Dimming sheet

Abstract

To provide a dimming sheet capable of increasing opaqueness when being energized.SOLUTION: A dimming layer 13 includes a first area being in contact with a first vertical orientation film 11 and a second area being in contact with a second vertical orientation film 12. The first area and the second area include liquid crystal molecules 13LM. As viewed from a visual point opposing a plane in which the dimming layer 13 is extended, in a state where voltage is applied to the dimming layer 13, the first vertical orientation film 11 has orientation regulating force that horizontally orients the liquid crystal molecules 13LM included in the first area in a first direction. The liquid crystal molecules 13LM included in the second area include the liquid crystal molecules 13LM that are horizontally oriented in directions other than the first direction.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] The reverse type dimming sheet includes a dimming layer containing liquid crystal molecules, and a pair of alignment films that are in contact with the dimming layer and sandwich the dimming layer. Each alignment film is, for example, a vertical alignment film, and in a state where no potential difference is generated between a pair of transparent electrode layers, the liquid crystal molecules are aligned so that the major axis of each liquid crystal molecule is substantially perpendicular to the alignment film. Therefore, the reverse type dimming sheet is transparent in a state where no potential difference is generated between a pair of transparent electrode layers. On the other hand, in a state where a potential difference is generated between a pair of transparent electrode layers, the liquid crystal molecules are aligned along a direction perpendicular to the electric field direction, whereby the dimming sheet has an opaque state (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the reverse type dimming sheet having such a structure, it is required to further enhance the opacity in a state where a potential difference is generated between a pair of transparent electrode layers.

Means for Solving the Problems

[0005] The dimming sheet for solving the above problems includes a first vertical alignment film, a second vertical alignment film, and a dimming layer located between the first vertical alignment film and the second vertical alignment film. The dimming layer includes a transparent resin layer having a plurality of domains and a dimming layer including a plurality of liquid crystal molecules located within the domains. The dimming layer includes a first region in contact with the first vertical alignment film and a second region in contact with the second vertical alignment film, and the first region and the second region include the liquid crystal molecules. When viewed from a viewpoint facing the plane in which the dimming layer extends, the first vertical alignment film has an alignment regulating force for horizontally aligning the liquid crystal molecules included in the first region in a first direction in a state where a voltage is applied to the dimming layer. The liquid crystal molecules included in the second region include liquid crystal molecules that are horizontally aligned in a direction other than the first direction.

[0006] According to the above dimming sheet, in a state where a voltage is applied to the dimming layer, the liquid crystal molecules included in the first region are horizontally aligned along the first direction. Therefore, compared with the case where the major axes of the liquid crystal molecules included in the first region are randomly oriented, the first region maintains, over the entire plane in which the dimming layer extends, a state where the difference in refractive index between the liquid crystal molecules and the resin layer is large with respect to a part of the light incident on the first region when viewed from the light incident on the first region. As a result, light scattering is likely to occur in the first region, so that the opacity of the dimming layer, and thus the dimming sheet including the dimming layer, is increased when a voltage is applied to the dimming layer.

[0007] In the above dimming sheet, when viewed from a viewpoint facing the plane in which the dimming layer extends, the second vertical alignment film has an alignment regulating force for horizontally aligning the liquid crystal molecules included in the second region in a second direction in a state where a voltage is applied to the dimming layer, and the second direction may be a direction intersecting the first direction.

[0008] When viewed from a part of the light incident on the first region, the refractive index difference between the liquid crystal molecules oriented in the first direction and the resin layer is not sufficiently high. Therefore, a part of the light is not sufficiently scattered in the first region. In this regard, according to the light control sheet, since the liquid crystal molecules contained in the second region are oriented along the second direction intersecting the first direction, among the light incident on the light control layer, the component that was not sufficiently scattered in the first region is scattered in the second region. Thereby, the opacity of the light control layer, and thus the light control sheet including the light control layer, is increased when a voltage is applied to the light control layer.

[0009] In the light control sheet, when viewed from a viewing point facing the plane in which the light control layer extends, the second direction may be a direction orthogonal to the first direction. The liquid crystal molecules have an extraordinary refractive index n in the major axis direction e and have an ordinary refractive index n in the direction perpendicular to the major axis. o Therefore, the component that was not scattered in the first region becomes most easily scattered by having its refractive index increased in the second direction, which is a direction orthogonal to the first direction. In this regard, as in the light control sheet, it is preferable that the second direction is a direction orthogonal to the first direction.

[0010] In the light control sheet, the light control layer is composed of the first region, the second region, and a central region located between the first region and the second region. The plurality of domains are composed of a plurality of first domains and a plurality of second domains. The first region includes a plurality of first domains, and a part of the liquid crystal molecules is located in each first domain. The second region includes a plurality of second domains, and a part of the liquid crystal molecules is located in each second domain. The central region may not include the domains.

[0011] According to the light control sheet, since no liquid crystal molecules are located in the central region, light scattering hardly occurs in the central region. As a result, when a voltage is applied to the light control layer, the opacity of the light control layer tends to be low. Therefore, in the light control sheet, the effectiveness of the first vertical alignment film in aligning the liquid crystal molecules in the first domain along the first direction is enhanced.

