Optical element

Abstract

Provided is an optical element capable of achieving good optical characteristics. This optical element has, 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.

Description

Technical Field

[0001] The invention relates to an optical element. Background Art

[0002] In recent years, an optical system using optical elements such as Pancharatnam-Berry phase optical elements (PBOE) has been proposed for display devices such as head-mounted displays. PBOE, for example, has an optical anisotropic layer formed using a liquid crystal composition containing liquid crystal molecules. PBOE is also called a PB lens.

[0003] As PBOE, patent document 1 discloses a polarization diffraction grating, which includes a photo-orientation layer (2) sensitive to polarized light and a liquid crystal composition (3) arranged on the above-mentioned photo-orientation layer (2), wherein an anisotropic orientation pattern corresponding to a polarization hologram is arranged in the photo-orientation layer, and the liquid crystal composition (3) is oriented according to the orientation pattern. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application No. 2008-532085 Summary of the invention Technical Problems to be Solved by the Invention

[0005] Fig.45 : is a cross-sectional schematic diagram showing the structure of a general PB lens. Fig.45 As shown, a general PB lens 10R includes a support substrate 100R, an alignment film 200R, and an optical anisotropic layer 300R as a λ / 2 plate in this order. The diffraction efficiency of the lens is maximum when the phase difference of the PB lens 10R is half a wavelength. Therefore, in order to achieve a wide-band diffraction efficiency, a wide-band half-wavelength plate is required.

[0006] Here, the PB lens 10R is obtained by, for example, performing an orientation treatment on the orientation film 200R on the support substrate 100R by mask exposure, and orienting anisotropic molecules (for example, also called reactive mesogens (also called RM)) on the orientation film 200R subjected to the orientation treatment to form an optical anisotropic layer 300R. The optical anisotropic layer 300R is also called an RM layer. The wavelength dispersion of the existing RM layer is not ideal, so even if a λ / 2 A-plate is produced, it is difficult to achieve good diffraction efficiency in a wide band.

[0007] In addition, the PB lens is configured so that the RM rotates in the plane. When the PB lens is made by multiple mask exposures, the mask alignment accuracy is required to be the same as the period of the molecular rotation of the RM. The shorter the focal length of the PB lens, the shorter the period of the molecular rotation, and thus the more difficult it is to manufacture.

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

[0009] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide an optical element capable of achieving excellent optical characteristics. Technical solutions for solving technical problems

[0010] (1) An optical element according to one embodiment of the present invention comprises, in 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, according to one embodiment of the present invention, based on the structure of (1) above, the optical element further comprises: a third orientation film, which is arranged on the opposite side of the second orientation film of the second optical anisotropic layer; and a third optical anisotropic layer, which is arranged on the opposite side of the second optical anisotropic layer of the third orientation film and contains third anisotropic molecules.

[0012] (3) In addition, according to one embodiment of the present invention, based on the configuration of (2) above, when the azimuth angle of the lag axis of the first optical anisotropic layer is set to 0°, the azimuth angle of the lag axis of the second optical anisotropic layer is greater than 35° and less than 50°, and the azimuth angle of the lag axis of the third optical anisotropic layer is greater than -25° and less than 25°.

[0013] (4) In addition, in one embodiment of the present invention, based on the structure of the above (3), the phase difference of the first optically anisotropic layer at a wavelength of 550nm is greater than 120nm and less than 150nm, the phase difference of the second optically anisotropic layer at a wavelength of 550nm is greater than 150nm and less than 350nm, and the phase difference of the third optically anisotropic layer at a wavelength of 550nm is greater than 120nm and less than 150nm.

[0014] (5) In addition, according to one embodiment of the present invention, based on the configuration of (2) above, when the azimuth angle of the lag axis of the first optical anisotropic layer is set to 0°, the azimuth angle of the lag axis of the second optical anisotropic layer is greater than 35° and less than 50°, and the azimuth angle of the lag axis of the third optical anisotropic layer is greater than -5° and less than 5°.

[0015] (6) In addition, in one embodiment of the present invention, based on the structure of the above (5), the phase difference of the first optically anisotropic layer at a wavelength of 550nm is greater than 120nm and less than 150nm, the phase difference of the second optically anisotropic layer at a wavelength of 550nm is greater than 210nm and less than 290nm, and the phase difference of the third optically anisotropic layer at a wavelength of 550nm is greater than 120nm and less than 150nm.

[0016] (7) In addition, in one embodiment of the present invention, based on the structure of (1) above, the orientation direction of the first anisotropic molecules and the orientation direction of the second anisotropic molecules are configured to rotate in a plane from the center portion to the end portion of the optical element when viewed from above, and the rotation direction of the first anisotropic molecules is opposite to the rotation direction of the second anisotropic molecules.

[0017] (8) In addition, one embodiment of the present invention satisfies the following (Formula A) based on the configuration of (7) above. [Mathematical formula 1]Molecular orientation [°] < 90 / (wavelength [m]) / (focal length [m])*(distance from the center of the lens [m]) 2 ……(Formula A) (The molecular orientation in the (Formula A) represents the azimuth 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 center of the lens represents the distance between the first anisotropic molecule and the second anisotropic molecule and the center of the optical element.)

[0018] (9) In addition, in one embodiment of the present invention, based on the structure of (1), (2), (3), (4), (5), (6), (7) or (8), the first anisotropic molecules and the second anisotropic molecules respectively have discrete molecular orientation patterns from the center portion to the end portion of the optical element. Beneficial Effects

