Polyimide precursor for display substrates, polyimide film for display substrates, and display substrates

Abstract

Provided is a polyimide precursor for a display substrate for forming a polyimide film for the display substrate in which the electrostatic charge attenuation rate for an electrostatic charge half-life of at least 48 seconds and / or after 120 seconds according to an electrostatic charge half-life measurement based on JIS L 1094 A is not more than 63%.

Description

Technical Field

[0001] The present invention relates to a polyimide precursor for a display substrate that can contribute to suppressing charge-up and can achieve high adhesion, a polyimide film for a display substrate obtained using the same, and a display substrate.

Background Art

[0002] Polyimide is widely used in applications such as flexible printed wiring boards and tapes for TAB (Tape Automated Bonding) in electric and electronic devices because of its excellent heat resistance, solvent resistance (chemical resistance), mechanical properties, electrical properties, etc. For example, polyimide obtained from aromatic tetracarboxylic dianhydride and aromatic diamine, particularly polyimide obtained from 3,3’,4,4’-biphenyltetracarboxylic dianhydride and paraphenylenediamine, is preferably used.

[0003] In addition, polyimide is being studied as an alternative to glass substrates in the field of display devices. By replacing the display substrate used in various display devices from a glass substrate with a plastic substrate made of polyimide, it is possible to provide a display that is lightweight, has excellent flexibility, and can be bent or rolled.

[0004] For example, as a polyimide precursor applicable to display substrate applications, Patent Document 1 proposes a method of using a polyimide precursor containing a specific unit structure.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When polyimide films are used as display substrates, in order to ensure sufficient gas barrier properties, their surface is usually coated with SiO2. x It is used with an inorganic gas barrier layer such as the above formed on it. On the other hand, when polyimide film is used for display substrate applications, charge buildup occurs at the interface between the polyimide film and the inorganic gas barrier layer. This charge buildup causes a small amount of current to flow through switching elements, etc., resulting in the problem of afterimages appearing on the display. [Means for solving the problem]

[0007] In response to this, the present inventors conducted diligent research and found that when applying polyimide film to display substrate applications, extending the charge half-life of the polyimide film used for display substrates, or lowering the charge decay rate after 120 seconds, promotes the elimination of charge accumulation at the interface between the polyimide film and the inorganic gas barrier layer, thereby contributing to the suppression of charge buildup. This led to the completion of the present invention. Furthermore, through diligent research by the inventors, it was discovered that adopting the above configuration can achieve high adhesion.

[0008] In other words, the present invention provides the following [1] to [9]. [1] A polyimide precursor for display substrates, for forming a polyimide film for display substrates having a charge half-life of 48 seconds or more, as measured according to JIS L 1094A.

[0009] [2] A polyimide precursor for display substrates, for forming a polyimide film for display substrates having a charge decay rate of 63% or less after 120 seconds, as measured by charge half-life measurement in accordance with JIS L 1094A.

[0010] [3]A polyimide precursor for a display substrate, as described in [1], for forming a polyimide film for a display substrate having a charge decay rate of 63% or less after 120 seconds by measuring the charge half-life according to JIS L 1094A.

[0011] [4]A polyimide precursor having a structural unit represented by the following general formula (2), wherein Y in the following general formula (2) 2 is a polyimide precursor for a display substrate according to any one of [1] to [3] containing a group represented by the following general formula (3). [Chemical formula] (In the above general formula (2), X 2 is a tetravalent aromatic or aliphatic group, Y 2 is a divalent aromatic group, and R 3 , R 4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.) [Chemical formula] (In the above general formula (3), R 5 , R 6 , R 7 , R 8 are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent.)

[0012] [5]A polyimide precursor for a display substrate according to [4], wherein the group represented by the general formula (3) includes a group represented by the following formula (5). [Chemical formula]

[0013] [6]Among the structural units represented by the general formula (2) constituting the polyimide precursor for a display substrate, Y 2A polyimide precursor for display substrates according to [4] or [5], wherein the proportion of structural units containing the group represented by general formula (3) is 50 to 100 mol% as the group represented by [4] or [5].

[0014] A composition containing a polyimide precursor, comprising the polyimide precursor for display substrates described in [7][1] and at least one inorganic oxide selected from SiO2, Al2O3, TiO2, PbTiO3, CaTiO3, SrTiO3, CaZrO3, and BaTiO3, A polyimide precursor composition for a display substrate, wherein the polyimide precursor for the display substrate has a structural unit represented by the following general formula (6). [ka] (In the above general formula (6), X 3 Y is a tetravalent aromatic group or aliphatic group. 3 is a divalent aromatic group, R 9 , R 10 These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

[0015] A polyimide film for a display substrate obtained using a polyimide precursor for a display substrate described in any of [8][1] to [6] or a polyimide precursor composition for a display substrate described in [7].

[0016] A display substrate comprising the polyimide film for display substrates described in [9][8]. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a polyimide precursor for display substrates that can help suppress charge buildup and achieve high adhesion. [Modes for carrying out the invention]

[0018] <Polyimide precursor for display substrates> The polyimide precursor for display substrates of the present invention is a polyimide precursor for forming polyimide for display substrates, and more specifically, a polyimide precursor for forming a polyimide film for display substrates having a charge half-life of 48 seconds or more, as measured according to JIS L 1094A.

[0019] The polyimide precursor for display substrates of the present invention is acceptable as long as the polyimide film obtained from the polyimide precursor has a charge half-life of 48 seconds or more, as measured in accordance with JIS L 1094A. However, from the viewpoint of more appropriately suppressing charge-up, a charge half-life of 50 seconds or more is preferable, and a charge half-life of 52 seconds or more is even more preferable. The charge half-life measured is the time it takes for the charge to be halved after the polyimide film is charged by performing corona discharge on it.

[0020] The charging half-life can be measured, for example, as follows: That is, the polyimide precursor for display substrates of the present invention can be subjected to an imidation reaction by known methods such as thermal imidation or chemical imidation to obtain a polyimide film. The obtained polyimide film can then be charged by corona discharge in accordance with JIS L 1094A, and the charging half-life can be measured. For example, when performing the imidation reaction by thermal imidation, thermal imidation can be carried out under a nitrogen atmosphere, preferably by heating to 350°C or higher and 500°C or lower, typically up to 450°C. The obtained polyimide film can then be measured for charging half-life in accordance with JIS L 1094A.

[0021] Alternatively, a polyimide precursor for display substrates according to another aspect of the present invention is a polyimide precursor for forming a polyimide for display substrates, wherein the polyimide film obtained from the polyimide precursor has a charge decay rate of 63% or less after 120 seconds, as measured by a charge half-life measurement in accordance with JIS L 1094A.

[0022] In another aspect of the present invention, a polyimide precursor for a display substrate is acceptable as long as the polyimide film obtained from the polyimide precursor has a charge decay rate of 63% or less after 120 seconds, as measured by charge half-life measurement in accordance with JIS L 1094A. However, from the viewpoint of more appropriately suppressing charge-up, it is preferable that the charge decay rate after 120 seconds be 61% or less. Furthermore, the lower limit of the charge decay rate after 120 seconds is preferably 30% or more. The charge decay rate after 120 seconds, as measured by charge half-life measurement, is the ratio of the decrease in charge amount after 120 seconds, after the polyimide film has been charged by corona discharge, to the charge amount immediately after charging. That is, the charge decay rate after 120 seconds (%) is calculated as follows: Charge decay rate after 120 seconds (%) = {(Charge amount immediately after charging - Charge amount after 120 seconds) ÷ Charge amount immediately after charging} × 100.

