Light-adjusting sheet and light-adjusting device

Abstract

Provided is a light modulating sheet, the design properties of which can be improved as a result of the following. The thickness of a light modulating layer 11 at a plurality of measurement positions is in a range of from 0.8 to 1.2 times a median thickness value. In a characteristic curve obtained by measuring the changes in the linear transmittance of visible light upon changing a drive voltage applied to transparent electrode layers 12A, 12B, a lower limit drive voltage in a range in which the rate of change of the linear transmittance is 0.5% / V or more is a first voltage Va, an upper limit drive voltage is a second voltage Vb, and a median value of the first voltage Va and the second voltage Vb is Vm. Among the median values Vm obtained from the characteristic curve at the measurement positions, a variation in the median values obtained by dividing the difference between a minimum value Vmin and a maximum value Vmax by an average value Vavr of the median values is no more than 35.0%.

Description

[Technical Field]

[0001] The present disclosure relates to a light control sheet and a light control device with variable in-line transmittance. [Background technology]

[0002] A light-controlling sheet comprises a light-controlling layer containing a liquid crystal composition and a pair of transparent electrode layers sandwiching the light-controlling layer (see, for example, Patent Document 1). A light-controlling device comprises the light-controlling sheet and a drive unit that controls the application of a drive voltage to the pair of transparent electrode layers. The alignment state of the liquid crystal molecules changes depending on the potential difference between the pair of transparent electrode layers, thereby changing the linear transmittance of the light-controlling sheet. The light-controlling sheet is attached to, for example, building materials such as window glass or glass walls, or automobile window glass, and functions as a partition member that separates two spaces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-187775 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, if a light-controlling sheet can also function as a decorative element in a space, like a shoji screen with shoji paper affixed with a pattern such as fading or shading, the range of its application as a partitioning material can be greatly expanded. However, the above-mentioned light-controlling sheet only exhibits either a colorless and transparent state across the entire sheet or a plain, cloudy white state due to light scattering, depending on the magnitude of the driving voltage. Therefore, there is a strong demand for improving the design of light-controlling sheets. [Means for solving the problem]

[0005] The light-controlling sheet that solves the above-mentioned problems includes a light-controlling layer including a resin layer and oriented particles, a pair of transparent electrode layers sandwiching the light-controlling layer, and a pair of transparent support layers sandwiching the light-controlling layer and the pair of transparent electrode layers, wherein the thickness of the light-controlling layer measured at a plurality of measurement positions is within a range of 0.8 to 1.2 times the median thickness, and the light-controlling layer has a structure in which the oriented particles are contained in a plurality of voids dispersed in the resin layer, and the linear transmittance of visible light obtained by measuring the change in the linear transmittance of visible light when the driving voltage applied to the transparent electrode layer is changed is In the characteristic curve, the lower limit driving voltage in the range where the absolute value of the rate of change of the linear transmittance is 0.5% / V or more is defined as a first voltage Va, and the upper limit driving voltage is defined as a second voltage Vb. The intermediate value between the first voltage Va and the second voltage Vb is defined as Vm. Of the intermediate values ​​Vm obtained from the characteristic curve at the multiple measurement positions, the variation of the intermediate values ​​{(Vmax-Vmin) / Vavr} x 100, which is obtained by dividing the difference between the minimum value Vmin and the maximum value Vmax by the average value Vavr of the intermediate values ​​Vm, is 35.0% or less.

[0006] A light control device that solves the above problem includes a light control sheet whose linear transmittance changes depending on the drive voltage, and a drive unit that controls the drive voltage applied to the light control sheet, and includes a light control layer containing a resin layer and oriented particles, a pair of transparent electrode layers that sandwich the light control layer, and a pair of transparent support layers that sandwich the light control layer and the pair of transparent electrode layers, wherein the thickness of the light control layer measured at multiple measurement positions is within a range of 0.8 to 1.2 times the median thickness, and the light control layer has a structure in which the oriented particles are contained in multiple voids dispersed in the resin layer, and among the characteristic curves obtained by measuring the change in linear transmittance of visible light when the drive voltage applied to the transparent electrode layer is changed, the lower limit of the range in which the absolute value of the rate of change in linear transmittance is 0.5% / V or more is selected as the first drive voltage. The first voltage is Va, the upper limit driving voltage is a second voltage Vb, the intermediate value between the first voltage Va and the second voltage Vb is Vm, and the variation of the intermediate values ​​Vm obtained from the characteristic curve at the multiple measurement positions, {(Vmax-Vmin) / Vavr} x 100, which is the difference between the minimum value Vmin and the maximum value Vmax divided by the average value Vavr of the intermediate values ​​Vm, is 35.0% or less, and the driving unit switches between a first mode in which the driving voltage is not applied, a second mode in which a voltage equal to or greater than the second voltage Vb is applied, and a third mode in which a voltage between the first voltage Va and the second voltage Vb is applied so that the linear transmittance of the light-controlling sheet is a linear transmittance between the linear transmittance in the first mode and the linear transmittance in the second mode.

[0007] A light-controlling sheet whose absolute value of the linear transmittance change rate per unit voltage is 0.5% / V or more can achieve a linear transmittance intermediate between the linear transmittance in the transparent mode and the linear transmittance in the opaque mode. According to the above configuration, the thickness of the light-controlling layer measured at multiple measurement positions is within a range of 0.8 to 1.2 times the median thickness, thereby suppressing the variation in the median value between the first voltage Va, which is the lower limit of the drive voltage achieving halftones, and the second voltage Vb, which is the upper limit. If the variation in the median value is 35.0% or less, the occurrence of visually noticeable non-uniformity in transparency in the light-controlling sheet can be suppressed when a constant drive voltage near the median value is applied to set the halftone mode. As a result, the aesthetic appearance of the light-controlling sheet in the halftone mode can be improved. Therefore, adding the halftone mode to one of the drive modes can enhance the design of the light-controlling sheet.

[0008] In the above-mentioned light-controlling sheet, the light-controlling layer may include spacers that control the gap between the pair of transparent electrode layers, and when the light-controlling layer is observed from the contact surface with the transparent electrode layer, the ratio of the total area occupied by the multiple spacers to the total area of ​​the light-controlling layer may be 0.9% or more and 30.0% or less.

[0009] According to the above configuration, the occupied area ratio, which is the ratio of the area occupied by multiple spacers, is 0.9% or more and 30.0% or less, so that the gap in the transparent electrode layer can be controlled to reduce the variation in the thickness of the dimming layer and reduce the haze caused by the spacers in the transparent mode.

[0010] In the light controlling sheet, the diameter of the voids may be 0.4 μm or more and 2.2 μm or less. According to the above configuration, by setting the diameter of the voids to 0.4 μm or more and 2.2 μm or less, the oriented particles in the voids of the resin layer are easily oriented along the electric field. This makes it easier to control the linear transmittance. Furthermore, in the opaque mode, there is no transparency, and it is possible to achieve good light scattering in the visible light range.

