JP6806141B2 - Method of manufacturing polyimide film - Google Patents

Description

The present invention relates to a method of manufacturing a polyimide film arm, and more particularly to a method for manufacturing a polyimide film flatness degradation at the time of winding the film into a roll can be improved by heat straightening.

Since polyimide has excellent bendability and high elastic modulus, it can be used as a member of a transparent flexible circuit board (FPC: Flexible Printed Circuits) or an organic electroluminescence device (also referred to as "organic EL device"). ing. However, it is colored yellowish brown due to intramolecular conjugation and formation of a charge transfer complex, and it is difficult to use it in a field where transparency is required.

As a countermeasure, for example, a method of introducing a fluorine group into polyimide, imparting flexibility to the main chain, or introducing a bulky side chain to inhibit the formation of a charge transfer complex has been proposed. Further, a method of expressing transparency by using a semi-alicyclic or full alicyclic polyimide that does not form a charge transfer complex in principle has also been proposed (see, for example, Patent Document 1).

Further, a polyimide film having no coloring and improved transparency has also been proposed (see Patent Document 2).

Polyimide films that are not colored and have improved transparency are expected to be used in display applications because they have excellent optical properties.

However, the colorless and transparent polyimide film has a problem that the films tend to stick to each other when the film is wound into a roll. Further, for this reason, there is a problem that deterioration of flatness due to the winding deformation of the roll is likely to occur.

In order to improve the deterioration of flatness caused by the above-mentioned winding deformation, an inorganic filler is mixed with the polyimide film to improve the slipperiness to prevent the polyimide films from sticking to each other, and the flat surface caused by the winding deformation. A method of reducing sexual deterioration can be considered. However, the polyimide film has a problem that only a small amount of the inorganic filler can be added, and the addition of the inorganic filler cannot be sufficiently improved.

Therefore, the present inventor has investigated a method for improving the flatness by heat-correcting a colorless and transparent polyimide film whose flatness has deteriorated due to the winding deformation by heat shrinkage.

However, it is known that the polyimide film has remarkably high strength and heat resistance as compared with a normal polymer film. Since it has the advantage that distortion due to heat is extremely small, its use as a circuit board for electronic materials has also been considered. Therefore, it has not been done to intentionally increase the heat shrinkage rate and utilize it.

In fact, even in the study of the present inventor, in the polyimide film, the heat shrinkage rate was small even when the film after film formation was heat-treated again.

Therefore, there is a problem that it is difficult to heat-correct the flatness by heat shrinkage.

Japanese Unexamined Patent Publication No. 2000-53767 Japanese Unexamined Patent Publication No. 2010-100674

The present invention has been made in view of the above problems or situation, the problem to be solved is the flatness degradation at the time of winding the film into a roll to provide a method for producing a polyimide film which can be improved by heat straightening Oh Ru.

In order to solve the above-mentioned problems according to the present invention, in the process of examining the cause of the above-mentioned problems, the polyimide film is rolled by setting the heat shrinkage rate of the polyimide film within the range of 0.5 to 20.0%. We have found that the deterioration of flatness when the film is wound up can be thermally corrected, and the present invention has been reached.

That is, the problem according to the present invention is solved by the following means.

1. 1. A method for producing a polyimide film, which produces a polyimide film containing polyimide as a main component.
The polyimide film has a total light transmittance of 80% or more, a yellow index value (YI value) of 4.0 or less, is dissolved in 1 g or more with 100 g of dichloromethane at 25 ° C., and is defined by the following formula. thermal shrinkage Ri der range of 0.5 to 20.0%,
The method for producing the polyimide film is
Doping preparation step of dissolving polyamic acid or polyimide in a solvent having a boiling point in the range of 40 to 80 ° C. to prepare a doping.
A casting step of casting the doping on a support to form a casting film,
A solvent evaporation step of evaporating a solvent from the casting film,
A peeling step of peeling the casting film obtained by evaporating the solvent from the support.
A drying step of drying the peeled cast film at 10 to 200 ° C. to obtain a film, and
Stretching step of stretching the dried film,
A method for producing a polyimide film , which comprises .
Heat shrinkage rate (%) = {(Lo-L) / Lo} x 100
(However , Lo represents the length of the sample before the test when measured at 25 ° C., and L represents the length of the sample when the sample is stored at 230 ° C. for 10 minutes and then cooled to 25 ° C. )

2. 2. The method for producing a polyimide film according to item 1, wherein the inorganic filler is contained in the range of 0.01 to 2.0% by mass.

3. 3. The method for producing a polyimide film according to item 1 or 2, wherein the polyimide contains a polyimide fluoride.

By the above means of the present invention, it is possible to provide a polyimide film capable of improving the flatness deterioration when the film is wound into a roll by heat straightening. Further, a method for producing the polyimide film can be provided.

Although the mechanism of expression or mechanism of action of the effect of the present invention has not been clarified, it is inferred as follows.

In the conventional polyimide film, a polyimide film having a rigid molecular structure is produced through a high temperature process of 300 ° C. or higher in the film forming process. Therefore, a polyimide film having high heat resistance can be obtained, but on the other hand, the heat shrinkage rate is small even if heating is performed again. Therefore, the deterioration of flatness when wound into a roll cannot be improved by heat correction.

In the process of producing a polyimide film, the present inventor adjusts and combines various conditions of drying temperature, solvent type, stretching speed, and residual solvent ratio at the time of stretching to reduce the heat shrinkage rate of the polyimide film to 0.5 to 0.5 to. It has been found that the temperature can be within the range of 20.0%, which can improve the flatness deterioration.

The reason why the heat shrinkage rate could be increased even in the polyimide film is that the polyimide does not become too rigid due to various conditions of these manufacturing processes (drying at low temperature, etc.), and the arrangement of flexible polymer chains that can shrink by reheating. I presume that it was made.

The polyimide film according to the present invention is a colorless and transparent polyimide film. As a guideline for colorlessness and transparency, it is preferable that the total light transmittance is 80% or more and the yellow index value (YI value) is 4.0 or less. A polyimide film having a total light transmittance of 80% or more and a yellow index value (YI value) of 4.0 or less is colored by introducing a bulky side chain to make it transparent or colorless. Since the formation of the charge transfer complex that causes the problem is inhibited, the molecular chains are more flexible than those of ordinary polyimide, and the gaps between the molecular chains tend to increase. Therefore, it is presumed that when the polymer chains that are forcibly oriented by applying stress during the film formation of the polyimide film are heat-treated again, the polymer chains are likely to undergo thermal shrinkage.

Further, a polyimide film in which 1 g or more is dissolved in 100 g of dichloromethane at 25 ° C. has high solubility, which facilitates solution casting. By adjusting various manufacturing conditions in the manufacturing process, the polymer chain undergoes thermal shrinkage. It is speculated that it will be easier to take a state that is likely to occur.

As described above, by adjusting and combining various conditions in the polyimide film manufacturing process, the heat shrinkage rate of the polyimide film could be set within the range of 0.5 to 20.0% for the first time.

By setting the heat shrinkage rate due to reheating within the range of 0.5 to 20.0%, the polyimide film whose flatness has deteriorated due to winding deformation can be stretched by reheating, so that the flatness is flat. Can be heat-corrected.

The polyimide film of the present invention is a colorless, transparent, highly soluble polyimide film in dichloromethane.

That is, the method for producing a polyimide film of the present invention is a method for producing a polyimide film containing polyimide as a main component, wherein the polyimide film has a total light transmittance of 80% or more and a yellow index. The value (YI value) is 4.0 or less, 1 g or more is dissolved in 100 g of polyimide at 25 ° C., and the heat shrinkage rate defined by the following formula is within the range of 0.5 to 20.0%. The method for producing the polyimide film is a dope preparation step in which polyamic acid or polyimide is dissolved in a solvent having a boiling point in the range of 40 to 80 ° C. to prepare a dope, and the dope is cast on a support. A casting step of forming a casting film, a solvent evaporation step of evaporating a solvent from the casting film, a peeling step of peeling the flown film obtained by evaporating the solvent from a support, and 10 to 10 of the peeled casting film. It is characterized by having a drying step of drying at 200 ° C. to obtain a film, and a stretching step of stretching the dried film .
Heat shrinkage rate (%) = {(Lo-L) / Lo} x 100
(However , Lo represents the length of the sample before the test when measured at 25 ° C., and L represents the length of the sample when the sample is stored at 230 ° C. for 10 minutes and then cooled to 25 ° C. )
This feature is a technical feature common to the inventions according to each claim.

As an embodiment of the present invention, it is preferable that the polyimide film contains an inorganic filler in the range of 0.01 to 2.0% by mass from the viewpoint of exhibiting the effect of the present invention. In the present invention, since the effect of the present invention can be obtained even when the amount of the inorganic filler added is less than 2.0% by mass, haze can be reduced.

Further, it is preferable that the polyimide is a fluoride polyimide from the viewpoint of having an effect of enhancing the transparency of the polyimide film and an effect of improving the flatness by heat straightening. Further, it is more preferable that the fluorine content is in the range of 1 to 40% by mass of the polyimide film because the effect of the present invention is large.

As a method for producing the polyimide film of the present invention, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl is used as a diamine, and 2,2-bis (3,4-) is used as an acid dianhydride. Dicarboxyphenyl) Hexafluoropropanedianehydride or biphenyltetracarboxylic dianhydride is used to synthesize polyimide, and the synthesized polyimide is used to produce a polyimide film, which has a great effect on heat-correcting flatness. It is preferable from the viewpoint of obtaining a polyimide film.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

<Overview of the polyimide film of the present invention>
The polyimide film of the present invention is a polyimide film containing colorless and transparent polyimide as a main component.

That is, the polyimide film of the present invention is a polyimide film containing polyimide as a main component, has a total light transmittance of 80% or more, a yellow index value (YI value) of 4.0 or less, and at 25 ° C. It is characterized in that 1 g or more is dissolved in 100 g of dichloromethane, and the heat shrinkage rate defined by the following formula is in the range of 0.5 to 20.0%.
Heat shrinkage rate (%) = {(Lo-L) / Lo} x 100
(However, Lo represents the length of the sample before the test when measured at 25 ° C., and L represents the length of the sample when the sample is stored at 230 ° C. for 10 minutes and then cooled to 25 ° C.).
In the present invention, the inclusion of polyimide as a main component indicates that the total amount of polyimide and polyamic acid in the film is 50% by mass or more. It is preferably 80% by mass or more.

<Polyimide>
The polyimide according to the present invention is a transparent heat-resistant resin having an imide structure (hereinafter, also referred to as polyimide), and is a transparent heat-resistant resin containing an imide bond in a repeating unit. The polyimide film of the present invention contains polyamic acid or polyimide. The polyamic acid or polyimide is preferably formed from a diamine or a derivative thereof and an acid anhydride or a derivative thereof.

Preferred polyimides for the present invention include polyimides, polyamideimides, polyetherimides, and polyesterimides having a structure represented by the following formula (1.1).

(1.1) Polyimide having a structure represented by the formula (1.1) or the formula (1.2) (1.1.1) Structure on the acid anhydride side Polyimide or polyamic acid that can be used in the present invention. In particular, a polyimide having a repeating unit represented by the following formula (1.1) (hereinafter referred to as polyimide (A)) or a polyamic acid having a repeating unit represented by the following formula (1.2). (Hereinafter referred to as polyamic acid (A')) is preferable.

As described above, the polyamic acid (A') corresponds to a structure in which a part of the imide bond of the polyimide (A) is dissociated, and the detailed description of the polyamic acid (A') can be considered in correspondence with the polyimide (A). Therefore, the polyimide (A) will be typically described in detail below.

In formulas (1.1) and (1.2), R is an aromatic hydrocarbon ring or an aromatic heterocycle, or a tetravalent aliphatic hydrocarbon group having 4 to 39 carbon atoms or an alicyclic hydrocarbon. It is a hydrocarbon group. Φ is a divalent aliphatic hydrocarbon group having 2 to 39 carbon atoms, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a group consisting of a combination thereof, and as a bonding group, −O−, At least selected from the group consisting of -SO _2- , -CO-, -CH _2- , -C (CH ₃ ) _2- , -OSi (CH ₃ ) _2- , -C ₂ H ₄ O- and -S- It may contain one group.

Examples of the aromatic hydrocarbon ring represented by R include a fluorene ring, a benzene ring, a biphenyl ring, a naphthalene ring, an azulene ring, an anthracene ring, a phenanthrene ring, a pyrene ring, a chrysene ring, a naphthacene ring, a triphenylene ring, o-. Terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaphthene ring, coronen ring, fluorantrene ring, naphthacene ring, pentacene ring, perylene ring, pentaphene ring, picene ring, pyrene ring, pyranthrene ring, anthra entre Benzene ring and the like.

Similarly, examples of the aromatic heterocycle represented by R include a silol ring, a furan ring, a thiophene ring, an oxazole ring, a pyrrole ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a triazine ring, and an oxadi ring. Azol ring, triazole ring, imidazole ring, pyrazole ring, thiazole ring, indole ring, benzimidazole ring, benzthiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, phthalazine ring, thienothiophene ring, carbazole ring, azacarbazole ring ( Any one or more of the carbon atoms constituting the carbazole ring are replaced with nitrogen atoms), dibenzosilol ring, dibenzofuran ring, dibenzothiophene ring, benzothiophene ring or any one of the carbon atoms constituting the dibenzofuran ring. Rings in which one or more are replaced by nitrogen atoms, benzodifuran ring, benzodithiophene ring, aclysine ring, benzoquinoline ring, phenazine ring, phenanthridin ring, phenanthroline ring, cyclazine ring, kindrin ring, tepenidin ring, quinindrin ring, triphenodi Thiadine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, naphthofuran ring, naphthothiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, anthrathiophene ring, anthrazi ring Examples thereof include a thiophene ring, a thiantolen ring, a phenoxatiin ring, a dibenzocarbazole ring, an indolocarbazole ring, and a dithienobenzene ring.

Examples of the tetravalent aliphatic hydrocarbon group having 4 to 39 carbon atoms represented by R include butane-1,1,4,4-tetrayl group and octane-1,1,8,8-tetrayl group. Examples include groups such as decane-1,1,10,10-tetrayl groups.

Examples of the tetravalent alicyclic hydrocarbon group having 4 to 39 carbon atoms represented by R include cyclobutane-1,2,3,4-tetrayl group and cyclopentane-1,2,4,5. -Tetrayl group, cyclohexane-1,2,4,5-tetrayl group, bicyclo [2.2.2] octo-7-en-2,3,5,6-tetrayl group, bicyclo [2.2.2] Octane-2,3,5,6-tetrayl group, 3,3', 4,4'-dicyclohexyltetrayl group, 3,6-dimethylcyclohexane-1,2,4,5-tetrayl group, 3,6- Examples thereof include groups such as diphenylcyclohexane-1,2,4,5-tetrayl groups.

Examples of the divalent aliphatic hydrocarbon group having 2 to 39 carbon atoms having or not having the above-mentioned bonding group represented by Φ include a group represented by the following structural formula.

