Polyimide resin precursor varnish and polyimide film

Abstract

Provided is a polyimide resin precursor varnish containing a solvent and a polyimide resin precursor having a constituent unit A derived from a tetracarboxylic dianhydride and a constituent unit B derived from a diamine, wherein the constituent unit A includes at least one constituent unit selected from the group consisting of a constituent unit derived from a compound represented by formula (a11) and a constituent unit (A12) derived from a compound represented by formula (a12), the constituent unit B includes a constituent unit derived from a compound represented by formula (b1), and the solvent includes a solvent having a boiling point of 190°C-250°C and a solvent having a boiling point of 110°C-160°C. (In the formulas, X is a sulfone group or the like, and Y is a hexafluoroisopropylidene group or a fluorenylidene group.)

Description

Polyimide resin precursor varnish and polyimide film

[0001] The present invention relates to a polyimide resin precursor varnish and a polyimide film.

[0002] Polyimide resins have excellent heat resistance and mechanical properties, and therefore various applications are being considered in fields such as electrical and electronic components. For example, among electrical and electronic components, polyimide resins that have heat resistance and transparency are used in the display field. In the display field, glass is generally used as the supporting substrate. For example, Patent Document 1 discloses a polyimide precursor having a structure in which the repeating unit is derived from 4-aminophenyl-4-aminobenzoate, with the aim of obtaining a polyimide film that has improved heat resistance, linear thermal expansion coefficient, and light transmittance, and further has improved adhesion between a laminate of a polyimide film and a glass substrate.

[0003] Patent No. 7235157

[0004] Polyimide resins are used not only in the display field but also as insulating film materials in the semiconductor field. Polyimide resins used in the semiconductor field require heat resistance capable of withstanding higher temperature processes. Specifically, with the advancement of three-dimensional packaging technology, processes such as CVD and hybrid bonding require heat resistance of at least 300°C. Furthermore, the miniaturization of semiconductors necessitates resins with even better heat resistance. In the semiconductor field, spin coating is the primary method for applying resin varnish, making it necessary to remove varnish that has spread to the periphery or backside of silicon wafers. However, polyimide resins and polyimide resin precursors (polyamic acids) generally have poor solubility in rinse solutions (e.g., propylene glycol monomethyl ether, cyclohexanone) used to remove varnish. Therefore, there is a need for polyimide resin precursor varnishes that are highly soluble in rinse solutions, i.e., have excellent coatability. The present invention was made in light of these circumstances, and its objective is to provide a polyimide resin precursor varnish that can produce a polyimide film with excellent heat resistance and has excellent rinsing suitability.

[0005] The present inventors have found that the above-mentioned problems can be solved by a varnish containing a polyimide resin precursor having specific structural units and a specific solvent, and have thus completed the present invention.

[0006] That is, the present invention relates to the following items [1] to

[12] : [1] A polyimide resin precursor varnish containing a polyimide resin precursor having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, and a solvent, wherein the structural unit A comprises structural unit (A1), which is at least one selected from the group consisting of a structural unit (A11) derived from a compound represented by the following formula (a11) and a structural unit (A12) derived from a compound represented by the following formula (a12), and the structural unit B comprises structural unit (B1) derived from a compound represented by the following formula (b1), and the solvent comprises a solvent (S1) having a boiling point of 190 to 250°C and a solvent (S2) having a boiling point of 110 to 160°C. (In formula (a11), X represents a single bond, an ether group, a carbonyl group, a sulfone group, a sulfide group, a phenylene group, an oxyphenyl ether group, a bisphenoxyfluorene group, or a fluorenylidene group. In formula (a12), Y represents a hexafluoroisopropylidene group or a fluorenylidene group.) [2] The polyimide resin precursor varnish according to item [1] above, wherein the solvent (S1) is 1,3-dimethyl-2-imidazolidinone, and the solvent (S2) is at least one selected from the group consisting of propylene glycol monomethyl ether, cyclohexanone, and cyclopentanone. [3] The polyimide resin precursor varnish according to item [1] above or [2] above, wherein the structural unit A includes a structural unit (A111) derived from a compound represented by the following formula (a111): [4] The polyimide resin precursor varnish according to any one of [1] to [3] above, wherein the solvent comprises propylene glycol monomethyl ether. [5] The polyimide resin precursor varnish according to any one of [1] to [4] above, wherein the proportion of the structural unit (A1) in the structural unit A is 30 to 100 mol %. [6] The polyimide resin precursor varnish according to any one of [1] to [5] above, wherein the structural unit A further comprises at least one selected from the group consisting of a structural unit (A2) derived from a compound represented by the following formula (a2): (In formula (a3), n is 1 or 2.) [7] The polyimide resin precursor varnish according to [6] above, wherein the molar ratio of the structural unit (A1) in the structural unit A to the sum of the structural units (A2), (A3), and (A4), [(A1) / ((A2)+(A3)+(A4)], is 30 / 70 to 100 / 0. [8] The polyimide resin precursor varnish according to any one of [1] to [7] above, wherein the sum of the contents of solvent (S1) and solvent (S2) in the solvent is 50 mass% or more based on the total amount of the solvent. [9] The polyimide resin precursor varnish according to any one of [1] to [8] above, wherein the mass ratio [(S1) / (S2)] of the content of solvent (S1) to the content of solvent (S2) in the solvent is 30 / 70 to 90 / 10.

[10] The polyimide resin precursor varnish according to any one of [1] to [9] above, wherein the proportion of the structural unit (B1) in the structural unit B is 30 to 100 mol %.

[11] A polyimide film obtained by applying the polyimide resin precursor varnish according to any one of [1] to

[10] above onto a support and heating it.

[12] The polyimide film according to

[11] above, wherein the glass transition temperature is 300°C or higher.

[0007] A polyimide film having excellent heat resistance can be obtained, and a polyimide resin precursor varnish having excellent rinsability can be provided. Furthermore, a polyimide film having excellent heat resistance can be provided. Because the polyimide resin precursor varnish of the present invention has the above-mentioned properties, it is useful as a raw material in the semiconductor field.

[0008] [Polyimide Resin Precursor Varnish] The polyimide resin precursor varnish of the present invention is a polyimide resin precursor varnish comprising a solvent and a polyimide resin precursor having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, wherein the structural unit A comprises a structural unit (A1) that is at least one selected from the group consisting of a structural unit (A11) derived from a compound represented by the following formula (a11) and a structural unit (A12) derived from a compound represented by the following formula (a12), and the structural unit B comprises a structural unit (B1) derived from a compound represented by the following formula (b1), and the solvent comprises a solvent (S1) having a boiling point of 190 to 250°C and a solvent (S2) having a boiling point of 110 to 160°C. (In formula (a11), X represents a single bond, an ether group, a carbonyl group, a sulfone group, a sulfide group, a phenylene group, an oxyphenyl ether group, a bisphenoxyfluorene group, or a fluorenylidene group. In formula (a12), Y represents a hexafluoroisopropylidene group or a fluorenylidene group.)

