Optically anisotropic layer, optical element, and image display device

Abstract

The present invention addresses the problem of providing an optical anisotropic layer excellent in zero-order light suppression performance. The present invention also addresses the problem of providing an optical element provided with the optically anisotropic layer, and an image display device.　This optically anisotropic layer is formed using a composition containing a liquid crystal compound, the optically anisotropic layer having a liquid crystal alignment pattern in which the orientation of an optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and having a region A in which the length of one period is 0.2-20.0 μm, where the one period is the length over which the orientation of the optical axis rotates by 180° in the plane in the one direction, the surface corresponding to the region A of the optically anisotropic layer having an uneven structure, and the maximum height of the uneven structure in the one direction being 60 nm or less.

Description

Optically anisotropic layer, optical element, image display device

[0001] The present invention relates to an optically anisotropic layer, an optical element, and an image display device.

[0002] Optical elements that control the direction of light are used in many optical devices or systems, such as backlights for liquid crystal display devices, head-mounted displays (HMDs) such as augmented reality (AR) glasses that display virtual images and various information superimposed on an actual scene, projectors, beam steering, and sensors for detecting objects and measuring the distance to the objects.

[0003] An optically anisotropic layer formed using a composition containing a liquid crystal compound is known as an optical member used in the above-mentioned optical elements, particularly diffraction elements, wavelength-selective reflection layers, etc. The optically anisotropic layer is formed by aligning the liquid crystal compound in a predetermined orientation state.

[0004] For example, Patent Document 1 discloses a polarization diffraction grating technology including a polarization-sensitive photo-alignment layer and a liquid crystal composition disposed on the photo-alignment layer, in which an anisotropic alignment pattern is disposed in the photo-alignment layer, and the liquid crystal composition is aligned by the alignment pattern. The alignment pattern of this polarization diffraction grating periodically changes along at least one straight line in a plane. By utilizing such an optically anisotropic layer in which the liquid crystal alignment pattern changes in a plane, a thin optical element that controls the transmission direction of incident light can be realized.

[0005] Special Publication No. 2008-532085

[0006] The application of a polarization diffraction element having a liquid crystal orientation pattern that changes while continuously rotating along at least one direction in a plane, as described in Patent Document 1, to an image display device has been considered. The inventors studied a head-mounted display (HMD) using the polarization diffraction element while referring to the description in Patent Document 1, and found that stray light (ghost) may occur when used in an HMD. Further investigation by the inventors revealed that zero-order light transmitted through the polarization diffraction element may become stray light and be observed by an observer.

[0007] In view of the above circumstances, an object of the present invention is to provide an optically anisotropic layer that is excellent in the performance of suppressing zero-order light, and an optical element and an image display device that include the optically anisotropic layer.

[0008] The present inventors have intensively studied the problems of the prior art and found that the above-mentioned problems can be solved by the following configuration. [1] An optically anisotropic layer formed using a composition containing a liquid crystal compound, the optically anisotropic layer having a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one in-plane direction, the optically anisotropic layer having a region A in which the length of one period is 0.2 to 20.0 μm, where the length of a 180° in-plane rotation of the direction of the optical axis in the one direction is one period, the optically anisotropic layer having a surface corresponding to the region A having a concave-convex structure, the maximum height of the concave-convex structure in the one direction being 60 nm or less. [2] The optically anisotropic layer according to [1], wherein the liquid crystal compound has a tolan structure. [3] The optically anisotropic layer according to [2], wherein the liquid crystal compound having a tolan structure further has a sulfide bond. [4] The optically anisotropic layer according to [1], wherein the liquid crystal compound comprises a polyfunctional polymerizable liquid crystal compound having two or more polymerizable groups and a monofunctional polymerizable liquid crystal compound having one polymerizable group. [5] The optically anisotropic layer according to [1], wherein the composition comprises at least one selected from the group consisting of a thiol compound and a phenol compound. [6] The optically anisotropic layer according to [1], wherein, when the length of one period is Λ (μm) and the maximum height of the uneven structure is d (nm), the value α calculated from Λ and d using the following formula (1) is 50 or less. α=(Λ) １／２ ×d (1) [7] The optically anisotropic layer according to [6], wherein the above α is 40 or less. [8] An optical element comprising the optically anisotropic layer according to any one of [1] to [7]. [9] An image display device comprising the optical element according to [8] and a display element that projects an image onto the optical element.

[0009] According to the present invention, an optically anisotropic layer having excellent performance in suppressing zero-order light can be provided, and further, according to the present invention, an optical element and an image display device including the optically anisotropic layer can be provided.

[0010] Fig. 2 is a cross-sectional view conceptually showing one example of the optically anisotropic layer of the present invention. Fig. 3 is a plan view of the optically anisotropic layer shown in Fig. 1. Fig. 4 is a cross-sectional view conceptually showing one example of the function of the optically anisotropic layer of the present invention. Fig. 5 is a cross-sectional view conceptually showing another example of the function of the optically anisotropic layer of the present invention. Fig. 6 is a diagram conceptually showing one example of an exposure device for forming an alignment pattern. Fig. 7 is a plan view conceptually showing another example of the optically anisotropic layer of the present invention. Fig. 8 is a diagram conceptually showing another example of an exposure device for forming an alignment pattern.

[0011] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In each drawing, the scale of the components is appropriately different from the actual scale for easier viewing and explanation.

[0012] In this specification, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits. In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. When two or more substances are used in combination for each component, the content of the component refers to the total content of the combined substances, unless otherwise specified. In this specification, the "solid content" of a composition refers to the components that form a composition layer formed using the composition. When the composition contains a solvent (organic solvent, water, etc.), it refers to all components excluding the solvent. Furthermore, liquid components that form a composition layer are also considered to be solids. In this specification, "(meth)acrylate" refers to either or both of acrylate and methacrylate. "(Meth)acryloyl group" refers to either or both of acryloyl group and methacryloyl group. "(Meth)acrylic" refers to either or both of acrylic and methacrylic.

[0013] In this specification, "same" includes a generally accepted error range in the technical field. Furthermore, in this specification, terms such as "all," "all," and "entire surface" include not only 100% but also generally accepted error ranges in the technical field, such as 99% or more, 95% or more, or 90% or more. Regarding angles, "orthogonal" or "perpendicular" refers to a range of 90°±5°, and "parallel" refers to a range of 0°±5°. Similarly, unless otherwise specified, angles refer to angles within a range of 5 degrees from the exact angle. The difference in the above angles is preferably within 4 degrees, and more preferably within 3 degrees.

[0014] In this specification, visible light refers to electromagnetic waves with wavelengths visible to the human eye, i.e., light in the wavelength range of 380 to 780 nm. Ultraviolet light is light in the wavelength range of 10 nm or more and less than 380 nm, and infrared light is light in the wavelength range of over 780 nm. Furthermore, within visible light, light in the wavelength range of 420 to 490 nm is blue (B) light, light in the wavelength range of 495 to 570 nm is green (G) light, and light in the wavelength range of 620 to 750 nm is red (R) light, although not limited thereto.

[0015] In this specification, Re(λ) represents the in-plane retardation at a wavelength λ. Unless otherwise specified, the wavelength λ is 550 nm. In this specification, Re(λ) is a value measured at a wavelength λ using an AxoScan (manufactured by Axometrics). By inputting the average refractive index ((nx + ny + nz) / 3) and film thickness (d (μm)) into AxoScan, the slow axis direction (°) Re(λ) = R0(λ) is calculated. Note that R0(λ) is displayed as a numerical value calculated by AxoScan, but it means Re(λ).

[0016] In this specification, unless otherwise specified, the thickness of a layer is a value obtained by observing a cross section cut by a microtome with a SEM (scanning electron microscope) or a TEM (transmission electron microscope) and measuring the thickness at 10 points, and averaging the thickness.

[0017] [Optically Anisotropic Layer] The optically anisotropic layer of the present invention is an optically anisotropic layer formed using a composition containing a liquid crystal compound, and has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one in-plane direction. The optically anisotropic layer of the present invention has a region A in which, when the length of a 180° in-plane rotation of the optical axis in this one direction is defined as one period, the length of one period is 0.2 to 20.0 μm, and the surface of the optically anisotropic layer corresponding to the region A has an uneven structure, and the maximum height of the uneven structure in the one direction is 60 nm or less.

[0018] 1 and 2 conceptually show an example of the optically anisotropic layer of the present invention. FIG. 2 is a plan view of the optically anisotropic layer shown in FIG. 1. That is, FIG. 2 is a view of the optically anisotropic layer 10 as viewed from the thickness direction (the direction indicated by arrow Z in FIG. 1). In other words, FIG. 2 is a view of the optically anisotropic layer 10 as viewed from a direction perpendicular to the main surface. FIG. 1 is a cross-sectional view taken along line A-A in FIG. 2. In FIG. 2, in order to clearly show the structure of the optically anisotropic layer 10 of the present invention, only the liquid crystal compound 30 on the surface of the optically anisotropic layer 10 is shown. However, the optically anisotropic layer 10 has a structure in which the liquid crystal compound 30 is stacked in the thickness direction, as shown in FIG. 1.

