Light-guiding plate and ar display

Abstract

To provide a resin-made image display light-guiding plate, which can display a clear image and has excellent visibility.SOLUTION: A light-guiding plate includes a resin base material having parallelism P of 5 μm or less per area of 50×100 mm2.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a light guide plate and an AR display using the same. This application claims priority based on Japanese Patent Application No. 2020-044442, filed in Japan on March 13, 2020, and Japanese Patent Application No. 2020-093092, filed in Japan on May 28, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] In some display devices, a light guide plate for image display is used. For example, in a display device using VR (virtual reality) technology, AR (augmented reality) technology, or MR (mixed reality), a light guide plate for image display in which a hologram layer is supported on a transparent substrate, or a light guide plate for image display made of a transparent substrate having a diffractive optical pattern with a concave-convex shape is used. In the hologram layer, a hologram having various optical functions, such as wave guiding, reflection, and diffraction functions, is formed. As the transparent substrate, a glass substrate is often used, but from the viewpoints of processability, light weight, 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 formed by laminating, in this order, 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. 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 indicates the surface smoothness of the hologram laminate, exceeds 50 μm, the appearance of the hologram changes significantly. When the maximum height Rmax is less than 25 μm, the appearance change of the hologram is within an acceptable range. However, Patent Document 1 does not particularly describe the necessity of nano-order surface smoothness with a maximum height Rmax of 1 μm or less. Patent Document 1 does not describe any specific examples of nano-order surface smoothness. Patent document 2 describes an optical device comprising a first light guide having a first light entrance portion and a first light exit portion, a first diffractive optical element provided at the first light entrance portion of the first light guide and diffracting a portion of the incident light to guide the light inside the first light guide by reflection, and a reflecting member provided on the surface of the first light guide opposite the first light entrance portion, wherein the reflecting member is arranged so that at least a portion of the incident light that is not diffracted by the first diffractive optical element is reflected by the reflecting member, and then diffracted by the first diffractive optical element, and guided inside the first light guide by reflection (Claim 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-296583 [Patent Document 2] Japanese Patent No. 6232863 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above related techniques have the following problems. The hologram laminate described in Patent Document 1 is mainly used in an in-vehicle head-up display viewed by the driver. For this reason, the image quality of the displayed image does not need to be particularly high. However, for example, in the case of a wearable display or a head-mounted display used for AR or MR, realistic images are often displayed in the user's entire field of vision, and small characters are often displayed. For such applications, even higher image quality is required. According to the study by the present inventors, 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, when undulations (gear marks) of a pitch corresponding to the meshing pitch of the drive gear of the extrusion roller are generated on the surface of the extrusion-molded resin substrate, the image is likely to become unclear in some places. Furthermore, in the optical device described in Patent Document 2, the light guide is a plate-like member (light guide plate) made of glass or a light-transmitting resin material. Glass is less lightweight, has lower impact resistance, and is less safe than resin materials. Meanwhile, resin materials are less dimensionally accurate, less optically stable, and less prone to yellowing than glass, due to dimensional changes caused by water absorption and heating. Therefore, when the light guide plate described in Patent Document 2 is made of a resin material, there is room for improvement, particularly in visibility.

[0006] The present invention has been made in view of the above problems, and has an object to provide a resin-made light guide plate for image display that can display a clear image and has excellent visibility. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above problems can be solved by using a resin base material molded into a specific shape as a light guide plate, and have arrived at the present invention.

[0008] In order to solve the above problems, for example, the present invention has the following aspects. [1] Area 50×100mm 2 The light guide plate has a resin substrate having a parallelism P per unit area of ​​5 μm or less, preferably 0.2 μm or more and 4 μm or less, more preferably 0.2 μm or more and 3 μm or less, even more preferably 0.2 μm or more and 1.2 μm or less, particularly preferably 0.2 μm or more and 1.0 μm or less, and most preferably 0.2 μm or more and 0.8 μm or less. [2] The light guide plate according to [1], wherein the dimensional change rate due to moisture absorption measured in accordance with JIS K7209:2000 is 1.0% or less, more preferably 0.01 to 1.0%, even more preferably 0.02 to 0.9%, and particularly preferably 0.03 to 0.8%. [3] The light guide plate according to [1] or [2], having a thermal shrinkage rate of 3% or less, preferably 0% or more and 2.5% or less, and further preferably 0% or more and 2.0% or less, as measured in accordance with JIS K6718-1 Appendix A. [4] The light guide plate according to any one of [1] to [3], wherein the resin substrate has a thickness of 0.05 to 2 mm, more preferably 0.1 mm or more and 1.5 mm or less, and further preferably 0.5 mm or more and 1 mm or less. [5] The light guide plate according to any one of [1] to [4], wherein the arithmetic mean roughness Ra of the surface of the resin substrate is 10 nm or less, more preferably 0.1 nm or more and 8 nm or less, even more preferably 0.5 nm or more and 5 nm or less, and particularly preferably 1 nm or more and 5 nm or less. [6] The light guide plate according to any one of [1] to [5], wherein the resin substrate has a refractive index of 1.48 or more, preferably from 1.48 to 2.00, more preferably from 1.48 to 1.90, and even more preferably from 1.48 to 1.80. [7] The light guide plate according to any one of [1] to [6], wherein the resin substrate contains at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins, and polycarbonates. [8] The light guide plate according to any one of [1] to [7], which has a barrier layer or a hard coat layer on at least one surface of the resin substrate. [9] The light guide plate according to any one of [1] to [8], having a diffractive optical pattern on at least one surface of the resin substrate, the diffractive optical pattern having a maximum height of preferably 0.05 mm or more and 0.15 μm or less, preferably 0.1 mm or more and 0.14 μm or less, and more preferably 0.5 mm or more and 0.13 μm or less.

[10] The light guide plate according to any one of [1] to [9], wherein the flatness of the light guide plate is preferably from 0.5 to 500 μm, more preferably from 0.6 to 450 μm, and even more preferably from 0.7 to 400 μm.

