JP2022027727A - Image display light guide plate - Google Patents

Abstract

To provide an image display light guide plate which minimizes deterioration of a resin base material caused by a hologram layer.SOLUTION: An image display light guide plate 6 provided herein comprises a first resin base material 1, a first protective layer 2 containing an acrylic resin having a polyfunctional acrylate-derived repeating unit, and a hologram layer 3 arranged in the described order in a thickness direction.SELECTED DRAWING: None

Description

The present invention relates to a light guide plate for displaying an image.

In the display device, a light guide plate for displaying an image may be used. For example, in a display device using VR (virtual reality) technology, AR (augmented reality) technology, or the like, an image display light guide plate in which a hologram layer is supported by a transparent base material is used. A hologram having various optical functions such as waveguide, reflection, and diffraction is formed on the hologram layer.

As the material used for the hologram material forming the hologram layer, there are many photosensitive compositions containing a radically polymerizable monomer, a polyhydric acid, a base such as an amine, and the like, which may deteriorate the resin base material. In particular, when the resin base material is gradually eroded over a long period of time and the resin base material is deteriorated, the visibility of the light guide plate tends to be deteriorated.

For example, Patent Document 1 describes that a light-sensitive material layer forming a hologram is formed on an optically transparent resin substrate, and the light-sensitive material layer is coated with an aqueous polymer protective barrier. .. Patent Document 1 suggests that the aqueous polymer protective barrier is provided for the purpose of withstanding the attack by moisture.
For example, Patent Document 2 describes a hologram laminate having a hologram sandwiched between resin substrates via an optical adhesive, and the entire outer peripheral portion thereof is covered with a protective coating layer. Patent Document 2 describes that the protective coating layer may be a coating that enhances airtightness and gas barrier properties.
Patent Document 3 describes a layer that blocks outgas and the like on the substrate side by the block layer.

Japanese Unexamined Patent Publication No. 5-181400 Japanese Unexamined Patent Publication No. 11-184363 Japanese Unexamined Patent Publication No. 2013-109301

However, the related technology as described above has the following problems.
In the technique described in Patent Document 1, a resin substrate is in close contact with the surface of the photosensitive material layer opposite to the aqueous polymer protective barrier. Therefore, the photosensitive material may erode the resin substrate in a high temperature environment.
In the technique described in Patent Document 2, the entire outer periphery of the laminate including the hologram is sealed by the protective coating layer. Therefore, it is possible to prevent the hologram from deteriorating due to the permeation of moisture from the outside of the hologram laminate to the inside. However, the photosensitive material may erode the resin substrate.
In the technique described in Patent Document 3, the resin base material can be prevented from outgassing by using a dielectric film, but there is a possibility that the resin base material deteriorates with time due to the hologram material. In particular, in a high temperature environment, the influence of the hologram material on the resin substrate becomes remarkable.
Further, in these related techniques, it is not described that the resin base material is deteriorated by the hologram material which is a photosensitive resin composition.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a light guide plate for image display capable of suppressing deterioration of the resin base material due to the hologram layer even when a resin base material is used.

In order to solve the above problems, for example, the present invention has the following aspects.
[1] An image display light guide plate in which a first protective layer containing a first resin base material, an acrylic resin containing a repeating unit derived from a polyfunctional acrylate, and a hologram layer are arranged in this order in the thickness direction.
[2] The light guide plate for image display according to [1], wherein the elastic modulus of the first protective layer is 2 GPa or more.
[3] The light guide plate for image display according to [1] or [2], wherein the thickness of the first protective layer is 2 μm or more.
[4] The image display according to any one of [1] to [3], wherein the first protective layer includes a first organic material layer containing the acrylic resin and a first inorganic material layer. Light guide plate for.
[5] The first inorganic material layer comprises at least one inorganic material selected from the group consisting of silicon oxide, silicon nitride, silicon nitride, silicon sulfide, aluminum oxide, aluminum nitride, aluminum nitride and aluminum sulfide. The light guide plate for image display according to [4].
[6] The light guide plate for image display according to [4] or [5], wherein the thickness of the first inorganic material layer is 50 nm or more and 5000 nm or less.
[7] The image display according to any one of [1] to [6], wherein the first glass layer is arranged on the surface of the first resin base material opposite to the first protective layer side. Light guide plate for.
[8] The light guide plate for image display according to [7], wherein the first adhesive layer is arranged between the first resin base material and the first glass layer.
[9] The light guide plate for image display according to any one of [1] to [8], wherein the hologram layer is made of a single or volume hologram material.

According to the present invention, it is possible to provide a light guide plate for image display capable of suppressing deterioration of the resin base material due to the hologram layer.

It is a schematic sectional drawing which shows an example of the light guide plate for image display of embodiment of this invention. It is a schematic cross-sectional view which shows an example of the light guide plate for image display of the 1st modification of embodiment of this invention. It is a schematic front view explaining the method of measuring a luminance value and FOV. It is a schematic cross-sectional view which shows an example of the light guide plate for image display of the 2nd modification of embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are designated by the same reference numerals, and common description will be omitted.
The numerical range represented by using "-" includes the numerical values at both ends of "-".
"UV" means ultraviolet light.
"(Meta) acrylic" means one or both of acrylic and methacrylic.
"(Meta) acrylate" means one or both of acrylate and methacrylate.

<Light guide plate for image display>
An image display light guide plate according to an embodiment of the present invention will be described.
The image display light guide plate of the present embodiment has a first resin base material, a first protective layer, and a hologram layer. The first resin base material, the first protective layer, and the hologram layer are arranged in this order in the thickness direction. The first resin base material and the first protective layer may be arranged on at least one surface of the hologram layer, but may be arranged on both surfaces of the hologram layer. In this case, the hologram layer is sandwiched between the first protective layer and the second protective layer, and the first resin base material is laminated on the other surface of the first protective layer, and the second protective layer is laminated. A second resin base material is laminated on the other surface of the above. In the present embodiment, the first resin base material and the second resin base material may be generically referred to as simply "resin base material". In addition, the first protective layer and the second protective layer may be collectively referred to hereinafter simply as "protective layer".

One or more transparent layers may be arranged between the first resin base material and the first protective layer, and between the first protective layer and the hologram layer. For example, an adhesive layer, a hard coat layer, an anchor coat layer and the like can be mentioned.

The light guide plate for image display has an incident portion for incident image light and a display unit for displaying an image by the image light. The hologram layer is arranged between the incident portion and the display portion. The hologram layer is formed with a diffraction grating pattern for waveguideing at least the image light incident from the incident portion to the display portion and emitting the image light from the display portion. The diffraction grating pattern in the display unit transmits at least a part of the external light incident from the outside of the light guide plate for image display. The external light is incident from the surface opposite to the display unit.

The image light incident on the incident portion is guided in the hologram layer and emitted from the display portion to the outside. On the other hand, as a result of the external light also passing through the resin base material and the display unit, the observer of the display unit can observe both the image light and the external light in the visual field.
The light guide plate for image display of the present embodiment is suitably used for a display device using VR technology, AR technology, and the like. For example, the light guide plate for image display of the present embodiment is a hologram optical element (HOE) typified by a combiner of a head-up display (HUD) mounted on an automobile and a reflective plate for a reflective liquid crystal display device, in addition to display applications. ) And the like.

Hereinafter, a detailed configuration of an example of the light guide plate for image display of the present embodiment will be described based on the example shown in FIG. FIG. 1 is a schematic cross-sectional view showing an example of an image display light guide plate according to an embodiment of the present invention.

In the image display light guide plate 6 shown in FIG. 1, the first resin base material 1, the first protective layer 2, the hologram layer 3, the second protective layer 4, and the second resin base material 5 are arranged in this order in the thickness direction. Has been done.
The plan view shape of the light guide plate 6 for image display is not particularly limited. For example, the light guide plate 6 for image display may be shaped into a shape that can be attached to the display device used.
For example, the light guide plate 6 for image display may be a rectangular plate having a shape larger than the shape attached to the display device. In this case, the light guide plate 6 for image display is formed by being cut into a shape that can be attached to the display device before being assembled to the display device.
The light guide plate 6 for image display may have a flat plate shape or, if necessary, a curved plate shape.
Hereinafter, an example will be described in which the light guide plate 6 for image display is made of a flat plate having a rectangular shape in a plan view.

