Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal light control element

Abstract

The purpose of the present invention is to provide a liquid crystal light control element which has good liquid crystal alignment properties, specifically exhibits a pretilt angle of 2 to 20°, and is excellent in electrical characteristics (high voltage holding ratio). Provided is a liquid crystal light control element in which liquid crystal alignment properties or electrical characteristics do not deteriorate even in a harsh environment. Further provided are a liquid crystal alignment film used for the liquid crystal light control element and a liquid crystal alignment agent for manufacturing the liquid crystal alignment film.　The liquid crystal alignment agent contains at least one polymer selected from a polyimide and a polyamide precursor obtained by reacting a diamine component including a diamine of formula [1a], a diamine of formula [2a] and a diamine of formula [3a] with a tetracarboxylic acid component.

Description

Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal light control element

[0001] The present invention relates to a liquid crystal aligning agent, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a liquid crystal light control device using 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. When horizontally aligning liquid crystals, such as in liquid crystal light control devices using a twisted nematic (TN) drive system or an in-plane switching (IPS) drive system, the baked liquid crystal alignment film is subjected to an alignment treatment such as a rubbing treatment in which the liquid crystal alignment film is rubbed in a certain direction with a roll wrapped with a cloth made of fibers such as nylon, rayon, or cotton, or a photoalignment treatment. There is also a system that uses a guest-host liquid crystal using a dichroic dye and liquid crystal (see Patent Documents 1 and 2).

[0003] Japanese Unexamined Patent Publication No. 2017-21097 Japanese Unexamined Patent Publication No. 9-40964

[0004] The liquid crystal alignment film of a horizontally aligned liquid crystal dimming element must provide a certain tilt angle (also called a pretilt angle) of 2 to 20° to the liquid crystal in order to align the liquid crystal in the liquid crystal dimming element. Furthermore, to prevent a decrease in the contrast of the element, a high voltage holding ratio, which is an electrical characteristic, is required. Because liquid crystal dimming elements are sometimes attached to the window glass of automobiles or buildings, they are exposed to light, including ultraviolet light, for long periods of time. Therefore, even in such harsh environments, they are required to maintain the alignment and electrical characteristics of the liquid crystal, i.e., to be highly reliable.

[0005] Therefore, an object of the present invention is to provide a liquid crystal light control element that exhibits good liquid crystal alignment, specifically a pretilt angle of 2 to 20°, and has excellent electrical properties (high voltage holding ratio). Another object of the present invention is to provide a liquid crystal light control element in which the alignment and electrical properties of the liquid crystal do not deteriorate even under harsh environments. Another object of the present invention is to provide a liquid crystal alignment film to be used in the liquid crystal light control element, and a liquid crystal aligning agent for producing the liquid crystal alignment film.

[0006] As a result of intensive research to achieve the above object, the present inventors have completed the present invention having the following gist: That is, a liquid crystal aligning agent containing at least one polymer (also referred to as a specific polymer) selected from a polyimide precursor and a polyimide obtained by reacting a diamine component including a diamine of the following formula [1a] (also referred to as a specific diamine (A)), a diamine of the following formula [2a] (also referred to as a specific diamine (B)), and a diamine of the following formula [3a] (also referred to as a specific diamine (C)) with a tetracarboxylic acid component: (X represents at least one structure selected from the following formula [1-1] and formula [1-2]. Each Xm independently represents an integer of 1 to 4. Xp represents an integer of 0 or 1. When there are multiple Xs, the multiple Xs may be the same or different.)

[0007] (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 at least one selected from the group consisting of —CO—, —COO—, and —OCO—. ２ is a single bond or -(CH ２ ) ｂ - (where b is an integer of 1 to 15). ３ is a single bond, -(CH ２ ) ｃ -(c is an integer of 1 to 15), -O-, -OCH ２ represents at least one selected from -, -COO-, and -OCO-. ４represents at least one divalent cyclic group selected from a benzene ring, a cyclohexane ring, and a heterocycle, or a divalent organic group having 17 to 51 carbon atoms and a steroid skeleton, and any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxyl group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxyl group having 1 to 3 carbon atoms, or a fluorine atom. X ５ represents at least one cyclic group selected from a benzene ring, a cyclohexane ring, and a heterocycle, and any hydrogen atom on these cyclic groups may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxyl group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxyl group having 1 to 3 carbon atoms, or a fluorine atom. Xn represents an integer of 0 to 4. X ６ represents at least one selected from an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 18 carbon atoms, an alkoxyl group having 1 to 18 carbon atoms, and a fluorine-containing alkoxyl group having 1 to 18 carbon atoms. * represents a bond.)

[0008] (X ７ represents a single bond, —O—, —CH ２ O-, -CONH-, -NHCO-, -CON(CH ３ ) -, -N(CH ３ ) represents at least one selected from the group consisting of —CO—, —COO—, and —OCO—. ８ indicates an alkyl group having 8 to 22 carbon atoms or a fluorine-containing alkyl group having 6 to 18 carbon atoms. * indicates a bond. (Y １ and Y ２ are each independently -(CH ２ ) ｂ - (where b is an integer of 1 to 12). ３ and Y ４ each independently represents a hydrogen atom or a tert-butoxycarbonyl group. (R １ and R ２ each independently represents a hydrogen atom or a methyl group. Pn represents an integer of 1 to 6.

[0009] According to the present invention, a liquid crystal light control element having good liquid crystal alignment and excellent electrical properties can be obtained. Therefore, the liquid crystal light control element of the present invention can be used in liquid crystal displays for display purposes, and light control windows and optical shutters that control the transmission and blocking of light. The mechanism by which the present invention can obtain a liquid crystal light control element having the above-mentioned excellent properties is not necessarily clear, but is roughly presumed to be as follows.

