Optical element

Abstract

To provide an optical element which can offer good optical characteristics.SOLUTION: An optical element of the present invention comprises a first alignment film, a first optically anisotropic layer containing first anisotropic molecules, a second alignment film, and a second optically anisotropic layer containing second anisotropic molecules arranged in the described order.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to optical elements. [Background technology]

[0002] In recent years, optical systems using optical elements such as Pancharatnam-Berry phase optical elements (PBOEs) have been proposed for display devices such as head-mounted displays. PBOEs include an optically anisotropic layer formed using a liquid crystal composition containing liquid crystal molecules. PBOEs are also called PB lenses.

[0003] As an example of a PBOE, Patent Document 1 discloses a polarization diffraction grating including a polarization-sensitive photo-alignment layer (2) and a liquid crystal composition (3) disposed on the photo-alignment layer (2), in which an anisotropic alignment pattern corresponding to a polarization hologram is disposed in the photo-alignment layer, and the liquid crystal composition (3) is aligned to the alignment pattern. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2008-532085 Summary of the Invention [Problem to be solved by the invention]

[0005] Fig. 45 is a cross-sectional schematic diagram showing the configuration of a general PB lens. As shown in Fig. 45, a general PB lens 10R includes a support substrate 100R, an alignment film 200R, and an optically anisotropic layer 300R, which is a λ / 2 plate, in this order. The diffraction efficiency of the lens is maximized when the phase difference of the PB lens 10R is a half wavelength. Therefore, in order to realize a wideband diffraction efficiency, a wideband half-wave plate is required.

[0006] Here, the PB lens 10R is obtained by, for example, performing an alignment treatment on an alignment film 200R on a support substrate 100R by mask exposure, and then aligning anisotropic molecules (e.g., reactive mesogens (RM)) on the alignment film 200R that has been subjected to the alignment treatment to form an optically anisotropic layer 300R. The optically anisotropic layer 300R is also called an RM layer. Since existing RM layers do not have ideal wavelength dispersion, it is difficult to achieve good diffraction efficiency in a wide band even if a λ / 2 A-plate is fabricated.

[0007] In addition, in the PB lens, the RM is arranged so that it rotates within the plane. When manufacturing a PB lens by multiple mask exposures, the mask alignment accuracy must be as high as the molecular rotation period of the RM. The shorter the focal length of the PB lens, the shorter the molecular rotation period, making it more difficult to manufacture.

[0008] On the other hand, Patent Document 1 does not disclose any technology for achieving good optical characteristics, such as achieving good diffraction efficiency over a wider band or achieving a shorter focal length.

[0009] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide an optical element capable of achieving good optical characteristics. [Means for solving the problem]

[0010] (1) One embodiment of the present invention is an optical element comprising, in this order, a first alignment film, a first optically anisotropic layer containing first anisotropic molecules, a second alignment film, and a second optically anisotropic layer containing second anisotropic molecules.

[0011] (2) In addition to the configuration of (1) above, one embodiment of the present invention provides an optical element further comprising: a third alignment film provided on the side of the second optically anisotropic layer opposite the second alignment film; and a third optically anisotropic layer provided on the side of the third alignment film opposite the second optically anisotropic layer and containing third anisotropic molecules.

[0012] (3) Furthermore, in one embodiment of the present invention, in addition to the configuration of (2) above, the optical element is such that, when the azimuth angle of the slow axis of the first optically anisotropic layer is 0°, the azimuth angle of the slow axis of the second optically anisotropic layer is greater than 35° and less than 50°, and the azimuth angle of the slow axis of the third optically anisotropic layer is greater than −25° and less than 25°.

[0013] (4) Furthermore, in one embodiment of the present invention, in addition to the configuration of (3), the first optically anisotropic layer has a phase difference at a wavelength of 550 nm of 120 nm or more and 150 nm or less, the second optically anisotropic layer has a phase difference at a wavelength of 550 nm of 150 nm or more and 350 nm or less, and the third optically anisotropic layer has a phase difference at a wavelength of 550 nm of 120 nm or more and 150 nm or less.

[0014] (5) Furthermore, in one embodiment of the present invention, in addition to the configuration of (2) above, the optical element is such that, when the azimuth angle of the slow axis of the first optically anisotropic layer is 0°, the azimuth angle of the slow axis of the second optically anisotropic layer is greater than 35° and less than 50°, and the azimuth angle of the slow axis of the third optically anisotropic layer is greater than −5° and less than 5°.

[0015] (6) Furthermore, in one embodiment of the present invention, in addition to the configuration of (5), the first optically anisotropic layer has a phase difference at a wavelength of 550 nm of 120 nm or more and 150 nm or less, the second optically anisotropic layer has a phase difference at a wavelength of 550 nm of 210 nm or more and 290 nm or less, and the third optically anisotropic layer has a phase difference at a wavelength of 550 nm of 120 nm or more and 150 nm or less.

[0016] (7) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1) above, the optical element is arranged such that, in a planar view, the orientation direction of the first anisotropic molecule and the orientation direction of the second anisotropic molecule rotate in-plane from the center to the end of the optical element, and the rotation direction of the first anisotropic molecule is opposite to the rotation direction of the second anisotropic molecule.

[0017] (8) Furthermore, an embodiment of the present invention is an optical element that satisfies the following formula A in addition to the configuration of (7) above.

number

[0018] (9) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7) or (8), the first anisotropic molecules and the second anisotropic molecules each have a discrete molecular orientation pattern from the center to the edge of the optical element. Effect of the Invention

[0019] According to the present invention, it is possible to provide an optical element that can achieve good optical characteristics. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of an optical element according to a first embodiment. [Diagram 2] 3 is a schematic diagram showing a first exposure step in the method for producing the optical element of the first embodiment. FIG. [Diagram 3] 4 is a schematic diagram showing a second exposure step in the method for producing the optical element of the first embodiment. FIG. [Figure 4] 3A to 3C are schematic views showing the state after a first exposure step and a second exposure step in the method for producing an optical element according to the first embodiment. [Diagram 5] 3 is a plan view showing an example of a mask group used in manufacturing the optical element of the first embodiment. FIG. [Figure 6] FIG. 1 is a schematic plan view showing an example of a normal mask group. [Figure 7] FIG. 5 is a cross-sectional view illustrating an optical element according to a second embodiment. [Figure 8]FIG. 11 is a cross-sectional view illustrating an optical element according to a third embodiment. [Figure 9] FIG. 11 is a diagram showing the molecular orientation of anisotropic molecules on a microscope photograph of the first optically anisotropic layer and the second optically anisotropic layer included in the optical element of embodiment 3. [Figure 10] FIG. 13 is a schematic diagram illustrating a case where a PB lens is produced by multiple mask exposures. [Figure 11] FIG. 13 is a schematic diagram showing a specific example of producing a PB lens by multiple mask exposures. [Figure 12] 1A and 1B are diagrams illustrating a case where the molecular rotation directions of two PB lenses are the same. [Figure 13] 13 is a diagram for explaining a case where the directions of molecular rotation of two PB lenses are opposite to each other. FIG. [Figure 14] 13 is a graph showing a phase difference of the half-wave plate of Comparative Example 1. [Figure 15] 13 is a graph showing calculated values ​​of the diffraction efficiency of the half-wave plate of Comparative Example 1. [Figure 16] 10 is a schematic cross-sectional view illustrating an alignment film forming step included in the manufacturing process of the PB lens of Reference Example 1. FIG. [Figure 17] 10 is a schematic cross-sectional view illustrating an alignment film exposure step included in the manufacturing process of the PB lens of Reference Example 1. FIG. [Figure 18] 1 is a schematic diagram showing a mask used when irradiating polarized UV light having a polarization axis of 0° in an alignment film exposure step provided in the PB lens of Reference Example 1. FIG. [Figure 19] 1 is a schematic diagram showing a mask used when irradiating polarized UV light having a polarization axis of 45° in an alignment film exposure step provided in the PB lens of Reference Example 1. FIG. [Figure 20] 1 is a schematic diagram showing a mask used when irradiating polarized UV light having a polarization axis of 90° in an alignment film exposure step provided in the PB lens of Reference Example 1. FIG. [Figure 21] 1 is a schematic diagram showing a mask used when irradiating polarized UV having a polarization axis of 135° in an alignment film exposure step provided in the PB lens of Reference Example 1. FIG. [Figure 22]FIG. 2 is a cross-sectional view illustrating an optically anisotropic layer forming step included in the manufacturing process of the PB lens of Reference Example 1. [Diagram 23] 1 is a microscope photograph of the PB lens of Reference Example 1. [Figure 24] FIG. 4 is a schematic diagram showing a method for measuring a focal length. [Diagram 25] 1 is a microscope photograph of the PB lens of Reference Example 1, and a graph showing the relationship between molecular orientation and the distance from the lens center. [Figure 26] FIG. 13 is a schematic diagram showing a specific example of producing a PB lens by multiple mask exposures. [Figure 27] 1 is a graph showing the calculated diffraction efficiency of the PB lens of Comparative Example 1 and the measured diffraction efficiency of the PB lens of Reference Example 1. [Figure 28] 1 is a schematic cross-sectional view of an optical element according to a first embodiment. [Figure 29] 3 is a diagram showing, on a Poincare sphere, the polarization state of light after passing through a circular polarizing plate included in the optical element of Example 1. FIG. [Diagram 30] 4 is a diagram showing, on a Poincare sphere, the polarization state of light after transmitting through a first retardation plate included in the optical element of Example 1. FIG. [Diagram 31] 4 is a diagram showing, on a Poincare sphere, the polarization state of light after transmitting through a second retardation plate included in the optical element of Example 1. FIG. [Diagram 32] 4 is a diagram showing, on a Poincare sphere, the polarization state of light after transmitting through a third retardation plate included in the optical element of Example 1. FIG. [Diagram 33] FIG. 4 is a diagram showing formula 4 obtained from the optical element of Example 1. [Diagram 34] FIG. 5 is a diagram showing formula 5 obtained from the optical element of Example 1. [Diagram 35] FIG. 2 is a cross-sectional view showing a configuration in which the retardation between the first optically anisotropic layer and the third optically anisotropic layer is set to 150 nm in the optical element of Example 1. [Diagram 36] FIG. 13 is a diagram illustrating a method for calculating the diffraction efficiency. [Figure 37]11 is a graph showing S3(x) of transmitted light versus wavelength of incident light when circularly polarized light with S3=+1 is incident on the optical element of Example 1. [Figure 38] 11 is a graph showing the diffraction efficiency versus wavelength of incident light when circularly polarized light with S3=+1 is incident on the optical element of Example 1. [Figure 39] FIG. 11 is a schematic cross-sectional view of an optical element according to a second embodiment. [Diagram 40] FIG. 11 is a schematic cross-sectional view of an optical element according to a third embodiment. [Diagram 41] FIG. 11 is a schematic cross-sectional view of an optical element according to a fourth embodiment. [Diagram 42] FIG. 11 is a schematic cross-sectional view of an optical element according to a fifth embodiment. [Diagram 43] FIG. 13 is a schematic cross-sectional view of an optical element according to a sixth embodiment. [Diagram 44] 13 is a graph showing the relationship between the distance from the lens center and the molecular orientation of the optical element of Example 7. [Diagram 45] FIG. 1 is a cross-sectional schematic diagram showing a configuration of a general PB lens. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiment, and appropriate design changes can be made within the scope of the configuration of the present invention. In the following description, the same reference numerals are appropriately used in common between different drawings for the same parts or parts having similar functions, and repeated explanations thereof will be omitted as appropriate. Each aspect of the present invention may be appropriately combined within the scope of the gist of the present invention.