[First resin base material 1]
The first resin base material 1 is arranged on the outermost side of the image display light guide plate 6 in the thickness direction. The first resin base material 1 is arranged on the surface of the light guide plate 6 for displaying an image on the side where the displayed image is emitted.
The first resin base material 1 has a shape similar to the outer shape of the light guide plate 6 for image display.
The first resin base material 1 transmits the image light emitted from the hologram layer 3 and the external light transmitted through the second resin base material 5 and the hologram layer 3, which will be described later.
The thickness of the first resin base material 1 is not particularly limited. For example, the thickness of the first resin base material 1 may be 0.1 mm or more and 10 mm or less.
In the present specification, the thickness of the first resin base material 1 can be measured by a dial gauge type using a stylus, a micrometer, or the like.

As the material forming the first resin base material 1, any known material can be used without particular limitation as long as it is a transparent resin material.
Considering optical properties such as transparency and light refractive index, as well as main properties such as impact resistance, heat resistance, and durability, for example, homopolymers or copolymers of ethylene, propylene, butene, etc. Polyolefin-based resin; Amorphous polyolefin-based resin such as cyclic polyolefin resin; Polyolefin-based resin such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); Cellulous resin such as triacetyl cellulose, diacetyl cellulose, cellophane; Nylon 6 , Nylon 66, Nylon 12, Copolymerized Nylon and other polyamide-based resins; Ethylene-vinyl acetate copolymer partially hydrolyzate (EVOH), polyimide-based resin, polyetherimide-based resin, polysulfone-based resin, polyether sulfone-based Resins, polyether ether ketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluororesins, poly (meth) acrylic resins, styrene resins such as polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymers, Polyvinyl chloride, cellulose, acetylcellulose, polyvinylidene chloride, polyphenylene sulfide, polyurethane, phenol resin, epoxy resin, polynorbornene, styrene-isobutylene-styrene block copolymer (SIBS), allyldiglycolcarbonate, biodegradable resin, etc. Organic materials can be mentioned. The first resin base material 1 may be formed of two or more kinds of materials, or may have a laminated structure in which two or more kinds of materials are laminated.
From the viewpoint of transparency, it is more preferable to use a polycarbonate resin, a poly (meth) acrylic resin, or the like. Further, from the viewpoint of process resistance, it is more preferable to use a poly (meth) acrylic resin, an epoxy resin, a cyclic polyolefin resin or the like.

[First protective layer 2]
The first protective layer 2 is arranged between the first resin base material 1 and the hologram layer 3 described later, and in the configuration of FIG. 1, the first protective layer 2 is in close contact with the respective surfaces of the first resin base material 1 and the hologram layer 3. ing.

The first protective layer 2 contains an acrylic resin containing a repeating unit derived from a polyfunctional acrylate. By arranging the first protective layer 2 on the surface of the first resin base material 1, deterioration of the first resin base material 1 due to the hologram layer 3 can be prevented. Can be increased.

The acrylic resin of the first protective layer 2 may contain repeating units derived from various polyfunctional (meth) acrylates, and may contain repeating units derived from various monofunctional (meth) acrylates.
The polyfunctional (meth) acrylate means a (meth) acrylate having two or more radically polymerizable functional groups in the molecule.
Examples of the polyfunctional (meth) acrylate used as a raw material for the acrylic resin include polyethylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and tricyclodidecanedimethanol dimethacrylate. Examples include functional (meth) acrylates.
Examples of the monofunctional (meth) acrylate include isobornyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, butoxyethyl acrylate, lauryl acrylate, stearyl acrylate, benzyl acrylate, and hexyldiglycol acrylate. , 2-Hydroxyethyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenoxyethyl acrylate, dicyclopentadiene acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, nonylphenoxyethyl cellosolve acrylate and the like.
These (meth) acrylates may be used alone or in combination of two or more to form a copolymer.

Further, in addition to the acrylic resin, an oligomer composed of the polyfunctional (meth) acrylate may be contained. For example, oligourethane (meth) acrylate, oligoester (meth) acrylate and the like can be mentioned.

Since the acrylic resin may have a crosslinked structure by having a repeating unit derived from polyfunctional (meth) acrylate, it does not swell with respect to the hologram material and has excellent chemical resistance and long-term visibility. A light plate can be obtained.
The method for forming the first protective layer is not particularly limited. For example, it can be formed by applying an acrylic resin composition containing a polyfunctional (meth) acrylate to the surface of the first resin base material and then curing the acrylic resin composition.
Examples of coating methods for acrylic resin compositions include air doctor coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, and calendar coating. , Electrodeposition coating, dip coating, die coating and other coating methods; letterpress printing method such as flexo printing, direct gravure printing method, concave plate printing method such as offset gravure printing method, flat plate printing method such as offset printing method, screen printing method. Examples thereof include a printing method such as a stencil printing method.

The acrylic resin composition may be diluted with various solvents and used as necessary for the purpose of adjusting the viscosity and improving the coatability. As such a diluting solvent, various general organic solvents can be used, for example, alcohol compounds such as methanol, ethanol, 1-propanol and 2-propanol; ketone compounds such as acetone and methyl ethyl ketone; ethyl acetate, Ester compounds such as propyl acetate and butyl acetate; aromatic compounds such as toluene and xylene can be mentioned. These diluting solvents can be used alone or in admixture of two or more.

The acrylic resin composition may contain a photopolymerization initiator, if necessary. Examples of the photopolymerization initiator include benzophenone, acetophenone, benzoin, benzoin isobutyl ether, benzoin isopropyl ether, benzoin ethyl ether, 4,4'-bis (dimethylamino) benzophenone, benzyl dimethyl ketal, 2-chlorothioxanthone, 2, 4-Dimethylthioxanthone, 2,2'-diisopropylthioxanthone, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one, 2,4,6 -Examples include trimethylbenzoylphenyldiphosphine oxide. These can be used alone or in combination of two or more.

If necessary, a silane coupling agent can be added to the acrylic resin composition to adjust the adhesion between the first protective layer and the first resin base material. That is, a silane coupling agent can be used for the purpose of enhancing the adhesion between the first protective layer and the first resin base material.

A typical example of the silane coupling agent is an aminosilane compound. Specific examples of the aminosilane compound include γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and γ. -N-Phenylaminopropyltrimethoxysilane can be mentioned. These aminosilanes can be used alone or in admixture of two or more. Further, a coupling agent other than aminosilane may be used in combination.

The thickness of the first protective layer 2 is preferably 2 μm or more, and more preferably 5 μm or more. When the thickness of the first protective layer 2 is 2 μm or more, deterioration of the resin base material due to the hologram layer 3 can be prevented. The thickness of the first protective layer 2 is preferably 15 μm or less, more preferably 12 μm or less. When the thickness of the first protective layer 2 is 15 μm or less, the elastic modulus of the first protective layer 2 can be increased.
The thickness of the first protective layer 2 can be measured by a non-contact optical interferometry film thickness meter or the like.

The elastic modulus of the first protective layer 2 is preferably 2 GPa or more, and more preferably 5 GPa or more. When the elastic modulus is 2 GPa or more, deterioration of the resin base material due to the hologram layer 3 can be prevented. The elastic modulus of the first protective layer 2 is preferably 20 GPa or less, more preferably 15 GPa or less. When the elastic modulus is 20 GPa or less, warpage due to curing shrinkage at the time of forming the protective layer can be suppressed.
The elastic modulus can be measured by a measuring device Shimadzu dynamic ultrafine hardness tester, DUH-W201 measurement condition: Triangular 115, and a pushing depth of 230 to 280 nm.

Further, the difference in refractive index between the first resin base material 1 and the first protective layer 2 is preferably 0.3 or less, and more preferably 0.2 or less.
The refractive index can be measured by a method using a commonly used Abbe refractive index meter or ellipsometer.

[Hologram layer 3]
The hologram layer 3 is laminated on the surface of the first protective layer 2. The configuration of the hologram layer 3 is not particularly limited. The hologram layer 3 is formed with an appropriate diffraction grating corresponding to the function required for the image display light guide plate 6.