[0010] X in the formula [1a], which is the specific diamine (A), has a moiety such as a benzene ring or a cyclohexane ring, or a long-chain alkyl group. Therefore, a liquid crystal alignment film obtained from a liquid crystal alignment agent containing this has a desired pretilt angle of the liquid crystal and is stable against heat and light. In addition, -N(Y) bonded to the benzene ring of the specific diamine (B) ３ )-C(=O)-N(Y ４ The amine at the -(CH)- moiety forms a hydrogen bond with the carbonyl group (-C(=O)-) at the same moiety or with the carbonyl group or amine in the specific polymer, resulting in interaction between the main chains of the specific polymer. This increases the stability of the pretilt angle and reduces the change in the pretilt angle due to heat or light. Furthermore, the -(CH)- moiety bonded to the benzene ring of the specific diamine (C) ２ ) CH at Pn-site ２ The group has a physically flexible structure, which is thought to facilitate the development of a desired pretilt angle in tilt alignment treatment such as rubbing treatment.

[0011] As described above, the liquid crystal aligning agent containing the specific polymer using the specific diamine (A), the specific diamine (B), and the specific diamine (C) can obtain the above-mentioned effects.

[0012] <Specific Polymer> The specific polymer is a polyimide precursor or polyimide (collectively referred to as a polyimide-based polymer) obtained by reacting a diamine component containing specific diamine (A), specific diamine (B), and specific diamine (C) with a tetracarboxylic acid. In the present invention, a polyimide-based polymer (also referred to as a second polymer) obtained by reacting a diamine component containing specific diamine (B) and specific diamine (C) without containing specific diamine (A) with a tetracarboxylic acid is preferably used together with the specific polymer. In this case, the ratio of the specific polymer to the second polymer is preferably 10 to 900 parts by mass of the second polymer per 100 parts by mass of the specific polymer. More preferably, the ratio is 100 to 600 parts by mass, and most preferably 100 to 400 parts by mass, per 100 parts by mass of the specific polymer. The polyimide precursor is preferably a polyamic acid or polyamic acid ester having a structure represented by the following formula [A]:

[0013] (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.) Polyimide has a structure of the following formula [A-4] and can be obtained by ring-closing (also called imidization) a polyamic acid of a polyimide precursor. In this case, if the ring-closure rate (also called imidization rate) of the amic acid group is less than 100%, the polyimide contains at least one structure of the following formulas [A-1] to [A-3] in addition to the structure of formula [A-4]. (R ａ , R ｂ , A １ ~A ４has the same meaning as defined in the 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 structural formula of a repeating unit 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 is the same as defined in the formula [A].) In addition, by a conventional synthesis method, A of the formula [A] can be added to the polymer of the formula [D]. １ and A ２ and A in formula [A] ３ and A ４ It is also possible to introduce an alkyl group having 1 to 5 carbon atoms or an acetyl group.

[0015] The specific diamine (A) is a diamine of the formula [1a]. In the formula [1a], Xm, Xp, and X are as defined above, but among them, the following are preferred. Each Xm is preferably an integer of 1 or 2 independently. Xp is preferably an integer of 1. X has a structure of the formula [1-1] or formula [1-2], and when there are multiple Xs, the multiple Xs may be the same or different. In the formula [1-1], X １ ~X ６ 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, ２ ) ａ -(a is an integer of 1 to 15), -O-, -CH２ Preferred are —O— and —COO—. More preferred are single bonds, —(CH ２ ) ａ -(a is an integer of 1 to 10), -O-, -CH ２ X is -O- or -COO-. ２ is a single bond or -(CH ２ ) ｂ - (b is an integer of 1 to 10) is preferred. ３ From the viewpoint of ease of synthesis, a single bond, -(CH ２ ) ａ -(a is an integer of 1 to 15), -O-, -CH ２ Preferred are —O—, —COO—, and —OCO—. More preferred are single bonds, —(CH ２ ) ａ -(a is an integer of 1 to 10), -O-, -CH ２ X is -O- or -COO-. ４ From the viewpoint of ease of synthesis, X is preferably an organic group having 17 to 51 carbon atoms and having a benzene ring, a cyclohexane ring, or a steroid skeleton. ５ is preferably a benzene ring or a cyclohexane ring. ６ is preferably an alkyl group having 1 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, or a fluorine-containing alkoxy group having 1 to 10 carbon atoms. More preferred are alkyl groups having 1 to 12 carbon atoms or alkoxy groups having 1 to 12 carbon atoms. Particularly preferred are alkyl groups having 1 to 9 carbon atoms or alkoxy groups having 1 to 9 carbon atoms. From the viewpoints of availability of raw materials and ease of synthesis, Xn is preferably 0 to 3. More preferred is 0 to 2.

[0016] In formula [1-2], X ７ and X ８ are as defined above, but among them, the following are preferred: ７ is a single bond, -O-, -CH ２ O-, -CONH-, -CON(CH ３ )- or -COO- is preferred. A single bond, -O-, -CONH- or -COO- is more preferred. X ８ is preferably an alkyl group having 8 to 18 carbon atoms.

[0017] Specific examples of the specific diamine (A) include diamine compounds of formulas [2-1] to [2-6] and formulas [2-9] to [2-36] described on pages 15 to 19 of International Publication WO2013 / 125595 (published on August 29, 2013). ２ and R in formula [2-4] to formula [2-6] ４ represents at least one selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, and a fluorine-containing alkoxy group having 1 to 18 carbon atoms. ４ represents a linear or branched alkyl group having 3 to 18 carbon atoms. ３ is -O-, -CH ２ It represents at least one selected from the group consisting of -O-, -COO-, and -OCO-. Among them, preferred specific diamine (A) are diamine compounds of formula [2-1] to formula [2-6], formula [2-9] to formula [2-13], or formula [2-22] to formula [2-31] described in International Publication WO2013 / 125595. From the viewpoint of the optical properties of the liquid crystal light control element, more preferred are diamines of formula [1a-32] to formula [1a-41] below. (R １ Each represents an alkyl group having 3 to 12 carbon atoms.

[0018] (R ２Each represents an alkyl group having 3 to 12 carbon atoms, and the cis-trans isomerism of 1,4-cyclohexylene is a trans isomer.) From the viewpoint of the optical properties of the liquid crystal light control element, the most preferred are the diamines of the formulas [1a-35] to [1a-37], [1a-40], or [1a-41]. Specific examples of the specific diamine (A) of formula [1-2] include the diamine compounds of formulas [DA1] to [DA11] described on page 23 of International Publication WO2013 / 125595 (published on August 29, 2013). In the description of International Publication WO2013 / 125595, the A in formulas [DA1] to [DA5] １ represents an alkyl group having 8 to 22 carbon atoms or a fluorine-containing alkyl group having 6 to 18 carbon atoms. Among these, diamines of the following formulas [1b-1] to [1b-5] are preferred from the viewpoint of the optical properties of the liquid crystal light control device.

