Dimming sheet

Abstract

This provides a dimmable sheet that allows for a clear and visible contrast between transparent and opaque states. [Solution] The dimming sheet 10 comprises a dimming layer 11 comprising an organic polymer layer having a plurality of voids and a liquid crystal composition containing a liquid crystal compound and a dichroic dye, a first transparent electrode layer 12A and a second transparent electrode layer 12B, and a first transparent support layer 13A and a second transparent support layer 13B. The dimming sheet 10 changes the orientation of the liquid crystal compound and the dichroic dye in response to a change in the potential difference between the first transparent electrode layer 12A and the second transparent electrode layer 12B, thereby switching from a transparent state to a colored opaque state. The dichroic dye appears black in the opaque state. The parallel line transmittance PTa in the opaque state and the parallel line transmittance PTb in the transparent state satisfy PTb / PTa > 80. The parallel line transmittance PTa in the opaque state is 0.6% or less. The total light transmittance in the opaque state is 30% or less.

Description

Technical Field

[0001] The present invention relates to a dimming sheet.

Background Art

[0002] A dimming sheet includes a dimming layer containing a liquid crystal composition and a pair of transparent electrode sheets sandwiching the dimming layer. The dimming layer changes its transparency by changing the alignment state of the liquid crystal composition in response to a driving voltage applied between the pair of transparent electrode sheets. When the alignment order of the liquid crystal composition is constructed, the dimming sheet exhibits high transparency. When the long axis direction of the liquid crystal composition is disordered, the dimming sheet exhibits low transparency.

[0003] Generally, the dimming sheet is colorless and transparent in the transparent state showing high transparency, and in the opaque state showing low transparency, visible light scatters inside the dimming sheet and appears cloudy white when viewed with the naked eye. From the viewpoint of design, the dimming sheet may preferably have a color other than cloudy white depending on the usage environment. For this reason, it has been proposed to add a dichroic dye to the liquid crystal composition (see, for example, Patent Document 1). A dichroic dye has anisotropy in absorbance and shows high absorbance when its long axis direction is disordered. At this time, the dimming sheet in the opaque state does not appear cloudy but exhibits the color derived from the dichroic dye, and accordingly becomes colored and shows low transparency.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the aforementioned dimmable sheets, increasing the contrast—the difference in appearance between the transparent and opaque states—will create new fields of application for dimmable sheets and develop the related industries. Therefore, it is desirable that the dimmable sheets have a configuration that allows the contrast between the transparent and opaque states to be clearly visible to the naked eye. [Means for solving the problem]

[0006] A light-adjusting sheet for solving the above problems comprises a laminate having an organic polymer layer having a plurality of voids, a liquid crystal composition filling the voids, the liquid crystal composition comprising a liquid crystal compound and a dichroic dye, a light-adjusting layer having a pair of transparent electrode layers sandwiching the light-adjusting layer, and a pair of transparent support layers sandwiching the light-adjusting layer and the pair of transparent electrode layers, wherein the orientation of the liquid crystal compound and the dichroic dye is changed in response to a change in the potential difference between the pair of transparent electrode layers, thereby switching from a transparent state to a colored opaque state, wherein the dichroic dye exhibits black in the opaque state, the parallel line transmittance PTa in the opaque state and the parallel line transmittance PTb in the transparent state satisfy PTb / PTa > 80, the parallel line transmittance PTa in the opaque state is 0.6% or less, and the total light transmittance in the opaque state is 30% or less.

[0007] If the ratio of the parallel line transmittance PTb in the transparent state to the parallel line transmittance PTa in the opaque state is greater than 80, the absorption of visible light functions in the dimming sheet to the extent that the difference in color intensity between the transparent and opaque states is perceptible to the observer. Therefore, the observer can clearly perceive the contrast between the transparent and opaque states.

[0008] Furthermore, increasing the concentration of the dichroic dye deepens the color of the opaque state, thereby increasing the contrast between the transparent and opaque states. Increasing the thickness of the photochromic layer also deepens the color of the opaque state, thereby increasing the contrast between the transparent and opaque states. However, the higher the concentration of the dichroic dye, the more difficult it becomes for the liquid crystal compounds to drive, and aggregation of the dichroic dye may occur. Also, the thicker the photochromic layer, the more difficult it becomes for the liquid crystal compounds to drive, and the light transmittance of the transparent state decreases. Therefore, there are limitations to simply increasing the concentration of the dichroic dye or increasing the thickness of the photochromic layer in order to increase contrast.

[0009] On the other hand, light entering the light-adjusting layer is scattered due to the difference in refractive index between the liquid crystal composition and the resin layer. Light scattered within the light-adjusting layer is more easily absorbed by the dichroic dye because it travels a longer optical path than parallel lines. Conversely, light that is not scattered within the light-adjusting layer is less easily absorbed by the dichroic dye because it travels a shorter optical path than the scattered light.

[0010] In this regard, if the parallel line transmittance PTa in an opaque state is 0.6% or less, the absorption of the dichroic dye can function in an environment where the transmission of parallel lines is suppressed. In other words, the dichroic dye is given an environment in which parallel lines, which are difficult for the dichroic dye to absorb, are suppressed, thereby improving contrast and thus increasing the effectiveness of contrast enhancement.

[0011] Furthermore, by having a total light transmittance of 30% or less in the opaque state, it is possible to sufficiently block visible light in the opaque state, thereby achieving sufficient darkness as the color of the dimming sheet.

[0012] A light-adjusting sheet for solving the above problems comprises a laminate having an organic polymer layer having a plurality of voids, a liquid crystal composition filling the voids, the liquid crystal composition comprising a liquid crystal compound and a dichroic dye, a light-adjusting layer having a pair of transparent electrode layers sandwiching the light-adjusting layer, and a pair of transparent support layers sandwiching the light-adjusting layer and the pair of transparent electrode layers, wherein the orientation of the liquid crystal compound and the dichroic dye is changed in response to a change in the potential difference between the pair of transparent electrode layers, thereby switching from a transparent state to a colored opaque state, wherein the parallel line transmittance PTa in the opaque state and the parallel line transmittance PTb in the transparent state satisfy PTb / PTa > 80, and the total light transmittance in the opaque state is 30% or less, and the light-adjusting sheet further comprises a colored layer located on the surface opposite to the surface in contact with the transparent electrode layer of at least one of the transparent support layers, wherein the colored layer exhibits the same color as the color exhibited by the dichroic dye in the opaque state.

[0013] According to the above configuration, the dimmable sheet in the opaque state exhibits a composite color resulting from the combination of the color exhibited by the dimmable layer and the color exhibited by the colored layer. Therefore, compared to the case where the color of the dimmable sheet in the opaque state is realized solely by the color exhibited by the dimmable layer, the color of the dimmable sheet in the opaque state can be made more vivid. In addition, the total light transmittance of the dimmable sheet in the opaque state can be further reduced by the amount that visible light is blocked by the colored layer.

[0014] In the above-mentioned dimming sheet, it is preferable that, in the opaque state, the chromaticity a* in the CIE1976 (L*a*b*) color system conforming to JIS-Z-8781-4 is between -15 and 15, and the chromaticity b* is between -15 and 15.

[0015] According to the above configuration, the color of the light-adjusting sheet in the opaque state can be black or a color close to black. That is, the dichroic dye suitably absorbs scattered light in the opaque state, and the light-adjusting layer suitably suppresses the transmission of parallel lines so that the PTb / PTa value is greater than 80, which is expressed as black.

