Dimming sheets and dimming devices

Abstract

The design appeal of dimmable sheets can be enhanced. [Solution] The thickness of the dimming layer 11 at multiple measurement positions is within the range of 0.8 times or more and 1.2 times the median thickness. The change in linear transmittance of visible light is measured when the driving voltage applied to each transparent electrode layer 12A, 12B is changed, and among the characteristic curves obtained, the lower limit of the driving voltage in the range where the rate of change of linear transmittance is 0.5% / V or more is defined as the first voltage Va, the upper limit as the second voltage Vb, and the midpoint of the first voltage Va and the second voltage Vb is defined as Vm. Among the midpoint values ​​Vm obtained from the characteristic curves at each measurement position, the variation of the midpoint values ​​obtained by dividing the difference between the minimum value Vmin and the maximum value Vmax by the average value Vavr of the midpoint values ​​Vm is 35.0% or less.

Description

Technical Field

[0001] The present disclosure relates to a dimming sheet and a dimming device with variable linear transmittance.

Background Art

[0002] The dimming sheet includes a dimming layer containing a liquid crystal composition and a pair of transparent electrode layers sandwiching the dimming layer (see, for example, Patent Document 1). The dimming device includes the above dimming sheet and a driving unit that controls the application of a driving voltage to the pair of transparent electrode layers. The linear transmittance of the dimming sheet changes as the orientation state of the liquid crystal molecules changes according to the potential difference between the pair of transparent electrode layers. The dimming sheet is attached, for example, to building materials such as window glass and glass walls, or window glass of automobiles, and functions as a partitioning member that partitions two spaces.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, the fact that the dimming sheet also functions as a decoration of the space, like a shoji with shoji paper having patterns such as streaks or shades, can greatly expand the scope of application as a partitioning member. However, the above-described dimming sheet only shows either a colorless and transparent state or a simple unpatterned white turbid state due to light scattering over the entire sheet according to the magnitude of the driving voltage. Therefore, there is a strong demand to enhance the designability of the dimming sheet.

Means for Solving the Problems

[0005] The dimmable sheet that solves the above problem comprises a dimmable layer containing a resin layer and oriented particles, a pair of transparent electrode layers sandwiching the dimmable layer, and a pair of transparent support layers sandwiching the dimmable layer and the pair of transparent electrode layers, wherein the thickness of the dimmable layer measured at multiple measurement positions falls within a range of 0.8 times or more and 1.2 times the median thickness, the dimmable layer has a structure in which the oriented particles are contained in a plurality of voids dispersed in the resin layer, and was obtained by measuring the change in the linear transmittance of visible light when the driving voltage applied to the transparent electrode layers is changed. In the characteristic curve, the lower limit of the 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 the first voltage Va, and the upper limit of the driving voltage is defined as the second voltage Vb. The midpoint between the first voltage Va and the second voltage Vb is defined as Vm. Among the midpoint Vm obtained from the characteristic curves at the multiple measurement positions, the variation of the midpoint Vm obtained by dividing the difference between the minimum value Vmin and the maximum value Vmax by the average value Vavr of the midpoint Vm, {(Vmax-Vmin) / Vavr} × 100, is 35.0% or less.

[0006] A dimming device that solves the above problems comprises a dimming sheet whose linear transmittance changes according to the drive voltage, and a drive unit that controls the drive voltage applied to the dimming sheet, and comprises a dimming layer containing a resin layer and oriented particles, a pair of transparent electrode layers sandwiching the dimming layer, and a pair of transparent support layers sandwiching the dimming layer and the pair of transparent electrode layers, wherein the thickness of the dimming layer measured at a plurality of measurement positions falls within a range of 0.8 times or more and 1.2 times the median thickness, the dimming layer has a structure in which the oriented particles are contained in a plurality of voids dispersed in the resin layer, and the lower limit of the drive voltage in the range in which the absolute value of the rate of change of the linear transmittance of visible light is 0.5% / V or more 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 is The first voltage Va is defined as the first voltage, the second voltage Vb as the upper limit of the drive voltage, and the midpoint between the first voltage Va and the second voltage Vb is defined as Vm. The variation of the midpoint obtained from the characteristic curves at the plurality of measurement positions, where the difference between the minimum value Vmin and the maximum value Vmax is divided by the average value Vavr of the midpoint Vm, is {(Vmax-Vmin) / Vavr} × 100, and the drive unit switches between a first mode in which no drive voltage is applied, a second mode in which a voltage of the second voltage Vb or higher is applied, and a third mode in which the linear transmittance of the dimming sheet is set to a linear transmittance between the linear transmittance in the first mode and the linear transmittance in the second mode by applying a voltage between the first voltage Va and the second voltage Vb.

[0007] A dimmable sheet with an absolute value of 0.5% / V or more for the rate of change of linear transmittance per unit voltage makes it possible to achieve a linear transmittance intermediate between the linear transmittance of the transparent mode and the linear transmittance of the opaque mode. With the above configuration, the thickness of the dimmable layer measured at multiple measurement positions falls within the range of 0.8 to 1.2 times the median thickness, so that the variation in the intermediate value between the first voltage Va, which is the lower limit of the driving voltage for achieving intermediate tone, and the second voltage Vb, which is the upper limit, is suppressed to 35.0% or less. If the variation in the intermediate value is 35.0% or less, it is possible to suppress the occurrence of transparency non-uniformity that can be seen with the naked eye in the dimmable sheet when a constant driving voltage near the intermediate value is applied to achieve intermediate tone mode. As a result, the aesthetic appearance of the dimmable sheet in intermediate tone mode can be enhanced. Therefore, the design of the dimmable sheet can be enhanced by adding intermediate tone mode as one of the driving modes.

[0008] Regarding the above-described dimming sheet, the dimming layer includes spacers that control the gap between the pair of transparent electrode layers, and when the dimming 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 dimming layer may be 0.9% or more and 30.0% or less.

