TW202100628A - Method for producing colorless transparent resin film - Google Patents

Abstract

A method for producing a colorless transparent resin film by a solvent casting method in which an organic solvent solution of a resin is flow cast onto a support body and then dried, wherein the organic solvent contains at least one type of organic solvent (S1) with a boiling point of 80° or lower and at least one type of organic solvent (S2) with a boiling point of 130° or higher.

Description

Manufacturing method of colorless transparent resin film

The present invention relates to a method of manufacturing a colorless transparent resin film.

Because polyimide resin has excellent mechanical properties and heat resistance, some people are exploring various applications in the fields of electrical parts or electronic parts. For example, for the purpose of lightweight or flexible parts, it is expected that glass substrates used in image display devices such as liquid crystal displays or organic EL displays will be replaced with plastic substrates, which are suitable as the polyimide resin of the plastic material. Research is also ongoing.

The general polyimide film is generally formed by casting an organic solvent solution containing polyamide acid on a belt or drum, heating the polyamide acid, etc. to cause the imidization reaction to proceed to perform solution casting film formation.

The commonly used polyimide is known to have high heat resistance. The general-purpose polyimine can be obtained from aromatic tetracarboxylic acid anhydrides and aromatic diamines. It has excellent heat resistance, chemical resistance, mechanical properties, and electrical properties due to the rigidity of the molecule, resonance stabilization, and strong chemical bonding. Therefore, it is widely used in the fields of forming materials, composite materials, electrical parts or electronic parts.

However, polyimines synthesized from the above-mentioned aromatic raw materials are not suitable for use due to absorption from the formation of intramolecular or intermolecular electron transfer complexes, which will be colored yellow or brown after the film is formed. Optical applications such as substrate materials such as flat panel displays and mobile phone devices, optical fibers, optical waveguides, optical sensors, and optical adhesives.

Therefore, in order to take advantage of the high heat resistance of polyimide and improve transparency, fluorinated polyimide with perfluoroalkyl group introduced into the repeating unit, or the use of 1, 2, 4, Alicyclic polyimide of alicyclic raw materials such as 5-cyclohexanetetracarboxylic anhydride.

Patent Document 1 discloses a method for producing a polyimide-based film, which produces releasability and appearance from a liquid containing a polyimide-based polymer, γ-butyrolactone and N,N-dimethylacetamide Excellent polyimide film.

Patent Document 2 shows a method of manufacturing an optical film, which reduces scaly unevenness by including an alcohol solvent in a liquid containing a soluble polyimide resin as a main component and dichloromethane as a solvent. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2017-25204 A [Patent Document 2] JP 2017-187617 A

[The problem to be solved by the invention]

However, in the method of Patent Document 1, when a high boiling point organic solvent such as γ-butyrolactone or N,N-dimethylacetamide is used, in order to remove the solvent, the temperature in the drying step needs to be high. There is a problem of reduced transparency due to coloring. In addition, in the method of Patent Document 2, in the case of a low boiling point solvent such as dichloromethane, the solvent may volatilize rapidly, and the polyimide aligned by the casting method may be fixed to produce optical anisotropy. Sexual issues.

The problem to be solved by the present invention is to provide a method for manufacturing a colorless transparent resin film, which can achieve no coloration under high-temperature drying and good optical properties. [Means to solve the problem]

The inventors of the present invention have found that when the film is produced by the solution casting method, the organic solvent in the organic solvent solution of the resin contains a low-boiling point solvent as the main component and contains a high-boiling point solvent, which can solve the above problem and completed this invention.

That is, the present invention relates to a method of manufacturing a colorless and transparent resin film by a solution casting method including the steps of casting an organic solvent solution of the resin on a support and drying the resin film. The organic solvent contains at least one organic solvent (S1) with a boiling point below 80°C and one or more organic solvents (S2) with a boiling point above 130°C. [Effects of Invention]

According to the method of the present invention, a colorless and transparent resin film with excellent transparency and optical properties can be produced. The colorless transparent resin film obtained by the method of the present invention has good optical properties such as total light transmittance, yellow index (YI) value, and haze, and has low retardation that exhibits optical equivalence. Therefore, the colorless and transparent resin film obtained by the method of the present invention exhibits good performance when used as a base material for a transparent substrate of a liquid crystal display device, an organic EL display device, or a transparent conductive film for a touch panel.