[0016] In the above-described dimming sheet, it is preferable that the dimming layer further includes a spacer that exhibits the same color as the color exhibited by the dichroic dye in the opaque state. According to the above configuration, since the spacer exhibits the same color as the color exhibited by the dichroic dye in the opaque state, the spacer can have an inconspicuous appearance. Further, since the spacer is colored, scattered light generated by the liquid crystal compound in the opaque state can be absorbed by the spacer. As a result, the parallel-line transmittance PTa in the opaque state can be lowered as compared with the case where the spacer is white or colorless and transparent. Therefore, the ratio of the parallel-line transmittance PTb in the transparent state to the parallel-line transmittance PTa in the opaque state can be increased.

Effects of the Invention

[0017] According to the present invention, the contrast between the transparent state and the opaque state can be clearly visually recognized.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing the laminated structure of the dimming sheet. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the dimming layer. [Figure 3] FIG. 3 is a table showing the evaluation results of an example of the dimming sheet. [Figure 4] FIG. 4 is a table showing the evaluation results of a comparative example of the dimming sheet.

Modes for Carrying Out the Invention

[0019] [Dimming Sheet] The dimming sheet is attached to a transparent substrate which is an object to be attached. The transparent substrate is a glass substrate or a resin substrate. An example of the transparent substrate is window glass mounted on a moving body such as a vehicle or an aircraft, window glass installed in a building, or a partition arranged inside a vehicle or a room. The surface to which the dimming sheet is attached is planar or curved. The dimming sheet may be sandwiched between two transparent substrates.

[0020] The dimming sheet can be driven by a normal or reverse type. A normal type dimming sheet transitions from an opaque state to a transparent state when a voltage is applied, and returns from the transparent state to an opaque state when the voltage is removed. A reverse type dimming sheet transitions from a transparent state to an opaque state when a voltage is applied, and returns from the opaque state to a transparent state when the voltage is removed. The dimming sheet in this embodiment is an example of a normal type, but it may also be a reverse type.

[0021] [Laminated structure of dimmable sheet] As shown in Figure 1, the dimming sheet 10 comprises a dimming layer 11, a first transparent electrode layer 12A, a second transparent electrode layer 12B, a first transparent support layer 13A, and a second transparent support layer 13B. The dimming layer 11 is sandwiched between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The first transparent support layer 13A supports the side of the first transparent electrode layer 12A opposite to the dimming layer 11. The second transparent support layer 13B supports the side of the second transparent electrode layer 12B opposite to the dimming layer 11.

[0022] The light-adjusting layer 11 has structures such as polymer dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC), and nematic curvilinear aligned phase (NCAP). The light-adjusting layer 11 containing polymer dispersed liquid crystal has a number of independent voids, or voids with a shape in which parts of independent shapes are joined, within the resin layer, and holds the liquid crystal composition within the voids. The polymer network liquid crystal has a polymer network, which is a resin layer having a three-dimensional mesh-like structure, and holds liquid crystal molecules as aligned particles in the voids of the polymer network. The nematic curvilinear aligned phase layer holds a liquid crystal composition having a capsule-like structure within the resin layer. The light-adjusting layer 11 of this embodiment contains polymer dispersed liquid crystal. The liquid crystal composition contains a liquid crystal compound and a dichroic dye.

[0023] The first transparent electrode layer 12A and the second transparent electrode layer 12B each have light transmittance that transmits visible light and electrical conductivity. An example of the material constituting the first transparent electrode layer 12A and the second transparent electrode layer 12B is at least 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.

[0024] The first transparent support layer 13A and the second transparent support layer 13B each have light transmittance that transmits visible light and electrical insulation properties. The materials constituting the first transparent support layer 13A and the second transparent support layer 13B are either organic polymer compounds or inorganic polymer compounds. An example of an organic polymer compound is at least one selected from the group consisting of polyester, polyacrylate, polycarbonate, and polyolefin. An example of an inorganic polymer compound is at least one selected from the group consisting of silicon dioxide, silicon oxynitride, and silicon nitride.

[0025] The first transparent electrode layer 12A is connected to the control unit 20 through the first wiring 21A and the first electrode 22A. The second transparent electrode layer 12B is connected to the control unit 20 through the second wiring 21B and the second electrode 22B. Each of the first wiring 21A and the second wiring 21B is composed of, for example, a metal wire and an insulating layer covering the metal wire. The wire is made of copper, for example. The insulating layer is made of resin, for example. Each of the first electrode 22A and the second electrode 22B is, for example, a flexible printed circuit board (FPC).

[0026] Each of the first electrode 22A and the second electrode 22B is attached to each of the first transparent electrode layer 12A and the second transparent electrode layer 12B, respectively, via a conductive adhesive layer (not shown). The conductive adhesive layer is composed of, for example, an anisotropic conductive film (ACF), anisotropic conductive paste (ACP), isotropic conductive film (ICF), isotropic conductive paste (ICP), etc.

[0027] The means for connecting the first transparent electrode layer 12A and the control unit 20, and the means for connecting the second transparent electrode layer 12B and the control unit 20 are not limited to the above examples. For example, the first wiring 21A may be directly soldered to the first transparent electrode layer 12A without going through the first electrode 22A. Similarly, the second wiring 21B may be directly soldered to the second transparent electrode layer 12B without going through the first electrode 22A.

[0028] The control unit 20 applies a voltage between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The light-adjusting layer 11 changes the orientation of its liquid crystal molecules in response to the voltage change occurring between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The change in the orientation of the liquid crystal molecules alters the degree of scattering, absorption, and transmission of visible light entering the light-adjusting layer 11. When no voltage signal is applied to the first transparent electrode layer 12A and the second transparent electrode layer 12B, the orientation of the liquid crystal molecules along their long axes is irregular. As a result, the degree of scattering of visible light incident on the light-adjusting layer 11 increases, and the light-adjusting layer 11 becomes a colored opaque state. The color exhibited by the light-adjusting layer 11 in the opaque state depends on the color of the dichroic dye. As an example, the color exhibited by the light-adjusting layer 11 in the opaque state is black or a color close to black.

[0029] On the other hand, when a voltage signal is applied to the first transparent electrode layer 12A and the second transparent electrode layer 12B, the liquid crystal molecules are oriented so that the long axis direction of the liquid crystal molecules is aligned with the direction of the electric field between the first transparent electrode layer 12A and the second transparent electrode layer 12B. As a result, light is more easily transmitted through the light-adjusting layer 11, and the light-adjusting layer 11 becomes colorless and transparent.

[0030] The dimming sheet 10 further comprises a colored layer 14. The colored layer 14 is located on the surface of the first transparent support layer 13A opposite to the surface in contact with the first transparent electrode layer 12A. The colored layer 14 may be fixed to the first transparent support layer 13A via an adhesive layer (not shown). The colored layer 14 exhibits the same color as the dimming layer 11 in the opaque state, that is, black or a color close to black in this embodiment. The dimming sheet 10 can exhibit a composite color obtained by superimposing the color of the dimming layer 11 and the color of the colored layer 14. Therefore, the color of the dimming sheet 10 in the opaque state can be made more vivid compared to the case where the color of the dimming sheet 10 in the opaque state is realized only by the color of the dimming layer 11.

[0031] The total light transmittance of the colored layer 14 is preferably 3% to 50%. By having the total light transmittance of the colored layer 14 within the above range, it is possible to lower the total light transmittance of the light-adjusting sheet 10 in the opaque state while suppressing an excessive decrease in the total light transmittance in the transparent state.

[0032] [Light-regulating layer] The photochromic layer 11 will be described in detail with reference to Figure 2. Figure 2 shows a part of the cross-sectional structure of the photochromic sheet 10, and includes the PDLC-type photochromic layer 11, the first transparent electrode layer 12A, and the second transparent electrode layer 12B.

