Light guide plate and AR display

Abstract

The present invention relates to a light guide plate and an AR display, the light guide plate having a resin base material having a parallelism P of 0.2 [mu] m or more and 4 [mu] m or less per 50 * 100 mm2 area, the arithmetic average roughness Ra of the surface of the resin base material being 1.7 nm or more and 3.2 nm or less.

Description

[0001] This application is a divisional application. The Chinese national application number of the application to which it is applied is 202180019318.2, the international application number is PCT / JP2021 / 009973, the application date is March 12, 2021, the date of entry into China is September 6, 2022, and the name of the invention is “Light guide plate and AR display”. Technical Field

[0002] The present invention relates to a light guide plate and an AR display using the same.

[0003] 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 Art

[0004] In display devices, light guide plates for image display are sometimes used. For example, in display devices using VR (virtual reality) technology, AR (augmented reality) technology, or MR (mixed reality), light guide plates for image display in which a holographic layer is supported by a transparent substrate, or light guide plates for image display composed of a transparent substrate having a concave-convex diffraction optical pattern are used. Holograms having various optical functions, such as waveguide, reflection, and diffraction functions, are formed on the holographic layer.

[0005] As the transparent substrate, a glass substrate is often used, but from the viewpoints of processability, lightness, durability, and portability, a resin substrate is more preferably used as the transparent substrate.

[0006] Patent Document 1 discloses a holographic laminate used in a vehicle-mounted head-up display. The holographic laminate comprises an acrylic resin substrate, an acrylic adhesive layer, a holographic layer made of an acrylic photopolymer, an acrylic adhesive layer, and an acrylic resin substrate laminated in this order.

[0007] Patent Document 1 describes that the appearance of a hologram changes by utilizing the surface smoothness of an acrylic resin substrate. According to Patent Document 1, if the maximum height Rmax indicating the surface smoothness of a holographic laminate is greater than 50 μm, the appearance change of the hologram becomes significant. When the maximum height Rmax is less than 25 μm, the appearance change of the hologram is within the permissible range. However, Patent Document 1 does not specifically describe the necessity of nanoscale surface smoothness with a maximum height Rmax of less than 1 μm. Patent Document 1 also does not describe any specific examples of nanoscale surface smoothness.

[0008] Patent document 2 describes an optical device, characterized in that it comprises: a first light guide having a first light incident portion and a first light emitting portion; a first diffraction optical element provided at the first light incident portion of the first light guide, causing a part of the incident light to be diffracted, thereby guiding light inside the first light guide by reflection; and a reflection component provided on the surface of the first light guide opposite to the first light incident portion; the reflection component is configured in the following manner: at least a part of the incident light that is not diffracted by the first diffraction optical element is reflected by the reflection component and then diffracted by the first diffraction optical element, thereby guiding light inside the first light guide by reflection (claim 1).

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2000-296583

[0012] Patent Document 2: Japanese Patent No. 6232863 Summary of the invention

[0013] Problems to be solved by the invention

[0014] However, the above-mentioned related art has the following problems.

[0015] The holographic laminate described in Patent Document 1 is mainly used for a head-up display for a driver to see. Therefore, the image quality of the displayed image may not be particularly high. However, in the case of a wearable display or a head-mounted display for AR or MR, for example, a realistic image is often displayed in the user's full field of vision, or fine text is displayed. In such applications, further high image quality is required.

[0016] According to the research of the present inventors, in the case where the holographic layer is sandwiched between resin substrates in the light guide plate for image display, even if the maximum height Rmax is less than 25 μm, image quality degradation is sometimes observed. For example, when ripples (gear marks) with 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, it is easy to produce a part where the image is not clear.

[0017] In addition, in the optical device described in Patent Document 2, the light guide is a plate-shaped component (light guide plate) formed of glass or a translucent resin material. Compared with resin materials, glass is less lightweight, has low impact resistance, and has poor safety. On the other hand, compared with glass, resin materials undergo dimensional changes accompanying water absorption and heating, and the dimensional accuracy, optical properties, and yellowing properties deteriorate due to the dimensional changes. Therefore, in the case of the light guide plate described in Patent Document 2 formed of a resin material, it is believed that there is room for improvement, especially in visibility.

[0018] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a light guide plate for image display made of resin that can display a clear image and has excellent visibility.

[0019] Means for solving problems

[0020] The present inventors have conducted intensive studies and have found that the above-mentioned problems can be solved by using a resin substrate molded into a specific shape as a light guide plate, thereby completing the present invention.

[0021] In order to solve the above-mentioned problems, the present invention has the following aspects, for example.

[0022] [1] A light guide plate having a resin substrate, wherein the resin substrate has a thickness of 50×100 mm. 2 The area parallelism P is 5 μm or less, preferably 0.2 μm to 4 μm or less, more preferably 0.2 μm to 3 μm or less, further preferably 0.2 μm to 1.2 μm or less, particularly preferably 0.2 μm to 1.0 μm or less, and most preferably 0.2 μm to 0.8 μm or less.

[0023] [2] The light guide plate as described in [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%, further preferably 0.02 to 0.9%, and particularly preferably 0.03 to 0.8%.

[0024] [3] The light guide plate described in [1] or [2], wherein the heat shrinkage rate measured in accordance with JIS K6718-1 Appendix A is 3% or less, more preferably 0% or more and 2.5% or less, and even more preferably 0% or more and 2.0% or less.

[0025] [4] The light guide plate as described in any one of [1] to [3], wherein the thickness of the resin substrate is 0.05 to 2 mm, more preferably 0.1 mm to 1.5 mm, and even more preferably 0.5 mm to 1 mm.

[0026] [5] A light guide plate as described in any one of [1] to [4], wherein the arithmetic mean roughness Ra of the surface of the above-mentioned resin substrate is less than 10 nm, more preferably greater than 0.1 nm and less than 8 nm, further preferably greater than 0.5 nm and less than 5 nm, and particularly preferably greater than 1 nm and less than 5 nm.

[0027] [6] A light guide plate as described in any one of [1] to [5], wherein the refractive index of the resin substrate is greater than or equal to 1.48, preferably greater than or equal to 1.48 and less than or equal to 2.00, more preferably greater than or equal to 1.48 and less than or equal to 1.90, and even more preferably greater than or equal to 1.48 and less than or equal to 1.80.

