Liquid crystal diffraction elements, optical elements, image display units, head-mounted displays, beam deflectors, and sensors

Abstract

The present invention aims to provide a liquid crystal diffraction element with low wavelength dependence of diffraction efficiency and diffraction at the same angle when the wavelength is the same, an optical element using the liquid crystal diffraction element, an image display unit, a head-mounted display, a beam deflector, and a sensor using the optical element. The liquid crystal diffraction element comprises an optically anisotropic layer containing a liquid crystal compound. The optically anisotropic layer has a liquid crystal alignment pattern in which the orientation of the optical axis of the liquid crystal compound rotates continuously in one direction. In an image of the cross-section observed using a scanning electron microscope, it has bright and dark regions extending from one surface to another, with the dark regions having two or more inflection points at different angles. Furthermore, it has regions with different tilt directions of the dark regions in the thickness direction, thereby solving the problem.

Description

Technical Field

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

[0002] A liquid crystal diffraction element is known to diffract and transmit incident light.

[0003] As such liquid crystal diffraction elements, liquid crystal diffraction elements having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound are known.

[0004] For example, Patent Document 1 describes a liquid crystal diffraction element (polarizing diffraction grating) having a substrate; a first polarizing diffraction grating layer, which is a first polarizing diffraction grating layer on the substrate, including a molecular structure twisted according to a first torsion on a first thickness defined between the two sides of the first polarizing diffraction grating layer; and a second polarizing diffraction grating layer, which is a second polarizing diffraction grating layer on the first polarizing diffraction grating layer, including a molecular structure twisted according to a second torsion opposite to the first torsion on a second thickness defined between the two sides of the second polarizing diffraction grating layer.

[0005] Patent document 1 describes that the polarization diffraction grating layer can diffract light by aligning the liquid crystal compound with a predetermined orientation pattern.

[0006] As described in Patent Document 1, a liquid crystal diffraction element having an alignment pattern of a liquid crystal compound can diffract incident light at an angle corresponding to the wavelength. Furthermore, if the alignment pattern of the liquid crystal compound is constant, light of the same wavelength can be diffracted at a certain angle regardless of the incident position.

[0007] Liquid crystal diffraction elements with alignment patterns of liquid crystal compounds can be used for a variety of applications by taking advantage of this property.

[0008] For example, in AR (Augmented Reality) glasses that overlay virtual images and various information onto 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 for total internal reflection.

[0009] As an incident element for directing light onto the light guide plate, by using a liquid crystal diffraction element having an alignment pattern of a liquid crystal compound as described in Patent Document 1, incident light (image) can be diffracted and incident onto the light guide plate at an angle capable of total internal reflection. Furthermore, by also using a liquid crystal diffraction element at the other end of the light guide plate, light guided within the light guide plate can be diffracted and emitted, allowing the user to visually recognize the image.

[0010] Furthermore, as described above, the liquid crystal diffraction element with an alignment pattern of 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 in-plane diffraction angles are equal if the wavelength is the same.

[0011] Therefore, this liquid crystal diffraction element can also be suitably used as a beam splitter in a hyperspectral camera that splits incident light into multiple wavelength regions for imaging.

[0012] Furthermore, by changing the orientation pattern of the liquid crystal compound in-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 expresses the function of a lens.

[0013] For example, there is a head-mounted display that has an image display unit that guides images to the user's eyes in order to provide an immersive virtual reality (VR) experience that prevents external light from passing through. In the image display unit used in such a head-mounted display, lenses are needed to focus the light emitted from the image display device at the position of the user's glasses.

[0014] As a lens element for VR head-mounted displays, by changing the orientation pattern of the liquid crystal compound in-plane and using a liquid crystal diffraction element with lens function, incident light (image) is diffracted, and the light emitted from the image display device is focused at the position of the user's eyes, thereby enabling the user to visually recognize the image.

[0015] Furthermore, in refractive lenses made of molded glass, plastic, etc., the direction of light traveled by the lens varies according to wavelength due to the wavelength dispersion of the refractive index of the material used as the lens, thus causing color splitting (chromatic aberration). Specifically, the shorter wavelength side is refracted at a larger angle by the lens, while the longer wavelength side is refracted at a smaller angle. On the other hand, by changing the orientation pattern of the liquid crystal compound in-plane, a liquid crystal diffraction element with lens function has the characteristic of having a smaller diffraction angle at short wavelengths and a larger angle at long wavelengths. Therefore, by combining a refractive lens and a liquid crystal diffraction element with lens function, the color splitting of the refractive lens can be improved.

[0016] Previous technical documents

[0017] Patent documents

[0018] Patent Document 1: Japanese Patent Publication No. 2010-525394 Summary of the Invention

[0019] The technical problem to be solved by the invention

[0020] The incident element of the light guide plate in AR glasses and the beam splitting element in a hyperspectral camera, for example, correspond to the entire wavelength range of visible light, or a wide wavelength range of light, and diffract light of various wavelengths.

[0021] Therefore, these optical elements require low wavelength dependence of diffraction efficiency, that is, they should be able to diffract light with the same diffraction efficiency regardless of the wavelength.

[0022] However, including the liquid crystal diffraction element described in Patent Document 1, the wavelength dependence of the diffraction efficiency of liquid crystal diffraction elements having conventional liquid crystal compound alignment patterns is not small enough.

[0023] Furthermore, the lens elements in the VR head-mounted display, and the lens elements that improve color splitting by combining with refractive lenses, such as light in a wide wavelength range corresponding to the entire wavelength range of visible light, and diffract light of various wavelengths.

[0024] Therefore, these optical elements require low wavelength dependence of diffraction efficiency, that is, they should be able to diffract light with the same diffraction efficiency regardless of the wavelength.

[0025] However, including the liquid crystal diffraction element described in Patent Document 1, the wavelength dependence of the diffraction efficiency of liquid crystal diffraction elements having conventional liquid crystal compound alignment patterns is not small enough.

[0026] The purpose of this invention is to solve the problems of the prior art and to provide a liquid crystal diffraction element with low wavelength dependence of diffraction efficiency, an optical element using the liquid crystal diffraction element, an image display unit using the optical element, a head-mounted display, a beam deflector, and a sensor.

[0027] means for solving technical problems

[0028] To address this issue, the present invention has the following structure.

[0029] [1] A liquid crystal diffraction element comprising an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound,

[0030] The optical anisotropy layer has a liquid crystal alignment pattern that changes while the orientation of the optical axis derived from the liquid crystal compound continuously rotates in at least one in-plane direction, and

[0031] In a cross-sectional image obtained by cutting along one direction in the thickness direction using a scanning electron microscope, the optical anisotropic layer has bright and dark areas extending from one surface to another. Furthermore, the dark areas have more than two inflection points at different angles, and there are regions with different tilt directions of the dark areas in the thickness direction.

[0032] [2] According to the liquid crystal diffraction element described in [1], wherein,

[0033] When the length of a period is defined as the length of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern when rotated 180° in the plane, the length of a period is constant.

[0034] [3] According to the liquid crystal diffraction element described in [1], wherein,

[0035] When the length of a 180° in-plane rotation of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern is defined as one cycle, the length of one cycle gradually changes in one direction.

[0036] [4] The liquid crystal diffraction element according to [1] or [3], wherein,

[0037] The liquid crystal alignment pattern is a concentric circle pattern, which changes direction as it rotates continuously from the inside to the outside of the concentric circles, with the orientation originating from the optical axis of the liquid crystal compound.

[0038] [5] The liquid crystal diffraction element according to any one of [1] to [4], wherein,

[0039] The dark areas have an odd number of inflection points where the angle of inflection turns back.

[0040] [6] According to the liquid crystal diffraction element described in [5], wherein,

[0041] The dark area has one inflection point where the angled direction turns back.

[0042] [7] According to the liquid crystal diffraction element described in [5], wherein,

[0043] The dark area has three inflection points that fold back in a sloping direction.

[0044] [8] The liquid crystal diffraction element according to any one of [1] to [7], wherein,

[0045] In a cross-sectional image of an optically anisotropic layer obtained by scanning electron microscopy by cutting along one direction in the thickness direction, the shape of the dark areas is symmetrical with respect to the centerline of the thickness direction of the optically anisotropic layer.

[0046] [9] The liquid crystal diffraction element according to any one of [1] to [7], wherein,

[0047] In a cross-sectional image of an optically anisotropic layer obtained by scanning electron microscopy by cutting along one direction in the thickness direction, the shape of the dark areas is asymmetrical with respect to the centerline of the thickness direction of the optically anisotropic layer.

[0048]

[10] The liquid crystal diffraction element according to any one of [1] to [9], wherein,

[0049] The refractive index difference Δn arising from the refractive index anisotropy of the optical anisotropic layer 550 It is above 0.2.

[0050]

[11] The liquid crystal diffraction element according to any one of [1] to [9], wherein,

[0051] When the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern is rotated 180° in-plane for one period, there is a region in-plane with a length of less than 1.0 μm for one period.

[0052]

[12] An optical element comprising a liquid crystal diffraction element and a circular polarizer as described in any one of [1] to

[11] .

[0053]

[13] The optical element according to

[12] , wherein,

[0054] The circular polarizer consists of a phase difference plate and a polarizer. The optical element is composed of a liquid crystal diffraction element, a phase difference plate and a polarizer arranged in sequence.

[0055]

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

[11] .

[0056]

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

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

[12] to

[14] , and having at least one phase modulation element.

[0057]

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

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

[12] to

[15] .

[0058]

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

[16] .

[0059]

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

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

[12] to

[15] .

[0060]

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

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

[12] to

[15] .

[0061] Invention Effects

[0062] According to the present invention, it is possible to provide a liquid crystal diffraction element with low wavelength dependence of diffraction efficiency, an optical element using the liquid crystal diffraction element, an image display unit using the optical element, a head-mounted display, a beam deflector, and a sensor. Attached Figure Description

[0063] Figure 1 This is a diagram that conceptually illustrates an example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0064] Figure 2 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0065] Figure 3 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0066] Figure 4 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0067] Figure 5 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0068] Figure 6 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0069] Figure 7 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0070] Figure 8 It is a magnified view of a planar image of the optical anisotropic layer.

[0071] Figure 9 It is a magnified cross-sectional view showing a portion of the optical anisotropic layer.

[0072] Figure 10 This is a diagram that conceptually represents an example of an exposure apparatus for exposing an alignment film.

[0073] Figure 11 This is a conceptual diagram used to illustrate the role of optical anisotropic layers.

[0074] Figure 12 This is a conceptual diagram used to illustrate the role of optical anisotropic layers.

[0075] Figure 13 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0076] Figure 14 This is a diagram that conceptually represents an example of an exposure apparatus for exposing an alignment film. Detailed Implementation

[0077] Hereinafter, with reference to the preferred embodiments shown in the accompanying drawings, the liquid crystal diffraction element, optical element, image display unit, head-mounted display, beam deflector, and sensor of the present invention will be described in detail.

[0078] In this specification, the numerical range indicated by “~” refers to the range encompassed by the values ​​recorded before and after “~” as the lower and upper limits.

[0079] In this specification, "(meth)acrylate" is used to mean "one or both of acrylate and methacrylate".

[0080] In this specification, visible light refers to light of electromagnetic waves with wavelengths observable to the naked eye, specifically light in the wavelength range of 380–780 nm. Non-visible light refers to light in the wavelength range below 380 nm and above 780 nm.

[0081] [Liquid Crystal Diffraction Element]

[0082] Figure 1 The above is a conceptual illustration of an example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention.

[0083] In the liquid crystal diffraction element of the present invention, the optical anisotropy layer is formed using a liquid crystal composition containing a liquid crystal compound, and has a liquid crystal alignment pattern in which the orientation of the optical axis originating from the liquid crystal compound is continuously changed in at least one in-plane direction.

[0084] Furthermore, in cross-sectional images obtained by scanning electron microscopy (SEM) of a section cut along the thickness direction in a direction that continuously changes along the optical axis, the optical anisotropic layer exhibits bright and dark areas extending from one surface to another, and the dark (bright) areas have more than two inflection points (angle inflection points) where the angle changes. Additionally, the optical anisotropic layer has regions with different tilt directions in the dark (bright) areas along the thickness direction.

[0085] The bright and dark areas (bright lines and dark lines) in the cross-sectional image observed by SEM are obtained from the observation of the liquid crystal phase with liquid crystal alignment pattern.

[0086] Figure 1 The optical anisotropic layer 36a shown is a rod-shaped liquid crystal compound used as liquid crystal compound 40. Therefore, the direction of the optical axis is aligned with the direction of the long side of the liquid crystal compound 40.

[0087] The optical anisotropy layer 36 has a predetermined liquid crystal alignment pattern that changes as the optical axis of the liquid crystal compound 40 rotates continuously in one direction.

[0088] Furthermore, in the optical anisotropy layer 36a, when the length of the orientation of the optical axis originating from the liquid crystal compound 40 rotating 180° in one direction within the plane is set as one cycle, the length of one cycle in the liquid crystal alignment pattern is constant.

[0089] The optical anisotropic layer 36a with this liquid crystal alignment pattern functions as a liquid crystal diffraction element, which diffracts (refracts) and transmits incident light according to one cycle of 180° rotation of the optical axis and the wavelength of the incident light. The function of this optical anisotropic layer 36a as a diffraction element will be described later.

[0090] In a cross-sectional image obtained by SEM observation of a section cut along the thickness direction in one direction of rotation along the optical axis, the optical anisotropic layer 36a exhibits a stripe pattern originating from the liquid crystal phase, alternating between bright areas 42 and dark areas 44 extending from one surface to another. Furthermore, in Figure 1 In the image, the bright area 42 and the dark area 44 are superimposed on the cross-section of the optical anisotropic layer 36a. In the following description, the cross-sectional image obtained by observing a cross-section cut along the thickness direction in one direction of rotation along the optical axis using SEM will also be referred to as a "cross-sectional SEM image".

[0091] In the cross-sectional SEM image of the optical anisotropic layer 36a in the figure example, the dark area 44 has two inflection points where the angle changes. That is, it can also be said that the optical anisotropic layer 36a has three regions, region 37a, region 37b, and region 37c, in the thickness direction according to the inflection points of the dark area 44.

[0092] like Figure 1 As shown, the optical anisotropy layer 36a has a liquid crystal alignment pattern in any position in the thickness direction, in the in-plane direction, where the optical axis originating from the liquid crystal compound 40 rotates clockwise toward the left in the figure.

[0093] Furthermore, in the liquid crystal alignment pattern, one cycle, which is the length of a 180° rotation of the optical axis in one direction, is constant in any region in the in-plane direction.

[0094] And, as Figure 1 As shown, the liquid crystal compound 40 is twisted in the lower region 37c in the thickness direction in a spiral manner, twisting clockwise (rotating to the right) from the upper side to the lower side in the thickness direction.

[0095] In region 37b, which is exactly in the middle of the thickness direction, the liquid crystal compound 40 is not twisted in the thickness direction, and the optical axes of the liquid crystal compounds 40 stacked in the thickness direction are oriented in the same direction. That is, the optical axes of the liquid crystal compounds 40 existing at the same position in the in-plane direction are oriented in the same direction.

[0096] In the upper region 37a in the thickness direction, the liquid crystal compound 40 is twisted in a spiral manner, twisting counterclockwise (rotating to the left) from the upper side to the lower side in the thickness direction.

[0097] Right now, Figure 1 In the optical anisotropic layer 36a shown, the torsional states of the liquid crystal compound 40 in the thickness direction of regions 37a, 37b and 37c are different.

[0098] In an optically anisotropic layer having a liquid crystal alignment pattern that is continuously rotated in one direction by an optical axis derived from a liquid crystal compound, bright areas 42 and dark areas 44 are observed in a cross-sectional SEM image of the optically anisotropic layer 36a to connect liquid crystal compounds 40 with the same orientation.

[0099] As an example, in Figure 1 The image shows the dark area 44 observed, which is connected to the optical axis in a direction orthogonal to the paper surface, and the liquid crystal compound 40.

[0100] In the lowest region 37c along the thickness direction, the dark area 44 slopes towards the upper left of the image. In the middle region 37b, the dark area 44 extends along the thickness direction. In the uppermost region 37a, the dark area 44 slopes towards the upper right of the image.

[0101] Right now, Figure 1 The optical anisotropy layer 36a shown has two inflection points at which the angle of the dark region 44 changes. Furthermore, in the uppermost region 37a, the dark region 44 is tilted towards the upper right, and in the lowermost region 37b, the dark region 44 is tilted towards the upper left. That is, the tilting direction of the dark region 44 is different in regions 37a and 37c.

[0102] also, Figure 1 In the optical anisotropic layer 36a shown, the dark part 44 has a point where the tilt direction is reversed.

[0103] Specifically, in the dark region 44 of the optical anisotropic layer 36a, the tilt direction in region 37a is opposite to the tilt direction in region 37b. Therefore, the inflection point at the interface between regions 37a and 37b is an inflection point where the tilt direction folds back in the opposite direction. That is, the optical anisotropic layer 36a has one inflection point where the tilt direction folds back in the opposite direction.

[0104] Furthermore, as an example, in the optical anisotropy layer 36a, the thicknesses of regions 37a and 37c are equal, and as described above, the torsion states in the thickness direction of the liquid crystal compound 40 are different. Therefore, as... Figure 1 As shown, the bright areas 42 and dark areas 44 in the cross-sectional SEM image are roughly C-shaped.

[0105] Therefore, in the optical anisotropic layer 36a, the shape of the dark part 44 (bright part 42) is symmetrical with respect to the center line of the thickness direction.

[0106] The liquid crystal diffraction element of the present invention has a bright portion 42 and a dark portion 44 extending from one surface to another in such an optical anisotropic layer 36a, i.e., in a cross-sectional SEM image. The dark portion 44 has two or more inflection points and has regions with different tilt directions in the thickness direction, thereby reducing the wavelength dependence of diffraction efficiency and enabling diffraction of light with the same diffraction efficiency regardless of the wavelength.

[0107] As described above, a liquid crystal diffraction element comprising an optically anisotropic layer having an optical axis derived from a liquid crystal compound and an orientation pattern of a liquid crystal continuously rotating in at least one direction, for example, across the entire visible light region and a wide wavelength range, is capable of diffracting incident light at different diffraction angles depending on the wavelength.

[0108] However, according to the research of the inventors, liquid crystal diffraction elements with conventional liquid crystal alignment patterns have dark areas tilted relative to the surface (main surface) in cross-sectional SEM images, but do not have inflection points where the angle changes, or as shown in Patent Document 1, they have only one inflection point. Therefore, conventional liquid crystal diffraction elements, for example, have high diffraction efficiency for red and green light, but lower diffraction efficiency for blue light than the other two colors, and the diffraction efficiency is highly wavelength-dependent.

[0109] In contrast, the liquid crystal diffraction element of the present invention exhibits two or more angular inflection points in the dark region 44 observed in the cross-sectional SEM image, and also has regions with different tilt directions in the thickness direction. Therefore, the diffraction efficiency of the liquid crystal diffraction element of the present invention has low wavelength dependence, and it can diffract light with the same diffraction efficiency regardless of the wavelength. Furthermore, this liquid crystal diffraction element of the present invention can diffract light with high diffraction efficiency regardless of the wavelength.

[0110] Furthermore, as described later, in the liquid crystal alignment pattern of the liquid crystal diffraction element of the present invention, the length of one cycle of 180° rotation of the optical axis can be constant. With a constant cycle length, the liquid crystal diffraction element of the present invention can diffract (refract) light at the same angle regardless of the incident position of the light within the plane, as long as the wavelength is the same. Therefore, the liquid crystal diffraction element of the present invention is preferably used in various optical devices that require light to be diffracted at the same angle regardless of the incident position, such as light incident elements in the light guide plate of AR glasses and beam splitters in hyperspectral cameras.

[0111] Furthermore, the liquid crystal diffraction element of the present invention having the optical anisotropic layer shown below also exhibits the same effect.

[0112] Figure 1 The optical anisotropic layer 36a shown has three regions in the thickness direction, the dark region 44 has two inflection points, and there is also one inflection point that folds back in the tilt direction.

