JP2023061044A - Light guide plate - Google Patents

Abstract

To provide a light guide plate for AR display with which it is possible to improve designability, and with which product freeform and molded article low distortion both are achieved.SOLUTION: Provided is a light guide plate for AR display which is formed with a light permeable resin material. The light guide plate has a relief-type diffraction element formed by transfer-shaping a diffractive optical pattern optically designed on a metal mold taking into account the curvature of the light guide plate in the plate width direction on the image light entering and image light emitting planes on the surface of the light guide plate. The curvature in the plate width direction is a circular arc or a free-form curved surface in radius of curvature of 100 mm or greater and is added to one or both of a first direction which is the plate width direction of the light guide plate and a second direction which is orthogonal to the first direction. The parallelism is 0.5-50 μm, the retardation is 1-200 nm, and the light intensity ratio to a plane light guide plate is 90% or greater.SELECTED DRAWING: None

Description

The present invention relates to a light guide plate.

2. Description of the Related Art An image display light guide plate may be used in a display device. 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 by a transparent substrate, or an uneven diffraction pattern An image display light guide plate composed of a transparent substrate having an optical pattern is used. The hologram layer is formed with holograms having various optical functions such as guiding, reflecting and diffractive functions.
A glass substrate is often used as the transparent substrate. However, from the viewpoint of workability, light weight, durability and portability, it is more preferable to use a resin base material as the transparent base material.

Patent Literature 1 discloses a first light guide including a first light entrance portion and a first light exit portion, and a portion of incident light provided in the first light entrance portion of the first light guide. a first diffractive optical element that diffracts and guides light through the inside of the first light guide by reflection; , wherein at least part of the incident light that is not diffracted by the first diffractive optical element is reflected by the reflective member and then diffracted by the first diffractive optical element, and An optical device is described, characterized in that it is arranged to guide light by reflection inside a first light guide.

US Pat. No. 6,201,200 discloses a transparent free-form waveguide prism for viewing a displayed virtual image, a see-through compensation lens for allowing proper viewing of real-world scenes when combined with the prism, and An ergonomic optical see-through head-mounted display device having the appearance of eyeglasses is described, consisting of a miniature image display unit for providing display content.

Patent Document 3 has a curved surface portion and microstructures formed on the curved surface portion at a predetermined pitch, and the predetermined pitch is characterized by narrowing as it approaches the outer edge of the curved surface portion. An optical member is described.

Japanese Patent No. 6232863 Japanese Patent Application Laid-Open No. 2020-184080 JP 2019-159203 A

Patent document 1 does not have a design concept of making the shape of the light guide plate into a curved surface shape, and the free-form design is poor and the design is restricted.
Although Patent Documents 2 and 3 have a design concept of free-form light guide plate, they do not specify a specific method for minimizing distortion and residual stress (deformation). Free shape and low distortion of the molded product cannot be achieved at the same time.

An object of the present invention is to provide a light guide plate for an AR display that is capable of improving designability and achieves both free shape of products and low distortion of molded products.

[1] A light guide plate for an AR display made of a light-transmitting resin material,
a relief-type diffraction element having a diffractive optical pattern designed on the image light incident surface and the image light exit surface of the surface of the light guide plate;
The curvature in the plate width direction is a circular arc or a free-form surface with a radius of curvature of 100 mm or more, and either a first direction in the plate width direction of the light guide plate or a second direction orthogonal to the first direction, or given to both
Parallelism is 0.5 to 50 μm,
Retardation is 1 to 200 nm,
A light guide plate having a light intensity ratio of 90% or more with respect to a flat light guide plate.
[2] The diffraction optical pattern on the image light incident surface has a line width of 100 to 300 nm, a height of 30 to 150 nm, and a ratio of the height to the line width (height/line width) of 0. .1 to 1.5, the light guide plate according to [1].
[3] The diffraction optical pattern on the image light exit surface has a line width of 50 to 250 nm, a height of 30 to 150 nm, and a ratio of the height to the line width (height/line width) of 0. .12 to 3.0, the light guide plate according to [1] or [2].
[4] The light guide plate according to any one of [1] to [3], wherein the light-transmitting resin material has a glass transition temperature of 50 to 200°C.
[5] The light-transmitting resin material has a moisture absorption rate of 0.01 to 1.0% by mass, and a dimensional change rate due to moisture absorption of 0.01 to 1.0%. [1] to [4] The light guide plate according to any one of .
[6] The light guide plate according to any one of [1] to [5], wherein the light-transmitting resin material has a heat shrinkage rate of 3.0% or less.
[7] Any one of [1] to [6], wherein the light transmissive resin material has a light transmittance of 85 to 100%, a yellowness index of 5 or less, and a yellowness index of 5 or less. Light guide plate as described.
[8] The light guide plate according to any one of [1] to [7], wherein the light-transmitting resin material has a refractive index of 1.2 to 2.0.
[9] The light guide plate according to any one of [1] to [8], wherein the light-transmitting resin material has a Charpy impact strength of 0.5 to 15 kJ/m ² .
[10] The light guide plate according to any one of [1] to [9], wherein the light-transmitting resin material has a specific gravity of 1.0 to 1.5 g/cm ³ .