The method of manufacturing a colorless transparent resin film of the present invention is a method of manufacturing a resin film by a solution casting method including the steps of casting an organic solvent solution of a resin on a support and drying it, and the organic solvent contains 1 More than one organic solvent (S1) with a boiling point below 80°C and one or more organic solvents (S2) with a boiling point above 130°C. "Colorless and transparent" in the present invention means that when a film with a thickness of 20-50μm is formed, the total light transmittance of the film should be 85% or more, and the yellow index (YI) should be less than 5, and the haze should be 2% The meaning of the following.

Regarding the resin that can be used in this embodiment, as long as it is a resin film that can be manufactured by a solution casting method including the steps of casting an organic solvent solution of the resin on a support and drying it, there is no particular However, the resin of the resin film is preferably polyimide. The organic solvent solution of the resin is preferably an organic solvent solution of polyamide acid or an organic solvent solution of polyimide. Hereinafter, a case where the resin of the resin film is polyimide is used as a representative example to describe this embodiment in detail.

式中，R係碳數4~39之4價之脂環基，Φ係合計之碳數為2~39之2價之脂肪族基、脂環基、芳香族基或由此等之組合構成之基，作為鍵結基，亦可具有選自於由-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。Regarding the resin that can be used in the resin film of this embodiment, considering transparency, optics, etc., it is more preferably a polyimide containing a repeating unit represented by the following formula [I]. [化1]

In the formula, R is a tetravalent alicyclic group with 4 to 39 carbons, and Φ is a divalent aliphatic, alicyclic, or aromatic group with a total of 2 to 39 carbons, or a combination of these The group, as a bonding group, may also have a group selected from -O-, -SO ₂ -, -CO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -OSi(CH ₃ ) _2- , At least 1 of the group consisting of -C ₂ H ₄ O- and -S-.

The content of the repeating unit of formula [I] in the polyimine is 100 mol%, preferably 10-100 mol%, more preferably 50-100 mol% relative to all repeating units of the polyimine, It is further preferably 70-100 mol%, and further preferably 90-100 mol%. In addition, the number of repeating units of formula [I] in 1 molecule of polyimide is preferably 10 to 2000, more preferably 20 to 200.

Polyimine is obtained by reacting an alicyclic tetracarboxylic acid or its derivative with a diamine or its derivative by using a tetravalent alicyclic tetracarboxylic acid and a divalent diamine as constituent components. As far as alicyclic tetracarboxylic acid or its derivatives are concerned, alicyclic tetracarboxylic acid, alicyclic tetracarboxylic acid esters, alicyclic tetracarboxylic dianhydride, etc. are mentioned, preferably alicyclic tetracarboxylic acid Dianhydride. Examples of diamines and their derivatives include diamines, diisocyanates, and diaminodisilanes, and diamines are preferred.

Regarding the alicyclic tetracarboxylic dianhydride used in the synthesis of polyimine, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,4,5-cyclic Pentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid The dianhydride, etc., is particularly preferably 1,2,4,5-cyclohexanetetracarboxylic dianhydride. Generally speaking, polyimides that use aliphatic diamines as their constituent components, because polyamide acid and diamine, which are intermediate products, form strong complexes that are not easy to polymerize, so they need to be dissolved by complexes. Disposal of more reactive solvents (such as cresol). However, the polyimide that uses 1,2,4,5-cyclohexanetetracarboxylic dianhydride and aliphatic diamine as the constituent components, because the complex of polyamide acid and diamine is weaker Bonding, it is easy to high molecular weight, easy to obtain flexible film. In addition, the above-mentioned tetracarboxylic acid component contains an isomer.

Among the above-mentioned tetracarboxylic acid components, tetracarboxylic acids or their derivatives other than alicyclic tetracarboxylic acids can be used in combination within the range that does not impair the solvent solubility of polyimide, the flexibility of the film, and the transparency, and especially the combination can be used 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 pyromellitic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic 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, double (3,4-dicarboxyphenyl) sulfide, bis(3,4-dicarboxyphenyl) ether, bis(2,3-dicarboxyphenyl) ether, 3,3',4,4'-diphenyl Ketonetetracarboxylic acid, 2,2',3,3'-benzophenonetetracarboxylic acid, 4,4-(terephthalic acid), 4,4-(isophthalic acid) Yl)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 dianhydrides, are at least one compound selected from these. Specific examples of linear or branched aliphatic tetracarboxylic acid include ethylenetetracarboxylic acid and the like.

