Polyimide precursor and resin composition containing same, polyimide resin film, resin film and method for producing same

Abstract

To provide a polyimide resin film that has low residual stress, small warpage, a small yellowness (YI value) at high temperature (in particular 430°C or higher), a small haze (haze value), and proper laser peelability from a base material, and a method for producing the same.SOLUTION: A polyimide precursor includes (a1) a constitutional unit L represented by general formula (1) and (a2) a constitutional unit M represented by general formula (2). The ratio of the amount of the constitutional unit M to the total amount of the constitutional unit L and the constitutional unit M is 0.005-0.5 mol%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polyimide precursor, a resin composition containing the polyimide precursor, a polyimide resin film, a resin film, and a method for producing the same, which are used, for example, in producing a substrate for a flexible device. [Background technology]

[0002] In general, polyimide resin films are used as resin films for applications requiring high heat resistance. Typical polyimide resins are highly heat-resistant resins produced by solution polymerization of an aromatic carboxylic acid dianhydride and an aromatic diamine to produce a polyimide precursor, followed by thermal imidization at high temperatures or chemical imidization using a catalyst.

[0003] Polyimide resins are insoluble, infusible, and extremely heat-resistant resins with excellent properties, including thermal oxidation resistance, heat resistance, radiation resistance, low temperature resistance, and chemical resistance. For this reason, polyimide resins are used in a wide range of fields, including electronic materials. Examples of applications of polyimide resins in the electronic materials field include insulating coatings, insulating films, semiconductors, and electrode protection films for thin-film transistor liquid crystal displays (TFT-LCDs). Recently, polyimide resins have been considered for use as flexible substrates, taking advantage of their lightness and flexibility, replacing the glass substrates traditionally used in the display materials field.

[0004] When polyimide resins are used as flexible substrates, a commonly used process involves applying a varnish containing a polyimide resin or its precursor and other components to a suitable support, such as a glass substrate, drying it to form a film, forming elements, circuits, etc. on the film, and then peeling the film from the glass substrate. However, when producing a laminate containing a polyimide resin, a heat treatment at a high temperature of 250°C or higher is required to dry and imidize the polyimide precursor. This heat treatment generates residual stress in the laminate, causing serious problems such as warping and peeling. This is because polyimides have a higher linear expansion coefficient than the materials constituting the support.

[0005] To reduce residual stress in the laminate, the use of polyimide resins with a thermal expansion coefficient as small as that of glass has been investigated, and the most well-known polyimide material with a low thermal expansion coefficient is polyimide formed from 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter also referred to as BPDA) and paraphenylenediamine. Although it depends on the film thickness and preparation conditions, this polyimide has been reported to exhibit a very low linear thermal expansion coefficient (Non-Patent Document 1). It has also been reported that polyimides having an ester structure in the molecular chain have suitable linearity and rigidity, and therefore exhibit a low coefficient of linear expansion (Patent Document 1).

[0006] However, general polyimide resins, including the polyimides described in the above documents, are colored brown or yellow due to their high electron density, and therefore have low light transmittance in the visible light region, making them difficult to use in fields where transparency is required. Regarding the yellowness index (YI value) of films, it is known that polyimides using diamines having a trifluoromethyl group, for example, exhibit extremely low yellowness index (YI value) (Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2005 / 113647 [Patent Document 2] International Publication No. 2019 / 211972 [Non-patent literature]

[0008] [Non-Patent Document 1] "Latest Polyimides - Fundamentals and Applications" edited by the Japan Polyimide Research Association Summary of the Invention [Problem to be solved by the invention]

[0009] In order to use polyimide resins as colorless, transparent, flexible substrates, they must have mechanical properties such as transparency, excellent elongation, and breaking strength, as well as laser peelability from the substrate. In particular, with the recent shift to low-temperature polysilicon TFT (LTPS) devices, films that exhibit these properties even under more severe thermal conditions are desired. However, the properties of known transparent polyimides are not sufficient for use as heat-resistant, colorless, transparent substrates for displays. Furthermore, the inventors have confirmed that although the polyimide resin described in Patent Document 1 exhibits a low linear thermal expansion coefficient, the polyimide resin film after peeling has problems such as a high yellowness index (YI value), high residual stress, low elongation, and low breaking strength.

[0010] Regarding laser peelability, the polyimide film described in Patent Document 2 exhibits excellent performance. However, the inventors have confirmed that the polyimide film described in Patent Document 2 exhibits low yellowness index (YI value) in the temperature range of about 350°C to 400°C, but in the high temperature range of 430°C or higher, the yellowness index (YI value) deteriorates significantly, the haze value increases, and visibility decreases.

[0011] The present invention aims to solve the above-mentioned problems and to provide a polyimide resin film having low residual stress, little warping, low yellowness index (YI value) at high temperatures (particularly 430°C or higher), low haze value, and excellent laser releasability from a substrate, as well as a method for producing the same. [Means for solving the problem]

[0012] The present invention includes the following aspects. [1] (a1) The following general formula (1): [ka] {wherein X represents a tetravalent organic group, and Y1 represents a divalent organic group}, and (a2) The following general formula (2): [ka] {wherein X represents a tetravalent organic group, Y2 represents a divalent organic group, and Z represents -NHNH- or -N=N-.}, Y2 in the general formula (2) is represented by the following general formulae (A-1) to (A-6): [ka] [ka] [ka] [ka] [ka] [ka] {In the formula, R1~R 13each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, a to m each independently represent an integer of 0 to 4, n is an integer of 1 or greater, and * represents a bond.} At least one selected from the group consisting of structures represented by A polyimide precursor in which the ratio of the amount of the structural unit M to the total amount of the structural unit L and the structural unit M is 0.005 to 0.5 mol %. [2] The polyimide precursor according to aspect 1, wherein Y2 is at least one selected from the group consisting of structures represented by general formula (A-1) and general formula (A-6). [3] (a1) The following general formula (1): [ka] {wherein X represents a tetravalent organic group, and Y1 represents a divalent organic group}, and (a2) The following general formula (2): [ka] {wherein X represents a tetravalent organic group, Y2 represents a divalent organic group, and Z represents -NHNH- or -N=N-.}, Y2 in the general formula (2) is represented by the following general formula (A-6): [ka] {where, R 13 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, m is an integer of 0 to 4, n is an integer of 1 or greater, and * represents a bond.} A polyimide precursor having a structure represented by the following formula: [4] In the general formula (1), Y1 is represented by the following general formulae (A-1) to (A-5): [ka] [ka] [ka] [ka] [ka] {In the formula, R1~R 12 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, a to l each independently represent an integer of 0 to 4, and * represents a bond.} The polyimide precursor according to any one of the above aspects 1 to 3, which is at least one selected from the group consisting of structures represented by the following formula: [5] The polyimide precursor according to any one of Aspects 1 to 4, wherein X in General Formula (1) or General Formula (2), or both, is a tetravalent group derived from at least one selected from the group consisting of pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), 4,4'-biphenylbis(trimellitic monoester anhydride) (TAHQ), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), and cyclopentanonebisspironorbornanetetracarboxylic dianhydride (CpODA). [6] A resin composition comprising: (a) the polyimide precursor according to any one of the above aspects 1 to 5; and (b) an organic solvent. [7] The resin composition according to aspect 6, further comprising at least one selected from the group consisting of (c) a surfactant and (d) an alkoxysilane compound. [8] The resin composition according to aspect 6 or 7, wherein a polyimide resin film obtained by curing the resin composition is used in a flexible device. [9] The resin composition according to aspect 6 or 7, wherein a polyimide resin film obtained by curing the resin composition is used for a flexible display.

[10] A polyimide film obtained from the polyimide precursor according to any one of the above aspects 1 to 5 or the resin composition according to any one of the above aspects 6 to 9.

[11] The following general formula (3): [ka] {In the formula, X independently represents a tetravalent organic group, Y1 and Y2 independently represent a divalent organic group, and l and m independently represent an integer of 1 or greater, provided that 0.005≦m / (l+m)≦0.5 is satisfied.} The structural unit is represented by The Y2 is represented by the following general formulas (A-1) and (A-6): [ka] [ka] wherein R1, R2, and R 13 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, a, b, and m each independently represent an integer of 0 to 4, n is an integer of 1 or greater, and * represents a bond. The polyimide is at least one selected from the group consisting of structures represented by the following formula:

[12] The following general formula (3): [ka] In the formula, X independently represents a tetravalent organic group, each Y independently represents a divalent organic group, and Y represents a group represented by the following general formula (A-6): [ka] (In the formula, R 13 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, each m independently represents an integer of 0 to 4, n is an integer of 1 or greater, and * represents a bond. wherein l and m are each independently an integer of 1 or greater, provided that 0.005≦m / (l+m)≦0.5 is satisfied.} A polyimide comprising a structural unit represented by the formula:

[13] A step of forming a coating film by applying the resin composition according to any one of the above aspects 6 to 9 onto a surface of a support; a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film; peeling the polyimide resin film from the support; A method for producing a resin film, comprising:

[14] The method for producing a resin film according to the above aspect 13, further comprising the step of irradiating the polyimide resin film with a laser from the support side prior to the step of peeling the polyimide resin film from the support.

[15] A step of forming a coating film by applying the resin composition according to any one of the above aspects 6 to 9 onto a surface of a support; a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film; A method for producing a laminate, comprising:

[16] A step of forming a coating film by applying the resin composition according to any one of the above aspects 6 to 9 onto a surface of a support; a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film; forming an element or a circuit on the polyimide resin film; peeling the polyimide resin film on which the elements or circuits are formed from the support; A method for manufacturing a display substrate, comprising: [Effects of the Invention]

[0013] The polyimide resin film obtained from the polyimide precursor and resin composition according to one embodiment of the present invention exhibits little warping, a small yellowness index (YI value) at high temperatures (particularly 430°C or higher), a small haze value, and excellent laser releasability from a substrate. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing the structure of a top-emission flexible organic EL display above a polyimide substrate, as an example of the display of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, exemplary embodiments of the present invention (hereinafter abbreviated as "present embodiments") will be described in detail. Note that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention. Furthermore, unless otherwise specified, the characteristic values ​​described in this disclosure are intended to be values ​​measured using the method described in the [Examples] section or a method that would be understood by a person skilled in the art to be equivalent thereto.

[0016] <Polyimide precursor> A first embodiment of the present disclosure includes: (a1) The following general formula (1): [ka] {wherein X represents a tetravalent organic group, and Y1 represents a divalent organic group}, and (a2) The following general formula (2): [ka] and a structural unit M represented by the following formula: {wherein X represents a tetravalent organic group, Y2 represents a divalent organic group, and Z represents -NHNH- or -N=N-.} In the present disclosure, an organic group refers to a group having one or more carbon atoms.

[0017] In one embodiment, the ratio of the amount of structural unit M to the total amount of structural unit L and structural unit M is 0.005 to 0.5 mol %. Here, the ratio of the amount of structural unit M to the total amount of structural unit L and structural unit M is calculated by the following method. That is, after separating a polyimide precursor into an acid component and an amine component by depolymerization, the amine component of general formula (1) and the amine component of general formula (2) are separated by high performance liquid chromatography-mass spectrometry (hereinafter also referred to as LC / MS). The peak areas of each component are determined in a photodiode array (PDA) chromatogram at 300 nm detection, and the peak area ratio [(peak area of ​​the amine component of general formula (2)) / {(peak area of ​​the amine component of general formula (1))+(peak area of ​​the amine component of general formula (2))}×100 is calculated as a percentage.