[0009] The reasons why the polyimide resin precursor varnish of the present invention has excellent rinsability and why its use can produce a polyimide film with excellent heat resistance are unclear, but are thought to be as follows. The polyimide resin precursor varnish of the present invention contains two solvents with different boiling points, resulting in a varnish in which the polyimide precursor is dissolved in a stable state. Furthermore, the inclusion of a solvent with a boiling point of 110 to 160°C is thought to contribute to its excellent rinsability. Furthermore, polyimide precursors that generally exhibit high heat resistance do not exhibit good solubility in solvents with low polarity. However, the polyimide resin precursor contained in the polyimide resin precursor varnish of the present invention contains a structure derived from a specific aromatic tetracarboxylic dianhydride having a bent structure, a structure with significant steric hindrance, or a freely rotatable structure, and a structure derived from a specific diamine having an ester skeleton with high linearity and relatively low water absorption. This enhances the solubility of the polyimide precursor, while the resin obtained after thermal imidization is thought to have excellent heat resistance. As described above, the polyimide resin precursor varnish of the present invention is thought to produce a polyimide resin with excellent heat resistance and excellent rinsability.

[0010] <Polyimide Resin Precursor> The polyimide resin precursor contained in the polyimide resin precursor varnish of the present invention has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, in which the structural unit A includes at least one structural unit (A1) selected from the group consisting of a structural unit (A11) derived from a compound represented by the following formula (a11) and a structural unit (A12) derived from a compound represented by the following formula (a12), and the structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (b1). (In formula (a11), X represents a single bond, an ether group, a carbonyl group, a sulfone group, a sulfide group, a phenylene group, an oxyphenyl ether group, a bisphenoxyfluorene group, or a fluorenylidene group. In formula (a12), Y represents a hexafluoroisopropylidene group or a fluorenylidene group.)

[0011] (Structural Unit A) The structural unit A is a structural unit derived from a tetracarboxylic dianhydride contained in a polyimide resin precursor. The structural unit A includes at least one structural unit (A1) selected from the group consisting of a structural unit (A11) derived from a compound represented by the following formula (a11) and a structural unit (A12) derived from a compound represented by the following formula (a12), and preferably includes a structural unit (A11) derived from a compound represented by the following formula (a11). When the structural unit A includes the structural unit (A1), the rinsability of the varnish and the heat resistance of the polyimide film can be improved. (In formula (a11), X represents a single bond, an ether group, a carbonyl group, a sulfone group, a sulfide group, a phenylene group, an oxyphenyl ether group, a bisphenoxyfluorene group, or a fluorenylidene group. In formula (a12), Y represents a hexafluoroisopropylidene group or a fluorenylidene group.)

[0012] In formula (a11), X represents a single bond, an ether group, a carbonyl group, a sulfone group, a sulfide group, a phenylene group, an oxyphenyl ether group, a bisphenoxyfluorene group, or a fluorenylidene group, and is preferably a sulfone group.

[0013] Examples of the compound represented by formula (a11) include 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic anhydride (ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 4,4'-thiodiphthalic anhydride, 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, and 5-[3-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione. The structural unit (A11) may contain one type of structural unit, or two or more types of structural units.

[0014] Among these, the structural unit (A11) preferably includes a structural unit (A111) derived from a compound represented by the following formula (a111), and more preferably a structural unit (A111) derived from a compound represented by the following formula (a111): As described above, the structural unit A preferably includes a structural unit (A111) derived from a compound represented by the following formula (a111): The compound represented by formula (a111) is 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA). When the structural unit A includes the structural unit (A111), the rinsability of the varnish and the heat resistance of the polyimide film can be further improved.

[0015] In formula (a12), Y is a hexafluoroisopropylidene group or a fluorenylidene group.

[0016] Examples of compounds represented by formula (a12) include 9,9-bis(trifluoromethyl)-9H-xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA) and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone (SFDA). The structural unit (A12) may contain one or two types of structural units. When the structural unit A contains the structural unit (A12), the rinsability of the varnish and the heat resistance of the polyimide film can be further improved.

[0017] The proportion of the structural unit (A1) in the structural unit A is preferably 30 to 100 mol %, more preferably 70 to 100 mol %, even more preferably 90 to 100 mol %, and even more preferably 95 to 100 mol %, or it may be 100 mol %, or the structural unit A may be composed solely of the structural unit (A1). By ensuring that the proportion of the structural unit (A1) is within the above range, the rinsability of the varnish and the heat resistance of the polyimide film can be improved.

[0018] The structural unit A may consist solely of the structural unit (A1), or may include a structural unit other than the structural unit (A1). When the structural unit A includes a structural unit other than the structural unit (A1), the structural unit A preferably further includes, as a structural unit other than the structural unit (A1), at least one selected from the group consisting of a structural unit (A2) derived from a compound represented by the following formula (a2), a structural unit (A3) derived from a compound represented by the following formula (a3), and a structural unit (A4) derived from a compound represented by the following formula (a4), and more preferably includes a structural unit (A2) derived from a compound represented by the following formula (a2). (In formula (a3), n is 1 or 2.)

[0019] The compound represented by formula (a2) is pyromellitic anhydride (PMDA). When structural unit A contains structural unit (A2), the heat resistance of the resulting polyimide film can be particularly enhanced. In formula (a3), n is 1 or 2, with n being preferably 2. Among the compounds represented by formula (a3), a compound in which n is 2 is 4,4-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (BP-TME). When structural unit A contains structural unit (A3), the heat resistance of the resulting polyimide film can be particularly enhanced. The compound represented by formula (a4) is 2,3,6,7-naphthalenetetracarboxylic acid 2,3:6,7-dianhydride (NTCDA). When structural unit A contains structural unit (A4), the heat resistance of the resulting polyimide film can be particularly enhanced.

[0020] The molar ratio of the structural unit (A1) to the sum of the structural units (A2), (A3), and (A4) in the structural unit A [(A1) / ((A2)+(A3)+(A4)] is preferably 30 / 70 to 100 / 0, more preferably 40 / 60 to 100 / 0, even more preferably 50 / 50 to 100 / 0, still more preferably 60 / 40 to 100 / 0, even more preferably 60 / 40 to 90 / 10, and still more preferably 60 / 40 to 80 / 20. When the molar ratio of the structural unit (A1) to the sum of the structural units (A2), (A3), and (A4) is 100 / 0, the structural unit A does not include the structural units (A2), (A3), and (A4).

