Light control sheet, light control device, and light control sheet manufacturing method

Abstract

To provide a light control sheet, a light control device, and a light control sheet manufacturing method which can suppress a deterioration in characteristics of a light control layer due to impurities generated from an alignment layer.SOLUTION: A light control sheet 10 includes: a light control layer 20 containing a liquid crystal composition; a pair of alignment layers 51, 52 sandwiching the light control layer 20; and a pair of transparent electrode layers 31, 32 sandwiching the light control layer 20 and the pair of alignment layers 51, 52. The alignment layers 51, 52 have 4% or less of a thermogravimetric decrease rate when heated at 130°C for 30 minutes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a light control sheet, a light control device, and a method for manufacturing a light control sheet. [Background technology]

[0002] The light-adjusting sheet includes a light-adjusting layer containing a liquid crystal composition, and a pair of electrode sheets sandwiching the light-adjusting layer. The electrode sheet includes a transparent electrode layer facing the light-adjusting layer, and a transparent support layer supporting the transparent electrode layer on the opposite side of the transparent electrode layer. A driving voltage is applied between the transparent electrode layers of the pair of electrode sheets. Since the orientation state of the liquid crystal compound in the light-adjusting layer changes depending on whether or not the driving voltage is applied, it is possible to switch between a transparent state in which light is transmitted through the light-adjusting layer and an opaque state in which light transmission through the light-adjusting layer is suppressed by scattering or the like.

[0003] The light-controlling film is mounted on a transparent substrate such as a glass substrate. During this mounting process, high heat may be applied to the light-controlling film. For example, the intermediate film mounting technology involves sandwiching the light-controlling film between two transparent substrates and heating the transparent substrates to fix the light-controlling film between the transparent substrates.

[0004] When high heat is applied to the light-adjusting sheet, impurities are generated from the constituent layers of the light-adjusting sheet, and these impurities may penetrate into the light-adjusting layer, which may reduce properties such as the reliability of the alignment control of the liquid crystal compound in the light-adjusting layer. To address this problem, the light-adjusting sheet of Patent Document 1 has a surface treatment layer with barrier properties on the surface of the transparent support layer. This prevents low-molecular-weight impurities generated by hydrolysis or the like from the resin transparent support layer from penetrating into the light-adjusting layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6447757 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, a structure in which an alignment layer is provided between the light control layer and the transparent electrode layer is also known as a light control sheet structure. The alignment layer has the function of controlling the alignment of the liquid crystal compound when no driving voltage is applied. When high heat is applied to the light control sheet, impurities may be generated in the alignment layer. For example, when the polymer compound constituting the alignment layer has a polyimide skeleton generated via polyamic acid, the unreacted polyamic acid contained in the alignment layer reacts upon heating, resulting in the formation of low molecular weight impurities such as H 2 O is generated.

[0007] Unlike Patent Document 1, which targets impurities arising from the transparent support layer, the formation of a surface treatment layer cannot be used to solve problems caused by impurities arising from the alignment layer, because forming a surface treatment layer on the surface of the alignment layer would result in the alignment layer losing its function of controlling the alignment of the liquid crystal compound.

[0008] Therefore, there is a need for a method for suppressing the deterioration of the characteristics of the light-controlling layer caused by impurities generated in the alignment layer. [Means for solving the problem]

[0009] Various aspects of a light controlling sheet, a light controlling device, and a method for manufacturing a light controlling sheet to solve the above problems will be described below. [Aspect 1] A light-controlling sheet comprising a light-controlling layer containing a liquid crystal composition, a pair of alignment layers sandwiching the light-controlling layer, and a pair of transparent electrode layers sandwiching the light-controlling layer and the pair of alignment layers, wherein the thermal weight loss rate of the alignment layer when heated at 130°C for 30 minutes is 4% or less.

[0010] According to the above configuration, even if high heat is applied to the light-adjusting sheet, the generation of impurities in the alignment layer is suppressed, thereby suppressing deterioration of characteristics caused by impurities entering the light-adjusting layer.

[0011] [Aspect 2] The light-controlling sheet according to [Aspect 1], wherein the alignment layer contains a polymer compound having a skeleton made of polyimide or a polyimide precursor. According to the above configuration, an alignment layer having a function of controlling the alignment of liquid crystal compounds is suitably realized.

[0012] [Aspect 3] The light-controlling sheet described in [Aspect 2], wherein the polymer compound includes a structure produced by reacting a polyamic acid with a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group.

[0013] [Aspect 4] The light-controlling sheet according to [Aspect 2], wherein the alignment layer contains a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group.

[0014] According to the above-mentioned configurations, the polymer compound constituting the alignment layer is prevented from containing unreacted polyamic acid structures having carboxyl groups. Therefore, the generation of water as an impurity due to dehydration reaction during high-temperature heating is prevented. Therefore, it is possible to accurately realize an alignment layer with a thermal weight loss rate of 4% or less.

[0015] [Aspect 5] A light-adjusting device comprising the light-adjusting sheet described in any one of [Aspect 1] to [Aspect 4] and a control unit that controls the application of a driving voltage to the light-adjusting sheet, and changes the haze of the light-adjusting sheet by applying the driving voltage. According to the above configuration, a light-adjusting device including a light-adjusting sheet in which deterioration of characteristics due to high-temperature heating is suppressed is realized.

[0016] [Aspect 6] A method for manufacturing a light-controlling sheet, comprising: forming a first alignment layer on a first transparent electrode layer supported by a first transparent support layer; forming a second alignment layer on a second transparent electrode layer supported by a second transparent support layer; and forming a light-controlling layer containing a liquid crystal composition between the first alignment layer and the second alignment layer, wherein the first alignment layer and the second alignment layer are formed such that the thermal weight loss rate of the alignment layer when heated at 130°C for 30 minutes is 4% or less.

