Light control sheet and light control device

Abstract

This light control sheet is provided with a first transparent electrode layer, a second transparent electrode layer, and a light control layer located between the first transparent electrode layer and the second transparent electrode layer, and exhibits a first state and a second state having a lower haze value than the first state according to the magnitude of voltage applied to the light control layer. The light control layer includes a transparent polymer layer that includes a plurality of voids, a liquid crystal composition that is filled in the voids and includes a dichroic pigment, and a spacer that defines the thickness of the light control layer. The spacer assumes a black color. The area occupancy rate of the spacer in the light control layer is 0.7% or more.

Description

Light-adjusting sheet and light-adjusting device

[0001] The present disclosure relates to a light control sheet and a light control device.

[0002] The light-controlling sheet includes a first transparent electrode layer, a second transparent electrode layer, and a light-controlling layer located between the first and second transparent electrode layers. The light-controlling layer includes a transparent polymer layer containing a plurality of voids and a liquid crystal composition filled in the voids. The orientation of the liquid crystal compound contained in the liquid crystal composition changes depending on the magnitude of the voltage applied between the transparent electrode layers. This allows the light-controlling sheet to have two states: a transparent state in which most of the light incident on the light-controlling sheet is transmitted, and an opaque state in which the light incident on the light-controlling sheet is scattered. For this reason, the light-controlling sheet is disposed at the boundary between two spaces and is used as a partition that can switch between a state in which one space is visible through the light-controlling sheet and a state in which the other space is not visible through the light-controlling sheet (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-177197

[0004] Incidentally, a configuration has been proposed for light-adjusting sheets that can be made black when opaque, as a configuration that can reduce the sense of transparency when opaque. On the other hand, it is required that light-adjusting sheets have high transmittance when transparent, while being able to reduce the sense of transparency when opaque, that is, that the contrast, which is the ratio of the transmittance when transparent to the transmittance when opaque, is increased in the light-adjusting sheet.

[0005] A light-controlling sheet that solves the above problem includes a first transparent electrode layer, a second transparent electrode layer, and a light-controlling layer located between the first and second transparent electrode layers, and exhibits a first state and a second state having a lower haze value than the first state depending on the magnitude of the voltage applied to the light-controlling layer. The light-controlling layer includes a transparent polymer layer containing a plurality of voids, a liquid crystal composition containing a dichroic dye that is filled in the voids, and spacers that determine the thickness of the light-controlling layer. The spacers are black. The area occupancy of the spacers in the light-controlling layer is 0.7% or more.

[0006] The light-adjusting device for solving the above problem includes the light-adjusting sheet and a drive unit configured to be able to apply a voltage to the light-adjusting layer of the light-adjusting sheet. With the light-adjusting sheet and the light-adjusting device, the area occupancy rate of the black spacers in the light-adjusting layer is 0.7% or more, so that the contrast of the light-adjusting sheet can be increased.

[0007] In the light-modulating sheet, the content of the dichroic dye in the light-modulating layer may be 2% by weight or more and 5% by weight or less. According to the light-modulating sheet, since the light-modulating layer contains 2% by weight or more and 5% by weight or less of the dichroic dye, it is possible to suppress variation in the total light transmittance within the plane of the light-modulating sheet in the second state.

[0008] In the above-mentioned light-adjusting sheet, the spacer content may be 2×(S / 2)% by weight or more and 5×(S / 2)% by weight or less, and in a two-dimensional coordinate system defined by the spacer content and the dichroic dye content, the spacer content and the dichroic dye content may be included within an area defined by the following two formulas:

[0009] y=(-3x+14)(S / 2) ...Equation (1) y=(-3x+17)(S / 2) ...Equation (2) Here, y is the content of the preceding spacer, x is the content of the dichroic dye, and S is the specific gravity of the spacer.

[0010] According to the above-mentioned dichroic dye sheet, the dichroic dye content and the spacer content are within the above-mentioned ranges, so that both the total light transmittance when the dimming sheet is in the second state and the contrast of the dimming sheet are within suitable ranges.

[0011] In the light-modulating sheet, the voids may have a void diameter of 0.1 μm or more and 30 μm or less, and the content of the liquid crystal composition in the light-modulating layer may be 30% by weight or more and 70% by weight or less.

[0012] According to the above-mentioned light-adjusting sheet, the void diameter is 0.1 μm or more and 30 μm or less, and the liquid crystal composition content is 30% by weight or more and 70% by weight or less, so it is possible to increase the effectiveness of the spacer content and the dichroic dye content.

[0013] In the light-adjusting sheet, the haze value of the light-adjusting sheet in the first state may be 80% or more. With this light-adjusting sheet, the haze value of the light-adjusting sheet in the first state is 80% or more, which makes it possible to increase the effectiveness of the spacer content and the dichroic dye content.

[0014] A light-controlling sheet that solves the above problem includes a first transparent electrode layer, a second transparent electrode layer, and a light-controlling layer located between the first and second transparent electrode layers, and exhibits a first state and a second state having a lower haze value than the first state depending on the magnitude of a voltage applied to the light-controlling layer. The light-controlling layer includes a transparent polymer layer containing a plurality of voids, a liquid crystal composition containing a dichroic dye that is filled in the voids, and spacers that determine the thickness of the light-controlling layer, the spacers exhibiting a black color. The content of the dichroic dye is 3% by weight or more and 5% by weight or less, and in a two-dimensional coordinate system defined by the area occupancy of the spacer and the content of the dichroic dye, the area occupancy of the spacer and the content of the dichroic dye fall within a region equal to or greater than the following formula:

[0015] y=−0.18x+0.99 where y is the area occupancy of the spacer, and x is the content of the dichroic dye.

[0016] According to the above-mentioned dimming sheet, the area occupancy rate of the black spacers and the content rate of the dichroic dye in the dimming layer are within the range specified by the above formula, thereby increasing the contrast of the dimming sheet, and since the dimming layer contains 3% by weight or more and 5% by weight or less of the dichroic dye, it is possible to suppress the variation in the total light transmittance within the plane of the dimming sheet in the second state.

[0017] In the light-modulating sheet, the area occupancy of the spacers may be 4.5% or less, and a point determined by the area occupancy of the spacers and the content of the dichroic dye may be included in a region defined by the following formula: y=-3x+13.5

[0018] According to the above-mentioned light controlling sheet, it is possible to increase the contrast of the light controlling sheet and also increase the total light transmittance when the light controlling sheet is in the second state.

[0019] According to the present disclosure, the contrast of the light-controlling sheet can be increased.

[0020] FIG. 1 is a cross-sectional view showing the structure of a first light-adjusting device equipped with a normal-type light-adjusting sheet. FIG. 2 is a partially enlarged cross-sectional view showing a portion of the structure of the light-adjusting sheet shown in FIG. 1 when no voltage is applied to the light-adjusting layer. FIG. 3 is a partially enlarged cross-sectional view showing a portion of the structure of the light-adjusting sheet shown in FIG. 1 when a voltage is applied to the light-adjusting layer. FIG. 4 is a cross-sectional view showing the structure of a second light-adjusting device equipped with a reverse-type light-adjusting sheet. FIG. 5 is a partially enlarged cross-sectional view showing a portion of the structure of the light-adjusting sheet shown in FIG. 4 when no voltage is applied to the light-adjusting layer. FIG. 6 is a partially enlarged cross-sectional view showing a portion of the structure of the light-adjusting sheet shown in FIG. 4 when a voltage is applied to the light-adjusting layer. FIG. 7 is a graph showing the relationship between the dichroic dye content and the total light transmittance when a voltage is applied to the light-adjusting layer. FIG. 8 is a graph showing the relationship between the dichroic dye content and the total light transmittance when no voltage is applied to the light-adjusting layer. FIG. 9 is a graph showing the relationship between the dichroic dye content and the contrast. FIG. 10 is a graph showing a two-dimensional coordinate system defined by the content of the dichroic dye and the content of the spacer.

[0021] An embodiment of a light controlling sheet will be described with reference to Figures 1 to 10. The light controlling sheet of the present disclosure may be of either a normal type or a reverse type. Below, a first light controlling device including a normal type light controlling sheet and a drive unit will be described with reference to Figures 1 to 3, and a second light controlling device including a reverse type light controlling sheet and a drive unit will be described with reference to Figures 4 to 6.

