CN111417605B

CN111417605B - Solution for coating glass substrate

Info

Publication number: CN111417605B
Application number: CN201880077795.2A
Authority: CN
Inventors: 杉本洋辅; 山田祐己; 吉田猛; 繁田朗; 越后良彰
Original assignee: Unitika Ltd
Current assignee: Unitika Ltd
Priority date: 2017-12-04
Filing date: 2018-12-04
Publication date: 2021-10-15
Anticipated expiration: 2038-12-04
Also published as: KR20200091865A; JP6537584B2; CN111417605A; WO2019111870A1; TWI765127B; JP2019099697A; TW201927943A

Abstract

The invention provides a coating solution which can fully ensure the adhesion to a glass substrate even if the temperature rising speed is increased when a polyamide acid (PAA) coating film is subjected to heat curing, can be easily peeled off from the glass substrate in the form of a polyimide film after the heat curing, and has good storage stability. The invention relates to a solution for coating a glass substrate, which comprises PAA, an amide solvent and an alkoxy silane compound, and is characterized in that: 1) the content of the alkoxysilane compound is more than 5ppm and less than 100ppm with respect to the mass of PAA, and 2) the molecular weight of the alkoxysilane compound is 100 to 300.

Description

Solution for coating glass substrate

Technical Field

The present invention relates to a coating solution containing polyamic acid (PAA) as a Polyimide (PI) precursor, which is applied to a glass substrate.

Background

Conventionally, in the field of Flat Panel Displays (FPDs) such as Liquid Crystal Displays (LCDs), Plasma Display Panels (PDPs), and organic EL displays (OLEDs), and electronic devices such as electronic paper, mechanisms in which electronic elements are formed on a glass substrate have been mainly used, but glass substrates are rigid and lack flexibility, and therefore have a problem in that they are not easily flexible.

Therefore, a method of using a PI film having flexibility and good heat resistance and dimensional stability as a flexible substrate has been proposed. For example, it is proposed to use a laminate of: a PAA solution that is a precursor of PI is applied and dried to form a PAA coating film, which is thermally cured to form a laminate in which a PI film is laminated and integrated on a glass substrate. That is, after an electronic component is formed on the surface of the PI film laminated on the glass substrate, the PI film is finally peeled off from the glass substrate, thereby producing a flexible substrate. In the heat curing process, when the PAA coating film formed on the glass substrate is converted into a PI film, the coating film may be peeled off from the glass substrate or air bubbles may remain on the surface of the PI film. This problem becomes remarkable particularly when the temperature rising rate at the time of thermosetting is increased in order to improve the production efficiency.

Therefore, it is necessary to sufficiently ensure adhesion of the PAA coating film to the glass substrate during heat curing. As a method for securing this adhesion, a method is known in which a solution prepared by blending an alkoxysilane compound with PAA is applied to a glass substrate, and then the PAA coating film is thermally cured to form a PI film. For example, patent document 1 (example) discloses an example of a PAA solution in which 200 to 500ppm of an alkoxysilane compound and 500 to 800ppm of a silicone surfactant are mixed in mass with respect to PAA. Patent document 2 (claim 1) discloses a method for improving the adhesion between a PI film and a glass substrate by using a PAA solution in which 100 to 20000ppm of an alkoxysilane compound is added to the mass of PAA. Patent document 3 (claim 1) discloses a method for improving the adhesion between a PI film and a glass substrate by using an alkoxysilane-modified PAA solution obtained by heating a PAA solution containing 500 to 1000ppm of an alkoxysilane compound based on the mass of PAA to about 50 ℃.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 6067740

Patent document 2: japanese patent No. 6172139

Patent document 3: international publication No. 2016/024457

Disclosure of Invention

However, in the methods disclosed in the related art, since a large amount of an alkoxysilane compound is mixed in a PAA solution, there is a concern that the mechanical properties, electrical properties, optical properties, and the like of the obtained PI film are impaired. Further, the adhesion between the PI film and the glass substrate is too strong, and there is a possibility that the PI film is not easily peeled off when the PI film is finally peeled off from the glass substrate after the electronic element is formed on the surface of the PI film. Further, these PAA solutions may change in viscosity during storage, and it is difficult to ensure good storage stability.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a coating solution which can sufficiently ensure the adhesion of a PAA coating film, can be easily peeled off from a glass substrate as a PI film after heat curing, and has good storage stability.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using a PAA solution containing a specific amount of a specific alkoxysilane compound, and have completed the present invention.