[0019] The specific diamine (B) is a diamine represented by the formula [2a]. １ ~Y ４ are as defined above, and among them, the following are preferred: １ and Y ２ are each independently -(CH ２ ) ｂ -(b is an integer of 1 to 6) is preferred. -(CH ２ ) ｂ - (b is an integer of 1 to 3). ３ and Y ４ are each independently preferably a hydrogen atom or a tert-butoxycarbonyl group (also referred to as a Boc group). Specific examples of the specific diamine (B) include those represented by the following formula [2a-1] or [2a-2], and it is preferable to use these.

[0020] The specific diamine (C) is a diamine represented by the formula [3a]. １ , R ２ and Pn are as defined above, but among them, the following are preferred: １ is preferably a hydrogen atom. ２is preferably a methyl group. Pn is preferably an integer of 1 to 3. Specific examples of the specific diamine (C) include those represented by the following formula [3a-1] or [3a-5], and it is preferable to use these.

[0021] The proportions of the specific diamine (A) to the specific diamine (C) used in the specific polymer, relative to the total diamine content, are preferably as follows, from the viewpoint of the optical properties of the liquid crystal light control device: The specific diamine (A) is preferably 5 to 50 mol %, more preferably 5 to 30 mol %. The specific diamine (B) is preferably 10 to 70 mol %, more preferably 30 to 70 mol %. The specific diamine (C) is preferably 10 to 70 mol %, more preferably 20 to 60 mol %. The proportions of the specific diamine (B) and the specific diamine (C) used in the second polymer, relative to the total diamine content, are preferably as follows, from the viewpoint of the optical properties of the liquid crystal light control device: The specific diamine (B) is preferably 10 to 70 mol %, more preferably 30 to 70 mol %. The specific diamine (C) is preferably 10 to 70 mol %, more preferably 20 to 60 mol %.

[0022] The polyimide polymer may contain diamines other than the specific diamines (A) to (C) as diamine components, as long as the effects of the present invention are not impaired. Specific examples include the other diamines described on pages 8 to 15 of International Publication WO 2023 / 074568 (published May 4, 2023). These other diamines may be used alone or in combination depending on the properties of the diamines. The tetracarboxylic acid component used to prepare the polyimide polymer is preferably a tetracarboxylic acid dianhydride represented by the following formula [4], or its tetracarboxylic acid derivatives, such as tetracarboxylic acid, tetracarboxylic acid dihalide, tetracarboxylic acid dialkyl ester, or tetracarboxylic acid dialkyl ester dihalide (collectively referred to as the specific tetracarboxylic acid component). (Z represents at least one structure selected from the following formulas [4a] to [4l].)

[0023] (ZＡ ~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.

[0024] Among these, from the viewpoint of ease of synthesis and ease of polymerization reactivity when producing a polymer, Z is preferably formula [4a], formula [4c], formula [4d], formula [4e], formula [4f], formula [4g], formula [4k] or formula [4l]. More preferred are formula [4a], formula [4e], formula [4f], formula [4g], formula [4k] or formula [4l]. Particularly preferred are formula [4a], formula [4e], formula [4f], formula [4g] or formula [4l].

[0025] The proportion of the specific tetracarboxylic acid component used is preferably 1 mol % or more relative to the total tetracarboxylic acid components. More preferably, it is 5 mol % or more. Particularly preferably, it is 10 mol % or more. From the viewpoint of the optical properties of the liquid crystal device, it is most preferably 10 to 100 mol %. The polyimide-based polymer may contain tetracarboxylic acid components other than the specific tetracarboxylic acid component, as long as the effects of the present invention are not impaired. Examples of other tetracarboxylic acid components include the following tetracarboxylic acid compounds, tetracarboxylic acid dianhydrides, dicarboxylic acid dihalide compounds, dicarboxylic acid dialkyl ester compounds, and dialkyl ester dihalide compounds. Specific examples include the other tetracarboxylic acid components described on pages 34 and 35 of International Publication WO 2015 / 012368 (published January 29, 2015). Furthermore, the specific tetracarboxylic acid component and other tetracarboxylic acid components may be used singly or in combination, depending on their respective properties.

[0026] 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 method described on pages 35-36 of International Publication WO2015 / 012368 (published January 29, 2015). 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.

[0027] The reaction between the diamine component and the tetracarboxylic acid component is usually carried out in a solvent containing the diamine component and the tetracarboxylic acid component. The solvent used 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. Furthermore, when the polyimide precursor has high solvent solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or solvents represented by the following formulas [D1] to [D3] can be used. (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.) These may be used alone or in combination. Furthermore, even if the solvent does not dissolve the polyimide precursor, it may be mixed with the solvent to the extent that it does not precipitate. 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 solvent that has been dehydrated and dried.

[0028] In the polymerization reaction of the polyimide precursor, the total number of moles of the tetracarboxylic acid components is preferably 0.8 to 1.2 when the total number of moles of the diamine components is 1.0. When the total number of moles of the tetracarboxylic acid components is smaller than 1.0, i.e., when the total number of moles of the tetracarboxylic acid components is smaller than the number of moles of the diamine components, the polymer ends in an amino group structure, and when the total number of moles of the tetracarboxylic acid components is larger than 1.0, i.e., when the total number of moles of the tetracarboxylic acid components is larger than the number of moles of the diamine components, the polymer ends in a carboxylic acid anhydride or dicarboxylic acid structure.

[0029] 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 preferred. A rate of 50 to 90% is even more preferred. In the present invention, the polyimide polymer is preferably a polyimide precursor. The polyimide polymer may be converted into a terminal-capped polymer using a terminal-capping agent. Terminal-capping polymers have the effect of increasing the film hardness of the liquid crystal alignment film and improving the adhesion between the liquid crystal alignment film and the sealant in a liquid crystal light control element.

