Light modulating sheet and method for manufacturing light modulating sheet

Abstract

This transparent polymer layer is a cured product of a vertical alignment agent, a polymerizable liquid crystal compound containing two functional groups, and a non-liquid crystalline polymerizable compound. In this light modulating layer, the mixing ratio of a liquid crystal compound is 60 mass% or more, the mixing ratio of the vertical alignment agent is 5-10 mass%, the mixing ratio of the polymerizable liquid crystal compound is 0.5-10 mass%, and the mixing ratio of polymerizable compound 23P3 is 15-25 mass%, on the basis of the total mass (100 mass%) of the transparent polymer layer and a liquid crystal composition.

Description

Light-adjusting sheet and method for manufacturing the light-adjusting sheet

[0001] The present disclosure relates to a light-controlling sheet and a method for manufacturing the light-controlling sheet.

[0002] One example of a type of light-controlling sheet is the reverse type. A reverse-type light-controlling sheet includes a light-controlling layer containing liquid crystal molecules, a pair of transparent electrode layers sandwiching the light-controlling layer, and an alignment layer located between each transparent electrode layer and the light-controlling layer. Each alignment layer is a vertical alignment layer, so when no voltage is applied between the pair of transparent electrode layers, the liquid crystal molecules are aligned approximately perpendicular to the plane of the alignment layer. Therefore, when no voltage is applied between the pair of transparent electrode layers, the light-controlling sheet is transparent. In contrast, when a voltage is applied between the pair of transparent electrode layers, the liquid crystal molecules are aligned approximately horizontally to the plane of the alignment layer. Therefore, when a voltage is applied between the pair of transparent electrodes, the light-controlling sheet is opaque (see, for example, Patent Document 1).

[0003] JP 2024-014588 A

[0004] Another example of a type of light-controlling sheet is the normal type. Unlike the reverse type light-controlling sheet, the normal type light-controlling sheet does not have a pair of alignment layers. Therefore, when manufacturing the reverse type light-controlling sheet, a process of forming a coating film to form an alignment layer and a process of baking the coating film are required, compared to when manufacturing the normal type light-controlling sheet. This may increase the number of steps and reduce the yield when manufacturing the reverse type light-controlling sheet.

[0005] One aspect of the light-controlling sheet is a light-controlling sheet comprising a first transparent conductive sheet, a second transparent conductive sheet, and a light-controlling layer located between the first transparent conductive sheet and the second transparent conductive sheet, the light-controlling layer comprising: a transparent polymer layer located between the first transparent conductive sheet and the second transparent conductive sheet and including a plurality of voids; and a liquid crystal composition located within the voids and including a non-polymerizable liquid crystal compound having negative dielectric anisotropy. The transparent polymer layer is a cured product of a vertical alignment agent, a polymerizable liquid crystal compound including two polymerizable functional groups, and a non-liquid crystal polymerizable compound. In the light-controlling layer, when the sum of the mass of the transparent polymer layer and the mass of the liquid crystal composition is 100% by mass, the blending ratio of the liquid crystal compound is 60% by mass or more, the blending ratio of the vertical alignment agent is 5% by mass or more and 10% by mass or less, the blending ratio of the polymerizable liquid crystal compound is 0.5% by mass or more and 10% by mass or less, and the blending ratio of the polymerizable compound is 15% by mass or more and 25% by mass or less.

[0006] One embodiment of a method for manufacturing a light-controlling sheet includes preparing a coating liquid, sandwiching the coating liquid between a first transparent conductive sheet and a second transparent conductive sheet, and exposing the coating liquid to light while the coating liquid is sandwiched between the first transparent conductive sheet and the second transparent conductive sheet to harden the coating liquid, thereby forming a light-controlling layer. When the total mass of the coating liquid is 100 mass%, the coating liquid contains 60 mass% or more of a liquid crystal compound having negative dielectric anisotropy, 5 mass% to 10 mass% of a vertical alignment agent, 0.5 mass% to 10 mass% of a polymerizable liquid crystal compound containing two functional groups, and 15 mass% to 25 mass% of a polymerizable compound.

[0007] FIG. 1 is a cross-sectional view showing the structure of a light-controlling device including a light-controlling sheet, together with a drive unit. FIG. 2 is a cross-sectional view showing the structure of the light-controlling layer of the light-controlling sheet, schematically illustrating the structure when no voltage is applied to the light-controlling layer. FIG. 3 is a cross-sectional view showing the structure of the light-controlling layer of the light-controlling sheet, schematically illustrating the structure when a voltage is applied to the light-controlling layer. FIG. 4 is a flowchart for explaining a method for manufacturing a light-controlling sheet. FIG. 5 is a process diagram showing one step included in the method for manufacturing a light-controlling sheet. FIG. 6 is a process diagram showing one step included in the method for manufacturing a light-controlling sheet. FIG. 7 is a process diagram showing one step included in the method for manufacturing a light-controlling sheet. FIG. 8 is a table showing the compounding ratios in the light-controlling sheet of the example. FIG. 9 is a voltage-haze curve for the light-controlling sheet of the example. FIG. 10 is a voltage-clarity curve for the light-controlling sheet of the example.

[0008] An embodiment of a light-controlling sheet will be described with reference to Figures 1 to 10. [Light Controlling Device] A light control device will be described with reference to Figure 1 .

[0009] 1 , the reverse-type light control device 10 includes a reverse-type light control sheet 11R and a drive unit 12. The light control sheet 11R includes a first transparent conductive sheet 21, a second transparent conductive sheet 22, and a light control layer 23. The light control sheet 11R is configured so that the light control layer 23 can be switched between a transparent state and an opaque state by switching between a state in which a voltage is applied between the first transparent conductive sheet 21 and the second transparent conductive sheet 22 and a state in which it is not applied.

[0010] The first transparent conductive sheet 21 includes a first transparent electrode layer 21A and a first transparent substrate 21B that supports the first transparent electrode layer 21A. The second transparent conductive sheet 22 includes a second transparent electrode layer 22A and a second transparent substrate 22B that supports the second transparent electrode layer 22A.

[0011] In the light-controlling sheet 11R, the light-controlling layer 23 is located between the first transparent conductive sheet 21 and the second transparent conductive sheet 22. The first transparent electrode layer 21A is located between the first transparent substrate 21B and the light-controlling layer 23. The second transparent electrode layer 22A is located between the second transparent substrate 22B and the light-controlling layer 23.

[0012] The light-adjusting sheet 11R is either transparent or opaque, with a haze value higher than that of transparency, depending on the magnitude of the voltage applied to the light-adjusting layer 23. Because the light-adjusting sheet 11R provided in the light-adjusting device 10 is of the reverse type, the light-adjusting sheet 11R is transparent when no voltage is applied to the light-adjusting layer 23. In contrast, the light-adjusting sheet 11R is opaque when a voltage is applied to the light-adjusting layer 23. For example, the haze value of a transparent light-adjusting sheet 11R may be 5% or less, and the haze value of an opaque light-adjusting sheet 11R may be 80% or more. The haze value of the light-adjusting sheet 11R is a value measured by a method in accordance with ASTM D 1003-00.

