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

Abstract

The invention provides an optically anisotropic layer, a light guide element, and an AR display device, which can make the brightness of light emitted from a light guide plate uniform. The optically anisotropic layer is characterized in that the optically anisotropic layer is formed using a composition containing a liquid crystal compound, and the optically anisotropic layer has a birefringence change region in at least a portion in the plane. The birefringence change region has a birefringence [Delta] n that differs in the thickness direction, and the average value [Delta] na of the birefringence in the thickness direction differs in the plane of the optically anisotropic layer.

Description

Technical Field

[0001] The present invention relates to an optically anisotropic layer formed using a composition containing a liquid crystal compound, a light guide element using the optically anisotropic layer, and an AR display device. Background Art

[0002] In recent years, AR (Augmented Reality) glasses that superimpose and display virtual images and various information in an actually seen scene, as described in Non-Patent Document 1, have been put into practical use. AR glasses are also called smart glasses, head-mounted displays (HMDs), and the like.

[0003] As shown in Non-Patent Document 1, as an example, AR glasses incident an image displayed by a display (optical engine) on one end of a light guide plate and propagate it, and emit it from the other end, so as to superimpose and display a virtual image in the scene actually seen by the user.

[0004] In AR glasses, a diffraction element is used to diffract (refract) light (projection light) from the display and incident it on one end of the light guide plate. Thereby, the light is introduced into the light guide plate at an angle, and while the light is reflected at the interface (surface) of the light guide plate, the light propagates in the light guide plate to the other end. The light propagating in the light guide plate is similarly diffracted by the diffraction element at the other end of the light guide plate and is emitted from the light guide plate to the position observed by the user.

[0005] As such a diffraction grating, a diffraction element using liquid crystal is known. For example, Patent Document 1 describes an optical element that includes a plurality of stacked birefringent sub-layers configured to change the propagation direction of light passing therethrough according to the Bragg condition, and each of the plurality of stacked birefringent sub-layers has a local optical axis that changes along a corresponding boundary surface between adjacent ones in the stacked birefringent sub-layers to define a corresponding grating period. The optical element described in Patent Document 1 is an optical element that diffracts transmitted light. It is described that by diffracting light incident on a substrate (light guide plate) with the optical element, the light is incident at an angle of total reflection in the substrate, so as to guide the light in a direction substantially perpendicular to the incident direction of the light in the substrate (refer to Figure 8 ) of Patent Document 1).

[0006] In Patent Document 2, there is described a polarization diffraction grating which includes a photo-alignment layer sensitive to polarized light and at least first and second liquid crystal compositions containing a polymerizable mesogen disposed on the photo-alignment layer. Among them, anisotropic alignment patterns corresponding to a polarization hologram are disposed in the photo-alignment layer. The first liquid crystal composition is disposed on the alignment layer and is thus aligned, and is at least partially polymerized. The second liquid crystal composition is disposed on the first liquid crystal composition and is thus aligned. The liquid crystal compositions both 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.

[0007] In Patent Document 3, there is described a reflection structure which includes a plurality of spiral structures each extending along a specified direction, and has a first incident surface which intersects the specified direction and into which light is incident, and a reflection surface which intersects the specified direction and reflects the light incident from the first incident surface. The first incident surface includes one end portion of each of the two end portions of the plurality of spiral structures. Each of the plurality of spiral structures includes a plurality of structural units connected along the specified direction. The plurality of structural units include a plurality of elements stacked in a helically rotating manner. Each of the plurality of structural units has a first end portion and a second end portion. The second end portion of one of the structural units adjacent to each other along the specified direction constitutes the first end portion of another structural unit. The orientation directions of the elements located at the plurality of first end portions included in the plurality of spiral structures are the same. The reflection surface includes at least one first end portion included in each of the plurality of spiral structures. The reflection surface is not parallel to the first incident surface.

[0008] Here, it is known that the field of view (exit pupil expansion) is expanded by adopting the following structure in an AR glasses: when diffracting the light propagating in a light guide plate with a diffraction element by adjusting the diffraction efficiency of the diffraction element, a part of the light is diffracted at a plurality of positions and emitted to the outside of the light guide plate.

[0009] For example, in Patent Document 4, there is described an optical waveguide including the following steps: an input coupler (diffraction element) of the optical waveguide couples light corresponding to an image having a corresponding FOV (field of View) into the optical waveguide. The input coupler divides the FOV of the image coupled to the optical waveguide into a first part and a second part, and diffracts a part of the light corresponding to the image in a second direction toward a second intermediate component. An intermediate coupler (diffraction element) and an output coupler (diffraction element) perform exit pupil expansion.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-522601

[0013] Patent Document 2: Japanese Patent No. 5276847

[0014] Patent Document 3: International Publication No. 2016 / 194961

[0015] Patent Document 4: International Publication No. 2017 / 180403

[0016] Non-Patent Document

[0017] Non-Patent Document 1: Bernard C. Kress et al., Towards the Ultimate Mixed Reality Experience: HoloLens Display Architecture Choices, SID 2017 DIGEST, pp. 127 - 131 Summary of the Invention

[0018] Technical Problem to be Solved by the Invention

[0019] When a liquid crystal diffraction element is used as a diffraction element for a light guide element of AR glasses, and in order to expand the visual field (exit pupil expansion) of the AR glasses, it is structured such that the liquid crystal diffraction element diffracts a part of light at multiple positions and emits it to the outside of the light guide plate. If the diffraction efficiency in the plane of the liquid crystal diffraction element is uniform, there is a problem that the brightness (light quantity) of the light emitted from the light guide plate becomes uneven.

[0020] The problem of the present invention is to solve the problems of such prior art and provide an optically anisotropic layer, a light guide element, and an AR display device capable of making the brightness of the light emitted from the light guide plate uniform.

[0021] Means for Solving the Technical Problem

[0022] To solve this problem, the present invention has the following structure.

[0023] [1] An optically anisotropic layer, characterized in that

[0024] the optically anisotropic layer is an optically anisotropic layer formed using a composition containing a liquid crystal compound,

[0025] at least a part of the optically anisotropic layer in the plane has a birefringence change region,

[0026] the birefringence Δn of the birefringence change region is different in the thickness direction,

[0027] and the average value Δna of the birefringence in the thickness direction is different within the plane of the optically anisotropic layer.

[0028] [2] The optical anisotropic layer according to [1], wherein,

[0029] In the birefringence change region, the average value Δna of the birefringence in the thickness direction gradually changes from one side to the other side in at least one direction in the plane of the optical anisotropic layer.

[0030] [3] The optical anisotropic layer according to [1] or [2], wherein,

[0031] In the birefringence change region, the birefringence Δn gradually changes in the thickness direction.

[0032] [4] An optical anisotropic layer, wherein,

[0033] The optical anisotropic layer is an optical anisotropic layer formed using a composition containing a liquid crystal compound,

[0034] At least a part of the optical anisotropic layer in the plane has a birefringence change region having a region with a large birefringence and a region with a small birefringence in the thickness direction,

[0035] In the birefringence change region, the ratio of the thickness of the region with a large birefringence to the thickness of the optical anisotropic layer is different in the plane of the optical anisotropic layer, whereby the average value Δna of the birefringence in the thickness direction is different in the plane of the optical anisotropic layer.

[0036] [5] The optical anisotropic layer according to [4], wherein,

[0037] In the birefringence change region, the ratio of the thickness of the region with a large birefringence to the thickness of the optical anisotropic layer gradually changes from one side to the other side in at least one direction in the plane of the optical anisotropic layer.

[0038] [6] The optical anisotropic layer according to [4] or [5], wherein,

[0039] The region with a small birefringence is optically isotropic.

[0040] [7] The optical anisotropic layer according to any one of [1] to [6], wherein,

[0041] In the birefringence change region, there is a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates and changes along at least one direction in the plane.

[0042] [8] The optical anisotropic layer according to [7], wherein,

[0043] In the birefringence change region, the direction in which the average value Δna of the birefringence in the thickness direction gradually changes is parallel to the direction in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates and changes.

[0044] [9] The optically anisotropic layer according to any one of [1] to [8], wherein,

[0045] In the birefringence change region, the liquid crystal compound is in a twisted alignment.

[0046]

[10] The optically anisotropic layer according to any one of [1] to [8], wherein,

[0047] In the birefringence change region, the liquid crystal compound is in a cholesteric alignment.

[0048]

[11] The optically anisotropic layer according to any one of [1] to

[10] , wherein,

[0049] In the optically anisotropic layer, at least a part of the in-plane region different from the birefringence change region is composed only of optically isotropic regions.

[0050]

[12] The optically anisotropic layer according to any one of [1] to

[11] , wherein,

[0051] In the optically anisotropic layer, at least a part of the in-plane region different from the birefringence change region is composed only of optically non-isotropic regions.

[0052]

[13] The optically anisotropic layer according to any one of [1] to

[12] , wherein,

[0053] In the optically anisotropic layer, the liquid crystal molecules in at least a part of the in-plane region different from the birefringence change region are aligned in the same plane in one direction.

[0054]

[14] The optically anisotropic layer according to any one of [7] to [8], wherein,

[0055] In the optically anisotropic layer, there are regions in which the rotation directions of the optical axes derived from the liquid crystal compound in the in-plane liquid crystal alignment pattern are different from each other.

[0056]

[15] The optically anisotropic layer according to any one of [1] to

[14] , wherein,

[0057] In the optically anisotropic layer, there are regions where the liquid crystal compound is in a right-handed helical cholesteric alignment and regions where it is in a left-handed helical cholesteric alignment.

[0058]

[16] The optically anisotropic layer according to any one of [1] to

[15] , wherein,

[0059] In the optically anisotropic layer, a region where the length of the helical pitch of the cholesteric liquid crystal layer varies in the thickness direction of the optically anisotropic layer.

[0060]

[17] The optically anisotropic layer according to any one of [1] to

[16] , wherein,

[0061] In the optically anisotropic layer, a region where the length of the helical pitch of the cholesteric liquid crystal layer is different in different in-plane regions of the optically anisotropic layer.

[0062]

[18] The optically anisotropic layer according to any one of [1] to

[17] , wherein,

[0063] There are regions in the plane of the optically anisotropic layer with different film thicknesses.

[0064]

[19] A laminate having a first optically anisotropic layer and a second optically anisotropic layer,

[0065] At least one of the first optically anisotropic layer and the second optically anisotropic layer is the optically anisotropic layer according to any one of [1] to

[18] .

[0066]

[20] The laminate according to

[19] , wherein,

[0067] When the length of the rotation of the optical axis derived from the liquid crystal compound in the optically anisotropic layer by 180° in the plane is set as one cycle, in the first optically anisotropic layer and the second optically anisotropic layer, the length of one cycle in the liquid crystal alignment pattern is different.

[0068]

[21] The laminate according to any one of

[19] to

[20] , which has a region where one direction of the liquid crystal alignment pattern continuously rotating in one direction in the plane of the first optically anisotropic layer is different from one direction of the liquid crystal alignment pattern continuously rotating in one direction in the plane of the second optically anisotropic layer.

[0069]

[22] The laminate according to any one of

[19] to

[21] , which has a region where the rotation direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern continuously rotating in one direction in the plane of the first optically anisotropic layer is different from the rotation direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern continuously rotating in one direction in the plane of the second optically anisotropic layer.

[0070]

[23] The laminate according to any one of

[19] to

[22] , which has a region where the length of the helical pitch of the cholesteric liquid crystal layer in the first optically anisotropic layer is different from the length of the helical pitch of the cholesteric liquid crystal layer in the second optically anisotropic layer.

[0071]

[24] The laminate according to any one of

[19] to

[23] , which has a region where the rotation direction of the helix of the cholesteric liquid crystal layer in the first optically anisotropic layer and the rotation direction of the helix of the cholesteric liquid crystal layer in the second optically anisotropic layer are different from each other.

[0072]

[25] An optical element having a protective layer on at least one surface of the optically anisotropic layer according to any one of [1] to

[18] .

[0073]

[26] A light guide element having:

[0074] A light guide plate; and

[0075] The optically anisotropic layer according to any one of [1] to

[18] , disposed on the surface of the light guide plate.

[0076]

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

[26] and an image display device.

[0077]

[28] A light guide element having:

[0078] A light guide plate; and

[0079] The optical element according to

[25] , disposed on the surface of the light guide plate.

[0080]

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

[28] and an image display device.

[0081] Advantages of the Invention

[0082] According to the present invention, an optically anisotropic layer, a light guide element, and an AR display device capable of making the brightness of light emitted from a light guide plate uniform can be provided. Brief Description of the Drawings

[0083] Figure 1 It is a conceptual diagram of an example of the optically anisotropic layer of the present invention.

[0084] Figure 2 It is Figure 1 A top view of the optically anisotropic layer.

[0085] Figure 3 It is a conceptual diagram of an example of an exposure device for exposing an alignment film.

[0086] Figure 4 It is for explaining Figure 1 The function of the optically anisotropic layer.

[0087] Figure 5A diagram conceptually showing an example of the relationship between the position of the optically anisotropic layer and the diffraction efficiency.

[0088] Figure 6 A diagram conceptually showing another example of the relationship between the position of the optically anisotropic layer and the diffraction efficiency.

[0089] Figure 7 A conceptual diagram of another example of the optically anisotropic layer of the present invention.

[0090] Figure 8 Is Figure 7 A top view of the optically anisotropic layer.

[0091] Figure 9 Is for explaining Figure 7 The function of the optically anisotropic layer.

[0092] Figure 10 Is for explaining Figure 7 The function of the optically anisotropic layer.

[0093] Figure 11 A diagram schematically showing an example of an AR display device having the optically anisotropic layer of the present invention.

[0094] Figure 12 A diagram conceptually showing the relationship between the position and the emitted light in the AR display device.

[0095] Figure 13 A diagram for explaining the method of measuring the intensity of the emitted light in the embodiment.

[0096] Figure 14 A schematic diagram explaining the method of measuring the diffraction efficiency.

[0097] Figure 15 A diagram showing an example of a method for forming a region where the diffraction efficiency gradually changes in the in-plane direction of the optically anisotropic layer.

[0098] Figure 16 A diagram schematically showing the change in thickness of regions with large and small birefringence of the liquid crystal compound in the thickness direction of the optically anisotropic layer.

[0099] Figure 17 A diagram showing the illuminance of light based on the position of the optically anisotropic layer.

[0100] Figure 18 A diagram showing the thickness of the high birefringence layer based on the position of the optically anisotropic layer.

[0101] Figure 19 A diagram showing the retardation value based on the position of the optically anisotropic layer.

[0102] Figure 20 It is a diagram showing the thickness of a high birefringence layer based on the position of an optically anisotropic layer.

[0103] Figure 21 It is a diagram showing the retardation value based on the position of an optically anisotropic layer.

[0104] Figure 22 It is a diagram showing the retardation value based on the position of an optically anisotropic layer.

[0105] Figure 23 It is a diagram showing the thickness distribution of a diffraction element based on the position of an optically anisotropic layer.

[0106] Figure 24 It is a diagram schematically showing an example of an AR display device having a conventional liquid crystal diffraction element.

[0107] Figure 25 It is a diagram showing an example of the in-plane distribution of diffraction efficiency represented by light and dark.

[0108] Figure 26 It is a diagram conceptually showing an example of the optically anisotropic layer of the present invention.

[0109] Figure 27 It is a diagram conceptually showing an example of the optically anisotropic layer of the present invention.

[0110] Figure 28 is Figure 27 a top view of.

[0111] Figure 29 It is a diagram conceptually showing another example of the optically anisotropic layer of the present invention.

[0112] Figure 30 It is a diagram conceptually showing an example of a laminate having multiple optically anisotropic layers of the present invention. Detailed Description of the Invention

[0113] Hereinafter, based on the preferred embodiments shown in the drawings, the liquid crystal diffraction element, light guide element, and AR display device of the present invention will be described in detail.

[0114] In this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0115] In this specification, "(meth)acrylate" is used in the meaning of "either or both of acrylate and methacrylate".

[0116] In this specification, "identical" includes the error range generally allowed in the technical field. Also, in this specification, when expressed as "all", "both", "the entire surface", etc., except for the case of 100%, it also includes the error range generally allowed in the technical field, such as the case of 99% or more, 95% or more, or 90% or more. Also, regarding "orthogonal" and "parallel" with respect to angles, it means within a range of a strict angle of ±5°, and regarding "identical" with respect to angles, unless otherwise specified, it means a difference from the strict angle within a range of less than 5 degrees. The difference from the strict angle is preferably less than 4 degrees, more preferably less than 3 degrees.

[0117] In this specification, visible light is light having a wavelength visible to the human eye among electromagnetic waves, representing light in the wavelength region of 380 to 780 nm. Non-visible light is light in the wavelength region less than 380 nm and exceeding 780 nm. Also, not limited thereto, among visible light, light in the wavelength region of 420 to 490 nm is blue light, light in the wavelength region of 495 to 570 nm is green light, and light in the wavelength region of 620 to 750 nm is red light.

[0118] In this specification, the selected reflection center wavelength means the average value of two wavelengths representing the half-value transmittance T1 / 2 (%) expressed by the following formula when the minimum value of the transmittance in an object (component) to be an object is set to Tmin (%).

[0119] Formula for obtaining the half-value transmittance: T1 / 2 = 100 - (100 - Tmin) ÷ 2

[0120] Also, "equal" for the selected reflection center wavelengths of multiple layers does not mean strictly equal, and an error within a range without optical influence is allowed. Specifically, "equal" for the selected reflection center wavelengths of multiple objects means that the difference in the selected reflection center wavelengths between each object is 20 nm or less, and this difference is preferably 15 nm or less, more preferably 10 nm or less.

[0121] The retardation value is measured using "Axoscan" manufactured by Axometrics Inc. The measurement wavelength is set to 750 nm. For the incident light from the normal direction to the sample surface, phase difference measurement is performed. For the detected slow axis and fast axis, phase difference measurement is performed from directions with incident angles of -40° and 40° respectively within the slow axis plane and the fast axis plane, and the average value of the measurement values from the four directions is taken as the in-plane retardation Re(40).

[0122] [Optical anisotropic layer]

[0123] The first mode of the optical anisotropic layer of the present invention is the following optical anisotropic layer:

[0124] The optical anisotropic layer has an optical anisotropic layer formed using a composition containing a liquid crystal compound,

[0125] At least a part of the optical anisotropic layer in the plane has a birefringence change region,

[0126] The birefringence Δn of the birefringence change region is different in the thickness direction,

[0127] And the average value Δna of the birefringence in the thickness direction is different in the plane of the optical anisotropic layer.

[0128] A second mode of the optical anisotropic layer of the present invention is the following optical anisotropic layer:

[0129] The optical anisotropic layer is an optical anisotropic layer formed using a composition containing a liquid crystal compound,

[0130] At least a part of the optical anisotropic layer in the plane has a birefringence change region having a region with a large birefringence and a region with a small birefringence in the thickness direction,

[0131] In the birefringence change region, the ratio of the thickness of the region with a large birefringence to the thickness of the optical anisotropic layer is different in the plane of the optical anisotropic layer, whereby the average value Δna of the birefringence in the thickness direction is different in the plane of the optical anisotropic layer.

[0132] And one mode of the optical anisotropic layer of the present invention is the following optical anisotropic layer:

[0133] The optical anisotropic layer has an optical anisotropic layer formed using a composition containing a liquid crystal compound,

[0134] The optical anisotropic layer has an optically isotropic region and an optically anisotropic region, and has a region where the ratio of the optically isotropic region to the optically anisotropic region in the thickness direction is different in the plane of the optical anisotropic layer.

[0135] Such an optical anisotropic layer is an optical anisotropic layer having a region where the magnitude of the phase difference is different in the plane of the optical anisotropic layer. As an example, the optical anisotropic layer is an optical anisotropic layer in which the phase difference increases as it moves from one side to the other along at least one direction in the plane of the optical anisotropic layer.

[0136] And one mode of the optical anisotropic layer of the present invention is the following optical anisotropic layer:

[0137] When the liquid crystal compound is cholesterically oriented in the optically anisotropic region of the optical anisotropic layer, it has a region where the magnitude of the reflectance is different in the plane of the optical anisotropic layer.

[0138] As an example, the optically anisotropic layer is an optically anisotropic layer whose reflectance increases as it goes from one side to the other along at least one direction in the plane of the optically anisotropic layer.

[0139] Moreover, one mode of the optically anisotropic layer of the present invention is the following optically anisotropic layer (liquid crystal diffraction element):

[0140] In the case of having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates along at least one direction in the plane, it has regions where the magnitude of the diffraction efficiency is different within the plane of the optically anisotropic layer.

[0141] As an example, the optically anisotropic layer is an optically anisotropic layer (liquid crystal diffraction element) whose diffraction efficiency increases as it goes from one side to the other along at least one direction in the plane of the optically anisotropic layer.

[0142] As will be described in detail later, by having such a structure, the liquid crystal diffraction element of the present invention can make the brightness of the light emitted from the light guide plate uniform when diffracting the light propagating in the light guide plate by the liquid crystal diffraction element and emitting it from the light guide plate. Regarding the change in the diffraction efficiency, the diffraction efficiency may also increase in a plurality of directions in the plane. An example of the in-plane distribution of the diffraction efficiency is shown in Figure 25 . In Figure 25 , the darker the black area, the higher the diffraction efficiency. However, it is not limited thereto, and various liquid crystal diffraction elements can be applied according to the design of the light guide plate.

[0143] [First Embodiment]

[0144] In Figure 1 , an example of the first embodiment of the optically anisotropic layer of the present invention is conceptually shown.

[0145] Figure 1 The liquid crystal diffraction element 10 shown is an element that selectively reflects light of a specific wavelength and includes the optically anisotropic layer 18 of the present invention. That is, Figure 1 the liquid crystal diffraction element 10 shown is a reflective liquid crystal diffraction element.

[0146] Figure 1 The liquid crystal diffraction element 10 shown has a structure in which a support 20, an alignment film 24, and an optically anisotropic layer 18 formed using a composition containing a liquid crystal compound are laminated in sequence.

[0147] At least a part of the optical anisotropic layer 18 in the plane has a birefringence change region, the birefringence Δn of which is different in the thickness direction and the average value Δna of the birefringence in the thickness direction (hereinafter, also simply referred to as the average value Δna of the birefringence) is different in the plane of the optical anisotropic layer. In the present invention, for example, a structure having a region where the average value Δna of the birefringence is different in the plane is achieved by changing the alignment state (degree of alignment) of the liquid crystal compound according to the position in the plane (corresponding to the first mode). Or, for example, a structure having a region where the average value Δna of the birefringence is different in the plane is achieved by forming a region with a large birefringence (high birefringence region) and a region with a small birefringence (low birefringence region) in the thickness direction and changing the ratio of the thickness of the high birefringence region according to the position in the plane (corresponding to the second mode). The structure for achieving such a structure having a region where the average value Δna of the birefringence is different in the plane will be described in detail later.

[0148] In addition, Figure 1 The liquid crystal diffraction element 10 shown has a support 20 and an alignment film 24, but the optical anisotropic layer of the present invention may also have a structure that is not laminated on the support 20 or further not laminated on the alignment film 24.

[0149] For example, the optical anisotropic layer of the present invention may be a structure in which the support 20 is peeled off from the above structure and laminated on the alignment film 24. Or, the support 20 and the alignment film 24 may be peeled off and the optical anisotropic layer 18 may be composed only of an optical anisotropic layer formed by using a composition containing a liquid crystal compound.

[0150] And, as one mode, as long as the optical anisotropic layer of the present invention is an optical anisotropic layer formed by using a composition containing a liquid crystal compound, the optical anisotropic layer has an optically isotropic region and an optically anisotropic region, and a region where the ratio of the optically isotropic region to the optically anisotropic region in the thickness direction is different in the plane of the optical anisotropic layer, various layer structures can be utilized.

[0151] And, as one mode, the optical anisotropic layer of the present invention may be an optical anisotropic layer in which the liquid crystal compound is cholesterically aligned in the optically anisotropic region.

