JP6834440B2 - Polyimide film and display device using the film - Google Patents

Description

The present invention relates to a polyimide film and a display device using the film.

Conventionally, a glass substrate has been used for the front plate of products such as tablet PCs and smartphones. On the other hand, competition for these products is intensifying, and various demands such as diversification of designs, flexibility and cost reduction are increasing. Attention has been paid to the use of plastic for the front panel to meet these requirements. For example, a polyimide cover substrate having a protective layer of a urethane acrylate compound provided on one or both surfaces of a polyimide film has been reported (for example, Patent Document 1).

Special Table 2016-521216

In recent years, tablet PCs and smartphones have been used in various countries, and therefore, performance according to the environment of each country is required. However, the polyimide cover substrate described in Patent Document 1 has a problem that when it is used in an environment of high temperature and high humidity, it turns yellow and its visibility is lowered.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyimide film capable of suppressing yellowing in an environment of high temperature and high humidity.

Another object of the present invention is to provide a polyimide film capable of suppressing turbidity in a high temperature and high humidity environment.

The present inventor has conducted diligent research to solve the above problems. As a result, they have found that the above problems can be solved by using a polyimide resin and a metal oxide filler having a specific shape and a specific compound on the surface, and completed the present invention.

That is, the above-mentioned purposes are a film containing a polyimide resin and a metal oxide filler, and the metal oxide filler has an aspect ratio (major axis / minor axis) of 100 to 3000 and an average diameter of 1 to 10 nm. There, the surface sulfonic acid group of the metal oxide filler _(-SO 3 H), carboxyl (-COOH) and phosphate groups; from _{(-P (= O) (OH} ) 3-n n = 1 or 2) It can be achieved by a film having a compound having at least one group selected from the group.

The polyimide film of the present invention can suppress changes in characteristics (particularly yellowing and turbidity) due to changes in temperature and humidity environment. Therefore, the film of the present invention can be suitably used for a front plate of a tablet PC, a smartphone, or the like.

The film according to one embodiment of the present invention contains a polyimide resin and a metal oxide filler. Here, the metal oxide filler has (a) an aspect ratio (major axis / minor axis) of 100 to 3000 and an average diameter of 1 to 10 nm, and (b) a sulfonic acid on the surface of the metal oxide filler. having at least one group selected from the group consisting of; (n = 1 or _{2 -P (= O) (OH} ) 3-n) group _(-SO 3 H), carboxyl (-COOH) and phosphate groups It is characterized by having a compound. According to the above configuration, it is possible to suppress characteristic changes (particularly yellowing (increase in ΔYI) and turbidity (increase in Δ haze)) due to temperature and humidity environment fluctuations (particularly in a high temperature and high humidity environment). Therefore, the film of the present invention exhibits high visibility even in an environment where the temperature and humidity fluctuate (particularly in a high temperature and high humidity environment) while maintaining the flexibility inherent in the plastic, so that it is in front of a tablet PC, a smartphone, or the like. It can be suitably used for a face plate. In the present specification, the film of the present invention is also referred to as a "polyimide film" or a "polyimide film of the present invention". Further, the polyimide resin is also simply referred to as "polyimide". Further, the metal oxide filler is also simply referred to as "filler according to the present invention" or "filler". Further, a sulfonic acid group _(-SO 3 H), carboxyl (-COOH) and phosphate groups; at least one selected from the group consisting of _{(-P (= O) (OH} ) 3-n n = 1 or 2) The compound having the group of is also simply referred to as "surface modifier according to the present invention" or "surface modifier".

The polyimide resin has a characteristic of being excellent in bending property (flexibility) as compared with other resins such as polycarbonate resin and (meth) acrylic resin. Therefore, the polyimide resin is suitable as a front plate for making a display device such as a smartphone flexible. On the other hand, polyimide resins are generally colored yellow by forming an intermolecular and intramolecular charge transfer (CT) complex, but the introduction of bulky groups such as fluorine atoms or groups having fluorine atoms can be used. By introducing an alicyclic structure, the intermolecular distance can be widened and the interaction between molecules can be suppressed to make it transparent. However, when a highly transparent film made of such a polyimide resin is placed under high temperature and high humidity, it turns yellow. Therefore, the polyimide resin film is not suitable for use in an environment where the temperature and humidity fluctuate (particularly, a high temperature and high humidity environment). When the cause of this is investigated, when the polyimide resin film is placed under high temperature and high humidity, water infiltrates between the molecules of the resin, the molecules are rearranged, and a charge transfer (CT) complex is formed. It was found that it absorbs visible light and turns yellow (YI rises). It was also found that in such a case, hydrolysis of the resin also occurs, which can also cause yellowing and turbidity of the film. Therefore, in order to suppress yellowing and turbidity under high temperature and high humidity, it is considered that a means for suppressing CT complex formation due to rearrangement of molecular chains is effective, and further studies have been conducted on the means. As a result, it was found that the above (a) is effective. Specifically, there are (unmodified) hydroxyl groups (-OH) derived from the filler on the surface of the metal oxide filler. The carbonyl group (-C (= O)-) of the polyimide resin is immobilized on the surface of the metal oxide filler via a hydrogen bond with this hydroxyl group. Further, the surface of the metal oxide filler has a compound having the specific functional group (surface modifier) (the metal oxide filler is surface-modified with the compound having the specific functional group) ((b) above). .. The specific functional group of this surface modifier is immobilized on the surface of the metal oxide filler via a dipole-dipole interaction with the carbonyl group (-C (= O)-) of the polyimide resin. Here, since the metal oxide filler having the aspect ratio as defined in (a) above has a large surface area (specific surface area) per volume, the bonding point between the carbonyl group of the polyimide resin and the hydroxyl group of the metal oxide filler ( There are many points of interaction). Therefore, even under high temperature and high humidity, the polyimide resin is sufficiently immobilized, and the rearrangement of molecules in the resin (hence, CT complex forming property) can be suppressed. Here, if the aspect ratio is less than 100, the number of bonding points (interaction points) is too small, so that the polyimide resin is not sufficiently immobilized on the filler and yellows under high temperature and high humidity (for example). See film 7 below). On the other hand, when the aspect ratio exceeds 3000, the visibility of the filler is extremely increased, and the film itself immediately after production becomes yellowish or turbid (see, for example, film 6 below).

Further, the polyimide resin is inferior in hardness (toughness) to glass and the like. Here, it is generally known that the mechanical strength is improved by adding a filler to the resin. However, the transmittance (total light transmittance) and haze, particularly haze, of the film formed by using the resin and the filler are lowered. In particular, by adding a filler having a high aspect ratio, the mechanical strength can be considerably improved, but the haze deteriorates (see, for example, film 6 below). However, if the filler has an average diameter (fiber diameter) as defined in (a) above, the produced film exhibits a sufficiently low haze (sufficient transparency). Here, if the average diameter is less than 1 nm, sufficient hardness (toughness) cannot be imparted to the film. On the other hand, if the average diameter exceeds 10 nm, the filler is too thick and the visibility is extremely improved, and the film itself immediately after production becomes yellowish or turbid (see, for example, film 5 below).

Therefore, the film formed by mixing the metal oxide filler satisfying both the above (a) and (b) with the polyimide resin causes yellowing and haze even in an environment where the temperature and humidity fluctuate (particularly in a high temperature and high humidity environment). It suppresses the decrease of the resin and has excellent durability. Further, since the film of the present invention is formed by using a polyimide resin as a main component, it is excellent in bending property (flexibility). Therefore, by using such a film as a front plate of a display device such as a tablet PC or a smartphone, flexibility of these display devices can be achieved.

The above mechanism is speculative, and the present invention is not bound by the above mechanism.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments. Further, in the present specification, "X to Y" indicating a range includes X and Y and means "X or more and Y or less". Unless otherwise specified, operations and physical properties are measured under the conditions of room temperature (20 to 25 ° C.) / relative humidity of 40 to 50% RH.

[Film (polyimide film)]
The film (polyimide film) of the present invention essentially contains a polyimide resin and a metal oxide filler. Here, the thickness of the film (polyimide film) is not particularly limited, but the thickness of the film (dry film thickness) is preferably in the range of, for example, 1 to 200 μm, particularly 10 to 100 μm. A film having such a film thickness can exhibit sufficient strength and transparency even as a flexible printed circuit board.

Further, the film (polyimide film) of the present invention may have any form, but is preferably long in terms of wide availability. Specifically, the film (polyimide film) of the present invention preferably 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.

(Polyimide resin (polyimide))
The film (polyimide film) of the present invention indispensably contains a polyimide resin (polyimide). Here, the polyimide resin is a resin having an imide structure (hereinafter, also referred to as “polyimide”), and is a polymer containing an imide bond in a repeating unit. The polyimide is preferably formed from a diamine or a derivative thereof and an acid anhydride or a derivative thereof.

Specifically, the polyimide resin is preferably a polyimide resin having a repeating unit represented by the following formula (A) (hereinafter, also referred to as "polyimide (A)"). In the following formula (A), the _{portion containing (-C (= O)) 2-} R- (C (= O)-) ₂ is a portion derived from an acid anhydride or a derivative thereof, and = N-AN. The portion containing = is a portion derived from diamine or a derivative thereof.

In the above formula (A), R consists of an aromatic hydrocarbon ring, an aromatic heterocycle, or a tetravalent group derived from an aliphatic hydrocarbon having 4 to 39 carbon atoms or an alicyclic hydrocarbon, or a combination thereof. Represents a tetravalent group. Here, when R is a combination of any two or more of the above, these are -O-, -SO _2- , -CO-, -CH _2- , -C (CH ₃ ) ₂ -,-. OSI (CH ₃ ) _2- , -C ₂ H ₄ O-, -CF _2- , -C (CF ₃ ) _2- , -OSI (CF ₃ ) _2- , -C ₂ F ₄ O- and -S- It may be linked via at least one binding group selected from the group consisting of. Further, at least one hydrogen atom in the aromatic hydrocarbon ring represented by R, the aromatic heterocycle, the aliphatic hydrocarbon having 4 to 39 carbon atoms or the alicyclic hydrocarbon is a halogen atom (for example, a fluorine atom). , Chlorine atom, iodine atom, bromine atom, preferably fluorine atom) or alkyl group having 1 to 8 carbon atoms (eg, methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl Group, isobutyl group, isobutyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, etc.) or alkyl halide groups thereof (for example, monofluoromethyl group (-CFH _2)). ), Difluoromethyl group (-CF ₂ H), trifluoromethyl group (-CF ₃ ), monofluoroethyl group (-CFH-CH ₃ , -CH _2- CFH ₂ ), difluoroethyl group (-CF _2- CH) ₃ , -CFH-CFH ₂ , -CH _2- CF ₂ H), etc.) may be substituted.