[0012] In the above-mentioned dimming sheet, each first domain may be in contact with the first vertical alignment film, and each second domain may be in contact with the second vertical alignment film. According to this dimming sheet, the distances between the liquid crystal molecules contained in the first region and the first vertical alignment film, and between the liquid crystal molecules contained in the second region and the second vertical alignment film become smaller. Therefore, when an electric current is applied to the dimming layer, among the liquid crystal molecules contained in the first region, the proportion of the liquid crystal molecules that are aligned according to the alignment regulating force of the first vertical alignment film is further increased, and the proportion of the liquid crystal molecules that are aligned according to the alignment regulating force of the second vertical alignment film is further increased. As a result, when a voltage is applied to the dimming layer, it is possible to increase the opacity.

Advantages of the Invention

[0013] According to the present invention, the opacity during energization can be increased.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0015] [First Embodiment] Referring to FIGS. 1 to 5, a first embodiment of the dimming sheet will be described. [Structure] Referring to FIGS. 1 to 3, the structure of the dimming sheet will be described. The dimming sheet is attached to, for example, a window provided in a moving body such as a vehicle and an aircraft. Further, the dimming sheet is attached to, for example, a window provided in various buildings such as a house, a station, and an airport, a partition installed in an office, a show window installed in a store, and a screen for projecting an image. The shape of the dimming sheet may be planar or curved.

[0016] FIG. 1 shows the structure of a dimming device including a dimming sheet. As shown in FIG. 1, the dimming sheet 10 includes a first vertical alignment film 11, a second vertical alignment film 12, and a dimming layer 13. The dimming layer 13 is located between the first vertical alignment film 11 and the second vertical alignment film 12. The dimming layer 13 is in contact with the first vertical alignment film 11 and the second vertical alignment film 12. The dimming layer 13 contains a plurality of liquid crystal molecules.

[0017] The dimming sheet 10 further includes a first transparent electrode layer 14 and a second transparent electrode layer 15. The first vertical alignment film 11 is located between the first transparent electrode layer 14 and the dimming layer 13. The second vertical alignment film 12 is located between the second transparent electrode layer 15 and the dimming layer 13. The dimming sheet 10 further includes a first transparent substrate 16 and a second transparent substrate 17. The first transparent substrate 16 supports the first transparent electrode layer 14. The second transparent substrate 17 supports the second transparent electrode layer 15.

[0018] The materials forming the respective transparent substrates 16 and 17 may be synthetic resins or inorganic compounds. The synthetic resins are, for example, polyesters, polyacrylates, polycarbonates, and polyolefins. The polyesters are, for example, polyethylene terephthalate and polyethylene naphthalate. The polyacrylates are, for example, polymethyl methacrylate. The inorganic compounds are, for example, silicon dioxide, silicon oxynitride, and silicon nitride. The thickness of each of the transparent substrates 16 and 17 may be, for example, 16 μm or more and 250 μm or less. When the thickness of the transparent substrates 16 and 17 is 16 μm or more, the dimming sheet 10 can be easily processed and installed. When the thickness of the transparent substrates 16 and 17 is 250 μm or less, the dimming sheet 10 can be manufactured by roll-to-roll.

[0019] The dimming device 20 includes the above-described dimming sheet 10, a first electrode 14A, a second electrode 15A, a driving unit 21, and wiring 22. The first electrode 14A is attached to a part of the first transparent electrode layer 14. The second electrode 15A is attached to a part of the second transparent electrode layer 15. The driving unit 21 is connected to the first electrode 14A and the second electrode 15A by the wiring 22.

[0020] Each of the electrodes 14A and 15A 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 metal thin film. The material forming the metal thin film may be, for example, copper. Each of the electrodes 14A and 15A is not limited to the FPC and may be, for example, a metal tape.

[0021] Note that each of the electrodes 14A and 15A is attached to each of the transparent electrode layers 14 and 15 by a conductive adhesive layer (not shown). In a portion of each of the electrodes 14A and 15A that is connected to the conductive adhesive layer, the conductor portion is exposed from the protective layer or the support layer.

[0022] The conductive adhesive layer may be formed by, for example, an anisotropic conductive film (ACF: Anisotropic Conductive Film), an anisotropic conductive paste (ACP: Anisotropic Conductive Paste), an isotropic conductive film (ICF: Isotropic Conductive Film), and an isotropic conductive paste (ICP: Isotropic Conductive Paste). From the viewpoint of handleability in the manufacturing process of the dimming device 20, the conductive adhesive layer is preferably an anisotropic conductive film.

[0023] The wiring 22 is formed by, for example, a metal wire and an insulating layer covering the metal wire. The wire is formed of, for example, copper or the like. The driving unit 21 applies an alternating voltage between the first transparent electrode layer 14 and the second transparent electrode layer 15. The driving unit 21 preferably applies an alternating voltage having a rectangular wave shape between the pair of transparent electrode layers 14 and 15. Note that the driving unit 21 may apply an alternating voltage having a shape other than a rectangular wave shape between the pair of transparent electrode layers 14 and 15. For example, the driving unit 21 may apply an alternating voltage having a sine wave shape between the pair of transparent electrode layers 14 and 15.

