KR20200140823A - Polyimide resin, polyimide varnish and polyimide film - Google Patents

Abstract

A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, wherein the structural unit A is derived from a compound represented by the following formula (a-1) (A-1 ) And a structural unit (A-2) derived from a compound represented by the following formula (a-2), and the structural unit B is a structural unit derived from a compound represented by the following formula (b-1) (B -1), and the structural unit A does not contain the structural unit (AX) derived from the compound represented by the following formula (ax), and a polyimide varnish and polyimide containing this polyimide resin Mid film.

Description

Polyimide resin, polyimide varnish and polyimide film

The present invention relates to a polyimide resin, a polyimide varnish, and a polyimide film.

In general, since polyimide resins have excellent mechanical properties and heat resistance, various uses are being studied in fields such as electric and electronic parts. For example, it is desired to replace glass substrates used in image display devices such as liquid crystal displays and OLED displays with plastic substrates for the purpose of reducing device weight or flexibility, and is a polyimide film suitable as a corresponding plastic substrate. Research is ongoing. The polyimide film for this purpose is required to have colorless transparency.

When the varnish applied on a glass support or a silicon wafer is heat-cured to form a polyimide film, residual stress is generated in the polyimide film. When the residual stress of the polyimide film is large, there is a problem that the glass support or the silicon wafer is warped, so that the polyimide film is also required to reduce the residual stress.

In Patent Document 1, as a polyimide resin that imparts a film of low residual stress, 4,4'-oxydiphthalic dianhydride is used as a tetracarboxylic acid component, and α,ω-amino having a number average molecular weight of 1000 as a diamine component. Polyimide resins synthesized using propylpolydimethylsiloxane and 4,4'-diaminodiphenyl ether are disclosed.

Japanese Patent Laid-Open No. 2005-232383

As described above, the polyimide film is required to have colorless transparency and low residual stress, but it is not easy to improve these properties while maintaining excellent mechanical properties and heat resistance.

The present invention has been made in view of such a situation, and the subject of the present invention includes a polyimide resin capable of forming a film having excellent mechanical properties, heat resistance, and colorless transparency, and further low residual stress, and the polyimide resin. It is to provide a polyimide varnish and a polyimide film.

The inventors of the present invention have found that a polyimide resin containing a combination of a specific structural unit can solve the above problems, and have come to complete the invention.

That is, the present invention relates to the following [1] to [5].

[One]

As a polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine,

Constituent unit A includes a structural unit (A-1) derived from a compound represented by the following formula (a-1), and a structural unit (A-2) derived from a compound represented by the following formula (a-2) and,

Constituent unit B includes a structural unit (B-1) derived from a compound represented by the following formula (b-1),

A polyimide resin in which the structural unit A does not contain a structural unit (A-X) derived from a compound represented by the following formula (a-x).

[Formula 1]

[2]

The proportion of the structural unit (A-1) in the structural unit A is 50 to 90 mol%,

The polyimide resin according to the above [1], wherein the proportion of the structural unit (A-2) in the structural unit A is 10 to 50 mol%.

[3]

The polyimide resin according to [1] or [2], wherein the proportion of the structural unit (B-1) in the structural unit B is 50 mol% or more.

[4]

A polyimide varnish obtained by dissolving the polyimide resin according to any one of the above [1] to [3] in an organic solvent.

[5]

A polyimide film containing the polyimide resin according to any one of the above [1] to [3].

According to the present invention, a film having excellent mechanical properties, heat resistance, and colorless transparency and low residual stress can be formed.

[Polyimide resin]

The polyimide resin of the present invention has a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, and the structural unit A is a structural unit derived from a compound represented by the following formula (a-1) (A-1) and a structural unit (A-2) derived from a compound represented by the following formula (a-2), and the structural unit B is derived from a compound represented by the following formula (b-1) The structural unit (B-1) is included, and the structural unit A does not include the structural unit (AX) derived from the compound represented by the following formula (ax).

