Imide-amic acid copolymer and its manufacturing method, varnish, and polyimide film

Abstract

Provided is an imide-amic acid copolymer including a repeating unit that comprises an imide moiety (IM), an amic acid moiety (AM1) and an amic acid moiety (AM2) and that is represented by formula (1). (In formula (1), Ｘ1 represents an aromatic group having a valency of 4 and having 4 to 39 carbon atoms; Ｘ2 represents an aromatic group being different from Ｘ1, having a valency of 4, and having 4 to 39 carbon atoms; Ｙ1 represents a group derived from diaminodiphenylsulfone or else; Ｙ2 represents a group derived from 4-aminophenyl-4-aminobenzoate or else; and each of s, t and u represents a positive integer.)

Description

[Technical field]

[0001] The present invention relates to an imide-amic acid copolymer which is a precursor of a polyimide resin, a method for producing the same, a varnish containing the copolymer, and a polyimide film. [Background technology]

[0002] Various applications of polyimide resins are being considered in the fields of electric and electronic components. For example, it is desirable to replace glass substrates used in image display devices such as liquid crystal displays and OLED displays with plastic substrates in order to make the devices lighter and more flexible, and research on polyimide films suitable for such plastic substrates is ongoing. Polyimide films for such applications are required to be transparent and have low yellowness. In addition, when a polyimide film is formed by heating and curing a varnish applied to a glass support or a silicon wafer, residual stress occurs in the polyimide film. If the residual stress in the polyimide film is large, the glass support or the silicon wafer may be warped, and therefore, the polyimide film is required to have reduced residual stress.

[0003] Regarding this point, for example, Patent Document 1 discloses a polyimide precursor that is characterized by containing two specific types of specific amic acid structural units in a specific ratio, for the purpose of obtaining a polyimide film that has low residual stress, little warping, low yellowness, and high elongation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 051827 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, polyimide films for specific applications require transparency and low yellowness. However, in the case of LTPS (low temperature polysilicon TFT) TFT device types, the process temperature exceeds 400°C, and the polyimide substrate is required to have heat resistance to temperatures of 400°C or higher, and is required to maintain transparency and low yellowness even under such heat history. In addition, it is necessary to reduce residual stress due to the problem of warping of the support as described above.Furthermore, it is also necessary to reduce the linear thermal expansion coefficient because of concerns about peeling at the bonding surface and deformation of the product due to the difference in linear thermal expansion coefficient with the inorganic layer that constitutes the device. Patent Document 1 discloses a technology for reducing residual stress and reducing yellowness, but this technology is still insufficient, and in particular, it has not been possible to obtain a polyimide film that is excellent in heat resistance and the like while maintaining transparency and low yellowness. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imide-amic acid copolymer, which is a precursor of a polyimide resin, from which a polyimide film having low residual stress, low coefficient of linear thermal expansion, excellent transparency and heat resistance, and low yellowness can be obtained, a method for producing the same, a varnish containing the copolymer, and a polyimide film. [Means for solving the problem]

[0006] The present inventors discovered that a copolymer containing a specific combination of structural units can solve the above problems, and thus completed the invention.

[0007] That is, the present invention relates to the following [1] to

[18] . [1] An imide-amido acid copolymer comprising repeating units each consisting of an imide portion (IM), an amic acid portion (AM1) and an amic acid portion (AM2), represented by the following formula (1): [ka] (In formula (1), X 1is a tetravalent aromatic group having 4 to 39 carbon atoms, which may have at least one bonding group selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-; X 2 isX 1 and may have at least one bond selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-, Y 1 is a group represented by at least one selected from the group consisting of the following formula (2), the following general formula (3), and the following general formula (4), Y 2 is a group represented by the following general formula (5): s, t, and u are positive integers.) [ka] (In formula (3), Z 1 represents a single bond or a group represented by -O-. In formula (4), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. [ka] (In formula (5), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4. [2] The imide-amic acid copolymer according to [1] above, wherein s is 1 to 50 and t is 1 to 50. [3] The imide-amic acid copolymer according to [1] or [2] above, wherein the u is 5 to 200. [4] X 1is a group represented by the following formula (6): [ka] [5] X 2 is a group represented by the following formula (7): [ka] [6] The imide portion (IM) has a structural unit X1A derived from a tetracarboxylic dianhydride and a structural unit Y1B derived from a diamine, the amic acid portion (AM1) has a structural unit X2A derived from a tetracarboxylic dianhydride and a structural unit Y1B derived from a diamine, the amic acid portion (AM2) has a structural unit X2A derived from a tetracarboxylic dianhydride and a structural unit Y2B derived from a diamine, The structural unit X1A contains a structural unit derived from an aromatic tetracarboxylic dianhydride, the structural unit X2A contains a structural unit derived from an aromatic tetracarboxylic dianhydride different from the structural unit X1A; The structural unit Y1B comprises a structural unit (B1) derived from a diamine (b1), and the structural unit (B1) comprises at least one selected from the group consisting of a structural unit (B11) derived from a compound represented by the following formula (b11), a structural unit (B12) derived from a compound represented by the following general formula (b12), and a structural unit (B13) derived from a compound represented by the following general formula (b13): The imide-amido acid copolymer according to any one of the above [1] to [5], wherein the structural unit Y2B contains a structural unit (B2) derived from a compound represented by the following general formula (b2): [ka] (In formula (b12), Z 1 represents a single bond or a group represented by -O-. In formula (b13), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. In formula (b2), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4. [7] The structural unit X2A contains a structural unit (A2) derived from an aromatic tetracarboxylic dianhydride (a2), The imide-amido acid copolymer according to item [6] above, wherein the structural unit (A2) comprises at least one selected from the group consisting of a structural unit (A21) derived from a compound represented by formula (a21) below, a structural unit (A22) derived from a compound represented by formula (a22) below, a structural unit (A23) derived from a compound represented by formula (a23) below, a structural unit (A24) derived from a compound represented by formula (a24) below, and a structural unit (A25) derived from a compound represented by formula (a25) below. [ka] [8] The imide-amido acid copolymer according to [6] or [7] above, further comprising a structural unit (B3) derived from a compound represented by the following general formula (b3): [ka] (In formula (b3), Z 4 and Z 5 each independently represents a divalent aliphatic group or a divalent aromatic group; R 4 and R 5 each independently represents a monovalent aromatic group or a monovalent aliphatic group; R 6 and R 7 each independently represents a monovalent aliphatic group; R 8 and R 9each independently represents a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represent an integer of 1 or more, and the sum of m and n represents an integer of 2 to 1000. 4 and R 5 At least one of represents a monovalent aromatic group. [9] R 4 and R 5 is a phenyl group, and R 6 and R 7 is a methyl group.

[10] The imide-amic acid copolymer according to [8] or [9] above, wherein the content of the polyorganosiloxane unit in the imide-amic acid copolymer is 1 to 20 mass %.

[11] The imide-amido acid copolymer according to any one of the above [6] to

[10] , wherein the structural unit X1A comprises a structural unit (A1) derived from a compound represented by the following formula (a1): [ka]

[12] A varnish obtained by dissolving the copolymer according to any one of the above [1] to

[11] in an organic solvent.

[13] A polyimide film comprising a polyimide resin obtained by imidizing an amide acid moiety in the copolymer according to any one of the above [1] to

[11] .

[14] The polyimide film according to

[13] above, wherein the polyimide resin has a weight average molecular weight (Mw) of 100,000 to 300,000.

[15] A method for producing an imide-amic acid copolymer, comprising the following steps 1 and 2: Step 1: A step of reacting a tetracarboxylic acid component constituting the imide portion (IM) with a diamine component to obtain an imide oligomer. Step 2: A step of reacting the imide oligomer obtained in step 1 with a tetracarboxylic acid component and a diamine component constituting the amic acid portion (AM2) to obtain an imide-amidic acid copolymer represented by the following formula (1), which contains repeating units composed of an imide portion (IM), an amic acid portion (AM1), and an amic acid portion (AM2). [ka] (In formula (1), X 1 is a tetravalent aromatic group having 4 to 39 carbon atoms, which may have at least one bonding group selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-; X 2 isX 1 and may have at least one bond selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-, Y 1 is a group represented by at least one selected from the group consisting of the following formula (2), the following general formula (3), and the following general formula (4), Y 2 is a group represented by the following general formula (5): s, t, and u are positive integers.) [ka] (In formula (3), Z 1 represents a single bond or a group represented by -O-. In formula (4), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. [ka] (In formula (5), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

[16] The method for producing an imide-amic acid copolymer according to

[15] above, wherein the imide oligomer obtained in step 1 has amino groups at both ends of the main chain of the molecular chain.

[17] The method for producing an imide-amido acid copolymer according to the above

[15] or

[16] , wherein in step 1, a molar ratio of the diamine component to the tetracarboxylic acid component (diamine / tetracarboxylic acid) is 1.01 to 2.