In the above structural formula, n represents the number of repeating units, preferably 1 to 5, and more preferably 1 to 3. Further, X is an alkanediyl group having 1 to 3 carbon atoms, that is, a methylene group, an ethylene group, a trimethylene group and a propane-1,2-diyl group, and a methylene group is preferable.

Examples of the divalent alicyclic hydrocarbon group having 2 to 39 carbon atoms having or not having the above-mentioned bonding group represented by Φ include a group represented by the following structural formula.

Examples of the divalent aromatic hydrocarbon group having 2 to 39 carbon atoms having or not having the above-mentioned bonding group represented by Φ include a group represented by the following structural formula.

Examples of the group composed of a combination of an aliphatic hydrocarbon group represented by Φ, an alicyclic hydrocarbon group and an aromatic hydrocarbon group include a group represented by the following structural formula.

The group represented by Φ is preferably a divalent aromatic hydrocarbon group having 2 to 39 carbon atoms having a bonding group, or a combination of the aromatic hydrocarbon group and an aliphatic hydrocarbon group, in particular. , A group represented by the following structural formula is preferable.

The acid anhydride used in the present invention is a carboxylic acid anhydride, preferably a derivative of an aliphatic or alicyclic tetracarboxylic acid, for example, an aliphatic or alicyclic tetracarboxylic acid ester, an aliphatic or Aliphatic tetracarboxylic dianhydride and the like can be mentioned. Of the aliphatic or alicyclic tetracarboxylic acid or its derivative, an alicyclic tetracarboxylic dianhydride is preferable.

Here, the derivative is a compound that can be changed to an aliphatic or alicyclic tetracarboxylic acid. For example, in the case of an aliphatic tetracarboxylic acid dianhydride, a compound having two carboxy groups instead of the anhydride. , A compound in which one or both of these two carboxy groups are esterified, or an acid chloride in which one or both of these two carboxy groups are chlorinated is preferably used.

By using such an acyl compound, a polyimide film having high heat resistance and excellent optical properties and less coloring (yellowing) can be obtained.

Examples of the aliphatic tetracarboxylic acid include 1,2,3,4-butanetetracarboxylic acid. Examples of the alicyclic tetracarboxylic acid include 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,4,5-cyclopentanetetracarboxylic acid, and 1,2,4,5-cyclohexanetetracarboxylic acid. , Bicyclo [2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic acid, Bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic acid, etc. Can be mentioned.

Examples of the aliphatic tetracarboxylic acid esters include monoalkyl esters, dialkyl esters, trialkyl esters, and tetraalkyl esters of the above aliphatic tetracarboxylic acids. Examples of the alicyclic tetracarboxylic acid ester include the monoalkyl ester, dialkyl ester, trialkyl ester, and tetraalkyl ester of the alicyclic tetracarboxylic acid. The alkyl group moiety is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms.

Examples of the aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride. Examples of the alicyclic tetracarboxylic dianhydride include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, 1,2. , 4,5-Cyclohexanetetracarboxylic dianhydride, Bicyclo [2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, Bicyclo [2.2.2] Examples thereof include octane-2,3,5,6-tetracarboxylic dianhydride. Particularly preferred is 1,2,4,5-cyclohexanetetracarboxylic dianhydride. In general, in polyimide containing an aliphatic diamine as a constituent component, polyamic acid and diamine, which are intermediate products, form a strong salt, so that a solvent having relatively high salt solubility (for example, cresol) is used to increase the molecular weight. , N, N-dimethylacetamide, γ-butyrolactone, N-methyl-2-pyrrolidone, etc.) are preferably used. However, even in the case of polyimide containing an aliphatic diamine as a constituent component, when 1,2,4,5-cyclohexanetetracarboxylic dianhydride is used as a constituent component, the polyamic acid and the salt of the diamine are bound by a relatively weak bond. Therefore, it is easy to increase the molecular weight, and it is easy to obtain a flexible film.

In addition, for example, 4,4'-biphthalic anhydride, 4,4'-(hexafluoroisopropyridene) diphthalic anhydride, 2,3,3', 4'-biphenyltetracarboxylic acid anhydride, 4,4'-oxydiphthalic anhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid anhydride, 1,2,3,4-cyclopentanetetracarboxylic acid anhydride, 4- (2,2) 5-Dioxo tetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3- Cyclohexene-1,2-dicarboxylic acid anhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic acid anhydride, 3,4'-oxydiphthalic acid anhydride, 3,4,9,10-perylenetetra Organic Acid Dianide (Pigment Red 224) 1,2,3,4-Tetramethyl-1,2,3,4-Cyclobutane Tetracarboxylic Acid Dianide Tricyclo [6.4.0.02,7] Dodecane- 1,8: 2,7-tetracarboxylic acid dianhydride and the like can be used.

Further, an acid anhydride having a fluorene skeleton or a derivative thereof may be used. It has the effect of improving the coloring peculiar to polyimide. Examples of the acid anhydride having a fluorene skeleton include 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride and 9,9-bis [4- (3,4-dicarboxyphenoxy) phenyl. ] Fluorenic dianhydride, 9,9-bis [4- (3,4-dicarboxyphenoxy) -3-phenylphenyl] fluorenic dianhydride and the like can be used.

Aromatic, aliphatic or alicyclic tetracarboxylic dians or derivatives thereof may be used alone or in combination of two or more. Further, other tetracarboxylic dians or derivatives thereof (particularly dianhydride) may be used in combination as long as the solvent solubility of the polyimide, the flexibility of the polyimide film, the thermocompression bonding property, and the transparency are not impaired.

Examples of such other tetracarboxylic acids or derivatives thereof 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, bis (3,4-dicarboxyphenyl) Phenyl) sulfone, bis (3,4-dicarboxyphenyl) ether, bis (2,3-dicarboxyphenyl) ether, 3,3', 4,4'-benzophenonetetracarboxylic acid, 2,2', 3, 3'-benzophenonetetracarboxylic acid, 4,4- (p-phenylenedioxy) diphthalic acid, 4,4- (m-phenylenedioxy) diphthalic acid, 1,1-bis (2,3-dicarboxyphenyl) Aromatic tetracarboxylic acids such as ethane, bis (2,3-dicarboxyphenyl) methane, bis (3,4-dicarboxyphenyl) methane and their derivatives (particularly dianhydride); ethylenetetracarboxylic acid and the like. Examples thereof include aliphatic tetracarboxylic acids having 1 to 3 carbon atoms and derivatives thereof (particularly dianhydride).

As the acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanedianehydride or biphenyltetracarboxylic dianhydride is excellent in transparency and heat due to heat shrinkage. It is preferable from the viewpoint of easy correction.

The repeating unit represented by the formula (1.1) is preferably 10 to 100 mol%, more preferably 50 to 100 mol%, still more preferably 80 to 100 mol%, particularly preferably 80 to 100 mol%, based on all the repeating units. Is 90-100 mol%. The number of repeating units of the formula (1.1) in one molecule of polyimide (A) is 10 to 2000, preferably 20 to 200, and the glass transition temperature is further 230 to 350 ° C. in this range. It is preferably 250 to 330 ° C., and more preferably 250 to 330 ° C.

(1.1.2) Structure on the diamine side As the diamine or its derivative, for example, aromatic diamine or isocyanic acid ester is preferable, and aromatic diamine is preferable.

The diamine or a derivative thereof used in the present invention may be any of aromatic diamines, aliphatic diamines and mixtures thereof, and aromatic diamines are preferable from the viewpoint of suppressing whitening of the polyimide film.

In the present invention, the "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or the like is part of the structure thereof. It may contain a substituent (for example, a halogen atom, a sulfonyl group, a carbonyl group, an oxygen atom, etc.). The "aliphatic diamine" represents a diamine in which an amino group is directly bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, and an aromatic hydrocarbon group or other substituent (a part of the structure thereof) is used. For example, it may contain a halogen atom, a sulfonyl group, a carbonyl group, an oxygen atom, etc.).

Examples of aromatic diamines include, for example, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, benzidine, o-trizine, m-trizine, bis (trifluoromethyl). Benzidine, Octafluorobenzidine, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl , 3,3'-difluoro-4,4'-diaminobiphenyl, 2,6-diaminonaphthalene, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4' −Diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 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-aminophenoxy) biphenyl, 4,4' -Bis (2,6-dimethyl-4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, bis (4- (4-aminophenoxy) phenyl) sulfone, bis (4- (2) −Methyl-4-aminophenoxy) phenyl) sulfone, bis (4- (2,6-dimethyl-4-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) ether, bis (4-) (2-Methyl-4-aminophenoxy) phenyl) ether, bis (4- (2,6-dimethyl-4-aminophenoxy) phenyl) ether, 1,4-bis (4-aminophenoxy) benzene, 1,4 -Bis (2-methyl-4-aminophenoxy) benzene, 1,4-bis (2,6-dimethyl-4-aminophenoxy) benzene, 1,3-bis (4-) Aminophenoxy) Benzene, 1,3-bis (2-methyl-4-aminophenoxy) benzene, 1,3-bis (2,6-dimethyl-4-aminophenoxy) benzene, 2,2-bis (4-amino) Benzene) propane, 2,2-bis (2-methyl-4-aminophenyl) propane, 2,2-bis (3-methyl-4-aminophenyl) propane, 2,2-bis (3-ethyl-4-aminophenyl) Aminophenyl) propane, 2,2-bis (3,5-dimethyl-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) hexafluoropropane, 2,2-bis (2,6-dimethyl-4-aminophenyl) hexafluoropropane, α, α'-bis (4-aminophenyl) -1,4-diisopropylbenzene, α, α'-bis (2-methyl-4-aminophenyl) -1,4-diisopropylbenzene, α, α'-bis (2) , 6-Dimethyl-4-aminophenyl) -1,4-diisopropylbenzene, α, α'-bis (3-aminophenyl) -1,4-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-diisopropylbenzene, α, α'-bis (3-aminophenyl) -1,3-diisopropylbenzene, 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, 1,4-phenylenediamine, 3,3'-diaminobenzophenone, 2,2-bis (3-aminophenyl) hexafluoropropane , 3-Aminobenzylamine, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 1,3-bis (3-aminophenoxy) benzene, 2,2-bis [4- (4- (4- (4- (4-) 4-) Aminophenoxy) phenyl] propane, bis [4- (3-aminophenoxy) phenyl] sulfone, 1,3-bis [2- (4-aminophenyl) -2-propyl] benzene, bis (2-aminophenyl) sulfide , Bis (4-aminophenyl) sulfide, 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 3,3'-diaminodiphenylmethane, 4 , 4'-ethylenedianiline, 4,4'-methylenebis (cyclohexylamine), 4,4'-methylenebis (2,6-diethylaniline), 4,4'-methylenebis (2-methylcyclohexylamine), etc. Be done.

Examples of the aliphatic diamine include ethylenediamine, hexamethylenediamine, polyethylene glycol bis (3-aminopropyl) ether, polypropylene glycol bis (3-aminopropyl) ether, 1,3-bis (aminomethyl) cyclohexane, and 1,4. -Bis (aminomethyl) cyclohexane, m-xylylene diamine, p-xylylene diamine, 1,4-bis (2-amino-isopropyl) benzene, 1,3-bis (2-amino-isopropyl) benzene, isophorone Diamine, norbornandiamine, siloxanediamine, 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 3,3'-diethyl-4,4'-diaminodicyclohexylmethane, 3 , 3', 5,5'-Tetramethyl-4,4'-diaminodicyclohexylmethane, 2,3-bis (aminomethyl) -bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) -Bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) -bicyclo [2.2.1] heptane, 2,2-bis (4,4'-diaminocyclohexyl) propane, 2,2 -Bis (4,4'-diaminomethylcyclohexyl) propane and the like can be mentioned.

Further, a diamine having a fluorene skeleton or a derivative thereof may be used for the purpose of improving the coloring peculiar to polyimide. For example, 9,9-bis [4- (4-aminophenoxy) phenyl] fluorene, 9,9-bis [4- (4-aminophenoxy) -3-phenylphenyl] fluorene, 9,9-bis [4- (3-Aminophenoxy) -3-phenylphenyl] fluorene, 9,9-bis [4- (2-aminophenoxy) -3-phenylphenyl] fluorene, 9,9-bis [4- (4-amino-3) -Methylphenoxy) -3-phenylphenyl] fluorene, 9,9-bis [4- (4-amino-2-methylphenoxy) -3-phenylphenyl] fluorene, 9,9-bis [4- (4-amino) -3-Ethylphenoxy) -3-Phenylphenyl] Fluolene and the like can be used.

Further, a diamine compound having a triazine mother nucleus represented by the following formula can be preferably used.

In the diamine compound of the above formula having a triazine mother nucleus, R ¹ represents a hydrogen atom or an alkyl group or an aryl group having 1 to 12 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms). R ² represents an alkyl group or an aryl group having 1 to 12 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms), and R ¹ and R ² may be different and are the same. You may.

Specific examples of the alkyl group or aryl group having 1 to 12 carbon atoms of R ¹ and R ² include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, phenyl, benzyl, naphthyl, methylphenyl and biphenyl. And so on.

The aminoanilino group connected to the two NH groups of triazine is 4-aminoanilino or 3-aminoanilino, which may be the same or different, but 4-aminoanilino is preferable.

Specific examples of the diamine compound having a triazine matrix and represented by the above formula include 2,4-bis (4-aminoanilino) -6-anilino-1,3,5-triazine and 2,4-bis ( 3-Aminoanilino) -6-anilino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-benzylamino-1,3,5-triazine, 2,4-bis (3-aminoanilino) ) -6-benzylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-naphthylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino)- 6-biphenylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-diphenylamino-1,3,5-triazine, 2,4-bis (3-aminoanilino) -6- Diphenylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-dibenzylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-di Naphthylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-N-methylanilino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-N -Methylnaphthylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-methylamino-1,3,5-triazine, 2,4-bis (3-aminoanilino) -6- Methylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-ethylamino-1,3,5-triazine, 2,4-bis (3-aminoanilino) -6-ethylamino -1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-dimethylamino-1,3,5-triazine, 2,4-bis (3-aminoanilino) -6-dimethylamino-1 , 3,5-Triazine, 2,4-bis (4-aminoanilino) -6-diethylamino-1,3,5-triazine, 2,4-bis (4-aminoanilino) -6-dibutylamino-1,3 5-triazine, 2,4-bis (4-aminoanilino) -6-amino-1,3,5-triazine, 2,4-bis (3-aminoanilino) -6-amino-1,3,5-triazine, etc. Can be mentioned.

Examples of the isocyanic acid ester which is a diamine derivative include diisocyanate obtained by reacting the above aromatic or aliphatic diamine with phosgene.

In addition, examples of other diamine derivatives include diaminodisilanes, and examples thereof include trimethylsilylated aromatic or aliphatic diamines obtained by reacting the above aromatic or aliphatic diamines with chlorotrimethylsilane.

As the diamine, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl is preferable from the viewpoint of excellent transparency and easy heat correction by heat shrinkage.

