Optical element and method for manufacturing the same

Abstract

An optical element includes a lens having a curved surface and a phase difference plate curved along the curved surface. The phase difference plate includes a transparent substrate and a liquid crystal layer formed on the transparent substrate. The phase difference plate has a slow axis and a fast axis. A glass transition point Tgne in the direction of the slow axis of the phase difference plate is greater than a glass transition point Tgno in the direction of the fast axis of the phase difference plate.

Description

Technical Field

[0001] This disclosure relates to optical elements and methods for manufacturing the same. Background Technology

[0002] Patent Document 1 describes a curved polarizing plate having a polarizer and a protective film laminated to the polarizer. The protective film has a retardation film. The retardation film is a stretched film containing polycarbonate (PC) resin as its main component. The curved polarizing plate is attached to the curved surface of a lens to obtain a polarizing lens. The polarizing lens is used, for example, as a lens in sunglasses or a camera.

[0003] Patent Document 2 describes a lens having a linear polarizer and a retardation plate. The retardation plate is, for example, a quarter-wavelength plate. A circular polarizer is formed by the linear polarizer and the quarter-wavelength plate. The retardation plate is formed from a cyclic olefin copolymer (COC) resin or the like. Alternatively, a liquid crystal polymer can be used instead of the COC resin to form the retardation plate. The linear polarizer and the retardation plate are each bent at high temperature and then bonded together with an adhesive.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-200731

[0007] Patent Document 2: Japanese Patent Publication No. 2013-519108 Summary of the Invention

[0008] The optical element has a lens and a retardation plate. The retardation plate comprises a transparent substrate and a liquid crystal layer formed on the transparent substrate. Depending on the application of the optical element, from a performance point of view, it is desirable for the lens to have a curved surface.

[0009] One aspect of this disclosure provides a technique for reducing the retardation deviation of a phase retardation plate that bends along the curved surface of a lens.

[0010] One aspect of the optical element disclosed herein includes a lens having a curved surface and a retardation plate curved along the curved surface. The retardation plate includes a transparent substrate and a liquid crystal layer formed on the transparent substrate. The retardation plate has a slow axis and a fast axis. The glass transition point Tgne in the slow axis direction of the retardation plate is larger than the glass transition point Tgno in the fast axis direction of the retardation plate.

[0011] According to one aspect of this disclosure, it is possible to reduce the retardation deviation of a phase retardation plate that bends along the curved surface of a lens. Attached Figure Description

[0012] Figure 1(A) in the figure is a cross-sectional view showing the state of the optical element of the first embodiment before the phase retardation plate is joined to the lens. Figure 1 (B) in the middle is to Figure 1 (A) shows a cross-sectional view of an optical element formed by combining a phase retardation plate and a lens. Figure 1 (C) in the middle is Figure 1 The top view of the optical element shown in (B) is shown in the figure.

[0013] Figure 2 (A) in the figure is a cross-sectional view showing the optical element of the first modified example of the first embodiment. Figure 2 (B) in the figure is a cross-sectional view showing the optical element of the second modification of the first embodiment. Figure 2 (C) in the figure is a cross-sectional view of the optical element of the third modified example of the first embodiment.

[0014] Figure 3 (A) in the figure is a perspective view showing an example of a transparent substrate and an alignment layer. Figure 3 (B) in the text indicates that it is passed through Figure 3 A perspective view of an example of an oriented liquid crystal molecule in an alignment layer shown in (A).

[0015] Figure 4 (A) in the figure is a top view showing the buckling of the phase retardation plate of the optical element in the first reference configuration. Figure 4 (B) in the middle is along Figure 4 A cross-sectional view of line B-B in (A).

[0016] Figure 5 (A) in the diagram is a cross-sectional view of the optical element in the second reference configuration, perpendicular to the Y-axis. Figure 5 (B) in the middle is Figure 5 A cross-sectional view of the optical element (A) perpendicular to the X-axis. Figure 5 (C) in the middle is Figure 5 Top view of the optical element (A) in the image.

[0017] Figure 6 (A) in the figure represents the view from the Y-axis direction. Figure 5 The image is obtained from the liquid crystal molecules at point P101. Figure 6 (B) in the figure represents the view from the X-axis direction. Figure 5 The image is obtained by analyzing the liquid crystal molecules at point P101.

[0018] Figure 7 (A) in the figure represents the view from the Y-axis direction. Figure 5 The image is obtained from the liquid crystal molecules at point P103. Figure 7 (B) in the figure represents the view from the X-axis direction. Figure 5 The image is obtained by analyzing the liquid crystal molecules at point P103.

[0019] Figure 8 This is a diagram illustrating an example of the relationship between the tilt angle of a flat liquid crystal layer and Rd.

[0020] Figure 9 This is a top view of the optical element according to the second embodiment.

[0021] Figure 10 (A) in the diagram is a cross-sectional view representing an example of dry etching. Figure 10 (B) in the diagram is a cross-sectional view representing another example of dry etching.

[0022] Figure 11 (A) in the diagram is a cross-sectional view showing the state of the optical element of the third reference mode before it is joined to the lens. Figure 11 (B) in the text indicates that... Figure 11 (A) shows a cross-sectional view of an optical element formed by combining a phase retardation plate and a lens. Figure 11 (C) in the text represents Figure 11 The top view of the distribution of Rd of the optical element shown in (B) is shown.

[0023] Figure 12 (A) in the figure is a cross-sectional view showing the state of the optical element before the phase retardation plate is joined to the lens in the modified example of the third reference method. Figure 12 (B) in the text indicates that... Figure 12 (A) shows a cross-sectional view of an optical element formed by combining a phase retardation plate and a lens. Figure 12 (C) in the text represents Figure 12 The top view of the distribution of Rd of the optical element shown in (B) is shown.

[0024] Figure 13 (A) in the figure is a cross-sectional view of the optical element according to the third embodiment. Figure 13 (B) in the image is an enlarged view. Figure 13 A cross-sectional view of region B in (A) of the diagram. Figure 13 (C) in the text is an enlarged view. Figure 13 A cross-sectional view of region C in (A).

[0025] Figure 14 (A) in the figure is a cross-sectional view of the optical element of a modified example of the third embodiment. Figure 14 (B) in the image is an enlarged view. Figure 14 A cross-sectional view of region B in (A) of the diagram. Figure 14 (C) in the text is an enlarged view. Figure 14 A cross-sectional view of region C in (A). Detailed Implementation

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that identical or corresponding components are labeled with the same symbols in the drawings, and explanations may sometimes be omitted. Furthermore, in the specification, the tilde “~” indicating a numerical range signifies that the values ​​described before and after it are included as a lower limit and an upper limit.

[0027] (First Embodiment)

[0028] Reference Figure 1 The optical element 1 of the first embodiment will now be described. For the optical element 1, from a performance point of view, it is desirable for the lens 2 to have a curved surface 21, depending on the application.

[0029] Optical element 1 includes lens 2. Lens 2 can be a spherical lens or an aspherical lens. Alternatively, lens 2 can also be any one of a biconcave lens, a plano-concave lens, a concave meniscus lens, a biconvex lens, a plano-convex lens, and a convex meniscus lens.

[0030] Lens 2 has a curved surface 21. The curved surface 21, for example, has a radius of curvature of 10 mm to 100 mm, either entirely or partially. The radius of curvature of the curved surface 21 is preferably 20 mm to 80 mm, more preferably 50 mm to 70 mm. The curved surface 21, for example, is as follows... Figure 1 (A) and Figure 1 (B) shows a concave surface. A concave surface is a surface whose centroid P0 is recessed from its edges. Whether in a section perpendicular to the X-axis or the Y-axis, the centroid P0 of the concave surface is recessed from its edges. The X-axis, Y-axis, and Z-axis are perpendicular to each other. The Z-axis is the normal direction at the centroid P0 of the concave surface. The XY plane is parallel to the tangent plane to the centroid P0 of the concave surface.