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 naphthalene ring, a triphenylene ring, o-. Terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaphthene ring, coronen ring, fluorantrene ring, naphthalene ring, pentacene ring, perylene ring, pentaphene ring, picene ring, pyrene ring, pyranthrene ring, anthra entre Benzene ring and the like.

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, an oxaziazole ring and a triazole ring. 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 (consisting of carbazole ring) Any one or more of the carbon atoms constituting the dibenzosilol ring, dibenzofuran ring, dibenzothiophene ring, benzothiophene ring or dibenzofuran ring are nitrogen. Atomically replaced ring, benzodifuran ring, benzodithiophene ring, aclysin ring, benzoquinoline ring, phenazine ring, phenanthridine ring, phenanthroline ring, cyclazine ring, kindrin ring, tepenidin ring, quinindrin ring, triphenodithiazine ring, Triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, naphthofuran ring, naphthophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, anthrathiophene ring, anthradithiophene ring, thianthrene Examples thereof include a 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-triyl group and octane-1,1,8,8-triyl group. Examples include groups such as decane-1,1,10,10-triyl 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-diphenylcyclohexane Examples include groups such as -1,2,4,5-tetrayl groups.

Of these, R is preferably a group represented by the following structural formula.

More preferably, R is a group represented by the following structural formula.

Particularly preferably, R is a group represented by the following structural formula.

Further, in the above formula (A), A is a divalent group consisting of a divalent aliphatic hydrocarbon having 2 to 39 carbon atoms, an alicyclic hydrocarbon, a divalent group derived from an aromatic hydrocarbon, or a combination thereof. Represents the group of. Here, when A is a combination of any two or more of the above, these are -O-, -SO _2- , -CO-, -CH _2- , -C (CH ₃ ) _2- , -OSi. (CH ₃ ) _2- , -C ₂ H ₄ O-, -CF _2- , -C (CF ₃ ) _2- , -OSI (CF ₃ ) _2- , -C ₂ F ₄ O- and -S- It may be linked via at least one binding group selected from the group. Further, at least one hydrogen atom in the aromatic hydrocarbon ring represented by R, the aromatic heterocycle, the aliphatic hydrocarbon having 4 to 39 carbon atoms or the alicyclic hydrocarbon is a halogen atom (for example, a fluorine atom, Chlorine atom, iodine atom, bromine atom, preferably fluorine atom) or alkyl group having 1 to 8 carbon atoms (eg, methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group) , Isobutyl group, isobutyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, etc.) or alkyl halide groups thereof (for example, monofluoromethyl group (-CFH ₂ )). , Difluoromethyl group (-CF ₂ H), trifluoromethyl group (-CF ₃ ), monofluoroethyl group (-CFH-CH ₃ , -CH _2- CFH ₂ ), difluoroethyl group (-CF _2- CH ₃₎ , -CFH-CFH ₂ , -CH _2- CF ₂ H), etc.).

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

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

Examples of the divalent alicyclic hydrocarbon group having 2 to 39 carbon atoms represented by A 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 A include a group represented by the following structural formula.

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

Of these, A is preferably a group represented by the following structural formula.

More preferably, A is a group represented by the following structural formula.

Even more preferably, A is a group represented by the following structural formula.

Particularly preferably, A is a group represented by the following structural formula.

Of these, the polyimide resin preferably has at least one of a fluorine atom and a saturated alicyclic group. By introducing fluorine or an alicyclic structure, the polyimide resin can be firmly immobilized on the surface of the metal oxide filler, and the CT complex formability of the polyimide resin can be reduced (hence, yellowing at high temperature and high humidity). Can be suppressed more effectively). More preferably, the polyimide resin has a fluorine atom. By using a polyimide resin having a fluorine atom, the fluorine atom portion and the hydroxyl group on the surface of the metal oxide filler are bonded via a dipole-dipole interaction, so that the polyimide resin is even stronger on the surface of the metal oxide filler. Can be fixed to. Therefore, even under high temperature and high humidity, the rearrangement of molecules in the polyimide resin (hence, CT complex forming property) can be suppressed even more effectively. Therefore, the polyimide resin has the following structure:

R with and the following structure:

It is preferable to have at least one of A having.

When the polyimide resin has a fluorine atom (fluorine polyimide resin), the fluorine content is not particularly limited, but is preferably about 1 to 40% by mass in the film. With such an amount, the obtained film has excellent transparency and is easy to perform heat correction by heat shrinkage.

The method for producing the polyimide resin of the above formula (A) is not particularly limited, and a known method can be applied in the same manner or appropriately modified. For example, a polyimide resin can be produced by reacting an aromatic, aliphatic or alicyclic tetracarboxylic acid or a derivative thereof with a diamine or a derivative thereof to prepare a polyamic acid, and imidizing the polyamic acid. ..

Examples of the derivative of the aliphatic or alicyclic tetracarboxylic acid include aliphatic or alicyclic tetracarboxylic acid esters, aliphatic or alicyclic tetracarboxylic dianhydride and the like. 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 carboxyl groups instead of the anhydride. , A compound in which one or both of these two carboxyl groups are esterified, or an acid chloride in which one or both of these two carboxyl groups are chlorinated is preferably used.

By using such a compound (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 dian, 1,2,4,5-cyclopentanetetracarboxylic dian, and 1,2,4,5-cyclohexanetetracarboxylic dian. , 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-mentioned aliphatic tetracarboxylic acids. Examples of the alicyclic tetracarboxylic acid esters include monoalkyl esters, dialkyl esters, trialkyl esters, and tetraalkyl esters of the alicyclic tetracarboxylic acids. 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 and 2,3,5-tricarboxycyclopentylacetic 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 a relatively high salt solubility (for example, in order to increase the molecular weight) is used. It is preferable to use cresol, N, N-dimethylacetamide, γ-butyrolactone, N-methyl-2-pyrrolidone, etc.). However, even in a 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 diamine salt have a relatively weak bond. Since it is tied with, it is easy to increase the molecular weight, and it is easy to obtain a flexible film.

Examples of the aromatic tetracarboxylic acid include 4,4'-biphthalic dianhydride, 4,4'-(hexafluoroisopropyridene) diphthalic anhydride, and 2,3,3', 4'-biphenyltetracarboxylic dian. Dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 4- (2,5-dioxotetracarboxylic dianhydride) -1, 2,3,4-Tetrahydronaphthalene-1,2-dicarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,4'-oxydiphthalic dianhydride, 3,4 , 9,10-Perylenetetracarboxylic dianhydride (Pigment Red 224), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2-bis (4- (3,4-dicarboxyphenoxy) ) Phenyl) Propane dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene, 9,9-bis [4- (3,4-dicarboxyphenoxy) -phenyl] fluorene anhydride and the like. Be done.

In addition, for example, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, Tricyclo [6.4.0.02,7] dodecane-1,8: 2,7-tetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene- 1,2-dicarboxylic 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'-benzophenone tetracarboxylic acid, 2,2', 3, 3'-benzophenone tetracarboxylic 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 derivatives thereof (particularly dianhydride); ethylene tetracarboxylic acid and the like. Examples thereof include aliphatic tetracarboxylic acids having 1 to 3 carbon atoms and derivatives thereof (particularly dianhydride).

Examples of the acid dianhydride include 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanedianehydride, biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4'-oxydiphthalic anhydride. Is preferable from the viewpoint of excellent transparency and easy heat correction by heat shrinkage. In addition, from the viewpoint of further suppressing yellowing and turbidity in an environment where temperature and humidity fluctuate (particularly in a high temperature and high humidity environment), 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanedianhydride. Is even more preferable.

The portion (part derived from acid anhydride or its derivative) containing (-C (= O)) _2- R- (C (= O)-) _{2 in the above formula (A) is used by being arbitrarily mixed.} However, the content of the above-mentioned preferable acid dianhydride-derived portion is preferably 50 to 100 mol%, more preferably 80 to 100 mol% of the whole.

As the diamine or a derivative thereof, for example, an aromatic diamine or an isocyanate ester is preferable, and an 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), 2, 2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2,5-diethyl-4,6-dimethylbenzene-1,3-diamine, 4,4'-[isopropyridenebis [(4,4) 1-Phenylene) oxy]] Bisaniline, bis (aminomethyl) norbornan and the like can be mentioned.

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, Norbornan Diamine, siloxane Diamine, 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 having the following structure may be 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 or the same. There may be.

Specific examples of the alkyl group or aryl group having 1 to 12 carbon atoms as R ¹ and R ² include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, phenyl, benzyl, naphthyl, and methylphenyl. Biphenyl and the like can be mentioned.

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 preferred.

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.

Diamines include 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2,5-diethyl-4,6-dimethylbenzene-1,3-diamine, 4,4'-[isopropi]. Redenbis [(4,1-phenylene) oxy]] Bisaniline, bis (aminomethyl) norbornane is preferable. In addition, from the viewpoint of further suppressing yellowing and turbidity in an environment where temperature and humidity fluctuate (especially in a high temperature and high humidity environment), 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl , Bis (aminomethyl) norbornane is more preferred, and 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl is particularly preferred.

The portion (part derived from diamine or its derivative) containing = N-AN = in the above formula (A) may be arbitrarily mixed and used, but the content of the above-mentioned preferable portion derived from diamine is the whole. It is preferably 20 to 80 mol%, and more preferably 40 to 60 mol%.

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

Polyamic acid is prepared by reacting the above tetracarboxylic acid or its derivative with diamine or its derivative. Specifically, the polyamic acid is obtained by polymerizing at least one of the tetracarboxylic acids and at least one of the diamines in a suitable solvent.

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, a polyamic acid can be obtained by sequentially adding a tetracarboxylic dianhydride and a diamine compound to a solvent and stirring the mixture at an appropriate temperature.

The amount of the diamine compound is not particularly limited, and is preferably an amount that gives the above-mentioned preferable polyimide composition. Specifically, the amount of the diamine compound is usually 0.8 mol or more, preferably 1 mol or more, with respect to 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.

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.

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 35 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, a polyamic acid can be obtained at low cost and in good yield.

As the terminal group of the polyamic acid, the acid anhydride group and the 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.

Further, when the terminal group is an amine terminal, the amino group can be prevented from remaining at the terminal by sealing the terminal amino group with a monofunctional acid anhydride. 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.

Next, a method of heating the polyamic acid (preferably in the form of a solution) obtained above to imidize the polyamic acid (thermal imidization method), or adding a ring-closing catalyst (imidization catalyst) to the polyamic acid solution. The polyimide resin can be obtained by a method of imidizing the polyamic acid (chemical imidization method).

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). As for the conversion method), the reaction kettle for polymerizing the polyamic acid from the acid anhydride and the diamine may be continuously imidized in the reaction kettle.

