Light guide plate for image display and image display device

Abstract

To provide a light guide plate for image display that can display a clear image despite use of resin base materials.SOLUTION: A light guide plate for image display 4005 is provided which has a first absorption layer 4004 that has an absorption peak within a wavelength range of 500-600 nm, a first resin base material 4001, a hologram layer 4002, and a second resin base material 4003 in this order, and can thereby display a clear image despite the use of the resin base materials.SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] The present invention relates to a light guide plate for image display. [Background technology]

[0002] A light guide plate for image display is sometimes used in a display device. For example, a display device using VR (virtual reality), AR (augmented reality), or MR (mixed reality) technology uses a light guide plate for image display in which a hologram layer is supported on a transparent substrate. Holograms having various optical functions, such as waveguiding, reflecting, and diffracting functions, are formed in the hologram layer. A glass substrate is often used as the transparent substrate, but from the viewpoints of processability, lightness, durability, and portability, it is more preferable to use a resin substrate as the transparent substrate.

[0003] Patent Document 1 discloses a hologram laminate for use in an in-vehicle head-up display, which is composed of an acrylic resin substrate, an acrylic adhesive layer, a hologram layer made of an acrylic photopolymer, an acrylic adhesive layer, and an acrylic resin substrate laminated in this order. Patent Document 1 describes that the appearance of a hologram changes depending on the surface smoothness of the acrylic resin substrate. According to Patent Document 1, when the maximum height Rmax, which represents the surface smoothness of the hologram laminate, exceeds 50 μm, the change in appearance of the hologram becomes significant. When the maximum height Rmax is less than 25 μm, the change in appearance of the hologram is within an acceptable range. However, Patent Document 1 does not specifically mention the need for nano-order surface smoothness, with a maximum height Rmax of 1 μm or less. Patent Document 1 also does not describe any specific examples of nano-order surface smoothness. Furthermore, the hologram material forming the hologram layer can corrode the resin substrate due to temperature changes. Hologram materials are also known to deteriorate due to moisture absorption. For this reason, display devices in which the hologram layer is supported by a resin substrate are prone to deterioration in high-temperature, high-humidity environments. Patent Document 2 describes forming a photosensitive material layer that forms a hologram on an optically transparent resin substrate, and covering the photosensitive material layer with an aqueous polymer protective barrier. Patent Document 2 suggests that the aqueous polymer protective barrier is provided for the purpose of resisting attack by moisture. Patent Document 3 describes a hologram laminate having a hologram sandwiched between resin substrates via an optical adhesive, the entire outer periphery of which is covered with a protective coating layer. Patent Document 3 also describes that the protective coating layer may be a coating that improves airtightness and gas barrier properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-296583 [Patent Document 2] Japanese Patent Application Publication No. 5-181400 [Patent Document 3] Japanese Patent Application Publication No. 11-184363 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned related techniques have the following problems. The hologram laminate described in Patent Document 1 is primarily used in in-vehicle head-up displays viewed by the driver. Therefore, 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 in AR or MR, realistic images and small characters are often displayed in the user's entire field of view. For such applications, even higher image quality is required. According to the inventor's investigations, when a hologram layer is sandwiched between resin substrates in a light guide plate for image display, degradation of image quality may be observed even if the maximum height Rmax is less than 25 μm. For example, if undulations (gear marks) with a pitch corresponding to the meshing pitch of the drive gear of the extrusion roller occur on the surface of the extrusion-molded resin substrate, areas where the image becomes unclear are likely to occur. In the technology described in Patent Document 2, a resin substrate is adhered to the surface of the photosensitive material layer opposite the aqueous polymer protective barrier. Therefore, there is a risk that the photosensitive material will corrode the resin substrate in a high-temperature environment. Furthermore, since moisture is contained within the resin substrate, the moisture diffuses into the photosensitive material layer through the contact surface with the photosensitive material layer. In addition, since the substrate is exposed to the outside, moisture continues to permeate the substrate from the outside. As a result, moisture permeates the photosensitive material layer via the resin substrate, and even if the moisture is blocked by the aqueous polymer protective barrier, it is not possible to prevent the photosensitive material layer from deteriorating over time due to moisture from the substrate side. In the technology described in Patent Document 3, the entire outer periphery of a laminate containing a hologram is sealed with a protective coating layer. This prevents moisture from penetrating from the outside of the hologram laminate into the interior, causing degradation of the hologram. However, moisture contained in the resin substrate when the protective coating layer is formed is trapped inside the protective coating layer. As a result, moisture contained in the resin substrate may also penetrate into the hologram, causing deterioration of the hologram over time. The impact of moisture release from the resin substrate is particularly pronounced in high-temperature environments.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a light guide plate for image display that can display a clear image even when a resin substrate is used. Another object of the present invention is to provide a light guide plate for image display that can suppress deterioration of the hologram layer even when a resin substrate is used. [Means for solving the problem]

[0007] The present inventors have conducted extensive research and have found that, in a resin substrate used in a light guide plate for image display, a clear image can be displayed by improving the flatness corresponding to the magnitude of surface waviness which varies at a pitch significantly larger than the pitch measured by surface roughness, and have arrived at the present invention. When the surface flatness of the resin substrate is reduced due to waviness, the thickness of the hologram layer laminated on the resin substrate fluctuates. Fluctuations in the thickness of the hologram layer cause fluctuations in the guided light, resulting in minute distortions and deformations in the image, making the image unclear. In the case of a color image, the fluctuations in the guided light cause color shifts and color bleeding, making the image unclear. On the other hand, if the smoothness of the surface of the resin substrate is reduced due to minute irregularities, the guided light will be scattered, resulting in a blurred image. Furthermore, the present inventors have conducted extensive 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, deterioration of the hologram layer can be suppressed and a clear image can be displayed, leading to the present invention.

[0008] In order to solve the above problems, for example, the present invention has the following aspects. [1] A light guide plate for image display having a first resin substrate and a hologram layer, The light guide plate for image display, wherein the first resin base material has an MC value of 0.120 or less as evaluated by shadow contrast. [2] A light guide plate for image display, comprising a first resin substrate, a first barrier layer, and a hologram layer. [3] The light guide plate for image display according to [2], wherein the first resin base material, the first barrier layer, and the hologram layer are arranged in this order in the thickness direction. [4] Further comprising a second resin substrate and a second barrier layer, The light guide plate for image display according to [3], wherein the first resin base material, the first barrier layer, the hologram layer, the second barrier layer, and the second resin base material are arranged in this order in the thickness direction. [5] The light guide plate for image display according to 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. [6] The light guide plate for image display according to any one of [2] to [5], wherein the refractive index of the first barrier layer is 1.48 or more. [7] The light guide plate for image display according to any one of [2] to [6], wherein the first barrier layer contains an inorganic material. [8] The light guide plate for image display according to [7], wherein the first barrier layer contains at least one inorganic material selected from the group consisting of silicon oxide, silicon nitride oxide, diamond-like carbon, aluminum oxide, and glass. [9] The light guide plate for image display according to any one of [2] to [8], wherein the first barrier layer is disposed on a resin film.

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

[11] The light guide plate for image display according to any one of [2] to

[10] , wherein the first barrier layer is disposed on the hologram layer.

[12] The light guide plate for image display according to any one of [1] to

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

[13] The light guide plate for image display according to any one of [1] to

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

[14] The light guide plate for image display according to any one of [1] to

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

[15] The light guide plate for image display according to any one of [1] to

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

[0009] According to the present invention, it is possible to provide a light guide plate for image display that can display a clear image even when a resin substrate is used. Furthermore, according to the present invention, it is possible to provide a light guide plate for image display that can suppress deterioration of the hologram layer even when a resin substrate is used. [Brief explanation of the drawings]

[0010] [Figure 1] 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] FIG. 1 is a schematic front view illustrating a method for evaluating an MC value. [Figure 3] FIG. 1 is a schematic plan view illustrating a method for evaluating an MC value. [Figure 4] FIG. 10 is a schematic diagram showing an example of an image for evaluating MC values. [Figure 5] FIG. 10 is a schematic diagram showing an example of an evaluation image in which MC values ​​have been digitized. [Figure 6] 10 is a schematic graph showing a method for calculating an MC value. [Figure 7] FIG. 10 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a first modified example of the first embodiment of the present invention. [Figure 8] 1 is a schematic vertical cross-sectional view showing an example of a resin substrate manufacturing apparatus according to a first embodiment. [Figure 9] FIG. 4 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. [Figure 10] 10A and 10B are schematic front views for explaining a method for measuring a luminance value and an FOV. [Figure 11] FIG. 10 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a first modified example of the second embodiment of the present invention. [Figure 12] FIG. 10 is a schematic cross-sectional view showing a light guide plate for image display according to a fifth embodiment. [Figure 13] FIG. 10 is a schematic cross-sectional view showing a light guide plate for image display according to a sixth embodiment. [Figure 14] FIG. 10 is a schematic diagram showing a layer structure of a light guide plate for image display according to a third embodiment of the present invention. [Figure 15]FIG. 10 is a schematic diagram showing a layer structure of a light guide plate for image display according to a first modified example of the third embodiment of the present invention. [Figure 16] FIG. 10 is a view showing a state in which two hard coat films according to a third embodiment are stacked on top of each other. [Figure 17] FIG. 10 is a diagram showing a state in which two hard coat films according to a first modified example of the third embodiment are stacked on top of each other. [Figure 18] FIG. 10 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a fourth embodiment of the present invention. [Figure 19] FIG. 10 is a schematic cross-sectional view showing an example of a display device including a light guide plate for image display according to a fourth embodiment of the present invention. [Figure 20] FIG. 13 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a first modified example of the fourth embodiment of the present invention. [Figure 21] FIG. 13 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a second modified example of the fourth embodiment of the present invention. [Figure 22] FIG. 13 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a third modified example of the fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all drawings, even if the embodiments are different, the same or corresponding components are designated by the same reference numerals, and common descriptions will be omitted. Numerical ranges expressed using "~" include the numerical values ​​on both sides of the "~". "UV" means ultraviolet light. "(Meth)acrylic" means one or both of acrylic and methacrylic. "(Meth)acrylate" means one or both of acrylate and methacrylate.

[0012] [First embodiment] <Basic example> A light guide plate for image display according to a first embodiment of the present invention will be described. The light guide plate for image display according to the first embodiment of the present invention includes a first resin substrate and a hologram layer. The light guide plate for image display according to this embodiment may further include a second resin substrate. In this embodiment, the first resin substrate and the second resin substrate may hereinafter be collectively referred to simply as "resin substrate." The resin substrate is transparent. The hologram layer is sandwiched between a first resin substrate and a second resin substrate, or between the first resin substrate and a glass substrate. The image display light guide plate has an incident portion for receiving image light and a display image output portion for displaying an image based on 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 thereon for guiding at least the image light incident from the incident portion to the display image output portion and outputting 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 image display light guide plate. The external light incident portion refers to the surface opposite to the display image output portion. The image light incident on the light entrance portion is guided within the hologram layer and then emitted to the outside from the display image exit portion. Meanwhile, external light also passes through the resin substrate and the display image exit portion, so that a viewer at the display image exit portion can observe both the image light and external light within their field of view. The light guide plate for image display of this embodiment is suitable for use in display devices using AR technology or MR technology. For example, the light guide plate for image display of this embodiment may be used in devices such as AR glasses like a head-mounted display or an in-vehicle head-up display.

[0013] The resin substrate used in the light guide plate for image display of this embodiment has an MC value of 0.120 or less, as evaluated by shadow contrast. The definition of the MC value and a specific evaluation method will be described later. The MC value is particularly effective for evaluating flatness, among the surface properties of the resin substrate. That is, with respect to irregularities having a spatial frequency lower than that of the irregularities of the surface roughness, the lower the MC value, the smaller the degree of unevenness. Therefore, the lower the MC value, the better the flatness of the resin substrate. The material of the resin substrate is not particularly limited as long as it is a transparent material. The material used for the resin substrate preferably contains at least one resin selected from the group consisting of acrylic resin, cyclic polyolefin resin, and polycarbonate resin, and more preferably acrylic resin. The refractive index of the material used for the resin substrate is preferably 1.48 to 1.70. The material used for the resin substrate preferably has a thermal shrinkage rate of less than 3%. Here, the thermal shrinkage rate is the rate of dimensional change upon heating based on Appendix A of JIS K 6718-1:2015, "Measurement of dimensional change (shrinkage) upon heating." It should be noted that this "measurement of dimensional change (shrinkage) upon heating" is a standard for cast plates, but the thermal shrinkage rate in the present invention is a value based on this standard even when the resin substrate using the material is an extruded plate, a continuous cast plate, etc. The smoothness of the resin substrate (expressed by, for example, surface roughness such as arithmetic mean roughness Ra or maximum height Rmax) is preferably 10 nm or less in terms of arithmetic mean roughness Ra of the surface of the resin substrate. Furthermore, in the light guide plate for image display of this embodiment, a barrier layer, which will be described later, can be incorporated. By incorporating a barrier layer, deterioration of the hologram layer can be suppressed, and a clear image can be maintained.

[0014] A resin substrate having excellent flatness and the above-mentioned MC value can be produced, for example, by using a manufacturing method such as a casting method or an extrusion method, or by subjecting the resin substrate to post-processing such as cutting, polishing, or hot pressing.

[0015] The casting method may be a glass casting method. In the glass casting method, the raw material of the resin substrate is poured between glass plates having good flatness and smoothness, and then a polymerization process is carried out to solidify the resin raw material. When the resin substrate is manufactured by the glass casting method, the surface shape of the glass used in the glass casting method (hereinafter sometimes referred to as "casting glass") is transferred to the resin substrate. Therefore, if the surface of the casting glass has good flatness and smoothness, the surface of the resin substrate will also have good flatness and smoothness.

[0016] The smaller the internal strain of the casting glass, the better the flatness of the surface of the casting glass, and therefore the flatness of the resin substrate can be improved. For example, non-tempered glass is preferable to tempered glass as the casting glass. However, even if the tempered glass is chemically tempered glass, which has less strain than air-cooled tempered glass, the flatness of the resin substrate can be improved. The thicker the casting glass, the higher the rigidity of the casting glass and the more suppressed deformation of the glass during production, thereby improving the flatness of the resin substrate. When the resin substrate is molded, pressing the casting glass with surface pressure can improve the smoothness and flatness of the resin substrate.

[0017] The casting method is not limited to the above-mentioned glass casting method. For example, opposing metal endless belts may be used as the cast. In this case, the polymerization process is performed while rotating the endless belt, thereby continuously producing the resin substrate. The surface shape of the endless belt is transferred to the resin substrate. Therefore, by mirror-finishing the surface of the endless belt, the smoothness of the resin substrate can be improved. Furthermore, by controlling the tension of the endless belt, the flatness of the resin substrate can be improved. Other casting methods include a method in which a metal plate is used instead of the above-mentioned casting glass.

[0018] In the polymerization step of the casting method, the lower the curing rate, the more easily the surface shape of the cast is transferred to the resin substrate, thereby improving the flatness and smoothness of the resin substrate. The curing rate may be reduced by, for example, reducing the amount of polymerization initiator or lowering the polymerization temperature. The smaller the amount of crosslinking agent added that crosslinks the material of the resin substrate, the slower the curing rate, and the easier it is for the surface shape of the cast to be transferred to the resin substrate, thereby improving the flatness of the resin substrate. The amount of the 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 the polymerizable monomer components and polymerizable oligomer components other than the crosslinking agent that are the raw materials of the resin substrate. A release agent can be used in the casting, but the smaller the amount used, the more preferable, as this makes it easier for the surface shape of the cast to be transferred to the resin substrate, thereby improving the flatness and smoothness of the resin substrate. In the polymerization step in the casting method, the monomer for forming the substrate is pre-polymerized, thereby improving the flatness and smoothness of the resin substrate. In the polymerization process in the casting method, cast polymerization is performed using a raw material in which a polymer for forming the substrate is dissolved in a monomer for forming the substrate, which reduces cure shrinkage and makes it easier for the surface shape of the cast to be transferred to the resin substrate, thereby improving the flatness and smoothness of the resin substrate. In the casting method, two or more of the above techniques may be used in combination. In this case, the flatness and smoothness of the resin substrate can be further improved by the synergistic effect of each technique.

[0019] When the resin substrate is produced by an extrusion method, for example, a polishing roll method or an air knife method may be used. Depending on the processing accuracy of the die line of the extrusion die, the fine irregularities of the die line may be transferred, which may reduce the smoothness of the surface of the resin substrate. For this reason, the extrusion die is finished with high precision so that the die line is smooth.

[0020] For example, in the polishing roll method, molten resin is generally clamped and cooled between a set of three polishing rolls. The pressure applied to the molten resin when clamped between the polishing rolls is a linear pressure. This linear pressure is easily affected by variations in the rotation of the polishing rolls and variations in the processing accuracy of the roll shaft or machine base. This makes the linear pressure uneven, which makes the resin substrate prone to thickness variations and reduced flatness, such as gear marks. The gear marks occur in a linear shape extending in a direction perpendicular to the feed direction of the resin substrate. If the surface temperature of the polishing roll is too high, the resin substrate is likely to deform, and therefore the surface temperature is preferably low.

[0021] It is more preferable that the feed mechanism for the polishing roll has a configuration that minimizes drive fluctuations. For example, a planetary roller may be used instead of a gear transmission mechanism, such as a reducer, in order to suppress the transmission of gear meshing vibrations. However, any gear transmission mechanism that is less susceptible to meshing vibrations than spur gears, such as worm gears or helical gears, may be used as the transmission mechanism for the feed mechanism. Instead of the polishing roll, a configuration may be used in which a pair of seamless metal belts for cooling the molten resin are arranged opposite each other at a predetermined interval at the molten resin outlet of the extruder. In this case, the molten resin is sandwiched between the pair of seamless metal belts and conveyed while being cooled, and the pressure applied to the molten resin becomes a surface pressure, so that the deterioration of flatness due to linear pressure as in the polishing roll method described above is suppressed.

[0022] The hologram layer is made of a known hologram-forming resin material. For example, known materials can be appropriately selected and used as the hologram-forming resin material. The photosensitive material can be appropriately selected taking into consideration the wavelength of the light to be guided, and an acrylic photosensitive resin material for forming a hologram, which has excellent optical properties, can also be used.

[0023] The hologram layer may be formed on the surface of the resin substrate, or may be laminated on the resin substrate with an appropriate transparent layer sandwiched therebetween. When the light guide plate for image display includes a glass substrate, the hologram layer may be formed on the surface of the glass substrate, or may be laminated on the glass substrate with an appropriate transparent layer sandwiched therebetween. The resin base material may be disposed at the outermost portion in the thickness direction of the light-guiding plate for image display, or may be disposed inside. When the light-guiding plate for image display includes the glass base material, the glass base material may be disposed at the outermost portion in the thickness direction of the light-guiding plate for image display, or may be disposed inside.

[0024] In the light guide plate for image display, one or more appropriate transparent layers may be disposed in the thickness direction between the resin substrate and the hologram layer, or between the glass substrate and the hologram layer when a glass substrate is included. In the light guide plate for image display, one or more appropriate transparent layers different from the resin substrate and the glass substrate may be disposed on the outermost portion in the thickness direction. For example, when a transparent layer is disposed on at least one surface of the resin substrate, the transparent layer may be a hard coat layer that protects the surface of the resin substrate. Examples of other transparent layers include an absorption layer having an absorption peak in the UV or in a specific wavelength range and an adhesive layer.

[0025] Hereinafter, a detailed configuration of an example of a light guide plate for image display of this embodiment will be described based on the example shown in Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of a light guide plate for image display of the first embodiment of the present invention.

[0026] In the light guide plate for image display 1004 shown in FIG. 1, a first resin base material 1001, a hologram layer 1002, and a second resin base material 1003 are arranged in this order in the thickness direction. The planar shape of the light guide plate 1004 for image display is not particularly limited. For example, the light guide plate 1004 for image display may be shaped into a shape that can be attached to the display device to be used. For example, the light guide plate 1004 for image display may be a rectangular plate that is larger than the shape that is attached to the display device. In this case, the light guide plate 1004 for image display is shaped, for example by cutting, into a shape that can be attached to the display device before being assembled into the display device. The image display light guide plate 1004 may be in the form of a flat plate, or may be in the form of a curved plate as required. In the following, an example will be described in which the image display light guide plate 1004 is made of a flat plate that is rectangular in plan view.

[0027] The first resin base material 1001 is disposed at the outermost part in the thickness direction of the light guide plate for image display 1004. The first resin base material 1001 is disposed on the surface of the light guide plate for image display 1004 on the image display side. The first resin base material 1001 has the same shape as the outer shape of the image display light guide plate 1004. The first resin base material 1001 transmits image light emitted from the hologram layer 1002 and external light transmitted through the second resin base material 1003 and the hologram layer 1002, which will be described later.

[0028] The thickness of the first resin base material 1001 is not particularly limited. For example, the thickness of the first resin base material 1001 may be 0.05 to 2 mm. A thickness of 0.05 mm or more of the first resin base material 1001 is preferable because it is easy to maintain a stable shape and measurement errors of the MC value (described later) can be reduced. A thickness of 2 mm or less of the first resin base material 1001 is preferable because it reduces the mass of the image display light guide plate 1004 and enables weight reduction. The thickness of the first resin base material 1001 is preferably 0.05 mm or more, more preferably 0.1 mm or more, and even more preferably 0.5 mm or more. On the other hand, from the viewpoint of deformation or residual strain of the base material due to water absorption of the base material, the thickness of the first resin base material 1001 is preferably 2 mm or less, more preferably 1.5 mm or less, and even more preferably 1 mm or less.

[0029] Materials that can be used for the first resin substrate 1001 include, for example, organic materials such as polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, fluororesin film, polyvinyl chloride, polyethylene, polypropylene, cyclic polyolefin, cellulose, acetyl cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, poly(meth)acrylic resin, phenolic resin, epoxy resin, polyarylate, polynorbornene, styrene-isobutylene-styrene block copolymer (SIBS), and allyl diglycol carbonate, but it is preferable that the first resin substrate 1001 contains at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin, and polycarbonate. From the viewpoint of the transparency of the first resin base material 1001, it is preferable to use polycarbonate or poly(meth)acrylic resin, and from the viewpoint of the process resistance such as chemical resistance and workability of the first resin base material 1001, it is preferable to use poly(meth)acrylic resin, epoxy resin or cyclic polyolefin, but among these, poly(meth)acrylic resin is more preferable because it can achieve both transparency and process resistance.

[0030] As the first resin base material 1001, a plate material having an MC value of 0.120 or less as evaluated by shadow contrast is used. Here, a specific method for evaluating and calculating the MC value will be described. 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 illustrating an example of an image for evaluating MC values. Fig. 5 is a schematic diagram illustrating an example of an image for evaluating digitized MC values. Fig. 6 is a schematic graph illustrating a method for calculating MC values.

[0031] (Shadow contrast evaluation) The shadow contrast evaluation can be performed using an evaluation device 1200 shown in FIGS. The evaluation device 1200 includes a light source 1201, a screen 1202, a camera 1203 (see FIG. 3), and a processing unit 1204 (see FIG. 3). The evaluation device 1200 forms a rear 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 rear projection image. The shape of the measurement sample S is the same as the outer shape of the first resin base material 1001. In the following, an example will be described in which the measurement sample S is a flat plate that is rectangular in plan view.

[0032] The type of light source 1201 is not particularly limited as long as it can form a rear projection image of the measurement sample S. For example, it is more preferable to use a point light source as the light source 1201, since the rear projection image projected onto the screen 1202 will be clear. Examples of point light sources include 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. When the measurement sample S is a resin substrate, the wavelength is preferably in the range of 400 to 780 nm.

[0033] Examples of the screen 1202 include a matte screen, a bead screen, and a pearl screen. 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 rear projection image of the measurement sample S in the required measurement range. It is more preferable that the screen 1202 be large enough to include the rear projection image of the entire measurement sample S.

[0034] The type of camera 1203 is not particularly limited as long as it can accurately capture the brightness of the rear projection image on the screen 1202. For example, the camera 1203 may be an analog camera or a digital camera. From the viewpoint of facilitating digital analysis, it is more preferable that the camera 1203 be a digital camera. Note that when an analog camera is used to capture an image, the image analysis described below is performed after the obtained image is converted into a digital image. The size of the digital image, expressed in terms of the number of horizontal and vertical pixels, is, for example, 800 x 600, 1024 x 768, 1600 x 1200, 2048 x 1536, or 5472 x 3648. However, the size of the digital image is not limited to these, as long as it has a resolution that allows acquisition of a curve of brightness change corresponding to unevenness of the measurement sample S caused by waviness or the like. The brightness value is the degree of shading when the data for each pixel is converted to monochrome. The resolution of the brightness value is determined by the number of gradations for each pixel. The number of gradations for each pixel is not particularly limited as long as an MC value of 0.120 or less can be calculated. The number of gradations for each pixel may be, for example, 128 gradations, 256 gradations, 512 gradations, or 1024 gradations. However, if the contrast of the rear projection image is low due to constraints such as the transmittance of the measurement sample S and the brightness of the light source 1201, it is more preferable to use as many gradations as possible to improve measurement accuracy.