[0113] However, in the liquid crystal diffraction element of the present invention, the optical anisotropy layer is not limited to this structure.

[0114] That is, in the liquid crystal diffraction element of the present invention, the optical anisotropy layer has the above-mentioned liquid crystal alignment pattern, and one period of the liquid crystal alignment pattern is constant. Furthermore, in the cross-sectional SEM image, due to the liquid crystal layer, there are bright parts 42 and dark parts 44 extending from one surface to another. Moreover, the dark parts 44 have two or more inflection points at different angles. In addition, in the thickness direction, there are regions with different tilt directions, so various structures can be utilized.

[0115] Figure 2 Another example of the optical anisotropy layer of the liquid crystal diffraction element of the present invention is shown.

[0116] Figure 2 The optically anisotropic layer 36b shown has a predetermined liquid crystal alignment pattern that changes as the optical axis of the liquid crystal compound rotates continuously in one direction. Therefore, the optically anisotropic layer 36b also exhibits a stripe pattern in the cross-sectional SEM image, derived from the liquid crystal layer, alternating between bright areas 42 and dark areas 44 extending from one surface to another.

[0117] Figure 2 also with Figure 1 Similarly, the bright area 42 and the dark area 44 are superimposed on the cross-section of the optical anisotropic layer 36a.

[0118] Figure 2 In the optical anisotropic layer 36b shown, the dark area 44 observed in the cross-sectional SEM image has three inflection points with angular changes.

[0119] That is, it can be said that the optical anisotropic layer 36b has four regions from top to bottom in the thickness direction, namely region 37d, region 37e, region 37f and region 37g, according to the inflection point of the dark part 44.

[0120] Figure 2 The optical anisotropic layer 36b also has a liquid crystal alignment pattern, in any position in the thickness direction, in the in-plane direction, in which the optical axis of the liquid crystal compound 40 rotates clockwise toward the left in the figure.

[0121] Furthermore, in the liquid crystal alignment pattern, one cycle, which is the length of a 180° rotation of the optical axis in one direction, is constant in any region in the in-plane direction.

[0122] exist Figure 2 In the optical anisotropic layer 36b shown, in the lowest region 37g in the thickness direction, the liquid crystal compound 40 is twisted and oriented in a spiral manner, twisting clockwise from the upper side to the lower side in the thickness direction.

[0123] In the second region 37f starting from the bottom, the liquid crystal compound 40 is twisted in a spiral shape, twisted counterclockwise from the upper side to the lower side in the thickness direction.

[0124] In the third region 37e starting from the bottom, the liquid crystal compound 40 is twisted in a spiral shape, twisted clockwise from the upper side to the lower side in the thickness direction.

[0125] Furthermore, in the uppermost region 37d, the liquid crystal compound 40 is twisted in a spiral shape, rotating counterclockwise from the upper side to the lower side in the thickness direction.

[0126] Right now, Figure 2 In the optical anisotropic layer 36b shown, the liquid crystal alignment pattern is uniform throughout the thickness direction, but the spiral twist 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. Furthermore, Figure 2 In the optical anisotropic layer 36b shown, the spiral twist of the liquid crystal compound 40 in the thickness direction is reversed between regions 37d and 37e.

[0127] As described above, in an optically anisotropic layer having a liquid crystal alignment pattern that is continuously rotated in one direction by an optical axis derived from a liquid crystal compound, bright areas 42 and dark areas 44 are observed in a cross-sectional SEM image of the optically anisotropic layer 36a to connect liquid crystal compounds 40 with the same orientation.

[0128] Therefore, in Figure 2In the optical anisotropic layer 36b shown, the tilt direction of the dark part 44 in regions 37d and 37f is the same, and the tilt direction of the dark part 44 in regions 37e and 37g is the same.

[0129] Specifically, in the lowest region 37g along the thickness direction, the dark area 44 slopes towards the upper left in the figure. In the second region 37f from the bottom, the dark area 44 slopes towards the upper right in the figure. In the third region 37e from the bottom, the dark area 44 slopes towards the upper left in the same manner as the lowest region 37g. Furthermore, in the highest region 37d, the dark area 44 slopes towards the upper right in the same manner as the second region 37f from the bottom.

[0130] Right now, Figure 2 The optical anisotropic layer 36b shown has three inflection points of the angle of the dark region 44 where the angle of the dark region changes.

[0131] Here, in the optical anisotropic layer 36b, the tilt directions of the dark areas are different in regions 37g and 37f adjacent to the thickness direction. Furthermore, the tilt directions of the dark areas are also different in regions 37f and 37e adjacent to the thickness direction. Additionally, the tilt directions of the dark areas are also different in regions 37e and 37d adjacent to the thickness direction. That is, in... Figure 2 In the optical anisotropic layer 36d shown, in the dark part 44, all three inflection points of the angle change in the dark part are inflection points that turn back in the tilt direction.

[0132] Furthermore, regions 37d and 37g, as well as regions 37e and 37f, are of the same thickness as a single example.

[0133] Therefore, in Figure 2 In the optical anisotropic layer 36b shown, the bright areas 42 and dark areas 44 in the cross-sectional SEM image are approximately W-shaped. Therefore, in the optical anisotropic layer 36b, the shape of the dark area 44 is symmetrical with respect to the centerline of the thickness direction.

[0134] Furthermore, in the liquid crystal diffraction element of the present invention, the structure of the optical anisotropy layer, in addition to the above examples, also has the above-described liquid crystal alignment pattern, and one period of the liquid crystal alignment pattern is constant. In addition, it has a bright portion 42 and a dark portion 44 that extend from one surface (main surface) to another surface due to the liquid crystal phase observed in the cross-sectional SEM image. The dark portion 44 has two or more inflection points at different angles. Furthermore, if there are regions with different tilt directions in the thickness direction, various structures can be utilized.

[0135] Furthermore, in the examples shown below, only the bright areas 42 and dark areas 44 in the cross-sectional SEM images of the optical anisotropy layer are illustrated. However, in any example, as shown by the enlarged view of the portion enclosed by the dashed lines in each figure, each region of the optical anisotropy layer has the aforementioned liquid crystal alignment pattern in which the optical axis rotates continuously in one direction. Moreover, in the liquid crystal alignment pattern, one cycle of 180° rotation of the optical axis originating from the liquid crystal compound is constant.

[0136] Furthermore, in the optical anisotropic layer shown below, in the region where the dark area 44 is inclined relative to the surface (main surface) of the optical anisotropic layer, the liquid crystal compound 40 is twisted and oriented in the thickness direction. In addition, the main surface is the largest surface in the sheet-like material (plate-like material, film, layer).

[0137] As an example, see the following: Figure 3 The optical anisotropy layer, conceptually represented in the middle, has four regions in the thickness direction based on the inflection point of the dark area 44.

[0138] In this example, in the lowest region, shadow 44 slopes towards the upper left of the image. In the second region from the bottom, shadow 44 slopes towards the upper left of the image relative to the surface at a greater angle than in the lowest region. In the third region from the bottom, shadow 44 slopes towards the upper right of the image. Furthermore, in the highest region, shadow 44 slopes towards the upper right of the image relative to the surface at a smaller angle than in the third region from the bottom.

[0139] Right now, Figure 3 The optical anisotropic layer shown has three inflection points where the angle of the dark region changes 44, and one inflection point where the dark region tilts back at the interface between the second region from the bottom and the third region from the bottom.

[0140] Figure 3 The optical anisotropic layer shown has the same thickness in the bottommost and topmost regions, as well as in the second and third regions from the bottom. Furthermore, the bottommost and topmost regions have different tilt directions, but the angle (absolute value) between the surface of the optical anisotropic layer and the dark area 44 is the same. Similarly, the second and third regions from the bottom have different tilt directions, but the angle between the surface of the optical anisotropic layer and the dark area 44 is the same.

[0141] Right now, Figure 3 The optical anisotropic layer shown is also roughly C-shaped in terms of the bright areas 42 and dark areas 44 in the cross-sectional SEM image. Therefore, Figure 3 In the optical anisotropic layer shown, the shape of the dark part 44 is symmetrical with respect to the centerline of the thickness direction.

[0142] Furthermore, the angle of the dark portion 44 relative to the surface of the optical anisotropic layer can be adjusted based on the length of one cycle, which is the length of the optical axis rotating 180° in one direction in the plane, and the magnitude of the twist of the liquid crystal compound 40 which is twisted in the thickness direction.

[0143] As another example, Figure 4 The concept represents an optical anisotropy layer with five regions in the thickness direction, based on the inflection point of the dark area 44.

[0144] In this example, in the lowest region, dark area 44 slopes towards the upper left of the image. In the second region from the bottom, dark area 44 slopes towards the upper left of the image relative to the surface at an angle greater than that in the lowest region. In the third region from the bottom, which is the central region in the thickness direction, dark area 44 extends towards the thickness direction of the optical anisotropic layer. In the fourth region from the bottom, dark area 44 slopes towards the upper right of the image. Furthermore, in the highest region, dark area 44 slopes towards the upper right of the image relative to the surface at an angle smaller than that in the fourth region from the bottom.

[0145] Right now, Figure 4 The optical anisotropic layer shown has four inflection points where the dark areas change at an angle of 44°.

[0146] Furthermore, in the lowest region, the second region from the bottom, the fourth region from the bottom, and the highest region, the tilt direction of the dark area 44 is opposite. Therefore, the inflection point at the interface between the second region from the bottom and the fourth region from the bottom is the inflection point where the tilt direction turns back in the opposite direction. That is, Figure 3 The optical anisotropic layer shown has one inflection point where the tilt direction folds back in the opposite direction.

[0147] Figure 4 The optical anisotropy layer shown has the same thickness in the bottommost region, the topmost region, the second region from the bottom, and the second region from the top.

[0148] In this optical anisotropic layer, the lowermost and uppermost regions have different tilt directions, but the angle between the surface of the optical anisotropic layer and the dark region 44 is the same. Similarly, the second and fourth regions from the bottom have different tilt directions, but the angle between the surface of the optical anisotropic layer and the dark region 44 is the same. Furthermore, in the third region from the bottom, located in the very center, the dark region 44 extends in the thickness direction of the optical anisotropic layer.

[0149] Right now, Figure 4 The optical anisotropic layer shown is also roughly C-shaped in terms of the bright areas 42 and dark areas 44 in the cross-sectional SEM image. Therefore, Figure 4In the optical anisotropic layer shown, the shape of the dark part 44 is symmetrical with respect to the centerline of the thickness direction.

[0150] Furthermore, the optical anisotropy layer of the liquid crystal diffraction element of the present invention, such as in... Figure 5 Examples with Figure 3 and Figure 4 The roughly C-shaped structure of the dark area 44 is shown and conceptually represented. By shortening the interval of the regions in the thickness direction, that is, the interval of the inflection points in the thickness direction, it is also possible to adopt a structure in which the dark area 44 changes continuously.

[0151] In the liquid crystal diffraction element of the present invention, the number of inflection points in the dark part 44 of the optical anisotropy layer is not limited, and there may be more than two.

[0152] Furthermore, there is no limit to the number of inflection points where the dark area 44 turns back in the direction of its tilt. However, as... Figures 1-5 As shown, in order to ensure that the shape of the dark area 44 is symmetrical with respect to the center line in the thickness direction, the number of inflection points that fold back in the oblique direction is preferably odd, more preferably 1 or 3. Furthermore, it is also preferable to use 5 or more inflection points that fold back in the oblique direction.

[0153] In the optical anisotropic layer described above, the shape of the dark portion 44 is symmetrical with respect to the centerline in the thickness direction. However, in the liquid crystal diffraction element of the present invention, the shape of the dark portion 44 in the optical anisotropic layer may be asymmetrical with respect to the centerline in the thickness direction.

[0154] As an example, this illustrates Figure 6 The optical anisotropy layer is conceptually represented in the middle.

[0155] Figure 6 The optical anisotropic layer shown has three regions based on the inflection point of the dark area 44.

[0156] In this example, in the lowest region, shadow 44 slopes towards the upper left of the image. In the second region from the bottom, shadow 44 slopes towards the upper left of the image at a greater angle relative to the surface than in the lowest region. Furthermore, in the highest region, shadow 44 slopes towards the upper right of the image.

[0157] Right now, Figure 6 The dark region 44 of the optical anisotropy layer shown has three inflection points. Furthermore, there is one inflection point at the interface between the second region from the bottom and the uppermost region, where the tilt direction of the dark region 44 turns back.

[0158] Here, the tilt angle of the dark region 44 relative to the surface of the optical anisotropic layer is different in all three regions, and the tilt direction varies, but the absolute value of the angle relative to the surface of the optical anisotropic layer gradually increases from the bottom to the top. That is, in Figure 6In the optical anisotropic layer shown, the shape of the dark part 44 is asymmetrical with respect to the centerline of the thickness direction.

[0159] The above Figures 1-5 The structure shown, where the shape of the dark region 44 is symmetrical with respect to the centerline in the thickness direction, is advantageous in terms of less wavelength dependence of diffraction efficiency.

[0160] In contrast, the shape of the dark area 44 is asymmetrical with respect to the centerline of the thickness direction, wherein, as... Figure 6 As shown, a structure in which the tilt angle increases sequentially relative to the surface of the optical anisotropic layer is advantageous in terms of improving diffraction efficiency even with a large diffraction angle (refraction angle). In this example, the tilt angle of the dark region 44 is the absolute value of the tilt angle.

[0161] In the liquid crystal diffraction element of the present invention, the tilt angle of the dark part 44 in the cross-sectional SEM image of the optical anisotropic layer is not limited.

[0162] Furthermore, in this invention, the average tilt angle of the dark area 44 is the angle between the line connecting the dark area 44 to its junction with one surface and its junction with another surface, and the perpendicular line to the surface of the optical anisotropic layer. Therefore, as... Figures 1-5 When the shape of the dark part 44 is symmetrical with respect to the centerline of the thickness direction, the average tilt angle of the dark part 44 is approximately 0°.

[0163] The above optical anisotropy layers all use rod-shaped liquid crystal compounds as liquid crystal compounds, but the present invention is not limited to this and can also use disk-shaped liquid crystal compounds.

[0164] In addition, in the case of disk-shaped liquid crystal compounds, the optical axis derived from the liquid crystal compound is defined as the axis perpendicular to the disk surface, also known as the fast axis.

[0165] Furthermore, in the liquid crystal diffraction element of the present invention, the optical anisotropy layer, such as Figure 7 The concept indicates that rod-shaped and disk-shaped liquid crystal compounds can be used in combination. By combining rod-shaped and disk-shaped liquid crystal compounds, it is possible to diffract light with high diffraction efficiency for light incident at different angles. Furthermore, the combination of rod-shaped and disk-shaped liquid crystal compounds is not limited to... Figure 7 The conceptual structure shown in the diagram can be used in various configurations. For example, in... Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 In this process, rod-shaped liquid crystal compounds can be combined into rod-shaped liquid crystal compounds and disk-shaped liquid crystal compounds. Furthermore, for example, in... Figure 7In addition to the above combinations, it can also be a structure in which rod-shaped liquid crystal compounds and disk-shaped liquid crystal compounds are further subdivided in the thickness direction and stacked together.

[0166] As an example, the liquid crystal diffraction element of the present invention, which includes such a liquid crystal alignment pattern and an optical anisotropic layer with dark portion 44 (bright portion 42), has a support, an alignment film formed on the surface of the support, and an optical anisotropic layer formed on the surface of the alignment film.

[0167] Figure 9 The diagram shows a magnified view of a tiny region of a liquid crystal diffraction element, including an optical anisotropic layer 36a (region 37c). Additionally, Figure 8 yes Figure 9 The plan view of the optical anisotropic layer 36a is shown.

[0168] Figure 9 The liquid crystal diffraction element shown, as described above, has a support 30, an alignment film 32, and an optical anisotropy layer 36a. However, the liquid crystal diffraction element of the present invention is not limited to this, and various layer structures can be utilized. For example, the liquid crystal diffraction element of the present invention can be composed of... Figure 9 The liquid crystal diffraction element shown is composed of an alignment film 32 and an optically anisotropic layer 36a, formed by peeling off the support 30. Furthermore, the liquid crystal diffraction element of the present invention can be formed solely from... Figure 9 The liquid crystal diffraction element shown is composed of an optically anisotropic layer 36a formed by peeling off the support 30 and the alignment film 32. Furthermore, the liquid crystal diffraction element of the present invention can be composed of a support 30 and an optically anisotropic layer 36a. In addition to these structures, the liquid crystal diffraction element of the present invention may also have other layers such as a protective layer (hard coating) and an anti-reflective layer.

[0169] Furthermore, the liquid crystal diffraction element of the present invention includes an optically anisotropic layer formed using a liquid crystal composition comprising a liquid crystal compound, the optically anisotropic layer having a liquid crystal alignment pattern that changes while continuously rotating in at least one in-plane direction originating from the optical axis of the liquid crystal compound.

[0170] When the length of a 180° in-plane rotation of the optical axis originating from the liquid crystal compound is defined as one period, the length of one period in the liquid crystal alignment pattern gradually changes along one direction.

[0171] The optical anisotropic layer can be a liquid crystal diffraction element as follows: in a cross-sectional image obtained by cutting a section along one direction in the thickness direction using a scanning electron microscope, there are bright and dark parts extending from one surface to another, the dark parts have two or more inflection points, and there are regions with different tilt directions of the dark parts in the thickness direction.

[0172] exist Figure 13In the example shown, the liquid crystal alignment pattern of the liquid crystal layer 36 is a concentric circle pattern, which changes in one direction (arrows A1-A3) as it continuously rotates from the inside to the outside of the concentric circles with the optical axis of the liquid crystal compound 40. A concentric circle pattern is defined as a pattern in which the lines connecting liquid crystal compounds with the same optical axis are circular, and these circular line segments form a concentric circle pattern. In other words, Figure 13 The liquid crystal alignment pattern of the optical anisotropy layer 36a shown is a liquid crystal alignment pattern that is radially arranged from the center of the liquid crystal layer 36, which changes as the optical axis of the liquid crystal compound 40 rotates continuously.

[0173] exist Figure 13 In the optical anisotropic layer 36a shown, the optical axis of the liquid crystal compound 40 (not shown) is the direction of the long side of the liquid crystal compound 40.

[0174] In the optical anisotropy layer 36a, the orientation of the optical axis of the liquid crystal compound 40 changes continuously while rotating along multiple directions from the center of the optical anisotropy layer 36a outward, such as the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3, etc. Arrows A1, A2, and A3 are arranged axes as described later.

[0175] The optical anisotropy layer 36a of the liquid crystal diffraction element has a liquid crystal alignment pattern in different regions within the plane, with one period Λ of the liquid crystal alignment pattern. Here, one period Λ of the liquid crystal alignment pattern refers to the length (distance) of the optical axis of the liquid crystal compound 40 rotating 180° in a direction in which the orientation of the in-plane optical axis of the liquid crystal alignment pattern changes continuously.

[0176] Specifically, for example, in Figure 13 Along the direction of arrow A1, the structure has the following characteristics: In a direction where the orientation of the optical axis of the liquid crystal compound 40 changes while rotating continuously, one period Λ gradually shortens from the center outwards. That is, in... Figure 13 In the middle, a cycle near the outer edge is shorter than a cycle near the center.

[0177] Furthermore, in this invention, a gradual change in one cycle Λ refers to both a continuous change in one cycle Λ and a phased change in one cycle Λ.

[0178] As will be explained in detail later, the diffraction angle of a liquid crystal diffraction element depends on one period Λ of the liquid crystal alignment pattern. The smaller the period Λ, the larger the diffraction angle.

[0179] If the optical anisotropy layer 36a has a liquid crystal alignment pattern that radiates from the center of the optical anisotropy layer 36a and changes direction as the optical axis of the liquid crystal compound 40 rotates continuously, and in each direction, the period Λ of the liquid crystal alignment pattern gradually shortens from the center outwards, then circularly polarized light incident on the optical anisotropy layer 36a having this liquid crystal alignment pattern will bend (diffuse) in different local regions where the optical axis of the liquid crystal compound 40 is oriented differently. In this case, each diffraction angle will differ according to one period in the region where the circularly polarized light is incident. The optical anisotropy layer 36a having a concentric liquid crystal alignment pattern, i.e., a liquid crystal alignment pattern that radiates as the optical axis rotates continuously, can transmit incident light as converging 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.