In the thermal imidization method in the reaction vessel, the polyamic acid in the polymerization solvent is used in a temperature range of, for example, 80 to 300 ° C. for 0.1 to 200 hours (preferably 1 to 100 hours, more preferably 3 to 50 hours). Time) Heat treatment to allow imidization to proceed. 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 a solvent.

Further, in the thermal imidization method, an azeotropic solvent can be added to the polymerization solvent in order to efficiently remove 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 closure 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 the molecular weight is less likely to decrease due to hydrolysis over time as compared with the polyimide solution. Further, since the imidization reaction has proceeded in advance, for example, in the case of polyimide having an imidization rate of 100%, imidization on the web becomes unnecessary and the drying temperature can be lowered.

Alternatively, the ring-closed polyimide may be reprecipitated and purified using a poor solvent such as methanol 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, it is polymerized and ring-closed with dimethylacedamide, solidified with methanol, dried, then made into a solution containing an additive with dichloromethane, and then cast and dried. As a result, high molecular weight and low temperature drying become possible.

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 isopropanol can also be used as appropriate.

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.

In addition to the above-mentioned polyimide, a polyamide-imide resin (also simply referred to as "polyamide-imide") can also be used. The polyamide-imide used is a polyamide-imide containing a tricarboxylic acid or a tetracarboxylic acid, a dicarboxylic acid as an acid component, and a diamine as a constituent unit as an amine component.

The polyamide-imide used has the following a) to c) as acid components:
a) Tricarboxylic acid; trimellitic acid, diphenyl ether-3,3', 4'-tricarboxylic acid, diphenylsulfone-3,3', 4'-tricarboxylic acid, benzophenone-3,3', 4'-tricarboxylic acid, naphthalene Monoanhydrides such as -1,2,4-tricarboxylic acids, tricarboxylic acids such as butane-1,2,4-tricarboxylic acids, singles such as esters, or mixtures of two or more;
b) Tetracarboxylic acid; 3,3,4', 4'-benzophenonetetracarboxylic acid, 3,3,4', 4'-biphenyltetracarboxylic acid, diphenylsulfone-3,3', 4,4'-tetra Dicarboxylic 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, esterified product, etc. alone or a mixture of two or more; and c) dicarboxylic acid; Adipic acid, azelaic acid, sebacic acid, dicarboxylic acid of cyclohexane-4,4'-dicarboxylic acid, and these monoanoxides and esterified products.

The amine components include 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4'-diaminobiphenyl, and 2,2'-dimethyl-4,4'-diamino. Biphenyl, 2,2'-diethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-diethoxy-4,4'-diaminobiphenyl, p-phenylene Diamine, 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'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfide, 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-amino) Phenoxy) 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-amino) Phenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, tetramethylenediamine, hexamethylenediamine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, cyclohexane-1,4-diamine, diaminosiloxane, 1 , 5-Naphthalenediamine or the corresponding diisocyanates alone, or a mixture of two or more thereof.

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

The molar ratio of the imide bond to the amide bond of the polyamide-imide (imide bond / amide bond (molar ratio)) is preferably 99/1 to 60/40, more preferably 99/1 to 75/25, and even more. It is preferably 90/10 to 80/20. 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.

In addition to the above-mentioned polyimide, the structure represented by the following formula (2) is an essential component, and at least one selected from the groups represented by the formulas (3), (4) and (5). A polyamide-imide resin contained in the molecular chain with the structure as a repeating unit can also be used.

Here, in the formula (3), _{it is preferable that X is SO 2} or a single bond (biphenyl bond), or n = 0. More preferably, X is a bond (biphenyl bond) or n = 0. In the formula (4), Y is preferably a benzophenone type (Y = CO) or a single bond type (biphenyl bond type, Y = binder).

In one preferred embodiment, formula (2) is a repeating unit from trimellitic anhydride and 1,5-naphthalenedi isocyanate, formula (3) is a repeating unit from terephthalic acid and 1,5-naphthalenedi isocyanate, formula (4). ) Is a repeating unit from biphenyltetracarboxylic acid dianhydride or benzophenone tetracarboxylic acid dianhydride and 1,5-naphthalene diisocyanate, and the content ratio is the 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, as described above. For reasons such as ensuring the reliability of peel strength (adhesive strength), production by the isocyanate method is preferable. It is also industrially preferable because the solution at the time of polymerization can be applied as it is.

In addition to the above-mentioned polyimide, a polyamide-imide resin containing the following formula (6) as a constituent unit can also be used.

Examples of the diamine component that the polyamideimide resin can contain include p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 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, 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-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, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4-methyl-1,3-phenylenediamine, 3,3'-diethyl-4,4'-diamino Biphenyl, 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, si) S 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] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantan, 4,4'-methylenebis (2-methylcyclohexyl) Amine), 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, Alone such as 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, or a mixture of two or more kinds, or a corresponding diisocyanate. Etc. alone or a mixture of two or more kinds can be used as a 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, cis, 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 the diamine component.

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

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.

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 cm 3} / g or more and 2.5 cm ³ / g or less in logarithmic viscosity at 30 ° C. in N-methyl-2-pyrrolidone (polymer concentration 0.5 g / cm ^3). It is preferable that it has a molecular weight corresponding to, and more preferably, it has a molecular weight corresponding to 0.5 cm ³ / g or more and 2.0 cm ³ / g or less. 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 2.5 cm ³ / g or less, the solution viscosity does not become too high, and the molding process becomes easy.

In addition to the above-mentioned polyimide, polyetherimide can also be used. Here, the polyetherimide is a thermoplastic resin containing an aromatic nucleus bond and an imide bond in its structural unit, and is not particularly limited. Specifically, the following formula (8) or the following formula (9) It is preferably a polyetherimide having a repeating unit having a structure represented by.

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 (registered trademark) 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)] Polyetherimide having a polycondensation of diphthalic acid dianhydride and m-phenylenediamine and having a 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.

In addition to the above-mentioned polyimide, a polyesterimide resin can also be used. Here, the polyesterimide resin is not particularly limited, but from the viewpoint of transparency and heat resistance, it is preferable that the polyesterimide structure represented by the following formula (10) is contained in the constituent unit.

In the above formula (10), R ₁ preferably represents a divalent group having a structure represented by the formula (11), the formula (12) or the formula (13).

In the above formula (11), R independently represents a divalent chain aliphatic group, a cyclic aliphatic group or an aromatic group, and a plurality of Rs may be identical to each other. It may be different. 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 may be "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 divalent hydroxy groups".

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, polypropylene glycol, and the like. 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 various polyhydric alcohols 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, cyclohexanedimethanol , Neopentyl hydroxypiparic acid ester, ethylene oxide adduct and propylene oxide adduct of bisphenol A, ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, 1,9-nonanediol, 2-methyloctanediol, Polyether polyols such as 1,10-dodecanediol, 2-butyl-2-ethyl-1,3-propanediol, tricyclodecanedimethanol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol 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 the biphenyl structure", "Compounds having two hydroxy groups in the 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, tricyclodecanedimethanol, 1,4-dihydroxycyclohexane, 1,3-Dihydroxycyclohexane, 1,2-dihydroxycyclohexane, 1,3-adamantandiol, dicyclopentadiene dihydrate, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5- Carboxyl group-containing diols such as dihydroxybenzoic 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.

As an example of the "compound having two hydroxy groups in the naphthalene skeleton", 2,6-naphthalenediol, 1,4-naphthalenediol, 1,5-naphthalenediol, 1,8-naphthalenediol and the like can be used.

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. When the number average molecular weight is in the above range, hygroscopicity, flexibility, mechanical properties, and colorless transparency can be sufficiently exhibited. The number average molecular weight is a value measured by gel filtration chromatography (GPC).

The polycarbonate diol may be a polycarbonate diol (copolymerized polycarbonate diol) having a plurality of types of alkylene groups in the 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.) Claret 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 T5652 (Asahi Kasei) Polycarbonate diols manufactured by Chemicals Co., Ltd .: 1,5-pentanediol / 1,6-hexanediol, number average molecular weight of about 2000) and the like can be mentioned. 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.

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

In the above formula (12), R ₃ is a direct bond (bonder), an alkylene group (-C _n H _2n- ), a perfluoroalkylene group (-C _n F _2n- ), an ether bond (-O-), Ester bond (-COO-), carbonyl group (-CO-), sulfonyl group (-S (= O) _2- ), sulfinyl group (-SO-), sulfenyl group (-S-), carbonate group (-S-) OCOO-), or represents a fluorenylidene 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-naphthalenediol, 1,4-naphthalenediol, 1,5-naphthalenediol, 1,8-naphthalenediol 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.

Next, a divalent group having a structure represented by the formula (13) will be described below.

In the above formula (13), R ₄ is a direct bond (bonder), an alkylene group (-C _n H _2n- ), a perfluoroalkylene group (-C _n F _2n- ), an ether bond (-O-), Ester bond (-COO-), carbonyl group (-CO-), sulfonyl group (-S (= O) _2- ), sulfinyl group (-SO-), sulfenyl group (-S-), carbonate group (-S-) OCOO-), or represents a fluorenylidene 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, halogen or alkyl group.

Specific examples of the divalent group having the structure represented by the formula (13) are not particularly limited, but are dicyclohexyl ether skeleton, dicyclohexylsulfone skeleton, hydrogenated bisphenol A skeleton, hydrogenated bisphenol F skeleton, hydrogenated bisphenol A. The skeleton of the ethylene oxide adduct of the above, the skeleton of the propylene oxide adduct of hydrogenated bisphenol A, and the like can be mentioned.

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) of diamine, diisocyanate, or the like.

The polyesterimide resin in the present embodiment 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} each independently a divalent chain aliphatic group is not particularly limited as long as it is a divalent cycloaliphatic radical, or a divalent aromatic group. 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), R 2 _'is a divalent group having a structure represented by the following formula (16).

_{Further, R 2} in the above formula (10) is preferably a divalent group having a structure represented by the following formula (15) from the viewpoint of a balance between heat resistance, flexibility, low hygroscopicity and the like. ..

In the above formula (15), R ₅ is a direct bond (bonder), an alkylene group (-C _n H _2n- ), a perfluoroalkylene group (-C _n F _2n- ), an ether bond (-O-), It represents an 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.

The R _{2 'in} formula (14), heat resistance, flexibility, from the viewpoint of the balance of the low hygroscopicity, is preferably a divalent group having a structure represented by the following formula (16).

In the above formula (16), _{R 5} 'is a direct bond (connector), an alkylene group _{(-C n H 2n} -), perfluoroalkylene group _{(-C n F 2n} -), ether bond (-O-) , Esther bond (-COO-), carbonyl group (-CO-), sulfonyl group (-S (= O) _2- ), sulfinyl group (-SO-) or 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 '~X} 16' can be the same or different and each represents hydrogen, halogen or alkyl group.

