Liquid crystal optical element and method for manufacturing the same

Abstract

The purpose of one embodiment is to provide a liquid crystal optical element that can have an increased area. According to one embodiment, the liquid crystal optical element comprises a substrate, an alignment film disposed on the substrate, and a liquid crystal layer disposed on the alignment film, wherein: the alignment film has a plurality of first regions subjected to an alignment treatment, and a second region surrounding each of the plurality of first regions; the liquid crystal layer has a first alignment region that overlaps the first region and has a plurality of first liquid crystal molecules forming an alignment pattern in which the major axes of the respective liquid crystal molecule continuously change, and a second alignment region that overlaps the second region and has a plurality of second liquid crystal molecules in which the major axes of the respective liquid crystal molecule are arranged side by side in the same direction; and the liquid crystal layer is cured in a state in which alignment directions of the first liquid crystal molecules and second liquid crystal molecules are fixed.

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid crystal optical element and a method for manufacturing the same.

Background Art

[0002] For example, a liquid crystal polarization grating using a liquid crystal material has been proposed. When light with a wavelength λ is incident on such a liquid crystal polarization grating, the incident light is split into zero-order diffracted light and first-order diffracted light. When realizing such a liquid crystal polarization grating, it is necessary to orient liquid crystal molecules complexly in the plane. As types of alignment treatment for aligning liquid crystal molecules, there are photo-alignment treatment and rubbing treatment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the embodiment is to provide a liquid crystal optical element capable of increasing the area and a method for manufacturing the same.

Means for Solving the Problems

[0005] According to one embodiment, a liquid crystal optical element includes a substrate, an alignment film disposed on the substrate, and a liquid crystal layer disposed on the alignment film. The alignment film has a plurality of first regions that have been alignment-treated and second regions that surround the plurality of first regions, respectively. The liquid crystal layer has a first alignment region that overlaps with the first regions and has a plurality of first liquid crystal molecules that form an alignment pattern in which the major axes of each are continuously changed, and a second alignment region that overlaps with the second regions and has a plurality of second liquid crystal molecules whose major axes are arranged in the same direction. The alignment directions of the first liquid crystal molecules and the second liquid crystal molecules are cured in a fixed state.

[0006] According to one embodiment, a method for manufacturing a liquid crystal optical element includes: forming an alignment film on a substrate, performing a first alignment process of interference exposure on the alignment film with a light beam of first circular polarization and a light beam of second circular polarization having a reverse rotation direction to the first circular polarization, performing a second alignment process of exposing the alignment film with a light beam of linear polarization, and forming a liquid crystal layer on the alignment film. According to another embodiment, a method for manufacturing a liquid crystal optical element includes: forming an alignment film on a substrate, performing a first alignment process of interference exposure on the alignment film with a light beam of first circular polarization and a light beam of second circular polarization having a reverse rotation direction to the first circular polarization, performing a second alignment process of rubbing the alignment film, and forming a liquid crystal layer on the alignment film.

Advantages of the Invention

[0007] According to one embodiment, a liquid crystal optical element capable of large area and a method for manufacturing the same can be provided.

Brief Description of the Drawings

[0008]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, this embodiment will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and those that can be easily conceived by those skilled in the art for appropriate changes while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. Also, in this specification and each drawing, components that exhibit the same or similar functions as those described above with respect to the already shown drawings may be given the same reference numerals, and detailed descriptions that overlap may be omitted as appropriate.

[0010] In the drawings, for ease of understanding if necessary, the X-axis, Y-axis, and Z-axis that are orthogonal to each other are described. The direction along the X-axis is referred to as the X-direction or the first direction, the direction along the Y-axis is referred to as the Y-direction or the second direction, and the direction along the Z-axis is referred to as the Z-direction or the third direction. The plane defined by the X-axis and the Y-axis is referred to as the X-Y plane, and the plane defined by the X-axis and the Z-axis is referred to as the X-Z plane. Looking at the X-Y plane is referred to as a plan view.

[0011] FIG. 1 is a diagram schematically showing a liquid crystal optical element 1 according to the present embodiment. The liquid crystal optical element 1 includes a substrate 10, an alignment film 20, and a liquid crystal layer LC.

[0012] The substrate 10 is a transparent substrate that transmits light, and is constituted by, for example, a transparent glass plate or a transparent synthetic resin plate. The substrate 10 may be constituted by, for example, a flexible transparent synthetic resin plate. The substrate 10 can take any shape. For example, the substrate 10 may be curved. The refractive index of the substrate 10 is, for example, larger than the refractive index of air.

[0013] In this specification, "light" includes visible light and invisible light. For example, the lower limit wavelength of the visible light region is 360 nm or more and 400 nm or less, and the upper limit wavelength of the visible light region is 760 nm or more and 830 nm or less. Visible light includes a first component (blue component) in a first wavelength band (for example, 400 nm to 500 nm), a second component (green component) in a second wavelength band (for example, 500 nm to 600 nm), and a third component (red component) in a third wavelength band (for example, 600 nm to 700 nm). Invisible light includes ultraviolet rays in a wavelength band shorter than the first wavelength band and infrared rays in a wavelength band longer than the third wavelength band. In this specification, "transparent" preferably means colorless and transparent. However, "transparent" may be translucent or colored and transparent.