ADVANTAGE OF THE INVENTION According to this invention, it is possible to improve designability, and can provide the light-guide plate for AR displays which compatible the product free shape and the low distortion of a molded product.

FIG. 1 is a cross-sectional view of a main part showing an example of the light guide plate of the present invention. FIG. 2 is a plan view of the light guide plate 20 viewed from the arrow A shown in FIG. FIG. 3 is a schematic diagram illustrating a method for measuring the parallelism (thickness) of the light guide plate of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the embodiments described later, and various modifications are possible without departing from the gist of the present invention.
In the present invention, the numerical range represented by "-" includes the numerical values on both sides of "-".

[Light guide plate]
The light guide plate of the present invention is a light guide plate for an AR display made of a light-transmitting resin material, wherein the image light entrance surface and the image light exit surface of the light guide plate are provided on the mold. It has a relief-type diffraction element formed by transferring and shaping a diffraction optical pattern optically designed based on the curvature of the plate width direction of the light plate. However, the image light incident surface is not limited to the relief type diffraction element as long as it has a similar function.

Hereinafter, the light guide plate of the present invention will be described with appropriate reference to the drawings.
FIG. 1 is a cross-sectional view of a main part showing an example of the light guide plate of the present invention. The light guide plate 20 shown in FIG. 1 is a relief-type diffraction element formed by transferring a diffractive optical pattern optically designed on a mold onto the image light entrance surface 20a and the image light exit surface 20b of the surface 200. (incident light side relief type diffraction element 30a, exit light side relief type diffraction element 30b).
FIG. 2 is a plan view of the light guide plate 20 viewed from the arrow A shown in FIG.
The overall appearance of the light guide plate 20 shown in FIGS. 1 and 2 is formed by curved members extending parallel to the YZ plane in the drawings. The light guide plate 20 is a plate-shaped member made of a light-transmitting resin material, and has a front surface 200 arranged to face the image forming section 10, and a first panel surface 201 and a rear surface 203 on the back side of the front surface 200. , and has a first panel surface 201 and a second panel surface 202 facing each other. Image light is incident through an image light incident surface 20a formed on the front surface 200. The second panel surface 202 guides the light to the image light exit surface 20b.

The image forming section 10 shown in FIG. 1 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. emit toward On the other hand, the projection optical system 12 is, for example, a collimating lens that converts the image light emitted from each point on the image display device 11 into a parallel light beam and makes the light beam enter the light guide plate 20 .

The light guide plate 20 has an image light incident surface 20a, which is a light incident portion that receives image light from the image forming section 10, on a surface 200 parallel to the YZ plane, and emits the image light toward the observer's eye EY. and an image light exit surface 20b. An incident light side relief type diffraction element 30a is formed on the image light incident surface 20a by transferring and forming an optically designed diffractive optical pattern on a mold. The output light side relief type diffraction element 30b that diffracts and transmits the image light emitted to the outside from 20b and projects it as virtual image light to the observer's eye EY forms a diffractive optical pattern optically designed on the mold. It is formed by transfer molding.

