Photomask, and a photo-alignment film and a diffraction element manufactured using the same.

Abstract

A photomask that has high light resistance and a fine structure and can be easily manufactured, and a photo-alignment film and a diffraction element manufactured using the same are provided. [Solution] The photomask of the present invention has a support substrate and a structural birefringence layer provided on the support substrate, and the structural birefringence layer has a structure in which, in a planar view, a plurality of repeating unit structures are periodically arranged, and each of the plurality of repeating unit structures has a structure in which, in a planar view, a plurality of optical unit structures having different azimuth angles of their slow axes are arranged along an arrangement direction of the plurality of repeating unit structures, and each of the plurality of optical unit structures has a structure in which a plurality of regions having different refractive indices are alternately arranged, and in a planar view, the slow axis of each of the plurality of optical unit structures is not perpendicular to the arrangement direction.

Description

[Technical Field]

[0001] The following disclosure relates to a photomask, a photoalignment film manufactured using the same, and a diffraction element. [Background technology]

[0002] Patent Document 1 discloses a liquid crystal element having a transparent substrate and a liquid crystal layer made of a liquid crystal material and including a concave-convex portion with periodic concave-convex patterns, wherein the concave-convex portion of the liquid crystal layer is located on the transparent substrate side and the long axis directions of the liquid crystal molecules located on the concave-convex surface that is the interface between the concave-convex portion of the liquid crystal layer are substantially perpendicular to the concave-convex surface on the transparent substrate side, or the concave-convex portion of the liquid crystal layer is located on the medium side opposite the transparent substrate and the long axis directions of the liquid crystal molecules located on the concave-convex surface that is the interface between the concave-convex portion of the liquid crystal layer are substantially perpendicular to the concave-convex surface on the medium side, thereby forming a diffraction grating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2009 / 084604 Summary of the Invention [Problem to be solved by the invention]

[0004] To fabricate Augmented Reality (AR) glasses using a light guide plate, a diffraction element is required to trap light from a light source in the light guide plate. The diffraction element has a periodic structure on the submicron order and can be obtained, for example, by forming a polymerizable liquid crystal film on a photo-alignment film that is fabricated so that the orientation of the alignment regulating force periodically rotates in one axial direction in a planar view. A photo-alignment film in which the orientation of the alignment regulating force periodically rotates in a planar view (a photo-alignment film with periodic patterning) can be obtained, for example, by a photo-alignment process using a polarization-dependent diffraction element as a photomask.

[0005] An example of a polarization-dependent diffraction element is a patterned retardation plate having polymerizable liquid crystals whose orientation direction is periodically rotated along one axis in a planar view. However, since liquid crystals deteriorate due to absorption of ultraviolet light, reducing the retardation, there are issues with the light resistance of polarization-dependent diffraction elements containing polymerizable liquid crystals. Another example of a polarization-dependent diffraction element is a patterned retardation plate using structural birefringence, but it is not easy to manufacture a patterned retardation plate using structural birefringence in terms of drawing a submicron-order structure.

[0006] The present invention has been made in consideration of the current situation, and aims to provide a photomask that has high light resistance and a fine structure and is easily manufacturable, and a photo-alignment film and a diffraction element manufactured using the same. [Means for solving the problem]

[0007] (1) One embodiment of the present invention relates to a photomask comprising: a support substrate; and a structural birefringence layer provided on the support substrate; the structural birefringence layer having a structure in which a plurality of repeating unit structures are periodically arranged in a planar view; each of the plurality of repeating unit structures having a structure in which a plurality of optical unit structures having different azimuth angles of slow axes are arranged along an arrangement direction of the plurality of repeating unit structures in a planar view; each of the plurality of optical unit structures having a structure in which a plurality of regions having different refractive indices are alternately arranged; and the slow axis of each of the plurality of optical unit structures is not perpendicular to the arrangement direction in a planar view.

[0008] (2) Furthermore, in addition to the configuration of (1), an embodiment of the present invention is a photomask in which the arrangement direction in a planar view is a direction of an azimuth angle of 0°-180°, and in each of the plurality of repeating unit structures, when the number of the plurality of optical unit structures is k and the azimuth angle of the slow axis of one optical unit structure among the plurality of optical unit structures is α, the azimuth angle A of the slow axis of each of the plurality of optical unit structures satisfies the following (Equation 1) and (Equation 2): Azimuth A=α+180°×i÷k (Formula 1) Azimuth A≠90° (Equation 2) (In the above formula 1, k is an integer of 2 or more, and i is an integer of 0 or more and (k-1) or less.)

[0009] (3) Furthermore, in addition to the configuration of (2), an embodiment of the present invention is a photomask, wherein the azimuth angle A satisfies the following (Formula 2-1) or (Formula 2-2). Azimuth angle A<85° (Equation 2-1) 95°<Azimuth A (Formula 2-2)

[0010] (4) Furthermore, in addition to the configuration of (2) or (3), an embodiment of the present invention is a photomask, wherein the azimuth angle A satisfies the following (Equation 3): Azimuth A≠0° (Equation 3)

[0011] (5) In one embodiment of the present invention, in addition to the configuration of (4), the azimuth angle A satisfies the following (Formula 3-1): 5°<Azimuth A<175° (Formula 3-1)

[0012] (6) In one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), or (5), the photomask is configured such that, in each of the plurality of repeating unit structures, the plurality of optical unit structures have a first optical unit structure having a first slow axis, a second optical unit structure having a second slow axis, a third optical unit structure having a third slow axis, and a fourth optical unit structure having a fourth slow axis, and when the arrangement direction in a planar view is defined as a direction of azimuth angle 0°-180°, the azimuth angle of the first slow axis is 22.5°, the azimuth angle of the second slow axis is 67.5°, the azimuth angle of the third slow axis is 112.5°, and the azimuth angle of the fourth slow axis is 157.5°.