[0022] The light-controlling sheet is attached to a transparent member provided in windows of various buildings such as houses, train stations, and airports, partitions installed in offices, and show windows installed in stores. Alternatively, the light-controlling sheet is attached to a transparent member provided in windows of moving objects such as vehicles and aircraft. The shape of the light-controlling sheet may be flat or curved.

[0023] [First light control device] The first light control device will be described with reference to Figures 1 to 3. Figure 1 shows the structure of a light control device equipped with a normal-type light control sheet. Figure 2 shows a portion of the structure of the light control sheet when no voltage is applied to the light control layer. Figure 3 shows a portion of the structure of the light control sheet when a voltage is applied to the light control layer.

[0024] 1 , the first light control device 10N includes a normal-type light control sheet 11N and a drive unit 12. The light control sheet 11N includes a first transparent electrode layer 21, a second transparent electrode layer 22, and a light control layer 23. The light control sheet 11N further includes a first transparent substrate 24 that supports the first transparent electrode layer 21, and a second transparent substrate 25 that supports the second transparent electrode layer 22.

[0025] In the light-controlling sheet 11N, the light-controlling layer 23 is located between the first transparent electrode layer 21 and the second transparent electrode layer 22. The first transparent electrode layer 21 is located between the first transparent substrate 24 and the light-controlling layer 23. The second transparent electrode layer 22 is located between the second transparent substrate 25 and the light-controlling layer 23.

[0026] The light-controlling sheet 11N exhibits a first state and a second state having a lower haze value than the first state, depending on the magnitude of the voltage applied to the light-controlling layer 23. Because the light-controlling sheet 11N provided in the first light-controlling device 10N is a normal type, the light-controlling sheet 11N exhibits the first state when no voltage is applied to the light-controlling layer 23. In contrast, the light-controlling sheet 11N exhibits the second state when a voltage is applied to the light-controlling layer 23. The light-controlling sheet 11N exhibiting the first state is opaque, and the light-controlling sheet 11N exhibiting the second state is transparent. For example, the haze value of the light-controlling sheet 11N exhibiting the first state may be 80% or more, and the haze value of the light-controlling sheet 11N exhibiting the second state may be 5% or less.

[0027] The light controlling sheet 11N includes a first electrode 21E attached to a portion of the first transparent electrode layer 21 and a second electrode 22E attached to a portion of the second transparent electrode layer 22. The light controlling sheet 11N further includes a wiring 26 connected to the first electrode 21E and a wiring 26 connected to the second electrode 22E. The first electrode 21E is connected to the drive unit 12 via the wiring 26. The second electrode 22E is connected to the drive unit 12 via the wiring 26.

[0028] The first transparent electrode layer 21 and the second transparent electrode layer 22 apply a voltage to the light control layer 23 to switch the light control layer 23 between transparent and opaque. Each transparent electrode layer 21, 22 has optical transparency that allows visible light to pass through. The optical transparency of the first transparent electrode layer 21 enables visual recognition of objects through the light control sheet 11N. The optical transparency of the second transparent electrode layer 22, like the optical transparency of the first transparent electrode layer 21, enables visual recognition of objects through the light control sheet 11N.

[0029] The material for forming each transparent electrode layer 21, 22 may be, for example, any one selected from the group consisting of indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, and poly(3,4-ethylenedioxythiophene).

[0030] The material forming each of the transparent substrates 24, 25 may be a synthetic resin or an inorganic compound. Examples of synthetic resins include polyester, polyacrylate, polycarbonate, and polyolefin. Examples of polyesters include polyethylene terephthalate and polyethylene naphthalate. Examples of polyacrylates include polymethyl methacrylate. Examples of inorganic compounds include silicon dioxide, silicon oxynitride, and silicon nitride.

[0031] Each of the electrodes 21E, 22E is, for example, a flexible printed circuit (FPC). The FPC includes a support layer, a conductor portion, and a protective layer. The conductor portion is sandwiched between the support layer and the protective layer. The support layer and the protective layer are formed of an insulating synthetic resin. The support layer and the protective layer are formed of, for example, polyimide. The conductor portion is formed of, for example, a thin metal film. The thin metal film may be formed of, for example, copper. Each of the electrodes 21E, 22E is not limited to an FPC, and may be, for example, a metal tape.

[0032] Each of the electrodes 21E and 22E is attached to the corresponding transparent electrode layer 21 or 22 by a conductive adhesive layer (not shown). In each of the electrodes 21E and 22E, the conductor portion is exposed from the protective layer or the support layer at the portion connected to the conductive adhesive layer.

[0033] The conductive adhesive layer may be formed of, for example, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), an isotropic conductive film (ICF), an isotropic conductive paste (ICP), etc. From the viewpoint of ease of handling in the manufacturing process of the light control device 10, the conductive adhesive layer is preferably an anisotropic conductive film.

[0034] Each wiring 26 is formed, for example, by a metal wire and an insulating layer covering the metal wire. The wire is formed, for example, by copper or the like. The driver 12 is configured to be able to apply a voltage to the light-controlling layer 23 provided in the light-controlling sheet 11N. The driver 12 applies an AC voltage between the first transparent electrode layer 21 and the second transparent electrode layer 22. It is preferable that the driver 12 apply an AC voltage having a rectangular waveform between the pair of transparent electrode layers 21, 22. In other words, it is preferable that the driver 12 output a rectangular wave voltage signal.

[0035] The light-controlling layer 23 will be described in more detail with reference to Figures 2 and 3. In Figures 2 and 3, for the sake of convenience in explaining the structure of the light-controlling layer 23 provided in the light-controlling sheet 11N, the thickness of the light-controlling layer 23 is greater than the thickness of the transparent substrates 24 and 25.

[0036] 2, the light-controlling layer 23 includes a transparent polymer layer 23T, a liquid crystal composition 23L, and spacers 23S. The transparent polymer layer 23T includes a plurality of voids 23D. The liquid crystal composition 23L is filled into the voids 23D of the transparent polymer layer 23T, and includes a dichroic dye 23DP.

[0037] The light-switching layer 23 satisfies the following conditions: (Condition 1) The spacers 23S are black, and (Condition 2) The area occupancy rate of the spacers 23S in the light-switching layer 23 is 0.7% or more.

[0038] According to the light controlling sheet 11N of the present disclosure, the area occupancy rate of the black spacers 23S in the light controlling layer 23 is 0.7% or more, so that the contrast of the light controlling sheet 11N can be increased.

[0039] Furthermore, it is preferable that the light-controlling layer 23 satisfy the following condition: (Condition 3) The content of the dichroic dye 23DP in the light-controlling layer 23 is 2% by weight or more and 5% by weight or less.

[0040] Because the light-controlling layer 23 contains 2 wt % or more and 5 wt % or less of the dichroic dye 23DP, it is possible to suppress variation in the total light transmittance within the plane of the light-controlling sheet 11N in the second state. The content of the spacers 23S in the light-controlling layer 23 is the percentage of the weight of the spacers 23S relative to the total weight of the light-controlling layer 23, i.e., the sum of the weight of the transparent polymer layer 23T, the weight of the liquid crystal composition 23L, and the weight of the spacers 23S. When the specific gravity of the spacers 23S is 2, the content of the spacers 23S may be, for example, 0.8 wt % or more. When the specific gravity of the spacers 23S is 2 and the content of the spacers 23S is 0.8 wt %, the area occupancy of the spacers 23S is 0.7%. The content of the dichroic dye 23DP in the light-controlling layer 23 is the percentage of the weight of the dichroic dye 23DP relative to the total weight of the light-controlling layer 23.

[0041] The retention type of the liquid crystal composition 23L is any one selected from the group consisting of a polymer network type, a polymer dispersion type, and a capsule type. The polymer network type has a transparent polymer network with a three-dimensional mesh shape, and retains the liquid crystal composition 23L in interconnected mesh-like voids 23D. The polymer network is an example of a transparent polymer layer 23T. The polymer dispersion type has a large number of isolated voids 23D in the transparent polymer layer 23T, and retains the liquid crystal composition in the voids 23D dispersed in the transparent polymer layer 23T. The capsule type retains the liquid crystal composition 23L having a capsule shape in the transparent polymer layer 23T. As a result, voids 23D into which the liquid crystal composition 23L is filled are formed in the transparent polymer layer 23T.