In FIG. 1, the incident light side relief type diffraction element 30a and the output light side relief type diffraction element 30b have the same grating period as an example. However, the grating periods of the incident-light-side relief-type diffraction element 30a and the exit-light-side relief-type diffraction element 30b may be different.
The light guide plate 20 has a first panel surface 201 and a second panel surface 202 which are opposed to each other and extend parallel to the YZ plane. The image light, which is totally reflected in the light guide plate and diffracted by the incident light side relief diffraction element 30a, is guided to the viewer's eye. In other words, the light L1 emitted from the image forming section 10 enters the image light incident surface 20a and is diffracted by the incident light side relief diffraction element 30a (light L2). It enters and is totally reflected (light L3), and then the light L3 enters the first panel surface 201 and is totally reflected. By repeating this operation, the image light is guided to the image light exit surface 20 b of the light guide plate 20 . The image light guided to the image light exit surface 20b is diffracted by the exit light side relief diffraction element 30b and then emitted toward the observer's eye EY (light L4).

Note that the first panel surface 201 and the second panel surface 202 are not coated with a reflective coating, and the external light incident on the first panel surface 201 and the second panel surface 202 from the outside is highly transmitted. The light may pass through the light guide plate 20 at a rate. Thereby, the light guide plate 20 can be of a see-through type that allows the see-through of the image of the outside world.

〈Curved〉
In the light guide plate of the present invention, the curvature in the plate width direction is an arc or a free-form surface with a radius of curvature of 100 mm or more, and the light guide plate has a first direction in the plate width direction and a second direction perpendicular to the first direction. in either or both directions.

The radius of curvature of the light guide plate 20 in the plate width direction is 100 mm or more, preferably 150 mm or more, and more preferably 200 mm or more.
When the radius of curvature of the light guide plate 20 in the plate width direction is 100 mm or more, the visibility of the light guide plate of the present invention is sufficient, and it can be adapted to the body when worn.
If the radius of curvature of the light guide plate 20 in the plate width direction is less than 100 mm, the visibility of the light guide plate is poor, making it difficult to fit the body when worn.
The radius of curvature of the light guide plate 20 in the plate width direction is a value obtained by measuring the positions of three points on the surface of the molded product on the same cross section with a three-dimensional measuring device.

A first direction in the plate width direction of the light guide plate 20 is, for example, the y-axis direction, and a second direction perpendicular to the first direction is, for example, the z-axis direction.

<Parallelism>
The parallelism (P) of the light guide plate 20 is 0.5 to 50 μm, preferably 0.6 to 45 μm, more preferably 0.7 to 40 μm.
When the parallelism (P) of the light guide plate 20 is within the above range, the dimensional accuracy of the light guide plate of the present invention is more excellent.
The parallelism (P) of the light guide plate 20 is obtained by collecting point cloud data of the light guide plate 20 with a 3D scanner, and measuring When the intersection of the straight line D and the curved surface E facing the curved surface A is the point F, the distance between the points B and F is obtained, and similar measurements are made at multiple locations on the light guide plate. , the difference between the maximum value and the minimum value in this data is taken as the degree of parallelism (Fig. 3).

<Retardation>
The retardation of the light guide plate 20 is 1 to 200 nm, preferably 3 to 150 nm, more preferably 4 to 100 nm.
When the retardation of the light guide plate 20 is within the above range, the light is properly guided and diffracted, no image distortion occurs, and the visibility of the light guide plate of the present invention is excellent.
The retardation of the light guide plate 20 is a value obtained by measuring using a two-dimensional birefringence evaluation system (PA-110, manufactured by Photonic Lattice). The area to be measured is divided into areas of several mm square, and the area is set horizontally on the measuring machine and measured.

<Light intensity>
The light intensity ratio of the light guide plate of the present invention to the flat light guide plate is 90% or more, preferably 95% or more.
When the light intensity ratio of the light guide plate of the present invention is within the above range, the intensity of light rays recognized as an image is sufficient, and the visibility of the light guide plate of the present invention is excellent.
The light intensity ratio of the light guide plate of the present invention is the relative light intensity calculated by simulation, and is the ratio to the light intensity of the flat light guide plate. The RCWA (Rigorous Coupled-Wave Analysis) method is used to analyze the diffraction grating characteristics, and a commercially available electromagnetic field simulator such as Rsoft DiffractMOD (trademark) is utilized. For the simulation of the light guide plate, the Monte Carlo ray tracing method [I. Powell "Ray Tracing through systems containing holographic optical elements", Appl. Opt. 31, pp. 2259-2264 (1992). ] is utilized, such as LightTools™.
On one surface of a light guide plate having a refractive index of 1.64 and a thickness of 1.5 mm, an incident diffraction grating of 5 mm×5 mm and an output diffraction grating of 40 mm×40 mm are installed, and a 1.5 mm gap is provided between the two kinds of diffraction gratings. Leave a gap. The light source is parallel light with a diameter of 4 mm and vertically incident on the center of the incident diffraction grating.
Curvature is given to one direction of the light guide plate so that the center of the light source, the center of the incident diffraction grating, the center of the outgoing diffraction grating, and the center of the surface light receiver are on the same plane as the curvature circle, and the average received light intensity on the same plane is calculated. A ratio to the light receiving intensity of the flat light guide plate is obtained.