The gist of the present invention is as follows.

< 1 > A solution for coating a glass substrate, comprising PAA, an amide solvent and an alkoxysilane compound, characterized by comprising:

1) the content of the alkoxysilane compound is more than 5ppm and less than 100ppm with respect to the mass of PAA,

2) the molecular weight of the alkoxysilane compound is 100 to 300.

< 2 > A method for producing a solution for coating a glass substrate, comprising a polyamic acid (PAA) which is a precursor of a Polyimide (PI), an amide solvent, and an alkoxysilane compound, characterized in that when the alkoxysilane compound having a molecular weight of 100 to 300 is added to the PAA solution, the amount of the alkoxysilane compound added is more than 5ppm and less than 100ppm with respect to the mass of the PAA, and the amount of the alkoxysilane compound added is adjusted according to the thickness of the target PI film.

< 3 > A method for producing a laminate comprising a PI film and a glass substrate, wherein a Polyimide (PI) film is formed on the glass substrate by applying the coating solution < 1 > to the glass substrate, drying the coating solution, and then thermally curing the coating solution, wherein the Polyimide (PI) film is thermally cured by continuously raising the temperature, and the upper limit temperature of the Polyimide (PI) film during thermal curing is set to 350 to 500 ℃.

By using the PAA solution of the present invention, adhesion to a glass substrate can be sufficiently ensured when a PAA coating film is thermally cured. In addition, the PI film after heat curing can be easily peeled off from the glass substrate in the form of a PI film. Therefore, the PAA solution can be suitably used as a solution for manufacturing a flexible substrate including a PI film on which an electronic element is formed.

Detailed Description

The present invention will be described in detail below.

The PAA solution of the present invention is coated on a glass substrate. As the glass substrate, for example, a substrate made of soda lime glass, borosilicate glass, alkali-free glass, or the like can be used, and among these, an alkali-free glass substrate can be preferably used. These glass substrates may be subjected to a known surface treatment such as a silane coupling agent treatment.

The thickness of the glass substrate is preferably 0.3 to 5.0 mm. If the thickness is thinner than 0.3mm, the workability of the substrate may be deteriorated. In addition, if the thickness is thicker than 5.0mm, the productivity may be lowered.

The PAA solution of the present invention is obtained by adding an alkoxysilane compound to a PAA solution obtained by polymerizing tetracarboxylic acids and diamines, which are raw materials, in an amide solvent in approximately equimolar amounts. Here, "substantially equimolar" means that the diamine is 0.9 to 1.0 mol based on 1 mol of the tetracarboxylic acid.

Examples of the tetracarboxylic acids (tetracarboxylic acids, dianhydrides thereof, esters thereof, and the like) include pyromellitic acid, 3,3 ', 4, 4' -biphenyltetracarboxylic acid, 4,4 '-hexafluoroisopropylidene phthalic acid, 2,3, 3', 4 '-biphenyltetracarboxylic acid, 2', 3,3 '-biphenyltetracarboxylic acid, 4, 4' -oxydiphthalic acid, 3,3 ', 4, 4' -benzophenone tetracarboxylic acid, 3,3 ', 4, 4' -diphenylsulfone tetracarboxylic acid, p-terphenyltetracarboxylic acid, and m-terphenyltetracarboxylic acid. These tetracarboxylic acids can be used individually or in the form of mixtures. Among these, from the viewpoint of the heat resistance and dimensional stability of the obtained PI, 3 ', 4,4 ' -biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), 4,4 ' -hexafluoroisopropylidene phthalic dianhydride (6FDA), and a mixture thereof are preferable.