[0042] The liquid crystal composition 23L includes a liquid crystal compound 23LM. An example of the liquid crystal compound 23LM is any one selected from the group consisting of Schiff bases, azo compounds, azoxy compounds, biphenyl compounds, terphenyl compounds, benzoate ester compounds, tolan compounds, pyrimidine compounds, cyclohexanecarboxylic acid ester compounds, phenylcyclohexane compounds, and dioxane compounds. The liquid crystal composition 23L includes a positive nematic liquid crystal having positive dielectric anisotropy as the liquid crystal compound 23LM.

[0043] In the photochromic layer 23, the gap diameter of the gap 23D is 0.1 μm or more and 30 μm or less, and the content of the liquid crystal composition 23L in the photochromic layer 23 is 30 wt % or more and 70 wt % or less. This makes it possible to increase the effectiveness of the content of the spacer 23S and the content of the dichroic dye 23DP. The gap diameter is measured in a cross section of the photochromic layer 23 along the thickness direction of the photochromic layer 23. In the cross section, if the gap 23D has a circular shape, the diameter of the gap 23D is the gap diameter. In the cross section, if the gap 23D has an elliptical shape, the major axis of the gap 23D is the gap diameter. In the case where the gap 23D has an irregular shape, the major axis of the ellipse with the smallest major axis among the ellipses circumscribing the gap 23D is the gap diameter of the gap 23D.

[0044] The content of the liquid crystal composition 23L in the light-controlling layer 23 is the percentage by weight of the liquid crystal composition 23L with respect to the total weight of the light-controlling layer 23. The content of the liquid crystal composition 23L is equal to the sum of the compounding ratio of the liquid crystal compound 23LM and the compounding ratio of the dichroic dye 23DP when the light-controlling layer 23 is produced.

[0045] The dichroic dye 23DP has an elongated shape. The absorbance in the visible region in the long axis direction of the dichroic dye 23DP molecule is greater than the absorbance in the visible region in the short axis direction of the molecule. The dichroic dye 23DP is nearly transparent when the long axis direction is parallel or nearly parallel to the incident direction of light. In contrast, the dichroic dye 23DP exhibits a predetermined color when the long axis direction is perpendicular or nearly perpendicular to the incident direction of light.

[0046] Therefore, the dichroic dye 23DP exhibits transparency when oriented such that its long axis direction is parallel or approximately parallel to the normal direction of the contact surface of the light-adjusting layer 23 with the first transparent electrode layer 21 and the contact surface of the light-adjusting layer 23 with the second transparent electrode layer 22. In contrast, the dichroic dye 23DP exhibits a predetermined color when oriented such that its long axis direction is perpendicular or approximately perpendicular to the normal direction of the contact surface of the light-adjusting layer 23 with the first transparent electrode layer 21 and the contact surface of the light-adjusting layer 23 with the second transparent electrode layer 22. The color exhibited by the dichroic dye 23DP is preferably black or a color close to black. The dichroic dye 23DP is driven in a guest-host mode using the liquid crystal compound 23LM as a host, thereby causing the dichroic dye 23DP to exhibit color.

[0047] The dichroic dye 23DP may be at least one selected from the group consisting of polyiodine, azo compounds, anthraquinone compounds, naphthoquinone compounds, azomethine compounds, tetrazine compounds, quinophthalone compounds, merocyanine compounds, perylene compounds, and dioxazine compounds. The dichroic dye 23DP may be a single dye or a combination of two or more dyes. From the viewpoint of improving the lightfastness of the dichroic dye 23DP and increasing the dichroic ratio, the dichroic dye 23DP is preferably at least one selected from the group consisting of azo compounds and anthraquinone compounds. The dichroic dye 23DP is more preferably an azo compound.

[0048] The liquid crystal composition 23L may contain, in addition to the liquid crystal compound 23LM and the dichroic dye 23DP, a monomer for forming the transparent polymer layer 23T, for example.

[0049] The spacers 23S are distributed throughout the transparent polymer layer 23T. The spacers 23S determine the thickness of the light-controlling layer 23 around the spacers 23S and reduce variations in the thickness of the light-controlling layer 23. The spacers are bead spacers. The spacers 23S are black, and the color of the spacers 23S is preferably the same color as the color of the dichroic dye 23DP. When the color of the spacers 23S is the same color as the color of the dichroic dye, it is possible to increase the color intensity of the light-controlling sheet 11N in the first state.

[0050] The spacers 23S may have a spherical shape or a columnar shape. The size of the spacers in the thickness direction of the photochromic layer 23 is appropriately changed based on the required thickness of the photochromic layer 23. The size of the spacers in the thickness direction of the photochromic layer 23 is, for example, 10 μm or more and 25 μm or less. When the spacers 23S have a spherical shape, the average particle diameter of the spacers 23S is, for example, 10 μm or more and 25 μm or less. The average particle diameter of the spacers is obtained using a particle size distribution measuring device using principles such as laser light scattering, electrical resistance change, and image analysis after imaging. The average particle diameter of the spacers 23S is the number average particle diameter. When the spacers 23S have a columnar shape, the average diameter of the spacers 23S is, for example, 10 μm or more and 25 μm or less.

[0051] The area occupancy of the spacers 23S may be, for example, 3% or more and 8% or less. The area occupancy of the spacers 23S is the ratio of the area occupied by the spacers 23S to the unit area of ​​the light-adjusting sheet 11N. The area occupied by the spacers 23S is obtained by observing the light-adjusting sheet 11N in the second state from a viewpoint opposite the plane on which the light-adjusting sheet 11N extends. An example of the unit area of ​​the light-adjusting sheet 11N is 1 mm x 1 mm. The area occupied by the spacers 23S is calculated by observing the unit area of ​​the light-adjusting sheet 11N in the transparent state using an optical microscope. Due to the black color of the spacers 23S, areas corresponding to the spacers 23S appear black in images captured with the optical microscope. The area occupied by the spacers 23S is obtained by binarizing the images captured with the optical microscope and summing the areas of the black granular areas. When the spacers 23S have a spherical shape, the granular areas also have a spherical shape. When the spacer 23S has a columnar shape, the granular region has a rectangular shape.

[0052] The area occupancy rate of the spacers 23S may be, for example, 0.7% or more and 8% or less, or 0.7% or more and 4.5% or less.

[0053] The material constituting the spacer 23S may include a transparent inorganic compound having insulating properties or a transparent resin having insulating properties. The transparent inorganic compound is any one selected from the group consisting of silicon dioxide and aluminum oxide. The transparent resin is at least one selected from the group consisting of acrylic resin, epoxy resin, phenolic resin, melamine resin, polyester, polycarbonate, polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, and acetyl cellulose.

[0054] As described above, the spacer 23S is black and therefore contains a black pigment. The black pigment is preferably a pigment capable of absorbing ultraviolet light. Examples of black pigments capable of absorbing ultraviolet light include carbon black, graphite, carbon nanotubes, and oxide-based black pigments. Note that oxide-based black pigments may also be composite oxides. If the black pigment is capable of absorbing ultraviolet light, it is possible to improve the light resistance of the light-control sheet 11N containing the spacer 23S.

[0055] When the spacer 23S is dispersed in the coating liquid for forming the dimming layer 23, i.e., a liquid containing a curable compound and a liquid crystal compound, the surface of the spacer 23S may be subjected to a surface treatment to make it lyophilic to the coating liquid.

[0056] As shown in FIG. 2 , when no voltage is applied to the light-controlling layer 23, the liquid crystal compound 23LM does not have a predetermined regularity in the orientation of its long axis direction. That is, the liquid crystal compound 23LM is irregularly oriented within the voids 23D. As a result, the dichroic dye 23DP is irregularly oriented within the voids 23D, similar to the liquid crystal compound 23LM. Therefore, the light-controlling layer 23, and therefore the light-controlling sheet 11N, is opaque when no voltage is applied to the light-controlling layer 23. As a result, the light-controlling sheet 11N exhibits a first state having a relatively high haze value. Furthermore, the light-controlling sheet 11N exhibits a predetermined color due to the dichroic dye 23DP.

[0057] The haze value of the light-controlling sheet 11N in the first state is 80% or more. This allows for increased effectiveness of the content of the spacer 23S and the content of the dichroic dye 23DP. The haze value is obtained by a measurement method conforming to ASTM D 1003-00. A haze value measuring instrument is, for example, a BYK haze-gard instrument (manufactured by BYK Gardner). When measuring the haze value, the light rays contained in the light beam incident on the light-controlling sheet 11N are straight rays. The maximum angle between the light rays contained in the light beam incident on the light-controlling sheet 11N and the optical axis of the light beam is less than 3°. The light-controlling sheet 11N is fixed so that the surface of the light-controlling sheet 11N and the light beam incident on the surface are approximately perpendicular, within ±2°.

