Exposure method for photo-aligned layers

Abstract

The present invention addresses the problem of providing an optical alignment layer exposure method with which an alignment pattern with no disturbance can be formed. This optical alignment layer exposure method comprises an exposure step in which an exposure mask and a substrate having a coating including a compound having an optical alignment group are disposed with the exposure mask and the coating facing each other, and the compound is irradiated from the exposure mask side with light to which the compound is photosensitive to expose the coating and form an alignment pattern. The light is circular polarization light having an ellipticity of 0.7 to 1.3. The exposure mask is a polarization diffraction element having an alignment pattern in which the orientation of an optical axis changes while continuously rotating along at least one in-plane direction. The exposure step exposes the coating with zero-order light and first-order light diffracted by the exposure mask, and the intensity ratio of the zero-order light relative to the first-order light is 0.5 to 2.

Description

[Technical Field]

[0001] The present invention relates to an exposure method for a photo-alignment layer used in the manufacture of polarizing diffraction elements and the like. [Background technology]

[0002] A known liquid crystal diffraction element has an optical anisotropic layer in which a liquid crystal compound is oriented in a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound rotates continuously along one direction in the plane. One example of how the optical anisotropy layer of such a liquid crystal diffraction element can be fabricated is by forming an orientation layer with an orientation pattern on a substrate, and then coating and drying a composition containing a liquid crystal compound onto this orientation layer to orient the liquid crystal compound.

[0003] Photo-alignment layers are known as orientation layers having an orientation pattern. Photo-alignment layers are formed by applying a paint containing a compound having photo-aligning groups to a substrate, drying it to form a photosensitive coating film, and then exposing this coating film to light corresponding to the orientation pattern to be formed. The orientation pattern of the photo-orientation layer is formed by exposure, for example, by superimposing two circularly polarized lights with opposite rotation directions to cause interference. When this interfered light is incident on a photosensitive coating, an interference pattern is generated on the coating due to interference fringes. By exposing the coating with this interfered light, an orientation pattern corresponding to the interference pattern is formed on the coating, becoming a photo-orientation layer.

[0004] The exposure of photosensitive coatings is performed, for example, using an interference exposure apparatus as shown below. In this exposure apparatus, parallel laser light is split into two orthogonal linearly polarized beams by a polarizing beam splitter. After focusing one of the linearly polarized beams with a convex lens, the two linearly polarized beams are superimposed by incidenting one linearly polarized beam onto one surface of a half-mirror and the other linearly polarized beam onto the other surface. Subsequently, the two superimposed linearly polarized beams are converted into circularly polarized beams with different rotation directions by a quarter-wave plate. The interference of the two superimposed circularly polarized beams generates an interference pattern due to interference fringes depending on the focal length of the convex lens, etc., when the circularly polarized beam incident on the coating film.

[0005] As a simple method for forming an orientation pattern on a photosensitive coating film without using such an exposure apparatus, a liquid crystal diffraction element using an optically anisotropic layer having the liquid crystal orientation pattern described above is used as an exposure mask, and the coating film is exposed through this exposure mask. This exposure method allows for the formation of an orientation pattern on a photosensitive coating, i.e., a photo-alignment layer, that corresponds to the liquid crystal orientation pattern of the liquid crystal diffraction element used as an exposure mask.

[0006] For example, Patent Document 1 discloses an exposure method (method for manufacturing an optical element) which includes the steps of: patterning an orientation surface by photolithography using a birefringent mask having a holographic pattern to create an orientation state on the orientation surface based on the holographic pattern; and forming a layer on the orientation surface so that the direction of the local optical axis of the layer is determined by the orientation state of the orientation surface. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5651753 [Overview of the project] [Problems that the invention aims to solve]

[0008] A concrete example of the exposure method described in Patent Document 1 is conceptually shown in Figure 12. In this exposure method, a photosensitive coating film 104 containing a compound having photo-aligning groups is formed on the surface of the substrate 106, and a liquid crystal diffraction element is used as an exposure mask 100 to irradiate the coating film 104 with light (linearly polarized Lp) from a light source 102 through the exposure mask 100. This exposes the coating film 104 to the liquid crystal alignment pattern of the liquid crystal diffraction element, which is the exposure mask 100, and forms an optical alignment layer with an alignment pattern corresponding to the liquid crystal alignment pattern.

[0009] As an example, the liquid crystal diffraction element used as the exposure mask 100 has a liquid crystal orientation pattern in which the orientation of the liquid crystal compound 30 rotates continuously along one direction in the plane, as conceptually shown in Figure 13. In Figure 13, a rod-shaped liquid crystal compound is used as an example of the liquid crystal compound 30, so the optical axis coincides with the longitudinal direction of the liquid crystal compound 30.

[0010] In Patent Document 1, the exposure mask 100 is designed such that the product of the refractive index difference Δn of the liquid crystal compound constituting the optical anisotropy layer of the liquid crystal diffraction element and the thickness d of the optical anisotropy layer, Δn × d, is half the wavelength (λ / 2) of the incident light wavelength λ. When linearly polarized light Lp is incident on such an exposure mask 100, the linearly polarized light Lp is diffracted and split into circularly polarized light +Cp, which is the first-order positive light, and circularly polarized light -Cp, which is the first-order negative light, as conceptually shown in Figure 14.

[0011] Here, the circularly polarized light +Cp, which is the first-order positive light, and the circularly polarized light -Cp, which is the first-order negative light, have the same wavelength, but their directions of rotation are opposite. Therefore, adjacent circularly polarized light +Cp and circularly polarized light -Cp interfere with each other, forming an interference pattern (interference fringes) on the coating film 104. As a result, the coating film 104 has an interference pattern that has the same orientation pattern as the liquid crystal orientation pattern of the liquid crystal diffraction element, which is the exposure mask 100, and has a diffraction period of 1 / 2. When this interference pattern is exposed, the coating film 104 forms an orientation pattern corresponding to the liquid crystal orientation pattern of the liquid crystal diffraction element.

[0012] In our investigation, we found that in conventional exposure methods using such liquid crystal diffraction elements as exposure masks, it is unavoidable that the zeroth-order light, i.e., linearly polarized light Lp that passes straight through the exposure mask 100, as shown by the dashed line in Figure 14, is incident on the coating film 104. Such zero-order light can act as noise that unnecessarily exposes the coating film 104, potentially disrupting the orientation pattern that is formed. In particular, when the pitch of the alignment pattern of the exposure mask 100, that is, the diffraction period is short, the zero-order light increases, and the alignment pattern may be greatly disturbed by noise.

[0013] An object of the present invention is to solve such problems of the prior art, and to provide an exposure method for an optical alignment layer that can form an optical alignment layer having an undisturbed alignment pattern by a simple method using an exposure mask.

Means for Solving the Problems

[0014] To solve this problem, the present invention has the following configuration.

[0015] [1] An exposure step of arranging an exposure mask and a substrate having a coating film containing a compound having an optically alignable group with the exposure mask and the coating film facing each other, irradiating light with which the compound has photosensitivity from the exposure mask side, exposing the coating film, and forming an alignment pattern is included, The light is circularly polarized light with an ellipticity of 0.7 to 1.3, The exposure mask is a polarization diffraction element having an alignment pattern in which the direction of the optical axis continuously changes while rotating along at least one direction in the plane, The exposure step is to expose the coating film with the zero-order light and the first-order light of the light diffracted by the exposure mask, and further, An exposure method for an optical alignment layer in which the intensity ratio of the zero-order light to the first-order light is 0.5 to 2. [2] The zero-order light and the first-order light are circularly polarized lights with an ellipticity of 0.6 to 2, and The zero-order light and the first-order light are circularly polarized lights having opposite rotation directions, the exposure method for an optical alignment layer according to [1]. [3] In the alignment pattern, when the length in which the direction of the optical axis rotates 180° along one direction in the plane is defined as one period, the coating film to which the exposure mask and the exposure step are applied has a ratio of the length of one period of the coating film to the length of one period of the exposure mask of 0.7 to 1.5, the exposure method for an optical alignment layer according to [1] or [2]. [4] In the alignment pattern of the exposure mask, when the length in which the direction of the optical axis rotates 180° in the plane is defined as one period, the coating film to which the exposure process is applied has a region where one period is 5 μm or less, and is the exposure method for the photo-alignment layer according to any one of [1] to [3]. [5] The exposure mask is a liquid crystal diffraction element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, The optically anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and is the exposure method for the photo-alignment layer according to any one of [1] to [4]. [6] The optically anisotropic layer has a bright part and a dark part extending from one main surface to the other main surface in an image obtained by observing a cross-section cut in the thickness direction along one direction with a scanning electron microscope, and the dark part has a region inclined with respect to the main surface, and is the exposure method for the photo-alignment layer according to [5]. [7] The angle of the dark part with respect to the perpendicular direction of the main surface of the optically anisotropic layer has different regions in the thickness direction of the optically anisotropic layer, and is the exposure method for the photo-alignment layer according to claim 6. [8] The optically anisotropic layer has a bending point of the dark part having one or more angles, and is the exposure method for the photo-alignment layer according to [6] or [7]. [9] The dark part has a bending point of two or more angles, and is the exposure method for the photo-alignment layer according to [8].

[10] When the length in which the direction of the optical axis rotates 180° along one direction in the plane is defined as one period, the optically anisotropic layer has a region where one period becomes shorter along one direction in the liquid crystal alignment pattern, The optically anisotropic layer has a region where the angle of the dark part with respect to the perpendicular direction of the main surface increases as one period becomes shorter, and is the exposure method for the photo-alignment layer according to any one of [6] to [9].

[11] The optically anisotropic layer has a region where the shapes of the bright part and the dark part are symmetric with respect to the center line in the thickness direction, and is the exposure method for the photo-alignment layer according to any one of [6] to

[10] .

[12] The optically anisotropic layer has a region where the shapes of the bright part and the dark part are asymmetric with respect to the center line in the thickness direction, and is the exposure method for the photo-alignment layer according to any one of [6] to

[11] .

[13] The method for exposing a photo-aligned layer according to any one of [1] to

[12] , wherein the orientation pattern of the exposure mask is a pattern having a radial direction from the center outward along at least one direction in the plane, in which the orientation of the optical axis changes while continuously rotating.

[14] A photo-aligned layer manufactured using the photo-aligned layer exposure method described in any of [1] to

[13] . [Effects of the Invention]

[0016] According to the photo-alignment layer exposure method of the present invention, a photo-alignment layer having a disorder-free orientation pattern can be formed by a simple method using an exposure mask. [Brief explanation of the drawing]

[0017] [Figure 1] This figure conceptually illustrates an example of an exposure method for the photo-alignment layer of the present invention. [Figure 2] This is a conceptual diagram illustrating an example of an exposure mask. [Figure 3] This is a schematic plan view of an example of an optically anisotropic layer. [Figure 4] This is a conceptual diagram illustrating the exposure method for the photo-alignment layer of the present invention. [Figure 5] This is a conceptual diagram illustrating an example of an exposure apparatus for coating films. [Figure 6] This is a schematic plan view of another example of an optically anisotropic layer. [Figure 7] This is a conceptual diagram illustrating another example of a coating exposure apparatus. [Figure 8] This is a conceptual diagram illustrating another example of an optically anisotropic layer. [Figure 9] This is a conceptual diagram illustrating another example of an optically anisotropic layer. [Figure 10] This is a conceptual diagram illustrating another example of an optically anisotropic layer. [Figure 11] This is a conceptual diagram illustrating another example of an optically anisotropic layer. [Figure 12] This is a conceptual diagram illustrating a conventional method for exposing photo-aligned layers. [Figure 13]This is a conceptual diagram illustrating a conventional method for exposing photo-aligned layers. [Figure 14] This is a conceptual diagram illustrating a conventional method for exposing photo-aligned layers. [Modes for carrying out the invention]

[0018] The method for exposing the photo-aligned layer of the present invention will be described in detail below, based on preferred embodiments shown in the attached drawings. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. Furthermore, the following diagrams are conceptual diagrams intended to explain the present invention, and the size, thickness, and positional relationships of each component and part do not necessarily correspond to those of actual objects. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively.

[0019] Figure 1 conceptually shows an example of an exposure apparatus for implementing the photo-alignment layer exposure method of the present invention. In the following explanation, "the method for exposing the photo-aligned layer of the present invention" will also be referred to as "the exposure method of the present invention."

