Manufacturing method of light-adjusting sheet and evaluation method of light-adjusting sheet

Abstract

To appropriately evaluate the visibility of a dimmer sheet when visually recognized at an angle.SOLUTION: Provided is a method for manufacturing a dimmer sheet 11 that comprises a dimmer layer 31 that includes a liquid crystal compound LCM, a first transparent electrode layer 34 and a second transparent electrode layer 35 that sandwich the dimmer layer 31, and a pair of a first transparent support layer 36 and a second transparent support layer 37 that sandwich the dimmer layer 31, the first transparent electrode layer 34 and the second transparent electrode layer 35, with transparent and opaque states switched by drive of the liquid crystal compound LCM. A diagonal diffuse transmittance which is a diffuse transmittance when visible light is entered at an incidence angle of 20° and over to less than 90° to an outside surface 11F of the dimmer sheet 11 when turned to a transparent state, is less than or equal to a threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a light controlling sheet and a method for evaluating a light controlling sheet. [Background technology]

[0002] The light-controlling sheet includes a first transparent electrode layer, a second transparent electrode layer, and a light-controlling layer sandwiched between the first transparent electrode layer and the second transparent electrode layer. The orientation state of the liquid crystal compound contained in the light-controlling layer changes the light transmittance of the light-controlling sheet according to the change in the potential difference between the two transparent electrode layers. For example, when the orientation order of the liquid crystal compound is established, the light-controlling sheet becomes transparent and exhibits high light transmittance. When the long axis direction of the liquid crystal compound is disordered, the light-controlling sheet becomes cloudy and enters an opaque state exhibiting low light transmittance. The cloudy state of the light-controlling layer means that light is scattered in the light-controlling layer, and the degree of cloudiness has been evaluated using a haze measurement method conforming to JIS-K-7136:2000 (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-200414 A Summary of the Invention [Problem to be solved by the invention]

[0004] The refractive index of the liquid crystal compound is different in the long axis direction and the short axis direction, and the refractive index in the direction parallel to the long axis direction is larger than the refractive index in the direction parallel to the short axis direction. When the orientation order of the liquid crystal compound is established, the light-controlling sheet is transparent when visible light is incident perpendicularly to the surface of the light-controlling sheet, but when visible light is incident obliquely to the surface of the light-controlling sheet at an incident angle of, for example, 60°, the degree of cloudiness becomes larger than when viewed from the front. In other words, when an observer views the light-controlling sheet in an oblique direction, the light-controlling sheet may appear slightly cloudy. It is preferable that the degree of cloudiness is small, but a method for evaluating oblique visibility, which indicates the degree of cloudiness when viewed from an oblique direction, has not been established. [Means for solving the problem]

[0005] A method for manufacturing a light-adjusting sheet that solves the above problem includes a light-adjusting layer containing a liquid crystal compound, a pair of transparent electrode layers sandwiching the light-adjusting layer, and a pair of transparent support layers sandwiching the light-adjusting layer and the pair of transparent electrode layers, and switches between a transparent state and an opaque state by driving the liquid crystal compound.The method includes selecting a light-adjusting sheet whose oblique diffuse transmittance, which is the diffuse transmittance when light including visible light is incident on the surface of the light-adjusting sheet in the transparent state at an incident angle of 20° or more and less than 90°, is below a threshold value.

[0006] A method for evaluating a light-adjusting sheet that solves the above-mentioned problems is a method for evaluating a light-adjusting sheet that comprises a light-adjusting layer containing a liquid crystal compound, a pair of transparent electrode layers sandwiching the light-adjusting layer, and a pair of transparent support layers sandwiching the light-adjusting layer and the pair of transparent electrode layers, and that switches between a transparent state and an opaque state by driving the liquid crystal compound, and a light-adjusting sheet that has an oblique diffuse transmittance below a threshold value, which is the diffuse transmittance when light including visible light is incident on the surface of the light-adjusting sheet in the transparent state at an incident angle of 20° or more and less than 90°, is evaluated as a light-adjusting sheet that has high visibility when observed obliquely.

[0007] According to the above-mentioned manufacturing method and evaluation method, the degree of cloudiness when an observer observes a transparent light-controlling sheet from an oblique direction can be evaluated as a numerical value based on the product of haze and total light transmittance, and therefore a light-controlling sheet with a small degree of cloudiness when observed from an oblique direction and high oblique visibility can be selected.

[0008] In the above-mentioned method for producing the light-adjusting sheet, the product of the total light transmittance and the haze is 6.0×10 2 It is preferable to select the light controlling sheet so that the light controlling sheet satisfies the following requirements: According to the above method, by selecting light-controlling sheets having an oblique diffuse transmittance equal to or lower than a threshold value, it is possible to select light-controlling sheets having high oblique visibility.

[0009] Regarding the manufacturing method of the above-mentioned light-adjusting sheet, it is preferable that the method further includes a step of applying a coating liquid of the light-adjusting layer to at least one of the pair of transparent electrode layers by adding the liquid crystal compound, a dichroic dye having anisotropy in absorbance, and a resin composition, and curing the resin composition to form the light-adjusting layer.

[0010] According to the above method, the dichroic dye contained in the light-controlling layer absorbs the light scattered by the liquid crystal compound, thereby improving the oblique visibility and producing a light-controlling sheet that is easily selected as a sheet having high oblique visibility in the selection process.

[0011] The method for producing the above-mentioned light-adjusting sheet preferably includes a step of bonding a colored and transparent light-absorbing layer that absorbs a portion of visible light to at least one of the pair of surfaces of the light-adjusting sheet. According to the above method, the light absorbing layer absorbs visible light scattered by the liquid crystal compound, and therefore a light controlling sheet with high oblique visibility can be obtained.

[0012] Regarding the manufacturing method of the above-mentioned light-adjusting sheet, it is preferable that the method further includes a step of applying a coating liquid containing the liquid crystal compound and a liquid crystal resin including a liquid crystal polymer having anisotropy in refractive index to at least one of the pair of transparent electrode layers, and aligning the alignment axis of the liquid crystal polymer to the alignment axis of the liquid crystal compound in the transparent state, thereby hardening the liquid crystal resin.

[0013] According to the above method, by aligning the orientation axis direction of the liquid crystal resin with the orientation axis direction of the liquid crystal compound in the transparent state, the difference in refractive index between the liquid crystal compound and the liquid crystal resin becomes small when the light-controlling sheet is in the transparent state, and therefore, a light-controlling sheet with high oblique visibility can be obtained. Effect of the Invention

[0014] According to the present invention, it is possible to appropriately evaluate the visibility when the light controlling sheet is viewed obliquely. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a schematic configuration of a light control device according to a first embodiment. [Diagram 2] 4 is a cross-sectional view of a main part of a normal-type light adjusting sheet in the same embodiment. FIG. [Diagram 3] 11A and 11B are diagrams illustrating the visibility of a conventional light controlling sheet when viewed from the front. [Figure 4] FIG. 13 is a diagram illustrating a conventional light controlling sheet as viewed obliquely. [Diagram 5] 11A and 11B are diagrams illustrating the visibility of a conventional light controlling sheet when viewed obliquely. [Figure 6] 11A and 11B are diagrams illustrating visibility when the light controlling sheet of the embodiment is viewed obliquely. [Figure 7] 4 is a cross-sectional view of a main part of a reverse-type light controlling sheet in the embodiment. FIG. [Figure 8] 11A to 11C are diagrams illustrating a method for evaluating the light adjusting sheet of the embodiment. [Figure 9] FIG. 11 is a diagram showing a schematic configuration of a light control device according to a second embodiment. [Figure 10] FIG. 11 is a diagram showing a schematic configuration of a light control device according to a third embodiment. [Figure 11] 1 is a table showing the compositions and properties of examples and comparative examples. [Figure 12] 11 is a diagram illustrating the correlation between the diffuse transmittance of a light controlling sheet and the visual level. FIG. [Figure 13] FIG. 13 is a diagram showing a visual level sample of the embodiment. [Figure 14] FIG. 13 is a diagram showing a visual level sample of the embodiment. [Figure 15] FIG. 13 is a diagram showing a visual level sample of the embodiment. [Figure 16] FIG. 13 is a diagram showing a visual level sample of the embodiment. [Figure 17] FIG. 13 is a diagram showing a visual level sample of the embodiment. [Figure 18] FIG. 13 is a diagram showing a visual level sample of the embodiment. [Figure 19] FIG. 13 is a diagram showing a visual level sample of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (First embodiment) A first embodiment of a method for producing a light adjusting sheet and a method for evaluating a light adjusting sheet will be described. The light-controlling sheet is attached to a transparent substrate, which is an object to which the light-controlling sheet is attached. The transparent substrate is a glass substrate or a resin substrate. Examples of transparent substrates are windowpanes mounted on moving objects such as vehicles and aircraft, windowpanes installed in buildings, and partitions placed inside vehicles or indoors. The surface to which the light-controlling sheet is attached is flat or curved. The light-controlling sheet may be sandwiched between two transparent substrates.

