JP2023016819A - Light guide plate for image display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate for image display, which can clearly display an image even when using a resin base material.

SOLUTION: A light guide plate 1004 for image display includes a first resin base material 1001 and a hologram layer 1002. The first resin base material 1001 has an MC value of 0.120 or less, which is obtained on the basis of evaluation by a shadow contrast.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

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

2. Description of the Related Art An image display light guide plate may be used in a display device. For example, in a display device using VR (virtual reality) technology, AR (augmented reality) technology or MR (mixed reality), an image display light guide plate in which a hologram layer is supported by a transparent substrate is used. The hologram layer is formed with holograms having various optical functions such as guiding, reflecting and diffractive functions. A glass substrate is often used as the transparent substrate. However, from the viewpoint of workability, light weight, durability and portability, it is more preferable to use a resin base material as the transparent base material.

Patent Literature 1 discloses a hologram laminate used for an in-vehicle head-up display. In this hologram laminate, an acrylic resin substrate, an acrylic adhesive layer, a hologram layer made of an acrylic photopolymer, an acrylic adhesive layer, and an acrylic resin substrate are laminated in this order.
Patent Document 1 describes that the surface smoothness of an acrylic resin substrate causes a change in the appearance of a hologram. According to Patent Document 1, when the maximum height Rmax representing the surface smoothness of the hologram laminate exceeds 50 μm, the change in appearance of the hologram becomes noticeable. If the maximum height Rmax is less than 25 μm, the appearance change of the hologram is acceptable. However, Patent Literature 1 does not particularly describe the need for nano-order surface smoothness with a maximum height Rmax of 1 μm or less. Patent Literature 1 does not describe any specific example having nano-order surface smoothness.
In addition, the hologram material forming the hologram layer may erode the resin substrate due to temperature changes. Hologram materials are also known to deteriorate due to moisture absorption. Therefore, a display device in which a hologram layer is supported by a resin base material is likely to deteriorate in a hot and humid environment.
Patent Document 2 describes forming a photosensitive material layer for forming a hologram on an optically transparent resin substrate, and coating the photosensitive material layer with an aqueous polymer protective barrier. US Pat. No. 6,200,000 suggests that a water-based polymeric protective barrier is provided for the purpose of resisting attack by moisture.
Patent Document 3 describes a hologram laminate having a hologram sandwiched between resin substrates via an optical adhesive, the entire outer periphery of which is covered with a protective coating layer. Patent Literature 3 describes that the protective coating layer may be a coating that enhances hermeticity and gas barrier properties.

JP-A-2000-296583 JP-A-5-181400 JP-A-11-184363

However, the above related techniques have the following problems.
The hologram laminate described in Patent Literature 1 is mainly used for an in-vehicle head-up display that is viewed by a driver. Therefore, the image quality of the display image does not have to be particularly high quality. However, in the case of wearable displays or head-mounted displays used for AR or MR, for example, realistic images are often displayed in the full visual field of the user, and fine characters are displayed. In such applications, further improvement in image quality is required. According to the study of the present inventors, when the hologram layer is sandwiched between the resin base materials in the light guide plate for image display, the deterioration of the image quality may be observed even if the maximum height Rmax is less than 25 μm. For example, if the surface of the extruded resin base material has undulations (gear marks) with a pitch corresponding to the meshing pitch of the driving gear of the extrusion roller, the image tends to be blurred in places.
In the technique described in Patent Document 2, a resin substrate is in close contact with the surface of the photosensitive material layer opposite to the water-based polymer protective barrier.
Therefore, the photosensitive material may corrode the resin substrate in a high-temperature environment. Furthermore, since the resin substrate contains moisture, the moisture diffuses into the photosensitive material layer through the contact surface with the photosensitive material layer. In addition, since the substrate is exposed to the outside, moisture continues to permeate the substrate from the outside. As a result, since moisture permeates into the photosensitive material layer through the resin substrate, even if moisture is blocked by the water-based polymer protective barrier, moisture from the substrate side causes the photosensitive material layer to deteriorate over time. I can't control it.
In the technique described in Patent Document 3, the entire periphery of the laminate containing the hologram is sealed with a protective coating layer. Therefore, deterioration of the hologram due to permeation of water from the outside to the inside of the hologram laminate is suppressed. However, moisture contained in the resin substrate during formation of the protective coating layer is confined inside the protective coating layer. As a result, the moisture contained in the resin substrate permeates the hologram, which may lead to deterioration of the hologram over time. In particular, in a high-temperature environment, the influence of moisture released from the resin substrate becomes significant.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image display light guide plate capable of displaying a clear image even when a resin base material is used.
Another object of the present invention is to provide an image display light guide plate capable of suppressing deterioration of the hologram layer even when a resin base material is used.

The present inventors have conducted intensive research, and in the resin base material used for the light guide plate for image display, the flatness corresponding to the magnitude of the undulation of the surface that changes at a pitch that is much larger than the pitch measured by the surface roughness. The inventors have found that a clear image can be displayed by improving this, and arrived at the present invention. When the flatness of the surface of the resin base material is deteriorated due to the undulations, the thickness of the hologram layer laminated on the resin base material fluctuates. When the thickness of the hologram layer fluctuates, the waveguide light fluctuates, resulting in fine distortion and deformation in the image, making the image unclear. In the case of a color image, the image is blurred as a result of color shift and color bleeding caused by waveguiding light.
On the other hand, when the smoothness of the surface of the resin substrate is reduced by fine irregularities, the guided light is scattered, resulting in an unclear image.
In addition, the present inventor conducted extensive research and found that by introducing a barrier layer into a resin base material having a hologram layer used in a light guide plate for image display, deterioration of the hologram layer can be suppressed and a clear image can be displayed. The headline led to the present invention.

In order to solve the above problems, the present invention has, for example, the following aspects.
[1] An image display light guide plate having a first resin base material and a hologram layer,
The light guide plate for image display, wherein the first resin base material has an MC value of 0.120 or less as evaluated by shadow contrast.
[2] A light guide plate for image display, comprising a first resin substrate, a first barrier layer, and a hologram layer.
[3] The light guide plate for image display according to [2], wherein the first resin base material, the first barrier layer and the hologram layer are arranged in this order in the thickness direction.
[4] further comprising a second resin substrate and a second barrier layer,
The image display according to [3], wherein the first resin substrate, the first barrier layer, the hologram layer, the second barrier layer and the second resin substrate are arranged in this order in the thickness direction. light guide plate.
[5] The light guide plate for image display according to any one of [2] to [4], wherein the refractive index of the first barrier layer is higher than the refractive index of the first resin base material.
[6] The light guide plate for image display according to any one of [2] to [5], wherein the first barrier layer has a refractive index of 1.48 or more.
[7] The light guide plate for image display according to any one of [2] to [6], wherein the first barrier layer contains an inorganic material.
[8] The first barrier layer according to [7], wherein the first barrier layer contains at least one inorganic material selected from the group consisting of silicon oxide, silicon nitrogen oxide, diamond-like carbon, aluminum oxide and glass. Light guide plate for image display.
[9] The light guide plate for image display according to any one of [2] to [8], wherein the first barrier layer is arranged on a resin film.
[10] The light guide plate for image display according to any one of [2] to [9], wherein a water vapor barrier material is used as the material of the first barrier layer.
[11] The light guide plate for image display according to any one of [2] to [10], wherein the first barrier layer is arranged on the hologram layer.
[12] The light guide plate for image display according to any one of [1] to [11], wherein the first resin base material has a refractive index of 1.48 to 1.70.
[13] Any one of [1] to [12], wherein the first resin substrate contains at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins and polycarbonates. 1. The light guide plate for image display according to 1 above.
[14] Any one of [1] to [13], wherein the thermal shrinkage of the first resin base material measured in accordance with JIS K 6718-1:2015 Annex A is less than 3% The light guide plate for image display according to 1.
[15] The light guide plate for image display according to any one of [1] to [14], wherein the surface of the first resin base has an arithmetic mean roughness Ra of 10 nm or less.

ADVANTAGE OF THE INVENTION According to this invention, the light-guide plate for image displays which can display a clear image even when a resin base material is used can be provided.
Further, according to the present invention, it is possible to provide an image display light guide plate that can suppress deterioration of the hologram layer even when a resin base material is used.

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing which shows an example of the light-guide plate for image displays of the 1st Embodiment of this invention. It is a typical front view explaining the evaluation method of MC value. FIG. 4 is a schematic plan view for explaining a method of evaluating an MC value; FIG. 4 is a schematic diagram showing an example of an evaluation image of MC values; FIG. 4 is a schematic diagram showing an example of an evaluation image in which MC values are digitized; It is a typical graph which shows the calculation method of MC value. FIG. 5 is a schematic cross-sectional view showing an example of an image display light guide plate of a first modified example of the first embodiment of the present invention; 1 is a schematic longitudinal sectional view showing an example of a resin substrate manufacturing apparatus of Example 1. FIG. FIG. 5 is a schematic cross-sectional view showing an example of an image display light guide plate according to a second embodiment of the present invention; It is a typical front view explaining the measuring method of a luminance value and FOV. FIG. 5 is a schematic cross-sectional view showing an example of an image display light guide plate of a first modified example of the second embodiment of the present invention; FIG. 11 is a schematic cross-sectional view showing an image display light guide plate of Example 5; FIG. 11 is a schematic cross-sectional view showing an image display light guide plate of Example 6; FIG. 7 is a schematic diagram showing the layer structure of an image display light guide plate according to a third embodiment of the present invention; FIG. 11 is a schematic diagram showing a layer structure of an image display light guide plate according to a first modified example of the third embodiment of the present invention; It is a figure which shows the state in which two hard-coat films which concern on 3rd Embodiment were piled up. It is a figure which shows the state in which two hard-coat films based on the 1st modification of 3rd Embodiment were piled up. FIG. 10 is a schematic cross-sectional view showing an example of an image display light guide plate according to a fourth embodiment of the present invention; FIG. 11 is a schematic cross-sectional view showing an example of a display device including an image display light guide plate according to a fourth embodiment of the present invention; FIG. 11 is a schematic cross-sectional view showing an example of an image display light guide plate of a first modified example of the fourth embodiment of the present invention; FIG. 11 is a schematic cross-sectional view showing an example of an image display light guide plate of a second modified example of the fourth embodiment of the present invention; FIG. 11 is a schematic cross-sectional view showing an example of an image display light guide plate of a third modified example of the fourth embodiment of the present invention;

Embodiments of the present invention are described below with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common explanations are omitted.
A numerical range represented using "-" includes the numerical values at both ends of "-".
"UV" means ultraviolet.
"(Meth)acrylic" means one or both of acrylic and methacrylic.
"(Meth)acrylate" means one or both of acrylate and methacrylate.

[First Embodiment]
<Basic example>
An image display light guide plate according to a first embodiment of the present invention will be described.
The light guide plate for image display according to the first embodiment of the present invention has a first resin base material and a hologram layer. The image display light guide plate of the present embodiment may further have a second resin base material. In the present embodiment, the first resin base material and the second resin base material may be collectively referred to hereinafter simply as "resin base material". The resin base material is transparent.
The hologram layer is sandwiched between the first resin substrate and the second resin substrate, or between the first resin substrate and the glass substrate.
The image display light guide plate has an incident portion for receiving image light and a display image output portion for displaying an image by the image light. The hologram layer is arranged between the entrance portion and the display image exit portion. The hologram layer is formed with a diffraction grating pattern for guiding at least the image light incident from the incident portion to the display image output portion and outputting the image light from the display image output portion. The diffraction grating pattern in the display image output portion transmits at least part of external light entering from the outside of the image display light guide plate. In addition, the said external light entrance part points out the surface opposite to the said display image output part.
The image light incident on the incident portion is guided in the hologram layer and emitted to the outside from the display image emitting portion. On the other hand, external light also passes through the resin base material and the display image output section, so that an observer of the display image output section can observe both the image light and the external light within the field of view.
The image display light guide plate of the present embodiment is suitably used in a display device using AR technology or MR technology. For example, the image display light guide plate of the present embodiment may be used in devices such as AR glasses such as head-mounted displays or head-up displays for vehicles.

The resin base material used for the light guide plate for image display according to the present embodiment has an MC value of 0.120 or less as evaluated by shadow contrast. A definition of the MC value and a specific evaluation method will be described later. Among the surface properties of the resin substrate, the MC value is particularly effective for evaluating flatness. That is, with respect to unevenness having a lower spatial frequency than the spatial frequency of the unevenness of the surface roughness, the lower the MC value, the smaller the degree of unevenness. Therefore, a resin base material having a lower MC value has better planarity.
The material of the resin base material is not particularly limited as long as it is a transparent material.
The material used for the resin substrate preferably contains at least one resin selected from the group consisting of acrylic resins, cyclic polyolefin resins, and polycarbonate resins, and more preferably acrylic resins.
The refractive index of the material used for the resin substrate is preferably 1.48 to 1.70.
The heat shrinkage rate of the material used for the resin substrate is preferably less than 3%. Here, the thermal shrinkage rate is the heating dimensional change rate based on JIS K 6718-1:2015 Annex A "Measurement of dimensional change (shrinkage) during heating".
This "measurement of dimensional change (shrinkage) during heating" is a standard for cast plates, but the thermal shrinkage rate in the present invention is determined when the resin base material using the above material is an extruded plate, a continuous cast plate, or the like. Even in the case of , adopt the value based on this standard.
The smoothness of the resin substrate (for example, represented by surface roughness such as arithmetic mean roughness Ra or maximum height Rmax) is the arithmetic mean roughness Ra of the surface of the resin substrate, and 10 nm or less preferable.
Further, in the image display light guide plate of the present embodiment, a barrier layer, which will be described later, can be introduced. By introducing the barrier layer, deterioration of the hologram layer can be suppressed and a clear image can be maintained.

A resin substrate having excellent flatness and having the above-mentioned MC value is produced, for example, using a production method such as a casting method or an extrusion method, or a resin substrate is subjected to cutting, polishing, hot pressing, or the like. Manufactured by post-processing of

As the casting method, a glass casting method may be used. In the glass casting method, after the raw material of the resin base material is poured between glass plates having good flatness and smoothness, the raw material of the resin is solidified by performing a polymerization process. When the resin substrate is manufactured by the glass casting method, the surface shape of the glass used in the glass casting method (hereinafter sometimes referred to as “casting glass”) is transferred to the resin substrate. Therefore, if the surface of the glass for casting has good flatness and smoothness, the surface of the resin substrate also has good flatness and smoothness.

The smaller the internal strain of the glass for casting, the better the flatness of the surface of the glass for casting, so that the flatness of the resin substrate can be improved. For example, as the casting glass, non-tempered glass is preferable to tempered glass. However, even if the tempered glass is chemically tempered glass, the flatness of the resin substrate can be improved as long as it is less distorted than the air-cooled tempered glass.
The greater the thickness of the casting glass, the higher the rigidity of the casting glass, which suppresses the deformation of the glass during production, thereby improving the flatness of the resin substrate.
Smoothness and flatness of the resin base material can be improved by applying surface pressure to the casting glass when molding the resin base material.

The casting method is not limited to the glass casting method described above.
For example, metal endless belts facing each other may be used as casts. In this case, the resin substrate can be continuously produced by performing the polymerization process while rotating the endless belt. The shape of the surface of the endless belt is transferred to the resin base material. Therefore, by mirror-finishing the surface of the endless belt, the smoothness of the resin substrate can be improved. Furthermore, by controlling the tension of the endless belt, the planarity of the resin substrate can be improved.
Other casting methods include a method of using a metal plate instead of the glass for casting.

In the polymerization step in the casting method, the lower the curing rate, the easier it is to transfer the cast surface shape to the resin base material, so that the flatness and smoothness of the resin base material can be improved.
As means for reducing the curing speed, for example, means such as reducing the amount of the polymerization initiator or lowering the polymerization temperature may be used.
The smaller the amount of the cross-linking agent added to cross-link the material of the resin base material, the lower the curing speed, and the surface shape of the cast is easily transferred to the resin base material, so the flatness of the resin base material is improved. can. The amount of the cross-linking agent to be added is preferably a very small amount of 0.5 parts by mass or less with respect to a total of 100 parts by mass of the polymerizable monomer component and the polymerizable oligomer component other than the cross-linking agent, which are raw materials for the resin base material. .
A release agent can be used in the casting, but the smaller the amount used, the better. Thereby, the surface shape of the cast is easily transferred to the resin base material, and the flatness and smoothness of the resin base material can be improved.
In the polymerization step in the casting method, the planarity and smoothness of the resin substrate can be improved by prepolymerizing the monomer for forming the substrate.
In the polymerization step in the casting method, by performing cast polymerization using a raw material obtained by dissolving a base-forming polymer in a base-forming monomer, curing shrinkage is reduced, and the surface shape of the cast is changed to the resin base. Since it becomes easier to transfer to the material, the flatness and smoothness of the resin base material can be improved.
In the casting method, two or more of the techniques described above may be used in combination. In this case, the synergistic effect of each technique can further improve the flatness and smoothness of the resin base material.

When the resin substrate is manufactured by an extrusion method, for example, a polishing roll method or an air knife method may be used.
Depending on the processing accuracy of the die line of the extrusion die, there is a risk that the smoothness of the surface of the resin base material will decrease due to the transfer of minute unevenness of the die line. Therefore, the extrusion die is finished with high precision so that the die line is smooth.

For example, in the polishing roll method, a molten resin is generally compressed by a set of three polishing rolls and cooled. The pressure applied to the molten resin when it is pressed between the polishing rolls is linear pressure. This linear pressure is easily affected by rotation unevenness of the polishing roll and variations in processing accuracy of the roll shaft or machine base. As a result, the linear pressure becomes non-uniform, and the resin substrate tends to suffer from thickness unevenness, gear marks, and other deterioration in flatness. The gear mark is generated in a linear shape extending in a direction orthogonal to the feed direction of the resin base material.
If the surface temperature of the polishing roll is too high, the resin base material tends to be deformed, so the surface temperature is preferably low.

It is more preferable that the feeding mechanism for the polishing roll is configured to reduce driving unevenness. For example, the transmission mechanism such as the speed reducer of the feed mechanism may use planetary rollers instead of the gear transmission mechanism in order to suppress transmission of meshing vibration of the gears. However, any gear transmission mechanism, such as a worm gear or a helical gear, which is less susceptible to meshing vibration than a spur gear, may be used as the transmission mechanism for the feed mechanism.
Instead of the polishing rolls, a configuration may be used in which a pair of seamless metal belts for cooling the molten resin are arranged facing each other at a predetermined interval at the molten resin outlet of the extruder. In this case, the molten resin is sandwiched between the pair of seamless metal belts and conveyed while being cooled. As a result, since the pressure applied to the molten resin becomes the surface pressure, it is possible to suppress the reduction in flatness due to the line pressure as in the polishing roll method described above.

A known hologram-forming resin material is used for the hologram layer. For example, as the hologram-forming resin material, a known material can be appropriately selected and used. The photosensitive material may be appropriately determined in consideration of the wavelength of light to be guided, or an acrylic hologram-forming photosensitive resin material having excellent optical properties may be used.

The hologram layer may be formed on the surface of the resin base material, or may be laminated on the resin base material with an appropriate transparent layer interposed therebetween. When the light guide plate for image display includes a glass base material, the hologram layer may be formed on the surface of the glass base material, or may be laminated on the glass base material with an appropriate transparent layer interposed therebetween. may
The resin base material may be arranged at the outermost part in the thickness direction of the light guide plate for image display, or may be arranged inside. When the image display light guide plate includes the glass substrate, the glass substrate may be arranged at the outermost portion in the thickness direction of the image display light guide plate, or may be arranged inside the image display light guide plate.

In the light guide plate for image display, one or more appropriate transparent layers are disposed between the resin substrate and the hologram layer in the thickness direction, or between the glass substrate and the hologram layer when a glass substrate is included. may
In the light guide plate for image display, one or more appropriate transparent layers different from the resin base material and the glass base material may be disposed on the outermost layer in the thickness direction.
For example, when a transparent layer is arranged on at least one surface of the resin substrate, the transparent layer may be a hard coat layer that protects the surface of the resin substrate.
Examples of other transparent layers include absorption layers and adhesive layers that have absorption peaks in the UV or specific wavelength ranges.

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

In the image display light guide plate 1004 shown in FIG. 1, the first resin base material 1001, the hologram layer 1002, and the second resin base material 1003 are arranged in this order in the thickness direction.
The planar view shape of the image display light guide plate 1004 is not particularly limited. For example, the image display light guide plate 1004 may be shaped into a shape that can be attached to the display device used. For example, the image display light guide plate 1004 may be a rectangular plate larger than the shape to be attached to the display device. In this case, the image display light guide plate 1004 is shaped, for example, by being cut into a shape that can be attached to the display device before being assembled into the display device.
The image display light guide plate 1004 may have a flat plate shape, or may have a curved plate shape as necessary.
In the following, an example in which the image display light guide plate 1004 is made of a rectangular flat plate in plan view will be described.

The first resin base material 1001 is arranged at the outermost part in the thickness direction of the image display light guide plate 1004 . The first resin base material 1001 is arranged on the surface of the image display light guide plate 1004 on the image display side.
The first resin base material 1001 has a shape similar to the outer shape of the image display light guide plate 1004 . Image light emitted from the hologram layer 1002 and external light passing through the second resin base material 1003 and the hologram layer 1002 , which will be described later, pass through the first resin base material 1001 .

The thickness of the first resin base material 1001 is not particularly limited. For example, the thickness of the first resin base material 1001 may be 0.05 to 2 mm. When the thickness of the first resin base material 1001 is 0.05 mm or more, it is preferable because the shape can be easily maintained in a stable manner and the measurement error of the MC value, which will be described later, can be reduced. When the thickness of the first resin base material 1001 is 2 mm or less, the weight of the image display light guide plate 1004 can be reduced, which is preferable because the weight can be reduced. The thickness of the first resin substrate 1001 is preferably 0.05 mm or more, more preferably 0.1 mm or more, and even more preferably 0.5 mm or more. On the other hand, the thickness of the first resin base material 1001 is preferably 2 mm or less, more preferably 1.5 mm or less, and even more preferably 1 mm or less, from the viewpoint of deformation or residual strain of the base material due to water absorption of the base material.

Examples of materials that can be used for the first resin substrate 1001 include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin film, and polyvinyl chloride. , polyethylene, 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 Organic materials such as block copolymers (SIBS) and allyl diglycol carbonate, including at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins and polycarbonates is preferred.
From the viewpoint of transparency of the first resin substrate 1001, it is preferable to use polycarbonate or poly(meth)acrylic resin. (Meth)acrylic resins, epoxy resins, or cyclic polyolefins are preferably used, and among them, poly(meth)acrylic resins are more preferable because both transparency and process resistance can be achieved.

As the first resin base material 1001, a plate material having an MC value of 0.120 or less as evaluated by shadow contrast is used.
Here, a specific evaluation method and calculation method of the MC value will be described.
FIG. 2 is a schematic front view for explaining the evaluation method of the MC value. FIG. 3 is a schematic plan view for explaining the MC value evaluation method. FIG. 4 is a schematic diagram showing an example of an MC value evaluation image. FIG. 5 is a schematic diagram showing an example of an evaluation image in which MC values are digitized. FIG. 6 is a schematic graph showing a method of calculating the MC value.

(Shadow contrast evaluation)
Shadow contrast evaluation can be performed using evaluation apparatus 1200 shown in FIGS.
The evaluation device 1200 includes a light source 1201, a screen 1202, a camera 1203 (see FIG. 3), and an arithmetic processing unit 1204 (see FIG. 3).
The evaluation apparatus 1200 forms a transmission projection image of the measurement sample S on a screen 1202 by irradiating the measurement sample S with measurement light emitted from a light source 1201, and determines the measurement sample S based on the brightness distribution of the transmission projection image. Calculate the MC value of
The shape of the measurement sample S is the same as the outer shape of the first resin base material 1001 . An example in which the measurement sample S is a flat plate having a rectangular shape in plan view will be described below.

The type of the light source 1201 is not particularly limited as long as a transmission projection image of the measurement sample S can be formed. For example, as the light source 1201, it is more preferable to use a point light source in that the transmitted projection image projected on the screen 1202 becomes clear. Examples of point light sources include, for example, metal halide lamps, halogen lamps and high pressure mercury lamps. The wavelength of light is preferably in the range of 280-780 nm. When the measurement sample S is a resin substrate, the range is preferably from 400 nm to 780 nm.

The screen 1202 includes, for example, a matte screen, a bead screen, and a pearl screen. The color of the screen 1202 is not particularly limited as long as it does not interfere with the brightness measurement of the projected image on the screen 1202 . The color of screen 1202 may be, for example, white or gray. The size of the screen 1202 is not particularly limited as long as it can include the transmission projection image of the measurement sample S in the required measurement range. It is more preferable that the screen 1202 has a size larger than or equal to the transmission projection image of the entire measurement sample S can be included.

The type of camera 1203 is not particularly limited as long as the brightness of the transmission projection image on the screen 1202 can be accurately captured. For example, camera 1203 may be an analog camera or a digital camera. Camera 1203 is more preferably a digital camera in terms of facilitating digital analysis. Note that when the image is captured by an analog camera, the image analysis, which will be described later, is performed after the obtained image is converted into a digital image.
As for the size of the digital image, for example, 800×600, 1024×768, 1600×1200, 2048×1536 or 5472×3648 is used when expressed by the number of horizontal pixels×vertical pixels. However, the size of the digital image is not limited to these as long as it has a resolution capable of obtaining a brightness change curve corresponding to unevenness of the measurement sample S caused by undulation or the like.
The brightness value is the density when the data in each pixel is converted to monochrome. The resolution of the brightness value is determined by the number of gradations of each pixel. The number of gradations of each pixel is not particularly limited as long as it is possible to calculate an MC value of 0.120 or less. The number of gradations of each pixel may be 128, 256, 512 or 1024, for example.
However, when the contrast of the transmission projection image is low due to restrictions such as the transmittance of the measurement sample S and the brightness of the light source 1201, it is more preferable to use as many gradations as possible in order to improve the measurement accuracy. .

It is more preferable that the photographing using the camera 1203 is performed under light shielding. When photographing with the camera 1203 is performed under light shielding, a more accurate lightness distribution can be obtained than when photographing is not performed under light shielding. A method of photographing under light shielding is not particularly limited. For example, if the shooting environment in which the evaluation device 1200 is arranged is a room with a window, the window may be closed to put the entire room in a light-shielding state. For example, the evaluation device 1200 may have a light shielding housing surrounding at least the optical path from the light source 1201 to the screen 1202 and the optical path from the screen 1202 to the camera 1203 .

