Liquid crystal diffraction element, optical element, image display unit, head-mounted display, beam steering, and sensor

Abstract

The present invention addresses the problem of providing a liquid crystal diffraction element that has little wavelength dependency in diffraction efficiency and that performs diffraction by the same angle for the same wavelength. The present invention also addresses the problem of providing an optical element employing said liquid crystal diffraction element, as well as an image display unit, a head-mounted display, a beam steering, and a sensor employing said optical element. The present invention solves the problem with an optically anisotropic layer containing a liquid crystal compound, the optically anisotropic layer including a liquid crystal alignment pattern in which the direction of the optical axis of the liquid crystal compound rotates continuously in one direction, wherein an image obtained by observing a cross-section by means of a scanning electron microscope includes a bright portion and a dark portion extending from one surface to the other surface, the dark portion including two or more angle inflection points, and also includes a region in which the slope angle of the dark portion varies along the thickness direction.

Description

Technical Field

[0001] The present invention relates to a liquid crystal diffraction element that diffracts and transmits incident light, an optical element using this liquid crystal diffraction element, and an image display unit, a head-mounted display, beam steering, and a sensor using the same.

Background Art

[0002] A liquid crystal diffraction element that diffracts and transmits incident light is known. As such a liquid crystal diffraction element, a liquid crystal diffraction element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound is known.

[0003] For example, Patent Document 1 discloses a substrate and a first polarization diffraction grating layer on the substrate, the first polarization diffraction grating layer including a molecular structure that is twisted according to a first twist property over a first thickness defined between both surfaces of the first polarization diffraction grating layer, a second polarization diffraction grating layer on the first polarization diffraction grating layer, the second polarization diffraction grating layer including a molecular structure that is twisted according to a second twist property opposite to the first twist property over a second thickness defined between both surfaces of the second polarization diffraction grating layer, and a liquid crystal diffraction element (polarization diffraction grating). Patent Document 1 describes that this polarization diffraction grating layer can diffract light by aligning a liquid crystal compound in a predetermined alignment pattern.

[0004] A liquid crystal diffraction element having an alignment pattern of a liquid crystal compound as described in Patent Document 1 can diffract incident light at an angle corresponding to the wavelength. Further, when the alignment pattern of the liquid crystal compound is constant, light of the same wavelength can be diffracted at a constant angle regardless of the incident position. A liquid crystal diffraction element having an alignment pattern of a liquid crystal compound can be used for various applications by utilizing such characteristics.

[0005] For example, in AR (Augmented Reality) glasses that superimpose virtual images, various types of information, etc. on the actual scene being viewed, the image displayed by the image display device needs to be incident on the light guide plate at an angle that allows total reflection. By using a liquid crystal diffraction element having an alignment pattern of a liquid crystal compound described in Patent Document 1 as an incident element for incident light on this light guide plate, the incident light (image) can be diffracted and incident on the light guide plate at an angle that allows total reflection. Also, by using a liquid crystal diffraction element at the other end of the light guide plate, the light that has guided through the light guide plate can be diffracted to emit light, allowing the user to visually recognize the image.

[0006] Also, as described above, the liquid crystal diffraction element having an alignment pattern of a liquid crystal compound described in Patent Document 1 can diffract incident light at a diffraction angle corresponding to the wavelength, and when the alignment pattern of the liquid crystal compound is constant, the diffraction angle in the plane is equal for the same wavelength. Therefore, this liquid crystal diffraction element can also be suitably used as a spectroscopic element in a hyperspectral camera that spectrally photographs incident light in a number of wavelength ranges.

[0007] Also, by changing the alignment pattern of the liquid crystal compound in the plane, the diffraction angle can be changed according to the incident position of light, and for example, it can be used as an element that exhibits a lens function.

[0008] For example, there is a head-mounted display having an image display unit that is worn by a user and guides an image to the user's eyes in order to experience a so-called immersive virtual reality (VR) that does not allow external light from the real world to pass through. In the image display unit used in such a head-mounted display, a lens that condenses light at the position of the user's eyes is required for the light emitted from the image display device. As a lens element for a head-mounted display for VR, by using a liquid crystal diffraction element having a lens function by changing the alignment pattern of a liquid crystal compound in a plane, incident light (image) is diffracted, and the light emitted from the image display device is condensed at the position of the user's eye, so that the user can view the image.

[0009] In addition, a refractive lens formed by molding glass, plastic, or the like has chromatic aberration because the traveling direction of the light refracted by the lens changes depending on the wavelength due to the wavelength dispersion of the refractive index of the material used as the lens. Specifically, light with a shorter wavelength is refracted at a larger angle by the lens, and light with a longer wavelength is refracted at a smaller angle. On the other hand, a liquid crystal diffraction element having a lens function by changing the alignment pattern of a liquid crystal compound in a plane has a characteristic that the diffraction angle is smaller for shorter wavelengths and larger for longer wavelengths. Therefore, by combining a refractive lens with a liquid crystal diffraction element having a lens function by changing the alignment pattern of a liquid crystal compound in a plane, the chromatic aberration of the refractive lens can be improved.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] Both the incident element on the light guide plate in the AR glass and the spectroscopic element in the hyperspectral camera diffract light of each wavelength corresponding to light in a wide wavelength range, such as the entire visible light wavelength range. Therefore, these optical elements are required to have a small wavelength dependence of the diffraction efficiency, that is, to be able to diffract light with a similar diffraction efficiency regardless of the wavelength. However, including the liquid crystal diffraction element described in Patent Document 1, the conventional liquid crystal diffraction element having an alignment pattern of a liquid crystal compound does not have a sufficiently small wavelength dependence of the diffraction efficiency.

[0012] In addition, a lens element for a head-mounted display for VR and a lens element that improves color breakup when combined with a refractive lens diffract light of each wavelength corresponding to light in a wide wavelength range, such as the entire wavelength range of visible light. Therefore, these optical elements are required to have a small wavelength dependence of the diffraction efficiency, that is, to be able to diffract light with a similar diffraction efficiency regardless of the wavelength. However, a liquid crystal diffraction element having an alignment pattern of a conventional liquid crystal compound, including the liquid crystal diffraction element described in Patent Document 1, does not have a sufficiently small wavelength dependence of the diffraction efficiency.

[0013] An object of the present invention is to solve such problems of the prior art, and to provide a liquid crystal diffraction element having a small wavelength dependence of the diffraction efficiency, an optical element using the same, and an image display unit, a head-mounted display, a beam steering, and a sensor using the same.

Means for Solving the Problems

[0014] To solve this problem, the present invention has the following configuration. [1] An optical anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, The optical anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously changes while rotating along at least one direction in the plane, and The optical anisotropic layer has a bright part and a dark part extending from one surface to the other surface in a cross-sectional image observed with a scanning electron microscope of a cross-section cut in the thickness direction along one direction, and the dark part having two or more change points of the angle where the angle changes, Furthermore, in the thickness direction, a liquid crystal diffraction element having regions with different inclination directions of the dark part. [2] The liquid crystal diffraction element according to [1], wherein when the length of a 180° rotation of the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern is defined as one period, the length of one period is constant. [3] The liquid crystal diffraction element according to [1], wherein when the length over which the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotates by 180° in the plane is defined as one period, the length of one period gradually changes along one direction. [4] The liquid crystal diffraction element according to [1] or [3], wherein the liquid crystal alignment pattern is a concentric pattern having, in a concentric circle shape from the inside to the outside, one direction in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating. [5] The dark part has in the reverse direction inflection points where the inclination direction is folded, at an odd number of locations, in the liquid crystal diffraction element according to any one of [1] to [4]. [6] The liquid crystal diffraction element according to [5], wherein the dark part has one inflection point. [7] The liquid crystal diffraction element according to [5], wherein the dark part has three inflection points. [8] The liquid crystal diffraction element according to any one of [1] to [7], wherein in a cross-sectional image obtained by observing, with a scanning electron microscope, a cross-section of the optically anisotropic layer cut along one direction in the thickness direction, the shape of the dark part is symmetric with respect to the center line in the thickness direction of the optically anisotropic layer. [9] The liquid crystal diffraction element according to any one of [1] to [7], wherein in a cross-sectional image obtained by observing, with a scanning electron microscope, a cross-section of the optically anisotropic layer cut along one direction in the thickness direction, the shape of the dark part is asymmetric with respect to the center line in the thickness direction of the optically anisotropic layer.

[10] The refractive index difference Δn 550 associated with the refractive index anisotropy of the optically anisotropic layer is 0.2 or more, in the liquid crystal diffraction element according to any one of [1] to [9].

[11] The liquid crystal diffraction element according to any one of [1] to [9], having, in the plane, a region where when the length over which the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotates by 180° in the plane is defined as one period, the length of one period is 1.0 μm or less.

[12] An optical element having the liquid crystal diffraction element according to any one of [1] to

[11] and a circular polarizing plate.

[13] The circular polarizing plate is composed of a retardation plate and a polarizer, and the liquid crystal diffraction element, the retardation plate, and the polarizer are arranged in this order, in the optical element according to

[12] .

[14] An optical element having, in this order, a liquid crystal diffraction element, a silicon oxide layer, and a support, as described in any one of [1] to

[11] .

[15] An optical element having at least one or more liquid crystal diffraction elements described in any one of [1] to

[11] or optical elements described in any one of

[12] to

[14] , and having at least one or more phase modulation elements.

[16] An image display unit having a liquid crystal diffraction element described in any one of [1] to

[11] or an optical element described in any one of

[12] to

[15] .

[17] A head-mounted display having the image display unit described in

[16] .

[18] A beam steering having a liquid crystal diffraction element described in any one of [1] to

[11] or an optical element described in any one of

[12] to

[15] .

[19] A sensor having a liquid crystal diffraction element described in any one of [1] to

[11] or an optical element described in any one of

[12] to

[15] . [Effect of the Invention]

[0015] According to the present invention, it is possible to provide a liquid crystal diffraction element with little wavelength dependence of diffraction efficiency, an optical element using the same, and an image display unit, a head-mounted display, a beam steering, and a sensor using the same. [Brief Description of the Drawings]

[0016]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, the liquid crystal diffraction element, optical element, image display unit, head-mounted display, beam steering, and sensor of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0018] In this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In this specification, "(meth)acrylate" is used to mean "either one or both of acrylate and methacrylate".

[0019] In this specification, visible light is light within the electromagnetic waves that can be seen by the human eye and represents light in the wavelength range of 380 to 780 nm. Non-visible light is light in the wavelength range less than 380 nm and greater than 780 nm.

[0020] [Liquid crystal diffraction element] FIG. 1 conceptually shows an example of the optically anisotropic layer of the liquid crystal diffraction element of the present invention. In the liquid crystal diffraction element of the present invention, the optically anisotropic layer is formed using a liquid crystal composition containing a liquid crystal compound, and has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously changes in at least one direction in the plane. Further, in the cross-sectional image obtained by observing, with a scanning electron microscope (SEM (Scanning Electron Microscope)), a cross-section cut in the thickness direction along the direction in which the direction of the optical axis continuously changes, the optically anisotropic layer has a bright part and a dark part extending from one surface to the other surface, and the dark part (bright part) change point of the angle where the angle changes has two or more. Further, the optically anisotropic layer has regions in the thickness direction where the inclination directions of the dark part (bright part) are different. The bright part and the dark part (bright line and dark line) in the image obtained by observing the cross-section with SEM are observed to be derived from the liquid crystal phase having the liquid crystal alignment pattern.

[0021] The optically anisotropic layer 36a shown in FIG. 1 uses a rod-shaped liquid crystal compound as the liquid crystal compound 40. Therefore, the direction of the optical axis coincides with the longitudinal direction of the liquid crystal compound 40. The optically anisotropic layer 36 has a predetermined liquid crystal alignment pattern in which the optical axis derived from the liquid crystal compound 40 continuously rotates and changes in one direction. Further, when the length in which the direction of the optical axis derived from the liquid crystal compound 40 rotates 180° in the plane in one direction is defined as one cycle, the length of one cycle in the liquid crystal alignment pattern of the optically anisotropic layer 36a is constant. The optical anisotropic layer 36a having such a liquid crystal alignment pattern acts as a liquid crystal diffraction element that diffracts (refracts) and transmits incident light in one cycle in which the optical axis rotates by 180° and according to the wavelength of the incident light. The action of this optical anisotropic layer 36a as a diffraction element will be described in detail later.

[0022] In a cross-sectional image obtained by observing, with SEM, a cross-section of the optical anisotropic layer 36a cut in the thickness direction along one direction in which the optical axis rotates, a striped pattern is observed that alternately has bright portions 42 and dark portions 44 extending from one surface to the other surface, originating from the liquid crystal phase. In FIG. 1, the bright portions 42 and the dark portions 44 are shown superimposed on the cross-section of the optical anisotropic layer 36a. In the following description, a cross-sectional image obtained by observing, with SEM, a cross-section of the optical anisotropic layer 36a cut in the thickness direction along one direction in which the optical axis rotates is also simply referred to as a 'cross-sectional SEM image'. In the optical anisotropic layer 36a of the illustrated example, in the cross-sectional SEM image, the dark portions 44 have change point of the angle angles that change at two locations. That is, it can also be said that the optical anisotropic layer 36a has three regions, namely region 37a, region 37b, and region 37c, in the thickness direction according to the change point of the angle dark portions 44.

[0023] As shown in FIG. 1, the optical anisotropic layer 36a has a liquid crystal alignment pattern in which the optical axis originating from the liquid crystal compound 40 rotates clockwise in the in-plane direction toward the left direction in the figure at any position in the thickness direction. Also, in the liquid crystal alignment pattern, one cycle, which is the length in which the optical axis rotates by 180° in one direction, is constant in any region in the in-plane direction.

[0024] Also, as shown in FIG. 1, in the lower region 37c in the thickness direction, the liquid crystal compound 40 is twisted and aligned so as to be spirally twisted clockwise (right-handed) from the upper side to the lower side in the thickness direction. In the middle region 37b in the thickness direction, the liquid crystal compound 40 is not twisted in the thickness direction, and the liquid crystal compounds 40 stacked in the thickness direction have their optical axes oriented in the same direction. That is, the liquid crystal compounds 40 existing at the same position in the in-plane direction have their optical axes oriented in the same direction. In the upper region 37a in the thickness direction, the liquid crystal compound 40 is twisted and oriented so as to be twisted in a counterclockwise (left-handed) spiral direction from the upper side to the lower side in the figure in the thickness direction. That is, in the optically anisotropic layer 36a shown in FIG. 1, the regions 37a, 37b, and 37c have different twisting states of the liquid crystal compound 40 in the thickness direction.

[0025] In an optically anisotropic layer having a liquid crystal alignment pattern in which the optical axes derived from the liquid crystal compound continuously rotate in one direction, the bright portions 42 and the dark portions 44 in the cross-sectional SEM image of the optically anisotropic layer 36a are observed to connect the liquid crystal compounds 40 in the same direction. As an example, FIG. 1 shows that the dark portion 44 is observed so as to connect the liquid crystal compound 40 whose optical axis is oriented in a direction perpendicular to the plane of the paper. In the lowermost region 37c in the thickness direction, the dark portion 44 is inclined so as to face the upper left in the figure. In the middle region 37b, the dark portion 44 extends in the thickness direction. In the uppermost region 37a, the dark portion 44 is inclined so as to face the upper right in the figure. That is, the optically anisotropic layer 36a shown in FIG. 1 has two points where the angle of the dark portion 44 changes. change point of the angle Also, in the uppermost region 37a, the dark portion 44 is inclined so as to face the upper right, and in the lowermost region 37b, the dark portion 44 is inclined so as to face the upper left. That is, the inclination directions of the dark portion 44 are different between the regions 37a and 37c.

[0026] Furthermore, the optically anisotropic layer 36a shown in FIG. 1 has one inflection point where the inclination direction of the dark portion 44 is folded back in the reverse direction. Specifically, the dark portion 44 of the optically anisotropic layer 36a has an inclination direction in the region 37a and an inclination direction in the region 37c that are in opposite directions. Therefore, in the region 37a region 37c ​and Region 37b with Located on the interface the change point of the angle and the change point of the angle located at the interface between region 37b and region 37c Has an inflection point where the tilt direction is folded back in the opposite direction constitute it. That is, the optically anisotropic layer 36a has one inflection point where the tilt direction is folded back in the opposite direction.

[0027] In addition, in the optically anisotropic layer 36a, regions 37a and 37c, as an example, have the same thickness, and as described above, the states of the twist in the thickness direction of the liquid crystal compound 40 are different from each other. Therefore, as shown in FIG. 1, the bright part 42 and the dark part 44 in the cross-sectional SEM image form a substantially C shape. Therefore, in the optically anisotropic layer 36a, the shape of the dark part 44 (bright part 42) is symmetric with respect to the center line in the thickness direction.

[0028] The liquid crystal diffraction element of the present invention has such an optically anisotropic layer 36a, that is, in the cross-sectional SEM image, it has a bright part 42 and a dark part 44 extending from one surface to the other surface, and the dark part 44 has two or more change point of the angle By having regions with different tilt directions in the thickness direction, the wavelength dependence of the diffraction efficiency is reduced, and light can be diffracted with the same diffraction efficiency regardless of the wavelength.

[0029] As described above, a liquid crystal diffraction element having an optically anisotropic layer having a liquid crystal alignment pattern in which the direction of the optical axis derived from a liquid crystal compound continuously rotates in at least one direction can diffract incident light at different diffraction angles according to the wavelength over a wide wavelength range such as the entire visible light range. However, according to the studies of the present inventors, a conventional liquid crystal diffraction element having a liquid crystal alignment pattern has a dark part inclined with respect to the surface (main surface) in the cross-sectional SEM image, but does not have a change point of the angle changing angle, or, as shown in Patent Document 1, change point of the angle has only one point. Therefore, in a conventional liquid crystal diffraction element, for example, the diffraction efficiencies of red light and green light are high, but the diffraction efficiency of blue light is low compared to the other two colors, and the wavelength dependence of the diffraction efficiency is large.

[0030] In contrast, in the liquid crystal diffraction element of the present invention, the dark portions 44 observed in the cross-sectional SEM image have two or more change point of the angle and have regions with different inclination directions in the thickness direction. Therefore, the liquid crystal diffraction element of the present invention has a small wavelength dependence of the diffraction efficiency and can diffract light with a similar diffraction efficiency regardless of the wavelength. Moreover, such a liquid crystal diffraction element of the present invention can diffract light with a high diffraction efficiency regardless of the wavelength. Also, as will be described later, the liquid crystal alignment pattern of the liquid crystal diffraction element of the present invention may have a constant length for one period in which the optical axis rotates 180°. When the length of one period is constant, the liquid crystal diffraction element of the present invention diffracts (refracts) light at the same angle if the wavelength is the same regardless of the incident position of light in the plane. Therefore, the liquid crystal diffraction element of the present invention can be suitably used for various optical devices such as a light incident element to a light guide plate in an AR glass and a spectroscopic element in a hyperspectral camera, which are required to diffract light of the same wavelength at the same angle regardless of the incident position. Regarding such an operation and effect, the same applies to the liquid crystal diffraction element of the present invention having the optically anisotropic layer shown below.

[0031] The optically anisotropic layer 36a shown in FIG. 1 has three regions in the thickness direction, and the dark portion 44 has change point of the angle at two locations, and further has one inflection point where the inclination direction is in the reverse direction folded back. However, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer is not limited to this configuration. That is, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has the above-described liquid crystal alignment pattern, the one period of the liquid crystal alignment pattern is constant, and further, in the cross-sectional SEM image, due to the liquid crystal layer, it has a bright portion 42 and a dark portion 44 extending from one surface to the other surface, and the dark portion 44 has two or more change point of the angle and further has regions with different inclination directions in the thickness direction, any various configurations can be used.

[0032] FIG. 2 shows another example of the optically anisotropic layer of the liquid crystal diffraction element of the present invention. The optical anisotropic layer 36b shown in FIG. 2 also has a predetermined liquid crystal alignment pattern in which the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction. Therefore, also in the cross-sectional SEM image, a stripe pattern having bright portions 42 and dark portions 44 extending from one surface to the other surface alternately is observed in the optical anisotropic layer 36b due to the liquid crystal layer. Similar to FIG. 1, FIG. 2 also shows the bright portion 42 and the dark portion 44 superimposed on the cross-section of the optical anisotropic layer 36a.

[0033] In the optical anisotropic layer 36b shown in FIG. 2, the dark portion 44 observed in the cross-sectional SEM image has change point of the angle three positions where the angle changes. That is, the optical anisotropic layer 36b can be said to have four regions, namely, region 37d, region 37e, region 37f, and region 37g, in the thickness direction from top to bottom according to change point of the angle the dark portion 44.

