Dimming sheet

Abstract

To provide a dimming sheet that makes it possible for all of a haze value when a dimming sheet exhibits transparency, a drive voltage of the dimming sheet, and a response speed of the dimming sheet to be included within an appropriate range.SOLUTION: A dimming sheet 11R comprises: a first orientation layer 21; a second orientation layer 22; and a dimming layer 23 positioned between the first orientation layer 21 and the second orientation layer 22, the dimming layer 23 including a transparent polymer layer with a plurality of domains dispersed therein and liquid crystal compositions each that contain liquid crystal molecules and are filled in the domain. A domain diameter D being an indicator in a size of the domain and a first polar angle anchoring coefficient Wa1 being a polar angle anchoring coefficient of the first orientation layer 21 relative to the liquid crystal molecules satisfy the numerical formula (1): 3.6≤|D*log10(Wa1)|≤9.3.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A reverse-type dimming sheet includes a dimming layer containing liquid crystal molecules, a pair of transparent electrode layers sandwiching the dimming layer, and alignment layers positioned between each transparent electrode layer and the dimming layer. Since each alignment layer is a vertical alignment layer, in a state where no voltage is applied between the pair of transparent electrode layers, the liquid crystal molecules are aligned substantially perpendicular to the plane in which the alignment layer spreads. Therefore, in a state where no voltage is applied between the pair of transparent electrode layers, the dimming sheet exhibits transparency. In contrast, in a state where a voltage is applied between the pair of transparent electrode layers, the liquid crystal molecules are aligned substantially horizontally with respect to the plane in which the alignment layer spreads. Therefore, in a state where a voltage is applied between the pair of transparent electrodes, the dimming sheet exhibits opacity (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, reverse-type dimming sheets are transparent when no voltage is applied to the dimming layer. Therefore, even if the dimming sheet cannot be powered due to a power outage or malfunction, the sheet does not obstruct the view. Because reverse-type dimming sheets offer high safety in this way, their application is expanding beyond transparent components in buildings to include moving objects such as automobiles, trains, and airplanes. With this expansion of applications, from the standpoint of safety and aesthetics, dimming sheets are required to have higher transparency when they are transparent. Furthermore, from the perspective of limiting the magnitude of the voltage that can be applied to the dimming sheet, it is required to lower the driving voltage used to drive the liquid crystal molecules. Moreover, even in low-temperature environments where moving objects may be used, it is required that the response speed, which is the speed at which the dimming sheet changes from an opaque state to a transparent state, does not decrease significantly. [Means for solving the problem]

[0005] A light-adjusting sheet for solving the above problems comprises a first alignment layer, a second alignment layer, and a light-adjusting layer located between the first and second alignment layers, the light-adjusting layer comprising a transparent polymer layer in which a plurality of domains are dispersed, and a liquid crystal composition containing liquid crystal molecules and filled within the domains. In the light-adjusting sheet, the domain diameter D is an index of the size of the domains, and the first pole-angle anchoring coefficient W is the pole-angle anchoring coefficient of the first alignment layer with respect to the liquid crystal molecules. a1 The equation (1) is satisfied. 3.6 ≤ | D * log 10 (W a1 )|≦9.3 … Formula (1)

[0006] According to the above dimming sheet, in the vicinity of the first orientation layer, the first pole angle anchoring coefficient W of the first orientation layer a1It is possible to suppress the situation where it becomes excessively small and the domain diameter D becomes excessively large. As a result, it is possible to suppress the situation where the force of the first alignment layer for aligning liquid crystal molecules becomes excessively small, so that the haze value when the dimming sheet exhibits transparency increases and the response speed in a low-temperature environment slows down. Also, the first polar angle anchoring coefficient W a1 It is possible to suppress the situation where it becomes excessively large and the domain diameter D becomes excessively small. As a result, it is possible to suppress the situation where the force of the first alignment layer for aligning liquid crystal molecules becomes excessively large, so that an increase in the driving voltage of the dimming sheet is suppressed.

[0007] In the above dimming sheet, the domain diameter D and the second polar angle anchoring coefficient Wa2, which is the polar angle anchoring coefficient of the second alignment layer with respect to the liquid crystal molecules, may satisfy the mathematical formula (2). 3.6≦|D*log 10 (W a2 )|≦9.3 … Mathematical formula (2)

[0008] According to the above dimming sheet, in the vicinity of the second alignment layer, similar to the vicinity of the first alignment layer, it is possible to suppress the situation where the second polar angle anchoring coefficient W a2 of the second alignment layer becomes excessively small and the domain diameter D becomes excessively large. As a result, it is possible to suppress the situation where the force of the second alignment layer for aligning liquid crystal molecules becomes excessively small, so that the haze value when the dimming sheet exhibits transparency increases and the response speed in a low-temperature environment slows down. Also, it is possible to suppress the situation where the second polar angle anchoring coefficient W a2 becomes excessively large and the domain diameter D becomes excessively small. As a result, it is possible to suppress the situation where the force of the second alignment layer for aligning liquid crystal molecules becomes excessively large, so that an increase in the driving voltage of the dimming sheet is suppressed.

[0009] In the above-described dimming sheet, the domain diameter may be 0.5 μm or more and 4.0 μm or less. With this dimming sheet, the increase in the haze value of the dimming sheet when no voltage is applied is suppressed by having a domain diameter of 0.5 μm or more and 4.0 μm or less.

[0010] In the above dimming sheet, the first pole angle anchoring coefficient W a1 However, 1.0 × 10 -4 The above 1.0 × 10 -2 The following is acceptable. According to this dimming sheet, the first pole angle anchoring coefficient W a1 is 1.0 × 10 -4 The above 1.0 × 10 -2 The first pole angle anchoring coefficient W is determined to fall within the following range. a1 Compared to the case where the value falls below the lower limit, the size of the domain diameter D that satisfies equation (1) is suppressed to increase. This suppresses the increase in the haze value when transparency is observed, and the slowing of the response speed in low-temperature environments. On the other hand, the first pole angle anchoring coefficient W a1 Compared to the case where the value exceeds the upper limit, the decrease in the size of the domain diameter D that satisfies equation (1) is suppressed. This suppresses an increase in the driving voltage of the dimming sheet.