[0028] [7] The light guide plate according to any one of [1] to [6], wherein the resin substrate comprises at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins, and polycarbonates.

[0029] [8] The light guide plate according to any one of [1] to [7], wherein a barrier layer or a hard coating layer is provided on at least one surface of the resin substrate.

[0030] [9] A light guide plate as described in any one of [1] to [8], wherein at least one surface of the above-mentioned resin substrate has a diffraction optical pattern, and the maximum height of the diffraction optical pattern is preferably greater than 0.05 mm and less than 0.15 μm, preferably greater than 0.1 mm and less than 0.14 μm, and further preferably greater than 0.5 mm and less than 0.13 μm.

[0031]

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

[0032]

[11] The light guide plate as described in any one of [1] to

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

[0033]

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

[11] , wherein the Charpy impact strength of the resin substrate is preferably 0.5 to 15 kJ / m 2 , more preferably 0.8 to 14.5 kJ / m 2 , more preferably 1.0 to 14.0 kJ / m 2 .

[0034]

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

[12] , wherein the specific gravity of the resin substrate is preferably 1.0 to 1.5 g / cm 3, more preferably 1.05 to 1.45 g / cm 3 , more preferably 1.1 to 1.4 g / cm 3 .

[0035]

[14] A light guide plate as described in any one of [1] to

[13] , wherein the light transmittance of the above-mentioned resin substrate is preferably 85% to 100%, more preferably 86% to 100%, and further preferably 87% to 100%.

[0036]

[15] A light guide plate as described in any one of [1] to

[14] , wherein the yellowness (YI) of the above-mentioned resin substrate is preferably greater than or equal to 0 and less than or equal to 5, more preferably greater than or equal to 0 and less than or equal to 4, and even more preferably greater than or equal to 0 and less than or equal to 3.

[0037]

[16] The light guide plate as described in any one of [1] to

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

[0038]

[17] The light guide plate as described in [1] to

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

[0039]

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

[17] .

[0040]

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

[18] for AR image display.

[0041]

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

[19] .

[0042]

[21] An AR display with a light guide plate as described in

[20] , wherein a diffraction optical pattern is provided on the image light incident surface, and a line width (L IN ) is preferably 100 to 300 nm, more preferably 120 to 280 nm, and further preferably 140 to 260 nm.

[0043]

[22] An AR display with a light guide plate as described in

[20] or

[21] , wherein a diffraction optical pattern is provided on the image light incident surface, and a height (H IN ) is preferably 30 to 150 nm, more preferably 40 to 140 nm, and further preferably 50 to 130 nm.

[0044]

[23] An AR display with a light guide plate as described in any one of

[20] to

[22] , wherein a diffraction optical pattern is provided on the image light incident surface, and a height (H IN ) and line width (L IN ) ratio (height (H IN ) / Line Width(L IN )) is preferably 0.1 to 1.5, more preferably 0.14 to 1.17, further preferably 0.19 to 0.93.

[0045]

[24] An AR display having a light guide plate as described in any one of

[20] to

[23] , wherein a diffraction optical pattern is provided on the image light exit surface, and a line width (L OUT ) is preferably 50 to 250 nm, more preferably 70 to 230 nm, and further preferably 90 to 210 nm.

[0046]

[25] An AR display having a light guide plate as described in any one of

[20] to

[24] , wherein a diffraction optical pattern is provided on the image light exit surface, and a height (H OUT ) is preferably 30 to 150 nm, more preferably 40 to 140 nm, and further preferably 50 to 130 nm.

[0047]

[26] An AR display having a light guide plate as described in any one of

[20] to

[25] , wherein a diffraction optical pattern is provided on the image light exit surface, and a value of a ratio of a height to a line width of the diffraction 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, further preferably 0.24 to 1.44.

[0048] Effects of the Invention

[0049] According to the present invention, it is possible to provide a light guide plate for image display made of resin, which can display a clear image and has excellent visibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a cross-sectional view of a main part showing an example of the light guide plate of the present invention.

[0051] Figure 2 is a cross-sectional view showing another example of the light guide plate of the present invention.

[0052] Figure 3 It is a top view of an example of the light guide plate of the present invention.

[0053] Figure 41 is a schematic diagram showing a part of a pattern for forming a relief-type diffraction element on the incident light side of an injection molding die used in Examples.

[0054] Figure 5 1 is a schematic diagram showing a part of a pattern for forming a relief-type diffraction element on the light-emitting side of an injection molding die used in Examples. DETAILED DESCRIPTION

[0055] The resin substrate used in the light guide plate of the present invention has a thickness of 50×100 mm. 2 The area parallelism P is 5 μm or less.

[0056] The resin substrate is preferably a flat plate. The flat plate may or may not have concavities and convexities on the surface. When the flat plate has concavities and convexities on the surface, the depth of the concave portion and the height of the convex portion are preferably 30 to 150 nm, more preferably 40 to 140 nm, and further preferably 50 to 130 nm.

[0057] The parallelism P is the value of the measured surface (upper surface or lower surface) of the resin substrate measured by the laser interferometer per 50×100 mm. 2 The value is obtained by multiplying the number of interference fringes of the area by the change in thickness of each interference fringe Δd. The number of interference fringes is counted in four directions from the center of the molded product to the upper, lower, left and right ends of the molded product using the interference image measured by the laser interferometer, and the average value is taken as the number of interference fringes. This Δd can be calculated by the following formula (1).

[0058] Here, n is the refractive index of the resin substrate, and λ is 632.8 nm (wavelength of He-Ne laser). The refractive index of the resin substrate is a value measured at 23° C. using a 589 nm D line using an Abbe refractometer in accordance with JIS K7142.

[0059] It should be noted that the area of ​​the resin substrate to be measured is less than 50×100 mm 2 In the case of , the number of interference fringes is converted to per 50×100mm 2 The value of the area is used to calculate the parallelism P.

[0060] [Number 1]

[0061]

[0062] The value of the parallelism P means the frequency of the thickness variation that can affect the characteristics of the light guide plate, which can also be called the thickness variation. The smaller the value, the closer the upper and lower surfaces of the resin substrate are to parallelism, and the higher the accuracy of the thickness of the resin substrate can be judged.

[0063] That is, by making the parallelism P of the resin substrate 5 μm or less, an image can be clearly displayed via a light guide plate using the resin substrate. The parallelism P is preferably 4 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.

