JP2023059007A - Light guide plate laminate - Google Patents

Abstract

To provide a light guide plate laminate with two or more light guide plates allowing a gap thereof to be maintained easily and alignment thereof to be performed easily.SOLUTION: A light guide plate laminate is formed of a light-transmitting resin material, by lamination of light guide plates for an AR display. The light guide plate laminate has a relief type diffraction element formed by imprint of a diffractive optical pattern optically designed on a mold onto an image light emitting surface of a surface of the light guide plate. A structure of the two or more light guide plates for maintaining a gap and for alignment is arranged at a position that does not interfere with the relief type diffraction element.SELECTED DRAWING: None

Description

The present invention relates to a light guide plate laminate.

In recent years, an AR (augmented reality) display, which uses a light guide plate to guide an image from an image display device as one of the image projection devices and displays it in front of the observer's eyes, has been commercialized. Developments related to widening the angle of view and improving efficiency are being carried out. Among them, a diffractive optical element is attracting attention as one of the elements for making light enter and exit the light guide plate. This diffractive optical element can control the traveling direction of light using the diffraction phenomenon, so that it has the characteristics of being smaller and having a higher degree of freedom in manipulating light than using reflection or refraction.

Patent Document 1 discloses a substrate, an incident diffraction grating for diffracting incident light, and an exit diffraction grating for exiting the light diffracted by the incident diffraction grating, wherein the exit diffraction grating is located on the substrate surface. The uneven pattern is formed of a first parallel straight line group and a second parallel straight line group intersecting the first parallel straight line group, and the first parallel straight line group The pitch of the straight line group is equal to the pitch of the second parallel straight line group, and the relationship between the pitch P of the first parallel straight line group and the second parallel straight line group and the width W of the uneven pattern is W A light guide plate module configured by laminating a plurality of light guide plates, wherein /P is 0.15 or more and 0.85 or less, wherein two light guide plates are provided on the surface of the substrate of the light guide plate. It is described that the gap between the two light guide plates can be maintained at the height of the gap holding pattern by arranging them close to each other via the gap holding pattern of columnar shape.

JP 2021-001955 A

In the light guide plate module (light guide plate laminate) described in Patent Literature 1, since the gap holding pattern is arranged within the diffraction grating area, optical characteristics such as diffraction efficiency are degraded. In addition, since no mechanism for fixing the light guide plate is provided, misalignment occurs due to lamination.

An object of the present invention is to provide a light guide plate laminate in which it is easy to maintain a gap between two or more light guide plates and to align them.

[1] A light guide plate laminate formed by laminating light guide plates 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 exit surface of the surface of the light guide plate;
A light guide plate laminate, wherein a structure for maintaining the gap and aligning the two or more light guide plates is arranged at a position that does not interfere with the relief type diffraction element.
[2] A light guide plate laminate formed by laminating light guide plates 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;
A light guide plate laminate, wherein two or more of the light guide plates are laminated with a gap holding and alignment structure arranged at a position not interfering with the relief type diffraction element.
[3] According to [1] or [2], wherein the gap holding and alignment structure is an adhesive protrusion arranged at a position not related to the image on the surface opposite to the surface having the relief type diffraction element. light guide plate laminate.
[4] [1] or [2], wherein the spacing and alignment structure is a mating pawl located at a non-image related position on the outside of the surface opposite the surface having the relief-type diffractive element; The light guide plate laminate according to 1.
[5] [1] or [2], wherein the gap-holding and alignment structure is unevenness or projections that fit into the surface having the relief-type diffraction element and the surface opposite to the surface having the relief-type diffraction element. The light guide plate laminate according to 1.
[6] The diffractive optical pattern on the image light exit surface of the light guide plate has a line width of 50 to 250 nm and a height of 30 to 150 nm, and a ratio of the height to the line width (height/line width) is 0.12 to 3.0, the light guide plate laminate according to any one of [1] to [5].
[7] The light guide plate laminate according to any one of [1] to [6], wherein the light guide plate has a flatness of 0.5 to 500 μm.
[8] The light guide plate laminate according to any one of [1] to [7], wherein the light guide plate has a parallelism of 0.5 to 50 μm.
[9] The light guide plate laminate according to any one of [1] to [8], wherein the light-transmitting resin material has a glass transition temperature of 50 to 200°C.
[10] The light-transmitting resin material of [1] to [9] has a moisture absorption rate of 0.01 to 1.0% and a dimensional change rate due to moisture absorption of 0.01 to 1.0%. The light guide plate laminate according to any one of the above.
[11] The light guide plate laminate according to any one of [1] to [10], wherein the light-transmitting resin material has a heat shrinkage rate of 3.0% or less.
[12] The light transmissive resin material according to any one of [1] to [11], wherein the light transmittance is 85% or more, the yellowness is 5 or less, and the yellowness is 5 or less. light guide plate laminate.
[13] The light guide plate laminate according to any one of [1] to [12], wherein the optically transparent resin material has a refractive index of 1.2 to 2.0.
[14] The light guide plate laminate according to any one of [1] to [13], wherein the light guide plate has a retardation of 1 to 200 nm.
[15] The light guide plate laminate according to any one of [1] to [14], wherein the light-transmitting resin material has a Charpy impact strength of 0.5 to 15 kJ/m ² .
[16] The light guide plate laminate according to any one of [1] to [15], 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, the light-guide plate laminated|stacked body which the gap maintenance of two or more light-guide plates and position alignment are easy can be provided.