[0020] As shown in Figure 1, the exposure method of the present invention involves irradiating a coating film 14 formed on the surface of a substrate 16 with light (circularly polarized Cp) emitted from a light source 12, which is then diffracted by an exposure mask 10. Various known exposure apparatuses can be used to implement the exposure method of the present invention. Suitable examples include proximity exposure apparatuses, laser light source apparatuses, and parallel light source apparatuses.

[0021] The substrate 16 is the same as the support 20 of the exposure mask 10, which will be described later. Furthermore, the coating film 14 is the same as the coating film that forms the photo-alignment layer in the orientation layer 24 of the exposure mask 10, which will be described later. That is, the coating film 14 is obtained by applying a paint containing a compound having photo-aligning groups to the surface of the substrate 16 and drying it. In the following description, the "compound having photo-aligning groups" will also be referred to as the "photo-aligning material".

[0022] The light source 12 irradiates the photo-oriented material contained in the coating film 14 with light of a wavelength that is photosensitive. The exposure mask 10 is a polarization diffraction element having an orientation pattern in which the orientation of the optical axis changes while continuously rotating along at least one direction in the plane. In the illustrated example, the exposure mask 10 is a liquid crystal diffraction element having an optically anisotropic layer formed using a composition containing a liquid crystal compound. This optically anisotropic layer has a liquid crystal orientation pattern in which the orientation of the optical axes originating from the liquid crystal compound changes while continuously rotating along at least one direction in the plane.

[0023] As will be described in detail later, the exposure method of the present invention involves irradiating the coating film 14 with light emitted from the light source 12 via the exposure mask 10. This aligns the photo-oriented material in the coating film 14, forming an orientation pattern on the coating film 14 that is the same as the liquid crystal orientation pattern in the exposure mask 10, i.e., the liquid crystal diffraction element (optical anisotropy layer).

[0024] In the exposure method of the present invention, the light source 12 irradiates the exposure mask 10 with circularly polarized light having an ellipticity of 0.7 to 1.3. That is, in the present invention, circularly polarized light that is close to a perfect circle is incident on the exposure mask. If the ellipticity of the light irradiated onto the exposure mask 10 exceeds 0.7 to 1.3, problems such as disorder in the orientation pattern formed on the coating film 14 (photo-orientation layer) and a decrease in the orientation-regulating force of the coating film 14 (photo-orientation layer) will occur. The ellipticity of the irradiation light irradiated onto the exposure mask 10 is preferably 0.8 to 1.2, and more preferably 0.9 to 1.1.

[0025] Any known light irradiation means can be used as the light source 12, as long as it is capable of irradiating parallel light with coherence and ellipticity within the above range. Examples include a light source combining a laser light source that emits diffusive, unpolarized laser light, a circular polarizer, and a collimator lens; a light source combining a laser light source that emits unpolarized, parallel laser light, and a circular polarizer; a light source combining a laser light source that emits diffusive, linearly polarized laser light, a quarter-wave plate, and a collimator lens; and a light source combining a laser light source that emits parallel, linearly polarized laser light, and a quarter-wave plate. Furthermore, any known light irradiation means can be used as the light source 12, as long as it is capable of irradiating parallel light with an ellipticity within the above-mentioned range and having sufficient coherence to form an orientation pattern on the coating film 14 after passing through the exposure mask 10. Examples include light sources that combine an exposure light source for proximity exposure with a circular polarizer, light sources that combine a mercury light source with a collimator lens and a circular polarizer, and light sources that combine an LED light source with a collimator lens and a circular polarizer.

[0026] Figure 2 conceptually shows an example of an exposure mask 10. The exposure mask 10 shown in Figure 2 is, as an example, a liquid crystal diffraction element having a support 20, an alignment layer 24, and an optical anisotropy layer 26. As described above, the optical anisotropy layer 26 is formed using a 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 changes while continuously rotating along at least one direction in the plane. In the exposure method of the present invention, the exposure mask 10 is not limited to the configuration shown in Figure 2. For example, the exposure mask may consist of an optically anisotropic layer 26 and an alignment layer 24 obtained by peeling off the support 20 from the exposure mask 10 shown in Figure 2, or it may consist only of the optically anisotropic layer 26 obtained by peeling off the support 20 and the alignment layer 24 from the exposure mask 10. Alternatively, the exposure mask may have another support attached to the optically anisotropic layer 26.

[0027] <<Support>> In the exposure mask 10, the support 20 supports the alignment layer 24 and the optical anisotropy layer 26. The support 20 can be any type of sheet material (film, plate) as long as it can support the orientation layer 24 and the optical anisotropy layer 26. The support 20 is preferably a transparent support, and examples include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, cycloolefin polymer films (for example, "Arton" (trade name), manufactured by JSR Corporation, "Zeonor" (trade name), manufactured by Nippon Zeon Co., Ltd.), polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride. The support is not limited to a flexible film, but may also be a non-flexible substrate such as a glass substrate.

[0028] There are no restrictions on the thickness of the support 20; the thickness should be set appropriately to accommodate the orientation layer and the optical anisotropy layer, depending on the application of the exposure mask 10 and the material used to form the support 20. The thickness of the support 20 is preferably 1 to 2000 μm, more preferably 3 to 500 μm, and even more preferably 5 to 150 μm.

[0029] <<Orientation layer>> In the exposure mask 10, an orientation layer 24 is formed on the surface of the support 20. The alignment layer 24 is an alignment layer used to orient the liquid crystal compound 30 into a predetermined liquid crystal alignment pattern when forming the optical anisotropy layer 26 of the exposure mask 10, which is a liquid crystal diffraction element. In Figure 2, etc., a rod-shaped liquid crystal compound is shown as an example of liquid crystal compound 30.

[0030] As described above, in the illustrated example of a transmissive exposure mask 10, the optical anisotropic layer 26 has a liquid crystal orientation pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes while continuously rotating along one direction in the plane (direction of arrow A in the figure), as shown in Figure 3, for example. Therefore, the alignment layer 24 of the exposure mask 10 is formed such that the optical anisotropy layer 26 can form this liquid crystal alignment pattern. In this invention, when the liquid crystal compound 30 is a rod-shaped liquid crystal compound, the optical axis 30A of the liquid crystal compound 30 is intended to be the molecular long axis of the rod-shaped liquid crystal compound. On the other hand, when the liquid crystal compound 30 is a disc-shaped liquid crystal compound, the optical axis 30A of the liquid crystal compound 30 is intended to be an axis parallel to the normal direction (orthogonal direction) with respect to the disc surface of the disc-shaped liquid crystal compound. In the following explanation, "the direction of the optical axis 30A rotates" will also be referred to simply as "the optical axis 30A rotates."

[0031] Various known materials can be used for the orientation layer 24. Examples include rubbing-treated films made of organic compounds such as polymers, obliquely vapor-deposited films of inorganic compounds, films having microgrooves, and films formed by accumulating Langmuir-Blodgett (LB) films of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate using the Langmuir-Blodgett method.

[0032] An oriented layer formed by rubbing can be created by rubbing the surface of a polymer layer several times in a specific direction with paper or cloth. Preferred materials for the orientation layer include polyimide, polyvinyl alcohol, polymers having polymerizable groups as described in Japanese Patent Publication No. 9-152509, materials used for forming orientation layers as described in Japanese Patent Publication No. 2005-97377, Japanese Patent Publication No. 2005-99228, and Japanese Patent Publication No. 2005-128503.

[0033] In the exposure mask 10, the orientation layer is preferably a so-called photo-alignment layer, which is formed by irradiating a photo-alignable material with polarized or unpolarized light to create an orientation layer. In other words, in the exposure mask 10, a photo-oriented layer 24 is preferably used, which is formed by applying a coating containing a photo-oriented material to the support 20, drying it to form a coating film, and irradiating this coating film with light according to the orientation pattern to form an oriented photo-oriented layer. As mentioned above, the "photo-oriented material" is a "compound having a photo-oriented group."

[0034] Examples of photo-oriented materials include those described in Japanese Patent Publication No. 2006-285197, Japanese Patent Publication No. 2007-76839, Japanese Patent Publication No. 2007-138138, Japanese Patent Publication No. 2007-94071, Japanese Patent Publication No. 2007-121721, Japanese Patent Publication No. 2007-140465, Japanese Patent Publication No. 2007-156439, and Japanese Patent Publication No. 2007-133184. Azo compounds described in Japanese Patent Publication No. 2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746, aromatic ester compounds described in Japanese Patent Publication No. 2002-229039, maleimides and / or azo compounds having photo-orienting units described in Japanese Patent Publication No. 2002-265541 and Japanese Patent Publication No. 2002-317013 Examples of preferred materials include lukenyl-substituted nadiimide compounds, photocrosslinkable silane derivatives described in Japanese Patent No. 4205195 and Japanese Patent No. 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides and photocrosslinkable esters described in Japanese Patent Publication No. 2003-520878, Japanese Patent Publication No. 2004-529220 and Japanese Patent No. 4162850, and photodimerizable compounds described in Japanese Patent Publication No. 9-118717, Japanese Patent Publication No. 10-506420, Japanese Patent Publication No. 2003-505561, International Publication No. 2010 / 150748, Japanese Patent Publication No. 2013-177561 and Japanese Patent Publication No. 2014-12823, particularly cinnamate compounds, chalcone compounds and coumarin compounds. Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable esters, cinnamate compounds, and chalcone compounds are particularly suitable for use.

[0035] There are no restrictions on the thickness of the orientation layer 24; the thickness should be set appropriately to obtain the required orientation function depending on the material used to form the orientation layer 24. The thickness of the orientation layer 24 is preferably 0.01 to 5 μm, and more preferably 0.02 to 2 μm.

[0036] There are no restrictions on the method for forming the orientation layer 24, and various known methods depending on the material used to form the orientation layer can be used. As an example, a method is described in which a coating containing a photo-aligning material is applied to the surface of a support 20 and dried to form a coating film. Subsequently, the coating film is exposed to laser light to form an orientation pattern, thereby creating a photo-aligned layer.

[0037] Figure 5 conceptually shows an example of an exposure apparatus that exposes the orientation layer 24 to form the orientation pattern described above. The exposure apparatus 60 shown in Figure 5 comprises a light source 64 equipped with a laser 62, a λ / 2 plate 65 that changes the polarization direction of the laser light M emitted by the laser 62, a polarizing beam splitter 68 that separates the laser light M emitted by the laser 62 into two beams MA and MB, mirrors 70A and 70B positioned on the optical paths of the two separated beams MA and MB, respectively, and λ / 4 plates 72A and 72B. The light source 64 emits linearly polarized light P0. The λ / 4 plate 72A converts the linearly polarized light P0 (ray MA) into right-circularly polarized light P R The λ / 4 plate 72B converts linearly polarized light P0 (ray MB) to left-circularly polarized light P L Convert them to the following:

[0038] A support 20 having an orientation layer 24 before the orientation pattern is formed is placed in the exposure section, two light rays MA and MB are intersected and interfered with on the orientation layer 24, and the resulting interference light is irradiated onto the orientation layer 24 to expose it. Due to the interference in this process, the polarization state of the light irradiated onto the orientation layer 24 changes periodically in an interference fringe pattern. As a result, an orientation layer having an orientation pattern in which the orientation state changes periodically (hereinafter also referred to as a pattern orientation layer) is obtained. In the exposure apparatus 60, the period of the orientation pattern can be adjusted by changing the intersection angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the intersection angle α, the length of one period (one period Λ, described later) in which the optical axis 30A rotates 180° in one direction of rotation of the optical axis 30A can be adjusted in an orientation pattern in which the optical axis 30A originating from the liquid crystal compound 30 rotates continuously along one direction. By forming an optically anisotropic layer 26 on an orientation layer 24 having an orientation pattern in which such an orientation state changes periodically, it is possible to form an optically anisotropic layer 26 having a liquid crystal orientation pattern in which the optical axis 30A derived from the liquid crystal compound 30 rotates continuously along one direction, as will be described later. Furthermore, by rotating the optical axes of the λ / 4 plates 72A and 72B by 90°, the rotation direction of the optical axis 30A can be reversed.