[0018] If the ratio is 0.005 mol% or more, the laser releasability tends to be good, and if it is 0.5 mol% or less, the yellowness of the polyimide film tends to be good and ash generation after laser peeling tends to be suppressed. Note that the polyimide film may be burned by the laser light during laser peeling, and the resulting residue is ash. From the viewpoint of suppressing yellowness, the ratio is preferably 0.35 mol% or less, and more preferably 0.3 mol% or less. Furthermore, from the viewpoint of improving laser peelability, the ratio is preferably 0.01 mol% or more, and more preferably 0.05 mol% or more.

[0019] The polyimide precursor of the first embodiment, when formed into a polyimide film, exhibits low residual stress, little warping, a small yellowness index (YI value), and excellent laser peelability from a substrate. Furthermore, the polyimide precursor of the first embodiment, when formed into a polyimide film, exhibits a small yellowness index (YI value) and a small haze value in the high temperature range.

[0020] (Structural unit represented by general formula (1)) In the general formula (1), X is a tetravalent organic group, and multiple Xs present in the polyimide precursor may be the same or different. Examples of X include tetravalent organic groups derived from the following tetracarboxylic dianhydrides.

[0021] Examples of the tetracarboxylic dianhydride include aromatic tetracarboxylic dianhydrides having 8 to 36 carbon atoms, aliphatic tetracarboxylic dianhydrides having 6 to 36 carbon atoms, and alicyclic tetracarboxylic dianhydrides having 6 to 36 carbon atoms. Among these, aromatic tetracarboxylic dianhydrides having 8 to 36 carbon atoms are preferred from the viewpoint of yellowness in high temperature regions. The number of carbon atoms referred to here includes the number of carbon atoms contained in the carboxyl group.

[0022] Examples of the aromatic tetracarboxylic dianhydride having 8 to 36 carbon atoms include 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (hereinafter also referred to as 6FDA), 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2-dicarboxylic anhydride, pyromellitic dianhydride (hereinafter also referred to as PMDA), 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'- Biphenyltetracarboxylic dianhydride (hereinafter also referred to as BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (hereinafter also referred to as DSDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, methylene-4,4-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride (hereinafter also referred to as ODPA), p-phenylenebis(trimellitate anhydride) (hereinafter also referred to as TAHQ)thio-4,4'-diphthalic dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl) )-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,Examples of the dianhydride include 4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, and 1,2,7,8-phenanthrenetetracarboxylic dianhydride.

[0023] Examples of aliphatic tetracarboxylic dianhydrides having 6 to 50 carbon atoms include ethylene tetracarboxylic dianhydride and 1,2,3,4-butane tetracarboxylic dianhydride; Examples of the alicyclic tetracarboxylic dianhydride having 6 to 36 carbon atoms include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclopentanonebisspironorbornanetetracarboxylic dianhydride (hereinafter also referred to as CpODA), 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride, carbonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic) dianhydride, methylene-4,4'-bis(cyclohexane-12-dicarboxylic) dianhydride, 1,2-ethylene-4,4'-bis(cyclohexane-1,2-dicarboxylic) dianhydride, 1,1-ethylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic) dianhydride, 2, 2-Propylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, thio-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, sulfonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, rel-[1S,5R,6R]-3-oxabicyclo[3,2]octane-2,4-dione-6-spiro-3′-(tetrahydrofuran-2′,5′-dione), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, ethylene glycol-bis-3,4-dicarboxylic acid anhydride (phenyl) ether, and the like.

[0024] From the viewpoint of the balance of the coefficient of thermal expansion (CTE), chemical resistance, glass transition temperature (Tg), and yellowness in the high temperature region, PMDA, BPDA, DSDA, TAHQ, ODPA, and CpODA are preferred, and BPDA and TAHQ are more preferred.

[0025] The polyimide precursor of this embodiment may be obtained by using a dicarboxylic acid in addition to the tetracarboxylic dianhydride described above, provided that its performance is not impaired. By using such a precursor, various properties of the resulting film can be adjusted, such as improved mechanical elongation, improved glass transition temperature, and reduced yellowness. Examples of such dicarboxylic acids include dicarboxylic acids having an aromatic ring and alicyclic dicarboxylic acids. Particularly preferred is at least one compound selected from the group consisting of aromatic dicarboxylic acids having 8 to 36 carbon atoms and alicyclic dicarboxylic acids having 6 to 34 carbon atoms. The number of carbon atoms referred to here includes the number of carbon atoms contained in the carboxyl group. Among these, dicarboxylic acids having an aromatic ring are preferred.

[0026] Specific examples include isophthalic acid, terephthalic acid, 4,4'-biphenyldicarboxylic acid, 3,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-sulfonylbisbenzoic acid, 3,4'-sulfonylbisbenzoic acid, 3,3'-sulfonylbisbenzoic acid, 4,4'-oxybisbenzoic acid, 3,4'-oxybisbenzoic acid, 3,3'-oxybisbenzoic acid, 2,2-bis(4-carbo 2,2-bis(3-carboxyphenyl)propane, 2,2'-dimethyl-4,4'-biphenyldicarboxylic acid, 3,3'-dimethyl-4,4'-biphenyldicarboxylic acid, 2,2'-dimethyl-3,3'-biphenyldicarboxylic acid, 9,9-bis(4-(4-carboxyphenoxy)phenyl)fluorene, 9,9-bis(4-(3-carboxyphenoxy)phenyl)fluorene, 4,4'-bis(4-carboxyphenoxy)biphenyl, 4,4'-bis(3-carboxyphenoxy)biphenyl, 3,4'-bis (4-carboxyphenoxy)biphenyl, 3,4'-bis(3-carboxyphenoxy)biphenyl, 3,3'-bis(4-carboxyphenoxy)biphenyl, 3,3'-bis(3-carboxyphenoxy)biphenyl, 4,4'-bis(4-carboxyphenoxy)-p-terphenyl, 4,4'-bis(4-carboxyphenoxy)-m-terphenyl, 3,4'-bis(4-carboxyphenoxy)-p-terphenyl, 3,3'-bis(4-carboxyphenoxy)-p-terphenyl, 3,4'-bis(4-carboxyphenoxy) -m-terphenyl, 3,3'-bis(4-carboxyphenoxy)-m-terphenyl, 4,4'-bis(3-carboxyphenoxy)-p-terphenyl, 4,4'-bis(3-carboxyphenoxy)-m-terphenyl, 3,4'-bis(3-carboxyphenoxy)-p-terphenyl, 3,3'-bis(3-carboxyphenoxy)-p-terphenyl, 3,4'-bis(3-carboxyphenoxy)-m-terphenyl, 3,3'-bis(3-carboxyphenoxy)-m-terphenyl, 1,1-cyclobutanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid, etc.; and Examples include 5-aminoisophthalic acid derivatives described in WO 2005 / 068535. When these dicarboxylic acids are actually copolymerized into a polymer, they may be used in the form of an acid chloride derived from thionyl chloride or an active ester.

[0027] In the above general formula (1), Y1 is a divalent organic group and may preferably be at least one of the structures represented by the following general formulae (A-1) to (A-5): Y1 is preferably a structure represented by general formula (A-1) from the viewpoints of yellowness index (YI value) in the high temperature range and laser peelability.

[0028] General formula (A-1): [ka] {In the formula, R1 and R2 each independently represent a monovalent organic group having 1 to 20 carbon atoms or a halogen, a and b each independently represent an integer of 0 to 4, and * represents a bond.}

[0029] Here, R1 and R2 are each independently a monovalent organic group having 1 to 20 carbon atoms or a halogen, but are not limited thereto. Examples of the organic group include alkyl groups such as methyl, ethyl, and propyl; halogen-containing groups such as trifluoromethyl; and alkoxy groups such as methoxy and ethoxy. Examples of the halogen include fluoro groups. Among these, methyl and fluoro groups are preferred from the viewpoints of yellowness (YI value) and haze (Haze value) in the high temperature range.

[0030] Here, a and b are not limited as long as they are each an integer of 0 to 4. Among these, from the viewpoints of yellowness index (YI value) and residual stress, an integer of 0 to 2 is preferred, and from the viewpoint of yellowness index (YI value) in the high temperature range, 0 is particularly preferred.

[0031] General formula (A-2): [ka] {In the formula, R3 and R4 each independently represent a monovalent organic group having 1 to 20 carbon atoms or a halogen, d and e each independently represent an integer of 0 to 4, and * represents a bonding site.}

[0032] Here, R3 and R4 are each independently a monovalent organic group having 1 to 20 carbon atoms or a halogen, but are not limited thereto. Examples of such organic groups include alkyl groups such as methyl, ethyl, and propyl groups, halogen-containing groups such as trifluoromethyl groups, and alkoxy groups such as methoxy and ethoxy groups. Among these, a methyl group is preferred from the viewpoint of yellowness index (YI value) in the high temperature range.

[0033] Here, c and d are not limited as long as they are each independently an integer of 0 to 4. Among these, from the viewpoints of yellowness index (YI value) and residual stress, an integer of 0 to 2 is preferred, and from the viewpoint of yellowness index (YI value) in the high temperature range, 0 is particularly preferred.

[0034] General formula (A-3): [ka] {In the formula, R5 to R8 each independently represent a monovalent organic group having 1 to 20 carbon atoms or a halogen, e to h each independently represent an integer of 0 to 4, and * represents a bond.}

[0035] Here, R5 to R8 are each independently a monovalent organic group having 1 to 20 carbon atoms or a halogen, but are not limited thereto. Examples of such organic groups include alkyl groups such as methyl, ethyl, and propyl groups, halogen-containing groups such as trifluoromethyl groups, and alkoxy groups such as methoxy and ethoxy groups. Among these, a methyl group is preferred from the viewpoint of yellowness index (YI value) in the high temperature range.

[0036] Here, e to h are not limited as long as they are each independently an integer of 0 to 4. Among these, from the viewpoints of yellowness index (YI value) and residual stress, integers of 0 to 2 are preferred, and from the viewpoint of yellowness index (YI value) in the high temperature range, 0 is particularly preferred.

[0037] General formula (A-4): [ka] wherein R9 and R 10 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, i and j each independently represents an integer of 0 to 4, and * represents a bonding site.}

[0038] where R9 and R 10 are each independently a monovalent organic group having 1 to 20 carbon atoms or a halogen, but are not limited thereto. Examples of such organic groups include alkyl groups such as methyl, ethyl, and propyl groups, halogen-containing groups such as trifluoromethyl groups, and alkoxy groups such as methoxy and ethoxy groups. Among these, a methyl group is preferred from the viewpoint of yellowness index (YI value) in the high temperature range.

[0039] Here, i and j are not limited as long as they are each independently an integer of 0 to 4. Among these, from the viewpoints of yellowness index (YI value) and residual stress, an integer of 0 to 2 is preferred, and from the viewpoint of yellowness index (YI value) in the high temperature region, 0 or 1 is particularly preferred.