[0024] The dimming layer 13 receives a change in voltage generated between the two transparent electrode layers 14 and 15, thereby changing the alignment of liquid crystal molecules. The change in the alignment of the liquid crystal molecules changes the degree of scattering, absorption, and transmittance of visible light entering the dimming layer 13. The reverse-type dimming sheet 10 has a relatively high haze when the dimming sheet 10 is energized, that is, when a potential difference is generated between the first transparent electrode layer 14 and the second transparent electrode layer 15. The reverse-type dimming sheet 10 has a relatively low haze when the dimming sheet 10 is not energized, that is, when no potential difference is generated between the first transparent electrode layer 14 and the second transparent electrode layer 15.

[0025] Figure 2 schematically shows a cross-sectional structure of the dimming sheet 10 along the thickness direction of the dimming layer 13. In FIG. 2, for the convenience of explaining the structure of the dimming layer 13 in detail, the dimming layer 13 is illustrated as being significantly thicker than the vertical alignment films 11 and 12, the transparent electrode layers 14 and 15, and the transparent substrates 16 and 17. Further, FIG. 2 schematically shows a cross-sectional structure of the dimming sheet 10 in a state where no voltage is applied to the dimming layer 13.

[0026] As shown in FIG. 2, the dimming layer 13 includes a transparent resin layer 13P and a liquid crystal composition 13L. The liquid crystal composition 13L is filled in domains of the resin layer 13P. The liquid crystal composition 13L contains a plurality of liquid crystal molecules 13LM. An example of the liquid crystal molecule 13LM is any one selected from the group consisting of a Schiff base type, an azo type, an azoxy type, a biphenyl type, a terphenyl type, a benzoic acid ester type, a trans type, a pyrimidine type, a cyclohexanecarboxylic acid ester type, a phenylcyclohexane type, and a dioxane type. The liquid crystal molecule 13LM is a negative type liquid crystal having negative dielectric anisotropy.

[0027] In addition to the above-described liquid crystal molecules 13LM, the liquid crystal composition 13L may contain a polymerizable composition for forming the resin layer 13P, a dichroic dye, and the like. The polymerizable composition is a monomer or oligomer capable of polymerization by irradiation with ultraviolet rays.

[0028] The resin layer 13P is a polymer of the polymerizable composition. As described above, the polymerizable composition is a monomer or polymer capable of polymerization by irradiation with ultraviolet rays. The dimming layer 13 is composed of a first region, a second region, and a central region. The first region is in contact with the first vertical alignment film 11. The second region is in contact with the second vertical alignment film 12. The central region is located between the first region and the second region in the thickness direction of the dimming layer 13. Each region has a layered shape extending over the entire dimming layer 13 when viewed from a viewpoint facing the plane over which the dimming layer 13 extends. The central region includes a portion located at the center in the thickness direction of the dimming layer 13.

[0029] The first region includes a plurality of first domains 13D1. A part of the liquid crystal molecules 13LM in the dimming layer 13 is located within each first domain 13D1. The second region includes a plurality of second domains 13D2. A part of the liquid crystal molecules 13LM in the dimming layer 13 is located within each second domain 13D2. The central region does not include domains.

[0030] Each of the domains 13D1, 13D2 is a void formed in the resin layer 13P. Each of the domains 13D1, 13D2 is filled with a liquid crystal composition 13L, whereby a part of the liquid crystal molecules 13LM in the dimming layer 13 is located within each of the domains 13D1, 13D2. Therefore, in the dimming layer 13, the density of the first domains 13D1 in the first region and the density of the second domains 13D2 in the second region are higher than the density of the domains in the central region. In other words, in the dimming layer 13, the density of the liquid crystal molecules 13LM in the first region and the density of the liquid crystal molecules 13LM in the second region are higher than the density of the liquid crystal molecules 13LM in the central region. Note that the density of the domains in each region may be, for example, the ratio of the total area of the domains to the total area of each region.

[0031] In the present embodiment, the first region has a thickness capable of including the entirety of all the first domains 13D1. Also, the second region has a thickness capable of including the entirety of all the second domains 13D2. The thickness of the first region is equal to the maximum value of the distance between the first vertical alignment film 11 and the first domain 13D1. Also, the thickness of the second region is equal to the maximum value of the distance between the second vertical alignment film 12 and the second domain 13D2.

[0032] Each first domain 13D1 is in contact with the first vertical alignment film 11. Also, each second domain 13D2 is in contact with the second vertical alignment film 12. In a cross-section along the thickness direction of the light control layer 13, the outer shape of each domain 13D1, 13D2 has a substantially arc shape. Each domain 13D1, 13D2 may have a semi-circular shape, a circular shape larger than a semi-circle, or a circular shape smaller than a semi-circle. From the viewpoint of shortening the distance between each vertical alignment film 11, 12 and the liquid crystal molecules 13LM, it is preferable that each domain 13D1, 13D2 has a size of not more than a semi-circle.