[0039] As described above, the pattern orientation layer has an orientation pattern that orients the liquid crystal compound such that the orientation of the optical axis of the liquid crystal compound in the optical anisotropy layer 26 formed on the pattern orientation layer changes while continuously rotating along at least one direction in the plane. If the orientation axis of the pattern orientation layer is the axis along the direction in which the liquid crystal compound is oriented, then the pattern orientation layer can be said to have an orientation pattern in which the orientation axis changes while continuously rotating along at least one direction in the plane. The orientation axis of a pattern orientation layer can be detected by measuring its absorption anisotropy. For example, when a pattern orientation layer is irradiated with linearly polarized light while rotating it, and the amount of light transmitted through the pattern orientation layer is measured, the direction in which the light intensity is maximum or minimum is observed to gradually change along one direction within the plane.

[0040] As mentioned above, the orientation layer 24 in the exposure mask 10 is provided as a preferred embodiment and is not an essential component. For example, by forming an orientation pattern on the support 20 using methods such as rubbing the support 20 or processing the support 20 with laser light, it is possible to configure the optical anisotropic layer 26, etc., to have a liquid crystal orientation pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes while continuously rotating along one direction.

[0041] <<Optical Anisotropy Layer>> In the exposure mask 10 shown in Figure 2, an optically anisotropic layer 26 is formed on the surface of the alignment layer 24.

[0042] As described above, in the exposure mask 10, which is a liquid crystal diffraction element, the optical anisotropy layer 26 is formed using a composition containing a liquid crystal compound.

[0043] The optically anisotropic layer 26 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes while continuously rotating in one direction (direction of arrow A in Figure 3, etc.) within the plane of the optically anisotropic layer. The optical axis 30A derived from the liquid crystal compound 30 is the axis in the liquid crystal compound 30 where the refractive index is highest, also known as the slow axis. For example, if the liquid crystal compound 30 is a rod-shaped liquid crystal compound, the optical axis 30A is aligned with the long axis of the rod shape. In the following explanation, the optical axis 30A derived from the liquid crystal compound 30 will also be referred to as "the optical axis 30A of the liquid crystal compound 30" or "optical axis 30A".

[0044] Figure 3 is a schematic diagram showing the orientation state of the liquid crystal compound 30 within the plane of the main surface of the optically anisotropic layer 26. The main surface is the largest surface of the sheet-like material (film, plate-like material, layer). As described above, the optically anisotropic layer 26 has a liquid crystal alignment pattern that changes while the optical axis 30A continuously rotates in one direction indicated by arrow A within the plane.

[0045] In the optically anisotropic layer 26, the liquid crystal compound 30 is oriented two-dimensionally in a plane parallel to the direction indicated by arrow A and the Y direction which is perpendicular to the direction of arrow A. In the following explanation, "the one direction indicated by arrow A" will also simply be referred to as "the direction of arrow A."

[0046] The plan view is a view of the optically anisotropic layer 26 from the thickness direction (= the stacking direction of each layer (film)). In other words, it is a view of the optically anisotropic layer 26 from a direction perpendicular to the main surface. Furthermore, in Figure 3, in order to clearly show the structure of the exposure mask 10, only the liquid crystal compound 30 on the surface of the alignment layer 24 is shown. However, this optical anisotropy layer 26 also has a structure in which the liquid crystal compound 30 is stacked from the liquid crystal compound 30 on the surface of this alignment layer in the thickness direction, as shown in Figure 2.

[0047] The optically anisotropic layer 26 has a liquid crystal orientation pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 changes while continuously rotating along the direction of arrow A within the plane of the optically anisotropic layer 26. Specifically, the statement that the orientation of the optical axis 30A of the liquid crystal compound 30 changes while continuously rotating in the direction of arrow A (a predetermined one direction) means that the angle between the optical axis 30A of the liquid crystal compound 30 arranged along the direction of arrow A and the direction of arrow A differs depending on the position in the direction of arrow A, and that the angle between the optical axis 30A and the direction of arrow A changes sequentially from θ to θ+180° or θ-180° along the direction of arrow A. Furthermore, the difference in angle between the optical axes 30A of adjacent liquid crystal compounds 30 in the direction of arrow A is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0048] On the other hand, in the liquid crystal compound 30 that forms the optical anisotropy layer 26, in the Y direction perpendicular to the direction of arrow A, that is, in the Y direction perpendicular to the direction in which the optical axis 30A rotates continuously, the liquid crystal compound 30 with the same orientation of the optical axis 30A is arranged at equal intervals. In other words, in the liquid crystal compounds 30 that form the optical anisotropy layer 26, the angle between the direction of the optical axis 30A and the direction of arrow A is equal for liquid crystal compounds 30 arranged in the Y direction.

[0049] The optically anisotropic layer 26 is formed using a liquid crystal composition containing a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and has a liquid crystal alignment pattern in which the optical axis of the rod-shaped liquid crystal compound or the optical axis of the disc-shaped liquid crystal compound is oriented as described above. An alignment layer 24 having an alignment pattern corresponding to the above-described liquid crystal alignment pattern is formed on the support 20, and a liquid crystal composition is applied to the alignment layer 24 and cured to obtain an optically anisotropic layer consisting of a cured layer of liquid crystal composition. Note that multilayer coating, as shown in the examples later, is also suitably used for applying the liquid crystal composition. The liquid crystal composition for forming the optically anisotropic layer 26 contains a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and may also contain other components such as leveling agents, orientation control agents, surfactants, polymerization initiators, crosslinking agents, and orientation aids.

[0050] Furthermore, the optical anisotropy layer 26 is preferably broadband with respect to the wavelength of the incident light, and is preferably composed of a liquid crystal material with inverse dispersion birefringence. It is also preferable to make the optical anisotropy layer substantially broadband with respect to the wavelength of the incident light by imparting a torsion component to the liquid crystal composition or by laminating different phase difference layers. For example, a method for realizing a broadband patterned λ / 2 plate by laminating two liquid crystal layers with different torsion directions in the optical anisotropy layer 26 is shown in Japanese Patent Application Publication No. 2014-089476, and can be preferably used in the present invention.

[0051] -Rod-shaped liquid crystal compound- Preferred rod-shaped liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyanosubstituted phenylpyrimidines, alkoxysubstituted phenylpyrimidines, phenyldioxanes, trans, and alkenylcyclohexylbenzonitriles. In addition to the low molecular weight liquid crystal molecules described above, high molecular weight liquid crystal molecules can also be used.

[0052] In the optically anisotropic layer 26, it is more preferable to fix the orientation of the rod-shaped liquid crystal compound by polymerization. As polymerizable rod-shaped liquid crystal compounds, compounds described in Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials Vol. 5, p. 107 (1993), U.S. Patent No. 4683327, No. 5622648, No. 5770107, International Publication Nos. 95 / 22586, 95 / 24455, 97 / 00600, 98 / 23580, 98 / 52905, Japanese Patent Publication No. 1-272551, 6-16616, 7-110469, 11-80081, and Japanese Patent Publication No. 2001-328973 can be used. Furthermore, as rod-shaped liquid crystal compounds, those described in Japanese Patent Publication No. 11-513019 and Japanese Patent Application Publication No. 2007-279688 can also be preferably used.

[0053] —Disc-shaped liquid crystal compounds— As disc-shaped liquid crystal compounds, those described in Japanese Patent Publication No. 2007-108732 and Japanese Patent Publication No. 2010-244038 can be preferably used. Furthermore, when a disc-shaped liquid crystal compound is used in the optically anisotropic layer, the liquid crystal compound 30 rises in the thickness direction within the optically anisotropic layer, and the optical axis 30A derived from the liquid crystal compound is defined as an axis perpendicular to the disc surface, the so-called phase-advancing axis.

[0054] As described above, the optically anisotropic layer 26 of the exposure mask 10 has a liquid crystal alignment pattern in which the optical axis 30A derived from the liquid crystal compound 30 rotates continuously along the direction of arrow A. In the illustrated example, the exposure mask 10 is designed such that, in a preferred embodiment, the optical anisotropy layer 26 is designed such that the product of the refractive index difference Δn of the liquid crystal compound 30 constituting the optical anisotropy layer 26 and the thickness d of the optical anisotropy layer 26, Δn × d, is approximately 1 / 4 wavelength (λ / 4) of the wavelength λ of the light irradiated onto the exposure mask 10. Specifically, the optical anisotropy layer 26 preferably has a Δn×d of 0.2λ to 0.3λ [nm] with respect to the wavelength λ [nm] of the light irradiated onto the exposure mask 10, and more preferably 0.225λ to 0.275λ [nm].

[0055] The following explanation will describe the effect of exposure of the coating film 14 by the exposure mask 10, or optical anisotropy layer 26, with reference to the conceptual diagram in Figure 4. As described above, the coating film 14 is obtained by applying a paint containing a photo-aligning material to the substrate 16 and drying it. As also described above, this coating film 14 is the same as the coating film in the photo-alignment layer of the alignment layer 24 of the exposure mask 10 described above. A photo-aligning material is a compound having photo-aligning groups.

[0056] As described above, the optically anisotropic layer 26 constituting the exposure mask 10, which is a liquid crystal diffraction element, has a liquid crystal orientation pattern in which the orientation of the optical axis 30A originating from the liquid crystal compound 30 rotates continuously in the direction of arrow A. In addition, in a preferred embodiment, the optical anisotropy layer 26 has a Δn × d of approximately 1 / 4 wavelength relative to the wavelength λ of the incident light. Alternatively, in a preferred embodiment, as described later, the liquid crystal compound 30 of the optical anisotropy layer 26 is spirally swirled in the thickness direction. Furthermore, as described above, the light source 12 illuminates the exposure mask 10 with circularly polarized light having an ellipticity of 0.7 to 1.3.

[0057] When circularly polarized light Cp is incident on an exposure mask 10 having such an optically anisotropic layer 26, as shown in Figure 4, about half of the circularly polarized light Cp is diffracted by the optically anisotropic layer 26 to become circularly polarized light Cp1, which is the first-order positive light. Furthermore, due to diffraction, the circularly polarized light Cp1 becomes circularly polarized light with the opposite direction of rotation to the circularly polarized light Cp. Here, approximately half of the circularly polarized light Cp incident on the optical anisotropy layer 26 passes through the optical anisotropy layer 26 as is, becoming the zero-order circularly polarized light Cp0. In other words, the optically anisotropic layer 26 has a diffraction efficiency of approximately 50%.

[0058] Here, the first-order circularly polarized light Cp1 and the zero-order circularly polarized light Cp0, which is the same as the original circularly polarized light Cp, have the same wavelength, but their directions of rotation are opposite. Therefore, adjacent circularly polarized light Cp1 and circularly polarized light Cp0 interfere with each other, forming the same interference pattern on the coating film 14 as the liquid crystal alignment pattern of the optical anisotropy layer 26. In other words, an alignment pattern is formed on the coating film 14 in which the direction of the line segments corresponding to the optical axes rotates continuously in the direction of arrow A. As a result, the coating film 14 forms an orientation pattern that is the same as the liquid crystal orientation pattern of the optical anisotropy layer 26 of the exposure mask 10, and also has a nearly identical period Λ, which will be described later.

[0059] As described above, the exposure method of the present invention effectively utilizes the zeroth-order light, which was previously considered noise, to interfere with the first-order light, thereby forming an interference pattern on the coating film 14 and creating an orientation pattern corresponding to the interference pattern. Therefore, according to the present invention, a photo-aligned layer having a clean orientation pattern free from disturbances caused by noise light can be formed using a simple method with an exposure mask. Accordingly, by using a photo-aligned layer exposed by the exposure method of the present invention, a liquid crystal diffraction element with high diffraction efficiency can be obtained.

[0060] As described above, in the exposure method of the present invention, the coating film 14 is exposed to light to form a photo-oriented layer by an interference pattern obtained by interfering circularly polarized light Cp1, which is a first-order light, and circularly polarized light Cp0, which is a zero-order light. Therefore, if the intensity difference between circularly polarized light Cp1 and circularly polarized light Cp0 is large, a proper interference pattern, i.e., an orientation pattern, cannot be formed. In the exposure method of the present invention, the intensity ratio of circularly polarized light Cp1 and circularly polarized light Cp0 is 0.5 to 2, which is the intensity ratio of 'circularly polarized light Cp0 / circularly polarized light Cp1 (0th order light / 1st order light)'. When the intensity ratio of circularly polarized light Cp1 to circularly polarized light Cp0 exceeds 0.5 to 2, problems such as disturbances in the orientation pattern occur. The intensity ratio of circularly polarized light Cp1 to circularly polarized light Cp0 is preferably 0.7 to 1.5, and more preferably 0.8 to 1.3.