[0023] The charge decay rate after 120 seconds can be measured, for example, as follows: That is, the polyimide precursor for display substrates of the present invention can be subjected to an imidation reaction by known methods such as thermal imidation or chemical imidation to obtain a polyimide film. The obtained polyimide film can then be charged by corona discharge in accordance with JIS L 1094A, and the charge amount immediately after charging and the charge amount after 120 seconds can be measured. This measurement may be performed simultaneously with the measurement of the charge half-life. For example, when performing the imidation reaction by thermal imidation, thermal imidation can be carried out under a nitrogen atmosphere, preferably by heating to 350°C or higher and 500°C or lower, typically up to 450°C. The obtained polyimide film can then be measured for charge decay after 120 seconds in accordance with JIS L 1094A.

[0024] Furthermore, it is preferable that the polyimide film obtained from the polyimide precursor for display substrates according to the present invention has both a charge half-life measured in accordance with JIS L 1094A and a charge decay rate after 120 seconds measured in accordance with JIS L 1094A, both of which are within the above range. By adopting such an embodiment, charge-up can be suppressed more effectively.

[0025] Furthermore, in the present invention, from the viewpoint of more appropriately suppressing charge-up, it is preferable that the inorganic material forming the inorganic layer as a gas barrier layer laminated on the polyimide film for the display substrate exhibits a charge half-life or a charge decay rate after 120 seconds that is close to that of the inorganic material used for display substrate applications. In particular, as the inorganic material forming the inorganic layer, SiO X SiO is preferably used. X Inorganic materials such as SiO have a relatively long charge half-life and a relatively small charge decay rate after 120 seconds. Therefore, as mentioned above, by making the charge half-life longer and the charge decay rate after 120 seconds lower, SiO X This allows for closer approximation of the half-life of the charge and the charge decay rate after 120 seconds for inorganic materials, thereby enabling more effective suppression of charge buildup. The half-life of the charge and the charge decay rate after 120 seconds for the inorganic material forming the inorganic layer can be determined in the same manner as above by measuring the half-life and charge decay rate after 120 seconds in accordance with JIS L 1094A.

[0026] Furthermore, the polyimide precursor for display substrates of the present invention preferably has a 90-degree peel strength of 15 mN / mm or more, and more preferably 20 mN / mm or more, of the polyimide film obtained from the polyimide precursor. The 90-degree peel strength can be measured by performing an imidation reaction on the polyimide precursor for display substrates of the present invention using known methods such as thermal imidation or chemical imidation, forming a polyimide film on the surface of a glass, and then performing a 90-degree peel test on the formed polyimide film. For example, when performing an imidation reaction by thermal imidation, thermal imidation can be carried out by heating under a nitrogen atmosphere, preferably at 350°C or higher and 500°C or lower, typically up to 450°C.

[0027] The polyimide precursor for display substrates of the present invention is not particularly limited, as long as the charge half-life of the polyimide film obtained from the polyimide precursor, or the charge decay rate after 120 seconds, falls within the above range. For example, the polyimide precursor for display substrates according to the first embodiment, second embodiment, or third embodiment described below are preferred.

[0028] <Polyimide precursor for display substrate according to the first embodiment> The polyimide precursor for display substrates according to the first embodiment (hereinafter referred to as "the polyimide precursor of the first embodiment") is a polyimide precursor having a structural unit represented by the following general formula (1), wherein X in the following general formula (1) 1 The base represented by the following general formula (1), Y 1 The group represented by and at least some of the terminal groups include an acidic group, The acid group content is 15 × 10 -3 That concludes the explanation. [ka] (In the above general formula (1), X 1 Y is a tetravalent aromatic group or aliphatic group. 1 is a divalent aromatic group, R 1, R 2 These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

[0029] In the above general formula (1), X 1 This is a residue obtained by removing four COOH groups from a tetracarboxylic acid (i.e., a residue obtained by removing two carboxylic acid anhydride groups (CO)2O) from a tetracarboxylic dianhydride, and Y 1 This is a residue obtained by removing two NH2 groups from a diamine. 1 , R 2 This is preferably a hydrogen atom, an alkylsilyl group having 3 to 9 carbon atoms, and more preferably a hydrogen atom.

[0030] The structural unit represented by the above general formula (1) can be obtained by reacting a tetracarboxylic acid component with a diamine component to form an amide bond (-CONH-).

[0031] Examples of tetracarboxylic acid components include aromatic tetracarboxylic dianhydrides or aliphatic tetracarboxylic dianhydrides.

[0032] Specific examples of aromatic tetracarboxylic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic acid dianhydride, diphenylsulfone-3,4,3',4'-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (also known as 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride), 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, and 2,2-bis(3,4-dicarboxyphenyl) Examples include siphenyl)propane dianhydride, p-phenylenebis(trimellitic acid monoester acid anhydride), p-biphenylenebis(trimellitic acid monoester acid anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid dianhydride. These can be used individually or in combination of two or more types.

[0033] As aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides can be suitably used. Specific examples of alicyclic tetracarboxylic dianhydrides include (1S,2R,4S,5R)-cyclohexanetetracarboxylic dianhydride, cis,cis,cis-1,2,4,5-cyclohexanetetracarboxylic dianhydride, (1S,2S,4R,5R)-cyclohexanetetracarboxylic dianhydride, (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride, and bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride. Bicyclo[2.2.2]octo-7-en-2,3,5,6-tetracarboxylic dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-tetralin-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclo-3,3',4,4'-tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter sometimes referred to as "CBDA"), 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,4-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, Pentacyclo[8.2.1.1 4,7 .0 2,9 .0 3,8 Examples include tetradecane-5,6,11,12-tetracarboxylic dianhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, cyclohexa-1-ene-2,3,5,6-tetracarboxylic dianhydride, and bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride. These can be used individually or in combination of two or more.

[0034] As the tetracarboxylic acid component, the tetracarboxylic acid compound is preferably an acid dianhydride selected from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA), pyromellitic acid dianhydride (PMDA), 4,4'-oxydiphthalic acid dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA), and 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride (DSDA), with 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA) being more preferred.

[0035] Examples of diamine compounds as diamine components include 4,4'-diaminodiphenyl ether, 2,2'-dimethylbenzidine, 4,4'-diaminodiphenylmethane, 4,4'-diamino-1,2-diphenylethane, p-phenylenediamine (PPD), m-phenylenediamine, 2,4-diaminotoluene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, m-xylylenediamine, p-xylylenediamine, Aromatic diamines having aromatic groups such as 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-methylenebis(2,6-xylidine), α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, 2,2'-dimethyl-4,4'-aminobiphenyl, 3,3'-dimethyl-4,4'-aminobiphenyl, 2,2'-ethylenedianiline; 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2 -n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 1,2-diaminocyclohexane, 1,3-diaminocyclobutane, 1,4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobicycloheptane, diaminomethylbicyclo Alicyclic diamines having an alicyclic structure, such as heptane, diaminooxybicycloheptane, diaminomethyloxybicycloheptane, isophorone diamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobindan, and 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobindan;2,2'-Bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,3,5,6-Tetrafluoro-1,4-diaminobenzene, 2,4,5,6-Tetrafluoro-1,3-diaminobenzene, 2,3,5,6-Tetrafluoro-1,4-benzene(dimethaneamine), 2,2'-Difluoro-(1,1'-biphenyl)-4,4'-diamine, 2,2',6,6'-Tetrafluoro-(1,1'-biphenyl)-4,4'-diamine, 4,4'-Diaminooctafluorobiphenyl, 2,2-Bis(4-aminophenyl)hexafluoropropane, 4,4'-Oxybis(2,3,5 Examples include fluorine-containing fluorine-based diamines such as 6-tetrafluoroaniline, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether, 1,4-bis[4-amino-2-(trifluoromethyl)phenoxy]benzene, 2,2-bis[4-[4-amino-2-(trifluoromethyl)phenoxy]hexafluoropropane, 3,5-diaminobenzene trifluoride, and 4,4-diamino-2-(trifluoromethyl)diphenyl ether; and ester-bonded diamines such as 4-aminophenyl 4-aminobenzoate and bis(4-aminophenyl) terephthalate. These can be used individually or in combination of two or more.