Examples of the diamine include p-Phenylenediamine (PDA), m-phenylenediamine, 4 ' -Oxyaniline (ODA), 3 ' -bis (trifluoromethyl) -4,4 ' -diaminobiphenyl (TFMB), 3,4 ' -diaminodiphenyl ether, 4 ' -diaminodiphenylmethane, 3 ' -dimethyl-4, 4 ' -diaminodiphenylmethane, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 1, 2-bis (anilino) ethane, diaminodiphenylsulfone, diaminobenzanilide, diaminobenzoate, diaminodiphenylsulfide, 2-bis (p-aminophenyl) propane, 2-bis (p-aminophenyl) hexafluoropropane, 1, 5-diaminonaphthalene, diaminotoluene, and the like, Diaminobenzotrifluoride, 1, 4-bis (p-aminophenoxy) benzene, 4 '-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4' -bis (3-aminophenoxyphenyl) diphenylsulfone, and the like. These aromatic diamines may be used alone or in a mixture. Among these, PDA, ODA, TFMB and mixtures thereof are preferable from the viewpoint of the heat resistance and dimensional stability of the obtained PI.

Examples of the amide solvent include N-methyl-2-pyrrolidone (NMP), N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), and the like. These solvents may be used alone or in the form of a mixture. Among these, NMP, DMAc, and a mixture thereof are preferable from the viewpoint of solubility in PAA. These solvents are preferably dehydrated, and the water content thereof is preferably 500ppm or less, more preferably 200ppm or less. By setting as described above, the water content in the PAA solution can be reduced, and hydrolysis of the alkoxysilane compound and the like during storage can be prevented.

The reaction temperature for producing the PAA solution is preferably-30 to 70 ℃, and more preferably-15 to 60 ℃. In this reaction, the order of addition of the monomer and the solvent is not particularly limited, and may be any order. The solid content concentration of PAA is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass. The PAA may be partially imidized. The viscosity of the PAA solution thus obtained is preferably 3Pa · s to 100Pa · s as the solution viscosity at 30 ℃. Commercially available products may be used as the PAA solution. As commercially available products, it is preferable to use "U Imide Varnish AH, AR" (manufactured by Youngco), UPIA-ST "(manufactured by Youguko Co., Ltd.), and" PI-2611 "(manufactured by Hitachi Chemical Dupont MicroSystems). These are all solutions of PAA in NMP obtained using BPDA as the acid component and PDA as the diamine component.

The PAA solution of the present invention can be obtained by compounding an alkoxysilane compound in the PAA solution obtained in the above-described manner. Here, the amount of the alkoxysilane compound to be added needs to be more than 5ppm and less than 100ppm with respect to the mass of PAA. Further, the molecular weight of the alkoxysilane compound is required to be 100 to 300.

Examples of such alkoxysilane compounds include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-Aminopropyltrimethoxysilane (APMS), 3-Aminopropyltriethoxysilane (APES), 3-triethoxysilyl-N- (1, 3-dimethyl-butylene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, p-vinyltrimethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, N-tert-butyl-3-aminopropyltrimethoxysilane, N-tert-butyl-3-aminobutylidenedimethoxysilane, N-tert-butylidenedimethoxysilane, N-propyltrimethoxysilane, N-ethyltrimethoxysilane, p-ethyltrimethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-epoxypropylmethyldimethoxysilane, N-2-aminopropylmethyldimethoxysilane, N-propyltrimethoxysilane, N-ethyltrimethoxysilane, N-propyltrimethoxysilane, N-ethyltrimethoxysilane, p-ethyltrimethoxysilane, 2-epoxycyclohexyl-ethyltrimethoxysilane, p-propylmethyldimethoxysilane, p-ethyltrimethoxysilane, p-propylmethyldimethoxysilane, p-propyltrimethoxysilane, p-isopropyltrimethoxysilane, p-ethyltrimethoxysilane, p-isopropyltrimethoxysilane, p-butyltrimethoxysilane, or a mixture of a mixture, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-Ureidopropyltriethoxysilane (UPES), 3-ureidopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, etc. Among these, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-ureidopropyltriethoxysilane and mixtures thereof are preferred.