[0017] According to the above manufacturing method, the generation of impurities due to high-temperature heating in the alignment layer is suppressed, so that a light-controlling sheet can be obtained that can suppress the deterioration of the characteristics of the light-controlling layer due to the intrusion of impurities even when high heat is applied.

[0018] [Aspect 7] A method for manufacturing a light-controlling sheet as described in [Aspect 6], in which forming the first alignment layer and the second alignment layer includes firing each of the first alignment layer and the second alignment layer, and the firing temperature is set so that the thermal weight loss rate is 4% or less.

[0019] According to the above-mentioned manufacturing method, it is possible to precisely form an orientation layer having a thermal weight loss rate of 4% or less by controlling the firing temperature. Effect of the Invention

[0020] According to the present disclosure, it is possible to suppress deterioration of the characteristics of the light-controlling layer caused by impurities generated in the alignment layer. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing the configuration of a light adjusting sheet and a light adjusting device according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] An embodiment of a light controlling sheet, a light controlling device, and a method for manufacturing the light controlling sheet will be described with reference to the drawings. [Configuration of light control sheet and light control device] The overall configuration of the light controlling sheet and the light controlling device will be described with reference to FIG.

[0023] As shown in FIG. 1, the light-adjusting sheet 10 comprises a light-adjusting layer 20, a pair of transparent electrode layers, a first transparent electrode layer 31 and a second transparent electrode layer 32, a pair of transparent support layers, a first transparent support layer 41 and a second transparent support layer 42, and a pair of alignment layers, a first alignment layer 51 and a second alignment layer 52.

[0024] The light-adjusting layer 20 is located between the first transparent electrode layer 31 and the second transparent electrode layer 32. The first transparent support layer 41 supports the first transparent electrode layer 31 on the side opposite the light-adjusting layer 20 with respect to the first transparent electrode layer 31, and the second transparent support layer 42 supports the second transparent electrode layer 32 on the side opposite the light-adjusting layer 20 with respect to the second transparent electrode layer 32.

[0025] Furthermore, a first alignment layer 51 is located between the light control layer 20 and the first transparent electrode layer 31, and the first alignment layer 51 is in contact with both the light control layer 20 and the first transparent electrode layer 31. A second alignment layer 52 is located between the light control layer 20 and the second transparent electrode layer 32, and the second alignment layer 52 is in contact with both the light control layer 20 and the second transparent electrode layer 32. That is, the pair of alignment layers sandwich the light control layer 20, and the pair of transparent electrode layers sandwich the light control layer 20 and the pair of alignment layers.

[0026] The light-controlling layer 20 includes a transparent polymer layer and a liquid crystal composition. The transparent polymer layer has voids, and the voids are filled with the liquid crystal composition. The voids are spherical, ellipsoidal, or amorphous. The liquid crystal composition includes a liquid crystal compound having negative dielectric anisotropy. That is, the dielectric constant of the liquid crystal compound in the minor axis direction is higher than the dielectric constant in the major axis direction.

[0027] The light control layer 20 has a liquid crystal holding structure of any one of a polymer network type, a polymer dispersion type, and an capsule type. The polymer network type light control layer 20 has a polymer network having a three-dimensional mesh shape. The polymer network is an example of a transparent polymer layer, and a liquid crystal composition is held in the voids of the interconnected mesh in the polymer network. The polymer dispersion type light control layer 20 has a transparent polymer layer that defines a large number of isolated voids, and a liquid crystal composition is held in the voids dispersed in the transparent polymer layer. The capsule type light control layer 20 holds a liquid crystal composition in the voids in capsules dispersed in the transparent polymer layer.

[0028] Each of the first transparent electrode layer 31 and the second transparent electrode layer 32 has electrical conductivity and is transparent to light in the visible region. The material of the transparent electrode layers 31 and 32 is, for example, indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, poly(3,4-ethylenedioxythiophene), a silver alloy, or the like.

[0029] Each of the first transparent support layer 41 and the second transparent support layer 42 is a base material that is transparent to light in the visible region. The material of the transparent support layers 41 and 42 is, for example, a synthetic resin or an inorganic compound. Examples of the synthetic resin include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyacrylates such as polymethyl methacrylate, polycarbonates, polyolefins, etc. Examples of the inorganic compound include silicon dioxide, silicon oxynitride, silicon nitride, etc.

[0030] The transparent support layers 41 and 42 may have a surface treatment layer having a barrier property for suppressing the permeation of low molecular weight compounds on the surface thereof. The surface treatment layer is, for example, a photocurable resin film, a thermosetting resin film, an inorganic oxide film, or the like.

[0031] Each of the first alignment layer 51 and the second alignment layer 52 is a vertical alignment film that is transparent to light in the visible region. The first alignment layer 51 aligns the liquid crystal compound contained in the light-adjusting layer 20 so that the long axis direction of the liquid crystal compound is perpendicular to the surface of the first alignment layer 51 that is in contact with the light-adjusting layer 20. The second alignment layer 52 aligns the liquid crystal compound contained in the light-adjusting layer 20 so that the long axis direction of the liquid crystal compound is perpendicular to the surface of the second alignment layer 52 that is in contact with the light-adjusting layer 20.

[0032] A first connection portion 61 is disposed at an end of the first transparent electrode layer 31 for electrically connecting the first transparent electrode layer 31 to a control unit 60 that generates a voltage for driving the light adjusting sheet 10. A second connection portion 62 is disposed at an end of the second transparent electrode layer 32 for electrically connecting the second transparent electrode layer 32 to the control unit 60.