[0022] (Embodiment 1) Fig. 1 is a schematic cross-sectional view of an optical element of embodiment 1. As shown in Fig. 1, an optical element 10 of this embodiment includes a first alignment film 210, a first optically anisotropic layer 310 containing first anisotropic molecules 311, a second alignment film 220, and a second optically anisotropic layer 320 containing second anisotropic molecules 321, in this order. By adopting such an embodiment, it is possible to realize good optical characteristics. The anisotropic molecules are, for example, reactive mesogens (also referred to as RM).

[0023] The above-mentioned Patent Document 1 discloses a polarization diffraction grating in which a plurality of optically anisotropic layers containing RM are laminated. Specifically, it discloses that a second liquid crystal composition 13 (RM) is provided on a first liquid crystal composition 3 (RM), and the second liquid crystal composition 13 is aligned by the first liquid crystal composition 3. That is, the second liquid crystal composition 13 is aligned according to the alignment regulating force of the first liquid crystal composition 3. Therefore, the degree of freedom in design is low, and it is difficult to realize good optical characteristics.

[0024] On the other hand, the optical element 10 of the embodiment includes the second alignment film 220 between the first optically anisotropic layer 310 and the second optically anisotropic layer 320, so that the second anisotropic molecules 321 contained in the second optically anisotropic layer 320 can be aligned by the alignment regulating force of the second alignment film 220. As a result, it is possible to increase the degree of freedom in designing the optical element 10, and good optical characteristics can be achieved.

[0025] The optical element 10 of this embodiment includes a support substrate 100, a first alignment film 210, a first optically anisotropic layer 310, a second alignment film 220, and a second optically anisotropic layer 320, in this order. The optical element 10 of this embodiment is a Pancharatnam-Berry phase optical element (PBOE). A PBOE is also called a PB lens. A PB lens is a liquid crystal diffractive lens that provides a lens effect to incident circularly polarized light. The optical element of this embodiment will be described in detail below.

[0026] Examples of the support substrate 100 include a glass substrate, a plastic substrate, etc. Examples of materials for the glass substrate include glass such as float glass and soda glass. Examples of materials for the plastic substrate include plastics such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, and alicyclic polyolefin.

[0027] The first alignment film 210 has a function of controlling the alignment of the first anisotropic molecules 311 in the first optically anisotropic layer 310. The second alignment film 220 has a function of controlling the alignment of the second anisotropic molecules 321 in the second optically anisotropic layer 320. The first alignment film 210 and the second alignment film 220 are also simply referred to as alignment films 200. The first optically anisotropic layer 310 and the second optically anisotropic layer 320 are also simply referred to as optically anisotropic layer 300. The optically anisotropic layer 300 is also referred to as an RM layer. The first anisotropic molecules 311 and the second anisotropic molecules 321 are also simply referred to as anisotropic molecules 301.

[0028] The material of the alignment film 200 may be a material commonly used in the field of liquid crystal panels, such as a polymer having polyimide in the main chain, a polymer having polyamic acid in the main chain, or a polymer having polysiloxane in the main chain. The materials of the first alignment film 210 and the second alignment film 220 may be different from each other or the same.

[0029] The alignment film 200 can be formed by applying an alignment film material, and examples of the application method include flexographic printing, inkjet application, etc. The application methods of the alignment film material of the first alignment film 210 and the alignment film material of the second alignment film 220 may be different or the same.

[0030] The alignment film 200 is preferably a photo-aligned film. The photo-aligned film is obtained, for example, by forming an alignment film material containing a photo-alignable polymer having a photofunctional group on a substrate. The alignment film 200 is subjected to an alignment treatment. For example, the alignment film 200 containing a photo-alignable polymer is irradiated with polarized ultraviolet light (also called polarized UV, PUV) to generate anisotropy on the surface of the alignment film 200, thereby performing the alignment treatment. The structures of the photo-aligned polymers contained in the first alignment film 210 and the second alignment film 220 may be different from each other or the same.

[0031] Examples of the photo-alignable polymer include photo-alignable polymers having at least one photofunctional group selected from a cyclobutane group, an azobenzene group, a chalcone group, a cinnamate group, a coumarin group, a stilbene group, a phenol ester group, and a phenyl benzoate group. The photo-alignable polymer contained in the photo-alignment film may be one type or two or more types. The photofunctional group of the photo-alignable polymer may be present in the main chain of the polymer, may be present in the side chain of the polymer, or may be present in both the main chain and the side chain of the polymer.

[0032] Suitable examples of the photo-alignable polymer include photodegradable polymers, photorearrangement polymers (preferably photo-fries rearrangement polymers), photoisomerization polymers, photodimerization polymers, and photocrosslinking polymers. Any of these can be used alone, or two or more can be used in combination. Among them, from the viewpoint of alignment stability, photodegradable polymers having a reaction wavelength (main sensitivity wavelength) of around 254 nm and photorearrangement polymers having a reaction wavelength (main sensitivity wavelength) of around 254 nm are particularly preferred. Photoisomerization polymers and photodimerization polymers having a photofunctional group in the side chain are also preferred.

[0033] The main chain structure of the photoalignable polymer preferably contains at least one of a polyamic acid structure, a polyimide structure, a poly(meth)acrylic acid structure, a polysiloxane structure, a polyethylene structure, a polystyrene structure, and a polyvinyl structure.

[0034] The alignment film 200 may be a horizontal alignment film that aligns the anisotropic molecules 301 substantially horizontally to the film surface, or a vertical alignment film that aligns the anisotropic molecules 301 substantially vertically to the film surface. The horizontal alignment film has a function of aligning the anisotropic molecules 301 in the optically anisotropic layer 300 in a horizontal direction to the surface of the horizontal alignment film when no voltage is applied. Here, the anisotropic molecules being aligned in a horizontal direction to the surface of the horizontal alignment film means that the pretilt angle of the anisotropic molecules is 0 to 5°, preferably 0 to 2°, and more preferably 0 to 1°, to the surface of the horizontal alignment film. The vertical alignment film has a function of aligning the anisotropic molecules 301 in the optically anisotropic layer 300 in a vertical direction to the surface of the vertical alignment film when no voltage is applied. Here, the anisotropic molecules being aligned in a direction perpendicular to the surface of the vertical alignment film means that the pretilt angle of the anisotropic molecules is 86 to 90°, preferably 87 to 89°, and more preferably 87.5 to 89°, relative to the surface of the vertical alignment film. The pretilt angle of the anisotropic molecules means the angle at which the major axes of the liquid crystal molecules are inclined relative to the major surfaces of the substrates in the absence of applied voltage.

[0035] The first optically anisotropic layer 310 contains first anisotropic molecules 311, and the second optically anisotropic layer 320 contains second anisotropic molecules 321. The first anisotropic molecules 311 and the second anisotropic molecules 321 may be different from each other or may be the same.

[0036] For example, a cured product of a polymerizable liquid crystal material (also called "reactive mesogen") is preferably used as the optically anisotropic layer 300. In this case, at least one of the polymerized and unpolymerized polymerizable liquid crystal material corresponds to the anisotropic molecules 301. The polymerizable liquid crystal material is preferably a photopolymerizable liquid crystal material that is cured by irradiation with light.