[18] The method for producing an imide-amic acid copolymer according to any one of the above

[15] to

[17] , further comprising reacting a diamine containing a polyorganosiloxane unit after completion of step 2. Effect of the Invention

[0008] According to the present invention, it is possible to provide an imide-amic acid copolymer, which is a precursor of a polyimide resin, capable of producing a polyimide film having low residual stress, low coefficient of linear thermal expansion, excellent transparency and heat resistance, and low yellowness, a method for producing the same, a varnish containing the copolymer, and a polyimide film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Imide-Amic acid copolymer] The imide-amic acid copolymer of the present invention contains repeating units represented by the following formula (1) and consisting of an imide moiety (IM), an amic acid moiety (AM1), and an amic acid moiety (AM2). [ka] (In formula (1), X 1 is a tetravalent aromatic group having 4 to 39 carbon atoms, which may have at least one bonding group selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-; X 2 isX 1and may have at least one bond selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-, Y 1 is a group represented by at least one selected from the group consisting of the following formula (2), the following general formula (3), and the following general formula (4), Y 2 is a group represented by the following general formula (5): s, t, and u are positive integers.) [ka] (In formula (3), Z 1 represents a single bond or a group represented by -O-. In formula (4), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. [ka] (In formula (5), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

[0010] The reason why the imide-amic acid copolymer of the present invention is an excellent raw material for polyimide films and the obtained polyimide films have excellent properties, such as low residual stress, low linear thermal expansion coefficient, excellent transparency, and high heat resistance while maintaining low yellowness, is not clear, but is thought to be as follows. A copolymer consisting of a component derived from a tetracarboxylic acid having an aromatic group and the specific diamine component has a bulky skeleton having a trifluoromethyl group, a sulfone group, or a cardo structure, and a rigid biphenyl skeleton and an ester skeleton in an appropriate ratio, and is therefore considered to be able to achieve low residual stress, a low coefficient of linear thermal expansion, transparency, low yellowness, and high heat resistance, all of which are necessary for TFT substrates, etc. On the other hand, even when the ratio is appropriate, polyamic acid components containing a cardo structure are unlikely to undergo thermal imidization during film formation, and when a polymer containing a polyamic acid component containing a cardo structure is formed into a film, it is usually difficult for it to exhibit good physical properties. However, in the imide-amic acid copolymer of the present invention, a portion of the component containing a cardo structure is imidized in advance during polymer polymerization, and it is therefore believed that the physical properties will be excellent after film formation.

[0011] <Imide portion (IM)> The imide portion (IM) constituting the imide-amic acid copolymer of the present invention is the portion represented by (IM) in the above formula (1). In the formula (1), X 1 is a tetravalent aromatic group having 4 to 39 carbon atoms, which may have at least one bond selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O- and -S-. Here, the tetravalent aromatic group means that all of the four carbons bonded to the imide group are aromatic carbons. The bond is also represented by X 1 When a compound contains two or more aromatic rings, the term "bonding group" refers to a bonding group that bonds each aromatic ring. However, the bonding group is not limited to these. X 1 is an aromatic group, the polyimide has good heat resistance, which is preferable.

[0012] X 1 is preferably one in which two dicarboxylic acid anhydride moieties (four carboxy group moieties) have been removed from a tetracarboxylic acid dianhydride which is a raw material for the structural unit X1A derived from a tetracarboxylic acid dianhydride described below. Among these, X 1is more preferably a group represented by the following formula (6). [ka]

[0013] In the formula (1), Y 1 is at least one group selected from the group consisting of the following formula (2), the following general formula (3), and the following general formula (4): [ka] (In formula (3), Z 1 represents a single bond or a group represented by -O-. In formula (4), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms.

[0014] Y 1 is preferably one in which two amino group moieties have been removed from a diamine that is a raw material for the diamine-derived structural unit Y1B described below.

[0015] <Amic acid portion (AM2)> The amic acid portion (AM2) constituting the imide-amic acid copolymer of the present invention is the portion represented by (AM2) in the above formula (1). In the formula (1), X 2 X 1 and a tetravalent aromatic group having 4 to 39 carbon atoms different from the above, which may have at least one bond selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O- and -S- as a bonding group. Here, the tetravalent aromatic group means that all of the four carbons bonded to the imide group are aromatic carbons. The bonding group is also represented by X 1 When a compound contains two or more aromatic rings, the term "bonding group" refers to a bonding group that bonds each aromatic ring. However, the bonding group is not limited to these.

[0016] X 2is preferably one in which two dicarboxylic acid anhydride moieties (four carboxy group moieties) have been removed from a tetracarboxylic acid dianhydride which is the raw material for the structural unit X2A derived from a tetracarboxylic acid dianhydride described below. Among these, X 2 is more preferably a group represented by the following formula (7). [ka]

[0017] In the formula (1), Y 2 is a group represented by the following general formula (5). [ka] (In formula (5), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

[0018] Y 2 is preferably one in which two amino group moieties have been removed from a diamine that is a raw material for the diamine-derived structural unit Y2B described below.

[0019] <Amic acid portion (AM1)> The amic acid portion (AM1) constituting the imide-amic acid copolymer of the present invention is the portion represented by (AM1) in the above formula (1). The amic acid moiety (AM1) is a bonding portion between the imide moiety (IM) and the amic acid moiety (AM2), and X in the amic acid moiety (AM1) is 2 is the same as that of the amic acid portion (AM2), and Y in the amic acid portion (AM1) 1 is the same as the imide moiety (IM).

[0020] <Structure of imide-amic acid copolymer> In the formula (1), s is the number of repeating units of the imide portion (IM) and is a positive integer. From the viewpoints of transparency, low yellowness, and high heat resistance, s is preferably 1 to 50, more preferably 1 to 15, even more preferably 1 to 10, and even more preferably 1 to 5. The average repeat number of the imide moiety (IM), i.e., the average value of s, is preferably 1 to 10, more preferably 1.5 to 9, even more preferably 1.5 to 8, and even more preferably 1.7 to 5. The average repeat number of the imide moiety (IM) refers to the average value of the repeat numbers of the imide moieties (IM) of all the imide-amic acid copolymers contained in the polyimide varnish or polyimide film described below, and the average value of s refers to the average value of s of all the imide-amic acid copolymers contained in the polyimide varnish or polyimide film described below.

[0021] In the formula (1), t is the number of repeating units of the amic acid portion (AM2) and is a positive integer. From the viewpoints of high heat resistance, low residual stress, and low linear thermal expansion coefficient, t is preferably 1 to 50, more preferably 1 to 15, even more preferably 1 to 10, and even more preferably 1 to 5. The average repeat number of the amic acid portion (AM2), i.e., the average value of t, is preferably 1 to 10, more preferably 1.5 to 9, even more preferably 1.5 to 8, and even more preferably 1.7 to 5. The average repeat number of the amic acid portion (AM2) refers to the average value of the repeat numbers of the amic acid portions (AM2) of all imide-amic acid copolymers contained in the polyimide varnish or polyimide film described below, and the average value of t refers to the average value of t of all imide-amic acid copolymers contained in the polyimide varnish or polyimide film described below.

[0022] In the formula (1), u is the number of repeating units consisting of the imide moiety (IM), the amic acid moiety (AM1) and the amic acid moiety (AM2), and is a positive integer. From the viewpoints of heat resistance, low residual stress, and low linear thermal expansion coefficient, u is preferably 5 to 200, more preferably 6 to 150, and further preferably 10 to 120. The average number of repetitions of the repeating units consisting of the imide moiety (IM), the amic acid moiety (AM1) and the amic acid moiety (AM2), i.e., the average value of u, is preferably 5 to 200. The average number of repetitions of the repeating units consisting of the imide moiety (IM), the amic acid moiety (AM1) and the amic acid moiety (AM2) refers to the average number of repetitions of the repeating units consisting of the imide moiety (IM), the amic acid moiety (AM1) and the amic acid moiety (AM2) of all the imide-amic acid copolymers contained in the polyimide varnish or polyimide film described below, and the average value of u refers to the average value of u of all the imide-amic acid copolymers contained in the polyimide varnish or polyimide film described below.

[0023] The total ratio of the imide portion (IM), the amic acid portion (AM1) and the amic acid portion (AM2) to the imide-amic acid copolymer is preferably 80% by mass or more, more preferably 82% by mass or more, and even more preferably 85% by mass or more, with no upper limit being 100% by mass or less.

[0024] In conventional imide-amido acid copolymers, the imide moieties and amido acid moieties are present randomly, whereas in the imide-amido acid copolymer of the present invention, the imide moieties (IM), amido acid moieties (AM1) and amido acid moieties (AM2) have specific structures, which is believed to result in a copolymer having low residual stress, low linear thermal expansion coefficient, and excellent transparency, low yellowness and heat resistance.

[0025] <Each structural unit of imide-amic acid copolymer> The imide-amic acid copolymer of the present invention contains repeating units consisting of an imide portion (IM), an amic acid portion (AM1), and an amic acid portion (AM2) represented by the above formula (1), and the structural units constituting the copolymer are described below.

[0026] In the imide-amido acid copolymer of the present invention, the imide portion (IM) has a structural unit X1A derived from a tetracarboxylic dianhydride and a structural unit Y1B derived from a diamine, the amic acid portion (AM1) has a structural unit X2A derived from a tetracarboxylic dianhydride and a structural unit Y1B derived from a diamine, the amic acid portion (AM2) has a structural unit X2A derived from a tetracarboxylic dianhydride and a structural unit Y2B derived from a diamine, The structural unit X1A contains a structural unit derived from an aromatic tetracarboxylic dianhydride, the structural unit X2A contains a structural unit derived from an aromatic tetracarboxylic dianhydride different from the structural unit X1A; The structural unit Y1B comprises a structural unit (B1) derived from a diamine (b1), and the structural unit (B1) comprises at least one selected from the group consisting of a structural unit (B11) derived from a compound represented by the following formula (b11), a structural unit (B12) derived from a compound represented by the following general formula (b12), and a structural unit (B13) derived from a compound represented by the following general formula (b13): The structural unit Y2B preferably contains a structural unit (B2) derived from a compound represented by the following general formula (b2). [ka] (In formula (b12), Z 1 represents a single bond or a group represented by -O-. In formula (b13), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. In formula (b2), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, k, and n are integers of 0 to 4.

