample (S).

[0116] The type of camera (1203) is not particularly limited as long as it can capture the brightness of the projected image on the screen (1202) with good precision. For example, the camera (1203) may be an analog camera or a digital camera. It is more preferable for the camera (1203) to be a digital camera in order to facilitate digital analysis. Also, in the case of capturing with an analog camera, the image analysis described below is performed after the obtained image is converted into a digital image.

[0117] As for the size of the digital image, when expressed in terms of the number of pixels in width × height, for example, 800 × 600, 1024 × 768, 1600 × 1200, 2048 × 1536, or 5472 × 3648 are used. However, the size of the digital image is not limited to these, as long as it has a resolution capable of acquiring a curve of brightness change corresponding to the irregularities of the measurement sample (S) caused by curvature, etc.

[0118] The brightness value is the shade of color when the data for each pixel is converted to monochrome. The resolution of the brightness value is determined by the number of grayscale levels of each pixel. The number of grayscale levels of each pixel is not particularly limited as long as it is possible to calculate an MC value of 0.120 or less. The number of grayscale levels of each pixel may be, for example, 128 grayscale levels, 256 grayscale levels, 512 grayscale levels, or 1024 grayscale levels.

[0119] However, if the contrast of the transmission projection image is low due to constraints such as the transmittance of the measurement sample (S) or the brightness of the light source (1201), it is more desirable to use as high a grayscale value as possible to increase the measurement precision.

[0120] It is more preferable that shooting using the camera (1203) be performed under light shielding. When shooting with the camera (1203) is performed under light shielding, a brightness distribution with higher precision can be obtained compared to when it is not performed under light shielding. The method of shooting under light shielding is not particularly limited. For example, if the shooting environment in which the evaluation device (1200) is placed is a room with a window, the window may be covered so that the entire room is in a light-shielded state. For example, the evaluation device (1200) may have a light-shielding casing that surrounds at least the light path from the light source (1201) to the screen (1202) and the light path from the screen (1202) to the camera (1203).

[0121] The shooting mode of the camera (1203) may be a color image mode or a black and white image mode. When shooting in color image mode, it is more preferable to convert it into a black and white image using image processing software.

[0122] For example, due to the influence of the optical characteristics of the lens of the camera (1203), the brightness of the edges of the captured image may be lower than the brightness of the center. If the noise caused by the level of such brightness non-uniformity is excessively large, it is more desirable to perform shading correction on the captured image according to the optical characteristics of the lens beforehand, and then obtain the brightness distribution of the measurement sample (S). Shading correction may be performed by appropriate image processing software before analyzing the captured image. The amount of correction for shading correction may be determined, for example, by taking a shot using a correction glass plate with good flatness and smoothness instead of the measurement sample (S), so that the brightness distribution becomes uniform. In this case, brightness non-uniformity based on the optical characteristics of the light source (1201) is also corrected.

[0123] For simplicity, the following description is based on an example where the camera (1203) is a digital camera and a transmitted-projected image on the screen (1202) is captured in a black-and-white image mode. In this case, the output value of the digital image pixel is proportional to the brightness of the transmitted-projected image.

[0124] If the camera (1203) is an analog camera, the digital image described below can be read by converting it into a digital image generated from an image captured by the camera (1203).

[0125] The computation processing unit (1204) obtains a brightness distribution based on a digital image captured by a camera (1203) and calculates an MC value based on the brightness distribution. The computation processing unit (1204) is configured to include a computer capable of executing appropriate image processing software.

[0126] The arrangement of each part in the evaluation device (1200) and the arrangement of the measurement sample (S) during measurement will be explained.

[0127] In the following, positional relationships may be described based on the XYZ orthogonal coordinate system. The X-axis extends into the horizontal plane. The Y-axis is orthogonal to the X-axis in the horizontal plane. The Z-axis is the vertical axis and is orthogonal to the X-axis and the Y-axis. The direction along the X-axis, the direction along the Y-axis, and the direction along the Z-axis are referred to as the X-direction, the Y-direction, and the Z-direction, respectively.

[0128] As shown in FIG. 2, in the evaluation device (1200), the screen (1202) is positioned parallel to the YZ plane. The light source (1201) is positioned at a distance of (d1 + d2) in the X direction from the screen (1202). The optical axis (O) of the light source (1201) is parallel to the X-axis.

[0129] As shown in FIG. 3, the measurement sample (S) is positioned in the middle of the light source (1201) and the screen (1202) on the optical axis (O). If the vertices of the rectangular shape in the cross-section passing through the center of the thickness direction of the measurement sample (S) are denoted as A, B, C, and D, then sides AD and BC are each parallel to the Y-axis. Side AD represents the side near the light source (1201), and side BC represents the side near the screen (1202).

[0130] As shown in FIG. 2, the center SO of the rectangle ABCD in the measurement sample (S) is positioned on the optical axis (O) at a distance d1 from the light source (1201) in the X direction. Additionally, the measurement sample (S) is positioned from the horizontal plane at an elevation angle θ in the illustrated clockwise direction, centered on an axis line parallel to the Y-axis passing through the center SO. A It is positioned in a rotated position. However, if the thickness of the measurement sample (S) is thin, instead of the center SO of the measurement sample (S), the center of one surface in the thickness direction of the measurement sample (S) may be positioned at the same location as described above.

[0131] Here, distances d1 and d2 are appropriately set according to, for example, the radiation angle and light intensity of the light source (1201), the size of the measurement sample (S), and the size of the screen (1202). For example, distances d1 and d2 may be 30 to 1000 cm.

[0132] For example, it is more preferable that the distance d1 be as short as possible within the range where the light source (1201) can be installed. It is more preferable that the distance d2 be as short as possible within the range where the screen (1202) can be installed. The shorter the distances d1 and d2, the more efficiently the measurement light irradiated from the light source (1201) can be utilized.

[0133] angle of elevation θ A It is preferably 5 to 90°. For example, angle of elevation θ A It can be measured at 20°.

[0134] The position of the camera (1203) is not particularly limited as long as it is a position where its own shadow and reflected light do not fall within the shooting range and where it can capture the entire projected image on the screen (1202). In the example shown in FIG. 3, when viewed from a plane, the camera (1203) is positioned at a position adjacent to the camera (1203) in the Y direction. However, although not specifically illustrated, the camera (1203) is positioned at a different height from the measurement sample (S) in the Z direction so that its own shadow and reflected light do not fall within the shooting range.

[0135] According to this arrangement, the measurement light emitted from the light source (1201) passes through the measurement sample (S) and is projected onto the screen (1202). When the light source (1201) is a point light source, the measurement light is diffused radially, so a transmission projection image based on the light intensity of the transmitted light of the measurement sample (S) is formed on the screen (1202). The transmission projection image is captured by the camera (1203) and transmitted to the computation processing unit (1204) as a digital image.

[0136] For example, a digital image schematically shown in FIG. 4 is transmitted to the computation processing unit (1204). In FIG. 4, the outermost frame represents the end of the screen (1202). The central trapezoid PaPbPcPd represents the transmission projection image (I) of the measurement sample (S). Points Pa, Pb, Pc, and Pd correspond to points A, B, C, and D of the measurement sample (S), respectively.

[0137] The transmitted projected image (I) has a brightness distribution. In the example shown in FIG. 4, it has a high brightness portion (Ib) and a low brightness portion (Is). The high brightness portion (Ib) is formed by the measurement light transmitted according to the transmittance of the measurement sample (S) being projected onto the screen (1202).

[0138] The brightness distribution on the transmission projection image (I) includes brightness non-uniformity caused by the optical path length and the radiation intensity distribution of the light source (1201). This brightness non-uniformity occurs to some extent even if there are no irregular defects in the measurement sample (S).

[0139] Since the measurement light is radiant light, the light intensity of the measurement light traveling along the optical axis (O) is at its maximum and decreases as it moves toward the periphery of the measurement sample (S). The same applies to the radiant light intensity distribution of the light source (1201).

[0140] If this brightness non-uniformity is greater than the brightness non-uniformity caused by uneven surface defects, it is corrected in advance. For example, when the difference between the brightness value on the optical axis (O) and the brightness value of the outer edge of the measurement sample (S) is 5 or more, it is more desirable to correct the brightness non-uniformity described above.

[0141] Brightness non-uniformity caused by the light intensity distribution of the measured light can be corrected, for example, based on the law of light attenuation (the intensity of the light attenuated by the attenuation of light is inversely proportional to the square of the distance from the light source). For example, brightness non-uniformity caused by the radiant light intensity distribution of the light source (1201) can be corrected based on the radiant light intensity distribution of the light source (1201).

[0142] For example, as described above, correction data may be acquired by performing shooting using a correction glass plate.

[0143] However, depending on the measurement conditions, if there is only a brightness non-uniformity smaller than the brightness non-uniformity caused by uneven defects, the correction of the light intensity distribution of the measurement light and the light source (1201) may be omitted.

[0144] In the following, the explanation assumes that brightness non-uniformity, which is measurement noise, has been eliminated.

[0145] The low brightness area (Is) is thought to be formed by irregular defects corresponding to errors in flatness on the surface of the measurement sample (S).

[0146] For example, if the radius of curvature of the irregularities formed on the measurement sample (S) is somewhat small, it is thought that the measurement light is diffused until it reaches the screen (1202) by the lens action of the irregularities. This depends on the smoothness.

[0147] For example, when the measurement sample (S) is deformed into a waveform, the thickness may not change even if there are surface irregularities. This depends on flatness. In this case, although the irregularities do not act as lenses, it is thought that they contribute to brightness non-uniformity because refraction and diffraction of the same measurement light occur.

[0148] In addition, for example, it is also thought that a distortion distribution occurs near the uneven part due to the unevenness formed in the measurement sample (S), and the direction of the measurement light emission is disrupted, and the light intensity on the screen (1202) changes.

[0149] For example, as the angle of incidence on the measurement sample (S) increases, the change in transmittance characteristics dependent on the angle of incidence increases. Because of this, it is thought that the transmittance at the uneven surface formed on the measurement sample (S) changes and contributes to brightness non-uniformity. In addition, it is thought that the transmittance changing due to refractive index non-uniformity caused by distortion inside the measurement sample (S) also contributes to brightness non-uniformity.

[0150] It is thought that any or a combination of these factors causes the unevenness of brightness. Additionally, the magnitude of the brightness unevenness is thought to be highly correlated with the depth of the unevenness. For this reason, the flatness of the measurement sample (S) can be evaluated based on the difference in brightness between the low brightness area (Is) and the high brightness area (Ib).

[0151] In the example shown in FIG. 4, the low-brightness portion (Is) is elliptical. Such a low-brightness portion (Is) corresponds to an elliptical concave or convex portion on the surface of the measurement sample (S). For example, if a gear mark is formed on the measurement sample (S), the low-brightness portion (Is) is formed in a striped shape. In this case, the low-brightness portion (Is) is formed at an equal pitch approximately parallel to a direction perpendicular to the extrusion direction of the first resin substrate (1001).

[0152] The calculation processing unit (1204) calculates the MC value by interpreting the digital image as follows.

[0153] The digital image used for measuring the MC value may be the entire trapezoidal PaPbPcPd. However, for example, if a part of the measurement sample (S) is cut and used in a display device, it may be measured over the entire range of the size used in the display device.

[0154] In some cases, the digital image used for measuring the measurement sample (S) may be a trapezoidal image of a portion of the inner side of the trapezoidal PaPbPcPd. For example, if the directionality, pitch, etc. of the defect to be detected by the MC value is known in advance, such as a gear mark, a portion of the trapezoidal PaPbPcPd may be used, provided that the size and range include multiple gear marks, taking into account the measurement error. For example, the same applies even if the shape of the measurement sample (S) has a gentle curve in the design.

[0155] For example, if the measurement sample (S) is rectangular when viewed from a plane of 200 mm × 200 mm, it is more preferable that the measurement range includes a rectangular range of at least 180 mm × 80 mm on the measurement sample (S). Here, the length direction of the measurement range is aligned with the direction in which the change in brightness becomes greater.

[0156] For example, if the measurement sample (S) is a curved plate rather than a flat plate, it is more preferable that the width of the measurement range in the direction having the curve is 50 mm or more. For example, if the measurement sample (S) has a spherical curve overall, it is more preferable to include a rectangular range of size 50 mm × 50 mm centered on the top of the curve.

[0157] Below, as an example, the case where the entire trapezoid PaPbPcPd is used will be explained.

[0158] The operation processing unit (1204) obtains a lightness distribution on a predetermined measurement line. For example, the measurement line is (N-1) line segments qiQi that each connect point qi (where i = 1, ···, N-1) that divides side AD on the measurement sample (S) into N equal parts and point Qi (where i = 1, ···, N-1) that divides side BC on the measurement sample (S) into N equal parts.

[0159] In this case, on the measurement sample (S), points qi and Qi are points on a plane parallel to the ZX plane.

[0160] In Fig. 4, points qi and Qi are shown on the transmission projection image (I).

[0161] For example, N can be appropriately selected between 2 and 10,000 depending on the size of the uneven defect. For example, in the case of a defect with a width of 100 mm, N should be selected so that the pitch of the measurement line is approximately 1 to 20 mm.

[0162] For example, if the low brightness area (Is) is striped, a digital image is acquired by changing the arrangement of the measurement sample (S) so that the measurement line intersects the low brightness area (Is). In this case, N can be selected so that the pitch of the measurement line along the length direction of the low brightness area (Is) is approximately 1 to 20 mm.

[0163] In the example shown in Fig. 4, N = 8. The measurement line L3 in Fig. 5 schematically represents the measurement line corresponding to the line segment q3Q3 in Fig. 4. Since the measurement line on the measurement sample (S) is projected as a slope line, the measurement line L3 on the transmission projection image (I) becomes a digitized slope line.

[0164] The operation processing unit (1204) extracts the brightness value of each measurement line by converting the coordinates of points qi and Qi on the measurement sample (S) into pixel coordinates on the transmission projection image (I), based on the positional relationship of the light source (1201), the screen (1202), and the measurement sample (S).

[0165] Figure 6 schematically shows an example of a brightness distribution along the measurement line L3. In Figure 6, the horizontal axis represents the position of the pixel in the Z direction, and the vertical axis represents the brightness value.

[0166] As shown in the curve (1210), the brightness along the measurement line L3 decreases from a roughly constant high brightness value from point q3 toward point Q3, becomes a minimum brightness value, and then becomes a roughly flat high brightness value again. In the Z direction, the interval from q3 to p1 and the interval from p2 to Q3 are both included in the high brightness region (Ib). The interval from p1 to p2 is included in the low brightness region (Is).

[0167] The calculation processing unit (1204) obtains the minimum value Lmin and maximum value Lmax of the brightness from the brightness distribution.

[0168] The MC value is defined by the following formula (1). The operation processing unit (1204) calculates the MC value based on Lmin and Lmax according to the following formula (1).

[0169]

[0170] The MC value serves as an objective indicator of the magnitude of the decrease in the low-luminosity part (Is) of the luminosity distribution.

[0171] As described above, the brightness of the low brightness part (Is) decreases as the flatness of the measurement sample (S) deteriorates. For this reason, the larger the MC value, the worse the flatness of the surface of the measurement sample (S), and the smaller the MC value, the better the flatness of the surface of the measurement sample (S).

[0172] In the same way, the calculation processing unit (1204) calculates the MC value for each measurement line.

[0173] The MC value of the measurement sample (S) becomes the maximum value among the MC values ​​of each measurement line.

[0174] As described above, in the light guide plate for image display according to the present invention, the MC value of the resin substrate needs to be 0.120 or less. This improves the clarity of the display image using a hologram such as AR or MR formed using this light guide plate. The MC value of the resin substrate is 0.120 or less, preferably 0.110 or less, more preferably 0.100 or less, even more preferably 0.080 or less, and particularly preferably 0.070 or less.

[0175] Meanwhile, by making this MC value 0.001 or higher, blocking between substrates during substrate lamination can be prevented, and handling characteristics during substrate processing tend to improve. The MC value of the resin substrate is preferably 0.001 or higher, more preferably 0.005 or higher, even more preferably 0.010 or higher, and particularly preferably 0.020 or higher.

[0176] In addition, as described above, in the light guide plate for image display according to the present invention, the refractive index of the resin substrate is preferably 1.48 to 1.70. This allows the viewing angle to be expanded when used as a light guide plate for image display.

[0177] In addition, as described above, in the light guide plate for image display according to the present invention, it is preferable that the thermal shrinkage rate of the resin substrate, measured in accordance with Annex A of JIS K 6718-1:2015, is less than 3%. As a result, the clarity of the display image using a hologram such as AR or MR formed using this light guide plate tends to be improved. The thermal shrinkage rate is preferably less than 3.0%, more preferably 2.5% or less, and even more preferably 2.0% or less.

[0178] In addition, as described above, in the light guide plate for image display according to the present invention, it is preferable that the arithmetic mean roughness Ra of the surface of the resin substrate is 10 nm or less. As a result, the clarity of the display image using a hologram such as AR or MR formed using this light guide plate tends to be good. The arithmetic mean roughness Ra of the surface of the resin substrate is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 5 nm or less.

[0179] Here, we return to the description of the light guide plate (1004) for image display shown in FIG. 1.

[0180] The hologram layer (1002) in the image display light guide plate (1004) is laminated on the surface of the first resin substrate (1001). The composition of the hologram layer (1002) is not particularly limited. A suitable diffraction grating corresponding to the function required for the image display light guide plate (1004) is formed in the hologram layer (1002).

[0181] The second resin substrate (1003) is laminated on the surface opposite to the first resin substrate (1001) in the hologram layer (1002). The same composition as the first resin substrate (1001) is used for the second resin substrate (1003). However, the thickness and material of the second resin substrate (1003) may be different from that of the first resin substrate (1001). In particular, since the second resin substrate (1003) is placed on the surface opposite to the display image emission side in the light guide plate (1004) for image display, an external light incident side may be used, and a material with a higher surface hardness than that of the first resin substrate (1001) may be used.

[0182] Such a light guide plate (1004) for displaying images can be manufactured, for example, as follows.

[0183] Using the manufacturing method described above, a first resin substrate (1001) and a second resin substrate (1003) having an MC value of 0.120 or less are prepared. For example, a photopolymer material for forming a hologram is applied on the first resin substrate (1001). At this time, a transparent seal layer having the same thickness as the hologram layer (1002) may be formed on the outer periphery of the first resin substrate (1001). In this case, the photopolymer material is applied to the concave portion formed by surrounding the seal layer. The seal layer seals the outer periphery of the hologram layer (1002) after the hologram layer (1002) is formed. A material with excellent gas barrier properties may be used as the seal layer. In this case, the durability of the hologram layer (1002) can be improved.

[0184] After this, a second resin substrate (1003) is placed on the photopolymer material.

[0185] However, the manufacturing sequence described above is an example. For example, after the photopolymer material is applied to the second resin substrate (1003), the first resin substrate (1001) may be placed on the photopolymer material.

[0186] Afterwards, a laminate of the first resin substrate (1001), photopolymer material, and second resin substrate (1003) is bonded by a pressure press.

[0187] Afterwards, an interference pattern corresponding to the diffraction pattern is formed on the photopolymer material of the laminate, and a diffraction grating is formed within the photopolymer material.

[0188] In this way, a light guide plate (1004) for displaying images is manufactured.

[0189] According to the light guide plate (1004) for image display, the MC value of the first resin substrate (1001) and the second resin substrate (1003) is 0.120 or less, so the unevenness defects on each surface are reduced. As a result, the image light that passes through the first resin substrate (1001) to display an image, and the external light that passes through the second resin substrate (1003) and the first resin substrate (1001) and polymerizes into the image light, are suppressed from being disrupted by the influence of unevenness defects. Thus, a clear image is displayed on the light guide plate (1004) for image display.

[0190] As explained above, according to the present embodiment, a light guide plate for displaying images can be provided that can display a clear image even when a resin substrate is used.

[0191] <Example of Variation 1>

[0192] A first variation of the first embodiment of the present invention will be described.

[0193] FIG. 7 is a schematic cross-sectional view showing an example of a light guide plate for image display of a first variation of the first embodiment of the present invention.

[0194] As shown in FIG. 7, the image display light guide plate (1014) of the first modified example of the first embodiment of the present invention has a first hard coat layer (1011A) and a second hard coat layer (1011B) added to the image display light guide plate (1004) of the first embodiment of the present invention.

[0195] Hereinafter, the differences from the basic example of the first embodiment of the present invention will be explained focusing on the following.

[0196] The first hard coat layer (1011A) and the second hard coat layer (1011B) are formed primarily for the purpose of protecting the surface of the first resin substrate (1001). The materials of the first hard coat layer (1011A) and the second hard coat layer (1011B) are made of a transparent material in which the hardness of at least one surface is higher than that of the surface of the first resin substrate (1001). The first hard coat layer (1011A) and the second hard coat layer (1011B) may have a multilayer structure made of a plurality of transparent materials with different hardness, provided that the hardness of at least one surface is higher than that of the first resin substrate (1001).

[0197] In the example shown in FIG. 7, the first hard coat layer (1011A) is disposed on the first surface (1001a) opposite to the hologram layer (1002) in the first resin substrate (1001). The first hard coat layer (1011A) forms the outermost surface of the light guide plate (1014) for image display.

[0198] The second hard coat layer (1011B) is disposed on the second surface (1001b) facing the hologram layer (1002) in the first resin substrate (1001).

[0199] The thickness of the first hard coat layer (1011A) is more preferably 1 to 50 μm.

[0200] The thickness of the second hard coat layer (1011B) is more preferably 1 to 50 μm.

[0201] The flatness of the surface of the first hard coat layer (1011A) and the second hard coat layer (1011B) is more preferably 0.120 or less when the MC value is measured as a laminate of the first hard coat layer (1011A) and the second hard coat layer (1011B) and the first resin substrate (1001) (hereinafter referred to as the coated substrate).

[0202] It is more preferable that the arithmetic mean roughness Ra on the surface of the first hard coat layer (1011A) and the second hard coat layer (1011B) is 10 nm or less.

[0203] The refractive index of the material of the first hard coat layer (1011A) and the second hard coat layer (1011B) is not particularly limited.

[0204] For example, the refractive index of the material of the first hard coat layer (1011A) and the second hard coat layer (1011B) should be equal to or lower than that of the first resin substrate (1001) in terms of real image visibility, but if a target material such as one that increases the hardness of the hard coat layer is selected, it may be higher than the refractive index of the first resin substrate (1001).

[0205] For example, if the refractive index of the material of the first hard coat layer (1011A) and the second hard coat layer (1011B) is equivalent to the refractive index of the material of the first resin substrate (1001), the interface between the surface of the first resin substrate (1001) and the first hard coat layer (1011A) and the second hard coat layer (1011B) is optically lost. In this case, the MC value of the coated substrate substantially indicates the degree of unevenness defects on the surface of the first hard coat layer (1011A) and the second hard coat layer (1011B). For example, when the surface of the first resin substrate (1001) has fewer irregular defects than the surface of the first hard coat layer (1011A) and the second hard coat layer (1011B) by forming the first hard coat layer (1011A) and the second hard coat layer (1011B), it is more preferable that the refractive index of the material of the first hard coat layer (1011A) and the second hard coat layer (1011B) be close to the refractive index of the material of the first resin substrate (1001).

[0206] Generally, since the refractive index of the material of the first hard coat layer (1011A) and the second hard coat layer (1011B) and the refractive index of the material of the first resin substrate (1001) are different, the MC value of the coated substrate is evaluated to include the surface irregularity defects of the first hard coat layer (1011A) and the second hard coat layer (1011B) and the surface irregularity defects of the first resin substrate (1001). However, if the thickness of the first hard coat layer (1011A) and the second hard coat layer (1011B) is formed uniformly such that the surface irregularity defects of the first hard coat layer (1011A) and the second hard coat layer (1011B) follow the surface irregularity defects of the first resin substrate (1001), the MC value of the first resin substrate (1001) itself is considered to be equivalent to the MC value of the first resin substrate (1001) on which the first hard coat layer (1011A) and the second hard coat layer (1011B) are formed.

[0207] For example, the refractive index of the material of the first hard coat layer (1011A) and the second hard coat layer (1011B) is preferably equal to or greater than the refractive index of the material of the hologram layer (1002) in terms of wide viewing angle. As the refractive index increases, there is a tendency to increase the critical angle of light that guides the light.

[0208] The surface hardness of the first hard coat layer (1011A) and the second hard coat layer (1011B) is not particularly limited as long as it is higher than the surface hardness of the first resin substrate (1001). For example, the pencil hardness (JIS K 5600-5-4: 1999) of the first hard coat layer (1011A) and the second hard coat layer (1011B) is more preferably H or higher, and even more preferably 2H or higher.

[0209] Materials suitable for the first hard coat layer (1011A) and the second hard coat layer (1011B) may include, for example, a hard coat agent comprising a polymerizable monomer or a polymerizable oligomer that forms a cured product upon irradiation with an active energy beam. Examples of the polymerizable monomer may include a (meth)acrylate monomer having a radical polymerizable unsaturated group in its molecule. Examples of the polymerizable oligomer may include a (meth)acrylate oligomer having a radical polymerizable unsaturated group in its molecule.