[0180] That is, by setting the liquid crystal alignment pattern of the optical anisotropic layer 36a to a concentric circle, the liquid crystal diffraction element 10a can function as a convex lens, for example.

[0181] Here, in this invention, as Figure 1 As shown, the optical anisotropic layer 36a has a bright part 42 and a dark part 44 extending from one surface to another in the SEM image. The dark part 44 has more than two inflection points and has regions with different tilt directions of the dark part 44 in the thickness direction.

[0182] exist Figure 1 In the example shown, the optical anisotropic layer 36a has a stripe pattern of bright areas 42 and dark areas 44. Each dark area 44 has a different tilt angle relative to the surface at two locations in the thickness direction. That is, each dark area 44 has two inflection points. Furthermore, in any dark area 44, the tilt direction in the upper region of the figure is opposite to the tilt direction in the lower region of the figure. That is, each dark area 44 has regions with different tilt directions.

[0183] and, Figure 9 The liquid crystal diffraction element shown has a support 30, but the support 30 may not be provided.

[0184] For example, the optical element of the present invention can also be constructed according to the above structure by peeling off the support 30 and making only the alignment film and liquid crystal layer, or by peeling off the alignment film and making only the liquid crystal layer.

[0185] That is, any liquid crystal diffraction element can utilize various layer structures as long as the liquid crystal layer has a liquid crystal alignment pattern that originates from the optical axis of the liquid crystal compound and rotates in one direction.

[0186] As described above, in the liquid crystal diffraction element of the present invention, the dark region 44 observed in the cross-sectional SEM image has two or more inflection points at different angles, and has regions with different tilt directions in the thickness direction. Therefore, the diffraction efficiency of the liquid crystal diffraction element of the present invention has low wavelength dependence, and it can diffract light with the same diffraction efficiency regardless of the wavelength. Furthermore, this liquid crystal diffraction element of the present invention can diffract light with high diffraction efficiency regardless of the wavelength.

[0187] Furthermore, in the liquid crystal alignment pattern of the liquid crystal diffraction element of the present invention, the length of one cycle of a 180° rotation of the optical axis can be varied in-plane. When the length of one cycle is varied in-plane, the liquid crystal diffraction element of the present invention diffracts (refracts) light of the same wavelength at different angles depending on the incident position of the light in the plane. Therefore, the liquid crystal diffraction element of the present invention can also be used in various optical devices that require lens elements in VR head-mounted displays and lens elements that improve color splitting by combining with refractive lenses to diffract light of the same wavelength at different angles regardless of the incident position.

[0188] <<Support>>

[0189] The support 30 supports the orientation film 32 and the optical anisotropy layer 36a.

[0190] As long as it can support the alignment film and the optical anisotropic layer, the support 30 can utilize various sheet-like materials (films, plates).

[0191] The support 30 is preferably a transparent support, and examples include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, cyclic olefin polymer films (e.g., those manufactured under the trade name "ARTON" by JSR Corporation, and those manufactured under the trade name "ZEONOR" by Zeon Corporation), polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride. The support is not limited to flexible films and can be a non-flexible substrate such as a glass substrate.

[0192] Furthermore, the support 30 can be multi-layered. Examples of multi-layered supports include any of the aforementioned supports serving as a substrate, with other layers disposed on the surface of that substrate.

[0193] There is no limitation on the thickness of the support 30. As long as the thickness is appropriately set according to the application of the liquid crystal diffraction element and the forming material of the support 30, the thickness of the alignment film and the optical anisotropy layer can be maintained.

[0194] 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.

[0195] <<Orientation Membrane>>

[0196] An orientation film 32 is formed on the surface of the support 30.

[0197] The alignment film 32 is an alignment film used to align the liquid crystal compound 40 into the liquid crystal alignment pattern specified above when forming the optical anisotropic layer 36a.

[0198] As described above, in the liquid crystal diffraction element of the present invention, the optical anisotropy layer has an optical axis 40A derived from the liquid crystal compound 40 (see reference). Figure 8 The orientation of the liquid crystal alignment pattern changes as it rotates continuously in one in-plane direction (arrow X direction described later). Therefore, the alignment film is formed so that the optical anisotropic layer can form this liquid crystal alignment pattern.

[0199] Furthermore, in one direction where the orientation of the optical axis 30A changes continuously as it rotates in the liquid crystal alignment pattern, the length of 180° rotation of the orientation of the optical axis 30A is defined as one cycle Λ (rotation cycle of the optical axis).

[0200] In the following description, "orientation rotation of optical axis 40A" will also be referred to as "rotation of optical axis 40A".

[0201] Orientation films can utilize a variety of known orientation films.

[0202] Examples include triboelectric films formed from organic compounds such as polymers, tilted vapor-deposited films of inorganic compounds, films with microgrooves, and films formed by accumulating organic compounds such as ω-trisanoic acid, dioctadecylmethylammonium chloride, and methyl stearate using the Langmuir-Blodgett process.

[0203] The alignment film based on friction treatment can be formed by repeatedly rubbing the surface of the polymer layer with paper or cloth in a specified direction. Preferred materials used in the alignment film include polyimide, polyvinyl alcohol, polymers with polymerizable groups as described in Japanese Patent Application Publication No. 9-152509, and alignment films as described in Japanese Patent Application Publication Nos. 2005-97377, 2005-99228, and 2005-128503.

[0204] In the liquid crystal diffraction element of the present invention, the alignment film is preferably a so-called photoalignment film formed by irradiating polarized or unpolarized light with a light-oriented raw material. That is, in the liquid crystal diffraction element of the present invention, as the alignment film, a photoalignment film formed by coating a light-oriented material on a support 30 is preferably used.

[0205] Regarding the irradiation of polarized light, it can be performed from a direction perpendicular to or inclined relative to the photo-alignment film; regarding the irradiation of unpolarized light, it can be performed from a direction inclined relative to the photo-alignment film.

[0206] Examples of photoalignment materials that can be used in the photoalignment film of the present invention include Japanese Patent Application Publication Nos. 2006-285197, 2007-76839, 2007-138138, 2007-94071, 2007-121721, 2007-140465, and 2007-156. The azo compounds described in Japanese Patent Publication No. 439, Japanese Patent Application Publication No. 2007-133184, Japanese Patent Application Publication No. 2009-109831, Japanese Patent Publication No. 3883848 and Japanese Patent Publication No. 4151746, the aromatic ester compounds described in Japanese Patent Application Publication No. 2002-229039, and Japanese Patent Application Publication No. 2002-265541 and Japanese Patent Application Publication No. 2002-317013 The described maleimide and / or alkenyl-substituted nadicimide compounds having photooriented units, the photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, the photocrosslinkable polyimides, photocrosslinkable polyamides and photocrosslinkable polyamides described in Japanese Patent Nos. 2003-520878, 2004-529220 and 4162850, are all examples of such compounds. Esters and photodimerizable compounds, particularly cinnamic acid esters, chalcone compounds and coumarin compounds, as described in Japanese Patent Application Publication Nos. 9-118717, 10-506420, 2003-505561, International Publication No. 2010 / 150748, 2013-177561 and 2014-12823, are preferred examples.

[0207] Among them, azo compounds, photocrosslinked polyimides, photocrosslinked polyamides, photocrosslinked esters, cinnamic acid ester compounds and chalcone compounds are preferred.

[0208] There is no limit to the thickness of the alignment film; as long as the thickness is appropriately set according to the forming material of the alignment film, the required alignment function can be obtained.

[0209] The thickness of the alignment film is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0210] There are no limitations on the method of forming the alignment film, and various known methods corresponding to the materials used to form the alignment film can be used. As an example, a method can be illustrated by coating the alignment film onto the surface of the support 30 and drying it, and then exposing the alignment film with a laser beam to form an alignment pattern.

[0211] exist Figure 10 The image shows an example of an exposure apparatus that forms the aforementioned orientation pattern by exposing an alignment film.

[0212] Figure 10 The exposure apparatus 60 shown includes: a light source 64 with a laser 62; a λ / 2 plate 65 for changing the polarization direction of the laser beam M emitted from the laser 62; a beam splitter 68 for separating the laser beam M emitted from the laser 62 into two beams, MA and MB; mirrors 70A and 70B respectively disposed on the optical paths of the two separated beams MA and MB; and λ / 4 plates 72A and 72B.

[0213] Additionally, although the illustration is omitted, light source 64 emits linearly polarized light P0. Plate 72A λ / 4 converts the linearly polarized light P0 (ray MA) into right-handed circularly polarized light P... R The λ / 4 plate 72B converts linearly polarized light P0 (ray MB) into left-handed circularly polarized light P L .

[0214] A support 30 having an alignment film 32 before the alignment pattern is formed is disposed in the exposure section, so that two rays MA and MB cross and interfere on the alignment film 32, and the interference light is irradiated onto the alignment film 32 for exposure.

[0215] Through this interference, the polarization state of the light incident on the alignment film 32 changes periodically in the form of interference fringes. Thus, an alignment pattern in the alignment film 32 in which the alignment state changes periodically can be obtained. That is, an alignment film (hereinafter also referred to as a patterned alignment film) with an alignment pattern in which the alignment state changes periodically can be obtained.

[0216] In the exposure apparatus 60, the period of the alignment pattern can be adjusted by changing the cross angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the cross angle α, in an alignment pattern in which the optical axis 40A originating from the liquid crystal compound 40 rotates continuously in one direction, the length of one period (one period Λ) of rotating the optical axis 40A 180° in the direction in which the optical axis 40A is rotated can be adjusted.

[0217] By forming an optically anisotropic layer on a patterned alignment film having an alignment pattern that periodically changes in such an alignment state, as described later, it is possible to form an optically anisotropic layer 36a having a liquid crystal alignment pattern that continuously rotates in one direction along an optical axis 40A derived from the liquid crystal compound 40.

[0218] Furthermore, the rotation direction of optical axis 40A can be reversed by rotating the optical axes of λ / 4 plates 72A and 72B by 90° respectively.

[0219] As described above, the patterned alignment film has an alignment pattern that aligns the liquid crystal compound 40 to form a liquid crystal alignment pattern in which the orientation of the optical axis originating from the liquid crystal compound in the optical anisotropy layer formed on the patterned alignment film changes while continuously rotating in at least one in-plane direction. If the axis along which the liquid crystal compound 40 is oriented is defined as the alignment axis of the patterned alignment film, it can be said that the patterned alignment film has an alignment pattern in which the orientation of the alignment axis changes while continuously rotating in at least one in-plane direction. The alignment axis of the patterned alignment film can be detected by measuring absorption anisotropy. For example, when linearly polarized light is irradiated onto the patterned alignment film while rotating, and the amount of light transmitted through the patterned alignment film is measured, it can be observed that the direction in which the light amount becomes maximum or minimum gradually changes in one in-plane direction.

[0220] Furthermore, in the liquid crystal diffraction element of the present invention, the alignment film is preferably provided, but it is not a necessary component.

[0221] For example, an orientation pattern can be formed on the support 30 by a method of rubbing the support 30 or by processing the support 30 with a laser beam, etc., so that it can also be configured as a structure such as the optical anisotropy layer 36a having a liquid crystal orientation pattern that changes as the orientation of the optical axis 40A originating from the liquid crystal compound 40 rotates continuously in at least one direction in the plane.

[0222] The exposure device for the alignment film 32 is not limited to, for example, Figure 10 The example shown. Figure 14 Another example of an exposure apparatus for exposing alignment film 32 is shown. Figure 14 The exposure apparatus shown is formed in the alignment film as follows Figure 13 An example of an exposure apparatus with a concentric circle orientation pattern is shown.

[0223] The exposure apparatus 80 includes a light source 84 with a laser 82, a polarization beam splitter 86 that splits the laser beam M from the laser 82 into S-polarized MS and P-polarized MP, a reflector 90A disposed in the optical path of P-polarized MP and a reflector 90B disposed in the optical path of S-polarized MS, a lens 92 disposed in the optical path of S-polarized MS, a polarization beam splitter 94, and a λ / 4 plate 96.

[0224] The P-polarized MP, separated by polarization beam splitter 86, is reflected by mirror 90A and incident on polarization beam splitter 94. On the other hand, the S-polarized MS, separated by polarization beam splitter 86, is reflected by mirror 90B, converged by lens 92, and incident on polarization beam splitter 94.

[0225] P-polarized MP and S-polarized MS are combined by polarization beam splitter 94, and then passed through λ / 4 plate 96 to become right-hand circularly polarized light and left-hand circularly polarized light corresponding to the polarization direction, and then incident on the alignment film 32 on the support 30.

[0226] Here, through the interference of right-handed and left-handed circularly polarized light, the polarization state of the light illuminating the alignment film changes periodically in the form of interference fringes. Since the cross angle between the left-handed and right-handed circularly polarized light changes from the inside to the outside of the concentric circles, an exposure pattern in which the pitch changes from the inside to the outside can be obtained. Thus, a concentric circular alignment pattern in the alignment film with a periodically changing alignment state can be obtained.

[0227] In this exposure apparatus 80, one cycle Λ of the liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 40 rotates continuously by 180° in one direction can be controlled by changing the refractive power (F-value of the lens 92), the focal distance of the lens 92, and the distance between the lens 92 and the alignment film 32.

[0228] Furthermore, by adjusting the refractive power of lens 92 (F-value of lens 92), the length Λ of one cycle of the liquid crystal orientation pattern can be changed in one direction of continuous rotation of the optical axis.

[0229] Specifically, by adjusting the expansion angle of the light, which is expanded by lens 92 and interferes with parallel light, the length Λ of one cycle of the liquid crystal alignment pattern can be changed in one direction of continuous rotation of the optical axis. More specifically, if the refractive power of lens 92 is reduced, the light approaches parallelism, and therefore the length Λ of one cycle of the liquid crystal alignment pattern gradually shortens from the inside to the outside, and the F-value increases. Conversely, when the refractive power of lens 92 is increased, the length Λ of one cycle of the liquid crystal alignment pattern suddenly shortens from the inside to the outside, and the F-value decreases.

[0230] Furthermore, for example, when it is desired to set the light intensity distribution of transmitted light, depending on the application of the liquid crystal diffraction element, a structure can be used that does not gradually change the direction of one period Λ towards the alignment axis D, but has a region that is locally different for one period Λ in the direction of the alignment axis D. For example, as a method to locally change one period Λ, a method of patterning the photo-alignment film by scanning and exposing while arbitrarily changing the polarization direction of the focused laser beam can be used.

[0231] Furthermore, the wavelength of the laser used for exposing the alignment film can be appropriately set according to the type of alignment film used. For example, lasers with wavelengths in the deep ultraviolet, visible, and infrared ranges are preferred. As an example, lasers with wavelengths of 266nm, 325nm, 355nm, 370nm, 385nm, 405nm, and 460nm can be used, but they are not limited to the above, and various wavelengths of lasers can be used depending on the type of alignment film.

[0232] After an optical anisotropic layer is formed on an alignment film, the optical anisotropic layer can be peeled off and transferred from the alignment film. The transfer can also be performed multiple times depending on the bonding surface of the optical anisotropic layer. The peeling and transfer method can be freely selected according to the purpose; however, for example, after transferring once onto a substrate with an adhesive layer, and then transferring to the object to be transferred, peeling off the substrate allows the alignment film side of the optical anisotropic layer to become the object side. Furthermore, if the side of the optical anisotropic layer opposite to the alignment film is set as the object side to be transferred, the optical anisotropic layer and the object to be transferred can be bonded together with an adhesive, and then the optical anisotropic layer can be peeled off from the alignment film.

[0233] When peeling the optical anisotropic layer from the alignment film, in order to reduce damage (cracks, fissures, etc.) to the optical anisotropic layer and the alignment film, it is preferable to adjust the peeling angle and speed.

[0234] Furthermore, the alignment film can be reused within the range where orientation is not an issue. Before applying an optical anisotropy layer to the alignment film, it can be cleaned with organic solvents or the like.

[0235] <<Optical Anisotropic Layer>>

[0236] An optically anisotropic layer 36a is formed on the surface of the alignment film 32.

[0237] In addition, Figure 8 In the diagram, only the liquid crystal compound 40 (liquid crystal compound molecules) on the surface of the alignment film is shown in the optical anisotropic layer 36a to simplify the figures and clearly illustrate the structure of the optical anisotropic layer 36a. However, as in Figure 9 The optical anisotropy layer 36a is illustrated and conceptually shown. The optical anisotropy layer 36a has a structure formed by stacking liquid crystal compounds 40 in the same manner as optical anisotropy layers formed using compositions containing conventional liquid crystal compounds.

[0238] Furthermore, as described above, the optical anisotropy layer 36a has three regions—region 37c, region 37b, and region 37a—from below, based on the inflection point of the dark area 44. However, in Figure 9 In order to simplify the accompanying drawings, only the lowermost region 37c (side of support 30) is shown.

[0239] As described above, in the liquid crystal diffraction element of the present invention, the optical anisotropy layer 36a is formed using a composition comprising a liquid crystal compound.

[0240] When the in-plane delay is set to λ / 2, the optical anisotropic layer functions as a general λ / 2 plate, that is, it imparts a half-wavelength, or 180°, phase difference to the two orthogonal linearly polarized light components contained in the light incident on the optical anisotropic layer.

[0241] Here, because the liquid crystal compound rotates and aligns in the in-plane direction, the optical anisotropy layer causes the incident circularly polarized light to be refracted (diffracted) and transmitted in the direction in which the optical axis rotates continuously. At this time, the direction of diffraction varies depending on the rotation direction of the incident circularly polarized light.

[0242] That is, the optical anisotropic layer transmits circularly polarized light and diffracts the transmitted light.

[0243] Furthermore, the optical anisotropic layer changes the rotation direction of the transmitted circularly polarized light to the opposite direction.

[0244] The optical anisotropy layer 36a has a liquid crystal alignment pattern that changes as it rotates continuously in a direction indicated by arrow D (hereinafter also referred to as alignment axis D) within the plane of the optical anisotropy layer, originating from the optical axis of the liquid crystal compound. Figure 8 In the example shown, the direction of the arrangement axis D is set as the X direction, and the direction orthogonal to the direction of the arrangement axis D is set as the Y direction.

[0245] Furthermore, the optical axis 40A originating from the liquid crystal compound 40 is the axis with the highest refractive index in the liquid crystal compound 40, also known as the slow axis. For example, in the case where 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.

[0246] In the following description, the optical axis 40A derived from the liquid crystal compound 40 will also be referred to as "optical axis 40A of liquid crystal compound 40" or "optical axis 40A".

[0247] In the optical anisotropic layer, the liquid crystal compound 40 is oriented in two dimensions in the optical anisotropic layer 36a in a direction parallel to both the X-direction of the arrow and the Y-direction orthogonal to the X-direction. Furthermore, in Figures 1-6 In this case, the Y direction becomes the direction perpendicular to the plane of the paper.

[0248] Figure 8 The diagram above is a conceptual representation of the planar structure of the optical anisotropy layer 36a.

[0249] Floor plan Figure 9The middle image is a view of the liquid crystal diffraction element from above, that is, a view of the liquid crystal diffraction element viewed from the thickness direction (= the stacking direction of each layer (film)). In other words, it is a view of the optical anisotropic layer 36a viewed from a direction orthogonal to the surface.

[0250] Furthermore, in Figure 8 In this diagram, only the liquid crystal compound 40 on the surface of the alignment film 32 is shown to clearly illustrate the structure of the liquid crystal diffraction element of the present invention. However, as... Figure 9 As shown, the optical anisotropy layer 36a has a structure in the thickness direction formed by stacking liquid crystal compounds 40 from the surface of the alignment film 32.

[0251] In addition, Figure 8 In this example, a portion of the plane of the optical anisotropic layer 36a is used as a representative example. However, the structure and function are basically the same at each position within the plane of the optical anisotropic layer.