[0035] It is more preferable that the imaging using the camera 1203 be performed under light-shielding conditions. When imaging using the camera 1203 is performed under light-shielding conditions, a more accurate brightness distribution can be obtained compared to when imaging is not performed under light-shielding conditions. The method for imaging under light-shielding conditions is not particularly limited. For example, when the imaging environment in which the evaluation device 1200 is placed is a room with a window, the window may be sealed to make the entire room light-shielded. For example, the evaluation device 1200 may have a light-shielding housing that encloses at least the optical path from the light source 1201 to the screen 1202 and the optical path from the screen 1202 to the camera 1203.

[0036] The photographing mode of the camera 1203 may be either a color image mode or a monochrome image mode. When photographing in color image mode, it is more preferable to convert the image into a monochrome image using image processing software. For example, the optical characteristics of the lens of the camera 1203 may cause the brightness of the edges of the captured image to be lower than the brightness of the center. If the noise caused by such brightness unevenness is too large, it is more preferable to perform shading correction on the captured image in advance according to the optical characteristics of the lens and then determine the brightness distribution of the measurement sample S. The shading correction may be performed using appropriate image processing software before analyzing the captured image. For example, the amount of shading correction may be determined so that the brightness distribution becomes uniform when a correction glass plate with good flatness and smoothness is used instead of the measurement sample S. In this case, brightness unevenness due to the optical characteristics of the light source 1201 is also corrected.

[0037] For simplicity, the following description will be given using an example in which the camera 1203 is a digital camera and a rear projection image is captured on the screen 1202 in monochrome image mode. In this case, the output value of a pixel in the digital image is proportional to the brightness of the rear projection image. If the camera 1203 is an analog camera, the digital images in the following description should be interpreted as digital images generated from images captured by the camera 1203.

[0038] The arithmetic processing unit 1204 obtains a brightness distribution based on the digital image captured by the camera 1203, and calculates an MC value based on the brightness distribution. The arithmetic processing unit 1204 is configured to include a computer capable of executing appropriate image processing software.

[0039] The arrangement of each part in the evaluation device 1200 and the arrangement of the measurement sample S during measurement will be described. In the following, positional relationships may be described based on an XYZ Cartesian coordinate system. The X axis extends in a horizontal plane. The Y axis is perpendicular to the X axis in the horizontal plane. The Z axis is a vertical axis and perpendicular to the X and Y axes. The directions along the X axis, Y axis, and Z axis are referred to as the X direction, Y direction, and Z direction, respectively. 2, in the evaluation device 1200, a screen 1202 is arranged parallel to the YZ plane. A light source 1201 is arranged at a distance (d1+d2) from the screen 1202 in the X direction. An optical axis O of the light source 1201 is parallel to the X axis.

[0040] As shown in Fig. 3, the measurement sample S is placed midway between the light source 1201 and the screen 1202 on the optical axis O. If the vertices of the rectangular outer shape in a cross section passing through the center in the thickness direction of the measurement sample S are represented by A, B, C, and D, sides AD and BC are each parallel to the Y axis. Side AD represents the side closer to the light source 1201, and side BC represents the side closer to the screen 1202. 2, the center SO of the rectangle ABCD of the measurement sample S is located on the optical axis O, at a distance d1 from the light source 1201 in the X direction. Furthermore, the measurement sample S is located in an orientation rotated clockwise by an elevation angle θA from the horizontal plane around an axis that passes through the center SO and is parallel to the Y axis. However, if the thickness of the measurement sample S is thin, the center of one surface in the thickness direction of the measurement sample S may be located at the same position as above, instead of the center SO of the measurement sample S. Here, the distances d1 and d2 are set appropriately depending on, 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, the distances d1 and d2 may be 30 to 1000 cm. For example, it is more preferable that the distance d1 is as short as possible within the range in which the light source 1201 can be installed. It is more preferable that the distance d2 is as short as possible within the range in which the screen 1202 can be installed. The shorter the distances d1 and d2 are, the more efficiently the measurement light irradiated from the light source 1201 tends to be utilized. Elevation angle θ A For example, the elevation angle θ is preferably 5 to 90°. A can be measured as 20°.

[0041] The placement 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 appear in the capture range and where it can capture the entire rear projection image on the screen 1202. In the example shown in Fig. 3, in a plan view, the camera 1203 is placed at a position adjacent to the camera 1203 in the Y direction. However, although not particularly shown, the camera 1203 is placed at a different height from the measurement sample S in the Z direction, so that its own shadow and reflected light do not appear in the capture range.

[0042] 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 spreads radially, and a transmission projection image based on the light intensity of the light transmitted through the measurement sample S is formed on the screen 1202. The transmission projection image is photographed by the camera 1203 and sent to the calculation processing unit 1204 as a digital image. For example, a digital image as shown schematically in Fig. 4 is sent to the calculation processing unit 1204. In Fig. 4, the outermost frame represents the edge of the screen 1202. The central trapezoid PaPbPcPd represents the rear 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.

[0043] The rear projection 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 projecting the measurement light transmitted through the measurement sample S according to its transmittance onto the screen 1202. The brightness distribution on the transmission projection image I includes brightness unevenness caused by the optical path length and the distribution of the emitted light intensity of the light source 1201. This brightness unevenness occurs to some extent even if the measurement sample S does not have any unevenness defects. Since the measurement light is radiated light, the light intensity of the measurement light traveling along the optical axis O is maximum and decreases toward the periphery of the measurement sample S. The radiated light intensity distribution of the light source 1201 is similar. If this brightness unevenness is larger than the brightness unevenness caused by unevenness defects, it is corrected in advance. For example, when the difference between the brightness value on the optical axis O and the brightness value at the outer edge of the measurement sample S is 5 or more, it is more preferable to correct the brightness unevenness described above.

[0044] The brightness unevenness caused by the light intensity distribution of the measurement light can be corrected, for example, based on the law of light attenuation (the intensity of attenuated light is inversely proportional to the square of the distance from the light source). For example, the brightness unevenness caused by the radiation light intensity distribution of the light source 1201 can be corrected based on the radiation light intensity distribution of the light source 1201. For example, as described above, correction data may be acquired by taking an image using a correction glass plate. However, if the measurement conditions result in brightness unevenness smaller than that caused by unevenness defects, correction of the light intensity distribution of the measurement light and the light source 1201 may be omitted. In the following description, it is assumed that brightness unevenness that becomes measurement noise has been removed.

[0045] The low-brightness portion Is is considered to be formed by uneven defects corresponding to errors in the flatness of the surface of the measurement sample S. For example, if the radius of curvature of the unevenness formed on the measurement sample S is relatively small, the measurement light may be diffused by the lens effect of the unevenness before reaching the screen 1202. This depends on the smoothness. For example, if the measurement sample S is deformed into a wave shape, the thickness may not change even if there are surface irregularities. This depends on the flatness. In this case, the irregularities do not have a lens effect, but they do cause refraction and diffraction of the measurement light, which may contribute to uneven brightness. In addition, for example, unevenness formed on the measurement sample S may cause a distortion distribution near the uneven portion, which may disturb the emission direction of the measurement light, causing the light intensity on the screen 1202 to change. For example, as the angle of incidence on the measurement sample S increases, the change in transmittance characteristics that depends on the angle of incidence also increases. This may result in changes in the transmittance at the uneven portions formed on the measurement sample S, which may contribute to uneven brightness. In addition, the transmittance that changes due to uneven refractive index caused by distortion inside the measurement sample S may also contribute to uneven brightness. It is believed that unevenness in brightness occurs due to one or a combination of these factors. Furthermore, it is believed that the magnitude of unevenness in brightness is highly correlated with the depth of the unevenness defect. Therefore, 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.

[0046] 4, the low-lightness portions Is are elliptical. Such low-lightness portions Is correspond to elliptical concave or convex portions on the surface of the measurement sample S. For example, if a gear mark is formed on the measurement sample S, the low-lightness portions Is are formed in the shape of stripes. In this case, the low-lightness portions Is are formed at equal intervals and substantially parallel to the direction perpendicular to the extrusion direction of the first resin base material 1001.

[0047] The calculation processing unit 1204 analyzes the digital image as follows to calculate the MC value. The digital image used to measure the MC value may be the entire trapezoid PaPbPcPd. However, for example, if a portion of the measurement sample S is cut out and used in a display device, it is sufficient to measure the entire range of the size used in the display device. In some cases, a partial area inside the trapezoid PaPbPcPd may be extracted in a trapezoidal shape from the digital image used to measure the measurement sample S. For example, if the defect to be detected using the MC value is a gear mark, for example, whose directionality, pitch, etc. are known in advance, a partial area of ​​the trapezoid PaPbPcPd may be used as long as it is large and has a range that includes multiple gear marks, taking into account measurement error. The same applies, for example, when the shape of the measurement sample S has a gentle curve due to its design. For example, if the measurement sample S is rectangular in plan view and measures 200 mm x 200 mm, the measurement range preferably includes a rectangular area measuring at least 180 mm x 80 mm on the measurement sample S. Here, the longitudinal direction of the measurement range is aligned with the direction in which the brightness change is greatest. 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 of the curvature be 50 mm or more. For example, if the measurement sample S has a spherical curvature as a whole, it is more preferable that the measurement range include a rectangular range of 50 mm x 50 mm centered at the apex of the curvature. In the following, an example will be described in which the entire trapezoid PaPbPcPd is used.

[0048] The calculation processing unit 1204 acquires the brightness distribution on a predetermined measurement line. For example, the measurement line is (N-1) line segments qiQi connecting points qi (where i = 1, . . . , N-1) obtained by dividing side AD on the measurement sample S into N equal parts and points Qi (where i = 1, . . . , N-1) obtained by dividing side BC on the measurement sample S into N equal parts. In this case, on the measurement sample S, the points qi and Qi are points on a plane parallel to the ZX plane. FIG. 4 shows points qi and Qi on the rear projection image I. For example, N can be appropriately selected depending on the size of the uneven defect between 2 and 10000. For example, in the case of a defect with a width of 100 mm, N may be selected so that the pitch of the measurement lines is about 1 to 20 mm. For example, if the low-lightness portion Is is streaky, the position of the measurement sample S is changed so that the measurement line intersects with the low-lightness portion Is, and a digital image is acquired. In this case, the measurement line N may be selected so that the pitch of the measurement line along the longitudinal direction of the low-lightness portion Is is approximately 1 to 20 mm.

[0049] In the example shown in Fig. 4, N = 8. Measurement line L3 in Fig. 5 schematically shows the measurement line corresponding to line segment q3Q3 in Fig. 4. Since the measurement line on the measurement sample S is projected as an oblique line, measurement line L3 on the rear projection image I appears as a digitized oblique line. The calculation processing unit 1204 extracts the brightness value of each measurement line by converting the coordinates of points qi, Qi on the measurement sample S into pixel coordinates on the rear projection image I based on the positional relationship between the light source 1201, the screen 1202, and the measurement sample S.

[0050] An example of the brightness distribution along the measurement line L3 is shown schematically in Fig. 6. In Fig. 6, the horizontal axis represents the pixel position in the Z direction, and the vertical axis represents the brightness value. As shown in curve 1210, the brightness on measurement line L3 decreases from a substantially constant high brightness value from point q3 to point Q3, reaches a minimum brightness value, and then returns to a substantially flat high brightness value. In the Z direction, the section from q3 to p1 and the section from p2 to Q3 are both included in the high brightness section Ib. The section from p1 to p2 is included in the low brightness section Is. The calculation processing unit 1204 obtains the minimum value Lmin and maximum value Lmax of the brightness from such a brightness distribution. The MC value is defined by the following formula (1): The calculation processing unit 1204 calculates the MC value based on Lmin and Lmax in the following formula (1).

[0051]

number

[0052] The MC value is an index that objectively represents the magnitude of the drop in the low-lightness portion Is in the lightness distribution. As described above, the lightness of the low-lightness portion Is decreases as the flatness of the measurement sample S decreases. Therefore, the larger the MC value, the poorer 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.

[0053] Similarly, the arithmetic processing unit 1204 calculates the MC value for each measurement line. The MC value of the measurement sample S is set to the maximum value of the MC values ​​of each measurement line.

[0054] As described above, in the light guide plate for image display of the present invention, the MC value of the resin substrate must be 0.120 or less. This improves the clarity of the displayed image formed using this light guide plate and utilizing an AR or MR hologram. 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. On the other hand, by setting this MC value to 0.001 or more, blocking between substrates during lamination can be prevented, and handling during substrate processing tends to be improved. The MC value of the resin substrate is preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.010 or more, and particularly preferably 0.020 or more.

[0055] As described above, in the light guide plate for image display of the present invention, the refractive index of the resin substrate is preferably 1.48 to 1.70, which allows the viewing angle to be widened when used as a light guide plate for image display.

[0056] Furthermore, as described above, in the light guide plate for image display of the present invention, the resin substrate preferably has a thermal shrinkage of less than 3% as measured in accordance with Appendix A of JIS K 6718-1:2015. This tends to improve the clarity of a display image formed using this light guide plate and utilizing an AR or MR hologram. The thermal shrinkage is preferably less than 3.0%, more preferably 2.5% or less, and even more preferably 2.0% or less.

[0057] As described above, in the light guide plate for image display of the present invention, the arithmetic mean roughness Ra of the surface of the resin substrate is preferably 10 nm or less. This tends to improve the clarity of a display image formed using this light guide plate and utilizing an AR or MR hologram. 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.

[0058] Here, we return to the description of the light guide plate for image display 1004 shown in FIG. The hologram layer 1002 in the light guide plate 1004 for image display is laminated on the surface of the first resin base material 1001. There are no particular limitations on the configuration of the hologram layer 1002. An appropriate diffraction grating corresponding to the function required for the light guide plate 1004 for image display is formed in the hologram layer 1002.

[0059] The second resin base material 1003 is laminated on the surface of the hologram layer 1002 opposite to the first resin base material 1001. The second resin base material 1003 has the same configuration as the first resin base material 1001. However, the thickness, material, etc. of the second resin base material 1003 may be different from those of the first resin base material 1001. In particular, since the second resin base material 1003 is disposed on the surface of the image display light guide plate 1004 on the external light incident side opposite to the display image exit side, a material having a higher surface hardness than the first resin base material 1001 may be used.

[0060] Such a light guide plate for image display 1004 can be manufactured, for example, as follows. Using the above-described manufacturing method, a first resin base material 1001 and a second resin base material 1003 having an MC value of 0.120 or less are prepared. For example, a photopolymer material for forming a hologram is applied to the first resin base material 1001. At this time, a transparent sealing layer having the same thickness as the hologram layer 1002 may be provided on the outer periphery of the first resin base material 1001. In this case, the photopolymer material is applied to a recess formed and surrounded by the sealing layer. The sealing 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 for the sealing layer. In this case, the durability of the hologram layer 1002 can be improved. After this, a second resin base material 1003 is placed on the photopolymer material. However, the above-described manufacturing order is merely an example. For example, the photopolymer material may be applied to the second resin base material 1003, and then the first resin base material 1001 may be placed on the photopolymer material. Thereafter, the laminate of first resin base material 1001, photopolymer material, and second resin base material 1003 is bonded together by a reduced pressure press. Thereafter, interference fringes corresponding to the diffraction pattern are formed in the photopolymer material of the laminate, forming a diffraction grating in the photopolymer material. In this manner, the light guide plate for image display 1004 is manufactured.

[0061] According to the light guide plate for image display 1004, the MC values ​​of the first resin base material 1001 and the second resin base material 1003 are 0.120 or less, and therefore irregularity defects on the surfaces of each are reduced. As a result, the optical paths of the image light that transmits through the first resin base material 1001 to display an image and the external light that transmits through the second resin base material 1003 and the first resin base material 1001 to be superimposed on the image light are prevented from being affected by irregularity defects and becoming disrupted. This allows the light guide plate for image display 1004 to display a clear image. As described above, according to this embodiment, it is possible to provide a light guide plate for image display that can display a clear image even when a resin substrate is used.

[0062] <First Modification> A first modification of the first embodiment of the present invention will be described. FIG. 7 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a first modified example of the first embodiment of the present invention.

[0063] As shown in FIG. 7, a light guide plate 1014 for image display according to the first modified example of the first embodiment of the present invention is obtained by adding a first hard coat layer 1011A and a second hard coat layer 1011B to the light guide plate 1004 for image display according to the basic example of the first embodiment of the present invention. The following description will focus on the differences from the basic example of the first embodiment of the present invention.

[0064] The first hard coat layer 1011A and the second hard coat layer 1011B are provided mainly for the purpose of protecting the surface of the first resin base material 1001. The first hard coat layer 1011A and the second hard coat layer 1011B are made of a transparent material having at least one surface with a higher hardness than the surface of the first resin base material 1001. The first hard coat layer 1011A and the second hard coat layer 1011B may have a multilayer structure made of multiple transparent materials with different hardnesses, as long as at least one surface with a higher hardness than the first resin base material 1001. 7, the first hard coat layer 1011A is disposed on the first surface 1001a of the first resin substrate 1001, opposite the hologram layer 1002. The first hard coat layer 1011A forms the outermost surface of the light guide plate 1014 for image display. The second hard coat layer 1011B is disposed on a second surface 1001b of the first resin substrate 1001 that faces the hologram layer 1002. The thickness of the first hard coat layer 1011A is more preferably 1 to 50 μm. The thickness of the second hard coat layer 1011B is more preferably 1 to 50 μm. It is more preferable that the flatness of the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B is 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). The arithmetic mean roughness Ra of the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B is more preferably 10 nm or less.

[0065] The refractive index of the material of the first hard coat layer 1011A and the second hard coat layer 1011B is not particularly limited. 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 less than that of the first resin base material 1001 from the viewpoint of visibility of the real image, but if a material is selected for the purpose of increasing the hardness of the hard coat layer, for example, the refractive index may be higher than that of the first resin base material 1001. For example, if the refractive index of the material of the first hard coat layer 1011A and the second hard coat layer 1011B is equal 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 will optically disappear. In this case, the MC value of the coated substrate essentially represents the degree of unevenness defects on the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B. For example, if forming the first hard coat layer 1011A and the second hard coat layer 1011B results in fewer unevenness defects than the surface of the first resin substrate 1001, 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. Generally, the refractive index of the material of the first hard coat layer 1011A and the second hard coat layer 1011B differs from the refractive index of the material of the first resin substrate 1001, and therefore the MC value of the coated substrate is evaluated to include both the irregularity defects on the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B and the irregularity defects on the surface of the first resin substrate 1001. However, if the first hard coat layer 1011A and the second hard coat layer 1011B are formed to a uniform thickness so that the irregularity defects on the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B match the irregularity defects on the surface of the first resin substrate 1001, the MC value of the first resin substrate 1001 itself is considered to be equal 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.

[0066] For example, from the viewpoint of a wide viewing angle, 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 higher than the refractive index of the material of the hologram layer 1002. As the refractive index increases, the critical angle of the guided light tends to increase.

[0067] There are no particular limitations on the surface hardness of the first hard coat layer 1011A and the second hard coat layer 1011B, 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 preferably H or higher, and more preferably 2H or higher.

[0068] Suitable materials for the first hard coat layer 1011A and the second hard coat layer 1011B include, for example, hard coat agents containing polymerizable monomers or polymerizable oligomers that form a cured product upon irradiation with active energy rays. Examples of the polymerizable monomers include (meth)acrylate monomers having a radically polymerizable unsaturated group in the molecule. Examples of the polymerizable oligomers include (meth)acrylate oligomers having a radically polymerizable unsaturated group in the molecule. Examples of the (meth)acrylate monomer having a radically polymerizable unsaturated group in the molecule 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 silicone (meth)acrylate. Examples of the (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule include oligomers containing a structural unit 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 silicone (meth)acrylate. Two or more of the polymerizable monomers or oligomers may be used in combination. Among these, urethane (meth)acrylate monomers or oligomers are preferred due to their high surface hardness. Examples of urethane (meth)acrylates include 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. The first hard coat layer 1011A and the second hard coat layer 1011B may contain a cured product of a polyfunctional (meth)acrylate. Examples of polyfunctional (meth)acrylates include 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, Examples of the acrylate include tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, 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, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and those modified with PO, EO, caprolactone, or the like. When forming the first hard coat layer 1011A and the second hard coat layer 1011B, 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 for preventing stains and adhesion may be added to the hard coat agent within a range that does not impair the physical properties. 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 base material 1001. In this case, the first hard coat layer 1011A and the second hard coat layer 1011B can change the refractive index of the outermost surface of the light guide plate for image display 1014 and the refractive index at the interface with the hologram layer 1002 from the refractive index of the first resin base material 1001.

[0069] Such a light guide plate for image display 1014 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, except that, after forming a first resin base material 1001 in the same manner as the basic example of the first embodiment of the present invention described above, a first hard coat layer 1011A and a second hard coat layer 1011B are formed on a first surface 1001a and a second surface 1001b of the first resin base material 1001, respectively, before laminating the first resin base material with a photopolymer material that forms a hologram layer 1002. The first hard coat layer 1011A and the second hard coat layer 1011B can be formed by applying a hard coat liquid, which is a raw material for each, to the first surface 1001a and the second surface 1001b, respectively, and then curing the hard coat liquid. The method for applying the hard coat liquid is not particularly limited. Examples of methods for applying the hard coat liquid include casting, roller coating, bar coating, spray coating, air knife coating, and dipping, in which a photocurable resin composition is directly applied to the surface of a substrate, and the applied film is irradiated with light to cure it, thereby forming a cured film on the substrate. Another example is a method in which a photocurable resin composition is applied to the surface of at least one mold material for constituting a mold for cast polymerization by the above-mentioned coating method or the like, and the applied film is irradiated with light to harden it, thereby forming a cured film on the mold material, and a mold for cast polymerization is assembled using this mold material so that the cured film is on the inside, and raw materials for the substrate are injected into this mold to perform cast polymerization, and after polymerization is completed, a laminate in which the cured film is integrated with the surface of the substrate is removed. However, the first hard coat layer 1011A and the second hard coat layer 1011B may be formed in the same manner as the first resin base material 1001 during the manufacturing process of the first resin base material 1001.

[0070] The materials and application methods for the first hard coat layer 1011A and the second hard coat layer 1011B are preferably those that do not increase the unevenness of irregularity defects on the surface of the first resin substrate 1001. The materials and application methods for the first hard coat layer 1011A and the second hard coat layer 1011B are more preferably those that reduce the unevenness of irregularity defects on the surface of the first resin substrate 1001. For example, the above-mentioned hard coating agent, alkoxysilane polycondensation curable resin, melamine resin, etc. can be used as the material. For example, the coating method may be a conventionally known coating method such as bar coating, dip coating, reverse gravure coating, direct gravure coating, roll coating, die coating, or curtain coating, with dip coating, die coating, or gravure coating being particularly preferred.

[0071] According to the first modified example of the first embodiment of the present invention, the MC values ​​of the first resin base material 1001 and the second resin base material 1003 are 0.120 or less, similar to the basic example of the first embodiment of the present invention. Therefore, similar to the basic example of the first embodiment of the present invention, a light guide plate for image display that can display clear images even when resin base materials are used can be provided. Furthermore, according to the first modification of the first embodiment of the present invention, the first hard coat layer 1011A and the second hard coat layer 1011B are laminated on the first resin base material 1001, thereby preventing the surface of the first resin base material 1001 from being scratched. For example, in the manufacturing process of the light guide plate 1014 for image display and the display device, deterioration of flatness due to scratches on the surface of the first resin base material 1001 can be prevented, and therefore the defective rate of the light guide plate 1014 for image display and the display device caused by handling during the manufacturing process, such as transportation, can be reduced. For example, the first hard coat layer 1011A constitutes the outermost surface of the light guide plate for image display 1014, and therefore, deterioration in image quality due to scratches on the outermost surface during use of the light guide plate for image display 1014 is suppressed.

[0072] In the above description of the first modified example, a hard coat layer is formed on each surface in the thickness direction of the first resin base material 1001. However, one of the first hard coat layer 1011A and the second hard coat layer 1011B may be omitted. In the above description of the first modified example, a hard coat layer is formed only on the first resin base material 1001. 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 base material 1003.

[0073] [Second embodiment] <Basic example> Hereinafter, a light guide plate for image display according to a second embodiment of the present invention will be described. A light guide plate for image display according to a second embodiment of the present invention includes a first resin substrate, a first barrier layer, and a hologram layer. The first barrier layer is preferably disposed on the surface of at least one of the first resin substrate and the hologram layer, and more preferably on the hologram layer. The first resin substrate, the first barrier layer, and the hologram layer are preferably disposed in this order in the thickness direction. The light guide plate for image display according to the second embodiment of the present invention may further include a second barrier layer and a second resin substrate. Preferably, 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 layer. More preferably, 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 layer, respectively. Preferably, 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. In the present embodiment, the first resin substrate and the second resin substrate may be collectively referred to simply as "resin substrates." Furthermore, the first barrier layer and the second barrier layer may be collectively referred to simply as "barrier layers."

