JP2005179565A - Polyamide imide resin and its varnish - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide imide resin causing very little coloring without injuring heat resistance of the polyamide imide resin and further being soluble in a low boiling point solvent, and to provide its varnish. <P>SOLUTION: The polyamide imide resin is characterized in that it has a logarithmic viscosity of at least 0.1 dl/g and not more than 2.0 dl/g and it includes a structure represented by formula 1 (in the formula, R<SP>1</SP>-R<SP>9</SP>are each hydrogen, an alkyl group or an aryl group, R<SP>10</SP>is a 1-18C alkylene group or arylene group that may contain nitrogen, oxygen, sulfur and a halogen). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel polyamideimide resin and its varnish. More specifically, because it has good heat resistance and little coloration, it is not only for films, fibers, molding materials, coating agents, adhesives, paints, inks but also coating agents for various molded products, adhesives, light for liquid crystal displays, etc. The present invention provides a polyamideimide resin and its varnish that are useful for a light-sensitive substrate, a phase difference plate, a polarizing film cover film, a color filter ink binder, a plastic lens, an optical disk substrate, and the like.

  Polyamideimide resins are generally excellent in heat resistance, chemical resistance, and electrical insulation, but are colored, so their use in applications requiring transparency has been limited. In addition, since it is soluble only in a polar solvent having a high boiling point, it has been applied to molding materials, insulating paints, coating agents, etc., but its use has been limited. In order to solve this problem, for example, in Patent Document 1, Patent Document 2, and Patent Document 3, a polyamideimide resin composition that is soluble in a low boiling point solvent and has a light transmittance of 75% or more at a wavelength of 500 nm with a dry film thickness of 30 μm. And its varnish. Patent Document 3 discloses a polyamideimide resin having a light transmittance at 81 nm of 81% or more when a film having a thickness of 25 μm is formed. Patent Document 4 discloses a polyamideimide film having an average light transmittance of 77% or more in a wavelength region of 400 nm to 550 nm. However, since the light transmittance is lower at a lower wavelength of 400 nm, use in applications that require light transmittance at a lower wavelength has been limited.

Japanese Patent Application Laid-Open No. 08-113646 Japanese Patent Laid-Open No. 08-283356 JP 2002-275263 A JP 2003-238707 A

  An object of the present invention is to provide a polyamide-imide resin and its varnish that are extremely little colored without impairing the heat resistance of the polyamide-imide resin and that are soluble in a low boiling point solvent.

  In order to solve these problems, the present inventors have intensively studied, and as a result, have reached the present invention. That is, the present invention is the following polyamideimide resin and varnish.

（Ｒ¹〜Ｒ⁹は水素、アルキル基またはアリール基であり、Ｒ¹⁰は炭素数１〜１８のアルキレン基又はアリーレン基であり窒素、酸素、硫黄、ハロゲンを含んでも良い） (1) A polyamideimide resin having a logarithmic viscosity of 0.1 dl / g or more and 2.0 dl / g or less and containing the structure of Formula 1.

(R ^{1 to} R ⁹ are hydrogen, an alkyl group, or an aryl group, and R ¹⁰ is an alkylene group or arylene group having 1 to 18 carbon atoms, and may contain nitrogen, oxygen, sulfur, or halogen)

(2) The polyamide-imide resin according to (1) having a glass transition temperature of 120 ° C. or higher and a light transmittance at a wavelength of 400 nm at a dry film thickness of 30 μm of 81% or higher.

(3) The polyamideimide resin according to (1) or (2), wherein R ¹⁰ contains an isophorone skeleton and / or a dicyclohexylmethane skeleton.

(4) The polyamideimide resin according to any one of (1) to (3), wherein the repeating unit of formula 1 is contained in an amount of 20 mol% to 100 mol%.

(5) Any one of (1) to (4) characterized by being dissolved in a solvent selected from ethanol, toluene, cyclohexanone, cyclopentanone and tetrahydrofuran alone or in an amount of 5% by weight or more in two or more mixed solvents. The polyamideimide resin described in 1.

(6) A varnish in which the polyamideimide resin according to any one of (1) to (5) is dissolved.

  Since the polyamideimide resin and varnish of the present invention contain an acid component having a specific structure, the heat resistance is good and the coloring is extremely reduced. As a result, it is possible to provide a polyamideimide resin and a varnish that can be used for applications requiring light transmittance at a low wavelength.