The material of the hologram layer 3 is not particularly limited, and may be a known hologram-forming resin material.
For example, a hologram recording material composed of a thermosetting resin having at least one solvent-soluble and cationically polymerizable ethylene oxide ring in a structural unit and a radically polymerizable ethylenic monomer (Japanese Patent Laid-Open No. 9-62169, JP-A-11-). 161141A, JP-A-2002-310932) and the like.
Specifically, epoxy resins such as bisphenol-based epoxy resins; (meth) acrylates such as triethylene glycol diacrylate; photopolymerization initiators such as 4,4'-bis (tert-butylphenyl) iodonium hexafluorophosphate; It is preferably formed from a photosensitive material containing a wavelength sensitizer such as 3,3'-carbonylbis (7-diethylamino) coumarin; an organic solvent such as 2-butanone.
Above all, it is preferable that the hologram layer is made of a single or volume hologram material.

[Second protective layer 4]
The second protective layer 4 is laminated on the opposite side of the first protective layer 2 via the hologram layer 3. As the second protective layer 4, the same configuration as exemplified in the description of the first protective layer 2 is used. However, the thickness, material, etc. of the second protective layer 4 may be different from those of the first protective layer 2.

[Second resin base material 5]
The second resin base material 5 is laminated on the surface of the second protective layer 4. As the second resin base material 5, the same configuration as exemplified in the description of the first resin base material 1 is used. However, the thickness, material, and the like of the second resin base material 5 may be different from those of the first resin base material 1. In particular, since the second resin base material 5 is arranged on the surface of the light guide plate 6 for displaying an image on the external light incident side located opposite to the display image emitting side, the surface hardness is higher than that of the first resin base material 1. Higher materials may be used.

[Light guide plate for image display 6]
The image display light guide plate 6 has a first protective layer 2 and a second protective layer 4 between the first resin base material 1 and the hologram layer 3 and between the second resin base material 5 and the hologram layer 3, respectively. And are arranged.
The chemical resistance of the first resin base material 1 and the second resin base material 5 is much lower than that of glass, although the degree of chemical resistance varies depending on the type of resin material. Therefore, the first resin base material 1 and the second resin base material 5 have lower solvent resistance and hologram resistance than glass.
When the first resin base material 1 and the second resin base material 5 are in contact with the hologram layer 3, the hologram agent which is a component of the hologram layer 3 permeates the first resin base material 1 and the second resin base material 5. Or, the hologram agent tends to accumulate inside the first resin base material 1 and the second resin base material 5. When the first resin base material 1 and the second resin base material 5 are exposed to the hologram agent, the first resin base material 1 and the second resin base material 5 are deteriorated, and the FOV (field of view) is lowered or sharpened. The degree of decrease is likely to occur.
Therefore, in the present invention, the first resin base material 1 is provided by providing the first protective layer 2 and the second protective layer 4, respectively, between the first resin base material 1, the second resin base material 5, and the hologram layer 3. And by suppressing the penetration of the hologram agent into the second resin base material 5, deterioration of the resin base material is prevented.

In particular, when the refractive index of the first protective layer 2 and the second protective layer 4 is higher than that of the first resin base material 1 and the second resin base material 5, as described above, the first protective layer The emission angle of light from 2 toward the first resin base material 1 becomes large. Similarly, the emission angle of the light incident on the second protective layer 4 from the second resin base material 5 is narrowed. Therefore, the light incident from the outside on the side of the second resin base material 5 and transmitted through the light guide plate 6 for image display is incident in a wider angle range than the case where the second protective layer 4 is not provided. However, it is emitted in a wider angle range as compared with the case where the first protective layer 2 is not provided. As a result, the range of the field of view of the external light is further expanded, and the FOV on the display side is also expanded.
Regarding the image light from the hologram layer 3, as described above, as a result of increasing the emission angle of the light from the first protective layer 2 to the first resin base material 1, the first protective layer 2 and the second protective layer 4 are provided. Compared with the case of not having it, the FOV of the display screen is widened.
In particular, in the present embodiment, the first protective layer 2 and the second protective layer 4 are laminated on the hologram layer 3, so that the diffusion position of the external light and the image light and the hologram layer 3 constituting the display screen are obtained. Since the diffraction position is close to the hologram layer 3, a clearer image can be observed from a wide range of angles as compared with the case where the first protective layer 2 and the second protective layer 4 are provided at positions away from the hologram layer 3.

<First modification>
A first modification of the embodiment of the present invention will be described. In the present embodiment, the first organic material layer and the second organic material layer may be collectively referred to as simply "organic material layer". Further, the first inorganic material layer and the second inorganic material layer may be generically referred to as simply "inorganic material layer".
FIG. 2 is a schematic cross-sectional view showing an example of an image display light guide plate according to a first modification of the embodiment of the present invention.
As shown in FIG. 2, in the image display light guide plate 16 of the first modification of the embodiment of the present invention, the first protective layer is the first protective layer in the image display light guide plate 6 of the basic example of the embodiment of the present invention. It has been changed to include one organic material layer and a second inorganic material layer.

As shown in FIG. 2, the first protective layer 22 is provided with the first inorganic material layer 22B on at least one surface of the first organic material layer 22A containing an acrylic resin containing a repeating unit derived from a polyfunctional acrylate. Is preferable.
By further having the first inorganic material layer 22B in the first protective layer 22, long-term visibility can be improved.

[First organic material layer 22A]
Examples of the organic material used for the first organic material layer 22A include those similar to those described for the acrylic resin of the first protective layer 2.
The thickness of the first organic material layer 22A is preferably 2 μm or more, and more preferably 5 μm or more. When the thickness of the first organic material layer 22A is 2 μm or more, deterioration of the resin base material due to the hologram layer 3 can be prevented. The thickness of the first organic material layer 22A is preferably 15 μm or less, more preferably 12 μm or less. When the thickness of the first organic material layer 22A is 15 μm or less, the elastic modulus of the first organic material layer 22A can be increased.

[First Inorganic Material Layer 22B]
Examples of the inorganic material used for the first inorganic material layer 22B include silicon oxide, silicon nitride, silicon nitride, silicon sulfide, aluminum oxide, aluminum nitride, aluminum nitride and aluminum sulfide.
Of these, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride are preferable. In particular, it is preferable that the alkali oxide component such as sodium and potassium is low.

The thickness of the first inorganic material layer 22B is preferably 50 nm or more and 5000 nm or less, and more preferably 50 nm or more and 3000 nm or less. When the layer thickness is 50 nm or more, sufficient hologram resistance can be obtained. When the layer thickness is 5000 nm or less, cracks are less likely to occur in the protective layer 22, so that delamination can be suppressed. A particularly preferable layer thickness is 50 nm or more and 1000 nm or less.

The inorganic material used for the first inorganic material layer 22B may have a higher refractive index than the first resin base material 1 and the first organic material layer 22A. For example, the refractive index of the first inorganic material layer 22B may be 1.48 or more and 3.0 or less. When the first inorganic material layer 22B has a high refractive index, the light transmitted through the first protective layer 22 and the first resin base material 1 is optically dense from the optically dense first inorganic material layer 22B. It passes through the coarse first organic material layer 22A and is incident on the first resin base material 1. Therefore, the emission angle of light from the first protective layer 22 toward the first resin base material 1 increases according to the difference in refractive index between the first protective layer 2 and the first resin base material 1. As a result, the FOV (field of view) in the image display light guide plate 6 can be expanded.

The method for forming the first inorganic material layer 22B is not particularly limited. For example, it can be formed by any conventionally known method such as a vacuum vapor deposition method, a sputtering method, an ion plating method, and a plasma CVD method. When the first inorganic material layer 22B is formed of the silicon oxide, the film-forming surface is subjected to corona discharge treatment, low-temperature plasma treatment, or in order to improve the adhesiveness between the film-forming surface and the silicon oxide. Surface treatment such as applying a silane coupling agent or a mixture of saturated polyester and isocyanate may be applied.
For example, when a thin film of silicon oxide is formed by a vacuum vapor deposition method, silicon, silicon monoxide, silicon dioxide, or a mixture thereof is used as an evaporative substance, and 1.0 × 10 ^-3 Torr to 1.0. × ^10-5 Under vacuum of Torr, heat and evaporate by electron beam, resistance heating or high frequency heating method. Further, a reaction vapor deposition method performed while supplying oxygen gas can also be adopted.

When a layer made of silicon nitrogen oxide is formed as the first inorganic material layer 22B, it is the same as the first inorganic material layer 22B containing silicon oxide as a main component, except that the silicon oxide is replaced with silicon nitrogen oxide. Configuration is used.