[0013] The light controlling sheet 11R includes a first electrode 21E attached to a portion of the first transparent electrode layer 21A and a second electrode 22E attached to a portion of the second transparent electrode layer 22A. The light controlling sheet 11R further includes a wiring 24 connected to the first electrode 21E and a wiring 24 connected to the second electrode 22E. The first electrode 21E is connected to the drive unit 12 via the wiring 24. The second electrode 22E is connected to the drive unit 12 via the wiring 24.

[0014] The first transparent conductive sheet 21 and the second transparent conductive sheet 22 apply a voltage to the light-controlling layer 23 to switch the light-controlling layer 23 between transparent and opaque. Each transparent conductive sheet 21, 22 has optical transparency that allows visible light to pass through. The optical transparency of the first transparent conductive sheet 21 allows visual recognition of objects through the light-controlling sheet 11R. The optical transparency of the second transparent conductive sheet 22, like the optical transparency of the first transparent conductive sheet 21, allows visual recognition of objects through the light-controlling sheet 11R.

[0015] The material for forming each transparent electrode layer 21A, 22A may be, for example, any one selected from the group consisting of indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, poly(3,4-ethylenedioxythiophene), and silver.

[0016] The material forming each of the transparent substrates 21B, 22B may be a synthetic resin or an inorganic compound. Examples of synthetic resins include polyester, polyacrylate, polycarbonate, and polyolefin. Examples of polyesters include polyethylene terephthalate and polyethylene naphthalate. Examples of polyacrylates include polymethyl methacrylate. Examples of inorganic compounds include silicon dioxide, silicon oxynitride, and silicon nitride.

[0017] Each of the electrodes 21E, 22E is, for example, a flexible printed circuit (FPC). The FPC includes a support layer, a conductor portion, and a protective layer. The conductor portion is sandwiched between the support layer and the protective layer. The support layer and the protective layer are formed of an insulating synthetic resin. The support layer and the protective layer are formed of, for example, polyimide. The conductor portion is formed of, for example, a thin metal film. The thin metal film may be formed of, for example, copper. Each of the electrodes 21E, 22E is not limited to an FPC, and may be, for example, a metal tape.

[0018] Each of the electrodes 21E and 22E is attached to the corresponding transparent electrode layer 21A and 22A by a conductive adhesive layer (not shown). In each of the electrodes 21E and 22E, the conductor portion is exposed from the protective layer or the support layer at the portion connected to the conductive adhesive layer.

[0019] The conductive adhesive layer may be formed of, for example, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), an isotropic conductive film (ICF), an isotropic conductive paste (ICP), etc. From the viewpoint of ease of handling in the manufacturing process of the light control device 10, the conductive adhesive layer is preferably an anisotropic conductive sheet.

[0020] Each wiring 24 is formed, for example, by a metal wire and an insulating layer covering the metal wire. The wire is formed, for example, by copper or the like. The driving unit 12 is configured to be able to apply a voltage to the light-controlling layer 23 provided in the light-controlling sheet 11R. The driving unit 12 applies an AC voltage between the first transparent electrode layer 21A and the second transparent electrode layer 22A. It is preferable that the driving unit 12 apply an AC voltage having a rectangular waveform between the pair of transparent electrode layers 21A, 22A. In other words, it is preferable that the driving unit 12 output a rectangular wave voltage signal.

[0021] [Light Control Layer] The light control layer 23 provided in the light control sheet 11R will be described with reference to Figures 2 and 3. Figure 2 schematically shows the structure of the light control layer 23 when no voltage is applied to the light control sheet 11R. In contrast, Figure 3 schematically shows the structure of the light control layer 23 when a voltage is applied to the light control sheet 11R.

[0022] 2, the light-controlling layer 23 includes a transparent polymer layer 23P and a liquid crystal composition 23L. The transparent polymer layer 23P is located between the first transparent conductive sheet 21 and the second transparent conductive sheet 22. The transparent polymer layer 23P includes a plurality of voids 23D. The liquid crystal composition 23L is located within the voids 23D and includes a non-polymerizable liquid crystal compound LC having negative dielectric anisotropy. The transparent polymer layer 23P is a cured product of a vertical alignment agent 23P1, a polymerizable liquid crystal compound 23P2 containing two polymerizable functional groups, and a non-liquid crystal polymerizable compound 23P3.

[0023] When the sum of the mass of the transparent polymer layer 23P and the mass of the liquid crystal composition 23L is 100% by mass, the light-modulating layer 23 satisfies the following conditions 1 to 4.

[0024] (Condition 1) The blending ratio of the liquid crystal compound LC is 60% by mass or more. (Condition 2) The blending ratio of the vertical alignment agent 23P1 is 5% by mass or more and 10% by mass or less. (Condition 3) The blending ratio of the polymerizable liquid crystal compound 23P2 is 0.5% by mass or more and 10% by mass or less. (Condition 4) The blending ratio of the polymerizable compound 23P3 is 15% by mass or more and 25% by mass or less.

[0025] The sum of the mass of the liquid crystal composition 23L and the mass of the transparent polymer layer 23P includes at least the mass of the liquid crystal compound LC, the mass of the vertical alignment agent 23P1, the mass of the polymerizable liquid crystal compound 23P2, and the mass of the polymerizable compound 23P3. The sum of the mass of the liquid crystal composition 23L and the mass of the transparent polymer layer 23P may be composed only of the mass of the liquid crystal compound LC, the mass of the vertical alignment agent 23P1, the mass of the polymerizable liquid crystal compound 23P2, and the mass of the polymerizable compound 23P3.

[0026] The light controlling sheet 11R of the present disclosure does not require the formation of an alignment layer in a separate process from the process of forming the light controlling layer 23, and therefore does not require the process of forming a coating film by applying a coating liquid or the process of baking the coating film. This reduces the number of steps and improves yield in the production of the light controlling sheet 11R, thereby reducing the cost required to produce the light controlling sheet 11R.

[0027] Furthermore, since it is not necessary to form the alignment layer in a process separate from the process of forming the light-controlling layer 23, there is no need to store the transparent conductive sheets 21, 22 with the alignment film after formation. This reduces the variation in the functionality of the surface of the alignment film that is caused by variations in the storage period of the alignment film, and ultimately reduces the variation in the quality of the light-controlling sheet 11R.

[0028] By setting the blending ratio of the liquid crystal compound LC to 60% by mass or more and the blending ratio of the additive-type vertical alignment agent 23P1 to 5% by mass or more and 10% by mass or less, the liquid crystal compound LC can be vertically aligned on the surfaces 21AS, 22AS of each transparent electrode layer 21A, 22A via the vertical alignment agent 23P1 and the polymerizable liquid crystal compound 23P2. Furthermore, the inventor's tests showed that when the blending ratio of the vertical alignment agent 23P1 is higher than 10% by mass, there is no significant difference in the function of forming vertical alignment order compared to when the blending ratio is 10% by mass. However, when the blending ratio of the vertical alignment agent 23P1 is higher than 10% by mass, the blending ratio of the liquid crystal compound LC required to obtain electro-optical response is reduced by the amount of the higher blending ratio of the vertical alignment agent 23P1. This results in a narrower temperature range in which the light control sheet can be operated. To prevent this narrowing of the operating temperature range, it is preferable that the blending ratio of the vertical alignment agent 23P1 be 10% by mass or less.

