Beam combiner, method for forming an alignment film, and method for manufacturing an optical element

Abstract

The present invention addresses the problem of providing: a beam combiner capable of forming a fine and clear interference pattern; a method which is for forming an alignment film and with which a fine and clear alignment pattern can be obtained; and a method for producing an optical element having a fine and clear liquid crystal alignment pattern. The problem is solved by: having a beam combiner element that emits light obtained by combining light having transmitted through a first surface and light reflected by a second surface, a light adjustment element disposed on the upstream of the beam combiner, and a polarization conversion layer that converts polarization of light emitted from the beam combiner element; and setting the absolute value of ellipticity of light emitted from the polarization conversion layer to 0.7 or more.

Description

[Technical Field]

[0001] The present invention relates to a beam combiner that generates interference light, a method for forming an alignment film using this beam combiner, and a method for manufacturing an optical element using this alignment film. [Background technology]

[0002] Beam combiners are known to form interference patterns by interfering two beams of light. For example, Non-Patent Document 1 describes a beam combiner shown in Figure 17.

[0003] The beam combiner 100 includes a light source 102, a polarizing beam splitter 104 that splits the coherent light M from the light source 102, a mirror 106A positioned in one optical path of the light split by the polarizing beam splitter 104 and a mirror 106B positioned in the other optical path, a dimming element 108, a half mirror 110, and a λ / 4 plate 112.

[0004] In the beam combiner 100, the coherent light M emitted from the light source 102 is split by the polarizing beam splitter 104 into, for example, P-polarized MP and S-polarized MS. The S-polarized MS beam, split by the polarizing beam splitter 104, is reflected by mirror 106a, passes through the dimming element 108, and enters the half-mirror 110. On the other hand, the P-polarized MP beam, split by the polarizing beam splitter 104, is reflected by mirror 106b and enters the half-mirror 110. The P-polarized MP is reflected by the half-mirror 110. On the other hand, the S-polarized MS that has passed through the dimming element 108 passes through the half-mirror 110. As a result, the P-polarized MP and the S-polarized MS are superimposed on the half-mirror 110 and interfere with each other. P-polarized MP and S-polarized MS are converted into right-circularly polarized and left-circularly polarized light according to their polarization direction by the λ / 4 plate 112, and are incident on, for example, a photosensitive material Z to form an interference pattern. For example, if the photosensitive material Z has a coating film containing a compound having photo-orienting groups, an orientation film having an orientation pattern corresponding to the interference pattern is obtained.

[0005] This beam combiner 100 can form various interference patterns depending on the dimming element 108. For example, if a convex lens is used as the dimming element 108, an interference pattern is formed that has a pattern of continuous rotation and change in one direction, as conceptually shown in Figure 2 below, radiating from the inside outwards. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] “Fabrication of ideal geometric-phase holograms with arbitrary wavefronts” Optica Vol.2,No.11 / November 2015 / pp958-964 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the beam combiner 100 described in Non-Patent Literature 1, the larger the angle at which the light dimmed by the dimming element 108 is incident on the normal to the photosensitive material Z, that is, the wider the angle at which it is incident on the photosensitive material Z, the finer the interference pattern can be obtained. For example, if the photochromic element 108 is a convex lens, shortening the focal point of the photochromic element 108 and greatly widening the diameter of the light emitted from the half mirror 110 allows light to be incident on the photosensitive material Z at a wide angle, resulting in a fine interference pattern.

[0008] However, according to the inventors' research, conventional beam combiners, such as the beam combiner 100 described in Non-Patent Literature 1, have a problem in that when a fine interference pattern is formed, the interference pattern becomes unclear.

[0009] The object of the present invention is to solve the problems of the prior art and to provide a beam combiner that can obtain a fine and clear interference pattern, a method for forming an alignment film using this beam combiner, and a method for manufacturing an optical element using the alignment film formed by this alignment film formation method. [Means for solving the problem]

[0010] To solve this problem, the present invention has the following configuration.

[0011] [1] A beam combiner element having a first surface that transmits at least a portion of the incident light and a second surface that reflects at least a portion of the incident light, and emitting light obtained by superimposing the light transmitted through the first surface and the light reflected from the second surface, At least one dimming element is provided in at least one of the optical paths of a first light incident on the first surface of the beam combiner element and a second light incident on the second surface of the beam combiner element, which focuses or diverges light. It comprises at least one polarization conversion layer that converts the polarization of light emitted from a beam combiner element, When a first linearly polarized beam is incident on the first surface of the beam combiner element, and no light is incident on the second surface, the absolute value of the ellipticity of the light emitted from the polarization conversion layer is 0.7 or greater. A beam combiner in which, when a second linearly polarized beam perpendicular to the first linearly polarized beam is incident on the second surface of the beam combiner element, and no light is incident on the first surface, the absolute value of the ellipticity of the light emitted from the polarization conversion layer is 0.7 or greater, and the sign of the ellipticity is opposite to that of the light due to the first linearly polarized beam. [2] The beam combiner according to [1], wherein when parallel light is incident on the dimming element, at least a portion of the light emitted from the beam combiner element is at an angle of 15° or more with respect to the optical axis. [3] The wavelengths of the first and second light are λnm, The beam combiner according to [1] or [2], wherein the polarization conversion layer is a stacked waveplate comprising two A plates with different axial angles, and the absolute value of the angle between the slow axes of the two A plates is 45°. [4] The wavelengths of the first and second light are λnm, A beam combiner according to any one of [1] to [3], wherein the polarization conversion layer is a laminated waveplate containing two A plates with different axial angles, and the retardation of both A plates is 0.24λ to 0.26λ. [5] The wavelengths of the first and second light are λnm, A beam combiner according to any of [1] to [4], wherein the retardation of the polarization conversion layer is 0.24λ to 0.26λ when light of wavelength λnm is obliquely incident at 15°. [6] The first surface of the beam combiner element has a transmittance for p-polarized light at wavelength λnm, A beam combiner according to any one of [1] to [5], wherein the angle between the optical axis of the first light and the plane perpendicular to the first plane and parallel to the direction of incidence of the second light to the beam combiner element is in the range of -20° to 20° and is 70% or more. [7] A method for forming an alignment film, comprising irradiating a coating film containing a compound having a photo-aligning group with light emitted from a beam combiner described in any of [1] to [6]. A method for manufacturing an optical element, comprising the steps of applying a composition containing a liquid crystal compound to an alignment film formed by the alignment film formation method described in [8] [7] and drying it. [Effects of the Invention]

[0012] The beam combiner of the present invention can form a fine and clear interference pattern. Furthermore, the method for forming an alignment film of the present invention can form an alignment film having a fine and clear alignment pattern. Moreover, the method for manufacturing an optical element of the present invention can manufacture an optical element having a fine and clear liquid crystal alignment pattern. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a diagram conceptually showing an example of the beam combiner of the present invention. [Figure 2] Figure 2 is a diagram conceptually showing an example of an interference pattern by the beam combiner of the present invention. [Figure 3] Figure 3 is a diagram conceptually showing another example of the beam combiner of the present invention. [Figure 4] Figure 4 is a schematic plan view of an example of an optical element manufactured by the manufacturing method of the present invention. [Figure 5] Figure 5 is a schematic cross-sectional view of an example of an optical element manufactured by the manufacturing method of the present invention. [Figure 6] Figure 6 is a conceptual diagram for explaining the optical element manufactured by the manufacturing method of the present invention. [Figure 7] Figure 7 is a conceptual diagram for explaining the optical element manufactured by the manufacturing method of the present invention. [Figure 8] Figure 8 is a conceptual diagram for explaining the optical element manufactured by the manufacturing method of the present invention. [Figure 9] Figure 9 is a schematic cross-sectional view of another example of an optical element manufactured by the manufacturing method of the present invention. [Figure 10] Figure 10 is a conceptual diagram for explaining another example of the optical element manufactured by the manufacturing method of the present invention. [Figure 11] Figure 11 is a conceptual diagram for explaining another example of the optical element manufactured by the manufacturing method of the present invention. [Figure 12] Figure 12 is a conceptual diagram for explaining another example of the optical element manufactured by the manufacturing method of the present invention. [Figure 13] Figure 13 is a diagram conceptually showing another example of the beam combiner of the present invention. [Figure 14] Figure 14 is a conceptual diagram for explaining the beam combiner shown in Figure 13. [Figure 15] Figure 15 is a diagram conceptually showing another example of the beam combiner of the present invention. [Figure 16] Figure 16 is a diagram showing the characteristics of the beam combiner used in the examples. [Figure 17] Figure 17 is a conceptual diagram illustrating an example of a conventional beam combiner. [Modes for carrying out the invention]

[0014] The beam combiner, the method for forming the alignment film, and the method for manufacturing the optical element of the present invention will be described in detail below based on the 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.

[0015] Figure 1 conceptually shows an example of the beam combiner of the present invention. The beam combiner 50 shown in Figure 1 includes a light source 52, a beam splitter 54, mirrors 56a and 56b, a dimming element 58, a beam combiner element 60, and a polarization conversion layer 62.

[0016] The beam combiner 50 splits the coherent light M emitted from the light source 52 into mutually orthogonal linearly polarized beams using the beam splitter 54, dims one of the linearly polarized beams using the dimming element 58, and then superimposes the two linearly polarized beams using the beam combiner element 60, converting them into circularly polarized beams using the polarization conversion layer 62. This beam combiner 50 generates interference fringes by interfering two circularly polarized beams with opposite rotation directions and incident them onto the photosensitive material Z, thereby exposing the photosensitive material Z and forming an interference pattern on the photosensitive material Z.

[0017] In the beam combiner 50, the light source 52 can be any known light source as long as the emitted light is coherent. In particular, a laser light source is preferably used as a light source with excellent coherence.

[0018] The coherent light M emitted from the light source 52 is incident on the beam splitter 54. The beam splitter 54 splits the coherent light M into a first light M1 and a second light M2, which are linearly polarized and orthogonal to each other. For example, the beam splitter 54 splits the incident coherent light M into a first light M1 with S polarization and a second light M2 with P polarization. The first light M1 is the first light in this invention, and the second light M2 is the second light in this invention.

[0019] Any known polarization beam splitter, such as cube-shaped or plate-shaped beam splitters, can be used as the beam splitter 54, as long as it can split coherent light M into mutually orthogonal linearly polarized beams. Furthermore, the beam splitter 54 can also be a combination of an optical element that splits coherent light M, such as a half mirror and an unpolarized beam splitter, and at least one polarizing element. The light split by the half mirror and the unpolarized beam splitter is not linearly polarized and orthogonal to each other, but by combining it with a polarizing element, it can be made linearly polarized and orthogonal. Here, the polarizing element is not particularly limited, and various known types such as reflective polarizers such as wire grid polarizers, dichroic absorbing polarizers, and polarizing prisms such as Grant-Thomson prisms can be suitably used.

[0020] The first beam of light M1 is reflected by the mirror 56a, dimmed by the dimming element 58, and then incident on the beam combiner element 60. In the illustrated example, the dimming element 58 is, for example, a convex lens. Therefore, the light that passes through the dimming element 58 is focused and then widened beyond the focal point. The dimming element 58 will be described in detail later. On the other hand, the second beam M2 is reflected by the mirror 56b and incident on the beam combiner element 60.

[0021] The beam combiner element 60 has a first surface 60a that transmits at least a portion of the incident light and a second surface 60b that reflects at least a portion of the incident light. The light that is incident on and transmitted through the first surface 60a of the beam combiner element 60 and the light that is incident on and reflected by the second surface 60b are superimposed and emitted from the beam combiner element 60. In the following explanation, for the sake of brevity, the phrase "at least a portion" will be omitted from descriptions such as "transmits at least a portion of the incident light" and "reflects at least a portion of the incident light."

