Optical layer, laminate, light guide element, and ar display device

Abstract

Provided are: an optical layer with which it is possible to emit light having high clarity from a light guide plate; a laminate; and a light guide element and an AR display device that use the same. This optical layer is formed by using a composition containing a liquid crystal compound. The optical layer has, in the same in-plane direction of the optical layer, a region having a liquid crystal alignment pattern in which the orientation of an optical axis derived from the liquid crystal compound changes while continuously rotating along at least one in-plane direction, and a region not having the liquid crystal alignment pattern. The region having the liquid crystal alignment pattern and the region not having the liquid crystal alignment pattern are adjacent to each other. In the region having the liquid crystal alignment pattern, the optical layer has, in the plane, a transition region in which optical characteristics change. The transition region is adjacent to the region not having the liquid crystal alignment pattern.

Description

Optical layer, laminate, light guide element, and AR display device

[0001] The present invention relates to an optical layer that diffracts incident light, a laminate, a light guide element using the same, and an AR display device.

[0002] In recent years, Augmented Reality (AR) glasses, such as those described in Non-Patent Document 1, which overlay virtual images and various types of information onto the actual view, have been put into practical use. AR glasses are also known as smart glasses, head-mounted displays (HMDs), and AR glasses.

[0003] As shown in Non-Patent Document 1, AR glasses, as an example, display a virtual image overlaid on the scene the user is actually seeing by having the image displayed by a display (optical engine) incident on one end of a light guide plate, propagating through it, and emitting it from the other end. In AR glasses, a diffraction element is used to diffract (refract) the light (projected light) from the display and have it incident on one end of the light guide plate. This introduces the light into the light guide plate at an angle, causing the light to reflect at the interface (surface) of the light guide plate and propagate within the light guide plate to the other end. The light that has propagated through the light guide plate is then diffracted again by the diffraction element at the other end of the light guide plate and emitted from the light guide plate to the user's observation position.

[0004] As such diffraction gratings, diffraction elements using liquid crystals are known. For example, Patent Document 1 describes an optical element comprising a plurality of stacked birefringent sublayers configured to change the direction of propagation of light passing through the interior according to the Bragg condition, wherein each stacked birefringent sublayer has a local optical axis that changes along the respective interface between adjacent stacked birefringent sublayers so as to define its respective grating period. The optical element described in Patent Document 1 is an optical element that diffracts transmitted light. It describes diffracting light incident on a substrate (light guide plate) with the optical element so that the light is incident at an angle of total internal reflection within the substrate and guided through the substrate in a direction substantially perpendicular to the direction of incidence of the light (see Figure 8 in Patent Document 1).

[0005] Patent Document 2 describes a polarization diffraction grating comprising a polarization-sensitive photo-alignment layer and at least first and second liquid crystal compositions containing polymerizable mesogens disposed on the photo-alignment layer, wherein an anisotropic alignment pattern corresponding to a polarization hologram is disposed within the photo-alignment layer, the first liquid crystal composition is disposed on the alignment layer and thereby aligned, and at least partially polymerized, and the second liquid crystal composition is disposed on the first liquid crystal composition and thereby aligned, and both liquid crystal compositions have a layer thickness d determined by d ≤ dmax = Λ / 2, where d is the thickness of the layer and Λ is the pitch of the polarization diffraction grating.

[0006] Patent Document 3 describes a reflective structure comprising a plurality of helical structures, each extending along a predetermined direction, having a first incident surface intersecting the predetermined direction and onto which light is incident, and a reflective surface intersecting the predetermined direction and reflecting light incident from the first incident surface, wherein the first incident surface includes one end of each of the plurality of helical structures, each of the plurality of helical structures includes a plurality of structural units connected along a predetermined direction, each of the plurality of structural units includes a plurality of elements spirally spiraled and stacked, each of the plurality of structural units has a first end and a second end, the second end of one of the structural units adjacent to each other along the predetermined direction constitutes the first end of the other structural unit, the orientation directions of the elements located at the plurality of first ends included in the plurality of helical structures are aligned, the reflective surface includes at least one first end included in each of the plurality of helical structures, and the reflective surface is nonparallel to the first incident surface.

[0007] Here, it is known that in AR glasses, the field of view can be expanded (exit pupil dilation) by adjusting the diffraction efficiency of the diffracting element so that when light propagating within the light guide plate is diffracted by the diffracting element, a portion of the light is diffracted at multiple points and emitted outside the light guide plate. For example, Patent Document 4 describes an optical waveguide in which an input coupler (diffracting element) of the optical waveguide couples light corresponding to an image having a corresponding FOV (field of view) into the optical waveguide, and the input coupler divides the FOV of the image coupled to the optical waveguide into first and second parts, and diffracts a portion of the light corresponding to the image toward a second intermediate component in a second direction, and it is described that an intermediate coupler (diffracting element) and an output coupler (diffracting element) perform exit pupil dilation.

[0008] Japanese Patent Publication No. 2017-522601, Japanese Patent No. 5276847, International Publication No. 2016 / 194961, International Publication No. 2017 / 180403

[0009] Bernard C. Kress et al., Towards the Ultimate Mixed Reality Experience: HoloLens Display Architecture Choices, SID 2017 DIGEST, pp.127-131

[0010] When using liquid crystal diffraction elements as the diffraction elements in the light guide elements used in AR glasses, and configuring the AR glasses so that the liquid crystal diffraction elements diffract a portion of the light at multiple points and emit it outside the light guide plate in order to expand the field of view (exit pupil enlargement), there was a problem that the image clarity was not sufficient.

[0011] The object of the present invention is to solve the problems of the prior art described above, and to provide an optical layer, a laminate, and a light guide element and AR display device using the same, which can emit highly vivid light from a light guide plate.

[0012] [1] An optical layer formed using a composition containing a liquid crystal compound, wherein the optical layer has a region having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and a region not having a liquid crystal alignment pattern, both within the plane of the optical layer, the region having a liquid crystal alignment pattern and the region not having a liquid crystal alignment pattern are adjacent to each other, and the region having a liquid crystal alignment pattern has a transition region in the plane in which the optical properties change, and the transition region is adjacent to the region not having a liquid crystal alignment pattern. [2] The optical layer according to [1], wherein the optical layer has a plurality of regions having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, both within the plane of the optical layer. [3] The optical layer according to [2], wherein the optical layer has a plurality of regions having a liquid crystal alignment pattern in the in-plane direction of the optical layer, and between the regions of the liquid crystal alignment pattern arranged at different positions in the plane, there are regions not having a liquid crystal alignment pattern, both within the plane of the optical layer. [4] An optical layer according to any one of [1] to [3], wherein at least a portion of the plane is optically isotropic in a region that does not have a liquid crystal alignment pattern. [5] An optical layer according to any one of [1] to [4], wherein the transition region is a region in which the birefringence (Δn) gradually changes. [6] An optical layer according to any one of [1] to [3], wherein at least a portion of the plane is optically anisotropic in a region that does not have a liquid crystal alignment pattern. [7] An optical layer according to any one of [1] to [6], wherein the transition region is a region in which the diffraction efficiency gradually changes. [8] An optical layer according to any one of [1] to [7], wherein in a region having a liquid crystal alignment pattern, regions with different diffraction efficiencies are located in the in-plane direction. [9] An optical layer according to any one of [2] to [8], wherein in an optical layer having multiple regions having a liquid crystal alignment pattern in the in-plane direction of the same optical layer, the regions having liquid crystal alignment patterns are located in the plane in which one direction of the liquid crystal alignment pattern is different from the others.

[10] An optical layer having multiple regions having a liquid crystal alignment pattern in the in-plane direction of the same optical layer, wherein the regions having a liquid crystal alignment pattern have different lengths in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in the plane. The optical layer according to any one of [2] to [9].

[11] An optical layer according to any one of [1] to

[10] , wherein in a region having a liquid crystal alignment pattern, at least one region having a liquid crystal alignment pattern is a cholesterically oriented cholesteric liquid crystal layer.

[12] An optical layer according to

[11] , wherein in a region having a liquid crystal alignment pattern, the helical pitch length of the cholesteric liquid crystal layer is different in the in-plane direction of the region.

[13] An optical layer according to any one of

[11] to

[12] , wherein in a region having a liquid crystal alignment pattern, the helical pitch length of the cholesteric liquid crystal layer is different in the thickness direction of the optical layer.

[14] An optical layer according to any one of

[11] to

[13] , wherein in a region having a liquid crystal alignment pattern, the region has multiple layers in which the helical pitch lengths of the cholesteric liquid crystal layer are different.

[15] An optical layer according to any one of

[11] to

[14] , wherein in an optical layer having multiple regions having a liquid crystal alignment pattern in the in-plane direction of the same optical layer, the helical pitch lengths of the cholesteric liquid crystal layers are different from each other.

[16] An optical layer according to any one of [1] to

[15] , wherein the entire layer is smooth and does not have an uneven structure.

[17] A laminate having two or more optical layers according to any one of [1] to

[16] .

[18] A light guide element having a light guide plate and an optical layer according to any one of [1] to

[17] disposed on the surface of the light guide plate.

[19] The light guide element according to

[18] , further having a phase difference layer.

[20] An AR display device having the light guide element according to

[18] or

[19] and an image display device.

[21] The AR display device according to

[20] , wherein the emitted light of the image display device is polarized.

[22] The AR display device according to

[20] or

[21] , wherein the image display device is a laser beam scanning type image display device.

[0013] According to the present invention, it is possible to provide an optical layer, a laminate, and a light guide element and AR display device using the same, which can emit highly vivid light from a light guide plate.

[0014] This is a conceptual diagram of an example of regions A and B of the optical anisotropic layer of the present invention. This is a top view of Figure 1. This is a conceptual diagram of an example of an exposure apparatus for exposing an alignment film. This is a diagram for explaining the operation of regions A and / or B of the optical anisotropic layer in Figure 1. This is a graph conceptually representing an example of the relationship between position and diffraction efficiency in regions A and / or B of the optical anisotropic layer. This is a graph conceptually representing another example of the relationship between position and diffraction efficiency in regions A and / or B of the optical anisotropic layer. This is a conceptual diagram of another example of regions A and B of the optical anisotropic layer of the present invention. This is a top view of Figure 7. This is a diagram for explaining the operation of regions A and / or B of the optical anisotropic layer in Figure 7. This is a diagram for explaining the operation of regions A and / or B of the optical anisotropic layer in Figure 7. This is a schematic diagram of an example of an AR display device having the optical anisotropic layer of the present invention. This is a graph conceptually representing the relationship between position and emitted light in the AR display device. This is a diagram for explaining the method of measuring emitted light intensity in the embodiment. This is a schematic diagram illustrating a method for measuring diffraction efficiency. This is a diagram illustrating an example of a method for forming a region in the in-plane direction of the optical anisotropy layer where the diffraction efficiency gradually changes. This is a diagram illustrating another example of a method for forming a region in the in-plane direction of the optical anisotropy layer where the diffraction efficiency gradually changes. This is a diagram showing the amount of light irradiation depending on the position of the optical anisotropy layer. This is a diagram showing the diffraction efficiency depending on the position of the optical anisotropy layer. This is a diagram showing the retardation value depending on the position of the optical anisotropy layer. This is a diagram showing the amount of light irradiation depending on the position of the optical anisotropy layer. This is a diagram showing the diffraction efficiency depending on the position of the optical anisotropy layer. This is a diagram showing the retardation value depending on the position of the optical anisotropy layer. This is a schematic diagram illustrating an example of an AR display device having a conventional liquid crystal diffraction element. This is a diagram showing an example of the in-plane distribution of diffraction efficiency represented by grayscale. This is a schematic diagram illustrating the cross-section of the X-Z plane of region A and / or region B of the optical anisotropy layer. This is a schematic diagram showing the cross-section of the X-Z plane of region A and / or region B of the optically anisotropic layer. This is a schematic diagram showing the cross-section of the X-Z plane of region A and / or region B of the optically anisotropic layer. This is a conceptual diagram showing an example of the optically anisotropic layer of the present invention. This is a top view of Figure 28. This is a conceptual diagram showing another example of the optically anisotropic layer of the present invention.This figure conceptually shows an example of a laminate having multiple optically anisotropic layers of the present invention. This figure shows the diffraction efficiency of Example 1. This figure schematically shows the change in thickness between the region with a large birefringence and the region with a small birefringence of the liquid crystal compound in the thickness direction of the optically anisotropic layer. This figure conceptually shows an example of a transition region of the optical layer of the present invention.

[0015] The optical layer, laminate, light guide element, and AR display device of the present invention will be described in detail below based on preferred embodiments shown in the attached drawings.

[0016] In this specification, numerical ranges expressed using "~" mean a range that includes the numbers before and after "~" as the lower and upper limits. In this specification, "(meth)acrylate" is used to mean "either acrylate or methacrylate, or both." In this specification, terms such as "identical" and "same" include the error range generally accepted in the art. In this specification, when terms such as "all," "all," and "entire" are used, they include not only 100% but also the error range generally accepted in the art, such as 99% or more, 95% or more, or 90% or more. In terms of angles, "perpendicular," "orthogonal," and "parallel" mean within ±5° of the exact angle, and in terms of angles, "identical" means that the difference from the exact angle is within 5 degrees unless otherwise specified. The difference from the exact angle is preferably less than 4 degrees, and more preferably less than 3 degrees.

[0017] In this specification, visible light refers to electromagnetic waves with wavelengths visible to the human eye, specifically light in the wavelength range of 380 to 780 nm. Invisible light refers to light in the wavelength range of less than 380 nm and light in the wavelength range of more than 780 nm. However, within visible light, light in the wavelength range of 420 to 490 nm is blue light, light in the wavelength range of 495 to 570 nm is green light, and light in the wavelength range of 620 to 750 nm is red light.

[0018] In this specification, the selective reflection center wavelength refers to the average value of two wavelengths that exhibit the half-maximum transmittance: T1 / 2 (%), given that Tmin (%) is the minimum transmittance of the object (component) in question. Formula for calculating half-maximum transmittance: T1 / 2 = 100 - (100 - Tmin) ÷ 2 Furthermore, the statement that the selective reflection center wavelengths of multiple layers are "equal" does not mean that they are strictly equal, and errors within a range that does not affect the optical performance are permitted. Specifically, the statement that the selective reflection center wavelengths of multiple objects are "equal" means that the difference in the selective reflection center wavelengths between each object is 20 nm or less, preferably 15 nm or less, and more preferably 10 nm or less.

[0019] The retardation value was measured using an AxoScan from Axometrics. The measurement wavelength was 750 nm. Phase difference measurements were performed for incident light from the normal direction to the sample surface. For the detected slow and fast phase axes, phase difference measurements were performed from the -40° and 40° incident angles within the slow and fast phase planes, respectively. The average of the measurements from the four directions was defined as the oblique retardation Re(40).

[0020] [Optical Layer (Optical Anisotropic Layer)] The optical layer (optical anisotropic layer) of the present invention is an optical anisotropic layer formed using a composition containing a liquid crystal compound. The optical anisotropic layer has a region A having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and a region without a liquid crystal alignment pattern, both within the same plane of the optical anisotropic layer. In the following description, the optical layer will also be referred to as the optical anisotropic layer. Furthermore, the optical layer (optical anisotropic layer) of the present invention has a configuration in which a region A having a liquid crystal alignment pattern and a region without a liquid crystal alignment pattern are adjacent, and within region A having a liquid crystal alignment pattern, there is a transition region in the plane in which the optical properties change, and the transition region is adjacent to a region without a liquid crystal alignment pattern. Region A is known to act as a liquid crystal diffraction element, and therefore, the optical layer of the present invention can be rephrased as having a configuration in which a liquid crystal diffraction element and a liquid crystal layer without diffraction properties are integrally formed.

[0021] Conventional liquid crystal diffraction elements typically involve cutting the optical anisotropy layer within a liquid crystal alignment pattern region and stacking the resulting single-wafer optical anisotropy layer onto a predetermined substrate (such as a light guide plate, as described later). From the perspective of refractive index distribution, the cut surface represents a discontinuous change in refractive index, causing light rays crossing this area to be refracted in unintended directions, resulting in stray light. Therefore, for example, when a liquid crystal diffraction element is placed on a light guide plate and used in a head-mounted display, it was found that the image clarity deteriorates due to the effects of stray light. The inventors therefore discovered that stray light can be reduced by surrounding the liquid crystal diffraction element with a liquid crystal layer that does not exhibit diffraction properties, thereby reducing these discontinuous changes in refractive index. However, it was found that even with this configuration, the reduction of discontinuous changes in refractive index is insufficient, and therefore stray light reduction is not adequate.

[0022] As a result of diligent research, the inventors have found that by having a configuration in which a liquid crystal diffraction element and a liquid crystal layer that does not exhibit diffraction properties are integrally formed, and by providing a transition region in which the optical properties change at a position adjacent to the region that acts as a liquid crystal diffraction element and the region that does not exhibit diffraction properties, the generation of stray light can be more effectively suppressed and the reduction in image clarity can be suppressed.

[0023] Here, the optical layer of the present invention may have a plurality of regions in the plane having a liquid crystal alignment pattern. When there are a plurality of regions in the plane having a liquid crystal alignment pattern, for example, a region A having a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and a region B having a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and a region having no liquid crystal alignment pattern. As will be described later, the regions A and B having a liquid crystal alignment pattern act as so-called liquid crystal diffraction elements that diffract incident light. Therefore, the optically anisotropic layer of the present invention may have a configuration in which two liquid crystal diffraction elements and a liquid crystal layer having no diffraction action are integrally formed. By having such a structure, the optically anisotropic layer of the present invention can be laminated on a light guide plate to emit light with high sharpness from the light guide plate. Also, in at least one of the regions A and B, it is preferable that the diffraction efficiency increases as it goes from one side to the other side in one direction in the liquid crystal alignment pattern. By having such a structure, when the light propagating in the light guide plate is diffracted by the liquid crystal diffraction element (region A or region B) and emitted from the light guide plate, the brightness of the emitted light can be made uniform.

[0024] The change in the diffraction efficiency may be such that the diffraction efficiency is high for a plurality of directions in the plane. An example of the in-plane distribution of the diffraction efficiency is shown in FIG. 24. In FIG. 24, the darker the black region, the higher the diffraction efficiency. Without being limited to this, various liquid crystal diffraction elements can be applied according to the design of the light guide plate.

[0025] FIG. 28 is a diagram conceptually showing an example of the optically anisotropic layer of the present invention. FIG. 29 is a top view of FIG. 28. The optically anisotropic layer 400 shown in FIGS. 28 and 29 is formed using a composition containing a liquid crystal compound. In the in-plane direction, by making the alignment states of the liquid crystal compounds different, a region A45a, a region having no liquid crystal alignment pattern (hereinafter also referred to as a non-diffraction region) 45b, and a region B45c are formed. The non-diffraction region 45b is disposed between the region A45a and the region B45c. In the following description, the region A45a and the region B45c are also referred to as diffraction regions.

[0026] Each of the region A45a and the region B45c has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously changes while rotating along at least one direction in the plane, and acts as a liquid crystal diffraction element that diffracts incident light. Note that the liquid crystal alignment pattern of the region A45a and the liquid crystal alignment pattern of the region B45c may be the same or different.

[0027] Also, the region A45a, the non-diffraction region 45b, and the region B45c have substantially the same thickness, and both main surfaces of the optically anisotropic layer 400 are smooth flat surfaces having no concavo-convex structure.

[0028] The shapes of the region A45a and the region B45c in plan view are not particularly limited and may be appropriately set according to the use of the optical layer, and may be various shapes such as a square shape, a rectangular shape, a quadrangular shape, a polygonal shape, a circular shape, an elliptical shape, and an irregular shape. Also, the shapes of the region A45a and the region B45c may be the same or different. Also, the sizes of the region A45a and the region B45c are not particularly limited and may be appropriately set according to the use of the optical layer. Also, the sizes of the region A45a and the region B45c may be the same or different.

[0029] Also, the arrangement of the region A45a and the region B45c in the plane of the optical layer is not particularly limited and may be appropriately set according to the use of the optical layer.

[0030] Furthermore, region A45a and / or region B45c only need to be in contact with the non-diffraction region 45b at least a portion of their edges, and may be in contact with the non-diffraction region 45b over their entire edges. In other words, region A45a and / or region B45c may be surrounded on all sides by the non-diffraction region 45b.

[0031] The transition region may be provided in at least a portion of the position in contact with the non-diffraction region 45b of region A45a and / or region B45c, but it is preferable that it be provided over the entire area in contact with the non-diffraction region 45b.

[0032] [Regions A and B] An embodiment of a liquid crystal diffraction element including a cholesteric liquid crystal layer that can be used as regions A and B of the optical anisotropy layer of the present invention will be described below.

[0033] [First Embodiment] Figure 1 conceptually shows an example of a first embodiment of a liquid crystal diffraction element. The liquid crystal diffraction element 10 shown in Figure 1 is a liquid crystal diffraction element that selectively reflects light of a specific wavelength and diffracts the reflected light. The liquid crystal diffraction element 10 shown in Figure 1 has a structure in which a support 20, an alignment film 24, and a cholesteric liquid crystal layer 18 are stacked in this order.

[0034] Although the liquid crystal diffraction element 10 shown in Figure 1 has a support 20 and an alignment film 24, the liquid crystal diffraction element may also have a configuration that does not have a support 20 or even an alignment film 24. For example, the liquid crystal diffraction element may be configured by peeling off the support 20 from the above configuration, and consisting only of the alignment film 24 and the cholesteric liquid crystal layer 18. Alternatively, the support 20 and the alignment film 24 may be peeled off, and the liquid crystal diffraction element may consist only of the cholesteric liquid crystal layer 18. In other words, the optical anisotropy layer of the present invention may be laminated on the support and the alignment film, or it may be laminated with the alignment film, or it may consist only of the optical anisotropy layer.

[0035] In other words, any type of layer configuration can be used for a liquid crystal diffraction element, as long as it has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. The same applies to all of the liquid crystal diffraction elements of each embodiment described later.

[0036] <Support> The support 20 is a film-like material (sheet-like material, plate-like material) that supports the alignment film 24 and the cholesteric liquid crystal layer 18. Preferably, the support 20 has a transmittance of 50% or more, more preferably 70% or more, and even more preferably 85% or more for light diffracted by the cholesteric liquid crystal layer 18.

[0037] There are no restrictions on the thickness of the support 20, and the thickness that can hold the alignment film 24 and the cholesteric liquid crystal layer 18 should be appropriately set according to the application of the liquid crystal diffraction element 10 and the material used to form the support 20. The thickness of the support 20 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and even more preferably 5 to 150 μm.

[0038] The support 20 may be single-layered or multi-layered. In the case of a single-layered support 20, various materials used as support materials in optical elements can be used. Specifically, examples of materials for the support 20 include glass, triacetylcellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, and polyolefin. Examples of a multi-layered support 20 include one of the single-layered supports mentioned above as a substrate, with other layers provided on the surface of this substrate.

[0039] <Alignment Film> An alignment film 24 is formed on the surface of the support 20. The alignment film 24 is an alignment film used to orient the liquid crystal compound 30 into a predetermined liquid crystal alignment pattern when forming the cholesteric liquid crystal layer 18. As will be described later, in the liquid crystal diffraction element 10, the cholesteric liquid crystal layer 18 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A (see Figure 2) derived from the liquid crystal compound 30 changes while continuously rotating along one direction in the plane. In this invention, in the liquid crystal alignment pattern, the length of a 180° rotation of the optical axis 30A in one direction in which the orientation of the optical axis 30A changes while continuously rotating is defined as one period (referred to as Λ in Figure 2, also called the "optical axis rotation period").