[0152] Also, as one mode, as long as the optically anisotropic layer of the present invention has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates and changes along at least one direction in the plane, and has a structure in which the diffraction efficiency is different in different regions in the plane of the optically anisotropic layer, various layer structures can be used. And, as an example, the optically anisotropic layer of the present invention has the following optically anisotropic layer (liquid crystal diffraction element), which has a structure in which the diffraction efficiency increases as it goes from one side to the other side of a direction rotated from the optical axis derived from the liquid crystal compound.

[0153] Regarding the above points, the optically anisotropic layers of the respective modes of the present invention described later are all the same.

[0154] <Support>

[0155] The support 20 is a thin film (sheet-like material, plate-like material) that supports the alignment film 24 and the optically anisotropic layer 18.

[0156] In addition, the transmittance of the support 20 for the light diffracted by the optically anisotropic layer 18 is preferably 50% or more, more preferably 70% or more, and further preferably 85% or more.

[0157] The thickness of the support 20 is not limited, as long as it can appropriately maintain the thickness of the alignment film 24 and the optically anisotropic layer 18 according to the use of the liquid crystal diffraction element 10, the forming material of the support 20, etc.

[0158] The thickness of the support 20 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and further preferably 5 to 150 μm.

[0159] The support 20 can be a single layer or a multilayer.

[0160] As the support 20 in the case of a single layer, various materials that can be used as the support material in various optical elements can be used.

[0161] Specifically, as the material of the support 20, glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, polyolefin, etc. can be exemplified. As an example of the support 20 in the case of a multilayer, a support that includes any one of the above single-layer supports as a substrate and has other layers provided on the surface of the substrate can be exemplified.

[0162] <Alignment Film>

[0163] An alignment film 24 is formed on the surface of the support 20.

[0164] The alignment film 24 is an alignment film that aligns the liquid crystal compound 30 into a specified liquid crystal alignment pattern when forming the optically anisotropic layer 18.

[0165] As described later, in the liquid crystal diffraction element 10, the optically anisotropic layer 18 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A (refer to Figure 2 ) derived from the liquid crystal compound 30 continuously rotates along one direction in the plane while changing.

[0166] In addition, in the present invention, the length in which the orientation of the optical axis 30A rotates 180° in one direction in which the orientation of the optical axis 30A continuously rotates while changing in the liquid crystal alignment pattern is defined as one period ( Figure 2 symbol Λ in, also referred to as "rotation period of the optical axis").

[0167] In the following description, "rotation of the orientation of the optical axis 30A" is also simply referred to as "rotation of the optical axis 30A".

[0168] The alignment film can be various known alignment films.

[0169] For example, a rubbed film made of an organic compound such as a polymer, an inclined vapor deposition film of an inorganic compound, a film having microgrooves, and a film formed by accumulating LB (Langmuir - Blodgett) films of organic compounds such as ω - tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate based on the Langmuir - Blodgett method can be exemplified.

[0170] The alignment film based on rubbing treatment can be formed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.

[0171] As the material used in the alignment film, materials used in the formation of polyimide, polyvinyl alcohol, polymers having polymerizable groups described in Japanese Patent Laid - Open No. 9 - 152509, alignment films described in Japanese Patent Laid - Open Nos. 2005 - 097377, 2005 - 099228, and 2005 - 128503 are preferred.

[0172] In the liquid crystal diffraction element 10, the alignment film is preferably a so - called photo - alignment film formed by irradiating a photo - aligning raw material with polarized light or non - polarized light. That is, in the liquid crystal diffraction element 10, as the alignment film, a photo - alignment film formed by coating a photo - aligning material on the support 20 is preferred.

[0173] Polarized light can be irradiated on the photo - alignment film from the vertical direction or an inclined direction, and non - polarized light can be irradiated on the photo - alignment film from an inclined direction.

[0174] As the photoalignment material used in the photoalignment film that can be utilized in the present invention, for example, azo compounds described in JP-A No. 2006-285197, JP-A No. 2007-76839, JP-A No. 2007-138138, JP-A No. 2007-94071, JP-A No. 2007-121721, JP-A No. 2007-140465, JP-A No. 2007-156439, JP-A No. 2007-133184, JP-A No. 2009-109831, Japanese Patent No. 3883848, and Japanese Patent No. 4151746, aromatic ester compounds described in JP-A No. 2002-229039, maleimide and / or alkenyl-substituted nadimide compounds having a photoalignment unit described in JP-A No. 2002-265541 and JP-A No. 2002-317013, photocrosslinkable silane derivatives described in Japanese Patent No. 4205195 and Japanese Patent No. 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides, and photocrosslinkable polyesters described in JP-T No. 2003-520878, JP-T No. 2004-529220, and Japanese Patent No. 4162850, and compounds capable of photodimerization described in JP-A No. 9-118717, JP-T No. 10-506420, JP-T No. 2003-505561, International Publication No. 2010 / 150748, JP-A No. 2013-177561, and JP-A No. 2014-12823, particularly cinnamate compounds, chalcone compounds, and coumarin compounds, etc. are exemplified as preferred examples.

[0175] Among them, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable polyesters, cinnamate compounds, and chalcone compounds are preferably used.

[0176] The thickness of the alignment film is not limited as long as the thickness capable of obtaining the required alignment function is appropriately set according to the material for forming the alignment film.

[0177] The thickness of the alignment film is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0178] The method for forming the alignment film is not limited, and various known methods corresponding to the material for forming the alignment film can be used. As an example, a method of forming an alignment pattern by applying the alignment film on the surface of the support 20, drying it, and then exposing the alignment film with a laser beam can be exemplified.

[0179] In Figure 3Conceptually shown is an example of an exposure apparatus for exposing an alignment film to form an alignment pattern.

[0180] Figure 3 The exposure apparatus 60 shown includes: a light source 64 having a laser 62 and a λ / 2 plate (not shown), a beam splitter 68 that separates the laser beam M emitted from the light source 64 into two light beams, light beam MA and light beam MB, mirrors 70A and 70B respectively disposed on the optical paths of the two separated light beams MA and MB, and λ / 4 plates 72A and 72B.

[0181] In addition, although not shown, the light source 64 emits 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 (light beam MA) into right-handed circularly polarized light P R and the λ / 4 plate 72B converts the linearly polarized light P0 (light beam MB) into left-handed circularly polarized light P L .

[0182] A support 20 having an alignment film 24 before forming the alignment pattern is disposed in the exposure section. By causing the two light beams MA and MB to cross on the alignment film 24 to cause interference, and irradiating the interference light onto the alignment film 24 for exposure.

[0183] Due to the interference at this time, the polarization state of the light irradiated onto the alignment film 24 changes periodically in an interference fringe pattern. Thus, an alignment pattern in which the alignment state changes periodically can be obtained in the alignment film 24.

[0184] In the exposure apparatus 60, by changing the crossing angle α of the two light beams MA and MB, the period of the alignment pattern can be adjusted. That is, in the exposure apparatus 60, by adjusting the crossing angle α, the length of one period in which the optical axis 30A rotates 180° in one direction of the rotation of the optical axis 30A in the alignment pattern in which the optical axis 30A of the liquid crystal compound 30 continuously rotates in one direction can be adjusted.

[0185] By forming an optically anisotropic layer on the alignment film having such an alignment pattern in which the alignment state changes periodically, as will be described later, an optically anisotropic layer 18 having a liquid crystal alignment pattern in which the optical axis 30A of the liquid crystal compound 30 continuously rotates in one direction can be formed.

[0186] Moreover, by rotating the optical axes of the λ / 4 plates 72A and 72B by 90° respectively, the rotation direction of the optical axis 30A can be reversed.

[0187] In addition, in the liquid crystal diffraction element, the alignment film is provided as a preferred mode and is not an essential component.

[0188] For example, it can also be configured as follows: an alignment pattern is formed on the support 20 by a method of rubbing the support 20, a method of processing the support 20 with a laser beam, etc., so that the optically anisotropic layer has a liquid crystal alignment pattern in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 continuously rotates along at least one direction in the plane while changing.

[0189] <Optically Anisotropic Layer>

[0190] An optically anisotropic layer 18 is formed on the surface of the alignment film 24.

[0191] As described above, at least a part of the optically anisotropic layer in the plane has a birefringence change region, and the birefringence Δn of this birefringence change region is different in the thickness direction, and the average value Δna of the birefringence in the thickness direction is different in the plane of the optically anisotropic layer.

[0192] Moreover, as a preferred mode, the optically anisotropic layer 18 (birefringence change region) in the illustrated example is a layer formed using a composition containing a liquid crystal compound, and it has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates along at least one direction in the plane.

[0193] In Figure 1 In the example shown, the optically anisotropic layer 18 has a structure in which the liquid crystal compound is cholesterically aligned. That is, the optically anisotropic layer 18 is a layer in which the cholesteric liquid crystal phase is fixed, and it has a cholesteric liquid crystal structure in which the liquid crystal compound is helically twisted and oriented along a helical axis parallel to the thickness direction. The optically anisotropic layer 18 has a structure in which a plurality of pitch layers of the liquid crystal compound 30 that are stacked by rotating the liquid crystal compound 30 once (rotating 360°) in a spiral shape and are spirally rotated as one helical pitch are stacked.

[0194] The optically anisotropic layer 18 having a cholesteric liquid crystal structure has wavelength-selective reflectivity.

[0195] For example, when the optically anisotropic layer 18 has a selective reflection center wavelength in the green wavelength region, it reflects the right-handed circularly polarized light G R of green light and transmits the other light.

[0196] Here, in the optically anisotropic layer 18, the liquid crystal compound 30 rotates and aligns in the plane direction, so that the incident circularly polarized light is refracted (diffracted) toward the direction in which the orientation of the optical axis continuously rotates and is reflected. At this time, the direction of diffraction is different depending on the rotation direction of the incident circularly polarized light.

[0197] That is, the optically anisotropic layer 18 reflects the right-handed circularly polarized light or the left-handed circularly polarized light of the selective reflection wavelength and diffracts the reflected light.

[0198] Moreover, the optically anisotropic layer 18 changes the direction of rotation of the reflected circularly polarized light to the opposite direction.

[0199] <<Cholesteric liquid crystal phase>>

[0200] The cholesteric liquid crystal phase exhibits selective reflectivity for left-handed circularly polarized light or right-handed circularly polarized light at a specific wavelength.

[0201] The central 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 λ = n × P with the average refractive index n of the cholesteric liquid crystal phase. Therefore, by adjusting the pitch of the helical structure, the selective reflection center wavelength can be adjusted. The pitch of the cholesteric liquid crystal phase depends on the type of chiral reagent used together with the liquid crystal compound or its addition concentration when forming the optically anisotropic layer. Therefore, by adjusting them, the desired pitch can be obtained.

[0202] In addition, the adjustment of the pitch is described in detail in Fuji Film Research Report No. 50 (2005), pp. 60-63. Regarding the method for measuring the helix handedness and pitch, the methods described on pages 46 of "Introduction to Liquid Crystal Chemistry Experiments" edited by the Japanese Liquid Crystal Society and published by Sigma in 2007 and on page 196 of "Liquid Crystal Handbook" edited by the Liquid Crystal Handbook Editorial Committee and published by Maruzen can be used.

[0203] Whether the reflected light based on the cholesteric liquid crystal phase is right-handed circularly polarized light or left-handed circularly polarized light depends on the twisting direction (handedness) of the helix of the cholesteric liquid crystal phase. Regarding the selective reflection of circularly polarized light based on the cholesteric liquid crystal phase, when the twisting direction of the helix of the cholesteric liquid crystal phase is right, right-handed circularly polarized light is reflected, and when the twisting direction of the helix is left, left-handed circularly polarized light is reflected.

[0204] In Figure 1 the liquid crystal diffraction element 10, the optically anisotropic layer 18 is a layer in which a right-twisted cholesteric liquid crystal phase is fixed.

[0205] In addition, the direction of rotation of the cholesteric liquid crystal phase can be adjusted according to the type of liquid crystal compound forming the optically anisotropic layer and / or the type of chiral reagent added.

[0206] Moreover, the half-width Δλ (nm) of the selective reflection band (circularly polarized light reflection band) showing selective reflection depends on Δn of the cholesteric liquid crystal phase and the pitch P of the helix, and follows the relationship Δλ = Δn × P. Therefore, the control of the width of the selective reflection band can be performed by adjusting Δn. Δn can be adjusted according to the type of liquid crystal compound forming the optically anisotropic layer and its mixing ratio, and the temperature at the time of orientation fixing.

[0207] The half-width of the reflection wavelength region can be adjusted according to the use of the liquid crystal diffraction element 10, for example, it can be 10 to 500 nm, preferably 20 to 300 nm, and more preferably 30 to 100 nm.

[0208] <<Method for forming an optically anisotropic layer having a cholesteric liquid crystal structure>>

[0209] The optically anisotropic layer having a cholesteric liquid crystal structure can be formed by fixing the cholesteric liquid crystal phase in a layered manner.

[0210] The structure formed by fixing the cholesteric liquid crystal phase only needs to be a structure in which the orientation of the liquid crystal compound that has become the cholesteric liquid crystal phase is maintained. Typically, the following structure is preferred: on the basis of making the polymerizable liquid crystal compound in an oriented state of the cholesteric liquid crystal phase, polymerization and curing are carried out by ultraviolet irradiation, heating, etc., thereby forming a non-fluid layer, and at the same time changing to a state in which the orientation morphology will not change due to an external field or external force.

[0211] In addition, in the structure formed by fixing the cholesteric liquid crystal phase, it is sufficient as long as the optical properties of the cholesteric liquid crystal phase are maintained. In the optically anisotropic layer, the liquid crystal compound 30 may not exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound can be polymerized to a high molecular weight through a curing reaction and lose its liquid crystallinity.

[0212] As a material for forming the optically anisotropic layer in which the cholesteric liquid crystal phase is fixed, as an example, a liquid crystal composition containing a liquid crystal compound can be cited. The liquid crystal compound is preferably a polymerizable liquid crystal compound.

[0213] Furthermore, the liquid crystal composition for forming the optically anisotropic layer may also contain a surfactant and a chiral reagent.

[0214] --Polymerizable liquid crystal compound--

[0215] The polymerizable liquid crystal compound can be a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound.

[0216] As an example of the rod-shaped polymerizable liquid crystal compound for forming the cholesteric liquid crystal phase, a rod-shaped nematic liquid crystal compound can be cited. As the rod-shaped nematic liquid crystal compound, it is preferable to use azomethines, azo oxides, cyanobiphenyls, cyanobenzoates, benzoates, phenyl cyclohexanecarboxylates, cyanophenyl cyclohexanes, cyanide-substituted phenyl pyrimidines, alkoxy-substituted phenyl pyrimidines, phenyl dioxanes, diphenylacetylenes, and alkenyl cyclohexyl benzonitriles, etc. Not only low molecular liquid crystal compounds can be used, but also high molecular liquid crystal compounds can be used.

[0217] The polymeric liquid crystal compound can be obtained by introducing a polymerizable group into a liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, with an unsaturated polymerizable group being preferred, and an ethylenically unsaturated polymerizable group being more preferred. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups possessed by the polymeric liquid crystal compound is preferably 1 to 6, more preferably 1 to 3.

[0218] Examples of the polymeric liquid crystal compound include the compounds described in Makromol.Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Patent No. 4683327, U.S. Patent No. 5622648, U.S. Patent No. 5770107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Application Laid-Open No. 1-272551, Japanese Patent Application Laid-Open No. 6-016616, Japanese Patent Application Laid-Open No. 7-110469, Japanese Patent Application Laid-Open No. 11-080081, and Japanese Patent Application Laid-Open No. 2001-328973, etc. Further, as the rod-shaped liquid crystal compound, for example, the rod-shaped liquid crystal compounds described in Japanese Patent Application Laid-Open No. 11-513019 and Japanese Patent Application Laid-Open No. 2007-279688 can be preferably used. Two or more kinds of polymeric liquid crystal compounds can be used simultaneously. If two or more kinds of polymeric liquid crystal compounds are used simultaneously, the alignment temperature can be lowered.

[0219] In addition, as the polymeric liquid crystal compound other than the above, a cyclic organopolysiloxane compound having a cholesteric phase as disclosed in Japanese Patent Application Laid-Open No. 57-165480 can be used. Further, as the above-mentioned polymeric liquid crystal compound, a polymer in which a mesogenic group showing liquid crystal is introduced into the main chain, side chain, or both the main chain and side chain, a polymeric cholesteric liquid crystal in which a cholesteryl group is introduced into the side chain, a liquid crystalline polymer as disclosed in Japanese Patent Application Laid-Open No. 9-133810, and a liquid crystalline polymer as disclosed in Japanese Patent Application Laid-Open No. 11-293252, etc. can be used.

[0220] --Discotic liquid crystal compound--

[0221] As the discotic liquid crystal compound, for example, the discotic liquid crystal compounds described in Japanese Patent Application Laid-Open No. 2007-108732 and Japanese Patent Application Laid-Open No. 2010-244038 can be preferably used.

[0222] Further, relative to the mass of the solid components of the liquid crystal composition (mass after removing the solvent), the addition amount of the polymerizable liquid crystal compound in the liquid crystal composition is preferably 75 to 99.9% by mass, more preferably 80 to 99% by mass, and still more preferably 85 to 90% by mass.

[0223] From the viewpoint of more excellent effects of the present invention and the viewpoint of obtaining diffracted light with high diffraction efficiency at a large diffraction angle, the birefringence Δn of the liquid crystal compound in the high birefringence region of the optically anisotropic layer is preferably 0.15 or more, more preferably 0.20 or more, still more preferably 0.25 or more, still more preferably 0.30 or more, and most preferably 0.35 or more. The upper limit is not particularly limited, but is mostly 1.00 or less.

[0224] Most of the liquid crystal compounds showing such high refractive index anisotropy are compounds with positive dispersion 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, for example, it is 0.5 to 2.0, and mostly 1.0 to 1.5. In the case of a compound with positive dispersion, by adjusting the selective reflection band showing selective reflection as described above, the degree of orientation, the thickness, etc. described later, the diffraction efficiency at each wavelength can be kept constant.

[0225] For example, by forming a layer having a selective reflection band that diffracts incident light with a wavelength of 450 nm to be thin and forming a layer having a selective reflection band that diffracts incident light with a wavelength of 550 nm to be thick, the diffraction efficiency at each wavelength can be kept constant.

[0226] From the viewpoint of more excellent effects of the present invention and the viewpoint of being able to perform AR display with a large viewing angle, the maximum value of the extraordinary refractive index of the liquid crystal compound inside the optically anisotropic layer is preferably 1.8 or more, more preferably 1.9 or more, and still more preferably 2.0 or more. Further, the ordinary refractive index of the liquid crystal compound inside the optically anisotropic layer is preferably 1.4 or more, more preferably 1.5 or more, and still more preferably 1.6 or more.

[0227] The birefringence Δn and the refractive index preferably satisfy the above preferred ranges within the range of 380 to 780 nm. In particular, it is preferably satisfied within the range of 400 to 650 nm.

[0228] From the viewpoint of more excellent effects of the present invention and the viewpoint of being able to perform AR display with excellent transparency and high light utilization efficiency, the absorption rate of the optically anisotropic layer at 450 nm is preferably 1% or less, more preferably 0.1% or less, and still more preferably 0.01% or less. Further, the molar extinction coefficient of the liquid crystal compound used in the optically anisotropic layer at 450 nm is preferably 100 (mol·cm)-1 Hereinafter, more preferably 10 (mol·cm) -1 Hereinafter, even more preferably 1 (mol·cm) -1 Hereinafter.

[0229] The absorption rate and the molar extinction coefficient preferably satisfy the above preferred ranges within the range of 380 to 780 nm. In particular, it is preferably within the range of 400 to 650 nm.

[0230] The birefringence Δn of the liquid crystal compound in the low birefringence region of the optically anisotropic layer is preferably 0.00 to 0.40, more preferably 0.00 to 0.30, and even more preferably 0.00 to 0.20.

[0231] In the plane of the optically anisotropic layer, the maximum value of the average value Δna of the birefringence in the thickness direction is preferably 0.15 or more, more preferably 0.20 or more, and even more preferably 0.25 or more. The upper limit is not particularly limited, but is mostly 0.50 or less.

[0232] In the plane of the optically anisotropic layer, the minimum value of the average value Δna of the birefringence in the thickness direction is preferably 0.00 to 0.40, more preferably 0.00 to 0.30, and even more preferably 0.00 to 0.20.

[0233] As specific examples of the polymerizable liquid crystal compound having a large refractive index anisotropy, for example, Japanese Patent Application Laid-Open No. 2009-102245, Japanese Patent No. 4655348, Japanese Patent No. 4524827, Japanese Patent No. 4720200, Japanese Patent Application Laid-Open No. 2004-091380, Japanese Patent No. 3972430, Japanese Patent No. 4517416, Japanese Patent Application Laid-Open No. 2002-128742, Japanese Patent No. 4810750, Japanese Patent No. 5888544, Japanese Patent Application Laid-Open No. 2014-019654, Japanese Patent No. 6241654, Japanese Patent No. 6372060, Japanese Patent No. 6323144, Japanese Patent Application Laid-Open No. 2005-015406, Japanese Patent Application Laid-Open No. 2007-230968, Japanese Patent No. 6761484, Japanese Patent No. 6681992, International Publication No. 19 / 182129, CN01134217A, KR101069555B, KR101690767B, CN20120229730A, Japanese Patent No. 4053782, Japanese Patent Application Laid-Open No. 2009-249406, Japanese Patent No. 4121075, Japanese Patent Application Laid-Open No. 2005-528416, US6514578, International Publication No. 06 / 006819, Japanese Patent Application Laid-Open No. 2011-184417, Japanese Patent Application Laid-Open No. 2013-095685, Japanese Patent Application Laid-Open No. 2013-103897, Japanese Patent Application Laid-Open No. 2002-088008, Japanese Patent Application Laid-Open No. 2002-226412, Japanese Patent Application Laid-Open No. 2012-167214, Japanese Patent Application Laid-Open No. 2012-167068, Japanese Patent Application Laid-Open No. 2018-084511, Japanese Patent Application Laid-Open No. 2003-055317, Japanese Patent Application Laid-Open No. 2001-329264, Japanese Patent Application Laid-Open No. 2002-030016, Japanese Patent Application Laid-Open No. 2003-055664, Japanese Patent Application Laid-Open No. 2018-070889, CN102557896, US2015369982, Japanese Patent Application Laid-Open No. 2020-105264, Japanese Patent Application Laid-Open No. 2014-224237, Japanese Patent Application Laid-Open No. 2012-051862, Japanese Patent Application Laid-Open No. 2010-106274, Japanese Patent Application Laid-Open No. 2005-179557, Japanese Patent Application Laid-Open No. 2005-035985, Japanese Patent Application Laid-Open No. 2002-012579, Japanese Patent Application Laid-Open No. 2002-003845, Japanese Patent Application Laid-Open No. 2001-233837, Japanese Patent Application Laid-Open No. 2019-532167, Japanese Patent Application Laid-Open No. 2016-509247, Japanese Patent Application Laid-Open No. 2010-503733,Compounds and the like described in Japanese Patent Application Laid-Open 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.

[0234] Furthermore, as the polymeric liquid crystal compound, in addition to the above, the following compounds can be cited.

[0235] [Chemical formula 1]

[0236]

[0237] [Chemical formula 2]

[0238]

[0239] [Chemical formula 3]

[0240]

[0241] [Chemical formula 4]

[0242]

[0243] [Chemical formula 5]

[0244]

[0245] [Chemical formula 6]

[0246]

[0247] [Chemical formula 7]

[0248]

[0249] [Chemical formula 8]

[0250]

[0251] --Surfactant--

[0252] The liquid crystal composition used for forming the optically anisotropic layer may contain a surfactant.