[0009] With the above configuration, the occupied area ratio, which is the ratio of the area occupied by multiple spacers, is between 0.9% and 30.0%. Therefore, the gap in the transparent electrode layer can be controlled to reduce variations in the thickness of the photochromic layer, and the haze originating from the spacers in transparent mode can be reduced.

[0010] The above-mentioned dimming sheet may have a void diameter of 0.4 μm or more and 2.2 μm or less. According to the above configuration, by setting the void diameter to 0.4 μm or more and 2.2 μm or less, oriented particles within the voids of the resin layer are more likely to orient along the electric field. This makes it easier to control linear transmittance. Furthermore, transparency is not produced in opaque mode, and good light scattering in the visible light range is possible.

[0011] For the dimming sheet described above, the difference between the first voltage Va and the second voltage Vb may be 22V or less. With the above configuration, the response speed required for transitioning between transparent and opaque modes can be set to an appropriate level. In addition, the power consumption required for transitioning between transparent and opaque modes can be reduced. [Effects of the Invention]

[0012] According to this disclosure, the design aesthetics of dimming sheets and dimming devices equipped with such dimming sheets can be enhanced. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a cross-sectional view showing a normal type of dimmable sheet. [Figure 2] Figure 2 is a plan view showing the dimming sheet in opaque mode. [Figure 3] Figure 3 is a plan view showing the dimming sheet in transparent mode. [Figure 4] Figure 4 is a plan view showing the dimming sheet in mid-tone mode. [Figure 5] Figure 5 is a cross-sectional view showing the dimming sheet in opaque mode. [Figure 6] Figure 6 is a cross-sectional view showing the dimming sheet in transparent mode. [Figure 7] Figure 7 is a plan view showing a reference example of a dimming sheet that exhibits halftones. [Figure 8] Figure 8 is a graph showing the voltage-linear transmittance curve of a dimmable sheet as an example. [Figure 9] Figure 9 is a graph showing the voltage-linear transmittance curve of the dimming sheet. [Figure 10] Figure 10 is a graph showing the voltage-linear transmittance curve of a dimmable sheet as an example. [Figure 11] Figure 11 is a cross-sectional view showing a reverse-type dimming sheet. [Figure 12] Figure 12 is a table showing the evaluation results for Examples 1-4 and Comparative Examples 1 and 2. [Figure 13] Figure 13 is a graph showing the voltage-linear transmittance curve of the dimming sheet of Example 1. [Figure 14] Figure 14 is a graph showing the voltage-linear transmittance curve of the dimming sheet of Example 2. [Figure 15] Figure 15 is a graph showing the voltage-linear transmittance curve of the dimming sheet of Example 3. [Figure 16] Figure 16 is a graph showing the voltage-linear transmittance curve of the dimming sheet of Example 4. [Figure 17] Figure 17 is a graph showing the voltage-linear transmittance curve of the dimming sheet of Comparative Example 1. [Figure 18] Figure 18 is a graph showing the voltage-linear transmittance curve of the dimming sheet of Comparative Example 2. [Figure 19] Figure 19 is an electron micrograph showing the dimming layer of the dimming sheet of Example 1. [Figure 20] Figure 20 is an electron micrograph showing the dimming layer of the dimming sheet of Example 2. [Figure 21] Figure 21 is an electron micrograph showing the dimming layer of the dimming sheet of Example 3. [Figure 22] Figure 22 is an electron micrograph showing the dimming layer of the dimming sheet of Example 4. [Figure 23] Figure 23 is an electron micrograph showing the dimming layer of the dimming sheet of Comparative Example 1. [Figure 24] Figure 24 is an electron micrograph showing the dimming layer of the dimming sheet of Comparative Example 2.

Embodiments for Carrying Out the Invention

[0014] Referring to the drawings, an embodiment of the dimming sheet and the dimming device will be described. [Basic Structure of Dimming Device] Referring to FIG. 1, the basic structure of the dimming sheet and the dimming device will be described.

[0015] As shown in Figure 1, the dimming device 1 comprises a dimming sheet 10 and a drive unit 20 that controls the application of a drive voltage to the dimming sheet 10. The dimming sheet 10 may have a normal type structure in which the linear transmittance of visible light is high when energized and low when not energized. The dimming sheet 10 may have a reverse type structure in which the linear transmittance is low when energized and high when not energized. This embodiment primarily describes the normal type of dimming sheet 10N. Furthermore, components common to both the normal and reverse types will simply be described as the dimming sheet 10. Linear transmittance T represents the transmittance of incident light parallel to the normal direction of the surface of the dimming sheet 100, and is also called parallel line transmittance.

[0016] The normal type dimming sheet 10N comprises a dimming 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 dimming layer 11. The first transparent support layer 13A and the second transparent support layer 13B sandwich the dimming layer 11, the first transparent electrode layer 12A, and the second transparent electrode layer 12B. The dimming layer 11 is located between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The dimming 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 portion 15A. The first terminal portion 15A is connected to the drive unit 20 via wiring 16A. The surface of the second transparent electrode layer 12B is connected to the second terminal portion 15B. The second terminal portion 15B is connected to the drive unit 20 via wiring 16B. The first terminal portion 15A is located in the area of ​​the edge of the dimming sheet 10N where the first transparent electrode layer 12A is exposed. The second terminal portion 15B is located in the area of ​​the edge of the dimming sheet 10N where the second transparent electrode layer 12B is exposed. The first terminal portion 15A and the second terminal portion 15B constitute a part of the dimming sheet 10N.

[0018] The drive unit 20 applies a drive voltage between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The magnitude of the drive voltage is variable and controlled by the drive unit 20. The light-adjusting layer 11 comprises a transparent resin layer and a liquid crystal composition. The light-adjusting layer 11 includes, for example, polymer dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC), nematic curvilinear aligned phase (NCAP), etc. The light-adjusting layer 11 containing polymer dispersed liquid crystal has a number of independent voids, or voids having a shape in which parts of independent shapes are joined together, within the resin layer, and holds the liquid crystal composition within the voids. The polymer network liquid crystal has a polymer network 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.