[0040] In the following explanation, "the direction of the optical axis 30A rotates" will also be referred to simply as "the optical axis 30A rotates."

[0041] Various known orientation films are available. Examples include rubbing films made of organic compounds such as polymers, obliquely deposited films of inorganic compounds, films having microgrooves, and films formed by accumulating Langmuir-Blodgett (LB) films of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearylate using the Langmuir-Blodgett method.

[0042] An orientation film can be formed by rubbing the surface of a polymer layer several times in a certain direction with paper or cloth. Preferred materials for the orientation film include polyimide, polyvinyl alcohol, polymers having polymerizable groups as described in Japanese Patent Publication No. 9-152509, materials used for forming orientation films as described in Japanese Patent Publication No. 2005-097377, Japanese Patent Publication No. 2005-099228, and Japanese Patent Publication No. 2005-128503.

[0043] In the liquid crystal diffraction element 10, a so-called photo-alignment film is preferably used as the alignment film, which is formed by irradiating a photo-alignable material with polarized or unpolarized light. That is, in the liquid crystal diffraction element 10, a photo-alignment film formed by coating a photo-alignment material onto a support 20 is preferably used as the alignment film. Irradiation with polarized light can be performed perpendicularly or obliquely to the photo-alignment film, and irradiation with unpolarized light can be performed obliquely to the photo-alignment film.

[0044] Examples of photo-alignment materials used in the photo-alignment film applicable to the present invention include those described in Japanese Patent Publication No. 2006-285197, Japanese Patent Publication No. 2007-076839, Japanese Patent Publication No. 2007-138138, Japanese Patent Publication No. 2007-094071, Japanese Patent Publication No. 2007-121721, Japanese Patent Publication No. 2007-140465, Japanese Patent Publication No. 2007-156439, and Japanese Patent Publication No. 2 Azo compounds described in Japanese Patent Publication No. 007-133184, Japanese Patent Publication No. 2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746, aromatic ester compounds described in Japanese Patent Publication No. 2002-229039, maleimides having photo-orienting units described in Japanese Patent Publication No. 2002-265541 and Japanese Patent Publication No. 2002-317013 Examples of preferred materials include and / or alkenyl-substituted nadiimide compounds, photocrosslinkable silane derivatives described in Japanese Patent No. 4205195 and Japanese Patent No. 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides and photocrosslinkable polyesters described in Japanese Patent Publication No. 2003-520878, Japanese Patent Publication No. 2004-529220 and Japanese Patent No. 4162850, and photodimerizable compounds described in Japanese Patent Publication No. 9-118717, Japanese Patent Publication No. 10-506420, Japanese Patent Publication No. 2003-505561, International Publication No. 2010 / 150748, Japanese Patent Publication No. 2013-177561 and Japanese Patent Publication No. 2014-12823, particularly cinnamate compounds, chalcone compounds and coumarin compounds. Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable polyesters, cinnamate compounds, and chalcone compounds are particularly suitable for use.

[0045] There are no restrictions on the thickness of the orientation film; the thickness should be set appropriately to obtain the required orientation function depending on the material used to form the orientation film. The thickness of the orientation film is preferably 0.001 to 5 μm, and more preferably 0.005 to 2 μm.

[0046] There are no limitations on the method for forming the alignment film, and various known methods depending on the material used to form the alignment film can be used. As an example, one method involves coating the surface of the support 20 with the alignment film, drying it, and then exposing the alignment film with laser light to form an alignment pattern.

[0047] Figure 3 conceptually shows an example of an exposure apparatus for exposing an alignment film to form an alignment pattern. The exposure apparatus 60 shown in Figure 3 comprises a light source 64 equipped with a laser 62 and a λ / 2 plate (not shown), a beam splitter 68 that separates the laser light M emitted from the light source 64 into two rays MA and MB, mirrors 70A and 70B positioned on the optical paths of the two separated rays MA and MB, respectively, and λ / 4 plates 72A and 72B. Although not shown in the figure, the light source 64 has a λ / 2 plate that changes the polarization direction of the laser light M emitted from the laser 62 to emit linearly polarized light P0. The λ / 4 plates 72A and 72B have optical axes parallel to each other. The λ / 4 plate 72A converts the linearly polarized light P0 (ray MA) into right-circularly polarized light P R λ / 4 plate 72B converts linearly polarized light P0 (light ray MB) to left-circularly polarized light P L Convert each of them accordingly.

[0048] A support 20 having an alignment film 24 before the alignment pattern is formed is placed in the exposure section, and two light rays MA and MB are intersected and interfered with on the alignment film 24, and the resulting interfered light is irradiated onto the alignment film 24 for exposure. Due to this interference, the polarization state of the light irradiated onto the alignment film 24 changes periodically in an interference fringe pattern. As a result, an alignment pattern in which the alignment state changes periodically is obtained on the alignment film 24. In the exposure apparatus 60, the period of the alignment pattern can be adjusted by changing the intersection angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the intersection angle α, the length of one period in which the optical axis 30A rotates 180° in one direction can be adjusted in an alignment pattern in which the optical axis 30A derived from the liquid crystal compound 30 rotates continuously in one direction. By forming a cholesteric liquid crystal layer on an alignment film having an alignment pattern in which the orientation state changes periodically, a cholesteric liquid crystal layer 18 can be formed having a liquid crystal alignment pattern in which the optical axis 30A originating from the liquid crystal compound 30 rotates continuously in one direction, as will be described later. Furthermore, the direction of rotation of the optical axis 30A can be reversed by rotating the optical axes of the λ / 4 plates 72A and 72B by 90°, respectively.

[0049] In liquid crystal diffraction elements, the alignment film is provided as a preferred embodiment and is not an essential component. For example, by forming an alignment pattern on the support 20 using a rubbing method or a laser beam or the like, the cholesteric liquid crystal layer can be configured to have a liquid crystal alignment pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes while continuously rotating along at least one direction in the plane.

[0050] <Cholesteric Liquid Crystal Layer> A cholesteric liquid crystal layer 18 is formed on the surface of the alignment film 24. The cholesteric liquid crystal layer 18 is a layer formed using a composition containing a liquid crystal compound, and has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound rotates continuously along at least one direction in the plane.

[0051] In the example shown in Figure 1, the cholesteric liquid crystal layer 18 has a structure in which the liquid crystal compound is cholesterically oriented. That is, the cholesteric liquid crystal layer 18 is a layer in which the cholesteric liquid crystal phase is fixed, and has a cholesteric liquid crystal structure in which the liquid crystal compound is spirally oriented along a helical axis parallel to the thickness direction. The cholesteric liquid crystal layer 18 has a structure in which multiple pitches of liquid crystal compound 30 are stacked, with each pitch being a helical pitch in which the liquid crystal compound 30 is spirally rotated once (360° rotation).

[0052] The cholesteric liquid crystal layer 18, having a cholesteric liquid crystal structure, possesses wavelength-selective reflectivity and circular polarization-selective reflectivity. For example, if the cholesteric liquid crystal layer 18 has a selective reflection center wavelength in the green wavelength region, then right-circularly polarized green light G R It reflects light and transmits other light. Here, in the cholesteric liquid crystal layer 18, the liquid crystal compound 30 is rotated and oriented in the planar direction, so it refracts (diffracts) incident circularly polarized light in the direction in which the optical axis is continuously rotating (azimuth direction) and reflects it. At that time, the azimuth direction of diffraction differs depending on the rotation direction of the incident circularly polarized light. That is, the cholesteric liquid crystal layer 18 reflects right-circularly polarized or left-circularly polarized light of the selected reflection wavelength and diffracts this reflected light.

[0053] <<Cholesteric Liquid Crystal Phase>> The cholesteric liquid crystal phase exhibits selective reflectivity to either left- or right-handed circularly polarized light at specific wavelengths. The center wavelength of selective reflection (selective reflection center wavelength) λ depends on the pitch P (= period of the helix) of the helical structure in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal phase and λ = n × P. Therefore, the selective reflection center wavelength can be adjusted by adjusting the pitch of this helical structure. The pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used with the liquid crystal compound during the formation of the optical anisotropy layer, or the concentration of its addition; therefore, the desired pitch can be obtained by adjusting these. For details on adjusting the pitch, see Fujifilm Research Report No. 50 (2005), pp. 60-63. For methods of measuring the helical sense and pitch, see "Introduction to Liquid Crystal Chemistry Experiments," edited by the Japanese Liquid Crystal Society, Sigma Publishing, 2007, p. 46, and "Liquid Crystal Handbook," Liquid Crystal Handbook Editorial Committee, Maruzen, p. 196.

[0054] Whether the reflected light from the cholesteric liquid crystal phase is right-circularly polarized or left-circularly polarized depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. Selective reflection of circularly polarized light by the cholesteric liquid crystal phase reflects right-circularly polarized light when the twist direction of the helix of the cholesteric liquid crystal phase is to the right, and left-circularly polarized light when the twist direction of the helix is ​​to the left. In the liquid crystal diffraction element 10 of Figure 1, the cholesteric liquid crystal layer 18 is a layer formed by fixing a right-twisted cholesteric liquid crystal phase. The direction of the twist of the cholesteric liquid crystal phase can be adjusted by the type of liquid crystal compound that forms the optical anisotropy layer and / or the type of chiral agent added.

[0055] Furthermore, the half-width Δλ (nm) of the selective reflection band (circularly polarized reflection band) exhibiting selective reflection depends on the Δn of the cholesteric liquid crystal phase and the helical pitch P, following the relationship Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by the type of liquid crystal compound forming the optical anisotropy layer, its mixing ratio, and the temperature during orientation fixing. The half-width of the reflection wavelength region is adjusted according to the application of the liquid crystal diffraction element 10, and is, for example, 10 to 500 nm, preferably 20 to 300 nm, and more preferably 30 to 100 nm.

[0056] <<Method for Forming a Cholesteric Liquid Crystal Layer Having a Cholesteric Liquid Crystal Structure>> A cholesteric liquid crystal layer having a cholesteric liquid crystal structure (region A and / or region B in the optically anisotropic layer) can be formed by fixing a cholesteric liquid crystal phase in layers. The structure in which the cholesteric liquid crystal phase is fixed only needs to be a structure in which the orientation of the liquid crystal compound that constitutes the cholesteric liquid crystal phase is maintained. Typically, a polymerizable liquid crystal compound is brought into the oriented state of the cholesteric liquid crystal phase, and then polymerized and cured by ultraviolet irradiation, heating, etc., to form a non-fluid layer, and at the same time, a structure is preferred in which the orientation form does not change due to an external field or external force. The method for forming an optically anisotropic layer having region A and / or region B that constitute the cholesteric liquid crystal layer and a non-diffractive region will be described later. In the structure in which the cholesteric liquid crystal phase is fixed, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained, and the liquid crystal compound 30 does not need to exhibit liquid crystalline properties in the cholesteric liquid crystal layer. For example, the polymerizable liquid crystal compound may lose its liquid crystalline properties due to its high molecular weight due to the curing reaction.

[0057] As an example of a material used to form a cholesteric liquid crystal layer by fixing a cholesteric liquid crystal phase, a liquid crystal composition containing a liquid crystal compound is used. The liquid crystal compound is preferably a polymerizable liquid crystal compound. Furthermore, the liquid crystal composition used to form the cholesteric liquid crystal layer may also contain a surfactant and a chiral agent.

[0058] --Polymerizable Liquid Crystal Compounds-- Polymerizable liquid crystal compounds may be rod-shaped or disc-shaped liquid crystal compounds. Examples of rod-shaped polymerizable liquid crystal compounds that form the cholesteric liquid crystal phase include rod-shaped nematic liquid crystal compounds. Preferred rod-shaped nematic liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyanosubstituted phenylpyrimidines, alkoxysubstituted phenylpyrimidines, phenyldioxanes, trans, and alkenylcyclohexylbenzonitriles. Not only low molecular weight liquid crystal compounds but also high molecular weight liquid crystal compounds can be used.

[0059] Polymerizable liquid crystal compounds are obtained by introducing polymerizable groups into liquid crystal compounds. Examples of polymerizable groups include unsaturated polymerizable groups, epoxy groups, oxetanyl groups, and azilidinyl groups, with unsaturated polymerizable groups being preferred and ethylenically unsaturated polymerizable groups being more preferred. Polymerizable groups can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups in a polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. An example of a polymerizable liquid crystal compound is Makromol. Chem. This includes compounds described in Volume 190, page 2255 (1989), Advanced Materials Volume 5, page 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, International Publication No. 95 / 022586, International Publication No. 95 / 024455, International Publication No. 97 / 000600, International Publication No. 98 / 023580, International Publication No. 98 / 052905, Japanese Patent Publication No. 1-272551, Japanese Patent Publication No. 6-016616, Japanese Patent Publication No. 7-110469, Japanese Patent Publication No. 11-080081, and Japanese Patent Publication No. 2001-328973, etc. Furthermore, as rod-shaped liquid crystal compounds, those described in Japanese Patent Publication No. 11-513019 and Japanese Patent Application Publication No. 2007-279688 can also be preferably used. Two or more polymerizable liquid crystal compounds may be used in combination. Using two or more polymerizable liquid crystal compounds in combination can lower the orientation temperature.

[0060] Furthermore, as polymerizable liquid crystal compounds other than those mentioned above, cyclic organopolysiloxane compounds having a cholesteric phase, such as those disclosed in Japanese Patent Publication No. 57-165480, can be used. In addition, as the aforementioned polymeric liquid crystal compounds, polymers in which liquid crystal-resisting mesogenic groups are introduced in the main chain, side chains, or both the main chain and side chains, polymeric cholesteric liquid crystals in which cholesteryl groups are introduced in the side chains, liquid crystalline polymers such as those disclosed in Japanese Patent Publication No. 9-133810, and liquid crystalline polymers such as those disclosed in Japanese Patent Publication No. 11-293252 can be used.

[0061] --Disk-shaped liquid crystal compounds-- As disc-shaped liquid crystal compounds, those described in Japanese Patent Publication No. 2007-108732 and Japanese Patent Publication No. 2010-244038 can be preferably used.

[0062] Furthermore, the amount of polymerizable liquid crystal compound added to the liquid crystal composition is preferably 75 to 99.9% by mass, more preferably 80 to 99% by mass, and even more preferably 85 to 90% by mass, based on the solid content mass (mass excluding solvent) of the liquid crystal composition.

[0063] From the viewpoint of achieving superior effects of the present invention and obtaining diffracted light with high diffraction efficiency at large diffraction angles, the maximum value of the birefringence Δn of the liquid crystal compound inside the cholesteric liquid crystal layer is preferably 0.15 or higher, more preferably 0.20 or higher, even more preferably 0.25 or higher, even more preferably 0.30 or higher, and most preferably 0.35 or higher. The upper limit is not particularly limited, but is often 1.00 or lower. Liquid crystal compounds exhibiting such high refractive index anisotropy are often forward-dispersive compounds in which the birefringence Δn450 for incident light with a wavelength of 450 nm is greater than the birefringence Δn550 for incident light with a wavelength of 550 nm. The value of Δn450 / Δn550 is not particularly limited, but is often, for example, 0.5 to 2.0 and 1.0 to 1.5. In the case of forward-dispersive compounds, the diffraction efficiency at each wavelength can be kept constant by adjusting the selective reflection band exhibiting the aforementioned selective reflection, the degree of orientation described later, and the thickness. For example, by forming a thin layer with a selective reflection band that diffracts incident light at 450 nm and a thick layer with a selective reflection band that diffracts incident light at 550 nm, the diffraction efficiency at each wavelength can be kept constant.

[0064] From the viewpoint of achieving superior effects of the present invention and enabling AR display with a wide viewing angle, the maximum value of the anomalous refractive index of the liquid crystal compound inside the optical anisotropic layer is preferably 1.8 or higher, more preferably 1.9 or higher, and even more preferably 2.0 or higher. Furthermore, the ordinary refractive index of the liquid crystal compound inside the optical anisotropic layer is preferably 1.4 or higher, more preferably 1.5 or higher, and even more preferably 1.6 or higher.

[0065] The birefringence Δn and refractive index preferably satisfy the above preferred range over the range of 380 to 780 nm. In particular, it is preferable that they satisfy the above preferred range over the range of 400 to 650 nm.

[0066] From the viewpoint of achieving superior effects of the present invention, and from the viewpoint of enabling AR display with excellent transparency and high light utilization efficiency, the absorption rate of the optical anisotropic layer at 450 nm is preferably 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less. Furthermore, the molar extinction coefficient at 450 nm of the liquid crystal compound used in the optical anisotropic layer is 100 (mol·cm). －１ The following is preferable: 10 (mol·cm) －１ The following is more preferable: 1 (mol·cm) －１ The following are even more preferable.

[0067] The absorption rate and molar extinction coefficient preferably satisfy the above preferred range over the range of 380 to 780 nm. In particular, it is preferable that they satisfy the above preferred range over the range of 400 to 650 nm.

[0068] Within the cholesteric liquid crystal layer, the minimum value of the birefringence Δn of the liquid crystal compound is preferably 0.00 to 0.40, more preferably 0.00 to 0.30, and even more preferably 0.00 to 0.20. Specific examples of polymerizable liquid crystal compounds with high refractive index anisotropy include, for example, Japanese Patent Publication No. 2009-102245, Japanese Patent No. 4655348, Japanese Patent No. 4524827, Japanese Patent No. 4720200, Japanese Patent Publication No. 2004-091380, Japanese Patent No. 3972430, Japanese Patent No. 4517416, Japanese Patent Publication No. 2002-128742, Japanese Patent No. 4810750, Japanese Patent No. 5888544, Japanese Patent Publication No. 2014-019654, Japanese Patent No. 6241654, Japanese Patent No. 6372060, and Japanese Patent No. 6323144. , JP 2005-015406 A, JP 2007-230968 A, Patent No. 6761484, Patent No. 6681992, International Publication No. 19 / 182129, CN01134217A, KR101069555B, KR101690767B, CN20120229730A, Patent No. 4053782, JP 2009-249406 A, Patent No. 4121075, JP 2005-528416 A, US 6514578, International Publication No. 06 / 006819, JP 2011 A -184417, JP 2013-095685, JP 2013-103897, JP 2002-088008, JP 2002-226412, JP 2012-167214, JP 2012-167068, JP Application 2018-084511, JP 2003-055317, JP 2001-329264, JP 2002-030016, JP 2003-055664, JP 2018-070889, CN10255789 Japanese Patent Publication No. 6, US2015369982, JP 2020-105264, JP 2014-224237, JP 2012-051862, JP 2010-106274, JP 2005-179557, JP 2005-035985, JP 2002-012579, JP 2002-003845, JP 2001-233837, JP 2019-532167, JP 2016-509247, JP 2010-503733,Examples include the compounds described in Japanese Patent Publication No. 2003-533557, International Publication No. 19 / 098115, International Publication No. 18 / 034216, International Publication No. 18 / 221236, International Publication No. 18 / 123396, International Publication No. 18 / 003482, International Publication No. 17 / 086143, International Publication No. 14 / 192655, International Publication No. 13 / 161669, and International Publication No. 09 / 104468.

[0069] In addition to the above, polymerizable liquid crystal compounds include the following compounds.

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079] --Surfactants-- The liquid crystal composition used to form the cholesteric liquid crystal layer may contain surfactants. The surfactant is preferably a compound that can function as an orientation control agent that contributes to stably or rapidly forming a planar-oriented cholesteric liquid crystal phase. Examples of surfactants include silicate surfactants and fluorine-based surfactants, with fluorine-based surfactants being preferred.

[0080] Specific examples of surfactants include the compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Publication No. 2014-119605, the compounds described in paragraphs

[0031] to

[0034] of Japanese Patent Publication No. 2012-203237, the compounds exemplified in paragraphs

[0092] and

[0093] of Japanese Patent Publication No. 2005-099248, the compounds exemplified in paragraphs

[0076] to

[0078] and paragraphs

[0082] to

[0085] of Japanese Patent Publication No. 2002-129162, and fluorine (meth)acrylate polymers described in paragraphs

[0018] to

[0043] of Japanese Patent Publication No. 2007-272185, etc. Note that a single surfactant may be used alone, or two or more may be used in combination. As a fluorine-based surfactant, the compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605 are preferred.

[0081] The amount of surfactant added to the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass, relative to the total mass of the liquid crystal compound.

[0082] --Chiral Agents (Optically Active Compounds)-- Chiral agents have the function of inducing a helical structure in the cholesteric liquid crystal phase. Since different chiral agents induce different helical twist directions or helical pitches, they should be selected according to the purpose. There are no particular restrictions on chiral agents, and known compounds (for example, described in Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Agents for TN (twisted nematic) and STN (Super Twisted Nematic), page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide, and isomannide derivatives can be used. Chiral agents generally contain an asymmetric carbon atom, but axially asymmetric compounds or planar asymmetric compounds that do not contain an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric compounds or planar asymmetric compounds include binaphthyl, helicene, paracyclophane, and their derivatives. Chiral agents may have polymerizable groups. When both the chiral agent and the liquid crystal compound have polymerizable groups, a polymer can be formed by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound, having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral agent. In this embodiment, it is preferable that the polymerizable groups of the polymerizable chiral agent are of the same type as the polymerizable groups of the polymerizable liquid crystal compound. Therefore, the polymerizable groups of the chiral agent are preferably unsaturated polymerizable groups, epoxy groups, or aziridinyl groups, more preferably unsaturated polymerizable groups, and even more preferably ethylenically unsaturated polymerizable groups. The chiral agent may also be a liquid crystal compound.

[0083] When the chiral agent has a photoisomerizing group, it is preferable because, after coating and orientation, a pattern of the desired reflected wavelength corresponding to the emission wavelength can be formed by photomask irradiation with active light or the like. Preferred photoisomerizing groups are the isomerization site of a photochromic compound, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds that can be used include those described in Japanese Patent Publication No. 2002-080478, 2002-080851, 2002-179668, 2002-179669, 2002-179670, 2002-179681, 2002-179682, 2002-338575, 2002-338668, 2003-313189, and 2003-313292, etc.

[0084] —Photoreactive Chiral Agents— Photoreactive chiral agents consist of compounds represented by the following general formula (I), for example, and have the characteristic of being able to control the orientation structure of liquid crystalline compounds and to change the helical pitch of liquid crystals, i.e., the torsional force (HTP: helical twisting power) of the helical structure, by irradiation with light. That is, they are compounds that induce a change in the torsional force of the helical structure in liquid crystalline compounds, preferably nematic liquid crystal compounds, by light irradiation (ultraviolet to visible light to infrared light), and have chiral sites (molecular structural units) and sites that undergo structural changes by light irradiation as necessary sites (molecular structural units). Moreover, photoreactive chiral agents represented by the following general formula (I) can particularly significantly change the HTP of liquid crystal molecules.

[0085] Furthermore, the aforementioned HTP represents the torsional force of the helical structure of the liquid crystal, i.e., HTP = 1 / (pitch × chiral agent concentration [mass fraction]). For example, the helical pitch (one period of the helical structure; μm) of the liquid crystal molecule at a certain temperature is measured, and this value is converted from the concentration of the chiral agent [μm]. -1This can be determined by the following. When a selective reflectance color is formed by light intensity using a photoreactive chiral agent, the rate of change of HTP (= HTP before irradiation / HTP after irradiation) is preferably 1.5 or more if HTP becomes smaller after irradiation, more preferably 2.5 or more, and preferably 0.7 or less if HTP becomes larger after irradiation, and more preferably 0.4 or less.

[0086] Next, we will explain compounds represented by general formula (I).

