Light control sheet

Abstract

To provide a light control sheet capable of suppressing unevenness of appearance in a plane of the light control sheet.SOLUTION: A light control sheet comprises a first transparent electrode sheet, a second transparent electrode sheet, and a light control layer located between the first transparent electrode sheet and the second transparent electrode sheet. The light control layer includes a transparent polymer layer containing a plurality of voids, a liquid crystal composition located in the void, and a spacer. The liquid crystal composition contains a liquid crystal compound and a dichroic dye. The first brightness of the spacer is L*1. The second brightness of the light control sheet in an opaque state is L*2. A brightness difference, which is an absolute value obtained by subtracting the first brightness L*1 from the second brightness L*2, is ΔL*. In a plan view taken from a side opposite to a plane on which the light control sheet extends, an area occupancy (%) of the spacer in the light control layer is SR. A multiplication value of the brightness difference ΔL* and the area occupancy SR satisfies: 20≤ΔL*×SR≤81.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a light-control sheet. [Background technology]

[0002] The light-control sheet includes a first transparent electrode sheet, a second transparent electrode sheet, and a light-control layer. The light-control layer is located between the first transparent electrode sheet and the second transparent electrode sheet. The light-control layer includes a transparent polymer layer containing a plurality of voids, a liquid crystal compound located in the voids, and spacers that determine the thickness of the light-control layer. The spacers are dispersed throughout the light-control layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-078443 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, light-controlling sheets installed on window glass in buildings are required to have high transmittance in order to increase the efficiency of light transmission through the light-controlling sheet. For this reason, white granular spacers are often used as the spacers contained in the light-controlling layer.

[0005] In recent years, the applications of light-controlling sheets have become increasingly diverse, including partitions installed in offices and medical facilities, and windows in vehicles and aircraft. Light-controlling sheets used in these applications are required to be able to protect privacy, so light-controlling sheets containing dichroic dyes that exhibit a specific color have been proposed. Compared to light-controlling sheets that do not contain dichroic dyes, these light-controlling sheets tend to have a larger difference in the amount of light transmitted through the spacer-located areas of the light-controlling layer and the transparent polymer layer or liquid crystal compound-located areas. As a result, the light-controlling sheet is prone to exhibiting uneven appearance across its surface. [Means for solving the problem]

[0006] A light-controlling sheet for solving the above problems includes a first transparent electrode sheet, a second transparent electrode sheet, and a light-controlling layer located between the first transparent electrode sheet and the second transparent electrode sheet. The light-controlling sheet can be reversibly switched between a transparent state and an opaque state depending on whether or not a voltage is applied to the light-controlling sheet. The light-controlling layer includes a transparent polymer layer including a plurality of voids, a liquid crystal composition located in the voids, and spacers. The liquid crystal composition includes a liquid crystal compound and a dichroic dye. The first brightness of the spacer is L * 1, and the second lightness of the light-controlling sheet exhibiting the opaque state is L * 2, and the second lightness L * 2 to the first lightness L * The absolute value of the brightness difference, which is the difference between 1 and ΔL, is * In a plan view opposite to the plane on which the light-controlling sheet spreads, the area occupancy (%) of the spacers in the light-controlling layer is SR. * and the area occupancy SR satisfy the following. 20≦ΔL * ×SR≦81

[0007] When the amount of spacers contained in the light-controlling layer is small and the brightness difference between the first brightness of each spacer and the second brightness of the light-controlling sheet is large, the individual spacers dispersed throughout the light-controlling sheet are easily visible to an observer viewing the sheet. On the other hand, even if the brightness difference is small, if the area occupied by all spacers in the light-controlling layer is high, the probability that each spacer will be visible to an observer is high, and the possibility that a group of multiple spacers will be perceived by the observer as a single object also increases. This causes the observer to perceive unevenness in the appearance of the light-controlling sheet across its surface.

[0008] In this regard, because the product of the lightness difference between the spacer and the light-controlling sheet and the area occupancy of the spacer satisfies the above range, the lightness difference and the area occupancy are prevented from becoming excessively large, making the spacers in the light-controlling layer less visible and reducing unevenness in the appearance of the light-controlling sheet within its plane.

[0009] In the light controlling sheet, the outer surface of the spacer may be black. According to the light controlling sheet, light transmission is suppressed on the outer surface of the spacer, so that the transmitted light is prevented from being visible locally within the plane of the light controlling sheet, thereby further reducing unevenness in the appearance within the plane of the light controlling sheet.

[0010] In the above light controlling sheet, the spacer may have the outer surface and a center portion covered by the outer surface, and the center portion may be black. According to the light-controlling sheet, the spacer's center as well as its outer surface is black, further increasing the spacer's light absorbance. This further reduces light transmission through the spacer, making the spacer less visible. As a result, the in-plane appearance of the light-controlling sheet is further reduced.

[0011] In the above light controlling sheet, the spacer may have a total light transmittance of 30% or less. According to the above-mentioned light controlling sheet, light transmission through the spacers is suppressed, and therefore transmitted light is prevented from being visible locally within the plane of the light controlling sheet.

[0012] In the above light-controlling sheet, the brightness difference ΔL * may be 20 or more and 74 or less, and the area occupancy SR may be 1% or more and 3% or less. According to the above light-control sheet, the brightness difference ΔL * is within the range of 20 to 74 and the area occupancy rate SR is within the range of 1% to 3%, * This enhances the effectiveness of the multiplication of the area occupancy SR and the area occupancy SR satisfying the above-mentioned range.