[0031] It should be noted that although surface 21 is a concave surface in this embodiment, as... Figure 2 (B) and Figure 2 (C) in the diagram can also represent a convex surface. A convex surface is a surface whose centroid P0 is higher (protrudes) than its edges. Whether the cross-section is perpendicular to the X-axis or the Y-axis, the centroid P0 of the convex surface is higher than its edges.

[0032] The shape of lens 2 is not limited to Figure 1 The circle shown in (C) can also be an ellipse or a polygon (including quadrilaterals), etc.

[0033] Lens 2 can be made of resin or glass. For example, the resin in a resin lens is polycarbonate, polyimide, polyacrylate, or cyclic olefin. For a glass lens, the glass is, for example, BK7 or synthetic quartz.

[0034] Optical element 1 includes a retardation plate 3. The retardation plate 3 is curved along the curved surface 21 of lens 2. The retardation plate 3 includes, for example, a transparent substrate 4, an alignment layer 5 formed on the transparent substrate 4, and a liquid crystal layer 6 formed on the alignment layer 5. The alignment layer 5 can be arbitrarily configured or may not be present.

[0035] Phase retardation plate 3 has a slow axis and a fast axis. When viewed along the Z-axis, the slow axis is along the X-axis, and the fast axis is along the Y-axis. The slow axis is the direction of maximum refractive index, and the fast axis is the direction of minimum refractive index.

[0036] Phase difference plate 3 is, for example, a quarter-wavelength plate. A quarter-wavelength plate and a linear polarizing plate (not shown) can be used in combination. The absorption axis of the linear polarizing plate is offset by 45° from the slow axis of the quarter-wavelength plate. A circular polarizing plate is constructed from the linear polarizing plate and the quarter-wavelength plate.

[0037] The linear polarizer can be positioned on the side opposite to the lens 2 with the phase difference plate 3 as a reference, or it can be positioned between the phase difference plate 3 and the lens 2, or it can be positioned on the side opposite to the phase difference plate 3 with the lens 2 as a reference.

[0038] Phase difference plate 3, for example Figure 1 As shown in (B), from the lens 2 side, it sequentially includes a transparent substrate 4, an alignment layer 5, and a liquid crystal layer 6. It should be noted that, as... Figure 2 (A) and Figure 2 As shown in (C), the phase retardation plate 3 may also include, from the lens 2 side, a liquid crystal layer 6, an alignment layer 5 and a transparent substrate 4 in sequence.

[0039] The transparent substrate 4 is made of, for example, a glass substrate or a resin substrate. The glass substrate or resin substrate may be configured to reflect or absorb one or more of infrared, visible, and ultraviolet light while allowing light of a specific wavelength band to pass through. The transparent substrate 4 may be a single-layer structure of a single substrate, or a multi-layer structure in which films with reflective and absorptive functions are laminated onto the main substrate (glass substrate or resin substrate) to allow light of a specific wavelength band to pass through. Furthermore, the transparent substrate 4 may also be laminated with films that, in addition to reflective and absorptive functions, also provide anti-fouling or other functions.

[0040] For example, the transparent substrate 4 may further comprise a resin film or an inorganic film in addition to a glass substrate or a resin substrate. The resin film may be, for example, a base film for a tone correction filter, a silane coupling agent, or a functional film such as an antifouling film. The resin film may be formed, for example, by screen printing, vapor deposition, spraying, or spin coating. The inorganic film may be, for example, a metal oxide film that functions as an optical interference film (anti-reflection film, wavelength selective filter). The inorganic film may be formed, for example, by sputtering, vapor deposition, or CVD.

[0041] From the viewpoint of bending processability, the transparent substrate 4 is preferably a resin substrate. Specific examples of resins that can be used as resin substrates include polymethyl methacrylate (PMMA), cellulose triacetate (TAC), cyclic olefin polymer (COP), cyclic olefin copolymer (COC), polyethylene terephthalate (PET), or polycarbonate (PC).

[0042] The phase difference (retardation) of the transparent substrate 4 is, for example, 5 nm or less, preferably 3 nm or less. From the viewpoint of reducing color deviation, the smaller the phase difference of the transparent substrate 4, the better; it can also be zero. The phase difference of the transparent substrate 4 is measured, for example, by the parallel Nicol rotation method.

[0043] The glass transition point (Tgf) of the transparent substrate 4 is, for example, 80°C to 200°C, preferably 90°C to 160°C. If the Tgf is within this range, the bending processability is good. The glass transition point of the transparent substrate 4 is determined, for example, by thermomechanical analysis (TMA).

[0044] The thickness T1 of the transparent substrate 4 (refer to) Figure 3 For example, the thickness T1 is 0.01 mm to 0.3 mm, preferably 0.02 mm to 0.1 mm, and more preferably 0.03 mm to 0.09 mm. If T1 is within the above range, both bending processability and handlingability can be obtained. The thickness T1 of the transparent substrate 4 is measured in the normal direction at each point on the curved surface 21 of the lens 2.

[0045] The alignment layer 5 aligns the liquid crystal molecules in the liquid crystal layer 6. The alignment layer 5 may be subjected to processes such as polyimide rubbing, photodecomposition of silane coupling agents or polyimide based on polarized UV irradiation, photodimerization or photoisomerization based on polarized UV irradiation, the use of fine parallel groove structures, flow alignment treatment based on shear force, or alignment treatment based on tilted evaporation of inorganic materials. Multiple processes can be used in combination. Among these, from the viewpoints of alignment constraint force, applicability to curved surfaces, and reduction of foreign matter, the use of photodimerization based on polarized UV irradiation, photoisomerization, or the use of fine parallel groove structures is preferred.

[0046] Materials that undergo photodimerization by polarized UV irradiation can be coumarin, diphenylacetylene, or anthracene. Materials that undergo photoisomerization by polarized UV irradiation can be azobenzene, stilbene, α-imino-β-keto esters, or spiropyran. Materials that undergo both photodimerization and photoisomerization by polarized UV irradiation can be cinnamate, chalcone, or stilbene.

[0047] The alignment layer 5 is applied to the transparent substrate 4. The application method may include, for example, spin coating, rod coating, dip coating, casting, spraying, bead coating, wire rod coating, doctor blade coating, roller coating, curtain coating, slot die coating, gravure coating, reverse slot die coating, microgravure coating, or comma coating. The resin composition is applied to the curved surface 21 of the lens 2 and dried. The solvent in the resin composition is removed by heating after coating. It should be noted that the coating method may also be a solvent-free vapor deposition method.

[0048] The thickness T2 of orientation layer 5 (refer to) Figure 3 For example, the thickness is 1 nm to 20 μm, preferably 50 nm to 10 μm, and more preferably 100 nm to 5 μm. The thickness T2 of the alignment layer 5 is measured in the normal direction at each point on the surface of the transparent substrate 4 where the alignment layer 5 is formed. When the alignment layer 5 has a groove 51, in this specification, the thickness T2 of the alignment layer 5 refers to the distance between the bottom of the groove 51 and the surface of the transparent substrate 4.

[0049] The alignment layer 5 may have multiple grooves 51 that are parallel to each other when viewed in the Z-axis direction on the surface in contact with the liquid crystal layer 6 (see reference). Figure 3 (A)). Multiple grooves 51 are formed, for example, by an embossing method after the resin composition is coated. Multiple grooves 51 are formed, for example, in a striped pattern.

[0050] When viewed along the Z-axis, the long side of groove 51 is in the X-axis direction, and the width of groove 51 is in the Y-axis direction. Compared with forming groove 51 by friction, forming groove 51 by embossing allows for precise control of the size and shape of groove 51 and reduces the ingress of foreign matter.

[0051] The depth D of the groove 51 is, for example, 5 nm to 1000 nm, preferably 10 nm to 300 nm, and more preferably 15 nm to 150 nm. The deeper the groove 51, the greater the orientation confinement force of the liquid crystal molecules 61 in the liquid crystal layer 6. The depth D of the groove 51 can be constant or can be varied as described later.

[0052] The opening width W of the groove 51 is, for example, 5nm to 800nm, preferably 20nm to 300nm, and more preferably 30nm to 150nm.