[0011] In the above-described dimming sheet, the density of the domains per unit thickness of the dimming layer may be lowest in the central part in the thickness direction of the dimming layer. With this dimming sheet, the lowest domain density in the central part in the thickness direction of the dimming layer makes it possible to reduce the number of liquid crystal molecules located in areas far from each alignment layer. As a result, the alignment restricting force of each alignment layer acts more easily on the liquid crystal molecules, making it possible to increase the transparency of the dimming sheet, i.e., to lower the haze value, when no voltage is applied to the dimming sheet. [Effects of the Invention]

[0012] According to the present invention, the haze value when the dimming sheet is transparent, the driving voltage of the dimming sheet, and the response speed of the dimming sheet are all within an appropriate range. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing the structure of a dimming sheet in one embodiment. [Figure 2] Figure 1 is a schematic cross-sectional view showing the structure of the dimming layer. [Figure 3] Figure 1 is a schematic diagram illustrating the polar-angle anchoring coefficient of the first orientation layer in the dimming layer shown. [Figure 4] This table shows the evaluation results for the dimming sheets in the examples and comparative examples. [Modes for carrying out the invention]

[0014] An embodiment of the dimming sheet will be described with reference to Figures 1 to 4. [Dimmer] The dimming device will be explained with reference to Figure 1.

[0015] As shown in Figure 1, the dimming device 10R comprises a reverse-type dimming sheet 11R and a drive unit 12. The dimming sheet 11R may be applied to, for example, windows of moving objects such as vehicles and aircraft. Alternatively, the dimming sheet 11R may be applied to, for example, windows of various buildings such as houses, train stations, and airports, partitions installed in offices, display windows installed in stores, and screens for projecting images. The dimming sheet 11R is attached to these applications, for example, by an adhesive layer. The shape of the dimming sheet 11R may be flat or curved. The dimming sheet 11R may have a degree of flexibility that allows it to conform to the shape of the application.

[0016] The dimming sheet 11R comprises a first alignment layer 21, a second alignment layer 22, and a dimming layer 23. The dimming layer 23 is located between the first alignment layer 21 and the second alignment layer 22. The dimming layer 23 comprises a transparent polymer layer in which multiple domains are dispersed, and a liquid crystal composition containing liquid crystal molecules and filling the domains.

[0017] The dimming sheet 11R further comprises a first transparent electrode layer 24, a second transparent electrode layer 25, a first transparent substrate 26, and a second transparent substrate 27. In the thickness direction of the dimming sheet 11R, the first transparent electrode layer 24 and the second transparent electrode layer 25 sandwich a pair of orientation layers 21 and 22. The first orientation layer 21 is located between the first transparent electrode layer 24 and the dimming layer 23. The second orientation layer 22 is located between the second transparent electrode layer 25 and the dimming layer 23. The first transparent substrate 26 supports the first transparent electrode layer 24. The second transparent substrate 27 supports the second transparent electrode layer 25.

[0018] The dimming sheet 11R comprises a first electrode 24A attached to a portion of the first transparent electrode layer 24 and a second electrode 25A attached to a portion of the second transparent electrode layer 25. The dimming sheet 11R further comprises wiring 28 connected to the first electrode 24A and wiring 28 connected to the second electrode 25A. The first electrode 24A and the second electrode 25A are each connected to the drive unit 12 by the wiring 28.

[0019] The first transparent electrode layer 24 and the second transparent electrode layer 25 have light transmittance that transmits visible light. The light transmittance of the first transparent electrode layer 24 enables visual recognition of objects through the dimming sheet 11R. The light transmittance of the second transparent electrode layer 25, similar to that of the first transparent electrode layer 24, enables visual recognition of objects through the dimming sheet 11R. The thickness of each transparent electrode layer 24, 25 may be, for example, 0.005 μm or more and 0.1 μm or less. This ensures proper driving of the dimming sheet 11R and suppresses the occurrence of cracks in the dimming sheet 11R when the dimming sheet 11R is bent.

[0020] The material for forming each transparent electrode layer 24, 25 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, and poly(3,4-ethylenedioxythiophene).

[0021] The material forming each transparent substrate 26, 27 may be a synthetic resin or an inorganic compound. Synthetic resins may include, for example, polyester, polyacrylate, polycarbonate, and polyolefin. Polyesters may include, for example, polyethylene terephthalate and polyethylene naphthalate. Polyacrylates may include, for example, polymethyl methacrylate. Inorganic compounds may include, for example, silicon dioxide, silicon oxynitride, and silicon nitride. The thickness of each transparent substrate 26, 27 may be, for example, 16 μm or more and 250 μm or less. A thickness of 16 μm or more for the transparent substrate 26, 27 facilitates the processing and installation of the dimming sheet 11R. A thickness of 250 μm or less for the transparent substrate 26, 27 enables the production of the dimming sheet 11R by roll-to-roll method.

[0022] Each electrode 24A, 25A is, for example, a flexible printed circuit (FPC). The FPC comprises a support layer, a conductor, and a protective layer. The conductor is sandwiched between the support layer and the protective layer. The support layer and the protective layer are formed of an insulating synthetic resin. The support layer and the protective layer are formed of, for example, polyimide. The conductor is formed of, for example, a thin metal film. The material forming the thin metal film may be, for example, copper. Each electrode 24A, 25A is not limited to an FPC; for example, it may be a metal tape.

[0023] Each electrode 24A and 25A is attached to the respective transparent electrode layers 24 and 25 by a conductive adhesive layer (not shown). In the portion of each electrode 24A and 25A connected to the conductive adhesive layer, the conductive portion is exposed from the protective or support layer.

[0024] The conductive adhesive layer may be formed from, for example, an anisotropic conductive film (ACF), anisotropic conductive paste (ACP), isotropic conductive film (ICF), and isotropic conductive paste (ICP). From the viewpoint of ease of handling in the manufacturing process of the dimming device 10R, the conductive adhesive layer is preferably an anisotropic conductive film.