[0019] Examples of liquid crystal molecules as oriented particles include one or more of the following: Schiff bases, azos, azoxys, biphenyls, terphenyls, benzoic acid esters, transanes, pyrimidines, cyclohexanecarboxylic acid esters, phenylcyclohexanes, and dioxanes. The liquid crystal molecules contained in the light-adjusting layer 11 have, for example, positive dielectric anisotropy, and the dielectric constant in the long axis direction of the liquid crystal molecule is greater than the dielectric constant in the short axis direction of the liquid crystal molecule.

[0020] Each of the first transparent electrode layer 12A and the second transparent electrode layer 12B has transparency that transmits visible light. The materials constituting the first transparent electrode layer 12A and the second transparent electrode layer 12B may be any one selected from the group consisting of, for example, 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 polyester include polyethylene terephthalate (PET) and polyethylene naphthalate. Examples of polyacrylate include polymethyl methacrylate. Examples of inorganic compounds include silicon dioxide, silicon oxynitride, and silicon nitride.

[0022] The first terminal section 15A and the second terminal section 15B are, for example, flexible printed circuit boards (FPCs). The FPC comprises a support layer, a conductor, and a protective layer. The conductor is sandwiched between the support layer and the protective layer. The support layer and the protective layer are formed of an insulating synthetic resin. The support layer and the protective layer are formed of, for example, polyimide. The conductor is formed of, for example, a thin metal film. The material forming the thin metal film may be, for example, copper. The first terminal section 15A and the second terminal section 15B are not limited to FPCs, but may also be, for example, a metal tape.

[0023] The first terminal portion 15A and the second terminal portion 15B are bonded to the first transparent electrode layer 12A and the second transparent electrode layer 12B by a conductive adhesive layer (not shown). Of the first terminal portion 15A and the second terminal portion 15B, the portions bonded to the conductive adhesive layer have their conductive parts exposed from the protective or support layer. The conductive adhesive layer may be formed from, for example, an anisotropic conductive film (ACF), anisotropic conductive paste (ACP), isotropic conductive film (ICF), and isotropic conductive paste (ICP). From the viewpoint of ease of handling in the manufacturing process of the dimming device 1, the conductive adhesive layer is preferably an anisotropic conductive film.

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

[0025] The light-adjusting layer 11 changes the orientation of liquid crystal molecules in response to changes in voltage between the first transparent electrode layer 12A and the second transparent electrode layer 12B. Changes in the orientation of the liquid crystal molecules alter the degree of scattering, absorption, and transmission of visible light entering the light-adjusting layer 11.

[0026] [Dimmable sheet] Referring to Figures 2 to 6, the structure of the normal type dimmable sheet 10N will be described along with the drive modes of the dimming device 1. The dimming device 1 has three drive modes: transparent mode, opaque mode, and intermediate mode. In the dimmable 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 intermediate mode is an example of the third mode.

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

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

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

[0030] The dimming layer 11 will be described in detail with reference to Figures 5 and 6. Figure 5 schematically shows the cross-sectional structure of the dimming sheet 10N in opaque mode, and the first transparent support layer 13A and the second transparent support layer 13B are omitted from the illustration. The dimming layer 11 comprises a resin layer 111 and a liquid crystal composition 112, as well as a plurality of spacers 115. The spacers 115 are located between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The spacers 115 can 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 mainly composed 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 the spacers 115 scattered in that space. The resin layer 111 has a number of voids 116. The voids 116 may be independent in shape, or a part of the independent shape of one void 116 may be 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 dimming sheet 10N is in opaque mode, the liquid crystal molecules 114 orient their long axes in directions other than the normal direction of the first transparent electrode layer 12A, for example, in an irregular direction. As a result, the visible light incident on the dimming layer 11 is scattered due to the difference between the refractive index of the liquid crystal composition 112 in the void 116 and the refractive index of the resin layer 111, and the linear transmittance decreases and the transparency becomes lower compared to the dimming sheet 10N in transparent mode.

[0032] Figure 6 shows a dimmable sheet 10N driven in transparent mode, where a drive voltage for transparent mode is applied between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The long axis of the liquid crystal molecules 114 is oriented to be parallel or approximately parallel to the normal direction of the first transparent electrode layer 12A. As a result, scattering of light incident on the dimmable layer 11 is reduced, and the linear transmittance increases and transparency is improved compared to the dimmable sheet 10N in opaque mode.

[0033] Furthermore, in the dimming sheet 10N driven in intermediate mode, the long axis of the liquid crystal molecule 114 intersects with the normal of the first transparent electrode layer 12A. As a result, the scattering of incident light is greater compared to the dimming sheet 10N in transparent mode, and less compared to the dimming sheet 10N in opaque mode.

[0034] The ratios of the thickness of each layer to the thickness of other layers that constitute the dimming sheet 10N shown in Figures 1 and 5, 6 are shown for convenience only, and the actual ratios of the thickness of each layer to the thickness of other layers will differ. The thickness of the first transparent support layer 13A and the thickness of the second transparent support layer 13B are, for example, 50 μm or more and 250 μm or less. The thickness of the first transparent electrode layer 12A and the thickness of the second transparent electrode layer 12B are, for example, 5 nm or more and 100 nm or less. When the thickness of the first transparent electrode layer 12A and the thickness of the second transparent electrode layer 12B are 5 nm or more and 100 nm or less, the driving of the dimming sheet 10N is stable and cracks occurring in the transparent electrode layer can be reduced. The thickness of the dimming layer 11 is, for example, 2 μm or more and less than 30 μm. When it is required that the phase separation between the resin layer 111 and the liquid crystal composition 112 proceeds easily in the formation of the dimming layer 11, the thickness of the dimming layer 11 is preferably 30 μm or less.