[0019] The optically anisotropic layer 10 is formed using a composition containing a liquid crystal compound 30. The optically anisotropic layer 10 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 changes while continuously rotating in one direction within the plane of the optically anisotropic layer 10. In the embodiment shown in FIG. 2, the orientation of the optical axis 30A derived from the liquid crystal compound 30 changes while continuously rotating counterclockwise along one direction indicated by arrow X. However, the present invention is not particularly limited to this embodiment, and the orientation of the optical axis derived from the liquid crystal compound may change while continuously rotating clockwise along one direction. The optical axis 30A derived from the liquid crystal compound 30 is the axis along which the refractive index of the liquid crystal compound 30 is highest, i.e., 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 aligned with the long axis direction of the rod shape. As shown in FIG. 1, in the optically anisotropic layer 10 of the present invention, a concave-convex structure 20 is formed on the surface 10A corresponding to the above-mentioned region A. Region A and the concave-convex structure 20 will be described in detail later.

[0020] In the following description, the optical axis derived from the liquid crystal compound is also referred to as the "optical axis of the liquid crystal compound" or simply as the "optical axis." In the following description, the in-plane direction in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating in the optically anisotropic layer, and the direction indicated by the arrow X, are also simply referred to as the "X direction." In the optically anisotropic layer 10, the liquid crystal compound 30 is two-dimensionally aligned in a plane including the X direction and a direction indicated by the arrow Y (hereinafter also referred to as the "Y direction") perpendicular to the X direction. In FIG. 1, the Y direction is perpendicular to the paper surface. In FIG. 1, the direction indicated by the arrow Z (hereinafter also referred to as the "Z direction") is the thickness direction of the optically anisotropic layer 10, and is also perpendicular to the X direction and the Y direction in the optically anisotropic layer 10. In FIG. 2, the Z direction is perpendicular to the paper surface.

[0021] FIG. 2 conceptually shows a plan view of the optically anisotropic layer 10. The optically anisotropic layer 10 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 changes while continuously rotating along the X direction within the plane of the optically anisotropic layer 10. The phrase "the orientation of the optical axis 30A of the liquid crystal compound 30 changes while continuously rotating along the X direction (a predetermined direction)" specifically means that the angle between the optical axis 30A of the liquid crystal compound 30 aligned along the X direction and the X direction varies depending on the position in the X direction, and the angle between the optical axis 30A and the X direction changes sequentially from θ to θ+180° or θ−180° along the X direction. The difference in angle between the optical axes 30A of the liquid crystal compounds 30 adjacent to each other in the X direction is preferably 45° or less, more preferably 15° or less, and even smaller angles are preferred. In the present invention, the liquid crystal compounds are rotated in a direction such that the angle formed by the optical axes 30A of the liquid crystal compounds 30 adjacent to each other in the X direction becomes smaller. Therefore, in the optically anisotropic layer 10 shown in Figures 1 and 2, the optical axes 30A of the liquid crystal compounds 30 are rotated leftward (counterclockwise) along the X direction.

[0022] On the other hand, the liquid crystal compounds 30 forming the optically anisotropic layer 10 have the same orientation of the optical axis 30A in the Y direction perpendicular to the X direction, i.e., the Y direction perpendicular to the one direction in which the optical axis 30A continuously rotates. In other words, among the liquid crystal compounds 30 forming the optically anisotropic layer 10, the orientation of the optical axis 30A of the liquid crystal compounds 30 aligned in the Y direction has the same angle between the X direction and the X direction.

[0023] In the optically anisotropic layer 10, the angle between the optical axis 30A and the X direction (one direction in which the optical axis of the liquid crystal compound 30 rotates) is equal for the liquid crystal compounds 30 aligned in the Y direction. A region R is defined as a region in which the liquid crystal compounds 30, with the optical axis 30A and the X direction forming the same angle, are arranged in the Y direction. In this case, the in-plane retardation (Re) value in each region R is preferably half the wavelength, i.e., λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn associated with the refractive index anisotropy of region R and the thickness of the optically anisotropic layer. Here, the refractive index difference associated with the refractive index anisotropy of region R in the optically anisotropic layer is a refractive index difference defined by the difference between the refractive index in the direction of the slow axis in the plane of region R and the refractive index in the direction perpendicular to the direction of the slow axis. That is, the refractive index difference Δn due to the refractive index anisotropy of region R is equal to the difference between the refractive index of liquid crystal compound 30 in the direction of optical axis 30A and the refractive index of liquid crystal compound 30 in the direction perpendicular to optical axis 30A in the plane of region R. In other words, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

[0024] In such a liquid crystal orientation pattern of the liquid crystal compound 30, the length (distance) over which the optical axis 30A of the liquid crystal compound 30 rotates 180° in the X direction, in which the orientation of the optical axis 30A continuously changes in plane, is defined as the length Λ of one period of the liquid crystal orientation pattern. In other words, the length of one period of the liquid crystal orientation pattern is defined as the distance from the angle between the optical axis 30A of the liquid crystal compound 30 and the X direction, from θ to θ+180°. That is, the distance between the centers in the X direction of two liquid crystal compounds 30 that have the same angle with the X direction is defined as the length Λ of one period. Specifically, as shown in FIGS. 1 and 2 , the distance between the centers in the X direction of two liquid crystal compounds 30 whose optical axes 30A coincide with the X direction 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 alignment pattern of the optically anisotropic layer 10 of the present invention, this one period Λ is repeated in the X direction, that is, in one direction in which the orientation of the optical axis 30A changes by continuously rotating.

[0025] The optically anisotropic layer of the present invention has a region A in which the period Λ of the liquid crystal alignment pattern is 0.2 to 20.0 μm. Region A may be a part of the liquid crystal alignment pattern of the optically anisotropic layer, or may be the entire surface of the liquid crystal alignment pattern, but it is preferable that the entire surface of the liquid crystal alignment pattern of the optically anisotropic layer is region A. As long as at least a part of the optically anisotropic layer is region A, the period Λ of the optically anisotropic layer does not need to be uniform over the entire surface. That is, the optically anisotropic layer may have regions in which the period Λ varies within the plane.

[0026] In the optically anisotropic layer and region A, one period Λ is preferably 10 μm or less, more preferably 5 μm or less, in order to achieve better suppression performance of zero-order light. There is no particular lower limit for one period Λ, but it is preferably 0.5 μm or more.

[0027] The optically anisotropic layer may have a liquid crystal alignment pattern formed in a part thereof, in which the direction of the optical axis is rotated in the X direction, and may have a region in which the direction of the optical axis is constant.

[0028] In the liquid crystal alignment pattern of the optically anisotropic layer, the direction of the X direction and the length Λ of one period in which the optical axis derived from the liquid crystal compound rotates by 180° along the X direction can be measured by observing the optically anisotropic layer using a polarizing microscope or by observing a cross section of the optically anisotropic layer including the Z direction using an atomic force microscope (AFM).

[0029] <Relief Structure> The optically anisotropic layer 10 of the present invention has a relief structure 20 having a maximum height in the X direction of 60 nm or less on the surface 10A corresponding to the region A where one period Λ is 0.2 to 20.0 μm. It is believed that by having such a relief structure 20 on the surface 10A of the optically anisotropic layer 10, it is possible to suppress a component of circularly polarized light (e.g., right-handed circularly polarized light) having a rotation direction opposite to that of circularly polarized light having a desired rotation direction (e.g., left-handed circularly polarized light), i.e., zero-order light, in the transmitted light diffracted by the optically anisotropic layer 10.

[0030] The maximum height in the X direction of the uneven structure 20 on the surface 10A corresponding to region A of the optically anisotropic layer 10 (hereinafter also referred to as the "maximum height d of the uneven structure") means the difference between the highest and lowest points on a roughness curve representing the shape of the surface of the optically anisotropic layer 10 along the X direction. The maximum height d of the uneven structure is preferably 30 nm or less, and more preferably 20 nm or less, in terms of better performance in suppressing zero-order light. The lower limit is not particularly limited and may be, for example, 1 nm or more.

[0031] The maximum height d of the concave-convex structure can be adjusted by the composition of the liquid crystal compound-containing composition used to form the optically anisotropic layer, and the curing conditions when the optically anisotropic layer is formed using the composition.

[0032] The shape of the uneven structure is not particularly limited, but it is preferable that the surface corresponding to region A has a periodic structure in which convex portions and concave portions are periodically repeated along the X direction. When the uneven structure has the periodic structure in the X direction, it is preferable that the length of one period of the periodic structure in which convex portions and concave portions are periodically repeated (hereinafter also referred to as the "average length P of one period of the uneven structure") is equal to one period Λ of the liquid crystal alignment pattern. Here, "the average length P of one period of the uneven structure is equal to one period Λ of the liquid crystal alignment pattern" means that the absolute value of the value calculated using the following formula (A) is 5% or less: {(one period Λ of the liquid crystal alignment pattern) - (average length P of one period of the uneven structure)} / (one period Λ of the liquid crystal alignment pattern) x 100 (A)

[0033] The average length P of one period of the concave-convex structure refers to the distance between two adjacent convex portions or two adjacent concave portions in a periodic structure in which convex portions and concave portions are periodically repeated. More precisely, the average length P of one period of the concave-convex structure is determined by determining the positions showing the maximum (or minimum) values ​​of each of two adjacent convex portions (or concave portions) from a roughness curve showing the surface shape of the concave-convex structure in the X direction, and then calculating the distance between both positions. The absolute value of the average length P of one period of the concave-convex structure is, for example, 0.2 to 20.0 μm, preferably 0.2 to 10 μm, and more preferably 0.5 to 5 μm.

[0034] The shape of the concave-convex structure formed on the surface of the optically anisotropic layer, including the maximum height d and the average length P of one period, can be measured using a non-contact surface / layer cross-sectional shape measurement system VertScan (manufactured by Hitachi High-Technologies Corporation) and its built-in data analysis software (VS-Measure). The method for measuring the shape of the concave-convex structure will be described in detail in the examples below.