[0019] According to the present invention, an optical element capable of achieving good optical characteristics can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic cross-sectional view of the optical element according to the first embodiment. Figure 2 It is a schematic diagram showing a first exposure step in the method for manufacturing an optical element according to the first embodiment. Figure 3 It is a schematic diagram which shows the 2nd exposure process in the manufacturing method of the optical element of 1st Embodiment. Figure 4 This is a schematic diagram showing the process after the first exposure step and the second exposure step in the method for manufacturing the optical element according to the first embodiment. Figure 5 This is a schematic plan view showing an example of a mask set used for manufacturing the optical element according to the first embodiment. Figure 6 It is a plan view schematically showing an example of a general mask set. Figure 7 It is a schematic cross-sectional view of an optical element according to a second embodiment. Figure 8 It is a schematic cross-sectional view of an optical element according to a third embodiment. Fig. 9 This is a diagram showing the molecular orientation of anisotropic molecules in a microscope observation photograph of the first optically anisotropic layer and the second optically anisotropic layer included in the optical element according to the third embodiment. Fig.10 It is a schematic diagram explaining the process of manufacturing a PB lens by multiple mask exposures. Fig.11 It is a schematic diagram showing a specific example of manufacturing a PB lens by multiple mask exposure. Fig.12 This is a diagram for explaining the case where the directions of molecular rotation of two PB lenses are the same. Fig.13 This is a diagram for explaining the case where the directions of molecular rotation of two PB lenses are opposite to each other. Fig.14 : is a graph showing the phase difference of the half-wavelength plate of Comparative Example 1. Fig.15 3 is a graph showing the calculated value of the diffraction efficiency of the half-wavelength plate of Comparative Example 1. Fig.16 It is a schematic cross-sectional view for explaining an alignment film forming step included in the manufacturing process of the PB lens of Reference Example 1. Fig.17 It is a schematic cross-sectional view for explaining an alignment film exposure step included in the manufacturing process of the PB lens of Reference Example 1. Fig.18 This 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 manufacturing process of the PB lens of Reference Example 1. Fig.19 This 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 manufacturing process of the PB lens of Reference Example 1. Fig. 20This 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 manufacturing process of the PB lens of Reference Example 1. Fig.21 This 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 manufacturing process of the PB lens of Reference Example 1. Fig. 22 It is a schematic cross-sectional view for explaining the optically anisotropic layer forming step included in the manufacturing process of the PB lens of Reference Example 1. Fig.23 This is a microscopic observation photograph of the PB lens of Reference Example 1. Fig.24 This is a schematic diagram showing the method of measuring focal length. Fig.25 It is a microscope observation photograph of the PB lens of Reference Example 1, and a graph showing the relationship between the molecular orientation and the distance from the center of the lens. Fig.26 It is a schematic diagram showing a specific example of manufacturing a PB lens by multiple mask exposure. Fig. 27 3 is a graph showing the calculated value of the diffraction efficiency of the PB lens of Comparative Example 1 and the measured value of the diffraction efficiency of the PB lens of Reference Example 1. Fig.28 It is a schematic cross-sectional view of the optical element of Example 1. Fig.29 This is a diagram showing the polarization state of light after passing through the circular polarization plate included in the optical element of Example 1 using a Poincare sphere. Fig.30 This is a diagram showing the polarization state of light after passing through the first phase difference plate included in the optical element of Example 1 using the Poincare sphere. Fig.31 This is a diagram showing the polarization state of light after passing through the second phase difference plate included in the optical element of Example 1 using the Poincare sphere. Fig.32 This is a diagram showing the polarization state of light after passing through the third phase difference plate included in the optical element of Example 1 using the Poincare sphere. Fig.33 This is a diagram showing Formula 4 obtained by the optical element of Example 1. Fig.34 This is a diagram showing Formula 5 obtained by the optical element of Example 1. Fig.35 This is a schematic cross-sectional view showing the structure when the phase difference between the first optically anisotropic layer and the third optically anisotropic layer in the optical element of Example 1 is set to 150 nm. Fig.36 This is a diagram for explaining the calculation method of diffraction efficiency. Fig.37 This is a graph showing S3(x) of transmitted light relative to the wavelength of incident light when circularly polarized light with S3=+1 is incident on the optical element of Example 1. Fig.38 This is a graph showing the diffraction efficiency with respect to the wavelength of incident light when circularly polarized light with S3 = +1 is incident on the optical element of Example 1. Fig.39 It is a schematic cross-sectional view of the optical element of Example 2. Fig.40 It is a schematic cross-sectional view of the optical element of Example 3. Fig.41 It is a schematic cross-sectional view of the optical element of Example 4. Fig.42 It is a schematic cross-sectional view of the optical element of Example 5. Fig.43 It is a schematic cross-sectional view of the optical element of Example 6. Fig.44 This is a graph showing the relationship between the distance from the lens center and the molecular orientation of the optical element of Example 7. Fig.45 It is a schematic cross-sectional view showing the structure of a general PB lens. DETAILED DESCRIPTION

[0021] Hereinafter, the embodiments of the present invention will be described. The present invention is not limited to the contents described in the following embodiments, and design changes can be appropriately made within the scope of the configuration of the present invention. In addition, in the following description, for the same parts or parts with the same functions, the same figure numerals are appropriately used between different drawings, and the repeated descriptions are appropriately omitted. The various modes of the present invention can also be appropriately combined within the scope of not departing from the gist of the present invention.

[0022] (First Embodiment) Figure 1 Schematic cross-sectional view of the optical element of the first embodiment. Figure 1 As shown, the optical element 10 of this embodiment sequentially comprises a first alignment film 210, a first optical anisotropic layer 310 containing first anisotropic molecules 311, a second alignment film 220, and a second optical anisotropic layer 320 containing second anisotropic molecules 321. By adopting such a method, good optical properties can be achieved. The anisotropic molecules are, for example, reactive mesogens (RM).

[0023] The above-mentioned Patent Document 1 discloses a polarization diffraction grating having a plurality of optically anisotropic layers containing RMs stacked together. Specifically, it is disclosed 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 oriented by the first liquid crystal composition 3. That is, the second liquid crystal composition 13 is oriented according to the orientation restriction force of the first liquid crystal composition 3. Therefore, the degree of freedom of design is low, and it is difficult to achieve good optical characteristics.

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

[0025] The optical element 10 of the present embodiment includes a supporting substrate 100, a first alignment film 210, a first optical anisotropic layer 310, a second alignment film 220, and a second optical anisotropic layer 320 in sequence. The optical element 10 of the present embodiment is a Pancharatnam-Berry phase optical element (PBOE). PBOE is also called a PB lens. The PB lens is a liquid crystal diffraction lens that imparts a lens effect to incident circularly polarized light. The optical element of the present embodiment is described in detail below.

[0026] Examples of the support substrate 100 include substrates such as glass substrates and plastic substrates. Examples of the material of the glass substrate include glass such as float glass and soda-lime glass. Examples of the material of the plastic substrate include plastics such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, and alicyclic polyolefin.

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

[0028] As the material of the alignment film 200, common materials in the field of liquid crystal panels such as polymers having polyimide in the main chain, polymers having polyamic acid in the main chain, and polymers having polysiloxane in the main chain can be used. The materials of the first alignment film 210 and the second alignment film 220 may be different or the same.

[0029] The alignment film 200 can be formed by coating an alignment film material, and examples of the coating method include flexographic printing and inkjet coating. The coating 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-alignment film. The photo-alignment film is obtained, for example, by forming an alignment film material containing a photo-alignment polymer having a photo-functional group on a substrate. The alignment film 200 is subjected to an alignment treatment. For example, the alignment film 200 containing the photo-alignment polymer is irradiated with polarized ultraviolet rays (also called polarized UV, PUV), and the alignment treatment is performed by generating anisotropy on the surface of the alignment film 200. The structures of the photo-alignment polymers contained in the first alignment film 210 and the second alignment film 220 may be different from each other or the same.

[0031] As the above-mentioned photo-alignment polymer, for example, a photo-alignment polymer having at least one photo-functional group selected from cyclobutane, azophenyl, chalcone, cinnamate, coumarin, stilbene, phenolic ester and phenyl benzoate can be cited. The photo-alignment polymer contained in the photo-alignment film can be one or more. The photo-functional group of the photo-alignment polymer can exist in the main chain of the polymer, in the side chain of the polymer, or in both the main chain and the side chain of the polymer.

[0032] As the above-mentioned photo-orientation polymer, photodegradable polymers, photo-rearrangement polymers (preferably photo-Fries rearrangement polymers), photo-isomerization polymers, photo-dimerization polymers and photo-crosslinking polymers can be cited as preferred examples. Any one of these can be used alone, or two or more can be used simultaneously. Among them, from the viewpoint of orientation stability, photodegradable polymers with a reaction wavelength (main sensitivity wavelength) of around 254 nm and photo-rearrangement polymers with a reaction wavelength (main sensitivity wavelength) of around 254 nm are particularly preferred. Photo-isomerization polymers and photo-dimerization polymers having photofunctional groups in the side chains are also preferred.

[0033] The main chain structure of the photo-alignment polymer preferably includes at least one structure selected from the group consisting 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 polyethylene structure.

[0034] The alignment film 200 may be a horizontal alignment film that orients the anisotropic molecules 301 approximately horizontally relative to the film surface, or a vertical alignment film that orients the anisotropic molecules 301 approximately vertically relative to the film surface. The horizontal alignment film has a function of orienting the anisotropic molecules 301 in the optical anisotropic layer 300 in a horizontal direction relative to the surface of the horizontal alignment film when no voltage is applied. Here, the anisotropic molecules are oriented in a horizontal direction relative to the surface of the horizontal alignment film, which means that the pretilt angle of the anisotropic molecules is 0 to 5°, preferably 0 to 2°, and more preferably 0 to 1° relative to the surface of the horizontal alignment film. In addition, the vertical alignment film has a function of orienting the anisotropic molecules 301 in the optical anisotropic layer 300 in a vertical direction relative to the surface of the vertical alignment film when no voltage is applied. Here, the anisotropic molecules are oriented in a vertical direction relative to the surface of the vertical alignment film, which 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 anisotropic molecules refers to an angle at which the major axis of the liquid crystal molecules is tilted relative to the main surface of each substrate in a state where no voltage is applied.