[0033] In a cross-section along the thickness direction of the light control layer 13, the maximum value of the distance between the first vertical alignment film 11 and the first domain 13D1 may be, for example, 4 μm or less. Similarly, the maximum value of the distance between the second vertical alignment film 12 and the second domain 13D2 may be, for example, 4 μm or less.

[0034] The thickness of the light control layer 13 may be, for example, 2 μm or more and 11 μm or less. The fact that the thickness of the light control layer 13 is 2 μm or more is preferable in that it is possible to generate at least two regions with different densities of liquid crystal molecules 13LM within the light control layer 13. Also, when the thickness of the light control layer 13 is 11 μm or less, when the coating liquid containing liquid crystal molecules is exposed during the manufacture of the light control sheet 10, the liquid crystal molecules 13LM and the resin layer 13P are appropriately separated. Note that the maximum value of the distance between the first vertical alignment film 11 and the first domain 13D1, and the maximum value of the distance between the second vertical alignment film 12 and the second domain 13D2 described above are less than 1 / 2 of the thickness of the light control layer 13.

[0035] The first transparent electrode layer 14 and the second transparent electrode layer 15 have light transmissibility that allows visible light to pass through. The light transmissibility of the first transparent electrode layer 14 enables visual recognition of an object through the dimming sheet 10. The light transmissibility of the second transparent electrode layer 15, similar to that of the first transparent electrode layer 14, enables visual recognition of an object through the dimming sheet 10. The thickness of each transparent electrode layer 14, 15 may be, for example, 0.005 μm or more and 0.1 μm or less. Thereby, while ensuring proper driving of the dimming sheet 10, it is possible to reduce cracks that may occur when the dimming sheet 10 is bent.

[0036] The material for forming each of the transparent electrode layers 14, 15 may be any one selected from the group consisting of, for example, indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, poly(3,4-ethylenedioxythiophene), and silver.

[0037] The material for forming the first vertical alignment film 11 and the second vertical alignment film 12 is an organic compound, an inorganic compound, or a mixture thereof. Examples of the organic compound include polyimide, polyamide, polyvinyl alcohol, and cyanide compounds. Examples of the inorganic compound include silicon oxide and zirconium oxide. Note that the material for forming the vertical alignment films 11, 12 may be silicone. Silicone is a compound having an inorganic part and an organic part. The thickness of each vertical alignment film 11, 12 is, for example, 0.02 μm or more and 0.5 μm or less.

[0038] In FIG. 3, the alignment regulating force of the first vertical alignment film 11 is schematically shown together with the liquid crystal molecules 13LM. FIG. 3 shows the state of the liquid crystal molecules 13LM when no voltage is applied to the dimming layer 13.

[0039] As shown in FIG. 3, the first vertically aligned film 11 has a surface 11F. The surface 11F is the surface of the first vertically aligned film 11 on the side opposite to the surface in contact with the first transparent electrode layer 14. The first vertically aligned film 11 aligns the liquid crystal molecules 13LM such that the major axis of the liquid crystal molecules 13LM is perpendicular to the surface 11F when the dimming layer 13 is non-energized.

[0040] The second vertically aligned film 12 has a surface 12F. The surface 12F is the surface of the second vertically aligned film 12 on the side opposite to the surface in contact with the second transparent electrode layer 15. The second vertically aligned film 12 aligns the liquid crystal molecules 13LM such that the major axis of the liquid crystal molecules 13LM is perpendicular to the surface 12F when the dimming layer 13 is non-energized. Note that the angle formed by each of the vertically aligned films 11, 12 and the major axis of the liquid crystal molecules 13LM may have a deviation from a right angle within a range where it can be regarded as substantially a right angle.

[0041] The first vertically aligned film 11 has an alignment regulating force for horizontally aligning the liquid crystal molecules 13LM included in the first region in the first direction D1 when viewed from a viewpoint facing the plane in which the dimming layer 13 expands in a state where a voltage is applied to the dimming layer 13. A voltage is applied to the dimming layer 13 by applying a voltage between the first transparent electrode layer 14 and the second transparent electrode layer 15.

[0042] The liquid crystal molecules 13LM included in the dimming layer 13 are aligned along a direction perpendicular to the electric field formed in the dimming layer 13. Thereby, the liquid crystal molecules 13LM are aligned along the surface 11F of the first vertically aligned film 11. At this time, the first vertically aligned film 11 horizontally aligns the liquid crystal molecules 13LM included in the first region in the first direction D1. Therefore, the liquid crystal molecules 13LM included in the first region are arranged along a plane parallel to the surface 11F of the first vertically aligned film 11 with their major axes along the first direction D1.

[0043] The surface 11F of the first vertically aligned film 11 is subjected to a rubbing treatment. Thereby, an alignment regulating force is imparted to the surface 11F of the first vertically aligned film 11 so as to align the major axes of the horizontally aligned liquid crystal molecules 13LM along the first direction D1.