<Diffraction optical pattern>
《Line Width, Height and Height/Line Width》
The line width (L) of the diffraction optical pattern of the image light incident surface 20a is 100 to 300 nm, preferably 120 to 280 nm, more preferably 140 to 260 nm. The height (H) of the diffraction optical pattern on the image light incident surface 20a is 30 to 150 nm, preferably 40 to 140 nm, more preferably 50 to 130 nm.
The ratio of the height (H) to the line width (L) of the diffraction optical pattern on the image light incident surface 20a (height (H)/line width (L)) is 0.1 to 1.5, 0.14 to 1.17 is preferred, and 0.19 to 0.93 is more preferred.
When the line width (L), height (H), and height (H)/line width (L) of the diffraction grating pattern on the image light incident surface 20a are within the above ranges, the image light emitted from the image forming unit is within a predetermined range after passing through the image light incident surface, and the diffracted light can propagate in the light guide plate by total reflection and reach the image light exit surface.
The line width (L) and height (H) of the diffraction grating pattern on the image light incident surface 20a are values obtained by measurement using an atomic force microscope (Nano-R, manufactured by Pacific Nanotechnology). The ratio (H/L) between the height (H) and the line width (L) of the diffraction grating pattern on the image light incident surface 20a is obtained from the height (H) and the line width (L) measured by the method described above. It is a calculated value.

The line width (L′) of the diffraction optical pattern of the image light exit surface 20b is 50-250 nm, preferably 70-230 nm, more preferably 90-210 nm.
The height (H′) of the diffraction optical pattern on the image light exit surface 20b is 30 to 150 nm, preferably 40 to 140 nm, more preferably 50 to 130 nm.
The value of the ratio of the height to the line width (height (H')/line width (L')) of the diffraction optical pattern of the image light exit surface 20b is 0.12 to 3.0, and 0.28 to 2.0. 0.00 is preferred, and 0.24 to 1.44 is more preferred.
When the line width (L′), height (H′), and height (H′)/line width (L′) of the diffraction grating pattern on the image light exit surface 20b are within the above ranges, After the image light that has passed through the exit surface, the diffraction angle falls within a predetermined range, and an image with excellent visibility can reach the observer without image blurring or ghosting.
The line width (L′), height (H′), and height (H′)/line width (L′) of the diffraction grating pattern of the image light exit surface 20b are respectively the diffraction grating pattern of the image light entrance surface 20a. are values obtained in the same manner as the line width (L), height (H), and height (H)/line width (L).

<Light transmissive resin material>
《Resin material》
Examples of the light-transmitting resin material include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, fluororesin film, polyvinyl chloride, polyethylene, and polypropylene. , cyclic polyolefin, cellulose, acetylcellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, poly(meth)acrylic resin, phenolic resin, epoxy resin, polyarylate, polynorbornene, styrene-isobutylene-styrene block copolymer (SIBS), and organic materials such as allyl diglycol carbonate. The light-transmissive resin material preferably contains at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins and polycarbonates.

These resin materials can be obtained by polymerizing polymerizable materials by known methods. The polymerizable material preferably contains a monomer, a polymerization initiator, an emulsifier, and the like. Examples of monomers for poly(meth)acrylic resins include (meth)acrylic acid esters, aliphatic methacrylates (e.g. methyl methacrylate, ethyl methacrylate, butyl methacrylate), alicyclic methacrylates (e.g. , cyclohexyl methacrylate), aromatic methacrylates (eg, phenyl methacrylate), and the like. Examples of polymerization initiators include azo polymerization initiators and organic peroxides. Azo polymerization initiators include 2,2'-azobis-(2,4-dimethylvaleronitrile) and the like. Organic peroxides include t-hexyl peroxypivalate and the like. Emulsifiers include dioctyl sodium sulfosuccinate and the like.