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.

Diamine component or the corresponding diisocyanate component to that of the R _{2 'R 2} and formula (14) in equation (10) may or may not be the same. It is preferably the same, based on the preferred manufacturing method described below.

R ₂ and R _{2 'About} diamine component or the corresponding diisocyanate component thereto as a basic skeleton is 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) phenyl) Examples thereof include enyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, and diaminoterphenyl. Further, these may be used in combination of two or more.

Further, examples of the "cyclic aliphatic diamine or the corresponding cyclic aliphatic diisocyanate" 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) (trans, cis, 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] 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.

Heat resistance, flexibility, low hygroscopicity such as the balance, preferred component as the diamine component or the corresponding diisocyanate component to that of the R _{2 'R 2} and formula (14) in equation (10) is illustrated 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.

(Metal oxide filler)
The film (polyimide film) of the present invention indispensably contains a metal oxide filler in addition to the polyimide resin. As a result, the polyimide resin has a metal oxide filler via a hydrogen bond between its own carbonyl group (-C (= O)-) and a functional group existing on the surface of the metal oxide filler or a dipole-dipole interaction. It is immobilized on the surface, and rearrangement of molecules in the resin (hence, CT complex forming property) can be suppressed. Therefore, the film formed by mixing the metal oxide filler with the polyimide resin suppresses yellowing and haze reduction even in an environment where the temperature and humidity fluctuate (particularly, a high temperature and high humidity environment), and is excellent in durability. The content of the metal oxide filler is not particularly limited, but is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, and 1 to 10% by mass with respect to the polyimide resin. It is particularly preferably by mass%. A film containing a polyimide resin and a metal oxide filler in such a ratio can more effectively suppress yellowing and turbidity in a high temperature and high humidity environment, and can provide high visibility even under such severe conditions. Can be demonstrated.

Here, the metal oxide filler has (a) an aspect ratio (major axis / minor axis) of 100 to 3000 and an average diameter of 1 to 10 nm, and (b) a sulfonic acid on the surface of the metal oxide filler. having at least one group selected from the group consisting of; (n = 1 or _{2 -P (= O) (OH} ) 3-n) group _(-SO 3 H), carboxyl (-COOH) and phosphate groups is selected from the group consisting of n = 1 or 2); a compound (sulfonic acid group _(-SO 3 H), carboxyl (-COOH) and phosphate group _{(-P (= O) (OH} ) 3-n It is surface-modified with a compound having at least one group). In this specification, "metal oxide surface sulfonic acid group _(-SO 3 H) of the filler, a carboxyl group (-COOH) and phosphate group _{(-P (= O) (OH} ) 3-n; n = at least a compound having an one group "that is selected from the group consisting of 1 or 2)," metal oxide filler, a sulfonic acid group (-SO 3 _H), carboxyl (-COOH) and phosphate groups (Surface-modified with a compound having at least one group selected from the group consisting of (-P (= O) (OH) _3-n ; n = 1 or 2) "or" Metal oxide filler is surface-modified. The surface is modified with an agent. "

In the above (a), the metal oxide filler has an aspect ratio (major axis / minor axis) of 100 to 3000. Here, when the aspect ratio is less than 100, there are too few bonding points (interaction points) between the carbonyl group (-C (= O)-) of the polyimide resin and the hydroxyl group (-OH) on the surface of the metal oxide filler. Therefore, the polyimide resin cannot be sufficiently immobilized on the filler and turns yellow under high temperature and high humidity (see, for example, film 7 below). On the other hand, when the aspect ratio exceeds 3000, the visibility of the filler is extremely increased, and the film itself immediately after production becomes yellowish or turbid (see, for example, film 6 below). The aspect ratio (major axis / minor axis) of the metal oxide filler is preferably considered in consideration of the suppression of deterioration of characteristics (for example, yellowing, haze) under high temperature and high humidity and a better balance with the visibility of the film. It is 110 to 2000, more preferably 120 to 1000.

In the present specification, the aspect ratios of the metal oxide filler and the metal oxide filler precursor described later are values measured according to the following method. That is, at least 100 metal oxide fillers (samples) were randomly selected, photographed by a scanning electron microscope (SEM), and obtained from the obtained image (SEM image) in major axis (x) and minor axis (SEM image). Each of y) is measured, a value (x / y) obtained by dividing the major axis (x) by the minor axis (y) is calculated, and the average value thereof is defined as an “aspect ratio”. Of the short and long sides of the circumscribed rectangle when a circumscribed rectangle (circumscribed rectangle) is drawn for each filler, the length of the short side is defined as the minor axis, and the length of the long side is defined as the major axis. Generally, the major axis (x) and minor axis (y) of the metal oxide filler correspond to the average length and the average diameter, respectively.

The metal oxide filler has an average diameter of 1 to 10 nm. Here, if the average diameter is less than 1 nm, sufficient hardness (toughness) cannot be imparted to the film. On the other hand, when the diameter exceeds 10 nm, the filler is too thick and the visibility is extremely improved, and the film itself immediately after production becomes yellowish or turbid (see, for example, film 5 below). Considering a better balance between the hardness (toughness) of the film and the visibility of the film, the average diameter of the metal oxide filler is preferably more than 1 nm and less than 10 nm, more preferably 4-8 nm. The average diameter is the minor diameter (y) in the "aspect ratio".

Whether or not the produced film satisfies the above (a) can be evaluated by a known method. For example, it can be confirmed by evaluating the cross section of the film in the same manner as described above.

With respect to the above (b), the metal oxide surface sulfonic acid group _(-SO 3 H) of the filler, a carboxyl group (-COOH) and phosphate group _{(-P (= O) (OH} ) 3-n; n = 1 or 2) is selected from the group consisting of with a compound having at least one group (sulfonic acid group _(-SO 3 H), carboxyl (-COOH) and phosphate groups (-P (= O) ( OH) _3-n ; surface-modified with a compound having at least one group selected from the group consisting of n = 1 or 2)). Preferably, the surface modifier has either a sulfonic acid group, a carboxyl group or a phosphate group. Here, when the surface of the metal oxide filler has a compound having no specific functional group (surface modified with the compound having no specific functional group), the functional group and the carbonyl group of the polyimide resin ( Since the dipole-dipole interaction does not occur with −C (= O) −), the polyimide resin is not sufficiently immobilized on the surface of the metal oxide filler. Therefore, although yellowness and turbidity do not occur in the film at the initial stage, the molecules in the polyimide resin are rearranged (hence CT complex forming property) under high temperature and high humidity, and yellowishness and turbidity occur. (For example, see film 9 below).

Whether or not the produced film satisfies the above (b) can be evaluated by a known method. For example, by thinning the film and performing elemental analysis of the cross section with a transmission electron microscope (TEM), it can be confirmed that sulfonic acid groups, carboxyl groups and phosphate groups are present on the surface of the particles.

Hereinafter, preferred forms of the surface modifier according to the present invention will be described, but the present invention is not limited to the following forms.

Compounds having a sulfonic acid group (-SO 3 _H) is not particularly limited as long as it has a sulfonic acid group, such as methanesulfonic acid, alkylsulfonic acids such as ethanesulfonic acid, benzenesulfonic acid, p- toluene Examples include aromatic sulfonic acids such as alkylbenzene sulfonic acids such as sulfonic acids, styrene sulfonic acids and dodecylbenzene sulfonic acids, alkali metal and ammonium salts of these sulfonic acids, and esters of these sulfonic acids with lower alcohols. ..

The compound having a carboxyl group (-COOH) is not particularly limited as long as it has a carboxyl group, and for example, a monocarboxylic acid such as formic acid, acetic acid and propionic acid, and a dicarboxylic acid such as citric acid, fumaric acid and maleic acid. , Hydroxycarboxylic acids such as lactic acid, malic acid and citric acid, aromatic carboxylic acids such as benzoic acid and salicylic acid, and salts thereof.

The compound having a phosphate group (-P (= O) (OH) _3-n ; n = 1 or 2) is not particularly limited as long as it has a phosphate group, and for example, ethyl acid phosphate, butyl acid phosphate, etc. Butylpyrophosphate, butoxyethyl acid phosphate ((C ₄ H ₉ OC ₂ H ₄ O) _n- P (= O) (OH) _3-n ; n = 1, 2), 2-ethylhexyl acid phosphate, oleyl acid phosphate , Tetracosyl acid phosphate, phenyl acid phosphate, diphenyl acid phosphate, benzyl acid phosphate, n-octyl acid phosphate, (2-hydroxyethyl) methacrylate acid phosphate, dibutyl phosphate, bis (2-ethylhexyl) phosphate, lauryl acid Examples thereof include phosphate, stearyl acid phosphate, ethylene glycol monoethyl ether acid phosphate, triethylene glycol monoethyl ether acid phosphate, and triethylene glycol monobutyl ether acid phosphate.

Of these, the surface modifier preferably has an aryl group. According to this form, a π-π interaction between the aromatic group (aryl group) of the polyimide resin and the aryl group of the surface modifier is formed, further suppressing the rearrangement of molecules in the resin (hence the CT complex forming property). it can. Therefore, it is possible to suppress changes in characteristics (particularly, turbidity (increase in Δ haze)) due to changes in the temperature and humidity environment of the film (particularly in a high temperature and high humidity environment) (see, for example, comparison between film 1 and film 11 below). .. That is, according to a preferred embodiment of the present invention, a sulfonic acid group _(-SO 3 H), carboxyl (-COOH) and phosphate groups; from _{(-P (= O) (OH} ) 3-n n = 1 or 2) A compound having at least one group selected from the above group (surface modifier) has an aryl group. Specifically, aromatic sulfonic acids such as benzenesulfonic acid, p-toluenesulfonic acid, styrenesulfonic acid, and dodecylbenzenesulfonic acid, alkali metal and ammonium salts of these sulfonic acids, and these sulfonic acids and lower alcohols. Esters with; aromatic carboxylic acids such as benzoic acid and salicylic acid, and salts thereof are preferred.

The metal oxide constituting the metal oxide filler is not particularly limited. For example, silica (silicon dioxide), magnesium oxide, zinc oxide, lead oxide, alumina (aluminum oxide), boehmite, pseudo-boehmite, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, oxidation. Examples thereof include selenium, iron oxide, zirconia (zirconium oxide), germanium oxide, tin oxide, titanium oxide, niobium oxide, molybdenum oxide and vanadium oxide. The metal oxide may be used alone or in a mixture of two or more. Of these, alumina, boehmite, pseudo-boehmite, silica, and zirconia are preferable, alumina and boehmite are more preferable, and alumina is particularly preferable, in consideration of hydrogen bonding property with the carbonyl group of the polyimide resin. That is, according to the preferred embodiment of the present invention, the metal oxide is at least one selected from the group consisting of alumina, boehmite, pseudoboehmite, silica, and zirconia. Also, according to a more preferred embodiment of the invention, the metal oxide is alumina or boehmite. Further, according to a particularly preferable form of the present invention, the metal oxide is alumina.

