Liquid crystal light control element

Abstract

Provided is a liquid crystal light control element using a liquid crystal composition including a liquid crystal and a chiral compound, in which display defects due to alignment defects of the liquid crystal and burn-in defects do not occur even in an environment of prolonged exposure to light irradiation.　Provided is a liquid crystal light control element having a variable transmittance in response to voltage application, the liquid crystal light control element being characterized by comprising a pair of substrates provided with electrodes, a liquid crystal layer provided between the substrates and including liquid crystal molecules twist-aligned when a voltage is not applied, and a liquid crystal alignment film that substantially horizontally aligns the liquid crystal molecules in at least one direction between the substrate and the liquid crystal layer, the liquid crystal layer having a liquid crystal composition including liquid crystal molecules having positive dielectric anisotropy and a chiral compound, the liquid crystal alignment film including a polymer having a structure indicated by formula [1]of the following formula [1], and d / p being 1 to 10, where d is the thickness of the liquid crystal layer and p is the chiral pitch of the liquid crystals of the liquid crystal layer. (Each symbol in formula [1] is as defined in the specification.)

Description

Liquid crystal dimming element

[0001] The present invention relates to a liquid crystal light control element, a liquid crystal alignment film used therein, and a liquid crystal aligning agent for forming the liquid crystal alignment film.

[0002] As an alternative to conventional curtains and blinds, many electric light control devices have been proposed that variably control the amount of light transmission and visibility depending on the level of externally applied voltage, and liquid crystal light control devices are one such device. Various liquid crystal light control device types are known, including a guest-host liquid crystal type that uses liquid crystal and a dichroic dye. This type requires an increased amount of dichroic dye to increase the difference in transmittance between the transmissive state and the non-transmissive state (hereinafter also referred to as the "transmittance difference"). However, dichroic dyes generally have low solubility in liquid crystals, making it difficult to increase the amount. On the other hand, in the guest-host liquid crystal type, the transmittance difference can be increased by adding a chiral compound to the liquid crystal (see Patent Documents 1 to 3).

[0003] Japanese Unexamined Patent Publication No. 6-67173 Japanese Unexamined Patent Publication No. 2018-106080 Japanese Special Publication No. 2023-530439

[0004] In systems using a liquid crystal composition containing liquid crystal and a chiral compound, a large amount of chiral compound must be added to the liquid crystal to increase the transmittance difference. However, this large amount of chiral compound can cause poor alignment of the liquid crystal, making the liquid crystal light control device prone to display defects. Furthermore, because liquid crystal light control devices are sometimes attached to the window glass of automobiles or buildings, they must be able to withstand harsh environments where they are exposed to light for long periods of time. Furthermore, in such harsh environments, the voltage holding ratio, one of the electrical characteristics of the liquid crystal light control device, decreases, making them prone to image sticking, a type of display defect. Therefore, it is necessary for the voltage holding ratio to remain stable even when exposed to light for long periods of time. Therefore, an object of the present invention is to provide a liquid crystal light control device using a liquid crystal composition containing liquid crystal and a chiral compound that does not suffer from display defects due to poor alignment of the liquid crystal. Another object of the present invention is to provide a liquid crystal light control device that does not suffer from display defects and image sticking due to poor alignment of the liquid crystal, even when exposed to light for long periods of time.

[0005] As a result of intensive research by the inventors to achieve the above object, they have completed the present invention, which has the following gist: A liquid crystal light control element whose transmittance is variable in response to the application of voltage, comprising: a pair of substrates each having an electrode; a liquid crystal layer provided between the substrates and containing liquid crystal molecules that are twist-aligned when no voltage is applied; and a liquid crystal alignment film provided on at least one side between the substrates and the liquid crystal layer and having the function of aligning the liquid crystal molecules approximately horizontally, wherein the liquid crystal layer contains a liquid crystal composition containing liquid crystal molecules having positive dielectric anisotropy and a chiral compound, and the liquid crystal alignment film contains a polymer (hereinafter also referred to as a "specific polymer") having a structure (hereinafter also referred to as a "specific structure") of the following formula [1], wherein d / p is 1 to 10, where d is the thickness of the liquid crystal layer and p is the chiral pitch of the liquid crystal in the liquid crystal layer.

[0006] (X １ is a single bond, -(CH ２ ) ａ -(a is an integer of 1 to 15), -O-, -CH２ O-, -CONH-, -NHCO-, -CON(CH ３ ) -, -N(CH ３ ) represents CO—, —COO—, or —OCO—. X ２ and X ３ each independently represents at least one divalent cyclic group selected from a benzene ring, a cyclohexane ring, and a heterocycle, and any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. X ４ represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, or an alkoxy group having 1 to 18 carbon atoms. Xn represents an integer of 0 or 1. * represents a bond.

[0007] According to the present invention, a liquid crystal light control device using a liquid crystal composition containing a liquid crystal having positive dielectric anisotropy and a chiral compound does not suffer from display defects due to poor liquid crystal alignment, and furthermore, even when exposed to high temperature, high humidity, or light irradiation for long periods of time, a liquid crystal light control device is obtained that does not suffer from display defects and image sticking due to poor liquid crystal alignment. Therefore, the liquid crystal light control device of the present invention is useful for light control windows and optical shutters that control the transmission and blocking of light. The mechanism by which the present invention provides a liquid crystal light control device with the above-mentioned excellent properties is not necessarily clear, but is roughly presumed to be as follows.

[0008] The liquid crystal alignment film of the present invention is obtained from a liquid crystal aligning agent containing a specific polymer having the specific structure of the above formula [1]. Because this specific structure is rigid, it is possible to obtain more stable liquid crystal alignment than with conventional flexible alkyl group structures. Therefore, a liquid crystal light control device exhibiting good optical properties can be obtained. Furthermore, because the specific structure of the present invention is rigid, it is less likely to decompose even when irradiated with light. Therefore, it is possible to suppress the generation of ionic impurities, which are a cause of a decrease in voltage holding ratio.

[0009] The present invention will be described in detail below. <Specific Structure> The specific structure is a structure of the above formula [1]. In formula [1], X １ ~X４ and Xn are as defined above, but among them, the following are preferred: X １ From the viewpoint of availability of raw materials and ease of synthesis, -O-, -CH ２ O-, -CONH-, -NHCO-, -CON(CH ３ ) -, -N(CH ３ )CO—, —COO—, or —OCO— is preferred. —O—, —CH ２ X is —O—, —CONH—, —NHCO—, —COO—, or —OCO—. ２ and X ３ are each independently preferably a benzene ring or a cyclohexane ring. ４ is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. More preferably, it is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. Xn is preferably an integer of 1.

[0010] <Specific Polymer> The specific polymer is not particularly limited, but is preferably at least one polymer selected from a polyimide precursor and a polyimide. When a polyimide precursor or a polyimide (hereinafter also collectively referred to as a "polyimide-based polymer") is used as the specific polymer, it is preferably obtained by reacting a diamine component with a tetracarboxylic acid component. The polyimide precursor is preferably a polyamic acid or a polyamic acid ester having a structure of the following formula [A]:

[0011] (R ａ represents a tetravalent organic group. ｂ represents a divalent organic group. １ and A ２ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and may be the same or different. ３ and A ４ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an acetyl group, and may be the same or different. n represents a positive integer.

[0012] The polyimide has a structure of the following formula [A-4] and can be obtained by ring-closing (hereinafter also referred to as "imidization") a polyamic acid of a polyimide precursor. In this case, if the ring-closure rate of the amic acid group (hereinafter also referred to as "imidization rate") is less than 100%, the polyimide contains at least one of the structures of the following formulas [A-1] to [A-3] in addition to the structure of formula [A-4].

[0013] (R ａ , R ｂ and A １ ~A ４ is defined as in the above formula [A].) The diamine component is a diamine having two primary or secondary amino groups in the molecule, and examples of the tetracarboxylic acid component include a tetracarboxylic acid compound, a tetracarboxylic acid dianhydride, a tetracarboxylic acid dihalide compound, a tetracarboxylic acid dialkyl ester compound, and a tetracarboxylic acid dialkyl ester dihalide compound.