[0033] Each of the first connecting portion 61 and the second connecting portion 62 includes, for example, a conductive adhesive layer and a wiring board. The conductive adhesive layer is formed of, for example, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), an isotropic conductive film (ICF), an isotropic conductive paste (ICP), or the like. The wiring board is, for example, a flexible printed circuit board (FPC). Alternatively, each of the first connecting portion 61 and the second connecting portion 62 may have a structure in which a conductive material, such as a conductive tape, and a conductor are joined by soldering.

[0034] The transparent electrode layers 31, 32 are connected to a control unit 60 via wiring extending from connection parts 61, 62. The control unit 60 applies a driving voltage, which is a voltage for changing the alignment state of the liquid crystal compound, to the transparent electrode layers 31, 32 through the connection parts 61, 62. The control unit 60 controls the potential difference between the transparent electrode layers 31, 32 by controlling whether or not a voltage is applied and the magnitude of the voltage to be applied. The light control sheet 10, the control unit 60, and the connection parts 61, 62 constitute a light control device.

[0035] When no driving voltage is applied to the transparent electrode layers 31, 32, the liquid crystal compound is oriented perpendicular to the surfaces of the orientation layers 51, 52, that is, with the long axis direction aligned with the thickness direction of the light-controlling layer 20, due to the orientation restricting force of the orientation layers 51, 52. As a result, light is easily transmitted through the light-controlling layer 20. Therefore, when no driving voltage is applied, the light-controlling sheet 10 is in a transparent state.

[0036] When a drive voltage is applied to the transparent electrode layers 31 and 32, the liquid crystal compounds are oriented perpendicular to the direction of the electric field, i.e., with their long axes parallel to the surfaces of the alignment layers 51 and 52. As a result, light incident on the light-adjusting sheet 10 is easily scattered in the light-adjusting layer 20. Therefore, when a drive voltage is applied, the light-adjusting sheet 10 is in an opaque state and appears cloudy white. In the opaque state, the haze of the light-adjusting sheet 10 is greater than in the transparent state. As described above, the light controlling sheet 10 is switched between a transparent state and an opaque state by switching between application and release of the driving voltage.

[0037] The light-controlling sheet 10 is attached to a transparent substrate, which is the object to which it is attached. The transparent substrate is a glass substrate or a resin substrate. Examples of transparent substrates are windowpanes mounted on moving bodies such as vehicles and aircraft, windowpanes installed in buildings, and partitions installed inside vehicles or indoors. The surface to which the light-controlling sheet 10 is attached is flat or curved. The light-controlling sheet 10 may also be sandwiched between two transparent substrates. Furthermore, the light-controlling sheet 10 in an opaque state may be used as a screen onto which an image is projected.

[0038] [Materials for light control layer and alignment layer] The materials of the photochromic layer 20 and the alignment layers 51 and 52 will now be described in detail. The transparent polymer layer contained in the light-controlling layer 20 is a cured product of a photopolymerizable compound. The photopolymerizable compound has compatibility with the liquid crystal composition. The photopolymerizable compound may be an ultraviolet-curable compound or an electron beam-curable compound. When the photopolymerizable compound is an ultraviolet-curable compound, the size controllability of the voids in the transparent polymer layer can be improved. The photopolymerizable compound may be one type of polymerizable compound or may contain two or more types of polymerizable compounds.

[0039] An example of the ultraviolet curable compound includes a polymerizable unsaturated bond at the end of the molecular structure. Another example of the ultraviolet curable compound includes a polymerizable unsaturated bond at a position other than the end of the molecular structure. The ultraviolet curable compound is at least one selected from the group consisting of acrylate compounds, methacrylate compounds, thiol compounds, styrene compounds, and oligomers of each of these compounds. The acrylate compounds include diacrylate compounds, triacrylate compounds, and tetraacrylate compounds. Examples of the acrylate compounds are butyl ethyl acrylate, ethylhexyl acrylate, and cyclohexyl acrylate. The methacrylate compounds include dimethacrylate compounds, trimethacrylate compounds, and tetramethacrylate compounds. Examples of the methacrylate compounds are N,N-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, and tetrahydrofurfuryl methacrylate. Examples of the thiol compounds are 1,3-propanedithiol and 1,6-hexanedithiol. Examples of the styrene compounds are styrene and methylstyrene.

[0040] The liquid crystal composition contained in the light-controlling layer 20 contains a liquid crystal compound having a negative dielectric anisotropy. The liquid crystal compound is a non-polymerizable compound. The liquid crystal composition may contain one type of liquid crystal compound or two or more types of liquid crystal compounds.

[0041] The liquid crystal compound is at least one selected from the group consisting of Schiff base-based, azo-based, azoxy-based, biphenyl-based, terphenyl-based, benzoate-based, tolane-based, pyrimidine-based, pyridazine-based, cyclohexane carboxylate-based, phenylcyclohexane-based, biphenylcyclohexane-based, dicyanobenzene-based, naphthalene-based, and dioxane-based compounds.

[0042] The liquid crystal compound is, for example, a compound represented by the following structural formulas (1-1) to (1-11). The liquid crystal composition may contain only one of the compounds represented by the following structural formulas (1-1) to (1-11), or may contain two or more of them. In the following structural formulas (1-1) to (1-11), R 1 and R 2 are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkenyloxy group having 2 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is replaced by fluorine or chlorine.

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka] If the liquid crystal compound is a compound represented by any of the structural formulas (1-1) to (1-11) above, the alignment can be accurately controlled by the alignment layers 51 and 52 containing a polymer compound described below.