[0253] The surfactant is preferably a compound that can function as an alignment control agent that helps to stably or rapidly achieve a planar alignment of a cholesteric liquid crystal phase. As the surfactant, for example, silicone surfactants and fluorine surfactants can be cited, and fluorine surfactants can be preferably exemplified.

[0254] Specific examples of the surfactant include the compounds described in paragraphs

[0082] to

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

[0031] to

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

[0092] and

[0093] of Japanese Patent Application Laid-Open No. 2005-99248, the compounds exemplified in paragraphs

[0076] to

[0078] and

[0082] to

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

[0018] to

[0043] of Japanese Patent Application Laid-Open No. 2007-272185, etc.

[0255] In addition, the surfactant may be used alone or two or more kinds may be used simultaneously.

[0256] As the fluorine surfactant, the compounds described in paragraphs

[0082] to

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

[0257] Relative to the total mass of the liquid crystal compound, the addition amount of the surfactant in the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and still more preferably 0.02 to 1% by mass.

[0258] --Chiral agent (optically active compound)--

[0259] The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. Since the twisting direction or the helical pitch of the helix induced by the chiral agent varies depending on the compound, it can be selected according to the purpose.

[0260] As the chiral agent, there is no particular limitation, and known compounds can be used (for example, described in the liquid crystal device manual, 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 isomannitol derivatives, etc.).

[0261] Chiral reagents usually contain asymmetric carbon atoms, but axially asymmetric compounds or surface asymmetric compounds that do not contain asymmetric carbon atoms can also be used as chiral reagents. Examples of axially asymmetric compounds or surface asymmetric compounds include binaphthyl, helicene, p-cyclophane, and their derivatives. Chiral reagents can have polymerizable groups. When both the chiral reagent and the liquid crystal compound have polymerizable groups, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral reagent can be formed by the polymerization reaction of the polymerizable chiral reagent and the polymerizable liquid crystal compound. In this way, the polymerizable group of the polymerizable chiral reagent is preferably the same type of group as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral reagent is also preferably an unsaturated polymerizable group, an epoxy group, or an aziridinyl group, more preferably an unsaturated polymerizable group, and further preferably an ethylenically unsaturated polymerizable group.

[0262] Moreover, the chiral reagent can also be a liquid crystal compound.

[0263] When the chiral reagent has a photo-isomerizable group, it is preferable because a pattern of a desired reflection wavelength corresponding to the emission wavelength can be formed by irradiating a photomask with activating light or the like after coating and alignment. As the photo-isomerizable group, an isomerization site of a compound showing photochromism, an azo group, an azoxy group, or a cinnamoyl group is preferable. As specific compounds, those described in JP-A-2002-80478, JP-A-2002-80851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, JP-A-2002-179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, and JP-A-2003-313292 can be used.

[0264] -Photo-reactive chiral reagent-

[0265] The photo-responsive chiral reagent is composed of compounds represented by the following general formula (I), has the ability to control the alignment structure of liquid crystalline compounds, and has the property of changing the helical pitch of liquid crystal compounds, that is, the twisting force (HTP: helical twisting power) of the helical structure by light irradiation. That is, the liquid crystalline compound is preferably a compound that causes a change in the twisting force of the helical structure induced in a nematic liquid crystal compound by light irradiation (ultraviolet light - visible light - infrared light), and has a chiral site and a site where the structure changes by light irradiation as required sites (molecular structure units). In particular, the photo-responsive chiral reagent represented by the following general formula (I) can significantly change the HTP of liquid crystal molecules.

[0266] In addition, the above HTP represents the twisting force of the helical structure of the liquid crystal, that is, HTP = 1 / (pitch × chiral reagent concentration [parts by mass]). For example, it can be obtained by measuring the helical pitch (one period of the helical structure; μm) of liquid crystal molecules at a certain temperature and converting this value according to the concentration of the chiral agent [μm-1]. When forming a selective reflection color by the illuminance of light using a photo-responsive chiral reagent, as the change rate of the above HTP (= HTP before irradiation / HTP after irradiation), when the HTP becomes smaller after irradiation, it is preferably 1.5 or more, more preferably 2.5 or more. When the HTP becomes larger after irradiation, it is preferably 0.7 or less, more preferably 0.4 or less.

[0267] Hereinafter, the compound represented by the general formula (I) will be described.

[0268] General formula (I)

[0269] [Chemical formula 9]

[0270]

[0271] In the above formula, R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, an acryloyloxyalkoxy group having a total of 3 to 15 carbon atoms, or a methacryloyloxyalkoxy group having a total of 4 to 15 carbon atoms.

[0272] Examples of the alkoxy group having 1 to 15 carbon atoms include methoxy, ethoxy, propoxy, butoxy, hexyloxy, dodecyloxy, etc. Among them, an alkoxy group having 1 to 12 carbon atoms is preferred, and an alkoxy group having 1 to 8 carbon atoms is particularly preferred.

[0273] Examples of the acryloyloxyalkoxy group having a total of 3 to 15 carbon atoms include acryloyloxyethoxy, acryloyloxybutoxy, acryloyloxydecoxy, etc. Among them, an acryloyloxyalkoxy group having 5 to 13 carbon atoms is preferred, and an acryloyloxyalkoxy group having 5 to 11 carbon atoms is particularly preferred.

[0274] Examples of the above methacryloyloxyalkoxy group having 4 to 15 carbon atoms in total include methacryloyloxyethoxy group, methacryloyloxybutoxy group, methacryloyloxydecoxy group, etc. Among them, the methacryloyloxyalkoxy group having 6 to 14 carbon atoms is preferred, and the methacryloyloxyalkoxy group having 6 to 12 carbon atoms is particularly preferred.

[0275] The molecular weight of the photoreactive chiral reagent represented by the above general formula (I) is preferably 300 or more. Also, a substance having high solubility with the liquid crystalline compound described later is preferred, and a substance having a solubility parameter SP value close to that of the liquid crystalline compound is more preferred.

[0276] Hereinafter, specific examples of the compound represented by the above general formula (I) (exemplified compounds (1) to (15)) are shown, but the present invention is not limited to these.

[0277] [Chemical formula 10]

[0278]

[0279] [Chemical formula 11]

[0280]

[0281] [Chemical formula 12]

[0282]

[0283] As the photoreactive optically active compound, for example, a compound represented by the following general formula (II) can also be used.

[0284] General formula (II)

[0285] [Chemical formula 13]

[0286]

[0287] In the above formula, R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, an acryloyloxyalkoxy group having 3 to 15 carbon atoms in total, or a methacryloyloxyalkoxy group having 4 to 15 carbon atoms in total.

[0288] Examples of the above alkoxy group having 1 to 15 carbon atoms include methoxy group, ethoxy group, propoxy group, butoxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc. Among them, the alkoxy group having 1 to 10 carbon atoms is preferred, and the alkoxy group having 1 to 8 carbon atoms is particularly preferred.

[0289] As the acryloyloxyalkyloxy group having 3 to 15 carbon atoms in total, for example, acryloyloxy, acryloyloxyethyloxy, acryloyloxypropyloxy, acryloyloxyhexyloxy, acryloyloxybutyloxy, acryloyloxydecyloxy, etc. can be mentioned. Among them, an acryloyloxyalkyloxy group having 3 to 13 carbon atoms is preferable, and an acryloyloxyalkyloxy group having 3 to 11 carbon atoms is particularly preferable.

[0290] As the methacryloyloxyalkyloxy group having 4 to 15 carbon atoms in total, for example, methacryloyloxy, methacryloyloxyethyloxy, methacryloyloxyhexyloxy, etc. can be mentioned. Among them, a methacryloyloxyalkyloxy group having 4 to 14 carbon atoms is preferable, and a methacryloyloxyalkyloxy group having 4 to 12 carbon atoms is particularly preferable.

[0291] As the molecular weight of the photoreactive optically active compound represented by the above general formula (II), 300 or more is preferable. And a substance having high solubility with the liquid crystalline compound described later is preferable, and a substance having a solubility parameter SP value close to that of the liquid crystalline compound is more preferable.

[0292] Hereinafter, specific examples of the photoreactive optically active compound represented by the above general formula (II) (exemplified compounds (21) to (32)) are shown, but the present invention is not limited to these.

[0293] [Chemical formula 14]

[0294]

[0295] [Chemical formula 15]

[0296]

[0297] [Chemical formula 16]

[0298]

[0299] In addition, the photoreactive chiral reagent can also be used simultaneously with a non-photoreactive chiral reagent such as a chiral compound having a large temperature dependence of the twisting force. As the above-mentioned known non-photoreactive chiral reagent, for example, those described in JP-A-2000-44451, JP-T-10-509726, WO98 / 00428, JP-T-2000-506873, JP-T-9-506088, Liquid Crystals (1996, 21, 327), Liquid Crystals (1998, 24, 219), etc. can be mentioned.

[0300] With respect to the molar amount of the liquid crystal compound contained, the content of the chiral reagent in the liquid crystal composition is preferably 0.01 to 200 mol%, more preferably 1 to 30 mol%.

[0301] --Polymerization initiator--

[0302] When the liquid crystal composition contains a polymerizable compound, a polymerization initiator is preferably contained. In the method of polymerization reaction by ultraviolet irradiation, the polymerization initiator used is preferably a photoinitiator capable of initiating a polymerization reaction by ultraviolet irradiation.

[0303] Examples of photoinitiators include α-carbonyl compounds (described in the specifications of U.S. Patent Nos. 2367661 and 2367670), benzoin ethers (described in the specification of U.S. Patent No. 2448828), α-hydrocarbon-substituted aromatic benzoin compounds (described in the specification of U.S. Patent No. 2722512), polynuclear quinone compounds (described in the specifications of U.S. Patent Nos. 3046127 and 2951758), a combination of triarylimidazole dimer and p-aminophenyl ketone (described in the specification of U.S. Patent No. 3549367), acridine and phenazine compounds (described in Japanese Patent Laid-Open No. 60-105667 and the specification of U.S. Patent No. 4239850), and oxadiazole compounds (described in the specification of U.S. Patent No. 4212970), etc.

[0304] Relative to the content of the liquid crystal compound, the content of the photoinitiator in the liquid crystal composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 12% by mass.

[0305] --Crosslinking agent--

[0306] In order to improve the film strength after curing and improve the durability, the liquid crystal composition may optionally contain a crosslinking agent. As the crosslinking agent, a crosslinking agent curable by ultraviolet rays, heat, moisture, etc. can be preferably used.

[0307] There is no particular limitation on the crosslinking agent, and it can be appropriately selected according to the purpose. For example, polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate can be cited; epoxy compounds such as glycidyl (meth)acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bis(hydroxymethyl)butanol-tris[3-(1-aziridinyl)propionate] and 4,4-bis(ethyleneimino carbonylamino)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, etc. Moreover, a known catalyst can be used according to the reactivity of the crosslinking agent. In addition to improving the film strength and durability, it can also improve the productivity. They can be used alone or two or more of them can be used simultaneously.

[0308] With respect to the solid content mass of the liquid crystal composition, the content of the crosslinking agent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass. As long as the content of the crosslinking agent is within the above range, the effect of increasing the crosslinking density can be easily obtained, and the stability of the cholesteric liquid crystal phase can be further improved.

[0309] --Other additives--

[0310] In the liquid crystal composition, according to need, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, etc. can be added within the range that does not reduce the optical properties, etc. From the viewpoint of improving the AR display, high refractive index nanoparticles such as zirconia nanoparticles and titanium oxide nanoparticles can be added.

[0311] When forming the optically anisotropic layer, the liquid crystal composition is preferably used in a liquid form.

[0312] The liquid crystal composition may contain a solvent. The solvent is not limited and can be appropriately selected according to the purpose, but an organic solvent is preferred.

[0313] The organic solvent is not limited and can be appropriately selected according to the purpose. For example, ketones, halogenated alkanes, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, ethers, etc. can be cited. They can be used alone or two or more of them can be used simultaneously. Among these, considering the environmental load, ketones are preferred.

[0314] When forming the optically anisotropic layer, it is preferred to coat the liquid crystal composition on the formation surface of the optically anisotropic layer and orient the liquid crystal compound into a cholesteric liquid crystal phase state, and then cure the liquid crystal compound to form the optically anisotropic layer.

[0315] That is, when forming an optically anisotropic layer on an alignment film, the following is preferred: after coating a liquid crystal composition on the alignment film and aligning the liquid crystal compound into a cholesteric liquid crystal phase state, the liquid crystal compound is cured to form an optically anisotropic layer in which the cholesteric liquid crystal phase is fixed.

[0316] Regarding the coating of the liquid crystal composition, printing methods such as inkjet and roll printing, as well as all known methods capable of uniformly coating a liquid on a sheet-like object, such as spin coating, bar coating, and spray coating, can be used.

[0317] The coated liquid crystal composition is dried and / or heated as needed, and then cured to form an optically anisotropic layer. In this drying and / or heating process, as long as the liquid crystal compound in the liquid crystal composition is aligned into a cholesteric liquid crystal phase. When heating, the heating temperature is preferably 200 °C or lower, more preferably 130 °C or lower.

[0318] The aligned liquid crystal compound is polymerized as needed. The polymerization can be either thermal polymerization or photopolymerization based on light irradiation, but photopolymerization is preferred. Light irradiation preferably uses ultraviolet light. The irradiation energy is preferably 20 mJ / cm 2 ~50 J / cm 2 , more preferably 50~1500 mJ / cm 2 . To promote the photopolymerization reaction, light irradiation can be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the irradiated ultraviolet light is preferably 250~430 nm.

[0319] The thickness of the optically anisotropic layer is not limited, as long as it is appropriately set according to the use of the liquid crystal diffraction element 10, the required light reflectance of the optically anisotropic layer, and the formation material of the optically anisotropic layer, etc., to obtain a thickness that can achieve the required light reflectance.

[0320] <<Liquid crystal alignment pattern of the optically anisotropic layer>>

[0321] As described above, as a preferred mode, the optically anisotropic layer 18 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 continuously rotates and changes in one direction in the plane of the optically anisotropic layer 18. In Figure 1 the example shown, it has a liquid crystal alignment pattern in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 forming a cholesteric liquid crystal phase continuously rotates and changes in one direction in the plane of the optically anisotropic layer.

[0322] In addition, the optical axis 30A derived from the liquid crystal compound 30 refers to the axis with the highest refractive index in the liquid crystal compound 30, which is the so-called slow axis. For example, when the liquid crystal compound 30 is a rod-shaped liquid crystal compound, the optical axis 30A is along the long axis direction of the rod shape. In the following description, the optical axis 30A derived from the liquid crystal compound 30 is also referred to as "the optical axis 30A of the liquid crystal compound 30" or "the optical axis 30A".

[0323] In Figure 2 is conceptually shown Figure 1 a plan view of the optical anisotropic layer 18 shown.

[0324] In addition, the plan view is a view of the liquid crystal diffraction element 10 observed from above in Figure 1 i.e., a view of the liquid crystal diffraction element 10 observed from the thickness direction ( = the stacking direction of each layer (film)).

[0325] And, in Figure 2 in order to clearly show the structure of the optical anisotropic layer 18, only the liquid crystal compound 30 on the surface of the alignment film 24 is shown for the liquid crystal compound 30.

[0326] As Figure 2 shown, on the surface of the alignment film 24, the liquid crystal compound 30 constituting the optical anisotropic layer 18 becomes a state of two-dimensional arrangement in a specified one direction shown by the arrow X and a direction orthogonal to this one direction (arrow X direction).

[0327] In the following description, for convenience, the direction orthogonal to the arrow X direction is set as the Y direction. That is, in Figure 1 and Figure 4 and in the following Figure 7 , Figure 9 and Figure 10 in, the Y direction becomes the direction perpendicular to the paper surface.

[0328] And, the liquid crystal compound 30 forming the optical anisotropic layer 18 has a liquid crystal alignment pattern in which the orientation of the in-plane optical axis 30A continuously rotates and changes along the arrow X direction. In Figure 1 and Figure 2 the example shown, it has a liquid crystal alignment pattern in which the optical axis 30A of the liquid crystal compound 30 continuously rotates clockwise along the arrow X direction and changes.

[0329] Specifically, the change in the orientation of the optical axis 30A of the liquid crystal compound 30 while continuously rotating along the arrow X direction (a specified one direction) means that the angle formed by the optical axis 30A of the liquid crystal compound 30 arranged along the arrow X direction and the arrow X direction is different according to the position in the arrow X direction. Along the arrow X direction, the angle formed by the optical axis 30A and the arrow X direction changes from θ to θ + 180° or θ - 180° in sequence.

[0330] In addition, the angular difference between the optical axes 30A of the liquid crystal compounds 30 adjacent to each other in the arrow X direction is preferably 45° or less, more preferably 15° or less, and still more preferably an even smaller angle.

[0331] On the other hand, regarding the liquid crystal compound 30 forming the optically anisotropic layer 18, in the Y direction orthogonal to the arrow X direction, that is, in the Y direction orthogonal to the direction in which the optical axis 30A continuously rotates, the orientation of the optical axis 30A is the same.

[0332] In other words, for the liquid crystal compound 30 forming the optically anisotropic layer 18 in the Y direction, the angle formed by the optical axis 30A of the liquid crystal compound 30 and the arrow X direction is the same.

[0333] In the present invention, in the liquid crystal alignment pattern of such a liquid crystal compound 30, the length (distance) at which the optical axis 30A of the liquid crystal compound 30 rotates 180° in the arrow X direction in which the optical axis 30A continuously rotates and changes in the plane is set as the length Λ of one period in the liquid crystal alignment pattern.

[0334] That is, the distance between the centers of two liquid crystal compounds 30 in the arrow X direction having the same angle with respect to the arrow X direction is set as the length Λ of one period. Specifically, as Figure 2 shown, the distance between the centers of two liquid crystal compounds 30 in the arrow X direction where the arrow X direction is consistent with the direction of the optical axis 30A is set as the length Λ of one period.

[0335] In the following description, this length Λ of one period is also referred to as "one period Λ".

[0336] In the liquid crystal diffraction element 10 of the present invention, the liquid crystal alignment pattern of the optically anisotropic layer repeats this one period Λ in the arrow X direction, that is, in one direction in which the orientation of the optical axis 30A continuously rotates and changes.

[0337] A normal cholesteric liquid crystal layer in which the cholesteric liquid crystal phase is fixed usually specularly reflects incident light (circularly polarized light).

[0338] In contrast, the optically anisotropic layer 18 having the liquid crystal alignment pattern as described above reflects the incident light in a direction that is angled with respect to specular reflection in the direction of arrow X. For example, the optically anisotropic layer 18 does not reflect the light incident from the normal direction in the normal direction, but rather reflects it obliquely in the direction of arrow X with respect to the normal direction. The light incident from the normal direction is the light incident from the front surface and is perpendicular to the main surface. The main surface refers to the largest surface of the sheet-like object.

[0339] Hereinafter, reference will be made to Figure 4 for explanation.

[0340] As described above, the optically anisotropic layer 18 is an optically anisotropic layer (cholesteric liquid crystal layer) that selectively reflects one circularly polarized light of the selective reflection wavelength. For example, considering the case where the selective reflection wavelength of the optically anisotropic layer 18 is red light and it reflects right-handed circularly polarized light, if light R R is incident on the optically anisotropic layer 18, the optically anisotropic layer 18 reflects only the right-handed circularly polarized light R of red light R and transmits the other light.

[0341] Here, based on the optically anisotropic layer in which the optical axis 30A of the liquid crystal compound 30 continuously rotates in one direction (the direction of arrow X), the reflection angle of the light varies according to the wavelength of the reflected light. Specifically, the longer the wavelength of the light, the larger the angle of the reflected light with respect to the incident light becomes.

[0342] Furthermore, based on the optically anisotropic layer in which the optical axis 30A of the liquid crystal compound 30 continuously rotates in the direction of arrow X (one direction), the reflection angle of the light varies according to the length Λ of one period of the liquid crystal alignment pattern in which the optical axis 30A rotates 180° in the direction of arrow X, that is, one period Λ. Specifically, the shorter the one period Λ, the larger the angle of the reflected light with respect to the incident light becomes.

[0343] In the present invention, there is no limitation on one period Λ in the alignment pattern of the optically anisotropic layer, and it can be appropriately set according to the use of the optically anisotropic layer and the like.

[0344] Here, as an example, the optically anisotropic layer of the present invention is preferably used as a diffraction element that reflects the light propagating on the light guide plate in an AR glasses and causes it to exit the light guide plate to the position observed by the user.

[0345] At this time, in order to reliably emit the light that has propagated through the light guide plate, it is necessary to reflect the light at a relatively large angle with respect to the incident light.

[0346] Further, as described above, regarding the reflection angle of light based on the optically anisotropic layer, by shortening one period Λ in the liquid crystal alignment pattern, the reflection angle with respect to incident light can be increased.

[0347] In view of this, one period Λ in the liquid crystal alignment pattern of the optically anisotropic layer is preferably 50 μm or less, more preferably 10 μm or less, and still more preferably 1 μm or less.

[0348] In addition, considering the accuracy of the liquid crystal alignment pattern, etc., one period Λ in the liquid crystal alignment pattern of the optically anisotropic layer is preferably set to 0.1 μm or more.

[0349] Here, in the present invention, the optically anisotropic layer has the following structure: in one direction in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates in the plane (hereinafter, referred to as one direction of optical axis rotation), the diffraction efficiency becomes higher as it goes from one side to the other side.

[0350] For example, in the case of the optically anisotropic layer shown in Figure 1 and Figure 2 , the diffraction efficiency becomes higher as it goes from one side in the X direction to the other side.

[0351] In Figure 5 and Figure 6 , a graph schematically showing the relationship between the position in one direction (X direction) of the optical axis rotation of the optically anisotropic layer 18 and the diffraction efficiency at that position is shown.

[0352] In the X direction, the diffraction efficiency of the optically anisotropic layer 18 can be a structure that continuously changes as shown in Figure 5 , or can be a structure that changes stepwise as shown in Figure 6 .

[0353] Here, the diffraction efficiency means that the optically anisotropic layer 18 is transferred onto a double prism 110 (refractive index = 1.517, inclined surface angle = 45°) as shown in Figure 14 , and a laser beam with a specified wavelength is transmitted through a linear polarizer 112 and a λ / 4 plate 114 to become a right-handed circularly polarized light, and is incident on the surface of the optically anisotropic layer 18 at an angle set such that the diffracted light exits perpendicularly from the inclined surface. The intensity Lr of the outgoing light is measured using a power meter 1918-C manufactured by Newport Corporation, and the ratio (Lr / Li × 100 [%]) of this to the intensity Li of the incident light is taken as the diffraction efficiency.

[0354] In the present invention, the optically anisotropic layer has a structure including a region (birefringence change region) where the diffraction efficiency increases as it moves from one side to the other side in one direction of the optical axis rotation. Therefore, in a light guide element used in an AR (Augmented Reality) display device such as AR glasses, when the optically anisotropic layer of the present invention is used as a diffraction element that diffracts the light propagating in the light guide plate and emits the light from the light guide plate, even if the exit pupil is enlarged, the brightness (light quantity) of the light emitted from the light guide plate can be made uniform.

[0355] This will be described in detail later.

[0356] In addition, in the optically anisotropic layer, the direction of change in the diffraction efficiency may or may not be consistent with one direction of the optical axis rotation. That is, the direction of change in the diffraction efficiency may cross one direction of the optical axis rotation. Even in a structure where the direction of change in the diffraction efficiency crosses one direction of the optical axis rotation, it will be a structure where the diffraction efficiency increases as it moves from one side to the other side in one direction of the optical axis rotation.

[0357] As described later, in the optically anisotropic layer, the change in the diffraction efficiency is achieved by changing the average value Δna of the birefringence in the thickness direction in the plane. Therefore, it is sufficient that the direction of change in the average value Δna of the birefringence crosses one direction of the optical axis rotation, and parallel is preferred.