[0030] The method for obtaining the end-capped polymer is not particularly limited. Specific examples include the method described on pages 24 to 25 of International Publication WO2023 / 074568 (published May 4, 2023). 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 in terms of Mw (weight average molecular weight) measured by Gel Permeation Chromatography (GPC). A more preferred molecular weight is 10,000 to 150,000.

[0031] <Liquid Crystal Alignment Agent> The liquid crystal alignment agent is a solution for forming a liquid crystal alignment film, and is a solution containing a specific polymer and a solvent. In addition to the specific polymer, a second polymer may be contained. Furthermore, two or more types of specific polymer and second polymer may be used. The polymer component does not have to be entirely these specific polymers, and a polyimide-based polymer that does not use the specific diamines (A) to (C) may be mixed. In this case, the proportion of the polyimide-based polymer that does not use the specific diamines (A) to (C) is preferably 10 to 900 parts by mass, more preferably 10 to 500 parts by mass, per 100 parts by mass of the specific polymer. Furthermore, a polymer other than a polyimide-based polymer may be mixed with the polymer component. Specific examples include cellulose-based polymers, acrylic polymers, methacrylic polymers, polystyrene, polyamides, and polysiloxanes.

[0032] The content of the solvent in the liquid crystal aligning agent can be appropriately selected from the viewpoint of the application method and obtaining the desired film thickness of the liquid crystal alignment film. In particular, from the viewpoint of forming a uniform liquid crystal alignment film by application, the content of the solvent in the liquid crystal aligning agent is preferably 50 to 99.9 mass %, more preferably 60 to 99 mass %, and particularly preferably 65 to 99 mass %. The solvent used in the liquid crystal aligning agent is not particularly limited as long as it is a solvent that can dissolve the specific polymer. In particular, it is preferable to use the following solvents (also referred to as solvent type A):

[0033] Examples include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and 4-hydroxy-4-methyl-2-pentanone. Among these, it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone. These may be used alone or in combination. When the specific polymer has high solubility in the solvent, the following solvent (also referred to as solvent type B) can be used.

[0034] Examples of such solvents include the solvent B type described on pages 58 to 60 of International Publication WO2014 / 171493 (published October 23, 2014). Among these, 1-hexanol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, propylene glycol monobutyl ether, ethylene glycol monobutyl ether, dipropylene glycol dimethyl ether, cyclohexanone, cyclopentanone, or the solvents represented by formulas [D1] to [D3] are preferably used. Furthermore, when using solvent B type, it is preferable to use it in combination with N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone, which are included in solvent A type, in order to improve the coatability of the liquid crystal alignment agent. Since solvent B type can improve the coatability and surface smoothness of the liquid crystal alignment film, it is preferable to use it in combination with solvent A type. In this case, solvent B type preferably accounts for 1 to 60% by mass of the total solvent contained in the liquid crystal alignment agent. Of these, 10 to 50% by mass is preferred, and 20 to 40% by mass is more preferred.

[0035] In order to increase the film strength of the liquid crystal alignment film, it is preferable to incorporate a compound (collectively referred to as a crosslinkable compound) having at least one selected from an epoxy group, an isocyanate group, an oxetane group, a cyclocarbonate group, a hydroxy group, a hydroxyalkyl group, and a lower alkoxyalkyl group. In this case, the compound must contain two or more of these groups. Specific examples of crosslinkable compounds having an epoxy group or an isocyanate group include the crosslinkable compounds having an epoxy group or an isocyanate group described on pages 63-64 of International Publication WO2014 / 171493 (published October 23, 2014). Specific examples of crosslinkable compounds having an oxetane group include the crosslinkable compounds of formulas [4a] to [4k] described on pages 58-59 of International Publication WO2011 / 132751 (published October 27, 2011).

[0036] Specific examples of crosslinkable compounds having a cyclocarbonate group include the crosslinkable compounds of formula [5-1] to formula [5-42] listed on pages 76 to 82 of International Publication WO2012 / 014898 (published February 2, 2012). Specific examples of crosslinkable compounds having a hydroxyl group, a hydroxyalkyl group, and a lower alkoxyalkyl group include the melamine derivatives or benzoguanamine derivatives listed on pages 65 to 66 of International Publication WO2014 / 171493 (published October 23, 2014), and the crosslinkable compounds of formula [6-1] to formula [6-48] listed on pages 62 to 66 of International Publication WO2011 / 132751 (published October 27, 2011).

[0037] 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, a proportion of 0.1 to 50 parts by mass is more preferred. A proportion of 1 to 30 parts by mass is particularly preferred. A compound that promotes the imidization of a specific polymer can be used as the liquid crystal aligning agent. Specific examples include compounds for promoting imidization represented by formulas [B-1] to [B-17] described on pages 48 to 49 of International Publication WO 2022 / 176680 (published August 25, 2022), and these are preferred. The proportion of the crosslinkable compound used is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of all polymer components. A proportion of 1 to 20 parts by mass is more preferred. A proportion of 5 to 15 parts by mass is particularly preferred.

[0038] As long as the effects of the present invention are not impaired, the liquid crystal aligning agent can be a compound that improves the uniformity of the film 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 film 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 on page 67 of International Publication WO 2014 / 171493 (published October 23, 2014). The amount of the surfactant used is preferably 0.01 to 2 parts by mass per 100 parts by mass of all polymer components. A range of 0.01 to 1 part by mass is more preferred.

[0039] Specific examples of compounds that improve adhesion between a liquid crystal alignment film and a substrate include the compounds described on pages 67 to 69 of International Publication WO2014 / 171493 (published October 23, 2014). The proportion of the compound used is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, relative to 100 parts by mass of all polymer components. In addition to the compounds described above, the liquid crystal alignment agent may contain a dielectric or conductive substance added thereto for the purpose of changing the electrical properties, such as the dielectric constant and conductivity, of the cured film.

[0040] <Liquid Crystal Alignment Film / Liquid Crystal Light Control Element> The liquid crystal alignment agent can be applied to a substrate, baked, and then, if necessary, subjected to alignment treatment such as rubbing or photo-alignment treatment, to form an alignment film. 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, as well as films thereof, can be used. Plastic substrates and films are particularly preferred for use in light control windows, etc. From the perspective of process simplification, 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, or the like is formed for liquid crystal drive. Furthermore, when forming a reflective liquid crystal light control element, a substrate on which a metal such as a silicon wafer or aluminum or a dielectric multilayer film is formed can be used as the substrate on only one side.