[Formula 2]

<Constituent Unit A>

Structural unit A is a structural unit derived from a tetracarboxylic dianhydride occupied in a polyimide resin, a structural unit (A-1) derived from a compound represented by the following formula (a-1), and the following formula (a- The structural unit (A-2) derived from the compound represented by 2) is included, and the structural unit (AX) derived from the compound represented by the following formula (ax) is not included.

[Formula 3]

In the compound represented by formula (a-1), nobonane-2-spiro-α-cyclopentanone-α'-spiro-2”- nobonane-5,5”,6,6”-tetracarboxylic acid is It is anhydrous.

The compound represented by formula (a-2) is biphenyltetracarboxylic dianhydride (BPDA), and as a specific example, 3,3',4,4'- represented by the following formula (a-2s) Biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a-2a), the following formula (a) 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by -2i) is mentioned.

[Formula 4]

When the structural unit A contains both the structural unit (A-1) and the structural unit (A-2), the mechanical properties, heat resistance, and colorless transparency of the film are improved, and residual stress is reduced.

The compound represented by formula (a-x) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride.

In the present invention, the structural unit A does not include the structural unit (A-X) derived from the compound represented by the formula (a-x). That is, the polyimide resin of the present invention does not contain the structural unit (A-X).

The proportion of the structural unit (A-1) in the structural unit A is preferably 50 to 90 mol%, more preferably 55 to 85 mol%, and still more preferably 60 to 80 mol%.

The proportion of the structural unit (A-2) in the structural unit A is preferably 10 to 50 mol%, more preferably 15 to 45 mol%, and still more preferably 20 to 40 mol%.

The proportion of the sum of the structural units (A-1) and (A-2) in the structural unit A is preferably 50 mol% or more, more preferably 70 mol% or more, and still more preferably 90 mol% % Or more, and particularly preferably 99 mol% or more. The upper limit of the ratio of the total of the structural units (A-1) and (A-2) is not particularly limited, that is, 100 mol%. Constituent unit A may consist of only the constituent unit (A-1) and the constituent unit (A-2).

Constituent unit A may include constituent units other than constituent units (A-1) and (A-2) (except for constituent units (A-X)). The tetracarboxylic acid dianhydride imparting such a structural unit is not particularly limited, but pyromellitic dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, and 4,4' -(Hexafluoroisopropylidene)diphthalic anhydride and other aromatic tetracarboxylic dianhydrides (except for compounds represented by formula (a-2)); Alicyclic tetracarboxylic dianhydride, such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride (however, compounds represented by formula (a-1) and compounds represented by formula (ax) are excluded) ; And aliphatic tetracarboxylic dianhydrides, such as 1,2,3,4-butane tetracarboxylic dianhydride, are mentioned.

Meanwhile, in the present specification, the aromatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing one or more aromatic rings, and the alicyclic tetracarboxylic dianhydride includes one or more alicyclic rings, and further aromatic rings It means a tetracarboxylic acid dianhydride which does not contain, and the aliphatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride which does not contain neither an aromatic ring nor an alicyclic ring.

The structural units other than the structural units (A-1) and (A-2) optionally included in the structural unit A may be one type, or may be two or more types.

<Constituent Unit B>

The structural unit B is a structural unit derived from a diamine occupied in the polyimide resin, and includes a structural unit (B-1) derived from a compound represented by the following formula (b-1).

[Formula 5]

The compound represented by formula (b-1) is 2,2'-bis(trifluoromethyl)benzidine.

When the structural unit B contains the structural unit (B-1), the colorless transparency and heat resistance of the film are improved, and residual stress is reduced.

The proportion of the structural unit (B-1) in the structural unit B is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, and particularly preferably It is more than 99 mol%. The upper limit of the proportion of the structural unit (B-1) is not particularly limited, that is, 100 mol%. Constituent unit B may consist of only constituent units (B-1).

Constituent unit B may include constituent units other than the constituent unit (B-1). The diamine giving such a structural unit is not particularly limited, but 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'- Dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylether, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4 ,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indene-5- Amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl) terephthalamide, 4,4'-bis(4-aminophenoxy) Si) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, and 9,9 -Aromatic diamines such as bis(4-aminophenyl)fluorene (however, the compound represented by formula (b-1) is excluded); Alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; And aliphatic diamines, such as ethylenediamine and hexamethylenediamine, are mentioned.