[0053] The spacing p of the grooves 51 is, for example, 10 nm to 1000 nm, preferably 50 nm to 500 nm, and more preferably 80 nm to 300 nm. The smaller the spacing p, the greater the orientation confinement force of the liquid crystal molecules 61 in the liquid crystal layer 6, and the less likely it is to generate diffraction light.

[0054] The section of groove 51 perpendicular to the long side direction (X-axis direction) is in Figure 3The center can be rectangular, but it can also be triangular. The shallower the groove 51, the wider it is. In this case, the model used in the embossing method is easier to peel off.

[0055] As the material for forming the groove structure, energy-curable resins, such as photocurable or thermocurable resins, are included. Photocurable resins are preferred, especially considering their excellent processability, heat resistance, and durability. Photocurable resin compositions are, for example, compositions comprising monomers, photopolymerization initiators, solvents, and additives (e.g., surfactants, polymerization inhibitors) as needed.

[0056] The glass transition point Tg_al of the alignment layer 5 is, for example, 40°C to 200°C, preferably 50°C to 160°C, and more preferably 70°C to 150°C. If Tg_al is within the above range, the bending processability is good. The glass transition point of the alignment layer 5 is determined, for example, by TMA.

[0057] It should be noted that, as described above, the alignment layer 5 can have any configuration, or it may be absent. In this case, a process can be performed on the transparent substrate 4 to align the liquid crystal molecules of the liquid crystal layer 6. This process can be, for example, the rubbing of polyimide, photodecomposition of silane coupling agents or polyimide based on polarized UV irradiation, photodimerization or photoisomerization based on polarized UV irradiation, flow alignment processing based on shear force, or alignment processing based on tilted evaporation of inorganic materials, etc.

[0058] Liquid crystal layer 6 has a slow axis and a fast axis. The product of the difference Δn (Δn = ne - no) between the refractive index ne of the slow axis and the refractive index no of the fast axis and the dimension d of the liquid crystal layer 6 along the Z-axis is called the retardation Rd. In short, Rd is calculated by the formula Rd = Δn × d.

[0059] like Figure 3 As shown in (B), the liquid crystal layer 6 comprises a plurality of liquid crystal molecules 61 aligned parallel to each other by the alignment layer 5. When viewed along the Z-axis, the long axis of the liquid crystal molecules 61 is along the X-axis, and the short axis is along the Y-axis. In this embodiment, the liquid crystal molecules 61 are rod-shaped liquid crystals, but they can also be disc-shaped liquid crystals.

[0060] The liquid crystal composition used can be a liquid crystal composition with a positive wavelength dispersion of Δn value after curing, or a liquid crystal composition with a negative wavelength dispersion.

[0061] The liquid crystal composition may contain, for example, compounds represented by formulas (a-1) to (a-13) as polymerizable compounds.

[0062]

[0063]

[0064]

[0065] In formulas (a-5) and (a-8) above, n is an integer from 2 to 6. In formulas (a-6) and (a-7) above, R is an alkyl group with 3 to 6 carbon atoms. In formulas (a-11), (a-12) and (a-13) above, n means "positive", indicating a straight chain.

[0066] The liquid crystal layer 6 is formed by coating and drying the liquid crystal composition. The liquid crystal composition may be, for example, a photocurable polymeric liquid crystal containing acrylic or methacrylic groups. The liquid crystal composition may also be a component that does not exhibit a liquid crystal phase on its own. As long as the liquid crystal phase is generated through polymerization, it is acceptable. For example, monofunctional (meth)acrylates, difunctional (meth)acrylates, and trifunctional or higher (meth)acrylates may be used as components that do not exhibit a liquid crystal phase. The polymerizable liquid crystal composition may contain additives. As additives, polymerization initiators, leveling agents, chiral agents, polymerization inhibitors, ultraviolet absorbers, antioxidants, light stabilizers, or dichroic pigments may be used. Multiple additives may also be used in combination.

[0067] The coating method for the liquid crystal composition can be any general coating method. Examples of coating methods for the liquid crystal composition include spin coating, rod coating, extrusion coating, direct gravure coating, reverse gravure coating, or die coating. The solvent in the liquid crystal composition is removed by heating after coating.

[0068] The solvent for the liquid crystal composition is, for example, an organic solvent. Organic solvents include alcohols (e.g., isopropanol), amides (e.g., N,N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), hydrocarbons (e.g., benzene or hexane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate, or propylene glycol monoethyl ether acetate), ketones (e.g., acetone, cyclohexanone, or methyl ethyl ketone), or ethers (e.g., tetrahydrofuran or 1,2-dimethoxyethane). Two or more organic solvents may be used in combination. It should be noted that the liquid crystal layer 6 can also be formed by solvent-free vapor deposition or vacuum implantation.

[0069] The thickness T3 of liquid crystal layer 6 (refer to) Figure 3 The thickness of the liquid crystal layer 6 is determined based on the wavelength of light, the phase difference, and Δn (Δn = ne - no). For example, when the wavelength of light is 543 nm and the phase difference is 1 / 4 wavelength, Rd is 136 nm. When Rd is 136 nm and Δn is 0.1, the thickness T3 of the liquid crystal layer 6 is 1360 nm.

[0070] As described above, the thickness T3 of the liquid crystal layer 6 is determined based on the wavelength, phase difference, and Δn of the light, and is not particularly limited. For example, it is 0.1 μm to 20 μm, preferably 0.2 μm to 10 μm, and more preferably 0.5 μm to 5 μm. It should be noted that the liquid crystal layer 6 is not limited to a quarter-wavelength plate, and can also be a half-wavelength plate, etc.

[0071] The thickness T3 of the liquid crystal layer 6 is measured in the normal direction at each point on the surface of the transparent substrate 4 where the liquid crystal layer 6 is formed. When the alignment layer 5 has a groove 51, in this specification, the thickness T3 of the liquid crystal layer 6 is the distance between the bottom of the groove 51 and the surface of the liquid crystal layer 6 on the side opposite to the transparent substrate 4.

[0072] The glass transition point Tg_a of the liquid crystal layer 6 is, for example, 50°C to 200°C, preferably 80°C to 180°C. If Tg_a is within this range, the bending processability is good. The glass transition point Tg_a of the liquid crystal layer 6 is measured, for example, by TMA.

[0073] The thickness T4 of the phase retardation plate 3 is not particularly limited, for example, it is 0.011 mm to 0.301 mm, preferably 0.021 mm to 0.101 mm, and more preferably 0.031 mm to 0.091 mm. The thickness T4 of the phase retardation plate 3 is measured in the normal direction at each point on the surface of the transparent substrate 4 where the liquid crystal layer 6 is formed.

[0074] Although not shown in the figure, the retardation plate 3 can also be a broadband retardation plate that further includes a second liquid crystal layer stacked on the liquid crystal layer 6. The broadband retardation plate can contain two or more liquid crystal layers, or even three or more. When viewed along the Z-axis, the multiple liquid crystal layers have slow axes with different orientations. When the retardation plate 3 contains multiple liquid crystal layers, it can contain multiple alignment layers, or it can repeatedly contain groups of liquid crystal layers and alignment layers. The multiple alignment layers can be of the same material or different materials.

[0075] The delay of the phase retardation plate 3 is not particularly limited. If it is a quarter-wavelength plate, the delay is, for example, 100nm to 180nm, preferably 110nm to 170nm, and more preferably 120nm to 160nm. When the phase retardation plate 3 is a half-wavelength plate, the delay is, for example, 200nm to 280nm, preferably 210nm to 270nm, and more preferably 220nm to 260nm.

[0076] A broadband retardation plate can be, for example, a retardation plate formed by alternately stacking an alignment layer 5 and a liquid crystal layer 6. The alignment layer 5 and the liquid crystal layer 6 are stacked sequentially from the lens 2 side. It should be noted that a liquid crystal layer formed on a transparent substrate different from that of the lens 2 can be bonded to a liquid crystal layer formed on the lens 2 to form a broadband retardation plate.