[0021] The molar ratio of the structural unit (A1) to the structural unit (A2) in the structural unit A [(A1) / (A2)] is preferably 30 / 70 to 100 / 0, more preferably 40 / 60 to 100 / 0, even more preferably 40 / 60 to 90 / 10, still more preferably 40 / 60 to 80 / 20, even more preferably 40 / 60 to 70 / 30, and even more preferably 40 / 60 to 60 / 40. When the molar ratio of the structural unit (A1) to the structural unit (A2) is 100 / 0, the structural unit A does not contain the structural unit (A2). When the structural units constituting the structural unit A are in the above molar ratio, the rinsability of the varnish and the heat resistance of the polyimide film can be improved, and the heat resistance of the resulting polyimide film can be particularly enhanced.

[0022] The structural unit A may contain structural units other than the structural unit (A1), the structural unit (A2), the structural unit (A3), and the structural unit (A4). The tetracarboxylic acid dianhydride that provides such a structural unit is not particularly limited, but examples include aromatic tetracarboxylic acid dianhydrides excluding compounds represented by formula (a1), excluding compounds represented by formula (a2), excluding compounds represented by formula (a3), and excluding compounds represented by formula (a4), alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides. When the structural unit A contains structural units other than the structural unit (A1), the structural unit (A2), the structural unit (A3), and the structural unit (A4), it is preferable for the structural unit A to contain an aromatic tetracarboxylic acid dianhydride, among tetracarboxylic acid dianhydrides excluding compounds represented by formula (a1), excluding compounds represented by formula (a2), excluding compounds represented by formula (a3), and excluding compounds represented by formula (a4). Examples of aromatic tetracarboxylic dianhydrides include 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (BPF-PA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, hydroquinone diphthalic anhydride (HQDEA), ethylene glycol bis(trimellitate) dianhydride (TMEG), and p-phenylene bis(trimellitate) dianhydride (TAHQ).Examples of alicyclic tetracarboxylic dianhydrides include cyclohexane-1,2,4,5-tetracarboxylic dianhydride (HPMDA), cyclohexane-1,2,3,4-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5',6,6'-tetracarboxylic dianhydride (CpODA), 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopent ... Examples of the aliphatic tetracarboxylic dianhydride include 1,2,4,5-cyclopentanetetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride, 2,2-propylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, and bicyclo[4.4.0]decane-2,3,6,7-tetracarboxylic acid dianhydride. Examples of the aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic acid dianhydride. In this specification, "aromatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more aromatic rings, "alicyclic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and "aliphatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring. The structural unit A may optionally contain one type of structural unit, or two or more types of structural units.

[0023] (Structural Unit B) The structural unit B is a structural unit derived from a diamine contained in a polyimide resin precursor. The structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (b1). When the structural unit B includes the structural unit (B1), the rinsability of the varnish and the heat resistance of the polyimide film can be improved.

[0024] The compound represented by formula (b1) is 4-aminophenyl-4-aminobenzoate (4-BAAB).

[0025] The proportion of the structural unit (B1) in the structural unit B is preferably 30 to 100 mol %, more preferably 70 to 100 mol %, even more preferably 90 to 100 mol %, and even more preferably 95 to 100 mol %, or it may be 100 mol %, or the structural unit B may be composed solely of the structural unit (B1). By ensuring that the proportion of the structural unit (B1) is within the above range, the rinsability of the varnish and the heat resistance of the polyimide film can be improved.

[0026] The structural unit B may contain a structural unit other than the structural unit (B1). Diamines that provide such a structural unit are not particularly limited, but include aromatic diamines other than the compound represented by formula (b1), alicyclic diamines, and aliphatic diamines. Examples of aromatic diamines include bis(4-aminophenyl)terephthalate (APTP), 1,4-bis(4-aminobenzoyloxy)benzene, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFMB), 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 2,2'-bis(trifluoromethyl)-5,5'-diaminobiphenyl. phenyl, 2,2-bis(4-aminophenyl)hexafluoropropane (HFDA), 2,2-bis(3-amino-4-methylphenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP), 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 3,3'-Diaminodiphenyl sulfone (3,3'-DDS), 4,4'-diamino-2,2'-dimethylbiphenyl (mTB), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4,4'-diaminobiphenyl (benzidine), 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminobenzophenone, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 5-aminophenyl No-1,3,3-trimethyl-1-(4-aminophenyl)-indan (5-TMDM), 6-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indan (6-TMDM), 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAM), 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene (BisAP), 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl (BODA), 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone [4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-diaminobenzanilide, 4-aminobenzoate-4-aminophenyl, 3,4-diaminobenzanilide, and the like. Examples of alicyclic diamines include 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane, 1,3-cyclohexyldiamine, 1,4-cyclohexyldiamine, isophoronediamine, bis(aminomethyl)norbornane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexyl ether, and 2,2-bis(4-aminocyclohexyl)propane. Examples of aliphatic diamines include ethylenediamine and hexamethylenediamine. In this specification, aromatic diamine refers to a diamine containing one or more aromatic rings, alicyclic diamine refers to a diamine containing one or more alicyclic rings but no aromatic rings, and aliphatic diamine refers to a diamine containing neither an aromatic ring nor an alicyclic ring. The structural units other than the structural unit (B1) optionally contained in structural unit B may be of one type or two or more types.

[0027] <Characteristics of Polyimide Resin Precursor> The number-average molecular weight of the polyimide resin precursor is preferably 5,000 to 500,000 from the viewpoint of the mechanical strength of the resulting polyimide film. Furthermore, from the same viewpoint, the weight-average molecular weight (Mw) is preferably 10,000 to 800,000, more preferably 30,000 to 300,000. The number-average molecular weight and weight-average molecular weight of the polyimide resin precursor can be determined from values ​​converted into standard polymethyl methacrylate (PMMA) by gel filtration chromatography measurement.

[0028] The polyimide resin precursor of the present invention is preferably a polyimide resin precursor having a polyamic acid structure, and more preferably a polyamic acid.

[0029] <Method for Producing Polyimide Resin Precursor> The polyimide resin precursor may be produced by any method, but the following production method is preferred. The polyimide resin precursor is preferably produced by a production method in which a compound (tetracarboxylic acid component) that provides the above-mentioned structural unit A is reacted with a compound (diamine component) that provides the above-mentioned structural unit B to obtain a polyimide resin precursor having a polyamic acid structure. More specifically, a preferred method for producing a polyimide resin precursor is a production method in which a tetracarboxylic acid component containing a compound that provides the structural unit (A1) (at least one selected from the group consisting of compounds represented by formula (a11) and compounds represented by formula (a12)) is reacted with a diamine component containing a compound that provides the structural unit (B1) (compound represented by formula (b1)) to obtain a polyimide resin precursor having a polyamic acid structure.