[0011] In the light controlling sheet, the difference between the first voltage Va and the second voltage Vb may be 22V or less. According to the above configuration, the response speed required for transition between the transparent mode and the opaque mode can be made appropriate, and the power consumption required for transition between the transparent mode and the opaque mode can be reduced. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to improve the design of a light-controlling sheet and a light-controlling device including the light-controlling sheet. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing a normal-type light-control sheet. [Figure 2] FIG. 2 is a plan view showing the light controlling sheet in the opaque mode. [Figure 3] FIG. 3 is a plan view showing a light controlling sheet in the transparent mode. [Figure 4] FIG. 4 is a plan view showing a light controlling sheet in the halftone mode. [Figure 5] FIG. 5 is a cross-sectional view showing a light-controlling sheet in the opaque mode. [Figure 6] FIG. 6 is a cross-sectional view showing a light-controlling sheet in the transparent mode. [Figure 7] FIG. 7 is a plan view showing a light controlling sheet of a reference example that exhibits intermediate tones. [Figure 8] FIG. 8 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of the reference example. [Figure 9] FIG. 9 is a graph showing the voltage-linear transmittance curve of the light-control sheet. [Figure 10] FIG. 10 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of the reference example. [Figure 11] FIG. 11 is a cross-sectional view showing a reverse-type light controlling sheet. [Figure 12] FIG. 12 is a table showing the evaluation results of Examples 1 to 4 and Comparative Examples 1 and 2. [Figure 13] FIG. 13 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of Example 1. [Figure 14] FIG. 14 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of Example 2. [Figure 15] FIG. 15 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of Example 3. [Figure 16] FIG. 16 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of Example 4. [Figure 17] FIG. 17 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of Comparative Example 1. [Figure 18] FIG. 18 is a graph showing the voltage-linear transmittance curve of the light controlling sheet of Comparative Example 2. [Figure 19] FIG. 19 is an electron microscope photograph showing the light-control layer of the light-control sheet of Example 1. [Figure 20] FIG. 20 is an electron microscope photograph showing the light-control layer of the light-control sheet of Example 2. [Figure 21] FIG. 21 is an electron microscope photograph showing the light-control layer of the light-control sheet of Example 3. [Figure 22] FIG. 22 is an electron microscope photograph showing the light-control layer of the light-control sheet of Example 4. [Figure 23] FIG. 23 is an electron microscope photograph showing the light control layer of the light control sheet of Comparative Example 1. [Figure 24] FIG. 24 is an electron microscope photograph showing the light control layer of the light control sheet of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of a light controlling sheet and a light controlling device will be described with reference to the drawings. [Basic structure of dimming device] The basic structure of the light controlling sheet and the light controlling device will be described with reference to FIG.

[0015] As shown in Figure 1, the light-adjusting device 1 includes a light-adjusting sheet 10 and a drive unit 20 that controls the application of a drive voltage to the light-adjusting sheet 10. The light-adjusting sheet 10 may have a normal structure in which the linear transmittance of visible light is high when current is applied and low when current is not applied. The light-adjusting sheet 10 may also have a reverse structure in which the linear transmittance is low when current is applied and high when current is not applied. In this embodiment, the normal-type light controlling sheet 10N will be mainly described. Furthermore, the configuration common to the normal-type and reverse-type light controlling sheets will be simply described as the light controlling sheet 10. The linear transmittance T indicates the transmittance of incident light parallel to the normal direction of the surface of the light controlling sheet 100, and is also called the parallel transmittance.

[0016] The normal-type light control sheet 10N includes a light control layer 11, a pair of transparent electrode layers, a first transparent electrode layer 12A and a second transparent electrode layer 12B, and a pair of transparent support layers, a first transparent support layer 13A and a second transparent support layer 13B. The first transparent electrode layer 12A and the second transparent electrode layer 12B sandwich the light control layer 11. The first transparent support layer 13A and the second transparent support layer 13B sandwich the light control layer 11, the first transparent electrode layer 12A, and the second transparent electrode layer 12B. The light control layer 11 is located between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The light control layer 11 is in contact with the first transparent electrode layer 12A and the second transparent electrode layer 12B. The first transparent support layer 13A supports the first transparent electrode layer 12A. The second transparent support layer 13B supports the second transparent electrode layer 12B.

[0017] The surface of the first transparent electrode layer 12A is connected to the first terminal 15A. The first terminal 15A is connected to the drive unit 20 through wiring 16A. The surface of the second transparent electrode layer 12B is connected to the second terminal 15B. The second terminal 15B is connected to the drive unit 20 through wiring 16B. The first terminal 15A is disposed in an area at the end of the light controlling sheet 10N where the first transparent electrode layer 12A is exposed. The second terminal 15B is disposed in an area at the end of the light controlling sheet 10N where the second transparent electrode layer 12B is exposed. The first terminal 15A and the second terminal 15B form part of the light controlling sheet 10N.

[0018] The driving unit 20 applies a driving voltage between the first transparent electrode layer 12 A and the second transparent electrode layer 12 B. The magnitude of the driving voltage is variable and controlled by the driving unit 20. The light-controlling layer 11 includes a transparent resin layer and a liquid crystal composition. Examples of the light-controlling layer 11 include polymer-dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC), and nematic curvilinear aligned phase (NCAP). The light-controlling layer 11 including the polymer-dispersed liquid crystal has a resin layer with a large number of independent voids or voids having a shape in which parts of independent shapes are joined together, and holds the liquid crystal composition in the voids. The polymer network liquid crystal has a polymer network with a three-dimensional mesh structure, and holds liquid crystal molecules as aligned particles in the voids of the polymer network. The encapsulated nematic liquid crystal layer holds a liquid crystal composition in an encapsulated shape in a resin layer. The light-controlling layer 11 of this embodiment includes a polymer-dispersed liquid crystal.

[0019] Examples of liquid crystal molecules as alignment particles include one or more of Schiff base-based, azo-based, azoxy-based, biphenyl-based, terphenyl-based, benzoate ester-based, tolan-based, pyrimidine-based, cyclohexanecarboxylic acid ester-based, phenylcyclohexane-based, and dioxane-based. The liquid crystal molecules contained in the light-controlling layer 11 have, for example, a positive dielectric anisotropy, and the dielectric constant in the long axis direction of the liquid crystal molecules is larger than the dielectric constant in the short axis direction of the liquid crystal molecules.

[0020] Each of the first transparent electrode layer 12A and the second transparent electrode layer 12B has a transparency that allows visible light to pass through. The material constituting the first transparent electrode layer 12A and the second transparent electrode layer 12B may be any one selected from the group consisting of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide, zinc oxide, carbon nanotubes (CNT), and poly(3,4-ethylenedioxythiophene) (PEDOT).

[0021] The first transparent support layer 13A and the second transparent support layer 13B transmit visible light. The first transparent support layer 13A and the second transparent support layer 13B may be synthetic resins or inorganic compounds. Examples of synthetic resins include polyester, polyacrylate, polycarbonate, and polyolefin. Examples of polyesters include polyethylene terephthalate (PET) and polyethylene naphthalate. Examples of polyacrylates include polymethyl methacrylate. Examples of inorganic compounds include silicon dioxide, silicon oxynitride, and silicon nitride.