[0027] (Structural unit X1A) The structural unit X1A is a structural unit derived from a tetracarboxylic dianhydride that occupies the imide portion (IM) of the copolymer of the present invention, and includes a structural unit derived from an aromatic tetracarboxylic dianhydride.

[0028] There are no limitations on the structural unit X1A as long as it contains a structural unit derived from an aromatic tetracarboxylic dianhydride, but it is preferable that the structural unit X1A contains a structural unit (A1) derived from a compound represented by the following formula (a1). [ka]

[0029] The compound represented by formula (a1) is 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). By including the structural unit (A1) derived from the compound represented by formula (a1), transparency, low yellowness, and high heat resistance are achieved, which is preferable.

[0030] When the structural unit X1A contains the structural unit (A1), the content ratio of the structural unit (A1) in the structural unit X1A is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 60 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more. The upper limit of the content ratio of the structural unit (A1) is not particularly limited, and is 100 mol% or less. The structural unit A may be composed of only the structural unit (A1).

[0031] The structural unit X1A may contain a structural unit other than the structural unit (A1). The tetracarboxylic dianhydride that gives such a structural unit is not particularly limited, but includes alicyclic tetracarboxylic dianhydrides such as 1,2,4,5-cyclohexanetetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, and dicyclohexyltetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride. In this specification, an alicyclic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride in which, among the four α carbons of two acid anhydrides (four carboxy groups), the two α carbons of at least one acid anhydride (two adjacent carboxy groups) are carbons that constitute an alicyclic ring; an aromatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride in which the four α carbons of two acid anhydrides (four carboxy groups) are carbons that constitute an aromatic ring; and an aliphatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride that does not fall into the category of an alicyclic tetracarboxylic acid dianhydride or an aromatic tetracarboxylic acid dianhydride. The structural unit optionally contained in the structural unit X1A may be of one type, or of two or more types.

[0032] (Composition unit X2A) The structural unit X2A is a structural unit derived from a tetracarboxylic dianhydride that occupies the amic acid portion (AM2) and the amic acid portion (AM1) of the copolymer of the present invention, and contains a structural unit derived from an aromatic tetracarboxylic dianhydride different from the structural unit X1A.

[0033] There are no limitations on the structural unit X2A, so long as it contains a structural unit derived from an aromatic tetracarboxylic dianhydride different from the structural unit X1A, but it is preferable that the structural unit X2A contains a structural unit (A2) derived from an aromatic tetracarboxylic dianhydride (a2). Here, the structural unit (A2) includes at least one selected from the group consisting of a structural unit (A21) derived from a compound represented by the following formula (a21), a structural unit (A22) derived from a compound represented by the following formula (a22), a structural unit (A23) derived from a compound represented by the following formula (a23), a structural unit (A24) derived from a compound represented by the following formula (a24), and a structural unit (A25) derived from a compound represented by the following formula (a25). [ka]

[0034] The compound represented by formula (a21) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a21s), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a21a), and 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a21i). Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a21s) is preferred.

[0035] [ka]

[0036] The compound represented by the formula (a22) is p-phenylenebis(trimellitate)dianhydride (TAHQ).

[0037] The compound represented by formula (a23) is oxydiphthalic anhydride (ODPA), and specific examples thereof include 4,4'-oxydiphthalic anhydride (s-ODPA) represented by the following formula (a23s), 3,4'-oxydiphthalic anhydride (a-ODPA) represented by the following formula (a23a), and 3,3'-oxydiphthalic anhydride (i-ODPA) represented by the following formula (a23i). Among these, 4,4'-oxydiphthalic anhydride (s-ODPA) represented by the following formula (a23s) is preferred.

[0038] [ka]

[0039] The compound represented by formula (a24) is pyromellitic dianhydride (PMDA).

[0040] The compound represented by the formula (a25) is 2,3,6,7-naphthalenetetracarboxylic dianhydride.

[0041] From the standpoint of high heat resistance and low residual stress, the structural unit (A2) preferably includes at least one selected from the group consisting of the structural unit (A21) and the structural unit (A22), and more preferably includes the structural unit (A21). In particular, the structural unit (A21) is preferable from the viewpoints of being able to improve the heat resistance and thermal stability of the film and further reduce residual stress, and the structural unit (A22) is preferable from the viewpoints of being able to reduce residual stress and also reduce the coefficient of linear thermal expansion.

[0042] The structural unit X2A may contain a structural unit other than the structural unit (A2). The tetracarboxylic dianhydride that gives such a structural unit is not particularly limited, but includes alicyclic tetracarboxylic dianhydrides such as 1,2,4,5-cyclohexanetetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, and dicyclohexyltetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride. The structural unit optionally contained in the structural unit X2A may be of one type, or of two or more types.

[0043] The total proportion of the structural units (A21) to (A25) in the structural unit (A2) is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There are no particular limitations on the upper limit of this proportion, and it is 100 mol% or less. The structural unit (A2) need only contain at least one selected from the structural units (A21) to (A25), and may be composed of only one selected from the structural units (A21) to (A25). When the structural unit (A2) contains two or more structural units selected from the structural units (A21) to (A25), there are no particular limitations on the ratio of the respective structural units within the structural unit (A2), and any ratio can be used.

[0044] The proportion of the structural unit (A2) in the structural unit X2A is preferably at least 45 mol%, more preferably at least 60 mol%, and even more preferably at least 85 mol%. There is no upper limit to this content, but it is up to 100 mol%.

[0045] When the structural unit X1A contains the structural unit (A1) and the structural unit X2A contains the structural unit (A2), the molar ratio of the structural unit (A1) to the structural unit (A2) [(A1) / (A2)] in the structural units derived from the tetracarboxylic dianhydride of the imide-amido acid copolymer is preferably 10 / 90 to 55 / 45, more preferably 15 / 85 to 50 / 50, and even more preferably 20 / 80 to 45 / 55.

[0046] (Structural unit Y1B) The structural unit Y1B is a structural unit derived from a diamine contained in the imide portion (IM) and the amic acid portion (AM1) of the copolymer of the present invention, and includes a structural unit (B1) derived from a diamine (b1). The structural unit (B1) includes at least one selected from the group consisting of a structural unit (B11) derived from a compound represented by formula (b11) below, a structural unit (B12) derived from a compound represented by general formula (b12) below, and a structural unit (B13) derived from a compound represented by general formula (b13) below. From the viewpoint of heat resistance, it is preferable to contain a structural unit (B13) derived from a compound represented by formula (b13) having a cardo structure, and from the viewpoint of transparency, it is preferable to contain a structural unit (B11) derived from a compound represented by formula (b11) having an electron-withdrawing group, and a structural unit (B12) derived from a compound represented by formula (b12). The total proportion of the structural units (B11) to (B13) in the structural unit (B1) is preferably at least 45 mol%, more preferably at least 70 mol%, even more preferably at least 90 mol%, and particularly preferably at least 99 mol%. There is no upper limit to this proportion, but it is up to 100 mol%. [ka] (In formula (b12), Z 1 represents a single bond or a group represented by -O-. In formula (b13), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms.

[0047] The structural unit (B11) is preferably at least one selected from the group consisting of a structural unit (B111) derived from a compound represented by the following formula (b111) and a structural unit (B112) derived from a compound represented by the following formula (b112). The structural unit (B11) may be only the structural unit (B111), or only the structural unit (B112), or a combination of the structural unit (B111) and the structural unit (B112). [ka]

[0048] The compound represented by formula (b111) is 4,4'-diaminodiphenyl sulfone (4,4'-DDS), and the compound represented by formula (b112) is 3,3'-diaminodiphenyl sulfone (3,3'-DDS).

[0049] The structural unit (B12) preferably includes at least one structural unit selected from the group consisting of a structural unit (B121) derived from a compound represented by the following formula (b121) and a structural unit (B122) derived from a compound represented by the following formula (b122), and more preferably includes a structural unit (B122) derived from a compound represented by the following formula (b122). [ka]

[0050] The compound represented by formula (b121) is 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA). The compound represented by formula (b122) is 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0051] The structural unit (B13) is a structural unit derived from the compound represented by the above formula (b13).

[0052] In the formula (b13), R's are each independently a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom, a fluorine atom, or a methyl group, and more preferably a hydrogen atom. Examples of the compound represented by the formula (b13) include 9,9-bis(4-aminophenyl)fluorene (BAFL), 9,9-bis(3-fluoro-4-aminophenyl)fluorene, and 9,9-bis(3-methyl-4-aminophenyl)fluorene. At least one selected from the group consisting of these three compounds is preferred, and from the viewpoint of heat resistance, 9,9-bis(4-aminophenyl)fluorene is more preferred.

[0053] The structural unit Y1B may contain a structural unit other than the structural unit (B1). The diamine that gives such a structural unit is not particularly limited, but may be 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl- Examples of the diamines include aromatic diamines such as 1H-indene-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine. In this specification, an aromatic diamine refers to a diamine containing one or more aromatic rings, an alicyclic diamine refers to a diamine containing one or more alicyclic rings but no aromatic rings, and an aliphatic diamine refers to a diamine containing neither an aromatic ring nor an alicyclic ring. The structural unit optionally contained in the structural unit Y1B may be of one type, or of two or more types.

