Manufacturing method for liquid crystal optical element

Abstract

To provide a manufacturing method for a liquid crystal optical element, capable of forming regions with different reflection wavelengths.SOLUTION: A manufacturing method for a liquid crystal optical element includes applying a liquid crystal material, drying the liquid crystal material under reduced pressure, baking the liquid crystal material, forming a liquid crystal layer with cholesteric liquid crystal including a plurality of liquid crystal molecules stacked in a spiral manner by semi-curing the liquid crystal material with ultraviolet irradiation, forming, with respect to a first region with first cholesteric liquid crystal of a first spiral pitch, a second region with second cholesteric liquid crystal of a second spiral pitch that is smaller than the first spiral pitch in the liquid crystal layer, and fully curing the liquid crystal layer with ultraviolet irradiation.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a method for manufacturing a liquid crystal optical element. [Background technology]

[0002] It is known that changing the helical pitch of cholesteric liquid crystals changes the reflected wavelength. One method for partially changing the reflected wavelength of a liquid crystal layer containing cholesteric liquid crystals is to change the helical pitch by infiltrating a solution into only a specified area. However, this method requires a complicated process because it uses a solution. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-169662 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of this embodiment is to provide a method for manufacturing a liquid crystal optical element that can form regions with different reflection wavelengths. [Means for solving the problem]

[0005] According to this embodiment, a method for manufacturing a liquid crystal optical element is provided, which includes applying a liquid crystal material, drying the liquid crystal material under reduced pressure, baking the liquid crystal material, and semi-curing the liquid crystal material by irradiating it with ultraviolet light to form a liquid crystal layer having cholesteric liquid crystals containing a plurality of liquid crystal molecules stacked in a helical shape, forming a second region in the liquid crystal layer having second cholesteric liquid crystals with a second helical pitch smaller than the first helical pitch in comparison with a first region having first cholesteric liquid crystals with a first helical pitch, and irradiating the liquid crystal layer with ultraviolet light to fully cure the liquid crystal layer. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the liquid crystal optical element according to this embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the first cholesteric liquid crystal and the second cholesteric liquid crystal contained in the liquid crystal layer. [Figure 3] FIG. 3 is a plan view showing an example of the liquid crystal optical element according to this embodiment. [Figure 4] FIG. 4 is a flowchart showing a method for manufacturing a liquid crystal optical element. [Figure 5] FIG. 5 is a diagram showing a process of forming a second region in the liquid crystal layer on the first alignment film. [Figure 6] FIG. 6 is a diagram showing a process of forming a second region in the liquid crystal layer on the first alignment film. [Figure 7] FIG. 7 is a diagram showing a process of forming a second region in the liquid crystal layer on the first alignment film. [Figure 8] FIG. 8 is a cross-sectional view showing an example of the liquid crystal optical element according to this embodiment. [Figure 9] FIG. 9 is a diagram showing a method for manufacturing a liquid crystal optical element. [Figure 10] FIG. 10 is a diagram showing a process of forming a second region in the liquid crystal layer on the transparent substrate. [Figure 11] FIG. 11 is a diagram showing a process of forming a second region in the liquid crystal layer on the transparent substrate. [Figure 12] FIG. 12 is a diagram showing a process of forming a second region in the liquid crystal layer on the transparent substrate. [Figure 13] FIG. 13 is a diagram illustrating an example of the first cholesteric liquid crystal and the second cholesteric liquid crystal contained in the liquid crystal layer. [Figure 14] FIG. 14 is a diagram showing an example of an orientation pattern of the liquid crystal molecules shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present embodiment will be described below with reference to the drawings. The disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily make while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual embodiment for clarity of explanation, but these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are designated by the same reference numerals, and redundant detailed descriptions may be omitted as appropriate.

[0008] In the drawings, mutually perpendicular X-axis, Y-axis, and Z-axis are shown as necessary to facilitate understanding. The direction along the X-axis is referred to as the X-direction or first direction, the direction along the Y-axis is referred to as the Y-direction or second direction, and the direction along the Z-axis is referred to as the Z-direction or third direction. The plane defined by the X-axis and Y-axis is referred to as the XY plane. Viewing the XY plane is referred to as planar view. The first direction X and the second direction Y correspond to directions parallel to the main surfaces of the substrates included in the liquid crystal optical element 100, for example, and the third direction Z corresponds to the thickness direction of the liquid crystal optical element 100.

[0009] [First embodiment] First, the first embodiment will be described with reference to FIGS.

[0010] FIG. 1 is a cross-sectional view showing an example of a liquid crystal optical element 100 according to this embodiment. The liquid crystal optical element 100 includes a transparent substrate 1 , a first alignment film 2 , and a liquid crystal layer 3 .

[0011] The transparent substrate 1 is made of, for example, a transparent glass plate or a transparent synthetic resin plate. The transparent substrate 1 may be made of, for example, a flexible transparent synthetic resin plate. The transparent substrate 1 may have any shape. For example, the transparent substrate 1 may be curved.