As for the diamine-based components constituting the nitrogen of the imine ring of the formula [I] and Φ, diamines, diisocyanates, diaminodisilanes, etc., are exemplified, and diamines are preferred. The diamine content in the diamine component is preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 90 mol% or more (including 100 mol%).

The diamine used in the synthesis of polyimine can be any one of aromatic diamine, aliphatic diamine or a mixture of these. In addition, the "aromatic diamine" in the present invention means a diamine in which an amine group is directly bonded to an aromatic ring, and an aliphatic group, alicyclic group, and other substituents may be contained in one part of the structure. "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.

Regarding the aromatic diamines used in the synthesis of polyimines, for example, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, and Aniline, o-tolidine, m-tolidine, 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'-di Aminodiphenyl, 2,6-diaminonaphthalene, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4 ,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone , 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-aminobenzene) Oxy)biphenyl, 4,4'-bis(2,6-dimethyl-4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, Bis(4-(4-aminophenoxy)phenyl) chrysene, bis(4-(2-methyl-4-aminophenoxy)phenyl) chrysene, bis(4-(2,6- Dimethyl-4-aminophenoxy)phenyl) benzene, bis(4-(4-aminophenoxy)phenyl)ether, bis(4-(2-methyl-4-aminobenzene) Oxy)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-amino) Phenoxy)benzene, 2,2-bis(4-aminophenyl)propane, 2,2-bis(2-methyl-4-aminophenyl)propane, 2,2-bis(2,6 -Dimethyl-4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis(2-methyl-4-aminophenyl)hexa Fluoropropane, 2,2-bis(2,6-dimethyl-4-aminophenyl)hexafluoropropane, α,α'-bis(4-aminophenyl)-1,4-diisopropyl Benzene, 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-diisopropylbenzene, 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-diiso Propylbenzene, α,α'-bis(3-aminophenyl)-1,3-diisopropylbenzene, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis( 2-methyl-4-aminophenyl)fluorene, 9,9-bis(2,6-dimethyl-4-aminophenyl)fluorene, 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)cyclohexane, 1,1-bis(2-methyl-4-aminophenyl)cyclohexane, 1,1-bis(2,6- Dimethyl-4-aminophenyl)cyclohexane, 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-aminophenyl)adamantane, 1,1-bis(2-methyl-4-aminophenyl)adamantane, 1,1-bis(2,6-dimethyl 4-aminophenyl) adamantane and the like.

In addition, the aliphatic diamine used in the synthesis of polyimine includes, for example, ethylene diamine, hexamethylene diamine, polyethylene glycol bis(3-aminopropyl) ether, polyimide Propylene glycol bis(3-aminopropyl) ether, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, m-xylylenediamine, p-benzene Dimethylamine, 1,4-bis(2-amino-isopropyl)benzene, 1,3-bis(2-amino-isopropyl)benzene, isophorone diamine, norbornane diamine , Silicone diamines, etc.

Polyimide is usually manufactured as an organic solvent solution (varnish). The method of the present invention uses organic solvents containing more than one organic solvent (S1) with a boiling point below 80°C and more than one organic solvent (S2) with a boiling point above 130°C. In the present invention, by using an organic solvent (S1) with a lower boiling point and an organic solvent (S2) with a higher boiling point, the organic solvent (S1) can be volatilized efficiently in the drying step to suppress the film Yellowing, and deliberately leaving the organic solvent (S2) in the film to obtain a film with excellent optical isotropy.

The boiling point of the organic solvent (S1) is 80°C or less, preferably 75°C or less, more preferably 70°C or less, further preferably 65°C or less, and still more preferably 60°C or less. The lower limit of the boiling point of the organic solvent (S1) is not particularly limited, but from the viewpoint of working efficiency, it is preferably 30°C or higher. By using an organic solvent (S1) with a relatively low boiling point below 80°C, the organic solvent (S1) can be volatilized at a relatively low drying temperature of about 120 to 150°C to obtain a resin film.

The organic solvent (S1) is not particularly limited. For example, dichloromethane (DCM, boiling point 39.6°C), 1,3-dioxolane (boiling point 75°C), tetrahydrofuran (THF, boiling point 66°C) can be used , Acetone (boiling point 56°C), chloroform (boiling point 61°C), ethyl acetate (boiling point 77°C), etc., can also be used in combination of two or more. Among these, as for the organic solvent (S1), considering the performance of the polyimide varnish, it is preferably at least one selected from the group consisting of dichloromethane and 1,3-dioxolane 1 kind.