[0030] The tetracarboxylic acid component used in this production method includes a compound that provides the structural unit (A1), and may also include a tetracarboxylic acid component 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 this production method preferably includes a compound that provides the structural unit (B1), and may also include 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. The amount of the diamine component relative to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0031] The method for reacting the tetracarboxylic acid component and the diamine component in this production method is not particularly limited, and known methods can be used. Specific reaction methods include charging a reactor with the tetracarboxylic acid component, the diamine component, a solvent, and, if necessary, an end-capping agent, and stirring the mixture at preferably 0 to 120°C, more preferably 5 to 80°C, for 1 to 72 hours. Reaction at 80°C or less is more preferred, since this prevents the molecular weight of the polyimide resin precursor from varying depending on the temperature history during polymerization, suppresses the progress of thermal imidization, and allows for the stable production of a polyimide resin precursor having a polyamic acid structure.

[0032] The above method provides a polyimide resin precursor solution having a polyamic acid structure dissolved in a solvent. The concentration of the polyimide resin precursor in the resulting solution is preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass. Next, the raw materials used in this production method will be described.

[0033] (Tetracarboxylic Acid Component) The tetracarboxylic acid component used as a raw material in the present production method is preferably the tetracarboxylic acid dianhydride described above in the section (Structural Unit A), and preferred tetracarboxylic acid dianhydrides are also the same as those described above in the section (Structural Unit A). The tetracarboxylic acid dianhydride used as the tetracarboxylic acid component in the present production method may be in the form of a dianhydride, a tetracarboxylic acid (free acid), or an alkyl ester of a tetracarboxylic acid, but is preferably a dianhydride. The tetracarboxylic acid component used as a raw material in the present production method contains at least one compound (a compound that provides structural unit (A1)) selected from the group consisting of compounds represented by formula (a11) and compounds represented by formula (a12). The total ratio of the compound represented by formula (a11) and the compound represented by formula (a12) in the tetracarboxylic acid component is preferably 30 to 100 mol %, more preferably 70 to 100 mol %, even more preferably 90 to 100 mol %, and still more preferably 95 to 100 mol %, or may be 100 mol %, and the tetracarboxylic acid component may consist solely of the compound represented by formula (a11) and the compound represented by formula (a12). When the total ratio of the compound represented by formula (a11) and the compound represented by formula (a12) is within the above range, the rinsability of the varnish and the heat resistance of the polyimide film can be improved.

[0034] The tetracarboxylic acid component may consist only of the compound represented by formula (a11) and the compound represented by formula (a12), or may contain tetracarboxylic acid components other than the compound represented by formula (a11) and the compound represented by formula (a12). As the tetracarboxylic acid component other than the compound represented by formula (a11) and the compound represented by formula (a12), preferably, it further contains at least one selected from the group consisting of the compound represented by formula (a2), the compound represented by formula (a3), and the compound represented by formula (a4), more preferably, it contains the compound represented by formula (a2).

[0035] The molar ratio of the total of the compounds represented by formula (a11) and the compounds represented by formula (a12) to the total of the compounds represented by formula (a2), the compounds represented by formula (a3), and the compounds represented by formula (a4) in the structural unit A [((a11) + (a12)) / ((a2) + (a3) ​​+ (a4))] is preferably 30 / 70 to 100 / 0, more preferably 40 / 60 to 100 / 0, even more preferably 50 / 50 to 100 / 0, still more preferably 60 / 40 to 100 / 0, still more preferably 60 / 40 to 90 / 10, and still more preferably 60 / 40 to 80 / 20. When the molar ratio of the total of the compound represented by formula (a11) and the compound represented by formula (a12) to the total of the compound represented by formula (a2), the compound represented by formula (a3), and the compound represented by formula (a4) is 100 / 0, the tetracarboxylic acid component does not include the compound represented by formula (a2), the compound represented by formula (a3), and the compound represented by formula (a4).

[0036] The molar ratio [(a11) / (a2)] of the compound represented by formula (a11) to the compound represented by formula (a2) in the tetracarboxylic acid component is preferably 30 / 70 to 100 / 0, more preferably 40 / 60 to 100 / 0, even more preferably 40 / 60 to 90 / 10, still more preferably 40 / 60 to 80 / 20, even more preferably 40 / 60 to 70 / 30, and even more preferably 40 / 60 to 60 / 40. When the molar ratio of the compound represented by formula (a11) to the compound represented by formula (a2) is 100 / 0, the tetracarboxylic acid component does not contain the compound represented by formula (a2). When the tetracarboxylic acids constituting the tetracarboxylic acid component are in the above molar ratio, the heat resistance of the polyimide resin can be enhanced while maintaining good varnish coatability and polyimide resin adhesion.

[0037] The tetracarboxylic acid component may contain a tetracarboxylic acid component other than the compound represented by formula (a11), the compound represented by formula (a12), the compound represented by formula (a2), the compound represented by formula (a3), and the compound represented by formula (a4). Such tetracarboxylic acid components are not particularly limited, and examples thereof include aromatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides other than the compound represented by formula (a11), the compound represented by formula (a12), the compound represented by formula (a2), the compound represented by formula (a3), and the compound represented by formula (a4). When the tetracarboxylic acid component contains a tetracarboxylic acid component other than the compound represented by formula (a11), the compound represented by formula (a12), the compound represented by formula (a2), the compound represented by formula (a3), and the compound represented by formula (a4), it is preferable to contain an aromatic tetracarboxylic acid dianhydride among tetracarboxylic acid dianhydrides excluding the compound represented by formula (a11), the compound represented by formula (a12), the compound represented by formula (a2), the compound represented by formula (a3), and the compound represented by formula (a4). Specific examples of preferred tetracarboxylic acid dianhydrides are the same as those described above in the section (Structural Unit A). These tetracarboxylic acid dianhydrides may be used alone or in combination of two or more.

[0038] (Diamine Component) The diamine component used as a raw material in this production method is preferably the diamine described above in the section (Structural Unit B), and preferred diamine components are also the same as those described above in the section (Structural Unit (B)). The diamine used as the diamine component in this production method may be in the form of either a diamine or a diisocyanate corresponding to the diamine, but is preferably a diamine. The diamine component used as a raw material in this production method includes a compound represented by formula (b1) (a compound that provides structural unit (B1)). The proportion of the compound represented by formula (b1) in the diamine component is preferably 30 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%. It may even be 100 mol%, and the diamine component may consist solely of the compound represented by formula (b1). By having the proportion of the compound represented by formula (b1) within the above range, the rinsability of the varnish and the heat resistance of the polyimide film can be improved.

[0039] The diamine component may contain a diamine component other than the compound represented by formula (b1). Examples of such diamine components include, but are not limited to, aromatic diamines other than the compound represented by formula (b1), alicyclic diamines, and aliphatic diamines. Specific examples of preferred diamines are the same as those described above in the section (Structural Unit B). One or more diamines may be used.