[0034] The optical anisotropic layer 36b in FIG. 2 also has a liquid crystal alignment pattern in which the optical axis derived from the liquid crystal compound 40 rotates clockwise in the in-plane direction toward the left direction in the drawing at any position in the thickness direction. Also, in the liquid crystal alignment pattern, one period, which is the length at which the optical axis rotates 180° in one direction, is constant in any region in the in-plane direction.

[0035] In the optical anisotropic layer 36b shown in FIG. 2, in the lowermost region 37g in the thickness direction, the liquid crystal compound 40 is twisted and aligned so as to be spirally twisted clockwise from the upper side to the lower side in the drawing in the thickness direction. In the second region 37f from the bottom, the liquid crystal compound 40 is twisted and aligned so as to be spirally twisted counterclockwise from the upper side to the lower side in the drawing in the thickness direction. In the third region 37e from the bottom, the liquid crystal compound 40 is twisted and aligned so as to be spirally twisted clockwise from the upper side to the lower side in the drawing in the thickness direction. Furthermore, in the uppermost region 37d, the liquid crystal compound 40 is twisted and oriented so as to be twisted in a counterclockwise spiral from the upper side to the lower side in the thickness direction as shown in the figure. That is, in the optical anisotropic layer 36b shown in FIG. 2, the liquid crystal alignment pattern is uniform throughout the thickness direction, but the spiral twist state of the liquid crystal compound 40 in the thickness direction is the same in regions 37d and 37f, and the same in regions 37e and 37g. Also, in the optical anisotropic layer 36b shown in FIG. 2, the spiral twist state of the liquid crystal compound 40 in the thickness direction is opposite between regions 37d and 37e.

[0036] As described above, in the optical anisotropic layer having a liquid crystal alignment pattern in which the optical axis derived from the liquid crystal compound continuously rotates in one direction, the bright part 42 and the dark part 44 in the cross-sectional SEM image of the optical anisotropic layer 36a are observed to connect the liquid crystal compounds 40 in the same direction. Therefore, in the optical anisotropic layer 36b shown in FIG. 2, the inclination directions of the dark parts 44 in regions 37d and 37f are the same, and the inclination directions of the dark parts 44 in regions 37e and 37g are the same. Specifically, in the lowermost region 37g in the thickness direction, the dark part 44 is inclined so as to face the upper left in the figure. In the second region 37f from the bottom, the dark part 44 is inclined so as to face the upper right in the figure. In the third region 37e from the bottom, the dark part 44 is inclined so as to face the upper left in the figure, similar to the lowermost region 37g. Furthermore, in the uppermost region 37d, the dark part 44 is inclined so as to face the upper right in the figure, similar to the second region 37f from the bottom. That is, the optical anisotropic layer 36b shown in FIG. 2 has, at three locations, a change in the angle of the dark part 44, the change point of the angle dark part.

[0037] Here, in the optically anisotropic layer 36b, the inclination directions of the dark portions are different between the region 37g and the region 37f, which are regions adjacent in the thickness direction. Also, the inclination directions of the dark portions are different between the region 37f and the region 37e, which are regions adjacent in the thickness direction. Furthermore, the inclination directions of the dark portions are different between the region 37e and the region 37d, which are regions adjacent in the thickness direction. That is, in the optically anisotropic layer 36d shown in FIG. 2, the dark portion 44 has three change point of the angle where all of the dark part 44 the inclination directions are in the reverse direction inflection points where they are folded back. Also, as an example, the regions 37d and 37g, and the regions 37e and 37f have the same thickness. Therefore, in the optically anisotropic layer 36b shown in FIG. 2, the bright portion 42 and the dark portion 44 in the cross-sectional SEM image are substantially W-shaped. Accordingly, also in the optically anisotropic layer 36b, the shape of the dark portion 44 is symmetric with respect to the center line in the thickness direction.

[0038] Also, in the liquid crystal diffraction element of the present invention, the configuration of the optically anisotropic layer, in addition to the above example, has the above-described liquid crystal alignment pattern, the one period of the liquid crystal alignment pattern is constant, and further, due to the liquid crystal phase observed in the cross-sectional SEM image, it has the bright portion 42 and the dark portion 44 extending from one surface (main surface) to the other surface, and the dark portion 44 has two or more change point of the angle and has regions with different inclination directions in the thickness direction, any configuration can be used.

[0039] Note that in the examples shown below, only the bright portion 42 and the dark portion 44 in the cross-sectional SEM image of the optically anisotropic layer are illustrated. However, in any of the examples, as shown by enlarging the portion surrounded by the broken line in each figure, each region of the optically anisotropic layer has the above-described liquid crystal alignment pattern in which the optical axis continuously rotates in one direction. Also, in the liquid crystal alignment pattern, one period in which the optical axis derived from the liquid crystal compound rotates 180° is constant. In addition, in the optically anisotropic layer shown below, in a region where the dark portion 44 is inclined with respect to the surface (main surface) of the optically anisotropic layer, the liquid crystal compound 40 is twisted and aligned in the thickness direction. Note that the main surface is the largest surface in a sheet-like object (plate-like object, film, layer).

[0040] As an example, depending on the change point of the angle dark portion 44, an optically anisotropic layer having four regions in the thickness direction is exemplified as conceptually shown in FIG. 3. In this example, in the lowermost region, the dark portion 44 is inclined toward the upper left in the figure. In the second region from the bottom, the dark portion 44 is inclined toward the upper left in the figure at a larger angle with respect to the surface than in the lowermost region. In the third region from the bottom, the dark portion 44 is inclined toward the upper right in the figure. Further, in the uppermost region, the dark portion 44 is inclined toward the upper right in the figure at a smaller angle with respect to the surface than in the third region from the bottom.

[0041] The optically anisotropic layer shown in FIG. 3 has three locations where the angle of the dark portion 44 changes, and change point of the angle has one inflection point where the inclination direction is of the dark part 44 folded back at the interface between the second region from the bottom and the third region from the bottom. in the reverse direction That is, in this example, the change point of the angle at the interface between the second region from the bottom and the third region from the bottom is the inflection point where the inclination direction of the dark part 44 is folded back in the reverse direction. The optically anisotropic layer shown in FIG. 3 also has the same thickness in the lowermost region and the uppermost region, and between the second region from the bottom and the third region from the bottom. Further, the lowermost region and the uppermost region have different inclination directions, but the angle (absolute value of the angle) formed by the surface of the optically anisotropic layer and the dark portion 44 is equal. Similarly, the second region from the bottom and the third region from the bottom have different inclination directions, but the angle formed by the surface of the optically anisotropic layer and the dark portion 44 is equal. That is, in the optically anisotropic layer shown in FIG. 3, the bright portion 42 and the dark portion 44 in the cross-sectional SEM image are substantially C-shaped. Therefore, in the optically anisotropic layer shown in FIG. 3, the shape of the dark portion 44 is symmetric with respect to the center line in the thickness direction.

[0042] ​Note that the angle of the dark portion 44 with respect to the surface of the optically anisotropic layer can be adjusted by the length of one period, which is the length at which the optical axis rotates 180° in one direction in the plane, and the magnitude of the twist of the liquid crystal compound 40 that is twisted and oriented in the thickness direction, which will be described later.

[0043] As another example, according to the change point of the angle dark portion 44 conceptually shown in FIG. 4, an optically anisotropic layer having five regions in the thickness direction is exemplified. In this example, in the lowermost region, the dark portion 44 is inclined toward the upper left in the figure. In the second region from the bottom, the dark portion 44 is inclined toward the upper left in the figure at a larger angle with respect to the surface than in the lowermost region. In the third region from the bottom, that is, the central region in the thickness direction, the dark portion 44 extends in the thickness direction of the optically anisotropic layer. In the fourth region from the bottom, the dark portion 44 is inclined toward the upper right in the figure. Further, in the uppermost region, the dark portion 44 is inclined toward the upper right in the figure at a smaller angle with respect to the surface than in the fourth region from the bottom.

[0044] That is, the optically anisotropic layer shown in FIG. 4 has change point of the angle changes in the angle of the dark portion 44 at four locations. Also, in the lowermost region and the second region from the bottom, and in the fourth region from the bottom and the uppermost region, the inclination directions of the dark portion 44 are opposite. Therefore, the change point of the angle located at the interface between the second region from the bottom and the fourth region from the bottom constitute it. is an inflection point where the inclination direction is folded back in the opposite direction of the dark part 44 That is, the optically anisotropic layer shown in FIG. 3 has

[0045] an inflection point where the inclination direction is folded back in the opposite direction at one location. In this optically anisotropic layer, the bottom region and the top region have different inclination directions, but the angles formed by the surface of the optically anisotropic layer and the dark portion 44 are equal. Similarly, the second region from the bottom and the fourth region from the bottom have different inclination directions, but the angles formed by the surface of the optically anisotropic layer and the dark portion 44 are equal. Further, in the third region from the bottom located in the middle, the dark portion 44 extends in the thickness direction of the optically anisotropic layer. That is, in the optically anisotropic layer shown in FIG. 4, the bright portion 42 and the dark portion 44 in the cross-sectional SEM image are substantially C-shaped. Therefore, in the optically anisotropic layer shown in FIG. 4, the shape of the dark portion 44 is symmetric with respect to the center line in the thickness direction.

[0046] Furthermore, as conceptually shown by exemplifying the configuration having the substantially C-shaped dark portion 44 shown in FIGS. 3 and 4 in FIG. 5, the optically anisotropic layer of the liquid crystal diffractive element of the present invention has an interval between regions in the thickness direction, that is, the interval in the thickness direction change point of the angle By shortening the interval, it is also possible to form a configuration in which the dark portion 44 changes continuously.

[0047] In the liquid crystal diffractive element of the present invention, there is no limit to the number of change point of the angle the dark portions 44 in the optically anisotropic layer, and it may have two or more. Also, there is no limit to the number of inflection points where the inclination direction of the dark portion 44 is in the reverse direction folded back. However, as shown in FIGS. 1 to 5, in terms of points such as being able to make the shape of the dark portion 44 symmetric with respect to the center line in the thickness direction, of the dark part 44 the inclination direction is in the reverse direction The number of inflection points where it is folded back is preferably an odd number, more preferably one or three. Further, of the dark part 44 the inclination direction is in the reverse direction The number of inflection points where it is folded back can also be preferably used with five or more.

[0048] As described above, in all of the optically anisotropic layers described, the shape of the dark portion 44 is symmetric with respect to the center line in the thickness direction. However, in the liquid crystal diffractive element of the present invention, the shape of the dark portion 44 in the optically anisotropic layer does not have to be symmetric with respect to the center line in the thickness direction. As an example, an optically anisotropic layer conceptually shown in FIG. 6 is exemplified.

[0049] The optically anisotropic layer shown in FIG. 6 has three regions corresponding to the dark portions 44. change point of the angle In this example, in the lowermost region, the dark portion 44 is inclined toward the upper left in the figure. In the second region from the bottom, the dark portion 44 is inclined toward the upper left in the figure at a larger angle with respect to the surface than in the lowermost region. Further, in the uppermost region, the dark portion 44 is inclined toward the upper right in the figure. That is, the optically anisotropic layer shown in FIG. 6 has three locations where the dark portion 44 is inclined. Also, there is one inflection point where the inclination direction of the dark portion 44 in the second region from the bottom and the uppermost region is reversed. That is, the optically anisotropic layer shown in FIG. 6 has three locations where the dark portion 44 is inclined. Also, there is one inflection point where the inclination direction of the dark portion 44 in the second region from the bottom and the uppermost region is reversed. change point of the angle Here, the inclination angle of the dark portion 44 with respect to the surface of the optically anisotropic layer is different in all three regions, and although there are differences in the inclination direction, the angle (absolute value of the angle) with respect to the surface of the optically anisotropic layer gradually increases from the bottom to the top. That is, in the optically anisotropic layer shown in FIG. 6, the shape of the dark portion 44 is asymmetric with respect to the center line in the thickness direction. the change point of the angle of the interface is Here, the inclination angle of the dark portion 44 with respect to the surface of the optically anisotropic layer is different in all three regions, and although there are differences in the inclination direction, the angle (absolute value of the angle) with respect to the surface of the optically anisotropic layer gradually increases from the bottom to the top. That is, in the optically anisotropic layer shown in FIG. 6, the shape of the dark portion 44 is asymmetric with respect to the center line in the thickness direction. in the reverse direction Here, the inclination angle of the dark portion 44 with respect to the surface of the optically anisotropic layer is different in all three regions, and although there are differences in the inclination direction, the angle (absolute value of the angle) with respect to the surface of the optically anisotropic layer gradually increases from the bottom to the top. That is, in the optically anisotropic layer shown in FIG. 6, the shape of the dark portion 44 is asymmetric with respect to the center line in the thickness direction. an inflection point, Here, the inclination angle of the dark portion 44 with respect to the surface of the optically anisotropic layer is different in all three regions, and although there are differences in the inclination direction, the angle (absolute value of the angle) with respect to the surface of the optically anisotropic layer gradually increases from the bottom to the top. That is, in the optically anisotropic layer shown in FIG. 6, the shape of the dark portion 44 is asymmetric with respect to the center line in the thickness direction.

[0050] Here, the inclination angle of the dark portion 44 with respect to the surface of the optically anisotropic layer is different in all three regions, and although there are differences in the inclination direction, the angle (absolute value of the angle) with respect to the surface of the optically anisotropic layer gradually increases from the bottom to the top. That is, in the optically anisotropic layer shown in FIG. 6, the shape of the dark portion 44 is asymmetric with respect to the center line in the thickness direction.

[0051] The configuration in which the shape of the dark portion 44 shown in FIGS. 1 to 5 described above is symmetric with respect to the center line in the thickness direction is advantageous in that the wavelength dependence of the diffraction efficiency is smaller. On the other hand, a configuration in which the shape of the dark portion 44 is asymmetric with respect to the center line in the thickness direction, and in particular, a configuration in which the inclination angle gradually increases with respect to the surface of the optically anisotropic layer as shown in FIG. 6, is advantageous in that the diffraction efficiency can be increased even when the diffraction angle (refraction angle) is large. In this example, the inclination angle of the dark portion 44 is the absolute value of the inclination angle.

[0052] In the liquid crystal diffraction element of the present invention, there is no limitation on the inclination angle of the dark portion 44 in the cross-sectional SEM image of the optically anisotropic layer. In the present invention, the average inclination angle of the dark portion 44 is the angle formed by the line connecting the contact point of one surface of the dark portion 44 and the contact point of the other surface with the perpendicular line to the surface of the optically anisotropic layer. Therefore, when the shape of the dark portion 44 is symmetric with respect to the center line in the thickness direction as shown in FIGS. 1 to 5, the average inclination angle of the dark portion 44 becomes approximately 0°.

[0053] In the above-described optically anisotropic layers, a rod-shaped liquid crystal compound is used as the liquid crystal compound. However, the present invention is not limited thereto, and a disc-shaped liquid crystal compound can also be used. In the case of a disc-shaped liquid crystal compound, the optical axis derived from the liquid crystal compound is defined as an axis perpendicular to the disc plane, so-called the homeotropic axis. Further, in the liquid crystal diffraction element of the present invention, as conceptually shown in FIG. 7, the optically anisotropic layer may be used in combination with a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound. By combining a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, light incident at different angles can be diffracted with high diffraction efficiency. The combination of the rod-shaped liquid crystal compound and the disc-shaped liquid crystal compound is not limited to the configuration conceptually shown in FIG. 7, and can be used in various configurations. For example, in FIGS. 2, 3, 4, 5, and 6, the rod-shaped liquid crystal compound may be combined with a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound. Further, for example, in FIG. 7 and the above-described combination, the rod-shaped liquid crystal compound and the disc-shaped liquid crystal compound may be laminated in a more subdivided manner in the thickness direction.

[0054] The liquid crystal diffraction element of the present invention having such a liquid crystal alignment pattern and the optically anisotropic layer having the dark portion 44 (bright portion 42) has, as an example, a support, an alignment film formed on the surface of the support, and an optically anisotropic layer formed on the surface of the alignment film. FIG. 9 shows a conceptual diagram in which a minute region of the liquid crystal diffraction element including the optically anisotropic layer 36a (region 37c) is enlarged. Note that FIG. 8 is a plan view of the optically anisotropic layer 36a shown in FIG. 9. As described above, the liquid crystal diffraction element shown in FIG. 9 has a support 30, an alignment film 32, and an optically anisotropic layer 36a. However, the liquid crystal diffraction element of the present invention is not limited thereto, and various layer configurations can be used. For example, the liquid crystal diffraction element of the present invention may be composed of an alignment film 32 and an optically anisotropic layer 36a obtained by peeling off the support 30 from the liquid crystal diffraction element shown in FIG. 9. Further, the liquid crystal diffraction element of the present invention may be composed only of the optically anisotropic layer 36a obtained by peeling off the support 30 and the alignment film 32 from the liquid crystal diffraction element shown in FIG. 9. Also, the liquid crystal diffraction element of the present invention may be composed of the support 30 and the optically anisotropic layer 36a. Furthermore, the liquid crystal diffraction element of the present invention may have other layers such as a protective layer (hard coat layer) and an antireflection layer in addition to these configurations.

[0055] Also, the liquid crystal diffraction element of the present invention comprises an optically anisotropic layer formed using a liquid crystal 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 continuously changes while rotating along at least one direction in the plane, when the length of one cycle is defined as the length over which the direction of the optical axis derived from the liquid crystal compound rotates 180° in the plane, the length of one cycle in the liquid crystal alignment pattern gradually changes along one direction, the optically anisotropic layer having a bright part and a dark part extending from one surface to the other surface in a cross-sectional image observed with a scanning electron microscope of a cross-section cut in the thickness direction along one direction, and the dark part having two or more change point of the angle having, regions in which the inclination direction of the dark part is different in the thickness direction may also be a liquid crystal diffraction element.

[0056] In the example shown in FIG. 13, the liquid crystal alignment pattern of the liquid crystal layer 36 has a concentric pattern having one direction (arrows A1 to A3) in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating, from the inside to the outside. The concentric pattern means that a line connecting liquid crystal compounds having the optical axis in the same direction is circular, and the circular line segments are concentric. In other words, the liquid crystal alignment pattern of the optically anisotropic layer 36a shown in FIG. 13 is a liquid crystal alignment pattern in which one direction in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating is provided radially from the center of the liquid crystal layer 36.

[0057] In the optically anisotropic layer 36a shown in FIG. 13, the optical axis (not shown) of the liquid crystal compound 40 is the longitudinal direction of the liquid crystal compound 40. In the optically anisotropic layer 36a, the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating along a number of directions from the center of the optically anisotropic layer 36a to the outside, for example, the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3... Arrows A1, A2, and A3 are arrangement axes described later.

[0058] The optically anisotropic layer 36a of the liquid crystal diffraction element has one period Λ of the liquid crystal alignment pattern having different regions in the plane. Here, one period Λ of the liquid crystal alignment pattern is the length (distance) in which the optical axis of the liquid crystal compound 40 rotates 180° in one direction in which the direction of the optical axis in the plane continuously rotates and changes. Specifically, for example, in the direction along arrow A1 in FIG. 13, in the direction in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating, as it goes from the center to the outside, it has a configuration in which one period Λ gradually becomes shorter. That is, in FIG. 13, one period in the vicinity of the outside is shorter than one period in the vicinity of the center. In the present invention, the gradual change of one period Λ is intended to include both a case where one period Λ changes continuously and a case where one period Λ changes stepwise.

[0059] As will be described in detail later, the diffraction angle by the liquid crystal diffraction element depends on one period Λ of the liquid crystal alignment pattern, and the smaller the one period Λ is, the larger the diffraction angle becomes.

[0060] When the optical anisotropic layer 36a is provided radially from the center of the optical anisotropic layer 36a in a direction in which the liquid crystal alignment pattern changes while the orientation of the optical axis of the liquid crystal compound 40 continuously rotates, and in each direction, the one period Λ of the liquid crystal alignment pattern gradually becomes shorter as it goes from the center to the outside, the circularly polarized light incident on the optical anisotropic layer 36a having this liquid crystal alignment pattern is bent (diffracted) in each of the individual local regions where the orientation of the optical axis of the liquid crystal compound 40 is different. At this time, each diffraction angle differs according to the one period in the region where the circularly polarized light is incident. The optical anisotropic layer 36a having a concentric liquid crystal alignment pattern, that is, a liquid crystal alignment pattern in which the optical axis continuously rotates and changes radially, can transmit the incident light as convergent light according to the rotation direction of the optical axis of the liquid crystal compound 40 and the direction of the incident circularly polarized light. That is, by making the liquid crystal alignment pattern of the optical anisotropic layer 36a concentric, the liquid crystal diffraction element 10a exhibits a function as, for example, a convex lens.

[0061] Here, in the present invention, as shown in FIG. 1, the optical anisotropic layer 36a has a bright part 42 and a dark part 44 extending from one surface to the other surface in the SEM image, and the dark part 44 has two or more change point of the angle and has regions where the inclination directions of the dark part 44 are different in the thickness direction.

