Optically anisotropic layer, laminate, light guide element, and AR display device

Abstract

Provided are an optically anisotropic layer capable of emitting highly clear light from a light guide plate, a laminate, and a light guide element and an AR display device using the optically anisotropic layer. Provided is an optically anisotropic layer which is formed using a composition containing a liquid crystal compound and which has, in the in-plane direction of the same optically anisotropic layer: a region A in which the liquid crystal compound is contained in a region B in which the liquid crystal compound is contained; a liquid crystal alignment pattern in which the orientation from the optical axis of the liquid crystal compound changes while continuously rotating in at least one direction in the plane; a region B having a liquid crystal alignment pattern in which the orientation originating from the optical axis of the liquid crystal compound changes while continuously rotating in at least one direction in the plane; and a region that does not have a liquid crystal alignment pattern.

Description

Technical Field

[0001] The present invention relates to an optically anisotropic layer that diffracts incident light, a laminate, 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 referred to as smart glasses, head-mounted displays (HMDs (Head Mounted Displays)), and the like.

[0003] As shown in Non-Patent Document 1, as an example, an AR glass incident the image displayed by a display (optical engine) on one end of a light guide plate and propagates it, and emits it from the other end, thereby superimposing and displaying a virtual image in the scene actually seen by the user. In the AR glass, a diffraction element is used to diffract (refract) the 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.

[0004] As such a diffraction grating, a diffraction element using liquid crystal is known. For example, Patent Document 1 describes an optical element including 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 stacked birefringent sub-layers having a local optical axis that changes along a corresponding interface between adjacent ones of 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 the 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, thereby guiding 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).

[0005] In Patent Document 2, there is described a polarization diffraction grating including 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, an anisotropic alignment pattern corresponding to a polarization hologram is 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 each have a layer thickness d determined by d ≤ dmax = Λ / 2, where d is the layer thickness and Λ is the pitch of the polarization diffraction grating.

[0006] In Patent Document 3, there is described a reflection structure including a plurality of helical structures each extending along a specified direction, and having a first incident surface that intersects the specified direction and allows light to enter, and a reflection surface that 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 plurality of helical structures. Each of the plurality of helical 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 structural unit among 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 helical structures are the same. The reflection surface includes at least one first end portion included in each of the plurality of helical structures. The reflection surface is not parallel to the first incident surface.

[0007] Here, it is known to expand the viewing field (exit pupil expansion) by adopting the following structure in an AR glasses: when diffracting the light propagating in a light guide plate with a diffraction element while 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.

[0008] For example, Patent Document 4 describes 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.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-522601

[0012] Patent Document 2: Japanese Patent No. 5276847

[0013] Patent Document 3: International Publication No. 2016 / 194961

[0014] Patent Document 4: International Publication No. 2017 / 180403

[0015] Non-Patent Document

[0016] 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

[0017] Technical Problem to be Solved by the Invention

[0018] 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 of the AR glasses (exit pupil expansion), a structure is provided in which the liquid crystal diffraction element diffracts a part of light at multiple positions and emits it outside the light guide plate, there is a problem that the clarity of the image is insufficient.

[0019] The subject of the present invention is to solve the problems of such prior art, and to provide an optically anisotropic layer, a laminate, a light guide element using the optically anisotropic layer, and an AR display device that can emit light with high clarity from the light guide plate.

[0020] Means for Solving the Technical Problem

[0021] [1] An optically anisotropic layer, characterized in that

[0022] the optically anisotropic layer is an optically anisotropic layer formed using a composition containing a liquid crystal compound,

[0023] the optically anisotropic layer has, in the in-plane direction of the same optically anisotropic layer:

[0024] Region A, 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 while changing;

[0025] Region B, 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 while changing; and

[0026] A region without a liquid crystal alignment pattern.

[0027] [2] The optically anisotropic layer according to [1], wherein,

[0028] the optically anisotropic layer further has a region C in the in-plane direction of the same optically anisotropic layer, and the region C 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.

[0029] [3] The optically anisotropic layer according to any one of [1] or [2], wherein,

[0030] the optically anisotropic layer has a region without a liquid crystal alignment pattern between the region A with a liquid crystal alignment pattern and the region B with a liquid crystal alignment pattern in the in-plane direction of the same optically anisotropic layer.

[0031] [4] The optically anisotropic layer according to any one of [1] to [3], wherein,

[0032] in at least one of the regions A and B, there are regions with different diffraction efficiencies in the in-plane direction.

[0033] [5] The optically anisotropic layer according to [4], wherein,

[0034] in at least one of the regions A and B, there are regions with gradually increasing diffraction efficiencies in the in-plane direction.

[0035] [6] The optically anisotropic layer according to any one of [1] to [5], wherein,

[0036] the rotation direction of the optical axis derived from the liquid crystal compound along one direction in the liquid crystal alignment pattern of region A is different from the rotation direction of the optical axis derived from the liquid crystal compound along one direction in the liquid crystal alignment pattern of region B.

[0037] [7] The optically anisotropic layer according to any one of [1] to [6], wherein,

[0038] one direction of the liquid crystal alignment pattern in region A is different from one direction of the liquid crystal alignment pattern in region B.

[0039] [8] The optically anisotropic layer according to any one of [1] to [7], wherein,

[0040] the length of the in-plane rotation of 180° of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of region A is different from the length of the in-plane rotation of 180° of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of region B.

[0041] [9] The optically anisotropic layer according to any one of [1] to [8], wherein

[0042] At least one of region A and region B is a cholesteric liquid crystal layer in which a liquid crystal compound is cholesterically oriented.

[0043]

[10] The optically anisotropic layer according to [9], wherein

[0044] Region A and region B are cholesteric liquid crystal layers,

[0045] The optically anisotropic layer has a region in which the pitch length of the cholesteric liquid crystal layer in region A is different from the pitch length of the cholesteric liquid crystal layer in region B.

[0046]

[11] The optically anisotropic layer according to [9] or

[10] , wherein

[0047] Region A and region B are cholesteric liquid crystal layers,

[0048] The rotational direction of the helix of the cholesteric orientation in region A is different from the rotational direction of the helix of the cholesteric orientation in region B.

[0049]

[12] The optically anisotropic layer according to any one of [9] to

[11] , wherein

[0050] In at least one of region A and region B, there is a region in which the pitch length of the cholesteric liquid crystal layer is different in the in-plane direction of the region.

[0051]

[13] The optically anisotropic layer according to any one of [9] to

[12] , wherein

[0052] In at least one of region A and region B, there is a region in which the pitch length of the cholesteric liquid crystal layer varies in the thickness direction of the optically anisotropic layer.

[0053]

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

[13] , wherein

[0054] In a region without a liquid crystal alignment pattern, at least a part of the in-plane is optically isotropic.

[0055]

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

[13] , wherein

[0056] In a region without a liquid crystal alignment pattern, at least a part of the liquid crystal compound in the in-plane is aligned in the same in-plane direction.

[0057]

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

[13] , wherein

[0058] In a region without a liquid crystal alignment pattern, at least a part of the in-plane is a retardation plate in which a liquid crystal compound is uniaxially aligned or twisted.

[0059]

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

[16] , wherein

[0060] The whole layer is smooth and does not have an uneven structure.

[0061]

[18] The optical anisotropic layer according to [4], wherein

[0062] At least one of region A and region B has a different in-plane thickness direction retardation Rth, thereby forming regions with different diffraction efficiencies.

[0063]

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

[18] .

[0064]

[20] The laminate according to

[19] , having two optical anisotropic layers, namely a first optical anisotropic layer and a second optical anisotropic layer,

[0065] Region A of the first optical anisotropic layer and region A of the second optical anisotropic layer are arranged at overlapping positions,

[0066] The region without a liquid crystal alignment pattern of the first optical anisotropic layer and the region without a liquid crystal alignment pattern of the second optical anisotropic layer are arranged at overlapping positions,

[0067] Region B of the first optical anisotropic layer and region B of the second optical anisotropic layer are arranged at overlapping positions.

[0068]

[21] The laminate according to

[20] , satisfying at least one of the following:

[0069] The length of one cycle in which the orientation of the optical axis derived from the liquid crystal compound in region A of the first optical anisotropic layer rotates 180° in the plane is different from the length of one cycle in region A of the second optical anisotropic layer; and

[0070] The length of one cycle in which the orientation of the optical axis derived from the liquid crystal compound in region B of the first optical anisotropic layer rotates 180° in the plane is different from the length of one cycle in region B of the second optical anisotropic layer.

[0071]

[22] The laminate according to

[20] or

[21] , satisfying at least one of the following:

[0072] One direction of the liquid crystal alignment pattern in region A of the first optically anisotropic layer is different from one direction of the liquid crystal alignment pattern in region A of the second optically anisotropic layer; and

[0073] One direction of the liquid crystal alignment pattern in region B of the first optically anisotropic layer is different from one direction of the liquid crystal alignment pattern in region B of the second optically anisotropic layer.

[0074]

[23] The laminate according to any one of

[20] to

[22] satisfies at least one of the following:

[0075] Region A of the first optically anisotropic layer and region A of the second optically anisotropic layer are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in region A of the first optically anisotropic layer is different from the length of the helical pitch of the cholesteric liquid crystal layer in region A of the second optically anisotropic layer; and

[0076] Region B of the first optically anisotropic layer and region B of the second optically anisotropic layer are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in region B of the first optically anisotropic layer is different from the length of the helical pitch of the cholesteric liquid crystal layer in region B of the second optically anisotropic layer.

[0077]

[24] The laminate according to any one of

[20] to

[23] satisfies at least one of the following:

[0078] Region A of the first optically anisotropic layer and region A of the second optically anisotropic layer are cholesteric liquid crystal layers, and the rotation direction of the helix of the cholesteric liquid crystal layer in region A of the first optically anisotropic layer is different from the rotation direction of the helix of the cholesteric liquid crystal layer in region A of the second optically anisotropic layer; and

[0079] Region B of the first optically anisotropic layer and region B of the second optically anisotropic layer are cholesteric liquid crystal layers, and the rotation direction of the helix of the cholesteric liquid crystal layer in region B of the first optically anisotropic layer is different from the rotation direction of the helix of the cholesteric liquid crystal layer in region B of the second optically anisotropic layer.

[0080]

[25] A light guide element having:

[0081] A light guide plate; and

[0082] The optically anisotropic layer according to any one of [1] to

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

[0083]

[26] The light guide element according to

[25] further has a retardation layer.

[0084]

[27] An AR display device having the light guide element and the image display device described in

[25] or

[26] .

[0085]

[28] The AR display device according to

[27] , wherein

[0086] The light emitted from the image display device is polarized light.

[0087]

[29] The AR display device according to

[27] or

[28] , wherein

[0088] The image display device is an image display device using a laser beam scanning method.

[0089] Effects of the Invention

[0090] According to the present invention, there can be provided an optically anisotropic layer, a laminate, a light guide element, and an AR display device using the optically anisotropic layer, which can emit light with high clarity from a light guide plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Figure 1 It is a conceptual diagram of an example of regions A and B included in the optically anisotropic layer of the present invention.

[0092] Figure 2 It is Figure 1 a top view of

[0093] Figure 3 It is a conceptual diagram of an example of an exposure device for exposing an alignment film.

[0094] Figure 4 It is for explaining Figure 1 the functions of regions A and / or B of the optically anisotropic layer of

[0095] Figure 5 It is a graph conceptually showing an example of the relationship between the position and the diffraction efficiency in regions A and / or B of the optically anisotropic layer.

[0096] Figure 6 It is a graph conceptually showing another example of the relationship between the position and the diffraction efficiency in regions A and / or B of the optically anisotropic layer.

[0097] Figure 7 It is a conceptual diagram of another example of regions A and B included in the optically anisotropic layer of the present invention.

[0098] Figure 8 It is Figure 7 a top view of

[0099] Figure 9 It is for explainingFigure 7 A diagram showing the functions of region A and / or region B of the optically anisotropic layer.

[0100] Figure 10 It is used to illustrate Figure 7 A diagram showing the functions of region A and / or region B of the optically anisotropic layer.

[0101] Figure 11 A diagram schematically showing an example of an AR display device having the optically anisotropic layer of the present invention.

[0102] Figure 12 A diagram conceptually showing the relationship between the position and the emitted light in the AR display device.

[0103] Figure 13 A diagram for explaining the method of measuring the intensity of the emitted light in the examples.

[0104] Figure 14 A schematic diagram for explaining the method of measuring the diffraction efficiency.

[0105] Figure 15 A diagram showing an example of the method of forming a region where the diffraction efficiency gradually changes in the in-plane direction of the optically anisotropic layer.

[0106] Figure 16 A diagram showing another example of the method of forming a region where the diffraction efficiency gradually changes in the in-plane direction of the optically anisotropic layer.

[0107] Figure 17 A diagram showing the amount of light irradiation based on the position of the optically anisotropic layer.

[0108] Figure 18 A diagram showing the diffraction efficiency based on the position of the optically anisotropic layer.

[0109] Figure 19 A diagram showing the retardation value based on the position of the optically anisotropic layer.

[0110] Figure 20 A diagram showing the amount of light irradiation based on the position of the optically anisotropic layer.

[0111] Figure 21 A diagram showing the diffraction efficiency based on the position of the optically anisotropic layer.

[0112] Figure 22 A diagram showing the retardation value based on the position of the optically anisotropic layer.

[0113] Figure 23 A diagram showing the diffraction efficiency based on the position of the optically anisotropic layer.

[0114] Figure 24 It is a diagram schematically showing an example of an AR display device having a conventional liquid crystal diffraction element.

[0115] Figure 25 It is a diagram showing an example of the in-plane distribution of diffraction efficiency represented by light and shade.

[0116] Figure 26 It is a diagram schematically showing a cross-section of the X-Z plane of region A and / or region B of the optically anisotropic layer.

[0117] Figure 27 It is a diagram schematically showing a cross-section of the X-Z plane of region A and / or region B of the optically anisotropic layer.

[0118] Figure 28 It is a diagram schematically showing a cross-section of the X-Z plane of region A and / or region B of the optically anisotropic layer.

[0119] Figure 29 It is a diagram conceptually showing an example of the optically anisotropic layer of the present invention.

[0120] Figure 30 It is Figure 29 a top view.

[0121] Figure 31 It is a diagram conceptually showing another example of the optically anisotropic layer of the present invention.

[0122] Figure 32 It is a diagram conceptually showing an example of a laminate having a plurality of optically anisotropic layers of the present invention. Detailed Description of the Invention

[0123] Hereinafter, based on the preferred embodiments shown in the drawings, the optically anisotropic layer, laminate, light guide element, and AR display device of the present invention will be described in detail.

[0124] In this specification, the numerical range represented by "~" means the range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In this specification, "(meth)acrylate" is used in the meaning of "either one or both of acrylate and methacrylate". In this specification, "the same" includes the error range generally allowed in the technical field. And, 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. And, regarding "orthogonal" and "parallel" of an angle, it means the range of a strict angle ±5°, and regarding "the same" of an angle, unless otherwise specified, it means the difference from the strict angle is within a range less than 5 degrees. The difference from the strict angle is preferably less than 4 degrees, and more preferably less than 3 degrees.

[0125] In this specification, visible light is light with 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. And, 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.

[0126] 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 the object (component) to be the object is set to Tmin (%).

[0127] Formula for obtaining the half-value transmittance: T1 / 2 = 100 - (100 - Tmin) ÷ 2

[0128] And, "equal" of 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" of 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, and more preferably 10 nm or less.

[0129] 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 the 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).

[0130] [Optically anisotropic layer]

[0131] The optically anisotropic layer of the present invention is an optically anisotropic layer formed using a composition containing a liquid crystal compound. The optically anisotropic layer has: region A, 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 while changing; region B, 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 while changing; and a region without a liquid crystal alignment pattern. As will be described later, regions A and B having a liquid crystal alignment pattern function as so-called liquid crystal diffraction elements that diffract incident light. Therefore, it can be said that the optically anisotropic layer of the present invention has a structure in which two liquid crystal diffraction elements and a liquid crystal layer without a diffraction effect are integrally formed. By having such a structure, the optically anisotropic layer of the present invention can be laminated on a light guide plate and emit light with high clarity from the light guide plate. Further, in at least one of regions A and B, it is preferable that the diffraction efficiency increases as one moves from one side to the other side in one direction of the liquid crystal alignment pattern. By having such a structure, when the light propagating in the light guide plate is diffracted by the liquid crystal diffraction element (region A or B) and emitted from the light guide plate, the brightness of the emitted light can be made uniform.

[0132] Regarding the change in the diffraction efficiency, the diffraction efficiency may also increase in a plurality of directions in the plane. Examples of the in-plane distribution of the diffraction efficiency are shown in Figure 25 . In Figure 25 , the darker the black region, 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.

[0133] Figure 29 is a diagram conceptually showing an example of the optically anisotropic layer of the present invention. Figure 30 is Figure 29 a top view of

[0134] Figure 29 and Figure 30 The optically anisotropic layer 400 shown is formed by using a composition containing a liquid crystal compound and forming an optically anisotropic layer having different alignment states of the liquid crystal compound in the in-plane direction, thereby forming region A45a, a region without a liquid crystal alignment pattern (hereinafter, also referred to as a non-diffraction region) 45b, and region B45c. The non-diffraction region 45b is disposed between region A45a and region B45c. In the following description, regions A45a and B45c are also referred to as diffraction regions.

[0135] Region A45a and region B45c each have a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one in-plane direction, and function as a liquid crystal diffraction element that diffracts incident light. Additionally, the liquid crystal alignment pattern of region A45a and the liquid crystal alignment pattern of region B45c may be the same or different.

[0136] Moreover, the thicknesses of region A45a, the non-diffraction region 45b, and region B45c are substantially the same, and the two main surfaces of the optically anisotropic layer 400 are smooth flat surfaces without an uneven structure.