[0210] Examples of (meth)acrylate monomers having radical polymerizable unsaturated groups among the molecules include at least one monomer selected from the group consisting of urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicon (meth)acrylate. Examples of (meth)acrylate oligomers having radical polymerizable unsaturated groups among the molecules include oligomers comprising constituent units derived from at least one monomer selected from the group consisting of urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicon (meth)acrylate. Two or more of the polymerizable monomers or polymerizable oligomers may be used in combination. Among these, urethane (meth)acrylate monomers or oligomers are preferred due to their high surface hardness, etc.

[0211] Urethane (meth)acrylates are exemplified by, for example, urethane (meth)acrylates obtained by reacting a polyisocyanate compound with a (meth)acrylate compound having one hydroxyl group in its molecular structure, and urethane (meth)acrylates obtained by reacting a polyisocyanate compound with a (meth)acrylate compound having one hydroxyl group in its molecular structure and a polyol compound.

[0212] The first hard coat layer (1011A) and the second hard coat layer (1011B) may include a cured product of a polyfunctional (meth)acrylate.

[0213] Polyfunctional (meth)acrylates include, for example, trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, Examples include isocyanuric acid di(meth)acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornel di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, or ditrimethylolpropane tetra(meth)acrylate, or these modified with PO, EO, or caprolactone, etc.

[0214] In forming the first hard coat layer (1011A) and the second hard coat layer (1011B), additives such as a crosslinking agent, a polymerization initiator, a lubricant, a plasticizer, an organic particle, an inorganic particle, an antifouling agent, an antioxidant, or a catalyst, or additives such as silicone-based or fluorine-based additives to prevent contamination and adhesion may be added to the hard coat agent to the extent that the physical properties are not impaired.

[0215] The first hard coat layer (1011A) and the second hard coat layer (1011B) may be made of a material having a refractive index different from that of the first resin substrate (1001). In this case, the refractive index of the outermost surface of the light guide plate (1014) for image display and the refractive index at the interface of the hologram layer (1002) can be changed from the refractive index of the first resin substrate (1001) by the first hard coat layer (1011A) and the second hard coat layer (1011B).

[0216] The light guide plate (1014) for image display of the first modified example of the first embodiment of the present invention can be manufactured in the same manner as the basic example of the first embodiment of the present invention, for example, by forming a first resin substrate (1001) in the same manner as the basic example of the first embodiment of the present invention described above, and then forming a first hard coat layer (1011A) and a second hard coat layer (1011B) on the first surface (1001a) and the second surface (1001b) of the first resin substrate (1001) respectively during the period from forming the first resin substrate (1001) to laminating it with a photopolymer material that forms a hologram layer (1002).

[0217] The first hard coat layer (1011A) and the second hard coat layer (1011B) can be formed by applying a hard coat liquid, which serves as the respective raw material, to the first surface (1001a) and the second surface (1001b), respectively, and then curing the hard coat liquid. The method of applying the hard coat liquid is not particularly limited. For example, as a method of applying the hard coat liquid, there is a method of forming a cured film on the substrate by directly applying a photocurable resin composition onto the substrate surface using a coating method such as a flex method, roller coating method, bar coating method, spray coating method, air knife coating method, or dipping method, and then curing the coating film by irradiating it with light.

[0218] In addition, for example, a method may be described in which a photocurable resin composition is applied by the coating method or the like to the surface of at least one mold material for forming a mold polymerization, and a cured film is formed on the mold material by curing the coating film through light irradiation, and a mold polymerization shape is assembled using the mold material such that the cured film becomes the inner side, and a substrate material is injected into the mold to perform mold polymerization, and after the polymerization is completed, a laminate in which the cured film is integrated with the surface of the substrate is removed.

[0219] However, the first hard coat layer (1011A) and the second hard coat layer (1011B) may be formed in the same way as the first resin substrate (1001) in the manufacturing process of the first resin substrate (1001).

[0220] It is more preferable that the material and the method of applying the material used for the first hard coat layer (1011A) and the second hard coat layer (1011B) be a material and a method of applying the material that is difficult to increase the irregularity of the surface defects of the first resin substrate (1001). It is even more preferable that the material and the method of applying the material used for the first hard coat layer (1011A) and the second hard coat layer (1011B) be a material and a method of applying the material that alleviates the irregularity of the surface defects of the first resin substrate (1001).

[0221] For example, the hard coat agent described above, alkoxysilane polycondensation curing resin, melamine-based resin, etc. can be used as a material.

[0222] For example, as a coating method, conventionally known coating methods such as bar coating, dip coating, reverse gravure coating, direct gravure coating, roll coating, die coating, or curtain coating can be used, and dip coating, die coating, or gravure coating is particularly preferred.

[0223] According to the first modified example of the first embodiment of the present invention, since the MC value of the first resin substrate (1001) and the second resin substrate (1003) is 0.120 or less, as in the basic example of the first embodiment of the present invention, a light guide plate for displaying an image can be provided that can display a clear image even when using a resin substrate, as in the basic example of the first embodiment of the present invention.

[0224] In addition, according to the first variation of the first embodiment of the present invention, since the first hard coat layer (1011A) and the second hard coat layer (1011B) are laminated on the first resin substrate (1001), scratches on the surface of the first resin substrate (1001) are prevented.

[0225] For example, in the manufacturing process of a light guide plate (1014) for image display and a display device, deterioration of flatness due to scratches on the surface of the first resin substrate (1001) is prevented. Because of this, the defect rate of the light guide plate (1014) for image display and the display device caused by handling during the manufacturing process, such as transport, can be reduced.

[0226] For example, since the first hard coat layer (1011A) forms the outermost surface of the light guide plate (1014) for image display, the degradation of image quality caused by scratches on the outermost surface during use of the light guide plate (1014) for image display is suppressed.

[0227] In addition, the description of the first modified example above was described as an example in which a hard coat layer is formed on each surface in the thickness direction of the first resin substrate (1001). However, either the first hard coat layer (1011A) or the second hard coat layer (1011B) may be omitted.

[0228] In the description of the first modified example above, the case in which a hard coat layer is formed only on the first resin substrate (1001) was described. However, at least one of the first hard coat layer (1011A) and the second hard coat layer (1011B) may also be formed on the second resin substrate (1003).

[0229] [Second Embodiment]

[0230] <Basic Example>

[0231] Hereinafter, a light guide plate for image display according to a second embodiment of the present invention will be described.

[0232] A light guide plate for image display according to a second embodiment of the present invention comprises a first resin substrate, a first barrier layer, and a hologram layer. Preferably, the first barrier layer is disposed on the surface of at least one of the first resin substrate and the hologram layer, and more preferably, the first barrier layer is disposed on the hologram layer. Preferably, the first resin substrate, the first barrier layer, and the hologram layer are disposed in this order in the thickness direction.

[0233] The light guide plate for image display according to the second embodiment of the present invention may additionally have a second barrier layer and a second resin substrate. It is preferable that the first barrier layer is disposed on at least one of the surface of the first resin substrate facing the hologram layer and the surface of the hologram layer facing the first resin substrate, and the second barrier layer is disposed on the surface of the second resin substrate facing the hologram layer and the surface of the hologram layer facing the second resin substrate, and it is more preferable that the first barrier layer and the second barrier layer are disposed on the surface of the hologram layer facing the first resin substrate and the surface of the hologram layer facing the second resin substrate, respectively. It is preferable that the first resin substrate, the first barrier layer, the hologram layer, the second barrier layer, and the second resin substrate are laminated in this order in the thickness direction.

[0234] In this embodiment, the first resin substrate and the second resin substrate may be collectively referred to simply as "resin substrate." Also, the first barrier layer and the second barrier layer may be collectively referred to simply as "barrier layer."

[0235] One or more transparent layers may be disposed between the barrier layer and the resin substrate. Additionally, one or more transparent layers may be disposed between the barrier layer and the hologram layer.

[0236] Examples of the above transparent layer include a hard coat layer, an adhesive layer, or an anchor coat layer.

[0237] In the light guide plate for image display according to the second embodiment of the present invention, a glass substrate may be formed to sandwich the barrier layer and the hologram layer between the resin substrate and the barrier layer. In this case, since the glass substrate itself has barrier properties, the glass substrate may be disposed on the surface opposite to the surface facing the barrier layer in the hologram layer.

[0238] As the resin substrate above, the resin substrate in the first embodiment described above can be preferably used.

[0239] The material used in the above resin substrate is not particularly limited as long as it is a transparent material, but it is preferable to include at least one resin selected from the group consisting of acrylic resin, cyclic polyolefin resin, and polycarbonate resin.

[0240] The refractive index of the barrier layer is preferably higher than the refractive index of the resin substrate, and 1.48 or higher is more preferable.

[0241] It is preferable to use a water vapor barrier material as the material of the above barrier layer.

[0242] In addition, the material of the barrier layer is preferably an inorganic material, and more preferably includes at least one inorganic material selected from the group consisting of silicon oxide, silicon nitrate oxide, diamond-like carbon (DLC), aluminum oxide, and glass.

[0243] In addition, by using an auxiliary layer comprising a fluorine-based material, a cycloolefin-based polymer, or vinylidene chloride as part of the barrier layer and combining it with the inorganic material described above, the barrier layer may be made into a multilayer structure, and the water vapor barrier properties may be further enhanced.

[0244] Additionally, the barrier layer may be disposed on a resin film. In this case, it is more preferable that the resin film be disposed between the barrier layer and the resin substrate.

[0245] The above hologram layer is sandwiched between the first resin substrate and the second resin substrate, or between the first resin substrate and the glass substrate.

[0246] The light guide plate for image display described above has an incident portion for incident image light and a display portion for displaying an image formed by the image light. The hologram layer is disposed between the incident portion and the display portion. The hologram layer has a diffraction grating pattern formed therein for guiding image light incident from the incident portion to the display portion and emitting it from the display portion. The diffraction grating pattern in the display portion transmits at least a portion of external light incident from outside the light guide plate for image display.

[0247] The image light incident on the above-mentioned incident portion is guided into the hologram layer and emitted to the outside from the display portion. Meanwhile, as external light also passes through the resin substrate and the display portion, an observer of the display portion can observe both the image light and the external light within their field of view.

[0248] The light guide plate for image display according to the second embodiment of the present invention is preferably used in a display device using VR technology or AR technology. For example, in addition to display applications, the light guide plate for image display according to the second embodiment of the present invention may be used in devices such as holographic optical elements (HOE), represented by a combiner for a head-up display (HUD) for automobiles or a reflector for a reflective liquid crystal display device.

[0249] A known resin material for forming a hologram is used in the above hologram layer. Examples of the resin material for forming a hologram include a hologram recording material comprising a thermosetting resin having at least one solvent-soluble cation-polymerizable ethylene oxide ring among its structural units and an ethylenically polymerizable monomer (Japanese Patent Publication No. Hei 8-1676, Japanese Patent Publication No. Hei 8-1677, Japanese Patent Publication No. Hei 8-1678, Japanese Patent Publication No. Hei 8-1679).

[0250] Hereinafter, based on the example shown in FIG. 9, a detailed configuration of an example of a light guide plate for image display according to the second embodiment of the present invention will be described. FIG. 9 is a schematic cross-sectional view showing an example of a light guide plate for image display according to the second embodiment of the present invention.

[0251] In the light guide plate (2006) for image display shown in FIG. 9, a first resin substrate (2001), a first barrier layer (2002), a hologram layer (2003), a second barrier layer (2004), and a second resin substrate (2005) are arranged in this order in the thickness direction.

[0252] The shape of the light guide plate (2006) for image display viewed from a planar perspective is not particularly limited. For example, the light guide plate (2006) for image display may be shaped into a form that can be mounted on a display device used.

[0253] For example, the light guide plate (2006) for image display may be a rectangular plate larger than the shape mounted on the display device. In this case, the light guide plate (2006) for image display is formed by being cut or shaped into a shape that can be mounted on the display device before being assembled on the display device.

[0254] The light guide plate (2006) for displaying images may be flat, or, if necessary, may be curved.

[0255] Below, an example is described in which a light guide plate (2006) for displaying images is formed as a flat plate in the shape of a rectangle when viewed from a flat plane.

[0256] The first resin substrate (2001) is disposed on the outermost portion in the thickness direction of the light guide plate (2006) for image display. The first resin substrate (2001) is disposed on the surface of the light guide plate (2006) for image display on the side of the image output.

[0257] The first resin substrate (2001) has the same shape as the external shape of the light guide plate (2006) for image display.

[0258] In the first resin substrate (2001), image light emitted from the hologram layer (2003) and external light passing through the second resin substrate (2005) and the hologram layer (2003) described later are transmitted.

[0259] The thickness of the first resin substrate (2001) is not particularly limited. For example, the thickness of the first resin substrate (2001) may be 0.1 to 10 mm.

[0260] The material forming the first resin substrate (2001) is not particularly limited as long as it is a transparent resin material. The material forming the first resin substrate (2001) may be, considering optical properties such as transparency and refractive index of light, and furthermore, various physical properties such as impact resistance, heat resistance, and durability, for example, a polyolefin-based resin such as a homopolymer or copolymer of olefins such as ethylene, propylene, or butene; an amorphous polyolefin-based resin such as a cyclic polyolefin; a polyester-based resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN); a cellulose-based resin such as triacetylcellulose, diacetylcellulose, or cellophane; a polyamide-based resin such as nylon 6, nylon 66, nylon 12, or copolymer nylon; Examples of organic materials include ethylene-vinyl acetate copolymer partial hydrolysate (EVOH), polyimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluoropolymers, poly(meth)acrylic resins, styrene resins such as polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinyl chloride, cellulose, acetylcellulose, polyvinylidene chloride, polyphenylene sulfide, polyurethane, phenolic resin, epoxy resin, polyarylate resin, polynorbornene, styrene-isobutylene-styrene block copolymer (SIBS), allyl diglyglycol carbonate, and biodegradable resins. Among these, it is preferable to include at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin, and polycarbonate. Additionally, the first resin substrate (2001) may be formed from two or more materials, or may have a laminated structure in which two or more materials are laminated.

[0261] In terms of transparency of the first resin substrate (2001), polycarbonate or poly(meth)acrylic resin is preferred. In terms of process resistance, such as chemical resistance and processability of the first resin substrate (2001), poly(meth)acrylic resin, epoxy resin, or cyclic polyolefin is preferred. Poly(meth)acrylic resin is more preferred in that it can achieve both transparency and process resistance.

[0262] The first barrier layer (2002) is disposed between the first resin substrate (2001) and the hologram layer (2003) described later, and in the configuration shown in FIG. 9, it is in close contact with the respective surfaces of the first resin substrate (2001) and the hologram layer (2003). However, the first barrier layer (2002) does not need to be in close contact with both surfaces of the first resin substrate (2001) and the hologram layer (2003), but it is preferable that it be disposed on at least the hologram layer (2003). The first barrier layer (2002) prevents gas penetrating from the outside of the image display light guide plate (2006) and the first resin substrate (2001) from penetrating into the hologram layer (2003).

[0263] The first barrier layer (2002) is preferably composed of a material with excellent water vapor barrier properties (low water vapor permeability) in that it can suppress the deterioration of the hologram layer.

[0264] For example, the oxygen permeability of the first barrier layer (2002) may be 1 cm³ / m²·day or less.

[0265] For example, the water vapor permeability of the first barrier layer (2002) may be 1 g / m²·day or less. It is more preferable that the water vapor permeability of the first barrier layer (2002) be 0.5 g / m²·day or less.

[0266] The first barrier layer (2002) is not particularly limited in its material as long as it has the property of being able to block gases that cause deterioration of the hologram layer (2003), but it is preferable to include an inorganic material in that it has excellent gas barrier properties and also tends to have excellent clarity of the displayed image.

[0267] In this case, the inorganic material used for the first barrier layer (2002) may have a higher refractive index than the first resin substrate (2001). For example, the refractive index of the first barrier layer (2002) may be 1.48 to 3.00. If the first barrier layer (2002) has a high refractive index, the light passing through the first barrier layer (2002) and the first resin substrate (2001) is incident from the optically dense first barrier layer (2002) to the optically sparse first resin substrate (2001), so the angle of emission of light from the first barrier layer (2002) toward the first resin substrate (2001) increases according to the difference in refractive index between the first barrier layer (2002) and the first resin substrate (2001). Thus, the FOV (Field Of View) in the light guide plate (2006) for image display can be expanded.

[0268] Examples of materials for the first barrier layer (2002) include silicon oxide, silicon nitrate oxide, DLC, aluminum oxide, and glass.

[0269] The material of the first barrier layer (2002) is as described above, but may be an oxide such as zinc oxide, antimony oxide, indium oxide, cerium oxide, calcium oxide, cadmium oxide, silver oxide, gold oxide, chromium oxide, silicon oxide, cobalt oxide, zirconium oxide, tin oxide, titanium oxide, iron oxide, copper oxide, nickel oxide, platinum oxide, palladium oxide, bismuth oxide, magnesium oxide, manganese oxide, molybdenum oxide, vanadium oxide, or barium oxide.

[0270] When the first barrier layer (2002) is made of silicon oxide, the thickness of the layer may be 10 to 300 nm. If the thickness of the layer is less than 10 nm, there is a risk that moisture resistance will be insufficient. If the thickness of the layer exceeds 300 nm, cracks may easily occur in the thin film of the silicon oxide, and there is a risk that it may peel off from the film surface.

[0271] A particularly desirable layer thickness is 20 to 200 nm.

[0272] The method of forming the first barrier layer (2002) using the silicon oxide is not particularly limited. For example, the first barrier layer (2002) can be formed by any conventionally known method such as vacuum deposition, sputtering, ion plating, or plasma CVD. When forming the first barrier layer (2002) using the silicon oxide, surface treatment may be performed to improve the adhesion between the film surface and the silicon oxide, such as performing corona discharge treatment or low-temperature plasma treatment on the film surface, applying a silane coupling agent to the film surface, or applying a mixture of saturated polyester and isocyanate.

[0273] For example, when forming a silicon oxide thin film by vacuum deposition, silicon, silicon monoxide, silicon dioxide, or a mixture thereof is used as the evaporation material, and 1.0 × 10 -3 ~ 1.0 × 10 -5 Under a vacuum of Torr, heat and evaporate using an electron beam, resistance heating, or high-frequency heating method.

[0274] In addition, a reaction deposition method performed while supplying oxygen gas can also be employed.

[0275] In the silicon oxide forming the first barrier layer (2002), calcium, magnesium, or their oxides may be incorporated as impurities if the amount is 10 mass% or less.

[0276] In the case where the first barrier layer (2002) is made of silicon nitrate oxide, the same configuration as the first barrier layer (2002) having silicon oxide as the main component is used, except that the silicon oxide is replaced with the silicon nitrate oxide.

[0277] DLC is an amorphous carbon material that generally consists of a ternary structure comprising a diamond-like structure, a graphite-like structure, and a polyethylene-type polymer structure containing hydrogen atoms in its structure. In the production of the above DLC, when a hydrocarbon such as ethylene, acetylene, or benzene is used as a carbon source, it typically has a ternary structure containing hydrogen.

[0278] The above DLC has excellent hardness, lubricity, wear resistance, chemical stability, heat resistance, and surface smoothness. Because the above DLC forms the dense polymer structure described above, it also has excellent gas barrier and water vapor barrier properties.

[0279] The method of forming the first barrier layer (2002) by the above DLC is not particularly limited. As a coating method for the above DLC, a known suitable coating method may be used, such as a plasma CVD method, or a physical vapor deposition method such as an ion plating method or an ion beam sputtering method.

[0280] When the first barrier layer (2002) is made of aluminum oxide, the first barrier layer (2002) may be formed, for example, only with Al2O3, or may be formed by mixing two or more types selected from the group consisting of Al, AlO, and Al2O3. The atomic ratio of Al to O in the aluminum oxide layer varies depending on the manufacturing conditions of the aluminum oxide layer. The aluminum oxide layer that can be used as the first barrier layer (2002) may contain trace amounts of other components (at most 3% of the total components) within a range where the barrier performance is not impaired.

[0281] The layer thickness of the aluminum oxide layer may be set according to the requirements for barrier performance. For example, the layer thickness of the aluminum oxide layer may be 5 to 800 nm.

[0282] The method of forming the first barrier layer (2002) by aluminum oxide is not particularly limited. For example, as a method of forming the first barrier layer (2002), PVD methods (physical vapor deposition), such as vacuum deposition, sputtering, or ion plating, or CVD methods (chemical vapor deposition) may be used.

[0283] For example, in vacuum deposition, materials such as Al and Al2O3 are used as deposition source materials, and resistance heating, high-frequency induction heating, or electron beam heating may be used as the heating method for the deposition source. In vacuum deposition, oxygen, nitrogen, or water vapor may be introduced as a reactive gas, or reactive deposition using means such as ozone addition or ion assist may be used. Additionally, bias may be applied to the deposited surface, or the temperature of the deposited surface may be raised or lowered. The same applies to other film deposition methods other than vacuum deposition, such as sputtering, PVD, and CVD.

[0284] When the first barrier layer (2002) is made of glass, the material of the first barrier layer (2002) may be, for example, borosilicate glass, alkali-free glass, low-alkali glass, soda-lime glass, or sol-gel glass, or glass that has undergone heat treatment or surface treatment. As for the material of the first barrier layer (2002), alkali-free glass is particularly preferred from the viewpoint of avoiding discoloration by impurities.

[0285] When the first barrier layer (2002) is made of glass, the thickness of the layer may be 10 to 200 μm. If the thickness of the layer is 10 μm or more, there is a tendency for excellent gas barrier properties along with mechanical strength. The thickness of the layer is preferably 10 μm or more, and more preferably 30 μm or more. In addition, if the thickness of the layer is 200 μm or less, there is a tendency for excellent optical properties as a light guide plate, such as light transmittance. The thickness of the layer is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 75 μm or less, and particularly preferably 50 μm or less.

[0286] The method of forming the first barrier layer (2002) using glass is not particularly limited. As a method of forming the first barrier layer (2002) using glass, for example, the slot-down draw method, the fusion method, or the float method may be adopted. Also, the glass used may be commercially available glass used as is, or commercially available glass may be polished to a desired thickness and used. Examples of the commercially available glass include Corning's "EAGLE2000", Asahi Glass's "AN100", Nippon Electric Glass's "OA10G", and Schott's "D263".

[0287] Additionally, as part of the first barrier layer (2002), an auxiliary layer including a fluorine-based material, a cycloolefin-based polymer, or vinylidene chloride may be introduced, and by making the first barrier layer (2002) a multilayer structure with the inorganic material layer described above, the water vapor barrier properties can be further enhanced.

[0288] For example, PCTFE (polychlorotrifluoroethylene) can be used as this fluorine-based material. Also, as the cycloolefin-based polymer, cycloolefin polymers or cycloolefin copolymers can be used.

[0289] The thickness of this auxiliary layer can be set according to the requirements for water vapor barrier performance. For example, when using a fluorine-based material, the thickness of the layer may be 0.1 to 100 μm.

[0290] The hologram layer (2003) is laminated on the surface of the first barrier layer (2002). The composition of the hologram layer (2003) is not particularly limited. A suitable diffraction grating corresponding to the function required for the image display light guide plate (2006) is formed in the hologram layer (2003).

[0291] The second barrier layer (2004) is laminated on the surface of the hologram layer (2003) opposite to the surface of the hologram layer (2003) on which the first barrier layer (2002) is formed.

[0292] The composition of the second barrier layer (2004) is the same as that exemplified in the description of the first barrier layer (2002). However, the material, thickness, etc. of the second barrier layer (2004) may be different from that of the first barrier layer (2002).

[0293] The second resin substrate (2005) is laminated on the surface of the second barrier layer (2004) opposite to the hologram layer (2003). The second resin substrate (2005) uses the same configuration as exemplified in the description of the first resin substrate (2001). However, the thickness and material of the second resin substrate (2005) may differ from those of the first resin substrate (2001). In particular, since the second resin substrate (2005) is placed on the surface of the external light incident side located opposite to the display image emission side of the light guide plate (2006) for image display, a material with a higher surface hardness than that of the first resin substrate (2001) may be used.

[0294] Such a light guide plate (2006) for displaying images can be manufactured, for example, as follows.

[0295] A first resin substrate (2001) and a second resin substrate (2005) are prepared, and a first barrier layer (2002) and a second barrier layer (2004) are formed on the surfaces of the first resin substrate (2001) and the second resin substrate (2005), respectively. As for the manufacturing method of the first barrier layer (2002) and the second barrier layer (2004), an appropriate manufacturing method is selected according to the material of the first barrier layer (2002) and the second barrier layer (2004).

[0296] For example, a photosensitive material for forming a hologram is applied to the surface of the first barrier layer (2002) in the first resin substrate (2001) on which the first barrier layer (2002) is formed. At this time, a transparent seal layer having the same thickness as the hologram layer (2003) may be formed on the outer periphery of the first barrier layer (2002). In this case, the photosensitive material is applied to the concave portion formed by surrounding the seal layer. The seal layer seals the outer periphery of the hologram layer (2003) after the hologram layer (2003) is formed. In addition, a material with excellent gas barrier properties, such as that used in the first barrier layer (2002), may be used for this seal layer, thereby improving the durability of the hologram layer (2003).