[0054] (Structural unit Y2B) The structural unit Y2B is a structural unit derived from a diamine in the amide acid portion (AM2) of the copolymer of the present invention, and from the standpoints of low residual stress, low linear thermal expansion coefficient, and heat resistance, the structural unit Y2B contains a structural unit (B2) derived from a compound represented by the following general formula (b2): [ka] (In formula (b2), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

[0055] From the standpoints of heat resistance, low residual stress, and a low coefficient of linear thermal expansion, the structural unit (B2) preferably includes a structural unit (B21) derived from a compound represented by the following formula (b21). [ka]

[0056] The compound represented by formula (b21) is 4-aminophenyl-4-aminobenzoate (4-BAAB).

[0057] The structural unit Y2B may contain a structural unit other than the structural unit (B2). The diamine that gives such a structural unit is not particularly limited, but may be 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro aromatic diamines such as 1,3,3-trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine. The structural unit optionally contained in the structural unit Y2B may be of one type, or of two or more types.

[0058] When the total of the structural units Y1B and Y2B is taken as 100 mol %, the proportion of the structural unit (B1) in the structural units derived from diamine in the copolymer is preferably 10 to 55 mol %, more preferably 20 to 50 mol %, and even more preferably 25 to 45 mol %. When the total of the structural units Y1B and Y2B is taken as 100 mol %, the proportion of the structural unit (B2) in the structural units derived from diamine in the copolymer is preferably 45 to 90 mol %, more preferably 50 to 80 mol %, and even more preferably 55 to 75 mol %. When the structural unit Y1B contains the structural unit (B1) and the structural unit Y2B contains the structural unit (B2), the molar ratio of the structural unit (B1) to the structural unit (B2) [(B1) / (B2)] in the diamine-derived structural units of the imide-amidic acid copolymer is preferably 10 / 90 to 55 / 45, more preferably 20 / 80 to 50 / 50, and even more preferably 25 / 75 to 45 / 55. When the total of the structural units Y1B and Y2B is taken as 100 mol%, the total proportion of the structural units (B1) and (B2) in the structural units derived from diamine in the copolymer is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, with no particular upper limit being set, and is 100 mol% or less.

[0059] The ratio of the total of the structural units X1A, X2A, Y1B and Y2B to the total of the structural units constituting the imide-amidic acid copolymer is preferably 80 mass% or more, more preferably 82 mass% or more, and even more preferably 85 mass% or more, and there is no upper limit, but is 100 mass% or less.

[0060] (Other building blocks) The imide-amic acid copolymer of the present invention may contain structural units other than the structural unit X1A, the structural unit X2A, the structural unit Y1B, and the structural unit Y2B. The imide-amic acid copolymer of the present invention may further contain a structural unit (B3) derived from a compound represented by the following general formula (b3): ​​By containing the structural unit (B3), the residual stress is reduced. [ka]

[0061] In formula (b3), Z 4 and Z 5 each independently represents a divalent aliphatic group or a divalent aromatic group; R 4 and R 5 each independently represents a monovalent aromatic group or a monovalent aliphatic group; R 6 and R 7each independently represents a monovalent aliphatic group; R 8 and R 9 each independently represents a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represent an integer of 1 or more, and the sum of m and n represents an integer of 2 to 1000. 4 and R 5 At least one of these represents a monovalent aromatic group. In formula (b3), the two or more different repeating units described in parallel in brackets [ ] may be repeated in any form and order of random, alternating, or block.

[0062] In formula (b3), Z 4 and Z 5 The divalent aliphatic group or divalent aromatic group in may be substituted with a fluorine atom or may contain an oxygen atom. When an oxygen atom is contained as an ether bond, the number of carbon atoms shown below refers to the total number of carbon atoms contained in the aliphatic group or aromatic group. The divalent aliphatic group may be a divalent saturated or unsaturated aliphatic group having 1 to 20 carbon atoms. The divalent aliphatic group preferably has 3 to 20 carbon atoms. Examples of the divalent saturated aliphatic group include alkylene groups and alkyleneoxy groups having 1 to 20 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, an octamethylene group, a decamethylene group, and a dodecamethylene group. Examples of the alkyleneoxy group include a propyleneoxy group and a trimethyleneoxy group. Examples of the divalent unsaturated aliphatic group include alkenylene groups having 2 to 20 carbon atoms, such as a vinylene group, a propenylene group, and an alkylene group having an unsaturated double bond at the terminal. Examples of the divalent aromatic group include an arylene group having 6 to 20 carbon atoms and an aralkylene group having 7 to 20 carbon atoms. 4 and Z 5Specific examples of the arylene group having 6 to 20 carbon atoms in the formula include an o-phenylene group, an m-phenylene group, a p-phenylene group, a 4,4'-biphenylylene group, and a 2,6-naphthylene group. Z 4 and Z 5 As the alkyl group, a trimethylene group or a p-phenylene group is particularly preferable, and a trimethylene group is more preferable.

[0063] In formula (b3), R 4 ~R 9 In the above, examples of the monovalent aliphatic group include monovalent saturated or unsaturated aliphatic groups. Examples of the monovalent saturated aliphatic group include alkyl groups having 1 to 22 carbon atoms, such as methyl, ethyl, and propyl groups. Examples of the monovalent unsaturated aliphatic group include alkenyl groups having 2 to 22 carbon atoms, such as vinyl and propenyl groups. These groups may be substituted with a fluorine atom. R in formula (b3) 4 , R 5 , R 8 and R 9 Examples of the monovalent aromatic group in the formula (I) include an aryl group having 6 to 20 carbon atoms, an aryl group having 7 to 30 carbon atoms and substituted with an alkyl group, and an aralkyl group having 7 to 30 carbon atoms. As the monovalent aromatic group, an aryl group is preferable, and a phenyl group is more preferable. R 4 and R 5 At least one of Z represents a monovalent aromatic group. 4 and Z 5 are preferably both monovalent aromatic groups, and R 4 and R 5 More preferably, both are phenyl groups. R 6 and R 7 As the alkyl group, an alkyl group having 1 to 6 carbon atoms is preferable, and a methyl group is more preferable. R 8 and R 9 As the group, a monovalent aliphatic group is preferable, and a methyl group is more preferable.

[0064] As described above, among the compounds represented by the above general formula (b3), the compounds represented by the following formula (b31) are preferred.

[0065] [ka] (In formula (b31), m and n have the same meanings as m and n in formula (b3), and the preferred ranges are also the same.)

[0066] In formulae (b3) and (b31), m represents the number of repeating siloxane units to which at least one monovalent aromatic group is bonded, and n in formulae (b3) and (b31) represents the number of repeating siloxane units to which a monovalent aliphatic group is bonded. In formula (b3) and formula (b31), m and n each independently represent an integer of 1 or more, and the sum of m and n (m+n) represents an integer of 2 to 1000. The sum of m and n is preferably an integer of 3 to 500, more preferably an integer of 3 to 100, and even more preferably an integer of 3 to 50. The ratio of m / n in formula (b3) and formula (b31) is preferably from 5 / 95 to 50 / 50, more preferably from 10 / 90 to 40 / 60, and even more preferably from 20 / 80 to 30 / 70.

[0067] The functional group equivalent (amine equivalent) of the compound represented by formula (b3) is preferably 150 to 5,000 g / mol, more preferably 400 to 4,000 g / mol, and further preferably 500 to 3,000 g / mol. The functional group equivalent means the mass of the compound represented by formula (b3) per mole of the functional group (amino group).

[0068] Among the compounds represented by the above general formula (b3), examples of commercially available products include “X-22-9409”, “X-22-1660B”, “X-22-161A”, and “X-22-161B” manufactured by Shin-Etsu Chemical Co., Ltd.

[0069] When the structural unit (B3) is contained, the ratio of the structural unit (B3) to the total amount of the structural unit (B3), the structural unit Y1B, and the structural unit Y2B is preferably 0.01 to 15.0 mol %, more preferably 0.5 to 12.0 mol %, and even more preferably 1.0 to 8.0 mol %.

[0070] When the structural unit (B3) is contained, the content of the polyorganosiloxane unit relative to the total of the structural units constituting the imide-amic acid copolymer is preferably 1 to 20 mass%, more preferably 2 to 18 mass%, and even more preferably 5 to 15 mass%. When the content of the polyorganosiloxane unit is within the above range, low retardation and low residual stress can be more highly achieved at the same time.

[0071] Commercially available examples of the compound represented by formula (b3) include "X-22-9409" and "X-22-1660B-3" manufactured by Shin-Etsu Chemical Co., Ltd.

[0072] [Method of manufacturing imide-amide acid copolymer] The imide-amic acid copolymer of the present invention may be produced by any method, but is preferably obtained by the following method. The method for producing an imide-amic acid copolymer of the present invention includes the following steps 1 and 2. Step 1: A step of reacting a tetracarboxylic acid component constituting the imide portion (IM) with a diamine component to obtain an imide oligomer. Step 2: A step of reacting the imide oligomer obtained in step 1 with a tetracarboxylic acid component and a diamine component constituting the amic acid portion (AM2) to obtain an imide-amidic acid copolymer represented by the following formula (1), which contains repeating units composed of an imide portion (IM), an amic acid portion (AM1), and an amic acid portion (AM2). [ka] (In formula (1), X 1is a tetravalent aromatic group having 4 to 39 carbon atoms, which may have at least one bonding group selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-; X 2 isX 1 and may have at least one bond selected from the group consisting of -O-, -SO2-, -CO-, -CH2-, -C(CH3)2-, -C2H4O-, and -S-, Y 1 is a group represented by at least one selected from the group consisting of the following formula (2), the following general formula (3), and the following general formula (4), Y 2 is a group represented by the following general formula (5): s, t, and u are positive integers.) [ka] (In formula (3), Z 1 represents a single bond or a group represented by -O-. In formula (4), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. [ka] (In formula (5), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

[0073] According to the method for producing an imide-amic acid copolymer of the present invention, it is possible to control the imide moieties and the amic acid moieties to have specific structures. Therefore, unlike conventional imide-amic acid copolymers in which the imide moieties and the amic acid moieties are present randomly, it is believed that it is possible to obtain an imide-amic acid copolymer which is expected to have improved heat resistance, low residual stress, and a low linear thermal expansion coefficient because it has polyimide moieties and polyamic acid moieties depending on the thermal imidization reactivity of each component.