[0012] The transparent substrate 1 is formed in a flat plate shape along the XY plane and has a first main surface (outer surface) F1 and a second main surface (inner surface) F2. The first main surface F1 and the second main surface F2 are surfaces that are substantially parallel to the XY plane and face each other in the third direction Z.

[0013] The first alignment film 2 is disposed on the second main surface F2. The first alignment film 2 is a horizontal alignment film having an alignment regulating force along the XY plane. The first alignment film 2 is, for example, a photo-alignment film that is aligned by light irradiation, but may also be an alignment film that is aligned by rubbing, or an alignment film having minute irregularities. The film thickness of the first alignment film 2 along the third direction Z is 5 nm to 300 nm, and preferably 10 nm to 200 nm.

[0014] The liquid crystal layer 3 overlaps the first alignment film 2 in the third direction Z. That is, the first alignment film 2 is located between the transparent substrate 1 and the liquid crystal layer 3, and is in contact with the transparent substrate 1 and the liquid crystal layer 3.

[0015] The liquid crystal layer 3 has a third main surface (inner surface) F3 and a fourth main surface (outer surface) F4. The third main surface F3 is a surface substantially parallel to the XY plane, and the fourth main surface F4 is an uneven surface. The third main surface F3 and the fourth main surface F4 face each other in the third direction Z. The third main surface F3 is in contact with the first alignment film 2. The fourth main surface F4 may be covered with a transparent protective layer.

[0016] The liquid crystal layer 3 is formed using, for example, a mixture of a polymerizable liquid crystal monomer, a polymerizable chiral liquid crystal monomer, and a photoinitiator to which a crosslinking agent is added.

[0017] Examples of photoinitiators that can be used include alkylphenone-based photopolymerization initiators (Omnirad 651), acylphosphine oxide-based photopolymerization initiators (Omnirad TPO H), intramolecular hydrogen abstraction photopolymerization initiators (Omnirad MBF), intramolecular hydrogen abstraction photopolymerization initiators (Irgacure OXE01), and cationic photopolymerization initiators (Omnirad 250).

[0018] As the crosslinking agent, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, trimethylolpropane triacrylate, etc. can be used.

[0019] The liquid crystal layer 3 has a first region AR1 and a second region AR2. As shown in an enlarged schematic view, the first region AR1 contains a first cholesteric liquid crystal CL1. The second region AR2 contains a second cholesteric liquid crystal CL2.

[0020] The first cholesteric liquid crystal CL1 is twisted in a first twisting direction. The first cholesteric liquid crystal CL1 has a helical axis AX1 that is substantially parallel to the third direction Z, and a first helical pitch P11 along the third direction Z. The first helical pitch P11 indicates one period of the helix (the layer thickness along the helical axis AX1 required for the liquid crystal molecules to rotate 360 ​​degrees).

[0021] The second cholesteric liquid crystal CL2 is twisted in the first twisting direction. The second cholesteric liquid crystal CL2 has a helical axis AX2 that is substantially parallel to the third direction Z, and has a second helical pitch P12 along the third direction Z. The second helical pitch P12 indicates one period of the helix (the layer thickness along the helical axis AX2 required for the liquid crystal molecules to rotate 360 ​​degrees). Furthermore, the second helical pitch P12 is different from the first helical pitch P11 and is smaller than the first helical pitch P11.

[0022] The first region AR1 has a thickness T1 along the third direction Z. The second region AR2 has a thickness T2 along the third direction Z. The thickness T2 is smaller than the thickness T1. The thicknesses T1 and T2 are larger than the thickness of the first alignment film 2, and are, for example, 1 μm to 10 μm, and preferably 2 μm to 7 μm.

[0023] The liquid crystal layer 3 has a reflective surface 321 in the first region AR1. Of the light incident on the liquid crystal layer 3, the reflective surface 321 reflects circularly polarized light in a selective reflection band determined according to the first helical pitch P11 of the first cholesteric liquid crystal CL1 and the refractive index anisotropy Δn of the liquid crystal layer 3. For example, when the first rotation direction is clockwise, clockwise circularly polarized light is reflected by the reflective surface 321, and when the first rotation direction is counterclockwise, counterclockwise circularly polarized light is reflected by the reflective surface 321.

[0024] The liquid crystal layer 3 has a reflective surface 322 in the second region AR2. Of the light incident on the liquid crystal layer 3, the reflective surface 322 reflects circularly polarized light in a selective reflection band determined according to the second helical pitch P12 of the second cholesteric liquid crystal CL2 and the refractive index anisotropy Δn of the liquid crystal layer 3. For example, when the first rotation direction is clockwise, clockwise circularly polarized light is reflected by the reflective surface 322, and when the first rotation direction is counterclockwise, counterclockwise circularly polarized light is reflected by the reflective surface 322. In this specification, "reflection" in the liquid crystal layer 3 involves diffraction within the liquid crystal layer 3. In addition, in this specification, circularly polarized light may be strictly circularly polarized light or may be circularly polarized light that approximates elliptically polarized light.