[0014] The polyimide polymer is preferably a polyamic acid having a repeating unit structure of the following formula [D] or a polyimide obtained by imidizing the polyamic acid, because the polyimide polymer can be obtained relatively easily by using a tetracarboxylic dianhydride of the following formula [B] and a diamine of the following formula [C] as raw materials. (R ａ and R ｂ has the same meaning as defined in the above formula [A]. (R ａ and R ｂ has the same meaning as defined in the above formula [A]. n represents a positive integer.

[0015] In addition, a polymer having a repeating unit structure of the above formula [D] may be synthesized by a conventional synthesis method. １ and A ２ and A in formula [A] ３ and A ４It is also possible to introduce an alkyl group or an acetyl group having 1 to 5 carbon atoms. In the method for introducing the specific structure into the polyimide polymer, it is preferable to use a diamine having the specific structure as part of the raw material. In particular, it is preferable to use a diamine of the following formula [1a] (hereinafter also referred to as "specific diamine").

[0016] X represents the structure of the above formula [1]. １ ~X ４ Details of Xn and preferred combinations are as described above. Xm represents an integer of 1 to 4. Of these, an integer of 1 or 2 is preferred. An integer of 1 is more preferred. Specific examples of the specific diamine include diamines of the following formulas [1a-1] to [1a-18], and it is preferable to use these. Of these, formula [1a-1], formula [1a-2], formula [1a-4], formula [1a-5], formula [1a-7], formula [1a-8], formula [1a-10], formula [1a-11], formula [1a-13], or formula [1a-14] is preferred. From the viewpoint of suitably obtaining the effects of the present invention, formula [1a-1], formula [1a-2], formula [1a-4], formula [1a-5], formula [1a-10], formula [1a-11], formula [1a-13] or formula [1a-14] is more preferred.

[0017]

[0018] (R １ respectively represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. The cis-trans isomer of 1,4-cyclohexylene is a trans isomer.)

[0019] From the viewpoint of optimally achieving the effects of the present invention, the proportion of the specific diamine used is preferably 1 to 20 mol % relative to the total diamine component. More preferably, it is 2 to 20 mol %. Particularly preferably, it is 5 to 20 mol %. Furthermore, the specific diamine can be used alone or in a mixture of two or more types depending on the properties. For the polyimide polymer, diamines other than the specific diamine can be used as other diamines as the diamine component. Specific examples include the other diamine compounds described in paragraphs

[0044] to

[0051] of WO 2013 / 125595 and the diamines of the following formulas [DA-1] to [DA-103]. Furthermore, the other diamines can be used alone or in a mixture of two or more types depending on the properties.

[0020]

[0021]

[0022]

[0023]

[0024]

[0025] As the tetracarboxylic acid component for producing the polyimide-based polymer, it is preferable to use a tetracarboxylic acid dianhydride represented by the following formula [2], or a tetracarboxylic acid derivative thereof, such as a tetracarboxylic acid, a tetracarboxylic acid dihalide, a tetracarboxylic acid dialkyl ester, or a tetracarboxylic acid dialkyl ester dihalide (hereinafter, all of these are also collectively referred to as a "specific tetracarboxylic acid component").

[0026] Z represents at least one selected from the structures of the following formulae [2a] to [2l]. (Z Ａ ~Z Ｄ each independently represents a hydrogen atom, a methyl group, a chlorine atom or a benzene ring. Ｅ and Z Ｆeach independently represents a hydrogen atom or a methyl group.

[0027] Among these, from the viewpoints of ease of synthesis and ease of polymerization reactivity when producing a polymer, Z is preferably Formula [2a], Formula [2c], Formula [2d], Formula [2e], Formula [2f], Formula [2g], Formula [2k], or Formula [2l]. Formula [2a], Formula [2e], Formula [2f], Formula [2g], Formula [2k], or Formula [2l] is more preferred. Formula [2a], Formula [2e], Formula [2f], Formula [2g], Formula [2k], or Formula [2l] is particularly preferred. The proportion of the specific tetracarboxylic acid component used is preferably 1 mol% or more relative to the total tetracarboxylic acid components used in the synthesis of the polyimide polymer. More preferably, it is 5 mol% or more. Particularly preferably, it is 10 mol% or more. Most preferably, it is 10 to 100 mol% from the viewpoint of optimally obtaining the effects of the present invention.

[0028] The polyimide polymer can use tetracarboxylic acid components other than the specific tetracarboxylic acid component. Examples of the other tetracarboxylic acid components include the tetracarboxylic acid compounds, tetracarboxylic acid dianhydrides, dicarboxylic acid dihalide compounds, dicarboxylic acid dialkyl ester compounds, and dialkyl ester dihalide compounds shown below. Specific examples include the other tetracarboxylic acid components described in paragraph

[0057] of WO 2015 / 012368, and the tetracarboxylic acid dianhydrides and derivatives thereof represented by the following formulae [CA-1] to [CA-26]. The specific tetracarboxylic acid component and the other tetracarboxylic acid component can be used alone or in combination of two or more depending on the respective properties.

[0029]

[0030] The method for synthesizing a polyimide polymer is not particularly limited. It is typically obtained by reacting a diamine component with a tetracarboxylic acid component. Specific examples include the methods described in paragraphs

[0059] and

[0059] of WO 2015 / 012368. Polyamic acid esters can be synthesized by known methods, such as reacting a polyamic acid of a polyimide precursor obtained by reacting a diamine component with a tetracarboxylic acid component with an esterifying agent, reacting the tetracarboxylic acid diester with a diamine, or reacting the tetracarboxylic acid diester with a dihalide. The solvent used in the reaction between the diamine component and the tetracarboxylic acid component is not particularly limited as long as it dissolves the resulting polyimide precursor. Specific examples include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and 1,3-dimethyl-imidazolidinone. When the polyimide precursor has high solvent solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or a solvent represented by the following formulas [D1] to [D3] can be used.

[0031] (D １ and D ２ represents an alkyl group having 1 to 3 carbon atoms. ３ represents an alkyl group having 1 to 4 carbon atoms.)

[0032] These may be used alone or in combination. Furthermore, even if a solvent does not dissolve the polyimide precursor, it may be mixed with the above solvent to the extent that precipitation does not occur. Furthermore, since moisture in the solvent inhibits the polymerization reaction and may even cause hydrolysis of the polyimide precursor, it is preferable to use a dehydrated and dried solvent. In the polymerization reaction of the polyimide precursor, the total number of moles of tetracarboxylic acid components is preferably 0.8 to 1.2 when the total number of moles of diamine components is 1.0. When the total number of moles of tetracarboxylic acid components is less than 1.0, i.e., when the total number of moles of tetracarboxylic acid components is smaller than the number of moles of diamine components, the polymer will have an amino group structure at its terminal. When the total number of moles of tetracarboxylic acid components is greater than the number of moles of diamine components, the polymer will have a carboxylic acid anhydride or dicarboxylic acid structure at its terminal.

[0033] Polyimides are obtained by ring-closing a polyimide precursor, and the imidization rate does not necessarily need to be 100% and can be adjusted as desired depending on the application and purpose. From the viewpoint of solubility in solvents, an imidization rate of 30 to 90% is preferable. A rate of 40 to 90% is even more preferable. Polyimide-based polymers may be converted into end-capped polymers using an end-capping agent. End-capped polymers have the effect of increasing the film hardness of liquid crystal alignment films and improving adhesion between the liquid crystal alignment film and the sealant in liquid crystal dimming devices. Furthermore, the method for obtaining end-capped polymers is not particularly limited. Specific examples include the methods described in paragraphs

[0046] and

[0047] of WO 2023 / 074568. From the viewpoints of the strength of the liquid crystal alignment film obtained therefrom, workability during film formation, and coating properties, the molecular weight of the polyimide polymer is preferably 5,000 to 1,000,000, more preferably 10,000 to 150,000, in terms of polyethylene glycol oxide (Mw) measured by Gel Permeation Chromatography (GPC).