[0022] The first terminal portion 15A and the second terminal portion 15B are, for example, flexible printed circuits (FPCs). 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. The first terminal portion 15A and the second terminal portion 15B are not limited to FPCs, and may be, for example, a metal tape.

[0023] The first terminal 15A and the second terminal 15B are bonded to the first transparent electrode layer 12A and the second transparent electrode layer 12B by a conductive adhesive layer (not shown). In the first terminal 15A and the second terminal 15B, the portions bonded to the conductive adhesive layer have conductor portions exposed from the protective layer or the support layer. 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), or an isotropic conductive paste (ICP). From the viewpoint of ease of handling in the manufacturing process of the light control device 1, the conductive adhesive layer is preferably an anisotropic conductive film.

[0024] Each of the wirings 16A and 16B is formed of, for example, a metal wire and an insulating layer covering the metal wire. The wire is formed of, for example, copper. The driving unit 20 applies a driving voltage between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The driving voltage may be an AC voltage having a rectangular waveform. The driving voltage may be an AC voltage having a sinusoidal waveform. The driving voltage may be a DC voltage.

[0025] The light-controlling layer 11 changes the orientation of the liquid crystal molecules in response to a change in the voltage between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The change in the orientation of the liquid crystal molecules changes the degree of scattering, absorption, and transmission of visible light that enters the light-controlling layer 11.

[0026] [Light-adjusting sheet] 2 to 6, the structure of a normal-type light controlling sheet 10N will be described together with the driving modes of the light controlling device 1. The light controlling device 1 has three driving modes: a transparent mode, an opaque mode, and a halftone mode. In the light controlling sheet 10N of this embodiment, the opaque mode is an example of the first mode, the transparent mode is an example of the second mode, and the halftone mode is an example of the third mode.

[0027] 2 shows the light controlling sheet 10N in the opaque mode. The opaque mode is a mode in which the linear transmittance of visible light through the light controlling sheet 10N is the smallest within the range of linear transmittance variation in the light controlling sheet 10N. In the opaque mode, no driving voltage is applied between the first transparent electrode layer 12A and the second transparent electrode layer 12B.

[0028] 3 shows the light controlling sheet 10N in the transparent mode. The transparent mode is a mode in which the linear transmittance of visible light through the light controlling sheet 10N is the largest within the range of linear transmittance variation in the light controlling sheet 10N. In the transparent mode, a driving voltage of a predetermined magnitude is applied between the first transparent electrode layer 12A and the second transparent electrode layer 12B.

[0029] FIG. 4 shows the light-controlling sheet 10N in halftone mode. The halftone mode is a driving mode that causes the light-controlling sheet 10N to exhibit a linear transmittance between the linear transmittance of visible light in the opaque mode and the linear transmittance in the transparent mode. The halftone mode is a driving mode that makes the light-controlling sheet 10N semi-transparent and semi-scattering. The haze, which is the degree of cloudiness in halftones, can be adjusted depending on the application, etc. In the halftone mode, a voltage smaller than the driving voltage applied in the transparent mode is applied between the first transparent electrode layer 12A and the second transparent electrode layer 12B.

[0030] The light-controlling layer 11 will be described in detail with reference to FIGS. 5 and 6. FIG. 5 schematically shows the cross-sectional structure of the light-controlling sheet 10N in the opaque mode, with the first transparent support layer 13A and the second transparent support layer 13B omitted from the illustration. The light-controlling layer 11 includes a resin layer 111, a liquid crystal composition 112, and a plurality of spacers 115. The spacers 115 are positioned between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The spacers 115 may have any shape that can control the gap between the first transparent electrode layer 12A and the second transparent electrode layer 12B. For example, the spacers 115 are primarily made of resin and have a spherical or columnar shape. The spacers 115 transmit visible light.

[0031] The resin layer 111 and the liquid crystal composition 112 are located in the space between the first transparent electrode layer 12A and the second transparent electrode layer 12B, and fill the space around spacers 115 dispersed in the space. The resin layer 111 has a large number of voids 116. The voids 116 may be independent, or one void 116 may have a shape in which a part of the independent shape is joined to another void 116. The liquid crystal composition 112 fills the voids 116. The liquid crystal composition 112 contains liquid crystal molecules 114. When the driving mode of the light-controlling sheet 10N is the opaque mode, the liquid crystal molecules 114 align their long axes in a direction other than the normal direction to the first transparent electrode layer 12A, for example, in an irregular direction. As a result, the difference between the refractive index of the liquid crystal composition 112 in the gaps 116 and the refractive index of the resin layer 111 scatters visible light incident on the light-controlling layer 11, and the linear transmittance decreases compared to the light-controlling sheet 10N in the transparent mode, resulting in lower transparency.

[0032] 6 shows a light-controlling sheet 10N driven in transparent mode when a transparent mode drive voltage is applied between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The long axes of the liquid crystal molecules 114 are aligned parallel or approximately parallel to the normal direction of the first transparent electrode layer 12A. This reduces scattering of light incident on the light-controlling layer 11, and increases the linear transmittance and transparency compared to the light-controlling sheet 10N in opaque mode.

[0033] Furthermore, in the light controlling sheet 10N driven in the halftone mode, the long axes of the liquid crystal molecules 114 intersect with the normal to the first transparent electrode layer 12A. This results in greater scattering of incident light than the light controlling sheet 10N in the transparent mode, and less scattering of incident light than the light controlling sheet 10N in the opaque mode.

[0034] The ratios of the thickness of each layer constituting the light-controlling sheet 10N to the thickness of other layers shown in Figures 1, 5, and 6 are shown for convenience, and the actual ratios of the thickness of each layer to the thickness of other layers may differ. The thicknesses of the first transparent support layer 13A and the second transparent support layer 13B are, for example, 50 μm or more and 250 μm or less. The thicknesses of the first transparent electrode layer 12A and the second transparent electrode layer 12B are, for example, 5 nm or more and 100 nm or less. When the thicknesses of the first transparent electrode layer 12A and the second transparent electrode layer 12B are 5 nm or more and 100 nm or less, the operation of the light-controlling sheet 10N is stabilized and cracks occurring in the transparent electrode layers can be reduced. The thickness of the light-controlling layer 11 is, for example, 2 μm or more and less than 30 μm. When easy phase separation between the resin layer 111 and the liquid crystal composition 112 is required during the formation of the light-controlling layer 11, the thickness of the light-controlling layer 11 is preferably 30 μm or less.

[0035] This light controlling sheet 10 is attached to windows of moving objects such as vehicles and aircraft. The light controlling sheet 10 can also be attached to windows of various buildings such as homes, train stations, and airports, partitions installed in offices, shop windows installed in stores, and screens for projecting images. The shape of the light controlling sheet 10 may be either flat or curved as long as it matches the object to which it is attached. By attaching the light controlling sheet 10 to these objects and controlling it to the halftone mode, an observer can visually recognize the presence of an object located on the opposite side of the light controlling sheet 10 from the observer's position, but the object cannot be clearly seen.