[11] The light guide plate according to any one of [1] to

[10] , wherein the glass transition temperature (Tg) of the resin substrate is preferably from 50 to 200°C, more preferably from 60 to 190°C, and even more preferably from 70 to 180°C.

[12] The Charpy impact strength of the resin substrate is 0.5 to 15 kJ / m 2 is preferable, and 0.8 to 14.5 kJ / m 2 More preferably, 1.0 to 14.0 kJ / m 2 The light guide plate according to any one of [1] to

[11] , further preferably:

[13] The specific gravity of the resin substrate is 1.0 to 1.5 g / cm 3 is preferable, and 1.05 to 1.45 g / cm 3 More preferably, 1.1 to 1.4 g / cm 3 The light guide plate according to any one of [1] to

[12] , further preferably:

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

[13] , wherein the light transmittance of the resin base material is preferably 85% or more and 100% or less, more preferably 86% or more and 100% or less, and even more preferably 87% or more and 100% or less.

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

[14] , wherein the yellowness index (YI) of the resin substrate is preferably 0 or more and 5 or less, more preferably 0 or more and 4 or less, and even more preferably 0 or more and 3 or less.

[16] The light guide plate according to any one of [1] to

[15] , wherein the refractive index of the resin substrate is preferably from 1.2 to 2.0, more preferably from 1.3 to 1.9, and even more preferably from 1.4 to 1.8.

[17] The light guide plate according to any one of [1] to

[16] , wherein the retardation is preferably from 1 to 200 nm, more preferably from 3 to 150 nm, and even more preferably from 4 to 100 nm.

[18] A light guide plate for AR image display, comprising the light guide plate according to any one of [1] to

[17] .

[19] Use of the light guide plate according to any one of [1] to

[18] for AR image display.

[20] An AR display comprising the light guide plate according to any one of [1] to

[19] .

[21] A diffractive optical pattern is provided on the image light incidence surface, and the line width (L IN ) is preferably 100 to 300 nm, more preferably 120 to 280 nm, and even more preferably 140 to 260 nm.

[22] A diffractive optical pattern is provided on the image light incidence surface, and the height (H IN ) is preferably 30 to 150 nm, more preferably 40 to 140 nm, and even more preferably 50 to 130 nm.

[23] A diffractive optical pattern is provided on the image light incidence surface, and the height (H IN ) and line width (L IN ) ratio value (height (H IN ) / Line width (L IN )) is preferably 0.1 to 1.5, more preferably 0.14 to 1.17, and even more preferably 0.19 to 0.93. An AR display comprising the light guide plate according to any one of

[20] to

[22] .

[24] A diffractive optical pattern is provided on the image light exit surface, and the line width (L OUT ) is preferably 50 to 250 nm, more preferably 70 to 230 nm, and even more preferably 90 to 210 nm.

[25] A diffractive optical pattern is provided on the image light exit surface, and the height (H OUT ) is preferably 30 to 150 nm, more preferably 40 to 140 nm, and even more preferably 50 to 130 nm.

[26] A diffractive optical pattern is provided on the image light exit surface, and the ratio of the height to the line width of the diffractive optical pattern on the image light exit surface (height (H OUT ) / Line width (L OUT)) is preferably 0.12 to 3.0, more preferably 0.28 to 2.00, and even more preferably 0.24 to 1.44. Effect of the Invention

[0009] According to the present invention, it is possible to provide a resin light guide plate for image display, which is capable of displaying clear images and has excellent visibility. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a main part showing an example of a light guide plate of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing another example of the light guide plate of the present invention. [Diagram 3] FIG. 3 is a plan view of an example of the light guide plate of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a part of the incident light side relief type diffraction element forming pattern of the injection molding die used in the examples. [Diagram 5] FIG. 5 is a schematic diagram showing a part of a pattern for forming a light-emitting side relief type diffraction element of the injection molding die used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The resin substrate used in the light guide plate of the present invention has an area of ​​50 × 100 mm 2 The parallelism P of the contact is 5 μm or less. The resin substrate is preferably a flat plate. The flat plate may or may not have unevenness on the surface. When the flat plate has unevenness on the surface, the depth of the recesses and the height of the protrusions are preferably 30 to 150 nm, more preferably 40 to 140 nm, and further preferably 50 to 130 nm.

[0012] This parallelism P is measured by a laser interferometer on the measurement surface (upper or lower surface) of the resin substrate with an area of ​​50 × 100 mm 2It is a value calculated as the product of the number of interference fringes per unit area and the thickness change amount Δd per interference fringe. The number of interference fringes is calculated by counting the number of interference fringes in four directions from the center of the molded product to the top, bottom, left, and right ends of the molded product in the interference image measured by the laser interferometer, and the average value is the number of interference fringes. This Δd can be calculated by the following formula (1). Here, n is the refractive index of the resin substrate, and λ is 632.8 nm (the wavelength of the He-Ne laser). The refractive index of the resin substrate is a value obtained by measuring with an Abbe refractometer at 23° C. and D line at 589 nm based on JIS K7142. The area of ​​the resin substrate to be measured is 50 x 100 mm 2 If it is less than 50 × 100 mm, the number of interference fringes is 2 Convert this into the hit area value to calculate the parallelism P.

[0013]

number

[0014] The value of parallelism P means the frequency of thickness change that may affect the characteristics of the light guide plate, and can also be called the thickness change degree. The smaller this value is, the closer the upper and lower surfaces of the resin substrate are to being parallel, and the higher the accuracy of the thickness of the resin substrate can be determined.

[0015] That is, by making the parallelism P of this resin substrate 5 μm or less, an image passing through a light guide plate using this resin substrate can be displayed clearly. It is preferably 4 μm or less, more preferably 3 μm or less, even more preferably 1.2 μm or less, particularly preferably 1.0 μm or less, and most preferably 0.8 μm or less.

[0016] On the other hand, it is preferable to set the parallelism P of the resin substrate to 0.2 μm or more, since this makes it possible to suppress deterioration and variation in the quality of the light guide plate caused by deterioration of the parallelism P due to deformation of the resin substrate during handling or adhesion of foreign matter, etc.