[0044] On the other hand, on the surface 12F of the second vertical alignment film 12, there is no alignment regulating force that causes the major axis of the liquid crystal molecules 13LM to align along a specific direction. Therefore, in a state where a voltage is applied to the light control layer 13, the liquid crystal molecules 13LM included in the second region are arranged along a plane parallel to the second vertical alignment film 12, while the major axis of the liquid crystal molecules 13LM is randomly oriented. In other words, the liquid crystal molecules 13LM included in the second region include liquid crystal molecules that are horizontally aligned in directions other than the first direction D1.

[0045] [Function] With reference to FIGS. 2 to 5, the function of the light control sheet 10 will be described. Note that FIGS. 2 and 3 schematically show a state where no voltage is applied to the light control layer 13 as described above, while FIGS. 4 and 5 schematically show a state where a voltage is applied to the light control layer 13.

[0046] As shown in FIG. 2, in a state where no voltage is applied to the light control layer 13, each of the vertical alignment films 11 and 12 vertically aligns the liquid crystal molecules 13LM located in the vicinity of the vertical alignment films 11 and 12.

[0047] That is, as shown in FIG. 3, the first vertical alignment film 11 aligns the liquid crystal molecules 13LM such that the major axis of the liquid crystal molecules 13LM located in the first domain 13D1 is perpendicular to the surface 11F. Also, the second vertical alignment film 12 aligns the liquid crystal molecules 13LM such that the major axis of the liquid crystal molecules 13LM located in the second domain 13D2 is perpendicular to the surface 12F.

[0048] As a result, when viewed from the light incident on the light control layer 13 through the first vertical alignment film 11 and the light incident on the light control layer 13 through the second vertical alignment film 12, there is almost no difference between the refractive index of the resin layer 13P included in the light control layer 13 and the refractive index of the liquid crystal molecules 13LM. As a result, both the light incident on the light control layer 13 through the first vertical alignment film 11 and the light incident on the light control layer 13 through the second vertical alignment film 12 are less likely to be scattered within the light control layer 13, and thus travel straight within the light control layer 13. Thereby, the light control sheet 10 including the light control layer 13 exhibits transparency.

[0049] On the other hand, as shown in FIG. 4, when a voltage is applied to the dimming layer 13, the liquid crystal molecules 13LM located in each domain 13D1, 13D2 are oriented such that the major axis of the liquid crystal molecules 13LM is perpendicular to the electric field direction.

[0050] As shown in FIG. 5 and as described above, an alignment regulating force is applied to the surface 11F of the first vertical alignment film 11 so as to align the major axis of the liquid crystal molecules 13LM along the first direction D1. Therefore, the liquid crystal molecules 13LM located in the vicinity of the first vertical alignment film 11, that is, within the first domain 13D1, are horizontally aligned such that the major axis is along the first direction D1. On the other hand, the liquid crystal molecules 13LM located in the vicinity of the second vertical alignment film 12, that is, within the second domain 13D2, are horizontally aligned such that the major axis faces a random direction.

[0051] Here, in the liquid crystal molecules 13LM, the refractive index in the major axis direction is different from the refractive index in the direction perpendicular to the major axis. The refractive index in the major axis direction is the refractive index n of the extraordinary light e and the refractive index in the direction perpendicular to the major axis is the refractive index n of the ordinary light o . The refractive index n of the extraordinary light e is larger than the refractive index n of the ordinary light o . Therefore, when the liquid crystal molecules 13LM are horizontally aligned, the difference between the refractive index of the liquid crystal molecules 13LM and the refractive index of the resin layer 13P becomes larger compared to the case where the liquid crystal molecules 13LM are vertically aligned. As a result, the light incident on the dimming layer 13 is scattered in the dimming layer 13. As a result, the dimming layer 13, and thus the dimming sheet 10 including the dimming layer 13, becomes cloudy.

[0052] When the liquid crystal molecules 13LM are horizontally aligned and the major axis of the liquid crystal molecules 13LM is randomly oriented, the refractive index of the liquid crystal molecules 13LM varies depending on the direction in which the major axis of the liquid crystal molecules 13LM points, as seen from the light incident on the dimming layer 13. Therefore, when the direction in which the major axis of the liquid crystal molecules 13LM points is random, the direction of the major axis of the liquid crystal molecules 13LM includes directions that reduce the difference in refractive index between the liquid crystal molecules 13LM and the resin layer 13P from each other.

[0053] In this regard, in the dimming layer 13 of the present embodiment, the first vertical alignment film 11 aligns the liquid crystal molecules 13LM in the first domain 13D1 in the first direction D1. Therefore, for a part of the light incident on the first region, the first region maintains a state where the refractive index difference between the liquid crystal molecules 13LM and the resin layer 13P is large over the entire plane in which the dimming layer 13 extends. As a result, light scattering is likely to occur in the first region, so the opacity of the dimming layer 13, and thus the dimming sheet 10 including the dimming layer 13, is increased when a voltage is applied to the dimming layer 13.

[0054] In the dimming layer 13, while the liquid crystal molecules 13LM are located in the first region and the second region, no liquid crystal molecules 13LM are located in the central region. Therefore, light scattering is less likely to occur in the central region, and as a result, the opacity of the dimming layer 13 tends to be low when a voltage is applied to the dimming layer 13. That is, when a voltage is applied to the dimming layer 13, the haze of the dimming layer 13 tends to decrease. Therefore, in the dimming layer 13 of the present embodiment, the effectiveness of the first vertical alignment film 11 in aligning the liquid crystal molecules 13LM in the first domain 13D1 along the first direction D1 is enhanced.