[0029] The polymerizable liquid crystal compound 23P2 is also vertically aligned along the vertical alignment agent 23P1. Because the polymerizable liquid crystal compound 23P2 constrains the non-polymerizable liquid crystal compound LC, the liquid crystal compound LC in the gap 23D attempts to maintain its vertical alignment. If the blending ratio of the polymerizable liquid crystal compound 23P2 is too high, the liquid crystal subjected to the alignment restraining force of the polymerizable liquid crystal compound 23P2 becomes less likely to undergo alignment deformation when a voltage is applied. In other words, when a voltage is applied to the light control layer 23, the alignment of the liquid crystal compound LC becomes less likely to change, which increases the driving voltage required to cause alignment deformation. In particular, it is practically preferable that the applied voltage that produces a haze value of 50% or more be less than 100 V, which is the household voltage in Japan.

[0030] On the other hand, if the blending ratio of the polymerizable liquid crystal compound 23P2 is too low, the liquid crystal compound LC is less susceptible to the alignment control force of the polymerizable liquid crystal compound 23P2, resulting in a response delay when returning from a voltage-on state to a voltage-off state. In this regard, by setting the blending ratio of the polymerizable liquid crystal compound 23P2 to 0.5% by mass or more and 10% by mass or less, the vertical alignment of the liquid crystal compound LC is stabilized, and the change in alignment of the liquid crystal compound LC when a voltage is applied is less likely to be hindered by the polymerizable liquid crystal compound 23P2. Furthermore, by setting the blending ratio of the polymerizable compound 23P3 to 15% by mass or more and 25% by mass or less, it is possible to form a transparent polymer layer 23P having a plurality of voids 23D.

[0031] By setting the compounding ratio of the liquid crystal compound LC to 60% by mass or more, the electro-optical response can be improved. The vertical alignment agent 23P1 contained in the transparent polymer layer 23P is adsorbed to the surfaces 21AS, 22AS of each transparent electrode layer 21A, 22A. At this time, the vertical alignment agent 23P1 is adsorbed to the surfaces 21AS, 22AS so as to be approximately perpendicular to the surfaces 21AS, 22AS. The polymerizable liquid crystal compound 23P2 is aligned along the vertical alignment agent 23P1. Furthermore, the vertical alignment agent 23P1 and the polymerizable liquid crystal compound 23P2 are maintained in a vertically aligned state by the curing of the polymerizable compound 23P3.

[0032] The light-controlling layer 23 may be a polymer dispersion type or a polymer network type. The transparent polymer layer 23P may include at least one of independent voids 23D and interconnected voids 23D. The transparent polymer layer 23P may also include at least one of a plurality of voids 23D unevenly distributed within the transparent polymer layer 23P and fibers.

[0033] 2, in the light-controlling sheet 11R, the liquid crystal compound LC is vertically aligned when no voltage is applied between the pair of transparent electrode layers 21A and 22A. As a result, light incident on the light-controlling layer 23 is less likely to be scattered within the light-controlling layer 23, and the diffuse transmittance of the light-controlling sheet 11R is reduced. In other words, the light-controlling sheet 11R is transparent.

[0034] 3, in the light-adjusting sheet 11R, the liquid crystal compound LC is horizontally aligned when a voltage is applied between the pair of transparent electrode layers 21A and 22A. As a result, light incident on the light-adjusting layer 23 is easily scattered within the light-adjusting layer 23, increasing the diffuse transmittance of the light-adjusting sheet 11R. In other words, the light-adjusting sheet 11R is opaque.

[0035] [Liquid Crystal Compound] As described above, the liquid crystal composition 23L contains a non-polymerizable liquid crystal compound LC. The liquid crystal composition 23L may contain additives such as an antifoaming agent, an antioxidant, a weathering agent, a solvent, and a viscosity reducing agent. The weathering agent may be an ultraviolet absorber or a light stabilizer. The liquid crystal composition 23L may also contain a dichroic dye.

[0036] As described above, the liquid crystal compound LC has negative dielectric anisotropy: the dielectric constant ε∥ in the long axis direction of the liquid crystal compound LC is lower than the dielectric constant ε⊥ in the short axis direction of the liquid crystal compound LC.

[0037] The liquid crystal compound LC is at least one selected from the group consisting of, for example, Schiff base-based, azo-based, azoxy-based, biphenyl-based, terphenyl-based, benzoate ester-based, tolan-based, pyrimidine-based, pyridazine-based, cyclohexanecarboxylic acid ester-based, phenylcyclohexane-based, biphenylcyclohexane-based, dicyanobenzene-based, naphthalene-based, and dioxane-based compounds. The liquid crystal compound LC is one type of liquid crystal compound LC or a combination of two or more types of liquid crystal compounds LC. The refractive index difference of the liquid crystal compounds LC may be 0.05 or more. The dielectric constant difference of the liquid crystal compounds LC may be 2 or more or -2 or less.

[0038] An example of the structure of the liquid crystal compound LC is represented by the following formula 1: １１ -A １１ -Z １１ -A １２ -Z １２ -A １３ -Z １３ -A １４ -R １２ ...Equation (1) R shown in Equation 1 １１ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. １１One or two or more non-adjacent methylene bonds contained in the alkyl group of formula (1) can be substituted with any one selected from the group consisting of an oxygen atom, an ethylene bond, an ester bond, and a diether bond. １２ is a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group, or an alkyl group having 1 to 15 carbon atoms. １２ One or two or more non-adjacent methylene bonds contained in the alkyl group can be substituted with any bond selected from the group consisting of an oxygen atom, an ethylene bond, an ester bond, and a diether bond.

[0039] A shown in formula (1) １１ , A １２ , A １３ , A １４ each independently represents a 1,4-phenylene group or a 2,6-naphthylene group. One or more hydrogen atoms in the 1,4-phenylene group or the 2,6-naphthylene group can be substituted with a fluorine atom, a chlorine atom, a trifluoromethyl group, or a trifluoromethoxy group. １１ , A １２ , A １３ , A １４ may each independently represent a 1,4-cyclohexylene group, a 3,6-cyclohexenylene group, a 1,3-dioxane-2,5-diyl group, or a pyridine-2,5-diyl group. １３ , A １４ may each independently be a single bond. １１ , Z １２ , Z １３ each independently represents any one bond selected from the group consisting of a single bond, an ester bond, a diether bond, an ethylene bond, a fluoroethylene bond, and a carbonyl bond.

[0040] The dichroic dye exhibits color when driven in a guest-host mode using a liquid crystal compound LC as a host. The dichroic dye is, for example, at least one selected from the group consisting of polyiodine, azo compounds, anthraquinone compounds, naphthoquinone compounds, azomethine compounds, tetrazine compounds, quinophthalone compounds, merocyanine compounds, perylene compounds, and dioxazine compounds. The dichroic dye may be a single compound or a combination of two or more compounds. When increased light resistance and an increased dichroic ratio are required, the dichroic dye is preferably at least one selected from the group consisting of azo compounds and anthraquinone compounds, and more preferably an azo compound.