[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] As the optical anisotropic layer 300, for example, a cured product of a polymerizable liquid crystal material (also referred to as "reactive mesogen") is preferably used. In this case, at least one of the polymerized polymerizable liquid crystal material and the 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 optical anisotropic layer 300 is formed, for example, by coating a polymerizable liquid crystal material (reactive mesogen) and curing. As a polymerizable liquid crystal material, a liquid crystal polymer (liquid crystal polymer) with a photoreactive group is used. As a polymerizable liquid crystal material, for example, a side chain having a structure of a photoreactive group such as a biphenyl, a terphenyl, a naphthyl, a phenyl benzoate group, an azophenyl group, a derivative thereof, and a cinnamoyl group, a chalcone group, a cinnamoyl group, a β-(2-phenyl) acryloyl group, a cinnamic acid group, a derivative thereof, and a polymer having a structure such as an acrylate, a methacrylate, a maleimide, a N-phenyl maleimide, a siloxane, etc. on the main chain. The polymer can be a homopolymer comprising a single repeating unit, or a copolymer comprising more than two repeating units having different side chain structures. As the above-mentioned copolymer, any one of alternating type, random type, process type (craft-type), etc. can be included. Furthermore, in the copolymer, the side chain of at least one repeating unit may be a side chain having a structure having both a mesogenic group and a photoreactive group as described above, and the side chains of other repeating units do not have the mesogenic group and the photoreactive group.

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

[0039] As the solvent for coating the polymerizable liquid crystal material, for example, 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. can be listed. Any one 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 according to the present embodiment will be described.

[0041] The manufacturing method of the optical element 10 of the present embodiment comprises: a first orientation film exposure step of exposing the first orientation film 210 and performing an orientation treatment; a first optical anisotropic layer forming step of disposing a first polymerizable liquid crystal material on the exposed first orientation film 210 and curing it to provide a first optical anisotropic layer 310; a second orientation film forming step of providing a second orientation film 220 on the first optical anisotropic layer 310; a second orientation film exposure step of exposing the second orientation film 220 and performing an orientation treatment; a second optical anisotropic layer forming step of disposing a second polymerizable liquid crystal material on the exposed second orientation film 220 and curing it to provide a second optical anisotropic layer 320. The first orientation film exposure step and the second orientation film exposure step are also referred to as the orientation film exposure step. The first optical anisotropic layer forming step and the second optical anisotropic layer forming step are also referred to as the optical anisotropic layer forming step.

[0042] The above-mentioned orientation film exposure process sequentially includes: a first exposure process, exposing a first exposure area of ​​the orientation film 200 with a first polarized light having a first polarization axis; and a second exposure process, exposing a second exposure area of ​​the orientation film 200 that only overlaps with a portion of the above-mentioned first exposure area with a second polarized light having a second polarization axis whose angle is different from that of the above-mentioned first polarization axis.

[0043] By adopting such a method, only the first polarized light can be exposed in the portion of the first exposure area that does not overlap with the second exposure area, only the second polarized light can be exposed in the portion of the second exposure area that does not overlap with the first exposure area, and the first polarized light and the second polarized light can be exposed in a overlapping manner in the portion of the first exposure area that overlaps with the second exposure area.

[0044] like Figure 2 to Figure 4 As shown, in the overlapping exposure area, the molecular orientation is determined by the average of the two exposures. Therefore, the orientation directions of the alignment film 200 can be different between the portion of the first exposure area that does not overlap with the second exposure area, the portion of the second exposure area that does not overlap with the first exposure area, and the portion of the first exposure area that overlaps with the second exposure area. That is, by exposing the alignment film 200 twice, three orientation directions can be given. As a result, the arrangement pattern of the anisotropic molecules 301 can be increased with fewer exposure times, and the optical element 10 with high diffraction efficiency can be manufactured more simply. For example, the optical element 10 with high diffraction efficiency can be manufactured without increasing the number of masks. Figure 2 It is a schematic diagram showing a first exposure step in the method for manufacturing an optical element according to the first embodiment. Figure 3 It is a schematic diagram which shows the 2nd exposure process in the manufacturing method of the optical element of 1st Embodiment. Figure 4This is a schematic diagram showing the process after the first exposure step and the second exposure step in the method for manufacturing the optical element according to the first embodiment.

[0045] like Figure 2 to Figure 4 As shown, the portion of the first exposure region that does not overlap with the second exposure region corresponds to the first region 301, the portion of the second exposure region that does not overlap with the first exposure region corresponds to the third region 303, and the portion of the first exposure region that overlaps with the second exposure region, that is, the region that is overlapped and exposed, corresponds to the second region 302. In the first region 301 and the third region 303, the anisotropic molecules 301 are not twisted and oriented in the film thickness direction of the optical anisotropic layer 300, and in the second region 302, the anisotropic molecules 301 are twisted and oriented in the film thickness direction of the optical anisotropic layer 300.

[0046] The manufacturing method of the optical element 10 of this embodiment may include a first alignment film forming step of coating an alignment film material including a photo-alignment polymer having a photofunctional group on the support substrate 100 to form the first alignment film 210 before the first alignment film exposure step. In the first alignment film forming step, a coating device such as a slit coater or a spin coater may be appropriately used in coating the alignment film material. In addition, after coating the alignment film material with a uniform thickness, pre-baking may be performed at a temperature of about 70 to 100° C. for 1 to 10 minutes, for example.

[0047] The second alignment film forming step is the same as the first alignment film forming step. Various setting conditions in the first alignment film forming step and various setting conditions in the second alignment film forming step may be different from each other or the same. The first alignment film forming step and the second alignment film forming step are also referred to as alignment film forming steps.

[0048] The exposure process of the orientation film in this embodiment can be performed by mask exposure. That is, in this embodiment, the orientation direction can be patterned by mask exposure. On the other hand, in the above-mentioned Patent Document 1, the method of forming an optical anisotropic layer by patterning the orientation direction by a polarization hologram is different from this embodiment.

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

[0050] The orientation film exposure process sequentially includes: a first exposure process, exposing a first exposure area of ​​the orientation film 200 with a first polarized light having a first polarization axis; and a second exposure process, exposing a second exposure area of ​​the orientation film 200 that only overlaps a portion of the first exposure area with a second polarized light having a second polarization axis whose angle is different from that of the first polarization axis.

[0051] Preferably, a portion of the first exposure region overlaps with the second exposure region, and the other portion of the first exposure region does not overlap with the second exposure region, and a portion of the second exposure region overlaps with the first exposure region, and the other portion of the second exposure region does not overlap with the first exposure region. By adopting such a method, the arrangement pattern of the anisotropic molecules 301 can be increased with a more effective and reduced number of exposures, and the optical element 10 with high diffraction efficiency can be manufactured more simply.

[0052] The angle of the second polarization axis is preferably greater than the angle of the first polarization axis by 10° or more and less than 60°, more preferably greater than 20° or more and less than 50°, and further preferably greater than 30° or more and less than 45°. By adopting such a method, the arrangement pattern of the anisotropic molecules 301 can be changed more continuously, and an optical element 10 with higher diffraction efficiency can be manufactured. In this specification, the angle of the axis is positive in the counterclockwise direction.