[0035] This dimming sheet 10 can be attached to windows of moving objects such as vehicles and aircraft. It can also be attached to windows of various buildings such as houses, train stations, and airports, partitions in offices, display windows in stores, and screens for projecting images. The shape of the dimming sheet 10 can be any shape appropriate to the object it is attached to, and it can be flat or curved. By attaching the dimming sheet 10 to these objects and controlling it to a neutral dimming mode, an observer can see an object located on the opposite side of the dimming sheet 10 from their position, while the object is not clearly visible.

[0036] [Manufacturing method for dimmable sheets] An example of a manufacturing method for the dimming sheet 10N is described below. A sheet is prepared consisting of a first transparent support layer 13A having a first transparent electrode layer 12A on its surface, and a sheet consisting of a second transparent support layer 13B having a second transparent electrode layer 12B on its surface. The first transparent electrode layer 12A and the second transparent electrode layer 12B are formed by known thin film formation methods such as sputtering, vacuum deposition, and coating.

[0037] Next, a liquid mixture containing spacers 115, primarily composed of divinylbenzene, 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 mixture has been applied is heated to remove the dispersion medium.

[0038] A coating material, which is a precursor for the dimming layer 11, is prepared. The coating material includes a polymerizable composition and a liquid crystal composition. Then, the coating material is applied to at least one of the first transparent electrode layer 12A and the second transparent electrode layer 12B, on which spacers 115 are scattered, 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. For forming the precursor layer, known coating methods such as inkjet coating, gravure coating, spin coating, slit coating, bar coating, flexo coating, die coating, dip coating, and roll coating can be used.

[0039] Next, the laminate comprising the precursor layer, 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 is irradiated with light of a wavelength that promotes the polymerization reaction of the polymerizable composition, such as ultraviolet light. As a result, monomers and oligomers contained in the polymerizable composition of the precursor layer polymerize, and phase separation between the resin layer 111 and the liquid crystal composition 112 progresses. Then, a light-adjusting layer 11 is formed in which liquid crystal molecules are held in the voids 116.

[0040] The laminate is formed into a large sheet, for example, by using a roll-to-roll method. A portion of the laminate is cut into a desired shape according to the surface to which the dimming sheet 10N will be applied. Then, the dimming sheet 10N is formed by forming a first terminal portion 15A and a second terminal portion 15B on the cut sheet, which is a portion of the laminate.

[0041] [Mid-key] Next, we will explain how to set the dimmable sheet 100 in the reference example to an intermediate tone. In the reference example, the dimmable sheet 100 is of the normal type. The drive voltage applied to the dimmable sheet 100 in the reference example is higher than the drive voltage applied in opaque mode and lower than the drive voltage applied in transparent mode. This makes it possible to drive the dimmable sheet 100 to an intermediate tone, which is between transparent and opaque. However, simply adjusting the drive voltage alone does not make it possible to obtain the aesthetic appearance of the dimmable sheet 100 when it is driven to an intermediate tone.

[0042] Figure 7 shows a reference example of a dimmable sheet 100 driven to intermediate tones, schematically illustrating a portion of the dimmable sheet 100. The dimmable sheet 100 exhibits variations in linear transmittance. This dimmable sheet 100 includes a region 101 with high linear transmittance, a region 103 with low linear transmittance, and a region 102 between the high-transmittance region 101 and the low-transmittance region 103. When the variation in linear transmittance within the plane of the dimmable sheet 100 is large in this way, the linear transmittance of a portion of the dimmable sheet 100 differs from that portion in other adjacent portions. As a result, a portion of the dimmable sheet 100 appears patchy, reducing its aesthetic appearance. Furthermore, if a dimmable sheet 100 driven to intermediate tones is partially transparent, the intermediate tone function may not be fully realized. Note that the example shown in Figure 7 schematically illustrates a dimmable sheet 100 exhibiting a patchy appearance. In a dimmable sheet 100 driven to a midtone, the linear transmittance is divided to such an extent that one dimmable sheet 100 is visible in three or more separate regions, or the regions with mutually different linear transmittances are divided in such a way that they exhibit geometric shapes other than stripes or irregular shapes.

[0043] Figure 8 shows the VT curves illustrating the change in linear transmittance T with respect to the drive voltage applied to the dimmable sheet 100 in the reference example. VT curves 51-53 are VT curves measured at three different measurement positions on a single dimmable sheet 100. In opaque mode, the linear transmittance T converges to a minimum value Ta. In transparent mode, the linear transmittance converges to a maximum value Tb. In the intermediate mode, where the linear transmittance T is between the minimum value Ta and the maximum value Tb, when a drive voltage capable of exhibiting intermediate tone is applied to the dimmable sheet 100, the variation in linear transmittance T at multiple different measurement positions may become large. This is because the rate of change ΔT / V of linear transmittance T per 1V is larger when a drive voltage capable of exhibiting intermediate tone is applied to the dimmable sheet 100 compared to the opaque and transparent modes. A large rate of change ΔT / V makes it possible to achieve intermediate linear transmittance, but it also makes differences in the electric field formed within the plane of the dimmable sheet 100 apparent as differences in linear transmittance T. When the linear transmittance T varies greatly in this way, areas with mutually different transparency may form in a patchy manner, as shown in Figure 7.

[0044] Next, the characteristics of the dimming sheet 10N in this embodiment will be described. (Variation in linear transmittance) The magnitude of the variation in the linear transmittance T of the dimming 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] - On the plane of the dimming sheet 10N, the linear transmittance T at three or more measurement positions is measured while varying the drive voltage, and a VT curve is obtained for each measurement position. For each measurement position's VT curve, the voltage range between the drive voltage that makes the dimming sheet 10N opaque and the drive voltage that makes it transparent is identified. Specifically, for each measurement position's VT curve, the voltage range in which the absolute value of the rate of change per "1V" of the linear transmittance T is 0.5 (% / V) or more is identified. This voltage range is the range of drive voltages that allows the dimming sheet 10N to exhibit an intermediate tone at the measurement position in which the voltage range has been identified.