[0013] In the light controlling sheet, the spacers may have an average diameter of 5 μm or more and 30 μm or less. According to the light-controlling sheet, the average diameter of the spacers is within the range of 5 μm to 30 μm, so that the brightness difference ΔL * This enhances the effectiveness of the multiplication of the area occupancy SR and the area occupancy SR satisfying the above-mentioned range. [Effects of the Invention]

[0014] According to the light controlling sheet of the present disclosure, it is possible to reduce unevenness in appearance within the surface of the light controlling sheet. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of a normal-type light-control sheet. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of a reverse-type light controlling sheet. [Figure 3] FIG. 3 is a cross-sectional view showing the structure of a light-controlling layer included in the light-controlling sheet shown in FIG. [Figure 4] FIG. 4 is a schematic diagram for explaining a testing method for the light controlling sheet. [Figure 5] FIG. 5 is a table showing the evaluation results of the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0016] One embodiment of a light controlling sheet will be described with reference to Figures 1 to 3. The light controlling sheet of the present disclosure may be of either a normal type or a reverse type. Below, we will explain the conditions that the light controlling sheet of the present disclosure satisfies regardless of the type of light controlling sheet, and then we will explain a normal type light controlling device equipped with a normal type light controlling sheet with reference to Figure 1, and we will explain a reverse type light controlling device equipped with a reverse type light controlling sheet with reference to Figure 2.

[0017] The light-controlling sheet is attached to a transparent member provided in a window of a moving object such as a vehicle or an aircraft. Alternatively, the light-controlling sheet may be attached to a transparent member provided in a window of various buildings such as a house, a station, or an airport, a partition installed in an office, or a show window installed in a store. The shape of the light-controlling sheet may be flat or curved.

[0018] [Light-adjusting sheet] The light-controlling sheet of the present disclosure comprises a first transparent electrode sheet, a second transparent electrode sheet, and a light-controlling layer located between the first transparent electrode sheet and the second transparent electrode sheet. The light-controlling sheet can be reversibly switched between a transparent state and an opaque state depending on whether or not a voltage is applied to the light-controlling sheet. The light-controlling layer includes a transparent polymer layer containing a plurality of voids, a liquid crystal composition located in the voids, and a spacer. The liquid crystal composition includes a liquid crystal compound and a dichroic dye. The first brightness of the spacer is L * 1, and the second lightness of the light-controlling sheet in the opaque state is L * 2 and the second lightness L * 2 to 1st brightness L * The absolute value of the brightness difference, which is the difference between 1 and ΔL, is * When viewed from a plane opposite to the plane on which the light-control sheet spreads, the area occupancy rate (%) of the spacers in the light-control layer is SR. The light-control sheet satisfies the following condition 1. (Condition 1) Brightness difference ΔL *The multiplication value of and the area occupancy rate SR satisfies the following. 20≦ΔL * ×SR≦81

[0019] When the amount of spacers contained in the light-controlling layer is small and the brightness difference between the first brightness of each spacer and the second brightness of the light-controlling sheet is large, the individual spacers dispersed throughout the light-controlling sheet are easily visible to an observer viewing the sheet. On the other hand, even if the brightness difference is small, if the area occupied by all spacers in the light-controlling layer is high, the probability that each spacer will be visible to an observer is high, and the possibility that a group of multiple spacers will be perceived by the observer as a single object also increases. This causes the observer to perceive unevenness in the appearance of the light-controlling sheet across its surface.

[0020] In this regard, because the product of the lightness difference between the spacer and the light-controlling sheet and the area occupancy of the spacer satisfies the above range, the lightness difference and the area occupancy are prevented from becoming excessively large, making the spacers in the light-controlling layer less visible and reducing unevenness in the appearance of the light-controlling sheet within its plane.

[0021] If it is required to further reduce the unevenness of the appearance within the surface of the light-controlling sheet, the lightness difference ΔL * It is preferable that the upper limit of the multiplication value of the surface area ratio SR be small.

[0022] The light controlling sheet may satisfy the following conditions 2 and 3. (Condition 2) Brightness difference ΔL * However, it is between 20 and 74. (Condition 3) The area occupancy rate SR is 1% or more and 3% or less.

[0023] When the light-control sheet satisfies conditions 2 and 3, the brightness difference ΔL * This enhances the effectiveness of the multiplication of the area occupancy SR and the area occupancy SR satisfying the above-mentioned range.

[0024] [Normal type dimmer] 1, the normal-type light control device 10N includes a normal-type light control sheet 11N and a drive unit 12. The light control sheet 11N includes a first transparent electrode sheet 21, a second transparent electrode sheet 22, and a light control layer 23. The light control sheet 11N 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 electrode sheet 21 and the second transparent electrode sheet 22 and a state in which it is not applied.

[0025] The first transparent electrode sheet 21 includes a first transparent electrode layer 21A and a first transparent base material 21B that supports the first transparent electrode layer 21A. The second transparent electrode sheet 22 includes a second transparent electrode layer 22A and a second transparent base material 22B that supports the second transparent electrode layer 22A.

[0026] In the light-controlling sheet 11N, the light-controlling layer 23 is located between the first transparent electrode sheet 21 and the second transparent electrode 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.

[0027] The light controlling sheet 11N 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 controlling layer 23. Because the light controlling sheet 11N provided in the normal-type light controlling device 10N is a normal type, the light controlling sheet 11N is opaque when no voltage is applied to the light controlling layer 23. In contrast, the light controlling sheet 11N is transparent when a voltage is applied to the light controlling layer 23. Therefore, the normal-type light controlling sheet 11N is opaque when no voltage is applied to the light controlling sheet 11N. For the normal-type light controlling sheet 11N, when a voltage is applied to the light controlling sheet 11N, the state in which the haze value is saturated on the V (voltage)-H (haze) curve is the transparent state of the light controlling sheet 11N.