The method for producing the metal oxide filler is not particularly limited, and a known method such as JP-A-2016-44114 can be applied in the same manner or appropriately modified. For example, the metal oxide raw material is hydrolyzed in an acid aqueous solution to obtain alumina hydrate, the produced alcohol is distilled off, and then the metal oxide filler precursor (aqueous metal oxide sol) is obtained. A method of treating this with a surface modifier (dehydration treatment) or the like can be used. The above method will be described below. The present invention is not limited to the following forms.

First, the metal oxide raw material is hydrolyzed in an aqueous acid solution to obtain alumina hydrate. Here, the metal oxide raw material is not particularly limited, but alkoxides, oligomers, acetoacetates, and the like of the metals constituting the metal oxide can be used. Specifically, aluminum alkoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum sec-butoxide, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrasec-butoxysilane, tetra n-butoxysilane, tetra. Metal alkoxides such as isopropoxytitanium, tetra-n-butoxytitanium, tetra-t-butoxytitanium, tetra-n-butoxyzaldehyde, zirconium alkoxide; cyclic aluminum oligomers, diisopropoxy (ethylacetoacetate) aluminum, tris (ethyl) Acetoacetate) Aluminum and the like. These metal oxide raw materials may be used alone or in a mixture of two or more. Of these metal oxide raw materials, aluminum, silicon or zirconium alkoxides are preferably used, and aluminum, silicon or zirconium alkoxides having 2 to 4 carbon atoms are more preferable.

The acid used for hydrolysis is not particularly limited, but for example, hydrochloric acid, nitric acid, formic acid, acetic acid, propionic acid, butyric acid and the like can be used. Of these, formic acid, acetic acid, propionic acid, and butyric acid are preferable, and acetic acid is more preferable, from the viewpoint of ease of handling. The amount of the acid used is not particularly limited, but is preferably 0.2 to 2.0 mol, more preferably 0.3 to 1.8 mol, with respect to 1 mol of the metal oxide raw material. With such an amount, the metal oxide raw material can be efficiently hydrolyzed to produce a filler having a desired shape (aspect ratio, diameter). The acid may be used in the form of an aqueous solution, and the concentration of the acid at this time is not particularly limited, but is, for example, about 10 to 50% by mass, preferably about 15 to 30% by mass.

The hydrolysis conditions are not particularly limited as long as they can hydrolyze the metal oxide raw material, and can be appropriately selected depending on the type of the metal oxide raw material and the amount of acid used. For example, the hydrolysis temperature is preferably about 50 to 100 ° C. The hydrolysis time is preferably about 10 minutes to 3 hours. Under such conditions, the metal oxide raw material can be efficiently hydrolyzed to produce a filler having a desired shape (aspect ratio, diameter).

The alumina hydrate thus obtained is gelatinized while distilling off the produced alcohol to obtain an aqueous metal oxide sol. Here, the alumina hydrate is in the form of a solution (for example, an aqueous solution), and the alumina hydrate concentration (solid content concentration) at this time is not particularly limited, but is preferably 2 to 15% by mass, for example. , More preferably 3 to 10% by mass. With such a concentration, gelatinization can be performed efficiently.

The deflocculation conditions are not particularly limited as long as they can deflocate the alumina hydrate. For example, the gelatinization temperature is preferably 100 to 200 ° C, more preferably 110 to 180 ° C. The gelatinization time is preferably 1 to 20 hours, more preferably 2 to 15 hours. Under such conditions, the alumina hydrate can be efficiently gelatinized to produce a filler having a desired shape (aspect ratio, diameter).

From the above, a metal oxide filler precursor (aqueous metal oxide sol) can be obtained. Here, the shape of the metal oxide filler precursor is not particularly limited, but is substantially the same as that of the final product, the metal oxide filler. That is, the average diameter of the metal oxide filler precursor is 1 to 10 nm, preferably more than 1 nm and less than 10 nm, more preferably 4 to 8 nm. Similarly, the aspect ratio of the metal oxide filler precursor is 100-3000, preferably 110-2000, more preferably 120-1000.

Next, the metal oxide filler precursor (aqueous metal oxide sol) is treated with a surface modifier.
Specifically, an organic solvent and a surface coating agent are added to and mixed with the metal oxide filler precursor (aqueous metal oxide sol) obtained above, and then solvent substitution is performed. The method of solvent substitution is not particularly limited, and for example, a method using an ultrafiltration membrane, a dehydration method using the boiling point difference between water and an organic solvent, and the like can be used. Since the surface modifier is the same as described above, description thereof will be omitted here.

The amount of the surface modifier used is not particularly limited as long as the metal oxide filler precursor can be surface-modified (the surface modifier is arranged on the surface of the metal oxide filler). Specifically, the amount of the surface modifier used is preferably 1 to 100% by mass, more preferably 10 to 20% by mass, based on the metal oxide filler precursor. With such an amount, the metal oxide filler precursor can be surface-modified to a desired degree (a desired degree of surface modifier can be arranged on the surface of the metal oxide filler).

The organic solvent that can be used for surface modification is not particularly limited, and can be appropriately selected depending on the type of metal oxide filler precursor and surface modifier. Specifically, benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, triethylbenzene, cyclohexane, cyclohexene, decahydronaphthalene, dipentene, pentane, hexane, heptane, octane, nonane, decane, ethylcyclohexane, methylcyclohexane, p. -Mentane, dipropyl ether, dibutyl ether, anisole, butyl acetate, amyl acetate, and methylisobutylketone and the like. These solvents may be used alone or in the form of a mixture of two or more. The amount of the solvent is also not particularly limited, but the total concentration of the metal oxide filler precursor and the surface modifier is, for example, about 1 to 20% by mass, preferably about 2 to 10% by mass.

The surface modification (dehydration treatment) conditions are not particularly limited as long as the metal oxide filler precursor can be surface-modified to a desired degree with a surface modifier. Under such conditions, the metal oxide filler precursor can be treated with a surface modifier to produce a filler having a desired shape (aspect ratio, diameter).

The film (polyimide film) of the present invention essentially contains a polyimide and a metal oxide filler, but may contain other additives in addition to these. The other additives are not particularly limited, and the same additives as before can be used. Specific examples thereof include matting agents, ultraviolet absorbers, antioxidants, retardation control agents, and peeling accelerators.

Of these, the use of a matting agent can improve handleability. Specifically, inorganic fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate and the like and cross-linking. Examples include polymers. Of these, silicon dioxide is preferable from the viewpoint of reducing the haze of the film. The matting agent may be used alone or in combination of two or more. When the matting agent is fine particles, the primary average particle size of the fine particles is not particularly limited, but is preferably 1 to 20 nm, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm. At this time, the fine particles preferably form secondary particles having a particle size of 0.1 to 5 μm and are contained in the polyimide, and the average particle size is preferably 0.1 to 2 μm, more preferably 0.2. It is ~ 0.6 μm. As a result, unevenness having a height of about 0.1 to 1.0 μm is formed on the film surface, whereby appropriate slipperiness can be imparted to the film surface. In the present specification, the primary average particle size of fine particles is measured by observing the particles with a transmission electron microscope (magnification: 500,000 to 2,000,000 times), observing 100 particles, measuring the particle size, and averaging the particles. The value is taken as the primary average particle size.

Light resistance can be improved by using an ultraviolet absorber. The ultraviolet absorber aims to improve the light resistance by absorbing ultraviolet rays having a wavelength 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%. It is preferably 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 (registered trademark) 109, chinubin (registered trademark) 171 and chinubin (registered trademark). ) 234, Tinubin (registered trademark) 326, Tinubin (registered trademark) 327, Tinubin (registered trademark) 328, Tinubin (registered trademark) 928 and other Tinubin (registered trademark), all of which are BASF Japan Co., Ltd. It is a commercially available product manufactured by the company 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. Specific examples thereof include Chinubin (registered trademark) 400 and Chinubin (registered trademark) 405 manufactured by BASF Japan Ltd. and LA-46 manufactured by ADEKA Corporation. The above-mentioned ultraviolet absorber may be used alone or in combination of two or more. 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. Those that do not dissolve in an organic solvent, such as inorganic powder, are dispersed in an organic solvent and a polyimide film using a dissolver or sand mill, and then added to the dope. 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 resin. Is preferable, and the range of 0.6 to 4% by mass is more preferable.

When an electronic device or the like is placed in a high humidity and high temperature state, the polyimide film may be deteriorated, but deterioration can be prevented by using an antioxidant. 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, and 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 above-mentioned antioxidants may be used alone or in combination of two or more. The amount of the antioxidant added is not particularly limited, but is preferably in the range of 1% by mass to 1.0% by mass, more preferably 10 to 1000% by mass with respect to the polyimide resin.

By using the phase difference control agent, the display quality of an image display device such as a liquid crystal display device can be improved. Alternatively, the polyimide film can be imparted with optical compensation ability by forming an alignment film, providing a liquid crystal layer, and combining the polarizing plate protective film and the phase difference derived from the liquid crystal layer. 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 the retardation control agent added is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 1 to 10% by mass with respect to the polyimide resin.

By using a peeling accelerator, the peeling resistance of the polyimide film can be reduced. It is preferable to use a surfactant as a peeling accelerator because the effect is remarkable. As preferable release agents, phosphoric acid ester-based surfactants, carboxylic acid or carboxylic acid salt-based surfactants, 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. 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 resin.

It is needless to say that the other additives contained in the polyimide film of the present invention are not limited to the above, and components generally added to the film may be added in the same manner.

[Manufacturing of polyimide film]
Hereinafter, a specific example of a method for producing a polyimide film will be described. The following form is a preferable form, and the present invention is not limited to the following form.

The method for producing a polyimide film includes a step of dissolving polyimide and a metal oxide filler in a solvent to prepare a dope (dope preparation step), and a step of casting the dope onto a support to form a cast film (a flow film). Casting step), step of evaporating the solvent from the casting film on the support (solvent evaporation step), step of peeling the casting film from the support (peeling step), step of drying the obtained film (first). It includes a step of stretching the film (stretching step), a step of further drying the stretched film (second drying step), and a step of winding up the obtained polyimide film (winding step). When polyamic acid is used instead of polyimide, it is preferable to further have a step (heating step) of heat-treating the stretched film to imidize it.