[0064] On the other hand, the parallelism P of the resin substrate is preferably 0.2 μm or more because it can suppress degradation or unevenness in the quality of the light guide plate caused by deterioration in parallelism P due to deformation of the resin substrate during handling or adhesion of foreign matter.

[0065] 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 even more preferably in the range of 0.03 to 0.8%.

[0066] In the light guide plate of the present invention, the dimensional change rate due to moisture absorption is preferably 1.0% or less, more preferably in the range of 0.01 to 1.0%, further preferably in the range of 0.02 to 0.9%, and particularly preferably in the range of 0.03 to 0.8%.

[0067] By setting the dimensional change rate due to moisture absorption to 1.0% or less, the dimensional accuracy of the light guide plate of the present invention is further improved, and there is a tendency to suppress the temporal variation of the image display characteristics of the light guide plate. The dimensional change rate is more preferably 0.9% or less, and particularly preferably 0.8% or less.

[0068] Furthermore, by setting the dimensional change rate due to moisture absorption to 0.01% or more, the light guide plate of the present invention does not need to be excessively processed, thereby improving its productivity. The dimensional change rate is more preferably 0.02% or more, and particularly preferably 0.03% or more.

[0069] The moisture absorption rate of the light guide plate of the present invention (which is also a light-transmitting resin material) is a value obtained as follows: According to JIS K7209:2000, the test piece is immersed in distilled water at 23° C., and the weight increase rate per 24 hours due to water absorption is calculated and obtained. The obtained value is the moisture absorption rate.

[0070] In addition, 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 obtained as follows: According to JIS K 7209:2000, the test piece is immersed in distilled water at 23°C, and the weight increase rate per 24 hours due to water absorption is divided by the specific gravity of the resin material, and the value obtained by calculation is the dimensional change rate.

[0071] In addition, in the light guide plate of the present invention, the heat shrinkage rate measured in accordance with Appendix A of JIS K 6718-1:2015 is preferably 3% or less. As a result, the display image using a hologram such as AR or MR formed using the light guide plate tends to have good clarity. The heat shrinkage rate is more preferably 2.5% or less, and further preferably 2.0% or less.

[0072] In the image display light guide plate of the present invention, the arithmetic mean roughness Ra of the surface of the resin substrate is preferably 10 nm or less. As a result, the clarity of the display image formed using the light guide plate tends to be better. The arithmetic mean roughness Ra is more preferably 8 nm or less, and further preferably 5 nm or less.

[0073] In addition, in the image display light guide plate of the present invention, the arithmetic mean roughness Ra of the surface of the resin substrate is preferably 0.1 nm or more. This has the tendency to suppress the reduction or unevenness of the quality of the light guide plate caused by the deterioration of the parallelism P due to deformation of the resin substrate during handling or adhesion of foreign matter. The arithmetic mean roughness Ra is more preferably 0.5 nm or more, and further preferably 1 nm or more.

[0074] In the image display light guide plate of the present invention, the refractive index of the resin substrate is preferably 1.20 or more. This has a tendency to have good visibility when used as an image display light guide plate. The refractive index is more preferably 1.30 or more, and further preferably 1.40 or more. In addition, from the perspective of being able to expand the viewing angle, the refractive index of the resin substrate is preferably 1.48 or more. More preferably, it is 1.49 or more.

[0075] The refractive index of the resin substrate is a value measured using a D line of 589 nm at 23° C. using an Abbe refractometer in accordance with JIS K7142.

[0076] In the image display light guide plate of the present invention, the refractive index of the resin substrate is preferably 2.00 or less. Thus, the resin substrate does not become extremely thin, and can be processed to a thickness that is easy to process into an image display light guide plate. The refractive index is more preferably 1.90 or less, and further preferably 1.80 or less.

[0077] In the image display light guide plate of the present invention, as a material that can be used for the above-mentioned resin substrate, a light-transmitting resin material can be used, for example, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin film, polyvinyl chloride, polyethylene, polypropylene, cyclic polyolefin, cellulose, acetyl cellulose, polyvinylidene chloride, aromatic polyamide, polyphenylene sulfide, polyurethane, polycarbonate, poly (meth) acrylic resin, phenol resin, epoxy resin, polyarylate, polynorbornene, styrene-isobutylene-styrene block copolymer (SIBS), allyl diglycol carbonate and other organic materials can be cited. Preferably, at least one resin selected from the group consisting of poly (meth) acrylic resin, epoxy resin, cyclic polyolefin and polycarbonate is included.

[0078] These resin materials can be obtained by polymerizing polymerizable materials using a known method. The polymerizable material preferably includes a monomer, a polymerization initiator, an emulsifier, etc. As a monomer, for example, in the case of a poly(meth)acrylic resin, (meth)acrylates can be cited, and aliphatic methacrylates (such as methyl methacrylate, ethyl methacrylate, butyl methacrylate), alicyclic methacrylates (such as cyclohexyl methacrylate), aromatic methacrylates (such as phenyl methacrylate), etc. can be cited. As a polymerization initiator, an azo polymerization initiator, an organic peroxide, etc. can be cited. As an azo polymerization initiator, 2,2'-azobis-(2,4-dimethylvaleronitrile), etc. can be cited. As an organic peroxide, tert-hexyl peroxypivalate, etc. can be cited. As an emulsifier, dioctyl sodium sulfosuccinate, etc. can be cited.

[0079] From the perspective of transparency of the above-mentioned resin substrate, polycarbonate or poly(meth)acrylic resin is preferably used. From the perspective of chemical resistance and processing resistance such as processability of the above-mentioned resin substrate, poly(meth)acrylic resin, epoxy resin or cyclic polyolefin is preferably used. Among them, poly(meth)acrylic resin is more preferred because it can achieve both transparency and processing resistance.

[0080] When a holographic layer is used in the light guide plate of the present invention, a barrier layer may be introduced between the resin substrate and the holographic layer. By introducing the barrier layer, degradation of the holographic layer can be suppressed and a clear image can be maintained. In addition, in the light guide plate of the present invention, a hard coating layer may be introduced into the resin substrate. By introducing the hard coating 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 coating layers may be used. Figure 2 A cross-sectional view of a light guide plate having a barrier layer and a hard coating layer is shown in FIG. Figure 2In the embodiment, the barrier layer 3 is provided between the resin substrate 1 and the hologram layer 2, and the hard coating layer 4 is provided on the surface of the resin substrate 1 opposite to the surface on the barrier layer 3 side.