[0055] Further, the first domain 13D1 is in contact with the first vertical alignment film 11, and the second domain 13D2 is in contact with the second vertical alignment film 12. As a result, the distance between the liquid crystal molecules 13LM included in the first region and the first vertical alignment film 11, and the distance between the liquid crystal molecules 13LM included in the second region and the second vertical alignment film 12 become even smaller. Therefore, when the dimming layer 13 is energized, the ratio of the liquid crystal molecules 13LM that align according to the alignment regulating force of the first vertical alignment film 11 among the liquid crystal molecules 13LM included in the first region is further increased. Also, the ratio of the liquid crystal molecules 13LM that align according to the alignment regulating force of the second vertical alignment film 12 is further increased. As a result, when a voltage is applied to the dimming layer 13, it is possible to increase the opacity.

[0056] As described above, the dimming sheet 10 with enhanced opacity during energization can withstand use in environments where privacy protection is more required. In addition, the contrast between the transparency when not energized and the opacity when energized is enhanced, thereby making it possible to enhance the design quality of the environment to which the dimming sheet 10 is applied.

[0057] In addition, as in the present embodiment, in the reverse-type dimming sheet 10 using the pair of vertical alignment films 11 and 12 and the negative-type liquid crystal molecules 13LM, the resin layer 13P contacts the vertical alignment films 11 and 12 in portions other than the domains 13D1 and 13D2. Therefore, the adhesion between the dimming layer 13 and the vertical alignment films 11 and 12 is enhanced. Therefore, the dimming sheet 10 also has a structure suitable for manufacturing using the roll-to-roll method.

[0058] As described above, according to the first embodiment of the dimming sheet, the following effects can be obtained. (1-1) In the first region, as viewed from the light incident on the first region, the dimming layer 13 maintains, over the entire plane in which the dimming layer 13 spreads, a state in which the refractive index difference between the liquid crystal molecules 13LM and the resin layer 13P is large with respect to a part of the light. As a result, light scattering is likely to occur in the first region, so that the opacity of the dimming layer 13, and thus the dimming sheet 10 including the dimming layer 13, is increased when a voltage is applied to the dimming layer 13.

[0059] (1-2) Since the liquid crystal molecules 13LM are not located in the central region, light scattering is less likely to occur in the central region. As a result, in a state where a voltage is applied to the dimming layer 13, the opacity of the dimming layer 13 is likely to be low. Therefore, in the dimming sheet 10, the effectiveness of the first vertical alignment film 11 in aligning the liquid crystal molecules 13LM in the first domain 13D1 along the first direction D1 is enhanced.

[0060] (1-3) When the dimming layer 13 is energized, among the liquid crystal molecules 13LM included in the first region, the ratio of the liquid crystal molecules 13LM that are aligned according to the alignment regulating force of the first vertical alignment film 11 is further increased. Also, the ratio of the liquid crystal molecules 13LM that are aligned according to the alignment regulating force of the second vertical alignment film 12 is further increased. Thereby, when a voltage is applied to the dimming layer 13, it is possible to increase the opacity.

[0061] [Second Embodiment] Referring to FIGS. 6 to 8, a second embodiment of the dimming sheet will be described. In the second embodiment of the dimming sheet, the second alignment film included in the dimming sheet is different from the second alignment film included in the dimming sheet of the first embodiment. Therefore, hereinafter, while explaining such differences in detail, for the components in the dimming sheet of the second embodiment that are equivalent to those in the dimming sheet of the first embodiment, the same reference numerals as those in the first embodiment are given, and the detailed description of such components is omitted.

[0062] [Structure] Referring to FIG. 6, the structure of the dimming sheet will be described. FIG. 6 schematically shows the alignment regulating forces of the first vertical alignment film and the second vertical alignment film together with the liquid crystal molecules 13LM. FIG. 6 shows the state of the liquid crystal molecules 13LM when no voltage is applied to the dimming layer 13.

[0063] As shown in FIG. 6, the second vertical alignment film 32 includes a surface 32F. The surface 32F is the surface on the side opposite to the surface in contact with the second transparent electrode layer 15. Similar to the second vertical alignment film 12 of the first embodiment, the second vertical alignment film 32 aligns the liquid crystal molecules 13LM so that the long axis of the liquid crystal molecules 13LM is perpendicular to the surface 32F when the dimming layer 13 is not energized.

[0064] When a voltage is applied to the light control layer 13, the second vertical alignment film 32 has an alignment regulating force that horizontally aligns the liquid crystal molecules 13LM included in the second region in the second direction D2 when viewed from a viewing point facing the plane in which the light control layer 13 extends. The second direction D2 is a direction intersecting the first direction D1. In the present embodiment, the second direction D2 is a direction perpendicular to the first direction D1 when viewed from a viewing point facing the plane in which the light control layer 13 extends.