[0062] In the example shown in FIG. 1, the optical anisotropic layer 36a has a stripe pattern of a bright part 42 and a dark part 44, and each dark part 44 changes the inclination angle with respect to the surface at two positions in the thickness direction. That is, each dark part 44 has two change point of the angle respectively. Also, in any of the dark parts 44, the inclination direction in the upper region in the figure and the inclination direction in the lower region in the figure are opposite to each other. That is, each dark part 44 has regions where the inclination directions are different.

[0063] In addition, the liquid crystal diffraction element shown in FIG. 9 has a support 30, but the support 30 may not be provided. For example, from the above configuration, the optical element of the present invention may be configured by peeling off the support 30 and using only the alignment film and the liquid crystal layer, or by peeling off the alignment film as well and using only the liquid crystal layer.

[0064] That is, for the liquid crystal diffraction element, various layer configurations can be used as long as the liquid crystal layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound rotates in one direction.

[0065] As described above, in the liquid crystal diffraction element of the present invention, the dark portions 44 observed in the cross-sectional SEM image have two or more change point of the angle and have regions with different inclination directions in the thickness direction. Therefore, the liquid crystal diffraction element of the present invention has a small wavelength dependence of the diffraction efficiency and can diffract light with a similar diffraction efficiency regardless of the wavelength. Moreover, such a liquid crystal diffraction element of the present invention can diffract light with a high diffraction efficiency regardless of the wavelength. In addition, the liquid crystal alignment pattern of the liquid crystal diffraction element of the present invention may change the length of one period in which the optical axis rotates by 180° in the plane. When the length of one period changes in the plane, the liquid crystal diffraction element of the present invention diffracts (refracts) light with the same wavelength at different angles depending on the incident position of light in the plane. Therefore, the liquid crystal diffraction element of the present invention can also be suitably used for various optical devices that are required to diffract light with the same wavelength at different angles regardless of the incident position, such as lens elements in head-mounted displays for VR and lens elements that improve color breakup when combined with refractive lenses.

[0066] <<Support>> The support 30 supports the alignment film 32 and the optically anisotropic layer 36a. As long as the support 30 can support the alignment film and the optically anisotropic layer, various sheet-like materials (films, plate-like materials) can be used. As the support 30, a transparent support is preferred, and examples thereof include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, cycloolefin polymer films (for example, trade name "Arton", manufactured by JSR Corporation, trade name "Zeonoa", manufactured by Nippon Zeon Co., Ltd.), polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride. The support is not limited to a flexible film, and may be a non-flexible substrate such as a glass substrate. Further, the support 30 may be multilayered. Examples of the multilayered support include those containing any of the above-described supports as a substrate and having another layer provided on the surface of this substrate.

[0067] There is no limitation on the thickness of the support 30, and the thickness capable of holding the alignment film and the optically anisotropic layer may be appropriately set according to the use of the liquid crystal diffraction element and the forming material of the support 30. The thickness of the support 30 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and even more preferably 5 to 150 μm.

[0068] <<Alignment Film>> An alignment film 32 is formed on the surface of the support 30. The alignment film 32 is an alignment film for aligning the liquid crystal compound 40 in the above-described predetermined liquid crystal alignment pattern when forming the optically anisotropic layer 36a.

[0069] As described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis 40A (see FIG. 8) derived from the liquid crystal compound 40 continuously changes while rotating along one direction (arrow X direction described later) in the plane. Therefore, the alignment film is formed so that the optically anisotropic layer can form this liquid crystal alignment pattern. Also, in one direction in which the direction of the optical axis 30A continuously changes while rotating in the liquid crystal alignment pattern, the length in which the direction of the optical axis 30A rotates 180° is defined as one period Λ (rotation period of the optical axis).

[0070] In the following description, "the direction of the optical axis 40A rotates" is also simply referred to as "the optical axis 40A rotates".

[0071] Various known alignment films can be used. For example, a rubbed film made of an organic compound such as a polymer, an obliquely deposited film of an inorganic compound, a film having microgrooves, and a film formed by accumulating an LB (Langmuir - Blodgett) film of an organic compound such as ω - tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate are exemplified.

[0072] The alignment film formed by rubbing can be formed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. As materials used for the alignment film, polyimide, polyvinyl alcohol, polymers having polymerizable groups described in JP - A - 9 - 152509, alignment films described in JP - A - 2005 - 97377, JP - A - 2005 - 99228, and JP - A - 2005 - 128503 are preferably exemplified.

[0073] In the liquid crystal diffraction element of the present invention, as the alignment film, a so - called photo - alignment film formed by irradiating a photo - aligning material with polarized or non - polarized light is preferably used. That is, in the liquid crystal diffraction element of the present invention, as the alignment film, a photo - alignment film formed by coating a photo - aligning material on the support 30 is preferably used. The polarized light irradiation can be performed on the photo - alignment film from the vertical direction or an oblique direction, and the non - polarized light irradiation can be performed on the photo - alignment film from an oblique direction.

[0074] Examples of the photo-orienting material used for the photo-orienting film that can be used in the present invention include, for example, azo compounds described in JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, JP-A-2007-133184, JP-A-2009-109831, Patent No. 3883848, and Patent No. 4151746; aromatic ester compounds described in JP-A-2002-229039; maleimide and / or alkenyl-substituted nadimide compounds having a photo-orienting unit described in JP-A-2002-265541 and JP-A-2002-317013; photocrosslinkable silane derivatives described in Patent No. 4205195 and Patent No. 4205198; photocrosslinkable polyimide, photocrosslinkable polyamide, and photocrosslinkable ester described in JP-T-2003-520878, JP-T-2004-529220, and Patent No. 4162850; and photo-dimerizable compounds described in JP-A-9-118717, JP-T-10-506420, JP-T-2003-505561, WO2010 / 150748, JP-A-2013-177561, and JP-A-2014-12823, particularly cinnamate compounds, chalcone compounds, coumarin compounds, etc., are exemplified as preferred examples. Among them, azo compounds, photocrosslinkable polyimide, photocrosslinkable polyamide, photocrosslinkable ester, cinnamate compounds, and chalcone compounds are preferably used.

[0075] There is no limitation on the thickness of the alignment film, and the thickness capable of obtaining the necessary alignment function may be appropriately set according to the material for forming the alignment film. The thickness of the alignment film is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0076] There is no limitation on the method for forming the alignment film, and various known methods according to the material for forming the alignment film can be used. As an example, a method of forming an alignment pattern by applying the alignment film on the surface of the support 30, drying it, and then exposing the alignment film with laser light is exemplified.

[0077] Fig. 10 conceptually shows an example of an exposure apparatus that exposes an alignment film to form the above-described alignment pattern.

[0078] The exposure apparatus 60 shown in Fig. 10 includes a light source 64 having a laser 62, a λ / 2 plate 65 that changes the polarization direction of the laser beam M emitted from the laser 62, a beam splitter 68 that separates the laser beam M emitted from the laser 62 into two laser beams MA and MB, and mirrors 70A and 70B respectively disposed on the optical paths of the two separated laser beams MA and MB, and λ / 4 plates 72A and 72B. Although not shown, the light source 64 emits linearly polarized light P0. The λ / 4 plate 72A converts linearly polarized light P0 (laser beam MA) into right circularly polarized light P R and the λ / 4 plate 72B converts linearly polarized light P0 (laser beam MB) into left circularly polarized light P L respectively.

[0079] A support 30 having an alignment film 32 before the alignment pattern is formed is disposed in the exposure section, and the two laser beams MA and MB are made to intersect and interfere on the alignment film 32, and the interference light is irradiated onto the alignment film 32 for exposure. Due to the interference at this time, the polarization state of the light irradiated onto the alignment film 32 changes periodically in an interference fringe pattern. As a result, an alignment pattern in which the alignment state changes periodically is obtained in the alignment film 32. That is, an alignment film (hereinafter also referred to as a pattern alignment film) having an alignment pattern in which the alignment state changes periodically is obtained. In the exposure apparatus 60, the period of the alignment pattern can be adjusted by changing the intersection angle α between the two laser beams MA and MB. That is, in the exposure apparatus 60, by adjusting the intersection angle α, in an alignment pattern in which the optical axis 40A derived from the liquid crystal compound 40 rotates continuously along one direction, the length of one period (one period Λ) in which the optical axis 40A rotates 180° in one direction in which the optical axis 40A rotates can be adjusted. By forming an optically anisotropic layer on a patterned alignment film having an alignment pattern in which such an alignment state changes periodically, as will be described later, an optically anisotropic layer 36a having a liquid crystal alignment pattern in which the optical axis 40A derived from the liquid crystal compound 40 rotates continuously in one direction can be formed. Also, by rotating the optical axes of the λ / 4 plates 72A and 72B by 90° each, the rotation direction of the optical axis 40A can be reversed.

[0080] As described above, the patterned alignment film has an alignment pattern for aligning the liquid crystal compound 40 so that the direction of the optical axis derived from the liquid crystal compound in the optically anisotropic layer formed on the patterned alignment film becomes a liquid crystal alignment pattern that changes while continuously rotating along at least one direction in the plane. If the axis along the direction in which the patterned alignment film aligns the liquid crystal compound 40 is defined as the alignment axis, it can be said that the patterned alignment film has an alignment pattern in which the direction of the alignment axis changes while continuously rotating along at least one direction in the plane. The alignment axis of the patterned alignment film can be detected by measuring the absorption anisotropy. For example, when linearly polarized light is irradiated while rotating it on the patterned alignment film and the amount of light transmitted through the patterned alignment film is measured, the direction in which the amount of light becomes maximum or minimum is observed to gradually change along one direction in the plane.

[0081] Note that in the liquid crystal diffraction element of the present invention, the alignment film is provided as a preferred embodiment and is not an essential component. For example, by forming an alignment pattern on the support 30 by a method of rubbing the support 30, a method of processing the support 30 with laser light or the like, etc., the optically anisotropic layer 36a or the like can have a configuration having a liquid crystal alignment pattern in which the direction of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating along at least one direction in the plane.

[0082] The exposure apparatus for the alignment film 32 is not limited to the example shown in FIG. 10. FIG. 14 shows another example of the exposure apparatus for exposing the alignment film 32. The exposure apparatus shown in FIG. 14 is an example of an exposure apparatus that forms a concentric alignment pattern as shown in FIG. 13 on the alignment film.

[0083] The exposure apparatus 80 includes a light source 84 having a laser 82, a polarization beam splitter 86 that splits the laser light M from the laser 82 into an S-polarized light MS and a P-polarized light MP, a mirror 90A disposed in the optical path of the P-polarized light MP, a mirror 90B disposed in the optical path of the S-polarized light MS, a lens 92 disposed in the optical path of the S-polarized light MS, a polarization beam splitter 94, and a λ / 4 plate 96.

[0084] The P-polarized light MP split by the polarization beam splitter 86 is reflected by the mirror 90A and enters the polarization beam splitter 94. On the other hand, the S-polarized light MS split by the polarization beam splitter 86 is reflected by the mirror 90B, condensed by the lens 92, and enters the polarization beam splitter 94. The P-polarized light MP and the S-polarized light MS are combined by the polarization beam splitter 94, and become right-circularly polarized light and left-circularly polarized light according to the polarization direction by the λ / 4 plate 96, and enter the alignment film 32 on the support 30. Here, due to the interference between the right-circularly polarized light and the left-circularly polarized light, the polarization state of the light irradiated on the alignment film changes periodically in an interference fringe shape. As going from the inside to the outside of the concentric circles, since the intersection angle between the left-circularly polarized light and the right-circularly polarized light changes, an exposure pattern with a changing pitch from the inside to the outside is obtained. Thereby, a concentric alignment pattern in which the alignment state changes periodically is obtained in the alignment film.

[0085] In this exposure apparatus 80, one period Λ of the liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 40 continuously rotates 180° along one direction can be controlled by changing the refractive power (F-number of the lens 92) of the lens 92, the focal length of the lens 92, the distance between the lens 92 and the alignment film 32, and the like. Also, by adjusting the refractive power (F-number of the lens 92) of the lens 92, the length Λ of one period of the liquid crystal alignment 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 alignment pattern can be changed in one direction in which the optical axis continuously rotates, depending on the divergence angle of the light spread by the lens 92 that is interfered with the parallel light. More specifically, when the refractive power of the lens 92 is weakened, since it approaches the parallel light, the length Λ of one period of the liquid crystal alignment pattern gradually shortens from the inside to the outside, and the F-number increases. Conversely, when the refractive power of the lens 92 is strengthened, the length Λ of one period of the liquid crystal alignment pattern suddenly shortens from the inside to the outside, and the F-number decreases.

[0086] In addition, when it is desired to provide a light quantity distribution in the transmitted light, for example, depending on the application of the liquid crystal diffraction element, instead of gradually changing the one period Λ in the direction of the array axis D, a configuration having a region where the one period Λ is partially different in the direction of the array axis D can also be used. For example, as a method of partially changing the one period Λ, a method of scanning and exposing the photo-alignment film while arbitrarily changing the polarization direction of the focused laser light to perform patterning can be used.

[0087] Also, the wavelength of the laser used for exposing the alignment film can be appropriately set according to the type of the alignment film used and the like. For example, lasers with wavelengths in the deep ultraviolet to visible light to infrared range can be preferably used. As an example, lasers with wavelengths such as 266 nm, 325 nm, 355 nm, 370 nm, 385 nm, 405 nm, and 460 nm can be used, but it is not limited to the above, and lasers with various wavelengths can be used according to the type of the alignment film and the like.

[0088] After providing an optically anisotropic layer on the alignment film, the optically anisotropic layer may be peeled off and transferred from the alignment film. The transfer may be carried out multiple times according to the bonding surface of the optically anisotropic layer. The peeling and transfer method can be freely selected according to the purpose. For example, after transferring once to a substrate having an adhesive layer, re-transferring to an object to be transferred, and peeling off the substrate, the interface on the alignment film side of the optically anisotropic layer can be made to be on the object side to be transferred. Further, when the surface on the side opposite to the alignment film of the optically anisotropic layer is made to be the object side to be transferred, after bonding the optically anisotropic layer and the object to be transferred via an adhesive, the optically anisotropic layer may be peeled off from the alignment film. When peeling off the optically anisotropic layer from the alignment film, it is preferable to adjust the peeling angle, speed, etc. in order to reduce damage (such as tearing, knicks, etc.) to the optically anisotropic layer and the alignment film. Also, the alignment film may be repeatedly used within a range where there is no problem with the alignment property. Before providing the optically anisotropic layer on the alignment film, the alignment film can also be cleaned with an organic solvent or the like.

[0089] <<Optically Anisotropic Layer>> An optically anisotropic layer 36a is formed on the surface of the alignment film 32. In addition, in FIG. 8, in order to simplify the drawing and clearly show the configuration of the optically anisotropic layer 36a, the optically anisotropic layer 36a only shows the liquid crystal compound 40 (liquid crystal compound molecules) on the surface of the alignment film. However, as conceptually shown by exemplifying the optically anisotropic layer 36a in FIG. 9, the optically anisotropic layer 36a has a structure in which aligned liquid crystal compounds 40 are stacked, similar to an optically anisotropic layer formed using a composition containing a normal liquid crystal compound. Also, as described above, the optically anisotropic layer 36a has three regions, namely region 37c, region 37b, and region 37a, according to the change point of the angle dark part 44 from the bottom. However, in FIG. 9, only the lowermost region 37c (on the support 30 side) is shown in order to simplify the drawing.

[0090] As described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer 36a is formed using a composition containing a liquid crystal compound. When the value of the in-plane retardation of the optically anisotropic layer is set to λ / 2, it functions as a general λ / 2 plate, that is, it has a function of imparting a phase difference of half a wavelength, i.e., 180°, to two linearly polarized light components orthogonal to each other contained in the light incident on the optically anisotropic layer. Here, since the liquid crystal compound rotates and is aligned in the in-plane direction in the optically anisotropic layer, the incident circularly polarized light is refracted (diffracted) and transmitted in the direction in which the direction of the optical axis continuously rotates. At this time, the diffraction direction differs depending on the swirling direction of the incident circularly polarized light. That is, the optically anisotropic layer transmits circularly polarized light and diffracts this transmitted light. In addition, the optically anisotropic layer changes the swirling direction of the transmitted circularly polarized light in the reverse direction.

[0091] The optically anisotropic layer 36a has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously changes while rotating in one direction indicated by an arrow D (hereinafter also referred to as the alignment axis D) in the plane of the optically anisotropic layer. In the example shown in FIG. 8, the direction of the alignment axis D is the X direction, and the direction orthogonal to the direction of the alignment axis D is the Y direction. Note that the optical axis 40A derived from the liquid crystal compound 40 is the axis along which the refractive index is highest in the liquid crystal compound 40, that is, the so-called slow axis. For example, when the liquid crystal compound 40 is a rod-shaped liquid crystal compound, the optical axis 40A is along the long axis direction of the rod shape. In the following description, the optical axis 40A derived from the liquid crystal compound 40 is also referred to as the 'optical axis 40A of the liquid crystal compound 40' or the 'optical axis 40A'. In the optically anisotropic layer, the liquid crystal compounds 40 are two-dimensionally aligned in a plane parallel to the arrow X direction and the Y direction orthogonal to the arrow X direction in the optically anisotropic layer 36a. In FIGS. 1 to 6, the Y direction is the direction perpendicular to the paper surface.

[0092] FIG. 8 conceptually shows a plan view of the optically anisotropic layer 36a. Note that the plan view is a view of the liquid crystal diffraction element from above in FIG. 9, that is, a view of the liquid crystal diffraction element from the thickness direction (= the stacking direction of each layer (film)). In other words, it is a view of the optical anisotropic layer 36a from a direction orthogonal to the surface. In addition, in FIG. 8, in order to clearly show the configuration of the liquid crystal diffraction element of the present invention, only the liquid crystal compound 40 on the surface of the alignment film 32 is shown for the liquid crystal compound 40. However, as shown in FIG. 9 in the thickness direction, the optical anisotropic layer 36a has a structure in which the liquid crystal compounds 40 are stacked from the liquid crystal compound 40 on the surface of the alignment film 32.

[0093] Note that in FIG. 8, a part of the in-plane of the optical anisotropic layer 36a is described as a representative example, but basically, the same configuration and effects are provided at each position in the in-plane of the optical anisotropic layer.

[0094] The optical anisotropic layer 36a has a liquid crystal alignment pattern in which the direction of the optical axis 40A continuously changes while rotating along the array axis D direction in the in-plane of the optical anisotropic layer 36a. The fact that the direction of the optical axis 40A continuously changes while rotating along the array axis D direction (a predetermined one direction) specifically means that the angle formed by the optical axis 40A of the liquid crystal compound 40 arranged along the array axis D direction and the array axis D direction is different depending on the position in the array axis D direction, and along the array axis D direction, the angle formed by the optical axis 40A and the array axis D direction changes sequentially from θ to θ + 180° or θ - 180°. Note that the difference in the angles of the optical axes 40A of the liquid crystal compounds 40 adjacent to each other in the array axis D direction is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0095] On the other hand, for the liquid crystal compound 40 forming the optical anisotropic layer 36a, in the Y direction orthogonal to the array axis D direction, that is, in the Y direction orthogonal to the one direction in which the optical axis 40A continuously rotates, the liquid crystal compounds 40 having the same direction of the optical axis 40A are arranged at equal intervals. In other words, in the liquid crystal compound 40 that forms the optically anisotropic layer 36a, the angles formed by the directions of the optical axes 40A of the liquid crystal compounds 40 arranged in the Y direction and the direction of the alignment axis D are equal.

[0096] In the liquid crystal diffraction element of the present invention, in such a liquid crystal alignment pattern of the liquid crystal compound 40, the length (distance) by which the optical axis 40A rotates 180° in the direction of the alignment axis D in which the direction of the optical axis 40A continuously rotates and changes in the plane is defined as the length Λ of one period in the liquid crystal alignment pattern. In other words, the length of one period in the liquid crystal alignment pattern is defined by the distance until the angle formed by the optical axis 40A and the direction of the alignment axis D changes from θ to θ + 180°. The length of one period in the liquid crystal alignment pattern is the length of one period in the periodic structure of the diffraction element. That is, the distance between the centers in the direction of the alignment axis D of two liquid crystal compounds 40 having equal angles with respect to the direction of the alignment axis D is defined as the length Λ of one period. Specifically, as shown in FIG. 8, the distance between the centers in the direction of the alignment axis D of two liquid crystal compounds 40 in which the direction of the alignment axis D and the direction of the optical axis 40A coincide is defined as the length Λ of one period. In the following description, this length Λ of one period is also referred to as 'one period Λ'. In the liquid crystal diffraction element of the present invention, the liquid crystal alignment pattern of the optically anisotropic layer repeats this one period Λ in the direction of the alignment axis D, that is, in one direction in which the direction of the optical axis 40A continuously rotates and changes.