[0017] In the light guide plate of the present invention, the moisture absorption rate is preferably in the range of 0.01 to 1.0%, more preferably in the range of 0.02 to 0.9%, and further preferably in the range of 0.03 to 0.8%. In addition, in the light guide plate of the present invention, the rate of dimensional change due to moisture absorption is preferably 1.0% or less, more preferably in the range of 0.01 to 1.0%, even more preferably in the range of 0.02 to 0.9%, and particularly preferably in the range of 0.03 to 0.8%. By keeping the moisture-induced dimensional change rate at 1.0% or less, the dimensional accuracy of the light guide plate of the present invention is improved, and the time-dependent fluctuation of the image display characteristics of the light guide plate tends to be suppressed, more preferably at 0.9% or less, and particularly preferably at 0.8% or less. Moreover, by making the dimensional change rate due to moisture absorption 0.01% or more, it becomes unnecessary to process the light guide plate of the present invention excessively, and therefore the productivity can be improved. It is more preferably 0.02% or more, and particularly preferably 0.03% or more. The moisture absorption rate of the light guide plate of the present invention, which is also a light-transmitting resin material, is a value determined in accordance with JIS K 7209:2000 by immersing a test piece in distilled water at 23°C and calculating the rate of weight increase per 24 hours due to water absorption. The dimensional change rate due to moisture absorption of the light guide plate of the present invention, which is also a light-transmitting resin material, is a value calculated in accordance with JIS K 7209:2000 by immersing a test piece in distilled water at 23°C and dividing the rate of weight increase per 24 hours due to water absorption by the specific gravity of the resin material.

[0018] Furthermore, in the light guide plate of the present invention, the thermal shrinkage rate measured in accordance with Appendix A of JIS K 6718-1:2015 is preferably 3% or less. This tends to improve the clarity of a display image using a hologram such as AR or MR formed using this light guide plate. This thermal shrinkage rate is more preferably 2.5% or less, and even more preferably 2.0% or less.

[0019] 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 the display image formed using this light guide plate. It is more preferably 8 nm or less, and even more preferably 5 nm or less.

[0020] 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 0.1 nm or more. This tends to suppress deterioration and variation in the quality of the light guide plate caused by deterioration of the parallelism P due to deformation of the resin substrate during handling or adhesion of foreign matter, etc. It is more preferably 0.5 nm or more, and even more preferably 1 nm or more.

[0021] In the light guide plate for image display of the present invention, the refractive index of the resin substrate is preferably 1.20 or more. This tends to improve visibility when used as a light guide plate for image display. It is more preferably 1.30 or more, and even more preferably 1.40 or more. In addition, from the viewpoint of being able to expand the viewing angle, the refractive index of the resin substrate is preferably 1.48 or more. It is more preferably 1.49 or more. The refractive index of this resin substrate is a value obtained by measurement at 23° C. using an Abbe refractometer with D line of 589 nm in accordance with JIS K7142.

[0022] In the light guide plate for image display of the present invention, the refractive index of the resin substrate is preferably 2.00 or less. This allows the resin substrate to be handled at a thickness that is easy to process as a light guide plate for image display without being made extremely thin. The refractive index is more preferably 1.90 or less, and even more preferably 1.80 or less.

[0023] In the light guide plate for image display of the present invention, the material usable for the resin substrate can be a light-transmitting resin material, and examples thereof include 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. It is preferable that the resin substrate contains at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin, and polycarbonate.

[0024] These resin materials can be obtained by polymerizing a polymerizable material by a known method. The polymerizable material preferably contains a monomer, a polymerization initiator, an emulsifier, and the like. For example, in the case of poly(meth)acrylic resin, examples of the monomer include (meth)acrylic acid esters, and examples of the monomer include aliphatic methacrylates (e.g., methyl methacrylate, ethyl methacrylate, butyl methacrylate), alicyclic methacrylates (e.g., cyclohexyl methacrylate), aromatic methacrylates (e.g., phenyl methacrylate), and the like. Examples of the polymerization initiator include azo polymerization initiators and organic peroxides. Examples of the azo polymerization initiator include 2,2'-azobis-(2,4-dimethylvaleronitrile). Examples of the organic peroxide include t-hexyl peroxypivalate. Examples of the emulsifier include sodium dioctyl sulfosuccinate.

[0025] From the viewpoint of the transparency of the resin substrate, it is preferable to use a polycarbonate or poly(meth)acrylic resin, and from the viewpoint of the process resistance such as chemical resistance and workability of the resin substrate, it is preferable to use a poly(meth)acrylic resin, an epoxy resin, or a cyclic polyolefin, and among these, a poly(meth)acrylic resin is more preferable since it can achieve both transparency and process resistance.

[0026] When a hologram layer is used in the light guide plate of the present invention, a barrier layer can be introduced between the resin substrate and the hologram layer. By introducing a barrier layer, deterioration of the hologram layer can be suppressed, and a clear image can be maintained. In addition, in the light guide plate of the present invention, a hard coat layer can be introduced to the resin substrate. By introducing a hard coat layer, scratches on the surface of the resin substrate can be suppressed, and a clear image can be maintained. Either or both of these barrier layers and hard coat layers may be used. FIG. 2 shows a cross-sectional view of a light guide plate having a barrier layer and a hard coat layer. In FIG. 2, a barrier layer 3 is provided between the resin substrate 1 and the hologram layer 2, and a hard coat layer 4 is provided on the surface of the resin substrate 1 opposite to the surface on the barrier layer 3 side.

[0027] Examples of materials for the barrier layer include silicon oxide, silicon nitride oxide, DLC, aluminum oxide, and glass, but may also be oxides 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. This barrier layer preferably has a thickness in the range of 10 to 300 nm, and can be formed by a method such as vacuum deposition, sputtering, ion plating, or plasma CVD.