[0041] The dichroic dye preferably exhibits black color. When the dichroic dye exhibits black color, the dichroic dye may be a single compound exhibiting black color. Alternatively, the dichroic dye may exhibit black color by combining two or more compounds exhibiting colors different from black.

[0042] [Transparent Polymer Layer] The transparent polymer layer 23P is a cured product of a vertical alignment agent 23P1, a polymerizable liquid crystal compound 23P2, and a non-liquid crystal polymerizable compound 23P3. The polymerizable compound 23P3 is a photopolymerizable compound. The light for polymerizing the photopolymerizable compound may be ultraviolet light or an electron beam. The photopolymerizable compound may be an ultraviolet-polymerizable composition or an electron-beam polymerizable composition.

[0043] The lower and upper limits of the compounding ratio of the transparent polymer layer 23P in the light-controlling layer 23 are within a range in which the liquid crystal particles composed of the liquid crystal compound LC phase-separate from the polymer of the photopolymerizable compound during the polymerization process of the photopolymerizable compound. When it is necessary to increase the mechanical strength of the transparent polymer layer 23P, it is preferable that the lower limit of the compounding ratio of the transparent polymer layer 23P is high. When it is necessary to lower the voltage for driving the liquid crystal compound LC, it is preferable that the upper limit of the compounding ratio of the transparent polymer layer 23P is low.

[0044] The polymerizable compound 23P3 forming the transparent polymer layer 23P may be at least one selected from the group consisting of acrylate compounds, methacrylate compounds, styrene compounds, thiol compounds, and oligomers of each of these compounds. The acrylate compound may be at least one selected from the group consisting of monoacrylate compounds, diacrylate compounds, triacrylate compounds, and tetraacrylate compounds. The acrylate compound may be a monofunctional acrylate containing a saturated alkyl group having 2 to 12 carbon atoms, or a monofunctional acrylate containing a saturated alkoxyalkyl group having 2 to 12 carbon atoms. The acrylate compound may be at least one selected from ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, hexyl acrylate, butyl ethyl acrylate, ethylhexyl acrylate, and cyclohexyl acrylate. The acrylate compound may be a multifunctional urethane acrylate. The polyfunctional urethane acrylate may be a difunctional urethane acrylate or a urethane prepolymer such as pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer. The methacrylate compound may be at least one selected from the group consisting of dimethacrylate compounds, trimethacrylate compounds, and tetramethacrylate compounds. The methacrylate compound may be at least one selected from the group consisting of N,N-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, and tetrahydrofurfuryl methacrylate. The thiol compound may be 1,3-propanedithiol or 1,6-hexanedithiol. The styrene compound may be styrene or methylstyrene.

[0045] The polymerizable compound 23P3 may include a polymerizable compound containing only one polymerizable functional group. In this case, since the polymerizable compound 23P3 includes a monofunctional polymerizable compound, the unit structure derived from the polymerizable compound 23P3 in the transparent polymer layer 23P is sterically hindered, which tends to disrupt the order of the liquid crystal compound LC. This makes the liquid crystal compound LC more easily driven, and as a result, the drive voltage of the light controlling sheet 11R tends to be lower.

[0046] The polymerizable compound 23P3 may include a polymerizable compound having two or more polymerizable functional groups. In this case, since the polymerizable compound 23P3 includes a polyfunctional polymerizable compound, a dense structure is more likely to be included in the transparent polymer layer 23P, and therefore the transparent polymer layer 23P is less likely to peel off from the transparent conductive sheets 21 and 22.

[0047] The number of polymerizable functional groups in the polymerizable compound 23P3 may be 2 or more and 4 or less, which causes the transparent polymer layer 23P to have a mesh-like structure, which makes the transparent polymer layer 23P less likely to peel off from the transparent conductive sheets 21 and 22 and also makes it less likely that the transparent polymer layer 23P will interfere with the driving of the liquid crystal compound LC.

[0048] The vertical alignment agent 23P1 is a compound configured to be able to vertically align the liquid crystal compound LC, such that the major axis of the liquid crystal compound LC is aligned at a predetermined angle within a range of 70° to 90° with respect to the surfaces 21AS and 22AS of the transparent electrode layers 21A and 22A.

[0049] From the viewpoint of reducing the haze value in the transparent state, it is preferable that high vertical alignment property is imparted to the liquid crystal compound LC. From the viewpoint of reducing the haze value in the transparent state, the vertical alignment agent 23P1 is preferably an organic compound having a polar group at a molecular end and having 8 or more carbon atoms, more preferably an organic compound having 10 or more carbon atoms.

[0050] The polar group located at the molecular end of the vertical alignment agent 23P1 is, for example, -OR ２ , -N(R ２ R ３ ) ２ , -COR２ , -CO ２ R ２ , -COOCH=CHR ２ , -NR ２ COMe, -CON(R ２ R ３ ) ２ , -SR ２ , ammonium salts, carboxylates, etc. ２ and R ３ represents hydrogen or a methyl group. From the viewpoint of imparting high vertical alignment to the liquid crystal compound LC and suppressing a decrease in the haze value in the transparent state due to crystal precipitation or the like, it is preferable that the polar group is -OR ２ , -COR ２ , -COOCH=CHR ２ Preferably, the polar group is either of the following, and more preferably is —OH. ２ R ３ ) ２ In this case, the vertical alignment agent 23P1 is preferably an aromatic-substituted -N(R ２ R ３ ) ２ It is preferred that the compound contains:

[0051] The vertical alignment agent 23P1 may be a non-polymerizable vertical alignment agent or a polymerizable vertical alignment agent. When the vertical alignment agent is a non-polymerizable vertical alignment agent, it is preferable that the vertical alignment agent 23P1 has a polar group at one molecular end from the viewpoint of imparting vertical alignment to the liquid crystal compound LC, and the polar group is selected from the group consisting of —OH, —N(R ２ ) ２ It is preferable that the group has at least one of the following groups, and more preferable that the group has —OH. ２ represents hydrogen or a methyl group. When the vertical alignment agent 23P1 is a polymerizable vertical alignment agent, a polar group such as -OH or -COOCH=CHR ２ Preferably, the polymerizable vertical alignment agent 23P1 has a polar group at the molecular end, and more preferably has a polar group at both molecular ends. Furthermore, the polymerizable vertical alignment agent 23P1 preferably contains only —OH as the polar group.

[0052] The vertical alignment agent 23P1 may contain a mesogen in its main chain and have a hydroxyl group (—OH) at the end of the main chain, i.e., at the molecular end. The vertical alignment agent 23P1 may be a compound containing a mesogen selected from the group consisting of cyclohexylcyclohexane, phenylcyclohexane, and biphenyl, and having a hydroxyl group at the end of its molecular structure and a linear alkyl group at the other end of its molecular structure. In this case, each transparent conductive sheet 21, 22 may have an oxygen atom, a hydroxyl group, or a silanol group on the surface in contact with the transparent polymer layer. The surfaces of each transparent conductive sheet 21, 22 are surfaces 21AS, 22AS of the transparent electrode layers 21A, 22A. This allows the hydroxyl groups of the vertical alignment agent 23P1 to hydrogen bond with the silanol groups, thereby allowing the vertical alignment agent 23P1 to be adsorbed onto the transparent conductive sheets 21, 22.