[0054] The ratio of the transparent polymer layer to the liquid crystal composition is preferably 20% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 60% by mass or less. If the ratio of the transparent polymer layer is within the above range, the size of the voids formed in the transparent polymer layer is appropriately ensured. Within the above range, the larger the ratio of the transparent polymer layer, the higher the mechanical strength of the transparent polymer layer can be, and the smaller the ratio of the transparent polymer layer, the lower the driving voltage of the light control sheet 10 can be.

[0055] In addition to the liquid crystal compound, the liquid crystal composition may contain a dichroic dye, a viscosity reducer, an antifoaming agent, an antioxidant, a weathering agent, and the like. When the liquid crystal composition contains a dichroic dye, the opaque light-control sheet can be colored differently from white. Examples of weathering agents include ultraviolet absorbers and light stabilizers. In addition to the transparent polymer layer and the liquid crystal composition, the light-control layer 20 may contain a spacer that defines the thickness of the light-control layer 20. The spacer is, for example, a bead spacer or a photospacer, and is dispersed in the transparent polymer layer. The thickness of the light-control layer 20 is, for example, 10 μm or more and 30 μm or less.

[0056] The alignment layers 51 and 52 contain a polymer compound. Examples of the polymer compound include polyimide polymers, polyamide polymers, acrylic polymers, polyester polymers, and polysiloxane polymers. In particular, the main chain of the polymer compound preferably has a skeleton made of polyimide or a polyimide precursor. The skeleton made of a polyimide precursor has a structure represented by the following general formula (2).

[0057] [ka] In the above general formula (2), R 1 represents a tetravalent organic group, and R 2 represents a divalent organic group, and A 1 and A 2 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms; A 3 and A 4 each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an acetyl group having 1 to 5 carbon atoms, and n represents a positive integer. An example of a polyimide precursor is a polyamic acid.

[0058] When the alignment layers 51, 52 contain a polymeric compound having a skeleton made of polyimide or a polyimide precursor, particularly when the polymeric compound is a compound generated from polyamic acid, it is preferable that the polymeric compound includes a structure generated by a reaction between a polyamic acid and a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group.

[0059] Hereinafter, a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group is referred to as a "specific compound", and a polymer compound including a structure produced by the reaction of a polyamic acid with a specific compound is referred to as a "specific polymer compound".

[0060] The specific compound may be a low molecular weight compound or a high molecular weight compound having the above-mentioned functional group. There are many types of low molecular weight compounds among the specific compounds having an epoxy group, but among them, it is preferable to use a compound having a functional group that reacts with the material of the light-controlling layer 20, since this increases the adhesion between the alignment layers 51, 52 and the light-controlling layer 20. Examples of such compounds include glycidyl acrylate, glycidyl methacrylate, (3,4-epoxycyclohexyl)methyl acrylate, allyl glycidyl ether, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, vinyl ethylene oxide, allyl glycidyl ether, 4-vinyl-1,2-epoxycyclohexane, and the like.

[0061] Among the specific compounds having an epoxy group, examples of polymeric compounds include copolymers containing glycidyl methacrylate. Commercially available products include Marproof (manufactured by NOF Corp.) and ARUFON UG-4000 series (manufactured by Toa Gosei Co., Ltd.).

[0062] Among the specific compounds having an oxazoline group, examples of low molecular weight compounds include 2-alkyl-2-oxazoline, 2-phenyl-2-oxazoline, 2,2'-bis(2-oxazoline), and 2,2'-(1,4-phenylene)bis(2-oxazoline).

[0063] Among the specific compounds having an oxazoline group, polymeric compounds can be obtained by copolymerization of oxazoline-containing monomers. Commercially available products include EPOCROS (manufactured by Nippon Shokubai). Among the specific compounds having a carbodiimide group, examples of low molecular weight compounds include N,N'-diisopropylcarbodiimide, N,N'-dicyclohexylcarbodiimide, N,N'-di-tert-butylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and the like.

[0064] Among the specific compounds having a carbodiimide group, the polymeric compound can be obtained by condensation polymerization of diisocyanate. An example of a commercially available product is Carbodilite (manufactured by Nisshinbo Chemical).

[0065] When the alignment layers 51 and 52 contain a specific polymer compound, the alignment layers 51 and 52 may contain unreacted specific compounds. The alignment layers 51 and 52 may contain one type of specific compound or two or more types of specific compounds.

[0066] The specific polymer compound can be produced by using a known method for producing polyimide. Specifically, a polyamic acid is produced by polymerization of a diamine compound and a tetracarboxylic acid, and an imidization reaction is carried out by dehydration and cyclization of the polyamic acid to obtain a polymer compound having a polyimide skeleton. At this time, the specific compound is added to the polyamic acid to carry out the imidization reaction, thereby obtaining the specific polymer compound.

[0067] [Manufacturing method of light control sheet] A method for manufacturing the light control sheet 10 will be described. First, a first sheet having a first transparent electrode layer 31 formed on a first transparent support layer 41 and a second sheet having a second transparent electrode layer 32 formed on a second transparent support layer 42 are prepared. The first transparent electrode layer 31 and the second transparent electrode layer 32 are formed by a known thin film formation method such as sputtering or vacuum deposition.

[0068] Next, a first alignment layer 51 is formed on the first transparent electrode layer 31, and a second alignment layer 52 is formed on the second transparent electrode layer 32. The alignment layers 51 and 52 are formed by forming a coating film by applying an alignment layer coating liquid and drying the coating film. The alignment layer coating liquid used to form the alignment layers 51 and 52 containing a specific polymer compound contains a polyamic acid, a specific compound, and a solvent.