[0046] As illustrated in Figure 9, the lower limit of the voltage range exhibiting intermediate tone is defined as the "first voltage Va," the upper limit as the "second voltage Vb," and the midpoint between them {(Va+Vb) / 2} is defined as the "intermediate value Vm." The first voltage Va, the second voltage Vb, and the intermediate value Vm are then obtained for each measurement position. This intermediate value Vm is the driving voltage that brings the linear transmittance T of the dimming sheet 10N approximately midway between the minimum value Ta and the maximum value Tb.

[0047] When the number of measurement locations is "n (≧3)", the "minimum value Vmin", "maximum value Vmax", and the average value of the intermediate values ​​Vm, "Vavr", are determined from the intermediate values ​​Vm(Vm1, Vm2, ..., Vmn) obtained at each measurement location P(P1, P2, ..., Pn). Then, as shown in equation (1) below, the variability of the intermediate values ​​Vm is taken as the percentage of the difference between the maximum value Vmax and the minimum value Vmin divided by the average value Vavr.

[0048] Vmv(%)={(Vmax-Vmin) / Vavr}×100 …(1) As shown above, the variation Vmv of the median value Vm for the dimming sheet 10N is 35.0% or less. When the variation Vmv of the median value Vm exceeds 35.0%, the variation in linear transmittance T becomes visible to the naked eye.

[0049] (Thickness of the dimming layer) The thickness of the dimming layer 11 measured at multiple measurement positions within the dimming layer 11 falls within a range of 0.8 to 1.2 times the median value among the thicknesses measured at multiple measurement positions. In other words, the difference between the thickness of the dimming layer 11 measured at each measurement position and the median value falls within a range of -20% to +20% of the median value. The inventors have found that the variation in the linear transmittance T of the dimming sheet 10N is due to the variation in the thickness of the dimming layer 11. By reducing the variation in the thickness of the dimming layer 11, the variation in the median value Vmv can be reduced. The number of measurement positions is 3 or more, preferably 10 or more, in an A4 size of 210 mm x 297 mm. The median value is the value located in the middle when the thicknesses of the dimming layer 11 at the measurement positions are arranged in ascending order.

[0050] (Spacer occupied area) When the light-adjusting layer 11 is observed through the first transparent electrode layer 12A or the second transparent electrode layer 12B, the area occupied by the spacer 115 is preferably 0.9% or more and 30.0% or less of the entire observed surface. The area occupied by the spacer 115 can be calculated by observing a predetermined range of the light-adjusting layer 11 with an optical microscope. The predetermined range to be observed is, for example, a range of 1 mm × 1 mm. Although the presence of the spacer 115 is difficult to see with the naked eye in transparent mode, because the refractive index of the spacer 115 is different from that of the resin layer 111, it appears slightly whiter than the area without the spacer 115, and can be distinguished from the area without the spacer 115 when observed with an optical microscope. For this reason, the area occupied by the spacer 115 can be calculated by taking the sum of the areas of multiple spacers 115 observed in the predetermined range as the occupied area and dividing the area occupied by the spacer 115 by the total area of ​​the predetermined range. If the area occupied by the spacer 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, and the thickness variation of the dimming layer 11 becomes large. If the area occupied by the spacer 115 exceeds 30.0%, the proportion of the spacer 115 in the dimming layer 11 is too large, and the transparency of the dimming sheet 10N in the transparent state decreases. On the other hand, if the area occupied by the spacer 115 is 15.0% or less, the transparency of the dimming sheet 10N when it is driven transparent can be further increased.

[0051] (Mode switching voltage) The phenomenon of variation in the linear transmittance of the dimmable sheet 10N becomes noticeable when the curve is steep in the range of the VT curve, from the first voltage Va where the linear transmittance T is at its minimum value Ta, to the second voltage Vb where the linear transmittance T is at its maximum value Tb. When the slope of the VT curve is gentle, even if there is variation in linear transmittance at mutually different positions within the plane, the amount of change in linear transmittance T per unit voltage is small, making it difficult to discern 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 opaque mode and transparent mode becomes longer. For this reason, when it is required to improve the responsiveness of the switching, when the dimming sheet 10N is a so-called A4 size of 210 mm x 297 mm, it is preferable that the voltage difference for reversibly switching between opaque mode and transparent mode be 22V or less.

[0053] In a dimmable sheet 10N composed of polymer-dispersed liquid crystal, if the resin layer constituting the dimmable layer 11 does not contain a number of independent voids 116, or voids 116 having a shape in which a part of an independent shape is joined, in an appropriate manner, the difference between the first voltage Va and the second voltage Vb will not be 22V or less, and the response speed will decrease. To ensure 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 a diameter of 2.2 μm or less, and that a large number of voids are provided in the resin layer 111. If the diameter of the voids 116 is 0.4 μm or more, transparency is suppressed in opaque mode and sufficient haze is obtained. Furthermore, if the diameter of the voids 116 is 2.2 μm or less, the proportion of the resin layer in the dimmable layer 11 is suppressed, thereby suppressing insufficient strength of the dimmable layer 11. If the dimming layer 11 contains a number of voids 116 in an appropriate manner, and at least the thickness of the dimming layer 11 and the variation Vmv of the median value Vm of the dimming sheet 10N satisfy the above conditions, then it becomes possible to suppress variations in linear transmittance in the intermediate tones and achieve an appropriate response speed at the same time.

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

[0055] (2) By making the dimming layer 11 a structure in which liquid crystal molecules 114 are contained in a plurality of 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 opaque mode and transparent mode.

