TW202039655A - Colorless transparent polyimide film - Google Patents

Abstract

A colorless and transparent polyimide film containing a polyimide and a volatile component, wherein if the volatile fraction mass in the film is deemed to be the reduction in mass from the total mass of the film prior to measurement, measured using a differential thermal-thermogravimetric simultaneous measuring device when the temperature is raised from 120°C to 300°C under a stream of nitrogen at a rate of temperature increase of 10°C/min and subsequently held at 300°C for 30 minutes, then the volatile fraction content, which represents the ratio of the above volatile fraction mass relative to the total mass of the film prior to measurement, is within a range from 0.5 to 15% by mass.

Description

Colorless transparent polyimide film

The present invention relates to a polyimide film, and specifically relates to a colorless and transparent polyimide film.

Polyimide resin has excellent mechanical properties and heat resistance, and has been studied for various applications in the fields of electrical and electronic parts. For example, for the purpose of reducing the weight and flexibility of the device, it is expected that the glass substrate used in image display devices such as liquid crystal displays and organic EL displays will be replaced with plastic substrates, and polyamides suitable as plastic materials are also being developed. Research on amine resins.

For example, Patent Document 1 discloses a polyimide-based polymer containing silicon dioxide particles having a specific range of average particle diameter and an alkoxysilane compound with reactive groups to obtain transparency and total light An optical film with improved bend resistance as well as optical properties such as transmittance and YI value.

Patent Document 2 discloses that by using a polyimide-based varnish containing a polyimide-based polymer and a specific ratio of water to form a polyimide-based film, the presence of water can make the polyimide-based film The appearance and flexibility of the film are good. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2017-203159 A [Patent Document 2] International Publication No. 2017/014286

[The problem to be solved by the invention]

However, if inorganic silica particles are contained in the resin, poor dispersion of the silica particles may result in deterioration of transparency and bending resistance and poor stability. In addition, when water is contained in the polyimide varnish, the viscosity of the varnish may change with time due to the influence of water, and there may be doubts about the stability of quality such as stable film thickness and stable appearance during continuous film formation. The problem to be solved by the present invention is to provide a colorless and transparent polyimide film that maintains the optical properties of the optical film such as transparency, total light transmittance, YI value, and haze, and improves the bending resistance. [Means to solve the problem]

The inventors of the present invention have found that by including a specific content of an organic solvent in a polyimide film, the above-mentioned problems can be solved and completed the present invention.

That is to say, the present invention relates to a colorless and transparent polyimide film, which is a polyimide film containing polyimide and volatile components. It will use a differential thermogravimetric simultaneous measurement device under a nitrogen stream at a heating rate of 10°C/min. When the conditions are raised from 120°C to 300°C, and then kept at 300°C for 30 minutes, the total mass reduction from the film before the measurement is measured, and the mass is defined as the volatile content in the film. When the volatile content is relative to the previous measurement The ratio of the total mass of the film, that is, the volatile content is 0.5-15% by mass. [Effects of Invention]

The polyimide film of the present invention, by containing a specific content of organic solvent, can provide optical properties such as the transparency, total light transmittance, yellow index (YI) value, and haze of the optical film, while also improving the durability. Flexible colorless transparent polyimide film. The polyimide film of the present invention can be ideally used for substrates of various components of flexible displays.

The polyimide film of the present invention is a colorless and transparent polyimide film, which contains polyimine and volatile components. The differential thermogravimetric simultaneous measuring device will be used to measure the temperature under the condition of 10℃/min under nitrogen flow. After heating at 120°C to 300°C, and then keeping it at 300°C for 30 minutes, the total mass reduction from the film before the measurement is measured, and the mass is defined as the volatile content in the film. When the volatile content is relative to the film before the measurement The ratio of the total mass, that is, the volatile content rate is 0.5-15% by mass.

式中，R為碳數4~39之4價脂環基，Φ為合計之碳數為2~39之2價脂肪族基、脂環基、芳香族基或由它們的組合構成之基，亦可含有選自於由-O-、-SO₂ -、-CO-、-CH₂ -、-C(CH₃ )₂ -、-OSi(CH₃ )₂ -、-C₂ H₄ O-及-S-構成之群組中之至少1者作為鍵結基。Regarding the polyimide resin of this embodiment, from the viewpoint of transparency and flexibility, for example, polyimide containing a repeating unit represented by the following formula [I] is preferable. [化1]

In the formula, R is a tetravalent alicyclic group with carbon number of 4 to 39, and Φ is a divalent aliphatic group, alicyclic group, aromatic group or a combination of them with a total carbon number of 2 to 39. May also contain selected from -O-, -SO ₂ -, -CO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -OSi(CH ₃ ) ₂ -, -C ₂ H ₄ O- And at least one of the group consisting of -S- is used as the bonding base.