[0013] (7) In one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), or (6), the photomask is such that, in each of the plurality of optical unit structures, the plurality of regions have first regions and second regions having mutually different refractive indices, and includes two or more of the first regions and two or more of the second regions.

[0014] (8) In one embodiment of the present invention, in addition to the configuration of (7), the refractive index of the first region is 1 or less, and the refractive index of the second region is greater than 1.

[0015] (9) In one embodiment of the present invention, in addition to the configuration of (7) or (8), the first region is an air layer.

[0016] (10) In one embodiment of the present invention, in addition to the configuration of (7), (8), or (9), the photomask further comprises: each of the plurality of optical unit structures in which the first region and the second region are alternately stacked; and the slow axis of each of the plurality of optical unit structures is perpendicular to the stacking direction of the first region and the second region.

[0017] (11) Another embodiment of the present invention is a photo-alignment film that has been subjected to a photo-alignment treatment using a photomask described in any one of (1), (2), (3), (4), (5), (6), (7), (8), (9), and (10).

[0018] (12) Another embodiment of the present invention is a diffraction element comprising: a photo-alignment film that has been subjected to a photo-alignment treatment using a photomask described in any one of (1), (2), (3), (4), (5), (6), (7), (8), (9), and (10); and a liquid crystal layer that is provided on the photo-alignment film and contains a polymerizable liquid crystal. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a photomask that has high light resistance and a fine structure and that can be easily manufactured, and a photo-alignment film and a diffraction element manufactured using the same. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an optical element according to an embodiment. [Figure 2]1 is a cross-sectional view schematically illustrating a diffraction element according to an embodiment. [Figure 3] 1 is a schematic cross-sectional view showing the polarization state when right-handed circularly polarized light is incident on a polarization-dependent diffraction element. FIG. [Figure 4] 1 is a cross-sectional schematic diagram showing the polarization state when left-handed circularly polarized light is incident on a polarization-dependent diffraction element. FIG. [Figure 5] 10A and 10B are schematic diagrams showing patterning of linearly polarized light by zero-order light and first-order light emitted from a polarization-dependent diffraction element. [Figure 6] 10A and 10B are cross-sectional schematic diagrams illustrating a method for patterning an alignment regulating force on a photo-alignment film using a polarization-dependent diffraction element as a photomask. [Figure 7] FIG. 1 is a schematic plan view of a conventional photomask including a liquid crystal layer containing a polymerizable liquid crystal. [Figure 8] 1 is a schematic cross-sectional view of a conventional photomask including a liquid crystal layer containing a polymerizable liquid crystal. [Figure 9] FIG. 1 is a schematic plan view of a photomask according to an embodiment. [Figure 10] FIG. 2 is an enlarged perspective schematic view of a photomask according to an embodiment. [Figure 11] FIG. 1 is a perspective schematic diagram of a conventional photomask having a form birefringent layer. [Figure 12] FIG. 1 is a schematic plan view of a conventional photomask having a form birefringent layer. [Figure 13] 1 is a schematic perspective view of an optical unit structure according to Reference Example 1. FIG. [Figure 14] 1 is an SEM image of the optical unit structure of Reference Example 1. [Figure 15] FIG. 10 is a schematic perspective view of a photomask according to Reference Example 2. [Figure 16] 1 is a polarizing microscope photograph of the photomask of Reference Example 2. [Figure 17] FIG. 10 is a schematic diagram illustrating a method for measuring the polarization state. [Figure 18] 10 is a polarizing microscope photograph of the diffraction element of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, identical or equivalent elements are designated by the same reference numerals, and redundant explanations will be omitted. Only the main parts are shown in the drawings. The following description will focus on the main parts and parts related to the present disclosure.

[0022] In this specification, the term "observer side" refers to the side closer to the observer when the observer observes the optical element, and the term "rear side" refers to the side opposite to the observer side.

[0023] (Embodiment) FIG. 1 is a cross-sectional view of an optical element according to an embodiment. FIG. 2 is a cross-sectional view of a diffraction element according to an embodiment. As shown in FIG. 1, the optical element 1 of this embodiment includes a light guide plate 20 and a diffraction element 10 located on the back side of the light guide plate 20. The diffraction element 10 has a function of trapping light L incident from the viewer side in the light guide plate 20. The light L incident on the optical element 1 is trapped in the light guide plate 20 by the diffraction element 10, and is emitted to the viewer side while repeatedly reflecting within the light guide plate 20. The optical element 1 can be used, for example, as AR (Augmented Reality) glasses.

[0024] The diffraction element 10 has a periodic structure on the submicron order. The diffraction element 10 includes, for example, a support substrate 110, a photo-alignment film 120, and a liquid crystal layer 130, arranged in this order, as shown in FIG.

[0025] Examples of the support substrate 110 include insulating substrates such as glass substrates and plastic substrates. The support substrate 110 is preferably transparent. "Transparent" means that the total light transmittance defined by JIS7361-1 (ISO13468-1) is 85% or more.

[0026] The liquid crystal layer 130 contains polymerizable liquid crystal 131. The liquid crystal layer containing polymerizable liquid crystal means that the liquid crystal layer contains a polymer of polymerizable liquid crystal. The liquid crystal layer 130 is obtained by forming a film of a liquid crystal material containing a chiral agent and the polymerizable liquid crystal 131, and polymerizing the polymerizable liquid crystal 131.

