Polyimide laminate and method for producing the same

Abstract

The present application provides a kind of polyimide laminated body and its preparation method.The polyimide laminated body, characterized in that, including: support substrate;And polyimide layer, laminated on support substrate, and made by polyamide acid solution, wherein, the mole mass of four carboxylic acid, four carboxylic acid dianhydride, diamine in polyamide acid solution The relationship as shown in formula (1), (2) and formula (3) is as follows: the mole mass of four carboxylic acid dianhydride / the mole mass of diamine=0.900~1.100…(1) the mole mass of four carboxylic acid / the mole mass of diamine=0.001~0.500…(2) [the mole mass of four carboxylic acid dianhydride+the mole mass of four carboxylic acid] / the mole mass of diamine=0.900~1.100…(3).

Description

[0001] This application is a divisional application of the patent application with the application date of May 27, 2022, the application number of 202210594772.7, and the invention name of "Polyamide acid solution, polyimide film and preparation method thereof", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of organic polymer materials, in particular to a polyamide acid solution and a polyimide film and preparation methods thereof. BACKGROUND

[0003] Polyimide (PI) refers to a high polymer containing imide bond (-CO-N-CO-) in the main chain. Polyimide is considered to be one of the organic polymer materials with excellent comprehensive performance, and its heat resistance temperature can reach above 400℃. Its insulation is high, its dielectric constant and dielectric loss are very small, and its chemical properties are good. Therefore, polyimide has excellent thermal stability, chemical stability, mechanical properties and special electrical properties, thus showing the possibility of application in many fields. However, polyimide is difficult to dissolve and melt, so its processability is poor when used as a material. Due to poor processability, polyimide is mainly prepared by a two-step method. First, diamine and tetracarboxylic dianhydride as monomers are polymerized to prepare a polyamide acid solution (polyimide precursor). To prevent the viscosity of the solution from increasing, tetracarboxylic acid (which does not substantially participate in the growth of the molecular chain) can be added. Tetracarboxylic acid can be used as a viscosity regulator (additive) to improve the processability of the polyamide acid solution. And when preparing polyimide by thermal (heating) or chemical (adding dehydrating agent, catalyst, etc.) methods, tetracarboxylic acid helps the reaction by dehydration and ring formation. On the other hand, when tetracarboxylic acid is used for the above-mentioned role as a viscosity regulator, it is basically added after the polymerization reaction of diamine and tetracarboxylic dianhydride. Therefore, a technology is expected to enable tetracarboxylic acid to be stably dissolved in the polyamide acid solution.

[0004] Here, an example is disclosed in the prior art in which p-phenylenediamine (PPD) and biphenyl tetracarboxylic dianhydride (BPDA) are used as monomers, and dimethylacetamide (DMAc) is used as a solvent.

[0005] In Non-Patent Literature 1, a diamine monomer containing an imidazole structure, 2-(4-aminophenyl)-5-aminobenzimidazole, is introduced into the molecular structure of BPDA and PPD. Then, a polyimide fiber with excellent mechanical properties is prepared by a dry spinning process.

[0006] In Patent Literature 1, a method for producing a transparent polyimide having excellent mechanical properties by adding an imidazole compound is disclosed. In Patent Literature 2, it is disclosed that a polyimide resin tubular body prepared from BPDA and PPD exhibits excellent thermal and mechanical properties.

[0007] However, none of the above methods discloses a technique for improving the solubility of tetracarboxylic acid in a polyamic acid solution.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: CN109535423A

[0011] Patent Document 2: Japanese Patent No. 62-263228

[0012] Non-Patent Documents

[0013] Non-Patent Document 1: Zheng Sen, Guo Tao, Dong Jie, Wang Shihua, Zhang Qinghua. Preparation, structure and properties of high-strength high-modulus polyimide fibers containing benzimidazole moiety [J]. Journal of Textile Research, 2021, 42(02): 7-11 + 20. SUMMARY

[0014] Technical Problem to be Solved by the Invention

[0015] As monomers for preparing a polyamic acid solution, diamines and tetracarboxylic dianhydrides can be exemplified. The solubility of tetracarboxylic dianhydrides in a solvent such as N-methylpyrrolidone (NMP) is low. However, by dissolving a diamine having high solubility in a solvent first, the solubility problem can be solved. If tetracarboxylic dianhydride is added to a solution in which a diamine is dissolved, a polyamic acid can be synthesized by a polymerization reaction. At this time, the reaction rate of the polymerization reaction is sufficiently fast, and it is easy to dissolve tetracarboxylic dianhydride in the solution. On the other hand, tetracarboxylic acid used as a viscosity modifier for a polyamic acid solution also has low solubility in a solvent. When tetracarboxylic acid is used as a viscosity modifier, tetracarboxylic acid is dissolved in a polyamic acid solution. However, it is difficult to improve the solubility of tetracarboxylic acid having low solubility in a solvent.