[0028] For example, the haze value of the opaque light-controlling sheet 11N may be 80% or more, and the haze value of the transparent light-controlling sheet 11N may be 5% or less. The haze value of the light-controlling sheet 11N is a value measured by a method in accordance with JIS K 7136:2000 "Method for determining haze of plastic transparent materials."

[0029] The light controlling sheet 11N 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 11N 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 driving unit 12 by the wiring 24. The second electrode 22E is connected to the driving unit 12 by the wiring 24.

[0030] The first transparent electrode sheet 21 and the second transparent electrode sheet 22 apply a voltage to the light-controlling layer 23 to switch the light-controlling layer 23 between transparent and opaque. Each transparent electrode sheet 21, 22 has optical transparency that allows visible light to pass through. The optical transparency of the first transparent electrode sheet 21 enables visual recognition of objects through the light-controlling sheet 11N. The optical transparency of the second transparent electrode sheet 22, like the optical transparency of the first transparent electrode sheet 21, enables visual recognition of objects through the light-controlling sheet 11N.

[0031] 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, and poly(3,4-ethylenedioxythiophene).

[0032] 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.

[0033] 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 made of insulating synthetic resin. The support layer and the protective layer are made of, for example, polyimide. The conductor portion is made of, for example, a metal thin film. The material that forms the metal thin film may be, for example, copper. Each of the electrodes 21E, 22E is not limited to an FPC, and may be, for example, a metal tape.

[0034] 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.

[0035] 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 10N, the conductive adhesive layer is preferably an anisotropic conductive sheet.

[0036] Each of the wirings 24 is formed of, for example, a metal wire and an insulating layer covering the metal wire. The wire is formed of, for example, copper.

[0037] The driver 12 is configured to be able to apply a voltage to the light-controlling layer 23 included in the light-controlling sheet 11N. The driver 12 applies an AC voltage between the first transparent electrode layer 21A and the second transparent electrode layer 22A. The driver 12 preferably applies an AC voltage having a rectangular waveform between the pair of transparent electrode layers 21A, 22A. In other words, the driver 12 preferably outputs a rectangular wave voltage signal.

[0038] [Reverse type dimming device] The reverse-type dimming device 10R shown in Fig. 2 differs from the above-described normal-type dimming device 10N in that it includes a reverse-type dimming sheet 11R. The differences between the reverse-type dimming device 10R and the normal-type dimming device 10N will be described in detail below. Meanwhile, the components of the reverse-type dimming device 10R that are common to the normal-type dimming device 10N will be assigned the same reference numerals as those of the normal-type dimming device 10N, and detailed descriptions of those components will be omitted.

[0039] As shown in Fig. 2, the reverse dimming device 10R includes a reverse dimming sheet 11R and a drive unit 12. In addition to the layer structure of the normal dimming sheet 11N, the dimming sheet 11R includes a first alignment film 21C and a second alignment film 22C. Therefore, in the reverse dimming device 10R, the first transparent electrode sheet 21 includes the first alignment film 21C in addition to the first transparent electrode layer 21A and the first transparent substrate 21B. The second transparent electrode sheet 22 includes the second alignment film 22C in addition to the second transparent electrode layer 22A and the second transparent substrate 22B.

[0040] The light control layer 23 is located between the first alignment film 21C and the second alignment film 22C. The first alignment film 21C is located between the light control layer 23 and the first transparent electrode layer 21A and is in contact with the light control layer 23. The second alignment film 22C is located between the light control layer 23 and the second transparent electrode layer 22A and is in contact with the light control layer 23.

[0041] The material for forming the first alignment film 21C and the second alignment film 22C may be an organic compound, an inorganic compound, or a mixture thereof. The organic compound may be, for example, polyimide, polyamide, polyvinyl alcohol, or a cyanide compound. The inorganic compound may be silicon oxide, zirconium oxide, or the like. The material for forming the alignment films 21C and 22C may be silicone. Silicone is a compound having both an inorganic portion and an organic portion.

[0042] The first alignment film 21C and the second alignment film 22C are, for example, vertical alignment films. The vertical alignment film aligns the long axis direction of the liquid crystal compound so that it is perpendicular to the surface opposite to the surface in contact with the first transparent electrode layer 21A and the surface opposite to the surface in contact with the second transparent electrode layer 22A. In this way, the alignment films 21C and 22C regulate the orientation of the multiple liquid crystal compounds contained in the light control layer 23.

[0043] The light controlling 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 controlling layer 23. The light controlling sheet 11R provided in the reverse light controlling device 10R is of the reverse type, and therefore is transparent when no voltage is applied to the light controlling layer 23. In contrast, the light controlling sheet 11R is opaque when a voltage is applied to the light controlling layer 23. Therefore, the reverse type light controlling sheet 11R is transparent when no voltage is applied to the light controlling sheet 11R. With the reverse type light controlling sheet 11R, when a voltage is applied to the light controlling sheet 11R, the opaque state of the light controlling sheet 11R is the state where the haze value is saturated in the V (voltage)-H (haze) curve.

[0044] For example, the haze value of the opaque light-controlling sheet 11R may be 80% or more, and the haze value of the transparent light-controlling sheet 11R may be 5% or less. The haze value of the light-controlling sheet 11N is a value measured by a method in accordance with JIS K 7136:2000 "Method for determining haze of plastic transparent materials."

[0045] [Photochromic layer] Fig. 3 shows the cross-sectional structure of a normal-type light controlling sheet 11N. Note that a reverse-type light controlling sheet 11R has the same layer structure as the structure shown in Fig. 3, except that it includes a first alignment film 21C and a second alignment film 22C.