The shooting mode of the camera 1203 may be a color image mode or a monochrome image mode. If the image is captured in the color image mode, it is more preferable to convert the image into a monochrome image using image processing software.
For example, due to the influence of the optical characteristics of the lens of the camera 1203, the brightness at the edges of the captured image may be lower than the brightness at the center. If the noise due to the uneven brightness level is too large, it is more preferable to determine the brightness distribution of the measurement sample S after performing shading correction on the captured image in advance according to the optical characteristics of the lens. Shading correction may be performed by appropriate image processing software before analysis of the captured image. The correction amount of the shading correction is determined by, for example, photographing using a correction glass plate with good flatness and smoothness instead of the measurement sample S, and determining the correction amount so that the brightness distribution becomes uniform. good too. In this case, brightness unevenness based on the optical characteristics of the light source 1201 is also corrected.

For simplicity, an example in which the camera 1203 is a digital camera and a transmission projection image on the screen 1202 is captured in monochrome image mode will be described below. In this case, the output value of a pixel of the digital image is proportional to the brightness of the transmission projection image.
If the camera 1203 is an analog camera, the digital image described below can be read as a digital image generated from an image captured by the camera 1203 .

The arithmetic processing unit 1204 obtains the brightness distribution based on the digital image captured by the camera 1203, and calculates the MC value based on the brightness distribution. The arithmetic processing unit 1204 includes a computer capable of executing appropriate image processing software.

The arrangement of each part in the evaluation device 1200 and the arrangement of the measurement sample S at the time of measurement will be described.
Below, the positional relationship may be explained based on the XYZ orthogonal coordinate system. The X-axis extends in the horizontal plane. The Y-axis is orthogonal to the X-axis in the horizontal plane. The Z-axis is the vertical axis. Yes and orthogonal to the X and Y axes. A direction along the X axis, a direction along the Y axis, and a direction along the Z axis are referred to as an X direction, a Y direction, and a Z direction, respectively.
As shown in FIG. 2, in the evaluation device 1200 the screen 1202 is arranged parallel to the YZ plane. The light source 1201 is arranged apart from the screen 1202 by (d1+d2) in the X direction. The optical axis O of the light source 1201 is parallel to the X axis.

As shown in FIG. 3, the measurement sample S is arranged on the optical axis O in the middle part between the light source 1201 and the screen 1202 . A, B, C, and D represent the vertices of the rectangular outline in the cross section passing through the center of the thickness direction of the measurement sample S. Side AD and side BC are parallel to the Y-axis, respectively. A side AD is closer to the light source 1201 and a side BC is closer to the screen 1202 .
As shown in FIG. 2, the center SO of the rectangle ABCD in the measurement sample S is located on the optical axis O and at a distance d1 from the light source 1201 in the X direction. Further, the measurement sample S is arranged in a posture rotated clockwise from the horizontal plane by an elevation angle θ _A about an axis line parallel to the Y-axis through the center SO. However, when the thickness of the measurement sample S is thin, instead of the center SO of the measurement sample S, the center of one surface of the measurement sample S in the thickness direction may be arranged at the same position as described above.
Here, the distances d1 and d2 are appropriately set according to, for example, the radiation angle and light intensity of the light source 1201, the size of the measurement sample S, and the size of the screen 1202. FIG. For example, the distances d1 and d2 may be 30-1000 cm.
For example, the distance d1 is preferably as short as possible within the range where the light source 1201 can be installed. It is more preferable that the distance d2 be as short as possible within the range where the screen 1202 can be installed. There is a tendency that the shorter the distances d1 and d2, the more efficiently the measurement light emitted from the light source 1201 can be used.
The elevation angle θ _A is preferably 5 to 90°. For example, the elevation angle θ _A can be measured as 20°.

The arrangement position of the camera 1203 is not particularly limited as long as the camera 1203 is located at a position where its own shadow and reflected light do not appear in the photographing range and where the entire transmitted projection image on the screen 1202 can be photographed. In the example shown in FIG. 3, the camera 1203 is arranged at a position adjacent to the camera 1203 in the Y direction in plan view. However, although not shown, the camera 1203 is arranged at a height different from that of the measurement sample S in the Z direction, so that its own shadow and reflected light do not appear in the photographing range.

With such an arrangement, the measurement light emitted from the light source 1201 is transmitted through the measurement sample S and projected onto the screen 1202 . When the light source 1201 is a point light source, the measurement light spreads radially, so that a transmission projection image based on the light intensity of the transmission light of the measurement sample S is formed on the screen 1202 . The transmission projection image is captured by camera 1203 and sent to arithmetic processing unit 1204 as a digital image.
For example, a digital image schematically shown in FIG. 4 is sent to the arithmetic processing unit 1204 . The outermost frame in FIG. 4 represents the edge of the screen 1202 . The central trapezoid PaPbPcPd represents the transmission projection image I of the measurement sample S. FIG. Points Pa, Pb, Pc, and Pd correspond to points A, B, C, and D of the measurement sample S, respectively.

The transmission projection image I has a brightness distribution. The example shown in FIG. 4 has a high brightness portion Ib and a low brightness portion Is. The high brightness portion Ib is formed by projecting the measurement light transmitted through the measurement sample S in accordance with the transmittance onto the screen 1202 .
The brightness distribution on the transmission projection image I includes brightness unevenness caused by the optical path length and the radiant light intensity distribution of the light source 1201 . This brightness unevenness occurs to some extent even if the measurement sample S does not have unevenness defects.
Since the measurement light is radiant light, the light intensity of the measurement light traveling along the optical axis O is maximized and decreases toward the periphery of the measurement sample S. FIG. The same applies to the radiant light intensity distribution of the light source 1201 .
If this unevenness in brightness is greater than the unevenness in brightness caused by unevenness defects, it is corrected in advance. For example, when the difference between the brightness value on the optical axis O and the brightness value at the outer edge of the measurement sample S is 5 or more, it is more preferable to correct the brightness unevenness described above.

Brightness unevenness caused by the light intensity distribution of the measurement light can be corrected, for example, based on the law of light attenuation (the intensity of light attenuated is inversely proportional to the square of the distance from the light source). For example, brightness unevenness caused by the radiant light intensity distribution of the light source 1201 can be corrected based on the radiant light intensity distribution of the light source 1201 .
For example, as described above, correction data may be obtained by photographing using a correction glass plate.
However, depending on the measurement conditions, if there is only brightness unevenness that is smaller than brightness unevenness caused by unevenness defects, correction of the light intensity distribution of the measurement light and the light source 1201 may be omitted. In the following description, it is assumed that lightness unevenness, which causes measurement noise, has been removed.

The low brightness portion Is is considered to be formed by unevenness defects corresponding to flatness errors on the surface of the measurement sample S. FIG.
For example, when the radius of curvature of the unevenness formed on the measurement sample S is small to some extent, it is conceivable that the measuring light diffuses before reaching the screen 1202 due to the lens effect of the unevenness. This depends on smoothness.
For example, when the measurement sample S is deformed into a wave shape, the thickness may not change even if there are irregularities on the surface. This depends on planarity. In this case, the unevenness does not have a lens effect, but similar refraction and diffraction of the measurement light occurs, which may contribute to brightness unevenness.
In addition, for example, it is conceivable that the unevenness formed on the measurement sample S causes a strain distribution in the vicinity of the unevenness, disturbing the emission direction of the measurement light and changing the light intensity on the screen 1202 .
For example, when the angle of incidence on the measurement sample S increases, the change in transmittance characteristics depending on the angle of incidence increases. For this reason, it is conceivable that the transmittance of the irregularities formed on the measurement sample S changes and contributes to the brightness unevenness. It is also conceivable that the transmittance that changes due to the uneven refractive index due to the strain inside the measurement sample S also contributes to the uneven brightness.
It is considered that unevenness in brightness is caused by any one or a combination of such factors. Furthermore, it is considered that the magnitude of brightness unevenness is highly correlated with the depth of unevenness defects. Therefore, the flatness of the measurement sample S can be evaluated based on the difference in brightness between the low brightness portion Is and the high brightness portion Ib.

In the example shown in FIG. 4, the low brightness portion Is is elliptical. Such a low brightness portion Is corresponds to an elliptical concave portion or convex portion on the surface of the measurement sample S. As shown in FIG. For example, when a gear mark is formed on the measurement sample S, the low brightness portion Is is formed in a streaky shape. In this case, the low-brightness portions Is are formed substantially parallel to the direction orthogonal to the extrusion direction of the first resin base material 1001 at regular pitches.

The arithmetic processing unit 1204 analyzes the digital image as follows and calculates the MC value. The digital image used to measure the MC value may be the entire trapezoid PaPbPcPd. However, for example, when a part of the measurement sample S is cut and used for a display device, the measurement may be performed in the entire size range used for the display device.
In some cases, the digital image used for measuring the measurement sample S may have a trapezoidal partial region inside the trapezoid PaPbPcPd. For example, if the defect to be detected by the MC value is known in advance in directionality, pitch, etc., such as gear marks, the size and range including a plurality of gear marks in consideration of measurement errors A partial region of the trapezoidal PaPbPcPd, if any, may be used. For example, the same applies to the case where the shape of the measurement sample S has a gently curved design.
For example, when the measurement sample S has a rectangular shape of 200 mm×200 mm in plan view, it is more preferable that the measurement range includes at least a rectangular area of 180 mm×80 mm on the measurement sample S. Here, the longitudinal direction of the measurement range is aligned with the direction in which the brightness changes more.
For example, when the measurement sample S is a curved plate instead of a flat plate, it is more preferable that the width of the measurement range in the curved direction is 50 mm or more. For example, if the measurement sample S has a generally spherical curvature, it is more preferable to include a rectangular area measuring 50 mm×50 mm centered at the top of the curvature.
In the following, as an example, the case of using the entire trapezoid PaPbPcPd will be described.

Arithmetic processing unit 1204 obtains a lightness distribution on a predetermined measurement line. For example, the measurement line consists of points qi (where i=1, . Qi (where i=1, . . . , N−1) are (N−1) line segments qiQi.
In this case, on the measurement sample S, the points qi and Qi are points on a plane parallel to the ZX plane.
Points qi and Qi on the transmission projection image I are shown in FIG.
For example, N can be appropriately selected between 2 and 10000 according to the size of the uneven defect. For example, in the case of a defect with a width of 100 mm, N may be selected so that the pitch of the measurement lines is about 1 to 20 mm.
For example, when the low brightness portion Is is streak-like, the digital image is obtained by changing the placement of the measurement sample S so that the measurement line intersects the low brightness portion Is. In this case, N may be selected so that the pitch of the measurement lines along the longitudinal direction of the low brightness portion Is is about 1 to 20 mm.

In the example shown in FIG. 4, N=8. A measurement line L3 in FIG. 5 schematically shows a measurement line corresponding to the line segment q3Q3 in FIG. Since the measurement line on the measurement sample S is projected as an oblique line, the measurement line L3 on the transmission projection image I is a digitized oblique line.
Based on the positional relationship between the light source 1201, the screen 1202, and the measurement sample S, the arithmetic processing unit 1204 converts the coordinates of the points qi and Qi on the measurement sample S into the pixel coordinates on the transmission projection image I. Extract the brightness value of each measurement line.

FIG. 6 schematically shows an example of the brightness distribution along the measurement line L3. The horizontal axis of FIG. 6 represents the pixel position in the Z direction, and the vertical axis represents the brightness value.
As shown in curve 1210, the lightness in measurement line L3 decreases from point q3 to point Q3 from a substantially constant high lightness value, reaches a minimum lightness value, and then returns to a substantially flat high lightness value. It's becoming In the Z direction, both the section from q3 to p1 and the section from p2 to Q3 are included in the high brightness portion Ib. A section from p1 to p2 is included in the low brightness portion Is.
The arithmetic processing unit 1204 obtains the minimum value Lmin and the maximum value Lmax of lightness from such a lightness distribution.
The MC value is defined by the following formula (1). The arithmetic processing unit 1204 calculates the MC value based on the following formula (1) for Lmin and Lmax.

The MC value is an index that objectively represents the magnitude of the drop in the low brightness portion Is in the brightness distribution.
As described above, the brightness of the low brightness portion Is decreases as the flatness of the measurement sample S deteriorates. Therefore, the larger the MC value, the poorer the flatness of the surface of the measurement sample S, and the smaller the MC value, the better the flatness of the surface of the measurement sample S.

Similarly, the arithmetic processing unit 1204 calculates the MC value for each measurement line.
The MC value of the measurement sample S is the maximum value among the MC values of each measurement line.

As described above, in the light guide plate for image display of the present invention, the MC value of the resin base material must be 0.120 or less. As a result, the clearness of a display image using a hologram such as AR or MR, which is formed using this light guide plate, is improved. The MC value of the resin base material is 0.120 or less, preferably 0.110 or less, more preferably 0.100 or less, still more preferably 0.080 or less, and particularly preferably 0.070 or less.
On the other hand, by setting the MC value to 0.001 or more, it is possible to prevent blocking between the base materials during lamination of the base materials, and there is a tendency that the handleability during processing of the base materials is improved. The MC value of the resin substrate is preferably 0.001 or more, more preferably 0.005 or more, still more preferably 0.010 or more, and particularly preferably 0.020 or more.

Further, as described above, in the light guide plate for image display of the present invention, the resin substrate preferably has a refractive index of 1.48 to 1.70. As a result, the viewing angle can be increased when used as a light guide plate for image display.

Furthermore, as described above, in the light guide plate for image display of the present invention, the thermal shrinkage of the resin base material measured according to Annex A of JIS K 6718-1:2015 is less than 3%. is preferred. This tends to improve the clarity of display images using holograms such as AR and MR, which are formed using this light guide plate. The heat shrinkage rate is preferably less than 3.0%, more preferably 2.5% or less, even more preferably 2.0% or less.

Further, as described above, in the light guide plate for image display of the present invention, the surface arithmetic mean roughness Ra of the resin base material is preferably 10 nm or less. This tends to improve the clarity of display images using holograms such as AR and MR, which are formed using this light guide plate. The arithmetic mean roughness Ra of the surface of the resin substrate is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 5 nm or less.

Here, the description returns to the image display light guide plate 1004 shown in FIG.
The hologram layer 1002 in the image display light guide plate 1004 is laminated on the surface of the first resin base material 1001 . The configuration of the hologram layer 1002 is not particularly limited. The hologram layer 1002 is formed with an appropriate diffraction grating corresponding to the functions required for the image display light guide plate 1004 .

The second resin base material 1003 is laminated on the surface of the hologram layer 1002 opposite to the first resin base material 1001 . As the second resin base material 1003, a structure similar to that of the first resin base material 1001 is used. However, the thickness, material, etc. of the second resin base material 1003 may be different from those of the first resin base material 1001 . In particular, since the second resin base material 1003 is disposed on the surface of the image display light guide plate 1004 on the side of the light guide plate 1004 on which the external light is incident, which is opposite to the display image emission side, the surface hardness of the second resin base material 1003 is higher than that of the first resin base material 1001. may be used.

Such an image display light guide plate 1004 can be manufactured, for example, as follows.
Using the manufacturing method described above, first resin base material 1001 and second resin base material 1003 having MC values of 0.120 or less are prepared. For example, a photopolymer material for forming a hologram is applied onto the first resin substrate 1001 . At this time, a transparent seal layer having the same thickness as the hologram layer 1002 may be provided on the outer peripheral portion of the first resin base material 1001 . In this case, the photopolymer material is applied to the recess formed surrounded by the sealing layer. The seal layer seals the outer periphery of the hologram layer 1002 after the hologram layer 1002 is formed. A material having excellent gas barrier properties may be used as the sealing layer. In this case, durability of the hologram layer 1002 can be improved.
A second resin substrate 1003 is then placed on the photopolymer material.
However, the manufacturing order described above is an example. For example, a photopolymer material may be applied to the second resin substrate 1003 before the first resin substrate 1001 is placed on the photopolymer material.
Thereafter, a laminate of the first resin base material 1001, the photopolymer material, and the second resin base material 1003 is bonded together by vacuum pressing.
Thereafter, interference fringes corresponding to the diffraction pattern are formed in the photopolymer material of the laminate, and a diffraction grating is formed in the photopolymer material.
Thus, the image display light guide plate 1004 is manufactured.

According to the image display light guide plate 1004, since the MC value of the first resin base material 1001 and the second resin base material 1003 is 0.120 or less, uneven defects on the respective surfaces are reduced. As a result, each optical path of the image light that transmits the first resin base material 1001 to display an image and the external light that transmits the second resin base material 1003 and the first resin base material 1001 and is superimposed on the image light. is suppressed from being disturbed by the influence of unevenness defects. Accordingly, a clear image is displayed on the image display light guide plate 1004 .
As described above, according to the present embodiment, it is possible to provide an image display light guide plate capable of displaying a clear image even when a resin base material is used.

<First modification>
A first modification of the first embodiment of the present invention will be described.
FIG. 7 is a schematic cross-sectional view showing an example of the image display light guide plate of the first modified example of the first embodiment of the present invention.

As shown in FIG. 7, the image display light guide plate 1014 of the first modified example of the first embodiment of the present invention is the same as the image display light guide plate 1004 of the basic example of the first embodiment of the present invention. A hard coat layer 1011A and a second hard coat layer 1011B are added.
In the following, differences from the basic example of the first embodiment of the present invention will be mainly described.

The first hard coat layer 1011A and the second hard coat layer 1011B are provided mainly for the purpose of surface protection of the first resin base material 1001 . The material of the first hard coat layer 1011A and the second hard coat layer 1011B is made of a transparent material whose hardness on at least one surface is higher than that of the surface of the first resin substrate 1001 . If at least one surface of the first hard coat layer 1011A and the second hard coat layer 1011B has a hardness higher than that of the first resin base material 1001, each of the first hard coat layer 1011A and the second hard coat layer 1011B has a multilayer structure composed of a plurality of transparent materials having different hardnesses. may be
In the example shown in FIG. 7, the first hard coat layer 1011A is arranged on the first surface 1001a of the first resin base material 1001 opposite to the hologram layer 1002 . The first hard coat layer 1011A forms the outermost surface of the light guide plate 1014 for image display.
The second hard coat layer 1011B is arranged on the second surface 1001b of the first resin base material 1001 facing the hologram layer 1002 .
More preferably, the thickness of the first hard coat layer 1011A is 1 to 50 μm. More preferably, the thickness of the second hard coat layer 1011B is 1 to 50 μm. The planarity of the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B is determined by the laminate of the first hard coat layer 1011A and the second hard coat layer 1011B and the first resin substrate 1001 (hereinafter referred to as coated It is more preferable that the MC value of the base material is 0.120 or less.
More preferably, the arithmetic mean roughness Ra of the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B is 10 nm or less.

The refractive index of the material of the first hard coat layer 1011A and the second hard coat layer 1011B is not particularly limited.
For example, the refractive index of the material of the first hard coat layer 1011A and the second hard coat layer 1011B is preferably equal to or lower than that of the first resin substrate 1001 from the viewpoint of visibility of a real image, but the hardness of the hard coat layer is increased. When the target material is selected, the refractive index may be higher than that of the first resin base material 1001 .
For example, when the refractive index of the material of the first hard coat layer 1011A and the second hard coat layer 1011B is equal to the refractive index of the material of the first resin base material 1001, the surface of the first resin base material 1001 and the first hard coat layer The interface between 1011A and the second hard coat layer 1011B optically disappears. In this case, the MC value of the coated substrate substantially represents the degree of unevenness defects on the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B. For example, when forming the first hard coat layer 1011A and the second hard coat layer 1011B to reduce unevenness defects on the surface of the first resin substrate 1001, the first hard coat layer 1011A and the second hard coat layer 1011A and the second hard coat layer 1011B More preferably, the refractive index of the material of layer 1011B is close to the refractive index of the material of first resin substrate 1001 .
In general, the refractive index of the material of the first hard coat layer 1011A and the second hard coat layer 1011B is different from the refractive index of the material of the first resin base material 1001, so the MC value of the coated base material is the first An evaluation including both uneven defects on the surface of the hard coat layer 1011A and the second hard coat layer 1011B and uneven defects on the surface of the first resin substrate 1001 is obtained. However, since the layer thicknesses of the first hard coat layer 1011A and the second hard coat layer 1011B are formed to be constant, uneven defects on the surfaces of the first hard coat layer 1011A and the second hard coat layer 1011B are eliminated by the first resin base. In the case of following the unevenness defect of the surface of the material 1001, the MC value of the first resin base material 1001 itself is considered equal to the MC value.

For example, the refractive indices of the materials of the first hard coat layer 1011A and the second hard coat layer 1011B are preferably equal to or higher than the refractive index of the material of the hologram layer 1002 from the viewpoint of a wide viewing angle. As the refractive index increases, the critical angle of guided light tends to increase.

The surface hardness of the first hard coat layer 1011A and the second hard coat layer 1011B is not particularly limited as long as it is higher than the surface hardness of the first resin substrate 1001 . For example, the pencil hardness (JIS K 5600-5-4:1999) of the first hard coat layer 1011A and the second hard coat layer 1011B is preferably H or higher, more preferably 2H or higher.

Suitable materials for the first hard coat layer 1011A and the second hard coat layer 1011B include, for example, hard coat agents containing polymerizable monomers or polymerizable oligomers that form a cured product upon exposure to active energy rays. Examples of the polymerizable monomer include (meth)acrylate monomers having a radically polymerizable unsaturated group in the molecule. Examples of the polymerizable oligomer include a (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule.
Examples of the (meth)acrylate monomer having a radically polymerizable unsaturated group in the molecule include urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl ( At least one monomer selected from the group consisting of meth)acrylates and silicone (meth)acrylates is included. Examples of the (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule include urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl ( Examples include oligomers containing structural units derived from at least one monomer selected from the group consisting of meth)acrylates and silicone (meth)acrylates. You may use the said polymerizable monomer or the said polymerizable oligomer in combination of 2 or more types. Among these, urethane (meth)acrylate monomers or oligomers are preferred because of their high surface hardness.
Urethane (meth)acrylate is, for example, a urethane (meth)acrylate obtained by reacting a polyisocyanate compound with a (meth)acrylate compound having one hydroxyl group in its molecular structure, or a polyisocyanate compound with a hydroxyl group in its molecular structure. A urethane (meth)acrylate obtained by reacting one (meth)acrylate compound with a polyol compound is exemplified.
The first hard coat layer 1011A and the second hard coat layer 1011B may contain a cured polyfunctional (meth)acrylate.
Examples of polyfunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth) ) acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, Ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, isocyanuric acid di(meth)acrylate acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate ) acrylate, tricyclodecane di(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, or those modified with PO, EO, caprolactone, or the like.
In forming the first hard coat layer 1011A and the second hard coat layer 1011B, a cross-linking agent, a polymerization initiator, a lubricant, a plasticizer, organic particles, inorganic particles, an antifouling agent, an antioxidant, or a catalyst is used as long as the physical properties are not impaired. or other additives such as silicone-based or fluorine-based additives for preventing stains and adhesion may be added to the hard coating agent.
A material having a refractive index different from that of the first resin substrate 1001 may be used for the first hard coat layer 1011A and the second hard coat layer 1011B. In this case, the refractive index of the outermost surface of the image display light guide plate 1014 and the refractive index of the interface with the hologram layer 1002 are controlled by the first hard coat layer 1011A and the second hard coat layer 1011B. can be changed from the refractive index of .

The image display light guide plate 1014 of the first modified example of the first embodiment of the present invention is formed by, for example, forming the first resin base material 1001 in the same manner as the basic example of the first embodiment of the present invention described above. After forming the first hard coat layer 1011A and the second hard coat layer 1011A and the second hard coat layer 1011A and the second Except for forming the hard coat layer 1011B, it can be manufactured in the same manner as the basic example of the first embodiment of the present invention.
The first hard coat layer 1011A and the second hard coat layer 1011B can be formed by applying hard coat liquids, which are raw materials, to the first surface 1001a and the second surface 1001b, respectively, and then curing the hard coat liquids. The method of applying the hard coat liquid is not particularly limited. For example, as a method for applying the hard coating liquid, a casting method, a roller coating method, a bar coating method, a spray coating method, an air knife coating method, a dipping method, or the like can be used to apply the photocurable resin composition to the substrate surface. There is a method in which a cured film is formed on a substrate by directly coating the substrate and curing the coating film by irradiating it with light.
Alternatively, for example, a photocurable resin composition is applied to the surface of at least one mold material for forming a mold for cast polymerization by the above coating method or the like, and the coating film is irradiated with light to be cured. A cured film is formed on the mold material, and a mold for casting polymerization is assembled using this mold material so that the cured film is on the inside. , a method of taking out the laminate in which the cured film is integrated with the surface of the substrate after the completion of the polymerization, and the like.
However, the first hard coat layer 1011A and the second hard coat layer 1011B may be formed in the same manner as the first resin base material 1001 in the manufacturing process of the first resin base material 1001 .

As for the material used for the first hard coat layer 1011A and the second hard coat layer 1011B and the method of applying the material, the material and the method of applying the material that do not easily increase the unevenness of the irregularity defect on the surface of the first resin base material 1001 are used. is more preferred. As a material used for the first hard coat layer 1011A and the second hard coat layer 1011B and a method of applying the material, a material and a method of applying the material that reduce unevenness caused by uneven defects on the surface of the first resin substrate 1001 may be used. More preferred.
For example, the above hard coating agent, alkoxysilane polycondensation curing resin, melamine resin, or the like can be used as the material.
For example, as the coating method, conventionally known coating methods such as bar coating, dip coating, reverse gravure coating, direct gravure coating, roll coating, die coating or curtain coating can be used. Coatings are particularly preferred.

According to the first modification of the first embodiment of the present invention, similar to the basic example of the first embodiment of the present invention, the MC values of the first resin base material 1001 and the second resin base material 1003 are 0. 0.120 or less, it is possible to provide an image display light guide plate capable of displaying a clear image even when a resin base material is used, as in the basic example of the first embodiment of the present invention.
Furthermore, according to the first modification of the first embodiment of the present invention, since the first hard coat layer 1011A and the second hard coat layer 1011B are laminated on the first resin substrate 1001, the first resin substrate Damage to the surface of the material 1001 is prevented.
For example, in the process of manufacturing the image display light guide plate 1014 and the display device, deterioration of flatness due to scratches on the surface of the first resin base material 1001 can be prevented. Therefore, the defect rate of the image display light guide plate 1014 and the display device due to handling in the manufacturing process such as transportation can be reduced.
For example, since the first hard coat layer 1011A constitutes the outermost surface of the image display light guide plate 1014, deterioration in image quality due to damage to the outermost surface during use of the image display light guide plate 1014 is suppressed.