[0016] To solve at least one of the above technical problems, the object of the present invention is to easily dissolve tetracarboxylic acid as a viscosity modifier in a solvent, and to obtain a polyamic acid solution having excellent processability, and a polyimide material having excellent thermal stability and film uniformity through a curing process.

[0017] Means for Solving the Technical Problem

[0018] To solve the above technical problems, the present application provides a method for preparing polyimide, comprising the following steps. First, add tetracarboxylic acid in a solvent, and then make diamine and tetracarboxylic dianhydride polymerize to synthesize polyamic acid after the tetracarboxylic acid is completely dissolved in the solvent. Make the polyamic acid solution be heat-cured into polyimide.

[0019] The present application relates to a method for preparing a polyamic acid solution, characterized in that it comprises the following steps: adding tetracarboxylic acid in a solvent, making the tetracarboxylic acid completely dissolve in the solvent to obtain a mixed solution; adding tetracarboxylic dianhydride and diamine into the mixed solution to make polymerization reaction, and obtaining the polyamic acid solution, wherein the molar mass of the added tetracarboxylic acid, tetracarboxylic dianhydride and diamine is shown in formula (1), (2) and (3):

[0020] Molar mass of tetracarboxylic dianhydride / Molar mass of diamine = 0.900-1.100…(1)

[0021] Molar mass of tetracarboxylic acid / Molar mass of diamine = 0.001-0.500…(2)

[0022] [Molar mass of tetracarboxylic dianhydride + Molar mass of tetracarboxylic acid] / Molar mass of diamine = 0.900-1.100…(3).

[0023] Preferably, the molar mass of tetracarboxylic dianhydride / Molar mass of diamine = 0.900-0.990;

[0024] The molar mass of tetracarboxylic acid / Molar mass of diamine = 0.005-0.100;

[0025] The [Molar mass of tetracarboxylic dianhydride + Molar mass of tetracarboxylic acid] / Molar mass of diamine = 0.940-0.995.

[0026] In the above preparation method, the tetracarboxylic acid can be converted into tetracarboxylic dianhydride when heated, and then reacts with the diamine.

[0027] In the above preparation method, the solvent is selected from one or more of the group consisting of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, ethyl acetate, diethylformamide, diethylacetamide, propylene glycol monomethyl ether, m-cresol, tetrahydrofuran, chloroform and γ-butyrolactone, preferably, the solvent is dimethylacetamide and / or N-methylpyrrolidone.

[0028] In the above preparation method, the tetracarboxylic acid can be selected from one or more of the group consisting of 3,3',4,4'-diphenyltetracarboxylic acid, 2,3,3',4'-diphenyltetracarboxylic acid, 4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic acid), 4,4'-(hexafluoroisopropylidene)diphthalic acid, 4,4'-hydroxydiphthalic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, preferably the tetracarboxylic acid is 3,3',4,4'-diphenyltetracarboxylic acid and / or 2,3,3',4'-diphenyltetracarboxylic acid.

[0029] In the above preparation method, the diamine can be selected from one or more of the group consisting of p-phenylenediamine, m-phenylenediamine, 4,4'-oxydianiline, p-xylylenediamine, m-xylylenediamine, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis(trifluoromethyl)benzidine, 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(3-aminophenyl)hexafluoropropane, 2,2'-bis(4-aminophenyl)hexafluoropropane, bis(4-aminophenyl)sulfone, bis(3-aminophenyl)sulfone, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 2,2-bis[4-(4-aminophenoxy)-phenyl]propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene, preferably the diamine is selected from one or more of the group consisting of p-phenylenediamine, m-phenylenediamine, 4,4'-oxydianiline.