[0040] General formula (A-5): [ka] {where, R 11 and R 12 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, k and l are integers of 0 to 4, and * represents a bonding site.}

[0041] where R 11 and R 12are each independently a monovalent organic group having 1 to 20 carbon atoms or a halogen, but are not limited thereto. Examples of the organic group include alkyl groups such as methyl, ethyl, and propyl; halogen-containing groups such as trifluoromethyl; and alkoxy groups such as methoxy and ethoxy. Examples of the halogen include fluoro groups. Among these, methyl and fluoro groups are preferred from the viewpoint of yellowness index (YI value) in the high temperature range.

[0042] Here, k and l are not limited as long as they are each independently an integer of 0 to 4. Among these, from the viewpoints of yellowness index (YI value) and residual stress, an integer of 0 to 2 is preferred, and from the viewpoint of yellowness index (YI value) in the high temperature range, 0 is particularly preferred.

[0043] In one embodiment, the structural unit represented by general formula (A-1) is represented by the following general formula (B-1): [ka] {In the formula, R1, R2, a, and b are defined as in general formula (A-1).} It is derived from a diamine represented by the formula:

[0044] More specific examples of diamines represented by general formula (B-1) include 4-aminophenyl-4-aminobenzoate (hereinafter also referred to as APAB), 2-methyl-4-aminophenyl-4-aminobenzoate (hereinafter also referred to as 2Me-APAB), 3-methyl-4-aminophenyl-4-aminobenzoate (hereinafter also referred to as 3Me-APAB), 2-fluoro-4-aminophenyl-4-aminobenzoate (hereinafter also referred to as 2F-APAB), 3-fluoro-4-aminophenyl-4-aminobenzoate (hereinafter also referred to as 3F-APAB), and 3-methyl-4-aminophenyl-3-methyl-4-aminobenzoate (hereinafter also referred to as 3,3Me-APAB). From the viewpoint of reducing the haze value, APAB, 3Me-APAB, 3F-APAB, and 3,3Me-APAB are preferred.

[0045] In one embodiment, the structural unit represented by general formula (A-2) is represented by the following general formula (B-2): [ka] {In the formula, R3, R4, c, and d are defined as in general formula (A-2).} It is derived from a diamine represented by the formula:

[0046] More specific examples of the diamine represented by general formula (B-2) include 4,4'-diaminodiphenyl sulfone (hereinafter also referred to as 44DAS), 3,3'-diaminodiphenyl sulfone, and the like.

[0047] In one embodiment, the structural unit represented by general formula (A-3) is represented by the following general formula (B-3): [ka] {In the formula, R5 to R8 and e to h are defined as in general formula (A-3).} It is derived from a diamine represented by the formula:

[0048] More specifically, examples of diamines represented by general formula (B-3) include 9,9-bis(aminophenyl)fluorene (hereinafter also referred to as BAFL), 9,9-bis(4-amino-3-methylphenyl)fluorene, 9,9-bis(4-amino-3-fluorophenyl)fluorene, 9,9-bis(4-hydroxy-3-aminophenyl)fluorene, and 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, and it is preferable to use one or more selected from these.

[0049] In one embodiment, the structural unit represented by general formula (A-4) is represented by the following general formula (B-4): [ka] {where, R9, R 10 , i and j are defined as in general formula (A-4). It is derived from a diamine represented by the formula:

[0050] A more specific example of the diamine represented by general formula (B-4) is 2,2'-bis(trifluoromethyl)benzidine (hereinafter also referred to as TFMB).

[0051] In one embodiment, the structural unit represented by general formula (A-5) is represented by the following general formula (B-5): [ka] {where, R 11 , R 12 , k and l are defined as in general formula (B-5). It is derived from a diamine represented by the formula:

[0052] More specifically, examples of diamines represented by general formula (B-5) include 4,4'-diaminobenzanilide (hereinafter also referred to as DABA).

[0053] (Structural unit represented by general formula (2)) In the above general formula (2), X may have the same structure as exemplified as X in the above general formula (1).

[0054] In the above general formula (2), Y2 is preferably a structure represented by any one of the general formulae (A-1) to (A-5) described above for the general formula (1), and the following general formula (A-6): [ka] {where, R 13 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, m is an integer of 0 to 4, n is an integer of 1 or greater, and * represents a bond.} The structure is at least one selected from the group consisting of structures represented by the following formula:

[0055] where R 13are each independently a monovalent organic group having 1 to 20 carbon atoms or a halogen, but are not limited thereto. Examples of the organic group include alkyl groups such as methyl, ethyl, and propyl; halogen-containing groups such as trifluoromethyl; and alkoxy groups such as methoxy and ethoxy. Examples of the halogen include fluoro groups. Among these, methyl and fluoro groups are preferred from the viewpoint of yellowness index (YI value) in the high temperature range.

[0056] Here, m is not limited as long as it is an integer of 0 to 4. Among these, from the viewpoints of yellowness (YI value) and laser peelability, an integer of 0 to 2 is preferred, and from the viewpoint of yellowness (YI value) in the high temperature region, 0 is particularly preferred.

[0057] Here, n is an integer of 1 or more, preferably an integer of 1 to 4. Among these, from the viewpoints of YI and laser peelability, an integer of 1 to 2 is preferred, and from the viewpoint of yellowness (YI value) in the high temperature range, 1 is particularly preferred.

[0058] As Y2, from the viewpoints of yellowness index (YI value) in the high temperature region and laser peelability, at least one selected from the group consisting of structures represented by general formulas (A-1) and (A-6) is preferred, or a structure represented by general formula (A-1) is preferred, or a structure represented by general formula (A-6) is preferred.

[0059] In the general formula (2), Z is a bond represented by -NHNH- or -N=N-, and the polyimide precursor may contain either one or both. Among these, the -N=N- bond is preferred from the viewpoint of yellowness index (YI value) at high temperatures. Azo compounds having an -N=N- bond are generally known to undergo photoisomerization. It is believed that the azo structure is excited by the energy of the laser irradiated during laser delamination, improving laser delamination. Therefore, absorbance near commonly used laser delamination wavelengths (e.g., 308 nm) is important. The structure represented by general formula (2) is preferred because it has good absorbance at the above-mentioned laser delamination wavelength. As mentioned above, the content of the structure represented by general formula (2) is determined from a PDA chromatogram measured by LC / MS with a 300 nm detector. Since the -NHNH- bond is reduced to an -N=N- bond during thermal imidization, it can contribute to improving laser delamination similarly to the -N=N- bond.

[0060] In the general formula (2), when Y2 has a structural unit represented by the above general formula (A-6), the structure of -Y2-Z-Y2- in one embodiment is represented by the following general formula (B-6): [ka] {where, R 13 , m and n are defined as in general formula (A-6). It is derived from a diamine represented by the formula:

[0061] More specifically, examples of diamines represented by general formula (B-6) include 4,4'-azodianiline (hereinafter also referred to as AzBz).

[0062] More specific examples of diamines used to form the structural unit represented by general formula (2) include, but are not limited to, diamines represented by the following formulas (C-1) to (C-4). [ka] (Bis(4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl, Azo-APAB) [ka] (Bis(2-fluoro-4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl, Azo-2F-APAB) [ka] (Bis(3-fluoro-4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl, Azo-3F-APAB) [ka] (Bis(3-methyl-4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl, Azo-3Me-APAB)

[0063] The weight-average molecular weight (Mw) of the polyimide precursor in this embodiment is preferably 10,000 to 300,000, and particularly preferably 30,000 to 200,000. When the weight-average molecular weight is 10,000 or more, the mechanical properties such as elongation and breaking strength are excellent, the residual stress is low, and the YI is low. When the weight-average molecular weight is 300,000 or less, it becomes easy to control the weight-average molecular weight during synthesis of the polyamic acid, and a resin composition with an appropriate viscosity can be obtained, improving the coatability of the resin composition. In the present disclosure, the weight-average molecular weight is a value determined as a standard polystyrene equivalent value using gel permeation chromatography (hereinafter also referred to as GPC).

[0064] In this embodiment, the content of molecules having a molecular weight of less than 1,000 in the polyimide precursor is preferably less than 5% by mass, more preferably less than 1% by mass, based on the total amount of the polyimide precursor. A polyimide film formed from a resin composition obtained using such a polyimide precursor has low residual stress, and the haze value of an inorganic film formed on the polyimide film is low. The content of molecules having a molecular weight of less than 1,000 based on the total amount of the polyimide precursor can be calculated from the peak area obtained by GPC measurement using a solution in which the polyimide precursor is dissolved.

[0065] <Polyimide> A second embodiment of the present disclosure comprises: The following general formula (3): [ka] {In the formula, X independently represents a tetravalent organic group, Y1 and Y2 independently represent a divalent organic group, and l and m independently represent an integer of 1 or greater, provided that 0.005≦m / (l+m)≦0.5 is satisfied.} The present invention provides a polyimide comprising a structural unit represented by the formula:

[0066] In the general formula (3), examples of X, Y1 and Y2 may be the same as the examples of X, Y1 and Y2 described above in the general formulas (1) and (2).

[0067] As X in general formula (3), from the viewpoint of the balance of CTE, chemical resistance, Tg, and yellowness index (YI value) in the high temperature region, PMDA, BPDA, DSDA, TAHQ, ODPA, and CpODA are preferred, and BPDA and TAHQ are more preferred.

[0068] Y1 in general formula (3) may be the same as exemplified as Y1 in general formula (1), for example, a divalent organic group represented by general formulas (A-1) to (A-5), and may be derived from a diamine having a structure represented by general formulas (B-1) to (B-5). Y2 and Z may be the same as exemplified as Y2 and Z in general formula (2), for example, Y2 may be a divalent organic group represented by general formulas (A-1) to (A-6), and the -Y2-Z-Y2- structure may be derived from a diamine represented by general formula (B-6).

[0069] Y2 in general formula (3) is preferably at least one selected from the group consisting of structures represented by general formulas (A-1) and (A-6), and more preferably a structure represented by general formula (A-6).

[0070] The polyimide precursor in the first embodiment and the polyimide in the second embodiment may contain other diamines in addition to the diamines represented by the general formulas (B-1) to (B-6) and (C-1) to (C-4) described above, within the range that does not impair the elongation, strength, stress, laser peelability, yellowness index, etc.

[0071] Other diamines include, for example, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-bis( Examples of suitable diamines include 4-aminophenoxy)biphenyl, 4,4-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and 1,4-bis(3-aminopropyldimethylsilyl)benzene. The content of the other diamines in the total diamines is preferably 20 mol% or less, and particularly preferably 10 mol% or less.

[0072] [Production of polyimide precursor] The polyimide precursor (specifically, polyamic acid) of this embodiment can be synthesized by polycondensation of a tetracarboxylic dianhydride, a diamine (e.g., APAB) used in the structural unit represented by the general formula (1), and a diamine (e.g., AzBz) used in the structural unit represented by the general formula (2). This reaction is preferably carried out in a suitable solvent. Specifically, for example, a method can be used in which predetermined amounts of APAB and AzBz are dissolved in a solvent, and then a predetermined amount of tetracarboxylic dianhydride is added to the resulting diamine solution and stirred.