[0014] The substrate 10 is formed in a flat plate shape along the X-Y plane and has a first main surface F1 and a second main surface F2. The first main surface F1 and the second main surface F2 are planes substantially parallel to the X-Y plane and face each other in the Z direction. The second main surface F2 is in contact with, for example, air, but may be covered with other thin films.

[0015] The alignment film 20 is disposed on the substrate 10. In the example shown in FIG. 1, the alignment film 20 is in contact with the first main surface F1.

[0016] The liquid crystal layer LC is disposed on the alignment film 20. In the example shown in FIG. 1, the liquid crystal layer LC has a plurality of first alignment regions LC1 and a second alignment region LC2. The plurality of first alignment regions LC1 are arranged in a matrix in the X direction and the Y direction. The second alignment region LC2 is arranged so as to surround the first alignment regions LC1. Among the liquid crystal layer LC, at least each of the first alignment regions LC1 functions as a diffraction portion that diffracts incident light. Although the liquid crystal layer LC will be described in detail later, each of the first alignment region LC1 and the second alignment region LC2 has liquid crystal molecules aligned in a predetermined direction. However, the alignment direction of the liquid crystal molecules in the first alignment region LC1 is different from the alignment direction of the liquid crystal molecules in the second alignment region LC2.

[0017] FIG. 2 is a diagram showing a cross section along the Y direction of the liquid crystal optical element 1 shown in FIG. 1.

[0018] The alignment film 20 is disposed on the substrate 10. The alignment film 20 has a plurality of first regions A1 that have been subjected to alignment treatment and a second region A2 that surrounds these first regions A1. The width W20 of the second region A2 along the Y direction is, for example, about several μm to several cm. Note that the width of the second region A2 along the X direction is also equal to the width W20.

[0019] As will be described in detail later, the alignment process for forming the first region A1 and the second region A2 is a process of imparting an alignment regulating force that defines the alignment direction of the liquid crystal molecules contained in the liquid crystal layer LC to the alignment film 20. For example, it is an optical alignment process that performs alignment processing by light irradiation or an alignment process by rubbing. The alignment film 20 is formed of, for example, polyimide.

[0020] In the liquid crystal layer LC, the first alignment region LC1 is formed on the first region A1, and the second alignment region LC2 is formed on the second region A2. The first alignment region LC1 and the second alignment region LC2 have substantially the same thickness DLC. In one example, the thickness DLC is 1000 nm to 10 μm, and preferably 2000 nm to 6000 nm. The thickness DLC described here corresponds to the thickness along the Z direction when the liquid crystal layer LC is a single layer. Note that the liquid crystal layer LC may be a multilayer body in which a plurality of layers are stacked.

[0021] From the viewpoint of suppressing undesired refraction and reflection at the interface between the alignment film 20 and the liquid crystal layer LC and at the interface between the substrate 10 and the alignment film 20, it is desirable that the refractive indices of the substrate 10, the alignment film 20, and the liquid crystal layer LC are equivalent. Here, equivalent means that the difference in refractive index is 0.1 or less.

[0022] FIG. 3 is a plan view schematically showing an example of the alignment pattern in the liquid crystal layer LC. In the alignment film 20, a plurality of first regions A1 indicated by dotted lines are formed in a matrix in the X direction and the Y direction. The first alignment region LC1 overlapping the first region A1 has a plurality of first liquid crystal molecules LM1. The second alignment region LC2 overlapping the second region A2 has a plurality of second liquid crystal molecules LM2.

[0023] In FIG. 3, among the plurality of first liquid crystal molecules LM1, the alignment direction of the major axis of the first liquid crystal molecule LM11 located near the alignment film 20 is shown, and among the plurality of second liquid crystal molecules LM2, the alignment direction of the major axis of the second liquid crystal molecule LM21 located near the alignment film 20 is shown.

[0024] In the first alignment region LC1, the alignment directions of the first liquid crystal molecules LM11 arranged along the Y direction are different from each other.

[0025] For example, a plurality of first liquid crystal molecules LM11 arranged along the Y direction form an alignment pattern in which the major axes of each continuously change. That is, the alignment direction of each of the first liquid crystal molecules LM11 arranged along the Y direction changes by a certain angle from left to right in the figure. Specifically, the alignment direction of each of the first liquid crystal molecules LM11 arranged along the Y direction changes clockwise from left to right in the figure. Here, although the amount of change in the alignment direction of the first liquid crystal molecules LM11 is constant along the Y direction, it may gradually increase or gradually decrease.

[0026] The alignment directions of the first liquid crystal molecules LM11 arranged along the X direction are substantially the same.

[0027] That is, the spatial phase in the X - Y plane of the first alignment region LC1 is substantially the same along the X direction and different along the Y direction.