[0137] [Region A and Region B]

[0138] Hereinafter, embodiments of a liquid crystal diffraction element including a cholesteric liquid crystal layer that can be used as region A and region B of the optically anisotropic layer of the present invention will be described.

[0139] [First Embodiment]

[0140] In Figure 1 a conceptual example of a first embodiment of a liquid crystal diffraction element is shown.

[0141] Figure 1 The liquid crystal diffraction element 10 shown selectively reflects light of a specific wavelength and diffracts the reflected light.

[0142] Figure 1 The liquid crystal diffraction element 10 shown has a structure in which a support 20, an alignment film 24, and a cholesteric liquid crystal layer 18 are laminated in sequence.

[0143] Additionally, Figure 1 the liquid crystal diffraction element 10 shown has a support 20 and an alignment film 24, but the liquid crystal diffraction element may also have a structure without the support 20 or further without the alignment film 24.

[0144] For example, the liquid crystal diffraction element can be configured to have only the alignment film 24 and the cholesteric liquid crystal layer 18 by peeling off the support 20 from the above structure. Or, the support 20 and the alignment film 24 can be peeled off to form the liquid crystal diffraction element consisting only of the cholesteric liquid crystal layer 18.

[0145] That is, the optically anisotropic layer of the present invention can be structured to be laminated on a support and an alignment film, can be structured to be laminated with an alignment film, or can be only the optically anisotropic layer.

[0146] That is, as long as the liquid crystal diffraction element 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 in-plane direction, various layer structures can be utilized. Regarding the above points, the liquid crystal diffraction elements of the respective embodiments described later are all the same.

[0147] <Support>

[0148] The support 20 is a thin film (sheet-like, plate-like) that supports the alignment film 24 and the cholesteric liquid crystal layer 18. In addition, the transmittance of the support 20 for the light diffracted by the cholesteric liquid crystal layer 18 is preferably 50% or more, more preferably 70% or more, and further preferably 85% or more.

[0149] 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 cholesteric liquid crystal layer 18 according to the use of the liquid crystal diffraction element 10 and the material for forming the support 20. 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.

[0150] The support 20 can be a single layer or a multi-layer. As the support 20 in the case of a single layer, various materials that can be used as a support in an optical element can be used. 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 multi-layer, a support including any one of the above single-layer supports as a substrate and having another layer provided on the surface of the substrate can be exemplified.

[0151] <Alignment Film>

[0152] An alignment film 24 is formed on the surface of the support 20. The alignment film 24 is an alignment film for aligning the liquid crystal compound 30 into a specified liquid crystal alignment pattern when forming the cholesteric liquid crystal layer 18.

[0153] As described later, in the liquid crystal diffraction element 10, the cholesteric liquid crystal layer 18 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A (reference Figure 2 ) derived from the liquid crystal compound 30 continuously rotates and changes along one in-plane direction. 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 and changes 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").

[0154] In the following description, "rotation of the orientation of the optical axis 30A" will also be simply referred to as "rotation of the optical axis 30A".

[0155] The alignment film can be any of various known alignment films. For example, a friction-treated 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 an LB (Langmuir-Blodgett) film of an organic compound such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate based on the Langmuir-Blodgett method can be exemplified.

[0156] The alignment film based on friction treatment can be formed by rubbing the surface of a polymer layer several times in a certain direction with paper or cloth. As the material used in the alignment film, polyimide, polyvinyl alcohol, a polymer having a polymerizable group described in Japanese Patent Laid-Open No. 9-152509, and materials used in the formation of the alignment films described in Japanese Patent Laid-Open Nos. 2005-097377, 2005-099228, and 2005-128503 are preferred.

[0157] In the liquid crystal diffraction element 10, the alignment film is preferably a so-called photo-alignment film formed by irradiating a raw material having photo-alignment properties 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-alignment material on the support 20 is preferred.

[0158] The photo-alignment film can be irradiated with polarized light from the vertical direction or an inclined direction, and can be irradiated with non-polarized light from an inclined direction.

[0159] Examples of the photoalignment material that can be used in the photoalignment film applicable to the present invention include azo compounds described in JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, JP-A-2007-133184, JP-A-2009-109831, Japanese Patent No. 3883848, and Japanese Patent No. 4151746; aromatic ester compounds described in JP-A-2002-229039; maleimide and / or alkenyl-substituted nadimide compounds having a photoalignment unit described in JP-A-2002-265541 and JP-A-2002-317013; photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198; photocrosslinkable polyimide, photocrosslinkable polyamide, and photocrosslinkable polyester described in JP-T-2003-520878, JP-T-2004-529220, and Japanese Patent No. 4162850; and compounds capable of photodimerization described in JP-A-9-118717, JP-T-10-506420, JP-T-2003-505561, WO2010 / 150748, JP-A-2013-177561, and JP-A-2014-12823, particularly cinnamate compounds, chalcone compounds, and coumarin compounds, etc. are preferred examples. Among them, azo compounds, photocrosslinkable polyimide, photocrosslinkable polyamide, photocrosslinkable polyester, cinnamate compounds, and chalcone compounds are preferably used.

[0160] The thickness of the alignment film is not limited as long as it is appropriately set according to the material for forming the alignment film so that the required alignment function can be obtained. The thickness of the alignment film is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0161] 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.

[0162] In Figure 3 a conceptual example of an exposure apparatus for exposing the alignment film to form an alignment pattern is shown. Figure 3The exposure device 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, namely 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. Additionally, although not shown in the figure, the light source 64 has a λ / 2 plate, and linearly polarized light P0 is emitted by changing the polarization direction of the laser beam M emitted from the laser 62. 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 .

[0163] A support 20 having an alignment film 24 before forming an 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. Through the interference at this time, the polarization state of the light irradiated onto the alignment film 24 changes periodically in an interference fringe pattern. Thereby, an alignment pattern with a periodically changing alignment state can be obtained in the alignment film 24. In the exposure device 60, by changing the crossing angle α between the two light beams MA and MB, the period of the alignment pattern can be adjusted. That is, in the exposure device 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 where the optical axis 30A of the liquid crystal compound 30 continuously rotates in one direction can be adjusted. By forming a cholesteric liquid crystal layer on the alignment film having such an alignment pattern with a periodically changing alignment state, as will be described later, a cholesteric liquid crystal 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. And 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.

[0164] In addition, in a liquid crystal diffraction element, the alignment film is provided as a preferred mode and is not an essential component. For example, it can also be set to the following structure: By methods such as rubbing the support 20 or processing the support 20 with a laser beam, etc., an alignment pattern is formed on the support 20, so that the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which the orientation of the optical axis 30A of the liquid crystal compound 30 continuously rotates along at least one direction in the plane while changing.

[0165] <Cholesteric liquid crystal layer>

[0166] A cholesteric liquid crystal layer 18 is formed on the surface of the alignment film 24. The cholesteric liquid crystal layer 18 is a layer formed using a composition containing a liquid crystal compound, and has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates along at least one direction in the plane.

[0167] In Figure 1 In the example shown, the cholesteric liquid crystal layer 18 has a structure in which the liquid crystal compound is cholesterically aligned. That is, the cholesteric liquid crystal layer 18 is a layer in which the cholesteric liquid crystal phase is fixed, and has a cholesteric liquid crystal structure in which the liquid crystal compound is helically twisted and oriented along a helical axis parallel to the thickness direction. The cholesteric liquid crystal 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 in a spiral (rotating 360°) are helically rotated as one helical pitch.

[0168] The cholesteric liquid crystal layer 18 having a cholesteric liquid crystal structure has wavelength-selective reflectivity. For example, when the cholesteric liquid crystal layer 18 has a selective reflection center wavelength in the green wavelength region, it reflects the right-handed circularly polarized light G R , and transmits the light other than this. Here, in the cholesteric liquid crystal layer 18, the liquid crystal compound 30 rotates and aligns in the plane direction, so that the incident circularly polarized light is refracted (diffracted) and reflected in the direction (azimuth direction) in which the orientation of the optical axis continuously rotates. At this time, the azimuth direction of diffraction is different depending on the rotation direction of the incident circularly polarized light. That is, the cholesteric liquid crystal 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. Further, the cholesteric liquid crystal layer 18 changes the rotation direction of the reflected circularly polarized light to the opposite direction.

[0169] <<Cholesteric liquid crystal phase>>

[0170] The cholesteric liquid crystal phase exhibits selective reflectivity for left-handed circularly polarized light or right-handed circularly polarized light at specific wavelengths. The central wavelength of the selective reflection (selective reflection central 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 this helical structure, the selective reflection central 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. 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 page 196 of "Liquid Crystal Handbook" edited by the Liquid Crystal Handbook Editorial Committee and published by Maruzen can be used.

[0171] 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.

[0172] In Figure 1 the liquid crystal diffraction element 10, the cholesteric liquid crystal layer 18 is a layer in which a right-twisted cholesteric liquid crystal phase is fixed. In addition, the rotation direction 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.

[0173] 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 carried out by adjusting Δn. Δn can be adjusted according to the type of liquid crystal compound forming the optically anisotropic layer and its mixing ratio, as well as the temperature at the time of orientation fixation. 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 - 500 nm, preferably 20 - 300 nm, and more preferably 30 - 100 nm.

[0174] <<Method for Forming a Cholesteric Liquid Crystal Layer Having a Cholesteric Liquid Crystal Structure>>

[0175] A cholesteric liquid crystal layer having a cholesteric liquid crystal structure (region A and / or region B in the optically anisotropic layer) can be formed by fixing the cholesteric liquid crystal phase in a layered manner. 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, a structure is preferably as follows: based on the orientation state of the polymerizable liquid crystal compound being the cholesteric liquid crystal phase, polymerization and curing are performed by ultraviolet irradiation, heating, etc., thereby forming a layer without fluidity, 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. In addition, the method for forming an optically anisotropic layer having region A and / or region B that becomes a cholesteric liquid crystal layer and a non-diffraction region will be described later.

[0176] In addition, in the structure formed by fixing the cholesteric liquid crystal phase, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained. In the cholesteric liquid crystal 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.

[0177] As a material used in the formation of a cholesteric liquid crystal layer formed by fixing the cholesteric liquid crystal phase, 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. In addition, the liquid crystal composition used in the formation of the cholesteric liquid crystal layer may also contain a surfactant and a chiral agent.

[0178] --Polymerizable liquid crystal compound--

[0179] The polymerizable liquid crystal compound can be a rod-like liquid crystal compound or a disc-like liquid crystal compound.

[0180] As an example of a rod-like polymerizable liquid crystal compound for forming a cholesteric liquid crystal phase, a rod-like nematic liquid crystal compound can be cited. As the rod-like nematic liquid crystal compound, it is preferably to use azomethines, azo oxides, cyanobiphenyls, cyanobenzoates, benzoates, phenyl cyclohexane carboxylates, cyanophenyl cyclohexanes, cyanide-substituted phenyl pyrimidines, alkoxy-substituted phenyl pyrimidines, phenyl dioxanes, diethynylbenzenes, alkenyl cyclohexyl benzonitriles, etc. Not only can low molecular liquid crystal compounds be used, but also high molecular liquid crystal compounds can be used.

[0181] The polymerizable 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, an oxetanyl 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 polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3.

[0182] Examples of the polymerizable 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 Laid-Open No. 1-272551, Japanese Patent Laid-Open No. 6-016616, Japanese Patent Laid-Open No. 7-110469, Japanese Patent Laid-Open No. 11-080081, and Japanese Patent Laid-Open No. 2001-328973, etc. Moreover, 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 also be preferably used. Two or more polymerizable liquid crystal compounds can be used simultaneously. If two or more polymerizable liquid crystal compounds are used simultaneously, the alignment temperature can be reduced.

[0183] Furthermore, as polymerizable liquid crystal compounds other than the above, a cyclic organopolysiloxane compound having a cholesteric phase as disclosed in Japanese Patent Laid-Open No. 57-165480 can be used. Moreover, as the above-mentioned high molecular liquid crystal compound, a polymer in which a mesogenic group exhibiting liquid crystal is introduced into the main chain, side chain, or both the main chain and side chain, a high molecular cholesteric liquid crystal in which a cholesteryl group is introduced into the side chain, a liquid crystalline polymer as disclosed in Japanese Patent Laid-Open No. 9-133810, and a liquid crystalline polymer as disclosed in Japanese Patent Laid-Open No. 11-293252 can be used.

[0184] --Discotic liquid crystal compound--

[0185] 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.

[0186] Moreover, relative to the solid component mass of the liquid crystal composition (the 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.

[0187] 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, inside the cholesteric liquid crystal layer, the maximum value of the birefringence Δn of the liquid crystal compound 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.

[0188] Most liquid crystal compounds showing such a 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, thickness, etc. described later, the diffraction efficiency of each wavelength can be kept constant.

[0189] For example, by forming a layer having a selective reflection band that diffracts incident light with a wavelength of 450 nm to be thinner and forming a layer having a selective reflection band that diffracts incident light with a wavelength of 550 nm to be thicker, the diffraction efficiency of each wavelength can be kept constant.

[0190] 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. Moreover, 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.

[0191] 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.

[0192] 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. Moreover, 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.

[0193] 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 satisfied within the range of 400 to 650 nm.

[0194] Inside the cholesteric liquid crystal layer, the minimum value of the birefringence Δn of the liquid crystal compound is preferably 0.00 to 0.40, more preferably 0.00 to 0.30, and even more preferably 0.00 to 0.20.

[0195] As specific examples of the polymeric liquid crystal compound having a large refractive index anisotropy, for example, Japanese Unexamined Patent Application Publication No. 2009-102245, Japanese Patent No. 4655348, Japanese Patent No. 4524827, Japanese Patent No. 4720200, Japanese Unexamined Patent Application Publication No. 2004-091380, Japanese Patent No. 3972430, Japanese Patent No. 4517416, Japanese Unexamined Patent Application Publication No. 2002-128742, Japanese Patent No. 4810750, Japanese Patent No. 5888544, Japanese Unexamined Patent Application Publication No. 2014-019654, Japanese Patent No. 6241654, Japanese Patent No. 6372060, Japanese Patent No. 6323144, Japanese Unexamined Patent Application Publication No. 2005-015406, Japanese Unexamined Patent Application Publication 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 Unexamined Patent Application Publication No. 2009-249406, Japanese Patent No. 4121075, Japanese Patent Application Laid-Open No. 2005-528416, US6514578, International Publication No. 06 / 006819, Japanese Unexamined Patent Application Publication No. 2011-184417, Japanese Unexamined Patent Application Publication No. 2013-095685, Japanese Unexamined Patent Application Publication No. 2013-103897, Japanese Unexamined Patent Application Publication No. 2002-088008, Japanese Unexamined Patent Application Publication No. 2002-226412, Japanese Unexamined Patent Application Publication No. 2012-167214, Japanese Unexamined Patent Application Publication No. 2012-167068, Japanese Patent Application Publication No. 2018-084511, Japanese Unexamined Patent Application Publication No. 2003-055317, Japanese Unexamined Patent Application Publication No. 2001-329264, Japanese Unexamined Patent Application Publication No. 2002-030016, Japanese Unexamined Patent Application Publication No. 2003-055664, Japanese Unexamined Patent Application Publication No. 2018-070889, CN102557896, US2015369982, Japanese Unexamined Patent Application Publication No. 2020-105264, Japanese Unexamined Patent Application Publication No. 2014-224237, Japanese Unexamined Patent Application Publication No. 2012-051862, Japanese Unexamined Patent Application Publication No. 2010-106274, Japanese Unexamined Patent Application Publication No. 2005-179557, Japanese Unexamined Patent Application Publication No. 2005-035985, Japanese Unexamined Patent Application Publication No. 2002-012579, Japanese Unexamined Patent Application Publication No. 2002-003845, Japanese Unexamined Patent Application Publication 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. 2010-503733Compounds 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.

[0196] In addition to the above, as the polymeric liquid crystal compound, the following compounds can also be cited.

[0197] [Chemical formula 1]

[0198]

[0199] [Chemical formula 2]

[0200]

[0201] [Chemical formula 3]

[0202]

[0203] [Chemical formula 4]

[0204]

[0205] [Chemical formula 5]

[0206]

[0207] [Chemical formula 6]

[0208]

[0209] [Chemical formula 7]

[0210]

[0211] [Chemical formula 8]

[0212]

[0213] [Chemical formula 9]

[0214]

[0215] --Surfactant--

[0216] The liquid crystal composition used when forming a cholesteric liquid crystal layer may contain a surfactant. The surfactant is preferably a compound that can function as an alignment control agent that helps to stably or rapidly achieve planar alignment of the cholesteric liquid crystal phase. As the surfactant, for example, silicone-based surfactants and fluorine-based surfactants can be cited, and fluorine-based surfactants can be preferably exemplified.

[0217] As specific examples of the surfactant, compounds described in paragraphs

[0082] to

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

[0031] to

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

[0092] and

[0093] of Japanese Patent Application Laid-Open No. 2005-99248, 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. can be cited. In addition, the surfactant can be used alone or two or more thereof can be used simultaneously.

[0218] As the fluorine-based surfactant, the compounds described in paragraphs

[0082] to

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

[0219] 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.

[0220] --Chiral reagent (optically active compound)--

[0221] A chiral agent has the function of inducing the helical structure of a cholesteric liquid crystal phase. The chiral agent induces different twisting directions or helical pitches of the helix depending on the compound, so it can be selected according to the purpose. There is no particular limitation on the chiral agent, and known compounds can be used (for example, those described in the liquid crystal device manual, Chapter 3, Item 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, isomannitol derivatives, etc.). Chiral agents 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 agents. Examples of axially asymmetric compounds or surface asymmetric compounds include binaphthyl, helicene, p-cyclophane, and their derivatives. The chiral agent can have a polymerizable group. When both the chiral agent 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 agent can be formed by the polymerization reaction of the polymerizable chiral agent and the polymerizable liquid crystal compound. In this way, the polymerizable group of the polymerizable chiral agent is preferably the same type of group as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent 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.