By defining the compounding amount and molecular weight of the alkoxysilane compound as described above, when the PAA coating film is thermally cured, adhesion to the glass substrate can be sufficiently ensured even if the temperature rise rate is increased, and the PAA coating film can be easily peeled off from the glass substrate as a PI film after thermal curing. By using such a combination, a PAA solution having excellent storage stability can be obtained. The amount of the alkoxysilane compound to be added can be confirmed by a liquid chromatography mass spectrometer (LC-MS).

The PAA solution of the present invention may also be modified with an alkoxysilane compound in part by heating it to about 50 ℃.

In the PAA solution of the present invention, by setting the amount of the alkoxysilane compound to the above range, adhesion to a glass substrate and peelability can be ensured even if the temperature rise rate is increased, and therefore, it is preferable to substantially not mix other additives which may impair the mechanical properties of the PI film, for example, a surfactant such as a silicone surfactant and a fluorine-based surfactant as disclosed in patent document 1. Here, "not substantially blended" means that the blending amount is less than 1 ppm. By setting in this manner, the original good mechanical properties, electrical properties, optical properties, and the like of the PI can be ensured.

The PAA solution of the present invention may contain fine particles of silica, alumina, or the like in a range that does not impair optical characteristics such as transparency of the PI film. The volume average particle diameter of these fine particles (based on dynamic light scattering) is preferably 10nm to 100 nm. The amount of the PAA is preferably 5 to 20% by mass based on the mass of PAA.

Other polymers may be added to the PAA solution of the present invention within a range not to impair the effects of the present invention.

The PAA solution of the present invention is applied to a glass substrate, dried, and thermally cured to convert a PAA coating film into a PI film to prepare a laminate, and then an electronic element is formed on the surface, and finally the PI film is peeled off from the glass substrate, thereby preparing a flexible substrate.

When the PAA solution of the present invention is applied to a glass substrate, the amount of alkoxysilane compound to be added is preferably adjusted according to the thickness of the target PI film. That is, the amount of the PI film to be blended is preferably reduced as the thickness of the PI film is reduced. Further, it is preferable that the amount of the PI film is increased as the thickness of the PI film is increased. By setting in this manner, adhesion to the glass substrate and peelability from the glass substrate can be more sufficiently ensured, and the amount of the alkoxysilane compound to be added can be minimized depending on the thickness.

As a method for applying the PAA solution to the glass substrate, coating can be performed continuously or batchwise by using a known method such as mesa coating, dip coating, bar coating, spin coating, die coating, spray coating, and the like.

For drying and thermosetting, a general hot air dryer, an infrared lamp, or the like can be used. The drying temperature is preferably 40 to 150 ℃ and the drying time is preferably about 5 to 30 minutes.

In the thermosetting of the dried PAA coating film obtained in the above manner, it is preferable to continuously raise the temperature to prepare a thermosetting PI film. Here, "continuously raising the temperature" means raising the temperature of the atmosphere at the time of thermal curing at a controlled temperature raising rate. From the viewpoint of ensuring the adhesion of the PAA coating film to the glass substrate, the temperature increase rate is preferably 1 to 15 ℃/min, more preferably 3 to 10 ℃/min. The upper limit temperature at the time of temperature rise is preferably 350 to 500 ℃. The temperature raising process may include a step of maintaining the atmospheric temperature for a certain period of time during the temperature raising.

The atmosphere during thermal curing is preferably an inert gas atmosphere such as nitrogen or argon. Patent documents 1 to 3 do not describe or suggest a method of continuously raising the temperature of the PAA coating film to perform thermosetting. That is, in the examples of patent document 1, the following methods are described: as the heat curing conditions, after coating so that the film thickness after curing becomes 20 μm, the coating was cured under the conditions of "a: 140 ℃ X1 hr +250 ℃ X1 hr +350 ℃ X1 hr, B: 140 ℃ X1 hr +450 ℃ X1 hr, C: the thermosetting under the conditions of 140 ℃ C.. times.1 hr +500 ℃ C.. times.1 hr "is a method of heating continuously. In the examples of patent document 2, it is described that "baking (drying) with a hot plate at 130 ℃ for 2 minutes as a heat curing condition forms a film to have a thickness of 18 μm. Next, the polyimide precursor in the resin composition was imidized "by heat curing at 200 ℃ for 30 minutes and further at 450 ℃ for 60 minutes in a curing oven, which was a method of heating up discontinuously. When such a discontinuous temperature raising method is used, when the amount of alkoxysilane compound to be added to the PAA solution is reduced, sufficient adhesion of the obtained PI film may not be ensured.