[0035] <α> With respect to one period Λ and the maximum height d of the concave-convex structure of the optically anisotropic layer, when the unit of one period Λ is "μm" and the unit of the maximum height d of the concave-convex structure is "nm", the value α calculated from Λ and d using the following formula (1) is preferably 50 or less, more preferably 40 or less. α=(Λ) １／２ ×d (1) This is because when the value α is in the above range, the performance of suppressing the zero-order light is superior. There is no particular lower limit to the value α, and it may be, for example, 1 or more.

[0036] The thickness of the optically anisotropic layer is not particularly limited, but is preferably greater than ¼ of the minimum length of one period in which the orientation of the optical axis derived from the liquid crystal compound rotates 180° in the plane. The upper limit is not particularly limited, but is often not more than twice the minimum length of one period. The thickness of the optically anisotropic layer is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1.5 μm or more. The upper limit is not particularly limited, but is preferably 20 μm or less, more preferably 15 μm or less.

[0037] <Function of Optically Anisotropic Layer> The optically anisotropic layer of the present invention has the function of, for example, transmitting incident circularly polarized light and refracting (diffracting) it in the direction in which the optical axis is continuously rotating. That is, the optically anisotropic layer can be used as a transmission-type optically anisotropic layer (liquid crystal diffraction grating) that transmits circularly polarized light and diffracts the transmitted light. In this case, the direction of diffraction differs depending on the rotation direction of the incident circularly polarized light. Furthermore, the optically anisotropic layer changes the rotation direction of the transmitted circularly polarized light to the opposite direction. This function is conceptually shown in Figures 3 and 4. It is assumed that the product of the refractive index difference of the liquid crystal compound and the thickness of the optically anisotropic layer is λ / 2. As shown in Figure 3, when the product of the refractive index difference of the liquid crystal compound of the optically anisotropic layer and the thickness of the optically anisotropic layer is λ / 2, left-handed circularly polarized incident light L １ When incident, the incident light L １ is given a phase difference of 180° by passing through the optically anisotropic layer, and the transmitted light L ２ In addition, since the liquid crystal orientation pattern formed in the optically anisotropic layer is a periodic pattern in the X direction, the transmitted light L ２ is the incident light L １ In this way, the left-handed circularly polarized incident light L １ is the right-handed circularly polarized transmitted light L that is tilted at a certain angle in the X direction with respect to the incident direction. ２ In the example shown in FIG. ２ is diffracted to travel in the lower right direction.

[0038] On the other hand, as shown in FIG. 4, when the product of the refractive index difference of the liquid crystal compound in the optically anisotropic layer and the thickness of the optically anisotropic layer is λ / 2, right-handed circularly polarized incident light L ４ When incident, the incident light L ４ is given a phase difference of 180° by passing through the optically anisotropic layer, and becomes the left-handed circularly polarized transmitted light L ５ In addition, since the liquid crystal orientation pattern formed in the optically anisotropic layer is a periodic pattern in the X direction, the transmitted light L ５ is the incident light L ４ At this time, the transmitted light L ５ is the transmitted light L２ In other words, the incident light L travels in the direction opposite to the X direction. ４ is the transmitted light L of left-handed circularly polarized light inclined at a certain angle in the direction opposite to the X direction with respect to the incident direction. ５ In the example shown in FIG. ５ is diffracted to travel in the lower left direction.

[0039] As described above, the optically anisotropic layer has a structure in which the transmitted light L ２ and L ５ Specifically, in the optically anisotropic layer, the shorter the period Λ of the liquid crystal alignment pattern, the stronger the interference between the lights passing through the adjacent liquid crystal compounds 30, and therefore the angle of refraction of the transmitted light L ２ and L ５ can be greatly refracted.

[0040] Furthermore, by reversing the rotation direction of the optical axis of the liquid crystal compound 30, which rotates along the X direction, the direction of refraction of transmitted light can be reversed. Specifically, in Figures 3 and 4, when the rotation direction of the optical axis pointing toward the X direction is counterclockwise, left-handed circularly polarized light incident on the optically anisotropic layer from above in the figure is converted into right-handed circularly polarized light as it passes through the optically anisotropic layer, and is diffracted to travel in the lower left direction in the figure. Also, right-handed circularly polarized light incident on the optically anisotropic layer from above in the figure is converted into left-handed circularly polarized light as it passes through the optically anisotropic layer, and is diffracted to travel in the lower right direction in the figure.

[0041] <Method for forming an optically anisotropic layer> The optically anisotropic layer can be formed by applying a liquid crystal composition containing a liquid crystal compound onto an alignment film for orienting the liquid crystal compound in a predetermined liquid crystal alignment pattern, forming a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and fixing this in a layer form.

[0042] (Support) The optically anisotropic layer and the alignment film used to form the optically anisotropic layer are preferably supported by a support.As the support for supporting the alignment film and the optically anisotropic layer, various sheet-like materials (films, plate-like materials) can be used as long as they can support the alignment film and the optically anisotropic layer.In addition, the support preferably has a transmittance of 50% or more for diffracted light, more preferably 70% or more, and even more preferably 85% or more.

[0043] The thickness of the support is not particularly limited, and may be appropriately set to a thickness that can support the alignment film and the optically anisotropic layer depending on the application of the optical element, the material forming the support, etc. The thickness of the support is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and even more preferably 5 to 150 μm.

[0044] The support may be a single layer or a multilayer. Examples of single-layer supports include supports made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, polyolefin, etc. Examples of multilayer supports include those that include any of the above-mentioned single-layer supports as a substrate and have other layers provided on the surface of this substrate.

[0045] (Alignment Film) The alignment film is a film for aligning the liquid crystal compound 30 into a predetermined liquid crystal alignment pattern when forming an optically anisotropic layer. As described above, the optically anisotropic layer of the present invention has a liquid crystal alignment pattern in which the direction of the optic axis 30A (see FIG. 2) derived from the liquid crystal compound 30 changes while continuously rotating along one in-plane direction. Therefore, the alignment film is formed so that the optically anisotropic layer can form this liquid crystal alignment pattern. In the following description, "the direction of the optic axis 30A rotates" will also be simply referred to as "the optic axis 30A rotates."

[0046] Various known alignment films can be used, including, for example, a rubbed film made of an organic compound such as a polymer, an obliquely evaporated film of an inorganic compound, a film having microgrooves, and a film formed by accumulating LB (Langmuir-Blodgett) films made of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate by the Langmuir-Blodgett method.

[0047] The alignment film formed by rubbing treatment can be formed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. Preferred materials for the alignment film include polyimide, polyvinyl alcohol, polymers having polymerizable groups as described in JP-A-9-152509, and materials used to form alignment film 18 as described in JP-A-2005-97377, JP-A-2005-99228, and JP-A-2005-128503.

[0048] The alignment film is preferably a so-called photo-alignment film, which is formed by irradiating a photo-alignable material with polarized or non-polarized light. That is, the alignment film is preferably a photo-alignment film formed by applying a photo-alignment material onto a support. The polarized light can be irradiated perpendicularly or obliquely to the photo-alignment film, and the non-polarized light can be irradiated obliquely to the photo-alignment film.

[0049] Examples of photo-alignment materials used in the alignment film that can be used in the present invention include those 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, and JP-A-200 azo compounds described in JP-A-7-133184, JP-A-2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746, aromatic ester compounds described in JP-A-2002-229039, maleimides having photo-alignable units described in JP-A-2002-265541 and JP-A-2002-317013, and / or alkenyl-substituted nadimide compounds, photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides, and photocrosslinkable polyesters described in JP-T-2003-520878, JP-T-2004-529220, and JP-T-4162850, and photodimerizable compounds described in JP-A-9-118717, JP-A-10-506420, JP-A-2003-505561, WO 2010 / 150748, JP-A-2013-177561, and JP-A-2014-12823, particularly cinnamate compounds, chalcone compounds, and coumarin compounds, are exemplified as preferred examples. Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable polyesters, cinnamate compounds, and chalcone compounds are preferably used.

[0050] The thickness of the alignment film is not particularly limited, and may be appropriately set to a thickness that provides the necessary alignment function depending on the material used to form the alignment film. The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[0051] The method for forming the alignment film is not particularly limited, and various known methods can be used depending on the material for forming the alignment film. One example is a method in which an alignment film is applied to the surface of a support and dried, and then the alignment film is exposed to laser light to form an alignment pattern.

[0052] Fig. 5 conceptually shows an example of an exposure device for forming an alignment pattern by exposing an alignment film. The exposure device 60 shown in Fig. 5 includes a light source 64 equipped with a laser 62, a λ / 2 plate 65 for changing the polarization direction of laser light M emitted by the laser 62, a beam splitter 68 for splitting the laser light M emitted by the laser 62 into two beams MA and MB, mirrors 70A and 70B arranged on the optical paths of the two split beams MA and MB, and λ / 4 plates 72A and 72B. The light source 64 emits linearly polarized light P ０ The λ / 4 plate 72A emits linearly polarized light P ０ (ray MA) is right circularly polarized P Ｒ The λ / 4 plate 72B is a linearly polarized light P ０ (Light ray MB) is polarized by left-handed circular polarization P Ｌ are converted to , respectively.