[0297] Afterwards, a second resin substrate (2005) having a second barrier layer (2004) formed thereon is placed on a photosensitive material with the second barrier layer (2004) facing toward the photosensitive material.

[0298] However, the manufacturing sequence described above is merely an example. For instance, after a photosensitive material is applied to a second resin substrate (2005) on which a second barrier layer (2004) is formed, a first resin substrate (2001) on which a first barrier layer (2002) is formed may be placed on the photosensitive material.

[0299] Afterwards, a laminate comprising a first resin substrate (2001), a first barrier layer (2002), a photosensitive material, a second barrier layer (2004), and a second resin substrate (2005) is laminated by a pressure press.

[0300] Afterwards, an interference pattern corresponding to the diffraction pattern is formed on the photosensitive material of the laminate, and a diffraction grating is formed within the photosensitive material.

[0301] In this way, a light guide plate (2006) for displaying images is manufactured.

[0302] According to the light guide plate (2006) for image display, a first barrier layer (2002) and a second barrier layer (2004) are respectively disposed between the first resin substrate (2001) and the hologram layer (2003), and between the second resin substrate (2005) and the hologram layer (2003).

[0303] The gas barrier properties of the first resin substrate (2001) and the second resin substrate (2005) are significantly lower than those of glass, although the degree varies depending on the type of resin material. For this reason, the first resin substrate (2001) and the second resin substrate (2005) have higher hygroscopicity and water vapor permeability than glass.

[0304] As a result, external gas of the light guide plate (2006) for image display penetrates the first resin substrate (2001) and the second resin substrate (2005) to some extent, or accumulates inside. In particular, moisture is prone to accumulating in the first resin substrate (2001) and the second resin substrate (2005).

[0305] However, gas and moisture that have penetrated into the first resin substrate (2001) and the second resin substrate (2005) from the outside are shielded by the first barrier layer (2002) and the second barrier layer (2004) even if they diffuse within the light guide plate (2006) for image display. As a result, the penetration of gas and water vapor into the hologram layer (2003) is suppressed.

[0306] For example, by suppressing the penetration of moisture into the hologram layer (2003), the deterioration of the hologram layer (2003) is prevented.

[0307] In addition, in the image display light guide plate (2006), since it has the layer configuration described above, the hologram layer (2003) is not in contact with the first resin substrate (2001) and the second resin substrate (2005). Thus, even if the image display light guide plate (2006) is placed in a high-temperature environment, the hologram layer (2003) is prevented from eroding the first resin substrate (2001) and the second resin substrate (2005).

[0308] In particular, if the refractive index of the first barrier layer (2002) and the second barrier layer (2004) is higher than that of the first resin substrate (2001) and the second resin substrate (2005), as described above, the angle of emission of light directed from the first barrier layer (2002) toward the first resin substrate (2001) increases. Likewise, the angle of emission of light incident from the second resin substrate (2005) toward the second barrier layer (2004) decreases. For this reason, light incident from the outside of the second resin substrate (2005) and passing through the image display light guide plate (2006) is incident in a wider angle range compared to the case where the second barrier layer (2004) is not present, and is emitted in a wider angle range compared to the case where the first barrier layer (2002) is not present. As a result, the field of view of the external light becomes wider, and the FOV of the display side is also expanded.

[0309] Regarding the image light from the hologram layer (2003), as described above, as a result of the light emission angle from the first barrier layer (2002) toward the first resin substrate (2001) increasing, the FOV of the display screen is expanded compared to the case where the first barrier layer (2002) is not present.

[0310] In particular, in this embodiment, the first barrier layer (2002) and the second barrier layer (2004) are laminated on the hologram layer (2003), so that the diffusion position of the external light and image light and the diffraction position of the hologram layer (2003) constituting the display screen are brought closer together. Therefore, compared to the case where the first barrier layer (2002) and the second barrier layer (2004) are formed at a position away from the hologram layer (2003), a clearer image can be observed from a wide angle.

[0311] Here, an example of a method for measuring luminance value and FOV in a light guide plate (2006) for image display is briefly explained.

[0312] FIG. 10 is a schematic front view illustrating the measurement method of luminance value and FOV.

[0313] As shown in FIG. 10, in order to measure the brightness value and FOV of the light guide plate (2006) for image display, a display device (2010) is manufactured using the light guide plate (2006) for image display.

[0314] The display device (2010) is equipped with an image light projection unit (2013) and an incident optical system (2012) in addition to the image display light guide plate (2006).

[0315] The image light projection unit (2013) projects image light to be displayed on an image display light guide plate (2006) according to an image signal transmitted from a controller that is omitted from the city.

[0316] The incident optical system (2012) is equipped with, for example, a prism, etc. The incident optical system (2012) directs image light emitted from the image light projection unit (2013) onto an incident portion (2006a) formed on the surface of the image display light guide plate (2006). For example, the incident portion (2006a) is formed on the surface of the first resin substrate (2001).

[0317] The image light incident on the incident portion (2006a) passes through the waveguide diffraction grating portion (2003b) formed on the hologram layer (2003) and reaches the display diffraction grating portion (2003c) of the hologram layer (2003). In the display diffraction grating portion (2003c), the image light is diffracted at a position corresponding to each display pixel. The diffracted light is emitted outward from the display portion (2006d) on the surface of the image display light guide plate (2006). In the example shown in FIG. 10, the display portion (2006d) is formed at a position separated from the incident portion (2006a) on the surface of the first resin substrate (2001).

[0318] The measurement of the brightness value and FOV of the light guide plate (2006) for image display is carried out by placing the display device (2010) in the measuring device (2015).

[0319] The measuring device (2015) is equipped with a support base (not shown), a luminance meter (2014), and a goniometer stage (not shown).

[0320] The above-mentioned support base holds the display device (2010). The luminance meter (2014) measures the luminance value of the received light. The above-mentioned goniometer stage supports the luminance meter (2014) so ​​as to be oscillating on a circumference centered on its rotation center.

[0321] The distance d between the luminance meter (2014) and the display surface (2003a) is a distance corresponding to the position of the user's eyes when the display device (2010) is mounted. For example, if the display device (2010) is a head-mounted display, the distance d is 15 mm.

[0322] The luminance value of the light guide plate (2006) for image display is measured by placing a luminance meter (2014) at a position with a oscillation angle of 0° (see the solid line luminance meter (2014) in FIG. 10). The display device (2010) is positioned such that the center of the display surface (2003a) is positioned opposite the luminance meter (2014) on the measurement optical axis of the luminance meter (2014) by means of the support base.

[0323] The above luminance value is the luminance measured by a luminance meter (2014) when a white image of maximum luminance is displayed on a display device (2010).

[0324] In measuring the FOV of the light guide plate (2006) for image display, with a white image of maximum brightness displayed on the display device (2010), the oscillation angle θ B Luminance is measured by changing the value. The luminance corresponding to the point where the white image becomes invisible is set as a threshold value, and is obtained as an angle range in which luminance greater than or equal to the threshold value is obtained. When luminance greater than or equal to the threshold value is obtained in the range from -θ1 to +θ2, the FOV is θ1 + θ2.

[0325] The FOV of the light guide plate (2006) for displaying images is preferably 24 to 160°, and more preferably 35 to 160°. Also, as the FOV increases, the viewing angle of the image expands, the amount of image information increases, and the range of applicable uses widens. On the other hand, if the FOV is smaller than the upper limit, the amount of light emitted per unit area tends to increase, and the image becomes brighter, which is desirable.

[0326] For example, the closer the distance between the first barrier layer (2002) and the second barrier layer (2004) and the hologram layer (2003), the greater the FOV can be improved by about 10° or more. The distance is preferably 1000 nm or less, more preferably 500 nm or less, and most preferably 100 nm or less.

[0327] As explained above, according to the present embodiment, it is possible to provide a light guide plate for image display that can suppress the degradation of the hologram layer even when a resin substrate is used.

[0328] <Example of Variation 1>

[0329] A first variation of the second embodiment of the present invention will be described.

[0330] FIG. 11 is a schematic cross-sectional view showing an example of a light guide plate for image display of a first variation of a second embodiment of the present invention.

[0331] As shown in FIG. 11, the light guide plate (2016) for image display of the first variant of the second embodiment of the present invention has a first barrier film (2022) and a second barrier film (2024) instead of the first barrier layer (2002) and the second barrier layer (2004) of the light guide plate (2006) for image display of the second embodiment of the present invention.

[0332] The following describes the differences from the above embodiment, focusing on the points of difference.

[0333] The first barrier film (2022) comprises a barrier layer (2022A) and a resin film (2022B).

[0334] The barrier layer (2022A) is configured in the same way as the first barrier layer (2002) in the above embodiment.

[0335] The resin film (2022B) is a gas that forms a barrier layer (2022A). The material of the resin film (2022B) is not particularly limited as long as it is a transparent resin film capable of forming a barrier layer (2022A).

[0336] For example, as a material for the resin film (2022B), resins such as polypropylene, ABS, amorphous polyester resin, polyimide, polyamide, polyethersulfone (PES), polycarbonate (PC), polynorbornene which is a cyclic polyolefin copolymer, cyclic polyolefin resin, polycyclohexene, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), fluoropolymer, polyarylate (PAR), polyetherketone (PEK), or polyetheretherketone (PEEK) may be used.

[0337] For example, considering the coefficient of thermal expansion, the coefficient of humidity expansion, and the glass transition temperature, more desirable materials for the resin film (2022B) include, in the case of crystalline resins, thermoplastic resins such as polyamide, polyacetal, polybutylene terephthalate, polyethylene terephthalate, or syndiotactic polystyrene, and in the case of thermosetting resins, polyphenylene sulfide, polyetheretherketone, liquid crystal polymer, fluoropolymer, or polyethernitrile. For example, in the case of amorphous resins, thermoplastic resins such as polycarbonate or modified polyphenylene ether, and in the case of thermosetting resins, polysulfone, polyethersulfone, polyarylate, polyamideimide, polyetherimide, or thermoplastic polyimide may be cited. Among them, since polycarbonate has low water absorption, the first barrier film (2022) constructed using it is particularly desirable because the humidity expansion coefficient is low.

[0338] The thickness of the resin film (2022B) is not particularly limited. However, it is more preferable that the resin film (2022B) be thinner than the first resin substrate (2001). For example, the thickness of the resin film (2022B) may be 1 to 200 μm.

[0339] For the resin film (2022B), it is more preferable to use a material with high surface smoothness. In this case, the surface smoothness of the barrier layer (2022A) is improved, and it is easy to make the layer thickness of the barrier layer (2022A) uniform. As for the surface smoothness of the resin film (2022B), it is more preferable that the arithmetic mean roughness Ra is 2 nm or less.

[0340] The surface of the resin film (2022B) may be subjected to various surface modification treatments to improve adhesion with the barrier layer (2022A) and adhesion with the first adhesive layer (2026) described later. For example, the surface of the resin film (2022B) may be subjected to treatments such as corona discharge treatment, flame treatment, oxidation treatment, plasma treatment, or lamination of a primer layer.

[0341] Such a first barrier film (2022) is manufactured by forming a resin film (2022B) on a barrier layer (2022A). Such a first barrier film (2022) is manufactured by forming a barrier layer (2022A) on a resin film (2022B).

[0342] Examples of methods for forming the barrier layer (2022A) include physical vapor deposition (PVD), chemical vapor deposition (CVD), plating, coating, and sol-gel methods. In particular, CVD offers excellent formation efficiency for the barrier layer (2022A). In CVD, the heat applied to the resin film (2022B) during film formation is lower than in the physical vapor deposition method, thereby reducing the degradation of the resin film (2022B) caused by heating. Among CVD methods, the plasma CVD method is more preferable. In the plasma CVD method, a source gas is introduced into the film formation chamber, and then a high frequency is applied to induce a discharge and create a plasma state, thereby promoting a chemical reaction on the surface of the resin film (2022B). For this reason, the temperature during the film formation process is low, ranging from -10°C to 200°C, and film formation is possible even at 30°C or lower. Thus, thermal damage is not easily applied to the resin film (2022B).

[0343] The barrier layer (2022A) in the first barrier film (2022) is disposed on the surface of the hologram layer (2003).

[0344] The resin film (2022B) in the first barrier film (2022) is fixed to the surface of the first resin substrate (2001) by the interposition of the first adhesive layer (2026).

[0345] The material of the first adhesive layer (2026) is not particularly limited as long as it is a material that has good adhesion to the resin film (2022B) and the first resin substrate (2001).

[0346] For example, preferred materials for the first adhesive layer (2026) include polyester resin, acrylic resin, urethane resin, melamine resin, epoxy resin, etc.

[0347] The second barrier film (2024) comprises a barrier layer (2024A) identical to the barrier layer (2022A) and a resin film (2024B) identical to the resin film (2022B).

[0348] However, the material, thickness, etc. of the barrier layer (2024A) may be the same as or different from the barrier layer (2022A). The material, thickness, etc. of the resin film (2024B) may be the same as or different from the resin film (2022B).

[0349] The second barrier film (2024) is fixed to the surface of the second resin substrate (2005) by the interposition of a second adhesive layer (2027) configured in the same way as the first adhesive layer (2026).

[0350] To manufacture such an image display light guide plate (2016), for example, a first barrier film (2022) and a second barrier film (2024) are prepared, and by interposing a first adhesive layer (2026) and a second adhesive layer (2027), the first barrier film (2022) and the second barrier film (2024) are adhered to the respective surfaces of a first resin substrate (2001) and a second resin substrate (2005), thereby forming a first intermediate laminate (P1) and a second intermediate laminate (P2).

[0351] Afterwards, a hologram layer (2003) is formed in the same manner as the basic example of the second embodiment of the present invention, except that the first intermediate laminate (P1) and the second intermediate laminate (P2) are used respectively instead of the first resin substrate (2001) and the second resin substrate (2005) of the basic example of the second embodiment of the present invention. Thus, a light guide plate (2016) for image display is manufactured.

[0352] According to the image display light guide plate (2016) of the first modified example of the second embodiment of the present invention, a first resin substrate (2001), a barrier layer (2022A), and a hologram layer (2003) are arranged in this order, and a second resin substrate (2005), a barrier layer (2024A), and a hologram layer (2003) are arranged in this order. Because of this, the penetration of moisture into the hologram layer (2003) is suppressed, just like in the embodiment, thereby preventing the deterioration of the hologram layer (2003). In addition, since the hologram layer (2003) does not come into contact with the first resin substrate (2001) and the second resin substrate (2005), the first resin substrate (2001) and the second resin substrate (2005) are prevented from being eroded by the material of the hologram layer (2003).

[0353] For this reason, according to the light guide plate for image display (2016), a clear image can be displayed even when a resin substrate is used.

[0354] In addition, if the refractive index of the barrier layer (2022A, 2024A) is made higher than that of the first resin substrate (2001) and the second resin substrate (2005), the FOV of the light guide plate (2016) for image display is improved, so that a clear image can be observed from a wide angle.

[0355] In particular, according to the first variation of the second embodiment of the present invention, in the manufacturing process of a light guide plate (2016) for image display, a first barrier film (2022) and a second barrier film (2024) are bonded to a first resin substrate (2001) and a second resin substrate (2005), thereby forming a barrier layer (2022A, 2024A) on the first resin substrate (2001) and the second resin substrate (2005). Because of this, even in cases where the barrier layer (2022A, 2024A) cannot be directly formed depending on the type, shape, size, etc. of the material of the first resin substrate (2001) and the second resin substrate (2005), the barrier layer (2022A, 2024A) can be easily formed.

[0356] As explained above, according to the first variation of the second embodiment of the present invention, a light guide plate for image display can be provided that can suppress the deterioration of the hologram layer even when a resin substrate is used.

[0357] In addition, although the basic example and the first modified example of the second embodiment described above were described as cases where a barrier layer is disposed on the surface of the hologram layer, for the purpose of shielding moisture that penetrates through the resin substrate and for the purpose of preventing contact between the hologram layer and the resin substrate, the barrier layer may be disposed between the resin substrate and the hologram layer.

[0358] However, in this case, if the transparent layer sandwiched between the barrier layer and the hologram layer has high hygroscopicity, there is a risk of moisture penetrating through the sides of the transparent layer. For this reason, it is more desirable for the transparent layer between the barrier layer and the hologram layer to be formed from a material with low hygroscopicity. If the transparent layer between the barrier layer and the hologram layer is hygroscopic, it is more desirable to reduce the thickness of the transparent layer. In this case, since the exposed surface area of ​​the sides that serve as penetration points for moisture is reduced, the amount of absorbed moisture can be reduced.

[0359] [Third Embodiment]

[0360] In order to prevent a decrease in optical properties caused by scratches on the surface of the light guide plate for image display according to the present invention, for example, when the light guide plate is used in a glasses-type display, a hard coat film can be mounted on the side opposite to the side where the hologram layer of the resin substrate is located so as to be peelable from the substrate.

[0361] <Basic Example>

[0362] Hereinafter, a third embodiment of the light guide plate for image display according to the present invention will be described.

[0363] FIG. 14 shows the layer configuration of a light guide plate for image display (hereinafter simply referred to as "light guide plate") (3001) according to the third embodiment of the present invention.

[0364] As shown in FIG. 14, the light guide plate (3001) comprises a hologram layer (3010), two substrates of a first substrate (3021) and a second substrate (3022) that fit the hologram layer (3010) in the thickness direction, and a hard coat film (3030) formed on the first substrate (3021).

[0365] The first substrate (3021) and the second substrate (3022) are sheet-shaped resin substrates having light transmittance. The material of the first substrate (3021) and the second substrate (3022) may be the same material as the resin substrate used in the first and second embodiments described above, but acrylic is preferred in terms of transparency, etc. The thickness of the first substrate (3021) and the second substrate (3022) can be, for example, around 1 mm.

[0366] For the hologram layer (3010), a known configuration identical to the first and second embodiments described above may be appropriately selected and used. An optical structure such as a diffraction grating may be appropriately determined by considering the wavelength of the light guiding the light.

[0367] The hard coat film (3030) has a film substrate (3031), an adhesive layer (3032), a hard coat layer (3033), and a release layer (3034). The adhesive layer (3032) is formed on a first surface (3031a) of the film substrate (3031). The hard coat layer (3033) is formed on a second surface (3031b) of the film substrate (3031) opposite to the first surface (3031a). The release layer (3034) is formed on the hard coat layer (3033).

[0368] The hard coat film (3030) is mounted so as to be peelable from the first substrate (3021) by the adhesive layer (3032) adhering to the first substrate (3021).

[0369] Below, each part of the hard coat film (3030) will be described in detail.

[0370] (Film entry (3031))

[0371] As a film substrate (3031), a film or sheet made of various organic polymers may be used. For example, a substrate commonly used in optical components such as displays may be used. Considering optical properties such as transparency and refractive index of light, and furthermore, various properties such as impact resistance, heat resistance, and durability, a polyolefin-based material such as polyethylene and polypropylene, a cyclic polyolefin-based material, a polyester-based material such as polyethylene terephthalate and polyethylene naphthalate, a cellulose-based material such as triacetylcellulose, diacetylcellulose, and cellophane, a polyamide-based material such as 6-nylon and 6,6-nylon, an acrylic-based material such as polymethyl methacrylate, or an organic polymer such as polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, and ethylene vinyl alcohol may be used. In particular, polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA) are preferred as materials.

[0372] In addition, a film substrate (3031) with added functionality can be used by adding known additives to these organic polymers, such as ultraviolet absorbers, infrared absorbers, plasticizers, lubricants, colorants, antioxidants, flame retardants, etc. Also, the film substrate (3031) may be composed of one or more mixtures of two or more organic polymers selected from the above-mentioned organic polymers, or of a polymer, or may be a laminate of multiple layers.

[0373] It is preferable that the film substrate (3031) has a low birefringence and good transparency. It is preferable that the thickness of the first substrate (3021) and the second substrate (3022) be within the range of 5 to 200 μm.

[0374] (Adhesive layer (3032))

[0375] The adhesive layer (3032) bonds the film substrate (3031) to the first substrate (3021) so that it can be peeled off with a small force. The adhesive layer (3032) is bonded to the surface opposite to the surface facing the hologram layer (3010) on the first substrate (3021).

[0376] The adhesive layer (3032) can be formed with adhesives such as, for example, rubber-based adhesive, polyester-based adhesive, epoxy-based adhesive, acrylic-based adhesive, silicone-based adhesive, urethane-based adhesive, vinylalkyl ether-based adhesive, polyvinyl alcohol-based adhesive, polyacrylamide-based adhesive, cellulose-based adhesive. Among these, an acrylic-based adhesive that is UV-curing or heat-curing is preferred in terms of optical properties such as transparency.

[0377] Examples of acrylic adhesives include those formed from an adhesive composition (hereinafter referred to as “this adhesive composition”) using a (meth)acrylic acid ester-based polymer (hereinafter referred to as “acrylic acid ester-based (co)polymer” in the sense that it includes copolymers) as a base resin.

[0378] As a base resin, an acrylic acid ester-based (co)polymer can be prepared by appropriately adjusting physical properties such as glass transition temperature (Tg) and molecular weight by appropriately selecting the type, composition ratio, and further polymerization conditions of the acrylic monomer or methacrylic monomer used for polymerization.

[0379] Examples of acrylic monomers or methacrylate monomers used to polymerize acrylic acid ester (co)polymers include 2-ethylhexyl acrylate, n-octyl acrylate, iso-octyl acrylate, n-butyl acrylate, ethyl acrylate, methyl methacrylate, methyl acrylate, etc. In addition, acrylic monomers having hydrophilic groups or organic functional groups, such as hydroxyethyl acrylate, acrylic acid, glycidyl acrylate, acrylamide, acrylonitrile, methacrylonitrile, fluoride acrylate, silicon acrylate, etc., may be copolymerized with the above acrylic monomers. Furthermore, various vinyl monomers such as vinyl acetate, alkyl vinyl ether, and hydroxyalkyl vinyl ether may also be suitably used for polymerization.

[0380] As a polymerization treatment using these monomers, known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization may be employed, and at that time, an acrylic acid ester copolymer can be obtained by using a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator depending on the polymerization method.

[0381] The thickness of the adhesive layer (3032) is preferably in the range of 1 to 50 μm, and more preferably in the range of 1 to 30 μm.

[0382] As a method for forming an adhesive layer on a film substrate (3031), conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating may be used. Regarding coating methods, examples are described in “Coating Methods” (Maki Shoten, written by Yuji Harasaki, published in 1979).

[0383] The drying method of the adhesive is not particularly limited, but generally, drying should be performed at 30 to 160°C. In addition, as for the curing method of the adhesive, a known method may be appropriately selected depending on the composition of the adhesive. For example, if the adhesive is of the active energy curing type, it may be cured by irradiating it with active energy rays (visible light, ultraviolet rays, X-rays, γ-rays). At this time, the amount of irradiation with active energy rays may be appropriately adjusted according to the characteristics of the adhesive, but generally, it is preferable to irradiate at 10 to 10,000 mJ / m².

[0384] In terms of making the hard coat film easy to peel off, the peel strength of the adhesive layer (3032) is preferably 0.01 to 50 N / 20 mm width when peeling in the 180-degree direction (peeling speed 50 mm / min).

[0385] (Hard coat layer (3033))

[0386] The hard coat layer (3033) has a hardness sufficient to prevent scratches caused by contact with other structures, etc. When expressed in terms of pencil hardness (load 750 g) as specified in JIS K 5600-5-4:1999, it is generally H or higher. Therefore, the pencil hardness of the hard coat layer is preferably H or higher, and more preferably 2H or higher.

[0387] The hard coat layer (3033) can be formed by a cured material formed using various hard coat agents. For example, the hard coat layer (3033) can be formed using a hard coat agent containing an active energy beam curable composition or a thermosetting composition.

[0388] The hard coat material may be an organic-inorganic hybrid material.

[0389] Polymerizable monomers or polymerizable oligomers that form a cured product by irradiation with active energy rays can also be used as materials for the hard coat layer (3033). Examples of the polymerizable monomers include (meth)acrylate monomers having radical polymerizable unsaturated groups in their molecules. Examples of the polymerizable oligomers include (meth)acrylate oligomers having radical polymerizable unsaturated groups in their molecules.

[0390] Among the above molecules, at least one monomer selected from the group consisting of urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicon (meth)acrylate may be cited as a (meth)acrylate monomer having a radical polymerizable unsaturated group.

[0391] Examples of (meth)acrylate oligomers having radical polymerizable unsaturated groups among the above molecules include, for instance, oligomers comprising constituent units derived from at least one monomer selected from the group consisting of urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicon (meth)acrylate. Two or more of the polymerizable monomers or polymerizable oligomers may be used in combination. Among these, urethane (meth)acrylate monomers or oligomers are preferred due to high surface hardness, etc.