  The production method of the polyamide-imide resin used in the present invention is an isocyanate method produced from an acid component and an isocyanate component, an acid chloride method produced from an acid chloride (acid component) and an amine, or a direct method produced from an acid component and an amine component. It manufactures by well-known methods, such as.

（Ｒ¹〜Ｒ⁹は水素、アルキル基、アリール基である）
尚、Ｒ¹〜Ｒ⁹は互いに同一でも異なっていても良い。これらのうち、アルキル基であれば重合反応性の観点から炭素数６以下のものが好ましい。特に好ましいのはＲ¹〜Ｒ⁹の全てが水素であるヘキサヒドロトリメリット酸無水物である。 In the polyamideimide resin of the present invention, an acid anhydride compound having the following structure is preferably used as the acid component.

(R ^{1 to} R ⁹ are hydrogen, an alkyl group, and an aryl group)
R ^{1 to} R ⁹ may be the same as or different from each other. Among these, alkyl groups are preferably those having 6 or less carbon atoms from the viewpoint of polymerization reactivity. Particularly preferred is hexahydrotrimellitic anhydride in which all of R ^{1 to} R ⁹ are hydrogen.

  As the acid component, in addition to the above chemical formula 3 or a derivative thereof, trimellitic anhydride, ethylene glycol bisanhydro trimellitate, propylene glycol bis anhydro trimellitate, 1,4-butanediol bis anhydro trimellitate, Hexamethylene glycol bisanhydro trimellitate, polyethylene glycol bis anhydro trimellitate, polypropylene glycol bis anhydro trimellitate, etc., alkylene glycol bis anhydro trimellitate, pyromellitic anhydride, hexahydropyromellitic anhydride , Benzophenone tetracarboxylic anhydride, 3,3′-4,4′-diphenylsulfone tetracarboxylic anhydride, 3,3′-4,4′-diphenyltetracarboxylic anhydride, 4,4′-oxyphthalate Acid free , Terephthalic acid, isophthalic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-biphenyl ether dicarboxylic acid, 4,4'-benzophenone dicarboxylic acid, pyromellitic acid, 3,3 ', 4,4'- Benzophenone tetracarboxylic acid, 3,3 ′, 4,4′-biphenylsulfonetetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, maleic acid, fumar Acid, dimer acid, stilbene dicarboxylic acid and the like may be used. These acid components can be used alone or in combination with an acid anhydride compound of Chemical Formula 3. As these acid components, it is preferable to use hexahydropyromellitic acid anhydride, cyclohexanedicarboxylic acid, trimellitic acid anhydride in addition to the chemical anhydride compound of Chemical Formula 3 because of reactivity, heat resistance, transparency, cost, and the like. . More preferred is cyclohexanedicarboxylic acid.

  In the polyamideimide resin of the present invention, the repeating unit of Formula 1 is preferably contained in an amount of 20 mol% to 100 mol%. If it is less than 20 mol%, the intended transparency and solvent solubility may not be obtained. Preferably it is 30 mol% or more, More preferably, it is 40 mol% or more.

  In the polyamidoimide resin of the present invention, when hexahydrotrimellitic anhydride and cyclohexanedicarboxylic acid are used in combination as the acid component, the copolymerization amount of hexahydrotrimellitic anhydride is acid from the viewpoint of heat resistance and transparency and cost. When the component is 100 mol%, 100 mol% or less and 20 mol% or more and cyclohexane dicarboxylic acid 80 mol% or less are preferable. When the content of cyclohexanedicarboxylic acid exceeds 80 mol%, the solubility in alcohol solvents decreases, and amide solvents such as dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, and γ-butyrolactone are used. If a high boiling point solvent is not used together, it may not dissolve.

As the isocyanate component, dicyclohexylmethane-4,4′-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, 3,3′-diethyldiphenylmethane-4,4′-diisocyanate, 3,3′-dichlorodiphenylmethane-4,4′-diisocyanate, 3,3 ′ -Dichlorodiphenyl-4,4'-diisocyanate, 4,4'-diisocyanate-3,3'-dimethylbiphenyl, hexamethylene diisocyanate, isophorone diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, etc. That. Among these isocyanate components, dicyclohexylmethane-4,4′-diisocyanate and isophorone diisocyanate are preferable from the viewpoints of solubility, heat resistance, and transparency. When dicyclohexylmethane-4,4′-diisocyanate or isophorone diisocyanate is used, R ¹⁰ is introduced into the above formula 1 as an isophorone skeleton and / or a dicyclohexylmethane skeleton.