[0017] The driving type of the light-controlling sheet is either normal type or reverse type. A normal type light-controlling sheet transitions from an opaque state to a transparent state when a voltage is applied, and returns from the transparent state to the opaque state when the voltage application is removed. A reverse type light-controlling sheet transitions from a transparent state to an opaque state when a voltage is applied, and returns from the opaque state to the transparent state when the voltage application is removed.

[0018] The normal type and reverse type have in common the fact that they are provided with two transparent electrode layers and a light control layer. In the following, the configuration and operation of the normal type will be described first, followed by a description of the normal type and a description of the reverse type.

[0019] [Structure of dimming device] The schematic structures of the light control device 10 and the light control sheet 11 will be described with reference to FIG. 1. The light control device 10 includes a light control sheet 11 and a driving unit 12. The light control sheet 11 includes a light control layer 31, a first transparent electrode layer 34, a second transparent electrode layer 35, a first transparent support layer 36, and a second transparent support layer 37. At least one of the outer surfaces 11F of the light control sheet 11 is supported by a transparent substrate, which is an object to which the light control sheet 11 is attached. Hereinafter, the direction in which the light control layer 31, the first transparent electrode layer 34, the second transparent electrode layer 35, the first transparent support layer 36, and the second transparent support layer 37 are stacked is referred to as the stacking direction X. The outer surface 11F corresponds to the surface of the light control sheet 11.

[0020] The light control layer 31 is located between the first transparent electrode layer 34 and the second transparent electrode layer 35. The first transparent electrode layer 34 is connected to the drive unit 12 through the first connection terminal 22A and the first wiring 23A. The first transparent electrode layer 34 is located between the first transparent support layer 36 and the light control layer 31, and is in contact with the first transparent support layer 36 and the light control layer 31. The second transparent electrode layer 35 is located between the second transparent support layer 37 and the light control layer 31, and is in contact with the second transparent support layer 37 and the light control layer 31.

[0021] The light control layer 31 has a structure such as polymer dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC), encapsulated nematic liquid crystal (NCAP), etc. The light control layer 31 containing polymer dispersed liquid crystal has a large number of independent voids or voids having a shape in which parts of independent shapes are joined in an organic polymer layer, and holds a liquid crystal composition in the voids. The polymer network liquid crystal has a polymer network having a three-dimensional mesh shape, and holds liquid crystal molecules as oriented particles in the voids of the polymer network. The encapsulated nematic liquid crystal layer holds a liquid crystal composition having an encapsulated shape in a resin layer. The light control layer 31 of this embodiment contains polymer dispersed liquid crystal. Note that the light control layer 31 does not necessarily have to be classified into any one of the types of polymer dispersed type, polymer network type, and encapsulated type. For example, it may be a hybrid type in which these types are mixed.

[0022] The first transparent electrode layer 34 and the second transparent electrode layer 35 are each colorless and transparent. The materials constituting the first transparent electrode layer 34 and the second transparent electrode layer 35 are each a conductive inorganic oxide, a metal, or a conductive organic polymer compound. An example of the conductive inorganic oxide is any one selected from the group consisting of indium tin oxide, fluorine-doped tin oxide, tin oxide, and zinc oxide. The metal is gold or silver nanowires. An example of the conductive organic polymer compound is any one selected from the group consisting of carbon nanotubes and poly(3,4-ethylenedioxythiophene).

[0023] The materials constituting the first transparent support layer 36 and the second transparent support layer 37 are each an organic polymer compound or an inorganic polymer compound. An example of the organic polymer compound is any one selected from the group consisting of polyester, polyacrylate, polycarbonate, and polyolefin. An example of the inorganic polymer compound is any one selected from the group consisting of silicon oxide, silicon oxynitride, and silicon nitride. It is preferable that the first transparent support layer 36 and the second transparent support layer 37 are each colorless and transparent.

[0024] In addition, the light-adjusting sheet 11 may have one or more other functional layers as long as the light-adjusting sheet 11 is configured to switch between a transparent state and an opaque state based on a change in the alignment state of the liquid crystal compound LCM. The other functional layer may be a gas barrier layer that suppresses the transmission of oxygen and moisture toward the light-adjusting layer 31, or an ultraviolet barrier layer that suppresses the transmission of ultraviolet light rays other than a specific wavelength toward the light-adjusting layer 31. The other functional layer may be a hard coat layer that mechanically protects each layer of the light-adjusting sheet 11, or an adhesive layer that enhances adhesion between layers in the light-adjusting sheet 11.

[0025] The driving unit 12 is connected to the first transparent electrode layer 34 and the second transparent electrode layer 35. The driving unit 12 applies a driving voltage to the first transparent electrode layer 34 and the second transparent electrode layer 35 to control the orientation of the liquid crystal compound LCM according to the potential difference between the first transparent electrode layer 34 and the second transparent electrode layer 35. The driving voltage is a voltage for changing the orientation state of the liquid crystal compound LCM. The driving unit 12 changes the orientation state of the liquid crystal compound LCM to switch the light control sheet 11 from one of a transparent state and an opaque state to the other.

[0026] [Light control layer] Next, the light control layer 31 will be described in detail with reference to Fig. 2. Fig. 2 shows a part of the light control sheet 11, and shows cross sections of the light control layer 31, the first transparent electrode layer 34, and the second transparent electrode layer 35. Here, an example of the light control layer 31 will be described as including a polymer dispersed liquid crystal.

[0027] The light control layer 31 includes an organic polymer layer 31P, a liquid crystal composition 31LC, and a spacer SP. The organic polymer layer 31P is a cured product of a resin composition that is a photopolymerizable compound. The resin composition may be an ultraviolet-curable compound or an electron beam-curable compound. The resin composition is compatible with the liquid crystal composition 31LC.

[0028] The organic polymer layer 31P defines a gap 31D in the light control layer 31. The liquid crystal composition 31LC fills the gap 31D in the organic polymer layer 31P. The gap 31D has two or more sizes, and the gap 31D has a spherical shape, an ellipsoidal shape, or an irregular shape. When it is necessary to improve the controllability of the size of the gap 31D, the resin composition is preferably an ultraviolet curable compound. An example of the ultraviolet curable compound includes a polymerizable unsaturated bond at the end of the molecular structure. Alternatively, the ultraviolet curable compound includes a polymerizable unsaturated bond other than at the end of the molecular structure. The resin composition is one type of polymerizable compound, or a combination of two or more types of polymerizable compounds. The ultraviolet curable compound is at least one selected from the group consisting of an acrylate compound, a methacrylate compound, a styrene compound, a thiol compound, and an oligomer of each compound. The acrylate compound includes a diacrylate compound, a triacrylate compound, and a tetraacrylate compound. Examples of acrylate compounds are butyl ethyl acrylate, ethylhexyl acrylate, and cyclohexyl acrylate. Examples of methacrylate compounds are dimethacrylate compounds, trimethacrylate compounds, and tetramethacrylate compounds. Examples of methacrylate compounds are N,N-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, and tetrahydrofurfuryl methacrylate. Examples of thiol compounds are 1,3-propanedithiol and 1,6-hexanedithiol. Examples of styrene compounds are styrene and methylstyrene.