FIG. 1 is a fragmentary cross-sectional view of an example of a light guide plate that constitutes the light guide plate laminate of the present invention. FIG. 2 is a plan view of an example of a light guide plate that constitutes the light guide plate laminate of the present invention. FIG. 3 is a longitudinal sectional view showing one embodiment of the light guide plate laminate of the present invention. FIG. 4 is a longitudinal sectional view showing another embodiment of the light guide plate laminate of the present invention. FIG. 5 is a longitudinal sectional view showing still another embodiment of the light guide plate laminate of the present invention.

In the present invention, the numerical range represented by "-" includes the numerical values on both sides of "-".
Embodiments of the present invention will be described below, but 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.

[Light guide plate laminate]
The light guide plate laminate of the present invention is formed by laminating two or more of the light guide plates described later, and the structure for maintaining the gap and aligning the two or more light guide plates is positioned so as not to interfere with the relief type diffraction element. are placed in In other words, the light guide plate laminate of the present invention is formed by laminating two or more of the light guide plates described later, and the two or more light guide plates are arranged at a position where they do not interfere with the relief type diffraction element. Laminated with a holding and alignment structure.

<Gap retention and alignment structure>
The gap holding and alignment structure is not particularly limited as long as it is arranged at a position that does not interfere with the relief-type diffraction element of the light guide plate and can hold the gap and align between two or more light guide plates.
The gap holding and alignment structure may be integrally molded with the light guide plate, or may be molded separately from the light guide plate and adhered to the light guide plate.
The size of the gap holding and alignment structure is not particularly limited as long as it does not interfere with the behavior of light such as light guiding and diffraction in the light guide plate and allows gap holding and alignment between two or more light guide plates. .
Examples of such a gap holding and alignment structure include the following aspects.

"protrude"
One aspect of the spacing and alignment structure is the non-image related position of the surface of the light guide plate 301 (302) opposite the surface having the relief-type diffractive elements 301a and 301b (302a and 302b), as shown in FIG. is a protrusion 303 for adhesion arranged on the . Bonding is performed by conventionally known bonding techniques such as ultrasonic waves and adhesives.
The protrusion-shaped spacing and alignment structures may be located on either side of the light guide plate with or without the relief-type diffractive elements. Moreover, the structure which fixes only the adjacent light-guide plate of 2 or more light-guide plates may be sufficient, and the structure which fixes all the light-guide plates of 2 or more light-guide plates may be sufficient.

"nail"
Another aspect of the spacing and alignment structure is the image of the outside of the surface opposite the surface having the relief-type diffractive elements 401a and 401b (402a and 402b) of the light guide plate 401 (402), as shown in FIG. It is a claw 403 for fitting arranged at a position unrelated to the position.
The pawl-shaped spacing and alignment structures may be located on either side of the light guide plate with or without the relief-type diffractive elements. Moreover, the structure which fixes only the adjacent light-guide plate of 2 or more light-guide plates may be sufficient, and the structure which fixes all the light-guide plates of 2 or more light-guide plates may be sufficient.

<<Concavities and convexities or protrusions that engage with each other>>
Yet another aspect of the gap holding and alignment structure is a surface having relief type diffractive elements 501a and 501b (502a and 502b) of light guide plate 501 (502) and the relief type diffractive elements as shown in FIG. Concavities and convexities or protrusions 503 that engage with each other on the surface having and facing each other.
The interdigitated gap-holding and alignment structures in the form of projections and depressions may be placed on either side of the light guide plate with or without the relief-type diffractive elements. Moreover, the structure which fixes only the adjacent light-guide plate of 2 or more light-guide plates may be sufficient, and the structure which fixes all the light-guide plates of 2 or more light-guide plates may be sufficient.