[0097] As described above, in the optically anisotropic layer, the liquid crystal compounds arranged in the Y direction have equal angles formed by the optical axis 40A and the direction of the alignment axis D (the one direction in which the direction of the optical axis of the liquid crystal compound 40 rotates). The region where the liquid crystal compound 40 having equal angles formed by the optical axis 40A and the direction of the alignment axis D is arranged in the Y direction is defined as region R. In this case, the value of the in-plane retardation (Re) in each region R is preferably a half wavelength, i.e., λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn due to the refractive index anisotropy of region R and the thickness of the optically anisotropic layer. Here, the refractive index difference due to the refractive index anisotropy of region R in the optically anisotropic layer is the refractive index difference defined by the difference between the refractive index in the direction of the slow axis in the plane of region R and the refractive index in the direction orthogonal to the direction of the slow axis. That is, the refractive index difference Δn due to the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 40 in the direction of the optical axis 40A and the refractive index of the liquid crystal compound 40 in the direction perpendicular to the optical axis 40A in the plane of region R. That is, the above refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

[0098] When circularly polarized light is incident on such an optically anisotropic layer 36a, the light is diffracted (refracted) and the direction of the circularly polarized light is converted. This action is conceptually shown in FIGS. 11 and 12 by exemplifying the optically anisotropic layer 36a. In FIGS. 11 and 12, in order to simplify the drawing and clearly show the configuration of the liquid crystal diffraction element, the optically anisotropic layer 36a shows only the liquid crystal compound 40 (liquid crystal compound molecules) on the surface of the alignment film. Also, it is assumed that the value of the product of the refractive index difference of the liquid crystal compound and the thickness of the optically anisotropic layer 36a is λ / 2.

[0099] As shown in FIG. 11, when the value of the product of the refractive index difference of the liquid crystal compound of the optically anisotropic layer 36a and the thickness of the optically anisotropic layer is λ / 2, when incident light L1 which is left circularly polarized light is incident on the optically anisotropic layer 36a, the incident light L1 passes through the optically anisotropic layer 36a and a phase difference of 180° is given, and the transmitted light L2 is converted into right circularly polarized light. Also, since the liquid crystal alignment pattern formed on the optically anisotropic layer 36a is a periodic pattern in the direction of the array axis D, the transmitted light L2 travels in a direction different from the traveling direction of the incident light L1. Thus, the incident light L1 which is left circularly polarized light is converted into the transmitted light L2 which is right circularly polarized light and is inclined by a certain angle in the direction of the array axis D with respect to the incident direction.

[0100] On the one hand, as shown in FIG. 12, when the value of the product of the refractive index difference of the liquid crystal compound in the optically anisotropic layer 36a and the thickness of the optically anisotropic layer 36a is λ / 2, when the right-circularly polarized incident light L4 is incident on the optically anisotropic layer 36a, the incident light L4 passes through the optically anisotropic layer 36a, thereby being given a phase difference of 180° and converted into the transmitted light L5 of left-circular polarization. Further, since the liquid crystal alignment pattern formed in the optically anisotropic layer 36a is a periodic pattern in the direction of the alignment axis D, the transmitted light L5 travels in a direction different from the traveling direction of the incident light L4. At this time, the transmitted light L5 travels in a direction different from the transmitted light L2, that is, in a direction opposite to the direction of the alignment axis D with respect to the incident direction. In this way, the incident light L4 is converted into the transmitted light L5 of left-circular polarization that is inclined by a certain angle in a direction opposite to the direction of the alignment axis D with respect to the incident direction.

[0101] The optically anisotropic layer 36a can adjust the diffraction (refraction) angles of the transmitted lights L2 and L5 by changing one period Λ of the liquid crystal alignment pattern formed. Specifically, the shorter one period Λ of the liquid crystal alignment pattern of the optically anisotropic layer 36a is, the stronger the interference between the lights passing through the adjacent liquid crystal compounds 40, so that the transmitted lights L2 and L5 can be diffracted greatly. Also, by reversing the rotation direction of the optical axis 40A of the liquid crystal compound 40 that rotates along the direction of the alignment axis D, the diffraction direction of the transmitted light can be reversed. That is, in the examples shown in FIGS. 11 to 12, the rotation direction of the optical axis 40A toward the direction of the alignment axis D is clockwise, but by changing this rotation direction to counterclockwise, the diffraction direction of the transmitted light can be reversed.

[0102] Here, the diffraction angle (refraction angle) by the optically anisotropic layer 36a varies depending on the wavelength of the incident light. Specifically, the longer the wavelength of the light, the greater the diffraction. That is, for red light, green light, and blue light, the red light is diffracted the most, the green light is diffracted next, and the diffraction of the blue light is the smallest. In the present invention, one period Λ in the liquid crystal alignment pattern of the optically anisotropic layer 36a is uniform. Therefore, lights of the same wavelength are diffracted at the same angle.

[0103] As described above, the angle of the dark portion 44 with respect to the surface of the optically anisotropic layer can be adjusted by the length of one period, which is the length over which the optical axis of the liquid crystal compound rotates 180° in one direction in the plane, and the magnitude of the twist of the liquid crystal compound 40 that is twisted and oriented in the thickness direction. The shorter the one period Λ and the smaller the twist in the thickness direction, the larger the angle of the dark portion 44 with respect to the surface of the optically anisotropic layer. That is, the shorter the one period and the smaller the twist in the thickness direction, the more the dark portion 44 rises with respect to the surface of the optically anisotropic layer. As described above, the shorter the one period Λ of the liquid crystal alignment pattern, the larger the diffraction angle of the incident light.

[0104] Also, the tilt direction of the dark portion 44, for example, the tilt direction toward the upper right in the figure and the tilt direction toward the upper left in the figure, can be selected by the rotation direction (clockwise or counterclockwise) of the optical axis 40A in one direction in the plane and the twist direction (clockwise or counterclockwise) of the liquid crystal compound 40 in the thickness direction.

[0105] In the optically anisotropic layer 36a, the value of the in-plane retardation of the plurality of regions R is preferably half a wavelength, but the in-plane retardation Re(550) = Δn of the plurality of regions R of the optically anisotropic layer 36a with respect to incident light having a wavelength of 550 nm 550 ×d is preferably within the range defined by the following formula (1). Here, Δn 550 is the refractive index difference associated with the refractive index anisotropy of the region R when the wavelength of the incident light is 550 nm, and d is the thickness of the optically anisotropic layer 36a. 200 nm ≤ Δn 550 ×d ≤ 350 nm ··· (1) That is, if the in-plane retardation Re(550) = Δn 550 ×d of the plurality of regions R of the optically anisotropic layer 36a satisfies formula (1), a sufficient amount of circular polarization component of the light incident on the optically anisotropic layer 36a can be converted into circularly polarized light traveling in a direction inclined in the forward or reverse direction with respect to the array axis D direction. The in-plane retardation Re(550) = Δn 550 ×d is 225 nm ≤ Δn 550Δn×d≦340nm is more preferable, and 250nm≦Δn 550 ×d≦330nm is even more preferable. Note that the above formula (1) is the range for incident light with a wavelength of 550nm. However, for incident light with a wavelength of λnm, the in-plane retardation Re(λ)=Δn of the plurality of regions R of the optically anisotropic layer λ ×d is preferably within the range defined by the following formula (1-2) and can be set as appropriate. 0.7×(λ / 2)nm≦Δn λ ×d≦1.3×(λ / 2)nm ···(1-2)

[0106] Also, the values of the in-plane retardation of the plurality of regions R in the optically anisotropic layer 36a can also be used outside the range of the above formula (1). Specifically, Δn 550 ×d<200nm or 350nm<Δn 550 By setting Δn×d, light traveling in the same direction as the traveling direction of the incident light and light traveling in a direction different from the traveling direction of the incident light can be separated. 550 As Δn×d approaches 0nm or 550nm, the component of light traveling in the same direction as the traveling direction of the incident light increases, and the component of light traveling in a direction different from the traveling direction of the incident light decreases.

[0107] Furthermore, for each in-plane retardation Re(450)=Δn of the region R of the optically anisotropic layer 36a with respect to incident light having a wavelength of 450nm 450 ×d and for each in-plane retardation Re(550)=Δn of the region R of the optically anisotropic layer 36a with respect to incident light having a wavelength of 550nm 550 ×d preferably satisfies the following formula (2). Here, Δn 450 is the refractive index difference due to the refractive index anisotropy of the region R when the wavelength of the incident light is 450nm. (Δn 450 ×d) / (Δn 550 ×d)<1.0 ···(2) Equation (2) represents that the liquid crystal compound 40 contained in the optically anisotropic layer 36a has reverse dispersibility. That is, when Equation (2) is satisfied, the optically anisotropic layer 36a can respond to incident light of a wide range of wavelengths.

[0108] The optically anisotropic layer is composed of a cured layer of a liquid crystal composition containing a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and the optical axis of the rod-shaped liquid crystal compound or the optical axis of the disc-shaped liquid crystal compound has the liquid crystal alignment pattern oriented as described above.

[0109] The optically anisotropic layer is formed by forming an alignment film 32 having the above-described alignment pattern on the support 30, and applying and curing a liquid crystal composition on this alignment film. In addition, the structure in which the optical axis of the liquid crystal compound possessed by the optically anisotropic layer is twisted and rotated in a spiral shape in the thickness direction of the optically anisotropic layer can be formed by adding a chiral agent that helically aligns the liquid crystal compound in the thickness direction to the liquid crystal composition.

[0110] Furthermore, in order for the optically anisotropic layer to have two or more change point of the angle dark portions 44 and to have regions in which the inclination directions of the dark portions 44 are different in the thickness direction, optically anisotropic layers having different configurations may be formed for each region in the thickness direction.

[0111] For example, when forming the optically anisotropic layer 36a shown in FIG. 1, first, a liquid crystal composition containing a chiral agent that induces a right twist in the thickness direction is applied on the alignment film 32 having the alignment pattern formed on the support 30, and after the liquid crystal compound 40 is helically aligned in the thickness direction by heating or the like, the liquid crystal composition is cured to form the region 37c. The alignment pattern formed on the alignment film 32 is an alignment pattern in which the optical axis 40A derived from the liquid crystal compound 40 continuously rotates toward one direction (array axis D) in the plane. Therefore, in the in-plane direction, in the region 37c, the optical axis 40A derived from the liquid crystal compound 40 continuously rotates in one direction, and in the thickness direction, the liquid crystal compound 40 is twisted and aligned in the clockwise direction from the top to the bottom in the thickness direction.

[0112] Next, a liquid crystal composition similar to the region 37c except that it does not contain a chiral agent is applied on the formed region 37c, and the liquid crystal composition is cured to form the region 37b. When a liquid crystal layer is formed on the liquid crystal layer by a coating method, the in-plane alignment pattern of the liquid crystal compound follows the alignment pattern of the lower liquid crystal layer. Therefore, in the in-plane direction, the region 37b is the same as the region 37c, and the optical axis 40A derived from the liquid crystal compound 40 continuously rotates in one direction. In the thickness direction, the liquid crystal compound 40 is not twisted and aligned, and the directions of the optical axes 40A of the liquid crystal compound 40 are aligned.

[0113] Furthermore, a liquid crystal composition similar to the region 37c except that a chiral agent that induces left-handed twist in the thickness direction is used is applied on the formed region 37b. After the liquid crystal compound 40 is twisted and aligned in the thickness direction by heating or the like, the liquid crystal composition is cured to form the region 37a. As described above, the liquid crystal layer formed by the coating method follows the alignment pattern of the lower layer. Therefore, in the in-plane direction, the region 37a is the same as the region 37b and the like, and the optical axis 40A continuously rotates in one direction. In the thickness direction, the liquid crystal compound 40 is twisted and aligned counterclockwise from top to bottom in the thickness direction. Thereby, an optically anisotropic layer 36a having a region 37c in which the inclination direction of the dark portion 44 is directed upward to the left, a region 37b in which the dark portion 44 extends in the thickness direction, and a region 37a in which the inclination direction of the dark portion 44 is directed upward to the left as shown in FIG. 1 can be formed.

[0114] The magnitude of the twist alignment of the liquid crystal compound twisted and aligned in the thickness direction can be adjusted by the type of the chiral agent added to the liquid crystal composition and the amount of the chiral agent added. Also, the twist direction (right-handed twist / left-handed twist) of the liquid crystal compound in the thickness direction can be selected by selecting the type of the chiral agent added to the liquid crystal composition.

[0115] Further, as shown in FIG. 1, an example of the optically anisotropic layer of the present invention is shown in which the optical axis derived from the liquid crystal compound is not inclined with respect to the interface of the optically anisotropic layer at the interface of the optically anisotropic layer. However, in the optically anisotropic layer of the present invention, the optical axis derived from the liquid crystal compound may be inclined. For example, as described in WO2019 / 189586 A1, the optical axis derived from the liquid crystal compound may have a pretilt angle with respect to the interface of the optically anisotropic layer. Further, as described in WO2020 / 122127 A1, the optical axis derived from the liquid crystal compound may change in the thickness direction with an inclination angle from one interface of the optically anisotropic layer toward the other interface. By inclining the optical axis derived from the liquid crystal compound with respect to the interface of the optically anisotropic layer, the retardation of the optically anisotropic layer can be adjusted, and it can be adjusted as appropriate so as to obtain a high diffraction efficiency.

[0116] Further, in the optically anisotropic layer of the present invention, the film thickness of the optically anisotropic layer may change in the plane. In particular, in a liquid crystal diffraction element in which the length of one cycle in the liquid crystal alignment pattern changes in the plane, by changing the film thickness of the optically anisotropic layer in the plane, it is possible to appropriately adjust to obtain a high diffraction efficiency for light with different incident positions.

[0117] Further, in a liquid crystal diffraction element in which the length of one cycle in the liquid crystal alignment pattern changes in the plane, in the example of FIG. 1, the regions 37a, 37b, and 37c of the optically anisotropic layer may have the same thickness or different thicknesses at the central portion and the outer portion. Not limited to the above example, in the liquid crystal diffraction element of the present invention, the thicknesses of the respective regions of the optically anisotropic layer may be the same or changed in the plane. The thickness of each region of the optically anisotropic layer can be appropriately set according to the desired performance.

[0118] Note that although the optically anisotropic layer functions as a so-called λ / 2 plate, the present invention includes an aspect in which a laminate integrally including a support and an alignment film functions as a λ / 2 plate. In addition, the liquid crystal composition for forming the optically anisotropic layer contains a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and may further contain other components such as a leveling agent, an alignment control agent, a polymerization initiator, and an alignment aid.

[0119] In the present invention, there is no limitation on the thickness of the optically anisotropic layer, and the thickness that can obtain the desired optical characteristics may be appropriately set according to one period Λ of the liquid crystal alignment pattern, the required diffraction angle, diffraction efficiency, and the like. Also, the change point of the angle thickness of each region corresponding to the dark part 44 may be uniform or non-uniform, and may be appropriately set according to the required diffraction angle and the like.

[0120] - Rod-shaped liquid crystal compound - As the rod-shaped liquid crystal compound, azomethines, azoxyes, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, phenyl esters of cyclohexanecarboxylic acid, cyanophenylcyclohexanes, cyanophenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, transes, and alkenylcyclohexylbenzonitriles are preferably used. Not only low-molecular liquid crystalline molecules as described above, but also high-molecular liquid crystalline molecules can be used.

[0121] It is more preferable to fix the orientation of the rod-like liquid crystal compound by polymerization. As the polymerizable rod-like liquid crystal compound, the compounds described in Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials 5, p. 107 (1993), U.S. Patent No. 4,683,327, No. 5,622,648, No. 5,770,107, International Publication No. WO 95 / 22586, No. 95 / 24455, No. 97 / 00600, No. 98 / 23580, No. 98 / 52905, JP-A-1-272551, No. 6-16616, No. 7-110469, No. 11-80081, and Japanese Patent Application No. 2001-64627 can be used. Further, as the rod-like liquid crystal compound, for example, those described in JP-T-11-513019 and JP-A-2007-279688 can also be preferably used.

[0122] —Discotic liquid crystal compound— As the discotic liquid crystal compound, for example, those described in JP-A-2007-108732 and JP-A-2010-244038 can be preferably used. When a discotic liquid crystal compound is used in the optically anisotropic layer, in the optically anisotropic layer, the liquid crystal compound 40 stands up in the thickness direction, and the optical axis 40A derived from the liquid crystal compound is defined as an axis perpendicular to the disc plane, so-called the advancing axis.

[0123] As the liquid crystal compound, in order to obtain a high diffraction efficiency, a liquid crystal compound having a high refractive index anisotropy Δn can be preferably used. By increasing the refractive index anisotropy, the diffraction efficiency when the incident angle changes can be maintained high. The liquid crystal compound having a high refractive index anisotropy Δn is not particularly limited, but the compounds exemplified in WO2019 / 182129 A1 and the compounds represented by the following general formula (I) can be preferably used.

[0124] [Chemical formula]

[0125] In the general formula (I), P 1 and P 2 each independently represents a hydrogen atom, -CN, -NCS, or a polymerizable group. Sp 1 and Sp 2 each independently represents a single bond or a divalent linking group. However, Sp 1 and Sp 2 do 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. Z 1 , Z 2 and Z 3 each independently represents a single bond, -O-, -S-, -CHR-, -CHRCHR-, -OCHR-, -CHRO-, -SO-, -SO2-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NR-, -NR-CO-, -SCHR-, -CHRS-, -SO-CHR-, -CHR-SO-, -SO2-CHR-, -CHR-SO2-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -OCHRCHRO-, -SCHRCHRS-, -SO-CHRCHR-SO-, -SO2-CHRCHR-SO2-, -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 a plurality of R's are present, they may be the same or different. Z 1 and Z 2 when a plurality of each are present, they may be the same or different. When a plurality of Z's 3 are present, they may be the same or different. However, the Z 2 linked to Sp 3 represents a single bond. X 1 and X2 Each independently represents a single bond or -S-. When there are a plurality of X 1 and X 2 may be the same or different from each other. However, among the plurality of X 1 and the plurality of X 2 at least one of them represents -S-. k represents an integer from 2 to 4. m and n each independently represent an integer from 0 to 3. When there are a plurality of m, they may be the same or different from each other. A 1 , A 2 , A 3 and A 4 each independently represent a group represented by any one of the following general formulas (B-1) to (B-7), or a group formed by connecting two or more and three or less groups represented by any one of the following general formulas (B-1) to (B-7). When there are a plurality of A 2 and A 3 may be the same or different from each other. A 1 and A 4 when there are a plurality of them respectively, they may be the same or different from each other.

[0126]

Chemical formula

[0127] In order to maintain a high diffraction efficiency when the incident angle changes, the refractive index anisotropy Δn of the liquid crystal compound 550 is preferably 0.15 or more, more preferably 0.2 or more, still more preferably 0.25 or more, and most preferably 0.3 or more.

[0128] Also, in the liquid crystal diffraction element of the present invention, the refractive index anisotropy Δn and the average refractive index of the optically anisotropic layer may be changed in-plane. By changing the refractive index anisotropy Δn and the average refractive index of the optically anisotropic layer in-plane, the diffraction efficiency can be appropriately adjusted for light having different incident positions.

[0129] - Chiral agent - A chiral agent has a function of inducing a helical structure that twists and orients a liquid crystal compound in the thickness direction. Since the twisting direction of the induced helix and / or the degree of twist (helical pitch) vary depending on the compound, it can be selected according to the purpose. There are no particular restrictions on the chiral agent, and known compounds (for example, described in Liquid Crystal Device Handbook, Chapter 3, Section 4-3, chiral agents for TN (Twisted Nematic) and STN (Super Twisted Nematic), page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide (a chiral agent having an isosorbide structure), and isomannide derivatives, etc. can be used. In addition, chiral agents that can be suitably used also include those that cause back isomerization, dimerization, and isomerization and dimerization, etc. upon irradiation with light, resulting in a decrease in the helical induction force (HTP: Helical Twisting Power).

[0130] Chiral agents generally contain asymmetric carbon atoms, but axial asymmetric compounds or planar asymmetric compounds that do not contain asymmetric carbon atoms can also be used as chiral agents. Examples of axial asymmetric compounds or planar asymmetric compounds include binaphthyl, helicene, paracyclophane, and their derivatives. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have polymerizable groups, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent can be formed by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. In this embodiment, the polymerizable group of the polymerizable chiral agent is preferably the same type of group as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group, or an aziridinyl group, more preferably an unsaturated polymerizable group, and even more preferably an ethylenically unsaturated polymerizable group. Also, the chiral agent may be a liquid crystal compound.

[0131] When the chiral agent has a photo-isomerizable group, it is preferable because a pattern of a desired reflection wavelength corresponding to the emission wavelength can be formed by irradiating a photomask such as actinic rays after coating and alignment. As the photo-isomerizable group, an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group is preferable. As specific compounds, those described in JP-A-2002-080478, JP-A-2002-080851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, JP-A-2002-179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, and JP-A-2003-313292 can be used.