[0053] The support 12 having the alignment film 18 before the alignment pattern is placed in an exposure section, and two light beams MA and MB are caused to intersect and interfere on the alignment film 18, and the alignment film 18 is exposed to the interference light. This interference causes the polarization state of the light irradiating the alignment film 18 to periodically change in the form of interference fringes. This results in an alignment film having an alignment pattern in which the alignment state periodically changes (hereinafter also referred to as a "pattern alignment film"). In the exposure device 60, the period of the alignment pattern can be adjusted by changing the crossing angle θ of the two light beams MA and MB. That is, in the exposure device 60, the length of one period (one period Λ) in which the optical axis 30A derived from the liquid crystal compound 30 rotates 180° in an alignment pattern in which the optical axis 30A continuously rotates along one direction can be adjusted by adjusting the crossing angle θ. By forming an optically anisotropic layer on the alignment film 18 having such an alignment pattern in which the alignment state changes periodically, it is possible to form an optically anisotropic layer having a liquid crystal alignment pattern in which the optical axis 30A derived from the liquid crystal compound 30 continuously rotates along one direction. Furthermore, 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.

[0054] As described above, the patterned alignment film has an alignment pattern that aligns liquid crystal compounds in an optically anisotropic layer formed on the patterned alignment film, so that the orientation of the optical axis of the liquid crystal compound changes while continuously rotating along at least one in-plane direction. If the patterned alignment film defines an axis along the direction in which the liquid crystal compound is aligned as the alignment axis, then the patterned alignment film can be said to have an alignment pattern in which the orientation of the alignment axis changes while continuously rotating along at least one in-plane direction. The alignment axis of the patterned alignment film can be detected by measuring absorption anisotropy. For example, when the patterned alignment film is irradiated with linearly polarized light while being rotated and the amount of light transmitted through the patterned alignment film is measured, the direction in which the amount of light is maximized or minimized is observed to gradually change along one in-plane direction.

[0055] In the present invention, the alignment film is provided as a preferred embodiment but is not an essential component. For example, by forming an alignment pattern on the support by a method of rubbing the support or a method of processing the support with laser light or the like, it is possible to configure the optically anisotropic layer to have a liquid crystal alignment pattern in which the direction of the optical axis 30A derived from the liquid crystal compound 30 changes while continuously rotating along at least one direction in the plane. That is, in the present invention, the support may function as an alignment film.

[0056] (Formation of Optically Anisotropic Layer) The optically anisotropic layer can be formed by forming a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and then fixing (curing) this to form a layer. The fixed liquid crystal orientation pattern may be a structure in which the orientation of the liquid crystal compound is maintained. Typically, a polymerizable liquid crystal compound is oriented along the liquid crystal orientation pattern, and then polymerized and cured by ultraviolet irradiation, heating, etc. to form a non-fluid layer, and at the same time, a structure in which the orientation form is changed to a state in which it does not change due to an external field or external force is preferred. Note that it is sufficient for the fixed liquid crystal orientation pattern to maintain the optical properties that function as an optically anisotropic layer, and the liquid crystal compound in the optically anisotropic layer does not need to exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may be polymerized by a curing reaction and lose its liquid crystallinity.

[0057] The optically anisotropic layer of the present invention is formed using a liquid crystal composition containing a liquid crystal compound. The liquid crystal compound is preferably a polymerizable liquid crystal compound. The liquid crystal composition used to form the optically anisotropic layer may further contain a surfactant, a polymerization initiator, a crosslinking agent, etc.

[0058] --Polymerizable Liquid Crystal Compound-- The polymerizable liquid crystal compound may be a rod-shaped liquid crystal compound or a discotic liquid crystal compound. Examples of rod-shaped polymerizable liquid crystal compounds that form optically anisotropic layers include rod-shaped nematic liquid crystal compounds. Preferred rod-shaped nematic liquid crystal compounds include azomethines, azoxy compounds, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles. Furthermore, both low-molecular-weight liquid crystal compounds and high-molecular-weight liquid crystal compounds can be used as the liquid crystal compound. Here, "low-molecular-weight liquid crystal compounds" refer to liquid crystal compounds that do not have repeating units in their chemical structure, and "high-molecular-weight liquid crystal compounds" refer to liquid crystal compounds that have repeating units in their chemical structure.

[0059] A polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into a liquid crystal compound. The polymerizable group is not particularly limited, but a polymerizable group capable of radical polymerization or cation polymerization is preferred. As the radical polymerizable group, known radical polymerizable groups can be used, and a preferred example is a (meth)acryloyloxy group. In this case, the polymerization rate of an acryloyloxy group is generally known to be fast, and an acryloyloxy group is preferred from the viewpoint of improving productivity, but a methacryloyloxy group can also be used as the polymerizable group. As the cationically polymerizable group, known cationically polymerizable groups can be used, and specific examples include an alicyclic ether group, a cyclic acetal group, a cyclic lactone group, a cyclic thioether group, a spiro orthoester group, and a vinyloxy group. Among these, an alicyclic ether group or a vinyloxy group is preferred, and an epoxy group, an oxetanyl group, or a vinyloxy group is particularly preferred. Particularly preferred examples of the polymerizable group include polymerizable groups represented by any of the following formulas (P-1) to (P-20), and among these, an acryloyloxy group represented by the following formula (P-1) or a methacryloyloxy group represented by the following formula (P-2) is more preferred.

[0060]

[0061] Examples of the polymerizable liquid crystal compound include compounds described in JP 2013-112631 A, JP 2010-70543 A, Japanese Patent No. 4725516 A, JP 2001-328973 A, JP 2011-207942 A, JP 2012-006996 A, JP 2012-006843 A, JP-T-2005-531618 A, JP-T-2004-534100 A, JP-T-2008-512504 A, JP-T-2011-510915 A, JP-T-2016-509247 A, and WO 2019 / 182129.

[0062] The type of liquid crystal compound is not particularly limited as long as it can be oriented in a pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. However, liquid crystal compounds having a tolan structure (diphenylacetylene structure) (hereinafter also referred to as "tolane-type liquid crystal compounds") are preferred because they have a high birefringence (refractive index difference) Δn of the optically anisotropic layer and can reduce the thickness of the optically anisotropic layer, resulting in better optical performance of the optically anisotropic layer. Preferred tolan-type liquid crystal compounds are the compounds described in WO 2019 / 182129. Preferred tolan-type liquid crystal compounds are compounds represented by the following general formula (I):

[0063]

[0064] In general formula (I), P １ and P ２ each independently represents a hydrogen atom, —CN, —NCS, or a polymerizable group. １ and P ２ At least one of P represents a polymerizable group. １ and P ２ Each of Sp preferably represents a polymerizable group. １ and Sp ２ each independently represents a single bond or a divalent linking group. １ and Sp ２ does not represent a divalent linking group containing at least one group selected from the group consisting of an aromatic hydrocarbon ring group, an aromatic heterocyclic group, and an aliphatic hydrocarbon ring group. １ , Z ２ and Z ３ each independently represents a single bond, —O—, —S—, —CHR—, —CHRCHR—, —OCHR—, —CHRO—, —SO—, or —SO ２ -, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NR-, -NR-CO-, -SCHR-, -CHRS-, -SO-CHR-, -CHR-SO-, -SO ２ -CHR-, -CHR-SO ２ -, -CF ２ O-, -OCF ２ -, -CF ２S-, -SCF ２ -, -OCHRCHRO-, -SCHRCHRS-, -SO-CHRCHR-SO-, -SO ２ -CHRCHR-SO ２ -, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -COO-CHRCHR-, -OCO-CHRCHR-, -CHRCHR-COO-, -CHRCHR-OCO-, -COO-CHR-, -OCO-CHR-, -CHR-COO-, -CHR-OCO-, -CR=CR-, -CR=N-, -N=CR-, -N=N-, -CR=N-N=CR-, -CF=CF- or -C≡C-. R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When multiple Rs are present, they may be the same or different. Z １ and Z ２ When there are a plurality of Z, they may be the same or different. ３ may be the same or different, provided that Sp ２ Z connected to ３ represents a single bond. １ and X ２ Each of X independently represents a single bond or -S-. １ and X ２ may be the same or different. k represents an integer of 2 to 4. m and n each independently represent an integer of 0 to 3. A １ , A ２ , A ３ and A ４ each independently represents a group represented by any one of the following general formulae (B-1) to (B-7), or a group formed by linking two to three groups represented by any one of the following general formulae (B-1) to (B-7). ２ and A ３ may be the same or different. １ and A ４ When there are a plurality of each, they may be the same or different.

[0065]

[0066] In general formulas (B-1) to (B-7), W １ ~W １８ are each independently CR １ or N, R １ represents a hydrogen atom or the following substituent L. １ ~Y ６ are each independently NR ２ , O or S, R ２ represents a hydrogen atom or the following substituent L. １ ~G ４ are each independently CR ３ R ４ , N.R. ５ , O or S, R ３ ~R ５ each independently represents a hydrogen atom or the following substituent L. １ and M ２ are each independently CR ６ or N, R ６ represents a hydrogen atom or the following substituent L. * represents a bonding position. The substituent L is an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkanoyl group having 1 to 10 carbon atoms, an alkanoyloxy group having 1 to 10 carbon atoms, an alkanoylamino group having 1 to 10 carbon atoms, an alkanoylthio group having 1 to 10 carbon atoms, an alkyloxycarbonyl group having 2 to 10 carbon atoms, an alkylaminocarbonyl group having 2 to 10 carbon atoms, an alkylthiocarbonyl group having 2 to 10 carbon atoms, a hydroxy group, an amino group, a mercapto group, a carboxy group, a sulfo group, an amido group, a cyano group, a nitro group, a halogen atom, or a polymerizable group. However, when the above groups described as the substituent L are not —CH ２ When the group has -, -CH contained in the above group ２Groups in which at least one of - is replaced by -O-, -CO-, -CH=CH- or -C≡C- are also included in the substituent L. Furthermore, when the above groups described as the substituent L have a hydrogen atom, groups in which at least one of the hydrogen atoms contained in the above groups is replaced by at least one selected from the group consisting of a fluorine atom and a polymerizable group are also included in the substituent L.