[0222] Moreover, the chiral agent can also be a liquid crystal compound.

[0223] When the chiral agent has a photo-isomerizable group, it is preferable because a pattern of the desired reflection wavelength corresponding to the emission wavelength can be formed by irradiating with a photomask such as activation light after coating and alignment. As the photo-isomerizable group, the 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 Japanese Patent Application Laid-Open No. 2002-80478, Japanese Patent Application Laid-Open No. 2002-80851, Japanese Patent Application Laid-Open No. 2002-179668, Japanese Patent Application Laid-Open No. 2002-179669, Japanese Patent Application Laid-Open No. 2002-179670, Japanese Patent Application Laid-Open No. 2002-179681, Japanese Patent Application Laid-Open No. 2002-179682, Japanese Patent Application Laid-Open No. 2002-338575, Japanese Patent Application Laid-Open No. 2002-338668, Japanese Patent Application Laid-Open No. 2003-313189, and Japanese Patent Application Laid-Open No. 2003-313292 can be used.

[0224] - Photo-reactive chiral agent -

[0225] The photo-responsive chiral reagent is composed of compounds represented by the following general formula (I), has the property of being able to control the alignment structure of liquid crystalline compounds, and changes 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 a structural change occurs by light irradiation as required sites (molecular structural units). Moreover, the photo-responsive chiral reagent represented by the following general formula (I) can particularly significantly change the HTP of liquid crystal molecules.

[0226] 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, and when the HTP becomes larger after irradiation, it is preferably 0.7 or less, more preferably 0.4 or less.

[0227] Hereinafter, the compound represented by the general formula (I) will be described.

[0228] General formula (I)

[0229] [Chemical formula 10]

[0230]

[0231] 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. As the alkoxy group having 1 to 15 carbon atoms, for example, methoxy, ethoxy, propoxy, butoxy, hexyloxy, dodecyloxy, etc. can be cited. 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.

[0232] As the acryloyloxyalkoxy group having a total of 3 to 15 carbon atoms, for example, acryloyloxyethoxy, acryloyloxybutoxy, acryloyloxydecoxy, etc. can be cited. 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.

[0233] As the above methacryloyloxyalkoxy group having 4 to 15 carbon atoms in total, for example, methacryloyloxyethoxy group, methacryloyloxybutoxy group, methacryloyloxydecoxy group, etc. can be cited. Among them, a methacryloyloxyalkoxy group having 6 to 14 carbon atoms is preferred, and a methacryloyloxyalkoxy group having 6 to 12 carbon atoms is particularly preferred.

[0234] As the molecular weight of the photoreactive chiral reagent represented by the above general formula (I), 300 or more is preferred. And a substance having high solubility with the liquid crystalline compound described later is preferred, and a substance having an SP value of solubility parameter close to that of the liquid crystalline compound is more preferred.

[0235] Hereinafter, specific examples (exemplified compounds (1) to (15)) of the compound represented by the above general formula (I) are shown, but the present invention is not limited to these.

[0236] [Chemical formula 11]

[0237]

[0238] [Chemical formula 12]

[0239]

[0240] [Chemical formula 13]

[0241]

[0242] As the photoreactive optically active compound, for example, a compound represented by the following general formula (II) can also be used.

[0243] General formula (II)

[0244] [Chemical formula 14]

[0245]

[0246] 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. As the above alkoxy group having 1 to 15 carbon atoms, for example, methoxy group, ethoxy group, propoxy group, butoxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc. can be cited. Among them, an alkoxy group having 1 to 10 carbon atoms is preferred, and an alkoxy group having 1 to 8 carbon atoms is particularly preferred.

[0247] As the acryloyloxyalkyloxy group having 3 to 15 total carbon atoms, for example, acryloyloxy, acryloyloxyethyloxy, acryloyloxypropyloxy, acryloyloxyhexyloxy, acryloyloxybutyloxy, acryloyloxydecyloxy, etc. can be cited. Among them, an acryloyloxyalkyloxy group having 3 to 13 carbon atoms is preferred, and an acryloyloxyalkyloxy group having 3 to 11 carbon atoms is particularly preferred.

[0248] As the methacryloyloxyalkyloxy group having 4 to 15 total carbon atoms, for example, methacryloyloxy, methacryloyloxyethyloxy, methacryloyloxyhexyloxy, etc. can be cited. Among them, a methacryloyloxyalkyloxy group having 4 to 14 carbon atoms is preferred, and a methacryloyloxyalkyloxy group having 4 to 12 carbon atoms is particularly preferred.

[0249] As the molecular weight of the photoreactive optically active compound represented by the above general formula (II), 300 or more is preferred. Also, a substance having high solubility in 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.

[0250] 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.

[0251] [Chemical formula 15]

[0252]

[0253] [Chemical formula 16]

[0254]

[0255] [Chemical formula 17]

[0256]

[0257] Moreover, 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 non-photoreactive known chiral reagents, 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 cited.

[0258] Relative 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%.

[0259] --Polymerization initiator--

[0260] When the liquid crystal composition contains a polymerizable compound, a polymerization initiator is preferably contained. In the method of performing a polymerization reaction by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating a polymerization reaction by ultraviolet irradiation. Examples of the photopolymerization initiator include α-carbonyl compounds (described in the specifications of U.S. Patent Nos. 2367661 and 2367670), acyloin ethers (described in the specification of U.S. Patent No. 2448828), α-hydrocarbon-substituted aromatic acyloin 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. The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 12% by mass, relative to the content of the liquid crystal compound.

[0261] --Crosslinking agent--

[0262] In order to improve the strength of the cured film 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. 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 (meth)acrylic acid glycidyl ester 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. And, a known catalyst can be used according to the reactivity of the crosslinking agent, and in addition to improving the film strength and durability, the productivity can also be improved.

[0263] They can be used alone or two or more of them can be used simultaneously. With respect to the mass of the solid components 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.

[0264] --Other additives--

[0265] In the liquid crystal composition, if necessary, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, etc. can also be added within the range that does not reduce the optical properties, etc. From the perspective of improving AR display, high refractive index nanoparticles such as zirconia nanoparticles and titanium oxide nanoparticles can be added.

[0266] When forming the cholesteric liquid crystal layer, the liquid crystal composition is preferably used in a liquid form. 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. 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.

[0267] They can be used alone or two or more of them can be used simultaneously. Among these, considering the environmental load, ketones are preferred.

[0268] When forming the cholesteric liquid crystal layer, the following is preferred: after coating the liquid crystal composition on the formation surface of the cholesteric liquid crystal layer and orienting the liquid crystal compound into a cholesteric liquid crystal phase state, the liquid crystal compound is cured to form a cholesteric liquid crystal layer. That is, when forming a cholesteric liquid crystal layer on the alignment film, the following is preferred: after coating the liquid crystal composition on the alignment film and orienting the liquid crystal compound into a cholesteric liquid crystal phase state, the liquid crystal compound is cured to form a cholesteric liquid crystal layer in which the cholesteric liquid crystal phase is fixed. Regarding the coating of the liquid crystal composition, printing methods such as inkjet and roll printing, as well as all known methods such as spin coating, bar coating, and spray coating that can uniformly coat a liquid on a sheet can be used.

[0269] The coated liquid crystal composition is dried and / or heated as needed, and then cured to form a cholesteric liquid crystal layer. In this drying and / or heating process, as long as the liquid crystal compound in the liquid crystal composition is oriented into a cholesteric liquid crystal phase. In the case of heating, the heating temperature is preferably 200 °C or lower, more preferably 130 °C or lower.

[0270] The aligned liquid crystal compound may be polymerized as needed. The polymerization may be either thermal polymerization or photo-polymerization based on light irradiation, but photo-polymerization is preferred. Ultraviolet light is preferably used for light irradiation. The irradiation energy is preferably 20 mJ / cm 2 ~50 J / cm 2 and more preferably 50~1500 mJ / cm 2 . To promote the photo-polymerization reaction, light irradiation may be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the irradiated ultraviolet light is preferably 250~430 nm.

[0271] The thickness of the cholesteric liquid crystal layer is not limited, and 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 forming material of the optically anisotropic layer, etc., a thickness that can obtain the required light reflectance can be obtained.

[0272] <<Cholesteric liquid crystal layer's liquid crystal alignment pattern>>

[0273] As described above, in the liquid crystal diffraction element 10, the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 continuously rotates in one direction in the plane of the cholesteric liquid crystal layer while changing. 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 the cholesteric liquid crystal phase continuously rotates in one direction in the plane of the cholesteric liquid crystal layer while changing. 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, 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".

[0274] In Figure 2 conceptually shows Figure 1 the plan view of the cholesteric liquid crystal layer 18 shown in Figure 1 . In addition, the plan view is a view of the liquid crystal diffraction element 10 observed from above in

[0275] that is, it is a view of the liquid crystal diffraction element 10 observed from the thickness direction (=the stacking direction of each layer (film)). Figure 2 And in

[0276] As Figure 2As shown, on the surface of the alignment film 24, the liquid crystal compound 30 constituting the cholesteric liquid crystal layer 18 is in a two-dimensionally arranged state in a specified one direction shown by arrow X and in a direction orthogonal to this one direction (arrow X direction) according to the alignment pattern of the alignment film 24 formed on the underlying layer. In the following description, for convenience, the direction orthogonal to the arrow X direction is defined as the Y direction.

[0277] That is, in Figure 1 and Figure 4 and those described later Figure 7 , Figure 9 and Figure 10 the Y direction becomes the direction perpendicular to the paper surface. And the liquid crystal compound 30 forming the cholesteric liquid crystal layer 18 has a liquid crystal alignment pattern in which the orientation of the in-plane optical axis 30A of the cholesteric liquid crystal layer 18 continuously rotates and changes along the arrow X direction. In the examples shown in Figure 1 and Figure 2 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.

[0278] Specifically, the fact that the orientation of the optical axis 30A of the liquid crystal compound 30 continuously rotates and changes along the arrow X direction (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, and 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.

[0279] 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.

[0280] On the other hand, regarding the liquid crystal compound 30 forming the cholesteric liquid crystal layer 18, in the Y direction orthogonal to the arrow X direction, that is, in the Y direction orthogonal to the one direction in which the optical axis 30A continuously rotates, the orientation of the optical axis 30A is equal. In other words, in the Y direction of the liquid crystal compound 30 forming the cholesteric liquid crystal layer 18, the angle formed by the optical axis 30A of the liquid crystal compound 30 and the arrow X direction is equal.

[0281] In the present invention, in such a liquid crystal alignment pattern of the 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 in the plane is defined as the length Λ of one cycle in the liquid crystal alignment pattern. That is, the distance between the centers in the arrow X direction of two liquid crystal compounds 30 having equal angles with respect to the arrow X direction is defined as the length Λ of one cycle. Specifically, as shown in Figure 2As shown in the figure, the distance between the centers of two liquid crystal compounds 30 in the direction of arrow X, where the direction of arrow X is the same as the direction of the optical axis 30A, is defined as the length Λ of one period. In the following description, this length Λ of one period is also referred to as "one period Λ". In the liquid crystal diffraction element 10, the liquid crystal alignment pattern of the cholesteric liquid crystal layer 18 repeats this one period Λ in one direction in which the liquid crystal alignment continuously rotates and changes in the direction of arrow X, i.e., the orientation of the optical axis 30A.

[0282] As Figure 1 shown in the liquid crystal diffraction element 10 as described above, when observing the X-Z plane of the cholesteric liquid crystal layer 18 having 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, using a SEM (Scanning Electron Microscope), a stripe pattern in which bright portions 42 and dark portions 44 conceptually shown in Figure 26 alternately arranged and the arrangement direction is inclined at a predetermined angle with respect to the main surface (X-Y plane) is observed.

[0283] In the following description, the cholesteric liquid crystal layer 18 is also referred to as the liquid crystal layer 18.

[0284] In such a SEM cross-section, the interval in the normal direction of the line formed by the bright portion 42 or the dark portion 44 between adjacent bright portions 42 to bright portions 42 or dark portions 44 to dark portions 44 corresponds to 1 / 2 of the tilt plane pitch. When the optical axis 30A of the liquid crystal compound 30 is parallelly aligned with respect to the main surface (X-Y plane) of the liquid crystal layer 18, as described above, the helix 1 pitch amount is Figure 1 the pitch P shown in the figure. On the other hand, when the liquid crystal compound 30 is inclined with respect to the main surface of the liquid crystal layer 18, especially when the inclination angle of the liquid crystal compound 30 with respect to the main surface of the liquid crystal layer 18 is equal to the angle formed by the line formed by the bright portion 42 or the dark portion 44 and the main surface of the liquid crystal layer 18, as Figure 26 shown by P in the figure, two bright portions 42 and two dark portions 44 correspond to the helix 1 pitch amount (the amount of one turn of the helix).

[0285] Here, in the example Figure 1 shown in the figure, it is assumed that the structure is such that on the X-Z plane of the liquid crystal layer 18, the optical axis 30A of the liquid crystal compound 30 is parallelly aligned with respect to the main surface (X-Y plane), but the present invention is not limited thereto. For example, as Figure 27 [[ID=2,4]]shown in the figure, it may also be a structure in which on the X-Z plane of the liquid crystal layer 18, the optical axis 30A of the liquid crystal compound 30 is inclinedly aligned with respect to the main surface (X-Y plane).

[0286] And, in Figure 27In the example shown, it is assumed that on the X-Z plane of the liquid crystal layer 18, the tilt angle (tilt angle) of the liquid crystal compound 30 with respect to the main surface (X-Y plane) is the same in the thickness direction (Z direction), but the present invention is not limited thereto. In the liquid crystal layer 18, there may also be a region where the tilt angle of the liquid crystal compound 30 is different in the thickness direction.

[0287] For example, Figure 28 The example shown has the following structure: on the interface on the alignment film 24 side of the liquid crystal layer 18, the optical axis 30A of the liquid crystal compound 30 is parallel to the main surface (pretilt angle is 0°), and as it moves away from the interface on the alignment film 24 side in the thickness direction, the tilt angle of the liquid crystal compound 30 increases, and then the liquid crystal compound is oriented at a specified tilt angle toward the other interface (air interface) side.

[0288] In this way, in the liquid crystal layer 18, the structure may be such that the optical axis 30A of the liquid crystal compound 30 has a pretilt angle on one of the upper and lower interfaces, or the structure may be such that pretilt angles are present on both interfaces. And, the pretilt angles may be different on the two interfaces.

[0289] In this way, by giving the liquid crystal compound 30 a tilt angle (tilt), the birefringence of the liquid crystal compound effective in light diffraction becomes higher, and the diffraction efficiency can be improved. And, the refractive index of the liquid crystal compound effective in light diffraction becomes higher, for example, in the case of being used for AR glasses applications, the FOV can be expanded.

[0290] The average angle (average tilt angle) formed by the optical axis 30A of the liquid crystal compound 30 and the main surface (X-Y plane) is preferably 5 to 80°, more preferably 10 to 50°. In addition, the average tilt angle can be measured by observing the X-Z plane of the liquid crystal layer 18 with a polarized light microscope. Among them, on the X-Z plane of the liquid crystal layer 18, it is preferable that the optical axis 30A of the liquid crystal compound 30 is tilted and oriented in the same direction with respect to the main surface (X-Y plane).

[0291] In addition, the above tilt angle is the following value: when observing the cross section of the cholesteric liquid crystal layer with a polarized light microscope, the angles formed by the optical axis 30A of the liquid crystal compound 30 and the main surface are measured at any 5 or more locations, and the value obtained by arithmetically averaging them.

[0292] Light perpendicularly incident on the liquid crystal diffraction element (liquid crystal layer 18) is applied with a bending force in the tilt direction and travels obliquely in the liquid crystal layer 18. If the light travels in the liquid crystal layer 18, it deviates from conditions such as the diffraction period originally set to obtain a desired diffraction angle for perpendicular incidence, and thus diffraction loss occurs.

[0293] When the liquid crystal compound 30 is tilted, there is an azimuth in which a higher birefringence is generated with respect to the azimuth of light diffraction compared to the case where it is not tilted. In this direction, the extraordinary light refractive index effective in this direction becomes larger, so the birefringence, which is the difference between the extraordinary light refractive index and the ordinary light refractive index, becomes higher.

[0294] By setting the azimuth of the tilt angle according to the azimuth of the target diffraction, it is possible to suppress the deviation of this azimuth from the original diffraction conditions. As a result, it is considered that a higher diffraction efficiency can be obtained when using a liquid crystal compound having a tilt angle.

[0295] Also, the tilt angle can be controlled by the treatment of the interface of the liquid crystal layer 18. On the interface on the support side, by performing a pretilt treatment on the alignment film, the tilt angle of the liquid crystal compound 30 can be controlled. For example, by exposing the alignment film to ultraviolet light from the front and then from an oblique side when forming the alignment film, a pretilt angle can be generated in the liquid crystal compound 30 in the liquid crystal layer 18 formed on the alignment film. In this case, the pretilt is performed in the direction of the uniaxial side where the liquid crystal compound 30 can be observed with respect to the second irradiation direction. However, the liquid crystal compound 30 in the azimuth perpendicular to the second irradiation direction is not pretilted, so there are regions where pretilt is performed and regions where pretilt is not performed in the plane. This is because when diffracting light in the target azimuth, it is most helpful for increasing birefringence in this direction, so it is suitable for increasing the diffraction efficiency.

[0296] Moreover, an additive that promotes the pretilt angle can also be added to the liquid crystal layer 18 or the alignment film. In this case, the additive can be utilized as a factor for further increasing the diffraction efficiency.

[0297] This additive can also be used to control the pretilt angle of the air-side interface.