The above diamines and their derivatives may be arbitrarily mixed and used, but the amount of diamine in them is preferably 50 to 100 mol%, more preferably 80 to 100 mol%.

(1.1.3) Synthesis method and imidization of polyamic acid (1.1.3.1) Synthesis of polyamic acid Polyamic acid contains at least one of the tetracarboxylic acids and the diamine in a suitable solvent. It is obtained by polymerizing at least one of the above species.

The polyamic acid ester is formed by diesterifying the tetracarboxylic acid dianhydride with an alcohol such as methanol, ethanol, isopropanol, or n-propanol, and the obtained diester is prepared in an appropriate solvent. It can be obtained by reacting with a diamine compound. Further, the polyamic acid ester can also be obtained by esterifying the carboxylic acid group of the polyamic acid obtained as described above by reacting with the alcohol as described above.

The reaction between the tetracarboxylic dianhydride and the diamine compound can be carried out under conventionally known conditions. The order and method of adding the tetracarboxylic dianhydride and the diamine compound are not particularly limited. For example, polycarboxylic acid can be obtained by sequentially adding tetracarboxylic dianhydride and a diamine compound to a solvent and stirring at an appropriate temperature.

The amount of the diamine compound is usually 0.8 mol or more, preferably 1 mol or more, based on 1 mol of the tetracarboxylic dianhydride. On the other hand, it is usually 1.2 mol or less, preferably 1.1 mol or less. By setting the amount of the diamine compound in such a range, the yield of the obtained polyamic acid can be improved.

The concentrations of the tetracarboxylic dianhydride and the diamine compound in the solvent are appropriately set according to the reaction conditions and the viscosity of the polyamic acid solution. For example, the total mass of the tetracarboxylic dianhydride and the diamine compound is not particularly limited, but is usually 1% by mass or more, preferably 5% by mass or more, based on the total amount of the solution, while usually 70. It is mass% or less, preferably 30 mass% or less. By setting the amount of the reaction substrate in such a range, polyamic acid can be obtained at low cost and in good yield.

The reaction temperature is not particularly limited, but is usually 0 ° C. or higher, preferably 20 ° C. or higher, while it is usually 100 ° C. or lower, preferably 80 ° C. or lower. The reaction time is not particularly limited, but is usually 1 hour or more, preferably 2 hours or more, while it is usually 100 hours or less, preferably 24 hours or less. By carrying out the reaction under such conditions, polyamic acid can be obtained at low cost and in good yield.

Examples of the polymerization solvent used in this reaction include hydrocarbon solvents such as hexane, cyclohexane, heptane, benzene, toluene, xylene and mesityrene; carbon tetrachloride, dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene and dichlorobenzene. And halogenated hydrocarbon solvents such as fluorobenzene; ether solvents such as diethyl ether, tetrahydrofuran, 1,4-dioxane and methoxybenzene; ketone solvents such as acetone and methyl ethyl ketone; N, N-dimethylformamide, N, N- Amid solvents such as dimethylacetamide and N-methyl-2-pyrrolidone; aproton polar solvents such as dimethylsulfoxide and γ-butyrolactone; heterocyclic solvents such as pyridine, picolin, lutidine, quinoline and isoquinolin; Such as phenolic solvent, etc., but are not particularly limited. As the polymerization solvent, only one kind may be used, or two or more kinds of solvents may be mixed and used.

As the terminal group of the polyamic acid, an acid anhydride group and an amino group can be arbitrarily selected by excessively using either one of the tetracarboxylic dianhydride and the diamine compound at the time of the polymerization reaction.

When the terminal group is an acid anhydride terminal, the acid anhydride terminal may be left as it is without further treatment, or it may be hydrolyzed to obtain a dicarboxylic acid. Further, an alcohol having 4 or less carbon atoms may be used as an ester. Further, the end may be sealed with a monofunctional amine compound or isocyanate compound. The amine compound or isocyanate compound used here is not particularly limited as long as it is a monofunctional primary amine compound or isocyanate compound. For example, aniline, methylaniline, dimethylaniline, trimethylaniline, ethylaniline, diethylaniline, triethylaniline, aminophenol, methoxyaniline, aminobenzoic acid, biphenylamine, naphthylamine, cyclohexylamine, phenylisocyanate, xylylene isocyanate, cyclohexylisocyanate. , Methylphenyl isocyanate, trifluoromethylphenyl isocyanate and the like.

When the terminal group is an amine terminal, the terminal amino group can be sealed with a monofunctional acid anhydride to prevent the amino group from remaining at the terminal. The acid anhydride used here is not particularly limited as long as it is a monofunctional acid anhydride that becomes a dicarboxylic acid or a tricarboxylic acid when hydrolyzed. For example, maleic anhydride, methylmaleic anhydride, dimethylmaleic anhydride, succinic anhydride, norbornendicarboxylic acid anhydride, 4- (phenylethynyl) phthalic anhydride, 4-ethynylphthalic anhydride, phthalate. Acid anhydride, methylphthalic anhydride, dimethylphthalic anhydride, trimellitic anhydride, naphthalenedicarboxylic acid anhydride, 7-oxabicyclo [2.2.1] heptane-2,3-dicarboxylic acid anhydride, bicyclo [2.2.1] Heptane-2,3-dicarboxylic acid anhydride, bicyclo [2.2.2] Octa-5-ene-2,3-dicarboxylic acid anhydride, 4-oxatricyclo [5.2] .2.0 ^2,6 ] Undecane-3,5-dione, octahydro-1,3-dioxoisobenzofuran-5-carboxylic acid, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, dimethylcyclohexanedicarboxylic Acid anhydrides, 1,2,3,6-tetrahydrophthalic anhydrides, methyl-4-cyclohexene-1,2-dicarboxylic acid anhydrides and the like can be mentioned.

(1.1.3.2) Imidization Method Here, the polyimide is a method of heating a polyamic acid solution to imidize the polyamic acid (thermal imidization method), or a ring-closing catalyst (imidization) in the polyamic acid solution. It can be obtained by a method (chemical imidization method) of adding a catalyst) to imidize the polyamic acid.

《Film imidization treatment》
When a casting film is formed using polyamic acid, a polyimide film can be produced by subjecting the obtained film to an imidization treatment.

The polyamic acid casting film of the present invention is preferably heated stepwise. For example, polyimide can be preferably obtained by removing the solvent by heat treatment and imidizing (dehydrating ring closure).

The heat treatment conditions are not particularly limited, but it is preferable that the hair is dried in a temperature range of 50 to 150 ° C. and 150 to 250 ° C., and then further heat-treated at a temperature of 300 to 400 ° C., preferably 350 to 400 ° C. This is because imidization is promoted by heating at a temperature that matches the glass transition temperature of the polyamic acid and the polyimide according to the imidization reaction rate.

In the method for producing a polyimide film of the present invention, a solution of a polyamic acid containing no ring-closing catalyst is cast to form a film, heat-dried on a support, the film is peeled off from the support, and the temperature is further increased. (Thermal imidization method) can be used for imidization by dry heat treatment with. In the case of this method, the reaction rate of imidization can be improved by containing a dehydrating agent in the polyamic acid solution, but it is preferable not to contain the dehydrating agent. By not containing the dehydrating agent, it is possible to suppress a decrease in the durability of the polyimide film due to the residual dehydrating agent.

In the thermal imidization method, heat treatment can be performed by using, for example, an infrared heater. As the infrared heater, for example, a heater body formed so as to surround the filament with an inner tube is covered with an outer tube so that a cooling fluid can flow between the heater body and the outer tube. The filament is energized and heated to 700-1200 ° C. and emits infrared rays having a peak at a wavelength of around 3 μm. The inner tube and outer tube are made of quartz glass, crown glass borosilicate, or the like, and function as a filter that passes infrared rays having a wavelength of 3.5 μm or less and absorbs infrared rays having a wavelength exceeding 3.5 μm. In such an infrared heater, when infrared rays having a peak in the wavelength of about 3 μm are emitted from the filament, infrared rays having a wavelength of 3.5 μm or less are emitted to the film through the inner tube or the outer tube. By irradiating infrared rays of this wavelength, the mixed solvent in the film can be efficiently evaporated and the polyamic acid in the film can be imidized. The inner and outer tubes absorb infrared rays with a wavelength exceeding 3.5 μm, but are cooled by the cooling fluid flowing through the flow path, so the temperature can be maintained below the ignition point of the mixed solvent that evaporates from the film. It is possible.

Alternatively, a solution of a polyamic acid containing a ring-closing catalyst and a dehydrating agent is cast to form a film, and imidization is partially promoted on the support to form a film, and then the film is peeled off from the support. , Heat-drying / imidization and heat treatment (chemical imidization method) can also be used. Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylenediamine and heterocyclic amines such as isoquinolin, pyridine and picolin. Examples thereof include cyclic tertiary amines, but it is preferable to use at least one amine selected from heterocyclic tertiary amines. The content of the ring-closing catalyst with respect to the polyamic acid is preferably in the range of 0.5 to 8.0 in terms of the content of the ring-closing catalyst (mol) / the content of the polyamic acid (mol).

In the case of this method, by adding a dehydrating agent to the polyamic acid solution, imidization can proceed at a low temperature, so that deterioration of the durability of the polyimide film can be suppressed.

Further, a method of heating the polyamic acid solution to imidize the polyamic acid (thermal imidization method) or a method of adding a ring-closing catalyst (imidization catalyst) to the polyamic acid solution to imidize the polyamic acid (chemical imid). The chemical conversion method) is not limited to the above-mentioned casting film, and for example, a reaction kettle for polymerizing polyamic acid from acid anhydride and diamine may be continuously imidized in the reaction kettle.

In the thermal imidization method in a reaction vessel, the polyamic acid in the polymerization solvent is heat-treated in a temperature range of, for example, 80 to 300 ° C. for 0.1 to 200 hours to proceed with imidization. Further, the temperature range is preferably 150 to 200 ° C., and by setting the temperature to 150 ° C. or higher, imidization can be reliably advanced and completed, while by setting the temperature to 200 ° C. or lower, the solvent or the like can be used. It is possible to prevent an increase in resin concentration due to oxidation of unreacted raw materials and volatilization of solvent.

Further, in the thermal imidization method, an azeotropic solvent can be added to the above-mentioned polymerization solvent in order to efficiently remove the water generated by the imidization reaction. As the co-boiling solvent, for example, aromatic hydrocarbons such as toluene, xylene and solvent naphtha, and alicyclic hydrocarbons such as cyclohexane, methylcyclohexane and dimethylcyclohexane can be used. When an azeotropic solvent is used, the amount added is about 1 to 30% by mass, preferably 5 to 20% by mass, based on the total amount of the organic solvent.

On the other hand, in the chemical imidization method, a known ring closure catalyst is added to the polyamic acid in the polymerization solvent to promote imidization. Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylenediamine and heterocyclic tertiary amines such as isoquinoline, pyridine and picolin, and other examples thereof include substitution or non-substituted or non-substituted amines. Substituted nitrogen-containing heterocyclic compounds, N-oxide compounds of nitrogen-containing heterocyclic compounds, substituted or unsubstituted amino acid compounds, aromatic hydrocarbon compounds having a hydroxy group, or aromatic heterocyclic compounds are mentioned in particular 1,2. Lower alkyl imidazoles such as -dimethyl imidazole, N-methyl imidazole, N-benzyl-2-methyl imidazole, 2-methyl imidazole, 2-ethyl-4-methyl imidazole, 5-methylbenz imidazole, N-benzyl-2-methyl Imidazole derivatives such as imidazole, substituted pyridines such as isoquinolin, 3,5-dimethylpyridine, 3,4-dimethylpyridine, 2,5-dimethylpyridine, 2,4-dimethylpyridine, 4-n-propylpyridine, p-toluene. A sulfonic acid or the like can be preferably used. The amount of the ring-closing catalyst added is preferably 0.01 to 2 times equivalent, particularly about 0.02 to 1 times equivalent with respect to the amic acid unit of the polyamic acid. By using a ring-closing catalyst, the physical characteristics of the obtained polyimide, particularly elongation and breaking resistance, may be improved.

Further, in the above thermal imidization method or chemical imidization method, a dehydrating agent may be added to the polyamic acid solution, and examples of such a dehydrating agent include an aliphatic acid anhydride such as acetic anhydride and phthal. Examples thereof include aromatic acid anhydrides such as acid anhydrides, which can be used alone or in combination. Further, it is preferable to use a dehydrating agent because the reaction can proceed at a low temperature. Although it is possible to imidize the polyamic acid only by adding a dehydrating agent to the polyamic acid solution, it is preferable to imidize the polyamic acid by heating or adding a ring-closing catalyst as described above because the reaction rate is slow. ..

The polyimide solution imidized in the reaction vessel in this way is advantageous because it is difficult to reduce the molecular weight due to hydrolysis over time.

Further, since the imidization reaction has proceeded in advance, for example, in the case of polyimide having an imidization rate of 100%, imidization on a casting film or a film becomes unnecessary, and the drying temperature can be lowered.

Alternatively, the ring-closed polyimide may be reprecipitated and purified using a poor solvent or the like to form a solid, then dissolved in a solvent and cast-dried to form a film.

According to this method, it is possible to use different types of the polymerization solvent and the casting solvent, and by selecting the optimum solvent for each, it is possible to further bring out the performance of the polyimide film.

For example, in order to increase the molecular weight of polyamic acid, polymerization and ring closure with dimethyl acedamide, solidification with methanol, drying, solution with dichloromethane, casting and drying are performed to increase the molecular weight. It can be polymerized and dried at low temperature.

When dichloromethane is used as the solvent, it can be used in combination with other solvents. Auxiliary solvents such as tetrahydrofuran (THF), dioxolane, cyclohexanone, cyclopentanone, γ-butyrolactone, ethanol, methanol, butanol, and iropropanol can also be used as appropriate.

Further, the polyamic acid may be imidized at the time of casting, and the imidization ratio at the time of casting is preferably 10 to 100%. Here, as the imidization rate, the remaining amount of the carboxy group can be measured from the 1H-NMR spectrum to obtain the imidization rate.

In the method for producing a polyimide film of the present invention, any of the above ring-closing methods may be adopted, but a method of casting a thermally imidized polyimide solution in a reaction vessel onto a support is performed in the polyimide solution. It can be said that this is a more preferable method from the viewpoint that there is little residue and the film forming temperature can be lowered.

(1.1.4) Other Polyimide In addition to the above-mentioned polyimide, a polyimide containing atoms such as phosphorus, silicon, and sulfur can also be used.

For example, as the polyimide containing phosphorus, the polyimides described in paragraphs [0010]-[0021] of JP2011-74209A and paragraphs [0011]-[0025] of JP2011-074177 are used. Can be done.

As the polyimide containing silicon, the polyimide obtained by imidizing the polyimide precursor described in paragraphs [0030]-[0045] of JP2013-028996A can be used.

Examples of the polyimide containing sulfur include paragraphs [0009]-[0025] of JP2010-189322A, paragraphs [0012]-[0025] of JP2008-274234, and paragraphs of JP2008-274229. The polyimide obtained by imidizing the polyimide precursor described in [0012]-[0023] can be used.