The content of the repeating unit of formula [I] in the polyimine is preferably 10-100 mol%, and more preferably 50-100 mol% relative to 100 mol% of all repeating units of the polyimine. In addition, the number of repeating units of formula [I] in one molecule of polyimide should preferably fall within the range of 10 to 2000, more preferably 20 to 200.

Polyimide can be obtained by reacting alicyclic tetracarboxylic acid or its derivative with diamine or its derivative using tetravalent alicyclic tetracarboxylic acid and divalent diamine as constituent components . Regarding the alicyclic tetracarboxylic acid or its derivatives, for example, alicyclic tetracarboxylic acid, alicyclic tetracarboxylic acid esters, alicyclic tetracarboxylic dianhydride, etc., preferably alicyclic tetracarboxylic acid Carboxylic dianhydride. As for diamines and their derivatives, diamines, diisocyanates, diaminodisilanes, etc. can be cited, and diamines are preferred.

Regarding the alicyclic tetracarboxylic dianhydride used in the synthesis of polyimine, exemplified are 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,4,5-cyclopentane Alkyltetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride Anhydride etc., from the viewpoint of film transparency and suppression of coloration, 1,2,4,5-cyclohexanetetracarboxylic dianhydride is particularly preferred. Generally speaking, polyimide, which is a component of aliphatic diamine, is difficult to polymerize because polyamide acid and diamine, which are an intermediate product, form a strong complex. Therefore, it is necessary to study the use of complexes. Solvents with higher solubility (such as cresol) and so on. However, the polyimide that uses 1,2,4,5-cyclohexanetetracarboxylic dianhydride and aliphatic diamine as the constituent components, because the complex formed by polyamide acid and diamine is compared Weak bond to connect, so high molecular weight is easy, and flexible film can be easily obtained. In addition, the tetracarboxylic acid component includes isomers.

In the tetracarboxylic acid component, a tetracarboxylic acid or its derivative other than alicyclic tetracarboxylic acid may be used in combination within a range that does not impair the solvent solubility of polyimine, the flexibility of the film, and the transparency. It is dianhydride.

Examples of tetracarboxylic acids other than alicyclic tetracarboxylic acids include aromatic tetracarboxylic acids and linear or branched aliphatic tetracarboxylic acids. Specific examples of aromatic tetracarboxylic acids include those selected from pyromellitic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyl Benzenetetracarboxylic acid, 2,2-bis(3,4-dicarboxyphenyl)propane, 2,2-bis(2,3-dicarboxyphenyl)propane, 2,2-bis(3 ,4-Dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1 ,3,3,3-hexafluoropropane, bis(3,4-dicarboxyphenyl) sulfide, bis(3,4-dicarboxyphenyl) ether, bis(2,3-dicarboxylic acid) Phenyl)ether, 3,3',4,4'-diphenyl ketone tetracarboxylic acid, 2,2',3,3'-diphenyl ketone tetracarboxylic acid, 4,4-(paraben Dioxy)diphthalic acid, 4,4-(m-phenylenedioxy)diphthalic acid, 1,1-bis(2,3-dicarboxyphenyl)ethane, Bis(2,3-dicarboxyphenyl)methane, bis(3,4-dicarboxyphenyl)methane and derivatives of these tetracarboxylic acids, especially at least one compound of dianhydrides. Specific examples of linear or branched aliphatic tetracarboxylic acid include ethylene tetracarboxylic acid and the like.

As for the diamine-based components constituting the nitrogen and Φ of the imine ring of the formula [I], diamines, diisocyanates, diaminodisilanes, etc. can be cited, and diamines are preferred. The content of diamine in the diamine-based component is more than 50 mol% (including 100 mol%).