[0029] The lower limit of the content of the organic polymer layer 31P in the light-controlling layer 31 is 20% by mass, and more preferably 30% by mass. The upper limit of the content of the organic polymer layer 31P in the total amount of the organic polymer layer 31P and the liquid crystal composition 31LC is 70% by mass, and more preferably 60% by mass.

[0030] The lower limit and upper limit of the content of the organic polymer layer 31P are determined according to the range in which the liquid crystal compound LCM can be phase-separated from the cured resin composition during the curing process of the resin composition. When it is necessary to increase the mechanical strength of the organic polymer layer 31P, it is preferable that the lower limit of the content of the organic polymer layer 31P is high. When it is necessary to reduce the driving voltage of the liquid crystal composition 31LC, it is preferable that the upper limit of the content of the organic polymer layer 31P is low.

[0031] The liquid crystal composition 31LC includes a liquid crystal compound LCM. The liquid crystal compound LCM has an elongated shape. The dielectric constant of the liquid crystal compound LCM in the long axis direction is larger than the dielectric constant of the liquid crystal compound LCM in the short axis direction, i.e., it has a positive dielectric anisotropy. Alternatively, the dielectric constant of the liquid crystal compound LCM in the long axis direction is lower than the dielectric constant of the liquid crystal compound LCM in the short axis direction, i.e., it has a negative dielectric anisotropy. The dielectric anisotropy of the liquid crystal compound LCM is appropriately selected based on the presence or absence of each alignment layer in the light control sheet 11 and the driving type. In addition, the liquid crystal compound LCM has optical anisotropy, and the refractive index in the long axis direction is larger than the refractive index in the short axis direction. The liquid crystal compound LCM is about the same size as or larger than the wavelength of visible light, and scatters visible light to make the light control layer 31 opaque.

[0032] The liquid crystal compound LCM is at least one selected from the group consisting of Schiff base-based, azo-based, azoxy-based, biphenyl-based, terphenyl-based, benzoic acid ester-based, tolan-based, pyrimidine-based, pyridazine-based, cyclohexane carboxylate-based, phenylcyclohexane-based, biphenylcyclohexane-based, dicyanobenzene-based, naphthalene-based, and dioxane-based. The non-polymerizable liquid crystal compound is one type of liquid crystal compound or a combination of two or more types of liquid crystal compounds. The liquid crystal composition 31LC may further contain a viscosity reducing agent, an antifoaming agent, an antioxidant, a weathering agent, and a solvent. Examples of weathering agents include ultraviolet absorbers and light stabilizers.

[0033] The liquid crystal composition 31LC in this embodiment contains a liquid crystal compound LCM and a dichroic dye DP. The dichroic dye DP has an elongated shape, and the absorbance in the visible region in the direction of the molecular long axis is greater than the absorbance in the direction of the molecular short axis. The dichroic dye DP in this embodiment appears almost transparent when oriented parallel or approximately parallel to the incident direction of light. The dichroic dye DP exhibits color when the molecular long axis direction is perpendicular or approximately perpendicular to the incident direction of light. That is, the dichroic dye DP exhibits color when oriented such that the molecular long axis direction is perpendicular or approximately perpendicular to the normal direction of the contact surface of the light control layer 31 with the first transparent electrode layer 34 and the contact surface with the second transparent electrode layer 35. The color exhibited by the dichroic dye DP is preferably black or a color close to black. The dichroic dye DP exhibits color when driven by a guest-host system in which the liquid crystal compound LCM is a host.

[0034] The dichroic dye DP is 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 DP is one dye or a combination of two or more dyes. When it is required to increase the light resistance and the dichroic ratio, the dichroic dye is at least one selected from the group consisting of azo compounds and anthraquinone compounds, and more preferably an azo compound.

[0035] The content of the dichroic dye DP is 10% by weight or less with respect to the weight of the light-adjusting layer 31. When the content of the dichroic dye DP is 1% by weight or more and 10% by weight or less, it is possible to improve visibility when an observer views the light-adjusting sheet 11 with the naked eye from an oblique angle. When the content of the dichroic dye DP is 1% by weight or less, the color density in the light-adjusting layer 31 is low, and it is possible to obtain a light-adjusting sheet 11 with excellent aesthetics.

[0036] The spacers SP are dispersed throughout the organic polymer layer 31P. The spacers SP determine the thickness of the light-controlling layer 31 around the spacers SP and make the thickness of the light-controlling layer 31 uniform. The spacers SP may be bead spacers or photospacers formed by exposing and developing a photoresist. The spacers SP have light-transmitting properties and may be colorless and transparent or colored and transparent. When a colored and transparent spacer SP is used, the color exhibited by the spacers SP is preferably the same color as the color exhibited by the dichroic dye DP.

[0037] When the application of the driving voltage is released, the long axis directions of the liquid crystal compound LCM and the dichroic dye DP become disordered. As a result, the light-adjusting sheet 11 scatters light in the light-adjusting layer 31 over the entire visible light range, and becomes opaque. The long axis directions of the dichroic dye DP also become disordered. At least the dichroic dyes DP whose smallest angle between the long axis direction and the stacking direction X of the light-adjusting layer 31 is close to 90° exhibit color.

[0038] When a driving voltage is applied, the liquid crystal compound LCM is subjected to an orientation restricting force by the electric field, and the long axis directions of the liquid crystal compound LCM and the dichroic dye DP are aligned along the electric field direction. This makes the total light transmittance of the light-adjusting sheet 11 higher than in the opaque state. The long axis direction of the dichroic dye DP is also aligned along the electric field direction. Therefore, when the light-adjusting sheet 11 is viewed from the front, the color of the light-adjusting sheet 11 becomes colorless or nearly colorless.

[0039] [Diagonal visibility of light control sheet] 3 to 6, a method for quantifying the visibility when an observer observes the light controlling sheet 11 from an oblique angle will be described. Note that, hereinafter, this visibility will be referred to as "oblique visibility."

[0040] FIG. 3 shows a part of the light-controlling layer 31 of the conventional light-controlling sheet 11 in a transparent state. The liquid crystal compound LCM has an orientation order, and the long axis of the liquid crystal compound LCM is parallel or approximately parallel to the lamination direction X of the light-controlling layer 31. When light 100 including visible light is incident parallel or approximately parallel to the lamination direction X of the light-controlling sheet 11, the refractive index of the liquid crystal compound LCM becomes the refractive index no of ordinary light. The difference between this refractive index no and the refractive index np of the organic polymer layer 31P is small. Therefore, the scattered light 101 of the light 100 by the liquid crystal compound LCM is relatively small. In other words, when an observer observes the light-controlling sheet 11 in a transparent state from the front, the light-controlling sheet 11 has high transparency, and the cloudiness is hardly observed by the naked eye.