[0034] <Liquid Crystal Alignment Agent> The liquid crystal aligning agent is a solution for forming a liquid crystal alignment film, and is a solution containing a specific polymer and a solvent. Two or more types of specific polymers can be used. The polymer components do not have to be all specific polymers, and a polymer without a specific structure may be mixed. In this case, the proportion of the polymer without a specific structure used is preferably 10 to 200 parts by mass, more preferably 10 to 100 parts by mass, per 100 parts by mass of the specific polymer. The solvent content in the liquid crystal aligning agent can be appropriately selected from the viewpoints of the application method of the liquid crystal aligning agent and obtaining the desired film thickness. In particular, from the viewpoint of forming a uniform liquid crystal alignment film by application, the solvent content in the liquid crystal aligning agent is preferably 50 to 99.9% by mass, more preferably 60 to 99% by mass, and particularly preferably 65 to 99% by mass.

[0035] The solvent used for the liquid crystal aligning agent is not particularly limited as long as it is a solvent that can dissolve the specific polymer. Among them, the following solvents (hereinafter also referred to as "Solvent A") are preferably used. For example, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyllactamide, N,N-dimethylpropionamide, tetramethylurea, N,N-diethylformamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, γ-valerolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropanamide, Examples of suitable solvents include 3-butoxy-N,N-dimethylpropanamide, N-(n-propyl)-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-(n-butyl)-2-pyrrolidone, N-(tert-butyl)-2-pyrrolidone, N-(n-pentyl)-2-pyrrolidone, N-methoxypropyl-2-pyrrolidone, N-ethoxyethyl-2-pyrrolidone, N-methoxybutyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone (hereinafter, these are also collectively referred to as "good solvents"). Among these, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, and γ-butyrolactone are preferred. These solvents may be used alone or in combination of two or more.

[0036] When the specific polymer has high solubility in the solvent, the following solvent (hereinafter also referred to as "Solvent B") can be used.For example, diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, 1-(2-butoxyethoxy)-2-propanol, 2-(2-butoxyethoxy) (oxy)-1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, diethylene glycol monopropyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, ethylene glycol monoethyl ether, n-butyl acetate, propylene glycol monoethyl ether acetate, cyclohexyl acetate, 4-methyl-2-pentyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isoamyl lactate, diethylene glycol monoethyl ether, or diisobutyl ketone (2,6-dimethyl-4-heptanone).Among these, diisobutyl carbinol, propylene glycol monobutyl ether, propylene glycol diacetate, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, or diisobutyl ketone are preferably used. These may be used alone or in combination of two or more.

[0037] In the present invention, from the viewpoint of the coating properties of the liquid crystal alignment film, it is preferable to use a solvent that is a combination of Solvent A and Solvent B. Specific examples include N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone, N-ethyl-2-pyrrolidone and propylene glycol diacetate, N,N-diphenyl ether, N-methyl-2-pyrrolidone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolact ...methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-buty Methyl lactamide and diisobutyl ketone, N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate, N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate, N-methyl-2-pyrrolidone, ethyl 3-ethoxypropionate and dipropylene glycol monomethyl ether, N-ethyl-2-pyrrolidone, ethyl 3-ethoxypropionate and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, ethyl 3-ethoxypropionate and diethylene glycol monopropyl ether, N -Ethyl-2-pyrrolidone, ethyl 3-ethoxypropionate, and diethylene glycol monopropyl ether, N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether acetate, N-ethyl-2-pyrrolidone and dipropylene glycol dimethyl ether, N,N-dimethyl lactamide and ethylene glycol monobutyl ether, N,N-dimethyl lactamide and propylene glycol diacetate, N-ethyl-2-pyrrolidone and diethylene glycol diethyl ether, N-ethyl-2-pyrrolidone N-methyl-2-pyrrolidone, diethylene glycol monomethyl ether, and butyl cellosolve acetate, N-methyl-2-pyrrolidone, diethylene glycol monomethyl ether, and butyl cellosolve acetate, N,N-dimethyl lactamide and diethylene glycol diethyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone, and diethylene glycol diethyl ether, N-ethyl-2-pyrrolidone, N-methyl-2-pyrrolidone, and 4-hydroxy-4-methyl-2-pentanone,N-ethyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and diisobutyl ketone, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and dipropylene glycol monomethyl ether, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone, and dipropylene glycol monomethyl ether Methyl-2-pentanone and propylene glycol diacetate, N-ethyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and dipropylene glycol dimethyl ether, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutyl ketone, N-methyl-2-pi rolidone, γ-butyrolactone, propylene glycol monobutyl ether, and diisopropyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether, and diisobutylcarbinol, N-methyl-2-pyrrolidone, γ-butyrolactone, and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone, propylene glycol monobutyl ether, and dipropylene glycol dimethyl ether, N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and dipropylene glycol pyrene glycol monomethyl ether, N-ethyl-2-pyrrolidone, diethylene glycol diethyl ether, and dipropylene glycol monomethyl ether, N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and propylene glycol diacetate, N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and diisobutyl ketone, N-ethyl-2-pyrrolidone, γ-butyrolactone, and diisobutyl ketone, N-ethyl-2-pyrrolidone, N,N-dimethyl lactamide, and diisobutyl ketone,Examples of the combination include N-methyl-2-pyrrolidone, ethylene glycol monobutyl ether, and ethylene glycol monobutyl ether acetate, γ-butyrolactone, ethylene glycol monobutyl ether acetate, and dipropylene glycol dimethyl ether, N-ethyl-2-pyrrolidone, ethylene glycol monobutyl ether acetate, and propylene glycol dimethyl ether, N-methyl-2-pyrrolidone, 4-methyl-2-pentyl acetate, and ethylene glycol monobutyl ether, N-ethyl-2-pyrrolidone, cyclohexyl acetate, and 4-hydroxy-4-methyl-2-pentanone, cyclohexanone, and propylene glycol monomethyl ether, cyclopentanone, and propylene glycol monomethyl ether, and N-methyl-2-pyrrolidone, cyclohexanone, and propylene glycol monomethyl ether, and combinations of these are preferred.

[0038] When solvents A and B are used in combination, solvent B preferably accounts for 1 to 99% by mass of the total solvent contained in the liquid crystal aligning agent. More preferably, it is 10 to 99% by mass. Most preferably, it is 20 to 95% by mass. In order to increase the film strength of the liquid crystal alignment film, it is preferable that the liquid crystal aligning agent incorporates a compound having at least one structure selected from an epoxy group, an isocyanate group, an oxetanyl group, a cyclocarbonate group, a hydroxy group, a hydroxyalkyl group, a lower alkoxyalkyl group, and a polymerizable unsaturated group (hereinafter, collectively referred to as a "crosslinkable compound"). In this case, the compound must contain two or more of these groups.

[0039] Specific examples of the crosslinkable compound having an epoxy group or an isocyanate group include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, bisphenol A type epoxy resins such as Epicoat 828 (manufactured by Mitsubishi Chemical Corporation), bisphenol F type epoxy resins such as Epicoat 807 (manufactured by Mitsubishi Chemical Corporation), YX-8000 (manufactured by Mitsubishi Chemical Corporation), ), biphenyl skeleton-containing epoxy resins such as YX6954BH30 (manufactured by Mitsubishi Chemical Corporation), phenol novolac epoxy resins such as EPPN-201 (manufactured by Nippon Kayaku Co., Ltd.), (o, m, p-) cresol novolac epoxy resins such as EOCN-102S (manufactured by Nippon Kayaku Co., Ltd.), compounds in which a tertiary nitrogen atom is bonded to an aromatic carbon atom such as tetrakis(glycidyloxymethyl)methane, N,N,N',N'-tetraglycidyl-1,4-phenylenediamine, N,N,N',N'-tetraglycidyl-2,2'-dimethyl-4.4'-diaminobiphenyl, 2,2-bis[4-(N,N-diglycidyl-4-aminophenoxy)phenyl]propane, and N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane;N,N,N',N'-tetraglycidyl-1,2-diaminocyclohexane, N,N,N',N'-tetraglycidyl-1,3-diaminocyclohexane, N,N,N',N'-tetraglycidyl-1,4-diaminocyclohexane, bis(N,N-diglycidyl-4-aminocyclohexyl)methane, bis(N,N-diglycidyl-2-methyl-4-aminocyclohexyl)methane, bis(N,N-diglycidyl-3-methyl-4-aminocyclohexyl)methane, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,4-bis(N,N-diglycidylaminomethyl)cyclohexane, 1 ,3-bis(N,N-diglycidylaminomethyl)benzene, 1,4-bis(N,N-diglycidylaminomethyl)benzene, 1,3,5-tris(N,N-diglycidylaminomethyl)cyclohexane, 1,3,5-tris(N,N-diglycidylaminomethyl)benzene and other compounds in which a tertiary nitrogen atom is bonded to an aliphatic carbon atom; isocyanurate compounds such as triglycidyl isocyanurate such as TEPIC (manufactured by Nissan Chemical Industries, Ltd.); and those described in paragraph

[0037] of Japanese Patent Laid-Open Publication No. 10-338880 and paragraphs

[0051] to

[0054] of WO2017 / 170483.