In addition, the alicyclic polyimide described in paragraphs [0008]-[0012] of JP2009-256590 and paragraphs [0008]-[0012] of JP2009-256589 are preferably used. it can.

(1.2) Polyamide-imide The polyamide-imide used in the present invention is a polyamide-imide containing tricarboxylic acid or tetracarboxylic acid, dicarboxylic acid as an acid component and diamine as an amine component as a constituent unit.

The polyamide-imide used has an acid component as an acid component.
a) Tricarboxylic acid; diphenyl ether-3,3', 4'-tricarboxylic acid, diphenylsulfone-3,3', 4'-tricarboxylic acid, benzophenone-3,3', 4'-tricarboxylic acid, naphthalene-1,2 , 4-Tricarboxylic acid, monoanhydrides such as tricarboxylic acids such as butane-1,2,4-tricarboxylic acid, singles such as esterified products, or a mixture of two or more.

b) Tetracarboxylic acid; diphenylsulfone-3,3', 4,4'-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid, naphthalene-1,2,4,5-tetracarboxylic acid , Naphthalene-1,4,5,8-tetracarboxylic acid, butane-1,2,3,4-tetracarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, dianhydride , Alone, such as an esterified product, or a mixture of two or more.

c) Dicarboxylic acid; adipic acid, azelaic acid, sebacic acid, dicarboxylic acid of cyclohexane-4,4'-dicarboxylic acid, and these monoanhydrides and esters.

As an amine component,
d) Amin component 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2 , 2'-diethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-diethoxy-4,4'-diaminobiphenyl, p-phenylenediamine, m −Phenylenediamine, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 3,4′-diaminobiphenyl, 3,3′ −Diaminobiphenyl, 3,3′-diaminobenzanilide, 4,4′-diaminobenzanilide, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 2,6- Tolylene diamine, 2,4-tolylene diamine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 3, 3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, p-xylene diamine, m-xylene diamine, 2,2'-bis (4-aminophenyl) propane, 1,3-bis (3-aminophenoxy) benzene , 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- ( 4-Aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] propane, 4,4'-bis (4-aminophenoxy) biphenyl , 4,4'-bis (3-aminophenoxy) biphenyl, tetramethylenediamine, hexamethylenediamine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, cyclohexane-1,4-diamine, diaminosiloxane, or corresponding Diisocyanate alone or a mixture of two or more.

In particular, as acid components, trimellitic anhydride (TMA), 3,3,4', 4'-benzophenonetetracarboxylic dianhydride (BTDA), and 3,3,4', 4'-biphenyltetracarboxylic acid. A polyamide imide resin polymerized with a raw material containing dianhydride (BPDA) and 1,5-naphthalenedi isocyanate (NDI) as an isocyanate component is preferable.

The molar ratio of the imide bond to the amide bond of the polyamide-imide is preferably 99/1 to 60/40 molar ratio, more preferably 99/1 to 75/25, and even more preferably 90/10 to 80/20. is there. When the molar ratio of the imide bond to the amide bond is 60/40 or more, the heat resistance, the moisture resistance reliability, and the heat resistance reliability are improved. Further, when it is 99/1 or less, the elastic modulus tends to be low, and the folding resistance characteristics and the bending characteristics tend to be improved.

(1.2.1) Polyamide-imide having a structure represented by the formula (2) as an essential component One preferred embodiment has a structure represented by the formula (2) as an essential component, and further, the structure represented by the formula (2) is an essential component. , A polyamide-imide resin containing at least one structure selected from the group represented by the formula (4) and the formula (5) as a repeating unit in the molecular chain.

（Ｘは、酸素原子、ＣＯ、ＳＯ_２、又は、結合を表し、ｎは０又は１を表す。）

(X represents an oxygen atom, CO, SO ₂ or bond, and n represents 0 or 1.)

(Y represents an oxygen atom, CO, or OOC-R-COO, n represents 0 or 1, and R represents a divalent organic group.)

Here, in the formula (3), X is preferably SO ₂ or a bond (biphenyl bond) or n = 0, and more preferably a bond (biphenyl bond) or n = 0. In the formula (4), Y is preferably a benzophenone type (CO) or a bound type (biphenyl bond).

In one preferred embodiment, formula (2) is a repeating unit from trimellitic anhydride and 1,5-naphthalenediocyanate, formula (3) is a repeating unit from terephthalic acid and 1,5-naphthalenediocyanate, formula (4). Is a repeating unit from biphenyltetracarboxylic dianhydride or benzophenonetetracarboxylic dianhydride and 1,5-naphthalenediocyanate, and the content ratio is formula (2) / {formula (3) + formula (4). + Formula (5)} = 1/99 to 40/60 molar ratio, and formula (3) / formula (4) = 10/90 to 90/10 molar ratio is preferable.

The higher the imidization rate, the more preferably the upper limit is 100%. The above-mentioned polyamide-imide resin can be synthesized by a usual method. For example, the isocyanate method, the amine method (acid chloride method, low temperature solution polymerization method, room temperature solution polymerization method, etc.), etc., but the polyamide-imide resin used in the present invention is preferably soluble in an organic solvent, and as described above, peel. For reasons such as ensuring the reliability of strength (adhesive strength), production by the isocyanate method is preferable. Also, industrially, it is preferable because the solution at the time of polymerization can be applied as it is.

(1.2.2) Polyamideimide having a structure represented by the formula (6) or (7) As a preferable polyamide-imide resin, a compound containing the following formula (6) as a constituent unit can be preferably used. The compound having the structure represented by the formula (6) will be described below.

(In the formula, R ₁ is an aryl group or a cycloalkane group, and may contain nitrogen, oxygen, sulfur, and halogen.)
(Diamine component of polyamide-imide resin)
The diamine components include p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, and 3,3'-diaminodiphenyl sulfone. , 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 3,3'-diaminobenzanilide, 4,4'-diaminobenzanilide, 4,4'-diaminobenzophenylone, 3,3'- Diaminobenzophenylone, 3,4'-diaminobenzophenylone, 2,6-tolylene diamine, 2,4-tolylene diamine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4 , 4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, P-xylene diamine, m-xylene diamine, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, 2,7-naphthalenediamine, 2,2'-bis (4-aminophenyl) propane, 1,3-bis (3-aminophenoxy) benzene, 1, 3-Bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (4-amino) Phenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] propane, 4,4'-bis (4-aminophenoxy) biphenyl, 4, 4'-bis (3-aminophenoxy) biphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4-methyl-1,3-phenylenediamine, 3,3'-diethyl-4,4'- Diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-diethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3, 3'-diethoxy-4,4'-diaminobiphenyl, trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-diaminocyclohexane (trans / cis mixture), 1,3-diaminocyclohexane , Dicyclohexylmethane-4,4'-diamine (trans-form, cis-form, trans / cis mixture) , Isophoronediamine, 1,4-cyclohexanebis (methylamine), 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) bicyclo [2.2.1] ] Heptan, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantan, 4,4'-methylenebis (2-methylcyclohexylamine), 4,4'- Methylenebis (2-ethylcyclohexylamine), 4,4'-methylenebis (2,6-dimethylcyclohexylamine), 4,4'-methylenebis (2,6-diethylcyclohexylamine), 2,2-bis (4) -Aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylene Diamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, etc. alone, or a mixture of two or more, or the corresponding diisocyanate, etc. alone, or A mixture of two or more can be used as the diamine component.

Preferably, 3,3'-dimethyl-4,4'-diaminobiphenyl, dicyclohexylmethane-4,4'-diamine (trans-form, cis-form, trans / cis mixture), 4,4'-diaminodiphenyl ether, p. -Alone or a mixture of two or more kinds of phenylenediamine, 4-methyl-1,3-phenylenediamine, etc., or a single or a mixture of two or more kinds of diisocyanates corresponding thereto shall be used as a diamine component. Can be done.

More preferably, 3,3'-dimethyl-4,4'-diaminobiphenyl, dicyclohexylmethane-4,4'-diamine (trans-form, cis-form, trans / cis mixture), 4,4'-diaminodiphenyl ether, A single or a mixture of two or more kinds of 4-methyl-1,3-phenylenediamine or the like, or a single or a mixture of two or more kinds of diisocyanates corresponding thereto can be used as a diamine component.

More preferably, 3,3'-dimethyl-4,4'-diaminobiphenyl, dicyclohexylmethane-4,4'-diamine (trans, cis, trans / cis mixture), 4-methyl-1,3- A single or a mixture of two or more kinds such as phenylenediamine, or a single one such as diisocyanate corresponding thereto or a mixture of two or more kinds can be used as a diamine component.

(Preferable combination of acid component and diamine component)
Among the above acid components and diamine components, the following components are based on the heat resistance, solvent resistance, and durability in the film forming process, and the heat resistance, surface smoothness, and transparency of the produced polyamide-imide film. Is preferably used.

As the acid component, cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride can be used. A polyamide-imide resin containing cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride as an acid component can be used.

As the diamine component, at least one or two compounds selected from the group consisting of 3,3'-dimethyl-4,4'-diaminobiphenyl and 4-methyl-1,3-phenylenediamine, or 3,3 At least one or two compounds selected from the group consisting of ′ -dimethyl-4,4 ′-diisocyanate biphenyl (o-trizine diisocyanate) and 4-methyl-1,3-phenylenediocyanate (toluene diisocyanate). Can be used.

Further, as a preferable polyamide-imide resin, a compound containing a structure represented by the following formula (7) as a constituent unit can be used.

(In the formula, R ₂ and R ₃ are hydrogen and an alkyl group or an aryl group having 1 to 3 carbon atoms, respectively, and may contain nitrogen, oxygen, sulfur and halogen, respectively.)
When the total acid component is 100 mol%, the illustrated acid component is preferably contained in an amount of 50 mol% or more and 100% or less, and more preferably 70 mol% or more and 100% or less. When the total diamine component is 100 mol%, the illustrated diamine component is preferably contained in an amount of 50 mol% or more and 100% or less, and more preferably 70 mol% or more and 100% or less. Within these ranges, the heat resistance and durability in the film forming process are good, and the heat resistance, surface smoothness, and transparency of the obtained polyamide-imide film are particularly good.

The molecular weight of the polyamide-imide resin used is 0.3 to 2.5 cm ³ / g in logarithmic viscosity at 30 ° C. in N-methyl-2-pyrrolidone (polymer concentration 0.5 g / cm ³ ). Is preferable, and more preferably, it has a molecular weight corresponding to 0.5 to 2.0 cm ³ / g. If the logarithmic viscosity is 0.3 cm ³ / g or more, the mechanical properties will be sufficient when a molded product such as a film is formed. Further, when it is 2.0 cm ³ / g or less, the solution viscosity does not become too high, and the molding process becomes easy.

(1.3) Polyetherimide The polyetherimide used in the present invention is a thermoplastic resin containing an aromatic nucleus bond and an imide bond in its structural unit, and is not particularly limited. It is preferably a polyetherimide having a repeating unit having a structure represented by the formula (8) or the following formula (9).

Polyetherimides having a repeating unit having a structure represented by the above formula (8) are trade names "Ultem 1000" (glass transition temperature: 216 ° C.) and "Ultem 1010" (glass transition temperature: 216) manufactured by General Electric Co., Ltd. ° C.), Examples of the polyetherimide having a repeating unit of the structure represented by the above formula (9) include "Ultem CRS5001" (glass transition temperature Tg226 ° C.), and as another specific example, manufactured by Mitsui Chemicals Co., Ltd. The trade name "Aurum PL500AM" (glass transition temperature 258 ° C.) and the like can be mentioned.

The method for producing the polyetherimide is not particularly limited, but usually, the amorphous polyetherimide having the structure represented by the above formula (8) is 4,4'-[isopropyridenebis (p.). -Phenyleneoxy)] As a polycondensate of diphthalic acid dianhydride and m-phenylenediamine, and the polyetherimide having the structure represented by the above structural formula (9) is 4,4'-[isopropyridenebis. (P-Phenyleneoxy)] It is synthesized by a method known as a polycondensate of diphthalic acid dianhydride and p-phenylenediamine.

Further, the polyetherimide may contain other copolymerizable monomer units such as an amide group, an ester group and a sulfonyl group within a range not exceeding the gist of the present invention. The polyetherimide may be used alone or in combination of two or more.

(1.4) Polyesterimide The resin having an imide structure used in the present invention preferably contains the polyesterimide structure represented by the formula (10) in its constituent unit.

(In the formula (10), R ₁ represents a divalent group having a specific structure. R ₂ represents a divalent chain aliphatic group, a divalent cyclic aliphatic group or a divalent aromatic group. Represent.)
In formula (10), R ₁ represents a divalent group having a structure represented by formula (11), formula (12) or formula (13), respectively.

(A divalent group having a structure represented by the formula (11))

In the formula (11), R represents a divalent chain aliphatic group, a cyclic aliphatic group or an aromatic group, respectively, and a plurality of Rs may be the same as or different from each other. .. These chain aliphatic groups, cyclic aliphatic groups or aromatic groups may be used alone or in combination of two or more.

m is a positive integer of 1 or more, preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. The upper limit of m is not particularly limited, but is preferably 25 or less, more preferably 20 or less, and further preferably 10 or less. If it exceeds 25, the heat resistance tends to decrease.

The chain aliphatic group, cyclic aliphatic group or aromatic group is "chain aliphatic compound having a divalent hydroxy group", "cyclic aliphatic compound having a divalent hydroxy group" or "2. It is desirable that the residue is derived from a diol such as "an aromatic compound having a valent hydroxy group". Further, it may be a residue derived from "polycarbonate diol" which can be polymerized from the diol and carbonic acid esters, phosgene and the like.

As the "chain-type aliphatic compound having a divalent hydroxy group", a branched or linear diol having two hydroxy groups can be used. For example, alkylene diol, polyoxyalkylene diol, polyester diol, polycaprolactone diol and the like can be mentioned. The following are branched or linear diols having two hydroxy groups that can be used as "chain aliphatic compounds having a divalent hydroxy group".

Examples of the alkylene diol include ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and the like. 1,6-Hexanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanediol, 1,4- Cyclohexanedimethanol and the like can be mentioned.

Examples of the polyoxyalkylene diol include dimethylol propionic acid (2,2-bis (hydroxymethyl) propionic acid), dimethylolbutanoic acid (2,2-bis (hydroxymethyl) butanoic acid), polyethylene glycol and polypropylene glycol. Examples thereof include polytetramethylene glycol, polyoxytetramethylene glycol, and random copolymers of tetramethylene glycol and neopentyl glycol. Preferably, polyoxytetramethylene glycol is preferable.

Examples of the polyester diol include a polyester diol obtained by reacting a polyhydric alcohol exemplified below with a polybasic acid.