[0028] In the second alignment region LC2, the alignment directions of the plurality of second liquid crystal molecules LM21 are substantially the same. That is, a plurality of second liquid crystal molecules LM21 arranged along the X direction and a plurality of second liquid crystal molecules LM21 arranged along the Y direction are arranged such that their major axes face the same direction. The alignment direction of the second liquid crystal molecules LM21 may be in any direction in the X - Y plane. In the illustrated example, the alignment direction of each of the second liquid crystal molecules LM21 is parallel to the X direction. Note that the alignment direction of the second liquid crystal molecules LM21 may be parallel to the Y direction.

[0029] Such a spatial phase in the X - Y plane of the second alignment region LC2 is substantially the same along the X direction and substantially the same along the Y direction.

[0030] Next, a specific configuration example of the liquid crystal optical element 1 according to the present embodiment will be described.

[0031] (First Configuration Example) FIG. 4 is a cross-sectional view schematically showing a first configuration example of the liquid crystal optical element 1. FIG. 4 corresponds to a cross-sectional view including the first alignment region LC1 of the liquid crystal optical element 1 shown in FIG. 1. The first configuration example corresponds to an example in which the liquid crystal layer LC functions as a reflective diffraction grating.

[0032] The liquid crystal layer LC has a plurality of liquid crystal structures LMS. The liquid crystal structure LMS located in the first alignment region LC1 has a first liquid crystal molecule LM11 located on one end side thereof and a first liquid crystal molecule LM12 located on the other end side thereof. The liquid crystal structure LMS located in the second alignment region LC2 has a second liquid crystal molecule LM21 located on one end side thereof and a second liquid crystal molecule LM22 located on the other end side thereof. The first liquid crystal molecules LM11 and the second liquid crystal molecules LM21 are close to the alignment film 20, and the first liquid crystal molecules LM12 and the second liquid crystal molecules LM22 are close to the upper surface US of the liquid crystal layer LC.

[0033] The alignment directions of the first liquid crystal molecules LM11 and the second liquid crystal molecules LM21 are defined by the alignment regulating force of the alignment film 20. Each liquid crystal structure LMS located in the first alignment region LC1 can be regarded as a continuum in which a plurality of first liquid crystal molecules LM1 including the first liquid crystal molecules LM11 and LM12 are arranged in the Z direction. Therefore, when the alignment direction of the first liquid crystal molecule LM11 is defined, the alignment directions of the plurality of first liquid crystal molecules LM1 arranged in the Z direction including the first liquid crystal molecule LM12 are defined according to the alignment direction of the first liquid crystal molecule LM11. As a result, the plurality of first liquid crystal molecules LM1 including the first liquid crystal molecules LM11 and LM12 in each liquid crystal structure LMS are aligned in a predetermined direction in the X-Y plane, respectively. Each liquid crystal structure LMS located in the second alignment region LC2 can be regarded as a continuum in which a plurality of second liquid crystal molecules LM2 including the second liquid crystal molecules LM21 and LM22 are arranged in the Z direction. Therefore, when the alignment direction of the second liquid crystal molecule LM21 is defined, the alignment directions of the plurality of second liquid crystal molecules LM2 arranged in the Z direction including the second liquid crystal molecule LM22 are defined according to the alignment direction of the second liquid crystal molecule LM21. As a result, the plurality of second liquid crystal molecules LM2 in each liquid crystal structure LMS are aligned in a predetermined direction in the X-Y plane, respectively.

[0034] In the liquid crystal layer LC of this embodiment, the alignment directions of a plurality of first liquid crystal molecules LM1 and a plurality of second liquid crystal molecules LM2 are fixed and cured. That is, the alignment directions of the first liquid crystal molecules LM1 and the second liquid crystal molecules LM2 are not controlled according to an electric field. Therefore, the liquid crystal optical element 1 does not include electrodes for alignment control. Such a liquid crystal layer LC is formed, for example, by applying energy such as light to a monomer to polymerize it.

[0035] In Configuration Example 1 shown in FIG. 4, the liquid crystal layer LC has a cholesteric liquid crystal as a liquid crystal structure LMS. In FIG. 4, for the sake of simplicity of the drawing, one liquid crystal molecule LM represents a liquid crystal molecule facing the average alignment direction among a plurality of liquid crystal molecules located in the X-Y plane. The alignment directions of a plurality of first liquid crystal molecules LM11 arranged along the alignment film 20 in the first alignment region LC1 continuously change along the Y direction. The alignment directions of a plurality of second liquid crystal molecules LM21 arranged along the alignment film 20 in the second alignment region LC2 are the same direction.

[0036] Focusing on one liquid crystal structure LMS located in the first alignment region LC1, a plurality of first liquid crystal molecules LM1 are stacked in a spiral shape along the Z direction while rotating. The alignment directions of the first liquid crystal molecule LM11 and the first liquid crystal molecule LM12 are substantially the same. The liquid crystal structure LMS has a helical pitch P. The helical pitch P indicates one period (360 degrees) of the helix.