[0028] In addition, the material of the hard coat layer may be, for example, a hard coat agent containing a polymerizable monomer or a polymerizable oligomer that forms a cured product by irradiation with active energy rays. The polymerizable monomer may be, for example, a (meth)acrylate monomer having a radical polymerizable unsaturated group in the molecule. The polymerizable oligomer may be, for example, a (meth)acrylate oligomer having a radical polymerizable unsaturated group in the molecule. This hard coat layer preferably has a pencil hardness (JIS K 5600-5-4:1999) of H or more and a layer thickness in the range of 1 to 50 μm. In addition, this hard coat layer can be formed, for example, by directly applying the above-mentioned hard coat agent onto a resin substrate by a coating method such as a casting method, a roller coating method, a bar coating method, a spray coating method, an air knife coating method, or a dipping method, and irradiating the resulting coating film with light.

[0029] As described above, when a barrier layer or a hard coat layer is introduced on the surface of a resin substrate, the light guide plate is also 50×100 mm 2 It is preferable that the parallelism P of the contact is 5 μm or less.

[0030] A resin substrate having the above-mentioned parallelism P and excellent thickness accuracy can be produced, for example, by a casting method. It can also be produced by subjecting the resin substrate to post-processing such as cutting, polishing, and press molding.

[0031] The above-mentioned post-processing such as cutting, polishing and press molding can also be applied to resin substrates having a barrier layer or hard coat layer introduced therein.

[0032] 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 smooth surfaces, and then a polymerization process is performed to solidify the raw material of the resin. 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 "glass for casting") is transferred to the resin substrate.

[0033] The smaller the internal strain of the casting glass, the more the parallelism P of the resin substrate tends to improve. For example, non-tempered glass is more preferable than 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 parallelism P of the resin substrate tends to be improved. The thicker the casting glass is, the higher the rigidity of the casting glass is, and deformation of the glass during the production of the resin base material is suppressed, so that the parallelism P of the resin base material can be improved. The more difficult the deformation of the casting glass is, the higher the rigidity of the casting glass is, and deformation of the glass during the production of the resin substrate is suppressed, so that the parallelism P of the resin substrate can be improved. For example, it is more preferable to use synthetic quartz glass rather than non-strengthened glass.

[0034] In the polymerization step in 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 planarity and smoothness of the resin substrate. The curing rate can be reduced by, for example, reducing the amount of polymerization initiator or lowering the polymerization temperature. A release agent can be used for the cast, but the smaller the amount of the release agent used, the more preferable it is, since 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 planarity and smoothness of the resin substrate. In the polymerization process in the cast 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. This 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 which case the parallelism P of the resin substrate can be further improved by the synergistic effect of each technique.

[0035] The post-processing such as cutting, polishing, press molding, etc. of the resin substrate can be carried out by appropriately selecting known techniques.

[0036] The thickness of the resin substrate is not particularly limited, but the thickness of the resin substrate is preferably 0.05 to 2 mm. When the thickness of the resin substrate is 0.05 mm or more, it is preferable because it is easy to maintain a stable shape and tends to be possible to reduce measurement errors in the parallelism P. The thickness is more preferably 0.1 mm or more, and further preferably 0.5 mm or more. In addition, when the thickness of the resin substrate is 2 mm or less, the mass of the light guide plate for image display can be reduced, making it possible to reduce the weight, and deformation and residual distortion caused by the water absorption of the resin substrate tend to be reduced, which is preferable, more preferably 1.5 mm or less, and further preferably 1 mm or less. The thickness of the resin substrate is a value obtained by measuring the thickness at four points with a micrometer at 23° C. and calculating the average value of these values. The thickness tolerance of the resin substrate is preferably within a range of ±0 mm to 0.2 mm, and more preferably within a range of ±0.001 mm to 0.2 mm.

[0037] The light guide plate of the present invention can also be provided with a diffractive optical pattern on at least one surface of the light-transmitting resin substrate, making it suitable for use as a light guide plate for image display in AR displays and the like. For example, a diffractive optical pattern optically designed on a mold can be transferred and molded onto the image light entrance surface and image light exit surface of a resin substrate, thereby obtaining a light guide plate having a relief-type diffractive element formed thereon. Although the diffractive optical pattern is not particularly limited, it is preferable that the maximum height of the diffractive optical pattern is 0.15 μm or less. This reduces the effect of the diffractive optical pattern on the parallelism P described above, and tends to display a clear image. It is more preferably 0.14 μm or less, and even more preferably 0.13 μm or less. When a diffractive optical pattern is applied to the surface of a resin substrate as described above, the light guide plate also has a size of 50×100 mm. 2 It is preferable that the parallelism P of the contact is 5 μm or less.

[0038] Hereinafter, an example of a light guide plate for an AR display having a relief type diffraction element will be described with appropriate reference to the drawings. Fig. 1 is a cross-sectional view of a main part showing an example of a light guide plate of the present invention. The light guide plate 20 shown in Fig. 1 has relief-type diffraction elements (incident light side relief-type diffraction element 30a, exit light side relief-type diffraction element 30b) formed by transferring and molding a diffractive optical pattern optically designed on a mold on an image light incident surface 20a and an image light exit surface 20b of a surface 200 of a resin base material 30c. FIG. 3 is a plan view of the light guide plate 20 as viewed from the arrow A shown in FIG.

[0039] 1 and 3, the overall appearance of the light guide plate 20 is formed by a resin base material 30c, which is a flat plate-like member extending parallel to the YZ plane in the figures. The light guide plate 20 is a plate-like member formed by a light-transmitting resin material, and has a front surface 200 arranged to face the image forming unit 10, a first panel surface 201 which is the back side of the front surface 200, and a second panel surface 202 which is the back side of the back surface 203 and faces the first panel surface 201. Image light is incident through an image light incident surface 20a formed on the front surface 200, and is guided to an image light exit surface 20b by the first panel surface 201 and the second panel surface 202.

[0040] 1 includes an image display device 11 and a projection optical system 12. The image display device 11 is, for example, a liquid crystal display device, which generates light including three colors, red, green, and blue, from a light source, diffuses the light from the light source to form a light beam with a rectangular cross section, and emits the light toward the projection optical system 12. On the other hand, the projection optical system 12 is, for example, a collimator lens that converts image light emitted from each point on the image display device 11 into a parallel light beam and causes the light beam to enter the light guide plate 20.