As the "multihydric alcohol component" used for the polyester diol, any kind of polyhydric alcohol can be used. For example, ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5. -Pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, cyclohexanemethanol, Neopentyl hydroxypiparic acid ester, ethylene oxide adduct and propylene oxide adduct of bisphenol A, ethylene oxide adduct and propylene oxide adduct of water-added bisphenol A, 1,9-nonanediol, 2-methyloctanediol, 1 , 10-Dodecanediol, 2-butyl-2-ethyl-1,3-propanediol, tricyclodecanemethanol, polyethylene glycol, polypropylene glycol, polyether polyols such as polytetramethylene glycol and the like can be used.

Any various polybasic acids can be used as the "polybasic acid component" used in the polyester diol. For example, terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalic acid, 2,6-naphthalic acid, 4,4'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid. Acid, adipic acid, sebacic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dimer acid, etc. Fat group and alicyclic dibasic acids can be used.

Specific examples of commercially available polyester diols include ODX-688 (aliphatic polyester diol manufactured by DIC Co., Ltd .: adipic acid / neopentyl glycol / 1,6-hexanediol, number average molecular weight of about 2000), Vylon (registered). Trademark) 220 (polyester diol manufactured by Toyobo Co., Ltd., number average molecular weight of about 2000) and the like can be mentioned.

Examples of the polycaprolactone diol include polycaprolactone diol obtained by ring-opening addition reaction of lactones such as γ-butyllactone, ε-caprolactone and δ-valerolactone.

The above-mentioned "chain-type aliphatic compound having a divalent hydroxy group" can be used alone or in combination of two or more.

Examples of the "cyclic aliphatic compound having a divalent hydroxy group" or the "aromatic compound having a divalent hydroxy group" include "a compound having two hydroxy groups on an aromatic ring or a cyclohexane ring" and "two. "Compounds in which phenol or alicyclic alcohol is bonded with a divalent functional group", "Compounds having one hydroxy group in both nuclei of biphenyl structure", "Compounds having two hydroxy groups in naphthalene skeleton", etc. Is used.

As "compounds having two hydroxy groups on aromatic rings and cyclohexane rings", hydroquinone, 2-methylhydroquinone, resorcinol, catechol, 2-phenylhydroquinone, cyclohexanedimethanol, tricyclodecanemethanol, 1,4-dihydroxycyclohexane, 1 , 3-Dihydroxycyclohexane, 1,2-dihydroxycyclohexane, 1,3-adamantandiol, dicyclopentadiene dihydrate, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxy Carboxy group-containing diols such as benzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, and 3,5-dihydroxybenzoic acid can be used.

Examples of "two phenols" or "compounds in which an alicyclic alcohol is bonded with a divalent functional group" include 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4, 4'-(9-fluorenylidene) diphenol, 4,4'-dihydroxydicyclohexyl ether, 4,4'-dihydroxydicyclohexylsulfone, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F and the like can be used.

Further, as an example of "a compound having one hydroxy group in both nuclei of the biphenyl structure", 4,4'-biphenol, 3,4'-biphenol, 2,2'-biphenol, 3,3', 5 , 5'-Tetramethyl-4,4'-biphenol and the like can be used.

Examples of the "compound having two hydroxy groups in the naphthalene skeleton" include 2,6-naphthalenediol, 1,4-naphthalenediol, 1,5-naphthalenediol, 1,8-naphthalenediol and the like.

The number average molecular weight of the diol is preferably 100 or more and 30,000 or less, more preferably 150 or more and 20,000 or less, and further preferably 200 or more and 10,000 or less. If the number average molecular weight is less than 100, low hygroscopicity and flexibility cannot be sufficiently exhibited, and if it is larger than 30,000, depending on the composition and structure of the "diol" and the composition and structure of the diamine component (or isocyanate component) described later. Is phase-separated and may not be able to sufficiently exhibit its mechanical properties and colorless transparency.

The polycarbonate diol may be a polycarbonate diol (copolymerized polycarbonate diol) having a plurality of types of alkylene groups described above in its skeleton. For example, a combination of 2-methyl-1,8-octanediol and 1,9-nonanediol, a combination of 3-methyl-1,5-pentanediol and 1,6-hexanediol, a combination of 1,5-pentanediol and 1 , Copolymerized polycarbonate diol that can be synthesized by a combination of 6-hexanediol and the like can be mentioned. Preferably, it is a copolymerized polycarbonate diol that can be synthesized from a combination of 2-methyl-1,8-octanediol and 1,9-nonanediol. Two or more of these polycarbonate diols can be used in combination.

Examples of commercially available polycarbonate diols that can be used include Kuraray polyol C series manufactured by Kuraray Co., Ltd. and Duranol series manufactured by Asahi Kasei Chemicals Co., Ltd. For example, Clare polyol C-1015N, Clare polyol C-1065N (carbonate diol manufactured by Clare Co., Ltd .: 2-methyl-1,8-octanediol / 1,9-nonanediol, number average molecular weight of about 1000), Clare polyol C -2015N, Clare Polyol C2065N (Carlate Diol Co., Ltd .: 2-Methyl-1,8-octanediol / 1,9-nonanediol, number average molecular weight about 2000), Clare polyol C-1050, Clare polyol C- 1090 (Carlate carbonate diol manufactured by Clare Co., Ltd .: 3-methyl-1,5-pentanediol / 1,6-hexanediol, number average molecular weight of about 1000), Clare polyol C-2050, Clare polyol C-2090 (Co., Ltd.) Kuraray carbonate diol: 3-methyl-1,5-pentanediol / 1,6-hexanediol, number average molecular weight: about 2000), DURANOL-T5650E (Polycarbonate diol manufactured by Asahi Kasei Chemicals Co., Ltd .: 1,5-pentanediol / 1,6-Hexanediol, number average molecular weight about 500), DURANOL-T5651 (Polycarbonate diol manufactured by Asahi Kasei Chemicals Co., Ltd .: 1,5-pentanediol / 1,6-hexanediol, number average molecular weight about 1000), DURANOL- Examples thereof include T5652 (polycarbonate diol manufactured by Asahi Kasei Chemicals Co., Ltd .: 1,5-pentanediol / 1,6-hexanediol, number average molecular weight of about 2000). Preferably, Kuraray polyol C-1015N and the like can be mentioned.

Examples of the method for producing the polycarbonate diol include transesterification of the raw material diol and carbonic acid esters, and a dehydrochlorination reaction between the raw material diol and phosgene. Examples of the carbonic acid ester as a raw material include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; diaryl carbonates such as diphenyl carbonate; and alkylene carbonates such as ethylene carbonate and propylene carbonate.

(A divalent group having a structure represented by the formula (12))
A divalent group having a structure represented by the formula (12) will be described.

In formula (12), R ₃ is directly linked, alkylene group (-C _n H _2n- ), perfluoroalkylene group (-C _n F _2n- ), ether bond (-O-), ester bond (-COO-). ), Carbonyl group (-CO-), sulfonyl group (-S (= O) _2- ), sulfinyl group (-SO-), sulfenyl group (-S-), carbonate group (-OCOO-), or fluorenylidene. Represents a group. n is a positive integer greater than or equal to 1. The upper limit of n is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and further preferably 3 or less. X _{1 to} X ₈ may be the same or different, respectively, and represent hydrogen, halogen or alkyl groups, respectively.

Specific examples of the divalent group having the structure represented by the formula (12) are not particularly limited, but a diphenyl ether skeleton, a diphenyl sulfone skeleton, a 9-fluorenylidene diphenol skeleton, a bisphenol A skeleton, and a bisphenol F skeleton. Examples thereof include an ethylene oxide adduct skeleton of bisphenol A, a propylene oxide adduct skeleton of bisphenol A, a biphenyl skeleton, and a naphthalene skeleton.

The skeleton is preferably a residue derived from a compound having one hydroxy group each on both benzene rings of the formula (12). Examples of the raw material of the divalent group having the structure represented by the formula (12) include 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-(9-fluorenylidene) diphenol, and the like. Bisphenol A, bisphenol F, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, 4,4'-biphenol, 3,4'-biphenol, 2,2'-biphenol, 3,3', 5, 5'-tetramethyl-4,4'-biphenol, 2,6-naphthalene diol, 1,4-naphthalene diol, 1,5-naphthalene diol, 1,8-naphthalene diol and the like can be used.

Preferably, an ethylene oxide adduct of 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-(9-fluorenylidene) diphenol or bisphenol A is preferable. More preferably, it is an ethylene oxide adduct of 4,4'-dihydroxydiphenyl ether or bisphenol A.

These compounds can be used alone or in combination of two or more. By using these materials, it is possible for R ₁ position of formula (10), introducing the diphenyl ether skeleton, or the like.

(A divalent group having a structure represented by the formula (13))

In formula (13), R ₄ is directly linked, alkylene group (-C _n H _2n- ), perfluoroalkylene group (-C _n F _2n- ), ether bond (-O-), ester bond (-COO-). ), Carbonyl group (-CO-), sulfonyl group (-S (= O) _2- ), sulfinyl group (-SO-), sulfenyl group (-S-), carbonate group (-OCOO-), or fluorenylidene. Represents a group. n is a positive integer greater than or equal to 1. The upper limit of n is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and further preferably 3 or less. X 1 _{'~X 8'} can be respectively the same or different, each represents hydrogen, a halogen or an alkyl group.

Specific examples of the divalent group having the structure represented by the formula (13) are not particularly limited, but are a dicyclohexyl ether skeleton, a dicyclohexylsulfone skeleton, a hydrogenated bisphenol A skeleton, a hydrogenated bisphenol F skeleton, and a hydrogenated bisphenol A skeleton. Examples thereof include the ethylene oxide adduct skeleton of hydrogenated bisphenol A and the propylene oxide adduct skeleton of hydrogenated bisphenol A.

The skeleton is preferably a residue derived from a compound having one hydroxy group each on both cyclohexane rings of formula (13). Examples of the raw material of the divalent group having the structure represented by the formula (13) include 4,4′-dihydroxydicyclohexyl ether, 4,4′-dihydroxydicyclohexylsulfone, hydrogenated bisphenol A, hydrogenated bisphenol F, and hydrogenated. An ethylene oxide adduct of bisphenol A or a propylene oxide adduct of hydrogenated bisphenol A can be used.

Preferably, 4,4'-dihydroxydicyclohexyl ether or 4,4'-dihydroxydicyclohexylsulfone is preferable.

These compounds can be used alone or in combination of two or more. By using these materials, it is possible for R ₁ position of formula (10), introducing said dicyclohexyl ether skeleton or the like.

For example, the structure of the formula (10) is obtained by reacting a halide of a cyclohexanetricarboxylic acid anhydride with diols to obtain an ester group-containing tetracarboxylic acid dianhydride, and then the ester group-containing tetracarboxylic acid. It can be obtained by subjecting a dianoxide to a condensation reaction (polymethylation) with a diamine, diisocyanate, or the like.

(A divalent group having a structure represented by the formula (14))
The polyesterimide resin may further contain a structure represented by the formula (14) in the structural unit.

Described _{R 2} 'of _{R 2} of the formula (10) (14). R ₂ and R ₂ ′ are not particularly limited as long as they are independently divalent chain aliphatic groups, divalent cyclic aliphatic groups or divalent aromatic groups. These "divalent chain aliphatic groups", "divalent cyclic aliphatic groups", and "divalent aromatic groups" can be used alone or in combination of two or more.

Preferably, R ₂ is a divalent group having a structure represented by the following formula (15), and R ₂ ′ is a divalent group having a structure represented by the following formula (16).

(A divalent group having a structure represented by the formula (15))
R ₂ in the formula (10) is preferably a divalent group having a structure represented by the formula (15) in view of the balance between heat resistance, flexibility, and low hygroscopicity.

In formula (15), R ₅ is directly linked, alkylene group (-C _n H _2n- ), perfluoroalkylene group (-C _n F _2n- ), ether bond (-O-), ester bond (-COO-). ), A carbonyl group (-CO-), a sulfonyl group (-S (= O) _2- ), a sulfinyl group (-SO-) or a sulfenyl group (-S-). n is preferably a positive integer of 1 or more and 10 or less, more preferably 1 or more and 5 or less, and further preferably 1 or more and 3 or less. X _{9 to} X ₁₆ may be the same or different and represent hydrogen, halogen or alkyl groups, respectively.

(A divalent group having a structure represented by the formula (16))
The R ₂ ′ in the formula (14) is preferably a divalent group having a structure represented by the formula (16) in view of the balance between heat resistance, flexibility, low hygroscopicity and the like.

Wherein (16), _{R 5} 'are directly connected, an alkylene group _{(-C n H 2n} -), perfluoroalkylene group _{(-C n F 2n} -), ether bond (-O-), an ester bond (-COO Represents a −), a carbonyl group (−CO−), a sulfonyl group (−S (= O) ₂₋ ), a sulfinyl group (−SO−) or a sulfenyl group (−S−). n is preferably a positive integer of 1 or more and 10 or less, more preferably 1 or more and 5 or less, and further preferably 1 or more and 3 or less. X ₉ ′ to X ₁₆ ′ may be the same or different and represent hydrogen, halogen or alkyl groups, respectively.

In the formula (10) and (14), "a divalent chain aliphatic group", "divalent cyclic aliphatic group" or "divalent aromatic group" of R ₂ position of formula (10) and to introduce the R _{2 'position} of formula (14), it is preferable to use the corresponding diamine or diisocyanate component. That is, "aromatic diamine or corresponding aromatic diamine", "cyclic aliphatic diamine or corresponding cyclic aliphatic diamine", "chain aliphatic diamine or corresponding chain aliphatic diamine" are appropriately used. By selecting it, a polyesterimide resin having excellent heat resistance, flexibility, and low moisture absorption can be obtained.

The diamine component of R _{2 of the} formula (10) and the diamine component of R ₂ ′ of the formula (14) or the corresponding diisocyanate component may be the same or different. If it is based on the preferred manufacturing method described later, it is preferable that they are the same.

The diamine component having R ₂ and R ₂ ′ as the basic skeleton or the corresponding diisocyanate component will be described.

Specific examples of the "aromatic diamine or the corresponding aromatic diisocyanate" include 2,2'-bis (trifluoromethyl) benzidine, p-phenylenediamine, m-phenylenediamine, 2 as a diamine compound. , 4-Diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4,4'-diaminodiphenylmethane, 4,4'-methylenebis (2-methylaniline), 4, 4'-methylenebis (2-ethylaniline), 4,4'-methylenebis (2,6-dimethylaniline), 4,4'-methylenebis (2,6-diethylaniline), 4,4'-diaminodiphenyl ether, 3 , 4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 2,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 4,4′-diaminobenzophenone, 3 , 3'-diaminobenzophenone, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminobenz Anilide, P-xylene diamine, m-xylene diamine, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, 2,7-naphthalenediamine, benzidine, 3,3'-dihydroxybenzidine, 3,3'-Dimethoxybenzidine, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'- Diaminobiphenyl, 2,2'-diethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-diethoxy-4,4'-diaminobiphenyl, o- Trizine, m-trizine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4'- Bis (4-aminophenoxy) biphenyl, bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4-aminophenoxy) phenyl) ) Phenyl) propane, 2,2-bis (4- (4-aminophenoxy) fe Nyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, diaminoterphenyl and the like can be mentioned. Further, these may be used in combination of two or more.