[0087] General formula (I)

[0088]

[0089] In the above formula, R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group having a total of 3 to 15 carbon atoms, or a methacryloyloxyalkyloxy group having a total of 4 to 15 carbon atoms. Examples of the alkoxy group having 1 to 15 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a hexyloxy group, a dodecyloxy group, etc. Among these, an alkoxy group having 1 to 12 carbon atoms is preferred, and an alkoxy group having 1 to 8 carbon atoms is particularly preferred.

[0090] Examples of the aforementioned acryloyloxyalkyloxy groups having a total of 3 to 15 carbon atoms include acryloyloxyethyloxy groups, acryloyloxybutyloxy groups, and acryloyloxydecyloxy groups. Among these, acryloyloxyalkyloxy groups having 5 to 13 carbon atoms are preferred, and acryloyloxyalkyloxy groups having 5 to 11 carbon atoms are particularly preferred.

[0091] Examples of the aforementioned methacryloyloxyalkyloxy groups having a total of 4 to 15 carbon atoms include methacryloyloxyethyloxy group, methacryloyloxybutyloxy group, and methacryloyloxydecyloxy group. Among these, methacryloyloxyalkyloxy groups having 6 to 14 carbon atoms are preferred, and methacryloyloxyalkyloxy groups having 6 to 12 carbon atoms are particularly preferred.

[0092] The molecular weight of the photoreactive chiral agent represented by the general formula (I) described above is preferably 300 or more. Furthermore, it is preferable that it has high solubility with the liquid crystalline compound described later, and it is even more preferable that its solubility parameter SP value is similar to that of the liquid crystalline compound.

[0093] The following are specific examples of compounds represented by the general formula (I) mentioned above (exemplary compounds (1) to (15)), but the present invention is not limited to these.

[0094]

[0095]

[0096]

[0097] Photoreactive optically active compounds include, for example, compounds represented by the following general formula (II).

[0098] General formula (II)

[0099]

[0100] In the above formula, R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group having a total of 3 to 15 carbon atoms, or a methacryloyloxyalkyloxy group having a total of 4 to 15 carbon atoms. Examples of the alkoxy groups having 1 to 15 carbon atoms include methoxy, ethoxy, propoxy, butoxy, hexyloxy, octyloxy, and dodecyloxy groups. Among these, alkoxy groups having 1 to 10 carbon atoms are preferred, and alkoxy groups having 1 to 8 carbon atoms are particularly preferred.

[0101] Examples of the aforementioned acryloyloxyalkyloxy groups having a total of 3 to 15 carbon atoms include acryloyloxy groups, acryloyloxyethyl groups, acryloyloxypropyl groups, acryloyloxyhexyl groups, acryloyloxybutyl groups, and acryloyloxydecyl groups. Among these, acryloyloxyalkyloxy groups having 3 to 13 carbon atoms are preferred, and acryloyloxyalkyloxy groups having 3 to 11 carbon atoms are particularly preferred.

[0102] Examples of the aforementioned methacryloyloxyalkyloxy groups having a total of 4 to 15 carbon atoms include methacryloyloxy groups, methacryloyloxyethyloxy groups, and methacryloyloxyhexyloxy groups. Among these, methacryloyloxyalkyloxy groups having 4 to 14 carbon atoms are preferred, and methacryloyloxyalkyloxy groups having 4 to 12 carbon atoms are particularly preferred.

[0103] The molecular weight of the photoreactive optically active compound represented by the general formula (II) described above is preferably 300 or more. Furthermore, it is preferable that it has high solubility with the liquid crystalline compound described later, and it is even more preferable that its solubility parameter SP value is similar to that of the liquid crystalline compound.

[0104] The following are specific examples of photoreactive optically active compounds represented by the general formula (II) mentioned above (exemplary compounds (21) to (32)), but the present invention is not limited to these.

[0105]

[0106]

[0107]

[0108] Furthermore, photoreactive chiral agents can be used in combination with non-photoreactive chiral agents, such as chiral compounds with a high temperature dependence of torsional force. Examples of known non-photoreactive chiral agents include those described in Japanese Patent Publication No. 2000-044451, Japanese Patent Publication No. 10-509726, WO98 / 000428, Japanese Patent Publication No. 2000-506873, Japanese Patent Publication No. 9-506088, Liquid Crystals (1996, 21, 327), Liquid Crystals (1998, 24, 219), etc.

[0109] In the liquid crystal composition, the content of the chiral agent is preferably 0.01 to 200 mol%, and more preferably 1 to 30 mol%, relative to the molar amount of the liquid crystal compound.

[0110] --Polymerization Initiator-- If the liquid crystal composition contains a polymerizable compound, it is preferable that it also contains a polymerization initiator. In embodiments in which the polymerization reaction is carried out by ultraviolet irradiation, it is preferable that the polymerization initiator used is a photopolymerization initiator capable of initiating the polymerization reaction by ultraviolet irradiation. Examples of photopolymerization initiators include α-carbonyl compounds (as described in U.S. Patent No. 2,367,661 and U.S. Patent No. 2,367,670), acyloin ethers (as described in U.S. Patent No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (as described in U.S. Patent No. 2,722,512), polynuclear quinone compounds (as described in U.S. Patent No. 3,046,127 and U.S. Patent No. 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketones (as described in U.S. Patent No. 3,549,367), acridine and phenazine compounds (as described in Japanese Patent Publication No. 60-105,667 and U.S. Patent No. 4,239,850), and oxadiazole compounds (as described in U.S. Patent No. 4,212,970). The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, and more preferably 0.5 to 12% by mass, relative to the content of the liquid crystal compound.

[0111] --Crosslinking Agent-- The liquid crystal composition may optionally contain a crosslinking agent to improve the strength and durability of the film after curing. Suitable crosslinking agents are those that cure with ultraviolet light, heat, and moisture. There are no particular restrictions on the crosslinking agent, and it can be appropriately selected depending on the purpose. Examples include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl(meth)acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. In addition, known catalysts can be used depending on the reactivity of the crosslinking agent, which can improve productivity in addition to improving film strength and durability. These may be used individually or in combination of two or more. The crosslinking agent content is preferably 3 to 20% by mass, and more preferably 5 to 15% by mass, relative to the solid content mass of the liquid crystal composition. When the crosslinking agent content is within the above range, the effect of improving the crosslink density is easily obtained, and the stability of the cholesteric liquid crystal phase is further improved.

[0112] --Other Additives-- Polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and metal oxide nanoparticles may be added to the liquid crystal composition as needed, within limits that do not degrade optical performance. High refractive index nanoparticles such as zirconia oxide nanoparticles and titanium oxide nanoparticles may be added to increase the viewing angle of AR display.

[0113] When forming a cholesteric liquid crystal layer, the liquid crystal composition is preferably used as a liquid. The liquid crystal composition may contain a solvent. There are no restrictions on the solvent, and it can be appropriately selected according to the purpose, but an organic solvent is preferred. There are no restrictions on the organic solvent, and it can be appropriately selected according to the purpose. Examples include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used alone or in combination of two or more. Among these, ketones are preferred when considering the environmental load.

[0114] When forming a cholesteric liquid crystal layer, it is preferable to apply the liquid crystal composition to the formation surface of the cholesteric liquid crystal layer, orient the liquid crystal compound in the cholesteric liquid crystal phase state, and then cure the liquid crystal compound to form a cholesteric liquid crystal layer. That is, when forming a cholesteric liquid crystal layer on an alignment film, it is preferable to apply the liquid crystal composition to the alignment film, orient the liquid crystal compound in the cholesteric liquid crystal phase state, and then cure the liquid crystal compound to form a cholesteric liquid crystal layer in which the cholesteric liquid crystal phase is fixed. For the application of the liquid crystal composition, all known methods such as printing methods such as inkjet and screen printing, and methods capable of uniformly applying a liquid to a sheet-like material such as spin coating, bar coating, and spray coating can be used.

[0115] The applied liquid crystal composition is dried and / or heated as necessary, and then cured to form a cholesteric liquid crystal layer. In this drying and / or heating process, the liquid crystal compound in the liquid crystal composition may be oriented in the cholesteric liquid crystal phase. When heating is performed, the heating temperature is preferably 200 °C or lower, and more preferably 130 °C or lower.

[0116] The oriented liquid crystal compound is further polymerized as necessary. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. It is preferable to use ultraviolet light for light irradiation. The irradiation energy is preferably 20 mJ / cm 2 ~50 J / cm 2 and is preferably 50 to 1500 mJ / cm 2This is more preferable. To promote the photopolymerization reaction, light irradiation may be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the ultraviolet light used for irradiation is preferably 250 to 430 nm.

[0117] There are no restrictions on the thickness of the cholesteric liquid crystal layer. The thickness should be set appropriately to obtain the required light reflectivity, depending on the application of the liquid crystal diffraction element 10, the required light reflectivity of the optical anisotropy layer, and the material used to form the optical anisotropy layer.

[0118] <<Liquid Crystal Alignment Pattern of Cholesteric Liquid Crystal Layer>> As described above, in the liquid crystal diffraction element 10, the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes while continuously rotating in one direction within the plane of the cholesteric liquid crystal layer. In the example shown in Figure 1, the orientation of the optical axis 30A originating from the liquid crystal compound 30 forming the cholesteric liquid crystal phase changes while continuously rotating in one direction within the plane of the cholesteric liquid crystal layer. The optical axis 30A originating from the liquid crystal compound 30 is the axis in the liquid crystal compound 30 where the refractive index is highest, the so-called slow axis. For example, if the liquid crystal compound 30 is a rod-shaped liquid crystal compound, the optical axis 30A is along the long axis of the rod shape. In the following explanation, the optical axis 30A originating from the liquid crystal compound 30 is also referred to as the "optical axis 30A of the liquid crystal compound 30" or "optical axis 30A".

[0119] Figure 2 conceptually shows a plan view of the cholesteric liquid crystal layer 18 shown in Figure 1. The plan view is a view of the liquid crystal diffraction element 10 from above in Figure 1, that is, a view of the liquid crystal diffraction element 10 from the thickness direction (i.e., the stacking direction of each layer (film)). Furthermore, in Figure 2, to clearly show the structure of the cholesteric liquid crystal layer 18, only the liquid crystal compound 30 on the surface of the alignment film 24 is shown.

[0120] As shown in Figure 2, on the surface of the alignment film 24, the liquid crystal compounds 30 constituting the cholesteric liquid crystal layer 18 are arranged two-dimensionally in a predetermined direction indicated by arrow X, and in a direction perpendicular to this direction (arrow X direction), according to the alignment pattern formed on the underlying alignment film 24. In the following description, the direction perpendicular to arrow X direction will be conveniently referred to as the Y direction. That is, in Figures 1 and 4, and in Figures 7, 9, and 10 described later, the Y direction is perpendicular to the plane of the paper. Furthermore, the liquid crystal compounds 30 forming the cholesteric liquid crystal layer 18 have a liquid crystal alignment pattern in which the orientation of the optical axis 30A changes while continuously rotating along the direction of arrow X within the plane of the cholesteric liquid crystal layer 18. In the examples shown in Figures 1 and 2, the liquid crystal compounds 30 have a liquid crystal alignment pattern in which the optical axis 30A changes while continuously rotating clockwise along the direction of arrow X. The statement that the orientation of the optical axis 30A of the liquid crystal compound 30 changes while continuously rotating in the direction of arrow X (a predetermined one direction) means that, specifically, the angle between the optical axis 30A of the liquid crystal compounds 30 arranged along the direction of arrow X and the direction of arrow X differs depending on the position in the direction of arrow X, and that the angle between the optical axis 30A and the direction of arrow X changes sequentially from θ to θ+180° or θ-180° along the direction of arrow X. The difference in angle between the optical axes 30A of liquid crystal compounds 30 adjacent to each other in the direction of arrow X is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0121] On the other hand, in the liquid crystal compound 30 that forms the cholesteric liquid crystal layer 18, the orientation of the optical axis 30A is the same in the Y direction perpendicular to the direction of arrow X, that is, in the Y direction perpendicular to the direction in which the optical axis 30A rotates continuously. In other words, in the liquid crystal compound 30 that forms the cholesteric liquid crystal layer 18, the angle between the optical axis 30A of the liquid crystal compound 30 and the direction of arrow X is the same in the Y direction.

[0122] In the present invention, in the liquid crystal alignment pattern of such a liquid crystal compound 30, the length (distance) of a 180° rotation of the optical axis 30A of the liquid crystal compound 30 in the direction of arrow X, where the optical axis 30A rotates continuously in the plane and changes, is defined as the length of one period Λ in the liquid crystal alignment pattern. That is, the distance between the centers of two liquid crystal compounds 30 whose angles with respect to the direction of arrow X are equal in the direction of arrow X is defined as the length of one period Λ. Specifically, as shown in Figure 2, the distance between the centers of two liquid crystal compounds 30 whose directions of arrow X and the direction of the optical axis 30A coincide is defined as the length of one period Λ. In the following description, this length of one period Λ will also be referred to as "period Λ". In the liquid crystal diffraction element 10, the liquid crystal alignment pattern of the cholesteric liquid crystal layer 18 repeats this period Λ in one direction, i.e., the direction of the optical axis 30A rotates continuously and changes, in the direction of arrow X.

[0123] As shown in Figure 1, when the X-Z plane of a cholesteric liquid crystal layer 18 having a liquid crystal orientation pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes due to continuous rotation, an X-Z plane is observed using a Scanning Electron Microscope (SEM), a striped pattern is observed in which the arrangement direction of alternating bright areas 42 and dark areas 44, conceptually shown in Figure 25, is inclined at a predetermined angle with respect to the main plane (X-Y plane). In the following description, the cholesteric liquid crystal layer 18 will also be referred to as the liquid crystal layer 18. In such an SEM cross-section, the spacing between adjacent bright areas 42 and dark areas 44 in the direction normal to the line formed by the bright areas 42 or dark areas 44 corresponds to the 1 / 2 inclined plane pitch. When the optical axis 30A of the liquid crystal compound 30 is oriented parallel to the main plane (X-Y plane) of the liquid crystal layer 18, as described above, one helical pitch is the pitch P shown in Figure 1. On the other hand, when the liquid crystal compound 30 is inclined with respect to the main surface of the liquid crystal layer 18, in particular when the inclination angle of the liquid crystal compound 30 with respect to the main surface of the liquid crystal layer 18 is equal to the angle that the line formed by the bright area 42 or the dark area 44 makes with the main surface of the liquid crystal layer 18, as shown by P in Figure 25, two bright areas 42 and two dark areas 44 correspond to one helical pitch (one turn of the helix).

[0124] In the example shown in Figure 1, the liquid crystal compound 30 is configured such that its optical axis 30A is oriented parallel to the main plane (X-Y plane) in the X-Z plane of the liquid crystal layer 18. However, the present invention is not limited to this configuration. For example, as shown in Figure 26, the optical axis 30A of the liquid crystal compound 30 may be oriented at an angle to the main plane (X-Y plane) in the X-Z plane of the liquid crystal layer 18.

[0125] Furthermore, in the example shown in Figure 26, the tilt angle of the liquid crystal compound 30 with respect to the main plane (X-Y plane) in the X-Z plane of the liquid crystal layer 18 is uniform in the thickness direction (Z direction), but the present invention is not limited thereto. The liquid crystal layer 18 may have regions in which the tilt angle of the liquid crystal compound 30 differs in the thickness direction. For example, in the example shown in Figure 27, the optical axis 30A of the liquid crystal compound 30 is parallel to the main plane (pre-tilt angle is 0°) at the interface on the alignment film 24 side of the liquid crystal layer 18, and as it moves away from the interface on the alignment film 24 side in the thickness direction, the tilt angle of the liquid crystal compound 30 increases, and thereafter the liquid crystal compound is oriented at a constant tilt angle all the way to the other interface (air interface).

[0126] Thus, in the liquid crystal layer 18, the optical axis 30A of the liquid crystal compound 30 may have a pre-tilt angle at one of the upper and lower interfaces, or it may have a pre-tilt angle at both interfaces. Furthermore, the pre-tilt angles may be different at the two interfaces. By having a tilt angle (inclination) in this way, the effective birefringence of the liquid crystal compound increases when light diffracts, thereby increasing the diffraction efficiency. In addition, the effective refractive index of the liquid crystal compound increases when light diffracts, which allows for a wider field of view (FOV) when used, for example, in AR glasses.

[0127] The average angle (average tilt angle) between the optical axis 30A of the liquid crystal compound 30 and the main plane (X-Y plane) is preferably 5 to 80°, and more preferably 10 to 50°. The average tilt angle can be measured by observing the X-Z plane of the liquid crystal layer 18 with a polarizing microscope. In particular, it is preferable that the optical axis 30A of the liquid crystal compound 30 is tilted in the same direction as the main plane (X-Y plane) in the X-Z plane of the liquid crystal layer 18. The above tilt angle is the value obtained by measuring the angle between the optical axis 30A of the liquid crystal compound 30 and the main plane at five or more arbitrary locations during polarizing microscope observation of the cross-section of the cholesteric liquid crystal layer, and arithmetically averaging these values.

[0128] Light incident perpendicularly on a liquid crystal diffraction element (liquid crystal layer 18) propagates obliquely within the liquid crystal layer 18 due to a bending force. As light propagates within the liquid crystal layer 18, a deviation occurs from the conditions such as the diffraction period, which are originally set to obtain the desired diffraction angle for perpendicular incidence, resulting in diffraction loss. When the liquid crystal compound 30 is tilted, there is a direction in which a higher birefringence is generated relative to the direction in which light diffracts, compared to when it is not tilted. In this direction, the effective anomalous refractive index becomes larger, and therefore the birefringence, which is the difference between the anomalous refractive index and the ordinary refractive index, becomes higher. By setting the direction of the tilt angle to match the desired diffraction direction, the deviation from the original diffraction conditions in that direction can be suppressed, and as a result, it is thought that a higher diffraction efficiency can be obtained when using a liquid crystal compound with a tilt angle.

[0129] Furthermore, the tilt angle may be controlled by processing the interface of the liquid crystal layer 18. At the interface on the support side, the tilt angle of the liquid crystal compound 30 can be controlled by performing a pre-tilt treatment on the alignment film. For example, when forming the alignment film, if the alignment film is exposed to ultraviolet light from the front and then from an oblique angle, a pre-tilt angle can be generated in the liquid crystal compound 30 in the liquid crystal layer 18 formed on the alignment film. In this case, the liquid crystal compound 30 is pre-tilted in a direction where the uniaxial side is visible with respect to the second irradiation direction. However, since the liquid crystal compound 30 in the direction perpendicular to the second irradiation direction is not pre-tilted, there are regions in the plane that are pre-tilted and regions that are not. This is suitable for increasing diffraction efficiency because it contributes to increasing birefringence in the direction in which light is diffracted when diffracting light in the target direction. Furthermore, an additive that promotes the pre-tilt angle can be added to the liquid crystal layer 18 or the alignment film. In this case, the additive can be used as a factor to further increase diffraction efficiency. This additive can also be used to control the pre-tilt angle of the interface on the air side.

[0130] Here, in the cross-section observed by SEM, the bright areas 42 and dark areas 44 originating from the cholesteric liquid crystal phase of the liquid crystal layer 18 are inclined with respect to the main plane. When retardation is measured in the liquid crystal layer 18 from the normal direction and a direction inclined with respect to the normal, it is preferable that the direction in which retardation is minimized, either within the slow-phase axis plane or the fast-phase axis plane, is inclined with respect to the normal direction. Specifically, it is preferable that the absolute value of the measurement angle that the direction in which retardation is minimized makes with the normal is 5° or more. In other words, it is preferable that the liquid crystal compound 30 of the liquid crystal layer 18 is inclined with respect to the main plane, and that the direction of inclination substantially coincides with the bright areas 42 and dark areas 44 of the liquid crystal layer 18. The normal direction is the direction perpendicular to the main plane. By having such a configuration, the liquid crystal layer 18 can diffract circularly polarized light with higher diffraction efficiency compared to a liquid crystal layer in which the liquid crystal compound 30 is parallel to the main plane.

[0131] In a configuration where the liquid crystal compound 30 of the liquid crystal layer 18 is tilted with respect to the main surface, and the direction of the tilt substantially coincides with the bright areas 42 and the dark areas 44, the bright and dark areas corresponding to the reflective surfaces coincide with the optical axis 30A of the liquid crystal compound 30. Therefore, the effect of the liquid crystal compound on the reflection (diffraction) of light is increased, and the diffraction efficiency can be improved. As a result, the amount of reflected light relative to the incident light can be further improved.

[0132] In the phase-advancing or phase-lagging axis plane of the liquid crystal layer 18, the absolute value of the optical axis inclination angle of the liquid crystal layer 18 is preferably 5° or more, more preferably 15° or more, and even more preferably 20° or more. Setting the absolute value of the optical axis inclination angle to 15° or more is preferable because it more preferably aligns the direction of the liquid crystal compound 30 with the light and dark areas, thereby improving diffraction efficiency.

[0133] A typical cholesteric liquid crystal layer, which has a fixed cholesteric liquid crystal phase, usually specularly reflects incident light (circularly polarized light). In contrast, the cholesteric liquid crystal layer 18 having the liquid crystal alignment pattern described above reflects incident light in a direction that is at an angle to specular reflection in the direction of arrow X. For example, the cholesteric liquid crystal layer 18 does not reflect light incident from the normal direction in the normal direction, but rather reflects it at an angle to the normal direction in the direction of arrow X. Light incident from the normal direction is light incident from the front, that is, light incident perpendicular to the principal surface. The principal surface is the largest surface of the sheet-like material. The following explanation will be given with reference to Figure 4.

[0134] As mentioned above, the cholesteric liquid crystal layer 18 is a cholesteric liquid crystal layer that selectively reflects one of the circularly polarized wavelengths of the selective reflection wavelength. For example, if the selective reflection wavelength of the cholesteric liquid crystal layer 18 is red light and it reflects right-circularly polarized light, then light R R When R is incident on it, the cholesteric liquid crystal layer 18 reacts to the right-circular polarization of red light. R It reflects only certain types of light, while transmitting all other light.

[0135] Here, the angle of reflection of light by the cholesteric liquid crystal layer, where the optical axis 30A of the liquid crystal compound 30 rotates continuously in one direction (arrow X direction), differs depending on the wavelength of the reflected light. Specifically, the longer the wavelength of light, the larger the angle of reflected light relative to the incident light. Furthermore, the angle of reflection of light by the cholesteric liquid crystal layer, where the optical axis 30A of the liquid crystal compound 30 rotates continuously in the direction of arrow X (one direction), differs depending on the length Λ of one period of the liquid crystal orientation pattern in which the optical axis 30A rotates 180° in the direction of arrow X, i.e., the period Λ. Specifically, the shorter the period Λ, the larger the angle of reflected light relative to the incident light.

[0136] In the liquid crystal diffraction element 10, there are no restrictions on the period Λ in the orientation pattern of the cholesteric liquid crystal layer, and it can be set appropriately according to the application of the liquid crystal diffraction element 10.

[0137] Here, the liquid crystal diffraction element 10 is suitably used, for example, in AR glasses as a diffraction element that reflects light propagated through a light guide plate and emits it from the light guide plate to the user's observation position. In this case, in order to reliably emit the light that has propagated through the light guide plate, it is necessary to reflect the light at a sufficiently large angle with respect to the incident light. Furthermore, as mentioned above, the reflection angle of light by the cholesteric liquid crystal layer can be increased by shortening the period Λ in the liquid crystal alignment pattern to increase the reflection angle with respect to the incident light.