[0065] The liquid crystal molecules 13LM included in the light control layer 13 are aligned along a direction perpendicular to the electric field formed in the light control layer 13. As a result, the liquid crystal molecules 13LM are aligned along the surface 32F of the second vertical alignment film 32. At this time, the second vertical alignment film 32 horizontally aligns the liquid crystal molecules 13LM included in the second region in the second direction D2. Therefore, the liquid crystal molecules 13LM included in the second region are arranged along a plane parallel to the surface 32F of the second vertical alignment film 32 with their major axes along the second direction D2.

[0066] The surface 32F of the second vertical alignment film 32 is subjected to a rubbing treatment. As a result, an alignment regulating force is imparted to the surface 32F of the second vertical alignment film 32 so as to align the major axes of the horizontally aligned liquid crystal molecules 13LM along the second direction D2.

[0067] On the other hand, as described in the first embodiment, an alignment regulating force is imparted to the surface 11F of the first vertical alignment film 11 so as to align the major axes of the horizontally aligned liquid crystal molecules 13LM along the first direction D1. Therefore, when a voltage is applied to the light control layer 13, the major axes of the liquid crystal molecules 13LM included in the first region and the major axes of the liquid crystal molecules 13LM included in the second region are perpendicular to each other when viewed from a viewing point facing the surface 11F of the first vertical alignment film 11.

[0068] [Function] Referring to FIGS. 6 to 8, the operation of the dimming sheet 10 will be described. As described above, FIG. 6 schematically shows a state where no voltage is applied to the dimming layer 13, while FIGS. 7 and 8 schematically show a state where a voltage is applied to the dimming layer 13. Note that the dimming sheet 10 of the second embodiment has the same state as the dimming sheet 10 of the first embodiment in a state where no voltage is applied to the dimming layer 13. Therefore, in the second embodiment, the illustration of the dimming sheet 10 in a state where no voltage is applied to the dimming layer 13 is omitted.

[0069] As shown in FIG. 6, the first vertical alignment film 11 aligns the liquid crystal molecules 13LM such that the major axis of the liquid crystal molecules 13LM located in the first domain 13D1 is perpendicular to the surface 11F. Further, the second vertical alignment film 32 aligns the liquid crystal molecules 13LM such that the major axis of the liquid crystal molecules 13LM located in the second domain 13D2 is perpendicular to the surface 32F.

[0070] Thus, when viewed from the light incident on the dimming layer 13 through the first vertical alignment film 11 and the light incident on the dimming layer 13 through the second vertical alignment film 32, there is almost no difference between the refractive index of the resin layer 13P included in the dimming layer 13 and the refractive index of the liquid crystal molecules 13LM. As a result, both the light incident on the dimming layer 13 through the first vertical alignment film 11 and the light incident on the dimming layer 13 through the second vertical alignment film 12 are less likely to be scattered within the dimming layer 13, and thus travel straight within the dimming layer 13. Thereby, the dimming sheet 10 including the dimming layer 13 exhibits transparency.

[0071] On the other hand, as shown in FIG. 7, in a state where a voltage is applied to the dimming layer 13, the liquid crystal molecules 13LM located in each of the domains 13D1 and 13D2 are aligned such that the major axis of the liquid crystal molecules 13LM is perpendicular to the electric field direction.

[0072] As shown in FIG. 8 and as described above, an alignment regulating force is applied to the surface 11F of the first vertical alignment film 11 so as to align the major axis of the liquid crystal molecules 13LM along the first direction D1. Therefore, the liquid crystal molecules 13LM located in the vicinity of the first vertical alignment film 11, that is, within the first domain 13D1, are horizontally aligned so that their major axes are along the first direction D1.

[0073] On the other hand, an alignment regulating force is applied to the surface 32F of the second vertical alignment film 32 so as to align the major axis of the liquid crystal molecules 13LM along the second direction D2. Therefore, the liquid crystal molecules 13LM located in the vicinity of the second vertical alignment film 32, that is, within the second domain 13D2, are horizontally aligned so that their major axes are along the second direction D2.

[0074] As described above, the first vertical alignment film 11 aligns the liquid crystal molecules 13LM within the first domain 13D1 in the first direction D1. Therefore, for a part of the light incident on the first region, the first region maintains a state in which the refractive index difference between the liquid crystal molecules 13LM and the resin layer 13P is large over the entire plane where the light control layer 13 extends. As a result, light scattering is likely to occur in the first region, so that the opacity of the light control layer 13, and thus the light control sheet 10 including the light control layer 13, is increased when a voltage is applied to the light control layer 13.

[0075] On the other hand, when viewed from a part of the light incident on the first region, the refractive index difference between the liquid crystal molecules 13LM aligned in the first direction D1 and the resin layer 13P is not sufficiently high. Therefore, a part of the light is not sufficiently scattered in the first region. In this regard, since the liquid crystal molecules 13LM included in the second region are aligned along the second direction D2 orthogonal to the first direction D1, a component of the light incident on the light control layer 13 that was not sufficiently scattered in the first region is scattered in the second region. As a result, the opacity of the light control layer 13, and thus the light control sheet 10 including the light control layer 13, is further increased when a voltage is applied to the light control layer 13.

