Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element using same

Abstract

The purpose of the present invention is to provide a liquid crystal display element in which an AC afterimage does not readily occur. A further purpose of the present invention is to provide a liquid crystal alignment film used in the liquid crystal display element, and a liquid crystal alignment agent for manufacturing the liquid crystal alignment film.　Provided is a liquid crystal alignment agent containing at least one type of polymer selected from a polyimide and a polyimide precursor having a structure represented by formula (1). (In the formula, Xa and Xc each independently represent a divalent organic group, Xb represents an organic group having 4-30 carbon atoms, Xd represents a monovalent organic group, and aX represents an integer of 2.)

Description

Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element using the same

[0001] The present invention relates to a liquid crystal aligning agent used in the production of a liquid crystal display element, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a liquid crystal display element using the liquid crystal alignment film.

[0002] Currently, highly durable polyimide-based organic films are used in industrially utilized resin coatings. In particular, these polyimide-based organic films are also used as liquid crystal alignment films in liquid crystal display elements. Polyimide-based organic films are formed from resin compositions containing polyimide precursors, such as polyamic acid and polyimide. That is, they are formed by applying a resin composition containing polyamic acid or polyimide to a substrate and then undergoing a baking process (see, for example, Patent Document 1). In lateral electric field drive liquid crystal display elements, such as those using the IPS (In Plane Switching) drive system and the FFS (Fringe Field Switching) drive system, alignment treatments, such as a rubbing treatment in which the baked 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, are performed to horizontally align the liquid crystal.

[0003] In recent years, with the increase in size and resolution of liquid crystal display elements, problems have arisen, such as scratches and dust generation on liquid crystal alignment films caused by rubbing treatment, and low in-plane uniformity of liquid crystal alignment. In response to these problems, a new alignment treatment method has begun to be adopted, in which the alignment of liquid crystals is controlled by irradiating polarized radiation (light) (also known as photoalignment treatment). As this photoalignment treatment, methods utilizing photoisomerization reaction, photocrosslinking reaction, and photodecomposition reaction have been proposed (see, for example, Patent Document 1 and Patent Document 2).

[0004] Japanese Unexamined Patent Publication No. 9-297313 Japanese Unexamined Patent Application No. 2004-206091

[0005] Liquid crystal alignment films used in IPS-driven and FFS-driven liquid crystal display elements are required to have high liquid crystal alignment control properties (also known as liquid crystal alignment stability) to suppress image retention (also known as AC image retention) that occurs during long-term AC driving. Therefore, an object of the present invention is to provide a liquid crystal alignment film with high liquid crystal alignment stability using a liquid crystal aligning agent containing a polyimide-based polymer having a specific structure. Another object of the present invention is to provide a liquid crystal display element equipped with a liquid crystal alignment film that meets the above requirements. Additionally, an object of the present invention is to provide a diamine having a specific structure.

[0006] As a result of intensive research to achieve the above object, the present inventors have completed the present invention, which has the following gist: A liquid crystal aligning agent containing a polyimide precursor having a structure (also referred to as a specific structure) of the following formula [1] and at least one polymer (also referred to as a specific polymer) selected from polyimides. (X ａ and X ｃ Each of X independently represents a divalent organic group. ｂ represents an organic group having 4 to 30 carbon atoms. ｄ represents a monovalent organic group. aX represents an integer of 2.

[0007] According to the present invention, a liquid crystal display element that is less susceptible to AC image retention can be provided. Therefore, the liquid crystal display element of the present invention is suitable for use in in-plane switching drive elements such as IPS drive systems and FFS drive systems, and is used in smartphones, tablet terminals, etc. The mechanism by which the present invention provides a liquid crystal display element with the above-described excellent characteristics is not entirely clear, but is presumed to be roughly as follows.

[0008] X in the formula [1] ｂ is an organic group having 4 to 30 carbon atoms, but when a cyclic structure such as a cyclobutane ring or a benzene ring is used, the imide group in the specific polymer after baking is likely to assume a similar state due to its high planarity and linearity. As a result, in the liquid crystal alignment film, the imide group, which has a strong interaction with the liquid crystal, is more likely to interact with the liquid crystal. Furthermore, since these cyclic structures are highly rigid, the stability of the interaction is also increased. In addition, X in formula [1]ｂ -C(=O)-OX bonded to ｄ The moiety -C(=O)-O- has high polarity and serves as a moiety that strengthens interaction with the liquid crystal.

[0009] From the above points, the liquid crystal alignment film has a strong interaction with the liquid crystal, and its stability is increased, so that a liquid crystal display element in which AC afterimages are unlikely to occur can be obtained.

[0010] <Specific Structure> The specific structure is a structure of the above formula [1]. Among them, in the present invention, a structure of the following formula [1-1] is preferred.

[0011] * indicates a bond. X １ and X ５ Each of X independently represents at least one cyclic group selected from a benzene ring, a biphenyl group, a naphthalene group, and a pyridine ring. Of these, a benzene ring, a biphenyl group, or a pyridine ring is preferred. Any hydrogen atom on these cyclic groups may be substituted with a monovalent organic group, and in this case, it is preferred that the hydrogen atom be substituted with an alkyl group having 1 to 3 carbon atoms. ２ is a single bond, *1-OCH ２ - and *1-OCH ２ CH ２ - represents at least one selected from, and *1 represents X １ Among them, a single bond or *1-OCH ２ CH ２ - is preferred. ３ represents at least one cyclic group selected from a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, and a benzene ring. Among these, a cyclobutane ring, a cyclohexane ring, or a benzene ring is preferred. ６ Any hydrogen atom of a carbon atom not bonded to may be substituted with a monovalent organic group, a chlorine atom, or a fluorine atom, and in this case, it is preferably substituted with an alkyl group having 1 to 3 carbon atoms.

[0012] X ４ is a single bond, -CH ２ O-*2 and -CH ２ CH ２O-*2, where *2 is X ５ In particular, a single bond or -CH ２ CH ２ O-*2 is preferred. ６ represents at least one selected from an optionally branched alkyl group having 1 to 10 carbon atoms, a benzene ring, and a tert-butoxycarbonyl group. Among these, an optionally branched alkyl group having 1 to 10 carbon atoms is preferred. a1 represents an integer of 2, and X ６ All of these may be the same or different.