[0252] The optical anisotropy layer 36a has a liquid crystal alignment pattern in which the orientation of the optical axis 40A changes as it rotates continuously in the plane of the optical anisotropy layer 36a along the alignment axis D direction.

[0253] The orientation of the optical axis 40A changes as it rotates continuously along the arrangement axis D (a specified direction). Specifically, the angle between the optical axis 40A of the liquid crystal compound 40 arranged along the arrangement axis D and the arrangement axis D varies depending on the position of the arrangement axis D. Along the arrangement axis D, the angle between the optical axis 40A and the arrangement axis D changes sequentially from θ to θ+180° or θ-180°.

[0254] Furthermore, the angle difference between the optical axes 40A of the liquid crystal compounds 40 that are adjacent to each other in the direction of the arrangement axis D is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0255] On the other hand, in the liquid crystal compound 40 that forms the optical anisotropic layer 36a, the liquid crystal compounds 40 with the same orientation of the optical axis 40A are arranged at equal intervals in the Y direction orthogonal to the arrangement axis D direction, that is, in the Y direction orthogonal to a direction in which the optical axis 40A rotates continuously.

[0256] In other words, in the liquid crystal compound 40 that forms the optical anisotropic layer 36a, the orientation of the optical axis 40A of the liquid crystal compounds 40 arranged in the Y direction is equal to the angle formed by the direction of the arrangement axis D.

[0257] In the liquid crystal diffraction element of the present invention, in the liquid crystal alignment pattern of the liquid crystal compound 40, the length (distance) by which the orientation of the in-plane optical axis 40A changes by continuously rotating along the alignment axis D is defined as the length Λ of one cycle in the liquid crystal alignment pattern. In other words, the length of one cycle in the liquid crystal alignment pattern is defined by the distance from θ to θ+180° between the angle formed by the optical axis 40A and the alignment axis D. The length of one cycle in the liquid crystal alignment pattern is the length of one cycle in the periodic structure of the diffraction element.

[0258] That is, the distance between the centers of two liquid crystal compounds 40 with equal angles relative to the alignment axis D along the alignment axis D is defined as the length Λ of one period. Specifically, as... Figure 8 As shown, the distance between the centers of two liquid crystal compounds 40 whose alignment axis D is aligned with the optical axis 40A is defined as the length Λ of one period. In the following description, this length Λ of one period will also be referred to as "one period Λ".

[0259] In the liquid crystal diffraction element of the present invention, the liquid crystal alignment pattern of the optical anisotropy layer repeats one cycle Λ in a direction that changes continuously by rotating along the alignment axis D, i.e., the orientation of the optical axis 40A.

[0260] As described above, in the optical anisotropic layer, among the liquid crystal compounds arranged in the Y direction, the angle formed by the optical axis 40A and the arrangement axis D direction (a direction in which the optical axis of the liquid crystal compound 40 is rotated) is equal. The region in the Y direction where the liquid crystal compound 40 with the angle formed by the optical axis 40A and the arrangement axis D direction is equal is designated as region R.

[0261] In this case, the preferred value of the in-plane retardation (Re) in each region R is half the wavelength, i.e., λ / 2. These in-plane retardations are calculated by multiplying the refractive index difference Δn associated with the refractive index anisotropy of region R by the thickness of the optical anisotropy layer. The refractive index difference associated with the refractive index anisotropy of region R in the optical anisotropy layer is defined as the difference between the refractive index in the direction passing through the slow axis within the plane of region R and the refractive index in the direction orthogonal to the slow axis. That is, the refractive index difference Δn associated with 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 within the plane of region R. In other words, the aforementioned refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

[0262] If circularly polarized light is incident on this optical anisotropic layer 36a, the light is diffracted (refracted), and the direction of the circularly polarized light is reversed.

[0263] Through Figure 11 and Figure 12 The optical anisotropic layer 36a is illustrated and conceptually represented. Additionally, in Figure 11 and Figure 12 In the figure, only the liquid crystal compound 40 (liquid crystal compound molecules) on the surface of the alignment film is shown in the optical anisotropy layer 36a to simplify the figure and clearly show the structure of the liquid crystal diffraction element.

[0264] Furthermore, the optical anisotropy layer 36a is set to have a value of λ / 2, which is the product of the refractive index difference of the liquid crystal compound and the thickness of the optical anisotropy layer.

[0265] like Figure 11 As shown, when the product of the refractive index difference of the liquid crystal compound in the optical anisotropic layer 36a and the thickness of the optical anisotropic layer is λ / 2, if the incident light L1, which is left-handed circularly polarized light, is incident on the optical anisotropic layer 36a, the incident light L1 passes through the optical anisotropic layer 36a and is given a phase difference of 180°, thereby converting the transmitted light L2 into right-handed circularly polarized light.

[0266] Furthermore, the liquid crystal alignment pattern formed on the optical anisotropic layer 36a is a periodic pattern along the alignment axis D, so the transmitted light L2 travels in a direction different from the direction of travel of the incident light L1. In this way, the incident light L1 of left-handed circularly polarized light is converted into the transmitted light L2 of right-handed circularly polarized light that is tilted at a predetermined angle relative to the incident direction along the alignment axis D.

[0267] On the other hand, such as Figure 12 As shown, when the product of the refractive index difference of the liquid crystal compound in the optical anisotropic layer 36a and the thickness of the optical anisotropic layer 36a is λ / 2, if the incident light L4 of right-hand circularly polarized light is incident on the optical anisotropic layer 36a, the incident light L4 passes through the optical anisotropic layer 36a and is given a phase difference of 180°, thereby being converted into the transmitted light L5 of left-hand circularly polarized light.

[0268] Furthermore, the liquid crystal alignment pattern formed on the optical anisotropic layer 36a is a periodic pattern along the alignment axis D, so the transmitted light L5 travels in a direction different from the direction of travel 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 relative to the incident direction. In this way, the incident light L4 is converted into the transmitted light L5, which is left-handed circularly polarized light tilted at a predetermined angle relative to the incident direction in a direction opposite to the direction of the alignment axis D.

[0269] The optical anisotropy layer 36a can adjust the diffraction (refraction) angles of transmitted light L2 and L5 by changing one period Λ of the formed liquid crystal alignment pattern. Specifically, the shorter the one period Λ of the liquid crystal alignment pattern in the optical anisotropy layer 36a, the stronger the interference between the light passing through adjacent liquid crystal compounds 40, thus enabling greater diffraction of transmitted light L2 and L5.

[0270] Furthermore, by reversing the rotation direction of the optical axis 40A of the liquid crystal compound 40, which rotates along the alignment axis D, the direction of diffraction of the transmitted light can be reversed. That is, in Figures 11-12 In the example shown, the optical axis 40A, which is oriented toward the alignment axis D, rotates clockwise. However, by setting the rotation direction to counterclockwise, the direction of diffraction of the transmitted light can be reversed.

[0271] Here, the diffraction angle (refractive angle) based on the optical anisotropy layer 36a varies depending on the wavelength of the incident light. Specifically, the longer the wavelength of light, the greater the diffraction. That is, among red, green, and blue light, red light diffracts the most, followed by green light, and blue light diffracts the least.

[0272] Furthermore, in this invention, one period Λ in the liquid crystal alignment pattern of the optical anisotropy layer 36a is uniform. Therefore, light of the same wavelength diffracts at the same angle.

[0273] As described above, the angle of the dark portion 44 relative to the surface of the optical anisotropic layer can be adjusted according to the length of one cycle of the optical axis of the liquid crystal compound rotating 180° in one direction in the plane and the magnitude of the twist of the liquid crystal compound 40 which is twisted in the thickness direction.

[0274] The shorter the period Λ and the smaller the twist in the thickness direction, the larger the angle of the dark part 44 relative to the surface of the optical anisotropic layer. That is, the shorter the period and the smaller the twist in the thickness direction, the more the dark part 44 becomes upright relative to the surface of the optical anisotropic layer.

[0275] As mentioned above, the shorter the period Λ of the liquid crystal alignment pattern, the larger the diffraction angle of the incident light.

[0276] Furthermore, the tilt direction of the dark area 44, such as the tilt direction towards the upper right of the figure and the tilt direction towards the upper left of the figure, can be selected according to 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 thickness direction of the liquid crystal compound 40.

[0277] In the optical anisotropy layer 36a, the in-plane retardation value of the plurality of regions R is preferably half a wavelength, but more preferably the in-plane retardation Re(550) = Δn of the plurality of regions R of the optical anisotropy layer 36a relative to incident light with a wavelength of 550 nm. 550 ×d is within the range specified in equation (1) below. Here, Δn 550 d is the refractive index difference associated with the anisotropy of the refractive index in region R when the wavelength of the incident light is 550 nm, and d is the thickness of the optical anisotropy layer 36a.

[0278] 200nm≤Δn 550 ×d≤350nm……(1)

[0279] That is, if the in-plane delay Re(550) of multiple regions R of the optical anisotropy layer 36a is Δn 550 If ×d satisfies equation (1), then a sufficient amount of circularly polarized light components incident on the optical anisotropic layer 36a can be converted into circularly polarized light traveling in a direction inclined in the positive or negative direction relative to the arrangement axis D. In-plane delay Re(550)=Δn 550 ×d is more preferably 225nm≤Δn 550 ×d≤340nm, more preferably 250nm≤Δn 550 ×d≤330nm.

[0280] Equation (1) above represents the in-plane delay Re(λ) = Δn of multiple regions R of the optical anisotropy layer relative to incident light with a wavelength of 550 nm and an incident light with a wavelength of λ nm. λ ×d is preferably set appropriately within the range specified in the following formula (1-2).

[0281] 0.7×(λ / 2)nm≤Δn λ ×d≤1.3×(λ / 2)nm……(1-2)

[0282] Furthermore, the in-plane delay values ​​of multiple regions R in the optical anisotropy layer 36a can also be used outside the range of the above equation (1). Specifically, by setting it as Δn 550 ×d < 200nm or 350nm < Δn 550 ×d can be divided into light traveling in the same direction as the incident light and light traveling in a different direction than the incident light. When Δn 550 When ×d approaches 0nm or 550nm, the component of light traveling in the same direction as the incident light increases, while the component of light traveling in a different direction from the incident light decreases.

[0283] Furthermore, the in-plane retardation Re(450) = Δn in region R of the optical anisotropy layer 36a relative to incident light with a wavelength of 450 nm 450 ×d, the in-plane retardation Re(550)=Δn of region R of optical anisotropy layer 36a relative to incident light with wavelength of 550nm. 550 ×d preferably satisfies the following equation (2). Here, Δn 450 It is the refractive index difference caused by the anisotropy of the refractive index in region R when the wavelength of the incident light is 450nm.

[0284] (Δn 450 ×d) / (Δn 550 ×d)<1.0……(2)

[0285] Equation (2) indicates that the liquid crystal compound 40 contained in the optical anisotropic layer 36a has reverse dispersion. That is, by satisfying equation (2), the optical anisotropic layer 36a can correspond to incident light with a wide bandwidth wavelength.

[0286] The optical anisotropy layer is composed of a cured layer of a liquid crystal composition containing rod-shaped liquid crystal compounds or disk-shaped liquid crystal compounds, and has a liquid crystal alignment pattern with the optical axes of the rod-shaped liquid crystal compounds or the optical axes of the disk-shaped liquid crystal compounds as described above.

[0287] An optical anisotropic layer is formed on a support 30 by forming an alignment film 32 with the above-mentioned alignment pattern, and then coating the alignment film with a liquid crystal composition and curing it.

[0288] Furthermore, the structure in which the optical axis of the liquid crystal compound is spirally twisted and rotated in the thickness direction of the optical anisotropic layer can be formed by adding a chiral agent to the liquid crystal composition to cause the liquid crystal compound to be spirally oriented in the thickness direction.

[0289] Furthermore, in order to create a structure in which the optical anisotropic layer has regions with more than two inflection points in the dark region 44 and different tilt directions in the thickness direction, it is sufficient to form an optical anisotropic layer with a different structure in each region in the thickness direction.

[0290] For example, in the formation Figure 1 In the case of the optical anisotropy layer 36a shown, firstly, a liquid crystal composition containing a chiral reagent that causes right-hand twisting in the thickness direction is coated on an alignment film 32 with an alignment pattern formed on the support 30. 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 region 37c.

[0291] The alignment pattern formed on the alignment film 32 is an alignment pattern derived from the continuous rotation of the optical axis 40A of the liquid crystal compound 40 in one in-plane direction (alignment axis D). Therefore, in region 37c, the state is such that the optical axis 40A of the liquid crystal compound 40 rotates continuously in one in-plane direction, and in the thickness direction, the liquid crystal compound 40 is oriented in a clockwise twist from above to below in the thickness direction.

[0292] The bonding process involves coating the same liquid crystal composition as region 37c with the liquid crystal composition, except that the formed region 37c does not contain a chiral reagent, and then curing the liquid crystal composition to form region 37b.

[0293] When a liquid crystal layer is formed on a liquid crystal layer by a coating method, the alignment pattern of the liquid crystal compound in the plane follows the alignment pattern of the underlying liquid crystal layer. Therefore, region 37b is the same as region 37c in the in-plane direction, originating from the continuous rotation of the optical axis 40A of the liquid crystal compound 40 in one direction, and is aligned without twisting in the thickness direction, with the optical axis 40A of the liquid crystal compound 40 in the same direction.

[0294] In addition, the same liquid crystal composition as that in region 37c is coated on region 37b except for the use of a chiral reagent that causes leftward twisting in the thickness direction. After the liquid crystal compound 40 is twisted and oriented in the thickness direction by heating or the like, the liquid crystal composition is cured to form region 37a.

[0295] As described above, the liquid crystal layer formed by the coating method follows the orientation pattern of the underlying layer. Therefore, region 37a is the same as region 37b in the in-plane direction, and the optical axis 40A rotates continuously in one direction. Furthermore, in the thickness direction, the liquid crystal compound 40 is oriented in a counterclockwise twist from the top to the bottom in the thickness direction.

[0296] Therefore, it is possible to form such as Figure 1 The optical anisotropy layer 36a shown includes a region 37c with the dark portion 44 tilted towards the upper left, a region 37b with the dark portion 44 extending along the thickness direction, and a region 37a with the dark portion 44 tilted towards the upper left.

[0297] The magnitude of the twist orientation of a liquid crystal compound in the thickness direction can be adjusted according to the type and amount of chiral reagent added to the liquid crystal composition.

[0298] Furthermore, the twisting direction (right-hand twist / left-hand twist) of the liquid crystal compound in the thickness direction can also be selected by choosing the type of chiral reagent added to the liquid crystal composition.

[0299] And, as Figure 1The illustration shows an example where the optical axis originating from the liquid crystal compound at the interface of the optical anisotropy layer of the present invention is not tilted relative to the interface of the optical anisotropy layer. However, in the optical anisotropy layer of the present invention, the optical axis originating from the liquid crystal compound can be tilted. For example, as described in WO2019 / 189586A1, the optical axis originating from the liquid crystal compound can have a pretilt angle relative to the interface of the optical anisotropy layer. Furthermore, as described in WO2020 / 122127A1, the tilt angle of the optical axis originating from the liquid crystal compound from one interface of the optical anisotropy layer toward another interface in the thickness direction can be changed. By tilting the optical axis originating from the liquid crystal compound relative to the interface of the optical anisotropy layer, the phase difference of the optical anisotropy layer can be adjusted, and it can be appropriately adjusted to obtain high diffraction efficiency.

[0300] Furthermore, in the optical anisotropic layer of the present invention, the film thickness of the optical anisotropic layer can be varied in-plane. In particular, in a liquid crystal diffraction element in which the length of one period in the liquid crystal alignment pattern varies in-plane, by changing the film thickness of the optical anisotropic layer in-plane, it is possible to appropriately adjust and obtain high diffraction efficiency relative to light with different incident positions.

[0301] Furthermore, in liquid crystal diffraction elements where the length of one period in the liquid crystal alignment pattern varies in-plane, the [variable]... Figure 1 The examples illustrate regions 37a, 37b, and 37c of the optical anisotropic layer, located in the central and outer portions, where the thickness of each region can be the same or different. Not limited to the above examples, the liquid crystal diffraction element of the present invention can make the thickness of each region of the optical anisotropic layer the same in plane, or it can vary. The thickness of each region of the optical anisotropic layer can be appropriately set according to the desired performance.

[0302] Furthermore, while optical anisotropic layers function as so-called λ / 2 plates, the present invention includes a laminated body integrally comprising a support and an alignment film, which functions as a λ / 2 plate.

[0303] Furthermore, the liquid crystal composition used to form the optical anisotropic layer contains rod-shaped liquid crystal compounds or disk-shaped liquid crystal compounds, and may contain other components such as leveling agents, orientation control agents, polymerization initiators, and orientation aids.

[0304] In this invention, the thickness of the optical anisotropic layer is not limited. The thickness that can achieve the target optical properties can be appropriately set according to one period Λ of the liquid crystal alignment pattern, the required diffraction angle and diffraction efficiency, etc.

[0305] Furthermore, the thickness of each region corresponding to the inflection point of the dark area 44 can be uniform or non-uniform, as long as it is set appropriately according to the required diffraction angle, etc.

[0306] -Rod-shaped liquid crystal compounds-

[0307] As rod-shaped liquid crystal compounds, preferably used are methylimine derivatives, azo derivatives, cyanobiphenyl derivatives, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane derivatives, cyano-substituted phenylpyrimidine derivatives, alkoxy-substituted phenylpyrimidine derivatives, phenyl dioxane derivatives, diphenylacetylene derivatives, and alkenylcyclohexylbenzonitrile derivatives. Not only can low-molecular-weight liquid crystal molecules like those mentioned above be used, but high-molecular-weight liquid crystal molecules can also be used.

[0308] More preferably, the orientation of the rod-shaped liquid crystal compound is fixed by polymerization. As a polymerizable rod-shaped liquid crystal compound, it can be used in Makromol. Chem., Vol. 190, pp. 2255 (1989), Advanced Materials. Compounds described in 5 volumes, 107 pages (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Application Publication No. 1-272,551, Japanese Patent Application Publication No. 6-16616, Japanese Patent Application Publication No. 7-110,469, Japanese Patent Application Publication No. 11-80081, and Japanese Patent Application Publication No. 2001-64627. Furthermore, as rod-shaped liquid crystal compounds, compounds described in Japanese Patent Application Publication No. 11-513019 and Japanese Patent Application Publication No. 2007-279688 are preferred.

[0309] -Disc-shaped liquid crystal compound-

[0310] As a disc-shaped liquid crystal compound, the disc-shaped liquid crystal compound described in Japanese Patent Application Publication No. 2007-108732 and Japanese Patent Application Publication No. 2010-244038 is preferred.

[0311] Furthermore, when a disk-shaped liquid crystal compound is used in the optical anisotropic layer, the liquid crystal compound 40 rises in the thickness direction in the optical anisotropic layer, and the optical axis 40A derived from the liquid crystal compound is defined as an axis perpendicular to the disk surface, the so-called fast axis.

[0312] To obtain high diffraction efficiency, liquid crystal compounds with high refractive index anisotropy Δn are preferred. By increasing the refractive index anisotropy, the diffraction efficiency can be maintained at a relatively high level when the incident angle changes. There are no particular limitations on the liquid crystal compound with high refractive index anisotropy Δn, but compounds exemplified in WO2019 / 182129A1 and compounds represented by the following general formula (I) are preferred.

[0313] [Chemical Formula 1]

[0314]

[0315] In general formula (I),

[0316] P 1 and P 2 Each can be used independently to represent a hydrogen atom, -CN, -NCS, or a polymeric group.

[0317] Sp 1 and Sp 2 Each can independently represent a single bond or a divalent linker. Where Sp 1 and Sp 2 It does not mean that it contains a divalent linker consisting of at least one group selected from the group consisting of aromatic hydrocarbon cyclic groups, aromatic heterocyclic groups and aliphatic hydrocarbon cyclic groups.