[0058] As shown in FIG. 3, when a voltage is applied to the light-controlling layer 23, the liquid crystal compound 23LM is aligned parallel to the electric field. The light-controlling sheet 11N is configured so that when a voltage is applied to the light-controlling layer 23, the long axis direction of the liquid crystal compound 23LM is perpendicular to the contact surface. That is, the liquid crystal compound 23LM is aligned vertically. As a result, the dichroic dye 23DP is aligned vertically, just like the liquid crystal compound 23LM. Therefore, the light-controlling layer 23, and therefore the light-controlling sheet 11N, is transparent when a voltage is applied to the light-controlling layer 23. As a result, the light-controlling sheet 11N has a relatively low haze value. Furthermore, the light-controlling sheet 11N does not exhibit the specified color due to the dichroic dye 23DP, that is, it is transparent.

[0059] [Second light control device] The second light control device will be described with reference to Figures 4 to 6. The second light control device differs from the first light control device 10N described above in that it includes a reverse-type light control sheet. Therefore, the following will describe in detail the differences between the second light control device and the first light control device, while the components of the second light control device that are common to the first light control device will be denoted by the same reference numerals as those of the first light control device, and detailed descriptions of those components will be omitted.

[0060] 4, the second light control device 10R includes a reverse-type light control sheet 11R and a drive unit 12. In addition to the layers included in the normal-type light control sheet 11N, the light control sheet 11R includes a first alignment film 27 and a second alignment film 28. The light control layer 23 is located between the first alignment film 27 and the second alignment film 28. The first alignment film 27 is located between the light control layer 23 and the first transparent electrode layer 21 and is in contact with the light control layer 23. The second alignment film 28 is located between the light control layer 23 and the second transparent electrode layer 22 and is in contact with the light control layer 23.

[0061] The materials for forming the first alignment film 27 and the second alignment film 28 are organic compounds, inorganic compounds, and mixtures thereof. Examples of organic compounds include polyimide, polyamide, polyvinyl alcohol, and cyanide compounds. Examples of inorganic compounds include silicon oxide and zirconium oxide. The material for forming the alignment films 27 and 28 may be silicone. Silicone is a compound having both inorganic and organic portions.

[0062] The first alignment film 27 and the second alignment film 28 are, for example, vertical alignment films. The vertical alignment films align the long axis direction of the liquid crystal compound so that it is perpendicular to the surface opposite to the surface in contact with the first transparent electrode layer 21 and the surface opposite to the surface in contact with the second transparent electrode layer 22. In this way, the alignment films 27 and 28 regulate the orientation of the multiple liquid crystal compounds contained in the light control layer 23.

[0063] The light-controlling layer 23 will be described in more detail with reference to Figures 5 and 6. In Figures 5 and 6, for the sake of convenience in explaining the structure of the light-controlling layer 23 provided in the light-controlling sheet 11R, the thickness of the light-controlling layer 23 is greater than the thickness of the transparent substrates 24 and 25.

[0064] 5, the light-controlling layer 23, like the light-controlling layer 23 of the normal-type light-controlling sheet 11N, includes a transparent polymer layer 23T including voids 23D, and a liquid crystal composition 23L filled in the voids 23D. The liquid crystal composition 23L includes a liquid crystal compound 23LM and a dichroic dye 23DP. However, the liquid crystal composition 23L includes a negative-type nematic liquid crystal with negative dielectric anisotropy as the liquid crystal compound 23LM. Like the normal-type light-controlling sheet 11N, the light-controlling layer 23 satisfies conditions 1 to 3.

[0065] As shown in Figure 5, when no voltage is applied to the light-adjusting layer 23, the liquid crystal compound 23LM is aligned perpendicular to the contact surface due to the alignment restriction force of the alignment films 27 and 28. As a result, the dichroic dye 23DP is aligned perpendicular to the liquid crystal compound 23LM. Therefore, the light-adjusting layer 23, and therefore the light-adjusting sheet 11R, is transparent when no voltage is applied to the light-adjusting layer 23. As a result, the light-adjusting sheet 11R exhibits a second state having a relatively low haze value. Furthermore, the light-adjusting sheet 11R does not exhibit the color due to the dichroic dye 23DP, i.e., it is transparent.

[0066] As shown in FIG. 6 , when a voltage is applied to the light-controlling layer 23, the liquid crystal compound 23LM is aligned perpendicular to the electric field. The light-controlling sheet 11R is configured so that when a voltage is applied to the light-controlling layer 23, the long axis direction of the liquid crystal compound 23LM is parallel to the contact surface. That is, the liquid crystal compound 23LM is aligned horizontally. As a result, the dichroic dye 23DP is aligned horizontally, similar to the liquid crystal compound 23LM. Therefore, the light-controlling layer 23, and therefore the light-controlling sheet 11R, is opaque when a voltage is applied to the light-controlling layer 23. As a result, the light-controlling sheet 11R exhibits a first state having a relatively high haze value. Furthermore, the light-controlling sheet 11R exhibits a predetermined color due to the dichroic dye 23DP.

[0067] [Test Example] A test example will be described with reference to Fig. 7 to Fig. 10. [Light Control Sheet] A specific test example of the light controlling sheet 11N will be described below.

[0068] The materials common to the light-controlling sheet 11N produced in the test example are as follows: (a) transparent electrode layers 21, 22: indium tin oxide (b) transparent substrates 24, 25: polyethylene terephthalate film (c) spacer 23S: spherical silica particles containing carbon black (diameter 15 μm, specific gravity 2) (d) liquid crystal compound 23LM: fluorine-based liquid crystal compound (e) polymerization initiator: photopolymerization initiator (Irgacure Oxe04, manufactured by BASF) (f) polymerizable composition: mixture of isobornyl acrylate, pentaerythritol triacrylate, and urethane acrylate (g) dichroic dye 23DP: azo-based compound mixed dye (Irgaphor Black X12 DC, manufactured by BASF)

[0069] First, a light-controlling sheet was prepared that did not contain spacer 23S and dichroic dye 23DP. A first transparent substrate 24 with a first transparent electrode layer 21 and a second transparent substrate 25 with a second transparent electrode layer 22 were prepared. Next, a coating liquid containing liquid crystal compound 23LM, a polymerization initiator, and a polymerizable composition was prepared. A coating film was then formed between the first transparent electrode layer 21 and the second transparent electrode layer 22 using the coating liquid, and the polymerizable composition was then polymerized in the coating film to obtain a light-controlling sheet. The thickness of the light-controlling layer in the light-controlling sheet was 15 μm.

[0070] The compounding ratios of materials (d) to (f) relative to the total weight of the coating liquid were set as follows: Before preparing the coating liquid, a mixture of liquid crystal compound 23LM and a polymerizable composition was prepared at the following compounding ratio.

[0071] (d) Liquid crystal compound 23LM: 55% by weight (f) Polymerizable compound: 45% by weight

[0072] Next, the compounding ratio of the mixture of (d) liquid crystal compound 23LM and (f) polymerizable composition to the material (e) was set as follows:

[0073] Mixture of (d) and (f): 99% by weight (e) Polymerization initiator: 1% by weight

[0074] Seven types of light-controlling sheets with different spacer 23S contents were created by changing the blending ratio of the spacer 23S to 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt% in the light-controlling sheet described above, which did not contain the dichroic dye 23DP and the spacer 23S. The area occupancy of the spacer 23S was 0.27% when the blending ratio was 0.3 wt%, 0.45% when the blending ratio was 0.5 wt%, and 0.9% when the blending ratio was 1 wt%. The area occupancy of the spacer 23S was 1.8% when the blending ratio was 2 wt%, 2.7% when the blending ratio was 3 wt%, 3.6% when the blending ratio was 4 wt%, and 4.5% when the blending ratio was 5 wt%.

[0075] In this case, the blending ratio of the mixture of (d) liquid crystal compound 23LM, (f) polymerizable composition, and (e) polymerization initiator was reduced by the amount of the spacer 23S content, based on the blending ratio when preparing a light-controlling sheet not containing spacer 23S. That is, when the blending ratio of spacer 23S was 0.3 wt%, the blending ratio of the mixture was set to 99.7 wt%, when the blending ratio of spacer 23S was 0.5 wt%, the blending ratio of the mixture was set to 99.5 wt%, and when the blending ratio of spacer 23S was 1 wt%, the blending ratio of the mixture was set to 99 wt%. When the blending ratio of spacer 23S was 2 wt%, the blending ratio of the mixture was set to 98 wt%, and when the blending ratio of spacer 23S was 3 wt%, the blending ratio of the mixture was set to 97 wt%. Furthermore, when the compounding ratio of the spacer 23S was 4% by weight, the compounding ratio of the mixture was set to 96% by weight, and when the compounding ratio of the spacer 23S was 5% by weight, the compounding ratio of the mixture was set to 95% by weight.