[0036] [Light control sheet manufacturing method] An example of a method for manufacturing the light control sheet 10N will be described. A sheet made of a first transparent support layer 13A having a first transparent electrode layer 12A on its surface, and a sheet made of a second transparent support layer 13B having a second transparent electrode layer 12B on its surface are prepared. The first transparent electrode layer 12A and the second transparent electrode layer 12B are formed by a known thin film formation method such as sputtering, vacuum deposition, or coating.

[0037] Next, a liquid containing spacers 115 whose main ingredient is divinylbenzene or the like and a dispersion medium in which the spacers 115 are dispersed is applied to at least one of the first transparent electrode layer 12A and the second transparent electrode layer 12B. Furthermore, the sheet to which the liquid has been applied is heated to remove the dispersion medium.

[0038] A coating material, which is a precursor of the light-controlling layer 11, is prepared. The coating material contains a polymerizable composition and a liquid crystal composition. The coating material is then applied to at least one of the first transparent electrode layer 12A and the second transparent electrode layer 12B, on which the spacers 115 have been dispersed, to form a precursor layer. Next, a pair of sheets are bonded together so that the precursor layer is sandwiched between the first transparent electrode layer 12A and the second transparent electrode layer 12B. To form the precursor layer, a known coating method such as an inkjet method, gravure coating method, spin coating method, slit coating method, bar coating method, flexographic coating method, die coating method, dip coating method, or roll coating method can be used.

[0039] Next, the laminate including the precursor layer, first transparent electrode layer 12A, second transparent electrode layer 12B, first transparent support layer 13A, and second transparent support layer 13B is irradiated with light, such as ultraviolet light, having a wavelength that promotes the polymerization reaction of the polymerizable composition. This polymerizes the monomers and oligomers contained in the polymerizable composition of the precursor layer, and promotes phase separation between resin layer 111 and liquid crystal composition 112. This results in the formation of light-controlling layer 11, with liquid crystal molecules held in voids 116.

[0040] The laminate is formed into a large sheet shape, for example, using a roll-to-roll method. A portion of the laminate is cut out into a desired shape according to the object to which the light controlling sheet 10N is to be attached. Then, the first terminal portion 15A and the second terminal portion 15B are formed on the cut sheet that is part of the laminate, thereby forming the light controlling sheet 10N.

[0041] Midtones Next, we will explain how to make the light-adjusting sheet 100 of the reference example halftone. In the reference example, the light-adjusting sheet 100 is a normal type. The driving voltage applied to the light-adjusting sheet 100 of the reference example is higher than the driving voltage applied in the opaque mode and lower than the driving voltage applied in the transparent mode. This makes it possible to drive the light-adjusting sheet 100 to a halftone that is between transparent and opaque. However, simply adjusting the driving voltage makes it difficult to achieve the beautiful appearance of the light-adjusting sheet 100 when the light-adjusting sheet 100 of the reference example is driven to a halftone.

[0042] FIG. 7 is a schematic diagram of a portion of a light-adjusting sheet 100 of a reference example driven to a halftone. The light-adjusting sheet 100 exhibits variations in linear transmittance. This light-adjusting sheet 100 includes a region 101 with high linear transmittance, a region 103 with low linear transmittance, and a region 102 between the high and low linear transmittance regions 101 and 103. When the linear transmittance varies significantly across the plane of the light-adjusting sheet 100, the linear transmittance of a portion of the light-adjusting sheet 100 differs from that of adjacent portions. As a result, portions of the light-adjusting sheet 100 appear mottled, detracting from the aesthetic appeal of the light-adjusting sheet 100. Furthermore, if the light-adjusting sheet 100 driven to a halftone is partially transparent, the halftone function may not be fully realized. The example shown in FIG. 7 is a schematic diagram of a light-adjusting sheet 100 with a mottled appearance. The linear transmittance of the light-adjusting sheet 100 driven to a halftone may be divided to such an extent that one light-adjusting sheet 100 is visible as three or more separate areas, or the areas with different linear transmittance may be divided to exhibit a geometric shape other than stripes or an irregular shape.

[0043] FIG. 8 is a VT curve showing the change in linear transmittance T with respect to the driving voltage applied to the light-controlling sheet 100 of the reference example. VT curves 51 to 53 are VT curves measured at three different measurement positions on one light-controlling sheet 100. In the opaque mode, the linear transmittance T converges to a minimum value Ta. In the transparent mode, the linear transmittance converges to a maximum value Tb. In the halftone mode, where the linear transmittance T is between the minimum value Ta and the maximum value Tb, when a driving voltage capable of producing halftones is applied to the light-controlling sheet 100, the linear transmittance T at multiple different measurement positions may vary greatly. This is because the rate of change ΔT / V of linear transmittance T per 1 V when a driving voltage capable of producing halftones is applied to the light-controlling sheet 100 is larger than in the opaque mode and transparent mode. A large rate of change ΔT / V makes it possible to achieve intermediate linear transmittances, while also exposing differences in the electric field formed within the plane of the light-controlling sheet 100 as differences in linear transmittance T. When the in-line transmittance T varies greatly in this way, areas with mutually different transparency may be formed in a patchy pattern as shown in FIG.

[0044] Next, the characteristics of the light controlling sheet 10N in this embodiment will be described. (variation in in-line transmittance) The magnitude of the variation in the linear transmittance T of the light controlling sheet 10N in the halftone mode can be expressed by the variation in the driving voltage in the halftone mode, which is determined according to the following procedure.

[0045] At three or more measurement positions on the plane of the light-controlling sheet 10N, the linear transmittance T at each measurement position is measured while changing the driving voltage, and a VT curve is obtained for each measurement position. For the VT curve at each measurement position, identify the voltage range between the drive voltage that puts the light-controlling sheet 10N in opaque mode and the drive voltage that puts it in transparent mode. Specifically, identify the voltage range of the VT curve at each measurement position where the absolute value of the rate of change of linear transmittance T per 1V is 0.5 (% / V) or more. This voltage range is the range of drive voltage that can cause the light-controlling sheet 10N to exhibit intermediate tones at the measurement position where the voltage range is identified.

[0046] As shown in FIG. 9, the lower limit of the voltage range that produces intermediate tones is the "first voltage Va," the upper limit is the "second voltage Vb," and the intermediate value {(Va+Vb) / 2} between them is the "intermediate value Vm." The first voltage Va, the second voltage Vb, and the intermediate value Vm are obtained for each measurement position. This intermediate value Vm is the driving voltage that sets the linear transmittance T of the light-controlling sheet 10N approximately halfway between the minimum value Ta and the maximum value Tb.

[0047] Assuming the number of measurement positions is "n (≧3)", the "minimum value Vmin", "maximum value Vmax", and the average value "Vavr" of the intermediate values ​​Vm are calculated from the intermediate values ​​Vm (Vm1, Vm2, ... Vmn) obtained at each measurement position P (P1, P2, ... Pn). Then, the difference between the maximum value Vmax and the minimum value Vmin is divided by the average value Vavr, and the resulting percentage is used as the variation Vmv of the intermediate values ​​Vm, as shown in the following formula (1).