[0037] The liquid crystal layer LC has a plurality of reflecting surfaces RS as indicated by the dashed line. In one example, the plurality of reflecting surfaces RS are substantially parallel to each other. The reflecting surface RS is inclined at an inclination angle φ with respect to the X-Y plane and has a substantially planar shape extending in a certain direction. The reflecting surface RS selectively reflects a part of the incident light LTi, i.e., the light LTr, and transmits the other light LTt according to Bragg's law. The reflecting surface RS reflects the light LTr according to the inclination angle φ.

[0038] Here, the reflecting surface RS corresponds to a surface where the alignment directions of the liquid crystal molecules LM are aligned, or a surface where the spatial phases are aligned (equiphase surface). Note that the shape of the reflecting surface RS is not limited to a planar shape, and may be a concave or convex curved surface shape, and is not particularly limited.

[0039] The cholesteric liquid crystal, which is the liquid crystal structure LMS, reflects circularly polarized light with the same turning direction as that of the cholesteric liquid crystal among the light of a predetermined wavelength λ included in the selective reflection band Δλ. For example, when the turning direction of the cholesteric liquid crystal is clockwise, among the light of the predetermined wavelength λ, the clockwise circularly polarized light is reflected and the counterclockwise circularly polarized light is transmitted. Similarly, when the turning direction of the cholesteric liquid crystal is counterclockwise, among the light of the predetermined wavelength λ, the counterclockwise circularly polarized light is reflected and the clockwise circularly polarized light is transmitted.

[0040] If the helical pitch of the cholesteric liquid crystal is denoted as P, the refractive index of the liquid crystal molecules for extraordinary light is denoted as ne, and the refractive index of the liquid crystal molecules for ordinary light is denoted as no, generally, the selective reflection band Δλ of the cholesteric liquid crystal for perpendicularly incident light is represented by "no*P~ne*P". In detail, the selective reflection band Δλ of the cholesteric liquid crystal varies according to the tilt angle φ of the reflecting surface RS, the incident angle θi, etc. with respect to the range of "no*P~ne*P".

[0041] Note that the liquid crystal layer LC may be a single layer or a multilayer. When the liquid crystal layer LC is a multilayer, liquid crystal layers with different helical pitches may be laminated, or liquid crystal layers with opposite helical turning directions may be laminated. Also, when the liquid crystal layer LC is a single layer, it may be a liquid crystal layer in which the helical pitch continuously changes.

[0042] (Second Configuration Example) FIG. 5 is a cross-sectional view schematically showing a second configuration example of the liquid crystal optical element 1. FIG. 5 corresponds to a cross-sectional view including the first alignment region LC1 of the liquid crystal optical element 1 shown in FIG. 1. The second configuration example corresponds to an example in which the liquid crystal layer LC functions as a transmissive diffraction grating.

[0043] The liquid crystal layer LC has nematic liquid crystals with aligned alignment directions. In the first alignment region LC1, the alignment directions of a plurality of first liquid crystal molecules LM11 arranged along the alignment film 20 continuously change along the Y direction. In the second alignment region LC2, the alignment directions of a plurality of second liquid crystal molecules LM21 arranged along the alignment film 20 are in the same direction. In addition, when the liquid crystal layer LC is a multilayer body as described above, a part thereof may be a nematic liquid crystal with twisted alignment.

[0044] When the refractive index anisotropy or birefringence of the liquid crystal layer LC is Δn (the difference between the refractive index ne for extraordinary light and the refractive index no for ordinary light of the liquid crystal molecules), the thickness of the liquid crystal layer LC is DLC, and the wavelength of the diffracted light is λ, it is desirable that the retardation Δn·DLC of the liquid crystal layer LC be λ / 2.

[0045] Focusing on one liquid crystal structure LMS located in the first alignment region LC1, the alignment directions of the first liquid crystal molecules LM11 and the alignment directions of the first liquid crystal molecules LM12 are substantially the same. Also, the alignment directions of the first liquid crystal molecules LM1 arranged in the Z direction including the first liquid crystal molecules LM11 and the first liquid crystal molecules LM12 are substantially the same.

[0046] For such a liquid crystal optical element 1, light may be incident from the side of the liquid crystal layer LC, or light may be incident from the side of the substrate 10. Here, the case where light is incident from the side of the liquid crystal layer LC will be described. The incident light LTi is divided into a zero-order diffracted light LT0 and a first-order diffracted light LT1 after passing through the liquid crystal optical element 1. The diffraction angle θd0 of the zero-order diffracted light LT0 is equal to the incident angle θi of the incident light LTi. The diffraction angle θd1 of the first-order diffracted light LT1 is different from the incident angle θi.