[0040] (End-capping agent) In addition to the tetracarboxylic acid component and diamine component described above, an end-capping agent may be used in the production of the polyimide resin precursor. As the end-capping agent, monoamines or dicarboxylic acids are preferred, and monoamines are more preferred. The amount of the end-capping agent introduced is preferably 0.0001 to 0.2 mol, more preferably 0.0001 to 0.1 mol, even more preferably 0.001 to 0.06 mol, and still more preferably 0.01 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. Examples of monoamine end-capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, o-aminophenol (2-aminophenol), m-aminophenol (3-aminophenol), p-aminophenol (4-aminophenol), o-aminobenzoic acid, m-aminobenzoic acid, and p-aminobenzoic acid. Of these, benzylamine, aniline, and p-aminophenol (4-aminophenol) are preferred, with p-aminophenol (4-aminophenol) being more preferred. Examples of dicarboxylic acid end-capping agents include dicarboxylic acids, which may be partially ring-closed. Examples include 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. Of these, phthalic acid and phthalic anhydride are preferred.

[0041] (Solvent (reaction solvent)) The solvent (reaction solvent) used in the production of the polyimide resin precursor may be any solvent capable of dissolving the polyimide resin precursor produced, but preferably, the solvent (S1) contained in the varnish described below has a boiling point of 190 to 250 ° C. or a solvent (S2) having a boiling point of 110 to 160 ° C. is preferably used, more preferably, solvent (S1) is used, and it is even more preferable to use both solvent (S1) and solvent (S2). When only solvent (S1) is used as the reaction solvent, the solvent (S2) may be added as a dilution solvent to the polyimide resin precursor solution after the production of the polyimide resin precursor, and when only solvent (S2) is used as the reaction solvent, the solvent (S1) may be added as a dilution solvent to the polyimide resin precursor solution after the production of the polyimide resin precursor. Moreover, by using both solvent (S1) and solvent (S2) as reaction solvents, the polyimide resin precursor solution itself after the production of the polyimide resin precursor, or the polyimide resin precursor varnish can be used simply by adding a solvent and adjusting the concentration, which is convenient and preferable.

[0042] The boiling point of the solvent (S1) is 190 to 250°C, preferably 190 to 240°C, more preferably 200 to 240°C, even more preferably 210 to 235°C, and still more preferably 220 to 230°C.

[0043] The boiling point of the solvent (S2) is 110 to 160° C., preferably 110 to 150° C., more preferably 110 to 140° C., even more preferably 110 to 130° C., and still more preferably 115 to 125° C. When the boiling points of the solvent (S1) and the solvent (S2) are within the above range, the rinsing suitability is improved, and a polyimide film having better heat resistance can be obtained.

[0044] The solvent (S1) having a boiling point of 190 to 250° C. is preferably a solvent having the above boiling point and capable of dissolving the polyimide resin precursor. Examples of the solvent (S1) include phenol-based solvents, ether-based solvents, carbonate-based solvents, amide-based solvents, lactone-based solvents, phosphorus-containing amide-based solvents, sulfur-containing solvents, ketone-based solvents, and ester-based solvents. Amide-based solvents or lactone-based solvents are preferred, and amide-based solvents are more preferred.

[0045] The solvent (S1) is preferably at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone (boiling point 222°C, DMI), 3-methyl-2-oxazolidone (boiling point 248°C), γ-butyrolactone (boiling point 204°C, GBL), N-methylpyrrolidone (boiling point 204°C, NMP), γ-valerolactone (boiling point 207°C), and 3-methoxy-N,N-dimethylpropanamide (boiling point 215°C), more preferably at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidone, and γ-butyrolactone, even more preferably at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone and 3-methyl-2-oxazolidone, and still more preferably 1,3-dimethyl-2-imidazolidinone.

[0046] The solvent (S2) having a boiling point of 110 to 160° C. is preferably a solvent having the above boiling point and capable of dissolving the polyimide resin precursor. Examples of the solvent (S2) include phenol-based solvents, ether-based solvents, carbonate-based solvents, amide-based solvents, lactone-based solvents, phosphorus-containing amide-based solvents, sulfur-containing solvents, ketone-based solvents, and ester-based solvents. Ether-based solvents or ketone-based solvents are preferred, and ether-based solvents are more preferred.

[0047] The solvent (S2) is preferably at least one selected from the group consisting of propylene glycol monomethyl ether (boiling point 120°C, PGME), cyclohexanone (boiling point 155.6°C), and cyclopentanone (boiling point 130.6°C), more preferably at least one selected from the group consisting of propylene glycol monomethyl ether, cyclohexanone, and cyclopentanone, and even more preferably propylene glycol monomethyl ether.

[0048] Therefore, preferred combinations of solvent (S1) and solvent (S2) are as follows: It is preferred that solvent (S1) is 1,3-dimethyl-2-imidazolidinone and solvent (S2) is at least one selected from the group consisting of propylene glycol monomethyl ether, cyclohexanone, and cyclopentanone, and it is more preferred that solvent (S1) is 1,3-dimethyl-2-imidazolidinone and solvent (S2) is propylene glycol monomethyl ether. The above combination of solvent (S1) and solvent (S2) results in better rinsing suitability and a polyimide film with better heat resistance.

[0049] The solvent (reaction solvent) used in this step may contain solvents other than solvent (S1) and solvent (S2), but preferably does not substantially contain solvents other than solvent (S1) and solvent (S2). The total content of solvent (S1) and solvent (S2) contained in the solvent (reaction solvent) used in this step is preferably 50% by mass or more, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, still more preferably 98 to 100% by mass, still more preferably 99 to 100% by mass, and even more preferably 100% by mass, based on the total amount of solvent (reaction solvent) used in this step. The solvent (reaction solvent) used in this step may consist only of solvent (S1) and solvent (S2).

[0050] Examples of the solvent other than the solvent (S1) and the solvent (S2) include phenol-based solvents other than the solvent (S1) and the solvent (S2), ether-based solvents, carbonate-based solvents, amide-based solvents, lactone-based solvents, phosphorus-containing amide-based solvents, sulfur-containing solvents, ketone-based solvents, and ester-based solvents, among which amide-based solvents or lactone-based solvents are preferred, and amide-based solvents are more preferred. The above organic solvents may be used alone or in combination of two or more.

[0051] <Solvent> The polyimide resin precursor varnish of the present invention contains a solvent in addition to the polyimide resin precursor described above. The solvent includes a solvent (S1) having a boiling point of 190 to 250°C and a solvent (S2) having a boiling point of 110 to 160°C. That is, the polyimide resin precursor is dissolved in a solvent containing solvent (S1) and solvent (S2). Since the varnish contains a polyimide resin precursor having the structure described above and a solvent containing solvent (S1) and solvent (S2), the varnish of the present invention has excellent rinsability and can produce a polyimide film with excellent heat resistance.