[0073] In the diamine component, the molar ratio of the diamine used in the structural unit represented by general formula (1) to the diamine used in the structural unit represented by general formula (2) is (number of moles of structural unit represented by general formula (2)) / [(number of moles of structural unit represented by general formula (1)) + (number of moles of structural unit represented by general formula (2)], and is not limited as long as it is 0.005 to 0.5 mol %. When the diamine used in the structural unit represented by general formula (2) is 0.005 mol % or more in the diamine component, laser peelability tends to be good, and when it is 0.5 mol % or less, the yellowness index (YI value) of the polyimide film tends to be good and ash generation after laser peeling tends to be suppressed. When the diamine used in the structural unit represented by general formula (1) is 99.5 mol % or more, the residual stress of the resulting polyimide film tends to be good. (Number of moles of structural units represented by general formula (2)) / [(Number of moles of structural units represented by general formula (1))+(Number of moles of structural units represented by general formula (2)] is preferably 0.0075 to 0.3 mol %, more preferably 0.009 to 0.1 mol %.

[0074] When synthesizing the polyimide precursor of this embodiment, the molar ratio of the tetracarboxylic dianhydride component to the diamine component is preferably in the range of 100:90 to 100:110 (0.90 to 1.10 molar parts of diamine per 1 molar part of tetracarboxylic dianhydride), and more preferably in the range of 100:95 to 100:105 (0.95 to 1.05 molar parts of diamine per 1 molar part of dianhydride), from the viewpoint of controlling the linear thermal expansion coefficient, residual stress, elongation, and yellowness index (YI value) of the resulting resin film within desired ranges.

[0075] In the present embodiment, when synthesizing a polyamic acid, which is a preferred polyimide precursor, the molecular weight can be controlled by adjusting the ratio of the tetracarboxylic dianhydride component to the diamine component and by adding an end-capping agent. The closer the ratio of the tetracarboxylic dianhydride component to the diamine component is to 1:1 and the smaller the amount of end-capping agent used, the higher the molecular weight of the polyamic acid can be.

[0076] It is recommended to use high-purity products as the tetracarboxylic dianhydride component and the diamine component. The purity is preferably 98% by mass or more, more preferably 99% by mass or more, and even more preferably 99.5% by mass or more. When multiple types of acid dianhydride components or diamine components are used in combination, it is sufficient for the acid dianhydride components or diamine components as a whole to have the above-mentioned purity, but it is preferable that all types of acid dianhydride components and diamine components used have the above-mentioned purity. Other components may include a diamine used to form the structural unit M represented by general formula (2). On the other hand, it is preferable that no impurities other than the diamine used to form the structural unit M represented by general formula (2) are contained.

[0077] The reaction solvent is not particularly limited as long as it can dissolve the tetracarboxylic dianhydride component, the diamine component, and the resulting polyamic acid and can produce a high-molecular-weight polymer. Specific examples of such solvents include aprotic solvents, phenolic solvents, ether and glycol solvents. Specific examples of these include aprotic solvents such as amide solvents, such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N-methylcaprolactam, 1,3-dimethylimidazolidinone, tetramethylurea, Equamide M100 (trade name: manufactured by Idemitsu Kosan Co., Ltd.), and Equamide B100 (trade name: manufactured by Idemitsu Kosan Co., Ltd.); Lactone solvents such as γ-butyrolactone and γ-valerolactone; Phosphorus-containing amide solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as cyclohexanone and methylcyclohexanone; tertiary amine solvents such as picoline and pyridine; Ester solvents such as 2-methoxy-1-methylethyl acetate etc.: Examples of the phenolic solvent include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol. Examples of the ether and glycol solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Each of them can be mentioned.

[0078] The boiling point of the solvent used in synthesizing the polyamic acid at normal pressure is preferably 60°C to 300°C, more preferably 140°C to 280°C, and particularly preferably 170°C to 270°C. If the boiling point of the solvent is higher than 300°C, the drying process will require a long time. On the other hand, if the boiling point of the solvent is lower than 60°C, the surface of the resin film may become rough or air bubbles may be mixed into the resin film during the drying process, making it difficult to obtain a uniform film.

[0079] Thus, from the viewpoints of solubility and edge repellency during coating, it is preferable to use a solvent having a boiling point of preferably 170°C to 270°C, more preferably a vapor pressure of 250 Pa or less at 20°C. More specifically, it is preferable to use one or more solvents selected from the group consisting of N-methyl-2-pyrrolidone and γ-butyrolactone. The water content in the solvent is preferably 3,000 mass ppm or less. These solvents may be used alone or in combination of two or more.

[0080] As described above, the polyimide precursor of this embodiment preferably contains less than 5% by mass of molecules with a molecular weight of less than 1,000. The presence of molecules with a molecular weight of less than 1,000 in the polyimide precursor is thought to be due to the water content of the solvent used during synthesis. Specifically, it is thought that the acid anhydride groups of some of the acid dianhydride monomers are hydrolyzed by water to form carboxyl groups, which remain in a low-molecular-weight state without becoming high-molecular-weight. Therefore, it is desirable that the water content of the solvent used in the polymerization reaction be as low as possible. From this perspective, the water content of the solvent is preferably 3,000 ppm by mass or less, and more preferably 1,000 ppm by mass or less.

[0081] The moisture content of the solvent is likely to be affected by factors such as the grade of solvent used (e.g., dehydrating grade, general-purpose grade), the solvent container (e.g., bottle, 18L can, canister), the solvent storage condition (e.g., whether it contains a noble gas), and the time between opening and use (e.g., whether it is used immediately after opening or after aging after opening). It is also likely to be affected by factors such as the replacement of the reactor with noble gas before synthesis and the presence or absence of noble gas flow during synthesis. Therefore, when synthesizing polyimide precursors, it is recommended to use high-purity raw materials and solvents with low moisture content, as well as take measures to prevent moisture from the environment from entering the system before and during the reaction.

[0082] When dissolving each monomer component in the solvent, heating may be performed as necessary. The reaction temperature during synthesis of the polyimide precursor is preferably 0°C to 120°C, more preferably 40°C to 100°C, and even more preferably 60°C to 100°C. By carrying out the polymerization reaction at this temperature, a polyimide precursor with a high degree of polymerization can be obtained. The polymerization time is preferably 1 to 100 hours, and more preferably 2 to 10 hours. By setting the polymerization time to 1 hour or more, a polyimide precursor with a high degree of polymerization can be obtained, and by setting it to 100 hours or less, a polyimide precursor with a uniform degree of polymerization can be obtained.

[0083] In a preferred aspect of this embodiment, the polyimide precursor has the following properties: The polyimide precursor is dissolved in a solvent (e.g., N-methyl-2-pyrrolidone), the resulting solution is applied to the surface of a support, and the solution is then heated (e.g., for 1 hour) at 300°C to 550°C (e.g., 430°C) in a nitrogen atmosphere (e.g., nitrogen with an oxygen concentration of 2,000 mass ppm or less) to imidize the polyimide precursor, thereby obtaining a resin that has a yellowness index (YI value) of 30 or less in a film thickness of 10 μm.

[0084] The polyimide precursor is dissolved in a solvent (e.g., N-methyl-2-pyrrolidone), the resulting solution is applied to the surface of a support, and the solution is then heated (e.g., for 1 hour) at 300°C to 550°C (e.g., 430°C) in a nitrogen atmosphere (e.g., nitrogen with an oxygen concentration of 2,000 mass ppm or less) to imidize the polyimide precursor, resulting in a resin having a residual stress of 25 MPa or less.

[0085] In a preferred aspect of this embodiment, the polyimide precursor may be partially imidized (i.e., partially imidized). In this case, the imidization rate is preferably 80% or less, and more preferably 50% or less. Partial imidization can be achieved by heating the polyimide precursor to dehydrate and close the ring. Heating for partial imidization can be carried out at a temperature of preferably 120°C to 200°C, more preferably 150°C to 180°C, for preferably 15 minutes to 20 hours, more preferably 30 minutes to 10 hours.

[0086] Furthermore, a resin composition having improved viscosity stability during storage at room temperature can be obtained by adding N,N-dimethylformamide dimethyl acetal or N,N-dimethylformamide diethyl acetal to the polyamic acid obtained by the above reaction, heating the mixture to esterify all or part of the carboxylic acid, and then using the resulting mixture as a polyimide precursor in this embodiment. These ester-modified polyamic acids can also be obtained by sequentially reacting the above-mentioned acid dianhydride component with one equivalent of a monohydric alcohol relative to the acid anhydride groups, and a dehydration condensing agent such as thionyl chloride or dicyclohexylcarbodiimide, followed by a condensation reaction with a diamine component.

[0087] <Resin composition> Another aspect of the present invention provides a resin composition, typically a varnish, containing (a) a polyimide precursor and (b) an organic solvent.

[0088] [(a) Polyimide precursor] The polyimide precursor (a) in the resin composition may be the polyimide precursor of the present disclosure described above. From the viewpoint of film-forming properties, the proportion of the polyimide precursor (a) (preferably polyamic acid) in the resin composition is preferably 3 to 50 mass %, more preferably 5 to 40 mass %, and particularly preferably 10 to 30 mass %.

[0089] [(b) Organic solvent] The (b) organic solvent is not particularly limited as long as it can dissolve the (a) polyimide precursor and other optional components. As such (b) organic solvent, the solvents described above as solvents that can be used in synthesizing the (a) polyimide precursor can be used. The preferred organic solvents are also the same as those described above. The (b) organic solvent in the resin composition of this embodiment may be the same as or different from the solvent used in synthesizing the (a) polyimide precursor.

[0090] The amount of (b) organic solvent is preferably such that the solids concentration of the resin composition is 3 to 50 mass %. Furthermore, the composition and amount of (b) organic solvent are preferably adjusted before addition so that the viscosity of the resin composition (25°C) is 500 mPa·s to 100,000 mPa·s.

[0091] [Other ingredients] The resin composition of the present embodiment may further contain, in addition to the above components (a) and (b), a surfactant (c), an alkoxysilane compound (d), and the like.

[0092] The resin composition according to this embodiment contains (a) a polyimide precursor, (b) an organic solvent, and at least one selected from the group consisting of (c) a surfactant and (d) an alkoxysilane compound.

[0093] Examples of the skeleton of the polyimide precursor include the skeletons described above in the first and second embodiments. In one aspect, the skeleton of the polyimide precursor may be a skeleton having a structural unit represented by the general formula (1) described above.

[0094] [(c) Surfactant] By adding a surfactant to the resin composition of the present embodiment, the coatability of the resin composition can be improved, specifically, the occurrence of streaks in the coating film can be prevented.