[0074] Among them, a preferred method for producing the copolymer of the present invention includes the following steps 1 and 2. Step 1: A step of reacting a compound that provides a structural unit X1A derived from a tetracarboxylic dianhydride with a compound that provides a structural unit Y1B derived from a diamine to obtain an imide oligomer. Step 2: A step of reacting the imide oligomer obtained in step 1 with a compound that gives a structural unit X2A derived from a tetracarboxylic dianhydride and a compound that gives a structural unit Y2B derived from a diamine to obtain an imide-amido acid copolymer represented by the formula (1) above, which contains repeating units composed of an imide portion (IM), an amic acid portion (AM1), and an amic acid portion (AM2). However, the compound that provides the structural unit X1A contains an aromatic tetracarboxylic dianhydride, the compound providing the structural unit X2A contains an aromatic tetracarboxylic dianhydride different from that of the structural unit X1A, the compound providing the structural unit Y1B includes a compound providing the structural unit (B1), and the compound providing the structural unit (B1) includes at least one selected from the group consisting of a compound represented by the following formula (b11), a compound represented by the following general formula (b12), and a compound represented by the following general formula (b13): Compounds which provide the structural unit Y2B include compounds represented by the following general formula (b2). [ka] (In formula (b12), Z 1 represents a single bond or a group represented by -O-. In formula (b13), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. In formula (b2), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

[0075] By using the production method including the above steps 1 and 2, it is possible to produce a copolymer capable of forming a film having excellent transparency and heat resistance, low yellowness, and low residual stress. The method for producing the copolymer of the present invention will now be described.

[0076] <Process 1> Step 1 is a step in which a tetracarboxylic acid component constituting the imide portion (IM) is reacted with a diamine component to obtain an imide oligomer. The tetracarboxylic acid component constituting the imide portion (IM) is preferably an aromatic tetracarboxylic dianhydride.

[0077] More preferably, step 1 is a step of reacting a compound that provides a structural unit X1A derived from a tetracarboxylic dianhydride with a compound that provides a structural unit Y1B derived from a diamine to obtain an imide oligomer. The compound that provides the structural unit X1A includes an aromatic tetracarboxylic dianhydride. The compound that provides the structural unit Y1B includes a compound that provides the structural unit (B1), and the compound that provides the structural unit (B1) includes at least one selected from the group consisting of the compound represented by formula (b11), the compound represented by general formula (b12), and the compound represented by general formula (b13).

[0078] The tetracarboxylic acid component used in step 1 preferably contains a compound that provides the structural unit (A1), and it is preferable to use the entire amount of the tetracarboxylic acid component in step 1. The tetracarboxylic acid component may contain tetracarboxylic acid components other than the compound that provides the structural unit (A1), as long as the effects of the present invention are not impaired. The diamine component used in step 1 preferably contains a compound that provides the structural unit (B1), and may contain a diamine component other than the compound that provides the structural unit (B1) as long as the effects of the present invention are not impaired. In step 1, the ratio of the diamine component to the tetracarboxylic acid component is preferably from 1.01 to 2 mol, more preferably from 1.05 to 1.9 mol, and further preferably from 1.1 to 1.7 mol.

[0079] The method for reacting the tetracarboxylic acid component with the diamine component to obtain the imide oligomer in step 1 is not particularly limited, and any known method can be used. Specific reaction methods include: (1) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours, and then the temperature is raised to carry out the imidization reaction; (2) a method in which a diamine component and a reaction solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component is charged, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours as necessary, and then the temperature is raised to carry out the imidization reaction; and (3) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the temperature is immediately raised to carry out the imidization reaction.

[0080] In the imidization reaction, it is preferable to carry out the reaction while removing water generated during the production using a Dean-Stark apparatus, etc. By carrying out such an operation, it is possible to further increase the degree of polymerization and the imidization rate.

[0081] In the above imidization reaction, a known imidization catalyst can be used, such as a base catalyst or an acid catalyst. Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate, and sodium hydrogencarbonate. Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid, etc. The above imidization catalysts may be used alone or in combination of two or more kinds. Among the above, from the viewpoint of handleability, a base catalyst is preferred, an organic base catalyst is more preferred, one or more selected from triethylamine and triethylenediamine is even more preferred, and triethylamine is even more preferred.

[0082] The temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 200° C., from the viewpoints of reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

[0083] The imide oligomer obtained in step 1 preferably has imide repeating structural units formed from a compound that provides the structural unit (A1) and a compound that provides the structural unit (B1). In addition, the oligomer obtained in step 1 preferably has amino groups at both ends of the main chain of the molecular chain. The above method provides a solution containing an imide oligomer dissolved in a solvent. The imide oligomer-containing solution obtained in step 1 may contain at least a portion of the components used as the tetracarboxylic acid component or diamine component in step 1 as unreacted monomers, as long as the effects of the present invention are not impaired.

[0084] <Process 2> Step 2 in the production method of the present invention is a step of reacting the imide oligomer obtained in step 1 with a tetracarboxylic acid component and a diamine component constituting the amic acid portion (AM2) to obtain an imide-amic acid copolymer represented by the above formula (1) which contains repeating units consisting of the imide portion (IM), the amic acid portion (AM1), and the amic acid portion (AM2). The tetracarboxylic acid component constituting the amic acid portion (AM2) used in step 2 is preferably an aromatic tetracarboxylic dianhydride.

[0085] More preferably, step 2 is a step of reacting a compound that provides a structural unit X2A derived from a tetracarboxylic dianhydride with a compound that provides a structural unit Y2B derived from a diamine to obtain an imide-amido acid copolymer. The compound that provides the structural unit X2A includes an aromatic tetracarboxylic dianhydride. Compounds that provide the structural unit Y2B include compounds that provide the structural unit (B2), and the compounds that provide the structural unit (B2) include compounds represented by general formula (b2) above, and preferably include compounds represented by formula (b21) above.

[0086] The tetracarboxylic acid component used in step 2 preferably contains a compound that gives the structural unit (A2), and may contain a tetracarboxylic acid component other than the compound that gives the structural unit (A2) as long as the effect of the present invention is not impaired. Examples of tetracarboxylic acid components other than the compound that gives the structural unit (A2) include compounds that give the structural unit (A1), but it is preferable that the tetracarboxylic acid component used in step 2 does not contain a compound that gives the structural unit (A1). It is also preferable that the entire amount of the compound that gives the structural unit (A2) is used in step 2. The diamine component used in step 2 preferably contains a compound that gives the structural unit (B2), and may contain a diamine component other than the compound that gives the structural unit (B2) as long as the effects of the present invention are not impaired. When polyorganosiloxane units are to be introduced into the imide-amic acid copolymer after completion of step 2, a diamine or tetracarboxylic dianhydride containing a polyorganosiloxane unit may be reacted, preferably a diamine containing a polyorganosiloxane unit, and more preferably a compound that gives the structural unit (B3).

[0087] The method for reacting the tetracarboxylic acid component with the imide oligomer obtained in step 1 to obtain an imide-amic acid copolymer in step 2 is not particularly limited, and any known method can be used. Specific examples of the reaction method include: (1) a method in which the imide oligomer obtained in step 1, a tetracarboxylic acid component, a diamine component, and a solvent are charged into a reactor and stirred at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours; and (2) a method in which the imide oligomer obtained in step 1 and a solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component and the diamine component are charged and stirred at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. When the reaction is carried out at 80°C or lower, the molecular weight of the copolymer obtained in step 2 does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, so that the copolymer can be stably produced.

[0088] By the above method, a copolymer solution containing the imide-amic acid copolymer dissolved in the solvent is obtained. The concentration of the copolymer in the obtained copolymer solution is usually in the range of 1 to 50% by mass, preferably 3 to 35% by mass, and more preferably 5 to 30% by mass.

[0089] The number average molecular weight of the imide-amic acid copolymer obtained by the production method of the present invention is preferably 5,000 to 500,000 from the viewpoint of the mechanical strength of the resulting polyimide film. From the same viewpoint, the weight average molecular weight (Mw) is preferably 10,000 to 800,000, more preferably 100,000 to 300,000. The number average molecular weight of the copolymer can be determined, for example, from a standard polymethyl methacrylate (PMMA) equivalent value measured by gel filtration chromatography. Next, the raw materials and the like used in this production method will be described.