[0041] The method for applying the liquid crystal aligning 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. After applying the liquid crystal aligning 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 aligning 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.

[0042] The thickness of the liquid crystal alignment film is preferably 5 to 500 nm, since too much thickness is disadvantageous in terms of power consumption of the liquid crystal light control element, and too thin thickness may reduce the reliability of the element. A thickness of 10 to 300 nm is more preferable, and a thickness of 10 to 250 nm is particularly preferable. In the present invention, in order to impart a pretilt angle to the liquid crystal, the baked liquid crystal alignment film is subjected to an alignment treatment such as a rubbing treatment in which the liquid crystal alignment film is rubbed in a certain direction with a roll wrapped with a cloth made of fibers such as nylon, rayon, or cotton, or a photo-alignment treatment. The photo-alignment treatment is a method in which the surface of the liquid crystal alignment film is irradiated with polarized radiation in a certain direction, and optionally a heat treatment is performed at a temperature of 150 to 250°C. The required pretilt angle is 2 to 20°, preferably 2 to 16°.

[0043] The liquid crystal of the liquid crystal composition used in the liquid crystal dimming element can be nematic, smectic, or cholesteric liquid crystal. From the viewpoint of low-voltage operation, a liquid crystal with a large dielectric constant anisotropy and a large refractive index anisotropy is preferred. Furthermore, two or more types of liquid crystals can be mixed and used depending on the physical properties of the phase transition temperature, dielectric constant anisotropy, and refractive index anisotropy. In the present invention, it is preferable to use nematic liquid crystals with positive dielectric anisotropy. In the present invention, it is preferable to use liquid crystals and a dichroic dye in the liquid crystal composition. This causes the dichroic dye to rotate 90° along the direction of the liquid crystal director (orientation direction) depending on whether or not a voltage is applied, resulting in differences in the absorption characteristics of the dichroic dye and resulting in a difference in brightness of the total light transmittance.

[0044] 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. Of these, it is preferable to use phthalocyanine dyes, azo dyes, or anthraquinone dyes. 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 (manufactured by Mitsui Chemicals, Inc.), M-1012 (manufactured by Mitsui Fine 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, the dichroic dyes can be used alone or in combination of two or more, depending on the properties.

[0045] The proportion of the dichroic dye used is preferably 0.01 to 10 parts by mass per 100 parts by mass of liquid crystal. From the viewpoint of the difference between colorless and transparent and colored (also referred to as the contrast in total light transmittance), a proportion of 0.1 to 5 parts by mass is more preferable. When a dichroic dye is used in a liquid crystal composition, the liquid crystal and the dichroic dye can be mixed and heated from the viewpoint of the solubility of the dichroic dye in the liquid crystal. In this case, it is preferable to heat the mixture to a temperature not exceeding the phase transition temperature of the liquid crystal.

[0046] In the present invention, a known chiral compound may be used in the liquid crystal composition. Specific examples include Schiff-based, azoxy-based, biphenyl-based, phenyl ester-based, phenylcyclohexane-based, and pyridine-based compounds, as well as mixtures thereof. The method for injecting the liquid crystal composition is not particularly limited, but may include, for example, the following method. That is, when glass substrates are used as the substrates, a pair of substrates each having a liquid crystal alignment film formed thereon is prepared, and a sealant is applied to four edges of one substrate, excluding a portion, and then the other substrate is attached to the other substrate with the liquid crystal alignment film facing inward to produce an empty cell. The liquid crystal composition is then injected under reduced pressure from the area where the sealant is not applied, thereby obtaining a liquid crystal composition-injected cell. Furthermore, when plastic substrates or films are used as the substrates, a pair of substrates each having a liquid crystal alignment film formed thereon is prepared, and the liquid crystal composition is dropped onto one substrate by an ODF (One Drop Filling) method or an inkjet method, and then the other substrate is attached to the other substrate to obtain a liquid crystal composition-injected cell.

[0047] The method for controlling the thickness (also referred to as the gap) of the liquid crystal layer of the liquid crystal light control element is not particularly limited, but 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. The gap of the liquid crystal layer is preferably 1 to 100 μm, more preferably 1 to 50 μm, and particularly preferably 2 to 30 μm. If the gap is too small, the contrast of the liquid crystal light control element decreases, and if it is too large, the driving voltage of the element increases. In order to increase the contrast of the total light transmittance of the liquid crystal light control element of the present invention, a polarizing plate can be attached to the outer surface thereof, or two liquid crystal cells can be attached to form a liquid crystal light control element.

[0048] The present invention will be described in more detail below with reference to examples, but is not limited to these examples. The abbreviations used in the examples and comparative examples and the methods for measuring each physical property are as follows. <Specific diamine (A)> <Specific diamine (B)> (Boc represents a tert-butoxycarbonyl group.) <Specific Diamine (C)>

[0049] <Tetracarboxylic acid dianhydride> <Crosslinkable compound>

[0050] <Adhesion compound> M1: LS-4668 (3-glycidoxypropyltriethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd.) <Solvent> NMP: N-methyl-2-pyrrolidone NEP: N-ethyl-2-pyrrolidone γ-BL: γ-butyrolactone BCS: ethylene glycol monobutyl ether PB: propylene glycol monobutyl ether

[0051] "Molecular Weight Measurement" The number average molecular weight (also referred to as Mn) and weight average molecular weight (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 Resonaq (formerly Showa Denko) K.K.) Column: GPC KD-803 and KD-805 (manufactured by Resonaq (formerly Showa Denko) K.K.) in series Column temperature: 50°C Eluent: N,N'-dimethylformamide (containing lithium bromide hydrate (LiBr.H) as an additive) ２ o-Phosphoric acid) at 30 mmol / L, tetrahydrofuran (THF) at 10 ml / L. Flow rate: 1.0 mL / min. Standard samples for preparing a calibration curve: TSK standard polyethylene oxide (molecular weight: approximately 900,000, 150,000, 100,000, and 30,000) (manufactured by Tosoh Corporation), and polyethylene glycol (molecular weight: approximately 12,000, 4,000, and 1,000) (manufactured by Polymer Laboratory Co., Ltd.).