[0037] The optically anisotropic layer 300 is formed, for example, by applying and curing a polymerizable liquid crystal material (reactive mesogen). As the polymerizable liquid crystal material, a liquid crystal polymer having a photoreactive group is used. As the polymerizable liquid crystal material, for example, a polymer having a side chain with a structure having a combination of a substituent (mesogen group) such as a biphenyl group, a terphenyl group, a naphthalene group, a phenylbenzoate group, an azobenzene group, or a derivative thereof, and a photoreactive group such as a cinnamoyl group, a chalcone group, a cinnamylidene group, a β-(2-phenyl)acryloyl group, a cinnamic acid group, or a derivative thereof, and having a structure such as acrylate, methacrylate, maleimide, N-phenylmaleimide, or siloxane in the main chain can be mentioned. Such a polymer may be a homopolymer consisting of a single repeating unit, or may be a copolymer consisting of two or more repeating units having different structures of the side chain. Such a copolymer includes any of an alternating type, a random type, and a craft type. In such a copolymer, the side chain of at least one repeating unit may be a side chain having a structure containing both a mesogenic group and a photoreactive group as described above, and the side chains of the other repeating units may not have such a mesogenic group or photoreactive group.

[0038] The polymerizable liquid crystal material may contain additives such as a photopolymerization initiator. The photopolymerization initiator is not particularly limited, and any conventionally known initiator may be used.

[0039] Examples of solvents used for coating the polymerizable liquid crystal material include toluene, ethylbenzene, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, dibutyl ether, acetone, methyl ethyl ketone, ethanol, propanol, cyclohexane, cyclopentanone, methylcyclohexane, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, methoxybutyl acetate, N-methylpyrrolidone, dimethylacetamide, etc. Any of these can be used alone, or two or more can be used in combination.

[0040] Next, a method for manufacturing the optical element 10 of this embodiment will be described.

[0041] The manufacturing method of the optical element 10 of this embodiment includes a first alignment film exposure step of exposing the first alignment film 210 to perform an alignment treatment, a first optically anisotropic layer formation step of disposing a first polymerizable liquid crystal material on the exposed first alignment film 210 and curing it to provide a first optically anisotropic layer 310, a second alignment film formation step of disposing a second alignment film 220 on the first optically anisotropic layer 310, a second alignment film exposure step of exposing the second alignment film 220 to perform an alignment treatment, and a second optically anisotropic layer formation step of disposing a second polymerizable liquid crystal material on the exposed second alignment film 220 and curing it to provide a second optically anisotropic layer 320. The first alignment film exposure step and the second alignment film exposure step are also simply referred to as alignment film exposure steps. The first optically anisotropic layer formation step and the second optically anisotropic layer formation step are also simply referred to as optically anisotropic layer formation steps.

[0042] The alignment film exposure process includes, in order, a first exposure process of exposing a first exposure region of the alignment film 200 with a first polarized light having a first polarization axis, and a second exposure process of exposing a second exposure region of the alignment film 200, which overlaps only a portion of the first exposure region, with a second polarized light having a second polarization axis that is at a different angle from the first polarization axis.

[0043] By adopting such an embodiment, it is possible to expose only the first polarized light to the portion of the first exposure area that does not overlap with the second exposure area, to expose only the second polarized light to the portion of the second exposure area that does not overlap with the first exposure area, and to expose the first polarized light and the second polarized light in a superimposed manner to the portion of the first exposure area that overlaps with the second exposure area.

[0044] As shown in Figs. 2 to 4, in the overlapping exposed region, the molecular orientation is determined by the average of the two exposures. Therefore, it is possible to make the orientation direction of the alignment film 200 different between the part of the first exposed region that does not overlap with the second exposed region, the part of the second exposed region that does not overlap with the first exposed region, and the part of the first exposed region that overlaps with the second exposed region. That is, it is possible to impart three kinds of alignment directions to the alignment film 200 by performing two exposures. As a result, it is possible to increase the arrangement pattern of the anisotropic molecules 301 with a smaller number of exposures, and it is possible to more easily manufacture the optical element 10 having high diffraction efficiency. For example, it is possible to manufacture the optical element 10 having high diffraction efficiency without increasing the number of masks. Fig. 2 is a schematic diagram showing the first exposure step in the manufacturing method of the optical element of the first embodiment. Fig. 3 is a schematic diagram showing the second exposure step in the manufacturing method of the optical element of the first embodiment. Fig. 4 is a schematic diagram showing the first exposure step and the second exposure step in the manufacturing method of the optical element of the first embodiment.

[0045] 2 to 4, a portion of the first exposed region that does not overlap with the second exposed region corresponds to the first region 301, a portion of the second exposed region that does not overlap with the first exposed region corresponds to the third region 303, and a portion of the first exposed region that overlaps with the second exposed region, i.e., an overlapping exposed region corresponds to the second region 302. In the first region 301 and the third region 303, the anisotropic molecules 301 are not twistedly aligned along the film thickness direction of the optically anisotropic layer 300, while in the second region 302, the anisotropic molecules 301 are twistedly aligned along the film thickness direction of the optically anisotropic layer 300.

[0046] The manufacturing method of the optical element 10 of this embodiment may include a first alignment film formation step of forming the first alignment film 210 by applying an alignment film material containing a photo-alignable polymer having a photofunctional group onto the support substrate 100 before the first alignment film exposure step. In the first alignment film formation step, a coating device such as a slit coater or a spin coater can be suitably used for applying the alignment film material. After applying the alignment film material to a uniform thickness, the alignment film material may be pre-baked at a temperature of about 70 to 100° C. for 1 to 10 minutes.

[0047] The second alignment film forming process is the same as the first alignment film forming process. The various set conditions in the first alignment film forming process and the various set conditions in the second alignment film forming process may be different or the same. The first alignment film forming process and the second alignment film forming process are also simply referred to as alignment film forming processes.

[0048] The alignment film exposure step of this embodiment can be performed by mask exposure. That is, in this embodiment, the alignment direction can be patterned by mask exposure. On the other hand, in the above Patent Document 1, the alignment direction is patterned by a polarization hologram, and the method of forming the optically anisotropic layer is different from that of this embodiment.

[0049] The alignment film exposure step is a step of exposing and aligning the alignment film 200. The alignment film exposure step is performed, for example, by using an exposure device that irradiates light (ultraviolet rays) with a wavelength of 313 to 365 nm.

[0050] The alignment film exposure process includes, in order, a first exposure process in which a first exposure area of ​​the alignment film 200 is exposed with a first polarized light having a first polarization axis, and a second exposure process in which a second exposure area of ​​the alignment film 200, which overlaps only a portion of the first exposure area, is exposed with a second polarized light having a second polarization axis that is at a different angle from the first polarization axis.

[0051] It is preferable that a part of the first exposed region overlaps with the second exposed region, and another part of the first exposed region does not overlap with the second exposed region, and a part of the second exposed region overlaps with the first exposed region, and another part of the second exposed region does not overlap with the first exposed region. By adopting such an embodiment, it is possible to increase the arrangement pattern of the anisotropic molecules 301 more effectively with a smaller number of exposures, and it is possible to more easily manufacture the optical element 10 having high diffraction efficiency.

[0052] The angle of the second polarization axis is preferably 10° to 60° larger than the angle of the first polarization axis, more preferably 20° to 50° larger, and even more preferably 30° to 45° larger. By adopting such an embodiment, it becomes possible to change the arrangement pattern of the anisotropic molecules 301 more continuously, and an optical element 10 having higher diffraction efficiency can be manufactured. In this specification, the axis angle is defined as a positive angle in the counterclockwise direction.

[0053] The alignment film exposure step may include the first exposure step and the second exposure step to the Mth exposure step in that order. The first exposure step to the Mth exposure step are steps of exposing the first exposure area to the Mth exposure area of ​​the alignment film 200 with the first polarized light to the Mth polarized light having the first polarization axis to the Mth polarization axis, respectively. The angles of the first polarization axis to the Mth polarization axis are different from each other. Among the first exposure region to the Mth exposure region, a portion of the rth exposure region overlaps with the (r-1)th exposure region, and another portion of the rth exposure region does not overlap with the (r-1)th exposure region; among the first exposure region to the Mth exposure region, a portion of the (r-1)th exposure region overlaps with the rth exposure region, and another portion of the (r-1)th exposure region does not overlap with the rth exposure region; and the rth exposure region does not overlap with the first exposure region to the (r-2)th exposure region. Here, M is an integer of 3 or more. r is an integer of 3 or more and M or less. By adopting such an embodiment, it is possible to easily increase the arrangement pattern of the anisotropic molecules 301, and it is possible to more easily manufacture the optical element 10 having high diffraction efficiency.

[0054] M is an integer of 3 or more, and preferably an integer of 4 or more. M is preferably an integer of 7 or less, and more preferably an integer of 6 or less. M is preferably an integer of 3 or more and 7 or less, and more preferably an integer of 4 or more and 6 or less.

[0055] The angle of the rth polarization axis is preferably 10° to 60° larger than the angle of the (r-1)th polarization axis, more preferably 20° to 50° larger, and even more preferably 30° to 45° larger. By adopting such an embodiment, it becomes possible to change the arrangement pattern of the anisotropic molecules 301 more continuously, and an optical element 10 having higher diffraction efficiency can be manufactured.

[0056] Specifically, when M is 3, the exposure step further includes a third exposure step after the second exposure step. The third exposure step is a step of exposing a third exposure region of the alignment film 200 to a third polarized light having a third polarization axis. The angles of the first polarization axis to the third polarization axis are different from each other. A part of the third exposure region overlaps with the second exposure region, and another part of the third exposure region does not overlap with the second exposure region, a part of the second exposure region overlaps with the third exposure region, and another part of the second exposure region does not overlap with the third exposure region, and the third exposure region does not overlap with the first exposure region.