[0074] One or more transparent layers may be disposed between the barrier layer and the resin substrate, and one or more transparent layers may be disposed between the barrier layer and the hologram layer. Examples of the transparent layer include a hard coat layer, an adhesive layer, and an anchor coat layer. In the light guide plate for image display according to the second embodiment of the present invention, a glass substrate may be provided to sandwich the barrier layer and the hologram layer between the resin substrate and the glass substrate. In this case, since the glass substrate itself has barrier properties, the glass substrate may be disposed on the surface of the hologram layer opposite to the surface facing the barrier layer.

[0075] As the resin substrate, the resin substrate in the first embodiment described above can be suitably used. The material used for the resin substrate is not particularly limited as long as it is a transparent material, but it preferably contains at least one resin selected from the group consisting of acrylic resin, cyclic polyolefin resin, and polycarbonate resin.

[0076] The refractive index of the barrier layer is preferably higher than the refractive index of the resin substrate, and more preferably 1.48 or higher. The barrier layer is preferably made of a water vapor barrier material. Furthermore, the material of the barrier layer preferably contains an inorganic material, and more preferably contains at least one inorganic material selected from the group consisting of silicon oxide, silicon nitride oxide, diamond-like carbon (DLC), aluminum oxide, and glass. Furthermore, by using an auxiliary layer containing a fluorine-based material, a cycloolefin-based polymer, vinylidene chloride, or the like as part of the barrier layer in combination with the inorganic material, the barrier layer can have a multilayer structure, and the water vapor barrier property can be further improved. Furthermore, the barrier layer may be disposed on a resin film, and in this case, it is more preferable that the resin film is disposed between the barrier layer and the resin substrate.

[0077] The hologram layer is sandwiched between a first resin substrate and a second resin substrate, or between the first resin substrate and a glass substrate. The light guide plate for image display has an incident section for receiving image light and a display section for displaying an image based on the image light. The hologram layer is disposed between the incident section and the display section. The hologram layer has a diffraction grating pattern formed thereon for guiding at least the image light incident from the incident section to the display section and for emitting the image light from the display section. The diffraction grating pattern in the display section transmits at least a portion of external light incident from outside the light guide plate for image display. The image light incident on the incident portion is guided within the hologram layer and then emitted to the outside from the display portion, while external light also passes through the resin substrate and the display portion, allowing a viewer of the display portion to observe both the image light and external light within their field of view. The light guide plate for image display according to the second embodiment of the present invention is suitable for use in display devices using VR or AR technology. For example, the light guide plate for image display according to the second embodiment of the present invention may be used in devices such as a combiner for a head-up display (HUD) mounted on an automobile or a holographic optical element (HOE) such as a reflector for a reflective liquid crystal display device, in addition to display applications.

[0078] The hologram layer is made of a known hologram-forming resin material, such as a hologram recording material comprising a solvent-soluble thermosetting resin having at least one cationically polymerizable ethylene oxide ring in its structural unit and a radically polymerizable ethylenic monomer (see JP-A-8-1676, JP-A-8-1677, JP-A-8-1678, and JP-A-8-1679).

[0079] Hereinafter, a detailed configuration of an example of the light guide plate for image display according to the second embodiment of the present invention will be described based on the example shown in Fig. 9. Fig. 9 is a schematic cross-sectional view showing an example of the light guide plate for image display according to the second embodiment of the present invention.

[0080] In the light guide plate 2006 for image display shown in FIG. 9, a first resin base material 2001, a first barrier layer 2002, a hologram layer 2003, a second barrier layer 2004, and a second resin base material 2005 are arranged in this order in the thickness direction. The planar shape of the light guide plate for image display 2006 is not particularly limited. For example, the light guide plate for image display 2006 may be shaped into a shape that can be attached to the display device to be used. For example, the light guide plate for image display 2006 may be a rectangular plate that is larger than the shape that is attached to the display device. In this case, the light guide plate for image display 2006 is shaped, for example, by cutting into a shape that can be attached to the display device before being assembled into the display device. The image display light guide plate 2006 may be in the form of a flat plate, or may be in the form of a curved plate as required. In the following, an example will be described in which the image display light guide plate 2006 is made of a flat plate that is rectangular in plan view.

[0081] The first resin base material 2001 is disposed at the outermost part in the thickness direction of the light guide plate for image display 2006. The first resin base material 2001 is disposed on the surface of the light guide plate for image display 2006 on the display image output side. The first resin base material 2001 has the same shape as the outer shape of the image display light guide plate 2006. The first resin base material 2001 transmits image light emitted from the hologram layer 2003 and external light transmitted through the second resin base material 2005 and the hologram layer 2003, which will be described later. There is no particular limitation on the thickness of the first resin base material 2001. For example, the thickness of the first resin base material 2001 may be 0.1 to 10 mm.

[0082] There are no particular limitations on the material forming the first resin substrate 2001 as long as it is a transparent resin material. Considering optical properties such as transparency and refractive index, as well as physical properties such as impact resistance, heat resistance, and durability, the material forming the first resin substrate 2001 may be, for example, polyolefin-based resins such as homopolymers or copolymers of olefins such as ethylene, propylene, or butene; amorphous polyolefin-based resins such as cyclic polyolefins; polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); cellulose-based resins such as triacetyl cellulose, diacetyl cellulose, and cellophane; polyamide-based resins such as nylon 6, nylon 66, nylon 12, and copolymer nylon; ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide-based resins, poly Examples of suitable organic materials include etherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluororesins, poly(meth)acrylic resins, styrene resins such as polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinyl chloride, cellulose, acetylcellulose, polyvinylidene chloride, polyphenylene sulfide, polyurethane, phenolic resins, epoxy resins, polyarylate resins, polynorbornene, styrene-isobutylene-styrene block copolymers (SIBS), allyl diglycol carbonate, and biodegradable resins. Among these, at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins, and polycarbonates is preferred. The first resin substrate 2001 may be formed from two or more materials, or may have a laminate structure in which two or more materials are laminated. Polycarbonate or poly(meth)acrylic resin is preferred from the viewpoint of transparency of the first resin substrate 2001. Poly(meth)acrylic resin, epoxy resin, or cyclic polyolefin is preferred from the viewpoint of process resistance such as chemical resistance and workability of the first resin substrate 2001. Poly(meth)acrylic resin is more preferred because it can achieve both transparency and process resistance.

[0083] 9, the first barrier layer 2002 is disposed between the first resin substrate 2001 and the hologram layer 2003 described below, and is in close contact with the surfaces of both 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 the surfaces of both the first resin substrate 2001 and the hologram layer 2003, and it is preferable that the first barrier layer 2002 is disposed at least on the hologram layer 2003. The first barrier layer 2002 prevents gases permeating from the outside of the light guide plate for image display 2006 and from the first resin substrate 2001 from permeating into the hologram layer 2003. For example, the smaller the oxygen permeability and water vapor permeability of the first barrier layer 2002, the more preferable it is. In particular, the first barrier layer 2002 is more preferably made of a material with excellent water vapor barrier properties (low water vapor permeability) because this can suppress deterioration of the hologram layer. For example, the oxygen permeability of the first barrier layer 2002 is 1 cm 3 / m 2 · days or less may be used. For example, the water vapor transmission rate of the first barrier layer 2002 is 1 g / m 2 The water vapor transmission rate of the first barrier layer 2002 may be 0.5 g / m 2 ·day or less is preferable.

[0084] The material of the first barrier layer 2002 is not particularly limited as long as it has the property of being able to barrier against gases that cause deterioration of the hologram layer 2003, but it is preferable that the first barrier layer 2002 contains an inorganic material, as this tends to provide excellent gas barrier properties and also excellent clarity of the displayed image. In this case, the inorganic material used for the first barrier layer 2002 may have a higher refractive index than the first resin base material 2001. For example, the refractive index of the first barrier layer 2002 may be 1.48 to 3.00. When the first barrier layer 2002 has a high refractive index, light passing through the first resin base material 2001 via the first barrier layer 2002 is incident from the optically dense first barrier layer 2002 to the optically coarse first resin base material 2001. Therefore, the exit angle of the light from the first barrier layer 2002 toward the first resin base material 2001 increases according to the difference in refractive index between the first barrier layer 2002 and the first resin base material 2001. This enables the FOV (Field Of View) of the image display light guide plate 2006 to be widened.

[0085] Materials for the first barrier layer 2002 include, for example, silicon oxide, silicon nitroxide, DLC, aluminum oxide, and glass. The material of the first barrier layer 2002 is as described above, but may also 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.

[0086] When the first barrier layer 2002 is made of silicon oxide, its thickness may be 10 to 300 nm. If the thickness is less than 10 nm, moisture resistance may be insufficient. If the thickness is more than 300 nm, cracks may easily occur in the silicon oxide thin film, which may peel off from the deposition surface. A particularly preferred layer thickness is 20 to 200 nm. There is no particular limitation on the method for forming the first barrier layer 2002 from silicon oxide. 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, the deposition surface may be subjected to a surface treatment such as corona discharge treatment or low-temperature plasma treatment, or may be coated with a silane coupling agent or a mixture of saturated polyester and isocyanate in order to improve adhesion between the deposition surface and the silicon oxide. For example, when forming a thin film of silicon oxide by vacuum deposition, silicon, silicon monoxide, silicon dioxide, or a mixture thereof is used as the evaporation material, and the evaporation rate is 1.0 × 10 -3 ~1.0×10 -5 Under a vacuum of Torr, evaporation is carried out by heating using an electron beam, resistance heating, or high-frequency heating. Alternatively, reactive vapor deposition can be performed while supplying oxygen gas. The silicon oxide forming the first barrier layer 2002 may contain calcium, magnesium, or oxides thereof as impurities, as long as the amount is 10 mass % or less.

[0087] When the first barrier layer 2002 is made of silicon nitride, the same structure as the first barrier layer 2002 containing silicon oxide as the main component is used, except that the silicon oxide is replaced with the silicon nitride.

[0088] DLC is an amorphous carbon material generally consisting of a ternary structure consisting of a diamond-like structure, a graphite-like structure, and a polyethylene-like polymer structure containing hydrogen atoms. When a hydrocarbon such as ethylene, acetylene, or benzene is used as the carbon source to generate the DLC, the resulting structure is basically a ternary structure containing hydrogen atoms. The DLC has excellent hardness, lubricity, abrasion resistance, chemical stability, heat resistance, and surface smoothness. Because the DLC forms the dense polymer structure described above, it also has excellent gas barrier properties and water vapor barrier properties. There are no particular limitations on the method for forming the first barrier layer 2002 using DLC. As a coating method for the DLC, any known appropriate coating method can 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.

[0089] When the first barrier layer 2002 is made of aluminum oxide, the first barrier layer 2002 may be made of, for example, Al2O3 only, or may be made of a mixture of two or more selected from the group consisting of Al, AlO, and Al2O3. The atomic ratio of Al:O in the aluminum oxide layer varies depending on the conditions for producing the aluminum oxide layer. The aluminum oxide layer usable as the first barrier layer 2002 may contain trace amounts (up to 3% of the total components) of other components as long as the barrier performance is not impaired. The thickness of the aluminum oxide layer may be set according to the barrier performance required, and may be, for example, 5 to 800 nm. There is no particular limitation on the method for forming the first barrier layer 2002 from aluminum oxide. For example, the first barrier layer 2002 may be formed by a PVD method (physical vapor deposition method) such as vacuum deposition, sputtering, or ion plating, or a CVD method (chemical vapor deposition method). For example, in vacuum deposition, Al, Al2O3, etc. are used as deposition source materials, and resistance heating, high-frequency induction heating, electron beam heating, etc. may be used as the deposition source heating method. In vacuum deposition, oxygen, nitrogen, water vapor, etc. may be introduced as a reactive gas, or reactive deposition using ozone addition or ion-assisted means may be used. Furthermore, a bias may be applied to the deposition surface, or the temperature of the deposition surface may be increased or cooled. The same applies to other deposition methods other than sputtering and other vacuum deposition methods, such as PVD and CVD.

[0090] When the first barrier layer 2002 is made of glass, examples of the material for the first barrier layer 2002 include borosilicate glass, alkali-free glass, low-alkali glass, soda-lime glass, sol-gel glass, and these glasses that have been subjected to heat treatment or surface treatment. From the viewpoint of avoiding coloration due to impurities, alkali-free glass is particularly preferable as the material for the first barrier layer 2002. When the first barrier layer 2002 is made of glass, its thickness may be 10 to 200 μm. A thickness of 10 μm or more tends to provide excellent mechanical strength and gas barrier properties. The thickness is preferably 10 μm or more, and more preferably 30 μm or more. Furthermore, a thickness of 200 μm or less tends to provide excellent optical properties as a light guide plate, such as light transmittance. The 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.

[0091] The method for forming the first barrier layer 2002 from glass is not particularly limited. For example, a slot downdraw method, a fusion method, or a float method can be used as the method for forming the first barrier layer 2002 from glass. Furthermore, commercially available glass may be used as is, or may be polished to a desired thickness before use. Examples of commercially available glass include "EAGLE2000" manufactured by Corning Incorporated, "AN100" manufactured by Asahi Glass Co., Ltd., "OA10G" manufactured by Nippon Electric Glass Co., Ltd., and "D263" manufactured by Schott.

[0092] Furthermore, an auxiliary layer containing a fluorine-based material, a cycloolefin-based polymer, vinylidene chloride, or the like can be introduced as part of the first barrier layer 2002, and by making the first barrier layer 2002 into a multilayer structure with the inorganic material layer described above, the water vapor barrier properties can be further improved. The fluorine-based material may be, for example, PCTFE (polychlorotrifluoroethylene), and the cycloolefin-based polymer may be, for example, a cycloolefin polymer or a cycloolefin copolymer. The thickness of this auxiliary layer may be set according to the requirements for water vapor barrier performance, For example, when a fluorine-based material is used, the thickness may be 0.1 to 100 μm.

[0093] Hologram layer 2003 is laminated on the surface of first barrier layer 2002. There is no particular limitation on the configuration of hologram layer 2003. In hologram layer 2003, an appropriate diffraction grating corresponding to the function required for image display light guide plate 2006 is formed.

[0094] Second barrier layer 2004 is laminated on the surface of hologram layer 2003 opposite to the surface of hologram layer 2003 on which first barrier layer 2002 is formed. The second barrier layer 2004 has the same configuration 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 those of the first barrier layer 2002.

[0095] Second resin base material 2005 is laminated on the surface of second barrier layer 2004 opposite to hologram layer 2003. The second resin base material 2005 has the same configuration as that exemplified in the description of first resin base material 2001. However, the thickness, material, etc. of second resin base material 2005 may be different from those of first resin base material 2001. In particular, since second resin base material 2005 is disposed on the surface of image display light guide plate 2006 on the external light incident side, which is opposite to the display image exit side, a material having a higher surface hardness than first resin base material 2001 may be used.

[0096] Such a light guide plate for image display 2006 can be manufactured, for example, as follows. A first resin base material 2001 and a second resin base material 2005 are prepared, and a first barrier layer 2002 and a second barrier layer 2004 are formed on the surfaces of the first resin base material 2001 and the second resin base material 2005, respectively. As a manufacturing method for the first barrier layer 2002 and the second barrier layer 2004, an appropriate manufacturing method is selected depending on the materials of the first barrier layer 2002 and the second barrier layer 2004. For example, a photosensitive material for forming a hologram is applied to the surface of first barrier layer 2002 of first resin substrate 2001 on which first barrier layer 2002 has been formed. At this time, a transparent sealing layer having the same thickness as hologram layer 2003 may be provided on the outer periphery of first barrier layer 2002. In this case, the photosensitive material is applied to a recess surrounded by the sealing layer. The sealing layer seals the outer periphery of hologram layer 2003 after hologram layer 2003 has been formed. Note that this sealing layer can be made of a material with excellent gas barrier properties, such as that used for first barrier layer 2002, thereby improving the durability of hologram layer 2003. Thereafter, a second resin base material 2005 on which a second barrier layer 2004 has been formed is placed on the photosensitive material with the second barrier layer 2004 facing the photosensitive material. However, the above-mentioned manufacturing order is merely an example. For example, a photosensitive material may be applied to the second resin base material 2005 on which the second barrier layer 2004 has been formed, and then the first resin base material 2001 on which the first barrier layer 2002 has been formed may be placed on the photosensitive material. Thereafter, a laminate consisting of first resin base material 2001, first barrier layer 2002, photosensitive material, second barrier layer 2004, and second resin base material 2005 is bonded together by a reduced pressure press. Thereafter, interference fringes corresponding to the diffraction pattern are formed on the photosensitive material of the laminate, and a diffraction grating is formed in the photosensitive material. In this way, the light guide plate for image display 2006 is manufactured.

[0097] According to the light guide plate 2006 for image display, a first barrier layer 2002 and a second barrier layer 2004 are arranged between the first resin base material 2001 and the hologram layer 2003, and between the second resin base material 2005 and the hologram layer 2003, respectively. The gas barrier properties of the first resin base material 2001 and the second resin base material 2005 are significantly lower than that of glass, although the degree of this varies depending on the type of resin material, and therefore the first resin base material 2001 and the second resin base material 2005 have higher moisture absorption and water vapor permeability than glass. As a result, gas outside the image display light guide plate 2006 passes through the first resin base material 2001 and the second resin base material 2005 to some extent and accumulates inside. In particular, moisture is likely to accumulate in the first resin base material 2001 and the second resin base material 2005. However, even if gas and moisture that have permeated into the first resin base material 2001 and the second resin base material 2005 from the outside diffuses within the light guide plate for image display 2006, they are blocked by the first barrier layer 2002 and the second barrier layer 2004. This prevents gas and moisture from permeating into the hologram layer 2003. For example, by suppressing the penetration of moisture into the hologram layer 2003, deterioration of the hologram layer 2003 is prevented. Furthermore, since light guide plate for image display 2006 has the above-described layer configuration, hologram layer 2003 is not in contact with first resin base material 2001 and second resin base material 2005. This prevents hologram layer 2003 from corroding first resin base material 2001 and second resin base material 2005 even if light guide plate for image display 2006 is placed in a high-temperature environment.

[0098] In particular, when the refractive index of the first barrier layer 2002 and the second barrier layer 2004 is higher than that of the first resin base material 2001 and the second resin base material 2005, the exit angle of light traveling from the first barrier layer 2002 toward the first resin base material 2001 becomes larger, as described above. Similarly, the exit angle of light traveling from the second resin base material 2005 to the second barrier layer 2004 becomes narrower. Therefore, light that enters from the outside on the second resin base material 2005 side and transmits through the image display light-guiding plate 2006 enters at a wider angle range than when the second barrier layer 2004 is not provided, and exits at a wider angle range than when the first barrier layer 2002 is not provided. As a result, the field of view of external light is broadened, and the FOV on the display side is also broadened. As for the image light from the hologram layer 2003, as described above, the angle of emission of light from the first barrier layer 2002 toward the first resin base material 2001 becomes larger, resulting in a wider FOV of the display screen compared to when the first barrier layer 2002 is not present. In particular, in this embodiment, the first barrier layer 2002 and the second barrier layer 2004 are stacked on the hologram layer 2003, so that the diffusion position of external light and image light and the diffraction position of the hologram layer 2003 that constitutes the display screen are brought closer together. As a result, a clearer image can be observed from a wider range of angles than when the first barrier layer 2002 and the second barrier layer 2004 are provided at a position away from the hologram layer 2003.

[0099] Here, an example of a method for measuring the luminance value and FOV of the image display light guide plate 2006 will be briefly described. FIG. 10 is a schematic front view illustrating a method for measuring the luminance value and the FOV.

[0100] As shown in FIG. 10, in order to measure the luminance value and FOV of a light guide plate for image display 2006, a display device 2010 is manufactured using the light guide plate for image display 2006. The display device 2010 includes an image light projection unit 2013 and an incident optical system 2012 in addition to the light guide plate 2006 for image display. The image light projection unit 2013 projects image light to be displayed on the image display light guide plate 2006 in response to an image signal sent from a controller (not shown). The incident optical system 2012 includes, for example, a prism, etc. The incident optical system 2012 causes the image light emitted from the image light projection unit 2013 to be incident on an incident unit 2006a provided on the surface of the image display light guide plate 2006. For example, the incident unit 2006a is provided on the surface on the first resin base material 2001 side. The image light incident on the incident portion 2006a passes through the waveguide diffraction grating portion 2003b formed in the hologram layer 2003 and reaches the display diffraction grating portion 2003c of the hologram layer 2003. The display diffraction grating portion 2003c diffracts the image light at positions corresponding to the respective display pixels. The diffracted light is emitted to the outside 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 spaced apart from the incident portion 2006a on the surface on the side of the first resin base material 2001.

[0101] The luminance value and FOV of the image display light guide plate 2006 are measured by placing the display device 2010 on a measurement device 2015 . The measuring device 2015 includes a holding table (not shown), a luminance meter 2014, and a goniostage (not shown). The support base supports the display device 2010. A luminance meter 2014 measures the luminance value of the received light. The goniostage supports the luminance meter 2014 so that it can swing around the circumference of the goniostage. The distance d between the luminance meter 2014 and the display surface 2003a corresponds to the position of the user's eyes when wearing the display device 2010. For example, if the display device 2010 is a head-mounted display, the distance d is set to 15 mm.

[0102] The luminance value of the light guide plate for image display 2006 is measured by placing a luminance meter 2014 at a position where the oscillation angle is 0° (see the luminance meter 2014 indicated by the solid line in FIG. 10). The display device 2010 is placed by the holding stand at a position where the center of the display surface 2003a faces the luminance meter 2014 on the measurement optical axis of the luminance meter 2014. The luminance value is the luminance measured by the luminance meter 2014 when the display device 2010 displays a white image with maximum luminance. In measuring the FOV of the light guide plate for image display 2006, a white image with maximum brightness is displayed on the display device 2010, and the FOV is measured by adjusting the oscillation angle θ B The brightness is measured by changing the angle. The brightness corresponding to when the white image becomes invisible is set as a threshold, and the FOV is calculated as the angle range where brightness equal to or greater than the threshold is obtained. When brightness equal to or greater than the threshold is obtained in the range from -θ1 to +θ2, the FOV is θ1 + θ2. The FOV of the image display light guide plate 2006 is preferably 24 to 160°, and more preferably 35 to 160°. The larger the FOV, the wider the angle at which the image is viewed, the greater the amount of image information, and the wider the range of applications to which it can be applied. On the other hand, if the FOV is smaller than the upper limit, the amount of light extracted per unit area tends to increase, resulting in a brighter image, which is preferable.

[0103] For example, the FOV can be improved by approximately 10° or more as the distance between the first barrier layer 2002 and the second barrier layer 2004 and the hologram layer 2003 decreases. The distance is preferably 1000 nm or less, more preferably 500 nm or less, and most preferably 100 nm or less.

[0104] As described above, according to this embodiment, it is possible to provide a light guide plate for image display that can suppress deterioration of the hologram layer even when a resin substrate is used.

[0105] <First Modification> A first modification of the second embodiment of the present invention will be described. FIG. 11 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a first modified example of the second embodiment of the present invention.

[0106] As shown in FIG. 11, the light guide plate 2016 for image display of the first modified example 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 basic example of the second embodiment of the present invention. The following description will focus on the differences from the above embodiment.

[0107] The first barrier film 2022 includes a barrier layer 2022A and a resin film 2022B. The barrier layer 2022A is configured similarly to the first barrier layer 2002 in the above embodiment.

[0108] The resin film 2022B is a substrate on which the barrier layer 2022A is formed. The material of the resin film 2022B is not particularly limited as long as it is a transparent resin film on which the barrier layer 2022A can be formed. For example, resins such as polypropylene, ABS, amorphous polyester resin, polyimide, polyamide, polyethersulfone (PES), polycarbonate (PC), cyclic polyolefin copolymer polynorbornene, cyclic polyolefin resin, polycyclohexene, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), fluororesin, polyarylate (PAR), polyether ketone (PEK), or polyether ether ketone (PEEK) may be used as the material of the resin film 2022B. For example, when considering the thermal expansion coefficient, humidity expansion coefficient, and glass transition temperature, more suitable materials for the resin film 2022B include crystalline resins such as thermoplastic resins like polyamide, polyacetal, polybutylene terephthalate, polyethylene terephthalate, and syndiotactic polystyrene, and thermosetting resins like polyphenylene sulfide, polyether ether ketone, liquid crystal polymer, fluororesin, and polyether nitrile. For example, amorphous resins such as thermoplastic resins like polycarbonate and modified polyphenylene ether, and thermosetting resins like polysulfone, polyethersulfone, polyarylate, polyamideimide, polyetherimide, and thermoplastic polyimide are suitable. Among these, polycarbonate is particularly preferred because it has low water absorption and therefore a first barrier film 2022 made using it has a low humidity expansion coefficient.

[0109] There are no particular limitations on the thickness of the resin film 2022B, but it is more preferable that the resin film 2022B be thinner than the first resin base material 2001. For example, the thickness of the resin film 2022B may be 1 to 200 μm.