[0061] Both the circularly polarized Cp1, which is the first-order light, and the circularly polarized Cp0, which is the zero-order light, are circularly polarized. Preferably, both the circularly polarized Cp1 and Cp0 have an ellipticity of 0.6 to 2. Setting the ellipticity of circularly polarized light Cp1 and Cp0 to 0.6-2 is preferable because it allows for the formation of a cleaner, less disordered orientation pattern. Furthermore, the ellipticity of circularly polarized light Cp1 and Cp0 is more preferably 0.8 to 1.3, and even more preferably 0.9 to 1.2.

[0062] Furthermore, the circularly polarized Cp1 and Cp0 are preferably circularly polarized with opposite rotation directions, as described above. By using circularly polarized light Cp1 and Cp0 with opposite rotation directions, it is preferable in that a cleaner orientation pattern with less disturbance can be formed.

[0063] In the optically anisotropic layer 26 of the exposure mask 10, which has a liquid crystal alignment pattern in which the optical axis 30A rotates continuously along one direction, the length (distance) over which the optical axis 30A of the liquid crystal compound 30 rotates 180° along one direction is defined as one period Λ in the liquid crystal alignment pattern. In other words, for the optically anisotropic layer 26 shown in Figures 2 and 3, the length (distance) over which the optical axis 30A of the liquid crystal compound 30 rotates by 180° in the direction of arrow A, where the orientation of the optical axis 30A continuously rotates and changes within the plane, is defined as one period Λ in the liquid crystal alignment pattern. In other words, one period Λ in the liquid crystal alignment pattern is defined by the distance over which the angle between the optical axis 30A of the liquid crystal compound 30 and the direction of arrow A changes from θ to θ+180°. In other words, the distance between the centers in the direction of arrow A of two liquid crystal compounds 30 whose angles with respect to arrow A are equal is defined as one period Λ. Specifically, as shown in Figure 3, the distance between the centers in the direction of arrow A of two liquid crystal compounds 30 whose directions coincide with the direction of the optical axis 30A is defined as one period Λ. In the exposure mask 10, the liquid crystal alignment pattern of the optical anisotropy layer 26 repeats this one period Λ in one direction, where the direction of arrow A, i.e., the direction of the optical axis 30A, continuously rotates and changes. Furthermore, the exposure mask 10 (optical anisotropy layer 26) is also a liquid crystal diffraction element, and this one period Λ becomes the period (one period) of the diffraction structure.

[0064] Similarly, in the coating film 14, i.e., the photo-alignment layer, one period Λ is the length of a 180° rotation along one direction of the alignment axis corresponding to the optical axis 30A of the liquid crystal compound 30, which is one period Λ in the alignment pattern. The period Λ of the optically aligned layer can be determined, for example, by forming an optically anisotropic layer on top of the optically aligned layer and measuring the period Λ of this optically anisotropic layer.

[0065] As described above, in the exposure method of the present invention, the optical anisotropy layer 26, the liquid crystal alignment pattern, and the alignment pattern formed on the coating film 14, i.e., the photo-alignment layer, have the same alignment pattern, and their periods Λ are also approximately equal. Specifically, it is preferable that the length of one period Λ of the liquid crystal alignment pattern in the optical anisotropic layer 26 and the length of one period Λ of the alignment pattern formed on the coating film 14 are in a ratio of 'coating film / optical anisotropic layer' of 0.7 to 1.5. In the optically anisotropic layer 26 and the coating film 14, setting the ratio of the lengths of one period Λ to 0.7 to 1.5 is preferable because it allows for the formation of a more disorder-free and beautiful orientation pattern. The ratio of the length of one period Λ of the liquid crystal alignment pattern in the optical anisotropic layer 26 to the length of one period Λ of the alignment pattern formed on the coating film 14 is more preferably 0.8 to 1.3, and even more preferably 0.9 to 1.2.

[0066] As described above, in the formation of orientation patterns on coating films using conventional exposure masks, the finer the orientation pattern becomes, that is, the shorter the period Λ in the orientation pattern becomes, the more zero-order light, which acts as noise, is produced, resulting in disorder in the orientation pattern. In contrast, the exposure method of the present invention, which effectively utilizes zero-order light, exhibits extremely small disturbances in the orientation pattern, even when the orientation pattern is made finer. Considering this point, in the exposure method of the present invention, it is preferable that the orientation pattern formed on the coating film 14 (photo-orientation layer) has a region where the length of one period Λ is 5 μm or less. In other words, the exposure method of the present invention is more suitably used for forming a fine orientation pattern on the coating film 14. The orientation pattern formed on the coating film 14 (photo-orientation layer) is more preferably one in the region where the period Λ is 3 μm or less, and even more preferably one in the region where the period Λ is 2 μm or less.

[0067] As shown in Figure 3, the optical anisotropy layer 26 of the exposure mask 10 has an optical axis 30A originating from the liquid crystal compound 30 that rotates continuously along only one direction. In the exposure method of the present invention, the liquid crystal alignment pattern of the exposure mask 10 (optical anisotropy layer 26), which is a liquid crystal diffraction element, that is, the alignment pattern formed on the coating film 14, is not limited thereto, and various liquid crystal alignment patterns can be used.

[0068] As an example, an exposure mask having an optically anisotropic layer 26 having a liquid crystal alignment pattern conceptually shown in the plan view of Figure 6 is provided. This optically anisotropic layer 26 has a liquid crystal alignment pattern that radiates from the inside outward, in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along one direction. That is, the liquid crystal alignment pattern of the optically anisotropic layer 26 shown in Figure 6 is a concentric pattern in which the orientation of the optical axis derived from the liquid crystal compound 30 changes while continuously rotating along one direction, radiating from the inside outward in a concentric pattern.

[0069] In the optically anisotropic layer 26, the orientation of the optical axis of the liquid crystal compound 30 changes while continuously rotating along a number of directions extending outward from the center of the optically anisotropic layer 26, for example, the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3, the direction indicated by arrow A4, and so on. Therefore, in the optically anisotropic layer 26, the rotation direction of the optical axis of the liquid crystal compound 30 is the same in all directions (unidirectional). In the illustrated example, the rotation direction of the optical axis of the liquid crystal compound 30 is counterclockwise in all directions indicated by arrows A1, A2, A3, and A4. In other words, if we consider arrows A1 and A4 as a single straight line, then along this line, the direction of rotation of the optical axis of the liquid crystal compound 30 reverses at the center of the optical anisotropy layer 26. For example, let's assume that the straight line formed by arrows A1 and A4 points to the right in the figure (in the direction of arrow A1). In this case, the optical axis of the liquid crystal compound 30 initially rotates clockwise from the outside of the optical anisotropy layer 26 toward the center, the direction of rotation reverses at the center of the optical anisotropy layer 26, and thereafter rotates counterclockwise from the center of the optical anisotropy layer 26 toward the outside.

[0070] In the exposure mask 10, as in the example described above, the optical anisotropic layer 26 with such a liquid crystal alignment pattern is exposed by diffraction to generate circularly polarized light Cp1, which is the first order of light, and circularly polarized light Cp0, which is the same as the original circularly polarized light Cp, and the coating film 14 is exposed by the interference light of the two. This makes it possible to form an orientation pattern on the coating film 14 that has the same orientation pattern as the liquid crystal orientation pattern of the optical anisotropy layer 26 of the exposure mask 10, where the optical axis rotates radially and changes continuously, and where the period Λ is also approximately the same.

[0071] Figure 7 conceptually shows an example of an exposure apparatus that exposes a coating film which will serve as the alignment layer 24 (photo-alignment layer) for forming the optical anisotropy layer 26, thereby forming an alignment pattern corresponding to the liquid crystal alignment pattern shown in Figure 6, in which the optical axes rotate radially and change continuously. The exposure apparatus 80 shown in Figure 7 includes a light source 84 equipped with a laser 82, a polarizing beam splitter 86 that splits the laser light M from the laser 82 into S-polarized MS and P-polarized MP, a mirror 90A arranged in the optical path of the P-polarized MP and a mirror 90B arranged in the optical path of the S-polarized MS, a lens 92 arranged in the optical path of the S-polarized MS, the polarizing beam splitter 94, and a λ / 4 plate 96.

[0072] The P-polarized MP beam, split by the polarizing beam splitter 86, is reflected by the mirror 90A and incident on the polarizing beam splitter 94. On the other hand, the S-polarized MS beam, also split by the polarizing beam splitter 86, is reflected by the mirror 90B, focused by the lens 92, and incident on the polarizing beam splitter 94. P-polarized MP and S-polarized MS are combined by the polarization beam splitter 94 and converted into right-circularly polarized and left-circularly polarized beams according to their polarization direction by the λ / 4 plate 96, and then incident on the orientation layer 24 on the support 20. Here, the interference between right-circularly polarized and left-circularly polarized light causes the polarization state of the light irradiated onto the orientation layer 24 to change periodically in an interference fringe pattern. As you move from the inside to the outside of the concentric circles, the intersection angle between the left-circularly polarized and right-circularly polarized light changes, resulting in an exposure pattern where the pitch changes from the inside to the outside. This results in a radial (concentric) orientation pattern in the orientation layer 24 in which the orientation state changes periodically.

[0073] In this exposure apparatus 80, the period Λ of the liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 30 rotates continuously by 180° along one direction can be controlled by changing the refractive power of the lens 92, the focal length of the lens 92, and the distance between the lens 92 and the alignment layer 24. Furthermore, by adjusting the refractive power of lens 92 (the F-number of lens 92), the length of one cycle of the liquid crystal alignment pattern can be changed in one direction in which the optical axis rotates continuously. Specifically, by interfering with parallel light and changing the divergence angle of the light spread by lens 92, the length of one period of the liquid crystal alignment pattern can be changed in one direction in which the optical axis rotates continuously. More specifically, if the refractive power of lens 92 is weakened, it approaches parallel light, so the length of one period Λ of the liquid crystal alignment pattern gradually shortens from the inside to the outside. Conversely, if the refractive power of lens 92 is strengthened, the length of one period Λ of the liquid crystal alignment pattern shortens abruptly from the inside to the outside.

[0074] In the above example, the optical anisotropy layer 26 constituting the liquid crystal diffraction element that serves as the exposure mask 10 has the liquid crystal compound 30 oriented in the same direction in the thickness direction, as shown in Figure 2. However, in the exposure method of the present invention, the optical anisotropy layer 26 constituting the liquid crystal diffraction element that serves as the exposure mask 10 is not limited thereto. In other words, in the exposure method of the present invention, the optical anisotropic layer 26 constituting the liquid crystal diffraction element that serves as the exposure mask 10 may have the liquid crystal compound 30 spiraling in a helical manner in the thickness direction. That is, the liquid crystal compound 30 constituting the optical anisotropic layer 26 may be spirally oriented in a twisted manner in the thickness direction.

[0075] In an optically anisotropic layer having the above-described liquid crystal alignment pattern, in which the liquid crystal compound 30 spirals in a helical manner in the thickness direction, when a cross-section cut in the thickness direction along one direction in which the orientation of the optical axis 30A of the liquid crystal compound 30 changes as it continuously rotates is observed with a scanning electron microscope (SEM), a striped pattern of light and dark areas tilted relative to the main surface is observed due to the spiraling of the liquid crystal compound 30. In the following explanation, the image obtained by observing a cross-section cut in the thickness direction along one direction of rotation of the optical axis 30A using a SEM will also simply be referred to as a "cross-sectional SEM image."

[0076] An optically anisotropic layer 26 in which the liquid crystal compound 30 spirals in the thickness direction can be formed by adding a chiral agent to the composition for forming the optically anisotropic layer 26 described above. --Chiral agents (optically active compounds)-- Chiral agents have the function of inducing a helical structure in the liquid crystal phase. Since the direction of the helical twisting and the helical twisting power (HTP) induced differ depending on the chiral agent, they should be selected according to the purpose. There are no particular restrictions on the chiral agent, and known compounds (for example, described in the Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Agents for TN (twisted nematic) and STN (Super Twisted Nematic), page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide, and isomannide derivatives can be used. Chiral agents generally contain an asymmetric carbon atom, but axially asymmetric compounds or planar asymmetric compounds that do not contain an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric compounds or planar asymmetric compounds include binaphthyl, helicene, paracyclophane, and their derivatives. Chiral agents may have polymerizable groups. If both the chiral agent and the liquid crystal compound have polymerizable groups, a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound can form a polymer having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral agent. In this embodiment, it is preferable that the polymerizable group of the polymerizable chiral agent is of the same type as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group, or an azilidinyl group, more preferably an unsaturated polymerizable group, and even more preferably an ethylenically unsaturated polymerizable group. Furthermore, the chiral agent may be a liquid crystal compound.