On the other hand, in the present specification, the aromatic diamine means a diamine containing one or more aromatic rings, the alicyclic diamine means a diamine containing one or more alicyclic rings and does not contain an aromatic ring, and aliphatic diamine means It means a diamine which does not contain neither an aromatic ring nor an alicyclic ring.

Constituent units other than the constituent unit (B-1) optionally included in the constituent unit B may be one type or two or more types.

The number average molecular weight of the polyimide resin of the present invention is preferably 5,000 to 100,000 from the viewpoint of the mechanical strength of the obtained polyimide film. On the other hand, the number average molecular weight of the polyimide resin can be calculated from, for example, a standard polymethyl methacrylate (PMMA) conversion value measured by gel filtration chromatography.

The polyimide resin of the present invention may contain structures other than a polyimide chain (a structure formed by imide bonding of structural units A and B). Examples of structures other than the polyimide chain that may be contained in the polyimide resin include structures including an amide bond.

It is preferable that the polyimide resin of the present invention contains a polyimide chain (a structure formed by imide bonding of the structural unit A and the structural unit B) as a main structure. Therefore, the proportion of the polyimide chain in the polyimide resin of the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably It is 99% by mass or more.

By using the polyimide resin of the present invention, a film having excellent mechanical properties, heat resistance, and colorless transparency and low residual stress can be formed, and suitable physical properties of the film are as follows.

The tensile modulus is preferably 2.5 GPa or more, more preferably 3.0 GPa or more, and still more preferably 3.5 GPa or more.

The tensile strength is preferably 100 MPa or more, more preferably 120 MPa or more, and even more preferably 150 MPa or more.

The glass transition temperature (Tg) is preferably 320°C or higher, more preferably 350°C or higher, and still more preferably 365°C or higher.

When the total light transmittance is made into a film having a thickness of 10 μm, it is preferably 88% or more, more preferably 89% or more, and still more preferably 90% or more.

When the yellow index (YI) is set as a film having a thickness of 10 μm, it is preferably 3.5 or less, more preferably 3.0 or less, and still more preferably 2.8 or less.

The residual stress is preferably 18.0 MPa or less, more preferably 17.0 MPa or less, and still more preferably 15.0 MPa or less.

On the other hand, the above-described physical property values in the present invention can be specifically measured by the method described in Examples.

[Method for producing polyimide resin]

The polyimide resin of the present invention includes a compound that provides the above-described structural unit (A-1) and a compound that provides the above-described structural unit (A-2), It can be produced by reacting a tetracarboxylic acid component not containing &lt;RTI ID=0.0&gt;(B-1)&lt;/RTI&gt;

Examples of the compound that imparts the structural unit (A-1) include, but are not limited to, a compound represented by the formula (a-1), and may be a derivative thereof within the range of imparting the same structural unit. As the derivative, tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by formula (a-1) (that is, nobonan-2-spiro-α-cyclopentanone-α'-spiro-2”-Novo Nan-5,5", 6,6"-tetracarboxylic acid), and alkyl esters of the tetracarboxylic acid are mentioned. As the compound giving the structural unit (A-1), a compound represented by formula (a-1) (that is, a dianhydride) is preferable.

Likewise, as the compound giving the structural unit (A-2), a compound represented by formula (a-2) may be exemplified, but is not limited thereto, and may be a derivative thereof within the range to which the same structural unit is given. . Examples of the derivatives include tetracarboxylic acids corresponding to tetracarboxylic dianhydrides represented by formula (a-2) and alkyl esters of the tetracarboxylic acids. As the compound giving the structural unit (A-2), a compound represented by formula (a-2) (that is, a dianhydride) is preferable.

In the present invention, the tetracarboxylic acid component does not contain a compound that imparts a structural unit (A-X). Accordingly, the tetracarboxylic acid component does not include the compound represented by the formula (a-x), and does not include derivatives thereof within the range of giving the same structural unit. Examples of the derivatives include tetracarboxylic acids corresponding to tetracarboxylic dianhydrides represented by formula (a-x) and alkyl esters of the tetracarboxylic acids.