[0033] The light-adjusting layer 11 includes an organic polymer layer 31, a liquid crystal composition 32, and a spacer 33. The organic polymer layer 31 is a cured product of a photopolymerizable compound. The photopolymerizable compound may be an ultraviolet-curable compound or an electron-beam-curable compound. The photopolymerizable compound is compatible with the liquid crystal composition 32.

[0034] The organic polymer layer 31 partitions the void 31D within the light-adjusting layer 11. When it is necessary to improve the controllability of the dimensions in the void 31D, the photopolymerizable compound is preferably an ultraviolet-curable compound. An example of an ultraviolet-curable compound is one that contains polymerizable unsaturated bonds at the ends of its molecular structure. Alternatively, an ultraviolet-curable compound may contain polymerizable unsaturated bonds in addition to those at the ends of its molecular structure. The photopolymerizable compound is one polymerizable compound or a combination of two or more polymerizable compounds. The ultraviolet-curable compound is at least one selected from the group consisting of acrylate compounds, methacrylate compounds, styrene compounds, thiol compounds, and oligomers of each compound. Acrylate compounds include diacrylate compounds, triacrylate compounds, and tetraacrylate compounds. Examples of acrylate compounds are butyl ethyl acrylate, ethylhexyl acrylate, and cyclohexyl acrylate. Examples of methacrylate compounds are dimethacrylate compounds, trimethacrylate compounds, and tetramethacrylate compounds. Examples of methacrylate compounds include N,N-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, and tetrahydrofurfuryl methacrylate. Examples of thiol compounds include 1,3-propanedithiol and 1,6-hexanedithiol. Examples of styrene compounds include styrene and methylstyrene.

[0035] The liquid crystal composition 32 contains a liquid crystal compound LCM and a dichroic dye DP. The liquid crystal composition 32 may further contain viscosity reducers, defoamers, antioxidants, weather stabilizers, etc. Examples of weather stabilizers include ultraviolet absorbers and light stabilizers.

[0036] The retention type of the liquid crystal composition 32 by the organic polymer layer 31 is one of the group consisting of polymer dispersion type, polymer network type, and capsule type. Alternatively, the retention type of the liquid crystal composition 32 by the organic polymer layer 31 may be a combination of several types from these groups.

[0037] In the polymer-dispersed type of light-adjusting layer 11, the organic polymer layer 31 partitions a number of isolated voids 31D. In the polymer-network type of light-adjusting layer 11, the organic polymer layer 31 has a three-dimensional mesh-like void structure 31D. The liquid crystal composition 32 is located within the interconnected mesh-like voids 31D. In the capsule-type light-adjusting layer 11, the organic polymer layer 31 has dispersed capsule-shaped voids 31D. The voids 31D can be of two or more sizes, and their shape can be spherical, ellipsoidal, or irregular.

[0038] The dielectric constant in the long axis direction of the liquid crystal compound (LCM) is higher than the dielectric constant in the short axis direction, indicating positive dielectric anisotropy. Alternatively, the dielectric constant in the long axis direction of the liquid crystal compound (LCM) is lower than the dielectric constant in the short axis direction, indicating negative dielectric anisotropy. The dielectric anisotropy of the liquid crystal compound (LCM) is appropriately selected based on the presence or absence of each alignment layer in the dimming sheet 10 and the driving type.

[0039] Liquid crystal compounds (LCMs) are at least one selected from the group consisting of Schiff bases, azos, azoxys, biphenyls, terphenyls, benzoic acid esters, trans, pyrimidines, pyridazines, cyclohexanecarboxylic acid esters, phenylcyclohexanes, biphenylcyclohexanes, dicyanobenzenes, naphthalenes, and dioxanes. Non-polymerizable liquid crystal compounds are one liquid crystal compound or a combination of two or more liquid crystal compounds.

[0040] The dichroic dye DP has an elongated molecular shape, and its absorbance in the visible region along the molecular long axis is greater than its absorbance along the molecular short axis. In this embodiment, the dichroic dye DP exhibits a black or near-black color when its molecular long axis intersects the direction of incident light at a predetermined angle. In other words, the dichroic dye DP exhibits a black or near-black color when its molecular long axis is oriented approximately perpendicular to the normal direction of the contact surface with the first transparent electrode layer 12A and the contact surface with the second transparent electrode layer 12B of the light-adjusting layer 11. The dichroic dye DP exhibits color when driven by a guest-host type with a liquid crystal compound LCM as the host.

[0041] The dichroic dye DP used is one that ensures that the chromaticity a* of the opaque light-adjusting layer 11 in the CIE1976(L*a*b*) color system is between -15 and 15, and the chromaticity b* is between -15 and 15. The chromaticity a* and chromaticity b* in the CIE1976(L*a*b*) color system are determined in accordance with the method for calculating the color coordinates in the CIE1976(L*a*b*) color space as specified in JIS-Z-8781-4 (ISO 11664-4).

[0042] The dichroic dye DP is 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 DP is one dye or a combination of two or more dyes. When it is necessary to increase lightfastness and the dichroic ratio, the dichroic dye DP is at least one selected from the group consisting of azo compounds and anthraquinone compounds, and is more preferably an azo compound.

[0043] The lower limit of the content of the organic polymer layer 31 relative to the total amount of the organic polymer layer 31 and the liquid crystal composition 32 is 20% by mass, and the lower limit of a more preferable content is 30% by mass. The upper limit of the content of the organic polymer layer 31 relative to the total amount of the organic polymer layer 31 and the liquid crystal composition 32 is 70% by mass, and the upper limit of a more preferable content is 60% by mass.

[0044] The lower and upper limits of the content of the organic polymer layer 31 are determined according to the range in which the liquid crystal particles made of the liquid crystal composition 32 can be phase-separated from the cured product of the photopolymerizable compound during the curing process of the photopolymerizable compound. When it is necessary to increase the mechanical strength of the organic polymer layer 31, it is preferable that the lower limit of the content of the organic polymer layer 31 is high. When it is necessary to lower the driving voltage of the liquid crystal compound LCM, it is preferable that the upper limit of the content of the organic polymer layer 31 is low.

[0045] The spacers 33 are dispersed throughout the organic polymer layer 31. The spacers 33 define the thickness of the photochromic layer 11 around the spacers 33 and make the thickness of the photochromic layer 11 uniform. The spacers 33 may be bead spacers or photospacers formed by exposure and development of photoresist. The spacers 33 are translucent and may be colorless and transparent or colored and transparent. Preferably, the color exhibited by a colored and transparent spacer 33 is the same as the color exhibited by the dichroic dye DP.

[0046] The control unit 20 controls the orientation of the liquid crystal compound LCM and dichroic dye DP by applying a driving voltage to the first transparent electrode layer 12A and the second transparent electrode layer 12B, thereby controlling the orientation of the liquid crystal compound LCM and dichroic dye DP based on the potential difference between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The driving voltage is a voltage used to change the orientation state of the liquid crystal compound LCM and dichroic dye DP. The control unit 20 switches the dimming sheet 10 from one state to the other, either transparent or opaque, by changing the orientation state of the liquid crystal compound LCM and dichroic dye DP. In the opaque state, the dimming sheet 10 appears black or nearly black, and its total light transmittance is lower than in the transparent state. In other words, the haze value of the dimming sheet 10 in the opaque state is higher than in the transparent state.

[0047] When the driving voltage is released, the longitudinal directions of the liquid crystal compound LCM and the dichroic dye DP become disordered. As a result, the dimming sheet 10 becomes opaque due to scattering in the dimming layer 11 across the entire visible light spectrum. The dichroic dye DP also becomes disordered along its longitudinal direction. Among the dichroic dye DP, those whose smaller angle between the longitudinal direction and the normal direction of the contact surface with the first transparent electrode layer 12A of the dimming layer 11 and the contact surface with the second transparent electrode layer 12B of the dimming layer 11 is close to a predetermined angle such as 90° will appear black. Note that the above normal direction is equivalent to the thickness direction of the dimming layer 11.