[0013] X in the formula [1] ｂ Examples of the compound include structures of the following formulas [b-1] to [b-23]. (** are each independently *3-X ａ -O-C(=O)-, *3-C(=O)-O-X ｃ - or *3-C(=O)-O-X ６ *3 indicates the bond to the side.)

[0014] <Specific Polymer> The specific polymer is a polyimide precursor or polyimide (collectively referred to as a polyimide polymer) having a specific structure. It is preferable that it is obtained by reacting a diamine component with a tetracarboxylic acid component. The polyimide precursor is preferably a polyamic acid or polyamic acid ester having a structure of the following formula [A]:

[0015] (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.

[0016] 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 of the structures of the following formulas [A-1] to [A-3] in addition to the structure of formula [A-4].

[0017] (R ａ , R ｂ , A １ ~A ４ is defined as 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.

[0018] 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].

[0019] (R ａ and R ｂ has the same meaning as defined in the above formula [A].

[0020] In addition, a polymer of formula [D] can be synthesized by a conventional synthesis method. １ and A ２ and A in formula [A] ３ and A ４ It 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] (also called a specific diamine):

[0021] X represents at least one selected from the formula [1] and the formula [1-1], and X in X ａ ~X ｄ , aX,X １ ~X ６ The details and preferences of a1 and a2 are the same as those of the formula [1] and formula [1-1]. １ and R ２ are each independently a hydrogen atom or a monovalent organic group, and are preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0022] Specific examples of the specific diamine include those represented by the following formulas [1a-a] to [1a-d]. X １ , X ２ , X ４ ~X ６ , R １ and R ２ The details and preferences of are the same as those of the formula [1a].

[0023] More specific specific diamines include those represented by the following formulae [1a-1] to [1a-6], and it is preferable to use these.

[0024] From the viewpoint of reducing AC image retention in liquid crystal display elements, the proportion of the specific diamine used is 20 to 80 mol % relative to the total diamine components. It is more preferably 30 to 70 mol %, and particularly preferably 30 to 60 mol %. Furthermore, the specific diamine can be used alone or in combination of two or more types depending on the properties.

[0025] The polyimide polymer may use diamines other than the specific diamines as the diamine component, 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 WO2023 / 074568 (published May 4, 2023). In the present invention, diamines represented by the following formulas [DA-1] to [DA-103] may be used.

[0026]

[0027]

[0028]

[0029]

[0030] These "other diamines" can be used alone or in combination of two or more depending on the properties. As the tetracarboxylic acid component for producing the polyimide polymer, it is preferable to use a tetracarboxylic acid dianhydride represented by the following formula [2] 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 a specific tetracarboxylic acid component).

[0031] (Z represents at least one structure selected from the following formulas [2a] to [2l].)

[0032] (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.) Among these, from the viewpoint 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]. More preferred are formula [2a], formula [2d], formula [2e], formula [2f] or formula [2k]. Particularly preferred are formula [2a], formula [2d], formula [2e] or formula [2f].

[0033] The proportion of the specific tetracarboxylic acid component used is preferably 1 mol % or more, more preferably 5 mol % or more, and particularly preferably 10 mol % or more, relative to the total tetracarboxylic acid components. From the viewpoint of the optical properties of the liquid crystal display element, the proportion is most preferably 50 to 100 mol %.

[0034] The polyimide polymer may contain "other 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 tetracarboxylic acid compounds, tetracarboxylic acid dianhydrides, dicarboxylic acid dihalide compounds, dicarboxylic acid dialkyl ester compounds, and dialkyl ester dihalide compounds shown below. Specific examples of the "other tetracarboxylic acid components" include those described on pages 34 to 35 of International Publication WO 2015 / 012368 (published January 29, 2015). In the present invention, tetracarboxylic acid dianhydrides and derivatives thereof represented by the following formulae [CA-1] to [CA-26] may be used.

[0035]

[0036] The specific tetracarboxylic acid component and the other tetracarboxylic acid component can be used alone or in combination of two or more depending on their respective properties. The method for synthesizing the polyimide polymer is not particularly limited. It is typically obtained by reacting a diamine component with a tetracarboxylic acid component. Specifically, the method described on pages 35 and 36 of International Publication WO2015 / 012368 (published January 29, 2015) can be mentioned.

[0037] The polyamic acid ester can be synthesized by known methods such as a method of reacting a polyamic acid of a polyimide precursor obtained by reacting a diamine component with a tetracarboxylic acid component with an esterifying agent, a method of reacting the tetracarboxylic acid diester with a diamine, or a method of reacting the tetracarboxylic acid diester with a dihalide.

[0038] 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.

[0039] (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.

[0040] 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 taken as 1.0. When the total number of moles of the tetracarboxylic acid components is less 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 will have an amino group structure at its terminal. When the total number of moles of the tetracarboxylic acid components is greater than 1.0, i.e., when the total number of moles of the tetracarboxylic acid components is greater than the number of moles of the diamine components, the polymer will have a carboxylic anhydride or dicarboxylic acid structure at its terminal. 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, a rate of 40 to 90% is preferred. A rate of 50 to 80% is more preferred. The polyimide-based polymer may be converted into a terminal-capped polymer using a terminal-capping agent. Terminal-capped polymers have the effect of increasing the film hardness of resin coatings and liquid crystal alignment films and improving the adhesion between liquid crystal alignment films and sealants in liquid crystal display elements.

[0041] 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 resin coating or 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.

[0042] <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 this case, two or more types of specific polymers can be used. The polymer components do not all need to be specific polymers, and polyimide-based polymers without a specific structure may be mixed. In this case, the proportion of the polyimide-based polymer without a specific structure used is preferably 10 to 1,000 parts by mass per 100 parts by mass of the specific polymer. More preferably, it is 10 to 400 parts by mass. Furthermore, polymers other than polyimide-based polymers may be mixed with the polymer components. Specific examples include cellulose-based polymers, acrylic polymers, methacrylic polymers, polystyrene, polyamides, and polysiloxanes.

[0043] 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):

[0044] 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, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and γ-butyrolactone are preferred. These may be used alone or in combination.

[0045] When the specific polymer has high solubility in the solvent, the following solvents (also referred to as solvent type B) can be used. Examples include solvent type B 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 solvent type B is used, 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 type A, in order to improve the coatability of the liquid crystal aligning agent.