The diamine used in the synthesis of polyimine may also be any one of aromatic diamine, aliphatic diamine or their mixture. From the viewpoint of heat resistance, aromatic diamines are particularly preferable. In addition, the term "aromatic diamine" in the present invention refers to a diamine in which an amine group is directly bonded to an aromatic ring, and a part of its structure may also include aliphatic groups, alicyclic groups, and other substituents. The so-called "aliphatic diamine" refers to a diamine in which an amine group is directly bonded to an aliphatic group or an alicyclic group, and a part of its structure may also contain an aromatic group and other substituents.

Aromatic diamines used in the synthesis of polyimides, from the viewpoint of low birefringence and coloration suppression, diamines with ether groups, diamines with isopropyl groups, and fluorine-based substituents The diamines are ideal, and diamines with ether groups and diamines with isopropyl groups are more desirable. As far as aromatic diamines are concerned, for example, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, benzidine, o-tolidine, m-xylidine Aniline, bis(trifluoromethyl)benzidine, octafluorobenzidine, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4' -Diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,6-di Aminonaphthalene, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl Methane, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl ketone, 2,2-bis(4-( 4-aminophenoxy)phenyl)propane, 2,2-bis(4-(2-methyl-4-aminophenoxy)phenyl)propane, 2,2-bis(4-(2 ,6-Dimethyl-4-aminophenoxy)phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis( 4-(2-Methyl-4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-(2,6-dimethyl-4-aminophenoxy)phenyl ) Hexafluoropropane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(2-methyl-4-aminophenoxy)biphenyl, 4,4' -Bis(2,6-Dimethyl-4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy) Oxy) phenyl) bis(4-(2-methyl-4-aminophenoxy)phenyl) bis(4-(2,6-dimethyl-4-aminophenoxy) Phenyl) benzene, bis(4-(4-aminophenoxy)phenyl)ether, bis(4-(2-methyl-4-aminophenoxy)phenyl)ether, bis( 4-(2,6-Dimethyl-4-aminophenoxy)phenyl)ether, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(2-methyl -4-aminophenoxy)benzene, 1,4-bis(2,6-dimethyl-4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene , 1,3-bis(2-methyl-4-aminophenoxy)benzene, 1,3-bis(2,6-dimethyl-4-aminophenoxy)benzene, 2,2- Bis(4-aminophenyl)propane, 2,2-bis(2-methyl-4-aminophenyl)propane, 2,2-bis(2,6-dimethyl-4-aminophenyl) Yl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis(2-methyl-4-aminophenyl)hexafluoropropane, 2,2-bis(2 ,6-Dimethyl-4-aminophenyl)hexafluoropropane, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, α,α'-bis( 2-methyl-4-aminophenyl)-1,4-diisopropylbenzene, α,α'-bis(2,6-dimethyl-4-aminophenyl)-1,4- Diisopropylbenzene, α,α'-bis(3-aminophenyl)-1,4-diiso Propylbenzene, α,α'-bis(4-aminophenyl)-1,3-diisopropylbenzene, α,α'-bis(2-methyl-4-aminophenyl)-1 ,3-Diisopropylbenzene, α,α'-bis(2,6-dimethyl-4-aminophenyl)-1,3-diisopropylbenzene, α,α'-bis(3 -Aminophenyl)-1,3-diisopropylbenzene, 9,9-bis(4-aminophenyl)pyridium, 9,9-bis(2-methyl-4-aminophenyl) Chrysanthemum, 9,9-bis(2,6-dimethyl-4-aminophenyl)pyridium, 1,1-bis(4-aminophenyl)cyclopentane, 1,1-bis(2- Methyl-4-aminophenyl)cyclopentane, 1,1-bis(2,6-dimethyl-4-aminophenyl)cyclopentane, 1,1-bis(4-aminophenyl) Yl)cyclohexane, 1,1-bis(2-methyl-4-aminophenyl)cyclohexane, 1,1-bis(2,6-dimethyl-4-aminophenyl) ring Hexane, 1,1-bis(4-aminophenyl)4-methyl-cyclohexane, 1,1-bis(4-aminophenyl)norbornane, 1,1-bis(2- Methyl-4-aminophenyl)norbornane, 1,1-bis(2,6-dimethyl-4-aminophenyl)norbornane, 1,1-bis(4-aminobenzene) Yl)adamantane, 1,1-bis(2-methyl-4-aminophenyl)adamantane, 1,1-bis(2,6-dimethyl-4-aminophenyl)adamantane, etc. Among them, 4,4'-diaminodiphenyl ether and α,α'-bis(4-aminophenyl)-1,3-diisopropylbenzene are particularly preferred.