[0027] The polymerizable liquid crystal 131 is not particularly limited. Examples of the polymerizable liquid crystal 131 include conventionally known liquid crystals. The polymerizable liquid crystal 131 preferably has a mesogenic group, a photoreactive group, and a polymerizable group. The mesogenic group is, for example, a substituent such as a biphenyl group, a terphenyl group, a naphthalene group, a phenylbenzoate group, an azobenzene group, or a derivative thereof. The photoreactive group is, for example, a substituent such as a cinnamoyl group, a chalcone group, a cinnamylidene group, a β-(2-phenyl)acryloyl group, a cinnamic acid group, or a derivative thereof. The polymerizable group is, for example, a substituent such as an acrylate group, a methacrylate group, a maleimide group, an N-phenylmaleimide group, a siloxane group, or a derivative thereof.

[0028] The polymerizable liquid crystal 131 is, for example, a monomer. The number of polymerizable groups per molecule of the polymerizable liquid crystal 131 is not particularly limited, but is preferably one or two.

[0029] The chiral agent is not particularly limited. Examples of the chiral agent include conventionally known chiral agents. For example, S-811 (manufactured by Merck) is used.

[0030] The photo-alignment film 120 is an alignment film that exhibits the function of aligning liquid crystal molecules (e.g., polymerizable liquid crystal 131) in a specific direction by forming a film of a photo-alignment film material and performing a photo-alignment process. The photo-alignment film material refers to a material that undergoes a structural change when irradiated with light (electromagnetic waves) such as ultraviolet light or visible light, and exhibits a property (alignment regulation force) that regulates the alignment of nearby liquid crystal molecules, or a material in which the magnitude and / or direction of the alignment regulation force changes. The photo-alignment film material includes a photoreactive site where reactions such as dimerization (dimer formation), isomerization, photo-Fries rearrangement, and decomposition occur upon light irradiation.

[0031] Examples of photoreactive moieties (functional groups) that undergo dimerization and isomerization upon irradiation with light include cinnamate groups, chalcone groups, coumarin groups, and stilbene groups (cinnamate, cinnamoyl, 4-chalcone, coumarin, stilbene). Examples of photoreactive moieties (functional groups) that undergo isomerization upon irradiation with light include azobenzene groups (azobenzene). Examples of photoreactive moieties that undergo photo-induced Fries rearrangement upon irradiation with light include phenol ester groups (phenol ester structures). Examples of photoreactive moieties that decompose upon irradiation with light include cyclobutane ring groups (dianhydrides containing a cyclobutane ring, such as 1,2,3,4-cyclobutanetetracarboxylic acid-1,2:3,4-dianhydride (CBDA)).

[0032] 2, the photo-alignment film 120 has a structure in which a plurality of photo-alignment film repeating unit structures 200PA are periodically arranged in a plan view, and each of the plurality of photo-alignment film repeating unit structures 200PA has a structure in which a plurality of alignment regions having mutually different azimuth angles of the alignment restricting force 120X are arranged along an arrangement direction 1DA of the plurality of photo-alignment film repeating unit structures 200PA in a plan view. In each of the plurality of photo-alignment film repeating unit structures 200PA in a plan view, the azimuth angle of the alignment restricting force 120X rotates 180° along the arrangement direction 1DA. That is, throughout the photo-alignment film 120, the orientation of the alignment restricting force 120X periodically rotates in one axial direction (specifically, along the arrangement direction 1DA) in a plan view.

[0033] One method for patterning the alignment regulating force of a photo-alignment film is to expose the photo-alignment film using a polarization-dependent diffraction element as a photomask. Figure 3 is a cross-sectional schematic diagram showing the polarization state when right-handed circularly polarized light is incident on a polarization-dependent diffraction element. Figure 4 is a cross-sectional schematic diagram showing the polarization state when left-handed circularly polarized light is incident on a polarization-dependent diffraction element. Polarization-dependent diffraction elements have a phase difference and have a structure in which the orientation of the slow axis rotates periodically along one axis in a planar view. As shown in Figures 3 and 4, when circularly polarized light is incident on a polarization-dependent diffraction element, it is separated into zeroth-order light and first-order light. The zeroth-order light is circularly polarized in the same direction as the incident light, while the first-order light is circularly polarized in the opposite direction to the incident light.

[0034] Figure 5 is a schematic diagram showing the patterning of linearly polarized light by the zeroth-order and first-order light emitted from a polarization-dependent diffraction element. The ratio of first-order light to the transmitted light intensity is defined as the diffraction efficiency, which depends on the phase difference and is 50% at a quarter wavelength. When the beam diameter of the light incident on the polarization-dependent diffraction element is sufficiently large, right-handed and left-handed circularly polarized light (zeroth-order and first-order light) overlap, as shown in Figure 5. In this region, the overlapping circularly polarized light becomes linearly polarized, and the orientation of the polarization axis rotates periodically along one axis in a planar view. The patterning period of this linearly polarized light matches the patterning period of the polarization-dependent diffraction element.

[0035] Fig. 6 is a cross-sectional schematic diagram illustrating a method for patterning an alignment control force on a photo-alignment film using a polarization-dependent diffraction element as a photomask. When circularly polarized light is irradiated onto the photo-alignment film using the polarization-dependent diffraction element as a photomask, an alignment control force is patterned on the photo-alignment film at the same pitch as the photomask in the region where the two light beams (zeroth-order light and first-order light) overlap, as shown in Fig. 6.

[0036] An example of a conventional photomask is a polarization-dependent diffraction element containing polymerizable liquid crystal. FIG. 7 is a schematic plan view of a conventional photomask including a liquid crystal layer containing polymerizable liquid crystal. FIG. 8 is a schematic cross-sectional view of a conventional photomask including a liquid crystal layer containing polymerizable liquid crystal. As shown in FIGS. 7 and 8, a conventional photomask 1000R1 includes, for example, a support substrate 1110R, a photo-alignment film 1120R, and a liquid crystal layer 1130R containing polymerizable liquid crystal 1131R, in that order. The photomask 1000R1 containing the polymerizable liquid crystal 1131R has a phase difference. The orientation of the slow axis of the polymerizable liquid crystal 1131R rotates periodically in one axis direction in a planar view.