[0077] The phase retardation plate 3 is bent and bonded to the lens 2. The bonding layer 7 is, for example, a transparent optical adhesive (OCA), an optically active adhesive (OSA), polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), a cyclic olefin polymer (COP), or a thermoplastic polyurethane (TPU).

[0078] The phase difference (retardation) of the bonding layer 7 is, for example, 5 nm or less, preferably 3 nm or less. From the viewpoint of reducing tone deviation, the smaller the phase difference of the bonding layer 7, the better; it can also be zero. The phase difference of the bonding layer 7 is measured, for example, by the parallel Nicol rotation method.

[0079] The glass transition point of the bonding layer 7 is, for example, -60°C to 100°C, preferably -40°C to 50°C. If the glass transition point of the bonding layer 7 is within the above range, both bending processability and shape conformability can be achieved. The glass transition point of the bonding layer 7 is determined, for example, by TMA.

[0080] The thickness of the bonding layer 7 is, for example, 0.001 mm to 0.1 mm, preferably 0.005 mm to 0.05 mm. If the thickness of the bonding layer 7 is within the above range, both bending processability and shape following ability can be obtained. The thickness of the bonding layer 7 is measured in the normal direction at each point on the curved surface 21 of the lens 2.

[0081] The phase retardation plate 3 and lens 2 are joined while being heated. The glass transition point Tgf of the transparent substrate 4 is set as a reference, and the heating temperature is set, for example, in the range of (Tgf-10)℃ to (Tgf+30)℃, preferably in the range of (Tgf-10)℃ to (Tgf+20)℃. The joining of the phase retardation plate 3 and lens 2 can be performed in a vacuum.

[0082] It should be noted that a phase retardation plate 3 can be installed inside the mold used for injection molding. After bending the phase retardation plate 3, the lens 2 can be injection molded. When the lens 2 and the phase retardation plate 3 are integrated through in-mold molding, the bonding layer 7 is not required.

[0083] Next, refer to Figure 4 The buckling of the retardation plate of the optical element in the first reference configuration will be explained. The optical element 1A in the first reference configuration includes a lens 2A and a retardation plate 3A. The retardation plate 3A includes a transparent substrate 4A, an alignment layer 5A, and a liquid crystal layer 6A. The lens 2A and the retardation plate 3A are bonded, for example, through a bonding layer 7A.

[0084] Previously, during the bending process of the retardation plate 3A, the hardness of the alignment layer 5A and the liquid crystal layer 6A was too high compared to the hardness of the transparent substrate 4A. Consequently, the ease of stretching the alignment layer 5A and the liquid crystal layer 6A was lower than that of stretching the transparent substrate 4A, sometimes causing the retardation plate 3A to buckle. As a result, the thickness of the liquid crystal layer 6A would locally increase, and sometimes the Rd of the retardation plate 3A would change locally. Therefore, the color tone would sometimes change locally.

[0085] Therefore, in the optical element 1 of this embodiment, Ene / Ef is 0.10 to 5.00, and Eno / Ef is 0.10 to 5.00. Ef is the Young's modulus of the transparent substrate 4, Ene is the Young's modulus of the retardation plate 3 in the slow axis direction, and Eno is the Young's modulus of the retardation plate 3 in the fast axis direction. Ef, Ene, and Eno are the Young's moduli of the transparent substrate 4 and the retardation plate 3 at the glass transition point Tgf of the transparent substrate 4. Ef, Ene, and Eno are measured by TMA.

[0086] During the bending process of the retardation plate 3, as described above, the temperature of the retardation plate 3 is heated to a temperature of (Tgf-10)℃~(Tgf+30)℃. If Ene / Ef and Eno / Ef are 5.00 or less, the hardness of the alignment layer 5 and the liquid crystal layer 6 is relatively soft during the bending process of the retardation plate 3, and the ease of stretching of the alignment layer 5 and the liquid crystal layer 6 is as good as the ease of stretching of the transparent substrate 4. Therefore, buckling of the retardation plate 3 can be suppressed, local changes in Rd can be suppressed, and local changes in hue can be suppressed. On the other hand, if Ene / Ef and Eno / Ef are 0.10 or more, the hardness of the alignment layer 5 and the liquid crystal layer 6 is appropriately harder during the bending process of the retardation plate 3. Therefore, flow of the alignment layer 5 and the liquid crystal layer 6 due to gravity and flow of airflow during molding can be suppressed. Preferably, Ene / Ef and Eno / Ef are 0.50 to 4.00, and more preferably, Ene / Ef and Eno / Ef are 0.70 to 3.00.

[0087] (Second Implementation)

[0088] Next, the optical element 1 of the second embodiment will be described. The diagram of the optical element 1 in this embodiment is the same as that of the optical element 1 in the first embodiment described above, and therefore is omitted. Hereinafter, the differences from the first embodiment will be mainly described. It should be noted that the technology of this embodiment can be combined with the technology of the first embodiment described above.

[0089] First, the main reference Figure 5 The optical element 1B of the second reference configuration will be described. For example... Figure 5 (A) and Figure 5 As shown in (B), optical element 1B includes lens 2B and retardation plate 3B. Retardation plate 3B includes transparent substrate 4B, alignment layer 5B, and liquid crystal layer 6B. Lens 2B and retardation plate 3B are bonded, for example, through bonding layer 7B.

[0090] The liquid crystal layer 6B contains a plurality of parallel liquid crystal molecules 61 (see reference). Figure 3 (B)). When viewed along the Z-axis, the long axis of the liquid crystal molecule 61 is the X-axis, and the short axis of the liquid crystal molecule 61 is the Y-axis.

[0091] Through experiments, the inventors discovered the following problem: if a liquid crystal layer 6B of uniform thickness is formed on the curved surface 21B of lens 2B, the deviation of the delay Rd of the liquid crystal layer 6B becomes larger.

[0092] The reasons for the aforementioned problems arising when the thickness of the liquid crystal layer 6B is uniform will be explained. For example... Figure 5 (A) and Figure 5 As shown in (B), the liquid crystal layer 6B is formed on the curved surface 21B of the lens 2B. As a result, at a position on the curved surface 21B that is offset from the centroid P100, the liquid crystal molecules 61 are tilted relative to the XY plane.

[0093] The tilt of liquid crystal molecule 61 in Figure 5 Points P101 and P102 on the first virtual line L101 shown in (C) are different from points P103 and P104 on the second virtual line L102. When viewed along the Z-axis, the first virtual line L101 is a virtual line that passes through the centroid P100 and is parallel to the slow axis. Similarly, when viewed along the Z-axis, the second virtual line L102 is a virtual line that passes through the centroid P100 and is parallel to the fast axis.

[0094] Figure 6 The image shows the tilt of the liquid crystal molecule 61 at point P101 on the first virtual line L101. Figure 6 In the diagram, the dashed line represents liquid crystal molecule 61 at the centroid P100, and the solid line represents liquid crystal molecule 61 at point P101. According to... Figure 6 It can be seen that, compared with the centroid P100, the dimension of liquid crystal molecule 61 in the X-axis direction is smaller at point P101, while the dimension in the Y-axis direction remains unchanged. The same applies at point P102.

[0095] As a result, for points P101 and P102 on the first virtual line L101, compared to the centroid P100, ne decreases while no remains unchanged; therefore, Δn decreases. Additionally, for points P101 and P102, d increases compared to the centroid P100. The decrease in Rd due to the decrease in Δn is greater than the increase in Rd due to the increase in d. Consequently, for points P101 and P102, the product of Δn and d, i.e., Rd, decreases compared to the centroid P100.

[0096] Figure 7 The image shows the tilt of liquid crystal molecule 61 at point P103 on the second virtual line L102. Figure 7 In the diagram, the dashed line represents liquid crystal molecule 61 at the centroid P100, and the solid line represents liquid crystal molecule 61 at point P103. According to... Figure 7It can be seen that, compared with the centroid P100, the Y-axis dimension of liquid crystal molecule 61 at point P103 is slightly smaller, while the X-axis dimension of liquid crystal molecule 61 remains unchanged. The same is true at point P104.