The tetracarboxylic acid component preferably contains 50 to 90 mol%, more preferably 55 to 85 mol%, and still more preferably 60 to 80 mol% of the compound that imparts the structural unit (A-1) Include %.

The tetracarboxylic acid component preferably contains 10 to 50 mol%, more preferably 15 to 45 mol%, and even more preferably 20 to 40 mol% of the compound that imparts the structural unit (A-2) Include %.

The tetracarboxylic acid component contains, in total, preferably 50 mol% or more, and more preferably 70 mol%, in total, of the compound giving the structural unit (A-1) and the compound giving the structural unit (A-2). It contains more than, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content of the compound to give the structural unit (A-1) and the compound to give the structural unit (A-2) is not particularly limited, that is, 100 mol%. The tetracarboxylic acid component may consist of only the compound which gives the structural unit (A-1) and the compound which gives the structural unit (A-2).

The tetracarboxylic acid component may contain a compound other than the compound giving the structural unit (A-1) and the compound giving the structural unit (A-2) (however, the compound giving the structural unit (AX) Except), as the compound, the above-described aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydride, and their derivatives (tetracarboxylic acid, alkyl ester of tetracarboxylic acid, etc.) Can be mentioned.

The compound other than the compound which imparts the structural unit (A-1) optionally contained in the tetracarboxylic acid component and the compound which imparts the structural unit (A-2) may be one, or may be two or more.

Examples of the compound that imparts the structural unit (B-1) include, but are not limited to, the compound represented by the formula (b-1), and may be a derivative thereof within the range of imparting the same structural unit. Examples of the derivatives include diisocyanates corresponding to diamines represented by formula (b-1). As the compound giving the structural unit (B-1), a compound represented by formula (b-1) (ie, diamine) is preferable.

The diamine component contains a compound that imparts the structural unit (B-1), preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, particularly Preferably it contains 99 mol% or more. The upper limit value of the content of the compound that imparts the structural unit (B-1) is not particularly limited, that is, it is 100 mol%. The diamine component may consist of only a compound which imparts a structural unit (B-1).

The diamine component may contain compounds other than the compound that imparts the structural unit (B-1), and as the compound, the aromatic diamine, alicyclic diamine, and aliphatic diamine described above, and their derivatives (diisocyanate, etc.) Can be lifted.

The number of compounds other than the compound which imparts the structural unit (B-1) optionally contained in the diamine component may be one or two or more.

In the present invention, it is preferable that the amount ratio of the tetracarboxylic acid component and the diamine component used in the production of the polyimide resin is 0.9 to 1.1 moles of the diamine component per 1 mole of the tetracarboxylic acid component.

In addition, in the present invention, in the production of the polyimide resin, in addition to the above-described tetracarboxylic acid component and diamine component, an end capping agent can also be used. As the terminal sealing agent, monoamines or dicarboxylic acids are preferable. The amount of the terminal sealing agent to be introduced is preferably 0.0001 to 0.1 mol, and particularly preferably 0.001 to 0.06 mol with respect to 1 mol of the tetracarboxylic acid component. Examples of monoamine end caps include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, and 3-methylbenzylamine , 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. are recommended. Among these, benzylamine and aniline can be used suitably. As the dicarboxylic acid terminal sealing agent, dicarboxylic acids are preferable, and a part thereof may be closed ring. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, Cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and the like are recommended. Among these, phthalic acid and phthalic anhydride can be suitably used.

There is no particular limitation on the method of reacting the above-described tetracarboxylic acid component and diamine component, and a known method can be used.

As a specific reaction method, (1) a tetracarboxylic acid component, a diamine component, and a reaction solvent are introduced into a reactor, stirred at room temperature to 80°C for 0.5 to 30 hours, and then heated to perform an imidation reaction, ( 2) After dissolving the diamine component and the reaction solvent in the reactor, the tetracarboxylic acid component is added and, if necessary, stirred at room temperature to 80° C. for 0.5 to 30 hours, and then heated to perform an imidation reaction, (3) A method of introducing a tetracarboxylic acid component, a diamine component, and a reaction solvent into a reactor, and immediately raising the temperature to perform an imidation reaction, etc. are mentioned.