[0037] When the photo-alignment film is exposed using the conventional photomask 1000R1, the polymerizable liquid crystal 1131R is degraded by light (ultraviolet light (UV)) with a wavelength to which the photo-alignment film is sensitive, and the phase difference of the photomask 1000R1 is reduced. Therefore, it is difficult to mass-produce the photo-alignment film 120 using the conventional photomask 1000R1.

[0038] On the other hand, as shown in FIGS. 9 and 10 , the photomask 1000 of this embodiment includes a support substrate 210 and a form birefringence layer 200 provided on the support substrate 210. The form birefringence layer 200 has a structure in which a plurality of repeating unit structures 200P are periodically arranged in a planar view. Each of the repeating unit structures 200P has a structure in which a plurality of optical unit structures 220 having different azimuth angles of the slow axes 220X are arranged along an arrangement direction 1D of the repeating unit structures 200P in a planar view. Each of the optical unit structures 220 has a structure in which a plurality of regions 220G having different refractive indices are alternately arranged. The form birefringence layer 200 exhibits a phase difference due to the difference in refractive index between the regions 220G. That is, in the photomask 1000 of this embodiment, a phase difference is exhibited by the form birefringence layer 200, not by a liquid crystal layer containing a polymerizable liquid crystal. Therefore, the photomask 1000 can suppress a decrease in retardation due to ultraviolet light, and can achieve good light resistance. Therefore, the photomask 1000 of the embodiment can be used to mass-produce the photo alignment film 120. Fig. 9 is a schematic plan view of the photomask according to the embodiment. Fig. 10 is an enlarged perspective schematic view of the photomask according to the embodiment.

[0039] In addition, in plan view, the slow axis 220X of each of the plurality of optical unit structures 220 is not orthogonal to the arrangement direction 1D.

[0040] Here, a conventional photomask having a form birefringent layer will be described. Fig. 11 is a schematic perspective view of a conventional photomask having a form birefringent layer. Fig. 12 is a schematic plan view of a conventional photomask having a form birefringent layer.

[0041] 11 and 12 includes a support substrate 210R and a structural birefringence layer 200R provided on the support substrate 210R. The structural birefringence layer 200R has a structure in which a plurality of repeating unit structures 200PR are periodically arranged in a plan view. Each of the plurality of repeating unit structures 200PR has a structure in which a plurality of optical unit structures 220R, the azimuth angles of which are different from one another in the slow axis 220XR, are arranged along an arrangement direction 1DR of the plurality of repeating unit structures 200PR in a plan view. Each of the plurality of optical unit structures 220R has a structure in which a plurality of regions 220G (first regions 220A and second regions 220B) having different refractive indices are alternately arranged.

[0042] In addition, in a plan view, the slow axis 220XR of at least one optical unit structure 220R among the plurality of optical unit structures 220R is perpendicular to the arrangement direction 1DR. Specifically, in each of the plurality of repeating unit structures 200PR included in the conventional photomask 1000R2, the plurality of optical unit structures 220R include a first optical unit structure 221R having a first slow axis 221XR, a second optical unit structure 222R having a second slow axis 222XR, a third optical unit structure 223R having a third slow axis 223XR, and a fourth optical unit structure 224R having a fourth slow axis 224XR. When the arrangement direction 1DR in a planar view is defined as a direction with an azimuth angle of 0°-180°, the azimuth angle of the first slow axis 221XR is 0°, the azimuth angle of the second slow axis 222XR is 45°, the azimuth angle of the third slow axis 223XR is 90°, and the azimuth angle of the fourth slow axis 224XR is 135°. The first optical unit structure 221R, the second optical unit structure 222R, the third optical unit structure 223R, and the fourth optical unit structure 224R may also be collectively referred to as optical unit structure 220R. The first slow axis 221XR, the second slow axis 222XR, the third slow axis 223XR, and the fourth slow axis 224XR may also be collectively referred to as slow axis 220XR.

[0043] To fabricate the above-described photo-alignment film 120, the distance (pitch P) at which the orientation of the slow axis of the optical unit structure rotates 180° in one axial direction in plan view must be on the order of submicrons (e.g., several hundred nm). Therefore, to fabricate the photo-alignment film 120, an even finer structure is required for the optical unit structure. However, with the conventional photomask 1000R2 having a slow axis 220XR perpendicular to the alignment direction 1DR in plan view, it is difficult to design such a fine optical unit structure.

[0044] 11 and 12, in order to increase the total number of regions 220G included in the optical unit structure 220R (specifically, the third optical unit structure 223R) whose azimuth angle of the slow axis 220XR is 90°, it is necessary to narrow the width W of each region 220G. The width W of each of the regions 220G included in the optical unit structure (specifically, the third optical unit structure 223R) whose azimuth angle of the slow axis 220XR is 90° can be expressed by the following (Equation 1W):

[0045] Width W = Pitch P ÷ (number of optical unit structures included in the repeating unit structure) ÷ (number of regions included in the optical unit structure in which the azimuth angle of the slow axis is 90°) (Equation 1W)

[0046] In the above formula 1W, the number of optical unit structures 220R included in the repeating unit structure 200PR is 4 in Figures 11 and 12. The number of optical unit structures 220R included in the repeating unit structure 200P is also referred to as the division number.

[0047] On the other hand, in the photomask 1000 of this embodiment, the slow axis 220X of each of the plurality of optical unit structures 220 is not perpendicular to the arrangement direction 1D in plan view. The photomask 1000 of this aspect can increase the total number of regions 220G without narrowing the width W of the regions 220G in all of the optical unit structures 220, making it easy to manufacture a photomask 1000 having a fine structure (specifically, having a pitch on the submicron order). The photomask 1000 of this embodiment will be described in detail below.