[0053] The alignment film exposure process may include the first exposure process and the second exposure process to the Mth exposure process in sequence. The first exposure process to the Mth exposure process are processes for exposing the first exposure region to the Mth exposure region 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. A portion of the rth exposure region in the first exposure region to the Mth exposure region overlaps with the (r-1)th exposure region, and the other portion of the rth exposure region does not overlap with the (r-1)th exposure region, a portion of the (r-1)th exposure region in the first exposure region to the Mth exposure region overlaps with the rth exposure region, and the other 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 greater than or equal to 3. r is an integer greater than or equal to 3 and less than or equal to M. By adopting such a method, the arrangement pattern of the anisotropic molecules 301 can be easily increased, and the optical element 10 having a high diffraction efficiency can be manufactured more simply.

[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 greater than the angle of the (r-1)th polarization axis by 10° or more and 60° or less, more preferably greater than 20° or more and 50° or less, and further preferably greater than 30° or more and 45° or less. By adopting such a method, the arrangement pattern of the anisotropic molecules 301 can be changed more continuously, and an optical element 10 with higher diffraction efficiency can be manufactured.

[0056] Specifically, when M is 3, the exposure process further includes a third exposure process after the second exposure process. The third exposure process is a process for exposing the third exposure area of ​​the alignment film 200 using 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 portion of the third exposure area overlaps with the second exposure area, and the other portion of the third exposure area does not overlap with the second exposure area. A portion of the second exposure area overlaps with the third exposure area, and the other portion of the second exposure area does not overlap with the third exposure area. The third exposure area does not overlap with the first exposure area.

[0057] The angle of the third polarization axis is preferably greater than the angle of the second polarization axis by 10° or more and 60° or less, more preferably greater than 20° or more and 50° or less, and further preferably greater than 30° or more and 45° or less. By adopting such a method, the arrangement pattern of the anisotropic molecules 301 can be changed more continuously, and an optical element 10 with higher diffraction efficiency can be manufactured.

[0058] When M is 4, the exposure process may further include a third exposure process and a fourth exposure process after the above-mentioned second exposure process. The third exposure process and the fourth exposure process are processes for exposing the third exposure area and the fourth exposure area of ​​the alignment film 200 with a third polarized light and a 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 portion of the third exposure area overlaps with the second exposure area, and the other portion of the third exposure area does not overlap with the second exposure area, a portion of the second exposure area overlaps with the third exposure area, and the other portion of the second exposure area does not overlap with the third exposure area, and the third exposure area does not overlap with the first exposure area. A portion of the fourth exposure area overlaps with the third exposure area, and the other 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 the other 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 greater than the angle of the third polarization axis by 10° or more and less than 60°, more preferably greater than 20° or more and less than 50°, and further preferably greater than 30° or more and less than 45°. By adopting such a method, the arrangement pattern of the anisotropic molecules 301 can be changed more continuously, and an optical element 10 with higher diffraction efficiency can be manufactured.

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

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

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

[0063] Figure 5 1 is a schematic plan view showing an example of a mask set used in manufacturing the optical element of the first embodiment. Figure 5 The mask set 20 shown in FIG. 1 is manufactured. The mask set 20 includes a first mask 201 provided with a first light-transmitting portion (opening portion) 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 in such a manner that the center of the first mask 201 overlaps with the center of the second mask 202, the first light-transmitting portion 20A1 overlaps with a portion of the second light-transmitting portion 20A2 and a portion of the second light-shielding portion 20B2, and the second light-transmitting portion 20A2 overlaps with a portion of the first light-transmitting portion 20A1 and a portion of the first light-shielding portion 20B1. By adopting such a method, the optical element 10 can be manufactured by using the first mask 201 in the first exposure process in the above-mentioned manufacturing process and using the second mask 202 in the second exposure process.

[0064] In this way, the mask group 20 used in the manufacture of the optical element 10 of the present embodiment is designed as an annular mask having multiple repeated light-transmitting portions and light-shielding portions, and through the multiple annular masks, areas where multiple polarized UVs with different polarization axes overlap and are irradiated and areas where other polarized UVs with different polarization axes do not overlap and are irradiated with one polarized UV are alternately formed on the orientation film 200.

[0065] On the other hand, when exposure is performed using a plurality of masks, it is common to use, for example, Figure 6 Mask set 20R is shown. Figure 6 FIG. 1 is a plan view schematically showing an example of a conventional mask set. Figure 6 In the figure, a conventional mask set 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. The first mask 20R1 to the fourth mask 20R4 are overlapped so that when the centers of the first mask 20R1 to the fourth mask 20R4 overlap, the light-transmitting portions of the respective masks do not overlap.

[0066] As described above, the optical element 10 of the present embodiment can be produced by exposing the alignment film 200 containing the photo-alignment polymer to a plurality of predetermined patterns and performing light patterning to pattern the desired pattern by overlapping 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 concentric circular patterns having a predetermined width, and different patterns are formed on the first mask 201 and the second mask 202.

[0067] like Figure 5 As shown, the mask set 20 may also include a first mask 201 and a second mask 202 to an Mth mask 20M. The rth mask 20r in the first mask 201 to the Mth mask 20M is provided with an rth light-transmitting portion 20Ar and an rth light-shielding portion 20Br, the (r-1)th mask 20r-1 is provided with an (r-1)th light-transmitting portion 20Ar-1 and an (r-1)th light-shielding portion 20Br-1, and the (r-2)th mask 20r-2 is provided with an (r-2)th light-transmitting portion 20Ar-2 and an (r-2)th light-shielding portion 20Br-2. When the center of the rth mask 20r is overlapped with the center of the (r-1)th mask 20r-1, the (r-1)th light-transmitting portion 20Ar-1 overlaps with a portion of the rth light-transmitting portion 20Ar and the rth light-shielding portion 20Br, and the rth light-transmitting portion 20Ar overlaps with a portion of the (r-1) light-transmitting portion 20Ar-1 and the (r-1) light-shielding portion 20Br-1, and does not overlap with the (r-2) light-transmitting portion 20Ar-2. Here, M is an integer greater than 3. r is an integer greater than 3 and less than M. By adopting such a method, the arrangement pattern of the anisotropic molecules 301 can be simply increased, and the optical element 10 with high diffraction efficiency can be manufactured more simply.

[0068] Specifically, when M is 3, the mask set 20 has 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 portion of the third mask 203 is overlapped with the center portion of the second mask 202, the second light-transmitting portion 20A2 overlaps with a portion of the third light-transmitting portion 20A3 and the third light-shielding portion 20B3, and the third light-transmitting portion 20A3 overlaps with a portion of the second light-transmitting portion 20A2 and the second light-shielding portion 20B2, and does not overlap with the first light-transmitting portion 20A1. By adopting such a method, the third mask 203 can be used in the third exposure process in the above-mentioned manufacturing process to manufacture the optical element 10.

[0069] Specifically, when M is 4, the mask set 20 has a third mask 203 and a fourth mask 204 in addition to the first mask 201 and the second mask 202. The fourth mask 204 is provided with a fourth light-transmitting portion 20A4 and a fourth light-shielding portion 20B4. When the center of the fourth mask 204 overlaps with the center of the third mask 203, the third light-transmitting portion 20A3 overlaps with a portion of the fourth light-transmitting portion 20A4 and the fourth light-shielding portion 20B4, and the fourth light-transmitting portion 20A4 overlaps with a portion of the third light-transmitting portion 20A3 and the third light-shielding portion 20B3, and does not overlap with the first light-transmitting portion 20A1 and the second light-transmitting portion 20A2. By adopting such a method, the third mask 203 can be used in the third exposure process in the above-mentioned manufacturing process, and the fourth mask 204 can be used in the fourth exposure process to manufacture the optical element 10.

[0070] Each mask included in the mask set 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% to 100%. The light-shielding portion is a portion that does not transmit light and has a transmittance of, for example, 0% to 10%.

[0071] (Second Embodiment) In this embodiment, features unique to this embodiment are mainly described, and description of contents overlapping with those of the first embodiment is omitted. The optical element of this embodiment further includes a third alignment film and a third optical anisotropic layer in addition to the configuration of the first embodiment.