  The polyamideimide resin of the present invention is produced from the above-mentioned acid, isocyanate (or amine), but if necessary, at the end of polyether, polyester, polyacrylonitrile = butadiene copolymer, polybutadiene, polycarbonate diol, polydimethylsiloxane, etc. A component having a functional group may be copolymerized.

  The polyamideimide resin of the present invention can introduce a functional group having reactivity at the terminal, such as a carbon-carbon double bond, an epoxy group, an isocyanate group, a cyanate group, a carboxylic acid, a hydroxyl group, and a thiol.

  As the amine component when the polyamideimide resin used in the present invention is produced by the acid chloride method or the direct method, 4,4′-diaminodicyclohexylmethane, 1,3-cyclohexanebis (methylamine), o-chloropara Phenylenediamine, p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,4 ′ -Diaminodiphenylsulfone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 2,2'-bis (aminophenyl) propane, 2,4-tolylenediamine, 2,6-tolylenediamine, p -Xylerin diamine, isophorone diamine, Sa diamine, p- phenylenediamine, m- phenylenediamine, and the like.

  The logarithmic viscosity of the polyamideimide resin of the present invention is from 0.1 dl / g to 2.0 dl / g, preferably from 0.2 dl / g to 1.8 dl / g. When the logarithmic viscosity is 0.1 dl / g or less, the coating film may be brittle. Moreover, if it is 2.0 dl / g or more, the viscosity of a varnish may become high and handling may become difficult.

  The light transmittance at a wavelength of 400 nm with a dry film thickness of 30 μm of the polyamide-imide resin of the present invention is desirably 81% or more. Preferably it is 83% or more, More preferably, it is 85% or more, Most preferably, it is 87% or more. If it is less than 81%, it may be used in applications where transparency is not required, but problems may arise when used in applications where transparency is markedly required, such as optical applications.

  The glass transition temperature of the polyamideimide resin of the present invention is 120 ° C. or higher, preferably 150 ° C. or higher, more preferably 180 ° C. or higher, and most preferably 200 ° C. or higher. If it is 120 ° C. or lower, the heat resistance is insufficient when used for optical applications, and as a result, the resin may block. Although an upper limit is not specifically limited, 400 degreeC or less is preferable from a solvent solubility viewpoint.

  Solvents used in the synthesis of the polyamideimide resin used in the present invention include amide solvents such as dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone and dimethylimidazolidinone, nitro solvents such as nitrobenzene, Examples include urea-based solvents such as dimethylurea, sulfur-based solvents such as dimethylsulfoxide, and ester-based solvents such as γ-butyrolactone, but dimethylimidazolidinone and γ-butyrolactone from the viewpoint of few side reactions. N-methyl-2-pyrrolidone alone or a mixed solvent is preferable. More preferred are γ-butyrolactone and N-methyl-2-pyrrolidone.

  The polyamideimide resin of the present invention is synthesized by stirring in the above solvent at 50 to 230 ° C., preferably 80 to 200 ° C., but in order to promote the reaction, triethylamine, lutidine, picoline, undecene, triethyldiamine, etc. Amines, lithium methylates, sodium methylates, sodium ethylates, potassium butoxides, potassium fluorides, sodium fluorides and other alkali metals, alkaline earth metal compounds or metals such as cobalt, tin and zinc, metalloids The reaction may be performed in the presence of a catalyst such as a compound. Preferably, those containing an alkali metal or halogen in the molecule such as potassium fluoride and sodium methylate are preferable because of high catalytic activity.

  The varnish comprising the polyamideimide resin synthesized in this way and the high boiling point solvent may be used as it is for coating or the like, but it can also be used by substituting it with a low boiling point solvent.

  Although there is no limitation on the method of substituting with a low boiling point solvent, for example, a varnish composed of a high boiling point solvent is added to a solvent miscible with the high boiling point solvent as a non-solvent of polyamideimide resin and reprecipitated.

  In order to effectively elute the high boiling polar solvent from the resin composition and to adjust the elution rate, alcohol solvents such as ethylene glycol and triethylene glycol, hydrocarbon solvents such as toluene and xylene, acetone, A ketone solvent such as methyl ethyl ketone, an ether solvent such as dioxane and ethylene glycol dimethyl ether, and an ester solvent such as methyl acetate and ethyl acetate may be added to the resin composition and the coagulation bath.