In addition, in the description of the first modified example, an example in which a hard coat layer is formed on each surface in the thickness direction of the first resin base material 1001 has been described. However, one of the first hard coat layer 1011A and the second hard coat layer 1011B may be omitted.
In the description of the first modified example, the example in which the hard coat layer is formed only on the first resin base material 1001 has been described. However, at least one of the first hard coat layer 1011A and the second hard coat layer 1011B may be formed on the second resin base material 1003 as well.

[Second embodiment]
<Basic example>
An image display light guide plate according to a second embodiment of the present invention will be described below.
The image display light guide plate of the second embodiment of the present invention has a first resin base material, a first barrier layer, and a hologram layer. The first barrier layer is preferably arranged on the surface of at least one of the first resin base material and the hologram layer, and more preferably the first barrier layer is arranged on the hologram layer. . The first resin base material, the first barrier layer, and the hologram layer are preferably arranged in this order in the thickness direction.
The image display light guide plate of the second embodiment of the present invention may further have a second barrier layer and a second resin base material. The first barrier layer is disposed on at least one surface of the surface of the first resin base facing the hologram layer and the surface of the hologram layer facing the first resin base, The second barrier layer is preferably disposed on the surface of the second resin substrate facing the hologram layer and the surface of the hologram layer facing the second resin layer. The first barrier layer and the second barrier layer are arranged on the surface of the hologram layer facing the first resin base material and the surface of the hologram layer facing the second resin layer, respectively. More preferably. The first resin substrate, the first barrier layer, the hologram layer, the second barrier layer, and the second resin substrate are preferably laminated in this order in the thickness direction.
In the present embodiment, the first resin base material and the second resin base material may be collectively referred to simply as "resin base material". Further, the first barrier layer and the second barrier layer may be collectively referred to simply as "barrier layer".

One or more transparent layers may be arranged between the barrier layer and the resin substrate. Also, one or more transparent layers may be arranged between the barrier layer and the hologram layer.
Examples of the transparent layer include a hard coat layer, an adhesive layer, and an anchor coat layer.
In the image display light guide plate of the second embodiment of the present invention, a glass substrate may be provided that sandwiches the barrier layer and the hologram layer between itself and the resin substrate. In this case, since the glass substrate itself has barrier properties, the glass substrate may be arranged on the surface of the hologram layer opposite to the surface facing the barrier layer.

As the resin base material, the resin base material in the above-described first embodiment can be suitably used.
The material used for the resin substrate is not particularly limited as long as it is a transparent material, but it preferably contains at least one resin selected from the group consisting of acrylic resins, cyclic polyolefin resins and polycarbonate resins.

The refractive index of the barrier layer is preferably higher than that of the resin base material, more preferably 1.48 or more.
As a material for the barrier layer, a water vapor barrier material is preferably used.
Further, the material of the barrier layer preferably contains an inorganic material, and at least one selected from the group consisting of silicon oxide, silicon nitrogen oxide, diamond-like carbon (DLC), aluminum oxide and glass. More preferably, it contains an inorganic material.
In addition, by using an auxiliary layer containing a fluorine-based material, a cycloolefin-based polymer, vinylidene chloride, or the like as a part of the barrier layer in combination with the above inorganic material, the barrier layer can have a multi-layer structure, and a water vapor barrier. You can further increase your sexuality.
Furthermore, the barrier layer may be arranged on a resin film. In this case, the resin film is more preferably arranged between the barrier layer and the resin substrate.

The hologram layer is sandwiched between the first resin substrate and the second resin substrate or between the first resin substrate and the glass substrate.
The image display light guide plate has an incident portion for receiving image light, and a display portion for displaying an image based on the image light. The hologram layer is arranged between the entrance section and the display section. A diffraction grating pattern is formed on the hologram layer for guiding at least the image light incident from the incident portion to the display portion and for emitting the image light from the display portion. The diffraction grating pattern in the display section transmits at least part of external light incident from the outside of the image display light guide plate.
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, external light also passes through the resin base material and the display section, so that an observer of the display section can observe both the image light and the external light within the field of view.
The image display light guide plate of the second embodiment of the present invention is suitably used in a display device using VR technology or AR technology. For example, the image display light guide plate of the second embodiment of the present invention is typically used as a combiner for a head-up display (HUD) mounted on an automobile or a reflector for a reflective liquid crystal display device, in addition to display applications. It may be used in devices such as a hologram optical element (HOE).

A known hologram-forming resin material is used for the hologram layer. As the hologram-forming resin material, for example, a thermosetting resin having at least one solvent-soluble and cationic polymerizable ethylene oxide ring in a structural unit and a hologram recording material comprising a radically polymerizable ethylenic monomer 8-1676, JP-A-8-1677, JP-A-8-1678, JP-A-8-1679).

Hereinafter, based on the example shown in FIG. 9, a detailed configuration of an example of the light guide plate for image display according to the second embodiment of the present invention will be described. FIG. 9 is a schematic cross-sectional view showing an example of the image display light guide plate of the second embodiment of the present invention.

In the image display light guide plate 2006 shown in FIG. 9, a first resin base material 2001, a first barrier layer 2002, a hologram layer 2003, a second barrier layer 2004, and a second resin base material 2005 are arranged in the thickness direction. are arranged in this order.
The plan view shape of the image display light guide plate 2006 is not particularly limited. For example, the image display light guide plate 2006 may be shaped into a shape that can be attached to the display device used. For example, the image display light guide plate 2006 may be a rectangular plate larger than the shape to be attached to the display device. In this case, the image display light guide plate 2006 is molded by being cut into a shape that can be attached to the display device before being assembled into the display device.
The image display light guide plate 2006 may have a flat plate shape, or may have a curved plate shape as necessary.
In the following, an example in which the image display light guide plate 2006 is made of a rectangular flat plate in plan view will be described.

The first resin base material 2001 is arranged at the outermost part in the thickness direction of the image display light guide plate 2006 . The first resin base material 2001 is arranged on the surface of the image display light guide plate 2006 on the display image exit side.
The first resin base material 2001 has a shape similar to the outer shape of the image display light guide plate 2006 . Image light emitted from the hologram layer 2003 and external light passing through the second resin base material 2005 and the hologram layer 2003 , which will be described later, pass through the first resin base material 2001 .
The thickness of the first resin base material 2001 is not particularly limited. For example, the thickness of the first resin base material 2001 may be 0.1 to 10 mm.

The material forming the first resin substrate 2001 is not particularly limited as long as it is a transparent resin material. As a material for forming the first resin substrate 2001, considering optical properties such as transparency and light refractive index, and various physical properties such as impact resistance, heat resistance and durability, ethylene, propylene, and the like are selected. or polyolefin resins such as homopolymers or copolymers of olefins such as butene; amorphous polyolefin resins such as cyclic polyolefins; polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); triacetyl Cellulose-based resins such as cellulose, diacetylcellulose, and cellophane; polyamide-based resins such as nylon 6, nylon 66, nylon 12, copolymerized nylon; ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide-based resins, polyethers Imide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluorine resins, poly(meth)acrylic resins, styrenes such as polystyrene resin, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinyl chloride, cellulose, acetyl cellulose, polyvinylidene chloride, polyphenylene sulfide, polyurethane, phenolic resin, epoxy resin, polyarylate resin, polynorbornene, styrene-isobutylene-styrene block Organic materials such as copolymers (SIBS), allyl diglycol carbonate, and biodegradable resins are included. Among these, it is preferable to include at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins and polycarbonates. The first resin base material 2001 may be made 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 of the first resin substrate 2001, polycarbonate or poly(meth)acrylic resin is preferable. From the viewpoint of process resistance such as chemical resistance and workability of the first resin base material 2001, poly(meth)acrylic resin, epoxy resin, or cyclic polyolefin is preferable. A poly(meth)acrylic resin is more preferable because it can achieve both transparency and process resistance.

The first barrier layer 2002 is arranged between the first resin base material 2001 and a hologram layer 2003 which will be described later, and in the configuration shown in FIG. are doing. However, the first barrier layer 2002 does not need to adhere to both surfaces of the first resin base material 2001 and the hologram layer 2003 , and is preferably arranged at least on the hologram layer 2003 . The first barrier layer 2002 prevents gas permeating from the outside of the image display light guide plate 2006 and the first resin base material 2001 from permeating the hologram layer 2003 .
It is preferable that the first barrier layer 2002 has, for example, a lower oxygen permeability and a lower water vapor permeability. In particular, the first barrier layer 2002 is more preferably made of a material with excellent water vapor barrier properties (low water vapor transmission rate), since deterioration of the hologram layer can be suppressed.
For example, the oxygen permeability of the first barrier layer 2002 may be 1 cm ³ /m ² ·day or less.
For example, the first barrier layer 2002 may have a water vapor transmission rate of 1 g/m ² ·day or less. The water vapor transmission rate of the first barrier layer 2002 is more preferably 0.5 g/m ² ·day or less.

The material of the first barrier layer 2002 is not particularly limited as long as it has the property of being able to block gases that cause deterioration of the hologram layer 2003. However, the gas barrier property tends to be excellent and the clarity of the displayed image is also excellent. It is preferable that the inorganic material is included because it is in
In this case, the inorganic material used for the first barrier layer 2002 may have a higher refractive index than the first resin base material 2001 . For example, the refractive index of the first barrier layer 2002 may be between 1.48 and 3.00. When the first barrier layer 2002 has a high refractive index, the light passing through the first resin base material 2001 via the first barrier layer 2002 is transferred from the optically dense first barrier layer 2002 to the optically coarse one. Since the light is incident on the first resin base material 2001, the output angle of the light traveling from the first barrier layer 2002 to the first resin base material 2001 depends on the refractive index difference between the first barrier layer 2002 and the first resin base material 2001. grow larger. Thereby, the FOV (Field Of View) in the image display light guide plate 2006 can be widened.

Examples of materials for the first barrier layer 2002 include silicon oxide, silicon nitrogen oxide, DLC, aluminum oxide, and glass.
Materials for the first barrier layer 2002 are as described above, but zinc oxide, antimony oxide, indium oxide, cerium oxide, calcium oxide, cadmium oxide, silver oxide, gold oxide, chromium oxide, silicon oxide, cobalt oxide, oxide Oxide such as zirconium, tin oxide, titanium oxide, iron oxide, copper oxide, nickel oxide, platinum oxide, palladium oxide, bismuth oxide, magnesium oxide, manganese oxide, molybdenum oxide, vanadium oxide or barium oxide may be used.

When the first barrier layer 2002 is made of silicon oxide, its layer thickness may be 10 to 300 nm. If the layer thickness is less than 10 nm, the moisture resistance may be insufficient. If the layer thickness exceeds 300 nm, the silicon oxide thin film is likely to crack and peel off from the film formation surface.
A particularly preferable layer thickness is 20 to 200 nm.
The method of forming the first barrier layer 2002 with the silicon oxide is not particularly limited. For example, the first barrier layer 2002 can be formed by any conventionally known method such as a vacuum deposition method, a sputtering method, an ion plating method, or a plasma CVD method. When forming the first barrier layer 2002 from the silicon oxide, the film formation surface is subjected to corona discharge treatment or low-temperature plasma treatment in order to improve adhesion between the film formation surface and the silicon oxide. A surface treatment such as applying a silane coupling agent or applying a mixture of saturated polyester and isocyanate to the film formation surface may be performed.
For example, when forming a thin film of silicon oxide by ^vacuum evaporation, silicon, silicon monoxide, silicon dioxide, or a mixture thereof is used as the evaporation material, and the Under a vacuum of ^-5 Torr, it is heated and evaporated by an electron beam, resistance heating, or high-frequency heating method.
Also, a reactive vapor deposition method that is performed while supplying oxygen gas can be employed.
The silicon oxide forming the first barrier layer 2002 may contain calcium, magnesium, or oxides thereof as impurities as long as the content is 10% by mass or less.

When the first barrier layer 2002 is made of silicon nitrogen oxide, the structure is the same as that of the first barrier layer 2002 mainly composed of silicon oxide, except that the silicon oxide is replaced with the silicon nitrogen oxide. Used.

DLC is generally an amorphous carbon material having a ternary structure of a diamond-like structure, a graphite-like structure, and a polyethylene-like polymer structure containing hydrogen atoms in the structure. When a hydrocarbon such as ethylene, acetylene, or benzene is used as a carbon source for the production of the DLC, it usually has a ternary structure containing hydrogen.
The DLC is excellent in hardness, lubricity, wear resistance, chemical stability, heat resistance and surface smoothness. Since the DLC forms the dense polymer structure described above, it is also excellent in gas barrier properties and water vapor barrier properties.
A formation method for forming the first barrier layer 2002 with the DLC is not particularly limited. As a method for coating the DLC, a suitable well-known coating method such as a plasma CVD method or a physical vapor deposition method such as an ion plating method or an ion beam sputtering method can be used.

When the first barrier layer 2002 is made of aluminum oxide, the first barrier layer 2002 may be made of _{only Al2O3} , for example, or selected from the group consisting of Al _, AlO and _Al2O3 . It may be formed by mixing two or more kinds. The atomic ratio of Al:O in the aluminum oxide layer varies depending on the manufacturing conditions of the aluminum oxide layer. The aluminum oxide layer that can be used as the first barrier layer 2002 may contain other components in trace amounts (up to 3% with respect to all components) as long as the barrier performance is not impaired.
The layer thickness of the aluminum oxide layer may be set as required for barrier performance. For example, the layer thickness of the aluminum oxide layer may be 5-800 nm.
The method of forming the first barrier layer 2002 with aluminum oxide is not particularly limited. For example, as a method of forming the first barrier layer 2002, a PVD method (physical vapor deposition method) such as a vacuum 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 deposition method, Al, Al ₂ O ₃ or the like may be used as the deposition source material, and resistance heating, high-frequency induction heating, electron beam heating, or the like may be used as the heating method for the deposition source. . In the vacuum deposition method, oxygen, nitrogen, water vapor, or the like may be introduced as a reactive gas, or reactive deposition using means such as addition of ozone or ion assist may be used. Furthermore, a bias may be applied to the film formation surface, or the temperature of the film formation surface may be raised or cooled. The same applies to other film forming methods such as the PVD method and the CVD method other than the sputtering method and other vacuum vapor deposition methods.

When the first barrier layer 2002 is made of glass, examples of materials for the first barrier layer 2002 include borosilicate glass, alkali-free glass, low-alkali glass, soda-lime glass, sol-gel glass, or heat treatment or surface treatment of these glasses. Examples include those that have undergone processing. As the material for the first barrier layer 2002, non-alkali glass is particularly preferable from the viewpoint of avoiding coloration due to impurities.
When the first barrier layer 2002 is made of glass, its layer thickness may be 10-200 μm. When the layer thickness is 10 μm or more, the mechanical strength and gas barrier properties tend to be excellent. The layer thickness is preferably 10 μm or more, more preferably 30 μm or more. Further, when the layer thickness is 200 μm or less, the optical properties of the light guide plate such as light transmittance tend to be excellent. The layer thickness is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 75 μm or less, and particularly preferably 50 μm or less.

The method of forming the first barrier layer 2002 with glass is not particularly limited. As a method of forming the first barrier layer 2002 with glass, for example, a slot down draw method, a fusion method, or a float method can be adopted. In addition, as the glass to be used, commercially available glass may be used as it is, or commercially available glass may be used after polishing so as to have a desired thickness. Examples of the commercially available glass include "EAGLE2000" manufactured by Corning, "AN100" manufactured by Asahi Glass, "OA10G" manufactured by Nippon Electric Glass, and "D263" manufactured by Schott.

Also, as part of the first barrier layer 2002, an auxiliary layer containing a fluorine-based material, a cycloolefin-based polymer, vinylidene chloride, or the like can be introduced, and the first barrier layer 2002 has a multi-layer structure with the inorganic material layer described above. By doing so, the water vapor barrier property can be further enhanced.
PCTFE (polychlorotrifluoroethylene), for example, can be used as this fluorine-based material. As the cycloolefin-based polymer, a cycloolefin polymer, a cycloolefin copolymer, or the like can be used.
The layer thickness of this auxiliary layer may be set as required for the water vapor barrier performance. For example, the layer thickness may be 0.1 to 100 μm when a fluorine-based material is used.

A hologram layer 2003 is laminated on the surface of the first barrier layer 2002 . The configuration of the hologram layer 2003 is not particularly limited. The hologram layer 2003 is formed with an appropriate diffraction grating corresponding to the functions required for the image display light guide plate 2006 .

The second barrier layer 2004 is laminated on the surface of the hologram layer 2003 opposite to the surface of the hologram layer 2003 on which the first barrier layer 2002 is formed.
As for the configuration of the second barrier layer 2004, the same configuration as exemplified in the description of the first barrier layer 2002 is used. However, the material, thickness, etc. of the second barrier layer 2004 may be different from those of the first barrier layer 2002 .

A second resin base material 2005 is laminated on the surface of the second barrier layer 2004 opposite to the hologram layer 2003 . As the second resin base material 2005, the same configuration as exemplified in the description of the first resin base material 2001 is used. However, the thickness, material, etc. of the second resin base material 2005 may be different from those of the first resin base material 2001 . In particular, the second resin base material 2005 is disposed on the surface of the image display light guide plate 2006 on the side opposite to the display image emission side and on the outside light incidence side. Expensive materials may be used.

Such an image display light guide plate 2006 can be manufactured, for example, as follows.
A first resin base material 2001 and a second resin base material 2005 are prepared, and a first barrier layer 2002 and a second barrier layer 2004 are formed on the surfaces of the first resin base material 2001 and the second resin base material 2005, respectively. . As a method for manufacturing the first barrier layer 2002 and the second barrier layer 2004, an appropriate manufacturing method is selected according to the materials of the first barrier layer 2002 and the second barrier layer 2004. FIG.
For example, a photosensitive material for forming a hologram is applied to the surface of the first barrier layer 2002 in the first resin base material 2001 on which the first barrier layer 2002 is formed. At this time, a transparent seal layer having the same thickness as the hologram layer 2003 may be provided on the outer periphery of the first barrier layer 2002 . In this case, the photosensitive material is applied to the recess formed by being surrounded by the sealing layer. The seal layer seals the outer periphery of the hologram layer 2003 after the hologram layer 2003 is formed. For this seal layer, a material having excellent gas barrier properties such as that used for the first barrier layer 2002 can be used, thereby improving the durability of the hologram layer 2003 .
After that, a second resin base material 2005 having a second barrier layer 2004 formed thereon is placed on the photosensitive material with the second barrier layer 2004 facing the photosensitive material.
However, the manufacturing order described above is an example. For example, after the photosensitive material is applied to the second resin substrate 2005 having the second barrier layer 2004 formed thereon, the first resin substrate 2001 having the first barrier layer 2002 formed thereon is placed on the photosensitive material. good too.
Thereafter, a laminate composed of the first resin base material 2001, the first barrier layer 2002, the photosensitive material, the second barrier layer 2004, and the second resin base material 2005 is bonded together by vacuum pressing.
Thereafter, interference fringes corresponding to the diffraction pattern are formed on the photosensitive material of the laminate, and a diffraction grating is formed in the photosensitive material.
Thus, the image display light guide plate 2006 is manufactured.

According to the image display light guide plate 2006, between the first resin substrate 2001 and the hologram layer 2003 and between the second resin substrate 2005 and the hologram layer 2003, the first barrier layer 2002 and the second A barrier layer 2004 is disposed.
The gas barrier property of the first resin base material 2001 and the second resin base material 2005 varies depending on the type of resin material, but is much lower than that of glass. Therefore, the first resin base material 2001 and the second resin base material 2005 have higher hygroscopicity and water vapor permeability than glass.
As a result, the gas outside the image display light guide plate 2006 passes through the first resin base material 2001 and the second resin base material 2005 to some extent or accumulates inside. In particular, moisture tends to accumulate in the first resin base material 2001 and the second resin base material 2005 .
However, the gas and moisture that have permeated the first resin base material 2001 and the second resin base material 2005 from the outside are blocked by the first barrier layer 2002 and the second barrier layer 2004 even if they diffuse in the image display light guide plate 2006. be done. This suppresses permeation of gas and water vapor into the hologram layer 2003 .
For example, by suppressing penetration of moisture into the hologram layer 2003, deterioration of the hologram layer 2003 is prevented.
Furthermore, since the image display light guide plate 2006 has the layer structure described above, the hologram layer 2003 is not in contact with the first resin base material 2001 and the second resin base material 2005 . This prevents the hologram layer 2003 from corroding the first resin base material 2001 and the second resin base material 2005 even if the image display light guide plate 2006 is placed in a high-temperature environment.

In particular, when the refractive indices of the first barrier layer 2002 and the second barrier layer 2004 are higher than those of the first resin substrate 2001 and the second resin substrate 2005, as described above, the first barrier layer The output angle of the light from 2002 toward the first resin base material 2001 increases. Similarly, light incident on the second barrier layer 2004 from the second resin base material 2005 has a narrower output angle. Therefore, the light incident from the outside on the side of the second resin base material 2005 and transmitted through the image display light guide plate 2006 is incident in a wider angle range than when the second barrier layer 2004 is not provided. , and is emitted in a wider angle range than when the first barrier layer 2002 is not provided. This results in a wider field of view for external light and a wider FOV on the display side.
As for the image light from the hologram layer 2003, as described above, the output angle of the light from the first barrier layer 2002 toward the first resin base material 2001 is increased. , the FOV of the display screen is expanded.
In particular, in the present embodiment, the first barrier layer 2002 and the second barrier layer 2004 are laminated on the hologram layer 2003 so that external light and image light are diffused and the hologram layer 2003 constituting the display screen is positioned. Therefore, compared to the case where the first barrier layer 2002 and the second barrier layer 2004 are provided at positions distant from the hologram layer 2003, a clearer image can be observed from a wide range of angles. Become.

Here, an example of a method for measuring the luminance value and the FOV in the image display light guide plate 2006 will be briefly described.
FIG. 10 is a schematic front view for explaining a method of measuring luminance values and FOV.

As shown in FIG. 10, in order to measure the luminance value and FOV of the light guide plate 2006 for image display, the display device 2010 is manufactured using the light guide plate 2006 for image display.
The display device 2010 includes an image light projection section 2013 and an incident optical system 2012 in addition to the image display light guide plate 2006 .
The image light projection unit 2013 projects image light to be displayed on the image display light guide plate 2006 according to an image signal sent from a controller (not shown).
The incident optical system 2012 includes, for example, a prism. The incident optical system 2012 causes the image light emitted from the image light projection section 2013 to enter the incident section 2006 a provided on the surface of the image display light guide plate 2006 . For example, the incident part 2006a is provided on the surface on the first resin base material 2001 side.
The image light incident on the incident portion 2006 a reaches the display diffraction grating portion 2003 c of the hologram layer 2003 via the waveguide diffraction grating portion 2003 b formed on the hologram layer 2003 . The display diffraction grating portion 2003c diffracts the image light at positions corresponding to the respective display pixels. The diffracted light is emitted to the outside from the display portion 2006d on the surface of the light guide plate 2006 for image display. In the example shown in FIG. 10, the display section 2006d is formed on the surface of the first resin base material 2001 at a position spaced apart from the incident section 2006a.

The brightness value and FOV of the image display light guide plate 2006 are measured by placing the display device 2010 on the measurement device 2015 .
The measuring device 2015 includes a holding table (not shown), a luminance meter 2014, and a goniometer stage (not shown).
The holding base holds the display device 2010 . A luminance meter 2014 measures the luminance value of the received light. The goniometer stage swingably supports the luminance meter 2014 on a circumference around its rotation center.
A distance d between the luminance meter 2014 and the display surface 2003a corresponds to the position of the user's eyes when the display device 2010 is worn. For example, if the display device 2010 is a head-mounted display, the distance d is 15 mm.

The luminance value of the image display light guide plate 2006 is measured by arranging the luminance meter 2014 at the position of the swing angle of 0° (see the solid line luminance meter 2014 in FIG. 10). The display device 2010 is placed at a position where the center of the display surface 2003a faces the luminance meter 2014 on the measurement optical axis of the luminance meter 2014 by the holding stand.
The luminance value is the luminance measured by the luminance meter 2014 when the display device 2010 displays a white image with maximum luminance.
In the measurement of the FOV of the image display light guide plate 2006, the luminance is measured by changing the swing angle θ _B while displaying a white image with maximum luminance on the display device 2010 . Using the brightness corresponding to the disappearance of the white image as a threshold, the angular range in which the brightness equal to or higher than the threshold is obtained is obtained. When the brightness above the threshold is obtained in the range from -θ1 to +θ2, the FOV is θ1+θ2.
The FOV of the image display light guide plate 2006 is preferably 24 to 160°, more preferably 35 to 160°. In addition, the larger the FOV, the wider the viewing angle of the image, the greater the amount of information in the image, and the wider the range of applications that can be applied. On the other hand, when the FOV is smaller than the upper limit, the amount of light extracted with respect to a given area tends to increase, which is preferable because the image becomes brighter.

For example, the closer the distance between the first barrier layer 2002 and the second barrier layer 2004 and the hologram layer 2003 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, most preferably 100 nm or less.

As described above, according to the present embodiment, it is possible to provide an image display light guide plate that can suppress deterioration of the hologram layer even when a resin base material is used.

<First modification>
A first modification of the second embodiment of the present invention will be described.
FIG. 11 is a schematic cross-sectional view showing an example of the image display light guide plate of the first modified example of the second embodiment of the present invention.

As shown in FIG. 11, the image display light guide plate 2016 of the first modified example of the second embodiment of the present invention is the same as the image display light guide plate 2006 of the basic example of the second embodiment of the present invention. A first barrier film 2022 and a second barrier film 2024 are provided instead of the barrier layer 2002 and the second barrier layer 2004 .
In the following, the points different from the above embodiment will be mainly described.

The first barrier film 2022 includes a barrier layer 2022A and a resin film 2022B.
The barrier layer 2022A is configured similarly to the first barrier layer 2002 in the above embodiment.