[0072] Figure 7 is a schematic cross-sectional view of an optical element according to the second embodiment. Figure 7As shown, the optical element 10 of this embodiment has the structure of the first embodiment, and further includes a third alignment film 230 provided on the opposite side of the second alignment film 220 of the second optical anisotropic layer 320, and a third optical anisotropic layer 330 provided on the opposite side of the second optical anisotropic layer 320 of the third alignment film 230 and containing third anisotropic molecules 331. By adopting such a mode, since more optical anisotropic layers are arranged than in the first embodiment, the degree of freedom of design is further improved, and better optical characteristics can be achieved.

[0073] The third alignment film 230 is the same as 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 the same as 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 the same as the anisotropic molecule 301. The first anisotropic molecule 311, the second anisotropic molecule 321, and the third anisotropic molecule 331 are 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 optical anisotropic layer 310 is 0°, the azimuth angle of the slow axis of the second optical anisotropic layer 320 is preferably greater than 35° and less than 50°, and the azimuth angle of the slow axis of the third optical anisotropic layer 330 is greater than -25° and less than 25°. In this way, high diffraction efficiency can be achieved in a wide visible light region of 450nm to 650nm.

[0077] The azimuth refers to the direction when the direction of the object is projected onto the optical element, and is expressed by the angle (azimuth) formed with the azimuth used as a reference. Here, the orientation (0°) used as a reference is set as the lag axis of the first optical anisotropic layer. The azimuth is set to a positive angle in the counterclockwise direction from the reference azimuth, and a negative angle in the clockwise direction from the reference azimuth. Both the counterclockwise direction and the clockwise direction indicate the rotation direction when the optical element is observed from the observation surface side (front). In addition, the angle represents the value measured in a state of looking down at the optical element.

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

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

[0080] "nx" is the refractive index in the direction of maximum refractive index in the plane (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 for light at 23°C and a wavelength of 550nm.

[0081] When the azimuth angle of the slow axis of the first optical anisotropic layer 310 is 0°, the azimuth angle of the slow axis of the second optical anisotropic layer 320 is preferably greater than 35° and less than 50°, and the azimuth angle of the slow axis of the third optical anisotropic layer 330 is greater than -5° and less than 5°. By adopting this method, higher diffraction efficiency can be achieved in a wide visible light region of 450nm to 650nm.

[0082] Preferably, when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the azimuth angle of the slow axis of the third optical anisotropic layer 330 exceeds -5° and is less than 5°, the phase difference of the first optical anisotropic layer 310 at a wavelength of 550nm is 120nm to 150nm, the phase difference of the second optical anisotropic layer 320 at a wavelength of 550nm is 210nm to 290nm, and the phase difference of the third optical anisotropic layer 330 at a wavelength of 550nm is 120nm to 150nm. By adopting such a method, a higher diffraction efficiency can be achieved in a wide visible light region of 450nm to 650nm.

[0083] For example, the azimuth angle of the lag axis of the first optical anisotropic layer 310 is 0°, and the phase difference is λ / 4; the azimuth angle of the lag axis of the second optical anisotropic layer 320 is 45°, and the phase difference is λ / 2; and the azimuth angle of the lag axis of the third optical anisotropic layer 330 is 0°, and the phase difference is λ / 4.

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

[0085] On the other hand, two λ / 2 plates are used to achieve broadbanding in Patent Document 1. The polarization diffraction grating in Patent Document 1 is a broadband half-wavelength plate that converts linear polarization into linear polarization.

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

[0087] The manufacturing method of the optical element 10 of the present embodiment includes: a first orientation film exposure step of exposing the first orientation film 210 and performing an orientation treatment; a first optical anisotropic layer forming step of disposing a first polymerizable liquid crystal material on the exposed first orientation film 210 and curing it to provide a first optical anisotropic layer 310; a second orientation film forming step of providing a second orientation film 220 on the first optical anisotropic layer 310; a second orientation film exposure step of exposing the second orientation film 220 and performing an orientation treatment; a second optical anisotropic layer forming step of disposing a second polymerizable liquid crystal material on the exposed second orientation film 220 and curing it to provide a second optical anisotropic layer 320; a third orientation film forming step of providing a third orientation film 230 on the second optical anisotropic layer 320; a third orientation film exposure step of exposing the third orientation film 230 and performing an orientation treatment; and a third optical anisotropic layer forming step of disposing a third polymerizable liquid crystal material on the exposed third orientation film 230 and curing it to provide a third optical anisotropic layer 330.

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

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

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

[0091] (Third Embodiment) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the first embodiment is omitted. In the optical element 10 of this embodiment, the rotation direction of the first anisotropic molecule 311 and the rotation direction of the second anisotropic molecule 321 of the optical element 10 of the first embodiment are opposite.

[0092] Figure 8 It is a schematic cross-sectional view of an optical element according to a third embodiment. Fig. 9FIG. 4 is a diagram showing the molecular orientation of anisotropic molecules in a microscope observation photograph of the first optical anisotropic layer and the second optical anisotropic layer included in the optical element of the third embodiment. Figure 8 as well as Fig. 9 As shown, in a top 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 in a manner rotating in the plane from the center toward 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, if Fig.10 As shown in FIG. 1 , in the case of manufacturing a PB lens by multiple mask exposures, alignment accuracy is important. Fig.11 As shown, when manufacturing a lens with a focal length of 50 cm and a diameter of 5 cm, an alignment accuracy of several μm is required. Fig.10 It is a schematic diagram for explaining the process of manufacturing a PB lens by multiple mask exposures. Fig.11 It is a schematic diagram showing a specific example of manufacturing a PB lens by multiple mask exposure.

[0094] Thus, the shorter the focal length of the PB lens or the larger the lens diameter, the smaller the required alignment accuracy and the more difficult it is to manufacture.

[0095] On the other hand, in this embodiment, when viewed from above, the orientation direction of the first anisotropic molecule 311 and the orientation direction of the second anisotropic molecule 321 are arranged in a manner of rotating in a plane from the center portion toward the end portion 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. By adopting such a method, a structure in which a plurality of PB lenses are stacked can be formed. When a plurality of PB lenses are stacked, since the refractive power is the sum of the plurality of PB lenses, a short focal length lens can be realized by a lens with a long period of molecular rotation. As a result, a lens with a short focal length can be manufactured more easily. In this way, in this embodiment, the necessary alignment accuracy can be relaxed, and the PB lens can be manufactured easily.

[0096] In addition, if Fig. 9 As shown in , 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, as shown in Fig.12 and Fig.13 As shown, the rotation direction of the molecules in the first layer and the second layer needs to be opposite. Fig.12 This is a diagram for explaining the case where the directions of molecular rotation of two PB lenses are the same. Fig.13 This is a diagram for explaining the case where the directions of molecular rotation of two PB lenses are opposite to each other.

[0097] That is, Fig.12 As shown in FIG. 1 , when the molecular rotation directions of the two PB lenses are the same, the refractive power of the first optical anisotropic layer 310 is +1 / f, and the refractive power of the second optical anisotropic layer 320 is -1 / f, and the refractive power after lamination is (+1 / f)+(-1 / f)=0. On the other hand, Fig.13 As shown, when the molecular rotation directions of the two PB lenses are opposite, the refractive power of the first optical anisotropic layer 310 is +1 / f, and the refractive power of the second optical anisotropic layer 320 is also +1 / f. Therefore, the refractive power after stacking 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 orientation film 210, and the second anisotropic molecules 321 are oriented by the second orientation 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 rotated in opposite directions to each other, thereby improving the refractive power.

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

[0100] For example, the phase difference of the first optical anisotropic layer 310 is λ / 2, and the phase difference of the second optical anisotropic layer 320 is λ / 2.