[0025] Each wiring 28 is formed, for example, by a metal wire and an insulating layer covering the metal wire. The wire is made of, for example, copper. The drive unit 12 applies an AC voltage between the first transparent electrode layer 24 and the second transparent electrode layer 25. Preferably, the drive unit 12 applies an AC voltage having a rectangular wave shape between the pair of transparent electrode layers 24 and 25. However, the drive unit 12 may also apply an AC voltage having a shape other than a rectangular wave between the pair of transparent electrode layers 24 and 25. For example, the drive unit 12 may apply an AC voltage having a sinusoidal wave shape between the pair of transparent electrode layers 24 and 25.

[0026] In the dimming layer 23, the orientation of the liquid crystal molecules changes in response to the voltage change occurring between the two transparent electrode layers 24 and 25. This change in the orientation of the liquid crystal molecules alters the degree of scattering, absorption, and transmission of visible light entering the dimming layer 23. The reverse-type dimming sheet 11R has a relatively high haze value when the dimming sheet 11R is energized, that is, when a potential difference exists between the first transparent electrode layer 24 and the second transparent electrode layer 25. The reverse-type dimming sheet 11R has a relatively low haze value when the dimming sheet 11R is not energized, that is, when no potential difference exists between the first transparent electrode layer 24 and the second transparent electrode layer 25. For example, the reverse-type dimming sheet 11R is opaque when the dimming sheet 11R is energized and transparent when the dimming sheet 11R is not energized. The haze of the dimming sheet 11R is calculated according to the method conforming to JIS K 7136:2000 "Plastics - Method for determining haze of transparent materials".

[0027] [Dimmable sheet] Referring to Figure 2, the structure of the dimming sheet 11R, in particular the structure of the dimming layer 23 provided in the dimming sheet 11R, will be explained in more detail. Figure 2 schematically shows the cross-sectional structure of the dimming sheet 11R. Note that in Figure 2, for ease of illustration, the transparent substrates 26 and 27 are omitted from the illustration. Also, in Figure 2, for ease of explaining the structure of the dimming layer 23, the ratio of the thickness of the dimming layer 23 to the thickness of each orientation layer 21 and 22, and the thickness of each transparent electrode layer 24 and 25 is larger than the actual ratio. Furthermore, Figure 2 shows the state of the dimming layer 23 when no potential difference is generated between the pair of transparent electrode layers 24 and 25.

[0028] As described above, the dimming sheet 11R comprises a first orientation layer 21 and a second orientation layer 22. The materials for forming the first orientation layer 21 and the second orientation layer 22 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 orientation layers 21 and 22 may also be silicone. Silicone is a compound having an inorganic portion and an organic portion. The thickness of each orientation layer 21 and 22 may be, for example, 0.02 μm or more and 0.5 μm or less.

[0029] The first alignment layer 21 and the second alignment layer 22 are vertical alignment layers. The vertical alignment layers orient the long axes of the liquid crystal molecules so that they are perpendicular to the surface opposite to the surface in contact with the first transparent electrode layer 24 and the surface opposite to the surface in contact with the second transparent electrode layer 25. In addition, the alignment layers 21 and 22 may orient the liquid crystal molecules 23LM such that their long axes are tilted a few degrees relative to the vertical, within a range where the long axes of the liquid crystal molecules 23LM are judged to be substantially perpendicular to each surface.

[0030] As described above, the light-adjusting layer 23 comprises a transparent polymer layer 23P and a liquid crystal composition 23L. Multiple domains 23D are dispersed within the transparent polymer layer 23P. The liquid crystal composition 23L contains liquid crystal molecules 23LM and is filled within the domains 23D.

[0031] The domain diameter, which is an indicator of the size of domain 23D, may be between 0.5 μm and 4.0 μm. The domain diameter is determined in the domain 23D included in a cross-section perpendicular to the plane over which the photochromic layer 23 extends. If domain 23D has a circular shape, the diameter of domain 23D is the domain diameter. If domain 23D has an elliptical shape, the major axis of domain 23D is the domain diameter. If domain 23D has an irregular shape, the diameter of the circle circumscribing domain 23D is the domain diameter.

[0032] The liquid crystal molecules 23LM contained in the liquid crystal composition 23L are negative-type liquid crystal molecules with negative dielectric anisotropy. An example of the liquid crystal molecule 23LM may be selected from the group consisting of Schiff bases, azos, azoxys, biphenyls, terphenyls, benzoic acid esters, transanes, pyrimidines, cyclohexanecarboxylic acid esters, cyclohexanes, phenylcyclohexanes, and dioxanes. The liquid crystal composition 23L may contain a first liquid crystal molecule and a second liquid crystal molecule of a different type from the first liquid crystal molecule.

[0033] The liquid crystal molecule 23LM is preferably one of the following: cyclohexane-based, phenylcyclohexane-based, biphenyl-based, terphenyl-based, alkyne-based, or cyclohexanecarboxylic acid ester-based. Furthermore, the liquid crystal molecule 23LM is more preferably one of the liquid crystal molecules represented by the following chemical formulas (1) to (11).

[0034] In chemical formulas (1) to (11), R1 and R2 are, independently, a C1 to C12 alkyl group, a C1 to C12 alkoxy group, a C2 to C12 alkenyl group, a C2 to C12 alkenyloxy group, or a C1 to C12 alkyl group in which one or more hydrogen atoms are replaced by fluorine or chlorine.

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] The transparent polymer layer 23P is a cured product of a photopolymerizable compound. The photopolymerizable compound may be an ultraviolet-curable compound or an electron-beam-curable compound. The photopolymerizable compound is compatible with the liquid crystal composition. To improve the dimensional controllability of domain 23D, it is preferable that the photopolymerizable compound be an ultraviolet-curable compound. An example of an ultraviolet-curable compound is one that contains polymerizable unsaturated bonds at the ends of its molecular structure. Alternatively, the ultraviolet-curable compound may contain polymerizable unsaturated bonds in addition to those at the ends of its molecular structure. The photopolymerizable compound may be one polymerizable compound or a combination of two or more polymerizable compounds.