Then, as for the aliphatic diamine used in the synthesis of polyimine, ethylene diamine, hexamethylene diamine, polyethylene glycol bis(3-aminopropyl) ether, polypropylene glycol bis( 3-aminopropyl) ether, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, meta-xylylenediamine, p-xylenediamine , 1,4-bis(2-amino-isopropyl)benzene, 1,3-bis(2-amino-isopropyl)benzene, isophorone diamine, norbornane diamine, silicone Diamines and so on.

Polyimide is usually manufactured in the form of an organic solvent solution. The organic solvent is not particularly limited. For example, N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N-methylcaprolactam, hexamethylphosphamide, tetramethylene sulfonium, dimethyl sulfide, M-cresol, phenol, p-chlorophenol, 2-chloro-4-hydroxytoluene, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, γ-butyl Lactone (GBL), dioxolane, cyclohexanone, cyclopentanone, 1,4-dioxane, ε-caprolactone, dichloromethane, chloroform, etc., can also be used in combination of two or more. However, if the performance of the polyimide varnish composed of polyimide and solvent is considered, use selected from γ-butyrolactone, N,N-dimethylacetamide and N-methyl-2 -At least one selected from the group consisting of pyrrolidone is preferable, and it is more preferable to use at least one selected from the group consisting of γ-butyrolactone and N,N-dimethylacetamide. In addition, when manufacturing by solution polymerization, poor solvents such as hexane, heptane, benzene, toluene, xylene, chlorobenzene, and o-dichlorobenzene can be used together with these solvents without precipitating the polymer. .

Regarding the manufacturing method of the organic solvent solution of polyimide, the following methods (1) to (3) can be mentioned, but it is not limited to these methods.

(1) Add the tetracarboxylic acid component to the organic solvent solution of the diamine component, or add the diamine component to the organic solvent solution of the tetracarboxylic acid component, and preferably below 80°C, especially around room temperature or Keep it at the temperature below it for 0.5 to 3 hours. An azeotropic dehydration solvent such as toluene or xylene is added to the polyamide acid solution of the obtained reaction intermediate, and dehydration reaction is performed while azeotropically removing the generated water from the system to obtain an organic solvent solution of polyimide .

(2) After adding a dehydrating agent such as acetic anhydride to the polyamide acid solution of the reaction intermediate obtained by the same method as the above (1), the polyimide is not dissolved by adding methanol or the like. The solvent is capable of precipitating polyimide. After separating the solid by filtration, washing, and drying, it is dissolved in an organic solvent to obtain an organic solvent solution of polyimide.

(3) In the above (1), use a high-boiling solvent such as cresol to prepare a polyamide acid solution, and maintain this state at 150~220℃ for 3~12 hours to polyimide, then add methanol etc. Solvents lacking dissolving power for polyimine cause polyimide to precipitate. After the solid is separated by filtration, washing, and drying, it is dissolved in an organic solvent such as N,N-dimethylacetamide to obtain an organic solvent solution of polyimide.

In addition, when polyimide is produced by solution polymerization, it is preferable to use a tertiary amine compound as a catalyst. As for them, for example, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethyl Ethanolamine, triethylenediamine, N-methylpyrrolidine, N-ethylpyrrolidine, N-methylpiperidine, N-ethylpiperidine, imidazole, pyridine, quinoline, isoquinoline. Among these tertiary amines, TEA is particularly desirable.

Moreover, in the concentration of the organic solvent solution of the polyimide used in the present invention, the polyimide component is preferably 1-50% by mass, and more preferably 10-40% by mass. If it falls within this range, the surface smoothness of the obtained polyimide film is good.

The weight average molecular weight of the polyimide used in the present invention is preferably 10,000 or more from the viewpoint of the flexibility and mechanical strength of the obtained polyimide, and more preferably 50,000 or more. In addition, the weight average molecular weight of polyimine can be measured by a known method, for example, it can be measured by a method such as gel filtration chromatography. In addition, a method of measuring absolute molecular weight with a light scattering detector using N,N-dimethylformamide in a developing solvent can be mentioned.

Surfactants such as fluorine-based and silicone-based surfactants may also be added to the organic solvent solution of polyimide. By adding a surfactant, it is easy to obtain a film with good surface smoothness.

In the organic solvent solution of polyimide, antioxidants such as phenol, sulfur, phosphoric acid, and phosphorous acid may be added.