[0076] In the light-controlling sheet not containing the dichroic dye 23DP and the spacer 23S, the compounding ratio of the dichroic dye 23DP was changed to 2 wt%, and the compounding ratio of the spacer 23S was changed to 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%, respectively, to produce seven types of light-controlling sheets 11N containing 2 wt% of the dichroic dye 23DP and different contents of the spacer 23S.

[0077] In this case, the blending ratio of the mixture of (d) liquid crystal compound 23LM, (f) polymerizable composition, and (e) polymerization initiator was reduced by the blending ratio of dichroic dye 23DP and spacer 23S, based on the blending ratio when preparing a light-adjusting sheet that does not contain dichroic dye 23DP and spacer 23S. That is, when the blending ratio of spacer 23S is 0.3 wt%, the blending ratio of the mixture was set to 97.7 wt%, when the blending ratio of spacer 23S is 0.5 wt%, the blending ratio of the mixture was set to 97.5 wt%, and when the blending ratio of spacer 23S is 1 wt%, the blending ratio of the mixture was set to 97 wt%. Furthermore, when the blending ratio of spacer 23S is 2 wt%, the blending ratio of the mixture was set to 96 wt%, and when the blending ratio of spacer 23S is 3 wt%, the blending ratio of the mixture was set to 95 wt%. Furthermore, when the compounding ratio of the spacer 23S was 4% by weight, the compounding ratio of the mixture was set to 94% by weight, and when the compounding ratio of the spacer 23S was 5% by weight, the compounding ratio of the mixture was set to 93% by weight.

[0078] In the light-controlling sheet 11N containing 2 wt% dichroic dye 23DP described above, the compounding ratio of dichroic dye 23DP was changed to 3 wt%, thereby producing seven types of light-controlling sheets 11N containing 3 wt% dichroic dye and differing contents of spacer 23S. In this case, the compounding ratio when producing a light-controlling sheet not containing dichroic dye 23DP and spacer 23S was used as a reference, and the compounding ratio of the mixture of (d) liquid crystal compound 23LM, (f) polymerizable composition, and (e) polymerization initiator was reduced by the compounding ratio of dichroic dye 23DP and spacer 23S.

[0079] That is, when the blending ratio of the spacer 23S was 0.3 wt%, the blending ratio of the mixture was set to 96.7 wt%, when the blending ratio of the spacer 23S was 0.5 wt%, the blending ratio of the mixture was set to 96.5 wt%, when the blending ratio of the spacer 23S was 1 wt%, the blending ratio of the mixture was set to 96 wt%, when the blending ratio of the spacer 23S was 2 wt%, the blending ratio of the mixture was set to 95 wt%, when the blending ratio of the spacer 23S was 3 wt%, the blending ratio of the mixture was set to 94 wt%, when the blending ratio of the spacer 23S was 4 wt%, the blending ratio of the mixture was set to 93 wt%, and when the blending ratio of the spacer 23S was 5 wt%, the blending ratio of the mixture was set to 92 wt%.

[0080] In the light-controlling sheet 11N containing 3 wt% dichroic dye 23DP described above, the compounding ratio of dichroic dye 23DP was changed to 4 wt%, thereby producing seven types of light-controlling sheets 11N containing 4 wt% dichroic dye 23DP and differing contents of spacer 23S. In this case, the compounding ratio when producing the light-controlling sheet 11N containing 3 wt% dichroic dye 23DP was used as a reference, and the compounding ratio of the mixture of (d) liquid crystal compound 23LM, (f) polymerizable composition, and (e) polymerization initiator was reduced by the amount of the compounding ratio of dichroic dye 23DP and spacer 23S.

[0081] That is, when the blending ratio of spacer 23S was 0.3 wt%, the blending ratio of the mixture was set to 95.7 wt%, when the blending ratio of spacer 23S was 0.5 wt%, the blending ratio of the mixture was set to 95.5 wt%, when the blending ratio of spacer 23S was 1 wt%, the blending ratio of the mixture was set to 95 wt%, when the blending ratio of spacer 23S was 2 wt%, the blending ratio of the mixture was set to 94 wt%, when the blending ratio of spacer 23S was 3 wt%, the blending ratio of the mixture was set to 93 wt%, when the blending ratio of spacer 23S was 4 wt%, the blending ratio of the mixture was set to 92 wt%, and when the blending ratio of spacer 23S was 5 wt%, the blending ratio of the mixture was set to 91 wt%.

[0082] In the light-controlling sheet 11N containing 3 wt% dichroic dye 23DP described above, the compounding ratio of dichroic dye 23DP was changed to 5 wt%, thereby producing seven types of light-controlling sheets 11N containing 5 wt% dichroic dye 23DP and differing contents of spacer 23S. In this case, the compounding ratio when producing the light-controlling sheet 11N containing 2 wt% dichroic dye 23DP was used as a reference, and the compounding ratio of the mixture of (d) liquid crystal compound 23LM, (f) polymerizable composition, and (e) polymerization initiator was reduced by the amount of the compounding ratio of dichroic dye 23DP and spacer 23S.

[0083] That is, when the blending ratio of spacer 23S was 0.3 wt%, the blending ratio of the mixture was set to 94.7 wt%, when the blending ratio of spacer 23S was 0.5 wt%, the blending ratio of the mixture was set to 94.5 wt%, when the blending ratio of spacer 23S was 1 wt%, the blending ratio of the mixture was set to 94 wt%, when the blending ratio of spacer 23S was 2 wt%, the blending ratio of the mixture was set to 93 wt%, when the blending ratio of spacer 23S was 3 wt%, the blending ratio of the mixture was set to 92 wt%, when the blending ratio of spacer 23S was 4 wt%, the blending ratio of the mixture was set to 91 wt%, and when the blending ratio of spacer 23S was 5 wt%, the blending ratio of the mixture was set to 90 wt%.

[0084] [Evaluation Method] [Total Light Transmittance] For each of the above-described light-controlling sheets, the total light transmittance in the first state and the total light transmittance in the second state were calculated using a method in accordance with ASTM D 1003-00. For each light-controlling sheet, the first state was defined as a state in which no potential difference occurred between the pair of transparent electrode layers, i.e., a state in which no AC voltage was applied between the pair of transparent electrode layers. The second state was defined as a state in which an AC voltage having a square waveform of 50 Hz and 40 V was applied between the pair of transparent electrode layers. The haze value in the second state was calculated for each light-controlling sheet using a method in accordance with ASTM D 1003-00. The haze value and total light transmittance were calculated using a haze and transparency measuring instrument (BYK haze-gard i instrument, manufactured by BYK Gardner).

[0085] [Contrast] The contrast of each light-controlling sheet was calculated using the following formula: (Contrast) = (Total light transmittance in the second state) / (Total light transmittance in the first state).

[0086] [Evaluation Results] The evaluation results for each light-adjusting sheet will be described with reference to Tables 1 to 5. The evaluation results for the light-adjusting sheets that did not contain the dichroic dye 23DP were as shown in Table 1 below.

[0087]

[0088] As shown in Table 1, the total light transmittance in the first state was 100% when the spacer 23S content was 0 wt %, and 94% when the spacer 23S content was 0.3 wt % and 0.5 wt %. The total light transmittance in the first state was 94% when the spacer 23S content was 1 wt %, 88% when the spacer 23S content was 2 wt %, and 82% when the spacer 23S content was 3 wt %. The total light transmittance in the first state was 76% when the spacer 23S content was 4 wt %, and 70% when the spacer 23S content was 5 wt %.

[0089] The total light transmittance in the second state was found to be 100% when the spacer 23S content was 0 wt %, and 99% when the spacer 23S content was 0.3 wt % and 0.5 wt %. The total light transmittance in the second state was found to be 99% when the spacer 23S content was 1 wt %, 97% when the spacer 23S content was 2 wt %, and 95% when the spacer 23S content was 3 wt %. The total light transmittance in the second state was found to be 94% when the spacer 23S content was 4 wt %, and 92% when the spacer 23S content was 5 wt %.