[0067] The tolan type liquid crystal compound preferably further contains a sulfide bond (—S—). For example, in the tolan type liquid crystal compound represented by the general formula (I), １ , multiple X ２ , Z １ , Z ２ and Z ３ Preferably, at least one of X represents -S-, and １ and multiple Xs ２ The number of sulfide bonds contained in the tolan type liquid crystal compound is not particularly limited and is, for example, 1 to 6, preferably 1 to 3, and more preferably 2.

[0068] The liquid crystal composition preferably contains a polyfunctional polymerizable liquid crystal compound having two or more polymerizable groups, since it is easier to control the thickness of the coating film to be laminated when laminating the liquid crystal composition to prepare an optically anisotropic layer. The polymerizable groups of the polyfunctional polymerizable liquid crystal compound, including preferred embodiments, are the same as the polymerizable groups of the above-mentioned polymerizable liquid crystal compound. The number of polymerizable groups of the polyfunctional polymerizable liquid crystal compound is, for example, 2 to 6, preferably 2 to 4, and more preferably 2. As the polyfunctional polymerizable liquid crystal compound, for example, among the compounds represented by the above formula (I), P １ and P ２ and wherein both represent polymerizable groups.

[0069] When the liquid crystal composition contains a polyfunctional polymerizable liquid crystal compound, the content of the polyfunctional polymerizable liquid crystal compound is preferably 50% by mass or more, more preferably 50 to 98% by mass, and even more preferably 60 to 95% by mass, based on the total mass of the solid content of the liquid crystal composition.

[0070] Specific examples of the polyfunctional polymerizable liquid crystal compound include the following compounds.

[0071] The liquid crystal composition preferably contains a monofunctional polymerizable liquid crystal compound having only one polymerizable group, in that it can control the uneven structure of the surface of the optically anisotropic layer while maintaining the function of the optically anisotropic layer based on the alignment of the liquid crystal compound. The polymerizable group of the monofunctional polymerizable liquid crystal compound, including preferred embodiments, is the same as the polymerizable group of the above-mentioned polymerizable liquid crystal compound. As the monofunctional polymerizable liquid crystal compound, for example, among the compounds represented by the above formula (I), P １ and P ２ and a compound represented by the following formula (II):

[0072] In the above formula (II), P represents a polymerizable group. １ represents a hydrogen atom, a halogen atom, —CN, —NCS, or an alkyl group having 1 to 15 carbon atoms. １ represents an alkyl group having 1 to 15 carbon atoms, a hydrogen atom contained in the alkyl group may be substituted with a fluorine atom, and —CH ２- may be substituted by -O-, -S-, -CQQ-, -SO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NQ-, -NQ-CO-, -CQ=CQ-, -CQ=N-, -N=CQ-, -N=N-, -CQ=N-N=CQ-, or -C≡C-. Q represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 10 carbon atoms. When multiple Qs are present, the multiple Qs may be the same or different. Sp represents a single bond or a divalent linking group. However, Sp does not represent a divalent linking group containing at least one group selected from the group consisting of an aromatic hydrocarbon ring group, an aromatic heterocyclic group, and an aliphatic hydrocarbon ring group. n represents an integer of 1 to 5. Z is a single bond, —O—, —S—, —CHR—, —CHRCHR—, —OCHR—, —CHRO—, —SO—, or —SO ２ -, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NR-, -NR-CO-, -SCHR-, -CHRS-, -SO-CHR-, -CHR-SO-, -SO ２ -CHR-, -CHR-SO ２ -, -CF ２ O-, -OCF ２ -, -CF ２ S-, -SCF ２ -, -OCHRCHRO-, -SCHRCHRS-, -SO-CHRCHR-SO-, -SO ２ -CHRCHR-SO ２-, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -COO-CHRCHR-, -OCO-CHRCHR-, -CHRCHR-COO-, -CHRCHR-OCO-, -COO-CHR-, -OCO-CHR-, -CHR-COO-, -CHR-OCO-, -CR=CR-, -CR=N-, -N=CR-, -N=N-, -CR=N-N=CR-, -CF=CF-, or -C≡C-. R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When multiple Rs are present, the multiple Rs may be the same or different. However, when n represents 1, Z represents -C≡C-, and when n represents an integer of 2 to 5, multiple Zs may be the same or different, but at least one Z represents -C≡C-. A and B each independently represent a 5-membered ring, a 6-membered ring, or a 7-membered ring, or a divalent cyclic group formed by condensing these rings and which may have a substituent, and at least one of A and B represents a substituted or unsubstituted 1,4-phenylene group. However, A and B each independently may be substituted with a halogen atom, -CN, -NCS, or an alkyl group having 1 to 8 carbon atoms. When A and B are substituted with an alkyl group having 1 to 8 carbon atoms, a hydrogen atom contained in the alkyl group may be substituted with a fluorine atom, and -CH contained in the alkyl group may be substituted with a fluorine atom. ２ - may be substituted by -O-, -S-, -CQQ-, -SO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NQ-, -NQ-CO-, -CQ=CQ-, -CQ=N-, -N=CQ-, -N=N-, -CQ=N-N=CQ-, or -C≡C-. Q represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. When multiple Qs are present, the multiple Qs may be the same or different. When n represents an integer of 2 to 5, the multiple A's may be the same or different.

[0073] Here, examples of the polymerizable group represented by P in the above formula (II) include the same as those described for the polymerizable group contained in the polymerizable liquid crystal compound described above. Furthermore, examples of the divalent linking group represented by one aspect of Sp include a linear or branched alkylene group having 1 to 12 carbon atoms, or a —CH ２ Examples of the divalent linking group include a divalent linking group in which one or more - are replaced by -O-, -S-, -NH-, -N(Q)-, or -CO-. Examples of the divalent cyclic group represented by A and B include the above-mentioned 5-membered ring, 6-membered ring, or 7-membered ring, or a divalent cyclic group formed by condensing these rings, specifically, a 1,4-phenylene group, a naphthalene-2,6-diyl group, etc. Examples of the substituent that the divalent cyclic group may have include the same substituents as the above-mentioned substituent L, and among these, an alkyl group or a halogen atom is preferred.

[0074] When the liquid crystal composition contains a monofunctional polymerizable liquid crystal compound, the content of the monofunctional polymerizable liquid crystal compound is preferably 10% by mass or more, more preferably 15 to 60% by mass, and even more preferably 15 to 40% by mass, based on the total mass of the solid content of the liquid crystal composition.

[0075] Specific examples of the monofunctional polymerizable liquid crystal compound include the following compounds.

[0076] The liquid crystal composition preferably contains both a polyfunctional polymerizable liquid crystal compound and a monofunctional polymerizable liquid crystal compound as liquid crystal compounds. In this case, the content of the polyfunctional polymerizable liquid crystal compound is preferably 50% by mass or more, more preferably 60 to 90% by mass, and even more preferably 70 to 90% by mass, based on the total mass of the monofunctional polymerizable liquid crystal compound and the polyfunctional polymerizable liquid crystal compound.

[0077] The content of the polymerizable liquid crystal compound (the total content of the monofunctional polymerizable liquid crystal compound and the polyfunctional polymerizable liquid crystal compound) in the liquid crystal composition is preferably 60 mass % or more, more preferably 70 to 99 mass %, and even more preferably 80 to 95 mass %, based on the total mass of the solid content of the liquid crystal composition.

[0078] --Thiol Compound-- The liquid crystal composition may contain a thiol compound having at least one thiol group (-SH) in the molecule, and preferably contains a thiol compound in that it can reduce the molecular weight of the polymerized units and suppress cure shrinkage. The number of thiol groups contained in the thiol compound is not particularly limited and is, for example, 1 to 4, and preferably 1 to 3.

[0079] Examples of thiol compounds include aliphatic thiols (1-hexanethiol, 1-heptanethiol, 1-octanethiol, hexane-1,6-dithiol, etc.), aromatic thiols (1,4-benzenedithiol, etc.), and mono- or poly(mercaptoacylate) polyhydric alcohols (ethylene glycol bis(mercaptoacetate), propylene glycol bis(mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), 1,4-bis(3-mercaptobutyryloxy)butane, etc.). Commercially available thiol compounds include PEMP (manufactured by SC Organic Chemical Co., Ltd.), Suncerer M (manufactured by Sanshin Chemical Industry Co., Ltd.), and Karenz MT-BD1 (manufactured by Showa Denko K.K.).

[0080] Furthermore, as the thiol compound, a thiol compound exhibiting liquid crystallinity is also preferred in that it has better compatibility with liquid crystal compounds. Examples of the thiol compound exhibiting liquid crystallinity include the compounds described in U.S. Patent No. 6,096,241.

[0081] The content of the thiol compound in the liquid crystal composition is, for example, 0.01 to 10% by mass, and preferably 0.05 to 5% by mass, based on the content of the liquid crystal compound.

[0082] The liquid crystal composition may contain a phenolic compound having at least one phenolic hydroxyl group in the molecule, and preferably contains a phenolic compound in that it can reduce the molecular weight of the polymerized units and suppress cure shrinkage. The number of phenolic hydroxyl groups contained in the phenolic compound is not particularly limited and is, for example, 1 to 4, and preferably 1 to 3.