[0022] In the beam combiner 50 shown in the illustration, the first light M1, which has been focused after passing through the dimming element 58, is incident on the first surface 60a of the beam combiner element 60 and is transmitted, and the second light M2 is incident on the second surface 60b and is reflected. As shown in Figure 1, the first light M1 that is incident on and transmitted through the first surface 60a and the second light M2 that is incident on and reflected by the second surface 60b are superimposed. As described above, the first light M1 and the second light M2 are originally the same coherent light M that has been split. Therefore, the superimposed first light M1 and second light M2 interfere with each other.

[0023] There are no restrictions on the beam combiner element 60; any known element can be used as long as it has a first surface 60a that transmits incident light and a second surface 60b that reflects incident light, and can superimpose the light transmitted by the first surface 60a and the light reflected by the second surface 60b. As examples of beam combiner elements 60, known beam splitters such as cube-type and plate-type beam splitters, as well as half-mirrors, can be used. The beam combiner element 60 may be a polarized beam combiner (polarized beam splitter) or a non-polarized beam combiner (non-polarized beam splitter). A polarized beam combiner is a device in which, on the first surface 60a (transmission surface), only a specific polarization, such as S polarization, is transmitted and other polarizations are reflected, and on the second surface 60b (reflection surface), only a specific polarization, such as P polarization, is reflected and other polarizations are transmitted. On the other hand, a non-polarized beam combiner combines light so that the intensity ratio of the transmitted and reflected light is a specific ratio, regardless of polarization. The beam splitter preferably has the property of transmitting the first light M1 without changing its polarization state and reflecting the second light M2 without changing its polarization state.

[0024] The first surface 60a of the beam combiner element 60 is preferably highly transparent even to wide-angle incident light, as it is the first light M1 that has been focused after passing through the dimming element 58 that is incident on it. This configuration allows for the creation of clearer interference patterns even with fine patterns, and enables the formation of interference patterns over a wider area. This point will be explained in more detail later.

[0025] The first light M1 and the second light M2, which are superimposed by the beam combiner element 60, are then converted into circularly polarized light by the polarization conversion layer 62. As described above, the first light M1 and the second light M2 are linearly polarized light that is orthogonal to each other. Therefore, the first light M1 and the second light M2 converted by the polarization conversion layer 62 are converted such that the first light M1 is right-circularly polarized and the second light M2 is left-circularly polarized. Alternatively, the first light M1 and the second light M2 converted by the polarization conversion layer 62 are converted such that the first light M1 is left-circularly polarized and the second light M2 is right-circularly polarized.

[0026] As the polarization conversion layer 62, a so-called quarter-wave plate (1 / 4 phase difference plate, λ / 4 plate) is preferably exemplified, which has a planar retardation (retardation Re, phase difference) that is approximately 1 / 4 wavelength at the wavelength of the incident light, i.e., the first light M1 and the second light M2. As an example of a quarter-wave plate, a quarter-wave plate with a retardation-to-wavelength ratio of 0.24 to 0.26 in the planar direction is preferably exemplified, and a quarter-wave plate with a ratio of 0.245 to 0.255 is more preferably exemplified. The polarization conversion layer 62 may be a combination of multiple optical elements. In this case, the retardation measured by the method described later should be approximately 1 / 4 wavelength.

[0027] In the beam combiner 50 of the present invention, it is preferable that the polarization conversion layer 62 has a planar retardation of 0.24λ to 0.26λ when incident light, i.e., the wavelengths of the first light M1 and the second light M2, are λnm and the light is obliquely incident at an angle of 15° with respect to the optical axis. This point will be discussed in more detail later.

[0028] As described above, the beam combiner 50 generates interference fringes by interfering two circularly polarized beams with opposite rotation directions and incident them onto the photosensitive material Z, thereby exposing the photosensitive material Z and forming an interference pattern on the photosensitive material Z. In the beam combiner 50, the interference pattern formed is changed by the dimming element 58. In other words, by selecting the dimming element 58 to be used, the interference pattern to be formed can be selected.

[0029] As described above, in the illustrated example beam combiner 50, the dimming element 58 is, for example, a convex lens. When the dimming element 58 is a convex lens, the interference pattern formed by the beam combiner 50 on the photosensitive material Z is an interference pattern having short straight lines that continuously rotate and change in one direction, as indicated by the arrows in the figure, as conceptually shown in Figure 2. In other words, when the dimming element 58 is a convex lens, the interference pattern formed by the beam combiner 50 on the photosensitive material Z is a concentric interference pattern having short straight lines that continuously rotate and change in one direction, as shown in Figure 2, in a concentric pattern from the inside to the outside.

[0030] In the beam combiner 50, the interference between right-circularly polarized and left-circularly polarized light causes the polarization state of the light irradiated onto the photosensitive material Z to change periodically in an interference fringe pattern. Here, as shown in Figure 1, the first light M1 is focused by the photochromic element 58 (convex lens) and diverges (diffuses) beyond the focal point. As a result, the intersection angle of the left-circularly polarized light and the right-circularly polarized light changes as you move from the inside to the outside of the concentric circles. Consequently, an interference pattern is obtained in which the period shortens from the inside to the outside. This results in a radial (concentric) interference pattern in the photosensitive material Z in which the interference pattern changes periodically.

[0031] Specifically, in this interference pattern, short straight lines continuously rotate and change along multiple directions moving outward from the center, for example, the direction indicated by arrow A1, arrow A2, arrow A3, arrow A4, and so on. In the following explanation, these short straight lines whose direction continuously rotates and changes will be referred to as "short lines" for convenience. The direction of rotation of the short lines is the same in all directions (unidirectional). In the illustrated example, the direction of rotation of the short lines 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, the direction of rotation of the short line reverses at the center along this line. For example, suppose the straight line formed by arrows A1 and A4 points to the right in the diagram (in the direction of arrow A1). In this case, the short line initially rotates clockwise from the outside towards the center, the direction of rotation reverses at the center, and thereafter rotates counterclockwise from the center outwards. Note that the direction of rotation of the short lines is not limited to the direction shown in Figure 2, and may be the opposite direction to that shown in Figure 2.

[0032] Furthermore, in this interference pattern, if we define one period Λ as the length of a 180° rotation of the direction of the short lines in one direction, where the direction of the short lines changes while continuously rotating, then the length of one period Λ gradually decreases from the inside to the outside. One period Λ will be explained in detail later.

[0033] In the beam combiner of the present invention, the dimming element 58 is not limited to a convex lens, and various optical elements can be used. As the light-adjusting element 58, not only spherical lenses, such as convex and concave lenses, but also aspherical lenses can be suitably used. For example, by using a lens array in which multiple lenses are arranged in a plane as the dimming element 58, an interference pattern consisting of multiple concentric circles can be formed.

[0034] The irradiated object, such as the photosensitive material Z, may be positioned outside or inside the focal point of the dimming element 58. By positioning the object to be irradiated outside the focal point of the dimming element 58, space can be secured between the dimming element 58 and the object to be irradiated for the placement of the beam combiner element 60 and the polarization conversion layer 62, etc. Furthermore, by positioning the object to be irradiated inside the focal point of the dimming element 58, the beam combiner 50 can be miniaturized.

[0035] Furthermore, the dimming element 58 may be configured by combining multiple optical elements for purposes such as suppressing aberrations and improving the degree of freedom of interference patterns. For example, a dimming element 58 that focuses light like a convex lens may be combined with a concave lens that emits light to form a dimming element 58 that focuses light like a convex lens. Alternatively, the photochromic element 58 may be a relay optical system in which multiple lenses are arranged according to their respective focal lengths. By using a relay optical system for the photochromic element 58, space can be secured for arranging larger optical elements.

[0036] In the illustrated example of the beam combiner 50, the dimming element 58 is placed only in the optical path of the first light M1 that passes through the first surface 60a of the beam combiner element 60, but the present invention is not limited thereto. In other words, the dimming element 58 may be placed only in the optical path of the second light M2 reflected by the second surface 60b of the beam combiner element 60, or it may be placed in both the optical path of the first light M1 and the optical path of the second light M2. However, if the dimming element 58 is placed in both the optical path of the first light M1 and the optical path of the second light M2, different dimming elements 58 are placed in the optical path of the first light M1 and the optical path of the second light M2. In this case, for example, a pattern is formed by the interference of two spherical waves, which increases the degree of freedom of the interference pattern.

[0037] Furthermore, the placement of the dimming element 58 is not limited to upstream of the beam combiner element 60, and various positions can be used. In this case, there may be multiple dimming elements 58. As an example, a dimming element 58 may be provided in at least one of the optical paths of the first light M1 and the second light M2, and furthermore, a dimming element 58 may be placed between the beam combiner element 60 and the polarization conversion layer 62. In this invention, upstream and downstream refer to the upstream and downstream directions of light propagation from the light source 52 to the photosensitive material Z.

[0038] Incidentally, the first light beam M1 is focused by the dimming element 58 (convex lens) and diverges beyond the focal point. That is, a portion of the first light beam M1 emitted from the beam combiner element 60 has an angle with respect to the optical axis. The larger the angle of the first light M1, the finer the interference pattern formed on the photosensitive material Z. Specifically, when the direction perpendicular to the main surface of the photosensitive material Z, i.e., the normal direction, is set to 0°, the larger the angle of the first light M1 incident on the photosensitive material Z, the finer the interference pattern that can be obtained. In other words, the wider the angle of the first light M1 incident on the photosensitive material Z, the finer the interference pattern formed on the photosensitive material Z. For example, if the pattern is one in which short lines continuously rotate in one direction, as shown in Figure 2, the wider the angle of the first light M1 incident on the photosensitive material Z, the shorter the period Λ in which the short lines rotate 180° in one direction (direction of the arrow) becomes. The main surface refers to the largest surface area of ​​a sheet-like material (film, layer).

[0039] However, conventional beam combiners, such as Non-Patent Document 1 shown in Figure 17, have a problem in that when fine interference patterns are formed, the interference pattern becomes unclear. In particular, when the period Λ is 1.2 μm or less, the interference pattern becomes unclear.

[0040] The inventors of this invention conducted extensive research on this point. As a result, they found that in conventional beam combiners, the polarization conversion by the quarter-wave plate is insufficient, which is the reason why the interference pattern becomes unclear. As described above, in a beam combiner, the wider the angle of the light incident on the photosensitive material Z, the finer the interference pattern that can be formed on the photosensitive material Z. However, if the light that passes through the dimming element and enters the photosensitive material Z is wide-angle, then the light also enters the quarter-wave plate at an oblique angle. Furthermore, the wider the angle of light entering the photosensitive material Z, the larger the angle of oblique incidence of the light on the quarter-wave plate. Therefore, the light that passes through the dimming element undergoes insufficient polarization conversion by the quarter-wave plate, resulting in elliptical polarization instead of circular polarization. Consequently, in conventional beam combiners, the interference pattern obtained from the interference of circularly polarized light becomes unclear.

[0041] In contrast, the beam combiner 50 of the present invention, when a first light M1 is incident on the beam combiner element 60 and a second light M2 is not incident on it, has an absolute value of ellipticity of the first light M1 transmitted through the polarization conversion layer 62 of 0.7 or more, and When the second light M2 is incident on the beam combiner element 60 and the first light M1 is not incident, the absolute value of the ellipticity of the second light M2 transmitted through the polarization conversion layer 62 is 0.7 or greater.