[0110] It is more preferable to use a material with high surface smoothness for the resin film 2022B. In this case, the surface smoothness of the barrier layer 2022A is improved, making it easier to make the thickness of the barrier layer 2022A uniform. It is more preferable that the surface smoothness of the resin film 2022B be 2 nm or less in terms of arithmetic mean roughness Ra. The surface of the resin film 2022B may be subjected to various surface modification treatments in order to improve adhesion to the barrier layer 2022A and to the first adhesive layer 2026 described below. 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.

[0111] 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. Examples of methods for forming the barrier layer 2022A include physical vapor deposition (PVD), chemical vapor deposition (CVD), plating, coating, and sol-gel processes. CVD is particularly effective in forming the barrier layer 2022A. In CVD, the amount of heat applied to the resin film 2022B during film formation is less than in physical vapor deposition, reducing deterioration of the resin film 2022B due to heating. Among CVD methods, plasma CVD is more preferable. In plasma CVD, after introducing source gas into a film formation chamber, high-frequency waves are applied to generate a discharge, creating a plasma state, which promotes a chemical reaction on the surface of the resin film 2022B. Therefore, the temperature during the film formation process is low, ranging from approximately -10°C to 200°C, and film formation is possible even at temperatures below 30°C. This reduces thermal damage to the resin film 2022B.

[0112] The barrier layer 2022 A of the first barrier film 2022 is disposed on the surface of the hologram layer 2003 . The resin film 2022B of the first barrier film 2022 is fixed to the surface of the first resin base material 2001 with the first adhesive layer 2026 interposed therebetween. The material of the first adhesive layer 2026 is not particularly limited as long as it has good adhesiveness to the resin film 2022B and the first resin base material 2001. For example, preferred materials for the first adhesive layer 2026 include polyester resins, acrylic resins, urethane resins, melamine resins, and epoxy resins.

[0113] The second barrier film 2024 includes a barrier layer 2024A similar to the barrier layer 2022A, and a resin film 2024B similar to the resin film 2022B. However, the material, thickness, etc. of the barrier layer 2024A may be the same as or different from those of the barrier layer 2022A. The material, thickness, etc. of the resin film 2024B may be the same as or different from those of the resin film 2022B. The second barrier film 2024 is fixed to the surface of the second resin base material 2005 via a second adhesive layer 2027 that has a similar structure to the first adhesive layer 2026 .

[0114] To manufacture such a light guide plate 2016 for image display, for example, a first barrier film 2022 and a second barrier film 2024 are prepared, and the first barrier film 2022 and the second barrier film 2024 are adhered to the surfaces of the first resin base material 2001 and the second resin base material 2005, respectively, via a first adhesive layer 2026 and a second adhesive layer 2027, thereby forming a first intermediate laminate P1 and a second intermediate laminate P2. Thereafter, the hologram layer 2003 is formed in the same manner as in 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 instead of the first resin base material 2001 and the second resin base material 2005 of the basic example of the second embodiment of the present invention, respectively, thereby producing a light guide plate 2016 for image display.

[0115] According to light guide plate 2016 for image display of the first modified example of the second embodiment of the present invention, first resin base material 2001, barrier layer 2022A, and hologram layer 2003 are arranged in this order, and second resin base material 2005, barrier layer 2024A, and hologram layer 2003 are arranged in this order. Therefore, as in the embodiment, permeation of moisture into hologram layer 2003 is suppressed, thereby preventing deterioration of hologram layer 2003. Furthermore, since hologram layer 2003 does not come into contact with first resin base material 2001 and second resin base material 2005, erosion of first resin base material 2001 and second resin base material 2005 by the material of hologram layer 2003 is prevented. Therefore, the light guide plate for image display 2016 can display clear images even when a resin base material is used. Furthermore, if the refractive index of the barrier layers 2022A, 2024A is made higher than that of the first resin base material 2001 and the second resin base material 2005, the FOV of the image display light guide plate 2016 is improved, making it possible to view clear images from a wide range of angles.

[0116] In particular, according to the first modified example of the second embodiment of the present invention, in the manufacturing process of the light guide plate for image display 2016, the first barrier film 2022 and the second barrier film 2024 are bonded to the first resin base material 2001 and the second resin base material 2005, thereby disposing the barrier layers 2022A and 2024A on the first resin base material 2001 and the second resin base material 2005. Therefore, even if the barrier layers 2022A and 2024A cannot be directly formed due to the type, shape, size, etc. of the material of the first resin base material 2001 and the second resin base material 2005, the barrier layers 2022A and 2024A can be easily disposed.

[0117] As described above, according to the first modification of the second embodiment of the present invention, it is possible to provide a light guide plate for image display that can suppress deterioration of the hologram layer even when a resin base material is used.

[0118] In the basic example and first modified example of the second embodiment, examples have been described in which barrier layers are disposed on the front and back surfaces of the hologram layer. However, for the purposes of blocking moisture and the like that may penetrate through the resin substrate and preventing contact between the hologram layer and the resin substrate, the barrier layer may be disposed between the resin substrate and the hologram layer. However, in this case, if the transparent layer sandwiched between the barrier layer and the hologram layer has high hygroscopicity, moisture may penetrate through the side surfaces of the transparent layer. Therefore, it is more preferable that the transparent layer between the barrier layer and the hologram layer be made of a material with low hygroscopicity. If the transparent layer between the barrier layer and the hologram layer has hygroscopicity, it is more preferable that the thickness of the transparent layer be thin. In this case, the exposed area of ​​the side surfaces that serve as a moisture penetration port is reduced, thereby reducing the amount of moisture absorbed.

[0119] [Third embodiment] When the light guide plate for image display of the present invention is used in, for example, an eyeglass-type display, in order to prevent deterioration of optical properties due to scratches on the surface, a hard coat film can be attached to the surface of the resin substrate opposite to the side on which the hologram layer is located so as to be peelable from the substrate.

[0120] <Basic example> A third embodiment of the light guide plate for image display of the present invention will be described below. FIG. 14 shows the layer structure 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. As shown in Figure 14, the light guide plate 3001 includes a hologram layer 3010, two substrates, a first substrate 3021 and a second substrate 3022, which sandwich the hologram layer 3010 in the thickness direction, and a hard coat film 3030 provided on the first substrate 3021.

[0121] First substrate 3021 and second substrate 3022 are sheet-shaped resin substrates having optical transparency. Materials similar to those used in the first and second embodiments can be used as materials for first substrate 3021 and second substrate 3022, but acrylic is preferable in terms of transparency, etc. The thickness of first substrate 3021 and second substrate 3022 can be, for example, about 1 mm.

[0122] As in the first and second embodiments, a known configuration can be appropriately selected and used for the hologram layer 3010. The optical structure such as the diffraction grating may be appropriately determined taking into consideration the wavelength of the guided light, etc.

[0123] 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 provided on a first surface 3031a of the film substrate 3031. The hard coat layer 3033 is provided on a second surface 3031b of the film substrate 3031, the second surface 3031b being opposite to the first surface 3031a. The release layer 3034 is provided on the hard coat layer 3033. The hard coat film 3030 is attached so as to be releasable from the first substrate 3021 by the adhesive layer 3032 adhering to the first substrate 3021 .

[0124] Each part of the hard coat film 3030 will be described in detail below. (Film base material 3031) Films or sheets made of various organic polymers can be used as the film substrate 3031. Examples include substrates commonly used in optical components such as displays. Taking into consideration optical properties such as transparency and refractive index, as well as various properties such as impact resistance, heat resistance, and durability, organic polymers such as polyolefins (e.g., polyethylene, polypropylene), cyclic polyolefins, polyesters (e.g., polyethylene terephthalate, polyethylene naphthalate), celluloses (e.g., triacetyl cellulose, diacetyl cellulose, cellophane), polyamides (e.g., 6-nylon, 6,6-nylon), acrylics (e.g., polymethyl methacrylate), polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, and ethylene vinyl alcohol can be used. In particular, polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA) are preferred materials.

[0125] Furthermore, known additives such as ultraviolet absorbers, infrared absorbers, plasticizers, lubricants, colorants, antioxidants, flame retardants, etc. may be added to these organic polymers to impart functionality to the film substrate 3031. The film substrate 3031 may be made of one or a mixture of two or more selected from the organic polymers described above, or may be made of a polymer, or may be made by laminating multiple layers. It is preferable that the film substrate 3031 has a small birefringence and good transparency. It is preferable that the thickness of the first substrate 3021 and the second substrate 3022 is in the range of 5 to 200 μm.

[0126] (Adhesive layer 3032) The adhesive layer 3032 bonds the film base 3031 to the first substrate 3021 so that the film base 3031 can be peeled off with a small force. The adhesive layer 3032 is bonded to the surface of the first substrate 3021 opposite to the surface facing the hologram layer 3010. The adhesive layer 3032 can be formed from an adhesive such as a rubber-based adhesive, a polyester-based adhesive, an epoxy-based adhesive, an acrylic-based adhesive, a silicone-based adhesive, a urethane-based adhesive, a vinyl alkyl ether-based adhesive, a polyvinyl alcohol-based adhesive, a polyacrylamide-based adhesive, a cellulose-based adhesive, etc. Among these, an ultraviolet-curable or heat-curable acrylic adhesive is preferred in terms of optical properties such as transparency.

[0127] Examples of acrylic adhesives include those formed from adhesive compositions (hereinafter referred to as "the adhesive composition") that use (meth)acrylic acid ester polymers (which include copolymers and are hereinafter referred to as "acrylic acid ester (co)polymers") as the base resin. The acrylic acid ester (co)polymer as the base resin can be prepared by appropriately adjusting physical properties such as the glass transition temperature (Tg) and molecular weight by appropriately selecting the type, composition ratio, and polymerization conditions of the acrylic monomer or methacrylic monomer used for polymerization. Examples of acrylic or methacrylic monomers used for polymerizing acrylic acid ester (co)polymers include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, ethyl acrylate, methyl methacrylate, methyl acrylate, etc. In addition, acrylic monomers having a hydrophilic group or an organic functional group, such as hydroxyethyl acrylate, acrylic acid, glycidyl acrylate, acrylamide, acrylonitrile, methacrylonitrile, fluorine acrylate, and silicone acrylate, may be copolymerized with the above acrylic monomers. In addition, various vinyl monomers such as vinyl acetate, alkyl vinyl ethers, and hydroxyalkyl vinyl ethers can also be used appropriately in the polymerization. As the polymerization treatment using these monomers, known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization can be used, and in this case, 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.

[0128] The thickness of adhesive layer 3032 is preferably in the range of 1 to 50 μm, and more preferably in the range of 1 to 30 μm. A conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. can be used as a method for forming an adhesive layer on the film substrate 3031. Examples of coating methods are described in "Coating Methods" (Maki Shoten, written by Harasaki Yuji, published in 1979). The method for drying the adhesive is not particularly limited, but drying is generally carried out at 30 to 160°C. Furthermore, a known method may be appropriately selected as a method for curing the adhesive depending on the composition of the adhesive, etc. For example, if the adhesive is an active energy ray curable type, it may be cured by irradiating it with active energy rays (visible light, ultraviolet light, X-rays, gamma rays). The amount of irradiation of the active energy rays may be adjusted appropriately depending on the properties of the adhesive, but is generally 10 to 10,000 mJ / m. 2 It is preferable to irradiate with From the viewpoint of enabling easy peeling of the hard coat film, the peel strength of adhesive layer 3032 is preferably 0.01 to 50 N / 20 mm width when peeling is measured in a 180-degree direction (peel speed 50 mm / min).

[0129] (Hard coat layer 3033) The hard coat layer 3033 has a hardness sufficient to prevent scratches due to contact with other structures, etc. When expressed in terms of pencil hardness (750 g load) as defined in JIS K 5600-5-4:1999, this hardness 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.

[0130] The hard coat layer 3033 can be formed from a cured product 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 ray curable composition or a thermosetting composition. The hard coating agent may be an organic-inorganic hybrid material.

[0131] Polymerizable monomers or polymerizable oligomers that form a cured product upon 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 a radically polymerizable unsaturated group in the molecule. Examples of the polymerizable oligomers include (meth)acrylate oligomers having a radically polymerizable unsaturated group in the molecule. Examples of the (meth)acrylate monomer having a radically polymerizable unsaturated group in the molecule 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 silicone (meth)acrylate. Examples of the (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule include oligomers containing a structural unit 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 silicone (meth)acrylate. The polymerizable monomers or oligomers may be used in combination of two or more. Among these, urethane (meth)acrylate monomers or oligomers are preferred due to their high surface hardness. Examples of urethane (meth)acrylates include 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.

[0132] The hard coat layer 3033 may contain a cured product of a polyfunctional (meth)acrylate. Examples of polyfunctional (meth)acrylates include 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, and dipentaerythritol penta(meth)acrylate. , tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, 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, isoboronyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, or ditrimethylolpropane tetra(meth)acrylate, or any of these modified with PO, EO, or caprolactone. Among these, tri- to hexa-functional polyfunctional (meth)acrylates are preferred because they can suitably satisfy the required 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.

[0133] When forming the hard coat layer 3033, additives such as a crosslinking agent, a polymerization initiator, a lubricant, a plasticizer, organic particles, inorganic particles, an antifouling agent, an antioxidant or a catalyst, or additives such as silicone-based or fluorine-based additives for preventing staining and adhesion may be added to the hard coat agent within a range that does not impair the physical properties. If necessary, the hard coating agent may contain a solvent. Examples of the solvent 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); amides (dimethylformamide, dimethylacetamide, n-methylpyrrolidone); ethers (diethyl ether, dioxane, tetrahydrofuran); ether alcohols (1-methoxy-2-propanol); carbonates (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate), etc. These solvents may be used alone or in combination of two or more.

[0134] The thickness of 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. When the thickness of hard coat layer 3033 satisfies this range, scratches on first substrate 3021 can be effectively prevented, and scratches on hard coat film 3030 itself can also be suppressed. Furthermore, when hard coat layer 3033 is formed, warping of the hard coat film due to cure shrinkage of the hard coat agent can be suppressed.

[0135] The procedure for providing the hard coat layer 3033 on the film substrate 3031 can be roughly the same as the procedure for providing the adhesive layer 3032. The various methods described above can also be used for the coating method, drying method, and curing method.

[0136] (Release layer 3034) The release layer 3034 allows the adhesive layer of the overlapping hard coat film to be easily peeled off when the hard coat film is wound into a roll during production or storage. The release layer 3034 can be formed by applying and drying a paint containing resins and surfactants such as silicone resin, fluororesin, aminoalkyd resin, polyester resin, paraffin wax, acrylic resin, urethane resin, melamine resin, urea resin, urea-melamine system, cellulose, benzoguanamine, etc., alone or as a mixture thereof, dissolved in an organic solvent or water, by a normal printing method such as gravure printing, screen printing, offset printing, etc. Note that curable coatings such as thermosetting resin, ultraviolet curing resin, electron beam curing resin, and radiation curing resin can be formed by curing. It is particularly preferable to carry out a release treatment using a silicone, fluorine compound or alkyd resin-based release agent.

[0137] The hard coat film 3030 preferably has predetermined optical properties because it affects the visibility of the surrounding real image seen through the light guide plate 3001 and the image displayed on the light guide plate. For example, when sandwiched between 0.5 mm thick soda lime glass, it preferably satisfies the following (A), and more preferably satisfies the following (B) and (C). (A) Retardation value is within the range of 0 to 100 nm (B) Total light transmittance measured in accordance with JIS K 7361-1:1997 is 85% or more. (C) Haze value measured in accordance with JIS K 7136:2000 is 5% or less.

[0138] In the light guide plate 3001 of the third embodiment of the present invention, the hard coat film 3030 attached to the first substrate 3021 prevents scratches on the first substrate 3021 and maintains the optical properties of the first substrate 3021. The hard coat film 3030 is provided with a hard coat layer 3033, and therefore is resistant to scratches. Furthermore, because the adhesive layer 3032 is removably adhered to the first substrate 3021, if the hard coat film 3030 is damaged, the damaged hard coat film can be easily peeled off from the first substrate 3021 and replaced with another undamaged hard coat film. This prevents a deterioration in the clarity of the light guide plate.

[0139] <First Modification> A first modified example of the third embodiment of the present invention will be described. In the following description, the same components as those already described will be assigned the same reference numerals and redundant description will be omitted.

[0140] FIG. 15 shows a hard coat film 3130 according to a first modified example of the third embodiment of the present invention. The hard coat film 3130 includes an adhesive layer 3032, a hard coat layer 3033, and a release layer 3034. The hard coat film 3130 according to the first modified example of the third embodiment of the present invention differs from the hard coat film 3030 according to the basic example described above in that the hard coat film 3130 does not include a film substrate 3031.

[0141] An example of the manufacturing procedure for the hard coat film 3130 is shown below. A paint that will become release layer 3034 and a hard coating agent that will become hard coating layer 3033 are applied in that order onto the release-treated surface of a resin film that has been subjected to a release treatment, thereby forming release layer 3034 and hard coating layer 3033 on the resin film. Next, an adhesive composition that will become adhesive layer 3032 is applied onto hard coating layer 3033 to form adhesive layer 3032. Finally, the resin film is peeled off, thereby completing hard coating film 3130. As another configuration, a resin film having one side subjected to a release treatment can be used as the release layer 3034 by forming the hard coat layer 3033 and the adhesive layer 3032 by the above-mentioned procedure on the untreated side of the resin film.

[0142] The hard coat film 3130 of the first modified example of the third embodiment of the present invention is used in substantially the same manner and functions as the hard coat film 3030 of the basic example described above, and has similar effects. In addition, since the film is bonded to the light guide plate, it also has the effect of preventing fragments from scattering when the light guide plate is broken.

[0143] <Multiple layers of hard coated film> The hard coat films of the basic example and modified examples described above may be attached to 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, because a release layer 3034 is present at the contact area between the two stacked hard coat films, the upper second hard coat films 3030B, 3130B can be easily peeled off from the lower first hard coat films 3030A, 3130A. With such a hard coat film structure, if the hard coat film located on the outermost surface becomes damaged, simply peel it off and the undamaged hard coat film underneath becomes a new outermost surface. Therefore, there is no need to attach another hard coat film after removing the damaged hard coat film, and the surface condition of the light guide plate can be easily maintained. In this configuration, the number of hard coat films to be stacked is not limited to two as shown in the figure, but may be three or more.

[0144] There are no particular limitations on the method for obtaining a hard-coated film in a stacked state, and examples include a method in which one hard-coated film is laminated with another hard-coated film, or a method in which the hard-coated film is wound into a roll and then cut out. Furthermore, a method of forming layers corresponding to a plurality of hard coat films at once can 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 active energy rays, a method of curing or semi-curing the lower layer with active energy rays and then coating the upper layer, and then curing with active energy rays again, a method of coating each layer on a release film or base film, and then laminating the layers together in an uncured or semi-cured state can be applied, but from the viewpoint of improving the adhesion between layers, a method of laminating in an uncured state and then curing with active energy rays is preferred.As a method of laminating in an uncured state, known methods such as sequential coating in which a lower layer is coated and then an upper layer is coated, or simultaneous multi-layer coating in which two or more layers are coated at the same time from multiple slits can be applied, but are not limited thereto.

[0145] [Fourth embodiment] In the light guide plate for image display of the present invention, the hologram layer may yellow during its production and long-term use, which may adversely affect 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 deteriorating the hologram layer.

[0146] <Basic example> A fourth embodiment of the light guide plate for image display of the present invention will be described below. A light guide plate for image display according to a fourth embodiment of the present invention includes a first resin substrate, a hologram layer, and a first absorption layer, and the first absorption layer, the first resin substrate, and the hologram layer are preferably arranged in this order in the thickness direction. The image display surface light guide plate of the fourth embodiment of the present invention may further include a second resin substrate, in which case the first absorption layer, the first resin substrate, the hologram layer, and the second resin substrate are preferably laminated in this order in the thickness direction. 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 substrates." Furthermore, in the present embodiment, the first absorption layer and the second absorption layer may be collectively referred to simply as "absorption layers." The light guide plate for image display according to the fourth embodiment of the present invention may further include an appropriate transparent layer, such as a barrier layer, an adhesive layer, a hard coat layer, or an anchor coat layer. The light guide plate for image display according to the fourth embodiment of the present invention may further include a glass substrate.

[0147] The image display light guide plate has an incident portion for receiving image light and a display image output portion for displaying an image based on 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 thereon for guiding at least the image light incident from the incident portion to the display image output portion and outputting 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 image display light guide plate. The external light incident portion refers to the surface opposite to the display image output portion. The image light incident on the light entrance portion is guided within the hologram layer and then emitted to the outside from the display image exit portion. Meanwhile, external light also passes through the resin substrate and the display image exit portion, so that a viewer at the display image exit portion can observe both the image light and external light within their field of view. The light guide plate for image display according to the fourth embodiment of the present invention is suitable for use in display devices using VR, AR, or MR technology. For example, in addition to display applications, the light guide plate for image display according to the fourth embodiment of the present invention may be used in devices such as a combiner for a head-up display (HUD) mounted on an automobile or a holographic optical element (HOE) such as a reflector for a reflective liquid crystal display device.

[0148] The material of the resin substrate is not particularly limited as long as it is a transparent material. The material used for the resin substrate can be appropriately selected from those used in the above-described first to third embodiments. The material used for the resin substrate preferably contains at least one resin selected from the group consisting of acrylic resin, cyclic polyolefin resin, and polycarbonate resin.

[0149] In the light guide plate for image display according to the fourth embodiment of the present invention, when the resin substrate is made up of two layers, 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. In the light guide plate for image display according to the fourth embodiment of the present invention, when the light guide plate for image display includes a first resin substrate and a glass substrate, the hologram layer may be disposed between the first resin substrate and the glass substrate. The resin substrate and the hologram layer, or the glass substrate and the hologram layer, may be in contact with each other, or an appropriate transparent layer may be disposed between them.

[0150] The hologram layer is sandwiched between a first resin substrate and a second resin substrate, or between the first resin substrate and a glass substrate. The hologram layer uses a known hologram-forming resin material, as in the first to third embodiments. Examples of the hologram-forming resin material include hologram recording materials composed of a solvent-soluble thermosetting resin having at least one cationically polymerizable ethylene oxide ring in its structural unit and a radically polymerizable ethylenic monomer (see JP-A-8-1676, JP-A-8-1677, JP-A-8-1678, and JP-A-8-1679).

[0151] The absorption layer has wavelength characteristics that absorb the yellow component of light that passes through at least a portion of the light guide plate for image display. (Absorption peak) The absorbing layer has an absorption peak in the wavelength range of 500 to 600 nm (hereinafter sometimes referred to as "wavelength range A"). Here, the "absorption peak" refers to the spectral distribution where the minimum value is the smallest in the U-shaped spectral distribution in which the transmittance in the spectral transmittance curve of the absorbing layer in the visible light range (400 to 800 nm) decreases, passes through a minimum value, and then increases. It is more preferable that the U-shaped spectral distribution is formed at one point in the visible light range. In this specification, the term "having an absorption peak in a specific wavelength range" is defined as the wavelength at which the minimum value (peak top) of such an "absorption peak" is found in a specific wavelength range. The absorption peak is more preferably in the wavelength range of 550 to 585 nm (hereinafter sometimes referred to as "wavelength range B"). The half width of the absorption peak is preferably 100 nm or less, more preferably 70 nm or less, and particularly preferably 40 nm or less. Here, the half-width of the absorption peak means the wavelength width of the absorption peak at which the transmittance at the peak top of the absorption peak is Th=(100-Tp) / 2 or less, where Tp (%) is the transmittance at the peak top of the absorption peak. If the half-value width is 100 nm or less, the color balance and brightness of the transmitted light can be ensured well. The transmittance at the absorption peak is preferably 80% or less, more preferably 70% or less, and particularly preferably 60% or less.

[0152] (Transmittance characteristics) The average transmittance of the absorbing layer in the wavelength range of 590 to 700 nm (hereinafter sometimes referred to as "wavelength range C") is preferably 20% or more, more preferably 50% or more, and even more preferably 70% or more. In the wavelength range C, the average transmittance is set to 20% or more in order to maintain the brightness of red light. The average transmittance of the absorbing layer in the wavelength range of 470 to 550 nm (hereinafter sometimes referred to as "wavelength range D") is preferably 20% or more, more preferably 50% or more, and even more preferably 70% or more. The reason why the average transmittance is set to 20% or more in the wavelength range D is to ensure the color balance and brightness of the transmitted light. The transmittance of the absorbing layer is preferably as low as possible for ultraviolet light, which is prone to photodegradation. For example, the transmittance of the absorbing layer in the wavelength range of 380 nm or less is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

[0153] (yellowness) The YI value (JIS K 7373:2006) representing the yellowness of the absorbing layer is preferably 10 or less, more preferably 5 or less, and particularly preferably 3 or less.

[0154] (absorbance) The absorbance of the absorbing 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.

[0155] (b* in the L*a*b* color system) The b* of the absorbing layer is preferably 5 or less, more preferably 3 or less, and particularly preferably 1 or less.