[0040] Specific examples of the crosslinkable compound having an oxetanyl group include 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene (Aronoxetane OXT-121 (XDO)), bis[2-(3-oxetanyl)butyl]ether (Aronoxetane OXT-221 (DOX)), 1,4-bis[(3-ethyloxetan-3-yl)methoxy]benzene (HQOX), 1,3-bis[(3-ethyloxetan-3-yl)methoxy]benzene (RSOX), 1,2-bis[(3-ethyloxetan-3-yl)methoxy]benzene (CTOX), and those described in paragraphs

[0170] to

[0175] of WO2011 / 132751.

[0041] Specific examples of crosslinkable compounds having an oxazoline group include compounds such as 2,2'-bis(2-oxazoline) and 2,2'-bis(4-methyl-2-oxazoline), polymers and oligomers having an oxazoline group such as EPOCROS (manufactured by Nippon Shokubai Co., Ltd.), and those described in paragraph

[0115] of Japanese Patent Publication No. 2007-286597. Specific examples of crosslinkable compounds having a cyclocarbonate group include N,N,N',N'-tetra[(2-oxo-1,3-dioxolan-4-yl)methyl]-4,4'-diaminodiphenylmethane, N,N'-di[(2-oxo-1,3-dioxolan-4-yl)methyl]-1,3-phenylenediamine, and those described in paragraphs

[0025] to

[0030] and

[0032] of WO2011 / 155577.

[0042] Specific examples of crosslinkable compounds having a blocked isocyanate group include Coronate AP Stable M, Coronate 2503, 2515, 2507, 2513, 2555, and Millionate MS-50 (manufactured by Tosoh Corporation), Takenate B-830, B-815N, B-820NSU, B-842N, B-846N, B-870N, B-874N, and B-882N (manufactured by Mitsui Chemicals, Inc.), and those described in paragraphs

[0046] to

[0047] of Japanese Patent Publication No. 2014-224978 and paragraphs

[0119] to

[0120] of WO2015 / 141598.

[0043] Specific examples of crosslinkable compounds having a hydroxy group, a hydroxyalkyl group, or a lower alkoxyalkyl group include N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide, 2,2-bis(4-hydroxy-3,5-dihydroxymethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethoxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dihydroxymethylphenyl)-1,1,1,3,3,3-hexafluoropropane, and those described in paragraph

[0058] of Japanese Patent Publication No. 2016-118753, paragraph

[0055] of Japanese Patent Publication No. 2016-200798, and paragraphs

[0017] to

[0029] of WO2010 / 074269.

[0044] Specific examples of the crosslinkable compound having a polymerizable unsaturated group include glycerin mono(meth)acrylate, glycerin di(meth)acrylate (1,2-, 1,3-mixture), glycerin tris(meth)acrylate, glycerol 1,3-diglycerolate di(meth)acrylate, pentaerythritol tri(meth)acrylate, diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, tetraethylene glycol mono(meth)acrylate, pentaethylene glycol mono(meth)acrylate, and hexaethylene glycol mono(meth)acrylate.

[0045] The proportion of the crosslinkable compound used in the liquid crystal aligning agent is preferably 0.1 to 100 parts by mass relative to 100 parts by mass of all polymer components. From the viewpoint of promoting the crosslinking reaction and achieving the desired effect, it is more preferably 0.1 to 50 parts by mass. It is particularly preferably 1 to 30 parts by mass.

[0046] The liquid crystal aligning agent may be a compound that improves the uniformity of the thickness and surface smoothness of the liquid crystal alignment film, or a compound that improves the adhesion between the liquid crystal alignment film and the substrate. Examples of compounds that improve the uniformity of the thickness and surface smoothness of the liquid crystal alignment film include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants. Specific examples include the surfactants described in paragraph

[0122] of WO 2014 / 171493. The amount of the surfactant used is preferably 0.01 to 2 parts by mass relative to 100 parts by mass of all polymer components. A range of 0.01 to 1 part by mass is more preferred.

[0047] Specific examples of compounds that improve the adhesion between a liquid crystal alignment film and a substrate include the compounds described in paragraph

[0123] of WO2014 / 171493. More specific examples include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylmethyldimethoxysilane. Examples of suitable compounds include glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris[3-(trimethoxysilyl)propyl]isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane. The amount of such compounds used is preferably 0.1 to 30 parts by mass relative to 100 parts by mass of all polymer components. A more preferred amount is 1 to 20 parts by mass. In addition to the compounds listed above, the liquid crystal aligning agent may contain a dielectric or conductive substance added for the purpose of changing the electrical properties, such as the dielectric constant and conductivity, of the liquid crystal alignment film.

[0048] <Liquid Crystal Alignment Film / Liquid Crystal Light Control Element> A liquid crystal alignment agent can be applied to a substrate, baked, and then, if necessary, subjected to alignment treatments such as rubbing or photo-alignment, to form a liquid crystal alignment film. The liquid crystal alignment film of the present invention has the function of approximately horizontally aligning liquid crystal molecules. Nearly horizontal alignment refers, for example, to a state in which the tilt angle of liquid crystal molecules relative to the surface of the substrate with the liquid crystal alignment film is in the range of 0 to 20°, or a state in which light is transmitted when a liquid crystal cell is sandwiched between two polarizing plates in a crossed Nicol configuration so that the polarization axes of the two plates are perpendicular to each other and light is irradiated from one side of the liquid crystal cell. The substrate used to form the liquid crystal alignment film is not particularly limited as long as it is a highly transparent substrate. In addition to glass substrates, plastic substrates such as acrylic substrates, polycarbonate substrates, and PET (polyethylene terephthalate) substrates, and even films of these substrates, can be used. Plastic substrates and films are particularly preferred for use in light control windows, etc. From the viewpoint of simplifying the process, it is preferable to use a substrate on which an ITO electrode, an IZO (indium zinc oxide) electrode, an IGZO (indium gallium zinc oxide) electrode, an organic conductive film, etc. for driving the liquid crystal are formed. In addition, when a reflective liquid crystal light control element is used, a substrate on which a silicon wafer, a metal such as aluminum, or a dielectric multilayer film is formed can be used as the substrate on only one side.

[0049] The liquid crystal light control element has the liquid crystal alignment film of the present invention on at least one of the substrates. In particular, it is preferable that the liquid crystal alignment film is present on both substrates in the present invention. The method for applying the liquid crystal alignment agent is not particularly limited, but industrially, a dipping method, a roll coater method, a slit coater method, a spinner method, a spray method, a screen printing method, an offset printing method, a flexographic printing method, an inkjet method, or the like is used. These application methods are used depending on the purpose.