[0081] The material of the barrier layer may include, for example, silicon oxide, silicon oxynitride, DLC, aluminum oxide and glass; it 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.

[0082] The 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.

[0083] In addition, as a material for the hard coat layer, for example, a hard coat agent including a polymerizable monomer or a polymerizable oligomer that forms a cured product by irradiation with active energy rays can be cited. As the above-mentioned polymerizable monomer, for example, a (meth)acrylate monomer having a free radical polymerizable unsaturated group in the molecule can be cited. As the above-mentioned polymerizable oligomer, a (meth)acrylate oligomer having a free radical polymerizable unsaturated group in the molecule can be cited.

[0084] The hard coat layer preferably has a pencil hardness (JIS K 5600-5-4:1999) of H or higher and a layer thickness in the range of 1 to 50 μm.

[0085] The hard coat layer can be formed by directly applying the hard coat agent described above on the resin substrate by a coating method such as casting, roll coating, bar coating, spray coating, air knife coating, dipping, and irradiating the obtained coating film with light.

[0086] When a barrier layer or a hard coat layer is introduced on the surface of the resin substrate as described above, the light guide plate is preferably 2 The parallelism P is less than 5 μm.

[0087] The resin substrate having the above-mentioned parallelism P and excellent thickness accuracy can be manufactured by, for example, casting. Alternatively, the resin substrate can be manufactured by subjecting the resin substrate to post-processing such as cutting, grinding, and press molding.

[0088] The above-mentioned post-processing such as cutting, grinding, and press molding can also be applied to the resin substrate introduced with the barrier layer or hard coating layer.

[0089] As the above-mentioned casting method, a glass casting method can be used. In the above-mentioned glass casting method, the raw material of the above-mentioned resin substrate is flowed into between glass plates with smooth surfaces, and then a polymerization process is performed to solidify the raw material of the above-mentioned resin. In the case where the above-mentioned resin substrate is manufactured by the above-mentioned 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 above-mentioned resin substrate.

[0090] The smaller the internal strain of the casting glass is, the more the parallelism P of the resin substrate tends to be improved. For example, as the casting glass, non-strengthened glass is preferred over tempered glass. However, even if it is tempered glass, if it is chemically strengthened glass with a smaller strain than air-cooled tempered glass, the parallelism P of the resin substrate tends to be further improved.

[0091] The thicker the cast glass is, the higher the rigidity of the cast glass is, and the more deformation of the glass during the manufacture of the resin substrate can be suppressed, so the parallelism P of the resin substrate can be improved.

[0092] The less likely the casting glass is to deform, the higher the rigidity of the casting glass is, and the deformation of the glass during the manufacture of the resin substrate can be suppressed, thereby improving the parallelism P of the resin substrate. For example, synthetic quartz glass is more preferably used than non-strengthened glass.

[0093] In the polymerization step in the casting method, the lower the curing speed, the easier it is for the cast surface shape to be transferred to the resin substrate, so that the planarity and smoothness of the resin substrate can be improved.

[0094] As a means for reducing the curing speed, for example, a means such as reducing the amount of the polymerization initiator or lowering the polymerization temperature can be used.

[0095] A release agent may be used in the casting, but the smaller the amount used, the better. Thus, the surface shape of the casting is more easily transferred to the resin substrate, and the planarity and smoothness of the resin substrate can be improved.

[0096] In the polymerization step in the casting method, by pre-polymerizing the monomer for forming the substrate, the planarity and smoothness of the resin substrate can be improved.

[0097] In the polymerization step in the above-mentioned casting method, casting polymerization is carried out by using a raw material obtained by dissolving a substrate-forming polymer in a substrate-forming monomer, thereby reducing curing shrinkage and making it easier for the casting surface shape to be transferred to the above-mentioned resin substrate, thereby improving the planarity and smoothness of the above-mentioned resin substrate.

[0098] In the above-mentioned pouring method, two or more of the above-mentioned techniques may be used in combination. In this case, the parallelism P of the above-mentioned resin substrate can be further improved by the synergistic effect of each technique.

[0099] The resin substrate may be subjected to post-processing such as cutting, grinding, and press molding by appropriately selecting a known technique.

[0100] The thickness of the resin substrate is not particularly limited, but the thickness of the resin substrate is preferably 0.05 to 2 mm.

[0101] When the thickness of the resin substrate is 0.05 mm or more, it is preferred because it is easy to maintain a stable shape and there is a tendency to be able to suppress small measurement errors of parallelism P. The thickness is more preferably 0.1 mm or more, and even more preferably 0.5 mm or more.

[0102] In addition, when the thickness of the resin substrate is 2 mm or less, it is preferred because it can reduce the mass of the light guide plate for image display and achieve lightweight, and can reduce deformation or residual strain caused by water absorption of the resin substrate. The thickness is more preferably 1.5 mm or less, and further preferably 1 mm or less.

[0103] The thickness of the resin substrate is a value obtained by measuring the thickness at four locations using a micrometer at 23° C. and calculating the average value of the thicknesses. The value obtained is the thickness of the resin substrate.

[0104] The thickness tolerance of the resin substrate is preferably from ±0 mm to 0.2 mm, and preferably from ±0.001 mm to 0.2 mm.

[0105] In the light guide plate of the present invention, a diffractive optical pattern may be provided on at least one surface of the light-transmitting resin substrate, whereby the light guide plate can be suitably used for an AR display or the like as an image display light guide plate.

[0106] For example, by transferring and shaping a diffraction optical pattern optically designed on a mold onto an image light incident surface and an image light emitting surface on the surface of a resin substrate, a light guide plate having relief-type diffraction elements formed thereon can be obtained.

[0107] The diffraction optical pattern is not particularly limited, but the maximum height of the diffraction optical pattern is preferably 0.15 μm or less. This can reduce the influence of the diffraction optical pattern on the parallelism P, and has a tendency to display a clear image. The maximum height is more preferably 0.14 μm or less, and further preferably 0.13 μm or less.

[0108] When the diffraction optical pattern is provided on the surface of the resin substrate as described above, the light guide plate is preferably 2The parallelism P is less than 5 μm.

[0109] An example of a light guide plate for an AR display having a relief-type diffraction element will be described below with reference to the drawings as appropriate.