When forming a layer made of aluminum oxide as the first inorganic material layer 22B, for example, it may be formed only of Al ₂ O ₃ , or it may be formed by mixing Al, AlO, Al ₂ O ₃ , and the like. good. The atomic number ratio of Al: O in the aluminum oxide layer differs depending on the preparation conditions of the aluminum oxide layer. The aluminum oxide layer that can be used as the first inorganic material layer 22B may contain a small amount of other components (up to 3% with respect to all components) as long as the compactness performance is not impaired.

The thickness of the aluminum oxide layer may be set as necessary, such as chemical resistance. For example, the thickness of the aluminum oxide layer may be 5 nm or more and 800 nm or less.

The method for forming the first inorganic material layer 22B from the aluminum oxide is not particularly limited. For example, for the first inorganic material layer 22B, a PVD method (physical vapor deposition method) such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a CVD method (chemical vapor deposition method) may be used.
For example, in the vacuum vapor deposition method, Al, Al ₂ O ₃ , etc. may be used as the vapor deposition source material, and resistance heating, high frequency induction heating, electron beam heating, or the like may be used as the heating method of the vapor deposition source. .. In the vacuum vapor deposition method, oxygen, nitrogen, water vapor or the like may be introduced as the reactive gas, or reactive vapor deposition using means such as ozone addition and ion assist may be used. Further, a bias or the like may be applied to the substrate on the film-forming surface, or the temperature of the film-forming surface may be raised or cooled. The same applies to other film forming methods such as the spatter method and the CVD method.

[Second organic material layer 24A]
As the second organic material layer 24A, the same configuration as exemplified in the description of the first organic material layer 22A is used. However, the thickness, material, etc. of the second organic material 24A may be different from that of the first organic material layer 22A.

[Second Inorganic Material Layer 24B]
The second inorganic material layer 24B is laminated on the opposite side of the first inorganic material layer 22B via the hologram layer 3. As the second inorganic material layer 24B, the same configuration as exemplified in the description of the first inorganic material layer 22B is used. However, the thickness, material, etc. of the second inorganic material 24B may be different from that of the first inorganic material layer 22B.
The organic material layer preferably does not contain an inorganic material.
The inorganic material layer preferably does not contain an organic material.

[Light guide plate 16 for image display]
The image display light guide plate 16 has a first protective layer 22 and a second protective layer 24 between the first resin base material 1 and the hologram layer 3 and between the second resin base material 5 and the hologram layer 3, respectively. And are arranged. The first protective layer 22 includes a first organic material layer 22A and a first inorganic material layer 22B, and the second protective layer 24 includes a second organic material layer 24A and a second inorganic material layer 24B.
In the first protective layer 22, it is preferable that the first organic material layer 22A is arranged on the side of the first resin base material 1 and the first inorganic material layer 22B is arranged on the side of the hologram layer 3. Further, in the second protective layer 24, it is preferable that the second organic material layer 24A is arranged on the side of the second resin base material 2 and the second inorganic material layer 24B is arranged on the side of the hologram layer 3. By arranging the first inorganic material layer 22B and the second inorganic material layer 24B so as to be in contact with the hologram layer 3 in this way, the hologram agent resistance can be further improved and the long-term visibility can be improved. ..

<Second modification>
A second modification of the embodiment of the present invention will be described. In the present embodiment, the first glass layer and the second glass layer are generically referred to as simply "glass layer". Further, the first adhesive layer and the second adhesive layer may be generically referred to as simply "adhesive layer".
FIG. 4 is a schematic cross-sectional view showing an example of an image display light guide plate of a second modification of the embodiment of the present invention.
As shown in FIG. 4, the image display light guide plate 26 of the second modification of the embodiment of the present invention is the first resin base material 1 in the image display light guide plate 6 of the basic example of the embodiment of the present invention. The first glass layer 37 and the first adhesive layer 38 are provided on the outside of the second resin base material 5, and the second glass layer 40 and the second adhesive layer 39 are provided on the outside of the second resin base material 5.

[First glass layer 37]
The first glass layer 37 is arranged outside the first resin base material 1, and in the configuration of FIG. 4, is in close contact with the surface of the first resin base material 1. The first glass layer 37 prevents scratches and prevents gas permeating from the outside of the image display light guide plate 26 and the first resin base material 1 from permeating into the hologram layer 3.
The first glass layer 37 is more preferably, for example, having a smaller oxygen permeability and water vapor permeability.
For example, the oxygen permeability of the first glass layer 37 may be 1 cm ³ / m ² · day or less.
For example, the water vapor transmittance of the first glass layer 37 may be 1 g / m ² · day or less. The water vapor transmittance of the first glass layer 37 is more preferably 0.5 g / m ² · day or less.

Since the gas barrier property tends to be excellent as well as the mechanical strength, the thickness of the first glass layer 37 is preferably 10 μm or more. More preferably, it is 30 μm or more. Further, since the optical characteristics of the light guide plate such as light transmittance tend to be excellent, the thickness of the first glass layer 37 is preferably 200 μm or less. It is more preferably 100 μm or less, further preferably 75 μm or less, and particularly preferably 50 μm or less.
Examples of the material of the first glass layer 37 include borosilicate glass, non-alkali glass, low-alkali glass, soda lime glass, solgel glass, and those obtained by heat-treating or surface-treating these glasses. .. Particularly preferred is non-alkali glass from the viewpoint of avoiding coloring due to impurities in the glass material.
The method for forming the first glass layer 37 can be appropriately selected, and for example, a slot down draw method, a fusion method, a float method, or the like can be adopted. Further, as the first glass layer 37, a commercially available one may be used as it is, or a commercially available glass may be polished to a desired thickness and used. Examples of commercially available glass include "EAGLE2000" manufactured by Corning Inc., "AN100" manufactured by Asahi Glass Co., Ltd., "OA10G" manufactured by Nippon Electric Glass Co., Ltd., and "D263" manufactured by Schott AG.

[First Adhesive Layer 38]
In the image display light guide plate 26 of the second modification, if the adhesion between the first resin base material 1 and the first glass layer 37 is good, the first adhesive layer 38 is not essential, but particularly the first. 1 When the above-mentioned resin material is used as the resin base material 1, it is preferable to use the first adhesive layer 38 in order to maintain excellent adhesion to the first glass layer 37. The material forming the first adhesive layer 38 is not particularly limited as long as it is a material having good adhesiveness between the first resin base material 1 and the first glass layer 37.
For example, a preferable material for the first adhesive layer 38 includes a curable resin composition containing a heat and ultraviolet curable resin, for example, a curable resin such as an acrylic resin, a urethane resin, an epoxy resin, and a silicone resin. The resin composition constituting the first adhesive layer 38 is filled with a silane coupling agent, a sensitizer, a cross-linking agent, an ultraviolet absorber, a polymerization inhibitor, a surfactant, and a filler as long as the object of the present invention is not impaired. An agent, a mold release agent, and a thermoplastic resin can be optionally added. It should be noted that these can be used alone or in combination of two or more as appropriate.
Examples of the thermoplastic resin include fluororesins, polyether sulfone resins, polycarbonate resins, acrylic resins, silicone resins, cycloolefin resins, thermoplastic polyimide resins, polyamide resins, polyamideimide resins, and polys. Examples thereof include allylate-based resins, polysulfone-based resins, polyetherimide-based resins, polyether ether ketone-based resins, polyether silicon-based resins, polyester-based resins, and polyphenylene sulfide-based resins.
Since an excellent luminance value can be imparted to the light guide plate for image display of the present invention, the total light transmittance of the first adhesive layer 38 is preferably 80% or more. More preferably, it is 90% or more. Further, since it is possible to impart an excellent luminance value to the light guide plate and prevent color unevenness, the refractive index of the first adhesive layer 38 is set to that of the first resin base material 1 and the first glass layer 37. It is preferably n ± 0.20 with respect to the average refractive index n. It is more preferably n ± 0.15, and even more preferably n ± 0.10.
Further, since the first resin base material 1 and the first glass layer 37 tend to maintain excellent adhesiveness, the thickness of the first adhesive layer 38 is preferably 1 μm or more. More preferably, it is 5 μm or more. Further, since the color unevenness of the light guide plate tends to be suppressed, the thickness of the first adhesive layer 38 is preferably 700 μm or less. It is more preferably 100 μm or less.
The first adhesive layer 38 can be formed, for example, by laminating a glass plate on an adhesive applied on a resin base material and treating the laminate by a method such as pressing, nip roll, or thermal laminating. can. When this adhesive is a curable resin, a curing step of the adhesive may be included in the formation of the first adhesive layer 38.