[0041] FIG. 4 shows a state in which the observer 105 views the light-adjusting sheet 11 obliquely. In this embodiment, the state in which the viewing angle θ1 between the direction 106 (direction vector) from the observer 105 toward the outer surface 11F of the light-adjusting sheet 11 at the shortest distance and the stacking direction X of the light-adjusting layer 31, in other words, the normal direction of the outer surface 11F of the light-adjusting sheet 11, is 20° or more and less than 90° is the state in which the observer 105 views the light-adjusting sheet 11 obliquely. When the viewing angle θ1 is 20° or less, scattering is small, so that oblique visibility is not recognized and appropriate evaluation cannot be performed. The viewing angle θ1 may be 20° or more and 60° or less. When the viewing angle θ1 exceeds 60°, the visible sample area becomes narrow, and the influence of the total reflected light on the outer surface 11F on the observer 105 side becomes strong, so that the measurement accuracy decreases. In this embodiment, the range in which the incident angle of visible light corresponding to the viewing angle θ1 is between 20° and 60° is used as the range for evaluating the oblique visibility by quantifying it. Note that the observer 105 may be located on the left or right side of the light controlling sheet 11, or may be located above or below the light controlling sheet 11.

[0042] As shown in FIG. 5, when light 100 is incident on the light control sheet 11 in a direction oblique to the stacking direction X, the refractive index of the liquid crystal composition 31LC is a refractive index ne. This refractive index ne is greater than the refractive index no. As a result, the difference Δn between the refractive index ne of the liquid crystal compound LCM and the refractive index np of the organic polymer layer 31P becomes large. By increasing the refractive index difference Δn, the intensity of the scattered light 101 by the liquid crystal compound LCM becomes greater than that in the case shown in FIG. 3 in which the light 100 is incident parallel or approximately parallel to the stacking direction X. This causes multiple scattering in the light control layer 31. That is, when an observer observes the light control sheet 11 in a transparent state from an oblique angle, the light control sheet 11 is visually recognized as being cloudy. Note that the degree of cloudiness at this time is smaller than the degree of cloudiness when the light control sheet 11 is in an opaque state.

[0043] FIG. 6 shows a part of the light-adjusting layer 31 of the light-adjusting sheet 11 of this embodiment. When light 100 is incident on the light-adjusting sheet 11 in a direction oblique to the lamination direction X, the light 100 is scattered as much as in the state shown in FIG. 5, but part of the scattered light 101 is absorbed by the dichroic dye DP present around the liquid crystal compound LCM during the scattering process. This reduces multiple scattering in the light-adjusting layer 31, and reduces the degree of cloudiness in the transparent state compared to a conventional light-adjusting sheet 11 that does not contain the dichroic dye DP. As a result, the diagonal visibility of the light-adjusting sheet 11 is improved.

[0044] [Structure of reverse-type light-control sheet] Next, the reverse-type light controlling sheet 11 will be described with reference to Fig. 7. The reverse-type light controlling sheet 11 differs from the normal-type light controlling sheet 11 in that the reverse-type light controlling sheet 11 includes a first alignment layer 32 between the light controlling layer 31 and the first transparent electrode layer 34, and a second alignment layer 33 between the light controlling layer 31 and the second transparent electrode layer 35. Similarly to the normal-type light controlling sheet 11, the light controlling layer 31 contains a dichroic dye DP.

[0045] When the application of the drive voltage to the first transparent electrode layer 34 and the second transparent electrode layer 35 is released, the liquid crystal compound LCM receives an alignment restriction force from the first alignment layer 32 and the second alignment layer 33, and the long axis direction of the liquid crystal compound LCM is aligned with the stacking direction X. This causes the light-controlling sheet 11 to be in a transparent state by suppressing scattering in the light-controlling layer 31 over the entire visible light range. Since the light-controlling layer 31 contains the dichroic dye DP, the diagonal visibility is improved compared to when the light-controlling layer 31 does not contain the dichroic dye DP.

[0046] When the driving voltage starts to be applied, the liquid crystal compound LCM is subjected to an orientation restricting force by the electric field, and the long axis direction of the liquid crystal compound LCM starts to move in a direction perpendicular to the electric field direction. At this time, the long axis direction of the liquid crystal compound LCM is restricted by the intermolecular interactions in the liquid crystal composition 31LC and the size of the voids 31D, and cannot move sufficiently, becoming disordered. As a result, the light control sheet 11 causes scattering in the light control layer 31 over the entire visible light range, and becomes opaque.

[0047] [Evaluation method for light control film] The method for evaluating the oblique visibility will be described with reference to FIGS. The oblique visibility is evaluated by the diffuse transmittance when light is obliquely incident on the light-controlling sheet 11. In this embodiment, this diffuse transmittance is referred to as the oblique diffuse transmittance Td (%). In this embodiment, the oblique diffuse transmittance Td is a value based on the product of the oblique total light transmittance Tt (%) and the oblique haze H (%) when light is obliquely incident on the light-controlling sheet 11.

[0048] The oblique total light transmittance Tt is measured in the same manner as the general total light transmittance, although the angle of incidence of light is changed. The general total light transmittance is based on the definition of JIS-K-7375:2008. In other words, the total light transmittance is the ratio of the total transmitted light flux to the parallel incident light flux on the test piece 55. The oblique total light transmittance Tt in this embodiment refers to the ratio of the total transmitted light flux to the incident light flux that is obliquely incident on the incident surface of the test piece 55. The oblique total light transmittance Tt becomes smaller as the incident angle on the light control sheet 11 becomes larger.

[0049] Oblique haze H is measured in the same way as general haze, although the angle of incidence of light is changed. General haze is based on the definition of JIS-K-7136. In other words, it is the ratio of the light flux diffused by the test piece 55 and the measuring device to the total light flux transmitted through the test piece 55, minus the ratio of the light flux diffused by the device. Haze can be expressed as a percentage of the diffuse transmittance to the total light transmittance ({Td / Tt} x 100). Oblique haze H is the haze when a light flux is incident obliquely on the entrance surface of the test piece 55. In other words, it is the haze when a light flux is incident obliquely on the entrance surface of the test piece 55, excluding the parallel light flux that is parallel or nearly parallel to the obliquely incident light flux, from the total light transmittance when the light flux is incident obliquely. Diffuse transmittance The oblique haze H is a percentage of the total light transmittance Tt (%). The oblique haze H increases as the angle of incidence to the light controlling sheet 11 increases. In this embodiment, the product of the oblique total light transmittance Tt (%) and the oblique haze H (%) is multiplied by a coefficient α of "1 / 100" to obtain the oblique diffuse transmittance Td, so that the product is 100% or less.

[0050] In addition, as the degree of cloudiness of the light-controlling sheet 11 increases, the oblique haze H also tends to increase. However, since the oblique haze H indicates the ratio of the diffuse transmittance to the total light transmittance, it is affected by the magnitude of the light flux of the total transmitted light. In other words, even if two light-controlling sheets 11 have the same diffuse transmittance, if one light-controlling sheet 11 has a configuration that absorbs light including parallel light, the total light transmittance of that light-controlling sheet 11 becomes smaller, and the haze value tends to be larger than that of the other light-controlling sheet 11. On the other hand, the oblique diffuse transmittance Td indicates the ratio of the light flux transmitted and diffused by the test piece 55 to the incident light flux. For this reason, the oblique diffuse transmittance Td is less affected by the total light transmittance.

[0051] FIG. 8 is a schematic diagram showing an example of a system for measuring the oblique total light transmittance Tt and the oblique haze H. The measurement system includes a haze meter 50. The haze meter 50 includes a light-emitting unit 51 including optical mechanisms such as a light source, a condenser lens, and an aperture, and a light-receiving unit 52 including optical mechanisms such as an integrating sphere and a light-receiving element. The light-emitting unit 51 emits parallel light to the light-receiving unit 52. The measurement system also includes an angle adjustment unit 53. The angle adjustment unit 53 has a holding unit that holds a test piece 55 obtained by cutting the light-controlling sheet 11 to a predetermined size, and an adjustment mechanism that adjusts the angle of the holding unit. The angle adjustment unit 53 holds the test piece 55 between the light-emitting unit 51 and the light-receiving unit 52. The angle adjustment unit 53 also adjusts the angle of the holding unit to adjust the incident angle θ when the light beam 56 emitted from the light-emitting unit 51 enters the test piece 55.