[0048] Vmv(%)={(Vmax-Vmin) / Vavr}×100 …(1) The variation Vmv of the mean value Vm of the light controlling sheet 10N obtained as described above is 35.0% or less. If the variation Vmv of the mean value Vm exceeds 35.0%, the variation in the linear transmittance T becomes visible to the naked eye.

[0049] (Thickness of the photochromic layer) The thickness of the photochromic layer 11 measured at multiple measurement positions on the photochromic layer 11 is within a range of 0.8 to 1.2 times the median of the thicknesses measured at the multiple measurement positions. In other words, the difference between the thickness of the photochromic layer 11 measured at each measurement position and the median is within a range of -20% to +20% of the median. The inventors discovered that the variation in the in-line transmittance T of the photochromic sheet 10N is caused by the variation in the thickness of the photochromic layer 11. By reducing the variation in the thickness of the photochromic layer 11, the variation Vmv in the median value Vm can be reduced. The number of measurement positions is three or more, preferably ten or more, on an A4-sized sheet measuring 210 mm x 297 mm. The median is the value located in the middle when the thicknesses of the photochromic layer 11 at the measurement positions are arranged in ascending order.

[0050] (Spacer area) When the light-switching layer 11 is observed through the first transparent electrode layer 12A or the second transparent electrode layer 12B, the area of ​​the spacers 115 relative to the entire surface is preferably 0.9% to 30.0%. The area occupied by the spacers 115 can be calculated by observing a predetermined area of ​​the light-switching layer 11 with an optical microscope. The predetermined area to be observed is, for example, a 1 mm × 1 mm area. The spacers 115 are difficult to see with the naked eye in the transparent mode. However, because the refractive index of the spacers 115 differs from that of the resin layer 111, the spacers 115 appear slightly whiter than areas without the spacers 115, making them distinguishable from areas without the spacers 115 when observed with an optical microscope. Therefore, the sum of the areas of the spacers 115 in the predetermined area is taken as the occupied area, and the occupied area ratio of the spacers 115 can be calculated by dividing the occupied area by the total area of ​​the predetermined area. If the area ratio of the spacers 115 is less than 0.9%, the gap between the first transparent electrode layer 12A and the second transparent electrode layer 12B cannot be properly controlled, resulting in greater variation in the thickness of the light-controlling layer 11. If the area ratio of the spacers 115 exceeds 30.0%, the proportion of the spacers 115 in the light-controlling layer 11 is too large, reducing the transparency of the light-controlling sheet 10N in the transparent state. Furthermore, if the area ratio of the spacers 115 is 15.0% or less, the transparency of the light-controlling sheet 10N when operated in the transparent state can be further improved.

[0051] (mode switching voltage) The phenomenon of variation in the linear transmittance of the light controlling sheet 10N is noticeable when the VT curve is steep in the range from the first voltage Va, at which the linear transmittance T has a minimum value Ta, to the second voltage Vb, at which the linear transmittance T has a maximum value Tb. When the slope of the VT curve is gentle, even if there is variation in the linear transmittance at different positions within the plane, the amount of change in the linear transmittance T per unit voltage is small, making it difficult to distinguish the variation in linear transmittance visually.

[0052] Figure 10 shows a VT curve with a gentle slope in the range where the linear transmittance is greater than the minimum value Ta and less than the maximum value Tb. In this case, although the variation in linear transmittance is difficult to see with the naked eye, the response time required for reversible switching between the opaque mode and the transparent mode is long. Therefore, when improved switching response is required, it is preferable that the voltage difference required for reversible switching between the opaque mode and the transparent mode be 22 V or less when the light controlling sheet 10N is 210 mm x 297 mm, or so-called A4 size.

[0053] In a light-controlling sheet 10N made of polymer-dispersed liquid crystal, if the resin layer constituting the light-controlling layer 11 does not appropriately contain a large number of independent voids 116 or voids 116 having a shape in which parts of independent shapes are joined, the difference between the first voltage Va and the second voltage Vb will not be 22 V or less, resulting in a reduced response speed. To achieve good light scattering in the visible light range, it is preferable that the voids 116 have a maximum inner diameter of 0.4 μm or more and 2.2 μm or less, and that a large number of voids 116 are provided in the resin layer 111. If the diameter of the voids 116 is 0.4 μm or more, transparency is reduced in the opaque mode, and sufficient haze is achieved. Furthermore, if the diameter of the voids 116 is 2.2 μm or less, the proportion of the resin layer in the light-controlling layer 11 is prevented from being too small, thereby preventing the light-controlling layer 11 from becoming weak. When the dimming layer 11 contains a large number of voids 116 in an appropriate state and at least the thickness of the dimming layer 11 and the variation Vmv of the intermediate value Vm of the dimming sheet 10N satisfy the above conditions, it becomes possible to achieve both suppression of variation in linear transmittance in intermediate tones and an appropriate response speed.

[0054] According to this embodiment, the following effects can be obtained. (1) When the absolute value of the linear transmittance change rate per unit voltage of the light-controlling sheet 10N is 0.5% / V or more, the light-controlling sheet 10N can achieve a linear transmittance intermediate between the linear transmittance in the transparent mode and the linear transmittance in the opaque mode. According to this embodiment, by including the thickness of the light-controlling layer 11 measured at multiple measurement positions within a range of 0.8 to 1.2 times the median thickness, the variation in the median value Vm between the first voltage Va, which is the lower limit of the drive voltage corresponding to the halftone, and the second voltage Vb, which is the upper limit, can be suppressed to 35.0% or less. Reducing the variation in the median value Vm can reduce the variation in linear transmittance when a constant drive voltage near the median value Vm is applied to set the halftone mode. As a result, the appearance of the light-controlling sheet 10N in the halftone mode can be improved. Furthermore, according to the above embodiment, by configuring the light-controlling layer 11 so that the liquid crystal molecules 114 are contained in the multiple voids 116, it is possible to suppress variations in the linear transmittance of the light-controlling sheet 10N without reducing the response speed required for mode switching. Therefore, it is possible to provide a practical light-controlling sheet with a halftone mode that maintains aesthetics and practicality. Therefore, adding the halftone mode as one of the driving modes can enhance the design of the light-controlling sheet 10N.

[0055] (2) By configuring the dimming layer 11 to contain liquid crystal molecules 114 in multiple voids 116, it is possible to suppress variations in the linear transmittance of intermediate tones without excessively reducing the response speed required for switching between the opaque mode and the transparent mode.

[0056] (3) Since the occupied area ratio, which is the ratio of the area occupied by the multiple spacers 115, is 0.9% or more and 30.0% or less, the gap between the first transparent electrode layer 12A and the second transparent electrode layer 12B can be controlled to reduce the variation in the thickness of the dimming layer 11 and reduce the linear transmittance caused by the spacers 115 in the transparent mode.