Further, examples of the "cyclic aliphatic diamine or the corresponding cyclic aliphatic diamine" as a diamine compound include trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, and 1,4-diamino. Cyclohexane (trans / cis mixture), 1,3-diaminocyclohexane, 4,4'-methylenebis (cyclohexylamine) (totans, cis, trans / cis mixture), isophorone diamine, 1,4-cyclohexanebis (methylamine) ), 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] Decane, 1,3-diaminoadamantan, 4,4'-methylenebis (2-methylcyclohexylamine), 4,4'-methylenebis (2-ethylcyclohexylamine), 4,4' -Methylenebis (2,6-dimethylcyclohexylamine), 4,4'-Methylenebis (2,6-diethylcyclohexylamine), 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis (4-amino) Cyclohexyl) hexafluoropropane and the like can be mentioned. Further, these may be used in combination of two or more.

Examples of the "chain-type aliphatic diamine or the corresponding chain-type aliphatic diamine" include 1,3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1, Examples thereof include 6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, and 1,9-nonamethylenediamine. Further, these may be used in combination of two or more.

From the viewpoint of the balance of heat resistance, flexibility, low moisture absorption, etc., the diamine component of R ₂ in the formula (10) and the diamine component of R ₂ ′ in the formula (14) or the corresponding diamine component is exemplified as a diamine compound. Then, p-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 1,5-naphthalenediamine, o-trizine, diaminoterphenyl, 4,4'- It is a residue derived from methylenebis (cyclohexylamine), isophorone diamine, etc. More preferred are 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 1,5-naphthalenediamine, o-trizine, and even more preferred are 4,4'-diaminodiphenylmethane, 4,4'. -Diaminodiphenyl ether, o-trizine. Most preferably, it is a residue derived from 4,4'-diaminodiphenylmethane, o-tridine.

It is preferable that the polyimide according to the present invention contains a polyimide fluoride from the viewpoint of excellent transparency of the polyimide film and easy heat correction by heat shrinkage. As for the fluorine content, it is more preferable that the fluorine content is contained in the film in the range of 1 to 40% by mass because the effect of the present invention is large.

<Physical characteristics of polyimide film>
(Total light transmittance)
The polyimide film of the present invention is a transparent polyimide film, and it is preferable that the total light transmittance is 80% or more as a measure of transparency. It is more preferably 85% or more, and further preferably 90% or more. The higher the total light transmittance, the higher the transparency, which is preferable. The description of the numerical value that the total light transmittance is 80% or more indicates the preferable range.

The total light transmittance of the polyimide film is 23 ° C. and 55% R.I. H. One polyimide film sample that has been humidity-controlled for 24 hours in the air-conditioned room can be measured according to JIS K 7375-2008. For the measurement, the transmittance in the visible light region (range of 400 to 700 nm) can be measured using a spectrophotometer U-3300 of Hitachi High-Technologies Corporation.

In order to make the total light transmittance 80% or more, it can be adjusted by selecting the type of the above-mentioned polyimide.

(Yellow index value (YI value))
The polyimide film of the present invention is a colorless polyimide film, and as a guideline for being colorless, the yellow index value (YI value) is preferably 4.0 or less. It is more preferably in the range of 0.3 to 2.0, and particularly preferably in the range of 0.3 to 1.6. The smaller the yellow index value (YI value), the less the coloring, which is preferable. The description of the numerical value that the yellow index value (YI value) is 4.0 or less indicates the preferable range.

The value of the YI value can be adjusted by selecting the type of the polyimide.

The yellow index value can be obtained according to the YI (yellow index: yellowish index) of the film defined in JIS K 7103.

As a method for measuring the yellow index value, a film sample is prepared, and a light source specified in JIS Z 8701 is used by using a spectrophotometer U-3300 of Hitachi High-Technologies Corporation and an attached saturation calculation program. The tristimulus values X, Y, and Z of the color are obtained, and the yellow index value is obtained according to the definition of the following equation.

Yellow index (YI) = 100 (1.28X-1.06Z) / Y
(solubility)
The polyimide film of the present invention preferably has a solubility (dissolution limit amount) of 1 g or more in 100 g of dichloromethane at 25 ° C. If the solubility is 1 g or more, it can be easily produced by the solution casting method. The higher the solubility, the easier it is to produce by the solution casting method, which is preferable. The description of the numerical value of the solubility of 1 g or more indicates the preferable range. It is more preferable that the polyimide contained in the polyimide film has a solubility (dissolution limit amount) of 1 g or more in 100 g of dichloromethane at 25 ° C.

(Heat shrinkage rate)
The polyimide film of the present invention has a heat shrinkage rate defined by the following formula in the range of 0.5 to 20.0%.
Heat shrinkage rate (%) = {(Lo-L) / Lo} x 100
(However, Lo represents the length of the sample before the test when measured at 25 ° C., and L represents the length of the sample when the sample is stored at 230 ° C. for 10 minutes and then cooled to 25 ° C.).
The heat shrinkage rate can be measured according to the ASTM standard D-1204 by the following procedure.
[1] Measure the length of the test piece before heating.
[2] The test piece is suspended at 230 ° C. for 10 minutes in a hot air circulation type constant temperature bath under a load.
[3] After cooling to room temperature, the length of the test piece is measured for the same portion as previously measured.
[4] The heat shrinkage rate is calculated based on the calculation formula defined by the above heat shrinkage rate (%) formula.

When the polyimide film has a long roll shape, the heat shrinkage rate in the width direction (direction perpendicular to the transport direction) of the film is measured.

When the heat shrinkage rate is larger than 0.5%, it becomes easy to heat-correct the polyimide film to improve the flatness. If the heat shrinkage rate is larger than 20.0%, the shrinkage rate is too large and the flatness tends to deteriorate.

The heat shrinkage rate can be adjusted by selecting the type of polyimide described above, the drying temperature in the polyimide film manufacturing process described later, and the type of solvent used in the preparation of the dope. Further, in some cases, it is also necessary to adjust the heat shrinkage rate by changing the stretching speed of the polyimide film and the content concentration of the residual solvent during stretching.

<Inorganic filler>
An inorganic filler can be mixed with the polyimide film of the present invention.

When the mixing ratio of the inorganic filler in the polyimide film is 0.01% by mass or more, the slipperiness is improved and the flatness is less likely to deteriorate. Further, when the content is 2.0% by mass or less, there is an effect of preventing an increase in haze of the polyimide film.

It was difficult to add a large amount of fine particles in the polyimide film, but by adopting the configuration of the present invention, even when the amount of fine particles added is small (0.01 to 2.0% by mass added to the polyimide film). , There is an advantage that deterioration of flatness can be heat-corrected.

As the inorganic filler, it is preferable to use fine particles of the following inorganic compounds. Examples of fine particles of inorganic compounds are silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, silicic acid. Examples thereof include magnesium and calcium phosphate. The fine particles containing silicon are preferable in that the turbidity is low, and silicon dioxide is particularly preferable.

The average particle size of the primary particles of the fine particles is preferably in the range of 5 to 400 nm, more preferably in the range of 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size in the range of 0.05 to 0.3 μm, and particles having an average particle size in the range of 80 to 400 nm do not aggregate and are used as primary particles. It is also preferable that it is contained.

The content of these fine particles in the polyimide film is more preferably in the range of 0.01 to 1% by mass, and particularly preferably in the range of 0.05 to 0.5% by mass.

In the case of a polyimide film having a multi-layer structure by the cocurrent spreading method, it is preferable that the surface contains fine particles in this amount.

Fine particles of silicon dioxide are commercially available under the trade names of Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (manufactured by Nippon Aerosil Co., Ltd.) and can be used. it can.

The fine particles of zirconium oxide are commercially available under the trade names of Aerosil R976 and R811 (all manufactured by Nippon Aerosil Co., Ltd.) and can be used.

Examples of the fine particles of the resin include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are preferable, and for example, trade names of Tospearl 103, 105, 108, 120, 145, 3120 and 240 (all manufactured by Toshiba Silicone Co., Ltd.). It is commercially available at and can be used.

Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of lowering the friction coefficient while keeping the haze of the polyimide film low.

<Other additives>
(UV absorber)
It is preferable that the polyimide film of the present invention contains an ultraviolet absorber from the viewpoint of improving light resistance. The ultraviolet absorber aims to improve the light resistance by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 370 nm is preferably in the range of 0.1 to 30%, which is more preferable. Is in the range of 1 to 20%, more preferably in the range of 2 to 10%.

The ultraviolet absorbers preferably used in the present invention are benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and triazine-based ultraviolet absorbers, and particularly preferably benzotriazole-based ultraviolet absorbers and benzophenone-based ultraviolet absorbers.

For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazole-2-yl) -6- (straight and side). Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., as well as chinubin 109, chinubin 171, chinubin 234, chinubin 326, chinubin 327, chinubin 328, There are butyls such as butyl 928, all of which are commercially available products manufactured by BASF Japan Co., Ltd. and can be preferably used. Of these, halogen-free ones are preferable.

In addition, a disk-shaped compound such as a compound having a 1,3,5-triazine ring is also preferably used as an ultraviolet absorber.

The polyimide film of the present invention preferably contains two or more types of ultraviolet absorbers.

Further, as the ultraviolet absorber, a polymer ultraviolet absorber can also be preferably used, and in particular, the polymer type ultraviolet absorber described in JP-A-6-148430 is preferably used. Moreover, it is preferable that the ultraviolet absorber does not have a halogen group.

The method of adding the ultraviolet absorber is to dissolve the ultraviolet absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane, or a mixed solvent thereof, and then add the ultraviolet absorber to the dope. Alternatively, it may be added directly into the dope composition.

For inorganic powders that do not dissolve in organic solvents, use a dissolver or sand mill in the organic solvent and polyimide film to disperse them before adding them to the doping.

The amount of the UV absorber used is not uniform depending on the type of UV absorber, usage conditions, etc., but when the dry film thickness of the polyimide film is 15 to 50 μm, it is 0.5 to 10% by mass with respect to the polyimide film. Is preferable, and the range of 0.6 to 4% by mass is more preferable.

(Antioxidant)
Antioxidants are also called anti-deterioration agents. When an electronic device or the like is placed in a high humidity and high temperature state, the polyimide film may be deteriorated.

The antioxidant has a role of delaying or preventing the decomposition of the polyimide film due to, for example, halogen in the residual solvent amount in the polyimide film, phosphoric acid of the phosphoric acid-based plasticizer, or the like, and thus the polyimide film of the present invention. It is preferable to contain it in.

As such an antioxidant, a hindered phenol-based compound is preferably used, for example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrax [3- (3,5-di). -T-Butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3] -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t) -Butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4 , 6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, Tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate and the like.

In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-T-Butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, a hydrazine-based metal inactivating agent such as N, N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine or tris (2,4-di-). A phosphorus-based processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

The amount of these compounds added is preferably in the range of 1 ppm to 1.0% in terms of mass ratio with respect to the polyimide film, and more preferably in the range of 10 to 1000 ppm.

(Phase difference controller)
In order to improve the display quality of image display devices such as liquid crystal display devices, a retardation control agent is added to the polyimide film, or an alignment film is formed to provide a liquid crystal layer, which is derived from the polarizing plate protective film and the liquid crystal layer. By combining the phase differences, it is possible to impart optical compensation ability to the polyimide film.

Examples of the retardation control agent include aromatic compounds having two or more aromatic rings as described in European Patent No. 911656A2, rod-shaped compounds described in JP-A-2006-2025, and the like. Further, two or more kinds of aromatic compounds may be used in combination. The aromatic ring of this aromatic compound is preferably an aromatic heterocycle containing an aromatic heterocycle in addition to the aromatic hydrocarbon ring. Aromatic heterocycles are generally unsaturated heterocycles. Of these, the 1,3,5-triazine ring described in JP-A-2006-2026 is preferable.

The amount of these retardation control agents added is preferably in the range of 0.5 to 20% by mass and more preferably in the range of 1 to 10% by mass with respect to 100% by mass of the polyimide film. ..

(Peeling accelerator)
A peeling accelerator may be added to the polyimide film of the present invention in order to improve the peelability during film production.

Many of the additives that reduce the peeling resistance of the polyimide film have a remarkable effect on surfactants, and preferable peeling agents are phosphoric acid ester-based surfactants, carboxylic acid or carboxylate-based surfactants, and the like. Sulfonic acid or sulfonate-based surfactants and sulfate ester-based surfactants are effective. Further, a fluorine-based surfactant in which a part of hydrogen atoms bonded to the hydrocarbon chain of the above-mentioned surfactant is replaced with a fluorine atom is also effective. The release agent is illustrated below.
RZ-1 C ₈ H ₁₇ OP (= O)-(OH) ₂
RZ-2 C ₁₂ H ₂₅ OP (= O)-(OK) ₂
RZ-3 C ₁₂ H ₂₅ OCH ₂ CH ₂ OP (= O)-(OK) ₂
RZ-4 C ₁₅ H ₃₁ (OCH ₂ CH ₂ ) ₅ OP (= O)-(OK) ₂
RZ-5 {C ₁₂ H ₂₅ O (CH ₂ CH ₂ O) ₅ } _2- P (= O) -OH
RZ-6 {C ₁₈ H ₃₅ (OCH ₂ CH ₂ ) ₈ O} _2- P (= O) -ONH _{4
RZ-7 (t-C 4} H 9) 3 -C 6 H 2 -OCH 2 CH 2 O-P (= O) - (OK) 2 RZ-8 (iso-C 9 H 19 -C 6 H 4 - O- (CH ₂ CH ₂ O) _5- P (= O)-(OK) (OH)
RZ-9 C ₁₂ H ₂₅ SO ₃ Na
RZ-10 C ₁₂ H ₂₅ OSO ₃ Na
RZ-11 C ₁₇ H ₃₃ COOH
RZ-12 C ₁₇ H ₃₃ COOH ・ N (CH ₂ CH ₂ OH) ₃
RZ-13 iso-C ₈ H _17- C ₆ H _4- O- (CH ₂ CH ₂ O) _3- (CH ₂ ) ₂ SO ₃ Na
RZ-14 (iso-C ₉ H ₁₉ ) _2- C ₆ H _3- O- (CH ₂ CH ₂ O) _3- (CH ₂ ) ₄ SO ₃ Na
RZ-15 Sodium triisopropylnaphthalene sulphonate RZ-16 Sodium tri-t-butylnaphthalene sulphonate RZ-17 C ₁₇ H ₃₃ CON (CH ₃ ) CH ₂ CH ₂ SO ₃ Na
RZ-18 C ₁₂ H _25- C ₆ H ₄ SO ₃・ NH ₄
The amount of the peeling accelerator added is preferably 0.05 to 5% by mass, more preferably 0.1 to 2% by mass, and most preferably 0.1 to 0.5% by mass with respect to the polyimide.

<Manufacturing method of polyimide film>
A specific example of the method for producing the polyimide film will be described below.