[Second adhesive layer 39]
In the image display light guide plate 26 of the second modification, if the adhesion between the second resin base material 5 and the second glass layer 40 is good, the second adhesive layer 39 is not essential, but in particular, the second one. 2 When the above-mentioned resin material is used as the resin base material 5, it is preferable to use the second adhesive layer 39 in order to maintain excellent adhesion to the second glass layer 40. As the second adhesive layer 39, the same configuration as exemplified in the description of the first adhesive layer 38 is used. However, the thickness, material, and the like of the second adhesive layer 39 may be different from those of the first adhesive layer 38.

[Second glass layer 40]
The second glass layer 40 is arranged outside the second resin base material 5, and in the configuration of FIG. 4, is in close contact with the surface of the second resin base material 5. As the second glass layer 40, the same configuration as exemplified in the description of the first glass layer 37 is used. However, the thickness, material, and the like of the second glass layer 40 may be different from those of the first glass layer 37.

[Light guide plate for image display 26]
The image display light guide plate 26 has a glass layer, a resin base material, a protective layer, and a hologram layer. In the image display light guide plate 26, the glass layer, the resin base material, the protective layer, and the hologram layer are arranged in this order in the thickness direction.
An adhesive layer may be arranged between the glass layer and the resin base material, if necessary.
From the viewpoint of suppressing scratches on the surface of the light guide plate for image display, the glass layer is preferably the outermost layer on at least one of the light guide plates for image display, and is the outermost layer on both sides of the light guide plate for image display. More preferred.

One or more transparent layers may be arranged on at least one surface of the glass layer.
One or more transparent layers may be arranged between the glass layer and the resin base material.
Examples of the type of the transparent layer include a hard coat layer and an anchor coat layer.

Hereinafter, a detailed configuration of an example of the light guide plate for image display of the present embodiment will be described with reference to FIG.
FIG. 4 is a schematic cross-sectional view showing an example of an image display light guide plate according to a second modification of the present invention.
In the image display light guide plate 26 shown in FIG. 4, in the thickness direction, the first glass layer 37, the first adhesive layer 38, the first resin base material 1, the first protective layer 2, the hologram layer 3, and the second protective layer are used. 4. The second resin base material 5, the second adhesive layer 39, and the second glass layer 40 are arranged in this order.

The light guide plate 26 for image display of the present embodiment has the first glass layer 37 and the first adhesive layer 38 on the outside of the first resin base material 1, and the second glass on the outside of the second resin base material 5. It is the same as the basic example of the present invention except that it has the layer 40 and the second adhesive layer 39. Therefore, the configurations of the first resin base material 1, the first protective layer 2, the hologram layer 3, the second protective layer 4, and the second resin base material 5 in the present embodiment are each in the basic example of the embodiment of the present invention. The same configurations as those exemplified in the description of the first resin base material 1, the first protective layer 2, the hologram layer 3, the second protective layer 4, and the second resin base material 5 are used.
Hereinafter, the first glass layer 37 and the second glass layer 40, and the first adhesive layer 38 and the second adhesive layer 39 will be described.

The first glass layer 37 and the second glass layer 40 are arranged on the outermost side of the image display light guide plate 26 in the thickness direction to prevent the surface of the image display light guide plate 26 from being scratched or to guide the image display. The first resin base material 1 can be protected from the gas outside the light plate 26.

<Manufacturing method of light guide plate for image display>
The light guide plate 6 for image display can be manufactured, for example, as follows.
The first resin base material 1 and the second resin base material 5 are prepared ([Substrate preparation step]), and the first protective layer 2 and the second protection are provided on the surfaces of the first resin base material 1 and the second resin base material 5. Each layer 4 is formed ([protective layer forming step]). As a method for producing the first protective layer 2 and the second protective layer 4, an appropriate manufacturing method is selected depending on the materials of the first protective layer 2 and the second protective layer 4.
For example, a photosensitive material for forming a hologram is applied to the surface of the first protective layer 2 in the first resin base material 1 on which the first protective layer 2 is formed. At this time, a transparent seal layer having the same thickness as the hologram layer 3 may be provided on the outer peripheral portion of the first protective layer 2. In the sealing layer, the photosensitive material seals the outer peripheral portion of the hologram layer 3 after the hologram layer 3 is formed. The seal layer is made of a transparent material, and for example, an epoxy resin, a silicone resin, an en-thiol resin, or the like is used.
After that, the second resin base material 5 on which the second protective layer 4 is formed is placed on the photosensitive material in a state where the second protective layer 4 is directed toward the photosensitive material ([Making a light guide plate]. Process]).
However, the above-mentioned production sequence is an example. For example, even if the photosensitive material is applied to the second resin base material 5 on which the second protective layer 4 is formed and then the first resin base material 1 on which the protective layer 2 is formed is placed on the hologram layer 3. good.
After that, a laminate composed of the first resin base material 1, the first protective layer 2, the hologram layer 3, the second protective layer 4, and the second resin base material 5 is bonded by a vacuum press.
After that, interference fringes corresponding to the diffraction pattern are formed on the photosensitive material of the laminated body, and a diffraction grating is formed in the photosensitive material.
In this way, the light guide plate 6 for image display is manufactured.

The light guide plate 16 for image display can be manufactured, for example, as follows.
The first resin base material 1 and the second resin base material 5 are prepared ([Substrate preparation step]), and the first organic material layer 22A and the second are placed on the surfaces of the first resin base material 1 and the second resin base material 5. Each of the organic material layers 24A is formed ([organic material layer forming step]). The first inorganic material layer 22B and the second inorganic material layer 24B are formed on the surfaces of the first organic material layer 22A and the second organic material layer 24A, which are intermediates composed of the resin base material and the organic material layer, respectively (inorganic). Material layer forming process).
A photosensitive material for forming a hologram is applied to the surface of the first inorganic material layer 22B. At this time, a transparent sealing layer having the same thickness as the hologram layer 3 may be provided on the outer peripheral portion of the first inorganic material layer 22B. In this case, the photosensitive material is applied to the recess formed by being surrounded by the seal layer. The seal layer seals the outer peripheral portion of the hologram layer 3 after the hologram layer 3 is formed.
After that, the second resin base material 5 on which the second protective layer 24 is formed is placed on the photosensitive material with the second protective layer 24 facing toward the photosensitive material ([Making a light guide plate]. Process]).

When the inorganic material is a silicon oxide, the inorganic material layer can be formed as follows.
After the intermediate composed of the resin base material and the organic material layer is placed in the vacuum vapor deposition apparatus, the silicon oxide is vacuum-deposited. The ultimate vacuum degree of the chamber of the vacuum vapor deposition apparatus is preferably 3 × 10 ^-3 Torr or less. Under this vacuum, silicon monoxide having a purity of 99.9% is heated and evaporated by a high frequency induction heating method to form a silicon oxide thin film on the surface of the resin substrate. As a result, an intermediate having a silicon oxide thin film layer formed therein can be obtained.
After that, the light guide plate 16 for image display is formed in the same manner as in the light guide plate manufacturing step in the method for manufacturing the light guide plate 6 for image display.

When the inorganic material is alumina, the inorganic material layer can be formed as follows.
An intermediate composed of a resin base material and an organic material layer is placed in an electron beam vapor deposition apparatus, and an appropriate amount of alpha alumina particles having a purity of 99.999% and a particle size of 0.5 to 5 mm are arranged as a vapor deposition source, and vacuum exhausted. I do. The distance from the vapor deposition source to the shutter is preferably about 3 to 15 cm, and the distance from the vapor deposition source to the surface of the resin substrate is preferably about 5 to 50 cm.
After the pressure of the electron beam vapor deposition apparatus reaches 3 × 10 ^-3 Torr or less, the filament current of the electron beam is increased to 25 to 50 mA, the shutter is opened, and alumina film formation is performed. When the temperature of the wall surface in the device reaches 45 ° C. or higher, the shutter is closed and the filament current of the electron beam is stopped. After cooling to 35 ° C. or lower, the filament current of the electron beam is increased to 25 to 50 mA, the vapor deposition source is heated, the shutter is opened, and alumina film formation is performed. This is repeated to form an alumina film. As a result, an intermediate in which an alumina thin film layer is formed is obtained.
After that, the light guide plate 16 for image display is formed in the same manner as in the light guide plate manufacturing step in the method for manufacturing the light guide plate 6 for image display.