[0046] Since Solvent Type B can improve the coating properties and surface smoothness of the liquid crystal alignment film, it is preferably used in combination with Solvent Type A. In this case, Solvent Type B preferably accounts for 1 to 60 mass% of the total solvent contained in the liquid crystal alignment agent. Of these, 10 to 50 mass% is preferred. 20 to 40 mass% is even more preferred. In order to increase the film strength of the liquid crystal alignment film, it is preferable to incorporate a 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 (collectively referred to as a crosslinkable compound) into the liquid crystal alignment agent. In this case, the compound must have two or more of these groups.

[0047] 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 to 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 to 59 of International Publication WO2011 / 132751 (published October 27, 2011). Specific examples of crosslinkable compounds having a cyclocarbonate group include the crosslinkable compounds of formulas [5-1] to [5-42] described on pages 76 to 82 of International Publication WO2012 / 014898 (published February 2, 2012). Specific examples of the crosslinkable compound having a hydroxyl group, a hydroxyalkyl group, and a lower alkoxyalkyl group include the melamine derivatives or benzoguanamine derivatives described on pages 65 to 66 of International Publication WO2014 / 171493 (published on October 23, 2014), and the crosslinkable compounds of formulas [6-1] to [6-48] described on pages 62 to 66 of International Publication WO2011 / 132751 (published on October 27, 2011).

[0048] 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.

[0049] 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.

[0050] 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 relative to 100 parts by mass of all polymer components. A more preferred proportion is 1 to 20 parts by mass. In addition to the compounds other than those mentioned 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 liquid crystal alignment film.

[0051] <Liquid Crystal Alignment Film / Liquid Crystal Display Element> A liquid crystal alignment agent can be applied to a substrate, baked, and then subjected to alignment treatment such as rubbing or photo-alignment treatment to form a liquid crystal alignment film. The substrate used for 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 and polycarbonate substrates can also be used. From the perspective of simplifying the manufacturing process, it is preferable to use a substrate formed with an ITO (Indium Tin Oxide) electrode for liquid crystal drive. Furthermore, in reflective liquid crystal display elements, an opaque substrate such as a silicon wafer can be used for only one substrate. In this case, light-reflecting materials such as aluminum can also be used for the electrodes. The application method for the liquid crystal alignment agent is not particularly limited, but industrially, screen printing, offset printing, flexographic printing, inkjet printing, etc. are commonly used. Other application methods include dipping, roll coating, slit coating, spinning, and spraying, and these may be used depending on the purpose.

[0052] 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. In particular, 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 after baking is preferably 5 to 500 nm, because if it is too thick, it will be disadvantageous in terms of power consumption of the liquid crystal display 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. When liquid crystal is to be tilted or horizontally aligned, as in the case of liquid crystal display elements of the TN (Twisted Nematic) drive system, the IPS drive system, and the FFS drive system, the liquid crystal alignment film after baking 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. On the other hand, in the case of the VA (Vertical Alignment) drive system, the alignment treatment is not required.

[0053] Photo-alignment treatment is a method in which the surface of a liquid crystal alignment film is irradiated with polarized radiation in a certain direction, and optionally heat-treated at a temperature of 150 to 250°C. The radiation can be ultraviolet light or visible light having a wavelength of 100 to 800 nm. Of these, ultraviolet light having a wavelength of 100 to 400 nm is preferred. Ultraviolet light having a wavelength of 200 to 400 nm is more preferred. The radiation dose is 1 to 10,000 mJ / cm. ２ Among these, 100 to 5,000 mJ / cm is preferable. ２ When irradiating with radiation, it is preferable to irradiate the substrate with the liquid crystal alignment film while heating it at 50 to 250° C. in order to increase the stability of the liquid crystal alignment. This allows the liquid crystal to be stably aligned in a certain direction.

[0054] The liquid crystal alignment film treated by the above method can be subjected to a contact treatment or heat treatment using water or an organic solvent. The organic solvent used in the contact treatment is not particularly limited as long as it dissolves decomposition products generated from the liquid crystal alignment film upon irradiation with radiation. Specific examples include methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, and cyclohexyl acetate. These organic solvents and water can be used alone or in combination. The heat treatment temperature is preferably 50 to 300°C, more preferably 120 to 250°C. The heat treatment time is preferably 1 to 30 minutes. The liquid crystal used in the liquid crystal display element can be a nematic liquid crystal, a smectic liquid crystal, or a cholesteric liquid crystal. From the viewpoint of low-voltage driving, a liquid crystal having a large dielectric anisotropy and a large refractive index anisotropy is preferable. Two or more types of liquid crystals can be mixed and used depending on the physical properties of the phase transition temperature, dielectric anisotropy, and refractive index anisotropy. Spacers can also be introduced into the liquid crystal to control the electrode gap (also called the gap) of the liquid crystal display element.

[0055] The method for injecting the liquid crystal is not particularly limited, and examples thereof include the following. That is, when glass substrates are used as the substrates, a pair of substrates on which a liquid crystal alignment film is formed is prepared, and a sealant is applied to four edges of one substrate, excluding a portion, and then the other substrate is attached with the liquid crystal alignment film facing inward to prepare an empty cell. A method is also available in which a 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 plastic substrates or films are used as the substrates, a pair of substrates on which a liquid crystal alignment film is formed 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 obtain a liquid crystal composition-injected cell. The gap of the liquid crystal display element can be controlled using the spacers described above. Examples of such a method include, as described above, introducing spacers of the desired size into the liquid crystal or using substrates having column spacers of the desired size. Furthermore, when plastic or film substrates are used as the substrates and the substrates are bonded together by lamination, the gap can be controlled without introducing spacers. The size of the gap in the liquid crystal display element 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 display element will decrease, and if it is too large, the driving voltage of the liquid crystal display element will increase.

[0056] The present invention will be described in more detail below with reference to examples, but is not limited to these. The abbreviations used in the synthesis examples, examples, and comparative examples, and the methods for measuring each physical property are as follows. <Solvents> THF: tetrahydrofuran DMF: N,N-dimethylformamide IPA: 2-propanol NMP: N-methyl-2-pyrrolidone BCS: ethylene glycol monobutyl ether

[0057] <Specific diamines> A1 to A5: Diamines of the following formulae [A1] to [A5]

[0058] <Other diamines> B1 to B6: Diamines of the following formulas [B1] to [B6] (Boc represents a tert-butoxycarbonyl group.)