[0298] Among them, on the cross-section of the liquid crystal layer 18 observed by SEM, the bright part 42 and the dark part 44 derived from the cholesteric liquid crystal phase are tilted with respect to the main surface. The liquid crystal layer 18 preferably has the direction with the minimum retardation in either the slow axis plane or the fast axis plane tilted from the normal direction when measuring the retardation from the normal direction and the direction tilted with respect to the normal direction. Specifically, it is preferable that the absolute value of the measurement angle formed by the direction with the minimum retardation and the normal is 5° or more. In other words, it is preferable that the liquid crystal compound 30 of the liquid crystal layer 18 is tilted with respect to the main surface, and the tilt direction is substantially the same as the bright part 42 and the dark part 44 of the liquid crystal layer 18. In addition, the normal direction refers to the direction orthogonal to the main surface.

[0299] By making the liquid crystal layer 18 have such a structure, it is possible to diffract circularly polarized light with a high diffraction efficiency compared to a liquid crystal layer in which the liquid crystal compound 30 is parallel to the main surface.

[0300] In a structure in which the liquid crystal compound 30 in the liquid crystal layer 18 is inclined with respect to the main surface and the inclination direction is substantially the same as that of the bright portion 42 and the dark portion 44, the bright portion and the dark portion corresponding to the reflection surface coincide with the optical axis 30A of the liquid crystal compound 30. Therefore, the effect of the liquid crystal compound on light reflection (diffraction) becomes larger, and the diffraction efficiency can be improved. As a result, the amount of reflected light with respect to incident light can be further increased.

[0301] On the fast axis plane or the slow axis plane of the liquid crystal layer 18, the absolute value of the inclination angle of the optical axis of the liquid crystal layer 18 is preferably 5° or more, more preferably 15° or more, and still more preferably 20° or more.

[0302] By setting the absolute value of the inclination angle of the optical axis to 15° or more, the direction of the liquid crystal compound 30 can be made to coincide more appropriately with the bright portion and the dark portion, and the diffraction efficiency can be improved, which is preferable in this regard.

[0303] A normal cholesteric liquid crystal layer in which the cholesteric liquid crystal phase is fixed generally specularly reflects incident light (circularly polarized light). In contrast, the cholesteric liquid crystal layer 18 having the liquid crystal alignment pattern as described above reflects the incident light in a direction having an angle with respect to specular reflection in the arrow X direction. For example, the cholesteric liquid crystal layer 18 does not reflect the light incident from the normal direction in the normal direction, but reflects it obliquely with respect to the normal direction in the arrow X direction. The light incident from the normal direction is the light incident from the front and is the light incident perpendicularly to the main surface. The main surface refers to the largest surface of the sheet-like object.

[0304] Hereinafter, with reference to Figure 4 it will be described.

[0305] As described above, the cholesteric liquid crystal layer 18 is a 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 cholesteric liquid crystal layer 18 is red light and it reflects right-handed circularly polarized light, if light R R is incident on the cholesteric liquid crystal layer 18, the cholesteric liquid crystal layer 18 only reflects the right-handed circularly polarized light R of red light R and transmits the light other than this.

[0306] Here, regarding the reflection angle of light with respect to a cholesteric liquid crystal layer in which the optical axis 30A based on the liquid crystal compound 30 continuously rotates in one direction (arrow X direction), the angle varies depending on 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. Also, regarding the reflection angle of light with respect to a cholesteric liquid crystal layer in which the optical axis 30A based on the liquid crystal compound 30 continuously rotates in the arrow X direction (one direction), it varies depending on the length Λ of one cycle of the liquid crystal alignment pattern in which the optical axis 30A rotates 180° in the arrow X direction, that is, one cycle Λ. Specifically, the shorter one cycle Λ is, the larger the angle of the reflected light with respect to the incident light becomes.

[0307] In the liquid crystal diffraction element 10, there is no limitation on one cycle Λ in the alignment pattern of the cholesteric liquid crystal layer, and it can be appropriately set according to the use of the liquid crystal diffraction element 10 and the like.

[0308] Here, as an example, the liquid crystal diffraction element 10 is preferably used as a diffraction element that reflects the light propagating in the light guide plate and emits it from the light guide plate to the position observed by the user in the AR glasses.

[0309] 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. And, as described above, regarding the reflection angle of light with respect to the cholesteric liquid crystal layer, by shortening one cycle Λ in the liquid crystal alignment pattern, the reflection angle with respect to the incident light can be increased.

[0310] Taking this into consideration, one cycle Λ in the liquid crystal alignment pattern of the cholesteric liquid crystal layer is preferably 50 μm or less, more preferably 10 μm or less, and further preferably 1 μm or less. Additionally, considering the accuracy of the liquid crystal alignment pattern and the like, one cycle Λ in the liquid crystal alignment pattern of the cholesteric liquid crystal layer is preferably set to 0.1 μm or more.

[0311] Here, in the present invention, the cholesteric liquid crystal layer preferably 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 moves from one side to the other side.

[0312] For example, in Figure 1 and Figure 2 in the case of the cholesteric liquid crystal layer shown, the diffraction efficiency becomes higher as it moves from one side to the other side in the X direction.

[0313] In Figure 5 and Figure 6 the relationship between the position in one direction (X direction) of the optical axis rotation of the cholesteric liquid crystal layer 18 and the diffraction efficiency at that position is shown as a schematic diagram.

[0314] In the X direction, the diffraction efficiency of the cholesteric liquid crystal layer 18 may have a structure in which it continuously changes as shown, or may have a structure in which it changes stepwise as shown. Figure 5 shown, or may have a structure in which it changes stepwise as shown. Figure 6 shown.

[0315] Here, the diffraction efficiency means that the cholesteric liquid crystal layer 18 is transferred as shown Figure 14 onto a double prism 110 (refractive index = 1.517, inclined surface angle = 45°), and laser light of a specified wavelength is transmitted through a linear polarizer 112 and a λ / 4 plate 114 to make it right-handed circularly polarized light, and the angle is set so that the diffracted light exits perpendicularly from the inclined surface and is incident on the surface of the cholesteric liquid crystal layer 18. 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.

[0316] The liquid crystal diffraction grating preferably has the following structure: the diffraction efficiency of the cholesteric liquid crystal layer becomes higher as it moves from one side to the other in one direction of the optical axis rotation. That is, it preferably has the following structure: in region A and / or region B of the optically anisotropic layer or further in region C described later, the diffraction efficiency becomes higher as it moves from one side to the other in one direction of the optical axis rotation. Thus, in a light guide element used in an AR (Augmented Reality) display device such as an AR glasses, when a liquid crystal diffraction element is used as a diffraction element for diffracting the light propagating in the light guide plate and causing it to exit from the light guide plate, even when the exit pupil is enlarged, the brightness (light quantity) of the light exiting from the light guide plate can be made uniform. This will be described in detail later.

[0317] In addition, if the direction in which regions with a constant diffraction efficiency are arranged in the cholesteric liquid crystal layer is set as the direction of change in the diffraction efficiency, this direction of change in the diffraction efficiency may coincide with one direction of the optical axis rotation or may not. 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 become a structure in which the diffraction efficiency becomes higher as it moves from one side to the other in one direction of the optical axis rotation.

[0318] In addition, it may have a structure in which regions with different diffraction efficiencies in the in-plane direction are present in the cholesteric liquid crystal layer (at least one of region A, region B, and region C), or may have a structure in which the diffraction efficiency gradually changes in one in-plane direction, or may have a structure in which the diffraction efficiency gradually increases (or gradually decreases) in one in-plane direction.

[0319] A structure in which the diffraction efficiency of a cholesteric liquid crystal layer increases as it goes from one side to the other in a direction where the orientation of the optical axis of the liquid crystal compound rotates continuously in the plane can be achieved by the cholesteric liquid crystal layer having any one of the following structures (i) and (ii). From the viewpoint of the smoothness of the optically anisotropic layer, the structure of (ii) is preferred.

[0320] (i) A structure in which the film thickness increases as it goes from one side to the other in a direction where the optical axis rotates.

[0321] (ii) A structure in which the thickness direction retardation Rth increases as it goes from one side to the other in a direction where the optical axis rotates.

[0322] In the cholesteric liquid crystal layer, the diffraction efficiency is high in the region with a thick film thickness and low in the region with a thin film thickness. Therefore, by making the cholesteric liquid crystal layer have a structure in which the film thickness increases as it goes from one side to the other in a direction where the optical axis rotates, the diffraction efficiency can be changed.

[0323] As described above, in the cholesteric liquid crystal layer, the liquid crystal compounds are arranged in a desired orientation pattern. In the region where this arrangement is not disrupted, since light can be diffracted appropriately, the diffraction efficiency is high. Also, the thickness direction retardation Rth of the region where the arrangement of the liquid crystal compounds is not disrupted is high. On the other hand, in the region where the arrangement of the liquid crystal compounds is disrupted, since it is difficult to diffract light appropriately, the diffraction efficiency is low. Also, the thickness direction retardation Rth of the region where the arrangement of the liquid crystal compounds is disrupted is low. Therefore, by making the cholesteric liquid crystal layer have a structure in which the thickness direction retardation Rth increases as it goes from one side to the other in a direction where the optical axis rotates, the diffraction efficiency can be changed. As a method for forming such a cholesteric liquid crystal layer, for example, the method described in WO2020-122119 can be cited.

[0324] A method for detecting a region having a different thickness direction retardation Rth at each position in the plane will be described. Since there is a proportional relationship between the tilt direction retardation Re(40) and the thickness direction retardation Rth, by confirming a region having a different tilt direction retardation Re(40) in the plane, a region having a different thickness direction retardation Rth in the plane can be detected. Also, by confirming that the tilt direction retardation Re(40) gradually changes in the plane, it can be detected that the thickness direction retardation Rth gradually changes in the plane.

[0325] Also, in the cholesteric liquid crystal layer, there are regions with a large birefringence and regions with a small birefringence in the thickness direction. By setting the ratio of the thickness of the region with a large birefringence to the thickness of the cholesteric liquid crystal layer to be different within the plane of the cholesteric liquid crystal layer, the diffraction efficiency can be changed. In the thickness direction of the cholesteric liquid crystal layer, when the ratio of the thickness of the region with a large birefringence is high, the diffraction efficiency is high; when the ratio of the thickness of the region with a large birefringence is low, the diffraction efficiency is low. In the region with a small birefringence in the thickness direction, a structure including an optically isotropic region can be preferably used.

[0326] In Figure 16 the method for detecting different birefringences at each position in the thickness direction at a certain position within the plane is described. In the optically anisotropic layer in which the liquid crystal compound is cholesterically oriented, when the optically anisotropic layer 324 is cut along the thickness direction and the SEM image of the exposed optically anisotropic layer 324 is analyzed, bright and dark portions caused by the cholesteric orientation of the liquid crystal compound clearly appear in the region 326 with a high birefringence. On the other hand, regarding the region 328 with a low birefringence, the contrast between the bright and dark portions is small, and particularly when the region 328 is optically isotropic, the bright and dark portions cannot be visually recognized. Therefore, by measuring the thickness of the region where the bright and dark portions clearly appear, the film thickness of the region with a high birefringence can be obtained.

[0327] However, in the case where the liquid crystal compound is not cholesterically oriented and in the case where 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 tilt direction 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 tilt direction retardation Re(40) using Axoscan (manufactured by Axometrics), an etching process of 100 nm is performed from the surface of the optically anisotropic layer. Based on the difference in the tilt direction retardation Re(40) before and after the 100-nm etching, the magnitude of the tilt direction retardation Re(40) in the etched region is calculated. Since there is a proportional relationship between the tilt direction retardation Re(40) and the birefringence Δn, by obtaining the film thickness of the region with a large tilt direction 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.

[0328] A structure in which the diffraction efficiency of a cholesteric liquid crystal layer increases as it goes from one side to the other along at least one direction in the plane of the cholesteric liquid crystal layer can be achieved by a structure in which the ratio of the thickness of a region with a large birefringence to the thickness of the cholesteric liquid crystal layer gradually changes. As an example, by gradually increasing the ratio of the thickness of the region with a large birefringence to the thickness of the cholesteric liquid crystal layer along at least one direction in the plane of the cholesteric liquid crystal layer, the diffraction efficiency of the cholesteric liquid crystal layer can be increased as it goes from one side to the other.

[0329] In a cholesteric liquid crystal layer, in a structure having a region with a large birefringence and a region with a small birefringence in the thickness direction, there are regions with different birefringences Δn in the thickness direction. Therefore, when the diffraction efficiency changes in the plane of the cholesteric liquid crystal layer, the average value Δna of the birefringence in the thickness direction changes in the plane. That is, when the diffraction efficiency of the cholesteric liquid crystal layer changes as it goes from one side to the other along at least one direction in the plane of the cholesteric liquid crystal layer, the average value Δna of the birefringence in the thickness direction gradually changes in the plane. Thus, 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, as an example, it can be achieved by setting the structure as follows: in at least a part of the plane of the cholesteric liquid crystal layer, the thickness of the optically isotropic region gradually decreases and the thickness of the optically anisotropic region gradually increases as it goes from one side to the other along at least one direction in the plane of the cholesteric liquid crystal layer.

[0330] In the plane of the cholesteric liquid crystal 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.

[0331] In the plane of the cholesteric liquid crystal 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.

[0332] However, the maximum value of the thickness of the high birefringence region and the minimum value of the thickness of the high birefringence region are preferably appropriately set according to the performance required for the optically anisotropic layer and the light guiding element, and are not limited to the above.

[0333] [Second Embodiment]

[0334] Here, in Figure 1 the example shown, the region A and / or region B (or, further region C) of the optically anisotropic layer is set as the region where the liquid crystal compound is cholesterically oriented, but it is not limited thereto, and it can also be the region where the liquid crystal compound is not cholesterically oriented. In Figure 7Conceptually shows an example of a second embodiment of a liquid crystal diffraction element. Figure 7 The shown liquid crystal diffraction element 12 is a liquid crystal diffraction element that diffracts incident light and transmits it. Figure 7 The shown liquid crystal diffraction element 12 has a structure in which a support 20, an alignment film 24, and a liquid crystal diffraction layer 16 are laminated in sequence.

[0335] In addition, regarding the support 20 and the alignment film 24, they have the same structure as the support 20 and the alignment film 24 of the Figure 1 shown liquid crystal diffraction element 10, so their description is omitted.

[0336] <Liquid Crystal Diffraction Layer>

[0337] The liquid crystal diffraction layer 16 is formed on the surface of the alignment film 24.

[0338] The liquid crystal diffraction layer 16 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.

[0339] In Figure 8 shows Figure 7 a plan view of the shown liquid crystal diffraction element. In addition, the plan view is a view of the liquid crystal diffraction element observed from above in Figure 7 , that is, a view of the liquid crystal diffraction element observed from the thickness direction (= the lamination direction of each layer (film)). In other words, it is a view of the liquid crystal diffraction layer 16 observed from a direction perpendicular to the main surface. And in Figure 8 , in order to clearly show the structure of the liquid crystal diffraction element, as the liquid crystal compound 30 in the liquid crystal diffraction layer 16, only the liquid crystal compound 30 on the surface of the alignment film 24 is shown. However, as Figure 7 shown, the liquid crystal diffraction layer 16 has a structure in which the liquid crystal compound 30 is stacked from the liquid crystal compound 30 on the surface of the alignment film 24 in the thickness direction.

[0340] As Figure 8As shown, the liquid crystal diffraction layer 16 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 within the plane of the liquid crystal diffraction layer 16 continuously rotates and changes in one direction shown by the arrow X. Specifically, the continuous rotation and change of the orientation of the optical axis 30A of the liquid crystal compound 30 in the direction of the arrow X (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. 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 further preferably an even smaller angle.

[0341] On the other hand, regarding the liquid crystal compound 30 forming the liquid crystal diffraction layer 16, in the Y direction orthogonal to the arrow X direction, that is, in the Y direction orthogonal to the one direction in which the optical axis 30A continuously rotates, the liquid crystal compounds 30 with equal orientations of the optical axis 30A are arranged at equal intervals. In other words, among the liquid crystal compounds 30 forming the liquid crystal diffraction layer 16, between the liquid crystal compounds 30 arranged in the Y direction, the angles formed by the orientations of the optical axes 30A and the arrow X direction are equal. In the liquid crystal alignment pattern of the liquid crystal diffraction layer 16, the length Λ of one cycle in the liquid crystal alignment pattern is repeated in the arrow X direction, that is, in the one direction in which the orientation of the optical axis 30A continuously rotates and changes.

[0342] As described above, in the liquid crystal diffraction layer 16, the angles formed by the optical axes 30A of the liquid crystal compounds arranged in the Y direction and the arrow X direction (the one 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 arrow X direction being equal is arranged in the Y direction is set as region R. In this case, 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 accompanying region R and the thickness of the liquid crystal diffraction layer 16. Here, the refractive index difference generated by the refractive index anisotropy in region R of the liquid crystal diffraction layer 16 is defined as the refractive index difference between the refractive index in the direction of the slow axis in the plane of region R and the refractive index in the direction orthogonal to the direction of the slow axis. That is, the refractive index difference Δn generated by the refractive index anisotropy in 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.

[0343] If circularly polarized light is incident on such a liquid crystal diffraction layer 16, the light is refracted and the direction of the circularly polarized light is converted.

[0344] In Figure 9 the liquid crystal diffraction layer 16 is illustrated conceptually to show its function. As Figure 9 shown, if incident light L1, which is left-handed circularly polarized light, is incident on the liquid crystal diffraction layer 16, the incident light L1 passes through the liquid crystal diffraction layer 16, and thus a phase difference of 180° is imparted, and the transmitted light L2 is converted into right-handed circularly polarized light.

[0345] Moreover, since the liquid crystal alignment pattern formed in the liquid crystal diffraction layer 16 is a periodic pattern in the arrow X direction, the transmitted light L2 is refracted 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.

[0346] On the other hand, as Figure 10 conceptually shown, if incident light L4, which is right-handed circularly polarized light, is incident on the liquid crystal diffraction layer 16, the incident light L4 passes through the liquid crystal diffraction layer 16 and a phase difference of 180° is imparted, and thus it is converted into the transmitted light L5 of left-handed circularly polarized light. Moreover, since the liquid crystal alignment pattern formed in the liquid crystal diffraction 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 azimuth direction opposite to the arrow X direction.