[0132] In the liquid crystal composition, the content of the chiral agent may be appropriately set according to the target amount of helical twist in the thickness direction and the type of the chiral agent.

[0133] <Function of Liquid Crystal Diffraction Element> As described above, the optically anisotropic layer having a liquid crystal alignment pattern in which the direction of the optical axis 40A rotates along the alignment axis D direction, formed using a composition containing a liquid crystal compound, refracts circularly polarized light. Here, in the liquid crystal diffraction element of the present invention, the dark portions 44 observed in the cross-sectional SEM image have two or more change point of the angle and have regions with different inclination directions in the thickness direction. Therefore, the liquid crystal diffraction element of the present invention has a small wavelength dependence of the diffraction efficiency and can diffract light with a similar diffraction efficiency regardless of the wavelength. That is, for example, light can be diffracted with a similar diffraction efficiency for red light, green light, and blue light. Moreover, light can be diffracted with a high diffraction efficiency regardless of the wavelength, and the higher the diffraction efficiency, the lower the wavelength dependence of the diffraction efficiency can be made. In addition, in the liquid crystal diffraction element of the present invention, in the liquid crystal alignment pattern, one period Λ in which the optical axis derived from the liquid crystal compound rotates by 180° is constant. Therefore, regardless of the incident position of light in the plane, if the wavelengths are the same, light is diffracted (refracted) at the same angle. That is, for example, for red light, light can be diffracted at the same angle regardless of the incident position on the liquid crystal diffraction element.

[0134] Also, in the example shown in FIG. 13 and the like, the optically anisotropic layer has a concentric liquid crystal alignment pattern having a direction in which the direction of the optical axis derived from the liquid crystal compound continuously rotates and changes in a concentric shape from the inside to the outside, but the present invention is not limited to this configuration. For example, the liquid crystal alignment pattern of the optically anisotropic layer may have an array axis D in one direction, and one period Λ may gradually change along this one direction. Further, the liquid crystal alignment pattern may be an asymmetric liquid crystal alignment pattern instead of a symmetric concentric shape from the inside to the outside. At that time, the center of the liquid crystal alignment pattern may be different from the center of the liquid crystal diffraction element. The liquid crystal alignment pattern is not limited to the above-described configuration, and may be appropriately set according to the function required for the liquid crystal diffraction element.

[0135] Such a liquid crystal diffraction element of the present invention can also be preferably used in a form combined with a circular polarizing plate. A part of the circularly polarized light incident on the liquid crystal diffraction element of the present invention may pass through the liquid crystal diffraction element without being diffracted (0th-order light). The circularly polarized light that is not diffracted by the liquid crystal diffraction element may deteriorate the performance depending on the application. On the other hand, by combining the liquid crystal diffraction element and the circular polarizing plate, it is possible to reduce the light (0th-order light) that passes through the liquid crystal diffraction element without being diffracted.

[0136] Hereinafter, the optical element of the present invention having the liquid crystal diffraction element and the circular polarizing plate of the present invention will be described. The circular polarizing plate has, as an example, a retardation plate and a linear polarizing plate, and the optical element of the present invention is obtained by arranging a liquid crystal diffraction element, a retardation plate, and a linear polarizing plate in this order. When right-circularly polarized light is incident on the liquid crystal diffraction element of the present invention, the incident right-circularly polarized light is diffracted and emitted from the liquid crystal diffraction element. Also, when being diffracted, the right-circularly polarized light is converted into left-circularly polarized light. The left-circularly polarized light (i.e., the first-order light) diffracted by the liquid crystal diffraction element is converted into linearly polarized light by the retardation plate (quarter-wave plate) of the circular polarizing plate. The linearly polarized light converted by the retardation plate passes through the linear polarizing plate and is emitted.

[0137] Here, when some light is not diffracted by the liquid crystal diffraction element, a part of the right-circularly polarized light incident on the liquid crystal diffraction element is not diffracted and passes through the liquid crystal diffraction element. In the case where there is no circular polarizing plate, the right-circularly polarized light that is not diffracted by the liquid crystal diffraction element travels straight as it is. This straight-traveling right-circularly polarized light becomes unnecessary light depending on the application and degrades the performance.

[0138] On the other hand, in the optical element of the present invention having the liquid crystal diffraction element and the circular polarizing plate of the present invention, the right-circularly polarized light (i.e., the zero-order light) that is not diffracted by the liquid crystal diffraction element is incident on the retardation plate of the circular polarizing plate and is converted into linearly polarized light in a direction orthogonal to the left-circularly polarized light (first-order light) that has been diffracted, and is incident on the linear polarizing plate and absorbed. That is, the right-circularly polarized light that is not diffracted by the liquid crystal diffraction element is absorbed by the circular polarizing plate. Therefore, the desired first-order light by the left-circularly polarized light can be transmitted, and the right-circularly polarized light that is not diffracted can be reduced. Thus, it is possible to suppress the degradation of performance due to unnecessary light (zero-order light).

[0139] In the optical element of the present invention, which is a combination of the liquid crystal diffraction element and the circular polarizing plate of the present invention, other optical elements may be combined and used downstream of the circular polarizing plate. As an example, a retardation plate may be arranged downstream of the circular polarizing plate. As described above, the circular polarizing plate is one in which a retardation plate and a linear polarizing plate are arranged in this order. Specifically, a configuration in which the linearly polarized light transmitted through the circular polarizing plate is converted into circularly polarized light, elliptically polarized light, linearly polarized light with a different polarization direction, etc. by the retardation plate arranged downstream of the circular polarizing plate can also be preferably used. Alternatively, instead of the retardation plate, a depolarizing layer that depolarizes the polarization state of light in at least a part of the wavelength range may be used. Examples of the depolarizing layer include a high retardation film and a light scattering layer. By controlling the polarization state of the light emitted from the circular polarizing plate in this way, the polarization state can be adjusted according to the application. Note that the high retardation film is, for example, a film having an in-plane retardation of 3000 nm or more. As another example, an optical element that deflects light may be disposed downstream of the circular polarizing plate. For example, by disposing an optical element that deflects light, such as a lens, downstream of the circular polarizing plate, the traveling direction of the light emitted from the circular polarizing plate can be changed. By controlling the deflection direction of the light emitted from the circular polarizing plate in this way, the emission direction of the light can be adjusted according to the application.

[0140] <Polarizing plate> The linear polarizing plate used in the present invention is not particularly limited as long as it has a function of transmitting linearly polarized light in one polarization direction and absorbing linearly polarized light in the other polarization direction, and a conventionally known linear polarizing plate can be used. The linear polarizing plate may be an absorption type linear polarizing plate or a reflection type linear polarizing plate.

[0141] As the absorption type linear polarizing plate, iodine-based polarizers that are absorption type polarizers, dye-based polarizers using dichroic dyes, polyene-based polarizers, and the like are used. The iodine-based polarizer and the dye-based polarizer include a coating type polarizer and a stretched type polarizer, and either can be applied. Among them, a polarizer produced by adsorbing iodine or a dichroic dye to polyvinyl alcohol and stretching it is preferable. In addition, as a method for obtaining a polarizer by performing stretching and dyeing in a state of a laminated film in which a polyvinyl alcohol layer is formed on a substrate, the methods described in Japanese Patent No. 5048120, Japanese Patent No. 5143918, Japanese Patent No. 4691205, Japanese Patent No. 4751481, and Japanese Patent No. 4751486 can be mentioned. Furthermore, known techniques related to these polarizers can also be preferably used. As the absorption type polarizer, a polarizer in which a dichroic dye is oriented using the orientation of liquid crystal without stretching is particularly preferable. This polarizer has many advantages, such as being able to be made into a very thin layer with a thickness of about 0.1 to 5 μm, being less likely to crack when bent as described in JP-A-2019-194685, having little thermal deformation, being excellent in durability even for a polarizing plate with a transmittance exceeding 50% as described in Japanese Patent No. 6483486, and being excellent in thermoformability. The polarizer in which the dichroic dye is oriented can utilize these advantages and is applicable to applications requiring high brightness, applications requiring small size and light weight, fine optical system applications, forming applications to curved parts, and applications to flexible parts. It is also possible to peel off the support and transfer the polarizer for use. In applications such as in-vehicle display optical systems such as head-up displays, optical systems such as AR glasses and VR glasses, LiDAR, face recognition systems, and optical sensors such as polarization imaging, it is also preferable to incorporate an absorption type polarizer for the purpose of suppressing stray light.

[0142] As the reflective linear polarizing plate, for example, a film obtained by stretching a layer containing two kinds of polymers as described in JP-A-2011-053705, a wire grid polarizer, etc. can be used. From the viewpoint of brightness, a film obtained by stretching a layer containing a polymer is preferable. Commercially available products can also be used as the reflective linear polarizing plate. As commercially available products of the reflective linear polarizing plate, a reflective polarizer (trade name APF) manufactured by 3M, a wire grid polarizer (trade name WGF) manufactured by Asahi Kasei Corporation, etc. can be preferably used. Alternatively, a reflective linear polarizing plate combined with a cholesteric liquid crystal film and a λ / 4 plate may be used.

[0143] The polarizing plate used in the present invention preferably has a smooth surface. In particular, when the polarizing plate is applied to a lens or the like, since even slight surface irregularities may lead to image distortion due to the image magnification effect of the lens, it is desirable that the surface has no irregularities. Specifically, the polarizing plate preferably has an average arithmetic roughness Ra of the surface of 50 nm or less, more preferably 30 nm or less, still more preferably 10 nm or less, and particularly preferably 5 nm or less. Further, on the surface of the polarizing plate, the height difference of the surface unevenness within a range of 1 square millimeter is preferably 100 nm or less, more preferably 50 nm or less, and still more preferably 20 nm or less. The surface unevenness and the average arithmetic roughness can be measured using a roughness meter, an interferometer, or the like. For example, it can be measured using an interferometer "vertscan" manufactured by Ryoka Systems, Ltd.

[0144] <Retardation plate> The retardation plate used in the present invention is a retardation plate that converts the phase of the incident polarized light. The retardation plate is arranged by adjusting the direction of the slow axis according to whether it converts the incident polarized light to be closer to linearly polarized light or to be closer to circularly polarized light. Specifically, the retardation plate may be arranged such that the slow axis is +45° or -45° with respect to the absorption axis of the linearly polarized plate arranged adjacent thereto.

[0145] The retardation plate used in the present invention may be a single-layer type composed of one layer of an optically anisotropic layer, or may be a multi-layer type composed of a laminate of two or more optically anisotropic layers each having a plurality of different slow axes. Examples of the multi-layer type retardation plate include, but are not limited to, International Publication No. WO2013 / 137464, International Publication No. WO2016 / 158300, JP-A-2014-209219, JP-A-2014-209220, International Publication No. WO2014 / 157079, JP-A-2019-215416, and International Publication No. WO2019 / 160044.

[0146] From the viewpoint of converting linearly polarized light to circularly polarized light or converting circularly polarized light to linearly polarized light, the retardation plate is preferably a λ / 4 plate.

[0147] There is no limitation on the λ / 4 plate, and various plates having a known λ / 4 function are available. Specific examples of the λ / 4 plate include, for example, those described in U.S. Patent Application Publication No. 2015 / 0277006.

[0148] For example, as an aspect where the λ / 4 plate has a single-layer structure, specifically, a stretched polymer film, a retardation film provided with an optically anisotropic layer having a λ / 4 function on a support, etc. can be mentioned. Further, as an aspect where the λ / 4 plate has a multilayer structure, specifically, a broadband λ / 4 plate formed by laminating a λ / 4 plate and a λ / 2 wavelength plate can be mentioned.

[0149] The thickness of the λ / 4 plate is not particularly limited, but is preferably 1 to 500 μm, more preferably 1 to 50 μm, and still more preferably 1 to 5 μm.

[0150] The retardation plate used in the present invention preferably has inverse wavelength dispersion. By having inverse wavelength dispersion, the phase change in the retardation plate becomes ideal, and the conversion between linearly polarized light and circularly polarized light becomes ideal.

[0151] In a form in which the liquid crystal diffraction element of the present invention and a circularly polarizing plate are combined, other optical elements may be combined and used downstream of the circularly polarizing plate. As an example, a retardation plate may be arranged downstream of the circularly polarizing plate. A configuration in which linearly polarized light transmitted through a circularly polarizing plate (a retardation plate and a linearly polarizing plate arranged in this order) is converted into circularly polarized light, elliptically polarized light, and linearly polarized light with different polarization directions by a retardation plate arranged downstream of the circularly polarizing plate can also be preferably used. Further, instead of the retardation plate, a depolarizing layer that eliminates the polarization state of light in at least a part of the wavelength range may be used. As the depolarizing layer, a high retardation film (in-plane retardation of 3000 nm or more), a light scattering layer, etc. can be used. By controlling the polarization state of the light emitted from the circularly polarizing plate in this way, the polarization state can be adjusted according to the application. As another example, an optical element that deflects light may be disposed downstream of the circularly polarizing plate. For example, by disposing an optical element that deflects light, such as a lens, downstream of the circularly polarizing plate, the traveling direction of the light emitted from the circularly polarizing plate can be changed. By controlling the deflection direction of the light emitted from the circularly polarizing plate in this way, the emission direction of the light can be adjusted according to the application.

[0152] <Adhesive layer (adhesive layer), adhesive> The optical film may include an adhesive layer for bonding the respective layers. In this specification, "bonding" is used as a concept that also includes "adhesion". Examples include water-soluble adhesives, ultraviolet curable adhesives, emulsion adhesives, latex adhesives, mastic adhesives, multi-layer adhesives, paste adhesives, foaming adhesives, supported film adhesives, thermoplastic adhesives, hot melt adhesives, thermosetting adhesives, thermally active adhesives, heat seal adhesives, thermosetting adhesives, contact adhesives, pressure-sensitive adhesives (i.e., adhesives), polymerization adhesives, solvent-based adhesives, solvent-active adhesives, ceramic adhesives, and the like. Specifically, an aqueous solution of a boron compound, a curable adhesive of an epoxy compound containing no aromatic ring in the molecule as disclosed in JP-A-2004-245925, an active energy ray curable adhesive containing a photoinitiator having a molar extinction coefficient of 400 or more at a wavelength of 360 to 450 nm and an ultraviolet curable compound as essential components as described in JP-A-2008-174667, and an active energy ray curable adhesive containing (a) a (meth)acrylic compound having two or more (meth)acryloyl groups in the molecule, (b) a (meth)acrylic compound having a hydroxyl group in the molecule and only one polymerizable double bond, and (c) a phenol ethylene oxide modified acrylate or a nonylphenol ethylene oxide modified acrylate in a total amount of 100 parts by mass of the (meth)acrylic compounds as described in JP-A-2008-174667 are also included. If necessary, various adhesives can be used alone or in combination.

[0153] In a laminated optical film, from the viewpoint of reducing unnecessary reflection, it is preferable that the adhesive layer has a small refractive index difference from the adjacent layer. Specifically, the refractive index difference between adjacent layers is preferably 0.05 or less, more preferably 0.01 or less. There is no particular limitation on the method for adjusting the refractive index of the adhesive layer, but known methods such as adding fine particles of zirconia-based, silica-based, acrylic-based, acrylic-styrene-based, melamine-based, etc., adjusting the resin refractive index, and the method described in JP-A-11-223712 can be used. Also, when the adjacent layer has refractive index anisotropy in the plane, it is preferable that the refractive index difference from the adjacent layer is 0.05 or less in all directions in the plane. Therefore, the adhesive layer may have refractive index anisotropy in the plane. When the refractive index difference between the interfaces to be bonded is large, the interface reflectance can be reduced by imparting a distribution to the refractive index in the thickness direction of the adhesive layer. Examples of the method for imparting a distribution to the refractive index in the thickness direction include a method of providing a plurality of adhesive layers, a method of mixing the interfaces between the plurality of provided adhesive layers, and a method of controlling the uneven distribution state of the material in the adhesive layer to impart a refractive index distribution.

[0154] Also, the adhesive layer can be provided on one or both of the members to be bonded by any method such as coating, vapor deposition, transfer, etc. From the viewpoint of increasing the bonding strength, post-treatments such as heat treatment and ultraviolet irradiation can be performed according to the type of the adhesive. The thickness of the adhesive layer can be arbitrarily adjusted, but is preferably 20 μm or less, more preferably 0.1 μm or less. Examples of the method for forming an adhesive layer of 0.1 μm or less include a method of vapor-depositing a ceramic adhesive such as silicon oxide (SiOx layer) on the bonding surface. The bonding surface of the bonding member can be subjected to surface modification treatments such as plasma treatment, corona treatment, saponification treatment, etc. before bonding, and a primer layer can be provided. Also, when there are a plurality of bonding surfaces, the type and thickness of the adhesive layer can be adjusted for each bonding surface.

[0155] <Cutting of the laminate> The fabricated laminate can be cut into a predetermined size. There is no limitation on the cutting method of the laminate, and various known methods such as physically cutting using a blade such as a Thomson blade and cutting by irradiating a laser can be used. When using a laser, it is preferable to select the pulse width (nanosecond, picosecond, femtosecond) and wavelength in consideration of the cuttability and damage to the material. Further, after processing the laminate into a predetermined shape, for example, polishing of the end face may be performed. From the viewpoints of improving processability during cutting and suppressing dust generation, etc., it is also possible to cut in a state with a peelable protective film attached. Also, for example, by the method shown in JP-A-2004-141889, it is possible to arbitrarily determine the cutting position by cutting while observing the liquid crystal alignment pattern. At this time, in order to make the liquid crystal alignment pattern more visible, it is also possible to observe through a polarizing plate, a retardation film, etc. Further, when a plurality of optical elements are provided on one substrate, it is preferable to cut the plurality of optical elements simultaneously.

[0156] <Other processes> For the purpose of accurately installing the laminate on the device, improving the accuracy of the axis and cutting position during cutting, etc., arbitrary-shaped marks can be provided as necessary. The type of mark can be arbitrarily selected, and methods such as physically providing by laser, inkjet method, etc., a method of partially changing the alignment state of the liquid crystal, a method of providing a partially decolorized or dyed region, etc. can be selected. Also, for the purpose of protecting the liquid crystal layer, a protective layer (such as a gas barrier layer, a barrier layer against moisture, etc., an ultraviolet absorption layer, a scratch-resistant layer, etc.) can be provided as necessary. The protective layer can be formed directly on the liquid crystal layer, or can be provided via an adhesive layer or another optical film. An antireflection layer (such as an LR layer, an AR layer, a moth-eye layer, etc.) may be provided for the purpose of reducing the reflectance of the surface. Various protective layers can be appropriately selected from known ones. When providing a gas barrier layer, polyvinyl alcohol is preferred. Polyvinyl alcohol can also serve as a polarizer. Further, the ultraviolet absorption layer is a layer containing an ultraviolet absorber, and as the ultraviolet absorber, those having excellent absorption ability for ultraviolet rays with a wavelength of 370 nm or less and little absorption of visible light with a wavelength of 400 nm or more from the viewpoint of good display properties are preferably used. Only one type of ultraviolet absorber may be used, or two or more types may be used in combination. For example, the ultraviolet absorbers described in JP-A-2001-72782 and JP-T-2002-543265 can be mentioned. Specific examples of the ultraviolet absorber include, for example, oxybenzone-based compounds, benzotriazole-based compounds, salicylic acid ester-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and the like.

[0157] <Combination of multiple liquid crystal diffraction elements> The liquid crystal diffraction element of the present invention can be used by combining a plurality of liquid crystal diffraction elements. For example, as disclosed in Optics Express, Vol.28, No16 / 3 August 2020, by combining a plurality of liquid crystal diffraction elements and changing the polarization state of light incident on the liquid crystal diffraction element, the condensing property / diverging property of the emitted light can be switched in multiple ways. By combining such a plurality of liquid crystal diffraction elements, in an HMD such as AR glasses and VR glasses, a foveated display corresponding to the fovea can be performed.

[0158] <Combination with a phase modulation element> The liquid crystal diffraction element of the present invention can also preferably be used in a configuration combined with a phase modulation element. For example, by combining a switchable half-wave plate that can modulate the phase difference with a voltage as disclosed in US10,379,419B1 and the liquid crystal diffraction element of the present invention (used as a passive element), a variable-focus lens with high diffraction efficiency can be realized regardless of the incident position of light within the element plane. Further, by combining a plurality of sets of the combination of the phase modulation element and the liquid crystal diffraction element, the number of adjustable focal lengths can be increased. By using such a variable-focus lens in AR glasses and VR glasses, the focal position of the display image of the HMD can be arbitrarily changed.