[0095] Examples of such surfactants include silicone surfactants, fluorine surfactants, and other nonionic surfactants. Examples of these include silicone surfactants such as organosiloxane polymers KF-640, 642, 643, KP341, X-70-092, and X-70-093 (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), SH-28PA, SH-190, SH-193, SZ-6032, SF-8428, DC-57, and DC-190 (all trade names, manufactured by Toray Dow Corning Silicones Co., Ltd.), and SILWET L-77, L-7001, FZ-2105, FZ-210, FZ-2154, FZ-2164, FZ-2166, L-7604 (all trade names, manufactured by Nippon Unicar Co., Ltd.), DBE-814, DBE-224, DBE-621, CMS-66, CMS-222, KF-352A, KF-354L, KF-355A, KF-600, DBE-821, DBE-712 (Gelest), BYK-307, BYK-30, BYK-378, BYK-333 (all trade names, manufactured by BYK Japan), Granol (trade name, manufactured by Kyoeisha Chemical Co., Ltd.), etc. Examples of fluorine-based surfactants include Megafac F171, F173, and R-08 (trade names, manufactured by Dainippon Ink and Chemicals, Inc.), and Fluorad FC4430 and FC4432 (trade names, manufactured by Sumitomo 3M Limited); Other nonionic surfactants include, for example, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octylphenyl ether, and the like.

[0096] Among these surfactants, silicone surfactants and fluorine surfactants are preferred from the viewpoint of the coatability (streak prevention) of the resin composition, and silicone surfactants are preferred from the viewpoint of the influence of the oxygen concentration during the curing step on the yellowness index (YI value) and total light transmittance. When (c) surfactant is used, its amount is preferably 0.001 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, per 100 parts by mass of (a) polyimide precursor in the resin composition.

[0097] [(d) Alkoxysilane Compound] In order to ensure that the resin film obtained from the resin composition according to this embodiment exhibits sufficient adhesion to the support in the manufacturing process of a flexible device or the like, the resin composition may contain (a) 0.01 to 20 parts by mass of an alkoxysilane compound per 100 parts by mass of the polyimide precursor. By ensuring that the content of the alkoxysilane compound is 0.01 part by mass or more per 100 parts by mass of the polyimide precursor, good adhesion to the support can be obtained. Furthermore, from the viewpoint of the storage stability of the resin composition, it is preferable that the content of the alkoxysilane compound is 20 parts by mass or less. The content of the alkoxysilane compound is more preferably 0.02 to 15 parts by mass, even more preferably 0.05 to 10 parts by mass, and particularly preferably 0.1 to 8 parts by mass per 100 parts by mass of the polyimide precursor.

[0098] By using an alkoxysilane compound as an additive to the resin composition according to this embodiment, in addition to the improvement in adhesion described above, it is possible to further improve the coatability of the resin composition (suppress streaks) and reduce the dependency of the yellowness index (YI value) of the resulting cured film on the oxygen concentration during curing.

[0099] Examples of alkoxysilane compounds include 3-ureidopropyltriethoxysilane, bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltripropoxysilane, γ-aminopropyltributoxysilane, γ-aminoethyltriethoxysilane, γ-aminoethyltrippropoxysilane, γ-aminoethyltributoxysilane, γ-aminobutyltriethoxysilane, γ-aminobutyltrimethoxysilane, γ-aminobutyltrippropoxysilane, γ-aminobutyltributoxysilane, phenylsilanetriol, trimethoxyphenylsilane, trimethoxy(p-tolyl)silane, diphenylsilanediol, dimethoxydiphenylsilane, diethoxydiphenylsilane, dimethoxydi-p-tolylsilane, and triphenylsilanol. It is preferable to use at least one selected from these.

[0100] The method for producing the resin composition in this embodiment is not particularly limited, and can be, for example, the following method.

[0101] When the solvent used in synthesizing (a) the polyimide precursor and the organic solvent (b) are the same, the synthesized polyimide precursor solution can be used as a resin composition as is. If necessary, the organic solvent (b) and one or more other components may be added to the polyimide precursor at a temperature ranging from room temperature (25°C) to 80°C, followed by stirring and mixing, and then the resulting mixture may be used as a resin composition. For this stirring and mixing, an appropriate device such as a Three-One Motor (manufactured by Shinto Chemical Co., Ltd.) equipped with stirring blades or a planetary centrifugal mixer may be used. If necessary, heat of 40°C to 100°C may be applied.

[0102] On the other hand, when the solvent used in synthesizing (a) the polyimide precursor and (b) the organic solvent are different, the solvent in the synthesized polyimide precursor solution may be removed by an appropriate method such as reprecipitation or solvent distillation to isolate (a) the polyimide precursor, and then (b) the organic solvent and, if necessary, other components may be added and stirred and mixed in a temperature range of room temperature to 80°C to prepare a resin composition.

[0103] After preparing the resin composition as described above, the composition solution may be heated, for example, at 130°C to 200°C for 5 minutes to 2 hours to dehydrate and imidize a portion of the polyimide precursor to the extent that the polymer does not precipitate. The imidization rate can be controlled by controlling the heating temperature and heating time. Partially imidizing the polyimide precursor can improve the viscosity stability of the resin composition during storage at room temperature. A range of 5% to 70% imidization rate is preferred from the viewpoint of balancing the solubility of the polyimide precursor in the resin composition solution and the storage stability of the solution.

[0104] The resin composition according to the present embodiment preferably has a water content of 3,000 ppm by mass or less. From the viewpoint of viscosity stability during storage of the resin composition, the water content of the resin composition is more preferably 1,000 ppm by mass or less, and even more preferably 500 ppm by mass or less. Although a lower water content of the resin composition is preferred, from the viewpoint of ease of production of the resin composition, the water content may be, for example, 10 ppm by mass or more, or 100 ppm by mass or more.

[0105] The solution viscosity of the resin composition according to this embodiment at 25°C is preferably 300 to 200,000 mPa·s, more preferably 2,000 to 100,000 mPa·s, and particularly preferably 3,000 to 30,000 mPa·s. This solution viscosity can be measured using an E-type viscometer (VISCONICEHD, manufactured by Toki Sangyo Co., Ltd.). If the solution viscosity is lower than 300 mPa·s, coating during film formation may be difficult, while if it is higher than 200,000 mPa·s, stirring during synthesis may be difficult. (a) Even if the solution becomes highly viscous during synthesis of the polyimide precursor, it is possible to obtain a resin composition with a viscosity that is easy to handle by adding a solvent and stirring the solution after completion of the reaction.

[0106] In a preferred embodiment, the resin composition of the present embodiment has the following properties. The resin composition is applied to the surface of a support to form a coating film, and then the coating film is heated at 300°C to 550°C in a nitrogen atmosphere (for example, in nitrogen with an oxygen concentration of 2,000 mass ppm or less) to imidize the polyimide precursor contained in the coating film. The resulting resin film has a yellowness index (YI value) of 30 or less at a film thickness of 10 μm.

[0107] The resin composition is applied to the surface of a support to form a coating film, and then the coating film is heated at 300°C to 550°C in a nitrogen atmosphere (for example, in nitrogen with an oxygen concentration of 2,000 mass ppm or less). The polyimide precursor contained in the coating film is imidized to obtain a resin film having a residual stress of 25 MPa or less.

[0108] The polyimide resin film obtained by curing the polyimide precursor and resin composition according to this embodiment can be suitably used to form transparent substrates for display devices such as liquid crystal displays, organic electroluminescence displays, field emission displays, and electronic paper, and is particularly suitable for flexible devices or flexible displays. Specifically, it can be used to form substrates for thin film transistors (TFTs), color filters, and transparent conductive films (ITO, indium tin oxide). The polyimide precursor of this embodiment can form a polyimide film having a residual stress of 25 MPa or less, and is therefore easily applicable to the manufacturing process of a display having a TFT element device on a colorless and transparent polyimide substrate.

[0109] <Resin film> Another aspect of the present invention provides a resin film formed from the aforementioned polyimide precursor. Yet another aspect of the present invention provides a method for producing a resin film from the aforementioned resin composition. The resin film in this embodiment is characterized by including a step of forming a coating film by applying the above-mentioned resin composition onto the surface of a support (coating step), a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film (heating step), and a step of peeling the polyimide resin film from the support (peeling step).

[0110] The support is not particularly limited as long as it has heat resistance at the heating temperature in the subsequent steps and has good releasability, for example, a glass (e.g., alkali-free glass) substrate; Silicon wafers; Resin substrates such as PET (polyethylene terephthalate), OPP (oriented polypropylene), polyethylene glycol terephthalate, polyethylene glycol naphthalate, polycarbonate, polyimide, polyamideimide, polyetherimide, polyetheretherketone, polyethersulfone, polyphenylenesulfone, and polyphenylene sulfide; Metal substrates such as stainless steel, alumina, copper, and nickel etc. are used.

[0111] When forming a polyimide molded product in the form of a film, for example, a glass substrate or a silicon wafer is preferred, and when forming a polyimide molded product in the form of a film or sheet, for example, a support made of polyethylene terephthalate (PET), oriented polypropylene (OPP), etc. is preferred.

[0112] Examples of the coating method include coating methods using a doctor blade knife coater, air knife coater, roll coater, rotary coater, flow coater, die coater, bar coater, etc.; coating methods such as spin coating, spray coating, and dip coating; and printing techniques such as screen printing and gravure printing. The coating thickness should be adjusted appropriately depending on the desired resin film thickness and the content of the polyimide precursor in the resin composition, but is preferably about 1 to 1,000 μm. The coating step can be carried out at room temperature, but the resin composition may be heated to a temperature in the range of 40° C. to 80° C. to reduce the viscosity and improve workability.

[0113] Following the coating step, a drying step may be carried out, or the drying step may be omitted and the process may proceed directly to the next heating step. This drying step is carried out for the purpose of removing the organic solvent. When carrying out the drying step, an appropriate device such as a hot plate, a box-type dryer, or a conveyor-type dryer may be used. The drying step is preferably carried out at a temperature of 80°C to 200°C, more preferably at 100°C to 150°C. The drying step is preferably carried out for 1 minute to 10 hours, more preferably 3 minutes to 1 hour. As described above, a coating film containing a polyimide precursor is formed on a support.

[0114] Subsequently, a heating step is carried out, which is a step for removing the organic solvent remaining in the coating film in the drying step and for promoting the imidization reaction of the polyimide precursor in the coating film, thereby obtaining a film made of polyimide. This heating step can be carried out using an apparatus such as an inert gas oven, a hot plate, a box-type dryer, a conveyor-type dryer, etc. This step can be carried out simultaneously with the drying step, or both steps can be carried out sequentially.

[0115] The heating step may be carried out in an air atmosphere, but from the viewpoints of safety and the transparency and yellowness index (YI value) of the resulting polyimide film, it is recommended to carry out the heating step in an inert gas atmosphere, such as nitrogen or argon.

[0116] The heating temperature may be set appropriately depending on the type of (b) organic solvent, but is preferably 250°C to 500°C, and more preferably 300°C to 450°C. If the temperature is 250°C or higher, imidization is sufficient, and if the temperature is 500°C or lower, there are no problems such as a decrease in transparency and deterioration in heat resistance of the resulting polyimide film. The heating time is preferably about 0.5 to 3 hours.

[0117] In this embodiment, the oxygen concentration of the ambient atmosphere in the heating step is preferably 2,000 ppm by mass or less, more preferably 100 ppm by mass or less, and even more preferably 10 ppm by mass or less, from the viewpoints of the transparency and yellowness index (YI value) of the resulting polyimide film. By performing heating in an atmosphere with an oxygen concentration of 2,000 ppm by mass or less, the YI value of the resulting polyimide film can be reduced to 30 or less.