[0090] The contrast was found to be 1 when the spacer 23S content was 0 wt%, and 1.1 when the spacer 23S content was 0.3 wt%, and 0.5 wt%. The contrast was also found to be 1.1 when the spacer 23S content was 1 wt%, 1.1 when the spacer 23S content was 2 wt%, and 1.16 when the spacer 23S content was 3 wt%. The contrast was also found to be 1.24 when the spacer 23S content was 4 wt%, and 1.31 when the spacer 23S content was 5 wt%. These results suggest that in a light-control sheet that does not contain dichroic dye 23DP, the contrast is improved when the light-control layer contains 0.3 wt% or more of spacers 23S compared to when the light-control layer 23 does not contain spacers 23S.

[0091] The evaluation results for the light-modulating sheet 11N containing 2% by weight of the dichroic dye 23DP are shown in Table 2 below.

[0092]

[0093] As shown in Table 2, the total light transmittance in the first state was 11.0% when the spacer 23S content was 0.3 wt%, 10.7 wt% when the spacer 23S content was 0.5 wt%, and 10.3% when the spacer 23S content was 1 wt%. The total light transmittance in the first state was 9.7% when the spacer 23S content was 2 wt%, and 9.0% when the spacer 23S content was 3 wt%. The total light transmittance in the first state was 8.4% when the spacer 23S content was 4 wt%, and 7.7% when the spacer 23S content was 5 wt%.

[0094] The total light transmittance in the second state was found to be 32.1% when the spacer 23S content was 0.3 wt%, 31.8% when the spacer 23S content was 0.5 wt%, and 31.5% when the spacer 23S content was 1 wt%. The total light transmittance in the second state was found to be 30.9% when the spacer 23S content was 2 wt%, and 30.3% when the spacer 23S content was 3 wt%. The total light transmittance in the second state was found to be 30.0% when the spacer 23S content was 4 wt%, and 29.3% when the spacer 23S content was 5 wt%.

[0095] The contrast was found to be 2.9 when the spacer 23S content was 0.3 wt %, 3.0 when the spacer 23S content was 0.5 wt % and 1 wt %, 3.2 when the spacer 23S content was 2 wt %, 3.4 when the spacer 23S content was 3 wt %, 3.6 when the spacer 23S content was 4 wt %, and 3.8 when the spacer 23S content was 5 wt %.

[0096] The evaluation results for the light-modulating sheet 11N containing 3% by weight of the dichroic dye 23DP are shown in Table 3 below.

[0097]

[0098] As shown in Table 3, the total light transmittance in the first state was 3.11% when the spacer 23S content was 0.3 wt %, 2.93% when the spacer 23S content was 0.5 wt %, and 2.75% when the spacer 23S content was 1 wt %. The total light transmittance in the first state was 2.57% when the spacer 23S content was 2 wt %, and 2.39% when the spacer 23S content was 3 wt %. The total light transmittance in the first state was 2.22% when the spacer 23S content was 4 wt %, and 2.04% when the spacer 23S content was 5 wt %.

[0099] The total light transmittance in the second state was found to be 16.5% when the spacer 23S content was 0.3 wt%, 15.2% when the spacer 23S content was 0.5 wt%, and 14.9% when the spacer 23S content was 1 wt%. The total light transmittance in the second state was found to be 14.6% when the spacer 23S content was 2 wt%, and 14.3% when the spacer 23S content was 3 wt%. The total light transmittance in the second state was found to be 14.1% when the spacer 23S content was 4 wt%, and 13.8% when the spacer 23S content was 5 wt%.

[0100] The contrast was found to be 5.0 when the spacer 23S content was 0.3 wt %, 5.2 when the spacer 23S content was 0.5 wt %, and 5.4 when the spacer 23S content was 1 wt %. The contrast was also found to be 5.7 when the spacer 23S content was 2 wt %, 6 when the spacer 23S content was 3 wt %, 6.4 when the spacer 23S content was 4 wt %, and 6.8 when the spacer 23S content was 5 wt %.

[0101] Thus, it was found that the total light transmittance in the first and second states was significantly lowered by including 3 wt% of the dichroic dye 23DP in the photochromic layer 23 compared to when the photochromic layer 23 did not include the dichroic dye 23DP. Additionally, it was found that the decrease in the total light transmittance in the first state was greater than the decrease in the total light transmittance in the second state. It was also found that the contrast increased with an increase in the content of the spacer 23S.

[0102] The evaluation results for the light-modulating sheet 11N containing 4% by weight of the dichroic dye 23DP are shown in Table 4 below.

[0103]

[0104] As shown in Table 4, the total light transmittance in the first state was 1.41% when the spacer 23S content was 0.3 wt%, 1.33% when the spacer 23S content was 0.5 wt%, and 1.25% when the spacer 23S content was 1 wt%. The total light transmittance in the first state was 1.17% when the spacer 23S content was 2 wt%, and 1.09% when the spacer 23S content was 3 wt%. The total light transmittance in the first state was 1.01% when the spacer 23S content was 4 wt%, and 0.93% when the spacer 23S content was 5 wt%.

[0105] The total light transmittance in the second state was found to be 11.6% when the spacer 23S content was 0.3 wt%, 11.4% when the spacer 23S content was 0.5 wt%, and 11.2% when the spacer 23S content was 1 wt%. The total light transmittance in the second state was found to be 11% when the spacer 23S content was 2 wt%, and 10.8% when the spacer 23S content was 3 wt%. The total light transmittance in the second state was found to be 10.7% when the spacer 23S content was 4 wt%, and 10.4% when the spacer 23S content was 5 wt%.

[0106] The contrast was found to be 8.2 when the spacer 23S content was 0.3 wt %, 8.6 when the spacer 23S content was 0.5 wt %, and 9.0 when the spacer 23S content was 1 wt %, and the contrast was found to be 9.4 when the spacer 23S content was 2 wt %, 9.9 when the spacer 23S content was 3 wt %, 10.5 when the spacer 23S content was 4 wt %, and 11.2 when the spacer 23S content was 5 wt %.

[0107] Thus, it was found that the contrast was further improved when the dichroic dye 23DP was contained in the photochromic layer 23 at 4 wt % compared to when the dichroic dye 23DP was contained in the photochromic layer 23 at 3 wt %. It was also found that the contrast increased as the content of the spacer 23S increased.

[0108] The evaluation results for the light-modulating sheet 11N containing 5% by weight of dichroic dye 23DP are shown in Table 5 below.

[0109]

[0110] As shown in Table 5, the total light transmittance in the first state was 0.60% when the spacer 23S content was 0.3 wt%, 0.57% when the spacer 23S content was 0.5 wt%, and 0.54% when the spacer 23S content was 1 wt%. The total light transmittance in the first state was 0.51% when the spacer 23S content was 2 wt%, and 0.48% when the spacer 23S content was 3 wt%. The total light transmittance in the first state was 0.44% when the spacer 23S content was 4 wt%, and 0.41% when the spacer 23S content was 5 wt%.

[0111] The total light transmittance in the second state was found to be 7.3% when the spacer 23S content was 0.3 wt%, 7.2% when the spacer 23S content was 0.5 wt%, and 7.1% when the spacer 23S content was 1 wt%. The total light transmittance in the second state was found to be 7.0% when the spacer 23S content was 2 wt%, and 6.9% when the spacer 23S content was 3 wt%. The total light transmittance in the second state was found to be 6.8% when the spacer 23S content was 4 wt%, and 6.6% when the spacer 23S content was 5 wt%.

[0112] The contrast was found to be 12.2 when the spacer 23S content was 0.3 wt %, 12.6 when the spacer 23S content was 0.5 wt %, 13.1 when the spacer 23S content was 1 wt %, 13.7 when the spacer 23S content was 2 wt %, 14.4 when the spacer 23S content was 3 wt %, 15.4 when the spacer 23S content was 4 wt %, and 16.4 when the spacer 23S content was 5 wt %.

[0113] Thus, it was found that the contrast was further improved when the dichroic dye 23DP was contained in the photochromic layer 23 at 5 wt % compared to when the dichroic dye 23DP was contained in the photochromic layer 23 at 4 wt %. It was also found that the contrast increased as the content of the spacer 23S increased.