[0052] "Synthesis of Polyimide Polymer" <Synthesis Example 1> A2 (2.07 g, 5.94 mmol), B1 (8.86 g, 29.7 mmol), C1 (3.57 g, 23.8 mmol), and NMP (118.5 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and dissolved by stirring at 25 ° C while introducing nitrogen. The mixture was then cooled to 25 ° C, and D1 (11.3 g, 57.6 mmol) and NMP (27.8 g) were added and stirred at 40 ° C for 24 hours to obtain a polyamic acid solution (1) with a resin solids concentration of 15% by mass. The NA of this polyamic acid was 10,900 and Mw was 26,800. Synthesis Example 2: A3 (2.26 g, 5.94 mmol), B1 (8.86 g, 29.7 mmol), C1 (3.57 g, 23.8 mmol), and NMP (119.5 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 25 ° C. while introducing nitrogen to dissolve the mixture. The mixture was then cooled to 25 ° C., and D1 (11.3 g, 57.6 mmol) and NMP (28.0 g) were added. The mixture was stirred at 40 ° C. for 24 hours to obtain a polyamic acid solution (2) with a resin solids concentration of 15% by mass. The Mn of this polyamic acid was 9,200 and the Mw was 23,000. Synthesis Example 3: A4 (1.29 g, 2.97 mmol), B1 (9.75 g, 32.7 mmol), C1 (3.57 g, 23.8 mmol), and NMP (119.0 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 25 ° C. while introducing nitrogen to dissolve the mixture. The mixture was then cooled to 25 ° C., and D1 (11.3 g, 57.6 mmol) and NMP (28.0 g) were added. The mixture was stirred at 40 ° C. for 24 hours to obtain a polyamic acid solution (3) with a resin solids concentration of 15% by mass. The Mn of this polyamic acid was 9,400 and the Mw was 25,000.

[0053] Synthesis Example 4: A2 (2.07 g, 5.94 mmol), B1 (5.32 g, 17.8 mmol), B2 (4.73 g, 11.9 mmol), C1 (3.57 g, 23.8 mmol), and NMP (124.0 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 25 ° C. while introducing nitrogen to dissolve the mixture. The mixture was then cooled to 25 ° C., and D1 (11.3 g, 57.6 mmol) and NMP (29.0 g) were added. The mixture was stirred at 40 ° C. for 24 hours to obtain a polyamic acid solution (4) with a resin solids concentration of 15% by mass. The Mn of this polyamic acid was 9,500 and the Mw was 25,800. Synthesis Example 5: A1 (1.74 g, 5.94 mmol), B1 (8.86 g, 29.7 mmol), C1 (3.57 g, 23.8 mmol), and NMP (117.0 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 25 ° C. while introducing nitrogen to dissolve the mixture. The mixture was then cooled to 25 ° C., and D1 (11.3 g, 57.6 mmol) and NMP (27.5 g) were added. The mixture was stirred at 40 ° C. for 24 hours to obtain a polyamic acid solution (5) with a resin solids concentration of 15% by mass. The Mn of this polyamic acid was 9,300 and the Mw was 24,500. Synthesis Example 6: A2 (2.07 g, 5.94 mmol), B1 (16.0 g, 53.5 mmol), and NMP (134.5 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and dissolved by stirring at 25°C while passing nitrogen. The mixture was then cooled to 25°C, and D1 (11.3 g, 57.6 mmol) and NMP (31.5 g) were added and stirred at 40°C for 24 hours to obtain a polyamic acid solution (6) with a resin solids concentration of 15% by mass. The polyamic acid had an Mn of 9,200 and an Mw of 23,800. Synthesis Example 7: A2 (2.07 g, 5.94 mmol), C1 (8.03 g, 53.5 mmol), and NMP (134.3 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and dissolved by stirring at 25°C while passing nitrogen. The mixture was then cooled to 25° C., and D1 (11.3 g, 57.6 mmol) and NMP (23.0 g) were added thereto, followed by stirring at 40° C. for 24 hours to obtain a polyamic acid solution (7) with a resin solids concentration of 15% by mass. The polyamic acid had an Mn of 9,100 and an Mw of 22,100.

[0054] Synthesis Example 8: B1 (10.6 g, 35.7 mmol), C1 (3.57 g, 23.8 mmol), and NMP (117.0 g) were added to a 300 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 25°C while introducing nitrogen to dissolve the mixture. The mixture was then cooled to 25°C, and D1 (11.3 g, 57.6 mmol) and NMP (27.5 g) were added. The mixture was stirred at 40°C for 24 hours to obtain a polyamic acid solution (8) with a resin solids concentration of 15% by mass. The Mn of this polyamic acid was 10,300 and the Mw was 26,800. The specifications of the polyimide polymer obtained above are shown in Table 1.

[0055]

[0056] "Production of Liquid Crystal Alignment Agents" Examples 1 to 9 and Comparative Examples 1 to 3 below describe production 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 Table 2.

[0057]

[0058] *1: Ratio (mass %) of specific polymer to other polymer in polyimide polymer *2: Amount (mass parts) of crosslinkable compound introduced per 100 mass parts of polyimide polymer

[0059] "Preparation of Liquid Crystal Composition" PA-1492 (positive liquid crystal) (manufactured by DIC Corporation) (10.0 g) and M-1012 (manufactured by Mitsui Fine Chemicals Co., Ltd.) (0.2 g) were mixed and stirred at 23°C for 24 hours to obtain liquid crystal composition (A).

[0060] "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. 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. Two rubbed substrates were then prepared. An 8 μm spacer was applied to the liquid crystal alignment film surface of one substrate, and 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. The substrates were then bonded together so that the liquid crystal alignment film surfaces faced each other. The bonded substrates were then pressed together and heated 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 liquid crystal cell was obtained by heating at 120°C for 30 minutes. The alignment uniformity of the liquid crystal was confirmed by observation under a polarizing microscope, and the liquid crystal was uniformly aligned in both liquid crystal cells (liquid crystal dimming elements).