[0083] Examples of phenol compounds include 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-methylphenol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), and 4,4'-butylidenebis(3-methyl-6-t-butylphenol). Commercially available phenol compounds include Sumilizer GM (manufactured by Sumitomo Chemical Co., Ltd.) and Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.).

[0084] The content of the phenol compound contained in the liquid crystal composition is, for example, 0.01 to 10% by mass, and preferably 0.05 to 5% by mass, based on the content of the liquid crystal compound.

[0085] The liquid crystal composition preferably contains at least one selected from the group consisting of a thiol compound and a phenol compound. When the liquid crystal composition contains at least one selected from the group consisting of a thiol compound and a phenol compound, the total content of the thiol compound and the phenol compound is, for example, 0.01 to 10% by mass, and preferably 0.05 to 5% by mass, relative to the total mass of the solid content of the liquid crystal composition.

[0086] --Surfactant-- The liquid crystal composition may contain a surfactant. The surfactant is preferably a compound that can function as an alignment control agent that contributes to the stable or rapid alignment of the liquid crystal compound. Examples of the surfactant include silicone surfactants and fluorine surfactants, and fluorine surfactants are preferred.

[0087] Specific examples of the surfactant include the compounds described in paragraphs

[0082] to

[0090] of JP-A No. 2014-119605, the compounds described in paragraphs

[0031] to

[0034] of JP-A No. 2012-203237, the compounds exemplified in paragraphs

[0092] and

[0093] of JP-A No. 2005-99248, the compounds exemplified in paragraphs

[0076] to

[0078] and paragraphs

[0082] to

[0085] of JP-A No. 2002-129162, and the fluorine (meth)acrylate polymers described in paragraphs

[0018] to

[0043] of JP-A No. 2007-272185, etc. As the fluorine-based surfactant, the compounds described in paragraphs

[0082] to

[0090] of JP-A-2014-119605 are preferred.

[0088] The amount of surfactant added to the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass, based on the total mass of the liquid crystal compound.

[0089] --Polymerization initiator-- When the liquid crystal composition contains a polymerizable liquid crystal compound, it preferably contains a polymerization initiator. In an embodiment in which the polymerization reaction is caused to proceed by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator that can initiate the polymerization reaction by ultraviolet irradiation. Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Pat. No. 2,722,512), polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketones (described in U.S. Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A No. 60-105,667 and U.S. Pat. No. 4,239,850), and oxadiazole compounds (described in U.S. Pat. No. 4,212,970). 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, based on the content of the polymerizable liquid crystal compound.

[0090] Crosslinking Agent The liquid crystal composition may optionally contain a crosslinking agent to improve the film strength and durability after curing. Suitable crosslinking agents are those that cure under ultraviolet light, heat, moisture, or the like. The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl (meth)acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Furthermore, known catalysts can be used depending on the reactivity of the crosslinking agent, which can improve productivity in addition to improving film strength and durability. These may be used alone or in combination of two or more. The content of the crosslinking agent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, based on the total mass of the solid content of the liquid crystal composition. When the content of the crosslinking agent is within the above range, the effect of improving the crosslink density is easily obtained, and the stability of the liquid crystal alignment pattern is further improved.

[0091] --Other Additives-- If necessary, the liquid crystal composition may further contain a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, and the like, within a range that does not impair optical performance, etc.

[0092] The liquid crystal composition is preferably used as a liquid when forming an optically anisotropic layer (when coated on an alignment film). The liquid crystal composition may contain a solvent. The solvent is not particularly limited and can be appropriately selected depending on the purpose, but organic solvents are preferred. The organic solvent is not particularly limited and can be appropriately selected depending on the purpose, and examples include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used alone or in combination of two or more. Among these, ketones are preferred when considering the environmental impact.

[0093] When forming an optically anisotropic layer, it is preferable to coat a liquid crystal composition on the surface on which the optically anisotropic layer is formed, align the liquid crystal compound in a predetermined liquid crystal alignment pattern, and then harden the liquid crystal compound to form an optically anisotropic layer. That is, when forming an optically anisotropic layer on an alignment film, it is preferable to coat a liquid crystal composition on the alignment film, align the liquid crystal compound in a predetermined liquid crystal alignment pattern, and then harden the liquid crystal compound to form an optically anisotropic layer. The liquid crystal composition can be coated by any of printing methods such as inkjet printing and scroll printing, as well as any of known methods that can uniformly coat a liquid on a sheet-like material, such as spin coating, bar coating, and spray coating.

[0094] The applied liquid crystal composition is dried and / or heated as necessary, and then cured to form an optically anisotropic layer. During this drying and / or heating process, the liquid crystal compound in the liquid crystal composition may be oriented in a predetermined liquid crystal orientation pattern. When heating is performed, the heating temperature is preferably 200° C. or less, more preferably 130° C. or less.

[0095] The aligned liquid crystal compound is further polymerized as needed. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. The light irradiation is preferably performed using ultraviolet light. The irradiation energy is 20 mJ / cm. ２ ~50 J / cm ２ is preferred, and 50 to 1500 mJ / cm ２In order to promote the photopolymerization reaction, the irradiation may be carried out under heated conditions or in a nitrogen atmosphere. The wavelength of the ultraviolet light to be irradiated is preferably 250 to 430 nm.

[0096] Furthermore, when the aligned liquid crystal compound is photopolymerized and fixed, it is preferable to irradiate the liquid crystal compound with light for a longer time at a lower illuminance, since this makes it easier to form an optically anisotropic layer having a small maximum height d of the concave-convex structure. ２ is preferred, and 10 to 100 mW / cm ２ The irradiation dose varies depending on the thickness of the layer to be fixed, but is, for example, 50 to 500 mJ / cm ２ and 100 to 300 mJ / cm ２ is preferred.

[0097] The optically anisotropic layer may be formed to a desired thickness by repeating the above-described steps from coating to polymerization.

[0098] The optically anisotropic layer may be used in a state in which it is laminated on a support and an alignment film. Alternatively, the optically anisotropic layer may be used in a state in which, for example, the support is peeled off and only the alignment film and the optically anisotropic layer are laminated. Alternatively, the optically anisotropic layer may be used in a state in which, for example, the support and the alignment film are peeled off and only the optically anisotropic layer is left.

[0099] 1 and 2, the orientation of the optical axis 30A of the liquid crystal compound 30 in the liquid crystal alignment pattern continuously rotates only along the X direction. However, the present invention is not limited to this, and various configurations are available as long as the orientation of the optical axis 30A of the liquid crystal compound 30 continuously rotates along one direction and the optical anisotropic layer has a region A in which one period Λ is within a predetermined range.

[0100] 6 is a plan view conceptually showing another example of the optically anisotropic layer of the present invention. As shown in the figure, the optically anisotropic layer may have a liquid crystal alignment pattern radially arranged from the center. In the optically anisotropic layer 34 shown in FIG. 6, the direction of the optical axis (not shown) is in a number of directions from the center of the optically anisotropic layer 34 toward the outside, for example, in the directions indicated by arrow A. １ The direction indicated by arrow A ２ The direction indicated by arrow A ３ The direction of the arrow A is shown. １ , A ２ and A ３ is the array axis.

[0101] 6, the optical axes of the liquid crystal compound 30 change while rotating in the same direction from the center of the optically anisotropic layer 34 to the outside. １ , A ２ and A ３ The rotation direction of the optical axis, which changes along each arrow in the figure, becomes counterclockwise as it moves from the center to the outside. In this way, in a radial liquid crystal alignment pattern, the lines connecting liquid crystal compounds whose optical axes are oriented in the same direction form a circle, and the line segments of the circle form a concentric pattern.

[0102] The optically anisotropic layer 34 having such a radial liquid crystal alignment pattern has a large number of directions (A １ ~A ３ When the incident light is diffracted along the direction (A, etc.) so that the azimuth direction is directed toward the center, the transmitted light can be focused. １ ~A ３ When incident light is diffracted outward along the lattice plane, the transmitted light can be diffused. Whether the transmitted light is diffracted toward the center or outward depends on the polarization state of the incident light and the direction of rotation of the optical axis in the liquid crystal alignment pattern.

[0103] In the present invention, by forming the liquid crystal orientation pattern of the optically anisotropic layer into such a radial pattern, it is possible to form a lens that condenses or diverges light. When an optical element having an optically anisotropic layer is used as a lens, it is preferable that the diffraction angle gradually increases from the center of the optical element toward the outside. This allows the optical element to condense or diverge light more effectively.

[0104] An optically anisotropic layer having a radial liquid crystal orientation pattern as shown in Fig. 6 can be formed, for example, using an alignment film having an orientation pattern that orients liquid crystal compounds in a radial liquid crystal orientation pattern. Fig. 7 conceptually shows another example of an exposure device that forms an orientation pattern by exposing an alignment film. The exposure device 80 shown in Fig. 7 includes a light source 84 equipped with a laser 82, a polarizing beam splitter 86 that splits laser light M from the laser 82 into S-polarized light MS and P-polarized light MP, a mirror 90A arranged in the optical path of the P-polarized light MP and a mirror 90B arranged in the optical path of the S-polarized light MS, a lens 92 arranged in the optical path of the S-polarized light MS, a polarizing beam splitter 94, and a λ / 4 plate 96.