[0114] 7 to 10 are graphs based on the above-described evaluation results. In each of FIGS. 7 to 9 , the evaluation results when the spacer 23S content is 0.3 wt % are indicated by filled circles, the evaluation results when the spacer 23S content is 0.5 wt % are indicated by filled triangles, and the evaluation results when the spacer 23S content is 1 wt % are indicated by filled squares. Furthermore, in each figure, the evaluation results when the spacer 23S content is 2 wt % are indicated by open circles, and the evaluation results when the spacer 23S content is 3 wt % are indicated by open triangles. Furthermore, in each figure, the evaluation results when the spacer 23S content is 4 wt % are indicated by open diamonds, and the evaluation results when the spacer 23S content is 5 wt % are indicated by open squares.

[0115] 7 and 8, it is difficult to separate the values ​​when the content of spacer 23S is 0.3 wt %, when the content of spacer 23S is 0.5 wt %, and when the content of spacer 23S is 1 wt %, and therefore only the value when the content of spacer 23S is 0.3 wt % is shown.

[0116] 7, when the dichroic dye 23DP content is 2% by weight or more and 5% by weight or less, the total light transmittance when the light-controlling sheet 11N is in the second state is found to change less per unit dichroic dye 23DP content, regardless of the content of the spacer 23S, compared to when the dichroic dye 23DP content is less than 2% by weight. Therefore, when the light-controlling sheet 11N contains 2% by weight or more of dichroic dye 23DP, it can be said that even if the dichroic dye 23DP has a distribution within the plane of the light-controlling sheet 11N, the total light transmittance when the light-controlling sheet 11N is in the second state is less likely to vary within the plane of the light-controlling sheet 11N.

[0117] 8, when the dichroic dye 23DP content is 2% by weight or more and 5% by weight or less, the change in total light transmittance per unit dichroic dye 23DP content is smaller than when the dichroic dye 23DP content is less than 2% by weight, regardless of the content of spacer 23S. Therefore, when the dichroic dye 23DP content of the dichroic dye 23DP in the light-adjusting sheet 11N is 2% by weight or more, even if the dichroic dye 23DP has a distribution within the plane of the light-adjusting sheet 11N, it can be said that the total light transmittance when the light-adjusting sheet 11N is in the first state is less likely to vary within the plane of the light-adjusting sheet 11N.

[0118] 9, it was found that the higher the content of dichroic dye 23DP, the greater the difference in contrast due to the content of spacer 23S. In other words, it was found that the higher the content of dichroic dye 23DP, the more pronounced the effect of increasing the content of spacer 23S in enhancing the contrast of light controlling sheet 11N.

[0119] Fig. 10 shows a two-dimensional coordinate system defined by the content of the spacer 23S and the content of the dichroic dye 23DP. As shown in Fig. 10, a point defined by the content of the spacer 23S and the content of the dichroic dye 23DP is preferably included in an area defined by the following conditions in the above-mentioned two-dimensional coordinate system.

[0120] (Condition B1) The content of the dichroic dye 23DP is 3% by weight or more and 5% by weight or less. (Condition C1) A point determined by the content of the spacer 23S and the content of the dichroic dye 23DP is included in the region defined by the following formula (1): y=-0.2x+1.1 (Formula (1))

[0121] In formula (1), the content of the spacer 23S is y, and the content of the dichroic dye 23DP is x. The straight line corresponding to formula (1) is shown as a solid line in FIG.

[0122] The point determined by the content of the spacer 23S and the content of the dichroic dye 23DP is preferably included in the region defined by the following condition A1 in addition to conditions B1 and C1: (Condition A1) The content of the spacer 23S is 5 wt % or less.

[0123] Furthermore, in a two-dimensional coordinate system defined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP, it is preferable that the point defined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP is included within an area defined by the following conditions:

[0124] (Condition B2) The content of the dichroic dye 23DP is 3% by weight or more and 5% by weight or less. (Condition C2) A point determined by the area occupancy of the spacers 23S and the content of the dichroic dye 23DP is included in the region defined by the following formula (2): y = -0.18x + 0.99 ... formula (2)

[0125] In the formula (2), the area occupancy of the spacer 23S is y, and the content of the dichroic dye 23DP is x.

[0126] The point determined by the area occupancy of the spacers 23S and the content of the dichroic dye 23DP is preferably included in the region defined by the following condition A2 in addition to conditions B2 and C2: (Condition A2) The area occupancy of the spacers 23S is 4.5% or less.

[0127] According to this test example, it was found that by including both the content of spacer 23S and the content of dichroic dye 23DP in the region defined by the above-mentioned conditions B1 and C1, preferably in the region defined by conditions A1 to C1, the contrast exceeded 5. Furthermore, the same effect can also be obtained by including both the area occupancy rate of spacer 23S and the content of dichroic dye 23DP in the region defined by the above-mentioned conditions B2 and C2, preferably in the region defined by conditions A2 to C2.

[0128] A point determined by the content of the spacer 23S and the content of the dichroic dye 23DP may be included in a region defined by the following conditions in the above-mentioned two-dimensional coordinate system: (Condition A3) The content of the spacer 23S is 2% by weight or more and 5% by weight or less. (Condition B3) The content of the dichroic dye 23DP is 2% by weight or more and 5% by weight or less.

[0129] (Condition C3) A point determined by the content of the spacer 23S and the content of the dichroic dye 23DP is included in the region defined by the following two formulas: y=-3x+14 (formula (3)) y=-3x+17 (formula (4))

[0130] In formula (3) and formula (4), the content of the spacer 23S is y, and the content of the dichroic dye 23DP is x. The straight lines corresponding to formula (3) and formula (4) are shown as solid lines in FIG.

[0131] Furthermore, in a two-dimensional coordinate system determined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP, a point determined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP may be included within an area defined by the following conditions.

[0132] (Condition A4) The area occupancy of the spacers 23S is 1.8% or more and 4.5% or less. (Condition B4) The content of the dichroic dye 23DP is 2% or more and 5% or less by weight.

[0133] (Condition C4) A point determined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP is included in the region defined by the following two formulas: y=-3x+12.6 (Formula (5)) y=-3x+15.3 (Formula (6))

[0134] In the formulas (5) and (6), the area occupancy of the spacer 23S is y, and the content of the dichroic dye 23DP is x.

[0135] According to this test example, it was confirmed that by including both the content of spacers 23S and the content of dichroic dye 23DP in the region defined by the above-mentioned conditions A3 to C3, it is possible to achieve both a total light transmittance of 7% or more in the second state and a contrast of 6.5 or more. In other words, it can be said that while increasing the contrast, the light controlling sheet 11N is prevented from becoming too dark when it is in the second state. Furthermore, this effect can also be achieved by including both the area occupancy rate of spacers 23S and the content of dichroic dye 23DP in the region defined by the above-mentioned conditions A4 to C4.

[0136] The area and surface area occupied by the spacers 23S in the light-adjusting sheet 11N contribute significantly to enhancing the contrast of the light-adjusting sheet 11N. Furthermore, the area and surface area occupied by the spacers 23S correlate with the number of spacers 23S. Since the specific gravity of the spacers 23S used in this embodiment is 2, the above-mentioned condition A3, formula (3), and formula (4) can be generalized as follows using the specific gravity S. Furthermore, in a light-adjusting sheet 11N having spacers 23S with a specific gravity S, it is preferable that a point determined by the content of the spacers 23S and the content of the dichroic dye 23DP is included within a region defined by the following conditions in a two-dimensional coordinate system. The specific gravity S is the ratio of the mass of the target substance per unit volume to the mass of the reference substance per unit volume. The spacers 23S are an example of a target substance.

[0137] (Condition A3') The content of the spacer 23S is 2×(S / 2)% by weight or more and 5×(S / 2)% by weight or less. (Condition B3) The content of the dichroic dye 23DP is 2% by weight or more and 5% by weight or less.

[0138] (Condition C3') A point determined by the content of the spacer 23S and the content of the dichroic dye 23DP is included in the region defined by the following two formulas: y=(-3x+14)(S / 2) ...formula (3') y=(-3x+17)(S / 2) ...formula (4')

[0139] Similarly to condition A3, the above-mentioned condition A1 can also be generalized as follows using the specific gravity S: (Condition A1') The content of the spacer 23S is 5 x (S / 2) wt% or less.

[0140] When the specific gravity S is 1, the straight line corresponding to the formula (3') and the straight line corresponding to the formula (4') are shown by dashed lines in FIG.