The resin film 2022B is a substrate on which the barrier layer 2022A is deposited. The material of the resin film 2022B is not particularly limited as long as it is a transparent resin film capable of forming the barrier layer 2022A.
For example, materials for the resin film 2022B include polypropylene, ABS, amorphous polyester resin, polyimide, polyamide, polyethersulfone (PES), polycarbonate (PC), polynorbornene which is a cyclic polyolefin copolymer, and cyclic polyolefin resin. , polycyclohexene, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), fluororesin, polyarylate (PAR), polyetherketone (PEK), or polyetheretherketone (PEEK) may be used. .
For example, considering the coefficient of thermal expansion, the coefficient of humidity expansion, and the glass transition temperature, more suitable materials for the resin film 2022B include, among crystalline resins, thermoplastic resins such as polyamide, polyacetal, polybutylene terephthalate, and polyethylene terephthalate. , or syndiotactic polystyrene, and thermosetting resins such as polyphenylene sulfide, polyetheretherketone, liquid crystal polymer, fluororesin, polyethernitrile, and the like. For example, amorphous resins include thermoplastic resins such as polycarbonate or modified polyphenylene ether, and thermosetting resins include polysulfone, polyethersulfone, polyarylate, polyamideimide, polyetherimide, or thermoplastic polyimide. can be mentioned. Among them, since polycarbonate has low water absorption, the first barrier film 2022 formed using this has a low humidity expansion coefficient, and is particularly preferable.

The thickness of the resin film 2022B is not particularly limited. However, it is more preferable that the resin film 2022B is thinner than the first resin base material 2001 . For example, the thickness of the resin film 2022B may be 1-200 μm.

As the resin film 2022B, it is more preferable to use a material having a highly smooth surface. In this case, the smoothness of the surface of the barrier layer 2022A is improved, and the layer thickness of the barrier layer 2022A can be easily made uniform. As for the smoothness of the surface of the resin film 2022B, it is more preferable that the arithmetic mean roughness Ra is 2 nm or less.
The surface of the resin film 2022B may be subjected to various surface modification treatments in order to improve adhesion with the barrier layer 2022A and adhesion with the first adhesive layer 2026, which will be described later. For example, the surface of the resin film 2022B may be subjected to corona discharge treatment, flame treatment, oxidation treatment, plasma treatment, lamination of a primer layer, or the like.

Such a first barrier film 2022 is manufactured by depositing a resin film 2022B on the barrier layer 2022A. Such a first barrier film 2022 is manufactured by forming a barrier layer 2022A on a resin film 2022B.
Examples of methods for forming the barrier layer 2022A include physical vapor deposition (PVD), chemical vapor deposition (CVD), plating, coating, sol-gel, and the like. In particular, CVD is excellent in the formation efficiency of the barrier layer 2022A. In CVD, less heat is applied to the resin film 2022B during film formation than in the physical vapor phase method, so deterioration of the resin film 2022B due to heating is reduced. Among the CVD methods, the plasma CVD method is more preferable. In the plasma CVD method, after the material gas is introduced into the film forming chamber, a high frequency wave is applied to cause discharge to create a plasma state, thereby promoting a chemical reaction on the surface of the resin film 2022B. For this reason, the temperature in the film formation process is as low as -10.degree. C. to 200.degree. As a result, the resin film 2022B is less likely to be thermally damaged.

A barrier layer 2022 A in the first barrier film 2022 is arranged on the surface of the hologram layer 2003 .
The resin film 2022B in the first barrier film 2022 is fixed to the surface of the first resin substrate 2001 with the first adhesive layer 2026 interposed therebetween.
The material of the first adhesive layer 2026 is not particularly limited as long as it has good adhesiveness to the resin film 2022B and the first resin substrate 2001 .
For example, preferred materials for the first adhesive layer 2026 include polyester-based resins, acrylic-based resins, urethane-based resins, melamine-based resins, epoxy-based resins, and the like.

The second barrier film 2024 includes a barrier layer 2024A similar to the barrier layer 2022A and a resin film 2024B similar to the resin film 2022B.
However, the material, thickness, etc. of the barrier layer 2024A may be the same as or different from those of the barrier layer 2022A. The material, thickness, etc. of the resin film 2024B may be the same as or different from those of the resin film 2022B.
The second barrier film 2024 is fixed to the surface of the second resin substrate 2005 with a second adhesive layer 2027 having the same structure as the first adhesive layer 2026 .

In order to manufacture such an image display light guide plate 2016, for example, the first barrier film 2022 and the second barrier film 2024 are prepared, and the first adhesive layer 2026 and the second adhesive layer 2027 are interposed therebetween. A first intermediate laminate P1 and a second intermediate laminate P2 are formed by adhering a first barrier film 2022 and a second barrier film 2024 to the respective surfaces of the first resin substrate 2001 and the second resin substrate 2005. be.
After that, instead of the first resin substrate 2001 and the second resin substrate 2005 of the basic example of the second embodiment of the present invention, the first intermediate laminate P1 and the second intermediate laminate P2 are used respectively. , the hologram layer 2003 is formed in the same manner as in the basic example of the second embodiment of the present invention. Thus, the image display light guide plate 2016 is manufactured.

According to the image display light guide plate 2016 of the first modified example of the second embodiment of the present invention, the first resin base material 2001, the barrier layer 2022A, and the hologram layer 2003 are arranged in this order, and the second A resin base material 2005, a barrier layer 2024A, and a hologram layer 2003 are arranged in this order. Therefore, as in the embodiment, deterioration of the hologram layer 2003 is prevented by suppressing penetration of water into the hologram layer 2003 . Furthermore, since the hologram layer 2003 does not come into contact with the first resin base material 2001 and the second resin base material 2005, the first resin base material 2001 and the second resin base material 2005 are prevented from being eroded by the material of the hologram layer 2003. be done.
Therefore, according to the image display light guide plate 2016, a clear image can be displayed even when a resin base material is used.
Furthermore, if the barrier layers 2022A and 2024A have a higher refractive index than the first resin base material 2001 and the second resin base material 2005, the FOV of the image display light guide plate 2016 is improved, resulting in clear images. becomes observable from a wide range of angles.

In particular, according to the first modification of the second embodiment of the present invention, the first barrier film 2022 and the first barrier film 2022 and the Barrier layers 2022A and 2024A are arranged on the first resin substrate 2001 and the second resin substrate 2005 by bonding the second barrier film 2024 . Therefore, even when the barrier layers 2022A and 2024A cannot be formed directly due to the type, shape, size, etc. of the materials of the first resin base material 2001 and the second resin base material 2005, the barrier layers 2022A and 2024A can be easily formed. can be placed.

As described above, according to the first modification of the second embodiment of the present invention, it is possible to provide an image display light guide plate that can suppress deterioration of the hologram layer even when a resin base material is used.

In addition, in the basic example and the first modified example of the second embodiment, the example in which the barrier layers are arranged on the front and back surfaces of the hologram layer has been described, but the For the purpose and for the purpose of preventing contact between the hologram layer and the resin base material, the barrier layer may be arranged between the resin base material and the hologram layer.
However, in this case, if the transparent layer sandwiched between the barrier layer and the hologram layer is highly hygroscopic, moisture may permeate through the side surfaces of the transparent layer. Therefore, it is more preferable that the transparent layer between the barrier layer and the hologram layer is made of a material with low hygroscopicity. When the transparent layer between the barrier layer and the hologram layer is hygroscopic, it is more preferable to reduce the thickness of the transparent layer. In this case, since the exposed area of the side surface serving as the permeation port for moisture is reduced, the amount of moisture absorbed can be reduced.

[Third embodiment]
When the light guide plate for image display of the present invention is used, for example, in a spectacle-type display, the hologram layer of the resin substrate is added for the purpose of preventing deterioration of optical properties due to scratches on the surface. A hard coat film can be releasably attached from this substrate on the side opposite to the located side.

<Basic example>
A third embodiment of the light guide plate for image display of the present invention will be described below.
FIG. 14 shows the layer structure of an image display light guide plate (hereinafter simply referred to as “light guide plate”) 3001 according to the third embodiment of the present invention.
As shown in FIG. 14, the light guide plate 3001 is provided on the hologram layer 3010, two substrates of a first substrate 3021 and a second substrate 3022 sandwiching the hologram layer 3010 in the thickness direction, and the first substrate 3021. and a hard coat film 3030 formed thereon.

The first substrate 3021 and the second substrate 3022 are sheet-shaped resin substrates having optical transparency. As the material of the first substrate 3021 and the second substrate 3022, the same material as the resin base material used in the above-described first and second embodiments can be adopted. acrylic is preferred. The thickness of the first substrate 3021 and the second substrate 3022 can be, for example, around 1 mm.

As the hologram layer 3010, a known structure can be appropriately selected and used as in the above-described first and second embodiments. An optical structure such as a diffraction grating may be appropriately determined in consideration of the wavelength of light to be guided.

The hard coat film 3030 has a film substrate 3031 , an adhesive layer 3032 , a hard coat layer 3033 and a release layer 3034 . The adhesive layer 3032 is provided on the first surface 3031 a of the film substrate 3031 . The hard coat layer 3033 is provided on the second surface 3031b of the film substrate 3031 opposite to the first surface 3031a. A release layer 3034 is provided on the hard coat layer 3033 .
The hard coat film 3030 is detachably attached to the first substrate 3021 by the adhesive layer 3032 adhering to the first substrate 3021 .

Each part of the hard coat film 3030 will be described in detail below.
(Film substrate 3031)
Films or sheets made of various organic polymers can be used as the film substrate 3031 . For example, substrates that are commonly used in optical members such as displays can be mentioned. Polyolefins such as polyethylene and polypropylene, cyclic polyolefins, polyesters such as polyethylene terephthalate and polyethylene naphthalate, celluloses such as triacetyl cellulose, diacetyl cellulose and cellophane, polyamides such as 6-nylon and 6,6-nylon, Acrylic materials such as polymethyl methacrylate, and organic polymers such as polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, and ethylene vinyl alcohol are used. In particular, polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA) are preferred materials.

Furthermore, by adding known additives such as ultraviolet absorbers, infrared absorbers, plasticizers, lubricants, colorants, antioxidants, flame retardants, etc. to these organic polymers, the film substrate 3031 can function. Added ones can also be used. The film substrate 3031 may be composed of one, a mixture of two or more selected from the above organic polymers, or a polymer, or may be a laminate of a plurality of layers.
The film substrate 3031 preferably has a small birefringence and good transparency. The thickness of the first substrate 3021 and the second substrate 3022 is preferably in the range of 5-200 μm.

(Adhesive layer 3032)
The adhesive layer 3032 bonds the film substrate 3031 to the first substrate 3021 so that it can be peeled off with a small force. The adhesive layer 3032 is bonded to the surface of the first substrate 3021 opposite to the surface facing the hologram layer 3010 .
The adhesive layer 3032 is made of, for example, a rubber-based adhesive, a polyester-based adhesive, an epoxy-based adhesive, an acrylic-based adhesive, a silicone-based adhesive, a urethane-based adhesive, a vinyl alkyl ether-based adhesive, a polyvinyl alcohol-based adhesive, a poly It can be formed from an adhesive such as an acrylamide-based adhesive or a cellulose-based adhesive. Among these, UV-curing or heat-curing acrylic pressure-sensitive adhesives are preferable in terms of optical properties such as transparency.

As the acrylic pressure-sensitive adhesive, a pressure-sensitive adhesive composition using a (meth)acrylic acid ester polymer (hereinafter referred to as "acrylic acid ester (co)polymer", including copolymers) as a base resin. (hereinafter referred to as "this adhesive composition").
The acrylic acid ester-based (co)polymer used as the base resin has a glass transition temperature ( It can be prepared by appropriately adjusting physical properties such as Tg) and molecular weight.
Examples of acrylic monomers or methacrylic monomers used for polymerizing acrylic acid ester (co)polymers include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, ethyl acrylate, methyl methacrylate, and methyl acrylate. etc. can be mentioned. Also, an acrylic monomer having a hydrophilic group or an organic functional group such as hydroxyethyl acrylate, acrylic acid, glycidyl acrylate, acrylamide, acrylonitrile, methacrylonitrile, fluorine acrylate, silicone acrylate, or the like may be copolymerized with the above acrylic monomer. In addition, various vinyl monomers such as vinyl acetate, alkyl vinyl ethers and hydroxyalkyl vinyl ethers can be appropriately used for polymerization.
As polymerization treatment using these monomers, known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization can be employed. An acrylic acid ester copolymer can be obtained by using a polymerization initiator such as an initiator.

The thickness of the adhesive layer 3032 is preferably in the range of 1-50 μm, more preferably in the range of 1-30 μm.
As a method for forming the adhesive layer on the film substrate 3031, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating can be used. As for the coating method, there is an example described in "Coating Method" (Maki Shoten, Yuji Harasaki, published in 1979).
The method of drying the adhesive is not particularly limited, but it is generally recommended to dry at 30 to 160°C. Moreover, as a method for curing the adhesive, a known method may be appropriately selected according to the composition of the adhesive. For example, if the adhesive is active energy ray-curable, it may be cured by irradiating it with active energy rays (visible light, ultraviolet rays, X-rays, γ-rays). At this time, the irradiation amount of the active energy ray may be appropriately adjusted according to the properties of the adhesive, but it is generally preferable to irradiate at 10 to 10,000 mJ/m ² .
From the viewpoint of making the hard coat film easily peelable, the peel strength of the adhesive layer 3032 is 0.01 to 50 N/20 mm width when the peel in the 180 degree direction is measured (peeling speed 50 mm/min). is preferred.

(Hard coat layer 3033)
The hard coat layer 3033 has hardness enough to prevent damage due to contact with other structures. Such hardness is approximately H or higher in terms of pencil hardness (load 750 g) defined in JIS K 5600-5-4:1999. Therefore, the pencil hardness of the hard coat layer is preferably H or higher, more preferably 2H or higher.

The hard coat layer 3033 can be formed from a cured material formed using various hard coat agents. For example, the hard coat layer 3033 can be formed using a hard coat agent containing an active energy ray-curable composition or a thermosetting composition.
The hard coating agent may be an organic/inorganic hybrid material.

A polymerizable monomer or polymerizable oligomer that forms a cured product by irradiation with active energy rays can also be used as a material for the hard coat layer 3033 . Examples of the polymerizable monomer include (meth)acrylate monomers having a radically polymerizable unsaturated group in the molecule. Examples of the polymerizable oligomer include a (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule.
Examples of the (meth)acrylate monomer having a radically polymerizable unsaturated group in the molecule include urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl ( At least one monomer selected from the group consisting of meth)acrylates and silicone (meth)acrylates is included.
Examples of the (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule include urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl ( Examples include oligomers containing structural units derived from at least one monomer selected from the group consisting of meth)acrylates and silicone (meth)acrylates. You may use the said polymerizable monomer or the said polymerizable oligomer in combination of 2 or more types. Among these, urethane (meth)acrylate monomers or oligomers are preferred because of their high surface hardness.
Urethane (meth)acrylate is, for example, a urethane (meth)acrylate obtained by reacting a polyisocyanate compound with a (meth)acrylate compound having one hydroxyl group in its molecular structure, or a polyisocyanate compound with a hydroxyl group in its molecular structure. A urethane (meth)acrylate obtained by reacting one (meth)acrylate compound with a polyol compound is exemplified.

The hard coat layer 3033 may contain a cured polyfunctional (meth)acrylate. Examples of polyfunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth) ) acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, Ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, isocyanuric acid di(meth)acrylate acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate ) acrylate, tricyclodecane di(meth)acrylate or ditrimethylolpropane tetra(meth)acrylate, or those modified with PO, EO or caprolactone.
Among these, 3- to 6-functional polyfunctional (meth)acrylates are preferred because they can satisfactorily satisfy the surface hardness. Specific examples include pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), and pentaerythritol. Tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), trimethylolpropane tri(meth)acrylate, tripentaerythritol octa(meth)acrylate and tetrapentaerythritol deca(meth)acrylate.

When forming the hard coat layer 3033, additives such as cross-linking agents, polymerization initiators, lubricants, plasticizers, organic particles, inorganic particles, antifouling agents, antioxidants, catalysts, etc., or stains and adhesions are used as long as the physical properties are not impaired. A silicone-based or fluoro-based additive may be added to the hard coating agent to prevent this.
Further, the hard coating agent may contain a solvent, if necessary. Examples of the solvent include alcohols (methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol, diacetone alcohol); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, heptanone, diisobutyl ketone, diethyl ketone, diacetone alcohol); esters (methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, methyl formate, PGMEA); aliphatic hydrocarbons (hexane , cyclohexane); halogenated hydrocarbons (methylene chloride, chloroform, carbon tetrachloride); aromatic hydrocarbons (benzene, toluene, xylene); amides (dimethylformamide, dimethylacetamide, n-methylpyrrolidone); ethers (diethyl ether, dioxane, tetrahydrofuran); ether alcohol (1-methoxy-2-propanol); carbonates (dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate) and the like. These solvents may be used alone or in combination of two or more.

The thickness of the hard coat layer 3033 is preferably 1 μm to 50 μm, more preferably 2 μm to 40 μm, even more preferably 3 μm to 25 μm. When the thickness of the hard coat layer 3033 satisfies this range, damage to the first substrate 3021 can be effectively prevented, and damage to the hard coat film 3030 itself can also be suppressed. In addition, when the hard coat layer 3033 is formed, warping of the hard coat film due to curing shrinkage of the hard coat agent is suppressed.

The procedure for providing the hard coat layer 3033 on the film substrate 3031 can be roughly the same as the procedure for providing the adhesive layer 3032 . The various methods described above can also be used for the coating method, drying method, and curing method.

(Release layer 3034)
The release layer 3034 allows the overlaid adhesive layer of the hard coat film to be easily peeled off when the hard coat film is rolled into a roll during manufacture or storage.
The release layer 3034 is made of, for example, silicone resin, fluororesin, aminoalkyd resin, polyester resin, paraffin wax, acrylic resin, urethane resin, melamine resin, urea resin, urea-melamine system, cellulose, resins such as benzoguanamine, and surfactants. alone or a mixture of these as the main component, and a paint dissolved in an organic solvent or water is applied and dried by a normal printing method such as gravure printing, screen printing, or offset printing. be able to. A curable coating such as a thermosetting resin, an ultraviolet curable resin, an electron beam curable resin, or a radiation curable resin can be formed by curing.
In particular, it is preferable to perform a release treatment with a silicone, fluorine compound, or alkyd resin-based release treatment agent.

Since the hard coat film 3030 affects the visibility of the surrounding real image seen through the light guide plate 3001 and the image displayed on the light guide plate, it preferably has predetermined optical properties. As an example, when sandwiched between soda lime glasses having a thickness of 0.5 mm, the following (A) is preferably satisfied, and the following (B) and (C) are more preferably satisfied.
(A) Retardation value within the range of 0 to 100 nm (B) Total light transmittance measured according to JIS K 7361-1: 1997 of 85% or more (C) Haze measured according to JIS K 7136: 2000 Value less than 5%

In the light guide plate 3001 of the third embodiment of the present invention, the hard coat film 3030 attached to the first substrate 3021 prevents the first substrate 3021 from being damaged, etc., and preferably maintains the optical properties of the first substrate 3021. do. Since hard coat film 3030 includes hard coat layer 3033, hard coat film 3030 itself is not easily damaged. Furthermore, since the adhesive layer 3032 is releasably adhered to the first substrate 3021, when the hard coat film 3030 is damaged, the damaged hard coat film can be easily peeled off from the first substrate 3021, and another undamaged hard coat film can be removed. can be replaced with a hard coat film. This can prevent deterioration of the definition of the light guide plate.

<First modification>
A first modification of the third embodiment of the present invention will be described. In the following description, the same reference numerals are given to the same configurations as those already described, and duplicate descriptions will be omitted.

FIG. 15 shows a hard coat film 3130 according to the first modified example of the third embodiment of the invention.
The hard coat film 3130 includes an adhesive layer 3032 , a hard coat layer 3033 and a release layer 3034 . The hard coat film 3130 according to the first modified example of the third embodiment of the present invention differs from the hard coat film 3030 according to the basic example described above in that the film substrate 3031 is not provided.

An example of the manufacturing procedure of the hard coat film 3130 is shown below.
A paint that will be the release layer 3034 and a hard coating agent that will be the hard coat layer 3033 are applied in this order on the release-treated surface of the resin film that has been subjected to the release treatment, and the release layer 3034 and the hard coat are formed on the resin film. Layer 3033 is formed. Next, the adhesive layer 3032 is formed by applying an adhesive composition to form the adhesive layer 3032 on the hard coat layer 3033 . Finally, when the resin film is peeled off, the hard coat film 3130 is completed.
As another configuration, the hard coat layer 3033 and the adhesive layer 3032 are formed in the above-described procedure on the non-treated surface of the resin film which has been subjected to mold release treatment on one side, and the resin film can be used as the mold release layer 3034. .

The usage mode and function of the hard coat film 3130 of the first modified example of the third embodiment of the present invention are substantially the same as those of the hard coat film 3030 of the basic example described above, and the same effects are exhibited. In addition, since the film is stuck on the light guide plate, there is also an effect of preventing fragments from scattering when the light guide plate is damaged.

<Multi-ply hard coat film>
A plurality of the hard coat films of the basic example and modified example described above may be attached to the first substrate 3021 in a state of being stacked. FIG. 16 shows two hard coat films 3030 and FIG. 17 shows two hard coat films 3130 . In either case, since the release layer 3034 is present at the contact portion of the two superimposed hard coat films, the upper second hard coat films 3030B and 3130B are placed on top of the lower first hard coat film. It can be easily peeled off from the coat films 3030A and 3130A. When the hard coat film has such a structure, when the hard coat film located on the outermost surface is damaged, it is simply peeled off, and the undamaged hard coat film underneath becomes the new outermost surface. Therefore, it is not necessary to attach another hard coat film after removing the damaged hard coat film, and the surface condition of the light guide plate can be easily maintained. In this configuration, the number of hard coat films to be stacked is not limited to two as shown in the figure, and may be three or more.

There is no particular limitation on the method for obtaining a hard coat film in which a plurality of layers are stacked. Examples thereof include a method of bonding one hard coat film to another hard coat film, or a method of winding the hard coat film into a roll and then cutting it out.
Furthermore, a method of forming layers corresponding to a plurality of hard coat films at once can also be adopted. In this case, a method of laminating all the continuously laminated layers in an uncured state and then curing with active energy rays, curing or semi-curing the lower layer with active energy rays, applying the upper layer, and applying the active energy rays again A known method such as a method of curing with , a method of applying each layer to a release film or a base film, and then bonding the layers together in an uncured or semi-cured state can be applied, but the adhesion between the layers from the viewpoint of increasing the strength, a method of laminating the layers in an uncured state and then curing with an active energy ray is preferable. As a method for laminating in an uncured state, a known method such as sequential coating in which the lower layer is applied and then the upper layer is applied, or simultaneous multilayer coating in which two or more layers are applied at the same time from multiple slits is applied. It is possible, but not limited to this.

[Fourth embodiment]
In the light guide plate for image display of the present invention, the hologram layer turns yellow during production and long-term use, which may adversely affect the displayed image. However, by introducing an absorption layer having an absorption peak in the wavelength range of 500-600 nm, this can be reduced without degrading the hologram layer.

<Basic example>
A fourth embodiment of the light guide plate for image display of the present invention will be described below.
An image display light guide plate according to a fourth embodiment of the present invention has a first resin base material, a hologram layer, and a first absorption layer. It is preferable that the first absorption layer, the first resin base material, and the hologram layer are arranged in this order in the thickness direction.
The image display surface light guide plate of the fourth embodiment of the present invention may further have a second resin base material. In this case, the first absorption layer, the first resin base material, the hologram layer, and the second resin base material are preferably laminated in this order in the thickness direction. In the fourth embodiment of the present invention, the first resin base material and the second resin base material may be collectively referred to simply as "resin base material". Further, in the present embodiment, the first absorption layer and the second absorption layer may be collectively referred to simply as "absorption layer".
The image display light guide plate of the fourth embodiment of the present invention may further have an appropriate transparent layer. Examples of the transparent layer include a barrier layer, an adhesive layer, a hard coat layer and an anchor coat layer.
The image display light guide plate of the fourth embodiment of the present invention may further have a glass substrate.

The image display light guide plate has an incident portion for receiving image light, and a display image output portion for displaying an image based on the image light. The hologram layer is arranged between the entrance portion and the display image exit portion. A diffraction grating pattern is formed on the hologram layer for guiding at least image light incident from the incident portion to the display image output portion and outputting the image light from the display image output portion. The diffraction grating pattern in the display image output portion transmits at least part of external light entering from the outside of the image display light guide plate. In addition, the said external light entrance part points out the surface opposite to the said display image output part.
The image light incident on the incident portion is guided in the hologram layer and emitted to the outside from the display image emitting portion. On the other hand, external light also passes through the resin base material and the display image output section, so that an observer of the display image output section can observe both the image light and the external light within the field of view.
The image display light guide plate of the fourth embodiment of the present invention is suitably used in a display device using VR technology, AR technology, or MR technology. For example, the light guide plate for image display according to the fourth embodiment of the present invention is typified by a combiner of a head-up display (HUD) for automobiles or a reflector for a reflective liquid crystal display device, in addition to display applications. It may be used in devices such as a hologram optical element (HOE).

The material of the resin base material is not particularly limited as long as it is a transparent material.
The material used for the resin base material can be appropriately selected and used from those used in the first to third embodiments described above. The material used for the resin substrate preferably contains at least one resin selected from the group consisting of acrylic resins, cyclic polyolefin resins and polycarbonate resins.

In the image display light guide plate of the fourth embodiment of the present invention, when the resin base material is composed of two sheets of a first resin base material and a second resin base material, the first resin base material and the second resin base material The hologram layer may be arranged between the resin substrate.
In the image display light guide plate of the fourth embodiment of the present invention, when the image display light guide plate includes a first resin base material and a glass base material, the first resin base material and the glass base material The hologram layer may be arranged therebetween.
The resin substrate and the hologram layer, or the glass substrate and the hologram layer may be in contact with each other, or an appropriate transparent layer may be arranged between them.

The hologram layer is sandwiched between the first resin base and the second resin base or between the first resin base and the glass base.
A known hologram-forming resin material is used for the hologram layer, as in the first to third embodiments described above. As the hologram-forming resin material, for example, a thermosetting resin having at least one solvent-soluble and cationic polymerizable ethylene oxide ring in a structural unit and a hologram recording material comprising a radically polymerizable ethylenic monomer (Japanese Unexamined Patent Publication No. 8-1676, JP-A-8-1677, JP-A-8-1678, JP-A-8-1679).