Since the PAA coating film obtained from the PAA solution of the present invention has good adhesion to a glass substrate, the PAA coating film can be prevented from generating bubbles or swelling even if the temperature rise rate at the time of temperature rise is set to a fast temperature rise rate of, for example, 3 to 10 ℃/min as described above.

The laminate obtained as described above is useful for manufacturing electronic devices because it is possible to easily peel off the PI film from the glass substrate after forming an electronic element on the surface of the PI film.

The thickness of the PI film after peeling from the glass substrate is preferably 1 to 50 μm, more preferably 5 to 40 μm. When the PAA solution of the present invention is used, the amount of alkoxysilane to be added is adjusted, whereby the PAA solution can be thermally cured without causing bubbles or swelling even when the thickness is as thick as about 30 μm. For example, when the thickness of the target PI film is 10 μm or more (particularly, 15 μm to 40 μm), the amount of the alkoxysilane compound to be incorporated is preferably 25ppm or more (particularly, 25ppm or more and less than 100 ppm).

As the electronic component, all electronic components conventionally used in the field of electronic devices can be used. As a method for forming an electronic element, a method known in the field of electronic devices using a PI film as a flexible substrate can be used.

Examples of the electronic device include a Flat Panel Display (FPD) such as a Liquid Crystal Display (LCD), a Plasma Display Panel (PDP), and an organic EL display (OLED), and a flexible device such as electronic paper.

Examples

< PAA solution A-1 >

As PAA solution A-1, U Imide Varnish AR (BPDA/PDA NMP solution) was prepared. The PAA solution had a solution viscosity of 4.3 pas at 30 ℃ and a PAA solid content concentration of 19.1 mass% based on the A-1 mass.

< PAA solution B-1 >

PDA (0.600 mol) and NMP (polymerization solvent) having a water content of 200ppm or less were put into a glass reaction vessel under a nitrogen atmosphere and stirred to dissolve the PDA. BPDA (0.612 mol) was slowly added to the solution while the solution was cooled to 30 ℃ or lower with a cannula, and then polymerization was carried out at 60 ℃ for 100 minutes to obtain a PAA solution having a solution viscosity of 75 pas at 25 ℃ and a PAA solid content concentration of 20 mass% relative to the mass of B-1.

< PAA solution C-1 >

PDA (0.550 mol), ODA (0.050 mol) and NMP (polymerization solvent) having a water content of 200ppm or less were put into a glass reaction vessel under a nitrogen atmosphere and stirred to dissolve the PDA and ODA. BPDA (0.605 mol) was slowly added to the solution while the solution was cooled to 30 ℃ or lower with a cannula, and then polymerization was carried out at 60 ℃ for 100 minutes to obtain a PAA solution having a solution viscosity of 98.5 pas at 25 ℃ and a PAA solid content concentration of 20 mass% based on the mass of C-1.

< PAA solution D-1 >

PDA (0.5 mol), TFMB (0.1 mol) and NMP (polymerization solvent) having a water content of 200ppm or less were put into a glass reaction vessel under nitrogen atmosphere and stirred to dissolve PDA and TFMB. While the solution was cooled to 30 ℃ or lower with a cannula, BPDA (0.505 mol) and 6FDA (0.1 mol) were slowly added, and then polymerization was carried out at 60 ℃ for 100 minutes to obtain a PAA solution having a solution viscosity of 86.4Pa · s at 25 ℃ and a PAA solid content concentration of 20 mass% relative to D-1 mass.

< example 1 >

3-aminopropyltrimethoxysilane (APMS, molecular weight: 179.3) was added to A-1 at room temperature (25 ℃ C.) in an amount of 30ppm relative to the mass of PAA and stirred, whereby a uniform PAA solution (A-2) was obtained.