[0053] The polymerizable liquid crystal compound 23P2 containing two functional groups contains a mesogen, which is a rigid structure that exhibits liquid crystallinity, and a polymerizable functional group, which is a polymerizable terminal group. The polymer compound constituting the transparent polymer layer 23P contains the mesogen of the polymerizable liquid crystal compound 23P2. The mesogen contains, as a partial structure, a structure in which two or more six-membered rings are linked in a linear chain. In addition to the mesogen, the polymer compound constituting the transparent polymer layer 23P may also contain a flexible chain such as polyethylene.

[0054] The polymer compound constituting the transparent polymer layer 23P may or may not have liquid crystallinity at room temperature. The polymer compound constituting the transparent polymer layer 23P is a main-chain polymer compound having a structure containing the mesogen of the polymerizable liquid crystal compound 23P2 in the main chain. The polymer compound constituting the transparent polymer layer 23P may be a side-chain polymer compound having a structure containing the mesogen of the polymerizable liquid crystal compound 23P2 in the side chain, or may be a combination of a main-chain polymer compound and a side-chain polymer compound.

[0055] The polymerizable liquid crystal compound 23P2 has a nematic phase at room temperature. As described above, the mesogen of the polymerizable liquid crystal compound 23P2 has a structure in which two or more six-membered rings are linked in a linear chain, and may be, for example, the same as the mesogen of the liquid crystal compound LC. The polymerizable functional group of the polymerizable liquid crystal compound 23P2 initiates polymerization by the action of a UV-sensitive polymerization initiator. The polymerizable functional groups of the polymerizable liquid crystal compound 23P2 are located at both ends of the linear structure containing the mesogen. The polymerizable functional group of the polymerizable liquid crystal compound 23P2 is, for example, an allyl group, an acyl group, a vinyl group, or a vinyloxy group. The polymerizable liquid crystal compound may be a single compound or a combination of two or more compounds. Examples of the polymerizable liquid crystal compound 23P2 include ROC-107 (manufactured by BASF) and LC242 (manufactured by BASF).

[0056] [Spacer] The photochromic layer 23 may include a plurality of spacers. The spacers are dispersed throughout the transparent polymer layer 23P. The thickness of the spacers determines the thickness of the photochromic layer 23. The thickness of the spacers may be the particle size of the spacers. The spacers make the thickness of the photochromic layer 23 uniform. The spacers may be bead spacers or photospacers formed by exposing and developing a photoresist. The spacers may be colorless and transparent, colored and transparent, or colored and opaque. When the photochromic layer 23 includes a dichroic dye, it is preferable that the color of the spacers be the same as the color of the dichroic dye.

[0057] The spacers may have a spherical shape or a columnar shape. The size of the spacers in the thickness direction of the light-controlling layer 23 is changed as appropriate based on the required thickness of the light-controlling layer 23. The size of the spacers in the thickness direction of the light-controlling layer 23 may be, for example, 5 μm or more and 50 μm or less. When the spacers have a columnar shape, the average diameter of the spacers is, for example, 5 μm or more and 50 μm or less. When power saving of the light-controlling sheet 11R is required, in order to reduce the thickness of the light-controlling layer 23, the average particle diameter of the spacers or the average diameter of the spacers is preferably, for example, 5 μm or more and 30 μm or less.

[0058] The material forming the spacer may be a transparent inorganic compound having insulating properties or a transparent resin having insulating properties. The transparent inorganic compound is any one selected from the group consisting of silicon dioxide and aluminum oxide. The transparent resin is at least one selected from the group consisting of acrylic resin, epoxy resin, phenolic resin, melamine resin, polyester, polycarbonate, polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, and acetyl cellulose. When the spacer is colored and transparent, the material forming the spacer may be a transparent resin in which a colored pigment is dispersed. When the spacer is dispersed in the coating liquid for forming the light-controlling layer 23, the surface of the spacer may be subjected to a surface treatment to impart lyophilicity to the coating liquid.

[0059] The refractive index of the material forming the spacers SP may be 1.4 or more and 1.6 or less. The refractive index of the material forming the spacers SP is different from the refractive index of the transparent polymer layer 23P constituting the light-controlling layer 23.

[0060] [Manufacturing Method of Light Control Sheet] A manufacturing method of the light control sheet 11R will be described with reference to Figures 4 to 7. The manufacturing method of the light control sheet 11R includes preparing a coating liquid, sandwiching the coating liquid between the first transparent conductive sheet 21 and the second transparent conductive sheet 22, and curing the coating liquid. Curing the coating liquid involves exposing the coating liquid to light while it is sandwiched between the first transparent conductive sheet 21 and the second transparent conductive sheet 22.

[0061] The coating liquid contains the following when the total mass of the coating liquid is 100 mass %: (A) 60 mass % or more of a liquid crystal compound having negative dielectric anisotropy, (B) 5 mass % to 10 mass % of a vertical alignment agent, (C) 0.5 mass % to 10 mass % of a polymerizable liquid crystal compound containing two functional groups, and (D) 15 mass % to 25 mass % of a polymerizable compound.

[0062] The method for manufacturing the light controlling sheet 11R will be described in more detail below with reference to the drawings. As shown in Fig. 4, the method for manufacturing the light controlling sheet 11R includes a preparation step (step S11), a coating step (step S12), and an exposure step (step S13).

[0063] In the preparation step, a coating liquid for forming the light-controlling layer 23 is prepared. The coating liquid contains the above-described components (A) to (D). The coating liquid further contains a spacer and a photopolymerization initiator. In the preparation step, the above-described components (A) to (D), the spacer, and the photopolymerization initiator are mixed together to prepare the coating liquid.

[0064] The photopolymerization initiator is, for example, at least one selected from the group consisting of diketone compounds, acetophenone compounds, benzoin compounds, benzophenone compounds, thioxanthone compounds, and oxime ester compounds. The polymerization initiator may be one type of compound or a combination of two or more types of compounds. An example of the polymerization initiator is any one selected from the group consisting of benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, cyclohexyl phenyl ketone, and phenylacetophenone.

[0065] 5 , the coating liquid CL is applied to, for example, the first transparent conductive sheet 21. At this time, the coating liquid CL is applied to the surface of the first transparent electrode layer 21A included in the first transparent conductive sheet 21 opposite to the surface in contact with the first transparent substrate 21B. The coating liquid CL may also be applied to the second transparent conductive sheet 22.

[0066] 6 , the second transparent conductive sheet 22 is placed on the coating liquid CL. At this time, the second transparent conductive sheet 22 is placed on the coating liquid CL so that the coating liquid CL is sandwiched between the first transparent electrode layer 21A and the second transparent electrode layer 22A. Note that when the coating liquid CL is applied to the second transparent conductive sheet 22, the first transparent conductive sheet 21 is placed on the second transparent conductive sheet 22.