[0318] Z 1 Z 2 and Z 3These characters independently represent single bonds, -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-, and -SO-CH RCHR-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=NN=CR-, -CF=CF- or C≡C-. R represents a hydrogen atom or an alkyl group with 1 to 10 carbon atoms. When multiple Rs exist, they can be the same or different. When Z 1 and Z 2 When multiple Z exist, they can be the same or different. 3 They can be the same or different. Among them, those connected to Sp... 2 Z 3 Indicates a single key.

[0319] X 1 and X 2 Each can independently represent a single bond or an S-bond. Multiple X's exist. 1 and X 2 They can be the same or different. There are multiple X's. 1 And there are multiple X 2 In the above, at least one of them represents -S-.

[0320] k represents an integer from 2 to 4.

[0321] m and n each independently represent an integer from 0 to 3. There can be multiple m values, which can be the same or different.

[0322] A 1 A 2 A 3 and A 4Each of the following formulas (B-1) to (B-7) can independently represent a group formed by linking two or three groups represented by any one of the following formulas (B-1) to (B-7). Multiple A's exist. 2 and A 3 They can be the same or different. When A 1 and A 4 When multiple instances exist, they can be the same or different.

[0323] [Chemical Formula 2]

[0324]

[0325] In general formulas (B-1) to (B-7),

[0326] W 1 ~W 18 CR are represented independently. 1 Or N, R 1 L represents a hydrogen atom or the following substituent.

[0327] Y 1 ~Y 6 NR are represented independently. 2 O or S, R 2 L represents a hydrogen atom or the following substituent.

[0328] G 1 ~G 4 CR are represented independently. 3 R 4 NR 5 O or S, R 3 ~R 5 Each can be represented independently by a hydrogen atom or a substituent L as described below.

[0329] M 1 and M 2 CR are represented independently. 6 Or N, R 6 L represents a hydrogen atom or the following substituent.

[0330] * indicates the bonding location.

[0331] Substituent L is an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkanoyl group having 1 to 10 carbon atoms, an alkanoyloxy group having 1 to 10 carbon atoms, an alkanoylamino group having 1 to 10 carbon atoms, an alkanoylthio group having 1 to 10 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an alkylaminocarbonyl group having 2 to 10 carbon atoms, an alkanothiocarbonyl group having 2 to 10 carbon atoms, a hydroxyl group, an amino group, a mercapto group, a carboxyl group, a sulfonyl group, an amide group, a cyano group, a nitro group, a halogen atom, or a polymerizable group. Wherein, if the group described as substituent L has -CH2-, a group formed by replacing at least one of the -CH2- groups with -O-, -CO-, -CH=CH-, or -C≡C- is also included in substituent L. Furthermore, when the group described as substituent L has hydrogen atoms, a group formed by replacing at least one of the hydrogen atoms contained in the group with at least one selected from the group consisting of fluorine atoms and polymerizable groups is also included in substituent L.

[0332] To maintain high diffraction efficiency with varying incident angles, the refractive index anisotropy Δn of the liquid crystal compound is... 550 Preferably, it is 0.15 or more, more preferably 0.2 or more, even more preferably 0.25 or more, and most preferably 0.3 or more.

[0333] Furthermore, the liquid crystal diffraction element of the present invention can also change the refractive index anisotropy Δn or the average refractive index of the optical anisotropy layer in-plane. By changing the refractive index anisotropy Δn or the average refractive index of the optical anisotropy layer in-plane, the diffraction efficiency can be appropriately adjusted for light with different incident positions.

[0334] Chiral reagents

[0335] Chiral reagents have the function of inducing helical structures in which liquid crystal compounds are twisted and oriented in the thickness direction. Since the direction and / or degree of twist (helical pitch) of the helix induced by the compound are different, the chiral reagent can be selected according to the purpose.

[0336] There are no particular restrictions on the use of chiral reagents, and well-known compounds can be used (e.g., those described in the Liquid Crystal Device Handbook, Chapter 3, Item 4-3, TN (Twisted Nematic), STN (Super Twisted Nematic) chiral reagents, page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide (a chiral reagent with an isosorbide structure), and isomannitol derivatives, etc.

[0337] Furthermore, chiral reagents that undergo deisomerization, dimerization, and isomerization and dimerization through light irradiation, and chiral reagents that reduce helical torsion power (HTP) can also be preferentially utilized.

[0338] Chiral reagents typically contain asymmetric carbon atoms, but axially asymmetric or surface-asymmetric compounds that do not contain asymmetric carbon atoms can also be used as chiral reagents. Examples of axially asymmetric or surface-asymmetric compounds include naphthalene, helicene, p-xylene dimers, and their derivatives. Chiral reagents may also have polymerizable groups. When both the chiral reagent and the liquid crystal compound have polymerizable groups, a polymer having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral reagent can be formed by the polymerization reaction of the polymerizable chiral reagent and the polymerizable liquid crystal compound. In this manner, the polymerizable groups possessed by the polymerizable chiral reagent are preferably the same as those possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable groups of the chiral reagent are preferably unsaturated polymerizable groups, epoxy groups, or acridine groups, more preferably unsaturated polymerizable groups, and even more preferably olefinic unsaturated polymerizable groups.

[0339] Furthermore, the chiral reagent can also be a liquid crystal compound.

[0340] When the chiral reagent has a photoisomerizing group, it is preferable that a pattern corresponding to the emission wavelength can be formed by irradiation with a photomask such as activated light after coating and orientation. As the photoisomerizing group, it is preferable to be an isomerization site of a compound exhibiting photochromic properties, an azo group, an oxyazo group, or a cinnamyl group. As specific compounds, the compounds described in Japanese Patent Application Publication Nos. 2002-080478, 2002-080851, 2002-179668, 2002-179669, 2002-179670, 2002-179681, 2002-179682, 2002-338575, 2002-338668, 2003-313189, and 2003-313292 may be used.

[0341] The content of the chiral reagent in the liquid crystal composition can be appropriately set according to the helical twist amount in the target thickness direction and the type of chiral reagent.

[0342] <The function of liquid crystal diffraction elements>

[0343] As described above, an optically anisotropic layer formed using a composition containing a liquid crystal compound, having a liquid crystal alignment pattern rotating along the alignment axis D in the direction of optical axis 40A, refracts circularly polarized light.

[0344] In this invention, the liquid crystal diffraction element has two or more inflection points in the dark region 44 observed in the cross-sectional SEM image, and also has regions with different tilt directions in the thickness direction. Therefore, the liquid crystal diffraction element of this invention exhibits low wavelength dependence of diffraction efficiency, and can diffract light with the same diffraction efficiency regardless of the wavelength. That is, for example, red light, green light, and blue light can all be diffracted with the same diffraction efficiency. Moreover, it can diffract light with high diffraction efficiency regardless of the wavelength, and the higher the diffraction efficiency, the lower the wavelength dependence of the diffraction efficiency.

[0345] Furthermore, in the liquid crystal diffraction element of the present invention, one cycle of 180° rotation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern is constant. Therefore, regardless of the incident position of the light within the plane, as long as the wavelength is the same, the light is diffracted (refracted) at the same angle. That is, for example, if it is red light, the light can be diffracted at the same angle regardless of the incident position on the liquid crystal diffraction element.

[0346] Furthermore, in Figure 13 In the examples shown, the optical anisotropy layer is configured as a structure with a concentric liquid crystal alignment pattern, which changes in one direction as the orientation of the concentric circles originating from the optical axis of the liquid crystal compound rotates continuously from the inside to the outside, but is not limited to this.

[0347] For example, the alignment axis D of a liquid crystal alignment pattern having an optically anisotropic layer in one direction, with one period Λ gradually changing along that direction.

[0348] Furthermore, the liquid crystal alignment pattern is not necessarily a symmetrical concentric circle from the inside to the outside; it can also be an asymmetrical liquid crystal alignment pattern. In this case, the center of the liquid crystal alignment pattern may differ from the center of the liquid crystal diffraction element. The liquid crystal alignment pattern is not limited to the above structure and can be appropriately set according to the required function of the liquid crystal diffraction element.

[0349] The liquid crystal diffraction element of this invention can also preferably be used in combination with a circular polarizer.

[0350] A portion of the circularly polarized light incident on the liquid crystal diffraction element of this invention is not diffracted and sometimes transmits through the liquid crystal diffraction element (0th order light). The circularly polarized light that is not diffracted by the liquid crystal diffraction element may degrade performance depending on the application. In contrast, by combining the liquid crystal diffraction element and a circular polarizer, it is possible to reduce the amount of light transmitted without being diffracted by the liquid crystal diffraction element (0th order light).

[0351] The optical element of the present invention, which incorporates the liquid crystal diffraction element and the circular polarizer of the present invention, will be described below. Furthermore, the circular polarizer is used as an example to incorporate a phase retardation plate and a linear polarizer; the optical element of the present invention comprises a liquid crystal diffraction element, a phase retardation plate, and a linear polarizer arranged sequentially.

[0352] When right-handed circularly polarized light is incident on the liquid crystal diffraction element of the present invention, the incident right-handed circularly polarized light is diffracted and emitted from the liquid crystal diffraction element. Furthermore, the right-handed circularly polarized light is converted into left-handed circularly polarized light during diffraction. The left-handed circularly polarized light (i.e., first-order light) diffracted by the liquid crystal diffraction element is converted into linearly polarized light by a phase difference plate (quarter-wave plate) of the circular polarizer. The linearly polarized light converted by the phase difference plate is emitted after passing through the linear polarizer.

[0353] Here, when a portion of the light is not diffracted by the liquid crystal diffraction element, a portion of the right-handed circularly polarized light incident on the liquid crystal diffraction element is not diffracted and passes through the liquid crystal diffraction element. Without a circular polarizer, the right-handed circularly polarized light that is not diffracted by the liquid crystal diffraction element travels in a straight line. This straight-traveling right-handed circularly polarized light becomes unnecessary light depending on the application, and degrades performance.

[0354] In contrast, in the optical element of the present invention, which includes a liquid crystal diffraction element and a circular polarizer, right-handed circularly polarized light (i.e., 0th-order light) not diffracted by the liquid crystal diffraction element is converted into linearly polarized light in a direction orthogonal to left-handed circularly polarized light (1st-order light) diffracted by a phase difference plate incident on the circular polarizer, and can be incident on the linear polarizer and absorbed. That is, the right-handed circularly polarized light not diffracted by the liquid crystal diffraction element is absorbed by the circular polarizer. Therefore, the desired 1st-order light based on left-handed circularly polarized light can be transmitted, and the amount of undiffracted right-handed circularly polarized light can be reduced. Therefore, performance degradation caused by the transmission of unwanted light (0th-order light) can be suppressed.

[0355] In the optical element of the present invention, which is formed by combining the liquid crystal diffraction element of the present invention with a circular polarizer, other optical elements may be used downstream of the circular polarizer.

[0356] As an example, a phase retardation plate can be disposed downstream of the circular polarizer. As described above, the circular polarizer is disposed in sequence with a phase retardation plate and a linear polarizer. Specifically, it is also preferable to use a structure that converts linearly polarized light transmitted through the circular polarizer into circularly polarized light, elliptically polarized light, and linearly polarized light with different polarization directions by passing the phase retardation plate disposed downstream of the circular polarizer.

[0357] Furthermore, instead of a phase retardation plate, a depolarization layer that eliminates the polarization state of light in at least a portion of the wavelength region can be used. Examples of depolarization layers include high phase retardation films and light scattering layers. By controlling the polarization state of light emitted from a circular polarizer in this way, the polarization state can be adjusted according to the application. In addition, a high phase retardation film is, for example, a film with an in-plane phase difference of 3000 nm or more.

[0358] As another example, an optical element that deflects light can be placed downstream of the circular polarizer. For instance, by placing an optical element such as a lens downstream of the circular polarizer, the direction of light traveled from the circular polarizer can be changed. By controlling the deflection direction of light emitted from the circular polarizer in this way, the direction of light emission can be adjusted according to the application.

[0359] <Polarizer>

[0360] The linear polarizer used in this invention is not particularly limited as long as it has the function of transmitting linearly polarized light in one polarization direction and absorbing linearly polarized light in another polarization direction; conventionally known linear polarizers can be used. The linear polarizer can be an absorptive type or a reflective type.

[0361] As an absorptive linear polarizer, iodine-based polarizers, dye-based polarizers utilizing dichroic dyes, and polyene-based polarizers can be used. Iodine-based polarizers and dye-based polarizers include coated polarizers and stretched polarizers, and either type can be used. Among these, a polarizer made by adsorbing iodine or dichroic dye onto polyvinyl alcohol and then stretching it is preferred.

[0362] Furthermore, as a method for obtaining a polarizer by stretching and dyeing a laminated film in which a polyvinyl alcohol layer is formed on a substrate, examples include the methods described in Japanese Patent Nos. 5048120, 5143918, 4691205, 4751481, and 4751486. ​​In addition, known techniques concerning these polarizers are also preferred.

[0363] As an absorption-type polarizer, a polarizer that orients dichroic pigments by utilizing the orientation properties of liquid crystals without stretching is particularly preferred. This polarizer has many advantages, including: it can be made into an extremely thin layer with a thickness of about 0.1 to 5 μm; as described in Japanese Patent Application Publication No. 2019-194685, it is not prone to cracking when bent, has small thermal deformation, and as described in Japanese Patent Publication No. 6483486, it has excellent durability as a polarizer with a transmittance of over 50%, and excellent thermoforming properties.

[0364] Taking advantage of these advantages, polarizers with dichroic pigment orientation can be used in applications requiring high brightness, small and lightweight applications, micro-optical systems, applications shaped into curved surfaces, and applications in flexible parts. Furthermore, the polarizer can be peeled off from the support and transferred for use.

[0365] However, it is also preferred to assemble an absorptive polarizer for the purpose of suppressing stray light in applications such as head-up displays and other automotive display optical systems, AR glasses and VR glasses, LiDAR, facial recognition systems, and optical sensors such as polarization imagers.

[0366] As a reflective linear polarizer, for example, as described in Japanese Patent Application Publication No. 2011-053705, a thin film formed by stretching a layer containing two polymers and a wire grid polarizer can be used. From the viewpoint of brightness, a thin film formed by stretching a layer containing polymers is preferred.

[0367] Commercially available reflective linear polarizers can also be used. Among commercially available reflective linear polarizers are the reflective polarizer (APF) manufactured by 3M Company and the wire grid polarizer (WGF) manufactured by Asahi Kasei Corporation. Alternatively, a reflective linear polarizer composed of a cholesteric liquid crystal film and a λ / 4 plate can also be used.

[0368] The polarizer used in this invention preferably has a smooth surface. In particular, when the polarizer is applied to lenses or the like, minute surface irregularities can sometimes cause image distortion due to the magnification effect of the lens, so a smooth surface is desirable.

[0369] Specifically, the average arithmetic roughness Ra of the polarizer surface is preferably 50 nm or less, more preferably 30 nm or less, even more preferably 10 nm or less, and particularly preferably 5 nm or less. Furthermore, the surface unevenness difference within a 1 square millimeter range on the polarizer surface is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 20 nm or less.

[0370] The roughness and average arithmetic roughness of a surface can be measured using roughness gauges and interferometers. For example, the "vertscan" interferometer manufactured by Mitsubishi Chemical Systems, Inc. can be used for measurement.

[0371] <Phase difference plate>

[0372] The phase retarder used in this invention is a phase retarder that converts the phase of the incident polarization. The phase retarder is configured to adjust the direction of the slow axis according to whether the incident polarized light is converted into near-linear polarization or near-circular polarization. Specifically, the phase retarder is configured such that the slow axis is +45° or -45° relative to the absorption axis of the adjacent linear polarizer.

[0373] The retardation plate used in this invention can be a single-layer type consisting of one optical anisotropic layer, or a multi-layer type consisting of two or more optical anisotropic layers each having multiple different slow axes. Examples of multi-layer retardation plates include International Publication No. 2013 / 137464, International Publication No. 2016 / 158300, Japanese Patent Application Publication No. 2014-209219, Japanese Patent Application Publication No. 2014-209220, International Publication No. 2014 / 157079, Japanese Patent Application Publication No. 2019-215416, and International Publication No. 2019 / 160044, but are not limited thereto.

[0374] From the viewpoint of converting linearly polarized light into circularly polarized light or vice versa, the phase difference plate is preferably a λ / 4 plate.

[0375] There are no restrictions on the λ / 4 plate; various known plates with λ / 4 functionality can be used. Specific examples of λ / 4 plates include those described in U.S. Patent Application Publication No. 2015 / 0277006.

[0376] For example, as a single-layer structure of the λ / 4 plate, examples include a stretchable polymer film and a phase retardation film on a support having an optical anisotropy layer with λ / 4 functionality. Furthermore, as a multi-layer structure of the λ / 4 plate, examples include a broadband λ / 4 plate formed by stacking λ / 4 plates and λ / 2 waveplates.

[0377] 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 even more preferably 1 to 5 μm.

[0378] The phase difference plate used in this invention preferably has inverse wavelength dispersion. By having inverse wavelength dispersion, the phase change on the phase difference plate becomes ideal, and the conversion between linearly polarized light and circularly polarized light becomes ideal.

[0379] In the configuration of combining the liquid crystal diffraction element of the present invention with a circular polarizer, other optical elements may be used downstream of the circular polarizer.

[0380] As an example, a phase retardation plate can be disposed downstream of a circular polarizer. It is also preferable to use a structure that converts linearly polarized light transmitted through a circular polarizer (with a phase retardation plate and a linear polarizer disposed sequentially) into circularly polarized light, elliptically polarized light, and linearly polarized light with different polarization directions via a phase retardation plate disposed downstream of the circular polarizer. Furthermore, instead of a phase retardation plate, a depolarization layer that eliminates the polarization state of light in at least a portion of the wavelength region can be used. As the depolarization layer, a high phase retardation film (with an in-plane phase difference of 3000 nm or more) and a light scattering layer can be used. By controlling the polarization state of the light emitted from the circular polarizer in this way, the polarization state can be adjusted according to the application.

[0381] As another example, an optical element that deflects light can be placed downstream of the circular polarizer. For instance, by placing an optical element such as a lens downstream of the circular polarizer, the direction of light traveled from the circular polarizer can be changed. By controlling the deflection direction of light emitted from the circular polarizer in this way, the direction of light emission can be adjusted according to the application.

[0382] <Adhesive layer (adhesive layer), adhesive>

[0383] Optical films may include adhesive layers for bonding the various layers together. In this specification, "adhesion" is used in conjunction with the concept of "bonding".

[0384] Examples include water-soluble adhesives, UV-curable adhesives, emulsion adhesives, latex adhesives, adhesive bonding agents, multilayer adhesives, paste adhesives, foamed adhesives, support film adhesives, thermoplastic adhesives, hot-melt adhesives, thermosetting adhesives, thermoactive adhesives, heat-sealing adhesives, thermosetting adhesives, contact adhesives, pressure-sensitive adhesives (i.e., binders), polymeric adhesives, solvent-based adhesives, solvent-active adhesives, and ceramic adhesives. Specifically, examples include aqueous solutions of boron compounds, curable adhesives containing epoxy compounds that do not contain aromatic rings in the molecule, as shown in Japanese Patent Application Publication No. 2004-245925, active energy ray-curable adhesives that use a photopolymerization initiator with a molar absorptivity of 400 or more at wavelengths of 360 to 450 nm and an ultraviolet curable compound as essential components, as described in Japanese Patent Application Publication No. 2008-174667, and active energy ray-curable adhesives that contain (a) a (meth)acrylic acid compound having two or more (meth)acryloyl groups in the molecule, (b) a (meth)acrylic acid compound having a hydroxyl group and only one polymerizable double bond in the molecule, and (c) an active energy ray-curable adhesive containing phenol ethylene oxide modified acrylate or nonylphenol ethylene oxide modified acrylate, etc. Various adhesives can be used individually or in combination, depending on the need.