[0036] Preferred diamine compounds as the diamine component include 4,4'-diaminodiphenyl ether, 2,2'-dimethylbenzidine, 4,4'-diaminodiphenylmethane, 4,4'-diamino-1,2-diphenylethane, p-phenylenediamine (PPD), and 2,2-bis[4-(4-aminophenoxy)phenyl]propane, with p-phenylenediamine (PPD) being more preferred.

[0037] The polyimide precursor of the first embodiment is X in the general formula (1) above. 1 The base represented by the above general formula (1), Y 1The group represented by and at least some of the terminal groups include an acidic group, and the acidic group content is 15 × 10 ―3 The above is the case. The acidic group content is preferably 16 × 10 ―3 More preferably 18 × 10 ―3 The above, and more preferably 20 × 10 ―3 This concludes the explanation. By including acidic groups in this concentration, the polyimide film obtained from the polyimide precursor of the first embodiment can be made to contain a predetermined amount of acidic groups, thereby extending the charge half-life and keeping the charge decay rate after 120 seconds low.

[0038] The acidic group content can be determined by the following formula. Acidity of acidic groups = {(Number of moles of acidic group-containing monomers used to form the polyimide precursor) × (Number of acidic groups per molecule of acidic group-containing monomer)} ÷ (Total number of moles of monomers forming the polyimide precursor) Here, when using multiple acidic group-containing monomers with different numbers of acidic groups per molecule, the acidic group content should be calculated and used according to the above formula, depending on the proportion of use of these monomers. Furthermore, with respect to tetracarboxylic acids, it is assumed that four of the acidic groups in one molecule react with the diamine during polymerization and do not remain as acidic groups when polyimide is formed. Therefore, when calculating the amount of acidic groups, the number of acidic groups will be calculated by subtracting 4 from the number of acidic groups (including acid anhydride groups) in one molecule of tetracarboxylic acid. In other words, the acidic group content is calculated based on the number of free carboxyl groups that do not contribute to imide bond formation. For example, 3,3',4,4'-biphenyltetracarboxylic dianhydride has only four carboxyl groups, all of which contribute to imide bond formation, so the number of acidic groups in the above calculation of acidic group content is zero. Furthermore, while merittic acid can exist in a mixture of states—without anhydride groups, with one anhydride group, or with two anhydride groups—four of the six carboxyl groups constituting merittic acid are used to form imide bonds. Therefore, after forming polyimide precursors or polyimide films, there are usually two free carboxyl groups. Thus, for merittic acid, the acidity can be calculated by assuming that there are two carboxyl groups acting as acidic groups.

[0039] The acidic group is not particularly limited, but examples include carboxyl groups (-COOH), sulfonic acid groups (-SO3H), and phosphonic acid groups (-PO3H2). Among these, carboxyl groups and sulfonic acid groups are preferred because they have a high effect in suppressing charge-up. In this context, the acidic group may be one that yields an acidic group that has not been esterified or otherwise modified by hydrolysis.

[0040] X in the general formula (1) above 1The method for making the group represented by the above general formula (1) include a group containing an acidic group is not particularly limited, but for example, one method is to use a specific tetracarboxylic acid compound as at least a part of the tetracarboxylic acid component. Such a specific tetracarboxylic acid compound is the -COOR in the above general formula (1). 1 ,-COOR 2 Examples include compounds having acidic groups such as carboxyl groups in addition to the carboxyl groups that constitute the two amide bonds (-CONH-) (hereinafter referred to as tetracarboxylic acid compounds having acidic groups). In other words, tetracarboxylic acid compounds having acidic groups are compounds that contain acidic groups that do not contribute to the imidation reaction, in addition to the tetracarboxylic acid structure that contributes to the imidation reaction.

[0041] Specific examples of tetracarboxylic acid compounds having an acidic group include compounds having a carboxyl group as the acidic group, such as meritol acid, meritol anhydride, methyl meritol ester, dimethyl meritol ester, trimethyl meritol ester, ethyl meritol ester, diethyl meritol ester, triethyl meritol ester, propyl meritol ester, dipropyl meritol ester, tripropyl meritol ester, butyl meritol ester, dibutyl meritol ester, tributyl meritol ester, phenyl meritol ester, diphenyl meritol ester, and triphenyl meritol ester. These can be used individually or in combination of two or more. Among these, meritol acid and meritol anhydride are preferred.

[0042] The amount of the tetracarboxylic acid compound having the above-mentioned acidic group used can be appropriately selected according to the amount of acidic group to be contained in the polyimide precursor of the first embodiment, but is preferably 1 mol% or more, more preferably 2 mol% or more, preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 50 mol% or less, even more preferably 10 mol% or less, and particularly preferably 6 mol% or less, out of 100 mol% of the total amount of the tetracarboxylic acid component.

[0043] Also, Y in the above general formula (1) 1 The method for making the group represented by include an acidic group is not particularly limited, but one example is to use an acidic group-containing diamine compound as at least a part of the diamine component. Such an acidic group-containing diamine compound can be any compound that has an acidic group such as a carboxyl group in addition to the diamine structure, but examples of compounds that have a carboxyl group as the acidic group include 3,5-diaminobenzoic acid (3,5-DABA), 5,5'-methylenebis(2-aminobenzoic acid), 3,3'-diamino-4,4'-dicarboxybiphenyl, 4,4'-diamino-3,3'-dicarboxydiphenylmethane, 3,3'-diamino-4,4'-dicarboxydiphenylmethane, and 2,2-bis[4-(4-amino-3-carboxyphenyl)phenyl]propane. Furthermore, examples of compounds having a sulfonic acid group as an acidic group include 1,4-phenylenediamine-2-sulfonic acid, 1,3-phenylenediamine-2-sulfonic acid, 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid, and 4,4'-diaminostilbene-2,2'-disulfonic acid and 4,4'-bis(4-aminophenoxy)biphenyl-3,3'-disulfonic acid. These can be used individually or in combination of two or more. Among these, 3,5-diaminobenzoic acid (3,5-DABA) is preferred as a compound having a carboxyl group as an acidic group, and 1,4-phenylenediamine-2-sulfonic acid and 1,3-phenylenediamine-2-sulfonic acid are preferred as compounds having a sulfonic acid group as an acidic group.

[0044] The amount of the above-mentioned acidic group-containing diamine compound used can be appropriately selected according to the amount of acidic group to be contained in the polyimide precursor of the first embodiment, but is preferably 2 mol% or more, more preferably 3 mol% or more, even more preferably 4 mol% or more, preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 50% or less, even more preferably 10 mol% or less, and particularly preferably 6 mol% or less, out of 100 mol% of the total amount of the diamine component.