(Dope preparation process)
In this step, a polyimide, a metal oxide filler and a solvent, and if necessary, other additives are mixed to prepare a dope (main dope). Here, the polyimide, the metal oxide filler, and other additives that may be used if necessary are the same as described above, and thus the description thereof will be omitted here.

The solvent is not particularly limited as long as it can dissolve polyimide and other additives (if necessary), and can be appropriately selected depending on these types. For example, the chlorine-based solvent is dichloromethane, and the non-chlorine-based solvent is methyl acetate, ethyl acetate, amyl acetate, acetone, 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, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n -Propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like can be mentioned. The above-mentioned solvent may be used alone or in combination of two or more. Of these, it is preferable to use a solvent having a boiling point of 80 ° C. or lower. Specifically, dichloromethane (40 ° C.), ethyl acetate (77 ° C.), methyl ethyl ketone (79 ° C.), tetrahydrofuran (66 ° C.), acetone (56.5 ° C.), and 1,3-dioxolane (75 ° C.) are preferable. (Note that each in parentheses indicates the boiling point).

Moreover, the said solvent may be used in combination with another solvent (mixed solvent). Here, as the mixed solvent, any solvent that can dissolve polyimide and other additives (if necessary) can be used as long as it does not impair the effects of the present invention. Solvents other than those described above include, for example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, N-methyl. Caprolactam, hexamethylphosphoramide, tetramethylene sulfoxide, dimethyl sulfoxide, m-cresol, phenol, p-chlorophenol, 2-chloro-4-hydroxytoluene, diglyme, triglime, tetraglyme, γ-butyrolactone, cyclopentanone, Epsilon caprolactam, chloroform and the like 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, o-dichlorobenzene, etc. is precipitated by the polyimide according to the present invention and other additives (when added). You may use it to the extent that it does not. As the mixed solvent, one kind may be used alone or two or more kinds may be used in combination.

Moreover, 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.

The amount of the solvent used is not particularly limited. Considering the ease of casting in the next step, the solid content concentration (total amount of metal oxide filler and solvent and other additives (if added)) in the dope (main dope) is preferable. The amount is 1 to 30% by mass, more preferably about 3 to 10% by mass.

Dissolution of polyimide and other additives (when added) is carried out at normal pressure, below the boiling point of the main solvent, pressurized above the boiling point of the main solvent, JP-A-9-95544. Various dissolution methods such as the method of performing by the cooling dissolution method described in JP-A, JP-A-9-95557, JP-A-9-95538, and the method of performing at high pressure described in JP-A-11-21379. Can be used.

The prepared dope may be guided to a filter by a liquid feed pump or the like and filtered. As the filter medium used for filtration, a metal firing filter, a metal non-woven fabric filter, a cotton cloth filter, a paper filter and the like can be appropriately used. Further, the dope and the metal oxide filler may be filtered separately before the addition, or may be filtered after the addition. Regarding the temperature at the time of filtration, for example, when the main solvent of the doping is dichloromethane, the gel-like foreign matter in the doping is removed by filtering the doping at a temperature of + 5 ° C. or higher at the boiling point of the dichloromethane at 1 atm. Can be done. 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 dope 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 obtained by pelletizing polyimide or other compounds in advance can also be used.

(Cushion film forming process)
In this step, the dope (main dope) prepared in the above (doping preparation step) is cast on the support to form a casting film. For example, the position of the dope on a metal support such as a stainless belt or a rotating metal drum that feeds the dope to the die through a liquid feed pump (eg, a pressurized metering gear pump) and transfers it indefinitely. Dope is cast from the die into (eg, endless belt casting device).

The metal support in casting is preferably a mirror-finished surface, and the support is a stainless steel belt or a drum whose surface is plated with a casting, or a metal support such as a stainless steel belt or a stainless steel belt. 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 polyimide is used as the flexible substrate, the polyimide may be wound together with the metal support in which the polyimide is cast.

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 casting film can be increased, but if it is too high, the casting film may foam or the flatness may deteriorate. It is preferably carried out within a temperature 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 lower traveling direction, and the 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.

It is preferable to use a pressure die that can adjust the slit shape of the die base portion 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 step)
In this step, the solvent is evaporated from the casting film on the support. That is, the solvent evaporation step is a pre-drying step performed on the metal support, heating the cast film on the metal support, and evaporating 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.

In the solvent evaporation step, it is preferable to dry the casting film until the residual solvent amount is in 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 specification, the amount of residual solvent is represented by the following formula.

(Peeling process)
In this step, the casting film in which the solvent is evaporated on the metal support in the above (solvent evaporation step) is peeled from the support 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.

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 most preferably in the range of 15 to 40 ° C.

The peeled film may be sent directly to the stretching step, or may be sent to the stretching step after being sent to the first drying step so as to achieve a desired residual solvent amount. 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 30 to 200 ° C. in consideration of the amount of residual solvent, the expansion / contraction rate during transportation, and the like.

(Stretching process)
In this step, the film is stretched. By stretching the film peeled from the metal support in this way, the film thickness, flatness, orientation, etc. of the film can be controlled.

In the manufacturing method according to this embodiment, the film is stretched in the longitudinal direction and / or the lateral 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 amount of residual solvent at the start of stretching is preferably in the range of 0.1 to 200% by mass. When the amount of the residual solvent is in the above range, the effect of improving the flatness by stretching can be obtained, and sufficient film strength can be obtained.

In the production method according to the present embodiment, the film may be stretched in the longitudinal direction and / 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 film in a temperature range of (Tg-200) to (Tg + 100) ° C. with respect to the glass transition temperature (Tg) of the film. Stretching in the above temperature range lowers the haze because the stretching stress can be reduced. Further, it is possible to obtain a polyimide film which suppresses the occurrence of breakage and has excellent flatness and colorability of the film itself. The stretching temperature is more preferably in the range of (Tg-150) to (Tg + 50) ° C. In addition, this step may be performed (simultaneously) in the same step as the above (first drying step).

In the manufacturing method according to the present embodiment, the self-supporting film peeled from the support can be stretched in the longitudinal direction by regulating the traveling speed with a stretching roller.

In order to stretch in the width direction, for example, the width of both ends of the film is held by a clip or a pin in the width direction by performing a total drying treatment or a part of the drying treatment as shown in JP-A-62-46625. 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 clip-type tenter. 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. When 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. When 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 speed is defined by the following formula.

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 stretching 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)
In this step, the stretched film is further 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 more preferably in the range of 40 to 350 ° C. in consideration of the amount of residual solvent, the expansion / contraction rate during transportation, and the like.

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)
In this step, the film obtained above is wound up. Preferably, in the winding step, the obtained film is wound and then cooled to room temperature. The winder may be one that is generally used, 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.

Here, the thickness of the obtained film is not particularly limited, and is preferably in the range of, for example, 1 to 200 μm, particularly 10 to 100 μm.

In the winding step, both ends of the film sandwiched by a clip-type tenter (tenter clip) or the like when stretched and conveyed may be slit. It is preferable that the slit end of the 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 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 preferably performed in consideration of the explosive limit concentration of the solvent in the atmosphere.

(Heating process)
As described above, when polyamic acid is used instead of polyimide, it is preferable to heat-treat the stretched film to imidize it. Specifically, after the winding step, the film dried in the second drying step is further heat-treated in order to promote imidization within the polymer chain molecule and between the polymer chain molecules to improve the mechanical properties. Perform the process.

Further, even when the dope is prepared using polyimide (imidization rate 100%) or the film imidization rate becomes 100% by performing the second drying step, the residual stress of the film is obtained. A heating process is performed for the purpose of alleviating the problem. 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.

The heat treatment conditions are preferably carried out within a temperature range of 200 to 450 ° C. for 30 seconds to 1 hour. Thereby, the dimensional stability of the polyimide film can be improved. In the heating step, if the 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.

If the heating temperature in the second drying step and the heating step exceeds 450 ° C., the energy required for heating becomes very large, so that the manufacturing cost increases and the environmental load increases. Therefore, the heating temperature is 450 ° C. It is preferable to make the following.

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.

As described above, the film (polyimide film) of the present invention can be obtained. The polyimide film of the present invention has excellent transparency (high total light transmittance), low yellowness (low initial yellowness and low initial YI), and low turbidity (low initial haze). Specifically, the total light transmittance of the polyimide film is preferably 80% or more, more preferably 84% or more, and further preferably 85% or more. By setting the total light transmittance to 80% or more, there is an advantage that the range of application to various electronic devices as a film for optical applications is widened. The "total light transmittance of the film" is a value measured according to the method described in the following Examples. The haze (total haze, initial haze) of the polyimide film is preferably 3% or less, more preferably less than 3.0%, and particularly preferably 2% or less. Such a haze film has excellent visibility. The yellowness (initial yellowness, initial YI) of the polyimide film is preferably 3% or less, more preferably 2% or less, and particularly preferably 1.5% or less. Such a yellowish film has excellent visibility. That is, according to the preferred embodiment of the present invention, the film (polyimide film) of the present invention has a total light transmittance of 80% or more, and at least one of the initial yellowness (initial YI) and the initial haze is 3% or less. .. In addition, the polyimide film of the present invention can suppress changes in characteristics (particularly, increase in yellowness and haze) due to changes in temperature and humidity environment, and is excellent in durability (ΔYI and Δhaze are small). The "yellowness (initial yellowness, initial YI)" and "haze (total haze, initial haze)" of the film are values measured according to the method described in the following Examples, and the durability of the film. (ΔYI and Δhaze) can be evaluated according to the method described in the examples below.

Therefore, the film of the present invention can be suitably used for a front plate of a tablet PC, a smartphone, or the like. That is, the present invention also provides a display device having the film of the present invention as a front plate.

As described above, the film of the present invention does not turn yellow or become turbid due to changes in temperature and humidity environment when laminated with an electronic device. Therefore, the present invention is not limited to the following, but for example, an organic EL device, a liquid crystal display device (LCD), an organic photoelectric conversion device, a printed substrate, a thin film, and a touch panel (for example, a touch panel for car navigation or a portable image called a smartphone or tablet). It can be suitably used for electronic devices such as display devices), polarizing plates, and retardation films. From the viewpoint of more efficiently obtaining the effects of the present invention, it is preferably used for flexible printed circuit boards, LED lighting devices, and front members for flexible displays.

The flexible printed circuit board is obtained by using the polyimide film of the present invention as a base film and pressure-bonding a metal foil to the base film with an adhesive. Examples of the adhesive used here include acrylic, polyimide, and epoxy adhesives. Further, the metal foil that is thermocompression-bonded to the polyimide film via an adhesive is preferably a copper foil from the viewpoint of cost reduction, but other metal foils such as aluminum, gold, silver, nickel, and tin may also be used.