[0048] 9 and 10, the photomask 1000 has a support substrate 210 and a form birefringent layer 200 provided on the support substrate 210. The photomask 1000 is a polarization-dependent diffraction element.

[0049] Examples of the support substrate 210 include a glass substrate, a plastic substrate, etc. The support substrate 110 is preferably transparent.

[0050] The structural birefringent layer 200 has a structure in which a plurality of repeating unit structures 200P are periodically arranged in a planar view. In a planar view, the arrangement direction 1D of the plurality of repeating unit structures 200P is set to an azimuth angle direction of 0°-180°. In this specification, the azimuth angle and the direction refer to those in a planar view. In this specification, a clockwise angle from an azimuth angle of 0° is a positive angle, and a counterclockwise angle is a negative angle. The length of one period is also referred to as a pitch P. When the photomask 1000 has a longitudinal shape, in a planar view, the arrangement direction 1D of the plurality of repeating unit structures 200P is, for example, parallel to the longitudinal direction of the photomask 1000.

[0051] In a plan view, the arrangement direction 1D of the repeating unit structures 200P is, for example, perpendicular to the boundary line between adjacent repeating unit structures 200P. That is, the boundary line between adjacent repeating unit structures 200P is set in the azimuth angle direction of 90°-270°, for example.

[0052] Each of the plurality of repeating unit structures 200P has a structure in which, in a plan view, a plurality of optical unit structures 220 having different azimuth angles of the slow axes 220X are arranged along an arrangement direction 1D of the plurality of repeating unit structures 200P. In a plan view, the arrangement direction of the plurality of optical unit structures 220 is parallel to the arrangement direction 1D of the plurality of repeating unit structures 200P.

[0053] The azimuth angle of the slow axis 220X of each of the multiple optical unit structures 220 is greater than or equal to 0° and less than 180°, taking the smaller angle (for example, when the slow axis 220X is oriented in the 45°-225° direction, the azimuth angle of the slow axis 220X is 45°, taking the smaller angle of 45° or 225°). In plan view, the slow axis 220X of each of the multiple optical unit structures 220 is not perpendicular to the arrangement direction 1D. This type of photomask 1000 allows the total number of regions 220G to be increased without narrowing the width W of the regions 220G in all of the optical unit structures 220, making it easy to manufacture a photomask 1000 having a fine structure (specifically, a pitch on the submicron order). The slow axis 220X of each optical unit structure 220 is parallel to the in-plane direction of the region 220G (the in-plane direction of the boundary surface with another adjacent region 220G).

[0054] In each of the plurality of repeating unit structures 200P, the orientations of the plurality of slow axes 220X of the plurality of optical unit structures 220 change in a uniaxial direction (along the arrangement direction 1D) in plan view so as to rotate by 180° at one pitch P. That is, in the entire form of the form birefringent layer 200, the orientations of the slow axes 220X periodically rotate in a uniaxial direction (along the arrangement direction 1D) in plan view.

[0055] In each of the plurality of repeating unit structures 200P, it is preferable that the azimuth angles of the plurality of slow axes 220X of the plurality of optical unit structures 220 gradually increase or decrease discretely along the arrangement direction 1D in plan view. The photomask 1000 of this embodiment can produce a diffraction element 10 suitable for AR glasses.

[0056] When the arrangement direction 1D in plan view is defined as the direction of azimuth angle 0°-180°, the number of optical unit structures 220 in each of the plurality of repeating unit structures 200P is k, and the azimuth angle of the slow axis 220X of one optical unit structure 220 among the plurality of optical unit structures 220 is α, it is preferable that the azimuth angle A of the slow axis 220X of each of the plurality of optical unit structures 220 satisfies the following (Equation 1) and (Equation 2). By adopting such an embodiment, the photomask 1000 having a fine structure can be manufactured more easily.

[0057] Azimuth angle A=α+180°×i÷k (Formula 1) Azimuth angle A≠90° (Equation 2) (In the above formula 1, k is an integer of 2 or more, and i is an integer of 0 or more and (k-1) or less.)

[0058] In the above formula 1, k is preferably 2 or more, more preferably 4 or more, and even more preferably 8 or more. There are no particular limitations on the upper limit of k, but it is, for example, 50 or less.

[0059] It is preferable that the azimuth angle A satisfies the following (Formula 2-1) or (Formula 2-2): By adopting such an embodiment, it is possible to more easily manufacture the photomask 1000 having a fine structure.

[0060] Azimuth angle A<85° (Equation 2-1) 95°<Azimuth A (Formula 2-2)

[0061] It is preferable that the azimuth angle A satisfies the following formula (3): That is, it is preferable that the azimuth angles A of the slow axes 220X of the plurality of optical unit structures 220 are not all 0°. By adopting such an embodiment, it is possible to more easily manufacture the photomask 1000 having a fine structure.

[0062] Azimuth angle A≠0° (Equation 3)

[0063] It is preferable that the azimuth angle A satisfies the following formula (3-1): By adopting such an embodiment, it is possible to more easily manufacture the photomask 1000 having a fine structure.

[0064] 5°<Azimuth A<175° (Formula 3-1)

[0065] It is more preferable that the azimuth angle A satisfies the following (Formula 4-1) or (Formula 4-2): By adopting such an embodiment, it is possible to more easily manufacture the photomask 1000 having a fine structure.

[0066] 5°<Azimuth A<85° (Formula 4-1) 95°<Azimuth A<175° (Formula 4-2)

[0067] In each of the plurality of repeating unit structures 200P, the plurality of optical unit structures 220 include a first optical unit structure 221 having a first slow axis 221X, a second optical unit structure 222 having a second slow axis 222X, a third optical unit structure 223 having a third slow axis 223X, and a fourth optical unit structure 224 having a fourth slow axis 224X. For example, the azimuth angle of the first slow axis 221X is 22.5°, the azimuth angle of the second slow axis 222X is 67.5°, the azimuth angle of the third slow axis 223X is 112.5°, and the azimuth angle of the fourth slow axis 224X is 157.5°.