[0047] The UV-curable compound is at least one selected from the group consisting of acrylate compounds, methacrylate compounds, styrene compounds, thiol compounds, and oligomers of each compound.

[0048] Acrylate compounds include monoacrylate compounds, diacrylate compounds, triacrylate compounds, and tetraacrylate compounds. Examples of acrylate compounds include butyl ethyl acrylate, ethylhexyl acrylate, and cyclohexyl acrylate. Examples of methacrylate compounds include dimethacrylate compounds, trimethacrylate compounds, and tetramethacrylate compounds. Examples of methacrylate compounds include N,N-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, and tetrahydrofurfuryl methacrylate. Examples of thiol compounds include 1,3-propanedithiol and 1,6-hexanedithiol. Examples of styrene compounds include styrene and methylstyrene.

[0049] The lower limit of the content of the transparent polymer layer 23P relative to the total amount of the transparent polymer layer 23P and the liquid crystal composition 23L may be 30% by mass, and the lower limit of a more preferable content may be 40% by mass. The upper limit of the content of the transparent polymer layer 23P relative to the total amount of the transparent polymer layer 23P and the liquid crystal composition 23L may be 70% by mass, and the upper limit of a more preferable content may be 60% by mass.

[0050] The lower and upper limits of the transparent polymer layer 23P content are the ranges in which liquid crystal particles made of the liquid crystal composition 23L phase-separate from the cured product of the photopolymerizable compound during the curing process of the photopolymerizable compound. When it is necessary to increase the mechanical strength of the transparent polymer layer 23P, it is preferable that the lower limit of the transparent polymer layer 23P content be high. When it is necessary to lower the driving voltage of the liquid crystal molecules 23LM, it is preferable that the upper limit of the transparent polymer layer 23P content be low.

[0051] In this embodiment, the liquid crystal composition 23L may contain a dichroic dye. The dichroic dye has an elongated shape. The absorbance in the visible region along the long axis of the dichroic dye molecule is greater than the absorbance in the visible region along the short axis of the molecule. The dichroic dye is nearly transparent when its long axis is parallel or substantially parallel to the direction of incident light. Conversely, the dichroic dye exhibits a predetermined color when its long axis is perpendicular or substantially perpendicular to the direction of incident light.

[0052] Therefore, the dichroic dye exhibits transparency when oriented so that its long axis is parallel or substantially parallel to the normal direction of the contact surface with the first alignment layer 21 and the contact surface with the second alignment layer 22 in the light-adjusting layer 23. Conversely, the dichroic dye exhibits a predetermined color when oriented so that its long axis is perpendicular or substantially perpendicular to the normal direction of the contact surface with the first alignment layer 21 and the contact surface with the second alignment layer 22 in the light-adjusting layer 23. The color exhibited by the dichroic dye is preferably black or a color close to black. The dichroic dye is driven by a guest-host type with liquid crystal molecules 23LM as the host, thereby causing the dichroic dye to exhibit color.

[0053] The dichroic dye 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 may be one dye or a combination of two or more dyes. From the viewpoint of improving the lightfastness of the dichroic dye and improving the dichroic ratio, it is preferable that the dichroic dye is at least one selected from the group consisting of azo compounds and anthraquinone compounds. It is more preferable that the dichroic dye is an azo compound.

[0054] In addition to the liquid crystal molecules and dichroic dyes described above, the liquid crystal composition may also contain, for example, monomers for forming a transparent polymer layer. The thickness of the light-adjusting layer 23 may be, for example, 2 μm or more and 10 μm or less. Alternatively, the thickness of the light-adjusting layer 23 may be 3.0 μm or more and 8.0 μm or less.

[0055] The density of domains 23D per unit thickness of the dimming layer 23 may be lowest in the central part of the dimming layer 23 in the thickness direction. The density of domains 23D per unit thickness is the value obtained by dividing the number of domains 23D per cross-section perpendicular to the plane on which the dimming layer 23 extends by the thickness of the dimming layer 23. The central part of the dimming layer 23 in the thickness direction is the part that bisects the distance from the surface in contact with the first orientation layer 21 to the surface in contact with the second orientation layer 22 in the thickness direction of the dimming layer 23.

[0056] As shown in Figure 2, it is preferable that no domain 23D is located in the central part of the dimming layer 23 in the thickness direction. Furthermore, it is preferable that the dimming layer 23 contains only the domain 23D in contact with the first alignment layer 21 and the domain 23D in contact with the second alignment layer 22.

[0057] The lowest density of domains 23D in the central part of the thickness direction of the dimming layer 23 makes it possible to reduce the number of liquid crystal molecules 23LM located in areas far from each alignment layer 21, 22. As a result, the alignment restricting force of each alignment layer 21, 22 acts more easily on the liquid crystal molecules 23LM, making it possible to increase the transparency of the dimming sheet 11R, i.e., reduce the haze value, when no voltage is applied between the transparent electrode layers 24, 25.

[0058] [Polar Anchoring Coefficient] Refer to Figure 3 to explain the polar angle anchoring coefficient acting on the liquid crystal molecule 23LM. The liquid crystal molecules 23LM are subjected to an orientation-restricting force at the interface with the orientation layers 21 and 22, and align to a predetermined state. In this embodiment, since the orientation layers 21 and 22 are vertical orientation layers, the liquid crystal molecules 23LM are subjected to an orientation-restricting force and align to a vertical state. The orientation-restricting force is assumed to be due to either a chemical interaction between the liquid crystal molecules 23LM and the orientation layers 21 and 22, or a physical interaction between the liquid crystal molecules 23LM and the orientation layers 21 and 22.

[0059] The orientation regulating force includes a polar-angle anchoring coefficient and an azimuthal-angle anchoring coefficient. The polar-angle anchoring coefficient is the anchoring coefficient that acts on the rotation of the director in the normal direction of the orientation layers 21 and 22. The azimuthal-angle anchoring coefficient is the anchoring coefficient that acts on the rotation of the director in the in-plane direction of the orientation layers 21 and 22. The director is a unit vector representing the average orientation along the major axis of the liquid crystal molecules 23LM in a region that is sufficiently large from the perspective of the liquid crystal molecules 23LM and sufficiently small from a macroscopic perspective.