[0041] The resin base material 30c light guide plate 20 has, on a surface 200 parallel to the YZ plane, an image light incident surface 20a which is a light incident portion that takes in image light from the image forming unit 10, and an image light exit surface 20b which exits the image light toward the observer's eye EY. On the image light incident surface 20a, an incident light side relief type diffractive element 30a is formed by transferring and forming a diffractive optical pattern optically designed on a mold, and on the image light exit surface 20b, an exit light side relief type diffractive element 30b which diffracts and transmits the image light exited from the image light exit surface 20b to the outside, and projects it as virtual image light to the observer's eye EY is formed by transferring and forming a diffractive optical pattern optically designed on a mold.

[0042] 1, the incident light side relief type diffraction element 30a and the exit light side relief type diffraction element 30b have the same grating period, for example. However, the incident light side relief type diffraction element 30a and the exit light side relief type diffraction element 30b may have different grating periods. The resin base material 30c light guide plate 20 has a first panel surface 201 and a second panel surface 202 that face each other and extend parallel to the YZ plane, and the image light diffracted by the incident light side relief type diffraction element 30a is totally reflected in the resin base material 30c light guide plate 20, and the image light diffracted by the incident light side relief type diffraction element 30a is guided to the viewer's eye. In other words, the light L1 emitted from the image forming unit 10 enters the image light incident surface 20a and is diffracted by the incident light side relief type diffraction element 30a (light L2), the light L2 enters the second panel surface 202 and is totally reflected (light L3), and then the light L3 enters the first panel surface 201 and is totally reflected. This operation is repeated, and the image light is guided to the image light exit surface 20b of the resin base material 30c light guide plate 20. The image light guided to the image light exit surface 20b is diffracted by the exit light side relief type diffraction element 30b, and then exits toward the eye EY of the observer (light L4).

[0043] Alternatively, the first panel surface 201 and the second panel surface 202 may not be provided with a reflective coating, and outside light incident on the first panel surface 201 and the second panel surface 202 from the outside may pass through the resin base material 30c and the light guide plate 20 with high transmittance. This allows the light guide plate 20 to be a see-through type that allows an outside image to be seen through.

[0044] The light guide plate 20 is a light guide plate for an AR display that is made of a light-transmitting resin material and has excellent visibility.

[0045] The line width (L IN ) is preferably from 100 to 300 nm, more preferably from 120 to 280 nm, and even more preferably from 140 to 260 nm. The height (H IN ) is preferably from 30 to 150 nm, more preferably from 40 to 140 nm, and even more preferably from 50 to 130 nm. The height (H IN ) and line width (L IN ) ratio value (height (H IN ) / Line width (LIN )) is preferably from 0.1 to 1.5, more preferably from 0.14 to 1.17, and even more preferably from 0.19 to 0.93. The line width (L IN ), height (H IN ) and height (H IN ) / Line width (L IN ) is within the above range, the diffraction angle of the image light emitted from the image forming unit after passing through the image incident surface falls within a predetermined range, and the diffracted light can propagate through the light guide plate by total reflection and reach the image light exit surface. The line width (L IN ) and height (H IN ) is a value obtained by measurement using an atomic force microscope (Nano-R, manufactured by Pacific Nano Technology, Inc.). The height (H IN ) and line width (L IN ) ratio value (H IN / L IN ) is the height (H IN ) and line width (L IN ) is the value calculated from

[0046] The line width (L OUT ) is preferably from 50 to 250 nm, more preferably from 70 to 230 nm, and even more preferably from 90 to 210 nm. The height (H OUT ) is preferably from 30 to 150 nm, more preferably from 40 to 140 nm, and even more preferably from 50 to 130 nm. The ratio of the height to the line width of the diffractive optical pattern on the image light exit surface 20b (height (H OUT ) / Line width (L OUT )) is preferably from 0.12 to 3.0, more preferably from 0.28 to 2.00, and even more preferably from 0.24 to 1.44. The line width (L OUT ), height (H OUT ) and height (H OUT ) / Line width (LOUT ) is within the above range, the diffraction angle of the image light propagated within the light guide plate after passing through the exit surface falls within a predetermined range, and an image with excellent visibility can reach the viewer without image blurring or ghosting. The line width (L OUT ), height (H OUT ) and height (H OUT ) / Line width (L OUT ) are the line widths (L IN ), height (H IN ) and height (H IN ) / Line width (L IN ) is a value calculated in the same manner.

[0047] The flatness of the light guide plate 20 is preferably from 0.5 to 500 μm, more preferably from 0.6 to 450 μm, and further preferably from 0.7 to 400 μm. When the flatness of the light guide plate 20 is within the above range, the dimensional accuracy of the light guide plate of the present invention is improved. The flatness of the light guide plate 20 is a value obtained by placing the light guide plate 20 with the back surface 203 facing down on a granite surface plate, and inserting a thickness gauge into the gap between the surface plate and the light guide plate 20 to measure the flatness.

[0048] As described above, the parallelism P of the light guide plate 20 is preferably 5 μm or less, more preferably 3 μm or less, further preferably 1.2 μm or less, particularly preferably 1.0 μm or less, and most preferably 0.8 μm or less.

[0049] The glass transition temperature (Tg) of the light-transmitting resin material is preferably from 50 to 200°C, more preferably from 60 to 190°C, and even more preferably from 70 to 180°C. When the glass transition temperature (Tg) of the optically transparent resin material is within the above range, the dimensional accuracy of the light guide plate of the present invention becomes superior. The glass transition temperature (Tg) of the light-transmitting resin material is a value obtained by measurement by differential scanning calorimetry using a differential scanning calorimeter (Diamond DSC, manufactured by PerkinElmer Japan).

[0050] The Charpy impact strength of the light-transmitting resin material is 0.5 to 15 kJ / m 2 is preferable, and 0.8 to 14.5 kJ / m 2 More preferably, 1.0 to 14.0 kJ / m 2 is more preferred. When the Charpy impact strength of the light-transmitting resin material is within the above range, the safety of the light guide plate of the present invention becomes superior. The Charpy impact strength of the optically transparent resin material is a value obtained by applying a notch to a test piece and measuring the impact strength when the test piece is struck by a pendulum using a universal impact tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) based on JIS K 7111:2012.