[0061] "Evaluation of light stability of pretilt angle" The pretilt angle of the liquid crystal cell was measured before (initial) and after light irradiation, and the smaller the change in the value after light irradiation from the initial value, the better the evaluation. Specifically, the pretilt angle was measured using an AxoScan (manufactured by AXOMETRICS). For light irradiation, a film that cuts wavelengths of 380 nm or less was attached to the liquid crystal cell obtained above, 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. ２ The film was irradiated with light for 168 hours using a 340 nm wavelength cut filter (DayLight F Filter), and an internal layer temperature of 55° C. The results of the evaluation of the light stability of the pretilt angle are shown in Table 3.

[0062] "Evaluation of Light Stability of Voltage Holding Ratio" The voltage holding ratio of the liquid crystal cell was measured before (initial) and after light irradiation, and the smaller the change in value after light irradiation from the initial value, the better the evaluation. Specifically, the voltage holding ratio was measured using a voltage holding ratio measuring device (VHR-1) (manufactured by Toyo Corporation) by applying a voltage of 4 V for 60 μs at a temperature of 60°C, measuring the voltage after 166.7 ms, and calculating the voltage holding ratio as the extent to which the voltage was maintained. Light irradiation was performed under the same conditions as in the "Evaluation of Light Stability of Pretilt Angle" above. In Examples 1 to 5, in addition to the standard test, a stress test was also performed, measuring after 504 hours of light irradiation. The results of the evaluation of the light stability of the voltage holding ratio are shown in Table 3.

[0063] Example 1 NMP (8.40 g) and BCS (3.60 g) were added to a polyamic acid solution (1) (6.00 g) having a resin solid content of 15% by mass obtained by the synthesis method of Synthesis Example 1, and the mixture was stirred at 25°C for 5 hours to obtain a liquid crystal aligning agent (1). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that the solution was homogeneous. Using the obtained liquid crystal aligning agent (1), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed. Example 2 To a polyamic acid solution (1) (0.84 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 1 and a polyamic acid solution (8) (3.36 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 8, a 1.0% by mass solution of M1 in NMP (0.60 g), NMP (1.20 g), γ-BL (6.60 g), and BCS (5.40 g) were added, and the mixture was stirred at 25 ° C. for 5 hours to obtain a liquid crystal aligning agent (2). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that it was a homogeneous solution. Using the obtained liquid crystal aligning agent (2), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed. Example 3 Polyamic acid solution (1) (0.84 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 1 and polyamic acid solution (8) (3.36 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 8 were added with K1 (0.033 g), a 1.0 mass% solution of M1 in NMP (0.60 g), NMP (1.20 g), γ-BL (6.60 g), and BCS (5.40 g), and stirred at 25 ° C. for 5 hours to obtain a liquid crystal aligning agent (3). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed to be a homogeneous solution. Using the obtained liquid crystal aligning agent (3), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed.

[0064] Example 4 Polyamic acid solution (1) (0.84 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 1 and polyamic acid solution (8) (3.36 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 8 were added with K2 (0.033 g), a 1.0 mass% solution of M1 in NMP (0.60 g), NMP (1.20 g), γ-BL (6.60 g), and BCS (5.40 g), and stirred at 25 ° C. for 5 hours to obtain a liquid crystal aligning agent (4). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed to be a homogeneous solution. Using the obtained liquid crystal aligning agent (4), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed. Example 5 Polyamic acid solution (1) (0.84 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 1 and polyamic acid solution (8) (3.36 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 8 were added with K3 (0.033 g), a 1.0 mass% solution of M1 in NMP (0.60 g), NMP (1.20 g), γ-BL (6.60 g), and BCS (5.40 g), and stirred at 25 ° C. for 5 hours to obtain a liquid crystal aligning agent (5). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that it was a homogeneous solution. Using the obtained liquid crystal aligning agent (5), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed. Example 6 To a polyamic acid solution (2) (0.84 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 2 and a polyamic acid solution (8) (3.36 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 8, a 1.0 mass% solution of M1 in NMP (0.60 g), NMP (1.20 g), γ-BL (6.60 g), and BCS (5.40 g) were added, and the mixture was stirred at 25 ° C. for 5 hours to obtain a liquid crystal aligning agent (6). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that it was a homogeneous solution. Using the obtained liquid crystal aligning agent (6), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed.

[0065] Example 7 Polyamic acid solution (3) (0.84 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 3 and polyamic acid solution (8) (3.36 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 8 were added with a 1.0% by mass solution of M1 in NMP (0.60 g), NMP (1.20 g), γ-BL (6.60 g), and BCS (5.40 g), and stirred at 25 ° C. for 5 hours to obtain a liquid crystal aligning agent (7). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that it was a homogeneous solution. Using the obtained liquid crystal aligning agent (7), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed. Example 8 NEP (1.20 g), γ-BL (6.60 g), and PB (5.40 g) were added to a polyamic acid solution (4) (0.84 g) having a resin solid content of 15% by mass obtained by the synthesis method of Synthesis Example 4 and a polyamic acid solution (8) (3.36 g) having a resin solid content of 15% by mass obtained by the synthesis method of Synthesis Example 8, and the mixture was stirred at 25°C for 5 hours to obtain a liquid crystal aligning agent (8). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that the solution was a homogeneous solution. Using the obtained liquid crystal aligning agent (8), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed. Example 9 To a polyamic acid solution (1) (0.84 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 1 and a polyamic acid solution (5) (3.36 g) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 5, a 1.0 mass% NMP solution of M1 (0.60 g), NMP (1.20 g), γ-BL (6.60 g), and BCS (5.40 g) were added, and the mixture was stirred at 25 ° C. for 5 hours to obtain a liquid crystal aligning agent (9). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that it was a homogeneous solution. Using the obtained liquid crystal aligning agent (9), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were performed.