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

[0057] (4) By setting the diameter of the voids 116 in the resin layer 111 constituting the dimming layer 11 to 0.4 μm or more and 2.2 μm or less, the liquid crystal molecules 114 in the voids 116 of the resin layer 111 become more likely to orient along the electric field. This makes it easier to control the linear transmittance of the dimming sheet 10. In addition, transparency does not occur in opaque mode, and light scattering in the visible light range is improved.

[0058] (5) Since the difference between the first voltage Va, which is the lower limit of the driving voltage at which the rate of change of linear transmittance T is 0.5% / V, and the second voltage Vb, which is the upper limit, is 22V or less, the response speed required for transitions between transparent and opaque modes can be set to an appropriate speed. In addition, the power consumption required for transitions between transparent and opaque modes can be reduced.

[0059] [Differentiation] The above embodiment can be implemented with the following modifications. Furthermore, the following modifications may be implemented in combination.

[0060] In the above embodiment, the dimming sheet 10N is a normal type dimming sheet. Alternatively, the dimming sheet 10 may be a reverse type dimming sheet. Figure 11 shows a reverse-type dimming sheet 10R. The reverse-type dimming sheet 10R 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, as well as a pair of orientation layers, a first orientation layer 14A and a second orientation layer 14B, which sandwich the dimming layer 11. The first orientation layer 14A is located between the dimming layer 11 and the first transparent electrode layer 12A, and the second orientation layer 14B is located between the dimming layer 11 and the second transparent electrode layer 12B. The first alignment layer 14A and the second alignment layer 14B are oriented such that the long axis direction of the liquid crystal molecules 114 contained in the light-adjusting layer 11 is aligned with the normal direction of the first alignment layer 14A and the second alignment layer 14B when the first transparent electrode layer 12A and the second transparent electrode layer 12B are at the same potential. 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 long axis direction of the liquid crystal molecules 114 contained in the light-adjusting layer 11 is set to a direction other than the normal direction. For example, the long axis direction of the liquid crystal molecules 114 is made irregular, or they are arranged parallel to the substrate. Examples of materials that constitute the first alignment layer 14A and the second alignment layer 14B include polyamide, polyimide, polycarbonate, polystyrene, polysiloxane, polyester such as polyethylene terephthalate and polyethylene naphthalate, and polyacrylate such as polymethyl methacrylate. Furthermore, liquid crystal molecules also have negative dielectric anisotropy, and liquid crystal molecules can be used in which the dielectric constant in the long axis direction is smaller than the dielectric constant in the short axis direction. In this dimming sheet 10R, the transparent mode is an example of the first mode, the opaque mode is an example of the second mode, and the intermediate mode is an example of the third mode. In the reverse-type dimming sheet 10R as well, the conditions such as the variation Vmv of the intermediate value Vm of the dimming sheet 10R, the thickness of the dimming layer 11, the spacer occupied area, and the mode switching voltage are the same as those of the dimming sheet 10N in the above embodiment.

[0061] In the above embodiment, the dimming sheet 10N includes a dimming layer 11 that includes a spacer 115. Alternatively, the normal type dimming sheet 10N and the reverse type dimming sheet 10R may be configured to include a dimming layer 11 that does not include a spacer 115, provided that the variation in the thickness of the dimming layer 11 falls within the range of 0.8 times or more and 1.2 times or less of the median thickness.

[0062] In the above embodiment, the dimming layer 11 has a structure having a resin layer 111 and a liquid crystal composition 112. Alternatively, the dimming sheet 10 may be of the SPD (Suspended Particle Device) type, having light-adjusting particles as alignment particles. The SPD type is a method of dispersing a light-adjusting suspension containing light-adjusting particles in a resin matrix. In the SPD type dimming sheet, the variation Vmv of the intermediate value Vm of the dimming sheet 10, the thickness of the dimming layer 11, the spacer occupied area, and the mode switching voltage are the same as in the above embodiment.

[0063] [Examples] An example of the above embodiment will be specifically described with reference to Figures 12 to 24. Note that these embodiments are not limiting to the present invention.

[0064] [Example 1] A pair of PET substrates with an ITO film formed on them was prepared. The ITO film was 30 nm thick, and the PET substrate was 125 μm thick. Next, a dispersion was prepared by dispersing 25 μm diameter spacers, mainly composed of divinylbenzene, in an alcohol-based solvent. This dispersion was then sprayed onto the PET substrates with the ITO film, heated in an oven at 100°C, and the solvent was removed. The spacer area ratio was determined by observing a 1 mm × 1 mm area at an arbitrary position on the light-adjusting sheet using an optical microscope. The ratio of the white area observed within the observation area was calculated as the spacer area ratio. Similarly, 1 mm × 1 mm areas at other positions on the light-adjusting sheet were also observed, and the area ratio was determined for a total of five observation areas. The average of the area ratios was then calculated. The spacer area ratio in Example 1 was 1.50%.

[0065] After applying polymer-dispersible liquid crystal coating (KN-F-001-01-00, manufactured by Kyushu Nanotech Optics Co., Ltd.) to a transparent electrode layer with spacers already applied, the illuminance was 20 mW / cm². 2Using a high-pressure mercury lamp, wavelengths below 350 nm were filtered out, and ultraviolet irradiation was performed under a nitrogen atmosphere for a duration of 30 seconds. During this process, the temperature inside the irradiation device was controlled to 25°C. A light-adjusting sheet was obtained by laminating the other ITO-coated PET substrate onto the sheet with the light-adjusting layer and bonding them under pressure.