[0045] Alternatively, there are no particular limitations on the method of making the terminal group include a group containing an acidic group, but one example is to replace a part of the tetracarboxylic acid component with a dicarboxylic acid compound having an acidic group, or a dicarboxylic acid compound anhydride having an acidic group. A dicarboxylic acid compound having an acidic group is a compound that, in addition to the dicarboxylic acid structure that contributes to the imidation reaction, has an acidic group other than the carboxyl group that constitutes the dicarboxylic acid structure that does not contribute to the imidation reaction. Similarly, a dicarboxylic acid compound anhydride having an acidic group is a compound that, in addition to the dicarboxylic acid anhydride structure that contributes to the imidation reaction, has an acidic group other than the carboxyl group that constitutes the dicarboxylic acid anhydride structure that does not contribute to the imidation reaction.

[0046] Examples of dicarboxylic acid compounds having an acidic group, or dicarboxylic acid anhydrides having an acidic group, include compounds having a carboxyl group as the acidic group, such as trimellitic acid, trimellitic anhydride, hemimelittic acid, and hemimelittic anhydride. Examples of compounds having a sulfonic acid group as the acidic group include 3-sulfophthalic acid, 4-sulfophthalic acid, 3-sulfophthalic anhydride, and 4-sulfophthalic anhydride. These can be used individually or in combination of two or more. Among these, compounds having a carboxyl group as the acidic group are preferred, and trimellitic anhydride is preferred.

[0047] The amount of the above-mentioned dicarboxylic acid compound having an acidic group, or the anhydride of the dicarboxylic acid compound having an acidic group, used can be appropriately selected according to the amount of acidic group to be contained in the polyimide precursor of the first embodiment. However, in terms of tetracarboxylic acid, the amount is preferably 1 mol% or more, more preferably 1.5 mol% or more, even more preferably 2 mol% or more, preferably 35 mol% or less, more preferably 30 mol% or less, even more preferably 25 mol% or less, and particularly preferably 5 mol% or less, in terms of the tetracarboxylic acid, and in terms of the compound, the amount is preferably 2 mol% or more, more preferably 3 mol% or more, even more preferably 4 mol% or more, preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 50 mol% or less, even more preferably 10 mol% or less, and particularly preferably 6 mol% or less. Furthermore, since dicarboxylic acid compounds with acidic groups and anhydrides of dicarboxylic acid compounds with acidic groups contain a dicarboxylic acid structure rather than a tetracarboxylic acid structure as a structural component that contributes to the imidation reaction, the amount added in terms of tetracarboxylic acid is usually half the amount added in terms of the compound.

[0048] The polyimide precursor of the first embodiment can be easily prepared, for example, using conventionally known methods. The method for preparing the polyimide precursor of the first embodiment is not particularly limited, but for example, by reacting approximately equimolar amounts of a tetracarboxylic acid component and a diamine component in a solvent at a relatively low temperature of 100°C or less, preferably 80°C or less, so that the imidation reaction does not proceed or proceeds too much, the polyimide precursor can be obtained in a state in which it is dissolved in the solvent, i.e., in the state of a polyimide precursor solution. The polyimide precursor solution obtained in this way may contain, in addition to the polyamic acid as the polyimide precursor, a partially or completely imidized polyimide precursor or polyimide formed by the proceeding of the imidation reaction.

[0049] The polymerization temperature for obtaining the polyimide precursor of the first embodiment is preferably 25°C or higher and 100°C or lower, more preferably 40°C or higher and 80°C or lower, and even more preferably 50°C or higher and 80°C or lower. The polymerization time is preferably 0.1 hours or higher and 24 hours or lower, more preferably 2 hours or higher and 12 hours or lower. By setting the polymerization temperature and polymerization time within the above range, high molecular weight polyimide precursors can be easily obtained with production efficiency. Polymerization can be carried out in an air atmosphere, but is usually suitably carried out in an inert gas atmosphere, preferably nitrogen gas atmosphere. Specifically, the molar ratio of the tetracarboxylic acid component and the diamine component in approximately equimolar amounts is 0.90 or higher and 1.10 or lower, preferably 0.95 or higher and 1.05 or lower, more preferably greater than 0.98 and 1.04 or lower, and even more preferably greater than 0.98 and 1.03 or lower. In this specification, "approximately equimolar" means a molar ratio in the range of greater than 0.99 to 1.01, and "equomolar" means the significant figures of a molar ratio of 1.00.

[0050] When reacting a tetracarboxylic acid component with a diamine component, a preferred method is to add the diamine component to a polymerization apparatus filled with a solvent, confirm that the diamine component has dissolved, and then add the tetracarboxylic acid component.

[0051] The solvent used when reacting the tetracarboxylic acid component with the diamine component can be any solvent that is capable of polymerizing the polyimide precursor and in which the polyimide precursor is soluble, and can be either water or an organic solvent. The solvent may also be a mixture of two or more solvents, such as a mixed solvent of two or more organic solvents, or a mixed solvent of water and one or more organic solvents. The organic solvent is not particularly limited, but examples include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, hexamethylphosphorotriamide, 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, 1,2-bis(2-methoxyethoxy)ethane, tetrahydrofuran, bis[2-(2-methoxyethoxy)ethyl] ether, 1,4-dioxane, dimethyl sulfoxide, dimethyl sulfone, diphenyl ether, sulfolane, diphenyl sulfone, tetramethylurea, anisole, m-cresol, phenol, and γ-butyrolactone. In the first embodiment, the solvent used when polymerizing the polyimide precursor can be used directly as the solvent for the polyimide precursor solution when manufacturing the polyimide film for display substrates.

[0052] The polyimide precursor solution is not particularly limited, but the solid content concentration of the polyimide precursor is preferably 5% by mass or more and 45% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and even more preferably more than 10% by mass and 30% by mass or less, relative to the total amount of the polyimide precursor and the solvent. If the solid content concentration is lower than 5% by mass, it may be difficult to increase the thickness of the film, and if it is higher than 45% by mass, the solution viscosity may become too high, which may require special film manufacturing equipment.

[0053] Furthermore, while the viscosity of the polyimide precursor solution at 30°C is not limited, it is preferably 1000 Pa·sec or less, more preferably 0.5 Pa·sec or more and 500 Pa·sec or less, even more preferably 1 Pa·sec or more and 300 Pa·sec or less, and particularly preferably 2 Pa·sec or more and 200 Pa·sec or less for ease of handling.

[0054] The polyimide precursor solution may optionally contain additives that promote the imidation reaction, such as amine compounds and dehydrating agents, as well as known additives such as organophosphorus-containing compounds, the aforementioned fillers, surfactants, silane coupling agents, and leveling agents.

[0055] Examples of amine compounds include substituted or unsubstituted nitrogen-containing heterocyclic compounds, N-oxide compounds of said nitrogen-containing heterocyclic compounds, substituted or unsubstituted amino acid compounds, aromatic hydrocarbon compounds having a hydroxyl group, or aromatic heterocyclic compounds. Specific examples of imidation catalysts include imidazole derivatives such as 1,2-dimethylimidazole, N-methylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 5-methylbenzimidazole, and N-benzyl-2-methylimidazole, as well as substituted pyridine derivatives such as isoquinoline, 3,5-dimethylpyridine, 3,4-dimethylpyridine, 2,5-dimethylpyridine, 2,4-dimethylpyridine, and 4-n-propylpyridine. The amount of imidation catalyst used is preferably 0.01 equivalents or more and 2 equivalents or less, particularly 0.02 equivalents or more and 1 equivalent or less, relative to the amide acid units of the polyamide precursor. The use of an imidation catalyst can improve the physical properties of the resulting polyimide film, particularly its elongation and edge tear resistance.

[0056] Other amine compounds include aliphatic tertiary amines such as trimethylamine and triethylenediamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as isoquinoline, pyridine, α-picoline, and β-picoline, which can be added as needed.

[0057] Examples of dehydrating agents include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride.