<Effects of gap retention and alignment structure>
Since the light guide plate laminate of the present invention has a gap holding and alignment structure, the flatness of the light guide plate alone before and after lamination can easily be within the range of 0.5 to 50 μm, so the visibility of the light guide plate laminate is improved. It's easy to do.
The dimensional change rate after lamination can easily be suppressed within the range of 0.01 to 1.0% for the entire laminated light guide plate with respect to the projected view of the light guide plate before dimensional change and before lamination with respect to the XY plane.
The heat shrinkage rate after lamination is easily 3.0% or less in the entire laminated light guide plate with respect to the projected view of the light guide plate before heat shrinkage and before lamination with respect to the XY plane.

<Method for manufacturing light guide plate laminate>
The gap-holding and alignment structures are integrally or separately molded with the light guide plate. A light guide plate stack can be manufactured by stacking light guide plates in which the spacing and alignment structures are arranged.
A method for manufacturing the light guide plate will be described later.

[Light guide plate]
The light guide plate constituting the light guide plate laminate of the present invention (hereinafter also simply referred to as the "light guide plate of the present invention") is a light guide plate for an AR display made of a light-transmitting resin material, The image light incident surface and the image light exit surface of the light guide plate have a relief type diffraction element formed by transferring and molding a diffraction optical pattern optically designed on a mold.
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 an essential part of 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 a flat member 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 shaping.

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.

<Diffraction optical pattern>
《Line Width, Height and Height/Line Width》
The line width (L′) of the diffraction optical pattern on the image light exit surface 20b is not particularly limited, but is preferably 50-250 nm, more preferably 70-230 nm, and even more preferably 90-210 nm.
The height (H′) of the diffraction optical pattern on the image light exit surface 20b is not particularly limited, but is preferably 30 to 150 nm, more preferably 40 to 140 nm, even 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 diffractive optical pattern of the image light exit surface 20b is not particularly limited, but is preferably 0.12 to 3.0. 0.28 to 2.00 is more preferred, and 0.24 to 1.44 is even 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 were measured by an atomic force microscope (Nano-R, Pacific Nano Technology Co., Ltd.). The ratio (H'/L') between the height (H') and the line width (L') of the diffraction grating pattern on the image light exit surface 20b is the height (H') and line width (H') measured by the above-described method. This value is calculated from the width (L').

<Characteristics of the light guide plate>
《Flatness》
The flatness of the light guide plate 20 is not particularly limited, but is preferably 0.5 to 500 μm, more preferably 0.6 to 450 μm, even more preferably 0.7 to 400 μm.
When the flatness of the light guide plate 20 is within the above range, the dimensional accuracy of the light guide plate of the present invention is more excellent.
The flatness of the light guide plate 20 is obtained by measuring with a three-dimensional measuring device (XYZAX PJ-600A (manufactured by Tokyo Seimitsu Co., Ltd.)).

《Parallelism》
The parallelism (P) of the light guide plate 20 is not particularly limited, but is preferably 0.5 to 50 μm, more preferably 0.6 to 45 μm, even 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 the number of interference fringes per 50×100 mm ² area of the measurement surface (upper or lower surface) of the light guide plate measured by a laser interferometer, and the thickness per interference fringe. is a value obtained as a product of the amount of change Δd in . The number of interference fringes is obtained by counting the number of interference fringes in four directions from the center of the molded product to the upper, lower, left and right edges of the molded product from the interference image measured by the laser interferometer, and the average value of the interference fringes. number. This Δd can be calculated by the following formula (1).
Here, n is the refractive index of the light guide plate and λ is 632.8 nm (the wavelength of the He—Ne laser). The refractive index of the light guide plate is a value obtained by measuring the D line of 589 nm at 23° C. using an Abbe refractometer based on JIS K 7142:2014 “Plastics—Determination of refractive index”.
When the area of the light guide plate to be measured is less than 50×100 mm ² , the parallelism P is obtained by converting the number of interference fringes into an area value per 50×100 mm ² .

The value of the parallelism P means the frequency of thickness change at a level that can affect the characteristics of the light guide plate, and can be rephrased as the degree of thickness change. It can be judged that the smaller this value is, the closer the upper and lower surfaces of the light guide plate are parallel to each other and the higher the accuracy of the thickness of the light guide plate.

《Retardation》
Although the retardation of the light guide plate 20 is not particularly limited, it is preferably 1 to 200 nm, more preferably 3 to 150 nm, even 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 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 having 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 performing 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.

According to such a molding process, the residual stress can be reduced, the residual stress of the light guide plate itself is small, and deformation of the light guide plate alone and the light guide plate laminate is suppressed.