[0347] In the liquid crystal diffraction 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 liquid crystal diffraction layer 16 for incident light with a wavelength of 550 nm is preferably within the range defined by 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 liquid crystal diffraction layer 16.

[0348] 200 nm ≤ Δn550 × d ≤ 350 nm......(1)

[0349] That is, if the in-plane retardation Re(550) = Δn550 × d of the plurality of regions R of the liquid crystal diffraction layer 16 satisfies the formula (1), a sufficient amount of the circularly polarized light component of the light incident on the liquid crystal diffraction 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. 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 liquid crystal diffraction 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.

[0350] 0.35 × λ nm ≤ Δnλ × d ≤ 0.65 × λ nm ……(1-2)

[0351] Moreover, the values of the in-plane retardation of the plurality of regions R in the liquid crystal diffraction 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 is close to 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.

[0352] Furthermore, the in-plane retardation Re(450) = Δn450 × d of each region R of the liquid crystal diffraction layer 16 for incident light with a wavelength of 450 nm and the in-plane retardation Re(550) = Δn550 × d of each region R of the liquid crystal diffraction layer 16 for incident light with a wavelength of 550 nm 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.

[0353] (Δn450 × d) / (Δn550 × d) < 1.0 ……(2)

[0354] The formula (2) indicates that the liquid crystal compound 30 contained in the liquid crystal diffraction layer 16 has an inverse dispersion property. That is, by satisfying the formula (2), the liquid crystal diffraction layer 16 can handle incident light with a wide-band wavelength.

[0355] Here, by changing one period Λ of the liquid crystal alignment pattern formed in the liquid crystal diffraction 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 passing through the adjacent liquid crystal compounds 30 becomes, and thus the transmitted lights L2 and L5 can be refracted (diffracted) significantly. Also, the refraction angles of the transmitted lights L2 and L5 with respect to the incident lights L1 and L4 vary 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 lights are red light, green light, and blue light, the red light is refracted (diffracted) most significantly, and the blue light is refracted (diffracted) least. In addition, by setting the rotation direction of the optical axis 30A of the liquid crystal compound 30 rotating along the arrow X direction to the opposite direction, the refraction (diffraction) direction of the transmitted light can be made the opposite direction.

[0356] The liquid crystal diffraction 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.

[0357] By forming an alignment film 24 on the support 20, coating a liquid crystal composition on the alignment film 24, and curing it, a liquid crystal diffraction 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 the same as those of the above-mentioned cholesteric liquid crystal layer.

[0358] In addition, although it is the liquid crystal diffraction layer 16 that functions as an optically anisotropic 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 anisotropic region.

[0359] And, the liquid crystal composition for forming the liquid crystal diffraction 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. Also, the liquid crystal composition may contain a solvent. The rod-like liquid crystal compounds, disc-like liquid crystal compounds, etc. contained in the liquid crystal composition for forming the liquid crystal diffraction layer 16 can use the same compounds as those contained in the liquid crystal composition for forming the above-mentioned cholesteric liquid crystal layer 18. That is, the liquid crystal composition for forming the liquid crystal diffraction layer 16 does not contain a chiral reagent, and other than that, is the same as the liquid crystal composition for forming the above-mentioned cholesteric liquid crystal layer 18.

[0360] Further, the liquid crystal diffraction 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.

[0361] Further, the liquid crystal diffraction 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 anomalous dispersion. Further, from the viewpoint of more excellent effects of the present invention and the viewpoint of obtaining diffracted light with 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 still more 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 with normal 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. In this case, it is also preferable to make the liquid crystal diffraction layer 16 substantially broadband with respect to the wavelength of incident light by imparting a twist component to the liquid crystal composition and by laminating different liquid crystal diffraction 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 with different twist directions in the liquid crystal diffraction layer 16 is shown, and this method can be preferably used in the present invention.

[0362] 〔Non-diffraction region〕

[0363] As Figure 29 shown, the optically anisotropic layer 400 of the present invention has a non-diffraction region 45b.

[0364] The non-diffraction region 45b is a region that does not have the above-described liquid crystal alignment pattern and does not have the function of diffracting incident light.

[0365] 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 uniaxially oriented, twisted, or cholesterically oriented in the thickness direction, and uniaxial orientation or twisted orientation is preferred. In the non-diffraction region 45b, a structure in which a region where the liquid crystal compound is uniaxially oriented, twisted, or cholesterically oriented in the thickness direction and an isotropic region are laminated may be provided.

[0366] When the non-diffraction region 45b is a region where the liquid crystal compound is oriented 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, when the circularly polarized light diffracted in the incident-side region A45a is guided in the light guide plate, it is converted into elliptically polarized light by passing 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 passing 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 its polarization state during guiding, so that the light intensity of the light emitted from the emission-side region B45c can be made uniform.

[0367] Here, in the optically anisotropic layer of the present invention, the rotation direction of the optical axis derived from the liquid crystal compound in one direction in the liquid crystal alignment pattern of region A may be different from the rotation direction of the optical axis derived from the liquid crystal compound in one direction in the liquid crystal alignment pattern of region B.

[0368] Moreover, one direction of the liquid crystal alignment pattern in region A and one direction of the liquid crystal alignment pattern in region B may be different from each other.

[0369] Furthermore, the length in which the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of region A rotates 180° in the plane (the length of one period Λ) may be different from the length in which the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of region B rotates 180° in the plane (the length of one period Λ).

[0370] As will be described later, when the optically anisotropic layer is combined with a light guide plate and used as a light guiding element, for example, region A functions as an incident diffraction element for allowing light to enter the light guide plate, and region B functions as an emission diffraction element for allowing light to exit the light guide plate. Therefore, the diffraction performances required for region A and region B are different. Thus, region A and region B only need to set the rotation direction of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern, one period, the orientation in one direction, etc. according to the respectively required diffraction performances, and the liquid crystal alignment pattern in region A and the liquid crystal alignment pattern in region B may be different.

[0371] Moreover, in the optically anisotropic layer of the present invention, region A and region B may each be a cholesteric liquid crystal layer, region A and region B may each be a liquid crystal diffraction layer, region A may be a cholesteric liquid crystal layer and region B may be a liquid crystal diffraction layer, or region A may be a liquid crystal diffraction layer and region B may be a cholesteric liquid crystal layer.

[0372] Further, in the optically anisotropic layer of the present invention, when Region A and Region B are cholesteric liquid crystal layers, there may be regions where the pitch length of the cholesteric liquid crystal layer in Region A is different from the pitch length of the cholesteric liquid crystal layer in Region B.

[0373] For example, when the optically anisotropic layer is combined with a light guide plate and Region A is used as an incident diffraction element and Region B is used as an exit diffraction element, light is incident on Region A from a substantially perpendicular direction. In contrast, light is incident on Region B 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, a so-called blue shift occurs in which the wavelength of the selective reflection wave becomes shorter. Therefore, even when Regions A and B diffract light of the same wavelength, it is preferable to set an appropriate pitch length for each region according to the incident angle of light, etc.

[0374] Further, the rotational direction of the helix of the cholesteric orientation in Region A and the rotational direction of the helix of the cholesteric orientation in Region B may be different from each other. That is, the rotational direction of the circularly polarized light reflected by Region A and the rotational direction of the circularly polarized light reflected by Region B may be different from each other.

[0375] For example, when the optically anisotropic layer is combined with a light guide plate and Region A is used as an incident diffraction element and Region B is used as an exit diffraction element, even when right-handed circularly polarized light is incident on the light guide plate from Region A, during total reflection and guiding in the light guide plate, when the polarization is eliminated and the light is incident on Region B, the light may sometimes become 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 Region B and the circularly polarized light reflected and diffracted by Region A may be different.

[0376] Further, in the optically anisotropic layer of the present invention, when at least one of Region A and Region B is a cholesteric liquid crystal layer, there may be regions where the pitch length of the cholesteric liquid crystal layer is different in the in-plane direction of the region.

[0377] Thereby, for example, in the case of being used as AR glasses, it is possible to adjust to make the in-plane hue, brightness, etc. uniform. And by adjusting to strongly reflect a desired hue in a desired direction in the plane, it is possible to obtain AR glasses with high light utilization efficiency.

[0378] Further, in the optically anisotropic layer of the present invention, when at least one of Region A and Region B is a cholesteric liquid crystal layer, there may be regions in the region where the pitch length of the cholesteric liquid crystal layer varies in the thickness direction.

[0379] 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 wavelength of the selective reflection.

[0380] Here, in the Figure 29 and Figure 30 shown example, the optically anisotropic layer is configured to have two regions with a liquid crystal alignment pattern, but is not limited thereto. The optically anisotropic layer of the present invention may also have a structure in which a region C is provided in the in-plane direction of the same optically anisotropic layer, and the region C 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.

[0381] Figure 31 is a plan view conceptually showing another example of the optically anisotropic layer of the present invention.

[0382] Figure 31 The optically anisotropic layer 450 shown has a region A45a, a region B45c, a region C45d, and a non-diffraction region 45b. As Figure 31 shown, the region A45a and the region C45d are arranged separately in the left-right direction in the figure, and the region C45d and the region B45c are arranged separately in the up-down direction in the figure. A non-diffraction region 45b is formed between the region A45a and the region C45d and between the region C45d and the region B45c.

[0383] Similar to the region A45a and the region B45c, the region C45d 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. Similar to the region A45a and the region B45c, the region C45d may be a cholesteric liquid crystal layer or a liquid crystal diffraction layer. Also, the liquid crystal alignment pattern in the region C45d may be different from the liquid crystal alignment patterns of the region A45a and the region B45c, respectively.

[0384] Thus, the optical anisotropic layer 450 having the region C45d also has three light-diffracting regions. 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 region A45a functions as an incident diffracting element for allowing light to enter the light guide plate, the region B45c functions as an exit diffracting element for allowing light to exit from the light guide plate, and the region C45d functions as an intermediate diffracting element for diffracting the light incident from the region A45a in the direction of the region B45c. Thus, by providing a structure in the region C45d that functions as an intermediate diffracting element to diffract a part of the light at multiple sites and emit it to the outside of the light guide plate, exit pupil expansion can be performed. And in the region C45d, 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.

[0385] [Stacked body]

[0386] The stacked body of the present invention is a stacked body formed by stacking two or more of the above-described optical anisotropic layers.

[0387] Figure 32 It is a diagram conceptually showing an example of the stacked body of the present invention.

[0388] Figure 32 The shown stacked body 500 has a first optical anisotropic layer 400a and a second optical anisotropic layer 400b.

[0389] The first optical anisotropic layer 400a includes a region A410a and a region B410c having a liquid crystal alignment pattern and a non-diffracting region 410b. And the second optical anisotropic layer 400b includes a region A420a and a region B420c having a liquid crystal alignment pattern and a non-diffracting 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 the above-described optical anisotropic layer.

[0390] In Figure 32 the region A410a of the first optical anisotropic layer 400a and the region A420a of the second optical anisotropic layer 400b are arranged at overlapping positions, and the non-diffracting region 410b of the first optical anisotropic layer 400a that does not have a liquid crystal alignment pattern and the non-diffracting region 420b of the second optical anisotropic layer 400b that does not have a liquid crystal alignment pattern are arranged at overlapping positions, and the region B410c of the first optical anisotropic layer 400a and the region B420c of the second optical anisotropic layer 400b are arranged at overlapping positions.

[0391] In addition, in Figure 32In the example shown, the laminate is configured to have a structure in which two optically anisotropic layers are laminated, 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 laminated. In the case of a structure in which three or more optically anisotropic layers are laminated, it is also preferable to laminate at positions where regions A, regions B, and non-diffraction regions of each optically anisotropic layer overlap each other.

[0392] Moreover, it may also be a laminate having two or more Figure 31 The laminate of the optically anisotropic layer having region C shown in the example. In this case, it is preferable to laminate at positions where regions C of each optically anisotropic layer overlap each other.

[0393] In the case of Figure 32 In the laminate 500 shown, it is preferable to satisfy at least one of the following: Region A410a of the first optically anisotropic layer 400a and region A420a 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 region A410a of the first optically anisotropic layer 400a is different from the length of the helical pitch of the cholesteric liquid crystal layer in region A420a of the second optically anisotropic layer 400b; or region B410c of the first optically anisotropic layer 400a and region B420c 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 region B410c of the first optically anisotropic layer 400a is different from the length of the helical pitch of the cholesteric liquid crystal layer in region B420c of the second optically anisotropic layer 400b.

[0394] 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 regions A and / or regions B of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b to be different, regions A and / or regions B of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b reflect light of different wavelengths, respectively.

[0395] As will be described later, when the light guide element formed by combining the laminate 500 with a 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 preferably configured to be a structure in which optically anisotropic layers having regions A and regions B (and region C) that reflect and diffract light of these wavelengths are laminated. For example, it can be configured as follows: Regions A and B of the first optically anisotropic layer are cholesteric liquid crystal layers having a selective reflection wavelength in the red wavelength region, and regions A and B of the second optically anisotropic layer are cholesteric liquid crystal layers having a selective reflection wavelength in the green wavelength region.

[0396] Further, in the laminate 500 as shown in Figure 32 , it is preferable that at least one of the following is satisfied: the region A410a of the first optically anisotropic layer 400a and the region A420a 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 region A410a of the first optically anisotropic layer 400a is different from the rotation direction of the helix of the cholesteric liquid crystal layer in the region A420a of the second optically anisotropic layer 400b; or the region B410c of the first optically anisotropic layer 400a and the region B420c 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 region B410c of the first optically anisotropic layer 400a is different from the rotation direction of the helix of the cholesteric liquid crystal layer in the region B420c of the second optically anisotropic layer 400b.

[0397] As described above, the cholesteric liquid crystal layer has circularly polarized light selectivity according to the rotation direction of the helix in the helical structure. By making the rotation directions of the helices of the regions A of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b different from each other and / or the regions B different from each other, for example, it is possible to form a structure in which the first optically anisotropic layer 400a reflects and diffracts right-handed circularly polarized light of a certain wavelength in the region A410a, the second optically anisotropic layer 400b reflects and diffracts left-handed circularly polarized light of the same wavelength in the region A420a, and / or the first optically anisotropic layer 400a reflects and diffracts right-handed circularly polarized light of a certain wavelength in the region B410c, and the second optically anisotropic layer 400b reflects and diffracts left-handed circularly polarized light of the same wavelength in the region B420c.

[0398] Further, in the laminate 500 as shown in Figure 32 , it is preferable that at least one of the following is satisfied: the length of one cycle in which the orientation of the optical axis derived from the liquid crystal compound in the region A410a of the first optically anisotropic layer 400a rotates 180° in the plane is different from the length of one cycle in the region A420a of the second optically anisotropic layer 400b, or the length of one cycle in which the orientation of the optical axis derived from the liquid crystal compound in the region B410c of the first optically anisotropic layer 400a rotates 180° in the plane is different from the length of one cycle in the region B420c of the second optically anisotropic layer 400b.

[0399] As described above, the diffraction angles in regions A and B are determined by the length of one period in the liquid crystal alignment pattern. Also, even if the length of one period is the same, the diffraction angle varies depending on the wavelength of light. Thus, for example, as described above, when the lengths of the helical pitches of regions A of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or regions B of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b are made different to reflect and diffract light of different wavelengths by the first optically anisotropic layer 400a and the second optically anisotropic layer 400b, if the length of one period in the liquid crystal alignment pattern is the same, the diffraction angles are different, causing the light to be emitted in different directions. Therefore, it is preferable to make the lengths of one period of the liquid crystal alignment patterns of regions A of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or regions B of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b different so that the diffraction angles of light based on regions A of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b and / or regions B of the first optically anisotropic layer 400a and the second optically anisotropic layer 400b become the same.

[0400] And, in the laminate 500 as Figure 32 shown, it is preferable to satisfy at least one of the following: one direction of the liquid crystal alignment pattern in region A410a of the first optically anisotropic layer 400a is different from one direction of the liquid crystal alignment pattern in region A420a of the second optically anisotropic layer 400b; or one direction of the liquid crystal alignment pattern in region B410c of the first optically anisotropic layer 400a is different from one direction of the liquid crystal alignment pattern in region B420c of the second optically anisotropic layer 400b.

[0401] Thereby, for example, the light diffracted in region A410a of the first optically anisotropic layer 400a can be selectively diffracted in region B410c of the optically anisotropic layer 400a. And the light diffracted in region A420a of the second optically anisotropic layer 400b can be selectively diffracted in region B420c 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 it is desired to diffract light of different wavelengths in the first optically anisotropic layer 400a and the second optically anisotropic layer 400c, color crosstalk can be avoided.

[0402] [Light guide element and AR display device]

[0403] The light guide element using the optically anisotropic layer of the present invention has the above-described optically anisotropic layer and a light guide plate. The AR (Augmented Reality) display device of the present invention has a light guide element and an image display device.

[0404] (First Embodiment)

[0405] In Figure 11 FIG. 1 conceptually shows an example of a first embodiment of an AR display device of the present invention having a light guide element of the present invention.

[0406] Figure 11 The AR display device 50 shown has a display (image display device) 40 and a light guide element 45.

[0407] The light guide element 45 is a light guide element of the present invention, which has an optically anisotropic layer 400 and a light guide plate 144 of the present invention. In addition, the light guide element of the present invention may also be a structure including the laminate of the present invention having a multilayer optically anisotropic layer and a light guide plate. In other words, the light guide element of the present invention may have a multilayer optically anisotropic layer.