[0110] Figure 1 This is a cross-sectional view of a main part showing an example of the light guide plate of the present invention. Figure 1 The light guide plate 20 shown has an image light incident surface 20a and an image light emitting surface 20b on the surface 200 of the resin substrate 30c, which are formed by transferring and shaping a diffraction optical pattern optically designed on a mold (an incident light side relief type diffraction element 30a, an emitting light side relief type diffraction element 30b).

[0111] Figure 3 is from Figure 1 Arrow A shown is a top view of the light guide plate 20 .

[0112] Figure 1 and Figure 3 The overall appearance of the light guide plate 20 shown is formed by a resin base material 30c which is a flat plate-shaped member extending parallel to the YZ plane in the figure. The light guide plate 20 is a plate-shaped member formed of a light-transmitting resin material, and has a surface 200 arranged opposite to the image forming unit 10, a first plate surface 201 which is the back side of the surface 200, and a second plate surface 202 which is the back side of the back surface 203 and opposite to the first plate surface 201. Image light is incident through an image light incident surface 20a formed on the surface 200, and is guided to the image light emitting surface 20b by means of the first plate surface 201 and the second plate surface 202.

[0113] Figure 1 The image forming unit 10 shown has an image display device 11 and a projection optical system 12. The image display device 11 is, for example, a liquid crystal display device, and generates light including 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 it toward the projection optical system 12. On the other hand, the projection optical system 12 is, for example, a collimator that converts image light emitted from each point on the image display device 11 into a parallel light beam and injects it into the light guide plate 20.

[0114] The resin substrate 30c light guide plate 20 has an image light incident surface 20a as a light incident portion for introducing image light from the image forming portion 10, and an image light emitting surface 20b for emitting the image light toward the eye EY of the observer, on a surface 200 parallel to the YZ plane. The image light incident surface 20a is formed by transferring and shaping a diffraction optical pattern optically designed on a mold to form an incident light side relief type diffraction element 30a, and the image light emitted from the image light emitting surface 20b toward the outside is diffracted and transmitted on the image light emitting surface 20b, and the image light emitting from the image light emitting surface 20b is projected as a virtual image light into the eye EY of the observer by transferring and shaping a diffraction optical pattern optically designed on a mold to form an emitting light side relief type diffraction element 30b.

[0115] Figure 1 As an example, the grating periods of the incident light side relief type diffraction element 30a and the emitting light side relief type diffraction element 30b are the same. However, the grating periods of the incident light side relief type diffraction element 30a and the emitting light side relief type diffraction element 30b may also be different.

[0116] The resin substrate 30c light guide plate 20 has a first plate surface 201 and a second plate surface 202 that are opposite to each other and extend parallel to the YZ plane, so that the image light diffracted by the incident light side relief type diffraction element 30a is totally reflected in the resin substrate 30c light guide plate 20, and the image light diffracted by the incident light side relief type diffraction element 30a is guided to the eyes of the observer. In other words, the light L1 emitted from the image forming unit 10 is incident on the image light incident surface 20a and diffracted by the incident light side relief type diffraction element 30a (light L2), the light L2 is incident on the second plate surface 202 and is totally reflected (light L3), and then the light L3 is incident on the first plate surface 201 and is totally reflected. By repeating this operation, the image light is guided to the image light emission surface 20b of the resin substrate 30c light guide plate 20. The image light guided to the image light emitting surface 20b is diffracted by the light emitting side relief type diffraction element 30b and then emitted toward the eye EY of the observer (light L4).

[0117] It should be noted that, instead of applying reflective coating to the first plate surface 201 and the second plate surface 202, the external light incident from the external side to the first plate surface 201 and the second plate surface 202 can pass through the resin substrate 30c light guide plate 20 with high transmittance. In this way, the light guide plate 20 can be made into a transmissive type that can see through external images.

[0118] The light guide plate 20 is a light guide plate for an AR display that is formed of a light-transmitting resin material and has excellent visibility.

[0119] The line width (L IN) is preferably 100 to 300 nm, more preferably 120 to 280 nm, and further preferably 140 to 260 nm.

[0120] The height (H IN ) is preferably 30 to 150 nm, more preferably 40 to 140 nm, and further preferably 50 to 130 nm.

[0121] The height (H IN ) and line width (L IN ) ratio (height (H IN ) / Line Width(L IN )) is preferably 0.1 to 1.5, more preferably 0.14 to 1.17, further preferably 0.19 to 0.93.

[0122] 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 by the image forming unit after passing through the image incident surface is within the specified range, and the diffracted light propagates in the light guide plate by total reflection and can reach the image light emission surface.

[0123] 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 Nanotechnology).

[0124] The height (H IN ) and line width (L IN ) ratio (H IN / L IN ) is the height (H) measured by the above method IN ) and line width (L IN ) is the value obtained by calculation.

[0125] The line width (L OUT ) is preferably 50 to 250 nm, more preferably 70 to 230 nm, and further preferably 90 to 210 nm.

[0126] The height (H OUT) is preferably 30 to 150 nm, more preferably 40 to 140 nm, and further preferably 50 to 130 nm.

[0127] The value of the ratio of the height to the line width of the diffraction optical pattern of the image light exit surface 20b (height (H OUT ) / Line Width(L OUT )) is preferably 0.12 to 3.0, more preferably 0.28 to 2.00, further preferably 0.24 to 1.44.

[0128] The line width (L OUT ), height (H OUT ) and height (H OUT ) / Line Width(L OUT ) is within the above range, after the image light propagating in the light guide plate passes through the exit surface, the diffraction angle is within the specified range, no image blur or ghosting will occur, and an image with excellent visibility can reach the observer.

[0129] 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 obtained in the same way.

[0130] The flatness of the light guide plate 20 is preferably 0.5 to 500 μm, more preferably 0.6 to 450 μm, and further preferably 0.7 to 400 μm.

[0131] 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 further excellent.

[0132] The flatness of the light guide plate 20 is a value obtained by placing the light guide plate 20 with its back surface 203 facing downward on a granite plate, inserting a thickness gauge in the gap between the plate and the light guide plate 20, and measuring the flatness.

[0133] 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.

[0134] The glass transition temperature (Tg) of the light-transmitting resin material is preferably 50 to 200°C, more preferably 60 to 190°C, and even more preferably 70 to 180°C.

[0135] When the glass transition temperature (Tg) of the light-transmitting resin material is within the above range, the dimensional accuracy of the light guide plate of the present invention is further improved.