A-2 was applied to the surface of an alkali-free glass substrate (20cm square) having a thickness of 0.7mm by a mesa coater, and dried at 45 ℃ for 10 minutes, 70 ℃ for 5 minutes, and 150 ℃ for 5 minutes to form a PAA coating film.

Next, the PAA coating film was thermally cured by raising the temperature to 450 ℃ at a rate of 0.5 ℃/min or 5 ℃/min under a nitrogen gas flow, and holding at 450 ℃ for 10 minutes. Thus, a laminate having a PI film with a thickness of 18 μm formed on a glass substrate was obtained. The adhesion between the glass substrate and the PI film in this laminate was evaluated according to the following criteria, and the evaluation results are shown in table 1.

< evaluation of adhesion >

After the thermosetting, a case where a uniform PI film can be formed on the glass substrate is "very excellent", and a case where 1 or more places of the PI film portion rising or peeling are present on the glass substrate after the thermosetting is "Δ" (practically problematic).

The peeling properties between the glass substrate and the PI film in the laminate were evaluated according to the following criteria, and the evaluation results are shown in table 1.

< evaluation of peelability >

A cut was cut at a portion of the PI film 2.5cm from the end of the four sides by a cutter, and a PI tape with an adhesive was attached to the end of a sample of the PI film having a cut of a quadrilateral shape with one side of 15cm, and when the PI tape was pulled, the PI film adhered to the glass substrate was "very excellent" in that the PI film could be easily peeled off, and when the PI tape was peeled off, the PI film was stuck (that is, when the PI film was more firmly adhered to the glass substrate in a part of the interface between the PI film and the glass substrate, and peeling was inhibited), the PI film was "Δ" (practically problematic).

< example 2 >

A PAA solution (A-3) was obtained in the same manner as in example 1, except that the amount of APMS added was 75ppm based on the mass of PAA. A laminate was produced and evaluated in the same manner as in example 1 for A-3. The evaluation results are shown in table 1.

< examples 3 and 4 >

A laminate was produced and evaluated in the same manner as in example 1, except that PAA solutions (A-4 to A-5) were prepared using 3-aminopropyltriethoxysilane (APES, molecular weight: 221.4) as the alkoxysilane in such an amount that the amount of the alkoxysilane added was the amount described in Table 1. The evaluation results are shown in table 1.

< example 5 >

A laminate was produced and evaluated in the same manner as in example 1, except that a PAA solution (A-6) in which the amount of APMS added was 10ppm based on the mass of PAA and the thickness of the PI film was set to 9 μm. The evaluation results are shown in table 1.

< example 6 >

A laminate was produced and evaluated in the same manner as in example 1, except that a PAA solution (A-7) in which the amount of APMS added was 95ppm based on the mass of PAA and the thickness of the PI film was 21. mu.m. The evaluation results are shown in table 1.

< examples 7 and 8 >

APES was added to B-1 in an amount of 30ppm and 75ppm based on the weight of PAA, and the mixture was stirred, whereby a PAA solution (B-2) and a PAA solution (B-3) were uniformly obtained, respectively. Using these solutions, a laminate was produced and evaluated in the same manner as in example 1. The evaluation results are shown in table 1.

< examples 9 and 10 >

APMS was added to C-1 in an amount of 20ppm and 40ppm based on the mass of PAA, and the mixture was stirred, whereby a PAA solution (C-2) and a PAA solution (C-3) were uniformly obtained, respectively. Using these solutions, a laminate was produced and evaluated in the same manner as in example 1. The evaluation results are shown in table 1.

< examples 11 to 13 >

A laminate was produced and evaluated in the same manner as in example 1, except that the thickness of the PI film was changed to 27 μm by using A-6, A-7 and C-2. The evaluation results are shown in table 1.

< example 14 >

To A-1 was added 20ppm of 3-ureidopropyltriethoxysilane (UPES, molecular weight: 264) and stirred, thereby obtaining a uniform PAA solution (A-8). A laminate was produced and evaluated in the same manner as in example 1 using A-8. The evaluation results are shown in table 1.