The manufacturing method of the polyimide film of this invention is not specifically limited, A well-known method can be used. Examples include coating a solution containing the polyimide of the present invention, or a solution containing the polyimide of the present invention and a solution containing the various additives described above, or forming a film on a glass plate or a metal plate , Plastic and other smooth support after removing the organic solvent and other solvent components contained in the solution.

As an example of the manufacturing method of a polyimide film, the method of casting a polyimide organic solvent solution on a support body and drying the solution casting method, for example, is a film. Specifically, after an organic solvent solution of polyimide is cast on a support, a film forming machine with a system that blows a gas at 50°C to 300°C onto the support is used to make the organic solvent It is desirable to volatilize and then peel off from the support to obtain a self-supporting film. By using the film making machine of this blowing system to volatilize the organic solvent, the drying property can be better. In addition, although the reason has not yet been determined, it is considered that the blowing system can reduce the in-plane retardation and the thickness direction retardation of the film and improve the optical isotropy. It is ideal to perform a drying before blowing the gas. The conditions of the primary drying are not particularly limited. For example, it is desirable to maintain the temperature at 80 to 120°C for 10 to 30 minutes. As for the blowing gas, for example, air or nitrogen can be cited. From the viewpoint of cost, it is preferably air, and from the viewpoint of preventing the coloration of the film, it is preferably nitrogen. The temperature of the blowing gas is more preferably 50°C or more and 250°C or less, and more preferably 100°C or more and 220°C or less. When the temperature of the blowing gas is lower than 50°C, the organic solvent may not sufficiently volatilize, and the film may stick to the support when it is peeled from the support. In addition, when the temperature of the gas is higher than 300°C, the film foams due to the rapid volatilization of the solvent, and the solvent decomposes and the film may be colored. The time for blowing the gas varies according to the temperature of the blowing gas. 15-30 minutes is ideal, and 15-25 minutes is more ideal. In addition, it is possible to provide a plurality of regions where the temperature of the gas blown to the cast material is different.

The polyimide film of the present invention includes the above-mentioned polyimide and volatile components. In terms of volatile components, the above-mentioned organic solvents are preferable. Specifically, for example, N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-diethylacetamide, and N,N-dimethylacetamide can be used. Methyl methamide, N,N-diethyl methamide, N-methyl caprolactamide, hexamethyl phosphamide, tetramethylene sulfonium, dimethyl sulfide, m-cresol, phenol, P-chlorophenol, 2-chloro-4-hydroxytoluene, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, gamma-butyrolactone (GBL), Dioxolane, cyclohexanone, cyclopentanone, 1,4-dioxane, ε-caprolactone, dichloromethane, chloroform, etc., can also be used in combination of two or more kinds. From the point of view of the surface smoothness of the film, at least one selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide and N-methyl-2-pyrrolidone is more Ideally, it is more desirable to contain at least one selected from the group consisting of γ-butyrolactone and N,N-dimethylacetamide. In the present invention, a differential thermogravimetric simultaneous measuring device will be used to increase the temperature from 120°C to 300°C under a nitrogen flow at a heating rate of 10°C/min, and then hold at 300°C for 30 minutes to measure the film from before the measurement The total mass reduction of the film is defined as the volatile content of the film. In the polyimide film of the present invention, the ratio of the volatile component content to the total mass of the film before measurement, that is, the volatile component content is 0.5-15% by mass, preferably 0.7-10% by mass, and more preferably 1-5% by mass. As ideal. If the content of the volatile components in the film is 0.5-15% by mass, it has excellent bending resistance and can be used as a self-supporting film for practical purposes.

The polyimide film may further contain other components as long as the transparency and bending resistance are not impaired. As for other ingredients, colorants such as plasticizers, antioxidants, release agents, stabilizers, bluing agents, flame retardants, lubricants, tackifiers, and leveling agents can be cited. The mixing of additives for the purpose of white coloring, such as titanium dioxide, will increase the reflectance of white light. The addition of nanofillers will increase the macroscopic glass transition temperature of the resin composition molded body and increase the heat resistance. The amount of stretched elastic film increases, and the mechanical strength increases.

The thickness of the polyimide film can be adjusted appropriately according to the application, usually 10~500μm, 15~200μm is more ideal, 20~100μm is more ideal.