[0025] In the liquid crystal optical element 100 of this example, the reflective surface 321 of the liquid crystal layer 3 reflects a first circularly polarized light that corresponds to the first twirling direction of the first cholesteric liquid crystal CL1 within the selective reflection wavelength band. The reflective surface 322 of the liquid crystal layer 3 reflects a second circularly polarized light that corresponds to the first twirling direction of the second cholesteric liquid crystal CL2 within the selective reflection wavelength band.

[0026] The first main surface F1 is in contact with a low-refractive index medium having a refractive index smaller than that of the transparent substrate 1. Similarly, the fourth main surface F4 is in contact with a low-refractive index medium having a refractive index smaller than that of the liquid crystal layer 3. The low-refractive index medium is, for example, air. The first main surface F1 and the fourth main surface F4 can form the light entrance surface of the liquid crystal optical element 100.

[0027] In this specification, "light" includes visible light and invisible light. For example, the lower limit of the visible light range is 360 nm to 400 nm, and the upper limit of the visible light range is 760 nm to 830 nm. Visible light includes a first component (blue component) in a first wavelength band (e.g., 400 nm to 500 nm), a second component (green component) in a second wavelength band (e.g., 500 nm to 600 nm), and a third component (red component) in a third wavelength band (e.g., 600 nm to 700 nm). Invisible light includes ultraviolet light, which has a shorter wavelength than the first wavelength band, and infrared light, which has a longer wavelength than the third wavelength band. In this specification, "transparent" preferably means colorless transparency, but "transparent" may also mean translucent or colored transparency.

[0028] 2A and 2B are diagrams illustrating an example of the first cholesteric liquid crystal CL1 and the second cholesteric liquid crystal CL2 contained in the liquid crystal layer 3. Fig. 2A shows the first cholesteric liquid crystal CL1 in the first region AR1. Fig. 2B shows the second cholesteric liquid crystal CL2 in the second region AR2.

[0029] 2, the liquid crystal layer 3 is illustrated enlarged in the third direction Z. For simplicity, the liquid crystal molecule LM1 constituting the first cholesteric liquid crystal CL1 and the second cholesteric liquid crystal CL2 is illustrated as one of a plurality of liquid crystal molecules located on the same plane parallel to the XY plane. The alignment direction of the illustrated liquid crystal molecule LM1 corresponds to the average alignment direction of the plurality of liquid crystal molecules located on the same plane.

[0030] Focusing on one first cholesteric liquid crystal CL1, the first cholesteric liquid crystal CL1 is composed of a plurality of liquid crystal molecules LM1 that are spirally stacked along the Z direction while rotating. The plurality of liquid crystal molecules LM1 include a liquid crystal molecule LM11 at one end of the first cholesteric liquid crystal CL1 and a liquid crystal molecule LM12 at the other end of the first cholesteric liquid crystal CL1. The liquid crystal molecule LM11 is adjacent to the third main surface F3 or the first alignment film 2. The liquid crystal molecule LM12 is adjacent to the fourth main surface F4.

[0031] In the liquid crystal layer 3 of the illustrated example, the alignment directions of the plurality of first cholesteric liquid crystals CL1 adjacent to each other along the first direction X are aligned in one direction. That is, the alignment directions of the plurality of liquid crystal molecules LM11 are substantially aligned with each other along the first direction X. In addition, the alignment directions of the plurality of liquid crystal molecules LM12 are also substantially aligned with each other along the first direction X.

[0032] The configuration of the plurality of second cholesteric liquid crystals CL2 in the second region AR2 is similar to the configuration of the first cholesteric liquid crystals CL1.

[0033] In the liquid crystal layer 3, a reflective surface 321 formed in the first region AR1 and a reflective surface 322 formed in the second region AR2 are planar and extend along the XY plane. In the liquid crystal layer 3, the reflective surfaces 321 and 322 are parallel to the second main surface F2. Here, the reflective surfaces 321 and 322 correspond to surfaces on which the alignment direction of the liquid crystal molecules LM1 is aligned or surfaces on which the spatial phase is aligned (equal phase surfaces).

[0034] The liquid crystal layer 3 is hardened with the alignment direction of the liquid crystal molecules LM1 fixed. In other words, the alignment direction of the liquid crystal molecules LM1 is not controlled in response to an electric field. For this reason, the liquid crystal optical element 100 does not include electrodes for forming an electric field in the liquid crystal layer 3.

[0035] Generally, in a liquid crystal layer 3 containing cholesteric liquid crystal, the selective reflection band Δλ for perpendicularly incident light is expressed by the following formula (1) based on the helical pitch P of the cholesteric liquid crystal and the refractive index anisotropy Δn of the liquid crystal layer 3 (the difference between the refractive index ne for extraordinary light and the refractive index no for ordinary light). Δλ=Δn*P …(1) A specific wavelength range of the selective reflection band Δλ is a range of no*P or more and ne*P or less.