[0051] The specific gravity of the light-transmitting resin material is 1.0 to 1.5 g / cm 3 is preferable, and 1.05 to 1.45 g / cm 3 More preferably, 1.1 to 1.4 g / cm 3 is more preferred. When the specific gravity of the light-transmitting resin material is within the above range, the light guide plate of the present invention becomes more lightweight. The specific gravity of the optically transparent resin material is the reading of the scale at which the test piece floats when the test piece is placed in a density gradient tube in accordance with JIS K 7112:1999.

[0052] The light transmittance of the light-transmitting resin material is preferably 85% or more, more preferably 86% or more, and even more preferably 87% or more. The yellowness index (YI) of the light-transmitting resin material is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. The yellowing index (ΔYI) of the light-transmitting resin material is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. When the light transmittance, yellowness index (YI) and yellowness index (ΔYI) of the light-transmitting resin material are within the above ranges, the transparency and visibility of the light guide plate of the present invention will be more excellent.

[0053] The refractive index of the light-transmitting resin material is preferably from 1.2 to 2.0, more preferably from 1.3 to 1.9, and even more preferably from 1.4 to 1.8. When the refractive index of the light-transmitting resin material is within the above range, the visibility of the light guide plate of the present invention is improved. The refractive index of the light-transmitting resin material is a value obtained by measurement at 23° C. with an Abbe refractometer based on JIS K7142 using a D line of 589 nm.

[0054] The retardation of the light guide plate 20 is preferably from 1 to 200 nm, more preferably from 3 to 150 nm, and further preferably from 4 to 100 nm. When the retardation of the light guide plate 20 is within the above range, the visibility of the light guide plate of the present invention is improved. The thickness (d) of the light guide plate 20 is a value obtained by measuring the thickness at four points with a micrometer at 23° C. and calculating the average value of these values. The thickness tolerance of the light guide plate is preferably within a range from ±0 mm to 0.2 mm, and more preferably within a range from ±0.001 mm to 0.2 mm.

[0055] The light guide plate of the present invention can also be manufactured, for example, by preparing an injection molding mold having a diffraction pattern for forming an incident light side relief type diffraction element (FIG. 4) and a diffraction pattern for forming an exit light side relief type diffraction element (FIG. 5), and performing injection molding using the above-mentioned light-transmitting resin material. Specifically, the following production methods (1) to (3) can be mentioned: (1) A method for producing a light guide plate, comprising: injecting a polymerizable raw material into a polymerization cell (injection step); curing the polymerizable raw material (curing step); and peeling off a resin substrate from the polymerization cell (peeling step); (2) A method for producing a light guide plate, comprising cutting and polishing a resin plate (cutting and polishing process); and (3) A method for producing a light guide plate, comprising injection molding a resin material constituting a resin substrate using a mold for injection molding (injection molding step). In the injection step of the manufacturing method (1) above, it is preferable to use a polymerization cell having a space thickness of 0.05 mm or more and 4.0 mm or less and a thickness tolerance of ±0.0001 mm or more and ±0.2 mm or less, and it is more preferable to use a polymerization cell having a space thickness of 0.1 mm or more and 3.8 mm or less and a thickness tolerance of ±0.0001 mm or more and ±0.01 mm or less. In the curing step, the polymerizable raw material can be cured by thermal polymerization, photopolymerization, or the like. In the case of thermal polymerization, polymerization is preferably performed at 30°C to 150°C for 5 minutes to 120 minutes, and more preferably at 50°C to 130°C for 10 minutes to 60 minutes. In the case of photopolymerization, light with a wavelength of 200 nm to 500 nm is irradiated at an irradiation intensity of 10 mWcm. -2 More than 1000mWcm -2 It is preferable to carry out polymerization for an irradiation time of 1 second or more and 100 seconds or less, and to use light having a wavelength of 200 nm or more and 500 nm or less at an irradiation intensity of 50 mWcm. -2 More than 500mWcm -2 Hereinafter, it is preferable to carry out polymerization with an irradiation time of 2 seconds or more and 20 seconds or less. In the peeling step, it is preferable to cool the polymerization cell to room temperature after the curing step before peeling. In the cutting and polishing step of the manufacturing method (2), the resin plate used may be a commercially available product, but a continuous cast acrylic plate is preferable. As a cutting method, NC processing, grindstone processing, lapping processing, etc. are preferable. As a polishing method, buffing, chemical polishing, electrolytic polishing, chemical mechanical polishing (CMP polishing), etc. are preferable. Among these, chemical mechanical polishing (CMP polishing) is particularly preferable because it tends to reduce the parallelism P and surface roughness of the resin substrate in a shorter time. Chemical mechanical polishing is a polishing method that enhances the mechanical polishing (surface removal) effect caused by the relative movement between the abrasive and the object to be polished by utilizing the surface chemical action of the abrasive (abrasive grains) and the action of the chemical components in the slurry liquid containing this. For chemical mechanical polishing, for example, a process can be adopted in which a carrier with a resin plate attached is sandwiched between upper and lower platens with polishing pads attached thereto at a constant pressure, the temperature of the upper and lower platens is controlled to be kept below 40°C, a slurry liquid containing an abrasive is fed between the upper and lower platens and the carrier while the carrier is rotated and revolved, and at the same time the upper and lower platens are rotated at a constant speed. The conditions of this chemical mechanical polishing are not particularly limited and can be appropriately selected so that a resin substrate having the above-mentioned parallelism P can be obtained. In addition, known polishing pads and slurry liquids can be appropriately selected and used. In the injection molding step of the manufacturing method (3) above, in order to improve the transferability of the diffractive optical pattern optically designed on the mold, it is preferable to carry out the injection molding process with a higher cylinder temperature, faster injection speed, and higher mold temperature than the standard molding conditions for the injection molding material. It is also preferable to make the mold temperature distribution uniform in order to reduce the parallelism P. Furthermore, it is more preferable to carry out injection compression molding. EXAMPLES

[0056] 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 without departing from the gist of the present invention.