[0358] A structure in which the diffraction efficiency of the optically anisotropic layer increases as it moves from one side to the other side along at least one direction in the plane of the optically anisotropic layer can be achieved by having the following structure: having regions with different birefringences Δn in the thickness direction, and having a birefringence change region where the average value Δna of the birefringence in the thickness direction gradually changes as it moves from one side to the other side along at least one direction in the plane. Thus, as an example, a structure in which the birefringence Δn is different in the thickness direction and the average value Δna of the birefringence in the thickness direction gradually changes in the plane can be achieved by setting the following structure: in at least a part of the plane of the optically anisotropic layer, the thickness of the optically isotropic region (low birefringence region) gradually decreases as it moves from one side to the other side along at least one direction in the plane of the optically anisotropic layer, and the thickness of the optically non-isotropic region (high birefringence region) gradually increases.

[0359] Specifically, as Figure 16As in the example shown, the optically anisotropic layer (birefringence-changing region) 324 has a high birefringence region 326 with a large birefringence and a low birefringence region 328 with a small birefringence in the thickness direction. The total thickness of the high birefringence region 326 and the low birefringence region 328 (i.e., the thickness of the optically anisotropic layer 324) is constant in the in-plane direction, and the ratio of the thickness of the high birefringence region 326 to the thickness of the optically anisotropic layer 324 gradually increases along one direction in the plane as moving from one side to the other side ( Figure 16 in this case, as moving from the right side to the left side).

[0360] In the optically anisotropic layer (cholesteric liquid crystal layer) having the liquid crystal alignment pattern as described above, the liquid crystal compound is aligned with a high degree of alignment according to the desired liquid crystal alignment pattern, and when the desired cholesteric liquid crystal phase is in a highly aligned state, the birefringence becomes high (high birefringence region). In this case, an optically non-isotropic state is formed. And thus, when the optically anisotropic layer is highly aligned with the desired liquid crystal alignment pattern and cholesteric liquid crystal phase, the incident light can be appropriately reflected and diffracted, and the diffraction efficiency becomes high. On the other hand, when the liquid crystal compound is not sufficiently aligned with the desired liquid crystal alignment pattern and is not sufficiently aligned with the desired cholesteric liquid crystal phase, the birefringence becomes low (low birefringence region). In this case, an optically isotropic state (a state close to isotropic) is formed. And thus, when the optically anisotropic layer is not aligned with the desired liquid crystal alignment pattern and cholesteric liquid crystal phase, the incident light cannot be appropriately reflected and diffracted, and the diffraction efficiency becomes low.

[0361] Thus, in the optically anisotropic layer, the diffraction efficiency is high in the thick region of the non-isotropic region (high birefringence region), and the diffraction efficiency is low in the thin region of the non-isotropic region (high birefringence region). Therefore, by forming the optically anisotropic layer to have a structure in which the ratio of the thickness of the high birefringence region having a high birefringence region and a low birefringence region in the thickness direction and a high diffraction efficiency gradually increases along one direction in the plane as moving from one side to the other side, a structure can be formed in which the diffraction efficiency gradually increases along at least one direction in the plane of the optically anisotropic layer as moving from one side to the other side.

[0362] In addition, in Figure 16 the example shown, the structure is such that the ratio of the thickness of the high birefringence region gradually increases along one direction in the plane as moving from one side to the other side in the birefringence-changing region, but it is not limited thereto. It may also be a structure in which the ratio of the thickness of the high birefringence region changes stepwise, or may have regions with different ratios of the thickness of the high birefringence region.

[0363] In the plane of the optically anisotropic layer, the maximum value of the thickness of the high birefringence region is preferably 0.1 to 10 μm, more preferably 0.3 μm to 8 μm, and still more preferably 0.5 μm to 5 μm.

[0364] In the plane of the optically anisotropic layer, the minimum value of the thickness of the high birefringence region is preferably 0.0 to 5 μm, more preferably 0.0 μm to 3 μm, and still more preferably 0.0 μm to 1 μm.

[0365] And, in Figure 16 In the example shown, it is assumed that the birefringence change region has a structure of a high birefringence region and a low birefringence region, but it is not limited thereto, and it may also be like Figure 26 The optically anisotropic layer 340 shown has a birefringence change region structure (corresponding to the first mode) in which the birefringence Δn gradually changes in the thickness direction and this change is different in the in-plane direction, and the average value Δna of the birefringence in the thickness direction is different in the plane of the optically anisotropic layer. In addition, Figure 26 FIG. is a cross-sectional view showing the thickness direction of the optically anisotropic layer, and the birefringence of each position is represented by concentration. The darker the black, the higher the birefringence region.

[0366] The advantages of the method of changing the ratio of the thickness of the high birefringence region of the present invention are described with respect to other methods of changing the diffraction efficiency.

[0367] For example, when changing the thickness of the diffraction element in the in-plane direction, the guided light is scattered along with the uneven shape of the surface, and a uniform image cannot be obtained. In contrast, in the present invention, since the thickness of the diffraction element is uniform, the light is guided without being scattered, and thus a more uniform image can be obtained.

[0368] And, for example, when changing the birefringence of the diffraction element in the in-plane direction, since the birefringence of the region with low diffraction efficiency is small, the extraordinary refractive index must become small. In contrast, in the present invention, since the birefringence of the high birefringence region acting as the diffraction element is large, the extraordinary refractive index must become large. Therefore, for example, when used as an AR glasses, a large-angle-of-view display can be performed.

[0369] [Second Embodiment]

[0370] Here, in Figure 1 In the example shown, the optically anisotropic layer is a layer in which a liquid crystal compound is cholesterically oriented, but it is not limited thereto, and it may also be a layer in which the liquid crystal compound is not cholesterically oriented.

[0371] In Figure 7 An example of the second embodiment of the optically anisotropic layer of the present invention is conceptually shown.

[0372] Figure 7 The liquid crystal diffraction element 12 shown is a liquid crystal diffraction element that diffracts and transmits incident light and includes an optically anisotropic layer 16 of the present invention. That is, Figure 7 The illustrated liquid crystal diffraction element 12 is a transmissive liquid crystal diffraction element.

[0373] Figure 7 The liquid crystal diffraction element 12 shown has a structure in which a support 20, an alignment film 24, and an optically anisotropic layer 16 are stacked in this order.

[0374] In addition, the support 20 and the alignment film 24 have Figure 1 The support body 20 and the alignment film 24 of the liquid crystal diffraction element 10 shown have the same structure, so the description thereof is omitted.

[0375] <Optically anisotropic layer>

[0376] The optically anisotropic layer 16 is formed on the surface of the alignment film 24 .

[0377] The optically anisotropic layer 16 is a layer formed using a composition containing a liquid crystal compound, and has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously rotates in at least one direction in a plane.

[0378] exist Figure 8 Shown in Figure 7 The plan view of the optical anisotropic layer is shown in FIG. Figure 7 The figure is a figure observing the liquid crystal diffraction element from above, that is, a figure observing the liquid crystal diffraction element from the thickness direction (= lamination direction of each layer (film)). In other words, it is a figure observing the optically anisotropic layer from a direction perpendicular to the main surface.

[0379] And, in Figure 8 In order to clearly show the structure of the optically anisotropic layer, only the liquid crystal compound 30 on the surface of the alignment film 24 is shown as the liquid crystal compound 30 in the optically anisotropic layer. Figure 7 As shown, the optically anisotropic layer has a structure in which the liquid crystal compounds 30 are stacked from the liquid crystal compounds 30 on the surface of the alignment film 24 in the thickness direction.

[0380] like Figure 8 As shown, the optically anisotropic layer 16 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 indicated by the arrow X within the plane of the optically anisotropic layer.

[0381] 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 specified direction) means that the angle formed by the optical axis 30A of the liquid crystal compound 30 arranged along the direction of arrow X and the direction of arrow X is different according to the position in the direction of arrow X. Along the direction of arrow X, the angle formed by the optical axis 30A and the direction of arrow X changes from θ to θ + 180° or θ - 180° in sequence.

[0382] In addition, the angular difference between the optical axes 30A of the 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 still more preferably an even smaller angle.

[0383] On the other hand, regarding the liquid crystal compound 30 forming the optically anisotropic layer, in the Y direction orthogonal to the direction of arrow X, that is, in the Y direction orthogonal to the direction in which the optical axis 30A continuously rotates, the liquid crystal compounds 30 with the same orientation of the optical axis 30A are arranged at equal intervals.

[0384] In other words, among the liquid crystal compounds 30 forming the optically anisotropic layer, between the liquid crystal compounds 30 arranged in the Y direction, the angles formed by the orientations of the optical axes 30A and the direction of arrow X are equal.

[0385] The liquid crystal alignment pattern of the optically anisotropic layer 16 repeats the length Λ of one cycle in the liquid crystal alignment pattern in the direction of arrow X, that is, in the direction in which the orientation of the optical axis 30A continuously rotates and changes.

[0386] As described above, in the optically anisotropic layer 16, the angles formed by the optical axes 30A of the liquid crystal compounds arranged in the Y direction and the direction of arrow X (the direction in which the orientation of the optical axis of the liquid crystal compound 30 rotates) are equal. The region where the liquid crystal compound 30 with the angle formed by the optical axis 30A and the direction of arrow X equal is arranged in the Y direction is defined as region R.

[0387] In this case, when a high diffraction efficiency is obtained, the value of the in-plane retardation (Re) in each region R is preferably half a wavelength, that is, λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn generated by the refractive index anisotropy of region R and the thickness of the optically anisotropic layer 16. Here, the refractive index difference generated by the refractive index anisotropy of region R in the optically anisotropic layer 16 is the refractive index difference defined by the 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 orthogonal to the direction of the slow axis. That is, the refractive index difference Δn generated by 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 in 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.

[0388] When circularly polarized light is incident on such an optically anisotropic layer 16, the light is refracted (diffracted) and the direction of the circularly polarized light is converted.

[0389] In Figure 9 the optically anisotropic layer 16 is illustrated conceptually to show its function.

[0390] As Figure 9 shown, when incident light L1 which is left-handed circularly polarized light is incident on the optically anisotropic layer 16, the incident light L1 passes through the optically anisotropic layer 16, and thus a phase difference of 180° is imparted, and the transmitted light L2 is converted into right-handed circularly polarized light.

[0391] Moreover, since the liquid crystal alignment pattern formed in the optically anisotropic layer 16 is a periodic pattern in the arrow X direction, the transmitted light L2 is refracted (diffracted) and travels in a direction different from the traveling direction of the incident light L1. Thus, the incident light L1 of left-handed circularly polarized light is converted into the transmitted light L2 of right-handed circularly polarized light that is inclined at a certain angle with respect to the incident direction in the arrow X direction.

[0392] On the other hand, as Figure 10 conceptually shown, when incident light L4 which is right-handed circularly polarized light is incident on the optically anisotropic layer 16, the incident light L4 passes through the optically anisotropic layer 16, and thus a phase difference of 180° is imparted and it is converted into the transmitted light L5 of left-handed circularly polarized light.

[0393] Moreover, since the liquid crystal alignment pattern formed in the optically anisotropic layer 16 is a periodic pattern in the arrow X direction, the transmitted light L5 is refracted (diffracted) and travels in a direction different from the traveling direction of the incident light L4. Thus, the incident light L4 is converted into the transmitted light L5 of left-handed circularly polarized light that is inclined at a certain angle with respect to the incident direction in the direction opposite to the arrow X direction.

[0394] In the optically anisotropic layer 16, when a high diffraction efficiency is obtained, the in-plane retardation value of the plurality of regions R is preferably a half wavelength, but the in-plane retardation Re(550) = Δn550 × d of the plurality of regions R of the optically anisotropic layer 16 for incident light with a wavelength of 550 nm is preferably within the range specified in the following formula (1). Here, Δn550 is the refractive index difference caused by the refractive index anisotropy of the region R when the wavelength of the incident light is 550 nm, and d is the thickness of the optically anisotropic layer 16.

[0395] 200 nm ≤ Δn550 × d ≤ 350 nm……(1)

[0396] That is, if the in-plane retardation Re(550) = Δn550 × d of the plurality of regions R of the optically anisotropic layer 16 satisfies the formula (1), a sufficient amount of the circularly polarized light component of the light incident on the optically anisotropic layer 16 can be converted into circularly polarized light traveling in a direction inclined in the positive or negative direction with respect to the arrow X direction. The in-plane retardation Re(550) = Δn550 × d is more preferably 225 nm ≤ Δn550 × d ≤ 340 nm, and further preferably 250 nm ≤ Δn550 × d ≤ 330 nm.

[0397] In addition, the above formula (1) is the range for incident light with a wavelength of 550 nm. The in-plane retardation Re(λ) = Δnλ × d of the plurality of regions R of the optically anisotropic layer 16 for incident light with a wavelength of λ nm is preferably within the range specified in the following formula (1-2) and can be appropriately set.

[0398] 0.35 × λ nm ≤ Δnλ × d ≤ 0.65 × λ nm ……(1-2)

[0399] Moreover, the value of the in-plane retardation of the plurality of regions R in the optically anisotropic layer 16 can also be used outside the range of the above formula (1). Specifically, by setting Δn550 × d < 200 nm or 350 nm < Δn550 × d, the light traveling in the same direction as the traveling direction of the incident light and the light traveling in a direction different from the traveling direction of the incident light can be separated. If Δn550 × d approaches 0 nm or 550 nm, the component of the light traveling in the same direction as the traveling direction of the incident light increases, and the component of the light traveling in a direction different from the traveling direction of the incident light decreases.

[0400] Furthermore, the in-plane retardation Re(450) = Δn450 × d of the region R of the optically anisotropic layer 16 for incident light with a wavelength of 450 nm and the in-plane retardation Re(550) = Δn550 × d of the region R of the optically anisotropic layer 16 for incident light with a wavelength of 550 nm preferably satisfy the following formula (2). Here, Δn450 is the refractive index difference caused by the refractive index anisotropy of the region R when the wavelength of the incident light is 450 nm.

[0401] (Δn450 × d) / (Δn550 × d) < 1.0 ……(2)

[0402] The formula (2) indicates that the liquid crystal compound 30 contained in the optically anisotropic layer 16 has an inverse dispersion property. That is, by satisfying the formula (2), the optically anisotropic layer 16 can cope with incident light of a wide range of wavelengths.

[0403] Here, by changing one period Λ of the liquid crystal alignment pattern formed in the optically anisotropic layer 16, the refraction angles of the transmitted lights L2 and L5 can be adjusted. Specifically, the shorter one period Λ of the liquid crystal alignment pattern is, the stronger the interference between the lights that have passed through the adjacent liquid crystal compounds 30 becomes, and thus the transmitted lights L2 and L5 can be refracted (diffracted) significantly.

[0404] Moreover, the refraction angles of the transmitted lights L2 and L5 with respect to the incident lights L1 and L4 are different according to the wavelengths of the incident lights L1 and L4 (transmitted lights L2 and L5). Specifically, the longer the wavelength of the incident light is, the more significantly the transmitted light is refracted (diffracted). That is, when the incident light is red light, green light, and blue light, the red light is refracted (diffracted) most significantly, and the refraction (diffraction) of the blue light is the smallest.

[0405] In addition, by setting the rotation direction of the optical axis 30A of the liquid crystal compound 30 that rotates in the direction of the arrow X to the opposite direction, the refraction (diffraction) direction of the transmitted light can be made the opposite direction.

[0406] The optically anisotropic layer 16 is composed of a cured layer of a liquid crystal composition containing a rod-like liquid crystal compound or a disc-like liquid crystal compound, and has a liquid crystal alignment pattern in which the optical axes of the rod-like liquid crystal compounds or the optical axes of the disc-like liquid crystal compounds are aligned as described above.

[0407] By forming an alignment film 24 on the support 20 and coating and curing a liquid crystal composition on the alignment film 24, the optically anisotropic layer 16 composed of a cured layer of the liquid crystal composition can be obtained. The coating method and curing method of the liquid crystal composition are as described above.

[0408] In addition, although it is the optically anisotropic layer 16 that functions as an optically non-isotropic region, the present invention includes a mode in which a laminate integrally including the support 20 and the alignment film 24 functions as an optically non-isotropic region.

[0409] Moreover, the liquid crystal composition for forming the optically anisotropic layer 16 contains a rod-like liquid crystal compound or a disc-like liquid crystal compound, and may further contain other components such as a leveling agent, an alignment control agent, a polymerization initiator, a crosslinking agent, and an alignment aid. And the liquid crystal composition may contain a solvent.

[0410] The rod-like liquid crystal compounds, disc-like liquid crystal compounds, etc. contained in the liquid crystal composition for forming the optically anisotropic layer 16 can be the same compounds as the rod-like liquid crystal compounds, disc-like liquid crystal compounds, etc. contained in the liquid crystal composition for forming the optically anisotropic layer 18 described above.

[0411] That is, the liquid crystal composition used to form the optically anisotropic layer 16 does not contain a chiral agent, and is the same as the liquid crystal composition used to form the optically anisotropic layer 18 described above, except for this.

[0412] Moreover, the optically anisotropic layer 16 may have a so-called twist structure in which the orientation of the liquid crystal compound continuously changes from one interface side to the other interface side in the thickness direction. The twist structure is a structure in which the liquid crystal compound does not become a cholesteric liquid crystal phase and twists and rotates in the thickness direction to such an extent that selective reflectivity is not substantially exhibited. Specifically, the twist of the optical axis in the entire thickness direction of the twist structure is less than one rotation, that is, the twist angle is less than 360°. The twist structure can be formed by appropriately adding a chiral agent to the liquid crystal composition.

[0413] Moreover, the optically anisotropic layer 16 is preferably broadband with respect to the wavelength of incident light, and is preferably composed of a liquid crystal material in which the birefringence becomes an anomalous dispersion.

[0414] Moreover, from the viewpoint of more excellent effects of the present invention and the viewpoint of diffracted light having high diffraction efficiency even at a large diffraction angle, the refractive index anisotropy Δn of the liquid crystal compound is preferably 0.15 or more, more preferably 0.20 or more, and further preferably 0.25 or more. The upper limit is not particularly limited, but is mostly 1.00 or less. Most liquid crystal compounds showing such a high refractive index anisotropy are compounds having a normal dispersion in which the birefringence Δn450 for incident light with a wavelength of 450 nm is larger than the birefringence Δn550 for incident light with a wavelength of 550 nm. In this case, it is also preferable to make the optically anisotropic layer 16 substantially broadband with respect to the wavelength of incident light by imparting a twist component to the liquid crystal composition 16 and by laminating different retardation layers. For example, in Japanese Unexamined Patent Application Publication No. 2014-089476 and the like, a method of realizing a broadband patterned optically anisotropic layer by laminating two liquid crystal layers having different twist directions in the optically anisotropic layer 16 is shown, and this can be preferably used in the present invention.

[0415] Regarding the birefringence Δn of the liquid crystal compound in the high birefringence region of the optically anisotropic layer 16 and the birefringence Δn of the liquid crystal compound in the low birefringence region, etc., it is the same as in the case of the above-mentioned cholesteric liquid crystal layer.

[0416] Here, in the present invention, in the same manner as in the case of the above-mentioned optically anisotropic layer 18 (cholesteric liquid crystal layer), the optically anisotropic layer 16 has a structure in which the diffraction efficiency becomes higher as it moves from one side to the other side in one direction in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates in the plane. For example, in Figure 7 and Figure 8In the case of the optical anisotropic layer shown, the diffraction efficiency increases as one moves from one side in the X direction to the other side.

[0417] Similar to the case of the above-described optical anisotropic layer 18 (cholesteric liquid crystal layer), a structure in which the diffraction efficiency of the optical anisotropic layer 16 increases as one moves from one side to the other side along at least one direction in the plane of the optical anisotropic layer 16 can be achieved by having the following structure: having regions with different birefringences Δn in the thickness direction, and having a birefringence change region in which the average value Δna of the birefringence in the thickness direction gradually changes along at least one direction in the plane as one moves from one side to the other side. Thus, as an example, for a structure in which the birefringence Δn is different in the thickness direction and the average value Δna of the birefringence in the thickness direction gradually changes in the plane, it can be achieved by setting it to the following structure (refer to Figure 16 ): In at least a part of the plane of the optical anisotropic layer, the thickness of the optically isotropic region (low birefringence region) gradually decreases and the thickness of the optically non-isotropic region (high birefringence region) gradually increases along at least one direction in the plane of the optical anisotropic layer as one moves from one side to the other side.

[0418] Also, it can be a structure having the following birefringence change region (refer to Figure 26 ): The birefringence Δn gradually changes in the thickness direction, and this change is different in the in-plane direction, and the average value Δna of the birefringence in the thickness direction is different in the plane of the optical anisotropic layer.

[0419] Here, the optical anisotropic layer of the present invention may have a region different from the birefringence change region in the in-plane direction. As described above, the birefringence change region is a diffraction region that diffracts light. The optical anisotropic layer of the present invention may have such a diffraction region and a region that does not have a diffraction effect (hereinafter, also referred to as a non-diffraction region).

[0420] Figure 27 is a diagram conceptually showing another example of the optical anisotropic layer of the present invention. Figure 28 is Figure 27 a top view of

[0421] Figure 27 and Figure 28The optical anisotropic layer 400 shown is formed using a composition containing a liquid crystal compound, and the first diffraction region 45a, the non-diffraction region 45b, and the second diffraction region 45c are formed by making the alignment state of the liquid crystal compound different in the in-plane direction. The non-diffraction region 45b is disposed between the first diffraction region 45a and the second diffraction region B45c. In the following description, when it is not necessary to distinguish between the first diffraction region 45a and the second diffraction region 45c and the third diffraction region 45d described later, they are also simply referred to as diffraction regions.

[0422] As described above, the diffraction region has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates along at least one direction in the plane while changing, and functions as a liquid crystal diffraction element that diffracts incident light. And at least one of the diffraction regions has a birefringence change region in which the average value Δna of the birefringence in the thickness direction is different in the plane of the optical anisotropic layer. In addition, the structures such as the liquid crystal alignment patterns of the respective diffraction regions may be the same or different.

[0423] Moreover, the thicknesses of the first diffraction region 45a, the non-diffraction region 45b, and the second diffraction region 45c are substantially the same, and the two main surfaces of the optical anisotropic layer 400 are smooth flat surfaces without an uneven structure.

[0424] The non-diffraction region 45b may be an unoriented region where the liquid crystal compound is not oriented, that is, an optically isotropic region, or a region where the liquid crystal compound is oriented in one direction in the same plane. In the non-diffraction region 45b, the liquid crystal compound may be unoriented (isotropic), uniaxially oriented, twisted oriented, or cholesteric oriented in the thickness direction, and unoriented (isotropic), uniaxially oriented, or twisted oriented is preferred. In the non-diffraction region 45b, the liquid crystal compound may have a structure in which two or more different orientation states are stacked in the thickness direction.

[0425] The diffraction region and the non-diffraction region are preferably formed of substantially the same material (liquid crystal composition). Thereby, scattering at the interface between the diffraction region and the non-diffraction region can be avoided. The material forming each region can be confirmed, for example, by analyzing the composition using SIMS (secondary ion mass spectrometry) analysis.

[0426] When the non-diffraction region 45b is a region where the liquid crystal compound is aligned in the same plane in one direction, the non-diffraction region 45b preferably functions as a retardation region. The retardation region preferably imparts a retardation of λ / 8 to light from at least one incident direction. Thus, for example, as described later, when the optically anisotropic layer 400 is laminated on the light guide plate and used, when the circularly polarized light diffracted in the first diffraction region 45a on the incident side is guided in the light guide plate, it is converted into elliptically polarized light by transmitting through the non-diffraction region 45b, total reflection occurs at the interface between the non-diffraction region 45b and air, and it is converted into linearly polarized light by transmitting through the non-diffraction region 45b again. The polarization state of the circularly polarized light is eliminated during guiding, whereas the linearly polarized light can maintain the polarization state during guiding, so that the light intensity of the light emitted from the second diffraction region 45c on the emission side can be made uniform.