[0069] The alignment layer coating liquid can be applied by known coating methods such as inkjet coating, gravure coating, spin coating, slit coating, bar coating, flexo coating, die coating, dip coating, and roll coating. The coating film may be dried at a high temperature to bake the alignment layers 51 and 52. The baking temperature is preferably 100° C. or higher and 200° C. or lower.

[0070] Next, a light-controlling layer coating liquid containing the material of the light-controlling layer 20 is produced, and a coating film that will become the light-controlling layer 20 is formed between the alignment layers 51 and 52 of the first sheet and the second sheet by applying the light-controlling layer coating liquid. The light-controlling layer coating liquid contains at least a photopolymerizable compound, a liquid crystal composition, and a polymerization initiator. The polymerization initiator is, for example, a diketone compound, an acetophenone compound, a benzoin compound, a benzophenone compound, a thioxanthone compound, or the like. The polymerization initiator may be one type of compound or a combination of two or more types of compounds. Examples of the polymerization initiator are benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and cyclohexyl phenyl ketone.

[0071] In the coating film formation process, a light-adjusting layer coating liquid is applied onto the alignment layer of one of the first and second sheets to form a coating film, and the other of the first and second sheets is superimposed onto the coating film to form a laminate in which the coating film is sandwiched between the alignment layers of the first and second sheets.

[0072] The coating liquid for the light-controlling layer can be applied by known coating methods such as drop casting, inkjet, gravure coating, spin coating, slit coating, bar coating, flexo coating, die coating, dip coating, and roll coating.

[0073] Next, the laminate is irradiated with light of a predetermined wavelength that promotes a polymerization reaction. The light of the predetermined wavelength is an electron beam or an ultraviolet ray. The light may be irradiated toward the first sheet, toward the second sheet, or toward both the first sheet and the second sheet. This causes a polymerization reaction of the photopolymerizable compound in the coating film to proceed, causing phase separation of the liquid crystal composition, and forming the light-controlling layer 20.

[0074] As a result of the above, a laminate is formed comprising the light-controlling layer 20, the alignment layers 51, 52, the transparent electrode layers 31, 32, and the transparent support layers 41, 42, and the laminate is subjected to external shaping, etc. as necessary to form the light-control sheet 10.

[0075] [Characteristics of light control sheet] In the light-adjusting sheet 10, the thermal weight loss rate of the alignment layers 51, 52 is 4% or less. The thermal weight loss rate is the ratio of the weight loss of the alignment layers 51, 52 after heating to the weight of the alignment layers 51, 52 before heating when the alignment layers 51, 52 are heated at 130° C. The thermal weight loss rate is measured using a thermogravimetric measuring device by using the alignment layers 51, 52 cut out by disassembling the light-adjusting sheet 10 as samples.

[0076] If the thermal weight loss rate of the alignment layers 51, 52 is 4% or less, impurities are prevented from being discharged from the alignment layers 51, 52 even when high heat is applied to the light-controlling sheet 10. This prevents impurities from entering the light-controlling layer 20 and deteriorating the characteristics of the light-controlling layer 20. In particular, when the light-controlling sheet 10 is mounted between two glass substrates using the intermediate film method involving high-temperature heating, deterioration of the characteristics of the light-controlling layer 20 is prevented.

[0077] The relationship between the configuration of the light controlling sheet 10 and the thermal weight loss rate will be described for the case where the alignment layers 51 and 52 contain a polymer compound produced from polyamic acid. The following formula (1) is a reaction formula showing a reaction for producing polyimide from polyamic acid. In the following formula (1), R 1 represents a tetravalent organic group, and R 2 represents a divalent organic group, and n represents a positive integer. By heating a polyamic acid at high temperatures, dehydration and cyclization occur in the polyamic acid, as shown in the following (formula 1), causing imidization, and producing a polyimide.

[0078] [ka] In the polyimide production reaction, not all of the repeating units of the polymer compound are imidized, and the repeating units of the polymer compound contained in the alignment layers 51, 52 may include repeating units of polyamic acid that have not been imidized, i.e., unreacted repeating units. In particular, when a highly flexible base material is used for the transparent support layers 41, 42 for the purpose of expanding applications or improving productivity, the baking temperature of the alignment layers 51, 52 is limited to a low temperature at which thermal deformation of the transparent support layers 41, 42 is suppressed, and the imidization rate is likely to be low.

[0079] When high heat is applied to the manufactured light-controlling sheet 10, imidization occurs in the unreacted repeating units, and the reaction by-product H 2 O is produced. H 2When O gets into the light-adjusting layer 20, the alignment of the liquid crystal compound is disrupted, leading to deterioration of the optical properties of the light-adjusting layer 20, such as haze.

[0080] In contrast, if the thermal weight loss rate of the alignment layers 51 and 52 is 4% or less as described above, the H in the alignment layers 51 and 52 can be reduced to a degree that suppresses the deterioration of the optical properties of the light-controlling layer 20. 2 The production of O is suppressed.

[0081] The thermal weight loss rate can be controlled by at least one of the material of the alignment layers 51 and 52 and the firing temperature. By forming the alignment layers 51 and 52 so as to contain a specific polymer compound, the thermal weight loss rate can be reduced. In this case, the alignment layers 51 and 52 are formed by baking a coating film containing polyamic acid and the specific compound. At this time, imidization occurs in some of the repeating units of the polyamic acid, and in other parts of the repeating units, the epoxy group, carbodiimide group, or oxazoline group of the specific compound reacts with the carboxyl group of the polyamic acid. As a result, even if the imidization rate is low, there is little remaining unreacted repeating unit having a carboxyl group. Therefore, even if high heat is applied to the light-controlling sheet 10 after manufacture, H due to the dehydration reaction is not generated. 2 Since the generation of O is suppressed, the thermal weight loss rate of the alignment layers 51 and 52 is reduced.