  Furthermore, elution of the high boiling polar solvent can be further accelerated by lowering the polymer concentration of the resin composition or increasing the temperature of the coagulation bath. The coagulation bath used in the present invention is most preferably water.

  The method of charging the resin composition into the coagulation bath is not particularly limited, but it is preferable to discharge the resin composition from a fine nozzle for continuous and efficient production.

  The re-precipitated polymer is filtered, and after removing the solvent with a centrifugal dehydrator or the like, it is dried. Drying can be performed by a usual method such as hot air drying or vacuum drying.

  The main solvent used for redissolving in the present invention is an alcohol such as methanol and / or an ether such as tetrahydrofuran. Examples of the alcohol include monovalent fats such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol and the like. Aromatic alcohols such as polyhydric alcohols such as aromatic alcohol, ethylene glycol, propylene glycol, trimethylolpropane, glycerin and pentaerythritol, and benzyl alcohol. Examples of the ether include ethyl ether, propyl ether, butyl ether, phenyl ether, tetrahydrofuran, dioxane and the like.

  Furthermore, solvents other than alcohol and ether can be mixed and used. Solvents other than alcohol and ether include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, ester solvents such as methyl acetate, ethyl acetate, and cellosolve acetate, and hydrocarbon solvents such as benzene, toluene, xylene, and solvesso Solvent.

  The polyamideimide resin of the present invention is preferably dissolved in a solvent selected from ethanol, toluene, cyclohexanone, cyclopentanone and tetrahydrofuran alone or in an amount of 5% by weight or more in two or more mixed solvents. By dissolving in these solvents, the re-dissolution step can be performed efficiently.

  There is no particular limitation on the means for redissolving, and it can be dissolved by an ordinary method. For example, a solvent is put into a container, and a dry polymer is added little by little at room temperature or under heating while stirring.

  Although the polyamide-imide resin of the present invention is excellent in heat resistance and transparency, an additive may be used as long as the original properties of the polyamide-imide resin of the present invention are not impaired. For example, a UV absorber or an antioxidant may be added to improve weather resistance, and known UV absorbers and antioxidants can be used. Further, a flame retardant may be added to improve the flame retardancy. In order to improve physical properties, a curing agent such as epoxy, isocyanate, and melamine, and a modifier such as a silane coupling agent can also be used. In addition, other resins such as polyester resin, polyamide resin, polyimide resin, polyurethane resin, acrylic resin, melamine resin, and phenol resin, higher fatty acid, wax, surfactant, inorganic particles such as silica and alumina, etc. may be added. good.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited by these Examples. The characteristics shown in the examples are measured by the following method.

1. Logarithmic viscosity The logarithmic viscosity was defined by the following equation.
(Logarithmic viscosity) = (lnηrel) / C
ln: natural logarithm,
ηrel: the viscosity ratio (−) of the solution to the pure solvent by solvent fall time measurement,
C: Solution concentration (g / dl)
The measurement was performed at 25 ° C. using an Ubbelohde viscosity tube for a solution obtained by dissolving 0.5 g of polymer in 100 ml of N-methylpyrrolidone.

2. Light transmittance The light transmittance in a wavelength region of 400 nm was measured using a spectrophotometer (U-3210 manufactured by Hitachi, Ltd.).

3. Glass transition temperature It measured on condition of the following using the dynamic-viscoelasticity measuring apparatus (DVE-V4 by Rheology). The sample film and measurement conditions were as follows, and the inflection point was the glass transition point.
Sample size: 4 (width) x 15 (length) mm
Temperature increase rate: 4 ° C./min Measurement frequency: 110 Hz