The boiling point of the organic solvent (S2) is 130°C or higher, preferably 140°C or higher, more preferably 150°C or higher, and further preferably 160°C or higher. The upper limit of the boiling point of the organic solvent (S2) is not particularly limited. For example, it may be 300°C or lower or 250°C or lower. By using an organic solvent (S2) with a higher boiling point above 130°C, when the resin's organic solvent solution is dried at a drying temperature of about 120~150°C, a resin film with low retardation and excellent optical isotropy can be obtained . Although the reason is not yet clear, it is estimated that by drying the organic solvent solution of the resin at a relatively low drying temperature of about 120 to 150°C, the organic solvent (S2) remains in the resin film to a level that is not problematic for use. Relax the alignment of the polymer chain to achieve low delay.

The organic solvent (S2) is not particularly limited. For example, cyclopentanone (boiling point 131°C), cyclohexanone (boiling point 156°C), N-methyl-2-pyrrolidone (boiling point 202°C) can be used , N,N-dimethylacetamide (DMAc, boiling point 165℃), N,N-dimethylformamide (boiling point 153℃), γ-butyrolactone (GBL, boiling point 204℃), dimethyl Two or more of these may be used in combination, such as sulfide (boiling point 189°C), dimethyl isobutyrate (boiling point 179°C), etc. Among these, in terms of the organic solvent (S2), considering the performance of the polyimide varnish, it is preferably selected from N-methyl-2-pyrrolidone, N,N-dimethyl ethyl At least one of the group consisting of amide, γ-butyrolactone and dimethyl sulfoxide.

The mass ratio of the organic solvent (S1) to the organic solvent (S2) contained in the organic solvent solution of polyimide [(S1)/(S2)], consider drying the resin organic solvent solution at a lower drying temperature to suppress The yellowing point of the film is preferably 90/10~99/1, more preferably 93/7~97/3.

As for the production method of the organic solvent solution of polyimide, the following methods (1) to (3) can be cited, but the methods are 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, preferably below 80°C, especially around room temperature or more Maintain a low temperature 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 the generated water is azeotropically removed to the outside of the system for dehydration reaction to obtain an organic solvent solution of polyimide.

(2) Add a dehydrating agent such as acetic anhydride to the polyamide acid solution obtained in the same way as the above (1). After being imidized, add methanol and other solvents that lack the ability to dissolve polyimide. , The polyimide is precipitated. 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 point solvent such as cresol to prepare a polyamide acid solution, and directly maintain it at 150~220℃ for 3~12 hours to make it polyimide, then add methanol etc. to the polyamide The imine lacks solvents with dissolving power, which causes the polyimine to precipitate. After separating the solid by filtration, washing and drying, it is dissolved in an organic solvent to obtain an organic solvent solution of polyimide.

In addition, when polyimine is produced by solution polymerization, it is preferable to use a tertiary amine compound as a catalyst. In this regard, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, triethylenediamine can be cited , N-methylpyrrolidine, N-ethylpyrrolidine, N-methylpiperidine, N-ethylpiperidine, imidazole, pyridine, quinoline, isoquinoline, etc. Among these tertiary amine compounds, TEA is particularly preferred.

In addition, the concentration of the organic solvent solution of the polyimide used in the present invention is preferably 4 to 45% by mass, more preferably 10 to 40% by mass. Specifically, the organic solvent solution of the resin is relative to 100 g of the organic solvent, and the content of the dissolved resin is preferably in the range of 5 to 80 g, more preferably in the range of 10 to 70 g. If it is within this range, the surface smoothness of the obtained polyimide film will be good.

The weight average molecular weight of the polyimide used in the present invention, considering the flexibility and mechanical strength of the obtained polyimide, is preferably 10,000 or more, 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 gel filtration chromatography or the like. In addition, a method of measuring absolute molecular weight using a light scattering detector using N,N-dimethylformamide in the eluent can also be cited.

In the organic solvent solution of polyimide, fluorine-based, polysiloxane-based surfactants can also be added. 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 also be added.

The manufacturing method of the polyimide film of this invention is not specifically limited, A well-known method can be used. For example, a solution containing the polyimide of the present invention, or a solution containing the polyimide of the present invention and a solution containing various additives described, is applied to a smooth support such as a glass plate, a metal plate, and a plastic A method of removing the organic solvent and other solvent components contained in the solution after forming into a thin film.