[0068] Each of the multiple optical unit structures 220 has a structure in which multiple regions 220G with different refractive indices are alternately arranged. Such an optical unit structure 220 can exhibit a phase difference. Furthermore, a photomask 1000 having such an optical unit structure 220 can suppress a decrease in phase difference due to ultraviolet light, thereby achieving good light resistance. Specifically, each of the multiple optical unit structures 220 has a structure in which multiple regions 220G are alternately arranged at a period on the order of wavelength. The refractive index in this embodiment refers to the absolute refractive index. The stacking direction of the multiple regions 220G is parallel to the in-plane direction of the support substrate 210 (the in-plane direction of the boundary surface with the multiple regions 220G).

[0069] In each of the plurality of optical unit structures 220, the plurality of regions 220G preferably have a first region 220A and a second region 220B having mutually different refractive indices, and include two or more first regions 220A and two or more second regions 220B. In the photomask 1000 of this embodiment, each of the plurality of optical unit structures 220 can function as a retardation plate. For example, in FIG. 9, each of the first optical unit structure 221, the second optical unit structure 222, the third optical unit structure 223, and the fourth optical unit structure 224 can function as a retardation plate. Each of the plurality of optical unit structures 220 preferably has a periodic structure.

[0070] It is preferable that the refractive index of the first region 220A is 1 or less, and the refractive index of the second region 220B is greater than 1. The first region 220A is, for example, an air layer. The second region 220B includes, for example, an inorganic material or an organic material. Examples of the inorganic material include metal. Examples of the organic material include resin.

[0071] As described above, the diffraction element 10 suitable for use in AR glasses can be manufactured using the photomask 1000 of this embodiment. The photo-alignment film 120 included in the diffraction element 10 is a photo-alignment film that has been subjected to a photo-alignment process via the photomask 1000 of this embodiment.

[0072] The diffraction element 10 of this embodiment includes a photo-alignment film 120 that has been subjected to a photo-alignment treatment via a photomask 1000, and a liquid crystal layer 130 that is provided on the photo-alignment film 120 and contains polymerizable liquid crystal 131.

[0073] The diffraction element 10 is also called a liquid crystal diffraction element. When fabricating a liquid crystal diffraction element on a plastic substrate, a release layer can be used. A release layer can be formed on a glass substrate, and then a photo-alignment film 120 and a polymerizable liquid crystal 131 can be formed on the release layer in that order. The liquid crystal layer 130 containing the polymerizable liquid crystal 131 can be peeled off from the release layer and transferred onto a plastic substrate, thereby fabricating a liquid crystal diffraction element on the plastic substrate. In this case, the photo-alignment film 120 may remain on the release layer. [Example]

[0074] The effects of the present invention will be explained below with reference to examples, comparative examples and reference examples, but the present invention is not limited to these examples.

[0075] (Reference example 1) Fig. 13 is a perspective schematic diagram of an optical unit structure according to Reference Example 1. As shown in Fig. 13, the optical unit structure 220E of this Reference Example had a structure in which first regions 220A (specifically, air layers) and second regions 220B (specifically, resin layers) having different refractive indices were alternately arranged along a predetermined direction. The optical unit structure 220E had an uneven shape in which unevenness was repeated along the predetermined direction.

[0076] The optical unit structure 220E of this reference example was fabricated by nanoimprinting. Specifically, ultraviolet curable resin was applied onto the support substrate 210, and ultraviolet light was irradiated while a mold having a concave-convex shape was pressed against the ultraviolet curable resin before hardening. Next, the mold was peeled off to obtain the optical unit structure 220E having a concave-convex shape. Triacetyl cellulose film (TAC film) was used as the support substrate 210. WireGrid (Edmund) was used as the mold. The ultraviolet light irradiation was at 140 mW / cm 2 The test was carried out for 7 seconds.

[0077] The shape of the optical unit structure 220E of this reference example was observed using a scanning electron microscope (SEM). Fig. 14 is an SEM image of the optical unit structure of Reference Example 1. From Fig. 14, it was confirmed that the optical unit structure 220E of this reference example had the uneven shape shown in Fig. 13.

[0078] The retardation of the optical unit structure 220E was measured using an Axoscan manufactured by Axomertrix. It was found that the optical unit structure 220E exhibited a retardation of 8 nm at a wavelength of 550 nm. The slow axis 220XE of the optical unit structure 220E was in the direction shown by the arrow in FIG. 14.

[0079] (Reference example 2) FIG. 15 is a perspective schematic diagram of a photomask according to Reference Example 2. As shown in FIG. 15, the photomask 1000E of this Reference Example included a support substrate 210 and a structural birefringent layer 200E provided on the support substrate 210. The structural birefringent layer 200E had a structure in which a plurality of repeating unit structures 200PE were periodically arranged in a planar view. Each of the repeating unit structures 200PE had a structure in which a plurality of optical unit structures 220E, the azimuth angles of which were different from one another, were arranged along an arrangement direction 1DE of the repeating unit structures 200PE in a planar view. Each of the optical unit structures 220E had a structure in which a plurality of regions 220G, the refractive indexes of which were different from one another, were alternately arranged.

[0080] Each of the optical unit structures 220E included in the photomask 1000E had the same configuration as the optical unit structures 220E of Reference Example 1. That is, each optical unit structure 220E had a structure in which first regions 220A (specifically, air layers) and second regions 220B were alternately arranged along a predetermined direction. The concave-convex shape of the photomask 1000E of this Reference Example was formed by electron beam (EB) writing on a metal film. In this Reference Example, the second regions 220B were metal layers.