[0392] Urethane (meth)acrylates are exemplified by, for example, urethane (meth)acrylates obtained by reacting a polyisocyanate compound with a (meth)acrylate compound having one hydroxyl group in its molecular structure, and urethane (meth)acrylates obtained by reacting a polyisocyanate compound with a (meth)acrylate compound having one hydroxyl group in its molecular structure and a polyol compound.

[0393] The hard coat layer (3033) may include a cured product of polyfunctional (meth)acrylate.

[0394] Polyfunctional (meth)acrylates include, for example, trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, Examples include isocyanuric acid di(meth)acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornel di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, or ditrimethylolpropane tetra(meth)acrylate, or these modified with PO, EO, or caprolactone.

[0395] Among these, a polyfunctional (meth)acrylate with 3 to 6 functional groups is preferred in that it can preferably satisfy surface hardness, and specific examples include pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), trimethylolpropane tri(meth)acrylate, tripentaerythritol octa(meth)acrylate, and tetrapentaerythritol deca(meth)acrylate.

[0396] In forming the hard coat layer (3033), additives such as crosslinking agents, polymerization initiators, lubricants, plasticizers, organic particles, inorganic particles, antifouling agents, antioxidants, or catalysts, or silicone-based or fluorine-based additives to prevent contamination and adhesion may be added to the hard coat agent to the extent that the physical properties are not impaired.

[0397] Additionally, if necessary, the hard coat agent may contain a solvent. The above solvents include: alcohols (methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol, diacetone alcohol); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, heptanone, diisobutyl ketone, diethyl ketone, diacetone alcohol); esters (methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, methyl formate, PGMEA); aliphatic hydrocarbons (hexane, cyclohexane); halogenated hydrocarbons (methylene chloride, chloroform, carbon tetrachloride); aromatic hydrocarbons (benzene, toluene, xylene); Examples include amides (dimethylformamide, dimethylacetamide, n-methylpyrrolidone); ethers (diethyl ether, dioxane, tetrahydrofuran); ether alcohols (1-methoxy-2-propanol); carbonates (dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate), etc. These solvents may be used alone or in combination of two or more types.

[0398] The thickness of the hard coat layer (3033) is preferably 1 μm to 50 μm, more preferably 2 μm to 40 μm, and even more preferably 3 μm to 25 μm. By satisfying this range for the thickness of the hard coat layer (3033), scratches on the first substrate (3021) can be effectively prevented, and scratches on the hard coat film (3030) itself can also be suppressed. In addition, when the hard coat layer (3033) is formed, the occurrence of warping of the hard coat film caused by the curing shrinkage of the hard coat agent is suppressed.

[0399] The order of forming the hard coat layer (3033) on the film substrate (3031) can generally be the same as the order of forming the adhesive layer (3032). Various methods described above can also be used for the coating method, drying method, and curing method.

[0400] (Ideal layer (3034))

[0401] The release layer (3034) facilitates the easy peeling of the adhesive layer of the overlapping hard coat film when the hard coat film is rolled into a roll during manufacturing or storage.

[0402] The release layer (3034) can be formed by applying and drying a paint dissolved in an organic solvent or water, with the resin and surfactant being the main components, such as silicone resin, fluoropolymer resin, aminoalkyd resin, polyester resin, paraffin wax, acrylic resin, urethane resin, melamine resin, urea resin, urea-melamine system, cellulose, benzoguanamine, etc., or a mixture thereof, using a conventional printing method such as gravure printing, screen printing, or offset printing. Additionally, a curable film such as a thermosetting resin, UV-curable resin, electron beam-curable resin, or radiation-curable resin can be formed by curing.

[0403] In particular, it is desirable to perform a peeling treatment using silicone, fluorine compounds, or alkyd resin-based peeling agents.

[0404] Since the hard coat film (3030) affects the visibility of the surrounding actual image viewed through the light guide plate (3001) and the image displayed on the light guide plate, it is desirable to have certain optical properties. As an example, when clamped on 0.5 mm thick soda-lime glass, it is desirable to satisfy (A) below, and more desirable to satisfy (B) and (C) below.

[0405] (A) Retardation value within the range of 0 to 100 nm

[0406] (B) Total light transmittance measured in accordance with JIS K 7361-1:1997 is 85% or higher

[0407] (C) Haze value measured in accordance with JIS K 7136:2000 is 5% or less

[0408] In the light guide plate (3001) of the third embodiment of the present invention, a hard coat film (3030) mounted on a first substrate (3021) prevents scratches on the first substrate (3021) and maintains the optical properties of the first substrate (3021) in a desirable manner. Since the hard coat film (3030) is provided with a hard coat layer (3033), scratches do not easily occur on itself. In addition, since an adhesive layer (3032) is peelably attached to the first substrate (3021), if the hard coat film (3030) is scratched, the scratched hard coat film can be easily peeled off from the first substrate (3021) and replaced with another hard coat film that is not scratched. This prevents the clarity of the light guide plate from deteriorating.

[0409] <Example of Variation 1>

[0410] A first variation of the third embodiment of the present invention will be described. In the following description, components common to those already described will be given the same reference numerals to omit redundant descriptions.

[0411] A hard coat film (3130) related to a first variation of the third embodiment of the present invention is shown in FIG. 15.

[0412] The hard coat film (3130) comprises an adhesive layer (3032), a hard coat layer (3033), and a release layer (3034). The hard coat film (3130) related to the first variant of the third embodiment of the present invention differs from the hard coat film (3030) related to the basic example described above in that it does not have a film substrate (3031).

[0413] An example of the manufacturing sequence of a hard coat film (3130) is shown below.

[0414] A paint that forms a release layer (3034) and a hard coat agent that forms a hard coat layer (3033) are applied in sequence on the release treatment surface of a resin film that has undergone release treatment, and the release layer (3034) and the hard coat layer (3033) are formed on the resin film. Next, an adhesive composition that forms an adhesive layer (3032) is applied on the hard coat layer (3033) to form an adhesive layer (3032). Finally, when the resin film is peeled off, the hard coat film (3130) is completed.

[0415] As another configuration, a hard coat layer (3033) and an adhesive layer (3032) may be formed on the untreated surface of a resin film on which a release treatment has been performed on one side in the order described above, and the resin film may be used as a release layer (3034).

[0416] The usage mode and function of the hard coat film (3130) of the first variant of the third embodiment of the present invention are generally the same as the hard coat film (3030) of the basic example described above, and produce the same effect. Additionally, since the film is laminated onto a light guide plate, it also has the effect of preventing fragments from scattering when the light guide plate is damaged.

[0417] <Multiple Layered Hard Coat Film>

[0418] The hard coat films of the basic and modified examples described above may be mounted on the first substrate (3021) in a stacked state. Two stacked hard coat films (3030) are shown in FIG. 16, and two stacked hard coat films (3130) are shown in FIG. 17. In either case, since a release layer (3034) exists at the contact area of ​​the two stacked hard coat films, the second hard coat film (3030B, 3130B) located on the upper side can be easily peeled off from the first hard coat film (3030A, 3130A) located on the lower side.

[0419] If the hard coat film is configured in this way, when the hard coat film located on the outermost surface becomes scratched, it can be peeled off, and the hard coat film underneath that is not scratched becomes the new outermost surface. Therefore, there is no need to install another hard coat film after removing the scratched hard coat film, so the surface condition of the light guide plate can be easily maintained.

[0420] In this composition, the number of overlapping hard coat films is not limited to the two sheets shown, but may be three or more.

[0421] There are no specific restrictions on the method of obtaining a hard coat film in a stacked state. For example, methods include laminating another hard coat film onto one hard coat film, or cutting the hard coat film after winding it into a roll.

[0422] In addition, a method of forming layers equivalent to multiple hard coat films at once may also be adopted. In this case, known methods such as a method of laminating all continuously laminated layers in an uncured state and then curing with an active energy beam, a method of curing or semi-curing a lower layer with an active energy beam and then applying an upper layer and then curing again with an active energy beam, or a method of applying each layer to a release film or base film and then laminating the layers together in an uncured or semi-cured state may be applied; however, from the perspective of increasing adhesion between layers, a method of laminating in an uncured state and then curing with an active energy beam is preferred. As for the method of laminating in an uncured state, known methods such as sequential coating in which an upper layer is applied by overlapping after a lower layer is applied, or simultaneous multilayer coating in which two or more layers are applied by overlapping simultaneously from multiple slits may be applied, but are not limited thereto.

[0423] [Fourth Embodiment]

[0424] In the light guide plate for image display according to the present invention, the hologram layer may yellow during manufacturing and long-term use, which may have an adverse effect on the displayed image. However, by introducing an absorption layer having an absorption peak in the wavelength range of 500 to 600 nm, this can be reduced without degrading the hologram layer.

[0425] <Basic Example>

[0426] Hereinafter, a fourth embodiment of the light guide plate for image display according to the present invention will be described.

[0427] A light guide plate for image display according to the fourth embodiment of the present invention has a first resin substrate, a hologram layer, and a first absorption layer. It is preferable that the first absorption layer, the first resin substrate, and the hologram layer are arranged in this order in the thickness direction.

[0428] The light guide plate for image display according to the fourth embodiment of the present invention may additionally have a second resin substrate. In this case, it is preferable that the first absorption layer, the first resin substrate, the hologram layer, and the second resin substrate are laminated in this order in the thickness direction.

[0429] In the fourth embodiment of the present invention, the first resin substrate and the second resin substrate may be collectively referred to simply as "resin substrate." Also, in this embodiment, the first absorption layer and the second absorption layer may be collectively referred to simply as "absorption layer."

[0430] The light guide plate for image display according to the fourth embodiment of the present invention may additionally have a suitable transparent layer. Examples of the transparent layer include a barrier layer, an adhesive layer, a hard coat layer, or an anchor coat layer.

[0431] The light guide plate for image display of the fourth embodiment of the present invention may additionally have a glass substrate.

[0432] The light guide plate for image display described above has an incident portion for incident image light and a display image output portion for displaying an image using the image light. The hologram layer is disposed between the incident portion and the display image output portion. The hologram layer has a diffraction grating pattern formed therein for guiding image light incident from the incident portion to the display image output portion and emitting it from the display image output portion. The diffraction grating pattern in the display image output portion transmits at least a portion of external light incident from outside the light guide plate for image display. Additionally, the external light incident portion points to a side opposite to the display image output portion.

[0433] The image light incident on the above-mentioned incident portion is guided into the hologram layer and emitted to the outside from the display image emission portion. Meanwhile, as external light also passes through the resin substrate and the display image emission portion, an observer at the display image emission portion can observe both the image light and the external light within their field of view.

[0434] The light guide plate for image display according to the fourth embodiment of the present invention is preferably used in a display device using VR technology, AR technology, or MR technology. For example, the light guide plate for image display according to the fourth embodiment of the present invention may be used in devices such as a holographic optical element (HOE), represented by a combiner for a head-up display (HUD) for automobiles or a reflector for a reflective liquid crystal display device, in addition to for display purposes.

[0435] The material of the resin substrate above is not particularly limited as long as it is a transparent material.

[0436] The material used for the resin substrate above may be appropriately selected from those used in the first to third embodiments described above. The material used for the resin substrate above preferably comprises at least one resin selected from the group consisting of acrylic resin, cyclic polyolefin resin, and polycarbonate resin.

[0437] In the image display light guide plate of the fourth embodiment of the present invention, when the resin substrate is composed of two sheets of a first resin substrate and a second resin substrate, the hologram layer may be disposed between the first resin substrate and the second resin substrate.

[0438] In the image display light guide plate of the fourth embodiment of the present invention, when the image display light guide plate includes a first resin substrate and a glass substrate, the hologram layer may be disposed between the first resin substrate and the glass substrate.

[0439] The resin substrate and the hologram layer, or the glass substrate and the hologram layer, may be in contact with each other, and a suitable transparent layer may be disposed between them.

[0440] The above hologram layer is sandwiched between the first resin substrate and the second resin substrate, or between the first resin substrate and the glass substrate.

[0441] In the above hologram layer, a known resin material for forming a hologram is used, as in the case of the first to third embodiments described above. Examples of the resin material for forming a hologram include a thermosetting resin having at least one solvent-soluble cation-polymerizable ethylene oxide ring among its structural units and a hologram recording material composed of an ethylenically polymerizable monomer (Japanese Patent Publication No. Hei 8-1676, Japanese Patent Publication No. Hei 8-1677, Japanese Patent Publication No. Hei 8-1678, Japanese Patent Publication No. Hei 8-1679).

[0442] The above absorption layer has wavelength characteristics that absorb the yellow component of light transmitted through at least a portion of the light guide plate for image display.

[0443] (Absorption peak)

[0444] The absorption layer has an absorption peak in the wavelength range of 500 to 600 nm (hereinafter referred to as "wavelength range A").

[0445] Here, the "absorption peak" refers to the spectral distribution in which the minimum value is the point of minimum among the U-shaped spectral distributions in which the transmittance of the absorption layer in the visible light range (400 to 800 nm) changes from a decrease through a minimum value to an increase. It is more preferable that the U-shaped spectral distribution is formed at a single point in the visible light range.

[0446] In this specification, the wavelength that gives a minimum value (peak top) of such an "absorption peak" is defined as being in a specific wavelength range as having an "absorption peak in a specific wavelength range."

[0447] It is more preferable that the absorption peak be in the wavelength range of 550 to 585 nm (hereinafter referred to as "wavelength range B").

[0448] The full width at half maximum of the absorption peak is preferably 100 nm or less, more preferably 70 nm or less, and particularly preferably 40 nm or less.

[0449] Here, the full width at half maximum of the absorption peak refers to the wavelength width of the absorption peak where the transmittance is less than or equal to Th = (100 - Tp) / 2, where Tp (%) is the transmittance of the peak top of the absorption peak.

[0450] If the full width at half maximum is 100 nm or less, the color balance and brightness of the transmitted light can be secured well.

[0451] The transmittance at the absorption peak is preferably 80% or less, more preferably 70% or less, and particularly preferably 60% or less.

[0452] (Transmittance characteristics)

[0453] The average transmittance of the absorption layer in the wavelength range of 590 to 700 nm (hereinafter referred to as "wavelength range C") is preferably 20% or more, more preferably 50% or more, and even more preferably 70% or more.

[0454] In the wavelength range C, the average transmittance is set to 20% or more to maintain the brightness of red light.

[0455] The average transmittance of the absorption layer in the wavelength range of 470 to 550 nm (hereinafter referred to as "wavelength range D") is preferably 20% or more, more preferably 50% or more, and even more preferably 70% or more.

[0456] In the wavelength range D, the average transmittance is set to 20% or more in order to secure the color balance and brightness of the transmitted light.

[0457] The transmittance characteristics of the absorption layer are more desirable when the transmittance of ultraviolet light, which is prone to causing photodegradation, is low. For example, the transmittance of the absorption layer in a wavelength range of 380 nm or less is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

[0458] (Yellowness)

[0459] The YI value (JIS K 7373 : 2006) indicating the yellowness of the absorption layer is preferably 10 or less, more preferably 5 or less, and particularly preferably 3 or less.

[0460] (Absorbance)

[0461] The absorbance of the absorption layer at a wavelength of 580 nm is preferably 0.5 or less, more preferably 0.3 or less, and particularly preferably 0.2 or less.

[0462] (b* in the L*a*b* color system)

[0463] The b* of the absorption layer is preferably 5 or less, more preferably 3 or less, and particularly preferably 1 or less.

[0464] The composition of the absorption layer is not particularly limited as long as it has an absorption peak in wavelength range A.

[0465] For example, the absorbent layer may have a composition in which a colorant is dispersed in a transparent base resin.

[0466] The material of the base resin is not particularly limited as long as it is transparent. The refractive index of the base resin is also not particularly limited.

[0467] For example, the base resin may have a refractive index greater than or equal to the refractive index of the resin substrate, or may have a refractive index lower than the refractive index of the resin substrate.

[0468] For example, as the base resin, a resin material having a surface hardness higher than that of the resin substrate may be used.

[0469] For example, as the base resin, a resin material with low hygroscopicity may be used.

[0470] As for the colorant, it is not particularly limited as long as the wavelength characteristics described above are obtained. For example, dyes, pigments, etc., are used as colorants. It is particularly preferable to use a blueing agent as the colorant.

[0471] For example, the absorption layer may be formed by a multilayer thin film in which a high refractive index material and a low refractive index material are stacked in multiple layers.

[0472] (Bluing agent)

[0473] The bluing agent used in the absorption layer is not particularly limited, but generally, anthraquinone-based dyes are more preferable as they are readily available.

[0474] Specific examples of bluing agents include, for instance, Solvent Violet 13 [CA. No (Color Index No.) 60725], Solvent Violet 31 [CA. No. 68210], Solvent Violet 33 [CA. No. 60725], Solvent Blue 94 [CA. No. 61500], Solvent Violet 36 [CA. No. 68210], Solvent Blue 97 ["Macrolex Violet RR" manufactured by Bayer], and Solvent Blue 45 [CA. No. 61110]. These bluing agents may be used individually or in combination of two or more types. These bluing agents are blended in an appropriate amount relative to the base resin to obtain the optical properties required for the absorption layer. For example, if the base resin is polycarbonate resin, for every 100 parts by mass of polycarbonate resin, 0.1 × 10 -5 ~ 2 × 10-4 It may be mixed in a proportion of parts by mass.

[0475] Examples of other bluing agents include Dia Resin (registered trademark) Blue N (product name; manufactured by Mitsubishi Chemical Corporation), Dia Resin (registered trademark) Blue G (product name; manufactured by Mitsubishi Chemical Corporation), Macrolex (registered trademark) Blue RR (product name; manufactured by Bayer), Macrolex (registered trademark) Blue 3R (product name; manufactured by Bayer), and Polysynthlen (registered trademark) Blue RLS (product name; manufactured by Curariant).

[0476] The absorption layer is formed in a range through which at least image light and external light are transmitted. For example, the absorption layer may be positioned in a range that overlaps in the thickness direction with the display image emission portion of the hologram layer.

[0477] However, the absorption layer may be disposed in a range that covers the entire resin substrate or hologram layer when viewed in the thickness direction.

[0478] The arrangement of the absorption layer in the thickness direction of the light guide plate for image display is not particularly limited.

[0479] For example, the absorption layer may be formed at least one of a position closer to the incident surface of external light than the hologram layer and a position closer to the exit surface of image light than the hologram layer.

[0480] When the absorption layer is disposed outside the resin substrate, the absorption layer, the resin substrate, and the hologram layer may be arranged in this order in the thickness direction of the light guide plate for image display. That is, the absorption layer may be disposed outside the resin substrate in the thickness direction. For example, the absorption layer may be disposed at the outermost part in the thickness direction of the light guide plate for image display.

[0481] When an absorption layer is formed by dispersing a colorant within a resin substrate, the colorant may be uniformly dispersed within the resin substrate or may be dispersed in a biased manner in the thickness direction. If the colorant is biased in the thickness direction, it is more preferable that the colorant be biased toward the outer side of the thickness direction of the light guide plate for image display.

[0482] The barrier layer may employ the same material as the second embodiment described above, and it is preferable that it be composed of a transparent inorganic material. In addition, it is more preferable that the refractive index of the barrier layer be 1.48 or higher.

[0483] It is more preferable to use a water vapor barrier material as the material for the barrier layer. It is even more preferable that the barrier layer contains one or more materials selected from the group consisting of silicon oxide, silicon nitrate, and diamond-like carbon (DLC).

[0484] The barrier layer may be disposed on a resin film. In this case, it is more preferable that the resin film be disposed between the barrier layer and the resin substrate.

[0485] It is more preferable that the barrier layer is arranged in the order of a resin substrate, a barrier layer, and a hologram layer in the thickness direction of the light guide plate for image display. It is particularly preferable that the barrier layer is arranged on the surface of the hologram layer.

[0486] The barrier layer may be formed as two layers with the hologram layer in between. It is more preferable that the barrier layer be disposed on the surface and back surface of the hologram layer.

[0487] In the case where a glass substrate is disposed, since the glass substrate itself possesses barrier properties, the glass substrate may be disposed on the surface opposite to the surface facing the barrier layer in the hologram layer.

[0488] Hereinafter, based on the example shown in FIG. 18, a detailed configuration of an example of a light guide plate for image display according to the fourth embodiment of the present invention will be described. FIG. 18 is a schematic cross-sectional view showing an example of a light guide plate for image display according to the fourth embodiment of the present invention.

[0489] In the image display light guide plate (4005) shown in FIG. 18, a first absorption layer (4004), a first resin substrate (4001), a hologram layer (4002), and a second resin substrate (4003) are arranged in this order in the thickness direction. The image display light guide plate (4005) is an example of a case where it does not have a barrier layer.

[0490] The shape of the light guide plate (4005) for image display viewed from a flat surface is not particularly limited. For example, the light guide plate (4005) for image display may be shaped into a form that can be mounted on a display device used.

[0491] For example, the light guide plate (4005) for image display may be a rectangular plate larger than the shape mounted on the display device. In this case, the light guide plate (4005) for image display is shaped by being cut into a shape that can be mounted on the display device before being assembled on the display device.

[0492] The light guide plate (4005) for displaying images may be flat, or, if necessary, curved.

[0493] Below, an example is described in which the light guide plate (4005) for displaying images is formed as a flat plate in the shape of a rectangle when viewed from a flat plane.

[0494] The first absorption layer (4004) is disposed on the outermost portion in the thickness direction of the light guide plate (4005) for image display. The first absorption layer (4004) is disposed on the surface of the light guide plate (4005) for image display on the side of the image output.

[0495] The layer thickness of the first absorption layer (4004) is not particularly limited. For example, the layer thickness of the first absorption layer (4004) may be 0.1 to 10 μm.

[0496] In the example shown in FIG. 18, the first absorption layer (4004) is formed over the entire surface of the first resin substrate (4001) described later.

[0497] The method of forming the first absorption layer (4004) is not particularly limited. For example, the first absorption layer (4004) can be formed by applying a coating liquid made of a base resin material mixed with a colorant to a film-forming surface (the surface of the first resin substrate (4001)) and then curing the coating liquid.

[0498] As for the application method of the coating liquid, an appropriate application method can be selected depending on the viscosity of the coating liquid, etc. For example, as the application method, conventionally known coating methods such as bar coat, dip coat, reverse gravure coat, direct gravure coat, roll coat, die coat, curtain coat, etc. can be used.

[0499] As the base resin material, for example, polymerizable monomers or polymerizable oligomers that form a cured product upon irradiation with active energy rays, such as (meth)acrylate monomers having radical polymerizable unsaturated groups in their molecules or (meth)acrylate oligomers having radical polymerizable unsaturated groups in their molecules, or curable resin materials such as urethane, epoxy, or polyester may be used. As the colorant blended into the base resin material, for example, the bluing agent described above may be used.

[0500] The first resin substrate (4001) has the same shape as the external shape of the light guide plate (4005) for image display.

[0501] In the first resin substrate (4001), image light (Ld) emitted from the hologram layer (4002) and external light (Lo) passing through the second resin substrate (4003) and the hologram layer (4002) described later are transmitted.

[0502] The thickness of the first resin substrate (4001) is not particularly limited. For example, the thickness of the first resin substrate (4001) may be 0.01 to 10 mm.

[0503] The material forming the first resin substrate (4001) can be appropriately selected from the same material as the first to third embodiments described above, and there are no particular limitations as long as it is a transparent resin material. The material forming the first resin substrate (4001) may include, for example, a polyolefin-based resin such as a homopolymer or copolymer of olefins such as ethylene, propylene, or butene; an amorphous polyolefin-based resin such as a cyclic polyolefin; a polyester-based resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN); a polyamide-based resin such as nylon 6, nylon 66, nylon 12, or copolymer nylon; Examples of organic materials include ethylene-vinyl acetate copolymer partial hydrolysate (EVOH), polyimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluoropolymers, poly(meth)acrylic resins, styrene resins such as polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinyl chloride, cellulose, acetylcellulose, polyvinylidene chloride, polyphenylene sulfide, polyurethane, phenolic resin, epoxy resin, polyarylate resin, polynorbornene, styrene-isobutylene-styrene block copolymer (SIBS), allyl diglyglycol carbonate, and biodegradable resins. In addition, the first resin substrate (4001) may be formed from two or more types of materials, or may be a laminated structure in which two or more types of materials are laminated.

[0504] In terms of transparency of the first resin substrate (4001), polycarbonate or poly(meth)acrylic resin is preferred. Also, in terms of process resistance of the first resin substrate (4001), poly(meth)acrylic resin, epoxy resin, or cyclic polyolefin is preferred.

[0505] The hologram layer (4002) is laminated on the surface opposite to the surface of the first resin substrate (4001) on which the first absorption layer (4004) is formed. As described above, the composition of the hologram layer (4002) is not particularly limited. A suitable diffraction grating corresponding to the function required for an image display light guide plate (4005) is formed in the hologram layer (4002).