[0052] The haze meter 50 measures the oblique total light transmittance Tt and the oblique haze H. The oblique total light transmittance Tt is measured by a method conforming to "Plastics - Determination of total light transmittance and total light reflectance" specified in JIS-K-7375:2008. The oblique haze H is measured by a method conforming to "Plastics - Determination of haze of transparent materials" specified in JIS-K-7136:2000. However, the former regulation on the total light transmittance requires that parallel light rays are incident perpendicularly on the test piece, and the latter regulation on the haze requires that the test piece is fixed in the range of -2° to +2° with respect to the light flux. In this embodiment, however, the light flux 56, which is a parallel light ray emitted from the light emitting unit 51, is incident on the test piece 55 at an incident angle θ of 20° to 60°.

[0053] When performing the evaluation, the light controlling sheet 11 to be evaluated is used as a test piece 55 of a predetermined size, and the test piece 55 is held by the holding part of the angle adjustment part 53. The angle of the test piece 55 is adjusted by the adjustment mechanism, and the incident angle θ is set to a constant angle within the range of 20° to 60°, and the oblique total light transmittance Tt and the oblique haze H are measured. Then, the product of the oblique total light transmittance Tt and the oblique haze H is multiplied by the coefficient α to obtain the oblique diffuse transmittance Td. Note that the incident angle θ may be changed by a predetermined angle, for example, 10°, within the range of 20° to 60°, to measure the oblique total light transmittance Tt and the oblique haze H, and the product of these may be obtained. Then, the maximum or minimum value of these products may be multiplied by the coefficient α to obtain the oblique diffuse transmittance Td.

[0054] The light controlling sheet 11 is selected as having high oblique visibility when the oblique diffuse transmittance Td is equal to or less than a threshold value. The threshold value is preferably 10%. In order to reliably suppress cloudiness, it is particularly preferable that the threshold value of the oblique diffuse transmittance Td is 6%. When the coefficient α is not multiplied, the threshold value of the oblique diffuse transmittance Td is set to "10.0×10 2 " or "6.0 x 10 2 "

[0055] If the diagonal diffuse transmittance Td of the light-adjusting sheet 11 exceeds 6%, when the observer 105 observes the light-adjusting sheet 11 at an angle, the light-adjusting sheet 11 appears cloudy, and the observer 105 cannot recognize an object facing the light-adjusting sheet 11. If the diagonal diffuse transmittance Td is 6% or less, when the observer 105 observes the light-adjusting sheet 11 at an angle, the light-adjusting sheet 11 appears transparent or slightly cloudy while maintaining transparency, and the observer 105 can recognize an object facing the light-adjusting sheet 11.

[0056] As described above, when the light-adjusting layer 31 contains the dichroic dye DP, the dichroic dye DP absorbs the scattered light 101. Therefore, compared to the light-adjusting sheet 11 in which the light-adjusting layer 31 does not contain the dichroic dye DP, the diagonal diffuse transmittance Td is reduced, and it is easier to make the diagonal diffuse transmittance Td 6% or less.

[0057] [Manufacturing method of light control sheet] Next, an example of a method for manufacturing the light-adjusting sheet 11 will be described. A sheet consisting of a first transparent support layer 36 having a first transparent electrode layer 34 and a sheet consisting of a second transparent support layer 37 having a second transparent electrode layer 35 are prepared. Next, a coating liquid is applied to at least one of these sheets to form a coating film. Then, these sheets are bonded together to form a coating film between the first transparent electrode layer 34 and the second transparent electrode layer 35. In the reverse-type light-adjusting sheet 11, a coating film is formed between the first alignment layer 32 and the second alignment layer.

[0058] The coating film contains a resin composition which is a photopolymerizable compound, a liquid crystal composition 31LC, a dichroic dye DP, and a polymerization initiator for initiating polymerization of the resin composition. The coating film is irradiated with light to polymerize the resin composition of the coating film, thereby phase-separating the liquid crystal compound LCM from the resin composition. The light for polymerizing the resin composition may be irradiated toward the first transparent support layer 36, toward the second transparent support layer 37, or toward both the first transparent support layer 36 and the second transparent support layer 37. The coating liquid may also contain a plasticizer and a curing assistant. Coating films may be formed on both sheets and then bonded together. The sheets may also be bonded together via a spacer SP, and the coating liquid may be injected between the sheets.

[0059] In the phase separation of the liquid crystal composition 31LC, the intensity of the light irradiated to the resin composition, the irradiation time, and the processing temperature during polymerization of the resin composition are set so that the size of the liquid crystal particles is a desired size and the number of the liquid crystal particles is a desired number. That is, in the phase separation of the liquid crystal composition 31LC, the intensity of the light irradiated to the resin composition, the irradiation time, and the processing temperature during polymerization of the resin composition are set so that the size of the voids 31D is a desired size and the number of the voids 31D is a desired number. In this way, the light control sheet 11 having a laminate consisting of the light control layer 31, the first transparent electrode layer 34 and the second transparent electrode layer 35, the first transparent support layer 36, and the second transparent support layer 37 is formed. Furthermore, the second transparent support layer 37, the second transparent electrode layer 35, and the light control layer 31 in a predetermined region of the light control sheet 11 are peeled off to expose the first transparent electrode layer 34, and the first connection terminal 22A is electrically connected to the first transparent electrode layer 34. In addition, the first transparent support layer 36, the second transparent electrode layer 35 and the light-adjusting layer 31 are peeled off in a specified area of ​​the light-adjusting sheet 11 to expose the second transparent electrode layer 35, and the second connection terminal 22B is electrically connected to the second transparent electrode layer 35.

[0060] Next, a measurement step is performed. In the measurement step, a test piece 55 is prepared from this light controlling sheet 11, and the oblique total light transmittance Tt and the oblique haze H are measured using a measurement system. Then, the product of the oblique total light transmittance Tt and the oblique haze H is multiplied by a coefficient α to obtain the oblique diffuse transmittance Td.

[0061] Next, a selection step is performed. The light controlling sheets 11 having an oblique diffuse transmittance Td equal to or less than a threshold value, for example, 0.6, are selected. This selection step may be performed for each lot or for each type of light controlling sheet 11.

[0062] According to the first embodiment, the following effects can be obtained. (1-1) The oblique visibility, which is the degree of opacity when an observer observes the transparent light controlling sheet 11 from an oblique direction, can be evaluated as a numerical value based on the product of haze and total light transmittance. This makes it possible to select light controlling sheets with high oblique visibility.

[0063] (1-2) The product of the oblique total light transmittance Tt and the oblique haze H is a threshold value of 6.0 × 10 2 The light controlling sheet 11 having a diagonal diffuse transmittance Td of 6% or less, calculated by multiplying the product of the diagonal total light transmittance Tt and the diagonal haze H by the coefficient α, was determined to have high diagonal visibility. Therefore, the light controlling sheet 11 having high diagonal visibility can be selected.

[0064] (1-3) The dichroic dye DP contained in the light-controlling layer 31 absorbs the light scattered by the liquid crystal compound LCM. This improves the oblique visibility, and makes it possible to manufacture a light-controlling sheet that is likely to be selected as having high oblique visibility.

[0065] Second embodiment Next, a second embodiment of the method for producing a light controlling sheet will be described with reference to Fig. 9. The second embodiment differs from the first embodiment in that the light controlling sheet 11 has a layer that absorbs visible light. Hereinafter, the same parts as those in the first embodiment will be given the same reference numerals and detailed description thereof will be omitted.