[0046] As shown in Figure 3, the light-controlling layer 23 includes a transparent polymer layer 23P including a plurality of voids 23D, a liquid crystal composition 23LC located in the voids 23D, and spacers SP. The liquid crystal composition 23LC includes a liquid crystal compound LCM and a dichroic dye DD. As described above, the lightness difference ΔL * When the area occupancy of the spacers SP in the light-controlling layer 23 is SR in a plan view opposite to the plane on which the light-controlling sheet 11N spreads, the light-controlling sheet satisfies Condition 1. * When the multiplication value of the area occupancy rate SR is 20 or more, the photochromic layer 23 can contain a sufficient amount of spacers SP to suppress variation in the thickness of the photochromic layer 23 within the plane of the photochromic layer 23.

[0047] The light control layer 23 is of a polymer dispersion type. The polymer dispersion type light control layer 23 may be a polymer network type light control layer 23 or an encapsulated type light control layer 23. The polymer network type light control layer 23 has a transparent polymer layer 23P having a three-dimensional mesh shape, and holds a liquid crystal composition 23LC in interconnected mesh voids 23D. The encapsulated type light control layer 23 holds a liquid crystal composition 23LC in capsule-like voids 23D dispersed in the transparent polymer layer 23P.

[0048] [Liquid crystal composition] The liquid crystal composition 23LC contains a liquid crystal compound LCM. The mass content of the liquid crystal compound LCM relative to the mass of the light-controlling layer 23 may be, for example, 40 mass % or more and 65 mass % or less. That is, the mass M23 of the light-controlling layer 23 and the mass MLCM of the liquid crystal compound LCM may satisfy the following mathematical formula: The mass M23 of the light-controlling layer 23 is the sum of the mass MLCM of the liquid crystal compound LCM, the mass M23P of the transparent polymer layer 23P, and the mass MSP of the spacer SP. 40(mass%)≦(MLCM / M23)×100≦65(mass%)

[0049] The liquid crystal composition 23LC may contain additives such as an antifoaming agent, an antioxidant, a weathering agent, a solvent, a viscosity reducing agent, etc. The weathering agent may be an ultraviolet absorber or a light stabilizer.

[0050] The liquid crystal compound LCM may have positive dielectric anisotropy. When the liquid crystal compound LCM has positive dielectric anisotropy, the dielectric constant ε∥ of the liquid crystal compound LCM in the long axis direction is higher than the dielectric constant ε⊥ of the liquid crystal compound LCM in the short axis direction. The liquid crystal compound LCM may have negative dielectric anisotropy. When the liquid crystal compound LCM has negative dielectric anisotropy, the dielectric constant ε∥ of the liquid crystal compound LCM in the long axis direction is lower than the dielectric constant ε⊥ of the liquid crystal compound LCM in the short axis direction. The dielectric anisotropy of the liquid crystal compound LCM is appropriately selected based on the type of the light controlling sheets 11N and 11R. The normal-type light controlling sheet 11N may contain, for example, a liquid crystal compound LCM having positive dielectric anisotropy. The reverse-type light controlling sheet 11R may contain, for example, a liquid crystal compound LCM having negative dielectric anisotropy.

[0051] The liquid crystal compound LCM 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 LCM is a single liquid crystal compound LCM or a combination of two or more liquid crystal compounds LCM. The refractive index difference between the liquid crystal compounds LCM may be 0.05 or more. The dielectric constant difference between the liquid crystal compounds LCM may be 2 or more or -2 or less.

[0052] An example of the structure of the liquid crystal compound LCM is represented by the following formula 1. R 11 -A 11 -Z 11 -A 12 -Z 12 -A 13 -Z 13 -A 14 -R 12 ...Formula (1) R shown in Equation 1 11 is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. 11 One 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.

[0053] A shown in equation (1) 11 , A 12 , A 13 , A 14each 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. A represented by formula (1) 11 , A 12 , A 13 , A 14 may each independently be 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.

[0054] [Transparent polymer layer] The transparent polymer layer 23P is a cured product of 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. The lower and upper limits of the content of the transparent polymer layer 23P in the light-controlling layer 23 are within a range in which liquid crystal particles composed of the liquid crystal compound LCM phase-separate from the polymer of the photopolymerizable compound during the polymerization process of the photopolymerizable compound. If it is necessary to increase the mechanical strength of the transparent polymer layer 23P, it is preferable that the lower limit of the content of the transparent polymer layer 23P is high. If it is necessary to lower the voltage for driving the liquid crystal compound LCM, it is preferable that the upper limit of the content of the transparent polymer layer 23P is low.

[0055] The photocurable compound 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 at least one selected from the group consisting of butyl ethyl acrylate, ethylhexyl acrylate, and cyclohexyl acrylate. 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.

[0056] For example, by changing the size of the voids 23D in the transparent polymer layer 23P from a first value to a second value, the second brightness L of the light controlling sheet 11N can be increased. * 2 can be changed from the first value to the second value. The smaller the size of the voids 23D in the transparent polymer layer 23P, the more easily light scattering occurs in the light control layer 23. Therefore, the second brightness L * On the other hand, the larger the size of the voids 23D in the transparent polymer layer 23P, the less likely light scattering occurs in the light control layer 23. Therefore, the second lightness L * 2 tends to decrease.

