Polyimide resin, varnish, and polyimide film

Abstract

A polyimide resin having a constituent unit A derived from tetracarboxylic dianhydride and a constituent unit B derived from diamine, wherein constituent unit A comprises a constituent unit (A1) selected from at least one constituent unit (A11) of a compound represented by formula (a11) and a constituent unit (A12) of a compound represented by formula (a12), and constituent unit (A2) of a compound represented by formula (a2), and constituent unit B comprises a constituent unit (B1) of a compound represented by formula (b1).

Description

Technical Field

[0001] This invention relates to polyimide resins, varnishes, and polyimide films. Prior Technology

[0002] Polyimide resins possess excellent mechanical properties, leading to research into their various applications in electrical and electronic components. For example, with the aim of reducing device weight and increasing flexibility, there is a desire to replace glass substrates used in image display devices such as LCDs and OLEDs with plastic substrates. Research is also underway to identify suitable polyimide resins for these plastic materials. For such applications, polyimide resins require transparency, and furthermore, high heat resistance to withstand the high-temperature processing involved in the manufacturing of image display devices.

[0003] Furthermore, in recent years, laser peeling (LLO), a method for separating the support from the resin film in a support structure with laminated resin films, has attracted attention in the field of microelectronics. To enable polyimide films to undergo laser peeling, the development of polyimide films with excellent laser peeling properties is underway.

[0004] For example, Patent Document 1 discloses a polyimide resin containing units derived from norcamphene-2-spiro-α-cyclopentanone-α'-spiro-2''-norcamphene-5,5'',6,6''-tetracarboxylic acid dianhydride and units derived from 2,2'-bis(trifluoromethyl)benzidine, with the aim of improving mechanical properties, heat resistance, transparency, dimensional stability, and laser peelability. [Previous Technical Documents] [Patent Literature]

[0005] [Patent Document 1] International Publication No. 2019 / 065523 Summary of the Invention

[0006] [The problem that the invention aims to solve]

[0007] For polyimide films used in image display devices, good optical properties such as colorlessness and transparency are required. As mentioned above, high heat resistance is also required to withstand the high-temperature processing in the manufacturing process of image display devices. In particular, LTPS (Low Temperature Polycrystalline Silicon TFT) devices have processing temperatures exceeding 400°C, requiring the polyimide substrate to withstand multiple processing at temperatures above 400°C. High glass transition temperature and decomposition temperature indicate excellent heat resistance in the short term. However, in order to withstand multiple or prolonged high-temperature treatments as described above, polyimide films with minimal weight reduction during high-temperature treatment are required. Furthermore, in order to cope with laser stripping processes, laser stripping performance is also required. In particular, in order to cope with the stripping process performed by the XeCl excimer laser with a wavelength of 308nm, the polyimide film system is required to have excellent light absorption characteristics at a wavelength of 308nm (that is, low light transmittance at a wavelength of 308nm). Therefore, the object of the present invention is to provide polyimide resin, polyimide varnish, and polyimide film that can form films with excellent heat resistance, especially with minimal weight reduction during high-temperature processing and excellent laser peelability. [Methods for solving problems]

[0008] The inventors discovered that a polyimide resin containing a combination of constituent units from two specific tetracarboxylic dianhydrides and constituent units from a specific diamine can solve the above-mentioned problems, thus completing the present invention.

[0009] That is, the present invention relates to the following <1> ~ <18> . <1> A polyimide resin having a constituent unit A derived from tetracarboxylic dianhydride and a constituent unit B derived from diamine, wherein constituent unit A comprises a constituent unit (A1) selected from at least one of the groups consisting of constituent units (A11) derived from compounds represented by formula (a11) and constituent units (A12) derived from compounds represented by formula (a12), and a constituent unit (A2) derived from compounds represented by general formula (a2); and constituent unit B comprises a constituent unit (B1) derived from compounds represented by general formula (b1). [Chemistry 1] (In formula (b1), each of the R groups is independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, a trifluoromethyl group, or a hydroxyl group.) <2> like <1> The polyimide resin wherein the ratio of constituent unit (B1) in constituent unit B is 15 mol% or more. <3> like <1> or <2> The polyimide resin, wherein the constituent unit B further comprises a constituent unit (B2) from a compound represented by the following formula (b2); [Chemistry 2] <4> like <3> The polyimide resin, wherein the molar ratio [(B1) / (B2)] of the constituent unit (B1) and constituent unit (B2) in constituent unit B is 15 / 85 to 70 / 30. <5> like <1> ~ <4> The polyimide resin of any one of the following, wherein the constitutive unit (A11) comprises a constitutive unit (A111) from a compound represented by the following formula (a111); [Chemistry 3] <6> like <1> ~ <5> The polyimide resin of any one of the following, wherein the constituent unit (A2) comprises a constituent unit (A2s) from a compound represented by the following formula (a2s); [Chemistry 4] <7> like <1> ~ <6> The polyimide resin of any one of the following, wherein the constituent unit (B1) comprises a constituent unit (B11) from a compound represented by the following formula (b11); [Chemistry 5] <8> like <1> ~ <7> The polyimide resin of any one of the following, wherein the molar ratio of constituent unit (A1) to constituent unit (A2) in constituent unit A [(A1) / (A2)] is 30 / 70 to 85 / 15. <9> A type of varnish, such as <1> ~ <8> It is made by dissolving any one of the polyimide resins in an organic solvent. <10> A amide-amide copolymer comprising repeating units represented by formula (1) and repeating units represented by formula (2); [Chemistry 6] (In the formula, A1 is selected from at least one of the bases represented by the following formula (3) and the following formula (4), and A2 is the base represented by the following formula (5); B1 and B2 are divalent bases, and either B1 or B2 contains the base represented by the following equation (6); X1 and X2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. [Chemistry 7] <11> A type of varnish, such as <10> It is formed by dissolving aceimine-acetic acid copolymer in an organic solvent. <12> like <11> The varnish contains imidazole compounds represented by the following general formula (7). [Chemistry 8] (In formula (7), L1 and L2 are each independently hydrogen atoms, alkyl groups with 1 to 6 carbon atoms, carboxyl groups, and hydroxyl groups, and n is an integer from 1 to 4.) <13> A polyimide resin, which is made of... <10> It is formed by amide-imide copolymerization of amide-amide. <14> A polyimide film containing, for example <1> ~ <8> , <13> Polyimide resin of any one of the following. <15> like <14> The polyimide film exhibited a weight loss rate of less than 1.0% after being maintained at 430°C for 1 hour, and its glass transfer temperature was above 410°C. <16> like <14> or <15> Polyimide film is used as a transparent substrate for forming display devices. <17> A method for manufacturing a polyimide film, wherein the following steps are taken: <9> , <11> or <12> The clear varnish is applied to the support, and then heated. <18> An image display device, comprising such <14> ~ <16> Any of the following polyimide films can be used as transparent substrates. [Effects of the Invention]

[0010] According to the present invention, polyimide resin, polyimide varnish, and polyimide film with excellent heat resistance, especially with minimal weight reduction during high-temperature treatment and further excellent laser peelability can be provided. Implementation

[0011] [Polyimide resin] The polyimide resin of the present invention has a constituent unit A derived from tetracarboxylic dianhydride and a constituent unit B derived from diamine. The constituent unit A comprises a constituent unit (A1) selected from at least one of the constituent units (A11) of compounds represented by formula (a11) and constituent units (A12) of compounds represented by formula (a12), and a constituent unit (A2) of compounds represented by general formula (a2). The constituent unit B comprises a constituent unit (B1) of compounds represented by general formula (b1). [Chemistry 9] (In formula (b1), each of the R groups is independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, a trifluoromethyl group, or a hydroxyl group.)

[0012] Furthermore, although the reasons for the excellent heat resistance of the polyimide resin of the present invention, especially the small weight reduction during high-temperature treatment, have not yet been determined, they are believed to be as follows. It is believed that even if the carbon-carbon bonds in a portion of the polycyclic structure of the polyimide resin of this invention undergo homolytic cleavage due to heat, the resulting free radicals are still fixed in the matrix by multiple carbon atoms. Therefore, it is believed that rebonding will occur, resulting in a material that is less prone to decomposition. It is believed that this mechanism contributes to its excellent heat resistance. Furthermore, although the reason why the polyimide resin of the present invention can form a polyimide film with excellent laser peelability has not yet been determined, it is believed to be as follows. It is believed that the resin, derived from tetracarboxylic dianhydride, not only contains the constituent unit (A1), but also, more importantly, the constituent unit (A2) from the compound represented by formula (a2), thereby achieving a resin with high absorption at the irradiated laser wavelength, i.e., low transmittance. It is believed that the etching is therefore uniformly generated at the interface with the glass substrate, resulting in excellent laser ablation properties.