[0047] Next, an example of a method for manufacturing the liquid crystal optical element 1 will be described. FIG. 6 is a manufacturing flow for explaining an example of the method for manufacturing the liquid crystal optical element 1 shown in FIG. 1. First, in step 1 (S1) of FIG. 6, an alignment film 20 is formed on the first main surface F1 of the cleaned substrate 10. The alignment film 20 is formed of, for example, polyimide. Subsequently, in step 2 (S2) of FIG. 6, a first alignment process for forming a first region A1 on the alignment film 20 is performed. The first alignment process here is a process by two-beam interference exposure using a light beam of a first circular polarization and a light beam of a second circular polarization that rotates in the opposite direction to the first circular polarization, which will be described in detail later. In one example, the wavelengths of the light beams of the first circular polarization and the second circular polarization are ultraviolet rays. Depending on the type of the alignment film, the first alignment process may be performed using light rays in a first wavelength band instead of ultraviolet rays.

[0048] When manufacturing the liquid crystal optical element 1 having an area larger than the area that can be exposed in one first alignment process, the alignment film 20 is divided into a plurality of regions, and the first alignment process is sequentially performed on each region. The region where the first alignment process is performed by one exposure in this way corresponds to the first region A1 in FIG. 2. The alignment direction of the first region A1 is set to form the alignment pattern of the first liquid crystal molecules LM11 shown in FIG. 3.

[0049] Subsequently, in step 3 (S3) of FIG. 6, a second alignment process for forming a second region A2 on the alignment film 20 is performed. The second alignment process here is a photo-alignment process of exposing with a linearly polarized light beam or an alignment process of rubbing in one direction, which will be described in detail later. Also, the second alignment process is an alignment process performed on the entire alignment film 20. At this time, the region where the first alignment process has been performed may be covered with a mask. The region where the second alignment process is performed without the first alignment process corresponds to the second region A2 in FIG. 2. The alignment direction of the second region A2 is set to form a uniform alignment pattern of the first liquid crystal molecules LM21 shown in FIG. 3.

[0050] Note that the order of step 2 (S2) and step 3 (S3) described above may be reversed. Also, when using polyimide for the alignment film 20, the imidization of the polyimide may be performed before the first alignment process or after the second alignment process. Next, in step 4 (S4) of FIG. 6, a liquid crystal material containing a liquid crystal monomer is applied onto the alignment film 20 to form a film. The liquid crystal material is, for example, a solution in which a liquid crystal monomer for forming a cholesteric liquid crystal is dissolved in a solvent. Since the liquid crystal material contacts the alignment film 20, the solvent has the property of making the liquid crystal monomer soluble and the alignment film 20 insoluble. The liquid crystal material is applied over the entire surface of the alignment film 20 so as to cover the alignment-treated first region A1 and second region A2. Thereafter, the substrate 10 coated with the liquid crystal material is placed in a chamber, and the solvent contained in the liquid crystal material is dried by reducing the pressure inside the chamber.

[0051] Thereafter, the liquid crystal material is baked. As a result, among the liquid crystal molecules contained in the liquid crystal material, the first liquid crystal molecules LM1 overlapping the first region A1 and the second liquid crystal molecules LM2 overlapping the second region A2 are aligned in a predetermined direction according to the alignment treatment direction of the alignment film 20. At this time, the liquid crystal material is formed in a film state in an uncured state.

[0052] Subsequently, in step 5 (S5) of FIG. 6, the liquid crystal material is irradiated with ultraviolet rays to cure the liquid crystal material. The ultraviolet rays are irradiated onto the uncured liquid crystal monomers overlapping the alignment film 20. As a result, the liquid crystal monomers are polymerized to cure the liquid crystal material, thereby obtaining the liquid crystal layer LC.

[0053] According to such an embodiment, the liquid crystal layer LC has first alignment regions LC1 respectively overlapping a plurality of first regions A1. The plurality of first alignment regions LC1 each contain first liquid crystal molecules LM1 forming a predetermined alignment pattern and function as a diffraction grating. In this way, by forming the plurality of first alignment regions LC1 functioning as diffraction gratings on the same substrate, it becomes possible to increase the area of the liquid crystal optical element 1.

[0054] Further, the liquid crystal layer LC has second alignment regions LC2 overlapping the second region A2 between adjacent first alignment regions LC1. The second alignment regions LC2 each contain second liquid crystal molecules LM2 aligned such that their major axes all point in the same direction. Therefore, undesired scattering and clouding in the second alignment regions LC2 are suppressed, and a decrease in the light utilization efficiency in the liquid crystal optical element 1 can be suppressed.

[0055] The reason for forming the second alignment regions LC2 will be described below. As described above, when increasing the area of the liquid crystal optical element 1, it is necessary to divide the alignment film 20 into a plurality of regions, perform first alignment processing on each region, and form the first region A1. At this time, between the regions where the first alignment processing is performed, regions (gaps) where the first alignment processing is not performed with a width of about several μm to several cm may occur. Therefore, second alignment processing is performed on the entire alignment film 20. As a result, even if regions where the first alignment processing is not performed occur, those regions are formed as the second region A2 having an alignment regulating force in the same direction by the second alignment processing. For this reason, among the liquid crystal layer LC, the second liquid crystal molecules LM2 overlapping the second region A2 are aligned such that their respective major axes point in the same direction, forming the second alignment regions LC2. Therefore, it is possible to suppress the alignment disorder of the liquid crystal molecules in the gaps when the first alignment processing is performed.