[0050] After applying the liquid crystal alignment agent to the substrate, the solvent can be evaporated using a heating means such as a hot plate, a hot air circulation oven, or an IR (infrared) oven at a temperature of 30 to 300°C, preferably 30 to 250°C, depending on the type of substrate and the solvent used in the liquid crystal alignment agent, to form a liquid crystal alignment film. When a plastic substrate is used as the substrate, treatment at a temperature of 30 to 150°C is preferred. The thickness of the liquid crystal alignment film is preferably 5 to 500 nm, since if it is too thick, it will be disadvantageous in terms of power consumption of the liquid crystal light control element, and if it is too thin, the reliability of the element may decrease. Therefore, the thickness is preferably 5 to 500 nm, more preferably 10 to 300 nm, and particularly preferably 10 to 250 nm.

[0051] To align the liquid crystals horizontally, the liquid crystal alignment film may be subjected to alignment treatments such as rubbing in a certain direction with a roll wrapped with a cloth made of fibers such as nylon, rayon, or cotton, or photoalignment in which the surface of the liquid crystal alignment film is irradiated with polarized radiation in a certain direction. The liquid crystal composition contains liquid crystals having positive dielectric anisotropy and a chiral compound. Nematic liquid crystals, smectic liquid crystals, or cholesteric liquid crystals can be used as the liquid crystal. Among these, nematic liquid crystals having positive dielectric anisotropy are preferably used.

[0052] From the viewpoint of low-voltage operation, liquid crystals having large dielectric anisotropy and large refractive index anisotropy are preferred. Furthermore, liquid crystals can be used singly or in combination of two or more types depending on the physical properties of the phase transition temperature, dielectric anisotropy, and refractive index anisotropy. To operate a liquid crystal dimming element as an active element such as a thin film transistor (TFT), the liquid crystal is required to have high electrical resistance and a high voltage holding ratio (hereinafter also referred to as "VHR"). Therefore, it is preferable to use fluorine-based or chlorine-based liquid crystals, which have high electrical resistance and whose VHR is not reduced by active energy rays such as ultraviolet rays.

[0053] The chiral compound induces a helical structure in nematic liquid crystal, and known compounds can be used. Specific examples include Schiff compounds, azoxy compounds, biphenyl compounds, phenyl ester compounds, phenylcyclohexane compounds, and pyridine compounds, as well as mixtures thereof. More specific examples include S-811, R811, and CB-15 (manufactured by Merck). Furthermore, chiral compounds can be used singly or in combination, depending on their properties. The proportion of chiral compounds used can be adjusted so that the desired d / p ratio is achieved, where d is the thickness of the liquid crystal layer in the liquid crystal dimming element, and p is the chiral pitch of the liquid crystal in the liquid crystal layer (the distance required for one liquid crystal molecule to twist one period). In the present invention, d / p is preferably 1 to 10, more preferably 1 to 8, and particularly preferably 1 to 6, in order to optimally obtain the effects of the present invention.

[0054] The liquid crystal composition preferably contains a dichroic dye in addition to the liquid crystal and the chiral compound. This causes the dichroic dye to change direction by 90° along the direction of the director (orientation direction) of the liquid crystal depending on whether or not a voltage is applied, resulting in a difference in the absorption characteristics of the dichroic dye, thereby achieving a difference in total light transmittance. The dichroic dye preferably has a maximum absorption wavelength in the visible light region, for example, in the region of 300 to 700 nm. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, phthalocyanine dyes, azo dyes, and anthraquinone dyes. Among these, it is preferable to use a phthalocyanine dye, azo dye, or anthraquinone dye.

[0055] Specific examples of dichroic dyes include G-207, G-241, G-470 (all manufactured by Hayashibara Co., Ltd.), Yellow-8, KRD-901, KRD-902 (all manufactured by Showa Chemical Industry Co., Ltd.), SI-486, M-1012 (manufactured by Mitsui Chemicals, Inc.), Dichroic Dye Blue AB2, AB3, AB4, Dichroic Dye Cyan AC1, Dichroic Dye Orange AO1, AZO1, Dichroic Dye Red AR1, and Dichroic Dye Yellow AG1 (all manufactured by NEMATEL). Furthermore, one type of dichroic dye can be used, or two or more types can be mixed together, depending on the properties of the dye. The dichroic dye is preferably used in an amount of 0.01 to 10 parts by mass relative to 100 parts by mass of liquid crystal, and more preferably 0.1 to 5 parts by mass from the viewpoint of the difference between colorless transparency and colored (hereinafter also referred to as "contrast of total light transmittance").

[0056] The liquid crystal light control element of the present invention differs from PSA (Polymer Sustained Alignment) and PDLC (Polymer Dispersed Liquid Crystal) systems, and therefore does not contain a polymerizable compound that reacts with light or heat, which is required for these systems. The liquid crystal composition can be prepared by mixing a liquid crystal, a chiral compound, and a dichroic dye. In this case, heating is preferably performed during preparation from the viewpoint of the solubility of the dichroic dye in the liquid crystal. Specifically, heating is preferably performed to a temperature not exceeding the phase transition temperature of the liquid crystal. The method for injecting the liquid crystal composition is not particularly limited, but examples include the following method. That is, when glass substrates are used as the substrates, a pair of substrates is prepared, at least one of which has a liquid crystal alignment film formed thereon, and a sealant is applied to four pieces of one substrate, excluding a portion. Then, the other substrate is attached with the liquid crystal alignment film facing inward to prepare an empty cell. The liquid crystal composition is then injected under reduced pressure from the area where the sealant is not applied, to obtain a liquid crystal composition-injected cell. Furthermore, when a plastic substrate or a film is used as the substrate, a method can be used in which a pair of substrates on which a liquid crystal alignment film is formed is prepared, a liquid crystal composition is dropped onto one of the substrates by an ODF (One Drop Filling) method, an inkjet method, or the like, and then the other substrate is bonded to obtain a liquid crystal composition injection cell.

[0057] The method for controlling the thickness of the liquid crystal layer (hereinafter also referred to as "gap") of the liquid crystal light control element is not particularly limited, and examples include a method of introducing spacers of a desired size into the liquid crystal composition, a method of coating a substrate having column spacers of a desired size, and a method of using a liquid crystal composition containing column spacers of a desired size. From the viewpoint of optimally achieving the effects of the present invention, the thickness of the liquid crystal layer is preferably 1 to 100 μm, more preferably 1 to 75 μm, and particularly preferably 1 to 30 μm. If the gap is too small, the contrast of the liquid crystal light control element will decrease, and if it is too large, the driving voltage of the element will increase. A polarizing plate can also be attached to the outer surface of the liquid crystal light control element of the present invention to increase the contrast of the total light transmittance.

[0058] The present invention will be described in more detail below with reference to examples, but is not limited to these. "Abbreviations used in Synthesis Examples, Examples, and Comparative Examples" <Monomers for preparing polyimide polymers> (Specific diamines) A1 to A4: Diamines of the following formulae [A1] to [A4]

[0059] (Other diamines) B1 to B5: Diamines of the following formulas [B1] to [B5]

[0060] (Specific tetracarboxylic acid components) C1 to C3: tetracarboxylic acid dianhydrides of the following formulae [C1] to [C3]

[0061] <Crosslinkable Compounds> K1 to K3: Crosslinkable compounds of the following formulae [K1] to [K3]

[0062] <Solvent> NMP: N-methyl-2-pyrrolidone NEP: N-ethyl-2-pyrrolidone BCS: Ethylene glycol monobutyl ether PB: Propylene glycol monobutyl ether

[0063] "Molecular Weight Measurement" The number average molecular weight (hereinafter also referred to as "Mn") and weight average molecular weight (hereinafter also referred to as "Mw") of the polyimide polymer were measured using the following apparatus and conditions. Room temperature gel permeation chromatography (GPC) apparatus: GPC-101 (manufactured by Resonac Corporation) Column: GPC KD-803 and KD-805 (manufactured by Resonac Corporation) in series Column temperature: 50°C Eluent: N,N-dimethylformamide (containing lithium bromide monohydrate (LiBr.H) as an additive) ２ o-Phosphoric acid (o-Phosphoric acid) 30 mmol / L, tetrahydrofuran (THF) 10 ml / L) Flow rate: 1.0 mL / min Standard sample for creating a calibration curve: EasiVial PEG / PEO polyethylene glycol oxide PL2080-0201 (molecular weight: approximately 1,500, approximately 4,000, approximately 13,000, approximately 30,000, approximately 70,000, approximately 130,000, approximately 500,000, approximately 1,000,000, approximately 1,500,000) (GL Sciences)