[0066] Comparative Example 1: NMP (8.40 g) and BCS (3.60 g) were added to 6.00 g of a polyamic acid solution (6) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 6, and the mixture was stirred at 25°C for 5 hours to obtain a liquid crystal aligning agent (10). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was confirmed to be a homogeneous solution. Using the obtained liquid crystal aligning agent (10), "evaluation of the photostability of the pretilt angle" and "evaluation of the photostability of the voltage holding ratio" were performed. Comparative Example 2: NMP (8.40 g) and BCS (3.60 g) were added to 6.00 g of a polyamic acid solution (7) having a resin solids concentration of 15% by mass obtained by the synthesis method of Synthesis Example 7, and the mixture was stirred at 25°C for 5 hours to obtain a liquid crystal aligning agent (11). This liquid crystal aligning agent showed no abnormalities such as turbidity or precipitation, and was confirmed to be a homogeneous solution. Using the obtained liquid crystal aligning agent (11), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were carried out. <Comparative Example 3> NMP (8.40 g) and BCS (3.60 g) were added to polyamic acid solution (8) (6.00 g) having a resin solid content concentration of 15 mass % obtained by the synthesis method of Synthesis Example 8, and the mixture was stirred at 25 ° C. for 5 hours to obtain liquid crystal aligning agent (12). No abnormalities such as turbidity or precipitation were observed in this liquid crystal aligning agent, and it was confirmed that the solution was a homogeneous solution. Using the obtained liquid crystal aligning agent (12), "evaluation of the light stability of the pretilt angle" and "evaluation of the light stability of the voltage holding ratio" were carried out.

[0067]

[0068] As can be seen from the above results, the liquid crystal cells of the Examples exhibited the desired pretilt angle and were superior in light stability of the pretilt angle and voltage holding ratio compared to the liquid crystal cells of the Comparative Examples. Specifically, the comparison was made between Examples using a specific polymer and Comparative Examples using other polymers, i.e., between Example 1 and Comparative Examples 1 to 3. Furthermore, when the specific polymer and the second polymer were used, the decrease in voltage holding ratio in the stress test was smaller. Specifically, the comparison was made between Example 1 and Example 2 under the same conditions. Furthermore, when a crosslinkable compound was introduced into the liquid crystal alignment agent, the decrease in voltage holding ratio in the stress test was smaller. Specifically, the comparison was made between Example 2 and Examples 3 to 5 under the same conditions.

[0069] By using a liquid crystal aligning agent containing a polyimide polymer having a specific structure according to the present invention, a liquid crystal light control device can be obtained that exhibits good liquid crystal alignment and excellent electrical properties. In particular, these properties do not deteriorate even under harsh conditions of long-term exposure to light. Therefore, the liquid crystal light control device of the present invention is useful in liquid crystal displays for display purposes, as well as in light control windows and optical shutters that control the transmission and blocking of light.

[0070] The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2024-5688, filed on January 17, 2024, are hereby incorporated by reference as the disclosure of the present invention.

Claims

1. A liquid crystal aligning agent containing at least one polymer selected from a polyimide precursor and a polyimide obtained by reacting a diamine component containing a diamine of the following formula [1a], a diamine of the formula [2a], and a diamine of the formula [3a] with a tetracarboxylic acid component. (X represents at least one structure selected from the following formula [1-1] and formula [1-2]. Each Xm independently represents an integer of 1 to 4. Xp represents an integer of 0 or 1. When a plurality of Xs exist, the plurality of Xs may be the same as or different from each other.) (X １ represents 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 )CO-, -COO- and -OCO-, and represents at least one selected therefrom. X ２ represents a single bond or -(CH ２ ) ｂ -(b is an integer of 1 to 15). X ３ represents a single bond, -(CH ２ ) ｃ -(c is an integer of 1 to 15), -O-, -OCH ２ -, -COO- and -OCO-, and represents at least one selected therefrom. X ４ represents at least one divalent cyclic group selected from a benzene ring, a cyclohexane ring, and a heterocyclic ring, or a divalent organic group having 17 to 51 carbon atoms and having a steroid skeleton. Any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxyl group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxyl group having 1 to 3 carbon atoms, or a fluorine atom. X ５ represents at least one cyclic group selected from a benzene ring, a cyclohexane ring, and a heterocyclic ring. Any hydrogen atom on these cyclic groups may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxyl group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxyl group having 1 to 3 carbon atoms, or a fluorine atom. Xn represents an integer of 0 to 4. X ６ represents at least one selected from an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 18 carbon atoms, an alkoxyl group having 1 to 18 carbon atoms, and a fluorine-containing alkoxyl group having 1 to 18 carbon atoms. * represents a bond.) (X ７ is a single bond, -O-, -CH ２ O-, -CONH-, -NHCO-, -CON(CH ３ )-, -N(CH ３ )CO-, -COO- and -OCO-, and represents at least one selected therefrom. X ８ represents an alkyl group having 8 to 22 carbon atoms or a fluorine-containing alkyl group having 6 to 18 carbon atoms. * represents a bond.) (Y １ and Y ２ each independently represents -(CH ２ ) ｂ -(b is an integer from 1 to 12). Y ３ and Y ４ each independently represents a hydrogen atom or a tert-butoxycarbonyl group.) (R １ and R ２ each independently represents a hydrogen atom or a methyl group. Pn represents an integer from 1 to 6.) 2. At least one polymer selected from a polyimide precursor and a polyimide, obtained by reacting a diamine component containing no diamine of the formula [1] but containing a diamine of the formula [2] and a diamine of the formula [3] with a tetracarboxylic acid component, the liquid crystal aligning agent according to claim 1.

3. The liquid crystal aligning agent according to claim 1 or 2, wherein the tetracarboxylic acid component contains a tetracarboxylic acid represented by the following formula [4]. (Z represents at least one structure selected from the following formulas [4a] to [4l].) (Z Ａ to Z Ｄ each independently represents a hydrogen atom, a methyl group, a chlorine atom or a benzene ring. Z Ｅ and Z Ｆ each independently represents a hydrogen atom or a methyl group.) 4. The liquid crystal aligning agent according to claim 1 or 2, comprising a compound having at least one structure selected from an epoxy group, an isocyanate group, an oxetane group, a cyclocarbonate group, a hydroxyl group, a hydroxyalkyl group, and an alkoxyalkyl group having 1 to 3 carbon atoms.

5. A liquid crystal alignment film obtained from the liquid crystal aligning agent according to claim 1 or 2.

6. A liquid crystal light control element having the liquid crystal alignment film according to claim 5.

7. The liquid crystal light control element according to claim 6, wherein the liquid crystal composition used for the liquid crystal light control element contains a liquid crystal and a dichroic dye.

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