[0385] In a laminated optical film, from the viewpoint of reducing unnecessary reflections, it is preferable to have a small refractive index difference between the adhesive layer and adjacent layers. Specifically, the refractive index difference between adjacent layers is preferably 0.05 or less, and more preferably 0.01 or less. There are no particular limitations on the method for adjusting the refractive index of the adhesive layer, and known methods such as adding zirconia-based, silica-based, acrylic-based, acrylic-styrene-based, and melamine-based microparticles, adjusting the refractive index of the resin, and the method described in Japanese Patent Application Publication No. 11-223712 can be used.

[0386] Furthermore, when adjacent layers have anisotropic refractive indices in the plane, it is preferable that the refractive index difference between the layers and adjacent layers is less than 0.05 in all directions within the plane. Therefore, the adhesive layer can have anisotropic refractive indices in the plane.

[0387] When there is a large difference in refractive index between the bonded interfaces, the interfacial reflectivity can be reduced by distributing the refractive index along the thickness direction of the adhesive layer. Methods for distributing the refractive index along the thickness direction include methods such as setting multiple adhesive layers, mixing the interfaces between multiple adhesive layers, and controlling the non-uniformity of the raw materials within the adhesive layer to impart a refractive index distribution.

[0388] Furthermore, the adhesive layer can be applied to one or two bonded components using any method such as coating, vapor deposition, or transfer printing. From the viewpoint of improving adhesive strength, post-treatments such as heat treatment and ultraviolet irradiation can be performed depending on the type of adhesive. The thickness of the adhesive layer can be adjusted arbitrarily, but is preferably 20 μm or less, and more preferably 0.1 μm or less. As a method for forming an adhesive layer of 0.1 μm or less, a method of vapor deposition of a ceramic adhesive such as silicon dioxide (SiOx layer) on the bonding surface can be cited. The bonding surfaces of the bonded components can undergo surface modification treatments such as plasma treatment, corona treatment, or saponification treatment before bonding, and a primer layer can be applied. Furthermore, when there are multiple bonding surfaces, the type and thickness of the adhesive layer can be adjusted for each bonding surface.

[0389] <Cut-off of laminated bodies>

[0390] The fabricated laminate can be cut to a specified size. There is no limitation on the cutting method; various known methods can be used, such as physical cutting with tools like the Thomson caliper or laser cutting. When using a laser, considering cutability and material damage, the pulse width (nanosecond, picosecond, femtosecond) and wavelength are preferably selected. Furthermore, after the laminate is processed into a specified shape, for example, end face grinding can be performed.

[0391] From the viewpoint of improving processability during cutting and suppressing dust generation, cutting can also be performed while a peelable protective film is attached. Furthermore, for example, using the method shown in Japanese Patent Application Laid-Open No. 2004-141889, cutting can be performed while observing the liquid crystal alignment pattern, thereby allowing the cutting position to be determined arbitrarily. In this case, to facilitate observation of the liquid crystal alignment pattern, it is also possible to use a polarizer or retardation film for observation. Moreover, when multiple optical elements are disposed on a single substrate, it is preferable to cut multiple optical elements simultaneously.

[0392] <Other treatment>

[0393] For purposes such as precisely mounting the laminate onto the device and improving the accuracy of the axis or cutting position during cutting, marks of any shape can be applied as needed. The type of mark can be arbitrarily selected, including methods such as physical application via laser, inkjet, locally altering the alignment state of the liquid crystal, or applying localized decolorization or staining areas.

[0394] Furthermore, for the purpose of protecting the liquid crystal layer, protective layers (gas barrier layers, moisture barrier layers, ultraviolet absorption layers, scratch-resistant layers, etc.) can be provided as needed. The protective layer can be formed directly on the liquid crystal layer, or it can be provided through an adhesive layer or other optical films. To reduce surface reflectivity, anti-reflective layers (LR layers, AR layers, moth-eye layers, etc.) can be provided. Various protective layers can be appropriately selected from known protective layers. When a gas barrier layer is provided, polyvinyl alcohol is preferred. Polyvinyl alcohol can also function as a polarizer. Furthermore, the ultraviolet absorption layer is a layer containing an ultraviolet absorber. From the viewpoint of excellent absorption of ultraviolet light with wavelengths below 370 nm and good display performance, an ultraviolet absorber with low absorption of visible light with wavelengths above 400 nm is preferred. Only one type of ultraviolet absorber can be used, or two or more types can be used together. For example, the ultraviolet absorbers described in Japanese Patent Application Publication No. 2001-72782 or Japanese Patent Publication No. 2002-543265 can be cited. Specific examples of ultraviolet absorbers include benzophenone compounds, benzotriazole compounds, salicylates, benzophenone compounds, cyanoacrylate compounds, and nickel complex salt compounds.

[0395]

[0396] The liquid crystal diffraction element of the present invention can be used in combination with multiple liquid crystal diffraction elements.

[0397] For example, as disclosed in Optics Express, Vol. 28, No. 16 / 3 August 2020, by combining multiple liquid crystal diffraction elements and changing the polarization state of the incident light onto the liquid crystal diffraction elements, it is possible to switch the focusing / diverging properties of the emitted light multiple times.

[0398] By combining multiple liquid crystal diffraction elements, a foveated display corresponding to the central fovea can be achieved in HMDs such as AR glasses and VR glasses.

[0399] <Combination with phase modulation elements>

[0400] The liquid crystal diffraction element of the present invention can also preferably be used in combination with a phase modulation element.

[0401] For example, by combining the switchable half-waveplate disclosed in US10,379,419B1, which allows for voltage modulation of the phase difference, with the liquid crystal diffraction element of the present invention (used as a passive element), a focal variable lens with high diffraction efficiency regardless of the incident position of light within the element plane can be realized. Furthermore, by combining multiple sets of phase modulation elements with liquid crystal diffraction elements, multiple adjustable focal distances can be increased.

[0402] By using this type of variable-focus lens in AR and VR glasses, the focus position of the HMD's displayed image can be changed arbitrarily.

[0403] <Combination with lenses>

[0404] The liquid crystal diffraction element of the present invention can also preferably be used in combination with other lens elements.

[0405] For example, by using the liquid crystal diffraction element of the present invention in a combination of a Fresnel lens and a liquid crystal diffraction element disclosed in SID 2020 DIGEST, 40-4, pp. 579-582, 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 are no limitations on the combination lens; it is also preferable to use a combination with a refractive index lens, a pancake lens disclosed in US 3,443,858, and Optics Express, Vol. 29, No. 4 / 15 February 2021.

[0406] By using an optical system that combines such lenses and liquid crystal diffraction elements in AR glasses and VR glasses, it is possible to improve the color shift (color aberration of the lens) of the displayed image in HMD.

[0407] <Combination with light guide plate>

[0408] The liquid crystal diffraction element of the present invention can also preferably be used in combination with a light guide plate.

[0409] For example, in the combination of light guide plate and lens disclosed in Proc. of SPIE Vol. 11062, Digital Optical Technologies 2019, 110620J (July 16, 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.

[0410] By combining it with a light guide plate in this way, the focus position of the displayed image in HMDs such as AR glasses and VR glasses can be adjusted. Furthermore, when used in AR glasses, as disclosed in Proc. of SPIE Vol. 11062, Digital Optical Technologies 2019, 110620J (July 16, 2019), by using the liquid crystal diffraction element of this invention as a lens with different positive and negative sides sandwiching the light guide plate, both the actual scene and the displayed image output from the light guide plate can be observed without distortion.

[0411] <Combination with image display devices>

[0412] The liquid crystal diffraction element of the present invention is also preferably capable of being used in combination with an image display device.

[0413] 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 brightness distribution of the light emitted from the image display device can be adjusted.

[0414] In this way, by manufacturing an image display unit that is combined with an image display device, the brightness distribution of the HMD in AR glasses and VR glasses can be appropriately adjusted.

[0415] <Combination with beam steering>

[0416] The liquid crystal diffraction element of the present invention can also preferably be used in combination with a light deflection element (beam deflector).

[0417] For example, when using the liquid crystal diffraction element of the present invention as a diffraction element such as the light deflection element disclosed in WO2019 / 189675, it is possible to achieve high deflection angle of the emitted light with high diffraction efficiency.

[0418] In this way, by combining it with a light deflection element (beam deflector), the illumination angle of the light from ranging sensors such as LiDAR (Light Detection and Ranging) can be appropriately expanded.

[0419] The liquid crystal diffraction element, optical element, image display unit, head-mounted display, beam deflector, and sensor of the present invention have been described in detail above. However, the present invention is not limited to the above examples, and various improvements or modifications can be made without departing from the spirit of the present invention.

[0420] Example

[0421] The following examples illustrate the features of the present invention in more detail. The materials, reagents, dosages, quantities, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited by the specific examples shown below.

[0422] [Comparative Example 1]

[0423] <Fabrication of Liquid Crystal Diffraction Elements>

[0424] (Support structure)

[0425] A glass substrate was prepared as a support.

[0426] (Formation of the orientation film)

[0427] The following alignment film forming coating solution is applied to a support by spin coating. The support with the coating solution is then dried on a hot plate at 60°C for 60 seconds to form an alignment film.

[0428] Coating solution for oriented film formation

[0429]

[0430] -Raw material A for photoorientation-

[0431] [Chemical Formula 3]

[0432]

[0433] (Exposure of the alignment film)

[0434] use Figure 10 The exposure apparatus shown exposes the alignment film, thereby forming an alignment film P-1 with an alignment pattern.

[0435] In the exposure apparatus, a device that emits a laser beam with an emission wavelength of 325 nm is used as the laser. The exposure dose based on interference light is set to 1000 mJ / cm². 2 .

[0436] (Formation of an anisotropic optical layer)

[0437] As a liquid crystal composition for forming the first optical anisotropic layer, the following composition A-1 was prepared.

[0438] Composition A-1

[0439]

[0440] Liquid crystal compound L-1

[0441] [Chemical Formula 4]

[0442]

[0443] Chiral reagent M-1

[0444] [Chemical Formula 5]

[0445]

[0446] Leveling agent T-1

[0447] [Chemical Formula 6]

[0448]

[0449] The optical anisotropic layer is formed by multi-coating composition A-1 onto an alignment film P-1. Multi-coating refers to the following process: first, a first layer of composition A-1 is coated onto the alignment film, then heated and cured under ultraviolet light to form a liquid crystal immobilization layer; subsequently, a second and subsequent layers are overlapped onto this liquid crystal immobilization layer, and the process is similarly repeated with heating and ultraviolet curing. Through multi-coating, even as the total thickness of the optical anisotropic layer increases, the alignment direction of the alignment film is reflected from the bottom to the top of the optical anisotropic layer.

[0450] First, in the first layer, the following composition A-1 is coated onto the alignment film P-1. The coating is heated to 80°C on a hot plate, and then subjected to high-pressure mercury lamp at 300 mJ / cm under nitrogen atmosphere. 2 The irradiation dose is 365nm ultraviolet light applied to the coating to fix the orientation of the liquid crystal compound.

[0451] After the second layer, it is overlapped and coated onto the liquid crystal immobilization layer. Under the same conditions as described above, it is heated and then cured with ultraviolet light to create the liquid crystal immobilization layer. This overlapping coating process is repeated until the total thickness reaches the desired thickness, forming an optically anisotropic layer, thereby fabricating a liquid crystal diffraction element.

[0452] The birefringence Δn of the cured layer of liquid crystal composition A-1 was determined by measuring the retardation value and film thickness of the liquid crystal immobilized layer (cured layer) obtained by coating liquid crystal composition A-1 onto a separately prepared support with an alignment film for retardation measurement, ensuring the liquid crystal compound is horizontally aligned on the substrate, and then immobilizing it by irradiation with ultraviolet light. Δn can be calculated by dividing the retardation value by the film thickness. The retardation value was measured at the target wavelength using an Axoscan (Axometrix), and the film thickness was measured using SEM.

[0453] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 275 nm, and it becomes a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 70°. Hereinafter, unless otherwise stated, “Δn” will be used in the same manner. 550 The determination of ×d”, etc.

[0454] As a liquid crystal composition for forming the second optical anisotropy layer, the following composition A-2 was prepared.

[0455] Composition A-2

[0456]

[0457] Chiral reagent H-1

[0458] [Chemical Formula 7]

[0459]

[0460] Except for adjusting the film thickness of the optical anisotropic layer using composition A-2, the second optical anisotropic layer was formed in the same manner as the first optical anisotropic layer.

[0461] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550The thickness (Re(550)) ultimately becomes 275 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -70°.

[0462] [Example 1]

[0463] <Fabrication of Liquid Crystal Diffraction Elements>

[0464] (Formation of the orientation film)

[0465] An alignment film was formed on a glass substrate in the same manner as in Comparative Example 1, and the alignment film was exposed to form an alignment film P-1 with an alignment pattern.

[0466] (Formation of an anisotropic optical layer)

[0467] As a liquid crystal composition for forming the first optical anisotropic layer, the following composition B-1 was prepared.

[0468] Composition B-1

[0469]

[0470] Except for adjusting the film thickness of the optical anisotropic layer using composition B-1, the first optical anisotropic layer was formed in the same manner as in Comparative Example 1.

[0471] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 160 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 80°.

[0472] Composition B-2 was prepared as a liquid crystal composition for forming the second optical anisotropic layer.

[0473] Composition B-2

[0474]

[0475] Except for adjusting the film thickness of the optical anisotropic layer using composition B-2, the second optical anisotropic layer was formed in the same manner as the first optical anisotropic layer.

[0476] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550The thickness (Re(550)) ultimately becomes 330 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 0°.

[0477] As a liquid crystal composition for forming the third optical anisotropy layer, the following composition B-3 was prepared.

[0478] Composition B-3

[0479]

[0480] Except for adjusting the film thickness of the optical anisotropic layer using composition B-3, the third optical anisotropic layer was formed in the same manner as the first optical anisotropic layer.

[0481] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 160 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -80°.

[0482] [Example 2]

[0483] <Fabrication of Liquid Crystal Diffraction Elements>

[0484] (Formation of the orientation film)

[0485] An alignment film was formed on a glass substrate in the same manner as in Comparative Example 1, and the alignment film was exposed to form an alignment film P-1 with an alignment pattern.

[0486] (Formation of an anisotropic optical layer)

[0487] As a liquid crystal composition for forming the first optical anisotropic layer, in composition B-1 of Example 1, composition C-1 was prepared by changing the chiral reagent M-1 to 0.34 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the first optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 1.

[0488] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550The thickness (Re(550)) ultimately becomes 190 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 87°.

[0489] As a liquid crystal composition for forming the second optical anisotropic layer, in composition B-3 of Example 1, composition C-2 was prepared by changing the chiral reagent H-1 to 0.12 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the second optical anisotropic layer was formed in the same manner as the third optical anisotropic layer of Example 1.

[0490] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -14°.

[0491] As a liquid crystal composition for forming the third optical anisotropy layer, in composition B-1 of Example 1, composition C-3 was prepared by changing the chiral reagent M-1 to 0.07 parts by mass and adjusting the film thickness of the optical anisotropy layer. Otherwise, the third optical anisotropy layer was formed in the same manner as the first optical anisotropy layer of Example 1.

[0492] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 14°.

[0493] As a liquid crystal composition for forming the fourth optical anisotropic layer, in composition B-3 of Example 1, composition C-4 was prepared by changing the chiral reagent H-1 to 0.58 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the fourth optical anisotropic layer was formed in the same manner as the third optical anisotropic layer of Example 1.

[0494] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550The thickness (Re(550)) ultimately becomes 190 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -87°.

[0495] [Example 3]

[0496] <Fabrication of Liquid Crystal Diffraction Elements>

[0497] (Formation of the orientation film)

[0498] An alignment film was formed on a glass substrate in the same manner as in Comparative Example 1, and the alignment film was exposed to form an alignment film P-1 with an alignment pattern.

[0499] (Formation of an anisotropic optical layer)

[0500] As a liquid crystal composition for forming the first optical anisotropic layer, in composition B-1 of Example 1, composition D-1 was prepared by changing the chiral reagent M-1 to 0.40 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the first optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 1.

[0501] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 83°.

[0502] As a liquid crystal composition for forming the second optical anisotropic layer, in composition B-1 of Example 1, composition D-2 was prepared by changing the chiral reagent M-1 to 0.02 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the second optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 1.

[0503] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 335 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 8°.

[0504] As a liquid crystal composition for forming the third optical anisotropy layer, in composition B-3 of Example 1, composition D-3 was prepared by changing the chiral reagent H-1 to 0.57 parts by mass and adjusting the film thickness of the optical anisotropy layer. Otherwise, the third optical anisotropy layer was formed in the same manner as the third optical anisotropy layer of Example 1.

[0505] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 170 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -78°.

[0506] [Comparative Example 2]

[0507] <Fabrication of Liquid Crystal Diffraction Elements>

[0508] The first optical anisotropy layer was formed in the same manner as in Comparative Example 1.

[0509] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 275 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 10 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 70°.

[0510] [Comparative Example 3]

[0511] <Fabrication of Liquid Crystal Diffraction Elements>

[0512] In the orientation film exposure of Comparative Example 1, by changing Figure 10 The intersection angle α of the two rays MA and MB in the exposure apparatus shown adjusts the period of the orientation pattern. Otherwise, the orientation film P-2 was made in the same manner.

[0513] (Formation of an anisotropic optical layer)

[0514] The first and second optical anisotropic layers were formed on the alignment film P-2 in the same manner as in Comparative Example 1.

[0515] In the first and second optical anisotropy layers, the Δn of the liquid crystal was confirmed using polarization microscopy. 550The thickness (Re(550)) ultimately becomes 275 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Moreover, in the first optical anisotropy layer, the in-plane twist angle of the liquid crystal compound in the thickness direction is 70°, and in the second optical anisotropy layer, the twist angle in the thickness direction of the liquid crystal compound is -70°.

[0516] [Example 4]

[0517] <Fabrication of Liquid Crystal Diffraction Elements>

[0518] The alignment film P-2 was prepared in the same manner as in Comparative Example 3.

[0519] (Formation of an anisotropic optical layer)

[0520] As a liquid crystal composition for forming the first optical anisotropic layer, in composition B-1 of Example 1, composition E-1 was prepared by changing the chiral reagent M-1 to 0.52 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the first optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 1.

[0521] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 160 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 115°.

[0522] As a liquid crystal composition for forming the second optical anisotropic layer, in composition B-1 of Example 1, composition E-2 was prepared by changing the chiral reagent M-1 to 0.16 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the second optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 1.

[0523] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 335 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 76°.

[0524] As a liquid crystal composition for forming the third optical anisotropy layer, in composition B-3 of Example 1, composition E-3 was prepared by changing the chiral reagent H-1 to 0.38 parts by mass and adjusting the film thickness of the optical anisotropy layer. Otherwise, the third optical anisotropy layer was formed in the same manner as the third optical anisotropy layer of Example 1.

[0525] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 160 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -48°.

[0526] [Example 5]

[0527] <Fabrication of Liquid Crystal Diffraction Elements>

[0528] The alignment film P-2 was prepared in the same manner as in Comparative Example 3.

[0529] (Formation of an anisotropic optical layer)

[0530] As a liquid crystal composition for forming the first optical anisotropic layer, in composition C-1 of Example 2, composition F-1 was prepared by changing the chiral reagent M-1 to 0.44 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the first optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 2.

[0531] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 190 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 115°.

[0532] As a liquid crystal composition for forming the second optical anisotropic layer, in composition C-1 of Example 2, composition F-2 was prepared by changing the chiral reagent M-1 to 0.09 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the second optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 2.

[0533] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 18°.

[0534] As a liquid crystal composition for forming the third optical anisotropy layer, in composition C-3 of Example 2, composition F-3 was prepared by changing the chiral reagent M-1 to 0.04 parts by mass and adjusting the film thickness of the optical anisotropy layer. Otherwise, the third optical anisotropy layer was formed in the same manner as the third optical anisotropy layer of Example 2.

[0535] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 8°.

[0536] As a liquid crystal composition for forming the fourth optical anisotropic layer, in composition C-4 of Example 2, composition F-4 was prepared by changing the chiral reagent H-1 to 1.99 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the fourth optical anisotropic layer was formed in the same manner as the fourth optical anisotropic layer of Example 2.

[0537] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 190 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -237°.