[0506] The second resin substrate (4003) is laminated on the surface opposite to the surface on which the first resin substrate (4001) is placed in the hologram layer (4002). The same configuration as exemplified in the description of the first resin substrate (4001) is used for the second resin substrate (4003). However, the thickness, material, etc. of the second resin substrate (4003) may be different from that of the first resin substrate (4001). In particular, since the second resin substrate (4003) is placed on the surface of the external light incident side located opposite to the display image emission side in the light guide plate (4005) for image display, a material with a higher surface hardness than that of the first resin substrate (4001) may be used.

[0507] Such a light guide plate (4005) for displaying images can be manufactured, for example, as follows.

[0508] A first resin substrate (4001) and a second resin substrate (4003) are prepared, and a coating liquid that forms a first absorbent layer (4004) is prepared.

[0509] For example, a coating solution is applied to the surface of a first resin substrate (4001). Afterward, the coating solution is cured to form a first absorption layer (4004).

[0510] For example, a photopolymer material for forming a hologram is applied to the surface opposite to where the first absorption layer (4004) is formed on the first resin substrate (4001). At this time, a transparent seal layer of the same thickness as the hologram layer (4002) may be formed on the outer periphery of the surface of the first resin substrate (4001). In this case, the photopolymer material is applied to the concave portion formed by surrounding the seal layer. The seal layer seals the outer periphery of the hologram layer (4002) after the hologram layer (4002) is formed. Afterward, the second resin substrate (4003) is placed on the photopolymer material.

[0511] However, the manufacturing sequence described above is an example. For example, the photopolymer material may be applied to the surface of the second resin substrate (4003), and the first resin substrate (4001) having the first absorption layer (4004) formed thereon may be placed on the photopolymer material.

[0512] Afterwards, a laminate consisting of a first absorption layer (4004), a first resin substrate (4001), a photopolymer material, and a second resin substrate (4003) is laminated by a pressure reducing press.

[0513] Afterwards, an interference pattern corresponding to the diffraction pattern is formed on the photopolymer material of the laminate, and a diffraction grating is formed within the photopolymer material.

[0514] In this way, a light guide plate (4005) for displaying images is manufactured.

[0515] Next, an example of a display device including a light guide plate (4005) for displaying images will be described.

[0516] FIG. 19 is a schematic cross-sectional view showing an example of a display device including a light guide plate for image display according to the fourth embodiment of the present invention.

[0517] As shown in FIG. 19, the display device (4010) additionally includes an image light projection part (4012) and an incident optical system (4011) in addition to the image display light guide plate (4005).

[0518] The image light projection unit (4012) projects image light (Li) to be displayed on an image display light guide plate (4005) according to an image signal transmitted from a controller that is omitted from the view.

[0519] The incident optical system (4011) is equipped with an optical element, such as a prism, that causes image light (Li) to be incident on an image display light guide plate (4005). The incident optical system (4011) causes image light (Li) to be incident on an incident portion (4005a) formed on the surface of the image display light guide plate (4005). For example, the incident portion (4005a) is formed on a first absorption layer (4004).

[0520] Image light (Li) incident on the incident portion (4005a) passes through the waveguide diffraction grating portion (4003a) formed on the hologram layer (4002) and is guided to the display diffraction grating portion (4002b) of the hologram layer (4002). In the display diffraction grating portion (4002b), the image light (Li) is diffracted at a position corresponding to each display pixel to form image light (Ld). The image light (Ld) passes through the hologram layer (4002), the first resin substrate (4001), and the first absorption layer (4004), becomes image light (Ld'), and is emitted to the outside of the image display light guide plate (4005). For this reason, the display diffraction grating portion (4002b) in the thickness direction and the regions of the first resin substrate (4001) and the first absorption layer (4004) facing the display diffraction grating portion (4002b) in the thickness direction constitute a display image emission portion (4005b) that displays image light (Ld). The display image emission portion (4005b) is formed at a position separated from the incident portion (4005a) in the plane direction, which is a direction orthogonal to the thickness direction.

[0521] Meanwhile, external light (Lo) is incident on the image display light guide plate (4005) via the second resin substrate (4003). The external light (Lo) passes through the second resin substrate (4003), the hologram layer (4002), the first resin substrate (4001), and the first absorption layer (4004), and is emitted to the outside of the image display light guide plate (4005) as external light (Lo').

[0522] A user of the display device (4010) can view an image based on image light (Ld') and external light (Lo'). Because of this, a user who puts the display image emitter (4005b) into their field of view sees an image in which an external scene based on external light (Lo') and an image based on image light (Ld') are combined.

[0523] The transparent material used in the light guide plate (4005) for image display undergoes photodegradation over time due to the influence of, for example, ultraviolet light. Typical photodegradation is yellowing of the material. In particular, since the hologram layer (4002) is formed by a photopolymer material, it yellows to some extent immediately after manufacturing. Because of this, the light transmitted through the first resin substrate (4001), the second resin substrate (4003), and the hologram layer (4002) has a yellowish tint.

[0524] Because yellow has high visual sensitivity, human vision is sensitive to yellowing. As a result, images with a yellowish tint have lower contrast (brightness), so the observed image becomes unclear.

[0525] However, in the fourth embodiment of the present invention, since a first absorption layer (4004) is formed in the display image emission unit (4005b), the yellow components of the image light (Ld') and the external light (Lo) are reduced, respectively. In this way, the yellow components of the image light (Ld) and the external light (Lo) that have a yellowish tint are offset by the first absorption layer (4004), thereby eliminating the effect of yellowing of the first resin substrate (4001), the second resin substrate (4003), and the hologram layer (4002).

[0526] Specifically, light is absorbed by the first absorption layer (4004), mainly focusing on light components in the wavelength range of 500 to 600 nm, thereby reducing yellowness and relatively increasing blueness. As a result, the white balance and contrast of the image are improved.

[0527] In addition, even if photodegradation of transparent materials such as the first resin substrate (4001) and the second resin substrate (4003) progresses over time due to ultraviolet light, etc. exposed during use of the display device (4010), the degree of image degradation due to yellowing is reduced compared to the case where the first absorption layer (4004) is not present.

[0528] As described above, according to the fourth embodiment of the present invention, a light guide plate for image display can be provided that can reduce the effect on the display image caused by yellowing of the transparent material.

[0529] In particular, in the fourth embodiment of the present invention, the first absorption layer (4004) is disposed on the outermost part of the light guide plate (4005) for image display. For this reason, for example, if a material with higher hardness than the first resin substrate (4001) is used as the first absorption layer (4004), scratches on the surface of the first resin substrate (4001) are prevented. For example, if the transmittance of ultraviolet light is low in the wavelength characteristics of the first absorption layer (4004), the incidence of ultraviolet light from the first resin substrate (4001) side can be suppressed, so the light degradation over time in the light guide plate (4005) for image display can be reduced.

[0530] <Example of Variation 1>

[0531] A first variation of the fourth embodiment will be described.

[0532] FIG. 20 is a schematic cross-sectional view showing an example of a light guide plate for image display of a first variation of the fourth embodiment of the present invention.

[0533] As shown in FIG. 20, the image display light guide plate (4007) of the first modified example of the fourth embodiment of the present invention additionally has a second absorption layer (4006) in addition to the image display light guide plate (4005) of the basic example of the fourth embodiment of the present invention.

[0534] Hereinafter, the differences from the basic example of the fourth embodiment of the present invention will be explained focusing on the following.

[0535] The second absorption layer (4006) is laminated on the surface opposite to the surface on which the hologram layer (4002) is disposed in the second resin substrate (4003). That is, the second absorption layer (4006) is disposed on the outermost part of the image display light guide plate (4007), just like the first absorption layer (4004). In the image display light guide plate (4007), a laminate composed of the first resin substrate (4001), the hologram layer (4002), and the second resin substrate (4003) is fitted into the first absorption layer (4004) and the second absorption layer (4006).

[0536] For the second absorption layer (4006), the same configuration as exemplified in the description of the first absorption layer (4004) is used.

[0537] However, the thickness and material of the second absorption layer (4006) may be different from that of the first absorption layer (4004). For example, since the second absorption layer (4006) is placed on the surface opposite to the display image emission side of the light guide plate (4007) for image display, a material with a higher surface hardness than that of the second resin substrate (4003) or the first absorption layer (4004) may be used.

[0538] In the first variant of the fourth embodiment of the present invention, since the first absorption layer (4004) and the second absorption layer (4006) are disposed on the outermost part of the light guide plate (4007) for image display, it is more preferable that the transmittance of ultraviolet light is low in the wavelength characteristics of the first absorption layer (4004) and the second absorption layer (4006).

[0539] The light guide plate (4007) for image display is manufactured in the same manner as the light guide plate (4005) for image display in the basic example of the fourth embodiment of the present invention, except that a second absorption layer (4006) is formed on the second resin substrate (4003). The method of forming the second absorption layer (4006) is the same as the method of forming the first absorption layer (4004).

[0540] The light guide plate (4007) for image display according to the first modified example of the fourth embodiment of the present invention is configured in the same way as the light guide plate (4005) for image display, except that it has a second absorption layer (4006). Because of this, the image light (Ld) is configured in the same way as the light guide plate (4005) for image display, and the yellow component is reduced by passing through the first absorption layer (4004) (image light (Ld')).

[0541] In this regard, external light (Lo) passes through the second absorption layer (4006) and then enters the second resin substrate (4003). Because of this, when external light (Lo) passes through the second absorption layer (4006), the yellow component is reduced. When external light (Lo) passes through the second resin substrate (4003), the hologram layer (4002), and the first resin substrate (4001), the yellow component increases according to the degree of yellowing in each case, and then the yellow component is reduced by the first absorption layer (4004).

[0542] Since the second resin substrate (4003) is positioned on the incident side of external light (Lo) during use, photodegradation caused by external light (Lo) is likely to progress. As a result, over time, there is a concern that the yellowing of the second resin substrate (4003) is more likely to progress than the yellowing of the first resin substrate (4001). If the yellowing of the second resin substrate (4003) progresses, the external light (Lo) that passes through the second resin substrate (4003) is likely to have a stronger yellow component compared to the image light (Ld) that does not pass through the second resin substrate (4003).

[0543] However, in the first variant of the fourth embodiment of the present invention, since the second absorption layer (4006) is provided, it becomes possible to offset the increase in yellowness caused by yellowing of the second resin substrate (4003) by the second absorption layer (4006). Because of this, the yellowness of the external light (Lo'') emitted from the first absorption layer (4004) is reduced compared to the external light (Lo') emitted from the light guide plate (4005) for image display. As a result, the balance of yellowness in the image light (Ld') and the external light (Lo'') can be improved.

[0544] In particular, if the transmittance of ultraviolet light is low in the wavelength characteristics of the second absorption layer (4006), the photodegradation of the second resin substrate (4003) caused by external light (Lo) can be reduced.

[0545] As described above, according to the first variation of the fourth embodiment of the present invention, a light guide plate for image display can be provided that can reduce the effect on the display image caused by yellowing of the transparent material.

[0546] <Example 2 of the Variation>

[0547] A second variation of the fourth embodiment will be described.

[0548] FIG. 21 is a schematic cross-sectional view showing an example of a light guide plate for image display of a second variation of the fourth embodiment of the present invention.

[0549] As shown in FIG. 21, the image display light guide plate (4020) of the second variant of the fourth embodiment of the present invention additionally comprises a first barrier layer (4008) and a second barrier layer (4009) in addition to the image display light guide plate (4007) of the first variant. In the second variant of the fourth embodiment of the present invention, the first barrier layer (4008) and the second barrier layer (4009) may be collectively referred to simply as "barrier layer." Also, in the second variant of the fourth embodiment of the present invention, the first resin substrate (4001) and the second resin substrate (4003) may be collectively referred to simply as "resin substrate." In addition, in the second variation of the fourth embodiment of the present invention, the first absorption layer (4004) and the second absorption layer may be collectively referred to simply as the "absorption layer."

[0550] Hereinafter, the differences from the first variation of the fourth embodiment of the present invention will be explained focusing on the following.

[0551] The first barrier layer (4008) is disposed between the first resin substrate (4001) and the hologram layer (4002) and is in close contact with the respective surfaces of the first resin substrate (4001) and the hologram layer (4002). The first barrier layer (4008) prevents gas penetrating from the outside of the image display light guide plate (4020) and the first resin substrate (4001) from penetrating into the hologram layer (4002).

[0552] The material of the first barrier layer (4008) is not particularly limited as long as it can block the gas that causes the deterioration of the hologram layer (4002). It is preferable that the first barrier layer (4008) includes a transparent inorganic material, and it is more preferable that it includes at least one inorganic material selected from the group consisting of silicon oxide, silicon nitrate oxide, diamond-like carbon (DLC), aluminum oxide, and glass, similar to the barrier layer in the second embodiment described above.

[0553] Additionally, the barrier layer may be disposed on a resin film. In this case, it is more preferable that the resin film be disposed between the barrier layer and the resin substrate.

[0554] The first barrier layer (4008) is preferably composed of a material with excellent water vapor barrier properties (low water vapor permeability), for example, as low as possible oxygen permeability and water vapor permeability. In particular, it is more preferable that the first barrier layer (4008) be composed of a material with excellent water vapor barrier properties (low water vapor permeability).

[0555] For example, the oxygen permeability of the first barrier layer (4008) may be 1 cm³ / m²·day or less.

[0556] For example, the water vapor permeability of the first barrier layer (4008) may be 1 g / m²·day or less. It is more preferable that the water vapor permeability of the first barrier layer (4008) be 0.5 g / m²·day or less.

[0557] The inorganic material used for the first barrier layer (4008) may have a higher refractive index than the first resin substrate (4001). For example, the refractive index of the first barrier layer (4008) may be 1.48 to 3.00. If the first barrier layer (4008) has a high refractive index, light passing through the first barrier layer (4008) and the first resin substrate (4001) is incident from the optically dense first barrier layer (4008) to the optically sparse first resin substrate (4001), so the angle of emission of light from the first barrier layer (4008) toward the first resin substrate (4001) increases according to the difference in refractive index between the first barrier layer (4008) and the first resin substrate (4001). By doing so, the FOV (Field Of View) in the light guide plate (4020) for image display can be expanded.

[0558] The material of the first barrier layer (4008) is as described above, but may be an oxide such as zinc oxide, antimony oxide, indium oxide, cerium oxide, calcium oxide, cadmium oxide, silver oxide, gold oxide, chromium oxide, silicon oxide, cobalt oxide, zirconium oxide, tin oxide, titanium oxide, iron oxide, copper oxide, nickel oxide, platinum oxide, palladium oxide, bismuth oxide, magnesium oxide, manganese oxide, molybdenum oxide, vanadium oxide, or barium oxide.

[0559] When the first barrier layer (4008) is made of silicon oxide, the thickness of the layer may be 10 to 300 nm. If the thickness of the layer is less than 10 nm, there is a risk that moisture resistance will be insufficient. If the thickness of the layer exceeds 300 nm, cracks may easily occur in the thin film of the silicon oxide, and there is a risk that it may peel off from the film surface.

[0560] A particularly desirable layer thickness is 20 to 200 nm.

[0561] The method of forming the first barrier layer (4008) using the silicon oxide is not particularly limited. For example, the first barrier layer (4008) can be formed by any conventionally known method such as vacuum deposition, sputtering, ion plating, or plasma CVD. When forming the first barrier layer (4008) using the silicon oxide, surface treatment may be performed to improve the adhesion between the film surface and the silicon oxide, such as performing corona discharge treatment or low-temperature plasma treatment on the film surface, applying a silane coupling agent to the film surface, or applying a mixture of saturated polyester and isocyanate.

[0562] For example, when forming a silicon oxide thin film by vacuum deposition, silicon, silicon monoxide, silicon dioxide, or a mixture thereof is used as the evaporation material, and 1.0 × 10 -3 ~ 1.0 × 10 -5 Under a vacuum of Torr, heat and evaporate using an electron beam, resistance heating, or high-frequency heating method.

[0563] In addition, a reaction deposition method performed while supplying oxygen gas can also be employed.

[0564] In the silicon oxide forming the first barrier layer (4008), calcium, magnesium, or their oxides may be incorporated as impurities if the amount is 10 mass% or less.

[0565] In the case where the first barrier layer (4008) is made of silicon nitrate oxide, the same configuration as the first barrier layer (4008) having silicon oxide as the main component is used, except that the silicon oxide is replaced with the silicon nitrate oxide.

[0566] DLC is an amorphous carbon material that generally consists of a ternary structure comprising a diamond-like structure, a graphite-like structure, and a polyethylene-type polymer structure containing hydrogen atoms in its structure. In the production of the above DLC, when a hydrocarbon such as ethylene, acetylene, or benzene is used as a carbon source, it typically has a ternary structure containing hydrogen.

[0567] The above DLC has excellent hardness, lubricity, wear resistance, chemical stability, heat resistance, and surface smoothness. Because the above DLC forms the dense polymer structure described above, it also has excellent gas barrier and water vapor barrier properties.

[0568] The method of forming the first barrier layer (4008) by the above DLC is not particularly limited. As a coating method for the above DLC, a known suitable coating method may be used, such as a plasma CVD method, or a physical vapor deposition method such as an ion plating method or an ion beam sputtering method.

[0569] When the first barrier layer (4008) is made of aluminum oxide, the first barrier layer (4008) may be formed, for example, only with Al2O3, or may be formed by mixing two or more types selected from the group consisting of Al, AlO, and Al2O3. The atomic ratio of Al to O in the aluminum oxide layer varies depending on the manufacturing conditions of the aluminum oxide layer. The aluminum oxide layer that can be used as the first barrier layer (4008) may contain trace amounts of other components (at most 3% of the total components) within a range where the barrier performance is not impaired.

[0570] The layer thickness of the aluminum oxide layer may be set according to the requirements for barrier performance. For example, the layer thickness of the aluminum oxide layer may be 5 to 800 nm.

[0571] The method of forming the first barrier layer (4008) by aluminum oxide is not particularly limited. For example, as a method of forming the first barrier layer (4008), PVD methods (physical vapor deposition), such as vacuum deposition, sputtering, or ion plating, or CVD methods (chemical vapor deposition) may be used.

[0572] For example, in vacuum deposition, materials such as Al and Al2O3 are used as deposition source materials, and resistance heating, high-frequency induction heating, or electron beam heating may be used as the heating method for the deposition source. In vacuum deposition, oxygen, nitrogen, or water vapor may be introduced as a reactive gas, or reactive deposition using means such as ozone addition or ion assist may be used. Additionally, bias may be applied to the deposited surface, or the temperature of the deposited surface may be raised or lowered. The same applies to other film deposition methods other than vacuum deposition, such as sputtering, PVD, and CVD.

[0573] When the first barrier layer (4008) is made of glass, the material of the first barrier layer (4008) may be, for example, borosilicate glass, alkali-free glass, low-alkali glass, soda-lime glass, or sol-gel glass, or glass that has undergone heat treatment or surface treatment. As for the material of the first barrier layer (4008), alkali-free glass is particularly preferred from the viewpoint of avoiding discoloration by impurities.

[0574] When the first barrier layer (4008) is made of glass, the thickness of the layer may be 10 to 200 μm. If the layer thickness is 10 μm or more, there is a tendency for excellent gas barrier properties along with mechanical strength. The layer thickness is preferably 10 μm or more, and more preferably 30 μm or more. In addition, if the layer thickness is 200 μm or less, there is a tendency for excellent optical properties as a light guide plate, such as light transmittance. The layer thickness is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 75 μm or less, and particularly preferably 50 μm or less.

[0575] The method of forming the first barrier layer (4008) using glass is not particularly limited. As a method of forming the first barrier layer (4008) using glass, for example, the slot-down draw method, the fusion method, or the float method may be adopted. Also, the glass used may be commercially available glass used as is, or commercially available glass may be polished to a desired thickness and used. Examples of the commercially available glass include Corning's "EAGLE2000", Asahi Glass's "AN100", Nippon Electric Glass's "OA10G", and Schott's "D263".

[0576] The second barrier layer (4009) is laminated on the surface of the hologram layer (4002) opposite to the surface of the hologram layer (4002) on which the first barrier layer (4008) is formed.

[0577] The composition of the second barrier layer (4009) is the same as that exemplified in the description of the first barrier layer (4008). However, the material, thickness, etc. of the second barrier layer (4009) may be different from that of the first barrier layer (4008).

[0578] Such a light guide plate (4020) for displaying images can be manufactured, for example, as follows.

[0579] A first resin substrate (4001) and a second resin substrate (4003) are prepared, and a first barrier layer (4008) and a second barrier layer (4009) are formed on the surfaces of the first resin substrate (4001) and the second resin substrate (4003), respectively. As for the manufacturing method of the first barrier layer (4008) and the second barrier layer (4009), an appropriate manufacturing method is selected according to the material of the first barrier layer (4008) and the second barrier layer (4009).

[0580] For example, a photopolymer material for forming a hologram is applied to the surface of the first barrier layer (4008) in the first resin substrate (4001) on which the first barrier layer (4008) is formed. At this time, a transparent seal layer having the same thickness as the hologram layer (4002) may be formed on the outer periphery of the first barrier layer (4008). In this case, the photopolymer material is applied to the concave portion formed by surrounding the seal layer. The seal layer seals the outer periphery of the hologram layer (4002) after the hologram layer (4002) is formed.

[0581] Afterwards, a second resin substrate (4003) having a second barrier layer (4009) formed thereon is placed on a photopolymer material with the second barrier layer (4009) facing toward the photopolymer material.

[0582] However, the manufacturing sequence described above is merely an example. For instance, after a photopolymer material is applied to a second resin substrate (4003) on which a second barrier layer (4009) is formed, a first resin substrate (4001) on which a first barrier layer (4008) is formed may be placed on the photopolymer material.

[0583] Afterwards, a laminate comprising a first absorption layer (4004), a first resin substrate (4001), a first barrier layer (4008), a photopolymer material, a second barrier layer (4009), a second resin substrate (4003), and a second absorption layer (4006) is laminated by a pressure reducing press.

[0584] Afterwards, an interference pattern corresponding to the diffraction pattern is formed on the photopolymer material of the laminate, and a diffraction grating is formed within the photopolymer material.

[0585] In this way, a light guide plate (4020) for displaying images is manufactured.

[0586] The light guide plate (4020) for image display is configured in the same way as the light guide plate (4007) for image display of the first variant, except that the first barrier layer (4008) and the second barrier layer (4009) are added.

[0587] The first barrier layer (4008) and the second barrier layer (4009) are made of a transparent inorganic material such as DLC or silicon oxide, and since they are easy to absorb blue light in the wavelength range of 400 nm to 480 nm, the transmittance of the blue component is reduced, and the transmitted light has a yellowish tint.

[0588] In this way, the first barrier layer (4008) is likely to increase the yellowness of the external light (Lo) and image light (Ld), and the second barrier layer (4009) is likely to increase the yellowness of the external light (Lo). However, in the second variant of the fourth embodiment of the present invention, as in the first variant, the first absorption layer (4004) and the second absorption layer (4006) are provided, so by appropriately adjusting the wavelength characteristics of the first absorption layer (4004) and the second absorption layer (4006), the increase in yellowness caused by the first barrier layer (4008) and the second barrier layer (4009) can be offset. That is, the yellowness of the external light (Lo''') and image light (Ld'') emitted from the first absorption layer (4004) can be reduced. In addition, by doing the same as the first modified example, the balance of the yellowness of the external light (Lo''') and the image light (Ld'') can be improved.

[0589] As explained above, according to the second variation of the fourth embodiment of the present invention, a light guide plate for image display can be provided that can reduce the effect on the display image caused by yellowing of the transparent material.

[0590] In addition, according to the light guide plate (4020) for image display, since it is equipped with a first barrier layer (4008) and a second barrier layer (4009), the deterioration of the hologram layer (4002) over time can be suppressed.

[0591] The gas barrier properties of the first resin substrate (4001) and the second resin substrate (4003) are significantly lower than those of glass, although the degree varies depending on the type of resin material. For this reason, the first resin substrate (4001) and the second resin substrate (4003) have higher hygroscopicity and water vapor permeability than glass.

[0592] As a result, external gas of the light guide plate (4005) for image display passes through the first resin substrate (4001) and the second resin substrate (4003) to some extent, or accumulates inside. In particular, moisture is prone to accumulating in the first resin substrate (4001) and the second resin substrate (4003).

[0593] However, gas and moisture that have penetrated into the first resin substrate (4001) and the second resin substrate (4003) from the outside are shielded by the first barrier layer (4008) and the second barrier layer (4009) even if they diffuse within the light guide plate (4020) for image display. As a result, the penetration of gas and water vapor into the hologram layer (4002) is suppressed.

[0594] For example, by suppressing the penetration of moisture into the hologram layer (4002), the deterioration of the hologram layer (4002) is prevented.

[0595] In addition, since the image display light guide plate (4020) has the layer configuration described above, the hologram layer (4002) is not in contact with the first resin substrate (4001) and the second resin substrate (4003). Thus, even if the image display light guide plate (4020) is placed in a high-temperature environment, the hologram layer (4002) is prevented from eroding the first resin substrate (4001) and the second resin substrate (4003).