[0042] As described above, the first light M1 and the second light M2 are linearly polarized and orthogonal to each other. The first light M1 is incident on the first surface 60a of the beam combiner element 60, which transmits the incident light, and the second light M2 is incident on the second surface 60b of the beam combiner element 60, which reflects the incident light. As previously stated, the first light M1 is the first light in this invention, and the second light M2 is the second light in this invention. Furthermore, since the first light M1 and the second light M2 are linearly polarized and orthogonal to each other, the polarization conversion layer 62 converts them into circularly polarized light with opposite rotation directions: one to right circular polarization and the other to left circular polarization. Consequently, the signs of the ellipticity of the light transmitted through the polarization conversion layer 62 are opposite for the first light M1 and the second light M2.

[0043] The beam combiner 50 of the present invention, having such a configuration, can interfere appropriately with circularly polarized beams downstream of the polarization conversion layer 62. As a result, the beam combiner 50 of the present invention can form a fine and clear interference pattern on the photosensitive material Z.

[0044] Various methods can be used to ensure that the absolute value of the ellipticity of the first light M1 transmitted through the polarization conversion layer 62 when only the first light M1 is incident on the beam combiner element 60, and the absolute value of the ellipticity of the second light M2 transmitted through the polarization conversion layer 62 when only the second light M2 is incident on the beam combiner element 60, are both 0.7 or greater. As an example, a method is described in which a polarization conversion layer 62 is used in which, when the wavelengths of the first light M1 and the second light M2 are λnm, the in-plane retardation when obliquely incident at an angle of 15° with respect to the optical axis is 0.24λ to 0.26λ.

[0045] As the polarization conversion layer 62 having such retardation, a laminated waveplate composed of multiple layers is preferably used. Examples of multilayer waveplates include those described in International Publication No. 2013 / 137464, International Publication No. 2016 / 158300, Japanese Patent Publication No. 2014-209219, Japanese Patent Publication No. 2014-209220, International Publication No. 2014 / 157079, Japanese Patent Publication No. 2019-215416, and International Publication No. 2019 / 160044, etc. However, in the present invention, the multilayer waveplate is not limited to these. In the present invention, a polarization conversion layer 62, which is a laminated waveplate composed of an A plate and a positive C plate, is preferably used, particularly from the viewpoint of retardation control for oblique incidence described later. Furthermore, the laminated waveplate is preferably configured as a multilayer structure of three or more layers in order to provide the compensation function described later, and is particularly preferably a multilayer structure of three or more layers including at least an A plate and a positive C plate. Furthermore, from the viewpoint of providing the compensation function described later, the polarization conversion layer 62 can also preferably be a laminated waveplate in which at least two A plates with different axial angles are stacked. In addition, as a polarization conversion layer 62 having two A plates in this way, a laminated waveplate in which at least two A plates and a C plate with different axial angles are stacked can also preferably be exemplified. As mentioned above, for such a polarization conversion layer 62, the sum of the retardations of the individual optical elements (layers) constituting the polarization conversion layer should be approximately 1 / 4 wavelength.

[0046] In this invention, plates A, B, and C are defined as follows.

[0047] There are two types of A plates: positive A plates (+A plates) and negative A plates (-A plates). When the refractive index in the direction of the slow axis within the film plane is nx, the refractive index in the direction perpendicular to the slow axis within the plane is ny, and the refractive index in the thickness direction is nz, a positive A plate satisfies the relationship in equation (A1), and a negative A plate satisfies the relationship in equation (A2). Note that a positive A plate shows a positive value for Rth, and a negative A plate shows a negative value for Rth. Note that the slow axis within the film plane is the direction in which the refractive index within the plane is maximum. Formula (A1) nx>ny≒nz Formula (A2) ny <nx≒nz The above "≒" includes not only cases where the two are completely identical, but also cases where they are substantially identical. "Substantially identical" means, for example, that when (ny-nz)×d is -10 to 10 nm, preferably -5 to 5 nm, it is included in "ny≒nz", and when (nx-nz)×d is -10 to 10 nm, preferably -5 to 5 nm, it is included in "nx≒nz". In (ny-nz)×d, d is the thickness of the film.

[0048] There are two types of B plates: one where nx, ny, and nz all have different values ​​and Rth is negative, satisfying the relationship in equation (B1); and another where Rth is positive, satisfying the relationship in equation (B2). Equation (B1) (nx+ny) / 2>nz Equation (B2) (nx+ny) / 2 <nz

[0049] There are two types of C plates: positive C plates (+C plates) and negative C plates (-C plates). Positive C plates satisfy the relationship in equation (C1), and negative C plates satisfy the relationship in equation (C2). Note that positive C plates show a negative Rth value, and negative C plates show a positive Rth value. Formula (C1) nz>nx≒ny Formula (C2) nz <nx≒ny The above "≒" includes not only cases where the two are completely identical, but also cases where they are substantially identical. "Substantially identical" means, for example, that (nx-ny)×d is 0 to 10 nm, preferably 0 to 5 nm, which is included in "nx≒ny". In (ny-nz)×d, d is the thickness of the film.

[0050] The polarization direction of light transmitted through the beam combiner element 60 changes depending on the deflection direction (direction of the deflection axis) in a plane perpendicular to the optical axis. In the illustrated example, the light transmitted through the beam combiner element 60 is the first light M1. The degree of change in polarization direction varies depending on the polarization direction when incident on the beam combiner element 60, i.e., the azimuth angle of the polarization direction, and the change is particularly pronounced in the vertical direction. The vertical direction refers to the direction perpendicular to the plane of the paper in Figure 1, and in the illustrated example, it is the direction of S polarization.

[0051] Preferably, the polarization conversion layer 62 has the function of compensating for the change in polarization direction caused by the beam combiner element 60. As an example of a polarization conversion layer 62 having a function to compensate for changes in polarization direction, a laminated waveplate in which two A plates and C plates with different axis angles are stacked is preferably used. The axis angle of the incident A plate is preferably 0° or 90°, and the axis angle of the other A plate is preferably 45° or 135°. Furthermore, as a polarization conversion layer 62 having a function to compensate for changes in polarization direction, a laminated waveplate formed by stacking two A plates with different axis angles is also preferably exemplified. In this case, the two A plates constituting the laminated waveplate only need to have different axis angles, but it is preferable that the absolute value of the angle between their respective slow axes is 45°. Furthermore, it is preferable that the in-plane retardation of both A plates constituting this laminated waveplate is 0.24λ to 0.26λ when the wavelengths of the first light M1 and the second light M2 are λnm. That is, it is preferable that the phase difference between the two A plates is approximately 1 / 4 wavelength. The axis angle (lagging axis angle) is the angle of the lagging axis of the polarization conversion layer 62, defined as 0° when parallel to S-polarization and 90° when parallel to P-polarization.

[0052] The polarization conversion layer 62 preferably has an anti-reflective layer on at least one surface, and more preferably has an anti-reflective layer on both surfaces. The anti-reflective layer should preferably have high anti-reflective properties even for wide-angle incident light. The reflectance of the anti-reflective layer (polarization conversion layer 62) for P-polarized and S-polarized light at wavelengths λnm in the incident angle range of -20° to 20° is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.2% or less. The polarization conversion layer 62 has an anti-reflective function, which prevents stray light generated by surface reflection from irradiating the photosensitive material Z and forming an undesirable interference pattern.

[0053] For the anti-reflective layer, known anti-reflective films such as moth-eye films and anti-reflective films in which high-refractive-index layers and low-refractive-index layers are alternately laminated can be used. The anti-reflective layer may be formed directly on the surface of the polarization conversion layer 62, or the anti-reflective layer may be formed on an optically transparent substrate with low birefringence, such as glass or a resin film, and then the polarization conversion layer and the substrate may be bonded together. From the viewpoint of smoothness, it is preferable to form an anti-reflective layer on the glass substrate and bond it with the polarization conversion layer 62. Furthermore, in this case, it is more preferable to use quartz glass as the glass substrate. In addition to the polarization conversion layer 62, such anti-reflective layers may also be provided, if necessary, on at least one of the light incident surface and light output surface of at least one of the elements constituting the beam combiner, such as the beam splitter 54, mirrors 56a and 56b, dimming element 58, and beam combiner element 60.

[0054] As described above, in the beam combiner 50, the wider the angle of the first light M1 that passes through the dimming element 58 and is incident on the photosensitive material Z, the finer the interference pattern can be formed. In the beam combiner 50 of the present invention, there are no restrictions on the angle of the light emitted from the beam combiner element 60 after passing through the dimming element 58 with respect to the optical axis. Here, it is preferable that at least a portion of the light emitted from the beam combiner element 60 when parallel light is incident on the dimming element 58 is at an angle of 15° or more with respect to the optical axis. The light transmitted through the dimming element 58 is the first light M1 in the illustrated example. The angle of the light emitted from the beam combiner element 60 with respect to the optical axis is more preferably 17° or greater, and even more preferably 20° or greater. A fine interference pattern can be formed by ensuring that at least a portion of the light emitted from the beam combiner element 60 has an angle of 15° or more with respect to the optical axis. In particular, a fine interference pattern can be suitably formed when the light that does not pass through the dimming element 58 is parallel light, as shown in the illustrated example. In the illustrated example, the light that does not pass through the dimming element 58 is the second light M2.

[0055] When the first or second light M1 or M2 is incident on the photosensitive material Z at an angle, it is preferable that the projection component onto the photosensitive material Z is close to circularly polarized light. In other words, when observed in a plane perpendicular to the optical axis, being close to circularly polarized light is not necessarily preferable for forming fine interference patterns. In the present invention, it is preferable that the polarization conversion layer 62 has a compensation function that takes into account the effective polarization change due to projection.

[0056] Figure 3 shows an example of another embodiment of the beam combiner of the present invention. In the beam combiner 50 shown in Figure 1, the polarization conversion layer 62 is positioned orthogonally with respect to the optical axes of the superimposed first light M1 and second light M2. In contrast, in the beam combiner 50A shown in Figure 3, the polarization conversion layer 62A is parallel to the reflective surface of the beam combiner element 60, i.e., the second surface 60b.

[0057] As described above, the second light M2 reflected by the second surface 60b of the beam combiner element 60 is, for example, P-polarized. Here, when the second light M2 is reflected by the second surface 60b of the beam combiner element 60, its polarization direction may shift, and it may no longer be perfectly P-polarized. In this case, if the polarization conversion layer is perpendicular to the optical axis of the second light M2, the conversion by the polarization conversion layer will be insufficient, as before, and the second light M2 will become elliptically polarized. As a result, when a fine interference pattern is formed, the interference pattern will similarly become unclear.

[0058] In contrast, as shown in Figure 3, by aligning the polarization conversion layer 62A parallel to the second surface 60b of the beam combiner element 60, the polarization direction of the second light M2 that shifts when reflected by the second surface 60b of the beam combiner element 60 can be compensated. As a result, the polarization conversion layer 62A can convert the second light M2 into properly circularly polarized light, enabling the formation of a fine and clear interference pattern.

[0059] Various types of polarization conversion layers 62A, similar to those described above for the polarization conversion layer 62, can be used. Furthermore, in the beam combiner 50A shown in Figure 3, a polarization conversion layer 62A consisting only of an A plate that acts as a quarter-wave plate, without a C plate or the like, is also suitably used.

[0060] Here, the polarization conversion layer 62A only needs to be substantially parallel to the reflective surface, i.e., the second surface 60b, of the beam combiner element 60. For example, the polarization conversion layer 62A may be parallel to the second surface 60b of the beam combiner element 60 at an angle obtained by adding the physical angle and the optical angle.