[0538] [Example 6]

[0539] <Fabrication of Liquid Crystal Diffraction Elements>

[0540] The alignment film P-2 was prepared in the same manner as in Comparative Example 3.

[0541] (Formation of an anisotropic optical layer)

[0542] As a liquid crystal composition for forming the first optical anisotropic layer, in composition B-1 of Example 1, composition F-1 was prepared by changing the chiral reagent M-1 to 0.55 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the first optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 1.

[0543] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 114°.

[0544] As a liquid crystal composition for forming the second optical anisotropic layer, in composition B-1 of Example 1, composition F-2 was prepared by changing the chiral reagent M-1 to 0.18 parts by mass and adjusting the film thickness of the optical anisotropic layer. Otherwise, the second optical anisotropic layer was formed in the same manner as the first optical anisotropic layer of Example 1.

[0545] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 335 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 85°.

[0546] As a liquid crystal composition for forming the third optical anisotropy layer, in composition B-3 of Example 1, composition F-3 was prepared by changing the chiral reagent H-1 to 0.30 parts by mass and adjusting the film thickness of the optical anisotropy layer. Otherwise, the third optical anisotropy layer was formed in the same manner as the third optical anisotropy layer of Example 1.

[0547] In the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 170 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -41°.

[0548] [evaluate]

[0549] <Evaluation of the inflection point of the thickness direction angle and the inflection point of the tilt direction return>

[0550] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. The inflection points of the dark area angles and the number of inflection points where the dark area's tilt direction reversed were evaluated within the SEM-observed cross-sectional images.

[0551] The results are shown in Table 1.

[0552] <Evaluation of Diffraction Efficiency>

[0553] The diffraction efficiency of the emitted light was evaluated when incident light was directed onto the fabricated liquid crystal diffraction element from the front (at an angle of 0° relative to the normal).

[0554] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm are incident perpendicularly onto the fabricated liquid crystal diffraction element from a light source. The intensity of the emitted light—the diffracted light (1st order) diffracted from the liquid crystal diffraction element in the desired direction, the 0th order light diffracted in other directions, and the -1st order light—is measured using a photodetector. The diffraction efficiency at each wavelength is calculated using the following formula. Furthermore, the 0th order light is light emitted in the same direction as the incident light. The -1st order light is light diffracted in the -θ direction when the diffraction angle relative to the 1st order light (relative to the 0th order light) is set to θ.

[0555] Diffraction efficiency = 1st order light / (1st order light + 0th order light + (-1st order light))

[0556] The average diffraction efficiency was calculated 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.

[0557] Furthermore, after the light was incident perpendicularly onto a circularly polarized light plate corresponding to the wavelength of the laser beam, the incident light was then directed onto the fabricated liquid crystal diffraction element, and the results were evaluated.

[0558] A: The average diffraction efficiency is over 95%.

[0559] B: The average diffraction efficiency is above 90% and below 95%.

[0560] C: The average diffraction efficiency is less than 90%.

[0561] The results are shown in Table 1.

[0562] [Table 1]

[0563]

[0564] [Example 7]

[0565] <Fabrication of Liquid Crystal Diffraction Elements>

[0566] The alignment film P-2 was prepared in the same manner as in Comparative Example 3.

[0567] (Formation of an anisotropic optical layer)

[0568] In Example 6, liquid crystal compound L-1 was replaced with liquid crystal compound L-2, and the amounts of chiral reagent M-1, chiral reagent H-1, and leveling agent T-1 were appropriately changed to adjust the film thickness of the optical anisotropic layer. Otherwise, the first to third optical anisotropic layers were formed in the same manner as in Example 6.

[0569] Liquid crystal compound L-2

[0570] [Chemical Formula 8]

[0571]

[0572] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 114°.

[0573] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 335 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 85°.

[0574] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 170 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -41°.

[0575] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0576] [Example 8]

[0577] <Fabrication of Liquid Crystal Diffraction Elements>

[0578] The alignment film P-2 was prepared in the same manner as in Comparative Example 3.

[0579] (Formation of an anisotropic optical layer)

[0580] In Example 6, liquid crystal compound L-1 was replaced with liquid crystal compound L-3, and the amounts of chiral reagent M-1, chiral reagent H-1, and leveling agent T-1 were appropriately changed. The heating temperature of the coating film when forming the optical anisotropic layer was changed to 55°C, and the film thickness of the optical anisotropic layer was adjusted. Otherwise, the first to third optical anisotropic layers were formed in the same manner as in Example 6.

[0581] Liquid crystal compound L-3

[0582] [Chemical Formula 9]

[0583]

[0584] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 150 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 114°.

[0585] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 335 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is 85°.

[0586] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) ultimately becomes 170 nm, forming a periodically oriented surface. Furthermore, in the liquid crystal alignment pattern of this optically anisotropic layer, one period of 180° rotation of the optical axis of the liquid crystal compound is 1 μm. Also, in this optically anisotropic layer, the twist angle in the thickness direction of the liquid crystal compound is -41°.

[0587] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0588] In addition, the Δn of the liquid crystal layer (liquid crystal compound) in Example 6 550 The Δn of the liquid crystal layer in Example 7 is 0.15. 550 The Δn of the liquid crystal layer in Example 8 is 0.25. 550 It is 0.32.

[0589] <Evaluation of Diffraction Efficiency>

[0590] The diffraction efficiency of the emitted light was evaluated when light was incident on the fabricated liquid crystal diffraction element from the front (at an angle of 0° relative to the normal) with the incident angle changed by ±40° (10° scale).

[0591] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm are incident perpendicularly onto the fabricated liquid crystal diffraction element from a light source. The intensity of the emitted light—the diffracted light (1st order) diffracted from the liquid crystal diffraction element in the desired direction, the 0th order light diffracted in other directions, and the -1st order light—is measured using a photodetector. The diffraction efficiency at each wavelength is calculated using the following formula. Furthermore, the 0th order light is light emitted in the same direction as the incident light. The -1st order light is light diffracted in the -θ direction when the diffraction angle relative to the 1st order light (relative to the 0th order light) is set to θ.

[0592] Diffraction efficiency = 1st order light / (1st order light + 0th order light + (-1st order light))

[0593] The average diffraction efficiency was calculated from the measured values ​​at wavelengths of 405 nm, 450 nm, 532 nm and 650 nm at different incident angles, and the wavelength dependence of the diffraction efficiency was evaluated.

[0594] Furthermore, after the light was incident perpendicularly onto a circularly polarized light plate corresponding to the wavelength of the laser beam, the incident light was then directed onto the fabricated liquid crystal diffraction element, and the results were evaluated.

[0595] The evaluation results showed that the average diffraction efficiency of Examples 6 and 7 was improved, and the average diffraction efficiency of Example 8 was further improved.

[0596] As can be seen from the above, the refractive index difference Δn of the liquid crystal layer in the liquid crystal diffraction element 550 The higher the angle, the more efficient the utilization of light relative to different incident angles.

[0597] <Fabrication of Circular Polarizers>

[0598] (The fabrication of a phase difference plate)

[0599] A cellulose acylated film, an orientation film, and a film having an optically anisotropic layer C were obtained by means of the same method as that described in paragraphs 0102 to 0126 of Japanese Patent Application Publication No. 2019-215416 for the positive A plate.

[0600] The optical anisotropy layer C is a positive A plate (phase retardation plate), and the thickness of the positive A plate is controlled so that Re(550) is 138nm.

[0601] A circular polarizer was fabricated by bonding a phase retardation plate made with an adhesive onto a linear polarizer (polyvinyl alcohol layer type). Furthermore, the relative angle between the slow axis of the phase retardation plate and the absorption axis of the linear polarizer was set to 45°.

[0602] <Fabrication of Optical Components>

[0603] An optical element was fabricated by attaching the circular polarizer fabricated above onto the liquid crystal diffraction element fabricated in Examples 1 to 8. Furthermore, the optical element was fabricated by arranging the liquid crystal diffraction element, the phase refraction plate, and the linear polarizer in that order.

[0604] [evaluate]

[0605] The intensity of the emitted light was evaluated when light was incident on the fabricated optical element from the front (at an angle of 0° relative to the normal).

[0606] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm were incident perpendicularly onto the fabricated optical element. The intensity of the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the zero-order light diffracted in other directions were measured using a photodetector. Furthermore, light incident perpendicularly onto the liquid crystal diffraction element side of the fabricated optical element, after being circularly polarized by a circular polarizer corresponding to the wavelength of the laser beam, was evaluated.

[0607] It was confirmed that in the optical elements with circular polarizers attached to the liquid crystal diffraction elements fabricated in Examples 1 to 6, the light intensity of the 0th order light can be significantly reduced at any wavelength compared to before the circular polarizers were attached, and the contrast ratio (the light intensity ratio of the 1st order light to the 0th order light) is improved.

[0608] [evaluate]

[0609] <Evaluation of Diffraction Efficiency>

[0610] The intensity of the emitted light was evaluated when light was incident on an optical element using the liquid crystal diffraction element fabricated in Examples 6 to 8 by changing the incident angle by ±40° (10° scale) from the front (at an angle of 0° relative to the normal).

[0611] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm were irradiated from a light source and incident on the fabricated liquid crystal diffraction element. The intensity of the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the zero-order light (emitted in the same direction as the incident light) diffracted in other directions were measured using a photodetector.

[0612] The average value of light intensity relative to the incident angle was calculated based on the measured values ​​of wavelengths 405nm, 450nm, 532nm, and 650nm at different incident angles.

[0613] Furthermore, after the light was incident perpendicularly onto a circularly polarized light plate corresponding to the wavelength of the laser beam, the light was incident from the liquid crystal diffraction element side of the fabricated optical element and evaluated.

[0614] It was confirmed that in the optical elements with circular polarizers attached to the liquid crystal diffraction elements fabricated in Examples 6 to 8, the light intensity of the 0th order light can be significantly reduced at any wavelength compared to before the circular polarizers were attached, and the contrast ratio (the light intensity ratio of the 1st order light to the 0th order light) is improved.

[0615] Furthermore, the evaluation results showed that, compared with Example 6, the contrast ratio of the optical element in Example 7 was improved relative to the average incident angle, and the contrast ratio of the optical element in Example 8 was further improved relative to the average incident angle.

[0616] As can be seen from the above, even in optical elements where a circular polarizer is attached to a liquid crystal diffraction element, the refractive index difference Δn of the liquid crystal layer... 550 The side with a higher contrast ratio will also have a higher contrast ratio relative to different incident angles.

[0617] <Fabrication of Circular Polarizers>

[0618] In the fabrication of the circular polarizer described above, the circular polarizer was fabricated in the same manner, except that the linear polarizer (polyvinyl alcohol layer type) was changed to an absorption type polarizer fabricated as follows.

[0619] <Fabrication of Optical Components>

[0620] An optical element was fabricated by attaching a circular polarizer, made using an absorption polarizer, to a liquid crystal diffraction element fabricated in Examples 1 to 6. Furthermore, the optical element was fabricated by arranging the liquid crystal diffraction element, the phase refraction plate, and the absorption polarizer in that order.

[0621] [Fabrication of Absorption Polarizers (Linear Polarizers)]

[0622] <Fabrication of Transparent Support 1>

[0623] The coating solution PA1, used for forming the orientation layer (described later), was continuously coated onto a cellulose acylate film (40 μm thick TAC substrate; TG40, manufactured by FUJIFILM Corporation) using a wire rod. The coated support was dried with warm air at 140°C for 120 seconds, followed by polarized ultraviolet irradiation (10 mJ / cm²). 2 A photo-alignment layer PA1 was formed using an ultra-high pressure mercury lamp, thus obtaining a TAC thin film with a photo-alignment layer.

[0624] The thickness of the photo-alignment layer is 0.3 μm.

[0625] Alignment layer forming coating liquid PA1

[0626]

[0627] Polymer PA-1

[0628] [Chemical Formula 10]

[0629]

[0630] Acid-producing agent PAG-1

[0631] [Chemical Formula 11]

[0632]

[0633] Acid-producing agent CPI-110F

[0634] [Chemical Formula 12]

[0635]

[0636] <Formation of the light-absorbing anisotropic layer P1>

[0637] The following light-absorbing anisotropic layer forming composition P1 is continuously coated onto the obtained orientation layer PA1 using a wire rod, thereby forming the coating layer P1.

[0638] For bonding, heat coating layer P1 at 140°C for 30 seconds and then cool coating layer P1 to room temperature (23°C).

[0639] For bonding, heat at 90°C for 60 seconds and then cool to room temperature.

[0640] Then, using an LED light (center wavelength 365nm) at an illuminance of 200mW / cm² 2 By irradiating the product with ultraviolet light for 2 seconds under the specified irradiation conditions, an anisotropic light-absorbing layer P1 was fabricated on the alignment layer PA1.

[0641] The thickness of the light-absorbing anisotropic layer is 1.6 μm.

[0642] It is designated as layer 1B.

[0643] Composition P1 for forming anisotropic light-absorbing layers

[0644]

[0645] D-1

[0646] [Chemical Formula 13]

[0647]

[0648] [Chemical Formula 14]

[0649]

[0650] [Chemical Formula 15]

[0651]

[0652] P-1, a polymeric liquid crystal compound

[0653] [Chemical Formula 16]

[0654]

[0655] Low molecular weight liquid crystal compound M-1

[0656] [Chemical Formula 17]

[0657]

[0658] Surfactant F-1

[0659] [Chemical Formula 18]

[0660]

[0661] <Preparation of UV Adhesive>

[0662] The following UV adhesive composition was prepared.

[0663] UV adhesive composition

[0664]

[0665] CPI-100P

[0666] [Chemical Formula 19]

[0667]

[0668] <Fabrication of Absorption Polarizers>

[0669] Using the prepared UV adhesive as the resin substrate S1, TECHNOLLOY S001G (50 μm thick methacrylic resin, tanδ peak temperature 128 °C, SUMIKAACRYL CO.,LTD.) was bonded to the surface of the light-absorbing anisotropic layer of the laminate 1B. Then, by peeling off only the cellulose acylate film, an absorption polarizer with a single configuration of resin substrate / adhesive layer / light-absorbing anisotropic layer / orientation layer was fabricated. The thickness of the UV adhesive layer was 2 μm.

[0670] The average arithmetic roughness Ra of the obtained absorptive polarizer is less than 10 nm. On the other hand, the average arithmetic roughness Ra of the linear polarizer (polyvinyl alcohol layer type) is more than 20 nm.

[0671] Therefore, the resulting absorptive polarizer can reduce the deflection (refraction or scattering) of light caused by the unevenness of the polarizing film surface. Furthermore, when used in an image display device, it can suppress the distortion of the displayed image.

[0672] In addition, the average arithmetic roughness Ra was measured using an interferometer "vertscan" manufactured by Mitsubishi Chemical Systems, Inc.

[0673] [evaluate]

[0674] The intensity of the emitted light was evaluated when light was incident on the fabricated optical element from the front (at an angle of 0° relative to the normal).

[0675] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm were incident perpendicularly onto the fabricated optical element. The intensity of the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the zero-order light diffracted in other directions were measured using a photodetector. Furthermore, light incident perpendicularly onto the liquid crystal diffraction element side of the fabricated optical element, after being circularly polarized by a circular polarizer corresponding to the wavelength of the laser beam, was evaluated.

[0676] It was confirmed that in the optical elements with circular polarizers attached to the liquid crystal diffraction elements fabricated in Examples 1 to 6, the light intensity of the 0th order light can be significantly reduced at any wavelength compared to before the circular polarizers were attached, and the contrast ratio (the light intensity ratio of the 1st order light to the 0th order light) is improved.

[0677] [evaluate]

[0678] <Evaluation of Diffraction Efficiency>

[0679] The intensity of the emitted light was evaluated when light was incident on an optical element using the liquid crystal diffraction element fabricated in Examples 6 to 8 by changing the incident angle by ±40° (10° scale) from the front (at an angle of 0° relative to the normal).

[0680] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm were irradiated from a light source and incident on the fabricated liquid crystal diffraction element. The intensity of the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the zero-order light (emitted in the same direction as the incident light) diffracted in other directions were measured using a photodetector.

[0681] The average value of light intensity relative to the incident angle was calculated based on the measured values ​​of wavelengths 405nm, 450nm, 532nm, and 650nm at different incident angles.

[0682] Furthermore, after the light was incident perpendicularly onto a circularly polarized light plate corresponding to the wavelength of the laser beam, the light was incident from the liquid crystal diffraction element side of the fabricated optical element and evaluated.

[0683] It was confirmed that in the optical elements with circular polarizers attached to the liquid crystal diffraction elements fabricated in Examples 6 to 8, the light intensity of the 0th order light can be significantly reduced at any wavelength compared to before the circular polarizers were attached, and the contrast ratio (the light intensity ratio of the 1st order light to the 0th order light) is improved.

[0684] Furthermore, the evaluation results showed that, compared with Example 6, the contrast ratio of the optical element in Example 7 was improved relative to the average incident angle, and the contrast ratio of the optical element in Example 8 was further improved relative to the average incident angle.

[0685] As can be seen from the above, even in optical elements where a circular polarizer is attached to a liquid crystal diffraction element, the refractive index difference Δn of the liquid crystal layer... 550 The side with a higher contrast ratio will also have a higher contrast ratio relative to different incident angles.

[0686] [Comparative Example 11]

[0687] <Fabrication of Liquid Crystal Diffraction Elements>

[0688] (Exposure of the alignment film)

[0689] use Figure 14 The exposure apparatus shown exposes the alignment film, thereby forming an alignment film PL-1 with a concentric circle alignment pattern.

[0690] In the exposure apparatus, a device that emits a laser beam with an emission wavelength of 325 nm is used as the laser. The exposure dose based on interference light is set to 1000 mJ / cm². 2 By using Figure 14 The exposure apparatus shown causes one cycle of the orientation pattern to gradually shorten from the center outwards.

[0691] (Formation of an anisotropic optical layer)

[0692] In Comparative Example 1, an optical anisotropy layer was formed in the same manner, except that the alignment film PL-1 prepared above was used.

[0693] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 275nm, and becomes as... Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 70°.

[0694] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 275nm, and becomes as... Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, indicating a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -70°.

[0695] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, the number of inflection points at the angle to the dark area was 1, and the number of inflection points at the angle of reversal in the dark area was also 1.

[0696] [Example 11]

[0697] <Fabrication of Liquid Crystal Diffraction Elements>

[0698] (Exposure of the alignment film)

[0699] An alignment film PL-1 with a concentric circle alignment pattern was formed in the same manner as in Comparative Example 11.

[0700] (Formation of an anisotropic optical layer)

[0701] In Example 1, an optical anisotropic layer was formed in the same manner, except that the orientation film PL-1 prepared above was used.

[0702] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 160nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 80°.

[0703] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 330nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 0°.

[0704] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 160nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -80°.

[0705] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0706] [Example 12]

[0707] <Fabrication of Liquid Crystal Diffraction Elements>

[0708] (Formation of an anisotropic optical layer)

[0709] In Example 11, liquid crystal compound L-1 was replaced with liquid crystal compound L-2, and the amounts of chiral reagent M-1, chiral reagent H-1, and leveling agent T-1 were appropriately changed to adjust the film thickness of the optical anisotropic layer. Otherwise, the first to third optical anisotropic layers were formed in the same manner as in Example 11.

[0710] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 160nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 80°.

[0711] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 330nm, and becomes as Figure 13The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 0°.

[0712] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 160nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -80°.

[0713] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0714] [Example 13]

[0715] <Fabrication of Liquid Crystal Diffraction Elements>

[0716] (Formation of an anisotropic optical layer)

[0717] In Example 11, liquid crystal compound L-1 was replaced with liquid crystal compound L-3, and the amounts of chiral reagent M-1, chiral reagent H-1, and leveling agent T-1 were appropriately changed. The heating temperature of the coating film when forming the optical anisotropic layer was changed to 55°C, and the film thickness of the optical anisotropic layer was adjusted. Otherwise, the first to third optical anisotropic layers were formed in the same manner as in Example 11.

[0718] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 160nm, and becomes as Figure 13The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 80°.

[0719] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 330nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 0°.