The light guide plate 26 for image display can be manufactured, for example, as follows.
The first resin base material 1 and the second resin base material 5 are prepared ([Substrate preparation step]), and the first protective layer 2 and the second protection are provided on the surfaces of the first resin base material 1 and the second resin base material 5. Each layer 4 is formed ([protective layer forming step]).
As a method for producing the first protective layer 2 and the second protective layer 4, an appropriate manufacturing method is selected depending on the materials of the first protective layer 2 and the second protective layer 4.
The surface of the first resin base material 1 on which the first protective layer 2 is formed opposite to the side of the first protective layer 2, and the second protective layer in the second resin base material 5 on which the second protective layer 4 is formed. The first adhesive layer 38 and the second adhesive layer 39 are formed on the surface opposite to the fourth side ([adhesive layer forming step]).
A first glass layer 37 is formed on the surface of the first adhesive layer 38, and a second glass layer 40 is formed on the surface of the second adhesive layer 39 ([glass layer forming step]).
For example, a photosensitive material for forming a hologram is applied to the surface of the first protective layer 2 in the first resin base material 1 on which the first protective layer 2 is formed. At this time, a transparent seal layer having the same thickness as the hologram layer 3 may be provided on the outer peripheral portion of the first protective layer 2. In the sealing layer, the photosensitive material seals the outer peripheral portion of the hologram layer 3 after the hologram layer 3 is formed. The seal layer is made of a transparent material, and for example, an epoxy resin, a silicone resin, an en-thiol resin, or the like is used.
After that, the second resin base material 5 on which the second protective layer 4 is formed is placed on the photosensitive material in a state where the second protective layer 4 is directed toward the photosensitive material ([Making a light guide plate]. Process]).
However, the above-mentioned production sequence is an example. For example, after the photosensitive material is applied to the second resin base material 5 on which the second protective layer 4 is formed, the first resin base material 1 on which the first protective layer 2 is formed is placed on the hologram layer 3. You may.
After that, the first glass layer 37, the first adhesive layer 38, the first resin base material 1, the first protective layer 2, the hologram layer 3, the second protective layer 4, and the second resin base material 5 are pressed by a vacuum press. A laminate composed of the second adhesive layer 39 and the second glass layer 40 is bonded together.
After that, interference fringes corresponding to the diffraction pattern are formed on the photosensitive material of the laminated body, and a diffraction grating is formed in the photosensitive material.
In this way, the light guide plate 26 for image display is manufactured.

<Brightness value and FOV>
Here, an example of a method for measuring the luminance value and the FOV in the light guide plate 6 for image display will be briefly described.
FIG. 3 is a schematic front view illustrating a method of measuring the luminance value and the FOV.

As shown in FIG. 3, in order to measure the luminance value and the FOV of the light guide plate 6 for image display, the display device 10 is manufactured using the light guide plate 6 for image display.
The display device 10 includes an image light projection unit 13 and an incident optical system 12 in addition to the image display light guide plate 6.
The image light projection unit 13 projects image light to be displayed on the image display light guide plate 6 in response to an image signal transmitted from a controller (not shown).
The incident optical system 12 includes, for example, a prism or the like. The incident optical system 12 causes the image light emitted from the image light projection unit 13 to be incident on the incident unit 6a provided on the surface of the image display light guide plate 6. For example, the incident portion 6a is provided on the surface of the resin base material 1 side.
The image light incident on the incident portion 6a reaches the display diffraction grating portion 3c of the hologram layer 3 via the waveguide diffraction grating portion 3b formed on the hologram layer 3. The display diffraction grating unit 3c diffracts the image light at a position corresponding to each display pixel. The diffracted light is emitted to the outside from the display unit 6d on the surface of the image display light guide plate 6. In the example shown in FIG. 2, the display portion 6d is formed at a position separated from the incident portion 6a on the surface of the resin base material 1 side.

The brightness value and the FOV of the light guide plate 6 for image display are measured by arranging the display device 10 in the measuring device 15.
The measuring device 15 includes a holding table (not shown), a luminance meter 14, and a goniometer stage (not shown).
The holding table holds the display device 10. The luminance meter 14 measures the luminance value of the received light. The goniometer stage swingably supports the luminance meter 14 on the circumference centered on the center of rotation.
The distance d between the luminance meter 14 and the display surface 3a is a distance corresponding to the position of the user's eyes when the display device 10 is attached. For example, when the display device 10 is a head-mounted display, d is set to 15 mm.

The luminance value of the light guide plate 6 for image display is measured by arranging the luminance meter 14 at a position of a swing angle of 0 ° (see the solid luminance meter 14 in FIG. 2). The display device 10 is arranged by the holding table at a position where the center of the display surface 3a faces the luminance meter 14 on the measurement optical axis of the luminance meter 14.
The luminance value is the luminance measured by the luminance meter 14 when the display device 10 displays the white image with the maximum luminance.
The luminance value is preferably 1000 nit or more, and more preferably 1200 nit or more.
In the measurement of the FOV of the light guide plate 6 for image display, the brightness is measured by changing the swing angle θ while displaying the white image with the maximum brightness on the display device 10. The brightness corresponding to the invisible white image is set as a threshold value, and it is obtained as an angle range in which brightness equal to or higher than the threshold value can be obtained. The FOV is θ1 + θ2 when the luminance above the threshold is obtained in the range of −θ1 to +θ2.
The FOV of the light guide plate 6 for image display is more preferably 24 ° or more and 160 ° or less, and further preferably 35 ° or more and 160 ° or less. Further, as the FOV becomes larger, the angle at which the image is viewed increases, the amount of information in the image increases, and the range of applications to which the image can be applied increases. On the other hand, when the FOV is smaller than the upper limit value, the amount of light extracted for a certain area tends to be large, and the image becomes bright, which is preferable.

For example, the closer the distance between the first protective layer 2 and the second protective layer 4 and the hologram layer 3 is, the more the FOV can be improved by about 10 ° or more. The distance is preferably 1000 nm or less, more preferably 500 nm or less, and most preferably 100 nm or less.

Hereinafter, the present invention will be described in more detail with reference to Examples and Production Examples. The present invention is not limited by these Examples and Production Examples.

[Example 1]
PMMA (“Acrylic (registered trademark)” manufactured by Mitsubishi Chemical Corporation) is used as the material of the resin base material. The resin base material is a rectangular plate having a width of 60 mm, a length of 60 mm, and a thickness of 1 mm.
DCP (tricyclodidecanedimethanol dimethacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) is used as the material of the protective layer.

Using the above materials, the substrate preparation step and the protective layer forming step described below are performed to prepare a resin base material (hereinafter, also referred to as “intermediate”) on which the protective layer is formed.

[Board preparation process]
In the substrate preparation step, the resin base material is washed and dried.
The resin base material is ultrasonically cleaned for 5 minutes while immersed in a 5% aqueous surfactant solution of Semiclean (registered trademark) M-LO (trade name; manufactured by Yokohama Oil & Fats Industry Co., Ltd.), which is a neutral detergent. ..
After that, the resin base material is ultrasonically cleaned for 5 minutes while being immersed in ultrapure water. Further, the resin base material is rinsed with ultrapure water, and the resin base material is air-dried and then dried in an oven at 80 ° C. under a nitrogen atmosphere. After that, the air-dried evaluation sample B is washed with UV ozone for 1 minute with a UV ozone washing machine.
This completes the substrate preparation process.

[Protective layer forming process]
In the protective layer forming step, an organic material layer is formed on the surface of the resin base material.
Add 5 parts by weight of Irgacure 184 (manufactured by BASF Japan) as an initiator to 100 parts by weight of DCP (Tricyclodidecanedimethanol Dimethacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.), and add a high-pressure mercury lamp (integrated light amount: 200 mJ / cm ² ). ) Is irradiated to form an organic material layer so that the thickness after curing is 5 μm, and the intermediate of Example 1 is obtained.
This completes the protective layer forming step.

[Example 2]
In Example 2, an intermediate is prepared in the same manner as in Example 1 except that an inorganic material layer formed of a silicon oxide having a thickness of 100 nm is formed on the organic material layer of Example 1.
Hereinafter, the protective layer forming step of Example 2 will be described focusing on the differences from Example 1.