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.

A light guide plate having a structure for maintaining gaps and alignment was produced by injection molding, and a laminated light guide plate laminate was produced. Structures for maintaining gaps and alignment were as shown in Table 1.
The flatness, dimensional change rate, and thermal shrinkage rate of the manufactured light guide plate laminate were measured by the methods described above. Table 1 shows the results.

In Comparative Example 1, the degree of flatness increased due to the addition of misalignment, amount of warpage, dimensional change, and heat shrinkage associated with lamination.
On the other hand, in Examples 1 to 3, since each light guide plate was fixed, the flatness (amount of warp), dimensional change rate, and heat shrinkage rate were equivalent to those of one light guide plate.
Comparative Example 2 has a gap holding mechanism but no positioning mechanism, so the flatness increased due to the addition of positional deviation, warpage, dimensional change, and heat shrinkage due to lamination. Also, since the positioning mechanism is within the pattern area, the diffraction area is affected.

The light guide plate laminate obtained by laminating the light guide plates for an AR display of the present invention can easily hold the gap between two or more light guide plates and align them, and can display a clear image. It is useful for display devices such as head-mounted displays.

REFERENCE SIGNS LIST 10 image forming section 11 image display device 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 exit light side relief type diffraction element 30c resin substrate 301, 302, 401 , 402, 501, 502 Light guide plates 301a, 301b, 302a, 302b, 401a, 401b, 402a, 402b, 501a, 501b, 502a, 502b Relief type diffraction element 303 Projection 403 Claw 503 Concave and convex portions or projections EY that engage with each other Observer Eyes L1, L2, L3, L4 Light

Claims (16)

A light guide plate laminate formed by laminating light guide plates 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 exit surface of the surface of the light guide plate;
A light guide plate laminate, wherein a structure for maintaining the gap and aligning the two or more light guide plates is arranged at a position that does not interfere with the relief type diffraction element. A light guide plate laminate formed by laminating light guide plates 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;
A light guide plate laminate, wherein two or more of the light guide plates are laminated with a gap holding and alignment structure arranged at a position not interfering with the relief type diffraction element. 3. The light guide plate laminate according to claim 1 or 2, wherein said gap holding and alignment structure is an adhesive protrusion disposed at a non-image related position on the surface opposite to the surface having said relief type diffractive element. . 3. A light guide plate according to claim 1 or 2, wherein said spacing and alignment structure is a mating claw positioned at an image-independent position outside the surface opposite the surface having said relief-type diffractive element. laminate. 3. The light guide plate according to claim 1 or 2, wherein the gap holding and alignment structure is unevenness or projections that engage with each other on the surface having the relief-type diffraction element and the surface opposite to the surface having the relief-type diffraction element. laminate. The diffractive optical pattern on the image light exit surface of the light guide plate has a line width of 50 to 250 nm and a height of 30 to 150 nm, and the ratio of the height to the line width (height/line width) is The light guide plate laminate according to any one of claims 1 to 5, which is 0.12 to 3.0. The light guide plate laminate according to any one of claims 1 to 6, wherein the light guide plate has a flatness of 0.5 to 500 µm. The light guide plate laminate according to any one of claims 1 to 7, wherein the parallelism of the light guide plate is 0.5 to 50 µm. The light guide plate laminate according to any one of claims 1 to 8, wherein the light-transmitting resin material has a glass transition temperature of 50 to 200°C. The light-transmitting resin material according to any one of claims 1 to 9, wherein the moisture absorption rate of the light-transmitting resin material is 0.01 to 1.0%, and the dimensional change rate due to moisture absorption is 0.01 to 1.0%. The light guide plate laminate described above. The light guide plate laminate according to any one of claims 1 to 10, wherein the light-transmitting resin material has a heat shrinkage rate of 3.0% or less. The light guide plate according to any one of claims 1 to 11, wherein the light transmissive resin material has a light transmittance of 85% or more, a yellowness of 5 or less, and a yellowness of 5 or less. laminate. The light guide plate laminate according to any one of claims 1 to 12, wherein the light-transmitting resin material has a refractive index of 1.2 to 2.0. The light guide plate laminate according to any one of claims 1 to 13, wherein the light guide plate has a retardation of 1 to 200 nm. The light guide plate laminate according to any one of claims 1 to 14, wherein the light-transmitting resin material has a Charpy impact strength of 0.5 to 15 kJ/ ^m2 . The light guide plate laminate according to any one of claims 1 to 15, wherein the light transmitting resin material has a specific gravity of 1.0 to 1.5 g/ ^cm3 .

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