The LED lighting device is not particularly limited as long as it uses the LED substrate using the polyimide film of the present invention, and examples thereof include a double-sided substrate and a composite substrate with an aluminum plate. When higher heat dissipation is required as the brightness of the LED is increased, it is possible to improve the heat dissipation by combining it with an aluminum plate. It can also be applied to an organic electroluminescence illuminator using an organic material.

The front member for a flexible display is not particularly limited as long as it is made of the polyimide film of the present invention. As a flexible display on which the front member for a flexible display of the present invention is mounted, for example, an organic EL device in which an organic functional layer such as a light emitting layer is laminated on a substrate, a gas barrier film, a film color filter, one side or both sides. A polarizing plate having a polarizing plate protective film, a film-type touch sensor, and the like are laminated in this order. The front member for a flexible display of the present invention is laminated on, for example, a film-type touch sensor of a flexible display configured as described above. The polyimide film of the present invention may be used as a substrate for an organic EL device constituting the flexible display, or may be used as a polarizing plate protective film for a polarizing plate constituting the flexible display.

The effects of the present invention will be described with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In the following examples, the operation was performed at room temperature (25 ° C.) unless otherwise specified. Unless otherwise specified, "%" and "parts" mean "mass%" and "parts by mass", respectively.

Production Example 1: Preparation of Filler 1 130 g of ion-exchanged water and 8.8 g (0.146 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 27 g (0.132 mol) of aluminum isopropoxide was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, it was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. It was disassembled. The mixture was then reacted in an autoclave at 150 ° C. for 6 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the alumina filler precursor 1 (solid content concentration: about 5% by mass). Here, the average diameter and the average length of the alumina filler precursor 1 were 4 nm and 3000 nm (aspect ratio = 750), respectively.

Next, 50 g of the solution containing the alumina filler precursor 1 thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed, and dehydration treatment is performed using a Dean Stark apparatus to carry out alumina. A methyl isobutyl ketone dispersion was obtained by surface-modifying the filler precursor 1 with dodecylbenzenesulfonic acid. The alumina filler thus obtained is referred to as filler 1. The minor axis (y) and major axis (x) of the obtained filler 1 were 4 nm and 3,000 nm (aspect ratio (x / y) = 750), respectively. In this example, the minor axis and the major axis of the filler 1 corresponded to the average diameter and the average length, respectively.

Production Example 2: Preparation of Filler 2 130 g of ion-exchanged water and 6.8 g (0.112 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 27 g (0.132 mol) of aluminum isopropoxide was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, the mixture was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. It was disassembled. The mixture was then reacted in an autoclave at 160 ° C. for 6 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the alumina filler precursor 2 (solid content concentration: about 5% by mass). Here, the average diameter and the average length of the alumina filler precursor 2 were 4 nm and 500 nm (aspect ratio = 125), respectively.

Next, 50 g of the solution containing the alumina filler precursor 2 thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed, and dehydration treatment is performed using a Dean Stark apparatus to carry out alumina. A methyl isobutyl ketone dispersion was obtained by surface-modifying the filler precursor 2 with dodecylbenzenesulfonic acid. The alumina filler thus obtained is referred to as filler 2. The minor axis (y) and major axis (x) of the obtained filler 2 were 4 nm and 500 nm (aspect ratio (x / y) = 125), respectively. In this example, the minor axis and the major axis of the filler 2 corresponded to the average diameter and the average length, respectively.

Production Example 3: Preparation of Filler 3 130 g of ion-exchanged water and 15.6 g (0.257 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 35 g (0.171 mol) of aluminum isopropoxide was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, the mixture was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. It was disassembled. The mixture was then reacted in an autoclave at 160 ° C. for 6 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the alumina filler precursor 3 (solid content concentration: about 5% by mass). Here, the average diameter and the average length of the alumina filler precursor 3 were 4 nm and 10000 nm (aspect ratio = 2500), respectively.

Next, 50 g of the solution containing the alumina filler precursor 3 thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed, and dehydration treatment is performed using a Dean Stark apparatus to carry out alumina. A methyl isobutyl ketone dispersion was obtained by surface-modifying the filler precursor 3 with dodecylbenzenesulfonic acid. The alumina filler thus obtained is referred to as filler 3. The minor axis (y) and major axis (x) of the obtained filler 3 were 4 nm and 10000 nm (aspect ratio (x / y) = 2500), respectively. In this example, the minor axis and the major axis of the filler 3 corresponded to the average diameter and the average length, respectively.

Production Example 4: Preparation of Filler 4 130 g of ion-exchanged water and 1.1 g (0.158 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 27 g (0.132 mol) of aluminum isopropoxide was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, the mixture was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. It was disassembled. The mixture was then reacted in an autoclave at 150 ° C. for 10 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the alumina filler precursor 4 (solid content concentration: about 5% by mass). Here, the average diameter and the average length of the alumina filler precursor 4 were 10 nm and 5000 nm (aspect ratio = 500), respectively.

Next, 50 g of the solution containing the alumina filler precursor 4 thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed, and dehydration treatment is performed using a Dean Stark apparatus to carry out alumina. A methyl isobutyl keton dispersion was obtained by surface-modifying the filler precursor 4 with dodecylbenzenesulfonic acid. The alumina filler thus obtained is referred to as filler 4. The minor axis (y) and major axis (x) of the obtained filler 4 were 10 nm and 5,000 nm (aspect ratio (x / y) = 500), respectively. In this example, the minor axis and the major axis of the filler 4 corresponded to the average diameter and the average length, respectively.

Production Example 5: Preparation of Filler 5 130 g of ion-exchanged water and 15.6 g (0.257 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 35 g (0.171 mol) of aluminum isopropoxide was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, the mixture was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. It was disassembled. The mixture was then reacted in an autoclave at 160 ° C. for 12 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the alumina filler precursor 5 (solid content concentration: about 5% by mass). Here, the average diameter and the average length of the alumina filler precursor 5 were 30 nm and 10,000 nm (aspect ratio = 333), respectively.

Next, 50 g of the solution containing the alumina filler precursor 5 thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed, and dehydration treatment is performed using a Dean Stark apparatus to carry out alumina. A methyl isobutyl ketone dispersion was obtained by surface-modifying the filler precursor 5 with dodecylbenzenesulfonic acid. The alumina filler thus obtained is referred to as filler 5. The minor axis (y) and major axis (x) of the obtained filler 5 were 30 nm and 10,000 nm, respectively (aspect ratio (x / y) = 333). In this example, the minor axis and the major axis of the filler 5 corresponded to the average diameter and the average length, respectively.

Production Example 6: Preparation of Filler 6 130 g of ion-exchanged water and 17.7 g (0.293 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 40 g (0.195 mol) of aluminum isopropoxide was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, the mixture was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. It was disassembled. The mixture was then reacted in an autoclave at 160 ° C. for 6 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the alumina filler precursor 6 (solid content concentration: about 5% by mass). Here, the average diameter and the average length of the alumina filler precursor 6 were 4 nm and 15,000 nm (aspect ratio = 3750), respectively.

Next, 50 g of the solution containing the alumina filler precursor 6 thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed, and dehydration treatment is performed using a Dean Stark apparatus to carry out alumina. A methyl isobutyl ketone dispersion was obtained by surface-modifying the filler precursor 6 with dodecylbenzenesulfonic acid. The alumina filler thus obtained is referred to as filler 6. The minor axis (y) and major axis (x) of the obtained filler 6 were 4 nm and 15,000 nm (aspect ratio (x / y) = 3750), respectively. In this example, the minor axis and the major axis of the filler 6 corresponded to the average diameter and the average length, respectively.

Production Example 7: Preparation of Filler 7 130 g of ion-exchanged water and 6.8 g (0.112 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 27 g (0.132 mol) of aluminum isopropoxide was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, the mixture was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. It was disassembled. The mixture was then reacted in an autoclave at 160 ° C. for 10 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the alumina filler precursor 7 (solid content concentration: about 5% by mass). Here, the average diameter and average length of the alumina filler precursor 7 were 10 nm and 250 nm (aspect ratio = 25), respectively.

Next, 50 g of the solution containing the alumina filler precursor 7 thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed, and dehydration treatment is performed using a Dean Stark apparatus to carry out alumina. A methyl isobutyl ketone dispersion was obtained by surface-modifying the filler precursor 7 with dodecylbenzenesulfonic acid. The alumina filler thus obtained is referred to as filler 7. The minor axis (y) and major axis (x) of the obtained filler 7 were 10 nm and 250 nm (aspect ratio (x / y) = 25), respectively. In this example, the minor axis and the major axis of the filler 2 corresponded to the average diameter and the average length, respectively.

Production Example 8: Preparation of Filler 8 An alumina filler precursor 1 is produced in the same manner as in Production Example 1 above, and the alumina filler thus obtained is referred to as filler 8. The minor axis (y) and major axis (x) of the obtained filler 8 were 4 nm and 3,000 nm (aspect ratio (x / y) = 750), respectively. In this example, the minor axis and the major axis of the filler 8 corresponded to the average diameter and the average length, respectively.

Production Example 9: Preparation of Filler 9 An alumina filler precursor 1 was produced in the same manner as in Production Example 1 above.

Next, 19% by mass of 3-glyceride prepared by adding 50 g of the alumina filler precursor 1 thus obtained, 50 g of methyl isobutyl ketone, and 3-glycidoxypropyltrimethoxysilane to ethanol. Methyl isobutyl ketone dispersion of alumina filler precursor 1 surface-modified with 3-glycidoxypropyltrimethoxysilane by mixing 13 g of a sidoxypropyltrimethoxysilane ethanol solution and heating and stirring at 50 ° C. for 3 hours. Got The alumina filler thus obtained is referred to as filler 9. The minor axis (y) and major axis (x) of the obtained filler 9 were 4 nm and 3,000 nm (aspect ratio (x / y) = 750), respectively. In this example, the minor axis and the major axis of the filler 9 corresponded to the average diameter and the average length, respectively.

Production Example 10: Preparation of Filler 10 An alumina filler precursor 1 was produced in the same manner as in Production Example 1 above.

Next, the alumina filler precursor 1 thus obtained is mixed with 50 g of the alumina filler precursor 1, 50 g of methyl isobutyl ketone, and 0.4 g of benzoic acid, and dehydration treatment is performed using a distillation apparatus. As a result, a methyl isobutyl ketone dispersion of the alumina filler precursor 1 surface-modified with benzoic acid was obtained. The alumina filler thus obtained is referred to as filler 10. The minor axis (y) and major axis (x) of the obtained filler 10 were 4 nm and 3,000 nm (aspect ratio (x / y) = 750), respectively. In this example, the minor axis and the major axis of the filler 10 corresponded to the average diameter and the average length, respectively.