The absorption layer has a wavelength characteristic of absorbing a yellow component in light transmitted through at least a portion of the light guide plate for image display.
(absorption peak)
The absorption layer has an absorption peak in a wavelength range of 500 to 600 nm (hereinafter sometimes referred to as "wavelength range A").
Here, the “absorption peak” is a U-shaped spectral distribution in which the transmittance changes from a decrease to a minimum value and then to an increase in the spectral transmittance curve of the absorption layer in the visible light range (400 to 800 nm), where the minimum value is It refers to the minimum spectral distribution. It is more preferable that the U-shaped spectral distribution be formed at one point in the visible light region.
In this specification, the fact that the wavelength giving the minimum value (peak top) of such an "absorption peak" is in a specific wavelength range is defined as "having an absorption peak in a specific wavelength range".
More preferably, the absorption peak is in the wavelength range of 550 to 585 nm (hereinafter sometimes referred to as "wavelength range B").
The half width of the absorption peak is preferably 100 nm or less, more preferably 70 nm or less, and particularly preferably 40 nm or less.
Here, the half width of the absorption peak means the wavelength width of the absorption peak at which the transmittance is Th = (100-Tp) / 2 or less, where Tp (%) is the transmittance of the peak top of the absorption peak. do.
When the half width is 100 nm or less, it is possible to satisfactorily ensure the color balance and luminance of transmitted light. The transmittance at the absorption peak is preferably 80% or less, more preferably 70% or less, and particularly preferably 60% or less.

(Transmittance characteristics)
The average transmittance of the absorption layer in the wavelength range of 590 to 700 nm (hereinafter sometimes referred to as "wavelength range C") is preferably 20% or more, more preferably 50% or more, and even more preferably 70% or more.
The reason why the average transmittance is set to 20% or more in the wavelength range C is to maintain the luminance of red light.
The average transmittance of the absorption layer in the wavelength range of 470 to 550 nm (hereinafter sometimes referred to as "wavelength range D") is preferably 20% or more, more preferably 50% or more, and even more preferably 70% or more.
The reason why the average transmittance is set to 20% or more in the wavelength range D is to ensure the color balance and brightness of the transmitted light.
Regarding the transmittance characteristics of the absorption layer, the lower the transmittance of ultraviolet light, which tends to cause photodegradation, the more preferable. For example, the transmittance of the absorption layer in the wavelength range of 380 nm or less is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

(Yellowness)
The YI value (JIS K 7373:2006) representing the yellowness of the absorbing layer is preferably 10 or less, more preferably 5 or less, and particularly preferably 3 or less.

(absorbance)
The absorbance of the absorption layer at a wavelength of 580 nm is preferably 0.5 or less, more preferably 0.3 or less, and particularly preferably 0.2 or less.

(b* in the L*a*b* color system)
The b* of the absorbing layer is preferably 5 or less, more preferably 3 or less, and particularly preferably 1 or less.

The structure of the absorption layer is not particularly limited as long as it has an absorption peak in the wavelength range A.
For example, the absorption layer may have a structure in which a coloring material is dispersed in a transparent base resin.
The material of the base resin is not particularly limited as long as it is transparent. The refractive index of the base resin is also not particularly limited.
For example, the base resin may have a refractive index equal to or higher than the refractive index of the resin base material, or may have a refractive index lower than that of the resin base material.
For example, as the base resin, a resin material having a surface hardness higher than that of the resin substrate may be used.
For example, a resin material with low hygroscopicity may be used as the base resin.

The coloring material is not particularly limited as long as the wavelength characteristics described above can be obtained. For example, dyes, pigments, and the like are used as coloring materials. It is particularly preferable to use a bluing agent as the coloring material.
For example, the absorption layer may be formed of a multi-layer thin film in which a plurality of high refractive index materials and low refractive index materials are laminated.

(Bluing agent)
The bluing agent used in the absorbing layer is not particularly limited, but generally an anthraquinone dye is easily available and more preferable.
Specific bluing agents include, for example, general name Solvent Violet 13 [CA. No (color index No) 60725], general name Solvent Violet 31 [CA. No 68210], generic name Solvent Violet 33 [CA. No 60725], generic name Solvent Blue 94 [CA. No 61500], generic name Solvent Violet 36 [CA. No 68210], generic name Solvent Blue 97 [Bayer "Macrolex Violet RR"], generic name Solvent Blue 45 [CA. No. 61110] and the like are typical examples. These bluing agents may be used alone or in combination of two or more. These bluing agents are added to the base resin in an appropriate amount to obtain the optical properties required for the absorbing layer. For example, when the base resin is a polycarbonate resin, it may be blended at a ratio of 0.1×10 ⁻⁵ to 2×10 ⁻⁴ parts by weight per 100 parts by weight of the polycarbonate resin.
Examples of other bluing agents include Diaresin (registered trademark) Blue N (trade name; manufactured by Mitsubishi Chemical Corporation), Diaresin (registered trademark) Blue G (trade name; manufactured by Mitsubishi Chemical Corporation), and Macrolex (registered trademark). Trademark) Blue RR (trade name; manufactured by Bayer AG), Macrolex (registered trademark) Blue 3R (trade name; manufactured by Bayer AG), Polyshinthrene (registered trademark) Blue RLS (trade name; manufactured by Clariant AG), and the like.

The absorption layer is provided in a range through which at least image light and external light are transmitted. For example, the absorption layer may be arranged in a range overlapping in the thickness direction with the display image emitting portion of the hologram layer.
However, the absorbing layer may be arranged in a range covering the entire resin substrate or hologram layer when viewed from the thickness direction.

The arrangement of the absorption layers in the thickness direction of the light guide plate for image display is not particularly limited.
For example, the absorption layer may be provided at least one of a position closer to the incident surface of external light than the hologram layer and a position closer to the exit surface of image light than the hologram layer.
When the absorption layer is arranged outside the resin base material, the absorption layer, the resin base material, and the hologram layer may be arranged in this order in the thickness direction of the light guide plate for image display. That is, the absorbent layer may be arranged outside the resin substrate in the thickness direction. For example, the absorption layer may be arranged at the outermost part in the thickness direction of the light guide plate for image display.
When the absorbing layer is formed by dispersing the coloring material inside the resin base material, the coloring material may be uniformly dispersed in the resin base material, or may be unevenly distributed in the thickness direction. When the coloring material is biased in the thickness direction, it is more preferable that the coloring material is biased outward in the thickness direction of the light guide plate for image display.

The barrier layer can employ the same material as in the above-described second embodiment, and is preferably composed of a transparent inorganic material. Moreover, the refractive index of the barrier layer is more preferably 1.48 or more.
As the material for the barrier layer, it is more preferable to use a water vapor barrier material. More preferably, the barrier layer contains one or more substances selected from the group consisting of silicon oxide, silicon nitrogen oxide, and diamond-like carbon (DLC).
The barrier layer may be arranged on the resin film. In this case, the resin film is more preferably arranged between the barrier layer and the resin substrate.

More preferably, the barrier layer is arranged in the order of the resin base material, the barrier layer, and the hologram layer in the thickness direction of the light guide plate for image display. It is particularly preferred that the barrier layer is arranged on the surface of the hologram layer.
Two barrier layers may be provided with the hologram layer interposed therebetween. More preferably, the barrier layers are arranged on the front and back surfaces of the hologram layer.
When the glass substrate is arranged, the glass substrate itself has barrier properties, so the glass substrate may be arranged on the surface of the hologram layer opposite to the surface facing the barrier layer.

Hereinafter, based on the example shown in FIG. 18, a detailed configuration of an example of the light guide plate for image display according to the fourth embodiment of the present invention will be described. FIG. 18 is a schematic cross-sectional view showing an example of the image display light guide plate according to the fourth embodiment of the present invention.

In the image display light guide plate 4005 shown in FIG. 18, the first absorption layer 4004, the first resin base material 4001, the hologram layer 4002, and the second resin base material 4003 are arranged in this order in the thickness direction. The image display light guide plate 4005 is an example of a case without a barrier layer.
The plan view shape of the image display light guide plate 4005 is not particularly limited. For example, the image display light guide plate 4005 may be shaped into a shape that can be attached to the display device used. For example, the image display light guide plate 4005 may be a rectangular plate larger than the shape to be attached to the display device. In this case, the image display light guide plate 4005 is shaped, for example, by being cut into a shape that can be attached to the display device before being assembled to the display device.
The image display light guide plate 4005 may have a flat plate shape, or may have a curved plate shape as necessary.
In the following, an example in which the image display light guide plate 4005 is made of a rectangular flat plate in plan view will be described.

The first absorption layer 4004 is arranged at the outermost part in the thickness direction of the image display light guide plate 4005 . The first absorption layer 4004 is arranged on the surface of the image display light guide plate 4005 on the display image exit side.
The layer thickness of the first absorption layer 4004 is not particularly limited. For example, the layer thickness of the first absorption layer 4004 may be 0.1-10 μm.
In the example shown in FIG. 18, the first absorption layer 4004 is formed over the entire surface of the first resin base material 4001, which will be described later.
A method for forming the first absorption layer 4004 is not particularly limited. For example, the first absorption layer 4004 is formed by applying a coating liquid made of a base resin material containing a coloring material to the film forming surface (the surface of the first resin substrate 4001) and then curing the coating liquid. can.
As the coating method of the coating liquid, an appropriate coating method can be selected according to the viscosity of the coating liquid. Conventionally known coating methods such as curtain coating can be used.
As the base resin material, for example, a (meth)acrylate monomer having a radically polymerizable unsaturated group in the molecule, or a (meth)acrylate oligomer having a radically polymerizable unsaturated group in the molecule, etc. can be obtained by irradiation with active energy rays. A polymerizable monomer or polymerizable oligomer that forms a cured product, or a curable resin material such as urethane, epoxy, or polyester may be used. For example, the bluing agent described above may be used as the coloring material to be mixed with the base resin material.

The first resin base material 4001 has a shape similar to the outer shape of the image display light guide plate 4005 . Image light Ld emitted from the hologram layer 4002 and external light Lo passing through the second resin base 4003 and the hologram layer 4002, which will be described later, pass through the first resin base 4001 . The thickness of the first resin base material 4001 is not particularly limited. For example, the thickness of the first resin base material 4001 may be 0.01 to 10 mm.

The material for forming the first resin base material 4001 can be appropriately selected from materials similar to those of the above-described first to third embodiments, and is not particularly limited as long as it is a transparent resin material. Materials for forming the first resin substrate 4001 include, for example, polyolefin resins such as homopolymers or copolymers of olefins such as ethylene, propylene or butene; amorphous polyolefin resins such as cyclic polyolefins; polyethylene terephthalate. polyester resins such as (PET) and polyethylene naphthalate (PEN); polyamide resins such as nylon 6, nylon 66, nylon 12 and copolymerized nylon; ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polycarbonate resin, polyvinyl butyral resin, polyarylate resin, fluororesin, poly(meth)acrylic resin , styrene resins such as polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinyl chloride, cellulose, acetyl cellulose, polyvinylidene chloride, polyphenylene sulfide, polyurethane, phenolic resin, epoxy resin, polyarylate resin, polynorbornene, styrene - organic materials such as isobutylene-styrene block copolymers (SIBS), allyl diglycol carbonate, and biodegradable resins. In addition, the first resin base material 4001 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 of the first resin substrate 4001, polycarbonate or poly(meth)acrylic resin is preferable. From the viewpoint of process resistance of the first resin substrate 4001, poly(meth)acrylic resin, epoxy resin, or cyclic polyolefin is preferable.

The hologram layer 4002 is laminated on the surface opposite to the surface of the first resin substrate 4001 on which the first absorption layer 4004 is formed. The configuration of the hologram layer 4002 is not particularly limited as described above. The hologram layer 4002 is formed with an appropriate diffraction grating corresponding to the functions required for the image display light guide plate 4005 .

The second resin base material 4003 is laminated on the surface of the hologram layer 4002 opposite to the surface on which the first resin base material 4001 is arranged. As the second resin base material 4003, the same configuration as exemplified in the description of the first resin base material 4001 is used. However, the thickness, material, etc. of the second resin base material 4003 may be different from those of the first resin base material 4001 . In particular, the second resin base material 4003 is disposed on the surface of the image display light guide plate 4005 on the side of the light guide plate 4005 opposite to the display image emission side and on the outside light incidence side, so that the surface hardness is higher than that of the first resin base material 4001 . Expensive materials may be used.

Such an image display light guide plate 4005 can be manufactured, for example, as follows.
First resin base material 4001 and second resin base material 4003 are prepared, and a coating liquid for forming first absorption layer 4004 is prepared.
For example, a coating liquid is applied to the surface of the first resin base material 4001 . After that, the coating liquid is cured to form the first absorption layer 4004 .
For example, a photopolymer material for forming a hologram is applied to the surface of the first resin substrate 4001 opposite to the surface on which the first absorption layer 4004 is formed. At this time, a transparent seal layer having the same thickness as the hologram layer 4002 may be provided on the outer peripheral portion of the surface of the first resin base material 4001 . In this case, the photopolymer material is applied to the recess formed surrounded by the sealing layer. The seal layer seals the outer periphery of the hologram layer 4002 after the hologram layer 4002 is formed. A second resin substrate 4003 is then placed on the photopolymer material. However, the manufacturing order described above is an example. For example, a photopolymer material may be applied to the surface of the second resin substrate 4003 and the first resin substrate 4001 having the first absorption layer 4004 formed thereon may be placed on the photopolymer material.
Thereafter, a laminate composed of the first absorption layer 4004, the first resin base material 4001, the photopolymer material, and the second resin base material 4003 is bonded together by vacuum pressing.
Thereafter, interference fringes corresponding to the diffraction pattern are formed in the photopolymer material of the laminate, and a diffraction grating is formed in the photopolymer material.
Thus, the image display light guide plate 4005 is manufactured.

Next, an example of a display device including the image display light guide plate 4005 will be described.
FIG. 19 is a schematic cross-sectional view showing an example of a display device including the image display light guide plate of the fourth embodiment of the present invention.

As shown in FIG. 19, the display device 4010 includes an image light projection section 4012 and an incident optical system 4011 in addition to the image display light guide plate 4005 .
The image light projection unit 4012 projects image light Li to be displayed on the image display light guide plate 4005 according to an image signal sent from a controller (not shown).
The incident optical system 4011 includes an optical element such as a prism that causes the image light Li to enter the image display light guide plate 4005 . The incident optical system 4011 causes the image light Li to enter an incident portion 4005a formed on the surface of the light guide plate 4005 for image display. For example, the incident part 4005a is provided on the first absorption layer 4004 .
The image light Li incident on the incident portion 4005 a is guided to the display diffraction grating portion 4002 b of the hologram layer 4002 via the waveguide diffraction grating portion 4003 a formed in the hologram layer 4002 . In the display diffraction grating section 4002b, the image light Li is diffracted at positions corresponding to the respective display pixels to form image light Ld. The image light Ld passes through the hologram layer 4002, the first resin base material 4001, and the first absorption layer 4004, and is emitted to the outside of the image display light guide plate 4005 as image light Ld'. Therefore, the region of the display diffraction grating portion 4002b in the thickness direction, and the region of the first resin base material 4001 and the first absorption layer 4004 facing the display diffraction grating portion 4002b in the thickness direction is a display image that displays the image light Ld. It constitutes the emission part 4005b. The display image emitting portion 4005b is formed at a position spaced apart from the incident portion 4005a in the plane direction, which is the direction orthogonal to the thickness direction.

On the other hand, external light Lo enters the image display light guide plate 4005 via the second resin base material 4003 . The external light Lo passes through the second resin base material 4003, the hologram layer 4002, the first resin base material 4001, and the first absorption layer 4004, and is emitted to the outside of the image display light guide plate 4005 as the external light Lo'. be.
A user of the display device 4010 can see an image formed by the image light Ld' and the external light Lo'. Therefore, a user who has the display image output unit 4005b in his field of vision sees an image in which the external scene based on the external light Lo' and the image based on the image light Ld' are superimposed.

Transparent materials such as those used for the image display light guide plate 4005 are subject to photodegradation over time due to the influence of ultraviolet light, for example. A typical photodegradation is yellowing of the material. In particular, since the hologram layer 4002 is made of a photopolymer material, it is yellowed to some extent immediately after its manufacture. Therefore, the light after passing through the first resin base material 4001, the second resin base material 4003, and the hologram layer 4002 is tinged with yellow.
Since yellow has high relative luminosity, human vision is sensitive to yellowing. As a result, the contrast (brightness) of the yellowish image becomes low, and the observed image becomes unclear.
However, in the fourth embodiment of the present invention, since the display image output portion 4005b is provided with the first absorption layer 4004, in the image light Ld′ and the external light Lo′, the image light Ld and the external light Lo A yellow component is reduced. In this way, the first absorption layer 4004 offsets the yellowish image light Ld and the yellow component of the external light Lo, thereby forming the first resin base material 4001 and the second resin base material 4003 and the hologram layer. The yellowing effect of 4002 is eliminated.
Specifically, the first absorption layer 4004 absorbs light mainly in the wavelength range of 500 to 600 nm, thereby reducing yellowness and relatively increasing blueness. This improves the white balance and contrast of the image.
Furthermore, even if the transparent materials such as the first resin base material 4001 and the second resin base material 4003 deteriorate over time due to ultraviolet light or the like exposed when the display device 4010 is used, the degree of image deterioration due to yellowing is is reduced compared to the case without the first absorbing layer 4004 .

As described above, according to the fourth embodiment of the present invention, it is possible to provide an image display light guide plate capable of reducing the influence of yellowing of a transparent material on a displayed image.

Especially in the fourth embodiment of the present invention, the first absorption layer 4004 is arranged on the outermost part of the image display light guide plate 4005 . Therefore, for example, if a material having higher hardness than the first resin base material 4001 is used as the first absorption layer 4004, the surface of the first resin base material 4001 is prevented from being damaged. For example, when the transmittance of ultraviolet light in the wavelength characteristics of the first absorption layer 4004 is low, the incidence of ultraviolet light from the first resin base material 4001 side can be suppressed. can be reduced.

<First modification>
A first modification of the fourth embodiment will be described.
FIG. 20 is a schematic cross-sectional view showing an example of the image display light guide plate of the first modified example of the fourth embodiment of the present invention.

As shown in FIG. 20, the image display light guide plate 4007 of the first modified example of the fourth embodiment of the present invention is the same as the image display light guide plate 4005 of the basic example of the fourth embodiment of the present invention. A second absorbent layer 4006 is provided.
The following description focuses on points that differ from the basic example of the fourth embodiment of the present invention.

The second absorption layer 4006 is laminated on the surface of the second resin base material 4003 opposite to the surface on which the hologram layer 4002 is arranged. In other words, the second absorption layer 4006 is arranged at the outermost part of the image display light guide plate 4007 as with the first absorption layer 4004 . In the image display light guide plate 4007 , a laminate composed of a first resin base material 4001 , a hologram layer 4002 and a second resin base material 4003 is sandwiched between a first absorption layer 4004 and a second absorption layer 4006 .
As the second absorption layer 4006, the same configuration as exemplified in the description of the first absorption layer 4004 is used.
However, the thickness, material, etc. of the second absorption layer 4006 may be different from those of the first absorption layer 4004 . For example, since the second absorption layer 4006 is arranged on the surface of the image display light guide plate 4007 opposite to the display image output side, the surface hardness is higher than that of the second resin base material 4003 or the first absorption layer 4004. materials may be used.
In the first modification of the fourth embodiment of the present invention, since the first absorption layer 4004 and the second absorption layer 4006 are arranged on the outermost part of the image display light guide plate 4007, the first absorption layer 4004 and the second absorption layer 4006 It is more preferable that the absorption layer 4006 has a low transmittance for ultraviolet light in terms of wavelength characteristics.

The image display light guide plate 4007 is manufactured in the same manner as the image display light guide plate 4005 in the basic example of the fourth embodiment of the present invention, except that the second absorption layer 4006 is formed on the second resin base material 4003. be done. A method for forming the second absorption layer 4006 is the same as that for the first absorption layer 4004 .

An image display light guide plate 4007 according to the first modification of the fourth embodiment of the present invention is configured in the same manner as the image display light guide plate 4005 except that it has a second absorption layer 4006 . Therefore, the image light Ld passes through the first absorption layer 4004 in the same manner as the image display light guide plate 4005, so that the yellow component is reduced (image light Ld').
On the other hand, the external light Lo enters the second resin base material 4003 after passing through the second absorption layer 4006 . Therefore, the yellow component of the external light Lo is reduced when passing through the second absorption layer 4006 . When the external light Lo is transmitted through the second resin base material 4003, the hologram layer 4002, and the first resin base material 4001, the yellow component increases according to the degree of yellowing of each, and then passes through the first absorption layer 4004. A yellow component is reduced.
Since the second resin base material 4003 is arranged on the incident side of the external light Lo during use, it is easily deteriorated by the external light Lo. As a result, yellowing of the second resin base material 4003 may progress more easily than yellowing of the first resin base material 4001 over time. As yellowing of the second resin base material 4003 progresses, the external light Lo transmitted through the second resin base material 4003 may have a stronger yellow component than the image light Ld that does not transmit through the second resin base material 4003. .
However, since the first modification of the fourth embodiment of the present invention has the second absorption layer 4006, the second absorption layer 4006 can offset the increase in yellowness due to the yellowing of the second resin base material 4003. becomes possible. Therefore, the yellowness of the external light Lo″ emitted from the first absorption layer 4004 is reduced compared to the external light Lo′ emitted from the image display light guide plate 4005 . As a result, the image light Ld′ and the external light Lo″ can be well balanced in terms of yellowness.
In particular, when the transmittance of ultraviolet light in the wavelength characteristics of the second absorption layer 4006 is low, the photodegradation of the second resin base material 4003 due to the external light Lo can be reduced.

As described above, according to the first modification of the fourth embodiment of the present invention, it is possible to provide an image display light guide plate that can reduce the influence of yellowing of the transparent material on the displayed image.

<Second modification>
A second modification of the fourth embodiment will be described.
FIG. 21 is a schematic cross-sectional view showing an example of the image display light guide plate of the second modified example of the fourth embodiment of the present invention.

As shown in FIG. 21, the image display light guide plate 4020 of the second modified example of the fourth embodiment of the present invention is the same as the image display light guide plate 4007 of the first modified example, further including a first barrier layer 4008 and a first barrier layer 4008 . 2 barrier layer 4009 is provided. In the second modification of the fourth embodiment of the present invention, the first barrier layer 4008 and the second barrier layer 4009 may be collectively referred to simply as "barrier layers". Moreover, in the second modification of the fourth embodiment of the present invention, the first resin base material 4001 and the second resin base material 4003 may be collectively referred to simply as "resin base material". Furthermore, in the second modified example of the fourth embodiment of the present invention, the first absorbent layer 4004 and the second absorbent layer may be collectively referred to simply as "absorbent layers".
Hereinafter, the points different from the first modification of the fourth embodiment of the present invention will be mainly described.

The first barrier layer 4008 is arranged between the first resin base material 4001 and the hologram layer 4002 and adheres to the respective surfaces of the first resin base material 4001 and the hologram layer 4002 . The first barrier layer 4008 prevents gas permeating from the outside of the image display light guide plate 4020 and the first resin base material 4001 from permeating the hologram layer 4002 .
The material of the first barrier layer 4008 is not particularly limited as long as it can block gases that cause deterioration of the hologram layer 4002 . The first barrier layer 4008 preferably contains a transparent inorganic material, and similar to the barrier layer in the second embodiment described above, silicon oxide, silicon nitrogen oxide, diamond-like carbon (DLC), and aluminum oxide. and glass.
Furthermore, the barrier layer may be arranged on the resin film. In this case, the resin film is more preferably arranged between the barrier layer and the resin substrate.
The first barrier layer 4008 preferably has lower oxygen permeability and lower water vapor permeability, for example. In particular, the first barrier layer 4008 is more preferably made of a material with excellent water vapor barrier properties (low water vapor transmission rate).
For example, the oxygen permeability of the first barrier layer 4008 may be 1 cm ³ /m ² ·day or less.
For example, the first barrier layer 4008 may have a water vapor transmission rate of 1 g/m ² ·day or less. The water vapor transmission rate of the first barrier layer 4008 is more preferably 0.5 g/m ² ·day or less.

The inorganic material used for the first barrier layer 4008 may have a higher refractive index than the first resin base material 4001 . For example, the refractive index of the first barrier layer 4008 may be between 1.48 and 3.00. When the first barrier layer 4008 has a high refractive index, the light passing through the first resin base material 4001 via the first barrier layer 4008 is transferred from the optically dense first barrier layer 4008 to the optically coarse one. Since the light is incident on the first resin base material 4001 , the output angle of the light from the first barrier layer 4008 toward the first resin base material 4001 varies depending on the refractive index difference between the first barrier layer 4008 and the first resin base material 4001 . grow larger. Thereby, the FOV (Field Of View) in the image display light guide plate 4020 can be widened.

Materials for the first barrier layer 4008 are as described above, but zinc oxide, antimony oxide, indium oxide, cerium oxide, calcium oxide, cadmium oxide, silver oxide, gold oxide, chromium oxide, silicon oxide, cobalt oxide, oxide Oxide such as zirconium, tin oxide, titanium oxide, iron oxide, copper oxide, nickel oxide, platinum oxide, palladium oxide, bismuth oxide, magnesium oxide, manganese oxide, molybdenum oxide, vanadium oxide or barium oxide may be used.

When the first barrier layer 4008 is made of silicon oxide, its layer thickness may be 10 to 300 nm. If the layer thickness is less than 10 nm, the moisture resistance may be insufficient. If the layer thickness exceeds 300 nm, the silicon oxide thin film is likely to crack and peel off from the film formation surface.
A particularly preferable layer thickness is 20 to 200 nm.
The method of forming the first barrier layer 4008 with the silicon oxide is not particularly limited. For example, the first barrier layer 4008 can be formed by any conventionally known method such as a vacuum deposition method, a sputtering method, an ion plating method, or a plasma CVD method. When forming the first barrier layer 4008 from the silicon oxide, in order to improve adhesion between the film formation surface and the silicon oxide, the film formation surface is subjected to corona discharge treatment or low-temperature plasma treatment, or A surface treatment such as applying a silane coupling agent or applying a mixture of saturated polyester and isocyanate to the film formation surface may be performed.
For example, when forming a thin film of silicon oxide by ^vacuum evaporation, silicon, silicon monoxide, silicon dioxide, or a mixture thereof is used as the evaporation material, and the Under a vacuum of ^-5 Torr, it is heated and evaporated by an electron beam, resistance heating, or high-frequency heating method.
Also, a reactive vapor deposition method that is performed while supplying oxygen gas can be employed.
The silicon oxide forming the first barrier layer 4008 may contain calcium, magnesium, or their oxides as impurities as long as the content is 10% by mass or less.