[0156] The structure of the absorption layer is not particularly limited as long as it has an absorption peak in the wavelength range A. For example, the absorption layer may have a configuration in which a coloring material is dispersed in a transparent base resin. The material of the base resin is not particularly limited as long as it is transparent, and the refractive index of the base resin is also not particularly limited. For example, the base resin may have a refractive index equal to or higher than the refractive index of the resin substrate, or may have a refractive index lower than the refractive index of the resin substrate. For example, the base resin may be a resin material having a surface hardness higher than that of the resin substrate. For example, a resin material with low moisture absorption may be used as the base resin.

[0157] The coloring material is not particularly limited as long as it can provide the above-mentioned wavelength characteristics. For example, dyes, pigments, etc. are used as the coloring material. It is particularly preferable to use a bluing agent as the coloring material. For example, the absorbing layer may be formed of a multi-layer thin film in which a plurality of high refractive index materials and a plurality of low refractive index materials are stacked.

[0158] (Bluing agent) The bluing agent used in the absorbing layer is not particularly limited, but anthraquinone dyes are generally more preferable because they are readily available. Specific examples of bluing agents include 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 (Bayer's "Macrolex Violet RR"), and Solvent Blue 45 (CA No. 61110). These bluing agents may be used alone or in combination. These bluing agents are blended with the base resin in an appropriate amount to obtain the optical properties required for the absorbing layer. For example, when the base resin is a polycarbonate resin, the amount of the additive may be 0.1×10 −5 to 2×10 −4 parts by mass per 100 parts by mass of the polycarbonate resin. Examples of other bluing agents include Diaresin (registered trademark) Blue N (trade name; manufactured by Mitsubishi Chemical Corporation), Diaresin (registered trademark) Blue G (trade name; manufactured by Mitsubishi Chemical Corporation), Macrolex (registered trademark) Blue RR (trade name; manufactured by Bayer), Macrolex (registered trademark) Blue 3R (trade name; manufactured by Bayer), and Polythren (registered trademark) Blue RLS (trade name; manufactured by Clariant).

[0159] The absorbing layer is provided in a range through which at least the image light and external light pass. For example, the absorbing layer may be disposed in a range that overlaps the display image output portion of the hologram layer in the thickness direction. However, the absorbing layer may be disposed in a range that covers the entire resin substrate or the hologram layer when viewed in the thickness direction.

[0160] The arrangement of the absorption layer in the thickness direction of the light guide plate for image display is not particularly limited. For example, the absorption layer may be provided at least one of a position closer to the incident surface of the external light than the hologram layer and a position closer to the exit surface of the image light than the hologram layer. When the absorbing layer is disposed outside the resin substrate, the absorbing layer, the resin substrate, and the hologram layer may be disposed in this order in the thickness direction of the light guide plate for image display. That is, the absorbing layer may be disposed outside the resin substrate in the thickness direction. For example, the absorbing layer may be disposed at the outermost part in the thickness direction of the light guide plate for image display. When the absorbing layer is formed by dispersing a colorant inside the resin substrate, the colorant may be dispersed uniformly in the resin substrate or may be dispersed unevenly in the thickness direction. When the colorant is dispersed unevenly in the thickness direction, it is more preferable that the colorant is dispersed unevenly toward the outer side in the thickness direction of the light guide plate for image display.

[0161] The barrier layer may be made of the same material as in the second embodiment, and is preferably made of a transparent inorganic material. The refractive index of the barrier layer is more preferably 1.48 or higher. The barrier layer is preferably made of a water vapor barrier material, and more preferably contains one or more substances selected from the group consisting of silicon oxide, silicon nitride oxide, and diamond-like carbon (DLC). The barrier layer may be disposed on the resin film, and in this case, the resin film is more preferably disposed between the barrier layer and the resin substrate.

[0162] The barrier layer is more preferably arranged in the thickness direction of the light guide plate for image display in the order of the resin substrate, the barrier layer, and the hologram layer, and it is particularly preferable that the barrier layer is arranged on the surface of the hologram layer. Two barrier layers may be provided with the hologram layer sandwiched therebetween, and it is more preferable that the barrier layers are disposed on the front and back surfaces of the hologram layer. When a glass substrate is disposed, the glass substrate itself has barrier properties, and therefore the glass substrate may be disposed on the surface of the hologram layer opposite to the surface facing the barrier layer.

[0163] Hereinafter, 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 based on the example shown in Fig. 18. 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.

[0164] 18, a first absorption layer 4004, a first resin base material 4001, a hologram layer 4002, and a second resin base material 4003 are arranged in this order in the thickness direction. The light guide plate 4005 for image display is an example in which no barrier layer is provided. There is no particular limitation on the shape in plan view of the image display light guide plate 4005. For example, the image display light guide plate 4005 may be shaped so as to be attachable to the display device in which it is used. For example, the light guide plate for image display 4005 may be a rectangular plate larger than the shape to be attached to the display device. In this case, the light guide plate for image display 4005 is shaped, for example, by cutting into a shape that can be attached to the display device before being assembled into the display device. The image display light guide plate 4005 may be in the form of a flat plate, or may be in the form of a curved plate as required. In the following, an example will be described in which the image display light guide plate 4005 is made of a flat plate that is rectangular in plan view.

[0165] The first absorption layer 4004 is disposed at the outermost part in the thickness direction of the light guide plate for image display 4005. The first absorption layer 4004 is disposed on the surface of the light guide plate for image display 4005 on the display image output side. There is no particular limitation on the thickness of the first absorption layer 4004. For example, the thickness of the first absorption layer 4004 may be 0.1 to 10 μm. In the example shown in FIG. 18, the first absorption layer 4004 is formed on the entire surface of a first resin base material 4001, which will be described later. There is no particular limitation on the method for forming the first absorption layer 4004. 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 the film formation surface (the surface of the first resin base material 4001) and then curing the coating liquid. As a method for applying the coating liquid, an appropriate application method can be selected depending on the viscosity and other factors of the coating liquid. For example, as the application method, a conventionally known coating method such as bar coating, dip coating, reverse gravure coating, direct gravure coating, roll coating, die coating, curtain coating, etc. can be used. The base resin material may be, for example, a polymerizable monomer or oligomer that forms a cured product upon irradiation with active energy rays, such as a (meth)acrylate monomer having a radically polymerizable unsaturated group in the molecule, or a (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule, or a curable resin material such as urethane, epoxy, or polyester. The colorant to be blended into the base resin material may be, for example, the above-mentioned bluing agent.

[0166] The first resin base material 4001 has the same shape as the outer shape of the light guide plate 4005 for image display. The first resin base material 4001 transmits image light Ld emitted from the hologram layer 4002 and external light Lo transmitted through the second resin base material 4003 and the hologram layer 4002, which will be described later. There are no particular limitations on the thickness of first resin base material 4001. For example, first resin base material 4001 may have a thickness of 0.01 to 10 mm.

[0167] The material for forming the first resin substrate 4001 can be appropriately selected from the same materials as those in the first to third embodiments described above, and is not particularly limited as long as it is a transparent resin material. Examples of the material for forming the first resin substrate 4001 include polyolefin-based resins such as homopolymers or copolymers of olefins such as ethylene, propylene, or butene; amorphous polyolefin-based resins such as cyclic polyolefins; polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyamide-based resins such as nylon 6, nylon 66, nylon 12, and copolymer nylon; ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide-based resins, polyetherimide-based resins, polysulfone-based resins, polyethersulfone-based resins, and polyethersulfone-based resins. Examples of organic materials include ether ketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluororesins, poly(meth)acrylic resins, styrene resins such as polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinyl chloride, cellulose, acetyl cellulose, polyvinylidene chloride, polyphenylene sulfide, polyurethane, phenolic resins, epoxy resins, polyarylate resins, polynorbornene, styrene-isobutylene-styrene block copolymers (SIBS), allyl diglycol carbonate, and biodegradable resins. Note that first resin substrate 4001 may be formed of two or more materials, or may have a laminated structure in which two or more materials are laminated. Polycarbonate or poly(meth)acrylic resin is preferable from the viewpoint of transparency of first resin base material 4001. Furthermore, poly(meth)acrylic resin, epoxy resin, or cyclic polyolefin is preferable from the viewpoint of process resistance of first resin base material 4001.

[0168] The hologram layer 4002 is laminated on the surface of the first resin base material 4001 opposite to the surface on which the first absorption layer 4004 is formed. As described above, the configuration of the hologram layer 4002 is not particularly limited. An appropriate diffraction grating corresponding to the function required for the image display light-guiding plate 4005 is formed on the hologram layer 4002.

[0169] Second resin base material 4003 is laminated on the surface of hologram layer 4002 opposite to the surface on which first resin base material 4001 is disposed. Second resin base material 4003 may have the same configuration as that exemplified in the description of first resin base material 4001. However, the thickness, material, etc. of second resin base material 4003 may be different from those of first resin base material 4001. In particular, since second resin base material 4003 is disposed on the surface on the external light incident side, which is opposite to the display image exit side of image display light guide plate 4005, a material having a higher surface hardness than first resin base material 4001 may be used.

[0170] Such a light guide plate for image display 4005 can be manufactured, for example, as follows. A first resin base material 4001 and a second resin base material 4003 are prepared, and a coating liquid for forming a first absorption layer 4004 is prepared. For example, a coating liquid is applied to the surface of the first resin base material 4001. Thereafter, the coating liquid is cured to form the first absorption layer 4004. For example, a photopolymer material for forming a hologram is applied to the surface of the first resin base material 4001 opposite to the surface on which the first absorption layer 4004 is formed. At this time, a transparent sealing layer having the same thickness as the hologram layer 4002 may be provided on the outer periphery of the surface of the first resin base material 4001. In this case, the photopolymer material is applied to a recess formed and surrounded by the sealing layer. After the hologram layer 4002 is formed, the sealing layer seals the outer periphery of the hologram layer 4002. Thereafter, the second resin base material 4003 is placed on the photopolymer material. However, the above-described manufacturing order is an example. For example, the photopolymer material may be applied to the surface of the second resin base material 4003, and the first resin base material 4001 on which the first absorption layer 4004 is formed may be placed on the photopolymer material. Thereafter, a laminate consisting of the first absorption layer 4004, the first resin base material 4001, the photopolymer material, and the second resin base material 4003 is bonded together by a reduced pressure press. Thereafter, interference fringes corresponding to the diffraction pattern are formed in the photopolymer material of the laminate, forming a diffraction grating in the photopolymer material. In this way, the light guide plate for image display 4005 is manufactured.

[0171] Next, an example of a display device including the image display light guide plate 4005 will be described. 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.

[0172] As shown in FIG. 19, a display device 4010 includes an image light projection unit 4012 and an incident optical system 4011 in addition to a light guide plate 4005 for image display. The image light projection unit 4012 projects image light Li to be displayed on the image display light guide plate 4005 in response to an image signal sent from a controller (not shown). The incident optical system 4011 includes an optical element, such as a prism, that causes the image light Li to be incident on the light-guiding plate for image display 4005. The incident optical system 4011 causes the image light Li to be incident on an incident portion 4005a formed on the surface of the light-guiding plate for image display 4005. For example, the incident portion 4005a is provided on the first absorption layer 4004. The image light Li incident on the incident portion 4005a passes through the waveguide diffraction grating portion 4003a formed in 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 positions corresponding to each display pixel to form image light Ld. The image light Ld passes through the hologram layer 4002, the first resin base material 4001, and the first absorption layer 4004, and is emitted to the outside of the image display light guide plate 4005 as image light Ld'. Therefore, the display diffraction grating portion 4002b in the thickness direction and the regions of the first resin base material 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 the image light Ld. The display image output portion 4005b is formed at a position spaced apart from the input portion 4005a in the plane direction, which is a direction perpendicular to the thickness direction.

[0173] On the other hand, external light Lo is incident on the light guide plate 4005 for image display via the second resin base material 4003. The external light Lo passes through the second resin base material 4003, the hologram layer 4002, the first resin base material 4001, and the first absorption layer 4004, and is emitted to the outside of the light guide plate 4005 for image display as external light Lo'. A user of the display device 4010 can see an image based on the image light Ld' and the external light Lo'. Therefore, a user who has the display image output unit 4005b in their field of view sees an image in which the external scene based on the external light Lo' and the image based on the image light Ld' are superimposed on each other.

[0174] Transparent materials such as those used in image display light guide plate 4005 are subject to photodegradation over time due to the influence of, for example, ultraviolet light. Typical photodegradation is yellowing of the material. In particular, hologram layer 4002 is formed from a photopolymer material, and therefore yellows to some extent immediately after production. As a result, light that has passed through first resin base material 4001, second resin base material 4003, and hologram layer 4002 has a yellowish tint. Yellow has a high luminosity factor, so human vision is sensitive to yellowing. As a result, a yellowish image has low contrast (brightness / darkness), making the image unclear. However, in the fourth embodiment of the present invention, the first absorption layer 4004 is provided in the display image output portion 4005b, and therefore the yellow components of the image light Ld and the external light Lo are reduced in the image light Ld' and the external light Lo', respectively. In this way, the yellow components of the yellowish image light Ld and the external light Lo are canceled out by the first absorption layer 4004, thereby eliminating the influence of yellowing of the first resin base material 4001, the second resin base material 4003, and the hologram layer 4002. Specifically, the first absorption layer 4004 absorbs light, mainly light components in the wavelength range of 500 to 600 nm, thereby reducing the yellowish tint and relatively increasing the bluish tint, thereby improving the white balance and contrast of the image. Furthermore, even if the transparent materials such as the first resin base material 4001 and the second resin base material 4003 are photodegraded over time due to exposure to ultraviolet light, etc., when the display device 4010 is in use, the degree of image degradation due to yellowing is reduced compared to when the first absorption layer 4004 is not provided.

[0175] As described above, according to the fourth embodiment of the present invention, it is possible to provide a light guide plate for image display that can reduce the influence of yellowing of transparent materials on a displayed image.

[0176] In particular, in the fourth embodiment of the present invention, the first absorption layer 4004 is disposed at the outermost portion of the light guide plate for image display 4005. Therefore, for example, if a material having a higher hardness than the first resin base material 4001 is used for the first absorption layer 4004, scratches on the surface of the first resin base material 4001 can be prevented. For example, if the wavelength characteristics of the first absorption layer 4004 have a low transmittance for ultraviolet light, it is possible to suppress the incidence of ultraviolet light from the first resin base material 4001 side, thereby reducing photodegradation over time in the light guide plate for image display 4005.

[0177] <First Modification> A first modification of the fourth embodiment will be described. FIG. 20 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a first modified example of the fourth embodiment of the present invention.

[0178] As shown in FIG. 20, a light guide plate for image display 4007 of the first modified example of the fourth embodiment of the present invention further comprises a second absorption layer 4006 in addition to the light guide plate for image display 4005 of the basic example of the fourth embodiment of the present invention. The following description will focus on the differences from the basic example of the fourth embodiment of the present invention.

[0179] The second absorption layer 4006 is laminated on the surface of the second resin base material 4003 opposite to the surface on which the hologram layer 4002 is disposed. That is, like the first absorption layer 4004, the second absorption layer 4006 is disposed on the outermost side of the light guide plate for image display 4007. In the light guide plate for image display 4007, a laminate made up of the first resin base material 4001, the hologram layer 4002, and the second resin base material 4003 is sandwiched between the first absorption layer 4004 and the second absorption layer 4006. The second absorption layer 4006 has the same structure as that exemplified in the description of the first absorption layer 4004 . However, the thickness, material, etc. of the second absorption layer 4006 may be different from those of the first absorption layer 4004. For example, since the second absorption layer 4006 is disposed on the surface opposite to the display image output side of the image display light guide plate 4007, a material having a higher surface hardness than the second resin base material 4003 or the first absorption layer 4004 may be used. In the first modified example of the fourth embodiment of the present invention, since the first absorption layer 4004 and the second absorption layer 4006 are arranged on the outermost side of the light-guiding plate 4007 for image display, it is more preferable that the first absorption layer 4004 and the second absorption layer 4006 have low transmittance for ultraviolet light in their wavelength characteristics.

[0180] 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 base material 4003. The second absorption layer 4006 is formed by the same method as that for the first absorption layer 4004.

[0181] The light guide plate for image display 4007 according to the first modified example of the fourth embodiment of the present invention is configured similarly to the light guide plate for image display 4005, except that it has a second absorption layer 4006. Therefore, like the light guide plate for image display 4005, the image light Ld passes through the first absorption layer 4004, thereby reducing the yellow component (image light Ld'). In contrast, the external light Lo further passes through the second absorption layer 4006 before being incident on the second resin base material 4003. For this reason, the yellow component of the external light Lo is reduced when passing through the second absorption layer 4006. When the external light Lo passes through the second resin base material 4003, the hologram layer 4002, and the first resin base material 4001, the yellow component increases depending on the degree of yellowing of each, and then the yellow component is reduced by the first absorption layer 4004. The second resin base material 4003 is disposed on the side where external light Lo enters during use, and is therefore susceptible to photodegradation due to the external light Lo. As a result, over time, the second resin base material 4003 may yellow more easily than the first resin base material 4001. As the yellowing of the second resin base material 4003 progresses, the external light Lo that has passed through the second resin base material 4003 may have a stronger yellow component than the image light Ld that has not passed through the second resin base material 4003. However, in the first modified example of the fourth embodiment of the present invention, since the second absorption layer 4006 is provided, it is possible to offset the increase in yellowness due to the yellowing of the second resin base material 4003 by the second absorption layer 4006. As a result, 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 image display light-guiding plate 4005. As a result, it is possible to achieve a good balance between the yellowness of the image light Ld' and the external light Lo". In particular, when the second absorption layer 4006 has a low transmittance for ultraviolet light in its wavelength characteristics, the photodegradation of the second resin base material 4003 caused by the external light Lo can be reduced.

[0182] As described above, according to the first modified example of the fourth embodiment of the present invention, it is possible to provide a light guide plate for image display that can reduce the influence of yellowing of the transparent material on the displayed image.

[0183] <Second Modification> A second modification of the fourth embodiment will be described. FIG. 21 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a second modified example of the fourth embodiment of the present invention.

[0184] As shown in FIG. 21 , a light guide plate 4020 for an image display according to a second modified example of the fourth embodiment of the present invention further includes a first barrier layer 4008 and a second barrier layer 4009 in addition to the components of the light guide plate 4007 for an image display according to the first modified example. In the second modified example 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 layers." Furthermore, in the second modified example of the fourth embodiment of the present invention, the first resin base material 4001 and the second resin base material 4003 may be collectively referred to simply as "resin base materials." Furthermore, in the second modified example 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 "absorption layers." The following description will focus on the differences from the first modified example of the fourth embodiment of the present invention.

[0185] The first barrier layer 4008 is disposed between the first resin base material 4001 and the hologram layer 4002, and is in close contact with the surfaces of the first resin base material 4001 and the hologram layer 4002. The first barrier layer 4008 prevents gases permeating from the outside of the light guide plate for image display 4020 and from the first resin base material 4001 from permeating into the hologram layer 4002. The material of first barrier layer 4008 is not particularly limited as long as it can barrier gases that cause deterioration of hologram layer 4002. First barrier layer 4008 preferably contains a transparent inorganic material, and more preferably contains at least one inorganic material selected from the group consisting of silicon oxide, silicon nitride oxide, diamond-like carbon (DLC), aluminum oxide, and glass, similar to the barrier layer in the second embodiment described above. Furthermore, the barrier layer may be disposed on the resin film, and in this case, it is more preferable that the resin film is disposed between the barrier layer and the resin substrate. For example, the smaller the oxygen permeability and water vapor permeability of first barrier layer 4008, the more preferable. In particular, first barrier layer 4008 is more preferably made of a material with excellent water vapor barrier properties (low water vapor permeability). For example, the oxygen permeability of the first barrier layer 4008 is 1 cm 3 / m 2 · days or less may be used. For example, the water vapor transmission rate of the first barrier layer 4008 is 1 g / m 2 ·day or less. The water vapor transmission rate of the first barrier layer 4008 may be 0.5 g / m 2 ·day or less is preferable.

[0186] The inorganic material used for the first barrier layer 4008 may have a refractive index higher than that of the first resin base material 4001. For example, the refractive index of the first barrier layer 4008 may be 1.48 to 3.00. When the first barrier layer 4008 has a high refractive index, light passing through the first resin base material 4001 via the first barrier layer 4008 is incident from the optically dense first barrier layer 4008 to the optically coarse first resin base material 4001, and the exit angle of the light from the first barrier layer 4008 toward the first resin base material 4001 increases according to the difference in refractive index between the first barrier layer 4008 and the first resin base material 4001. This enables the FOV (Field Of View) of the image display light guide plate 4020 to be widened.

[0187] The material of the first barrier layer 4008 is as described above, but may also 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.

[0188] When first barrier layer 4008 is made of silicon oxide, its thickness may be 10 to 300 nm. If the thickness is less than 10 nm, moisture resistance may be insufficient. If the thickness is more than 300 nm, cracks may easily occur in the thin film of silicon oxide, and the thin film may peel off from the deposition surface. A particularly preferred layer thickness is 20 to 200 nm. There is no particular limitation on the method for forming first barrier layer 4008 using silicon oxide. For example, 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, the deposition surface may be subjected to a surface treatment such as corona discharge treatment or low-temperature plasma treatment, or may be coated with a silane coupling agent or a mixture of saturated polyester and isocyanate in order to improve adhesion between the deposition surface and the silicon oxide. For example, when forming a thin film of silicon oxide by vacuum deposition, silicon, silicon monoxide, silicon dioxide, or a mixture thereof is used as the evaporation material, and is heated and evaporated under a vacuum of 1.0 × 10-3 to 1.0 × 10-5 Torr using an electron beam, resistance heating, or high-frequency heating method. Alternatively, reactive vapor deposition can be performed while supplying oxygen gas. The silicon oxide forming first barrier layer 4008 may contain calcium, magnesium, or oxides thereof as impurities, as long as the amount is 10 mass % or less.

[0189] When the first barrier layer 4008 is made of silicon nitride oxide, the same structure as the first barrier layer 4008 containing silicon oxide as the main component is used, except that the silicon oxide is replaced with the silicon nitride oxide.

[0190] DLC is an amorphous carbon material generally consisting of a ternary structure consisting of a diamond-like structure, a graphite-like structure, and a polyethylene-like polymer structure containing hydrogen atoms. When a hydrocarbon such as ethylene, acetylene, or benzene is used as the carbon source to generate the DLC, the resulting structure is basically a ternary structure containing hydrogen atoms. The DLC has excellent hardness, lubricity, abrasion resistance, chemical stability, heat resistance, and surface smoothness. Because the DLC forms the dense polymer structure described above, it also has excellent gas barrier properties and water vapor barrier properties. There are no particular limitations on the method for forming the first barrier layer 4008 using DLC. As a coating method for the DLC, any known appropriate coating method can 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.

[0191] When the first barrier layer 4008 is made of aluminum oxide, the first barrier layer 4008 may be made of, for example, Al2O3 only, or may be made of a mixture of two or more selected from the group consisting of Al, AlO, and Al2O3. The atomic ratio of Al:O in the aluminum oxide layer varies depending on the conditions for producing the aluminum oxide layer. The aluminum oxide layer usable as the first barrier layer 4008 may contain trace amounts (up to 3% of the total components) of other components as long as the barrier performance is not impaired. The thickness of the aluminum oxide layer may be set according to the barrier performance required, and may be, for example, 5 to 800 nm. There is no particular limitation on the method for forming first barrier layer 4008 from aluminum oxide. For example, first barrier layer 4008 may be formed by a PVD (physical vapor deposition) method such as vacuum deposition, sputtering, or ion plating, or a CVD (chemical vapor deposition) method. For example, in vacuum deposition, Al, Al2O3, etc. are used as deposition source materials, and resistance heating, high-frequency induction heating, electron beam heating, etc. may be used as the deposition source heating method. In vacuum deposition, oxygen, nitrogen, water vapor, etc. may be introduced as a reactive gas, or reactive deposition using ozone addition or ion-assisted means may be used. Furthermore, a bias may be applied to the deposition surface, or the temperature of the deposition surface may be increased or cooled. The same applies to other deposition methods other than sputtering and other vacuum deposition methods, such as PVD and CVD.

[0192] When first barrier layer 4008 is made of glass, examples of the material for first barrier layer 4008 include borosilicate glass, alkali-free glass, low-alkali glass, soda-lime glass, sol-gel glass, and these glasses that have been subjected to heat treatment or surface treatment. From the viewpoint of avoiding coloration due to impurities, alkali-free glass is particularly preferable as the material for first barrier layer 4008.

[0193] When first barrier layer 4008 is made of glass, its thickness may be 10 to 200 μm. When the thickness is 10 μm or more, the mechanical strength and gas barrier properties tend to be excellent. The thickness is preferably 10 μm or more, and more preferably 30 μm or more. Furthermore, when the thickness is 200 μm or less, the optical properties as a light guide plate, such as light transmittance, tend to be excellent. The 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.

[0194] The method for forming the first barrier layer 4008 from glass is not particularly limited. For example, a slot downdraw method, a fusion method, or a float method can be used as the method for forming the first barrier layer 4008 from glass. Furthermore, commercially available glass may be used as is, or may be polished to a desired thickness before use. Examples of commercially available glass include "EAGLE2000" manufactured by Corning Incorporated, "AN100" manufactured by Asahi Glass Co., Ltd., "OA10G" manufactured by Nippon Electric Glass Co., Ltd., and "D263" manufactured by Schott Corporation.