[0057] (4) By setting the diameter of the voids 116 in the resin layer 111 that constitutes the light-controlling layer 11 to be 0.4 μm or more and 2.2 μm or less, the liquid crystal molecules 114 are more likely to be oriented along the electric field in the voids 116 of the resin layer 111. This makes it easier to control the linear transmittance of the light-controlling sheet 10. Furthermore, no transparency is created in the opaque mode, and it is possible to achieve good light scattering in the visible light range.

[0058] (5) The difference between the first voltage Va, which is the lower limit of the drive voltage at which the rate of change of the linear transmittance T is 0.5% / V, and the second voltage Vb, which is the upper limit, is 22 V or less, so that the response speed required for transitioning between the transparent state and the opaque mode can be made appropriate. In addition, the power consumption required for transitioning between the transparent state and the opaque mode can be reduced.

[0059] [Variations] The above embodiment can be modified as follows: In addition, the following modifications may be combined and implemented.

[0060] In the above embodiment, the light controlling sheet 10N is a normal type light controlling sheet. However, instead of this, the light controlling sheet 10 may be a reverse type light controlling sheet. 11 shows a reverse-type light control sheet 10R. The reverse-type light control sheet 10R includes a light control 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, as well as a pair of alignment layers, a first alignment layer 14A and a second alignment layer 14B, that sandwich the light control layer 11. The first alignment layer 14A is located between the light control layer 11 and the first transparent electrode layer 12A, and the second alignment layer 14B is located between the light control layer 11 and the second transparent electrode layer 12B. When the first transparent electrode layer 12A and the second transparent electrode layer 12B are at the same potential, the first alignment layer 14A and the second alignment layer 14B align the long axis direction of the liquid crystal molecules 114 contained in the light-controlling layer 11 along the normal direction of the first alignment layer 14A and the second alignment layer 14B. On the other hand, when a potential difference is generated between the first transparent electrode layer 12A and the second transparent electrode layer 12B, the first alignment layer 14A and the second alignment layer 14B align the long axis direction of the liquid crystal molecules 114 contained in the light-controlling layer 11 in a direction other than the normal direction. For example, the long axis direction of the liquid crystal molecules 114 is irregular or aligned parallel to the substrate. Examples of materials that can be used to form the first alignment layer 14A and the second alignment layer 14B include polyamide, polyimide, polycarbonate, polystyrene, polysiloxane, polyesters such as polyethylene terephthalate and polyethylene naphthalate, and polyacrylates such as polymethyl methacrylate. The liquid crystal molecules also have negative dielectric anisotropy, and the dielectric constant of the liquid crystal molecules in the long axis direction is smaller than the dielectric constant of the liquid crystal molecules in the short axis direction. In this light controlling sheet 10R, the transparent mode is an example of the first mode, the opaque mode is an example of the second mode, and the gray mode is an example of the third mode. In the reverse-type light controlling sheet 10R, the conditions such as the variation Vmv of the median value Vm of the light controlling sheet 10R, the thickness of the light controlling layer 11, the spacer occupation area, and the mode switching voltage are the same as those of the light controlling sheet 10N of the above embodiment.

[0061] In the above embodiment, the light controlling sheet 10N includes a light controlling layer 11 that includes spacers 115. Alternatively, the normal-type light controlling sheet 10N and the reverse-type light controlling sheet 10R may include a light controlling layer 11 that does not include spacers 115, as long as the variation in thickness of the light controlling layer 11 falls within a range of 0.8 to 1.2 times the median thickness.

[0062] In the above embodiment, the light-controlling layer 11 has a structure including a resin layer 111 and a liquid crystal composition 112. Alternatively, the light-controlling sheet 10 may be an SPD (Suspended Particle Device) type having light-controlling particles as oriented particles. The SPD type is a type in which a light-controlling suspension containing light-controlling particles is dispersed in a resin matrix. In an SPD type light-controlling sheet, the variation Vmv of the mean value Vm of the light-controlling sheet 10, the thickness of the light-controlling layer 11, the spacer occupation area, and the mode switching voltage are the same as in the above embodiment.

[0063] [Example] Examples that are examples of the above-described embodiment will be specifically described with reference to Figures 12 to 24. Note that these examples do not limit the present invention.

[0064] [Example 1] A pair of PET substrates with an ITO film formed thereon was prepared. The ITO film had a thickness of 30 nm, and the PET substrate had a thickness of 125 μm. Next, a dispersion was prepared by dispersing 25 μm-diameter spacers, primarily made of divinylbenzene, in an alcohol-based solvent. This dispersion was then sprayed onto the PET substrate with the ITO film and heated in an oven at 100°C to remove the solvent. The spacer occupation area ratio was determined by observing a 1 mm x 1 mm area at any position on the light-controlling sheet using an optical microscope. The ratio of the area that appeared white to the observed area was calculated as the spacer occupation area ratio. Similarly, 1 mm x 1 mm areas at other positions on the light-controlling sheet were also observed, and the occupation area ratio was calculated for each of the five observed areas. The average occupation area ratio was then calculated. The spacer occupation area of ​​Example 1 was 1.50%.

[0065] After applying a polymer-dispersed liquid crystal paint (KN-F-001-01-00, manufactured by Kyushu Nanotec Optics Co., Ltd.) to the transparent electrode layer on which the spacers had been sprayed, the illuminance was set to 20 mW / cm 2The sheet was irradiated with ultraviolet light for 30 seconds using a high-pressure mercury lamp to cut off wavelengths of 350 nm or less in a nitrogen atmosphere. The temperature inside the irradiation device was controlled at 25°C during ultraviolet irradiation. The other PET substrate with an ITO film was then laminated onto the sheet with the light-control layer in this way, and the two were bonded together under pressure to obtain a light-control sheet.

[0066] Next, the light-controlling sheet 10 was cut into a rectangle measuring 210 mm wide and 297 mm long. An incision was made in the edge of one of the short sides of the light-controlling sheet 10, and the PET substrate (one of the transparent support layers) and the transparent electrode layer supported by the PET substrate were peeled off from the light-controlling sheet using a metal plate over a width of 25 mm and a length of 3 mm. Furthermore, the portion of the light-controlling layer 11 exposed by the peeling of the PET substrate and the transparent electrode layer was removed from the light-controlling sheet 10 using a solvent such as isopropyl alcohol, ethyl acetate, or toluene, exposing the other transparent electrode layer. This formed a first terminal on the light-controlling sheet 10. The same process was performed on the other side of the light-controlling sheet 10, on the short side where the first terminal was formed, at a location away from the first terminal in the direction of the short side, exposing one of the transparent electrode layers. This formed a second terminal on the light-controlling sheet 10.

[0067] [Example 2] The spacers were dispersed so that the occupied area ratio of the spacers was 15.0%, and the light controlling sheet of Example 2 was produced in the same manner as Example 1 except for the occupied area ratio of the spacers.

[0068] [Example 3] The spacers were dispersed so that the occupied area ratio of the spacers was 0.9%, and the other conditions were the same as in Example 1, so that the light controlling sheet of Example 3 was produced.