When the first barrier layer 4008 is made of silicon nitrogen oxide, the structure is the same as that of the first barrier layer 4008 containing silicon oxide as a main component, except that the silicon oxide is replaced with the silicon nitrogen oxide. Used.

DLC is generally an amorphous carbon material having a ternary system structure of a diamond-like structure, a graphite-like structure, and a polyethylene-like polymer structure containing hydrogen atoms in the structure. When a hydrocarbon such as ethylene, acetylene, or benzene is used as the carbon source for the production of the DLC, it usually has a ternary structure containing hydrogen.
The DLC is excellent in hardness, lubricity, wear resistance, chemical stability, heat resistance and surface smoothness. Since the DLC forms the dense polymer structure described above, it is also excellent in gas barrier properties and water vapor barrier properties.
A formation method for forming the first barrier layer 4008 with the DLC is not particularly limited. As a method for coating the DLC, a suitable well-known coating method such as a plasma CVD method or a physical vapor deposition method such as an ion plating method or an ion beam sputtering method can be used.

When the first barrier layer 4008 is made of aluminum oxide, the first barrier layer 4008 may be made of _{only Al2O3} , for example, or selected from the group consisting of Al _, AlO and _Al2O3 . Two or more kinds may be mixed and formed. The atomic ratio of Al:O in the aluminum oxide layer varies depending on the manufacturing conditions of the aluminum oxide layer. The aluminum oxide layer that can be used as the first barrier layer 4008 may contain other components in trace amounts (up to 3% with respect to all components) as long as the barrier performance is not impaired.
The layer thickness of the aluminum oxide layer may be set as required for barrier performance. For example, the layer thickness of the aluminum oxide layer may be 5-800 nm.
The method of forming the first barrier layer 4008 with aluminum oxide is not particularly limited. For example, as a method of forming the first barrier layer 4008, a PVD method (physical vapor deposition method) such as a vacuum deposition method, a sputtering method or ion plating, or a CVD method (chemical vapor deposition method) may be used.
For example, in the vacuum deposition method, Al, Al ₂ O ₃ or the like is used as the 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 deposition source. . In the vacuum deposition method, oxygen, nitrogen, water vapor, or the like may be introduced as a reactive gas, or reactive deposition using means such as addition of ozone or ion assist may be used. Furthermore, a bias may be applied to the film formation surface, or the temperature of the film formation surface may be raised or cooled. The same applies to other film forming methods such as the PVD method and the CVD method other than the sputtering method and other vacuum vapor deposition methods.

When the first barrier layer 4008 is made of glass, examples of materials for the first barrier layer 4008 include borosilicate glass, non-alkali glass, low-alkaline glass, soda lime glass, sol-gel glass, or heat treatment or surface treatment of these glasses. Examples include those that have undergone processing. As a material for the first barrier layer 4008, non-alkali glass is particularly preferable from the viewpoint of avoiding coloring due to impurities.

When the first barrier layer 4008 is made of glass, its layer thickness may be 10-200 μm. When the layer thickness is 10 μm or more, the mechanical strength and gas barrier properties tend to be excellent. The layer thickness is preferably 10 μm or more, more preferably 30 μm or more. Further, when the layer thickness is 200 μm or less, the optical properties of the light guide plate such as light transmittance tend to be excellent. The layer thickness is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 75 μm or less, and particularly preferably 50 μm or less.

The method of forming the first barrier layer 4008 with glass is not particularly limited. As a method of forming the first barrier layer 4008 with glass, for example, a slot down draw method, a fusion method, or a float method can be adopted. In addition, as the glass to be used, commercially available glass may be used as it is, or commercially available glass may be used after polishing so as to have a desired thickness. Examples of the commercially available glass include "EAGLE2000" manufactured by Corning, "AN100" manufactured by Asahi Glass, "OA10G" manufactured by Nippon Electric Glass, and "D263" manufactured by Schott.

The second barrier layer 4009 is laminated on the surface of the hologram layer 4002 opposite to the surface of the hologram layer 4002 on which the first barrier layer 4008 is formed.
As for the configuration of the second barrier layer 4009, the same configuration as exemplified in the description of the first barrier layer 4008 is used. However, the material, thickness, etc. of the second barrier layer 4009 may be different from those of the first barrier layer 4008 .

Such an image display light guide plate 4020 can be manufactured, for example, as follows.
A first resin base material 4001 and a second resin base material 4003 are prepared, and a first barrier layer 4008 and a second barrier layer 4009 are formed on the surfaces of the first resin base material 4001 and the second resin base material 4003, respectively. . As a method for manufacturing the first barrier layer 4008 and the second barrier layer 4009, an appropriate manufacturing method is selected according to the materials of the first barrier layer 4008 and the second barrier layer 4009. FIG.
For example, a photopolymer material for forming a hologram is applied to the surface of the first barrier layer 4008 in the first resin substrate 4001 on which the first barrier layer 4008 is formed. At this time, a transparent seal layer having the same thickness as the hologram layer 4002 may be provided on the outer peripheral portion of the first barrier layer 4008 . In this case, the photopolymer material is applied to the recess formed surrounded by the sealing layer. The seal layer seals the outer periphery of the hologram layer 4002 after the hologram layer 4002 is formed.
Thereafter, a second resin substrate 4003 having a second barrier layer 4009 formed thereon is placed on the photopolymer material with the second barrier layer 4009 facing the photopolymer material.
However, the manufacturing order described above is an example. For example, after the photopolymer material is applied to the second resin substrate 4003 having the second barrier layer 4009 formed thereon, the first resin substrate 4001 having the first barrier layer 4008 formed thereon is placed on the photopolymer material. may be
After that, the first absorption layer 4004, the first resin base material 4001, the first barrier layer 4008, the photopolymer material, the second barrier layer 4009, the second resin base material 4003, and the second absorption layer 4006 are removed by vacuum pressing. laminates are laminated together.
Thereafter, interference fringes corresponding to the diffraction pattern are formed in the photopolymer material of the laminate, and a diffraction grating is formed in the photopolymer material.
Thus, the image display light guide plate 4020 is manufactured.

The image display light guide plate 4020 is configured in the same manner as the image display light guide plate 4007 of the first modified example except that a first barrier layer 4008 and a second barrier layer 4009 are added.
The first barrier layer 4008 and the second barrier layer 4009 are made of a transparent inorganic material such as DLC or silicon oxide, and since they easily absorb blue light in the wavelength range of 400 nm to 480 nm, the transmittance of the blue component is As a result, the transmitted light becomes yellowish.
Thus, the first barrier layer 4008 tends to increase the yellowness of the external light Lo and the image light Ld, and the second barrier layer 4009 tends to increase the yellowness of the external light Lo. However, in the second modified example of the fourth embodiment of the present invention, as in the first modified example, the first absorbent layer 4004 and the second absorbent layer 4006 are provided. By appropriately adjusting the wavelength characteristics of , the increase in yellowness due to the first barrier layer 4008 and the second barrier layer 4009 can be offset. That is, the yellowness of the external light Lo''' and the image light Ld'' emitted from the first absorption layer 4004 can be reduced. Furthermore, similarly to the first modified example, it is possible to improve the yellowish balance of the external light Lo''' and the image light Ld''.

As described above, according to the second modification of the fourth embodiment of the present invention, it is possible to provide an image display light guide plate capable of reducing the influence of yellowing of the transparent material on the displayed image.

Further, since the image display light guide plate 4020 includes the first barrier layer 4008 and the second barrier layer 4009, it is possible to suppress deterioration of the hologram layer 4002 over time.

The gas barrier property of the first resin base material 4001 and the second resin base material 4003 varies depending on the type of resin material, but is much lower than that of glass. Therefore, the first resin base material 4001 and the second resin base material 4003 have higher hygroscopicity and water vapor permeability than glass.
As a result, the gas outside the image display light guide plate 4005 passes through the first resin base material 4001 and the second resin base material 4003 to some extent or accumulates inside. In particular, moisture tends to accumulate on the first resin base material 4001 and the second resin base material 4003 .
However, the gas and moisture that have permeated the first resin base material 4001 and the second resin base material 4003 from the outside are blocked by the first barrier layer 4008 and the second barrier layer 4009 even if they diffuse in the image display light guide plate 4020. be done. This suppresses permeation of gas and water vapor into the hologram layer 4002 .
For example, by suppressing penetration of moisture into the hologram layer 4002, deterioration of the hologram layer 4002 is prevented.
Furthermore, since the image display light guide plate 4020 has the layer structure described above, the hologram layer 4002 is not in contact with the first resin base material 4001 and the second resin base material 4003 . This prevents the hologram layer 4002 from corroding the first resin base material 4001 and the second resin base material 4003 even if the image display light guide plate 4020 is placed in a high-temperature environment.

In particular, when the refractive indices of the first barrier layer 4008 and the second barrier layer 4009 are higher than those of the first resin base material 4001 and the second resin base material 4003, as described above, the first barrier layer The output angle of the light from 4008 toward the first resin base material 4001 increases. Similarly, light incident on the second barrier layer 4009 from the second resin base material 4003 has a narrower output angle. Therefore, the light that enters from the outside on the second resin base material 4003 side and passes through the image display light guide plate 4005 is incident in a wider angle range than in the case where the second barrier layer 4009 is not provided. , and is emitted in a wider angle range than when the first barrier layer 4008 is not provided. This results in a wider field of view for external light and a wider FOV on the display side.
Regarding the image light from the hologram layer 4002, as described above, the output angle of the light from the first barrier layer 4008 toward the first resin base material 4001 is increased. , the FOV of the display screen is expanded.
In particular, in the second modification of the fourth embodiment of the present invention, the first barrier layer 4008 and the second barrier layer 4009 are stacked on the hologram layer 4002 to provide diffusion positions for external light and image light. , and the diffraction position of the hologram layer 4002 that constitutes the display screen are closer to each other. images can be viewed from a wide range of angles.

Here, a method for measuring the luminance value and the FOV in the image display light guide plate 4020 will be briefly described.
The luminance value of the image display light guide plate 4020 is the same as that of the display device 4010 in the basic example of the fourth embodiment of the present invention described above, except that the image display light guide plate 4005 is replaced with the image display light guide plate 4020. Measured using a device and a luminance meter.
In measuring the luminance value, the display device is arranged such that the center of the display image output portion of the image display light guide plate 4020 faces the luminance meter on the measurement optical axis of the luminance meter. The distance between the display image output unit and the luminance meter corresponds to the position of the user's eyes when the display device is worn. For example, if the display device is a head-mounted display, the distance is 15 mm.
The luminance value is the luminance measured by the luminance meter when a white image with maximum luminance is displayed on the display device.

In the measurement of the FOV of the image display light guide plate 4020, the luminance is measured by tilting the measurement optical axis of the luminance meter with respect to the display image output part while displaying a white image with maximum luminance on the display device. do. For example, the luminance meter is supported by the goniometer stage or the like so as to be swingable at an appropriate angle from a vertical position with respect to the image display light guide plate 4020 .
The FOV is obtained as an angular range in which luminance equal to or higher than the threshold is obtained, with the luminance corresponding to the disappearance of the white image as a threshold. When the brightness above the threshold is obtained in the range from -θ1 to +θ2, the FOV is θ1+θ2. As for the angle, the angle normal to the image display light guide plate 4020 is assumed to be 0°.

<Third modification>
A third modification of the fourth embodiment will be described.
FIG. 22 is a schematic cross-sectional view showing an example of the image display light guide plate of the third modified example of the fourth embodiment of the present invention.

As shown in FIG. 22, in the image display light guide plate 4024 of the third modified example, the first absorption layer 4004 of the image display light guide plate 4005 of the basic example of the fourth embodiment of the present invention is removed, and the first absorption layer 4004 is removed. A first resin base material (absorbing layer) 4021 and a second resin base material (absorbing layer) 4023 are provided instead of the resin base material 4001 and the second resin base material 4003 .
The following description focuses on points that differ from the basic example of the fourth embodiment of the present invention.

The first resin base material (absorbing layer) 4021 includes a base resin similar to the first resin base material 4001 and a colorant dispersed in the base resin.
As the colorant contained in the first resin base material (absorption layer) 4021, the same colorant as the first absorption layer 4004 in the basic example of the fourth embodiment of the present invention is used. The blending amount of the coloring material is set so that the first resin base material (absorbing layer) 4021 has the same light absorbing property as the first absorbing layer 4004 in the basic example of the fourth embodiment of the present invention.
The second resin base material (absorbing layer) 4023 is configured similarly to the first resin base material (absorbing layer) 4021 .

In the image display light guide plate 4024, the first resin base material (absorption layer) 4021 and the second resin base material (absorption layer) 4023 prepared in the base material preparation process are each formed by kneading a coloring material into each base resin. It is manufactured in the same manner as the image display light guide plate 4005 in the basic example of the fourth embodiment of the present invention, except that the light guide plate 4005 is formed using the same material and the absorption layer forming step is not performed.

The image display light guide plate 4024 is an example in which the absorption layer is formed of the first resin base material (absorption layer) 4021 and the second resin base material (absorption layer) 4023 .
According to the image display light guide plate 4024, the first resin base material (absorption layer) 4021 and the second resin base material (absorption layer) 4023 are absorption layers. Yellowness in light and image light can be reduced.

As described above, according to the third modification of the fourth embodiment of the present invention, it is possible to provide an image display light guide plate that can reduce the influence of yellowing of the transparent material on the displayed image.

In addition, in the basic example and each modified example of the fourth embodiment of the present invention, an example in which the absorption layer is arranged at the outermost part of the light guide plate for image display has been described. However, the absorption layer can reduce the yellowness of the light emitted from the image display light guide plate wherever it is arranged on the optical path of the external light Lo and the image light Ld.

In the basic example and each modified example of the fourth embodiment of the present invention, an example in which the absorbent layer is in contact with the resin base material has been described. However, the absorbing layer may be laminated on a transparent resin film. In this case, for example, after forming the absorbing layer on the resin film, it can be fixed to the arrangement surface via an adhesive agent or the like, which facilitates the formation of the absorbing layer.

In the second modified example, an example in which barrier layers are arranged on the front and back surfaces of the hologram layer has been described. However, for the purpose of blocking moisture or the like permeating through the resin base material and for the purpose of preventing contact between the hologram layer and the resin base material, the barrier layer may be arranged between the resin base material and the hologram layer. .
However, in this case, if the transparent layer sandwiched between the barrier layer and the hologram layer is highly hygroscopic, moisture may permeate through the side surfaces of the transparent layer. Therefore, it is more preferable that the transparent layer between the barrier layer and the hologram layer is made of a material with low hygroscopicity. When the transparent layer between the barrier layer and the hologram layer is hygroscopic, it is more preferable to reduce the thickness of the transparent layer. In this case, since the exposed area of the side surface serving as the permeation port for moisture is reduced, the amount of moisture absorbed can be reduced.

In the second modified example, an example in which the barrier layer is in contact with the hologram layer and the resin substrate has been described. However, the barrier layer may be laminated to a transparent resin film. In this case, for example, after the barrier layer is formed on the resin film, it can be fixed to the resin base material via an adhesive or the like, which facilitates the formation of the barrier layer.

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

[Examples and Comparative Examples of the First Embodiment (Examples 1 to 3, Comparative Examples 1 to 3)]
Examples and comparative examples of the first embodiment will be described below.
Table 1 below shows the structures and evaluation results of the resin substrates used in Examples 1 to 3 and Comparative Examples 1 to 3.

Mitsubishi Chemical…Mitsubishi Chemical Co., Ltd. Kuraray…Kuraray Co., Ltd. Sumitomo Chemical…Sumitomo Chemical Co., Ltd. Asahi Kasei…Asahi Kasei Co., Ltd. Acrylite, Comoglass, Sumivex and Delaglas are registered trademarks of each company.

<Example 1>
Example 1 is an example corresponding to the image display light guide plate 1004 of the basic example of the first embodiment.
As shown in Table 1, an acrylic resin (PMMA) is used as the material of the first resin base material 1001 and the second resin base material 1003 ("resin base material" in Table 1). The plate thicknesses of the first resin base material 1001 and the second resin base material 1003 are both 1 mm.
The hologram layer 1002 is common to each example and each comparative example. Materials for the hologram layer 1002 include bisphenol epoxy resin JER1007 (degree of polymerization n=10.8, epoxy equivalent: 1750 to 2200, trade name of Mitsubishi Chemical) 100 parts by mass, triethylene glycol diacrylate 50 parts by mass and 4, 5 parts by mass of 4′-bis(t-butylphenyl)iodonium hexafluorophosphate and 0.5 parts by mass of 3,3′-carbonylbis(7-diethylamino)coumarin are mixed and dissolved in 100 parts by mass of 2-butanone to form a hologram. It is used as a photosensitive material for The thickness of the hologram layer 1002 is 5 μm. The size of the hologram layer 1002 in plan view is 50 mm×50 mm.

(Substrate manufacturing process)
The first resin base material 1001 and the second resin base material 1003 of Example 1 are manufactured as follows.
100 parts of MMA (methyl methacrylate) is put into a reactor (polymerization vessel) equipped with a cooling pipe, a thermometer and a stirrer, and stirred. After bubbling with nitrogen gas, heating is started. When the internal temperature reaches 80° C., 0.05 part of 2,2′-azobis-(2,4-dimethylvaleronitrile), which is a radical polymerization initiator, is added. After further heating to an internal temperature of 100° C., it is held for 10 minutes. The reactor is then cooled to room temperature to obtain a syrup. The polymerization rate of syrup is about 20% by mass.
After that, 0.2 parts by mass of t-hexyl peroxypivalate and 0.01 parts by mass of sodium dioctylsulfosuccinate are added to the syrup and completely dissolved at room temperature to form a polymerizable raw material.
After removing air dissolved in the polymerizable raw material under reduced pressure, the raw material is injected into a continuous polymerization apparatus equipped with a pair of mirror-finished stainless steel endless belts.

Here, the continuous polymerization apparatus used in this example will be described.
FIG. 8 is a schematic vertical cross-sectional view showing an example of the apparatus for manufacturing a resin substrate of Example 1. As shown in FIG.
As shown in FIG. 8, a continuous polymerization apparatus 1100 has a pair of endless belts 1101 and 1102 arranged vertically. The endless belts 1101, 1102 are tensioned by main pulleys 1103, 1104, 1105, 1106 respectively and driven to run at the same speed. A plurality of carrier rolls 1107 are arranged on the inner circumferences of the endless belts 1101 and 1102, respectively. Each carrier roll 1107 faces each other with the endless belts 1101 and 1102 facing each other interposed therebetween. Each carrier roll 1107 horizontally supports the running endless belts 1101 and 1102, and is perpendicular to the belt running direction of the endless belts 1101 and 1102 (the direction from left to right in the figure) and from the vertical direction of the belt surface to the belt surface. and apply a line load at least once. The line load may be 0.001-10.0 kg/cm. More preferably, the line load is 0.01 kg/cm or more.
The number of times the linear load is applied is preferably as large as possible. As the number of times the linear load is applied increases, the planarity of the obtained resin substrate improves. For example, the number of times the linear load is applied is more preferably 10 times or more.

A raw material injection device 1114 provided in the continuous polymerization apparatus 1100 supplies a polymerizable raw material between the endless belts 1101 and 1102 . The vicinity of both side ends of the endless belts 1101 and 1102 are sealed by two elastic gaskets 1112 .
As the endless belts 1101 and 1102 run, the polymerizable raw material is heated and polymerized by the hot water spray 1109 in the first polymerization zone 1108 . Furthermore, the polymerizable raw material is heated by a hot air heater in a second polymerization zone 1110 provided downstream in the belt running direction to complete the polymerization. The polymerizable raw material is cooled in a downstream cooling zone 1111 provided further downstream in the belt running direction, and then taken out as a plate-like polymer 1113 .

Specific manufacturing conditions for the polymerizable raw material of Example 1 described above are as follows.
In the continuous polymerization device 1100, the interval between the belt surfaces of the endless belts 1101 and 1102 is adjusted to 1.6 mm at the portion where the polymerizable raw material is supplied from the raw material injection device 1114, and the polymerization is completed and the plate-like polymer is taken out. , the interval is continuously adjusted so that the thickness of the plate-like polymer is finally 1 mm.
The line load applied by each carrier roll 1107 in the first polymerization zone 1108 is 0.3 kg/cm. The hot water temperature of the hot water spray 1109 is 80°C. While the polymerizable raw material stays in the first polymerization zone 1108, warm water is continuously applied to the belt inner peripheral surfaces of the endless belts 1101 and 1102. FIG. The residence time of the polymerizable material in the first polymerization zone 1108 is 40 minutes.
In the second polymerization zone 1110, while blowing hot air having a temperature of 120° C. from a hot air heater onto the inner peripheral surface of the belt, the polymerization is completed under the condition that the residence time of the polymerizable raw material is 10 minutes. Thus, a plate-like polymer 1113 having a thickness of 1 mm is obtained.

An evaluation sample 1A of the first resin base material 1001 and the second resin base material 1003 is formed by cutting the plate-like polymer 1113 into a rectangular shape of 200 mm×200 mm. The evaluation sample 1A is used for MC value measurement, arithmetic mean roughness Ra measurement, and thermal shrinkage measurement, which will be described later.
The evaluation sample 1B is formed by cutting the plate polymer 1113 into a rectangular shape of 60 mm×60 mm. The evaluation sample 1B forms the image display light guide plate 1004 and is used for image evaluation (described later) of the image display light guide plate 1004 .

Next, the manufacturing process of the image display light guide plate 1004 in Example 1 will be described. The image display light guide plate 1004 is manufactured by performing the substrate preparation step and the light guide plate manufacturing step described below in this order.

(Substrate preparation process)
In the substrate preparation process, the acrylic resin evaluation sample 1B of 60 mm×60 mm×1 mm in thickness obtained in the substrate manufacturing process is washed and dried.
Evaluation sample 1B was subjected to ultrasonic cleaning for 5 minutes while being immersed in a 5% surfactant aqueous solution of Semiclean (registered trademark) M-LO (trade name; manufactured by Yokohama Yushi Kogyo Co., Ltd.), which is a neutral detergent. be.
After that, the evaluation sample 1B is ultrasonically cleaned for 5 minutes while being immersed in ultrapure water. Further, the evaluation sample 1B is rinsed with ultrapure water, air-dried, and then dried in an oven at 100° C. under a nitrogen atmosphere. After that, the air-dried evaluation sample 1B is washed with UV ozone for 1 minute by a UV ozone washing machine.
Thus, the substrate preparation process is completed.

(Light guide plate manufacturing process)
In the light guide plate manufacturing process, the image display light guide plate 1004 is manufactured using the two evaluation samples 1B.
A seal layer having a width of 5 mm and a thickness of 5 μm is applied to the periphery of one evaluation sample 1B. The seal layer is made of a transparent material, and is not particularly limited as long as the material can adhere the evaluation samples 1B to each other.
As a result, an acrylic substrate with a seal layer having a size of 50 mm×50 mm and an opening surrounded by the seal layer is prepared.
Thereafter, an acrylic photosensitive material as a photopolymer material for hologram is applied onto the acrylic substrate by spin coating. The acrylic photosensitive material is applied so as to have a thickness of 5 μm after drying.
After that, the other evaluation sample 1B is laminated on the seal layer and the acrylic photosensitive material, and 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 this, a diffraction grating is recorded in the photopolymer material of the press-laminated laminate. In this step, the temperature of the laminate is kept at 20°C. The diffraction grating forms interference fringes by irradiating the laminated body with two laser beams and adjusting the respective irradiation angles and intensities so that the required diffraction pattern is formed. This records a diffraction grating in the photopolymer material. As a specific diffraction grating, each light in the wavelength regions of red, green, and blue incident as image light incident on the incident portion is diffracted, and is emitted from the display image output portion at positions corresponding to the pixels of the image light. A color display diffraction grating for emitting light is formed.
Thereafter, while the laminate is kept at 20° C., the entire laminate is irradiated with ultraviolet light (wavelength: 365 nm, irradiance: 80 W/cm ² ) from one side for 30 seconds. A high-pressure mercury lamp is used as a light source for ultraviolet light.
As a result, the acrylic photosensitive material is cured, and the image display light guide plate 1004 of Example 1 is formed.

<Example 2>
Example 2 is an example corresponding to the image display light guide plate 1014 of the first modification of the first embodiment.
As shown in Table 1, Example 2 is the same as Example 1 except that both sides of the first resin base material 1001 in the thickness direction were hard coated.
An evaluation sample 1A of Example 2 is formed by applying a hard coat, which will be described later, to both surfaces of the evaluation sample 1A of Example 1 in the thickness direction.
An evaluation sample 1B of Example 2 is manufactured in the same manner as in Example 1, except that the evaluation sample 1A of Example 2 is used instead of the evaluation sample 1A of Example 1. Therefore, unlike the mode shown in FIG. 7 of the first modified example, the first hard coat layer 1011A and the second hard coat layer 1011B are also laminated on the second resin base material 1003 .
The substrate manufacturing process of Example 2 will be described below, focusing on the differences from Example 1. FIG.

(Substrate manufacturing process)
The abbreviations used below are explained.
"C6DA" means 1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name; Viscoat #230).
"U6HA" is a urethane compound obtained by reacting 3 mol of 3-acryloyloxy-2-hydroxypropyl methacrylate with 1 mol of triisocyanate obtained by trimerizing hexamethylene diisocyanate (Shin-Nakamura Chemical Co., Ltd. product, trade name; NK Oligo U-6HA).
"M305" means a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Toagosei Co., Ltd., trade name; Aronix (registered trademark) M-305).

60 parts by weight of C6DA, 30 parts by weight of U6HA, 10 parts by weight of M305, 0.5 parts by weight of bis (2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide, 1-hydroxy-cyclohexyl-phenyl- Five parts by mass of ketone are mixed to prepare a hard coat liquid.
This hard coat liquid is applied to the endless belts 1101 and 1102 of the continuous polymerization apparatus 1100 in a thickness of 20 μm. After that, a hard coat is formed on the endless belt by irradiating ultraviolet light using a high-pressure mercury lamp with an irradiance of 120 W/cm ² to cure the hard coat liquid.
Polymerization of the resin substrate was carried out in the same manner as in Example 1 except that the hard coat was formed on the endless belts 1101 and 1102, thereby forming a 1 mm-thick plate-shaped polymer with a hard coat laminated on the surface. 1113 is obtained.