[0159] <Combination with a lens> The liquid crystal diffraction element of the present invention can also preferably be used in a configuration combined with other lens elements. For example, by using the liquid crystal diffraction element of the present invention in the combination of a Fresnel lens and a liquid crystal diffraction element as disclosed in SID 2020 DIGEST, 40-4, pp579-582., the chromatic aberration of the lens can be improved with high diffraction efficiency regardless of the incident position of light within the element plane. There is no limitation on the lens to be combined, and combinations with refractive index lenses, pancake lenses as disclosed in US3,443,858, and Optics Express, Vol.29, No4 / 15 February 2021, etc. can also be preferably used. By using an optical system combining such a lens and a liquid crystal diffraction element in AR glasses, VR glasses, etc., the color shift (chromatic aberration of the lens) of the display image of the HMD can be improved.

[0160] <Combination with a light guide plate> The liquid crystal diffraction element of the present invention can also preferably be used in a configuration combined with a light guide plate. For example, in a combination of a light guide plate and a lens as disclosed in Proc. of SPIE Vol.11062, Digital Optical Technologies 2019, 110620J (16 July 2019), by using the liquid crystal diffraction element of the present invention as the lens, the focal position of the display image emitted from the light guide plate can be changed. By combining with the light guide plate in this way, the focal position of the display image of HMDs such as AR glasses and VR glasses can be adjusted. When used in AR glasses, as disclosed in Proc. of SPIE Vol.11062, Digital Optical Technologies 2019, 110620J (16 July 2019), by sandwiching the light guide plate and using the liquid crystal diffraction element of the present invention as lenses with different positive / negative polarities, both the actual scene and the display image output from the light guide plate can be observed without distortion.

[0161] <Combination with an image display device> The liquid crystal diffraction element of the present invention can also be preferably used in combination with an image display device. For example, by combining an image display device and a liquid crystal diffraction element (used as a Diffractive Deflection Film) as disclosed in Crystals 2021, 11, 107, the luminance distribution of the light emitted from the image display device can be adjusted. By making an image display unit combined with the image display device in this way, the luminance distribution of HMDs such as AR glasses and VR glasses can be preferably adjusted.

[0162] <Combination with beam steering> The liquid crystal diffraction element of the present invention can also be preferably used in combination with an optical deflection element (beam steering). For example, by using the liquid crystal diffraction element of the present invention as the diffraction element of an optical deflection element as disclosed in WO2019 / 189675, high diffraction efficiency and high angular deflection of the emitted light are possible. By combining with an optical deflection element (beam steering) in this way, the irradiation angle of light of a ranging sensor such as LiDAR (Light Detection and Ranging) can be suitably widened.

[0163] As described above, the liquid crystal diffraction element, optical element, image display unit, head-mounted display, beam steering, and sensor of the present invention have been described in detail. However, 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, which goes without saying.

Example

[0164] The features of the present invention will be further specifically described with reference to the following examples. The materials, reagents, usage amounts, amounts of substances, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0165] [Comparative Example 1] [Fabrication of Liquid Crystal Diffraction Element] (Support) A glass substrate was prepared as the support.

[0166] (Formation of Alignment Film) The following coating solution for forming an alignment film was spin-coated on the support. The support on which the coating film of this coating solution for forming an alignment film was formed was dried on a hot plate at 60°C for 60 seconds to form an alignment film.

[0167] Coating Solution for Forming Alignment Film ―――――――――――――――――――――――――――――――― Photoalignment Material A 1.00 part by mass Water 16.00 parts by mass Butoxyethanol 42.00 parts by mass Propylene Glycol Monomethyl Ether 42.00 parts by mass ――――――――――――――――――――――――――――――――

[0168] -Material A for Photoalignment

Chem.

[0169] (Exposure of the Alignment Film) The alignment film was exposed using the exposure apparatus shown in Fig. 10 to form an alignment film P-1 having an alignment pattern. In the exposure apparatus, one that emits laser light with a wavelength of 325 nm was used as the laser. The exposure amount by interference light was set to 1000 mJ / cm 2 as such.

[0170] (Formation of the Optically Anisotropic Layer) As the liquid crystal composition for forming the first optically anisotropic layer, the following Composition A-1 was prepared. Composition A-1 ―――――――――――――――――――――――――――――――― 100.00 parts by mass of liquid crystal compound L-1 0.18 parts by mass of chiral agent M-1 Photoinitiator (manufactured by BASF, Irgacure OXE01) 1.00 parts by mass 0.08 parts by mass of leveling agent T-1 1050.00 parts by mass of methyl ethyl ketone ――――――――――――――――――――――――――――――――

[0171] Liquid crystal compound L-1

[0172]

Chem.

[0173] Chiral agent M-1

Chem.

[0174] Leveling Agent T-1 [Chemical formula]

[0175] The optically anisotropic layer was formed by applying the composition A-1 onto the alignment film P-1 in multiple layers. Multiple-layer coating means first applying the first layer of the composition A-1 onto the alignment film, heating it, and then performing ultraviolet curing to produce a liquid crystal immobilization layer. After that, for the second layer and subsequent layers, they are applied by overcoating on the liquid crystal immobilization layer, and the same process of heating and then ultraviolet curing is repeated. By forming it through multiple-layer coating, even when the total thickness of the optically anisotropic layer becomes thick, the alignment direction of the alignment film is reflected from the lower surface to the upper surface of the optically anisotropic layer.

[0176] First, for the first layer, the following composition A-1 was applied onto the alignment film P-1, the coating film was heated to 80 °C on a hot plate, and then under a nitrogen atmosphere, ultraviolet light with a wavelength of 365 nm from a high-pressure mercury lamp was irradiated onto the coating film at an irradiation dose of 300 mJ / cm 2 to fix the alignment of the liquid crystal compound.

[0177] For the second layer and subsequent layers, they were overcoated on this liquid crystal immobilization layer, heated under the same conditions as above, and then ultraviolet curing was performed to produce a liquid crystal immobilization layer. In this way, overcoating was repeated until the total thickness reached the desired film thickness to form an optically anisotropic layer and fabricate a liquid crystal diffraction element.

[0178] Note that the birefringence Δn of the cured layer of the liquid crystal composition A-1 was obtained by applying the liquid crystal composition A-1 onto a support with an alignment film for retardation measurement prepared separately, aligning the director of the liquid crystal compound to be horizontal with respect to the substrate, and then irradiating with ultraviolet light for fixation. The retardation value and film thickness of the obtained liquid crystal immobilization layer (cured layer) were measured. Δn can be calculated by dividing the retardation value by the film thickness. The retardation value was measured at the target wavelength using Axoscan manufactured by Axometrix, and the film thickness was measured using SEM.

[0179] The optically anisotropic layer finally has a Δn of the liquid crystal 550The thickness (Re(550)) was 275 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 70°. Hereinafter, unless otherwise specified, measurements such as 'Δn 550 ××d' were performed in the same manner.

[0180] As the liquid crystal composition for forming the second optically anisotropic layer, the following Composition A-2 was prepared. Composition A-2 ―――――――――――――――――――――――――――――――― Liquid crystal compound L-1 100.00 parts by mass Chiral agent H-1 0.32 parts by mass Photoinitiator (manufactured by BASF, Irgacure OXE01) 1.00 parts by mass Leveling agent T-1 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass ――――――――――――――――――――――――――――――――

[0181] Chiral agent H-1

Chemical formula

[0182] Using Composition A-2, the second optically anisotropic layer was formed in the same manner as the first optically anisotropic layer, except that the film thickness of the optically anisotropic layer was adjusted.

[0183] The optically anisotropic layer finally had a Δn of liquid crystal 550 × thickness (Re(550)) of 275 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -70°.

[0184] [Example 1] [Fabrication of Liquid Crystal Diffraction Element] (Formation of Alignment Film) In the same manner as in Comparative Example 1, an alignment film was formed on a glass substrate, and the alignment film was exposed to form an alignment film P-1 having an alignment pattern.

[0185] (Formation of Optically Anisotropic Layer) As a liquid crystal composition for forming the first optically anisotropic layer, the following Composition B-1 was prepared. Composition B-1 ―――――――――――――――――――――――――――――――― 100.00 parts by mass of liquid crystal compound L-1 0.36 part by mass of chiral agent M-1 Photoinitiator (manufactured by BASF, Irgacure OXE01) 1.00 part by mass 0.08 part by mass of leveling agent T-1 1050.00 parts by mass of methyl ethyl ketone ――――――――――――――――――――――――――――――――

[0186] The first optically anisotropic layer was formed in the same manner as in Comparative Example 1, except that the film thickness of the optically anisotropic layer was adjusted using Composition B-1.

[0187] The optically anisotropic layer finally had a Δn of liquid crystal 550 × thickness (Re(550)) of 160 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 80°.

[0188] As a liquid crystal composition for forming the second optically anisotropic layer, the following Composition B-2 was prepared. Composition B-2 ──────────────────────────────── 100.00 parts by mass of liquid crystal compound L-1 Polymerization initiator (manufactured by BASF, Irgacure OXE01) 1.00 part by mass 0.08 part by mass of leveling agent T-1 1050.00 parts by mass of methyl ethyl ketone ────────────────────────────────

[0189] The second optically anisotropic layer was formed in the same manner as the first optically anisotropic layer, except that the film thickness of the optically anisotropic layer was adjusted using Composition B-2.

[0190] The optically anisotropic layer finally had a Δn of liquid crystal 550 × thickness (Re(550)) of 330 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 0°.

[0191] As a liquid crystal composition for forming the third optically anisotropic layer, the following Composition B-3 was prepared. Composition B-3 ──────────────────────────────── 100.00 parts by mass of liquid crystal compound L-1 0.63 part by mass of chiral agent H-1 Polymerization initiator (manufactured by BASF, Irgacure OXE01) 1.00 part by mass 0.08 part by mass of leveling agent T-1 1050.00 parts by mass of methyl ethyl ketone ────────────────────────────────

[0192] The third optically anisotropic layer was formed in the same manner as the first optically anisotropic layer, except that Composition B-3 was used and the film thickness of the optically anisotropic layer was adjusted.

[0193] The optically anisotropic layer finally had a Δn of liquid crystal 550 × thickness (Re(550)) of 160 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -80°.

[0194] [Example 2] [Fabrication of Liquid Crystal Diffraction Element] (Formation of Alignment Film) In the same manner as in Comparative Example 1, an alignment film was formed on a glass substrate, and the alignment film was exposed to form an alignment film P-1 having an alignment pattern.

[0195] (Formation of Optically Anisotropic Layer) As the liquid crystal composition for forming the first optically anisotropic layer, in Composition B-1 of Example 1, the chiral agent M-1 was changed to 0.34 parts by mass to prepare Composition C-1, and the first optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1, except that the film thickness of the optically anisotropic layer was adjusted.

[0196] The optically anisotropic layer finally had a Δn of liquid crystal 550 × thickness (Re(550)) of 190 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 87°.

[0197] As the liquid crystal composition for forming the second optically anisotropic layer, in the composition B-3 of Example 1, the chiral agent H-1 was changed to 0.12 parts by mass to prepare the composition C-2, and the second optically anisotropic layer was formed in the same manner as the third optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0198] The optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 150 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -14°.

[0199] As the liquid crystal composition for forming the third optically anisotropic layer, in the composition B-1 of Example 1, the chiral agent M-1 was changed to 0.07 parts by mass to prepare the composition C-3, and the third optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0200] The optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 150 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 14°.

[0201] As the liquid crystal composition for forming the fourth optically anisotropic layer, in the composition B-3 of Example 1, the chiral agent H-1 was changed to 0.58 parts by mass to prepare the composition C-4, and the fourth optically anisotropic layer was formed in the same manner as the third optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0202] The optically anisotropic layer finally had a Δn of the liquid crystal 550The thickness (Re(550)) was 190 nm, and it was confirmed by a polarizing microscope that the surface had a periodic orientation. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -87°.

[0203] [Example 3] [Fabrication of Liquid Crystal Diffraction Element] (Formation of Alignment Film) In the same manner as in Comparative Example 1, an alignment film was formed on a glass substrate, and the alignment film was exposed to form an alignment film P-1 having an alignment pattern.

[0204] (Formation of Optically Anisotropic Layer) As the liquid crystal composition for forming the first optically anisotropic layer, in the composition B-1 of Example 1, the chiral agent M-1 was changed to 0.40 parts by mass to prepare a composition D-1, and the first optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0205] The optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) was 150 nm, and it was confirmed by a polarizing microscope that the surface had a periodic orientation. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 83°.

[0206] As the liquid crystal composition for forming the second optically anisotropic layer, in the composition B-1 of Example 1, the chiral agent M-1 was changed to 0.02 parts by mass to prepare a composition D-2, and the second optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0207] The optically anisotropic layer finally had a Δn of the liquid crystal 550The thickness (Re(550)) was 335 nm, and it was confirmed by a polarization microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound was 8°.

[0208] As the liquid crystal composition for forming the third optically anisotropic layer, in Composition B-3 of Example 1, the chiral agent H-1 was changed to 0.57 parts by mass to prepare Composition D-3, and the third optically anisotropic layer was formed in the same manner as the third optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0209] The optically anisotropic layer finally had a Δn of the liquid crystal 550 The thickness (Re(550)) was 170 nm, and it was confirmed by a polarization microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound was -78°.

[0210] [Comparative Example 2] <Fabrication of Liquid Crystal Diffraction Element> The first optically anisotropic layer was formed in the same manner as in Comparative Example 1.

[0211] The optically anisotropic layer finally had a Δn of the liquid crystal 550 The thickness (Re(550)) was 275 nm, and it was confirmed by a polarization microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound was 70°.

[0212] [Comparative Example 3] <Fabrication of Liquid Crystal Diffraction Element> In the alignment film exposure of Comparative Example 1, an alignment film P-2 was produced in the same manner except that the period of the alignment pattern was adjusted by changing the crossing angle α between two light beams MA and MB in the exposure apparatus shown in FIG. 10.

[0213] (Formation of the optically anisotropic layer) In the same manner as in Comparative Example 1, the first and second optically anisotropic layers were formed on the alignment film P-2.

[0214] The first and second optically anisotropic layers were finally confirmed by a polarizing microscope to have a Δn of the liquid crystal 550 × thickness (Re(550)) of 275 nm and a periodic alignment surface. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in the first optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 70° in the plane, and in the second optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -70°.

[0215] [Example 4] [Fabrication of liquid crystal diffraction element] An alignment film P-2 was produced in the same manner as in Comparative Example 3.

[0216] (Formation of the optically anisotropic layer) As the liquid crystal composition for forming the first optically anisotropic layer, in the composition B-1 of Example 1, the chiral agent M-1 was changed to 0.52 parts by mass to prepare a composition E-1, and the first optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0217] The optically anisotropic layer was finally confirmed by a polarizing microscope to have a Δn of the liquid crystal 550 × thickness (Re(550)) of 160 nm and a periodic alignment surface. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 115°.

[0218] As the liquid crystal composition for forming the second optically anisotropic layer, in the composition B-1 of Example 1, the chiral agent M-1 was changed to 0.16 parts by mass to prepare the composition E-2, and the second optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0219] The optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 335 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 76°.

[0220] As the liquid crystal composition for forming the third optically anisotropic layer, in the composition B-3 of Example 1, the chiral agent H-1 was changed to 0.38 parts by mass to prepare the composition E-3, and the third optically anisotropic layer was formed in the same manner as the third optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0221] The optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 160 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -48°.

[0222] [Example 5] [Fabrication of Liquid Crystal Diffraction Element] The alignment film P-2 was fabricated in the same manner as in Comparative Example 3.

[0223] [Formation of Optically Anisotropic Layer] As the liquid crystal composition for forming the first optically anisotropic layer, in the composition C-1 of Example 2, the chiral agent M-1 was changed to 0.44 parts by mass to prepare the composition F-1, and the first optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 2 except that the film thickness of the optically anisotropic layer was adjusted.

[0224] The optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 190 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 115°.

[0225] As the liquid crystal composition for forming the second optically anisotropic layer, in the composition C-1 of Example 2, the chiral agent M-1 was changed to 0.09 parts by mass to prepare the composition F-2, and the second optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 2 except that the film thickness of the optically anisotropic layer was adjusted.

[0226] The optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 150 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 18°.

[0227] As the liquid crystal composition for forming the third optically anisotropic layer, in the composition C-3 of Example 2, the chiral agent M-1 was changed to 0.04 parts by mass to prepare the composition F-3, and the third optically anisotropic layer was formed in the same manner as the third optically anisotropic layer of Example 2 except that the film thickness of the optically anisotropic layer was adjusted.

[0228] The optically anisotropic layer finally had a Δn of the liquid crystal 550It was confirmed by a polarizing microscope that the thickness (Re(550)) was 150 nm and the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 8°.

[0229] As the liquid crystal composition for forming the fourth optically anisotropic layer, in the composition C-4 of Example 2, the chiral agent H-1 was changed to 1.99 parts by mass to prepare a composition F-4, and the fourth optically anisotropic layer was formed in the same manner as the fourth optically anisotropic layer of Example 2 except that the film thickness of the optically anisotropic layer was adjusted.

[0230] The optically anisotropic layer finally has a Δn of the liquid crystal 550 It was confirmed by a polarizing microscope that the thickness (Re(550)) was 190 nm and the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -237°.

[0231] [Example 6] [Fabrication of Liquid Crystal Diffraction Element] The alignment film P-2 was fabricated in the same manner as in Comparative Example 3.

[0232] (Formation of Optically Anisotropic Layer) As the liquid crystal composition for forming the first optically anisotropic layer, in the composition B-1 of Example 1, the chiral agent M-1 was changed to 0.55 parts by mass to prepare a composition F-1, and the first optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0233] The optically anisotropic layer finally has a Δn of the liquid crystal 550It was confirmed by a polarizing microscope that the × thickness (Re(550)) was 150 nm and that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 114°.

[0234] As the liquid crystal composition for forming the second optically anisotropic layer, in the composition B-1 of Example 1, the chiral agent M-1 was changed to 0.18 parts by mass to prepare a composition F-2, and the second optically anisotropic layer was formed in the same manner as the first optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0235] The optically anisotropic layer finally had a liquid crystal Δn 550 It was confirmed by a polarizing microscope that the × thickness (Re(550)) was 335 nm and that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 85°.

[0236] As the liquid crystal composition for forming the third optically anisotropic layer, in the composition B-3 of Example 1, the chiral agent H-1 was changed to 0.30 parts by mass to prepare a composition F-3, and the third optically anisotropic layer was formed in the same manner as the third optically anisotropic layer of Example 1 except that the film thickness of the optically anisotropic layer was adjusted.

[0237] The optically anisotropic layer finally had a liquid crystal Δn 550 It was confirmed by a polarizing microscope that the × thickness (Re(550)) was 170 nm and that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -41°.

[0238] [Evaluation] <In the thickness direction of the change point of the angle and the tilt direction arein the reverse direction Evaluation of the inflection point to be folded When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark portions were observed. In the cross-sectional image observed by SEM, the number of inflection points where the dark portion and the inclination direction of the dark portion are folded was evaluated. change point of the angle and the inclination direction of the dark part in the reverse direction were evaluated for the number of inflection points to be folded. The results are shown in Table 1.

[0239] <Evaluation of diffraction efficiency> When light was incident on the fabricated liquid crystal diffraction element from the front (direction of an angle of 0° with respect to the normal), the diffraction efficiency of the emitted light was evaluated. Specifically, laser light having output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm was irradiated from a light source and perpendicularly incident on the fabricated liquid crystal diffraction element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in the desired direction from the liquid crystal diffraction element, the zero-order light emitted in other directions, and the -first-order light was measured with a photodetector, and the diffraction efficiency at each wavelength was calculated by the following formula. Note that the zero-order light is the light emitted in the same direction as the incident light. Also, the -first-order light is the light diffracted in the -θ direction when the diffraction angle of the first-order light with respect to the zero-order light is θ. Diffraction efficiency = first-order light / (first-order light + zero-order light + (-first-order light)) The average value of the diffraction efficiency was obtained from the measured values at wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm, and the wavelength dependence of the diffraction efficiency was evaluated according to the following criteria. Note that the evaluation was performed by making the light perpendicularly incident on a circular polarizing plate corresponding to the wavelength of the laser light, converting it into circularly polarized light, and then making the light incident on the fabricated liquid crystal diffraction element. A: The average value of the diffraction efficiency is 95% or more B: The average value of the diffraction efficiency is 90% or more and less than 95% C: The average value of the diffraction efficiency is less than 90% The results are shown in Table 1.

[0240]

Table 1

[0241] [Example 7] <Fabrication of Liquid Crystal Diffraction Element> An alignment film P-2 was fabricated in the same manner as in Comparative Example 3.

[0242] (Formation of Optically Anisotropic Layer) In Example 6, except that the liquid crystal compound L-1 was changed to the following liquid crystal compound L-2, the addition amounts of the chiral agent M-1, the chiral agent H-1, and the leveling agent T-1 were appropriately changed, and the film thickness of the optically anisotropic layer was adjusted, the first to third optically anisotropic layers were formed in the same manner as in Example 6.