[0059] <Tetracarboxylic acid dianhydrides> C1 to C2: Tetracarboxylic acid dianhydrides of the following formulae [C1] to [C2]

[0060] <Compounds that Promote Imidization> F1 to F2: Compounds of the following formulae [F1] to [F2] (Fmoc represents a 9-fluorenylmethoxycarbonyl group. Boc represents a tert-butoxycarbonyl group.)

[0061] <Crosslinkable Compound> K1: Compound of the following formula [K1]

[0062] <Compound for improving adhesion> M1: a compound of the following formula [M1]

[0063] "Viscosity Measurement" Measurement was carried out using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C, a sample amount of 1.1 mL, and a cone rotor TE-1 (1°34', R24). "Synthesis of specific diamines" The specific diamines (A1) to (A5) are novel compounds not disclosed in literature, and their synthesis methods are shown below. The specific diamines in the examples are １ The compound was identified by H-NMR analysis. Apparatus: Fourier transform superconducting nuclear magnetic resonance spectrometer (FT-NMR) "AVANCE III" (manufactured by BRUKER) 500 MHz, solvent: deuterated dimethyl sulfoxide (DMSO-d ６ , standard substance: tetramethylsilane)

[0064] Example 1 1,2,3,4-Cyclobutanetetracarboxylic acid 1,3-dimethyl ester (CBDE-Me) (26.0 g, 100 mol) was dissolved in THF (260 g), one drop of DMF was added, and the mixture was stirred in an ice bath. To this, oxalyl chloride (27.9 g, 220 mmol) was slowly added dropwise. After the addition was complete, the mixture was stirred at 23°C, and after confirming the completion of the reaction, the solution was used in the next step as is. 4-Nitrophenol (30.6 g, 220 mmol) was dissolved in THF (300 g), pyridine (27.7 g, 350 mmol) was added, and the mixture was stirred in an ice bath. To this, the crude product (acid chloride) obtained above was slowly added dropwise using a dropping funnel. After the addition was complete, the mixture was stirred at 0°C for 3 hours. After the reaction was stopped, pure water (520 g) was added to the reaction solution and stirred. The precipitated crystals were filtered off, and the resulting crystals were washed with pure water and then methanol. DMF (260 g) was added to the resulting crude product, and slurry washing was performed at 60 °C. The crystals were filtered off, and the cake was washed with DMF, THF, and methanol in that order, and dried to obtain compound (1-1) (yield: 30.1 g, 60.0 mmol, yield: 60%, white crystals). DMF (180 g) and methanol (180 g) were added to the compound (1-1) obtained above (30.1 g, 60.0 mmol), and the mixture was purged with nitrogen. Then, carbon-supported palladium (5% Pd carbon powder (hydrated product) K type, manufactured by N.E. Chemcat Corporation) (3.00 g) was added, and the mixture was purged with nitrogen again. A Tedlar bag containing hydrogen was attached, and the mixture was stirred at 23 °C for 25 hours. After the reaction was completed, the carbon-supported palladium was removed by passing the filtrate through a membrane filter, and the filtrate was concentrated to approximately 50 g. IPA (320 g) was added to precipitate crystals. The resulting crystals were washed with IPA and dried under reduced pressure at 40°C to obtain specific diamine (A1) (yield: 26.0 g, 58.8 mmol, yield: 98%, pink-white crystals). １ H-NMR (500MHz, DMSO-d6): δ (ppm) = 6.74 (4H, d), 6.56 (4H, d), 5.07 (4H, s), 3.92 (4H, m), 3.69 (6H, s).

[0065] Example 2 In a 500 mL four-neck flask, 4-nitrophenol (8.35 g, 60.0 mmol) and THF (83.5 g) were dissolved, and triethylamine (TEA) (6.68 g, 66.0 mmol) was added and stirred in an ice bath. A solution of dimethyl 2,4-bis(chlorocarbonyl)-2,4-dimethylcyclobutane-1,3-dicarboxylate (1,3-DMCBDECl) (9.75 g, 30.0 mmol) dissolved in THF (39.0 g) was slowly added dropwise using a dropping funnel. After the addition was completed, the mixture was stirred at 23°C for 15 hours. Purified water (300 g) was added to the reaction solution and stirred. The precipitated crystals were filtered off. The resulting crystals were cake-washed with methanol and dried under reduced pressure at 40°C to obtain compound (2-1) (yield: 14.5 g, 27.3 mmol, 91%). To the compound (2-1) (14.5 g, 27.3 mmol) obtained above, THF (290 g) was added and the mixture was purged with nitrogen. Then, carbon-supported palladium (5% Pd carbon powder (hydrated product) K type, manufactured by N.E. Chemcat Corporation) (1.45 g) was added, the mixture was purged with nitrogen again, a Tedlar bag containing hydrogen was attached, and the mixture was stirred at 23°C for 24 hours. After completion of the reaction, the carbon-supported palladium was removed by passing the mixture through a membrane filter, and the filtrate was concentrated to approximately 30 g, and methanol (290 g) was added to precipitate crystals. The obtained crystals were cake-washed with methanol and dried under reduced pressure at 40°C to obtain specific diamine (A2) (yield: 10.8 g, 23.0 mmol, yield: 84%, white crystals). １ H-NMR (500MHz, DMSO-d6): δ (ppm) = 6.77 (4H, d), 6.56 (4H, d), 5.08 (4H, s), 3.75 (2H, s), 3.67 (6H, s), 1.59 (6H, s).