[0069] [Example 4] The spacers were dispersed so that the occupied area ratio of the spacers was 30.0%, and the other conditions were the same as those in Example 1 except for the occupied area ratio of the spacers, to produce a light controlling sheet of Example 4.

[0070] [Comparative Example 1] The spacers were dispersed so that the occupied area ratio of the spacers was 0.45%, and the other conditions were the same as those of Example 1, so that the light controlling sheet of Comparative Example 1 was produced.

[0071] Comparative Example 2 As in Example 1, a polymer dispersed liquid crystal paint was applied to the transparent electrode layer on which the spacers had been sprayed, and then the temperature inside the irradiation device was controlled to 45°C when irradiating with ultraviolet light. Then, the light control sheet of Comparative Example 2 was produced in the same manner as in Example 1 except for the temperature during ultraviolet light irradiation.

[0072] [Evaluation of light control sheets] FIG. 12 shows the results of evaluation of Examples 1 to 4 and Comparative Examples 1 and 2 for each of the following items.

[0073] (variation in in-line transmittance) For the light-controlling sheets of Examples 1 to 4 and Comparative Examples 1 and 2, linear transmittance was measured at five measurement positions. The first and second terminals, which are portions of the transparent electrode layer exposed by peeling the PET substrate from the transparent electrode layer, were connected to an AC power supply (Kikusui Electronics PCR-3000WE), and the voltage between the transparent electrode layers was increased from 0 V at a frequency of 60 Hz until the linear transmittance was saturated. Furthermore, for each measurement position, the linear transmittance was measured using a haze meter (Suga Test Instruments NDH-7000SP). The relationship between driving voltage and linear transmittance was graphed to obtain VT curves. Figures 13 to 18 show examples of VT curves for Examples 1 to 4 and Comparative Examples 1 and 2.

[0074] Similarly, VT curves were obtained for other measurement positions within the surface of the light controlling sheet using the same procedure as described above. Of the five measurement positions, two were 30 mm away from one short side on which the first and second terminals were provided toward the other short side, 30 mm away from one long side and 30 mm away from the other long side. The other two were 30 mm away from the short side on which the first and second terminals were not provided toward the short side on which the first and second terminals were provided, 30 mm away from one long side and 30 mm away from the other long side. The remaining position was the center of the light-adjusting sheet when viewed from the front. That is, for a rectangular light-adjusting sheet 10 with a width of 210 mm and a length of 297 mm, the five measurement positions were the four corners 30 mm away from the edges of the light-adjusting sheet 10 and the center of the light-adjusting sheet 10. The measurement positions for linear transmittance were arranged to represent the variation in linear transmittance throughout the light-adjusting sheet 10N.

[0075] For the VT curves obtained at each measurement position, a range was identified where the absolute value of the rate of change in linear transmittance T was 0.5 (% / V) or greater. Furthermore, the lower limit of the identified voltage range was defined as the "first voltage Va," the upper limit as the "second voltage Vb," and the intermediate value {(Va + Vb) / 2} between them was defined as the "intermediate value Vm." Furthermore, among the intermediate values ​​Vm obtained at different measurement positions within a single light-control sheet, the "minimum value Vmin," the "maximum value Vmax," and the average value of the intermediate values ​​Vm, "Vavr," were determined. The difference between the maximum value Vmax and the minimum value Vmin divided by the average value Vavr, as shown in the above formula (1), was defined as the variation Vmv of the intermediate value Vm.

[0076] (Thickness of the photochromic layer) The cross section of the light-controlling sheet was observed using a scanning electron microscope, and the overall thickness of the light-controlling sheet was measured. The cross section of the light-controlling sheet was also observed using a scanning electron microscope, and the thickness of the transparent support layer with the transparent electrode layer, i.e., the support layer thickness, which is the sum of the thickness of the PET substrate and the thickness of the transparent electrode layer, was measured. The thickness of the light-controlling layer was obtained by subtracting the support layer thickness from the overall thickness. The overall thickness and support layer thickness were measured at 10 different locations on the front of the light-controlling sheet 10N, and the thickness of the light-controlling layer at each measurement location was determined. The measurement locations for the light-controlling layer thickness were positioned, similar to the measurement locations for the linear transmittance, to represent the overall thickness variation, including the periphery and center of the light-controlling sheet 10N. The median, minimum, and maximum thicknesses of the light-controlling layer at the 10 locations were also calculated. Furthermore, the absolute value of the difference between the minimum and median values, and the ratio of the absolute value of the difference between the median and maximum values ​​to the median were calculated.

[0077] (visual appearance) The driving voltage applied to the light-controlling sheet was changed, and the state of the intermediate tones was visually observed. A state in which the transparency was uniform was marked with "◎" or "◯", and a state in which the transparency was uneven and patchy was marked with "X". Note that a state in which the transparency in the transparent mode was sufficient for practical use was marked with "◯", and a state in which the transparency in the transparent mode was even higher was marked with "◎".

[0078] (mode switching voltage) The voltage required to switch between the opaque and transparent modes was calculated as the voltage (Vb-Va) from the first voltage Va to the second voltage Vb at each of the five measurement positions. Furthermore, the average voltage (Vb-Va) at the five measurement positions was calculated. Since the power consumed when reversibly switching between the opaque and transparent modes depends on the voltage, the lower the voltage (Vb-Va) required for switching, the lower the power consumption. Note that when the voltage (Vb-Va) is high, the response speed when switching from the opaque mode to the transparent state is slow, and it takes time to switch.

[0079] (Gap size) The size of the voids was determined by observing the cross section of the light-controlling layer using a scanning electron microscope. To determine the size of the voids, the liquid crystal composition containing liquid crystal molecules was first removed from the light-controlling layer. Square test pieces measuring 10 cm on a side were cut out from each of the light-controlling sheets of Examples 1 to 4 and Comparative Examples 1 and 2. The liquid crystal composition was then removed from the light-controlling layer by immersing each test piece in isopropyl alcohol. The liquid crystal composition can also be removed from the test piece by immersing the test piece in an organic solvent that dissolves the liquid crystal composition but does not dissolve the resin layer.

[0080] Then, a scanning electron microscope was used to image the cross section of the test piece from which the liquid crystal composition had been removed. At this time, 30 rectangular regions were arbitrarily set on the cross section of the test piece. Images were then obtained for each region using the scanning electron microscope at a magnification of 1000 times. The 30 rectangular regions were set so that the distance between adjacent rectangular regions was 1 mm or more.

[0081] 19 to 23 are electron microscope photographs of Examples 1 to 4 and Comparative Examples 1 and 2. Ten voids were randomly selected in each image, and the size of each void was measured. The maximum and minimum values ​​of the sizes of the 10 voids were set as the maximum and minimum values ​​of the void size in that image. The maximum and minimum values ​​of the void size in each image were calculated. The maximum value of the maximum values ​​found in the images of 30 locations was set as the maximum value of the void size in the test piece. In addition, the minimum value of the minimum values ​​found in the images of 30 locations was set as the minimum value of the void size in the test piece.