As for the production method of the colorless transparent polyimide film, a method of forming a film by a solution casting method of casting an organic solvent solution of polyimide on a support and drying it can be cited. Specifically, after the organic solvent solution of polyimide is cast on the support, it is advisable to use a film making machine in the form of a cast material sprayed on the support with a gas above 80°C and below 250°C. The organic solvent evaporates and is obtained as a self-supporting film peeled off from the support. It is advisable to perform a drying before blowing air. The conditions of the primary drying are not particularly limited. For example, it is preferable to maintain the temperature at a temperature of 80 to 120°C for 10 to 30 minutes.

As for the gas to be blown, air or nitrogen can be cited, air is preferred in terms of cost, and nitrogen is preferred in terms of preventing film coloring. The temperature of the blowing gas is more preferably 80°C or higher and 250°C or lower, and more preferably 100°C or higher and 220°C or lower. When the temperature of the blowing gas is lower than 80°C, the organic solvent may not be sufficiently volatilized, 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 250°C, the film may be colored due to the rapid volatilization of the solvent, or the film may be colored by solvent decomposition. The time for blowing the gas depends on the temperature of the gas being blown. It is preferably 15-30 minutes, and more preferably 15-25 minutes. In addition, it is also possible to set multiple regions where the temperature of the gas sprayed on the cast material is different.

In addition, in the manufacturing method of the colorless and transparent polyimide film of the present invention, the process of casting the organic solvent solution of the resin onto the support to dry it preferably includes the following steps: (i) using differential heat-heating weight Simultaneously measure the method that the weight reduction rate at 120~300℃ obtained becomes more than 1% and equal to or less than 10%, the step of removing a part of the above solvent, and (ii) the step of removing a part of the solvent (i) ) Afterwards, when the glass transition temperature of the resin is set to Tg (°C), a heat treatment step is performed within the range of (Tg-50)°C~(Tg+100)°C. The weight reduction rate in the above step (i) is preferably more than 1% and equal to or less than 10%, more preferably more than 1% and less than 5%, and further preferably more than 1% and less than 3%. As long as it is within this range, it does not take too much time for drying, and a colorless transparent resin film with excellent transparency and optical properties can be produced. The heat treatment temperature in the above step (ii) is preferably (Tg-50)°C or higher (Tg+100)°C, more preferably (Tg-30)°C or higher (Tg+80)°C, and further preferably (Tg- 10) ℃ above (Tg+60) ℃ below. As long as it is within this range, a colorless and transparent resin film excellent in transparency and optical orientation can be produced.

The polyimide film may contain other ingredients within the range of not impairing transparency and flexibility. As for other ingredients, for example, plasticizers, antioxidants, release agents, stabilizers, blueing agents and other colorants, flame retardants, lubricants, tackifiers, and leveling agents, etc. .

The thickness of the polyimide film obtained by this manufacturing method is appropriately adjusted due to the application, and is usually 10 to 500 μm, preferably 15 to 200 μm, and more preferably 20 to 100 μm.

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

The polyimide film preferably has a thickness direction retardation (Rth) of 50 nm or less, more preferably 40 nm or less, and further preferably 30 nm or less. The polyimide film preferably has an in-plane retardation (Re) of 20 nm or less, and more preferably 15 nm or less.

The polyimide film obtained by this manufacturing method may contain additives and the like in terms of other components. For example, by containing titanium dioxide, etc., the reflectance of white light can be improved. In addition, by containing nanofillers and the like, the apparent glass transition temperature of the resin composition molded body increases and heat resistance is improved, and the tensile modulus of elasticity increases, and the mechanical strength increases.

The colorless transparent resin film obtained by the method of the present invention can be suitably used as a film for various components such as touch sensors, color filters, flexible displays, semiconductor parts, and optical components. In addition, the colorless transparent resin film obtained by the method of the present invention can be used as a base material for a transparent substrate of a liquid crystal display device, an organic EL display device, or a transparent conductive film for a touch panel. [Example]

Hereinafter, the present invention will be explained in more detail with examples. However, the present invention is not limited by the embodiments. The measuring methods of the physical properties of the films obtained in the following examples are as follows.

(1) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Corporation.