[0056] Next, the first alignment processing by circularly polarized two - beam interference exposure will be described. FIG. 7 is a diagram for explaining the first alignment processing by circularly polarized two - beam interference exposure. A beam from a laser light source is expanded into a parallel light beam. After this light beam is split into two light beams by a polarization beam splitter, when each passes through a wave plate, it is converted into a first right - handed circular polarization 71 and a second left - handed circular polarization 72. These first circular polarization 71 and second circular polarization 72 interfere on the surface of the alignment film 20. In the region 73 where the first circular polarization 71 and the second circular polarization 72 interfere on the alignment film 20, a spatially varying polarization pattern is recorded as the alignment processing direction AD. An alignment regulating force along the alignment processing direction AD is imparted to the region 73. The first liquid crystal molecules LM1 of the liquid crystal layer LC are aligned along the alignment processing direction AD.

[0057] Hereinafter, some examples of the first alignment treatment described in step 2 (S2) of FIG. 6 and the second alignment treatment described in step 3 (S3) in the manufacturing method of the liquid crystal optical element 1 will be described.

[0058] (Example 1) FIG. 8 is a cross-sectional view for explaining the first alignment treatment and the second alignment treatment in Example 1 of the manufacturing method of the liquid crystal optical element 1.

[0059] In Example 1, the first alignment treatment is performed prior to the second alignment treatment. As shown in the upper part of FIG. 8, the first alignment treatment by interference exposure divides the alignment film 20 into a plurality of regions, and here, the state of performing the first alignment treatment on one region is shown. One region of the alignment film 20 is formed as the first region A1 by performing the first alignment treatment.

[0060] Thereafter, the second alignment treatment shown in the lower part of FIG. 8 is performed. The second alignment treatment in Example 1 is an alignment treatment by exposing with linearly polarized ultraviolet light, and is performed on the entire surface of the alignment film 20. However, in Example 1, in the second alignment treatment step, first, a mask MK having a shielding portion LS corresponding to the first region A1 and an opening AP corresponding to the second region A2 is prepared. Then, the mask MK is aligned so that the shielding portion LS overlaps with the first region A1. The mask MK may be in contact with the alignment film 20 or may be separated from the alignment film 20. Then, linearly polarized ultraviolet light 80 is irradiated through the mask MK. A part of the ultraviolet light 80 is blocked by the shielding portion LS, and the first region A1 is not exposed to the ultraviolet light 80. The ultraviolet light 80 transmitted through the opening AP is irradiated onto the surface of the alignment film 20. The region thus second-aligned is formed as the second region A2. That is, in Example 1, the first region A1 is formed only by the exposure of the first alignment treatment, and the second region A2 is formed only by the exposure of the second alignment treatment. Thereby, an alignment film 20 having the first region A1 and the second region A2 can be obtained. Note that an ND filter may be used instead of the mask MK.

[0061] (Example 2) FIG. 9 is a cross-sectional view for explaining a first alignment treatment and a second alignment treatment in Example 2 of the method for manufacturing the liquid crystal optical element 1. In Example 2, the second alignment treatment is the same as in Example 1 except that it is performed prior to the first alignment treatment.

[0062] First, as shown in the upper part of FIG. 9, a mask MK having a shielding portion LS corresponding to the region where the first region A1 is to be formed and an opening AP corresponding to the region where the second region A2 is to be formed is prepared. Then, the mask MK is disposed so as to overlap the alignment film 20. The mask MK may be in contact with the alignment film 20 or may be spaced apart from the alignment film 20. Then, linearly polarized ultraviolet light 80 is irradiated through the mask MK. A part of the ultraviolet light 80 is blocked by the shielding portion LS. For this reason, the region of the alignment film 20 that overlaps the shielding portion LS is not irradiated with the ultraviolet light 80. The ultraviolet light 80 that has passed through the opening AP is irradiated onto the surface of the alignment film 20. The region thus second-aligned is formed as the second region A2.

[0063] Next, as shown in the lower part of FIG. 9, the mask is removed, and the first alignment treatment is performed on the alignment film 20 that has been second-aligned. The region where the first alignment treatment is performed is the region that overlapped the shielding portion LS and was not aligned in the second alignment treatment, and alignment is performed so as to overlap this region. Then, this region is formed as the first region A1 by performing the first alignment treatment by interference exposure. Thereby, an alignment film 20 having the first region A1 and the second region A2 can be obtained. Also in Example 2, similar to Example 1, an ND filter may be used instead of the mask.

[0064] (Example 3) FIG. 10 is a cross-sectional view for explaining a first alignment treatment and a second alignment treatment in Example 3 of the method for manufacturing the liquid crystal optical element 1. Example 3 is different from the above-described Examples 1 and 2 in that the second alignment treatment is performed without using a mask. Note that the first alignment treatment is the same as in Example 1.

[0065] First, as shown in the upper part of FIG. 10, a first alignment treatment by interference exposure is performed on a plurality of regions of the alignment film 20. Thereby, a first region A1 is formed.