[0061] In a polarization conversion layer 62A acting as a quarter-wave plate, the slow axis is generally parallel to the main plane. Therefore, in this case, the polarization conversion layer 62A should be positioned parallel to the second surface 60b of the beam combiner element 60.

[0062] In the examples shown in Figures 1 and 3, the polarization conversion layer 62A may be a phase difference layer, or so-called O-plate, having an optical axis inclined with respect to the main surface of the polarization conversion layer. For example, suppose the second surface 60b (reflecting surface) of the beam combiner element 60 is tilted at 45° with respect to the optical axis of the second light M2. In this case, if the slow axis of the polarization conversion layer 62A is tilted at 25° with respect to the main surface, then the polarization conversion layer 62A should be positioned at a 20° tilt with respect to the optical axis of the second light M2. This makes it possible to make the second surface 60b of the beam combiner element 60, which is at 45° with respect to the optical axis, and the polarization conversion layer 62A physically and optically parallel (20° + 25° = 45°).

[0063] In the beam combiners shown in Figures 1 and 3 above, S-polarized light is incident on the first surface 60a of the beam combiner element 60, and P-polarized light is incident on the second surface 60b. However, the beam combiner of the present invention is not limited to this. In other words, as conceptually shown in Figure 13, the beam combiner of the present invention may superimpose the transmitted light (P-polarized) and the reflected light (S-polarized), by injecting P-polarized light as the first light M1 into the first surface 60a of the beam combiner element 60 and S-polarized light as the second light M2 into the second surface 60b of the beam combiner element 60.

[0064] Here, the first surface 60a of the beam combiner element 60 preferably has high transmittance even to wide-angle incident light, as the first light M1 that has been focused after passing through the dimming element 58 is incident on it, as described above. In particular, when P-polarized light is incident on and transmitted through the first surface 60a, increasing the transmittance of the first surface 60a allows for a clearer interference pattern even with a fine interference pattern, and furthermore, an appropriate interference pattern can be formed over a wide area.

[0065] Specifically, when the first light M1 is P-polarized, the first surface 60a of the beam combiner element 60 preferably has a transmittance of 70% or more, and more preferably 80% or more, for the P-polarized light of the first light M1 at wavelength λnm, in a plane perpendicular to the first surface 60a and parallel to the incident direction of the second light M2 to the beam combiner element 60, in the range of -20° to 20°. Furthermore, the optical axis Ax of the first light source M1 coincides with the optical axis of the light source 52. It is also preferable that the optical axis Ax of the first light source M1 coincides with the optical axis of the dimming element 58 (convex lens). Furthermore, when the first light M1 is P-polarized, the transmittance of the first surface 60a of the beam combiner element 60 for S-polarized light of wavelength λnm is preferably less than 5%, and more preferably less than 2%, in the range of -5° to 5° or less, where the angle made between the first light M1 and the optical axis Ax in a plane perpendicular to the first surface 60a and parallel to the incident direction of the second light M2 to the beam combiner element 60 is the first surface 60a.

[0066] The material constituting the polarization conversion layer 62 used in the present invention is not particularly limited. Therefore, the polarization conversion layer 62 may be a layer formed from a composition containing a liquid crystal compound, for example, or a layer formed from a polymer film. The polymer film is a film formed from a polymer (resin), and is particularly preferably a polymer film that has undergone stretching treatment. Examples of polymer films include polycarbonate films, cycloolefin polymer films, TAC films, and polyimide films. Cycloolefin polymer films are particularly preferred because they have excellent light resistance and can withstand long-term use.

[0067] If the polarization conversion layer 62 used in the present invention is a laminated waveplate consisting of multiple layers, each layer of the laminated waveplate may be independently composed of a different material.

[0068] The polarization conversion layer 62 used in the present invention is preferably a layer formed from a composition containing a liquid crystal compound. By forming the polarization conversion layer 62 from a composition containing a liquid crystal compound, the polarization conversion layer can be made thinner and its optical properties can be easily adjusted. The composition containing the liquid crystal compound is preferably a composition containing a polymerizable liquid crystal compound. The layer formed from the composition containing the polymerizable liquid crystal compound is preferably a layer formed by fixing the polymerizable liquid crystal compound by polymerization or the like.

[0069] The type of liquid crystal compound is not particularly limited. Liquid crystal compounds can be classified into rod-shaped liquid crystals (rod-shaped liquid crystal compounds) and disc-shaped liquid crystals (discotic liquid crystal compounds, discotic liquid crystals (compounds)) based on their shape. Furthermore, each type of liquid crystal compound has both low-molecular-weight and high-molecular-weight types. High-molecular-weight compounds generally refer to those with a degree of polymerization of 100 or more (Polymer Physics and Phase Transition Dynamics, by Masao Doi, p. 2, Iwanami Shoten, 1992). In this invention, any type of liquid crystal compound can be used. The liquid crystal composition may include two or more rod-shaped liquid crystals, two or more disc-shaped liquid crystals, and mixtures of rod-shaped and disc-shaped liquid crystals. As for the rod-shaped liquid crystal, for example, those described in claim 1 of Japanese Patent Publication No. 11-513019 and paragraphs

[0026] to

[0098] of Japanese Patent Application Publication No. 2005-289980 can be preferably used. On the other hand, as for the disc-shaped liquid crystal, for example, those described in paragraphs

[0020] to

[0067] of Japanese Patent Application Publication No. 2007-108732 and paragraphs

[0013] to

[0108] of Japanese Patent Application Publication No. 2010-244038 can be preferably used.

[0070] In the beam combiner 50 shown in Figure 1 (Figures 3 and 13), the light M emitted from the light source 52 is directly incident on the beam splitter 54. However, the present invention is not limited to this. That is, the beam combiner of the invention may have various optical elements for adjusting the light M emitted from the light source 52. Figure 15 shows an example.

[0071] In the example shown in Figure 15, a preferred embodiment includes a beam expander element 70 and an optical path adjustment optical system 72 between the light source 52 and the beam splitter 54. In the beam combiner of the present invention, the beam expander element 70 and the optical path adjustment optical system 72, which are provided as a preferred embodiment, are not limited to having both, and may have only one of them. However, in the present invention, it is more preferable to have both.

[0072] The beam expander element 70 expands the diameter of the light M (light beam) emitted from the light source 52 (beam expanding element). By having a beam expander element 70 in the beam combiner, the exposure area in the photosensitive material Z can be enlarged, making it suitable for manufacturing large diffractive elements (liquid crystal diffractive lenses), for example.

[0073] There are no restrictions on the beam expander element 70; any known beam expander, such as a transmissive expander or a reflective expander, can be used as long as it can expand the diameter of linearly polarized, coherent light M. Both fixed-magnification and variable-magnification types are available for transmission-type expanders. Furthermore, Keplerian beam expanders and Galilean beam expanders are preferably used as transmission-type expanders. A Keplerian beam expander consists of two lenses with a positive focal length, and from the viewpoint of shaping the beam, it is also preferable to have a pinhole between the two lenses. Furthermore, it is also preferable to use a beam shaper that has the function of adjusting light M, which has a Gaussian-type intensity distribution, to a top-hat-type intensity distribution.

[0074] In the beam combiner of the present invention, the position of the beam expander element 70 is not limited to between the light source 52 and the beam splitter 54. For example, the beam expander element 70 may be placed in the optical paths of the first light M1 and the second light M2 between the beam splitter 54 and the beam combiner element 60. It is preferable that the expansion ratios of the beam expander elements 70 placed in the optical paths of the first light M1 and the second light M2 are equal. However, in this case, the beam expander element 70 is placed upstream of the dimming element 58. The same applies in this respect when the dimming element is located in the optical path of the second light M2. Furthermore, in the beam combiner of the present invention, multiple beam expander elements 70 may be arranged in a single optical path. For example, beam expander elements 70 may be arranged both upstream and downstream of the beam splitter 54.

[0075] In the example shown in Figure 15, an optical path adjustment optical system 72 is provided between the light source 52 and the beam expander element 70. The optical path adjustment optical system 72 is an optical system that detects the light M emitted from the light source 52 and adjusts the optical path (optical axis) of the light M appropriately. In the illustrated example, the optical path adjustment optical system 72 includes working mirrors 74a and 74b, a mirror 76, and detectors 78a and 78b.

[0076] The working mirror and 74b are known angle-adjustable mirrors whose angle can be adjusted by an actuator such as a piezoelectric element. Detector 78a is a detector that detects the incident position of light M on the working mirror 74a. Detector 78b is a detector that detects the incident position of light M on the mirror 76. Mirror 76 is a known reflective mirror.

[0077] The optical path adjustment optical system 72 detects the incident position of light M on the working mirror 74a using detector 78a and the incident position of light M on the mirror 76 using detector 78b during exposure of the photosensitive material Z. The optical path adjustment optical system 72 adjusts the angles of the working mirrors 74a and 74b so that the optical path of the light M from the light source 52 to the beam expander element 70 is appropriate, according to the detection result of the light M.

[0078] In beam combiners, as well as various other optical systems, the light source 52 changes over time, causing the optical path of the light M to fluctuate. As a result, the incident position of the interference light on the photosensitive material Z shifts from the reference position, causing the exposure position on the photosensitive material Z to differ from the intended position. Furthermore, fluctuations in the optical path of light M result in deviations in the incident position and angle of light M to each optical element. When deviations occur in the incident position and angle to the optical elements, each optical element cannot exhibit the predetermined optical performance, and the exposure accuracy of the photosensitive material Z decreases. In contrast, the beam combiner shown in Figure 15, in a preferred embodiment, has an optical path adjustment optical system 72 that adjusts the optical path of light M. By having an optical path adjustment optical system 72 in the beam combiner, the optical path of light M can be positioned appropriately for exposure of the photosensitive material Z. As a result, the beam combiner can perform high-precision exposure of the photosensitive material Z at the desired position.

[0079] Furthermore, in the beam combiner of the present invention, the optical path adjustment optical system is not limited to the configuration shown in the illustration, and various known automatic optical path adjustment means for optical beams used in various optical systems (optical devices) can be utilized.

[0080] The present invention provides a method for forming an orientation film, which involves irradiating a coating film containing a compound having photo-orienting groups with interference light generated by the beam combiner of the present invention.

[0081] According to the method for forming an orientation film of the present invention, that is, the method for forming an orientation film of the present invention using the beam combiner of the present invention, a large-sized orientation pattern (interference pattern), i.e., interference light, can be incident on a coating film containing a compound having photo-orienting groups. Therefore, by using the alignment film formed by the light distribution film formation method of the present invention, as described later, large-sized optical elements can be manufactured. Specifically, it is preferable to have a diameter of 30 mm or more, more preferably 40 mm or more, and even more preferably 50 mm or more. When the orientation pattern to be formed is a concentric circular pattern as shown in Figure 2, the larger the diameter of the pattern, the shorter the period Λ of the liquid crystal orientation pattern at the edges of the pattern becomes. However, according to the present invention, a clear and fine interference pattern can be obtained.

[0082] In the method for forming an alignment film of the present invention, one example is a method of forming an alignment film 24 made of a photo-alignment film on a support 20, as conceptually shown in Figure 5, which will be described later.

[0083] The support 20 can be any type of sheet material (film, plate) as long as it can support the alignment film 24 and the optical anisotropy layer 26, which will be described later. 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.

[0084] A coating film containing a compound having photo-orienting groups is formed on the surface of such a support 20, and this coating film is dried. Subsequently, the dried coating film is irradiated with interference light, which is formed by superimposing the first circularly polarized light M1 and the second circularly polarized light M2, using the beam combiner 50 (50A) of the present invention described above. This forms an interference pattern on the coating film, creating an orientation film 24 having an orientation pattern. For example, if the dimming element 58 is a convex lens, as shown in the illustration, an alignment film 24 can be formed that has the same orientation pattern as the interference pattern shown in Figure 2, which has short lines (short straight lines) radially changing while continuously rotating in one direction.