[0066] Next, the dimming sheet 10 was cut into a rectangular shape with a width of 210 mm and a length of 297 mm. An incision was made at the short edge of one side of the dimming sheet 10, and the PET substrate, which is one of the transparent support layers, and the transparent electrode layer supported by the PET substrate were peeled off from the dimming sheet using a metal plate over a length of 25 mm in the width direction and 3 mm in the length direction. Furthermore, the portion of the dimming layer 11 that was exposed by the peeling of the PET substrate and the transparent electrode layer was removed from the dimming sheet 10 using a solvent such as isopropyl alcohol, ethyl acetate, or toluene, exposing the other transparent electrode layer. This formed a first terminal portion on the dimming sheet 10. On the other side of the dimming sheet 10, the same process was performed on a portion of the short edge where the first terminal portion was formed, away from the portion where the first terminal portion was formed in the direction of extension of the short edge, exposing the other transparent electrode layer. This formed a second terminal portion on the dimming sheet 10.

[0067] [Example 2] The dimming sheet for Example 2 was fabricated by scattering spacers so that the spacer area ratio was 15.0%, and keeping all other aspects the same as in Example 1.

[0068] [Example 3] The dimming sheet for Example 3 was fabricated by scattering spacers so that the spacer area ratio was 0.9%, and keeping all other aspects the same as in Example 1.

[0069] [Example 4] The dimming sheet of Example 4 was fabricated by scattering spacers so that the spacer area ratio was 30.0%, and keeping all other aspects the same as in Example 1.

[0070] [Comparative Example 1] A dimming sheet for Comparative Example 1 was prepared by scattering spacers so that the spacer occupancy rate was 0.45%, and keeping all other aspects the same as in Example 1.

[0071] [Comparative Example 2] Similar to Example 1, a polymer-dispersed liquid crystal coating was applied to a transparent electrode layer with spacers already in place. When irradiating with ultraviolet light, the temperature inside the irradiation device was controlled to 45°C. Then, a dimmable sheet for Comparative Example 2 was fabricated using the same method as in Example 1, except for the temperature during ultraviolet irradiation.

[0072] [Evaluation of dimmable sheets] Figure 12 shows the results of evaluations conducted for each of the following items for Examples 1-4 and Comparative Examples 1 and 2.

[0073] (Variation in linear transmittance) Linear transmittance measurements were performed at five measurement positions for the dimming sheets of Examples 1-4 and Comparative Examples 1 and 2. The first and second terminal sections, which are the transparent electrode layers 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 0V at a frequency of 60Hz until the linear transmittance saturated. In addition, for each measurement position, the linear transmittance was measured using a haze meter (Suga Test Instruments NDH-7000SP) each time the voltage was increased by 5V. Furthermore, the relationship between the drive voltage and linear transmittance was graphed to obtain a VT curve. Figures 13-18 show examples of VT curves for Examples 1-4 and Comparative Examples 1 and 2.

[0074] Similarly, VT curves were obtained for other measurement positions within the plane of the dimming sheet using the same procedure as described above. Of the five measurement locations, two are 30 mm away from one short side where the first and second terminals are located, in the direction toward the other short side, and are located 30 mm away from one long side and 30 mm away from the other long side. The other two locations are 30 mm away from the short side where the first and second terminals are not located, in the direction toward the short side where the first and second terminals are located, and are located 30 mm away from one long side and 30 mm away from the other long side. The remaining location is the center of the dimming sheet when viewed from the front. That is, in a rectangular dimming sheet 10 with a width of 210 mm and a length of 297 mm, the five measurement locations are the four corners 30 mm away from the edge of the dimming sheet 10, and the center of the dimming sheet 10. The linear transmittance measurement locations are arranged to represent the variation in linear transmittance throughout the dimming sheet 10N.

[0075] For each VT curve obtained at a given measurement location, a range was identified in which the absolute value of the rate of change of the 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 midpoint between them {(Va+Vb) / 2} was defined as the "intermediate value Vm." In addition, the "minimum value Vmin," the "maximum value Vmax," and the average value of the intermediate value Vm, "Vavr," were determined from the intermediate value Vm obtained for mutually different measurement locations within a single dimming sheet. Then, as shown in equation (1) above, the difference between the maximum value Vmax and the minimum value Vmin was divided by the average value Vavr to obtain the variation Vmv of the intermediate value Vm.

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

[0077] (Visual appearance) The driving voltage applied to the dimming sheet was varied, and the state of the intermediate dimming was visually observed. A state where the apparent transparency was uniform was marked with "◎" or "〇", and a state where the transparency was uneven and patchy was marked with "×". Furthermore, a state where the transparency in transparent mode was practically sufficient was marked with "〇", and a state where the transparency in transparent mode was even higher was marked with "◎".

[0078] (Mode switching voltage) The voltage required to switch between opaque and transparent modes was determined at each of the five measurement locations mentioned above, specifically the voltage from the first voltage Va to the second voltage Vb (Vb-Va). Furthermore, the average value of the voltages (Vb-Va) at the five measurement locations was calculated. Since the power consumed when reversibly switching between opaque and transparent modes depends on the voltage, a lower voltage (Vb-Va) required for switching results in lower power consumption. Note that a higher voltage (Vb-Va) leads to a slower response time when switching from opaque to transparent, requiring more time to switch.

[0079] (Size of the void) The size of the voids was determined by observing the cross-section of the light-adjusting 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-adjusting layer. From each of the light-adjusting sheets of Examples 1-4 and Comparative Examples 1 and 2, a square test piece with a side length of 10 cm was cut out. The liquid crystal composition was then removed from the light-adjusting layer by immersing each test piece in isopropyl alcohol. It is also possible to remove the liquid crystal composition from the test piece by immersing it in an organic solvent that dissolves the liquid crystal composition but does not dissolve the resin layer.

[0080] Next, a scanning electron microscope was used to image the cross-section of the test specimen from which the liquid crystal composition had been removed. During this process, 30 rectangular regions were arbitrarily defined on the cross-section of the test specimen. For each region, an image was obtained using the scanning electron microscope at a magnification of 1000x. The 30 rectangular regions were defined such that the distance between adjacent regions was 1 mm or more.