[0067] Next, as shown in FIG. 7 , light L is irradiated onto the coating liquid CL to form a cured body containing the vertical alignment agent 23P1, the polymerizable liquid crystal compound 23P2, and the polymerizable compound 23P3. This causes the liquid crystal particles composed of the liquid crystal compound LC to phase separate from the cured body. The light L for curing the coating liquid CL may be irradiated toward both the first transparent conductive sheet 21 and the second transparent conductive sheet 22. As a result, the light L transmitted through the first transparent conductive sheet 21 and the light L transmitted through the second transparent conductive sheet 22 reach the coating liquid CL. However, the light may be irradiated toward only one of the first transparent conductive sheet 21 and the second transparent conductive sheet 22. In this case, only the light L transmitted through the first transparent conductive sheet 21 or the light L transmitted through the second transparent conductive sheet 22 reaches the coating liquid CL.

[0068] By setting the compounding ratio of the liquid crystal compound LC to 60% by mass or more and the compounding ratio of the additive type vertical alignment agent 23P1 to 5% by mass or more and 10% by mass or less, it is possible to vertically align the liquid crystal compound LC on the surfaces 21AS, 22AS of each transparent electrode layer 21A, 22A.

[0069] At this time, polar groups of the vertical alignment agent 23P1 are adsorbed to functional groups located on the surfaces of each transparent conductive sheet 21, 22, thereby aligning the vertical alignment agent 23P1 on each transparent conductive sheet 21, 22. Subsequently, the liquid crystal compound LC is oriented along the main chain contained in the vertical alignment agent 23P1, thereby vertically aligning the liquid crystal compound LC. For example, if oxygen atoms, hydroxyl groups, or silanol groups are located on the surfaces of each transparent conductive sheet 21, 22 and the vertical alignment agent 23P1 contains a mesogen and a hydroxyl group, the hydroxyl group is hydrogen-bonded to the silanol group. As a result, the vertical alignment agent 23P1 is adsorbed on the surfaces of each transparent conductive sheet 21, 22. Subsequently, the liquid crystal compound LC is vertically aligned along the mesogen of the vertical alignment agent 23P1.

[0070] Furthermore, the polymerizable liquid crystal compound 23P2 is also vertically aligned along the vertical alignment agent 23P1. The polymerizable liquid crystal compound 23P2 and the polymerizable compound 23P3 are cured by irradiating the coating film with ultraviolet light. Because the polymerizable liquid crystal compound 23P2 is vertically aligned before exposure, the polymerizable liquid crystal compound 23P2 remains vertically aligned even after exposure.

[0071] Because the polymerizable liquid crystal compound 23P2 constrains the non-polymerizable liquid crystal compound LC, the liquid crystal compound LC in the gap 23D tends to maintain its vertical alignment. If the blending ratio of the polymerizable liquid crystal compound 23P2 is too high, the alignment of the liquid crystal compound LC becomes difficult to change when a voltage is applied to the light control layer 23. In this regard, by setting the blending ratio of the polymerizable liquid crystal compound 23P2 to 0.5% by mass or more and 10% by mass or less, the vertical alignment of the liquid crystal compound LC is stabilized, and the change in alignment of the liquid crystal compound LC when a voltage is applied is difficult to be prevented by the polymerizable liquid crystal compound 23P2.

[0072] Furthermore, by setting the compounding ratio of the polymerizable compound 23P3 to be 15% by mass or more and 25% by mass or less, it is possible to form a transparent polymer layer 23P having a plurality of voids 23D. Note that, when the polymerizable compound 23P3 includes one or more monofunctional polymerizable compounds 23P3, it is possible to reduce the driving voltage of the light-controlling sheet 11R and to reduce the clarity of the light-controlling sheet 11R when it is opaque.

[0073] The manufacturing method of the light controlling sheet 11R of the present disclosure does not require forming an alignment layer in a separate step from the step of forming the light controlling layer 23, and therefore does not require the step of forming a coating film by applying a coating liquid or the step of baking the coating film. This makes it possible to reduce the number of steps and improve yield in the manufacturing of the light controlling sheet 11R, and therefore reduces the cost required to manufacture the light controlling sheet 11R.

[0074] Furthermore, since it is not necessary to form the alignment layer in a separate process from the process of forming the light-controlling layer 23, there is no need to store the transparent conductive sheet with the alignment film after it has been formed. This reduces variations in the functionality of the surface of the alignment film due to variations in the storage period of the alignment film, and ultimately reduces variations in the quality of the light-controlling sheet 11R.

[0075] The phase separation of the liquid crystal particles composed of the liquid crystal compound LC proceeds through the polymerization of the photopolymerizable compound and the diffusion of the liquid crystal compound LC. The polymerization rate of the photopolymerizable compound varies depending on the intensity of light irradiated onto the photopolymerizable compound. The diffusion rate of the liquid crystal compound LC varies depending on the processing temperature during polymerization of the photopolymerizable compound. In the phase separation of the liquid crystal compound LC, the intensity of light irradiated onto the photopolymerizable compound is set so that the size of the liquid crystal particles is the desired size, i.e., so that the size of the voids 23D is the desired size. In addition, in the phase separation of the liquid crystal compound LC, heating may be performed to promote the diffusion of the liquid crystal compound LC.

[0076] When it is required to reduce the size of the voids 23D, it is preferable to increase the intensity of the light irradiated to the photopolymerizable compound and to proceed with polymerization at a low temperature to suppress diffusion of the liquid crystal compound LC. When it is required to increase the size of the voids 23D, it is preferable to decrease the intensity of the light irradiated to the photopolymerizable compound and to proceed with polymerization at a high temperature to promote diffusion of the liquid crystal compound LC.

[0077] [Example] An example will be described with reference to Figures 8 to 10. The following materials were used to form the light controlling sheet 11R of the example.

[0078] [Materials] First transparent electrode layer 21A: indium tin oxide Second transparent electrode layer 22A: indium tin oxide First transparent substrate 21B: polyethylene terephthalate film Second transparent substrate 22B: polyethylene terephthalate film Liquid crystal compound LC: mixture of cyano-based liquid crystal compound and fluorine-based liquid crystal compound Polymerization initiator: 1-hydroxycyclohexylphenyl ketone Spacer: spherical with a diameter of 25 μm Vertical alignment agent 23P1: cyclohexylcyclohexane compound having a hydroxyl group in the polar group at the molecular end and a linear alkyl at the other molecular end Polymerizable liquid crystal compound 23P2: ROC-107 (manufactured by BASF) Polymerizable compound 23P3: monofunctional acrylate Polymerizable compound 23P3: bifunctional urethane acrylate

[0079] As shown in Figure 8 and described below, in each of Examples 1 to 4, the compounding ratios of the liquid crystal compound LC, the vertical alignment agent 23P1, the polymerizable liquid crystal compound 23P2, the monofunctional polymerizable compound 23P3, and the bifunctional polymerizable compound 23P3 were each set.