[0085] Compounds having photo-oriented groups that can be used in the present invention, i.e., photo-oriented materials used in photo-oriented films, include, for example, 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, and Japanese Patent Publication No. 2007-1 Azo compounds described in Japanese Patent Publication No. 56439, Japanese Patent Publication No. 2007-133184, 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, and photo-orienting units described in Japanese Patent Publication No. 2002-265541 and Japanese Patent Publication No. 2002-317013 Examples of preferred examples include maleimide and / or alkenyl-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.

[0086] The present invention provides a method for manufacturing an optical element, which involves applying a composition containing a liquid crystal compound to the alignment film formed in this manner, drying it, and further curing the liquid crystal compound as necessary. Figures 4 and 5 conceptually show an example of an optical element manufactured by the optical element manufacturing method of the present invention. Figure 4 is a conceptual plan view of the optical element, and Figure 5 is a conceptual cross-sectional view of the optical element. A plan view is a view of the optical element from the thickness direction (= the stacking direction of each layer (film)).

[0087] As described above, the alignment film 24 is formed on the support 20. The optical element 10 shown in Figures 4 and 5 has an optically anisotropic layer 26 formed on this alignment film 24 using a composition containing a liquid crystal compound. As an example, the alignment film 24, as described above, has an interference pattern in which the direction of the short lines changes while continuously rotating in one direction, radiating from the inside outwards. The optically anisotropic layer 26 formed on such an alignment film 24 using a composition containing a liquid crystal compound has a liquid crystal alignment pattern radially from the inside outward, in which the orientation of the optical axis originating from the liquid crystal compound 30 changes while continuously rotating in one direction. That is, the liquid crystal alignment pattern of the optically anisotropic layer 26 shown in Figures 4 and 5 is a concentric pattern in which the orientation of the optical axis originating from the liquid crystal compound 30 changes while continuously rotating in one direction, radially from the inside outward. In Figures 4 to 8, a rod-shaped liquid crystal compound is used as an example of the liquid crystal compound 30, so the direction of the optical axis coincides with the longitudinal direction of the liquid crystal compound 30.

[0088] 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.

[0089] Furthermore, in the optical anisotropy layer 26 of the optical element 10, the liquid crystal alignment pattern is such that, when the length of one period is defined as the length of a 180° rotation of the optical axis direction originating from the liquid crystal compound in one direction in which the direction of the optical axis of the liquid crystal compound 30 changes while continuously rotating, the length of one period gradually decreases from the inside to the outside.

[0090] When circularly polarized light is incident on the optically anisotropic layer 26 having this liquid crystal alignment pattern, the absolute phase changes in each local region where the optical axis orientation of the liquid crystal compound 30 is different. In this case, the amount of change in the absolute phase differs depending on the orientation of the optical axis of the liquid crystal compound 30 to which the circularly polarized light is incident. In an optically anisotropic layer (optical element 10) having a liquid crystal orientation pattern in which the orientation of the optical axis of the liquid crystal compound 30 changes while continuously rotating in one direction, the direction of refraction of transmitted light depends on the direction of rotation of the optical axis of the liquid crystal compound 30. That is, in this liquid crystal orientation pattern, if the direction of rotation of the optical axis of the liquid crystal compound 30 is reversed, the direction of refraction of transmitted light will be in the opposite direction to the direction in which the optical axis rotates. Furthermore, the diffraction angle due to the optical anisotropy layer 26 increases as the period becomes shorter. In other words, the diffraction of light due to the optical anisotropy layer 26 increases as the period becomes shorter.

[0091] Therefore, an optically anisotropic layer 26 having such a concentric liquid crystal alignment pattern, that is, a liquid crystal alignment pattern that changes as the optical axes rotate radially, can transmit incident light (light beam) by diverging or focusing it, depending on the rotation direction of the optical axis of the liquid crystal compound 30 and the rotation direction of the incident circularly polarized light.

[0092] The optically anisotropic layer 26 is formed using a composition containing a liquid crystal compound. In Figure 4 (and in Figures 7 and 8 described later), the optical anisotropy layer 26 is shown only as the liquid crystal compound 30 (liquid crystal compound molecules) on the surface of the alignment film 24, in order to simplify the drawing and clearly show the structure of the optical element 10. However, the optical anisotropy layer 26 has a structure in which oriented liquid crystal compounds 30 are stacked, similar to an optical anisotropy layer formed using a composition containing a conventional liquid crystal compound, as conceptually shown in Figure 5.

[0093] The optical anisotropic layer 26, when the in-plane retardation value is set to λ / 2, functions as a general λ / 2 plate, that is, it has the function of giving a half-wavelength, or 180°, phase difference to two mutually orthogonal linearly polarized components contained in the light incident on the optical anisotropic layer. In-plane retardation refers to retardation in the plane direction.

[0094] The optically anisotropic layer 26 has a liquid crystal orientation pattern that radiates from the inside outward, in which the orientation of the optical axes originating from the liquid crystal compound changes while continuously rotating in one direction (such as the directions of arrows A1 to A4 in Figure 4) 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".

[0095] The optical anisotropy layer 26 will be described below with reference to the optical anisotropy layer 26A, which has a liquid crystal alignment pattern that changes as the optical axis 30A rotates continuously in one direction indicated by arrow A, as conceptually shown in Figure 6. In the liquid crystal alignment pattern shown in Figure 4, where the optical axis changes in one direction as it continuously rotates, radiating (concentrically) from the inside out, the same optical effects as those of the liquid crystal alignment pattern shown in Figure 6 are exhibited with respect to the one direction in which the optical axis changes as it continuously rotates.

[0096] In the optically anisotropic layer 26A, 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 Figures 7 and 8, which will be described later, the Y direction is perpendicular to the plane of the paper. In the following explanation, "the one direction indicated by arrow A" will also simply be referred to as "the direction of arrow A." In the optical anisotropy layer 26 shown in Figure 4, the circumferential direction of the concentric circles in the concentric liquid crystal alignment pattern corresponds to the Y direction in Figure 6.

[0097] The optically anisotropic layer 26A 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 26A. 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.

[0098] On the other hand, in the liquid crystal compound 30 that forms the optical anisotropy layer 26A, 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. In the optical anisotropy layer 26 shown in Figure 4, regions are formed in a ring shape with a coincident center, where the orientation of the optical axis 30A is the same.

[0099] Similar to the short lines described above, in the optically anisotropic layer 26, in a liquid crystal alignment pattern where the optical axis 30A rotates continuously in one direction, the length (distance) of the 180° rotation of the optical axis 30A of the liquid crystal compound 30 is defined as the length of one period in the liquid crystal alignment pattern Λ. In other words, for the optically anisotropic layer 26A shown in Figure 6, 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 6, 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 optically anisotropic layer 26A (optically anisotropic layer 26), the liquid crystal alignment pattern of the optically anisotropic layer 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.

[0100] Furthermore, in an optical element 10 having a liquid crystal alignment pattern in which the optical axis 30A rotates continuously, arranged radially (concentrically), the period Λ in the optical anisotropy layer 26 gradually shortens from the inside (center) outwards.

[0101] As described above, in the optically anisotropic layer 26A, the liquid crystal compounds arranged in the Y direction have an equal angle between the optical axis 30A and the direction of arrow A. The direction of arrow A is one direction in which the orientation of the optical axis of the liquid crystal compound 30 rotates. The region where the liquid crystal compounds 30, which have an equal angle between the optical axis 30A and the direction of arrow A, are arranged in the Y direction is defined as region R. In this case, the in-plane retardation (Re) value in each region R is preferably half a wavelength, i.e., λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn due to the refractive index anisotropy of region R and the thickness of the optical anisotropy layer. Here, the refractive index difference due to the refractive index anisotropy of region R in the optical anisotropy layer is defined as the refractive index difference between the refractive index in the direction of the slow axis within the plane of region R and the refractive index in the direction perpendicular to the direction of the slow axis. That is, the refractive index difference Δn due to the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 30 in the direction of the optical axis 30A and the refractive index of the liquid crystal compound 30 in the direction perpendicular to the optical axis 30A within the plane of region R. In other words, the above refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound. In an optical element 10 having a radial liquid crystal alignment pattern in which the optical axis 30A rotates continuously in one direction, the region where the optical axis 30A is oriented in the same direction and is formed in an annular shape with the center coinciding corresponds to region R in Figure 6. This is also true for the reflective optical element 10 having a cholesteric liquid crystal layer, which will be described later.

[0102] When circularly polarized light is incident on such an optically anisotropic layer 26A, the light is refracted and the direction of the circular polarization is changed. This effect is conceptually illustrated in Figures 7 and 8. The optical anisotropy layer 26A is assumed to have a product value of λ / 2 between the refractive index difference of the liquid crystal compound and the thickness of the optical anisotropy layer. As mentioned above, this effect is exactly the same even in an optical element 10 having a liquid crystal alignment pattern radially arranged such that the optical axis 30A rotates continuously in one direction.

[0103] As shown in Figure 7, when the product of the refractive index difference of the liquid crystal compound in the optical anisotropy layer 26 and the thickness of the optical anisotropy layer is λ / 2, when left-circularly polarized incident light L1 is incident on the optical anisotropy layer 26, the incident light L1 passes through the optical anisotropy layer 26A, giving it a phase difference of 180°, and the transmitted light L2 is converted to right-circularly polarized light. Furthermore, as the incident light L1 passes through the optically anisotropic layer 26A, its absolute phase changes according to the orientation of the optical axis 30A of each liquid crystal compound 30. At this time, the orientation of the optical axis 30A changes while rotating along the direction of arrow A, so the amount of change in the absolute phase of the incident light L1 differs depending on the orientation of the optical axis 30A. Moreover, since the liquid crystal alignment pattern formed in the optically anisotropic layer 26A is a periodic pattern in the direction of arrow A, the incident light L1 that has passed through the optically anisotropic layer 26 is given a periodic absolute phase Q1 in the direction of arrow A corresponding to the orientation of each optical axis 30A, as shown in Figure 7. As a result, an equiphase surface E1 tilted in the opposite direction to the direction of arrow A is formed. Therefore, the transmitted light L2 is refracted (diffracted) so as to be tilted perpendicular to the equiphase plane E1, and travels in a direction different from the direction of propagation of the incident light L1. In this way, the left-circularly polarized incident light L1 is converted into right-circularly polarized transmitted light L2, which is tilted by a certain angle in the direction of arrow A with respect to the direction of incidence.

[0104] On the other hand, as conceptually shown in Figure 8, when the product of the refractive index difference of the liquid crystal compound in the optical anisotropy layer 26A and the thickness of the optical anisotropy layer is λ / 2, when right-circularly polarized incident light L4 is incident on the optical anisotropy layer 26A, the incident light L4 passes through the optical anisotropy layer 26, is given a phase difference of 180°, and is converted into left-circularly polarized transmitted light L5. Furthermore, as the incident light L4 passes through the optically anisotropic layer 26A, its absolute phase changes according to the orientation of the optical axis 30A of each liquid crystal compound 30. At this time, the orientation of the optical axis 30A changes while rotating along the direction of arrow A, so the amount of change in the absolute phase of the incident light L4 differs depending on the orientation of the optical axis 30A. Moreover, since the liquid crystal alignment pattern formed in the optically anisotropic layer 26A is a periodic pattern in the direction of arrow A, the incident light L4 that has passed through the optically anisotropic layer 26 is given a periodic absolute phase Q2 in the direction of arrow A corresponding to the orientation of each optical axis 30A, as shown in Figure 5. Here, since the incident light L4 is right-circularly polarized, the periodic absolute phase Q2 in the direction of arrow A, which corresponds to the direction of the optical axis 30A, is opposite to that of the incident light L1, which is left-circularly polarized. As a result, for the incident light L4, an equiphase surface E2 is formed that is tilted in the direction of arrow A, opposite to that of the incident light L1. Therefore, the incident light L4 is refracted so as to be tilted perpendicular to the equiphase plane E2, and travels in a direction different from the direction of propagation of the incident light L4. In this way, the incident light L4 is converted into transmitted light L5, which is left-circularly polarized and tilted by a certain angle in the direction opposite to the direction of arrow A with respect to the direction of incidence.