[0081] Figures 19 to 23 are electron microscope images of Examples 1 to 4 and Comparative Examples 1 and 2. Ten voids were arbitrarily selected in each image, and the size of each void was measured. The maximum and minimum sizes of the 10 voids were set as the maximum and minimum void sizes in that image. The maximum and minimum void sizes were calculated for each image. The maximum value among the maximum values ​​obtained in the 30 images was set as the maximum void size in the test specimen. Also, the minimum value among the minimum values ​​obtained in the 30 images was set as the minimum void size in the test specimen.

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

[0083] [Evaluation Results] (Variations in the thickness of the dimming layer) For the dimming sheets of Examples 1-4 and Comparative Example 2, the absolute difference in the thickness of the dimming layer at each measurement position from the median value was within 20%. On the other hand, for Comparative Example 1, where the spacer's occupied area ratio fell below the preferred range, the absolute difference between the thickness of the dimming layer at each measurement position and the median value was up to 40%, indicating a large variation.

[0084] (Variation in linear transmittance) In Examples 1-4 and Comparative Example 2, the dimming sheets all showed a variation Vmv of the intermediate value Vm between the first voltage Va that converges the linear transmittance T to the minimum value Ta and the second voltage Vb that converges it to the maximum value Tb, which was 35.0% or less. On the other hand, in Comparative Example 1, the dimming sheet had a spacer area ratio below the preferred range and a variation in the thickness of the dimming layer above the preferred range, resulting in a large variation Vmv of 47.6% for the intermediate value Vm.

[0085] (Visual appearance) Examples 1-4 and Comparative Example 2 were rated "◎" or "〇". Example 4, in which the spacer's occupied area ratio exceeded the preferred range, was rated "〇" because it was slightly cloudy in transparent mode and lacked sufficient transparency. The smallest value of the maximum linear transmittance Tb in Example 4 was 76.3%, which was lower than that of Examples 1-3.

[0086] (Size of the void) Examples 1-4 and Comparative Example 1 had an average void size of 1.0 μm to 1.3 μm. The shape and spacing of the voids were similar in Examples 1-4 and Comparative Example 1. On the other hand, no voids were observed in Comparative Example 2.

[0087] (Mode switching voltage) In Examples 1-4 and Comparative Example 1, the voltage difference required to switch between transparent and opaque modes was 19.0V to 22.0V. In Comparative Example 2, the voltage difference required to switch between transparent and opaque modes was found to be a large 55.0V.

[0088] As described above, when the variation in the thickness of the dimming layer is small, such that the absolute value of the difference between the thickness of the dimming layer at each measurement position and the median value is 20% or less, it was found that the variation in linear transmittance Vmv in the midtones could be suppressed to 35.0% or less. Furthermore, for dimming sheets in which multiple voids are formed in the dimming layer, with a size of 0.4 μm to 2.2 μm and an average size of 1.0 μm to 1.3 μm, it was found that the variation in linear transmittance Vmv was small, power consumption was low, and the response speed was increased. Note that the effects observed in the above-described examples are obtained by specifying the distribution of the median value Vm. Therefore, the above-described effects can be similarly obtained in polymer network type dimming sheets, where the linear transmittance changes depending on the electric field formed in the dimming sheet, by specifying the distribution of the median value Vm, similar to polymer dispersion type dimming sheets. Also, the effects observed in the above-described examples are obtained by specifying the size of the voids in the dimming layer. Therefore, the effects described above can be similarly obtained in polymer network types where liquid crystal molecules respond to an electric field within the voids formed in the dimming sheet, by specifying the size of the voids. [Explanation of symbols]

[0089] 1… Dimming device 10… Dimming sheet 11…Dimming 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-adjusting layer containing a resin layer and oriented particles, A pair of transparent electrode layers sandwiching the light-adjusting layer, Equipped with, The light-adjusting layer has a structure in which the oriented particles are contained in a plurality of voids dispersed in the resin layer. When the driving voltage applied to the transparent electrode layer is changed, the change in the linear transmittance of visible light is measured, and among the characteristic curves obtained, the lower limit of the 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 the first voltage Va, the upper limit as the second voltage Vb, and the midpoint between the first voltage Va and the second voltage Vb is defined as Vm. The variation of the intermediate value Vm obtained from the characteristic curves at multiple measurement locations, calculated by dividing the difference between the minimum value Vmin and the maximum value Vmax by the average value Vavr of the intermediate value Vm, is {(Vmax - Vmin) / Vavr} × 100, which is 35.0% or less. Dimming sheet.

2. The light-adjusting layer includes a spacer that controls the gap between the pair of transparent electrode layers. When the light-adjusting 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-adjusting layer is 0.9% or more and 30.0% or less. The dimming sheet according to claim 1.

3. The diameter of the aforementioned void is 0.4 μm or more and 2.2 μm or less. The dimming sheet according to claim 1 or 2.

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

5. A dimmable sheet whose linear transmittance changes according to the driving voltage, The system includes a drive unit that controls the drive voltage applied to the dimming sheet, The aforementioned dimming sheet is A light-adjusting layer containing a resin layer and oriented particles, A pair of transparent electrode layers sandwiching the light-adjusting layer, Equipped with, The light-adjusting layer has a structure in which the oriented particles are contained in a plurality of voids dispersed in the resin layer. When the driving voltage applied to the transparent electrode layer is changed, the change in the linear transmittance of visible light is measured, and among the characteristic curves obtained, the lower limit of the 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 the first voltage Va, the upper limit as the second voltage Vb, and the midpoint between the first voltage Va and the second voltage Vb is defined as Vm. Of the intermediate values ​​Vm obtained from the characteristic curves at multiple measurement locations, the variation of the intermediate values ​​{(Vmax - Vmin) / Vavr} × 100, 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. The aforementioned drive unit is The system switches between a first mode in which no drive voltage is 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 to set the linear transmittance of the dimming sheet to a linear transmittance between the linear transmittance in the first mode and the linear transmittance in the second mode. Dimming device.

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