[0138] Considering this point, the period Λ in the liquid crystal alignment pattern of the cholesteric liquid crystal layer is preferably 50 μm or less, more preferably 10 μm or less, and even more preferably 1 μm or less. Furthermore, considering the accuracy of the liquid crystal alignment pattern, it is preferable that the period Λ in the liquid crystal alignment pattern of the cholesteric liquid crystal layer be 0.1 μm or more.

[0139] In this invention, it is preferable that the cholesteric liquid crystal layer has a region in which the diffraction efficiency increases as you move from one side to the other in one direction in which the orientation of the optical axis derived from the liquid crystal compound rotates continuously in the plane (hereinafter referred to as the one direction in which the optical axis rotates). For example, in the case of the cholesteric liquid crystal layer shown in Figures 1 and 2, the diffraction efficiency increases as you move from one side to the other in the X direction.

[0140] Figures 5 and 6 schematically show the relationship between the position of the cholesteric liquid crystal layer 18 in one direction (X direction) of optical axis rotation and the diffraction efficiency at that position. In the X direction, the diffraction efficiency of the cholesteric liquid crystal layer 18 may change continuously as shown in Figure 5, or it may change in steps as shown in Figure 6.

[0141] Here, the diffraction efficiency is measured as follows. The cholesteric liquid crystal layer 18 is transferred to a dove prism 110 (refractive index = 1.517, inclination angle = 45°) as shown in Figure 14. A laser of a predetermined wavelength is transmitted through a linear polarizer 112 and a λ / 4 plate 114 to obtain right-circular polarization, and the diffracted light is incident on the surface of the cholesteric liquid crystal layer 18 at an angle set so that it is emitted perpendicular to the inclination. The emitted light intensity Lr is measured using a Newport power meter 1918-C, and the ratio of Lr to the incident light intensity Li (Lr / Li × 100 [%]) is taken as the diffraction efficiency.

[0142] In a liquid crystal diffraction grating, it is preferable that the cholesteric liquid crystal layer has a region in which the diffraction efficiency increases as you move from one side to the other in one direction of rotation of the optical axis. That is, it is preferable that at least one region of the optical anisotropy layer, region A and / or region B, or further, region C (described later), has a region in which the diffraction efficiency increases as you move from one side to the other in one direction of rotation of the optical axis. This makes it possible to make the brightness (amount of light) of the light emitted from the light guide plate uniform even when the exit pupil is enlarged, when a liquid crystal diffraction element is used as a diffraction element in an AR (Augmented Reality) display device such as AR glasses to diffract light propagating within the light guide plate and emit it from the light guide plate. This point will be described in detail later.

[0143] Furthermore, if we define the direction in which regions with constant diffraction efficiency are arranged in the cholesteric liquid crystal layer as the direction of change in diffraction efficiency, this direction of change in diffraction efficiency may or may not coincide with the direction in which the optical axis rotates. In other words, the direction of change in diffraction efficiency and the direction in which the optical axis rotates may intersect. Even in a configuration where the direction of change in diffraction efficiency and the direction in which the optical axis rotates intersect, the diffraction efficiency will increase as one moves from one side to the other in the direction in which the optical axis rotates.

[0144] Furthermore, the cholesteric liquid crystal layer (at least one of region A, region B, and region C) may have a configuration in which regions with different diffraction efficiencies in the in-plane direction, a configuration in which the diffraction efficiency gradually changes in one direction in the in-plane direction, or a configuration in which the diffraction efficiency gradually increases (or gradually decreases) in one direction in the in-plane direction.

[0145] A configuration in which the diffraction efficiency of a cholesteric liquid crystal layer increases from one side to the other in one direction in which the orientation of the optical axis derived from the liquid crystal compound rotates continuously in the plane can be achieved by having a cholesteric liquid crystal layer with either of the following configurations (i) or (ii), and configuration (ii) is preferred because the optical anisotropy layer is smooth. (i) A configuration in which the film thickness increases from one side to the other in one direction in which the optical axis rotates. (ii) A configuration in which the thickness direction retardation Rth increases from one side to the other in one direction in which the optical axis rotates.

[0146] In a cholesteric liquid crystal layer, the diffraction efficiency is higher in areas with thicker film thickness and lower in areas with thinner film thickness. Therefore, by configuring the cholesteric liquid crystal layer so that the film thickness increases from one side to the other in one direction of rotation of the optical axis, the diffraction efficiency can be changed.

[0147] As mentioned above, in a cholesteric liquid crystal layer, the liquid crystal compounds are arranged in a desired orientation pattern. In regions where this arrangement is not disordered, light can be diffracted appropriately, resulting in high diffraction efficiency. Also, in regions where the arrangement of liquid crystal compounds is not disordered, the thickness-direction retardation Rth is high. On the other hand, in regions where the arrangement of liquid crystal compounds is disordered, light is not diffracted appropriately, resulting in low diffraction efficiency. Also, in regions where the arrangement of liquid crystal compounds is disordered, the thickness-direction retardation Rth is low. Therefore, by configuring the cholesteric liquid crystal layer so that the thickness-direction retardation Rth increases from one side to the other in one direction of rotation of the optical axis, the diffraction efficiency can be changed. An example of a method for forming such a cholesteric liquid crystal layer is the method described in WO2020-122119.

[0148] A method for detecting that the thickness direction retardation Rth differs in different regions within a plane at different positions is described below. Since the diagonal direction retardation Re(40) is proportional to the thickness direction retardation Rth, it is possible to detect that the thickness direction retardation Rth differs in different regions within a plane by confirming that the diagonal direction retardation Re(40) differs in different regions within the plane. Furthermore, it is possible to detect that the thickness direction retardation Rth is gradually changing within a plane by confirming that the diagonal direction retardation Re(40) is gradually changing within the plane.

[0149] Furthermore, the cholesteric liquid crystal layer has regions with high birefringence and regions with low birefringence in the thickness direction. By varying the ratio of the thickness of the region with high birefringence to the total thickness of the cholesteric liquid crystal layer within the plane of the cholesteric liquid crystal layer, the diffraction efficiency can be changed. A higher ratio of the thickness of the region with high birefringence in the thickness direction of the cholesteric liquid crystal layer results in higher diffraction efficiency, while a lower ratio results in lower diffraction efficiency. Preferably, the region with low birefringence in the thickness direction includes an optically isotropic region.

[0150] A method for detecting differences in birefringence at different positions in the thickness direction within a given plane is explained in Figure 33. In an optically anisotropic layer in which the liquid crystal compound is cholesterically oriented, when the optically anisotropic layer 324 is cut in the thickness direction and the SEM image of the exposed optically anisotropic layer 324 is analyzed, in the region 326 with a high birefringence, bright areas 332 and dark areas 330, which are due to the cholesterically oriented liquid crystal compound, are clearly visible. On the other hand, in the region 328 with a low birefringence, the contrast between the bright and dark areas is small, and especially when the region 328 is optically isotropic, the bright and dark areas are not visible. Therefore, by measuring the thickness of the region where the bright and dark areas are clearly visible, the film thickness in the region with a high birefringence can be determined.

[0151] However, when the liquid crystal compound is not cholesterically oriented, and when the birefringence changes continuously in the thickness direction, it is difficult to measure the thickness of the region with a high birefringence. In such cases, a portion of the optically anisotropic layer can be etched, and the ratio of the birefringence Δn in the thickness direction can be determined from the difference in the oblique retardation Re(40) before and after etching. For example, after determining the oblique retardation Re(40) using Axoscan (manufactured by Axometrics), the process of etching 100 nm from the surface of the optically anisotropic layer is repeated until the optically anisotropic layer is completely etched in the thickness direction. The magnitude of the oblique retardation Re(40) in the etched region can be calculated from the difference in the oblique retardation Re(40) before and after the 100 nm etching. Since the diagonal retardation Re(40) is proportional to the birefringence Δn, the thickness of the region with high birefringence in the liquid crystal compound can be determined by determining the film thickness in the region with large diagonal retardation Re(40) in the thickness direction.

[0152] A configuration in which the diffraction efficiency of a cholesteric liquid crystal layer increases from one side to the other along at least one direction within the plane of the cholesteric liquid crystal layer can be achieved by having a configuration in which the ratio of the thickness of the region with a high birefringence to the thickness of the cholesteric liquid crystal layer changes gradually. For example, by gradually increasing the ratio of the thickness of the region with a high birefringence to the thickness of the cholesteric liquid crystal layer along at least one direction within the plane of the cholesteric liquid crystal layer, the diffraction efficiency of the cholesteric liquid crystal layer can be increased from one side to the other.

[0153] In a cholesteric liquid crystal layer, if the thickness direction has regions with high and low birefringences, then the thickness direction has regions with different birefringences Δn. Therefore, if the diffraction efficiency changes within the plane of the cholesteric liquid crystal layer, the average value Δna of the birefringence in the thickness direction changes within the plane. In other words, if the diffraction efficiency of the cholesteric liquid crystal layer changes along at least one direction within the plane of the cholesteric liquid crystal layer, moving from one side to the other, then the average value Δna of the birefringence in the thickness direction gradually changes within the plane. Thus, a configuration in which the birefringence Δn differs in the thickness direction and the average value Δna of the birefringence in the thickness direction gradually changes within the plane can be realized, for example, by configuring the cholesteric liquid crystal layer so that, in at least a part of its plane, the thickness of the optically isotropic region gradually decreases and the thickness of the optically anisotropic region gradually increases along at least one direction within the plane of the cholesteric liquid crystal layer, moving from one side to the other. Within the plane of the cholesteric liquid crystal layer, the maximum thickness of the high birefringence region is preferably 0.01 to 10 μm, more preferably 0.03 μm to 8 μm, and even more preferably 0.05 μm to 5 μm. Within the plane of the cholesteric liquid crystal layer, the minimum thickness of the high birefringence region is preferably 0.0 to 5 μm, more preferably 0.0 μm to 3 μm, and even more preferably 0.0 μm to 1 μm. However, the maximum and minimum thicknesses of the high birefringence region are preferably set appropriately depending on the performance required for the optical anisotropy layer and the light guide element, and are not limited to the above.

[0154] [Second Embodiment] In the example shown in Figure 1, the region A and / or region B (or further region C) of the optical anisotropy layer is assumed to have a cholesterically oriented liquid crystal compound, but this is not limited to this, and the liquid crystal compound may not be cholesterically oriented. Figure 7 conceptually shows an example of a second embodiment of the liquid crystal diffraction element. The liquid crystal diffraction element 12 shown in Figure 7 is a liquid crystal diffraction element that diffracts and transmits incident light. The liquid crystal diffraction element 12 shown in Figure 7 has a structure in which a support 20, an alignment film 24, and a liquid crystal diffraction layer 16 are stacked in this order.

[0155] The support 20 and alignment film 24 have the same configuration as the support 20 and alignment film 24 of the liquid crystal diffraction element 10 shown in Figure 1, so their explanation will be omitted.

[0156] <Liquid Crystal Diffraction Layer> The liquid crystal diffraction layer 16 is formed on the surface of the alignment film 24. The liquid crystal diffraction layer 16 is a layer formed using a composition containing a liquid crystal compound, and has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound rotates continuously along at least one direction in the plane.

[0157] Figure 8 shows a plan view of the liquid crystal diffraction element shown in Figure 7. The plan view is a view of the liquid crystal diffraction element from above in Figure 7, that is, a view of the liquid crystal diffraction element from the thickness direction (i.e., the stacking direction of each layer (film)). In other words, it is a view of the liquid crystal diffraction layer 16 from a direction perpendicular to the main surface. Furthermore, in Figure 8, in order to clearly show the structure of the liquid crystal diffraction element, only the liquid crystal compound 30 on the surface of the alignment film 24 is shown as the liquid crystal compound 30 in the liquid crystal diffraction layer 16. However, in the thickness direction, as shown in Figure 7, the liquid crystal diffraction layer 16 has a structure in which the liquid crystal compound 30 is stacked from the liquid crystal compound 30 on the surface of the alignment film 24.

[0158] As shown in Figure 8, the liquid crystal diffraction layer 16 has a liquid crystal orientation pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes while continuously rotating in one direction indicated by arrow X within the plane of the liquid crystal diffraction layer 16. Specifically, the change in the orientation of the optical axis 30A of the liquid crystal compound 30 while continuously rotating in the direction of arrow X (a predetermined one direction) means that the angle between the optical axis 30A of the liquid crystal compounds 30 arranged along the direction of arrow X and the direction of arrow X differs depending on the position in the direction of arrow X, and that the angle between the optical axis 30A and the direction of arrow X changes sequentially from θ to θ+180° or θ-180° along the direction of arrow X. The difference in angle between the optical axes 30A of liquid crystal compounds 30 adjacent to each other in the direction of arrow X is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0159] On the other hand, in the liquid crystal compound 30 that forms the liquid crystal diffraction layer 16, in the Y direction perpendicular to the direction of arrow X, that is, in the Y direction perpendicular to the direction in which the optical axis 30A rotates continuously, liquid crystal compounds 30 with the same orientation of the optical axis 30A are arranged at equal intervals. In other words, in the liquid crystal compound 30 that forms the liquid crystal diffraction layer 16, the angle between the orientation of the optical axis 30A and the direction of arrow X is equal for liquid crystal compounds 30 arranged in the Y direction.

[0160] In the direction of arrow X, where the optical axis 30A rotates continuously within the plane and changes, the length (distance) of the 180° rotation of the optical axis 30A of the liquid crystal compound 30 is defined as the length of one period Λ in the liquid crystal alignment pattern. That is, the distance between the centers of two liquid crystal compounds 30 with the same angle to the direction of arrow X is defined as the length of one period Λ in the direction of arrow X. The liquid crystal alignment pattern of the liquid crystal diffraction layer 16 repeats one period Λ in the liquid crystal alignment pattern in one direction, i.e., the direction of the optical axis 30A rotates continuously and changes.

[0161] As described above, in the liquid crystal diffraction layer 16, the liquid crystal compounds arranged in the Y direction have an equal angle between the optical axis 30A and the direction of arrow X (one direction in which the orientation of the optical axis of the liquid crystal compound 30 rotates). The region in which the liquid crystal compounds 30 having an equal angle between the optical axis 30A and the direction of arrow X are arranged in the Y direction is defined as region R. In this case, it is preferable that the in-plane retardation (Re) value in each region R is half a wavelength, i.e., λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn due to the refractive index anisotropy of region R and the thickness of the liquid crystal diffraction layer 16. Here, the refractive index difference due to the refractive index anisotropy of region R in the liquid crystal diffraction layer 16 is defined as the refractive index difference between the refractive index in the direction of the slow axis in the plane of region R and the refractive index in the direction perpendicular to the direction of the slow axis. In other words, the refractive index difference Δn due to the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 30 in the direction of the optical axis 30A and the refractive index of the liquid crystal compound 30 in the direction perpendicular to the optical axis 30A within the plane of region R. That is, the above refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

[0162] When circularly polarized light is incident on such a liquid crystal diffraction layer 16, the light is refracted and the direction of its circular polarization is changed. This effect is conceptually illustrated in Figure 9, which illustrates the liquid crystal diffraction layer 16. As shown in Figure 9, when incident light L1, which is left-circularly polarized, is incident on the liquid crystal diffraction layer 16, the incident light L1 passes through the liquid crystal diffraction layer 16, resulting in a phase difference of 180°, and the transmitted light L2 is converted to right-circularly polarized light. Furthermore, since the liquid crystal alignment pattern formed on the liquid crystal diffraction layer 16 is a periodic pattern in the direction of arrow X, the transmitted light L2 is refracted and travels in a direction different from the direction of propagation of the incident light L1. In this way, the left-circularly polarized incident light L1 is converted to right-circularly polarized transmitted light L2, which is tilted by a certain angle in the direction of arrow X with respect to the direction of incidence.

[0163] On the other hand, as conceptually shown in Figure 10, when right-circularly polarized incident light L4 is incident on the liquid crystal diffraction layer 16, the incident light L4 passes through the liquid crystal diffraction layer 16, is given a phase difference of 180°, and is converted into left-circularly polarized transmitted light L5. Furthermore, since the liquid crystal alignment pattern formed on the liquid crystal diffraction layer 16 is a periodic pattern in the direction of arrow X, the transmitted light L5 is refracted (diffracted) and propagates in a direction different from the direction of propagation of the incident light L4. In this way, the incident light L4 is converted into left-circularly polarized transmitted light L5 that is tilted by a certain angle in the direction opposite to the direction of arrow X with respect to the direction of incidence.

[0164] In the liquid crystal diffraction layer 16, the in-plane retardation values ​​of multiple regions R are preferably half wavelengths in order to obtain high diffraction efficiency. However, it is preferable that the in-plane retardation Re(550) = Δn550 × d of multiple regions R of the liquid crystal diffraction layer 16 for incident light with a wavelength of 550 nm is within the range defined by the following equation (1). Here, Δn550 is the refractive index difference due to the refractive index anisotropy of region R when the wavelength of the incident light is 550 nm, and d is the thickness of the liquid crystal diffraction layer 16. 200 nm ≤ Δn550 × d ≤ 350 nm ... (1) That is, if the in-plane retardation Re(550) = Δn550 × d of multiple regions R of the liquid crystal diffraction layer 16 satisfies equation (1), then a sufficient amount of circularly polarized light component of the light incident on the liquid crystal diffraction layer 16 can be converted into circularly polarized light that propagates in a direction tilted forward or backward with respect to the direction of arrow X. The in-plane retardation Re(550) = Δn550 × d is more preferably 225 nm ≤ Δn550 × d ≤ 340 nm, and even more preferably 250 nm ≤ Δn550 × d ≤ 330 nm. Note that while the above formula (1) is a range for incident light with a wavelength of 550 nm, the in-plane retardation Re(λ) = Δnλ × d of multiple regions R of the liquid crystal diffraction layer 16 for incident light with a wavelength of λ nm is preferably within the range defined by the following formula (1-2), and can be set as appropriate: 0.35 × λ nm ≤ Δnλ × d ≤ 0.65 × λ nm ... (1-2)

[0165] Furthermore, the in-plane retardation values ​​of multiple regions R in the liquid crystal diffraction layer 16 can also be used outside the range of equation (1) above. Specifically, by setting Δn550×d < 200 nm or 350 nm < Δn550×d, the light can be separated into light traveling in the same direction as the incident light and light traveling in a different direction. As Δn550×d approaches 0 nm or 550 nm, the component of light traveling in the same direction as the incident light increases, and the component of light traveling in a different direction decreases.

[0166] Furthermore, it is preferable that the in-plane retardation Re(450) = Δn450 × d of each region R of the liquid crystal diffraction layer 16 for incident light with a wavelength of 450 nm, and the in-plane retardation Re(550) = Δn550 × d of each region R of the liquid crystal diffraction layer 16 for incident light with a wavelength of 550 nm, satisfy the following equation (2). Here, Δn450 is the refractive index difference due to the refractive index anisotropy of region R when the wavelength of the incident light is 450 nm. (Δn450 × d) / (Δn550 × d) < 1.0 ... (2) Equation (2) indicates that the liquid crystal compound 30 contained in the liquid crystal diffraction layer 16 has inverse dispersion properties. That is, by satisfying equation (2), the liquid crystal diffraction layer 16 can handle incident light of a broadband wavelength.

[0167] Here, the angle of refraction of transmitted light L2 and L5 can be adjusted by changing the period Λ of the liquid crystal alignment pattern formed on the liquid crystal diffraction layer 16. Specifically, the shorter the period Λ of the liquid crystal alignment pattern, the stronger the interference between light passing through adjacent liquid crystal compounds 30, allowing for greater refraction (diffraction) of transmitted light L2 and L5. Furthermore, the angle of refraction of transmitted light L2 and L5 relative to incident light L1 and L4 differs depending on the wavelength of the incident light L1 and L4 (transmitted light L2 and L5). Specifically, the longer the wavelength of the incident light, the greater the refraction (diffraction) of the transmitted light. That is, when the incident light is red, green, and blue light, the red light is refraction (diffraction) the greatest, and the blue light is refraction (diffraction) the smallest. In addition, by reversing the rotation direction of the optical axis 30A of the liquid crystal compound 30, which rotates along the direction of arrow X, the direction of refraction (diffraction) of transmitted light can be reversed.

[0168] The liquid crystal diffraction layer 16 consists of a cured layer of a liquid crystal composition containing a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and has a liquid crystal alignment pattern in which the optical axis of the rod-shaped liquid crystal compound or the optical axis of the disc-shaped liquid crystal compound is oriented as described above. By forming an alignment film 24 on a support 20, and coating and curing the liquid crystal composition on the alignment film 24, a liquid crystal diffraction layer 16 consisting of a cured layer of liquid crystal composition can be obtained. The method of coating and curing the liquid crystal composition is the same as that for the cholesteric liquid crystal layer described above. Although the liquid crystal diffraction layer 16 functions as an optically anisotropic region, the present invention also includes embodiments in which a laminate comprising the support 20 and the alignment film 24 integrally functions as an optically anisotropic region.

[0169] Furthermore, the liquid crystal composition for forming the liquid crystal diffraction layer 16 contains a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and may also contain other components such as a leveling agent, an orientation control agent, a polymerization initiator, a crosslinking agent, and an orientation aid. The liquid crystal composition may also contain a solvent. The rod-shaped liquid crystal compound, disc-shaped liquid crystal compound, etc., contained in the liquid crystal composition for forming the liquid crystal diffraction layer 16 can be the same as the rod-shaped liquid crystal compound, disc-shaped liquid crystal compound, etc., contained in the liquid crystal composition for forming the cholesteric liquid crystal layer 18 described above. That is, the liquid crystal composition for forming the liquid crystal diffraction layer 16 is the same as the liquid crystal composition for forming the cholesteric liquid crystal layer 18 described above, except that it does not contain a chiral agent. Furthermore, the liquid crystal diffraction layer 16 may have a so-called twist structure (torsed structure) in which the orientation of the liquid crystal compound changes continuously from one interface side to the other interface side in the thickness direction. The twist structure is a configuration in which the liquid crystal compound does not become a cholesteric liquid crystal phase and is twisted and rotated in the thickness direction to such an extent that it does not substantially exhibit selective reflectivity. Specifically, in a twisted structure, the twist of the optical axis over the entire thickness direction is less than one rotation, i.e., the twist angle is less than 360°. The twisted structure can be formed by appropriately adding a chiral agent to the liquid crystal composition.

[0170] Furthermore, it is desirable that the liquid crystal diffraction layer 16 has a broad bandwidth with respect to the wavelength of the incident light, and is preferably composed of a liquid crystal material with inverse dispersion birefringence. Also, from the viewpoint of achieving superior effects of the present invention and obtaining diffracted light with high diffraction efficiency even at large diffraction angles, the refractive index anisotropy Δn of the liquid crystal compound is preferably 0.15 or higher, more preferably 0.20 or higher, and even more preferably 0.25 or higher. There is no particular upper limit, but it is often 1.00 or lower. Liquid crystal compounds exhibiting such high refractive index anisotropy are often forward-dispersive compounds in which the birefringence Δn450 for incident light with a wavelength of 450 nm is greater than the birefringence Δn450 for incident light with a wavelength of 550 nm. In such cases, it is also preferable to make the liquid crystal diffraction layer 16 substantially broadband with respect to the wavelength of the incident light by imparting a torsion component to the liquid crystal composition or by stacking different liquid crystal diffraction layers. For example, a method for realizing a broadband patterned optical anisotropy layer in the liquid crystal diffraction layer 16 by stacking two liquid crystal layers with different twist directions is shown in Japanese Patent Application Publication No. 2014-089476, and can be preferably used in the present invention.