[0077] When the chiral agent has a photoisomerizing group, it is preferable because a desired twisted orientation corresponding to the emission wavelength can be formed by photomask irradiation with active light after coating and orientation. Preferred photoisomerizing groups are the isomerization site of a photochromic compound, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds that can be used include those described in Japanese Patent Publication No. 2002-80478, 2002-80851, 2002-179668, 2002-179669, 2002-179670, 2002-179681, 2002-179682, 2002-338575, 2002-338668, 2003-313189, and 2003-313292, etc.

[0078] In the liquid crystal composition, the content of the chiral agent is preferably 0.01 to 200 mol%, and more preferably 1 to 30 mol%, relative to the molar amount of the liquid crystal compound.

[0079] Thus, if the optically anisotropic layer 26 has a liquid crystal alignment pattern in which the orientation of the optical axis 30A changes while continuously rotating along one direction within the plane, and the liquid crystal compound 30 has a structure in which it spirals in the thickness direction, then in the cross-sectional SEM image, there will be bright and dark areas extending from one main surface to the other main surface, and in the thickness direction, there will be regions in the dark area that are inclined with respect to the main surface of the optically anisotropic layer 26. The bright and dark areas observed in the cross-sectional SEM image of the optically anisotropic layer 26 originate from the orientation of the optical axis of the liquid crystal compound. The measurement conditions for observing the cross-sectional SEM image of the optically anisotropic layer 26 can be set as appropriate.

[0080] In a cross-sectional SEM image of the optical anisotropy layer 26, if there are bright and dark areas extending from one main surface to the other main surface, and in the thickness direction, the dark areas have regions that are inclined with respect to the main surface of the optical anisotropy layer 26, the decrease in the diffraction efficiency of refracted light can be more effectively suppressed.

[0081] Here, the optical anisotropic layer 26 constituting the liquid crystal diffraction element that serves as the exposure mask 10 preferably has regions where the angle of the dark area (average inclination angle) with respect to the perpendicular direction (normal direction) of the main surface is different along one direction, and more preferably has regions where it gradually changes. In the case where the optically anisotropic layer 26 described above has regions in the in-plane direction where the orientation of the optical axis of the liquid crystal compound rotates by 180° in the plane, and regions where the magnitude of the twist angle in the thickness direction is different, and where the twist angle in the thickness direction is larger in regions where the period Λ of the liquid crystal alignment pattern is shorter, when a cross section cut in the thickness direction along one direction is observed with a scanning electron microscope, it is observed that the angle of the dark area with respect to the perpendicular direction of the main surface increases as the length of the period of the liquid crystal alignment pattern decreases.

[0082] A configuration in which the twist angle in the thickness direction differs in the plane direction can be formed by adding a photoreactive chiral agent to a liquid crystal composition, coating the liquid crystal composition on an alignment layer, and then irradiating each region with a different amount of light to cause the helical twisting power (HTP) of the photoreactive chiral agent to differ in each region.

[0083] Specifically, in an optically anisotropic layer, a configuration in which the torsion angle in the thickness direction differs for each region within the plane can be formed by using a chiral agent that undergoes reverse isomerization, dimerization, and isomerization and dimerization upon irradiation with light, thereby changing the HTP, and irradiating the liquid crystal composition forming the optically anisotropic layer with light of a wavelength that changes the HTP of the chiral agent, varying the irradiation amount for each region, either before curing the liquid crystal composition or during curing of the liquid crystal composition. For example, by using a chiral agent whose HTP decreases upon light irradiation, the HTP of the chiral agent decreases upon light irradiation. Here, by changing the amount of light irradiation in each region, for example, in regions with a high irradiation dose, the HTP decreases significantly, and the induction of helices decreases, so the twist angle of the twisted structure becomes smaller. On the other hand, in regions with a low irradiation dose, the decrease in HTP is small, so the twist angle of the twisted structure becomes larger.

[0084] There are no particular limitations on the method of changing the amount of light irradiation for each region; methods such as irradiating light through a gradient mask, changing the irradiation time for each region, or changing the irradiation intensity for each region can be used. A gradient mask is a mask in which the transmittance of light changes within the surface.

[0085] —Photoreactive chiral agents— Photoreactive chiral agents, for example, consist of compounds represented by the following general formula (I), and have the characteristic of being able to control the orientation structure of liquid crystal compounds and to change the helical pitch of liquid crystal compounds, i.e., the torsional force (HTP: helical twisting power) of the helical structure, by irradiation with light. That is, they are compounds that induce a change in the torsional force of the helical structure in liquid crystal compounds, preferably nematic liquid crystal compounds, by light irradiation (ultraviolet to visible light to infrared light), and have chiral sites (molecular structural units) and sites that undergo structural changes by light irradiation as necessary sites. Moreover, photoreactive chiral agents represented by the following general formula (I) can particularly significantly change the HTP of liquid crystal molecules.

[0086] Furthermore, the aforementioned HTP represents the torsional force of the helical structure of the liquid crystal, i.e., HTP = 1 / (pitch × chiral agent concentration [mass fraction]). For example, the helical pitch (one period of the helical structure; μm) of the liquid crystal molecule at a certain temperature is measured, and this value is converted from the concentration of the chiral agent [μm]. -1 This can be determined by the following. When a photoreactive chiral agent forms a selective reflectance color depending on the illuminance of light, the rate of change of HTP (= HTP before irradiation / HTP after irradiation) is preferably 1.5 or more if HTP becomes smaller after irradiation, more preferably 2.5 or more, and preferably 0.7 or less if HTP becomes larger after irradiation, and more preferably 0.4 or less.

[0087] Next, we will explain compounds represented by general formula (I). General formula (I)

[0088] [ka]

[0089] In the above formula, R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group having a total of 3 to 15 carbon atoms, and a methacryloyloxyalkyloxy group having a total of 4 to 15 carbon atoms. Examples of the aforementioned alkoxy groups having 1 to 15 carbon atoms include methoxy, ethoxy, propoxy, butoxy, hexyloxy, and dodecyloxy groups. Among these, alkoxy groups having 1 to 12 carbon atoms are preferred, and alkoxy groups having 1 to 8 carbon atoms are particularly preferred.

[0090] Examples of the aforementioned acryloyloxyalkyloxy groups having a total of 3 to 15 carbon atoms include acryloyloxyethyloxy group, acryloyloxybutyloxy group, and acryloyloxydecyloxy group. Among these, acryloyloxyalkyloxy groups having 5 to 13 carbon atoms are preferred, and acryloyloxyalkyloxy groups having 5 to 11 carbon atoms are particularly preferred.

[0091] Examples of the aforementioned methacryloyloxyalkyloxy groups having a total of 4 to 15 carbon atoms include methacryloyloxyethyloxy group, methacryloyloxybutyloxy group, and methacryloyloxydecyloxy group. Among these, methacryloyloxyalkyloxy groups having 6 to 14 carbon atoms are preferred, and methacryloyloxyalkyloxy groups having 6 to 12 carbon atoms are particularly preferred.

[0092] The molecular weight of the photoreactive chiral agent represented by the general formula (I) described above is preferably 300 or more. Furthermore, it is preferable that it has high solubility with the liquid crystal compound described later, and it is even more preferable that its solubility parameter SP value is similar to that of the liquid crystal compound.

[0093] The following are specific examples of compounds represented by the general formula (I) mentioned above (exemplary compounds (1) to (15)), but the present invention is not limited to these.

[0094] [ka]

[0095] [ka]

[0096] [ka]

[0097] In the present invention, as a photoreactive chiral agent, for example, a photoreactive optically active compound represented by the following general formula (II) can also be used.

[0098] General formula (II)

[0099] [ka]

[0100] In the above formula, R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group having a total of 3 to 15 carbon atoms, and a methacryloyloxyalkyloxy group having a total of 4 to 15 carbon atoms. Examples of the aforementioned alkoxy groups having 1 to 15 carbon atoms include methoxy, ethoxy, propoxy, butoxy, hexyloxy, octyloxy, and dodecyloxy groups. Among these, alkoxy groups having 1 to 10 carbon atoms are preferred, and alkoxy groups having 1 to 8 carbon atoms are particularly preferred.

[0101] Examples of the aforementioned acryloyloxyalkyloxy groups having a total of 3 to 15 carbon atoms include acryloyloxy groups, acryloyloxyethyl groups, acryloyloxypropyl groups, acryloyloxyhexyl groups, acryloyloxybutyl groups, and acryloyloxydecyl groups. Among these, acryloyloxyalkyloxy groups having 3 to 13 carbon atoms are preferred, and acryloyloxyalkyloxy groups having 3 to 11 carbon atoms are particularly preferred.

[0102] Examples of the aforementioned methacryloyloxyalkyloxy groups having a total of 4 to 15 carbon atoms include methacryloyloxy groups, methacryloyloxyethyloxy groups, and methacryloyloxyhexyloxy groups. Among these, methacryloyloxyalkyloxy groups having 4 to 14 carbon atoms are preferred, and methacryloyloxyalkyloxy groups having 4 to 12 carbon atoms are particularly preferred.

[0103] The molecular weight of the photoreactive optically active compound represented by the general formula (II) described above is preferably 300 or more. Furthermore, it is preferable that it has high solubility with the liquid crystal compound described later, and it is even more preferable that its solubility parameter SP value is similar to that of the liquid crystal compound.

[0104] The following are specific examples of photoreactive optically active compounds represented by the general formula (II) mentioned above (exemplary compounds (21) to (32)), but the present invention is not limited to these.

[0105] [ka]

[0106] [ka]

[0107] [ka]

[0108] Furthermore, photoreactive chiral agents can be used in combination with non-photoreactive chiral agents, such as chiral compounds with a large temperature dependence of torsional force. Examples of known non-photoreactive chiral agents include those described in Japanese Patent Publication No. 2000-44451, Japanese Patent Publication No. 10-509726, WO98 / 00428, Japanese Patent Publication No. 2000-506873, Japanese Patent Publication No. 9-506088, Liquid Crystals (1996, 21, 327), Liquid Crystals (1998, 24, 219), etc.

[0109] In the cross-sectional SEM image of the liquid crystal diffraction element that constitutes the exposure mask 10, the optical anisotropic layer in which the dark area 44 is inclined with respect to the direction perpendicular to the main surface preferably shows bright and dark areas extending from one main surface to the other main surface in the cross-sectional SEM image, and the dark area has one or more or two or more angular inflection points.

[0110] An example of such an optically anisotropic layer is shown in Figure 8. In Figure 8, the bright areas 42 and dark areas 44 are superimposed on the cross-section of the optically anisotropic layer 26a. In the cross-sectional SEM image of the optically anisotropic layer 26a shown in Figure 8, the dark area 44 has two inflection points where the angle changes. In other words, the optically anisotropic layer 26 can be said to have three regions in the thickness direction, region 27a, region 27b, and region 27c, corresponding to the inflection points of the dark area 44.

[0111] The optically anisotropic layer 26a has a liquid crystal alignment pattern in which, at any position in the thickness direction, the optical axis originating from the liquid crystal compound 30 rotates clockwise toward the left in the in-plane direction. Furthermore, one period of the liquid crystal alignment pattern is constant in the thickness direction.

[0112] Furthermore, as shown in Figure 8, the liquid crystal compound 30 is torsionally oriented in the lower region 27c in the thickness direction, twisting in a clockwise (right-handed) spiral from the top to the bottom in the figure. In the central region 27b in the thickness direction, the liquid crystal compound 30 is not twisted in the thickness direction, and the liquid crystal compounds 30 stacked in the thickness direction have the same optical axis oriented in the same direction. That is, the liquid crystal compounds 30 located at the same position in the in-plane direction have the same optical axis oriented in the same direction. In the upper region 27a in the thickness direction, the liquid crystal compound 30 is twisted and oriented so as to twist in a helical manner from the top to the bottom in the thickness direction. In other words, the optically anisotropic layer 26 shown in Figure 8 has different torsional states in the thickness direction of the liquid crystal compound 30 in regions 27a, 27b, and 27c.