[0427] Here, in Figure 27 and Figure 28 In the optically anisotropic layer 400 shown, the rotation direction of the optical axis derived from the liquid crystal compound in one direction in the liquid crystal alignment pattern of the first diffraction region 45a and the rotation direction of the optical axis derived from the liquid crystal compound in one direction in the liquid crystal alignment pattern of the second diffraction region 45c can be different from each other.

[0428] Moreover, one direction of the liquid crystal alignment pattern in the first diffraction region 45a and one direction of the liquid crystal alignment pattern in the second diffraction region 45c can be different from each other.

[0429] Furthermore, the length of the rotation of 180° in the plane of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of the first diffraction region 45a (the length of one period Λ) and the length of the rotation of 180° in the plane of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of the second diffraction region 45c (the length of one period Λ) can be different from each other.

[0430] As described later, when the optically anisotropic layer is combined with the light guide plate and used as a light guiding element, for example, the first diffraction region 45a functions as an incident diffraction element for allowing light to enter the light guide plate, and the second diffraction region 45c functions as an emission diffraction element for allowing light to exit from the light guide plate. Therefore, the diffraction performances required for the first diffraction region 45a and the second diffraction region 45c are different. Thus, the first diffraction region 45a and the second diffraction region 45c only need to set the rotation direction, one period, the orientation in one direction, etc. of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern according to the respectively required diffraction performances, and the liquid crystal alignment pattern in the first diffraction region 45a and the liquid crystal alignment pattern in the second diffraction region 45c can be different.

[0431] Moreover, in Figure 27 andFigure 28 In the optical anisotropic layer 400 shown, the first diffraction region 45a and the second diffraction region 45c can each be a cholesteric liquid crystal layer that reflects and diffracts light, or the first diffraction region 45a and the second diffraction region 45c can each be an optical anisotropic layer (also referred to as a transmission diffraction layer) that transmits and diffracts light. It is also possible that the first diffraction region 45a is a cholesteric liquid crystal layer and the second diffraction region 45c is a transmission diffraction layer, or that the first diffraction region 45a is a transmission diffraction layer and the second diffraction region 45c is a cholesteric liquid crystal layer.

[0432] Moreover, in Figure 27 and Figure 28 in the optical anisotropic layer 400 shown, when the first diffraction region 45a and the second diffraction region 45c are cholesteric liquid crystal layers, there can be a region where the length of the helical pitch of the cholesteric liquid crystal layer in the first diffraction region 45a is different from the length of the helical pitch of the cholesteric liquid crystal layer in the second diffraction region 45c.

[0433] For example, when the optical anisotropic layer is combined with a light guide plate and the first diffraction region 45a is used as an incident diffraction element and the second diffraction region 45c is used as an exit diffraction element, light is incident on the first diffraction region 45a from a substantially perpendicular direction. In contrast, light is incident on the second diffraction region 45c from an inclined direction. As described above, the cholesteric liquid crystal layer has wavelength-selective reflectivity, but when light is incident from an inclined direction, there is a so-called blue shift in which the wavelength of the selective reflection wave becomes shorter. Therefore, even when the first diffraction region 45a and the second diffraction region 45c diffract light of the same wavelength, it is preferable to set the length of the appropriate helical pitch for each region according to the incident angle of the light, etc.

[0434] Moreover, the direction of rotation of the helix of the cholesteric orientation in the first diffraction region 45a and the direction of rotation of the helix of the cholesteric orientation in the second diffraction region 45c can be different from each other. That is, the direction of rotation of the circularly polarized light reflected by the first diffraction region 45a and the direction of rotation of the circularly polarized light reflected by the second diffraction region 45c can be different from each other.

[0435] For example, when the optical anisotropic layer is combined with a light guide plate and the first diffraction region 45a is used as an incident diffraction element and the second diffraction region 45c is used as an exit diffraction element, even when right-handed circularly polarized light is incident from the first diffraction region 45a on the light guide plate, during the total reflection and guiding in the light guide plate, the polarization is eliminated and when it is incident on the second diffraction region 45c, the light sometimes becomes unpolarized light or light containing a left-handed circularly polarized light component such as elliptically polarized light. Therefore, the circularly polarized light reflected and diffracted by the second diffraction region 45c can be different from the circularly polarized light reflected and diffracted by the first diffraction region 45a.

[0436] Further, in the optically anisotropic layer 400 shown in Figure 27 and Figure 28 when at least one of the first diffraction region 45a and the second diffraction region 45c is a cholesteric liquid crystal layer, there may be a region where the length of the helical pitch of the cholesteric liquid crystal layer is different in the in-plane direction of this region.

[0437] Thereby, it is possible to selectively emit light of a desired wavelength with respect to a desired angle. For example, when used as AR glasses, it is possible to equalize the in-plane hue or brightness, thereby improving the light utilization efficiency.

[0438] Further, in the optically anisotropic layer 400 shown in Figure 27 and Figure 28 when at least one of the first diffraction region 45a and the second diffraction region 45c is a cholesteric liquid crystal layer, there may be a region where the length of the helical pitch of the cholesteric liquid crystal layer varies in the thickness direction in this region.

[0439] As described above, the cholesteric liquid crystal layer reflects a specific wavelength according to the length of the helical pitch. Therefore, by adopting a structure in which the length of the helical pitch of the cholesteric liquid crystal layer varies in the thickness direction, it is possible to broaden the frequency band of the selectively reflected wavelength.

[0440] Here, in the example shown in Figure 27 and Figure 28 the optically anisotropic layer is configured to have two diffraction regions, but it is not limited thereto. The optically anisotropic layer of the present invention may also have a structure in which a third diffraction region 45d having a diffraction effect is further provided in the in-plane direction of the same optically anisotropic layer.

[0441] Figure 29 is a plan view conceptually showing another example of the optically anisotropic layer of the present invention.

[0442] Figure 29 The optically anisotropic layer 450 shown in Figure 29 has a first diffraction region 45a, a second diffraction region 45c, a third diffraction region 45d, and a non-diffraction region 45b. As shown in Figure 29 the first diffraction region 45a and the third diffraction region 45d are arranged separately in the left-right direction in the figure, and the third diffraction region 45d and the second diffraction region 45c are arranged separately in the up-down direction in the figure. Non-diffraction regions 45b are formed between the first diffraction region 45a and the third diffraction region 45d and between the third diffraction region 45d and the second diffraction region 45c.

[0443] Similar to the first diffraction region 45a and the second diffraction region 45c, the third diffraction region 45d has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates along at least one direction in the plane while changing. Similar to the first diffraction region 45a and the second diffraction region 45c, the third diffraction region 45d can be a cholesteric liquid crystal layer or a transmissive diffraction layer. Also, the liquid crystal alignment pattern in the third diffraction region 45d can be different from the liquid crystal alignment patterns of the first diffraction region 45a and the second diffraction region 45c, respectively.

[0444] Thus, the optical anisotropic layer 450 having the third diffraction region 45d also has three regions that diffract light. Such an optical anisotropic layer 450 is combined with a light guide plate and used for a light guiding element. In this case, as will be described later, for example, the first diffraction region 45a functions as an incident diffraction element for allowing light to enter the light guide plate, the second diffraction region 45c functions as an exit diffraction element for allowing light to exit from the light guide plate, and the third diffraction region 45d functions as an intermediate diffraction element for diffracting the light incident from the first diffraction region 45a in the direction of the second diffraction region 45c. Thus, by providing a structure in the third diffraction region 45d that functions as an intermediate diffraction element to diffract a part of the light at multiple positions and emit it to the outside of the light guide plate, the exit pupil can be enlarged. Also, in the third diffraction region 45d, it is preferable to have regions with different diffraction efficiencies in the in-plane direction, and it is preferable that the diffraction efficiency gradually changes.

[0445] [Stacked body]

[0446] The stacked body is a stacked body formed by stacking two or more of the above-described optical anisotropic layers.

[0447] Figure 30 It is a diagram conceptually showing an example of the stacked body.

[0448] Figure 30 The shown stacked body 500 has a first optical anisotropic layer 400a and a second optical anisotropic layer 400b.

[0449] The first optical anisotropic layer 400a includes a first diffraction region 410a and a second diffraction region 410c having a liquid crystal alignment pattern and a non-diffraction region 410b. Also, the second optical anisotropic layer 400b includes a first diffraction region 420a and a second diffraction region 420c having a liquid crystal alignment pattern and a non-diffraction region 420b. The basic structures of the first optical anisotropic layer 400a and the second optical anisotropic layer 400b are the same as those of Figure 27 and Figure 28 the shown optical anisotropic layer 400.

[0450] In Figure 30In [the structure], the first diffraction region 410a of the first optically anisotropic layer 400a and the first diffraction region 420a of the second optically anisotropic layer 400b are disposed at overlapping positions, and the non-diffraction region 410b of the first optically anisotropic layer 400a and the non-diffraction region 420b of the second optically anisotropic layer 400b are disposed at overlapping positions, and the second diffraction region 410c of the first optically anisotropic layer 400a and the second diffraction region 420c of the second optically anisotropic layer 400b are disposed at overlapping positions.

[0451] In addition, in Figure 30 the example shown, the laminate is configured to have a structure in which two optically anisotropic layers are stacked, but it is not limited thereto, and it may also be configured to have a structure in which three or more optically anisotropic layers are stacked. In the case of a structure in which three or more optically anisotropic layers are stacked, it is also preferable that the first diffraction regions, the second diffraction regions, and the non-diffraction regions of the respective optically anisotropic layers are stacked at overlapping positions.

[0452] Moreover, it may be a laminate having an optically anisotropic layer further having a third diffraction region 45d as shown in Figure 29 the example of two or more layers. In this case, it is preferable that the third diffraction regions of the respective optically anisotropic layers are stacked at overlapping positions.

[0453] In the laminate 500 as shown in Figure 30 it is preferable to satisfy at least one of the following: the first diffraction region 410a of the first optically anisotropic layer 400a and the first diffraction region 420a of the second optically anisotropic layer 400b are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in the first diffraction region 410a of the first optically anisotropic layer 400a is different from the length of the helical pitch of the cholesteric liquid crystal layer in the first diffraction region 420a of the second optically anisotropic layer 400b; or the second diffraction region 410c of the first optically anisotropic layer 400a and the second diffraction region 420c of the second optically anisotropic layer 400b are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in the second diffraction region 410c of the first optically anisotropic layer 400a is different from the length of the helical pitch of the cholesteric liquid crystal layer in the second diffraction region 420c of the second optically anisotropic layer 400b.

[0454] As described above, the cholesteric liquid crystal layer reflects light of a specific wavelength according to the length of the helical pitch. By setting the lengths of the helical pitches of the first diffraction regions 45a of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or the second diffraction regions 45c of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b to be different from each other, the first diffraction regions 45a of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or the second diffraction regions 45c of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b reflect light of different wavelengths, respectively.

[0455] As will be described later, when the light guide element formed by combining the laminate 500 and the light guide plate is used in an AR display device or the like, in the case where the AR display device is a display device for displaying a color image, the light guide element needs to guide light of respective wavelengths of RGB, for example. Therefore, it is preferable to adopt a structure in which optically anisotropic layers having first diffraction regions and second diffraction regions (and further a third diffraction region) that reflect and diffract light of these wavelengths are laminated. For example, the following structure can be adopted: the first diffraction region and the second diffraction region of the first optically anisotropic layer are cholesteric liquid crystal layers having a selective reflection wavelength in the red wavelength region, and the first diffraction region and the second diffraction region of the second optically anisotropic layer are cholesteric liquid crystal layers having a selective reflection wavelength in the green wavelength region.

[0456] And, in the laminate 500 as shown in Figure 30 it is preferable to satisfy at least one of the following: the first diffraction region 410a of the first optically anisotropic layer 400a and the first diffraction region 420a of the second optically anisotropic layer 400b are cholesteric liquid crystal layers, and the rotation direction of the helix of the cholesteric liquid crystal layer in the first diffraction region 410a of the first optically anisotropic layer 400a is different from the rotation direction of the helix of the cholesteric liquid crystal layer in the first diffraction region 420a of the second optically anisotropic layer 400b; or the second diffraction region 410c of the first optically anisotropic layer 400a and the second diffraction region 420c of the second optically anisotropic layer 400b are cholesteric liquid crystal layers, and the rotation direction of the helix of the cholesteric liquid crystal layer in the second diffraction region 410c of the first optically anisotropic layer 400a is different from the rotation direction of the helix of the cholesteric liquid crystal layer in the second diffraction region 420c of the second optically anisotropic layer 400b.

[0457] As described above, the cholesteric liquid crystal layer has circularly polarized light selectivity depending on the rotation direction of the helix in the helical structure. By setting the rotation directions of the helices of the first diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or the second diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b to be different from each other, for example, it is possible to reflect and diffract right-handed circularly polarized light of a certain wavelength by the first diffraction region 410a of the first optically anisotropic layer 400a, reflect and diffract left-handed circularly polarized light of the same wavelength by the first diffraction region 420a of the second optically anisotropic layer 400b, and / or reflect and diffract right-handed circularly polarized light of a certain wavelength by the second diffraction region 410c of the first optically anisotropic layer 400a, and reflect and diffract left-handed circularly polarized light of the same wavelength by the second diffraction region 420c of the second optically anisotropic layer 400b.

[0458] And, in the laminate 500 as Figure 30 shown, it is preferable to satisfy at least one of the following: the length of one period in which the orientation of the optical axis derived from the liquid crystal compound in the first diffraction region 410a of the first optically anisotropic layer 400a rotates 180° in the plane is different from the length of one period in the first diffraction region 420a of the second optically anisotropic layer 400b; or the length of one period in which the orientation of the optical axis derived from the liquid crystal compound in the second diffraction region 410c of the first optically anisotropic layer 400a rotates 180° in the plane is different from the length of one period in the second diffraction region 420c of the second optically anisotropic layer 400b.

[0459] As described above, the diffraction angle in the first diffraction region and the second diffraction region is determined according to the length of one period in the liquid crystal alignment pattern. And even if the length of one period is the same, the diffraction angle varies depending on the wavelength of light. Therefore, for example, as described above, when the lengths of the helical pitches of the first diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or the second diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b are set to be different and the first optically anisotropic layer 400a and the second optically anisotropic layer 400b reflect and diffract light of different wavelengths, if the length of one period in the liquid crystal alignment pattern is the same, the diffraction angles are different, resulting in light being emitted in different directions. Therefore, it is preferable to set the lengths of one period of the liquid crystal alignment patterns of the first diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or the second diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b to be different so that the diffraction angles of the light based on the first diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or the second diffraction regions of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b become the same.

[0460] And, in the case of Figure 30In the laminate 500 shown, it is preferable to satisfy at least one of the following: one direction of the liquid crystal alignment pattern in the first diffraction region 410a of the first optically anisotropic layer 400a is different from one direction of the liquid crystal alignment pattern in the first diffraction region 420a of the second optically anisotropic layer 400b; or one direction of the liquid crystal alignment pattern in the second diffraction region 410c of the first optically anisotropic layer 400a is different from one direction of the liquid crystal alignment pattern in the second diffraction region 420c of the second optically anisotropic layer 400b.

[0461] Thereby, for example, the light diffracted in the first diffraction region 410a of the first optically anisotropic layer 400a can be selectively diffracted in the second diffraction region 410c of the optically anisotropic layer 400a. And the light diffracted in the first diffraction region 420a of the second optically anisotropic layer 400b can be selectively diffracted in the second diffraction region 420c of the second optically anisotropic layer 400b. That is, in the first optically anisotropic layer 400a and the second optically anisotropic layer 400b, light can be selectively diffracted respectively. Thereby, for example, when light of different wavelengths is to be diffracted in the first optically anisotropic layer 400a and the second optically anisotropic layer 400b, color crosstalk can be avoided.

[0462] [Light guide element and AR display device]

[0463] The light guide element of the present invention has the above-mentioned optically anisotropic layer and a light guide plate.

[0464] The AR (Augmented Reality) display device of the present invention has a light guide element and an image display device.

[0465] (First embodiment)

[0466] In Figure 11 shows an example of the first embodiment of the AR display device of the present invention conceptually.

[0467] Figure 11 The AR display device 50 shown has a display (image display device) 40 and a light guide element 45.

[0468] The light guide element 45 is the light guide element of the present invention, which has the optically anisotropic layer 400 of the present invention and a light guide plate 144. In addition, the light guide element of the present invention may be a structure including the laminate having the above-mentioned multiple optically anisotropic layers and a light guide plate. In other words, the light guide element of the present invention may have multiple optically anisotropic layers. And the light guide element of the present invention is not limited to a structure having an optically anisotropic layer with multiple diffraction regions, and may also be as Figure 1 or Figure 7A structure in which the optical anisotropic layer of a monomer is disposed at the incident position and the emission position on the surface of the light guide plate.

[0469] As described above, the optical anisotropic layer 400 is one optical anisotropic layer formed by three regions: the first diffraction region 45a, the non-diffraction region 45b, and the second diffraction region 45c. The light guide plate 144 is a rectangular parallelepiped shape that is long in one direction and guides light inside. As Figure 11 shown, the first diffraction region 45a of the optical anisotropic layer 400 is disposed on the surface (main surface) on one end side in the length direction of the light guide plate 144. And, the second diffraction region 45c of the optical anisotropic layer 400 is disposed on the surface on the other end side of the light guide plate 144. The arrangement position of the first diffraction region 45a of the optical anisotropic layer 400 corresponds to the incident position of light on the light guide plate 144, and the arrangement position of the second diffraction region 45c of the optical anisotropic layer 400 corresponds to the emission position of light from the light guide plate 144. And, an optically isotropic non-diffraction region 45b is formed between the first diffraction region 45a and the second diffraction region 45c.

[0470] The first diffraction region 45a of the optical anisotropic 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 that the light is totally reflected inside the light guide plate 144.

[0471] And, the second diffraction region 45c of the optical anisotropic layer 400 is an emission diffraction element region that diffracts light guided inside the light guide plate 144 so that the light is emitted from the light guide plate 144.

[0472] There is no particular limitation on the light guide plate 144, and a conventionally known light guide plate used in an image display device or the like can be used.

[0473] As the light guide plate 144, various materials that can be used as materials for a light guide plate in an optical element can be used. Specifically, as an example of the material of the light guide plate 144, glass, acrylic, polycarbonate, polystyrene, urethane, polyolefin, polyvinyl chloride, polyethylene terephthalate (PET), and triacetyl cellulose (TAC) can be exemplified.

[0474] There is no limitation on the thickness of the light guide plate 144, and it can be appropriately set in view of being able to maintain the thickness of the optical anisotropic layer, the light weight of the light guide plate, the uniformity of the brightness (light amount) of the light emitted from the light guide plate, etc. 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 further preferably 0.1 to 0.5 μm.

[0475] Furthermore, the refractive index of the light guide plate is preferably 1.5 or more, more preferably 1.8 or more, and still more preferably 2.0 or more. Moreover, the difference between the extraordinary refractive index of the liquid crystal compound inside the optically anisotropic layer and the refractive index of the light guide plate is preferably 0.5 or less, more preferably 0.3 or less, and still more preferably 0.1 or less.

[0476] As Figure 11 shown, the display 40 is arranged to face the surface of one end of the light guide plate 144 on the side opposite to the surface on which the optically anisotropic layer 400 is arranged. And the surface side of one end of the light guide plate 144 on the side opposite to the surface on which the optically anisotropic layer 400 is arranged becomes the observation position of the user U. In addition, in the following description, the length direction of the light guide plate 144 is set as the X direction, and the direction perpendicular to the X direction and perpendicular to the surface of the optically anisotropic layer is set as the Z direction. The Z direction is also the thickness direction of each layer in the optically anisotropic layer (refer to Figure 1 ). The display 40 is not limited. For example, various known displays used in AR display devices such as AR glasses can be used. As the display 40, as an example, a liquid crystal display (including LCOS: Liquid Crystal On Silicon, etc.), an organic electroluminescent display, DLP (Digital Light Processing), μLED (Micro Light Emitting Diode) display, a laser beam scanning method using MEMS (Micro-Electro-Mechanical Systems) mirrors, etc. can be exemplified.

[0477] In addition, the display 40 can be a display for displaying a monochromatic image, a display for displaying a dichromatic image, or a display for displaying a color image.

[0478] Since the optically anisotropic layer of the present invention has polarization selectivity, it is preferably to use a display that emits polarized light. For example, it can be configured as follows: use a display that displays red and blue images by emitting right-handed circularly polarized light and displays green images by emitting left-handed circularly polarized light, and stack the optically anisotropic layer (diffraction region) that diffracts the right-handed circularly polarized light for red, the optically anisotropic layer (diffraction region) that diffracts the left-handed circularly polarized light for green, and the optically anisotropic layer (diffraction region) that diffracts the right-handed circularly polarized light for blue on the light guide plate. Thus, since the polarization states of adjacent wavelengths of red and green, and green and blue are different, color crosstalk can be avoided.

[0479] Also, for example, by using a display that displays an image corresponding to a FOV of 0 to 50° by emitting right-handed circularly polarized light and an image corresponding to a FOV of -50 to 0° by emitting left-handed circularly polarized light, an optically anisotropic layer (diffraction region) that diffracts right-handed circularly polarized light and an optically anisotropic layer (diffraction region) that diffracts left-handed circularly polarized light are laminated on the light guide plate. As a result, the FOV can be doubled compared to the case where polarized light is not used.

[0480] In the AR display device 50 having such a structure, as shown by the arrow, the light displayed by the display 40 is incident on the light guide plate 144 from the surface on the side opposite to the surface on which the optically anisotropic layer 400 is disposed at one end of the light guide plate 144. The light incident on the light guide plate 144 is reflected in the first diffraction region 45a of the optically anisotropic layer 400. At this time, due to the diffraction effect of the first diffraction region 45a, specular reflection (regular reflection) does not occur, and the light is reflected in a direction different from the specular reflection direction. In Figure 11 the example shown, the light is incident on the first diffraction region 45a of the optically anisotropic layer 400 from a direction substantially perpendicular to the first diffraction region 45a of the optically anisotropic layer 400 (Z direction), and is reflected in a direction greatly inclined from the vertical direction toward the long side direction (X direction) of the light guide plate 144.

[0481] The light reflected in the first diffraction region 45a of the optically anisotropic layer 400 is reflected at a large angle with respect to the incident light. Therefore, the traveling direction of the light becomes smaller with respect to the surface of the light guide plate 144, and thus the light is totally reflected on the surface of the light guide plate 144 or the surface of the region 45b of the optically anisotropic layer 400 and is guided in the length direction (X direction) of the light guide plate 144. The guided light is reflected by the second diffraction region 45c of the optically anisotropic layer 400 at the other end in the length direction of the light guide plate 144. At this time, due to the diffraction effect of the second diffraction region 45c of the optically anisotropic layer 400, specular reflection does not occur, and the light is reflected in a direction different from the specular reflection direction. In Figure 11 the example shown, the light is incident on the second diffraction region 45c of the optically anisotropic layer 400 from an inclined direction and is reflected in a direction perpendicular to the surface of the second diffraction region 45c of the optically anisotropic layer 400.

[0482] The light reflected by the second diffraction region 45c of the optically anisotropic layer 400 reaches the surface of the light guide plate 144 on the side opposite to the surface where the optically anisotropic layer 400 is disposed. However, since it is incident on this surface almost perpendicularly, it is not totally reflected and is not emitted outside the light guide plate 144. That is, the light is emitted to the position viewed by the user U. In this way, the AR display device 50 causes the image displayed by the display 40 to be incident on one end of the light guide plate 144 and propagate, and is emitted from the other end, thereby overlapping and displaying a virtual image in the scene actually seen by the user U.