[0066] Example 3 2,5-bis(methoxycarbonyl)terephthalic acid (PMDE-Me) (11.3 g, 40.0 mmol) was dissolved in THF (226 g), one drop of DMF was added, and the mixture was stirred in an ice bath. To this, oxalyl chloride (12.7 g, 100 mmol) was slowly added dropwise. After the addition was completed, the mixture was stirred at 23°C, and after confirming the completion of the reaction, THF and oxalyl chloride were distilled off to obtain a crude product (acid chloride). This crude product was used in the next step. 4-Nitrophenol (13.9 g, 100 mmol) was dissolved in THF (56 g), and triethylamine (TEA) (14.2 g, 140 mmol) was added and the mixture was stirred in an ice bath. To this, a solution of the crude product (acid chloride) obtained above in THF (226 g) was slowly added dropwise using a dropping funnel. After the dropwise addition was completed, the mixture was stirred at 23°C for 19 hours. Pure water (450 g) was added to the reaction solution and stirred. The precipitated crystals were filtered off. The resulting crystals were cake-washed with pure water and then methanol, and dried under reduced pressure at 40°C to obtain compound (3-1) (yield: 19.0 g, 36.2 mmol, yield: 91%). To the compound (3-1) (17.2 g, 32.8 mmol) obtained above, NMP (258 g) was added and the mixture was purged with nitrogen. Then, carbon-supported palladium (5% Pd carbon powder (hydrated product) K type, manufactured by N.E. Chemcat Corporation) (1.72 g) was added and the mixture was purged with nitrogen again. A Tedlar bag containing hydrogen was attached, and the mixture was stirred at 50°C for 38 hours. After the reaction was completed, the carbon-supported palladium was removed by passing it through a membrane filter. The filtrate was concentrated to approximately 50 g, and IPA (100 g) was added to precipitate crystals. The obtained crystals were cake-washed with IPA and dried under reduced pressure at 40° C. to obtain specific diamine (A3) (yield: 14.0 g, 30.1 mmol, yield: 92%, beige crystals). １ H-NMR (500MHz, DMSO-d6): δ (ppm) = 8.35 (2H, s), 6.96 (4H, d), 6.62 (4H, d), 5.21 (4H, s), 3.91 (6H, s).

[0067] Example 4 In a 500 mL four-neck flask, 4-nitro-m-cresol (17.7 g, 116.0 mmol) and THF (70.0 g) were dissolved, and triethylamine (TEA) (15.6 g, 154 mmol) was added and stirred in an ice bath. A solution of dimethyl 2,4-bis(chlorocarbonyl)-2,4-dimethylcyclobutane-1,3-dicarboxylate (1,3-DMCBDECl) (17.9 g, 55.0 mmol) dissolved in THF (72.0 g) was slowly added dropwise using a dropping funnel. After the addition was complete, the mixture was stirred at 23°C for 2 hours. Purified water (340 g) was added to the reaction solution and stirred. The precipitated crystals were filtered off, washed with methanol, and dried under reduced pressure at 40°C to obtain compound (4-1) (yield: 28.0 g, 50.1 mmol, 91%). To the compound (4-1) (28.0 g, 50.1 mmol) obtained above, THF (420 g) was added and the mixture was purged with nitrogen. Then, carbon-supported palladium (5% Pd carbon powder (hydrated product) K type, manufactured by N.E. Chemcat Corporation) (2.80 g) was added and the mixture was purged with nitrogen again. A Tedlar bag containing hydrogen was attached and the mixture was stirred at 23°C for 22 hours. After completion of the reaction, the carbon-supported palladium was removed by passing the mixture through a membrane filter. The filtrate was concentrated to approximately 40 g, and crystals were precipitated. Ethanol (140 g) was added to the mixture to precipitate further crystals. The obtained crystals were cake-washed with ethanol and dried under reduced pressure at 40°C to obtain specific diamine (A4) (yield: 24.1 g, 48.3 mmol, yield: 97%, white crystals). １ H-NMR (500MHz, DMSO-d6): δ (ppm) = 6.77 (2H, s), 6.65 (2H, d), 6.60 (2H , d), 4.84 (4H, s), 3.74 (2H, s), 3.67 (6H, s), 2.05 (6H, s), 1.59 (6H, s).

[0068] Example 5 In a 500 mL four-neck flask, 4-hydroxy-4'-nitrobiphenyl (20.5 g, 95.0 mmol) and THF (143.1 g) were dissolved, triethylamine (TEA) (11.5 g, 114 mmol) was added, and the mixture was stirred in an ice bath. To this was added dimethyl 2,4-bis(chlorocarbonyl)-2,4-dimethylcyclobutane-1,3-dicarboxylate (1,3-DMCBDECl) (12.4 g, 38.0 mmol) in powder form, little by little. After the addition was complete, the mixture was stirred at 23°C for 22 hours. Pure water (500 g) was added to the reaction solution, and the mixture was stirred. The precipitated crystals were filtered off, washed with methanol, and dried under reduced pressure at 40°C to obtain compound (5-1) (yield: 18.4 g, 27.0 mmol, 71%). To the compound (5-1) (18.4 g, 27.0 mmol) obtained above, DMF (368 g) was added and the atmosphere was replaced with nitrogen. Then, carbon-supported palladium (5% Pd carbon powder (wet product) K type, manufactured by N.E. Chemcat Corporation) (1.84 g) was added, the atmosphere was replaced with nitrogen again, a Tedlar bag containing hydrogen was attached, and the mixture was stirred at 23°C for 19 hours. After completion of the reaction, the carbon-supported palladium was removed by passing through a membrane filter, and the filtrate was concentrated to approximately 70 g, to which IPA (100 g) was added to precipitate crystals. The crystals obtained by filtration were washed with IPA and dried under reduced pressure at 40°C to obtain specific diamine (A5) (yield: 16.6 g, 26.7 mmol, yield: 98%, white crystals). １ H-NMR (500MHz, DMSO-d6): δ (ppm) = 7.59 (4H, d), 7.36 (4H, d), 7.16 (4H , d), 6.65 (4H, d), 5.23 (4H, s), 3.90 (2H, m), 3.72 (6H, s), 1.66 (6H, s).

[0069] "Synthesis of Polyimide-Based Polymer" Example 6 B1 (0.977 g, 4.00 mmol), A1 (1.77 g, 4.00 mmol), and NMP (27.8 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 23° C. while supplying nitrogen to dissolve the mixture. Thereafter, C1 (1.67 g, 7.44 mmol) and NMP (4.60 g) were added under ice cooling, and the mixture was stirred at 40° C. for 12 hours to obtain a polyamic acid solution (PAA-1) (viscosity: 429 mPa s) with a solids concentration of 12% by mass.

[0070] Example 7 B1 (0.977 g, 4.00 mmol), A2 (1.88 g, 4.00 mmol), and NMP (28.9 g) were placed in a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and dissolved by stirring at 23° C. while supplying nitrogen. Thereafter, C1 (1.67 g, 7.44 mmol) and NMP (4.29 g) were added under ice cooling, and the mixture was stirred at 40° C. for 12 hours, yielding a polyamic acid solution (PAA-2) (viscosity: 285 mPa s) with a solids concentration of 12% by mass.