[0013] <Component A> Unit A is a constituent unit derived from tetracarboxylic dianhydride in polyimide resin. The constituent unit A includes at least one constituent unit (A1) selected from the group consisting of constituent units (A11) of compounds represented by the following formula (a11) and constituent units (A12) of compounds represented by the following formula (a12), and constituent units (A2) of compounds represented by the following general formula (a2). By including constituent units (A1) and (A2) in constituent unit A, the heat resistance of the film can be improved. In particular, it can suppress weight loss during high-temperature processing and further improve the laser peelability of the film. [Chemistry 10]

[0014] By including constituent unit (A1) in constituent unit A, the heat resistance of the film can be improved. In particular, it can suppress weight loss during high-temperature processing. The compound represented by formula (a11) is decahydro-1,4:5,8-dimethylbridged naphthalene-2,3,6,7-tetracarboxylic acid dianhydride (DNDA). By including constituent units (A11) in constituent unit A, transparency and heat resistance of the film can be improved. In particular, it can suppress weight loss during high-temperature processing. The compound represented by formula (a12) is bicyclooctane-2,3,5,6-tetracarboxylic anhydride (BODA). By including constituent units (A12) in constituent unit A, transparency and heat resistance of the film can be improved. In particular, it can suppress weight loss during high-temperature processing. The constituent unit (A1) should preferably contain constituent unit (A11), and more preferably be constituent unit (A11).

[0015] The constituent unit (A11) preferably includes a constituent unit (A111) from a compound represented by formula (a111), and more preferably a constituent unit (A111) from a compound represented by formula (a111). By including a constituent unit (A111) in the constituent unit (A111), transparency and heat resistance of the film can be improved. In particular, weight loss during high-temperature processing can be suppressed. Furthermore, the compound represented by formula (a111) is one of the stereoisomers of the compound represented by formula (a11). [Chemistry 11]

[0016] By including constituent unit (A2) in constituent unit A, the laser peelability of the film can be improved. The compound represented by formula (a2) is biphenyltetracarboxylic dianhydride (BPDA). Specific examples include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by formula (a2s), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by formula (a2a), and 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by formula (a2i). Preferably, it is 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by formula (a2s). That is, the constituent unit (A2) preferably includes the constituent unit (A2s) of the compound represented by the following formula (a2s), and more preferably the constituent unit (A2s) of the compound represented by the following formula (a2s). [Chemistry 12]

[0017] The molar ratio [(A1) / (A2)] of constituent unit A between constituent unit (A1) and constituent unit (A2) is preferably 30 / 70 to 85 / 15, more preferably 50 / 50 to 85 / 15, further preferably 55 / 45 to 85 / 15, and even more preferably 55 / 45 to 65 / 35. By achieving this molar ratio, transparency and the heat resistance of the film can be improved. In particular, it can suppress weight loss during high-temperature processing.

[0018] The ratio of constituent units (A1) in constituent unit A is preferably 30-85 mol%, more preferably 50-85 mol%, further preferably 55-85 mol%, and even more preferably 55-65 mol%. The ratio of constituent units (A2) in constituent unit A is preferably 15-70 mol%, more preferably 15-50 mol%, further preferably 15-45 mol%, and even more preferably 35-45 mol. The ratio of the total of constituent units (A1) and constituent units (A2) in constituent unit A should preferably be 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and preferably 100 mol% or less. Constituent unit A may also be composed solely of constituent units (A1) and constituent units (A2).

[0019] Constituent unit A may also include constituent units other than constituent units (A1) and (A2). There are no particular limitations on the tetracarboxylic dianhydrides given such constituent units, but examples include aromatic tetracarboxylic dianhydrides of compounds excluding those represented by formula (a2), alicyclic tetracarboxylic dianhydrides of compounds excluding those represented by formula (a11) and (a12), and aliphatic tetracarboxylic dianhydrides. Furthermore, in this specification, aromatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride containing one or more alicyclic rings but without aromatic rings, and aliphatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride without either aromatic or alicyclic rings. Constituent A may contain one or more constituent units.

[0020] <Component Unit B> Unit B is a diamine-derived unit that constitutes a portion of the polyimide resin. Constituent B contains constituents (B1) from the compound represented by the following formula (b1). [Chemistry 13] (In formula (b1), each of the R groups is independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, a trifluoromethyl group, or a hydroxyl group.)

[0021] By including constituent unit (B1) in constituent unit B, the heat resistance of the film can be improved. In particular, it can suppress weight loss during high-temperature processing, and further improve the laser peelability and optical isotropy of the film. In formula (b1), each R is independently selected from at least one group consisting of hydrogen atoms, fluorine atoms, alkyl groups having 1 to 5 carbon atoms, trifluoromethyl groups, and hydroxyl groups, preferably a hydrogen atom. Specific examples of compounds represented by formula (b1) include 9,9-bis(4-aminophenyl)furan, 9,9-bis(3-fluoro-4-aminophenyl)furan, and 9,9-bis(3-methyl-4-aminophenyl)furan, preferably 9,9-bis(4-aminophenyl)furan (BAFL) represented by formula (b11). That is, the constitutive unit (B1) preferably includes the constitutive unit (B11) of the compound represented by formula (b11), and more preferably the constitutive unit (B11) is the constitutive unit (B11) of the compound represented by formula (b11). [Chemistry 14]

[0022] The proportion of constituent units (B1) in constituent unit B should preferably be 15 moles or more, more preferably 30 moles or more, and considering the laser peelability and heat resistance of the film, it should preferably be 50 moles or more, further preferably 70 moles or more, even further preferably 80 moles or more, even further preferably 90 moles or more, even further preferably 95 moles or more, and in addition, it should preferably be 100 moles or less. Constituent unit B may also be composed solely of constituent units (B1).

[0023] Constituent B may consist solely of constituent (B1), or may include constituents other than constituent (B1), preferably constituents other than constituent (B1), and further includes constituent (B2) from compounds represented by the following formula (b2). [Chemistry 15] The compound represented by formula (b2) is 2,2'-bis(trifluoromethyl)benzidine (TFMB). By including the constituent unit (B2) in the constituent unit B, transparency can be improved while maintaining heat resistance.

[0024] When constituent unit B contains constituent unit (B2), the molar ratio [(B1) / (B2)] of constituent unit B to constituent unit (B2) is preferably 15 / 85 to 70 / 30, more preferably 15 / 85 to 50 / 50, further preferably 30 / 70 to 50 / 50, and even more preferably 30 / 70 to 45 / 55. By achieving this molar ratio, the heat resistance and laser peelability of the film can be improved, and the transparency can also be improved.

[0025] When constituent unit B contains constituent unit (B2), the ratio of constituent unit (B1) in constituent unit B is preferably 15-70 mol%, more preferably 15-50 mol%, further preferably 30-50 mol%, and even more preferably 30-45 mol. The ratio of constituent units (B2) in constituent unit B is preferably 30-85 mol%, more preferably 50-85 mol%, further preferably 50-70 mol%, and even more preferably 55-70 mol. The total ratio of constituent units (B1) and constituent units (B2) in constituent unit B should preferably be 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and preferably less than 100 mol%. Constituent unit B may also be composed solely of constituent units (B1) and constituent units (B2).

[0026] Constituent unit B may also include constituent units other than constituent units (B1) and (B2). There are no particular limitations on diamines given such constituent units, but compounds represented by formula (b11) and compounds represented by formula (b2) are excluded, including aromatic diamines, alicyclic diamines and aliphatic diamines. Furthermore, in this specification, aromatic diamines refer to diamines containing one or more aromatic rings, alicyclic diamines refer to diamines containing one or more alicyclic rings but without aromatic rings, and aliphatic diamines refer to diamines without aromatic rings and without alicyclic rings. The constituent unit B may contain one or more constituent units other than constituent unit (B1) and constituent unit (B2).