Evaluation samples 1A and 1B of Example 2 are formed from the plate-like polymer 1113 of Example 2 in the same manner as in Example 1.

<Example 3>
Example 3 is an example corresponding to the image display light guide plate 1004 of the basic example of the first embodiment.
As shown in Table 1, Example 3 is the same as Example 1 except that a cut-and-polished acrylic plate is used as the resin base material. The resin base material in Example 3 was obtained by processing Acrylite (registered trademark) L, which is a continuous cast acrylic plate having a thickness of 2 mm, to a thickness of 1 mm by cutting and polishing.

<Comparative Examples 1 to 3>
As shown in Table 1, Comparative Examples 1 to 3 are the same as Example 1, except that an existing extruded acrylic plate is used as the resin substrate. For this reason, the substrate manufacturing process of each comparative example is performed by extrusion molding, which is different for each manufacturer.
As the resin substrate in Comparative Example 1, Comoglass (registered trademark) P (trade name; manufactured by Kuraray Co., Ltd.), which is an extruded acrylic plate having a thickness of 3 mm, is used.
As the resin substrate in Comparative Example 2, Semipex (registered trademark) E (trade name; manufactured by Sumitomo Chemical Co., Ltd.), which is an extruded acrylic plate having a thickness of 3 mm, is used.
As the resin substrate in Comparative Example 3, Delaglas (registered trademark) A (trade name; manufactured by Asahi Kasei Corporation), which is an extruded acrylic plate having a thickness of 3 mm, is used.
In each comparative example, evaluation samples 1A and 1B having the same shape as that of Example 1 except that the thickness is 3 mm are prepared.
The light guide plate manufacturing process in each comparative example is performed in the same manner as in Example 1, except that the evaluation sample 1B of each comparative example is used.

<Evaluation method>
Next, evaluation methods for Examples 1 to 3 and Comparative Examples 1 to 3 will be described. As evaluations, MC value, Ra, heat shrinkage rate, and clarity of displayed image are evaluated.

(MC value)
Evaluation of the MC value is performed by the evaluation method described in the "Mode for Carrying Out the Invention" of this specification. As the measurement sample S, the evaluation sample 1A of each example and each comparative example is used.
As specific evaluation conditions, the distances d1 and d2 are each set to 1 m, and the elevation angle _θA is set to 20°.
Since Comparative Examples 1 to 3 have a gear mark, the evaluation sample 1A of each Comparative Example is arranged in the evaluation device 1200 in such a posture that the gear mark faces the Y direction.
In contrast, no gear mark is seen in Examples 1-3. However, in order to align the directionality at the time of manufacture, the evaluation samples 1A of each example are arranged so that the direction perpendicular to the traveling direction in the continuous polymerization apparatus 1100 is oriented in the Y direction.
The measurement range of the lightness distribution is such that the Y direction in the arrangement of the evaluation sample 1A in the evaluation device 1200 is the horizontal direction (the direction in which the line segments AD and BC extend), and the vertical direction (the direction perpendicular to the horizontal direction) is the vertical direction (line A rectangular area having a width of 180 mm in the vertical direction and a width of 80 mm in the horizontal direction (directions in which parts AB and DC extend).
The measurement range is provided at 41 points on the measurement sample S with a lateral shift of 2 mm. In each measuring range, the measuring lines are chosen to divide the measuring range horizontally into 40 equal parts.
Table 1 lists the maximum MC value obtained from the brightness distribution of each measurement line in each measurement range.

(Ra)
In evaluating Ra, the arithmetic mean roughness Ra of the surface of each evaluation sample 1A is measured.
As a measuring device, a white interference type surface profiler Zygo NewView (registered trademark) 6300 (trade name; manufactured by Zygo Corporation) is used. A magnification of 2.5 times is used for the objective lens. The observation range is a rectangular range of 2.8 mm×2.1 mm.

(Thermal shrinkage rate)
The thermal shrinkage rate is evaluated by measuring the dimensional change (shrinkage) in accordance with JIS K 6718:2015 Appendix A "Measurement of dimensional change (shrinkage) during heating".

(Clearness of display image)
The image display light guide plates of Examples 1 to 3 and Comparative Examples 1 to 3 are attached to an image display device. The image display device is provided with an optical system for causing image light for display to enter the incident portion of the image display light guide plate 1004, a drive power source, and a circuit system for supplying image information and the like for obtaining image light. .
As input images used for evaluation, a white image and a character display image are used.
The evaluation is performed by visually judging how the white image and the character display image look. As the character image, "ABCDE" within a size of 10 mm×100 mm is displayed. If 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 (described as "A" in Table 1).
If a rainbow color is slightly visible in the white image, but the characters are clearly visible in the character display image, it is determined as fair (described as "B" in Table 1).
If a rainbow color appears at least partially in the white image, and if the outline of the character appears blurred in the character display image, it is judged as not good (described as "C" in Table 1).

<Evaluation results>
As shown in Table 1, the MC values of Examples 1 to 3 are 0.074, 0.103 and 0.060, respectively, all of which are less than 0.120. On the other hand, the MC values of Comparative Examples 1 to 3 are 0.126, 0.183 and 0.148, respectively, and all exceed 0.120.
Examples 1-3 have no observable gear marks and corresponding MC values of less than 0.120. The reason for this is believed to be that the resin base material of each example is manufactured by a continuous casting method, or by cutting and polishing. In the continuous casting method, for example, the surface shape of the endless belts 1101 and 1102 is transferred to the surface of the raw material of the resin base material of each example. Therefore, the flatness of the surface of the resin base material is equivalent to the flatness of the endless belts 1101 and 1102 . By cutting and polishing, the flatness of the surface of the resin substrate can be made extremely high.
On the other hand, since gear marks are observed in Comparative Examples 1 to 3, it is considered that the MC values are increased by the gear marks. The reason why the gear marks are formed in Comparative Examples 1 to 3 is, for example, that the rolls in contact with the extruded material in the extruder are driven unevenly.

The arithmetic mean roughness Ra of Examples 1 to 3 are 4.9 nm, 4.7 nm and 2.6 nm, respectively, and all are less than 10 nm. On the other hand, the Ra values of Comparative Examples 1 to 3 are 5.5 nm, 2.9 nm, and 2.3 nm, respectively, and are all less than 10 nm. Therefore, in terms of smoothness represented by Ra, Examples 1-3 do not differ significantly from Comparative Examples 1-3.

The thermal shrinkage rates of Examples 1 to 3 are all less than 3%. In contrast, the heat shrinkage rates of Comparative Examples 1 to 3 are all 3% or more. The reason for this is thought to be that strain was accumulated in the resin substrates of Comparative Examples 1 to 3, which were produced by extrusion molding.

The sharpness of the displayed images of Examples 1 to 3 is all judged to be "good (A)". On the other hand, the sharpness of the display images of Comparative Examples 1 to 3 are all determined as "improper (C)". The reason for this is considered to be that in Comparative Examples 1 to 3, the MC values are larger than those in each of the Examples, and thus the diffraction direction of the image light is disturbed.
For example, the resin base materials of Comparative Examples 2 and 3 have lower Ra than those of Examples 1 and 2, and therefore are superior to Examples 1 and 2 in terms of smoothness. (that is, MC value) contributes greatly. At least, if Ra is 10 nm or less, it is considered that there is no significant difference in the magnitude of Ra in sharpness.

[Example of Second Embodiment]
Examples of the second embodiment will be described below.
Tables 2A to 2C below show the structures of the resin substrates and barrier layers used in Examples 4 to 7 and 12 to 21, and the evaluation results.

In the "auxiliary layer" column of Table 2B, "EVOH type" indicates "ethylene vinyl alcohol type" and "F type" indicates "fluorine type".

<Example 4>
Example 4 is an example corresponding to the image display light guide plate 2006 of the basic example of the second embodiment.
As shown in Table 2A, an acrylic resin (PMMA) is used as the material of the first resin base material 2001 and the second resin base material 2005 ("resin base material" in Table 2A).
The shapes of the first resin base material 2001 and the second resin base material 2005 are both rectangular plates of 60 mm×60 mm×1 mm.
The first barrier layer 2002 and the second barrier layer 2004 (“barrier layer” in Table 2B) of this example are DLC films with a layer thickness of 40 nm.
The hologram layer 2003 is common to Examples 4-7 and 11-20. The material for the hologram layer 2003 is 100 parts by mass of bisphenol-based epoxy resin JER (registered trademark) 1007 (degree of polymerization n=10.8, epoxy equivalent: 1750 to 2200, trade name of Mitsubishi Chemical), and 50 parts of triethylene glycol diacrylate. Parts by mass and 5 parts by mass of 4,4′-bis(t-butylphenyl)iodonium hexafluorophosphate and 0.5 parts by mass of 3,3′-carbonylbis(7-diethylamino)coumarin to 100 parts by mass of 2-butanone It is used as a photosensitive material for holograms by mixing and dissolving. The thickness of the hologram layer 2003 is 5 μm. The size of the hologram layer 2003 in plan view is 50 mm×50 mm.

Next, the manufacturing process of the image display light guide plate 2006 in Example 4 will be described. The image display light guide plate 2006 is manufactured by sequentially performing a substrate preparation step, a barrier layer forming step, and a light guide plate manufacturing step, which will be described below.

(Substrate preparation process)
In the substrate preparation step, the first resin base material 2001 and the second resin base material 2005 are washed and dried. Hereinafter, when there is no need to distinguish between the first resin base material 2001 and the second resin base material 2005, the reference numerals will be omitted and they will simply be referred to as resin base materials.
The resin substrate was ultrasonically cleaned for 5 minutes while immersed in a 5% surfactant aqueous solution of Semiclean (registered trademark) M-LO (trade name; manufactured by Yokohama Yushi Kogyo Co., Ltd.), which is a neutral detergent. be. After that, the resin substrate is ultrasonically cleaned for 5 minutes while being immersed in ultrapure water. Furthermore, the resin substrate is rinsed with ultrapure water, and after air-drying, the resin substrate is dried in an oven at 100° C. under a nitrogen atmosphere. After that, the air-dried evaluation sample 2B is washed with UV ozone for 1 minute by a UV ozone washing machine.
Thus, the substrate preparation process is completed.

(Barrier layer forming step)
In the barrier layer forming step, a DLC film is formed on the surface of the resin base material.
A resin base material was placed in a plasma chemical vapor deposition apparatus equipped with a space volume of 350 cm ³ , a high frequency power source (13.56 MHz), an internal electrode (φ10 mm) (also used as a gas introduction pipe, tip hole φ1 mm), and evacuation was performed. done. After the pressure of the plasma chemical vapor deposition apparatus reached 15 Pa, a 2:1 mixed gas of high-purity acetylene and tetramethylsilane was introduced at a flow rate of 45 sccm, and the film was formed under the conditions of a plasma generation setting power of 100 W and a film forming time of 0.8 seconds. A 40 nm-thick DLC film is formed.
Thus, the barrier layer forming process is completed.
Below, the resin base material with which the barrier layer was formed is called an intermediate|middle laminated body.

(Light guide plate manufacturing process)
In the light guide plate manufacturing process, the image display light guide plate 2006 is manufactured using two intermediate laminates.
A seal layer having a width of 5 mm and a thickness of 5 μm is applied to the periphery of the barrier layer of one of the intermediate laminates.
The seal layer is made of a transparent material, and is not particularly limited as long as it is a material capable of bonding the barrier layers of the intermediate laminate to each other. ; manufactured by Denki Kagaku Kogyo Co., Ltd.) is used.
As a result, an intermediate laminated body with a stepped sealing layer having an opening surrounded by the sealing layer and having a size of 50 mm×50 mm is prepared.
After that, the photosensitive material as a hologram photopolymer material is applied onto the intermediate laminate by spin coating. The photosensitive material is applied so as to have a thickness of 5 μm after drying.
Thereafter, the other intermediate laminate is laminated on the seal layer and the photosensitive material so that the barrier layer faces the barrier layer of the intermediate laminate with the seal layer, and 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, a diffraction grating is recorded on the photosensitive material of the press-laminated laminate. In this step, the temperature of the laminate is kept at 20°C. The diffraction grating forms interference fringes by irradiating the laminated body with two laser beams and adjusting the respective irradiation angles and intensities so that the required diffraction pattern is formed. Thereby, a diffraction grating is recorded on the photosensitive material.
A specific diffraction grating diffracts each light in the wavelength regions of red, green, and blue incident as image light incident on the incident portion, and emits the light from the display portion at positions corresponding to the pixels of the image light. A diffraction grating for color display is formed.
Thereafter, while the laminate is kept at 20° C., the entire laminate is irradiated with ultraviolet light (wavelength: 365 nm, irradiance: 80 W/cm ² ) from one side for 30 seconds. A high-pressure mercury lamp is used as a light source for ultraviolet light.
As a result, the sealing layer is cured, and the image display light guide plate 2006 of Example 3 is formed.

<Example 5>
Example 5 has the same configuration as Example 4, except that each DLC film is made of silicon oxide with a thickness of 10 nm.
The substrate manufacturing process of Example 5 will be described below, focusing on the differences from Example 4. FIG. The image display light guide plate 2006 of Example 5 is manufactured by performing, in this order, a substrate preparation step similar to Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step similar to Example 4. be done.

(Barrier layer forming step)
In the barrier layer forming step of this embodiment, a silicon oxide thin film layer is formed on the surface of the resin substrate. After the resin substrate is placed in the vacuum deposition device, vacuum deposition of silicon oxide is performed. The ultimate vacuum degree of the chamber of the vacuum deposition apparatus is set to 1.0×10 ⁻⁴ Torr. Under this vacuum, silicon monoxide with 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 50 nm on the surface of the resin substrate. As a result, an intermediate laminate having a silicon oxide thin film layer formed thereon is obtained.
Thus, the barrier layer forming process is completed.

The light guide plate manufacturing process of this example is the same as the light guide plate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer forming process described above is used, and thus description thereof is omitted.

<Examples 6 and 7>
As shown in Table 2A, Examples 6 and 7 are similar to Example 5 except for the placement of the barrier layer.
12 is a schematic cross-sectional view showing an image display light guide plate of Example 6. FIG. 13 is a schematic cross-sectional view showing an image display light guide plate of Example 7. FIG.
The points different from the fifth embodiment will be mainly described below.

As shown in FIG. 12, in the image display light guide plate 2101 of Example 6, the first barrier layer 2002, the first resin base material 2001, the hologram layer 2003, the second resin base material 2005, and the second barrier layer 2004 are They are stacked in order.
As the first barrier layer 2002 and the second barrier layer 2004, a silicon oxide thin film layer with a thickness of 50 nm, which is the same as that of the fifth embodiment, is used.
To manufacture the image display light guide plate 2101, an intermediate laminate is formed in the same manner as in Example 5. After that, a sealing layer is provided on the resin substrate of one intermediate laminate, and a photosensitive material is applied, and then the other intermediate laminate is laminated so that the resin substrates face each other. After that, the image display light guide plate 2101 is manufactured by carrying out pressure reduction pressing and formation of a diffraction grating in the same manner as in the fifth embodiment.

As shown in FIG. 13, the image display light guide plate 2102 of Example 7 has a third barrier layer covering the entire side surface (peripheral surface in the direction orthogonal to the thickness direction) of the image display light guide plate 2101 of Example 6. It is the same as Example 6 except that 2032 is provided.
The third barrier layer 2032 consists of a silicon oxide thin film layer similar to the first barrier layer 2002 of the sixth embodiment.
The image display light guide plate 2102 is manufactured by manufacturing the image display light guide plate 2101 and then forming a silicon oxide thin film layer on the side surface thereof.

<Example 12>
Example 12 has the same configuration as Example 4, except that each DLC film is made of alumina with a thickness of 40 nm.
The substrate manufacturing process of the twelfth embodiment will be described below, focusing on the differences from the fourth embodiment.
The image display light guide plate 2006 of Example 12 is manufactured by performing, in this order, a substrate preparation step similar to that of Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step of Example 4. .

(Barrier layer forming step)
In the barrier layer forming step of this embodiment, an alumina film is formed on the surface of the resin base material.
An appropriate amount of alpha-alumina particles having a purity of 99.999% and a particle size of 2 mm are placed in an electron beam vapor deposition apparatus as a resin base material and a vapor deposition source, and the apparatus is evacuated. The distance from the vapor deposition source to the shutter is approximately 8 cm, and the distance from the vapor deposition source to the surface of the resin substrate is approximately 35 cm.
After the pressure of the electron beam evaporator reaches 3×10 ⁻³ Pa, the electron beam filament current is increased to about 35 mA, the shutter is opened, and alumina film formation is performed. When the wall surface temperature in the apparatus reaches 50° C., the shutter is closed to stop the filament current of the electron beam. After cooling to 30° C. or less, the electron beam filament current is increased to about 35 mA to heat the vapor deposition source, 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.

The light guide plate manufacturing process of this example is the same as the light guide plate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer forming process described above is used, so the description thereof will be omitted.

<Example 13>
Example 13 has the same configuration as Example 4, except that each DLC film is made of silicon oxide with a thickness of 70 nm.
The substrate manufacturing process of the thirteenth embodiment will be described below, focusing on the differences from the fourth embodiment.
The image display light guide plate 2006 of Example 13 is manufactured by performing, in this order, a substrate preparation step similar to that of Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step similar to that of Example 4. be done.

(Barrier layer forming step)
In the barrier layer forming step of this embodiment, silicon oxide is formed on the surface of the resin base material. A resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a high frequency power supply (13.56 MHz) and vacuum evacuation is performed. After the pressure in the plasma chemical vapor deposition apparatus reached 1 Pa, tetraethoxysilane (TEOS) gas generated by bubbling helium gas was introduced at a flow rate of 6 sccm and oxygen gas was introduced at a flow rate of 95 sccm, and plasma generation power was set to 250 W. A silicon oxide film having a film thickness of 70 nm is formed under the conditions of .
Thus, the barrier layer forming process is completed.

The light guide plate manufacturing process of this example is the same as the light guide plate manufacturing process of Example 4, except that the intermediate laminate formed in the barrier layer forming process described above is used, and thus description thereof is omitted.

<Example 14>
Example 14 has the same configuration as Example 4, except that the silicon oxide film is made of silicon oxide with a thickness of 140 nm.
The substrate manufacturing process of the fourteenth embodiment will be described below, focusing on the differences from the fourth embodiment.
The image display light guide plate 2006 of Example 14 is manufactured by performing, in this order, a substrate preparation step similar to that of Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step similar to that of Example 4. be done.

(Barrier layer forming step)
In the barrier layer forming step of this embodiment, silicon oxide is formed on the surface of the resin base material. A resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a high frequency power source (13.56 MHz) and vacuum evacuation is performed. After the pressure of the plasma chemical vapor deposition apparatus reached 1 Pa, the TEOS gas generated by bubbling with helium gas was introduced at a flow rate of 6 sccm and the oxygen gas was introduced at a flow rate of 95 sccm, and the film thickness was formed under the conditions of the plasma generation setting power of 250 W. A silicon oxide film of 140 nm is formed.
Thus, the barrier layer forming process is completed.

The light guide plate manufacturing process of this embodiment is the same as the substrate manufacturing process of Embodiment 4, except that the intermediate laminate formed in the barrier layer forming process described above is used, so description thereof will be omitted.

<Example 15>
Example 15 has the same configuration as Example 4, except that the silicon oxide film is made of silicon oxide with a thickness of 170 nm.
The substrate manufacturing process of the fifteenth embodiment will be described below, focusing on the differences from the fourth embodiment.
The image display light guide plate 2006 of Example 15 is manufactured by performing, in this order, a substrate preparation step similar to that of Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step similar to that of Example 4. be done.

(Barrier layer forming step)
In the barrier layer forming step of this embodiment, silicon oxide is formed on the surface of the resin base material. A resin substrate is placed in a plasma chemical vapor deposition apparatus equipped with a high frequency power source (13.56 MHz) and vacuum evacuation is performed. After the pressure in the plasma chemical vapor deposition apparatus reached 1 Pa, the TEOS gas generated by bubbling with helium gas was introduced at a flow rate of 6 sccm and the oxygen gas was introduced at a flow rate of 95 sccm, and the film thickness was formed under the conditions of a plasma generation setting power of 250 W. A silicon oxide film of 170 nm is formed.
Thus, the barrier layer forming process is completed.

The light guide plate manufacturing process of this embodiment is the same as the substrate manufacturing process of Embodiment 4, except that the intermediate laminate formed in the barrier layer forming process described above is used, so description thereof will be omitted.

<Example 16>
Example 16 has the same configuration as Example 14, except that the barrier layer has an auxiliary layer. The substrate manufacturing process of Example 16 will be described below, focusing on the differences from Example 14. FIG.
The image display light guide plate 2006 of Example 16 is manufactured by carrying out, in this order, a substrate preparation step similar to Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step similar to Example 4. be done.

(Barrier layer forming step)
In the barrier layer forming step of this example, an auxiliary layer is formed on the surface of the inorganic material layer produced by the same method as in the fourteenth example. N-Phenyl-3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd. KBM-573) was added to an ethylene-vinyl alcohol copolymer aqueous solution to give a solid content concentration of 10% by weight based on the total solid content in the protective coat. Auxiliary coating agent 1 was prepared. An auxiliary coating agent 1 is applied to the surface of the inorganic material layer and dried to form an auxiliary layer having a thickness of 0.5 μm.
Thus, the barrier layer forming process is completed.

The light guide plate manufacturing process of this embodiment is the same as the substrate manufacturing process of Embodiment 4, except that the barrier layer having the multilayer structure formed in the barrier layer forming process described above is used, so the description thereof is omitted.

<Example 17>
Example 17 has the same configuration as Example 14, except that the barrier layer has a fluorine-based waterproof and moisture-proof coating layer as an auxiliary layer.
The substrate manufacturing process of the seventeenth embodiment will be described below, focusing on the differences from the fourteenth embodiment.
The image display light guide plate 2006 of Example 17 is manufactured by performing, in this order, a substrate preparation step similar to that of Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step similar to that of Example 4. be done.

(Barrier layer forming step)
In the protective layer forming step of this example, a fluorine-based waterproof and moisture-proof coating layer is formed on the surface of the barrier layer produced in the same manner as in Example 14.
Thus, the barrier layer forming process is completed.

The substrate manufacturing process of this embodiment is the same as the substrate manufacturing process of Embodiment 4 except that the barrier layer having a multilayer structure formed in the barrier layer forming process described above is used.

<Example 18>
Example 18 has the same configuration as Example 14, except that an anchor coat layer is arranged between the barrier layer and the resin substrate.
The substrate manufacturing process of the eighteenth embodiment will be described below, focusing on the differences from the fourteenth embodiment.
The image display light guide plate 2006 of Example 18 includes a substrate preparation process similar to that of Example 14, an anchor coat layer forming process and a barrier layer forming process described later, and a light guide plate manufacturing process similar to that of Example 4. It is manufactured by performing in this order.

(Anchor coat layer forming step)
In the anchor coat layer forming step of this embodiment, an anchor coat layer is formed on the surface of the resin substrate. A saturated polyester (Vylon 300, manufactured by Toyobo Co., Ltd.) and an isocyanate compound (Coronate L, manufactured by Tosoh Corporation) were blended at a mass ratio of 1:1 to prepare an anchor coating agent. An anchor coating agent was applied to the corona-treated surface of the resin substrate and dried to form an anchor coating layer having a thickness of 100 nm.
Thus, the anchor coat layer process is completed.

(Barrier layer forming step)
A barrier layer is formed on the anchor coat layer in the same manner as in Example 14.

The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4, except that the intermediate laminate formed in the above-described anchor coat layer forming process and barrier layer forming process is used, so description thereof will be omitted. .

<Example 19>
Example 19 has the same configuration as Example 16, except that an anchor coat layer is arranged between the barrier layer and the resin substrate.
The substrate manufacturing process of Example 19 will be described below, focusing on the differences from Example 16. FIG.
The image display light guide plate 2006 of Example 19 includes a substrate preparation process similar to that of Example 4, an anchor coat layer forming process, an inorganic material layer forming process, and a barrier layer forming process described later, and a guide similar to that of Example 4. The light plate manufacturing process is performed in this order.

(Anchor coat layer forming step)
An anchor coat layer is formed on the surface of the resin substrate in the same manner as in Example 18.

(Inorganic material layer forming step)
An inorganic material layer is formed on the anchor coat layer in the same manner as in Example 14.

(Barrier layer forming step)
An auxiliary layer is formed on the surface of the inorganic material layer in the same manner as in Example 16 to form a barrier layer.

The light guide plate manufacturing process of this example is the same as the substrate manufacturing process of Example 4, except that the intermediate laminate formed in the above-described anchor coat layer forming process, inorganic material layer forming process, and barrier layer forming process is used. Therefore, the explanation is omitted.

<Example 20>
Example 20 has the same configuration as Example 4, except that each silicon oxide film is made of silicon oxide having a thickness of 100 nm formed by a sputtering method.
The substrate manufacturing process of Example 20 will be described below, focusing on the differences from Example 4. FIG.
The image display light guide plate 2006 of Example 20 is manufactured by performing, in this order, a substrate preparation step similar to that of Example 4, a barrier layer forming step to be described later, and a light guide plate manufacturing step similar to that of Example 4. be done.

(Barrier layer forming step)
In the barrier layer forming step of this embodiment, a silicon oxide film is formed on the surface of the resin base material. A silicon oxide film having a thickness of 100 nm is formed by a sputtering method under a vacuum pressure of 4.0×10 ⁻⁵ Torr.

The light guide plate manufacturing process of this embodiment is the same as the substrate manufacturing process of Embodiment 4, except that the intermediate laminate formed in the barrier layer forming process described above is used, so description thereof will be omitted.

<Example 21>
Example 21 has the same configuration as Example 20, except that an anchor coat layer is arranged between the barrier layer and the resin base material.
The substrate manufacturing process of Example 21 will be described below, focusing on the differences from Example 20. FIG.
The image display light guide plate 2006 of Example 21 includes a substrate preparation process similar to that of Example 20, an anchor coat layer forming process similar to that of Example 18, a barrier layer forming process described later, and a barrier layer forming process similar to that of Example 20. and a light guide plate manufacturing step in this order.