When the thickness of the polyimide film is 20-50μm, the total light transmittance based on JIS K7361-1 is preferably 85% or more, and more preferably 90% or more. In addition, when the thickness of the polyimide film is 20-50 μm, the haze (haze) based on JIS K7361-1 is preferably 2% or less, and more preferably 1% or less. In addition, when the thickness of the polyimide film is 20 to 50 μm, the yellow index (YI) based on JIS K7361-1 is preferably 5 or less, and more preferably 3 or less.

The thickness direction retardation (Rth) of the polyimide film is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less. In the polyimide film, the in-plane retardation (Re) with a thickness of 20-50 μm is preferably below 100 nm, more preferably below 70 nm, and even more preferably below 50 nm.

The polyimide film of the present invention has excellent bending resistance. Specifically, the polyimide film is bent 180° at a speed of 40 times/min until R=1mm, and the number of times until breaking is more than 400,000 times, preferably more than 500,000 times, 700,000 times The above is more ideal.

The polyimide film of the present invention can be ideally used as a film for various components such as touch switches, color filters, flexible displays, semiconductor parts, and optical components. [Example]

Hereinafter, the present invention will be specifically explained based on examples. However, the present invention is not limited in any way by these embodiments. The methods for measuring the physical properties of the films obtained in the following examples are as follows.

(1) Film thickness The thickness of the film was measured using a micrometer manufactured by Mitutoyo Co., Ltd.

(2) Total light transmittance, haze (haze), yellow index (YI) The measurement was performed in accordance with JIS K7361-1, using a color turbidity simultaneous measuring device "COH400" manufactured by Nippon Denshoku Industries Co., Ltd.

(3) In-plane phase difference (Re) The in-plane phase difference (Re) was measured using an ellipsometer "M-220" manufactured by JASCO Corporation. The value of the in-plane retardation was measured at the measurement wavelength of 590 nm.

(4) Thickness direction phase difference (Rth) The thickness retardation (Rth) was measured using an ellipsometer "M-220" manufactured by JASCO Corporation. The thickness retardation value was measured at the measurement wavelength of 590 nm. In addition, Rth, when the maximum value of the in-plane refractive index of the polyimide film is defined as nx, the minimum value is defined as ny, the refractive index in the thickness direction is defined as nz, and the thickness of the film is defined as d, it is based on the following Expressed by. Rth=[{(nx+ny)/2}-nz]×d

(5) Flexibility In the measurement system, the polyimide film was bent 180° at a speed of 40 times/min until R=1 mm, and the number of times until breaking was recorded.

(6) Concentration of volatile components in the film The differential thermogravimetric simultaneous measurement device (TG/DTA6200) manufactured by Hitachi High-Tech Science Co., Ltd. was used to increase the temperature from 120°C to 300°C under nitrogen flow at a temperature increase rate of 10°C/min, and then at 300°C The total mass reduction of the film before the measurement measured after the retention for 30 minutes is defined as the volatile content in the film. The ratio of the volatile content to the total mass of the film before the measurement was defined as the volatile content.

>Example 1> In a 2L 5-neck glass round bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen introduction tube, a Dean-Stark device with a cooling tube, a thermometer, and a glass end cap, the α,α'- Bis(4-aminophenyl)-1,3-diisopropylbenzene (manufactured by Mitsui Fine Chemicals Co., Ltd.) 239.772g (0.696 mol), 4,4-diaminodiphenyl ether (Wakayama Refined Chemical Industry Co., Ltd.) 34.842 g (0.174 mol), γ-butyrolactone (Mitsubishi Chemical Co., Ltd.) 376.453 g, and triethylamine as a catalyst (Kanto Chemical Co., Ltd.) (Production) 44.018 g, 0.488 g of triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) were stirred at 200 rpm in a nitrogen atmosphere at a temperature of 70°C in the reaction system to obtain a solution. Among them, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Co., Ltd.) 195.028 g (0.870 mol) and γ-butyrolactone (Mitsubishi Chemical Co., Ltd.) (Production) 94.113 g was added together, and heated with a heating bag for about 20 minutes to raise the temperature in the reaction system to 200°C. The distilled components were collected, and the temperature in the reaction system was maintained at 200°C for 5 hours while adjusting the stirring speed to increase the viscosity. After adding 847.067 g of N,N-dimethylacetamide, it was stirred at about 100°C for about 1 hour to make it into a uniform solution, and a uniform polyimide varnish with a solid content of 25% by mass was obtained.