[0171] [Non-diffraction region] As shown in Figure 28, the optical anisotropy layer 400 of the present invention has a non-diffraction region 45b. The non-diffraction region 45b does not have the liquid crystal alignment pattern described above and is a region that does not have the function of diffracting incident light.

[0172] The non-diffraction region 45b may be an unoriented region where the liquid crystal compound is not oriented, i.e., an optically isotropic region, or it may be a region where the liquid crystal compound is oriented in one direction within the same plane (in this invention, the non-diffraction region is referred to as an optical layer, including the case where the non-diffraction region is an isotropic region. If the non-diffraction layer has optical anisotropy, the optical layer is an optically anisotropic layer). In the non-diffraction region 45b, the liquid crystal compound may be uniaxially oriented, twisted, or cholesterically oriented in the thickness direction, and uniaxially oriented or twisted is preferred. The non-diffraction region 45b may have a structure in which a region where the liquid crystal compound is uniaxially oriented, twisted, or cholesterically oriented in the thickness direction is laminated with an isotropic region. When the non-diffraction region 45b is a region where the liquid crystal compound is oriented in one direction within the same plane, it is preferable that the non-diffraction region 45b functions as a phase difference region. It is preferable that the phase difference region gives a phase difference of λ / 8 to light from at least one incident direction. As a result, for example, circularly polarized light diffracted in the incident region A45a is converted to elliptically polarized light by passing through the non-diffracting region 45b as it is guided through the light guide plate. Total internal reflection occurs at the interface between the non-diffracting region 45b and the air, and it is converted back to linearly polarized light by passing through the non-diffracting region 45b again. While the polarization state of circularly polarized light is lost during light guidance, the polarization state of linearly polarized light can be maintained during light guidance, making it possible to make the light intensity of the emitted light in the exit region B45c uniform.

[0173] Here, in the optically anisotropic layer of the present invention, the rotation direction of the optical axis derived from the liquid crystal compound along one direction in the liquid crystal alignment pattern of region A and the rotation direction of the optical axis derived from the liquid crystal compound along one direction in the liquid crystal alignment pattern of region B may be the same or different from each other. Also, one direction of the liquid crystal alignment pattern in region A and one direction of the liquid crystal alignment pattern in region B may be different from each other. That is, one direction of the liquid crystal alignment pattern in region A and one direction of the liquid crystal alignment pattern in region B may be parallel or intersect. Furthermore, the length (1 period Λ) over which the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of region A rotates 180° in the plane and the length (1 period Λ) over which the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of region B rotates 180° in the plane may be the same or different from each other.

[0174] As will be described later, when an optically anisotropic layer is used in combination with a light guide plate as a light guide element, for example, region A acts as an incident diffraction element for injecting light into the light guide plate, and region B acts as an exit diffraction element for ejecting light from the light guide plate. Therefore, the required diffraction performance of region A and region B is different. Accordingly, regions A and B can be set according to the required diffraction performance by determining the rotation direction, period, and direction of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern, and the liquid crystal alignment pattern in region A and the liquid crystal alignment pattern in region B may be different.

[0175] Furthermore, in the optical anisotropic layer of the present invention, region A and region B may each be cholesteric liquid crystal layers, region A and region B may each be liquid crystal diffraction layers, region A may be a cholesteric liquid crystal layer and region B may be a liquid crystal diffraction layer, or region A may be a liquid crystal diffraction layer and region B may be a cholesteric liquid crystal layer.

[0176] Furthermore, in the optical anisotropy layer of the present invention, if regions A and B are cholesteric liquid crystal layers, the helical pitch length of the cholesteric liquid crystal layer in region A and the helical pitch length of the cholesteric liquid crystal layer in region B may be different in each region. For example, when the optical anisotropy layer is used in combination with a light guide plate, with region A as the incident diffraction element and region B as the exit diffraction element, light is incident on region A from a substantially perpendicular direction, while light is incident on region B from an oblique direction. As mentioned above, the cholesteric liquid crystal layer has wavelength-selective reflectivity, but when light is incident from an oblique direction, a so-called blue shift occurs, in which the selectively reflected wavelength becomes shorter. Therefore, even when regions A and B diffract light of the same wavelength, it is preferable to set an appropriate helical pitch length for each region according to the angle of incidence of the light, etc.

[0177] Furthermore, the direction of rotation of the cholesteric orientation helix in region A and the direction of rotation of the cholesteric orientation helix in region B may be different from each other. That is, the direction of rotation of the circularly polarized light reflected by region A and the direction of rotation of the circularly polarized light reflected by region B may be different from each other. For example, when an optically anisotropic layer is used in combination with a light guide plate, with region A as the incident diffraction element and region B as the exit diffraction element, even if right-circularly polarized light is incident from region A to the light guide plate, as it is totally reflected and guided through the light guide plate, the polarization is depolarized and when it enters region B, the light may be unpolarized or contain left-circularly polarized components such as elliptic polarization. Therefore, the circularly polarized light reflected and diffracted by region B and the circularly polarized light reflected and diffracted by region A may be different.

[0178] Furthermore, in the optical anisotropic layer of the present invention, if at least one of region A and region B is a cholesteric liquid crystal layer, the length of the helical pitch of the cholesteric liquid crystal layer may be different in the in-plane direction of this region. This allows for adjustment to uniformize the color and brightness within the plane when used, for example, as AR glasses. Also, by adjusting to strongly reflect a desired color in a desired direction within the plane, AR glasses with high light utilization efficiency can be obtained.

[0179] Furthermore, in the optical anisotropic layer of the present invention, if at least one of region A and region B is a cholesteric liquid crystal layer, this region may have a region in which the length of the helical pitch of the cholesteric liquid crystal layer changes in the thickness direction, or it may have a region in which there are multiple layers in the thickness direction in which the helical pitch of the cholesteric liquid crystal layer has a different length. As described above, the cholesteric liquid crystal layer reflects specific wavelengths depending on the length of the helical pitch. Therefore, by configuring the cholesteric liquid crystal layer so that the length of the helical pitch changes in the thickness direction, or by configuring the cholesteric liquid crystal layer so that there are multiple layers in the thickness direction in which the helical pitch of the cholesteric liquid crystal layer has a different length, the bandwidth of the wavelengths that are selectively reflected can be broadened.

[0180] In the examples shown in Figures 28 and 29, the optical anisotropic layer is configured to have two regions having a liquid crystal alignment pattern, but it is not limited to this configuration. The optical anisotropic layer of the present invention may further have a region C in the in-plane direction of the same optical anisotropic layer, in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and which has a liquid crystal alignment pattern.

[0181] Figure 30 is a conceptual plan view showing another example of the optical anisotropy layer of the present invention. The optical anisotropy layer (optical layer) 450 shown in Figure 30 has region A45a, region B45c, region C45d, and a non-diffraction region 45b. As shown in Figure 30, region A45a and region C45d are spaced apart in the left-right direction in the figure, and region C45d and region B45c are spaced apart in the up-down direction in the figure. A non-diffraction region 45b is formed between region A45a and region C45d, and between region C45d and region B45c.

[0182] Region C45d, like regions A45a and B45c, has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. Similar to regions A45a and B45c, region C45d may be a cholesteric liquid crystal layer or a liquid crystal diffraction layer. Furthermore, the liquid crystal alignment pattern in region C45d may be different from the liquid crystal alignment patterns of regions A45a and B45c, respectively.

[0183] Thus, the optical anisotropic layer 450 having region C45d further has three regions that diffract light. Such an optical anisotropic layer 450 is used in combination with a light guide plate to form a light guide element. In this case, as will be described later, for example, region A45a acts as an incident diffraction element for causing light to enter the light guide plate, region B45c acts as an exit diffraction element for causing light to exit the light guide plate, and region C45d acts as an intermediate diffraction element that diffracts the light incident from region A45a in the direction of region B45c. By configuring region C45d, which acts as an intermediate diffraction element, to diffract a portion of the light at multiple locations, exit pupil dilation can be achieved. Furthermore, it is preferable that region C45d has regions with different diffraction efficiencies in the in-plane direction, and it is preferable that the diffraction efficiency changes gradually.

[0184] [Transition Region] As shown in Figures 28 and 29, the optical anisotropy layer (optical layer) 400 has three regions within the same optical layer plane: region A45a having a liquid crystal alignment pattern, region 45b without a liquid crystal alignment pattern (non-diffraction region), and region B45c having a liquid crystal alignment pattern. Regions A45a and B45c each have a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and act as liquid crystal diffraction elements that diffract incident light. The non-diffraction region 45b does not have the above-mentioned liquid crystal alignment pattern and is a region that does not have the function of diffracting incident light. As shown in Figures 28 and 29, region A45a having a liquid crystal alignment pattern and region 45b without a liquid crystal alignment pattern (non-diffraction region), and region B45c having a liquid crystal alignment pattern and region 45b without a liquid crystal alignment pattern (non-diffraction region) are arranged adjacent to each other.

[0185] Here, as an example, Figure 23 shows the configuration of a conventional light guide element. As will be described in detail later, as shown in Figure 23, in a conventional light guide element, two liquid crystal diffraction elements, an incident liquid crystal diffraction element 46 and an exit liquid crystal diffraction element 47, are spaced apart on the main surface of the light guide plate 144. In this case, it was found that a portion of the light diffracted by the liquid crystal diffraction element 46 and guided through the light guide plate 144 is scattered by the element end face X of the liquid crystal diffraction element 46 and the element end face Y of the liquid crystal diffraction element 47, causing a decrease in image clarity. Furthermore, it was found that a portion of the light reflected by the element end face X of the liquid crystal diffraction element 46 and the element end face Y of the liquid crystal diffraction element 47, which is also diffracted by the liquid crystal diffraction element 46 and guided through the light guide plate 144, is reflected by the element end face X of the liquid crystal diffraction element 46 and the element end face Y of the liquid crystal diffraction element 47, and is not guided in the desired direction, causing a decrease in image brightness.

[0186] In contrast, the optical anisotropy layer (optical layer) of the present invention has regions A and B having diffraction properties and a non-diffractive region integrally formed. Therefore, when combined with a light guide plate, it is possible to prevent the light guided within the light guide plate from being scattered at the end face of the diffractive element, and a highly clear image can be emitted from the light guide plate. Furthermore, light reflected at the end face of the diffractive element can also be suppressed, allowing a bright image to be emitted.

[0187] Furthermore, it was found that in order to improve the clarity and brightness of the image emitted from the light guide plate, it is beneficial to provide a transition region where the state gradually changes at the boundary between the diffractive region (the region with a liquid crystal alignment pattern) and the non-diffractive region (the region without a liquid crystal alignment pattern). For example, if the non-diffractive region without a liquid crystal alignment pattern is isotropic, the region with a liquid crystal alignment pattern has an extraordinary refractive index (ne) and an ordinary refractive index (no), and the refractive index of the optically isotropic region without a liquid crystal alignment pattern is the average refractive index of the extraordinary refractive index and the ordinary refractive index. As a result, a refractive index difference occurs at the boundary between the region with a liquid crystal alignment pattern and the region without a liquid crystal alignment pattern, causing some light to be reflected from the end face of the diffractive element. Reflected light from the end face of the diffractive element is a factor in reducing the brightness of the image emitted from the light guide plate. In addition, if some scattered light and stray light occur at the end face of the diffractive element, it is a factor in reducing the clarity of the image.

[0188] In contrast, the optical anisotropy layer (optical layer) of the present invention provides a transition region in which the optical properties gradually change at the boundary between the diffractive region (region having a liquid crystal alignment pattern) A and region B and the non-diffractive region (region not having a liquid crystal alignment pattern), that is, at a position adjacent to the non-diffractive region (region not having a liquid crystal alignment pattern). When combined with a light guide plate, this prevents the light guided through the light guide plate from being reflected and / or scattered at the end face of the diffractive element, and allows a bright and clear image to be emitted from the light guide plate. Examples of optical properties in this case include diffraction efficiency and birefringence (Δn).

[0189] If a region exhibiting diffraction (a region with a liquid crystal alignment pattern) has a transition region at its boundary with a non-diffraction region (a region without a liquid crystal alignment pattern) (adjacent to the region without a liquid crystal alignment pattern) where the optical properties gradually change, it is preferable that the transition region be configured such that the diffraction efficiency gradually changes in the plane from the region exhibiting diffraction towards the non-diffraction region.

[0190] More specifically, as shown in Figure 32, for example, in the transition regions of the regions having a liquid crystal alignment pattern (regions A and B), the diffraction efficiency within each region gradually decreases toward the non-diffraction region, changing to approximately 0%.

[0191] A configuration in which the diffraction efficiency gradually changes in the transition region can be achieved, for example, by a configuration in which the birefringence (Δn), as described later, changes.

[0192] When the non-diffractive region is optically isotropic (or when its birefringence is lower than that of the diffractive region), it is preferable to configure the diffractive region (the region with a liquid crystal alignment pattern) to have a transition region at the boundary with the non-diffractive region (the region without a liquid crystal alignment pattern) in which the birefringence (Δn) gradually changes in the plane from the diffractive region toward the non-diffractive region.

[0193] In other words, in the transition region of a region having a liquid crystal alignment pattern, the birefringence (Δn) within the region changes so that it approaches the value of the birefringence (Δn) in the non-diffraction region as one moves toward the non-diffraction region.

[0194] Here, the birefringence (Δn) in the transition region is the birefringence of the layer in a fine region within the plane. The fact that the birefringence (Δn) differs within the plane can be confirmed by detecting that there are regions within the plane with different diagonal retardations.

[0195] A configuration in which the birefringence (Δn) gradually changes in the transition region can be achieved by disorder in the orientation of the liquid crystal compound in the transition region (decrease in the degree of orientation). A specific example will be explained using Figure 34. The optical layer 1 shown in Figure 34 has a region 2a having a liquid crystal orientation pattern and a region 2c not having a liquid crystal orientation pattern, and a transition region 2d is located at a position where the region 2a having a liquid crystal orientation pattern is in contact with the region 2c not having a liquid crystal orientation pattern, and in the transition region 2d, the orientation of the liquid crystal compound 30 is disordered (the degree of orientation decreases) as you move toward the region 2c not having a liquid crystal orientation pattern. In Figure 34, the density of the line representing the liquid crystal compound 30 represents the disorder in the orientation of the liquid crystal compound 30, and the thinner the line of the liquid crystal compound 30, the more disordered the orientation (the lower the degree of orientation).

[0196] The width of the transition region is preferably 10 μm to 10 mm, more preferably 50 μm to 5 mm, and even more preferably 100 μm to 2 mm. A transition region width of 10 mm or less is preferable from the viewpoint of making the area of ​​the optical layer compact. A transition region width of 10 μm or more is preferable from the viewpoint of suppressing reflection and scattering at the edge of the region having diffraction properties (the region having a liquid crystal alignment pattern) (the interface between the region having a liquid crystal alignment pattern and the region not having a liquid crystal alignment pattern), and from the viewpoint of robustness when controlling the width of the transition region.

[0197] Although an example of applying the optical layer of the present invention to a light guide element has been described, the application of the optical layer of the present invention is not limited to light guide elements but can be applied to various optical applications. In applications other than light guide elements, light may be reflected and scattered at the end face of a diffractive element, causing stray light and degrading optical performance. The optical layer of the present invention has a transition region at the boundary between the diffractive region (the region having a liquid crystal alignment pattern) and the non-diffractive region (the region not having a liquid crystal alignment pattern), where the state gradually changes. This reduces the reflected and scattered light at the boundary of the diffractive element, thereby achieving good optical performance.

[0198] [Laminate] The laminate of the present invention is a laminate obtained by laminating two or more of the above-described optical anisotropy layers (optical layers). Figure 31 is a conceptual diagram showing an example of the laminate of the present invention. The laminate 500 shown in Figure 31 has a first optical anisotropy layer 400a and a second optical anisotropy layer 400b. The first optical anisotropy layer 400a has a region A410a and region B410c having a liquid crystal alignment pattern and a non-diffraction region 410b. The second optical anisotropy layer 400b has a region A420a and region B420c having a liquid crystal alignment pattern and a non-diffraction region 420b. The basic configuration of the first optical anisotropy layer 400a and the second optical anisotropy layer 400b is the same as that of the optical anisotropy layer described above.

[0199] In Figure 31, the region A410a of the first optical anisotropy layer 400a and the region A420a of the second optical anisotropy layer 400b are located at overlapping positions, and the non-diffraction region 410b of the first optical anisotropy layer 400a that does not have a liquid crystal alignment pattern and the non-diffraction region 420b of the second optical anisotropy layer 400b that does not have a liquid crystal alignment pattern are located at overlapping positions, and the region B410c of the first optical anisotropy layer 400a and the region B420c of the second optical anisotropy layer 400b are located at overlapping positions.

[0200] In the example shown in Figure 31, the laminate is configured with two optically anisotropic layers, but it is not limited to this configuration, and may also be configured with three or more optically anisotropic layers. In the case of a configuration with three or more optically anisotropic layers, it is preferable that the layers are stacked at positions where the regions A, regions B, and non-diffraction regions of each optically anisotropic layer overlap.

[0201] Furthermore, the example shown in Figure 30 may also be a laminate in which two or more optical anisotropic layers having region C are stacked. In this case, it is preferable that the layers be stacked at positions where the regions C of each optical anisotropic layer overlap. However, the above is not limited, and the layers may be stacked at positions where only a portion of the regions of the optical anisotropic layers overlap.

[0202] In the laminate 500 shown in Figure 31, region A410a of the first optical anisotropy layer 400a and region A420a of the second optical anisotropy layer 400b are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in region A410a of the first optical anisotropy layer 400a and the length of the helical pitch of the cholesteric liquid crystal layer in region A420a of the second optical anisotropy layer 400b are different from each other, or Alternatively, it is preferable that at least one of the following conditions is met: region B410c of the first optical anisotropy layer 400a and region B420c of the second optical anisotropy layer 400b are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in region B410c of the first optical anisotropy layer 400a and the length of the helical pitch of the cholesteric liquid crystal layer in region B420c of the second optical anisotropy layer 400b are different from each other.

[0203] As described above, the cholesteric liquid crystal layer reflects light of a specific wavelength depending on the length of the helical pitch. By making the helical pitch lengths of regions A and / or regions B of the first optical anisotropy layer 400a and the second optical anisotropy layer 400b different, regions A and / or regions B of the first optical anisotropy layer 400a and the second optical anisotropy layer 400b reflect light of different wavelengths. As will be described later, when a light guide element formed by combining the laminate 500 with a light guide plate is used in an AR display device or the like, if the AR display device displays a color image, the light guide element needs to guide light of each wavelength of RGB, for example. Therefore, it is preferable to have a configuration in which optical anisotropy layers having regions A and B (and further region C) that reflect and diffract light of these wavelengths are laminated. For example, the first optical anisotropy layer can be configured such that regions A and B are cholesteric liquid crystal layers having a selective reflection wavelength in the red wavelength range, and regions A and B of the second optical anisotropy layer are cholesteric liquid crystal layers having a selective reflection wavelength in the green wavelength range.

[0204] Furthermore, in the laminate 500 shown in Figure 31, region A410a of the first optical anisotropy layer 400a and region A420a of the second optical anisotropy layer 400b are cholesteric liquid crystal layers, and the direction of rotation of the helix of the cholesteric liquid crystal layer in region A410a of the first optical anisotropy layer 400a and the direction of rotation of the helix of the cholesteric liquid crystal layer in region A420a of the second optical anisotropy layer 400b are different from each other. It is preferable that at least one of the following conditions is met: or, region B410c of the first optical anisotropy layer 400a and region B420c of the second optical anisotropy layer 400b are cholesteric liquid crystal layers, and the direction of rotation of the helix of the cholesteric liquid crystal layer in region B410c of the first optical anisotropy layer 400a and the direction of rotation of the helix of the cholesteric liquid crystal layer in region B420c of the second optical anisotropy layer 400b are different from each other.

[0205] As described above, the cholesteric liquid crystal layer has circular polarization selectivity depending on the direction of rotation of the helix in the helical structure. By making the direction of rotation of the helix different between regions A of the first optical anisotropy layer 400a and the second optical anisotropy layer 400b, and / or between regions B, for example, a configuration can be made in which region A410a of the first optical anisotropy layer 400a reflects and diffracts right-circularly polarized light of a certain wavelength, region A420a of the second optical anisotropy layer 400b reflects and diffracts left-circularly polarized light of the same wavelength, and / or region B410c of the first optical anisotropy layer 400a reflects and diffracts right-circularly polarized light of a certain wavelength, and region B420c of the second optical anisotropy layer 400b reflects and diffracts left-circularly polarized light of the same wavelength.

[0206] Furthermore, in the laminate 500 as shown in Figure 31, it is preferable that at least one of the following conditions is met: the length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in plane in region A410a of the first optical anisotropy layer 400a is different from the length of one period in region A420a of the second optical anisotropy layer 400b; or the length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in plane in region B410c of the first optical anisotropy layer 400a is different from the length of one period in region B420c of the second optical anisotropy layer 400b.

[0207] As mentioned above, the diffraction angles in regions A and B are determined by the length of one period in the liquid crystal alignment pattern. Furthermore, even if the length of one period is the same, the diffraction angle will differ depending on the wavelength of light. Therefore, for example, as described above, if the helical pitch lengths of regions A and / or regions B of the first optical anisotropy layer 400a and the second optical anisotropy layer 400b are different, and the first optical anisotropy layer 400a and the second optical anisotropy layer 400b reflect and diffract light of different wavelengths, then if the length of one period in the liquid crystal alignment pattern is the same, the diffraction angles will be different, and the light will be emitted in different directions. Therefore, it is preferable to make the length of one period of the liquid crystal alignment pattern between regions A and / or regions B of the first optical anisotropy layer 400a and the second optical anisotropy layer 400b different so that the diffraction angles of light between regions A and / or regions B of the first optical anisotropy layer 400a and the second optical anisotropy layer 400b are the same.

[0208] Furthermore, in the laminate 500 as shown in Figure 31, it is preferable that at least one of the following conditions is met: one direction of the liquid crystal alignment pattern in region A410a of the first optical anisotropy layer 400a and one direction of the liquid crystal alignment pattern in region A420a of the second optical anisotropy layer 400b are different from each other, or one direction of the liquid crystal alignment pattern in region B410c of the first optical anisotropy layer 400a and one direction of the liquid crystal alignment pattern in region B420c of the second optical anisotropy layer 400b are different from each other.

[0209] This allows, for example, light diffracted in region A410a of the first optical anisotropy layer 400a to be selectively diffracted in region B410c of the optical anisotropy layer 400a. Similarly, light diffracted in region A420a of the second optical anisotropy layer 400b to be selectively diffracted in region B420c of the second optical anisotropy layer 400b. In other words, it becomes possible to selectively diffract light in both the first optical anisotropy layer 400a and the second optical anisotropy layer 400b. This makes it possible to avoid color crosstalk when, for example, it is desired to diffract light of different wavelengths in the first optical anisotropy layer 400a and the second optical anisotropy layer 400b.

[0210] [Light Guide Element and AR Display Device] The light guide element using the optical anisotropy layer of the present invention comprises the optical anisotropy layer and a light guide plate. The AR (Augmented Reality) display device of the present invention comprises the light guide element and an image display device.

[0211] (First Embodiment) Figure 11 conceptually shows an example of a first embodiment of the AR display device of the present invention having a light guide element of the present invention. The AR display device 50 shown in Figure 11 has a display (image display device) 40 and a light guide element 45.