[0066] In the first embodiment, the light-adjusting layer 31 contains the dichroic dye DP to lower the visual level LV. Alternatively, a colored and transparent first light-absorbing layer 38 and a second light-absorbing layer 39 may be provided on the outside of the first transparent support layer 36 and the second transparent support layer 37. The first light-absorbing layer 38 and the second light-absorbing layer 39 are, for example, black resin films. The first light-absorbing layer 38 and the second light-absorbing layer 39 are organic polymer compounds or inorganic polymer compounds. For example, polyethylene terephthalate, polyester, polyacrylate, polycarbonate, polyolefin, etc. The light-adjusting layer 31 may contain the dichroic dye DP and may be provided with the first light-absorbing layer 38 and the second light-absorbing layer 39.

[0067] The first light absorbing layer 38 and the second light absorbing layer 39 absorb scattered light that is generated by scattering visible light that is obliquely incident on the outer surface 11F of the light controlling sheet 11. In terms of maintaining light absorbency and transparency, the total light transmittance of the first light absorbing layer 38 and the second light absorbing layer 39 is preferably, for example, 20% or more and 60% or less.

[0068] A first light absorbing layer 38 and a second light absorbing layer 39 are respectively bonded to the first transparent support layer 36 and the second transparent support layer 37 of this light controlling sheet 11. The first light absorbing layer 38 and the second light absorbing layer 39 may be bonded by an adhesive or may be bonded by welding.

[0069] According to the second embodiment, in addition to the effects described in (1-1) and (1-2) above, the effects listed below can be obtained. (2-1) The first light absorbing layer 38 and the second light absorbing layer 39 absorb visible light scattered by the liquid crystal compound LCM, thereby making it possible to obtain a light controlling sheet 11 with high oblique visibility.

[0070] Third embodiment Next, a third embodiment of the manufacturing method and evaluation method of the light adjusting sheet will be described with reference to Fig. 10. In the third embodiment, the configuration of the light adjusting layer 31 is different from that of the first embodiment. Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0071] In the first embodiment, the light-adjusting layer 31 contains a dichroic dye DP, which absorbs scattered light and enhances oblique visibility. Alternatively, a liquid crystal polymer having anisotropic refractive index may be added to the organic polymer layer 31P. The light-adjusting layer 31 of the light-adjusting sheet 11 of the third embodiment may contain a dichroic dye DP. In addition, the light-adjusting sheet 11 may be provided with a first light-absorbing layer 38 and a second light-absorbing layer 39, or may have both of these configurations.

[0072] 10 shows a part of the light-controlling layer 31. The organic polymer layer 31P contains a liquid crystal polymer 310 made of a liquid crystal polymer 310. The liquid crystal polymer 310 has an elongated shape. The liquid crystal polymer 310 has a long axis, which is an alignment axis, aligned with the long axis of the liquid crystal compound LCM in the transparent state.

[0073] The liquid crystal polymer 310 is a polymer of a first monomer (2-propenonic acid, 2-methyl-, 6-[4-(4-heptylcyclohexyl)phenoxy]hexyl este), which is a liquid crystal monomer represented by the following formula 1.

[0074] Alternatively, the liquid crystalline polymer 310 is a polymer of a second monomer which is a liquid crystalline monomer represented by the following formula 2. Note that the "t" in the cyclohexane ring represents a trans form.

[0075] [ka]

[0076] [ka]

[0077] The greater the difference between the refractive index of the incident light in the organic polymer layer 31P and the refractive index of the incident light in the liquid crystal compound LCM, the greater the scattering in the light-controlling layer 31. When the alignment axes of the liquid crystal polymer 310 and the liquid crystal compound LCM are aligned in this manner, the refractive index difference becomes small, and therefore scattering becomes small.

[0078] An example of a method for producing the light controlling sheet 11 will be described, focusing on the points that differ from the first embodiment. The coating film contains a liquid crystal resin in a molten state, which is made of a liquid crystal composition 31LC and a liquid crystal polymer 310, and a polymerization initiator for initiating polymerization of the resin composition. The liquid crystal compound LCM is phase-separated from the resin composition by polymerizing the resin composition of the coating film. The coating liquid may also contain a plasticizer and a curing aid. For example, butyl adipate can be used as the plasticizer, and pentaerythritol tetrakis (3-mercaptobutyrate) can be used as the curing aid. This coating liquid is applied to at least one of a sheet made of a first transparent support layer 36 provided with a first transparent electrode layer 34 and a sheet made of a second transparent support layer 37 provided with a second transparent electrode layer 35. Then, an orientation control process is performed on the liquid crystal polymer 310 to align the orientation axis of the liquid crystal polymer 310. The liquid crystal and liquid crystal polymer are aligned using a known horizontal alignment film. For example, a method of rubbing a polymer film such as polyvinyl alcohol or polyimide can be used. After the orientation control treatment, the coating film is cooled to solidify the liquid crystalline resin while maintaining the oriented state.

[0079] These sheets are then bonded together to sandwich the coating film between the first transparent electrode layer 34 and the second transparent electrode layer. The pair of sheets is then irradiated with light from the outside to polymerize the resin composition of the coating film, thereby phase-separating the liquid crystal compound LCM from the resin composition. Coating films may be formed on both sheets and then bonded together, and the method of forming the coating film is not particularly limited.

[0080] According to the third embodiment, the following effects can be obtained. (3-1) In the third embodiment, the light control layer 31 contains a liquid crystal resin made of a liquid crystal polymer 310. By aligning the direction of the alignment axis of the liquid crystal polymer 310 with the direction of the alignment axis of the liquid crystal compound LCM in a transparent state, the difference in refractive index between the liquid crystal compound and the liquid crystal resin becomes small when the light control sheet 11 is in a transparent state. Therefore, it is possible to obtain a light control sheet 11 with high oblique visibility.

[0081] [Example] Examples and comparative examples will be specifically described with reference to Fig. 11. Note that the present invention is not limited to these examples.

[0082] [Example 1] The light-adjusting sheet 11 of Example 1 includes a first light-absorbing layer 38 and a second light-absorbing layer 39. A pair of sheets including a transparent support layer made of polyethylene terephthalate having a thickness of 125 μm and an indium tin oxide (ITO) transparent electrode layer having a thickness of 30 nm were prepared. The coating liquid had the following composition. The content of the materials constituting the coating liquid in the following Examples and Comparative Examples is the ratio to the total solid content of the coating liquid.

[0083] Liquid crystal compound LCM: positive nematic liquid crystal (nematic-isotropic phase transition temperature 110°C, Merck, MNC-6609), 50% by mass Photopolymerizable compound: Isobornyl acrylate (product name: A-IB, manufactured by Shin-Nakamura Chemical Co., Ltd.), 47% by mass Curing aid: pentaerythritol tetrakis(3-mercaptobutyrate) (manufactured by Showa Denko K.K.), 1% by mass Polymerization initiator: 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins BV), 1% by mass Spacer SP: PMMA spherical particles, particle size 15 μm, (manufactured by Sekisui Plastics Co., Ltd.), 1% by mass Using this coating liquid, a coating film was formed on one of the sheets, which was then laminated with the first transparent electrode layer 34 and the second transparent electrode layer 35. Both sides of the first transparent support layer 36 and the second transparent electrode layer 35 were irradiated with ultraviolet light of 365 nm to obtain a laminate. At this time, the intensity of the ultraviolet light was set to 5 mW / cm on one side. 2 and the UV irradiation time was set to 100 seconds.

[0084] Furthermore, a black first light absorbing layer 38 and a black second light absorbing layer 39 (Sylpheed SC-7045, manufactured by IKC Corporation) were attached to both sides of this laminate to obtain the light controlling sheet 11 of Example 1.