The reaction solvent used for production of the polyimide resin may be any one capable of dissolving the resulting polyimide without inhibiting the imidation reaction. For example, an aprotic solvent, a phenolic solvent, an ether solvent, a carbonate solvent, and the like can be mentioned.

Specific examples of the aprotic solvent include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazoli Amide solvents such as dinon and tetramethylurea, lactone solvents such as γ-butyrolactone and γ-valerolactone, phosphorus-containing amide solvents such as hexamethylphosphoricamide and hexamethylphosphinetriamide, dimethylsulfone , Sulfur-containing solvents such as dimethyl sulfoxide and sulfolane, ketone solvents such as acetone, cyclohexanone, and methylcyclohexanone, amine solvents such as picoline and pyridine, acetic acid (2-methoxy-1-methylethyl) ), and the like.

Specific examples of the phenolic solvent include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6 -Xylenol, 3,4-xylenol, 3,5-xylenol, etc. are mentioned.

Specific examples of the ether solvent include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, and bis[2-(2-methoxyethyl)ether. Oxyethoxy)ethyl] ether, tetrahydrofuran, and 1,4-dioxane.

Further, specific examples of the carbonate-based solvent include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate.

Among the above reaction solvents, an amide-based solvent or a lactone-based solvent is preferable. In addition, the above reaction solvents may be used alone or in combination of two or more.

In the imidation reaction, it is preferable to perform the reaction while removing water generated during production using a Dean Stark apparatus or the like. By performing such an operation, the degree of polymerization and the imidation rate can be further increased.

In the above imidization reaction, a known imidization catalyst can be used. Examples of the imidization catalyst include a base catalyst or an acid catalyst.

As the base catalyst, pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine , Triethylenediamine, imidazole, N,N-dimethylaniline, N,N-diethylaniline, and other organic base catalysts, and inorganic bases such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogen carbonate and sodium hydrogen carbonate Catalysts.

Further, examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxyanic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid, and the like. The imidation catalyst described above may be used alone or in combination of two or more.

Among the above, from the viewpoint of handling properties, it is preferable to use a base catalyst, more preferably an organic base catalyst, still more preferably use triethylamine, and particularly preferably use a combination of triethylamine and triethylenediamine. Do.

The temperature of the imidation reaction is preferably 120 to 250°C, more preferably 160 to 200°C, from the viewpoint of the reaction rate and suppression of gelation and the like. In addition, the reaction time is preferably 0.5 to 10 hours after the start of outflow of the generated water.

[Polyimide Varnish]

The polyimide varnish of the present invention is obtained by dissolving the polyimide resin of the present invention in an organic solvent. That is, the polyimide varnish of the present invention contains the polyimide resin and an organic solvent of the present invention, and the polyimide resin is dissolved in the organic solvent.

The organic solvent is not particularly limited as long as the polyimide resin is dissolved, but it is preferable to use the above-described compounds alone or in combination of two or more as the reaction solvent used in the production of the polyimide resin.

The polyimide varnish of the present invention may be a polyimide solution itself in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, or may be obtained by adding a further diluent solvent to the polyimide solution.

Since the polyimide resin of the present invention has solvent solubility, it can be obtained as a varnish of high concentration stable at room temperature. It is preferable that the polyimide varnish of this invention contains 5-40 mass% of the polyimide resin of this invention, and it is more preferable that it contains 10-30 mass %. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, and more preferably 5 to 150 Pa·s. The viscosity of the polyimide varnish is a value measured at 25°C using an E-type viscometer.

In addition, the polyimide varnish of the present invention is an inorganic filler, an adhesion promoter, a release agent, a flame retardant, an ultraviolet stabilizer, a surfactant, a leveling agent, an antifoaming agent, an optical whitening agent, a crosslinking agent, as long as the required properties of the polyimide film are not impaired. It may also contain various additives such as a polymerization initiator and a photosensitizer.

The method for producing the polyimide varnish of the present invention is not particularly limited, and a known method can be applied.