[0105] The P-polarized light MP split by the polarizing beam splitter 86 is reflected by a mirror 90A and enters a polarizing beam splitter 94. On the other hand, the S-polarized light MS split by the polarizing beam splitter 86 is reflected by a mirror 90B, collected by a lens 92, and enters the polarizing beam splitter 94. The P-polarized light MP and the S-polarized light MS are combined by the polarizing beam splitter 94 and converted into right- and left-circularly polarized light according to the polarization direction by a λ / 4 plate 96. The combined light then enters the alignment film 18 on the support 12. Here, due to interference between the right- and left-circularly polarized light, the polarization state of the light irradiating the alignment film 18 changes periodically, like an interference fringe pattern. The crossing angle between the left- and right-circularly polarized light changes from the inside to the outside of the concentric circles, resulting in an exposure pattern whose period changes from the inside to the outside. This results in a radial alignment pattern in the alignment film 18, in which the alignment state changes periodically.

[0106] In this exposure device 80, the length Λ of one period of the liquid crystal orientation pattern in which the optical axis of the liquid crystal compound 30 continuously rotates 180° can be controlled by changing the refractive power of the lens 92 (the F-number of the lens 92), the focal length of the lens 92, and the distance between the lens 92 and the orientation film 18. Furthermore, by adjusting the refractive power of the lens 92 (the F-number of the lens 92), the length Λ of one period of the liquid crystal orientation pattern can be changed in one direction in which the optical axis continuously rotates. Specifically, the length Λ of one period of the liquid crystal orientation pattern in one direction in which the optical axis continuously rotates can be changed by adjusting the spread angle of the light expanded by the lens 92, which interferes with the parallel light. More specifically, when the refractive power of the lens 92 is weakened, the light approaches parallel light, so the length Λ of one period of the liquid crystal orientation pattern gradually shortens from the inside to the outside, and the F-number increases. Conversely, when the refractive power of the lens 92 is increased, the length Λ of one period of the liquid crystal alignment pattern suddenly decreases from the inside to the outside, and the F-number decreases.

[0107] [Optical Element] The optical element of the present invention comprises the optically anisotropic layer described above. An example of the configuration of the optical element is a laminate comprising a support, an alignment film, and the optically anisotropic layer of the present invention, in this order. The support, alignment film, and optically anisotropic layer are as described above. Other examples of the configuration of the optical element include a laminate having no support but an alignment film and the optically anisotropic layer of the present invention, a laminate having no alignment film but a support and the optically anisotropic layer of the present invention, and an embodiment having only the optically anisotropic layer of the present invention but not a support or alignment film.

[0108] The optical element may be an optical element that can be used as an optical element that transmits and refracts visible light. Furthermore, the optical element is not limited to the above-mentioned embodiment, and may have a configuration that refracts and transmits infrared light and / or ultraviolet light, for example.

[0109] The optical element of the present invention can be used for various purposes that transmit light in a direction different from the incident direction, such as a polarizing diffraction element in an optical device, an optical path changing member, a light focusing element, and an element for diffusing light in a predetermined direction.

[0110] [Image Display Device] The image display device of the present invention is an image display device including the optical element described above. Examples of the image display device include AR (Augmented Reality) glasses, VR (Virtual Reality) head-mounted displays, liquid crystal display devices, and projectors.

[0111] For example, when the image display device is AR glasses, it is sufficient that the image display device has the same configuration as known AR glasses except for the above-mentioned optical element, and may have, for example, a display element for projecting an image, a projection lens, a λ / 4 plate, a linear polarizing plate, etc. Examples of the projection lens include known projection lenses (condensing lenses) used in AR glasses, etc.

[0112] Examples of display elements include liquid crystal displays (including LCOS (Liquid Crystal On Silicon)), organic electroluminescence displays, DLP (Digital Light Processing), and scanning displays using MEMS (Micro Electro Mechanical Systems) mirrors. Note that the display element may be one that displays a monochrome image (single color image), one that displays a two-color image, or one that displays a color image.

[0113] The light emitted by the display element may be unpolarized or polarized, but is preferably circularly polarized. Furthermore, when the display element projects an unpolarized image, the image display device preferably further includes a circular polarizer composed of a linear polarizer and a λ / 4 plate. Furthermore, when the display element projects a linearly polarized image, the image display device preferably further includes, for example, a λ / 4 plate. The light emitted by the display element may be polarized light other than circularly polarized light, such as linearly polarized light.

[0114] The optically anisotropic layer, the optical element, and the image display device of the present invention have been described in detail above. The present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the gist of the present invention.

[0115] The features of the present invention will be explained in more detail below with reference to examples. The materials, reagents, amounts used, amounts of substances, ratios, treatment details, and treatment procedures shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0116] Example 1 <Preparation of Liquid Crystal Diffraction Element> (Support) A glass substrate was prepared as a support.

[0117] (Formation of Orientation Film) The following coating solution for forming an alignment film was applied to a support by spin coating. The support on which the coating film of the coating solution for forming an alignment film had been formed was dried on a hot plate at 60° C. for 60 seconds to form an alignment film.

[0118] Coating liquid for forming alignment film ----------------------------------- Photoalignment material A 4.00 parts by mass Water 48.00 parts by mass Butoxyethanol 24.00 parts by mass Propylene glycol monomethyl ether 24.00 parts by mass ---------------------------------------------------

[0119] -Photo alignment material A-

[0120] (Exposure of Alignment Film) The alignment film was exposed using the exposure device shown in FIG. 5 to form an alignment film P-1 having an alignment pattern. More specifically, the support with the alignment film formed by the above method was placed in the exposure section of the exposure device, and the alignment film was exposed by irradiating it with interference light of two light beams MA and MB. This formed a patterned alignment film having an alignment pattern in which the alignment state changed periodically. The exposure device used a laser that emitted laser light with a wavelength (355 nm). The exposure dose of the interference light on the alignment film was 1000 mJ / cm. ２ It was decided.

[0121] (Formation of Optically Anisotropic Layer) The following composition A-1 was prepared as a liquid crystal composition for forming an optically anisotropic layer. Composition A-1 ----------------------------------- Liquid crystal compound L-1 80.00 parts by mass Liquid crystal compound L-2 20.00 parts by mass Polymerization initiator P-1 3.00 parts by mass Leveling agent T-1 0.40 parts by mass Methyl ethyl ketone 522.00 parts by mass Cyclopentanone 522.00 parts by mass

[0122] Liquid crystal compound L-1

[0123] Liquid crystal compound L-2

[0124] Photopolymerization initiator P-1

[0125] Leveling agent T-1

[0126] An optically anisotropic layer was formed by applying composition A-1 in multiple layers onto alignment film P-1. "Multi-layer application" refers to first applying composition A-1 as a first layer onto the alignment film, heating it, and then curing it with UV light to form a liquid crystal fixing layer, and then applying layers from the second layer onwards by recoating them on top of the liquid crystal fixing layer, and similarly heating it and curing it with UV light, and repeating this process.

[0127] First, the first layer was formed by applying the following composition A-1 onto the alignment film P-1, heating the coating to 80°C on a hot plate, and then irradiating ultraviolet light with a wavelength of 365 nm at an illuminance of 10 mW / cm using a high-pressure mercury lamp in a nitrogen atmosphere. ２ , irradiation amount 200mJ / cm ２ The alignment of the liquid crystal compound was fixed by irradiating the coating film under the conditions of

[0128] From the second layer onward, Composition A-1 was applied to the liquid crystal fixation layer, and the coating was heated under the same conditions as above, followed by UV curing to produce a multilayer liquid crystal fixation layer. In this way, a series of processes including application of the coating, heating, and UV curing were repeated until the total thickness reached the desired film thickness, forming an optically anisotropic layer, and producing a liquid crystal diffraction element 1 having a support, an alignment film, and an optically anisotropic layer.

[0129] The refractive index difference Δn of the cured layer of Composition A-1 was determined by measuring the retardation value and film thickness of the liquid crystal fixed layer (cured layer) obtained by applying Composition A-1 to a separately prepared support with an alignment film for retardation measurement, aligning the director of the liquid crystal compound so that it was horizontal to the substrate, and then irradiating it with ultraviolet light to fix it. Δn can be calculated by dividing the retardation value by the film thickness. The retardation value was measured at the desired wavelength using an Axoscan manufactured by Axometrix, and the film thickness was measured using a SEM.

[0130] In the optically anisotropic layer of the liquid crystal diffraction element 1, the Δn ５５０ It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the liquid crystal diffraction element 1 was 266 nm, and that a striped liquid crystal orientation pattern was formed in plan view as shown in Fig. 2. Measurement using the polarizing microscope revealed that the length Λ of one period in which the optical axis derived from the liquid crystal compound rotates by 180° along the X direction, in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating, was 4.0 µm over the entire surface of the liquid crystal orientation pattern of the optically anisotropic layer of the liquid crystal diffraction element 1.

[0131] Examples 2 to 6, 11 to 12 Optically anisotropic layers were formed in the same manner as in Example 1, except that compositions A-2 to A-8 having the compositions shown in Table 1 below were used instead of composition A-1 as the liquid crystal composition for forming the optically anisotropic layer, and liquid crystal diffraction elements 2 to 6 and 11 to 12 each having a support, an alignment film, and an optically anisotropic layer were fabricated.

[0132] Examples 7 to 9 In the process of forming the alignment film, the crossing angle θ of two light beams MA and MB irradiated onto the alignment film before the alignment pattern was formed was adjusted to form alignment films P-2 to P-4, respectively, having alignment patterns with different lengths Λ of one period of 180° rotation of the optical axis in the X direction, in which the direction of the optical axis derived from the liquid crystal compound changes while rotating. An optically anisotropic layer was formed in the same manner as in Example 6, and liquid crystal diffraction elements 7 to 9, each having a support, an alignment film, and an optically anisotropic layer, were fabricated.