[0048] When a driving voltage is applied, the liquid crystal compound (LCM) is subjected to an orientation-regulating force by the electric field. At this time, the long axis directions of the liquid crystal compound (LCM) and the dichroic dye (DP) become aligned along the direction of the electric field. As a result, the total light transmittance of the dimming sheet 10 becomes higher than in the opaque state. In addition, since the long axis direction of the dichroic dye (DP) also becomes aligned along the direction of the electric field, the color of the dimming sheet 10 becomes colorless or nearly colorless.

[0049] When the driving voltage is released again, the liquid crystal compound (LCM) and dichroic dye (DP) are freed from the orientation-restricting force imposed by the electric field, and their long axis directions become disordered. As a result, the dimming sheet 10 experiences scattering in the dimming layer 11 across the entire visible light spectrum and becomes opaque again.

[0050] [Optical properties of dimmable sheets] Next, we will describe the optical properties of the dimming sheet 10. The dimming sheet 10 satisfies the following condition 1.

[0051] (Condition 1) The relationship between the parallel line transmittance PTa in the opaque state and the parallel line transmittance PTb in the transparent state satisfies PTb / PTa > 80. When the dimming sheet 10 satisfies condition 1 above, the difference in the shade of color between the transparent and opaque states becomes larger. Therefore, the contrast between the transparent and opaque states can be clearly seen.

[0052] Regarding condition 1 above, the PTb / PTa value in the photochromic sheet 10 can be changed by changing the content of the dichroic dye DP in the photochromic layer 11. When the content of the dichroic dye DP in the photochromic layer 11 is increased, the parallel line transmittance PTa in the opaque state decreases. In this case, not only PTA but also the parallel line transmittance PTb in the transparent state decreases, but since the decrease rate of PTA is greater than the decrease rate of PTb, the PTb / PTa value increases. Conversely, when the content of the dichroic dye DP in the photochromic layer 11 is decreased, the PTb / PTa value decreases.

[0053] The content of the dichroic dye DP is, for example, 0.01% by mass or more and 10% by mass or less relative to the total amount of the organic polymer layer 31 and the liquid crystal composition 32. A dichroic dye DP content of 0.01% by mass or more allows for a sufficiently large PTb / PTa value. Furthermore, a dichroic dye DP content of 10% by mass or less suppresses the precipitation of aggregated dichroic dye DP particles.

[0054] Regarding condition 1 above, the PTb / PTa value in the dimming sheet 10 can also be changed by changing the color of the spacer 33 provided in the dimming layer 11. For example, if the spacer 33 provided in the dimming layer 11 is colored, the scattered light generated by the liquid crystal compound LCM in the opaque state can be absorbed by the spacer 33. This makes it possible to lower the parallel line transmittance PTa in the opaque state compared to when the spacer 33 is white or colorless and transparent. Therefore, by using a colored spacer 33 other than white, the PTb / PTa value can be made relatively larger. From the viewpoint of suitably absorbing scattered light, the color of the spacer 33 is preferably black. Also, if the spacer 33 is configured to exhibit the same color as the color exhibited by the dichroic dye DP in the opaque state, the appearance of the dimming sheet 10 can be made less conspicuous due to the color of the spacer 33.

[0055] Regarding condition 1 above, the PTb / PTa value in the dimming sheet 10 can also be changed by changing the thickness of the dimming layer 11. When the thickness of the dimming layer 11 increases, there may be some liquid crystal compounds (LCM) and dichroic dyes (DP) distributed in the thickness direction of the dimming layer 11 that are partially difficult to drive. In this case, even if a driving voltage is applied to make the dimming sheet 10 transparent, the liquid crystal compounds (LCM) and dichroic dyes (DP) are not partially aligned, resulting in a relatively lower parallel line transmittance PTb in the transparent state. Conversely, when the thickness of the dimming layer 11 decreases, it becomes easier to align the entire liquid crystal compounds (LCM) and dichroic dyes (DP) distributed in the thickness direction of the dimming layer 11 with the driving voltage. Therefore, PTb can be relatively increased by decreasing the thickness of the dimming layer 11.

[0056] Since the thickness of the dimming layer 11 is approximately equal to the size of the spacer 33, it can be controlled by changing the average particle size of the spacer 33. For example, the average particle size of the spacer 33 is between 10 μm and 30 μm for a median diameter D50. In this case, the thickness of the dimming layer 11 will be between 10 μm and 30 μm.

[0057] Regarding condition 1 above, the PTb / PTa value in the dimming sheet 10 can also be changed by changing the degree to which the liquid crystal particles composed of the liquid crystal composition 32 phase separate from the photopolymerizable compound during the curing process of the photopolymerizable compound.

[0058] For example, the lower the intensity of the light used to polymerize the photopolymerizable compound, the less the phase separation of liquid crystal particles from the photopolymerizable compound progresses, and the larger the size of the voids 31D formed by the curing of the photopolymerizable compound. A light-adjusting layer 11 with a small number of large voids 31D scatters light entering the light-adjusting layer 11 less than a light-adjusting layer 11 with a large number of small voids 31D. Therefore, the larger the size of the voids 31D, that is, the lower the intensity of the light used to polymerize the photopolymerizable compound, the less visible light is scattered in the opaque state where no driving voltage is applied. As a result, the larger the size of the voids 31D contained in the organic polymer layer 31, the higher the parallel line transmittance PTa in the opaque state tends to be.

[0059] In contrast, during the curing process of the photopolymerizable compound, increasing the intensity of the light used to polymerize the photopolymerizable compound promotes the phase separation of liquid crystal particles from the photopolymerizable compound, thereby reducing the size of the voids 31D contained in the organic polymer layer 31. Therefore, the PTa can be reduced when switching between the transparent and opaque states of the liquid crystal particles contained in the light-adjusting layer 11.

[0060] As mentioned above, increasing the concentration of the dichroic dye DP deepens the color of the opaque state, thereby increasing the contrast between the transparent and opaque states. Increasing the thickness of the photochromic layer 11 also deepens the color of the opaque state, thereby increasing the contrast between the transparent and opaque states. However, the higher the concentration of the dichroic dye DP, the more difficult it becomes for the liquid crystal compound LCM to drive, and the higher the possibility of aggregation of the dichroic dye DP. Also, the thicker the photochromic layer 11, the more difficult it becomes for the liquid crystal compound LCM to drive, and the higher the possibility of a decrease in light transmittance in the transparent state. Therefore, there are limitations to strategies such as increasing the concentration of the dichroic dye DP or increasing the thickness of the photochromic layer 11 in order to increase contrast.

[0061] On the other hand, light entering the light-adjusting layer 11 is scattered due to the difference in refractive index between the organic polymer layer 31 and the liquid crystal composition 32. The light scattered inside the light-adjusting layer 11 is more easily absorbed by the dichroic dye DP because it travels along a longer optical path than parallel lines. Conversely, the light that is not scattered inside the light-adjusting layer 11 is less easily absorbed by the dichroic dye DP because it travels along a shorter optical path than the scattered light.

[0062] From this perspective, it is preferable that the parallel line transmittance PTa in the opaque state is 0.6% or less. As a result, since the parallel line transmittance PTa in the opaque state is 0.6% or less, the absorption of the dichroic dye DP can function in an environment where the transmission of parallel lines is suppressed. In other words, the dichroic dye DP is given an environment in which parallel lines that are difficult to absorb by the dichroic dye DP are suppressed, thereby improving contrast and thus increasing the effectiveness of contrast improvement.