[0036] The central wavelength λm of the selective reflection band Δλ is expressed by the following formula (2) based on the helical pitch P of the cholesteric liquid crystal and the average refractive index nav (=(ne+no) / 2) of the liquid crystal layer 3. λm=nav*P …(2) As described above, the first helical pitch P11 is larger than the second helical pitch P12, so the center wavelength of the selective reflection band reflected by the first region AR1 is longer than the center wavelength of the selective reflection band reflected by the second region AR2.

[0037] FIG. 3 is a plan view showing an example of the liquid crystal optical element 100 according to this embodiment. The first area AR1 corresponds to the area indicated by diagonal hatching. The second area AR2 corresponds to the area indicated by dotted hatching. Figures 3(a) and 3(b) show cases where the patterns of the first area AR1 and the second area AR2 are different from each other.

[0038] The first region AR1 and the second region AR2 are perceived as different colors. The first region AR1 reflects light of a first color wavelength among the light incident on the liquid crystal layer 3. The second region AR2 reflects light of a second color wavelength among the light incident on the liquid crystal layer 3. The first color and the second color are different from each other. That is, the first region AR1 is perceived as the first color, and the second region AR2 is perceived as the second color.

[0039] The patterns of the first region AR1 and the second region AR2 are not limited to the examples shown in Figures 3(a) and 3(b). The liquid crystal optical element 100 may also have a third region of a different color from the first region AR1 and the second region AR2. In this case, the helical pitch of the cholesteric liquid crystal in the third region is different from the first helical pitch P11 and the second helical pitch P12.

[0040] FIG. 4 is a flowchart showing a method for manufacturing the liquid crystal optical element 100. First, the transparent substrate 1 is cleaned (step ST1).

[0041] Then, a first alignment film 2 is formed on the second main surface F2 of the transparent substrate 1 (step ST2). A predetermined alignment treatment is performed on the first alignment film 2. At this time, the alignment treatment is performed on the first alignment film 2 so that, for example, an alignment pattern of the liquid crystal molecules LM11 as shown in FIG. 2 is formed.

[0042] Then, a liquid crystal material (a solution containing a monomer material for forming a cholesteric liquid crystal) is applied onto the first alignment film 2 (step ST3).

[0043] Thereafter, the liquid crystal material is dried under reduced pressure (step ST4). Specifically, the pressure inside the chamber is reduced to dry the solvent of the liquid crystal material.

[0044] Furthermore, the liquid crystal material is baked (step ST5). The liquid crystal material is baked, for example, at about 110 degrees for about 3 minutes. By baking, the liquid crystal molecules contained in the liquid crystal material are aligned in a predetermined direction according to the alignment treatment direction of the first alignment film 2. Then, the liquid crystal material is cooled to about room temperature.

[0045] Thereafter, the liquid crystal material is irradiated with ultraviolet light to semi-cure it, thereby forming a liquid crystal layer 3 having cholesteric liquid crystals containing a plurality of liquid crystal molecules stacked in a spiral shape (step ST6). That is, the liquid crystal layer 3 is formed on the first alignment film 2. Here, the liquid crystal material is not completely cured, but is semi-cured by irradiating the liquid crystal material with ultraviolet light for approximately half the time required for complete curing.

[0046] Next, a second region AR2 is formed in the liquid crystal layer 3 on the first alignment film 2 (step ST7). That is, in the liquid crystal layer 3, a second region AR2 having a second cholesteric liquid crystal CL2 with a second helical pitch P12 smaller than the first helical pitch P11 is formed in the first region AR1 having a first cholesteric liquid crystal CL1 with a first helical pitch P11. That is, the helical pitch of the cholesteric liquid crystal in the region corresponding to the second region AR2 is changed. In the liquid crystal layer 3, the step of forming the second regions AR2 is any one of a step of pressing an object against the second regions AR2, a step of heating the second regions AR2, and a step of irradiating the second regions AR2 with ultraviolet light.

[0047] In step ST6, the liquid crystal material is semi-cured, which makes it easier to change the helical pitch of the cholesteric liquid crystal in the second region AR2, thereby shortening the time required for step ST7. Also, for example, if a liquid crystal material with a low degree of polymerization is used, the time and force required to press the object in step ST7 can be reduced.

[0048] Finally, the liquid crystal layer 3 is irradiated with ultraviolet light to be fully cured (step ST8). Here, the liquid crystal layer 3 is fully cured by irradiating it with ultraviolet light for an additional period of time that was shortened in step ST6. As a result, the liquid crystal layer 3 is formed with a first region AR1 and a second region AR2 having different reflection wavelengths.

[0049] 5 is a diagram showing a process of forming the second region AR2 in the liquid crystal layer 3 on the first alignment film 2. FIG. 5 shows a process of pressing an object 30 against the second region AR2 as a process of forming the second region AR2.