[0058] Examples of organophosphorus-containing compounds include phosphate esters such as monocaproyl phosphate, monooctyl phosphate, monolauryl phosphate, monomyristyl phosphate, monocetyl phosphate, monostearyl phosphate, monophosphate of triethylene glycol monotridecyl ether, monophosphate of tetraethylene glycol monolauryl ether, monophosphate of diethylene glycol monostearyl ether, dicaproyl phosphate, dioctyl phosphate, dicapryl phosphate, dilauryl phosphate, dimyristyl phosphate, dicetyl phosphate, distearyl phosphate, diphosphate of tetraethylene glycol mononeopentyl ether, diphosphate of triethylene glycol monotridecyl ether, diphosphate of tetraethylene glycol monolauryl ether, and diphosphate of diethylene glycol monostearyl ether, as well as amine salts of these phosphate esters. Examples of amines include ammonia, monomethylamine, monoethylamine, monopropylamine, monobutylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, monoethanolamine, diethanolamine, and triethanolamine.

[0059] <Polyimide precursor for display substrate according to the second embodiment> The polyimide precursor for display substrates according to the second embodiment (hereinafter referred to as "the polyimide precursor of the second embodiment") is a polyimide precursor having a structural unit represented by the following general formula (2), wherein Y in the following general formula (2) 2 It includes a group represented by the following general formula (3). [ka] (In the above general formula (2), X 2 Y is a tetravalent aromatic group or aliphatic group. 2 is a divalent aromatic group, R 3 , R 4 These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. [ka] (In the above general formula (3), R 5 , R 6 , R 7 , R 8 These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 12 carbon atoms (which may have substituents), or an aryl group having 6 to 12 carbon atoms (which may have substituents).

[0060] In general formula (2), X 2 This is a residue obtained by removing four COOH groups from a tetracarboxylic acid (i.e., a residue obtained by removing two carboxylic acid anhydride groups (CO)2O) from a tetracarboxylic dianhydride, and Y 2 This is a residue obtained by removing two NH2 groups from a diamine. 3 , R 4 This is preferably a hydrogen atom, an alkylsilyl group having 3 to 9 carbon atoms, and more preferably a hydrogen atom.

[0061] The structural unit represented by general formula (2) can be obtained by reacting a tetracarboxylic acid component with a diamine component to form an amide bond (-CONH-). In this case, by using a triazine structure-containing diamine compound represented by general formula (4) below as at least a part of the diamine component, the Y in general formula (2) can be obtained. 2 As such, it may have a group represented by the general formula (3) above.

[0062] [ka] (In the above general formula (4), R 5 , R6 , R 7 , R 8 This is the same as in general formula (3) above.

[0063] The polyimide precursor of the second embodiment is Y in the general formula (2) above. 2 The polyimide includes a group represented by the general formula (3) above, thereby increasing the relative permittivity of the polyimide obtained from the polyimide precursor of the second embodiment. By increasing the relative permittivity, the half-life of the charge can be extended. In particular, the inventors have found that there is a certain correlation between the relative permittivity and the half-life of the charge, and that the half-life of the charge can be extended by increasing the relative permittivity. Based on these findings, the second embodiment allows for a longer half-life of the charge and a lower rate of charge decay after 120 seconds.

[0064] In the above general formulas (3) and (4), R 5 , R 6 , R 7 These are independently a hydrogen atom, a C1-C12 alkyl group which may have substituents, or a C6-C12 aryl group which may have substituents, preferably a hydrogen atom, an unsubstituted C1-C12 alkyl group, or an unsubstituted C6-C12 aryl group, more preferably a hydrogen atom or an unsubstituted C1-C4 alkyl group, and even more preferably a hydrogen atom.

[0065] Furthermore, in the above general formulas (3) and (4), R 8 This is a hydrogen atom, a C1-C12 alkyl group which may have substituents, or a C6-C12 aryl group which may have substituents, preferably a hydrogen atom, an unsubstituted C1-C12 alkyl group which may not have substituents, or an unsubstituted C6-C12 aryl group which may not have substituents, more preferably a hydrogen atom or an unsubstituted C6-C12 aryl group which may not have substituents, and even more preferably a phenyl group.

[0066] Specific examples of diamine compounds containing a triazine structure represented by the above general formula (4) include 2,4-bis(3-aminoanilino)-6-anilino-1,3,5-triazine (p-ATDA), 2,4-bis(3-aminoanilino)-6-benzylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-naphthylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-biphenylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-diphenylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-dibenzylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-dinaphthylamino-1,3,5-triazine, 2 Examples include 4-bis(3-aminoanilino)-6-N-methylanilino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-N-methylnaphthylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-methylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-ethylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-dimethylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-diethylamino-1,3,5-triazine, 2,4-bis(3-aminoanilino)-6-dibutylamino-1,3,5-triazine, and 2,4-bis(3-aminoanilino)-6-amino-1,3,5-triazine. These can be used individually or in combination of two or more. Among these, 2,4-bis(3-aminoanilino)-6-anilino-1,3,5-triazine (p-ATDA) is preferred, and by using 2,4-bis(3-aminoanilino)-6-anilino-1,3,5-triazine (p-ATDA), Y in the above general formula (2) 2 As such, a group represented by the following formula (5) can be introduced. [ka]

[0067] The amount of the triazine structure-containing diamine compound represented by the above general formula (4) used is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 90 to 100 mol%, of the total amount of diamine components (100 mol%). That is, Y 2 The proportion of structural units containing the group represented by the above general formula (3) in 100 mol% of the group represented by is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 90 to 100 mol%.

[0068] Furthermore, in the second embodiment, a diamine compound other than the triazine structure-containing diamine compound represented by the general formula (4) above may be used as the diamine component. Such a diamine compound may be one of those exemplified in the first embodiment described above. Alternatively, an acidic group-containing diamine compound exemplified in the first embodiment described above may be used as the diamine compound, and in this case, the amount used may be the same as in the first embodiment described above.

[0069] Examples of tetracarboxylic acid components include aromatic tetracarboxylic dianhydrides or aliphatic tetracarboxylic dianhydrides, and those exemplified in the first embodiment described above can be used. Alternatively, as the tetracarboxylic acid component, a tetracarboxylic acid compound having an acidic group, or a dicarboxylic acid compound having an acidic group, or an anhydride of a dicarboxylic acid compound having an acidic group, as exemplified in the first embodiment described above, may be used, and the amount used in this case may be the same as in the first embodiment described above. Furthermore, as the solvent used when reacting the tetracarboxylic acid component with the diamine component, the solvent exemplified in the first embodiment described above may be used, and in the second embodiment as well, the solvent used when polymerizing the polyimide precursor can be used directly as the solvent for the polyimide precursor solution when manufacturing the polyimide film for display substrates.

[0070] The polyimide precursor of the second embodiment can be easily prepared, for example, using a conventionally known method. The method for preparing the polyimide precursor of the second embodiment is not particularly limited, but it can be prepared by the same method as in the first embodiment described above, and in the second embodiment as well, the polyimide precursor can be obtained in a state in which it is dissolved in a solvent, that is, in the state of a polyimide precursor solution. In addition to the polyamic acid as the polyimide precursor, the polyimide precursor solution obtained in this way may also contain a partially or completely imidized polyimide precursor or polyimide formed by the proceeding of the imidation reaction.

[0071] In the second embodiment as well, the solid content concentration of the polyimide precursor in the polyimide precursor solution and the viscosity of the polyimide precursor solution at 30°C may be the same as in the first embodiment. In addition, known additives such as amine compounds, dehydrating agents, and other additives that promote the imidation reaction, organophosphorus-containing compounds, the aforementioned fillers, surfactants, silane coupling agents, and leveling agents may be added to the polyimide precursor solution as needed.