Then, the obtained polyimide varnish was coated on a PET substrate and kept at 100° C. for 20 minutes, and a self-supporting colorless and transparent primary dried film was obtained by volatilizing the solvent. The film was further fixed to a stainless steel frame and dried by blowing hot air at 210° C. for 20 minutes in an air environment to obtain a film with a thickness of 35 μm. Table 1 shows the evaluation results of the polyimide film.

>Comparative Example 1> The polyimide varnish obtained in Example 1 was dropped into methanol to precipitate the polyimide powder, and the solid was suction filtered with a Kiriyama funnel, and then washed with methanol and dried at 200°C for 30 minutes The solvent is removed to obtain polyimide powder. In a 300 mL 5-neck glass round bottom flask equipped with stainless steel half-moon stirring blades, nitrogen introduction tube, Dean-Stark device with cooling tube, thermometer, and glass end cap, the obtained polyamide After 15 g of amine powder and 85 g of dichloromethane were added together, they were stirred at room temperature for 1 hour to become a uniform solution, and a uniform polyimide varnish with a solid content concentration of 15% by mass was obtained.

Then, by coating the obtained polyimide varnish on a PET substrate, keeping it at room temperature for 5 minutes, keeping it in an air environment at 50°C for 5 minutes, and finally blowing it in an air environment at 150°C for 30 minutes The hot air was dried to obtain a film with a thickness of 35 μm. Table 1 shows the evaluation results of the polyimide film.

[Table 1] Film thickness (μm) Total light transmittance (%) Haze (haze) (%) YI Re (nm) Rth (nm) Flexibility (times) Volatile content rate (mass%) Example 1 35 90.5 0.3 1.1 2.5 26 1000000 1.8 Comparative example 1 35 90.5 0.3 1.2 19.6 122 28 million 0.3

As shown in Table 1, the polyimide film of Example 1 has good optical properties such as total light transmittance, haze, and YI, and has excellent bending resistance. On the other hand, the bending resistance of the polyimide film of Comparative Example 1 was obviously poor.

Claims (9)

A colorless and transparent polyimide film, which is a polyimide film containing polyimide and volatile components. The temperature will be raised from 120°C under a nitrogen flow with a differential thermogravimetric simultaneous measurement device under the condition of a heating rate of 10°C/min. To 300°C, and then keep at 300°C for 30 minutes, the total mass reduction from the film before the measurement is measured as the volatile content in the film. When the volatile content is relative to the total mass of the film before the measurement The ratio of volatile components is 0.5-15% by mass. Such as the colorless transparent polyimide film of claim 1, wherein the volatile component is an organic solvent. The colorless and transparent polyimide film of claim 1 or 2, wherein the volatile component contains selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide and N-methyl-2-pyrrolidone At least one of the groups. Such as the colorless transparent polyimide film of any one of claims 1 to 3, wherein the total light transmittance of the film with a thickness of 20-50μm is 85% or more, and the yellow index (YI) is 5 or less, and the haze ( haze) less than 2%. The colorless transparent polyimide film according to any one of claims 1 to 4, wherein the in-plane retardation (Re) with a thickness of 20-50 μm is 50 nm or less, and the retardation (Rth) in the thickness direction is 100 nm or less. For example, the colorless transparent polyimide film of any one of claims 1 to 5 is a polyimide with a weight average molecular weight of 50,000 or more. The colorless and transparent polyimide film of any one of claims 1 to 6, wherein the polyimide comprises a repeating unit represented by the following formula [I],

In the formula, R is a tetravalent alicyclic group with carbon number of 4 to 39, and Φ is a divalent aliphatic group, alicyclic group, aromatic group or a combination of them with a total carbon number of 2 to 39. May also contain selected from -O-, -SO ₂ -, -CO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -OSi(CH ₃ ) ₂ -, -C ₂ H ₄ O- And at least one of the group consisting of -S- is used as the bonding base. A method for producing a colorless and transparent polyimide film according to any one of claims 1 to 7, using a solution casting method in which an organic solvent solution of polyimide is cast on a support and dried Make a film. For example, the method for producing a colorless and transparent polyimide film of claim 8 is to cast an organic solvent solution of polyimide on a support, and then use a method for blowing a gas above 50°C and below 300°C onto the support body. The film forming machine of the cast product system volatilizes the organic solvent, and then peels off from the support to obtain a colorless transparent polyimide film as a self-supporting film.