[0243] Liquid crystal compound L-2 [Chemical formula]

[0244] The first optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 150 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 114°.

[0245] The second optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 335 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 85°.

[0246] The third optically anisotropic layer finally had a Δn of the liquid crystal 550It was confirmed by a polarizing microscope that the thickness (Re(550)) was 170 nm and the surface had a periodic orientation. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound was -41°.

[0247] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark parts were observed. In the cross-sectional image observed by SEM, the number of change point of the angle dark parts was 2 and the number of inflection points where the inclination direction of the dark part was in the reverse direction folded back was 1.

[0248] [Example 8] [Fabrication of Liquid Crystal Diffraction Element] An alignment film P-2 was fabricated in the same manner as in Comparative Example 3.

[0249] (Formation of Optically Anisotropic Layer) In Example 6, the liquid crystal compound L-1 was changed to the following liquid crystal compound L-3, the addition amounts of the chiral agent M-1, chiral agent H-1, and leveling agent T-1 were appropriately changed, and the heating temperature of the coating film when forming the optically anisotropic layer was changed to 55°C. The first to third optically anisotropic layers were formed in the same manner as in Example 6, except that the film thickness of the optically anisotropic layer was adjusted.

[0250] Liquid crystal compound L-3 [Chemical formula]

[0251] The first optically anisotropic layer was finally confirmed by a polarizing microscope to have a Δn of the liquid crystal 550 × thickness (Re(550)) of 150 nm and a periodic alignment surface. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotated 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound was 114°.

[0252] The second optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 335 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was 85°.

[0253] The third optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 170 nm, and it was confirmed by a polarizing microscope that the surface had a periodic alignment. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 1 μm. Also, in this optically anisotropic layer, the twist angle of the liquid crystal compound in the thickness direction was -41°.

[0254] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark portions were observed. In the cross-sectional image observed by SEM, the number of change point of the angle dark portions was 2 and the number of inflection points where the inclination direction of the dark portion in the reverse direction was folded back was 1.

[0255] Note that the Δn 550 of the liquid crystal layer (liquid crystal compound) in Example 6 was 0.15, the Δn 550 of the liquid crystal layer in Example 7 was 0.25, and the Δn 550 of the liquid crystal layer in Example 8 was 0.32.

[0256] <Evaluation of diffraction efficiency> The diffraction efficiency of the emitted light was evaluated when light was incident on the fabricated liquid crystal diffraction element at incident angles changed by ±40° (in 10° increments) from the front (direction at an angle of 0° with respect to the normal). Specifically, laser light with output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm was irradiated from a light source and perpendicularly incident on the fabricated liquid crystal diffraction element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in a desired direction from the liquid crystal diffraction element, the zero-order light emitted in other directions, and the minus-first-order light was measured with a photodetector, and the diffraction efficiency at each wavelength was calculated using the following formula. Note that the zero-order light is the light emitted in the same direction as the incident light. Also, the minus-first-order light is the light diffracted in the -θ direction when the diffraction angle of the first-order light with respect to the zero-order light is θ. Diffraction efficiency = first-order light / (first-order light + zero-order light + (minus-first-order light)) The average value of the diffraction efficiency was obtained from the measured values at wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm measured at different incident angles, and the wavelength dependence of the diffraction efficiency was evaluated. Note that after making the light incident perpendicularly on a circular polarizing plate corresponding to the wavelength of the laser light to make it circularly polarized, the light was then incident on the fabricated liquid crystal diffraction element for evaluation.

[0257] As a result of the evaluation, the average value of the diffraction efficiency of Example 7 was improved compared to Example 6, and the average value of the diffraction efficiency of Example 8 was further improved.

[0258] From the above, it can be seen that the higher the refractive index difference Δn of the liquid crystal layer of the liquid crystal diffraction element 550 the better the utilization efficiency of light for different incident angles.

[0259] <Fabrication of circular polarizing plate> (Fabrication of retardation plate) A film having a cellulose acylate film, an alignment film, and an optically anisotropic layer C was obtained in the same manner as the positive A plate described in paragraphs 0102 to 0126 of Japanese Patent Application Laid-Open No. 2019-215416. The optically anisotropic layer C is a positive A plate (retardation plate), and the thickness of the positive A plate is controlled so that Re(550) becomes 138 nm.

[0260] A circular polarizing plate was fabricated by laminating a retardation plate fabricated via an adhesive on a linear polarizing plate (polyvinyl alcohol layer type). The relative angle between the slow axis of the retardation plate and the absorption axis of the linear polarizing plate was arranged to be 45°.

[0261] <Fabrication of Optical Element> An optical element was fabricated by laminating the circular polarizing plate fabricated above on the liquid crystal diffraction element fabricated in Examples 1 to 8. The optical element was fabricated by arranging the liquid crystal diffraction element, the retardation plate, and the linear polarizing plate in this order.

[0262] [Evaluation] The light intensity of the emitted light was evaluated when light was incident on the fabricated optical element from the front (direction at an angle of 0° with respect to the normal). Specifically, laser light having output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm was irradiated from a light source and perpendicularly incident on the fabricated optical element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in a desired direction from the liquid crystal diffraction element and the zero-order light emitted in other directions was measured with a photodetector. Note that the evaluation was performed by making the light incident from the liquid crystal diffraction element side of the fabricated optical element after converting it into circular polarization by perpendicularly incident on the circular polarizing plate corresponding to the wavelength of the laser light. In the optical elements obtained by laminating circular polarizing plates on the liquid crystal diffraction elements fabricated in Examples 1 to 6, it was confirmed that the light intensity of the zero-order light could be significantly reduced at any wavelength compared to before the lamination of the circular polarizing plate, and the contrast ratio (light intensity ratio of first-order light / zero-order light) was improved.

[0263] [Evaluation] <Evaluation of Diffraction Efficiency> The light intensity of the emitted light was evaluated when light was incident on the optical element using the liquid crystal diffraction element fabricated in Examples 6 to 8 from the front (direction at an angle of 0° with respect to the normal) at incident angles changed by ±40° (in 10° increments). Specifically, laser light with output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm respectively was irradiated from a light source and incident on the fabricated liquid crystal diffraction element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in a desired direction from the liquid crystal diffraction element and the zero-order light (emitted in the same direction as the incident light) emitted in other directions was measured with a photodetector.

[0264] The average value of the light intensity with respect to the incident angle was obtained from the measured values of wavelengths 405 nm, 450 nm, 532 nm, and 650 nm measured at different incident angles. Note that after making the laser light incident perpendicularly on a circular polarizer corresponding to the wavelength of the laser light to make it circularly polarized, light was incident from the liquid crystal diffraction element side of the fabricated optical element for evaluation.

[0265] In the optical element in which a circular polarizer was bonded to the liquid crystal diffraction element fabricated in Examples 6 to 8, it was confirmed that the light intensity of the zero-order light could be significantly reduced at any wavelength compared to before bonding the circular polarizer, and the contrast ratio (light intensity ratio of first-order light / zero-order light) was improved.

[0266] Also, as a result of the evaluation, for Example 6, the average value of the contrast ratio of the optical element of Example 7 with respect to the incident angle was improved, and the average value of the contrast ratio of the optical element of Example 8 with respect to the incident angle was further improved.

[0267] From the above, it can be seen that even in an optical element in which a circular polarizer is bonded to a liquid crystal diffraction element, a higher refractive index difference Δn of the liquid crystal layer 550 results in an improvement in the contrast ratio for different incident angles.

[0268] <Fabrication of circular polarizer> In the fabrication of the above-mentioned circular polarizer, a circular polarizer was fabricated in the same manner except that a linear polarizer (polyvinyl alcohol layer type) was changed to an absorption type polarizer fabricated as follows.

[0269] <Fabrication of optical element> Circular polarizing plates were fabricated by bonding absorption type polarizing plates fabricated as described below to the liquid crystal diffraction elements fabricated in Examples 1 to 6, and optical elements were fabricated. The optical elements were fabricated by arranging the liquid crystal diffraction element, the retardation plate, and the absorption type polarizing plate in this order.

[0270] [Fabrication of Absorption Type Polarizing Plate (Linear Polarizing Plate)]

[0271] [Fabrication of Transparent Support 1] The coating liquid PA1 for forming an alignment layer described later was continuously coated on a cellulose acylate film (TAC substrate with a thickness of 40 μm; TG40 manufactured by Fuji Film Co., Ltd.) using a wire bar. The support on which the coating film was formed was dried with warm air at 140 °C for 120 seconds, and then the coating film was irradiated with polarized ultraviolet light (10 mJ / cm 2 , using an ultra-high pressure mercury lamp) to form an optical alignment layer PA1, and a TAC film with an optical alignment layer was obtained. The film thickness of the optical alignment layer was 0.3 μm.

[0272] Coating Liquid PA1 for Forming Alignment Layer ―――――――――――――――――――――――――――――――― 100.00 parts by mass of the following polymer PA-1 5.00 parts by mass of the following acid generator PAG-1 0.005 parts by mass of the following acid generator CPI-110TF 1220.00 parts by mass of xylene 122.00 parts by mass of methyl isobutyl ketone ――――――――――――――――――――――――――――――――

[0273] Polymer PA-1 [Chemical Formula]

[0274] Acid Generator PAG-1 [Chemical Formula]

[0275] Acid generator CPI-110F

Chem.

[0276] <Formation of the light absorption anisotropic layer P1> On the obtained alignment layer PA1, the following composition P1 for forming a light absorption anisotropic layer was continuously coated with a wire bar to form a coating layer P1. Next, the coating layer P1 was heated at 140 °C for 30 seconds and cooled until it reached room temperature (23 °C). Next, it was heated at 90 °C for 60 seconds and cooled again until it reached room temperature. Thereafter, using an LED lamp (center wavelength 365 nm), ultraviolet rays were irradiated for 2 seconds under irradiation conditions of an illuminance of 200 mW / cm 2 to fabricate a light absorption anisotropic layer P1 on the alignment layer PA1. The film thickness of the light absorption anisotropic layer was 1.6 μm. This was designated as laminate 1B.

[0277] Composition P1 for forming a light absorption anisotropic layer ―――――――――――――――――――――――――――――――― The following dichroic substance D-1 0.25 parts by mass The following dichroic substance D-2 0.36 parts by mass The following dichroic substance D-3 0.59 parts by mass The following polymer liquid crystalline compound P-1 2.21 parts by mass The following low molecular liquid crystalline compound M-1 1.36 parts by mass Polymerization initiator IRGACURE OXE-02 (manufactured by BASF) 0.200 parts by mass The following surfactant F-1 0.026 parts by mass Cyclopentanone 46.00 parts by mass Tetrahydrofuran 46.00 parts by mass Benzyl alcohol 3.00 parts by mass ――――――――――――――――――――――――――――――――

[0278] D-1

Chem.

[0279] D-2

Chem.

[0280] D-3

Chem.

[0281] Polymeric liquid crystalline compound P-1

Chem.

[0282] Low molecular weight liquid crystalline compound M-1

Chem.

[0283] Surfactant F-1

Chem.

[0284] <Preparation of UV Adhesive> The following UV adhesive composition was prepared. UV Adhesive Composition ―――――――――――――――――――――――――――――――― CEL2021P (manufactured by Daicel Corporation) 70 parts by mass 1,4-Butanediol diglycidyl ether 20 parts by mass 2-Ethylhexyl glycidyl ether 10 parts by mass CPI-100P 2.25 parts by mass ────────────────────────────────

[0285] CPI-100P [Chemical formula]

[0286] [Fabrication of Absorptive Polarizer] On the surface of the light absorption anisotropic layer of the laminate 1B, using the prepared UV adhesive, Technolo S001G (methacrylic resin with a thickness of 50 μm, tanδ peak temperature of 128 °C, manufactured by Sumitomo Chemical Acryl Co., Ltd.) was bonded as the resin substrate S1. Thereafter, only the cellulose acetate film was peeled off to fabricate an absorptive polarizer in which the resin substrate / adhesive layer / light absorption anisotropic layer / alignment layer were arranged in this order. The thickness of the UV adhesive layer was 2 μm.

[0287] The average arithmetic roughness Ra of the obtained absorptive polarizer was 10 nm or less. On the other hand, the average arithmetic roughness Ra of the linear polarizer (polyvinyl alcohol layer type) was 20 nm or more. As a result, the fabricated absorptive polarizer can reduce the light deflection (refraction and scattering) due to the surface unevenness of the polarizing film. Further, when used in an image display device, it is possible to suppress the distortion of the displayed image. The average arithmetic roughness Ra was measured using an interferometer "vertscan" manufactured by Ryoka Systems Co., Ltd.

[0288] [Evaluation] The light intensity of the emitted light was evaluated when light was incident on the fabricated optical element from the front (the direction with an angle of 0° with respect to the normal). Specifically, laser light having output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm was irradiated from a light source and perpendicularly incident on the fabricated optical element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in the desired direction from the liquid crystal diffraction element and the zero-order light emitted in other directions was measured with a photodetector. Note that after being made circularly polarized by perpendicularly incident on a circular polarizing plate corresponding to the wavelength of the laser light, light was incident from the liquid crystal diffraction element side of the fabricated optical element for evaluation. In the optical elements obtained by attaching a circular polarizing plate to the liquid crystal diffraction elements fabricated in Examples 1 to 6, it was confirmed that the light intensity of the 0th-order light could be significantly reduced at any wavelength compared to before attaching the circular polarizing plate, and the contrast ratio (the ratio of the light intensity of the 1st-order light to the 0th-order light) was improved.

[0289] [Evaluation] [Evaluation of diffraction efficiency] For the optical elements using the liquid crystal diffraction elements fabricated in Examples 6 to 8, the light intensity of the emitted light was evaluated when light was incident at incident angles changed by ±40° (in 10° increments) from the front (the direction of an angle of 0° with respect to the normal). Specifically, laser light having output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm respectively was irradiated from a light source and made incident on the fabricated liquid crystal diffraction element. Among the emitted light, the light intensities of the diffracted light (1st-order light) diffracted in a desired direction from the liquid crystal diffraction element and the 0th-order light (emitted in the same direction as the incident light) emitted in other directions were measured with a photodetector.

[0290] The average value of the light intensity with respect to the incident angle was obtained from the measured values at wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm measured at different incident angles. Note that the evaluation was performed by making the light incident perpendicularly on a circular polarizing plate corresponding to the wavelength of the laser light, converting it into circularly polarized light, and then making the light incident from the liquid crystal diffraction element side of the fabricated optical element.

[0291] In the optical elements obtained by attaching a circular polarizing plate to the liquid crystal diffraction elements fabricated in Examples 6 to 8, it was confirmed that the light intensity of the 0th-order light could be significantly reduced at any wavelength compared to before attaching the circular polarizing plate, and the contrast ratio (the ratio of the light intensity of the 1st-order light to the 0th-order light) was improved.

[0292] Also, as a result of the evaluation, for Example 6, the average value of the contrast ratio of the optical element of Example 7 with respect to the incident angle was improved, and the average value of the contrast ratio of the optical element of Example 8 with respect to the incident angle was further improved.

[0293] From the above, even in the optical element in which a circular polarizing plate is bonded to the liquid crystal diffraction element, it can be seen that the higher the refractive index difference Δn of the liquid crystal layer, the better the contrast ratio for different incident angles. 550 It can be seen that the contrast ratio for different incident angles is improved when it is higher.

[0294] [Comparative Example 11] [Fabrication of Liquid Crystal Diffraction Element]

[0295] (Exposure of Alignment Film) Using the exposure apparatus shown in Fig. 14, the alignment film was exposed to form an alignment film PL-1 having a concentric alignment pattern. In the exposure apparatus, a laser that emits laser light with a wavelength (325 nm) was used. The exposure amount by the interference light was set to 1000 mJ / cm 2 Note that by using the exposure apparatus shown in Fig. 14, one period of the alignment pattern was gradually shortened from the center toward the outer direction.

[0296] (Formation of Optically Anisotropic Layer) In Comparative Example 1, an optically anisotropic layer was formed in the same manner except that the alignment film PL-1 fabricated above was used.

[0297] For the first optically anisotropic layer, it was confirmed by a polarizing microscope that finally the product of the Δn of the liquid crystal 550 × thickness (Re(550)) became 275 nm and the alignment surface was periodic in a concentric (radial) shape as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm at a distance of about 2 mm from the center, 1 μm at a distance of 25 mm from the center, and 0.6 μm at a distance of 30 mm from the center, and it was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 70°.

[0298] For the second optically anisotropic layer, finally the product of the Δn of the liquid crystal 550The thickness (Re(550)) was 275 nm, and it was confirmed by a polarizing microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates by 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was -70°.

[0299] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark parts were observed. In the cross-sectional image observed by SEM, the number of change point of the angle in the dark part was 1 and the number of inflection points where the inclination direction of the dark part was in the reverse direction folded back was 1.

[0300] [Example 11] <Fabrication of Liquid Crystal Diffraction Element>

[0301] (Exposure of Alignment Film) In the same manner as in Comparative Example 11, an alignment film PL-1 having a concentric alignment pattern was formed.

[0302] (Formation of Optically Anisotropic Layer) In Example 1, an optically anisotropic layer was formed in the same manner except that the alignment film PL-1 fabricated above was used.

[0303] The first optically anisotropic layer finally had a Δn of the liquid crystal 550The thickness (Re(550)) was 160 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 80°.

[0304] The second optically anisotropic layer finally has a Δn of the liquid crystal 550 The thickness (Re(550)) was 330 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 0°.

[0305] The third optically anisotropic layer finally has a Δn of the liquid crystal 550 The thickness (Re(550)) was 160 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was -80°.

[0306] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark parts were observed. In the cross-sectional image observed by SEM, the dark part change point of the angleThe number was 2 and the inclination direction of the dark part was in the reverse direction The number of inflection points where it folded back was 1.

[0307] [Example 12] [Fabrication of Liquid Crystal Diffraction Element]

[0308] (Formation of Optically Anisotropic Layer) In Example 11, except that the liquid crystal compound L-1 was changed to the liquid crystal compound L-2, the addition amounts of the chiral agent M-1, the chiral agent H-1, and the leveling agent T-1 were appropriately changed, and the film thickness of the optically anisotropic layer was adjusted, the first to third optically anisotropic layers were formed in the same manner as in Example 11.

[0309] The first optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 160 nm, and it was confirmed by a polarizing microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 80°.

[0310] The second optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 330 nm, and it was confirmed by a polarizing microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 0°.

[0311] The third optically anisotropic layer finally had a Δn of the liquid crystal550 It was confirmed by polarized microscopy that the thickness (Re(550)) was 160 nm and the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was -80°.

[0312] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark parts were observed. In the cross-sectional image observed by SEM, the number of change point of the angle of the dark part was 2 and the number of inflection points where the inclination direction of the dark part was in the reverse direction folded back was 1.

[0313] [Example 13] <Fabrication of Liquid Crystal Diffraction Element>

[0314] (Formation of Optically Anisotropic Layer) In Example 11, the liquid crystal compound L-1 was changed to the liquid crystal compound L-3, the addition amounts of the chiral agent M-1, the chiral agent H-1, and the leveling agent T-1 were appropriately changed, the heating temperature of the coating film when forming the optically anisotropic layer was changed to 55 °C, and the first to third optically anisotropic layers were formed in the same manner as in Example 11 except that the film thickness of the optically anisotropic layer was adjusted.

[0315] The first optically anisotropic layer finally had a Δn of the liquid crystal 550The thickness (Re(550)) was 160 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 80°.

[0316] The second optically anisotropic layer finally has a Δn of the liquid crystal 550 The thickness (Re(550)) was 330 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 0°.

[0317] The third optically anisotropic layer finally has a Δn of the liquid crystal 550 The thickness (Re(550)) was 160 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was -80°.

[0318] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark parts were observed. In the cross-sectional image observed by SEM, the dark part change point of the angleThe number was 2 and the inclination direction of the dark part was in the reverse direction The number of inflection points where it folded back was 1.

[0319] Incidentally, the Δn of the liquid crystal layer (liquid crystal compound) of Example 11 550 was 0.15, and the Δn of the liquid crystal layer of Example 12 550 was 0.25, and the Δn of the liquid crystal layer of Example 13 550 was 0.32.

[0320] [Example 14] [Fabrication of Liquid Crystal Diffraction Element]

[0321] (Exposure of Alignment Film) In the same manner as in Comparative Example 11, an alignment film PL-1 having a concentric alignment pattern was formed.

[0322] (Formation of Optically Anisotropic Layer) In Example 3, an optically anisotropic layer was formed in the same manner except that the alignment film PL-1 fabricated above was used.

[0323] The first optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 150 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in FIG. 13. Incidentally, in the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center, and it was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 83°.