[0072] <Polyimide precursor for display substrate according to the third embodiment> The polyimide precursor for display substrates according to the third embodiment is a composition containing a polyimide precursor having a structural unit represented by the following general formula (6), and at least one inorganic oxide selected from SiO2, Al2O3, TiO2, PbTiO3, CaTiO3, SrTiO3, CaZrO3, and BaTiO3 (hereinafter referred to as the "polyimide precursor composition of the third embodiment"). [ka] (In the above general formula (6), X 3 Y is a tetravalent aromatic group or aliphatic group. 3 is a divalent aromatic group, R 9 , R 10These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

[0073] In general formula (6), X 3 This is a residue obtained by removing four COOH groups from a tetracarboxylic acid (i.e., a residue obtained by removing two carboxylic acid anhydride groups (CO)2O) from a tetracarboxylic dianhydride, and Y 3 This is a residue obtained by removing two NH2 groups from a diamine. 9 , R 10 This is preferably a hydrogen atom, an alkylsilyl group having 3 to 9 carbon atoms, and more preferably a hydrogen atom.

[0074] The structural unit represented by general formula (6) that forms the polyimide precursor in the polyimide precursor composition of the third embodiment is obtained by reacting a tetracarboxylic acid component with a diamine component to form an amide bond (-CONH-).

[0075] The tetracarboxylic acid compound constituting the tetracarboxylic acid component and the diamine compound constituting the diamine component can be the same as those used in the first embodiment described above. Alternatively, as the tetracarboxylic acid compound, a tetracarboxylic acid compound having an acidic group as exemplified in the first embodiment, or a dicarboxylic acid compound having an acidic group, or an anhydride of a dicarboxylic acid compound having an acidic group may be used, and the amount used in this case may be the same as in the first embodiment described above. Furthermore, as the diamine compound, an acidic group-containing diamine compound as exemplified in the first embodiment described above, or a triazine structure-containing diamine compound represented by the general formula (4) as exemplified in the second embodiment described above, may be used, and the amount used in this case may be the same as in the first and second embodiments described above. Also, as the solvent used when reacting the tetracarboxylic acid component and the diamine component, the solvent exemplified in the first embodiment described above may be used, and in the third embodiment as well, the solvent used when polymerizing the polyimide precursor can be used directly as the solvent for the polyimide precursor solution when manufacturing the polyimide film for display substrates.

[0076] The polyimide precursor used in the third embodiment can be easily prepared, for example, using a conventionally known method. The method for preparing the polyimide precursor used in the third embodiment is not particularly limited, but it can be prepared by the same method as in the first embodiment described above, and in the third embodiment as well, the polyimide precursor can be obtained in a state in which it is dissolved in a solvent, that is, in the state of a polyimide precursor solution. The polyimide precursor solution obtained in this way may contain, in addition to the polyamic acid as the polyimide precursor, a partially or completely imidized polyimide precursor or polyimide formed by the proceeding of the imidation reaction.

[0077] The polyimide precursor composition of the third embodiment contains a polyimide precursor and at least one inorganic oxide selected from SiO2, Al2O3, TiO2, PbTiO3, CaTiO3, SrTiO3, CaZrO3, and BaTiO3. According to the third embodiment, by incorporating such an inorganic oxide, the polyimide film obtained using the polyimide precursor composition of the third embodiment can have a higher relative permittivity. As a result of increasing the relative permittivity, the charge half-life can be extended. In particular, the inventors have found that there is a certain correlation between relative permittivity and charge half-life, and that increasing the relative permittivity can extend the charge half-life. According to the third embodiment, based on these findings, the charge half-life can be extended and the charge decay rate after 120 seconds can be kept low.

[0078] As inorganic oxides, CaTiO3, SrTiO3, CaZrO3, and BaTiO3 are preferred, with BaTiO3 being more preferred, from the viewpoint that they can further enhance the effect of improving the relative permittivity, thereby extending the charge half-life.

[0079] The amount of inorganic oxide used is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of polyimide precursor. By setting the amount of inorganic oxide used within the above range, the effect of improving the dielectric constant can be further enhanced, thereby making the charge half-life longer and keeping the charge decay rate after 120 seconds low. In particular, it is possible to make the charge half-life longer and keep the charge decay rate after 120 seconds low while maintaining good film properties such as transmittance.

[0080] In the third embodiment, for example, an inorganic oxide can be incorporated into the polyimide precursor by adding a predetermined amount of inorganic oxide to the polyimide precursor solution and mixing it.

[0081] In the third embodiment as well, the solid content concentration of the polyimide precursor in the polyimide precursor solution and the viscosity of the polyimide precursor solution at 30°C may be the same as in the first embodiment. In addition, known additives such as amine compounds, dehydrating agents, and other additives that promote the imidation reaction, organophosphorus-containing compounds, the aforementioned fillers, surfactants, silane coupling agents, and leveling agents may be added to the polyimide precursor solution as needed.

[0082] <Polyimide film for display substrates> The polyimide film for display substrates of the present invention is obtained using the polyimide precursor or polyimide precursor composition for display substrates described above. The polyimide film for display substrates of the present invention is obtained using the polyimide precursor for display substrates described above, and therefore has a charge half-life of 48 seconds or more, or a charge decay rate of 63% or less after 120 seconds, as measured in accordance with JIS L 1094A, thereby contributing to the suppression of charge buildup.

[0083] The polyimide film for display substrates of the present invention can be manufactured by known methods, for example, using the polyimide precursor solution described above (a solution containing the polyimide precursor for display substrates of the present invention, more specifically, a solution containing the polyimide precursor for display substrates or the polyimide precursor composition for display substrates according to the first to third embodiments, also referred to as a "display substrate forming solution").

[0084] The polyimide film for display substrates of the present invention can be manufactured, for example, by a method of chemically imidizing / or thermally imidizing a laminate of a support obtained by coating a polyimide precursor solution onto a support and drying it, and a support and a polyimide precursor film obtained therefrom; by chemically imidizing / or thermally imidizing a laminate of a support obtained by coating a polyimide precursor solution onto a support and drying it, and then peeling the polyimide film off the support; or by obtaining a self-supporting film by coating a polyimide precursor solution onto a support and drying it, then peeling the polyimide precursor film off the support, and then fixing this self-supporting film and chemically imidizing / or thermally imidizing it.

[0085] The method for applying the polyimide precursor solution to the support is not particularly limited as long as it can form the desired coating film. For example, known methods such as spin coating, screen printing, bar coating, electrodeposition, saturation, and extrusion molding can be suitably used. Considering the subsequent drying, heating, and other steps required to form the polyimide film, the thickness of the coating film should, for example, be approximately 1 μm to 500 μm.

[0086] The drying conditions are not particularly limited, but the drying temperature can be, for example, in the range of 20°C to 200°C, preferably room temperature (25°C) to 180°C, and more preferably 30°C to 150°C. The drying time will vary depending on the heating temperature, but for example, it can be 1 minute to 60 minutes, preferably 30 minutes to 20 minutes. The heating means is not particularly limited and can be hot air, infrared rays, etc., and may be performed multiple times or with a gradual increase in temperature. These drying conditions may be selected, for example, under an atmosphere such as vacuum, an inert gas such as nitrogen, or air, while considering the properties of the polyimide film.

[0087] The support to which the polyimide precursor solution is applied is not particularly limited as long as it can be coated with the polyimide precursor solution and does not affect the subsequent formation of the polyimide precursor film by drying, or the heating, chemical imidation / or thermal imidation reaction, but it is preferable to use glass, metal, plastic substrates, etc.