[0090] <Tetracarboxylic acid component> The tetracarboxylic acid component used as the raw material for the imide-amidic acid copolymer in this production method is preferably a compound that gives each of the structural units described in (structural unit XIA) and (structural unit X2A) in <Each structural unit of the imide-amidic acid copolymer>. For example, a compound that gives the structural unit (A1) may be a compound represented by formula (a1), but is not limited thereto, and may be a derivative thereof as long as it gives the same structural unit. Examples of the derivative include a tetracarboxylic acid corresponding to the compound represented by formula (a1) and an alkyl ester of the tetracarboxylic acid. A compound represented by formula (a1) is preferable as a compound that gives the structural unit (A1). Similarly, examples of compounds that provide the structural unit (A2) include, but are not limited to, compounds represented by formula (a21), compounds represented by formula (a22), compounds represented by formula (a23), compounds represented by formula (a24), and compounds represented by formula (a25). Derivatives that provide the same structural unit may also be used. Examples of such derivatives include tetracarboxylic acids corresponding to the compounds represented by any of formulas (a21) to (a25) and alkyl esters of the tetracarboxylic acids. Compounds that provide the structural unit (A2) are preferably compounds represented by any of formulas (a21) to (a25).

[0091] In the tetracarboxylic acid component used as the raw material for the imide-amido acid copolymer in the present production method, the molar ratio of the compound providing the structural unit (A1) to the compound providing the structural unit (A2) [(A1) / (A2)] is preferably 10 / 90 to 55 / 45, more preferably 15 / 85 to 50 / 50, and even more preferably 20 / 80 to 45 / 55.

[0092] The total ratio of the compounds providing the structural units (A21) to (A25) among the compounds providing the structural unit (A2) is preferably at least 45 mol%, more preferably at least 70 mol%, even more preferably at least 90 mol%, and particularly preferably at least 99 mol%. There is no upper limit to this ratio, but it is 100 mol% or less. The tetracarboxylic acid component used as a raw material for the imide-amido acid copolymer may contain compounds other than the compound that provides the structural unit (A1), the compound that provides the structural unit (A21), the compound that provides the structural unit (A22), the compound that provides the structural unit (A23), the compound that provides the structural unit (A24), and the compound that provides the structural unit (A25), and such compounds may be one type or two or more types.

[0093] <Diamine component> In the diamine component used as the raw material for the imide-amidic acid copolymer in the present production method, the molar ratio of the compound providing the structural unit (B1) to the compound providing the structural unit (B2) [(B1) / (B2)] is preferably 10 / 90 to 55 / 45, more preferably 20 / 80 to 50 / 50, and even more preferably 25 / 75 to 45 / 55. The compound that gives the structural unit (B1) is preferably one or more selected from the group consisting of compounds that give the structural unit (B11), compounds that give the structural unit (B12), and compounds that give the structural unit (B13). The total ratio of the compounds that give the structural units (B11) to (B13) among the compounds that give the structural unit (B1) is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to this ratio, and it is 100 mol% or less. As the compound which provides the structural unit (B2), one or more compounds which provide the structural unit (B2) are preferred. The diamine component used as a raw material for the imide-amido acid copolymer may contain compounds other than the compound that provides the structural unit (B11), the compound that provides the structural unit (B12), the compound that provides the structural unit (B13), and the compound that provides (B2), and such compounds may be one type or two or more types. The compound that gives the structural unit (B1) and the compound that gives the structural unit (B2) include, but are not limited to, diamines, and may be derivatives thereof as long as they give the same structural unit. Examples of such derivatives include diisocyanates corresponding to diamines. The compound that gives the structural unit (B1) and the compound that gives the structural unit (B2) are preferably diamines.

[0094] When the copolymer contains a compound that provides the structural unit (B3), the compound that provides the structural unit (B3) is preferably contained in an amount of 0.01 to 15.0 mol %, more preferably 0.5 to 12.0 mol %, and even more preferably 1.0 to 8.0 mol %, based on the total amount of the compound that provides the structural unit (B3) and the diamine component.

[0095] In the present invention, the ratio of the amounts of the tetracarboxylic acid component and the diamine component used in all steps of the production of the copolymer, including step 1, step 2, and the reaction step with other components such as a compound that gives the structural unit (B3) after completion of step 2, is preferably 0.9 to 1.1 mol of the diamine component per 1 mol of the tetracarboxylic acid component.

[0096] <End-capping agent> In the present invention, in addition to the above-mentioned tetracarboxylic acid component and diamine component, a terminal blocking agent may be used in the production of the imide-amido acid copolymer. The terminal blocking agent is preferably used in the reaction step with other components such as the compound that gives the structural unit (B3) after step 2 or completion of step 2. As the terminal blocking agent, monoamines or dicarboxylic acids are preferred. The amount of the terminal blocking agent introduced is preferably 0.0001 to 0.1 mol, particularly preferably 0.001 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. As the monoamine terminal blocking agent, for example, methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. are recommended. Among these, benzylamine and aniline are preferably used. As the dicarboxylic acid terminal blocking agent, dicarboxylic acids are preferred, and a part of them may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. are recommended. Of these, phthalic acid and phthalic anhydride are preferably used.

[0097] <Solvent> The solvent used in the method for producing the copolymer of the present invention may be any solvent capable of dissolving the resulting imide-amic acid copolymer, such as aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0098] Specific examples of aprotic solvents include amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone-based solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide-based solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone-based solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone; and ester-based solvents such as 2-methoxy-1-methylethyl acetate.

[0099] Specific examples of phenol-based solvents 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. Specific examples of ether 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. Specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above reaction solvents, amide-based solvents or lactone-based solvents are preferred, amide-based solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above reaction solvents may be used alone or in combination of two or more.

[0100] [varnish] The varnish of the present invention is obtained by dissolving the imide-amic acid copolymer of the present invention, which is a precursor of a polyimide resin, in an organic solvent. That is, the varnish of the present invention contains the copolymer of the present invention and an organic solvent, and the copolymer is dissolved in the organic solvent. The organic solvent is not particularly limited as long as it dissolves the copolymer of the present invention. However, it is preferable to use the above-mentioned compounds alone or in combination of two or more kinds as the solvent used in the production of the copolymer of the present invention. The varnish of the present invention may be the above-mentioned copolymer solution itself, or may be the copolymer solution to which a dilution solvent has been further added.

[0101] The varnish of the present invention may further contain an imidization catalyst and a dehydration catalyst from the viewpoint of efficiently proceeding with the imidization of the amide acid moiety in the copolymer of the present invention. The imidization catalyst may be an imidization catalyst having a boiling point of 40°C or more and 180°C or less, and an amine compound having a boiling point of 180°C or less is preferred. If the imidization catalyst has a boiling point of 180°C or less, there is no risk of the film being colored and its appearance being impaired when dried at a high temperature after film formation. In addition, if the imidization catalyst has a boiling point of 40°C or more, the possibility of volatilization before imidization has progressed sufficiently can be avoided. Examples of amine compounds suitable for use as the imidization catalyst include pyridine and picoline. The imidization catalysts may be used alone or in combination of two or more. Examples of the dehydration catalyst include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; carbodiimide compounds such as dicyclohexylcarbodiimide; etc. These may be used alone or in combination of two or more kinds.

[0102] The copolymer contained in the varnish of the present invention has solvent solubility, so that a high-concentration varnish can be obtained. The varnish of the present invention preferably contains 3 to 40 mass %, more preferably 5 to 40 mass %, and even more preferably 10 to 30 mass % of the copolymer of the present invention. The viscosity of the varnish is preferably 0.1 to 100 Pa·s, and more preferably 0.1 to 20 Pa·s. The viscosity of the varnish is a value measured at 25°C using an E-type viscometer. In addition, the varnish of the present invention may contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoamers, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, as long as the additives do not impair the required properties of the polyimide film. The method for producing the varnish of the present invention is not particularly limited, and any known method can be applied.

[0103] [Polyimide film] The polyimide film of the present invention contains a polyimide resin obtained by imidizing the amic acid moiety in the imide-amic acid copolymer of the present invention. Therefore, the polyimide film of the present invention has excellent transparency and heat resistance, low yellowness, and low residual stress. The preferable physical properties of the polyimide film of the present invention are as described above. The polyimide film of the present invention can be produced by using a varnish obtained by dissolving the above-mentioned copolymer in an organic solvent.

[0104] The method of producing polyimide film using the varnish of the present invention is not particularly limited, and known methods can be used.For example, the varnish of the present invention is applied to a smooth support such as a glass plate, a metal plate, or a plastic plate, or formed into a film, and then the organic solvent contained in the varnish, such as a reaction solvent or a dilution solvent, is removed by heating to obtain a copolymer film, and the amide acid portion of the copolymer in the copolymer film is imidized (dehydration ring closure) by heating, and then peeled off from the support, thereby producing a polyimide film. The weight average molecular weight (Mw) of the polyimide resin contained in the polyimide film of the present invention is, from the viewpoint of the mechanical strength of the film, preferably 10,000 to 800,000, more preferably 30,000 to 500,000, even more preferably 50,000 to 400,000, and still more preferably 100,000 to 300,000. The number average molecular weight of the copolymer can be determined, for example, from a standard polymethyl methacrylate (PMMA) equivalent value measured by gel filtration chromatography.

[0105] The heating temperature when the varnish of the present invention is dried to obtain a copolymer film is preferably 50 to 150° C. The heating temperature when the copolymer of the present invention is imidized by heating is preferably 200 to 500° C., more preferably 250 to 450° C., and even more preferably 300 to 400° C. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour. Examples of the heating atmosphere include air gas, nitrogen gas, oxygen gas, hydrogen gas, and nitrogen / hydrogen mixed gas. In order to suppress coloration of the resulting polyimide resin, nitrogen gas having an oxygen concentration of 100 ppm or less and nitrogen / hydrogen mixed gas containing a hydrogen concentration of 0.5% or less are preferred. The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

[0106] The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., but is preferably 1 to 250 μm, more preferably 5 to 100 μm, and even more preferably 5 to 50 μm. When the thickness is 1 to 250 μm, practical use as a free-standing film becomes possible. The thickness of the polyimide film can be easily controlled by adjusting the solids concentration and viscosity of the varnish.