[0408] As described above, the optically anisotropic layer 400 is one optically anisotropic layer formed of three regions: a region A45a, a non-diffracting region 45b, and a region B45c. The light guide plate 144 is a rectangular parallelepiped shape elongated in one direction and guides light inside. As Figure 11 shown, the region A45a of the optically 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 region B45c of the optically anisotropic layer 400 is disposed on the surface on the other end side of the light guide plate 144. The arrangement position of the region A45a of the optically anisotropic layer 400 corresponds to the light incident position of the light guide plate 144, and the arrangement position of the region B45c of the optically anisotropic layer 400 corresponds to the light emission position of the light guide plate 144. And, an optically isotropic non-diffracting region 45b is formed between the region A45a and the region B45c.

[0409] The region A45a of the optically 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 as to be totally reflected inside the light guide plate 144.

[0410] And, the region B45c of the optically anisotropic layer 400 is an emission diffraction element region that diffracts light guided inside the light guide plate 144 so as to be emitted from the light guide plate 144.

[0411] 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.

[0412] As the light guide plate 144, various materials that are used as materials for light guide plates in optical elements 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), triacetyl cellulose (TAC), etc. can be exemplified.

[0413] The thickness of the light guide plate 144 is not limited, and it can be appropriately set in view of being able to maintain the thickness of the optically anisotropic layer, the light weight of the light guide plate, the uniformity of the brightness (light quantity) 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 m, and further preferably 0.1 to 0.5 μm.

[0414] Moreover, the refractive index of the light guide plate is preferably 1.5 or more, more preferably 1.8 or more, and further preferably 2.0 or more. Also, the difference between the extraordinary light 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 further preferably 0.1 or less.

[0415] As Figure 11 shown, the display 40 is arranged to face the surface on the side opposite to the surface on which the optically anisotropic layer 400 is arranged at one end of the light guide plate 144. And the surface side on the side opposite to the surface on which the optically anisotropic layer 400 is arranged at one end of the light guide plate 144 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, and 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.

[0416] In addition, the display 40 can be a display that displays a monochromatic image, a display that displays a dichromatic image, or a display that displays a color image.

[0417] The optical anisotropic layer of the present invention has polarization selectivity, so a display that emits polarized light is preferably used. For example, the structure can be set as follows: 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 an optical anisotropic layer having regions A and B that diffract right-handed circularly polarized light for red, an optical anisotropic layer having regions A and B that diffract left-handed circularly polarized light for green, and an optical anisotropic layer having regions A and B that diffract right-handed circularly polarized light for blue are stacked on the light guide plate. Thus, the polarization states of adjacent wavelengths of red and green, and green and blue are different, so color crosstalk can be avoided.

[0418] Moreover, for example, a display that displays an image corresponding to a FOV of 0 to 50° by emitting right-handed circularly polarized light and displays an image corresponding to a FOV of -50 to 0° by emitting left-handed circularly polarized light, and an optical anisotropic layer having regions A and B that diffract right-handed circularly polarized light and an optical anisotropic layer having regions A and B that diffract left-handed circularly polarized light are stacked on the light guide plate. Thus, compared with the case of not using polarized light, the FOV can be doubled.

[0419] Furthermore, the optical anisotropic layer of the present invention is also preferably used in a laser beam scanning type display. A laser beam scanning type display is a display that scans a laser beam with a MEMS mirror. At this time, when the optical system is designed to reflect the laser beam with a polarizing mirror and then scan it with a MEMS mirror, if the polarization selectivity of the polarizing mirror is insufficient, the problem of glare will occur. However, the optical anisotropic layer of the present invention itself has polarization selectivity, so it can supplement the polarization selectivity of the polarizing mirror and prevent glare.

[0420] In the AR display device 50 with this structure, as shown by the arrow, the light displayed by the display 40 enters the light guide plate 144 from the surface on the opposite side of the surface where the optical anisotropic layer 400 is arranged at one end of the light guide plate 144. The light incident on the light guide plate 144 is reflected in region A45a of the optical anisotropic layer 400. At this time, due to the diffraction effect of region A45a, 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 from a direction (Z direction) substantially perpendicular to region A45a of the optical anisotropic layer 400 and is reflected in a direction that is greatly inclined from the vertical direction to the long side direction (X direction) of the light guide plate 144.

[0421] The light reflected in region A45a 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 makes a smaller angle with the surface of the light guide plate 144. As a result, the light is totally reflected at the surface of the light guide plate 144 or the surface of the non-diffraction 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 region B45c 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 region B45c 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 In the example shown, the light is incident on region B45c of the optically anisotropic layer 400 from an inclined direction and is reflected in a direction perpendicular to the surface of region B45c of the optically anisotropic layer 400.

[0422] The light reflected in region B45c 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 emitted to the outside of the light guide plate 144. That is, the light is emitted to the position observed 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.

[0423] Here, in region B45c 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 region B45c of the optically anisotropic layer 400, a part of the light is diffracted at multiple positions and emitted to the outside of the light guide plate 144, thereby expanding the viewing field (expanding the exit pupil). Specifically, in Figure 11In [the figure], while the light I0 propagating in the light guide plate 144 is repeatedly reflected at the two surfaces (interfaces) of the light guide plate 144, it reaches the position of the region B45c of the optically anisotropic layer 400. A part of the light I0 that reaches the position of the region B45c of the optically anisotropic layer 400 is diffracted at the position P1 near the incident side and exits from the light guide plate 144 (the 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 region B45c of the optically anisotropic layer 400 and exits 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 region B45c of the optically anisotropic layer 400 and exits 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 region B45c of the optically anisotropic layer 400 and exits from the light guide plate 144.

[0424] Thus, by adopting a structure in which the light propagating in the light guide plate 144 is diffracted at multiple positions by the region B45c of the optically anisotropic layer 400 and is emitted to the outside of the light guide plate 144, the viewing field can be expanded (the exit pupil is expanded).

[0425] Here, in Figure 24 the structure of a conventional light guide element is shown.

[0426] As Figure 24 shown, in the conventional light guide element, the liquid crystal diffraction element is not formed of a single element, but the two liquid crystal diffraction elements, i.e., the incident-side liquid crystal diffraction element 46 and the emission-side liquid crystal diffraction element 47, are separately arranged on the main surface of the light guide plate 144.

[0427] At this time, it is known that a part of the light diffracted by the liquid crystal diffraction element 46 and guided in the light guide plate 144 is scattered at the element end face X of the liquid crystal diffraction element 46 and the element end face Y of the liquid crystal diffraction element 47, which causes a decrease in the clarity of the image.

[0428] In contrast, in the optically anisotropic layer of the present invention, since the diffracting regions A and B and the non-diffracting region are integrally formed, when combined with the light guide plate, it is possible to prevent the light guided in the light guide plate from being scattered at the end faces of the diffraction element, and thus it is possible to emit a high-clarity image from the light guide plate.

[0429] Also, consider the case where the diffraction efficiency of the liquid crystal diffraction element 47 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 47 to emit a part of the light R2. However, the light intensity of the light I1 is less than the light intensity of the light I0. Therefore, even if diffracted with the same diffraction efficiency, the light intensity of the light R2 will become less than the light intensity of the light R1 reflected in the region 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 47 to emit a part of the light R3. However, the light intensity of the light I2 is less than the light intensity of the light I1. Therefore, even if diffracted with the same diffraction efficiency, the light intensity of the light R3 will become less 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 less than the light intensity of the light R3. Thus, in the case where the diffraction efficiency of the liquid crystal diffraction element 47 is constant in the plane, as Figure 12 indicated by the dashed line in, light with a high light intensity is emitted in the region closer to the incident side, and light with a low light intensity is emitted in the region farther from the incident side. Therefore, there is a problem that the light intensity of the emitted light becomes non-uniform depending on the position.

[0430] In contrast, in the region B45c of the optical anisotropic layer 400 of the present invention, there is a structure in which the diffraction efficiency increases as it moves from one side to the other side in one direction of the optical axis rotation. The region B45c of the optical anisotropic layer 400 is preferably arranged such that the diffraction efficiency increases in the traveling direction of the light in the light guide plate 144. That is, in Figure 11 the example shown, the region B45c of the optical anisotropic layer 400 has a structure in which the diffraction efficiency increases from left to right in Figure 11 .

[0431] 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. Next, the non-diffracted light I1 propagates in the light guide plate 144 and is diffracted again at position P2 in region B45c of the optically anisotropic layer 400, and a part of the light R2 is emitted. 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 in the light guide plate 144 and is diffracted again at position P3 in region B45c of the optically anisotropic layer 400, and a part of the light R3 is emitted. 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 region B45c of the optically anisotropic layer 400 increases as it goes 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 region B45c of the optically anisotropic layer 400. Therefore, as Figure 12 shown by the solid line in

[0432] In addition, in Figure 11 , the light is indicated by arrows, but the light emitted from the display 40 can also be planar. The planar light can propagate in the light guide plate 144 while maintaining the positional relationship and be diffracted by region B45c of the optically anisotropic layer 400.

[0433] And, in Figure 11In [the above description], the light guide element 45 was described as a light guide element having one layer of optically anisotropic layer. However, as described above, the light guide element 45 may also have a structure with multiple optically anisotropic layers 400. That is, it may be a structure using the above-described laminate. As described above, when the laminate has a structure with multiple optically anisotropic layers, it is preferably a structure with multiple optically anisotropic layers having different selective reflection wavelengths in region A and / or region B. For example, it can be a structure with optically anisotropic layers having region A and / or region B that respectively use red light, green light, and blue light as the selective reflection wavelengths. Thus, the optically anisotropic layer (the laminate thereof) can diffract red light, green light, and blue light respectively, and the light guide element can appropriately guide the light of the color display monitor 40. 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, when region A and / or region B is a cholesteric liquid crystal layer, the helical pitch is preferably changed appropriately according to the selective reflection wavelength of each layer. Or, it can be a structure with two optically anisotropic layers having region A and / or region B that reflect circularly polarized light with the same selective reflection wavelength and opposite rotation directions. For example, it can be a structure with 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 light. Thus, the optically anisotropic layer (the laminate thereof) 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 the utilization efficiency of light can be improved. Or, it can be a structure with two optically anisotropic layers having region A and / or region B that reflect circularly polarized light with the same selective reflection wavelength and opposite rotation directions and different helical pitches. Thus, the optically anisotropic layer (the laminate thereof) 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 light at different angles, so the FOV (Field of View) can be increased.

[0434] And, in Figure 11In the example shown, the optically anisotropic layer 400 is configured to have a region A45a on the incident side, a region B45c on the emission side, and an isotropic non-diffracting region 45b, but it is not limited thereto. As described above, it may also be configured to have an intermediate diffracting region, i.e., region C. That is, it may be configured as follows: the light diffracted by the incident diffracting region (region A) and incident into the light guide plate is diffracted in the intermediate diffracting region (region C) to bend the traveling direction of the light in the light guide plate, and then the light is diffracted by the emission-side diffracting region (region B) and emitted to the outside of the light guide plate. At this time, it is possible to form an incident-side diffracting region and an intermediate diffracting region within one optically anisotropic layer (i.e., a structure in which region A functions as the incident-side diffracting region and region B functions as the intermediate diffracting region), form an intermediate diffracting region and an emission-side diffracting region within one optically anisotropic layer (i.e., a structure in which region A functions as the intermediate diffracting region and region B functions as the emission-side diffracting region), or form all diffracting regions within one optically anisotropic layer (i.e., a structure having the above-mentioned regions A, B, and C). However, from the viewpoint of improving the clarity of the image, it is preferable to form as many diffracting regions as possible for the light guide plate within one optically anisotropic layer. Also, in the case of a structure having an intermediate diffracting region, in order to make the light intensity of the emitted light uniform, it is preferably configured such that the efficiency of the intermediate diffracting region increases from one side to the other side. Further, in order to make the light intensity of the emitted light uniform, the intermediate diffracting region and the emission-side diffracting region can also preferably use a structure in which the in-plane distribution of the diffraction efficiency in the intermediate diffracting region and the emission-side diffracting region is different.

[0435] The light guide element 45 preferably further includes a retardation plate laminated in addition to the light guide plate 144 and the optically anisotropic layer 400. Thus, in the same manner as the case where the non-diffracting region 45b of the optically anisotropic layer 400 functions as a retardation region, by converting the light guided in the light guide plate into linearly polarized light, it is possible to make the light intensity of the emitted light in the region B45c on the emission side uniform. Also, the linearly polarized light guided in the light guide plate may have its polarization state eliminated in the region B45c on the emission side. Therefore, the retardation plate is preferably a retardation plate in which different retardations are patterned in the in-plane direction to maintain the linearly polarized state of the light guided in the light guide plate. As such a retardation plate, a retardation plate made of a liquid crystal compound can be cited, and for example, it can be realized by patterning the alignment axis, twist angle, degree of alignment, etc. of the liquid crystal compound.

[0436] Further, when the optically anisotropic layer has an intermediate diffraction region (region C), a structure that shortens the length of one cycle in which the direction of the optical axis derived from the liquid crystal compound rotates 180° in the plane with respect to the incident-side diffraction region can be preferably used. Thereby, the angle by which the light diffracted by the incident-side diffraction region and incident into the light guide plate is diffracted by the intermediate diffraction region and the traveling direction of the light in the light guide plate is bent can be increased, and thus the size of the light guide plate can be made compact. Further, when the pitch of one cycle in the intermediate diffraction region is shorter than that in the incident-side diffraction region, the pitch of the cholesteric liquid crystal layer in the intermediate diffraction region is preferably set to be larger than that in 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-side diffraction region and incident into the light guide plate is diffracted by the intermediate diffraction region and the traveling direction of the light in the light guide plate is bent can be changed, and thus the light can be appropriately guided toward the emission-side diffraction region.

[0437] Also, a plurality of incident diffraction regions and intermediate diffraction regions can be arranged in the plane. Among the plurality of 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. Light incident on the incident diffraction regions can be guided in different directions within the light guide plate respectively, and 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 cycle 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 plurality of 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 plurality of 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. Also, when the diffraction region is a cholesteric liquid crystal layer, among the plurality of 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 plurality of incident-side diffraction regions can be set as regions with a right-handed cholesteric orientation and regions with a left-handed cholesteric orientation of the cholesteric liquid crystal layer. Also, the intermediate diffraction region can preferably use a structure in which the length of one cycle 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 one cycle 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, the helical pitch of the intermediate diffraction region is preferably set to be larger than that of the incident-side diffraction region. Also, in such a structure, in order to make the light intensity of the emitted light uniform, the intermediate diffraction region and the emission-side diffraction region can also preferably use 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.

[0438] 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 light 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 cycle of the liquid crystal alignment pattern in each diffraction region according to the selective reflection wavelength of each diffraction region of each layer. Alternatively, a structure of two stacked optically anisotropic layers having diffraction regions that reflect circularly polarized light with the same selective reflection wavelength and opposite rotational directions can be adopted. For example, a structure can be adopted 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 diffraction 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 utilization efficiency of light can be improved. Alternatively, a structure of two stacked optically anisotropic layers having diffraction regions that reflect circularly polarized light with the same selective reflection wavelength and opposite rotational directions and different pitches of the helix can also be adopted. 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 light 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 diffraction regions with different rotation directions of the optical axis derived from the liquid crystal compound in one direction in the plane, the length of one cycle of the liquid crystal alignment pattern, and the rotation direction of the liquid crystal alignment pattern continuously rotating 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 diffraction regions with different pitches of the helix and different twisting rotation directions of the helix in the thickness direction (rotation direction 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, in order to make the light intensity of the emitted light uniform, it is also preferable to use a structure in which the in-plane distribution of the diffraction efficiency in the intermediate diffraction region and the emitted diffraction region is different for the intermediate diffraction region and the emitted diffraction region.Further, when stacking multiple optically anisotropic layers, in each optically anisotropic layer, it is also preferable to use, respectively, structures with different in-plane distributions of diffraction efficiency in the diffraction region for the intermediate diffraction region and the diffracted region emitted from each layer. The arrangement of the diffraction region is not limited, and it can be appropriately arranged in the in-plane and thickness directions (stacking) as needed.

[0439] Also, it is possible to stack a diffraction region that serves as both the intermediate diffraction region and the diffracted region emitted. The intermediate diffraction region and the diffracted region emitted can be respectively configured as structures of optically anisotropic layers stacked with different directions of a liquid crystal alignment pattern that continuously rotates along one direction in the plane. At this time, it is preferable to use multiple incident diffraction regions with different directions of a liquid crystal alignment pattern that continuously rotates along one direction in the plane for the incident diffraction region, and guide the light incident on the incident diffraction region to different directions within the light guide plate. The multiple incident diffraction regions can be arranged at different positions in the plane or configured as a stacked structure. The light diffracted by the incident diffraction region and incident into the light guide plate is diffracted in the intermediate diffraction region to bend the traveling direction of the light within the light guide plate, and then is diffracted by the diffracted region on the emission side 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 diffracted region on the emission side functions as the intermediate diffraction region and is diffracted, thereby bending the traveling direction of the light within the light guide plate, and the above-mentioned intermediate diffraction region functions as the diffracted region on the emission side and can emit the guided light at different angles. Thus, compared with the case where the intermediate diffraction region and the diffracted region emitted 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 / 20218, WO2021 / 256453, etc., when stacking multiple optically anisotropic layers, in the case of stacking a diffraction region that serves as both the intermediate diffraction region and the diffracted region emitted, it is also preferable to stack multiple optically anisotropic layers with different lengths of one period of the liquid crystal alignment pattern, different directions of a liquid crystal alignment pattern that continuously rotates along one direction in the plane, and different rotation directions of the optical axis derived from the liquid crystal compound in a liquid crystal alignment pattern that continuously rotates along 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 with different pitch of the helix and different directions of the helical twist rotation in the thickness direction (the rotation direction of the reflected circularly polarized light), which can be appropriately set according to the purpose. Further, in the structure of stacking a diffraction region that serves as both the intermediate diffraction region and the diffracted region emitted, in order to make the light intensity of the emitted light uniform, in each diffraction region, it is also preferable to use, respectively, structures with different in-plane distributions of diffraction efficiency in the diffraction region. The arrangement of the diffraction region is not limited, and it can be appropriately arranged in the in-plane and thickness directions (stacking) as needed.