[Polyimide Film]

The polyimide film of the present invention contains the polyimide resin of the present invention. Therefore, the polyimide film of the present invention is excellent in mechanical properties, heat resistance, and colorless transparency, and further has low residual stress. Suitable physical property values of the polyimide film of the present invention are as described above.

There is no restriction|limiting in particular in the manufacturing method of the polyimide film of this invention, A well-known method can be used. For example, after applying the polyimide varnish of the present invention onto a smooth support such as a glass plate, a metal plate, or plastic, or forming a film, an organic solvent such as a reaction solvent or a diluting solvent contained in the varnish is heated. A method of removing by, etc. are mentioned. If necessary, a release agent may be applied to the surface of the support in advance.

As a method of removing the organic solvent contained in the varnish by heating, the following method is preferable. That is, after evaporating the organic solvent at a temperature of 120°C or less to form a self-supporting film, the self-supporting film is peeled from the support, the end of the self-supporting film is fixed, and the temperature is above the boiling point of the used organic solvent. It is preferable to dry in to produce a polyimide film. In addition, it is preferable to dry it in a nitrogen atmosphere. The pressure in the dry atmosphere may be any of reduced pressure, normal pressure, and pressure. The heating temperature when drying the self-supporting film to prepare a polyimide film is not particularly limited, but is preferably 200 to 400°C.

Further, the polyimide film of the present invention can also be produced using a polyamic acid varnish obtained by dissolving a polyamic acid in an organic solvent.

The polyamic acid contained in the polyamic acid varnish is a precursor of the polyimide resin of the present invention, a compound that provides the above-described structural unit (A-1) and a compound that provides the above-described structural unit (A-2). It is a product of a polyaddition reaction between a tetracarboxylic acid component that contains and does not contain a compound that imparts the above-described structural unit (AX) and a diamine component that contains a compound that imparts the above-described structural unit (B-1). . By imidizing this polyamic acid (dehydration ring closure), the polyimide resin of the present invention as a final product is obtained.

As the organic solvent contained in the polyamic acid varnish, an organic solvent contained in the polyimide varnish of the present invention may be used.

In the present invention, the polyamic acid varnish includes a compound that provides the above-described structural unit (A-1) and a compound that provides the above-described structural unit (A-2), and contains the above-described structural unit (AX). It may be a polyamic acid solution itself obtained by polyaddition reaction of a tetracarboxylic acid component not containing a compound to be imparted and a diamine component including a compound to impart the structural unit (B-1) described above in a reaction solvent, or The polyamic acid solution may be further diluted with a solvent.

There is no particular limitation on the method of producing a polyimide film using a polyamic acid varnish, and a known method can be used. For example, a polyamic acid varnish is applied on a smooth support such as a glass plate, a metal plate, or plastic, or formed into a film, and an organic solvent such as a reactive solvent or a diluting solvent contained in the varnish is removed by heating. Thus, a polyamic acid film is obtained, and a polyimide film can be produced by imidizing the polyamic acid in the polyamic acid film by heating.

The heating temperature when drying the polyamic acid varnish to obtain a polyamic acid film is preferably 50 to 120°C. The heating temperature when the polyamic acid is imidized by heating is preferably 200 to 400°C.

On the other hand, the method of imidation is not limited to thermal imidization, and chemical imidization can also be applied.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the application, etc., preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, and still more preferably 10 to 80 μm. When the thickness is 1 to 250 µm, practical use as a self-supporting film becomes possible.

The thickness of the polyimide film can be easily controlled by adjusting the solid content concentration and viscosity of the polyimide varnish.

The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, and optical members. The polyimide film of the present invention is particularly suitably used as a substrate for an image display device such as a liquid crystal display or an OLED display.

Example

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited at all by these Examples.

The solid content concentration of the varnish obtained in Examples and Comparative Examples and the physical properties of each film were measured by the methods shown below.

(1) solid content concentration

The measurement of the solid content concentration of the varnish was performed by heating a sample at 320° C. x 120 min with a small electric furnace "MMF-1" manufactured by Asone Corporation, and was calculated from the difference in mass of the sample before and after heating.

(2) film thickness

The film thickness was measured using a micrometer manufactured by Mitsutoyo.