[0060] Polar angle anchoring coefficient W a This is expressed by the following formula (3).

[0061]

number

[0062] In equation (3), θ is the angle in the polar direction. θe is the angle of the easy orientation axis e in the polar direction. The easy orientation axis e is the direction in which the director on the surface of orientation layers 21 and 22 is most stable. The easy orientation axis e is given by orientation layers 21 and 22. However, in reality, the director on the surface of orientation layers 21 and 22 is influenced by the bulk director, so the easy orientation axis e is stable at a position that is a certain angle away from the surface of orientation layers 21 and 22.

[0063] Figure 3 shows the coordinates of the easy orientation axis e and the liquid crystal molecule 23LM on the surface of the first orientation layer 21. As shown in Figure 3, the angle of the easy orientation axis e in the polar angular direction is θe. The angle θe of the easy orientation axis e in the polar angular direction is the angle formed between the XY plane and the easy orientation axis e in a plane that includes the easy orientation axis e and is perpendicular to the XY plane. Also, the angle of the liquid crystal molecule 23LM in the polar angular direction is θ. The angle θ of the liquid crystal molecule 23LM in the polar angular direction is the angle formed between the XY plane and the director of the liquid crystal molecule 23LM in a plane that includes the director of the liquid crystal molecule 23LM and is perpendicular to the XY plane.

[0064] Furthermore, the angle in the azimuthal direction of the easy orientation axis e is Φe. The angle Φe in the azimuthal direction of the easy orientation axis e is the angle formed between the projection axis obtained by projecting the easy orientation axis e onto the XY plane and the X axis. Also, the angle in the azimuthal direction of the liquid crystal molecule 23LM is Φ. The angle Φ in the azimuthal direction of the liquid crystal molecule 23LM is the angle formed between the projection axis obtained by projecting the director of the liquid crystal molecule 23LM onto the XY plane and the X axis.

[0065] In Figure 3, the coordinates of the easy orientation axis e and the liquid crystal molecules 23LM on the surface of the first orientation layer 21 are shown. However, on the surface of the second orientation layer 22, the coordinates of the easy orientation axis e and the liquid crystal molecules 23LM are determined in the same way as on the surface of the first orientation layer 21.

[0066] Furthermore, the dielectric anisotropy Δε of the liquid crystal molecule 23LM is expressed by the following equation (4).

[0067]

number

[0068] In equation (4), ε0 is the permittivity of vacuum, and is 8.85 × 10⁻⁶. -12 It is F / m. ε ⊥ V is the dielectric constant perpendicular to the director. V is the voltage perpendicular to the director, and z is the thickness perpendicular to the director. Note that the dielectric anisotropy Δε is the dielectric constant perpendicular to the director ε ⊥ And the dielectric constant ε in the direction parallel to the director ∥ Using and , it can be expressed as follows:

[0069] Δε = ε ∥ - ε ⊥ Furthermore, the elastic constant of the liquid crystal molecule 23LM is expressed by the following equation (5).

[0070]

number

[0071] In equation (5), K 11 is the elastic constant for spray deformation, and K 33 This is the elastic constant for bending deformation.

[0072] Then, the energy U is given to the liquid crystal molecules 23LM present in the dimming layer 23. a This is expressed by the following formula (6).

[0073]

number

[0074] Furthermore, the energy U is given to the liquid crystal molecules 23LM located near the alignment layers 21 and 22, i.e., at a minute thickness Δd. b This is expressed by the following equation (7). In equation (7), F is (Fa + Fk).

[0075]

number

[0076] From the above, U, which is (Ua + Ub), can be expressed by the following equation (8).

[0077]

number

[0078] According to the Euler-Lagrange equations, when equation (8) is true, then equation (9) holds true.

[0079]

number

[0080] From these equations (3) to (9), the polar angle anchoring coefficient W in the orientation layers 21 and 22 is obtained. a It is possible to calculate this.

[0081] In this disclosure, the dimming layer 23 satisfies the following condition 1. (Condition 1) The domain diameter D, which is an indicator of the size of domain 23D, and the first pole angle anchoring coefficient Wa1, which is the pole angle anchoring coefficient of the first orientation layer 21 with respect to the liquid crystal molecule 23LM, satisfy equation (1). 3.6 ≤ | D * log 10 (W a1 )≦9.3| … Formula (1)

[0082] Furthermore, the first pole angle anchoring coefficient W a1 However, 1.0 × 10 -4 The above 1.0 × 10 -2 The following applies:

[0083] Furthermore, in this notice, the dimming layer 23 satisfies the following condition 2. (Condition 2) The second pole angle anchoring coefficient W of the second alignment layer 22 relative to the liquid crystal molecules 23LM. a2 The equation satisfies formula (2). 3.6 ≤ | D * log 10 (W a2 )|≦9.3 … Formula (2)

[0084] [Effect] By satisfying the above-described condition 1, the dimming sheet 11R has a first pole angle anchoring coefficient W of the first orientation layer 21 in the vicinity of the first orientation layer 21. a1 This prevents the first pole angle anchoring coefficient W from becoming excessively small and the domain diameter D from becoming excessively large. As a result, the force that the first alignment layer 21 exerts on the liquid crystal molecules 23LM from becoming excessively small is suppressed, which in turn suppresses an increase in the haze value when the dimming sheet 11R is transparent and a decrease in the response speed in low-temperature environments. a1 This prevents the domain diameter D from becoming excessively large and excessively small. As a result, the force with which the first alignment layer 21 aligns the liquid crystal molecules 23LM is prevented from becoming excessively large, and thus the driving voltage of the dimming sheet 11R is prevented from becoming excessive.