[0097] As a result, for points P103 and P104 on the second virtual line L102, compared to the centroid P100, no decreases while ne remains unchanged; therefore, Δn increases. Additionally, for points P103 and P104, d increases compared to the centroid P100. Therefore, for points P103 and P104, Rd increases compared to the centroid P100.

[0098] Figure 8 An example illustrating the relationship between the tilt angle of a flat liquid crystal layer and the measured value of Rd is shown. Figure 8 In this context, a tilt angle of 0° means that the flat liquid crystal layer is aligned parallel to the XY plane.

[0099] Figure 8 The black circles represent data obtained by rotating the flat liquid crystal layer clockwise and counterclockwise around the second virtual line L102, thus tilting it. A positive tilt angle indicates a clockwise rotation, while a negative tilt angle indicates a counterclockwise rotation.

[0100] Figure 8 The absolute value of the tilt angle of the black circle on the horizontal axis corresponds to the distance between points P101 and P102 on the first virtual line L101 and the centroid P100. The greater the distance between points P101 and P102 and the centroid P100, the greater the absolute value of the tilt angle of the liquid crystal molecule 61, and the smaller Rd.

[0101] on the other hand, Figure 8 The white circles represent data obtained by rotating the flat liquid crystal layer clockwise and counterclockwise around the first virtual line L101, thus tilting it. A positive tilt angle indicates a clockwise rotation, while a negative tilt angle indicates a counterclockwise rotation.

[0102] Figure 8 The absolute value of the tilt angle of the white circle on the horizontal axis corresponds to the distance between points P103 and P104 on the second virtual line L102 and the centroid P100. The greater the distance between points P103 and P104 and the centroid P100, the greater the absolute value of the tilt angle of the liquid crystal molecule 61, and the greater Rd.

[0103] If Figure 8 Comparing the black and white circles, we can see that the trends of Rd differ on the first virtual line L101 and the second virtual line L102. On the first virtual line L101, the greater the distance from the centroid P100, the smaller Rd becomes. On the other hand, on the second virtual line L102, the greater the distance from the centroid P100, the larger Rd becomes.

[0104] It should be noted that although the surface 21B of lens 2B is concave in this reference configuration, it can also be convex. In both convex and concave surfaces, the absolute values ​​of the tilt angles of the liquid crystal molecules 61 are the same. Therefore, the distribution of Rd is the same in both convex and concave surfaces.

[0105] Previously, the difference in Rd was large at points P101 and P102 on the first virtual line L101 and points P103 and P104 on the second virtual line L102. This is because... Figure 8 We can tell by comparing the black circle with the white circle.

[0106] Therefore, in this embodiment, in order to Figure 8 The white circle is close to the black circle, making the thickness of the liquid crystal layer 6 at points P103 and P104 on the second virtual line L102 thinner than the thickness of the liquid crystal layer 6 at points P101 and P102 on the first virtual line L101.

[0107] The thickness distribution of the liquid crystal layer 6 can be controlled, for example, by the anisotropy of the extension of the retardation plate 3 during the bending process. The anisotropy of the extension of the retardation plate 3 during the bending process can be controlled by the difference between Tgne and Tgno. Tgne is the glass transition point in the X-axis direction of the retardation plate 3, and Tgno is the glass transition point in the fast axis direction of the retardation plate 3.

[0108] In the optical element 1 of this embodiment, Tgne is greater than Tgno. During the bending process of the phase retardation plate 3, the temperature of the phase retardation plate 3 is heated to a temperature of (Tgf-10)℃~(Tgf+30)℃.

[0109] If Tgne is greater than Tgno, then during the bending process of the phase retardation plate 3, the extension of the phase retardation plate 3 in the Y-axis direction is greater than the extension of the phase retardation plate 3 in the X-axis direction. As a result, the thickness distribution of the liquid crystal layer 6 is optimized, and the difference in Rd becomes smaller.

[0110] Tgne is, for example, 90°C to 250°C, preferably 120°C to 180°C, and more preferably 130°C to 160°C. On the other hand, Tgno is, for example, 50°C to 180°C, preferably 80°C to 160°C, and more preferably 90°C to 150°C.

[0111] Next, refer to Figure 9 The thickness distribution of the liquid crystal layer 6 in this embodiment will be explained. Figure 9 In the diagram, when viewed along the Z-axis, the first virtual line L1 is a virtual line that passes through the center of gravity P0 and is parallel to the slow axis. Additionally, when viewed along the Z-axis, the second virtual line L2 is a virtual line that passes through the center of gravity P0 and is parallel to the fast axis.

[0112] When viewed along the Z-axis, the dividing line L3 divides each line segment connecting the centroid P0 and the edge of the surface 21 at a ratio of 4:1 from the centroid P0 side to the edge of the surface 21. Furthermore, when viewed along the Z-axis, the first virtual line L1 intersects the dividing line L3 at points P1 and P2, and the second virtual line L2 intersects the dividing line L3 at points P3 and P4.

[0113] The distance between point P1 and the centroid P0 is 0.8 times X1. X1 is the intersection of the straight line extending from the centroid P0 in the positive X-axis direction with the edge of surface 21 and the distance from the centroid P0. The distance between point P2 and the centroid P0 is 0.8 times X2. X2 is the intersection of the straight line extending from the centroid P0 in the negative X-axis direction with the edge of surface 21 and the distance from the centroid P0.

[0114] The distance between point P3 (point 3) and the centroid P0 is 0.8 times Y1. Y1 is the intersection of the straight line extending from the centroid P0 in the positive Y-axis direction with the edge of surface 21, and the distance between Y1 and the centroid P0. The distance between point P4 (point 4) and the centroid P0 is 0.8 times Y2. Y2 is the intersection of the straight line extending from the centroid P0 in the negative Y-axis direction with the edge of surface 21, and the distance between Y2 and the centroid P0.

[0115] According to this embodiment, Figure 9 The sum of the thicknesses ty1 and ty2 of the liquid crystal layer 6 at points P3 and P4 on the second virtual line L2 is less than the sum of the thicknesses tx1 and tx2 of the liquid crystal layer 6 at points P1 and P2 on the first virtual line L1. In short, the following equation (1) holds.

[0116] ty1+ty2<tx1+tx2…(1)

[0117] If equation (1) holds, then the difference in Rd at the position deviating from the center of gravity P0 can be reduced. Figure 8 The difference between the black and white circles (the difference between the black and white circles). This is because the thickness of the liquid crystal layer 6 is varied to reduce the difference in Rd. Therefore, it is possible to suppress color unevenness.

[0118] The thickness of the liquid crystal layer 6 is measured along the normal direction at various points on the curved surface 21 of the lens 2. The thickness of the liquid crystal layer 6 is calculated, for example, by spectral interferometry or by scanning electron microscopy (SEM) images.

[0119] In addition to the above formula (1), the following formula (2) is preferred.

[0120]

[0121] If equation (2) above holds true, the unevenness of Rd in the liquid crystal layer 6 becomes smaller compared to the case where only equation (1) above holds true. Therefore, it is possible to further suppress the unevenness of the color tone. (ty1+ty2) / (tx1+tx2) is preferably greater than 0.80, more preferably greater than 0.85. In addition, (ty1+ty2) / (tx1+tx2) is preferably less than 0.99, more preferably less than 0.98.

[0122] It should be noted that in this embodiment, the thickness distribution of the liquid crystal layer 6 is controlled by the anisotropy of the extension of the phase retardation plate 3 during bending processing, but the thickness distribution of the liquid crystal layer 6 can also be controlled by a dry etching method. As a dry etching method, plasma etching can be used, for example.

[0123] Dry etching is performed, for example, before bending. For example, as... Figure 10 (A) and Figure 10 As shown in (B), in the plasma etching method, a mask M covering a portion of the liquid crystal layer 6 is used, and plasma such as oxygen is used to etch the exposed portion of the liquid crystal layer 6. The mask M is preferably made of glass with excellent etching resistance and rigidity. Multiple masks M of different sizes can be used sequentially to smooth the variation in thickness T3 of the liquid crystal layer 6.