(2) Total light transmittance, 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 delay (Re) The in-plane retardation (Re) was measured using an ellipsometer "M-220" manufactured by JASCO Corporation. Measure the value of the in-plane retardation at the measurement wavelength of 590 nm.

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

(5) Organic solvent content in the film Using Hitachi High-Tech Science Corporation, the differential thermo-thermogravimetry simultaneous measuring device "TG/DTA6200", the measurement was carried out under nitrogen gas flow at a heating rate of 10°C/min, and the temperature was raised from 120°C to 300°C. Then maintain at 300°C for 30 minutes, so that the mass reduced during this period is the organic solvent content in the film.

(6) Glass transition temperature (Tg) Use the thermomechanical analysis device "TMA/SS6100" manufactured by Hitachi High-Tech Science Corporation. In the tensile mode, the sample size is 2mm×20mm, the load is 0.1N, and the heating rate is 10℃/min. The temperature of the stress is used to remove the residual stress, and then it is cooled to room temperature. Thereafter, the test piece elongation measurement was measured under the same conditions as the treatment for removing the above-mentioned residual stress, and the inflection point at which elongation was observed was determined as the glass transition temperature.

<Example 1> In a 2L 5-neck glass round bottom flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen introduction tube, a Dean-Stark apparatus equipped with a cooling tube, a thermometer, and a glass end cap , Α,α'-bis(4-aminophenyl)-1,3-diisopropylbenzene (manufactured by Mitsui Fine Chemicals, Inc.) 239.772g (0.696 mol), 4,4-diaminophenyl Diphenyl ether (manufactured by Wakayama Fine Chemical Industry Co., Ltd.) 34.842 g (0.174 mol), γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) 376.453 g, and triethylamine (Kanto) as a catalyst Chemical Co., Ltd. make) 44.018 g, triethylenediamine (Tokyo Chemical Industry Co., Ltd. make) 0.488 g, and stirred at 200 rpm in a nitrogen atmosphere at 70°C in the reaction system to obtain a solution. To this, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Co., Ltd.) 195.028g (0.870 mol) and γ-butyrolactone (Mitsubishi Chemical Co., Ltd.) 94.113 g after it was heated with a heating bag, and it took about 20 minutes to raise the temperature in the reaction system to 200°C. Collect the distilled components, adjust the stirring speed to match the viscosity increase, and maintain the temperature in the reaction system at 200°C for 5 hours. After adding 847.067 g of N,N-dimethylacetamide, it was stirred at around 100°C for about 1 hour to prepare a uniform solution, and a uniform polyimide varnish (a) with a solid content concentration of 25% by mass was obtained.

Then, the obtained polyimide varnish was added dropwise to methanol, the polyimide powder was precipitated and the solid was suction filtered through a Kiriyama funnel, further washed with methanol, and dried at 200°C for 30 minutes The solvent was removed to obtain polyimide powder. In a 300mL 5-neck glass round-bottomed flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen introduction tube, a Dean-Stark device equipped with a cooling tube, a thermometer, and a glass end cap, the obtained polyol 15g of imine powder, 80.75g of dichloromethane (DCM) and 4.25g of N,N-dimethylacetamide (DMAc) were added at once, and stirred at room temperature for 1 hour to make a uniform solution to obtain the solid content concentration 15% by mass of uniform polyimide varnish (b).

Then, the obtained polyimide varnish (b) was coated on the PET substrate, maintained at room temperature for 5 minutes, maintained in an air environment at 50°C for 5 minutes, and finally sprayed in an air environment at 150°C for 30 minutes The hot air is dried to obtain a film with a thickness of 35μm. Table 1 shows the evaluation results of the polyimide film.

<Example 2> The polyimide film obtained in Example 1 was further dried by blowing hot air at 250° 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 (a) obtained in Example 1 was added dropwise to methanol, the polyimide powder was precipitated and suction filtered with a Kiriyama funnel, and washed with methanol and dried at 200°C for 30 minutes The solvent was removed to obtain polyimide powder. In a 300mL 5-neck glass round-bottomed flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen introduction tube, a Dean-Stark device equipped with a cooling tube, a thermometer, and a glass end cap, the obtained polyol After 15 g of imine powder and 85 g of dichloromethane (DCM) were added at once, it was stirred at room temperature for 1 hour to prepare a uniform solution, and a uniform polyimide varnish with a solid content of 15% by mass was obtained.