[0088] In the present invention, chemical imidation / or thermal imidation can be carried out by heat treatment. For example, in thermal imidation, the maximum heating temperature in the heat treatment is usually 300°C or higher, preferably 350°C or higher, more preferably 450°C or higher, and even more preferably 470°C or higher. The upper limit of the heat treatment temperature is any temperature at which the properties of the polyimide film do not deteriorate, preferably 600°C or lower, more preferably 550°C or lower, and even more preferably 520°C or lower. The heat treatment can be carried out in an air atmosphere, but is usually suitably performed in an inert gas atmosphere, preferably nitrogen gas atmosphere. Chemical imidation can be performed under milder heat treatment conditions compared to thermal imidation, depending on the type of additive such as the chemical imidation catalyst. For example, heat treatment can be carried out in a temperature range of usually 100°C or higher, preferably 120°C or higher, more preferably 150°C or higher, even more preferably 200°C or higher, usually 360°C or lower, preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 220°C or lower.

[0089] The heat treatment for chemical imidation / or thermal imidation may be carried out in stages. For example, it is preferable to perform a primary heat treatment at a relatively low temperature of 100°C to 170°C for about 0.5 to 30 minutes, followed by a secondary heat treatment at a temperature above 170°C but below 220°C for about 0.5 to 30 minutes, and then a tertiary heat treatment at a high temperature above 220°C but below 350°C for about 0.5 to 30 minutes, and further a fourth high-temperature heat treatment from 350°C or above to the maximum heating temperature can be performed. It is preferable to carry out the heat treatment continuously. For example, it is preferable to heat treat from a relatively low temperature of 100°C to 170°C to the maximum heating temperature. There are no particular restrictions on the heating rate, but it is preferable to be between 1°C / min and 30°C / min, and particularly preferable to be between 2°C / min and 20°C / min. Within the above range, foaming due to rapid heating can be suppressed, which is preferable.

[0090] <Display board> The polyimide film for display substrates of the present invention is suitably used in display substrates such as displays and touch panels.

[0091] The display substrate is formed, for example, as follows: First, an inorganic gas barrier layer is formed on the surface of the polyimide film for display substrates of the present invention by sputtering, vapor deposition, or gel-sol method, as a gas barrier layer for water vapor, oxygen, etc. The inorganic gas barrier layer is, for example, SiO x It is formed by the above. Next, a conductive layer of a conductive material (metal or metal oxide, conductive organic material, conductive carbon, etc.) is formed on top of it to create a display substrate. The conductive layer is formed in a predetermined circuit pattern by methods such as photolithography, various printing methods, or inkjet printing. After that, elements, semiconductors, and other components for constituting the display may be additionally formed.

[0092] The display substrate of the present invention may be manufactured by forming an inorganic gas barrier layer on the surface of a polyimide film obtained using the polyimide precursor for display substrates of the present invention, forming a conductive layer in a circuit pattern on this layer, and then peeling the polyimide film with the inorganic gas barrier layer and conductive layer formed on its surface from a support. There are no particular restrictions on the peeling method, and it can be carried out by, for example, laser peeling, which is performed by irradiating the support with a laser or the like, and mechanical peeling, which is performed by mechanically pulling it off.

[0093] The display substrate obtained in this manner is formed by forming an inorganic gas barrier layer on the surface of a polyimide film for display substrates obtained using the polyimide precursor for display substrates of the present invention, and forming a conductive layer in a circuit pattern thereon. The display substrate of the present invention comprises a polyimide film for display substrates obtained using the polyimide precursor for display substrates of the present invention, and the polyimide film for display substrates of the present invention has a long charge half-life, and is therefore effective in eliminating charge accumulation at the interface with the inorganic gas barrier layer, thereby contributing to the suppression of charge buildup. [Examples]

[0094] The present invention will be described in more detail below with reference to examples, comparative examples, and reference examples, but the present invention is not limited thereto.

[0095] The measurement method used in the following example is shown below.

[0096] [Content of acidic groups] First, the total amount of acidic groups contained in the polyimide film was calculated for each raw material—acidic dianhydride, diamine, tetracarboxylic acid, and end-cap encapsulant—using the following formulas. However, for tetracarboxylic acid, it was assumed that four of the acidic groups in one molecule react with the diamine during polymerization and do not remain as acidic groups when the film is formed. Therefore, the number of acidic groups used in the calculation of the amount of acidic groups was calculated by subtracting 4 from the number of acidic groups in one molecule of tetracarboxylic acid (including acid anhydride groups). Amount of acidic groups in the raw material (mol) = Amount of substance of the raw material (mol) × (Number of acidic groups in one molecule of the raw material) Next, the total number of moles of acidic dianhydride, diamine, tetracarboxylic acid, and end-capping agent, excluding the catalyst, was defined as the total amount of monomer added (mol), and the content of acidic groups (-COOH groups, -SO3H groups) in the polyimide film was calculated using the following formula. The acidic group content in the film = Total amount of acidic groups in the raw materials (mol) / Total amount of monomer added (mol)

[0097] [Charge half-life measured, charge decay rate after 120 seconds] Sample pieces were prepared by cutting polyimide film to 55 mm in both length and width. For these test pieces, in accordance with JIS L 1094A, under conditions of 23±2°C and 50% RH, with an applied voltage of -10 kV, an application time of 30 s, and a maximum measurement time of 120 s, the half-life of the charge and the charge decay rate after 120 seconds were measured using a Static Honestmeter manufactured by Shishido Electrostatics Co., Ltd., employing the corona charging method.

[0098] [90-degree peel strength] The 90-degree peel strength was measured according to the following method. A glass plate coated with polyimide film was cut to a width of 25 mm to prepare a sample piece. For this sample piece, after positioning the head for fixing the test piece, the test piece was fixed to a Tensilon RTF-1350 peel test measuring jig, and peeled off at a speed of 50 mm / min for more than 50 mm using a tensile testing machine, and the load during this time was measured. The value obtained by dividing the peel load by the peel width (mm) of the test piece was calculated and defined as the 90-degree peel strength.

[0099] The abbreviations for the compounds used in the following examples are as follows: s-BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride PPD: p-phenylenediamine p-ATDA:2,4-bis(3-aminoanilino)-6-anilino-1,3,5-triazine 3,5-DABA:3,5-diaminobenzoic acid MPD: m-phenylenediamine HAB: 3,3'-Dihydroxybenzidine DATP: 4,4''-diamino-p-terphenyl

[0100] [Example 1] In a reaction vessel equipped with a stirrer and a nitrogen inlet tube, 34.4734 g of NMP (N-methylpyrrolidone), 1.4340 g of PPD, and 0.0842 g of 3,5-DABA were added. The mixture was stirred at 50°C for 30 minutes under a nitrogen atmosphere, and then 3.9820 g of s-BPDA was added and reacted to obtain a polyimide precursor solution (polyamic acid solution). At this time, the molar ratio of s-BPDA:PPD:3,5-DABA was 100:96:4. Next, the polyamic acid solution prepared in the synthesis example was spin-coated onto an alkali-free glass wafer and heated at 120°C, 150°C, 200°C, and 250°C for 10 minutes each, and at 450°C for 5 minutes to remove the solvent and imide, thereby obtaining a 10 μm thick polyimide film. The evaluation results are shown in Table 1.

[0101] [Example 2] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and tetracarboxylic acid component used were s-BPDA:trimellitic anhydride:PPD (molar ratio) = 98:4:100. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1.