[0124] In plasma etching methods, for example, a RIE (Reactive Ion Etching) device can be used. The gas used to generate the plasma contains, for example, oxygen, and may further contain halogen-containing gases such as CF4 or CCl4. The etching amount can be controlled by factors such as etching time and gas flow rate.

[0125] (Third Implementation)

[0126] Next, the optical element 1 of the third embodiment will be described. Hereinafter, the differences from the first and second embodiments described above will be mainly explained. It should be noted that the technology of this embodiment can be combined with one or more of the technologies of the first and second embodiments described above.

[0127] First, refer to Figure 11 and Figure 12 The optical element 1C of the third reference mode will be described. Figure 11 (C) and Figure 12 In (C), the size of Rd is represented by grayscale. The closer the color is to black from white, the larger the size of Rd of optical element 1C.

[0128] The optical element 1C in the third reference configuration includes a lens 2C and a retardation plate 3C. The retardation plate 3C includes a transparent substrate 4C, an alignment layer 5C, and a liquid crystal layer 6C. The lens 2C and the retardation plate 3C are bonded, for example, through a bonding layer 7C.

[0129] During the bending process of the phase retardation plate 3C, the elongation of the phase retardation plate 3C differs at its edge and center. As a result, the thickness of the phase retardation plate 3C and the thickness of the liquid crystal layer 6C change concentrically. Therefore, Rd shifts concentrically, and the hue shifts concentrically. It should be noted that when the dimension before bending is set as A1 and the dimension after bending is set as A2, the elongation (%) is calculated using the formula "(A2-A1) / A1×100".

[0130] For example, such as Figure 11 As shown in (A), when the curved surface 21C of lens 2C is a concave surface, if as... Figure 11 As shown in (B), when the phase difference plate 3C is bent, its thickness continuously decreases from the edge to the center. This is because the contact points between the phase difference plate 3C and the curved surface 21C are different at the edge and the center, with the center of the phase difference plate 3C contacting the curved surface 21C further back than the edge.

[0131] Therefore, as Figure 11 As shown in (B), the thickness of liquid crystal layer 6C continuously decreases from the edge to the center. The result is as follows: Figure 12 As shown in (C), Rd continuously decreases from the edge of the liquid crystal layer 6C towards the center. Therefore, the hue shifts in a concentric circle pattern.

[0132] In addition, such as Figure 12 As shown in (A), when the surface 21C of lens 2C is a convex surface, if as... Figure 12 As shown in (B), when the phase retardation plate 3C is bent, its thickness will continuously decrease from the center to the edge. This is because the contact time between the phase retardation plate 3C and the curved surface 21C is different at the edge and the center of the phase retardation plate 3C, with the edge of the phase retardation plate 3C contacting the curved surface 21C further back than the center.

[0133] Therefore, as Figure 12 As shown in (B), the thickness of liquid crystal layer 6C continuously decreases from the center to the edge. The result is as follows: Figure 12 As shown in (C), Rd continuously decreases from the center to the edge of the liquid crystal layer 6C. Therefore, the hue shifts in a concentric circle pattern.

[0134] like Figure 13 and Figure 14As shown, the optical element 1 of this embodiment includes a lens 2 and a retardation plate 3. The retardation plate 3 includes a transparent substrate 4, an alignment layer 5, and a liquid crystal layer 6. The lens 2 and the retardation plate 3 are bonded, for example, through a bonding layer 7. The alignment layer 5 has a plurality of parallel grooves 51 on the surface in contact with the liquid crystal layer 6.

[0135] During the bending process of the phase retardation plate 3, the elongation of the phase retardation plate 3 differs at its edge and center. As a result, similar to the third reference method described above, after the bending process of the phase retardation plate 3, the thickness T4 of the phase retardation plate 3 and the thickness T3 of the liquid crystal layer 6 differ at their edges and center.

[0136] For example, such as Figure 13 As shown in (A), when the curved surface 21 of the lens 2 is a concave surface, as explained in the third reference method above, if the phase retardation plate 3 is bent, the thickness T4 of the phase retardation plate 3 and the thickness T3 of the liquid crystal layer 6 continuously thin from the edge of the phase retardation plate 3 towards the center.

[0137] When the curved surface 21 of lens 2 is a concave surface, the elongation of the phase retardation plate 3 is as follows. The elongation of the phase retardation plate 3 at the edge of the phase retardation plate 3 is, for example, 0.1% to 20%, preferably 1% to 20%. In addition, the elongation of the phase retardation plate 3 at the center of the phase retardation plate 3 is, for example, 0.5% to 30%, preferably 1% to 20%.

[0138] In addition, such as Figure 14 As shown in (A), when the curved surface 21 of the lens 2 is a convex surface, as explained in the third reference method above, if the phase retardation plate 3 is bent, the thickness T4 of the phase retardation plate 3 and the thickness T3 of the liquid crystal layer 6 continuously decrease from the center of the phase retardation plate 3 to the edge.

[0139] When the curved surface 21 of lens 2 is a convex surface, the elongation of the phase retardation plate 3 is as follows. The elongation of the phase retardation plate 3 at the center of the phase retardation plate 3 is, for example, 0.1% to 20%, preferably 1% to 20%. In addition, the elongation of the phase retardation plate 3 at the edge of the phase retardation plate 3 is, for example, 0.5% to 30%, preferably 1% to 20%.

[0140] As described in the second embodiment above, these trends also occur when the extension of the phase difference plate 3 has anisotropy in both the X-axis and Y-axis directions. For example, in Figure 9 On the second virtual line L2, as the phase retardation plate 3 moves from its edge toward the center, the thickness T4 of the phase retardation plate 3 and the thickness T3 of the liquid crystal layer 6 continuously decrease or increase. Figure 9 The same trend also occurs on the first virtual line L1. It should be noted that this trend... Figure 9 It is particularly evident on the second virtual line L2.

[0141] Therefore, in the optical element 1 of this embodiment, the depth D of the groove 51 at the thinnest part of the phase retardation plate 3 (thickest ..."thickest part of the phase retardation plate 3 ("thickest part of the phase retardation plate 3 ("thickest part of the phase retardation plate 3 ("thickest

[0142] The deeper the groove 51, the greater the orientation constraint force of the liquid crystal molecules in the liquid crystal layer 6, and the larger Δn. The increase in Rd caused by the increase in Δn can offset the decrease in Rd caused by the decrease in d, thus suppressing the deviation of Rd.

[0143] For example, such as Figure 13 As shown in (A), when the curved surface 21 of lens 2 is a concave surface, if... Figure 13 (B) in Figure 13 By comparing (C) in the diagram, it can be seen that the depth D of the groove 51 in the center of the phase retardation plate 3 is deeper than the depth D of the groove 51 at the edge of the phase retardation plate 3. The depth D of the groove 51 increases continuously or intermittently from the edge of the phase retardation plate 3 towards the center. Therefore, it is possible to suppress concentric shifts in Rd and to suppress concentric shifts in hue.

[0144] In addition, such as Figure 14 As shown in (A), when the curved surface 21 of lens 2 is a convex surface, if... Figure 14 (B) in Figure 14 By comparing (C) in the diagram, it can be seen that the depth D of the groove 51 at the edge of the phase retardation plate 3 is deeper than the depth D of the groove 51 at the center of the phase retardation plate 3. The depth D of the groove 51 increases continuously or in stages from the center of the phase retardation plate 3 to the edge. Therefore, it is possible to suppress the concentric shift of Rd and the concentric shift of hue.

[0145] It should be noted that, as mentioned above, in Figure 9 On the second virtual line L2, with Figure 9 Compared to the first virtual line L1, the difference in thickness T4 of the phase retardation plate 3 is larger at its edge and center, and the difference in thickness T3 of the liquid crystal layer 6 is also larger. Therefore, it is preferable that, at least on the second virtual line L2, the depth D of the groove 51 at the thinnest part of the phase retardation plate 3 (thickest thickness T4) is deeper than the depth D of the groove 51 at the thickest part of the phase retardation plate 3 (thickest thickness T4).