In the protective layer forming step of this example, the organic material layer is formed on the resin base material in the same manner as in Example 1, and then the silicon oxide thin film layer is formed on the surface of the organic material layer.
After the intermediate composed of the resin base material and the organic material layer is placed in the vacuum vapor deposition apparatus, the silicon oxide is vacuum-deposited. The ultimate vacuum degree of the chamber of the vacuum vapor deposition apparatus shall be 1.0 × 10 ^-4 Torr. Under this vacuum, silicon monoxide having a purity of 99.9% is heated and evaporated by a high frequency induction heating method to form a silicon oxide thin film having a thickness of 100 nm on the surface of the resin substrate. As a result, the intermediate of Example 2 in which the silicon oxide thin film layer is formed is obtained.

[Example 3]
In Example 3, an intermediate is prepared in the same manner as in Example 2 except that the organic material layer has a thickness of 10 μm and the inorganic material layer is formed of alumina having a thickness of 500 nm.
Hereinafter, the protective layer forming step of Example 3 will be described focusing on the differences from Example 1.

In the protective layer forming step of this example, the organic material layer is formed on the resin base material in the same manner as in Example 1, and then the alumina thin film layer is formed on the surface of the organic material layer.
An intermediate composed of a resin base material and an organic material layer is placed in an electron beam vapor deposition apparatus, and an appropriate amount of alpha alumina particles having a purity of 99.999% and a particle size of 2 mm are arranged as a vapor deposition source to perform vacuum exhaust. The distance from the vapor deposition source to the shutter is about 8 cm, and the distance from the vapor deposition source to the surface of the resin substrate is about 35 cm.
After the pressure of the electron beam vapor deposition apparatus reaches 3 × 10 ^-3 Pa, the filament current of the electron beam is increased to about 35 mA, the shutter is opened, and alumina film formation is performed. When the temperature of the wall surface in the device reaches 50 ° C., the shutter is closed and the filament current of the electron beam is stopped. After cooling to 30 ° C. or lower, the filament current of the electron beam is raised to about 35 mA, the vapor deposition source is heated, the shutter is opened, and alumina film formation is performed. This is repeated to form an alumina film having a film thickness of 40 nm. As a result, the intermediate of Example 3 in which the alumina thin film layer is formed is obtained.

[Example 4]
Example 4 is an example corresponding to the image display light guide plate 26 of the second modification (see FIG. 4).
As shown in Table 1, Example 4 is the same as Example 1 except that the glass layer is arranged on the outermost surface.
Hereinafter, the points different from those of the first embodiment will be mainly described.

The image display light guide plate 26 of the fourth embodiment has a first glass layer 37, a first adhesive layer 38, a first resin base material 1, a first protective layer 2, a hologram layer 3, a second protective layer 4, and a second. The resin base material 5, the second adhesive layer 39, and the second glass layer 40 are laminated in this order (see FIG. 4).

[Glass layer bonding process]
In the glass layer bonding step, the resin substrates 1 and 5 on which the protective layers 2 and 4 are formed on the glass layers 37 and 40 via the adhesive layers 38 and 39 (intermediate obtained by the same method as in Example 1). Adhere to the surface of the body) opposite to the protective layer side.
Heat and UV curable epoxy resin (trade name "KRX-690-") as an uncured product of the adhesive layers 38 and 39 so that the thickness after curing with a bar coater on the resin substrates 1 and 5 is 3 μm. 5 ”, manufactured by ADEKA) are applied respectively. Further, as the glass layers 37 and 40, a thin plate glass (trade name "OA-10G", thickness: 50 μm, manufactured by Nippon Electric Glass Co., Ltd.) is hand-rolled (hardness: 90 °) toward the coated surfaces of the adhesive layers 38 and 39. ), Laminate on the resin substrates 1 and 5, respectively. By irradiating with a high-pressure mercury lamp (integrated light amount: 370 mJ / cm ² ) and then heat-treating at 150 ° C. for 30 minutes in a hot air circulation type dryer, the thermosetting resin composition is cured and the adhesive is applied. Obtain layers 38, 39.
The glass layers 37 and 40, the adhesive layers 38 and 39, and the resin base materials 1 and 5 are arranged so that the outer range (end edges) coincide with each other. As a result, a resin base material (hereinafter, also referred to as "intermediate laminate") in which a glass layer is adhered to a surface of the intermediate opposite to the protective layer side can be obtained.

[Comparative Example 1]
As shown in [Table 1], Comparative Example 1 is the same as that of Example 1 except that it has only a resin base material and no protective layer.

[Comparative Example 2]
As shown in [Table 1], Comparative Example 2 is the same as that of Example 3 except that there is no protective layer for the organic material and only the inorganic material layer.

[Comparative Example 3]
As shown in [Table 1], the same as in Example 1 except that BZA (benzyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat # 160"), which is a monofunctional monomer, is used as the material of the protective layer. The same is true.

<Measurement of elastic modulus>
Using the intermediates of each example and each comparative example as measurement samples, the elastic modulus of the protective layer is measured using the Shimadzu dynamic ultrafine hardness tester DUH-W201 under the measurement conditions: Triangular 115 and indentation depth of 230 to 280 nm. ..

The following [Table 1] shows the configurations and measurement results of each Example and each Comparative Example.

Next, an example of manufacturing a light guide plate for image display using an intermediate of each Example and each Comparative Example will be described. The light guide plate for image display can be manufactured by performing the light guide plate manufacturing process described below.

[Manufacturing Example 1]
In Production Example 1, the intermediate body of Example 1 is used to manufacture the image display light guide plate 6 of the embodiment.
As the photosensitive material for the hologram layer 3, 100 parts by weight of bisphenol-based epoxy resin jER (registered trademark) 1007 (polymerization degree n = 10.8, epoxy equivalent: 1750-2200, manufactured by Mitsubishi Chemical), triethylene glycol di. 50 parts by weight of acrylate, 5 parts by weight of 4,4'-bis (tert-butylphenyl) iodonium hexafluorophosphate, 0.5 part by weight of 3,3'-carbonylbis (7-diethylamino) coumarin, 100 parts by weight of 2-butanone. A material mixed and dissolved in a portion (hereinafter, also referred to as "photosensitive material A") is used.

[Light guide plate manufacturing process]
In the light guide plate manufacturing step of Production Example 1, the light guide plate 6 for image display is manufactured using the two intermediates of Example 1.
A seal layer having a width of 5 mm and a thickness of 5 μm is applied to the peripheral edge of the protective layer of one of the intermediates.
The seal layer is not particularly limited as long as it is made of a transparent material and can bond the protective layers of the intermediates to each other, but in Example 1, the optical adhesive Hard Rock (registered trademark) OP-1045K (trade name; (Made by Denka Co., Ltd.) is used.
As a result, an intermediate base material with a stepped seal layer having an opening having an opening surrounded by the seal layer having a size of 50 mm × 50 mm is prepared.
After that, the photosensitive material A as a photopolymer material for hologram is applied onto the intermediate substrate by spin coating. The photosensitive material is applied so that the thickness after drying is 5 μm.
After that, the other intermediate base material is laminated on the seal layer and the photosensitive material so that the protective layer faces the protective layer of the intermediate base material with the seal layer, and is press-bonded under reduced pressure. The conditions for press bonding are an absolute pressure of 5 kPa, a temperature of 70 ° C., and a press pressure of 0.04 MPa.
After that, the diffraction grating is recorded on the photosensitive material of the press-bonded laminate. In this step, the temperature of the laminate is maintained at 20 ° C. The diffraction grating irradiates the laminated body with two laser beams and adjusts the irradiation angle and intensity of each to form interference fringes so that a required diffraction pattern is formed. As a result, the diffraction grating is recorded on the photosensitive material.
As a specific diffraction grating, each light in the red, green, and blue wavelength regions incident as image light incident on the incident portion is diffracted and emitted from the display unit at a position corresponding to the pixel of the image light. A diffraction grating for color display is formed.
After that, with the laminated body kept at 20 ° C., ultraviolet light (wavelength 365 nm, irradiance 80 W / cm ² ) is irradiated over the entire surface from one side of the laminated body for 30 seconds. A high-pressure mercury lamp is used as a light source for ultraviolet light.
As a result, the seal layer is cured, and the image display light guide plate 6 of Production Example 1 is manufactured.

[Manufacturing Example 2]
In Production Example 2, the intermediate body of Example 2 is used to manufacture the image display light guide plate 16 of the embodiment. The image display light guide plate 16 of Production Example 2 is manufactured in the same manner as in Production Example 1 except that the intermediate of Example 2 is used.