[0212] The light guide element 45 is a light guide element of the present invention and comprises an optical anisotropy layer (optical layer) 400 of the present invention and a light guide plate 144. The light guide element of the present invention may have a configuration comprising a laminate of the present invention having multiple optical anisotropy layers and a light guide plate, as described above. In other words, the light guide element of the present invention may have multiple optical anisotropy layers. As described above, the optical anisotropy layer 400 is a single optical anisotropy layer formed from three regions: region A45a, non-diffraction region 45b, and region B45c. The light guide plate 144 is a rectangular parallelepiped with a long length in one direction and guides light internally. As shown in Figure 11, region A45a of the optical anisotropy layer 400 is arranged on the surface (main surface) of one end of the light guide plate 144 in the longitudinal direction. Region B45c of the optical anisotropy layer 400 is arranged on the surface of the other end of the light guide plate 144. The position of region A45a of the optically anisotropic layer 400 corresponds to the incident position of light on the light guide plate 144, and the position of region B45c of the optically anisotropic layer 400 corresponds to the exit position of light on the light guide plate 144. Furthermore, an optically isotropic non-diffractive region 45b is formed between region A45a and region B45c.

[0213] Region A45a of the optical anisotropy layer 400 is an incident diffraction element region that diffracts light irradiated from the display 40 and incident into the light guide plate 144 so as to undergo total internal reflection within the light guide plate 144. Region B45c of the optical anisotropy layer 400 is an exit diffraction element region that diffracts light guided within the light guide plate 144 so as to exit the light guide plate 144.

[0214] There are no particular limitations on the light guide plate 144; conventionally known light guide plates used in image display devices and the like can be used.

[0215] Various materials used as light guide plates in optical elements can be used for the light guide plate 144. Specifically, examples of materials for the light guide plate 144 include glass, acrylic, polycarbonate, polystyrene, urethane, polyolefin, polyvinyl chloride, lithium niobate, silicon carbide, polyethylene terephthalate (PET), and triacetylcellulose (TAC).

[0216] There are no restrictions on the thickness of the light guide plate 144. It can be set appropriately considering the thickness required to hold the optical anisotropy layer, the lightness of the light guide plate, and the uniformity of the brightness (light quantity) of the light emitted from the light guide plate. The thickness of the light guide plate 144 is preferably 0.02 to 2.0 mm, more preferably 0.05 to 1.0 mm, and even more preferably 0.1 to 0.5 mm. The refractive index of the light guide plate is preferably 1.5 or higher, more preferably 1.8 or higher, and even more preferably 2.0 or higher. The difference between the anomalous refractive index of the liquid crystal compound and the refractive index of the light guide plate within the optical anisotropy layer is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.1 or less.

[0217] As shown in Figure 11, the display 40 is positioned facing the surface of one end of the light guide plate 144 that is opposite to the surface on which the optical anisotropy layer 400 is located. The surface of one end of the light guide plate 144 that is opposite to the surface on which the optical anisotropy layer 400 is located is the observation position for the user U. In the following description, the longitudinal direction of the light guide plate 144 is defined as the X direction, and the direction perpendicular to the X direction and perpendicular to the surface of the optical anisotropy layer is defined as the Z direction. The Z direction is also the thickness direction of each layer in the optical anisotropy layer (see Figure 1).

[0218] There are no restrictions on the display 40; for example, various known displays used in AR display devices such as AR glasses can be used. Examples of displays 40 include liquid crystal displays (including LCOS: Liquid Crystal On Silicon, etc.), organic electroluminescent displays, DLP (Digital Light Processing), μLED (Micro Light Emitting Diode) displays, and laser beam scanning methods using MEMS (Micro-Electro-Mechanical Systems) mirrors. The display 40 may display monochrome images, two-color images, or color images.

[0219] Since the optical anisotropic layer of the present invention has polarization selectivity, displays that emit polarized light are suitably used. For example, using a display that displays red and blue images with right-circularly polarized light emission and a green image with left-circularly polarized light emission, an optical anisotropic layer having regions A and B that diffract the corresponding red right-circularly polarized light, an optical anisotropic layer having regions A and B that diffract the green left-circularly polarized light, and an optical anisotropic layer having regions A and B that diffract the blue right-circularly polarized light may be laminated on a light guide plate. As a result, since the polarization states of red and green, and green and blue, which are adjacent in wavelength, are all different, it is possible to avoid the occurrence of color crosstalk. Furthermore, for example, using a display that displays an image corresponding to an FOV of 0 to 50° with right-circularly polarized light emission and an image corresponding to an FOV of -50 to 0° with left-circularly polarized light emission, the FOV can be doubled compared to the case without polarization by laminating an optical anisotropic layer having regions A and B that diffract the corresponding right-circularly polarized light and an optical anisotropic layer having regions A and B that diffract the left-circularly polarized light onto a light guide plate.

[0220] Furthermore, the optical anisotropy layer of the present invention is also suitably used in laser beam scanning type displays. Laser beam scanning type displays scan laser light with MEMS mirrors. In this case, if the optical system is designed so that the laser light is reflected by a polarizing mirror and then scanned by a MEMS mirror, a problem of glare occurs if the polarization selectivity of the polarizing mirror is insufficient. However, since the optical anisotropy layer of the present invention has polarization selectivity itself, it can compensate for the polarization selectivity of the polarizing mirror and prevent glare.

[0221] In an AR display device 50 with this configuration, the light displayed by the display 40 enters the light guide plate 144 from the surface opposite to the surface on which the optical anisotropy layer 400 is located, as indicated by the arrow. The light that enters the light guide plate 144 is reflected by region A45a of the optical anisotropy layer 400. At this time, due to the diffraction effect of region A45a, the light is not reflected specularly but is reflected in a direction at an angle different from the specular reflection direction. In the example shown in Figure 11, the light enters the optical anisotropy layer 400 from a direction approximately perpendicular to region A45a (Z direction) and is reflected in a direction that is tilted at a large angle from the perpendicular direction toward the longitudinal direction (X direction) of the light guide plate 144.

[0222] Light reflected from region A45a of the optical anisotropy layer 400 is reflected at a large angle with respect to the angle of the incident light. As a result, the angle of the direction of light propagation with respect to the surface of the light guide plate 144 becomes small, and the light is totally reflected by the surface of the light guide plate 144 or the surface of the non-diffractive region 45b of the optical anisotropy layer 400, and guided in the longitudinal direction (X direction) of the light guide plate 144. The guided light is reflected by region B45c of the optical anisotropy layer 400 at the other end of the light guide plate 144 in the longitudinal direction. At this time, due to the diffraction effect of region B45c of the optical anisotropy layer 400, the light is not specularly reflected but is reflected in a direction at an angle different from the specular reflection direction. In the example shown in Figure 11, light is incident on region B45c of the optical anisotropy layer 400 from an oblique direction and is reflected perpendicularly to the surface of region B45c of the optical anisotropy layer 400.

[0223] Light reflected in region B45c of the optical anisotropy layer 400 reaches the surface of the light guide plate 144 opposite to the surface where the optical anisotropy layer 400 is located. However, because it is incident approximately perpendicular to this surface, it is not totally reflected and is emitted outside the light guide plate 144. In other words, it emits light at the observation position of the user U. In this way, the AR display device 50 displays a virtual image superimposed on the scene that the user U is actually seeing by having the image displayed by the display 40 incident on one end of the light guide plate 144, propagating, and emitting from the other end.

[0224] Here, in region B45c of the optical anisotropy layer 400, the diffraction efficiency is adjusted so that when light propagating within the light guide plate 144 is diffracted in region B45c of the optical anisotropy layer 400, a portion of the light is diffracted at multiple points and emitted outside the light guide plate 144, thereby expanding the field of view (exit pupil enlargement). Specifically, in Figure 11, light I0 propagating through the light guide plate 144 repeatedly reflects off both surfaces (interfaces) of the light guide plate 144 and reaches the position of region B45c of the optical anisotropy layer 400. Upon reaching the position of region B45c of the optical anisotropy layer 400, a portion of the light I0 is diffracted at a position P1 close to the incident side and emitted from the light guide plate 144 (exit light R1). Furthermore, the light I1 that was not diffracted propagates further within the light guide plate 144, and again, at position P2 in region B45c of the optical anisotropy layer 400, some of the light R2 is diffracted and emitted from the light guide plate 144. The light I2 that was not diffracted propagates further within the light guide plate 144, and again, at position P3 in region B45c of the optical anisotropy layer 400, some of the light R3 is diffracted and emitted from the light guide plate 144. The light I3 that was not diffracted propagates further within the light guide plate 144, and again, at position P4 in region B45c of the optical anisotropy layer 400, some of the light R4 is diffracted and emitted from the light guide plate 144.

[0225] In this way, by diffracting the light propagating within the light guide plate 144 at multiple points by the region B45c of the optical anisotropy layer 400 and emitting it out of the light guide plate 144, the field of view can be expanded (exit pupil enlargement).

[0226] Here, Figure 23 shows the configuration of a conventional light guide element. As shown in Figure 23, in a conventional light guide element, the incident liquid crystal diffraction element and the exit liquid crystal diffraction element are not formed from a single element, but rather two liquid crystal diffraction elements, the incident liquid crystal diffraction element 46 and the exit liquid crystal diffraction element 47, are spaced apart on the main surface of the light guide plate 144. In this case, it was found that a portion of the light diffracted by the liquid crystal diffraction element 46 and guided through the light guide plate 144 is scattered by the element end face X of the liquid crystal diffraction element 46 and the element end face Y of the liquid crystal diffraction element 47, causing a decrease in image clarity.

[0227] In contrast, the optical anisotropic layer of the present invention has diffractive regions A and B and a non-diffractive region integrally formed. Therefore, when combined with a light guide plate, it is possible to prevent the light guided within the light guide plate from being scattered at the end face of the diffractive element, and a highly clear image can be emitted from the light guide plate.

[0228] Let's also consider the case where the diffraction efficiency of the liquid crystal diffraction element 47 is constant in the plane. When the diffraction efficiency is constant, at position P1 close to the incident side, the light intensity (amount of light) of the incident light I0 is large, so the intensity of the emitted light R1 is also large. Next, the light I1 that was not diffracted propagates through the light guide plate 144 and is diffracted again at position P2 of the liquid crystal diffraction element 47, and some of the light R2 is emitted. However, since the light intensity of I1 is lower than that of I0, even if diffracted with the same diffraction efficiency, the light intensity of R2 will be lower than the light intensity of R1 reflected in the region close to the incident side. Similarly, the light I2 that was not diffracted propagates through the light guide plate 144 and is diffracted again at position P3 of the liquid crystal diffraction element 47, and some of the light R3 is emitted. However, since the light intensity of I2 is lower than that of I1, even if diffracted with the same diffraction efficiency, the light intensity of R3 will be lower than the light intensity of R2 reflected at position P2. Furthermore, the light intensity of light R4 reflected at position P4, which is further from the incident side, becomes lower than the light intensity of light R3. Thus, if the diffraction efficiency of the liquid crystal diffraction element 47 is constant in the plane, as shown by the dashed line in Figure 12, light with high light intensity is emitted in the region closer to the incident side, and light with low light intensity is emitted in the region further away from the incident side. Therefore, a problem arises in which the emitted light intensity becomes non-uniform depending on the position.

[0229] In contrast, the optical anisotropy layer 400 of the present invention has a configuration in region B45c such that the diffraction efficiency increases from one side to the other in one direction of rotation of the optical axis, and it is preferable that region B45c of the optical anisotropy layer 400 be arranged such that the diffraction efficiency increases in the direction of light propagation within the light guide plate 144. That is, in the example shown in Figure 11, region B45c of the optical anisotropy layer 400 has a configuration in Figure 11 such that the diffraction efficiency increases from left to right.

[0230] In this case, at position P1, which is close to the incident side, the light intensity (amount of light) of the incident light I0 is large, but because the diffraction efficiency is low, the intensity of the emitted light R1 is only a certain level. Next, the light I1 that was not diffracted propagates through the light guide plate 144 and is diffracted again at position P2 in region B45c of the optical anisotropy layer 400, and some of the light R2 is emitted. At this time, the light intensity of light I1 is lower than that of light I0, but because the diffraction efficiency at position P2 is higher than the diffraction efficiency at position P1, the light intensity of light R2 can be made equivalent to the light intensity of light R1 reflected at position P1. Similarly, the undiffracted light I2 propagates through the light guide plate 144 and is diffracted again at position P3 in region B45c of the optical anisotropy layer 400, causing some of the light R3 to be emitted. Although the light intensity of I2 is lower than that of I1, the diffraction efficiency at position P3 is higher than that at position P2, so the light intensity of R3 can be made equivalent to that of the light R2 reflected at position P2. Furthermore, since the diffraction efficiency at position P4, which is further from the incident side, is higher than that at position P3, the light intensity of R4 can be made equivalent to that of the light R3 reflected at position P3. In this way, by configuring the diffraction efficiency of region B45c of the optical anisotropy layer 400 to increase from one side to the other in one direction of rotation of the optical axis, it is possible to emit light of a constant light intensity at any position in region B45c of the optical anisotropy layer 400. Therefore, as shown by the solid line in Figure 12, the emitted light intensity can be made uniform regardless of the position.

[0231] In Figure 11, light is indicated by arrows, but the light emitted from the display 40 may also be planar. Planar light may propagate through the light guide plate 144 while maintaining its positional relationship and be diffracted by region B45c of the optical anisotropy layer 400.

[0232] Furthermore, although Figure 11 describes the light guide element 45 as having one optical anisotropy layer, as mentioned above, the light guide element 45 may have a configuration having multiple optical anisotropy layers 400. That is, it may be a configuration using the laminate described above. As mentioned above, when the laminate has a configuration having multiple optical anisotropy layers, it is preferable to have a configuration having multiple optical anisotropy layers with different selective reflection wavelengths in region A and / or region B. For example, it is possible to have a configuration having optical anisotropy layers having region A and / or region B, where red light, green light, and blue light are selected reflection wavelengths, respectively. As a result, the optical anisotropy layer (and its laminate) can diffract red light, green light, and blue light, respectively, and the light guide element can appropriately guide the light of the color display 40. In this case, it is preferable to appropriately change the length of one period of the liquid crystal alignment pattern according to the selected reflection wavelength of each layer. Also, if region A and / or region B are cholesteric liquid crystal layers, it is preferable to appropriately change the helical pitch according to the selected reflection wavelength of each layer. Alternatively, the configuration may have two optical anisotropic layers, each having region A and / or region B that reflect circularly polarized light with the same selective reflection wavelength but opposite rotation directions. For example, the configuration may have an optical anisotropic layer that reflects right-circularly polarized red light and an optical anisotropic layer that reflects left-circularly polarized red light. This allows the optical anisotropic layer (and its laminate) to diffract right-circularly polarized and left-circularly polarized light, respectively, and the light guide element to guide right-circularly polarized and left-circularly polarized light, thereby increasing the efficiency of light utilization. Alternatively, the configuration may have two optical anisotropic layers, each having region A and / or region B that reflect circularly polarized light with the same selective reflection wavelength but opposite rotation directions, and having different helical pitches. This allows the optical anisotropic layer (and its laminate) to diffract right-circularly polarized and left-circularly polarized light, respectively, and the light guide element to guide right-circularly polarized and left-circularly polarized light incident at different incident angles, and to emit the guided light at different angles, thereby increasing the FOV (Field of View).

[0233] Furthermore, in the example shown in Figure 11, the optical anisotropy layer 400 is configured to have an incident region A45a, an exit region B45c, and an isotropic non-diffraction region 45b, but it is not limited to this configuration, and as mentioned above, it may also have an intermediate diffraction region, i.e., region C. That is, the light that is diffracted by the incident diffraction region (region A) and incident into the light guide plate is diffracted by the intermediate diffraction region (region C) to bend the direction of light propagation within the light guide plate, and then diffracted by the exit diffraction region (region B) to emit the light outside the light guide plate. In this case, the incident diffraction region and the intermediate diffraction region can be formed within a single optical anisotropic layer (i.e., region A acts as the incident diffraction region and region B acts as the intermediate diffraction region), the intermediate diffraction region and the exit diffraction region can be formed within a single optical anisotropic layer (i.e., region A acts as the intermediate diffraction region and region B acts as the exit diffraction region), or all diffraction regions can be formed within a single optical anisotropic layer (i.e., a configuration having the aforementioned regions A, B, and C). However, from the viewpoint of improving image clarity, it is preferable to form as many diffraction regions as possible used in the light guide plate within a single optical anisotropic layer. Furthermore, in the case of a configuration with an intermediate diffraction region, it is preferable to configure the efficiency of the intermediate diffraction region to increase from one side to the other in order to make the light intensity of the emitted light uniform. Furthermore, in order to make the light intensity of the emitted light uniform, it is also preferable to use a configuration in which the in-plane distribution of diffraction efficiency differs between the intermediate diffraction region and the emitted diffraction region.

[0234] The light guide element 45 preferably includes a phase difference plate in addition to the light guide plate 144 and the optical anisotropy layer 400. This allows the light intensity of the emitted light in the output region B45c to be uniform, by converting the light guided through the light guide plate into linearly polarized light, similar to when the non-diffraction region 45b of the optical anisotropy layer 400 functions as a phase difference region. Furthermore, the polarization state of the linearly polarized light guided through the light guide plate may be eliminated in the output region B45c. For this reason, the phase difference plate is preferably a phase difference plate with different phase differences patterned in the in-plane direction so as to maintain the linearly polarized state of the light guided through the light guide plate. An example of such a phase difference plate is a phase difference plate made of a liquid crystal compound, which can be realized, for example, by patterning the orientation axis, twist angle, degree of orientation, etc., of the liquid crystal compound.

[0235] Furthermore, when the optically anisotropic layer has an intermediate diffraction region (region C), it is preferable to use a configuration in which the length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in plane is shortened relative to the diffraction region on the incident side. This makes it possible to increase the angle at which the light diffracted by the incident diffraction region and incident into the light guide plate is diffracted by the intermediate diffraction region, bending the direction of light propagation within the light guide plate, and thus making the size of the light guide plate more compact. Also, when one period of the intermediate diffraction region is shorter than that of the diffraction region on the incident side, it is preferable to make the helical pitch of the cholesteric liquid crystal layer larger in the intermediate diffraction region than in the diffraction region on the incident side. This makes it possible to efficiently bend the direction of light propagation within the light guide plate in the intermediate diffraction region. Furthermore, it is preferable to use a configuration in which the intermediate diffraction region has a different orientation in one direction from the diffraction region on the incident side, where the orientation of the optical axis derived from the liquid crystal compound rotates 180° in plane. Light that has been diffracted by the incident diffraction region and entered the light guide plate can be diffracted by the intermediate diffraction region, changing the direction of light propagation within the light guide plate and allowing the light to be appropriately guided toward the exit diffraction region.

[0236] Furthermore, multiple incident diffraction regions and intermediate diffraction regions may be arranged within the plane. Multiple incident diffraction regions have different orientations in the liquid crystal alignment pattern that rotates continuously along one direction within the plane. This allows light incident on the incident diffraction region to be guided in different directions within the light guide plate, diffracted by intermediate diffraction regions positioned at different locations within the plane, bending the direction of light propagation within the light guide plate, and then emitted at different angles by the exit diffraction region, thereby increasing the Field of View (FOV). For example, as described in WO2020 / 122128, the incident diffraction region and intermediate diffraction regions can be appropriately configured by setting the length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° within the plane, the direction of rotation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern that rotates continuously in one direction within the plane, and, in the case of a cholesteric liquid crystal layer, the length of the helical pitch and the direction of helical twisting rotation in the thickness direction. Multiple incident-side diffraction regions can appropriately set the rotation direction of the optical axis originating from the liquid crystal compound in a liquid crystal alignment pattern that rotates continuously in one direction within the plane, and the rotation direction of the optical axis originating from the liquid crystal compound in a liquid crystal alignment pattern that rotates continuously in one direction within the plane may be different in multiple incident-side diffraction regions. Furthermore, if the diffraction region is a cholesteric liquid crystal layer, the direction of the helical twisting rotation in the thickness direction (the rotation direction of the reflected circularly polarized light) can be appropriately set in multiple incident-side diffraction regions, and specifically, multiple incident-side diffraction regions may be a region in which the cholesteric liquid crystal layer is right-handed helical cholesteric orientation and a region in which it is left-handed helical cholesteric orientation. In addition, for intermediate diffraction regions, it is preferable to use a configuration in which the length of one period in which the orientation of the optical axis originating from the liquid crystal compound rotates 180° within the plane is shorter than that of the incident-side diffraction region, and as mentioned above, if one period of the intermediate diffraction region is shorter than that of the incident-side diffraction region, it is preferable to make the helical pitch of the cholesteric liquid crystal layer larger than that of the intermediate diffraction region. Furthermore, even in such a configuration, in order to make the light intensity of the emitted light uniform, it is also preferable to use a configuration in which the in-plane distribution of diffraction efficiency differs between the intermediate diffraction region and the emitted diffraction region.

[0237] Furthermore, diffraction regions for different incidents, intermediate diffraction regions, and exit diffraction regions may be stacked. As described above, when stacking multiple optical anisotropy layers, it is also preferable to stack multiple optical anisotropy layers with different selective reflection wavelengths (helical pitches). This allows the optical anisotropy layers (the stacked layers) to diffract light of different colors (wavelengths), and the light guide element to appropriately guide the light of the color display 40. In this case, it is preferable to appropriately set the length of one period of the liquid crystal alignment pattern in each diffraction region according to the selective reflection wavelength of each diffraction region in each layer. Alternatively, a configuration may be used in which two optical anisotropy layers are stacked, each having diffraction regions that reflect circularly polarized light with the same selective reflection wavelength but opposite rotation directions. For example, a configuration can be used in which an optical anisotropy layer having a diffraction region that reflects right-circularly polarized red light and an optical anisotropy layer having a diffraction region that reflects left-circularly polarized red light are stacked. As a result, the optically anisotropic layer (and its laminate) can diffract right-circularly polarized and left-circularly polarized light, respectively, and the light guide element can guide right-circularly polarized and left-circularly polarized light, thereby increasing the efficiency of light utilization. Alternatively, a configuration may be used in which two optically anisotropic layers are laminated, each having a diffraction region that reflects circularly polarized light with the same selective reflection wavelength but opposite rotation directions and has different helical pitches. As a result, the optically anisotropic layer (and its laminate) can diffract right-circularly polarized and left-circularly polarized light, respectively, and the light guide element can guide right-circularly polarized and left-circularly polarized light incident at different incident angles and emit the guided light at different angles, thereby increasing the field of view (FOV).Furthermore, as described in, for example, WO2020 / 122128, WO2020 / 075738, WO2020 / 226078, WO2021 / 060528, etc., when stacking multiple optical anisotropic layers, it is also preferable to stack multiple optical anisotropic layers having diffraction regions where the diffraction regions of each optical anisotropic layer (incident diffraction region, intermediate diffraction region, and exit diffraction region) differ in length of one period of the liquid crystal alignment pattern, direction of rotation of the liquid crystal alignment pattern that rotates continuously in one direction in the plane, and direction of rotation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern that rotates continuously in one direction in the plane. In the case of a cholesteric liquid crystal layer, it is also preferable to stack multiple optical anisotropic layers having diffraction regions where the pitch of the helix and direction of twisting rotation of the helix in the thickness direction (direction of rotation of reflected circularly polarized light) differ, and these can be appropriately set according to the purpose. Furthermore, when stacking multiple optically anisotropic layers, it is preferable to use a configuration in which the in-plane distribution of diffraction efficiency differs between the intermediate diffraction region and the outgoing diffraction region in order to make the light intensity of the outgoing light uniform. Also, when stacking multiple optically anisotropic layers, it is preferable to use a configuration in which the in-plane distribution of diffraction efficiency differs between the intermediate diffraction region and the outgoing diffraction region of each optically anisotropic layer. There are no limitations on the arrangement of the diffraction regions, and they can be appropriately arranged in the in-plane direction and in the thickness direction (stacked direction) as needed.