[0085] Furthermore, by satisfying the above-described condition 2, the second pole angle anchoring coefficient W of the second orientation layer 22 is determined in the vicinity of the second orientation layer 22, similar to the vicinity of the first orientation layer 21. a2 This prevents the second pole angle anchoring coefficient W from becoming excessively small and the domain diameter D from becoming excessively large. As a result, the force that the second alignment layer 22 exerts on the liquid crystal molecules 23LM from becoming excessively small is suppressed, which prevents the haze value from increasing when the dimming sheet 11R is transparent and prevents the response speed from slowing down in low-temperature environments. a2 This prevents the domain diameter D from becoming excessively large and excessively small. As a result, the force that the second alignment layer 22 exerts on the liquid crystal molecules 23LM becomes excessively large, and thus the driving voltage of the dimming sheet 11R does not become excessive.

[0086] Furthermore, by having a domain diameter of 0.5 μm or more and 4.0 μm or less, the increase in the haze value of the dimming sheet 11R when no voltage is applied to the dimming sheet 11R is suppressed.

[0087] [Examples] Examples and comparative examples will be described with reference to Figure 4. [Comparative Example 1] A mixture of Loctite 3736 (registered trademark, manufactured by Henkel) and 1,6-hexanediol diacrylate in a 1:1 mass ratio was prepared as a monomer for forming a transparent polymer layer. A liquid crystal composition containing MLC-6608 (manufactured by Merck) was also prepared. The liquid crystal molecules were negative-type nematic liquid crystals, and the refractive index anisotropy Δn of the liquid crystal molecules was 0.20. A coating solution containing 65 parts by mass of the liquid crystal composition and 55 parts by mass of the monomer was then prepared.

[0088] Two transparent films were prepared, each comprising an ITO layer with a thickness of 20 nm and a polyethylene terephthalate film with a thickness of 125 μm. An orientation layer made of polyimide with a thickness of 200 nm was formed on each ITO layer.

[0089] Then, a coating liquid was applied to the orientation layer of one transparent film to form a coating film with a cured thickness of 200 nm, and the orientation layer of the other transparent film was brought into contact with the coating film. In this way, the coating film was sandwiched between the pair of transparent films.

[0090] Then, a pair of ultraviolet lamps were placed so as to sandwich a pair of transparent films, and the coating was irradiated with ultraviolet light using the pair of lamps. At this time, the ultraviolet irradiance was set to 18 mW / cm². 2 The settings were adjusted, and the UV irradiation time was set to 150 seconds. Phase separation was induced in the coating film by UV irradiation, thereby forming a light-adjusting layer with an average domain diameter D of 0.6 μm. This resulted in obtaining the light-adjusting sheet of Comparative Example 1.

[0091] [Example 1] In Comparative Example 1, the ultraviolet irradiance was set to 16 mW / cm². 2 Except for the change made, the dimming sheet of Example 1 was obtained by the same method as in Comparative Example 1.

[0092] [Example 2] In Comparative Example 1, the ultraviolet irradiance was set to 10 mW / cm². 2 Except for the change made, the dimming sheet of Example 2 was obtained by the same method as in Comparative Example 1.

[0093] [Comparative Example 2] In Comparative Example 1, the ultraviolet irradiance was set to 6 mW / cm². 2 Except for the change made, the dimming sheet for Comparative Example 2 was obtained using the same method as for Comparative Example 1.

[0094] [Comparative Example 3] In Comparative Example 1, the ultraviolet irradiance was set to 2 mW / cm². 2Except for the change made, the dimming sheet of Comparative Example 3 was obtained in the same manner as in Comparative Example 1.

[0095] [Comparative Example 4] In Comparative Example 1, the dimming sheet of Comparative Example 4 was obtained by the same method as in Comparative Example 1, except that the mixture was changed to a mixture of Loctite 3736 (registered trademark, manufactured by Henkel) and 1,6-hexanediol diacrylate in a mass ratio of 3:4.

[0096] [Example 3] In Comparative Example 4, the ultraviolet irradiance was set to 10 mW / cm². 2 Except for the change made, the dimming sheet of Example 3 was obtained by the same method as in Comparative Example 4.

[0097] [Example 4] In Comparative Example 4, the ultraviolet irradiance was set to 8 mW / cm². 2 Except for the change made, the dimming sheet of Example 4 was obtained by the same method as in Comparative Example 4.

[0098] [Example 5] In Comparative Example 4, the ultraviolet irradiance was set to 5 mW / cm². 2 Except for the change made, the dimming sheet of Example 5 was obtained by the same method as in Comparative Example 4.

[0099] [Comparative Example 5] In Comparative Example 4, the ultraviolet irradiance was set to 2 mW / cm². 2 Except for the change made, the dimming sheet of Comparative Example 5 was obtained in the same manner as in Comparative Example 4.

[0100] [Comparative Example 6] In Comparative Example 1, the dimming sheet of Comparative Example 6 was obtained by the same method as in Comparative Example 1, except that the mixture was changed to a mixture of Loctite 3736 (registered trademark, manufactured by Henkel) and 1,6-hexanediol diacrylate in a mass ratio of 2:3.

[0101] [Comparative Example 7] In Comparative Example 6, the ultraviolet irradiance was set to 10 mW / cm². 2Except for the change made, the dimming sheet of Comparative Example 7 was obtained in the same manner as in Comparative Example 6.

[0102] [Example 6] In Comparative Example 6, the ultraviolet irradiance was set to 8 mW / cm². 2 Except for the change made, the dimming sheet of Comparative Example 8 was obtained by the same method as in Comparative Example 6.

[0103] [Example 7] In Comparative Example 6, the ultraviolet irradiance was set to 6 mW / cm². 2 Except for the change made, the dimming sheet of Example 6 was obtained by the same method as in Comparative Example 6.

[0104] [Example 8] In Comparative Example 6, the ultraviolet irradiance was set to 2 mW / cm². 2 Except for the change made, the dimming sheet of Example 7 was obtained by the same method as in Comparative Example 6.

[0105] [Evaluation Method] [Domain diameter] After embedding the photochromic sheets of each example and comparative example in paraffin, the sides of the photochromic sheets were microtomized along a plane perpendicular to the plane on which the photochromic sheet was spread. Then, a platinum film was deposited onto the microtomized surface of the photochromic sheet using sputtering, thereby creating an observation surface. Next, the observation surface was observed using a scanning electron microscope (Regulus8220, Hitachi High-Tech Corporation). At this time, the domain diameters of five domains contained in the observation surface were measured, and then the average value of the domain diameters for the five domains was calculated. This average value of domain diameters was set as the domain diameter for each photochromic sheet.