[0030] In the above preparation method, the tetracarboxylic dianhydride can be selected from one or more of the group consisting of 3,3',4,4'-diphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, 3,3,4,4-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydibenzoic dianhydride, bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride, 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, sulfonophthalic anhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic anhydride), 4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic anhydride), preferably the tetracarboxylic dianhydride is 3,3',4,4'-diphenyltetracarboxylic dianhydride and / or pyromellitic dianhydride.

[0031] The second aspect of the present application relates to a polyamic acid solution, which is prepared by the above preparation method.

[0032] The third aspect of the present application relates to a method for producing a polyimide film, characterized in that a polyamide acid solution is coated on a glass substrate, and the solvent is removed by low-temperature heating; and the glass substrate coated with the polyamide acid solution is placed in a nitrogen atmosphere, and a polyimide film is obtained by a curing process, preferably, the temperature during the low-temperature heating is 25°C or higher and 200°C or lower.

[0033] In the above production method, the curing process is gradient heating, preferably, the heating procedure is a procedure including heating at 100°C for 0.5 to 1 hour, heating up to 150°C for 0.5 to 1 hour, heating up to 200°C for 0.5 to 1 hour, heating up to 250°C for 0.5 to 1 hour, heating up to 300°C for 0.5 to 1 hour, and heating up to 350°C for 0.5 to 1 hour, and preferably, the temperature increasing rate of the gradient heating is 2 to 10°C / min.

[0034] The fourth aspect of the present application relates to a polyimide film, characterized in that it is produced by the above production method, and preferably, the polyimide film has an outgassing amount of 0.5 mass% or less, preferably 0.36 mass% or less.

[0035] Effects of the Invention

[0036] According to the present application, the tetracarboxylic acid used as a viscosity modifier is uniformly dissolved, and a polyamide acid solution having excellent processability is produced, thereby obtaining a polyimide material having excellent thermal stability and film uniformity. In addition, by the stepwise temperature increasing method, the secondary reaction and the dehydration reaction of the residual tetracarboxylic acid during the curing process are effectively controlled, and a more stable film layer is obtained. The secondary reaction makes the film structure and properties more stable. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A schematic diagram showing that the tetracarboxylic acid used in the examples of the present application is converted into tetracarboxylic dianhydride after heating.

[0038] Figure 2 (a) shows the appearance of the polyamide acid solution produced in Example 1, and (b) shows the appearance of the polyamide acid solution produced in Comparative Example 1. DETAILED DESCRIPTION

[0039] Hereinafter, a polyamide acid solution and a polyimide and a method for producing the same according to the present application will be described in detail.

[0040] POLYAMIDE ACID SOLUTION AND POLYIMIDE

[0041] With respect to the polyamic acid solution used in the present application, a tetracarboxylic acid is first added as a viscosity modifier to a solvent, and after the tetracarboxylic acid is completely dissolved in the solvent, a polyamic acid solution is obtained by polymerizing a diamine and a tetracarboxylic dianhydride in the solvent. Then, the polyamic acid solution is cured by heating to obtain a polyimide.

[0042] < Tetracarboxylic acid >

[0043] As the tetracarboxylic acid used in the present application, a tetracarboxylic acid that does not substantially increase the viscosity of the polyamic acid solution (i.e., does not actually participate in the growth of the molecular chain) is preferred. A tetracarboxylic acid that is converted to a tetracarboxylic dianhydride by heating and then reacts with a diamine to produce such a polyamic acid of the present application is preferred. In one embodiment, the temperature at which BPTA is converted to a tetracarboxylic dianhydride is 200°C (shown in FIG. 1). Figure 1

[0044] According to the method for producing a polyamic acid solution and a polyimide according to the present application, the tetracarboxylic acid is preferably 3,3',4,4'-biphenyl tetracarboxylic acid (BPTA), but is not limited thereto. It can also be one or a combination of two or more of 2,3,3',4'-biphenyl tetracarboxylic acid (a-BPTA), 4,4'-(4,4'-isopropylidene diphenoxyl) bis(phthalic acid) (BPABP), 4,4'-(hexafluoroisopropylidene) diphenyl dicarboxylic acid (6FDP), 4,4'-hydroxy diphenyl dicarboxylic acid (ODP), 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA).