[0082] Moreover, the imidization rate can be increased by increasing the baking temperature of the alignment layers 51 and 52. This can reduce the number of unreacted repeating units in the polymer compound contained in the alignment layers 51 and 52. Therefore, even if high heat is applied to the light controlling sheet 10 after production, the imidization rate can be increased. 2 Since the generation of O is suppressed, the thermal weight loss rate of the alignment layers 51, 52 is reduced. Specifically, the firing temperature of the alignment layers 51, 52 is preferably 170° C. or higher. Reducing the thermal weight loss rate by increasing the firing temperature is particularly suitable when a highly heat-resistant material is used for the transparent support layers 41, 42.

[0083] In addition, when a specific compound is used as the material for the alignment layers 51, 52, the thermal weight loss rate can be 4% or less even if the firing temperature for the alignment layers 51, 52 is low. For example, the firing temperature may be 150° C. or less. If the firing temperature is low, a material that is easily deformed by heat can be used for the transparent support layers 41, 42, which increases the degree of freedom in the material for the transparent support layers 41, 42.

[0084] On the other hand, if the firing temperature of the alignment layers 51 and 52 is increased, it is possible to make the thermal weight loss rate 4% or less without using a specific compound as the material of the alignment layers 51 and 52. Therefore, it is possible to reduce the material cost of the alignment layers 51 and 52.

[0085] Furthermore, by selecting a material for the transparent polymer layer such that the transparent polymer layer contained in the photochromic layer 20 is a dense film, it is possible to prevent impurities generated in the alignment layers 51 and 52 from entering the photochromic layer 20. By adopting such a configuration for the photochromic layer 20 of this embodiment, it is possible to further prevent the deterioration of the optical properties of the photochromic layer 20 caused by impurities. On the other hand, if the thermal weight loss rate of the alignment layers 51 and 52 is 4% or less, it is possible to prevent the deterioration of the optical properties of the photochromic layer 20 caused by impurities regardless of the state of the film of the transparent polymer layer, so that the degree of freedom in the material of the transparent polymer layer can be increased.

[0086] Furthermore, even if the material of the alignment layers 51, 52 is different from the polymer compound generated from polyamic acid, as long as the thermal weight loss rate of the alignment layers 51, 52 is 4% or less, the intrusion of impurities from the alignment layers 51, 52 into the switchable layer 20 can be suitably suppressed. Therefore, the deterioration of the characteristics of the switchable layer 20 can be suppressed.

[0087] [Example] The above-mentioned light controlling sheet will be described using specific examples and comparative examples. (Preparation of polyamic acid solution) <Material> The diamine compounds and tetracarboxylic acid components used in the synthesis of the polyamic acid are described below. Diamine compound B1: 4,4'-diaminodiphenylmethane (Tokyo Chemical Industry Co., Ltd.) Diamine compound B2: 3,5-diaminobenzoic acid (Tokyo Chemical Industry Co., Ltd.) Tetracarboxylic dianhydride C1: 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride (Tokyo Chemical Industry Co., Ltd.) Tetracarboxylic dianhydride C2: 1,2,3,4-cyclobutanetetracarboxylic dianhydride (Tokyo Chemical Industry Co., Ltd.)

[0088] <Manufacturing method> In the first step, diamine compounds B1 and B2 and tetracarboxylic dianhydride C1 were mixed in the following ratio in N-ethyl-2-pyrrolidone (NEP) as a solvent and reacted for 5 hours at 80° C. to generate a first reaction liquid. Note that the weight parts of each material below indicate the relative weight ratio of each material used in the first and second steps. B1: 10 parts by weight B2 :8 parts by weight C1 :4 parts by weight NEP: 75 parts by weight

[0089] In the second step, tetracarboxylic dianhydride C2 and NEP were added to the first reaction solution in the following ratio, and reacted at 40° C. for 6 hours. This resulted in a polyamic acid solution. The concentration of the resin solid content in the polyamic acid solution was 25% by mass. C2: 16 parts by weight NEP: 38 parts by weight

[0090] (Production of Orientation Layer Coating Fluid) The above-mentioned polyamic acid solution was used as the first component, and the first component, the second component, and the solvents NEP and butyl cellosolve were mixed in the following ratio and stirred for 24 hours at 50° C. to produce an alignment layer coating liquid for forming an alignment layer. Note that the weight parts of each material below indicate the relative weight ratios of each material used to produce the alignment layer coating liquid. First component (polyamic acid solution): 16 parts by weight Second component: 1 part by weight NEP: 36 parts by weight Butyl cellosolve: 48 parts by weight

[0091] The compounds used as the second component are described below. Compound A1: Glycidyl acrylate (Tokyo Chemical Industry Co., Ltd.) Compound A2: (3,4-epoxycyclohexyl)methyl acrylate (Tokyo Chemical Industry Co., Ltd.) Compound A3: Epoxy group-containing acrylic polymer (Marproof G-0150M, NOF Corp.) Compound A4: Oxazoline group-containing polystyrene (Epocross RPS-1005, manufactured by Nippon Shokubai) Compound A5: Carbodiimide group-containing polymer (Carbodilite V-02B, manufactured by Nisshinbo Chemical Co., Ltd.) Compound A6: Condensation product of pentaerythritol and acrylic acid (Viscoat #300, manufactured by Osaka Organic Chemical Industry Co., Ltd.) Among the second components, compounds A1, A2, and A3 have an epoxy group, compound A4 has an oxazoline group, and compound A5 has a carbodiimide group. That is, compounds A1, A2, A3, A4, and A5 are specific compounds. Compound A6 has a hydroxyl group.