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

"Glass-transition temperature"
The glass transition temperature of the light-transmissive resin material is not particularly limited, but is preferably 50 to 200.degree. C., more preferably 60 to 190.degree. C., and even more preferably 70 to 180.degree.
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 more excellent.
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 PerkinElmer Japan).

《Moisture Absorption Rate》
Although the moisture absorption rate of the light-transmitting resin material is not particularly limited, it is preferably 0.01 to 1.0% by mass, more preferably 0.02 to 0.9% by mass, and 0.03 to 0.8% by mass. is more preferred.
When the hygroscopicity of the light-transmitting resin material is within the above range, it becomes easy to keep the dimensional change ratio described later within a predetermined range, and as a result, the light guide plate of the present invention has superior dimensional accuracy. becomes.
The moisture absorption rate of the light-transmitting resin material is determined by immersing a test piece in distilled water at 23°C and measuring the weight per 24 hours of water absorption This value is obtained by calculating the rate of increase.

《Dimensional change rate due to moisture absorption》
The dimensional change rate of the light-transmitting resin material due to moisture absorption is not particularly limited, but is preferably 0.01 to 1.0%, more preferably 0.02 to 0.9%, and 0.03 to 0.8. % is more preferred.
When the dimensional change rate due to moisture absorption of the light-transmitting resin material is within the above range, the dimensional accuracy of the light guide plate of the present invention is more excellent, and the change over time of the image display characteristics of the light guide plate can be suppressed. Tend. Moreover, since the light guide plate of the present invention does not need to be processed excessively, the productivity can be improved.
The dimensional change rate due to moisture absorption of the light-transmitting resin material was measured by immersing the test piece in distilled water at 23 ° C. in accordance with JIS K 7209:2000 "Plastics - Determination of water absorption rate" and measuring the water absorption for 24 hours. It is a value obtained by dividing the weight increase rate per unit by the specific gravity of the resin material.

《Thermal shrinkage rate》
The heat shrinkage rate of the light-transmitting resin material is not particularly limited, but is preferably 3.0% or less, more preferably 2.5% or less, and even more preferably 2.0% or less.
When the heat shrinkage rate of the light-transmitting resin material is 3.0% or less, the clarity of the displayed image using a hologram such as AR formed using the light guide plate of the present invention is improved. Tend.
The heat shrinkage rate of the light-transmitting resin material is JIS K 6718-1: 2015 "Plastics-Methacrylic resin plate-Types, dimensions and characteristics-Part 1: Cast plate" Appendix A "Dimensional change during heating Measurement of (shrinkage)” is the thermal shrinkage rate measured in accordance with the measurement method described in “.

《Light transmittance》
The light transmittance of the light-transmitting resin material is not particularly limited, but is preferably 85 to 100%, more preferably 86 to 100%, and even more preferably 87 to 100%.
When the light transmittance of the light-transmitting resin material is within the above range, the visibility of the light guide plate of the present invention is more excellent.
The light transmittance of the light-transmitting resin material is the light transmittance at a wavelength of 450 to 650 nm measured using a spectrophotometer (UV-2400, manufactured by Shimadzu Corporation).

<<Yellowness and Yellowness>>
The yellowness index (YI) of the light-transmitting resin material is not particularly limited, but is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.
When the yellowness index (YI) of the light-transmitting resin material is 5 or less, the visibility of the light guide plate of the present invention becomes more excellent.
The yellowing index (ΔYI) of the light-transmitting resin material is not particularly limited, but is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.
When the yellowing index (ΔYI) of the light-transmitting resin material is 5 or less, the visibility of the light guide plate of the present invention becomes more excellent.
The yellowness (YI) and the yellowness (ΔYI) of the light-transmitting resin material are measured using a spectrocolorimeter (SE7700, manufactured by Nippon Denshoku Industries Co., Ltd.) with a C light source in a 2° field of view. is the value

《Refractive index》
The refractive index of the light-transmissive resin material is not particularly limited, but is preferably 1.2 to 2.0, more preferably 1.3 to 1.9, and even more preferably 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 becomes more excellent.
The refractive index of the light-transmitting resin material is obtained by measuring with the D line of 589 nm at 23 ° C. based on JIS K 7142: 2014 "Plastics - Determination of refractive index" using an Abbe refractometer. value.