[0027] Properties of Polyimide Resins The number average molecular weight of the polyimide resin, considering the mechanical strength of the obtained polyimide film, should preferably be between 5,000 and 300,000. Furthermore, the number average molecular weight of the polyimide resin can be obtained, for example, by using a standard polymethyl methacrylate (PMMA) conversion value determined by gel filtration chromatography.

[0028] Polyimide resins may also contain structures other than polyimide chains (structures formed by amide bonds between constituent units A and B). Examples of structures other than polyimide chains that may be present in polyimide resins include structures containing amide bonds. Polyimide resins preferably contain polyimide chains (structures formed by the amide bonding of constituent unit A and constituent unit B) as their main structure. Therefore, the proportion of polyimide chains in the polyimide resin is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and further preferably 99% by mass or more. Furthermore, it is preferably 100% by mass or less. Polyimide resins may also consist solely of polyimide chains.

[0029] [Manufacturing method of polyimide resin] The manufacturing method of the polyimide resin of the present invention is not particularly limited and can be either of the two methods described below. The first manufacturing method of the present invention is a method for obtaining polyimide resin by reacting the compound (tetracarboxylic acid component) that provides constituent unit A with the compound (diamine component) that provides constituent unit B. By this method, polyimide resin can be obtained directly from the tetracarboxylic acid component and the diamine component. The second manufacturing method of the present invention is to amide the amide site in an amide-amide copolymer having amide repeating structural units and amide repeating structural units, thereby obtaining a polyamide resin. The following explains each method.

[0030] <First Method for Manufacturing Polyimide Resin> According to this manufacturing method, polyimide resin can be manufactured by reacting the tetracarboxylic acid component containing the compound that provides the constituent unit (A1) and the compound that provides the constituent unit (A2) with the diamine component containing the compound that provides the constituent unit (B1).

[0031] Regarding compounds given the constituent unit (A1), compounds represented by formula (a11) and formula (a12) can be listed, but are not limited to these; derivatives thereof may also be given within the scope of compounds given the same constituent unit. Regarding such derivatives, tetracarboxylic acids corresponding to tetracarboxylic dianhydrides represented by formula (a11) and alkyl esters of such tetracarboxylic acids can be listed. Among these, tetracarboxylic dianhydrides represented by formula (a11) are preferred. Furthermore, as such derivatives, tetracarboxylic acids corresponding to tetracarboxylic dianhydrides represented by formula (a12) and alkyl esters of such tetracarboxylic acids can be listed. Among these, tetracarboxylic dianhydrides represented by formula (a12) are preferred.

[0032] Similarly, for compounds given the constitutive unit (A2), compounds represented by formula (a2) can be listed, but are not limited to these, and derivatives thereof may also be included within the scope of compounds given the same constitutive unit. For such derivatives, tetracarboxylic acids corresponding to tetracarboxylic dianhydrides represented by formula (a2) and alkyl esters of such tetracarboxylic acids can be listed. Among these, tetracarboxylic dianhydrides represented by formula (a2) are preferred.

[0033] The molar ratio [(A1) / (A2)] of the tetracarboxylic acid component, which is the ratio of the compound that gives the constituent unit (A1) to the compound that gives the constituent unit (A2), is preferably 30 / 70 to 85 / 15, more preferably 50 / 50 to 85 / 15, further preferably 55 / 45 to 85 / 15, and even more preferably 55 / 45 to 65 / 35.

[0034] The ratio of the compound that gives the constituent unit (A1) in the tetracarboxylic acid component is preferably 30-85 mol, more preferably 50-85 mol, further preferably 55-85 mol, and even more preferably 55-65 mol. The ratio of the compound that gives the constituent unit (A2) in the tetracarboxylic acid component is preferably 15-70 mol, more preferably 15-50 mol, further preferably 15-45 mol, and even more preferably 35-45 mol. The total ratio of the compounds of donor unit (A1) and donor unit (A2) in the tetracarboxylic acid component should preferably be 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and preferably less than 100 mol%. The tetracarboxylic acid component may also consist solely of compounds of donor unit (A1) and donor unit (A2).

[0035] The tetracarboxylic acid component may also contain tetracarboxylic dianhydrides other than compounds that provide the constituent unit (A1) and compounds that provide the constituent unit (A2). There are no particular limitations on such tetracarboxylic dianhydrides, but examples include aromatic tetracarboxylic dianhydrides that exclude compounds represented by formula (a2), alicyclic tetracarboxylic dianhydrides that exclude compounds represented by formula (a11) and alicyclic tetracarboxylic dianhydrides that exclude compounds represented by formula (a12), and aliphatic tetracarboxylic dianhydrides. The tetracarboxylic acid component may contain one or more tetracarboxylic acid dianhydrides.

[0036] As a compound that provides the constituent unit (B1), compounds represented by formula (b1) can be listed, but are not limited to these, and derivatives thereof may also be listed within the range where the same constituent unit can be provided. As such derivatives, diisocyanates corresponding to compounds (diamines) represented by formula (b1) can be listed. Among them, it is preferable to be a compound represented by formula (b1) (i.e., a diamine).

[0037] The proportion of the compound that provides the constituent unit (B1) in the diamine component should preferably be 15 mol% or more, more preferably 30 mol% or more, further preferably 50 mol% or more, further preferably 70 mol% or more, further preferably 80 mol% or more, further preferably 90 mol% or more, further preferably 95 mol% or more, and preferably less than 100 mol%. The diamine component may also consist solely of the compound that provides the constituent unit (B1).

[0038] The diamine component may also contain a compound other than the compound that gives the constituent unit (B1), and preferably contains a compound that gives the constituent unit (B2) of the compound represented by formula (b2).

[0039] When the diamine component contains a compound that provides a constituent unit (B2), the molar ratio [(B1) / (B2)] of the compound providing a constituent unit (B1) to the compound providing a constituent unit (B2) in the diamine component is preferably 15 / 85 to 70 / 30, more preferably 15 / 85 to 50 / 50, even more preferably 30 / 70 to 50 / 50, and even more preferably 30 / 70 to 45 / 55.

[0040] When the diamine component contains a compound that provides a constituent unit (B2), the ratio of the compound that provides a constituent unit (B1) in the diamine component is preferably 15 to 70 mol%, more preferably 15 to 50 mol%, further preferably 30 to 50 mol%, and even more preferably 30 to 45 mol. The ratio of the compound that gives the constituent unit (B2) in the diamine component is preferably 30-85 mol, more preferably 50-85 mol, further preferably 50-70 mol, and even more preferably 55-70 mol. The ratio of the compound representing the constituent unit (B1) and the compound representing the constituent unit (B2) in the diamine component should preferably be 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and preferably 100 mol% or less. The diamine component may also consist solely of the compound representing the constituent unit (B1) and the compound representing the constituent unit (B2).

[0041] The diamine component may also include diamines other than those that provide the constituent unit (B1) and those that provide the constituent unit (B2). There are no particular limitations on the diamines that provide such constituent units, but compounds represented by formula (b11) and compounds represented by formula (b2) are excluded, as are aromatic diamines, alicyclic diamines, and aliphatic diamines. The diamine component may contain any diamine other than the constituent unit (B1) and the constituent unit (B2), and may be one or more types.

[0042] In this invention, the ratio of tetracarboxylic acid component to diamine component used in the manufacture of polyimide resin is preferably 0.9 to 1.1 mol of diamine component relative to 1 mol of tetracarboxylic acid component.

[0043] Furthermore, in the manufacture of polyimide resin in this invention, in addition to the aforementioned tetracarboxylic acid component and diamine component, a capping agent may also be used. The capping agent is preferably a monoamine or a dicarboxylic acid. Regarding the amount of capping agent added, it is preferably 0.0001 to 0.1 mol relative to 1 mol of tetracarboxylic acid component, and more preferably 0.001 to 0.06 mol. Examples of monoamine capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline, with benzylamine and aniline being preferred. Regarding dicarboxylic acid capping agents, dicarboxylic acids are preferred, and a portion of them may also be cyclic-closed. Examples include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid, with phthalic acid and phthalic anhydride being the most suitable.