[0057] [Examples and Comparative Examples of the Embodiments (Examples 1 to 4, Comparative Examples 1 to 2)] Examples and comparative examples of the embodiment will be described below. The configurations and evaluation results of the resin substrates used in Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 1 below.

[0058] [Table 1]

[0059] High-precision quartz...Thickness 10mm, thickness tolerance ±0.001mm Regular glass: 6mm thick, thickness tolerance ±0.3mm Acrylite L is a registered trademark of Mitsubishi Chemical Corporation in Japan.

[0060] <Example> The following examples correspond to the manufacture of a light guide plate for image display. As shown in Table 1, acrylic resin (PMMA, refractive index 1.49) and photocurable resin (OGSOL EA-F5710, manufactured by Osaka Gas Chemicals Co., Ltd., refractive index 1.62) were used as the materials for the resin substrate. The plate thickness of the resin substrate was 1 mm or 1.5 mm.

[0061] Example 1 The resin substrate of Example 1 was produced as follows. 100 parts of MMA (methyl methacrylate) was added to a reactor (polymerization kettle) equipped with a cooling tube, a thermometer, and a stirrer, and stirred. After bubbling with nitrogen gas, heating was started. When the internal temperature reached 80°C, 0.05 parts of 2,2'-azobis-(2,4-dimethylvaleronitrile), a radical polymerization initiator, was added. The internal temperature was further heated to 100°C and then maintained for 10 minutes. The reactor was then cooled to room temperature to obtain a syrup, which was a viscous mixture in which MMA was partially polymerized. The polymerization rate of the syrup was about 20% by mass. Thereafter, 0.2 parts of t-hexyl peroxypivalate and 0.01 parts of sodium dioctyl sulfosuccinate were added to 100 parts of the syrup, and completely dissolved at room temperature to form a polymerizable raw material. After removing the dissolved air from the polymerizable raw material under reduced pressure, the raw material was poured into a pair of polymerization cells made of mirror-finished synthetic quartz glass having a thickness of 10 mm and a thickness tolerance of ±0.001 mm. The polymerization cell into which the polymerizable raw material was poured was kept in a hot water bath at 80°C for 60 minutes, then removed and heated in an oven at 130°C for 30 minutes to completely harden the syrup. After the polymerization cell was cooled to room temperature, the quartz glass was peeled off to obtain a resin substrate.

[0062] Example 2 The production conditions for the resin substrate of Example 2 were the same as those of Example 1, except that the polymerization cell into which the polymerizable raw material was poured was kept in a hot water bath at 80° C. for 30 minutes.

[0063] Example 3 As shown in Table 1, in Example 3, Acrylite L (registered trademark), which is a continuous cast acrylic plate (polymethyl methacrylate) having a thickness of 1.5 mm equivalent to that of Comparative Example 2, was used which was processed to a thickness of 1 mm by chemical mechanical polishing.

[0064] Example 4 A polymerizable raw material was prepared by adding 1 part and 0.1 part of Omnirad184 and Omnirad.TPO as photopolymerization initiators to 100 parts of OGSOL EA-F5710 (manufactured by Osaka Gas Chemicals Co., Ltd.), which is a photocurable resin having a structural unit derived from m-phenoxybenzyl acrylate and a fluorene structure. Next, the polymerizable raw material was injected into a pair of quartz glass polymerization cells, and a high-pressure mercury lamp was turned on at 50 mW / cm. 2 At an illuminance of 1000mJ / cm 2 A resin substrate with a thickness of 2.0 mm was obtained by photopolymerization at an exposure dose of 1.0 μm. This resin substrate was then processed to a thickness of 1 mm by chemical mechanical polishing.

[0065] Comparative Example 1 As shown in Table 1, Comparative Example 1 was the same as Example 1 except that a reinforced glass having a thickness of 6 mm and a thickness tolerance of ±0.3 mm was used for the polymerization cell.

[0066] Comparative Example 2 As shown in Table 1, the resin substrate in Comparative Example 2 was Acrylite L (registered trademark, manufactured by Mitsubishi Chemical Corporation), which is a continuous cast acrylic plate having a thickness of 1.5 mm.

[0067] <Evaluation method> Next, the evaluation methods for Examples 1 to 4 and Comparative Examples 1 and 2 will be described.

[0068] (Parallelism P) The parallelism P of the resin substrate was calculated as the product of the number of interference fringes measured using a laser Fizeau interferometer (product name: laser interferometer G102, manufactured by Fujifilm) with a He-Ne laser having a light source wavelength of 632.8 nm and the thickness change Δd per interference fringe. The thickness change amount Δd of one interference fringe is a value calculated by the following formula (1) where n is the refractive index of the resin substrate and λ is the laser wavelength. For example, when the resin substrate is an acrylic resin (polymethyl methacrylate, n=1.49), Δd is 0.212 μm.

[0069]

number

[0070] As a measurement sample for this parallelism P, a flat resin plate having a width of 50 mm, a length of 100 mm, and a thickness of 1.0 mm or 1.5 mm was used. The interference pattern obtained by the measurement was recorded by a charge-coupled device (CCD) camera and stored digitally. 2 The parallelism P was calculated from the product of the number of interference fringes per unit area and Δd. The number of interference fringes was counted in four directions from the center of the molded product to the top, bottom, left, and right ends of the molded product on the interference image measured by the laser interferometer, and the average value was taken as the number of interference fringes.

[0071] (Dimensional change rate due to moisture absorption) In accordance with JIS K 7209:2000, the test piece was immersed in distilled water at 23°C, and the weight increase rate per 24 hours due to water absorption was calculated by dividing it by the specific gravity of the resin material.

[0072] (Heat shrinkage rate) The calculation was made by measuring the dimensional change (shrinkage) in accordance with JIS K 6718:2015, Appendix A, "Measurement of dimensional change (shrinkage) upon heating."

[0073] (Ra) In the evaluation of Ra, the arithmetic mean roughness Ra of the surface of each evaluation sample was measured. A white light interference surface profiler Zygo NewView (registered trademark) 6300 (product name; manufactured by Zygo Corporation) was used as the measuring device. The objective lens had a magnification of 2.5 times. The observation area was a rectangular area of ​​2.8 mm × 2.1 mm.