[0066] Then, as shown in the lower part of FIG. 10, a second alignment treatment is performed. The second alignment treatment in Example 3 is an alignment treatment by exposing with linearly polarized ultraviolet light, similar to Example 1, and is performed on the entire surface of the alignment film 20. However, the second alignment treatment is performed with an exposure amount weaker than the exposure amount of the first alignment treatment. In one example, the exposure amount of the first alignment treatment is 900 mJ / cm 2 or more, and the exposure amount of the second alignment treatment is about 300 mJ / cm 2 or so.

[0067] As a result of the inventors' study, it was confirmed that an alignment regulating force is generated in the alignment film if the exposure amount of ultraviolet light to the alignment film is 300 mJ / cm 2 or more. Also, if the exposure amount in the second alignment treatment is 1 / 3 or less of the exposure amount in the first alignment treatment, the alignment treatment direction of the first region A1 formed by the first alignment treatment does not change even when exposed to linearly polarized ultraviolet light during the second alignment treatment. Thereby, an alignment film 20 having a first region A1 and a second region A2 can be obtained.

[0068] (Example 4) FIG. 11 is a cross-sectional view for explaining a first alignment treatment and a second alignment treatment in Example 4 of the method for manufacturing the liquid crystal optical element 1. In Example 4, it is the same as Example 3 except that the second alignment treatment is performed prior to the first alignment treatment.

[0069] First, as shown in the upper part of FIG. 11, a second alignment treatment is performed. Then, as shown in the lower part of FIG. 11, a first alignment treatment is performed. The second alignment treatment in Example 4 is performed with an exposure amount weaker than the exposure amount of the first alignment treatment, similar to Example 3.

[0070] As a result, an alignment film 20 having a first region A1 and a second region A2 can be obtained.

[0071] (Example 5) FIG. 12 is a cross-sectional view for explaining a first alignment process and a second alignment process in Example 5 of the method for manufacturing the liquid crystal optical element 1. Example 5 is different from the above Examples 1 to 4 in that, as the second alignment process, an alignment process of rubbing in one direction is performed instead of the photo-alignment process. Note that the first alignment process is the same as in Example 1.

[0072] In Example 5, the first alignment process is performed prior to the second alignment process. As shown in the upper part of FIG. 12, the first alignment process by interference exposure divides the alignment film 20 into a plurality of regions and performs it a plurality of times. As a result, the first region A1 is formed.

[0073] Subsequently, as shown in the lower part of FIG. 12, a second alignment process is performed on the alignment film 20 that has been subjected to the first alignment process. The second alignment process is performed by a rubbing alignment process.

[0074] Here, the alignment process by rubbing is a process of rubbing an alignment film by applying a rubbing cloth wound around a roller to form a fine groove structure on the surface of the alignment film. In the rubbing process, the rubbing strength can be changed by changing the processing speed (the rotation speed of the roller or the moving speed of the roller) or changing the amount of pressing of the roller against the alignment film.

[0075] The second alignment process of Example 5 is performed on the entire surface of the alignment film 20. However, in Example 5, in the second alignment process step, first, a mask MK having a shielding portion LS corresponding to the first region A1 and an opening AP corresponding to the second region A2 is prepared. Then, the mask MK is aligned so that the shielding portion LS overlaps the first region A1. The mask MK may be in contact with the alignment film 20 or may be spaced apart from the alignment film 20. Then, a rubbing process is performed through the mask MK. The pile 90 of the rubbing cloth contacts the alignment film 20 through the opening AP. By rubbing the surface of the alignment film 20 with the pile 90, a fine groove structure is formed on the alignment film 20. Thereby, the second region A2 is formed. Note that, since the shielding portion LS of the mask MK overlaps the first region A1, the pile 90 of the rubbing cloth does not contact the first region A1. That is, in Example 5, the first region A1 is formed only by the exposure of the first alignment process, and the second region A2 is formed only by the rubbing process of the second alignment process. Thereby, an alignment film 20 having a first region A1 and a second region A2 can be obtained.

[0076] (Example 6) FIG. 13 is a cross-sectional view for explaining a first alignment process and a second alignment process in Example 6 of the method for manufacturing the liquid crystal optical element 1. In Example 6, the second alignment process is the same as that of Example 5 except that it is performed prior to the first alignment process.

[0077] First, as shown in the upper part of FIG. 13, a mask MK having a shielding portion LS corresponding to the region where the first region A1 is to be formed and an opening AP corresponding to the region where the second region A2 is to be formed is prepared. Then, the mask MK is disposed so as to overlap the alignment film 20. The mask MK may be in contact with the alignment film 20 or may be spaced apart from the alignment film 20. Then, a rubbing process is performed through the mask MK. The pile 90 of the rubbing cloth that has contacted the alignment film 20 through the opening AP rubs the surface of the alignment film 20 to form a fine groove structure on the alignment film 20. Thereby, the second region A2 is formed. The pile 90 does not contact the region of the alignment film 20 that overlaps the shielding portion LS. Next, as shown in the lower part of FIG. 13, the mask is removed, and the first alignment treatment is performed on the second-aligned alignment film 20. The region where the first alignment treatment is performed is the region that did not overlap and was not aligned by the shielding portion LS during the second alignment treatment, and the alignment is performed by aligning so as to overlap this region. Then, this region is formed as the first region A1 by performing the first alignment treatment by interference exposure. Thereby, the alignment film 20 having the first region A1 and the second region A2 can be obtained.