[0057] [Spacer] The spacers SP are dispersed throughout the transparent polymer layer 23P. The thickness of the spacers SP determines the thickness of the light-controlling layer 23. The thickness of the spacers SP may be the particle size of the spacers SP. The spacers SP make the thickness of the light-controlling layer 23 uniform. The spacers SP may be bead spacers or photospacers formed by exposing and developing a photoresist. The spacers SP may be colorless and transparent, colored and transparent, or colored and opaque. It is preferable that the color of the spacers SP be the same as the color of the dichroic dye DD.

[0058] For example, the outer surface of the spacer SP may be black. In this case, light transmission through the outer surface of the spacer SP is suppressed, and the transmitted light is prevented from being locally visible within the plane of the light controlling sheet 11N. This further reduces unevenness in the appearance within the plane of the light controlling sheet 11N.

[0059] Alternatively, the spacer SP may have an outer surface and a center portion covered by the outer surface, and the center portion may be black. In this case, the center portion of the spacer SP as well as the outer surface of the spacer SP is black, further increasing the absorbance of the spacer SP. This further reduces light transmission through the spacer SP, making the spacer SP less visible. As a result, the in-plane appearance of the light controlling sheet 11N is further reduced.

[0060] The total light transmittance of the spacer SP may be 30% or less. In this case, light transmission through the spacer SP is suppressed, thereby preventing the transmitted light from being visible locally within the plane of the light controlling sheet 11N. If improved transmittance is required for the transparent light controlling sheet 11N, the total light transmittance of the material constituting the spacer may be, for example, 80% or more. The total light transmittance of the spacer SP is a value measured by a method in accordance with ASTM D 1003-00 "Standard Test Method For Haze And Luminous Transmittance Of Transparent Plastics."

[0061] For example, by changing the color of the spacer SP from a first color to a second color, the first brightness L of the spacer SP can be * It is possible to change the first brightness L of the spacer SP from a first value to a second value. For example, by changing the area occupancy rate of the area exhibiting a predetermined color on the outer surface of the spacer SP from a first value to a second value, the first brightness L of the spacer SP can be changed. * It is possible to change 1 from a first value to a second value.

[0062] For example, by changing the number of spacers SP per unit area from a first value to a second value, it is possible to change the area occupancy rate SR of the spacers SP from a first value to a second value. Also, for example, by changing the average diameter of the spacers SP from a first value to a second value, it is possible to change the area occupancy rate SR of the spacers SP from a first value to a second value.

[0063] The spacers SP may have a spherical or columnar shape. The size of the spacers SP in the thickness direction of the photochromic layer 23 is appropriately changed based on the required thickness of the photochromic layer 23. The size of the spacers SP in the thickness direction of the photochromic layer 23 may be, for example, 5 μm or more and 50 μm or less. When the spacers SP have a spherical shape, the average particle diameter of the spacers may be, for example, 5 μm or more and 50 μm or less. The average particle diameter of the spacers SP is measured using a particle size distribution measuring device that uses principles such as laser light scattering, electrical resistance change, and image analysis after imaging. The average particle diameter of the spacers SP is the number average particle diameter. When the spacers SP 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 is required for the photochromic sheets 11N and 11R, the average particle diameter of the spacers SP or the average diameter of the spacers SP is preferably, for example, 5 μm or more and 30 μm or less in order to reduce the thickness of the photochromic layer 23.

[0064] The average particle size of the spacers SP may be 5 μm or more and 30 μm or less. When the average particle size of the spacers SP is within the range of 5 μm or more and 30 μm or less, the brightness difference ΔL * This enhances the effectiveness of the multiplication of the area occupancy SR and the area occupancy SR satisfying the above-mentioned range.

[0065] As described above, the area occupancy SR of the spacers SP may be, for example, 1% or more and 3% or less. The area occupancy SR of the spacers SP is the ratio of the area occupied by the spacers SP to the unit area of ​​the light controlling sheet 11N. The area occupied by the spacers SP is obtained by observing the transparent light controlling sheet 11N from a viewpoint opposite one of a pair of surfaces facing each other in the thickness direction. An example of the unit area of ​​the light controlling sheet 11N is 1 mm x 1 mm. The area occupied by the spacers SP is calculated by observing the unit area of ​​the transparent light controlling sheet 11N using an optical microscope. The slight difference in refractive index between the spacers SP and the transparent polymer layer 23P makes the area corresponding to the spacers SP slightly whiter than the surrounding area in an image captured with the optical microscope. Alternatively, the area corresponding to the spacers SP appears slightly blacker than the surrounding area in an image captured with the optical microscope. The area occupied by the spacer SP is obtained by binarizing an image taken with an optical microscope and then calculating the total area of ​​the granular regions that are slightly whiter than the surrounding area. If the spacer SP has a spherical shape, the granular regions have a spherical shape. If the spacer SP has a cylindrical shape, the granular regions have a rectangular shape.

[0066] The material forming the spacer SP 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 SP is colored and transparent, the material forming the spacer SP may be a transparent resin in which a colored pigment is dispersed. When the spacer SP is dispersed in a coating liquid for forming the light-controlling layer 23, i.e., a liquid containing a photocurable compound and a liquid crystal composition, the surface of the spacer SP may be subjected to a surface treatment to impart lyophilicity to the coating liquid.

[0067] The refractive index of the material forming the spacers SP may be 1.4 or more and 1.6 or less, and is different from the refractive index of the transparent polymer layer 23P constituting the light-switching layer 23.

[0068] [Dichroic dye] The dichroic dye DD exhibits color when driven by a guest-host system using a liquid crystal compound LCM as a host. The dichroic dye DD 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 DD may be a single compound or a combination of two or more compounds. When improved light resistance and an increased dichroic ratio are required, the dichroic dye DD is preferably at least one selected from the group consisting of azo compounds and anthraquinone compounds, and more preferably an azo compound.