[0063] Furthermore, it is preferable that the dimming sheet 10 satisfies the following conditions 2 and 3. (Condition 2) The total light transmittance in the opaque state is 30% or less. • (Condition 3) The chromaticity a* in the CIE1976 (L*a*b*) color system conforming to JIS-Z-8781-4 is between -15 and 15, and the chromaticity b* is between -15 and 15.

[0064] By satisfying condition 2 above, the dimming sheet 10 can sufficiently block visible light in an opaque state. The total light transmittance is a value obtained using a measurement method compliant with JIS K 7361-1:1997 (ISO 1468-1).

[0065] By satisfying the above condition 3, the dichroic sheet 10 can be made black or close to black in its opaque state. In other words, the dichroic dye DP absorbs scattered light suitably in the opaque state, and the dichroic sheet 10 suitably suppresses parallel lines such that the PTb / PTa value is greater than 80, which is expressed as black.

[0066] Regarding condition 2 above, the total light transmittance of the photochromic sheet 10 in the opaque state can be changed by changing the content of the dichroic dye DP in the photochromic layer 11. When the content of the dichroic dye DP in the photochromic layer 11 is increased, the total light transmittance in the opaque state decreases. Conversely, when the content of the dichroic dye DP in the photochromic layer 11 is decreased, the total light transmittance in the opaque state increases. Therefore, when adjusting the total light transmittance in the opaque state to satisfy condition 2, the content of the dichroic dye DP should be increased within a range where the PTb / PTa value does not deviate from condition 1.

[0067] Regarding condition 2 above, the total light transmittance of the dimming sheet 10 in the opaque state can also be changed by changing the thickness of the dimming layer 11. The total light transmittance of the dimming sheet 10 in the opaque state decreases as the thickness of the dimming layer 11 increases, and increases as the thickness of the dimming layer 11 decreases. Therefore, when adjusting the total light transmittance in the opaque state to satisfy condition 2, the thickness of the dimming layer 11 should be increased within a range where the PTb / PTa value does not deviate from condition 1.

[0068] Regarding condition 2 above, the total light transmittance of the photochromic sheet 10 in the opaque state can also be changed by changing the total light transmittance of the colored layer 14. The lower the total light transmittance of the colored layer 14, the lower the total light transmittance of the photochromic sheet 10 in the opaque state, and the higher the total light transmittance of the colored layer 14, the higher the total light transmittance of the photochromic sheet 10 in the opaque state. In addition, the colored layer 14 lowers not only the total light transmittance of the photochromic sheet 10 in the opaque state, but also the parallel line transmittance PTa of the photochromic sheet 10 in the opaque state and the parallel line transmittance PTb of the photochromic sheet 10 in the transparent state. Therefore, by providing the colored layer 14, the total light transmittance of the photochromic sheet 10 in the opaque state can be lowered without significantly changing the PTb / PTa value.

[0069] Regarding condition 3 above, the chromaticity a* and chromaticity b* of the dimming sheet 10 in the opaque state can be controlled by appropriately selecting the absorbance spectrum of the dichroic dye DP. The absorbance spectrum of the dichroic dye DP can be controlled by changing the mixture of the three primary colors: cyan, magenta, and yellow.

[0070] Regarding condition 3 above, the chromaticity a* and chromaticity b* of the dimming sheet 10 in the opaque state can also be controlled by appropriately selecting the color of the colored layer 14. In the opaque state, the color of the colored layer 14 should be selected such that the composite color obtained by superimposing the color of the dimming layer 11 and the color of the colored layer 14 satisfies condition 3 above.

[0071] [Manufacturing method for dimmable sheets] A method for manufacturing the dimming sheet 10 will now be described. First, a first transparent support layer 13A equipped with a first transparent electrode layer 12A and a second transparent support layer 13B equipped with a second transparent electrode layer 12B are prepared. Next, a coating film for forming the dimming layer 11 is formed between the first transparent electrode layer 12A and the second transparent electrode layer 12B.

[0072] The coating film contains a photopolymerizable compound, a liquid crystal composition 32, a dichroic dye DP, and a polymerization initiator for initiating the polymerization of the photopolymerizable compound. The polymerization initiator is at least one selected from the group consisting of diketone compounds, acetophenone compounds, benzoin compounds, benzophenone compounds, and thioxanthone compounds. The polymerization initiator may be a single compound or a combination of two or more compounds. An example of a polymerization initiator is any one selected from the group consisting of benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and cyclohexylphenyl ketone.

[0073] The method for manufacturing the dimmable sheet 10 includes separating the liquid crystal particles made of the liquid crystal composition 32 from the photopolymerizable compound by polymerizing the photopolymerizable compound within the coating film. The light used to polymerize the photopolymerizable compound may be ultraviolet light or an electron beam. The light used to polymerize the photopolymerizable compound may be directed toward the first transparent support layer 13A, the second transparent support layer 13B, or both the first transparent support layer 13A and the second transparent support layer 13B.

[0074] Phase separation of liquid crystal particles made of liquid crystal composition 32 proceeds through polymerization of the photopolymerizable compound and diffusion of the liquid crystal composition 32. The polymerization rate of the photopolymerizable compound varies depending on the intensity of the light irradiated onto the photopolymerizable compound. The diffusion rate of the liquid crystal composition 32 varies depending on the processing temperature during polymerization of the photopolymerizable compound. In the phase separation of liquid crystal composition 32, the intensity of the light irradiated onto the photopolymerizable compound, the irradiation time, and the processing temperature during polymerization of the photopolymerizable compound are set so that the size of the liquid crystal particles is a desired size and the number of liquid crystal particles is a desired quantity. That is, in the phase separation of liquid crystal composition 32, the intensity of the light irradiated onto the photopolymerizable compound, the irradiation time, and the processing temperature during polymerization of the photopolymerizable compound are set so that condition 1 is satisfied by the size of the voids 31D and the number of voids 31D. As a result, a laminate consisting of a light-adjusting layer 11, a first transparent electrode layer 12A, a second transparent electrode layer 12B, a first transparent support layer 13A, and a second transparent support layer 13B is constructed.

[0075] Next, the colored layer 14 is bonded to the surface of the first transparent support layer 13A that is opposite to the surface in contact with the first transparent electrode layer 12A. The colored layer 14 may be bonded to the first transparent support layer 13A by an adhesive, or it may be bonded by other methods such as welding.

[0076] [Effects of the Embodiment] According to the above embodiment, the following effects can be obtained. (1) When the parallel line transmittance PTa of the dimming sheet 10 in the opaque state and the parallel line transmittance PTb of the dimming sheet 10 in the transparent state satisfy PTb / PTa > 80, the difference in the intensity of the visible color between the transparent state and the opaque state becomes large. Therefore, the contrast between the transparent state and the opaque state can be clearly seen.

[0077] (2) The total light transmittance of the dimming sheet 10 in the opaque state is 30% or less, which allows for sufficient blocking of visible light in the opaque state, and consequently, sufficient darkness to be obtained as the color of the dimming sheet 10.

[0078] (3) In the opaque state of the light-adjusting sheet 10, the chromaticity a* is between -15 and 15, and the chromaticity b* is between -15 and 15, thereby making the color of the light-adjusting sheet 10 in the opaque state black or close to black. In other words, the dichroic dye DP suitably absorbs scattered light in the opaque state, and the light-adjusting layer 11 suitably suppresses the transmission of parallel lines such that the PTb / PTa value is greater than 80, which is expressed as black.