(Barrier layer forming step)
A barrier layer is formed on the anchor coat layer in the same manner as in Example 20.

The light guide plate manufacturing process of this embodiment is the same as the substrate manufacturing process of Embodiment 20, except that the intermediate laminate formed in the barrier layer forming process described above is used, and thus description thereof is omitted.

<Evaluation method>
Next, an evaluation method for each example will be described. The evaluation includes luminance value measurement, FOV evaluation, and sharpness evaluation of the displayed image.

(Brightness value)
The samples for measuring the luminance value are samples subjected to the humidification test (“after humidification” in Table 2C), samples subjected to the heating test (“after heating” in Table 2C), and samples not subjected to the humidification test or the heating test (Table 2C). In 2C, three types of "initial") are prepared.
A small environmental tester SH-241 (trade name; manufactured by Espec Co., Ltd.) is used for the humidification test and the heating test.
The test conditions for the humidification test are 60° C., 90% RH, and 500 hours.
The test conditions for the heating test are 85° C. and 500 hours.
The luminance value of the measurement sample is determined based on the measurement method described above in the embodiment. Each measurement sample is assembled into the display device described above.
As the luminance meter 2014, a luminance meter BM-8 (trade name; manufactured by Topcon Corporation) is used. The measurement angle is 1°. A distance d from the display surface 2003a is 15 mm.
If the luminance value is 3500 nit or more, it is determined to be very good (described as "S" in Table 2C).
If the luminance value is 3000 nit or more and less than 3500 nit, it is determined to be good (described as "A" in Table 2C).
If the luminance value is 1000 nit or more and less than 3000 nit, it is determined to be fair (described as "B" in Table 2C).
If the luminance value is less than 1000 nit, it is determined as not good (not good, indicated as "C" in Table 2C).

(FOV)
The measurement of the FOV is performed using a display device assembled from samples for luminance value measurement that are not subjected to a humidification test or a heating test.
The FOV measurement is performed based on the measurement method described above in the embodiment.
As the luminance meter 2014, a luminance meter BM-8 (trade name; manufactured by Topcon Corporation) is used. The measurement angle is 1°. A distance d from the display surface 2003a is 15 mm.
If the FOV is 45° or more, it is judged to be very good (denoted as "S" in Table 2C).
If the FOV is 35° or more and less than 45°, it is determined to be good (described as "A" in Table 2C).
If the FOV is 24° or more and less than 35°, it is determined to be fair (described as "B" in Table 2C).
If the FOV is less than 24°, it is judged as no good (described as "C" in Table 2C).

(Vividness)
The sharpness of the displayed image is made with the display device used for the FOV measurement.
A white image and a character display image are used as input images for evaluation.
The evaluation is performed by visually judging how the white image and the character display image look. As the character image, "ABCDE" within 10 mm×100 mm is displayed.
If 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 (described as "A" in Table 2C).
If a rainbow color is slightly visible in the white image, but the characters are clearly visible in the character display image, it is determined to be fair (described as "B" in Table 2C).
If a rainbow color appears at least partially in the white image, and if the outline of the character appears blurred in the character display image, it is judged as not good (described as "C" in Table 2C).

<Evaluation results>
As shown in Table 2C, the luminance values of Examples 4, 5 and Examples 12-21 are all rated as "S" or "A" regardless of whether the humidification test or heat test is performed.
The reason for this is that, in these examples, the barrier layer prevents moisture from penetrating into the hologram layer and suppresses the hologram layer from corroding the resin base material. It is considered that this is because the optical path is not disturbed on the resin substrate.
Further, in these examples, since the hologram layer is not in contact with the resin base material, the material of the hologram layer does not erode the resin base material even when heated.
On the other hand, the luminance values of Examples 5 and 6 are inferior to Examples 4 and 5 and Examples 12 to 21 in the measurement samples after either the humidification test or the heating test. When the humidification test and the heating test are not performed, it is evaluated as "B", which is a practical level.

As shown in Table 2C, the FOV of Examples 4, 5 and Examples 12-21 are rated "S" and "A", respectively.
On the other hand, the FOVs of Examples 6 and 7 were evaluated as "C" and were at a practical level. The reason for this is considered to be the same as the reason for the difference in luminance value evaluation described above. In other words, in Examples 4 and 5 and Examples 12 to 21, the barrier layer prevents the penetration of water into the hologram layer and the corrosion of the resin substrate at a very high level, and as a result, the FOV is not lowered. .
It is believed that the FOV of Example 4 is even better than that of Example 5 due to the difference in barrier layer materials. Since the DLC film has a higher refractive index than the silicon oxide thin film layer, it is considered that the FOV becomes larger and becomes better.

Furthermore, the sharpness of the displayed images of Examples 4 and 5 and Examples 12 to 21 ("clearness" in Table 2C) was all judged to be "A", which was better than the results of Examples 6 and 7. is.
The reason for this is considered to be the same as the reason for the difference in luminance value evaluation described above. That is, in Examples 4 and 5 and Examples 12 to 21, the barrier layer prevented water from penetrating into the hologram layer and eroding the resin substrate at a very high level, and as a result, clear images were observed. .

[Example of the third embodiment]
Examples of the third embodiment will be described below.

<Example 8>
(Preparation of first substrate and second substrate)
Two acrylic resin plates (manufactured by Mitsubishi Chemical Corporation) processed to 60 mm × 60 mm × 1 mm (thickness) were immersed in a 5% surfactant aqueous solution of Semi-Clean M-L0 (manufactured by Yokohama Yushi Kogyo Co., Ltd.). Ultrasonic cleaning is performed for 5 minutes in this state. After that, ultrasonic cleaning is performed for 5 minutes while being immersed in ultrapure water. Furthermore, it is rinsed with ultrapure water, air-dried, and then dried in an oven at 100° C. under a nitrogen atmosphere. After that, the air-dried substrates are washed with UV ozone for 1 minute in a UV ozone washing machine to obtain a first substrate and a second substrate.

(Formation of hologram layer)
The hologram layer is common to each example. Materials for the hologram layer include 100 parts by mass of a bisphenol-based epoxy resin (degree of polymerization n=10.8, epoxy equivalent: 1750 to 2200, trade name jER1007 manufactured by Mitsubishi Chemical Corporation), 50 parts by mass of triethylene glycol diacrylate, and 4, 5 parts by mass of 4′-bis(t-butylphenyl)iodonium hexafluorophosphate and 0.5 parts by mass of 3,3′-carbonylbis(7-diethylamino)coumarin are mixed and dissolved in 100 parts by mass of 2-butanone to form a hologram. It is used as a photosensitive material for
A seal layer having a width of 5 mm and a thickness of 5 μm is applied to the periphery of the second substrate. The above photosensitive material, which will be a hologram layer, is applied to the opening of 50 mm×50 mm surrounded by the seal layer by spin coating so that the thickness after drying becomes 5 μm. After the photosensitive material is dried, the first substrate is laminated and press-bonded under reduced pressure (absolute pressure 5 kPa, temperature 70° C., press pressure 0.04 MPa).
Two laser beams are irradiated while the first substrate and the second substrate in which the photosensitive material is encapsulated are kept at 20°C. By adjusting the irradiation angle and intensity of each laser beam, interference fringes are formed by the interference, and a desired diffraction grating is recorded on the photosensitive material to form a hologram layer.

(Preparation of hard coat film)
As a film substrate, a polyethylene terephthalate biaxially stretched film (product name “Diafoil T612 type”, thickness: 50 μm) manufactured by Mitsubishi Chemical Corporation is prepared.
A curable composition for forming a hard coat layer is prepared using an organic/inorganic hybrid ultraviolet curable resin composition (UVHC7800G manufactured by MOMENTIVE, content of inorganic silica having a reactive functional group: 30 to 40% by mass). do. A cured resin layer obtained by curing this composition has a refractive index of 1.54.
The curable composition is applied to the second surface of the film substrate with a bar coater so that the film thickness after drying becomes 3 μm, and dried by heating at 90° C. for 1 minute. After that, a high-pressure mercury lamp (80 W/cm ² ) is used to irradiate ultraviolet rays with an accumulated light quantity of 400 mJ/cm ² to form a hard coat layer.

Next, a release layer-forming coating solution having the following composition is applied onto the hard coat layer and dried to form a release layer. The thickness of the release layer obtained is 500 nm.
・ Release agent Long-chain alkyl group-containing alkyd resin ("Tesfine" 303, manufactured by Hitachi Chemical Co., Ltd.) 10 parts by mass (in terms of solid content)
・ Acid catalyst p-toluenesulfonic acid (manufactured by Hitachi Chemical Co., Ltd. "Dryer" 900) 0.12 parts by mass (in terms of solid content)
・ Solvent toluene 45 parts by mass

Next, the pressure-sensitive adhesive-forming composition is applied to the first surface of the film substrate so that the film thickness after drying is 0.5 μm, and dried to form the pressure-sensitive adhesive layer.
A pressure-sensitive adhesive-forming composition is prepared as follows.
Per 1 kg of adhesive solution (SK Dyne 1882 manufactured by Soken Chemical Co., Ltd., solid content concentration of about 17%) made of acrylic copolymer, isocyanate cross-linking agent (L-45 manufactured by Soken Chemical Co., Ltd.) 1.85 g, epoxy cross-linking 0.5 g of an agent (E-5XM manufactured by Soken Kagaku Co., Ltd.) is added and uniformly mixed.

The adhesive layer of the obtained hard coat film is bonded to the first substrate and the hard coat film is attached to the first substrate to obtain the light guide plate for image display of Example 8.

<Example 9>
Example 9 differs only in the configuration of the hard coat film. The preparation mode of the hard coat film is shown below.
A mold release layer, a hard coat layer, and an adhesive layer are formed in the same manner as described above on a process release film ("MRA100" manufactured by Mitsubishi Chemical Corporation, thickness 100 μm), and the adhesive layer is bonded to the first substrate. . After the ultraviolet irradiation, the process release film is peeled off to obtain the image display light guide plate of Example 9.

<Evaluation method>
The following evaluations are made for each example.
(Clearness of image display)
Three light guide plates of each example are prepared, hologram layers are formed so as to diffract light in the red, green, and blue wavelength regions, respectively, and then the three light guide plates are laminated. An image display device, an optical system for inputting displayed information to the light guide plate, and a circuit system for supplying drive power and image information are attached to the laminated light guide plates to assemble the image display device according to each example.
An image in which characters are written on a white background is displayed on the light guide plate. The displayed image is visually observed from the side of the first substrate, and sensory evaluation is performed in the following three stages.
A (good): There is no rainbow-colored part in the image, and the characters are clearly visible B (average): There is a slight rainbow-colored part in the image, but the characters are clearly visible C (bad): Image There is clearly a part that looks like a rainbow in the image, and the contours of the characters also appear blurred. In Examples 8 and 9, after the scratch resistance evaluation, the hard coat film was peeled off, and a new hard coat film was attached, followed by evaluation.

(Scratch resistance)
Steel wool #0000 attached to the cross section of a cylinder with a diameter of 11 mm was reciprocated 10 times at a load of 400 g and 100 mm/sec against the surface of the hard coat film or hard coat layer on the outermost surface of the image display device of each example. After that, the state of the surface of the hard coat film or hard coat layer is observed within a test range of 100 mm in length and 20 mm in width, and evaluated according to the following three stages.
A (good): no scratches B (average): less than 20 scratches C (bad): 20 or more scratches

(Drop resistance)
A hard sphere with a diameter of 50 mm and a weight of 230 g is dropped to collide with the outermost surface side of the image display device of each example. After that, cracks in the first substrate and the second substrate are checked. Evaluation is made into the following two grades. A (good): No cracks are found in either the first substrate or the second substrate.
C (bad): A crack is found in at least one of the first substrate and the second substrate.
(Pencil hardness)
Pencil hardness is measured on the surface to be measured with a load of 750 g according to JIS K 5600-5-4:1999.

Table 3 shows the results of each evaluation.

In Examples 8 and 9, scratches occurred in the hard coat film or hard coat layer in the scratch resistance evaluation. This damage can be prevented from deteriorating in definition by replacing the hard coat film. In the light guide plate for image display of each example, the resin substrate does not crack in the evaluation of drop resistance, so safety is enhanced when applied to a spectacle-type display.

In the light guide plate according to the third embodiment of the present invention, the second substrate may be made of glass instead of resin. Even with such a configuration, the weight can be reduced and the safety of the wearer can be enhanced by, for example, configuring the eyeglass-type display with the first substrate facing the wearer side.
In the light guide plate according to the present invention, a hard coat film may also be attached to the second substrate. In this case, the first substrate and the second substrate may differ in configuration of the hard coat film, the number of laminated layers, and the like.

[Example of the fourth embodiment]
Examples 9 and 10 of the fourth embodiment will be described below. The present invention is not limited by these examples.

Table 4 below shows the structures of the resin base material and absorption layer of each example, and the evaluation results.

<Example 10>
Example 10 is an example corresponding to the image display light guide plate 4005 of the fourth embodiment. As shown in Table 4, acrylic resin (PMMA) is used as the material of the first resin base material 4001 and the second resin base material 4003 ("resin base material" in Table 4).
The shapes of the first resin base material 4001 and the second resin base material 4003 are both rectangular plates of 60 mm×60 mm×1 mm.
Hologram layer 4002 is common to each embodiment. The material of the hologram layer 4002 is 100 parts by mass of bisphenol-based epoxy resin JER (registered trademark) 1007 (degree of polymerization n=10.8, epoxy equivalent: 1750 to 2200, trade name of Mitsubishi Chemical), and 50 parts of triethylene glycol diacrylate. Parts by mass and 5 parts by mass of 4,4'-bis(t-butylphenyl)iodonium hexafluorophosphate and 0.5 parts by mass of 3,3'-carbonylbis(7-diethylamino)coumarin to 100 parts by mass of 2-butanone It is used as a photosensitive material for holograms by mixing and dissolving. The thickness of the hologram layer 4002 is 5 μm. The size of the hologram layer 4002 in plan view is 50 mm×50 mm.

Next, the manufacturing process of the image display light guide plate 4005 in Example 10 will be described. The image display light guide plate 4005 is manufactured by sequentially performing a substrate preparation step, an absorption layer forming step, and a light guide plate manufacturing step described below.

(Substrate preparation process)
In the substrate preparation step, the first resin base material 4001 and the second resin base material 4003 are washed and dried. Hereinafter, when there is no need to distinguish between the first resin base material 4001 and the second resin base material 4003, the reference numerals will be omitted and they will simply be referred to as resin base materials.
The resin substrate was ultrasonically cleaned for 5 minutes while immersed in a 5% surfactant aqueous solution of Semiclean (registered trademark) M-LO (trade name; manufactured by Yokohama Yushi Kogyo Co., Ltd.), which is a neutral detergent. be. After that, the resin substrate is ultrasonically cleaned for 5 minutes while being immersed in ultrapure water. Furthermore, the resin substrate is rinsed with ultrapure water, and after air-drying, the resin substrate is dried in an oven at 100° C. under a nitrogen atmosphere. After that, the air-dried evaluation sample B is washed with UV ozone for 1 minute in a UV ozone washing machine.
Thus, the substrate preparation process is completed.

(Absorptive layer forming step)
In the absorbing layer forming step, the first absorbing layer 4004 (“absorbing layer” in Table 4) is formed on the surface of the first resin base material 4001 .
5 parts by mass of a photopolymerization initiator was added to 100 parts by mass of acrylate (Iupimer (registered trademark) UV-HH2100 (trade name; manufactured by Mitsubishi Chemical Corporation)), and Diarrange (registered trademark) blue was added as a coloring material. 0.05 part by mass is added to prepare a curable resin composition (coating liquid).
This curable resin composition is applied onto the first resin substrate 4001 using a metal bar coater, dried at 90° C. for 1 minute, and then exposed with an exposure amount of 500 mJ/cm ² using an ultraviolet light irradiation device. to obtain a laminate having an absorption layer with a thickness of 5 μm.
With this, the absorption layer forming process is completed.
Hereinafter, the resin base material on which the absorbing layer is formed is referred to as an intermediate laminate.

(Light guide plate manufacturing process)
In the light guide plate manufacturing process, the intermediate laminate and the second resin base material 4003 are used to manufacture the image display light guide plate 4005 .
A seal layer having a width of 5 mm and a thickness of 5 μm is applied to the periphery of the surface of the intermediate laminate opposite to the absorbent layer.
The sealing layer is made of a transparent material, and is not particularly limited as long as it is a material that can bond the resin substrates to each other. Kogyo Co., Ltd.) is used.
As a result, an intermediate laminated body with a stepped sealing layer having an opening surrounded by the sealing layer and having a size of 50 mm×50 mm is prepared.
After that, the photosensitive material as a photopolymer material for hologram is applied onto the intermediate laminate by spin coating. The photosensitive material is applied so that the thickness after drying is 5 μm.
After that, the second resin base material 4003 is laminated on the seal layer and the photosensitive material so as to face the barrier layer of the intermediate laminate 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, a diffraction grating is recorded on the photosensitive material of the laminated body which is press-bonded. In this step, the temperature of the laminate is kept at 20°C. The diffraction grating forms interference fringes by irradiating the laminated body with two laser beams and adjusting the respective irradiation angles and intensities so that the required diffraction pattern is formed. Thereby, a diffraction grating is recorded on the photosensitive material.
A specific diffraction grating diffracts each light in the wavelength regions of red, green, and blue incident as image light incident on the incident portion, and emits the light from the display portion at positions corresponding to the pixels of the image light. A diffraction grating for color display is formed.
Thereafter, while the laminate is kept at 20° C., the entire laminate is irradiated with ultraviolet light (wavelength: 365 nm, irradiance: 80 W/cm ² ) from one side 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 4005 of Example 1 is formed.

<Example 11>
Example 11 is an example corresponding to the image display light guide plate 4007 of the first modification of the fourth embodiment.
As shown in Table 4, in Example 11, absorbent layers are provided on both sides. Specifically, the second absorption layer 4006 is formed on the surface of the second resin base material 4003 opposite to the hologram layer 4002 .
In this example, the second absorbent layer 4006 (“absorbent layer” in Table 4) is constructed similarly to the first absorbent layer 4004 of the tenth example.
Therefore, the substrate preparation process of the eleventh embodiment is similar to that of the tenth embodiment.
The absorbent layer forming step of Example 11 is characterized in that, in addition to the intermediate laminate having the first absorbent layer 4004, an intermediate laminate comprising the second resin substrate 4003 having the second absorbent layer 4006 formed thereon is formed. , different from Example 10.
The light guide plate manufacturing process of Example 11 differs from Example 10 in that two intermediate laminates are used.

<Evaluation method>
Next, an evaluation method for each example will be described. As the evaluation, sharpness evaluation is performed.

(Clearness evaluation)
The clarity of the displayed image is determined using each display device using each light guide plate for image display. Each display device is configured in the same manner as the display device 4010 except that the image display light guide plate of each embodiment is used.
As images used for evaluation, a display image by image light diffracted by the hologram layer and an external light image through which external light is transmitted are used.
A white image and a character image are used as the input image of the display image.
As the external light image, a scene of a room, a city, or a forest at a distance of 0.5 m to 50 m from the display device is used. In the evaluation of the external light image, a white image or a character image is displayed and evaluated.
The evaluation is performed by visually determining how the white image and the character image look and how the external light image looks. As the character image, hiragana, katakana, kanji, Arabic numerals, alphabets, or the like having a size of 0.1 to 2.0 in terms of visual acuity are displayed.

(Criteria for Evaluation of Clearness of Displayed Image)
The sharpness evaluation of the displayed image is performed in three stages.
If the rainbow color is not visible in the white image and the characters are clearly visible in the character image, it is judged to be good (described as "A" in Table 4).
If a rainbow color is slightly visible in the white image, but the characters are clearly visible in the character image, it is determined to be fair (described as "B" in Table 4).
If rainbow colors appear at least partially in the white image and the character outline appears blurred in the character image, it is determined to be no good (described as "C" in Table 4).

(Criteria for Evaluation of Clearness of External Light Image)
The sharpness evaluation of the external light image is performed in four stages.
If the color of the scenery in the external light image can be clearly seen without discomfort, it is judged to be very good (denoted as "S" in Table 4).
If the scenery in the external light image looks a little dark, it is judged to be good (described as "A" in Table 4).
If the scenery in the external light image is dark and there is a slight sense of incongruity in the color, it is determined to be fair (described as "B" in Table 4).
If the scenery due to the external light image looks blurred, it is judged as not good (described as "C" in Table 4).

(Weather resistance test)
As the image display light guide plate used for sharpness evaluation, a sample subjected to a weather resistance test (“after weather resistance test” in Table 4) and a sample not subjected to a weather resistance test (“before weather resistance test” in Table 4). is prepared.
The weather resistance test is performed using an ultraviolet fade meter U48AU (trade name; manufactured by Suga Test Instruments Co., Ltd.). The test conditions are a BP temperature of 63°C ± 3°C. The test time is 500 hours.

<Evaluation results>
As shown in Table 4, the sharpness of Example 10 is evaluated as "A" both before and after the weather resistance test for both the display image and the image under external light. The sharpness of Example 11 is rated "A", except that it is "S" during the weathering test for the ambient light image.
From this evaluation result, it can be seen that in Examples 10 and 11, the clearness of both the display image and the external light image is excellent due to the provision of the absorption layer. In particular, in Example 10, since the absorption layer is also provided on the incident side of external light, the clarity of the external light image is improved compared to Example 10 before the weather resistance test.

Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples. Additions, omissions, substitutions, and other changes in configuration are possible without departing from the scope of the present invention.
Moreover, the present invention is not limited by the foregoing description, but only by the appended claims.

INDUSTRIAL APPLICABILITY The light guide plate for image display of the present invention can display a clear image even when a resin base material is used, and can suppress deterioration of the hologram layer. be. For example, the light guide plate for image display of the present invention is useful for display devices such as entertainment, remote control, work support, and guidance support using head-up displays, wearable displays, and head-mounted displays.

1001 First resin substrate 1001a First surface 1001b Second surface 1002 Hologram layer 1003 Second resin substrate 1004, 1014 Light guide plate for image display 1011A First hard coat layer 1011B Second hard coat layer 1100 Continuous polymerization device 1101, 1102 Endless belts 1103, 1104, 1105, 1106 Main pulley 1107 Carrier roll 1108 First polymerization zone 1109 Hot water spray 1110 Second polymerization zone 1111 Downstream cooling zone 1112 Gasket 1113 Plate polymer 1114 Raw material injection device 1200 Evaluation device 1201 Light source 1202 Screen 1203 Camera 1204 Arithmetic processing section 1210 Curve 2001 First resin base material 2002 First barrier layer 2003 Hologram layer 2003a Display surface 2003b Waveguide diffraction grating section 2003c Display diffraction grating section 2004 Second barrier layer 2005 Second resin base material 2006, 2016 Image display light guide plate 2006a Incident portion 2006d Display portion 2010 Display device 2012 Incidence optical system 2013 Image light projection portion 2014 Luminance meter 2015 Measuring device 2022 First barrier film 2022A Barrier layer 2022B Resin film 2024 Second barrier film 2024A Barrier layer 2024B Resin Film 2026 First adhesive layer 2027 Second adhesive layer 2032 Third barrier layer 2101, 2102 Image display light guide plate 3001 Image display light guide plate (light guide plate)
3010 Hologram layer 3021 First substrate 3022 Second substrate 3030, 3130 Hard coat films 3030A, 3130A First hard coat films 3030B, 3130B Second hard coat film 3031 Film substrate 3031a First surface 3031b Second surface 3032 Adhesive layer 3033 Hard Coat layer 3034 release layer 4001 first resin substrate 4002 hologram layer 4002b display diffraction grating portion 4003 second resin substrate 4003a waveguide diffraction grating portion 4004 first absorption layers 4005, 4007, 4020, 4024 light guide plate for image display 4005a Incident portion 4005b Display image output portion 4006 Second absorption layer 4008 First barrier layer 4009 Second barrier layer 4010 Display device 4011 Incidence optical system 4012 Image light projection portion 4021 First resin substrate (absorption layer)
4023 Second resin base material (absorbing layer)
I Transmitted projection image Ib High brightness area Is Low brightness area Ld Image light Ld' Image light Ld'' Image light Li Image light Lo External light Lo' External light Lo'' External light Lo''' External light O Optical axis P1 1 Intermediate laminate P2 Second intermediate laminate S Measurement sample

Claims (15)

An image display light guide plate comprising a first resin base material and a hologram layer,
The light guide plate for image display, wherein the first resin base material has an MC value of 0.120 or less as evaluated by shadow contrast. A light guide plate for image display, comprising a first resin base material, a first barrier layer, and a hologram layer. 3. The light guide plate for image display according to claim 2, wherein said first resin base material, said first barrier layer and said hologram layer are arranged in this order in the thickness direction. Furthermore, having a second resin base material and a second barrier layer,
The image display according to claim 3, wherein the first resin substrate, the first barrier layer, the hologram layer, the second barrier layer and the second resin substrate are arranged in this order in the thickness direction. light guide plate. 5. The light guide plate for image display according to claim 2, wherein the first barrier layer has a higher refractive index than the first resin base material. 6. The light guide plate for image display according to claim 2, wherein said first barrier layer has a refractive index of 1.48 or more. 7. The light guide plate for image display according to claim 2, wherein said first barrier layer contains an inorganic material. 8. The image display device according to claim 7, wherein the first barrier layer contains at least one inorganic material selected from the group consisting of silicon oxide, silicon nitrogen oxide, diamond-like carbon, aluminum oxide and glass. Light guide plate. 9. The light guide plate for image display according to claim 2, wherein said first barrier layer is arranged on a resin film. 10. The light guide plate for image display according to claim 2, wherein a water vapor barrier material is used as a material of said first barrier layer. 11. The light guide plate for image display according to claim 2, wherein said first barrier layer is arranged on said hologram layer. 12. The light guide plate for image display according to claim 1, wherein said first resin base material has a refractive index of 1.48 to 1.70. The first resin base material according to any one of claims 1 to 12, wherein the first resin base material contains at least one resin selected from the group consisting of poly(meth)acrylic resins, epoxy resins, cyclic polyolefins and polycarbonates. Light guide plate for image display. The image display according to any one of claims 1 to 13, wherein the heat shrinkage of the first resin substrate measured in accordance with JIS K 6718-1:2015 Annex A is less than 3%. light guide plate. 15. The light guide plate for image display according to any one of claims 1 to 14, wherein the arithmetic mean roughness Ra of the surface of the first resin base material is 10 nm or less.

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