《Charpy Impact Strength》
The Charpy impact strength of the light-transmitting resin material is not particularly limited, but is preferably 0.5 to 15 kJ/m ² , more preferably 0.8 to 14.5 kJ/m ² , and 1.0 to 14.0 kJ. / ^m2 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 is further improved.
The Charpy impact strength of the light-transmitting resin material is determined by applying a notch to the test piece based on JIS K 7111: 2012 using a universal impact tester (manufactured by Yasuda Seiki Seisakusho) and colliding the test piece with a pendulum. It is a value obtained by measuring the impact strength when it is applied.

"specific gravity"
Although the specific gravity of the light-transmitting resin material is not particularly limited, it is preferably 1.0 to 1.5 g/cm ³ , more preferably 1.05 to 1.45 g/cm ³ , and 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 is more excellent in lightness.
The specific gravity of the light-transmitting resin material is the reading value of the scale when the test piece is suspended when the test piece is placed in the density gradient tube in accordance with JIS K 7112:1999.

[Method for manufacturing light guide plate]
For the light guide plate of the present invention, for example, an injection molding mold provided with a diffraction pattern for forming an incident light side relief type diffraction element and a diffraction pattern for forming an exiting light side relief type diffraction element is prepared, and the above-described light transmission plate is prepared. It can be manufactured by injection molding using a flexible resin material.

Specifically, the following production methods (1) to (3) are mentioned:
(1) A light guide plate including injecting a polymerizable raw material into a polymerization cell (injection step), curing the polymerizable raw material (curing step), and peeling a resin base material from the polymerization cell (peeling step). Production method;
(2) A method for manufacturing a light guide plate including cutting and polishing a resin plate (cutting and polishing process); and (3) Injecting a resin material constituting a resin base using an injection molding mold A method of manufacturing a light guide plate including molding (injection molding process).
In the injection step of the manufacturing method (1), the polymerization cell has a thickness of the space of 0.05 mm or more and 4.0 mm or less and a thickness tolerance of the space of ±0.0001 mm or more and ±0.2 mm or less. It is preferable to use a cell, and it is more preferable to use a polymerization cell having a space portion 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 carried out at 30° C. to 150° C. for 5 minutes to 120 minutes, more preferably 50° C. to 130° C. for 10 minutes to 60 minutes. In the case of photopolymerization, it is preferable to polymerize light with a wavelength of 200 nm or more and 500 nm or less at an irradiation intensity of 10 mWcm ^{−2 or} more and 1000 mWcm ⁻² or less for an irradiation time of 1 second or more and 100 seconds or less. , an irradiation intensity of 50 mWcm ⁻² or more and 500 mWcm ⁻² or less, and an irradiation time of 2 seconds or more and 20 seconds or less.
In the peeling step, after the curing step, it is preferable to cool the polymerization cell to room temperature 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 particularly preferable. As a cutting method, NC processing, grindstone processing, lapping processing, and the like are preferable. As a polishing method, buffing, chemical polishing, electrolytic polishing, chemical mechanical polishing (CMP polishing) and the like are preferable. Among these, chemical mechanical polishing (CMP polishing) tends to be able to reduce the parallelism P and surface roughness of the resin base material in a shorter period of time, and is particularly preferred.
This chemical mechanical polishing is mechanical polishing (surface removal) due to relative motion between the abrasive and the object to be polished due to the surface chemical action of the abrasive (abrasive grain) and the action of the chemical components in the slurry containing it. It is a polishing method that increases the effect.
As chemical mechanical polishing, for example, a carrier having a resin plate attached thereto is sandwiched between upper and lower surface plates to which polishing pads are attached at a constant pressure, and the temperature of the upper and lower surface plates is controlled so as to be kept at 40° C. or less. Alternatively, a slurry liquid containing an abrasive is fed between the upper and lower surface plates and the carrier while the carrier rotates and revolves, and the upper and lower surface plates are rotated at a constant speed at the same time.
The conditions for this chemical mechanical polishing are not particularly limited and can be appropriately selected so as to obtain a resin base material having the above-mentioned parallelism P. As for the polishing pad and the slurry liquid, well-known ones can be appropriately selected and used.
In the injection molding step of the manufacturing method (3), in order to improve the transferability of the diffractive optical pattern optically designed on the mold, the cylinder temperature is high and the injection speed is high compared to the standard molding conditions for injection molding materials. , the mold temperature is preferably high. Also, in order to reduce the parallelism P, it is preferable to make the mold temperature distribution uniform. Furthermore, it is more preferable to carry out injection compression molding.