[0105] In the optical anisotropic layer 26, the in-plane retardation values ​​of multiple regions R are preferably half a wavelength, but for incident light with a wavelength of 550 nm, the in-plane retardation of multiple regions R in the optical anisotropic layer 26 is Re(550) = Δn 550It is preferable that ×d is within the range defined by the following formula (1). Here, Δn 550 is the refractive index difference due to refractive index anisotropy in region R when the wavelength of the incident light is 550 nm, and d is the thickness of the optical anisotropy layer 26. 200nm ≤ Δn 550 ×d ≤ 350nm···(1) The optically anisotropic layer 26 functions as a so-called λ / 2 plate. However, in the present invention, when a support 20 and an alignment film 24 are present, the laminate comprising these integrally functions as a λ / 2 plate.

[0106] Here, the optically anisotropic layer 26A can adjust the refraction angles of transmitted light L2 and L5 by changing the period Λ of the formed liquid crystal alignment pattern. Specifically, the shorter the period Λ of the liquid crystal alignment pattern, the stronger the interference between light passing through adjacent liquid crystal compounds 30, thereby allowing for greater refraction of transmitted light L2 and L5. Furthermore, the angle of refraction of transmitted light L2 and L5 relative to incident light L1 and L4 differs depending on the wavelength of the incident light L1 and L4 (and transmitted light L2 and L5). Specifically, the longer the wavelength of the incident light, the greater the refraction of the transmitted light. That is, when the incident light is red, green, and blue light, the red light is refracted the most, and the blue light is refracted the least. Furthermore, by reversing the rotation direction of the optical axis 30A of the liquid crystal compound 30, which rotates along the direction of arrow A, the direction of refraction of transmitted light can be reversed.

[0107] As described above, in a liquid crystal alignment pattern in which the optical axis 30A rotates in one direction, the optical anisotropy layer 26 of the optical element 10 has a liquid crystal alignment pattern in which the period Λ of the liquid crystal alignment pattern gradually shortens from the inside (center) to the outside. Therefore, by setting the rotation direction of the optical axis 30A from the inside outward so that the light is refracted toward the center of the optical element 10 according to the wavelength and polarization state of the incident light, and by appropriately adjusting the degree of gradual decrease in the length of one period Λ of the liquid crystal alignment pattern, the degree of light focusing toward the center (optical axis) of the optical element 10 can be adjusted. In other words, by gradually decreasing the length of one period Λ of the liquid crystal alignment pattern, the optical element 10 can be made to act as a focusing lens (convex lens). Furthermore, by gradually decreasing the length of one period Λ of the liquid crystal alignment pattern, the optical element 10 can be made to act as a collimating lens.

[0108] 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 film 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 film 24 and cured to obtain an optically anisotropic layer consisting of a cured layer of the liquid crystal composition. The liquid crystal composition for forming the optically anisotropic layer 26 may contain a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and may also contain other components such as a leveling agent, an alignment control agent, a polymerization initiator, and an alignment aid.

[0109] 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.

[0110] -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.

[0111] 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 Application No. 2001-64627 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.

[0112] —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.

[0113] The optical element 10 described above is a transmission-type optical element 10 that transmits and diffracts circularly polarized light, but the optical element manufactured by the manufacturing method of the present invention is not limited to this. In other words, the optical element manufactured by the manufacturing method of the present invention may be a reflective optical element having a cholesteric liquid crystal layer.

[0114] Figure 9 conceptually shows an example of a reflective optical element manufactured by the manufacturing method of the present invention. Note that the optical element 36 shown in Figure 9 has many of the same components as the transmissive optical element 10 described above; therefore, the same components are denoted by the same reference numerals, and the following description will mainly focus on the different parts. Figure 9 is a conceptual diagram showing the layer structure of the reflective optical element 36. The optical element 36 comprises the support 20 and alignment film 24 described above, and a cholesteric liquid crystal layer 34 that exhibits the function of a reflective optical element 36. The liquid crystal alignment pattern of the liquid crystal compound 30 in the cholesteric liquid crystal layer 34 is similar to that of the optical element 10 described above, and has a radial liquid crystal alignment pattern that changes as the optical axis 30A continuously rotates in one direction indicated by arrow A, as shown in Figure 4.

[0115] Figure 10 is a schematic diagram illustrating the orientation state of the liquid crystal compound 30 within the plane of the main surface of the cholesteric liquid crystal layer 34. Figure 10 shows the orientation state of the cholesteric liquid crystal layer 34A on the surface facing the alignment film 24. Similar to Figure 6 above, the cholesteric liquid crystal layer 34A shown in Figure 10 is represented by a liquid crystal alignment pattern in which the optical axis 30A continuously rotates in one direction indicated by arrow A, in order to explain the cholesteric liquid crystal layer 34. However, even in a liquid crystal alignment pattern in which the optical axis continuously rotates in one direction and changes radially (concentrically) from the inside to the outside, the same optical effects as those shown in Figure 10 are exhibited with respect to the optical axis continuously rotating in one direction. Furthermore, similar to Figure 6 described above, in Figure 10, the circumferential direction of the concentric circles in the concentric liquid crystal alignment pattern shown in Figure 4 corresponds to the Y direction in Figure 10.

[0116] As shown in Figure 9, the cholesteric liquid crystal layer 34 is a layer in which the liquid crystal compound 30 is cholesterically oriented. Figures 9 and 10 also show examples where the liquid crystal compound constituting the cholesteric liquid crystal layer is a rod-shaped liquid crystal compound. In the following explanation, the cholesteric liquid crystal layer will also be referred to simply as the liquid crystal layer.

[0117] In the optical element 36, the support 20 and the alignment film 24 are the same as described above. The optical element 36 has a liquid crystal layer 34 (cholesteric liquid crystal layer) having a liquid crystal alignment pattern as shown in Figure 4, on top of an alignment film 24 having an alignment pattern as shown in Figure 2.

[0118] The liquid crystal layer 34 is a cholesteric liquid crystal layer formed by cholesterically oriented a liquid crystal compound and fixing a cholesteric liquid crystal phase. In this example, the cholesteric liquid crystal layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane.

[0119] As conceptually shown in Figure 9, the liquid crystal layer 34 has a helical structure in which the liquid crystal compound 30 is spirally stacked, similar to a cholesteric liquid crystal layer in which a normal cholesteric liquid crystal phase is fixed. The structure is such that multiple spirally spiraling liquid crystal compounds 30 are stacked, with one spiral rotation (360° rotation) of the liquid crystal compound 30 being defined as one spiral pitch (spiral pitch P).

[0120] As is well known, cholesteric liquid crystal phases exhibit selective reflectivity for either right-handed or left-handed circularly polarized light at specific wavelengths. Whether the reflected light is right-handed or left-handed depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. Selective reflection of circularly polarized light by the cholesteric liquid crystal phase occurs when the twist direction of the helix of the cholesteric liquid crystal phase is to the right, and when the twist direction of the helix is ​​to the left, it reflects left-handed circularly polarized light. Furthermore, the direction of rotation of the cholesteric liquid crystal phase can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer and / or the type of chiral agent added.

[0121] Furthermore, the half-width Δλ (nm) of the selective reflection band (circularly polarized reflection band) exhibiting selective reflection depends on the Δn of the cholesteric liquid crystal phase and the helical pitch P, following the relationship 'Δλ = Δn × helical pitch'. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer, its mixing ratio, and the temperature during orientation fixing. Therefore, the wavelength of light reflected (diffracted) by the liquid crystal layer 34 can be appropriately set by adjusting, for example, the helical pitch P of the liquid crystal layer 34 to set the selective reflection wavelength band of the liquid crystal layer.

[0122] As shown in Figure 10, in the liquid crystal layer 34, the liquid crystal compounds 30 are arranged along the direction of arrow A and the Y direction perpendicular to the direction of arrow A. The orientation of the optical axis 30A of the liquid crystal compounds 30 changes while continuously rotating in one direction within the plane, i.e., in the direction of arrow A. In the Y direction, liquid crystal compounds 30 with the same orientation of the optical axis 30A are oriented at equal intervals. Furthermore, the statement that "the orientation of the optical axis 30A of the liquid crystal compound 30 changes while continuously rotating in one direction within the plane" means that, similar to the optical anisotropy layer 26 described above, the angle between the optical axis 30A of the liquid crystal compound 30 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 gradually changes from θ to θ+180° or θ-180° along the direction of arrow A. In other words, as shown in Figure 10, the optical axis 30A of multiple liquid crystal compounds 30 arranged along the direction of arrow A changes while rotating by a constant angle 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.

[0123] Similar to the optically anisotropic layer 26 described above, in the liquid crystal layer 34, in the liquid crystal alignment pattern of such a liquid crystal compound 30, the length (distance) over which the optical axis 30A of the liquid crystal compound 30 rotates 180° in the direction of arrow A, where the optical axis 30A rotates continuously within the plane, is defined as the length of one period in the liquid crystal alignment pattern Λ. The liquid crystal alignment pattern of the liquid crystal layer 34 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. The optical element 36 is also a liquid crystal diffraction element, and as before, this one period Λ becomes the period (one period) of the diffraction structure.

[0124] On the other hand, in the liquid crystal compound 30 that forms the liquid crystal layer 34, the orientation of the optical axis 30A is the same in the direction perpendicular to the direction of arrow A (the Y direction in Figure 10), that is, in the Y direction perpendicular to the direction in which the optical axis 30A rotates continuously. As described above, in the liquid crystal alignment pattern shown in Figure 4, this Y direction is the circumferential direction of the concentric circles. In other words, in the liquid crystal compound 30 that forms the liquid crystal layer 34, the angle between the optical axis 30A of the liquid crystal compound 30 and the direction of arrow A (X direction) is equal in the Y direction.

[0125] When the cross-section of the liquid crystal layer 34 in the XZ direction shown in Figure 9 is observed with a scanning electron microscope (SEM), a striped pattern is observed in which bright areas 42 and dark areas 44 are arranged alternately, as shown in Figure 11, and the arrangement direction is inclined at a predetermined angle with respect to the main plane (XY plane). The spacing between the bright area 42 and the dark area 44 basically depends on the helical pitch P of the cholesteric liquid crystal layer. Therefore, the wavelength range of light selectively reflected by the cholesteric liquid crystal layer correlates with the distance between the bright areas 42 and the dark areas 44. That is, if the distance between the bright areas 42 and the dark areas 44 is long, the helical pitch P is long, and the wavelength range of light selectively reflected by the cholesteric liquid crystal layer becomes long wavelength. Conversely, if the distance between the bright areas 42 and the dark areas 44 is short, the helical pitch P is short, and the wavelength range of light selectively reflected by the cholesteric liquid crystal layer becomes short wavelength. In a cholesteric liquid crystal layer, basically, two repetitions of the bright areas 42 and dark areas 44 correspond to the helical pitch P. Therefore, in a cross-section observed with such an SEM, the spacing between adjacent bright areas 42 to bright areas 42, or dark areas 44 to dark areas 44, in the direction normal to (orthogonal to) the line formed by the bright areas 42 or dark areas 44, corresponds to half the helical pitch P. In other words, the helical pitch P can be measured by setting the interval in the direction normal to the line between the bright areas 42 and the bright areas 42, or between the dark areas 44 and the dark areas 44, as 1 / 2 pitch.