[0052] The boiling point of the solvent (S1) is 190 to 250°C, preferably 190 to 240°C, more preferably 200 to 240°C, even more preferably 210 to 235°C, and still more preferably 220 to 230°C.

[0053] The boiling point of the solvent (S2) is 110 to 160° C., preferably 110 to 150° C., more preferably 110 to 140° C., even more preferably 110 to 130° C., and still more preferably 115 to 125° C. When the boiling points of the solvent (S1) and the solvent (S2) are within the above range, the rinsing suitability is improved, and a polyimide film having better heat resistance can be obtained.

[0054] The solvent (S1) having a boiling point of 190 to 250° C. is preferably a solvent having the above boiling point and capable of dissolving the polyimide resin precursor. Examples of the solvent (S1) include phenol-based solvents, ether-based solvents, carbonate-based solvents, amide-based solvents, lactone-based solvents, phosphorus-containing amide-based solvents, sulfur-containing solvents, ketone-based solvents, and ester-based solvents. Amide-based solvents or lactone-based solvents are preferred, and amide-based solvents are more preferred.

[0055] The solvent (S1) is preferably at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone (boiling point 222°C, DMI), 3-methyl-2-oxazolidone (boiling point 248°C), γ-butyrolactone (boiling point 204°C, GBL), N-methylpyrrolidone (boiling point 204°C, NMP), γ-valerolactone (boiling point 207°C), and 3-methoxy-N,N-dimethylpropanamide (boiling point 215°C), more preferably at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidone, and γ-butyrolactone, even more preferably at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone and 3-methyl-2-oxazolidone, and still more preferably 1,3-dimethyl-2-imidazolidinone.

[0056] The solvent (S2) having a boiling point of 110 to 160° C. is preferably a solvent having the above boiling point and capable of dissolving the polyimide resin precursor. Examples of the solvent (S2) include phenol-based solvents, ether-based solvents, carbonate-based solvents, amide-based solvents, lactone-based solvents, phosphorus-containing amide-based solvents, sulfur-containing solvents, ketone-based solvents, and ester-based solvents. Ether-based solvents or ketone-based solvents are preferred, and ether-based solvents are more preferred.

[0057] The solvent (S2) is preferably at least one selected from the group consisting of propylene glycol monomethyl ether (boiling point 120°C, PGME), cyclohexanone (boiling point 155.6°C), and cyclopentanone (boiling point 130.6°C), more preferably at least one selected from the group consisting of propylene glycol monomethyl ether, cyclohexanone, and cyclopentanone, and even more preferably propylene glycol monomethyl ether.

[0058] Therefore, preferred combinations of solvent (S1) and solvent (S2) are as follows: It is preferred that solvent (S1) is at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone and 3-methyl-2-oxazolidone, and solvent (S2) is at least one selected from the group consisting of propylene glycol monomethyl ether, cyclohexanone, and cyclopentanone; it is more preferred that solvent (S1) is 1,3-dimethyl-2-imidazolidinone and solvent (S2) is at least one selected from the group consisting of propylene glycol monomethyl ether, cyclohexanone, and cyclopentanone; it is even more preferred that solvent (S1) is 1,3-dimethyl-2-imidazolidinone (S1) and solvent (S2) is propylene glycol monomethyl ether. The above combination of solvent (S1) and solvent (S2) results in a polyimide film with better rinsing suitability and better heat resistance.

[0059] The mass ratio of the content of solvent (S1) to the content of solvent (S2) in the solvent [(S1) / (S2)] is preferably 30 / 70 to 90 / 10, more preferably 40 / 60 to 80 / 20, even more preferably 50 / 50 to 70 / 30, and still more preferably 60 / 40 to 70 / 30. When the mass ratio of the contents of solvent (S1) and solvent (S2) is within the above range, a polyimide film having better rinsability and more excellent heat resistance can be obtained.

[0060] The polyimide resin precursor varnish of the present invention may contain solvents other than the solvent (S1) and the solvent (S2), but preferably does not substantially contain solvents other than the solvent (S1) and the solvent (S2). The total content of the solvent (S1) and the solvent (S2) contained in the polyimide resin precursor varnish is preferably 50% by mass or more, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, still more preferably 95 to 100% by mass, still more preferably 98 to 100% by mass, still more preferably 99 to 100% by mass, still more preferably 100% by mass, and the solvent contained in the polyimide resin precursor varnish may consist only of the solvent (S1) and the solvent (S2).

[0061] Examples of the solvent other than the solvent (S1) and the solvent (S2) include phenol-based solvents other than the solvent (S1) and the solvent (S2), ether-based solvents, carbonate-based solvents, amide-based solvents, lactone-based solvents, phosphorus-containing amide-based solvents, sulfur-containing solvents, ketone-based solvents, and ester-based solvents, among which amide-based solvents or lactone-based solvents are preferred, and amide-based solvents are more preferred. The above organic solvents may be used alone or in combination of two or more.

[0062] The varnish of the present invention may be the above-mentioned polyimide resin precursor solution itself after the production of the polyimide resin precursor, or may be a solution obtained by further mixing the polyimide resin precursor solution with a solvent to dilute it.

[0063] <Other Components> In addition to the polyimide resin precursor and the solvent, the polyimide resin precursor varnish of the present invention may contain other components to the extent that the required properties of the resulting polyimide film and varnish are not impaired. Examples of other components include an imidization catalyst, a dehydration catalyst, an inorganic filler, an adhesion promoter, a release agent, a flame retardant, an ultraviolet stabilizer, a surfactant, a leveling agent, an antifoaming agent, a fluorescent brightening agent, a crosslinking agent, a polymerization initiator, and a photosensitizer.

[0064] An imidization catalyst and a dehydration catalyst can be included from the viewpoint of efficiently proceeding with the imidization of the polyamic acid moiety contained in the polyimide resin precursor. The imidization catalyst preferably has a boiling point of 40°C or higher. An imidization catalyst with a boiling point of 40°C or higher allows the imidization to proceed sufficiently before volatilization. Examples of imidization catalysts include amine compounds such as pyridine and picoline; imidazole compounds such as imidazole, 1,2-dimethylimidazole, 1-benzylimidazole, 1-benzyl-2-methylimidazole, and benzimidazole; and the like. The above imidization catalysts may be used alone or in combination of two or more. Examples of dehydration catalysts include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; and carbodiimide compounds such as dicyclohexylcarbodiimide. These may be used alone or in combination of two or more.