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

[0102] [Mathematical formula 2] Molecular orientation [°] < 90 / (wavelength [m]) / (focal length [m])*(distance from lens center [m]) 2 ……(Formula A)

[0103] (In the above (Formula A), the molecular orientation represents the azimuth 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 center of the lens represents the distance from the center of the lens to the first anisotropic molecule and the second anisotropic molecule.) [Example]

[0104] Hereinafter, the effects of the present invention will be described 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-wavelength plate was produced using RM having positive dispersion, and the phase difference was measured. Here, positive dispersion refers to the wavelength dependence of the phase difference, that is, the phase difference measured at a long wavelength is smaller than the phase difference measured at a short wavelength.

[0106] The following is a procedure for producing a half-wavelength plate of Comparative Example 1. First, a photo-alignment film containing a photo-isomerizable polymer was applied to a glass substrate, and then irradiated with 100 mJ / cm 2 Polarized UV (365 nm) was applied. 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 while adjusting the film thickness so that the retardation (phase difference) at a wavelength of 550 nm was about 270 nm.

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

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

[0109] <Calculation of Diffraction Efficiency> The diffraction efficiency when making a PB lens was calculated using the half-wavelength plate (phase difference plate) of Comparative Example 1. The results are shown in Fig.15 . Fig.15 : is a graph showing the calculated value of the diffraction efficiency of the half-wavelength plate of Comparative Example 1. Here, when the retardation of the phase difference plate is Δnd, the value of the diffraction efficiency is proportional to "sin(Δnd / λ×π)2".

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

[0111] In Reference Example 1, the PB lens is produced using the RM having positive dispersion used in Comparative Example 1. The following is a production procedure for the PB lens of Reference Example 1. First, Fig.16 As shown, a photo-alignment film (alignment film 200 ) containing a photo-isomerization polymer is applied on a glass substrate (support substrate 100 ) (alignment film forming step).

[0112] Then, if Fig.17 As shown, the alignment film 200 is irradiated with 100 mJ / cm 2 The polarized UV (365 nm) of the alignment film exposure process is used. The alignment film exposure process includes a first exposure process, a second exposure process, a third exposure process, and a fourth exposure process. In the first exposure process, the first light-transmitting portion (opening portion) 20A1 and the first light-shielding portion 20B1 are repeatedly used. Fig.18 The annular mask (first mask 201) shown in FIG. 1 is used to set the first polarization axis to 0°. In the second exposure step, a second light-transmitting portion (opening portion) 20A2 and a second light-shielding portion 20B2 are repeated. Fig.19 The annular mask (second mask 202) shown in FIG. 1 is used to set the second polarization axis to 45°. In the third exposure step, the third light-transmitting portion (opening portion) 20A3 and the third light-shielding portion 20B3 are repeatedly used. Fig. 20 The third polarization axis is set to 90° using the annular mask (third mask 203) shown in FIG. 1. In the fourth exposure process, the fourth light-transmitting portion (opening portion) 20A4 and the fourth light-shielding portion 20B4 are repeated. Fig.21 The donut-shaped mask (fourth mask 204) shown sets the fourth polarization axis to 135°.

[0113] After irradiation with polarized UV, the samples were baked in an oven at 160°C for 20 minutes, and then, Fig. 22RM was applied as shown. RM was applied by a spin coater rotating at 1000 rpm. RM was applied while adjusting the film thickness so that the phase difference with respect to light of a wavelength of 550 nm was about 270 nm. That is, 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, Re(450nm) / Re(550nm)≈1.04, Re(650nm) / Re(550nm)≈0.97. After RM coating, curing was performed with 200mJ (365nm) of non-polarized UV (optically anisotropic layer formation step), and the PB lens of Reference Example 1 was obtained.

[0115] The PB lens of Reference Example 1 was observed using a polarizing microscope. The results are shown in Fig.23 In the PB lens of Reference Example 1, Fig.23 Confirm that RM is arranged normally.

[0116] <Focal length measurement> Fig.24 is a schematic diagram showing the method of measuring focal length. Fig.24 As shown, a 532 nm laser is irradiated to the periphery of the PB lens of Reference Example 1, and the focal length is measured by a ruler. The laser first passes through the circular polarization plate and becomes circularly polarized light and then is emitted. Then, the main light of the light that passes through the periphery of the PB lens is directed 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 (Formula 1) is established between the focal length and the molecular orientation.

[0118] [Mathematical formula 3] Molecular orientation [°] = 90 / (wavelength [m]) / (focal length [m])*(distance from lens center [m]) 2 ……(Formula 1)

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

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

[0121] [Formula 4] Molecular orientation [°] = 3.38*10 8 *(Distance from lens center [m]) 2 ……(Formula 2)

[0122] Comparing the proportionality coefficients of (Formula 1) and (Formula 2) above, it can be seen that when the wavelength is 532nm, the focal length is 50cm. In the case of shortening the focal length, the proportionality coefficient needs to be further increased. This means that the period of 180° rotation of the anisotropic molecules becomes shorter. If the period becomes shorter, manufacturing problems sometimes arise. In the case of making a PB lens by multiple mask exposures, the alignment accuracy of the mask needs to be shorter than the period of molecular rotation. For example, in the case of making a lens with a focal length of 50cm and a diameter of 5cm, if Fig.26 As shown, the region with the shortest period of molecular rotation is 11 μm. Therefore, mask alignment accuracy of several μm level is required, and there are cases where manufacturing is impossible due to the performance of the alignment device. Fig.26 It is a schematic diagram showing a specific example of manufacturing a PB lens by multiple mask exposure.

[0123] <Evaluation Method of Diffraction Efficiency> The diffraction efficiency of the PB lens of Reference Example 1 was measured. The diffraction efficiency was measured by Fig.24 The structure shown in the figure is carried out using three laser light sources with wavelengths of 445nm, 532nm and 632nm. Here, in the measurement of diffraction efficiency, the light emitted from the laser light source first passes through the circular polarizing plate to become circularly polarized light and is emitted to the PB lens. After that, the main light in the light that passes through the peripheral part of the PB lens is directed toward the focus. On the other hand, unnecessary light such as zero-order light is diffracted in a direction different from the main light. The diffraction efficiency is defined by the following (Formula 3).

[0124] [Formula 5] Diffraction efficiency = (main light intensity) ÷ (total transmitted light intensity) × 100... (Formula 3)

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

[0126] like Fig. 27As shown in FIG. 1 , the diffraction efficiency of the PB lens of Reference Example 1 at a wavelength of 445 nm is 83%, at a wavelength of 532 nm is 100%, and at a wavelength of 632 nm is 94%. Compared with the calculated result of Comparative Example 1, it can be seen that the measured value of the diffraction efficiency is consistent with the calculated result. Therefore, as in theory, it can be confirmed that the phase difference of the RM layer affects the diffraction efficiency. It can be seen that if the RM layer is a wide-band half-wavelength plate, a PB lens with wide-band diffraction efficiency can be realized.

[0127] (Example 1) Fig.28 1 is a schematic cross-sectional view of an optical element of Example 1. Example 1 is a PB lens corresponding to the optical element 10 of the second embodiment described above. Fig.28 As shown, the optical element 10 of Example 1 includes a circular polarizing plate 400, a first phase difference plate 410, a second phase difference plate 420, and a third phase difference plate 430 in sequence. The first phase difference plate 410 includes a first orientation film 210 and a first optical anisotropic layer 310 in sequence from the circular polarizing plate 400 side. The second phase difference plate 420 includes a second orientation film 220 and a second optical anisotropic layer 320 in sequence from the circular polarizing plate 400 side. The third phase difference plate 430 includes a third orientation film 230 and a third optical anisotropic layer 330 in sequence from the circular polarizing plate 400 side.