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the embodiments described later, and various modifications are possible as long as the gist of the present invention is not changed.

<Examples 1 to 3>
In the SRG light guide plate manufactured by injection molding, a curved light guide plate was manufactured by setting a curve in the mold.
Curvature radii of curvature were set to 100 mm, 200 mm, and 500 mm.

<Comparative Example 1>
In the SRG light guide plate manufactured by injection molding, a flat light guide plate was manufactured without setting a curve in the mold.
<Comparative Example 2>
In the SRG light guide plate manufactured by injection molding, a curved light guide plate was manufactured by setting a curve with a radius of curvature of 50 mm in the mold.

<Evaluation method>
It was evaluated as described below and the results are shown in Table 1.

(shape freedom)
○: When manufacturing a curved light guide plate ×: When manufacturing a flat light guide plate

(parallelism, retardation, light intensity ratio)
It was evaluated by the method described above.

The light guide plate for AR display of the present invention has both releasability from molds and optical properties, and can display clear images, so it is useful for display devices such as wearable displays and head-mounted displays. .

DESCRIPTION OF SYMBOLS 10... Image formation part 11... Image display apparatus 12... Projection optical system 20... Light guide plate 20a... Image light entrance surface 20b... Image light exit surface 30a... Incident light side relief type diffraction element 30b... Output Illumination-side relief-type diffraction element 30c Resin base material 200 Front surface 201 First panel surface 202 Second panel surface 203 Back surface EY Observer's eye L1, L2, L3, L4... light

Claims (10)

A light guide plate for an AR display made of a light-transmitting resin material,
a relief-type diffraction element having a diffractive optical pattern designed on the image light incident surface and the image light exit surface of the surface of the light guide plate;
The curvature in the plate width direction is a circular arc or a free-form surface with a radius of curvature of 100 mm or more, and either a first direction in the plate width direction of the light guide plate or a second direction orthogonal to the first direction, or granted to both
Parallelism is 0.5 to 50 μm,
Retardation is 1 to 200 nm,
A light guide plate having a light intensity ratio of 90% or more with respect to a flat light guide plate. The diffraction optical pattern on the image light incident surface has a line width of 100 to 300 nm, a height of 30 to 150 nm, and a ratio of the height to the line width (height/line width) of 0.1 to 0.1. 1. The light guide plate of claim 1, wherein the ratio is 1.5. The diffraction optical pattern on the image light exit surface has a line width of 50 to 250 nm, a height of 30 to 150 nm, and a ratio of the height to the line width (height/line width) of 0.12 to 0.12. 3. The light guide plate according to claim 1 or 2, which is 3.0. The light guide plate according to any one of claims 1 to 3, wherein the light-transmitting resin material has a glass transition temperature of 50 to 200°C. 5. The light-transmissive resin material has a moisture absorption rate of 0.01 to 1.0% by mass, and a dimensional change rate due to moisture absorption of 0.01 to 1.0%, according to any one of claims 1 to 4. The light guide plate described in . The light guide plate according to any one of claims 1 to 5, wherein the light-transmitting resin material has a heat shrinkage rate of 3.0% or less. The light transmitting resin material according to any one of claims 1 to 6, wherein the light transmittance is 85 to 100%, the yellowness is 5 or less, and the yellowing degree is 5 or less. light plate. The light guide plate according to any one of claims 1 to 7, wherein the light-transmitting resin material has a refractive index of 1.2 to 2.0. 9. The light guide plate according to claim 1, wherein the light-transmitting resin material has a Charpy impact strength of 0.5 to 15 kJ/m ² . The light guide plate according to any one of claims 1 to 9, wherein the light-transmitting resin material has a specific gravity of 1.0 to 1.5 g/ ^cm3 .

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