[0136] The glass transition temperature (Tg) of the light-transmitting resin material is a value measured by differential scanning calorimetry using a differential scanning calorimeter (Diamond DSC, manufactured by Perkin Elmer Japan).

[0137] The Charpy impact strength of the light-transmitting resin material is preferably 0.5 to 15 kJ / m 2 , more preferably 0.8 to 14.5 kJ / m 2 , more preferably 1.0 to 14.0 kJ / m 2 .

[0138] When the Charpy impact strength of the light-transmitting resin material is within the above range, the light guide plate of the present invention has further excellent safety.

[0139] The Charpy impact strength of the light-transmitting resin material is a value obtained by using a universal impact tester (manufactured by Yasuda Seiki Co., Ltd.) to give a notch to a test piece based on JIS K 7111:2012, causing a pendulum to collide with the test piece, and measuring the impact strength at this time. The obtained value is the Charpy impact strength.

[0140] The specific gravity of the light-transmitting resin material is preferably 1.0 to 1.5 g / cm 3 , more preferably 1.05 to 1.45 g / cm 3 , more preferably 1.1 to 1.4 g / cm 3 .

[0141] When the specific gravity of the light-transmitting resin material is within the above range, the light guide plate of the present invention is more excellent in lightness.

[0142] The specific gravity of the light-transmitting resin material is a value read from a scale at which a test piece is suspended when the test piece is placed in a density gradient tube in accordance with JIS K 7112:1999.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] When the light transmittance, yellowness (YI) and yellowing degree (ΔYI) of the light-transmitting resin material are within the above ranges, the light guide plate of the present invention has better transparency and visibility.

[0147] The refractive index of the light-transmitting resin material is preferably 1.2 to 2.0, more preferably 1.3 to 1.9, and even more preferably 1.4 to 1.8.

[0148] When the refractive index of the light-transmitting resin material is within the above range, the light guide plate of the present invention has better visibility.

[0149] The refractive index of the light-transmitting resin material is a value measured at 23° C. using a D line of 589 nm using an Abbe refractometer in accordance with JIS K7142.

[0150] The retardation of the light guide plate 20 is preferably 1 to 200 nm, more preferably 3 to 150 nm, and further preferably 4 to 100 nm.

[0151] When the retardation of the light guide plate 20 is within the above range, the light guide plate of the present invention has better visibility.

[0152] The thickness (d) of the light guide plate 20 is a value obtained by measuring the thickness at four locations with a micrometer at 23° C. and calculating the average value thereof. The thickness (d) is the value obtained.

[0153] The thickness tolerance of the light guide plate is preferably from ±0 mm to 0.2 mm, and preferably from ±0.001 mm to 0.2 mm.

[0154] The light guide plate of the present invention can also be manufactured, for example, as follows: a diffraction pattern ( Figure 4 ) and the diffraction pattern ( Figure 5 ) is used as an injection molding mold, and the above-mentioned light-transmitting resin material is used for injection molding to manufacture the light guide plate.

[0155] Specifically, the following production methods (1) to (3) can be mentioned:

[0156] (1) A method for manufacturing a light guide plate comprising the steps of: injecting a polymerizable raw material into a polymerization cell (polymerization cell) (injection step), curing the polymerizable raw material (curing step), and peeling off the resin substrate from the polymerization cell (peeling step);

[0157] (2) A method for manufacturing a light guide plate, comprising cutting and grinding a resin plate (cutting and grinding steps); and

[0158] (3) A method for producing a light guide plate including injection molding a resin material constituting a resin base material using an injection molding die (injection molding step).

[0159] In the injection process of the manufacturing method of the above (1), as the polymerization pool, it is preferred to use a polymerization pool in which the thickness of the space portion is between 0.05 mm and 4.0 mm and the thickness tolerance of the space portion is between ±0.0001 mm and ±0.2 mm. It is more preferred to use a polymerization pool in which the thickness of the space portion is between 0.1 mm and 3.8 mm and the thickness tolerance is between ±0.0001 mm and ±0.01 mm.

[0160] In the curing step, the polymerizable raw material can be cured by thermal polymerization, photopolymerization, etc. In the case of thermal polymerization, it is preferred to perform the polymerization 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, it is preferred to irradiate the raw material with light having a wavelength of 200nm to 500nm at an irradiation intensity of 10mWcm -2 Above 1000mWcm -2 The polymerization is carried out by irradiating the polymer for a time of 1 second to 100 seconds, and more preferably, the irradiation intensity is 50 mWcm with a wavelength of 200 nm to 500 nm. -2 Above 500mWcm -2 The polymerization is carried out with an irradiation time of 2 seconds to 20 seconds.

[0161] In the peeling step, it is preferred that the peeling be performed after the polymerization cell is cooled to room temperature after the curing step.

[0162] In the cutting and grinding process of the manufacturing method of the above-mentioned (2), the resin plate used can be a commercially available product, wherein a continuous casting acrylic resin plate is preferred. As a method for cutting, preferably NC processing, grinding stone processing, grinding processing, etc. As a method for grinding, preferably polishing grinding, chemical grinding, electrolytic grinding, chemical mechanical grinding (CMP grinding), etc. Among them, chemical mechanical grinding (CMP grinding) has a tendency to reduce the parallelism P and surface roughness of the resin substrate in a shorter time, and is particularly preferred.

[0163] Chemical mechanical polishing is a polishing method that enhances the mechanical polishing (surface removal) effect brought about by the relative motion between the polishing material and the polishing object through the surface chemical action of the polishing material (abrasive grains) or the action of chemical components in the slurry containing the polishing material.

[0164] As a chemical mechanical polishing, for example, the following process can be adopted: a carrier mounted with a resin plate is clamped with a certain pressure between upper and lower fixed plates to which a polishing pad is attached, and while the temperature of the upper and lower fixed plates is controlled so as to be maintained below 40°C, a slurry liquid containing a polishing material is fed between the upper and lower fixed plates and the carrier while the upper and lower fixed plates are rotated at a certain speed.

[0165] The chemical mechanical polishing conditions can be appropriately selected as long as a resin substrate having the above-mentioned parallelism P can be obtained, and are not particularly limited. In addition, the polishing pad and slurry can also be appropriately selected from known materials for use.