[0044] The above method for reacting the tetracarboxylic acid component with the diamine component has no particular limitations and known methods can be used. In terms of specific reaction methods, the following can be listed: (1) adding tetracarboxylic acid, diamine and reaction solvent into the reactor, stirring at 0~80℃ for 0.5~30 hours, and then raising the temperature to carry out acetilimation reaction; (2) adding diamine and reaction solvent into the reactor to dissolve them, then adding tetracarboxylic acid, stirring at room temperature (0~80℃) for 0.5~30 hours as needed, and then raising the temperature to carry out acetilimation reaction; (3) adding tetracarboxylic acid, diamine and reaction solvent into the reactor, and immediately raising the temperature to carry out acetilimation reaction, etc.

[0045] The reaction solvent used in the manufacture of polyimide resin should be one that does not interfere with the amide reaction and can dissolve the resulting polyimide. Examples of suitable solvents include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0046] Specific examples of aprotic solvents include acetylamines such as N,N-dimethylformamide, N,N-dimethylacetylamine, N-methyl-2-pyrrolidone (NMP), N-methylcaprolactam, 1,3-dimethylimidazolidine, and tetramethylurea; lactones such as γ-butyrolactone (GBL) and γ-valerolactone; phosphorus-containing acetylamines such as hexamethylphosphonamide and hexamethylphosphinetriamine; sulfur-containing solvents such as dimethyl sulfoxide, dimethyl sulfoxide, and cyclobutane; ketones such as acetone, cyclohexanone, and methylcyclohexanone; amines such as methylpyridine and pyridine; and esters such as acetic acid (2-methoxy-1-methylethyl ester).

[0047] Specific examples of phenolic 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-based solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl] ether, tetrahydrofuran, 1,4-dimethoxyethane, etc. In addition, specific examples of carbonate-based solvents include diethyl carbonate, methyl ethyl carbonate, ethyl carbonate, and propyl carbonate. The solvents used in the above reactions are preferably aprotic solvents, and more preferably amide-based and lactone-based solvents. Furthermore, the above reaction solvents can be used alone or in combination of two or more.

[0048] The amide reaction is best performed using a Dean-Stark apparatus or similar device, where water generated during manufacturing is removed simultaneously. This process can further enhance the degree of polymerization and the amide rate.

[0049] In the above amide imidization reaction, known amide imidization catalysts can be used. Examples of amide imidization catalysts include base catalysts and acid catalysts. Regarding alkaline catalysts, examples include organic alkaline catalysts such as pyridine, quinoline, isoquinoline, α-methylpyridine, β-methylpyridine, 2,4-dimethylpyridine, 2,6-dimethylpyridine, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline, as well as inorganic alkaline catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate. In addition, examples of acid catalysts include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. These aceimide catalysts can be used alone or in combination of two or more. From an operability perspective, alkaline catalysts are preferred, organic alkaline catalysts are more preferred, and at least one catalyst selected from the group consisting of triethylamine and triethylenediamine is even more preferred.

[0050] Considering the reaction rate and the need to inhibit gelation, the optimal temperature for the acetilimation reaction is 120–250 °C, and more preferably 160–200 °C. Furthermore, the reaction time, starting from the distillation of the generated water, should be 0.5–10 hours.

[0051] <Manufacturing Methods of Polyimide Varnish and Polyimide Film> The polyimide varnish of this invention is formed by dissolving the polyimide resin of this invention in an organic solvent. That is, the polyimide varnish of this invention contains the polyimide resin of this invention and an organic solvent, wherein the polyimide resin is dissolved in the organic solvent. Any organic solvent that can dissolve polyimide resin is acceptable; there are no particular restrictions. It is ideal to use the aforementioned compounds, which are used as reaction solvents in the manufacture of polyimide resin, either alone or in combination of two or more. The polyimide varnish of the present invention can be a polyimide solution obtained by dissolving polyimide resin obtained by polymerization in a reaction solvent, or it can be obtained by further diluting the polyimide solution with a solvent.

[0052] The polyimide resin of this invention has solvent solubility, thus it can be formulated into a high-concentration varnish that is stable at room temperature. The polyimide varnish of this invention preferably contains 5-40% by mass of the polyimide resin of this invention, more preferably 10-30% by mass. The viscosity of the polyimide varnish is preferably 1-200 Pa·s, more preferably 1-100 Pa·s. The viscosity of the polyimide varnish is measured using an E-type viscometer at 25°C. Furthermore, the polyimide varnish of the present invention may also contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, ultraviolet stabilizers, surfactants, leveling agents, defoamers, fluorescent whitening agents, crosslinking agents, polymerization initiators, and photosensitizers, without impairing the required properties of the polyimide film. The manufacturing method of the polyimide varnish of the present invention is not particularly limited, and known methods can be used.

[0053] The manufacturing method of the polyimide film of the present invention is not particularly limited, and known methods can be used. For example, a method of applying the varnish of the present invention onto a support and then heating it can be used. Specifically, methods such as applying the varnish onto a smooth support such as a glass plate, metal plate, or plastic, and then removing organic solvents such as reaction solvents and diluents contained in the varnish by heating can be listed.

[0054] In terms of coating methods, well-known methods such as spin coating, slot coating, and blade coating can be listed. Among them, slot coating is considered more ideal from the perspective of controlling the intermolecular orientation and improving chemical resistance and workability. Regarding the method of removing organic solvents from varnish by heating, it is advisable to evaporate the organic solvents to a temperature below 150°C until they become non-sticky, and then dry them at a temperature above the boiling point of the organic solvent used (without particular limitation, preferably 200~500°C). Furthermore, drying is preferably carried out in an air environment or a nitrogen environment. The pressure of the drying environment can be any of reduced pressure, normal pressure, or pressurized pressure. There are no particular limitations on the method for peeling the polyimide film formed on the support from the support. Examples include laser peeling, using a peeling sacrifice layer (pre-coating the surface of the support with a release agent), and adding a release agent.

[0055] <Second Method for Manufacturing Polyimide Resin> According to this manufacturing method, a polyimide resin can be obtained by amide-imidizing the amide site in a amide-amide copolymer having amide repeating structural units and amide repeating structural units. The obtained polyimide resin is the polyimide resin described in the above-mentioned [polyimide resin] section, and the ideal range is also the same. The above-mentioned amide-amide copolymer will be described below.

[0056] <Nimoimine-Nimosine Copolymer> The amide-amide copolymer of the present invention used in this manufacturing method is a precursor of polyamide resin and preferably includes repeating units represented by formula (1) and repeating units represented by formula (2). [Chemistry 16] (In the formula, A1 is selected from at least one of the groups consisting of the basis represented by the following formula (3) and the basis represented by the following formula (4), and A2 is the basis represented by the following formula (5). B1 and B2 are divalent bases, and either B1 or B2 contains the base represented by equation (6). [Chemistry 17]

[0057] In equation (1), A1 is selected from at least one of the groups consisting of the basis represented by equation (3) and the basis represented by equation (4), preferably including the basis represented by equation (3), and more preferably the basis represented by equation (3). In formulas (1) and (2), B1 and B2 are divalent groups, preferably divalent hydrocarbon groups that can be substituted, and more preferably divalent aromatic hydrocarbon groups that can be substituted. Either B1 or B2 contains a group represented by formula (6), preferably B2 contains a group represented by formula (6), and more preferably both B1 and B2 contain a group represented by formula (6). Furthermore, it is more preferable that B2 is a group represented by formula (6). In formula (2), X1 and X2 are each independently a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, or an alkylsilyl group with 3 to 9 carbon atoms.

[0058] The mole ratio [(1) / (2)] between the repeating unit represented by equation (1) and the repeating unit represented by equation (2) should be 5 / 95 to 60 / 40.

[0059] (Method for manufacturing amide-amide copolymer) The aforementioned aceimine-acetic acid copolymer is preferably manufactured by a method comprising steps 1 and 2 described below. Step 1: React the tetracarboxylic acid component of the repeating unit represented by formula (1) with the diamine component to obtain an oligomer with a repeating amide structural unit. Step 2: React the oligomer obtained in Step 1 with the tetracarboxylic acid component and the diamine component of the repeating unit represented by formula (2) to obtain a amide-amide copolymer having amide repeating structural units and amide repeating structural units. By means of the manufacturing method having the above steps 1 and 2, a copolymer that can form a polyimide film with excellent heat resistance, especially with small weight loss during high-temperature treatment, and further excellent laser peelability can be manufactured. The following describes the manufacturing method of aceimine-acetic acid copolymer.