[0128] The azimuth angle of the lag axis of the first phase difference plate 410 (i.e., the first optical anisotropic layer 310) is 0°, and the phase difference is λ / 4. The azimuth angle of the lag axis of the second phase difference plate 420 (i.e., the second optical anisotropic layer 320) is 45°, and the phase difference is λ / 2. The azimuth angle of the lag axis of the third phase difference plate 430 (i.e., the third optical anisotropic layer 330) is 0°, and the phase difference is λ / 4. In addition, since the orientation film does not contribute to the lag axis and phase difference of the phase difference plate, the azimuth angle and phase difference of the lag axis of the phase difference plate are the same as the azimuth angle and phase difference of the lag axis of the optical anisotropic layer possessed by the phase difference.

[0129] In Example 1, the diffraction efficiency when three RM layers are stacked is simulated. The design value of the RM layer is determined based on the azimuth angle of the slow axis and the phase difference with respect to light of a wavelength of 550 nm.

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

[0131] like Figure 29 to Figure 32 As shown, the three-layer phase difference plate (i.e., the first phase difference plate 410, the second phase difference plate 420, and the third phase difference plate 430) converts the visible light (wavelength 450nm to 650nm) converted into circularly polarized light by the circular polarization plate into reversed circularly polarized light. Figure 29 to Figure 32 In FIG. 1 , the Poincare sphere (S1-S3 plane) is used to represent the change in the polarization state of each phase difference plate.

[0132] Fig.33 This is a diagram showing Formula 4 obtained from the optical element of Example 1. Fig.33 Indicates the target value after transmission through the full phase difference plate. Fig.34 This is a diagram showing Formula 5 obtained by the optical element of Example 1. Fig.34 It shows the preferred polarization state before the third phase difference plate is transmitted.

[0133] In order to realize a broadband PB lens, Fig.33 As shown, it is preferred that the polarization state after passing through the third phase difference plate 430 satisfies the following (Formula 4).

[0134] [Mathematical formula 6] S3<-0.9……(Formula 4)

[0135] In order to satisfy the above (Formula 4), Fig.34 As shown, it is preferred that the polarization state before passing through the third phase difference plate 430 satisfies the following (Formula 5).

[0136] [Formula 7] (S1 2 +S3 2 )<1 2 -0.9 2 ……(Formula 5)

[0137] In order to satisfy the condition of the above-mentioned (Formula 5), ​​the phase difference of the first optical anisotropic layer 310 included in the first phase difference plate 410 can be set to Δnd, which can be expressed as the following (Formula 6).

[0138] [Mathematical formula 8] cos(Δnd / λ*2π)<(1-0.9 2 ) (1 / 2) ……(Formula 6)

[0139] In the above (Formula 6), λ represents wavelength. In order to make the above (Formula 6) inequality hold true in the wavelength range of 450nm to 650nm, for light with a wavelength of 550nm, Δnd is preferably greater than 120nm and less than 150nm. Here, it is assumed that the wavelength dispersion of the RM layer is plane dispersion or positive wavelength dispersion.

[0140] Fig.35 : is a schematic cross-sectional view showing the structure when the phase difference between the first optical anisotropic layer and the third optical anisotropic layer is set to 150 nm in the optical element of Example 1. In Example 1, further, as Fig.35 As shown, when the phase difference between the first optical anisotropic layer 310 and the third optical anisotropic layer 330 at a wavelength of 550 nm is set to 150 nm, the azimuth angle and phase difference of the slow axis of the second optical anisotropic layer 320 that can obtain good diffraction efficiency in a wide band are studied.

[0141] <Calculation of Diffraction Efficiency> Fig.36 is a diagram illustrating the calculation method of diffraction efficiency. Fig.36 As shown, the diffraction efficiency of the PB lens of the phase difference plate other than the A-plate can be calculated. That is, when S3 of the transmitted light when the circularly polarized light of S3=+1 is incident on the phase difference plate is x, the diffraction efficiency is proportional to "(1-x) / 2".

[0142] In this example, the value of x is calculated by LCDmaster. The results are shown in Fig.37 And, the wavelength characteristics of the diffraction efficiency were obtained using the value of x. The results are shown in Fig.38 . Fig.37 This is a graph showing S3(x) of transmitted light relative to the wavelength of incident light when circularly polarized light with S3=+1 is incident on the optical element of Example 1. Fig.38 This is a graph showing the diffraction efficiency with respect to the wavelength of the incident light when circularly polarized light with S3 = +1 is made incident on the optical element of Example 1. Fig.37 and Fig.38 The graph shows x and the diffraction efficiency when the azimuth angle of the slow axis of the second optical anisotropic layer 320 is 45° and the phase difference at a wavelength of 550 nm is 230 nm.

[0143] The diffraction efficiency was calculated in the same manner when the phase difference at a wavelength of 550 nm and the azimuth of the slow axis of the second optical anisotropic layer 320 were changed. The calculation results are shown in Table 1 below. Fig.38 As shown, only the value of the lowest diffraction efficiency in the visible light region (450 nm to 650 nm) is shown, and evaluation was performed using this value.

[0144] [Table 1]

[0145] In Table 1, a range with high effect is surrounded by a dotted line, and a range with low effect is surrounded by a bold line. Usually, when the diffraction efficiency is lower than 80%, the ghost image is conspicuous and the display is poor. Therefore, the diffraction efficiency needs to be at least 80%, and the diffraction efficiency of the PB lens with higher performance is preferably above 90%, and more preferably above 95%. In addition, when making the PB lens, there are slight deviations in the phase difference and axial direction due to errors during manufacturing. In summary, the design value in the area with high diffraction efficiency and a large allowable range of deviation is used as the effective range, which is surrounded by dotted lines and bold lines in Table 1.

[0146] According to Table 1, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 150 nm and is less than 350 nm, a higher effect can be obtained. In addition, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 210 nm and is less than 290 nm, a higher effect can be obtained.

[0147] (Example 2) Fig.39 Schematic diagram of a cross section of an optical element of Example 2. Fig.39 The diffraction efficiency of the optical element of Example 2 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 in Example 1 except that the phase difference between the first optical anisotropic layer 310 and the third optical anisotropic layer 330 at a wavelength of 550 nm was set to 140 nm.

[0148] [Table 2]

[0149] According to Table 2, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 150 nm and is less than 350 nm, a higher effect can be obtained. In addition, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 210 nm and is less than 290 nm, a higher effect can be obtained.

[0150] (Example 3) Fig.40 Schematic diagram of the cross section of the optical element of Example 3. Fig.40 The diffraction efficiency of the optical element of Example 3 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 in Example 1 except that the phase difference between the first optical anisotropic layer 310 and the third optical anisotropic layer 330 at a wavelength of 550 nm was set to 130 nm.

[0151] [Table 3]

[0152] According to Table 3, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 150 nm and is less than 350 nm, a higher effect can be obtained. In addition, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 210 nm and is less than 290 nm, a higher effect can be obtained.

[0153] (Example 4) Fig.41 Schematic diagram of a cross section of an optical element of Example 4. Fig.41 The diffraction efficiency of the optical element of Example 4 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 in Example 1 except that the phase difference between the first optical anisotropic layer 310 and the third optical anisotropic layer 330 at a wavelength of 550 nm was set to 120 nm.

[0154] [Table 4]

[0155] According to Table 4, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 150 nm and is less than 350 nm, a higher effect can be obtained. In addition, it can be seen that when the azimuth angle of the slow axis of the second optical anisotropic layer 320 exceeds 35° and is less than 50°, and the phase difference of the second optical anisotropic layer 320 at a wavelength of 550 nm exceeds 210 nm and is less than 290 nm, a higher effect can be obtained.