[0082] For voids included in the image that were circular, the diameter of the void was set as the void size. For voids included in the image that were elliptical, the major axis of the void was set as the void size. For voids included in the image that were irregular, the diameter of the circle circumscribing the void was set as the void size.

[0083] [Evaluation results] (Variation in thickness of photochromic layer) For the light-control sheets of Examples 1 to 4 and Comparative Example 2, the absolute value of the difference between the thickness of the light-control layer at each measurement position and the median was within a range of 20%. On the other hand, for Comparative Example 1, in which the spacer occupation area ratio was below the suitable range, the absolute value of the difference between the thickness of the light-control layer at each measurement position and the median was up to 40%, indicating a large variation.

[0084] (variation in in-line transmittance) The light-control sheets of Examples 1 to 4 and Comparative Example 2 were found to have a variation Vmv of 35.0% or less in the intermediate value Vm between the first voltage Va that causes the linear transmittance T to converge to the minimum value Ta and the second voltage Vb that causes it to converge to the maximum value Tb.On the other hand, the light-control sheet of Comparative Example 1, in which the spacer occupation area ratio was below the preferred range and the variation in the thickness of the light-control layer exceeded the preferred range, was found to have a large variation Vmv of 47.6% in the intermediate value Vm.

[0085] (visual appearance) Examples 1 to 4 and Comparative Example 2 were rated as "◎" or "◯". Example 4, in which the spacer occupation area ratio exceeded the preferred range, was slightly cloudy in the transparent mode and lacked transparency, so was rated as "◯". The smallest maximum value Tb of the linear transmittance T of Example 4 was 76.3%, which was lower than those of Examples 1 to 3.

[0086] (Gap size) The average void size was 1.0 μm to 1.3 μm in Examples 1 to 4 and Comparative Example 1. The void shapes and intervals were similar in Examples 1 to 4 and Comparative Example 1. On the other hand, in Comparative Example 2, no voids were observed.

[0087] (mode switching voltage) In Examples 1 to 4 and Comparative Example 1, the difference in voltage for switching between the transparent mode and the opaque mode was 19.0 V to 22.0 V. In Comparative Example 2, the difference in voltage for switching between the transparent mode and the opaque mode was as large as 55.0 V.

[0088] As described above, when the variation in the thickness of the photochromic layer is small, such that the absolute value of the difference between the thickness of the photochromic layer at each measurement position and the median is 20% or less, the variation in linear transmittance Vmv in intermediate tones can be suppressed to 35.0% or less. Furthermore, for a photochromic sheet in which multiple voids with a size of 0.4 μm to 2.2 μm and an average size of 1.0 μm to 1.3 μm are formed in the photochromic layer, the variation in linear transmittance Vmv is small, power consumption is low, and response speed is improved. The effects observed in the above-mentioned examples are obtained by specifying the distribution of the median value Vm. Therefore, the above-mentioned effects can be obtained in a polymer network type photochromic sheet, whose linear transmittance changes depending on the electric field formed in the photochromic sheet, as well as in a polymer dispersion type photochromic sheet, by specifying the distribution of the median value Vm. The effects observed in the above-mentioned examples are obtained by specifying the size of the voids in the photochromic layer. Therefore, the above-mentioned effect can be similarly obtained in a polymer network type in which liquid crystal molecules respond to an electric field within the voids formed in the light-controlling sheet by specifying the size of the voids. [Explanation of symbols]

[0089] 1...Dimmer 10...Light-adjusting sheet 11...Photochromic layer 12A, 12B…Transparent electrode layer 13A, 13B...Transparent support layer 20...Drive unit 111...Resin layer 114...Liquid crystal molecules as oriented particles 116...Void

Claims

1. a light-control layer including a resin layer and oriented particles; a pair of transparent electrode layers sandwiching the light control layer; a pair of transparent support layers sandwiching the light control layer and the pair of transparent electrode layers, the thickness of the light-controlling layer measured at a plurality of measurement positions is within a range of 0.8 times or more and 1.2 times or less of the median thickness, the light-controlling layer has a structure in which the oriented particles are contained in a plurality of voids dispersed in the resin layer, In a characteristic curve obtained by measuring a change in linear transmittance of visible light when a driving voltage applied to the transparent electrode layer is changed, a lower limit driving voltage in a range in which the absolute value of the rate of change in linear transmittance is 0.5% / V or more is defined as a first voltage Va, an upper limit driving voltage is defined as a second voltage Vb, and an intermediate value between the first voltage Va and the second voltage Vb is defined as Vm; The variation in the intermediate values ​​Vm obtained from the characteristic curve at the plurality of measurement positions, obtained by dividing the difference between the minimum value Vmin and the maximum value Vmax by the average value Vavr of the intermediate values ​​Vm, {(Vmax-Vmin) / Vavr} x 100, is 35.0% or less. Dimming sheet.

2. the light-controlling layer includes a spacer that controls a gap between the pair of transparent electrode layers; When the light-controlling layer is observed from the contact surface with the transparent electrode layer, the ratio of the total area occupied by the plurality of spacers to the entire area of ​​the light-controlling layer is 0.9% or more and 30.0% or less. The light-controlling sheet according to claim 1 .

3. The diameter of the voids is 0.4 μm or more and 2.2 μm or less. The light-controlling sheet according to claim 1 or 2.

4. The difference between the first voltage Va and the second voltage Vb is 22 V or less. The light-controlling sheet according to any one of claims 1 to 3.

5. a light-control sheet whose linear transmittance changes depending on the driving voltage; a drive unit that controls a drive voltage applied to the light controlling sheet, The light-controlling sheet is a light-control layer including a resin layer and oriented particles; a pair of transparent electrode layers sandwiching the light control layer; a pair of transparent support layers sandwiching the light control layer and the pair of transparent electrode layers, the thickness of the light-controlling layer measured at a plurality of measurement positions is within a range of 0.8 times or more and 1.2 times or less of the median thickness, the light-controlling layer has a structure in which the oriented particles are contained in a plurality of voids dispersed in the resin layer, In a characteristic curve obtained by measuring a change in linear transmittance of visible light when a driving voltage applied to the transparent electrode layer is changed, a lower limit driving voltage in a range in which the absolute value of the rate of change in linear transmittance is 0.5% / V or more is defined as a first voltage Va, an upper limit driving voltage is defined as a second voltage Vb, and an intermediate value between the first voltage Va and the second voltage Vb is defined as Vm; a variation in the intermediate values ​​Vm obtained from the characteristic curve at the plurality of measurement positions, obtained by dividing a difference between a minimum value Vmin and a maximum value Vmax by an average value Vavr of the intermediate values ​​Vm, {(Vmax-Vmin) / Vavr} x 100, is 35.0% or less; The drive unit is A first mode in which the driving voltage is not applied, a second mode in which a voltage equal to or higher than the second voltage Vb is applied, and a third mode in which a voltage between the first voltage Va and the second voltage Vb is applied to change the linear transmittance of the light controlling sheet to a linear transmittance between the linear transmittance in the first mode and the linear transmittance in the second mode. Dimmer.

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