[0483] Here, in the second diffraction region 45c of the optically anisotropic layer 400, the diffraction efficiency has been adjusted, and it is configured such that when diffracting the light propagating in the light guide plate 144 in the second diffraction region 45c of the optically anisotropic layer 400, a part of the light is diffracted at multiple positions and emitted outside the light guide plate 144, thereby expanding the viewing field (expanding the exit pupil). Specifically, in Figure 11 the light I0 propagating in the light guide plate 144 reaches the position of the second diffraction region 45c of the optically anisotropic layer 400 while being repeatedly reflected by the two surfaces (interfaces) of the light guide plate 144. A part of the light I0 that reaches the position of the second diffraction region 45c of the liquid crystal diffraction element is diffracted in the region P1 near the incident side and is emitted from the light guide plate 144 (emitted light R1). And, the non-diffracted light I1 further propagates in the light guide plate 144, and a part of the light R2 is diffracted again at the position P2 of the second diffraction region 45c of the optically anisotropic layer 400 and is emitted from the light guide plate 144. The non-diffracted light I2 further propagates in the light guide plate 144, and a part of the light R3 is diffracted again at the position P3 of the second diffraction region 45c of the optically anisotropic layer 400 and is emitted from the light guide plate 144. The non-diffracted light I3 further propagates in the light guide plate 144, and a part of the light R4 is diffracted again at the position P4 of the second diffraction region 45c of the optically anisotropic layer 400 and is emitted from the light guide plate 144.

[0484] In this way, by adopting a structure in which the second diffraction region 45c of the optically anisotropic layer 400 diffracts the light propagating in the light guide plate 144 at multiple positions and emits it outside the light guide plate 144, the viewing field can be expanded (the exit pupil is expanded).

[0485] Here, consider the case where the diffraction efficiency of the optically anisotropic layer (liquid crystal diffraction element) on the emission side is constant in the plane. In the case where the diffraction efficiency is constant, at the position P1 closer to the incident side, the light intensity (light quantity) of the incident light I0 is large, so the intensity of the emitted light R1 also becomes large. Next, the undiffracted light I1 propagates in the light guide plate 144, and is diffracted again at the position P2 of the liquid crystal diffraction element to emit a part of the light R2. However, the light intensity of the light I1 is smaller than the light intensity of the light I0. Therefore, even if it is diffracted with the same diffraction efficiency, the light intensity of the light R2 will become smaller than the light intensity of the light R1 reflected in the area closer to the incident side. Similarly, the undiffracted light I2 propagates in the light guide plate 144, and is diffracted again at the position P3 of the liquid crystal diffraction element to emit a part of the light R3. However, the light intensity of the light I2 is smaller than the light intensity of the light I1. Therefore, even if it is diffracted with the same diffraction efficiency, the light intensity of the light R3 will become smaller than the light intensity of the light R2 reflected at the position P2. Moreover, the light intensity of the light R4 reflected at the position P4 farther from the incident side is smaller than the light intensity of the light R3. Thus, in the case where the diffraction efficiency of the liquid crystal diffraction element is constant in the plane, as shown by the dashed line in Figure 12 , light with a high light intensity is emitted at positions closer to the incident side, and light with a low light intensity is emitted at positions farther from the incident side. Therefore, there is a problem that the light intensity of the emitted light becomes non-uniform according to the position.

[0486] In contrast, in the optically anisotropic layer (the second diffraction region 45c of the optically anisotropic layer) of the present invention, there is a structure in which the diffraction efficiency increases as it goes from one side to the other in one direction of the optical axis rotation. The optically anisotropic layer (the second diffraction region 45c) is preferably arranged so that the diffraction efficiency increases in the traveling direction of the light in the light guide plate 144. That is, in the example shown in Figure 11 , the second diffraction region 45c of the optically anisotropic layer 400 has a structure in which the diffraction efficiency increases from Figure 11 from left to right in

[0487] In this case, at position P1 near the incident side, the light intensity (light quantity) of the incident light I0 is high, but the diffraction efficiency is low. Therefore, the intensity of the emitted light R1 becomes a certain level of light intensity. Subsequently, the non-diffracted light I1 propagates within the light guide plate 144 and is diffracted again at position P2 in the second diffraction region 45c of the optically anisotropic layer 400 to emit a part of the light R2. At this time, the light intensity of the light I1 is less than that of the light I0, but the diffraction efficiency at position P2 is higher than that at position P1. Therefore, the light intensity of the light R2 can be made equal to the light intensity of the light R1 reflected at position P1. Similarly, the non-diffracted light I2 propagates within the light guide plate 144 and is diffracted again at position P3 in the second diffraction region 45c of the optically anisotropic layer 400 to emit a part of the light R3. However, the light intensity of the light I2 is less than that of the light I1, and the diffraction efficiency at position P3 is higher than that at position P2. Therefore, the light intensity of the light R3 can be made equal to the light intensity of the light R2 reflected at position P2. Moreover, the diffraction efficiency at position P4, which is farther from the incident side, is higher than that at position P3. Therefore, the light intensity of the light R4 can be made equal to the light intensity of the light R3 reflected at position P3. Thus, by adopting a structure in which the diffraction efficiency of the second diffraction region 45c of the optically anisotropic layer 400 becomes higher as it moves from one side to the other in one direction of the optical axis rotation, light with a constant light intensity can be emitted at any position in the second diffraction region 45c of the optically anisotropic layer 400. Therefore, as Figure 12 shown by the solid line in, the emitted light intensity can be made uniform regardless of the position.

[0488] In addition, in Figure 11 , the light is shown by arrows, but the light emitted from the display 40 can also be planar. The planar light can propagate within the light guide plate 144 while maintaining the positional relationship and be diffracted by the second diffraction region 45c of the optically anisotropic layer 400.

[0489] Moreover, in the light guide element having the optically anisotropic layer of the present invention, it is preferable to use one optically anisotropic layer having a plurality of diffraction regions, such as the optically anisotropic layer 400 shown in Figure 27 and Figure 28 . In the light guide element of the present invention, as Figure 24 shown, consider the case where the optically anisotropic layer (diffraction region) is not integrally formed but has two optically anisotropic layers, namely, the optically anisotropic layer 46 on the incident side and the optically anisotropic layer 47 on the emission side.

[0490] In this case, it is known that a part of the light diffracted by the optically anisotropic layer 46 is scattered at the element end face X of the optically anisotropic layer 46 and / or the element end face Y of the optically anisotropic layer 47, which causes a decrease in the clarity of the image.

[0491] In contrast, by forming the optically anisotropic layer into a structure in which two or more diffraction regions and non-diffraction regions are integrally formed, when combined with a light guide plate, it is possible to prevent the light guided in the light guide plate from being scattered at the end face of the diffraction element, and thus it is possible to emit an image with high clarity from the light guide plate.

[0492] And, in Figure 11 it has been described that the light guiding element 45 is a light guiding element including a single-layer optically anisotropic layer 400 having a plurality of diffraction regions. However, as described above, the light guiding element 45 may also have a structure including a plurality of optically anisotropic layers. Alternatively, it may be a structure in which a plurality of single-layer optically anisotropic layers are stacked on the incident side and the emission side, respectively. When the light guiding element 45 is formed into a structure including a plurality of optically anisotropic layers, it is preferably formed into a structure including a plurality of optically anisotropic layers having different selective reflection wavelengths. For example, it can be formed into a structure including optically anisotropic layers having red light, green light, and blue light as selective reflection wavelengths, respectively. Thus, the optically anisotropic layer (its laminate) can diffract red light, green light, and blue light, respectively, and the light guiding element can appropriately guide the light of the display 40 for color display. In this case, the length of one cycle of the liquid crystal alignment pattern is preferably changed appropriately according to the selective reflection wavelength of each layer. And, in the case of using a cholesteric liquid crystal layer, it is preferable to appropriately change the helical pitch according to the selective reflection wavelength of each layer. Alternatively, it may be a structure including two optically anisotropic layers that reflect circularly polarized light having the same selective reflection wavelength and opposite rotation directions. For example, it can be formed into a structure including an optically anisotropic layer that reflects right-handed circularly polarized light of red light and an optically anisotropic layer that reflects left-handed circularly polarized light of red. Thus, the optically anisotropic layer (its laminate) can diffract right-handed circularly polarized light and left-handed circularly polarized light, respectively, and the light guiding element can guide right-handed circularly polarized light and left-handed circularly polarized light, and thus the utilization efficiency of light can be improved. Alternatively, it may be a structure including two optically anisotropic layers that reflect circularly polarized light having the same selective reflection wavelength and opposite rotation directions and have different helical pitches. Thus, the optically anisotropic layer (its laminate) can diffract right-handed circularly polarized light and left-handed circularly polarized light, respectively, and the light guiding element can guide right-handed circularly polarized light and left-handed circularly polarized light incident at different incident angles and emit the guided light at different angles, and thus the FOV (Field of View) can be increased.

[0493] And, in Figure 11In the example shown, the optically anisotropic layer 400 is configured to have a first diffraction region 45a on the incident side, a second diffraction region 45c on the emission side, and an isotropic non-diffraction region 45b, but is not limited thereto. As described above, it may also be configured to have an intermediate diffraction region (third diffraction region). That is, it may be configured as follows: The light diffracted by the incident diffraction region (first diffraction region) and incident into the light guide plate is diffracted by the intermediate diffraction region (third diffraction region) to bend the traveling direction of the light in the light guide plate, and then is diffracted by the emission-side diffraction region (second diffraction region) to emit the light to the outside of the light guide plate. At this time, the first diffraction region on the incident side and the intermediate third diffraction region can be formed in one optically anisotropic layer, the intermediate third diffraction region and the second diffraction region on the emission side can be formed in one optically anisotropic layer, or all the diffraction regions can be formed in one optically anisotropic layer. However, from the viewpoint of improving the clarity of the image, it is preferable to form as many diffraction regions as possible that can be used for the light guide plate in one optically anisotropic layer. Further, when the optically anisotropic layer of the present invention has a structure with an intermediate diffraction region, in order to make the light intensity of the emitted light uniform, it is preferably configured such that the efficiency of the intermediate diffraction region increases as it goes from one side to the other side. Further, when the optically anisotropic layer of the present invention is used as the intermediate diffraction region and / or the emission-side diffraction region, in order to make the light intensity of the emitted light uniform, a structure in which the in-plane distribution of the diffraction efficiency in the intermediate diffraction region and the emission-side diffraction region is different can also be preferably used.

[0494] Further, when the optically anisotropic layer has an intermediate diffraction region, a structure in which the length of one cycle in which the direction of the optical axis derived from the liquid crystal compound rotates 180° in the plane is shortened with respect to the incident-side diffraction region can be preferably used. Thereby, the angle by which the light diffracted by the incident diffraction region and incident into the light guide plate is diffracted by the intermediate diffraction region to bend the traveling direction of the light in the light guide plate can be increased, and thus the size of the light guide plate can be made compact. Further, when the length of one cycle of the intermediate diffraction region is shorter than that of the incident-side diffraction region, with respect to the helical pitch of the cholesteric liquid crystal layer, it is preferable to set the helical pitch of the intermediate diffraction region to be larger than that of the incident-side diffraction region. Thereby, in the intermediate diffraction region, the traveling direction of the light in the light guide plate can be effectively bent. Further, the intermediate diffraction region can preferably use a structure in which one direction of the liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound rotates 180° in the plane is different from that of the incident-side diffraction region. Thereby, the direction in which the light diffracted by the incident diffraction region and incident into the light guide plate is diffracted by the intermediate diffraction region to bend the traveling direction of the light in the light guide plate can be changed, and thus the light can be appropriately guided toward the emission diffraction region.

[0495] Further, multiple incident diffraction regions and intermediate diffraction regions can also be arranged in the plane. Among the multiple incident diffraction regions, the directions of the liquid crystal alignment patterns that continuously rotate in one direction in the plane are different from each other, enabling the light incident on the incident diffraction regions to be guided in different directions within the light guide plate respectively, diffracted at the intermediate diffraction regions arranged at different positions in the plane to bend the traveling direction of the light within the light guide plate, and then the guided light is emitted at different angles through the emission-side diffraction region. Therefore, the FOV (Field of View) can be increased. For example, as described in WO2020 / 122128, in the incident diffraction regions and the intermediate diffraction regions, the length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in the plane and the rotation direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern that continuously rotates in one direction in the plane can be appropriately set. When the diffraction region is a cholesteric liquid crystal layer, the length of the helical pitch and the twisting rotation direction of the helix in the thickness direction can be appropriately set. Among the multiple incident-side diffraction regions, the rotation direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern that continuously rotates in one direction in the plane can be appropriately set. Among the multiple incident-side diffraction regions, the rotation direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern that continuously rotates in one direction in the plane can also be made different. Further, when the optically anisotropic layer is a cholesteric liquid crystal layer, among the multiple incident-side diffraction regions, the twisting rotation direction of the helix in the thickness direction (the rotation direction of the reflected circularly polarized light) can be appropriately set. Specifically, the multiple incident-side diffraction regions can be set as regions with a right-handed cholesteric alignment and regions with a left-handed cholesteric alignment of the cholesteric liquid crystal layer. Further, the intermediate diffraction region can preferably use a structure 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 shorter than that of the incident-side diffraction region. When the one period of the intermediate diffraction region is shorter than that of the incident-side diffraction region, as described above, regarding the helical pitch of the cholesteric liquid crystal layer, it is preferable to set the helical pitch of the intermediate diffraction region to be larger than that of the incident-side diffraction region. Further, in such a structure, when the optically anisotropic layer of the present invention is used as the intermediate diffraction region and / or the emission-side diffraction region, in order to make the light intensity of the emitted light uniform, a structure in which the in-plane distribution of the diffraction efficiency in the intermediate diffraction region and the emission-side diffraction region is different can also be preferably used.

[0496] Furthermore, different incident diffraction regions, intermediate diffraction regions, and emitted diffraction regions can be stacked. As described above, when stacking multiple optically anisotropic layers, it is also preferable to stack multiple optically anisotropic layers having different selective reflection wavelengths (pitches of the helix). Thereby, the optically anisotropic layer (its laminate) can diffract lights of different colors (wavelengths) respectively, and the light guide element can appropriately guide the light of the color display of the 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 of each layer. Alternatively, it can be a structure in which two optically anisotropic layers having diffraction regions that reflect circularly polarized lights with the same selective reflection wavelength and opposite rotation directions are stacked. For example, it can be a structure in which an optically anisotropic layer having a diffraction region that reflects right-handed circularly polarized light of red light and an optically anisotropic layer having a region that reflects left-handed circularly polarized light of red are stacked. Thereby, the optically anisotropic layer (its laminate) can diffract right-handed circularly polarized light and left-handed circularly polarized light respectively, and the light guide element can guide right-handed circularly polarized light and left-handed circularly polarized light, so that the light utilization efficiency can be improved. Alternatively, it can also be a structure in which two optically anisotropic layers having the same selective reflection wavelength and opposite rotation directions and different helix pitches are stacked. Thereby, the optically anisotropic layer (its laminate) can diffract right-handed circularly polarized light and left-handed circularly polarized light respectively, and the light guide element can guide right-handed circularly polarized light and left-handed circularly polarized light incident at different incident angles and emit the guided lights at different angles, so that the FOV can be increased. And, for example, as described in WO2020 / 122128, WO2020 / 075738, WO2020 / 226078, WO2021 / 060528, etc., when stacking multiple optically anisotropic layers, the diffraction regions (incident diffraction regions, intermediate diffraction regions, emitted diffraction regions) of each optically anisotropic layer are also preferably stacked with multiple optically anisotropic layers having a length of one period of the liquid crystal alignment pattern, a direction of the liquid crystal alignment pattern that continuously rotates in one direction in the plane, and different rotation directions of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern that continuously rotates in one direction in the plane. In the case where the diffraction region is a cholesteric liquid crystal layer, it is also preferable to stack multiple optically anisotropic layers having different pitches of the helix and different twisting rotation directions of the helix in the thickness direction (rotation directions of the reflected circularly polarized light), which can be appropriately set according to the purpose. And, in the case of stacking multiple optically anisotropic layers, when using the optically anisotropic layer of the present invention as the intermediate diffraction region and / or the emitted diffraction region, in order to make the light intensity of the emitted light uniform, it is also possible to preferably use a structure in which the in-plane distribution of the diffraction efficiency in the intermediate diffraction region and the emitted-side diffraction region is different.Further, when multiple optically anisotropic layers are stacked, in each optically anisotropic layer, for the intermediate diffraction region in each layer and the diffracted region emitted from each layer, it is also possible to preferably use structures with different in-plane distributions of diffraction efficiency in the diffraction region. As the optically anisotropic layer, it is possible to preferably use the optically anisotropic layer of the present invention. The arrangement of the diffraction region is not limited, and it can be appropriately arranged in the in-plane direction and the thickness direction (stacking) as needed.

[0497] Further, diffraction regions that also serve as both an intermediate diffraction region and an emission diffraction region can be stacked. The intermediate diffraction region and the emission diffraction region can each be configured as a structure of optically anisotropic layers in which the liquid crystal alignment patterns that are continuously rotated along one direction in the plane have different directions. At this time, it is preferable to use a plurality of incident diffraction regions in which the liquid crystal alignment patterns that are continuously rotated along one direction in the plane have different directions for the incident diffraction region, and guide the light incident on the incident diffraction region to different directions in the light guide plate. The plurality of incident regions can be arranged at different positions in the plane or can be configured as a stacked structure. The light diffracted by the incident diffraction region and incident into the light guide plate is diffracted by the intermediate diffraction region to bend the traveling direction of the light in the light guide plate, and then is diffracted by the emission-side diffraction region stacked with the intermediate diffraction region and the light is emitted to the outside of the light guide plate. Regarding the light diffracted by other incident diffraction regions and incident into the light guide plate, the above-mentioned emission-side diffraction region functions as an intermediate diffraction region and is diffracted, thereby bending the traveling direction of the light in the light guide plate, and the above-mentioned intermediate diffraction region functions as an emission-side diffraction region and can emit the guided light at different angles. Thus, compared with the case where the intermediate diffraction region and the emission diffraction region are arranged at different positions in the plane, a larger FOV can be achieved with a light guide plate of a compact size. For example, as described in WO2021 / 201218, WO2021 / 256453, etc., when stacking a plurality of optically anisotropic layers, in the case of stacking a diffraction region that also serves as both an intermediate diffraction region and an emission diffraction region, it is also preferable to stack a plurality of optically anisotropic layers in which the length of one period of the liquid crystal alignment pattern, the direction of one of the liquid crystal alignment patterns that are continuously rotated along one direction in the plane, and the rotation direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern that is continuously rotated along one direction in the plane are different. In the case where the diffraction region is a cholesteric liquid crystal layer, it is also preferable to stack a plurality of optically anisotropic layers in which the pitch of the helix and the twisting rotation direction of the helix in the thickness direction (the rotation direction of the reflected circularly polarized light) are different, and it can be appropriately set according to the purpose. Further, in the structure of stacking a diffraction region that also serves as both an intermediate diffraction region and an emission diffraction region, in order to make the light intensity of the emitted light uniform, in each diffraction region, it is also possible to preferably use a structure in which the in-plane distribution of the diffraction efficiency in the diffraction region is different. As the optically anisotropic layer, it is possible to preferably use the optically anisotropic layer of the present invention. The arrangement of the diffraction regions is not limited, and can be appropriately arranged in the plane and in the thickness direction (stacking) as needed.

[0498] In addition, in Figure 11In this case, as the optically anisotropic layer 400, an optically anisotropic layer having a reflective diffraction region is used, but it is not limited thereto, and an optically anisotropic layer having a transmissive diffraction region may also be used. That is, it can be configured such that the optically anisotropic layer (its incident-side diffraction region) is disposed on the surface of the light guide plate 144 on the display 40 side.

[0499] [Method for forming optically anisotropic layer]

[0500] The method for manufacturing the optically anisotropic layer of the present invention is not particularly limited, but from the viewpoint of being able to efficiently manufacture the optically anisotropic layer, a manufacturing method having steps 1 to 3 is preferred.

[0501] Step 1: A step of forming a coating film using a composition containing a liquid crystal compound having a polymerizable group and aligning the liquid crystal compound in the formed coating film

[0502] Step 2: A step of polymerizing the liquid crystal compound to form a region where the polymerization rate of the liquid crystal compound is different in the in-plane direction and the thickness direction of the coating film

[0503] Step 3: A step of performing a heat treatment on the coating film obtained in Step 2 and changing the birefringence Δn according to the polymerization rate in Step 2, thereby forming a region having a different birefringence

[0504] Hereinafter, the above steps 1 to 3 will be described in detail.

[0505] (Step 1)

[0506] Step 1 is a step of forming a coating film using a composition containing a liquid crystal compound having a polymerizable group and aligning the liquid crystal compound in the formed coating film. By performing this step, a coating film containing an aligned liquid crystal compound is formed.

[0507] As one of the preferred embodiments of this step, it is preferred to coat the composition on the alignment film of the support with an alignment film having a support and an alignment film to form a coating film and align the liquid crystal compound in the coating film. By performing this preferred method, as Figure 15 shown, a laminate including a support 320, an alignment film 322, and a coating film 324 (which becomes an optically anisotropic layer through subsequent steps) is formed.

[0508] The composition containing a liquid crystal compound having a polymerizable group used in this step is as described above.

[0509] In addition, as the liquid crystal compound used in this step, a liquid crystal compound having a radical polymerizable group or a cationic polymerizable group is preferred, and a liquid crystal compound having a radical polymerizable group is more preferred.

[0510] The coating of the composition can be carried out by using various known methods used in the coating of liquids such as bar coating, gravure coating, and spraying.

[0511] Next, an alignment treatment is performed on the coating film formed by coating to align the liquid crystal compound. By performing the alignment treatment, the liquid crystal compound in the coating film is aligned in a prescribed alignment state according to the alignment pattern of the alignment film.

[0512] As the alignment treatment, a heat treatment is preferably used. The conditions of heating are not particularly limited. The heating temperature is preferably 50 to 140 °C, and the heating time is preferably 0.5 to 20 minutes.

[0513] (Step 2)

[0514] Step 2 is a step of polymerizing the liquid crystal compound to form regions where the polymerization rate of the liquid crystal compound is different in the in-plane direction or the thickness direction of the coating film. The order of this step is not particularly limited. By performing this step, regions where the curing degree of the liquid crystal compound is different in the in-plane direction and the thickness direction are formed in at least a part of the in-plane.

[0515] As a method for forming regions where the curing degree of the liquid crystal compound is different in the in-plane direction, a method of performing exposure through a photomask (Method 1) etc. can be cited. By using a photomask whose transmittance gradually changes from one side to the other side, an optically anisotropic layer having a structure in which the average value Δna of the birefringence in the thickness direction gradually changes from one side to the other side can be formed.

[0516] As a method for forming regions where the curing degree of the liquid crystal compound is different in the thickness direction, a method of performing exposure or heat treatment in an atmosphere containing components that hinder polymerization such as oxygen and moisture (Method 2), a method of forming a coating film using a composition containing a compound that absorbs ultraviolet rays of the exposure wavelength such as an ultraviolet absorber and performing exposure on the formed coating film (Method 3) etc. can be cited.

[0517] As a method for forming an optically anisotropic layer having a structure in which the birefringence Δn in the thickness direction is different and the average value Δna of the birefringence in the thickness direction gradually changes from one side to the other side in the in-plane of the optically anisotropic layer, a method of combining a method for forming regions where the curing degree of the liquid crystal compound is different in the thickness direction and a method for forming regions where the curing degree of the liquid crystal compound is different in the in-plane direction can be cited.

[0518] For example, use Figure 15A case of combining the above-described Method 1 and Method 2 will be described. In the photomask 329, the white portion indicates a high transmittance, and the black portion indicates a low transmittance. If exposure is performed from the direction indicated by the hollow arrow of 327, the first region 326 on the alignment film 322 side in the coating film 324 does not contact 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 side opposite to the alignment film 322 side in the coating film 324 contacts the atmosphere, and the oxygen supply from the atmosphere is rapid, and polymerization does not occur. At this time, the thickness of the region 326 gradually changes according to the transmittance of the photomask 329.

[0519] Through Step 3 described later, the birefringence of the region 326 becomes high, and the birefringence of the region 328 becomes low. Therefore, the average value Δna of the birefringence gradually changes according to the thickness gradients of the two.