[0092] (Production of light-controlling layer coating liquid) A liquid crystal compound, a photopolymerizable compound, a polymerization initiator, and a spacer were mixed to produce a light-controlling layer coating liquid, which is a coating liquid for forming a light-controlling layer. Two types of coating liquids with different compositions were produced as the light-controlling layer coating liquid. Details of the materials in each coating liquid and their mixing ratios are listed below. In the following, the weight parts of each material indicate the relative weight ratio of each material used to produce the light-controlling layer coating liquid.

[0093] <Coating Liquid I> Liquid crystal composition: 50 parts by weight of fluorine-based nematic mixed liquid crystal (MLC-6608, manufactured by Merck) ·Photopolymerizable compounds: Isobornyl acrylate (A-IB, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 36 parts by weight Ethoxylated trimethylolpropane triacrylate (AT-20, manufactured by Shin-Nakamura Chemical Co., Ltd.) 10 parts by weight Pentaerythritol tetrakis(3-mercaptobutyrate) (Karends MT PE-1, manufactured by Showa Denko) 2 parts by weight Polymerization initiator: 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins BV) 1 part by weight Spacer: 1 part by weight of spherical particles made of divinylbenzene (manufactured by Sekisui Chemical Co., Ltd., particle size 10 μm) The liquid crystal composition is a nematic liquid crystal, and contains two liquid crystal compounds having negative dielectric anisotropy. The refractive index anisotropy Δn of the mixture of the two liquid crystal compounds is 0.20.

[0094] <Coating Liquid II> Liquid crystal composition: 50 parts by weight of fluorine-based nematic mixed liquid crystal (MLC-6608, manufactured by Merck) ·Photopolymerizable compounds: Isobornyl acrylate (A-IB, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 36 parts by weight Pentaerythritol tetraacrylate (A-TMMT, manufactured by Shin-Nakamura Chemical Co., Ltd.) 5 parts by weight Ethoxy polyethylene glycol acrylate (Light Acrylate 14EGA, Kyoeisha Chemical Co., Ltd.) 5 parts by weight Pentaerythritol tetrakis(3-mercaptobutyrate) (Karends MT PE-1, manufactured by Showa Denko) 2 parts by weight Polymerization initiator: 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins BV) 1 part by weight Spacer: 1 part by weight of spherical particles made of divinylbenzene (manufactured by Sekisui Chemical Co., Ltd., particle size 10 μm) The liquid crystal composition is a nematic liquid crystal, and contains two liquid crystal compounds having negative dielectric anisotropy. The refractive index anisotropy Δn of the mixture of the two liquid crystal compounds is 0.20.

[0095] (Formation of light control sheet) A first sheet, which is a laminate of the first transparent support layer and the first transparent electrode layer, was prepared by forming a first transparent electrode layer on the first transparent support layer by sputtering. Similarly, a second sheet, which is a laminate of the second transparent support layer and the second transparent electrode layer, was prepared by forming a second transparent electrode layer on the second transparent support layer by sputtering. For each of the first transparent support layer and the second transparent support layer, the material is polyethylene terephthalate and the thickness is 125 μm. For each of the first transparent electrode layer and the second transparent electrode layer, the material is indium tin oxide and the thickness is 30 nm.

[0096] Next, the alignment layer coating liquid was applied to the transparent electrode layers of the first and second sheets using a bar coater to form a coating film. The coating film was then baked by heating and drying for 4 minutes to form an alignment layer. The thickness of each alignment layer was 100 nm.

[0097] Next, the light-controlling layer coating liquid was dropped onto the alignment layer on the first sheet, and the first sheet and the second sheet were laminated together so that a coating film made of the light-controlling layer coating liquid was sandwiched between the alignment layers of the first sheet and the second sheet to obtain a laminate. The coating film had a thickness of 10 μm. A light-controlling layer was formed by irradiating the first transparent support layer of the laminate with 365 nm ultraviolet light, and a light-control sheet was obtained. The intensity of the ultraviolet light was 8 mW / cm. 2 The UV light irradiation time was 120 seconds.

[0098] (Configurations of Examples, Comparative Examples, and Reference Examples) Using the materials and processes described above, light-control sheets of Examples 1 to 8, Comparative Examples 1 and 2, and a reference example were obtained by varying at least one of the following: whether or not the second component was added to the alignment layer coating liquid, the compound used as the second component, the coating liquid used as the light-control layer coating liquid, and the baking temperature of the alignment layer.

[0099] (evaluation) <Thermogravimetric reduction rate> The alignment layer was cut out from the light-control sheet with a clean cutter, and the weight loss rate was measured when the alignment layer was heated at 130°C for 30 minutes in a nitrogen atmosphere. A differential thermal thermogravimetry device (STA7200RV, Hitachi High-Tech Science) was used to measure the thermal weight loss rate, and the sample was weighed in an aluminum cell.

[0100] <Haze> The haze of the light-controlling sheet in the transparent state was measured before and after the heat resistance test. The transparent state is when no AC voltage is applied between the transparent electrode layers of the light-controlling sheet, i.e., when no potential difference occurs between the transparent electrode layers. The haze was measured in accordance with JIS K 7136:2000. In the heat resistance test, the light-control sheet was heated in an oven at 130°C for 30 minutes. In the evaluation of haze, a haze of less than 10% was rated as good (◯), and a haze of 10% or more was rated as poor (×).

[0101] (Evaluation Results) Table 1 shows, for the examples, comparative examples, and reference examples, whether or not a second component was added to the alignment layer coating liquid, the compound used as the second component, the coating liquid used as the light-control layer coating liquid, the baking temperature of the alignment layer, and the results of each of the above-mentioned evaluation items.