[0045] < Diamine >

[0046] ​According to the polyamic acid solution and the polyimide preparation method related to the present application, preferably, the diamine can be selected from p-phenylenediamine (PPD), m-phenylenediamine (MPD), 4,4'-oxydianiline (4,4'-ODA), but not limited thereto. One or more than two combinations of p-methylenedianiline (pMDA), m-methylenedianiline (mMDA), 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis(4-aminophenoxy)benzene (134APB), bis(trifluoromethyl)diphenylamine (TFDB), 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane (4BDAF), 2,2'-bis(3-aminophenyl)hexafluoropropane (33-6F), 2,2'-bis(4-aminophenyl)hexafluoropropane (44-6F), bis(4-aminophenyl)sulfone (4DDS), bis(3-aminophenyl)sulfone (3DDS), 1,3-cyclohexanediamine (13CHD), 1,4-cyclohexanediamine (14CHD), 2,2-bis[4-(4-aminophenoxy)-phenyl]propane (6HMDA), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (DBOH), 4,4'-bis(3-aminophenoxy)diphenyl sulfone (DBSDA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) can be selected.

[0047] < Tetra-carboxylic dianhydride >

[0048] According to the polyamic acid solution and the polyimide preparation method related to the present application, preferably, the tetra-carboxylic dianhydride is selected from 3,3',4,4'-biphenyl tetra-carboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), but not limited thereto. It can also be a combination of one or more of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), 3,3,4,4-benzophenone tetra-carboxylic dianhydride, 3,3',4,4'-benzophenone tetra-carboxylic dianhydride (BTDA), 4,4'-oxydiphthalic dianhydride (ODPA), bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride (SiDA), 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA), sulfonated phthalic anhydride (SO2DPA), cyclobutane-1,2,3,4-tetra-carboxylic dianhydride (CBDA), 4,4'-(4,4'-isopropylidene diphenoxy) bis(phthalic anhydride), 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) (6HBDA).

[0049] < Solvent >

[0050] The solvent is preferably one or a mixture of two or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), acetone, ethyl acetate, diethylformamide (DEF), diethylacetamide (DEA), propylene glycol monomethyl ether (PGME), m-cresol, and the like. In addition, low-boiling-point solvents such as tetrahydrofuran (THF), chloroform, and the like, or low-absorbing solvents such as γ-butyrolactone and the like can also be used. More preferably, the solvent is DMAc or NMP, or a mixture of the two.

[0051] <MOLE RATIO OF DIAMINE TO TETRACARBOXYLIC ACID COMPONENT>

[0052] According to the method for producing a polyimide, the tetra carboxylic acid dianhydride and the diamine component are set to substantially equimolar amounts (preferably, the mole ratio of [tetra carboxylic acid dianhydride] / [diamine] is 0.900 to 1.100). More preferably, the mole ratio of [tetra carboxylic acid dianhydride] / [diamine] is 0.900 to 0.990. The amount of solvent is defined by the solid content concentration of the polyamic acid solution produced, and preferably, the solid content concentration of the polyamic acid solution is 5 to 50 mass%, and more preferably, 10 to 25 mass%.

[0053] In addition, when [(molar mass of tetra carboxylic acid dianhydride) + (molar mass of tetra carboxylic acid)] / [molar mass of dianhydride] is less than 1, the tetra carboxylic acid can be added in an amount corresponding substantially to the excess moles of the diamine component, as necessary. The mole ratio of [tetra carboxylic acid] / [diamine] is 0.001 to 0.500, and preferably, 0.005 to 0.100. As a result, the moles of the diamine and the tetra carboxylic acid dianhydride and the tetra carboxylic acid are substantially equimolar in the heating. The mole ratio of ([tetra carboxylic acid dianhydride] + [tetra carboxylic acid]) / [diamine] is 0.900 to 1.100, and preferably, 0.940 to 0.995.

[0054] <PRODUCTION METHOD FOR POLYAMIC ACID SOLUTION AND POLYIMIDE>

[0055] More specifically, the production process for the polyamic acid includes the steps of dissolving the diamine in an organic solvent, slowly adding the tetra carboxylic acid dianhydride while stirring the solution, and then continuously stirring at a temperature of 0°C to 120°C (preferably, 20°C to 80°C) for 1 to 72 hours. However, the production method is not limited thereto.