[0146] Example

[0147] The experimental data are explained below.

[0148] <Materials>

[0149] Monomer 1: NK ESTETR A-DCP, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., is a dimethyloltricyclodecane diacrylate.

[0150] Monomer 2: 1,6-Hexanediol acrylate, produced by Shin-Nakamura Chemical Industry Co., Ltd.

[0151] Monomer 3: Kyoei Chemical Co., Ltd.'s product name "Light Acrylate 4EG-A" triethylene glycol diacrylate

[0152] Monomer 4: Tokyo Chemical Industry Co., Ltd., product name: Trimethylolpropane trimethacrylate

[0153] Monomer 5: Product name "U-6LPA" from Shin-Nakamura Chemical Industry Co., Ltd.

[0154] Monomer 6: Tokyo Chemical Industry Co., Ltd. Product Name: "Tetrahydrofurfuryl acrylate"

[0155] LCD 1: BASF's product name "LC242"

[0156] Photopolymerization initiator 1: Ciba Specialty Chemicals' product name "IRGACURE907"

[0157] Solvent 1: Methyl ethyl ketone

[0158] Transparent substrate 1: PMMA film (manufactured by Okura Kogyo Co., Ltd., OXIS FZ-T13-W1-40, thickness 40μm)

[0159] Transparent substrate 2: TAC film (Fujifilm ZRD40SL, 40μm thick).

[0160] <Photocurable Composition 1>

[0161] Mix 20g of monomer 2, 50g of monomer 3, 30g of monomer 4 and 3.0g of photopolymerization initiator 1 to prepare photocurable composition 1.

[0162] <Photocurable Composition 2>

[0163] 70g of monomer 1, 10g of monomer 2, 20g of monomer 5 and 3.0g of photopolymerization initiator 1 were mixed to prepare photocurable composition 2.

[0164] <Photocurable Composition 3>

[0165] Mix 50g of monomer 1, 50g of monomer 5 and 3.0g of photopolymerization initiator 1 to prepare photocurable composition 3.

[0166] <Photocurable Composition 4>

[0167] 20g of monomer 1, 60g of monomer 2, 20g of monomer 5 and 3.0g of photopolymerization initiator 1 were mixed to prepare photocurable composition 4.

[0168] <Liquid Crystal Composition 1>

[0169] 100g of liquid crystal 1 and 3.0g of photopolymerization initiator 1 were mixed, and the resulting mixture was diluted with solvent 1 to a solid component concentration of 25% by mass to obtain liquid crystal composition 1.

[0170] <Liquid Crystal Composition 2>

[0171] Mix 50g of liquid crystal 1, 50g of monomer 6 and 3.0g of photopolymerization initiator 1, and dilute the resulting mixture with solvent 1 to a solid component concentration of 50% by mass to obtain liquid crystal composition 2.

[0172] <Model A>

[0173] As model A, a resin model (LSP70-140, groove spacing 140nm, groove depth 150nm) manufactured by Soken Chemical Co., Ltd. was prepared.

[0174] <Model B>

[0175] Model B was fabricated according to the following steps. First, the photocurable composition 2 was sandwiched between model A and a PET film (COSMOSHINE A4300 manufactured by Toyobo Co., Ltd., 250 μm thick). While maintaining a gap of 5 μm, the photocurable composition 2 was irradiated with 1000 mJ / cm² through the PET film. 2 Ultraviolet light is used to cure the photocurable composition 2. Then, model A is peeled off to create model B. The raised pattern of model B is formed by flipping the raised pattern of model A.

[0176] <Model C>

[0177] Model C was fabricated according to the following steps. First, a disc-shaped mask was placed in the center of model B, and model B was ashed under vacuum with oxygen at 200 ml / min and an output of 400 W. Then, photocurable composition 1 was sandwiched between model B and a PET film (COSMOSHINE A4300 manufactured by Toyobo Co., Ltd., with a thickness of 250 μm). While maintaining a gap of 5 μm, photocurable composition 1 was irradiated with 1000 mJ / cm through the PET film. 2Ultraviolet light is used to cure the photocurable composition 1. Then, model B is peeled off to create model C. The raised pattern of model C is formed by flipping the raised pattern of model B. The raised pattern of model C is a square with one side of 80 mm when viewed from above, with a groove depth of 95 nm in the center and groove depth of 25 nm at the outer edge 40 mm from the center.

[0178] <Optical Components>

[0179] In Examples 1 to 8 below, optical elements were fabricated using the materials and models described above. Examples 1, 2, 5, 6, and 8 below are exemplary cases, and Examples 3, 4, and 7 below are comparative examples.

[0180] (Example 1)

[0181] The alignment layer is fabricated according to the following steps. First, the photocurable composition 1 is sandwiched between model A and transparent substrate 1, maintaining a gap of 5 μm. Then, the photocurable composition 1 is irradiated with 1000 mJ / cm² through the transparent substrate 1. 2 Ultraviolet light is used to cure the photocurable composition 1. Then, model A is peeled off, thereby creating a laminate with an oriented layer 1 having an uneven surface and a transparent substrate 1. The groove spacing of the oriented layer 1 is 140 nm, and the groove depth is 140 nm.

[0182] The liquid crystal layer was fabricated according to the following steps. First, the above-mentioned liquid crystal composition 1 was coated onto the surface of the alignment layer with unevenness using a spin coating method, and dried at 90°C for 5 minutes to form a liquid film with a thickness of 1 μm. The liquid film was then irradiated with 1000 mJ / cm under a nitrogen atmosphere. 2 Ultraviolet light is used to cure the liquid crystal composition 1. This yields a retardation plate comprising a liquid crystal layer, an alignment layer, and a transparent substrate.

[0183] The optical element is fabricated according to the following steps. First, a plano-concave lens (manufactured by Edmund Optics, product code #45-038, diameter 50mm) is prepared as the lens. Next, an optical adhesive (manufactured by PANAC, PDS1, thickness 25μm) is applied to the surface of the transparent substrate of the retardation plate. Then, inside a vacuum chamber, the concave surface of the plano-concave lens is positioned upwards, and the retardation plate is placed above it. The retardation plate is positioned horizontally with the optical adhesive downwards. Next, the inside of the vacuum chamber is evacuated, and the retardation plate is heated to 115°C and brought into contact with the concave surface of the plano-concave lens. Under an air pressure of 300 kPa, the retardation plate is pressed against the concave surface, and the retardation plate is bent. Thus, the optical element is obtained.

[0184] (Example 2)

[0185] The optical element is fabricated in the same manner as in Example 1, except that a photocurable composition 2 is used instead of a photocurable composition 1.

[0186] (Example 3)

[0187] Using SIR-W044AP (liquid crystal composition 3) manufactured by Osaka Organic Chemicals Co., Ltd. instead of liquid crystal composition 1, the thickness of the liquid crystal layer was 1 μm. Otherwise, the optical element was fabricated in the same manner as in Example 1.

[0188] (Example 4)

[0189] The optical element is fabricated in the same manner as in Example 1, except that a photocurable composition 3 is used instead of a photocurable composition 1.

[0190] (Example 5)

[0191] Using transparent substrate 2 instead of transparent substrate 1, the phase retardation plate is heated to 145°C, and the optical element is fabricated in the same manner as in Example 4.

[0192] (Example 6)

[0193] The optical element is fabricated in the same manner as in Example 1, except that a photocurable composition 4 is used instead of a photocurable composition 1.

[0194] (Example 7)

[0195] Using transparent substrate 2 instead of transparent substrate 1, and liquid crystal composition 2 instead of liquid crystal composition 1, the thickness of the liquid crystal layer is 2μm. The phase retardation plate is heated to 145°C. Otherwise, the optical element is fabricated in the same manner as in Example 1.

[0196] (Example 8)

[0197] Use model C instead of model A to fabricate the alignment layer; otherwise, fabricate the optical elements in the same manner as in Example 1.