[0080] [Example 1] 70.1% by mass of liquid crystal compound LC, 5.6% by mass of vertical alignment agent 23P1, 0.7% by mass of polymerizable liquid crystal compound 23P2, 9.3% by mass of monofunctional polymerizable compound 23P3, and 14.3% by mass of bifunctional polymerizable compound 23P3 were mixed to prepare a coating film.

[0081] Next, 1% by mass of spacers and 1% by mass of polymerization initiator were mixed with 100% by mass of the coating liquid, and the mixed coating liquid was then sandwiched between the first transparent electrode layer 21A and the second transparent electrode layer 22A. Thereafter, ultraviolet light was irradiated from both the first transparent substrate 21B and the second transparent substrate 22B to phase-separate the liquid crystal particles from the transparent polymer layer 23P, thereby forming the light-controlling layer 23. At this time, the intensity of the ultraviolet light was set to 10 mW / cm. ２ The temperature was set to 100°C, and the irradiation time of ultraviolet light was set to 100 seconds. In this way, a light controlling sheet 11R of Example 1 was obtained.

[0082] [Example 2] In Example 1, the blending ratio of the liquid crystal compound LC was changed to 67.8% by mass, the blending ratio of the vertical alignment agent 23P1 was changed to 6.8% by mass, and the blending ratio of the polymerizable liquid crystal compound 23P2 was changed to 10.0% by mass. In addition, in Example 1, the blending ratio of the monofunctional polymerizable compound 23P3 was changed to 13.0% by mass, and the blending ratio of the bifunctional polymerizable compound 23P3 was changed to 2.4% by mass. Otherwise, the light control sheet 11R of Example 2 was obtained by the same method as in Example 1.

[0083] [Example 3] In Example 1, the blending ratio of the liquid crystal compound LC was changed to 68.1% by mass, the blending ratio of the vertical alignment agent 23P1 was changed to 7.1% by mass, and the blending ratio of the polymerizable liquid crystal compound 23P2 was changed to 10.0% by mass. In addition, in Example 1, the blending ratio of the monofunctional polymerizable compound 23P3 was changed to 6.5% by mass, and the blending ratio of the bifunctional polymerizable compound 23P3 was changed to 8.3% by mass. Otherwise, the light control sheet 11R of Example 3 was obtained by the same method as in Example 1.

[0084] [Example 4] In Example 1, the blending ratio of the liquid crystal compound LC was changed to 67.2% by mass, the blending ratio of the vertical alignment agent 23P1 was changed to 8.2% by mass, and the blending ratio of the polymerizable liquid crystal compound 23P2 was changed to 7.9% by mass. In addition, in Example 1, the blending ratio of the monofunctional polymerizable compound 23P3 was changed to 4.0% by mass, and the blending ratio of the bifunctional polymerizable compound 23P3 was changed to 12.7% by mass. Otherwise, the light control sheet 11R of Example 4 was obtained by the same method as in Example 1.

[0085] [Evaluation Method] [Haze Value] For the light-modulating sheets of each example, the haze value was measured using a method in accordance with ASTM D 1003-00 while applying a 50 Hz rectangular wave AC voltage between a pair of transparent electrode layers. In Examples 1 and 2, the haze value was measured when an AC voltage was applied between the pair of transparent electrode layers in 10 V increments in the range of 0 V to 70 V. A haze / transparency meter (BYK haze-gard i instrument, manufactured by BYK Gardner) was used to measure the haze value. In Examples 3 and 4, the haze value was measured when an AC voltage was applied between the pair of transparent electrode layers in 10 V increments in the range of 0 V to 150 V.

[0086] [Clarity Value] For the light-modulating sheets of each example, the clarity value was measured using a haze / transparency meter (Hazeguard i, manufactured by BYK-Gardner) while applying an AC voltage having a 50 Hz rectangular waveform between a pair of transparent electrode layers. In Examples 1 and 2, the clarity value was measured when an AC voltage was applied between the pair of transparent electrode layers in 10 V increments in the range of 0 V to 70 V. In addition, in Examples 3 and 4, the clarity value was measured when an AC voltage was applied between the pair of transparent electrode layers in 10 V increments in the range of 0 V to 150 V. The clarity value was calculated using the following formula (1):

[0087] 100 x (L Ｃ -L Ｒ ) / (L Ｃ +L Ｒ ) ... Equation (1) In equation (1), the amount of light L Ｃ is the amount of light that travels straight along the optical axis of the parallel light that entered the light-controlling layer 23 among the light that has passed through the light-controlling layer 23. In the formula (1), the amount of light L Ｒ is the amount of narrow-angle scattered light whose angle with respect to the optical axis of the parallel light is within ±2.5°.

[0088] [Evaluation Results] The haze value of each example of the light controlling sheet was measured, and the results are shown in Figure 9. The clarity value of each example of the light controlling sheet was measured, and the results are shown in Figure 10.

[0089] 9, in all of Examples 1 to 4, it was observed that the haze value of the light controlling sheet 11R increased as the voltage applied between the pair of transparent electrode layers 21A and 22A increased. When the response speeds of Examples 1 and 2 were compared, it was observed that the response speed of Example 1 was lower than that of Example 2. In Example 2, the compounding ratio of the polymerizable liquid crystal compound 23P2 was increased compared to Example 1, which can be said to have increased the response speed.

[0090] In Examples 3 and 4, compared to Example 2, the blending ratio of the polymerizable liquid crystal compound 23P2 was not reduced, and the total amount of the polymerizable compound 23P3 was not reduced. However, the blending ratio of the monofunctional polymerizable compound 23P3 was reduced and the blending ratio of the bifunctional polymerizable compound 23P3 was increased. Comparing Examples 2 to 4, it can be said that a lower blending ratio of the monofunctional polymerizable compound 23P3 increases the driving voltage of the light-controlling sheet 11R. When the blending ratio of the monofunctional polymerizable compound 23P3 is increased, the monofunctional polymerizable compound 23P3 acts as a steric hindrance within the transparent polymer layer 23P, thereby reducing the anchoring force at the interface between the liquid crystal compound LC and the transparent polymer layer 23P. As a result, it can be said that the driving voltage of the light-controlling sheet 11R is reduced.

[0091] Furthermore, it was found that the light-controlling sheet 11R of Example 4, which had the highest blending ratio of the vertical blending agent, had the lowest haze value at 0 V. Since the lower the haze value, the higher the vertical alignment property, it can be said that the light-controlling sheet 11R of Example 4 had a lower haze value at 0 V due to the improved vertical alignment property of the liquid crystal compound LC.

[0092] 10 , a comparison of Examples 1 and 2 with Examples 3 and 4 reveals that when the compounding ratio of the monofunctional polymerizable compound 23P3 is high, not only is the driving voltage of the light-controlling sheet 11R lowered, but the clarity value is also lowered. When a voltage is applied between the pair of transparent electrode layers 21A and 22A, the anchoring force at the boundary between the liquid crystal compound LC and the transparent polymer layer 23P is low, making it easier for the alignment of the liquid crystal compound LC to change. This increases the rate of change in refractive index, which is why the clarity value was lowered in Examples 1 and 2.