[0520] Next, a case of combining the above-described Method 1 and Method 3 will be described. In the case where the coating film 324 is formed using a composition containing an ultraviolet absorber, the ultraviolet absorber is dispersed in the coating film in the thickness direction. If this coating film is exposed from the direction indicated by the hollow arrow 327 of Figure 15 , the exposure energy on the alignment film 322 side in the coating film 324 is strong, so polymerization of the liquid crystal compound proceeds sufficiently. On the other hand, since the exposure energy gradually decreases toward the depth direction due to the influence of the ultraviolet absorber in the coating film 324, the energy sufficient to cause sufficient polymerization of the liquid crystal compound is not irradiated to the side opposite to the alignment film 322 side in the coating film 324. As a result, the polymerization rate of the liquid crystal compound in the coating film 324 gradually changes in the direction from the alignment film 322 side toward the side opposite to the alignment film 322 side. Moreover, at this time, according to the transmittance of the photomask 329, the polymerization rate of the liquid crystal compound in the coating film 324 gradually changes in the in-plane direction. The region 326 represents a region where the polymerization rate is above a certain threshold, and the region 328 represents a region where the polymerization rate is less than a certain threshold. According to the transmittance of the photomask 329, the thickness of the region 326 gradually changes.

[0521] Through Step 3 described later, the birefringence of the region 326 becomes high, and the birefringence of the region 328 becomes low. Therefore, the average value Δna of the birefringence gradually changes according to the thickness gradients of the two.

[0522] Step 2 can also be implemented by other methods.

[0523] In addition, regarding the determination of whether regions having different polymerization rates of the liquid crystal compound in the thickness direction of the coating film are formed, for example, it can be determined as follows: The coating film is cut along the thickness direction, and the cross section of the exposed coating film is analyzed by infrared absorption spectroscopy or the like, and the residual rate of the polymerizable groups in the thickness direction of the coating film is calculated.

[0524] In the method of forming a coating film using the above-described composition containing a liquid crystal compound having an aggregating group and exposing the formed coating film, ultraviolet irradiation treatment is preferably used as the exposure treatment.

[0525] The conditions for the ultraviolet irradiation treatment can be appropriately selected according to the coating film used, and as the irradiation amount, 0.1 to 3000 mJ / cm 2 is preferred, and more preferably 1 to 1000 mJ / cm 2 . As the illuminance, 0.1 to 1000 mW / cm 2 is preferred, and more preferably 1 to 300 mW / cm 2 .

[0526] (Step 3)

[0527] Step 3 is a step of performing a heat treatment on the coating film obtained in Step 2 to form regions having different birefringences Δn in the in-plane direction and the thickness direction.

[0528] In the coating film obtained in Step 2, regions having different polymerization rates of the liquid crystal compound in the in-plane direction and the thickness direction of the coating film are included. If such a coating film is heat-treated, the orientation state of the liquid crystal compound is maintained in the region where the polymerization rate of the liquid crystal compound is high. On the other hand, in the region where the polymerization rate of the liquid crystal compound is low, the orientation state of the liquid crystal compound cannot be maintained due to the heat treatment, and the degree of orientation of the liquid crystal compound decreases. If such a decrease in the degree of orientation of the liquid crystal compound occurs, the birefringence Δn in that region decreases. That is, by performing this step, the region where the polymerization rate of the liquid crystal compound is high becomes the region where the birefringence Δn is high, and the region where the polymerization rate of the liquid crystal compound is low becomes the region where the birefringence Δn is low.

[0529] From the viewpoint of making the average refractive indices equal, the region having a liquid crystal alignment pattern and the region not having a liquid crystal alignment pattern are preferably formed of substantially the same material (liquid crystal composition). Thereby, scattering at the interface between the region having a liquid crystal alignment pattern and the region not having a liquid crystal alignment pattern can be avoided. The material forming each region can be confirmed, for example, by analyzing the components using SIMS (secondary ion mass spectrometry) analysis.

[0530] The average refractive index of the region having a liquid crystal alignment pattern at this time is preferably within ±10% of the average refractive index of the region not having a liquid crystal alignment pattern.

[0531] The conditions of the heat treatment carried out in this step are not particularly limited, and the optimal conditions can be selected according to the coating film used. As the heating temperature during the heat treatment, 50 to 300 °C is preferred, and 100 to 200 °C is more preferred. As the heating time at the heating temperature, 0.5 to 30 minutes is preferred, and 1 to 5 minutes is more preferred. At this time, in the region where the polymerization rate of the liquid crystal compound is low, when the heating temperature is sufficiently higher than the phase transition temperature of the liquid crystal phase-isotropic phase (Iso) of the liquid crystal compound, an optically isotropic region will be formed.

[0532] After performing Step 3, Step 4 of performing an exposure treatment on the optically anisotropic layer obtained in Step 3 can be carried out. By performing the exposure treatment, unreacted polymerizable groups can be polymerized. As the exposure treatment, ultraviolet irradiation treatment is preferred.

[0533] The conditions of the ultraviolet irradiation treatment can be appropriately selected as the optimal conditions according to the coating film used. As the irradiation amount, 50 to 2000 mJ / cm 2 is preferred, and 100 to 1000 mJ / cm 2 .

[0534] The ultraviolet irradiation treatment is preferably carried out in an atmosphere with a low oxygen concentration. The ultraviolet irradiation treatment is preferably carried out in a nitrogen atmosphere.

[0535] Regarding the above-mentioned optically anisotropic layer of the present invention, the optical axis 30A of the liquid crystal compound 30 in the liquid crystal alignment pattern of any optically anisotropic layer (diffraction region) only continuously rotates along the arrow X direction.

[0536] However, the present invention is not limited to this. As long as the optical axis 30A of the liquid crystal compound 30 continuously rotates in one direction in the optically anisotropic layer (diffraction region), various structures can be utilized.

[0537] As described above, the optically anisotropic layer of the present invention can also be formed into a laminate by laminating a plurality of optically anisotropic layers. The lamination methods include a method of directly coating a liquid crystal composition on the first optically anisotropic layer to form the second optically anisotropic layer, a method of coating an alignment film on the first optically anisotropic layer, performing an alignment treatment, and then coating a liquid crystal composition, a method of bonding an optically anisotropic layer provided on another substrate, etc. The grating pitch, grating angle, and helical pitch of each optically anisotropic layer (diffraction region) can be arbitrarily adjusted.

[0538] The optically anisotropic layer (diffraction region) of the present invention preferably has a region where the length of the helical pitch of the cholesteric liquid crystal layer is different within the region, and more preferably the length of the helical pitch continuously changes within the region. By having different lengths of the helical pitch, the diffraction angle of the diffraction region for a certain wavelength can be controlled. Therefore, as Figure 11As shown, by designing the helical pitch at positions P1, P2, P3, and P4 in the second diffraction region 45c to achieve an appropriate diffraction angle, the amount of light reaching the eyes increases, and the brightness of the AR glasses can be improved.

[0539] Moreover, in the present invention, after forming an optically anisotropic layer having a plurality of birefringence-changing regions (diffraction regions) on one support, it is possible to cut each region to produce a plurality of optically anisotropic layers. Also, a region including at least the first diffraction region, the second region, and the non-diffraction region can be regarded as one unit, and a plurality of units can be formed in one substrate, and each unit can be cut to produce a plurality of optically anisotropic layers. By forming a plurality of optically anisotropic layers in one substrate, not only can the productivity of the forming process of the optically anisotropic layer of the present invention be improved, but also the productivity of the downstream process can be improved.

[0540] Next, a method for detecting regions where the average value Δna of the birefringence in the thickness direction is different in the plane will be described. Since the in-plane retardation Re(40) has a proportional relationship with the average value Δna of the birefringence in the thickness direction, by confirming regions where the in-plane retardation Re(40) is different in the plane, it is possible to detect regions where the average value Δna of the birefringence in the thickness direction is different in the plane. Also, by confirming that the in-plane retardation Re(40) gradually changes in the plane, it is possible to detect that the average value Δna of the birefringence in the thickness direction gradually changes in the plane.

[0541] Regarding the method for calculating the thickness of the region where the birefringence of the liquid crystal compound in the thickness direction is high, it is described in Figure 16 In the optically anisotropic layer in which the liquid crystal compound has a cholesteric orientation, when the optically anisotropic layer 324 is cut along the thickness direction and the SEM image of the exposed coating film is analyzed, bright portions 330 and dark portions 332 due to the cholesteric orientation of the liquid crystal compound clearly appear in the region 326 where the birefringence is high. On the other hand, regarding the region 328 where the birefringence is low, the contrast between the bright portion 330 and the dark portion 332 is small, and particularly when the region 328 is optically isotropic, the bright portion 330 and the dark portion 332 cannot be visually recognized. Therefore, by measuring the thickness of the region 326 where the bright portion 330 and the dark portion 332 clearly appear, the film thickness of the region where the birefringence is high can be obtained.

[0542] However, in the case where the liquid crystal compound is not in a cholesteric orientation or the birefringence continuously changes in the thickness direction, it is difficult to measure the thickness of the region with a high birefringence. In such a case, by etching a part of the optically anisotropic layer and based on the difference in the in-plane retardation Re(40) before and after etching, the ratio of the birefringence Δn in the thickness direction can be obtained. For example, the following operation is repeated until the optically anisotropic layer is completely etched in the thickness direction: After obtaining the in-plane retardation Re(40) using Axoscan (manufactured by Axometrics), an etching treatment of 100 nm is performed starting from the surface of the optically anisotropic layer. Based on the difference in the in-plane retardation Re(40) before and after the 100-nm etching, the magnitude of the in-plane retardation Re(40) in the etched region is calculated. Since there is a proportional relationship between the in-plane retardation Re(40) and the birefringence Δn, by obtaining the film thickness of the region with a large in-plane retardation Re(40) in the thickness direction, the thickness of the region with a high birefringence of the liquid crystal compound in the thickness direction can be obtained.

[0543] Regarding the liquid crystal diffraction element of the present invention described above, in the liquid crystal alignment pattern of the optically anisotropic layer of any liquid crystal diffraction element, the optical axis 30A of the liquid crystal compound 30 continuously rotates only along the arrow X direction.

[0544] However, the present invention is not limited to this. As long as the optical axis 30A of the liquid crystal compound 30 continuously rotates in one direction in the optically anisotropic layer, various structures can be utilized.

[0545] The light guide element of the present invention at least has an optically anisotropic layer, which has birefringence variation regions with different average values Δna of the birefringence in the thickness direction within the plane of the optically anisotropic layer. The in-plane variation rate of Δna of the optically anisotropic layer, the grating pitch, the grating angle, the helical pitch, the helical pitch variation in the thickness direction, the tilt angle, the tilt angle variation in the thickness direction, the Δn variation in the thickness direction, the size of the diffraction region, the shape of the diffraction region, the physical film thickness, the optical thickness, and the reflectivity for each wavelength can be arbitrarily adjusted. Also, in one diffraction region, it is possible to change the grating pitch, the grating angle, the helical pitch, the helical pitch variation in the thickness direction, the Δn variation in the thickness direction, the tilt angle, the tilt angle variation in the thickness direction, the physical thickness, the optical thickness, and the reflectivity for each wavelength in the in-plane direction, and it is also possible to arbitrarily adjust the direction of change and the degree of inclination of the change. Moreover, a plurality of optically anisotropic layers with the above parameters adjusted can be arbitrarily combined to form a light guide element.

[0546] <Adhesive layer (bonding agent layer), adhesive>

[0547] In a laminate and a light guide element, an adhesive layer may be included in order to bond optical anisotropic layers to each other and / or an optical anisotropic layer to a light guide plate. In this specification, "bonding" is used in a concept that also includes "adhesion".

[0548] For example, a water-soluble adhesive, an ultraviolet curable adhesive, an emulsion adhesive, a latex adhesive, an adhesive tape adhesive, a multilayer adhesive, a paste adhesive, a foaming adhesive, a support film adhesive, a thermoplastic adhesive, a hot melt (heat fusion) adhesive, a thermosetting adhesive, a thermally active adhesive, a heat seal adhesive, a thermosetting type adhesive, a contact type adhesive, a pressure-sensitive adhesive (i.e., an adhesive), a polymerizable adhesive, a solvent-based adhesive, a solvent-active adhesive, a ceramic adhesive, etc. may be cited. Specifically, an aqueous solution of a boron compound, a curable adhesive of an epoxy compound not containing an aromatic ring in the molecule as shown in Japanese Patent Application Laid-Open No. 2004-245925, a radiation curable adhesive having a photoinitiator having a molar extinction coefficient of 400 or more at a wavelength of 360 to 450 nm and a UV curable compound as essential components as described in Japanese Patent Application Laid-Open No. 2008-174667, a radiation curable adhesive containing (a) a (meth)acrylic acid-based compound having two or more (meth)acryloyl groups in the molecule, (b) a (meth)acrylic acid-based compound having a hydroxyl group in the molecule and only one polymerizable double bond, and (c) a phenol ethylene oxide modified acrylate or a nonylphenol ethylene oxide modified acrylate in 100 parts by mass of the total amount of (meth)acrylic acid-based compounds as described in Japanese Patent Application Laid-Open No. 2008-174667, etc. can be cited. As needed, various adhesives can be used alone or in combination.

[0549] In a laminate and a light guide element, from the viewpoint of reducing unnecessary reflection, it is preferable that the refractive index difference between the adhesive layer and the adjacent layer is small. Specifically, the refractive index difference between adjacent layers is preferably 0.1 or less, more preferably 0.05 or less, and further preferably 0.01 or less. As a method for adjusting the refractive index of the adhesive layer, there is no particular limitation, and known methods such as a method of adding fine particles of a zirconia-based, silica-based, acrylic-based, acrylic-styrene-based, melamine-based, etc., adjustment of the refractive index of the resin, and the method described in Japanese Patent Application Laid-Open No. 11-223712 can be used.

[0550] Further, when the adjacent layer has refractive index anisotropy in the plane, in all directions in the plane, the refractive index difference from the adjacent layer is preferably 0.2 or less, more preferably 0.1 or less, and further preferably 0.05 or less. Therefore, the adhesive layer may have refractive index anisotropy in the plane.

[0551] When the refractive index difference between the bonded interfaces is large, it is possible to reduce the interface reflectance by imparting a distribution of refractive index in the thickness direction of the adhesive layer. As methods for imparting a distribution of refractive index in the thickness direction, there can be mentioned a method of providing a multi-layer adhesive layer, a method of mixing the interfaces between multi-layer adhesive layers, a method of controlling the non-uniform state of raw materials in the adhesive layer to impart a refractive index distribution, and the like.

[0552] Moreover, the adhesive layer can be provided on one or two members to be bonded by any method such as coating, vapor deposition, transfer printing, etc. From the viewpoint of improving the bonding strength, post-treatments such as heat treatment and ultraviolet irradiation can be carried out according to the type of adhesive. The thickness of the adhesive layer can be adjusted arbitrarily, preferably 20 μm or less, more preferably 0.1 μm or less, and further preferably 0.01 μm or less. As a method for forming an adhesive layer with a thickness of 0.1 μm or less, there can be mentioned a method of vapor-depositing a ceramic adhesive such as silicon oxide (SiOx layer) on the bonding surface. The bonding surfaces of the bonded members can be subjected to surface modification treatments such as plasma treatment, corona treatment, saponification treatment, etc. before bonding, and a primer layer can be imparted. Moreover, when there are a plurality of bonding surfaces, the type and thickness of the adhesive layer can be adjusted for each bonding surface.

[0553] <Cutting of the optically anisotropic layer and the laminate>

[0554] The fabricated optically anisotropic layer and / or laminate can be cut into a specified size. The cutting method of the optically anisotropic layer and / or laminate is not limited, and various known methods such as a method of physically cutting using a tool such as a Thomson knife and a method of cutting by irradiating a laser can be used. In the case of using a laser, it is preferable to select the pulse width (nanosecond, picosecond, femtosecond) and wavelength in consideration of cuttability, damage to the material, etc. Moreover, after processing the optically anisotropic layer and / or laminate into a specified shape, for example, end face grinding can be carried out. From the viewpoints of improving the workability during cutting and suppressing dust generation, etc., it is also possible to carry out cutting in a state with a peelable protective film. Moreover, for example, by observing the liquid crystal alignment pattern while cutting using the method shown in Japanese Patent Application Laid-Open No. 2004-141889, the cutting position can be arbitrarily determined. At this time, in order to easily see the liquid crystal alignment pattern, it is also possible to observe through a polarizing plate, a retardation film, etc. Moreover, when there are a plurality of units provided on one substrate, it is preferable to cut out each unit.

[0555] <Other treatments>

[0556] Marks of any shape can be added as needed for the purpose of accurately placing the optical anisotropic layer (or laminate) on various devices (e.g., light guide plates) and improving the accuracy of the axis and cutting position during cutting. The type of mark can be selected arbitrarily, and can be selected from methods such as physically adding by laser, inkjet, etc., methods of locally changing the orientation state of liquid crystals, and methods of adding a locally decolorized or dyed area.

[0557] Furthermore, from the purpose of protecting the optical anisotropic layer, a protective layer (gas barrier layer, barrier layer for moisture, etc., ultraviolet absorbing layer, scratch-resistant layer, transparent coloring layer, etc.) can be provided as needed. The protective layer can be formed directly on the optical anisotropic layer, or it can be provided through other optical films such as an adhesive layer. For the purpose of reducing the reflectivity of the surface, an anti-reflection layer (LR (Low-Reflection: low reflection) layer, AR (Anti-Reflection: anti-reflection) layer, moth-eye layer, etc.) can be provided. Various protective layers can be appropriately selected from known protective layers. When a gas barrier layer is provided, polyvinyl alcohol, glass, etc. are preferred. Polyvinyl alcohol can also have the function of a polarizer. Furthermore, the ultraviolet absorbing layer is a layer containing an ultraviolet absorber. As an ultraviolet absorber, from the perspective of excellent absorption capacity of ultraviolet rays below a wavelength of 370nm and good display properties, it is preferred to use an ultraviolet absorber with less absorption of visible light above a wavelength of 400nm. Only one type of ultraviolet absorber can be used, or two or more types can be used at the same time. For example, ultraviolet absorbers described in Japanese Patent Publication No. 2001-072782 and Japanese Patent Table No. 2002-543265 can be cited. As specific examples of ultraviolet absorbers, for example, oxybenzophenone compounds, benzotriazole compounds, salicylate compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, etc. can be cited. The transparent coloring layer is a layer that absorbs or reflects at least a part of visible light. By combining the transparent coloring layer with the optical anisotropic layer, the color tone of the appearance of the optical element containing the optical anisotropic layer can be adjusted. For example, in the case where the optical anisotropic layer is colored, the transparent coloring layer can be combined to adjust to a neutral color tone.

[0558] The optically anisotropic layer of the present invention can be used in various applications such as optical path changing components, light focusing elements, light diffusing elements in a predetermined direction, and diffraction elements in optical devices that reflect (diffract) or transmit (diffract) light at an angle other than specular reflection.

[0559] The above examples are examples in which the optically anisotropic layer of the present invention is used in a liquid crystal diffraction element that reflects or transmits visible light, but the present invention is not limited thereto, and various structures can be used.

[0560] For example, the optically anisotropic layer of the present invention may be a structure that reflects or transmits infrared or ultraviolet rays, or may be a structure that only reflects or transmits light other than visible light.

[0561] As described above, the optically anisotropic layer, the light guide element, and the AR display device of the present invention have been described in detail. However, the present invention is not limited to the above examples, and various improvements and changes can be made without departing from the gist of the present invention.

[0562] Examples

[0563] Hereinafter, examples are given to more specifically illustrate the features of the present invention. The materials, reagents, usage amounts, amounts of substances, ratios, treatment contents, treatment steps, etc. shown in the following examples can be appropriately changed as long as they do not depart from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0564] [Example 1]

[0565] (Formation of alignment film)

[0566] As a support, a glass substrate was prepared. The following alignment film-forming coating solution was applied to the support by spin coating. The support having the coating film of the alignment film-forming coating solution was dried on a hot plate at 60 ° C for 60 seconds to form an alignment film.

[0567] Alignment film-forming coating solution

[0568]

[0569] -Raw materials for photo-alignment-

[0570] [Chemical formula 17]

[0571]

[0572] (Exposure of alignment film)

[0573] Using Figure 3 the exposure apparatus shown, the regions 1 and 2 of the alignment film were respectively exposed to form an alignment film P-1 having an alignment pattern. At this time, with respect to region 1, after rotating the alignment direction of the alignment film by 180 ° in region 2, exposure was performed, whereby the alignment patterns of regions 1 and 2 were inverted by 180 °. In the exposure apparatus, a device that emits a laser beam having an emission wavelength (325 nm) was used as the laser. The exposure amount based on the interference light was set to 300 mJ / cm 2 . In addition, one period (the length at which the optical axis rotates by 180 °) Λ of the alignment pattern formed by the interference of two laser beams was controlled to 0.43 μm by changing the crossing angle (crossing angle α) of the two lights.

[0574] (Formation of optically anisotropic layer)

[0575] As the liquid crystal composition for forming an optically anisotropic layer, the following composition LC-1 was prepared.

[0576] Composition LC-1

[0577]

[0578] Rod-like liquid crystal compound L-1

[0579] [Chemical formula 18]

[0580]

[0581] Rod-like liquid crystal compound L-2

[0582] [Chemical formula 19]

[0583]

[0584] Chiral reagent Ch-1

[0585] [Chemical formula 20]

[0586]

[0587] Leveling agent T-1

[0588] [Chemical formula 21]

[0589]

[0590] Leveling agent T-2

[0591] [Chemical formula 22]

[0592]

[0593] The prepared composition LC-1 was coated on the alignment film P-1 to form a composition layer. For the coating, a spin coater was used for coating at 1500 rpm. The support having the composition layer was heated on a hot plate at 90 °C for 1 minute. Then, a mask MK-1 was placed on the composition layer, and ultraviolet light with a wavelength of 365 nm was irradiated through the mask MK-1 at 40 °C under the atmosphere using a 365 nm LED UV exposure machine at an illuminance of 30 mW / cm 2 for 10 seconds. The relationship between the irradiation amount of the ultraviolet light irradiated through the mask MK-1 to the composition layer and the positions of the respective regions of the alignment film is as Figure 17 shown.

[0594] Next, a heat treatment was performed at 165 °C (above the liquid crystal phase-isotropic phase (Iso) of the liquid crystal composition) for 1 minute, and ultraviolet rays with a wavelength of 365 nm were irradiated onto the coating film with an irradiation dose of 300 mJ / cm 2 using a 365 nm LED UV exposure machine under a nitrogen atmosphere at 165 °C, thereby fixing the orientation of the liquid crystal compound and forming an optically anisotropic layer. According to cross-sectional SEM measurement, the optically anisotropic layer has a region with a high birefringence where bright and dark parts can be visually recognized and an optically isotropic region where bright and dark parts cannot be visually recognized in the thickness direction. In region 2, the thickness of the region with a high birefringence gradually changes. The thickness of the high birefringence layer is shown in Figure 18 .

[0595] The distribution of the retardation Re(40) in the tilt direction is shown in Figure 19 . The optically anisotropic layer has an average value Δna of the birefringence in the thickness direction in different regions (birefringence change regions) within the plane of the optically anisotropic layer.

[0596] [Evaluation]

[0597] (Evaluation of diffraction efficiency)

[0598] As shown in Figure 14 , the optically anisotropic layer 18 fabricated above was disposed on the surface of a double prism, and the diffraction efficiency at each position of the optically anisotropic layer was evaluated. In Figure 14 , as the double prism 110, a double prism made of glass with a refractive index of 1.5 was used. Also, the optically anisotropic layer was used after being peeled off from the glass substrate. The optically anisotropic layer and the double prism were bonded using a thermosensitive adhesive.

[0599] As shown in Figure 14 , the optically anisotropic layer was disposed on the upper surface of the double prism, a laser was disposed in such a manner as to face the inclined surface of the double prism, and a linear polarizer 112 and a λ / 4 plate 114 were disposed between the laser and the double prism 110.