[0064] "Measurement of imidization ratio of polyimide" The imidization ratio of polyimide in the synthesis examples was measured as follows. Polyimide powder (20 mg) was placed in an NMR (nuclear magnetic resonance) sample tube (NMR sampling tube standard, φ5 (Kusano Scientific Co., Ltd.)), and deuterated dimethyl sulfoxide (DMSO-d ６ A mixture of 0.53 ml of 0.05% by mass of TMS (tetramethylsilane) was added and sonicated to completely dissolve the solution. This solution was subjected to 500 MHz proton NMR analysis using an NMR spectrometer (JNW-ECA500, manufactured by JEOL Datum Co., Ltd.). A proton derived from a structure that remains unchanged before and after imidization was determined as the reference proton. The imidization ratio was calculated using the integrated peak value of this proton and the integrated peak value of a proton derived from the NH group of the amic acid, which appeared around 9.5 ppm to 10.0 ppm, according to the following formula: Imidization ratio (%) = (1 - α x / y) × 100. In this formula, x is the integrated peak value of the proton derived from the NH group of the amic acid, y is the integrated peak value of the reference proton, and α is the ratio of the number of reference protons to one NH group proton of the amic acid in the case of a polyamic acid (with an imidization ratio of 0%).

[0065] Synthesis of Polyimide Polymer Synthesis Example 1 A 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube was charged with A1 (0.66 g, 2.33 mmol), B1 (2.62 g, 13.2 mmol), C1 (3.00 g, 15.3 mmol), and NMP (18.8 g), and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen to obtain a polyamic acid solution (1) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 23,100 and the Mw was 70,800.

[0066] Synthesis Example 2: A1 (0.66 g, 2.33 mmol), B2 (0.76 g, 6.99 mmol), B4 (1.78 g, 6.21 mmol), C1 (3.00 g, 15.3 mmol), and NMP (18.6 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen, to obtain a polyamic acid solution (2) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 23,900 and the Mw was 71,800.

[0067] Synthesis Example 3: A2 (0.59 g, 1.55 mmol), B1 (2.77 g, 14.0 mmol), C1 (3.00 g, 15.3 mmol), and NMP (19.1 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen to obtain a polyamic acid solution (3) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 22,500 and the Mw was 69,400.

[0068] Synthesis Example 4: A2 (0.70 g, 1.85 mmol), B2 (0.80 g, 7.39 mmol), B3 (1.41 g, 9.24 mmol), C2 (1.37 g, 5.46 mmol), and NMP (11.2 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 50 ° C for 3 hours while introducing nitrogen. Subsequently, C1 (2.51 g, 12.8 mmol) and NMP (9.15 g) were added, and the mixture was reacted at 40 ° C for 6 hours to obtain a polyamic acid solution (4) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 20,200 and the Mw was 66,900.

[0069] Synthesis Example 5: NMP was added to the polyamic acid solution (4) (15.0 g) obtained by the method of Synthesis Example 4 to dilute it to 6% by mass, and then acetic anhydride (1.90 g) and pyridine (1.10 g) were added as imidization catalysts and reacted at 40°C for 3 hours. This reaction solution was poured into methanol (250 ml), and the resulting precipitate was filtered off. The precipitate was washed with methanol and dried under reduced pressure at 100°C to obtain polyimide powder (5). The imidization rate of this polyimide was 57%, Mn was 17,500, and Mw was 57,300.

[0070] Synthesis Example 6: A3 (0.31 g, 0.78 mmol), B2 (0.76 g, 6.99 mmol), B4 (2.22 g, 7.76 mmol), C2 (1.91 g, 7.65 mmol), and NMP (11.1 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 50 ° C for 4 hours while introducing nitrogen. Subsequently, C1 (1.50 g, 7.65 mmol) and NMP (9.04 g) were added, and the mixture was reacted at 40 ° C for 6 hours, yielding a polyamic acid solution (6) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 20,600 and the Mw was 63,500.

[0071] Synthesis Example 7: A4 (1.18 g, 3.11 mmol), B1 (2.46 g, 12.4 mmol), C1 (3.00 g, 15.3 mmol), and NMP (19.9 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen, to obtain a polyamic acid solution (7) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 20,500 and the Mw was 67,900.

[0072] Synthesis Example 8: A4 (0.81 g, 2.13 mmol), B3 (0.22 g, 1.42 mmol), B4 (3.06 g, 10.7 mmol), C2 (0.70 g, 2.80 mmol), and NMP (11.5 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 50 ° C for 4 hours while introducing nitrogen. Subsequently, C1 (2.20 g, 11.2 mmol) and NMP (9.43 g) were added, and the mixture was reacted at 40 ° C for 6 hours, yielding a polyamic acid solution (8) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 17,600 and the Mw was 58,200.

[0073] Synthesis Example 9: A1 (0.77 g, 2.72 mmol), B1 (1.08 g, 5.43 mmol), B4 (1.56 g, 5.43 mmol), C3 (3.00 g, 13.4 mmol), and NMP (19.2 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 8 hours while supplying nitrogen, to obtain a polyamic acid solution (9) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 21,300 and the Mw was 68,800.

[0074] Synthesis Example 10: A2 (0.52 g, 1.36 mmol), B2 (0.59 g, 5.43 mmol), B3 (1.03 g, 6.79 mmol), C3 (3.00 g, 13.4 mmol), and NMP (15.4 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 8 hours while supplying nitrogen, to obtain a polyamic acid solution (10) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 18,900 and the Mw was 63,200.

[0075] Synthesis Example 11: B1 (2.46 g, 12.4 mmol), B5 (0.91 g, 3.11 mmol), C1 (3.00 g, 15.3 mmol), and NMP (19.1 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen to obtain a polyamic acid solution (11) having a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 21,700 and the Mw was 68,800.

[0076] Synthesis Example 12: B1 (2.62 g, 13.2 mmol), B5 (0.68 g, 2.33 mmol), C1 (3.00 g, 15.3 mmol), and NMP (18.9 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen to obtain a polyamic acid solution (12) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 23,100 and the Mw was 70,600.

[0077] Synthesis Example 13: B1 (2.77 g, 14.0 mmol), B5 (0.45 g, 1.55 mmol), C1 (3.00 g, 15.3 mmol), and NMP (18.7 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen to obtain a polyamic acid solution (13) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 25,300 and the Mw was 73,700.

[0078] Synthesis Example 14: B1 (3.08 g, 15.5 mmol), C1 (3.00 g, 15.3 mmol), and NMP (18.2 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was reacted at 40° C. for 6 hours while supplying nitrogen to obtain a polyamic acid solution (14) with a resin solids concentration of 25% by mass. The Mn of this polyamic acid was 29,100 and the Mw was 91,800.

[0079] The specifications of the polyimide polymer obtained above are shown in Tables 1 and 2.

[0080] *1: Polyamic acid

[0081] "Preparation of Liquid Crystal Alignment Agents" Examples 1 to 15 and Comparative Examples 1 to 4 below describe preparation examples of liquid crystal alignment agents. These liquid crystal alignment agents are used for evaluation of liquid crystal light control devices. The specifications of the liquid crystal alignment agents are shown in Tables 3 and 4.

[0082] *1: Indicates the amount (parts by mass) of crosslinkable compound introduced relative to 100 parts by mass of polymer.