[0078] (Example 7) FIG. 14 is a cross-sectional view for explaining the first alignment treatment and the second alignment treatment in Example 7 of the manufacturing method of the liquid crystal optical element 1. Example 7 is different from Example 6 in that the second alignment treatment is performed without using a mask.

[0079] First, as shown in the upper part of FIG. 14, the first alignment treatment by interference exposure is performed on a plurality of regions of the alignment film 20. Thereby, the first region A1 is formed.

[0080] Then, as shown in the lower part of FIG. 14, the second alignment treatment is performed.

[0081] In the second alignment treatment of Example 7, it is desirable to perform the alignment treatment with a weak rubbing strength. The weak rubbing strength here corresponds to the strength at which the alignment treatment direction of the first region A1 does not change. As described above, the rubbing strength can be changed by changing the processing speed and the pushing amount. Thereby, the alignment film 20 having the first region A1 and the second region A2 can be obtained.

[0082] (Example 8) FIG. 15 is a cross-sectional view for explaining the first alignment treatment and the second alignment treatment in Example 8 of the manufacturing method of the liquid crystal optical element 1. Example 8 is the same as Example 7 except that the second alignment treatment is performed prior to the first alignment treatment.

[0083] First, as shown in the upper part of FIG. 15, the second alignment treatment is performed. Then, as shown in the lower part of FIG. 15, the first alignment treatment is performed. In the second alignment treatment of Example 8, similar to Example 7, it is desirable to perform the alignment treatment with a weak rubbing strength. Thereby, the alignment film 20 having the first region A1 and the second region A2 can be obtained.

[0084] As described above, according to the present embodiment, a liquid crystal optical element capable of increasing the area can be provided.

[0085] Although some embodiments of the present invention have been described, these embodiments are merely illustrative by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Description of Reference Numerals

[0086] 1... Liquid crystal optical element, 10... Substrate, 20... Alignment film, LC1... First liquid crystal layer, LC2... Second liquid crystal layer, A1... First region, A2... Second region

Claims

1. Forming an alignment film on a substrate, performing a first alignment treatment in which the alignment film is subjected to interference exposure with a first circularly polarized light beam and a second circularly polarized light beam having a rotation opposite to that of the first circularly polarized light beam; performing a second alignment treatment in which the alignment film is exposed to linearly polarized light; forming a liquid crystal layer on the alignment film; the first alignment treatment is performed on a plurality of regions of the alignment film prior to the second alignment treatment; the second alignment treatment is performed on the entire surface of the alignment film; The method for manufacturing a liquid crystal optical element, wherein the exposure amount in the second alignment treatment is smaller than the exposure amount in the first alignment treatment.

2. Forming an alignment film on a substrate, performing a first alignment treatment in which the alignment film is subjected to interference exposure with a first circularly polarized light beam and a second circularly polarized light beam having a rotation opposite to that of the first circularly polarized light beam; performing a second alignment treatment in which the alignment film is exposed to linearly polarized light; forming a liquid crystal layer on the alignment film; the second alignment treatment is performed on the entire surface of the alignment film prior to the first alignment treatment; the first alignment treatment is performed on a plurality of regions of the alignment film; The method for manufacturing a liquid crystal optical element, wherein the exposure amount in the second alignment treatment is smaller than the exposure amount in the first alignment treatment.

3. Forming an alignment film on a substrate, performing a first alignment treatment in which the alignment film is subjected to interference exposure with a first circularly polarized light beam and a second circularly polarized light beam having a rotation opposite to that of the first circularly polarized light beam; A second alignment treatment is performed to rub the alignment film. forming a liquid crystal layer on the alignment film; the first alignment treatment is performed on a plurality of regions of the alignment film prior to the second alignment treatment; The method for manufacturing a liquid crystal optical element, wherein the second alignment treatment is performed on the entire surface of the alignment film, and the rubbing strength of the second alignment treatment is weak enough not to affect the first alignment treatment.

4. Forming an alignment film on a substrate, performing a first alignment treatment in which the alignment film is subjected to interference exposure with a first circularly polarized light beam and a second circularly polarized light beam having a rotation opposite to that of the first circularly polarized light beam; A second alignment treatment is performed to rub the alignment film. forming a liquid crystal layer on the alignment film; the second alignment treatment is performed on the entire surface of the alignment film prior to the first alignment treatment; The method for manufacturing a liquid crystal optical element, wherein the first alignment treatment is performed on a plurality of regions of the alignment film, and the rubbing strength of the second alignment treatment is weak enough not to affect the first alignment treatment.

Images