[0057] The angle of the third polarization axis is preferably 10° to 60° larger than the angle of the second polarization axis, more preferably 20° to 50° larger, and even more preferably 30° to 45° larger. By adopting such an embodiment, it becomes possible to change the arrangement pattern of the anisotropic molecules 301 more continuously, and an optical element 10 having higher diffraction efficiency can be manufactured.

[0058] When M is 4, the exposure step may further include a third exposure step and a fourth exposure step after the second exposure step. The third exposure step and the fourth exposure step are steps of exposing the third exposure region and the fourth exposure region of the alignment film 200 to third polarized light and fourth polarized light having a third polarization axis and a fourth polarization axis, respectively. The angles of the first polarization axis to the fourth polarization axis are different from each other. A part of the third exposure region overlaps with the second exposure region, and another part of the third exposure region does not overlap with the second exposure region, a part of the second exposure region overlaps with the third exposure region, and another part of the second exposure region does not overlap with the third exposure region, and the third exposure region does not overlap with the first exposure region. A portion of the fourth exposure area overlaps with the third exposure area and another portion of the fourth exposure area does not overlap with the third exposure area, a portion of the third exposure area overlaps with the fourth exposure area and another portion of the third exposure area does not overlap with the fourth exposure area, and the fourth exposure area does not overlap with the first exposure area and the second exposure area.

[0059] The angle of the fourth polarization axis is preferably 10° to 60° larger than the angle of the third polarization axis, more preferably 20° to 50° larger, and even more preferably 30° to 45° larger. By adopting such an embodiment, it becomes possible to change the arrangement pattern of the anisotropic molecules 301 more continuously, and an optical element 10 having higher diffraction efficiency can be manufactured.

[0060] The various set conditions in the first alignment film exposure step and the various set conditions in the second alignment film exposure step may be different from each other or the same.

[0061] The optically anisotropic layer forming step is a step of disposing and curing a polymerizable liquid crystal material on the alignment film 200 after exposure. In the optically anisotropic layer forming step, the polymerizable liquid crystal material is disposed on the alignment film 200 by, for example, coating. A coating device such as a slit coater or a spin coater can be suitably used for coating. The polymerizable liquid crystal material is cured, for example, by using an exposure device that irradiates light (ultraviolet rays) with a wavelength of 313 to 365 nm.

[0062] The various conditions set in the step of forming the first optically anisotropic layer and the various conditions set in the step of forming the second optically anisotropic layer may be different from each other or the same.

[0063] 5 is a plan view schematic diagram showing an example of a mask group used in manufacturing the optical element of the first embodiment. The optical element 10 of the present embodiment can be manufactured using the mask group 20 shown in FIG. 5. The mask group 20 has a first mask 201 provided with a first light-transmitting portion (opening) 20A1 and a first light-shielding portion 20B1, and a second mask 202 provided with a second light-transmitting portion 20A2 and a second light-shielding portion 20B2. When the first mask 201 and the second mask 202 are overlapped so that the center of the first mask 201 and the center of the second mask 202 overlap, the first light-transmitting portion 20A1 overlaps with a part of the second light-transmitting portion 20A2 and a part of the second light-shielding portion 20B2, and the second light-transmitting portion 20A2 overlaps with a part of the first light-transmitting portion 20A1 and a part of the first light-shielding portion 20B1. By adopting such an embodiment, the optical element 10 can be produced by using the first mask 201 in the first exposure step and the second mask 202 in the second exposure step in the above manufacturing process.

[0064] In this way, the mask group 20 used in manufacturing the optical element 10 of this embodiment has a plurality of annular masks in which light-transmitting portions and light-shielding portions are repeated, and is designed so that the plurality of annular masks alternately form areas on the alignment film 200 where multiple types of polarized UV with different polarization axes are irradiated in an overlapping manner, and areas where one type of polarized UV is irradiated without overlapping with other polarized UV with different polarization axes.

[0065] On the other hand, when exposure is performed using a plurality of masks, a mask group 20R shown in FIG. 6 is usually used. FIG. 6 is a schematic plan view showing an example of a normal mask group. As shown in FIG. 6, the normal mask group 20R includes a first mask 20R1 having a light-transmitting portion 20RA1 and a light-shielding portion 20RB1, a second mask 20R2 having a light-transmitting portion 20RA2 and a light-shielding portion 20RB2, a third mask 20R3 having a light-transmitting portion 20RA3 and a light-shielding portion 20RB3, and a fourth mask 20R4 having a light-transmitting portion 20RA4 and a light-shielding portion 20RB4. When the first mask 20R1 to the fourth mask 20R4 are overlapped so that the centers of the first mask 20R1 to the fourth mask 20R4 overlap, the light-transmitting portions of each mask do not overlap.

[0066] As described above, the optical element 10 of this embodiment can be fabricated by exposing the alignment film 200 containing a photo-alignable polymer to a plurality of predetermined patterns and performing photopatterning to pattern a desired pattern by superposing the patterns. The first light-transmitting portion 20A1, the first light-shielding portion 20B1, the second light-transmitting portion 20A2, and the second light-shielding portion 20B2 are each a concentric pattern having a predetermined width, and the first mask 201 and the second mask 202 have different patterns formed thereon.

[0067] As shown in FIG. 5, the mask group 20 includes a first mask 201, a second mask 202 to an M-th mask 203, and a second mask 204. M The first mask 201 to the Mth mask 20 M Among them, the rth mask 20 r The rth light transmitting portion 20A r and the rth light-shielding portion 20B r The (r-1)th mask 20 r-1 The (r-1)th light transmitting portion 20A r-1 and (r-1) light-shielding portion 20B r-1 The (r-2)th mask 20 r-2 The (r-2)th light transmitting portion 20A r-2 and (r-2) light-shielding portion 20B r-2 The mask number 20 is provided. rThe center of the mask and the (r-1) mask 20 r―1 When the center of the (r-1)th light-transmitting portion 20A is overlapped with the center of the (r-2)th light-transmitting portion 20A, r-1 represents the rth light-transmitting portion 20A. r and the rth light-shielding portion 20B r rth light transmitting portion 20A r The (r-1)th light-transmitting portion 20A r-1 and (r-1) light-shielding portion 20B r-1 and overlaps with a part of the (r-2)-th light-transmitting portion 20A. r-2 Here, M is an integer of 3 or more. r is an integer of 3 or more and M or less. By adopting such an embodiment, it is possible to easily increase the arrangement pattern of the anisotropic molecules 301, and it is possible to more easily manufacture the optical element 10 having high diffraction efficiency.

[0068] Specifically, when M is 3, the mask group 20 further includes a third mask 203 in addition to the first mask 201 and the second mask 202. The third mask 203 is provided with a third light-transmitting portion 20A3 and a third light-shielding portion 20B3. When the center of the third mask 203 and the center of the second mask 202 are overlapped, the second light-transmitting portion 20A2 overlaps with a part of the third light-transmitting portion 20A3 and the third light-shielding portion 20B3, and the third light-transmitting portion 20A3 overlaps with a part of the second light-transmitting portion 20A2 and the second light-shielding portion 20B2, but does not overlap with the first light-transmitting portion 20A1. By adopting such an embodiment, the optical element 10 can be manufactured using the third mask 203 in the third exposure step in the above manufacturing process.

[0069] Specifically, when M is 4, mask group 20 further includes third mask 203 and fourth mask 204 in addition to first mask 201 and second mask 202. Fourth mask 204 is provided with fourth light transmitting portion 20A4 and fourth light shielding portion 20B4. When the center of fourth mask 204 and the center of third mask 203 are overlapped, third light transmitting portion 20A3 overlaps with parts of fourth light transmitting portion 20A4 and fourth light shielding portion 20B4, and fourth light transmitting portion 20A4 overlaps with parts of third light transmitting portion 20A3 and third light shielding portion 20B3, but does not overlap with first light transmitting portion 20A1 and second light transmitting portion 20A2. By adopting such an embodiment, the optical element 10 can be produced by using the third mask 203 in the third exposure step and the fourth mask 204 in the fourth exposure step in the above manufacturing process.

[0070] Each mask in the mask group 20 is provided with a concentric light-transmitting portion and a light-shielding portion. The light-transmitting portion is a portion that transmits light and has a transmittance of, for example, 80% or more and 100% or less. The light-shielding portion is a portion that does not transmit light and has a transmittance of, for example, 0% or more and 10% or less.

[0071] (Embodiment 2) In this embodiment, the characteristics unique to this embodiment will be mainly described, and the description of the contents overlapping with the above-mentioned embodiment 1 will be omitted. The optical element of this embodiment further includes a third alignment film and a third optically anisotropic layer in addition to the configuration of the above-mentioned embodiment 1.

[0072] Fig. 7 is a schematic cross-sectional view of an optical element of embodiment 2. As shown in Fig. 7, the optical element 10 of this embodiment further includes, in addition to the configuration of embodiment 1, a third alignment film 230 provided on the second optically anisotropic layer 320 opposite the second alignment film 220, and a third optically anisotropic layer 330 provided on the third alignment film 230 opposite the second optically anisotropic layer 320 and containing third anisotropic molecules 331. By adopting such an embodiment, more optically anisotropic layers are arranged than in embodiment 1, so that the degree of freedom in design is increased and even better optical characteristics can be realized.

[0073] The third alignment film 230 is similar to the alignment film 200. The first alignment film 210, the second alignment film 220, and the third alignment film 230 may be different from each other, or at least two of them may be the same.

[0074] The third optically anisotropic layer 330 is similar to the optically anisotropic layer 300. The first optically anisotropic layer 310, the second optically anisotropic layer 320, and the third optically anisotropic layer 330 may be different from each other, or at least two of them may be the same.