[0238] Furthermore, a diffraction region that serves as both an intermediate diffraction region and an exit diffraction region may be stacked. The intermediate diffraction region and the exit diffraction region can be configured by stacking optically anisotropic layers in which one direction of the liquid crystal alignment pattern, which rotates continuously along one direction in the plane, is different from that of the other. In this case, it is preferable to use multiple incident diffraction regions in which one direction of the liquid crystal alignment pattern, which rotates continuously along one direction in the plane, is different from that of the other, and to guide the light incident on each incident diffraction region to different directions within the light guide plate. The multiple incident diffraction regions may be arranged at different positions in the plane or may be stacked. Light diffracted by the incident diffraction region and incident into the light guide plate is diffracted by the intermediate diffraction region, bending the direction of light propagation within the light guide plate, and then diffracted by the exit diffraction region stacked with the intermediate diffraction region, and the light is emitted outside the light guide plate. Light diffracted by another incident diffraction region and entering the light guide plate is then diffracted by the aforementioned exit-side diffraction region, which acts as an intermediate diffraction region. This intermediate diffraction region then functions as the exit-side diffraction region, bending the direction of light propagation within the light guide plate, allowing the guided light to be emitted at a different angle. This makes it possible to increase the field of view (FOV) with a compact light guide plate compared to when the intermediate diffraction region and the exit diffraction region are placed at different positions in the plane. For example, as described in WO2021 / 201218, WO2021 / 256453, etc., when stacking multiple optical anisotropy layers, if a diffraction region that serves as both an intermediate diffraction region and an exit diffraction region is stacked, it is also preferable to stack multiple optical anisotropy layers with different lengths of one period of the liquid crystal alignment pattern, one direction of rotation of the liquid crystal alignment pattern that rotates continuously in one direction in the plane, and the direction of rotation of the optical axis derived from the liquid crystal compound within the liquid crystal alignment pattern that rotates continuously in one direction in the plane. Furthermore, if the diffraction region is a cholesteric liquid crystal layer, it is also preferable to stack multiple optical anisotropy layers with different helical pitches and directions of twisting rotation of the helix in the thickness direction (the direction of rotation of reflected circularly polarized light), and these can be appropriately set according to the purpose.Furthermore, in a configuration in which diffraction regions that serve as both intermediate diffraction regions and emission diffraction regions are stacked, in order to make the light intensity of the emitted light uniform, it is also preferable to use a configuration in which the in-plane distribution of diffraction efficiency in each diffraction region is different. There are no limitations on the arrangement of the diffraction regions, and they can be appropriately arranged in the in-plane direction and in the thickness direction (stacked) as needed.

[0239] In Figure 11, the optical anisotropy layer 400 is shown to have a reflective diffraction region, but it is not limited to this, and an optical anisotropy layer having a transmissive diffraction region may also be used. That is, the optical anisotropy layer (its incident diffraction region) may be arranged on the surface of the light guide plate 144 on the display 40 side.

[0240] [Method for Forming an Optically Anisotropic Layer] The method for manufacturing the optically anisotropic layer of the present invention is not particularly limited, but a manufacturing method having the following steps 1 to 3 is preferred in that it can efficiently manufacture an optically anisotropic layer. Step 1: A step of forming a coating film using a composition containing a liquid crystal compound having polymerizable groups, and oriented the liquid crystal compound in the formed coating film. Step 2: A step of polymerizing the liquid crystal compound. This step may include polymerizing the liquid crystal compound such that regions with different polymerization rates of the liquid crystal compound are formed in the in-plane direction of the coating film. Step 3: A step of applying a heat treatment to the coating film obtained in step 2 to polymerize the liquid crystal compound and form regions with different diffraction efficiencies in the in-plane direction of the coating film (for example, forming regions with a liquid crystal orientation pattern and regions without a liquid crystal orientation pattern). If regions with different polymerization rates of the liquid crystal compound are formed in the in-plane direction of the coating film in step 2, a step of forming regions with different diffraction efficiencies by changing the degree of orientation according to the polymerization rate in the corresponding region (for example, a region with a liquid crystal orientation pattern). Steps 1 to 3 described above will be explained in detail below.

[0241] (Step 1) Step 1 is a step of forming a coating film using a composition containing a liquid crystal compound having polymerizable groups, and aligning the liquid crystal compound in the formed coating film. By carrying out this step, a coating film containing oriented liquid crystal compounds is formed. In one preferred embodiment of this step, it is preferable to apply the composition onto the alignment film of a support with an alignment film, which has a support and an alignment film, to form a coating film and to align the liquid crystal compound in the coating film. By carrying out this preferred embodiment, a laminate is formed, as shown in Figure 15, which includes a support 320, an alignment film 322, and a coating film 324 (which will become an optically anisotropic layer in a later step).

[0242] The composition containing the polymerizable liquid crystal compound used in this process is as described above. The liquid crystal compound used in this process is preferably a liquid crystal compound having a radical polymerizable group or a cationic polymerizable group, and more preferably a liquid crystal compound having a radical polymerizable group.

[0243] The composition can be applied using various known methods used for applying liquids, such as bar coating, gravure coating, spin coating, and spray coating. Next, the coating film formed by the coating is subjected to an orientation treatment to orient the liquid crystal compound. By performing the orientation treatment, the liquid crystal compound in the coating film is oriented to a predetermined orientation state according to the orientation pattern of the orientation film. Heat treatment is preferred as the orientation treatment. The heating conditions are not particularly limited, but the heating temperature is preferably 20 to 140°C, and the heating time is preferably 0.5 to 20 minutes.

[0244] (Step 2) Step 2 is a step of polymerizing the liquid crystal compound. Step 2 includes a step of polymerizing the liquid crystal compound such that a transition region is formed at the boundary between a region having a liquid crystal alignment pattern and a region not having a liquid crystal alignment pattern, where the state gradually changes.

[0245] As an example of how to achieve this, a method using a photomask with different transmittances within the plane will be described. In step 2, when mainly polymerizing the liquid crystal compound in the region having a liquid crystal alignment pattern, a photomask is used in which the transmittance is high in the region having the liquid crystal alignment pattern and low (or occludes) the region without the liquid crystal alignment pattern. In the region with high transmittance of the photomask, the exposure energy is strong, so polymerization of the liquid crystal compound proceeds sufficiently. In the region with low (or occludes) transmittance of the photomask, the exposure energy is weak (or there is no light for exposure), so polymerization of the liquid crystal compound does not proceed. At this time, depending on the width of the transition region, a region is formed at the boundary between the region having the liquid crystal alignment pattern (the region with high transmittance of the photomask) and the region without the liquid crystal alignment pattern (the region with low transmittance of the photomask), in which the transmittance of the photomask is gradually changed. By exposing the liquid crystal compound through such a photomask and polymerizing it, a transition region is formed at the boundary between the region with a liquid crystal alignment pattern and the region without a liquid crystal alignment pattern, where the polymerization rate gradually changes (a region is formed where the polymerization rate gradually decreases from the region with a liquid crystal alignment pattern toward the region without a liquid crystal alignment pattern). Such a photomask can be fabricated by changing the optical density of dyes or metal coatings within the plane (changing the density, changing the film thickness, etc.).

[0246] Furthermore, the implementation method is not limited to the above, and various methods can be used to form the transition region. For example, a method in which the polymerization rate in the transition region is gradually changed by controlling the diffusivity of the exposure light source and gradually changing the exposure amount in the transition region; a method in which, in the process of forming an orientation pattern on an orientation film, the length of one period of the orientation pattern (length of the rotation period of the optical axis) is gradually changed at the boundary between the region having the orientation pattern and the region not having the orientation pattern, thereby forming a transition region in which the length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in the plane is gradually changed when a liquid crystal layer is formed; and, if the region having the liquid crystal orientation pattern is a cholesteric liquid crystal layer in which the region is cholesteric oriented, a method in which the diffraction efficiency in the transition region is gradually reduced by gradually changing the length of the helical pitch of the cholesteric liquid crystal layer by photoisomerization, etc.

[0247] Furthermore, step 2 may include a step of polymerizing the liquid crystal compound such that regions with different polymerization rates of the liquid crystal compound are formed in the in-plane direction of the coating film in the region having a liquid crystal alignment pattern. The procedure of this step is not particularly limited, but by performing this step, regions with different degrees of curing of the liquid crystal compound are formed in the in-plane direction of the coating film in at least a part of the plane.

[0248] An example of how this is achieved will be explained using Figure 15. In the photomask 329, the white areas represent high transmittance, and the black areas represent low transmittance. When exposure is performed from the direction indicated by the white arrow of reference numeral 327, in region 316 of the coating film 324, the exposure energy is strong according to the transmittance of the photomask 329, so polymerization of the liquid crystal compound proceeds sufficiently. On the other hand, in region 318 of the coating film 324, the exposure energy is weak according to the transmittance of the photomask 329, so polymerization of the liquid crystal compound does not proceed. As a result of step 3, which will be described later, the degree of orientation of the liquid crystal in region 316 becomes high and the degree of orientation of the liquid crystal in region 318 becomes low, so a gradient of the degree of orientation of the two is formed in the in-plane direction, and the diffraction efficiency gradually changes in the in-plane direction.

[0249] Step 2 may involve polymerizing the liquid crystal compound such that regions with different polymerization rate distributions are formed in the in-plane direction and the thickness direction. Means for forming regions with different degrees of curing of the liquid crystal compound in the thickness direction include exposure or heat treatment in an atmosphere containing polymerization-inhibiting components such as oxygen and moisture, and forming a coating film using a composition containing a compound that absorbs ultraviolet light of an exposure wavelength, such as an ultraviolet absorber, and then exposing the formed coating film.

[0250] An example of how this is achieved will be explained using Figure 16. In the photomask 329, the white areas represent high transmittance, and the black areas represent low transmittance. When exposure is performed from the direction indicated by the white arrow of reference numeral 327, the first region 326 on the alignment film 322 side of the coating film 324 is not in contact with the atmosphere, so the oxygen supply from the atmosphere is slow and polymerization proceeds sufficiently. On the other hand, the second region 328 on the opposite side of the alignment film 322 side of the coating film 324 is in contact with the atmosphere, so the oxygen supply from the atmosphere is fast and polymerization does not proceed. At this time, the thickness of the first region 326 gradually changes according to the transmittance of the photomask 329. In step 3, which will be described later, the degree of orientation of the liquid crystal in the first region 326 becomes high and the degree of orientation of the liquid crystal in the second region 328 becomes low, so a thickness gradient is formed in the in-plane direction, and the diffraction efficiency gradually changes in the in-plane direction. In particular, in step 3 described later, by making the second region 328 an unoriented state, only the first region 326 with a high degree of orientation can be made to function as a diffraction element. As a result, the effective birefringence of the liquid crystal compound increases when light is diffracted, and the diffraction efficiency can be increased. In addition, the effective refractive index of the liquid crystal compound increases when light is diffracted, which allows for a wider field of view (FOV) when used, for example, in AR glasses. Step 2 may be carried out by other methods.

[0251] Furthermore, whether regions with different degrees of curing of the liquid crystal compound are formed in the in-plane direction of the coating film can be determined, for example, by analyzing the surface of the coating film using infrared absorption spectroscopy and calculating the remaining polymerizable group rate in the in-plane direction of the coating film.

[0252] In a method for forming a coating film using a composition containing the polymerizable liquid crystal compound described above, and then exposing the formed coating film to light, ultraviolet irradiation is preferred as the exposure treatment. The conditions for the ultraviolet irradiation treatment are appropriately selected according to the coating film used, but the irradiation dose is 1 to 1000 mJ / cm². ２ Preferably, 10 to 300 mJ / cm ２ This is preferable.

[0253] (Step 3) Step 3 is a process in which the coating obtained in Step 2 is subjected to heat treatment to form regions with different diffraction efficiencies in the in-plane direction. The coating obtained in Step 2 contains regions in the in-plane direction of the coating film where the polymerization rate of the liquid crystal compound differs. When such a coating film is subjected to heat treatment, the orientation state of the liquid crystal compound is maintained in regions with a high polymerization rate of the liquid crystal compound. On the other hand, in regions with a low polymerization rate of the liquid crystal compound, the orientation state of the liquid crystal compound can no longer be maintained by the heat treatment, resulting in a decrease in the degree of orientation of the liquid crystal compound. When such a decrease in the degree of orientation of the liquid crystal compound occurs, the diffraction efficiency in that region decreases. In other words, by performing this step, regions with a high polymerization rate of the liquid crystal compound become regions with high diffraction efficiency, and regions with a low polymerization rate of the liquid crystal compound become regions with low diffraction efficiency. In particular, in regions with a sufficiently low polymerization rate, the liquid crystal becomes unoriented, so it is possible to form regions without a liquid crystal orientation pattern.

[0254] When the coating film is heat-treated in step 3, the orientation of the liquid crystal compound is maintained in regions with a high polymerization rate of the liquid crystal compound and a liquid crystal orientation pattern, while in regions without a liquid crystal orientation pattern and a low polymerization rate of the liquid crystal compound, the orientation state can no longer be maintained by the heat treatment (a decrease in the degree of orientation occurs). Therefore, in the transition region at the boundary between the region with a liquid crystal orientation pattern and the region without a liquid crystal orientation pattern, the polymerization rate gradually decreases from the region with a liquid crystal orientation pattern toward the region without a liquid crystal orientation pattern, causing the orientation state to gradually change (the degree of orientation to gradually change). In other words, by performing this step, a transition region is formed where the diffraction efficiency gradually decreases from the region with a liquid crystal orientation pattern toward the region without a liquid crystal orientation pattern. In such a transition region, as the polymerization rate decreases, the degree of orientation of the liquid crystal gradually decreases and approaches an unoriented state, so the birefringence (Δn) of the transition region gradually decreases.

[0255] As mentioned above, the methods for gradually changing the state in the transition region and gradually changing the diffraction efficiency are not limited to those described above.

[0256] From the viewpoint of having an equal average refractive index, it is preferable that the region having a liquid crystal alignment pattern and the region not having a liquid crystal alignment pattern be formed from substantially the same material (liquid crystal composition). This makes it possible to avoid scattering at the interface between the region having a liquid crystal alignment pattern and the region not having a liquid crystal alignment pattern. The materials forming each region can be confirmed by analyzing their components, for example, by SIMS (secondary ion mass spectrometry). In this case, it is preferable that the average refractive index of the region having a liquid crystal alignment pattern is within ±10% of the average refractive index of the region not having a liquid crystal alignment pattern. The method for forming the region not having a liquid crystal alignment pattern is not limited to this method, and examples include methods of performing non-patterned alignment treatment, such as uniaxial alignment, on the alignment film.

[0257] The conditions for the heat treatment carried out in this process are not particularly limited, and the optimal conditions are selected according to the coating film used. The heating temperature during the heat treatment is preferably 20 to 300°C, and more preferably 50 to 200°C. The heating time is preferably 0.5 to 30 minutes, and more preferably 1 to 5 minutes. At this time, in the region of low polymerization of the liquid crystal compound, if the heating temperature is sufficiently high above the phase transition temperature of the liquid crystal phase-isotropic phase (Iso) of the liquid crystal compound, an optically isotropic region without a liquid crystal alignment pattern is formed.

[0258] After performing step 3, step 4 may be performed, in which the optically anisotropic layer obtained in step 3 is subjected to exposure treatment. By performing the exposure treatment, unreacted polymerizable groups can be polymerized. As the exposure treatment, ultraviolet irradiation treatment is preferred. The conditions for the ultraviolet irradiation treatment are appropriately selected according to the coating film used, but the irradiation dose is 10 to 2000 mJ / cm². ２ Preferably, 100 to 1000 mJ / cm ２ It is preferable that the ultraviolet irradiation treatment be carried out in an atmosphere with a low oxygen concentration. It is preferable that the ultraviolet irradiation treatment be carried out in a nitrogen atmosphere.

[0259] In the optical anisotropic layers of the present invention described above, the optical axis 30A of the liquid crystal compound 30 in the liquid crystal orientation pattern of the diffraction region rotates continuously only along the direction of arrow X. However, the present invention is not limited thereto, and various configurations are available as long as the optical axis 30A of the liquid crystal compound 30 rotates continuously along one direction in the diffraction region. As mentioned above, the optical anisotropic layers of the present invention can also be formed by stacking multiple optical anisotropic layers to form a laminate. The lamination method includes a method of directly coating the liquid crystal composition onto the first optical anisotropic layer to form the second optical anisotropic layer, a method of coating the first optical anisotropic layer, then performing an alignment treatment, and finally coating the liquid crystal composition, and a method of laminating an optical anisotropic layer provided on another substrate. The grating pitch, grating angle, helical pitch, helical pitch change in the thickness direction, tilt angle, tilt angle change in the thickness direction, Δn change in the thickness direction, size of the diffraction region, shape of the diffraction region, physical film thickness, optical thickness, and reflectance for each wavelength of each optical anisotropic layer can be arbitrarily adjusted. Furthermore, within a single diffraction region, the grating pitch, grating angle, helical pitch, helical pitch change in the thickness direction, Δn change in the thickness direction, tilt angle, tilt angle change in the thickness direction, physical thickness, optical thickness, and reflectance for each wavelength can be changed in the in-plane direction, and the direction and angle of change can also be arbitrarily adjusted. In addition, diffraction regions with the above parameters adjusted can be arbitrarily combined. In the optical anisotropic layer of the present invention, it is preferable that in at least one of the aforementioned regions A and B, the length of the helical pitch of the cholesteric liquid crystal layer has different regions within that region, and more preferably, the length of the helical pitch changes continuously within that region. By having different lengths of helical pitch, it is possible to control the diffraction angle of the diffraction region for a certain wavelength. Therefore, as shown in Figure 11, by designing the helical pitch so that appropriate diffraction angles are obtained at positions P1, P2, P3, and P4 in region B45c, the amount of light reaching the eye can be increased, and the brightness of the AR glasses can be enhanced.Furthermore, the present invention allows for the formation of multiple units within a single substrate, each unit comprising at least one region A having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound rotates continuously along at least one direction in the plane, region B having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound rotates continuously along at least one direction in the plane, and a region without a liquid crystal alignment pattern. By forming multiple units within a single substrate, the productivity of not only the optical anisotropy layer formation process of the present invention but also the downstream processes can be improved.

[0260] <Adhesive Layer (Sticky Adhesive Layer), Adhesive> In laminates and light guide elements, an adhesive layer may be included for bonding optical anisotropy layers to each other and / or to the light guide plate. In this specification, "adhesion" is used as a concept that also includes "tackiness". Examples include water-soluble adhesives, UV-curing adhesives, emulsion-type adhesives, latex-type adhesives, mastic adhesives, multi-layer adhesives, paste-type adhesives, foam-type adhesives, supported film adhesives, thermoplastic adhesives, hot-melt adhesives, thermal-solidifying adhesives, thermally activated adhesives, heat-seal adhesives, thermosetting adhesives, contact-type adhesives, pressure-sensitive adhesives (i.e., tacks), polymerization-type adhesives, solvent-type adhesives, solvent-activated adhesives, ceramic adhesives, etc. Specifically, examples include aqueous solutions of boron compounds, curable epoxy compound adhesives that do not contain aromatic rings in their molecules, as shown in Japanese Patent Publication No. 2004-245925, active energy ray curable adhesives that contain a photopolymerization initiator having a molar extinction coefficient of 400 or more at wavelengths of 360 to 450 nm as described in Japanese Patent Publication No. 2008-174667, and an ultraviolet curable compound as essential components, and active energy ray curable adhesives that contain, in a total amount of 100 parts by mass of (meth)acrylic compounds as described in Japanese Patent Publication No. 2008-174667, (a) an (meth)acrylic compound having two or more (meth)acryloyl groups in its molecule, (b) an (meth)acrylic compound having a hydroxyl group in its molecule and only one polymerizable double bond, and (c) a phenol ethylene oxide modified acrylate or a nonylphenol ethylene oxide modified acrylate. Depending on the requirements, the various adhesives can be used individually or in mixtures.

[0261] In laminates and light guide elements, from the viewpoint of reducing unwanted reflections, it is preferable that the adhesive layer has a small refractive index difference with adjacent layers. Specifically, the refractive index difference with adjacent layers is preferably 0.1 or less, more preferably 0.05 or less, and even more preferably 0.01 or less. There are no particular restrictions on the method for adjusting the refractive index of the adhesive layer, but known methods such as adding fine particles of zirconia, silica, acrylic, acrylic-styrene, or melamine, adjusting the refractive index of the resin, and the method described in Japanese Patent Application Publication No. 11-223712 can be used. Furthermore, if adjacent layers have refractive index anisotropy in the plane, it is preferable that the refractive index difference with adjacent layers is 0.2 or less, more preferably 0.1 or less, and even more preferably 0.05 or less in all directions in the plane. Therefore, the adhesive layer may have refractive index anisotropy in the plane. If the refractive index difference between the bonding interfaces is large, the interfacial reflectance can be reduced by distributing the refractive index in the thickness direction of the adhesive layer. Methods for creating a refractive index distribution in the thickness direction include providing multiple adhesive layers, mixing the interfaces between multiple adhesive layers, and controlling the uneven distribution of materials within the adhesive layer to create a refractive index distribution.

[0262] Furthermore, the adhesive layer can be applied to one or both of the members to be bonded by any method such as coating, vapor deposition, or transfer. From the viewpoint of increasing adhesive strength, post-treatments such as heat treatment and ultraviolet irradiation can be applied according to the type of adhesive. The thickness of the adhesive layer can be adjusted arbitrarily, but it is preferably 20 μm or less, more preferably 0.1 μm or less, and even more preferably 0.01 μm or less. As a method for forming an adhesive layer of 0.1 μm or less, one method is to vapor-deposit a ceramic adhesive such as silicon dioxide (SiOx layer) onto the bonding surface. The bonding surface of the bonded members can be subjected to surface modification treatments such as plasma treatment, corona treatment, or saponification treatment before bonding, and a primer layer can be applied. Also, if there are multiple bonding surfaces, the type and thickness of the adhesive layer can be adjusted for each bonding surface.

[0263] <Cutting of Optically Anisotropic Layer (Optical Layer) and Laminate> The fabricated optically anisotropic layer (optical layer) and / or laminate can be cut to a predetermined size. There are no limitations on the method of cutting the optically anisotropic layer (optical layer) and / or laminate; various known methods can be used, such as physically cutting with a cutting tool like a Thomson blade or cutting by irradiating with a laser. When using a laser, it is preferable to select the pulse width (nanosecond, picosecond, femtosecond) and wavelength considering the cutability and damage to the material. After processing the optically anisotropic layer and / or laminate into a predetermined shape, for example, the end face may be polished. From the viewpoint of improving processability during cutting and suppressing dust generation, it is also possible to cut with a peelable protective film attached. Furthermore, for example, by cutting while observing the liquid crystal alignment pattern using the method shown in Japanese Patent Application Publication No. 2004-141889, the cutting position can be arbitrarily determined. In this case, the liquid crystal alignment pattern can be observed through a polarizing plate and a phase difference film to make it easier to see. Also, if multiple units are provided on a single substrate, it is preferable to cut and separate each unit.