[0440] In addition, in Figure 11 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, the structure may be 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.

[0441] [Method for forming optically anisotropic layer]

[0442] The manufacturing method of 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.

[0443] 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

[0444] 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 of the coating film

[0445] Step 3: A step of performing a heat treatment on the coating film obtained in Step 2 and changing the degree of alignment according to the polymerization rate in Step 2, thereby forming regions having different diffraction efficiencies

[0446] Hereinafter, the above steps 1 to 3 will be described in detail.

[0447] (Step 1)

[0448] 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 the aligned liquid crystal compound is formed.

[0449] 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.

[0450] The composition containing a liquid crystal compound having a polymerizable group used in this step is as described above.

[0451] 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.

[0452] Coating of the composition can be carried out by various known methods used in coating of liquids such as bar coating, gravure coating, and spraying.

[0453] 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 predetermined alignment state according to the alignment pattern of the alignment film.

[0454] As the alignment treatment, a heat treatment is preferably performed. The conditions for heating are not particularly limited, and the heating temperature is preferably 50 to 140 °C, and the heating time is preferably 0.5 to 20 minutes.

[0455] (Step 2)

[0456] Step 2 is a step of polymerizing the liquid crystal compound to form regions having different polymerization rates of the liquid crystal compound in the in-plane direction of the coating film. The order of this step is not particularly limited, and by performing this step, regions having different curing degrees of the liquid crystal compound in the in-plane direction are formed in at least a part of the in-plane.

[0457] Use Figure 15 An example of its implementation method 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 reference numeral 327, in the region 316 in the coating film 324, the exposure energy is strong according to the transmittance of the photomask 329, and thus the polymerization of the liquid crystal compound is sufficiently carried out. On the other hand, in the region 318 in the coating film 324, the exposure energy is weak according to the transmittance of the photomask 329, and thus the polymerization of the liquid crystal compound does not occur.

[0458] Through Step 3 described later, the degree of alignment of the liquid crystal in the region 316 becomes high, and the degree of alignment of the liquid crystal in the region 318 becomes low. Therefore, an alignment degree gradient between the two is formed in the in-plane direction, and thus the diffraction efficiency gradually changes in the in-plane direction.

[0459] In Step 2, the liquid crystal compound can be polymerized to form regions having different polymerization rate distributions of the liquid crystal compound in the in-plane direction and the thickness direction. As a method for forming regions having different curing degrees of the liquid crystal compound 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, 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 exposing the formed coating film, etc. can be cited.

[0460] Use Figure 16An example of its implementation method will be described. In the photomask 329, the white part indicates a high transmittance, and the black part indicates a low transmittance. If exposure is performed from the direction indicated by the hollow arrow of the symbol 327, the first region 326 on the alignment film 322 side in the coating film 324 is not in contact with the atmosphere. Therefore, 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 is in contact with the atmosphere, and the oxygen supply from the atmosphere is rapid, and polymerization does not occur. At this time, according to the transmittance of the photomask 329, the thickness of the first region 326 gradually changes.

[0461] Through process 3 described later, the alignment degree of the liquid crystal in the first region 326 becomes high, and the alignment degree of the liquid crystal in the second region 328 becomes low. Therefore, a thickness gradient of the two is formed in the in-plane direction, and thus the diffraction efficiency gradually changes in the in-plane direction.

[0462] In particular, in process 3 described later, by making the second region 328 in an unaligned state, only the first region 326 with a high alignment degree can function as a diffraction element. As a result, the birefringence of the liquid crystal compound effective during light diffraction becomes high, and the diffraction efficiency can be improved. Moreover, the refractive index of the liquid crystal compound effective during light diffraction becomes high. For example, when used for AR glasses, the FOV can be expanded.

[0463] Process 2 can also be implemented by other methods.

[0464] In addition, regarding the judgment of whether regions with different curing degrees of the liquid crystal compound are formed in the in-plane direction of the coating film, for example, it can be judged by analyzing the surface of the coating film using infrared absorption spectroscopy or the like and calculating the residual ratio of the polymerizable groups in the in-plane direction of the coating film.

[0465] In the method of forming a coating film using the above composition containing a liquid crystal compound having a polymerizable group and exposing the formed coating film, as the exposure treatment, ultraviolet irradiation treatment is preferred.

[0466] 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, 1 to 1000 mJ / cm 2 is preferred, and 10 to 300 mJ / cm 2 is more preferred.

[0467] (Process 3)

[0468] Process 3 is a process of performing a heat treatment on the coating film obtained in process 2 to form regions with different diffraction efficiencies in the in-plane direction.

[0469] In the coating film obtained in Step 2, there are regions where the polymerization rate of the liquid crystal compound is different in the in-plane direction of the coating film. If such a coating film is heat-treated, the alignment 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 alignment state of the liquid crystal compound cannot be maintained due to the heat treatment, and the degree of alignment of the liquid crystal compound decreases. If such a decrease in the degree of alignment of the liquid crystal compound occurs, the diffraction efficiency in this region decreases. That is, by performing this step, the region where the polymerization rate of the liquid crystal compound is high becomes a region with high diffraction efficiency, and the region where the polymerization rate of the liquid crystal compound is low becomes a region with low diffraction efficiency. In particular, in the region where the polymerization rate is sufficiently low, the liquid crystal becomes an unaligned state, so that a region without a liquid crystal alignment pattern can be formed.

[0470] From the viewpoint of making the average refractive indices equal, the region with a liquid crystal alignment pattern and the region without a liquid crystal alignment pattern are preferably formed of substantially the same material (liquid crystal composition). Thereby, scattering at the interface between the region with a liquid crystal alignment pattern and the region without a liquid crystal alignment pattern can be avoided. The material forming each region can be confirmed, for example, by analyzing the composition using SIMS (secondary ion mass spectrometry) analysis.

[0471] The average refractive index of the region with a liquid crystal alignment pattern at this time is preferably within ±10% of the average refractive index of the region without a liquid crystal alignment pattern.

[0472] As a method for forming the region without a liquid crystal alignment pattern, it is not limited to this method. For example, a method of performing non-patterned alignment treatment such as uniaxial alignment on the alignment film can also be cited.

[0473] The conditions of the heat treatment performed 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 without a liquid crystal alignment pattern is formed.

[0474] After performing Step 3, Step 4 of performing an exposure treatment on the optically anisotropic layer obtained in Step 3 can be performed. By performing the exposure treatment, unreacted polymerizable groups can be polymerized. As the exposure treatment, ultraviolet irradiation treatment is preferred.

[0475] The conditions of the ultraviolet irradiation treatment can be appropriately selected as the optimal conditions according to the coating film used. As the irradiation dose, 50 to 2000 mJ / cm2 , more preferably 100 to 1000 mJ / cm 2 .

[0476] 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.

[0477] Regarding the above-mentioned optical anisotropic layer of the present invention, the optical axis 30A of the liquid crystal compound 30 in the liquid crystal alignment pattern of the diffraction region of any optical anisotropic layer only continuously rotates along the arrow X direction.

[0478] However, the present invention is not limited thereto. As long as the optical axis 30A of the liquid crystal compound 30 continuously rotates in one direction in the diffraction region, various structures can be used.

[0479] As described above, the optical anisotropic layer of the present invention can also be formed by laminating a plurality of optical anisotropic layers to form a laminate. The lamination methods include a method of directly coating a liquid crystal composition on the optical anisotropic layer of the first layer to form the optical anisotropic layer of the second layer, a method of coating an alignment film on the optical anisotropic layer of the first layer, performing an alignment treatment, and then coating a liquid crystal composition, a method of bonding the optical anisotropic layer provided on another substrate, etc. The grating pitch, grating angle, helical pitch, helical pitch change in the thickness direction, tilt angle, tilt angle change in the thickness direction, Δn change in the thickness direction, size of the diffraction region, shape of the diffraction region, physical film thickness, optical thickness, and reflectance at each wavelength of each optical anisotropic layer can be arbitrarily adjusted. And in one diffraction region, it is also possible to change the grating pitch, grating angle, helical pitch, helical pitch change in the thickness direction, Δn change in the thickness direction, tilt angle, tilt angle change in the thickness direction, physical thickness, optical thickness, and reflectance at each wavelength in the in-plane direction, and it is also possible to arbitrarily adjust the direction and inclination of the change. And the diffraction regions with the above parameters adjusted can be arbitrarily combined.

[0480] The optical anisotropic layer of the present invention preferably has a region in at least one of the above-mentioned region A and region B 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 11 shown, by designing the helical pitch at positions P1, P2, P3, and P4 in region B45c to be an appropriate diffraction angle, the amount of light reaching the eyes increases, and the brightness of the AR glasses can be improved.

[0481] Further, in the present invention, regions with different orientations can be set as the following regions, and a region including at least the following regions can be regarded as one unit, and a plurality of units can be formed within one substrate: a region A having a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously rotates along at least one direction in the plane, a region B having a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously rotates along at least one direction in the plane, and a region without a liquid crystal alignment pattern. By forming a plurality of units within one substrate, not only can the productivity of the forming process of the optical anisotropic layer of the present invention be improved, but also the productivity of the downstream process can be improved.

[0482] <Adhesive layer (Binder layer), Adhesive>

[0483] In the laminate and the light guide element, an adhesive layer may be included in order to bond the optical anisotropic layers to each other and / or the optical anisotropic layer to the light guide plate. In the present specification, "bonding" is used in the concept including "adhesion".

[0484] For example, water-soluble adhesives, ultraviolet curable adhesives, emulsion adhesives, latex adhesives, pressure-sensitive adhesives, multi-layer adhesives, paste adhesives, foaming adhesives, support film adhesives, thermoplastic adhesives, hot melt adhesives, thermosetting adhesives, thermally active adhesives, heat-sealing adhesives, thermosetting adhesives, contact adhesives, pressure-sensitive adhesives (i.e., binders), polymeric adhesives, solvent-based adhesives, solvent-active adhesives, ceramic adhesives, etc. can 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 JP-A-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 JP-A-2008-174667, and a radiation curable adhesive containing (a) a (meth)acrylic acid compound having two or more (meth)acryloyl groups in the molecule, (b) a (meth)acrylic acid 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 the (meth)acrylic acid compounds as described in JP-A-2008-174667 can also be cited. As needed, various adhesives can be used alone or in combination.

[0485] 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 still more 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 Laid-Open No. 11-223712 can be used.

[0486] Moreover, 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 still more preferably 0.05 or less. Therefore, the adhesive layer may have refractive index anisotropy in the plane.

[0487] When the refractive index difference between the bonded interfaces is large, the interface reflectance can be reduced by imparting a distribution to the refractive index in the thickness direction of the adhesive layer. As a method for imparting a distribution to the 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 the multi-layer adhesive layers provided, a method of controlling the non-uniform state of the raw materials in the adhesive layer to impart a refractive index distribution, and the like.

[0488] Moreover, the adhesive layer can be provided on one or two members to be bonded by any method such as coating, vapor deposition, transfer, 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 the adhesive. The thickness of the adhesive layer can be adjusted arbitrarily, preferably 20 μm or less, more preferably 0.1 μm or less, and still more preferably 0.01 μm or less. As a method for forming an adhesive layer 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 surface of the bonded members can be subjected to surface modification treatments such as plasma treatment, corona treatment, saponification treatment, etc., 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.

[0489] <Cutting of the optically anisotropic layer and the laminate>

[0490] The fabricated optical anisotropic layer and / or laminate can be cut into a specified size. The method for cutting the optical anisotropic layer and / or laminate is not limited, and various known methods can be used, such as a physical cutting method using a tool such as a Thomson knife and a cutting method by irradiating a laser. 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. Further, after processing the optical anisotropic layer and / or laminate into a specified shape, for example, grinding processing of the end face can be performed. From the viewpoints of improving workability during cutting and suppressing dust generation, etc., cutting can also be performed in a state with a peelable protective film. Further, for example, by performing cutting while observing the liquid crystal alignment pattern by the method shown in JP-A-2004-141889, the cutting position can be arbitrarily determined. At this time, in order to easily see the liquid crystal alignment pattern, observation can also be performed through a polarizing plate, a retardation film, etc. Further, in the case where a plurality of cells are provided on one substrate, it is preferable to cut out each cell by cutting.

[0491] <Other processing>

[0492] For the purpose of accurately disposing the optical anisotropic layer (or laminate) on various devices (for example, a light guide plate) and improving the accuracy of the axis and cutting position during cutting, etc., a mark having an arbitrary shape can be provided as needed. The type of the mark can be arbitrarily selected, and a method of physically providing it by a laser, an inkjet method, etc., a method of locally changing the alignment state of the liquid crystal, a method of providing a locally decolorized or dyed region, etc. can be selected.

[0493] Further, from the purpose of protecting the optically anisotropic layer, a protective layer (gas barrier layer, moisture barrier layer, ultraviolet absorber layer, scratch-resistant layer, transparent coloring layer, etc.) can be provided as needed. The protective layer can be formed directly on the optically anisotropic layer or can be provided via other optical films such as an adhesive layer. An antireflection layer (LR (Low-Reflection) layer, AR (Anti-Reflection) layer, moth-eye layer, etc.) can be provided for the purpose of reducing the surface reflectance. The 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 serve as a polarizer. Further, the ultraviolet absorber layer is a layer containing an ultraviolet absorber. As the ultraviolet absorber, from the viewpoint of excellent absorption ability for ultraviolet rays of 370 nm or less and good display properties, an ultraviolet absorber with little absorption of visible light of 400 nm or more is preferably used. One type of ultraviolet absorber can be used alone, or two or more types can be used simultaneously. For example, the ultraviolet absorbers described in Japanese Unexamined Patent Application Publication No. 2001-072782 and Japanese Patent Application Laid-Open No. 2002-543265 can be cited. Specific examples of the ultraviolet absorber include oxybenzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, etc. 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 optically anisotropic layer, the appearance tone of the optical element including the optically anisotropic layer can be adjusted. For example, when the optically anisotropic layer is colored, a transparent coloring layer can be combined to adjust to a neutral tone.

[0494] The optically anisotropic layer of the present invention can be used for various applications such as an optical path changing component, a light focusing element, a light diffusing element in a specified direction, a diffraction element, etc. in an optical device that reflects (diffracts) or transmits (diffracts) light at an angle other than specular reflection.

[0495] In the above example, the optically anisotropic layer (diffraction region) of the present invention is used as an optically anisotropic layer that reflects or transmits visible light, but the present invention is not limited thereto, and various structures can be used.

[0496] For example, the optically anisotropic layer (diffraction region) of the present invention can be structured to reflect or transmit infrared rays or ultraviolet rays, or can be structured to reflect or transmit only light other than visible light.

[0497] Further, the optically anisotropic layer of the present invention can be used in combination with other components. For example, it can be used in combination with a structure sandwiched between two glasses, a low reflection layer, an ultraviolet absorber layer, a polarizer, a lens component, etc.

[0498] As described above, the optically anisotropic layer, laminate, light guide element, and 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.

[0499] Examples

[0500] 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.

[0501] [Example 1]

[0502] (Formation of alignment film)

[0503] 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.

[0504] Alignment film-forming coating solution

[0505]

[0506] -Materials for photo-alignment-

[0507] [Chemical formula 18]

[0508]

[0509] (Exposure of alignment film)

[0510] Using Figure 3 the exposure apparatus shown, a part of area 1 and area 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 area 1, after rotating the orientation of the alignment film by 180° in area 2, exposure was performed, whereby the alignment patterns of area 1 and area 2 were inverted by 180°. In the exposure apparatus, a device that emits a laser beam with 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 0.44 μm by changing the crossing angle (crossing angle α) of the two lights.

[0511] (Formation of optically anisotropic layer)

[0512] As a liquid crystal composition for forming an optically anisotropic layer, the following composition LC-1 was prepared.

[0513] Composition LC-1

[0514]

[0515] Rod-like liquid crystal compound L-1

[0516] [Chemical formula 19]

[0517]

[0518] Rod-like liquid crystal compound L-2

[0519] [Chemical formula 20]

[0520]

[0521] Chiral reagent Ch-1

[0522] [Chemical formula 21]

[0523]

[0524] Leveling agent T-1

[0525] [Chemical formula 22]

[0526]

[0527] 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 120 °C for 1 minute. Next, a mask MK-1 was placed on the composition layer, and ultraviolet light with a wavelength of 365 nm was irradiated onto the composition layer through the mask MK-1 at 40 °C in a nitrogen atmosphere using a 365 nm LED UV exposure machine at an irradiation dose of 20 mJ / cm 2 . The positional relationship between the irradiation dose of the ultraviolet light irradiated onto the composition layer through the mask MK-1 and the respective regions of the alignment film is as Figure 17 shown. Next, 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 an irradiation dose of 300 mJ / cm 2 using a 365 nm LED UV exposure machine at 200 °C in a nitrogen atmosphere, thereby fixing the alignment of the liquid crystal compound and forming an optically anisotropic layer. The thickness of the optically anisotropic layer was made 2 μm.

[0528] In the optically anisotropic layer, Figure 17The exposure shown is 0 mJ / cm 2 A non-diffraction region is formed at the position, and in region 1, where the exposure exceeds 0 mJ / cm 2 a region A (diffraction region) is formed at the position, and in region 2, where the exposure exceeds 0 mJ / cm 2 a region B (diffraction region) is formed at the position.

[0529] [Evaluation]

[0530] (Evaluation of diffraction efficiency)

[0531] As Figure 14 shown, the optically anisotropic layer fabricated above was placed on the surface of the double prism 110, 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.

[0532] As Figure 14 shown, the optically anisotropic layer was placed on the upper surface of the double prism 110, a laser was placed in such a way as to face the inclined surface of the double prism 110, and a linear polarizer 112 and a λ / 4 plate 114 were placed between the laser and the double prism 110.