[0198] <Glass transition point>

[0199] The glass transition points of the transparent substrate and the retardation plate were determined by TMA according to the following steps. A sample with a length of 8 mm and a width of 5 mm was mounted on the TMA. The tensile force along the length was maintained at 0.2 N, and the temperature was increased from 30 °C to 200 °C at a rate of 5 °C / min. The dimensional changes of the sample were measured. In the resulting TMA curve, the intersection of the extension of the straight line on the high-temperature side and the extension of the straight line on the low-temperature side was taken as the glass transition point, using the inflection point of the elongation change as a reference. If there were two inflection points, the inflection point on the higher-temperature side was taken as the glass transition point. Three measurements were performed, and the arithmetic mean was taken as the glass transition point. When measuring Tgne, the length direction of the sample was parallel to the slow axis; when measuring Tgno, the length direction of the sample was parallel to the fast axis.

[0200] Young's Modulus

[0201] The Young's modulus of the transparent substrate and the retardation plate was determined by TMA measurement according to the following steps. A specimen with a length of 8 mm and a width of 5 mm was mounted on the TMA. The tensile force along the length was increased from 0.01 N to 1 N at a rate of 0.02 N / min, and the dimensional change of the specimen was measured. When the transparent substrate was PMMA, the specimen temperature was pre-conditioned to 115 °C. Alternatively, when the transparent substrate was TAC, the specimen temperature was pre-conditioned to 145 °C. The Young's modulus was calculated in the strain range of 0.0125–0.05. Three measurements were performed, and the arithmetic mean was taken as the Young's modulus. When measuring Ene, the length direction of the specimen was parallel to the slow axis; when measuring Eno, the length direction of the specimen was parallel to the fast axis.

[0202] <Evaluation of Optical Components>

[0203] The optical elements fabricated in Examples 1-5 and Example 8 were visually inspected to confirm whether the phase retardation plate was buckled. The results are shown in Table 1.

[0204] [Table 1]

[0205]

[0206] As shown in Table 1, in Examples 1, 2, 5, and 8, Ene / Ef and Eno / Ef are below 5.00, therefore there is no buckling. On the other hand, in Examples 3 and 4, at least one of Ene / Ef and Eno / Ef is greater than 5.00, indicating buckling. A steep change in delay was confirmed at the locations of buckling.

[0207] The retardation Rd of the optical elements fabricated in Examples 1, 5-7 was measured. Rd was measured using a two-dimensional birefringence evaluation apparatus (Photonic Lattice, WPA-200), with the retardation plate positioned facing the camera of the evaluation apparatus, and the entire effective area of ​​the retardation plate (a circular area with a diameter of 40 mm) was measured simultaneously. It should be noted that Rd is the retardation of light with a wavelength of 543 nm. The results are shown in Table 2.

[0208] [Table 2]

[0209]

[0210] In Table 2, Rne is... Figure 9 The ratio of the maximum to the minimum value of Rd on the first virtual line L1 shown (maximum value / minimum value), Rno is... Figure 9The ratio of the maximum to the minimum value of Rd on the second virtual line L2 is shown as (maximum value / minimum value). The closer Rne / Rno is to 1.00, the smaller the difference in Rd at points P1 and P2 on the first virtual line L1 and points P3 and P4 on the second virtual line L2. When Rne / Rno is greater than 0.95 and less than 1.05, the distribution of Rd is considered isotropic (concentric circles).

[0211] According to Table 2, in Examples 1, 5, and 6, Tgne is greater than Tgno, therefore Rne / Rno is greater than 0.95 and less than 1.05, and the distribution of Rd is isotropic. On the other hand, in Example 7, Tgne is the same as Tgno, therefore Rne / Rno is greater than 1.05, and the distribution of Rd is not isotropic (concentric circles).

[0212] The retardation Rd of the optical elements fabricated in Examples 1 and 8 was measured. The method for measuring Rd is as described above. The results are shown in Table 3.

[0213] [Table 3]

[0214]

[0215] In Table 3, D1 represents the groove depth of the alignment layer at the thinnest position of the retardation plate within the effective region of the retardation plate, and D2 represents the groove depth of the alignment layer at the thickest position of the retardation plate within the effective region of the retardation plate. Additionally, in Table 3, D3 represents the second virtual line L2 (refer to...). Figure 9 D4 is the depth of the groove in the orientation layer at the position where the thickness of the phase retardation plate on the second virtual line L2 is the thickness of the groove in the orientation layer at the position where the thickness of the phase retardation plate on the second virtual line L2 is the thickness of the groove in the orientation layer.

[0216] In addition, in Table 3, Rmax is the maximum value of Rd in the entire effective region of the phase retardation plate, and Rmin is the minimum value of Rd in the entire effective region of the phase retardation plate. When 2×Rmax / (Rmax+Rmin) is less than 1.030 and 2×Rmin / (Rmax+Rmin) is greater than 0.970, the in-plane deviation of Rd is judged to be smaller.

[0217] According to Table 3, in Example 8, D1 is greater than D2; therefore, compared to Example 1, the in-plane deviation of Rd is smaller. Additionally, in Example 8, D3 is greater than D4; therefore, compared to Example 1, the in-plane deviation of Rd is smaller.

[0218] The optical element and its manufacturing method disclosed herein have been described above, but this disclosure is not limited to the embodiments described above. Various changes, modifications, substitutions, additions, deletions, and combinations can be made within the scope described in the patent claims. These also naturally fall within the technical scope of this disclosure.

[0219] This application claims priority based on Japanese Patent Application No. 2020-135092, filed on August 7, 2020, with the entire contents of which are incorporated herein by reference.

[0220] Symbol Explanation

[0221] 1 Optical Component

[0222] 2 lenses

[0223] 3 phase difference plates

[0224] 4 Transparent substrate

[0225] 5-Orientation Layer

[0226] 6 liquid crystal layers

Claims

1. An optical element comprising a lens having a curved surface and a phase retardation plate curved along said curved surface, The phase retardation plate comprises a transparent substrate and a liquid crystal layer formed on the transparent substrate. The phase difference plate has a slow axis and a fast axis. The glass transition point Tgne of the phase retardation plate in the slow axis direction is larger than the glass transition point Tgno in the fast axis direction of the phase retardation plate.

2. The optical element according to claim 1, wherein, When the temperature of the retardation plate is the glass transition point of the transparent substrate, the ratio of the Young's modulus Ef of the transparent substrate to the Young's modulus Ene in the slow axis direction of the retardation plate, i.e., Ene / Ef, is 0.10 to 5.00, and the ratio of the Young's modulus Ef of the transparent substrate to the Young's modulus Eno in the fast axis direction of the retardation plate, i.e., Eno / Ef, is 0.10 to 5.

00.

3. The optical element according to claim 1 or 2, wherein, The retardation plate includes an alignment layer formed between the transparent substrate and the liquid crystal layer. Viewed from the normal direction at the centroid of the curved surface of the lens, the alignment layer has a plurality of parallel grooves on the surface in contact with the liquid crystal layer.

4. The optical element according to claim 3, wherein, The groove at the thinnest part of the phase retardation plate is deeper than the groove at the thickest part of the phase retardation plate.

5. The optical element according to claim 4, wherein, On a virtual line passing through the center of gravity of the phase retardation plate and parallel to the fast axis, the groove at the thinnest part of the phase retardation plate is deeper than the groove at the thickest part of the phase retardation plate.

6. The optical element according to claim 4 or 5, wherein, The surface is a concave surface. The depth of the groove in the center of the phase retardation plate is greater than the depth of the groove at the edge of the phase retardation plate.

7. The optical element according to claim 4 or 5, wherein, The surface is a convex surface. The depth of the groove at the edge of the phase retardation plate is greater than the depth of the groove at the center of the phase retardation plate.

8. A method for manufacturing an optical element, which is a method for manufacturing the optical element according to claim 1 or 2. This includes bending the phase retardation plate to match the curved surface of the lens.

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