[0118] Depending on the intended use and purpose of the polyimide resin film, a peeling step of peeling the resin film from the support may be required after the heating step. This peeling step is preferably carried out after the resin film on the support is cooled to room temperature to about 50°C. The peeling step may take the following forms (1) to (4), for example.

[0119] (1) A method in which a structure containing a polyimide resin film and a support is prepared by the above-mentioned method, and then a laser is irradiated from the support side of the structure to ablate the interface between the support and the polyimide resin film, thereby peeling off the polyimide resin. Examples of the laser include a solid-state (YAG) laser and a gas (UV excimer) laser. It is preferable to use a spectrum with a wavelength of 308 nm or the like (see, for example, JP-A Nos. 2007-512568 and 2012-511173).

[0120] (2) A method in which a release layer is formed on a support before applying a resin composition to the support, and then a structure including a polyimide resin film / release layer / support is obtained, and the polyimide resin film is peeled off. Examples of the release layer include a method using Parylene (registered trademark, manufactured by Japan Parylene LLC) or tungsten oxide, and a method using a vegetable oil-based, silicone-based, fluorine-based, or alkyd-based release agent (see, for example, JP 2010-67957 A and JP 2013-179306 A). The above method (2) and the above method (1) laser irradiation may be used in combination.

[0121] (3) A method of obtaining a polyimide resin film by using an etchable metal substrate as a support, obtaining a structure including a polyimide resin film / support, and then etching the metal with an etchant. Examples of metals that can be used include copper (specifically, electrolytic copper foil "DFF" manufactured by Mitsui Mining & Smelting Co., Ltd.) and aluminum. Examples of etchants that can be used include ferric chloride for copper and dilute hydrochloric acid for aluminum.

[0122] (4) A method in which, after obtaining a structure containing a polyimide resin film / support by the above-mentioned method, an adhesive film is attached to the surface of the polyimide resin film, the adhesive film / polyimide resin film is separated from the support, and then the polyimide resin film is separated from the adhesive film.

[0123] Among these peeling methods, method (1) or (2) is appropriate from the viewpoints of the refractive index difference between the front and back surfaces of the resulting polyimide resin film, the yellowness index (YI value), and the elongation, and method (1) is more appropriate from the viewpoint of the refractive index difference between the front and back surfaces of the resulting polyimide resin film. In the method (3), when copper is used as the support, the yellowness index (YI value) of the obtained polyimide resin film tends to be large and the elongation tends to be small. This is thought to be due to the influence of copper ions.

[0124] The thickness of the resin film obtained by the above method is not particularly limited, but is preferably in the range of 1 to 100 μm, more preferably 5 to 20 μm.

[0125] The resin film according to this embodiment may have a yellowness index (YI value) of 30 or less at a film thickness of 10 μm. The resin film may also have a residual stress of 25 MPa or less. In particular, the resin film may have a yellowness index (YI value) of 30 or less at a film thickness of 10 μm, and a residual stress of 25 MPa or less. These properties are effectively achieved, for example, by imidizing the polyimide precursor of the present disclosure in a nitrogen atmosphere (e.g., nitrogen with an oxygen concentration of 2,000 mass ppm or less) at a temperature of preferably 300°C to 550°C, more preferably 350°C to 450°C.

[0126] <Laminate> Another aspect of the present invention provides a laminate comprising a support and a polyimide resin film formed on a surface of the support from the aforementioned resin composition. Yet another aspect of the present invention provides a method for producing the above laminate. The laminate in this embodiment is a step of forming a coating film by applying the resin composition onto the surface of a support (coating step); a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film (heating step); The laminate can be obtained by a method for producing the laminate, which includes the steps of: The method for producing the laminate can be carried out in the same manner as the method for producing the resin film described above, except that the peeling step is not performed.

[0127] This laminate can be suitably used, for example, in the manufacture of flexible devices. A more detailed explanation is as follows. When forming a flexible display, a glass substrate is used as a support, a flexible substrate is formed thereon, and TFTs and other components are then formed thereon. The process of forming TFTs and other components on a flexible substrate is typically carried out over a wide temperature range of 150°C to 650°C. However, to actually achieve the desired performance, it is necessary to form a TFT-IGZO (InGaZnO) oxide semiconductor or TFTs (a-Si-TFTs, poly-Si-TFTs) using inorganic materials at high temperatures of around 250°C to 450°C. However, due to this thermal history, various physical properties of polyimide films (especially yellowness index and elongation) tend to deteriorate, with the yellowness index and elongation decreasing particularly at temperatures above 400°C. However, polyimide films obtained from the polyimide precursor of the present invention exhibit minimal deterioration in yellowness index and elongation even at high temperatures above 400°C, allowing them to be used effectively in this range.

[0128] Furthermore, in this embodiment, the compound represented by the following general formula (3): [ka] {In the formula, X independently represents a tetravalent organic group, Y1 and Y2 independently represent a divalent organic group, and l and m independently represent an integer of 1 or greater, provided that 0.005≦m / (l+m)≦0.5 is satisfied.} It is possible to provide a laminate including a polyimide film layer containing a polyimide represented by the following formula (1): and an LTPS (low temperature polysilicon TFT) layer.

[0129] The laminate can be produced by producing a laminate including the support and a polyimide resin film formed on the surface of the support from the resin composition, forming an amorphous Si layer, performing dehydrogenation annealing at 400°C to 450°C for about 0.5 to 3 hours, and then crystallizing with an excimer laser or the like to form an LTPS layer. The glass and polyimide film are then peeled off by laser peeling or the like to obtain the laminate.

[0130] The process adaptability of this annealing treatment can be confirmed by annealing a laminate in which an SiOx film is formed on a polyimide resin film at 450°C (see <Annealing Evaluation of Inorganic Film / Polyimide Laminate> in the Examples section below). To obtain a good annealing evaluation, the ratio of the amount of structural unit M to the total amount of structural unit L and structural unit M is preferably 0.5% or less, and more preferably 0.1% or less. The reason why the annealing evaluation is better as the ratio of structural unit M is smaller is unclear, but it is thought to be correlated with the decomposition of azo bonds (mainly present at the terminals) contained in the polyimide precursor during the annealing treatment, resulting in the generation of gas.

[0131] A laminate including a polyimide film layer containing a polyimide represented by general formula (3) and an LTPS (low temperature polysilicon TFT) layer exhibits little peeling or swelling after a heat cycle test, and also shows little substrate warpage. Furthermore, if the residual stress generated between the flexible substrate and the polyimide resin film is high, when a laminate consisting of both expands during a high-temperature TFT process and then shrinks during cooling to room temperature, problems such as warping and breakage of the glass substrate and peeling of the flexible substrate from the glass substrate may occur. Generally, the thermal expansion coefficient of a glass substrate is smaller than that of a resin, so residual stress occurs between the glass substrate and the flexible substrate. As described above, the resin film according to this embodiment can reduce the residual stress generated between the glass substrate and the flexible substrate to 25 MPa or less, making it suitable for use in forming flexible displays.

[0132] Furthermore, the polyimide film according to this embodiment can have a yellowness index (YI value) of 30 or less at a film thickness of 10 μm, and can be easily peeled off from a glass substrate or the like using an excimer laser or the like, thereby improving the yield when manufacturing flexible displays. By setting the yellowness index (YI value) to 30 or less, a flexible substrate can be produced without degrading the image quality when used in a display. The yellowness index (YI value) is more preferably 18 or less, and particularly preferably 16 or less.

[0133] Accordingly, another aspect of the present invention provides a display substrate. The method for producing a display substrate in this embodiment includes a step of forming a coating film by applying the above-described resin composition to the surface of a support (coating step); a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film (heating step); a step of forming an element or a circuit on the polyimide resin film (element / circuit forming step); a step of peeling the polyimide resin film on which the element or circuit is formed from the support (peeling step); The present invention is characterized by comprising:

[0134] In the above method, the coating step, heating step, and peeling step can be carried out in the same manner as in the above-mentioned method for producing a resin film. The element and circuit formation step can be carried out by a method known to those skilled in the art.

[0135] The resin film according to this embodiment, which satisfies the above physical properties, is suitable for applications where the use of existing polyimide films is limited due to their yellow color, particularly for applications such as colorless and transparent substrates for flexible displays and protective films for color filters. Furthermore, it can also be used in fields requiring colorless transparency and low birefringence, such as protective films, light-diffusing sheets and coatings in TFT-LCDs (e.g., TFT-LCD interlayers, gate insulating films, liquid crystal alignment films, etc.), ITO substrates for touch panels, and resin substrates as a replacement for cover glass for smartphones. The use of the polyimide according to this embodiment as a liquid crystal alignment film enables the production of TFT-LCDs with a high aperture ratio and a high contrast ratio.

[0136] Hereinafter, a display and a method for producing a laminate will be described as examples of applications of the polyimide film of this embodiment.

[0137] <Display manufacturing method> The method for manufacturing a display of this embodiment includes: a coating step of coating the resin composition of this embodiment onto the surface of a support; a film formation step of heating the resin composition to form a polyimide resin film; an element formation step of forming elements on the polyimide resin film; and a peeling step of peeling the polyimide resin film on which the elements have been formed from the support.

[0138] Flexible OLED display manufacturing example FIG. 1 is a schematic diagram showing the structure of a top-emission flexible organic EL display above a polyimide substrate as an example of the display of this embodiment. The organic EL structure 25 of FIG. 1 will now be described. The organic EL structure 25 is arranged in a matrix, with each unit consisting of, for example, an organic EL element 250a that emits red light, an organic EL element 250b that emits green light, and an organic EL element 250c that emits blue light. The light-emitting region of each organic EL element is defined by a partition wall (bank) 251. Each organic EL element is composed of a lower electrode (anode) 252, a hole transport layer 253, a light-emitting layer 254, and an upper electrode (cathode) 255. Furthermore, a plurality of TFTs 256 (selected from low-temperature polysilicon (LTPS) or metal oxide semiconductor (IGZO, etc.)) for driving the organic EL elements, an interlayer insulating film 258 with contact holes 257, and lower electrodes 259 are provided on the lower substrate 2a, which exhibits a CVD multi-layer film (multi-barrier layer) made of silicon nitride (SiN) or silicon oxide (SiO). The organic EL elements are sealed with a sealing substrate 2b, and a hollow portion 261 is formed between each organic EL element and the sealing substrate 2b.

[0139] The manufacturing process of a flexible organic EL display includes the steps of preparing a polyimide film on a glass substrate support, and then preparing the organic EL substrate shown in Figure 1 on top of it, preparing a sealing substrate, assembling the two substrates together, and peeling off the organic EL display prepared on the polyimide film from the glass substrate support. The organic EL substrate manufacturing process, the encapsulation substrate manufacturing process, and the assembly process can be well-known manufacturing processes. Examples are given below, but the present invention is not limited to these. The peeling process is the same as the peeling process for the polyimide film described above.