[0533] If light is emitted from the laser, it passes through the linear polarizer 112 and the λ / 4 plate 114, thus becoming right-handed circularly polarized light and entering the double prism 110, propagating inside the double prism 110 and entering the optically anisotropic layer. The diffracted light reflected and diffracted by the optically anisotropic layer propagates inside the double prism 110 in the direction opposite to the surface where the optically anisotropic layer is placed. The light propagating in the double prism 110 reaches the lower surface of the double prism 110 and is emitted.

[0534] When Figure 17 the position of the end on the side where the laser beam enters of the optically anisotropic layer in was set to 0 mm, the diffraction efficiency at each position of the 5 mm scale was measured. Additionally, the wavelength of the laser beam was set to 532 nm, and the incident angle of the laser beam was set such that the 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.

[0535] 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 Iout When it is, it is calculated by the following formula.

[0536] Diffraction efficiency Deff = I out / I in

[0537] In addition, when calculating the diffraction efficiency, the loss of the transmittance at the interface when incident on the double prism 110 and when exiting is excluded, and the diffraction efficiency is calculated.

[0538] As a result of evaluating the diffraction efficiency of the optically anisotropic layer produced by the above method, the diffraction efficiency at the position of 25 mm is 13%, the diffraction efficiency at the position of 35 mm is 21%, and the diffraction efficiency at the position of 45 mm is 58%. In Figure 18 the distribution of the diffraction efficiency is shown. In Figure 18 it, symbol 221 corresponds to region A, symbol 222 corresponds to region B, and symbol 223 corresponds to the region without the alignment pattern (non-diffraction region). The diffraction efficiency of region A of symbol 221 is constant, and the diffraction efficiency of region B of symbol 222 becomes higher as it goes from one side to the other side. According to the above, Re(40) is zero, and it can be confirmed that the non-diffraction region of symbol 223 is isotropic. The measurement results of Re(40) at each position are shown in Figure 19 .

[0539] [Evaluation]

[0540] (Evaluation of the emitted light intensity distribution)

[0541] As Figure 13 shown, a light guide element was produced by disposing the optically anisotropic layer (symbol 400) produced above on the surface of the light guide plate 144. In Figure 13 it, as the light guide plate 144, a light guide plate made of glass 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.

[0542] As Figure 13 shown, a laser was disposed in such a manner that it faced the side opposite to the surface on which the optically anisotropic layer 400 was disposed at the end of the side of the light guide plate 144 where region A45a was disposed, and a linear polarizer 100 and a λ / 4 plate 102 were disposed between the laser and the light guide plate 144. A power meter (not shown) was disposed at a distance of 10 cm from the optically anisotropic layer 400 in such a manner that it faced the side opposite to the surface on which the optically anisotropic layer 400 was disposed at the end of the side of the light guide plate 144 where region B45c was disposed. In addition, the wavelength of the laser beam was set to 532 nm, and the beam diameter of the laser beam was set to 1 mm.

[0543] 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 region A45a of the optically anisotropic layer 400. Through the diffraction effect and the selective reflection effect of the region A45a of the optically anisotropic layer 400, the diffracted light that is reflected and diffracted propagates within the light guide plate 144. The light propagating within the light guide plate 144 is diffracted and reflected by the region B45c of the optically anisotropic layer 400 and is emitted toward the direction of the power meter.

[0544] Furthermore, a light shielding plate is disposed between the light guide plate 144 and the power meter in such a manner that the side opposite to the side where the optically anisotropic layer 400 is disposed faces each other. A pinhole 104a with a diameter of 2 mm is formed in the light shielding plate 104.

[0545] 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 region B45c. The intensity of the emitted light was measured using a power meter 1918-C manufactured by Newport Corporation.

[0546] The amount of light emitted from the light guide plate 144 was confirmed, and as a result, it was confirmed that the emission intensity was the same.

[0547] [Evaluation]

[0548] (Evaluation of brightness uniformity and image clarity)

[0549] The smart glasses (Vuzix Blade2) of Vuzix Corporation were disassembled, and the light guide element of the present invention was provided in place of the light guide plate of the product. Then, the brightness uniformity of the displayed image and the clarity of the image were evaluated. The brightness of the displayed image was uniform and the image was clear.

[0550] [Example 2]

[0551] The mask used was changed to the mask MK-2, and an optically anisotropic layer was formed in the same manner as in Example 1 except for this. The relationship between the irradiation amount of ultraviolet rays irradiated onto the composition layer through the mask MK-2 and the positions of the respective regions of the alignment film is as Figure 20 shown.

[0552] Next, the diffraction efficiency and Re(40) of the optically anisotropic layer were measured in the same manner as in Example 1. The diffraction efficiency is shown in Figure 21 , and the measurement results of Re(40) are shown in Figure 22 .

[0553] Next, the evaluation of brightness uniformity and image clarity was carried out in the same manner as in Example 1. The brightness of the displayed image was non-uniform in-plane, but the image was clear.

[0554] [Example 3]

[0555] The composition used was changed to Composition LC-3, and an optically anisotropic layer was formed in the same manner as in Example 1 except for this.

[0556] Composition LC-3

[0557]

[0558] Rod-like liquid crystal compound L-3

[0559] [Chemical formula 23]

[0560]

[0561] Next, the diffraction efficiency and Re(40) of the optically anisotropic layer were measured in the same manner as in Example 1. The diffraction efficiency and Re(40) were substantially the same as those in Example 1. Next, the evaluation of brightness uniformity and image clarity was carried out in the same manner as in Example 1. The brightness of the displayed image was uniform in-plane and the image was clear.

[0562] [Example 4]

[0563] The composition used was changed to Composition LC-4, and an optically anisotropic layer was formed in the same manner as in Example 1 except for this.

[0564] Composition LC-4

[0565]

[0566] Rod-like liquid crystal compound L-4

[0567] [Chemical formula 24]

[0568]

[0569] Next, the diffraction efficiency and Re(40) of the optically anisotropic layer were measured in the same manner as in Example 1. The diffraction efficiency and Re(40) were substantially the same as those in Example 1. Next, the evaluation of brightness uniformity and image clarity was carried out in the same manner as in Example 1. The brightness of the displayed image was uniform in-plane and the image was clear.

[0570] [Example 5]

[0571] As the liquid crystal composition for forming the optically anisotropic layer, the following Composition LC-5 was prepared.

[0572] Composition LC-5

[0573]

[0574]

[0575] Rod-like liquid crystal compound L-5

[0576] [Chemical formula 25]

[0577]

[0578] The prepared Composition LC-5 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 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 20 mW / cm 2 for 10 seconds.

[0579] 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 under a nitrogen atmosphere at 200 °C, thereby fixing the orientation of the liquid crystal compound and forming an optically anisotropic layer.

[0580] Then, the diffraction efficiency and Re(40) of the optically anisotropic layer were measured by the same method as in Example 1. The diffraction efficiency and Re(40) were substantially the same as those in Example 1. Then, the evaluation of brightness uniformity and image clarity was performed by the same method as in Example 1. The brightness of the displayed image was uniform in the plane, the image was clear, and the viewing angle was wider than that in Example 1.

[0581] [Example 6]

[0582] As the liquid crystal composition for forming the optically anisotropic layer, the following Composition LC-6 was prepared.

[0583] Composition LC-6

[0584]

[0585]

[0586] Rod-like liquid crystal compound L-6

[0587] [Chemical formula 26]

[0588]

[0589] 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 disposed on the composition layer, and ultraviolet rays with a wavelength of 365 nm were irradiated through the mask MK-1 at an illuminance of 20 mW / cm2 for 10 seconds at 120 °C under the atmosphere.

[0590] 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 amount of 300 mJ / cm 2 to fix the alignment of the liquid crystal compound, thereby forming an optically anisotropic layer.

[0591] Then, the diffraction efficiency and Re(40) of the optically anisotropic layer were measured by the same method as in Example 1. The diffraction efficiency and Re(40) were substantially the same as those in Example 1. Then, the evaluation of brightness uniformity and image clarity was performed by the same method as in Example 1. The brightness of the displayed image was uniform in the plane, the image was clear, and the viewing angle was wider than that in Example 1.

[0592] [Comparative Example 1]

[0593] (Exposure of the alignment film)

[0594] The alignment film was exposed using the Figure 3 shown exposure apparatus to form an alignment film P-2 having a single alignment pattern. In the exposure apparatus, a device that emits a laser beam with 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 180°) Λ of the alignment pattern formed based on the interference of two laser beams was controlled to 0.44 μm by changing the crossing angle (crossing angle α) of the two lights.

[0595] By the same method as in Example 1, the composition LC-1 was coated on the alignment film P-2 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, without using a mask, ultraviolet rays with a wavelength of 365 nm were irradiated at an irradiation amount of 300 mJ / cm 2The exposure amount irradiated ultraviolet rays with a wavelength of 365 nm to the coating film, thereby fixing the orientation of the liquid crystal compound and forming an optically anisotropic layer.

[0596] Next, the optically anisotropic layer was cut out, peeled off from the glass substrate, and the optically anisotropic layer was disposed on the incident side and the emission side of the light guide plate surface, respectively, so as to be Figure 23 the diffraction efficiency distribution shown (refer to Figure 24 ). 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 disposed after being cut out. 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.

[0597] Next, the evaluation of the brightness uniformity and the image sharpness was carried out by the same method as in Example 1. The brightness of the displayed image was uneven in the plane, and the image was not clear.

[0598] Industrial availability

[0599] It can be preferably used for various uses of reflecting light in optical devices such as diffraction elements that make light incident on and emit from the light guide plate of AR glasses.

[0600] Symbol description

[0601] 10, 12 - liquid crystal diffraction element, 16 - liquid crystal diffraction layer, 18 - cholesteric liquid crystal layer, 20 - support, 24 - alignment film, 30 - liquid crystal compound, 30A - optical axis, 40 - display (image display device), 42 - light part, 44 - dark part, 45 - light guide element, 45a - region A, 45b - non-diffraction region, 45c - region B, 45d - region C, 50 - AR display device, 60 - exposure device, 62 - laser, 64 - light source, 68 - beam splitter, 70A, 70B - mirror, 72A, 72B - λ / 4 plate, 100 - linear polarizer, 102 - λ / 4 plate, 104 - light shielding plate, 104a - pinhole, 110 - biprism, 112 - linear polarizer, 114 - λ / 4 plate, 144 - light guide plate, 316, 318 - region, 320 - support, 322 - alignment film, 324 - coating film, 326 - first region, 328 - second region, 329 - photomask, 400, 450 - optically anisotropic layer, 400a - first optically anisotropic layer, 400b - second optically anisotropic layer, 410a, 420a - region A, 410b, 420b - non-diffraction region, 410c, 420c - region B, 500 - laminate, M - laser beam, MA, MB - light ray, PO - Linearly polarized light, P R - Right-handed circularly polarized light, P L - Left-handed circularly polarized light, α - crossing angle, L1, L4 - incident light, L2, L5 - reflected light, R R - Right-handed circularly polarized light of red light, I0~I3 - light propagating in the light guide plate, P1~P4 - positions, R1~R4 - light.

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, the optically anisotropic layer has, in the in-plane direction of the same optically anisotropic layer: Region A, 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 while changing; Region B, 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 while changing; and a region without the liquid crystal alignment pattern.

2. The optically anisotropic layer according to claim 1, wherein, the optically anisotropic layer further has Region C in the in-plane direction of the same optically anisotropic layer, and Region C 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.

3. The optically anisotropic layer according to any one of claims 1 or 2, wherein, in the in-plane direction of the same optically anisotropic layer, the optically anisotropic layer has the region without the liquid crystal alignment pattern between Region A having the liquid crystal alignment pattern and Region B having the liquid crystal alignment pattern.

4. The optically anisotropic layer according to any one of claims 1 or 2, wherein, in at least one of Region A and Region B, there are regions having different diffraction efficiencies in the in-plane direction.

5. The optically anisotropic layer according to claim 4, wherein, in at least one of Region A and Region B, there are regions in which the diffraction efficiency gradually increases in the in-plane direction.

6. The optically anisotropic layer according to any one of claims 1 or 2, wherein, the rotation direction of the optical axis derived from the liquid crystal compound along the one direction in the liquid crystal alignment pattern of Region A is different from the rotation direction of the optical axis derived from the liquid crystal compound along the one direction in the liquid crystal alignment pattern of Region B.

7. The optically anisotropic layer according to any one of claims 1 or 2, wherein, the one direction of the liquid crystal alignment pattern in Region A is different from the one direction of the liquid crystal alignment pattern in Region B.

8. The optically anisotropic layer according to any one of claims 1 or 2, wherein, the length of the in-plane rotation of 180° of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of Region A is different from the length of the in-plane rotation of 180° of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern of Region B.

9. The optically anisotropic layer according to any one of claims 1 or 2, wherein, at least one of Region A and Region B is a cholesteric liquid crystal layer in which the liquid crystal compound is cholesterically aligned.

10. The optically anisotropic layer according to claim 9, wherein, Region A and Region B are cholesteric liquid crystal layers, The optically anisotropic layer has a region where the length of the helical pitch of the cholesteric liquid crystal layer in region A is different from the length of the helical pitch of the cholesteric liquid crystal layer in region B.

11. The optically anisotropic layer according to claim 9, wherein, Regions A and B are cholesteric liquid crystal layers, The direction of rotation of the helix of the cholesteric orientation in region A is different from the direction of rotation of the helix of the cholesteric orientation in region B.

12. The optically anisotropic layer according to claim 9, wherein, In at least one of region A and region B, there is a region where the length of the helical pitch of the cholesteric liquid crystal layer is different in the in-plane direction of the region.

13. The optically anisotropic layer according to claim 9, wherein, In at least one of region A and region B, there is 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.

14. The optically anisotropic layer according to any one of claims 1 or 2, wherein, In the region without the liquid crystal alignment pattern, at least a part of the in-plane is optically isotropic.

15. The optically anisotropic layer according to any one of claims 1 or 2, wherein, In the region without the liquid crystal alignment pattern, at least a part of the liquid crystal compound in the in-plane is aligned in the same direction in the in-plane.

16. The optically anisotropic layer according to any one of claims 1 or 2, wherein, In the region without the liquid crystal alignment pattern, at least a part of the in-plane is a retardation plate in which the liquid crystal compound is uniaxially aligned or twisted.

17. The optically anisotropic layer according to any one of claims 1 or 2, wherein, The whole layer is smooth and does not have an uneven structure.

18. The optically anisotropic layer according to claim 4, wherein, At least one of regions A and B has a different thickness direction retardation Rth in the in-plane direction, thereby forming regions with different diffraction efficiencies.

19. A laminate having two or more optically anisotropic layers according to any one of claims 1 or 2.

20. The laminate according to claim 19, wherein, The laminate has two optically anisotropic layers, namely a first optically anisotropic layer and a second optically anisotropic layer, Region A of the first optically anisotropic layer and region A of the second optically anisotropic layer are arranged at overlapping positions, The region without the liquid crystal alignment pattern of the first optically anisotropic layer and the region without the liquid crystal alignment pattern of the second optically anisotropic layer are arranged at overlapping positions, Region B of the first optically anisotropic layer and region B of the second optically anisotropic layer are arranged at overlapping positions.

21. The laminate according to claim 20, wherein, The laminate satisfies at least one of the following conditions: The length of one period in which the orientation of the optical axis derived from the liquid crystal compound in region A of the first optically anisotropic layer rotates 180° in the in-plane is different from the length of the one period in region A of the second optically anisotropic layer; And The orientation of the optical axis derived from the liquid crystal compound in region B of the first optically anisotropic layer rotates 180° in-plane, and the length of one period thereof is different from the length of one period in region B of the second optically anisotropic layer.

22. The laminate according to claim 20, wherein The laminate satisfies at least one of the following conditions: One direction of the liquid crystal alignment pattern in region A of the first optically anisotropic layer is different from one direction of the liquid crystal alignment pattern in region A of the second optically anisotropic layer; And One direction of the liquid crystal alignment pattern in region B of the first optically anisotropic layer is different from one direction of the liquid crystal alignment pattern in region B of the second optically anisotropic layer.

23. The laminate according to claim 20, wherein The laminate satisfies at least one of the following conditions: Region A of the first optically anisotropic layer and region A of the second optically anisotropic layer are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in region A of the first optically anisotropic layer is different from the length of the helical pitch of the cholesteric liquid crystal layer in region A of the second optically anisotropic layer; And Region B of the first optically anisotropic layer and region B of the second optically anisotropic layer are cholesteric liquid crystal layers, and the length of the helical pitch of the cholesteric liquid crystal layer in region B of the first optically anisotropic layer is different from the length of the helical pitch of the cholesteric liquid crystal layer in region B of the second optically anisotropic layer.

24. The laminate according to claim 20, wherein, The laminate satisfies at least one of the following conditions: Region A of the first optically anisotropic layer and region A of the second optically anisotropic layer are cholesteric liquid crystal layers, and the rotation direction of the helix of the cholesteric liquid crystal layer in region A of the first optically anisotropic layer is different from the rotation direction of the helix of the cholesteric liquid crystal layer in region A of the second optically anisotropic layer; and Region B of the first optically anisotropic layer and region B of the second optically anisotropic layer are cholesteric liquid crystal layers, and the rotation direction of the helix of the cholesteric liquid crystal layer in region B of the first optically anisotropic layer is different from the rotation direction of the helix of the cholesteric liquid crystal layer in region B of the second optically anisotropic layer.

25. A light guide element, comprising: A light guide plate; and The optically anisotropic layer according to any one of claims 1 or 2, disposed on the surface of the light guide plate.

26. The light guide element according to claim 25, wherein, The light guide element further has a retardation layer.

27. An AR display device, comprising the light guide element according to claim 25 and an image display device.

28. The AR display device according to claim 27, wherein The light emitted from the image display device is polarized light.

29. The AR display device according to claim 27, wherein The image display device is an image display device using a laser beam scanning method.

Images