[0126] The diffraction effect of the liquid crystal layer 34 will be explained below. In conventional cholesteric liquid crystal layers, the helical axis originating from the cholesteric liquid crystal phase is perpendicular to the principal plane, and its reflective surface is parallel to the principal plane. Furthermore, the optical axis of the liquid crystal compound is not inclined with respect to the principal plane. In other words, the optical axis is parallel to the principal plane. Therefore, when the XZ plane of a conventional cholesteric liquid crystal layer is observed by SEM, the arrangement direction of alternating light and dark areas is perpendicular to the principal plane. Because the cholesteric liquid crystal phase is specularly reflective, for example, when light is incident on the cholesteric liquid crystal layer from the normal direction, the light is reflected in the normal direction.

[0127] In contrast, the liquid crystal layer 34 reflects the incident light at an angle in the direction of arrow A relative to specular reflection. The liquid crystal layer 34 has a liquid crystal alignment pattern in which the optical axis 30A changes while continuously rotating along the direction of arrow A (a predetermined one direction) within the plane. The following explanation will be given with reference to Figure 12.

[0128] The liquid crystal layer 34, as an example, is a right-circularly polarized green light G R Assume that it is a cholesteric liquid crystal layer that selectively reflects green light. Therefore, when light is incident on the liquid crystal layer 34, the liquid crystal layer 34 reflects green light with right-circular polarization G R It reflects only certain types of light, while transmitting all other light.

[0129] In the liquid crystal layer 34, the optical axis 30A of the liquid crystal compound 30 changes while rotating along the direction of arrow A (one direction). The liquid crystal alignment pattern formed in the liquid crystal layer 34 is a periodic pattern in the direction of arrow A. Therefore, right-circularly polarized green light G incident on the liquid crystal layer 34 R As conceptually shown in Figure 12, the light is reflected (diffracted) in a direction corresponding to the period of the liquid crystal alignment pattern, and the reflected red light, which is right-circularly polarized RR, is reflected (diffracted) in a direction tilted in the direction of arrow A with respect to the XY plane (the main plane of the cholesteric liquid crystal layer).

[0130] Furthermore, when reflecting circularly polarized light of the same wavelength and direction of rotation, the direction of reflection of the circularly polarized light can be reversed by reversing the rotation direction of the optical axis 30A of the liquid crystal compound 30 facing the direction of arrow A. For example, in Figures 9 and 10, the rotation direction of the optical axis 30A in the direction of arrow A is clockwise, and a certain circularly polarized light is reflected tilted in the direction of arrow A. However, by changing this to counterclockwise rotation, a certain circularly polarized light is reflected tilted in the opposite direction to the direction of arrow A.

[0131] Furthermore, in liquid crystal layers having the same liquid crystal alignment pattern, the reflection direction is reversed depending on the spiral direction of the liquid crystal compound 30, i.e., the spiral direction of the reflected circularly polarized light. For example, if the spiral direction of the liquid crystal layer is a right-handed twist, it selectively reflects right-handed circularly polarized light. By having a liquid crystal orientation pattern in which the optical axis 30A rotates clockwise along the direction of arrow A, it reflects right-handed circularly polarized light at an angle in the direction of arrow A.

[0132] Furthermore, for example, if the spiral direction of the liquid crystal layer is a left twist, it selectively reflects left-circularly polarized light. A liquid crystal layer having a liquid crystal alignment pattern in which the optical axis 30A rotates clockwise along the direction of arrow A reflects left-circularly polarized light tilted in the opposite direction to the direction of arrow A.

[0133] Therefore, the optical element 36 can be used as a convex mirror that reflects incident light in a divergent manner, or as a concave mirror that reflects incident light in a focused manner, depending on the rotation direction of the optical axis 30A from the inside to the outside in the liquid crystal layer 34, and the rotation direction of the circularly polarized light selectively reflected by the liquid crystal layer 34.

[0134] As described above, in the liquid crystal layer 34 acting as a reflective optical element 36, the period Λ of the diffracting structure is the length of a 180° rotation of the optical axis 30A of the liquid crystal compound 30 in the liquid crystal alignment pattern of the liquid crystal compound 30. Furthermore, in the liquid crystal layer 34, the direction in which the optical axis 30A of the liquid crystal compound 30 changes while rotating (direction of arrow A) is the periodic direction of the diffracting structure.

[0135] In a liquid crystal layer with a liquid crystal alignment pattern, the shorter the period Λ, the larger the diffraction angle of the reflected light relative to the incident light. In other words, the shorter the period Λ, the more the incident light can be diffracted and reflected in a direction significantly different from specular reflection. In the present invention, there are no restrictions on the period Λ of the liquid crystal layer 34, and a period Λ that can separate the signal light 103 can be appropriately set according to the wavelength of the assumed signal light 103, etc. The period Λ of the liquid crystal layer 34 is preferably 0.1 to 20 μm, and more preferably 0.1 to 10 μm.

[0136] The liquid crystal layer 34 can be formed by fixing a liquid crystal phase, in which the liquid crystal compound 30 is oriented in a predetermined orientation, in a layered manner. For example, in the case of a cholesteric liquid crystal layer, it can be formed by fixing a cholesteric liquid crystal phase in a layered manner. The structure in which the cholesteric liquid crystal phase is fixed can be any structure in which the orientation of the liquid crystal compound that constitutes the liquid crystal phase is maintained. Typically, a polymerizable liquid crystal compound is brought into a predetermined liquid crystal phase orientation state, and then polymerized and cured by ultraviolet irradiation, heating, etc., to form a non-fluid layer, and at the same time, a structure is preferred in which the orientation form does not change due to an external field or external force. In a structure with a fixed liquid crystal phase, it is sufficient that the optical properties of the liquid crystal phase are maintained, and the liquid crystal compound 30 does not need to exhibit liquid crystalline properties in the liquid crystal layer. For example, a polymerizable liquid crystal compound may lose its liquid crystalline properties due to its high molecular weight resulting from a curing reaction. The same applies to the optically anisotropic layer 26 mentioned above.

[0137] As an example of a material used to form the liquid crystal layer 34, a liquid crystal composition containing a liquid crystal compound is used. Preferably, the liquid crystal compound is a polymerizable liquid crystal compound. Examples of liquid crystal compositions for forming the (cholesteric) liquid crystal layer 34 include a liquid crystal composition in which a chiral agent that causes the liquid crystal compound 30 to spirally orient is added to the liquid crystal composition on which the optical anisotropy layer 26 of the transmissive optical element 36 described above is formed.

[0138] --Chiral agents (optically active compounds)-- Chiral agents have the function of inducing a helical structure in the cholesteric liquid crystal phase. Since different chiral agents induce different helical twist directions or helical pitches (P), 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.

[0139] When the chiral agent has a photoisomerizing group, it is preferable because, after coating and orientation, a pattern of the desired reflected wavelength corresponding to the emission wavelength can be formed by photomask irradiation with active light or the like. 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.

[0140] 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.

[0141] When forming the liquid crystal layer 34, it is preferable to apply a liquid crystal composition to the formation surface of the liquid crystal layer 34, orient the liquid crystal compound 30 in a desired liquid crystal phase state, and then cure the liquid crystal compound 30 to obtain the liquid crystal layer 34. That is, when forming a cholesteric liquid crystal layer on the alignment film 24, it is preferable to apply a liquid crystal composition to the alignment film 24, orient the liquid crystal compound 30 in a cholesteric liquid crystal phase state, and then cure the liquid crystal compound 30 to form a liquid crystal layer 34 in which the cholesteric liquid crystal phase is fixed. The applied liquid crystal composition is dried and / or heated as necessary, and then cured to form a liquid crystal layer. In this drying and / or heating step, the liquid crystal compound 30 in the liquid crystal composition may be oriented in a cholesteric liquid crystal phase. When heating is performed, the heating temperature is preferably 200°C or lower, more preferably 130°C or lower.

[0142] The oriented liquid crystal compound 30 is further polymerized as necessary. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. In this regard, the same applies to the above-described optically anisotropic layer 26. It is preferable to use ultraviolet rays for light irradiation. The irradiation energy is preferably 20 mJ / cm 2 ~50 J / cm 2 and more preferably 50~1500 mJ / cm 2 Light irradiation may be performed under heating conditions or in a nitrogen atmosphere to promote the photopolymerization reaction. The wavelength of the irradiated ultraviolet rays is preferably 250~430 nm.

[0143] There is no limitation on the thickness of the liquid crystal layer 34, and the thickness that can obtain the required light reflectance may be appropriately set according to the use of the diffraction element, the light reflectance required for the liquid crystal layer, the formation material of the liquid crystal layer 34, and the like.

[0144] As described above, the beam combiner, the method for forming the alignment film, and the method for manufacturing the optical element of the present invention have been described in detail. However, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the gist of the present invention, which is of course.

Example

[0145] The features of the present invention will be further described in 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 without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[0146] A beam combiner with the configuration shown in Figure 1 was fabricated. A solid-state laser with a wavelength of 355 nm was used as the light source. A polarizing beam splitter (Sigma Koki Co., Ltd., PBSW-20-350) was used, and the laser beam was split so that the first beam was P-polarized and the second beam was S-polarized, as shown in the beam combiner in Figure 15. The optical element used was a convex lens with a focal length of 90 mm. A cube-shaped beam splitter was used as the beam combiner element. Specifically, the beam splitters used as beam combiner elements in Comparative Examples 1 and 2, and Examples 1 to 3 and 7 are polarized beam splitters A1, as shown in the upper part of Figure 16, in which the first surface (transmission surface) is perpendicular to the first surface and parallel to the incident direction of the second light (S-polarized) to the beam combiner element, and the angle between the optical axis of the first light and the incident light is in the range of -20° to 20°, and the transmittance of P-polarized light is 70% or more (see Figure 14). The polarized beam splitter A1 has a cubic shape with sides of 25 mm. Furthermore, the beam splitter used as the beam combiner element in Examples 4 and 5 was a polarizing beam splitter A2, which has the same transmission characteristics as the polarizing beam splitter A1 and has a cubic shape with dimensions of 75 mm on each side. In the following explanation, the angle between the optical axis of the first light and the incident light within this plane will also simply be called the "angle of incidence." In contrast, the beam splitter used as the beam combiner element in Example 6 is a polarizing beam splitter B, as shown in the lower part of Figure 16, in which the transmittance of P-polarized light decreases sharply when the incident angle is -10° or less on the first surface (transmission surface). This polarizing beam splitter has the same 75mm cube shape as polarizing beam splitter A2.