[0079] (4) By configuring the spacer 33 to exhibit the same color as the dichroic dye DP in the opaque state, the appearance of the light-adjusting sheet 10 can be made less conspicuous due to the color of the spacer 33. Furthermore, because the spacer 33 is colored, it can absorb scattered light generated by the liquid crystal compound LCM in the opaque state. As a result, the parallel line transmittance PTa in the opaque state can be reduced compared to when the spacer 33 is white or colorless and transparent. Therefore, the ratio of the parallel line transmittance PTb in the transparent state to the parallel line transmittance PTa in the opaque state can be increased. In particular, if the dichroic dye DP and the spacer 33 are configured to exhibit black, as in the above embodiment, scattered light in the opaque state can be absorbed effectively.

[0080] (5) The colored layer 14 is configured to exhibit the same color as the dichroic dye DP when opaque, so that when opaque, the light-adjusting sheet 10 exhibits a composite color of the color exhibited by the light-adjusting layer 11 and the color exhibited by the colored layer 14. Therefore, the color of the light-adjusting sheet 10 when opaque can be made more vivid compared to when the color of the light-adjusting sheet 10 when opaque is realized solely by the color exhibited by the light-adjusting layer 11. In addition, because the light-adjusting sheet 10 is equipped with a colored layer 14, the total light transmittance of the light-adjusting sheet 10 when opaque can be reduced by the amount that visible light is blocked by the colored layer 14.

[0081] [Examples] Examples and comparative examples of the dimming sheet 10 will be described with reference to Figures 3 and 4. Note that the following examples are merely illustrative examples for explaining the effects of the above embodiments and do not necessarily limit the present invention.

[0082] (Example 1) The dimming sheet 10 of Example 1 does not have a colored layer 14, and is composed of a dimming layer 11, a first transparent electrode layer 12A, a second transparent electrode layer 12B, a first transparent support layer 13A, and a second transparent support layer 13B. The dimming layer 11 of Example 1 also includes an organic polymer layer 31, a liquid crystal composition 32, and a black transparent spacer 33. The liquid crystal composition 32 of Example 1 includes a liquid crystal compound LCM and a dichroic dye DP that exhibits black color when the dimming sheet 10 is opaque.

[0083] The constituent materials of the dimming sheet 10 in Example 1 are shown below. • First transparent electrode layer 12A: Indium tin oxide, 30 nm thick • Second transparent electrode layer 12B: Indium tin oxide, 30 nm thick • First transparent support layer 13A: Polyethylene terephthalate film, 125 μm thick • Second transparent support layer 13B: Polyethylene terephthalate film, 125 μm thick • Spacer 33: Spherical particles made of PMMA, particle size 16 μm, black. UV-curable compounds: Isovonyl acrylate, pentaerythritol triacrylate, urethane acrylate, 40% by mass • Polymerization initiator: 1-hydroxycyclohexyl phenyl ketone, 3% by mass • Liquid crystal compound LCM: Cyanobiphenyl compound, 54% by mass • Dichroic dye DP: Black dichroic dye (product name YH-428: manufactured by Mitsui Chemicals Fine Co., Ltd.), 3.0% by mass A coating film with a thickness of 16 μm was formed on the first transparent electrode layer 12A using the coating solution of Example 1, and spacers 33 were scattered into the coating film. Then, the coating film with spacers 33 scattered on it was laminated with the first transparent electrode layer 12A and the second transparent electrode layer 12B, and by irradiating the first transparent support layer 13A with ultraviolet light at 365 nm, the light-adjusting sheet 10 of Example 1 was obtained. At this time, the intensity of the ultraviolet light was set to 10 mW / cm². 2 The settings were adjusted, and the ultraviolet light irradiation time was set to 100 seconds.

[0084] (Example 2) The dimming sheet 10 of Example 2 was configured in the same way as the dimming sheet 10 of Example 1, except that the spacer 33 included in the dimming layer 11 was white and transparent.

[0085] The differences between the constituent materials of the dimming sheet 10 in Example 2 and those in Example 1 are shown below. • Spacer 33: Spherical particles made of PMMA, particle size 16 μm, white. The coating film on which the spacers 33 described above were scattered was laminated with a first transparent electrode layer 12A and a second transparent electrode layer 12B, and the light-adjusting sheet 10 of Example 2 was obtained by irradiating the first transparent support layer 13A with ultraviolet light at 365 nm. At this time, the intensity of the ultraviolet light was set to 10 mW / cm². 2 The settings were adjusted, and the ultraviolet light irradiation time was set to 100 seconds.

[0086] (Example 3) The dimming sheet 10 of Example 3 had the same layer structure as the dimming sheet 10 of Example 1, but also included a black colored layer 14. The total light transmittance of the colored layer 14 was 46%.

[0087] The differences between the components of the dimming sheet 10 in Example 3 and those in Example 1 are shown below. • Colored layer 14: Black colored layer (Product name: Lumicool®, total light transmittance: 46%, manufactured by IKC Corporation) The coating film of Example 3 was laminated with a first transparent electrode layer 12A and a second transparent electrode layer 12B, and the light-adjusting sheet 10 of Example 3 was obtained by irradiating the first transparent support layer 13A with ultraviolet light at 365 nm. At this time, the intensity of the ultraviolet light was set to 10 mW / cm². 2 The settings were adjusted, and the ultraviolet light irradiation time was set to 100 seconds.

[0088] (Example 4) The dimming sheet 10 of Example 4 had the same layer configuration as the dimming sheet 10 of Example 2, but also included a black colored layer 14. The total light transmittance of the colored layer 14 was 46%. The colored layer 14 of the dimming sheet 10 of Example 4 has the same configuration as the colored layer 14 of the dimming sheet 10 of Example 3.

[0089] The coating film of Example 4 was laminated with a first transparent electrode layer 12A and a second transparent electrode layer 12B, and the light-adjusting sheet 10 of Example 4 was obtained by irradiating the first transparent support layer 13A with ultraviolet light at 365 nm. At this time, the intensity of the ultraviolet light was set to 10 mW / cm². 2 The settings were adjusted, and the ultraviolet light irradiation time was set to 100 seconds.

[0090] (Example 5) The dimming sheet 10 of Example 5 had the same layer structure as the dimming sheet 10 of Example 1, but also included a black colored layer 14. The total light transmittance of the colored layer 14 was 7%.

[0091] The differences between the materials used in the dimming sheet 10 of Example 5 and those of Example 1 are shown below. • Colored layer 14: Black colored layer (Product name: Lumicool®, total light transmittance: 7%, manufactured by IKC Corporation) The coating film of Example 5 was laminated with a first transparent electrode layer 12A and a second transparent electrode layer 12B, and the light-adjusting sheet 10 of Example 5 was obtained by irradiating the first transparent support layer 13A with ultraviolet light at 365 nm. At this time, the intensity of the ultraviolet light was set to 10 mW / cm². 2 The settings were adjusted, and the ultraviolet light irradiation time was set to 100 seconds.

[0092] (Example 6) The dimming sheet 10 of Example 6 had the same layer configuration as the dimming sheet 10 of Example 2, but also included a black colored layer 14. The total light transmittance of the colored layer 14 was 7%. The colored layer 14 of the dimming sheet 10 of Example 6 had the same configuration as the colored layer 14 of the dimming sheet 10 of Example 5.

[0093] The coating film of Example 6 was laminated with a first transparent electrode layer 12A and a second transparent electrode layer 12B, and the light-adjusting sheet 10 of Example 6 was obtained by irradiating the first transparent support layer 13A with ultraviolet light at 365 nm. At this time, the intensity of the ultraviolet light was set to 10 mW / cm². 2 The settings were adjusted, and the ultraviolet light irradiation time was set to 100 seconds.

[0094] (Example 7) The light-adjusting sheet 10 of Example 7 was configured similarly to the light-adjusting sheet 10 of Example 2, except that instead of a black dichroic dye DP, a dichroic dye DP that exhibits blue color when the light-adjusting sheet 10 is opaque was used.