[Example 1]
A reaction vessel was charged with 1 mol of hexahydrotrimellitic anhydride, 1.00 mol of isophorone diisocyanate, and 0.02 mol of potassium fluoride together with 332 g of γ-butyrolactone, reacted at 120 ° C. for 2 hours with stirring, and then further added 200 After continuing the reaction at 4 ° C. for 4 hours, N-methyl-2-pyrrolidone was added and the mixture was cooled to room temperature while diluting the polymer concentration to 20%. This solution was gradually added to about 6 liters of ion-exchanged water with stirring to precipitate a polymer. The polymer and ion exchange water were separated and the polymer was further washed 3 times with about 6 liters of ion exchange water. The polymer and ion exchange water were separated and the polymer was dried at 100 ° C. for 12 hours. The logarithmic viscosity of the obtained polyamideimide was 0.45 dl / g, and the glass transition temperature was 270 ° C. Polyamideimide varnish was prepared by dissolving 20 g of the obtained polymer in 80 g of tetrahydrofuran while stirring at room temperature. The obtained polyamide-imide varnish was coated on a polyester film E5100 manufactured by Toyobo Co., Ltd., dried at 60 ° C. for 10 minutes and 120 ° C. for 30 minutes, and then peeled from the film to prepare a 30 μm polyamide-imide film. . The light transmittance of this film was 82% at a wavelength of 400 nm.

[Example 2]
A reaction vessel was charged with 0.5 mol of hexahydrotrimellitic anhydride, 0.5 mol of 1,4-cyclohexanedicarboxylic acid, 0.99 mol of isophorone diisocyanate and 0.02 mol of potassium fluoride together with 320 g of γ-butyrolactone and stirred. The reaction was continued at 120 ° C. for 2 hours, and further continued at 200 ° C. for 4 hours. Then, N-methyl-2-pyrrolidone was added and the mixture was cooled to room temperature while diluting the polymer concentration to 20%. This solution was gradually added to about 6 liters of ion-exchanged water with stirring to precipitate a polymer. The polymer and ion exchange water were separated and the polymer was further washed 3 times with about 6 liters of ion exchange water. The polymer and ion exchange water were separated and the polymer was dried at 100 ° C. for 12 hours. The resulting polyamideimide had a logarithmic viscosity of 0.41 dl / g and a glass transition temperature of 250 ° C. Polyamideimide varnish was prepared by dissolving 20 g of the obtained polymer in 40 g of methanol and 40 g of toluene while stirring at room temperature. The obtained polyamide-imide varnish was coated on a polyester film E5100 manufactured by Toyobo Co., Ltd., dried at 60 ° C. for 10 minutes and 120 ° C. for 30 minutes, and then peeled from the film to prepare a 30 μm polyamide-imide film. . The light transmittance of this film was 85% at a wavelength of 400 nm.

[Comparative Example 1]
A reaction vessel was charged with 1 mol of trimellitic anhydride, 0.99 mol of diphenylmethane-4,4′-diisocyanate, and 0.02 mol of potassium fluoride together with 826 g of N-methyl-2-pyrrolidone. After reacting for 4 hours, the reaction was further continued at 180 ° C. for 4 hours, and then N-methyl-2-pyrrolidone was added to cool to room temperature while diluting the polymer concentration to 20% to obtain a polyamideimide varnish. The polyamideimide varnish is coated on a polyester film E5100 manufactured by Toyobo Co., Ltd., dried at 100 ° C. for 10 minutes, peeled off from the polyester film, attached to a mold having a length of 0.2 m × width of 0.3 m, and 200 The film was dried for 12 hours at a temperature of 30 μm to form a polyamideimide film. The logarithmic viscosity was 0.52 dl / g and the glass transition temperature was 290 ° C. This film was yellow and had a light transmittance of 0% at a wavelength of 400 nm.

[Comparative Example 2]
A reaction vessel was charged with 0.5 mol of trimellitic anhydride, 0.5 mol of 1,4-cyclohexanedicarboxylic acid, 0.99 mol of isophorone diisocyanate and 0.02 mol of potassium fluoride together with 314 g of γ-butyrolactone while stirring. After reacting at 120 ° C. for 2 hours, the reaction was further continued at 200 ° C. for 4 hours, and then N-methyl-2-pyrrolidone was added to cool to room temperature while diluting the polymer concentration to 20%. This solution was gradually added to about 6 liters of ion-exchanged water with stirring to precipitate a polymer. The polymer and ion exchange water were separated and the polymer was further washed 3 times with about 6 liters of ion exchange water. The polymer and ion exchange water were separated and the polymer was dried at 100 ° C. for 12 hours. The logarithmic viscosity of the obtained polyamideimide was 0.43 dl / g, and the glass transition temperature was 260 ° C. Polyamideimide varnish was prepared by dissolving 20 g of the obtained polymer in 40 g of ethanol and 40 g of toluene while stirring at room temperature. The obtained polyamide-imide varnish was coated on a polyester film E5100 manufactured by Toyobo Co., Ltd., dried at 60 ° C. for 10 minutes and 120 ° C. for 30 minutes, and then peeled from the film to prepare a 30 μm polyamide-imide film. . The film had a light transmittance of 75% at a wavelength of 400 nm.