[0264] <Other Processing> To accurately install the optical anisotropic layer (optical layer or laminate) on various devices (e.g., light guide plate), and to improve the accuracy of the axis and cutting position during cutting, markings of any shape can be added as needed. The type of markings can be arbitrarily selected, and methods such as physically adding them using laser or inkjet methods, partially changing the orientation of the liquid crystal, or adding partially decolorized or dyed areas can be selected. In addition, to protect the optical anisotropic layer (optical layer), protective layers (gas barrier layer, moisture barrier layer, UV absorption layer, scratch-resistant layer, transparent colored layer, etc.) can be provided as needed. The protective layer can be formed directly on the optical anisotropic layer, or it may be provided via other optical films such as an adhesive layer. Anti-reflective layers (LR (Low-Reflection) layer, AR (Anti-Reflection) layer, moth-eye layer, etc.) may be provided to reduce the reflectivity of the surface. Various protective layers can be appropriately selected from known ones. When a gas barrier layer is provided, polyvinyl alcohol, glass, etc., are preferred. Polyvinyl alcohol can also function as a polarizer. The ultraviolet absorption layer is a layer containing an ultraviolet absorber, and from the viewpoint of good displayability, an ultraviolet absorber that has excellent absorption ability for ultraviolet light with a wavelength of 370 nm or less and absorbs little visible light with a wavelength of 400 nm or more is preferably used. Only one type of ultraviolet absorber may be used, or two or more types may be used in combination. For example, ultraviolet absorbers described in Japanese Patent Publication No. 2001-072782 and Japanese Patent Publication No. 2002-543265 can be cited. Specific examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, etc. The transparent colored layer is a layer that absorbs or reflects at least a portion of visible light. By combining the transparent colored layer with the optical anisotropy layer, the color appearance of the optical element including the optical anisotropy layer can be adjusted. For example, if the optically anisotropic layer is colored, a transparent colored layer can be combined with it to adjust the color to a neutral shade.

[0265] The optical anisotropic layer of the present invention can be used in various applications in optical devices, such as optical path changing members, light focusing elements, light diffusion elements in a predetermined direction, and diffraction elements, where light is reflected (diffracted) or transmitted (diffracted) at an angle other than specular reflection.

[0266] The above examples utilize the optical anisotropy layer (diffraction region) of the present invention as an optical anisotropy layer that reflects or transmits visible light. However, the present invention is not limited to these examples, and various configurations are available. For example, the optical anisotropy layer (diffraction region) of the present invention may be configured to reflect or transmit infrared or ultraviolet light, or to reflect or transmit only light other than visible light. Furthermore, the optical anisotropy layer of the present invention can be used in combination with other components. For example, it can be used in combination with a configuration sandwiched between two pieces of glass, a low-reflection layer, an ultraviolet absorption layer, a polarizing plate, a lens component, and the like.

[0267] Although the optical anisotropic layer, laminate, light guide element, and AR display device of the present invention have been described in detail above, the present invention is not limited to the examples described above, and various improvements and modifications may be made without departing from the spirit of the present invention.

[0268] The features of the present invention will be further described in detail below with reference to examples. The materials, reagents, amounts used, amounts of substance, ratios, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[0269] [Reference Example 1] (Formation of Alignment Film) A glass substrate was prepared as a support. The following alignment film forming coating solution was applied to the support by spin coating. The support coated with this alignment film forming coating solution was dried on a 60°C hot plate for 60 seconds to form an alignment film.

[0270] Coating solution for forming alignment film ------------------------------------------------------------------- Photo-alignment material below 1.00 parts by mass Water 16.00 parts by mass Butoxyethanol 42.00 parts by mass Propylene glycol monomethyl ether 42.00 parts by mass -------------------------------------------------------------------

[0271] -Material for photo alignment-

[0272]

[0273] (Exposure of the alignment film) Using the exposure apparatus shown in Figure 3, a portion of the alignment film, region 1 and region 2, were exposed to light to form an alignment film P-1 having an alignment pattern. At this time, region 2 was exposed after rotating the orientation of the alignment film by 180° relative to region 1, thereby reversing the alignment patterns of region 1 and region 2 by 180°. The exposure apparatus used emitted laser light with a wavelength of 325 nm. The exposure dose due to interference was 300 mJ / cm². 2 The intersection angle (intersection angle α) of the two laser beams was controlled so that the period Λ (length of 180° rotation of the optical axis) of the orientation pattern formed by the interference of the two laser beams was 0.44 μm.

[0274] (Formation of the optical layer) The following composition LC-1 was prepared as a liquid crystal composition for forming the optical layer.

[0275] Composition LC-1 --------------------------------------------------- Rod-shaped liquid crystal compound L-1 90.00 parts by mass Rod-shaped liquid crystal compound L-2 10.00 parts by mass Polymerization initiator (BASF, Omnirad® 819) 3.00 parts by mass Chiral agent Ch-1 5.20 parts by mass Leveling agent T-1 0.10 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass ---------------------------------------------------

[0276] Rod-shaped liquid crystal compound L-1

[0277]

[0278] Rod-shaped liquid crystal compound L-2

[0279]

[0280] Chiral agent Ch-1

[0281]

[0282] Leveling agent T-1

[0283]

[0284] The prepared composition LC-1 was coated onto the alignment film P-1 to form a composition layer. The coating was performed using a spin coater at 1500 rpm. The support having the composition layer was heated on a hot plate at 90°C for 1 minute. Subsequently, mask MK-1 was placed on the composition layer, and 365 nm ultraviolet light at a wavelength of 500 mJ / cm was exposed to the mask MK-1 using a 365 nm LED UV exposure machine at 40°C in a nitrogen atmosphere. 2 The composition layer was exposed with the following irradiation dose. The relationship between the amount of ultraviolet light irradiated onto the composition layer through mask MK-1 and the position of each region of the alignment film is shown in Figure 17 (relative irradiation dose 1 in Figure 17 is 500 mJ / cm²). 2(Equivalent to...). Next, the mask MK-1 is removed, and the mixture is heated at 150°C (liquid crystal phase-isotropic phase (Iso) or higher of the liquid crystal composition) for 1 minute. Then, under a nitrogen atmosphere, a 365 nm LED UV exposure machine is used at 150°C to expose the mixture to ultraviolet light at a wavelength of 365 nm at a rate of 200 mJ / cm². 2 By irradiating the coating film with the specified irradiation dose, the orientation of the liquid crystal compound was fixed, and an optical layer was formed. The optical layer was fabricated to a thickness of 500 nm. In the optical layer, the irradiation dose shown in Figure 17 was 0 mJ / cm². 2 A non-diffractive region is formed at this location, and the irradiation dose in region 1 is 0 mJ / cm². 2 Region A (diffraction region) is formed at the position above, and the irradiation dose in region 2 is 0 mJ / cm². 2 Region B (diffraction region) is formed at the position of the ultrapoint.

[0285] [Evaluation] (Evaluation of diffraction efficiency) As shown in Figure 14, the optical layer prepared above was placed on the surface of the dove prism 110 and the diffraction efficiency of the optical layer at each position was evaluated. In Figure 14, a glass dove prism with a refractive index of 1.5 was used as the dove prism 110. The optical layer was peeled off from the glass substrate before use. The optical layer and the dove prism were bonded together using a heat-sensitive adhesive.

[0286] As shown in Figure 14, an optical layer is placed on the upper surface of the dove prism 110, a laser is placed facing the inclined surface of the dove prism 110, and a linear polarizer 112 and a λ / 4 plate 114 are placed between the laser and the dove prism 110.

[0287] When light is emitted from the laser, it passes through the linear polarizer 112 and the λ / 4 plate 114, becoming right-circularly polarized, and enters the dove prism 110. The light propagates within the dove prism 110 and enters the optical layer. The diffracted light, reflected and diffracted by the optical layer, propagates within the dove prism 110 in the direction opposite to the plane on which the optical layer is located. The light that has propagated through the dove prism 110 reaches the bottom surface of the dove prism 110 and is emitted.

[0288] In Figure 17, the diffraction efficiency was measured at each position in 5 mm increments, with the position of the end of the optical layer on the side where the laser light is incident being set to 0 mm. The wavelength of the laser light was 532 nm, and the incident angle of the laser light was set so that the light was incident on the optical layer at 55.6° relative to the normal direction of the optical layer. Reflection diffraction occurred in the optical layer, and the light intensity of the light emitted in the normal direction of the optical layer (normal direction of the lower surface of the dove prism 110) was measured.

[0289] The diffraction efficiency Def of the fabricated optical layer is determined by the light intensity of the laser light incident on the dove prism 110. ｉｎ The light intensity of the light diffracted by the optical layer and emitted from the dove prism 110 is I ｏｕｔ When this is the case, the following formula is used to calculate the diffraction efficiency: Def = I ｏｕｔ / I ｉｎ Furthermore, when calculating the diffraction efficiency, the loss of transmittance at the interface during incidence and emission into the dove prism 110 was excluded from the calculation.

[0290] Evaluating the diffraction efficiency of the optical layer fabricated using the above method, it was confirmed that the diffraction efficiency gradually increases from position 15 mm to position 45 mm. As shown in Figure 18, the diffraction efficiency distribution is as follows: reference numeral 221 corresponds to region A, reference numeral 222 to region B, and reference numeral 223 corresponds to a region without an orientation pattern (non-diffraction region). Region A (reference numeral 221) has a constant diffraction efficiency, while region B (reference numeral 222) has an increasing diffraction efficiency from one side to the other. No diffracted light was generated in the region without an orientation pattern (non-diffraction region). The isotropy of the non-diffraction region (reference numeral 223) can be confirmed from the fact that Re(40) is zero. The distribution of Re(40) at each position is as shown in Figure 19.

[0291] [Evaluation] (Evaluation of emitted light intensity distribution) As shown in Figure 13, the optical layer (reference numeral 400) prepared above was placed on the surface of the light guide plate 144 to create a light guide element. In Figure 13, a glass light guide plate with a refractive index of 1.8 and a thickness of 0.5 mm was used as the light guide plate 144. The optical layer was peeled from the glass substrate and bonded to the light guide plate 144.

[0292] As shown in Figure 13, a laser was positioned facing the side of the light guide plate 144 opposite to the side where the optical layer 400 is located, on the side where region A45a is located. A linear polarizer 100 and a λ / 4 plate 102 were placed between the laser and the light guide plate 144. A power meter (not shown) was positioned at a distance of 10 cm from the optical layer 400, facing the side of the light guide plate 144 opposite to the side where the optical layer 400 is located, on the side where region B45c is located. The wavelength of the laser light was 532 nm, and the beam diameter of the laser light was 1 mm.

[0293] When light is emitted from the laser, it passes through the linear polarizer 100 and the λ / 4 plate 102, becoming right-circularly polarized before entering the light guide plate 144. The light that enters the light guide plate 144 enters region A45a of the optical layer 400. Due to the diffraction and selective reflection effects of region A45a of the optical layer 400, the reflected and diffracted light propagates within the light guide plate 144. The light that has propagated within the light guide plate 144 is diffracted and reflected in region B45c of the optical layer 400 and emitted in the direction of the power meter.

[0294] Furthermore, a light-shielding plate 104 was placed between the light guide plate 144 and the power meter, facing the side opposite to the side where the optical layer 400 was located. A pinhole 104a with a diameter of 2 mm was formed in the light-shielding plate 104.

[0295] The intensity of light emitted from the light guide plate 144 (emitted light intensity) was measured through a pinhole 104a in the light shielding plate 104. By changing the position of the pinhole 104a, the emitted light intensity was measured at each position within the plane of region B45c. The emitted light intensity was measured using a Newport Power Meter 1918-C.

[0296] Upon checking the amount of light emitted from the light guide plate 144, it was confirmed that the emitted intensity was uniform.

[0297] [Evaluation] (Brightness uniformity and image clarity evaluation) The light guide element of the present invention was installed in the incident element (region A) of the fabricated light guide plate so that light from the LCOS display for AR glasses was incident on it. Subsequently, the brightness uniformity and image clarity of the displayed image were evaluated. The brightness of the displayed image was uniform, and the image was clear.

[0298] [Reference Example 2] An optically anisotropic layer was formed using the same method as in Example 1, except that the mask used was changed to mask MK-2. The relationship between the amount of ultraviolet radiation irradiated onto the composition layer through mask MK-2 and the position of each region of the alignment film is shown in Figure 20 (relative irradiation amount 1 in Figure 20 is 500 mJ / cm²). 2 (This corresponds to...). Mask MK-2 is a mask that has regions with a constant irradiation dose within region 1 and region 2, as shown in Figure 20.

[0299] Next, the diffraction efficiency and Re(40) of the optically anisotropic layer were measured using the same method as in Reference Example 1. The diffraction efficiency was distributed as shown in Figure 21, and Re(40) was distributed as shown in Figure 22. The diffraction efficiency of the optical layer was constant from position 15 mm to position 45 mm. In Figure 21, reference numeral 231 corresponds to region A, reference numeral 232 to region B, and reference numeral 233 to the non-diffraction region. Subsequently, brightness uniformity and image sharpness were evaluated using the same method as in Reference Example 1. The brightness of the displayed image was non-uniform within the plane, but the image was sharp.

[0300] [Comparative Example 1] (Exposure of Alignment Film) An alignment film P-2 having a single alignment pattern was formed by exposure of the alignment film using the exposure apparatus shown in Figure 3. In the exposure apparatus, a laser with a wavelength of 325 nm was used as the laser. The exposure amount due to interference was 300 mJ / cm 2 The following was done. The intersection angle (intersection angle α) of the two laser beams was controlled so that the period Λ (length of 180° rotation of the optical axis) of the orientation pattern formed by the interference of the two laser beams was 0.44 μm. Composition LC-1 was coated onto the orientation film P-2 using the same method as in Example 1 to form a composition layer. The coating was performed using a spin coater at 1500 rpm. The support having the composition layer was heated on a hot plate at 90°C for 1 minute. Subsequently, mask MK-1 was placed on the composition layer, and ultraviolet light with a wavelength of 365 nm was exposed at 500 mJ / cm using a 365 nm LED UV exposure machine at 40°C in a nitrogen atmosphere via mask MK-1. 2The composition layer was exposed with the following irradiation dose. The relationship between the amount of ultraviolet light irradiated onto the composition layer through mask MK-1 and the position of each region of the alignment film is shown in Figure 17. Subsequently, mask MK-1 was removed, and 365 nm ultraviolet light at a wavelength of 365 nm was irradiated at 200 mJ / cm using a 365 nm LED UV exposure machine at 40°C in a nitrogen atmosphere. 2 By irradiating the coating film with a specific irradiation dose, the orientation of the liquid crystal compound was fixed, forming an optical layer. The optical layer was fabricated to a thickness of 500 nm.

[0301] Using the same method as in Reference Example 1, the diffraction efficiency and Re(40) of the optical layer were evaluated, and it was confirmed that Comparative Example 1 had the same distribution as Reference Example 1. Next, the diffraction elements (regions corresponding to regions A and B) were cut out from the optical layer and peeled off from the glass substrate, and the diffraction elements corresponding to regions A and B of Reference Example 1 were placed on the incident and exit sides of the light guide plate surface, respectively (see Figure 23). That is, as shown in Figure 23, the incident optical layer and the exit optical layer are not continuous. Next, brightness uniformity and image clarity were evaluated using the same method as in Reference Example 1. The brightness of the displayed image was uniform within the plane, and the image was unclear.

[0302] [Example 1] An alignment film P-1 was prepared in the same manner as in Reference Example 1, and composition LC-1 was applied to the alignment film P-1 to form a composition layer. Mask MK-1G was prepared by adjusting the transmittance of mask MK-1 so that the transition region from the outer periphery of regions A and B of Reference Example 1 is 1 mm wide, and the transmittance at a position 1 mm away from the outer periphery of regions A and B is 0.1% or less. In other words, mask MK-1G is a mask in which the transmittance changes in a gradient so that the transition region from the outer periphery of regions A and B is 1 mm wide. Mask MK-1G was placed on the composition layer, and 365 nm ultraviolet light at a wavelength of 365 nm was applied through mask MK-1G using a 365 nm LED UV exposure machine at 40°C and a nitrogen atmosphere at 500 mJ / cm². 2The composition layer was exposed with the following irradiation dose. The irradiation dose of ultraviolet light irradiated onto the composition layer through the mask MK-1G in regions A and B, and the positional relationship between each region of the alignment film, are shown in Figure 17. As mentioned above, the transmittance of the mask MK-1G changes in a gradient so that the transition region from the outer periphery of regions A and B is 1 mm wide, and the transmittance is adjusted so that the transmittance at a position 1 mm away from the outer periphery of regions A and B is 0.1% or less. Next, the mask MK-1G was removed and heated at 150°C (liquid crystal phase - isotropic phase (Iso) or higher of the liquid crystal composition) for 1 minute, and under a nitrogen atmosphere, ultraviolet light with a wavelength of 365 nm was irradiated at 200 mJ / cm using a 365 nm LED UV exposure machine at 150°C. 2 By irradiating the coating film with this irradiation dose, the orientation of the liquid crystal compound was fixed, and an optical layer was formed. The optical layer was fabricated to a thickness of 500 nm. In the optical layer, as shown in Figure 17, the irradiation dose excluding the transition region is 0 mJ / cm². 2 A non-diffractive region is formed at this location, and in Figure 17, the irradiation dose in region 1 is 0 mJ / cm². 2 Region A (diffraction region and transition region) is formed at the position above, and the irradiation dose in region 2 is 0 mJ / cm². 2 Region B (diffraction region and transition region) is formed at the ultra-high position.

[0303] Next, the diffraction efficiency of the optical layer was evaluated using the same method as in Reference Example 1. The diffraction efficiency is shown in Figure 32. Similar to Reference Example 1, it was confirmed that the diffraction efficiency gradually increased from position 15 mm to position 45 mm.

[0304] Next, the diffraction efficiency within the transition region (width 1 mm) was evaluated. In Example 1, in both region A and region B, it was confirmed that the diffraction efficiency gradually decreased within a width of 1 mm, from the outer periphery of region A and region B (the edge of the transition region on the diffraction region side) toward the edge of the transition region on the non-diffraction region side. In Reference Example 1, since no transition region was provided at the boundary between the diffraction regions A and B and the non-diffraction region, the diffraction efficiency changed abruptly across the boundary between the diffraction and non-diffraction regions.

[0305] Next, the uniformity of brightness and image clarity of the displayed image were evaluated using the same method as in Reference Example 1. The brightness of the displayed image was uniform, and the image was clear. Compared to Reference Example 1, Example 1 displayed an even brighter image and had greater image clarity. From these results, the effects of the present invention are clear.

[0306] It can be suitably used in various applications of light reflection in optical devices, such as diffraction elements that cause light to enter and exit the light guide plate of AR glasses.

[0307] 1 Optical layer 2a Region having liquid crystal alignment pattern 2b Region not having liquid crystal alignment pattern 2c Transition region 10, 12, 46, 47 Liquid crystal diffraction element 16 Liquid crystal diffraction layer 18 Cholesteric liquid crystal layer 20 Support 24 Alignment film 30 Liquid crystal compound 30A Optical axis 40 Display (image display device) 42, 332 Bright area 44, 330 Dark area 45 Light guide element 45a, 221, 231 Region A 45b, 223, 233 Non-diffraction region 45c, 222, 232 Region B 45d Region C 50 AR display device 60 Exposure apparatus 62 Laser 64 Light source 68 Beam splitter 70A, 70B Mirror 72A, 72B λ / 4 plate 100 Linear polarizer 102 λ / 4 plate 104 Light-shielding plate 104a Pinhole 110 Dove prism 112 Linear polarizer 114 λ / 4 plate 144 Light guide plate 316, 318 Region 320 Support 322 Alignment film 324 Coating 326 First region 328 Second region 329 Photomask 400, 450 Optical anisotropy layer (optical layer) 400a First optical anisotropy layer 400b Second optical anisotropy layer 410a, 420a Region A 410b, 420b Non-diffractive region 410c, 420c Region B 500 Laminate M Laser light MA, MB Light P O Linear polarized light P R Right-circular polarization P L Left-circular polarization α Crossing angle L1, L4 Incident light L2, L5 Reflected light R RRight-circularly polarized red light I0-I3 Light propagating within the light guide plate P1-P4 Position R1-R4 Light

Claims

1. An optical layer formed using a composition containing a liquid crystal compound, wherein the optical layer has a region having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and a region not having a liquid crystal alignment pattern, both within the same plane of the optical layer, the region having the liquid crystal alignment pattern and the region not having a liquid crystal alignment pattern are adjacent to each other, the region having the liquid crystal alignment pattern has a transition region in the plane in which the optical properties change, and the transition region is adjacent to the region not having a liquid crystal alignment pattern.

2. The optical layer according to claim 1, wherein the optical layer has a plurality of regions within the same plane of the optical layer, each region having the liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane.

3. The optical layer according to claim 2, wherein the optical layer has a plurality of regions having the liquid crystal alignment pattern in the in-plane direction of the same optical layer, and between the regions of the liquid crystal alignment pattern arranged at different positions in the plane, there are regions without the liquid crystal alignment pattern within the plane of the same optical layer.

4. The optical layer according to claim 1, wherein in the region that does not have the liquid crystal alignment pattern, at least a portion of the plane is optically isotropic.

5. The optical layer according to claim 1, wherein the transition region is a region in which the birefringence (Δn) changes gradually.

6. The optical layer according to claim 1, wherein in the region that does not have the liquid crystal alignment pattern, at least a portion of the plane is optically anisotropic.

7. The optical layer according to claim 1, wherein the transition region is a region in which the diffraction efficiency changes gradually.

8. The optical layer according to claim 1, wherein the region having the liquid crystal orientation pattern has regions with different diffraction efficiencies in the in-plane direction.

9. The optical layer according to claim 2, wherein the optical layer has a plurality of regions having the liquid crystal alignment pattern in the same in-plane direction of the optical layer, and the regions having the liquid crystal alignment pattern have different directions in one direction of the liquid crystal alignment pattern.

10. The optical layer according to claim 2, wherein the optical layer has a plurality of regions having the liquid crystal alignment pattern in the same in-plane direction of the optical layer, and the regions having the liquid crystal alignment pattern have different lengths in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in the plane.

11. The optical layer according to claim 1, wherein in the region having the liquid crystal alignment pattern, at least one region having the liquid crystal alignment pattern is a cholesterically oriented cholesteric liquid crystal layer.

12. The optical layer according to claim 11, wherein in the region having the liquid crystal alignment pattern, the length of the helical pitch of the cholesteric liquid crystal layer is different in the in-plane direction within the region.

13. The optical layer according to claim 11, wherein in the region having the liquid crystal alignment pattern, the length of the helical pitch of the cholesteric liquid crystal layer is varied in the thickness direction of the optical layer.

14. The optical layer according to claim 12 or claim 13, wherein in the region having the liquid crystal alignment pattern, there is a region having a plurality of layers in which the helical pitch lengths of the cholesteric liquid crystal layer are different.

15. The optical layer according to claim 12 or claim 13, wherein the optical layer has a plurality of regions having the liquid crystal alignment pattern in the same in-plane direction of the optical layer, and the helical pitch lengths of the cholesteric liquid crystal layer are different in the regions.

16. The optical layer according to claim 1, wherein the entire layer is smooth and does not have an uneven structure.

17. A laminate having two or more optical layers as described in claim 1.

18. A light guide element comprising a light guide plate and an optical layer according to claim 1 disposed on the surface of the light guide plate.

19. The light guide element according to claim 18, further comprising a phase difference layer.

20. An AR display device having a light guide element according to claim 18 or claim 19 and an image display device.

21. The AR display device according to claim 20, wherein the emitted light of the image display device is polarized.

22. The AR display device according to claim 20, wherein the image display device is a laser beam scanning type image display device.

Images