[0106] Furthermore, it was found that the dimming sheets of each example and comparative example had only domains in contact with the first orientation layer and domains in contact with the second orientation layer as domains dispersed in the transparent polymer layer.

[0107] [Polar Anchoring Coefficient] The liquid crystal molecules used in the dimming sheets of each example and comparative example were sealed in evaluation liquid crystal cells (KSRP-05 / B111P1NSS05X, EHC Corporation), thereby creating measurement liquid crystal cells. In the evaluation liquid crystal cells, an ITO layer and a vertically aligned polyimide layer were formed on the corresponding surfaces, and the surface of the vertically aligned layer was rubbed in an antiparallel manner.

[0108] For each liquid crystal cell used for measurement, the dielectric constant ε in the vertical direction was measured using an LCR meter (E4980A, Keysight Technologies). ⊥ , and the dielectric constant ε in the horizontal direction ∥ The following values ​​were measured. From these values, the dielectric anisotropy Δε was calculated for each measurement liquid crystal cell. Next, the dielectric constant ε ⊥ ,ε ∥ , and the dielectric anisotropy Δε and the elastic constant K for spray deformation of each liquid crystal molecule. 11 And the elastic constant K for bending deformation. 33 Regarding this, using equations (3) to (9) above, the polar angle anchoring coefficient W a The first pole angle anchoring coefficient W in the first orientation layer 21 was calculated. a1 , and the second pole angle anchoring coefficient W in the second orientation layer 22 a2 Both are polar angle anchoring coefficients W a It is equal to.

[0109] [Haze value when transparent] For each example and comparative example of the dimming sheet, the haze value was calculated without applying voltage between the transparent electrode layers. The haze value was calculated using a method compliant with JIS K 7136:2000 "Plastics - Method for determining haze of transparent materials". A haze meter (NDH-7000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the haze value.

[0110] [Drive voltage] The driving voltage was measured for each example and comparative example of the dimming sheet. The driving voltage was set as follows: An AC voltage ranging from 0V to 150V was applied to the dimming sheet, thereby creating a voltage-haze curve. The minimum AC voltage at which the haze value was 90% of the maximum haze value on the voltage-haze curve was identified, and this minimum value was set as the driving voltage. The haze meter used to measure the haze value when the sheet was transparent was used to create the voltage-haze curve.

[0111] [Response time] The response speed in a -10°C environment was measured as follows. First, a 60V AC dynamic voltage was applied to the dimming sheets of each example and comparative example, and the state in which the haze value of the dimming sheet was increased was maintained. Next, the AC voltage was switched to 0V, and the time until the haze value of the dimming sheet reached the following haze value A was measured. Haze value A = (Haze value when transparent) + (Haze when transparent) × 0.1

[0112] [Evaluation Results] The evaluation results for each dimming sheet are shown in Figure 4.

[0113] As shown in Figure 4, in the dimming sheets of Examples 1 and 2 and Comparative Examples 1 to 3, the polar angle anchoring coefficient W a 10x10 -4 Furthermore, the domain diameter D of the dimming sheet was found to be 0.6 μm in Comparative Example 1, 0.9 μm in Example 1, 2.1 μm in Example 2, 3.0 μm in Comparative Example 2, and 4.2 μm in Comparative Example 3. Therefore, |D*log 10 (W a The value of )| was found to be 2.4 in Comparative Example 1, 3.6 in Example 1, 8.4 in Example 2, 12.0 in Comparative Example 2, and 16.8 in Comparative Example 3.

[0114] Furthermore, in the dimming sheets of Examples 3 to 5 and Comparative Examples 4 and 5, the polar angle anchoring coefficient Wa 10x10 -3 Furthermore, the domain diameter D of the dimming sheet was found to be 0.6 μm in Comparative Example 4, 1.2 μm in Example 3, 2.2 μm in Example 4, 3.1 μm in Example 5, and 4.1 μm in Comparative Example 5. Therefore, |D*log 10 (W a The value of )| was found to be 1.8 in Comparative Example 4, 3.6 in Example 3, 6.6 in Example 4, 9.3 in Example 5, and 12.3 in Comparative Example 5.

[0115] Furthermore, in the dimming sheets of Examples 6 to 8 and Comparative Examples 6 and 7, the polar angle anchoring coefficient W a 10x10 -2 Furthermore, the domain diameter D of the dimming sheet was found to be 0.5 in Comparative Example 6, 1.1 in Comparative Example 7, 2.2 in Example 6, 2.9 in Example 7, and 3.8 in Example 8. Therefore, |D*log 10 (W a The value of )| was found to be 1.0 in Comparative Example 6, 2.2 in Comparative Example 7, 4.4 in Example 6, 5.8 in Example 7, and 7.6 in Example 8.

[0116] In the dimmable sheets of Examples 1 to 8, it was observed that the haze value when the dimmable sheet was transparent was less than 6%. In contrast, in the dimmable sheets of Comparative Examples 1, 4, 6, and 7, the haze value when the dimmable sheet was transparent was less than 6%, while in the dimmable sheets of Comparative Examples 2, 3, and 5, the haze value when the dimmable sheet was transparent was 6% or more.

[0117] In the dimming sheets of Examples 1 to 8, it was observed that the driving voltage was less than 80V. Furthermore, while the driving voltage of the dimming sheets of Comparative Examples 2, 3, and 5 was less than 80V, it was observed that the driving voltage of the dimming sheets of Comparative Examples 1, 4, 6, and 7 was 80V or higher.

[0118] The dimming sheets of Examples 1 to 8 were found to have a response time of less than 20 seconds. In contrast, the dimming sheets of Comparative Examples 1, 4 to 7 had a response time of less than 20 seconds, while the dimming sheets of Comparative Examples 2 and 3 were found to have a response time of 20 seconds or more.