(3) Tensile modulus, tensile strength

Tensile modulus and tensile strength were measured in accordance with JIS K7127, using a tensile tester "Strograph VG-1E" manufactured by Toyo Seiki Corporation. The chuck distance was 10 mm x 50 mm, and the test speed was 20 mm/min. Tensile modulus and tensile strength are both superior as the numerical value increases.

(4) Glass transition temperature (Tg)

Using the thermomechanical analysis device "TMA/SS6100" manufactured by Hitachi Hi-Tech Science, in tension mode, the sample size is 2 mm × 20 mm, the load is 0.1 N, and the temperature rise rate is 10°C/min. The temperature is sufficient to remove the residual stress. The temperature was raised to remove residual stress, and then cooled to room temperature. Thereafter, the elongation of the test piece was measured under the same conditions as the treatment for removing the residual stress, and the point at which the inflection point of elongation was seen was determined as the glass transition temperature. The larger the value, the better the Tg.

(5) Total light transmittance, yellow index (YI)

The total light transmittance and YI were measured in accordance with JIS K7361-1:1997, using a color and turbidity measuring instrument "COH400" manufactured by Japan Electric Color Industry Co., Ltd. The closer the total light transmittance is to 100% and the smaller the value for YI, the better.

(6) residual stress

Spinning polyimide varnish or polyamic acid varnish on a 4-inch silicon wafer with a thickness of 525 μm±25 μm, which has previously measured the “warpage amount”, using the residual stress measuring device “FLX-2320” manufactured by KLA Tencor. It was applied using a coater and prebaked. Thereafter, using a hot air dryer, heat curing treatment was performed at 400° C. for 1 hour in a nitrogen atmosphere to prepare a silicone wafer adhered to a polyimide film having a thickness of 8 to 20 μm after curing. The amount of warpage of this wafer was measured using the above-described residual stress measuring device, and residual stress generated between the silicon wafer and the polyimide film was evaluated. The smaller the residual stress, the better.

The tetracarboxylic acid component and diamine component used in Examples and Comparative Examples, and their abbreviations are as follows.

<Tetracarboxylic acid component>

CpODA: Novonan-2-spiro-α-cyclopentanone-α'-spiro-2”-novonane-5,5”,6,6”-tetracarboxylic dianhydride (manufactured by JX Energy Corporation; formula (a Compound represented by -1))

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation; compound represented by formula (a-2))

<Diamine>

TFMB: 2,2'-bis(trifluoromethyl)benzidine (manufactured by Wakayama Seika Industrial Co., Ltd.; compound represented by formula (b-1))

<Example 1>

In a 1L 5-neck round bottom flask equipped with stainless steel half-moon stirring blades, nitrogen inlet pipe, cooling pipe, thermometer, and glass end cap, TFMB 32.024g (0.100 mole) and N-methylpyrrolidone ( 82.391 g (manufactured by Mitsubishi Chemical Co., Ltd.) was added, followed by stirring at a system temperature of 70°C and a nitrogen atmosphere at a rotation speed of 150 rpm to obtain a solution.

To this solution, 30.750 g (0.080 mol) of CpODA, 5.884 g (0.020 mol) of BPDA, and 20.598 g of N-methylpyrrolidone (manufactured by Mitsubishi Chemical Corporation) were added at once, and then triethyl as an imidation catalyst. 0.506 g of amine (manufactured by Kanto Chemical Co., Ltd.) was added and heated with a mantle heater to raise the temperature in the reaction system to 190°C over about 20 minutes. The components to be distilled were collected, the rotational speed was adjusted according to the viscosity increase, and the temperature in the reaction system was maintained at 190°C and refluxed for 3 hours.

After that, 482.505 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) was added, the temperature in the reaction system was cooled to 120° C., and then stirred for about 3 hours to homogenize the polyimide varnish having a solid content concentration of 10.0 mass%. Got it.

Subsequently, the obtained polyimide varnish was applied on a glass plate and on a silicon wafer, held on a hot plate at 80° C. for 20 minutes, and then heated at 400° C. in a hot air dryer for 30 minutes under a nitrogen atmosphere, and the solvent was evaporated. A film having a thickness of 10 μm was obtained. Table 1 shows the results.