[Comparative Example 3]
A reaction vessel was charged with 1 mol of trimellitic anhydride, 1.00 mol of isophorone diisocyanate and 0.02 mol of potassium fluoride together with 324 g of γ-butyrolactone, reacted at 120 ° C. for 2 hours with stirring, and further at 200 ° C. After the reaction was continued for 4 hours, N-methyl-2-pyrrolidone was added and the mixture was cooled to room temperature while diluting the polymer concentration to 20%. This solution was gradually added to about 6 liters of ion-exchanged water with stirring to precipitate a polymer. The polymer and ion exchange water were separated and the polymer was further washed 3 times with about 6 liters of ion exchange water. The polymer and ion exchange water were separated and the polymer was dried at 100 ° C. for 12 hours. The obtained polyamideimide had a logarithmic viscosity of 0.43 dl / g and a glass transition temperature of 290 ° C. Polyamideimide varnish was prepared by dissolving 20 g of the obtained polymer in 80 g of tetrahydrofuran while stirring at room temperature. The obtained polyamide-imide varnish was coated on a polyester film E5100 manufactured by Toyobo Co., Ltd., dried at 60 ° C. for 10 minutes and 120 ° C. for 30 minutes, and then peeled from the film to prepare a 30 μm polyamide-imide film. . The film had a light transmittance of 70% at a wavelength of 400 nm.

[Comparative Example 4]
A reaction vessel was charged with 0.5 mol of hexahydrotrimellitic anhydride, 0.5 mol of 1,4-cyclohexanedicarboxylic acid, 0.90 mol of isophorone diisocyanate and 0.02 mol of potassium fluoride together with 320 g of γ-butyrolactone and stirred. The reaction was continued at 120 ° C. for 2 hours, and further continued at 200 ° C. for 4 hours. Then, N-methyl-2-pyrrolidone was added and the mixture was cooled to room temperature while diluting the polymer concentration to 20%. This solution was gradually added to about 6 liters of ion-exchanged water with stirring to precipitate a polymer. The polymer and ion exchange water were separated and the polymer was further washed 3 times with about 6 liters of ion exchange water. The polymer and ion exchange water were separated and the polymer was dried at 100 ° C. for 12 hours. The resulting polyamideimide had a logarithmic viscosity of 0.07 dl / g. 30 g of the obtained polymer was dissolved in 35 g of methanol and 35 g of toluene while stirring at room temperature to prepare a polyamideimide varnish. The resulting polyamideimide varnish was coated on a polyester film E5100 manufactured by Toyobo Co., Ltd., dried at 60 ° C. for 10 minutes, and then at 120 ° C. for 30 minutes. The light transmittance could not be measured.

  Since the polyamideimide resin and varnish of the present invention contain an acid component having a specific structure, the heat resistance is good and the coloring is extremely reduced. As a result, it is possible to provide a polyamide-imide resin and a varnish that can be used for applications requiring light transmittance at a low wavelength.

Claims (6)

A polyamideimide resin having a logarithmic viscosity of 0.1 dl / g or more and 2.0 dl / g or less and containing the structure of Formula 1.

(R ^{1 to} R ⁹ are hydrogen, an alkyl group, or an aryl group, and R ¹⁰ is an alkylene group or arylene group having 1 to 18 carbon atoms, and may contain nitrogen, oxygen, sulfur, or halogen)   The polyamideimide resin according to claim 1, wherein the glass transition temperature is 120 ° C or higher, and the light transmittance at a wavelength of 400 nm at a dry film thickness of 30 µm is 81% or higher. The polyamide-imide resin according to claim 1 or 2, wherein R ¹⁰ contains an isophorone skeleton and / or a dicyclohexylmethane skeleton.   The polyamideimide resin according to any one of claims 1 to 3, which contains 20 mol% or more and 100 mol% or less of the repeating unit of Formula 1.   The polyamide-imide according to any one of claims 1 to 4, which is dissolved in a solvent selected from ethanol, toluene, cyclohexanone, cyclopentanone and tetrahydrofuran alone or in an amount of 5% by weight or more in two or more mixed solvents. resin.   The varnish which melt | dissolved the polyamide imide resin in any one of Claims 1-5.