[0102] [Example 3] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and tetracarboxylic acid component used were s-BPDA:meritic acid:PPD (molar ratio) = 98:2:100. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1. Regarding the meritic acid used in Example 3, it was assumed that, through a reaction similar to that of the tetracarboxylic acid component, the acidic groups remaining in the film would ultimately consist of 2 carboxylic acids (6 carboxylic acids, which is the number of acidic groups in meritic acid minus the 4 carboxylic acids in the tetracarboxylic acid component). Therefore, the number of acidic groups per molecule of raw material used to calculate the acidic group content was set to 2.

[0103] [Example 4] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of diamine and tetracarboxylic acid components used were set to s-BPDA:p-ATDA (molar ratio) = 100:100. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1.

[0104] [Example 5] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and the tetracarboxylic acid component used were set to s-BPDA:PPD (molar ratio) = 100:100. Then, to the polyimide precursor solution, 50 parts by mass of BaTiO3 particles (product name "Palseram® BTC-4FA", manufactured by Nippon Chemical Industrial Co., Ltd.) were added to 100 parts by mass of polyimide precursor. After that, the solvent was removed, imidization was performed, etc., in the same manner as in Example 1, to obtain a polyimide film. The evaluation results are shown in Table 1.

[0105] [Example 6] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and tetracarboxylic acid component used were s-BPDA:PPD:1,4-phenylenediamine-2-sulfonic acid (molar ratio) = 100:96:4. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1.

[0106] [Comparative Example 1] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and tetracarboxylic acid component used were set to s-BPDA:PPD = 100:100. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1.

[0107] [Comparative Example 2] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and tetracarboxylic acid component used were set to s-BPDA:PPD:MPD = 100:96:4. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1.

[0108] [Comparative Example 3] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and tetracarboxylic acid component used were set to s-BPDA:PPD:HAB = 100:96:4. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1.

[0109] [Comparative Example 4] A polyimide precursor solution was obtained in the same manner as in Example 1, except that the amounts of the diamine component and tetracarboxylic acid component used were set to s-BPDA:DATP = 100:100. Subsequently, a polyimide film was obtained by removing the solvent, imidization, etc. The evaluation results are shown in Table 1.

[0110] [Table 1]

[0111] As shown in Table 1, by incorporating acidic groups in a predetermined proportion into the polyimide precursor (Examples 1-3, 6), or by incorporating a group represented by the general formula (3) into the polyimide precursor (Example 4), or by incorporating a predetermined inorganic oxide into the polyimide precursor (Example 5), a polyimide film with a charge half-life of 48 seconds or more and a charge decay rate of 63% or less after 120 seconds can be obtained. Since the polyimide film obtained in this way has a long charge half-life and a low charge decay rate after 120 seconds, it can be said that it can be used as a polyimide film for display substrates to help suppress charge-up. Furthermore, regarding the 90° peel strength, the peel strength in Example 1 was 25 mN / mm, which is higher than the peel strength of 13 mN / mm in Comparative Example 1. In Examples 2 and 4, it was confirmed that the adhesion was so high that it was difficult to peel the film for setting it in the jig for measuring peel strength. [Industrial applicability]

[0112] The polyimide precursor for display substrates of the present invention is suitably used in display substrates.

Claims

1. A polyimide precursor composition for display substrates, for forming a polyimide film for display substrates having a charge half-life of 48 seconds or more, as measured according to JIS L 1094A, A polyimide precursor having a structural unit represented by the following general formula (6), CaTiO ３ SrTiO ３ CaZrO ３ and BaTiO ３ It contains at least one inorganic oxide selected from, A polyimide precursor composition for a display substrate, wherein the amount of the inorganic oxide relative to 100 parts by mass of the polyimide precursor is 30 parts by mass or more and 50 parts by mass or less. 【Chemistry 14】 (In the above general formula (6), X ３ Y is a tetravalent aromatic group or aliphatic group. ３ is a divalent aromatic group, R ９ , R １０ These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

2. A polyimide precursor composition for display substrates, for forming a polyimide film for display substrates having a charge decay rate of 63% or less after 120 seconds, as measured by charge half-life measurement in accordance with JIS L 1094A, A polyimide precursor having a structural unit represented by the following general formula (6), CaTiO ３ , SrTiO ３ , CaZrO ３ and at least one inorganic oxide selected from BaTiO ３ and contains A polyimide precursor composition for a display substrate, wherein the amount of the inorganic oxide relative to 100 parts by mass of the polyimide precursor is 30 parts by mass or more and 50 parts by mass or less. 【Chemistry 15】 (In the above general formula (6), X ３ Y is a tetravalent aromatic group or aliphatic group. ３ is a divalent aromatic group, R ９ , R １０ These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

3. The polyimide precursor composition for a display substrate according to claim 1, which is a polyimide precursor composition for a display substrate for forming a polyimide film for a display substrate having a charge decay rate of 63% or less after 120 seconds, as measured by a charge half-life measurement in accordance with JIS L 1094A.

4. The polyimide precursor is a polyimide precursor having a structural unit represented by the following general formula (2), wherein Y in the following general formula (2) ２ The polyimide precursor composition for display substrates according to claim 1, comprising a group represented by the following general formula (3). 【Chemistry 11】 (In the above general formula (2), X ２ Y is a tetravalent aromatic group or aliphatic group. ２ is a divalent aromatic group, R ３ , R ４ These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. 【Chemistry 12】 (In the above general formula (3), R ５ , R ６ , R ７ , R ８ These are, independently of each other, a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents.

5. The polyimide precursor composition for display substrates according to claim 4, comprising a group represented by the following formula (5) as the group represented by the general formula (3). 【Chemistry 13】

6. Among the structural units represented by the general formula (2) that constitute the polyimide precursor, Y ２ The polyimide precursor composition for display substrates according to claim 4, wherein the proportion of structural units containing the group represented by general formula (3) as the group represented by is 50 to 100 mol%.

7. A polyimide precursor composition for a display substrate, for forming a polyimide film for a display substrate having a charge half-life of 48 seconds or more, as measured according to JIS L 1094A, Polyimide precursor and It contains at least one inorganic oxide selected from CaTiO3, SrTiO3, CaZrO3, and BaTiO3, The polyimide precursor is a polyimide precursor having a structural unit represented by the following general formula (2), wherein the Y2 in the following general formula (2) comprises a group represented by the following general formula (3), making it a polyimide precursor composition for a display substrate. 【Chemistry 16】 (In the above general formula (2), X2 is a tetravalent aromatic group or aliphatic group, Y2 is a divalent aromatic group, and R3 and R4 are independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group.) 【Chemistry 17】 (In the above general formula (3), R5, R6, R7, and R8 are independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents.)

8. A polyimide precursor composition for a display substrate, for forming a polyimide film for a display substrate having a charge decay rate of 63% or less after 120 seconds, as measured by a charge half-life measurement in accordance with JIS L 1094A, Polyimide precursor and It contains at least one inorganic oxide selected from CaTiO3, SrTiO3, CaZrO3, and BaTiO3, The polyimide precursor is a polyimide precursor having a structural unit represented by the following general formula (2), wherein the Y2 in the following general formula (2) comprises a group represented by the following general formula (3), making it a polyimide precursor composition for a display substrate. [Chemistry 18] (In the above general formula (2), X2 is a tetravalent aromatic group or aliphatic group, Y2 is a divalent aromatic group, and R3 and R4 are independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group.) 【Chemistry 19】 (In the above general formula (3), R5, R6, R7, and R8 are independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents.)

9. A polyimide film for a display substrate obtained using the polyimide precursor composition for a display substrate described in any one of claims 1 to 8.

10. A display substrate comprising the polyimide film for display substrates described in claim 9.

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