<Example 2>

In the same manner as in Example 1, except that the amount of CpODA was changed from 30.750 g (0.080 mol) to 23.063 g (0.060 mol) and the amount of BPDA was changed from 5.884 g (0.020 mol) to 11.769 g (0.040 mol). A polyimide varnish was produced, and a polyimide varnish having a solid content concentration of 10.0% by mass was obtained.

Using the obtained polyimide varnish, a film was produced by the same method as in Example 1, and a film having a thickness of 7 μm was obtained. Table 1 shows the results.

<Comparative Example 1>

A polyimide varnish was prepared in the same manner as in Example 1 except that the amount of CpODA was changed from 30.750 g (0.080 mol) to 38.438 g (0.100 mol) and BPDA was not added, and the solid content concentration was 10.0% by mass. The polyimide varnish of was obtained.

Using the obtained polyimide varnish, a film was produced by the same method as in Example 1 to obtain a film having a thickness of 14 μm. Table 1 shows the results.

<Comparative Example 2>

In a 1L five-necked round bottom flask equipped with stainless steel half-moon stirring blades, nitrogen inlet pipe, cooling pipe, thermometer, and glass end cap, TFMB was added 32.024 g (0.100 mol) and N-methylpyrrolidone. 196.627 g of (manufactured by Mitsubishi Chemical Co., Ltd.) was added, followed by stirring at a system temperature of 50°C and a nitrogen atmosphere at a rotation speed of 150 rpm to obtain a solution.

To this solution, 294.22 g (0.100 mol) of BPDA and 49.157 g of N-methylpyrrolidone (manufactured by Mitsubishi Chemical Co., Ltd.) were put in a batch, and the mixture was stirred for 7 hours while maintaining at 50°C with a mantle heater.

Then, 307.230 g of N-methylpyrrolidone (manufactured by Mitsubishi Chemical Co., Ltd.) was added, followed by stirring for about 3 hours to homogenize to obtain a polyamic acid varnish having a solid content concentration of 10.0% by mass.

Subsequently, the obtained polyamic acid varnish was coated on a glass plate and on a silicon wafer, held on a hot plate at 80° C. for 20 minutes, and then heated at 400° C. in a hot air dryer for 30 minutes under a nitrogen atmosphere to evaporate the solvent. It was subjected to thermal imidation again to obtain a 12 μm-thick film. Table 1 shows the results.

[Table 1]

As shown in Table 1, the polyimide films of Examples 1 and 2 were excellent in mechanical properties, heat resistance, and colorless transparency, and also had low residual stress.

On the other hand, the polyimide film of Comparative Example 1 prepared using only CpODA as a tetracarboxylic acid component was inferior in tensile modulus and heat resistance, and high residual stress compared to the polyimide films of Examples 1 and 2. In addition, the polyimide film of Comparative Example 2 prepared using only BPDA as the tetracarboxylic acid component was inferior in heat resistance and colorless transparency and high residual stress compared to the polyimide films of Examples 1 and 2.

Claims (5)

As a polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine,
Constituent unit A includes a structural unit (A-1) derived from a compound represented by the following formula (a-1), and a structural unit (A-2) derived from a compound represented by the following formula (a-2) and,
Constituent unit B includes a structural unit (B-1) derived from a compound represented by the following formula (b-1),
A polyimide resin in which the structural unit A does not contain a structural unit (AX) derived from a compound represented by the following formula (ax).
[Formula 1]

The method of claim 1,
The proportion of the structural unit (A-1) in the structural unit A is 50 to 90 mol%,
The polyimide resin, wherein the proportion of the structural unit (A-2) in the structural unit A is 10 to 50 mol%. The method according to claim 1 or 2,
The polyimide resin, wherein the proportion of the structural unit (B-1) in the structural unit B is 50 mol% or more. A polyimide varnish obtained by dissolving the polyimide resin according to any one of claims 1 to 3 in an organic solvent. A polyimide film containing the polyimide resin according to any one of claims 1 to 3.