[0081] The obtained photomask 1000E was observed under a polarizing microscope. Fig. 16 is a polarizing microscope photograph of the photomask of Reference Example 2. As can be seen from Fig. 16, the distance (pitch P) over which the orientation of the concave-convex direction (slow axis) rotates by 180° was divided into four in this reference example.

[0082] The following measurements were performed to confirm that the photomask 1000E of this reference example is a polarization-dependent diffraction element. FIG. 17 is a schematic diagram illustrating a method for measuring the polarization state. As shown in FIG. 17, ultraviolet light with a wavelength of 355 nm irradiated from a laser light source 310 was transmitted through a wire grid 320 and a quarter-wave plate 330 (λ / 4 plate) to become circularly polarized light. The circularly polarized light was irradiated onto the photomask 1000E, and the polarization states of the incident light and zero-order light were measured using a polarimeter 341, and the polarization state of the first-order light was measured using a polarimeter 342. The results are shown in Table 1 below. Table 1 shows S3, one of the normalized Stokes parameters.

[0083] [Table 1]

[0084] An absolute value of S3 close to 1 indicates that the polarization state is close to circular polarization, and the sign indicates the direction of circular polarization. Table 1 shows that when the photomask 1000E of this reference example is used, the zero-order light and the incident light are circularly polarized in the same direction, and the polarization state of the diffracted light (first-order light) is opposite to the polarization states of the zero-order light and the incident light. From the above, it was confirmed that the photomask 1000E of this reference example functions as a polarization-dependent diffraction element. That is, in this reference example, it was found that the orientation of the slow axis 220XE of the optical unit structure 220E periodically rotates in a uniaxial direction in a planar view, thereby allowing the photomask 1000E to function as a polarization-dependent diffraction element.

[0085] (Comparative Example) The photomask of the comparative example is the conventional photomask 1000R2 in which the slow axis in the photomask 1000E of Reference Example 2 is set as shown in Figures 11 and 12. As shown in Figure 12, each optical unit structure 220R has first regions 220A (specifically, air layers) having a refractive index of 1 and second regions 220B having a refractive index greater than 1 alternately arranged along a predetermined direction.

[0086] The comparative photomask 1000R2 has a first slow axis 221XR with an azimuth angle of 0°, a second slow axis 222XR with an azimuth angle of 45°, a third slow axis 223XR with an azimuth angle of 90°, and a fourth slow axis 224XR with an azimuth angle of 135°.

[0087] Consider the width of region 220G of comparative photomask 1000R2. When producing diffraction element 10 used to trap light in the light guide plate of AR glass using comparative photomask 1000R2, the pitch P of photomask 1000R2 needs to be on the order of submicrons.

[0088] For example, consider a case where the pitch P (the length of the repeating unit structure 200PR in the arrangement direction 1DR) is 300 nm and each repeating unit structure 200PR includes four optical unit structures 220R, as shown in Figure 12. Focus is now on the region (third optical unit structure 223R) where the azimuth angle of the slow axis 220XR is 90°. The third optical unit structure 223R has four second regions 220B with a refractive index greater than 1 and three first regions 220A with a refractive index of 1 arranged between the second regions 220B, i.e., a total of seven regions 220G.

[0089] In this case, the width W of one region 220G is calculated as follows: pitch (300 nm) ÷ number of divisions (4) ÷ number of regions (7) ≈ 10 nm. However, it is not easy to draw a structure with a width of this scale. In other words, it is difficult to manufacture the comparative photomask 1000R2 capable of manufacturing the diffraction element 10.

[0090] Example 1 The photomask of Example 1 corresponds to the photomask 1000 according to the embodiment shown in Figures 9 and 10. The photomask 1000 of this example is a photomask in which the slow axis of the photomask 1000E of Reference Example 2 is set as shown in Figure 9. As shown in Figure 9, each optical unit structure 220 has first regions 220A (specifically, air layers) having a refractive index of 1 and second regions 220B having a refractive index greater than 1 alternately arranged along a predetermined direction.

[0091] The photomask 1000 of this embodiment had a first slow axis 221X with an azimuth angle of 22.5°, a second slow axis 222X with an azimuth angle of 67.5°, a third slow axis 223X with an azimuth angle of 112.5°, and a fourth slow axis 224X with an azimuth angle of 157.5°.

[0092] In this case, in plan view, the slow axis 220X of each of the plurality of optical unit structures 220 is not orthogonal to the arrangement direction 1D, and therefore the total number of regions 220G can be increased without narrowing the width W of the region 220G in any of the optical unit structures 220. That is, in Example 1, there is no restriction on the width W of the region 220G, and it is possible to easily manufacture a photomask 1000 capable of manufacturing a diffraction element 10 having a periodic structure on the submicron order.

[0093] Example 2 In this example, the diffraction element 10 of embodiment 1 shown in FIG. 2 was fabricated. First, a photo-alignment film 120 was patterned using the photomask 1000 of Example 1. Specifically, a photo-alignment film material was applied to a support substrate 110 at a spin speed of 2000 rpm for 30 seconds, and then baked at 90°C for 2 minutes to form a coating film. Next, the coating film was subjected to UV exposure. In the UV exposure, a laser with a wavelength of 355 nm was applied to the coating film through the photomask 1000 of Example 1.

[0094] The laser beam diameter used for UV exposure was small, about 2 mm, and was expanded and collimated using a lens to the same size as the exposure area. However, the beam diameter may be smaller than the target exposure area. In this case, the entire exposure area can be covered by scanning the beam. With the scanning method, scan unevenness is usually observed, but this is not a problem in this application. This is because there is a margin in the process conditions for the regulating force of the photo-alignment film to be expressed, so even if there are unevenness in the exposure conditions, scan unevenness will not be observed when the polymerizable liquid crystal film is formed.

[0095] After UV exposure, the coating film was baked at 160° C. for 10 minutes to obtain a photo-alignment film 120 .