[0060] (Tetracarboxylic acid and diamine components) The tetracarboxylic acid component of the repeating unit represented by formula (1) comprises at least one selected from the group consisting of compounds represented by formula (a11) and compounds represented by formula (a12). The tetracarboxylic acid component of the repeating unit represented by formula (1) preferably comprises a compound represented by formula (a11). More preferably, the tetracarboxylic acid component of the repeating unit represented by formula (1) is selected from the group consisting of compounds represented by formula (a11) and compounds represented by formula (a12), and more preferably is a compound represented by formula (a11). The compound represented by formula (a11) should preferably include the compound represented by formula (a111), and more preferably be the compound represented by formula (a111).

[0061] The diamine component of the repeating unit represented by formula (1) is not limited, but preferably includes at least one selected from the group consisting of compounds represented by formula (b1) and compounds represented by formula (b2), more preferably including compounds represented by formula (b1), and even more preferably compounds represented by formula (b1). The tetracarboxylic acid component and the diamine component of the repeating unit represented by formula (1) may also contain tetracarboxylic acid dianhydride and diamine other than the above-mentioned compounds, without impairing the effect of the present invention.

[0062] The tetracarboxylic acid component of the repeating unit represented by formula (2) includes the compound represented by formula (a2). The tetracarboxylic acid component of the repeating unit represented by formula (2) should preferably be the compound represented by formula (a2). The compound represented by formula (a2) should preferably include the compound represented by formula (a2s), and more preferably the compound represented by formula (a2s).

[0063] The diamine component of the repeating unit represented by formula (2) is not limited, but preferably includes at least one selected from the group consisting of the compound represented by formula (b1) and the compound represented by formula (b2), more preferably including the compound represented by formula (b1), further preferably including the compound represented by formula (b1) and the compound represented by formula (b2), and even more preferably including the compound represented by formula (b1) and the compound represented by formula (b2). The tetracarboxylic acid component and the diamine component of the repeating unit represented by formula (2) may also contain tetracarboxylic acid dianhydride and diamine other than the above-mentioned compounds, without impairing the effect of the present invention.

[0064] (solvent) The solvent used in the manufacture of the above copolymers may be any solvent capable of dissolving the resulting copolymers. Specific examples of reaction solvents are as described above in the section on [polyimide resins]. 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 mixtures of two or more.

[0065] (Step 1) Step 1 is a step of reacting the tetracarboxylic acid component of the repeating unit represented by formula (1) with the diamine component to obtain an oligomer having a repeating amide structural unit. The tetracarboxylic acid component used in step 1 contains a tetracarboxylic acid component that constitutes the repeating unit represented by the above formula (1). The diamine component used in step 1 is a diamine component containing a repeating unit represented by formula (1). The ratio of the components used in step 1 is the molar ratio of the diamine component to the tetracarboxylic acid component (diamine / tetracarboxylic acid), which is preferably 0.9 to 2 moles, more preferably 1.01 to 2 moles, further preferably 1.05 to 1.9 moles, and even more preferably 1.1 to 1.7 moles.

[0066] The method used in step 1 to react the tetracarboxylic acid component with the diamine component to obtain the oligomer is not particularly limited, and known methods can be used. Regarding the specific reaction method, it is as described in the <First Method for Manufacturing Polyimide Resin>.

[0067] In the above amide imidization reaction, a known amide imidization catalyst can be used. Regarding specific examples of amide imidization catalysts, the ideal range is the same as described in <First Method for Manufacturing Polyamide Resin>.

[0068] Considering the reaction rate and the need to inhibit gelation, the optimal temperature for the acetilimation reaction is 120–250 °C, and more preferably 160–200 °C. Furthermore, the reaction time, starting from the distillation of the generated water, should be 0.5–10 hours.

[0069] The oligomer obtained in step 1 has repeating units represented by formula (1). The oligomer obtained in step 1 should preferably have carboxyl groups at both ends of the main chain of the molecular chain. The carboxyl groups mentioned here also include derivatives. By means of the above method, a solution containing oligomers dissolved in a solvent is obtained. The solution containing the oligomers obtained in step 1 may also contain at least a portion of the components used as tetracarboxylic acid components and diamine components in step 1 as unreacted monomers, without impairing the effects of the present invention.

[0070] (Step 2) Step 2 involves reacting the oligomer obtained in Step 1 with the tetracarboxylic acid component and the diamine component of the repeating unit represented by formula (2) to obtain a amide-amide copolymer having amide repeating structural units and amide repeating structural units. The tetracarboxylic acid component used in step 2 includes the tetracarboxylic acid component represented by the repeating unit of the above-described formula (2). The diamine component used in step 2 includes the diamine component represented by the repeating unit of formula (2). The unreacted tetracarboxylic acid component remaining in the solution containing the oligomer obtained in step 1 can be used as the tetracarboxylic acid component in step 2, or the unreacted diamine component remaining in the solution containing the oligomer obtained in step 1 can be used as the diamine component in step 2. Furthermore, in step 1, if the oligomer has amine groups at both ends of the main chain of the molecular chain, and the diamine component used in step 1 uses a compound represented by formula (b1), then step 2 may also use only the tetracarboxylic acid component.

[0071] The method used in step 2 to react the oligomer obtained in step 1 with the tetracarboxylic acid component and diamine component of the repeating unit represented by formula (2) to obtain the copolymer is not particularly limited, and known methods can be used. Regarding specific reaction methods, examples include (1) adding the oligomer, diamine component, tetracarboxylic acid component, and solvent obtained in step 1 into a reactor and stirring for 1 to 72 hours at a temperature typically between 0 and 120°C, preferably between 5 and 80°C. When the reaction is carried out at temperatures below 80°C, the molecular weight of the copolymer obtained in step 2 does not change depending on the temperature during polymerization, and the thermoimidization process can also be suppressed, thus enabling the stable production of the copolymer.

[0072] The amide-amide copolymer is a copolymer having repeating amide structural units and repeating amide structural units. The copolymer is the product of the polyaddition reaction between the oligomer obtained in step 1 and the tetracarboxylic acid component and the diamine component in step 2.

[0073] By means of the above method, a copolymer solution containing aceimine-acetic acid copolymer dissolved in a solvent can be obtained. The concentration of the copolymer in the obtained copolymer solution is usually 1-50% by mass, preferably 3-35% by mass, and more preferably 10-30% by mass.

[0074] The number average molecular weight of the amide-amide copolymer, considering the mechanical strength of the obtained polyamide film, should preferably be between 5,000 and 500,000. Furthermore, the number average molecular weight of the copolymer can be obtained, for example, by gel filtration chromatography using a standard polymethyl methacrylate (PMMA) conversion value.

[0075] (Methods for manufacturing copolymer varnishes, polyimide resins, and polyimide films) In the second method for manufacturing polyimide resin, polyimide resin is obtained by amide-imidizing the amide acid sites in the copolymer, which is a precursor of polyimide resin. Typically, a copolymer solution (varnish) is fed to the amide-imidization reaction and formed into a film shape to obtain a polyimide resin film. Therefore, this section describes a method for manufacturing a copolymer solution (varnish) and a polyimide film of polyimide resin in film shape. The copolymer varnish is a precursor to polyimide resin, formed by dissolving a copolymer having repeating amide and amide units in an organic solvent. In other words, the copolymer varnish contains both a copolymer and an organic solvent, with the copolymer dissolved in the organic solvent. The organic solvent can be any solvent that dissolves the copolymer; there are no particular limitations. It is preferable to use the compound used as a solvent in the manufacture of the copolymer, either alone or in combination of two or more. The copolymer varnish may be the copolymer solution itself, or it may be obtained by further diluting the copolymer solution with a solvent.