[0071] Example 8 B1 (1.40 g, 5.75 mmol), A3 (2.67 g, 5.75 mmol), and NMP (41.2 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was dissolved by stirring at 23° C. while supplying nitrogen. Thereafter, C1 (2.40 g, 10.7 mmol) and NMP (6.26 g) were added under ice cooling, and the mixture was stirred at 40° C. for 12 hours, thereby obtaining a polyamic acid solution (PAA-3) (viscosity: 1,540 mPa s) with a solids concentration of 12% by mass.

[0072] Example 9 B1 (1.22 g, 5.00 mmol), A4 (2.49 g, 5.00 mmol), and NMP (37.0 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was dissolved by stirring at 23° C. while supplying nitrogen. Thereafter, C1 (2.08 g, 9.30 mmol) and NMP (5.51 g) were added under ice cooling, and the mixture was stirred at 40° C. for 12 hours, yielding a polyamic acid solution (PAA-4) (viscosity: 228 mPa s) with a solids concentration of 12% by mass.

[0073] Example 10 B1 (0.977 g, 4.00 mmol), A5 (2.49 g, 4.00 mmol), and NMP (35.1 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was dissolved by stirring at 23° C. while supplying nitrogen. Thereafter, C1 (1.67 g, 7.44 mmol) and NMP (2.60 g) were added under ice cooling, and the mixture was stirred at 23° C. for 12 hours, thereby obtaining a polyamic acid solution (PAA-5) (viscosity: 584 mPa s) with a solids concentration of 12% by mass.

[0074] Comparative Example 1 B1 (1.22 g, 5.00 mmol), B2 (1.73 g, 5.00 mmol), and NMP (29.9 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was dissolved by stirring at 23° C. while supplying nitrogen. Thereafter, C1 (2.02 g, 9.00 mmol) and NMP (6.50 g) were added under ice cooling, and the mixture was stirred at 40° C. for 12 hours to obtain a polyamic acid solution (PAA-6) (viscosity: 1,295 mPa s) having a solids concentration of 12% by mass.

[0075] Comparative Example 2 B1 (0.977 g, 4.00 mmol), B3 (1.39 g, 4.00 mmol), and NMP (24.3 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was dissolved by stirring at 23° C. while supplying nitrogen. Thereafter, C1 (1.67 g, 7.44 mmol) and NMP (5.33 g) were added under ice cooling, and the mixture was stirred at 40° C. for 12 hours, yielding a polyamic acid solution (PAA-7) (viscosity: 705 mPa s) with a solids concentration of 12% by mass.

[0076] Example 11: To a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, the polyamic acid solution (PAA-1) (30.0 g) obtained by the method of Example 6 was added, and NMP was added to adjust the solids concentration to 9% by mass. Subsequently, acetic anhydride (2.00 g) and pyridine (0.52 g) were added, and the mixture was stirred at 23°C for 30 minutes, followed by a reaction at 55°C for 3 hours. This reaction solution was poured into methanol (170 g), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 80°C to obtain a polyimide powder. The imidization rate of this polyimide powder was 82%. NMP was added to the obtained polyimide powder to adjust the solids concentration to 12% by mass, and the mixture was stirred and dissolved at 80°C for 12 hours to obtain a polyimide solution (PI-1) (viscosity: 278 mPa s).

[0077] Example 12: B1 (1.76 g, 7.20 mmol), A1 (3.19 g, 7.20 mmol), B4 (0.854 g, 3.60 mmol), and NMP (58.6 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 23 ° C. while supplying nitrogen to dissolve the mixture. Subsequently, C1 (3.79 g, 16.9 mmol) and NMP (11.7 g) were added under ice cooling, and the mixture was stirred at 40 ° C. for 12 hours to obtain a polyamic acid solution (viscosity: 468 mPa s) with a solids concentration of 12 wt%. The resulting polyamic acid solution (30.0 g) was placed in a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP was added to adjust the solids concentration to 9 wt%. Thereafter, acetic anhydride (2.07 g) and pyridine (0.53 g) were added, and the mixture was stirred at 23°C for 30 minutes, followed by a reaction at 55°C for 3 hours. This reaction solution was poured into methanol (170 g), and the resulting precipitate was separated by filtration. This precipitate was washed with methanol and dried under reduced pressure at 80°C to obtain a polyimide powder. The imidization rate of this polyimide powder was 82%. NMP was added to the obtained polyimide powder so that the solids concentration was 12% by mass, and the mixture was dissolved by stirring at 60°C for 12 hours to obtain a polyimide solution (PI-2) (viscosity: 152 mPa s).

[0078] Example 13: B1 (2.25 g, 9.20 mmol), A2 (4.33 g, 9.20 mmol), B4 (1.09 g, 4.60 mmol), and NMP (77.5 g) were added to a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at room temperature while nitrogen was introduced to dissolve the mixture. Then, C1 (4.85 g, 21.6 mmol) and NMP (14.2 g) were added under ice cooling, and the mixture was stirred at 40°C for 12 hours to obtain a polyamic acid solution with a solids concentration of 12% by weight (viscosity: 368 mPa·s). The resulting polyamic acid solution (30.0 g) was placed in a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP was added to adjust the solids concentration to 9% by weight. Then, acetic anhydride (2.02 g) and pyridine (0.52 g) were added, and the mixture was stirred at 23°C for 30 minutes, followed by a reaction at 55°C for 3 hours. This reaction solution was poured into methanol (170 g), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 80°C to obtain a polyimide powder. The imidization rate of this polyimide powder was 79%. NMP was added to the obtained polyimide powder so that the solids concentration was 12% by mass, and the mixture was stirred at 60°C for 12 hours to dissolve the polyimide, yielding a polyimide solution (PI-3) (viscosity: 118 mPa s).

[0079] Synthesis Example 1 B5 (8.28 g, 41.6 mmol), B6 ​​(3.10 g, 10.4 mmol), C2 (14.7 g, 50.0 mmol), and NMP (191 g) were placed in a 200 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 70° C. for 15 hours to obtain a polyamic acid solution (PAA-8) (viscosity: 461 mPa s) with a solids concentration of 12 mass %. The specifications of the polyimide polymer are shown in Table 1.