[0056] If the reaction is carried out at 80°C or higher, the molecular weight of the polyamic acid product varies depending on the temperature at which the polymerization is carried out, because the imidization is carried out by heat, and the polyimide precursor can become unstable. In addition, because the molecular weight of the polyamic acid tends to increase, the order of addition of the diamine and the tetracarboxylic dianhydride in the above production method is preferred, because the solubility of the tetracarboxylic dianhydride in the above solvent is very limited, but the dianhydride and the polyamic acid have good solubility. When the tetracarboxylic dianhydride is added to the solution in which the diamine is dissolved in the solvent, the polyamic acid is synthesized by the polymerization reaction. At this time, the reaction rate of the polymerization reaction is very fast, and thus the tetracarboxylic dianhydride is easily dissolved in the solvent. Therefore, the amount of precipitation (precipitation is the tetracarboxylic dianhydride that is not completely dissolved in the solvent) is reduced, and thus this order is preferred. In addition, in the above production method, the order of addition of the diamine and the tetracarboxylic dianhydride can be reversed.

[0057] According to the production method of the polyimide of the present application, in the process of "solidifying the polyamic acid solution to obtain a polyimide", first, the polyamic acid solution is coated and electrospinning or the like is performed to produce a coating film having a desired shape. Next, the polyimide is solidified by a heating method (gradient heating) in a nitrogen atmosphere. In the process of solidification at a high temperature, if gradient heating is used, the volatilization of the solvent becomes slow, a polyimide film having a smooth surface can be obtained, and the orientation in the surface can be positioned. Furthermore, based on the orientation effect of the polyimide molecular chain, a polyimide film having a low thermal expansion rate can be obtained. Therefore, the heat solidification is preferably gradient heating, and more preferably, the heating rate of the gradient heating is 2 to 10°C / min, and the process includes heating at 100°C for 0.5 to 1 hour, and heating at 150°C. The heating rate can be the same or different.

[0058] As an example, in the preferred embodiment, the heating rate of the gradient heating is 4 to 5°C / min, and the process includes heating at 100°C for 1 hour, and heating at 150°C for 1 hour. The heating at 200°C is performed for 0.5 hour, the heating at 250°C is performed for 0.5 hour, the heating at 300°C is performed for 0.5 hour, and the heating at 350°C is performed for 0.5 hour.

[0059] The polyimide can be obtained by dehydration and cyclization of the coating film of the polyamic acid solution by a heat method, i.e., under a high temperature condition. The present application is not particularly limited to the viscosity modifier used in a specific solidification process and a heating process.

[0060] The present application can produce a polyamic acid solution having excellent processability by adding a tetracarboxylic acid, and can produce a polyimide material having excellent thermal stability and mechanical properties through a curing process. The polyimide film obtained by the present application can be preferably applied to a substrate for a display, a touch panel, or a solar cell.

[0061] Another aspect of the present application provides a polyimide obtained by the above preparation method; preferably, the polyimide is a polyimide film.

[0062] Compared with the prior art, the present application has the following beneficial effects: in the present application, by adding a tetracarboxylic acid as a viscosity modifier at the beginning, the tetracarboxylic acid does not remain in the solvent during the polymerization and cyclization of the polyamic acid, thus having excellent uniformity and less air discharge during heating, and a better polyamic acid solution and polyimide can be obtained.

[0063] <Structural formulas of tetracarboxylic acid dianhydride and diamine>

[0064] Here, the abbreviations, full names, and structural formulas of the tetracarboxylic acid dianhydride, diamine, tetracarboxylic acid, and solvent are as follows:

[0065] BPDA: 3,3',4,4'-biphenyl tetracarboxylic dianhydride

[0066]

[0067] PMDA: pyromellitic dianhydride

[0068]

[0069] 4,4'-ODA: 4,4'-diamino diphenyl ether

[0070]

[0071] TFDB: bis(trifluoromethyl)benzidine

[0072]

[0073] PPD: p-phenylenediamine

[0074]

[0075] BPTA: 3,3',4,4'-biphenyl tetracarboxylic acid

[0076]

[0077] NMP: N-methyl pyrrolidone

[0078] Examples

[0079] In order to more clearly illustrate the present application, the present application will be described with reference to the following preferred embodiments. The following detailed description is merely exemplary in nature and is not intended to limit the present application, as described in the application.