[0600] If light is emitted from the laser, it passes through the linear polarizer 112 and the λ / 4 plate 114, thereby becoming right-handed circularly polarized light and entering the double prism 110, propagating within the double prism 110 and entering the optically anisotropic layer. The diffracted light reflected and diffracted by the optically anisotropic layer propagates in the double prism 110 in a direction opposite to the surface on which the optically anisotropic layer is disposed. The light propagating in the double prism 110 reaches the lower surface of the double prism 110 and is emitted.

[0601] When Figure 17When the position of the end on the side where the laser beam is incident on the optically anisotropic layer was set to 0 mm, the laser beam was incident on each position at the 5 mm scale, and the diffraction efficiency at each position was measured. In addition, the wavelength of the laser beam was set to 532 nm, and the incident angle of the laser beam was set such that light was incident on the optically anisotropic layer at 55.6° with respect to the normal direction of the optically anisotropic layer, and the light intensity of the light reflected and diffracted by the optically anisotropic layer and emitted in the normal direction of the optically anisotropic layer (the normal direction of the lower surface of the double prism 110) was measured.

[0602] Regarding the diffraction efficiency Deff of the fabricated optically anisotropic layer, when the light intensity of the laser beam incident on the double prism 110 is set to I in , and the light intensity of the light diffracted by the optically anisotropic layer and emitted from the double prism 110 is set to I out , it is calculated by the following formula.

[0603] Diffraction efficiency Deff = I out / I in

[0604] In addition, when calculating the diffraction efficiency, the loss of transmittance at the interfaces when incident on and exiting the double prism 110 was excluded, and the diffraction efficiency was calculated.

[0605] As a result of evaluating the diffraction efficiency of the optically anisotropic layer fabricated by the above method, the diffraction efficiency at the position of 25 mm was 13%, the diffraction efficiency at the position of 35 mm was 21%, and the diffraction efficiency at the position of 45 mm was 58%.

[0606] [Evaluation]

[0607] (Evaluation of the emitted light intensity distribution)

[0608] As Figure 13 shown, a light guide element was fabricated by disposing the optically anisotropic layer (symbol 400) fabricated above on the surface of the light guide plate 144. In Figure 13 , as the light guide plate 144, a glass light guide plate with a refractive index of 1.5, a thickness of 1 mm was used. And the optically anisotropic layer was used after being peeled off from the glass substrate. The optically anisotropic layer and the light guide plate 144 were bonded using a thermosensitive adhesive.

[0609] As Figure 13As shown, a laser is arranged to face the side opposite to the surface on which the optical anisotropic layer 400 is arranged, of the end on the side where the first diffraction region 45a is arranged in the light guide plate 144, and a linear polarizer 100 and a λ / 4 plate 102 are arranged between the laser and the light guide plate 144. A power meter (not shown) is arranged at a distance of 10 cm from the optical anisotropic layer, facing the side opposite to the surface on which the optical anisotropic layer 400 is arranged, of the end on the side where the second diffraction region 45c is arranged in the light guide plate 144. In addition, the wavelength of the laser beam is set to 532 nm, and the beam diameter of the laser beam is set to 1 mm.

[0610] When light is emitted from the laser, it passes through the linear polarizer 100 and the λ / 4 plate 102, and thus becomes right-handed circularly polarized light and is incident on the light guide plate 144. The light incident on the light guide plate 144 is incident on the first diffraction region 45a of the optical anisotropic layer 400. Through the diffraction action and the selective reflection action of the first diffraction region 45a of the optical anisotropic layer 400, the diffracted light that is reflected and diffracted propagates in the light guide plate 144. The light propagating in the light guide plate 144 is diffracted and reflected by the second diffraction region 45c of the optical anisotropic layer 400 and is emitted toward the direction of the power meter.

[0611] Moreover, a light shielding plate 104 is arranged between the light guide plate 144 and the power meter, facing the side opposite to the surface on which the optical anisotropic layer 400 is arranged. A pinhole 104a with a diameter of 2 mm is formed in the light shielding plate 104.

[0612] The intensity of the light emitted from the light guide plate 144 (the intensity of the emitted light) was measured through the pinhole 104a of the light shielding plate 104. By changing the position of the pinhole 104a, the intensity of the emitted light was measured at each position of the second diffraction region 45c. The intensity of the emitted light was measured using a power meter 1918-C manufactured by Newport Corporation.

[0613] The light quantity of the light emitted from the light guide plate 144 was confirmed, and as a result, it was confirmed that the emission intensity was the same.

[0614] [Example 2]

[0615] The prepared composition LC-1 was coated on the alignment film P-1 to form a composition layer. For the coating, a spin coater was used to perform the coating at 1500 rpm. The support having the composition layer was heated on a hot plate at 90 °C for 1 minute. Then, a mask MK-1 was arranged on the composition layer, and through the mask MK-1, a 365 nm LED UV exposure machine was used at 40 °C under the atmosphere at 30 mW / cm 2The illuminance was exposed to ultraviolet light with a wavelength of 365 nm for 5 seconds. The positional relationship between the illuminance of the ultraviolet light irradiated onto the composition layer through the mask MK-1 and each region of the alignment film is as Figure 17 shown.

[0616] Next, a heat treatment was performed at 150 °C (lower than the liquid crystal phase-isotropic phase (Iso) of the liquid crystal composition) for 1 minute, and at 150 °C in a nitrogen atmosphere, a 365 nm LED UV exposure machine was used to irradiate the coated film with ultraviolet light at an irradiation dose of 300 mJ / cm 2 Thereby, the alignment of the liquid crystal compound was fixed to form an optically anisotropic layer. According to cross-sectional SEM measurement, the optically anisotropic layer has a region with a high birefringence having a large contrast between the bright part and the dark part and a region with a low birefringence having a small contrast between the bright part and the dark part in the thickness direction, and the thickness of the region with a high birefringence gradually changes. The thickness of the high birefringence layer is shown in Figure 20 .

[0617] The distribution of the tilt direction retardation Re(40) is shown in Figure 21 . The optically anisotropic layer has an average birefringence Δna in the thickness direction that is different in the in-plane regions of the optically anisotropic layer.

[0618] As a result of evaluating the diffraction efficiency of the optically anisotropic layer by the same method as in Example 1, the diffraction efficiency at the position of 25 mm was 10%, the diffraction efficiency at the position of 35 mm was 21%, and the diffraction efficiency at the position of 45 mm was 60%.

[0619] A light guide element was fabricated by the same method as in Example 1, and the light quantity of the emitted light was confirmed. As a result, it was confirmed that the emission intensity was the same.

[0620] [Example 3]

[0621] (Formation of Optically Anisotropic Layer)

[0622] As the liquid crystal composition for forming the optically anisotropic layer, the following composition LC-3 was prepared.

[0623] Composition LC-3

[0624]

[0625]

[0626] Ultraviolet absorber UV-1: Octyl (2Z,4E)-5-(diethylamino)-2-(phenylsulfonyl)penta-2,4-dienoate

[0627] The prepared composition LC-3 was coated on the alignment film P-1 to form a composition layer. For the coating, a spin coater was used for coating at 1500 rpm. The support having the composition layer was heated on a hot plate at 90 °C for 1 minute. Then, a mask MK-1 was placed on the composition layer, and ultraviolet light with a wavelength of 365 nm was irradiated through the mask MK-1 using a 365 nm LED UV exposure machine at 40 °C in a nitrogen atmosphere with an illuminance of 30 mW / cm 2 for 2 seconds. The positional relationship between the illuminance of the ultraviolet light irradiated onto the composition layer through the mask MK-1 and each region of the alignment film is as Figure 17 shown.

[0628] Then, a heat treatment was performed at 165 °C (above the liquid crystal phase-isotropic phase (Iso) of the liquid crystal composition) for 1 minute, and ultraviolet light with a wavelength of 365 nm was irradiated onto the coating film through a 365 nm LED UV exposure machine at 165 °C in a nitrogen atmosphere with an irradiation dose of 300 mJ / cm 2 to fix the orientation of the liquid crystal compound, thereby forming an optically anisotropic layer. Then, a part of the optically anisotropic layer was etched, and the thickness-direction birefringence Δn was calculated based on the difference in the phase difference before and after etching, thereby measuring the thickness-direction birefringence distribution. As a result, it was confirmed that the birefringence gradually changed in the thickness direction.

[0629] The distribution of the tilt-direction retardation Re(40) is shown in Figure 22 . The optically anisotropic layer 3 has an average value Δna of the birefringence in the thickness direction that is different in different regions within the plane of the optically anisotropic layer.

[0630] As a result of evaluating the diffraction efficiency of the optically anisotropic layer by the same method as in Example 1, the diffraction efficiency at the position of 25 mm was 12%, the diffraction efficiency at the position of 35 mm was 20%, and the diffraction efficiency at the position of 45 mm was 59%.

[0631] A light guide element was fabricated by the same method as in Example 1, and the light quantity of the emitted light was confirmed. As a result, it was confirmed that the emission intensity was the same.

[0632] In addition, the optically anisotropic layers of Examples 1 to 3 were all smooth, and the in-plane film thickness distribution was within ±50 nm, and no scattered light caused by the unevenness of the optically anisotropic layer was confirmed.

[0633] [Example 4]

[0634] (Formation of Optically Anisotropic Layer)

[0635] As the liquid crystal composition for forming the optically anisotropic layer, the following composition LC-4 was prepared.

[0636] Composition LC-4

[0637]

[0638]

[0639] Rod-like liquid crystal compound L-4

[0640] [Chemical formula 23]

[0641]

[0642] The prepared Composition LC-4 was coated on the alignment film P-1 to form a composition layer. For the coating, spin coating was performed at 1500 rpm. The support having the composition layer was heated on a hot plate at 140 °C for 1 minute. Then, a mask MK-1 was placed on the composition layer, and ultraviolet light with a wavelength of 365 nm was irradiated through the mask MK-1 at 100 °C under atmospheric pressure using a 365 nm LED UV exposure machine at an illuminance of 30 mW / cm 2 for 5 seconds.

[0643] Then, a heat treatment was performed at 200 °C (above the liquid crystal phase-isotropic phase (Iso) of the liquid crystal composition) for 1 minute, and ultraviolet light with a wavelength of 365 nm was irradiated on the coating film at 200 °C under a nitrogen atmosphere using a 365 nm LED UV exposure machine at an irradiation dose of 300 mJ / cm 2 to fix the alignment of the liquid crystal compound and form an optically anisotropic layer.

[0644] Then, as a result of evaluating the diffraction efficiency of the optically anisotropic layer by the same method as in Example 1, the diffraction efficiency at the position of 25 mm was 13%, the diffraction efficiency at the position of 35 mm was 20%, and the diffraction efficiency at the position of 45 mm was 58%.

[0645] A light guide element was fabricated by the same method as in Example 1, and the amount of light emitted was confirmed. As a result, it was confirmed that the emission intensity was the same.

[0646] [Example 5]

[0647] (Formation of optically anisotropic layer)

[0648] As the liquid crystal composition for forming the optically anisotropic layer, the following Composition LC-5 was prepared.

[0649] Composition LC-5

[0650]

[0651] Rod-like liquid crystal compound L-5

[0652] [Chemical formula 24]

[0653]

[0654] The prepared composition LC-5 was coated on the alignment film P-1 to form a composition layer. For the coating, a spin coater was used for coating at 1500 rpm. The support having the composition layer was heated on a hot plate at 140 °C for 1 minute. Then, a mask MK-1 was placed on the composition layer, and ultraviolet light with a wavelength of 365 nm was irradiated through the mask MK-1 at 80 °C in the atmosphere using a 365 nm LED UV exposure machine at an illuminance of 30 mW / cm 2 for 5 seconds.

[0655] Then, a heat treatment was performed at 200 °C (above the liquid crystal phase-isotropic phase (Iso) of the liquid crystal composition) for 1 minute, and ultraviolet light with a wavelength of 365 nm was irradiated onto the coating film at 200 °C in a nitrogen atmosphere using a 365 nm LED UV exposure machine at an irradiation dose of 300 mJ / cm 2 to fix the alignment of the liquid crystal compound, thereby forming an optically anisotropic layer.

[0656] Then, as a result of evaluating the diffraction efficiency of the optically anisotropic layer by the same method as in Example 1, the diffraction efficiency at the position of 25 mm was 13%, the diffraction efficiency at the position of 35 mm was 21%, and the diffraction efficiency at the position of 45 mm was 58%.

[0657] A light guide element was fabricated by the same method as in Example 1, and the light quantity of the emitted light was confirmed. As a result, it was confirmed that the emission intensity was the same.

[0658] In addition, the optically anisotropic layers of Examples 4 to 5 were all smooth, and the in-plane film thickness distribution was within ±50 nm, and no scattered light caused by the unevenness of the optically anisotropic layer was confirmed.

[0659] [Example 6]

[0660] (Formation of optically anisotropic layer)

[0661] As the liquid crystal composition for forming the optically anisotropic layer, the following composition LC-6 was prepared.

[0662] Composition LC-6

[0663]

[0664] Rod-like liquid crystal compound L-6

[0665] [Chemical formula 25]

[0666]

[0667] The prepared composition LC-6 was coated on the alignment film P-1 to form a composition layer. For the coating, a spin coater was used for coating at 1500 rpm. The support having the composition layer was heated on a hot plate at 140 °C for 1 minute. Then, a mask MK-1 was placed on the composition layer, and ultraviolet light with a wavelength of 365 nm was irradiated through the mask MK-1 at 120 °C under the atmosphere using a 365 nm LED UV exposure machine at an illuminance of 30 mW / cm 2 for 5 seconds.

[0668] Then, a heat treatment was performed at 200 °C (above the liquid crystal phase-isotropic phase (Iso) of the liquid crystal composition) for 1 minute, and ultraviolet light with a wavelength of 365 nm was irradiated on the coating film at 200 °C under a nitrogen atmosphere using a 365 nm LED UV exposure machine at an irradiation dose of 300 mJ / cm 2 to fix the alignment of the liquid crystal compound and form an optically anisotropic layer.

[0669] Then, as a result of evaluating the diffraction efficiency of the optically anisotropic layer by the same method as in Example 1, the diffraction efficiency at the position of 25 mm was 13%, the diffraction efficiency at the position of 35 mm was 21%, and the diffraction efficiency at the position of 45 mm was 57%.

[0670] A light guide element was fabricated by the same method as in Example 1, and the light quantity of the emitted light was confirmed. As a result, it was confirmed that the emission intensity was the same.

[0671] In addition, the optically anisotropic layer was smooth, and the in-plane film thickness distribution was within ±50 nm, and no scattered light caused by the unevenness of the optically anisotropic layer was confirmed.

[0672] [Example 7]

[0673] (Formation of Optically Anisotropic Layer)

[0674] As the liquid crystal composition for forming the optically anisotropic layer, the following composition LC-7 was prepared.

[0675] Composition LC-7

[0676]

[0677] Rod-like liquid crystal compound L-7

[0678] [Chemical Formula 26]

[0679]

[0680] The prepared composition LC-7 was coated on the alignment film P-1 to form a composition layer. For the coating, a spin coater was used for coating at 1500 rpm. The support having the composition layer was heated on a hot plate at 140 °C for 1 minute. Then, a mask MK-1 was placed on the composition layer, and ultraviolet rays with a wavelength of 365 nm were exposed through the mask MK-1 at 120 °C under the atmosphere using a 365 nm LED UV exposure machine at an illuminance of 30 mW / cm 2 for 5 seconds.

[0681] Then, a heat treatment was performed at 200 °C (above the liquid crystal phase-isotropic phase (Iso) of the liquid crystal composition) for 1 minute, and ultraviolet rays with a wavelength of 365 nm were irradiated on the coating film at an irradiation dose of 300 mJ / cm 2 using a 365 nm LED UV exposure machine at 200 °C under a nitrogen atmosphere, thereby fixing the orientation of the liquid crystal compound and forming an optically anisotropic layer.

[0682] Then, as a result of evaluating the diffraction efficiency of the optically anisotropic layer by the same method as in Example 1, the diffraction efficiency at the position of 25 mm was 13%, the diffraction efficiency at the position of 35 mm was 21%, and the diffraction efficiency at the position of 45 mm was 57%.

[0683] A light guide element was fabricated by the same method as in Example 1, and the light quantity of the emitted light was confirmed. As a result, it was confirmed that the emission intensity was the same.

[0684] In addition, the optically anisotropic layer was smooth, and the in-plane film thickness distribution was within ±50 nm, and no scattered light caused by the unevenness of the optically anisotropic layer was confirmed.

[0685] [Comparative Example 1]

[0686] The alignment film fabricated by the same method as in Example 1 was exposed using the Figure 3 exposure apparatus shown, and an alignment film P-2 having a single alignment pattern was formed. In the exposure apparatus, a device that emits a laser beam with an emission wavelength (325 nm) was used as the laser. The exposure dose based on the interference light was set to 300 mJ / cm 2 . In addition, one period (the length of the optical axis rotation of 180°) Λ of the alignment pattern formed based on the interference of two laser beams was controlled to 0.43 μm by changing the crossing angle (crossing angle α) of the two lights.

[0687] The composition LC-1 was coated on the alignment film P-2 by the same method as in Example 1 to form a composition layer. For the coating, spin coating was performed at 1500 rpm. The support having the composition layer was heated on a hot plate at 90 °C for 1 minute. Then, without using a mask, ultraviolet rays with a wavelength of 365 nm were irradiated on the coating film at an irradiation dose of 300 mJ / cm 2 to fix the alignment of the liquid crystal compound, thereby forming an optically anisotropic layer.

[0688] Next, as a result of evaluating the diffraction efficiency of the optically anisotropic layer by the same method as in Example 1, the diffraction efficiency was 58% regardless of the position.

[0689] Next, the optically anisotropic layer was cut out, peeled off from the glass substrate, and disposed on the surface of the light guide plate to have the Figure 23 shown thickness distribution. In Figure 23 , the symbol 241 is the area where the optically anisotropic layer is disposed after being cut out. The symbol 242 is the area where the optically anisotropic layer is cut out and disposed in a direction reversed by 180 °C with respect to the symbol 241. The optically anisotropic layer is not disposed at the symbol 243, and the optically anisotropic layers corresponding to the symbol 241 and the symbol 242 are not continuous. That is, as Figure 24 shown, the optically anisotropic layer on the incident side and the optically anisotropic layer on the emission side are not continuous.

[0690] Next, by the same method as in Example 1, a laser beam was made incident on the optically anisotropic layer on the incident side of the light guide element, and the amount of light emitted was confirmed. As a result, it was confirmed that the emission intensity was uneven. Also, it was confirmed that scattered light was generated when the laser was irradiated on the stepped portion of the thickness.

[0691] Industrial Applicability

[0692] It can be preferably used for various applications that reflect light in optical devices, such as diffraction elements of a light guide plate for making light incident on and emitted from an AR glasses.

[0693] Symbol Explanation

[0694] 10, 12 - Liquid crystal diffraction element, 16, 18 - Optically anisotropic layer, 20 - Support, 24 - Alignment film, 30 - Liquid crystal compound, 30A - Optical axis, 40 - Display (image display device), 45 - Light guide element, 45a - First diffraction region, 45b - Non-diffraction region, 45c - Second diffraction region, 45d - Third diffraction region, 50 - AR display device, 60 - Exposure device, 62 - Laser, 64 - Light source, 68 - Beam splitter, 70A, 70B - Mirrors, 72A, 72B - λ / 4 plates, 100 - Linear polarizer, 102 - λ / 4 plate, 104 - Light shielding plate, 104a - Pinhole, 110 - Biprism, 112 - Linear polarizer, 114 - λ / 4 plate, 144 - Light guide plate, 320 - Support, 322 - Alignment film, 324 - Optically anisotropic layer (coating film), 326 - High birefringence region (first region), 328 - Low birefringence region (second region), 329 - Photomask, 330 - Dark part, 332 - Light part, 340, 400, 450 - Optically anisotropic layers, 400a - First optically anisotropic layer, 400b - Second optically anisotropic layer, 450 - Optically anisotropic layer, 410a, 420a - First diffraction regions, 410b, 420b - Non-diffraction regions, 410c, 420c - Second diffraction regions, 500 - Laminate, M - Laser beam, MA, MB - Light rays, P O - Linearly polarized light, P R - Right-handed circularly polarized light, P L - Left-handed circularly polarized light, α - Crossing angle, L1, L4 - Incident lights, L2, L5 - Reflected lights, R R - Right-handed circularly polarized light of red light, I0~I3 - Lights propagating in the light guide plate, P1~P4 - Positions, R1~R4 - Lights.

Claims

1. An optically anisotropic layer, characterized in that, the optically anisotropic layer is an optically anisotropic layer formed using a composition containing a liquid crystal compound, at least a part of the optically anisotropic layer in the plane has a birefringence change region, the birefringence Δn of the birefringence change region is different in the thickness direction, and the average value Δna of the birefringence in the thickness direction is different in the plane of the optically anisotropic layer.

2. The optically anisotropic layer according to claim 1, wherein, in the birefringence change region, from one side to the other side in at least one direction in the plane of the optically anisotropic layer, the average value Δna of the birefringence in the thickness direction gradually changes.

3. The optically anisotropic layer according to claim 1 or 2, wherein, in the birefringence change region, the birefringence Δn gradually changes in the thickness direction.

4. An optically anisotropic layer, wherein, the optically anisotropic layer is an optically anisotropic layer formed using a composition containing a liquid crystal compound, in at least a part of the optically anisotropic layer in the plane, there is a birefringence change region having a region with a large birefringence in the thickness direction and a region with a small birefringence, in the birefringence change region, the ratio of the thickness of the region with a large birefringence to the thickness of the optically anisotropic layer is different in the plane of the optically anisotropic layer, whereby the average value Δna of the birefringence in the thickness direction is different in the plane of the optically anisotropic layer.

5. The optically anisotropic layer according to claim 4, wherein, in the birefringence change region, from one side to the other side in at least one direction in the plane of the optically anisotropic layer, the ratio of the thickness of the region with a large birefringence to the thickness of the optically anisotropic layer gradually changes.

6. The optically anisotropic layer according to claim 4 or 5, wherein, the region with a small birefringence is optically isotropic.

7. The optically anisotropic layer according to claim 1 or 4, wherein, in the birefringence change region, there is a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates and changes along at least one direction in the plane.

8. The optically anisotropic layer according to claim 7, wherein, in the birefringence change region, the direction in which the average value Δna of the birefringence in the thickness direction gradually changes is parallel to the direction in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates and changes.

9. The optically anisotropic layer according to claim 7, wherein, in the birefringence change region, the liquid crystal compound is twisted.

10. The optically anisotropic layer according to claim 7, wherein, in the birefringence change region, the liquid crystal compound is cholesterically oriented.

11. The optically anisotropic layer according to claim 1 or 4, wherein, in the optically anisotropic layer, at least a part of the plane different from the birefringence change region is composed only of optically isotropic regions.

12. The optically anisotropic layer according to claim 1 or 4, wherein, in the optically anisotropic layer, at least a part of the plane different from the birefringence change region is composed only of optically non-isotropic regions.

13. The optically anisotropic layer according to claim 1 or 4, wherein, in the optically anisotropic layer, the liquid crystal compounds in at least a part of the plane different from the birefringence change region are aligned in one direction in the same plane.

14. The optically anisotropic layer according to claim 7, wherein, in the optically anisotropic layer, there are regions in the plane having different rotation directions of the optical axes derived from the liquid crystal compounds in the liquid crystal alignment pattern.

15. The optically anisotropic layer according to claim 7, wherein, in the optically anisotropic layer, there are regions where the liquid crystal compounds are in a right-handed helical cholesteric alignment and regions where they are in a left-handed helical cholesteric alignment.

16. A light guide element, comprising: a light guide plate; and the optically anisotropic layer according to claim 1 or 4 disposed on the surface of the light guide plate.

17. An AR display device, comprising the light guide element according to claim 16 and an image display device.

Images