[0133] Example 10 When forming an optically anisotropic layer, a coating film was formed using composition A-6 on alignment film P-4 or on a liquid crystal fixing layer formed immediately before, and then heated, and ultraviolet light having a wavelength of 365 nm was irradiated at an illuminance of 200 mW / cm. ２ , irradiation amount 200mJ / cm ２ An optically anisotropic layer was formed in the same manner as in Example 9, except that irradiation was performed under the conditions of (a) to (c), and a liquid crystal diffraction element 10 having a support, an alignment film, and an optically anisotropic layer was produced.

[0134] Comparative Example 1 In place of composition A-1, composition A-9 having the composition shown in Table 1 below was used as the liquid crystal composition for forming the optically anisotropic layer. In addition, when forming the optically anisotropic layer, a coating film formed on alignment film P-1 or on a liquid crystal fixing layer formed immediately before using composition A-1, and then heated was irradiated with ultraviolet light having a wavelength of 365 nm at an illuminance of 200 mW / cm. ２ , irradiation amount 200mJ / cm ２ An optically anisotropic layer was formed in the same manner as in Example 1, except that irradiation was performed under the conditions of (a) to (c), and a liquid crystal diffraction element C1 having a support, an alignment film, and an optically anisotropic layer was produced.

[0135] Table 1 shows the formulations of the liquid crystal compositions for forming the optically anisotropic layers used in each Example and Comparative Example 1.

[0136]

[0137] The compounds used in the preparation of the liquid crystal compositions are shown below.

[0138] Liquid crystal compound L-3

[0139] Liquid crystal compound L-4

[0140] Liquid crystal compound L-5

[0141] Liquid crystal compound L-6

[0142] Liquid crystal compound L-7

[0143] Liquid crystal compound L-8

[0144] Additive A-1: ​​Karenz MT (registered trademark) BD1 (1,4-bis(3-mercaptobutyryloxy)butane) manufactured by Showa Denko K.K.

[0145] Additive A-2: Sumilizer (registered trademark) GM manufactured by Sumitomo Chemical Co., Ltd.

[0146] [Measurement] <Maximum Height d of the Concave-Convex Structure> The shape of the concave-convex structure formed on the surface of an optically anisotropic layer having a liquid crystal alignment pattern was measured under the following conditions using a non-contact surface / layer cross-sectional shape measurement system, VertScan (manufactured by Hitachi High-Tech Corporation), and then analyzed using the built-in data analysis software (VS-Measure). The analysis software targeted the analysis of a section of the concave-convex structure in which the concave-convex structure repeated five or more cycles along the X direction, where the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating. Next, a roughness curve representing the surface shape of the target section and an average line of the roughness curve were created, and the difference between the highest and lowest points on the roughness curve was calculated. The above measurements and calculations were performed on 10 randomly selected locations on the surface of the formed optically anisotropic layer, and the arithmetic mean value of the eight points excluding the highest and lowest values ​​was taken as the maximum height d of the concave-convex structure formed on the surface of the optically anisotropic layer. The unit of the maximum height d of the concave-convex structure is "nm."

[0147] (Measurement conditions) Measurement mode: WAVE mode Objective lens: 50x Measurement area: 124 μm x 93 μm

[0148] <Average length P of one period of the uneven structure> Based on the roughness curve representing the surface shape of the optically anisotropic layer, created by the above-mentioned method using the VertScan, the distance between the positions showing the maximum values ​​of two adjacent convex portions in the X direction was calculated. The above calculation was performed for 10 arbitrarily selected locations on the surface of the optically anisotropic layer, and the arithmetic mean value of 8 points excluding the highest and lowest values ​​was taken as the average length P of one period of the uneven structure formed on the surface of the optically anisotropic layer. The unit of the average length P of one period of the uneven structure is "μm".

[0149] As a result of measurements and calculations, in all of the optically anisotropic layers formed in the Examples, the length Λ of one period in which the optical axis derived from the liquid crystal compound rotates by 180° in the X direction in which the optical axis derived from the liquid crystal compound changes while continuously rotating was equal to the average length P of one period of the uneven structure formed on the surface of the optically anisotropic layer.

[0150] [Evaluation] <Suppression performance of zero-order light> A circular polarizer (λ / 4 plate: "WPQSM05-532" manufactured by Thorlabs, linear polarizer: "SPF-50C-32" manufactured by Sigma Koki Co., Ltd.) was placed on the downstream side (output side) of the liquid crystal diffraction element in front of the zero-order light (at an angle of 0° relative to the normal). At this time, the arrangement of the λ / 4 plate and linear polarizer in the circular polarizer was such that left-handed circularly polarized light was transmitted and right-handed circularly polarized light was absorbed. Right-handed circularly polarized light with a wavelength of 532 nm and an ellipticity εin of 0.95 or more (0.99) was incident from the front of the liquid crystal diffraction element (at an angle of 0° relative to the normal) toward the center of the liquid crystal diffraction element. The light intensity of the incident light that entered the liquid crystal diffraction element and the light intensity of the zero-order light among the outgoing light that passed through the liquid crystal diffraction element and was emitted from the circular polarizer were measured with a photodetector, and the amount of the zero-order light (the amount of the zero-order light when the amount of the incident light is set to 1) was calculated using the following formula: Amount of zero-order light (%) = Light intensity of zero-order light / Light intensity of incident light × 100

[0151] The suppression performance of the zero-order light was evaluated based on the calculated light amount of the zero-order light according to the following evaluation criteria: The lower the light amount of the zero-order light, the more the transmission of the zero-order light through the optically anisotropic layer is suppressed, and the more the stray light transmitted through the circular polarizer is suppressed.

[0152] (Evaluation criteria) A: 1.0% or less B: More than 1.0% and 2.0% or less C: More than 2.0% and 5.0% or less D: More than 5.0%

[0153] Table 2 shows the composition numbers used to form the optically anisotropic layers, the curing conditions for forming the optically anisotropic layers, the physical properties of the formed optically anisotropic layers, and the evaluation results. In the table, the "Λ (μm)" column shows the length Λ (unit: μm) of one period in the liquid crystal alignment pattern of each optically anisotropic layer, measured using a polarizing microscope. In each example, the length Λ of one period was the value shown in the "Λ (μm)" column in the table across the entire surface of the liquid crystal alignment pattern of the formed optically anisotropic layer. The "P (μm)" column shows the measured value (unit: μm) of the average length P of one period of the concave-convex structure measured by the above method, and the "d (μm)" column shows the measured value (unit: nm) of the maximum height d of the concave-convex structure measured by the above method. The "α" column shows the value α calculated using the above formula (1) from the length Λ (μm) of one period and the maximum height d (nm) of the concave-convex structure.

[0154]

[0155] From the results shown in the table above, it was confirmed that the polarized diffraction elements having the optically anisotropic layer of the present invention produced in each example have superior zero-order light suppression performance compared to the polarized diffraction element having the optically anisotropic layer of Comparative Example 1, in which the maximum height d of the uneven structure formed on the surface corresponding to region A exceeds 60 nm.

[0156] 10, 34 Optically anisotropic layer 10A Surface 12 Support 18 Alignment film 20 Concave-convex structure 30 Liquid crystal compound 30A Optical axis 60, 80 Exposure device 62, 82 Laser 64, 84 Light source 65 λ / 2 plate 68 Beam splitter 70A, 70B, 90A, 90B Mirror 72A, 72B, 96 λ / 4 plate 86, 94 Polarizing beam splitter 92 Lens L １ , L ４ Incident light L ２ , L ５ Transmitted light M Laser light MA, MB Light MP P polarized light MS S polarized light P Ｏ Linear polarized light P ＬLeft circularly polarized light P Ｒ Right circularly polarized light R region

Claims

1. An optically anisotropic layer formed using a composition containing a liquid crystal compound, the optically anisotropic layer having a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while rotating continuously along at least one direction in a plane, the optically anisotropic layer having a region A with a length of 0.2 to 20.0 μm when the length of the direction of the optical axis rotating 180° in the plane in the one direction is defined as one period, the optically anisotropic layer having a surface corresponding to the region A having an uneven structure, and the maximum height of the uneven structure in the one direction is 60 nm or less.

2. The optically anisotropic layer according to claim 1, wherein said liquid crystal compound has a tolan structure.

3. The optically anisotropic layer according to claim 2, wherein the liquid crystal compound having a tolane structure further has a sulfide bond.

4. The optically anisotropic layer according to claim 1, wherein the liquid crystal compound comprises a polyfunctional polymerizable liquid crystal compound having two or more polymerizable groups, and a monofunctional polymerizable liquid crystal compound having one polymerizable group.

5. The optically anisotropic layer according to claim 1, wherein the composition comprises at least one selected from the group consisting of a thiol compound and a phenol compound.

6. The optically anisotropic layer according to claim 1, wherein, when the length of one period is Λ (μm) and the maximum height of the uneven structure is d (nm), a value α calculated from Λ and d using the following formula (1) is 50 or less. α=(Λ) １／２ ×d (1) 7. The optically anisotropic layer according to claim 6, wherein said α is 40 or less.

8. An optical element comprising the optically anisotropic layer according to any one of claims 1 to 7.

9. An image display device comprising the optical element according to claim 8 and a display element for projecting an image onto the optical element.

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