[0596] In particular, if the refractive index of the first barrier layer (4008) and the second barrier layer (4009) is higher than that of the first resin substrate (4001) and the second resin substrate (4003), as described above, the angle of emission of light directed from the first barrier layer (4008) toward the first resin substrate (4001) increases. Likewise, the angle of emission of light incident from the second resin substrate (4003) toward the second barrier layer (4009) decreases. Because of this, light incident from the outside of the second resin substrate (4003) side and passing through the image display light guide plate (4005) is incident in a wider angle range compared to the case where the second barrier layer (4009) is not present, and is emitted in a wider angle range compared to the case where the first barrier layer (4008) is not present. As a result, the field of view of the external light becomes wider, and the FOV of the display side is also expanded.

[0597] Regarding the image light from the hologram layer (4002), as described above, as a result of the light emission angle from the first barrier layer (4008) toward the first resin substrate (4001) increasing, the FOV of the display screen is expanded compared to the case where the first barrier layer (4008) is not present.

[0598] In particular, in the second variant of the fourth embodiment of the present invention, the first barrier layer (4008) and the second barrier layer (4009) are laminated on the hologram layer (4002), so that the diffusion position of the external light and image light and the diffraction position of the hologram layer (4002) constituting the display screen are brought closer together. Therefore, compared to the case where the first barrier layer (4008) and the second barrier layer (4009) are formed at a position away from the hologram layer (4002), a clearer image can be observed from a wide angle.

[0599] Here, the method for measuring the luminance value and FOV in the light guide plate (4020) for image display is briefly explained.

[0600] The luminance value of the light guide plate (4020) for image display is measured using the same display device and luminance meter as the display device (4010) in the basic example of the fourth embodiment of the present invention described above, except that the light guide plate (4005) for image display is replaced with the light guide plate (4020) for image display.

[0601] In measuring the luminance value, the display device is positioned such that the center of the display image emission part of the light guide plate (4020) for image display is positioned opposite the luminance meter on the measurement optical axis of the luminance meter. The distance between the display image emission part and the luminance meter is a distance corresponding to the position of the user's eye when the display device is mounted. For example, if the display device is a head-mounted display, the distance is 15 mm.

[0602] The above luminance value is the luminance measured by the luminance meter when a white image with maximum luminance is displayed on the display device.

[0603] In measuring the FOV of the light guide plate (4020) for image display, the brightness is measured by tilting the measurement optical axis of the brightness meter relative to the display image emission unit while the white image with maximum brightness is displayed on the display device. For example, the brightness meter is supported by the goniometer stage, etc., so as to be oscillating at an appropriate angle from a position perpendicular to the light guide plate (4020) for image display.

[0604] The FOV is determined as an angle range in which a luminance greater than or equal to the threshold value is obtained, with the luminance corresponding to the point at which the white image becomes invisible being set as the threshold value. When a luminance greater than or equal to the threshold value is obtained in the range from -θ1 to +θ2, the FOV is θ1 + θ2. Here, the angle is set to 0° as the normal angle of the light guide plate (4020) for image display.

[0605] <Third Variation Example>

[0606] A third variation of the fourth embodiment will be described.

[0607] FIG. 22 is a schematic cross-sectional view showing an example of a light guide plate for image display of a third variation of the fourth embodiment of the present invention.

[0608] As shown in FIG. 22, the light guide plate (4024) for image display of the third modified example has the first absorption layer (4004) of the light guide plate (4005) for image display of the fourth embodiment of the present invention removed, and instead of the first resin substrate (4001) and the second resin substrate (4003), it has a first resin substrate (absorption layer) (4021) and a second resin substrate (absorption layer) (4023).

[0609] Hereinafter, the differences from the basic example of the fourth embodiment of the present invention will be explained focusing on the following.

[0610] The first resin substrate (absorbent layer) (4021) has a base resin identical to the first resin substrate (4001) and a colorant dispersed in the base resin.

[0611] The colorant contained in the first resin substrate (absorption layer) (4021) is the same colorant as that of the first absorption layer (4004) in the basic example of the fourth embodiment of the present invention. The amount of colorant is set so that the first resin substrate (absorption layer) (4021) has the same light absorption properties as that of the first absorption layer (4004) in the basic example of the fourth embodiment of the present invention.

[0612] The second resin substrate (absorbent layer) (4023) is configured in the same way as the first resin substrate (absorbent layer) (4021).

[0613] The light guide plate (4024) for image display is manufactured in the same manner as the light guide plate (4005) in the basic example of the fourth embodiment of the present invention, except that the first resin substrate (absorption layer) (4021) and the second resin substrate (absorption layer) (4023) prepared in the substrate preparation process are molded using a material in which a colorant is mixed with each base resin, and the absorption layer formation process is not performed.

[0614] The light guide plate (4024) for displaying images is an example in which the absorption layer is formed by the first resin substrate (absorption layer) (4021) and the second resin substrate (absorption layer) (4023).

[0615] According to the light guide plate (4024) for image display, the first resin substrate (absorption layer) (4021) and the second resin substrate (absorption layer) (4023) are absorption layers, so the yellowness in external light and image light can be reduced in the same way as in the first modified example.

[0616] As explained above, according to the third variation of the fourth embodiment of the present invention, a light guide plate for image display can be provided that can reduce the effect on the display image caused by yellowing of the transparent material.

[0617] In addition, the basic example and each modified example of the fourth embodiment of the present invention described above were described as examples in which the absorption layer is placed at the outermost part of the light guide plate for image display. However, the absorption layer can reduce the yellowness of the light emitted from the light guide plate for image display regardless of where it is placed as long as it is in the light path of the external light (Lo) and the image light (Ld).

[0618] In the basic example and each modified example of the fourth embodiment of the present invention above, the case in which the absorbent layer is in contact with a resin substrate was described. However, the absorbent layer may be laminated onto a transparent resin film. In this case, for example, the absorbent layer can be formed on a resin film and then fixed to a placement surface by interposing an adhesive, etc., so the formation of the absorbent layer becomes easier.

[0619] In the above second modified example, it was described as an example where a barrier layer is disposed on the front surface of the hologram layer. However, for the purpose of shielding moisture, etc. penetrating through the resin substrate and preventing contact between the hologram layer and the resin substrate, the barrier layer only needs to be disposed between the resin substrate and the hologram layer.

[0620] However, in this case, if the transparent layer sandwiched between the barrier layer and the hologram layer has high hygroscopicity, there is a risk of moisture penetrating through the sides of the transparent layer. For this reason, it is more desirable for the transparent layer between the barrier layer and the hologram layer to be formed from a material with low hygroscopicity. If the transparent layer between the barrier layer and the hologram layer is hygroscopic, it is more desirable to reduce the thickness of the transparent layer. In this case, since the exposed surface area of ​​the sides that serve as penetration points for moisture is reduced, the amount of absorbed moisture can be reduced.

[0621] In the above second modified example, the case was described as one in which the barrier layer is in contact with the hologram layer and the resin substrate. However, the barrier layer may be laminated onto a transparent resin film. In this case, for example, the barrier layer can be formed on the resin film and then fixed to the resin substrate by interposing an adhesive, etc., so the formation of the barrier layer becomes easier.

[0622] Examples

[0623] The present invention will be explained in more detail below through examples. However, the present invention is not limited to the examples described below, and various modifications are possible as long as they do not alter the essence of the invention.

[0624] [Examples and Comparative Examples of the First Embodiment (Examples 1 to 3, Comparative Examples 1 to 3)]

[0625] Hereinafter, examples and comparative examples of the first embodiment will be described.

[0626] Table 1 below shows the composition and evaluation results of the resin substrates used in Examples 1 to 3 and Comparative Examples 1 to 3.

[0627] [Table 1]

[0628]

[0629] Mitsubishi Chemical … Mitsubishi Chemical Corporation

[0630] Kurare … Kurare Co., Ltd.

[0631] Sumitomo Chemical … Sumitomo Chemical Corporation

[0632] Asahi Kasei … Asahi Kasei Co., Ltd.

[0633] Acrylite, Comoglass, Sumipex, and Teraglass are each company's registered trademarks in Japan.

[0634] <Example 1>

[0635] Example 1 is an example corresponding to the light guide plate (1004) for image display of the basic example of the first embodiment.

[0636] As shown in Table 1, acrylic resin (PMMA) is used as the material for the first resin substrate (1001) and the second resin substrate (1003) ("resin substrate" in Table 1). The plate thickness of both the first resin substrate (1001) and the second resin substrate (1003) is 1 mm.

[0637] The hologram layer (1002) is common to each example and each comparative example. As the material for the hologram layer (1002), 100 parts by mass of bisphenol-based epoxy resin jER1007 (degree of polymerization n = 10.8, epoxy equivalent: 1750 to 2200, product name manufactured by Mitsubishi Chemical), 50 parts by mass of triethylene glycol diacrylate, 5 parts by mass of 4,4'-bis(t-butylphenyl)iodonium hexafluorophosphate, and 0.5 parts by mass of 3,3'-carbonylbis(7-diethylamino)coumarin are mixed and dissolved in 100 parts by mass of 2-butanone and used as a photosensitive material for holograms. The thickness of the hologram layer (1002) is 5 μm. The size of the hologram layer (1002) when viewed from a flat plane is 50 mm × 50 mm.

[0638] (Substrate manufacturing process)

[0639] The first resin substrate (1001) and the second resin substrate (1003) of Example 1 are manufactured as follows.

[0640] 100 parts of MMA (methyl methacrylate) are introduced into a reactor (polymerization vessel) equipped with a cooling tube, a thermometer, and a stirrer, and stirred. After bubbling with nitrogen gas, heating is started. When the internal temperature reaches 80°C, 0.05 parts of 2,2'-azobis-(2,4-dimethylvaleronitrile), a radical polymerization initiator, are added. The internal temperature is further heated to 100°C and maintained for 10 minutes. Afterward, the reactor is cooled to room temperature to obtain a syrup. The polymerization rate of the syrup is approximately 20 mass%.

[0641] Afterwards, 0.2 parts by mass of t-hexyl peroxypivalate and 0.01 parts by mass of sodium dioctyl sulfosuccinate are added to the syrup and completely dissolved at room temperature to form a polymerizable raw material.

[0642] After removing dissolved air from the polymerizable raw material under reduced pressure, the raw material is injected into a continuous polymerization apparatus equipped with a pair of mirror-finished stainless steel endless belts.

[0643] Here, the continuous polymerization apparatus used in this embodiment is described.

[0644] FIG. 8 is a schematic cross-sectional view showing an example of a manufacturing apparatus for a resin substrate of Example 1.

[0645] As shown in FIG. 8, a continuous polymerization device (1100) has a pair of endless belts (1101, 1102) arranged at the top and bottom. Each endless belt (1101, 1102) is tensioned by a main pulley (1103, 1104, 1105, 1106) and driven to run at the same speed. A plurality of carrier rolls (1107) are arranged at each inner circumference of the endless belt (1101, 1102). Each carrier roll (1107) faces each other with the endless belt (1101, 1102) facing each other in between. Each carrier roll (1107) horizontally supports the running endless belt (1101, 1102) and applies a linear load at least once to the belt surface in a direction perpendicular to the belt running direction (from left to right in the illustration) and also perpendicular to the belt surface.

[0646] The line load may be 0.001 to 10.0 kg / cm. It is more preferable for the line load to be 0.01 kg / cm or higher.

[0647] The more times the linear load is applied, the more desirable it is. As the number of times the linear load is applied increases, the flatness of the resulting resin substrate improves. For example, it is more desirable that the number of times the linear load is applied be 10 or more.

[0648] A raw material injection device (1114) formed in a continuous polymerization device (1100) supplies polymerizable raw materials between endless belts (1101, 1102). The ends of both sides of the endless belts (1101, 1102) are sealed by two elastic gaskets (1112).

[0649] The polymerizable raw material is heated by a hot water spray (1109) in the first polymerization zone (1108) and polymerized in conjunction with the operation of the endless belt (1101, 1102). Additionally, the polymerizable raw material is heated by a hot air heater in the second polymerization zone (1110) formed downstream of the belt's direction of travel to complete the polymerization. The polymerizable raw material is cooled in the downstream cooling zone (1111) formed further downstream of the belt's direction of travel and then discharged as a plate-shaped polymer (1113).

[0650] The specific manufacturing conditions of the polymerizable raw material of Example 1 described above are as follows.

[0651] In a continuous polymerization apparatus (1100), the gap between the belt surfaces of the endless belt (1101, 1102) at the part where polymerizable raw material is supplied from the raw material injection device (1114) is adjusted to 1.6 mm, and the gap is continuously adjusted so that the final plate-shaped polymer becomes 1 mm at the part where polymerization is completed and the plate-shaped polymer is ejected.

[0652] The linear load by each carrier roll (1107) in the first polymerization zone (1108) is 0.3 kg / cm. The temperature of the hot water spray (1109) is 80°C. The hot water is continuously sprayed onto the inner surface of the belt of the endless belt (1101, 1102) while the polymerizable raw material stays in the first polymerization zone (1108). The residence time of the polymerizable raw material in the first polymerization zone (1108) is 40 minutes.

[0653] In the second polymerization zone (1110), hot air at a temperature of 120°C is sprayed from a hot air heater onto the inner surface of the belt, and polymerization is completed under conditions where the residence time of the polymerizable raw material is 10 minutes.

[0654] In this way, a plate-shaped polymer (1113) with a plate thickness of 1 mm is obtained.

[0655] Evaluation sample 1A of the first resin substrate (1001) and the second resin substrate (1003) is formed by cutting a plate-shaped polymer (1113) into a square shape of 200 mm × 200 mm. Evaluation sample 1A is used for measuring the MC value, measuring the arithmetic mean roughness Ra, and measuring the thermal shrinkage rate, which will be described later.

[0656] Evaluation sample 1B is formed by cutting a plate-shaped polymer (1113) into a square shape of 60 mm × 60 mm. Evaluation sample 1B forms an image display light guide plate (1004) and is used for image evaluation of the image display light guide plate (1004) (described later).

[0657] Next, the manufacturing process of the image display light guide plate (1004) in Example 1 will be described. The image display light guide plate (1004) is manufactured by carrying out the substrate preparation process and the light guide plate manufacturing process described below in this order.

[0658] (Substrate preparation process)

[0659] In the substrate preparation process, cleaning and drying are performed on an evaluation sample 1B of an acrylic resin material with dimensions of 60 mm × 60 mm × 1 mm thickness obtained from the substrate manufacturing process.

[0660] Evaluation sample 1B is ultrasonically cleaned for 5 minutes while immersed in a 5% aqueous surfactant solution of the neutral cleaning agent Semi Clean (registered trademark) M-LO (product name; manufactured by Yokohama Yuji Industry Co., Ltd.).

[0661] Afterwards, evaluation sample 1B is ultrasonically cleaned for 5 minutes while immersed in ultrapure water. In addition, evaluation sample 1B is rinsed with ultrapure water, and after air drying, evaluation sample 1B is dried in an oven at 100°C under a nitrogen atmosphere. Afterwards, the air-dried evaluation sample 1B is UV ozone cleaned in a UV ozone cleaner for 1 minute.

[0662] With this, the substrate preparation process is completed.

[0663] (Light guide plate manufacturing process)

[0664] In the light guide plate manufacturing process, a light guide plate (1004) for image display is manufactured using two evaluation samples 1B.

[0665] A seal layer with a width of 5 mm and a thickness of 5 μm is applied to the periphery of one evaluation sample 1B.

[0666] The seal layer is made of a transparent material and is not particularly limited as long as it is a material capable of bonding evaluation samples 1B to each other, but in Example 1, an epoxy resin or a silicone resin is used.

[0667] Thus, an acrylic substrate with a seal layer step formed by an opening surrounded by a seal layer having a size of 50 mm × 50 mm is prepared.

[0668] Afterwards, an acrylic photosensitive material is applied to the acrylic substrate by spin coating as a photopolymer material for holograms. The acrylic photosensitive material is applied to a thickness of 5 μm after drying.

[0669] Afterwards, evaluation sample 1B of the other party is laminated onto a seal layer and an acrylic photosensitive material, and press-laminated under reduced pressure. The conditions for press lamination are an absolute pressure of 5 kPa, a temperature of 70°C, and a press pressure of 0.04 MPa.

[0670] Afterwards, a diffraction grating is recorded on the photopolymer material of the press-bonded laminate. In this process, the temperature of the laminate is maintained at 20°C. The diffraction grating forms an interference fringe by irradiating the laminate with two laser beams and adjusting the respective irradiation angles and intensities to form the required diffraction pattern. In this way, the diffraction grating is recorded on the photopolymer material.

[0671] As a specific diffraction grating, a color display diffraction grating is formed that diffracts each of the light in the red, green, and blue wavelength regions incident as image light incident on the incident part, and emits it from the display image output part at a position corresponding to the pixel of the image light.

[0672] Afterward, while maintaining the laminate at 20°C, ultraviolet light (wavelength 365 nm, irradiance 80 W / cm²) is irradiated onto the entire surface of the laminate from the direction of one side for 30 seconds. A high-pressure mercury lamp is used as the light source for the ultraviolet light.

[0673] Thus, the acrylic photosensitive material is cured, and the light guide plate (1004) for image display of Example 1 is formed.

[0674] <Example 2>

[0675] Example 2 is an example corresponding to the light guide plate (1014) for image display of the first variation of the first embodiment.

[0676] As shown in Table 1, Example 2 is identical to Example 1 except that a hard coat is applied to both sides in the thickness direction of the first resin substrate (1001).

[0677] Evaluation sample 1A of Example 2 is formed by applying the hard coat described below to both sides in the thickness direction of evaluation sample 1A of Example 1.

[0678] Evaluation sample 1B of Example 2 is manufactured in the same manner as Example 1, except that evaluation sample 1A of Example 2 is used instead of evaluation sample 1A of Example 1. For this reason, unlike the embodiment shown in FIG. 7 of the first variant example, the first hard coat layer (1011A) and the second hard coat layer (1011B) are laminated on the second resin substrate (1003).

[0679] Below, the substrate manufacturing process of Example 2 will be explained focusing on the differences from Example 1.

[0680] (Substrate manufacturing process)

[0681] The abbreviations used below are explained.

[0682] "C6DA" means 1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: Viscote #230).

[0683] "U6HA" refers to a urethane compound obtained by reacting 3 moles of 3-acryloyloxy-2-hydroxypropyl methacrylate with 1 mole of triisocyanate obtained by trimerizing hexamethylene diisocyanate (manufactured by Shinnakamura Chemical Industry Co., Ltd., trade name; NK Oligo U-6HA).

[0684] "M305" means a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Toa Synthetic Co., Ltd., trade name; Aronics (registered trademark) M-305).

[0685] 60 parts by mass of C6DA, 30 parts by mass of U6HA, 10 parts by mass of M305, 0.5 parts by mass of bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide, and 5 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone are mixed to prepare a hard coat solution.

[0686] This hard coat liquid is applied to the endless belt (1101, 1102) of a continuous polymerization device (1100) to a thickness of 20 μm. Afterwards, ultraviolet light is irradiated using a high-pressure mercury lamp with an irradiance of 120 W / cm², and the hard coat liquid is cured to form a hard coat on the endless belt.

[0687] By polymerizing a resin substrate in the same manner as in Example 1, except that a hard coat is formed on the endless belt (1101, 1102), a plate-shaped polymer (1113) with a thickness of 1 mm and a hard coat laminated on its surface is obtained.

[0688] Evaluation samples 1A and 1B of Example 2 are formed from the plate-shaped polymer (1113) of Example 2 in the same manner as in Example 1.

[0689] <Example 3>

[0690] Example 3 is an example corresponding to the light guide plate (1004) for image display of the basic example of the first embodiment.

[0691] As shown in Table 1, Example 3 is identical to Example 1 except that a cutting and polishing acrylic plate is used as the resin substrate. The resin substrate in Example 3 is Acrylite (registered trademark) L, a continuous cast acrylic plate with a thickness of 2 mm, processed to a thickness of 1 mm by cutting and polishing.

[0692] <Comparative Examples 1–3>

[0693] As shown in Table 1, Comparative Examples 1 to 3 are identical to Example 1 except that a ready-made extruded acrylic sheet is used as the resin substrate. For this reason, the substrate manufacturing process of each comparative example is carried out by extrusion molding, which varies by manufacturer.

[0694] In Comparative Example 1, the resin substrate used is Comoglass (registered trademark) P (product name; manufactured by Kuraray Co., Ltd.), an extruded acrylic sheet with a thickness of 3 mm.

[0695] In Comparative Example 2, the resin substrate used is Sumipex (registered trademark) E (product name; manufactured by Sumitomo Chemical Co., Ltd.), an extruded acrylic sheet with a thickness of 3 mm.

[0696] In Comparative Example 3, the resin substrate used is Deraglass (registered trademark) A (product name; manufactured by Asahi Kasei Co., Ltd.), an extruded acrylic sheet with a thickness of 3 mm.

[0697] In each comparative example, evaluation samples 1A and 1B are prepared having the same shape as Example 1 except that the thickness is 3 mm.

[0698] The light guide plate manufacturing process in each comparative example is carried out in the same manner as Example 1, except that evaluation sample 1B of each comparative example is used.

[0699] <Evaluation Method>

[0700] Next, the evaluation methods for Examples 1 to 3 and Comparative Examples 1 to 3 will be described. As for the evaluation, the MC value, Ra, thermal shrinkage rate, and the clarity of the displayed image will be evaluated.

[0701] (MC value)

[0702] The evaluation of the MC value is carried out by the evaluation method described in the “Specific details for carrying out the invention” of this specification. As the measurement sample (S), evaluation sample 1A of each example and each comparative example is used.

[0703] As for the specific evaluation conditions, distances d1 and d2 are each 1 m, and elevation angle θ A It becomes 20°.

[0704] Since Comparative Examples 1 to 3 have gear marks, evaluation sample 1A of each comparative example is placed in the evaluation device (1200) with the gear mark facing in the Y direction.

[0705] In contrast, gear marks are not visible in Examples 1 to 3. However, in order to ensure consistent directionality during manufacturing, evaluation sample 1A of each example is positioned so that the direction perpendicular to the driving direction in the continuous polymerization device (1100) faces the Y direction.

[0706] The measurement range of the brightness distribution is a rectangular area with a longitudinal width of 180 mm and a transverse width of 80 mm, where the Y direction in the arrangement of evaluation sample 1A in the evaluation device (1200) is the transverse direction (the direction in which line segments AD and BC are extended), and the direction perpendicular to the transverse direction on evaluation sample 1A is the longitudinal direction (the direction in which line segments AB and DC are extended).

[0707] The measurement range is formed at 41 points on the measurement sample (S) at intervals of 2 mm in the transverse direction. In each measurement range, the measurement line is selected to divide the measurement range into 40 equal parts in the transverse direction.

[0708] Table 1 lists the maximum MC values ​​obtained from the brightness distribution of each measurement line in each measurement range.

[0709] (Ra)

[0710] For the evaluation of Ra, the arithmetic mean roughness Ra of the surface of each evaluation sample 1A is measured.

[0711] As the measuring device, the white interferometric surface shape measuring instrument Zygo NewView (registered trademark) 6300 (trade name; manufactured by Zygo Corporation) is used. The objective lens magnification is 2.5x. The observation range is a square area of ​​2.8 mm × 2.1 mm.

[0712] (Thermal shrinkage rate)

[0713] The evaluation of the heat shrinkage rate is carried out by measuring the change in dimensions (shrinkage) in accordance with Annex A of JIS K 6718:2015, “Measurement of change in dimensions (shrinkage) upon heating.”

[0714] (Clarity of the displayed image)

[0715] The light guide plates for image display of Examples 1 to 3 and Comparative Examples 1 to 3 are mounted on an image display device. The image display device has an optical system that directs image light for displaying to an incident part of the light guide plate (1004), a driving power source, and a circuit system that supplies image information for obtaining image light.

[0716] White images and character display images are used as input images for evaluation.

[0717] The evaluation is performed by visually determining the appearance of the white image and the character display image. As for the character image, "ABCDE" within a size of 10 mm × 100 mm is displayed.

[0718] If no rainbow colors are visible in a white image and the characters are clearly visible in a text display image, it is judged as good (indicated as “A” in Table 1).

[0719] If a slight rainbow color is visible in a white image but the text is clearly visible in a text display image, it is judged as possible (fair, indicated as “B” in Table 1).

[0720] If rainbow colors are visible in at least part of the white image, and the outline of the characters is faint in the character display image, it is judged as impossible (no good, indicated as “C” in Table 1).

[0721] <Evaluation Results>

[0722] As shown in Table 1, the MC values ​​of Examples 1 to 3 are 0.074, 0.103, and 0.060, respectively, all of which are less than 0.120. In contrast, the MC values ​​of Comparative Examples 1 to 3 are 0.126, 0.183, and 0.148, respectively, all of which exceed 0.120.

[0723] Examples 1 to 3 do not show gear marks, and correspondingly, the MC value is less than 0.120. This is thought to be because the resin substrate of each example is manufactured by a continuous casting method or by cutting and polishing. In the continuous casting method, the surface shape of, for example, an endless belt (1101, 1102) is transferred to the surface of the raw material of the resin substrate of each example. Because of this, the flatness of the surface of the resin substrate becomes equivalent to the flatness of the endless belt (1101, 1102). In cutting and polishing, the flatness of the surface of the resin substrate can be made very high.