As a method for producing a polyimide film, a step of dissolving the above-mentioned polyamic acid or polyimide in a solvent to prepare a dope (dope preparation step), and a step of casting the dope on a support to form a cast film. (Collapse step), a step of evaporating the solvent from the cast film on the support (solvent evaporation step), a step of peeling the cast film from the support (peeling step), and drying the obtained cast film. A step of obtaining a film (first drying step), a step of stretching the dried film (stretching step), a step of further drying the stretched film (second drying step), and a step of winding the obtained polyimide film (a step of winding up the obtained polyimide film). It is preferable to have a winding step) and, if necessary, a step of heat-treating the film to imidize it (heating step).

In the present invention, it is preferable to take the following steps because the heat shrinkage rate tends to be increased.

That is, a dope adjustment step of dissolving polyamic acid or polyimide in a solvent having a boiling point in the range of 40 to 80 ° C. to prepare a dope, and spreading the dope on a support to form a casting film. Steps, a solvent evaporation step of evaporating a solvent from the cast film, a peeling step of peeling the cast film obtained by evaporating the solvent from a support, and drying the peeled cast film at 10 to 200 ° C. to form a film. It is preferable to use a method for producing a film containing polyimide, which comprises a drying step for obtaining the film and a stretching step for stretching the dried film.

Hereinafter, each step will be specifically described.

(Dope preparation process)
In the method for producing a polyimide film of the present invention, it is preferable that at least a polyimide and a hydrogen-bonding compound are dissolved in a low boiling point solvent to prepare a dope, and the dope is used to form a film by a solution casting film forming method.

As the low boiling point solvent, it is preferable to use a low boiling point solvent having a boiling point of 80 ° C. or lower as the main solvent because the film manufacturing process temperature (particularly the drying temperature) can be reduced and the heat shrinkage rate can be adjusted. Here, "used as the main solvent" means that 55% by mass or more is used with respect to the total amount of the solvent in the case of a mixed solvent, preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably. Is to be used in an amount of 90% by mass or more. Of course, if used alone, it will be 100% by mass.

The low boiling point solvent may be any one that dissolves polyimide and other additives at the same time. For example, the chlorine-based solvent is dichloromethane, and the non-chlorine-based solvent is methyl acetate, ethyl acetate, amyl acetate, acetone, etc. Methyl ethyl ketone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3- Difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2, Examples thereof include 2,3,3,3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like.

Among the above solvents, low boiling point solvents having a boiling point of 80 ° C. or lower include dichloromethane (40 ° C.), ethyl acetate (77 ° C.), methyl ethyl ketone (79 ° C.), tetrahydrofuran (66 ° C.), and acetone (56.5 ° C.). , And at least one selected from 1,3-dioxolane (75 ° C.) is preferably contained as the main solvent (the boiling points are shown in parentheses).

Further, as the solvent contained in the case of the mixed solvent, any solvent can be used as long as it can dissolve the polyimide and the organic compound having a carbonyl group according to the present invention, as long as the effect of the present invention is not impaired. Solvents other than those used include, for example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, N-methylcaprolactam, hexa. Methylphosphoramide, tetramethylenesulfone, dimethylsulfoxide, m-cresol, phenol, p-chlorophenol, 2-chloro-4-hydroxytoluene, diglime, triglime, tetraglime, dioxane, γ-butyrolactone, dioxolane, cyclopentanone , Epsilon caprolactam, chloroform, etc. can be used, and two or more of them may be used in combination. Further, in addition to these solvents, a poor solvent such as hexane, heptane, benzene, toluene, xylene, chlorobenzene and o-dichlorobenzene is used to the extent that the polyimide and the organic compound having a carbonyl group according to the present invention do not precipitate. You may.

Further, an alcohol solvent can also be used. It is preferable that the alcohol solvent is selected from methanol, ethanol and butanol from the viewpoint of improving the peelability and enabling high-speed casting. Of these, it is preferable to use methanol or ethanol. Higher proportions of alcohol in the dope gel the web, facilitating delamination from the metal support.

For dissolution of polyimide and other additives, a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed by pressurizing above the boiling point of the main solvent, JP-A-9-955544, JP-A-9- Various melting methods can be used, such as the method performed by the cooling melting method described in JP-A-95557 or JP-A-9-95538, the method performed at high pressure described in JP-A-11-21379, and the like.

The prepared dope is guided to a filter by a liquid feed pump or the like and filtered. For example, when the main solvent of the doping is dichloromethane, the gel-like foreign matter in the doping can be removed by filtering the doping at a temperature of + 5 ° C. or higher at a boiling point of the dichloromethane at 1 atm. The preferred temperature range is 45 to 120 ° C, more preferably 45 to 70 ° C, and even more preferably within the range of 45 to 55 ° C.

Further, in many cases, the main doping may contain a return material in the range of 10 to 50% by mass. The return material is a part that is reused as a raw material for some reason. For example, it is a finely crushed polyimide film, and both side parts of the film are cut off, which is generated when the polyimide film is formed. Or, a polyimide film raw fabric that exceeds the specified value of the film due to scratches or the like is used.

Further, as the raw material of the resin used for the doping preparation, those in which polyimide and other compounds are pelletized in advance can also be preferably used.

(Flow film forming process)
Flow of the prepared dope onto a metal support such as a stainless steel belt or a rotating metal drum that feeds the prepared dope to a die through a liquid feed pump (eg, a pressurized metering gear pump) and transfers it indefinitely. Dope is poured from the die to the extension position.

The metal support in casting is preferably one having a mirror-finished surface, and as the support, a metal support such as a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The width of the cast can be in the range of 1 to 4 m, preferably in the range of 1.5 to 3 m, more preferably in the range of 2 to 2.8 m. The support does not have to be made of metal, for example, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polybutylene terephthalate (PBT) film, nylon 6 film, nylon 6,6 film, polypropylene film. , A belt such as polytetrafluoroethylene can be used. When a polyimide film is used as the flexible substrate, the polyimide film may be wound together with the metal support on which the polyimide is cast or the film.

The traveling speed of the metal support is not particularly limited, but is usually 5 m / min or more, preferably 10 to 180 m / min, and particularly preferably 80 to 150 m / min. The higher the traveling speed of the metal support, the easier it is for companion gas to be generated, and the more remarkable the occurrence of film thickness unevenness due to disturbance.

The traveling speed of the metal support is the moving speed of the outer surface of the metal support.

The surface temperature of the metal support is preferably higher because the drying rate of the cast film can be increased, but if it is too high, the cast film may foam or the flatness may deteriorate. It is preferable that the temperature is in the range of −50 to −10 ° C. with respect to the boiling point of the solvent to be used.

The die has a shape that gradually becomes thinner toward the discharge port in a cross section perpendicular to the width direction. Specifically, the die usually has tapered surfaces on the downstream side and the upstream side in the traveling direction of the lower portion, and a discharge port is formed in a slit shape between the tapered surfaces. A metal die is preferably used, and specific examples thereof include stainless steel and titanium. In the present invention, when producing films having different thicknesses, it is not necessary to change to dies having different slit gaps.

As the die, it is preferable to use a pressure die that can adjust the slit shape of the base portion of the die and can easily make the film thickness uniform. The pressure die includes a coat hanger die, a T die, and the like, and any of them is preferably used. Even when films of different thicknesses are continuously produced, the discharge rate of the die is maintained at a substantially constant value. Therefore, when a pressure die is used, conditions such as extrusion pressure and shear rate are also omitted. It is maintained at a constant value. Further, in order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the doping amount may be divided and laminated.

(Solvent evaporation process)
The solvent evaporation step is a pre-drying step performed on the metal support, heating the cast film on the metal support to evaporate the solvent.

To evaporate the solvent, for example, a method of blowing heating air from the casting film side and the back side of the metal support with a dryer, a method of transferring heat from the back surface of the metal support with a heating liquid, and a method of transferring heat from the front and back by radiant heat. And so on. A method of appropriately selecting and combining them is also preferable. The surface temperature of the metal support may be the same as a whole or may differ depending on the position. The temperature of the heating air is preferably in the range of 10 to 220 ° C.

The temperature of the heating air (drying temperature) is preferably 200 ° C. or lower, more preferably 140 ° C. or lower, and even more preferably 120 ° C. or lower.

In the solvent evaporation step, it is preferable to dry the casting film until the residual solvent amount is within the range of 10 to 150% by mass from the viewpoint of the peelability of the casting film and the transportability after peeling.

In the present invention, the amount of residual solvent can be expressed by the following formula.

Residual solvent amount (mass%) = {(MN) / N} x 100
Here, M is the mass of the casting film (film) at a predetermined time point, and N is the mass of M when it is dried at 200 ° C. for 3 hours. In particular, M when calculating the residual solvent amount achieved in the solvent evaporation step is the mass of the cast film immediately before the peeling step.

(Peeling process)
The casting film in which the solvent has evaporated on the metal support is peeled off at the peeling position.

The peeling tension when peeling the metal support and the casting film is usually in the range of 60 to 400 N / m, but if wrinkles are likely to occur during peeling, the metal support is peeled at a tension of 190 N / m or less. Is preferable.

In the present invention, the temperature at the peeling position on the metal support is preferably in the range of −50 to 60 ° C, more preferably in the range of 10 to 40 ° C, and in the range of 15 to 40 ° C. Is the most preferable.

The peeled cast film (the cast film after peeling is also referred to as a film) may be sent directly to the stretching step, or may be sent to the first drying step so as to achieve a desired residual solvent amount. After being sent to the stretching step. In the present invention, from the viewpoint of stable transport in the stretching step, it is preferable that the film is sequentially fed to the first drying step and the stretching step after the peeling step.

(1st drying step)
The first drying step is a drying step of heating the film and further evaporating the solvent. The drying means is not particularly limited, and for example, hot air, infrared rays, a heating roller, microwaves, or the like can be used. From the viewpoint of convenience, it is preferable to dry the film with hot air or the like while transporting the film with rollers arranged in a staggered pattern. The drying temperature is preferably in the range of 10 to 200 ° C. in consideration of the amount of residual solvent, the expansion / contraction rate during transportation, and the like.

The drying temperature is preferably 200 ° C. or lower from the viewpoint of controlling the heat shrinkage rate of the polyimide film within the range of the present invention and preventing the polymer chains of the polyimide from becoming too rigid. The lower limit is 10 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 120 ° C. or higher from the viewpoint of production efficiency such as heat shrinkage and drying time.

By lowering the drying temperature to a low temperature of 200 ° C. or lower, the heat shrinkage rate of the film can be increased.

(Stretching process)
By stretching the film peeled from the metal support, the film thickness, flatness, orientation, etc. of the film can be controlled.

In the method for producing a film of the present invention, it is preferable to stretch the film in the longitudinal direction or the width direction.

The stretching operation may be carried out in multiple stages. Further, when biaxial stretching is performed, simultaneous biaxial stretching may be performed, or biaxial stretching may be performed step by step. In this case, the term “stepwise” means, for example, that stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any of the steps. Is also possible.

That is, for example, the following stretching steps are also possible:
・ Stretching in the longitudinal direction → Stretching in the width direction → Stretching in the longitudinal direction → Stretching in the longitudinal direction ・ Stretching in the width direction → Stretching in the width direction → Stretching in the longitudinal direction → Stretching in the longitudinal direction Also, for simultaneous biaxial stretching Also includes the case of stretching in one direction and contracting the other with relaxation of tension. The preferable stretching ratio of the simultaneous biaxial stretching can be in the range of × 1.01 times to × 1.5 times in both the width direction and the longitudinal direction. Here, the draw ratio is (width or length after stretching the film) / (width or length before stretching the film).

The amount of residual solvent at the start of stretching is preferably in the range of 0.1 to 200% by mass.

If the amount of the residual solvent is 0.1% by mass or more, the effect of improving the flatness by stretching can be obtained, and if it is 200% or less, stretching is easy.

In order to increase the heat shrinkage of the polyimide film of the present invention, the amount of the residual solvent in the film at the start of stretching is preferably 0.1 to 2.0% by mass, preferably 0.1 to 1. More preferably, it is 0% by mass.

In the method for producing a polyimide film of the present invention, the film may be stretched in the longitudinal direction or the width direction, preferably in the width direction so that the film thickness after stretching is within a desired range. It is preferable to stretch the polyimide film in a temperature range of (Tg-200 ° C.) to (Tg + 100 ° C.) with respect to the glass transition temperature (Tg). Stretching in the above temperature range lowers the haze because the stretching stress can be reduced. In addition, a polyimide film that suppresses the occurrence of breakage and is excellent in flatness and colorability of the polyimide film itself can be obtained. The stretching temperature is more preferably in the range of (Tg-150 ° C.) to (Tg + 50 ° C.).

In the method for producing a polyimide film according to the present invention, a self-supporting film peeled from a support can be stretched in the longitudinal direction by controlling the traveling speed with a stretching roller.

In order to stretch in the width direction, for example, the entire width of the film or a part of the drying process as shown in JP-A-62-46625 is performed by clipping or pinning in the width direction to hold both ends of the width of the film. While drying (called a tenter method), a tenter method using a clip is preferably used.

It is preferable that the film stretched in the longitudinal direction or the unstretched film is introduced into the tenter with both ends in the width direction gripped by the clip, and is stretched in the width direction while traveling together with the tenter clip.

When stretching in the width direction, it is preferable to stretch the film at a stretching speed in the range of 50 to 1000% / min in the width direction from the viewpoint of improving the flatness of the film.

If the stretching speed is 50% / min or more, the flatness is improved and the film can be processed at high speed, which is preferable from the viewpoint of production suitability. If the stretching speed is 1000% / min or less, the film breaks. It can be processed without any problem, which is preferable.

A more preferred stretching rate is in the range of 100-500% / min. The stretching rate is defined by the following formula.

Stretching rate (% / min) = [(d ₁ / d ₂ ) -1] × 100 (%) / t
(In the above formula, d ₁ is the width dimension in the stretching direction of the resin film after stretching, d ₂ is the width dimension in the stretching direction of the resin film before stretching, and t is the time (min) required for stretching. .)
In order to increase the heat shrinkage rate of the polyimide film of the present invention, the stretching speed is 200 to 500% / min, more preferably 300 to 500% / min.

In the stretching step, holding / relaxation is usually performed after stretching. That is, in this step, it is preferable to perform a stretching step of stretching the film, a holding step of holding the film in a stretched state, and a relaxing step of relaxing the film in the stretched direction in these orders. In the holding step, the stretching at the stretching ratio achieved in the stretching step is held at the stretching temperature in the stretching step. In the relaxation step, the stretching in the stretching step is held in the holding step, and then the tension for stretching is released to relax the stretching. The relaxation step may be performed at a temperature equal to or lower than the stretching temperature in the stretching step.

(Second drying step)
Then, the stretched film is heated and dried. When the film is heated by hot air or the like, a means for preventing the mixing of used hot air by installing a nozzle capable of exhausting used hot air (air containing a solvent or wet air) is also preferably used. The hot air temperature is more preferably in the range of 40 to 350 ° C. The drying time is preferably about 5 seconds to 30 minutes, more preferably 10 seconds to 15 minutes.