[0050] First, the first alignment film 2 and the liquid crystal layer 3 are formed on the transparent substrate 1 through steps ST1 to ST6 shown in FIG.

[0051] Next, the object 30 is pressed against the second region AR2 in the third direction Z. The shape of the object 30 along the XY plane is the same as the desired shape of the second region AR2. Alternatively, the second region AR2 may be formed by pressing the object 30 multiple times while changing locations. Furthermore, the second region AR2 shrinks in the third direction Z due to the pressure being applied, and the film thickness T2 of the second region AR2 is formed to be smaller than the film thickness T1 of the first region AR1. The apparent color of the second region AR2 changes compared to before the pressure was applied.

[0052] According to this embodiment, it is possible to form a second region AR2 in the liquid crystal layer 3, which has a reflection wavelength different from that of the first region AR1. For example, when changing the reflection wavelength by infiltrating a solution into only a predetermined region in the liquid crystal layer 3, the process is complicated because a solution is used. On the other hand, the manufacturing method of this embodiment makes it easier to form regions in the liquid crystal layer 3 with different reflection wavelengths. Furthermore, as shown in FIG. 3, it is possible to form a plurality of regions of different colors, making it possible to create stained glass and the like with sophisticated designs.

[0053] In a comparative example, in a method of changing the reflection wavelength by infiltrating a solution into the liquid crystal layer, the helical pitch in the infiltrated portion is lengthened, the reflection wavelength is shifted to a longer wavelength, and the film thickness is increased. On the other hand, in the manufacturing method of this embodiment, the helical pitch in the second region AR2 is shortened, the reflection wavelength is shifted to a shorter wavelength, and the film thickness is decreased.

[0054] [Second embodiment] Next, a second embodiment will be described with reference to FIG.

[0055] 6 is a diagram showing a process of forming the second region AR2 in the liquid crystal layer 3 on the first alignment film 2. FIG. 6 shows a process of heating the second region AR2 as a process of forming the second region AR2.

[0056] First, the first alignment film 2 and the liquid crystal layer 3 are formed on the transparent substrate 1 through steps ST1 to ST6 shown in FIG.

[0057] Next, the second region AR2 is heated by the heating device 40. At this time, heating is performed, for example, at approximately 230°C for approximately 20 minutes. This process is performed at a higher temperature and for a longer time than the baking process of step ST5 shown in FIG. 4. The shape of the heating device 40 along the XY plane is identical to the desired shape of the second region AR2. Alternatively, the second region AR2 may be formed by heating multiple times using the heating device 40 while changing locations. Furthermore, the second region AR2 shrinks along the third direction Z due to heating, and the film thickness T2 of the second region AR2 is formed to be smaller than the film thickness T1 of the first region AR1. The apparent color of the second region AR2 changes compared to before heating. In the second embodiment, the same effects as in the first embodiment can be obtained.

[0058] [Third embodiment] Next, a third embodiment will be described with reference to FIG.

[0059] Fig. 7 is a diagram showing a process of forming the second region AR2 in the liquid crystal layer 3 on the first alignment film 2. Fig. 7 shows a process of irradiating the second region AR2 with ultraviolet light as a process of forming the second region AR2.

[0060] First, the first alignment film 2 and the liquid crystal layer 3 are formed on the transparent substrate 1 through steps ST1 to ST6 shown in FIG.

[0061] Next, a mask MK is placed above the liquid crystal layer 3. The mask MK has openings OP. The mask MK is placed so that the openings OP overlap the second regions AR2. Then, ultraviolet light is irradiated onto the second regions AR2 from above the mask MK. The shape of the openings OP along the XY plane is the same as the desired shape of the second regions AR2. Alternatively, the second regions AR2 may be formed by irradiating the openings OP with ultraviolet light multiple times while changing their locations. Furthermore, the second regions AR2 are shrunk along the third direction Z by being irradiated with ultraviolet light, and the film thickness T2 of the second regions AR2 is formed to be smaller than the film thickness T1 of the first regions AR1. The apparent color of the second regions AR2 changes compared to before being irradiated with ultraviolet light.

[0062] The ultraviolet irradiation time in this step is, for example, longer than the ultraviolet irradiation time required to fully cure the liquid crystal material. For example, the ultraviolet irradiation time in this step is approximately three times longer than the ultraviolet irradiation time required to fully cure the liquid crystal material. In other words, the ultraviolet irradiation time in this step is approximately three times longer than the combined ultraviolet irradiation time in steps ST6 and ST8. Furthermore, the wavelength of the ultraviolet light in this step is, for example, equal to the wavelength of the ultraviolet light in steps ST6 and ST8. In the third embodiment, the same effects as in the first embodiment can be obtained.

[0063] [Fourth embodiment] Next, a fourth embodiment will be described with reference to FIGS. The fourth embodiment differs from the first embodiment in that the liquid crystal layer 3 is formed outside the liquid crystal optical element 100, and then the liquid crystal layer 3 is transferred onto the transparent substrate 1 to form the second region AR2.