[0195] Second barrier layer 4009 is laminated on the surface of hologram layer 4002 opposite to the surface of hologram layer 4002 on which first barrier layer 4008 is formed. The second barrier layer 4009 has the same configuration 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 those of the first barrier layer 4008.

[0196] Such a light guide plate 4020 for image display can be manufactured, for example, as follows. A first resin base material 4001 and a second resin base material 4003 are prepared, and a first barrier layer 4008 and a second barrier layer 4009 are respectively formed on the surfaces of the first resin base material 4001 and the second resin base material 4003. As a manufacturing method for the first barrier layer 4008 and the second barrier layer 4009, an appropriate manufacturing method is selected depending on the materials of the first barrier layer 4008 and the second barrier layer 4009. For example, a photopolymer material for forming a hologram is applied to the surface of first barrier layer 4008 of first resin base material 4001 on which first barrier layer 4008 has been formed. At this time, a transparent sealing layer having the same thickness as hologram layer 4002 may be provided on the outer periphery of first barrier layer 4008. In this case, the photopolymer material is applied to a recess formed by being surrounded by the sealing layer. The sealing layer seals the outer periphery of hologram layer 4002 after hologram layer 4002 has been formed. Thereafter, the second resin base material 4003 on which the second barrier layer 4009 has been formed is placed on the photopolymer material with the second barrier layer 4009 facing the photopolymer material. However, the above-described manufacturing order is merely an example. For example, a photopolymer material may be applied to the second resin base material 4003 on which the second barrier layer 4009 is formed, and then the first resin base material 4001 on which the first barrier layer 4008 is formed may be placed on the photopolymer material. Thereafter, a laminate consisting of the first absorption layer 4004, the first resin base material 4001, the first barrier layer 4008, the photopolymer material, the second barrier layer 4009, the second resin base material 4003, and the second absorption layer 4006 is bonded together by a vacuum press. Thereafter, interference fringes corresponding to the diffraction pattern are formed in the photopolymer material of the laminate, forming a diffraction grating in the photopolymer material. In this manner, the light guide plate for image display 4020 is manufactured.

[0197] The light guide plate for image display 4020 has the same structure as the light guide plate for image display 4007 of the first modified example, except that a first barrier layer 4008 and a second barrier layer 4009 are added. The first barrier layer 4008 and the second barrier layer 4009 are made of a transparent inorganic material such as DLC or silicon oxide, but they tend to absorb blue light in the wavelength range of 400 nm to 480 nm, which reduces the transmittance of the blue component and causes the transmitted light to take on a yellowish tint. As described above, the first barrier layer 4008 tends to increase the yellowness of the external light Lo and the image light Ld, and the second barrier layer 4009 tends to increase the yellowness of the external light Lo. However, similar to the first modification, the second modification of the fourth embodiment of the present invention includes the first absorption layer 4004 and the second absorption layer 4006. Therefore, by appropriately adjusting the wavelength characteristics of the first absorption layer 4004 and the second absorption layer 4006, it is possible to offset the increase in yellowness caused by the first barrier layer 4008 and the second barrier layer 4009. In other words, it is possible to reduce the yellowness of the external light Lo''' and the image light Ld'' emitted from the first absorption layer 4004. Furthermore, similar to the first modification, it is possible to achieve a good balance between the yellowness of the external light Lo''' and the image light Ld''.

[0198] As described above, according to the second modification of the fourth embodiment of the present invention, it is possible to provide a light guide plate for image display that can reduce the influence of yellowing of the transparent material on the displayed image.

[0199] Furthermore, according to light guide plate for image display 4020, since first barrier layer 4008 and second barrier layer 4009 are provided, deterioration of hologram layer 4002 over time can be suppressed.

[0200] The gas barrier properties of the first resin base material 4001 and the second resin base material 4003 are significantly lower than that of glass, although the degree of these properties varies depending on the type of resin material, and therefore the first resin base material 4001 and the second resin base material 4003 have higher moisture absorption and water vapor permeability than glass. As a result, gas outside the image display light guide plate 4005 passes through the first resin base material 4001 and the second resin base material 4003 to some extent and accumulates inside. In particular, moisture is likely to accumulate in the first resin base material 4001 and the second resin base material 4003. However, even if gas and moisture that have permeated into first resin base material 4001 and second resin base material 4003 from the outside diffuses within light guide plate for image display 4020, they are blocked by first barrier layer 4008 and second barrier layer 4009. This prevents gas and moisture from permeating into hologram layer 4002. For example, the permeation of moisture into the hologram layer 4002 is suppressed, thereby preventing the hologram layer 4002 from deteriorating. Furthermore, since light guide plate for image display 4020 has the above-described layer configuration, hologram layer 4002 is not in contact with first resin base material 4001 and second resin base material 4003. This prevents hologram layer 4002 from corroding first resin base material 4001 and second resin base material 4003 even if light guide plate for image display 4020 is placed in a high-temperature environment.

[0201] 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 base material 4001 and the second resin base material 4003, the exit angle of light traveling from the first barrier layer 4008 toward the first resin base material 4001 becomes larger, as described above. Similarly, the exit angle of light traveling from the second resin base material 4003 to the second barrier layer 4009 is narrowed. Therefore, light that enters from the outside on the second resin base material 4003 side and transmits through the image display light guide plate 4005 enters at a wider angle range than when the second barrier layer 4009 is not provided, and exits at a wider angle range than when the first barrier layer 4008 is not provided. As a result, the field of view of external light is wider, and the FOV on the display side is also wider. As for the image light from the hologram layer 4002, as described above, the angle of emission of light from the first barrier layer 4008 toward the first resin base material 4001 becomes larger, resulting in a wider FOV of the display screen compared to when the first barrier layer 4008 is not present. In particular, in the second variant of the fourth embodiment of the present invention, first barrier layer 4008 and second barrier layer 4009 are stacked on hologram layer 4002, so that the diffusion position of external light and image light and the diffraction position of hologram layer 4002 that constitutes the display screen are brought closer together. As a result, a clearer image can be observed from a wider range of angles than when first barrier layer 4008 and second barrier layer 4009 are provided at positions away from hologram layer 4002.

[0202] Here, a method for measuring the luminance value and FOV of the image display light guide plate 4020 will be briefly described. The luminance value of the light guide plate for image display 4020 is measured using a display device similar to the display device 4010 in the basic example of the fourth embodiment of the present invention described above, except that the light guide plate for image display 4005 is replaced with the light guide plate for image display 4020, and a luminance meter. In measuring the luminance value, the display device is placed in a position where the center of the display image output portion of the image display light guide plate 4020 faces the luminance meter on the measurement optical axis of the luminance meter. The distance between the display image output portion and the luminance meter corresponds to the position of the user's eyes when wearing the display device. For example, if the display device is a head-mounted display, the distance is set to 15 mm. The luminance value is the luminance measured by the luminance meter when a white image with maximum luminance is displayed on the display device.

[0203] In measuring the FOV of the light guide plate for image display 4020, the luminance is measured by tilting the measurement optical axis of the luminance meter with respect to the display image output portion while displaying a white image of maximum luminance on the display device. For example, the luminance meter is supported by the goniostage or the like so as to be swingable and tilted at an appropriate angle from a position perpendicular to the light guide plate for image display 4020. The FOV is calculated as the angle range where brightness equal to or greater than the threshold value is obtained, with the brightness corresponding to the disappearance of the white image being set as the threshold value. When brightness equal to or greater than the threshold value is obtained in the range from -θ1 to +θ2, the FOV is θ1+θ2. Here, the angle normal to the image display light-guiding plate 4020 is set to 0°.

[0204] <Third Modification> A third modification of the fourth embodiment will be described. FIG. 22 is a schematic cross-sectional view showing an example of a light guide plate for image display according to a third modified example of the fourth embodiment of the present invention.

[0205] As shown in FIG. 22, the light guide plate 4024 for image display of the third modified example is obtained by eliminating the first absorption layer 4004 of the light guide plate 4005 for image display of the basic example of the fourth embodiment of the present invention, and is provided with a first resin base material (absorption layer) 4021 and a second resin base material (absorption layer) 4023 instead of the first resin base material 4001 and the second resin base material 4003. The following description will focus on the differences from the basic example of the fourth embodiment of the present invention.

[0206] The first resin base material (absorption layer) 4021 comprises a base resin similar to that of the first resin base material 4001, and a color material dispersed in the base resin. The coloring material contained in the first resin base material (absorbing layer) 4021 is the same as that contained in the first absorbing layer 4004 in the basic example of the fourth embodiment of the present invention. The blending amount of the coloring material is set so that the first resin base material (absorbing layer) 4021 has the same light absorption properties as the first absorbing layer 4004 in the basic example of the fourth embodiment of the present invention. The second resin base material (absorbent layer) 4023 is configured in the same manner as the first resin base material (absorbent layer) 4021.

[0207] The light guide plate 4024 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 the first resin substrate (absorption layer) 4021 and the second resin substrate (absorption layer) 4023 prepared in the substrate preparation process are molded using materials in which coloring material is kneaded into the respective base resins, and the absorption layer formation process is not performed.

[0208] The light guide plate for image display 4024 is an example in which the absorbing layer is formed by a first resin base material (absorbing layer) 4021 and a second resin base material (absorbing layer) 4023. According to the light guide plate for image display 4024, the first resin base material (absorption layer) 4021 and the second resin base material (absorption layer) 4023 are absorption layers, so that the yellowish color of external light and image light can be reduced in the same way as in the first modified example.

[0209] As described above, according to the third modification of the fourth embodiment of the present invention, it is possible to provide a light guide plate for image display that can reduce the influence of yellowing of the transparent material on the displayed image.

[0210] In the basic example and each modified example of the fourth embodiment of the present invention, the absorbing layer is disposed on the outermost part of the light-guiding plate for image display. However, the absorbing layer can reduce the yellowish tint of the light emitted from the light-guiding plate for image display wherever it is disposed on the optical paths of the external light Lo and the image light Ld.

[0211] In the basic example and each modified example of the fourth embodiment of the present invention, the absorbing layer is in contact with the resin substrate. However, the absorbing layer may be laminated on a transparent resin film. In this case, for example, the absorbing layer can be formed on the resin film and then fixed to the placement surface via an adhesive or the like, which makes it easier to form the absorbing layer.

[0212] In the second modified example, a barrier layer is disposed on both the front and back surfaces of the hologram layer. However, for the purposes of blocking moisture and the like that may penetrate 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. However, in this case, if the transparent layer sandwiched between the barrier layer and the hologram layer has high hygroscopicity, moisture may penetrate through the side surfaces of the transparent layer. Therefore, it is more preferable that the transparent layer between the barrier layer and the hologram layer be made of a material with low hygroscopicity. If the transparent layer between the barrier layer and the hologram layer has hygroscopicity, it is more preferable that the thickness of the transparent layer be thin. In this case, the exposed area of ​​the side surfaces that serve as a moisture penetration port is reduced, thereby reducing the amount of moisture absorbed.

[0213] In the second modified example, the barrier layer is in contact with the hologram layer and the resin substrate. However, the barrier layer may be laminated on a transparent resin film. In this case, the barrier layer can be formed on the resin film and then fixed to the resin substrate via an adhesive or the like, which makes it easier to form the barrier layer. [Example]

[0214] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples described below, and various modifications are possible as long as they do not deviate from the gist of the present invention.

[0215] [Examples and Comparative Examples of the First Embodiment (Examples 1 to 3, Comparative Examples 1 to 3)] Examples and comparative examples of the first embodiment will be described below. Table 1 below shows the configurations of the resin substrates used in Examples 1 to 3 and Comparative Examples 1 to 3 and the evaluation results.

[0216] [Table 1]

[0217] Mitsubishi Chemical...Mitsubishi Chemical Corporation Kuraray...Kuraray Co., Ltd. Sumitomo Chemical...Sumitomo Chemical Co., Ltd. Asahi Kasei...Asahi Kasei Corporation Acrylite, Comoglass, Sumibex and Delaglass are registered trademarks of their respective companies.

[0218] Example 1 Example 1 is an example corresponding to the light guide plate for image display 1004 of the basic example of the first embodiment. As shown in Table 1, acrylic resin (PMMA) is used as the material for the first resin base material 1001 and the second resin base material 1003 (referred to as "resin base material" in Table 1). The thickness of each of the first resin base material 1001 and the second resin base material 1003 is 1 mm. The hologram layer 1002 is common to all Examples and Comparative Examples. The material for the hologram layer 1002 is a photosensitive material for the hologram, which is a mixture of 100 parts by mass of bisphenol-based epoxy resin jER1007 (polymerization degree n=10.8, epoxy equivalent: 1750-2200, product name: 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 in 100 parts by mass of 2-butanone. The thickness of the hologram layer 1002 is 5 μm. The planar size of the hologram layer 1002 is 50 mm × 50 mm.

[0219] (Substrate manufacturing process) The first resin base material 1001 and the second resin base material 1003 of Example 1 are produced as follows. 100 parts of MMA (methyl methacrylate) are placed in a reactor (polymerization vessel) equipped with a condenser, thermometer, and stirrer and stirred. Nitrogen gas is bubbled into the vessel, and heating is then initiated. 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 at this temperature for 10 minutes. The reactor is then cooled to room temperature to obtain a syrup. The polymerization rate of the syrup is approximately 20% by mass. Thereafter, 0.2 parts by mass of t-hexyl peroxypivalate and 0.01 parts by mass of dioctyl sodium sulfosuccinate are added to the syrup and completely dissolved at room temperature to form a polymerizable raw material. 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.

[0220] Here, the continuous polymerization apparatus used in this example will be described. FIG. 8 is a schematic vertical cross-sectional view showing an example of a resin substrate manufacturing apparatus according to the first embodiment. As shown in FIG. 8, a continuous polymerization apparatus 1100 has a pair of upper and lower endless belts 1101 and 1102 arranged thereon. The endless belts 1101 and 1102 are tensioned by main pulleys 1103, 1104, 1105, and 1106, respectively, and are driven to run at the same speed. A plurality of carrier rolls 1107 are arranged on the inner periphery of each of the endless belts 1101 and 1102. The carrier rolls 1107 face each other, sandwiching the opposing endless belts 1101 and 1102 therebetween. Each carrier roll 1107 horizontally supports the running endless belts 1101 and 1102 and applies a line load to the belt surface at least once from a direction perpendicular to the belt running direction of the endless belts 1101 and 1102 (from left to right in the figure) and perpendicular to the belt surface. The linear load may be 0.001 to 10.0 kg / cm, and more preferably 0.01 kg / cm or more. The more times the linear load is applied, the more preferable. The more times the linear load is applied, the more improved the flatness of the resulting resin substrate. For example, it is more preferable that the linear load be applied 10 times or more.

[0221] A raw material injector 1114 provided in the continuous polymerization apparatus 1100 supplies a polymerizable raw material between the endless belts 1101 and 1102. The ends of the endless belts 1101 and 1102 are sealed by two elastic gaskets 1112. As the endless belts 1101 and 1102 travel, the polymerizable raw material is heated by hot water spray 1109 in first polymerization zone 1108 and polymerized. The polymerizable raw material is further heated by a hot air heater in second polymerization zone 1110, which is provided downstream in the direction of belt travel, to complete the polymerization. The polymerizable raw material is cooled in downstream cooling zone 1111, which is provided further downstream in the direction of belt travel, and then taken out as a plate-like polymer 1113.

[0222] The specific production conditions for the polymerizable raw material of Example 1 described above are as follows. In the continuous polymerization apparatus 1100, the gap between the belt surfaces of the endless belts 1101 and 1102 at the portion where the polymerizable raw material is supplied from the raw material injector 1114 is adjusted to 1.6 mm, and the gap is continuously adjusted so that the final thickness of the plate-like polymer is 1 mm at the portion where the polymerization is completed and the plate-like polymer is removed. The line load applied 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. Hot water is continuously sprayed onto the inner circumferential surfaces of the endless belts 1101 and 1102 while the polymerizable raw material is staying in the first polymerization zone 1108. The residence time of the polymerizable raw material in the first polymerization zone 1108 is 40 minutes. In the second polymerization zone 1110, hot air at a temperature of 120° C. is blown onto the inner peripheral surface of the belt from a hot air heater, and polymerization is completed under the condition that the residence time of the polymerizable raw material is 10 minutes. In this way, a plate-like polymer 1113 having a thickness of 1 mm is obtained.

[0223] Evaluation sample 1A of first resin base material 1001 and second resin base material 1003 was formed by cutting plate-like polymer 1113 into a 200 mm × 200 mm rectangle. Evaluation sample 1A was used for measuring the MC value, arithmetic mean roughness Ra, and thermal shrinkage, which will be described later. Evaluation sample 1B is formed by cutting plate-like polymer 1113 into a 60 mm x 60 mm rectangle. Evaluation sample 1B is used to form light guide plate 1004 for image display and to perform image evaluation (described later) of light guide plate 1004 for image display.

[0224] Next, a description will be given of a manufacturing process of the light guide plate 1004 for image display in Example 1. The light guide plate 1004 for image display is manufactured by carrying out a substrate preparation process and a light guide plate manufacturing process, which will be described below, in this order.

[0225] (Substrate preparation process) In the substrate preparation step, the evaluation sample 1B made of acrylic resin and measuring 60 mm×60 mm×thickness 1 mm obtained in the substrate manufacturing step is washed and dried. Evaluation sample 1B is ultrasonically cleaned for 5 minutes while immersed in a 5% aqueous solution of a neutral detergent, Semiclean (registered trademark) M-LO (trade name; manufactured by Yokohama Yushi Kogyo Co., Ltd.). After this, evaluation sample 1B is ultrasonically cleaned for 5 minutes while immersed in ultrapure water. Evaluation sample 1B is then rinsed with ultrapure water, air-dried, and then dried in a nitrogen atmosphere in an oven at 100°C. After this, the air-dried evaluation sample 1B is UV ozone cleaned for 1 minute in a UV ozone cleaner. This completes the substrate preparation process.

[0226] (Light guide plate manufacturing process) In the light guide plate manufacturing process, the light guide plate for image display 1004 is manufactured using two sheets of evaluation sample 1B. A sealing layer having a width of 5 mm and a thickness of 5 μm is applied to the periphery of one of the evaluation samples 1B. The sealing layer is made of a transparent material and is not particularly limited as long as it is a material that can bond the evaluation samples 1B together. In Example 1, an epoxy resin or a silicone resin is used. This prepares an acrylic substrate with a stepped sealing layer, the opening of which is surrounded by the sealing layer and measures 50 mm x 50 mm. After this, an acrylic photosensitive material is applied onto the acrylic substrate by spin coating as a photopolymer material for the hologram, so that the thickness of the acrylic photosensitive material after drying is 5 μm. Thereafter, the other evaluation sample 1B is laminated on the sealing layer and the acrylic photosensitive material, and press-laminated under reduced pressure at an absolute pressure of 5 kPa, a temperature of 70° C., and a pressing pressure of 0.04 MPa. After this, a diffraction grating is recorded in the photopolymer material of the press-bonded laminate. During this process, the temperature of the laminate is maintained at 20°C. The diffraction grating is formed by irradiating the laminate with two laser beams and adjusting the irradiation angle and intensity of each to form interference fringes so that the required diffraction pattern is formed. This records the diffraction grating in the photopolymer material. A specific diffraction grating is a color display diffraction grating that diffracts light in the red, green, and blue wavelength regions that is incident as image light into the incident portion and outputs it from the display image output portion at positions corresponding to the pixels of the image light. After this, while the laminate is kept at 20°C, ultraviolet light (wavelength 365 nm, irradiance 80 W / cm2) is irradiated onto one side of the laminate for 30 seconds. A high-pressure mercury lamp is used as the light source for the ultraviolet light. As a result, the acrylic photosensitive material is hardened, and the light guide plate for image display 1004 of the first embodiment is formed.

[0227] <Example 2> Example 2 is an example corresponding to the light guide plate for image display 1014 of the first modified example of the first embodiment. As shown in Table 1, Example 2 is the same as Example 1 except that a hard coat is applied to both sides of the first resin base material 1001 in the thickness direction. Evaluation sample 1A of Example 2 is formed by applying a hard coat, which will be described later, to both sides of evaluation sample 1A of Example 1 in the thickness direction. Evaluation sample 1B of Example 2 is produced in the same manner as in Example 1, except that evaluation sample 1A of Example 2 is used instead of evaluation sample 1A of Example 1. Therefore, unlike the embodiment shown in Fig. 7 of the first modified example, a first hard coat layer 1011A and a second hard coat layer 1011B are also laminated on the second resin base material 1003. The following describes the substrate manufacturing process of the second embodiment, focusing on the differences from the first embodiment.

[0228] (Substrate manufacturing process) The abbreviations used below are explained below. "C6DA" means 1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Ltd., trade name: Viscoat #230). "U6HA" refers to a urethane compound obtained by reacting 1 mole of triisocyanate obtained by trimerizing hexamethylene diisocyanate with 3 moles of 3-acryloyloxy-2-hydroxypropyl methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK Oligo U-6HA). "M305" refers to a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Toagosei Co., Ltd., trade name: Aronix (registered trademark) M-305).

[0229] A hard coat liquid is prepared by mixing 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. This hard coat liquid is applied to a thickness of 20 μm on the endless belts 1101 and 1102 of the continuous polymerization device 1100. After this, the hard coat liquid is applied to the endless belts 1101 and 1102 at an irradiance of 120 W / cm 2 The hard coat is formed on the endless belt by irradiating the hard coat liquid with ultraviolet light using a high-pressure mercury lamp. Polymerization of the resin substrate is carried out in the same manner as in Example 1, except that a hard coat is formed on the endless belts 1101 and 1102, thereby obtaining a plate-shaped polymer 1113 having a thickness of 1 mm and a hard coat laminated on its surface.

[0230] Evaluation samples 1A and 1B of Example 2 are formed from the plate-like polymer 1113 of Example 2 in the same manner as Example 1.

[0231] Example 3 Example 3 is an example corresponding to the light guide plate for image display 1004 of the basic example of the first embodiment. As shown in Table 1, Example 3 is the same as Example 1, except that a cut and polished acrylic plate is used as the resin substrate. The resin substrate in Example 3 is a 2 mm thick continuous cast acrylic plate, Acrylite (registered trademark) L, which is cut and polished to a thickness of 1 mm.

[0232] <Comparative Examples 1 to 3> As shown in Table 1, Comparative Examples 1 to 3 are similar to Example 1 except that a pre-made extruded acrylic plate is used as the resin substrate. Therefore, the substrate manufacturing process for each comparative example is carried out by extrusion molding that differs depending on the manufacturer. The resin substrate in Comparative Example 1 is an extruded acrylic plate having a thickness of 3 mm, COMOGLASS (registered trademark) P (product name; manufactured by Kuraray Co., Ltd.). The resin substrate in Comparative Example 2 is Semipex (registered trademark) E (product name; manufactured by Sumitomo Chemical Co., Ltd.), an extruded acrylic plate having a thickness of 3 mm. The resin substrate in Comparative Example 3 is an extruded acrylic plate having a thickness of 3 mm, Delaglass (registered trademark) A (product name; manufactured by Asahi Kasei Corporation). In each comparative example, evaluation samples 1A and 1B having the same shape as in Example 1 except for the thickness of 3 mm were prepared. The light guide plate manufacturing process in each comparative example is carried out in the same manner as in Example 1, except that evaluation sample 1B in each comparative example is used.

[0233] <Evaluation method> Next, there will be explained the evaluation methods for Examples 1 to 3 and Comparative Examples 1 to 3. The evaluations carried out were the MC value, Ra, thermal shrinkage rate, and clarity of the displayed image.

[0234] (MC value) The MC value is evaluated by the evaluation method described in the "Mode for Carrying Out the Invention" of this specification. As the measurement sample S, the evaluation sample 1A of each example and each comparative example is used. As specific evaluation conditions, the distances d1 and d2 are each 1 m, and the elevation angle θA is 20°. Since Comparative Examples 1 to 3 have gear marks, the evaluation sample 1A of each comparative example is placed in the evaluation device 1200 with the gear mark facing the Y direction. In contrast, no gear marks are observed in Examples 1 to 3. However, in order to align the directionality during production, the evaluation sample 1A of each Example was arranged so that the direction perpendicular to the running direction in the continuous polymerization apparatus 1100 was oriented in the Y direction. The measurement range of the brightness distribution is a rectangular area with a vertical width of 180 mm and a horizontal width of 80 mm, with the Y direction in the arrangement of evaluation sample 1A in evaluation device 1200 being the horizontal direction (the direction in which line segments AD and BC extend) and the direction perpendicular to the horizontal direction on evaluation sample 1A being the vertical direction (the direction in which line segments AB and DC extend). The measurement ranges are set at 41 locations, shifted by 2 mm in the horizontal direction, on the measurement sample S. In each measurement range, the measurement lines are selected so as to divide the measurement range into 40 equal parts in the horizontal direction. Table 1 lists the maximum MC values ​​found from the brightness distribution of each measurement line in each measurement range.