[0080]

[0081] "Production of Liquid Crystal Alignment Agent" Example 14 To a sample tube containing a stirrer, the polyamic acid solution (PAA-1) obtained by the method of Example 6, F1 (blending ratio of F1: 10 parts by mass per 100 parts by mass of the polymer in PAA-1), NMP, and BCS were added, and the mixture was stirred at 25°C for 30 minutes to obtain a liquid crystal alignment agent (1) (solid content: NMP:BCS = 6:74:20 mass ratio). No abnormalities such as turbidity or the generation of precipitates were observed in this liquid crystal alignment agent, and it was confirmed that the solution was a homogeneous solution. In addition, using the obtained liquid crystal alignment agent (1), an "evaluation of the stability of liquid crystal alignment" was performed.

[0082] Examples 15 to 23, Comparative Examples 3 and 4 Liquid crystal aligning agents (2) to (12) were obtained by the same procedure as in Example 1, except that the types and ratios of the compounds added to the polyimide polymer and liquid crystal aligning agent used were changed as shown in Table 2. These liquid crystal aligning agents showed no abnormalities such as turbidity or precipitates, and were confirmed to be homogeneous solutions. Furthermore, an "evaluation of liquid crystal alignment stability" was performed using the obtained liquid crystal aligning agents. The specifications of the liquid crystal aligning agents are shown in Table 2. In Table 2, the parenthesized values ​​for specific polymers and other polymers in the polyimide polymer indicate the content (parts by mass) of each polymer in 100 parts by mass of the total polyimide polymer. Furthermore, the parenthesized values ​​for each compound in the compound indicate the content (parts by mass) of each compound in 100 parts by mass of the total polyimide polymer.

[0083]

[0084] "Evaluation of Liquid Crystal Alignment Stability" The liquid crystal alignment stability was evaluated using the liquid crystal alignment agents obtained by the methods of the Examples and Comparative Examples. This evaluation was intended to evaluate the AC afterimage of a liquid crystal display element, which occurs when the stability of the liquid crystal alignment decreases due to long-term AC driving. First, a liquid crystal cell using the FFS driving method was fabricated. A rectangular glass substrate measuring 30 mm x 35 mm and 0.7 mm thick was used as the substrate. A solid-patterned ITO electrode constituting a common electrode was formed on the substrate as the first layer. A SiN (silicon nitride) film deposited by CVD (chemical vapor deposition) was formed on the first common electrode as the second layer. The second SiN film had a thickness of 300 nm, which was thick enough to function as an interlayer insulating film. A comb-shaped pixel electrode formed by patterning an ITO film was placed on the second SiN film as the third layer, forming two pixels, a first pixel and a second pixel, each measuring 10 mm long and 5 mm wide. This electrode-equipped substrate had a structure in which a first-layer common electrode and a third-layer pixel electrode were insulated by a second-layer SiN film. The third-layer pixel electrode had a comb-like shape, with a central bend at an interior angle of 160° and multiple 3 μm-wide electrode lines arranged parallel to each other at 6 μm intervals. Each pixel was formed by multiple electrode lines, with a first region and a second region separated by a line connecting the bent portions. Next, the liquid crystal alignment agent was filtered through a 1.0 μm pore size filter and then spin-coated onto the electrode-equipped substrate (hereinafter referred to as the electrode substrate) and a glass substrate (hereinafter referred to as the counter substrate) with a 4 μm-tall columnar spacer and an ITO electrode formed on its backside. The resulting coating was then dried on a hot plate at 80°C for 2 minutes and further baked in an infrared oven at 180°C for 30 minutes (hereinafter also referred to as "baking A") to obtain an electrode substrate and a counter substrate with a 100 nm-thick liquid crystal alignment film. In Examples 19 to 23, the baking A after drying on a hot plate at 80° C. for 2 minutes was not carried out, and the electrode substrate and counter substrate with the liquid crystal alignment film were also prepared.The liquid crystal alignment film surfaces of both substrates were irradiated with 254 nm polarized ultraviolet light through a 240 nm low-cut filter and a polarizer at the exposure dose shown in Table 3 (optimal exposure dose for each liquid crystal alignment agent), and then baked for 30 minutes in an infrared heating furnace at 180 ° C or 230 ° C (hereinafter also referred to as "baking B") to obtain an electrode substrate and counter substrate with an alignment-treated liquid crystal alignment film. As a result, the liquid crystal alignment film of the electrode substrate was aligned so that the direction equally dividing the interior angle of the pixel bend was perpendicular to the alignment direction of the liquid crystal, and the liquid crystal alignment film of the counter substrate was aligned so that the alignment direction of the liquid crystal on the electrode substrate coincided with the alignment direction of the liquid crystal on the counter substrate when creating a liquid crystal cell. The electrode substrate and counter substrate with the alignment-treated liquid crystal alignment film were used as a pair, and a thermosetting sealant (XN-1500T, manufactured by Mitsui Chemicals, Inc.) was printed around the liquid crystal alignment film surface of one substrate, leaving a liquid crystal injection port. Next, the other substrate was bonded to the other substrate with the liquid crystal alignment film side facing inward, so that the alignment directions of the liquid crystal alignment films were 0°. After bonding, the bonded substrates were pressed together and heated in a hot air circulating oven at 150°C for 60 minutes to harden the sealant and produce an empty cell. Positive liquid crystal (MLC-3019, manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS drive type liquid crystal cell (hereinafter referred to as a liquid crystal cell).