[0113] In an optically anisotropic layer having a liquid crystal orientation pattern in which the optical axis 30A derived from the liquid crystal compound 30 rotates continuously in one direction, the bright and dark areas in the cross-sectional SEM image of the optically anisotropic layer are observed to connect liquid crystal compounds with the same orientation. As an example, Figure 8 shows that a dark area 44 is observed connecting the liquid crystal compounds 30 whose optical axes are oriented perpendicular to the plane of the paper. In the lowest region 27c in the thickness direction, the dark area 44 is inclined toward the upper left in the figure. In the middle region 27b, the dark area 44 extends in the thickness direction. In the uppermost region 27a, the dark area 44 is inclined toward the upper right in the figure. In other words, the optical anisotropic layer 26 shown in Figure 8 has two inflection points where the angle of the dark area 44 changes. Furthermore, in the uppermost region 27a, the dark area 44 is tilted upwards and to the right, while in the lowermost region 27b, the dark area 44 is tilted upwards and to the left. That is, the direction of the tilt of the dark area 44 is different in region 27a and region 27c.

[0114] Furthermore, the optically anisotropic layer 26a shown in Figure 8 has one inflection point in the dark area 44 where the inclination direction is reversed. Specifically, in the dark area 44 of the optical anisotropy layer 26a, the gradient direction in region 27a and the gradient direction in region 27b are opposite. Therefore, the inflection point located at the interface between region 27a and region 27b is an inflection point where the gradient direction is reversed. In other words, the optical anisotropy layer 26 has one inflection point where the gradient direction is reversed.

[0115] Furthermore, in the optically anisotropic layer 26a, regions 27a and 27c have, for example, equal thickness, and as described above, the torsional state of the liquid crystal compound 30 in the thickness direction is different in each region. Therefore, as shown in Figure 1, the bright areas 42 and dark areas 44 in the cross-sectional SEM image are roughly C-shaped. Therefore, the shape of the dark area 44 in the optically anisotropic layer 26a is symmetrical with respect to the center line in the thickness direction.

[0116] The liquid crystal diffraction element of the present invention has such an optically anisotropic layer 26a, that is, a bright area 42 and a dark area 44 that extend from one surface to the other surface in a cross-sectional SEM image, and the dark area 44 has one or more or two or more angular inflection points, thereby reducing the wavelength dependence of the diffraction efficiency and enabling the diffraction of light with a similar diffraction efficiency regardless of wavelength.

[0117] In the example shown in Figure 8, the dark area 44 is configured to have inflection points at two angles. However, the present invention is not limited to this configuration, and the dark area 44 may also be configured to have an inflection point at one angle, or to have inflection points at three or more angles. For example, if the dark area 44 of the optical anisotropy layer has an inflection point of one angle, it may consist of regions 27a and 27c as shown in Figure 9, or regions 27a and 27b, or regions 27b and 27c. Alternatively, if the dark area 44 of the optical anisotropy layer has an inflection point of three angles, it may consist of two alternating regions 27a and 27c as shown in Figure 8.

[0118] As described above, in the case of a radial liquid crystal alignment pattern as shown in Figure 6, the optical anisotropy layer has a period Λ that gradually shortens from the center outwards. Thus, when the optically anisotropic layer 26 has a region in which the period Λ of the liquid crystal alignment pattern gradually shortens in one direction, it is preferable that the helical rotation angle of the liquid crystal compound 30 in the thickness direction gradually increases in accordance with the gradual decrease of the period Λ. In other words, if the liquid crystal alignment pattern has a region in which one period Λ gradually shortens in one direction, it is preferable that the angle of the dark area 44 with respect to the perpendicular direction of the main surface increases in accordance with the gradual decrease of one period Λ.

[0119] An example of such an optically anisotropic layer is shown in Figure 10. The optically anisotropic layer 26b shown in Figure 10 has a liquid crystal alignment pattern that radiates from the center of the optically anisotropic layer 26 in one direction in which the orientation of the optical axis of the liquid crystal compound 30 changes while continuously rotating, and in each direction, the period Λ of the liquid crystal alignment pattern gradually shortens as you move from the center outwards.

[0120] Furthermore, the optically anisotropic layer 26b has a striped pattern of bright areas 42 and dark areas 44 extending from one surface to the other in the cross-sectional SEM image, and each dark area 44 has two inflection points. In addition, in each dark area 44, the slope direction in the upper region in the figure is opposite to the slope direction in the lower region in the figure. That is, each dark area 44 has regions with different slope directions. Specifically, in the optical anisotropy layer 26b shown in Figure 10, in the portion to the right of the center in the plane direction, the dark area 44 is tilted to the right in the upper region of the figure, and in the lower region of the figure, the dark area 44 is tilted to the left. On the other hand, in the portion to the left of the center of the optical anisotropy layer 26b, the dark area 44 is tilted to the left in the upper region of the figure, and in the lower region of the figure, the dark area 44 is tilted to the right.

[0121] Furthermore, in the optically anisotropic layer 26b, if the angle of the dark area 44 is defined as the angle formed by the line connecting the contact points of one surface of each dark area 44 to the other surface with the perpendicular direction of the main surface of the optically anisotropic layer 26b, then the angle of the dark area 44 gradually changes along one direction (arrows A1, A2, A3, etc.) in which the orientation of the optical axis of the liquid crystal compound 30 changes as it rotates continuously. Specifically, in the example shown in Figure 10, the angle of the dark area 44 near the center is approximately 0°, and the angle gradually increases as you move outward from the center. That is, in the illustrated example of the optically anisotropic layer 26b, the angle of the dark area 44 gradually increases as the period Λ of the liquid crystal alignment pattern gradually shortens. In this invention, the term "gradual change in the angle of the dark area" refers to both a continuous change in angle and a stepwise change in angle.

[0122] Such an optically anisotropic layer 26b has three regions (27a, 27b, and 27c) in the thickness direction, and it can also be said that the inclination angle of the dark area 44 at the same position in the planar direction is different in each region.

[0123] Here, the cross-sectional SEM image of the radial central portion of the optical anisotropy layer 26b shown in Figure 10 (the region indicated by A in Figure 10) is as shown in Figure 8. As shown in Figure 8, in the central portion, the liquid crystal compound 30 is oriented such that it is twisted clockwise (right-handed) in the thickness direction from the top to the bottom in the figure in the lower region 27c. On the other hand, in the middle region 27b in the thickness direction, the liquid crystal compound 30 is not twisted in the thickness direction, and the liquid crystal compounds 30 stacked in the thickness direction have the same optical axis oriented in the same direction. In other words, the liquid crystal compounds 30 located at the same position in the plane direction have the same optical axis oriented in the same direction. Furthermore, in the upper region 27a in the thickness direction, the liquid crystal compound 30 is oriented so as to twist counterclockwise (leftward) from the top to the bottom in the thickness direction.

[0124] In the radial central portion of the optically anisotropic layer 26b, the torsional state of the liquid crystal compound 30 in the thickness direction differs in regions 27a, 27b, and 27c. As a result, as shown in Figure 8, the bright areas 42 and dark areas 44 in the SEM image are roughly C-shaped.

[0125] Furthermore, in the example shown in Figure 8, the thickness of region 27a and the thickness of region 27c are approximately the same, and the twist angle in the thickness direction of the liquid crystal compound 30 in region 27a is approximately the same as the twist angle in the thickness direction of the liquid crystal compound 30 in region 27c. Therefore, the dark areas 44 in region 27a and the dark areas 44 in region 27c have opposite tilt directions and the same tilt angle. In region 27b, the liquid crystal compound 30 is not twisted in the thickness direction, so the dark areas 44 are not tilted. Therefore, the angle of the dark areas 44 in the central part of the optical anisotropy layer 26 is approximately 0°.

[0126] In other words, in the cross-section of the radial central portion of the optically anisotropic layer 26b, the shapes of the bright areas 42 and dark areas 44 are symmetrical with respect to the center line in the thickness direction of the optically anisotropic layer 26b.

[0127] On the other hand, the cross-sectional SEM image of the radial edges (outer portion, the region indicated as B in Figure 10) of the optical anisotropy layer 26b shown in Figure 10 is as shown in Figure 11.

[0128] In the outer portion shown in Figure 11, the liquid crystal compound 30 is oriented in the lower region 27c in the thickness direction to twist clockwise (right-handed) from the top to the bottom in the figure. The twist angle in the thickness direction is larger in the outer portion of region 27c compared to the central portion. Furthermore, in the middle region 27b in the thickness direction, the liquid crystal compound 30 is oriented so as to twist clockwise (right-handed) from the top to the bottom in the thickness direction. Furthermore, the torsion angle in the thickness direction in region 27c is different from the torsion angle in the thickness direction in region 27b. Therefore, the dark area 44 in region 27c and the dark area 44 in region 27b have the same inclination direction, but different inclination angles.

[0129] On the other hand, in the upper region 27a in the thickness direction, the liquid crystal compound 30 is oriented to twist counterclockwise (leftward) from the top to the bottom in the thickness direction. Therefore, the dark area 44 in region 27a is tilted in the opposite direction to that of regions 27c and 27b. Also, the twist angle in the thickness direction is smaller in the outer part of region 27a compared to the central part. Therefore, the absolute value of the tilt angle of the dark area 44 in region 27a is smaller than the absolute value of the tilt angle of the dark area 44 in region 27c.

[0130] Therefore, the angle of the dark area 44 in the outer portion of the optically anisotropic layer 26b is a value other than 0°.

[0131] In other words, the optically anisotropic layer 26b has asymmetric shapes of the bright areas 42 and dark areas 44 with respect to the center line in the thickness direction of the optically anisotropic layer 26b in the cross-section of the radial edges.

[0132] In the example shown in Figure 10, regions 27a, 27b, and 27c of the optically anisotropic layer 26b have a configuration in which the period Λ of the liquid crystal alignment pattern gradually shortens from the center outward. Furthermore, in region 27c, the right-handed twist in the thickness direction increases from the center outward, in region 27b, the right-handed twist in the thickness direction increases from the center outward, and in region 27a, the left-handed twist in the thickness direction decreases from the center outward. This can be described as adding a clockwise twist to the thickness direction in each region, with respect to the twist in the thickness direction at the center, as it moves outward. With this configuration, as shown in Figure 10, the optical anisotropy layer 26b has a configuration in which the shapes of the bright areas 42 and dark areas 44 are symmetrical with respect to the center line in the thickness direction of the optical anisotropy layer 26b in the cross section of the radial central part, and the shapes of the bright areas 42 and dark areas 44 are asymmetrical with respect to the center line in the thickness direction of the optical anisotropy layer 26b in the cross section of the radial ends.

[0133] The optical anisotropy layer having this configuration suppresses the decrease in diffraction efficiency even in regions where the diffraction angle is large. As a result, a liquid crystal diffraction element can be made that has high diffraction efficiency regardless of the diffraction angle and uniform light intensity of transmitted light, and the wavelength dependence of the diffraction efficiency can be reduced, allowing light to be diffracted with similar diffraction efficiency regardless of wavelength.

[0134] In the example shown in Figure 10, the optical anisotropy layer 26b is configured to have two inflection points where the tilt angle of each dark area 44 changes, but it is not limited to this configuration. Each dark area 44 may have one inflection point, or it may have three or more inflection points.

[0135] Furthermore, in the example shown in Figure 10, the optical anisotropy layer 26b has symmetrical shapes of the bright areas 42 and dark areas 44 with respect to the center line in the thickness direction of the optical anisotropy layer 26b in the cross-section of the radial central portion, and asymmetrical shapes of the bright areas 42 and dark areas 44 with respect to the center line in the thickness direction of the optical anisotropy layer 26b in the cross-section of the radial edges. In other words, in the planar direction, the optical anisotropy layer 26b has a mixture of regions where the shapes of the bright and dark areas are symmetrical with respect to the center line in the thickness direction, and regions where they are asymmetrical. However, the present invention is not limited thereto, and the optical anisotropy layer may be asymmetric with respect to the center line in the thickness direction across the entire surface direction.