[0235] (Ra) In the evaluation of Ra, the arithmetic mean roughness Ra of the surface of each evaluation sample 1A is measured. The measuring device used was a white light interferometer surface profiler, Zygo NewView (registered trademark). The objective lens used was a 6300 (trade name, manufactured by Zygo Corporation). The magnification of the objective lens used was 2.5 times. The observation area was a rectangular area of ​​2.8 mm x 2.1 mm.

[0236] (Thermal shrinkage rate) The thermal shrinkage rate is evaluated by measuring the dimensional change (shrinkage) in accordance with Appendix A of JIS K 6718:2015, "Measurement of dimensional change (shrinkage) upon heating."

[0237] (Image clarity) The light guide plates for image display in Examples 1 to 3 and Comparative Examples 1 to 3 are attached to an image display device. The image display device is provided with an optical system that causes image light to be displayed to enter the incident portion of the light guide plate for image display 1004, a driving power source, and a circuit system that supplies image information and the like to obtain the image light. The input images used for the evaluation are a white image and a character display image. The evaluation was carried out by visually judging the appearance of a white image and a character image, with the characters "ABCDE" displayed within a size of 10mm x 100mm. If no rainbow color is visible in the white image and the characters are clearly visible in the character display image, the image is judged as good (marked "A" in Table 1). If a slight rainbow color is visible in the white image, but the characters are clearly visible in the character display image, the image is judged as fair (marked as "B" in Table 1). If rainbow colors are visible in at least part of the white image and the outlines of the characters appear blurred in the character display image, the image is judged as "no good" (marked "C" in Table 1).

[0238] <Evaluation results> As shown in Table 1, the MC values ​​of Examples 1 to 3 were 0.074, 0.103, and 0.060, respectively, all of which were less than 0.120. In contrast, the MC values ​​of Comparative Examples 1 to 3 were 0.126, 0.183, and 0.148, respectively, all of which were greater than 0.120. In Examples 1 to 3, no gear marks were observed, and the corresponding MC values ​​were less than 0.120. The reason for this is thought to be that the resin substrates in each Example were manufactured by a continuous casting method or by cutting and polishing. In the continuous casting method, the surface shape of, for example, the endless belts 1101 and 1102 is transferred to the surface of the raw material of the resin substrate in each Example. Therefore, the surface flatness of the resin substrate becomes equivalent to the flatness of the endless belts 1101 and 1102. In cutting and polishing, the surface flatness of the resin substrate can be made extremely high. In contrast, gear marks are observed in Comparative Examples 1 to 3, which is thought to be the reason for the increased MC value. The reason for the formation of gear marks in Comparative Examples 1 to 3 is thought to be, for example, large unevenness in the driving of the rolls that come into contact with the extrusion material in the extruder.

[0239] The arithmetic mean roughness Ra of Examples 1 to 3 was 4.9 nm, 4.7 nm, and 2.6 nm, respectively, all of which were less than 10 nm. In contrast, the Ra of Comparative Examples 1 to 3 was 5.5 nm, 2.9 nm, and 2.3 nm, respectively, all of which were less than 10 nm. Therefore, with regard to smoothness represented by Ra, there was no significant difference between Examples 1 to 3 and Comparative Examples 1 to 3.

[0240] The heat shrinkage rates of Examples 1 to 3 are all less than 3%. In contrast, the heat shrinkage rates of Comparative Examples 1 to 3 are all 3% or more. The reason for this is thought to be that the resin substrates of Comparative Examples 1 to 3 were produced by extrusion molding, which caused strain to accumulate in the resin substrates.

[0241] The clarity of the displayed image in Examples 1 to 3 was all judged to be "good (A)." In contrast, the clarity of the displayed image in Comparative Examples 1 to 3 was all judged to be "poor (C)." The reason for this is thought to be that the MC values ​​in Comparative Examples 1 to 3 were larger than those in the Examples, which resulted in a disturbance in the diffraction direction of the image light, etc. For example, the resin substrates of Comparative Examples 2 and 3 have smaller Ra than those of Examples 1 and 2, and therefore are superior in smoothness to those of Examples 1 and 2. However, this is thought to be because flatness (i.e., MC value) contributes significantly to the clarity of the displayed image. At least, if Ra is 10 nm or less, it is thought that the magnitude of Ra does not make a significant difference in clarity.

[0242] [Example of the second embodiment] An example of the second embodiment will be described below. The following Tables 2A to 2C show the configurations of the resin substrates and barrier layers used in Examples 4 to 7 and 12 to 21, as well as the evaluation results.

[0243] [Table 2A]

[0244] [Table 2B]

[0245] In the "auxiliary layer" column of Table 2B, "EVOH-based" represents "ethylene vinyl alcohol-based" and "F-based" represents "fluorine-based."

[0246] [Table 2C]

[0247] Example 4 Example 4 is an example corresponding to the light guide plate for image display 2006 of the basic example of the second embodiment. As shown in Table 2A, acrylic resin (PMMA) is used as the material for first resin base material 2001 and second resin base material 2005 (referred to as "resin base material" in Table 2A). The first resin base material 2001 and the second resin base material 2005 are both rectangular plates measuring 60 mm×60 mm×1 mm. In this example, the first barrier layer 2002 and the second barrier layer 2004 (referred to as "barrier layer" in Table 2B) are DLC films with a layer thickness of 40 nm. The hologram layer 2003 is common to Examples 4 to 7 and 11 to 20. The material for the hologram layer 2003 is a photosensitive material for the hologram, which is a mixture of 100 parts by mass of bisphenol-based epoxy resin jER (registered trademark) 1007 (polymerization degree n = 10.8, epoxy equivalent: 1750 to 2200, product name of 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 in 100 parts by mass of 2-butanone. The thickness of the hologram layer 2003 is 5 μm. The planar size of the hologram layer 2003 is 50 mm × 50 mm.

[0248] Next, a description will be given of the manufacturing process of the light guide plate for image display 2006 in Example 4. The light guide plate for image display 2006 is manufactured by carrying out a substrate preparation process, a barrier layer formation process, and a light guide plate manufacturing process, which will be described below, in this order.

[0249] (Substrate preparation process) The substrate preparation step involves cleaning and drying the first resin base material 2001 and the second resin base material 2005. Hereinafter, when there is no need to distinguish between the first resin base material 2001 and the second resin base material 2005, the reference numerals will be omitted and they will simply be referred to as resin base materials. The resin substrate is ultrasonically cleaned for 5 minutes while immersed in a 5% aqueous solution of a neutral detergent, Semiclean (registered trademark) M-LO (trade name; manufactured by Yokohama Yushi Kogyo Co., Ltd.). The resin substrate is then ultrasonically cleaned for 5 minutes while immersed in ultrapure water. The resin substrate is then rinsed with ultrapure water, air-dried, and then dried in a nitrogen atmosphere in an oven at 100°C. The air-dried evaluation sample 2B is then UV-ozone cleaned for 1 minute in a UV-ozone cleaner. This completes the substrate preparation process.

[0250] (Barrier layer formation process) In the barrier layer forming step, a DLC film is formed on the surface of the resin substrate. Space volume 350cm 3 The resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a high-frequency power source (13.56 MHz), an internal electrode (φ10 mm) (also serving as a gas inlet tube, with a tip aperture of φ1 mm), and the apparatus is then evacuated. After the pressure in the plasma chemical vapor deposition apparatus reaches 15 Pa, a 2:1 mixture of high-purity acetylene and tetramethylsilane is introduced at a flow rate of 45 sccm, and a 40 nm thick DLC film is formed under the conditions of a plasma generation setting power of 100 W and a film formation time of 0.8 seconds. This completes the barrier layer forming process. Hereinafter, the resin substrate on which the barrier layer is formed will be referred to as an intermediate laminate.

[0251] (Light guide plate manufacturing process) In the light guide plate manufacturing process, the light guide plate for image display 2006 is manufactured using two intermediate laminates. A sealing layer having a width of 5 mm and a thickness of 5 μm is applied to the peripheral edge of the barrier layer of one of the intermediate laminates. The sealing layer is made of a transparent material and is not particularly limited as long as it is a material that can bond the barrier layers of the intermediate laminate to each other. In Example 3, the optical adhesive Hardlock (registered trademark) OP-1045K (product name; manufactured by Denki Kagaku Kogyo Co., Ltd.) is used. This prepares an intermediate laminate with a stepped seal layer, the opening of which is surrounded by the seal layer and measures 50 mm x 50 mm. After this, the above-mentioned photosensitive material is applied as a photopolymer material for a hologram onto this intermediate laminate by spin coating, so that the thickness of the photosensitive material after drying is 5 μm. Thereafter, the other intermediate laminate is laminated on the seal layer and the photosensitive material so that its barrier layer faces the barrier layer of the intermediate laminate with the seal layer, and they are press-laminated under reduced pressure at an absolute pressure of 5 kPa, a temperature of 70°C, and a press pressure of 0.04 MPa. After this, a diffraction grating is recorded on the photosensitive material of the press-bonded laminate. During this process, the temperature of the laminate is maintained at 20°C. The diffraction grating is formed by irradiating the laminate with two laser beams and adjusting the irradiation angle and intensity of each to form interference fringes so that the required diffraction pattern is formed. This records the diffraction grating on the photosensitive material. A specific diffraction grating is a color display diffraction grating that diffracts light in the red, green, and blue wavelength regions that is incident as image light on the incident portion and emits it from the display portion at positions corresponding to the pixels of the image light. After this, while the laminate is kept at 20°C, ultraviolet light (wavelength 365 nm, irradiance 80 W / cm2) is irradiated onto one side of the laminate for 30 seconds. A high-pressure mercury lamp is used as the light source for the ultraviolet light. As a result, the sealing layer is hardened, and the light guide plate for image display 2006 of the third embodiment is formed.

[0252] <Example 5> Example 5 has the same configuration as Example 4, except that each DLC film is made of silicon oxide and has a thickness of 10 nm. The following describes the substrate manufacturing process of the fifth embodiment, focusing on the differences from the fourth embodiment. The light guide plate for image display 2006 of Example 5 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described below, and the same light guide plate manufacturing process as in Example 4 in this order.

[0253] (Barrier layer formation process) In the barrier layer forming step of this embodiment, a silicon oxide thin film layer is formed on the surface of the resin substrate. After the resin substrate is placed in the vacuum deposition apparatus, silicon oxide is vacuum deposited. The ultimate vacuum in the chamber of the vacuum deposition apparatus is 1.0 × 10 -4 Torr. Under this vacuum, silicon monoxide with a purity of 99.9% is heated and evaporated using high-frequency induction heating to form a 50-nm-thick silicon oxide thin film on the surface of the resin substrate. This results in an intermediate laminate with a silicon oxide thin film layer formed on it. This completes the barrier layer forming process.

[0254] The light guide plate manufacturing process of this example is the same as the light guide plate manufacturing process of Example 4 except that the intermediate laminate formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0255] <Examples 6 and 7> As shown in Table 2A, Examples 6 and 7 are similar to Example 5 except for the placement of the barrier layer. Fig. 12 is a schematic cross-sectional view showing a light guide plate for image display of Example 6. Fig. 13 is a schematic cross-sectional view showing a light guide plate for image display of Example 7. The following description will focus on the differences from the fifth embodiment.

[0256] As shown in FIG. 12, the light guide plate for image display 2101 of Example 6 has a first barrier layer 2002, a first resin base material 2001, a hologram layer 2003, a second resin base material 2005, and a second barrier layer 2004 laminated in this order. As the first barrier layer 2002 and the second barrier layer 2004, a silicon oxide thin film layer having a thickness of 50 nm, similar to that in the fifth embodiment, is used. To manufacture the light guide plate 2101 for image display, an intermediate laminate is formed in the same manner as in Example 5. Thereafter, a seal layer is provided on the resin substrate of one of the intermediate laminates, and after applying a photosensitive material, the other intermediate laminate is laminated so that the resin substrates face each other. Thereafter, the light guide plate 2101 for image display is manufactured by carrying out vacuum pressing and forming a diffraction grating in the same manner as in Example 5.

[0257] As shown in FIG. 13, the light guide plate 2102 for image display of Example 7 is the same as that of Example 6, except that a third barrier layer 2032 is provided to cover the entire side surface (the outer peripheral surface in a direction perpendicular to the thickness direction) of the light guide plate 2101 for image display of Example 6. The third barrier layer 2032 is made of a silicon oxide thin film layer similar to the first barrier layer 2002 of the sixth embodiment. The light guide plate for image display 2102 is manufactured by manufacturing the light guide plate for image display 2101 and then forming a silicon oxide thin film layer on the side surface of the light guide plate for image display 2101.

[0258] Example 12 Example 12 has the same configuration as Example 4, except that each DLC film is made of alumina and has a thickness of 40 nm. The following describes the substrate manufacturing process of Example 12, focusing on the differences from Example 4. The light guide plate for image display 2006 of Example 12 is manufactured by carrying out the same substrate preparation step as in Example 4, the barrier layer formation step described below, and the light guide plate manufacturing step of Example 4 in this order.

[0259] (Barrier layer formation process) In the barrier layer forming step of this embodiment, an alumina film is formed on the surface of the resin substrate. A resin substrate and an appropriate amount of alpha alumina particles with a purity of 99.999% and a particle size of 2 mm were placed in an electron beam evaporation device, and the device was evacuated to a vacuum. The distance from the evaporation source to the shutter was approximately 8 cm, and the distance from the evaporation source to the surface of the resin substrate was approximately 35 cm. The pressure in the electron beam evaporation equipment is 3×10 -3After the pressure reaches 100 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 walls inside the device reaches 50°C, the shutter is closed and the electron beam filament current is stopped. After cooling to below 30°C, the electron beam filament current is increased to approximately 35 mA to heat the evaporation 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.

[0260] The light guide plate manufacturing process of this example is the same as the light guide plate manufacturing process of Example 4 except that the intermediate laminate formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0261] Example 13 Example 13 has the same configuration as Example 4, except that each DLC film is made of silicon oxide and has a thickness of 70 nm. The following describes the substrate manufacturing process of Example 13, focusing on the differences from Example 4. The light guide plate for image display 2006 of Example 13 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described below, and the same light guide plate fabrication process as in Example 4 in this order.

[0262] (Barrier layer formation process) In this example, a silicon oxide film is formed on the surface of a resin substrate. The resin substrate is placed in a plasma-enhanced chemical vapor deposition (PECVD) system equipped with a high-frequency power supply (13.56 MHz), and the system is evacuated to a vacuum. After the pressure in the PECVD system reaches 1 Pa, tetraethoxysilane (TEOS) gas, generated by bubbling with helium gas, is introduced at a flow rate of 6 sccm, and oxygen gas is introduced at a flow rate of 95 sccm. A silicon oxide film with a thickness of 70 nm is formed at a plasma generation power setting of 250 W. This completes the barrier layer forming process.

[0263] The light guide plate manufacturing process of this example is the same as the light guide plate manufacturing process of Example 4 except that the intermediate laminate formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0264] Example 14 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. The following describes the substrate manufacturing process of Example 14, focusing on the differences from Example 4. The light guide plate 2006 for image display of Example 14 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described below, and the same light guide plate fabrication process as in Example 4 in this order.

[0265] (Barrier layer formation process) In this example, a silicon oxide film is formed on the surface of a resin substrate. The resin substrate is placed in a plasma-enhanced chemical vapor deposition (PECVD) system equipped with a high-frequency power supply (13.56 MHz), and the system is evacuated to a vacuum. After the pressure in the PECVD system 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. A silicon oxide film with a thickness of 140 nm is formed at a plasma generation power setting of 250 W. This completes the barrier layer forming process.

[0266] The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4 except that the intermediate laminate formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0267] Example 15 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. The following describes the substrate manufacturing process of Example 15, focusing on the differences from Example 4. The light guide plate for image display 2006 of Example 15 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described below, and the same light guide plate fabrication process as in Example 4 in this order.

[0268] (Barrier layer formation process) In this example, a silicon oxide film is formed on the surface of a resin substrate. The resin substrate is placed in a plasma-enhanced chemical vapor deposition (PECVD) system equipped with a high-frequency power supply (13.56 MHz) and evacuated. After the pressure in the PECVD system 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. A silicon oxide film with a thickness of 170 nm is formed at a plasma power setting of 250 W. This completes the barrier layer forming process.

[0269] The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4 except that the intermediate laminate formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0270] Example 16 Example 16 has the same configuration as Example 14, except that the barrier layer has an auxiliary layer. The following describes the substrate manufacturing process of Example 16, focusing on the differences from Example 14. The light guide plate for image display 2006 of Example 16 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described below, and the same light guide plate fabrication process as in Example 4 in this order.

[0271] (Barrier layer formation process) In the barrier layer formation process of this example, an auxiliary layer is formed on the surface of an inorganic material layer prepared in the same manner as in Example 14. Auxiliary coating agent 1 was prepared by adding N-phenyl-3-aminopropyltrimethoxysilane (KBM-573, Shin-Etsu Chemical Co., Ltd.) to an ethylene-vinyl alcohol copolymer aqueous solution so that the solids concentration was 10 wt % relative to the total solids in the protective coating. Auxiliary coating agent 1 was applied to the surface of the inorganic material layer and dried to form an auxiliary layer with a thickness of 0.5 μm. This completes the barrier layer forming process.

[0272] The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4 except that the barrier layer having a multilayer structure formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0273] Example 17 Example 17 has the same structure as Example 14, except that the barrier layer has a fluorine-based waterproof and moisture-proof coating layer as an auxiliary layer. The following describes the substrate manufacturing process of Example 17, focusing on the differences from Example 14. The light guide plate for image display 2006 of Example 17 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described below, and the same light guide plate manufacturing process as in Example 4 in this order.

[0274] (Barrier layer formation process) In the protective layer forming step of this example, a fluorine-based waterproof and moisture-proof coating layer is formed on the surface of a barrier layer prepared in the same manner as in Example 14. This completes the barrier layer forming process.

[0275] The substrate manufacturing process of this example is the same as that of Example 4 except that the barrier layer having a multilayer structure formed in the barrier layer forming step described above is used, and therefore a description thereof will be omitted.

[0276] Example 18 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. The following describes the substrate manufacturing process of Example 18, focusing on the differences from Example 14. The light guide plate 2006 for image display of Example 18 is manufactured by carrying out, in this order, a substrate preparation process similar to that of Example 14, an anchor coat layer formation process and a barrier layer formation process described later, and a light guide plate fabrication process similar to that of Example 4.

[0277] (Anchor coat layer forming process) In the anchor coat layer forming step of this example, an anchor coat layer is formed on the surface of a resin substrate. A saturated polyester (Vylon 300 manufactured by Toyobo Co., Ltd.) and an isocyanate compound (Coronate L manufactured by Tosoh Corporation) were mixed in a 1:1 mass ratio to prepare an anchor coat agent. 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. This completes the anchor coat layer process.

[0278] (Barrier layer formation process) A barrier layer is formed on the anchor coat layer in the same manner as in Example 14.

[0279] The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4, except that the intermediate laminate formed in the anchor coat layer forming process and barrier layer forming process described above is used, so a description thereof will be omitted.

[0280] Example 19 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. The following describes the substrate manufacturing process of Example 19, focusing on the differences from Example 16. The light guide plate 2006 for image display of Example 19 is manufactured by carrying out, in this order, a substrate preparation step similar to that of Example 4, an anchor coat layer formation step, an inorganic material layer formation step, and a barrier layer formation step, which will be described later, and a light guide plate fabrication step similar to that of Example 4.

[0281] (Anchor coat layer forming process) An anchor coat layer is formed on the surface of the resin substrate in the same manner as in Example 18.

[0282] (Inorganic material layer formation process) An inorganic material layer is formed on the anchor coat layer in the same manner as in Example 14.

[0283] (Barrier layer formation process) An auxiliary layer is formed on the surface of the inorganic material layer in the same manner as in Example 16 to form a barrier layer.

[0284] The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4, except that the 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 a description thereof will be omitted.

[0285] Example 20 Example 20 has the same configuration as Example 4, except that each silicon oxide film is made of silicon oxide with a thickness of 100 nm and formed by sputtering. The following describes the substrate manufacturing process of Example 20, focusing on the differences from Example 4. The light guide plate 2006 for image display of Example 20 is manufactured by carrying out the same substrate preparation process as in Example 4, the barrier layer formation process described below, and the same light guide plate fabrication process as in Example 4 in this order.

[0286] (Barrier layer formation process) In the barrier layer forming process of this embodiment, a silicon oxide film is formed on the surface of the resin substrate by sputtering under a vacuum pressure of 4.0×10 -5 Under a vacuum pressure of Torr, a silicon oxide film is formed to a thickness of 100 nm.

[0287] The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4 except that the intermediate laminate formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0288] Example 21 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. The following describes the substrate manufacturing process of Example 21, focusing on the differences from Example 20. The light guide plate 2006 for image display of Example 21 is manufactured by carrying out the substrate preparation process similar to that of Example 20, the anchor coat layer formation process similar to that of Example 18, the barrier layer formation process described below, and the light guide plate fabrication process similar to that of Example 20, in this order.

[0289] (Barrier layer formation process) A barrier layer is formed on the anchor coat layer in the same manner as in Example 20.

[0290] The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 20 except that the intermediate laminate formed in the barrier layer forming process described above is used, so a description thereof will be omitted.

[0291] <Evaluation method> Next, the evaluation method for each example will be described. The evaluation includes brightness measurement, FOV evaluation, and display image clarity evaluation.

[0292] (brightness value) Three types of samples are prepared for measuring brightness values: a sample that undergoes a humidification test ("after humidification" in Table 2C), a sample that undergoes a heating test ("after heating" in Table 2C), and a sample that does not undergo either a humidification test or a heating test ("initial" in Table 2C). The humidity test and heating test are carried out using a small environmental tester SH-241 (trade name; manufactured by Espec Corporation). The test conditions for the humidity test are 60°C, 90% RH, and 500 hours. The test conditions for the heating test are 85°C and 500 hours. The brightness value of the measurement sample is measured based on the measurement method described above in the embodiment. Each measurement sample is assembled into the above-mentioned display device. A luminance meter BM-8 (product name: manufactured by Topcon Corporation) is used as the luminance meter 2014. The measurement angle is 1°. The distance d from the display surface 2003a is 15 mm. A luminance value of 3500 nits or greater is considered very good (denoted as "S" in Table 2C). A luminance value of 3000 nit or more and less than 3500 nit is judged as good (denoted as "A" in Table 2C). If the luminance value is 1000 nit or more and less than 3000 nit, it is judged as fair (denoted as "B" in Table 2C). If the luminance value is less than 1000 nit, it is judged as no good (marked as "C" in Table 2C).

[0293] (FOV) The FOV is measured using a display device assembled from samples for measuring luminance values ​​that have not undergone the humidity test or the heating test. The FOV is measured based on the measurement method described above in the embodiment. A luminance meter BM-8 (product name: manufactured by Topcon Corporation) is used as the luminance meter 2014. The measurement angle is 1°. The distance d from the display surface 2003a is 15 mm. If the FOV is 45° or greater, it is judged as very good (denoted as "S" in Table 2C). If the FOV is greater than or equal to 35° and less than 45°, it is judged as good (denoted as "A" in Table 2C). If the FOV is 24° or more and less than 35°, it is judged as fair (marked as "B" in Table 2C). If the FOV is less than 24°, it is judged as no good (marked as "C" in Table 2C).

[0294] (Clarity) The clarity of the displayed image is measured using the display device used to measure the FOV. The input images used for the evaluation are a white image and a character display image. The evaluation was carried out by visually judging the visibility of the white image and the character image, which was displayed as "ABCDE" within a 10mm x 100mm area. If no rainbow color is visible in the white image and the characters are clearly visible in the character display image, the image is judged as good (denoted as "A" in Table 2C). If a slight rainbow color is visible in the white image, but the characters are clearly visible in the character display image, the image is judged as fair (marked as "B" in Table 2C). If rainbow colors are visible in at least part of the white image and the outlines of the characters appear blurred in the character display image, the image is judged as "no good" (denoted as "C" in Table 2C).

[0295] <Evaluation results> As shown in Table 2C, the brightness values ​​of Examples 4, 5 and 12 to 21 are all evaluated as "S" or "A" regardless of whether or not they have undergone the humidity test or the heat test. The reason for this is thought to be that in these examples, the barrier layer prevents moisture from penetrating into the hologram layer and prevents the hologram layer from corroding the resin substrate, resulting in good diffraction performance of the hologram layer and no disturbance of the optical path in the resin substrate. Furthermore, in these examples, the hologram layer is not in contact with the resin substrate, so that the material of the hologram layer does not corrode the resin substrate even when heated. In contrast, the brightness values ​​of Examples 5 and 6 are inferior to those of Examples 4, 5 and Examples 12 to 21 for the measurement samples after either the humidification test or the heating test, but when the humidification test or the heating test is not performed, they are evaluated as "B" and are at a practical level.