[0075] The third anisotropic molecule 331 is similar to the anisotropic molecule 301. The first anisotropic molecule 311, the second anisotropic molecule 321, and the third anisotropic molecule 331 may be different from each other, or at least two of them may be the same.

[0076] When the azimuth angle of the slow axis of the first optically anisotropic layer 310 is 0°, it is preferable that the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the azimuth angle of the slow axis of the third optically anisotropic layer 330 is more than −25° and less than 25°. By adopting such an embodiment, high diffraction efficiency can be realized in a wide visible light region of 450 nm to 650 nm.

[0077] The azimuth refers to the direction when the target direction is projected onto the optical element, and is expressed as the angle (azimuth angle) between the target direction and the reference direction. Here, the reference direction (0°) is set to the slow axis of the first optically anisotropic layer. The azimuth angle is positive when it is counterclockwise from the reference direction, and negative when it is clockwise from the reference direction. Both counterclockwise and clockwise indicate the rotation direction when the optical element is viewed from the observation surface side (front). The angle indicates a value measured when the optical element is viewed in a planar state.

[0078] When the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the azimuth angle of the slow axis of the third optically anisotropic layer 330 is more than -25° and less than 25°, it is preferable that the phase difference of the first optically anisotropic layer 310 at a wavelength of 550 nm is 120 nm or more and 150 nm or less, the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is 150 nm or more and 350 nm or less, and the phase difference of the third optically anisotropic layer 330 at a wavelength of 550 nm is 120 nm or more and 150 nm or less. By adopting such an embodiment, higher diffraction efficiency can be realized in a wide visible light region of 450 nm to 650 nm.

[0079] Here, the retardation (Re) refers to the in-plane retardation of a layer (film) at 23° C. and at a wavelength of 550 nm unless otherwise specified. Re is calculated by Re=(nx-ny)×d, where d (nm) is the thickness of the layer (film). In this specification, unless otherwise specified, "retardation" refers to the in-plane retardation.

[0080] "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane, and "nz" is the refractive index in the thickness direction. Unless otherwise specified, the refractive index refers to the value at 23°C and for light with a wavelength of 550 nm.

[0081] When the azimuth angle of the slow axis of the first optically anisotropic layer 310 is 0°, it is preferable that the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the azimuth angle of the slow axis of the third optically anisotropic layer 330 is more than -5° and less than 5°. By adopting such an embodiment, higher diffraction efficiency can be realized in a wide visible light region of 450 nm to 650 nm.

[0082] When the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the azimuth angle of the slow axis of the third optically anisotropic layer 330 is more than -5° and less than 5°, it is preferable that the phase difference of the first optically anisotropic layer 310 at a wavelength of 550 nm is 120 nm or more and 150 nm or less, the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is 210 nm or more and 290 nm or less, and the phase difference of the third optically anisotropic layer 330 at a wavelength of 550 nm is 120 nm or more and 150 nm or less. By adopting such an embodiment, it is possible to realize even higher diffraction efficiency in a wide visible light region of 450 nm to 650 nm.

[0083] For example, the first optically anisotropic layer 310 has a slow axis with an azimuth angle of 0° and a phase difference of λ / 4, the second optically anisotropic layer 320 has a slow axis with an azimuth angle of 45° and a phase difference of λ / 2, and the third optically anisotropic layer 330 has a slow axis with an azimuth angle of 0° and a phase difference of λ / 4.

[0084] The optical element 10 of this embodiment is a PB lens that can achieve high diffraction efficiency in a wide visible light region of wavelengths from 450 nm to 650 nm. For example, in the optical element 10 of this embodiment, broadbanding can be achieved with three sheets of λ / 4, λ / 2, and λ / 4. The optical element 10 is a wideband half-wave plate that converts circularly polarized light to circularly polarized light. The half-wave plate in the PB lens does not need to be a single RM layer (A-plate) as long as it is a half-wave plate that converts right-handed circularly polarized light to left-handed circularly polarized light or left-handed circularly polarized light to right-handed circularly polarized light. In this embodiment, the wideband half-wave plate as described above can be realized by stacking three positive dispersion RM layers via an alignment film.

[0085] On the other hand, in the above-mentioned Patent Document 1, the band is broadened by two λ / 2 plates. The polarization diffraction grating in the above-mentioned Patent Document 1 is a broadband half-wave plate that converts linearly polarized light into linearly polarized light.

[0086] Here, the λ / 4 plate provides a phase difference of 100 nm or more and 176 nm or less to light with a wavelength of 550 nm, and is preferably a phase difference plate that provides a phase difference of 1 / 4 wavelength (strictly speaking, 137.5 nm) to light with a wavelength of 550 nm. The λ / 2 plate provides a phase difference of 238 nm or more and 313 nm or less to light with a wavelength of 550 nm, and is preferably a phase difference plate that provides a phase difference of 1 / 2 wavelength (strictly speaking, 275 nm) to light with a wavelength of 550 nm. Incidentally, light with a wavelength of 550 nm is the light with the highest human visual sensitivity.

[0087] The method for manufacturing the optical element 10 of this embodiment includes a first alignment film exposure step of exposing the first alignment film 210 to perform an alignment treatment, a first optically anisotropic layer formation step of disposing a first polymerizable liquid crystal material on the exposed first alignment film 210 and curing it to provide a first optically anisotropic layer 310, a second alignment film formation step of providing a second alignment film 220 on the first optically anisotropic layer 310, a second alignment film exposure step of exposing the second alignment film 220 to perform an alignment treatment, and a second alignment film exposure step of exposing the second alignment film 220 to perform an alignment treatment. The method includes a second optically anisotropic layer formation process of disposing a second polymerizable liquid crystal material on the film 220 and curing it to provide a second optically anisotropic layer 320, a third alignment film formation process of disposing a third alignment film 230 on the second optically anisotropic layer 320, a third alignment film exposure process of exposing the third alignment film 230 to perform an alignment treatment, and a third optically anisotropic layer formation process of disposing a third polymerizable liquid crystal material on the exposed third alignment film 230 and curing it to provide a third optically anisotropic layer 330.

[0088] The third alignment film forming process is the same as the above alignment film forming process. At least two of the various setting conditions in the first alignment film forming process, the various setting conditions in the second alignment film forming process, and the various setting conditions in the third alignment film forming process may be different from each other, or all of them may be the same.

[0089] The third alignment film exposure process is the same as the above alignment film exposure process. At least two of the various setting conditions in the first alignment film exposure process, the various setting conditions in the second alignment film exposure process, and the various setting conditions in the third alignment film exposure process may be different from each other, or all of them may be the same.

[0090] The third optically anisotropic layer forming step is the same as the above optically anisotropic layer forming step. At least two of the various setting conditions in the first optically anisotropic layer forming step, the various setting conditions in the second optically anisotropic layer forming step, and the various setting conditions in the third optically anisotropic layer forming step may be different from each other, or all of them may be the same.

[0091] (Embodiment 3) In this embodiment, the characteristics unique to this embodiment will be mainly described, and the description of the contents overlapping with the above-mentioned embodiment 1 will be omitted. In the optical element 10 of this embodiment, the rotation direction of the first anisotropic molecule 311 of the optical element 10 of the above-mentioned embodiment 1 is opposite to the rotation direction of the second anisotropic molecule 321.

[0092] Fig. 8 is a cross-sectional schematic diagram of the optical element of embodiment 3. Fig. 9 is a diagram showing the molecular orientation of anisotropic molecules on a microscope photograph of the first optically anisotropic layer and the second optically anisotropic layer included in the optical element of embodiment 3. As shown in Figs. 8 and 9, in a plan view, the orientation direction of the first anisotropic molecule 311 and the orientation direction of the second anisotropic molecule 321 of this embodiment are arranged to rotate in-plane from the center to the end of the optical element 10, and the rotation direction of the first anisotropic molecule 311 is opposite to the rotation direction of the second anisotropic molecule 321.

[0093] Here, as shown in Fig. 10, when a PB lens is produced by multiple mask exposures, alignment accuracy is important. For example, as shown in Fig. 11, when producing a lens with a focal length of 50 cm and a diameter of 5 cm, alignment accuracy on the order of several μm is required. Fig. 10 is a schematic diagram explaining the case where a PB lens is produced by multiple mask exposures. Fig. 11 is a schematic diagram showing a specific example of the case where a PB lens is produced by multiple mask exposures.

[0094] In this way, the shorter the focal length of the PB lens is, or the larger the lens diameter is, the finer the required alignment accuracy becomes, making manufacturing more difficult.

[0095] On the other hand, in this embodiment, the orientation direction of the first anisotropic molecule 311 and the orientation direction of the second anisotropic molecule 321 are arranged to rotate in the plane from the center to the end of the optical element 10 in a plan view, and the rotation direction of the first anisotropic molecule 311 is opposite to the rotation direction of the second anisotropic molecule 321. By adopting such an embodiment, it is possible to obtain a structure in which a plurality of PB lenses are stacked. When a plurality of PB lenses are stacked, the refractive power becomes the sum of the two PB lenses, so that a short focal length lens can be realized with a lens having a long period of molecular rotation. As a result, a short focal length lens can be manufactured more easily. In this way, in this embodiment, the required alignment accuracy can be relaxed, and the manufacture of the PB lens can be facilitated.

[0096] Also, as shown in FIG. 9, the sign of the focal length of the PB lens depends not only on the rotation direction of the incident circularly polarized light but also on the rotation direction of the molecules. Therefore, in order to increase the refractive power by stacking two PB lenses, the rotation direction of the molecules must be opposite in the first layer and the second layer, as shown in FIG. 12 and FIG. 13. FIG. 12 is a diagram for explaining a case where the molecular rotation directions of the two PB lenses are the same. FIG. 13 is a diagram for explaining a case where the molecular rotation directions of the two PB lenses are opposite.