[0080] [Example 1]

[0081] Into a reactor, under nitrogen atmosphere, N-methyl pyrrolidone (NMP) 28000 g was added, first, diphenyltetracarboxylic acid (BPTA) 169 g was added, and stirring was performed at room temperature (about 25°C). Then, to the solution, p-phenylenediamine (PPD) 1838 g and diphenyltetracarboxylic dianhydride (BPDA) 4790 g were added, and stirring was performed at room temperature (about 25°C) for 6 hours, to obtain a polyamic acid solution.

[0082] The above polyamic acid solution was coated on a glass substrate, and the solvent was removed by drying in a vacuum oven heated at 60°C. Further, the polyamic acid was put into a nitrogen oven per glass substrate, and heat curing was performed using a gradient temperature increase, the temperature increase process being: heating to 100°C for 1 hour; temperature increase to 150°C for 0.5 hour; temperature increase to 200°C for 0.5 hour; temperature increase to 250°C for 0.5 hour; temperature increase to 300°C for 0.5 hour; temperature increase to 400°C for 1 hour; temperature increase to 500°C for 0.5 hour, the temperature increase rate being 8°C / min.

[0083] [Example 2]

[0084] The addition amounts were changed as described below from Example 1, and a polyamic acid solution and a polyimide film were obtained in the same manner as described in Example 1. The addition amounts were NMP: 28000 g, BPTA: 225 g, PPD: 1838 g, and BPDA: 4790 g.

[0085] [Example 3]

[0086] The addition amounts were changed as described below from Example 1, and a polyamic acid solution and a polyimide film were obtained in the same manner as described in Example 1. The addition amounts were NMP: 28000 g, BPTA: 22 g, PPD: 1475 g, and BPDA: 3956 g.

[0087] [Example 4]

[0088] The addition amounts were changed as described below from Example 1, and a polyamic acid solution and a polyimide film were obtained in the same manner as described in Example 1. The addition amounts were NMP: 28000 g, BPTA: 160 g, PPD: 2100 g, and BPDA: 5267 g.

[0089] [Example 5]

[0090] The amounts of the additives were changed as described below from those of Example 1, and a polyamic acid solution and a polyimide film were obtained in the same manner as described in Example 1. The amounts of the additives were NMP: 28000 g, BPTA: 590 g, PPD: 2100 g, and BPDA: 5181 g.

[0091] [Comparative Example 1]

[0092] NMP 28000 g was charged in a reactor under a nitrogen atmosphere, and PPD 1838 g was first charged, followed by BPDA 4800 g, and stirring was performed at room temperature (about 25°C). Then, BPTA 225 g was added to the solution, and stirring was performed at room temperature (about 25°C) for 6 hours to obtain a polyamic acid solution.

[0093] The above polyamic acid solution was coated on a glass substrate, and the solvent was removed by drying in a vacuum oven heated at 60°C. Then, the dried glass substrate was put in a nitrogen oven, and was heated to 500°C to cure for 4 hours to obtain a polyimide film.

[0094] [Comparative Example 2]

[0095] NMP 28000 g was charged in a reactor under a nitrogen atmosphere, and PPD 1838 g was first charged, followed by BPDA 4800 g, and stirring was performed at room temperature (about 25°C). Then, BPTA 225 g was added to the solution, and stirring was performed at room temperature (about 25°C) for 6 hours to obtain a polyamic acid solution.

[0096] The above polyamic acid solution was subjected to the heat curing operation described in Example 1 to obtain a polyimide film.

[0097] [Comparative Example 3]

[0098] The amounts of the additives were changed as described below from those of Example 1, and a polyamic acid solution was obtained in the same manner as described in Example 1. The amounts of the additives were NMP: 28000 g, BPTA: 149 g, PPD: 1475 g, and BPDA: 3910 g.

[0099] The above polyamic acid solution was coated on a glass substrate, and the solvent was removed by drying in a vacuum oven heated at 70°C. Then, the dried glass substrate was put in a nitrogen oven, and was heated to 450°C to cure for 4 hours to obtain a polyimide film.

[0100] Evaluation of solubility of BPTA

[0101] The solubility of BPTA was evaluated by visual confirmation for the prepared polyamic acid solution. The results of the evaluation of whether or not BPTA was left in the polyamic acid by visual confirmation are shown in Table 1.