[0065] The polyimide resin precursor contained in the varnish of the present invention is solvent-soluble, allowing for the production of a high-concentration varnish that is stable at room temperature. The varnish of the present invention preferably contains 3 to 40 mass %, more preferably 5 to 30 mass %, of the polyimide resin precursor. The viscosity of the varnish is preferably 0.1 to 100 Pa·s, 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. The method for producing the varnish of the present invention is not particularly limited, and known methods can be applied. For example, the varnish can be obtained by mixing an additional solvent, as necessary, with the polyimide resin precursor solution obtained by the above-mentioned production method to adjust the concentration.

[0066] [Polyimide Film] The polyimide film of the present invention is preferably produced by using the polyimide resin precursor varnish described above, and is obtained by imidizing the polyimide resin precursor described above.

[0067] The method for producing a polyimide film using the varnish of the present invention is not particularly limited, and any known method can be used, but it is preferably obtained by applying the polyimide resin precursor varnish to a support and heating it. That is, the polyimide film of the present invention is preferably a polyimide film obtained by applying the polyimide resin precursor varnish to a support and heating it.

[0068] For example, the varnish of the present invention can be 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 solvents contained in the varnish, such as the reaction solvent and dilution solvent, are removed by heating to obtain a polyamic acid film. The polyamic acid in the polyamic acid film is imidized (dehydration ring closure) by heating, and then peeled off from the support to produce a polyimide film. Since the polyimide film of the present invention can be suitably used as an insulating film in the semiconductor field, silicon, silicon nitride, silicon oxide, etc. are preferred as the support, with silicon being more preferred. That is, the polyimide film of the present invention is preferably a film obtained by applying the above-mentioned varnish to a support and heating it, and the method for producing the polyimide film of the present invention is preferably a method of applying the above-mentioned varnish to a support and heating it.

[0069] The heating temperature when drying a varnish containing a polyimide resin precursor to obtain a polyimide resin precursor (polyamic acid) film is preferably 50 to 150°C. The heating temperature when imidizing the polyimide resin precursor by heating is preferably 300 to 420°C, more preferably 350 to 400°C. The heating time is preferably 1 minute to 6 hours, more preferably 5 minutes to 2 hours, and even more preferably 15 minutes to 1 hour. By using such a temperature and time, the physical properties of the resulting polyimide film are improved. Examples of the heating atmosphere include air gas, nitrogen gas, oxygen gas, hydrogen gas, and a nitrogen / hydrogen mixed gas. However, to suppress discoloration of the resulting polyimide resin, nitrogen gas with an oxygen concentration of 100 ppm or less and a nitrogen / hydrogen mixed gas containing hydrogen at a concentration of 0.5% or less are preferred. The imidization method is not limited to thermal imidization; chemical imidization can also be used.

[0070] The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., but is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 1 μm or more, even more preferably 5 μm or more, and even more preferably 7 μm or more. It is also preferably 250 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and even more preferably 20 μm or less. A thickness within the above range enables practical use as an insulating film. The thickness of the polyimide film can be easily controlled by adjusting the solids concentration and viscosity of the varnish.

[0071] The polyimide film of the present invention preferably has the following physical properties. When the polyimide film of the present invention satisfies the following physical properties, it has excellent heat resistance. The glass transition temperature (Tg) is preferably 300°C or higher, more preferably 330°C or higher, even more preferably 350°C or higher, still more preferably 400°C or higher, even more preferably 420°C or higher, and still more preferably 422°C or higher. The above-mentioned glass transition temperature in the present invention can be specifically measured by the method described in the examples.

[0072] The polyimide film of the present invention has the excellent properties described above and can be used in a variety of applications, and is particularly suitable as a film for various members of semiconductor components, particularly as an insulating film for semiconductors.

[0073] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples in any way.

[0074] [Physical Properties and Evaluation of Varnish and Polyimide Film] The physical properties and evaluation of the varnishes and polyimide films obtained in the Examples and Comparative Examples were performed using the methods described below. (1) Stability of Varnish The stability of the varnishes obtained in the Examples and Comparative Examples was evaluated based on the rate of change in viscosity of the varnish before and after storage. Within 24 hours after production of the varnishes produced by the methods of the Examples and Comparative Examples, the viscosity at 25°C (viscosity before storage) was measured using an E-type viscometer (TVE-25H, manufactured by Toki Sangyo Co., Ltd.). The varnishes were then allowed to stand at -15°C for one month. Thereafter, the viscosity at 25°C (viscosity after storage) was measured in the same manner as above. The rate of viscosity change (%) is the absolute value of the difference between the viscosity after storage and the viscosity before storage divided by the viscosity before storage. The smaller the rate of viscosity change, the more stable the varnish. The stability of the varnish was evaluated using the following criteria. (Evaluation Criteria) ⊚: The rate of viscosity change is less than 5%. ◯: The rate of viscosity change is 5% or more but less than 10%. ×: The viscosity change rate is 10% or more, or there is no fluidity and the viscosity cannot be measured.

[0075] (2) Rinsing Suitability of Varnish The varnishes obtained in the Examples and Comparative Examples were spin-coated (applied) onto 4-inch silicon wafers (substrates) using a spin coater (MS-B200, manufactured by Mikasa Co., Ltd.) so that the thickness (thickness due to solids) after drying was 1 μm. Next, the rinse liquid outlet was adjusted so that the silicon wafer was rinsed within a 5 mm width from the outer periphery, and edge rinsing was performed at 1,000 rpm for 30 seconds using PGME or cyclopentanone as the rinse liquid. The substrate was then dried on a hot plate at 80°C until the coated surface became tack-free, and the rinsing success (rinsing suitability) was evaluated visually. The evaluation criteria were as follows. A sample that could be rinsed with either rinse liquid was suitable for rinsing and was preferred. (Evaluation Criteria) ∘: A 5 mm range from the outer periphery was rinsed whether or not PGME or cyclopentanone was used as the rinse liquid. △: When either PGME or cyclopentanone was used as the rinse solution, the area within 5 mm from the periphery was rinsed, but when the other solvent was used, the area within 5 mm from the periphery was not rinsed. ×: When either PGME or cyclopentanone was used as the rinse solution, the area within 5 mm from the periphery was not rinsed.

[0076] (3) Heat Resistance of Film (Glass Transition Temperature (Tg)) Using a thermomechanical analyzer "TMA 7100C" manufactured by Hitachi High-Tech Science Corporation, TMA measurement was performed using a sample size of 4 mm x 20 mm, in tensile mode, with a load of 50 mN and a heating rate of 10°C / min, raising the temperature from 40°C to 500°C, and the point at which an inflection point of elongation was observed was extrapolated to determine the glass transition temperature (Tg). The higher the glass transition temperature (Tg), the better the heat resistance.