[0166] In the injection molding process of the manufacturing method of (3), in order to improve the transferability of the diffraction optical pattern optically designed on the mold, it is preferred to perform the process with a higher barrel temperature, a faster injection speed, and a higher mold temperature relative to the standard molding conditions of the injection molding material. In addition, in order to reduce the parallelism P, it is preferred to make the mold temperature distribution uniform. In addition, injection compression molding is more preferably performed.

[0167] Example

[0168] The present invention will be described in more detail below by way of examples. However, the present invention is not limited to the examples described below, and various modifications can be made without changing the gist of the present invention.

[0169] [Examples and Comparative Examples of the Embodiment (Examples 1 to 4, Comparative Examples 1 and 2)]

[0170] Examples and comparative examples of the embodiment will be described below.

[0171] Table 1 below shows the constitutions of the resin substrates used in Examples 1 to 4 and Comparative Examples 1 and 2 and the evaluation results.

[0172]

[0173] High-precision quartz…Thickness 10mm, plate thickness tolerance ±0.001mm

[0174] Conventional glass…thickness 6mm, thickness tolerance ±0.3mm

[0175] Acrylite L is a registered trademark of Mitsubishi Chemical Corporation in Japan.

[0176] <Example>

[0177] The following examples are examples corresponding to the production of a light guide plate for image display.

[0178] 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 of the resin substrate. The thickness of the resin substrate was 1 mm or 1.5 mm.

[0179] (Example 1)

[0180] The resin substrate of Example 1 was produced as follows.

[0181] 100 parts of MMA (methyl methacrylate) were added to a reactor (polymerization kettle) equipped with a cooling tube, a thermometer and a stirrer, and stirred. After bubbling with nitrogen, heating was started. When the internal temperature reached 80°C, 0.05 parts of 2,2'-azobis-(2,4-dimethylvaleronitrile) as a free radical polymerization initiator was added. After further heating to an internal temperature of 100°C, it was maintained for 10 minutes. Thereafter, the reactor was cooled to room temperature to obtain a slurry of a viscous mixture formed by partial polymerization of MMA. The polymerization rate of the slurry was about 20% by mass.

[0182] Then, 0.2 parts of tert-hexylperoxypivalate and 0.01 parts of dioctyl sodium sulfosuccinate were added to 100 parts of the slurry and completely dissolved at room temperature to form a polymerizable raw material.

[0183] After the dissolved air in the polymerizable raw material was removed under reduced pressure, the raw material was injected into a pair of polymerization cells made of synthetic quartz glass with a mirror finish and a thickness of 10 mm and a thickness tolerance of ±0.001 mm.

[0184] The polymerization cell with the polymerizable raw material injected was kept in a warm water bath at 80°C for 60 minutes, then taken out and heated in an oven at 130°C for 30 minutes to completely solidify the slurry. After the polymerization cell was cooled to room temperature, the quartz glass was peeled off to obtain a resin substrate.

[0185] (Example 2)

[0186] The conditions for producing 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 injected was kept in a warm water bath at 80° C. for 30 minutes.

[0187] (Example 3)

[0188] As shown in Table 1, in Example 3, a continuously cast acrylic resin plate (polymethyl methacrylate) Acrylite L (registered trademark) having a thickness of 1.5 mm, which was processed into a resin plate having a thickness of 1 mm by chemical mechanical polishing, was used, which was the same as in Comparative Example 2.

[0189] (Example 4)

[0190] To 100 parts of OGSOLEA-F5710 (manufactured by OSAKAGAS CHEMICALS CO., LTD.), a photocurable resin having a structural unit derived from m-phenoxybenzyl acrylate and a fluorene structure, 1 part and 0.1 parts of Omnirad184 and Omnirad.TPO as photopolymerization initiators were added, respectively, to prepare a polymerizable raw material. Next, the polymerizable raw material was injected into a pair of quartz glass polymerization cells, and the polymerizable raw material was heated at 50 mW / cm by a high-pressure mercury lamp. 2 At an illumination of 1000mJ / cm 2 The resin substrate was further processed by chemical mechanical polishing to a thickness of 1 mm.

[0191] (Comparative Example 1)

[0192] As shown in Table 1, in Comparative Example 1, the polymerization cell was the same as Example 1 except that tempered glass having a thickness of 6 mm and a thickness tolerance of ±0.3 mm was used.

[0193] (Comparative Example 2)

[0194] As shown in Table 1, the resin substrate in Comparative Example 2 was a 1.5 mm thick continuous cast acrylic resin plate, Acrylite L (registered trademark, manufactured by Mitsubishi Chemical Corporation).

[0195] <Evaluation method>

[0196] Next, the evaluation methods of Examples 1 to 4 and Comparative Examples 1 and 2 are described.

[0197] (Parallelism P)

[0198] The parallelism P of the resin substrate is calculated as follows: using a Fizeau laser interferometer (product name: Laser Interferometer G102, manufactured by Fujifilm), the product of the number of interference fringes measured using a He-Ne laser with a light source wavelength of 632.8 nm and the change in thickness Δd of each interference fringe is calculated, and this is taken as the parallelism P.

[0199] The change in thickness Δd of an interference fringe is a value calculated by the following formula (1) assuming that the refractive index of the resin substrate is n and the laser wavelength is λ. For example, when the resin substrate is an acrylic resin (polymethyl methacrylate, n=1.49), Δd is 0.212 μm.

[0200] [Number 2]

[0201]

[0202] As a measurement sample of the 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.

[0203] The interference pattern obtained by the measurement is recorded by an inductively coupled device (CCD) camera and stored digitally. 2 The product of the number of interference fringes of the area and Δd is used to calculate the parallelism P. The number of interference fringes is counted in four directions from the center of the molded product to the top, bottom, left and right ends of the molded product from the interference image measured by the laser interferometer, and the average value is taken as the number of interference fringes.

[0204] (Dimensional change rate due to moisture absorption)

[0205] According to 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 divided by the specific gravity of the resin material to calculate the dimensional change rate due to moisture absorption.

[0206] (Heat shrinkage)

[0207] The dimensional change (shrinkage) was measured and calculated in accordance with Appendix A “Measurement of dimensional change (shrinkage) during heating” of JIS K 6718:2015.

[0208] (Ra)

[0209] In the evaluation of Ra, the arithmetic mean roughness Ra of the surface of each evaluation sample was measured. As a measuring device, a white interference type surface shape measuring machine Zygo NewView (registered trademark) 6300 (trade name; manufactured by Zygo Corporation) was used. The magnification of the objective lens was set to 2.5 times. The observation range was set to a rectangular range of 2.8 mm × 2.1 mm.