[0064] Fig. 8 is a cross-sectional view showing an example of a liquid crystal optical element 100 according to this embodiment. The configuration shown in Fig. 8 differs from the configuration shown in Fig. 1 in that the first alignment film 2 is not formed.

[0065] An adhesive layer AD is interposed between the transparent substrate 1 and the liquid crystal layer 3. The adhesive layer AD is in contact with the second main surface F2 of the transparent substrate 1 and the third main surface F3 of the liquid crystal layer 3.

[0066] The adhesive layer AD is, for example, transparent. Examples of materials that can be used to form the adhesive layer AD include adhesives such as acrylic resins, urethane resins, enethiol resins, epoxy resins, silicone resins, polyvinyl alcohol resins, polyvinyl acetal resins, and polyvinyl butyral resins, and optical adhesive sheets. The transparent substrate 1 and the liquid crystal layer 3 do not have to be bonded to each other by the adhesive layer AD, and the adhesive layer AD may not be formed and the transparent substrate 1 and the liquid crystal layer 3 may be bonded to each other by intermolecular forces.

[0067] Figure 9 is a diagram showing a method for manufacturing the liquid crystal optical element 100. Figure 9(a) is a flowchart showing the method for manufacturing the liquid crystal optical element 100. Figure 9(b), Figure 9(c), and Figure 9(d) are diagrams showing each step. First, the production substrate 50 is cleaned (step ST11). Here, the production substrate 50 is a substrate different from the transparent substrate 1 and for forming the liquid crystal layer 3 outside the liquid crystal optical element 100.

[0068] Next, a second alignment film 4 is formed on the fifth main surface F5 of the production substrate 50 (step ST12). A predetermined alignment treatment is performed on the second alignment film 4. At this time, the alignment treatment is performed on the second alignment film 4 so that, for example, an alignment pattern of the liquid crystal molecules LM11 as shown in FIG. 2 is formed.

[0069] The second alignment film 4 is a horizontal alignment film having an alignment control force along the XY plane. The second alignment film 4 is, for example, a photo-alignment film that is aligned by light irradiation, but may also be an alignment film that is aligned by rubbing, or an alignment film with minute irregularities.

[0070] Then, a liquid crystal material (a solution containing a monomer material for forming a cholesteric liquid crystal) is applied onto the second alignment film 4 (step ST13).

[0071] Thereafter, the liquid crystal material is dried under reduced pressure (step ST14). Specifically, the pressure inside the chamber is reduced to dry the solvent of the liquid crystal material.

[0072] Furthermore, the liquid crystal material is baked (step ST15). The liquid crystal material is baked, for example, at about 110 degrees for about 3 minutes. By baking, the liquid crystal molecules contained in the liquid crystal material are aligned in a predetermined direction according to the alignment treatment direction of the second alignment film 4. Then, the liquid crystal material is cooled to about room temperature.

[0073] Thereafter, the liquid crystal material is irradiated with ultraviolet light to semi-cure it, thereby forming a liquid crystal layer 3 having cholesteric liquid crystals containing a plurality of liquid crystal molecules stacked in a spiral shape (step ST16). That is, the liquid crystal layer 3 is formed on the second alignment film 4. Here, the liquid crystal material is not completely cured, but is semi-cured by irradiating the liquid crystal material with ultraviolet light for approximately half the time required for complete curing. Note that FIG. 9(b) includes the above-mentioned steps ST11 to ST16.

[0074] Next, as shown in FIG. 9(c), the liquid crystal layer 3 is peeled off from the production substrate 50 and the second alignment film 4 using a release film or the like (step ST17).

[0075] 9(d), the peeled liquid crystal layer 3 is adhered to the transparent substrate 1 using an adhesive layer AD (step ST18). That is, the liquid crystal layer 3 formed on the production substrate 50 is transferred onto the transparent substrate 1. As described above, the liquid crystal layer 3 may be bonded to the transparent substrate 1 by intermolecular forces between the transparent substrate 1 and the liquid crystal layer 3, without using the adhesive layer AD.

[0076] Next, the second region AR2 is formed in the liquid crystal layer 3 on the transparent substrate 1 (step ST19). That is, in the liquid crystal layer 3, a second region AR2 having a second cholesteric liquid crystal CL2 with a second helical pitch P12 smaller than the first helical pitch P11 is formed in relation to a first region AR1 having a first cholesteric liquid crystal CL1 with a first helical pitch P11. In other words, the helical pitch of the cholesteric liquid crystal in the region corresponding to the second region AR2 is changed. In the liquid crystal layer 3, the step of forming the second regions AR2 is any one of a step of pressing an object against the second regions AR2, a step of heating the second regions AR2, and a step of irradiating the second regions AR2 with ultraviolet light.