[0097] That is, as shown in Fig. 12, when the molecular rotation directions of the two PB lenses are the same, the refractive power of the first optically anisotropic layer 310 is +1 / f, the refractive power of the second optically anisotropic layer 320 is -1 / f, and the refractive power after lamination is (+1 / f) + (-1 / f) = 0. On the other hand, as shown in Fig. 13, when the molecular rotation directions of the two PB lenses are opposite, the refractive power of the first optically anisotropic layer 310 is +1 / f, and the refractive power of the second optically anisotropic layer 320 is also +1 / f, so the refractive power after lamination is (+1 / f) + (+1 / f) = +2 / f.

[0098] In the optical element 10 of this embodiment, the first anisotropic molecules 311 are oriented by the first alignment film 210, and the second anisotropic molecules 321 are oriented by the second alignment film 220, so that the in-plane patterns of the orientation directions of the first anisotropic molecules 311 and the second anisotropic molecules 321 can be made to be opposite to each other, thereby increasing the refractive power.

[0099] On the other hand, the polarization diffraction grating of Patent Document 1 has a configuration in which PB lenses are stacked, but the in-plane pattern of the molecular orientation of the two PB lenses is the same, and the configuration is different from that of this embodiment.

[0100] For example, the first optically anisotropic layer 310 has a retardation of λ / 2, and the second optically anisotropic layer 320 has a retardation of λ / 2.

[0101] The optical element 10 of the present embodiment preferably satisfies the following formula A. By adopting such an embodiment, an optical element with a short focal length can be realized even if the period of 180° rotation of the molecules is long.

[0102]

number

[0103] (The molecular orientation in the above formula A represents the azimuthal angle of the molecular orientation of the first anisotropic molecule and the second anisotropic molecule, the wavelength represents the wavelength of the incident light, the focal length represents the focal length of the optical element, and the distance from the lens center represents the distance of the first anisotropic molecule and the second anisotropic molecule from the lens center.) EXAMPLES

[0104] The effects of the present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0105] Comparative Example 1 In Comparative Example 1, a half-wave plate was produced using an RM having positive dispersion, and the phase difference was measured. Here, positive dispersion refers to the wavelength dependency of the phase difference such that the phase difference measured at a long wavelength is smaller than the phase difference measured at a short wavelength.

[0106] The procedure for producing the half-wave plate of Comparative Example 1 is as follows. First, a photo-alignment film containing a photoisomerizable polymer is applied onto a glass substrate, and then a 100 mJ / cm 2 beam is applied. 2 The film was irradiated with polarized UV (365 nm). After irradiation with polarized UV, it was baked in an oven at 160°C for 20 minutes, and then RM was applied. RM was applied using a spin coater rotating at 1000 rpm. The film thickness was adjusted so that the retardation (phase difference) at a wavelength of 550 nm was approximately 270 nm.

[0107] The wavelength dispersion of the RM layer (optically anisotropic layer) was positive, with Re(450nm) / Re(550nm)≒1.04 and Re(650nm) / Re(550nm)≒0.97. After coating the RM, it was cured with 200mJ (365nm) of unpolarized UV to obtain a half-wave plate of Comparative Example 1. The phase difference is also called retardation or Re.

[0108] <Measurement of phase difference> The retardation of the half-wave plate of Comparative Example 1 was measured by Axoscan. The measurement wavelength was set to 400 nm to 700 nm. The results are shown in Fig. 14. Fig. 14 is a graph showing the retardation of the half-wave plate of Comparative Example 1.

[0109] <Calculation of diffraction efficiency> The diffraction efficiency was calculated when a PB lens was manufactured using the half-wave plate (phase difference plate) of Comparative Example 1. The results are shown in FIG. 15. FIG. 15 is a graph showing the calculated values ​​of the diffraction efficiency of the half-wave plate of Comparative Example 1. Here, if the retardation of the phase difference plate is Δnd, the value of the diffraction efficiency is calculated as "sin(Δnd / λ×π) 2 " is proportional to

[0110] (Reference example 1) FIG. 16 is a cross-sectional schematic diagram for explaining an alignment film forming step included in the manufacturing process of the PB lens of Reference Example 1. FIG. 17 is a cross-sectional schematic diagram for explaining an alignment film exposure step included in the manufacturing process of the PB lens of Reference Example 1. FIG. 18 is a schematic diagram showing a mask used when irradiating polarized UV having a polarization axis of 0° in the alignment film exposure step included in the PB lens of Reference Example 1. FIG. 19 is a schematic diagram showing a mask used when irradiating polarized UV having a polarization axis of 45° in the alignment film exposure step included in the PB lens of Reference Example 1. FIG. 20 is a schematic diagram showing a mask used when irradiating polarized UV having a polarization axis of 90° in the alignment film exposure step included in the PB lens of Reference Example 1. FIG. 21 is a schematic diagram showing a mask used when irradiating polarized UV having a polarization axis of 135° in the alignment film exposure step included in the PB lens of Reference Example 1. FIG. 22 is a cross-sectional schematic diagram for explaining an optically anisotropic layer forming step included in the manufacturing process of the PB lens of Reference Example 1. FIG. 23 is a microscopic photograph of the PB lens of Reference Example 1.

[0111] In Reference Example 1, a PB lens was produced using the RM having positive dispersion used in Comparative Example 1. The procedure for producing the PB lens of Reference Example 1 is as follows. First, as shown in Fig. 16, a photo-alignment film (alignment film 200) containing a photoisomerizable polymer was applied onto a glass substrate (support substrate 100) (alignment film formation process).

[0112] Then, as shown in FIG. 17, the alignment film 200 is irradiated with 100 mJ / cm 2The alignment film was exposed to polarized UV light of (365 nm) (alignment film exposure process). The alignment film exposure process included a first exposure process, a second exposure process, a third exposure process, and a fourth exposure process. In the first exposure process, a circular mask (first mask 201) shown in FIG. 18 in which a first light-transmitting portion (opening) 20A1 and a first light-shielding portion 20B1 were repeated was used, and the first polarization axis was set to 0°. In the second exposure process, a circular mask (second mask 202) shown in FIG. 19 in which a second light-transmitting portion (opening) 20A2 and a second light-shielding portion 20B2 were repeated was used, and the second polarization axis was set to 45°. In the third exposure step, a circular mask (third mask 203) shown in Fig. 20 in which third light transmitting portion (opening) 20A3 and third light blocking portion 20B3 are repeated was used, and the third polarization axis was set to 90°. In the fourth exposure step, a circular mask (fourth mask 204) shown in Fig. 21 in which fourth light transmitting portion (opening) 20A4 and fourth light blocking portion 20B4 are repeated was used, and the fourth polarization axis was set to 135°.

[0113] After irradiation with polarized UV, the film was baked in an oven at 160° C. for 20 minutes, and then RM was applied as shown in FIG. 22. RM was applied using a spin coater rotating at 1000 rpm. RM was applied with a thickness adjusted so that the phase difference for light with a wavelength of 550 nm was about 270 nm. In other words, RM was applied so that the phase difference of the optically anisotropic layer 300 was λ / 2.

[0114] The wavelength dispersion of the RM layer was positive, with Re(450 nm) / Re(550 nm) ≈ 1.04 and Re(650 nm) / Re(550 nm) ≈ 0.97. After coating the RM, it was cured with 200 mJ (365 nm) of unpolarized UV (optically anisotropic layer forming step) to obtain the PB lens of Reference Example 1.

[0115] The PB lens of Reference Example 1 was observed under a polarizing microscope. The results are shown in Figure 23. It was confirmed from Figure 23 that the RMs were normally aligned in the PB lens of Reference Example 1.

[0116] <Focal length measurement> Fig. 24 is a schematic diagram showing a method for measuring the focal length. As shown in Fig. 24, a 532 nm laser beam was applied to the outer periphery of the PB lens of Reference Example 1, and the focal length was measured with a ruler. The laser beam first passes through a circular polarizing plate, becomes circularly polarized light, and is emitted. After that, the main light of the light that passes through the outer periphery of the PB lens travels toward the focal length.

[0117] <Measurement results> The focal length of the PB lens of Reference Example 1 was measured to be 50 cm. Here, the focal length of the PB lens is related to the period of the molecular orientation pattern. The following (Equation 1) holds between the focal length and the molecular orientation.

[0118]

number

[0119] Fig. 25 is a microscope photograph of the PB lens of Reference Example 1, and a graph showing the relationship between molecular orientation and the distance from the lens center. The graph in Fig. 25 relates to the portion indicated by the dashed line in the microscope photograph.

[0120] The relationship between the molecular orientation of the PB lens of Reference Example 1 and the distance from the lens center is as shown in Fig. 25. The equation of the envelope curve of the graph (parabola) shown in Fig. 25 is expressed by the following (Equation 2).

[0121]

number

[0122] Comparing the proportionality coefficients of the above (Equation 1) and (Equation 2), it was found that the focal length is 50 cm when the wavelength is 532 nm. To shorten the focal length, the proportionality coefficient needs to be further increased. This means that the period in which the anisotropic molecules rotate 180° becomes shorter. If the period becomes shorter, manufacturing problems may occur. When a PB lens is manufactured by multiple mask exposures, the alignment accuracy of the mask needs to be shorter than the period of molecular rotation. For example, when making a lens with a focal length of 50 cm and a diameter of 5 cm, as shown in Figure 26, the period of molecular rotation is 11 μm in the shortest region. Therefore, a mask alignment accuracy of the order of several μm is required, and it may not be possible to manufacture it depending on the performance of the alignment device. Figure 26 is a schematic diagram showing a specific example of manufacturing a PB lens by multiple mask exposures.