[0102] [Table 1]

[0103] As shown in Table 1, in Examples 1 to 8, in which the thermal weight loss rate of the alignment layer is 4% or less, the haze of the transparent light control sheet after the heat resistance test is less than 10%, and the difference from the initial haze, i.e., before the heat resistance test, is small. Therefore, in Examples 1 to 8, it can be said that the deterioration of optical properties due to high-temperature heating is suppressed, and good optical properties are obtained even after the heat resistance test.

[0104] On the other hand, in Comparative Examples 1 and 2, in which the thermal weight loss rate of the alignment layer exceeded 4%, the haze of the transparent light-control sheet after the heat resistance test increased to more than 10%, indicating a significant decrease in optical properties due to high-temperature heating.

[0105] Among Examples 1 to 8 and Comparative Examples 1 and 2, in Examples 1 to 6, a specific compound is added as a second component to the alignment layer coating liquid. On the other hand, in Comparative Example 1, a second component is not added to the alignment layer coating liquid, and in Comparative Example 2, a compound different from the specific compound is added as a second component to the alignment layer coating liquid. The baking temperatures of the alignment layers in Examples 1 to 6 and Comparative Examples 1 and 2 are all the same low temperature. This suggests that it is possible to reduce the thermal weight loss rate by adding a specific compound to the alignment layer coating liquid.

[0106] In addition, in Examples 7 and 8, although no specific compound was added to the coating liquid for the alignment layer, the baking temperature of the alignment layer was as high as 170° C. or higher. This suggests that the thermal weight loss rate can also be reduced by increasing the baking temperature.

[0107] In the reference example, no specific compound is added to the alignment layer coating liquid, the baking temperature is low, and the thermal weight loss rate of the alignment layer exceeds 4%, but the deterioration of optical properties due to high-temperature heating is suppressed. The light-control layer coating liquid used in the reference example contains a monomer with a small double bond equivalent, which results in the formation of a dense transparent polymer layer in the light-control layer. As a result, even if impurities are generated in the alignment layer due to high-temperature heating, the intrusion of the impurities into the light-control layer is suppressed.

[0108] As in Example 6, if the thermal weight loss rate of the alignment layer is 4% or less and the coating liquid for the light-controlling layer contains a monomer with a small double bond equivalent, the deterioration of optical properties due to high-temperature heating can be further suppressed. On the other hand, even if the transparent polymer layer of the light-controlling layer is not highly dense as in Examples 1 to 5, 7, and 8, if the thermal weight loss rate of the alignment layer is 4% or less, the deterioration of optical properties due to high-temperature heating can be sufficiently suppressed, so that a high degree of freedom is obtained for the material of the light-controlling layer.

[0109] As described above in the embodiments and examples, the light controlling sheet can provide the following effects. (1) The thermal weight loss rate when the alignment layer is heated at 130°C for 30 minutes is 4% or less. This prevents impurities from being generated in the alignment layer even when high heat is applied to the light-control sheet, and prevents deterioration of properties caused by impurities entering the light-control layer. (2) If the alignment layer contains a polymer compound having a skeleton made of polyimide or a polyimide precursor, an alignment layer having a function of controlling the alignment of a liquid crystal compound can be suitably realized.

[0110] (3) The polymer compound contained in the alignment layer includes a structure produced by a reaction between a polyamic acid and a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group, and the alignment layer includes a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group.

[0111] According to the above-mentioned configuration, the polymer compound is prevented from containing unreacted polyamic acid structures having carboxyl groups. Therefore, the generation of water as an impurity due to dehydration reaction during high-temperature heating is prevented. Therefore, it is possible to accurately realize an alignment layer with a thermal weight loss rate of 4% or less.

[0112] (4) The firing temperature of the alignment layer is set to a high temperature so that the thermal weight loss rate is 4% or less. This makes it possible to accurately realize an alignment layer with a thermal weight loss rate of 4% or less. [Explanation of symbols]

[0113] 10. Light-adjusting sheet 20...Photochromic layer 31,32...Transparent electrode layer 41,42...Transparent support layer 51, 52...Alignment layer 60...Control unit

Claims

1. A light control layer including a liquid crystal composition; A pair of alignment layers sandwiching the light control layer; a pair of transparent electrode layers sandwiching the light control layer and the pair of alignment layers; The thermal weight loss rate of the alignment layer when heated at 130° C. for 30 minutes is 4% or less. Dimming sheet.

2. The alignment layer contains a polymer compound having a skeleton made of polyimide or a polyimide precursor. The light controlling sheet according to claim 1 .

3. The polymer compound includes a structure produced by a reaction between a polyamic acid and a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group. The light controlling sheet according to claim 2 .

4. The alignment layer contains a compound having at least one functional group selected from the group consisting of an epoxy group, a carbodiimide group, and an oxazoline group. The light controlling sheet according to claim 2 .

5. The light controlling sheet according to any one of claims 1 to 4, A control unit that controls application of a drive voltage to the light adjusting sheet, The haze of the light controlling sheet is changed by applying the driving voltage. Dimmer.

6. forming a first alignment layer on a first transparent electrode layer supported by a first transparent support layer, and forming a second alignment layer on a second transparent electrode layer supported by a second transparent support layer; forming a light control layer containing a liquid crystal composition between the first alignment layer and the second alignment layer; The first alignment layer and the second alignment layer are formed so that the thermal weight loss rate of the alignment layer is 4% or less when the alignment layer is heated at 130° C. for 30 minutes. A method for manufacturing light-controlling sheets.

7. forming the first alignment layer and the second alignment layer includes firing each of the first alignment layer and the second alignment layer; The baking temperature is set so that the thermal weight loss rate is 4% or less. A method for producing the light controlling sheet according to claim 6.

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