[0156] (Example 5) Fig.42 is a schematic cross-sectional view of the optical element of Example 5. Fig.42The diffraction efficiency of the optical element of Example 5 shown was calculated in the same manner as in Example 1. The results are shown in Table 5. In Example 5, the influence of the azimuth angles of the slow axes of the first optical anisotropic layer 310 and the third optical anisotropic layer 330 being non-parallel was evaluated by setting the azimuth angle of the slow axis of the first optical anisotropic layer 310 to 0° and the phase difference at a wavelength of 550 nm to 140 nm, setting the azimuth angle of the slow axis of the second optical anisotropic layer 320 to 45° and the phase difference at a wavelength of 550 nm to 220 nm, and setting the phase difference at a wavelength of 550 nm of the third optical anisotropic layer 330 to 140 nm, and changing the azimuth angle of the slow axis of the third optical anisotropic layer 330. The azimuth angle of the slow axis of the third optical anisotropic layer 330 was changed in the range of -25° to 25°.

[0157] [Table 5] Azimuth angle of the slow axis of the third optically anisotropic layer [°] Minimum diffraction efficiency -25 73％ -20 80％ -15 87％ -10 92％ -5 96％ 0 98％ 5 99％ 10 96％ 15 92％ 20 86％ 25 80％

[0158] It can be seen from Table 5 that a higher effect can be obtained when the azimuth angle of the slow axis of the third optical anisotropic layer 330 exceeds -25° and is less than 25°. In addition, it can be seen that a higher effect can be obtained when the azimuth angle of the slow axis of the third optical anisotropic layer 330 exceeds -5° and is less than 5°.

[0159] (Example 6) Fig.43 Schematic diagram of the cross section of the optical element of Example 6. Fig.43 The optical element of Example 6 shown in the figure was fabricated and the simulation was confirmed to be appropriate. The method for 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 Axostan. The polarization state of the outgoing light when polarized light with S3=+1 was incident from the Mueller matrix (x in Example 1) was calculated. The calculated values ​​compared with the measured values ​​were calculated by LCDmaster. The measured values ​​and calculated values ​​are shown in Table 6 below.

[0161] [Table 6] Measured value Calculated Value Diffraction efficiency is the smallest wavelength 450nm 450nm S3 of the transmitted light when incident S3 = +1 -0.975 -0.975 Predicted value of diffraction efficiency 99％ 99％

[0162] As shown in Table 6, the measured values ​​are consistent with the calculated values. Therefore, it can be seen that the calculated values ​​of Examples 1 to 5 are reproduced by the actual measurements.

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

[0164] The PB lens of Example 7 can be obtained by further manufacturing a PB lens on the sample of Reference Example 1. The steps of manufacturing the PB lens are shown below.

[0165] A photo-isomerization type photo-alignment film was coated on the optically anisotropic layer of the PB lens prepared in Reference Example 1 (alignment film formation step). Then, a ring-shaped mask with four repeated openings and sealing portions was used to irradiate the lens with 100 mJ / cm 2 Polarized UV (365 nm) (alignment film exposure process). At this time, the mask is designed so that the areas where the polarized UV overlaps and the areas where it does not overlap alternately. The polarization directions of PUV are 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. The film thickness was adjusted so that the phase difference with respect to light of a wavelength of 550 nm was about 270 nm, and RM was applied. That is, RM was applied so that the phase difference of the optical anisotropic layer 300 was λ / 2.

[0167] The wavelength dispersion of RM was positive, Re(450nm) / Re(550nm)≈1.04, Re(650nm) / Re(550nm)≈0.97. After RM coating, curing was performed with 200mJ (365nm) of non-polarized UV (optically anisotropic layer formation step), and the PB lens of Example 7 was obtained.

[0168] The focal length of the PB lens of Example 7 was measured in the same manner as in Reference Example 1, and the focal length was 25 cm. Since the lens was produced using the same mask as in Reference Example 1, the period of 180° rotation of the molecules was the same in the first layer and the second layer. Therefore, the above (Formula A) holds.

[0169] The above (Formula 1) as a general formula is an equation, but in this embodiment, it is an inequality as shown in (Formula A). This means that Fig.44 As shown, in Example 7, although the period of molecular rotation of 180° is long, it is still a single-focus lens. Due to the long period, the mask alignment accuracy required during manufacturing is relaxed, so manufacturing becomes easy. Thus, in Example 7, a method of shortening the focal length without changing the period of molecular rotation is shown, and a method of relaxing the difficulty of manufacturing by limiting the alignment accuracy can be verified. In addition, according to Fig.44 It can be seen that the first anisotropic molecules 311 and the second anisotropic molecules 321 each have a discrete molecular orientation pattern from the center portion toward the end portion of the optical element 10 . Fig.44 This is a graph showing the relationship between the distance from the lens center and the molecular orientation of the optical element of Example 7. Description of Reference Numerals

[0170] 10: Optical components; 10R: PB lens; 20, 20R: mask set; 201, 202, 203, 204, 20M, 20r, 20r-1, 20r-2, 20R1, 20R2, 20R3, 20R4: mask; 20A1, 20A2, 20A3, 20A4, 20Ar, 20Ar-1, 20Ar-2, 20RA1, 20RA2, 20RA3, 20RA4: light-transmitting portion (opening); 20B1, 20B2, 20B3, 20B4, 20Br, 20Br-1, 20Br-2, 20RB1, 20RB2, 20RB3, 20RB4: light shielding part; 301, 302, 303: area; 100, 100R: Support base plate; 200, 200R, 210, 220, 230: oriented film; 300, 300R, 310, 320, 330: optically anisotropic layer; 301, 311, 321, 331: anisotropic molecules; 400: Circular polarization plate; 410, 420, 430: phase difference plates.

Claims

1. An optical element, characterized in that: It has: a first orientation film; a first optically anisotropic layer containing first anisotropic molecules; a second orientation film; as well as The second optically anisotropic layer contains second anisotropic molecules.

2. The optical element according to claim 1, characterized in that The optical element also has: a third alignment film disposed on the second optically anisotropic layer on the opposite side of the second alignment film; as well as The third optically anisotropic layer is provided on the opposite side of the third alignment film to the second optically anisotropic layer and contains third anisotropic molecules.

3. The optical element according to claim 2, characterized in that When the azimuth angle of the slow axis of the first optically anisotropic layer is set to 0°, The azimuth angle of the slow axis of the second optical anisotropic layer is greater than 35° and less than 50°, The azimuth angle of the slow axis of the third optically anisotropic layer exceeds -25° and is less than 25°.

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

5. The optical element according to claim 2, characterized in that When the azimuth angle of the slow axis of the first optically anisotropic layer is set to 0°, The azimuth angle of the slow axis of the second optical anisotropic layer is greater than 35° and less than 50°, The azimuth angle of the slow axis of the third optically anisotropic layer exceeds -5° and is less than 5°.

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

7. The optical element according to claim 1, characterized in that In a plan view, the orientation direction of the first anisotropic molecules and the orientation direction of the second anisotropic molecules are arranged to rotate in a plane from the center portion to the end portion of the optical element. The rotation direction of the first anisotropic molecules is opposite to the rotation direction of the second anisotropic molecules.

8. The optical element according to claim 7, characterized in that The following (Formula A) is satisfied, wherein the molecular orientation in the (Formula A) represents the azimuth 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 center of the lens represents the distance between the first anisotropic molecule and the second anisotropic molecule and the center of the optical element, [Mathematical formula 1] Molecular orientation [°] < 90 / (wavelength [m]) / (focal length [m])*(distance from lens center [m]) 2 ……(Formula A).

9. The optical element according to any one of claims 1 to 8, characterized in that The first anisotropic molecules and the second anisotropic molecules each have a discrete molecular orientation pattern from a central portion to an end portion of the optical element.

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