Further, the heating and drying means is not limited to hot air, and for example, infrared rays, heating rollers, microwaves and the like can be used. From the viewpoint of convenience, it is preferable to dry the film with hot air or the like while transporting the film with rollers arranged in a staggered pattern. The drying temperature is preferably in the range of 40 to 150 ° C. from the viewpoint that heat shrinkage tends to be large. More preferably, it is 40 to 120 ° C.

In the second drying step, it is preferable to dry the film until the residual solvent amount becomes 0.5% by mass or less.

(Winding process)
The winding step is a step of winding the obtained polyimide film and cooling it to room temperature. The winder may be a generally used one, and can be wound by a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress.

The thickness of the polyimide film is not particularly limited, and is preferably in the range of, for example, 1 to 200 μm, particularly 1 to 100 μm.

In the winding step, both ends of the polyimide film sandwiched between tenter clips and the like when stretched and conveyed may be slit. It is preferable that the slit end of the polyimide film is finely cut within a width of 1 to 30 mm, then dissolved in a solvent and reused as a return material.

The ratio of the portion of the molded polyimide film that is reused as the return material is preferably in the range of 10 to 90% by mass, more preferably 20 to 80% by mass, and further preferably 30 to 70% by mass.

The input amount varies slightly depending on the amount of the return material generated during or finally in the film forming process, but usually, the mixing ratio of the return material with respect to the total solid content in the doping is about 10 to 50% by mass, preferably about 10 to 50% by mass. It is in the range of about 15 to 40% by mass. It is preferable that the mixing ratio of the return material is as constant as possible from the viewpoint of production stability.

Each step from the solvent evaporation step to the winding step described above may be carried out in an air atmosphere or an inert gas atmosphere such as nitrogen gas. Further, each step, particularly the drying step and the stretching step, is performed in consideration of the explosive limit concentration of the solvent in the atmosphere.

(Heating process)
After the winding step, a heating step of further heat-treating the polyimide film dried in the second drying step is performed in order to promote imidization within the polymer chain molecule and between the polymer chain molecules to improve the mechanical properties. May be good.

The second drying step may also serve as a heating step.

The heating means is performed by using a known means such as hot air, an electric heater, or a microwave. As the electric heater, the infrared heater described above can be used.

As for the heat treatment conditions, the heating temperature is preferably 200 ° C. or lower, more preferably 150 ° C. or lower, and even more preferably 140 ° C. or lower.

By lowering the drying temperature, the heat shrinkage rate of the polyimide film can be increased.

In the heating step, if the polyimide film is rapidly heated, problems such as an increase in surface defects occur. Therefore, it is preferable to appropriately select the heating method. Further, the heating step is preferably performed in a low oxygen atmosphere.

The heating temperature in the second drying step and the heating step is preferably 150 ° C. or lower from the viewpoint of increasing the heat shrinkage of the film. More preferably, it is 120 ° C. or lower.

After the winding step, before or after the heating step, a step of slitting the widthwise end portion of the polyimide film, a step of removing static electricity from the polyimide film when it is charged, and the like are further performed. May be.

Since the polyimide film of the present invention has a large heat shrinkage rate as a polyimide film, it is easy to correct the flatness by post-heat treatment. The temperature for post-heating can be in the range of 100 ° C to 200 ° C.

<Shape of polyimide film>
The polyimide film of the present invention is preferably long, specifically, has a length within the range of about 100 to 10,000 m, and is wound into a roll. The width of the polyimide film of the present invention is preferably 1 m or more, more preferably 1.4 m or more, and particularly preferably 1.4 to 4 m.

<Use>
The polyimide film of the present invention can heat-correct the flatness deteriorated when laminated with an electronic device. The applicable electronic device is not particularly limited, and examples thereof include an organic electroluminescence (EL) device, a liquid crystal display device (LCD), an organic photoelectric conversion device, a printed circuit board, a thin film, a touch panel, a polarizing plate, and a retardation film. be able to. From the viewpoint that the effects of the present invention can be obtained more efficiently, it is preferably used for flexible printed circuit boards, LED lighting devices, and front members for flexible displays.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the indication of "parts" or "%" is used, but unless otherwise specified, it indicates "parts by mass" or "% by mass".

[Example 1]
The structures of the compounds used in the examples are listed below.

The sources of commercially available products of the above compounds are as follows.
Acid anhydride 1: Daikin anhydride Co., Ltd. Acid anhydride 2: Manac Co., Ltd. Acid anhydride 3: Daicel acid anhydride Co., Ltd. 5: Mitsubishi Chemical Co., Ltd. Diamine 1: Daikin Industries, Ltd. Diamine 2: Mitsui Chemical Fine Co., Ltd. Diamine 4: Mitsui Chemical Fine Co., Ltd. <Manufacturing of polyimide film 101>
(Preparation of polyimide solution A)
2,2-Bis (3,4-dicarboxyphenyl) -1,1,1, in a 4-neck flask equipped with a dry nitrogen gas introduction tube, a cooler, a Dean-Stark aggregator filled with toluene, and a stirrer. Add 25.59 g (57.6 mmol) of 3,3,3-hexafluoropropane dianhydride (acid anhydride 1: manufactured by Daikin Industries, Ltd.) to N, N-dimethylacetamide (134 g) at room temperature under a nitrogen stream. Was stirred with.

To it, 19.2 g (60 mmol) of 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl (diamine 1: manufactured by Daikin Industries, Ltd.) was added, and the mixture was heated and stirred at 80 ° C. for 6 hours. Then, the outside temperature was heated to 190 ° C., and the water generated by imidization was azeotropically distilled off together with toluene. After continuing heating, refluxing and stirring for 6 hours, no water was generated. Subsequently, the mixture was heated for 7 hours while distilling off toluene, and after distilling off toluene, methanol was added to reprecipitate, and after drying the solid content, a dichloromethane solution of 8% by mass was prepared to prepare a polyimide solution A containing a polyimide resin A. did.

(Preparation of doping)
A main dope having the following composition was prepared. First, dichloromethane (boiling point 40 ° C.) was added to the pressure dissolution tank. The above-prepared polyimide solution A and the remaining components were put into a pressurized dissolution tank containing a solvent with stirring. This is heated and completely dissolved while stirring, and this is Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. Filtration was performed using 244 to prepare the main dope.

(Composition of main doping)
Dichloromethane 350 parts by mass Polyimide solution A 100 parts by mass Matte agent (Aerosil R812, manufactured by Nippon Aerosil Co., Ltd.)
0.5 parts by mass (casting process)
The dope was then uniformly cast on the stainless steel belt support at a temperature of 30 ° C. and a width of 1500 mm using an endless belt casting device. The temperature of the stainless steel belt was controlled to 30 ° C.

(Peeling process)
The solvent was evaporated on the stainless steel belt support until the amount of residual solvent in the cast film reached 75%, and then the solvent was peeled off from the stainless steel belt support at a peeling tension of 180 N / m. ..

(1st drying step)
In the first drying step, the peeled cast film was dried at a first drying temperature of 200 ° C. so that the amount of residual solvent at the start of stretching was a desired value to obtain a film.

(Stretching process)
The dried film was then heated at 120 ° C. and stretched 1.50 times in the width direction using a clip-type tenter at a stretching speed of 1% / sec. The amount of residual solvent at the start of stretching was 10% by mass.

(Second drying step)
The stretched film was dried at a second drying temperature of 120 ° C. with a transport tension of 100 N / m and a drying time of 15 minutes until the residual solvent amount was less than 0.5% by mass to obtain a polyimide film having a dry film thickness of 62 μm. .. The obtained polyimide film was wound up to obtain a polyimide film 101.

<Preparation of polyimide films 102 to 113>
With the polyimide film 101, except that the types of acid anhydride and diamine used, the type of solvent, the drying temperature, the stretching rate, and the amount of residual solvent during stretching were changed as shown in Table 1 in the production of the polyimide film 101. In the same manner, polyimide films 102 to 113 were produced. In the preparation of the polyimide films 102 to 113, the same molar amounts of the acid anhydride and the diamine as those of the polyimide film 101 were used.

Each of the above-mentioned polyimide films was produced in the form of a long film having a width of 1900 mm and a length of 8000 m.

<Making rolls 101-113>
The winding rolls of the above-mentioned polyimide films 101 to 113 (width 1900 mm, length 8000 m) were produced under the following winding conditions to prepare rolls 101 to 113.

(Winding conditions)
Touch roller: diameter 120 mm, length 2600 mm
Touch roller material: NBR rubber (manufactured by Meiwa Rubber Industry Co., Ltd.) White Elecon Hardness 35 degrees, thickness 10 mm, CFRP (Carbon Fiber Reinforced Plastics) core Touch roller pressure: 50 N / m
Winding tension: Initial tension 250 N / m Tapered 90% Corner 25%
Winding speed: 100m / min
Winding shaft diameter: 15.24 cm
Material of take-up shaft: FRP (Fiber Reinforced Plastics)
<Measurement of physical properties of polyimide film>
The total light transmittance, YI value, solubility, and heat shrinkage of the polyimide films 101 to 113 obtained as described above were measured.

In addition, the flatness and haze of the rolls 101 to 113 after heat correction were evaluated.

(Total light transmittance)
The total light transmittance of each polyimide film was measured by using a spectrophotometer U-3300 of Hitachi High-Technologies Co., Ltd. according to JIS K 7375 for one sample whose humidity was adjusted for 24 hours in an air conditioning room at 23 ° C. and 55% RH. The transmittance in the visible light region (range of 400 to 700 nm) was measured, the average value of 10-point measurement was obtained, and the evaluation was made according to the following evaluation criteria.

⊚: 88% or more ○: 80% or more, less than 88% ×: less than 80% (yellow index value (YI value))
Each polyimide film sample was measured according to JIS K 7373-2006 using a spectrophotometer U-3300 of Hitachi High-Technologies Corporation and an attached saturation calculation program. The average value of 10-point measurement was calculated and evaluated according to the following evaluation criteria.

⊚: 0.3 or more and less than 2.0
◯: 2.0 or more and 4.0 or less ×: More than 4.0 (solubility)
Each polyimide film was dissolved in 100 g of dichloromethane at 25 ° C., and the upper limit of dissolution was measured. It was evaluated according to the following evaluation criteria.

◯: Solubility 1 g or more ×: Solubility less than 1 g (heat shrinkage rate)
The heat shrinkage was measured according to the ASTM standard D-1204 according to the following procedure.
[1] The length of the test piece was measured at 25 ° C. before heating.
[2] The test piece was suspended at 230 ° C. for 10 minutes in a hot air circulation type constant temperature bath under a load.
[3] After cooling to room temperature, the length of the test piece was measured for the same portion as previously measured.
[4] The heat shrinkage rate was calculated based on the calculation formula defined by the following heat shrinkage rate (%) formula.
The heat shrinkage rate defined by the following formula was measured.
Heat shrinkage rate (%) = {(Lo-L) / Lo} x 100
(However, Lo represents the length of the sample before the test when measured at 25 ° C., and L represents the length of the sample when the sample is stored at 230 ° C. for 10 minutes and then cooled to 25 ° C.).
As for the heat shrinkage rate, the heat shrinkage rate in the width direction (direction perpendicular to the transport direction) of the roll film was measured.

<Evaluation of roll body>
(Flatness after heat correction)
Each roll was wrapped in an aluminum-deposited sheet (moisture permeability per 24 hours was 1 g / m ² ) and then stored in a warehouse kept at 23 ° C. for 3 months.

The polyimide film after storage was unwound and heat-treated at 230 ° C. for 1 minute in a drying oven while being conveyed.

After the heat treatment, the number of convex transfers per 1 m ² on the film at the intermediate point 1000 m of the film was evaluated.

⊚: less than 2 ○: less than 2-5 ×: 5 or more [galvanized iron failure]
Height difference of unevenness ◎: Less than 0.5 mm ○: 0.5 to less than 1.0 ×: 1 mm or more The composition and manufacturing conditions of each polyimide film and the evaluation results of total light transmittance, YI value, and heat shrinkage are shown. It is represented by 1.

Table 1 shows the results of flatness of each roll body after heat correction.

As shown in Table 1, it can be seen that the polyimide film of the present invention obtained a colorless and transparent polyimide film having a large heat shrinkage rate.

Further, as shown in Table 1, it can be seen that the roll body produced by using the polyimide film of the present invention has good flatness after heat treatment.

[Example 2]
In the polyimide film 101 of Example 1, the same polyimide films 2011 to 113 as the polyimide films 101-113 except that the content of the inorganic filler (matting agent) in the film was changed to 2.0% by mass. 213 was prepared.

For the polyimide films 2001 to 213, the total light transmittance, the YI value, and the heat shrinkage rate were measured in the same manner as in Example 1. Table 2 shows the composition and manufacturing conditions of each polyimide film, and the evaluation results of the total light transmittance, the YI value, and the heat shrinkage rate.

Further, using the polyimide films 201 to 213, roll bodies 201 to 213 similar to the roll bodies 101 to 113 of Example 1 were produced. The flatness and haze of each roll body after heat correction were measured in the same manner as in Example 1. Table 2 shows the results of flatness of each roll body after heat correction.

As shown in Table 2, it can be seen that the roll body produced by using the polyimide film of the present invention has good flatness after heat treatment even if the amount of the inorganic filler added is changed.

Since the polyimide film of the present invention is a polyimide film capable of heat-correcting the deterioration of flatness when wound into a roll, it has excellent flatness, no coloring, and excellent transparency. Therefore, it is a flexible printed circuit board and an LED lighting device. It is suitable for use as a front member for a flexible display.

Claims (3)

A method for producing a polyimide film, which produces a polyimide film containing polyimide as a main component.
The polyimide film has a total light transmittance of 80% or more, a yellow index value (YI value) of 4.0 or less, is dissolved in 1 g or more with 100 g of dichloromethane at 25 ° C., and is defined by the following formula. thermal shrinkage Ri der range of from 0.5 to 20.0%,
The method for producing the polyimide film is
Doping preparation step of dissolving polyamic acid or polyimide in a solvent having a boiling point in the range of 40 to 80 ° C. to prepare a doping.
A casting step of casting the doping on a support to form a casting film,
A solvent evaporation step of evaporating a solvent from the casting film,
A peeling step of peeling the casting film obtained by evaporating the solvent from the support.
A drying step of drying the peeled cast film at 10 to 200 ° C. to obtain a film, and
Stretching step of stretching the dried film,
A method for producing a polyimide film , which comprises .
Heat shrinkage rate (%) = {(Lo-L) / Lo} x 100
(However , Lo represents the length of the sample before the test when measured at 25 ° C., and L represents the length of the sample when the sample is stored at 230 ° C. for 10 minutes and then cooled to 25 ° C. ) The method for producing a polyimide film according to claim 1, wherein the inorganic filler is contained in the range of 0.01 to 2.0% by mass. The method for producing a polyimide film according to claim 1 or 2, wherein the polyimide contains a polyimide fluoride.