[0095] The differences between the constituent materials of the dimming sheet 10 in Example 7 and those in Example 1 are shown below. • Dichroic dye DP: Blue dichroic dye (product name M-412: manufactured by Mitsui Chemicals Fine Co., Ltd.), 3.0% by mass The coating film of Example 7 was laminated with a first transparent electrode layer 12A and a second transparent electrode layer 12B, and the light-adjusting sheet 10 of Example 7 was obtained by irradiating the first transparent support layer 13A with ultraviolet light at 365 nm. At this time, the intensity of the ultraviolet light was set to 10 mW / cm². 2 The settings were adjusted, and the ultraviolet light irradiation time was set to 100 seconds.

[0096] (Comparative Example 1) The light-adjusting sheet 10 of Comparative Example 1 was configured in the same way as the light-adjusting sheet 10 of Example 1, except that the light-adjusting layer 11 did not have a dichroic dye DP.

[0097] (Comparative Example 2) The light-adjusting sheet 10 of Comparative Example 2 was configured in the same way as the light-adjusting sheet 10 of Example 2, except that the light-adjusting layer 11 did not have a dichroic dye DP.

[0098] (Comparative Example 3) The light-adjustable sheet 10 of Comparative Example 3 was configured similarly to the light-adjustable sheet 10 of Example 4, except that the light-adjustable layer 11 did not contain a dichroic dye DP.

[0099] (Comparative Example 4) The light-adjustable sheet 10 of Comparative Example 4 was configured in the same way as the light-adjustable sheet 10 of Example 6, except that the light-adjustable layer 11 did not contain a dichroic dye DP.

[0100] [evaluation] The dimming sheets 10 of Examples 1-7 and Comparative Examples 1-4 were evaluated for the following evaluation items (a)-(d). Figure 3 shows the evaluation results for evaluation items (a)-(d).

[0101] (a) Evaluation of the ratio of the parallel line transmittance PTb in the transparent state of the dimmable sheet 10 to the parallel line transmittance PTA in the opaque state of the dimmable sheet 10. (b) Evaluation of total light transmittance of the dimming sheet 10 in the opaque state (c) Chromatic evaluation of the dimming sheet 10 in an opaque state (d) Appearance evaluation of the dimming sheet 10 in its opaque state. In the evaluation described in (a) above, the parallel line transmittance PTa was measured for the dimmable sheet 10 in an opaque state without the application of a driving voltage. Then, the parallel line transmittance PTb was measured for the dimmable sheet 10 in a transparent state with the application of a driving voltage. In the evaluation described in (a), a haze meter (product name: NDH2000, manufactured by Nippon Denshoku) was used. Furthermore, using a method compliant with JIS K 7136, the component detected with the light trap at the exit aperture functioning was defined as the diffusion component, and the component obtained by removing the diffusion component from the transmitted light of the total light rays was defined as the parallel component, and the parallel line transmittances PTa and PTb were measured.

[0102] In Examples 1-7, the dimming sheets 10 had a PTb / PTa value exceeding 80, which is the ratio of the parallel line transmittance PTb in the transparent state to the parallel line transmittance PTa in the opaque state. In particular, in Examples 1, 3, and 5, where the dimming layer 11 included a black transparent spacer 33, the PTb / PTa value exceeded 200. In Examples 2, 4, 6, and 7, where the dimming layer 11 included a white transparent spacer 33, the PTb / PTa value was around 100. Therefore, Examples 1-7 satisfied condition 1 described above. In contrast, the dimming sheets 10 in Comparative Examples 1-4 had a PTb / PTa value of 80 or less.

[0103] In the evaluation described in (b) above, the total light transmittance was measured for the dimming sheet 10, which was in an opaque state without any driving voltage applied, using a method compliant with JIS K 7361-1:1997 (ISO 1468-1). For the evaluation described in (b) above, a total light transmittance measuring device (product name: NDH2000, manufactured by Nippon Denshoku) was used.

[0104] The light-adjustable sheets 10 of Examples 1-6 had a total light transmittance of 30% or less in the opaque state. Therefore, Examples 1-6 satisfied condition 2 described above. Furthermore, among Examples 1-6, it was observed that the level of colored layer 14 with a low total light transmittance, as in Examples 5 and 6, tended to have a lower total light transmittance of the light-adjustable sheet 10 in the opaque state. In contrast, the light-adjustable sheet 10 of Example 7 had a total light transmittance of over 30% in the opaque state. This is thought to be due to the different type of dichroic dye DP present in the light-adjustable sheet 10 of Example 7 compared to Examples 1-6.

[0105] The dimmable sheets 10 of Comparative Examples 1-3 had a total light transmittance of over 30% in the opaque state. The dimmable sheet 10 of Comparative Example 4 had a total light transmittance of 30% or less in the opaque state. This is thought to be due to the colored layer 14 of the dimmable sheet 10 of Comparative Example 4 having a low total light transmittance (7%).

[0106] In the evaluation described in (c) above, the chromaticity a* and b* were measured using a colorimeter on the dimming sheet 10, which was in an opaque state without any driving voltage applied. Note that the chromaticity a* and b* are specified in the CIE1976 (L*a*b*) color system, which conforms to JIS-Z-8781-4.

[0107] The dimming sheets 10 of Examples 1-6 and Comparative Examples 1-4 had a chromaticity a* of -15 or more and a chromaticity b. Therefore, Examples 1-6 and Comparative Examples 1-4 satisfied condition 3 described above. In contrast, the dimming sheet 10 of Example 7 had a chromaticity a* of -15 or more and a chromaticity b* of greater than 15. This is thought to be due to the different type of dichroic dye DP present in the dimming sheet 10 of Example 7 compared to Examples 1-6.

[0108] In the evaluation described in (d) above, the dimming sheet 10, which was in an opaque state without a driving voltage applied, was judged by the naked eye to determine whether a clear black color could be obtained. The evaluation criteria were as follows: A clear black appearance was obtained, which was marked with "◎". A whitish appearance due to scattered light from the liquid crystal compound LCM was obtained within the black, which was marked with "〇". A color other than white was observed within the black, which was marked with "△". A relatively strong whiteness due to scattered light from the liquid crystal compound LCM was observed within the black, and black was not observed at all, which was marked with "×".

[0109] In Examples 1, 3, and 5, where the dimming layer 11 included a black transparent spacer 33, a clear black appearance was observed. In Examples 2, 4, and 6, a whitish appearance due to scattered light from the liquid crystal compound LCM was observed within the black. In Example 7, a yellowish appearance was observed within the black. This is presumed to be because the dimming sheet 10 in Example 7 had a higher total light transmittance when opaque compared to Examples 1-6, resulting in a relatively stronger effect of scattered light due to Rayleigh scattering, thus causing a yellowish appearance. In Comparative Examples 1-4, a relatively strong whiteness due to scattered light from the liquid crystal compound LCM was observed within the black.

[0110] [Example of changes] The above embodiment can be implemented with the following modifications. The dimming sheet 10 may also include two colored layers 14 sandwiching a laminate composed of a dimming layer 11, a first transparent electrode layer 12A, a second transparent electrode layer 12B, a first transparent support layer 13A, and a second transparent support layer 13B. In this case, one colored layer 14 is located on the surface of the first transparent support layer 13A opposite to the surface in contact with the first transparent electrode layer 12A, and the other colored layer 14 is located on the surface of the second transparent support layer 13B opposite to the surface in contact with the second transparent electrode layer 12B. With such a configuration, the total light transmittance of the dimming sheet 10 in the opaque state can be further reduced, and the values ​​of chromaticity a* and chromaticity b* can be brought closer to values ​​closer to black.