[0123] <Method for evaluating diffraction efficiency> The diffraction efficiency of the PB lens of Reference Example 1 was measured. The diffraction efficiency was measured using the configuration shown in FIG. 24, and three laser light sources with wavelengths of 445 nm, 532 nm, and 632 nm were used. Here, in the measurement of the diffraction efficiency, the light emitted from the laser light source first passes through a circular polarizing plate to become circularly polarized light and is emitted to the PB lens. Thereafter, the main light of the light that passes through the outer periphery of the PB lens moves toward the focal point. Meanwhile, unnecessary light such as zero-order light is diffracted in a direction different from that of the main light. The diffraction efficiency is defined by the following (Equation 3).

[0124]

number

[0125] Therefore, the light intensity was measured at the first and second measurement points shown in Fig. 24, the light intensity at the first measurement point was taken as the total transmitted light intensity, and the light intensity at the second measurement point was taken as the main light intensity, and the diffraction efficiency was calculated from the measured values ​​using the above (Equation 3). The results are shown in Fig. 27. Fig. 27 is a graph showing the calculated values ​​of the diffraction efficiency of the PB lens of Comparative Example 1 and the measured values ​​of the diffraction efficiency of the PB lens of Reference Example 1.

[0126] As shown in FIG. 27, the diffraction efficiency of the PB lens of Reference Example 1 was 83% at a wavelength of 445 nm, 100% at a wavelength of 532 nm, and 94% at a wavelength of 632 nm. When compared with the calculation results of Comparative Example 1, it was found that the measured values ​​of the diffraction efficiency were consistent with the calculation results. From this, it was confirmed that the phase difference of the RM layer affects the diffraction efficiency as the theory suggests. Therefore, it was found that if the RM layer is a wideband half-wave plate, a PB lens with wideband diffraction efficiency can be realized.

[0127] Example 1 FIG. 28 is a cross-sectional schematic diagram of the optical element of Example 1. Example 1 is a PB lens corresponding to the optical element 10 of the above-mentioned embodiment 2. As shown in FIG. 28, the optical element 10 of Example 1 was provided with a circular polarizer 400, a first retardation plate 410, a second retardation plate 420, and a third retardation plate 430 in this order. The first retardation plate 410 was provided with a first alignment film 210 and a first optically anisotropic layer 310 in this order from the circular polarizer 400 side. The second retardation plate 420 was provided with a second alignment film 220 and a second optically anisotropic layer 320 in this order from the circular polarizer 400 side. The third retardation plate 430 was provided with a third alignment film 230 and a third optically anisotropic layer 330 in this order from the circular polarizer 400 side.

[0128] The azimuth angle of the slow axis of the first retarder 410 (i.e., the first optically anisotropic layer 310) was 0°, and the phase difference was λ / 4. The azimuth angle of the slow axis of the second retarder 420 (i.e., the second optically anisotropic layer 320) was 45°, and the phase difference was λ / 2. The azimuth angle of the slow axis of the third retarder 430 (i.e., the third optically anisotropic layer 330) was 0°, and the phase difference was λ / 4. Since the alignment film does not contribute to the slow axis and phase difference of the retarder, the azimuth angle and phase difference of the slow axis of the retarder are the same as the azimuth angle and phase difference of the slow axis of the optically anisotropic layer that the retarder has.

[0129] In Example 1, a simulation was performed on the diffraction efficiency when three RM layers were laminated. The design values ​​of the RM layers were determined by the azimuth angle of the slow axis and the phase difference for light with a wavelength of 550 nm.

[0130] Fig. 29 is a diagram showing the polarization state of light after passing through a circular polarizer included in the optical element of Example 1, using a Poincare sphere. Fig. 30 is a diagram showing the polarization state of light after passing through a first retardation plate included in the optical element of Example 1, using a Poincare sphere. Fig. 31 is a diagram showing the polarization state of light after passing through a second retardation plate included in the optical element of Example 1, using a Poincare sphere. Fig. 32 is a diagram showing the polarization state of light after passing through a third retardation plate included in the optical element of Example 1, using a Poincare sphere.

[0131] As shown in Figures 29 to 32, three-layer retarder plates (i.e., first retarder plate 410, second retarder plate 420, and third retarder plate 430) convert visible light (wavelength 450 nm to 650 nm) that has been circularly polarized by the circular polarizers into reverse circularly polarized light. In Figures 29 to 32, the change in polarization state caused by each retarder plate is shown on the Poincaré sphere (S1-S3 plane).

[0132] Fig. 33 is a diagram showing formula 4 obtained from the optical element of Example 1. Fig. 33 shows the target value after transmission through all retardation plates. Fig. 34 is a diagram showing formula 5 obtained from the optical element of Example 1. Fig. 34 shows the desired polarization state before transmission through the third retardation plate.

[0133] To realize a broadband PB lens, it is preferable that the polarization state after transmission through the third retardation plate 430 satisfies the following (Formula 4), as shown in FIG.

[0134]

number

[0135] In order to satisfy the above formula (4), it is preferable that the following formula (5) be satisfied in the polarized state before transmission through the third retardation plate 430, as shown in FIG.

[0136]

number

[0137] The condition for satisfying the above formula (5) can be expressed as the following formula (6) with the phase difference of the first optically anisotropic layer 310 included in the first retardation plate 410 being Δnd.

[0138]

number

[0139] In the above formula (6), λ represents the wavelength. In order to make the inequality of the above formula (6) valid in the wavelength range of 450 nm to 650 nm, it is preferable that Δnd is 120 nm or more and 150 nm or less for light with a wavelength of 550 nm. Here, the chromatic dispersion of the RM layer is flat dispersion or positive chromatic dispersion.

[0140] Fig. 35 is a cross-sectional schematic diagram showing a configuration in which the phase difference between the first optically anisotropic layer and the third optically anisotropic layer is set to 150 nm in the optical element of Example 1. In Example 1, further, as shown in Fig. 35, in the case where the phase difference at a wavelength of 550 nm between the first optically anisotropic layer 310 and the third optically anisotropic layer 330 is set to 150 nm, the azimuth angle of the slow axis and phase difference of the second optically anisotropic layer 320 that provides good diffraction efficiency in a wide band were examined.

[0141] <Calculation of diffraction efficiency> Fig. 36 is a diagram explaining how to calculate the diffraction efficiency. The diffraction efficiency of a PB lens that uses a retardation plate that is not an A-plate can be calculated as shown in Fig. 36. That is, when circularly polarized light with S3=+1 is incident on the retardation plate, if S3 of the transmitted light is x, the diffraction efficiency is proportional to "(1-x) / 2".

[0142] In this embodiment, the value of x was calculated by LCDmaster. The result is shown in FIG. 37. In addition, the wavelength characteristic of the diffraction efficiency was obtained using the value of x. The result is shown in FIG. 38. FIG. 37 is a graph showing S3(x) of the transmitted light versus the wavelength of the incident light when circularly polarized light of S3=+1 is incident on the optical element of Example 1. FIG. 38 is a graph showing the diffraction efficiency versus the wavelength of the incident light when circularly polarized light of S3=+1 is incident on the optical element of Example 1. FIG. 37 and FIG. 38 show x and the diffraction efficiency when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is 45° and the phase difference at a wavelength of 550 nm is 230 nm.

[0143] The diffraction efficiency was similarly calculated when the retardation at a wavelength of 550 nm and the azimuth angle of the slow axis of the second optically anisotropic layer 320 were changed. The calculation results are shown in the following Table 1. In Table 1, as shown in FIG. 38, only the lowest value of the diffraction efficiency in the visible light region (450 nm to 650 nm) is shown, and evaluation was performed using that value.

[0144] [Table 1]

[0145] In Table 1, the range with high effect is surrounded by a dashed line, and the range with even higher effect is surrounded by a thick line. Usually, when the diffraction efficiency is below 80%, ghost images become noticeable, resulting in poor display. Therefore, the diffraction efficiency needs to be at least 80% or more, and for a PB lens with higher performance, the diffraction efficiency is preferably 90% or more, and more preferably 95% or more. In addition, when manufacturing a PB lens, it is considered that the phase difference and the axial direction vary to a certain extent due to manufacturing errors. For the above reasons, the design values ​​in the region with high diffraction efficiency and with a wide tolerance range for variation are surrounded by dashed and thick lines in Table 1 as effective ranges.

[0146] From Table 1, it was found that a high effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 150 nm and less than 350 nm. It was also found that an even higher effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 210 nm and less than 290 nm.

[0147] Example 2 Fig. 39 is a cross-sectional schematic diagram of an optical element of Example 2. For the optical element of Example 2 shown in Fig. 39, the diffraction efficiency was calculated in the same manner as in Example 1. The results are shown in Table 2. The optical element 10 of Example 2 had the same configuration as Example 1, except that the phase difference at a wavelength of 550 nm of the first optically anisotropic layer 310 and the third optically anisotropic layer 330 was set to 140 nm.

[0148] [Table 2]

[0149] From Table 2, it was found that a high effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 150 nm and less than 350 nm. It was also found that an even higher effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 210 nm and less than 290 nm.

[0150] Example 3 Fig. 40 is a cross-sectional schematic diagram of an optical element of Example 3. For the optical element of Example 3 shown in Fig. 40, the diffraction efficiency was calculated in the same manner as in Example 1. The results are shown in Table 3. The optical element 10 of Example 3 had the same configuration as Example 1, except that the phase difference at a wavelength of 550 nm of the first optically anisotropic layer 310 and the third optically anisotropic layer 330 was set to 130 nm.