[0136] The exposure mask 10 described above is a liquid crystal diffraction element having an optical anisotropy layer in which the orientation of the optical axis 30A derived from the liquid crystal compound 30 changes while continuously rotating along at least one direction. However, in the exposure method of the present invention, the exposure mask is not limited to one using a liquid crystal diffraction element. That is, in the exposure method of the present invention, various known materials can be used as exposure masks as long as they have an orientation pattern in which the orientation of the optical axis changes continuously along at least one direction in the plane. Metasurfaces are one example of this.

[0137] As described above, the exposure method of the present invention involves exposing a photosensitive coating film 14 containing a photo-aligning material, formed on a substrate 16, using an exposure mask 10 having, for example, an optically anisotropic layer 26 which is a liquid crystal diffraction element. The exposure method of the present invention thereby forms the liquid crystal alignment pattern of the exposure mask 10, i.e., the optically anisotropic layer 26, as an alignment pattern on the coating film 14, thereby creating a photo-alignment layer on the substrate 16. A transmissive liquid crystal diffraction element can be manufactured by forming an optical anisotropy layer on the optically aligned layer thus created using a liquid crystal composition, for example, in the same manner as the optical anisotropy layer 26 described above. Alternatively, by adding a chiral agent to the liquid crystal composition, coating the liquid crystal composition onto a photo-alignment layer, and then heating it to spirally align the liquid crystal compound in the thickness direction, a cholesteric liquid crystal layer that selectively reflects specific circularly polarized light in a specific wavelength range can be formed, thereby manufacturing a reflective liquid crystal diffraction element.

[0138] Although the exposure method for the photo-alignment layer of the present invention has been described in detail above, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the spirit of the present invention. [Examples]

[0139] The features of the present invention will be described in more detail below with reference to examples. The materials, reagents, amounts used, amounts of substance, ratios, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples.

[0140] [Comparative Example 1] <Fabrication of exposure mask> (Support) A glass substrate was prepared as the support.

[0141] (Formation of coating film) The orientation layer forming solution described below was applied to the support by spin coating. The support coated with this orientation layer forming solution was dried on a 60°C hot plate for 60 seconds to form the orientation layer forming solution film.

[0142] Coating solution for forming an orientation layer -------------------------------------------------- Photoalignment material A 1.00 parts by mass Water 16.00 parts by mass Butoxyethanol 42.00 parts by mass Propylene glycol monomethyl ether 42.00 parts by mass --------------------------------------------------

[0143] -Photo alignment material A- [ka]

[0144] (Exposure of the coating film (formation of the orientation layer)) Using the exposure apparatus shown in Figure 7, the coating film was exposed to form an orientation layer P-1 having an orientation pattern (concentric orientation pattern) radially extending outward from the center, in which the direction of the optical axis changes while continuously rotating, as shown in Figure 6. Hereafter, this orientation pattern will also be referred to as a radial orientation pattern. In the exposure apparatus, a laser with a wavelength of 325 nm was used as the laser source. The exposure dose due to interference was 1000 mJ / cm². 2 This was done. Furthermore, by using the exposure apparatus shown in Figure 7, the period of one cycle of the orientation pattern was made to gradually shorten from the center outwards.

[0145] (Formation of optically anisotropic layer) Composition A-1 was prepared as a liquid crystal composition for forming the first optically anisotropic layer. Composition A-1 -------------------------------------------------- Liquid crystal compound L-1 100.00 parts by mass Polymerization initiator (BASF, Irgacure OXE01) 1.00 parts by mass Leveling agent T-1: 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass --------------------------------------------------

[0146] Liquid crystal compound L-1 [ka]

[0147] Leveling agent T-1 [ka]

[0148] The optically anisotropic layer was formed by multilayer coating of composition A-1 on the alignment layer P-1. Multilayer coating refers to the process of first coating the first layer of composition A-1 on the alignment layer, heating and UV curing to create a liquid crystal immobilization layer, and then applying subsequent layers on top of this liquid crystal immobilization layer, repeating the heating and UV curing process. By forming the layer using multilayer coating, the orientation direction of the alignment layer is reflected from the bottom to the top surface of the optically anisotropic layer even when the total thickness of the optically anisotropic layer is increased.

[0149] First, for the first layer, composition A-1 is applied to the orientation layer P-1, the coating is heated to 80°C on a hot plate, and then, under a nitrogen atmosphere, ultraviolet light with a wavelength of 365 nm is applied at a rate of 300 mJ / cm² using a high-pressure mercury lamp. 2 By irradiating the coating film with this irradiation dose, the orientation of the liquid crystal compound was fixed.

[0150] For the second and subsequent layers, the liquid crystal immobilization layer was repeatedly applied, and after heating under the same conditions as above, UV curing was performed to create a liquid crystal immobilization layer. In this manner, the layering was repeated until the desired total thickness was achieved, forming an optically anisotropic layer and creating a liquid crystal diffraction element to serve as an exposure mask.

[0151] The complex refractive index Δn of the cured layer of composition A-1 was determined by coating composition A-1 onto a support with an orientation layer for retardation measurement, aligning the liquid crystal compound director horizontally to the substrate, and then fixing it by ultraviolet irradiation. The retardation value and film thickness of the resulting liquid crystal immobilized layer (cured layer) were then measured. Δn can be calculated by dividing the retardation value by the film thickness. The retardation value was measured at the desired wavelength using an Axoscan from Axometrix, and the film thickness was measured using a scanning electron microscope (SEM).

[0152] The optical anisotropy layer ultimately results in Δn of the liquid crystal. 365 The thickness (Re(365)) was confirmed to be 183 nm, and the surface was found to have a radial (concentric) periodic orientation as shown in Figure 6, as confirmed by polarizing microscope. In this optically anisotropic layer's liquid crystal alignment pattern, the period of rotation of the optical axis of the liquid crystal compound by 180° was 20 μm at a distance of approximately 3 mm from the center and 2 μm at a distance of 25 mm from the center, resulting in a liquid crystal alignment pattern where the period shortens towards the outside. Furthermore, the twist angle in the thickness direction of the optically anisotropic layer was ~0°. Unless otherwise specified, measurements such as 'Δn × thickness' ('Δn × d') were performed in the same manner. Cross-sectional images of the fabricated optical anisotropy layer were observed using a scanning electron microscope (SEM), revealing patterns of bright and dark areas. In the SEM-observed cross-sectional images, the dark areas extended in the direction normal to the main plane (the dark areas were not inclined relative to the main plane).

[0153] <Fabrication of liquid crystal diffraction elements>

[0154] (Formation of coating film) A coating film of the alignment layer forming solution was formed on the glass substrate in the same manner as the fabrication of the exposure mask (liquid crystal diffraction element) described above.

[0155] (Exposure of the coating film (formation of the photo-alignment layer)) Using the exposure apparatus shown in Figure 1, the coating film was exposed through the exposure mask prepared above to form a photo-aligned layer PA-1 having a concentric orientation pattern. The exposure apparatus used was a proximity exposure apparatus that emitted parallel light of a wavelength (365 nm). The exposure dose was 1000 mJ / cm². 2 The exposure mask was then treated with linearly polarized light (ellipticity < 0.1).

[0156] (Formation of optically anisotropic layer) Composition B-1 was prepared as a liquid crystal composition for forming the first optically anisotropic layer. Composition B-1 -------------------------------------------------- Liquid crystal compound L-1 100.00 parts by mass Chiral agent C-1: 0.32 parts by mass Polymerization initiator (BASF, Irgacure OXE01) 1.00 parts by mass Leveling agent T-1: 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass --------------------------------------------------

[0157] Chiral agent C-1 [ka]

[0158] Leveling agent T-1 [ka]

[0159] The first optically anisotropic layer was formed by multilayering composition B-1 on the photo-alignment layer PA-1. Multilayering means first applying the first layer of composition B-1 on the alignment layer, heating it, and then performing ultraviolet curing to produce a liquid crystal immobilization layer. After that, for the second and subsequent layers, coating is performed by overcoating on the liquid crystal immobilization layer, and ultraviolet curing is performed after heating in the same manner, repeating this process. By forming it through multilayering, even when the total thickness of the optically anisotropic layer becomes thick, the alignment direction of the alignment layer is reflected from the lower surface to the upper surface of the optically anisotropic layer.

[0160] First, for the first layer, the following composition B-1 was applied on the photo-alignment layer PA-1, the coating film was heated to 80 °C on a hot plate, and then, in a nitrogen atmosphere, ultraviolet light with a wavelength of 365 nm was irradiated on the coating film at an irradiation dose of 300 mJ / cm 2 to fix the alignment of the liquid crystal compound.

[0161] For the second and subsequent layers, overcoating was performed on this liquid crystal immobilization layer, and after heating under the same conditions as above, ultraviolet curing was performed to produce a liquid crystal immobilization layer. In this way, overcoating was repeated until the total thickness reached the desired film thickness, forming the first optically anisotropic layer and fabricating a liquid crystal diffraction element.

[0162] Note that the complex refractive index Δn of the cured layer of composition B-1 was obtained by applying composition B-1 on a support with an alignment layer for retardation measurement prepared separately, aligning the director of the liquid crystal compound to be horizontal with respect to the substrate, and then irradiating with ultraviolet light for fixation, and measuring the retardation value and film thickness of the obtained liquid crystal immobilization layer (cured layer). Δn can be calculated by dividing the retardation value by the film thickness. The retardation value was measured at the target wavelength using Axoscan from Axometrix, and the film thickness was measured using SEM.

[0163] The first optically anisotropic layer finally had a Δn of the liquid crystal 550 × thickness (Re(550)) of 275 nm, and it was confirmed by a polarizing microscope that the surface had a radial (concentric circular) periodic alignment as shown in Fig. 6. In this first optically anisotropic layer's liquid crystal alignment pattern, the period of rotation of the optical axis of the liquid crystal compound by 180° was 10 μm at a distance of approximately 3 mm from the center and 1 μm at a distance of 25 mm from the center, resulting in a liquid crystal alignment pattern where the period shortened towards the outside. Furthermore, the twist angle in the thickness direction of the first optically anisotropic layer was 70° (-70°) counterclockwise.

[0164] Composition B-2 was prepared as a liquid crystal composition to form the second optical anisotropy layer. Composition B-2 -------------------------------------------------- Liquid crystal compound L-1 100.00 parts by mass Chiral agent C-2 0.18 parts by mass Polymerization initiator (BASF, Irgacure OXE01) 1.00 parts by mass Leveling agent T-1: 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass --------------------------------------------------

[0165] Chiral agent C-2 [ka]

[0166] A second optical anisotropic layer was formed in the same manner as the first optical anisotropic layer, except that composition B-2 was used and the thickness of the optical anisotropic layer was adjusted.

[0167] The second optical anisotropy layer ultimately forms the Δn of the liquid crystal. 550 The thickness (Re(550)) was 275 nm, and it was confirmed using a polarizing microscope that the surface had a radial (concentric) periodic orientation as shown in Figure 6. Furthermore, the liquid crystal orientation pattern of this second optically anisotropic layer was such that the period shortened towards the outward direction. The twist angle in the thickness direction of the optically anisotropic layer was 70° clockwise.

[0168] [Example 1] <Fabrication of exposure mask>

[0169] (Preparation of the substrate and formation of the coating film) A glass plate similar to that used in Comparative Example 1 was used as a substrate, and a coating film of the orientation layer forming solution was formed in the same manner as in Comparative Example 1.

[0170] (Exposure of the coating film (formation of the photo-alignment layer)) In Comparative Example 1, the coating film was exposed in the same manner as in Comparative Example 1, except that the focal length of the lens used for exposure and the distance between the lens and the orientation layer were changed, to form a photo-alignment layer P-2 having a concentric orientation pattern.

[0171] (Formation of optically anisotropic layer) A liquid crystal diffraction element serving as an exposure mask was fabricated by forming the first and second optical anisotropy layers according to the procedure shown below.

[0172] Composition A-2 was prepared as a liquid crystal composition to form the first optical anisotropy layer. Composition A-2 -------------------------------------------------- Liquid crystal compound L-1 100.00 parts by mass Chiral agent C-1: 0.33 parts by mass Polymerization initiator (BASF, Irgacure OXE01) 1.00 parts by mass Leveling agent T-1: 0.20 parts by mass Methyl ethyl ketone 2000.00 parts by mass -------------------------------------------------- The first optically anisotropic layer was formed by multilayer coating of composition A-2 on the orientation layer P-2. The first optical anisotropy layer ultimately forms the Δn of the liquid crystal. 365 The thickness (Re(365)) was confirmed to be 183 nm, and the surface was found to have a concentric (radial) periodic orientation as shown in Figure 6, as confirmed by polarizing microscope. In this optically anisotropic layer's liquid crystal alignment pattern, the period of rotation of the optical axis of the liquid crystal compound by 180° was 10 μm at a distance of approximately 3 mm from the center and 1 μm at a distance of 25 mm from the center, resulting in a liquid crystal alignment pattern where the period shortens towards the outside. Furthermore, the twist angle in the thickness direction of the optically anisotropic layer was 36° (-36°) counterclockwise.