[0077] In step ST16, the liquid crystal material is semi-cured, which makes it easier to change the helical pitch of the cholesteric liquid crystal in the second region AR2, thereby shortening the time required for the process in step ST19. Also, for example, if a liquid crystal material with a low degree of polymerization is used, the time and force required to press the object in step ST19 can be reduced.

[0078] Finally, the liquid crystal layer 3 is irradiated with ultraviolet light to be fully cured (step ST20). Here, the liquid crystal layer 3 is fully cured by irradiating it with ultraviolet light for an additional period of time that was shortened in step ST16. As a result, the liquid crystal layer 3 is formed with a first region AR1 and a second region AR2 having different reflection wavelengths.

[0079] Fig. 10 is a diagram showing a step of forming a second region AR2 in the liquid crystal layer 3 on the transparent substrate 1. Fig. 10 shows a step of pressing an object 30 against the second region AR2 as a step of forming the second region AR2.

[0080] First, the liquid crystal layer 3 is formed on the transparent substrate 1 through steps ST11 to ST18 shown in FIG.

[0081] Next, the object 30 is pressed against the second area AR2 along the third direction Z. Details of this step are the same as those of the step shown in FIG.

[0082] Fig. 11 is a diagram showing a process of forming the second region AR2 in the liquid crystal layer 3 on the transparent substrate 1. Fig. 11 shows a process of heating the second region AR2 as a process of forming the second region AR2.

[0083] First, the liquid crystal layer 3 is formed on the transparent substrate 1 through steps ST11 to ST18 shown in FIG.

[0084] Next, the second region AR2 is heated by the heating device 40. At this time, heating is performed, for example, at about 230 degrees for about 20 minutes. This process is performed at a higher temperature and for a longer time than the baking process of step ST15 shown in FIG. 9. The details of this process are the same as those of the process shown in FIG.

[0085] Fig. 12 is a diagram showing a step of forming the second region AR2 in the liquid crystal layer 3 on the transparent substrate 1. Fig. 12 shows a step of irradiating the second region AR2 with ultraviolet light as a step of forming the second region AR2.

[0086] First, the liquid crystal layer 3 is formed on the transparent substrate 1 through steps ST11 to ST18 shown in FIG.

[0087] Next, a mask MK is placed above the liquid crystal layer 3. The mask MK has openings OP. The mask MK is placed so that the openings OP overlap the second regions AR2. Then, ultraviolet light is irradiated onto the second regions AR2 from above the mask MK. Note that the details of this step are the same as those of the step shown in FIG. 7. In the fourth embodiment, the same effects as in the first embodiment can be obtained.

[0088] [Fifth embodiment] Next, a fifth embodiment will be described with reference to FIGS.

[0089] Figure 13 is a diagram illustrating an example of the first cholesteric liquid crystal CL1 and the second cholesteric liquid crystal CL2 contained in the liquid crystal layer 3. Figure 13(a) shows the first cholesteric liquid crystal CL1 in the first region AR1. Figure 13(b) shows the second cholesteric liquid crystal CL2 in the second region AR2.

[0090] The example shown in FIG. 13(a) differs from the example shown in FIG. 2(a) in that the alignment directions of a plurality of first cholesteric liquid crystals CL1 adjacent to each other along the first direction X are different from each other. The example shown in FIG. 13(b) differs from the example shown in FIG. 2(b) in that the alignment directions of a plurality of second cholesteric liquid crystals CL2 adjacent to each other along the first direction X are different from each other. In each of the first region AR1 and the second region AR2, the alignment direction of a plurality of liquid crystal molecules LM11 continuously changes along the first direction X. In each of the first region AR1 and the second region AR2, the alignment direction of a plurality of liquid crystal molecules LM12 also continuously changes along the first direction X. These alignment directions will be described later.

[0091] In the liquid crystal layer 3, a reflective surface 321 formed in the first region AR1 and a reflective surface 322 formed in the second region AR2 are inclined with respect to the second principal surface F2. A first inclination angle θ1 of the reflective surface 321 with respect to the second principal surface F2 and a second inclination angle θ2 of the reflective surface 322 with respect to the second principal surface F2 are both acute angles in the clockwise direction with respect to the second principal surface F2. The first inclination angle θ1 is different from and larger than the second inclination angle θ2. Here, the reflective surfaces 321 and 322 correspond to surfaces on which the alignment directions of the liquid crystal molecules LM1 are aligned or surfaces on which the spatial phases are aligned (equal phase surfaces).

[0092] The second helical pitch P12 of the second cholesteric liquid crystal CL2 is smaller than the first helical pitch P11 of the first cholesteric liquid crystal CL1. As the helical pitch of the second region AR2 decreases, the tilt angle of the reflecting surface 322 also decreases.

[0093] FIG. 14 is a diagram showing an example of an orientation pattern of the liquid crystal molecules LM11 shown in FIG. In the liquid crystal layer 3, the alignment directions of the liquid crystal molecules LM11 aligned in the first direction X are different from one another. For example, when focusing on five liquid crystal molecules LM11 aligned along line A-A', the alignment direction of each of the liquid crystal molecules LM11 changes by a constant angle clockwise along the first direction X (from left to right in the figure). Here, the amount of change in the alignment direction of adjacent liquid crystal molecules LM11 is constant along the first direction X, but may gradually increase or decrease.