[0324] The second optically anisotropic layer finally had a Δn of the liquid crystal 550The thickness (Re(550)) was 335 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm at a distance of about 2 mm from the center, 1 μm at a distance of 25 mm from the center, and 0.6 μm at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 8°.

[0325] The third optically anisotropic layer finally has a Δn of the liquid crystal 550 The thickness (Re(550)) was 170 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm at a distance of about 2 mm from the center, 1 μm at a distance of 25 mm from the center, and 0.6 μm at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was -78°.

[0326] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark parts were observed. In the cross-sectional image observed by SEM, the number of change point of the angle of the dark parts was 2 and the number of inflection points where the inclination direction of the dark part was in the reverse direction folded back was 1.

[0327] [Example 15] [Fabrication of Liquid Crystal Diffraction Element]

[0328] (Formation of Optically Anisotropic Layer) In Example 14, except that the liquid crystal compound L-1 was changed to the liquid crystal compound L-2, the addition amounts of the chiral agent M-1, chiral agent H-1, and leveling agent T-1 were appropriately changed, and the film thickness of the optically anisotropic layer was adjusted, the first to third optically anisotropic layers were formed in the same manner as in Example 14.

[0329] The first optically anisotropic layer finally has a Δn of liquid crystal 550 × thickness (Re(550)) of 150 nm, and it was confirmed by a polarization microscope that the surface has a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° is 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period becomes shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 83°.

[0330] The second optically anisotropic layer finally has a Δn of liquid crystal 550 × thickness (Re(550)) of 335 nm, and it was confirmed by a polarization microscope that the surface has a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° is 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period becomes shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 8°.

[0331] The third optically anisotropic layer finally has a Δn of liquid crystal 550 × thickness (Re(550)) of 170 nm, and it was confirmed by a polarization microscope that the surface has a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° is 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period becomes shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was -78°.

[0332] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark portions were observed. In the cross-sectional image observed by SEM, the number of change point of the angle in the dark portion was 2 and the number of inflection points where the inclination direction of the dark portion was in the reverse direction folded back was 1.

[0333] [Example 16] [Fabrication of Liquid Crystal Diffraction Element]

[0334] (Formation of Optically Anisotropic Layer) In Example 14, except that the liquid crystal compound L-1 was changed to the liquid crystal compound L-3, the addition amounts of the chiral agent M-1, the chiral agent H-1, and the leveling agent T-1 were appropriately changed, and the film thickness of the optically anisotropic layer was adjusted, the first to third optically anisotropic layers were formed in the same manner as in Example 14.

[0335] The first optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 150 nm, and it was confirmed by a polarizing microscope that the surface had a concentric (radial) periodic alignment as shown in FIG. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 2 mm from the center, 1 μm for one period at a distance of 25 mm from the center, and 0.6 μm for one period at a distance of 30 mm from the center, and it was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 83°.

[0336] The second optically anisotropic layer finally had a Δn of the liquid crystal 550The thickness (Re(550)) was 335 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm at a distance of about 2 mm from the center, 1 μm at a distance of 25 mm from the center, and 0.6 μm at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 8°.

[0337] The third optically anisotropic layer finally has a Δn of the liquid crystal 550 The thickness (Re(550)) was 170 nm, and it was confirmed by a polarization microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 13. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm at a distance of about 2 mm from the center, 1 μm at a distance of 25 mm from the center, and 0.6 μm at a distance of 30 mm from the center. It was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was -78°.

[0338] When the cross-section of the fabricated optically anisotropic layer was observed by SEM, patterns of bright and dark parts were observed. In the cross-sectional image observed by SEM, the number of dark parts change point of the angle was 2 and the number of inflection points where the inclination direction of the dark part in the reverse direction was folded back was 1.

[0339] Incidentally, the Δn of the liquid crystal layer (liquid crystal compound) in Example 14 550 was 0.15, the Δn of the liquid crystal layer in Example 15 550 was 0.25, and the Δn of the liquid crystal layer in Example 16 550 was 0.32.

[0340] [Evaluation] <Evaluation of diffraction efficiency> The diffraction efficiency of the emitted light was evaluated when light was incident on the fabricated liquid crystal diffraction elements of Comparative Example 11 and Examples 11 to 16 from the front (direction at an angle of 0° with respect to the normal). Specifically, laser light having output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm was irradiated from a light source and perpendicularly incident on the fabricated liquid crystal diffraction element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in a desired direction from the liquid crystal diffraction element, the zero-order light (emitted in the same direction as the incident light) emitted in other directions, and the minus-first-order light (light diffracted in the -θ direction when the diffraction angle of the first-order light with respect to the zero-order light is θ) was measured with a photodetector, and the diffraction efficiency at each wavelength was calculated by the following formula. Diffraction efficiency = first-order light / (first-order light + zero-order light + (minus-first-order light))

[0341] The average value of the diffraction efficiency was obtained from the measured values at wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm, and the wavelength dependence of the diffraction efficiency was evaluated. Note that the evaluation was performed by making the light incident on the fabricated liquid crystal diffraction element after making it circularly polarized by perpendicularly incident on a circular polarizing plate corresponding to the wavelength of the laser light. In addition, the evaluation was performed at three locations: the center of the concentric circles of the liquid crystal alignment pattern in the fabricated liquid crystal diffraction element, near the center of the concentric circles (one period is 10 μm), near the end (one period is 1 μm), and the end (one period is 0.6 μm).

[0342] In Examples 11 to 16 compared with Comparative Example 11, high diffraction efficiency was obtained in terms of the wavelength dependence of the diffraction efficiency.

[0343] [Evaluation] <Evaluation of Diffraction Efficiency> The diffraction efficiency of the emitted light was evaluated when light was incident on the liquid crystal diffraction elements fabricated in Comparative Example 11, Examples 11 to 13, and Examples 14 to 16 from the front (direction at an angle of 0° with respect to the normal) at incident angles changed by ±40° (in 10° increments). Specifically, laser light with output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm respectively was irradiated from a light source and incident on the fabricated liquid crystal diffraction element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in the desired direction from the liquid crystal diffraction element, the zero-order light emitted in other directions (emitted in the same direction as the incident light), and the minus-first-order light (the light diffracted in the -θ direction when the diffraction angle of the first-order light with respect to the zero-order light is θ) was measured with a photodetector, and the diffraction efficiency at each wavelength was calculated using the following formula. Diffraction efficiency = first-order light / (first-order light + zero-order light + (-first-order light))

[0344] The average value of the diffraction efficiency was obtained from the measured values at wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm measured at different incident angles, and the wavelength dependence of the diffraction efficiency was evaluated. Note that after making the light incident perpendicularly on a circular polarizer corresponding to the wavelength of the laser light to make it circularly polarized, the light was incident on the fabricated liquid crystal diffraction element for evaluation. In addition, evaluation was performed at three locations in the fabricated liquid crystal diffraction element: the center of the concentric circles of the liquid crystal alignment pattern, the vicinity of the center of the concentric circles (one period is 10 μm), the vicinity of the end (one period is 1 μm), and the end (one period is 0.6 μm).

[0345] As a result of the evaluation, higher average values of diffraction efficiency were obtained for Examples 11 to 16 compared to Comparative Example 11.

[0346] In addition, as a result of the evaluation, the average value of the diffraction efficiency of Example 12 was improved compared to Example 11, and the average value of the diffraction efficiency of Example 13 was further improved.

[0347] In addition, as a result of the evaluation, the average value of the diffraction efficiency of Example 15 was improved compared to Example 14, and the average value of the diffraction efficiency of Example 16 was further improved.

[0348] From the above, it can be seen that the higher the refractive index difference Δn of the liquid crystal layer of the liquid crystal diffraction element 550 the better the utilization efficiency of light for different incident angles.

[0349] <Fabrication of Circular Polarizing Plate>

[0350] [Fabrication of Absorptive Polarizing Plate (Linear Polarizing Plate)] An absorptive polarizing plate (linear polarizing plate) and a retardation plate were fabricated by the above method, and a circular polarizing plate was fabricated.

[0351] <Fabrication of Optical Element> A circular polarizing plate fabricated using the absorptive polarizing plate fabricated as described above was bonded to the liquid crystal diffraction elements fabricated in Comparative Example 11 and Examples 11 to 16 to fabricate an optical element. The optical element was fabricated by arranging the liquid crystal diffraction element, the retardation plate, and the absorptive polarizing plate in this order.

[0352] [Evaluation] The light intensity of the emitted light was evaluated when light was incident on the optical elements fabricated in Comparative Example 11 and Examples 11 to 16 from the front (direction at an angle of 0° with respect to the normal). Specifically, laser light having output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm was irradiated from a light source and perpendicularly incident on the fabricated optical element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in a desired direction from the liquid crystal diffraction element and the zero-order light (emitted in the same direction as the incident light) emitted in other directions was measured with a photodetector. The evaluation was performed after making the light circularly polarized by perpendicularly incident on a circular polarizing plate corresponding to the wavelength of the laser light and then making the light incident from the liquid crystal diffraction element side of the fabricated optical element. In the optical elements in which a circular polarizing plate was bonded to the liquid crystal diffraction elements fabricated in Examples 1 to 7, it was confirmed that the light intensity of the zero-order light could be significantly reduced at any wavelength compared to before bonding the circular polarizing plate, and the contrast ratio (light intensity ratio of first-order light / zero-order light) was improved.

[0353] [Evaluation] <Evaluation of Incidence Angle Dependence> The light intensity of the emitted light was evaluated when light was incident on the optical elements using the liquid crystal diffraction elements fabricated in Comparative Example 11 and Examples 11 to 16 at an incident angle changed by ±40° (in 10° increments) from the front (direction at an angle of 0° with respect to the normal). Specifically, laser light with output center wavelengths of 405 nm, 450 nm, 532 nm, and 650 nm respectively was irradiated from a light source and incident on the fabricated liquid crystal diffraction element. Among the emitted light, the light intensity of the diffracted light (first-order light) diffracted in the desired direction from the liquid crystal diffraction element and the zero-order light (emitted in the same direction as the incident light) emitted in other directions was measured with a photodetector.

[0354] The average value of the light intensity with respect to the incident angle was obtained from the measured values of wavelengths 405 nm, 450 nm, 532 nm, and 650 nm measured at different incident angles. In addition, evaluation was performed at three locations in the fabricated liquid crystal diffraction element: the center of the concentric circles of the liquid crystal alignment pattern, the vicinity of the center of the concentric circles (one period is 10 μm), the vicinity of the end (one period is 1 μm), and the end (one period is 0.6 μm). Note that after making it circularly polarized by perpendicularly incident on a circular polarizer corresponding to the wavelength of the laser light, light was incident from the liquid crystal diffraction element side of the fabricated optical element for evaluation.

[0355] In the optical elements obtained by attaching a circular polarizer to the liquid crystal diffraction elements fabricated in Examples 11 to 16, it was confirmed that the light intensity of the zero-order light could be significantly reduced at any wavelength compared to before attaching the circular polarizer, and the contrast ratio (light intensity ratio of first-order light / zero-order light) was improved. In addition, high contrast ratios were obtained for the optical elements fabricated in Examples 11 to 16 compared to the optical element fabricated in Comparative Example 11.

[0356] In addition, as a result of the evaluation, the average value of the contrast ratio with respect to the incident angle of Example 12 was improved compared to Example 11, and the average value of the contrast ratio with respect to the incident angle of Example 13 was further improved.

[0357] In addition, as a result of the evaluation, the average value of the contrast ratio with respect to the incident angle of Example 15 was improved compared to Example 14, and the average value of the contrast ratio with respect to the incident angle of Example 16 was further improved.

[0358] From the above, even in the case of an optical element in which a circular polarizing plate is bonded to a liquid crystal diffraction element, it can be seen that the contrast ratio for different incident angles improves when the refractive index difference Δn of the liquid crystal layer is higher. 550 It can be seen that the contrast ratio for different incident angles improves when the refractive index difference Δn of the liquid crystal layer is higher.

[0359] <Change of the support> Using the method described below, the support of the liquid crystal diffraction element can be appropriately changed according to the purpose. Also, in the method described below, the thickness between the liquid crystal diffraction element and the changed support can be made thinner. For example, with respect to an adhesive (thickness: several μm to several tens of μm), the thickness within the plane of the liquid crystal diffraction element after the support change can be made uniform. Thus, even when the support of the liquid crystal diffraction element is changed, by making the thickness within the plane uniform, the direction of the light emitted from the liquid crystal diffraction element can be precisely controlled within the plane.

[0360] Note that the lamination of the liquid crystal diffraction element and the new support may be performed, for example, according to the following procedure. (1) Bond a temporary support to the side of the support, alignment film, and liquid crystal layer of the liquid crystal diffraction element to be laminated. In this example, as the temporary support, MASTACK AS3-304 manufactured by Fujimori Kogyo Co., Ltd. was used. (2) Next, peel off the support and alignment film that have existed since the manufacturing stage of the liquid crystal diffraction element, and expose the interface on the alignment film side of the liquid crystal diffraction element. (3) Form a silicon oxide layer (SiO x layer) on both the interface on the alignment film side of this liquid crystal diffraction element and the interface of the newly prepared support. There is no limitation on the method for forming the silicon oxide layer, but vacuum deposition is preferably exemplified. In this example, the formation of the silicon oxide layer was performed using an evaporation apparatus (model number ULEYES) manufactured by Ulvac, Inc. As the evaporation source, SiO2 powder was used. There is no limitation on the thickness of the silicon oxide layer, but it is preferably 50 nm or less. Also in this example, the thickness of the silicon oxide film was 50 nm or less. (4) Next, perform plasma treatment on both of the formed silicon oxide films, bond the formed silicon oxide layers together at 120 °C, and then peel off the temporary support.

[0361] Through the above steps (1) to (4), a diffractive element in which a liquid crystal diffractive element and a newly prepared support are laminated can be fabricated. Also, by changing the support to another liquid crystal diffractive element and repeating steps (1) to (4), a diffractive element in which two or more liquid crystal diffractive elements are laminated can be fabricated.

[0362] Through the above steps (1) to (4), the support of the liquid crystal diffractive element fabricated in Example 1 was changed to a glass substrate with a thickness of 0.3 mm. For comparison, using an adhesive with a thickness of 25 μm, the support of the liquid crystal diffractive element fabricated in Example 1 was changed to a glass substrate with a thickness of 0.3 mm (the liquid crystal diffractive element was bonded to the glass substrate via the adhesive). In the above steps (1) to (4), the fabricated liquid crystal diffractive element was able to make the thickness within the plane of the liquid crystal diffractive element more uniform than that fabricated via the adhesive.

[0363] <Fabrication of Laminated Body> Similarly, a laminated body of a liquid crystal diffractive element and other optical members or the like can be fabricated. As an example, a laminated body of a liquid crystal diffractive element, a retardation plate, and a polarizing plate was fabricated by the following method. On the liquid crystal layer side of a liquid crystal diffractive element having a support, an alignment film, and a liquid crystal layer to be laminated, and on the bonding surface side of the retardation plate to be bonded to the liquid crystal diffractive element, a silicon oxide layer (SiOx layer) was formed. There is no limitation on the method for forming the silicon oxide layer, but vacuum evaporation is preferably exemplified. In this example, the silicon oxide layer was formed using an evaporation apparatus (model number ULEYES) manufactured by Ulvac, Inc. The evaporation source used was SiO2 powder. There is no limitation on the thickness of the silicon oxide layer, but it is preferably 50 nm or less. Also in this example, the thickness of the silicon oxide film was set to 50 nm or less. Plasma treatment was performed on both of the formed silicon oxide films, and the silicon oxide layers were bonded at 120°C. Thereby, a laminated body of the liquid crystal diffractive element and the retardation plate was formed. Similarly, a polarizing plate layer was bonded onto the retardation plate, and by peeling off the above support and alignment film, a laminated body composed of a liquid crystal layer (liquid crystal diffractive element) / retardation plate / polarizing plate was fabricated. In addition, as the liquid crystal diffraction element, the liquid crystal diffraction elements fabricated in Examples 1 to 16 were used. As the retardation plate, the retardation plate used in the production of the above-described circular polarizing plate was used. As the polarizing plate, the above-described linear polarizing plate (polyvinyl alcohol layer type) and the absorption type polarizing plate were respectively used to fabricate a laminate. In the optical element formed by laminating the liquid crystal diffraction element, the retardation plate, and the polarizing plate, it was confirmed that the light intensity of the zero-order light can be significantly reduced at any wavelength before laminating the circular polarizing plate (a laminate of the retardation plate and the polarizing plate), and the contrast ratio (the light intensity ratio of the first-order light to the zero-order light) is improved. From the above results, the effect of the present invention is obvious.

Explanation of Reference Numerals

[0364] 30 Support 32 Alignment film 36a, 36b Optically anisotropic layer 37a to 37g Regions 40 Liquid crystal compound 40A Optical axis 42 Light part 44 Dark part 60 Exposure apparatus 62 Laser 64 Light source 65 λ / 2 plate 68 Beam splitter 70A, 70B, 90A, 90B Mirrors 72A, 72B, 96 λ / 4 plates 86, 94 Polarizing beam splitters 92 Lens Λ One period D Array axis R Region M Laser light MA, MB Light rays MP P polarization MS S polarization P O Linear polarization P R Right circular polarization P L Left circular polarization α Crossing angle L1, L4 Incident light Light transmitted through L2 and L5

Claims

1. An optical anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, wherein at least a part of the liquid crystal compound in the optical anisotropic layer is twisted and aligned in the thickness direction, and 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 which acts as a transmissive diffraction element having a liquid crystal alignment pattern, wherein in a cross-sectional image obtained by observing a cross-section cut in the thickness direction along the one direction with a scanning electron microscope, the optical anisotropic layer has a bright portion and a dark portion extending from one surface to the other surface, and the dark portion has two or more change points of an angle whose angle changes, and further has regions in the thickness direction where the inclination directions of the dark portion are different, A liquid crystal diffraction element, wherein when the length in which the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotates 180° in the plane is defined as one period, the length of the one period is constant.

2. The liquid crystal diffraction element according to claim 1, wherein the inclination direction of the dark portion extending from one surface to the other surface is folded back in the reverse direction an odd number of times.

3. The liquid crystal diffraction element according to claim 2, wherein the inclination direction of the dark portion extending from one surface to the other surface is folded back in the reverse direction once.

4. The liquid crystal diffraction element according to claim 2, wherein the inclination direction of the dark portion extending from one surface to the other surface is folded back in the reverse direction three times.

5. The optical anisotropic layer, in a cross-sectional image obtained by observing a cross-section cut in the thickness direction along the one direction with a scanning electron microscope, has a shape of the dark portion that is symmetric with respect to the center line in the thickness direction of the optical anisotropic layer. The liquid crystal diffraction element according to any one of claims 1 to 4.

6. The optical anisotropic layer, in a cross-sectional image obtained by observing a cross-section cut in the thickness direction along the one direction with a scanning electron microscope, has a shape of the dark portion that is asymmetric with respect to the center line in the thickness direction of the optical anisotropic layer. The liquid crystal diffraction element according to any one of claims 1 to 4.

7. The refractive index difference Δn associated with the refractive index anisotropy of the optical anisotropic layer 550 is 0.2 or more, and the liquid crystal diffraction element according to any one of claims 1 to 6.

8. The liquid crystal diffraction element according to any one of claims 1 to 6, having in the plane a region where when the length in which the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotates 180° in the plane is defined as one period, the length of the one period is 1.0 μm or less.

9. The liquid crystal diffraction element according to any one of claims 1 to 8, wherein the directions of the optical axes of the liquid crystal compounds facing each other with the change point of the angle interposed therebetween in the thickness direction are the same.

10. The liquid crystal diffraction element according to any one of claims 1 to 9, wherein the optically anisotropic layer has a region in which the twisting direction of the liquid crystal compound in the thickness direction is opposite and a region in which the inclination direction of the dark portion is opposite.

11. An optical element having the liquid crystal diffraction element according to any one of claims 1 to 10 and a circular polarizing plate.

12. The optical element according to claim 11, wherein the circular polarizing plate is composed of a retardation plate and a polarizer, and the liquid crystal diffraction element, the retardation plate, and the polarizer are arranged in this order.

13. An optical element having the liquid crystal diffraction element according to any one of claims 1 to 10, a silicon oxide layer, and a support in this order.

14. An optical element having at least one or more of the liquid crystal diffraction elements according to any one of claims 1 to 10 or the optical elements according to any one of claims 11 to 13, and further having at least one or more phase modulation elements.

15. An image display unit having the liquid crystal diffraction element according to any one of claims 1 to 10 or the optical element according to any one of claims 11 to 13.

16. A head-mounted display having the image display unit according to claim 15.

17. A beam steering having the liquid crystal diffraction element according to any one of claims 1 to 10 or the optical element according to any one of claims 11 to 13.

18. A sensor having the liquid crystal diffraction element according to any one of claims 1 to 10 or the optical element according to any one of claims 11 to 13.

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