[0107] <Polyimide film properties> By using the imide-amic acid copolymer of the present invention, a polyimide film having excellent transparency and heat resistance, low yellowness, and low residual stress can be formed. The preferable physical properties of the film are as follows: The total light transmittance, when made into a film having a thickness of 10 μm, is preferably 85% or more, more preferably 86% or more, and further preferably 87% or more. The yellow index (YI) of the resin when made into a film having a thickness of 10±3 μm is preferably 15.0 or less, more preferably 13.0 or less, even more preferably 12.0 or less, and still more preferably 11.0 or less. The glass transition temperature (Tg) is preferably 400° C. or higher, more preferably 420° C. or higher, and even more preferably 430° C. or higher. The residual stress is preferably 35 MPa or less, more preferably 30 MPa or less, and further preferably 24 MPa or less. The linear thermal expansion coefficient (in the range of 100° C. to 400° C.) is preferably 40 ppm / ° C. or less, more preferably 30 ppm / ° C. or less, and further preferably 20 ppm / ° C. or less. The above-mentioned physical properties in the present invention can be specifically measured by the methods described in the Examples.

[0108] The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, optical members, etc. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays and OLED displays. EXAMPLES

[0109] The present invention will be described in detail below with reference to examples, although the present invention is not limited to these examples in any way. The physical properties of the films obtained in the examples and comparative examples were measured by the methods shown below.

[0110] (1) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

[0111] (2) Total light transmittance, yellow index (YI) The total light transmittance and YI were measured in accordance with JIS K7105:1981 using a color / turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd.

[0112] (3) Hayes The measurements were performed in accordance with JIS K7361-1:1997 using a color and turbidity simultaneous measuring device "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd.

[0113] (4) Glass transition temperature (Tg) Using a thermomechanical analyzer "TMA / SS6100" manufactured by Hitachi High-Tech Science Corporation, the specimen was heated to a temperature sufficient to remove the residual stress under the following conditions: tensile mode, sample size 3mm x 20mm, load 0.1N, nitrogen gas flow (flow rate 200mL / min), heating rate 10℃ / min, and then cooled to room temperature. The specimen elongation was then measured under the same conditions as the treatment for removing the residual stress, and the point where the elongation inflection point was observed was determined as the glass transition temperature.

[0114] (5) Coefficient of linear thermal expansion (CTE) Using a thermomechanical analyzer "TMA / SS6100" manufactured by Hitachi High-Tech Science Corporation, the specimen was heated to a temperature sufficient to remove the residual stress under the following conditions: sample size 3mm x 20mm, load 0.1N, nitrogen gas flow (flow rate 200mL / min), and heating rate 10℃ / min in tensile mode to remove the residual stress, and then cooled to room temperature. The specimen elongation was then measured under the same conditions as the treatment for removing the residual stress, and the CTE from 100℃ to 400℃ was calculated.

[0115] (6)1% weight loss temperature (Td1%) A Hitachi High-Tech Science Corporation differential thermal and thermogravimetric simultaneous analyzer "TG / DTA6200" was used. The sample was heated from 40 to 550°C at a heating rate of 10°C / min, and the temperature at which the weight was reduced by 1% compared to the weight at 300°C was defined as the 1% weight loss temperature. The higher the weight loss temperature, the better.

[0116] (7) Tensile strength, tensile modulus The tensile strength and tensile modulus were measured in accordance with JIS K7127:1999 using a tensile tester "Strograph VG-1E" manufactured by Toyo Seiki Co., Ltd. The chuck distance was 50 mm, the test piece size was 10 mm × 70 mm, and the test speed was 20 mm / min.

[0117] (8) Residual stress The varnishes obtained in the examples and comparative examples were applied using a spin coater onto a 4-inch silicon wafer with a thickness of 525 μm ± 25 μm, whose "warpage" had been measured in advance using a residual stress measuring device "FLX-2320" manufactured by KLA-Tencor Corporation, and the wafer was prebaked. After that, the wafer was subjected to a heat curing treatment at 400°C for 60 minutes (heating rate 5°C / min) in a nitrogen atmosphere using a hot air dryer, and a silicon wafer with a polyimide film with a thickness of 6 to 15 μm after curing was produced. The amount of warpage of this wafer was measured using the residual stress measuring device mentioned above, and the residual stress generated between the silicon wafer and the polyimide film was evaluated.

[0118] The tetracarboxylic acid components and diamine components used in the examples and comparative examples, as well as their abbreviations, are as follows: <Tetracarboxylic acid component> BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (manufactured by JFE Chemical Corporation; compound represented by formula (a1)) s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation, a compound represented by formula (a21s)) <Diamine component> 4,4'-DDS: 4,4'-diaminodiphenyl sulfone (manufactured by Seika Corporation, a compound represented by formula (b111)) TFMB: 2,2'-bis(trifluoromethyl)benzidine (manufactured by Seika Corporation; compound represented by formula (b122)) 4-BAAB: 4-aminophenyl-4-aminobenzoate (manufactured by Nippon Junryo Pharmaceutical Co., Ltd.; compound represented by formula (b21))

[0119] The abbreviations for the solvents and catalysts used in the examples and comparative examples are as follows. NMP: N-methyl-2-pyrrolidone (Tokyo Pure Chemical Industries, Ltd.) TEA: Triethylamine (Kanto Chemical Co., Ltd.)

[0120] Example 1 9.932 g (0.040 mol) of 4,4'-DDS and 46.380 g of NMP were placed in a 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet tube, a Dean-Stark equipped with a cooling tube, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at an internal temperature of 70°C to obtain a solution. To this solution, 13.753g (0.030 mol) of BPAF and 11.595g of NMP were added all at once, and then 0.152g of TEA was added as an imidization catalyst, and the mixture was heated with a mantle heater, and the temperature in the reaction system was raised to 190°C over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190°C while adjusting the rotation speed according to the increase in viscosity, and refluxed for 1 hour. Then, 95.849g of NMP was added, and the temperature in the reaction system was cooled to 50°C, to obtain a solution containing an oligomer having an imide repeating structural unit. To the obtained solution, 20.595 g (0.070 mol) of s-BPDA, 13.695 g (0.060 mol) of 4-BAAB, and 16.858 g of NMP were added all at once, and the mixture was stirred at 50° C. for 5 hours. Thereafter, NMP was added so that the solid content concentration became about 15% by mass, and the mixture was homogenized to obtain a varnish containing a copolymer having imide repeating structural units and amic acid structural units. The resulting varnish was then applied onto a glass plate by spin coating, and held on a hot plate at 80°C for 20 minutes, after which it was heated in a nitrogen atmosphere in a hot air dryer at 430°C for 60 minutes to evaporate the solvent, yielding a polyimide film. The results are shown in Table 1.

[0121] Example 2 A varnish with a solid content concentration of approximately 15 mass% was obtained in the same manner as in Example 1, except that the amount of BPAF was changed from 13.753 (0.030 mol) to 9.169 g (0.020 mol) and the amount of s-BPDA was changed from 20.595 g (0.070 mol) to 23.538 g (0.080 mol). A film was obtained in the same manner as in Example 1 using the obtained varnish.

[0122] Example 3 A varnish with a solids concentration of approximately 15% by mass was obtained in the same manner as in Example 1, except that the amount of BPAF was changed from 13.753 (0.030 mol) to 9.169 g (0.020 mol), the amount of s-BPDA was changed from 20.595 g (0.070 mol) to 23.538 g (0.080 mol), the amount of 4,4'-DDS was changed from 9.932 (0.040 mol) to 7.449 g (0.030 mol), and the amount of 4-BAAB was changed from 13.695 (0.060 mol) to 15.978 g (0.070 mol). A film was obtained in the same manner as in Example 1 using the obtained varnish.

[0123] Example 4 A polyimide varnish having a solid content concentration of about 15 mass % was obtained in the same manner as in Example 1, except that 9.932 g (0.040 mol) of 4,4'-DDS was changed to 12.810 g (0.040 mol) of TFMB. A film was obtained in the same manner as in Example 1 using the obtained varnish.

[0124] Example 5 A varnish with a solids concentration of approximately 15% by mass was obtained in the same manner as in Example 4, except that the amount of BPAF was changed from 13.753 (0.030 mol) to 9.169 g (0.020 mol), the amount of s-BPDA was changed from 20.595 g (0.070 mol) to 23.538 g (0.080 mol), the amount of TFMB was changed from 12.810 g (0.040 mol) to 9.607 g (0.030 mol), and the amount of 4-BAAB was changed from 13.695 (0.060 mol) to 15.978 g (0.070 mol). A film was obtained in the same manner as in Example 1 using the obtained varnish.

[0125] Comparative Example 1 22.825 g (0.100 mol) of 4-BAAB and 167.190 g of NMP were placed in a 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at an internal temperature of 50°C to obtain a solution. To this solution, 29.422 g (0.100 mol) of s-BPDA and 41.798 g of NMP were added all at once, and the mixture was stirred at room temperature for 5 hours. Thereafter, 87.078 g of NMP was added so that the solid content concentration became about 15% by mass, and the mixture was further stirred for about 1 hour to be homogenized, thereby obtaining a polyamic acid (PAA) varnish. A film was obtained in the same manner as in Example 1 using the obtained varnish. The polyamic acid contained in the varnish obtained in Comparative Example 1 had only amic acid repeating structural units formed from s-BPDA and 4-BAAB.