[0069] The dichroic dye DD preferably exhibits black color. When the dichroic dye DD exhibits black color, the dichroic dye DD may be a single compound exhibiting black color. Alternatively, the dichroic dye DD may exhibit black color by combining two or more compounds exhibiting colors different from black.

[0070] For example, by changing the content of the dichroic dye DD in the light-controlling layer 23 from a first value to a second value, the second brightness L * It is possible to change 2 from the first value to the second value.

[0071] [Light control sheet manufacturing method] The manufacturing method of the light controlling sheet 11N includes forming a coating film containing a photopolymerizable compound, a liquid crystal compound LCM, and spacers SP between the first transparent electrode sheet 21 and the second transparent electrode sheet 22. When manufacturing the normal-type light controlling sheet 11N, the coating film is formed between the first transparent electrode layer 21A of the first transparent electrode sheet 21 and the second transparent electrode layer 22A of the second transparent electrode sheet 22. In contrast, when manufacturing the reverse-type light controlling sheet 11R, the coating film is formed between the first alignment film 21C of the first transparent electrode sheet 21 and the second alignment film 22C of the second transparent electrode sheet 22.

[0072] The coating film contains a polymerization initiator for initiating polymerization of the photopolymerizable compound. The polymerization 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.

[0073] The manufacturing method of the light control sheets 11N and 11R includes polymerizing a photopolymerizable compound in the coating film to phase-separate liquid crystal particles composed of the liquid crystal compound LCM from the polymer. The light irradiated onto the coating film may be irradiated toward the first transparent electrode sheet 21, the second transparent electrode sheet 22, or both the first transparent electrode sheet 21 and the second transparent electrode sheet 22.

[0074] Phase separation of liquid crystal particles composed of the liquid crystal compound LCM proceeds through polymerization of the photopolymerizable compound and diffusion of the liquid crystal compound LCM. 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 LCM varies depending on the processing temperature during polymerization of the photopolymerizable compound. In phase separation of the liquid crystal compound LCM, 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. Furthermore, in phase separation of the liquid crystal compound LCM, heating may be performed to promote diffusion of the liquid crystal compound LCM.

[0075] When it is desired to reduce the size of the voids 23D, it is preferable to increase the intensity of the light irradiated to the photopolymerizable compound and proceed with polymerization at a low temperature to suppress diffusion of the liquid crystal compound LCM.When it is desired to increase the size of the voids 23D, it is preferable to decrease the intensity of the light irradiated to the photopolymerizable compound and proceed with polymerization at a high temperature to promote diffusion of the liquid crystal compound LCM.

[0076] [Example] Examples and comparative examples of the light controlling sheet 11N will be described with reference to Figures 4 and 5. The light controlling sheet 11N in each example and comparative example is a normal-type light controlling sheet 11N. The light controlling sheet 11N was obtained by forming a coating film containing a photopolymerizable compound and a liquid crystal compound LCM between the first transparent electrode sheet 21 and the second transparent electrode sheet 22, and then polymerizing the photopolymerizable compound in the coating film.

[0077] The materials listed below were used to form the light controlling sheets 11N of the examples and comparative examples. [material] 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 LCM: biphenyl-based liquid crystal compounds, terphenyl-based liquid crystal compounds, tolan-based liquid crystal compounds, cyclohexanecarboxylic acid ester-based liquid crystal compounds, phenylcyclohexane-based liquid crystal compounds, biphenylcyclohexane-based liquid crystal compounds, cyano-based liquid crystal compounds, fluorine-based liquid crystal compounds, 54 parts by weight Dichroic dye DD: 0.5 parts by weight of blue dichroic dye (product name M-412, manufactured by Mitsui Fine Chemicals, Inc.), and 1.5 parts by weight of black dichroic dye (product name YH-428, manufactured by Mitsui Fine Chemicals, Inc.) Polymerization initiator: 1-hydroxycyclohexyl phenyl ketone, 3 parts by weight Spacer SP: 25μm diameter spherical UV-polymerizable compound: isobornyl acrylate, pentaerythritol triacrylate, urethane acrylate, 41 parts by weight

[0078] [Example 1] A coating liquid was prepared by mixing a liquid crystal compound LCM, a dichroic dye DD, and an ultraviolet-polymerizable compound. Next, 1 part by weight of a spacer SP was mixed with 100 parts by weight of the coating liquid, and 3 parts by weight of a polymerization initiator was mixed with the 100 parts by weight of the coating liquid. A spacer SP with a black color on both the outer surface and the center was used. Next, a coating film having a thickness of 25 μm was formed on the first transparent electrode layer 21A using the coating liquid. Next, with the coating film sandwiched between the first transparent electrode layer 21A and the second transparent electrode layer 22A, ultraviolet light having a wavelength of 365 nm was irradiated toward the first transparent substrate 21B. This resulted in the light-controlling sheet 11N of Example 1. At this time, the ultraviolet intensity was set to 10 mW / cm. 2 and the ultraviolet irradiation time was set to 100 seconds.

[0079] [Example 2] A light controlling sheet 11N of Example 2 was obtained in the same manner as in Example 1, except that 3 parts by weight of spacer SP was added to 100 parts by weight of the coating liquid.

[0080] [Example 3] The light-controlling sheet 11N of Example 3 was obtained in the same manner as in Example 1, except that the spacer SP in Example 1 was changed to a spacer SP having a black outer surface and a white central portion covered by the outer surface.

[0081] [Example 4] A light controlling sheet 11N of Example 4 was obtained in the same manner as in Example 3, except that the content of the spacer SP in Example 3 was changed to 3 parts by weight per 100 parts by weight of the coating liquid.