[0077] The tetracarboxylic acid components, diamine components, solvents and their abbreviations used in the examples and comparative examples are as follows: <Tetracarboxylic acid component> DSDA: 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (manufactured by ChinaTech Chemical (Tianjin) Co., Ltd., compound represented by formula (a111)) PMDA: pyromellitic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd., compound represented by formula (a2)) BP-TME: 4,4-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (compound represented by formula (a3), n is 2) <Diamine component> 4-BAAB: 4-aminophenyl-4-aminobenzoate (manufactured by Nihon Junryo Pharmaceutical Co., Ltd., compound represented by formula (b1)) <Solvent> DMI: 1,3-dimethyl-2-imidazolidinone (boiling point 222°C, manufactured by Mitsui Chemicals, Inc.) GBL: γ-butyrolactone (boiling point 204°C, manufactured by Mitsubishi Chemical Corporation) PGME: propylene glycol monomethyl ether (boiling point 120°C, manufactured by Kanto Chemical Co., Ltd.) NMP: N-methylpyrrolidone (boiling point 204°C)

[0078] [Production of Polyimide Resin Precursor Varnish and Polyimide Film] Example 1 Into a 1 L five-necked round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap, 22.825 g (0.100 mol) of 4-BAAB and 269.894 g of DMI were added, and the system temperature was 50 ° C. under a nitrogen atmosphere, and the stirring was carried out at 200 rpm to obtain a solution. 35.828 g (0.100 mol) of DSDA and 66.473 g of DMI were added to this solution, and the mixture was stirred for 3 hours while maintaining the temperature at 50 ° C. with a mantle heater. Thereafter, 195.510 g of PGME was added to a solids concentration of 10% by mass, and the mixture was stirred until uniform, obtaining a polyimide resin precursor (polyamic acid) varnish having a solids concentration of 10% by mass. The solvent ratios in the varnish were 63.0% by mass of DMI and 37.0% by mass of PGME. The evaluation results are shown in Table 1. The resulting polyamic acid varnish was then applied to a support substrate (support, 4-inch silicon wafer) so that the thickness after drying (thickness based on solid content) was 10 μm, and the coating was held at 80°C on a hot plate for 20 minutes. Thereafter, the coating was heated to 400°C at a heating rate of 5°C / min in a nitrogen atmosphere in a hot air dryer, and heated at 400°C for 60 minutes to evaporate the solvent and thermally imidize the coating to obtain a polyimide film. The evaluation results are shown in Table 1.

[0079] Examples 2 to 8 and Comparative Examples 1 to 4 A polyimide resin precursor (polyamic acid) varnish with a solids concentration of 10% by mass was obtained in the same manner as in Example 1, except that the type and amount of the tetracarboxylic acid component, diamine component, and solvent were changed as shown in Table 1 or Table 2. The solvent ratio in the varnish is as shown in Table 1 or Table 2. The evaluation results of the varnish are shown in Tables 1 and 2. In Comparative Example 3, the obtained varnish had a very high viscosity and no fluidity, so evaluation of rinsability and production of a polyimide film were not performed. Further, a polyimide film was obtained in the same manner as in Example 1. The evaluation results of the film are shown in Tables 1 and 2.

[0080]

[0081]

[0082] As shown in Tables 1 and 2, it can be seen that the polyimide resin precursor varnishes of the Examples have good rinsability. Furthermore, it can be seen that the polyimide films obtained from the polyimide resin precursors of the Examples have high glass transition temperatures and therefore excellent heat resistance. Furthermore, it can be seen that the polyimide resin precursor varnishes of the Examples also have excellent stability. From this, it can be seen that the polyimide resin precursor varnish of the present invention has excellent rinsability and can produce polyimide films with excellent heat resistance. Furthermore, the polyimide resin precursor varnish of the present invention also has excellent stability. Therefore, the polyimide resin precursor varnish and polyimide film of the present invention are useful as raw materials in the semiconductor field.

Claims

1. A polyimide resin precursor varnish comprising a polyimide resin precursor having a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine, and a solvent, wherein the structural unit A comprises structural unit (A1), which is at least one selected from the group consisting of a structural unit (A11) derived from a compound represented by the following formula (a11) and a structural unit (A12) derived from a compound represented by the following formula (a12), and the structural unit B comprises structural unit (B1) derived from a compound represented by the following formula (b1), and the solvent comprises a solvent (S1) having a boiling point of 190 to 250°C and a solvent (S2) having a boiling point of 110 to 160°C. (In formula (a11), X represents a single bond, an ether group, a carbonyl group, a sulfone group, a sulfide group, a phenylene group, an oxyphenyl ether group, a bisphenoxyfluorene group, or a fluorenylidene group. In formula (a12), Y represents a hexafluoroisopropylidene group or a fluorenylidene group.) 2. The polyimide resin precursor varnish according to claim 1, wherein the solvent (S1) is 1,3-dimethyl-2-imidazolidinone, and the solvent (S2) is at least one selected from the group consisting of propylene glycol monomethyl ether, cyclohexanone, and cyclopentanone.

3. The polyimide resin precursor varnish according to claim 1 or 2, wherein the structural unit A includes a structural unit (A111) derived from a compound represented by the following formula (a111):

4. The polyimide resin precursor varnish according to any one of claims 1 to 3, wherein the solvent comprises propylene glycol monomethyl ether.

5. A polyimide resin precursor varnish according to any one of claims 1 to 4, wherein the proportion of the structural unit (A1) in the structural unit A is 30 to 100 mol %.

6. The polyimide resin precursor varnish according to any one of claims 1 to 5, wherein the structural unit A further comprises at least one selected from the group consisting of a structural unit (A2) derived from a compound represented by the following formula (a2), a structural unit (A3) derived from a compound represented by the following formula (a3), and a structural unit (A4) derived from a compound represented by the following formula (a4): (In formula (a3), n is 1 or 2.) 7. The polyimide resin precursor varnish according to claim 6, wherein the molar ratio of the structural unit (A1) in structural unit A to the sum of the structural units (A2), (A3) and (A4) [(A1) / ((A2)+(A3)+(A4))] is 30 / 70 to 100 / 0.

8. A polyimide resin precursor varnish according to any one of claims 1 to 7, wherein the total content of solvent (S1) and solvent (S2) in the solvent is 50 mass% or more relative to the total amount of the solvent.

9. The polyimide resin precursor varnish according to any one of claims 1 to 8, wherein the mass ratio [(S1) / (S2)] of the content of solvent (S1) to the content of solvent (S2) in the solvent is 30 / 70 to 90 / 10.

10. The polyimide resin precursor varnish according to any one of claims 1 to 9, wherein the proportion of the structural unit (B1) in the structural unit B is 30 to 100 mol %.

11. A polyimide film obtained by applying the polyimide resin precursor varnish according to any one of claims 1 to 10 onto a support and heating the applied coating.

12. The polyimide film according to claim 11, having a glass transition temperature of 300°C or higher.

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