[0126] Comparative Example 2 A polyamic acid (PAA) varnish having a solid content concentration of about 15 mass % was obtained in the same manner as in Comparative Example 1, except that 29.422 g (0.100 mol) of s-BPDA was changed to 45.843 g (0.100 mol) of BPAF. A film was obtained in the same manner as in Example 1 using the obtained varnish. The polyamic acid contained in the varnish obtained in Comparative Example 1 had only the amic acid repeating structural unit formed from BPAF and 4-BAAB.

[0127] Comparative Example 3 9.932 g (0.040 mol) of 4,4'-DDS, 13.695 g (0.060 mol) of 4-BAAB, and 139.141 g of NMP were placed in a 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet tube, a Dean-Stark equipped with a cooling tube, a thermometer, and a glass end cap, and the mixture was stirred at a system temperature of 50°C under a nitrogen atmosphere at a rotation speed of 200 rpm to obtain a solution. To this solution, 13.753 g (0.030 mol) of BPAF, 20.595 g (0.070 mol) of s-BPDA, and 34.785 g of NMP were added all at once and stirred at room temperature for 5 hours. After that, NMP was added so that the solid concentration was about 15 mass% and homogenized to obtain a polyamic acid (PAA) varnish. A film was obtained in the same manner as in Example 1 using the obtained varnish. The polyamic acid contained in the varnish obtained in Comparative Example 3 had only amic acid repeating structural units formed from BPAF, s-BPDA, 4,4'-DDS, and 4-BAAB.

[0128] [Table 1]

[0129] As shown in Table 1, the polyimide films obtained from the imide-amic acid copolymers of the examples having specific imide repeating structural units and amic acid structural units have low residual stress and linear thermal expansion coefficients, excellent transparency and heat resistance, and low yellowness index. The raw material compositions constituting the polyimide films of Example 1 and Comparative Example 3 were the same. However, compared to the polyimide film of Comparative Example 3 obtained from polyamic acid, the polyimide film of Example 1 maintained transparency and low yellowness while exhibiting particularly excellent heat resistance, low residual stress, and low linear thermal expansion coefficient.

Claims

1. An imide-amic acid copolymer comprising repeating units each consisting of an imide portion (IM), an amic acid portion (AM1) and an amic acid portion (AM2) represented by the following formula (1). 【Chemistry 1】 (In formula (1), X 1 is a tetravalent aromatic group having 4 to 39 carbon atoms, and is -O-, -SO 2 -, -CO-, -CH 2 -, -C(CH 3 ) 2 -, -C 2 H 4 may have at least one selected from the group consisting of -O- and -S-; X 2 Is X 1 A tetravalent aromatic group having 4 to 39 carbon atoms different from the above, and a bonding group such as -O- or -SO 2 -, -CO-, -CH 2 -, -C(CH 3 ) 2 -, -C 2 H 4 may have at least one selected from the group consisting of -O- and -S-; Y 1 is a group represented by at least one selected from the group consisting of the following formula (2), the following general formula (3), and the following general formula (4), Y 2 is a group represented by the following general formula (5): s, t and u are positive integers. 【Chemistry 2】 (In formula (3), Z 1 represents a single bond or a group represented by --O--. In formula (4), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. 【Chemistry 3】 (In formula (5), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

2. 2. The imide-amic acid copolymer according to claim 1, wherein said s is 1 to 50 and said t is 1 to 50.

3. 3. The imide-amic acid copolymer according to claim 1, wherein u is 5 to 200.

4. The X 1 The imide-amido acid copolymer according to any one of claims 1 to 3, wherein is a group represented by the following formula (6): 【Chemistry 4】

5. The X 2 The imide-amido acid copolymer according to any one of claims 1 to 4, wherein is a group represented by the following formula (7): 【Chemistry 5】

6. The imide portion (IM) has a structural unit X1A derived from a tetracarboxylic dianhydride and a structural unit Y1B derived from a diamine, The amic acid portion (AM1) has a structural unit X2A derived from a tetracarboxylic dianhydride and a structural unit Y1B derived from a diamine, the amic acid portion (AM2) has a structural unit X2A derived from a tetracarboxylic dianhydride and a structural unit Y2B derived from a diamine, The structural unit X1A includes a structural unit derived from an aromatic tetracarboxylic dianhydride, the structural unit X2A includes a structural unit derived from an aromatic tetracarboxylic dianhydride different from the structural unit X1A; The structural unit Y1B includes a structural unit (B1) derived from a diamine (b1), and the structural unit (B1) includes at least one selected from the group consisting of a structural unit (B11) derived from a compound represented by the following formula (b11), a structural unit (B12) derived from a compound represented by the following general formula (b12), and a structural unit (B13) derived from a compound represented by the following general formula (b13): The imide-amic acid copolymer according to any one of claims 1 to 5, wherein the structural unit Y2B comprises a structural unit (B2) derived from a compound represented by the following general formula (b2): 【Chemistry 6】 (In formula (b12), Z 1 represents a single bond or a group represented by --O--. In formula (b13), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. In formula (b2), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

7. the structural unit X2A contains a structural unit (A2) derived from an aromatic tetracarboxylic dianhydride (a2); The imide-amido acid copolymer according to claim 6, wherein the structural unit (A2) comprises at least one selected from the group consisting of a structural unit (A21) derived from a compound represented by the following formula (a21), a structural unit (A22) derived from a compound represented by the following formula (a22), a structural unit (A23) derived from a compound represented by the following formula (a23), a structural unit (A24) derived from a compound represented by the following formula (a24), and a structural unit (A25) derived from a compound represented by the following formula (a25). 【Chemistry 7】

8. The imide-amido acid copolymer according to claim 6 or 7, further comprising a structural unit (B3) derived from a compound represented by the following general formula (b3): 【Chemistry 8】 (In formula (b3), Z 4 and Z 5 each independently represents a divalent aliphatic group or a divalent aromatic group; R 4 and R 5 each independently represents a monovalent aromatic group or a monovalent aliphatic group; R 6 and R 7 each independently represents a monovalent aliphatic group; R 8 and R 9 each independently represents a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represent an integer of 1 or more, and the sum of m and n represents an integer of 2 to 1000. 4 and R 5 At least one of represents a monovalent aromatic group.

9. The R 4 and R 5 is a phenyl group, R 6 and R 7 The imide-amic acid copolymer according to claim 8, wherein is a methyl group.

10. The imide-amic acid copolymer according to claim 8 or 9, wherein the content of the polyorganosiloxane unit in the imide-amic acid copolymer is 1 to 20 mass%.

11. The imide-amic acid copolymer according to any one of claims 6 to 10, wherein the structural unit X1A comprises a structural unit (A1) derived from a compound represented by the following formula (a1): 【Chemistry 9】

12. A varnish comprising the copolymer according to any one of claims 1 to 11 dissolved in an organic solvent.

13. A polyimide film comprising a polyimide resin obtained by imidizing an amic acid moiety in the copolymer according to any one of claims 1 to 11.

14. The polyimide film according to claim 13, wherein the weight average molecular weight (Mw) of the polyimide resin is 100,000 to 300,000.

15. A method for producing an imide-amic acid copolymer, comprising the following steps 1 and 2: Step 1: A step of reacting a tetracarboxylic acid component constituting the imide portion (IM) with a diamine component to obtain an imide oligomer. Step 2: A step of reacting the imide oligomer obtained in step 1 with a tetracarboxylic acid component and a diamine component constituting the amic acid portion (AM2) to obtain an imide-amic acid copolymer represented by the following formula (1), which includes repeating units composed of the imide portion (IM), the amic acid portion (AM1), and the amic acid portion (AM2). 【Chemistry 10】 (In formula (1), X 1 is a tetravalent aromatic group having 4 to 39 carbon atoms, and is -O-, -SO 2 -, -CO-, -CH 2 -, -C(CH 3 ) 2 -, -C 2 H 4 may have at least one selected from the group consisting of -O- and -S-; X 2 Is X 1 A tetravalent aromatic group having 4 to 39 carbon atoms different from the above, and a bonding group such as -O- or -SO 2 -, -CO-, -CH 2 -, -C(CH 3 ) 2 -, -C 2 H 4 may have at least one selected from the group consisting of -O- and -S-; Y 1 is a group represented by at least one selected from the group consisting of the following formula (2), the following general formula (3), and the following general formula (4), Y 2 is a group represented by the following general formula (5): s, t and u are positive integers. 【Chemistry 11】 (In formula (3), Z 1 represents a single bond or a group represented by --O--. In formula (4), each R independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. 【Chemistry 12】 (In formula (5), Z 2 , Z 3 R each independently represents a group represented by -COO- or a group represented by -OCO-. 1 , R 2 , R 3 each independently represents a monovalent organic group having 1 to 20 carbon atoms; and h, i, j, and k are integers of 0 to 4.

16. The method for producing an imide-amic acid copolymer according to claim 15, wherein the imide oligomer obtained in step 1 has amino groups at both ends of the main chain of the molecular chain.

17. The method for producing an imide-amic acid copolymer according to claim 15 or 16, wherein in step 1, a molar ratio of the diamine component to the tetracarboxylic acid component (diamine / tetracarboxylic acid) is 1.01 to 2.

18. The method for producing an imide-amic acid copolymer according to any one of claims 15 to 17, wherein a diamine containing a polyorganosiloxane unit is reacted after completion of step 2.

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