[0083] "Confirmation of the nearly horizontal alignment of the liquid crystal alignment film" The liquid crystal alignment agent obtained by the method of the examples and comparative examples was pressure-filtered through a membrane filter with a pore size of 1 μm, and spin-coated on the ITO surface of a substrate (40 mm long x 30 mm wide, 0.7 mm thick) with an ITO electrode that had been washed with pure water and IPA (isopropanol). The substrate was then heated at 80°C for 2 minutes on a hot plate and at 230°C for 20 minutes in a hot air circulation clean oven to obtain an ITO substrate with a liquid crystal alignment film having a film thickness of 100 nm. Next, the liquid crystal alignment film surface of this substrate was rubbed using a rubbing device with a roll diameter of 120 mm using a rayon cloth under the conditions of a roll rotation speed of 1000 rpm, a roll advance speed of 50 mm / sec, and a push-in depth of 0.3 mm. Next, two ITO substrates with liquid crystal alignment films were prepared. 12 μm spacers were sprayed onto the liquid crystal alignment film surface of one substrate. A sealant (XN-1500T) (manufactured by Kyoritsu Chemical Industry Co., Ltd.) was applied to the liquid crystal alignment film surface on all four sides of the other substrate. These substrates were then bonded together so that the liquid crystal alignment film surfaces faced each other and the valence and rubbing directions faced each other, i.e., in an antiparallel orientation. The bonded substrates were pressed together and heated at 80°C for 15 minutes, then at 150°C for 90 minutes to prepare an empty cell. A positive liquid crystal (PA-1492, manufactured by DIC Corporation) was injected into this empty cell by a reduced pressure injection method. The injection port was then sealed, and the cell was heated at 120°C for 30 minutes to obtain a liquid crystal cell. Next, the liquid crystal cell was sandwiched between two polarizing plates so that the polarization axes of the two plates were perpendicular to each other. A backlight was irradiated from one side of the liquid crystal cell to confirm the liquid crystal cell. As a result, it was confirmed that the liquid crystal was aligned almost horizontally in all the liquid crystal cells.

[0084] "Preparation of Liquid Crystal Composition (A)" 10.0 g of Sb-408030L (positive liquid crystal containing a chiral compound, chiral pitch (p) = 4.0 μm) (manufactured by Champagne) and 0.2 g of M-1012 (manufactured by Mitsui Fine Chemicals, Inc.) were mixed and stirred at 23°C for 24 hours to obtain liquid crystal composition (A).

[0085] "Preparation of Liquid Crystal Cell (Liquid Crystal Light Control Element)" The liquid crystal alignment agent obtained by the method of the Examples and Comparative Examples was pressure-filtered through a membrane filter with a pore size of 1 μm, and spin-coated onto the ITO surface of a substrate (40 mm long x 30 mm wide, 0.7 mm thick) with an ITO electrode that had been washed with pure water and IPA (isopropanol). The substrate was then heated at 80°C for 2 minutes on a hot plate and at 230°C for 20 minutes in a hot air circulation clean oven to obtain an ITO substrate with a liquid crystal alignment film having a film thickness of 100 nm. Next, the liquid crystal alignment film surface of the substrate was rubbed using a rubbing device with a roll diameter of 120 mm using a rayon cloth under the following conditions: roll rotation speed: 1000 rpm, roll advancement speed: 50 mm / sec, and indentation depth: 0.3 mm. Thereafter, two ITO substrates with liquid crystal alignment films were prepared. 12 μm spacers were sprayed onto the liquid crystal alignment film surface of one substrate. A sealant (XN-1500T) (manufactured by Kyoritsu Chemical Industry Co., Ltd.) was applied to the liquid crystal alignment film surface on all four sides of the other substrate. These substrates were then bonded together so that the liquid crystal alignment film surfaces faced each other. The bonded substrates were pressed together and heated at 80°C for 15 minutes, then at 150°C for 90 minutes to prepare an empty cell. Liquid crystal composition (A) was injected into this empty cell by a reduced pressure injection method. The injection port was then sealed, and the cell was heated at 120°C for 30 minutes to obtain a liquid crystal cell.

[0086] "Confirmation of display defects in liquid crystal cells" This evaluation was conducted to evaluate the in-plane transmittance uniformity associated with poor alignment of the liquid crystal and dye. Specifically, an AC voltage of ±50 V was applied for 10 seconds to the liquid crystal cells before (initial) and after light irradiation, respectively, and then the AC voltage was returned to 0 V. Thereafter, the liquid crystal cell and a polarizing plate were stacked, and the cells were checked visually and with a polarizing microscope. A cell with little variation in in-plane transmittance and high uniformity was evaluated as excellent in this evaluation. Note that high uniformity means that there are no boundary regions where the in-plane transmittance is discontinuous. After checking the liquid crystal cell prepared in the above "Preparation of liquid crystal cell (liquid crystal light control element)" using the above method, a film that cuts wavelengths of 380 nm or less was attached to the liquid crystal cell, and a Q-SUN Xenon Test Chamber Model Xe-1 (manufactured by Q-LAB) (0.55 W / m) was used as the light irradiation device. ２The sample was irradiated with light for 48 hours using a 340 nm wavelength cut filter (DayLight F Filter, temperature inside the layer: 55°C). After the light irradiation, the liquid crystal cell was checked by the above-mentioned method. The results of checking the in-plane transmittance uniformity of the liquid crystal cell are shown in Tables 5 and 6. In the tables, a high in-plane transmittance uniformity was marked with ○, and a low in-plane transmittance uniformity was marked with ×.

[0087] "Evaluation of Light Stability of Voltage Holding Ratio" This evaluation was conducted to evaluate image sticking defects of the liquid crystal dimming element. Specifically, the voltage holding ratios of the liquid crystal cells prepared in the above "Preparation of Liquid Crystal Cell (Liquid Crystal Dimming Element)" were measured before (initial) and after light irradiation, and the smaller the change in the value after light irradiation relative to the initial value, the better the evaluation. The voltage holding ratio was measured using a voltage holding ratio measuring device (VHR-1) (manufactured by Toyo Corporation) by applying a voltage of 1 V for 60 μs at a temperature of 23° C. and measuring the voltage after 16.67 ms. The voltage holding ratio was calculated as the extent to which the voltage was held. The light irradiation was conducted under the same conditions as in the above "Confirmation of Display Defects of Liquid Crystal Cell." The results of the evaluation of the light stability of the voltage holding ratio are shown in Tables 5 and 6.