[0076] Note that, not only when the first direction D1 and the second direction D2 are orthogonal when viewed from a viewpoint facing the plane in which the dimming layer 13 extends, but also when the angle formed by the first direction D1 and the second direction D2 is other than 90°, the opacity of the dimming sheet 10 is similarly increased. In this regard, as described above, the liquid crystal molecules 13LM have an extraordinary refractive index n e in the major axis direction and an ordinary refractive index n o in the direction perpendicular to the major axis. Therefore, the component that was not scattered in the first region has its refractive index increased in the second direction D2, which is the direction orthogonal to the first direction D1, and thus becomes most likely to be scattered. Therefore, the second direction D2 is preferably the direction orthogonal to the first direction D1.

[0077] As described above, according to the second embodiment of the dimming sheet, the following effects can be obtained. (2-1) Since the liquid crystal molecules 13LM included in the second region are oriented along the second direction D2 that intersects the first direction D1, among the light incident on the dimming layer 13, the component that was not sufficiently scattered in the first region is scattered in the second region. As a result, the opacity of the dimming layer 13, and thus the dimming sheet 10 including the dimming layer 13, is increased when a voltage is applied to the dimming layer 13.

[0078] (2-2) Since the second direction D2 is the direction orthogonal to the first direction D1, the component that was not scattered in the first region has its refractive index increased in the second direction D2, which is the direction orthogonal to the first direction D1, and thus becomes most likely to be scattered.

[0079] [Modification Example] Note that each of the above-described embodiments can be implemented with the following modifications. [Dimming Layer] · At least a part of the first domain 13D1 may not be in contact with the first vertical alignment film 11. Even in this case, when a voltage is applied to the dimming layer 13, the first vertical alignment film 11 can orient the liquid crystal molecules 13LM in the first direction D1 to obtain an effect similar to that described in (1-1) above.

[0080] ·At least a part of the second domain 13D2 may not be in contact with the second vertical alignment film 12. Even in this case, when a voltage is applied to the light control layer 13, the first vertical alignment film 11 can obtain an effect similar to that described in (1-1) above by aligning the liquid crystal molecules 13LM in the first direction D1.

[0081] ·A domain may be located in the central region of the light control layer 13. In this case, it is preferable that the density of the first domain 13D1 in the first region and the density of the second domain 13D2 in the second region are higher than the density of the domain in the central region. In other words, it is preferable that the density of the liquid crystal molecules 13LM in the first region and the density of the liquid crystal molecules 13LM in the second region are higher than the density of the liquid crystal molecules 13LM in the central region. Even in this case, when a voltage is applied to the light control layer 13, the first vertical alignment film 11 can obtain an effect similar to that described in (1-1) above by aligning the liquid crystal molecules 13LM in the first direction D1.

Explanation of Reference Numerals

[0082] 10…Light control sheet 11…First vertical alignment film 11F, 12F…Surfaces 12…Second vertical alignment film 13…Light control layer 13D1…First domain 13D2…Second domain 13LM…Liquid crystal molecules 14…First transparent electrode layer 15…Second transparent electrode layer 16…First transparent substrate 17…Second transparent substrate

Claims

1. a first vertical alignment film, a second vertical alignment film, a light control layer positioned between the first vertical alignment film and the second vertical alignment film, the light control layer including a transparent resin layer having a plurality of domains and a plurality of liquid crystal molecules positioned within the domains, the light control layer including a first region in contact with the first vertical alignment film and a second region in contact with the second vertical alignment film, the first region and the second region including the liquid crystal molecules, when viewed from a viewing point facing the plane in which the light control layer extends, the first vertical alignment film has an alignment restricting force for horizontally aligning the liquid crystal molecules included in the first region in a first direction when a voltage is applied to the light control layer, and the liquid crystal molecules included in the second region include liquid crystal molecules that are horizontally aligned in a direction intersecting the first direction when a voltage is applied to the light control layer, the light control layer is composed of the first region, the second region, and a central region positioned between the first region and the second region, the plurality of domains include a plurality of first domains and a plurality of second domains, the first region includes a plurality of first domains, and a part of the liquid crystal molecules is positioned within each first domain, the second region includes a plurality of second domains, and a part of the liquid crystal molecules is positioned within each second domain, the density of the first domains in the first region and the density of the second domains in the second region are higher than the density of the domains in the central region a light control sheet.

2. when viewed from a viewing point facing the plane in which the light control layer extends, the second vertical alignment film has an alignment restricting force for horizontally aligning the liquid crystal molecules included in the second region in a second direction when a voltage is applied to the light control layer, the second direction being a direction intersecting the first direction the light control sheet according to Claim 1.

3. when viewed from a viewing point facing the plane in which the light control layer extends, the second direction is a direction orthogonal to the first direction the light control sheet according to Claim 2.

4. The plurality of domains are composed of a plurality of first domains and a plurality of second domains, the central region does not include the domains the light control sheet according to any one of Claims 1 to 3.

5. each first domain is in contact with the first vertical alignment film, each second domain is in contact with the second vertical alignment film the light control sheet according to Claim 4.

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