[0102] Exhaustion test

[0103] The thermal stability of the polyimide films prepared was evaluated by a test based on weight reduction (outgassing) by heating. The test quantifies the outgassing components produced by heating the polyimide film. The thermal stability can be considered to be high in the case where the value of the outgassing is small.

[0104] The polyimide films obtained in the examples and comparative examples were peeled from the glass substrate. Then, the polyimide films were cut into 4 x 4 mm in size in such a manner that the weight of the film became about 10 mg. The outgassing test was performed using the above polyimide film by a thermogravimetric analysis device (DTG-60AH, Shimadzu Corporation). The measurement conditions were nitrogen atmosphere, temperature increase from 25°C to 450°C, temperature increase rate: 10°C / min, and 450°C for 2 hours.

[0105] The above measurement results are shown in Table 1 below.

[0106] [Table 1]

[0107]

[0108] According to the examples and comparative examples, the following can be mainly understood. According to Table 1, the outgassing values indicating the weight reduction were focused on. The outgassing values of Examples 1 to 5 were in the range of 0.26 mass% to 0.36 mass%, and were all 0.5 mass% or less. On the other hand, the outgassing values of Comparative Example 1 and Comparative Example 2 were 0.66 mass% and 0.56 mass%, respectively, and were higher than 0.5 mass%.

[0109] Regarding Comparative Example 1, the tetracarboxylic acid was not added first in the solvent, but was added in the solution after the polyamic acid polymerization, and the gradient temperature increase curing was not performed. In Comparative Example 2, the tetracarboxylic acid was added in the solution after the polyamic acid polymerization, and the gradient temperature increase curing was performed. In addition, regarding Comparative Example 3, the molar ratio of (BPDA + BPTA) / PPD was 1.004, which was outside the range of 0.940 to 0.995.

[0110] It was thus found that the order of adding BPTA before starting the polymerization of the polyamic acid solution was an effective means for reducing the outgassing amount.

[0111] In addition, according to Table 1, the residual BPTA was focused on, and the examples 1 to 5 all had no residual BPTA. On the other hand, the residual was visually confirmed in Comparative Examples 1 and 2.

[0112] Comparative Example 1 did not initially add the tetracarboxylic acid in the solvent, but added the tetracarboxylic acid in the solution after the polyamic acid polymerization.

[0113] Thus, the order of adding BPTA before the start of the polymerization of the polyamic acid solution is effective for the preparation of the polyamic acid solution without BPTA residue.

[0114] Here, Figure 2 (a) of FIG. 1 shows the appearance of the polyamic acid solution prepared in Example 1, Figure 2 (b) of FIG. 1 shows the appearance of the polyamic acid solution prepared in Comparative Example 1. Figure 2 The solution of (a) of FIG. 1 is transparent, and the tetracarboxylic acid is completely dissolved in the solution. On the other hand, Figure 2 The solution of (b) of FIG. 1 is opaque, and the tetracarboxylic acid remains as an insoluble substance in the solution.

[0115] As described above, it is known that if the tetracarboxylic acid is added first in the solvent, no insoluble substance of the tetracarboxylic acid appears in the solution, and a transparent polyamic acid can be obtained. At the same time, the combination of the stepwise heating curing method can promote the residual secondary reaction in the polyamic acid coating. The amount of exhaust gas generated by the stepwise heating curing method used in Comparative Example 2 is less than that of Comparative Example 1, and it can be considered that the dehydration reaction of the residual tetracarboxylic acid and the secondary reaction have been achieved during the curing process, resulting in a decrease in the final amount of exhaust gas.

[0116] In the embodiments of the present application, by adding the tetracarboxylic acid first in the solvent, a polyamic acid and a polyimide that are beneficial in that the tetracarboxylic acid does not remain undissolved and the amount of exhaust gas during heating is small can be obtained.

[0117] Obviously, the above examples are merely for the purpose of illustration, and are not intended to limit the embodiments. Based on the above description, those skilled in the art can make other different forms of changes or modifications. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or modifications derived therefrom are still within the protection scope of the present application.