[0724] In contrast, gear marks are observed in Comparative Examples 1 to 3, so it is thought that the MC value is increased due to the gear marks. The reason why gear marks are formed in Comparative Examples 1 to 3 is thought to be, for example, that the driving non-uniformity of the rolls in contact with the extrusion material in the extruder is large.

[0725] The arithmetic mean roughness Ra of Examples 1 to 3 is 4.9 nm, 4.7 nm, and 2.6 nm, respectively, all of which are less than 10 nm. In contrast, the Ra of Comparative Examples 1 to 3 is 5.5 nm, 2.9 nm, and 2.3 nm, respectively, all of which are less than 10 nm. Therefore, regarding smoothness represented by Ra, Examples 1 to 3 do not differ significantly from Comparative Examples 1 to 3.

[0726] The thermal shrinkage rates of Examples 1 to 3 are all less than 3%. In contrast, the thermal shrinkage rates of Comparative Examples 1 to 3 are all 3% or more. This is thought to be because distortion accumulated in the resin substrates as the resin substrates of Comparative Examples 1 to 3 were manufactured by extrusion molding.

[0727] The clarity of the displayed images of Examples 1 to 3 is all judged to be "Good (A)". In contrast, the clarity of the displayed images of Comparative Examples 1 to 3 is all judged to be "Impossible (C)". This is thought to be because, in Comparative Examples 1 to 3, the MC value is larger than that of each example, so the diffraction direction of the image light is disrupted.

[0728] For example, the resin substrates of Comparative Examples 2 and 3 have a smaller Ra than Examples 1 and 2, so they are superior to Examples 1 and 2 in terms of smoothness, but it is thought that the contribution of flatness (i.e., MC value) to the clarity of the displayed image is large. At least, it is thought that if Ra is 10 nm or less, there is no superior difference in clarity depending on the size of Ra.

[0729] [Example of the 2nd embodiment]

[0730] Hereinafter, an example of the second embodiment will be described.

[0731] Tables 2A to 2C below show the resin substrates and barrier layer compositions used in Examples 4 to 7 and 12 to 21, as well as the evaluation results.

[0732] [Table 2A]

[0733]

[0734] [Table 2B]

[0735]

[0736] In the column for “auxiliary layer” in Table 2B, “EVOH-based” indicates “ethylene vinyl alcohol-based” and “F-based” indicates “fluorine-based”.

[0737] [Table 2C]

[0738]

[0739] <Example 4>

[0740] Example 4 is an example corresponding to the light guide plate (2006) for image display of the basic example of the second embodiment.

[0741] As shown in Table 2A, acrylic resin (PMMA) is used as the material for the first resin substrate (2001) and the second resin substrate (2005) ("resin substrate" in Table 2A).

[0742] The shapes of the first resin substrate (2001) and the second resin substrate (2005) are both square plates of 60 mm × 60 mm × 1 mm.

[0743] The first barrier layer (2002) and the second barrier layer (2004) of this embodiment ("barrier layer" in Table 2B) are DLC films with a layer thickness of 40 nm.

[0744] The hologram layer (2003) is common to Examples 4 to 7 and 12 to 21. As the material for the hologram layer (2003), 100 parts by mass of bisphenol-based epoxy resin jER (registered trademark) 1007 (degree of polymerization n = 10.8, epoxy equivalent: 1750 to 2200, manufactured by Mitsubishi Chemical), 50 parts by mass of triethylene glycol diacrylate, 5 parts by mass of 4,4'-bis(t-butylphenyl)iodonium hexafluorophosphate, and 0.5 parts by mass of 3,3'-carbonylbis(7-diethylamino)coumarin are mixed and dissolved in 100 parts by mass of 2-butanone and used as a photosensitive material for holograms. The thickness of the hologram layer (2003) is 5 μm. The size of the holographic layer (2003) when viewed from a flat plane is 50 mm × 50 mm.

[0745] Next, the manufacturing process of the image display light guide plate (2006) in Example 4 will be described. The image display light guide plate (2006) is manufactured by carrying out the substrate preparation process, barrier layer formation process, and light guide plate manufacturing process described below in this order.

[0746] (Substrate preparation process)

[0747] In the substrate preparation process, the first resin substrate (2001) and the second resin substrate (2005) are cleaned and dried. Hereinafter, if there is no need to distinguish between the first resin substrate (2001) and the second resin substrate (2005), the symbol is omitted and simply referred to as a resin substrate.

[0748] The resin substrate is ultrasonically cleaned for 5 minutes while immersed in a 5% aqueous surfactant solution of the neutral cleaning agent Semiclean (registered trademark) M-LO (product name; manufactured by Yokohama Yuji Industry Co., Ltd.).

[0749] Afterwards, the resin substrate is ultrasonically cleaned for 5 minutes while immersed in ultrapure water. Additionally, the resin substrate is rinsed with ultrapure water, and after air drying, the resin substrate is dried in an oven at 100°C under a nitrogen atmosphere. Afterwards, the air-dried evaluation sample 2B is UV ozone cleaned in a UV ozone cleaner for 1 minute.

[0750] With this, the substrate preparation process is completed.

[0751] (Barrier layer formation process)

[0752] In the barrier layer formation process, a DLC film is formed on the surface of the resin substrate.

[0753] A resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a space volume of 350 cm³, a high-frequency power supply (13.56 MHz), and an internal electrode (φ10 mm) (which also serves as a gas inlet tube, with a tip pore of φ1 mm), and vacuum evacuation is performed. After the pressure of the plasma chemical vapor deposition apparatus reaches 15 Pa, a 2:1 mixed gas of high-purity acetylene and tetramethylsilane is introduced at a flow rate of 45 sccm, and a DLC film with a thickness of 40 nm is deposited under conditions of a plasma generation setting power of 100 W and a deposition time of 0.8 seconds.

[0754] With this, the barrier layer formation process is completed.

[0755] Hereinafter, a resin substrate with a barrier layer formed thereon is referred to as an intermediate laminate.

[0756] (Light guide plate manufacturing process)

[0757] In the light guide plate manufacturing process, a light guide plate (2006) for image display is manufactured using two intermediate laminates.

[0758] A seal layer with a width of 5 mm and a thickness of 5 μm is applied to the periphery of the barrier layer of one intermediate laminate.

[0759] The seal layer is made of a transparent material and is not particularly limited as long as it is a material capable of bonding the barrier layers of the intermediate laminate together, but in Example 3, the optical adhesive Hardlock (registered trademark) OP-1045K (product name; manufactured by Denki Chemical Industry Co., Ltd.) is used.

[0760] Thus, an intermediate laminate forming a seal layer step is prepared, in which an opening surrounded by a seal layer has a size of 50 mm × 50 mm.

[0761] Afterwards, the above-described photosensitive material is applied onto this intermediate laminate by spin coating as a photopolymer material for holograms. The photosensitive material is applied such that its thickness after drying is 5 μm.

[0762] Afterwards, the other intermediate laminate is laminated onto the seal layer and the photosensitive material such that the barrier layer faces the barrier layer of the intermediate laminate on which the seal layer is formed, and press-laminated under reduced pressure. The conditions for press lamination are an absolute pressure of 5 kPa, a temperature of 70°C, and a press pressure of 0.04 MPa.

[0763] Afterwards, a diffraction grating is recorded on the photosensitive material of the press-laminated laminate. In this process, the temperature of the laminate is maintained at 20°C. The diffraction grating forms an interference pattern by irradiating the laminate with two laser beams and adjusting the respective irradiation angles and intensities to form the required diffraction pattern. In this way, the diffraction grating is recorded on the photosensitive material.

[0764] As a specific diffraction grating, a color display diffraction grating is formed that diffracts each of the light in the red, green, and blue wavelength regions incident as image light incident on the incident part, and emits it from the display part at a position corresponding to the pixel of the image light.

[0765] Afterward, while maintaining the laminate at 20°C, ultraviolet light (wavelength 365 nm, irradiance 80 W / cm²) is irradiated onto the entire surface of the laminate from the direction of one side for 30 seconds. A high-pressure mercury lamp is used as the light source for the ultraviolet light.

[0766] Thus, the seal layer is cured, and the light guide plate (2006) for image display of Example 3 is formed.

[0767] <Example 5>

[0768] Example 5 has the same configuration as Example 4, except that each DLC film is formed of silicon oxide with a thickness of 10 nm.

[0769] Below, the substrate manufacturing process of Example 5 will be explained focusing on the differences from Example 4.

[0770] The image display light guide plate (2006) of Example 5 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0771] (Barrier layer formation process)

[0772] In the barrier layer formation process of this embodiment, a silicon oxide thin film layer is formed on the surface of a resin substrate.

[0773] After the resin substrate is placed in the vacuum deposition apparatus, vacuum deposition of silicon oxide is performed. The vacuum level reached in the chamber of the vacuum deposition apparatus is 1.0 × 10⁻⁶. -4 The pressure becomes Torr. Under this vacuum, silicon monoxide with a purity of 99.9% is heated and evaporated by a high-frequency induction heating method, and a silicon oxide thin film with a thickness of 50 nm is deposited on the surface of a resin substrate. In this way, an intermediate laminate with a silicon oxide thin film layer deposited is obtained.

[0774] With this, the barrier layer formation process is completed.

[0775] The light guide plate manufacturing process of this embodiment is identical to the light guide plate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer formation process described above is used, so the description is omitted.

[0776] <Examples 6, 7>

[0777] As shown in Table 2A, Examples 6 and 7 are identical to Example 5 except that the arrangement of the barrier layer is different.

[0778] FIG. 12 is a schematic cross-sectional view showing a light guide plate for image display according to Example 6. FIG. 13 is a schematic cross-sectional view showing a light guide plate for image display according to Example 7.

[0779] Below, the differences from Example 5 will be explained in detail.

[0780] As shown in FIG. 12, the image display light guide plate (2101) of Example 6 has a first barrier layer (2002), a first resin substrate (2001), a hologram layer (2003), a second resin substrate (2005), and a second barrier layer (2004) laminated in this order.

[0781] For the first barrier layer (2002) and the second barrier layer (2004), a silicon oxide thin film layer with a thickness of 50 nm, the same as in Example 5, is used.

[0782] To manufacture a light guide plate (2101) for image display, an intermediate laminate is formed in the same manner as in Example 5. Then, a seal layer is formed on a resin substrate of one intermediate laminate, a photosensitive material is applied, and then the other intermediate laminate is laminated so that the resin substrates face each other. After that, the light guide plate (2101) for image display is manufactured by performing a pressure press and forming a diffraction grating in the same manner as in Example 5.

[0783] As shown in FIG. 13, the image display light guide plate (2102) of Example 7 is identical to Example 6 except that a third barrier layer (2032) is formed covering the entire side surface (outer surface in a direction orthogonal to the thickness direction) of the image display light guide plate (2101) of Example 6.

[0784] The third barrier layer (2032) is composed of a silicon oxide thin film layer identical to the first barrier layer (2002) of Example 6.

[0785] The light guide plate (2102) for image display is manufactured by forming a silicon oxide thin film layer on its side after manufacturing the light guide plate (2101) for image display.

[0786] <Example 12>

[0787] Example 12 has the same configuration as Example 4, except that each DLC film is formed of alumina with a thickness of 40 nm.

[0788] Below, the substrate manufacturing process of Example 12 will be explained focusing on the differences from Example 4.

[0789] The image display light guide plate (2006) of Example 12 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the light guide plate manufacturing process of Example 4 in this order.

[0790] (Barrier layer formation process)

[0791] In the barrier layer formation process of this embodiment, an alumina film is formed on the surface of the resin substrate.

[0792] In an electron beam deposition apparatus, a suitable amount of alpha alumina particles with a purity of 99.999% and a particle size of 2 mm are placed as a resin substrate and a deposition source, and vacuum evacuation is performed. The distance from the deposition source to the shutter is about 8 cm, and the distance from the deposition source to the surface of the resin substrate is about 35 cm.

[0793] The pressure of the electron beam deposition device is 3 × 10 -3 After reaching Pa, the electron beam filament current is increased to approximately 35 mA, the shutter is opened, and an alumina film is deposited. When the temperature of the wall surface inside the apparatus reaches 50°C, the shutter is closed and the electron beam filament current is stopped. After cooling to 30°C or lower, the electron beam filament current is increased to approximately 35 mA to heat the deposition source, the shutter is opened, and an alumina film is deposited. This process is repeated to deposit an alumina film with a thickness of 40 nm.

[0794] The light guide plate manufacturing process of this embodiment is identical to the light guide plate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer formation process described above is used, so the description is omitted.

[0795] <Example 13>

[0796] Example 13 has the same configuration as Example 4, except that each DLC film is formed of silicon oxide with a thickness of 70 nm.

[0797] Below, the substrate manufacturing process of Example 13 will be explained focusing on the differences from Example 4.

[0798] The image display light guide plate (2006) of Example 13 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0799] (Barrier layer formation process)

[0800] In the barrier layer formation process of this embodiment, silicon oxide is formed on the surface of a resin substrate. A resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a high-frequency power supply (13.56 MHz), and vacuum evacuation is performed. After the pressure of the plasma chemical vapor deposition apparatus reaches 1 Pa, tetraethoxysilane (TEOS) gas generated by bubbling with helium gas is introduced at a flow rate of 6 sccm and oxygen gas at a flow rate of 95 sccm, and a silicon oxide film with a thickness of 70 nm is formed under conditions of a plasma generation setting power of 250 W.

[0801] With this, the barrier layer formation process is completed.

[0802] The light guide plate manufacturing process of this embodiment is identical to the light guide plate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer formation process described above is used, so the description is omitted.

[0803] <Example 14>

[0804] Example 14 has the same configuration as Example 4, except that the silicon oxide film is formed of silicon oxide with a thickness of 140 nm.

[0805] Below, the substrate manufacturing process of Example 14 will be explained focusing on the differences from Example 4.

[0806] The image display light guide plate (2006) of Example 14 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0807] (Barrier layer formation process)

[0808] In the barrier layer formation process of this embodiment, silicon oxide is formed on the surface of a resin substrate. A resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a high-frequency power supply (13.56 MHz), and vacuum evacuation is performed. After the pressure of the plasma chemical vapor deposition apparatus reaches 1 Pa, TEOS gas generated by bubbling with helium gas is introduced at a flow rate of 6 sccm and oxygen gas at a flow rate of 95 sccm, and a silicon oxide film with a thickness of 140 nm is formed under conditions of a plasma generation setting power of 250 W.

[0809] With this, the barrier layer formation process is completed.

[0810] The light guide plate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer formation process described above is used, so the description is omitted.

[0811] <Example 15>

[0812] Example 15 has the same configuration as Example 4, except that the silicon oxide film is formed of silicon oxide with a thickness of 170 nm.

[0813] Below, the substrate manufacturing process of Example 15 will be explained focusing on the differences from Example 4.

[0814] The image display light guide plate (2006) of Example 15 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0815] (Barrier layer formation process)

[0816] In the barrier layer formation process of this embodiment, silicon oxide is formed on the surface of a resin substrate. A resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a high-frequency power supply (13.56 MHz), and vacuum evacuation is performed. After the pressure of the plasma chemical vapor deposition apparatus reaches 1 Pa, TEOS gas generated by bubbling with helium gas is introduced at a flow rate of 6 sccm and oxygen gas at a flow rate of 95 sccm, and a silicon oxide film with a thickness of 170 nm is formed under conditions of a plasma generation setting power of 250 W.

[0817] With this, the barrier layer formation process is completed.

[0818] The light guide plate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer formation process described above is used, so the description is omitted.

[0819] <Example 16>

[0820] Example 16 has the same configuration as Example 14, except that the barrier layer has an auxiliary layer.

[0821] Below, the substrate manufacturing process of Example 16 will be explained focusing on the differences from Example 14.

[0822] The image display light guide plate (2006) of Example 16 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0823] (Barrier layer formation process)

[0824] In the barrier layer formation process of this embodiment, an auxiliary layer is formed on the surface of an inorganic material layer prepared in the same manner as in Example 14. N-phenyl-3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd. KBM-573) is added to an aqueous solution of an ethylene-vinyl alcohol copolymer so that the solid content concentration is 10 wt% relative to the total solid content in the protective coat, and auxiliary coat agent 1 is prepared. Auxiliary coat agent 1 is applied and dried on the surface of the inorganic material layer to form an auxiliary layer with a thickness of 0.5 μm.

[0825] With this, the barrier layer formation process is completed.

[0826] The light guide plate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 4, except that a barrier layer having a multilayer structure formed in the barrier layer forming process described above is used, so the description is omitted.

[0827] <Example 17>

[0828] Example 17 has the same configuration as Example 14, except that the barrier layer has a fluorine-based waterproof and moisture-proof coating layer as an auxiliary layer.

[0829] Below, the substrate manufacturing process of Example 17 will be explained focusing on the differences from Example 14.

[0830] The image display light guide plate (2006) of Example 17 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0831] (Barrier layer formation process)

[0832] In the protective layer formation process of this embodiment, a fluorine-based waterproof and moisture-proof coating layer is formed on the surface of the barrier layer manufactured in the same way as in Example 14.

[0833] With this, the barrier layer formation process is completed.

[0834] The substrate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 4, except that a barrier layer having a multilayer structure formed in the barrier layer formation process described above is used, so the description is omitted.

[0835] <Example 18>

[0836] Example 18 has the same configuration as Example 14, except that an anchor coat layer is disposed between the barrier layer and the resin substrate.

[0837] Below, the substrate manufacturing process of Example 18 will be explained focusing on the differences from Example 14.

[0838] The image display light guide plate (2006) of Example 18 is manufactured by carrying out the same substrate preparation process as in Example 14, the anchor coat layer formation process and barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0839] (Anchor coat layer formation process)

[0840] In the anchor coat layer formation process of the present embodiment, an anchor coat layer is formed on the surface of a resin substrate. An anchor coat agent was prepared by mixing a saturated polyester (Viron 300 manufactured by Toyo Spinning Co., Ltd.) and an isocyanate compound (Colonate L manufactured by Toso Co., Ltd.) in a mass ratio of 1:1. The anchor coat agent was applied to the corona-treated surface of the resin substrate and dried to form an anchor coat layer with a thickness of 100 nm.

[0841] With this, the anchor coat layer process is completed.

[0842] (Barrier layer formation process)

[0843] A barrier layer is formed on the anchor coat layer in the same manner as in Example 14.

[0844] The light guide plate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 4, except that the intermediate laminate formed in the anchor coat layer forming process and the barrier layer forming process described above is used, so the description is omitted.

[0845] <Example 19>

[0846] Example 19 has the same configuration as Example 16, except that an anchor coat layer is disposed between the barrier layer and the resin substrate.

[0847] Below, the substrate manufacturing process of Example 19 will be explained focusing on the differences from Example 16.

[0848] The light guide plate (2006) for image display of Example 19 is manufactured by carrying out the same substrate preparation process as in Example 4, the anchor coat layer formation process, the inorganic material layer formation process and the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0849] (Anchor coat layer formation process)

[0850] An anchor coat layer is formed on the surface of the resin substrate in the same manner as in Example 18.

[0851] (Inorganic material layer formation process)

[0852] An inorganic material layer is prepared on the above anchor coat layer in the same manner as in Example 14.

[0853] (Barrier layer formation process)

[0854] An auxiliary layer is prepared on the surface of the above inorganic material layer in the same manner as in Example 16, and a barrier layer is formed.

[0855] The light guide plate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 4, except that an intermediate laminate formed in the anchor coat layer forming process, inorganic material layer forming process, and barrier layer forming process described above is used, so the description is omitted.

[0856] <Example 20>

[0857] Example 20 has the same configuration as Example 4, except that each silicon oxide film is formed from silicon oxide with a thickness of 100 nm formed by a sputtering method.

[0858] Below, the substrate manufacturing process of Example 20 will be explained focusing on the differences from Example 4.

[0859] The image display light guide plate (2006) of Example 20 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described later, and the same light guide plate manufacturing process as in Example 4 in this order.

[0860] (Barrier layer formation process)

[0861] In the barrier layer formation process of this embodiment, a silicon oxide film is formed on the surface of the resin substrate. By sputtering at a vacuum pressure of 4.0 × 10 -5 Based on a vacuum pressure of Torr, a silicon oxide film with a thickness of 100 nm is formed.

[0862] The light guide plate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer formation process described above is used, so the description is omitted.

[0863] <Example 21>

[0864] Example 21 has the same configuration as Example 20, except that an anchor coat layer is disposed between the barrier layer and the resin substrate.

[0865] Below, the substrate manufacturing process of Example 21 will be explained focusing on the differences from Example 20.

[0866] The light guide plate (2006) for image display of Example 21 is manufactured by carrying out the same substrate preparation process as Example 20, the same anchor coat layer formation process as Example 18, the barrier layer formation process described later, and the same light guide plate manufacturing process as Example 20 in this order.

[0867] (Barrier layer formation process)

[0868] A barrier layer is formed on the anchor coat layer in the same manner as in Example 20.

[0869] The light guide plate manufacturing process of this embodiment is identical to the substrate manufacturing process of Example 20, except that the intermediate laminate formed in the barrier layer formation process described above is used, so the description is omitted.

[0870] <Evaluation Method>

[0871] Next, the evaluation method for each embodiment is described. The evaluation includes measuring the luminance value, evaluating the FOV, and evaluating the clarity of the displayed image.

[0872] (Luminance value)

[0873] Three types of samples for measuring luminance values ​​are prepared: a sample subjected to a humidification test ("after humidification" in Table 2C), a sample subjected to a heating test ("after heating" in Table 2C), and a sample not subjected to either a humidification test or a heating test ("initial" in Table 2C).

[0874] For humidification and heating tests, the small environmental tester SH-241 (product name; manufactured by Espect Co., Ltd.) is used.

[0875] The test conditions for the humidification test are 60 ℃, 90 %RH, and 500 hours.

[0876] The test conditions for the heating test are 85 ℃ and 500 hours.

[0877] The luminance value of the measurement sample is determined based on the measurement method described above in the embodiment.

[0878] Each measurement sample is assembled into the display device described above.

[0879] For the luminance meter (2014), the luminance meter BM-8 (product name; manufactured by Topcon Co., Ltd.) is used. The measurement angle is 1°. The distance d from the display surface (2003a) is 15 mm.

[0880] If the luminance value is 3500 nit or higher, it is judged as very good (indicated as “S” in Table 2C).

[0881] If the luminance value is 3000 nit or higher and less than 3500 nit, it is judged as good (indicated as “A” in Table 2C).

[0882] If the luminance value is 1000 nit or more and less than 3000 nit, it is determined to be possible (fair, indicated as “B” in Table 2C).

[0883] If the luminance value is less than 1000 nit, it is judged as impossible (no good, indicated as “C” in Table 2C).

[0884] (FOV)

[0885] The measurement of FOV is performed using a display device assembled from a sample that is not subjected to a humidification test or a heating test among the samples for measuring luminance values.

[0886] The measurement of FOV is carried out based on the measurement method described above in the embodiment.

[0887] For the luminance meter (2014), the luminance meter BM-8 (product name; manufactured by Topcon Co., Ltd.) is used. The measurement angle is 1°. The distance d from the display surface (2003a) is 15 mm.

[0888] If the FOV is 45° or more, it is judged as very good (indicated as “S” in Table 2C).

[0889] If the FOV is 35° or more and less than 45°, it is judged as good (good, indicated as “A” in Table 2C).

[0890] If the FOV is 24° or more and less than 35°, it is determined to be possible (fair, indicated as “B” in Table 2C).

[0891] If the FOV is less than 24°, it is judged as impossible (no good, indicated as “C” in Table 2C).

[0892] (Clarity)

[0893] The clarity of the displayed image is measured using a display device used for FOV measurement.

[0894] White images and character display images are used as input images for evaluation.

[0895] The evaluation is performed by visually determining the appearance of the white image and the character display image. As for the character image, "ABCDE" is displayed within 10 mm × 100 mm.

[0896] If no rainbow colors are visible in a white image and the characters are clearly visible in a character display image, it is judged as good (indicated as “A” in Table 2C).

[0897] If a slight rainbow color is visible in a white image but the characters are clearly visible in a character display image, it is judged as possible (fair, indicated as “B” in Table 2C).

[0898] If rainbow colors are visible in at least part of the white image, and the outline of the characters is faint in the character display image, it is judged as impossible (no good, indicated as “C” in Table 2C).

[0899] <Evaluation Results>

[0900] As shown in Table 2C, the luminance values ​​of Examples 4, 5 and Examples 12 to 21 are all evaluated as “S” or “A” regardless of whether a humidification test or a heating test is performed.

[0901] This reason is thought to be that, in these embodiments, the penetration of moisture into the hologram layer by the barrier layer is prevented and the erosion of the resin substrate by the hologram layer is suppressed, resulting in good diffraction performance of the hologram layer and no disruption of the optical path in the resin substrate.

[0902] In addition, in these embodiments, since the hologram layer is not in contact with the resin substrate, the material of the hologram layer does not erode the resin substrate even when heated.