[0141] Furthermore, a point determined by the content of the spacer 23S and the content of the dichroic dye 23DP may be included in a region defined by the following conditions in a two-dimensional coordinate system: (Condition A1) The content of the spacer 23S is 5% by weight or less. (Condition B1) The content of the dichroic dye 23DP is 3% by weight or more and 5% by weight or less.

[0142] (Condition C1) A point determined by the content of the spacer 23S and the content of the dichroic dye 23DP is included in a region equal to or greater than the following formula (1): y=−0.2x+1.1 (Formula (1))

[0143] (Condition C5) A point determined by the content of the spacer 23S and the content of the dichroic dye 23DP is included in the region defined by the following formula (4): y=−3x+17 (4)

[0144] Furthermore, a point determined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP may be included in a region defined by the following conditions in a two-dimensional coordinate system.

[0145] (Condition A2) The area occupancy of the spacers 23S is 4.5% or less. (Condition B2) The content of the dichroic dye 23DP is 3% by weight or more and 5% by weight or less.

[0146] (Condition C2) A point determined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP is included in a region equal to or greater than the following formula (2): y=−0.18x+0.99 (formula (2))

[0147] (Condition C6) A point determined by the area occupancy of the spacer 23S and the content of the dichroic dye 23DP is included in the region defined by the following formula (6): y=−3x+15.3 (6)

[0148] According to this test example, it was confirmed that by including both the content of spacers 23S and the content of dichroic dye 23DP in the region defined by the above-mentioned conditions A1 to C5, it is possible to achieve both a total light transmittance of 7% or more in the second state and a contrast of more than 5. In other words, it can be said that while increasing the contrast, the light controlling sheet 11N is prevented from becoming too dark when it is in the second state. Furthermore, this effect can also be obtained by including both the area occupancy rate of spacers 23S and the content of dichroic dye 23DP in the region defined by the above-mentioned conditions A2 to C6.

[0149] As described above, according to one embodiment of the light controlling sheet and the light controlling device, the following effects can be obtained: (1) Since the area occupancy rate of the black spacers 23S is 0.7% or more, the contrast of the light controlling sheets 11N and 11R can be increased.

[0150] (2) Since the light-controlling layer 23 contains 2% by weight or more and 5% by weight or less of the dichroic dye 23DP, it is possible to suppress variations in the total light transmittance within the plane of the light-controlling sheets 11N, 11R in the second state.

[0151] (3) By the content of dichroic dye 23DP and the content of spacer 23S being within the range determined by conditions A3' to C3', both the total light transmittance when the dimming sheets 11N, 11R are in the second state and the contrast of the dimming sheets 11N, 11R are within a suitable range.

[0152] (4) Since the void diameter is 0.1 μm or more and 30 μm or less, and the content of the liquid crystal composition 23L is 30% by weight or more and 70% by weight or less, it is possible to increase the effectiveness of the content of the spacer 23S and the content of the dichroic dye 23DP.

[0153] (5) Since the haze value of the light controlling sheets 11N and 11R in the first state is 80% or more, it is possible to increase the effectiveness of the content of the spacer 23S and the content of the dichroic dye 23DP.

[0154] (6) The area occupancy of the spacers 23S and the content of the dichroic dye 23DP fall within the range determined by the conditions B1 and C1, thereby increasing the contrast of the light controlling sheet 11N.

[0155] (7) By ensuring that the area occupancy of the spacer 23S and the content of the dichroic dye 23DP are within the range determined by conditions A2 to C6, the contrast of the dimming sheet 11N can be increased while also increasing the total light transmittance when the dimming sheet 11N is in the second state.

[0156] [Modifications] The above-described embodiment can be modified as follows. [Spacer 23S] The specific gravity of the spacer 23S is not limited to 2 and may be, for example, 1.2. For example, the specific gravity of a spacer 23S made of acrylic resin containing carbon black is 1.2. For the acrylic resin spacer 23S, the area occupancy is 0.45% when the content is 0.3 wt %, 0.75% when the content is 0.5 wt %, and 1.2% when the content is 0.8 wt %. For the acrylic resin spacer 23S, the area occupancy is 1.5% when the content is 1 wt %, 3% when the content is 2 wt %, and 4.5% when the content is 3 wt %. Even with the acrylic resin spacer 23S, it is possible to obtain the same effect as the silica spacer 23S described above by setting the area occupancy of the spacer 23S to 0.7% or more. That is, regardless of the specific gravity of the spacers 23S, the same effect can be obtained in a configuration in which the area occupancy of the spacers 23S in the light-controlling layer 23 is the same.

[0157] [Supplementary Notes] The following additional notes describe technical ideas derived from the above-described embodiments and modified examples. [Supplementary Note 1] A light-controlling sheet comprising: a first transparent electrode layer; a second transparent electrode layer; and a light-controlling layer located between the first and second transparent electrode layers, which exhibits a first state and a second state having a lower haze value than the first state depending on the magnitude of a voltage applied to the light-controlling layer, wherein the light-controlling layer comprises: a transparent polymer layer including a plurality of voids; a liquid crystal composition filled in the voids; and spacers that determine the thickness of the light-controlling layer, the spacers being black in color, and the light-controlling layer having a content of the spacers of 2% by weight or more.

[0158] According to the light-controlling sheet, the light-controlling layer contains 2% by weight or more of black spacers, so that the contrast of the light-controlling sheet can be increased compared to when no spacers are contained.

[0159] REFERENCE SIGNS LIST 10N, 10R... Light control device 11N, 11R... Light control sheet 12... Driving unit 21... First transparent electrode layer 22... Second transparent electrode layer 23... Light control layer 24... First transparent substrate 25... Second transparent substrate 27... First alignment layer 28... Second alignment layer

Claims

1. A first transparent electrode layer; A second transparent electrode layer; a light control layer located between the first transparent electrode layer and the second transparent electrode layer, A light-controlling sheet that exhibits a first state and a second state having a lower haze value than the first state depending on a magnitude of a voltage applied to the light-controlling layer, The light-controlling layer is a transparent polymer layer including a plurality of voids; a liquid crystal composition that fills the gap and contains a dichroic dye; A spacer that determines the thickness of the light-controlling layer; The spacer is black in color, The area occupancy rate of the spacer in the light-controlling layer is 0.7% or more. Dimming sheet.

2. The content of the dichroic dye in the light-adjusting layer is 2% by weight or more and 5% by weight or less. The light controlling sheet according to claim 1 .

3. The content of the spacer is 2×(S / 2)% by weight or more and 5×(S / 2)% by weight or less, In a two-dimensional coordinate system defined by the content of the spacer and the content of the dichroic dye, the content of the spacer and the content of the dichroic dye are included in a region defined by the following two formulas: y=(-3x+14)(S / 2)...Formula (1) y=(-3x+17)(S / 2)...Formula (2) Here, y is the content of the spacer, x is the content of the dichroic dye, and S is the specific gravity of the spacer. The light controlling sheet according to claim 1 or 2.

4. The pore diameter of the pores is 0.1 μm or more and 30 μm or less, The content of the liquid crystal composition in the light-controlling layer is 30% by weight or more and 70% by weight or less. The light controlling sheet according to claim 1 or 2.

5. The haze value of the light controlling sheet in the first state is 80% or more. The light controlling sheet according to claim 1 or 2.

6. A first transparent electrode layer; A second transparent electrode layer; a light control layer located between the first transparent electrode layer and the second transparent electrode layer, A light-controlling sheet that exhibits a first state and a second state having a lower haze value than the first state depending on a magnitude of a voltage applied to the light-controlling layer, The light-controlling layer is a transparent polymer layer including a plurality of voids; a liquid crystal composition that fills the gap and contains a dichroic dye; A spacer that determines the thickness of the light-adjusting layer; The spacer is black in color, The content of the dichroic dye is 3% by weight or more and 5% by weight or less, In a two-dimensional coordinate system defined by the area occupancy of the spacer and the content of the dichroic dye, the area occupancy of the spacer and the content of the dichroic dye are included within a region satisfying the following formula or more: y=-0.18x+0.99 In addition, y is the area occupancy of the spacer, and x is the area occupancy of the two-color The content of the active dye is Dimming sheet.

7. the area occupancy rate of the spacer is 4.5% or less, A point determined by the area occupancy of the spacer and the content of the dichroic dye is included in a region represented by the following formula: y=-3x+13.5 The light controlling sheet according to claim 6.

8. The light controlling sheet according to claim 1 or 2, A driving unit configured to be able to apply a voltage to the light-controlling layer of the light-controlling sheet. Dimmer.