[0082] [Example 5] In Example 1, the spacer SP was changed to a spacer SP whose outer surface and center were white, and when preparing a coating solution by mixing a liquid crystal compound LCM, a dichroic dye DD, and an ultraviolet-polymerizable compound, the proportion of the dichroic dye DD in the coating solution was reduced. Otherwise, a light-controlling sheet 11N of Example 5 was obtained in the same manner as in Example 1.

[0083] [Comparative Example 1] A light controlling sheet 11N of Comparative Example 1 was obtained in the same manner as in Example 1, except that the content of the spacer SP in Example 1 was changed to 4 parts by weight per 100 parts by weight of the coating liquid.

[0084] Comparative Example 2 A light controlling sheet 11N of Comparative Example 2 was obtained in the same manner as in Example 3, except that the content of the spacer SP in Example 3 was changed to 4 parts by weight per 100 parts by weight of the coating liquid.

[0085] Comparative Example 3 A light controlling sheet 11N of Comparative Example 3 was obtained in the same manner as in Example 1, except that the spacer SP in Example 1 was changed to a spacer SP whose outer surface and the central portion covered by the outer surface were white.

[0086] [Evaluation method] [Total light transmittance] The total light transmittance of the light controlling sheet 11N of each example and comparative example was measured using a method in accordance with ASTM D 1003-00. No voltage was applied to each light controlling sheet 11N during this measurement. In other words, the total light transmittance of the light controlling sheet 11N was measured when the light controlling sheet 11N was opaque and had the highest haze value.

[0087] As with the light-controlling sheet 11N, the total light transmittance of each spacer SP was measured using a method in accordance with ASTM D 1003-00. Measurement samples were prepared by filling a glass sample holder with the spacers SP so that they were tightly packed without any gaps. The total light transmittance of the measurement samples was then measured.

[0088] A haze meter (BYK haze-gard i instrument, manufactured by BYK Gardner) was used to measure the total light transmittance of the light-control sheet 11N and the spacer SP.

[0089] [Area occupancy rate] Nine measurement areas for measuring the area occupancy were set on the light-adjusting sheet 11N of each example and comparative example. These measurement areas were non-overlapping in plan view, facing the plane on which the light-adjusting sheet 11N was spread. Each measurement area was set to a square with a side length of 1 mm, and the nine measurement areas were set to be evenly spaced in a 3-by-3 matrix. Next, an image of each measurement area was obtained by capturing an image of each measurement area of ​​each light-adjusting sheet 11N using an optical microscope. After binarizing the captured image, the total area of ​​granular areas that were slightly whiter or blacker than their surroundings was calculated. The total area occupancy of the spacers SP in the measurement area was then calculated by dividing the total area by the area of ​​the measurement area. For each light-adjusting sheet 11N of each example and comparative example, the average value of the area occupancy in the nine measurement areas was calculated, and this average value was set as the area occupancy of the spacers SP in each example and comparative example.

[0090] [Lightness L* ] Light control sheet 11N second brightness L * To obtain 2, first, the Y value of the light-controlling sheet 11N was calculated when no voltage was applied to the light-controlling sheet 11N, i.e., when the light-controlling sheet was opaque. A spectrophotometer (UH4150, Hitachi High-Tech Corporation) was used to measure the spectral reflectance in the range from 360 nm to 830 nm. Then, using a method in accordance with JIS Z 8781-3:2016 "Colorimetry - Part 3: CIE Tristimulus Values," the Y value of the light-controlling sheet 11N, when the Y value of a perfect diffuse reflector was set to 100, was calculated from the measurement results using the spectrophotometer.

[0091] Next, JIS Z 8781-4:2013 "Colorimetry - Part 4: CIE 1976L * a * b * The second brightness L is calculated from the Y value of the light-control sheet 11N by a method conforming to the "color space" * 2 was calculated.

[0092] Spacer SP 1st Lightness L * To obtain the second lightness L 1, a measurement sample was prepared by first filling a glass sample holder with spacers SP so that the spacers SP were packed tightly together, in the same manner as when measuring the total light transmittance of the spacers SP. * After obtaining the Y value of the spacer SP using the same method as in the calculation of 2, the first brightness L * 1 was calculated.

[0093] [Visual evaluation] The light controlling sheet 11N was visually evaluated by the method shown in FIG. As shown in Figure 4, a light source was placed opposite the second transparent electrode sheet 22 of the light controlling sheet 11N, and an observer OB was placed on the opposite side of the light source from the light controlling sheet 11N. Next, light L was irradiated from the light source onto the second transparent electrode sheet 22 of the light controlling sheet 11N to which no voltage was applied, and the observer OB was asked to visually observe the light that had passed through the light controlling sheet 11N. The visual observation results were evaluated according to the following two levels.

[0094] A: The spacers SP are barely visible, so there is barely any visible unevenness in the appearance of the light controlling sheet 11N within the plane. B: Light transmitted through the spacers SP scattered within the surface of the light controlling sheet 11N is visible, and therefore, unevenness in the appearance within the surface of the light controlling sheet 11N is recognized.

[0095] [Evaluation results] The evaluation results for the light controlling sheets 11N of the examples and comparative examples are as shown in FIG.

[0096] The total light transmittance of the light controlling sheet 11N was found to be 6.6% in Example 1, 6.9% in Example 2, 6.7% in Example 3, 7.3% in Example 4, and 14.1% in Example 5. The total light transmittance of the light controlling sheet 11N was found to be 7.0% in Comparative Example 1, 7.5% in Comparative Example 2, and 5.1% in Comparative Example 3.