Claims

1. A method for producing a polyimide laminate, characterized by, comprising the steps of: adding a tetracarboxylic acid in a solvent to make the tetracarboxylic acid completely dissolved in the solvent to obtain a mixed solution; adding a tetracarboxylic dianhydride and a diamine to the mixed solution to perform a polymerization reaction to obtain a polyamic acid solution; coating the prepared polyamic acid solution on a glass substrate and removing the solvent by low-temperature heating; placing the glass substrate coated with the polyamic acid solution in a nitrogen atmosphere to obtain the polyimide laminate by a curing process, the temperature during the low-temperature heating is 25°C or higher and 200°C or lower; the polyimide laminate comprises the glass substrate; and a polyimide layer laminated on the glass substrate and prepared from the polyamic acid solution, wherein the molar ratio of the added tetracarboxylic acid, tetracarboxylic dianhydride and diamine is as shown in the following formulas (1), (2) and (3): the molar ratio of [the tetracarboxylic dianhydride] / [the diamine] is 0.900-0.990…(1) the molar ratio of [the tetracarboxylic acid] / [the diamine] is 0.005-0.100…(2) the molar ratio of ([the tetracarboxylic dianhydride]+[the tetracarboxylic acid]) / [the diamine] is 0.940-0.995…(3).

2. The polyimide laminate preparation method according to claim 1, wherein the curing process is gradient heating, the heating process comprises heating at 100°C for 0.5-1 hour, heating to 150°C for 0.5-1 hour, heating to 200°C for 0.5-1 hour, heating to 250°C for 0.5-1 hour, heating to 300°C for 0.5-1 hour, and heating to 350°C for 0.5-1 hour, the heating rate of the gradient heating is 2-10°C / min.

3. The polyimide laminate preparation method according to claim 1, wherein the tetracarboxylic acid can be converted into the tetracarboxylic dianhydride upon heating, and then reacts with the diamine.

4. The polyimide laminate preparation method according to claim 1, wherein the solvent is one or more selected from the group consisting of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, ethyl acetate, diethylformamide, diethylacetamide, propylene glycol monomethyl ether, m-cresol, tetrahydrofuran, chloroform and γ-butyrolactone.

5. The polyimide laminate preparation method according to claim 4, wherein the solvent is dimethylacetamide and / or N-methylpyrrolidone.

6. The polyimide laminate preparation method according to claim 1, wherein the tetracarboxylic acid can be selected from one or more of 3,3',4,4'-diphenyltetracarboxylic acid, 2,3,3',4'-diphenyltetracarboxylic acid, 4,4'-(4,4'-isopropylidene diphenyloxy) bis(phthalic acid), 4,4'-(hexafluoroisopropylidene) diphenyl dicarboxylic acid, 4,4'-hydroxydiphenyl dicarboxylic acid and 3,3',4,4'-benzophenonetetracarboxylic acid.

7. The polyimide laminate preparation method according to claim 6, wherein The tetracarboxylic acid is 3,3',4,4'-diphenyltetracarboxylic acid and / or 2,3,3',4'-diphenyltetracarboxylic acid.

8. The method for producing a polyimide laminate according to claim 1, wherein The diamine can be selected from one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-oxydianiline, p-methylenedianiline, m-methylenedianiline, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, bis(trifluoromethyl)diphenylamine, 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(3-aminophenyl)hexafluoropropane, 2,2'-bis(4-aminophenyl)hexafluoropropane, bis(4-aminophenyl)sulfone, bis(3-aminophenyl)sulfone, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 2,2-bis[4-(4-aminophenoxy)-phenyl]propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 4,4'-bis(3-aminophenoxy)diphenylsulfone, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene.

9. The method for producing a polyimide laminate according to claim 8, wherein The diamine is selected from one or more of p-phenylenediamine, m-phenylenediamine, and 4,4'-oxydianiline.

10. The method for producing a polyimide laminate according to claim 1, wherein The tetracarboxylic dianhydride can be selected from one or more of 3,3',4,4'-diphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, 3,3,4,4-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydibenzoic dianhydride, bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride, 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, sulfonephthalic anhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride), 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride).

11. The method for producing a polyimide laminate according to claim 10, wherein The tetracarboxylic dianhydride is 3,3',4,4'-diphenyltetracarboxylic dianhydride and / or pyromellitic dianhydride.

12. The method for producing a polyimide laminate according to claim 1, wherein The polyamic acid solution has a solid content concentration of 5 to 50 mass%.

13. The method for producing a polyimide laminate according to claim 12, wherein The polyamic acid solution has a solid content concentration of 10 to 25 mass%.

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