[0147] In the fabricated beam combiners, different polarization conversion layers were used in Comparative Examples 1 and 2, and in Examples 1 to 5. However, the same polarization conversion layer was used in Examples 4 and 6. The polarization conversion layer in Comparative Example 1 used a commercially available quarter-wave plate (Sigma Optical Co., Ltd., WPQ-3550-4M). This is a zero-order wave plate made by bonding two quartz plates together. The polarization conversion layer in Comparative Example 2 used an A-plate (axis angle 45°) with an in-plane retardation (Re) of 89 nm. The polarization conversion layer in Example 1 used a laminate consisting of an A plate (axis angle 45°) with an in-plane retardation (Re) of 89 nm in the first layer and a C plate with a thickness-direction retardation (Rth) of 33 nm in the second layer. The polarization conversion layer in Example 2 used a laminate consisting of a C plate with a retardation in the thickness direction (Rth) of 33 nm in the first layer and an A plate (axis angle 45°) with an in-plane retardation (Re) of 89 nm in the second layer. The polarization conversion layers in Examples 3 and 7 used a laminate consisting of an A plate with an in-plane retardation (Re) of 89 nm (axis angle 0°) as the first layer, an A plate with an in-plane retardation (Re) of 89 nm (axis angle 45°) as the second layer, and a C plate with a thickness-direction retardation (Rth) of 33 nm as the third layer. The polarization conversion layers in Examples 4 and 6 used a laminate consisting of a first layer of A-plate with an in-plane retardation (Re) of 89 nm (axis angle 0°) and a second layer of A-plate with an in-plane retardation (Re) of 89 nm (axis angle 45°). The polarization conversion layer in Example 5 used a laminate consisting of a first layer of A-plate with an in-plane retardation (Re) of 89 nm (axis angle 0°) and a second layer of A-plate with an in-plane retardation (Re) of 89 nm (axis angle -45°). In Examples 4-7, the polarization conversion layers were used by sandwiching both sides of the polarization conversion layer between glass substrates on which an anti-reflective layer was formed. The reflectance of the anti-reflective layer at a wavelength of 355 nm was 0.2% or less for both P-polarized and S-polarized light within an incident angle of ±30°.

[0148] The axis angle, as mentioned above, is the angle of the slow axis of the polarization conversion layer, defined as 0° when parallel to S-polarization and 90° when parallel to P-polarization. Furthermore, the first layer of the polarization conversion layer is on the side where the light is incident.

[0149] [Evaluation of Ellipticity] For the beam combiner fabricated in this manner, when only the first light (linearly polarized) is incident on the beam combiner element without the second light being incident, the absolute value of the ellipticity of the first light emitted from the polarization conversion layer (Requirement A) and, The absolute value of the ellipticity of the second light emitted from the polarization conversion layer (Requirement B) was measured when only the second light (linearly polarized) was incident on the beam combiner element without the first light being incident.

[0150] A λ / 4 plate and a polarizer were placed on the exit side of the polarization conversion layer. Then, an optical system was prepared in which the light intensity when light passing through the polarization conversion layer and then through the λ / 4 plate and polarizer in that order was measured using a power meter. To limit the measurement area, a light-shielding plate with a 1 mm diameter opening was placed in front of the power meter. The polarizer and power meter were positioned parallel to the installation angle of the photosensitive material, and the λ / 4 plate was positioned perpendicular to the optical axis of the light transmitted through the polarization conversion layer.

[0151] Using this optical system, the ellipticity was calculated from the change in intensity of transmitted light obtained by rotating a λ / 4 plate and a polarizer. The evaluation is as follows: A: Ellipticity is 0.92 or higher B: Ellipticity is between 0.8 and 0.92 C: Ellipticity is between 0.7 and 0, and less than 8. D: Ellipticity is less than 0.7

[0152] [Evaluation of retardation (phase difference) of the polarization conversion layer under oblique incidence] For the polarization conversion layer of each beam combiner, retardation at a 15° oblique angle with a wavelength λ (λ=355nm) was measured using a spectroscopic ellipsometer (JAWoollam, M-2000). The evaluation is as follows. A: Retardation is within the range of 0.24λ to 0.26λ B: Retardation exceeds the range of 0.24λ to 0.26λ

[0153] [Evaluation of interference patterns] (Support) A glass substrate was prepared as the support.

[0154] (Formation of orientation film) The following orientation film-forming coating solution was applied to the support by spin coating. The support coated with this orientation film-forming coating solution was dried on a 60°C hot plate for 60 seconds to form an orientation film.

[0155] Coating solution for forming alignment films -------------------------------------------------- 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 --------------------------------------------------

[0156] -Photo alignment material A- [ka]

[0157] (Exposure of alignment layer) Using the beam combiners described above in Comparative Examples 1 and 2, as well as in Examples 1 to 3, the formed orientation films were exposed to light to create an orientation film P-1 having an orientation pattern in which short straight lines (short lines) radially change while continuously rotating in one direction, as shown in Figure 2. The period Λ of the orientation pattern of the alignment film varies within the plane, but its minimum value was set to 1 μm. The period Λ of the orientation pattern was adjusted by the focal length of the convex lens used as an optical element. The light source used was the same as before, emitting laser light with a wavelength of 355 nm. The exposure dose due to interference was 1000 mJ / cm². 2 That's what I decided.

[0158] (Formation of an optically anisotropic layer for pattern observation) The following liquid crystal composition A-1 was prepared as the liquid crystal composition for forming the optical anisotropy layer A-1. Liquid crystal 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 --------------------------------------------------

[0159] Liquid crystal compound L-1 [ka]

[0160] Leveling agent T-1 [ka]

[0161] The above liquid crystal composition A-1 was applied to the alignment film P-1, and the coating was heated to 80°C on a hot plate. Then, under a nitrogen atmosphere, ultraviolet light with a wavelength of 365 nm was 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. In this way, an optical element for pattern observation was obtained in which an alignment film P-1 and an optically anisotropic layer A-1 were stacked in this order on a glass substrate.

[0162] (Pattern observation 1) The resulting optical element for pattern observation was rotated under a polarizer with its absorption axis arranged in crossed nicols for observation. This allowed us to confirm whether there was an angle arrangement that caused extinction, where the brightness remained constant and unchanged in the exposed area (the part with the orientation pattern) of the optical element. This indicates that, on an in-plane average, the optical properties are the same regardless of the angular relationship with the absorption axis of the crossed nicol polarizers, and that an orientation pattern is formed in which the orientation axis rotates.

[0163] (Pattern observation 2) Furthermore, when the resulting optical elements for pattern observation were observed under crossed nicols with an optical microscope, a clear orientation pattern with alternating dark and bright areas was confirmed. The interference pattern was evaluated based on the results of Pattern Observation 1 and Pattern Observation 2. The evaluation is as follows: A: Regardless of the sample's orientation, a clear orientation pattern can be observed in which dark and bright areas appear alternately, and the line widths of adjacent bright and dark areas are approximately equal. B: A clear orientation pattern can be observed in which dark and light areas appear alternately, but depending on the orientation of the sample, the line width of adjacent light and dark areas may differ. C: Depending on the orientation of the sample, the orientation pattern may be unclear. The results are shown in the table below. The table also includes the size (diameter) of the obtained orientation pattern.

[0164] [Table 1]

[0165] As shown in the table above, when only the first light or only the second light is incident on the beam combiner element, the ellipticity of the light emitted from the polarization conversion layer is 0.7 or higher according to the beam combiner of the present invention, which can clearly form fine interference patterns.

[0166] Furthermore, Examples 4 and 6, which use the same polarization conversion layer, both yield clear orientation patterns. However, the optical element in Example 6, which used a polarizing beam splitter B as a beam combiner element, having a first surface (transmitting surface) where the transmittance of P-polarized light decreases sharply when the incident angle is -10° or less, had a narrower region in which an appropriate liquid crystal alignment pattern was formed compared to the optical element in Example 4, which used a polarizing beam splitter A as a beam combiner element, having a first surface where the transmittance of P-polarized light is 70% or more in the incident angle range of -20° to 20°. Furthermore, in Example 7, which has an anti-reflective layer on the polarization conversion layer, light loss on the surface is reduced compared to Example 3, which has the same polarization conversion layer but no anti-reflective layer, and exposure becomes possible in a shorter time. Furthermore, as described above, in a concentric orientation pattern as shown in Figure 2, the larger the diameter, the shorter the period Λ of the orientation pattern at the edges. In contrast, according to the present invention, even with an orientation pattern of 50 mm in diameter, a clear and high-quality orientation pattern (interference pattern) can be formed in which the line widths of adjacent light and dark areas are approximately equal. Based on the above results, the effects of the present invention are clear. [Explanation of Symbols]

[0167] 10,36 Optical elements 20 Support 24 Alignment film 26,26A Optically anisotropic layer 30 Liquid crystal compounds 30A optical axis 34,34A (cholesteric) liquid crystal layer 50, 50A Beam Combiner 52 Light source 54 Beam Splitter 56a, 56b Miller 58 Dimming elements 60 Beam combiner elements 60a Page 1 60b 2nd side 62,62A Polarization conversion layer 100 Beam Combiner 102 Light source 104 Polarizing Beam Splitter 106a, 106b Miller 108 dimmers 110 Half Mirror 112 λ / 4 plate Ax optical axis M Coherent light M1 First Light M2 2nd light Z photosensitive material

Claims

1. A beam combiner element having a first surface that transmits at least a portion of incident light and a second surface that reflects at least a portion of incident light, and emitting light obtained by superimposing the light transmitted through the first surface and the light reflected from the second surface, At least one dimming element for focusing or diverging light is provided in at least one of the optical paths of a first light incident on the first surface of the beam combiner element and a second light incident on the second surface of the beam combiner element, The beam combiner element comprises at least one polarization conversion layer that converts the polarization of light emitted from the beam combiner element, When a first linearly polarized beam is incident on the first surface of the beam combiner element and no light is incident on the second surface, the absolute value of the ellipticity of the light emitted from the polarization conversion layer is 0.7 or more. When a second linearly polarized beam perpendicular to the first linearly polarized beam is incident on the second surface of the beam combiner element, and no light is incident on the first surface, the absolute value of the ellipticity of the light emitted from the polarization conversion layer is 0.7 or greater, and the sign of the ellipticity is opposite to that of the light due to the first linearly polarized beam. The wavelengths of the first light and the second light are λnm, A beam combiner in which the polarization conversion layer is a laminated waveplate containing two A plates with different axial angles, the absolute value of the angle between the slow axes of the two A plates is 45°, and the retardation of both A plates is 0.24λ to 0.26λ.

2. The beam combiner according to claim 1, wherein when parallel light is incident on the dimming element, at least a portion of the light emitted from the beam combiner element is at an angle of 15° or more with respect to the optical axis.

3. The beam combiner according to claim 1 or 2, wherein the retardation of the polarization conversion layer is 0.24λ to 0.26λ when light of wavelength λnm is obliquely incident at 15°.

4. The first surface of the beam combiner element has a transmittance for p-polarized light with a wavelength of λnm, A beam combiner according to any one of claims 1 to 3, wherein the angle made with the optical axis of the first light in a plane perpendicular to the first plane and parallel to the direction of incidence of the second light to the beam combiner element is in the range of -20° to 20° and accounts for 70% or more of the angle.

5. Furthermore, upstream of the beam combiner element, there is a light source and a beam splitter that splits the light emitted by the light source, A beam combiner according to any one of claims 1 to 4, comprising a beam expander element for expanding the diameter of light emitted from the light source and an optical path adjustment optical system for adjusting the optical path of light emitted from the light source, between the light source and the beam splitter.

6. The beam combiner according to any one of claims 1 to 5, wherein, if the angle is 0° when parallel to S-polarized light and 90° when parallel to P-polarized light, the angle of the slow axis of the A plate on the light incidence side of the two A plates is 0° or 90°.

7. A method for forming an alignment film, comprising irradiating a coating film containing a compound having a photo-aligning group with light emitted from a beam combiner according to any one of claims 1 to 6.

8. A method for manufacturing an optical element, comprising the steps of applying and drying a composition containing a liquid crystal compound to an alignment film formed by the alignment film formation method described in claim 7.

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