[0111] The colored layer 14 may be omitted if the light-adjusting sheet 10 is configured to satisfy at least condition 1. In this case, the thickness of the light-adjusting sheet 10 can be reduced. However, even in this case, it is preferable that the light-adjusting sheet 10 is configured to satisfy conditions 2 and 3. For example, the configuration of each layer constituting the light-adjusting sheet 10 may be changed by combining the first transparent electrode layer 12A, the second transparent electrode layer 12B, the first transparent support layer 13A, and the second transparent support layer 13B so that optical properties equivalent to those when the colored layer 14 is included can be achieved.

[0112] - As long as the light-adjusting sheet 10 is configured to satisfy at least condition 1, the color exhibited by the colored layer 14 may be different from the color exhibited by the dichroic dye DP in the opaque state. Even in this case, the colored layer 14 can reduce the total light transmittance of the light-adjusting sheet 10 in the opaque state.

[0113] - As long as the light-adjusting sheet 10 is configured to satisfy at least condition 1, the color exhibited by the spacer 33 may be different from the color exhibited by the dichroic dye DP in the opaque state. Even in this case, for example, if the spacer 33 is colored, the scattered light generated in the opaque state can be absorbed by the spacer 33. This can lower the parallel line transmittance PTa in the opaque state, and as a result, the ratio of the parallel line transmittance PTb in the transparent state to PTa can be increased. Alternatively, some or all of the spacer 33 added to the light-adjusting layer 11 may be made colorless and transparent, and the particle size may be adjusted to make the spacer 33 less noticeable.

[0114] • As long as the dimming sheet 10 is configured to satisfy at least condition 1, both or either of the chromaticity a* and chromaticity b* may fall outside the range of condition 3. That is, in the opaque state, the dimming sheet 10 may be configured to exhibit a color other than black or a color close to black. Even in this case, the effects similar to those in (1) and (2) above can be obtained.

[0115] • If the dimming sheet 10 is configured to satisfy at least condition 1, the total light transmittance of the dimming sheet 10 in the opaque state may exceed 30%. Even in this case, the contrast between the transparent state and the opaque state can be clearly seen because the ratio of PTb to PTa is large.

[0116] The dimming sheet 10 may have one or more other functional layers, provided that the configuration switches between a transparent state and an opaque state of the dimming sheet 10 based on a change in the orientation state of the liquid crystal compound LCM. The other functional layers may be gas barrier layers that suppress the transmission of oxygen and moisture to the dimming layer 11, or ultraviolet barrier layers that suppress the transmission of ultraviolet light other than specific wavelengths to the dimming layer 11. The other functional layers may be hard coat layers that mechanically protect each layer of the dimming sheet 10, or adhesive layers that improve the adhesion between layers in the dimming sheet 10.

[0117] In the above embodiment, the light-adjusting layer 11 has a structure comprising an organic polymer layer 31 and a liquid crystal composition 32. Alternatively, the light-adjusting sheet 10 may be of the SPD (Suspended Particle Device) type, having light-adjusting particles as aligning particles. The SPD method is a method in which a light-adjusting suspension containing light-adjusting particles is dispersed in a resin matrix.

[0118] Based on the above embodiments and modifications, the following technical ideas can be further derived. (Note 1) A light-adjusting layer comprising an organic polymer layer having multiple voids, and a liquid crystal composition filling the voids, the liquid crystal composition comprising a liquid crystal compound and a dichroic dye, A pair of transparent electrode layers sandwiching the light-adjusting layer, The laminate comprises the light-adjusting layer and a pair of transparent support layers sandwiching the pair of transparent electrode layers, A light-adjustable sheet that changes the orientation of the liquid crystal compound and the dichroic dye in response to a change in the potential difference between a pair of transparent electrode layers, thereby switching from a transparent state to a colored opaque state, The parallel line transmittance PTa in the opaque state and the parallel line transmittance PTb in the transparent state satisfy PTb / PTa > 80. Dimming sheet.

[0119] (Note 2) The parallel line transmittance PTa in the opaque state is 0.6% or less. The dimming sheet described in Appendix 1.

[0120] (Note 3) The total light transmittance in the opaque state is 30% or less. Dimming sheet as described in Appendix 1 or 2.

[0121] (Note 4) In the opaque state described above, the chromaticity a* in the CIE1976 (L*a*b*) color system conforming to JIS-Z-8781-4 is between -15 and 15, and the chromaticity b* is between -15 and 15. A dimming sheet as described in any one of the appendices 1 through 3.

[0122] (Note 5) The light-adjusting layer further comprises a spacer that exhibits the same color as the color exhibited by the dichroic dye in the opaque state. A dimming sheet as described in any one of the appendices 1 through 4.

[0123] (Note 6) The present invention further comprises a colored layer located on the surface of at least one of the transparent support layers opposite to the surface in contact with the transparent electrode layer, The colored layer exhibits the same color as the dichroic dye exhibits in the opaque state. A dimming sheet as described in any one of the appendices 1 through 5. [Explanation of symbols]

[0124] DP... Dichroic pigment LCM…liquid crystal compound 10… Dimming sheet 11…Dimming layer 12A...first transparent electrode layer 12B...Second transparent electrode layer 13A...First transparent support layer 13B…Second transparent support layer 14...Colored layer 31...Organic polymer layer 31D…Void 32…Liquid crystal composition 33…Spacer

Claims

1. A light-adjusting layer comprising an organic polymer layer having multiple voids, and a liquid crystal composition filling the voids, the liquid crystal composition comprising a liquid crystal compound and a dichroic dye, A pair of transparent electrode layers sandwiching the light-adjusting layer, The laminate comprises the light-adjusting layer and a pair of transparent support layers sandwiching the pair of transparent electrode layers, A light-adjustable sheet that changes the orientation of the liquid crystal compound and the dichroic dye in response to a change in the potential difference between a pair of transparent electrode layers, thereby switching from a transparent state to a colored opaque state, The dichroic dye exhibits black color in the opaque state. The parallel line transmittance PTa in the opaque state and the parallel line transmittance PTb in the transparent state satisfy PTb / PTa > 80. The parallel line transmittance PTa in the opaque state is 0.6% or less. The total light transmittance in the opaque state is 30% or less. Dimming sheet.

2. A light-adjusting layer comprising an organic polymer layer having multiple voids, and a liquid crystal composition filling the voids, the liquid crystal composition comprising a liquid crystal compound and a dichroic dye, A pair of transparent electrode layers sandwiching the light-adjusting layer, The laminate comprises the light-adjusting layer and a pair of transparent support layers sandwiching the pair of transparent electrode layers, A light-adjustable sheet that changes the orientation of the liquid crystal compound and the dichroic dye in response to a change in the potential difference between a pair of transparent electrode layers, thereby switching from a transparent state to a colored opaque state, The parallel line transmittance PTa in the opaque state and the parallel line transmittance PTb in the transparent state satisfy PTb / PTa > 80. The total light transmittance in the opaque state is 30% or less. The dimming sheet further comprises a colored layer located on the surface of at least one of the transparent support layers opposite to the surface in contact with the transparent electrode layer, The colored layer exhibits the same color as the dichroic dye exhibits in the opaque state. Dimming sheet.

3. In the opaque state, the chromaticity a* in the CIE 1976 (L*a*b*) color system conforming to JIS-Z-8781-4 is -15 or more and 15 or less, and the chromaticity b* is -15 or more and 15 or less. The dimming sheet according to claim 1 or 2.

4. The light-adjusting layer further comprises a spacer that exhibits the same color as the color exhibited by the dichroic dye in the opaque state. A dimming sheet according to any one of claims 1 to 3.

Images