[0903] In contrast, the luminance values ​​of Examples 5 and 6 are inferior to those of Examples 4, 5 and Examples 12 to 21 in the measurement samples taken after either the humidification test or the heating test, but when the humidification test and the heating test are not performed, they are evaluated as "B" and are at a practical level.

[0904] As shown in Table 2C, the FOVs of Examples 4, 5 and Examples 12 to 21 are evaluated as “S” and “A”, respectively.

[0905] In contrast, the FOV of Examples 6 and 7 was evaluated as "B" and was at a practical level.

[0906] This reason is thought to be the same as the reason for the difference in the luminance value evaluation described above. That is, in Examples 4, 5 and Examples 12 to 21, as a result of preventing moisture penetration into the hologram layer and erosion into the resin substrate to a very high level by the barrier layer, no decrease in FOV is observed.

[0907] It is thought that the FOV of Example 4 is better than the FOV of Example 5 due to the difference in the material of the barrier layer. It is thought that the FOV becomes larger and better because the DLC film has a higher refractive index than the silicon oxide thin film layer.

[0908] In addition, the clarity of the display images of Examples 4, 5 and Examples 12 to 21 ("clarity" in Table 2C) was all judged as "A," which is a better result than that of Examples 6 and 7.

[0909] This reason is thought to be the same as the reason for the difference in the brightness value evaluation described above. That is, in Examples 4, 5 and Examples 12 to 21, as a result of preventing moisture penetration into the hologram layer and erosion into the resin substrate to a very high level by the barrier layer, a clear image is observed.

[0910] [Example of the 3rd embodiment]

[0911] Hereinafter, an example of the third embodiment will be described.

[0912] <Example 8>

[0913] (Preparation of the first substrate and the second substrate)

[0914] Two acrylic resin plates (manufactured by Mitsubishi Chemical Co., Ltd.) processed to a thickness of 60 mm × 60 mm × 1 mm are immersed in a 5% aqueous surfactant solution of Semi Clean M-LO (manufactured by Yokohama Yuji Industrial Co., Ltd.) and ultrasonic cleaning is performed for 5 minutes. Afterward, ultrasonic cleaning is performed for 5 minutes while immersed in ultrapure water. Additionally, rinsing with ultrapure water is performed, and after air drying, the plates are dried in an oven at 100°C under a nitrogen atmosphere. Subsequently, the air-dried substrates are UV ozone cleaned in a UV ozone cleaner for 1 minute to become the first substrate and the second substrate.

[0915] (Formation of the holographic layer)

[0916] The hologram layer is common to each example. As the material for the hologram layer, 100 parts by mass of bisphenol-based epoxy resin (degree of polymerization n = 10.8, epoxy equivalent: 1750 to 2200, Mitsubishi Chemical Corporation product name jER1007), 50 parts by mass of triethylene glycol diacrylate, 5 parts by mass of 4,4'-bis(t-butylphenyl)iodonium hexafluorophosphate, and 0.5 parts by mass of 3,3'-carbonylbis(7-diethylamino)coumarin are mixed and dissolved in 100 parts by mass of 2-butanone and used as a photosensitive material for holograms.

[0917] A seal layer with a width of 5 mm and a thickness of 5 μm is applied to the periphery of the second substrate. The photosensitive material, which becomes a hologram layer, is applied by spin coating to a 50 mm × 50 mm opening surrounded by the seal layer so that its thickness becomes 5 μm after drying. After drying the photosensitive material, the first substrate is laminated and press-laminated under reduced pressure (absolute pressure 5 kPa, temperature 70°C, press pressure 0.04 MPa).

[0918] While maintaining the first substrate and the second substrate containing the above photosensitive material at 20°C, two laser lights are irradiated. By adjusting the irradiation angle and intensity of each laser light, interference patterns are formed by the interference, and a desired diffraction grating is recorded on the photosensitive material to form a hologram layer.

[0919] (Preparation of hard coat film)

[0920] As a film substrate, prepare a polyethylene terephthalate biaxially stretched film manufactured by Mitsubishi Chemical Co., Ltd. (product name "Dia Foil T612 Type", thickness: 50 μm).

[0921] A curable composition for forming a hard coat layer is prepared using an organic-inorganic hybrid ultraviolet curable resin composition (UVHC7800G manufactured by MOMENTIVE, containing 30 to 40 mass% of inorganic silica having reactive functional groups). The refractive index of the cured resin layer formed by curing this composition is 1.54.

[0922] A curable composition is applied to the second surface of the film substrate using a bar coater to a film thickness of 3 μm after drying, and then dried by heating at 90°C for 1 minute. After that, a hard coat layer is formed by using a high-pressure mercury lamp (80 W / cm²) and irradiating ultraviolet light with an integrated light intensity of 400 mJ / cm².

[0923] Next, a release layer forming solution having the following composition is applied onto the hard coat layer and dried to form a release layer. The thickness of the obtained release layer is 500 nm.

[0924] · Release agent long-chain alkyl group-containing alkyd resin ("Tespain" 303 manufactured by Hitachi Chemical Co., Ltd.) 10 parts by mass (converted to solid content)

[0925] · Acid catalyst p-toluenesulfonic acid (Hitachi Chemical Co., Ltd. "Dryer" 900) 0.12 parts by mass (converted to solid content)

[0926] · Solvent: Toluene 45 parts by mass

[0927] Next, an adhesive-forming composition is applied to the first surface of the film substrate such that the film thickness after drying is 0.5 μm, and dried to form an adhesive layer.

[0928] A composition for forming an adhesive is prepared as follows.

[0929] For 1 kg of an adhesive solution made of an acrylic copolymer (SK Dyne 1882 manufactured by Soken Chemical Co., Ltd., with a solid content of about 17%), 1.85 g of an isocyanate-based crosslinking agent (L-45 manufactured by Soken Chemical Co., Ltd.) and 0.5 g of an epoxy-based crosslinking agent (E-5XM manufactured by Soken Chemical Co., Ltd.) are added and uniformly mixed.

[0930] By bonding the adhesive layer of the obtained hard coat film to the first substrate and mounting the hard coat film on the first substrate, a light guide plate for image display according to Example 8 is obtained.

[0931] <Example 9>

[0932] Example 9 differs only in the composition of the hard coat film. The preparation mode of the hard coat film is described below.

[0933] A release layer, a hard coat layer, and an adhesive layer are formed on a process release film ("MRA100" manufactured by Mitsubishi Chemical Corporation, thickness 100 μm) in the same manner as described above, and the adhesive layer is bonded to a first substrate. After UV irradiation, the process release film is peeled off to obtain the light guide plate for image display of Example 9.

[0934] <Evaluation Method>

[0935] For each embodiment, the following evaluation is performed.

[0936] (Image display clarity)

[0937] Three light guide plates for each example are prepared, and a holographic layer is formed to diffract light in the red, green, and blue wavelength regions for each, and then the three light guide plates are stacked. An image display device, an optical system for inputting displayed information into the light guide plate, and a circuit system for supplying driving power and image information are mounted on the stacked light guide plates to manufacture an image display device related to each example.

[0938] An image with characters written on a white background is displayed on a light guide plate. The displayed image is viewed visually from the first substrate side, and the sensitivity is evaluated in the following three steps.

[0939] A (good): There are no rainbow-colored areas in the image, and the text is clearly visible.

[0940] B (average): There are slight areas in the image that appear rainbow-colored, but the characters are clearly visible.

[0941] C (bad): There are clearly rainbow-colored areas in the image, and the outlines of the characters are faint.

[0942] The evaluation of clarity is performed before and after the scratch resistance evaluation shown below. In Examples 8 and 9, the hard coat film is peeled off after the scratch resistance evaluation, and the evaluation is performed after a new hard coat film is installed.

[0943] (Scratch resistance)

[0944] For the surface of the outermost hard coat film or hard coat layer in the image display device of each example, a steel wool #0000 mounted on the cross-section of a cylinder with a diameter of 11 mm is reciprocated 10 times at a load of 400 g and 100 mm / sec. Afterwards, the surface condition of the hard coat film or hard coat layer is observed within a test range of 100 mm in length and 20 mm in width, and is judged in the following three steps.

[0945] A (good) : Flawless

[0946] B (average): Fewer than 20 scratches

[0947] C (bad): 20 or more scratches

[0948] (Fall resistance)

[0949] A steel ball with a diameter of 50 mm and a weight of 230 g is dropped and impacts the outermost surface of the image display device of each example. Afterward, cracks in the first substrate and the second substrate are checked. The evaluation is performed in the following two steps.

[0950] A (good): No cracks are found in either the first substrate or the second substrate.

[0951] C (bad): A crack is confirmed in at least one of the first substrate and the second substrate.

[0952] (Pencil hardness)

[0953] For the surface to be measured, the pencil hardness is measured with a load of 750 g in accordance with JIS K 5600-5-4:1999.

[0954] The results of each evaluation are shown in Table 3.

[0955] [Table 3]

[0956]

[0957] In Examples 8 and 9, scratches occur in the hard coat film or hard coat layer during the scratch resistance evaluation. These scratches can prevent the deterioration of clarity by replacing the hard coat film. Since the light guide plate for image display in each example does not cause cracks in the resin substrate during the drop resistance evaluation, the safety is enhanced when applied to a glasses-type display.

[0958] In the light guide plate related to the third embodiment of the present invention, the second substrate is not made of resin, but may be made of glass, for example. Even with such a configuration, by configuring the glasses-type display with the first substrate facing the wearer, it is possible to reduce weight and also increase the safety of the wearer.

[0959] In the light guide plate related to the present invention, a hard coat film may also be mounted on the second substrate. At this time, the configuration and number of overlaps of the hard coat film in the first substrate and the second substrate may be different.

[0960] [Example of the 4th embodiment]

[0961] Hereinafter, Examples 9 and 10 of the fourth embodiment will be described. The present invention is not limited by these examples.

[0962] Table 4 below shows the composition of the resin substrate and absorption layer, and the evaluation results for each example.

[0963] [Table 4]

[0964]

[0965] <Example 10>

[0966] Example 10 is an example corresponding to the image display light guide plate (4005) of the fourth embodiment.

[0967] As shown in Table 4, acrylic resin (PMMA) is used as the material for the first resin substrate (4001) and the second resin substrate (4003) ("resin substrate" in Table 4).

[0968] The shapes of the first resin substrate (4001) and the second resin substrate (4003) are both square plates of 60 mm × 60 mm × 1 mm.

[0969] The hologram layer (4002) is common to each embodiment. As the material for the hologram layer (4002), 100 parts by mass of bisphenol-based epoxy resin jER (registered trademark) 1007 (degree of polymerization n = 10.8, epoxy equivalent: 1750 to 2200, product name manufactured by Mitsubishi Chemical), 50 parts by mass of triethylene glycol diacrylate, 5 parts by mass of 4,4'-bis(t-butylphenyl)iodonium hexafluorophosphate, and 0.5 parts by mass of 3,3'-carbonylbis(7-diethylamino)coumarin are mixed and dissolved in 100 parts by mass of 2-butanone and used as a photosensitive material for holograms. The thickness of the hologram layer (4002) is 5 μm. The size of the hologram layer (4002) when viewed from a flat plane is 50 mm × 50 mm.

[0970] Next, the manufacturing process of the image display light guide plate (4005) in Example 10 will be described. The image display light guide plate (4005) is manufactured by carrying out the substrate preparation process, the absorption layer formation process, and the light guide plate manufacturing process described below in this order.

[0971] (Substrate preparation process)

[0972] In the substrate preparation process, the first resin substrate (4001) and the second resin substrate (4003) are cleaned and dried. Hereinafter, if there is no need to distinguish between the first resin substrate (4001) and the second resin substrate (4003), the symbol is omitted and simply referred to as a resin substrate.

[0973] The resin substrate is ultrasonically cleaned for 5 minutes while immersed in a 5% aqueous surfactant solution of the neutral cleaning agent Semiclean (registered trademark) M-LO (product name; manufactured by Yokohama Yuji Industry Co., Ltd.).

[0974] Afterwards, the resin substrate is ultrasonically cleaned for 5 minutes while immersed in ultrapure water. Additionally, the resin substrate is rinsed with ultrapure water, and after air drying, the resin substrate is dried in an oven at 100°C under a nitrogen atmosphere. Afterwards, the air-dried evaluation sample B is UV ozone cleaned in a UV ozone cleaner for 1 minute.

[0975] With this, the substrate preparation process is completed.

[0976] (Absorption layer formation process)

[0977] In the process of forming the absorption layer, a first absorption layer (4004) ("absorption layer" in Table 4) is formed on the surface of the first resin substrate (4001).

[0978] 5 parts by mass of a photopolymerization initiator is added to 100 parts by mass of acrylate (UPIMA (registered trademark) UV-HH2100 (product name; manufactured by Mitsubishi Chemical Corporation)), and additionally, 0.05 parts by mass of Dia Range (registered trademark) Blue is added as a colorant to prepare a curable resin composition (coat liquid).

[0979] This curable resin composition is applied onto a first resin substrate (4001) using a metal bar coater, dried at 90°C for 1 minute, and then exposed to light with an exposure amount of 500 mJ / cm² using an ultraviolet light irradiation device to obtain a laminate having an absorption layer with a thickness of 5 μm.

[0980] With this, the absorption layer formation process is completed.

[0981] Hereinafter, a resin substrate with an absorption layer formed thereon is referred to as an intermediate laminate.

[0982] (Light guide plate manufacturing process)

[0983] In the light guide plate manufacturing process, an image display light guide plate (4005) is manufactured using an intermediate laminate and a second resin substrate (4003).

[0984] A seal layer with a width of 5 mm and a thickness of 5 μm is applied to the periphery of the surface opposite to the absorption layer of the intermediate laminate.

[0985] The seal layer is made of a transparent material and is not particularly limited as long as it is a material capable of bonding resin substrates together, but in Example 1, optical adhesive Hardlock (registered trademark) OP-1045K (product name; manufactured by Denki Chemical Industry Co., Ltd.) is used.

[0986] Thus, an intermediate laminate forming a seal layer step is prepared, in which an opening surrounded by a seal layer has a size of 50 mm × 50 mm.

[0987] Afterwards, the photosensitive material is applied by spin coating as a photopolymer material for holograms onto this intermediate laminate. The photosensitive material is applied such that its thickness after drying is 5 μm.

[0988] Afterwards, the second resin substrate (4003) is laminated onto the seal layer and the photosensitive material so as to face the barrier layer of the intermediate laminate formed with the seal layer, and press-laminated under reduced pressure. The conditions for press-lamination are an absolute pressure of 5 kPa, a temperature of 70°C, and a press pressure of 0.04 MPa.

[0989] Afterward, a diffraction grating is recorded on the photosensitive material of the press-laminated laminate. In this process, the temperature of the laminate is maintained at 20°C. The diffraction grating forms an interference pattern by irradiating the laminate with two laser beams and adjusting the respective irradiation angles and intensities to form the required diffraction pattern. In this way, the diffraction grating is recorded on the photosensitive material.

[0990] As a specific diffraction grating, a color display diffraction grating is formed that diffracts each of the light in the red, green, and blue wavelength regions incident as image light incident on the incident part, and emits it from the display part at a position corresponding to the pixel of the image light.

[0991] Afterward, while maintaining the laminate at 20°C, ultraviolet light (wavelength 365 nm, irradiance 80 W / cm²) is irradiated onto the entire surface of the laminate from the direction of one side for 30 seconds. A high-pressure mercury lamp is used as the light source for the ultraviolet light.

[0992] Thus, the seal layer is cured, and the light guide plate (4005) for image display of Example 1 is formed.

[0993] <Example 11>

[0994] Example 11 is an example corresponding to the light guide plate (4007) for image display of the first variation of the fourth embodiment.

[0995] As shown in Table 4, Example 11 has an absorption layer formed on both sides. Specifically, a second absorption layer (4006) is formed on the surface opposite to the hologram layer (4002) in the second resin substrate (4003).

[0996] In this embodiment, the second absorption layer (4006) ("absorption layer" in Table 4) is configured in the same way as the first absorption layer (4004) of Example 10.

[0997] For this reason, the substrate preparation process of Example 11 is the same as that of Example 10.

[0998] The absorption layer formation process of Example 11 is different from Example 10 in that, in addition to the intermediate laminate having the first absorption layer (4004), an intermediate laminate is formed from a second resin substrate (4003) on which a second absorption layer (4006) is formed.

[0999] The light guide plate manufacturing process of Example 11 differs from Example 10 in that two intermediate laminates are used.

[1000] <Evaluation Method>

[1001] Next, the evaluation method for each embodiment is described. As for the evaluation, a clarity evaluation is performed.

[1002] (Clarity Evaluation)

[1003] The clarity of the displayed image is achieved by using each display device that uses a light guide plate for each image display. Each display device is configured in the same way as the display device (4010), except that the light guide plate for image display of each embodiment is used.

[1004] The images used for evaluation include a display image produced by image light diffracted from the holographic layer and an external light image through which external light is transmitted.

[1005] White images and character images are used as input images for the display image.

[1006] For the outdoor image, an indoor, street, or forest landscape located 0.5 m to 50 m away from the display device is used. In evaluating the outdoor image, a white image or a text image is displayed and evaluated, respectively.

[1007] The evaluation is performed by visually determining the way white images and text images are seen, and the way external light images are seen. As for the text images, Hiragana, Katakana, Kanji, Arabic numerals, or the alphabet are displayed with a size of 0.1 to 2.0 when converted to visual acuity.

[1008] (Criteria for evaluating the clarity of displayed images)

[1009] The clarity evaluation of the displayed image is performed in three stages.

[1010] If no rainbow colors are visible in a white image and the characters are clearly visible in a text image, it is judged as good (indicated as “A” in Table 4).

[1011] If a slight rainbow color is visible in a white image but the text is clearly visible in a text image, it is judged as possible (fair, indicated as “B” in Table 4).

[1012] If rainbow colors are visible in at least part of the white image and the outline of the characters is faint in the character image, it is judged as impossible (no good, indicated as “C” in Table 4).

[1013] (Criteria for evaluating the clarity of outdoor images)

[1014] The clarity evaluation of the external light image is performed in four stages.

[1015] If the color of the landscape in the external light image is clear and does not look unnatural, it is judged as very good (indicated as “S” in Table 4).

[1016] If the landscape in the outdoor image appears slightly dark, it is judged as good (indicated as “A” in Table 4).

[1017] If the landscape in the external light image is dark and there is a slight sense of incongruity in the color, it is judged as possible (fair, indicated as “B” in Table 4).

[1018] If the landscape appears faint due to the external light image, it is judged as impossible (no good, indicated as “C” in Table 4).

[1019] (Weather resistance test)

[1020] For the light guide plate used for image display in the clarity evaluation, a sample that undergoes a weathering test ("after weathering test" in Table 4) and a sample that does not undergo a weathering test ("before weathering test" in Table 4) are prepared.

[1021] The weathering test is conducted using a UV fade meter U48AU (product name: manufactured by Suga Testing Machine Co., Ltd.). The test conditions are a BP temperature of 63 ℃ ± 3 ℃. The test time is 500 hours.

[1022] <Evaluation Results>

[1023] As shown in Table 4, the clarity of Example 10 is evaluated as “A” regardless of whether the display image and the external light image are before or after the weathering test. The clarity of Example 11 is evaluated as “A” except that the weathering test of the external light image is “S”.

[1024] From this evaluation result, it can be seen that in Examples 10 and 11, by providing an absorption layer, both the display image and the external light image have good clarity. In particular, in Example 10, since an absorption layer is formed on the incident side of the external light as well, the clarity of the external light image is improved compared to Example 10 before the weather resistance test.

[1025] Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples. Within the scope of the present invention, additions, omissions, substitutions, and other modifications to the components are possible.

[1026] Furthermore, the present invention is not limited by the foregoing description, but is limited only by the appended claims.

[1027] Industrial applicability

[1028] The light guide plate for image display according to the present invention can display a clear image even when a resin substrate is used, and can also suppress the degradation of the hologram layer, so it is useful for display devices for, for example, VR and AR applications. For example, the light guide plate for image display according to the present invention is useful for display device applications such as entertainment, remote operation, work support, and guidance support using head-up displays, wearable displays, and head-mounted displays. Explanation of the symbols

[1029] 1001 : First resin material 1001a: First surface 1001b: Second surface 1002: Holographic layer 1003 : 2nd Resin Recording 1004, 1014: Light guide plate for image display 1011A: 1st hard coat layer 1011B: Second hard coat layer 1100: Continuous polymerization device 1101, 1102: Endless Belt 1103, 1104, 1105, 1106 : Jupulli 1107 : Carrier Roll 1108: 1st Polymerization Zone 1109 : Hot water spray 1110: Second Polymerization Zone 1111 : Downstream cooling zone 1112 : Gasket 1113 : Plate-shaped polymer 1114: Raw material injection device 1200 : Evaluation device 1201 : Light source 1202 : Screen 1203 : Camera 1204 : Calculation processing unit 1210 : Curve 2001: 1st Resin Recording 2002: 1st barrier layer 2003: Holographic layer 2003a : Display surface 2003b : Waveguide diffraction grating 2003c : Display diffraction grating 2004: 2nd barrier layer 2005: 2nd Resin Recording 2006, 2016: Light guide plate for image display 2006a : Admission Department 2006d : Display unit 2010 : Display device 2012 : Incident optical system 2013 : Image light projection unit 2014 : Luminance meter 2015 : Measuring device 2022: The 1st Barrier Film 2022A : Barrier layer 2022B : Resin Film 2024: Second Barrier Film 2024A : Barrier layer 2024B : Resin Film 2026: 1st adhesive layer 2027: 2nd adhesive layer 2032: Third barrier layer 2101, 2102: Light guide plates for image display 3001 : Light guide plate for image display (light guide plate) 3010: Holographic layer 3021 : 1st substrate 3022 : Second substrate 3030, 3130: Hardcoat film 3030A, 3130A: 1st Hard Coat Film 3030B, 3130B: Second hard coat film 3031 : Film material 3031a : 1st side 3031b : 2nd side 3032 : Adhesive layer 3033 : Hard coat layer 3034 : Heterogeneous layer 4001: First resin entry 4002: Holographic layer 4002b: Display diffraction grating 4003 : 2nd Resin Recording 4003a: Waveguide diffraction grating 4004: First absorption layer 4005, 4007, 4020, 4024: Light guide plates for image display 4005a : Incident part 4005b : Display image output unit 4006 : Second absorption layer 4008: 1st barrier layer 4009: Second barrier layer 4010 : Display device 4011 : Incident optical system 4012 : Image light projection unit 4021 : First resin substrate (absorbent layer) 4023 : Second resin substrate (absorbent layer) I : Transmission projection image Ib : High brightness part Is : Low-profile part Ld : Image light Ld' : Image light Ld'' : Image light Li: Imaging light Lo : External light Lo' : External light Lo'' : External light Lo''' : External light O : Optical axis P1: First intermediate laminate P2: Second intermediate laminate S: Measurement sample

Claims

Claim 1 A light guide plate for image display, wherein a first resin substrate, a first barrier layer, and a hologram layer are arranged in this order in the thickness direction, and the first barrier layer comprises at least one inorganic material selected from the group consisting of silicon oxide, silicon nitrate oxide, diamond-like carbon, aluminum oxide, and glass, and one or more transparent layers are disposed between the first barrier layer and the first resin substrate, or one or more transparent layers are disposed between the first barrier layer and the hologram layer, or an auxiliary layer is included as part of the first barrier layer, and the transparent layer is a hard coat layer, an adhesive layer, or an anchor coat layer, and the auxiliary layer comprises a fluorine-based material, an ethylene-vinyl alcohol-based copolymer, a cycloolefin-based polymer, or vinylidene chloride. Claim 2 A light guide plate for image display according to claim 1, additionally having a second resin substrate and a second barrier layer, wherein the first resin substrate, the first barrier layer, the hologram layer, the second barrier layer, and the second resin substrate are arranged in this order in the thickness direction. Claim 3 A light guide plate for image display according to claim 1 or 2, wherein the refractive index of the first barrier layer is higher than the refractive index of the first resin substrate. Claim 4 A light guide plate for image display according to claim 1 or 2, wherein the refractive index of the first barrier layer is 1.48 or higher. Claim 5 delete Claim 6 delete Claim 7 In claim 1 or 2, the first barrier layer is a light guide plate for image display disposed on a resin film. Claim 8 A light guide plate for image display according to claim 1 or 2, wherein a water vapor barrier material is used as the material of the first barrier layer. Claim 9 A light guide plate for image display according to claim 1 or 2, wherein the refractive index of the first resin substrate is 1.48 to 1.

70. Claim 10 A light guide plate for image display according to claim 1 or 2, wherein the first resin substrate comprises at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin, and polycarbonate. Claim 11 A light guide plate for image display according to claim 1 or 2, wherein the thermal shrinkage rate of the first resin substrate measured in accordance with Annex A of JIS K 6718-1:2015 is less than 3%. Claim 12 A light guide plate for image display according to claim 1 or 2, wherein the arithmetic mean roughness Ra of the surface of the first resin substrate is 10 nm or less.

Images