[0210] (Light transmittance)

[0211] The total light transmittance was measured using a HAZE METER NDH-5000 (manufactured by Nippon Denshoku Industries). The higher the total light transmittance obtained, the better the transparency.

[0212] (Yellowness ΔYI)

[0213] The yellowing degree ΔYI was measured using S&M Color Computer SM-T (manufactured by SUGATEST INSTRUMENTS). The lower the yellowing degree ΔYI value obtained, the better the transparency.

[0214] (Delay)

[0215] The sample was left to stand for more than 2 hours at 23°C and 55% relative humidity, and the retardation value at a wavelength of 550 nm was measured using a birefringence measuring apparatus KOBRA-WR (manufactured by Oji Scientific Instruments Co., Ltd.) The lower the obtained retardation value, the lower the birefringence, and the better the clarity of the displayed image described later.

[0216] (Display image clarity)

[0217] The image display light guide plates of Examples 1 to 4 and Comparative Examples 1 to 2 were installed in an image display device. The image display device includes an optical system for causing image light to be displayed to enter an incident portion of the image display light guide plate, a driving power source, and a circuit system for supplying image information for obtaining image light.

[0218] As input images used for evaluation, a white image and a text display image were used.

[0219] The evaluation was performed by visually judging the visual effects of the white image and the text display image. As the text image, "ABCDE" was displayed within a size of 10 mm x 100 mm.

[0220] When no rainbow color was observed in the white image and the characters were clearly observed in the character display image, it was judged as very good (described as "S" in Table 1).

[0221] When no rainbow color was observed in the white image and the characters were clearly observed in the character display image, it was judged as particularly good (good, described as "A" in Table 1).

[0222] When rainbow color was slightly observed in the white image, but characters were clearly observed in the character display image, it was judged as fair (described as "B" in Table 1).

[0223] When rainbow color was observed in at least a portion of the white image and the outline of the characters was observed to be blurred in the character display image, it was determined as a failure (no good, described as "C" in Table 1).

[0224] <Evaluation Results>

[0225] As shown in Table 1, the parallelism P of Examples 1 to 4 is 3.7 μm, 4.9 μm, 0.5 μm, and 0.8 μm, respectively. Compared with Example 1, the parallelism P of Example 2 is lower. The reason for this is believed to be that in Example 2, the retention time of the polymerization pool is shorter than that in Example 1, so a large amount of unpolymerized slurry remains, and it is quickly polymerized in the subsequent oven, thereby reducing the reaction uniformity on the surface. The parallelism P of Examples 1 to 4 is less than 5 μm, and the clarity of the displayed image is excellent. In contrast, the parallelism P of Comparative Examples 1 to 2 is greater than 30 μm, and the clarity of the displayed image is poor.

[0226] About its reason, it can be considered that the resin substrate of each embodiment is manufactured by casting or grinding. In the casting method, the surface shape of the quartz glass used in the polymerization cell is transferred to the surface of the raw material of the resin substrate of each embodiment. At this time, the planarity of the surface of the resin substrate is equivalent to the planarity of the quartz glass, so that the resin substrate obtains good thickness accuracy. In addition, by grinding, the resin substrate obtains extremely high thickness accuracy.

[0227] On the other hand, in Comparative Examples 1 and 2, it is found that sufficient parallelism P cannot be obtained because the surface shape of the tempered glass or the casting mold during production is transferred.

[0228] The arithmetic mean roughness Ra of Examples 1 to 4 is 3.2 nm, 2.3 nm, 1.7 nm, and 2.0 nm, respectively, all less than 10 nm. In contrast, the Ra of Comparative Examples 1 to 2 is 1.2 nm and 4.9 nm, respectively, all less than 10 nm. Therefore, regarding the smoothness represented by Ra, there is no significant difference between Examples 1 to 4 and Comparative Examples 1 to 2.

[0229] 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, and additions, omissions, substitutions, and other changes in structure may be made without departing from the gist of the present invention.

[0230] It should be noted that the present invention is not limited to the above description but is limited only by the appended claims.

[0231] Industrial Applicability

[0232] The resin-made light guide plate of the present invention can display a clear image and is useful in display device applications such as wearable displays or head-mounted displays used in AR or MR.

[0233] Explanation of symbols

[0234] 1…resin substrate, 2…holographic layer, 3…barrier layer, 4…hard coating layer, 10…image forming unit, 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…exit light side relief type diffraction element, 30c…resin substrate, 200…surface, 201…first plate surface, 202…second plate surface, 203…back surface, EY…eye of observer, L1, L2, L3, L4…light

Claims

1. A light guide plate having a resin substrate with a parallelism P of 0.2 μm or more and 4 μm or less, wherein the parallelism P is the square root of Δd calculated by the following formula (1) and the square root of 50×100 mm. 2 The product of the number of interference fringes of the area, the number of interference fringes is measured by a laser interferometer, The arithmetic mean roughness Ra of the surface of the resin substrate is 1.7 nm or more and 3.2 nm or less, In the formula, n is the refractive index of the resin substrate measured at 23° C. using a 589 nm D line using an Abbe refractometer in accordance with JIS K7142, and λ is the wavelength of He—Ne laser light, 632.8 nm.

2. The light guide plate according to claim 1, wherein: The light guide plate has a dimensional change rate due to moisture absorption measured in accordance with JIS K7209:2000 of 1.0% or less.

3. The light guide plate according to claim 1, wherein: The light guide plate has a heat shrinkage rate of 3% or less as measured in accordance with Appendix A of JIS K6718-1.

4. The light guide plate according to claim 1, wherein: The thickness of the resin substrate is 0.05 mm to 2 mm.

5. The light guide plate according to claim 1, wherein: The refractive index of the resin substrate is greater than or equal to 1.

48.

6. The light guide plate according to claim 1, wherein: The resin substrate includes at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins, and polycarbonates.

7. The light guide plate according to any one of claims 1 to 6, wherein: The resin substrate has a barrier layer or a hard coating layer on at least one surface thereof. 8 . A light guide plate for AR image display, comprising the light guide plate according to claim 1 . 9 . Use of the light guide plate according to claim 1 for AR image display. 10 . An AR display comprising the light guide plate according to claim 1 .

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