[Manufacturing Example 3]
In Production Example 3, the light guide plate 16 for image display of the embodiment is manufactured by using the intermediate of Example 3. The image display light guide plate 16 of Production Example 3 is manufactured in the same manner as in Production Example 1 except that the intermediate of Example 3 is used.

[Manufacturing Example 4]
In Production Example 4, the light guide plate 26 for image display of the embodiment is manufactured by using the intermediate laminate of Example 4. The image display light guide plate 26 of Production Example 4 is manufactured in the same manner as in Production Example 1 except that the intermediate laminate of Example 4 is used instead of the intermediate.

[Comparative Manufacturing Example 1]
In Comparative Production Example 1, a light guide plate for image display is manufactured using the resin base material of Comparative Example 1. The image display light guide plate of Comparative Production Example 1 is produced in the same manner as in Production Example 1 except that the resin base material of Comparative Example 1 is used instead of the intermediate of Example 1.

[Comparative Manufacturing Example 2]
In Comparative Manufacturing Example 2, a light guide plate for image display is manufactured using the intermediate of Comparative Example 2. The image display light guide plate of Comparative Production Example 2 is manufactured in the same manner as in Production Example 1 except that the intermediate of Comparative Production Example 2 is used.

[Comparative Manufacturing Example 3]
In Comparative Production Example 3, a light guide plate for image display is manufactured using the intermediate of Comparative Example 3. The image display light guide plate of Comparative Production Example 3 is produced in the same manner as in Production Example 1 except that the intermediate of Comparative Production Example 3 is used.

<Evaluation method>
Next, the evaluation method of each production example will be described. As the evaluation, FOV evaluation and sharpness evaluation of the displayed image are performed.

[FOV measurement]
As a sample for measuring the luminance value, a sample that is not subjected to the humidification test (“initial” in [Table 2]) is prepared.
For the humidification test, a small environmental tester SH-241 (trade name; manufactured by ESPEC CORPORATION) is used. The test conditions for the humidification test are 40 ° C., 90% RH, and 100 hours.
The measurement of the luminance value of the measurement sample is performed based on the measurement method described above in the embodiment.
Each measurement sample is assembled in the above-mentioned display device.
The measurement of FOV is performed based on the measurement method described above in the embodiment.
As the luminance meter 14, a luminance meter BM-8 (trade name; manufactured by Topcon Corporation) is used. The measurement angle is 1 °. The distance d from the display surface 3a is 15 mm.
When the luminance value is 1000 nit or more and the FOV is 45 ° or more, it is judged to be very good (very good, described as "S" in [Table 2]).
When the luminance value is 1000 nit or more and the FOV is 35 ° or more and less than 45 °, it is judged to be good (good, described as “A” in [Table 2]).
When the luminance value is 1000 nit or more and the FOV is 24 ° or more and less than 35 °, it is determined that it is possible (fair, described as “B” in [Table 2]).
When the luminance value is 1000 nit or less and the FOV is less than 24 °, it is determined that it is not possible (no good, described as "C" in [Table 2]).

[Evaluation of sharpness of displayed image]
The evaluation of the sharpness of the displayed image is performed using the display device used for the FOV measurement.
As the input image used for the evaluation, a white image and a character display image are used.
The evaluation is performed by visually determining how the white image and the character display image look. As a character image, "ABCDE" within 10 mm × 100 mm is displayed.
When the rainbow color is not visible in the white image and the characters are clearly visible in the character display image, it is judged to be good (good, described as "A" in [Table 2]).
If a slight rainbow color is visible in the white image but the characters are clearly visible in the character display image, it is determined to be acceptable (fair, described as "B" in [Table 2]).
If at least a part of the rainbow color is visible in the white image and the outline of the character appears blurry in the character display image, it is determined to be impossible (no good, described as "C" in [Table 2]).

The following [Table 2] shows the configuration of each production example and the evaluation results.

<Evaluation result>
As shown in [Table 2], the FOVs of Production Examples 1, 2, 3 and 4 can be evaluated as “good” or “very good”, respectively.
On the other hand, the FOVs of Comparative Production Examples 1, 2 and 3 can be evaluated as “OK”, respectively.
It is considered that this is because the protective layers of Production Examples 1, 2, 3 and 4 prevent the hologram agent from eroding into the resin substrate.
On the other hand, in Comparative Production Examples 1, 2 and 3, the hologram layer is eroded into the resin base material by not having the protective layer containing the acrylic resin containing the repeating unit derived from the polyfunctional acrylate. , FOV decreases.
It is considered that the reason why the FOVs of Production Examples 2 and 3 are more favorable than the FOVs of Production Examples 1 and 4 is due to the presence or absence of the inorganic material layer in the protective layer. It is considered that the inorganic material layer further prevents erosion by the hologram agent, and the inorganic material layer has a higher refractive index than the resin base material layer and the organic material layer, so that the FOV becomes large and becomes good.

The sharpness of the displayed images of Production Examples 1, 2, 3 and 4 (“clearness” in [Table 2]) can be determined to be “good” both at the initial stage and after moisture resistance. On the other hand, the sharpness of the displayed images of Comparative Production Examples 1, 2 and 3 is "possible" at the initial stage, but can be determined to be "impossible (C)" after the moisture resistance test.
The reason for this is considered to be the same as the reason for the difference in the luminance value evaluation described above. That is, in Production Examples 1, 2, 3 and 4, a clear image is observed as a result of the protective layer preventing the hologram layer from eroding into the resin substrate even at the initial stage and after the moisture resistance test.
On the other hand, in Comparative Production Examples 1, 2 and 3, the hologram layer is eroded into the resin base material by not having the protective layer containing the acrylic resin containing the repeating unit derived from the polyfunctional acrylate. , No clear image is observed.

Although the preferred embodiments, modifications, examples and manufacturing examples of the present invention have been described above, the present invention is not limited to these embodiments, modifications, examples and manufacturing examples. It is possible to add, omit, replace, and make other changes to the configuration without departing from the spirit of the present invention.
Further, the present invention is not limited by the above description, but is limited only by the appended claims.

The light guide plate for image display of the present invention can suppress deterioration of the hologram layer even if a resin base material is used, and is useful for display device applications in VR and AR applications, for example. For example, the light guide plate for image display of the present invention is useful for display device applications such as head-up displays, wearable displays, and head-mounted displays.

1 1st resin base material 2, 22 1st protective layer 3 Hologram layer 3a Display surface 3b waveguide diffractive lattice part 3c Display diffractive lattice part 4, 24 2nd protective layer 5 2nd resin base material 6, 16, 26 Light guide plate for image display 6a Incident part 6d Display unit 10 Display device 12 Incident optical system 13 Image light projection unit 14 Brightness meter 15 Measuring device 22A First organic material layer 22B First inorganic material layer 24A Second organic material layer 24B 2 Inorganic material layer 37 First glass layer 38 First adhesive layer 39 Second adhesive layer 40 Second glass layer

Claims (9)

An image display light guide plate in which a first protective layer containing a first resin base material, an acrylic resin containing a repeating unit derived from a polyfunctional acrylate, and a hologram layer are arranged in this order in the thickness direction. The light guide plate for image display according to claim 1, wherein the elastic modulus of the first protective layer is 2 GPa or more. The light guide plate for image display according to claim 1 or 2, wherein the thickness of the first protective layer is 2 μm or more. The light guide plate for image display according to any one of claims 1 to 3, wherein the first protective layer includes a first organic material layer containing the acrylic resin and a first inorganic material layer. The first inorganic material layer comprises at least one inorganic material selected from the group consisting of silicon oxide, silicon nitride, silicon nitride, silicon sulfide, aluminum oxide, aluminum nitride, aluminum nitride and aluminum sulfide. Item 4. The light guide plate for image display according to Item 4. The light guide plate for image display according to claim 4 or 5, wherein the thickness of the first inorganic material layer is 50 nm or more and 5000 nm or less. The light guide plate for image display according to any one of claims 1 to 6, wherein the first glass layer is arranged on a surface of the first resin base material opposite to the first protective layer side. The light guide plate for image display according to claim 7, wherein the first adhesive layer is arranged between the first resin base material and the first glass layer. The light guide plate for image display according to any one of claims 1 to 8, wherein the hologram layer is made of a single or volume hologram material.

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