[0296] As shown in Table 2C, the FOVs of Examples 4, 5 and 12 to 21 are rated as "S" and "A", respectively. In contrast, the FOV of Examples 6 and 7 was rated "C," which was at a practical level. The reason for this is thought to be the same as the reason for the difference in brightness value evaluation described above. That is, in Examples 4, 5, and 12 to 21, the barrier layer prevents moisture from penetrating into the hologram layer and eroding into the resin substrate at an extremely high level, so that no decrease in FOV is observed. It is believed that the difference in the material of the barrier layer is the reason why the FOV of Example 4 is better than that of Example 5. The DLC film has a higher refractive index than the silicon oxide thin film layer, which is thought to result in a larger and better FOV.

[0297] Furthermore, the clarity of the displayed image of Examples 4, 5 and 12 to 21 ("Clarity" in Table 2C) was rated "A" in all cases, which is a better result than that of Examples 6 and 7. The reason for this is thought to be the same as the reason for the difference in brightness value evaluation described above. That is, in Examples 4, 5, and 12 to 21, the barrier layer prevents moisture from penetrating into the hologram layer and eroding the resin substrate to an extremely high level, resulting in a clear image being observed.

[0298] [Example of the third embodiment] An example of the third embodiment will be described below.

[0299] Example 8 (Preparation of the first and second substrates) Two acrylic resin plates (manufactured by Mitsubishi Chemical Corporation) processed to 60 mm x 60 mm x 1 mm (thickness) were immersed in a 5% surfactant aqueous solution of Semiclean M-L0 (manufactured by Yokohama Yushi Kogyo Co., Ltd.) and ultrasonically cleaned for 5 minutes. Then, they were immersed in ultrapure water and ultrasonically cleaned for 5 minutes. They were then rinsed with ultrapure water, air-dried, and then dried in a nitrogen atmosphere in an oven at 100°C. The air-dried substrates were then UV-ozone cleaned for 1 minute in a UV-ozone cleaner to produce the first and second substrates.

[0300] (Formation of hologram layer) The hologram layer is common to all Examples. The material for the hologram layer is a photosensitive material for the hologram, which is prepared by mixing and dissolving 100 parts by mass of bisphenol-based epoxy resin (polymerization degree n=10.8, epoxy equivalent: 1750 to 2200, product name jER1007, manufactured by Mitsubishi Chemical Corporation), 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 in 100 parts by mass of 2-butanone. A 5 mm wide, 5 μm thick seal layer is applied to the periphery of the second substrate. The photosensitive material that will become the hologram layer is spin-coated in a 50 mm x 50 mm opening surrounded by the seal layer to a thickness of 5 μm after drying. After the photosensitive material has dried, the first substrate is laminated and press-laminated under reduced pressure (absolute pressure 5 kPa, temperature 70°C, press pressure 0.04 MPa). The first and second substrates containing the photosensitive material are irradiated with two laser beams while being kept at 20° C. The irradiation angle and intensity of each laser beam are adjusted to form interference fringes due to their interference, and a desired diffraction grating is recorded in the photosensitive material to form a hologram layer.

[0301] (Preparation of hard coat film) As a film substrate, a polyethylene terephthalate biaxially stretched film (product name "Diafoil T612 type", thickness: 50 μm) manufactured by Mitsubishi Chemical Corporation is prepared. A curable composition for forming a hard coat layer is prepared using an organic-inorganic hybrid ultraviolet-curable resin composition (UVHC7800G manufactured by MOMENTIVE Corporation, containing 30 to 40% by mass of inorganic silica having a reactive functional group). The refractive index of the cured resin layer obtained by curing this composition is 1.54. The curable composition is applied to the second surface of the film substrate using a bar coater so that the film thickness after drying is 3 μm, and the composition is dried by heating at 90° C. for 1 minute. Thereafter, the composition is applied using a high-pressure mercury lamp (80 W / cm 2 ) with an integrated light intensity of 400mJ / cm 2 The hard coat layer is formed by irradiating the hard coat layer with ultraviolet light.

[0302] Next, a coating liquid for forming a release layer having the following composition is applied onto the hard coat layer and dried to form a release layer having a thickness of 500 nm. Mold release agent: Alkyd resin containing long-chain alkyl groups (Hitachi Chemical Co., Ltd. "Tesfine" 303) 10 parts by mass (solid content) Acid catalyst: p-toluenesulfonic acid (Hitachi Chemical Co., Ltd. "Dryer" 900) 0.12 parts by mass (solid content) Solvent: toluene 45 parts by weight

[0303] Next, a pressure-sensitive adhesive-forming composition is applied to the first surface of the film substrate so that the film thickness after drying is 0.5 μm, and then dried to form a pressure-sensitive adhesive layer. The adhesive-forming composition is prepared as follows. To 1 kg of an adhesive solution consisting of an acrylic copolymer (SK Dyne 1882 manufactured by Soken Chemical Engineering Co., Ltd., solids concentration approximately 17%), 1.85 g of an isocyanate-based crosslinking agent (L-45 manufactured by Soken Chemical Engineering Co., Ltd.) and 0.5 g of an epoxy-based crosslinking agent (E-5XM manufactured by Soken Chemical Engineering Co., Ltd.) were added and mixed uniformly.

[0304] The adhesive layer of the obtained hard coat film is bonded to the first substrate to attach the hard coat film to the first substrate, thereby obtaining the light guide plate for image display of Example 8.

[0305] Example 9 Example 9 differs only in the structure of the hard coat film. The preparation of the hard coat film is described below. A release layer, a hard coat layer, and an adhesive layer are formed on a release film for processing (Mitsubishi Chemical Corporation "MRA100", thickness 100 μm) in the same manner as described above, and the adhesive layer is bonded to a first substrate. After ultraviolet irradiation, the release film for processing is peeled off to obtain the light guide plate for image display of Example 9.

[0306] <Evaluation method> The following evaluations are carried out for each example. (Image display clarity) Three light guide plates of each example are prepared, and a hologram layer is formed on each plate so that it diffracts light in the red, green, and blue wavelength regions.The three light guide plates are then stacked together.An image display device, an optical system that inputs the displayed information into the light guide plates, and a circuit system that supplies a driving power source and image information, etc. are attached to the stacked light guide plates, and the image display device of each example is assembled. An image with text written on a white background is displayed on the light guide plate. The displayed image is visually observed from the first substrate side and evaluated on a three-point scale. A (good): There are no rainbow-colored parts in the image, and the text is clearly visible. B (average): There are a few rainbow-colored areas in the image, but the text is clearly visible. C (bad): There are clearly rainbow-colored areas in the image, and the outlines of the characters appear blurred. The evaluation of clarity is carried out before and after the evaluation of scratch resistance shown below. In Examples 8 and 9, the hard coat film is peeled off after the scratch resistance evaluation, and a new hard coat film is attached, and then the evaluation is carried out.

[0307] (Scratch resistance) Steel wool #0000 attached to the cross section of an 11 mm diameter cylinder was moved back and forth 10 times at 100 mm / sec under a load of 400 g against the surface of the outermost hard coat film or hard coat layer of each image display device. After that, the condition of the surface of the hard coat film or hard coat layer was observed within a test area of ​​100 mm in length and 20 mm in width, and evaluated according to the following three levels. A(good): No scratches B (average): Less than 20 scratches C (bad): 20 or more scratches

[0308] (drop resistance) A hard ball with a diameter of 50 mm and a weight of 230 g is dropped onto the outermost surface of each example of image display device, and then the first and second substrates are checked for cracks. Evaluation is made into the following two stages. A (good): No cracks were observed on either the first or second substrate. C (bad): Cracks were observed in at least one of the first substrate and the second substrate. (Pencil hardness) The pencil hardness of the surface to be measured is measured with a load of 750 g in accordance with JIS K 5600-5-4:1999.

[0309] The results of each evaluation are shown in Table 3.

[0310] [Table 3]

[0311] In Examples 8 and 9, scratches were found on the hard coat film or hard coat layer during the scratch resistance evaluation. These scratches can be prevented from deteriorating the clarity by replacing the hard coat film. The light guide plates for image display of each Example did not develop cracks in the resin substrate during the drop resistance evaluation, enhancing safety when applied to eyeglass-type displays.

[0312] In the light guide plate according to the third embodiment of the present invention, the second substrate may be made of glass, instead of resin. Even with this configuration, the weight can be reduced by configuring the eyeglass display with the first substrate facing the wearer, and the safety of the wearer can be improved. In the light guide plate according to the present invention, a hard coat film may also be attached to the second substrate, and in this case, the configuration and number of layers of the hard coat film may differ between the first substrate and the second substrate.

[0313] [Example of the fourth embodiment] Examples 9 and 10 of the fourth embodiment will be described below, but the present invention is not limited to these examples.

[0314] Table 4 below shows the configurations of the resin substrates and absorbing layers of each example, as well as the evaluation results.

[0315] [Table 4]

[0316] Example 10 Example 10 is an example corresponding to the light guide plate for image display 4005 of the fourth embodiment. As shown in Table 4, acrylic resin (PMMA) is used as the material for the first resin base material 4001 and the second resin base material 4003 (referred to as "resin base material" in Table 4). The first resin base material 4001 and the second resin base material 4003 are both rectangular plates measuring 60 mm×60 mm×1 mm. The hologram layer 4002 is common to all examples. The material for the hologram layer 4002 is a photosensitive material for the hologram, which is a mixture of 100 parts by mass of bisphenol-based epoxy resin jER (registered trademark) 1007 (polymerization degree n = 10.8, epoxy equivalent: 1750 to 2200, product name of 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 in 100 parts by mass of 2-butanone. The thickness of the hologram layer 4002 is 5 μm. The size of the hologram layer 4002 in a plan view is 50 mm × 50 mm.

[0317] Next, a description will be given of a manufacturing process of the light guide plate 4005 for image display in Example 10. The light guide plate 4005 for image display is manufactured by carrying out a substrate preparation process, an absorption layer formation process, and a light guide plate manufacturing process, which will be described below, in this order.

[0318] (Substrate preparation process) The substrate preparation step involves cleaning and drying the first resin base material 4001 and the second resin base material 4003. Hereinafter, when there is no need to distinguish between the first resin base material 4001 and the second resin base material 4003, the reference numerals will be omitted and they will simply be referred to as resin base materials. The resin substrate is ultrasonically cleaned for 5 minutes while immersed in a 5% aqueous solution of a neutral detergent, Semiclean (registered trademark) M-LO (trade name; manufactured by Yokohama Yushi Kogyo Co., Ltd.). The resin substrate is then ultrasonically cleaned for 5 minutes while immersed in ultrapure water. The resin substrate is then rinsed with ultrapure water, air-dried, and then dried in a nitrogen atmosphere in an oven at 100°C. The air-dried evaluation sample B is then UV-ozone cleaned for 1 minute in a UV-ozone cleaner. This completes the substrate preparation process.

[0319] (Absorption layer forming process) In the absorbing layer forming step, a first absorbing layer 4004 (referred to as “absorbing layer” in Table 4) is formed on the surface of the first resin base material 4001 . A curable resin composition (coating liquid) is prepared by adding 5 parts by mass of a photopolymerization initiator to 100 parts by mass of an acrylate (Iupimer (registered trademark) UV-HH2100 (product name; manufactured by Mitsubishi Chemical Corporation)), and further adding 0.05 parts by mass of Diarrange (registered trademark) Blue as a coloring material. This curable resin composition was applied onto the first resin substrate 4001 using a metal bar coater, dried at 90°C for 1 minute, and then irradiated with 500 mJ / cm 2 using an ultraviolet light irradiation device. 2 to obtain a laminate having an absorbing layer with a thickness of 5 μm. This completes the absorber layer forming process. Hereinafter, the resin substrate on which the absorbent layer is formed will be referred to as an intermediate laminate.

[0320] (Light guide plate manufacturing process) In the light guide plate manufacturing step, the intermediate laminate and the second resin base material 4003 are used to manufacture the light guide plate 4005 for image display. A sealing layer having a width of 5 mm and a thickness of 5 μm is applied to the peripheral edge of the surface of the intermediate laminate opposite to the absorbing layer. The sealing layer is made of a transparent material and is not particularly limited as long as it is a material that can bond resin substrates to each other, but in Example 1, the optical adhesive Hardlock (registered trademark) OP-1045K (product name; manufactured by Denki Kagaku Kogyo Co., Ltd.) is used. This prepares an intermediate laminate with a stepped seal layer, the opening of which is surrounded by the seal layer and measures 50 mm x 50 mm. Thereafter, the photosensitive material as a photopolymer material for a hologram is applied onto the intermediate laminate by spin coating, so that the thickness of the photosensitive material after drying is 5 μm. Thereafter, the second resin substrate 4003 is laminated on the sealing layer and the photosensitive material so as to face the barrier layer of the intermediate laminate with the sealing layer, and then press-laminated under reduced pressure at an absolute pressure of 5 kPa, a temperature of 70°C, and a pressing pressure of 0.04 MPa. After this, a diffraction grating is recorded on the photosensitive material of the press-bonded laminate. In this process, the temperature of the laminate is maintained at 20°C. The diffraction grating is formed by irradiating the laminate with two laser beams and adjusting the irradiation angle and intensity of each beam to form interference fringes so that the required diffraction pattern is formed. This records the diffraction grating on the photosensitive material. A specific diffraction grating is a color display diffraction grating that diffracts light in the red, green, and blue wavelength regions that is incident as image light on the incident portion and emits it from the display portion at positions corresponding to the pixels of the image light. After this, while the laminate was kept at 20°C, it was irradiated with ultraviolet light (wavelength 365 nm, irradiance 80 W / cm 2 ) is irradiated onto the entire surface of the laminate from one side for 30 seconds. A high-pressure mercury lamp is used as the source of ultraviolet light. As a result, the sealing layer is hardened, and the light guide plate for image display 4005 of the first embodiment is formed.

[0321] Example 11 Example 11 corresponds to the light guide plate for image display 4007 of the first modified example of the fourth embodiment. As shown in Table 4, in Example 11, the absorbing layers are provided on both sides. Specifically, the second absorbing layer 4006 is formed on the surface of the second resin base material 4003 opposite to the hologram layer 4002. In this example, the second absorbent layer 4006 (referred to as "Absorbent Layer" in Table 4) is constructed similarly to the first absorbent layer 4004 of Example 10. Therefore, the substrate preparation process of the eleventh embodiment is the same as that of the tenth embodiment. The absorbent layer forming process of Example 11 differs from that of Example 10 in that in addition to an intermediate laminate having a first absorbent layer 4004, an intermediate laminate consisting of a second resin substrate 4003 on which a second absorbent layer 4006 is formed is formed. The light guide plate manufacturing process of Example 11 differs from that of Example 10 in that two intermediate laminates are used.

[0322] <Evaluation method> Next, the evaluation method for each example will be described. As the evaluation, a clarity evaluation was carried out.

[0323] (Clarity evaluation) The clarity of the displayed image is measured using each display device using each light guide plate for 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. The images used for evaluation include a display image formed by image light diffracted by the hologram layer and an external light image formed by transmitting external light. A white image and a character image are used as input images for the display image. The external light image is an indoor, city, or forest scene located 0.5 m to 50 m away from the display device. In evaluating the external light image, a white image or a character image is displayed and evaluated. The evaluation is carried out by visually judging the visibility of white images and character images, as well as the visibility of images in external light. Character images are displayed in the form of hiragana, katakana, kanji, Arabic numerals, or alphabets, each of which is equivalent to a visual acuity of 0.1 to 2.0.

[0324] (Criteria for evaluating the clarity of displayed images) The clarity of the displayed image is evaluated on a three-point scale. If no rainbow color is visible in the white image and the characters are clearly visible in the character image, the image is judged as good (marked "A" in Table 4). If a slight rainbow color is visible in the white image, but the letters are clearly visible in the letter image, the image is judged as fair (marked as "B" in Table 4). If rainbow colors are visible in at least part of the white image and the outlines of the characters in the character image appear blurred, the image is judged as "no good" (denoted as "C" in Table 4).

[0325] (Standards for evaluating clarity of images in external light) The clarity of the external light image is evaluated on a four-point scale. If the colors of the scenery in the outdoor image look natural and clear, it is very good. (Good, shown as "S" in Table 4). If the scenery in the external light image appears slightly dark, it is judged as good (marked as "A" in Table 4). If the scenery in the external light image is dark and there is a slight sense of incongruity in the color tone, it is judged as fair (marked as "B" in Table 4). If the scenery due to the external light image appears blurred, it is judged as no good (marked as "C" in Table 4).

[0326] (Weather resistance test) As the light guide plates for image display used for the clarity evaluation, samples to be subjected to a weather resistance test ("After weather resistance test" in Table 4) and samples not to be subjected to a weather resistance test ("Before weather resistance test" in Table 4) are prepared. The weather resistance test is carried out using an ultraviolet fade meter U48AU (product name; manufactured by Suga Test Instruments Co., Ltd.). The test conditions are a BP temperature of 63°C ± 3°C, and a test time of 500 hours.

[0327] <Evaluation results> As shown in Table 4, the clarity of Example 10 is rated "A" for both the displayed image and the external light image, regardless of whether it is before or after the weather resistance test. The clarity of Example 11 is rated "A" except for the external light image, which is rated "S" after the weather resistance test. The evaluation results show that the provision of an absorbing layer provides good clarity for both the displayed image and the external light image in Examples 10 and 11. In particular, in Example 10, an absorbing layer is also provided on the external light incident side, and therefore the clarity of the external light image is improved compared to Example 10 before the weather resistance test.

[0328] Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. Furthermore, the present invention is not limited by the foregoing description, but is limited only by the appended claims. [Industrial Applicability]

[0329] The light guide plate for image display of the present invention can display clear images even when a resin substrate is used, and can suppress deterioration of the hologram layer, and is therefore useful for display devices for VR and AR applications, for example. For example, the light guide plate for image display of the present invention is useful for display device applications such as entertainment, remote control, work assistance, and guidance assistance using head-up displays, wearable displays, and head-mounted displays. [Explanation of symbols]

[0330] 1001 First resin base material 1001a 1st surface 1001b 2nd surface 1002 Hologram Layer 1003 Second resin base material 1004,1014 Light guide plate for image display 1011A First hard coat layer 1011B Second hard coat layer 1100 Continuous Polymerization Equipment 1101,1102 Endless Belt 1103, 1104, 1105, 1106 Main pulley 1107 Carrier Roll 1108 First 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 Processing unit 1210 curve 2001 First resin base material 2002 First barrier layer 2003 Hologram Layer 2003a display surface 2003b Waveguide grating section 2003c Diffraction grating for display 2004 Second barrier layer 2005 2nd resin base material 2006,2016 Light guide plate for image display 2006a Input section 2006d display section 2010 Display device 2012 Injection optical system 2013 Image Light Projection Unit 2014 Luminance Meter 2015 Measuring Equipment 2022 First Barrier Film 2022A Barrier layer 2022B Resin Film 2024 Second barrier film 2024A Barrier layer 2024B resin film 2026 1st adhesive layer 2027 Second adhesive layer 2032 Third Barrier Layer 2101,2102 Light guide plate for image display 3001 Light guide plate for image display (light guide plate) 3010 Hologram Layer 3021 First board 3022 Second board 3030,3130 Hard coat film 3030A, 3130A Daiichi Hard Coat Film 3030B, 3130B Secondary Hard Coat Film 3031 Film substrate 3031a Front page 3031b Second side 3032 Adhesive layer 3033 Hard coat layer 3034 Release layer 4001 First resin base material 4002 Hologram Layer 4002b Diffraction grating for display 4003 Second resin base material 4003a Waveguide diffraction grating section 4004 First absorption layer 4005,4007,4020,4024 Light guide plate for image display 4005a Input part 4005b Display image output unit 4006 Second absorption layer 4008 First barrier layer 4009 Second barrier layer 4010 Display device 4011 Input optical system 4012 Image light projection unit 4021 First resin base material (absorption layer) 4023 Second resin base material (absorption layer) I Transmission projection image Ib High brightness area Is low brightness area Ld Image Light Ld' image light Ld'' image light Li Image Light Low external light Lo' outdoor light Lo'' external light Lo''' outdoor light O optical axis P1 First intermediate laminate P2 Second intermediate laminate S Measurement sample

Claims

1. A light guide plate for image display having a plate-shaped first resin substrate, a first barrier layer, and a hologram layer in this order, the first barrier layer and the hologram layer are formed on one surface side in a thickness direction of the first resin substrate, an incident portion for irradiating image light onto a surface of the light guide plate for image display, and a region of the light guide plate for image display on the side of the incident portion in a thickness direction and spaced apart from the incident portion in a plane direction perpendicular to the thickness direction constitutes a display image output portion; the incident portion is provided on the first resin base material, the hologram layer has a waveguide diffraction grating section on the incident portion side in the plane direction, and a display diffraction grating section on a side farther from the incident portion than the waveguide diffraction grating section, the display image output section is composed of the diffraction grating section for display and a region of the first barrier layer and the first resin base material facing the diffraction grating section for display in a thickness direction, a light guide plate for image display, wherein image light incident on the incident portion is guided to the diffraction grating portion for display via the waveguide diffraction grating portion, is diffracted, transmits through the first barrier layer and the region of the first resin base material of the display image output portion, and is output to the outside from the surface of the light guide plate for image display on which the incident portion is formed.

2. further comprising a second resin substrate and a second barrier layer; 2. The light guide plate for image display according to claim 1, wherein the first resin base material, the first barrier layer, the hologram layer, the second barrier layer, and the second resin base material are arranged in this order in a thickness direction.

3. 3. The light guide plate for image display according to claim 1, wherein the refractive index of the first barrier layer is higher than the refractive index of the first resin substrate.

4. 4. The light guide plate for image display according to claim 1, wherein the refractive index of the first barrier layer is 1.48 or more.

5. 5. The light guide plate for image display according to claim 1, wherein the first barrier layer contains an inorganic material.

6. 6. The light guide plate for image display according to claim 5, wherein the first barrier layer contains at least one inorganic material selected from the group consisting of silicon oxide, silicon nitride oxide, diamond-like carbon, aluminum oxide, and glass.

7. 7. The light guide plate for image display according to claim 1, wherein the first barrier layer comprises a first gas barrier film disposed on a resin film, and the resin film is disposed between the first barrier layer and the first resin substrate.

8. 8. The light guide plate for image display according to claim 1, wherein a water vapor barrier material is used as a material for the first barrier layer.

9. 9. The light guide plate for image display according to claim 1, wherein the first barrier layer is disposed on the hologram layer.

10. 10. The light guide plate for image display according to claim 1, wherein the refractive index of the first resin substrate is 1.48 to 1.

70.

11. The light guide plate for image display according to any one of claims 1 to 10, wherein the first resin substrate contains at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin, and polycarbonate.

12. The light guide plate for image display according to any one of claims 1 to 11, wherein the first resin substrate has a thermal shrinkage rate of less than 3% as measured in accordance with Appendix A of JIS K 6718-1:2015.

13. 13. The light guide plate for image display according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the first resin base material is 10 nm or less.

14. An image display device provided with a light guide plate for image display, the light guide plate having, in this order, a plate-shaped first resin substrate, a first barrier layer, a hologram layer, a second barrier layer, and a plate-shaped second resin substrate, the first resin base material and the second resin base material each have a thickness of 0.05 to 2 mm; the first barrier layer and the hologram layer are formed on one surface side in a thickness direction of the first resin substrate, an incident portion for allowing image light to be incident is formed on the other surface side in the thickness direction of the first resin base material, and a region of the light guide plate for image display, on the side of the incident portion in the thickness direction and spaced apart from the incident portion in a surface direction orthogonal to the thickness direction, constitutes a display image output portion; the hologram layer has a waveguide diffraction grating section on the incident portion side in the plane direction, and a display diffraction grating section on a side farther from the incident portion than the waveguide diffraction grating section, the display image output section is composed of the diffraction grating section for display and a region of the first barrier layer and the first resin base material facing the diffraction grating section for display in a thickness direction, the image light incident on the incident portion is guided to the display diffraction grating portion via the waveguide diffraction grating portion, is diffracted, transmits through the first barrier layer and the first resin base material region of the display image output portion, and is output to the outside from the surface of the image display light guide plate on which the incident portion is formed, the second barrier layer is formed on one surface side in a thickness direction of the second resin base material, an external light incident portion is formed on the other surface side in the thickness direction of the second resin base material; at least a part of the external light incident on the external light incident portion is transmitted through the display image output portion and output to the outside from a surface of the image display light guide plate on which the incident portion is formed, An image display device that displays an image in which an image created by image light and an image created by external light are superimposed.

15. The image display device according to claim 14 , wherein the first resin base material and the second resin base material contain a poly(meth)acrylic resin.

16. 16. The image display device according to claim 14, wherein the first resin base material and the second resin base material have an MC value of 0.120 or less as evaluated by shadow contrast.

17. 17. The image display device according to claim 14, wherein the first resin base material and the second resin base material have surfaces each having an arithmetic mean roughness Ra of 10 nm or less.

18. A head-up display comprising the image display device according to any one of claims 14 to 17.

19. A wearable display comprising the image display device according to any one of claims 14 to 17.

20. An eyeglass-type display comprising the image display device according to any one of claims 14 to 17.

21. AR glasses comprising the image display device according to any one of claims 14 to 17.

Images