[0096] Next, the polymerizable liquid crystal 131 was applied onto the formed photo-alignment film 120 at a spin speed of 4500 rpm and baked at 90°C for 1 minute to form a coating film. Next, ultraviolet light of 100 mW / cm was applied to the coating film containing the polymerizable liquid crystal 131. 2 The polymerizable liquid crystal 131 was cured to form a liquid crystal layer 130, thereby obtaining a diffraction element 10 (liquid crystal diffraction element).

[0097] The diffraction element 10 of Example 2 was observed using a polarizing microscope. Fig. 18 is a polarizing microscope photograph of the diffraction element of Example 2. As shown in Fig. 18, it was found that the orientation of the phase difference was patterned in the diffraction element 10 of Example 2. In this way, it was found that the photomask 1000 including the structural birefringent layer 200 can be used to fabricate a diffraction element 10 (liquid crystal diffraction element) suitable for AR glasses.

[0098] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and can be implemented in various forms without departing from the spirit of the present disclosure. Furthermore, the components disclosed in the above embodiments can be modified as appropriate. For example, some of the components shown in one embodiment may be added to the components of another embodiment, or some of the components shown in one embodiment may be deleted from the embodiment.

[0099] Furthermore, the drawings mainly show each component in a schematic manner to facilitate understanding of the invention, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of creating the drawings. Furthermore, the configurations of each component shown in the above embodiment are merely examples and are not particularly limited, and it goes without saying that various modifications are possible within a scope that does not substantially deviate from the effects of the present disclosure. [Explanation of symbols]

[0100] 1: Optical elements 1D, 1DA, 1DE, 1DR: Array direction 10: Diffraction element 20: Light guide plate 110, 210, 1110R: Support board 120, 1120R: Photo-alignment film 120X: Alignment control force 130, 1130R: Liquid crystal layer 131, 1131R: Polymerizable liquid crystal 200, 200E, 200R: structural birefringent layer 200P, 200PR: Repeating unit structure 200PA: Photo-alignment film repeating unit structure 220, 220E, 220R, 221, 221R, 222, 222R, 223, 223R, 224, 224R: Optical unit structure 220A, 220B, 220G: Area 220X, 220XE, 220XR, 221X, 221XR, 222X, 222XR, 223X, 223XR, 224X, 224XR: Slow axis 310: Laser light source 320: Wire grid 330: Quarter wave plate 341, 342: Polarimeter 1000, 1000E, 1000R1, 1000R2: Photomasks L:Light P: Pitch W: Width

Claims

1. A support substrate and a form birefringent layer provided on the support substrate, the form birefringent layer has a structure in which a plurality of repeating unit structures are periodically arranged in a plan view, each of the plurality of repeating unit structures has a structure in which, in a plan view, a plurality of optical unit structures having different azimuth angles of slow axes are arranged along an arrangement direction of the plurality of repeating unit structures; Each of the plurality of optical unit structures has a structure in which a plurality of regions having different refractive indices are alternately arranged, A photomask, wherein, in a plan view, the slow axis of each of the plurality of optical unit structures is not perpendicular to the arrangement direction.

2. The arrangement direction in a plan view is set to the azimuth angle direction of 0°-180°, 2. The photomask according to claim 1, wherein, in each of the plurality of repeating unit structures, when the number of the plurality of optical unit structures is k and the azimuth angle of the slow axis of one optical unit structure among the plurality of optical unit structures is α, the azimuth angle A of the slow axis of each of the plurality of optical unit structures satisfies the following (Equation 1) and (Equation 2): Azimuth angle A=α+180°×i÷k (Formula 1) Azimuth angle A≠90° (Formula 2) (In the above formula 1, k is an integer of 2 or more, and i is an integer of 0 or more and (k-1) or less.)

3. 3. The photomask according to claim 2, wherein the azimuth angle A satisfies the following (Formula 2-1) or (Formula 2-2): Azimuth angle A<85° (Formula 2-1) 95°<Azimuth A (Formula 2-2)

4. The photomask according to claim 2 , wherein the azimuth angle A satisfies the following formula (3): Azimuth angle A≠0° (Formula 3)

5. 5. The photomask according to claim 4, wherein the azimuth angle A satisfies the following (Equation 3-1): 5°<Azimuth A<175° (Formula 3-1)

6. In each of the plurality of repeating unit structures, the plurality of optical unit structures includes a first optical unit structure having a first slow axis, a second optical unit structure having a second slow axis, a third optical unit structure having a third slow axis, and a fourth optical unit structure having a fourth slow axis, 2. The photomask according to claim 1, wherein, when the arrangement direction in a planar view is a direction of an azimuth angle of 0°-180°, the azimuth angle of the first slow axis is 22.5°, the azimuth angle of the second slow axis is 67.5°, the azimuth angle of the third slow axis is 112.5°, and the azimuth angle of the fourth slow axis is 157.5°.

7. 2. The photomask of claim 1, wherein in each of the plurality of optical unit structures, the plurality of regions have first and second regions with different refractive indices, and include two or more of the first regions and two or more of the second regions.

8. The photomask of claim 7 , wherein the refractive index of the first region is less than or equal to 1, and the refractive index of the second region is greater than 1.

9. The photomask according to claim 7 , wherein the first region is an air layer.

10. each of the plurality of optical unit structures has the first region and the second region alternately stacked; The photomask according to claim 7 , wherein the slow axis of each of the plurality of optical unit structures is perpendicular to a stacking direction of the first region and the second region.

11. A photo-alignment film that has been subjected to a photo-alignment treatment through the photomask according to any one of claims 1 to 10.

12. a photo-alignment film that has been subjected to a photo-alignment treatment through the photomask according to any one of claims 1 to 10; a liquid crystal layer provided on the photo-alignment film and containing a polymerizable liquid crystal;

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