[0093] It was also found that the V-C curve for the light controlling sheets 11R of Examples 1 and 2 had a minimum value. That is, it was found that the light controlling sheets 11R of Examples 1 and 2 had a minimum value in the clarity value.

[0094] By making the orientation easily changeable when a voltage is applied to the pair of transparent electrode layers 21A and 22A, the orientation of the liquid crystal compound LC between the voids 23D becomes easily different from each other depending on the size of the voids 23D, the thickness of the polymer that defines the voids 23D, and the density of the polymer, which causes the direction and magnitude of the alignment vector in the liquid crystal compound LC to easily differ between the voids 23D.

[0095] The light-controlling sheets 11R of Examples 1 and 2 are thought to have a minimum clarity value due to a mismatch in the refractive index between the voids 23D contained in the transparent polymer layer 23P. If scattering in the light-controlling layer 23 were caused solely by a mismatch between the refractive index of the liquid crystal compound LC and the refractive index of the transparent polymer layer 23P, the clarity value would not have a minimum, and the higher the voltage applied between the pair of transparent electrode layers 21A and 22A, the lower the clarity value would be. Therefore, the minimum clarity value is thought to be caused by differences in the direction and magnitude of the alignment vector in the liquid crystal compound LC between the voids 23D.

[0096] According to the light controlling sheet 11R of Examples 1 and 2, the clarity value is at a minimum, so that high shielding properties can be obtained with a low applied voltage, and thus driving at a low voltage and reducing power consumption are possible.

[0097] As described above, one embodiment of the light-controlling sheet and the method for manufacturing the light-controlling sheet can achieve the following effects: (1) Because it is not necessary to form an alignment layer in a separate process from the process for forming the light-controlling layer 23, the process of forming a coating film by applying a coating liquid and the process of baking the coating film are not required. This makes it possible to reduce the number of steps and improve yield in the manufacture of the light-controlling sheet 11R, thereby reducing the cost required for manufacturing the light-controlling sheet 11R.

[0098] (2) Because it is not necessary to form an alignment layer in a separate process from the process of forming the light-controlling layer 23, there is no need to store the transparent conductive sheets 21 and 22 with the alignment film after formation. This reduces the variation in the functionality of the surface of the alignment film due to variations in the storage period of the alignment film, and ultimately reduces the variation in the quality of the light-controlling sheet 11R.

[0099] (3) By setting the blending ratio of the liquid crystal compound LC to 60% by mass or more and the blending ratio of the additive-type vertical alignment agent 23P1 to 5% by mass or more and 10% by mass or less, the liquid crystal compound LC can be vertically aligned on the surfaces 21AS, 22AS of the transparent electrode layers 21A, 22A via the vertical alignment agent 23P1 and the polymerizable liquid crystal compound 23P2. The polymerizable liquid crystal compound 23P2 also vertically aligns along the vertical alignment agent 23P1. Because the polymerizable liquid crystal compound 23P2 constrains the non-polymerizable liquid crystal compound LC, the liquid crystal compound LC in the gap 23D tends to maintain its vertical alignment. If the blending ratio of the polymerizable liquid crystal compound 23P2 is too high, the alignment of the liquid crystal compound LC becomes difficult to change when a voltage is applied to the light-controlling layer 23. In this regard, by setting the blending ratio of the polymerizable liquid crystal compound 23P2 to 1% by mass or more and 10% by mass or less, the vertical alignment of the liquid crystal compound LC is stabilized, and the change in alignment of the liquid crystal compound LC when a voltage is applied is less likely to be hindered by the polymerizable liquid crystal compound 23P2. Furthermore, by setting the blending ratio of the polymerizable compound 23P3 to 15% by mass or more and 25% by mass or less, it is possible to form the transparent polymer layer 23P having a plurality of voids 23D.

[0100] (4) The hydroxyl groups of the vertical alignment agent 23P1 can be hydrogen-bonded to oxygen atoms, hydroxyl groups, or silanol groups, thereby allowing the vertical alignment agent 23P1 to be adsorbed onto the transparent conductive sheets 21 and 22.

[0101] (5) Since the polymerizable compound 23P3 contains a monofunctional polymerizable compound, the unit structure derived from the polymerizable compound 23P3 in the transparent polymer layer 23P is sterically hindered, which tends to disrupt the order of the liquid crystal compound LC. This makes it easier for the liquid crystal compound LC to be driven, and as a result, the driving voltage of the light controlling sheet 11R tends to be lowered.

[0102] (6) When the polymerizable compound 23P3 contains a polyfunctional polymerizable compound, a dense structure is easily included in the transparent polymer layer 23P, and therefore the transparent polymer layer 23P is less likely to peel off from the transparent conductive sheets 21 and 22.

Claims

1. A light-controlling sheet comprising: a first transparent conductive sheet; a second transparent conductive sheet; and a light-controlling layer located between the first transparent conductive sheet and the second transparent conductive sheet, wherein the light-controlling layer comprises: a transparent polymer layer located between the first transparent conductive sheet and the second transparent conductive sheet and including a plurality of voids; and a liquid crystal composition located within the voids and including a non-polymerizable liquid crystal compound having negative dielectric anisotropy, wherein the transparent polymer layer is a cured product of a vertical alignment agent, a polymerizable liquid crystal compound including two polymerizable functional groups, and a non-liquid crystal polymerizable compound, and wherein, in the light-controlling layer, when the sum of the mass of the transparent polymer layer and the mass of the liquid crystal composition is 100 mass%, the blending ratio of the liquid crystal compound is 60 mass% or more, the blending ratio of the vertical alignment agent is 5 mass% or more and 10 mass% or less, the blending ratio of the polymerizable liquid crystal compound is 0.5 mass% or more and 10 mass% or less, and the blending ratio of the polymerizable compound is 15 mass% or more and 25 mass% or less.

2. The light-controlling sheet according to claim 1, wherein the vertical alignment agent contains a mesogen in its main chain and has a hydroxyl group at the end of the main chain, and each transparent conductive sheet has an oxygen atom, a hydroxyl group, or a silanol group on the surface in contact with the transparent polymer layer.

3. The light-controlling sheet according to claim 1 or 2, wherein the polymerizable compound includes a polymerizable compound containing only one polymerizable functional group.

4. The light-controlling sheet according to claim 3, wherein the polymerizable compound includes a polymerizable compound containing two or more polymerizable functional groups.

5. A method for manufacturing a light-controlling sheet, comprising: preparing a coating liquid; sandwiching the coating liquid between a first transparent conductive sheet and a second transparent conductive sheet; and exposing the coating liquid to light while the coating liquid is sandwiched between the first transparent conductive sheet and the second transparent conductive sheet to harden the coating liquid, thereby forming a light-controlling layer, wherein, when the total mass of the coating liquid is 100% by mass, the coating liquid contains: a liquid crystal compound having negative dielectric anisotropy of 60% by mass or more; 5% by mass to 10% by mass of a vertical alignment agent; 0.5% by mass to 10% by mass of a polymerizable liquid crystal compound containing two functional groups; and 15% by mass to 25% by mass of the polymerizable compound.

Images