[0140] For example, referring to Figure 1, first, a polyimide film is prepared on a glass substrate support using the above-mentioned method. Then, a multi-barrier layer (lower substrate 2a in Figure 1) consisting of a multi-layer structure of silicon nitride (SiN) and silicon oxide (SiO) is prepared on top of that using CVD or sputtering. A metal wiring layer for driving the TFT is then prepared on top of that using photoresist or the like. An active buffer layer such as SiO is then prepared on top of that using CVD, and a TFT device (TFT 256 in Figure 1) made of metal oxide semiconductor (IGZO) or low-temperature polysilicon (LTPS) or the like is then prepared on top of that. After the flexible display TFT substrate is prepared, an interlayer insulating film 258 with contact holes 257 is formed using a photosensitive acrylic resin or the like. An ITO film is then formed by sputtering or the like, and a lower electrode 259 is formed to pair with the TFT.

[0141] Next, partition walls (banks) 251 are formed using a photosensitive polyimide or the like, and then hole transport layers 253 and light-emitting layers 254 are formed in each space partitioned by the partition walls. An upper electrode (cathode) 255 is then formed to cover the light-emitting layers 254 and the partition walls (banks) 251. Then, using a fine metal mask or the like as a mask, a red-emitting organic EL material (corresponding to the red-emitting organic EL element 250a in FIG. 1), a green-emitting organic EL material (corresponding to the green-emitting organic EL element 250b in FIG. 1), and a blue-emitting organic EL material (corresponding to the blue-emitting organic EL element 250c in FIG. 1) are vapor-deposited by a known method to fabricate an organic EL substrate. The organic EL substrate is sealed with a sealing film or the like (sealing substrate 2b in FIG. 1), and the device above the polyimide substrate is peeled from the glass substrate support by a known peeling method, such as laser peeling, to fabricate a top-emission flexible organic EL display. When the polyimide of this embodiment is used, a see-through flexible organic EL display can be produced. Alternatively, a bottom-emission flexible organic EL display can be produced by a known method.

[0142] <Example of flexible LCD display manufacturing> Flexible liquid crystal displays can be fabricated using the polyimide film of this embodiment. Specifically, a polyimide film is fabricated on a glass substrate support using the method described above, and a TFT substrate made of, for example, amorphous silicon, a metal oxide semiconductor (e.g., IGZO), and low-temperature polysilicon is fabricated using the method described above. Separately, a polyimide film is fabricated on the glass substrate support using the coating and film-forming steps of this embodiment, and a color filter glass substrate (CF substrate) equipped with the polyimide film is fabricated using a color resist or the like according to a known method. A sealing material made of a thermosetting epoxy resin or the like is applied by screen printing to one of the TFT substrate and the CF substrate in a frame-shaped pattern, excluding the liquid crystal injection port. Spherical spacers made of plastic or silica and having a diameter corresponding to the thickness of the liquid crystal layer are dispersed on the other substrate.

[0143] Next, the TFT substrate and the CF substrate are bonded together, and the sealing material is cured. Liquid crystal material is then injected into the space surrounded by the TFT substrate, the CF substrate, and the sealing material using a vacuum method. A thermosetting resin is applied to the liquid crystal injection port, and the liquid crystal material is sealed by heating, forming a liquid crystal layer. Finally, the glass substrate on the CF side and the glass substrate on the TFT side are peeled off at the interface between the polyimide film and the glass substrate using a laser peeling method or other method, thereby producing a flexible liquid crystal display.

[0144] <Method of manufacturing laminate> The method for producing the laminate of the present embodiment includes a coating step of coating the resin composition of the present embodiment onto the surface of a support; a film formation step of heating the resin composition to form a polyimide resin film; and an element formation step of forming an element on the polyimide resin film.

[0145] The elements in the laminate may be those exemplified in the production of the flexible device described above. A glass substrate, for example, may be used as the support. The preferred specific procedures for the coating step and film formation step are the same as those described for the polyimide film production method described above. In the element formation step, the elements are formed on a polyimide resin film serving as a flexible substrate formed on a support. Thereafter, the polyimide resin film and the elements may be peeled off from the support in an optional peeling step.

[0146] The polyimide precursor according to this embodiment, and the resin film and laminate produced using the polyimide precursor can be used, for example, as a semiconductor insulating film, a TFT-LCD insulating film, an electrode protective film, etc., and can also be suitably used, particularly as a substrate, in the production of flexible devices. Examples of flexible devices to which the resin film and laminate according to this embodiment can be used include flexible displays, flexible solar cells, flexible touch panel electrode substrates, flexible lighting, and flexible batteries. [Example]

[0147] The present invention will be described in more detail below with reference to examples. However, these examples are provided for illustrative purposes only and the scope of the present invention is not limited to the following examples. Various evaluations in the examples and comparative examples were carried out as follows.

[0148] <Measurement of weight average molecular weight and number average molecular weight> The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions. The solvent used was N,N-dimethylformamide (Fujifilm Wako Pure Chemical Industries, Ltd., for high-performance liquid chromatography, dissolved immediately before measurement with 24.8 mmol / L lithium bromide monohydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.5%) and 63.2 mmol / L phosphoric acid (Fujifilm Wako Pure Chemical Industries, Ltd., for high-performance liquid chromatography)). A calibration curve for calculating the weight-average molecular weight was prepared using standard polystyrene (Easical Type PS-1, Agilent Technologies).

[0149] Device: HLC-8220GPC (Tosoh Corporation) Column: Tsk gel Super HM-H (Tosoh Corporation) Flow rate: 0.5mL / min Column temperature: 40℃ Detector: UV-8220 (UV-Vis: ultraviolet-visible spectrophotometer, manufactured by Tosoh Corporation)

[0150] <Evaluation of residual stress> Each resin composition was applied using a spin coater to a 6-inch silicon wafer with a thickness of 625 μm ± 25 μm, the "warpage amount" of which had been measured in advance, and pre-baked at 100°C for 7 minutes. Then, using a vertical curing furnace (Koyo Lindberg, model VF-2000B), the oxygen concentration inside the furnace was adjusted to 10 ppm by mass or less, and a heat curing treatment (cure treatment) was carried out at 430°C for 1 hour, producing a silicon wafer with a polyimide resin film with a thickness of 10 μm after curing. The amount of warpage of this wafer was measured using a residual stress measuring device (manufactured by Tencor Corporation, model name FLX-230) to evaluate the residual stress generated between the silicon wafer and the resin film. ◎: Residual stress is greater than -5 MPa and less than 15 MPa (residual stress rating: "excellent") ○: Residual stress is over 15 MPa and 25 MPa or less (residual stress evaluation: "Good") ×: Residual stress exceeds 25 MPa (residual stress evaluation: "poor")

[0151] <Evaluation of yellowness (YI value) and haze value> In the same manner as in the above <Evaluation of residual stress>, a polyimide resin film was formed on a wafer on which alumina had been previously vapor-deposited. The wafer was then immersed in a dilute hydrochloric acid solution, and the polyimide resin film was peeled off to obtain a resin film. The obtained polyimide resin film was measured for yellowness (YI value) and haze value (converted to a film thickness of 10 μm) using a D65 light source with a Spectotometer: SE600 manufactured by Nippon Denshoku Industries Co., Ltd.

[0152] <Evaluation method for content (ratio of structural unit M to the total of structural unit L and structural unit M)> Regarding the resin compositions prepared in the synthesis examples, After adjusting the concentration to 1.0% by mass, an appropriate amount of water is added, and the mixture is heated at 80°C for 3 days to depolymerize the acid component and the amine component into acid monomers and amine monomers; The solvent is evaporated to obtain a powder containing a mixture of acid and amine monomers; A 1 mg / mL acetonitrile solution was prepared and subjected to LC / MS measurement.

[0153] LC; Equipment: Waters, UPLC Column: Waters, ACQUITY UPLC HSS T3 1.8um (2.1mm ID x 100mm) Detection: PDA 200-800nm Flow rate: 0.2mL / min Mobile phase: A = water (0.1% HCOOH) B = acetonitrile (0.1% HCOOH) Gradient: Time(min) A% B% 0 98 2 12 0 100 12.1 98 2 20 98 2 Injection volume: 1μL

[0154] MS; Equipment: Waters, Synapt G2 Ionization: ESI+

[0155] The area of ​​each peak in the PDA chromatogram at 300 nm obtained by the LC / MS measurement was determined, and the ratio of the structural unit M to the total of the structural units L and M (M / (L+M) ratio) was calculated from the peak area ratio according to the following calculation formula (1). M / (L+M) ratio (%): [(peak area of ​​the amine component of general formula (2)) / {(peak area of ​​the amine component of general formula (1))+(peak area of ​​the amine component of general formula (2))}] × 100 (Formula 1)

[0156] <Evaluation of laser peeling energy> The resin compositions prepared in each of the examples and comparative examples were coated onto a glass substrate (thickness: 0.7 mm) so that the film thickness after curing would be 10 μm, and the coating was prebaked at 80° C. for 40 minutes. Thereafter, using a vertical curing oven (manufactured by Koyo Lindberg Co., Ltd., model name VF-2000B), the oxygen concentration inside the oven was adjusted to 10 ppm by mass or less, and a heat curing treatment was carried out at 400° C. for 1 hour to produce a laminate of a glass substrate and a polyimide resin film. The laminate obtained above was irradiated from the glass substrate side with an excimer laser (wavelength 308 nm) while increasing the irradiation energy stepwise. The minimum irradiation energy at which the polyimide could be peeled off and the minimum energy were 10 mJ / m 2Ash (ash content) was evaluated when irradiated with the added energy. Those that did not produce any ash were marked with ○, those that produced a little ash on the edges were marked with △, and those that produced ash all over were marked with ×. During laser peeling, the polyimide film may burn due to the laser light, and the resulting residue is ash.

[0157] <Annealing evaluation of inorganic film / polyimide laminate> Silicon wafers with polyimide resin films having a thickness of 10 μm after curing were produced in the same manner as in the above <Evaluation of residual stress> using the resin compositions of the Examples and Comparative Examples. A 50-nm-thick SiOx film was formed on the polyimide resin film by chemical vapor deposition (CVD). The resulting laminate was annealed at 450°C for 30 minutes in a vertical curing furnace (Koyo Lindberg, model VF-2000B) with the oxygen concentration adjusted to 10 ppm by mass or less. After the annealing treatment, the surface of the SiOx film was observed using a laser microscope (model: VK-8700, manufactured by Keyence Corporation) to check for the presence or absence of cracks during the annealing treatment in a 10 mm square field of view. Evaluation was based on the following criteria, and the results are shown in Table 4. A: No cracks observed B: The number of cracks is 1 or more but less than 9 C: 10 or more cracks

[0158] [Synthesis Examples 1 and 2] (Synthesis Example 1 (1-1)) A 500 mL separable flask was purged with nitrogen and charged with 90.00 g of N-methyl-2-pyrrolidone (NMP), 11.30 g (49.5 mmol) of 4-aminophenyl-4-aminobenzoate (APAB), and 1.06 mg (5.0 μmol) of 4,4-azodianiline (AzBz). The mixture was stirred to dissolve APAB and AzBz. Next, 14.7 g (50 mmol) of biphenyl-3,3',4,4'-tetracarboxylic dianhydride (BPDA) and 13.25 g of N-methyl-2-pyrrolidone (NMP) were added. The polyamic acid concentration was adjusted to 20% by mass, and the polymerization reaction was carried out under nitrogen flow at 80 °C for 3 hours with stirring. The mixture was then cooled to room temperature to obtain a polyamic acid NMP solution (hereinafter also referred to as a varnish containing a polyimide precursor). The weight average molecular weight (Mw) of the resulting polyamic acid was approximately 100,000.