[0094] 14, the interval between two liquid crystal molecules LM11 when the alignment direction of the liquid crystal molecules LM11 changes by 180 degrees along the first direction X in one plane is defined as the period T. Note that the first tilt angle θ1 of the reflecting surface 321 shown in Fig. 13 is appropriately set by the period T and the first helical pitch P11, and the second tilt angle θ2 of the reflecting surface 322 shown in Fig. 13 is appropriately set by the period T and the second helical pitch P12.

[0095] On the other hand, in the liquid crystal layer 3, the alignment directions of the liquid crystal molecules LM11 aligned in the second direction Y are substantially the same.

[0096] In this embodiment, the reflecting surfaces 321 and 322 are inclined with respect to the second main surface F2. Therefore, the light reflected by the reflecting surfaces 321 and 322 propagates inside the liquid crystal optical element 100. Therefore, the visible light corresponds to the light other than the light reflected by the reflecting surfaces 321 and 322.

[0097] When the reflecting surfaces 321 and 322 are inclined with respect to the second main surface F2, the liquid crystal optical element 100 can be applied to, for example, a solar cell device. Light that meets certain conditions and enters the liquid crystal optical element 100 can be guided to an end face of the liquid crystal optical element 100, and then received by a solar cell arranged on the end face, thereby generating electricity.

[0098] As described above, according to this embodiment, it is possible to obtain a method for manufacturing a liquid crystal optical element that is capable of forming regions with different reflection wavelengths.

[0099] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0100] 100...liquid crystal optical element, LM1...liquid crystal molecule, 1...transparent substrate, 2...first alignment film, 3...liquid crystal layer, AR1...first area, AR2...second area, F1...first main surface, F2...second main surface, F3...third main surface, F4...fourth main surface, F5...fifth main surface, P11...first helical pitch, P12...second helical pitch, CL1...first cholesteric liquid crystal, CL2...second cholesteric liquid crystal, T1, T2...film thickness, 30...object, 50...production substrate, 4...second alignment film, 321, 322...reflection surfaces, θ1...first inclination angle, θ2...second inclination angle.

Claims

1. Apply liquid crystal material, drying the liquid crystal material under reduced pressure; baking the liquid crystal material; The liquid crystal material is semi-cured by irradiating it with ultraviolet light to form a liquid crystal layer having cholesteric liquid crystals containing a plurality of liquid crystal molecules stacked in a spiral shape; In the liquid crystal layer, a first region having a first cholesteric liquid crystal having a first helical pitch is formed, and a second region having a second cholesteric liquid crystal having a second helical pitch smaller than the first helical pitch is formed. The method for producing a liquid crystal optical element includes irradiating the liquid crystal layer with ultraviolet light to completely cure the liquid crystal layer.

2. The method for manufacturing a liquid crystal optical element according to claim 1 , wherein the second region has a thickness smaller than that of the first region.

3. The method for manufacturing a liquid crystal optical element according to claim 1 , wherein the step of forming the second region in the liquid crystal layer is a step of pressing an object against the second region.

4. The method for manufacturing a liquid crystal optical element according to claim 1 , wherein the step of forming the second region in the liquid crystal layer is a step of heating the second region.

5. The method for manufacturing a liquid crystal optical element according to claim 1 , wherein the step of forming the second region in the liquid crystal layer is a step of irradiating the second region with ultraviolet light.

6. forming a first alignment film on a main surface of a transparent substrate before the step of applying the liquid crystal material; forming the liquid crystal layer on the first alignment film; The method for manufacturing a liquid crystal optical element according to claim 1 , wherein the second region is formed in the liquid crystal layer on the first alignment film.

7. forming a second alignment film on a main surface of the manufacturing substrate before the step of applying the liquid crystal material; forming the liquid crystal layer on the second alignment film; peeling the liquid crystal layer from the production substrate and the second alignment film; The peeled liquid crystal layer is transferred to a transparent substrate; The method for manufacturing a liquid crystal optical element according to claim 1 , wherein the second region is formed in the liquid crystal layer on the transparent substrate.

8. The method for manufacturing a liquid crystal optical element according to claim 6 , wherein in the liquid crystal layer, the reflective surface on which the liquid crystal molecules are aligned is parallel to the main surface.

9. The method for manufacturing a liquid crystal optical element according to claim 6 , wherein in the liquid crystal layer, the reflective surface on which the liquid crystal molecules are aligned is inclined with respect to the main surface.

10. The method for manufacturing a liquid crystal optical element according to claim 9 , wherein a first tilt angle of the reflecting surface formed in the first region with respect to the main surface is larger than a second tilt angle of the reflecting surface formed in the second region with respect to the main surface.

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