[0151] [Table 3]

[0152] From Table 3, it was found that a high effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 150 nm and less than 350 nm. It was also found that an even higher effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 210 nm and less than 290 nm.

[0153] Example 4 Fig. 41 is a cross-sectional schematic diagram of an optical element of Example 4. For the optical element of Example 4 shown in Fig. 41, the diffraction efficiency was calculated in the same manner as in Example 1. The results are shown in Table 4. The optical element 10 of Example 4 had the same configuration as Example 1, except that the phase difference at a wavelength of 550 nm of the first optically anisotropic layer 310 and the third optically anisotropic layer 330 was set to 120 nm.

[0154] [Table 4]

[0155] From Table 4, it was found that a high effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 150 nm and less than 350 nm. It was also found that an even higher effect can be obtained when the azimuth angle of the slow axis of the second optically anisotropic layer 320 is more than 35° and less than 50°, and the phase difference of the second optically anisotropic layer 320 at a wavelength of 550 nm is more than 210 nm and less than 290 nm.

[0156] Example 5 FIG. 42 is a cross-sectional schematic diagram of an optical element of Example 5. The diffraction efficiency of the optical element of Example 5 shown in FIG. 42 was calculated in the same manner as in Example 1. The results are shown in Table 5. In Example 5, the azimuth angle of the slow axis of the first optically anisotropic layer 310 was set to 0°, the phase difference at a wavelength of 550 nm was set to 140 nm, the azimuth angle of the slow axis of the second optically anisotropic layer 320 was set to 45°, the phase difference at a wavelength of 550 nm was set to 220 nm, and the phase difference at a wavelength of 550 nm of the third optically anisotropic layer 330 was set to 140 nm, and the azimuth angle of the slow axis of the third optically anisotropic layer 330 was changed to evaluate the influence of the case where the azimuth angles of the slow axes of the first optically anisotropic layer 310 and the third optically anisotropic layer 330 were not parallel. The azimuth angle of the slow axis of the third optically anisotropic layer 330 was changed in the range of -25° to 25°.

[0157] [Table 5]

[0158] From Table 5, it was found that a high effect can be obtained when the azimuth angle of the slow axis of the third optically anisotropic layer 330 is greater than -25° and less than 25°. It was also found that an even higher effect can be obtained when the azimuth angle of the slow axis of the third optically anisotropic layer 330 is greater than -5° and less than 5°.

[0159] Example 6 Fig. 43 is a cross-sectional schematic diagram of the optical element of Example 6. The optical element of Example 6 shown in Fig. 43 was fabricated, and it was confirmed that the simulation was valid. The method of fabricating the optical element was the same as that of Reference Example 1.

[0160] The diffraction efficiency of the optical element of Example 6 was calculated as follows. First, the Mueller matrix was measured by Axoscan. The polarization state of the emitted light when polarized light of S3=+1 was incident was calculated from the Mueller matrix (x in Example 1). The calculated values ​​to be compared with the actual measured values ​​were calculated by LCDmaster. The actual measured values ​​and the calculated values ​​are shown in Table 6 below.

[0161] [Table 6]

[0162] As shown in Table 6, the measured values ​​and the calculated values ​​were consistent. Therefore, it was found that the calculated values ​​of Examples 1 to 5 were reproduced by the actual measurements.

[0163] Example 7 In Example 7, it was verified that the focal length can be shortened without changing the molecular rotation period by stacking PB lenses using a PB lens corresponding to the optical element 10 of the above-mentioned third embodiment.

[0164] The PB lens of Example 7 can be obtained by further preparing a PB lens on the sample of Reference Example 1. The sample preparation procedure is shown below.

[0165] A photoisomerization type photo-alignment film was applied onto the optically anisotropic layer of the PB lens produced in Reference Example 1 (alignment film formation process). Then, 100 mJ / cm 2 was applied using four annular masks in which openings and closings were alternated. 2 The film was irradiated with polarized UV (365 nm) (alignment film exposure process). The mask was designed so that the polarized UV overlapped and non-overlapped areas alternated. The polarization directions of the PUV were 0°, -45°, -90°, and -135°.

[0166] After irradiation with polarized UV, the film was baked in an oven at 160°C for 20 minutes, and then RM was applied. RM was applied using a spin coater rotating at 1000 rpm. RM was applied with a thickness adjusted so that the phase difference for light with a wavelength of 550 nm was about 270 nm. In other words, RM was applied so that the phase difference of the optically anisotropic layer 300 was λ / 2.

[0167] The wavelength dispersion of RM was positive, with Re(450 nm) / Re(550 nm) ≈ 1.04, Re(650 nm) / Re(550 nm) ≈ 0.97. After coating, RM was cured with 200 mJ (365 nm) of unpolarized UV (optically anisotropic layer forming step) to obtain the PB lens of Example 7.

[0168] The focal length of the PB lens of Example 7 was measured in the same manner as in Reference Example 1, and was found to be 25 cm. Since the lens was produced using the same mask as in Reference Example 1, the period in which the molecules rotated 180° was the same in the first and second layers. Therefore, the above formula A was established.

[0169] The above general formula (Formula 1) is an equality, but in this embodiment, it becomes an inequality as shown in (Formula A). This shows that, as shown in FIG. 44, in Example 7, the lens has a single focal length even though the period of the molecule rotating 180° is long. The long period relaxes the mask alignment accuracy required during manufacturing, making manufacturing easier. Thus, in Example 7, a method of shortening the focal length without changing the period of molecular rotation was shown, and a method of relaxing the manufacturing difficulty limited by the alignment accuracy was verified. Also, from FIG. 44, it was found that the first anisotropic molecule 311 and the second anisotropic molecule 321 each have a discrete molecular orientation pattern from the center to the end of the optical element 10. FIG. 44 is a graph showing the relationship between the distance from the lens center of the optical element of Example 7 and the molecular orientation. [Explanation of symbols]

[0170] 10: Optical elements 10R:PB lens 20, 20R: Mask group 201, 202, 203, 204, 20 M , 20 r , 20 r-1 , 20 r-2 , 20R1, 20R2, 20R3, 20R4: Mask 20A1, 20A2, 20A3, 20A4, 20A r , 20A r-1 , 20A r-2 , 20RA1, 20RA2, 20RA3, 20RA4: Transparent part (opening) 20B1, 20B2, 20B3, 20B4, 20B r , 20B r-1 , 20B r-2 , 20RB1, 20RB2, 20RB3, 20RB4: Light shielding part 301, 302, 303: Area 100, 100R: Support board 200, 200R, 210, 220, 230: Alignment film 300, 300R, 310, 320, 330: Optically anisotropic layer 301, 311, 321, 331: Anisotropic molecules 400: Circularly polarized version 410, 420, 430: Retardation plate

Claims

1. A first alignment film; a first optically anisotropic layer containing first anisotropic molecules; A second alignment film; a second optically anisotropic layer containing second anisotropic molecules, in this order.

2. Furthermore, a third alignment film provided on the second optically anisotropic layer on the opposite side to the second alignment film; The optical element according to claim 1 , further comprising: a third optically anisotropic layer provided on the opposite side of the third alignment film to the second optically anisotropic layer, the third optically anisotropic layer containing third anisotropic molecules.

3. When the azimuth angle of the slow axis of the first optically anisotropic layer is 0°, the azimuth angle of the slow axis of the second optically anisotropic layer is greater than 35° and less than 50°; 3. The optical element according to claim 2, wherein the azimuth angle of the slow axis of the third optically anisotropic layer is greater than −25° and smaller than 25°.

4. the first optically anisotropic layer has a phase difference at a wavelength of 550 nm of 120 nm or more and 150 nm or less; the second optically anisotropic layer has a phase difference at a wavelength of 550 nm of 150 nm or more and 350 nm or less; 4. The optical element according to claim 3, wherein the retardation of the third optically anisotropic layer at a wavelength of 550 nm is 120 nm or more and 150 nm or less.

5. When the azimuth angle of the slow axis of the first optically anisotropic layer is 0°, the azimuth angle of the slow axis of the second optically anisotropic layer is greater than 35° and less than 50°; 3. The optical element according to claim 2, wherein the azimuth angle of the slow axis of the third optically anisotropic layer is greater than −5° and less than 5°.

6. the first optically anisotropic layer has a phase difference at a wavelength of 550 nm of 120 nm or more and 150 nm or less; the second optically anisotropic layer has a retardation of 210 nm or more and 290 nm or less at a wavelength of 550 nm; 6. The optical element according to claim 5, wherein the retardation of the third optically anisotropic layer at a wavelength of 550 nm is 120 nm or more and 150 nm or less.

7. In plan view, the first anisotropic molecules and the second anisotropic molecules are arranged so that their orientation directions rotate in-plane from the center to the end of the optical element; 2. The optical element according to claim 1, wherein the rotation direction of the first anisotropic molecules is opposite to the rotation direction of the second anisotropic molecules.

8. 8. The optical element according to claim 7, wherein the following formula A is satisfied: [0010] (The molecular orientation in the above formula A represents the azimuthal angle of the molecular orientation of the first anisotropic molecule and the second anisotropic molecule, the wavelength represents the wavelength of the incident light, the focal length represents the focal length of the optical element, and the distance from the lens center represents the distance of the first anisotropic molecule and the second anisotropic molecule from the center of the optical element.)

9. The optical element described in any one of claims 1 to 8, characterized in that from the center to the edge of the optical element, the first anisotropic molecules and the second anisotropic molecules each have a discrete molecular orientation pattern.

Images