[0097] The total light transmittance of the spacer SP was found to be 21.0% in Examples 1 and 2 and Comparative Example 1, 27.0% in Examples 3 and 4 and Comparative Example 2, and 86.0% in Example 5 and Comparative Example 3.

[0098] The area occupancy rate of the spacers SP was found to be 1% in Examples 1, 3, and 5 and Comparative Example 3, 3% in Examples 2 and 4, and 4% in Comparative Examples 1 and 2.

[0099] Light control sheet 11N second brightness L * The second lightness L of the light-controlling sheet 11N was found to be 0.1719 in Example 1, 0.1750 in Example 2, 0.1729 in Example 3, 0.1794 in Example 4, and 15.4247 in Example 5. *2 was found to be 0.1761 in Comparative Example 1, 0.1817 in Comparative Example 2, and 0.1582 in Comparative Example 3.

[0100] Spacer SP 1st Lightness L * It was found that the ρ of the pores was 21.0 in Examples 1 and 2 and Comparative Example 1, 27.0 in Examples 3 and 4 and Comparative Example 2, and 88.9 in Example 5 and Comparative Example 3.

[0101] 1st lightness L * 1 to 2nd brightness L * Lightness difference ΔL subtracted by 2 * It was found that the lightness difference ΔL was 20.828 in Example 1, 20.825 in Example 2, 26.827 in Example 3, 26.821 in Example 4, and 73.475 in Example 5. * was found to be 20.824 in Comparative Example 1, 26.818 in Comparative Example 2, and 88.742 in Comparative Example 3.

[0102] Lightness difference ΔL * The lightness difference ΔL multiplied by the surface area ratio SR was found to be 20.828 in Example 1, 62.475 in Example 2, 26.827 in Example 3, 80.462 in Example 4, and 73.475 in Example 5. * The product of the area occupancy rate SR and the surface area occupancy rate SR was found to be 83.296 in Comparative Example 1, 107.273 in Comparative Example 2, and 88.742 in Comparative Example 3.

[0103] The visual evaluation results were "A" for Examples 1 to 5, and "B" for Comparative Examples 1 to 3.

[0104] In this way, in the light controlling sheet 11N, the brightness difference ΔL *It was found that by multiplying the area occupancy rate SR by 20 or more and 81 or less, the spacers SP are prevented from being visually distinguished from the portions other than the spacers SP in the light-controlling layer 23. As a result, it was found that unevenness in the appearance within the surface of the light-controlling sheet 11N is reduced.

[0105] As described above, according to one embodiment of the light controlling sheet, the following effects can be obtained. (1) Brightness difference ΔL * and the area occupancy SR satisfy condition 1, so that unevenness in the appearance within the plane of the light controlling sheets 11N, 11R is hard to notice. In other words, it is possible to suppress unevenness in the appearance within the plane of the light controlling sheets 11N, 11R.

[0106] (2) When the outer surface of the spacer SP is black, light transmission through the outer surface of the spacer SP is suppressed, and the transmitted light is prevented from being visible locally within the plane of the light controlling sheets 11N, 11R. This further reduces unevenness in the appearance within the plane of the light controlling sheets 11N, 11R.

[0107] (3) If the center of the spacer SP is black in addition to the outer surface of the spacer SP, the absorbance of the spacer SP is further increased. This further reduces light transmission through the spacer SP, making the spacer SP less visible. As a result, the in-plane appearance of the light controlling sheets 11N and 11R is further reduced.

[0108] (4) When the total light transmittance of the spacer SP is 30% or less, the transmission of light through the spacer SP is suppressed, and therefore the transmitted light is prevented from being visible locally within the plane of the light controlling sheets 11N, 11R. [Explanation of symbols]

[0109] 10N...Normal type dimmer 10R...Reverse type dimmer 11N, 11R...Light-adjusting sheet 21...First transparent electrode sheet 22...Second transparent electrode sheet 23...Photochromic layer 23D…Void 23LC…Liquid crystal composition 23P…Transparent polymer layer DD…Dichroic dye LCM…liquid crystal compound SP...Spacer

Claims

1. a first transparent electrode sheet; A second transparent electrode sheet; a light control layer located between the first transparent electrode sheet and the second transparent electrode sheet, The light-controlling sheet can be reversibly switched between a transparent state and an opaque state depending on whether or not a voltage is applied to the light-controlling sheet, the light-controlling layer includes a transparent polymer layer including a plurality of voids, a liquid crystal composition positioned in the voids, and spacers; the liquid crystal composition contains a liquid crystal compound and a dichroic dye; The first brightness of the spacer is L ＊ 1, The second lightness of the light-controlling sheet exhibiting the opaque state is L ＊ 2, The second lightness L ＊ 2 to the first brightness L ＊ The absolute value of the brightness difference obtained by subtracting 1 is ΔL ＊ and In a plan view opposite to the plane on which the light-controlling sheet extends, the area occupancy (%) of the spacers in the light-controlling layer is SR, The brightness difference ΔL ＊ and the area occupancy SR satisfy the following: 20≦ΔL ＊ ×SR≦81 Dimming sheet.

2. The outer surface of the spacer is black. The light-controlling sheet according to claim 1 .

3. the spacer has the outer surface and a center portion covered by the outer surface; The center portion is black. The light-controlling sheet according to claim 2 .

4. The total light transmittance of the spacer is 30% or less. The light-controlling sheet according to claim 3 .

5. The brightness difference ΔL ＊ is between 20 and 74, The surface area ratio SR is 1% or more and 3% or less. The light-controlling sheet according to claim 1 .

6. The average diameter of the spacers is 5 μm or more and 30 μm or less. The light-controlling sheet according to claim 1 .

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