[0159] (Synthesis Example 1 (1-2 to 5-3) and Synthesis Example 2 (1 to 5)) Varnishes containing polyimide precursors were obtained in the same manner as in Synthesis Example 1 (1-1) above, except that the amounts of raw materials charged in Synthesis Example 1 (1-1) were changed as shown in Table 1. The numbers shown in Table 1 represent molar parts. The weight-average molecular weight (Mw) of the polyimide precursor contained in each varnish is shown in Table 2.

[0160] The abbreviations for each component in Table 1 have the following meanings: BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride TAHQ: p-phenylenebis(trimellitate anhydride) DSDA: 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic anhydride CpODA: Cyclopentanone bisspironorbornane tetracarboxylic dianhydride APAB: 4-aminophenyl-4-aminobenzoate 2F-APAB: 2-fluoro-4-aminophenyl-4-aminobenzoate 3F-APAB: 3-fluoro-4-aminophenyl-4-aminobenzoate 3Me-APAB: 3-methyl-4-aminophenyl-4-aminobenzoate 44DAS: 4,4'-diaminodiphenyl sulfone BAFL: 9,9-bis(aminophenyl)fluorene DABA: 4,4'-diaminobenzanilide TFMB: 2,2'-bis(trifluoromethyl)benzidine BAFL: 9,9-bis(aminophenyl)fluorene AzBz: 4,4'-azodianiline Azo-APAB: Bis(4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl (C-1) Azo-2F-APAB: bis(2-fluoro-4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl (C-2) Azo-3F-APAB: bis(3-fluoro-4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl (C-3) Azo-3Me-APAB: bis(3-methyl-4,1-phenylene)bis(4-aminobenzoate)diazene-1,2-diyl(C-4)

[0161] The varnish obtained in each synthesis example was used as a resin composition as it was, and films were produced according to the above-mentioned method, and evaluations were carried out (Examples 1 to 24 and Comparative Examples 1 to 5). The evaluation results are shown in Tables 2 and 3.

[0162] As is clear from Tables 2 and 3, the polyimide film of Comparative Example 1, which contained the structural units represented by general formula (2) relative to the structural units represented by general formula (1) in a ratio less than the range according to one embodiment of the present invention, could not be peeled off with a laser and generated ash. Furthermore, the polyimides of Comparative Examples 2 to 5, which contained the structural units represented by general formula (2) relative to the structural units represented by general formula (1) in a ratio exceeding the range according to one embodiment of the present invention, had high yellowness index (YI value) and haze value.

[0163] On the other hand, the polyimide films of Examples 1 to 24, which contained the structural unit represented by general formula (2) in a ratio of 0.005 to 0.5% relative to the structural unit represented by general formula (1), had a low yellowness index (YI value) of 30 or less, a low residual stress of 20 MPa or less, and a low haze value. Furthermore, warping after the formation of the inorganic film did not occur, or if it did occur, it was very slight. Furthermore, from the viewpoint of haze value, a content of 0.35% or less is more preferable (Examples 3 and 14), and from the viewpoint of laser peelability, a content of 0.005% or more is more preferable (Examples 1, 13, and 15). From the viewpoint of residual stress, it is more preferable that the composition contains 25 mol% or more of BPDA (Examples 4 to 8), from the viewpoint of warpage evaluation, it is more preferable that the composition contains 20 mol% or more of APAB (Examples 10 and 11), and from the viewpoint of yellowness index (YI value), it is more preferable that the composition contains 10 mol% or more of BPAF, TAHQ, ODPA, and CpODA (Examples 4 to 8).

[0164] From the experimental results in Table 2 above, it was confirmed that the polyimide resin film obtained from the resin composition according to the present invention is a resin film having a small yellowness index (YI value), low residual stress, small haze value, and excellent laser peelability.

[0165] Next, the measurement method using high-performance liquid chromatography-mass spectrometry (hereinafter also referred to as LC / MS) will be described. As described in the Examples, the resin composition prepared in the Synthesis Example was adjusted to a concentration of 1.0 mass %, and then an appropriate amount of water was added. The mixture was heated at 80°C for 3 days to depolymerize the acid and amine components, resulting in acid and amine monomers. The solvent was distilled off to obtain a powder containing the acid and amine monomers. A 1 mg / mL acetonitrile solution was prepared and subjected to LC / MS measurement. The content of each component was determined from the peak area at the elution time corresponding to each component in the PDA chromatogram at 300 nm.

[0166] For example, in the LC / MS measurement using the polyimide precursor described in Example 3, the experimental results shown in the PDA chromatogram at 300 nm were identified by MS (mass spectrometry) measurement as follows: 4.07 min (peak height: 15,176,803 counts, peak area: 1,473,470.38 counts) originated from APAB; 5.42 min (peak height: 76,120 counts, peak area: 2,649.47 counts) and 6.97 min (peak height: 38,570 counts, peak area: 1,502.06 counts) originated from the APAB dimer having an -NHNH- bond; and 9.28 min (peak height: 21,195 counts, peak area: 1,058.44 counts) originated from the APAB dimer having an -N=N- bond. The peak areas of the structural unit (APAB) represented by general formula (1) and the structural unit (2) were used to calculate the content according to the formula described in the above section "Evaluation method for content (ratio of structural unit M to the total of structural unit L and structural unit M)." The content was 0.35%.

[0167] [Table 1]

[0168] [Table 2]

[0169] [Table 3]

[0170] [Table 4] [Industrial Applicability]

[0171] The resin film formed from the polyimide precursor of the present invention can be applied to, for example, semiconductor insulating films, TFT-LCD insulating films, electrode protective films, etc., and can also be suitably used particularly as a substrate in the manufacture of flexible displays, substrates for ITO electrodes of touch panels, etc. [Explanation of symbols]

[0172] 2a Lower board 2b Sealing substrate 25 Organic EL structure 250a Red light-emitting organic EL element 250b Green light-emitting organic EL element 250c Blue light-emitting organic EL element 251 Partition (Bank) 252 Lower electrode (anode) 253 Hole transport layer 254 luminescent layer 255 Upper electrode (cathode) 256 TFT 257 Contact Hole 258 Interlayer insulating film 259 Lower Electrode 261 Hollow part

Claims

1. (a1) The following general formula (1): 【Chemistry 1】 wherein X represents a tetravalent organic group; 1 represents a divalent organic group; and (a2) The following general formula (2): 【Chemistry 2】 wherein X represents a tetravalent organic group; 2 represents a divalent organic group, and Z represents -NHNH- or -N=N-; and a structural unit M represented by the following formula (1): Y in the general formula (2) 2 is represented by the following general formulas (A-1) to (A-6): 【Transformation 3】 【Chemistry 4】 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 {In the formula, R 1 ~R 13 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, a to m each independently represent an integer of 0 to 4, n is an integer of 1 or greater, and * represents a bond. wherein Y 1 is a structure other than the structure represented by Y 2 -Z—Y 2 , A polyimide precursor in which the ratio of the amount of the structural unit M to the total amount of the structural unit L and the structural unit M is 0.005 to 0.5 mol %.

2. The Y 2 is at least one selected from the group consisting of structures represented by general formula (A-1) and general formula (A-6).

3. Y in the general formula (1) 1 is represented by the following general formulas (A-1) to (A-5): 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 {In the formula, R 1 ~R 12 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, a to l each independently represents an integer of 0 to 4, and * represents a bond. The polyimide precursor according to claim 1 or 2, which is at least one selected from the group consisting of structures represented by the following formula:

4. The polyimide precursor according to any one of claims 1 to 3, wherein X in the general formula (1) or the general formula (2), or both, is a tetravalent group derived from at least one selected from the group consisting of pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), 4,4'-biphenylbis(trimellitic acid monoester acid anhydride) (TAHQ), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), and cyclopentanone bisspironorbornanetetracarboxylic dianhydride (CpODA).

5. A resin composition comprising: (a) the polyimide precursor according to any one of claims 1 to 4; and (b) an organic solvent.

6. The resin composition according to claim 5 , further comprising at least one selected from the group consisting of (c) a surfactant and (d) an alkoxysilane compound.

7. The resin composition according to claim 5 or 6, wherein a polyimide resin film obtained by curing the resin composition is used for a flexible device.

8. The resin composition according to claim 5 or 6, wherein a polyimide resin film obtained by curing the resin composition is used for a flexible display.

9. A polyimide film obtained from the polyimide precursor according to any one of claims 1 to 4 or the resin composition according to any one of claims 5 to 8.

10. The following general formula (3): 【Chemistry 14】 In the formula, X independently represents a tetravalent organic group; Y 1 and Y 2 each independently represents a divalent organic group, provided that Y 1 is a structure other than the structure represented by Y 2 -N=N-Y 2 , and l and m are each independently an integer of 1 or greater, provided that 0.005≦m / (l+m)≦0.5 is satisfied. The structural unit is represented by The Y 2 is represented by the following general formulas (A-1) and (A-6): 【Chemistry 15】 【Chemistry 16】 {In the formula, R 1 , R 2 , and R 13 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen; a, b, and m each independently represent an integer of 0 to 4; n is an integer of 1 or greater; and * represents a bond. The polyimide is at least one selected from the group consisting of structures represented by the following formula:

11. The following general formula (3): 【Chemistry 17】 In the formula, X independently represents a tetravalent organic group; Y 1 each independently represents a divalent organic group; Y 2 is represented by the following general formula (A-6): [Chemistry 18] (In the formula, R 13 each independently represents a monovalent organic group having 1 to 20 carbon atoms or a halogen, each m independently represents an integer of 0 to 4, n is an integer of 1 or greater, and * represents a bond. wherein Y 1 is a structure other than the structure represented by Y 2 -N=N-Y 2 , and l and m are each independently an integer of 1 or greater, provided that 0.005≦m / (l+m)≦0.5 is satisfied. A polyimide comprising a structural unit represented by the formula:

12. A step of forming a coating film by applying the resin composition according to any one of claims 5 to 8 onto a surface of a support; a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film; peeling the polyimide resin film from the support; A method for producing a resin film, comprising:

13. The method for producing a resin film according to claim 12 , further comprising the step of irradiating the polyimide resin film with a laser from the support side prior to the step of peeling the polyimide resin film from the support.

14. A step of forming a coating film by applying the resin composition according to any one of claims 5 to 8 onto a surface of a support; a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film; A method for producing a laminate, comprising:

15. A step of forming a coating film by applying the resin composition according to any one of claims 5 to 8 onto a surface of a support; a step of heating the support and the coating film to imidize the polyimide precursor contained in the coating film to form a polyimide resin film; forming an element or a circuit on the polyimide resin film; peeling the polyimide resin film on which the elements or circuits are formed from the support; A method for manufacturing a display substrate, comprising:

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