[0076] From the viewpoint of making the amide formation of the copolymer more efficient, the copolymer varnish can contain more amide-imidizing catalysts and dehydration catalysts. As amide-imidizing catalysts, those with a boiling point of 40°C to 180°C are preferred, and amine compounds with a boiling point below 180°C are even more preferred. If the amide-imidizing catalyst has a boiling point below 180°C, there is no risk of the film discoloring during high-temperature drying after film formation, thus protecting its appearance. Furthermore, if the amide-imidizing catalyst has a boiling point of 40°C or higher, the possibility of volatilization before sufficient amide formation can be avoided. Among the amine compounds suitable as aceiminizing catalysts, pyridine or methylpyridine can be cited. The aforementioned aceiminizing catalysts can be used alone or in combination of two or more. Examples of acid anhydrides that can be used as dehydration catalysts include acetic anhydride, propionic anhydride, butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, and other acid anhydrides; as well as carbodiimide compounds such as dicyclohexylcarbodiimide. These can be used alone or in combination of two or more.

[0077] The copolymer contained in the copolymer varnish has solvent solubility, thus allowing for the production of high-concentration varnishes. The copolymer varnish preferably contains 5-40% by mass of the copolymer, more preferably 10-30% by mass. The viscosity of the copolymer varnish is preferably 0.1-100 Pa·s, more preferably 0.1-20 Pa·s. The viscosity of the copolymer varnish is measured using an E-type viscometer at 25°C. In addition, copolymer varnishes may contain various additives other than the aforementioned resin additives, such as inorganic fillers, adhesion promoters, flame retardants, ultraviolet stabilizers, leveling agents, defoamers, fluorescent whitening agents, crosslinking agents, polymerization initiators, photosensitizers, and adhesion enhancers, without impairing the required properties of the polyimide film. There are no particular restrictions on the manufacturing method of varnish; well-known methods may be used.

[0078] The copolymer varnish should preferably contain an imidazole compound represented by the following general formula (7). [Chemistry 18] (In formula (7), L1 and L2 are each independently hydrogen atoms, alkyl groups with 1 to 6 carbon atoms, carboxyl groups, and hydroxyl groups, and n is an integer from 1 to 4.)

[0079] By using an imidazole compound represented by the above general formula (7), a polyimide film can be efficiently obtained, which is composed of a polyimide resin having a constituent unit A derived from a tetracarboxylic dianhydride containing constituent units (A1) and (A2), and a constituent unit B derived from a diamine containing constituent unit (B1). The obtained polyimide film has excellent heat resistance and strength.

[0080] In formula (7), L1 and L2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a carboxyl group, or a hydroxyl group, preferably selected from at least one of the groups consisting of hydrogen atoms and alkyl groups having 1 to 6 carbon atoms, more preferably selected from at least one of the groups consisting of hydrogen atoms and methyl groups, and even more preferably a hydrogen atom. It is even more preferable that L1 is a methyl group and L2 is a hydrogen atom. In equation (7), n is an integer from 1 to 4, preferably an integer of 1 or 2, and more preferably 1.

[0081] Of the imidazole compounds represented by the above general formula (7), it is preferable to be at least one selected from the group consisting of imidazole compounds represented by formula (7-1) and imidazole compounds represented by formula (7-2), and more preferably imidazole compounds represented by formula (7-1). The imidazole compound represented by formula (7-1) is 1-benzyl-2-methylimidazolium, and the imidazole compound represented by formula (7-2) is 1-benzylimidazolium. That is, the imidazole compound represented by the above general formula (7) should preferably be selected from at least one of the group consisting of 1-benzylimidazolium and 1-benzyl-2-methylimidazolium, and more preferably 1-benzyl-2-methylimidazolium. [Chemistry 19]

[0082] In the copolymer varnish, the content of the imidazole compound represented by the above formula (7) is preferably 0.1 to 100 parts by weight, more preferably 1.0 to 50 parts by weight, further preferably 4.0 to 40 parts by weight, and even more preferably 10 to 30 parts by weight, relative to 100 parts by weight of the aceimine-acetic acid copolymer.

[0083] The method for manufacturing the polyimide film of this invention is not particularly limited, and known methods can be used. Examples include coating a support with the aforementioned varnish and then heating it. Specifically, methods include coating the varnish onto a smooth support such as a glass plate, metal plate, or plastic, and then removing organic solvents such as reaction solvents and diluents contained in the varnish by heating. When using a copolymer varnish, after removing the organic solvents, heating is then applied to perform amide formation. The heating temperature for drying the copolymer varnish to obtain a copolymer film is preferably 50-150°C. The heating temperature for amide-modifying the copolymer by heating is preferably 200-500°C, more preferably 250-450°C, and even more preferably 300-400°C. Furthermore, the heating time is typically 1 minute to 6 hours, preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour. The heating environment can include air, nitrogen, oxygen, hydrogen, and nitrogen / hydrogen mixtures. In order to suppress the coloring of the obtained polyimide resin, it is advisable to use nitrogen with an oxygen concentration of less than 100 ppm and nitrogen / hydrogen mixtures with a hydrogen concentration of less than 0.5%. Furthermore, the method of acetilimation is not limited to thermal acetilimation; chemical acetilimation can also be used.

[0084] There are no particular limitations on the method for peeling the polyimide film formed on the support from the support. Examples include laser peeling, using a release agent (pre-coating the surface of the support with a release agent), and adding a release agent.

[0085] [Polyimide film] The polyimide film of the present invention contains the aforementioned polyimide resin. Therefore, the polyimide film of the present invention has excellent heat resistance, especially with minimal weight loss during high-temperature processing, and also exhibits excellent laser peelability.

[0086] The thickness of the polyimide film of the present invention can be appropriately selected according to the application, preferably 1~250μm, more preferably 5~100μm, further preferably 8~80μm, and even more preferably 10~80μm. With a thickness of 1~250μm, it can be practically used as a self-supporting membrane. The thickness of polyimide films can be easily controlled by adjusting the concentration and viscosity of the solid components in the varnish.

[0087] The polyimide film of this invention exhibits excellent heat resistance, especially with minimal weight loss during high-temperature processing. The appropriate physical properties of the polyimide film of this invention are as follows. The weight loss rate after maintaining at 430°C for 1 hour should preferably be less than 1.0%, more preferably less than 0.5%, and even more preferably less than 0.3%. The glass transfer temperature should be above 410℃, more preferably above 420℃, and even more preferably above 430℃. Furthermore, the aforementioned physical property values ​​in this invention can be specifically measured using the methods described in the embodiments.

[0088] The polyimide film of this invention is suitable for use as a film in various components such as color filters, flexible displays, semiconductor parts, and optical components. The polyimide film of this invention is suitable for use as a substrate for display devices such as liquid crystal displays and OLED displays, and is even more suitable for use as a transparent substrate constituting a display device.

[0089] [Image display device] The image display device of the present invention uses the polyimide film of the present invention as a transparent substrate. The image display device of the present invention includes, for example, a transparent substrate made of the polyimide film of the present invention, and a display portion disposed on the transparent substrate. There are no particular limitations on display components. Examples include display components using TFT elements, organic EL elements, color filters, LEDs, transistors, electron emission elements, electronic inks, electrophoretic elements, GLV (grating light valve), MEMS (micro electromechanical system), DMD (digital micro mirror device), DMS (digital micro shutter), IMOD (interferometric modulator), electrowetting elements, piezoelectric ceramic displays, and carbon nanotubes. Examples of the image display device of the present invention include liquid crystal displays, OLED displays, and touch panels. The image display device of the present invention can be manufactured based on known information, except that the polyimide film of the present invention is used as a transparent substrate. The image display device of the present invention uses the polyimide film of the present invention, which has excellent heat resistance, as a transparent substrate. Therefore, it is not easy to produce cracks in the inorganic film or coloring of the transparent substrate, and has excellent reliability. [Example]

[0090] The present invention will be specifically described below by way of examples. However, the present invention is not limited by these examples.

[0091] [Thin Film Properties and Evaluation] The physical properties of the polyimide films obtained in the Examples and Comparative Examples were determined by the methods shown below. Furthermore, the polyimide films were evaluated by the methods shown below. In addition, the polyimide films used in the various property determinations and evaluations were films obtained by peeling using the method described in "(8) Minimum peelable energy density". Films that could not be peeled by this method were immersed in water at 40°C for 5 minutes and then peeled off. After removing surface moisture with clean paper, they were heated at 80°C for 10 minutes in a hot air dryer under atmospheric conditions to remove moisture before being used in the various property determinations and evaluations.