< example 15 >

80ppm of AMPS was added to D-1 and stirred, thereby obtaining a uniform PAA solution (D-2). Using D-2, a laminate was produced and evaluated in the same manner as in example 1. The evaluation results are shown in table 1.

The PAA solutions used in examples 1 to 15 were stored at 25 ℃ for 10 days, and as a result, the viscosity change rate was less than 5% in all the solutions, and good storage stability was confirmed.

< comparative examples 1 and 2 >

A laminate was produced and evaluated in the same manner as in example 1, except that 3-aminopropyltriethoxysilane (APES, molecular weight: 221.4) was used as the alkoxysilane and PAA solutions (A-9 and A-10) were used in such an amount that the amount of the alkoxysilane added was the amount described in Table 1. The evaluation results are shown in table 1. The change rate of viscosity after storing A-9 and A-10 at 25 deg.C for 10 days is more than 5% in both PAA solutions.

< comparative examples 3 to 5 >

A laminate was produced and evaluated in the same manner as in example 1, except that a PAA solution (A-11 to A-13) was prepared using bis (3-trimethoxysilylpropyl) -N-methylamine (BTMM, molecular weight: 355.6) as an alkoxysilane in such an amount that the amount of the alkoxysilane was changed to the amount shown in Table 1. The evaluation results are shown in table 1. The viscosity change rates of A-11 to A-13 after being respectively stored for 10 days at 25 ℃ are all less than 5 percent.

< comparative examples 6 to 8 >

Laminates were prepared and evaluated in the same manner as in example 1, except that A-1, B-1 and C-1 containing no alkoxysilane were used as the PAA solution. The evaluation results are shown in table 1. The viscosity change rates of A-1, B-1 and C-1 after being respectively stored for 10 days at 25 ℃ are all less than 5 percent.

< comparative example 9 >

A laminate was produced and evaluated in the same manner as in example 1, except that a PAA solution (A-14) was prepared so that the amount of APES added was 5ppm based on the mass of PAA. The evaluation results are shown in table 1. The viscosity change rate of A-14 after 10 days of storage at 25 ℃ is less than 5%.

< comparative example 10 >

A laminate was produced and evaluated in the same manner as in example 1, except that a PAA solution (A-15) in which the amount of APMS added was 5ppm based on the mass of PAA and the thickness of the PI film was 10 μm was prepared. The evaluation results are shown in table 1. The viscosity change rate of A-15 after being stored for 10 days at 25 ℃ is less than 5%.

[ Table 1]

"-": indicating no match or rating.

As is clear from the examples, when the PAA solution of the present invention is used, good adhesion and peeling properties can be secured even when the temperature increase rate during thermal curing is increased to 5 ℃/min by adjusting the amount of alkoxysilane compound to be added depending on the thickness of the PI film. This is clear from a comparison of example 11 with example 12 or a comparison of example 9 with example 13.

In addition, in the embodiment 1 and 2 comparison or embodiment 3 and 4 comparison, even make the alkoxy silane compound loading of 30ppm, 75ppm, adhesion, peeling can also obtain the same result. In this case, as described above, the amount of the alkoxysilane compound to be added is more preferably 30ppm which is less than the amount to be added.

In addition, it was found that the PAA solution of the present invention has good storage stability.

Industrial applicability

The PAA solution of the present invention can be suitably used as a solution for manufacturing a flexible substrate made of a PI film on which an electronic element is formed.

Claims

1. A solution for coating a glass substrate, comprising a polyamic acid (PAA), an amide solvent, and an alkoxysilane compound, characterized by comprising:

2) the alkoxy silane compound is 3-aminopropyl trimethoxy silane, 3-aminopropyl triethoxy silane or their mixture.

2. The solution for coating a glass substrate according to claim 1, wherein the amide solvent is N-methyl-2-pyrrolidone, N-dimethylacetamide, or a mixture thereof.

3. The solution for coating a glass substrate according to claim 1 or 2, wherein the water content of the amide solvent is 200ppm or less.