[0119] Thus, in a dimming sheet, |D*log 10 (W a It was found that the haze value, drive voltage, and response speed when transparency is exhibited are all within a suitable range, provided that the value of |D*log is within the range of 3.6 to 9.3. 10 (W a If the value of || is not within the range described above, it was found that at least one of the haze value, drive voltage, and response speed when transparency is exhibited is not within the appropriate range. For details, see |D*log 10 (W a It was observed that the drive voltage increased when the value of |D*log was less than 3.6. On the other hand, |D*log 10 (W a It was observed that when the value of )| exceeds 9.3, the haze value when exhibiting transparency increases, and the response speed at -10°C slows down.

[0120] As described above, according to one embodiment of the dimming sheet, the following effects can be obtained. (1) In the vicinity of the first orientation layer 21, the first pole angle anchoring coefficient W of the first orientation layer 21 a1 This prevents the first pole angle anchoring coefficient W from becoming excessively small and the domain diameter D from becoming excessively large. As a result, the force that the first alignment layer 21 exerts on the liquid crystal molecules 23LM from becoming excessively small is suppressed, which in turn suppresses an increase in the haze value when the dimming sheet 11R is transparent and a decrease in the response speed in low-temperature environments. a1It is possible to suppress the case where it becomes excessively large and the case where the domain diameter D becomes excessively small. Thereby, it is possible to suppress the case where the force by which the first alignment layer 21 aligns the liquid crystal molecules 23LM becomes excessively large, and thereby it is possible to suppress the increase in the drive voltage of the dimming sheet 11R.

[0121] (2) In the vicinity of the second alignment layer 22, the second polar angle anchoring coefficient W of the second alignment layer 22 a2 It is possible to suppress the case where it becomes excessively small and the case where the domain diameter D becomes excessively large. Thereby, it is possible to suppress the case where the force by which the second alignment layer 22 aligns the liquid crystal molecules 23LM becomes excessively small. Therefore, it is possible to suppress the increase in the haze value when the dimming sheet 11R exhibits transparency and the decrease in the response speed in a low-temperature environment. Further, the second polar angle anchoring coefficient W a2 It is possible to suppress the case where it becomes excessively large and the case where the domain diameter D becomes excessively small. Thereby, it is possible to suppress the case where the force by which the second alignment layer 22 aligns the liquid crystal molecules 23LM becomes excessively large. Therefore, it is possible to suppress the increase in the drive voltage of the dimming sheet 11R.

[0122] (3) By making the domain diameter D be 0.5 μm or more and 4.0 μm or less, it is possible to suppress the increase in the haze value of the dimming sheet 11R in a state where no voltage is applied to the dimming sheet 11R.

[0123] (4) By including the first polar angle anchoring coefficient W a1 within the range of 1.0×10 -4 or more and 1.0×10 -2 or less, it is possible to suppress the increase in the size of the domain diameter D that satisfies the formula (1) as compared with the case where the first polar angle anchoring coefficient W a1 falls below the lower limit value. Thereby, it is possible to suppress the increase in the haze value when exhibiting transparency and the decrease in the response speed in a low-temperature environment. On the other hand, as compared with the case where the first polar angle anchoring coefficient W a1 exceeds the upper limit value, it is possible to suppress the decrease in the size of the domain diameter D that satisfies the formula (1). Thereby, it is possible to suppress the increase in the drive voltage of the dimming sheet.

[0124] (5) The density of domains 23D is lowest in the central part of the thickness direction of the dimming layer 23, which makes it possible to reduce the number of liquid crystal molecules 23LM located in areas that are far from each alignment layer 21, 22. As a result, the alignment restricting force of each alignment layer 21, 22 acts more easily on the liquid crystal molecules 23LM, making it possible to increase the transparency of the dimming sheet 11R, i.e., reduce the haze, when no voltage is applied between the transparent electrode layers 24, 25.

[0125] The above-described embodiment can be implemented with the following modifications. [Light-regulating layer] The dimming layer 23 may have a domain 23D in the central part of the cross-section along the thickness direction of the dimming layer 23. Even in this case, the effect similar to (1) above can be obtained by satisfying the above condition 1.

[0126] [Dimmable sheet] • The dimming sheet 11R does not need to satisfy condition 2. Even in this case, the effect similar to (1) above can be obtained by the dimming sheet 11R satisfying condition 1. [Explanation of Symbols]

[0127] 11R…Photochromic sheet 21…First orientation layer 22…Second orientation layer 23…Dimming layer 23D…domain 23L…Liquid crystal composition 23LM…Liquid crystal molecule 24...First transparent electrode layer 25...Second transparent electrode layer

Claims

1. The first orientation layer, The second orientation layer, A light-adjusting layer located between the first alignment layer and the second alignment layer, comprising a transparent polymer layer in which a plurality of domains are dispersed, and a liquid crystal composition containing liquid crystal molecules and filled within the domains, The first orientation layer and the second orientation layer are vertical orientation layers, The domain diameter D [μm] is an indicator of the size of the domain, The first polar angle anchoring coefficient W is the polar angle anchoring coefficient of the first orientation layer for the liquid crystal molecules. ａ１ [J / m²] satisfies equation (1) 3.6≦|D*log １０ (W ａ１ ) | ≤ 9.3 … Formula (1) Dimming sheet.

2. The domain diameter and, The second pole angle anchoring coefficient W is the pole angle anchoring coefficient of the second orientation layer with respect to the liquid crystal molecules. ａ２ [J / m²] satisfies equation (2) 3.6≦|D*log １０ (Wa2) | ≤ 9.3 … Formula (2) The dimming sheet according to claim 1.

3. The domain diameter is 0.5 μm or more and 4.0 μm or less. The dimming sheet according to claim 1 or 2.

4. The first pole angle anchoring coefficient W ａ１ However, 1.0 × 10 －４ [J / m 2 ] or more 1.0×10 －２ [J / m²] or less The dimming sheet according to claim 1 or 2.

5. The density of the domains per unit thickness of the dimming layer is lowest in the central part in the thickness direction of the dimming layer. The dimming sheet according to claim 1 or 2.

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