[0092] (1) Thin film thickness The film thickness of the polyimide film in the examples and comparative examples was measured using a contact displacement sensor "SA-S110" manufactured by CITIZEN FINEDEVICE CO.,LTD., for the polyimide film after it was peeled off from the glass plate.

[0093] <Optical Properties> (2) Total light transmittance and yellowness index (YI) The total light transmittance and yI of the polyimide films in the examples and comparative examples were measured on the polyimide films after being peeled off from the glass plate. The total light transmittance was measured in accordance with JIS K7361-1, and the yI was measured in accordance with ASTM E313-05 (D light source, 65°). Both measurements were performed using a color and turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Kogyo Co., Ltd.

[0094] (3) Thickness phase difference (Rth) (Evaluation of optical isotropy) The thickness phase difference (Rth) of the polyimide films in the examples and comparative examples was measured using an ellipsometry "M-220" manufactured by Nippon Spectrophotometer Co., Ltd., for the polyimide films after being peeled from the glass plate. The thickness phase difference was measured at a wavelength of 590 nm. Furthermore, Rth is expressed by the following formula, where the largest in-plane refractive index of the polyimide film is defined as nx, the smallest as ny, the refractive index in the thickness direction is defined as nz, and the film thickness is defined as d. Rth=[{(nx+ny) / 2}-nz]×d

[0095] <Thermal Properties (Heat Resistance)> (4) Glass transition temperature (Tg) The glass transition temperature (Tg) of the polyimide films in the examples and comparative examples was obtained by using the polyimide films after peeling off the glass plates as test pieces, and by the following method. Using a thermomechanical analysis apparatus "TMA 7100C" manufactured by Hitachi High-Tech Corporation, the residual stress was removed by heating to a temperature sufficient to remove the residual stress in stretch mode with a test piece size of 4 mm × 20 mm, a load of 0.1 N, and a heating rate of 10 °C / min. The sample was then cooled to room temperature. Subsequently, the elongation of the test piece was measured under the same conditions as the treatment used to remove residual stress, and the glass transition temperature was obtained by interpolation of the elongation inflection point. (5) 1% weight reduction temperature (Td1%) The 1% weight loss temperature (Td1%) of the polyimide film in the examples and comparative examples was obtained by using the polyimide film after peeling it from the glass plate as the sample, and by the method described below. A differential thermal thermogravimetric analyzer "NEXTA STA200RV" manufactured by Hitachi High-Tech Corporation was used. The sample was heated from 40°C to 150°C at a heating rate of 10°C / min, held at 150°C for 30 minutes to remove moisture, and then heated to 550°C at 10°C / min. The temperature at which the weight decreased by 1% was compared with the weight after holding at 150°C for 30 minutes, and the 1% weight loss temperature (Td1%) was taken as the 1% weight loss temperature. The larger the weight loss temperature coefficient value, the better the heat resistance. (6) Weight loss rate at 430℃ The weight loss rate of the polyimide film at 430°C in the examples and comparative examples was obtained using the polyimide film after being peeled from the glass plate as the sample, by the method described below. A differential thermal gravimetric analyzer "NEXTA STA200RV" manufactured by Hitachi High-Tech Corporation was used. The sample was heated from 40°C to 150°C at a heating rate of 10°C / min, held at 150°C for 30 minutes to remove moisture, and then heated to a predetermined temperature (430°C) at a rate of 10°C / min and held at that temperature for 1 hour. The ratio of the weight loss during the 1-hour holding period at 430°C to the weight before the 1-hour holding period was taken as the weight loss rate at 430°C. The smaller the weight loss rate coefficient at 430°C, the better the heat resistance.

[0096] Laser ablation (LLO) peeling properties (7) Light transmittance at a wavelength of 308nm The light transmittance at a wavelength of 308 nm for the polyimide films in the examples and comparative examples was obtained using the method described below, referring to the polyimide films after peeling from the glass plate. The measurements were taken using a UV-3100PC UV-Vis-NIR spectrophotometer manufactured by Shimadzu Corporation. A lower light transmittance value at a wavelength of 308 nm indicates better LLO peelability. In addition, "<0.1" in Table 1 means "less than 0.1%". (8) Minimum energy density that can be stripped The LLO peelability was evaluated by irradiating the glass plate side of the laminates (glass plate / polyimide film) obtained in the examples and comparative examples with an excimer laser (oscillating gas: XeCl, wavelength 308 nm). The LLO conditions were set as follows: overlap 50%, frequency 60 Hz, beam size 14 mm × 1 mm. Laser irradiation was performed by progressively increasing the energy density by 10 mJ / cm², and the minimum energy density required to peel off the polyimide was measured. The results are shown in Tables 1 and 2. In the examples and comparative examples of this test, the glass plate used was AN-wizusFC (0.5 mmt). Furthermore, when the energy density reaches 400 mJ / cm², irradiation is terminated, and those that cannot be peeled off are evaluated as "unpeelable". The lower the minimum energy density required to peel polyimide, the better the LLO peelability. In other words, it has better efficiency and better productivity.

[0097] <Abbreviations for ingredients, etc.> The tetracarboxylic acid and diamine components used in the examples and comparative examples, and their abbreviations, are as follows.

[0098] (Tetracarboxylic acid component) DNDA:(4arH,8acH)-decahydro-1t,4t:5c,8c-dimethylbridged naphthalene-2t,3t,6c,7c-tetracarboxylic acid dianhydride (manufactured by DAXIN Corporation; compound represented by formula (a111)) BODA: Bicyclooctane-2,3,5,6-tetracarboxylic anhydride (manufactured by DAXIN Corporation; compound represented by formula (a12)). s-BPDA: 3,3',4,4'-Biphenyltetracarboxylic acid dianhydride (manufactured by Mitsubishi Chemical Corporation, a compound represented by the formula (a2s)) CpODA: norcamphene-2-spiro-α-cyclopentanone-α'-spiro-2”-norcamphene-5,5”,6,6”-tetracarboxylic dianhydride (manufactured by ENEOS Corporation)

[0099] (Diamine component) BAFL: 9,9-bis(4-aminophenyl) bacon (manufactured by JFE Chemical Co., Ltd., compound represented by formula (b11)) TFMB: 2,2'-bis(trifluoromethyl)benzidine (SEIKA CORPORATION., compound represented by formula (b2))

[0100] The abbreviations for solvents and catalysts used in the examples and comparative examples are as follows. GBL: γ-Butyrolactone (Made by Mitsubishi Chemical Corporation) NMP: N-Methyl-2-pyrrolidone (manufactured by Tokyo Pure Pharmaceutical Co., Ltd.) TEA: Triethylamine (manufactured by Kanto Chemical Co., Ltd.) TEDA: Triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0101] <Manufacturing of Polyimide Resins, Varnishes and Polyimide Films> [Example 1] A solution was obtained by adding 13.938 g (0.040 mol) of BAFL, 19.214 g (0.060 mol) of TFMB, and 93.686 g of GBL to a 1L five-necked round-bottom flask equipped with a stainless steel crescent-shaped stirring blade, a nitrogen inlet pipe, a Dean-Stark apparatus with a cooling pipe, a thermometer, and glass end caps. The solution was stirred at 200 rpm under nitrogen atmosphere at an internal temperature of 70°C. After adding 18.137 g (0.060 mol) of DNDA, 11.769 g (0.040 mol) of s-BPDA, and 19.908 g of GBL to the solution in a single step, 5.060 g of TEA, 0.056 g of TEDA, and 3.513 g of GBL as acetylation catalysts were added. The mixture was then heated using a heating pack, raising the temperature of the reaction system to 190°C for approximately 20 minutes. The distillate was collected, and the rotation speed was adjusted according to the viscosity increase, while the temperature of the reaction system was maintained at 190°C and refluxed for 5 hours. Subsequently, 417.978 g of GBL was added, and the temperature of the reaction system was cooled to 120°C. The mixture was then stirred for approximately 3 hours to homogenize it, yielding a polyimide varnish with a solid content of 10% by mass. The obtained polyimide varnish was then coated onto a glass plate and held at 80°C for 20 minutes on a hot plate. Afterward, it was heated at 400°C for 30 minutes in a hot air dryer under nitrogen atmosphere to evaporate the solvent, obtaining a polyimide film. The physical properties and evaluation results of the film are shown in Table 1.