[0085] [Example 2] The light-adjusting sheet 11 of Example 2 contains a dichroic dye DP in the light-adjusting layer 31. The light-adjusting sheet 11 of Example 2 differs from the light-adjusting sheet 11 of Example 1 only in that it does not include the first light-absorbing layer 38 and the second light-absorbing layer 39, and in the composition of the coating liquid. The coating liquid has the following composition. The types and contents of the curing assistant, polymerization initiator, and spacer SP are the same as those of Example 1.

[0086] Liquid crystal compound LCM: phenyl-cyclohexyl liquid crystal (Merck, MNC-6609), 50% by mass Photopolymerizable compound: Isobornyl acrylate (product name: A-IB, manufactured by Shin-Nakamura Chemical Co., Ltd.), 44% by mass Dichroic dye: dibutyl adipate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 3% by mass [Example 3] The light-adjusting sheet 11 of Example 3 uses a liquid crystalline polymer having anisotropy in refractive index for the light-adjusting layer 31. The light-adjusting sheet 11 of Example 3 differs from the light-adjusting sheet 11 of Example 1 only in that it does not include the first light absorbing layer 38 and the second light absorbing layer 39, and in the composition of the coating liquid. The coating liquid has the following composition. The types and contents of the curing assistant, polymerization initiator, and spacer SP are the same as those of Example 1.

[0087] Liquid crystal compound LCM: Phenyl-cyclohexyl liquid crystal (Merck, MNC-6609), 50% by mass based on the total solid content of the coating liquid Photopolymerizable compound: isobornyl acrylate (product name: A-IB, manufactured by Shin-Nakamura Chemical Co., Ltd.), 29.5% by mass Liquid crystal monomer: the first monomer (2-propenonic acid, 2-methyl-, 6-[4-(4-heptylcyclohexyl)phenoxy]hexyl este) described in the third embodiment, 17.5% by mass [Example 4] The light-adjusting sheet 11 of Example 3 uses a liquid crystalline polymer having anisotropy in refractive index for the light-adjusting layer 31. The light-adjusting sheet 11 of Example 3 differs from the light-adjusting sheet 11 of Example 1 only in that it does not include the first light absorbing layer 38 and the second light absorbing layer 39, and in the composition of the coating liquid. The coating liquid has the following composition. The types and contents of the curing assistant, polymerization initiator, and spacer SP are the same as those of Example 1.

[0088] Liquid crystal compound LCM: Phenyl-cyclohexyl liquid crystal (Merck, MNC-6609), 50% by mass based on the total solid content of the coating liquid Photopolymerizable compound: isobornyl acrylate (product name: A-IB, manufactured by Shin-Nakamura Chemical Co., Ltd.), 29.5% by mass Liquid crystal monomer: the second monomer described in the third embodiment, 17.5% by mass [Example 5] In the light-controlling sheet 11 of Example 5, the light-controlling layer 31 contains a liquid crystal polymer having anisotropy in refractive index and a dichroic dye DP. The monomer forming the liquid crystal polymer is a first monomer, which is the same as in Example 3. The light-controlling sheet 11 of Example 5 differs from the light-controlling sheet 11 of Example 3 only in that the content of the photopolymerizable compound is 26.5% by mass and the content of the dichroic dye DP is 3% by mass. The dichroic dye DP is the same as the dichroic dye DP used in Example 2.

[0089] [Example 6] In the light-controlling sheet 11 of Example 6, the light-controlling layer 31 contains a liquid crystalline polymer having anisotropy in refractive index and a dichroic dye DP. The monomer forming the liquid crystalline polymer is a second monomer, which is the same as in Example 4. The light-controlling sheet 11 of Example 6 differs from the light-controlling sheet 11 of Example 4 only in that the content of the photopolymerizable compound is 26.5% by mass and the content of the dichroic dye DP is 3% by mass. The dichroic dye DP is the same as the dichroic dye DP used in Example 2.

[0090] [Comparative Example 1] The light-adjusting sheet 11 of Comparative Example 1 does not include the first light-absorbing layer 38 and the second light-absorbing layer 39, the dichroic dye DP, and the liquid crystal polymer having anisotropic refractive index. In other words, the light-adjusting sheet 11 of Comparative Example 1 differs from the light-adjusting sheet 11 of Example 1 only in that it does not include the first light-absorbing layer 38 and the second light-absorbing layer 39.

[0091] (Evaluation of diagonal visibility) As the measurement system, a haze meter (NDH7000SP, manufactured by Nippon Denshoku Industries Co., Ltd.) and an angle adjustment unit 53 (self-made) having a holding unit and an adjustment mechanism for adjusting the angle were used. The angle adjustment unit 53 was disposed between the light emitting unit 51 and the light receiving unit 52. Then, the oblique total light transmittance Tt and the oblique haze H were measured for the test piece 55 of each example while changing the incident angle θ. The measurement conditions of the haze meter were set so that the measurement conditions of the oblique total light transmittance Tt conformed to JIS K 7361-1:1997 (ISO 1468-1) and the measurement conditions of the oblique haze H conformed to JIS K 7136:2000 (ISO 14782:1999). The incident angles θ were set to 20°, 30°, 40°, 50°, and 60°.

[0092] Furthermore, the product of the oblique total light transmittance Tt and the oblique haze H was calculated, and the product was multiplied by a coefficient that makes the product 1 / 100 to obtain the oblique diffuse transmittance Td. As shown in FIG. 11, the oblique diffuse transmittance Td in Comparative Example 1 was 5.05 to 9.35, and the oblique diffuse transmittance Td increased as the incident angle θ increased.

[0093] When the oblique diffuse transmittance Td in Examples 1 to 6 is compared with the oblique diffuse transmittance Td in Comparative Example 1 at the same incident angle θ, the oblique diffuse transmittance Td in Examples 1 to 6 is all smaller than the oblique diffuse transmittance Td in Comparative Example 1.

[0094] The oblique diffuse transmittance Td in Example 1 was 1.69 to 5.41, and the oblique diffuse transmittance Td in Example 2 was 0.45 to 4.42. When the oblique diffuse transmittance Td in Example 1 and the oblique diffuse transmittance Td in Example 2 are compared at the same incident angle θ, the oblique diffuse transmittance Td in Example 2 was smaller than that in Example 1. In other words, although it depends on the content of the dichroic dye DP, it was confirmed that the dichroic dye DP has a high effect of absorbing scattered light.

[0095] The oblique diffuse transmittance Td in Example 3 was 0.35 to 2.70, and the oblique diffuse transmittance Td in Example 4 was 0.24 to 2.87. In Example 5, in which the dichroic dye DP was included in the light-controlling sheet 11 of Example 3, the oblique diffuse transmittance Td was 0.27 to 3.21, which was smaller than the oblique diffuse transmittance Td in Example 3 except when the incident angle was 60°. In Example 6, the oblique diffuse transmittance Td was 0.27 to 3.02, which was smaller than the oblique diffuse transmittance Td in Example 4 except when the incident angle was 60°. In other words, it was confirmed that the effect of absorbing scattered light was enhanced by including the dichroic dye DP in the light-controlling layer 31 in addition to the liquid crystal polymer.

[0096] (Visual level evaluation) While changing the angle of the sample by the angle adjustment unit 53, the observer visually observed the test piece 55 with the naked eye from the same direction as the light emitting unit 51, and judged the visual level LV by comparing with a sample showing the degree of white turbidity. The visual angle θ1 between the direction from the observer toward the test piece 55 and the normal direction of the test piece 55 was set to 20°, 30°, 40°, 50°, and 60°, similar to the incidence angle θ of the oblique visibility. Then, the visual level of the test piece 55 was judged by comparing the degree of white turbidity of the test piece 55 with samples of "visual level 0" to "visual level 6".