[0074] (Light transmittance) The total light transmittance was measured using a haze meter NDH-5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) The higher the total light transmittance obtained, the more excellent the transparency.

[0075] (yellowing degree ΔYI) The yellowing index ΔYI was measured using an S&M color computer SM-T type (manufactured by Suga Test Instruments Co., Ltd.) The lower the obtained yellowing index ΔYI value, the more excellent the transparency.

[0076] (Retardation) The retardation value at a wavelength of 550 nm of the sample that had been left to stand at 23° C. and 55% relative humidity for 2 hours or more was measured using a birefringence measuring device KOBRA-WR (manufactured by Oji Measurement Instruments Co., Ltd.) The lower the retardation value obtained, the lower the birefringence, and the better the clarity of the displayed image, which will be described later.

[0077] (Image clarity) The light guide plates for image display of Examples 1 to 4 and Comparative Examples 1 and 2 were attached to an image display device. The image display device was provided with an optical system for making the image light for display incident on the incident part of the light guide plate for image display, a driving power source, and a circuit system for supplying image information for obtaining the image light. As input images used for the evaluation, a white image and an image displaying characters were used. The evaluation was performed by visually judging the visibility of the white image and the character display image. The character image displayed was "ABCDE" within the size of 10 mm x 100 mm. If no rainbow color is visible in a white image and the characters are very clearly visible in an image displaying characters, the image is judged to be very good (shown as "S" in Table 1). 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 (shown as "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, it is judged as fair (shown as "B" in Table 1). If rainbow colors are visible in at least a part of the white image and the outlines of the characters in the character display image are blurred, the image is judged as no good (marked as "C" in Table 1).

[0078] <Evaluation Results> As shown in Table 1, the parallelism P of Examples 1 to 4 was 3.7 μm, 4.9 μm, 0.5 μm, and 0.8 μm, respectively. The parallelism P of Example 2 was lower than that of Example 1. The reason for this is considered to be that the holding time of the polymerization cell in Example 2 was shorter than that of Example 1, so that a large amount of unpolymerized syrup remained and was rapidly polymerized in the next oven, which reduced the uniformity of the reaction on the surface. The parallelism P of Examples 1 to 4 was all less than 5 μm, and the clarity of the displayed image was excellent. In contrast, the parallelism P of Comparative Examples 1 and 2 was all more than 30 μm, and the clarity of the displayed image was poor. This is believed to be because the resin substrates of each Example were manufactured by casting or polishing. In the casting method, the surface shape of, for example, the quartz glass used in the polymerization cell is transferred to the surface of the raw material of the resin substrate of each Example. At this time, the flatness of the surface of the resin substrate becomes equivalent to the flatness of the quartz glass, so that good thickness accuracy of the resin substrate can be obtained. In addition, extremely high thickness accuracy of the resin substrate can be obtained by polishing. In contrast, in Comparative Examples 1 and 2, it is believed that the surface shape of the strengthened glass or the mold used during production was transferred, so sufficient parallelism P was not obtained.

[0079] The arithmetic mean roughness Ra of Examples 1 to 4 was 3.2 nm, 2.3 nm, 1.7 nm, and 2.0 nm, respectively, all of which were less than 10 nm. In contrast, the Ra of Comparative Examples 1 and 2 was 1.2 nm and 4.9 nm, respectively, all of which were less than 10 nm. Therefore, in terms of smoothness represented by Ra, Examples 1 to 4 did not differ significantly from Comparative Examples 1 and 2.

[0080] 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 without departing from the spirit of the present invention. Furthermore, the present invention is not limited by the foregoing description, but only by the scope of the appended claims. [Industrial Applicability]

[0081] INDUSTRIAL APPLICABILITY The resin light guide plate of the present invention can display clear images and is useful for display device applications such as wearable displays or head-mounted displays used in AR or MR. [Explanation of symbols]

[0082] 1...resin substrate, 2...hologram layer, 3...barrier layer, 4...hard coat layer, 10...image forming section, 11...image display device, 12...projection optical system, 20...light guide plate, 20a...image light incident surface, 20b...image light exit surface, 30a...incident light side relief type diffraction element, 30b...exiting light side relief type diffraction element, 30c...resin substrate, 200...surface, 201...first panel surface, 202...second panel surface, 203...rear surface, EY...observer's eye, L1, L2, L3, L4...light

Claims

1. Δd calculated from the following formula (1) and the area of ​​50 × 100 mm measured by a laser interferometer ２ a resin substrate having a parallelism P of 5 μm or less, which is the product of the number of interference fringes per unit area; The resin substrate has a refractive index of 1.49 or less. [Equation 1] (In the formula, n is the refractive index of the resin substrate measured at 23°C with an Abbe refractometer using D-line at 589 nm in accordance with JIS K7142, and λ is 632.8 nm (the wavelength of a He—Ne laser).)

2. A light guide plate as described in claim 1, having a dimensional change rate due to moisture absorption of 1.0% or less as measured in accordance with JIS K7209:2000.

3. A light guide plate as described in claim 1 or 2, having a thermal shrinkage rate of 3% or less as measured in accordance with JIS K6718-1 Appendix A.

4. A light guide plate as described in claim 1 or 2, wherein the thickness of the resin substrate is 0.05 to 2 mm.

5. A light guide plate as described in claim 1 or 2, wherein the arithmetic mean roughness Ra of the surface of the resin substrate is 10 nm or less.

6. A light guide plate as described in claim 1 or 2, wherein the resin substrate contains at least one resin selected from the group consisting of poly(meth)acrylic resin, epoxy resin, cyclic polyolefin, and polycarbonate.

7. A light guide plate as described in claim 1 or 2, having a barrier layer or a hard coat layer on at least one surface of the resin substrate.

8. A light guide plate for AR image display, having the light guide plate described in claim 1 or 2.

9. Use of the light guide plate described in claim 1 or 2 for AR image display.

10. An AR display equipped with a light guide plate according to claim 1 or 2.

Images