[0088] Example 1 NMP (20.3 g) and BCS (6.00 g) were added to the polyamic acid solution (1) (5.00 g) obtained by the method of Synthesis Example 1, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (1). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (1), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0089] Example 2 To the polyamic acid solution (1) (5.00 g) obtained by the method of Synthesis Example 1, K1 (0.125 g), NMP (20.3 g), and BCS (6.00 g) were added, and the mixture was stirred at 25°C for 4 hours to obtain a liquid crystal aligning agent (2). This liquid crystal aligning agent was a homogeneous solution, with no abnormalities such as turbidity or precipitation observed. Using the obtained liquid crystal aligning agent (2), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0090] Example 3 NMP (14.3 g) and BCS (12.0 g) were added to the polyamic acid solution (2) (5.00 g) obtained by the method of Synthesis Example 2, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (3). This liquid crystal aligning agent was a homogeneous solution, with no abnormalities such as turbidity or precipitation observed. Using the obtained liquid crystal aligning agent (3), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0091] Example 4 NMP (20.3 g) and BCS (6.00 g) were added to the polyamic acid solution (3) (5.00 g) obtained by the method of Synthesis Example 3, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (4). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (4), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0092] Example 5 NMP (17.3 g) and PB (9.00 g) were added to the polyamic acid solution (4) (5.00 g) obtained by the method of Synthesis Example 4, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (5). This liquid crystal aligning agent was a homogeneous solution, with no abnormalities such as turbidity or precipitation observed. Using the obtained liquid crystal aligning agent (5), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0093] Example 6 To the polyamic acid solution (4) (5.00 g) obtained by the method of Synthesis Example 4, K2 (0.188 g), NMP (20.3 g), and BCS (6.00 g) were added, and the mixture was stirred at 25°C for 4 hours to obtain a liquid crystal aligning agent (6). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was a homogeneous solution. Using the obtained liquid crystal aligning agent (6), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0094] Example 7 NEP (25.2 g) was added to polyimide powder (5) (1.50 g) obtained by the method of Synthesis Example 5, and the mixture was stirred at 70°C for 24 hours to dissolve. Then, BCS (7.20 g) and PB (3.60 g) were added, and the mixture was stirred at 25°C for 4 hours to obtain a liquid crystal alignment agent (7). This liquid crystal alignment agent showed no abnormalities such as turbidity or precipitation, and was a homogeneous solution. Using the obtained liquid crystal alignment agent (7), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0095] Example 8 NMP (17.3 g) and BCS (9.00 g) were added to the polyamic acid solution (6) (5.00 g) obtained by the method of Synthesis Example 6, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (8). This liquid crystal aligning agent was a homogeneous solution, with no abnormalities such as turbidity or precipitation observed. Using the obtained liquid crystal aligning agent (8), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0096] Example 9 To the polyamic acid solution (6) (5.00 g) obtained by the method of Synthesis Example 6, K1 (0.125 g), NMP (17.3 g), and BCS (9.00 g) were added, and the mixture was stirred at 25°C for 4 hours to obtain a liquid crystal aligning agent (9). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was a homogeneous solution. Using the obtained liquid crystal aligning agent (9), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0097] Example 10 NMP (20.3 g) and PB (6.00 g) were added to the polyamic acid solution (7) (5.00 g) obtained by the method of Synthesis Example 7, and the mixture was stirred at 25°C for 4 hours to obtain a liquid crystal aligning agent (10). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (10), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0098] Example 11 NEP (14.3 g), BCS (9.00 g) and PB (3.00 g) were added to the polyamic acid solution (8) (5.00 g) obtained by the method of Synthesis Example 8, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (11). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was a homogeneous solution. Using the obtained liquid crystal aligning agent (11), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0099] Example 12 To the polyamic acid solution (8) (5.00 g) obtained by the method of Synthesis Example 8, K2 (0.125 g), NEP (14.3 g), BCS (9.00 g) and PB (3.00 g) were added, and the mixture was stirred at 25°C for 4 hours to obtain a liquid crystal aligning agent (12). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was a homogeneous solution. Using the obtained liquid crystal aligning agent (12), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0100] Example 13 NMP (2.30 g), NEP (15.0 g) and PB (9.00 g) were added to the polyamic acid solution (9) (5.00 g) obtained by the method of Synthesis Example 9, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (13). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was a homogeneous solution. Using the obtained liquid crystal aligning agent (13), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0101] Example 14 NMP (20.3 g) and BCS (6.00 g) were added to the polyamic acid solution (10) (5.00 g) obtained by the method of Synthesis Example 10, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (14). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (14), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0102] Example 15 To the polyamic acid solution (10) (5.00 g) obtained by the method of Synthesis Example 10, K3 (0.063 g), NMP (20.3 g), and BCS (6.00 g) were added, and the mixture was stirred at 25°C for 4 hours to obtain a liquid crystal aligning agent (15). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was a homogeneous solution. Using the obtained liquid crystal aligning agent (15), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0103] <Comparative Example 1> NMP (20.3 g) and BCS (6.00 g) were added to the polyamic acid solution (11) (5.00 g) obtained by the method of Synthesis Example 11, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (16). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (16), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0104] <Comparative Example 2> NMP (20.3 g) and BCS (6.00 g) were added to the polyamic acid solution (12) (5.00 g) obtained by the method of Synthesis Example 12, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (17). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (17), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0105] <Comparative Example 3> NMP (20.3 g) and BCS (6.00 g) were added to the polyamic acid solution (13) (5.00 g) obtained by the method of Synthesis Example 13, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (18). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (18), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0106] <Comparative Example 4> NMP (20.3 g) and BCS (6.00 g) were added to the polyamic acid solution (14) (5.00 g) obtained by the method of Synthesis Example 14, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent (19). This liquid crystal aligning agent was a homogeneous solution without any abnormalities such as turbidity or precipitation. Using the obtained liquid crystal aligning agent (19), "confirmation of display defects of liquid crystal cell" and "evaluation of light stability of voltage holding ratio" were performed.

[0107]

[0108] As can be seen from the above results, the liquid crystal cells of the examples had high in-plane transmittance uniformity before and after light irradiation. Furthermore, the decrease in voltage holding ratio due to light irradiation was also small. Specifically, the examples using the specific polymer were compared with the comparative examples using other polymers, i.e., Example 1 was compared with Comparative Example 1, Example 4 was compared with Comparative Example 2, and Example 10 was compared with Comparative Example 3.

[0109] By using a liquid crystal aligning agent containing a polymer having a specific structure according to the present invention, a liquid crystal light control element can be obtained that exhibits good liquid crystal alignment and excellent electrical properties. In particular, these properties do not deteriorate even in harsh environments where the element is exposed to light for long periods of time. Therefore, the liquid crystal light control element of the present invention is useful in liquid crystal displays for display purposes, and in light control windows and optical shutters that control the transmission and blocking of light. The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2024-062976, filed on April 9, 2024, are incorporated herein by reference.

Claims

1. A liquid crystal light control element whose transmittance can be changed in response to the application of voltage, comprising: a pair of substrates each having an electrode; a liquid crystal layer provided between the substrates and containing liquid crystal molecules that are twistedly aligned when no voltage is applied; and a liquid crystal alignment film on at least one side between the substrates and the liquid crystal layer, the liquid crystal layer having the function of aligning the liquid crystal molecules approximately horizontally; wherein the liquid crystal layer contains a liquid crystal composition containing liquid crystal molecules with positive dielectric anisotropy and a chiral compound; the liquid crystal alignment film contains a polymer having a structure of the following formula [1]; and wherein d / p is 1 to 10, where d is the thickness of the liquid crystal layer and p is the chiral pitch of the liquid crystal in the liquid crystal layer. (X １ is a single bond, -(CH ２ ) ａ -(a is an integer of 1 to 15), -O-, -CH ２ O-, -CONH-, -NHCO-, -CON(CH ３ ) -, -N(CH ３ ) represents CO—, —COO—, or —OCO—. X ２ and X ３ each independently represents at least one divalent cyclic group selected from a benzene ring, a cyclohexane ring, and a heterocycle, and any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. X ４ represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, or an alkoxy group having 1 to 18 carbon atoms. Xn represents an integer of 0 or 1. * represents a bond.

2. The liquid crystal light control device according to claim 1, wherein the liquid crystal composition further contains a dichroic dye.

3. The liquid crystal light control device according to claim 1 or 2, wherein the liquid crystal layer has a thickness of 1 to 75 μm.

4. The liquid crystal light control element according to claim 1 or 2, wherein d / p in the liquid crystal light control element is 1 to 8.

5. The liquid crystal light control device according to claim 1 or 2, wherein the polymer contained in the liquid crystal alignment agent is at least one selected from a polyimide precursor and a polyimide.

6. The liquid crystal light control device according to claim 5, wherein the polymer is at least one selected from a polyimide precursor and a polyimide, which use a diamine having the structure of the formula [1] as part of a raw material.

7. The liquid crystal light control device according to claim 6, wherein the diamine is a diamine of the following formula [1a]: (X represents the structure of the formula [1]. Each Xm independently represents an integer of 1 to 4.) 8. The liquid crystal light control device according to claim 6, wherein the diamine is used in an amount of 2 to 20 mol % based on the total amount of diamine.

9. The liquid crystal light control element according to claim 5, wherein the polymer is a polyimide precursor using a tetracarboxylic acid of the following formula [2] as part of a raw material, or a polyimide obtained by imidizing the polyimide precursor. (Z represents at least one selected from the structures of the following formulas [2a] to [2l].) (Z Ａ ~Z Ｄ each independently represents a hydrogen atom, a methyl group, a chlorine atom or a benzene ring. Ｅ and Z Ｆ each independently represents a hydrogen atom or a methyl group.

10. The liquid crystal light control element described in claim 5, wherein the liquid crystal aligning agent contains a compound having at least one structure selected from an epoxy group, an isocyanate group, an oxetanyl group, an oxazoline group, a cyclocarbonate group, a hydroxyl group, a hydroxyalkyl group, a lower alkoxyalkyl group, and a polymerizable unsaturated group.

11. A liquid crystal alignment film used in the liquid crystal light control element according to claim 1 or 2.

12. A liquid crystal alignment agent for forming the liquid crystal alignment film according to claim 11.

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