[0097] As shown in Figs. 13 to 19, in the samples 60 to 66 of "visual level 0" to "visual level 6", the light control sheet 11 to be photographed is superimposed on a dial on which characters are printed. On the dial, multiple patterns of "TOPPAN" (registered trademark), the logo of "Toppan Printing Co., Ltd.", are displayed with different colors of characters and background colors of characters. The samples 60 to 66 are divided into seven levels from visual level 0 to visual level 6 according to the degree of cloudiness observed when the light control sheet 11 is visually recognized by the naked eye, and the degree of cloudiness increases from visual level 0 to visual level 6. Visual level 0 or more and visual level 2 or less indicate a state in which no cloudiness is observed and the sheet is transparent, and visual level 2 to visual level 4 or less indicate a state in which some cloudiness is observed. Visual level 2 to visual level 4 or less indicates a degree of cloudiness to the extent that the observer can recognize the object through the light control sheet 11. Visual level 4 or more indicates a state in which the degree of cloudiness is strong. At visual level 4 or higher, the observer cannot recognize the object through the light controlling sheet 11.

[0098] The visual level in Comparative Example 1 was 2 to 5, and the visual level increased as the incident angle θ increased. When the visual level in Examples 1 to 6 is compared with that in Comparative Example 1 at the same incident angle θ, the visual level in each of Examples 1 to 6 was lower than that in Comparative Example 1. The visual level in Example 1 was 1 to 4, the visual level in Examples 2 and 3 was 1.5 to 4, the visual level in Example 4 was 1 to 4, and the visual level in Examples 5 and 6 was 0.5 to 2. In particular, it was found that the visual level in Examples 5 and 6, which included both the liquid crystalline polymer and the dichroic dye DP, was lower than that of the light control sheets in Examples 3 and 4, which included only the liquid crystalline polymer.

[0099] (Comparison with diagonal visibility and visual level) The oblique diffuse transmittance Td at each incident angle θ in Examples 1 to 6 and Comparative Example 1, and the visual level LV evaluated with the naked eye for the presence or absence of cloudiness from a direction of a viewing angle θ1 that is the same as the incident angle θ, were plotted on a graph with the oblique diffuse transmittance Td on the vertical axis and the visual level LV on the horizontal axis.

[0100] FIG. 12 is a scatter diagram showing the correlation between the oblique diffuse transmittance Td and the visual level LV. When the visual level LV is "transparent" between level 0 and level 2, the oblique diffuse transmittance Td is 0.3% or more and 5.0% or less. When the visual level LV is "slightly cloudy" between level 2 and level 4, the oblique diffuse transmittance Td is 2.2% or more and 5.6% or less, which is larger than the oblique diffuse transmittance Td when the visual level LV is "cloudy" between level 0 and level 2. When the visual level LV is "cloudy" between level 4 and 6, the oblique diffuse transmittance Td is 6.4% or more and 9.3% or less, which tends to be higher than the oblique diffuse transmittance Td when the visual level LV is "slightly cloudy" between level 2 and level 4.

[0101] Thus, the visual level LV tends to increase as the diagonal diffuse transmittance Td increases, and a correlation was found between the diagonal diffuse transmittance Td and the visual level LV. In particular, when the diagonal diffuse transmittance Td was 6% or less, the difference with the diagonal diffuse transmittance Td when the test piece 55 was "cloudy" was significant, and the visual level LV was "transparent" or "slightly cloudy," indicating high diagonal visibility.

[0102] (Modification) The above-described embodiments may be modified as follows: The above-described embodiments and the following modifications may be combined with each other to the extent that no technical contradiction occurs.

[0103] In the above embodiment, the diagonal total light transmittance Tt and the diagonal haze H are measured, and the diagonal diffuse transmittance Td is measured by calculating the product thereof. Instead of or in addition to this, the diagonal diffuse transmittance Td may be measured directly. In this case, similar to FIG. 8, the test piece 55 is placed at an angle to the parallel light beam emitted from the light-emitting unit 51, and the diffuse transmittance is measured by the light-receiving unit 52.

[0104] In the above embodiment, the spacers SP have the same color as the black color of the photochromic layer in the opaque state. Instead of or in addition to this, the spacers SP may have a color similar to the black color of the photochromic layer 31 in the opaque state. Alternatively, some or all of the spacers SP added to the photochromic layer 31 may be colorless and transparent, and the particle size may be adjusted to make the spacers less noticeable.

[0105] In the above embodiment, the light control layer 31 has a structure including an organic polymer layer 31P and a liquid crystal composition 31LC. Alternatively, the light control sheet 11 may be of the SPD (Suspended Particle Device) type having light control particles as alignment particles. The SPD type is a type in which a light control suspension containing light control particles is dispersed in a resin matrix. [Explanation of symbols]

[0106] DP: Dichroic dye LCM…liquid crystal compound SP…Spacer 10...Light control device 11...Light-adjusting sheet

Claims

1. A method for producing a light-controlling sheet comprising: a light-controlling layer containing a liquid crystal compound; a pair of transparent electrode layers sandwiching the light-controlling layer; and a pair of transparent support layers sandwiching the light-controlling layer and the pair of transparent electrode layers; the light-controlling sheet being switched between a transparent state and an opaque state by driving the liquid crystal compound, The angle of the light controlling sheet is adjusted so that the angle of incidence of the parallel light beam when it is incident on the light controlling sheet in the transparent state is a constant angle within a range of 20° to 60°, and The total light transmittance and the haze are measured when the incident light is incident on the light-adjusting sheet whose angle has been adjusted; and A measuring step of calculating an oblique diffuse transmittance obtained by multiplying the total light transmittance and the haze, The measurement step is performed a plurality of times with different angles of incidence, and a light-adjusting sheet is selected in which all of the oblique diffuse transmittances calculated in each of the measurement steps are equal to or less than a threshold value. A method for manufacturing light-controlling sheets.

2. The light-adjusting sheet having the oblique diffuse transmittance of 6.0% or less is selected. A method for producing the light controlling sheet according to claim 1.

3. The method further includes a step of adding the liquid crystal compound, a dichroic dye having anisotropy in absorbance, and a resin composition to form a coating liquid for the light-controlling layer on at least one of the pair of transparent electrode layers, and curing the resin composition to form the light-controlling layer. A method for producing the light controlling sheet according to claim 1 or 2.

4. The method further includes a step of bonding a colored and transparent light absorbing layer that absorbs a portion of visible light to at least one of the pair of surfaces of the light controlling sheet. A method for producing the light controlling sheet according to claim 1 or 2.

5. The method further comprises a step of applying a coating liquid containing the liquid crystal compound and a liquid crystal resin containing a liquid crystal polymer having anisotropy in refractive index to at least one of the pair of transparent electrode layers, aligning an alignment axis of the liquid crystal polymer with an alignment axis of the liquid crystal compound in the transparent state, and curing the liquid crystal resin. A method for producing the light controlling sheet according to claim 1 or 2.

6. A method for evaluating a light-controlling sheet that includes a light-controlling layer containing a liquid crystal compound, a pair of transparent electrode layers sandwiching the light-controlling layer, and a pair of transparent support layers sandwiching the light-controlling layer and the pair of transparent electrode layers, and that switches between a transparent state and an opaque state by driving the liquid crystal compound, comprising: The angle of the light controlling sheet is adjusted so that the angle of incidence of the parallel light beam when it is incident on the light controlling sheet in the transparent state is a constant angle within a range of 20° to 60°, and The total light transmittance and the haze are measured when the incident light is incident on the light-adjusting sheet whose angle has been adjusted; and A measuring step of calculating an oblique diffuse transmittance obtained by multiplying the total light transmittance and the haze, A method for evaluating light-adjusting sheets, comprising: performing the measurement process multiple times with different angles of incidence; and evaluating a light-adjusting sheet for which all of the oblique diffuse transmittances calculated in each of the measurement processes are below a threshold value as a light-adjusting sheet having high visibility when observed from an oblique angle.

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