Then, the obtained polyimide varnish was coated on the PET substrate, maintained at room temperature for 5 minutes, and maintained at 50°C in an air environment for 5 minutes, and finally sprayed with hot air at 150°C for 20 minutes in the air environment. After drying, a film with a thickness of 35 μm was obtained. Table 1 shows the evaluation results of the polyimide film.

＜Comparative example 2＞ The polyimide film obtained in Comparative Example 1 was further dried by blowing hot air at 250° 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.

[Table 1] Organic solvents Drying temperature Film thickness (μm) Total light transmittance (%) Haze (%) YI Re (nm) Rth (nm) Tg (℃) Solvent content (mass%) Example 1 (S1)DCM (S2)DMAc 150°C 35 90.2 0.3 1.2 15.6 40 195 6.0 Example 2 (S1)DCM (S2)DMAc 150℃ /250℃ 35 90.0 0.7 1.8 11.8 26 195 0.8 Comparative example 1 (S1)DCM 150°C 35 90.2 0.6 1.2 19.9 134 195 1.5 Comparative example 2 (S1)DCM 150℃ /250℃ 35 91.0 0.5 2.3 12 62 195 0.005

As shown in Table 1, the polyimide films obtained in Examples 1 and 2 can obtain films with good total light transmittance, haze, YI and other optical properties, low Rth, and excellent optical properties. In contrast, the polyimide film systems obtained in Comparative Examples 1 and 2 have a large Rth and poor optical equivariance.

Claims (9)

A method for manufacturing a colorless transparent resin film, which is a method of manufacturing a resin film by a solution casting method including the steps of casting an organic solvent solution of the resin on a support and drying it, the organic solvent containing one or more kinds An organic solvent (S1) with a boiling point below 80°C and one or more organic solvents (S2) with a boiling point above 130°C. For example, the method for manufacturing a colorless and transparent resin film of claim 1, wherein when a film with a thickness of 20-50 μm is formed from the organic solvent solution of the resin, the total light transmittance of the film is 85% or more, and the yellow index (YI) is 5 or less, haze is 2% or less, in-plane retardation (Re) is 20 nm or less, and thickness direction retardation (Rth) is 50 nm or less. According to claim 1 or 2, the method for manufacturing a colorless transparent resin film, wherein the organic solvent solution of the resin is an organic solvent solution of polyamide acid or an organic solvent solution of polyimide. The method for producing a colorless transparent resin film according to any one of claims 1 to 3, wherein the resin of the resin film is a polyimide having a repeating unit represented by the following formula [I];

In the formula, R is a tetravalent alicyclic group with 4 to 39 carbons, and Φ is a divalent aliphatic, alicyclic, or aromatic group with a total of 2 to 39 carbons, or a combination of these The group, as a bonding group, may also have a group selected from -O-, -SO ₂ -, -CO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -OSi(CH ₃ ) _2- , At least 1 of the group consisting of -C ₂ H ₄ O- and -S-. The method for producing a colorless transparent resin film according to any one of claims 1 to 4, wherein the mass ratio of the organic solvent (S1) and the organic solvent (S2) contained in the organic solvent solution of the resin [(S1) /(S2)] is 90/10~99/1. The method for producing a colorless transparent resin film according to any one of claims 1 to 5, wherein the organic solvent (S1) is selected from the group consisting of dichloromethane and 1,3-dioxolane At least one. The method for manufacturing a colorless transparent resin film according to any one of claims 1 to 6, wherein the organic solvent (S2) is selected from N-methyl-2-pyrrolidone, N,N-dimethyl At least one of the group consisting of acetamide, γ-butyrolactone and dimethyl sulfoxide. The method for producing a colorless transparent resin film according to any one of claims 1 to 7, wherein the content of the dissolved resin in the organic solvent solution of the resin is in the range of 5 to 80 g relative to 100 g of the organic solvent. The method for producing a colorless transparent resin film according to any one of claims 1 to 8, wherein the step of casting and drying the organic solvent solution of the resin on the support includes the following steps: (i) The step of removing a part of the solvent so that the weight loss rate at 120 to 300°C obtained by simultaneous differential thermogravimetric measurement exceeds 1% and is equal to or less than 10%; and (ii) After the step (i) of removing a part of the solvent, when the glass transition temperature of the resin is set to Tg (℃), heat treatment is performed in the range of (Tg-50)℃~(Tg+100)℃ step.