[0173] Composition A-3 was prepared as a liquid crystal composition to form the second optical anisotropy layer. Composition A-3 -------------------------------------------------- Liquid crystal compound L-1 100.00 parts by mass Chiral agent C-2 0.19 parts by mass Polymerization initiator (BASF, Irgacure OXE01) 1.00 parts by mass Leveling agent T-1: 0.20 parts by mass Methyl ethyl ketone 2000.00 parts by mass -------------------------------------------------- The second optically anisotropic layer was formed by multilayer coating of composition A-3 on the first optically anisotropic layer. The second optical anisotropy layer ultimately forms the Δn of the liquid crystal. 365 The thickness (Re(365)) was 183 nm, and it was confirmed using a polarizing microscope that the surface had a concentric (radial) periodic orientation as shown in Figure 6. In this optically anisotropic layer's liquid crystal orientation pattern, one period corresponding to a 180° rotation of the optical axis of the liquid crystal compound was 10 μm at a distance of approximately 3 mm from the center and 1 μm at a distance of 25 mm from the center, indicating a liquid crystal orientation pattern where the period shortens towards the outside. Furthermore, the twist angle in the thickness direction of the optically anisotropic layer was 36° clockwise. Furthermore, the first and second optical anisotropic layers were designed so that the combined phase difference between the two layers was 1 / 4 wavelength (λ / 4). In the cross-sectional SEM image obtained by observing the cross-section of the fabricated optically anisotropic layer with SEM, patterns of bright and dark regions were observed. Also, in the cross-sectional image observed by SEM, in the dark region pattern, the dark region was inclined with respect to the main surface. Further, the inclination direction of the dark region was different between the first optically anisotropic layer and the second optically anisotropic layer, and it was confirmed that the dark region had inflection points with a certainty of 1 or more. In addition, the fabricated optically anisotropic layer had regions where the shapes of the bright and dark parts were symmetric with respect to the center line in the thickness direction.

[0174] <Fabrication of Liquid Crystal Diffractive Element> (Formation of Photoalignment Layer) In the same manner as the fabrication of the above exposure mask, an alignment layer (photoalignment layer) was formed on the glass substrate.

[0175] (Exposure of Photoalignment Layer) Using the exposure apparatus shown in FIG. 1, the photoalignment layer was exposed through the fabricated exposure mask to form a photoalignment layer PA-2 having a concentric alignment pattern. The exposure apparatus used was a proximity exposure apparatus that emits parallel light with a wavelength (365 nm). The exposure dose was 1000 mJ / cm 2 2. Circularly polarized light (ellipticity 0.9 - 1.1) was incident on the exposure mask.

[0176] (Formation of Optically Anisotropic Layer) An optically anisotropic layer was formed in the same manner as the fabrication of the liquid crystal diffractive element of Comparative Example 1.

[0177] The first optically anisotropic layer finally had a Δn of liquid crystal 550 × thickness (Re(550)) of 275 nm, and it was confirmed by a polarizing microscope that the surface had a concentric (radial) periodic alignment as shown in FIG. 6. In the liquid crystal alignment pattern of this optically anisotropic layer, one period in which the optical axis of the liquid crystal compound rotates 180° was 10 μm for one period at a distance of about 3 mm from the center and 1 μm for one period at a distance of 25 mm from the center, and it was a liquid crystal alignment pattern in which the period became shorter toward the outer direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 70° (-70°) in the counterclockwise direction.

[0178] The second optically anisotropic layer finally has a Δn of liquid crystal 550 × thickness (Re(550)) of 275 nm, and it was confirmed by a polarizing microscope that the surface had a concentric (radial) periodic alignment as shown in Fig. 6. The liquid crystal alignment pattern of this optically anisotropic layer was a liquid crystal alignment pattern with a shorter period in the outward direction. Also, the twist angle in the thickness direction of the optically anisotropic layer was 70° clockwise.

[0179] [Evaluation] [Evaluation of Exposure Mask] The intensity ratio (0th order light / 1st order light) of the diffracted light of the 0th order and 1st order emitted from the produced exposure mask was evaluated. The measurement was carried out using a parallel light source with an output center wavelength of 365 nm, and the light was perpendicularly incident on the produced exposure mask. At this time, the light intensities of the 0th order and 1st order of the diffracted light emitted from the exposure mask were measured with a photodetector. Using the measured light intensities of the 0th order and 1st order light, the intensity ratio (0th order light / 1st order light) was calculated. The measurement was carried out by perpendicularly incident the light on a circular polarizing plate corresponding to the wavelength of the light source, making it circularly polarized, and then incident the light on the produced exposure mask. In the comparative example, the intensity ratio was evaluated at the position where one period of the optical axis of the liquid crystal compound rotates 180° and is 2 μm, and in the example, the intensity ratio was evaluated at the position of 1 μm. The results are shown in Table 1. [Table 1]

[0180] [Evaluation of the Alignment Pattern of Liquid Crystal Diffractive Element] The polarizing microscope image of the produced liquid crystal diffractive element was evaluated. The liquid crystal alignment pattern at one period of 1 μm where the optical axis of the liquid crystal compound rotates 180° was evaluated.

[0181] When observing the liquid crystal alignment pattern of the liquid crystal diffractive element produced in Comparative Example 1 with a polarizing microscope, distortion was seen in the pattern of bright and dark lines. In contrast, the distortion of the bright and dark lines of the liquid crystal diffractive element produced in Example 1 was improved.

[0182] <Evaluation of diffraction efficiency> The diffraction efficiency of the emitted light was evaluated when light was incident on the fabricated liquid crystal diffraction element from the front (direction at an angle of 0° with respect to the normal). Specifically, a laser beam with an output center wavelength of 532 nm was irradiated from a light source and perpendicularly incident onto the fabricated liquid crystal diffraction element. The light intensity of the diffracted light (first-order light) diffracted in a desired direction from the liquid crystal diffraction element, the zero-order light (emitted in the same direction as the incident light) emitted in other directions, and the -1st-order light (light diffracted in the -θ direction when the diffraction angle of the first-order light relative to the zero-order light is θ) was measured with a photodetector, and the diffraction efficiency at each wavelength was calculated using the following formula. In the evaluation of the liquid crystal diffraction element, circularly polarized light was incident at a point where the optical axis of the liquid crystal compound rotates 180°, with a period of 1 μm. Diffraction efficiency = 1st order light / (1st order light + 0th order light + (-1st order light))

[0183] As a result, the liquid crystal diffraction element fabricated in Example 1 achieved a diffraction efficiency that was 5% or more higher than that of Comparative Example 1. Based on the above results, the effects of the present invention are clear. [Explanation of symbols]

[0184] 10 Exposure mask 12 light source 14. Coating film 16 circuit boards 20 Support 24 orientation layer 26, 26a, 26b Optically anisotropic layers 30 Liquid crystal compounds 30A optical axis 42 Akabe 44 Dark part 60 Exposure equipment 62 lasers 64 Light source 65 λ / 2 plate 68 Polarizing Beam Splitter 70A, 70B Mirror 72A,72B λ / 4 board 80 Exposure apparatus 82 lasers 84 Light source 86,94 Polarizing Beam Splitter 90A, 90B Mirror 92 lenses 96 λ / 4 plate

Claims

1. The process includes an exposure step in which an exposure mask and a substrate having a coating film containing a compound having photo-aligning groups are placed facing each other, and light in which the compound is photosensitive is irradiated from the exposure mask side to expose the coating film and form an orientation pattern, The aforementioned light is circularly polarized with an ellipticity of 0.7 to 1.

3. The exposure mask is a polarization diffraction element having an orientation pattern in which the orientation of the optical axis changes while continuously rotating along at least one direction in the plane, The exposure step involves exposing the coating film with the zeroth and first-order light diffracted by the exposure mask, and further, The 0th-order light and the 1st-order light are circularly polarized light having opposite rotation directions. A method for exposing a photo-aligned layer, wherein the intensity ratio of the zeroth-order light to the first-order light is 0.5 to 2.

2. The method for exposing a photo-aligned layer according to claim 1, wherein the zeroth-order light and the first-order light are circularly polarized with an ellipticity of 0.6 to 2.

3. The method for exposing a photo-aligned layer according to claim 1 or 2, wherein, in the orientation pattern, when the length over which the orientation of the optical axis rotates 180° along one direction in the plane is defined as one period, the exposure mask and the coating film to which the exposure process is applied each have regions where the ratio of the length of one period of the coating film to the length of one period of the exposure mask is 0.7 to 1.

5.

4. The method for exposing a photo-aligned layer according to any one of claims 1 to 3, wherein, in the orientation pattern of the exposure mask, when the length over which the orientation of the optical axis rotates 180° in the plane is defined as one period, the coating film to which the exposure process is applied has a region where one period is 5 μm or less.

5. The exposure mask is a liquid crystal diffraction element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, The method for exposing an optically aligned layer according to any one of claims 1 to 4, wherein the optically anisotropic layer has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane.

6. The method for exposing a photo-aligned layer according to claim 5, wherein the optical anisotropy layer has, in an image obtained by observing a cross-section cut in the thickness direction along one direction with a scanning electron microscope, a light area and a dark area extending from one main surface to the other main surface, and the dark area has a region that is inclined with respect to the main surface.

7. The method for exposing a photo-aligned layer according to claim 6, wherein the angle of the dark area with respect to the perpendicular direction of the main surface of the optical anisotropy layer has different regions in the thickness direction of the optical anisotropy layer.

8. The method for exposing a photo-aligned layer according to claim 6 or 7, wherein the optical anisotropy layer has an inflection point of 1 or more angles in the dark area.

9. The method for exposing a photo-aligned layer according to claim 8, wherein the dark area has inflection points at two or more angles.

10. When the length of a 180° rotation of the optical axis along one direction in the plane is defined as one period, the optical anisotropy layer has a region in the liquid crystal alignment pattern where the length of one period is shortened along that one direction. The method for exposing a photo-aligned layer according to any one of claims 6 to 9, wherein the optical anisotropy layer has regions in which the angle of the dark area with respect to the perpendicular direction of the main surface increases as the period becomes shorter.

11. The method for exposing a photo-aligned layer according to any one of claims 6 to 10, wherein the optically anisotropic layer has regions in which the shapes of the bright areas and the dark areas are symmetrical with respect to a center line in the thickness direction.

12. The method for exposing a photo-aligned layer according to any one of claims 6 to 11, wherein the optically anisotropic layer has regions in which the shapes of the bright areas and the dark areas are asymmetrical with respect to a center line in the thickness direction.

13. The method for exposing a photo-aligned layer according to any one of claims 1 to 12, wherein the orientation pattern of the exposure mask is a pattern having a radial direction from the center outward, along which the orientation of the optical axis changes while continuously rotating along at least one direction in the plane.

14. The exposure mask is a liquid crystal diffraction element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, The method for exposing a photo-aligned layer according to claim 1, wherein the product Δn × d (nm) of the refractive index difference Δn of the liquid crystal compound and the thickness d (nm) of the optical anisotropy layer is 0.2λ to 0.3λ with respect to the wavelength λ (nm) of the light incident on the exposure mask.

15. The method for exposing a photo-oriented layer according to claim 1 or 14, wherein in the exposure step, the light that makes the compound photosensitive is ultraviolet light.

16. The method for exposing a photo-aligned layer according to claim 1 or 14, wherein in the exposure step, light in which the compound is photosensitive is incident perpendicularly to the exposure mask.

17. The method for exposing a photo-aligned layer according to claim 15, wherein in the exposure step, light in which the compound is photosensitive is incident perpendicularly on the exposure mask.

18. The method for exposing a photo-aligned layer according to claim 1, wherein in the exposure step, the intensity ratio of the zeroth-order light to the first-order light is 0.7 to 1.5.

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