[0720] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 160nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -80°.

[0721] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0722] Additionally, the Δn of the liquid crystal layer (liquid crystal compound) in Example 11 550 The Δn of the liquid crystal layer in Example 12 is 0.15. 550 The Δn of the liquid crystal layer in Example 13 is 0.25. 550 It is 0.32.

[0723] [Example 14]

[0724] <Fabrication of Liquid Crystal Diffraction Elements>

[0725] (Exposure of the alignment film)

[0726] An alignment film PL-1 with a concentric circle alignment pattern was formed in the same manner as in Comparative Example 11.

[0727] (Formation of an anisotropic optical layer)

[0728] In Example 3, an optical anisotropic layer was formed in the same manner, except that the orientation film PL-1 prepared above was used.

[0729] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 150nm, and becomes as... Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with periods shortening outwards. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -83°.

[0730] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 335nm, and becomes as... Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, indicating a liquid crystal alignment pattern with periods shortening outwards. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 8°.

[0731] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 170nm, and becomes as Figure 13The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -78°.

[0732] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0733] [Example 15]

[0734] <Fabrication of Liquid Crystal Diffraction Elements>

[0735] (Formation of an anisotropic optical layer)

[0736] In Example 14, liquid crystal compound L-1 was replaced with liquid crystal compound L-2, and the amounts of chiral reagent M-1, chiral reagent H-1, and leveling agent T-1 were appropriately changed to adjust the film thickness of the optical anisotropic layer. Otherwise, the first to third optical anisotropic layers were formed in the same manner as in Example 14.

[0737] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 150nm, and becomes as... Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with periods shortening outwards. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -83°.

[0738] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 335nm, and becomes as... Figure 13The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, indicating a liquid crystal alignment pattern with periods shortening outwards. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 8°.

[0739] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 170nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -78°.

[0740] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0741] [Example 16]

[0742] <Fabrication of Liquid Crystal Diffraction Elements>

[0743] (Formation of an anisotropic optical layer)

[0744] In Example 14, liquid crystal compound L-1 was replaced with liquid crystal compound L-3, and the amounts of chiral reagent M-1, chiral reagent H-1, and leveling agent T-1 were appropriately changed to adjust the film thickness of the optical anisotropic layer. Otherwise, the first to third optical anisotropic layers were formed in the same manner as in Example 14.

[0745] In the first optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 150nm, and becomes as... Figure 13The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with periods shortening outwards. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -83°.

[0746] In the second optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 335nm, and becomes as... Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, indicating a liquid crystal alignment pattern with periods shortening outwards. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is 8°.

[0747] In the third optical anisotropy layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 550 The thickness (Re(550)) eventually becomes 170nm, and becomes as Figure 13 The concentric (radial) periodic alignment surfaces are shown. Furthermore, in the liquid crystal alignment pattern of this optical anisotropy layer, within one cycle of a 180° rotation of the optical axis of the liquid crystal compound, one cycle at a distance of approximately 2 mm from the center is 10 μm, one cycle at a distance of 25 mm from the center is 1 μm, and one cycle at a distance of 30 mm from the center is 0.6 μm, showing a liquid crystal alignment pattern with shorter periods in the outward direction. Moreover, the twist angle in the thickness direction of the optical anisotropy layer is -78°.

[0748] The cross-section of the fabricated optical anisotropic layer was observed using SEM, revealing patterns in both bright and dark areas. In the SEM-observed cross-sectional image, there were two inflection points at the angles of the dark areas and one inflection point at the angle of reversal in the dark areas.

[0749] Additionally, the Δn of the liquid crystal layer (liquid crystal compound) in Example 14 550 The Δn of the liquid crystal layer in Example 15 is 0.15. 550 The Δn of the liquid crystal layer in Example 16 is 0.25. 550 It is 0.32.

[0750] [evaluate]

[0751] <Evaluation of Diffraction Efficiency>

[0752] The diffraction efficiency of the emitted light when incident light is incident on the liquid crystal diffraction elements of Comparative Example 11 and Examples 11 to 16 from the front (at an angle of 0° relative to the normal) was evaluated.

[0753] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm are irradiated from a light source and incident perpendicularly onto the fabricated liquid crystal diffraction element. The intensity of the emitted light, including the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the 0th-order light (emitted in the same direction as the incident light) and the -1st-order light (light diffracted in the -θ direction when the diffraction angle relative to the 0th-order light is set to θ), is measured using a photodetector. The diffraction efficiency at each wavelength is calculated using the following formula.

[0754] Diffraction efficiency = 1st order light / (1st order light + 0th order light + (-1st order light))

[0755] The average diffraction efficiency was calculated 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.

[0756] Furthermore, after the light was incident perpendicularly onto a circularly polarized light plate corresponding to the wavelength of the laser beam, the incident light was then directed onto the fabricated liquid crystal diffraction element, and the results were evaluated.

[0757] Furthermore, the evaluation was conducted at three locations: the center of the concentric circles of the liquid crystal alignment pattern in the fabricated liquid crystal diffraction element, the vicinity of the center of the concentric circles (10 μm per period), the vicinity of the end (1 μm per period), and the end (0.6 μm per period).

[0758] Compared to Comparative Example 11, in Examples 11 to 16, a high diffraction efficiency was obtained in terms of wavelength dependence of diffraction efficiency.

[0759] [evaluate]

[0760] <Evaluation of Diffraction Efficiency>

[0761] 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 (at an angle of 0° relative to the normal) with the incident angle changed by ±40° (10° scale).

[0762] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm are irradiated from a light source and incident on the fabricated liquid crystal diffraction element. The intensity of the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the intensity of the 0th-order light (diffracted in the same direction as the incident light) and the -1st-order light (diffracted in the -θ direction when the diffraction angle of the first-order light relative to the 0th-order light is set to θ) in other directions are measured using a photodetector, and the diffraction efficiency at each wavelength is calculated using the following formula.

[0763] Diffraction efficiency = 1st order light / (1st order light + 0th order light + (-1st order light))

[0764] The average diffraction efficiency was calculated from the measured values ​​at wavelengths of 405 nm, 450 nm, 532 nm and 650 nm at different incident angles, and the wavelength dependence of the diffraction efficiency was evaluated.

[0765] Furthermore, after the light was incident perpendicularly onto a circularly polarized light plate corresponding to the wavelength of the laser beam, the incident light was then directed onto the fabricated liquid crystal diffraction element, and the results were evaluated.

[0766] Furthermore, the evaluation was conducted at three locations: the center of the concentric circles of the liquid crystal alignment pattern in the fabricated liquid crystal diffraction element, the vicinity of the center of the concentric circles (10 μm per period), the vicinity of the end (1 μm per period), and the end (0.6 μm per period).

[0767] The evaluation results showed that, compared to Comparative Example 11, Examples 11 to 16 achieved an average high diffraction efficiency.

[0768] Furthermore, the evaluation results showed that the average diffraction efficiency of Examples 11 and 12 was improved, and the average diffraction efficiency of Example 13 was further improved.

[0769] Furthermore, the evaluation results showed that the average diffraction efficiency of Examples 14 and 15 was improved, and the average diffraction efficiency of Example 16 was further improved.

[0770] As can be seen from the above, the refractive index difference Δn of the liquid crystal layer in the liquid crystal diffraction element 550 The higher the angle, the more efficient the utilization of light relative to different incident angles.

[0771] <Fabrication of Circular Polarizers>

[0772] [Fabrication of Absorption Polarizers (Linear Polarizers)]

[0773] Absorption-type polarizers (linear polarizers) and phase difference plates were fabricated using the methods described above, and circular polarizers were also fabricated.

[0774] <Fabrication of Optical Components>

[0775] An optical element was fabricated by attaching a circular polarizer, made using the absorption polarizer fabricated as described above, to a liquid crystal diffraction element fabricated in Comparative Example 11 and Examples 11 to 16. Furthermore, the optical element was fabricated by arranging the liquid crystal diffraction element, the phase refraction plate, and the absorption polarizer in that order.

[0776] [evaluate]

[0777] The 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 (at an angle of 0° relative to the normal).

[0778] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm were incident perpendicularly onto the fabricated optical element from a light source. The intensity of the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the zero-order light (emitted in the same direction as the incident light) diffracted in other directions were measured using a photodetector. Furthermore, light incident perpendicularly onto the liquid crystal diffraction element side of the fabricated optical element, after being circularly polarized by a circular polarizer corresponding to the wavelength of the laser beam, was evaluated.

[0779] It was confirmed that in the optical elements with circular polarizers attached to the liquid crystal diffraction elements fabricated in Examples 1 to 7, the light intensity of the 0th order light can be significantly reduced at any wavelength compared to before the circular polarizers were attached, and the contrast ratio (the light intensity ratio of the 1st order light to the 0th order light) is improved.

[0780] [evaluate]

[0781] <Evaluation of incident angle dependence>

[0782] The intensity of the emitted light was evaluated when light was incident on an optical element using the liquid crystal diffraction element fabricated in Comparative Example 11 and Examples 11 to 16 by changing the incident angle by ±40° (10° scale) from the front (0° angle relative to the normal).

[0783] Specifically, laser beams with output center wavelengths at 405 nm, 450 nm, 532 nm, and 650 nm were irradiated from a light source and incident on the fabricated liquid crystal diffraction element. The intensity of the diffracted light (first-order light) diffracted from the liquid crystal diffraction element in the desired direction and the zero-order light (emitted in the same direction as the incident light) diffracted in other directions were measured using a photodetector.

[0784] The average value of light intensity relative to the incident angle was calculated based on the measured values ​​of wavelengths 405nm, 450nm, 532nm and 650nm at different incident angles.

[0785] Furthermore, evaluations were conducted 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 (10 μm per period), the vicinity of the ends (1 μm per period), and the ends (0.6 μm per period).

[0786] Furthermore, after the light was incident perpendicularly onto a circularly polarized light plate corresponding to the wavelength of the laser beam, the light was incident from the liquid crystal diffraction element side of the fabricated optical element and evaluated.

[0787] It was confirmed that in the optical elements with circular polarizers attached to the liquid crystal diffraction elements fabricated in Examples 11 to 16, the light intensity of the 0th order light can be significantly reduced at any wavelength compared to before the circular polarizers were attached, and the contrast ratio (the light intensity ratio of the 1st order light to the 0th order light) is improved.

[0788] Furthermore, compared to the optical element fabricated in Comparative Example 11, the optical elements fabricated in Examples 11 to 16 achieved a high contrast ratio.

[0789] Furthermore, the evaluation results showed that, compared to Example 11, the contrast ratio of Example 12 was improved relative to the average incident angle, and the contrast ratio of Example 13 was further improved relative to the average incident angle.

[0790] Furthermore, the evaluation results showed that, compared to Example 14, the contrast ratio of Example 15 was improved relative to the average incident angle, and the contrast ratio of Example 16 was further improved relative to the average incident angle.

[0791] As can be seen from the above, even in optical elements where a circular polarizer is attached to a liquid crystal diffraction element, the refractive index difference Δn of the liquid crystal layer... 550 The side with a higher contrast ratio will also have a higher contrast ratio relative to different incident angles.

[0792] <Changes to the support structure>

[0793] Using the method described below, the support of the liquid crystal diffraction element can be appropriately modified according to the desired purpose. Furthermore, the method described below allows for thinning of the thickness between the liquid crystal diffraction element and the modified support; for example, for adhesives (thickness: several μm to tens of μm), the in-plane thickness of the modified liquid crystal diffraction element can be made uniform. Thus, even when the support of the liquid crystal diffraction element is modified, by making the in-plane thickness uniform, the direction of light emitted from the liquid crystal diffraction element can be precisely controlled in-plane.

[0794] In addition, as an example, the stacking of the liquid crystal diffraction element and the new support can be carried out in the following order.

[0795] (1) A dummy support is attached to the liquid crystal layer side of the stacked support, alignment film, and liquid crystal diffraction element. In this example, the dummy support is made of FUJIMORI KOGYO CO.,LTD. and is made of MASTACK AS3-304.

[0796] (2) Next, the support and alignment film present in the fabrication stage of the liquid crystal diffraction element are peeled off, so that the interface on the alignment film side of the liquid crystal diffraction element is exposed.

[0797] (3) A silicon oxide layer (SiO2) is formed between the interface on the alignment film side of the liquid crystal diffraction element and the interface of the newly prepared support. x The method for forming the silicon oxide layer is not limited, but vacuum evaporation is preferred. In this example, the silicon oxide layer is formed using an evaporation apparatus (model ULEYES) manufactured by ULVAC, Inc. SiO2 powder is used as the evaporation source. The thickness of the silicon oxide layer is not limited, but is preferably 50 nm or less. In this example, the thickness of the silicon oxide film is 50 nm or less.

[0798] (4) Next, plasma treatment is performed on both of the formed silicon oxide films. After the formed silicon oxide layers are bonded together at 120°C, the pseudo support is peeled off.

[0799] Through the above steps (1) to (4), a diffraction element composed of a liquid crystal diffraction element and a newly prepared support can be fabricated. Furthermore, by changing the support to another liquid crystal diffraction element and repeating steps (1) to (4), a diffraction element composed of two or more layers of liquid crystal diffraction elements can be fabricated.

[0800] Through the steps (1) to (4) above, the support for the liquid crystal diffraction element fabricated in Example 1 is 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 for the liquid crystal diffraction element fabricated in Example 1 is changed to a glass substrate with a thickness of 0.3 mm (the liquid crystal diffraction element is bonded to the glass substrate using the adhesive). In the steps (1) to (4) above, the liquid crystal diffraction element fabricated has a more uniform in-plane thickness compared to the liquid crystal diffraction element fabricated using the adhesive.

[0801] <Creating Layered Bodies>

[0802] Similarly, it is possible to fabricate laminates of liquid crystal diffraction elements and other optical components.

[0803] As an example, a stack of liquid crystal diffraction elements, phase difference plates, and polarizers was fabricated using the following method.

[0804] A silicon oxide layer (SiOx layer) is formed on the liquid crystal layer side of a liquid crystal diffraction element having a stacked support, alignment film, and liquid crystal layer, and on the bonding surface side of a retardation plate bonded to the liquid crystal diffraction element. The method for forming the silicon oxide layer is not limited, but vacuum evaporation is preferred. In this example, the silicon oxide layer is formed using an evaporation apparatus (model ULEYES) manufactured by ULVAC, Inc. SiO2 powder is used as the evaporation source. The thickness of the silicon oxide layer is not limited, but is preferably 50 nm or less. In this example, the thickness of the silicon oxide film is 50 nm or less. Both formed silicon oxide films are subjected to plasma treatment, and the silicon oxide layers are bonded together at 120°C. This forms a stack of the liquid crystal diffraction element and the retardation plate. Similarly, a polarizer layer is bonded to the retardation plate, and the support and alignment film are peeled off, thereby fabricating a stack composed of a liquid crystal layer (liquid crystal diffraction element), a retardation plate, and a polarizer.

[0805] Furthermore, the liquid crystal diffraction elements fabricated in Examples 1 to 16 were used as liquid crystal diffraction elements. The phase retardation plate used in the fabrication of the circular polarizer described above was used as a phase retardation plate. The polarizers were fabricated using the linear polarizer (polyvinyl alcohol layer type) and the absorption polarizer described above, respectively.

[0806] It was confirmed that in optical elements consisting of a stack of liquid crystal diffraction elements, a phase retardation plate, and a polarizer, the intensity of the 0th order light can be significantly reduced at any wavelength before the circular polarizer (the stack of the phase retardation plate and the polarizer) is bonded, and the contrast ratio (the intensity ratio of the 1st order light to the 0th order light) is improved.

[0807] Based on the above results, the effectiveness of the present invention can be clearly demonstrated.

[0808] Symbol Explanation

[0809] 30-Support, 32-Orientation film, 36a, 36b-Optical anisotropic layers, 37a~37g-Regions, 40-Liquid crystal compound, 40A-Optical axis, 42-Bright area, 44-Dark area, 60-Exposure device, 62-Laser, 64-Light source, 65-λ / 2 plate, 68-Beam splitter, 70A, 70B, 90A, 90B-Mirrors, 72A, 72B, 96-λ / 4 plate, 86, 94-Polarization beam splitter, 92-Lens, Λ-1 period, D-Arrangement axis, R-Region, M-Laser beam, MA, MB-Light rays, MP-P polarization, MS-S polarization, P O - Linearly polarized light, P R - Right-handed circularly polarized light, P L- Left-handed circularly polarized light, α - cross angle, L1, L4 - incident light, L2, L5 - transmitted light.

Claims

1. A liquid crystal diffraction element comprising an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, The optical anisotropic layer has a liquid crystal alignment pattern that changes while continuously rotating in at least one in-plane direction originating from the optical axis of the liquid crystal compound, and functions as a transmission-type diffraction element. In the optical anisotropic layer, at least a portion of the liquid crystal compound is twisted in the thickness direction. In a cross-sectional image obtained by cutting along the thickness direction in one direction using a scanning electron microscope, the optically anisotropic layer has bright and dark areas extending from one surface to another. Furthermore, the dark areas have two or more inflection points at different angles, and there are regions in the thickness direction with different tilt directions of the dark areas. When the length of one cycle is defined as the length of the orientation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern rotated 180° in the plane, the length of one cycle is constant.

2. The liquid crystal diffraction element according to claim 1, wherein, The oblique direction of the dark part extending from one surface to another folds back in the opposite direction an odd number of times.

3. The liquid crystal diffraction element according to claim 2, wherein, The oblique direction of the dark part extending from one surface to another folds back once in the opposite direction.

4. The liquid crystal diffraction element according to claim 2, wherein, The oblique direction of the dark part extending from one surface to another folds back three times in the opposite direction.

5. The liquid crystal diffraction element according to any one of claims 1 to 4, wherein, In a cross-sectional image of the optical anisotropic layer obtained by cutting along the thickness direction using a scanning electron microscope, the shape of the dark area is symmetrical with respect to the centerline of the thickness direction of the optical anisotropic layer.

6. The liquid crystal diffraction element according to any one of claims 1 to 4, wherein, In a cross-sectional image of the optical anisotropic layer obtained by cutting along the thickness direction using a scanning electron microscope, the shape of the dark area is asymmetrical with respect to the centerline of the thickness direction of the optical anisotropic layer.

7. The liquid crystal diffraction element according to any one of claims 1 to 4, wherein, The refractive index difference Δn arising from the refractive index anisotropy of the optical anisotropy layer 550 It is above 0.

2.

8. The liquid crystal diffraction element according to any one of claims 1 to 4, wherein, When the orientation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern is rotated 180° in the plane as one period, there is a region in the plane with a length of less than 1.0 μm for one period.

9. The liquid crystal diffraction element according to any one of claims 1 to 4, wherein, The optical axes of the liquid crystal compounds are oriented in the same direction as the inflection point of the angle in the thickness direction.

10. The liquid crystal diffraction element according to any one of claims 1 to 4, wherein, The optical anisotropic layer has regions where the torsion direction of the liquid crystal compound is opposite in the thickness direction, and regions where the tilt direction of the dark portion is opposite.

11. An optical element comprising a liquid crystal diffraction element and a circular polarizer as described in any one of claims 1 to 10.

12. The optical element according to claim 11, wherein, The circular polarizer consists of a phase difference plate and a polarizer, and the optical element includes the liquid crystal diffraction element, the phase difference plate and the polarizer arranged in sequence.

13. An optical element comprising, in sequence, a liquid crystal diffraction element, a silicon oxide layer, and a support as described in any one of claims 1 to 10.

14. An optical element having at least one liquid crystal diffraction element as described in any one of claims 1 to 10 or an optical element as described in any one of claims 11 to 13, and further having at least one phase modulation element.

15. An image display unit having a liquid crystal diffraction element according to any one of claims 1 to 10 or an optical element according to any one of claims 11 to 14.

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

17. A beam deflector having a liquid crystal diffraction element according to any one of claims 1 to 10 or an optical element according to any one of claims 11 to 14.

18. A sensor having a liquid crystal diffraction element according to any one of claims 1 to 10 or an optical element according to any one of claims 11 to 14.

Images