[0102] [Examples 2-7 and Comparative Examples 1-5] In Example 1, the tetracarboxylic acid and diamine components were changed to those listed in Table 1. Otherwise, a polyimide film was obtained in the same manner as in Example 1. The physical properties and evaluation results of the film are shown in Table 1.

[0103] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Polyimide resin (numbers indicate molar ratios) Tetracarboxylic acid components DNDA(a111) 60 60 60 45 70 50 100 100 100 BODA(a12) 45 s-BPDA(a2s) 40 40 40 55 55 30 50 40 30 CpODA 60 70 diamine component BAFL(b11) 40 20 60 40 40 100 100 40 40 0 100 100 TFMB(b2) 60 80 40 60 60 60 60 100 Evaluation of polyimide films - Thin film thickness [µm] 9.5 8.7 9.5 9.5 8.4 9.1 8.8 9.0 10.1 9.6 9.3 9.2 Optical properties Total light transmittance [%] 88.9 89.2 88.7 88.5 88.4 88.2 87.7 89.1 89.8 90.7 88.3 88.8 YI 3.9 3.2 4.4 5.0 4.9 4.8 7.1 3.7 1.1 1.0 4.5 1.1 Rth 326 395 243 381 362 58 90 314 175 327 69 12 thermal properties Tg[℃] 433 423 452 420 418 475 470 414 460 422 450 471 Td1%[℃] 503 484 520 496 507 518 526 471 511 504 502 525 Weight reduction rate [%] (430℃) 0.23 0.34 0.17 0.28 0.32 0.20 0.21 2.93 0.62 0.33 1.40 0.25 LLO peelability Light transmittance [%] (308nm) 0.1 0.1 0.1 0.1 0.1 <0.1 <0.1 0.1 2.7 28.5 <0.1 0.8 Minimum energy density that can be stripped [mJ / cm²] 230 230 220 190 200 230 200 230 Unable to peel Unable to peel 230 Unable to peel

[0104] As shown in Table 1, the polyimide film of the embodiment has excellent heat resistance, especially with minimal weight reduction during high-temperature treatment, and also excellent laser peelability.

[0105] [Example 8] In a 500 mL five-necked round-bottom flask equipped with a stainless steel crescent-shaped stirring blade, a nitrogen inlet tube, a Dean-Stark apparatus with a cooling tube, a thermometer, and glass end caps, 9.607 g (0.030 mol) of TFMB, 10.454 g (0.030 mol) of BAFL and 84.394 g of NMP were added. The solution was obtained by stirring at 200 rpm under a nitrogen atmosphere with the internal temperature set at 70 °C. For this solution, 15.114 g (0.050 mol) of DNDA and 17.934 g of NMP were added in a single batch, followed by 0.253 g of TEA as a amide catalyst and 3.165 g of NMP. The mixture was heated using a heating pack to raise the temperature of the reaction system to 190°C for approximately 20 minutes. While collecting the distillate, the temperature of the reaction system was maintained at 190°C and refluxed for 1 hour. Subsequently, 98.368 g of NMP was added, and the temperature of the reaction system was cooled to 50°C to obtain a solution containing oligomers with repeating amide structural units. For the obtained solution, 14.711 g (0.050 mol) of s-BPDA, 12.810 g (0.040 mol) of TFMB and 39.713 g of NMP were added in a single step, and the mixture was stirred at 50°C for 5 hours. Then, NMP was added at a solids concentration of approximately 10% by mass and homogenized. Further, 1-benzyl-2-imidazolium was added at a ratio of 15 parts by mass relative to 100 parts by mass of the amide-amide copolymer and homogenized to obtain a varnish containing a copolymer (amide-amide copolymer) having repeating amide and amide structural units. The obtained varnish was then spin-coated onto a glass plate and held at 80°C for 20 minutes. Afterward, the solvent was evaporated by heating at 400°C for 60 minutes in a hot air dryer under nitrogen atmosphere, yielding a polyimide film. The physical properties and evaluation results of the film are shown in Table 2.

[0106] [Table 2] Example 8 aceimine-acetic acid copolymer (Numbers represent Mohrby) aceimine portion Tetracarboxylic acid components DNDA(a111) 50 diamine component BAFL(b1) 30 TFMB(b2) 30 Acetic acid portion Tetracarboxylic acid components s-BPDA(a2s) 50 diamine component TFMB(b2) 40 additive (The numbers represent parts by mass relative to 100 parts by mass of the copolymer) imidazole compounds 1-Benzyl-2-imidazolium 15 Evaluation of polyimide films - Thin film thickness [µm] 8.7 Optical properties Total light transmittance [%] 88.4 YI 5.6 Rth 157 thermal properties Tg[℃] 417 Td1%[℃] 500 Weight reduction rate [%] (430℃) 0.56 LLO peelability Light transmittance [%] (308nm) 0.1 Minimum irradiation energy density for stripping [mJ / cm²] 200

[0107] As shown in Table 2, the polyimide film of the examples has excellent heat resistance, especially with minimal weight reduction during high-temperature treatment, and also excellent laser peelability.

Claims

1. A polyimide resin comprising a constituent unit A derived from tetracarboxylic dianhydride and a constituent unit B derived from diamine, wherein constituent unit A comprises at least one constituent unit (A1) selected from the group consisting of constituent units (A11) derived from compounds represented by formula (a11) and constituent units (A12) derived from compounds represented by formula (a12), and constituent units (A2) derived from compounds represented by general formula (a2); constituent unit B comprises constituent units (B1) derived from compounds represented by general formula (b1), wherein the ratio of constituent units (B1) in constituent unit B is 40 mol% or more; wherein in formula (b1), R is independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, a trifluoromethyl group, or a hydroxyl group.

2. The polyimide resin as claimed in claim 1, wherein, Unit B further comprises unit (B2) from the compound represented by formula (b2); 3. The polyimide resin as claimed in claim 2, wherein, The molar ratio [(B1) / (B2)] between constituent units (B1) and (B2) in constituent unit B is 15 / 85 to 70 / 30.

4. The polyimide resin as claimed in claim 1 or 2, wherein, The constituent unit (A11) comprises the constituent unit (A111) of a compound represented by the following formula (a111); 5. The polyimide resin as claimed in claim 1 or 2, wherein, The constituent unit (A2) comprises the constituent unit (A2s) of the compound represented by the following formula (a2s); 6. The polyimide resin as claimed in claim 1 or 2, wherein, The constituent unit (B1) comprises the constituent unit (B11) of the compound represented by the following formula (b11); 7. The polyimide resin as claimed in claim 1 or 2, wherein, The molar ratio [(A1) / (A2)] between constituent units (A1) and (A2) in constituent unit A is 30 / 70 to 85 / 15.

8. A varnish, formed by dissolving the polyimide resin of any one of claims 1 to 7 in an organic solvent.

9. A amide-amide copolymer comprising a repeating unit represented by formula (1) and a repeating unit represented by formula (2), wherein the molar ratio [(1) / (2)] of the repeating unit represented by formula (1) to the repeating unit represented by formula (2) is 5 / 95 to 60 / 40; wherein A1 is selected from at least one of the groups consisting of the base represented by formula (3) and the base represented by formula (4), and A2 is the base represented by formula (5); B1 and B2 are divalent bases, and either B1 or B2 comprises the base represented by formula (6); X1 and X2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms; 10. A varnish formed by dissolving the aceimide-acetic acid copolymer of claim 9 in an organic solvent.

11. The varnish of claim 10 further contains an imidazole compound represented by the following general formula (7); in formula (7), L1 and L2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a carboxyl group, or a hydroxyl group, and n is an integer from 1 to 4.

12. A polyimide resin, which is formed by amide-imidizing the amide group in the amide-amide copolymer of claim 9.

13. A polyimide film comprising a polyimide resin as claimed in any one of claims 1 to 7, 12.

14. The polyimide film of claim 13 has a weight loss rate of less than 1.0% after being maintained at 430°C for 1 hour, and the glass transfer temperature is above 410°C.

15. The polyimide film of claim 13 or 14, used as a transparent substrate constituting a display device.

16. A method for manufacturing a polyimide film, comprising applying a varnish as claimed in claims 8, 10 or 11 onto a support and then heating it.

17. An image display device comprising a polyimide film as a transparent substrate, as claimed in any one of claims 13 to 15.