[0085] The obtained liquid crystal cell was heated at 120°C for 1 hour and then left overnight at 23°C to evaluate the stability of the liquid crystal alignment. This liquid crystal cell was exposed to a high-intensity backlight (light source: LED, luminance: 20000 cd / m) with a surface temperature of 50°C. ２) and an AC voltage of ±4.3 V at a frequency of 30 Hz was applied for 168 hours. The pixel electrode and common electrode of the liquid crystal cell were then shorted and left at 23°C for one day. For the liquid crystal cell subjected to the above treatment, the deviation between the alignment direction of the liquid crystal in the first region of the pixel and the alignment direction of the liquid crystal in the second region of the pixel when no voltage was applied was calculated as an angle. Specifically, the liquid crystal cell was placed between two polarizing plates arranged so that their polarization axes were perpendicular to each other, and the backlight was inverted to adjust the alignment angle of the liquid crystal cell so that the transmitted light intensity of the first region of the first pixel was minimized. Next, the rotation angle Δ required to rotate the liquid crystal cell so that the transmitted light intensity of the second region of the first pixel was minimized was calculated. The first and second regions of the second pixel were similarly compared, and a similar angle Δ was calculated. The average of the angles Δ for the first and second pixels was then calculated as the rotation angle Δ of the liquid crystal cell. The smaller the rotation angle Δ, the better the stability of the liquid crystal alignment, and the less likely AC image retention will occur in the liquid crystal display element. As a specific evaluation standard, a rotation angle Δ value of less than 0.15° was rated as "good," and a rotation angle Δ value of 0.15° or more was rated as "poor."

[0086] The results of the evaluation of the stability of liquid crystal alignment are shown in Table 3. In Table 3, baking A and baking B in the baking indicate the above, and "-" in the table indicates cases where these baking steps were not performed. In Example 19, three conditions were performed: baking A and baking B were 180°C, and baking A was not performed and baking B was 180°C or 230°C. In Example 20, two conditions were performed: baking A and baking B were 180°C, and baking A was not performed and baking B was 230°C. In Example 21, two conditions were performed: baking A and baking B were 180°C, and baking A was not performed and baking B was 230°C. In Example 22, one condition was performed: baking A was not performed and baking B was 230°C. In Example 23, one condition was performed: baking A was not performed and baking B was 230°C.

[0087]

[0088] As can be seen from the above results, the liquid crystal display elements using the liquid crystal alignment films obtained from the liquid crystal aligning agents of the Examples of the present invention had higher stability of liquid crystal alignment than the liquid crystal display elements of the Comparative Examples. Specifically, the comparison is between Examples 14 to 18 (rotation angle Δ values ​​of 0.06° to 0.14°) and Comparative Examples 3 and 4 (rotation angle Δ values ​​of 1.29° or 0.15°).

[0089] By using a liquid crystal aligning agent containing a polyimide polymer having a specific structure according to the present invention, a liquid crystal display element is obtained that is less susceptible to AC image retention. Therefore, the liquid crystal display element of the present invention is suitable for use in in-plane switching drive devices such as IPS drive systems and FFS drive systems, and is useful for smartphones, tablet devices, etc. The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2024-013554, filed on January 31, 2024, are hereby incorporated by reference as part of the disclosure of the present invention.

Claims

1. A liquid crystal aligning agent containing at least one polymer selected from a polyimide precursor having a structure of the following formula [1] and a polyimide: (X ａ and X ｃ Each of X independently represents a divalent organic group. ｂ represents an organic group having 4 to 30 carbon atoms. ｄ represents a monovalent organic group. aX represents an integer of 2.

2. The liquid crystal aligning agent according to claim 1, wherein the structure of the formula [1] is the following formula [1-1]: (X １ and X ５ Each of X independently represents at least one cyclic group selected from a benzene ring, a biphenyl group, a naphthalene group, and a pyridine ring, and any hydrogen atom on these cyclic groups may be substituted with a monovalent organic group. ２ is a single bond, *1-OCH ２ - and *1-OCH ２ CH ２ - represents at least one selected from, and *1 represents X １ indicates the bond with X. ３ represents at least one cyclic group selected from a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, and a benzene ring, and —C(═O)—O—X ６ Any hydrogen atom of the carbon atom not bonded to X may be substituted with a monovalent organic group, a chlorine atom, or a fluorine atom. ４ is a single bond, -CH ２ O-*2 and -CH ２ CH ２ O-*2, where *2 is X ５ indicates the bond with X. ６ represents at least one selected from an optionally branched alkyl group having 1 to 10 carbon atoms, a benzene ring, and a tert-butoxycarbonyl group; a1 represents an integer of 2; and X ６ may all be the same or different. * indicates a bond.) 3. The liquid crystal aligning agent according to claim 1 or 2, wherein the polymer is at least one polymer selected from polyimide precursors and polyimides, which use a diamine having the structure of formula [1] or formula [1-1] as part of a raw material.

4. The liquid crystal aligning agent according to claim 3, wherein the diamine is a diamine of the following formula [1a]: (X represents the formula [1] or [1-1]. R １ and R ２ each independently represents a hydrogen atom or a monovalent organic group.

5. The liquid crystal aligning agent according to claim 4, wherein the diamine of the formula [1a] is at least one selected from the following formulas [1a-a] to [1a-d]: (X １ , X ２ , X ４ ~X ６ , R １ and R ２ has the same meaning as defined in formula [1a].

6. The liquid crystal aligning agent according to claim 1 or 2, wherein the polymer is at least one polymer selected from polyimide precursors and polyimides using a tetracarboxylic acid of the following formula [2] as part of a raw material: (Z represents at least one structure selected from 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.

7. The liquid crystal aligning agent according to claim 1 or 2, which contains a compound that promotes imidization of the polymer.

8. A liquid crystal alignment film obtained by using the liquid crystal aligning agent according to claim 1 or 2.

9. A liquid crystal display device having the liquid crystal alignment film according to claim 8.

10. The liquid crystal display element of claim 9, which is of an IPS drive system or an FFS drive system.

11. Diamines selected from the group consisting of the following formulae [1a-a] to [1a-d]: (X １ and X ５ Each of X independently represents at least one cyclic group selected from a benzene ring, a biphenyl group, a naphthalene group, and a pyridine ring, and any hydrogen atom on these cyclic groups may be substituted with a monovalent organic group. ２ is a single bond, *a-OCH ２ - and *a-OCH ２ CH ２ - represents at least one selected from, and *a represents X １ indicates the bond with X. ４ is a single bond, -CH ２ O-*b and -CH ２ CH ２ O-*b, *b is X ５ indicates the bond with X. ６ R each independently represents at least one selected from an optionally branched alkyl group having 1 to 10 carbon atoms, a benzene ring, and a tert-butoxycarbonyl group. １ and R ２ each independently represents a hydrogen atom or a monovalent organic group.

12. Diamines selected from the group consisting of the following formulas [1a-1] to [1a-6]:

13. A polymer selected from polyimide precursors and polyimides, which uses the diamine according to claim 11 or 12 as part of its raw material.

Images