Production Example 11: Preparation of Filler 11 An alumina filler precursor 1 was produced in the same manner as in Production Example 1 above.

Next, the alumina filler precursor 1 thus obtained was mixed with 50 g of the alumina filler precursor 1, 50 g of cyclohexanone, and 0.4 g of JP-506H manufactured by Johoku Chemical Industry Co., Ltd., and used a Dean Stark apparatus. By dehydrating the alumina filler precursor 1, butoxyethyl acid phosphate [manufactured by Johoku Chemical Industry Co., Ltd., trade name: JP-506H, structural formula: (C ₄ H ₉ OCH ₂ CH ₂ O) _n- P ( A cycloexanone dispersion was obtained after surface modification with = O)-(OH) _{3-n; n = 1, 2].} The alumina filler thus obtained is referred to as filler 11. The minor axis (y) and major axis (x) of the obtained filler 11 were 4 nm and 3,000 nm (aspect ratio (x / y) = 750), respectively. In this example, the minor axis and the major axis of the filler 11 corresponded to the average diameter and the average length, respectively.

Production Example 12: Preparation of Filler 12 130 g of ion-exchanged water and 8.8 g (0.146 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 30 g (0.142 mol) of tetraethyl orthosilicate was added dropwise over 30 minutes, and while distilling off isopropyl alcohol, the mixture was heated to 95 ° C. (liquid temperature) and hydrolyzed at the same temperature for 30 minutes. Was done. The mixture was then reacted in an autoclave at 150 ° C. for 6 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing a silica filler precursor (solid content concentration: about 5% by mass). Here, the average diameter and the average length of the silica filler precursor were 8 nm and 3,000 nm (aspect ratio = 375), respectively.

Next, 50 g of the solution containing the silica filler precursor thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed and dehydrated using a Dean Stark apparatus to carry out the silica filler. A methyl isobutyl ketone dispersion was obtained by surface-modifying the precursor with dodecylbenzenesulfonic acid. The silica filler thus obtained is referred to as filler 12. The minor axis (y) and major axis (x) of the obtained filler 12 were 8 nm and 3,000 nm, respectively (aspect ratio (x / y) = 375). In this example, the minor axis and the major axis of the filler 12 corresponded to the average diameter and the average length, respectively.

Production Example 13: Preparation of filler 13 130 g of ion-exchanged water and 8.8 g (0.146 mol) of acetic acid are charged in a 500 ml four-necked flask, and the obtained mixture is brought to 30 ° C. (liquid temperature) with stirring. It was heated so that it became. To this, 45 g (0.138 mol) of tetrapropoxyzirconium (IV) was added dropwise over 30 minutes, and the mixture was heated to 95 ° C. (liquid temperature) while distilling off isopropyl alcohol to 30 at the same temperature. Partial hydrolysis was performed. The mixture was then reacted in an autoclave at 150 ° C. for 6 hours with stirring. After carrying out the reaction for a predetermined time, the reaction solution was cooled to room temperature (25 ° C.) to obtain a solution containing the zirconia filler precursor (solid content concentration: about 5% by mass). Here, the average diameter and average length of the zirconia filler precursor were 8 nm and 3,000 nm (aspect ratio = 375), respectively.

Next, 50 g of the solution containing the zirconia filler precursor thus obtained, 50 g of methyl isobutyl ketone and 0.4 g of dodecylbenzenesulfonic acid are mixed and dehydrated using a Dean Stark apparatus to carry out the zirconia filler. A methyl isobutyl ketone dispersion was obtained by surface-modifying the precursor with dodecylbenzenesulfonic acid. The zirconia filler thus obtained is referred to as filler 13. The minor axis (y) and major axis (x) of the obtained filler 13 were 8 nm and 3,000 nm, respectively (aspect ratio (x / y) = 375). In this example, the minor axis and the major axis of the filler 13 corresponded to the average diameter and the average length, respectively.

Production Example 14: Filler 14
Alumina particles (average particle diameter (diameter): 31 nm, particle shape: spherical, manufactured by CI Kasei Co., Ltd., product name: NanoTek (registered trademark) Al ₂ O ₃ ) are referred to as filler 14.

Production Example 15: Filler 15
Silica particles (average particle diameter (diameter): 7 nm, particle shape: spherical, manufactured by Evonik Industries, product name: AEROSIL (registered trademark) R812) are referred to as filler 15.

Table 1 below summarizes the configurations of the fillers 1 to 15.

Production Example A: Preparation of Polyimide A 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropanedianhydride (acid) in a 3000 L reaction kettle. Anhydride A) (manufactured by Daikin Industries, Ltd.) 0.43 t was added to N, N-dimethylacetamide (1.68 t), and the mixture was stirred at room temperature under a nitrogen stream.

To it, 0.32 t of 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl (diamine A) (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. After continuing heating, refluxing and stirring for 6 hours, no water was generated. After completion of the reaction, methanol was added and reprecipitation was performed to obtain a polyimide A powder.

Production Examples B to D: Preparation of Polyimides B to D Production Example A except that the acid anhydrides and diamines shown in Table 2 below were used in place of the acid anhydrides A and the diamines, respectively. Polyimide B to D solutions were prepared in the same manner as in the above. In this example, the acid anhydride and the diamine were used in an amount so as to be equimolar to the acid anhydride A and the diamine A, respectively.

Example 1: Preparation of Polyimide Film 1 1200 parts by mass of dichloromethane (boiling point: 40 ° C.) was added to a pressure dissolution tank. In this pressurized dissolution tank, 100 parts by mass of polyimide A prepared in Production Example A (addition amount as polyimide A (in terms of solid content)) and 5 parts by mass of the methyl isobutyl ketone dispersion of filler 1 prepared in Production Example 1 Part (addition amount as filler 1 (solid content conversion)) was added while stirring. The mixture was heated and stirred to completely dissolve the polyimide A to prepare a main dope (solid content concentration = about 7% by mass) (doping preparation step).

The main dope thus prepared was then uniformly cast on the stainless belt support at a temperature of 30 ° C. with a width of 1500 mm via a die using an endless belt casting device (casting film). Formation process). The temperature of the stainless belt support was controlled to 30 ° C.

Further, the solvent was evaporated on the stainless belt support until the amount of residual solvent in the cast film reached 75% by mass (solvent evaporation step), and then the stainless belt was supported with a peeling tension of 180 N / m. A film was obtained by peeling from the body (peeling step).

The peeled film was stretched 1.50 times in the width direction using a clip-type tenter while applying heat at 200 ° C. (first drying step and stretching step). The amount of residual solvent at the start of stretching was 20% by mass.

The stretched film was dried at a drying temperature at which the residual solvent amount was less than 0.1% by mass under a transport tension of 100 N / m and a drying time of 15 minutes (second drying step) to obtain a film having a dry film thickness of 62 μm. .. The obtained film was wound (winding step) to obtain a polyimide film 1.

Examples 2 to 15, Reference Examples 16 to 18, Comparative Examples 1 to 8: Preparation of Polyimide Films 2 to 26 In Example 1, the types of polyimide and filler and the amount of filler added are as shown in Table 3 below. Polyimide films 2-26 were produced in the same manner except that they were changed.

With respect to the polyimide films 1 to 26 obtained as described above, the total light transmittance (%), the yellowness (%) (initial YI and ΔYI), and the haze (%) (initial haze and Δ haze) are according to the following methods. ) Is measured, and the results are shown in Table 3 below.

[Measurement of total light transmittance (%)]
The total light transmittance of each polyimide film is 23 ° C., 55% RH, and one film (sample) (size: 5 cm x 5 cm) whose humidity is adjusted for 24 hours in an air conditioning room is used according to JIS K7375: 2008. The transmittance in the visible light region (range of 400 to 700 nm) was measured using a spectrophotometer U-3300 of Hitachi High Technologies, and the average value (%) was obtained, which was taken as the total light transmittance (%).

[Evaluation of haze]
The haze (total haze) (%) of each polyimide film was measured with a haze meter NDH-2000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) in accordance with JIS K7136: 2000. The light source of the haze meter was a 5V9W halogen bulb, and the light receiving part was a silicon photocell (with a luminosity filter). The haze (%) was measured under the conditions of 23 ° C. and 55% RH. The haze (%) measured in this way is referred to as "initial haze (%)" in the table below.

Further, each polyimide film was left at 90 ° C. and 90% RH for 5000 hours. For these polyimide films, the haze (%) was measured in the same manner as above. The difference (Δ haze) between the haze measured in this way and the initial haze (%) measured above was measured, and this value (Δ haze) was evaluated according to the following criteria.

[Evaluation of yellowness]
The yellowness (%) (yellow index, YI) of each polyimide film can be determined according to the YI (yellow index: yellowish index) of the film defined in JIS K7373: 2006. Specifically, as a method for measuring yellowness (%), each film sample is prepared, and using the spectrophotometer U-3300 of Hitachi High-Technologies Corporation and the attached saturation calculation program, etc., JIS Z8701: The tristimulus values X, Y, and Z of the light source color defined in 1999 are obtained, and the chromaticity (%) is obtained according to the definition of the following equation. The yellowness (%) measured in this way is referred to as "initial YI (%)" in the table below.

Further, each polyimide film was left at 90 ° C. and 90% RH for 5000 hours. The yellowness (%) of these polyimide films was measured in the same manner as described above. The difference (ΔYI) between the yellowness (%) measured in this way and the initial YI (%) measured above was measured, and this value (ΔYI) was evaluated according to the following criteria.

From Table 3, the films 1 to 4, 10 to 13 and 15 to 24 of the present invention are ΔYI compared to the films 5 to 9, 14 and 25 to 26 which do not satisfy the aspect ratio, average diameter or surface modification of the filler. It can be seen that the Δ haze is suppressed to a low level and the durability is excellent.

Examples 19 to 30, Reference Examples 31 to 33, Comparative Examples 9 to 16.
Organic EL display devices 1 to 14, 18 to 26, respectively, using the polyimide films prepared in Examples 1 to 8 and 12 to 15, Reference Examples 16 to 18 and Comparative Examples 1 to 8 according to the following methods. Was prepared and evaluated.

(1) Preparation of Polyimide Film with Hard Coat Layer The following hard coat layer was provided on one side of each polyimide film to prepare a polyimide film with a hard coat layer.

(Formation of hard coat layer)
The following materials were stirred and mixed to prepare a hard coat layer composition.

The hard coat layer composition thus prepared was filtered through a polypropylene filter having a pore size of 0.4 μm to prepare a coating liquid for forming a hard coat layer. This coating liquid for forming a hard coat layer was applied onto a polyimide film with a die coater and dried at 70 ° C. to form a coating layer on the polyimide film. Next, while purging nitrogen so that the oxygen concentration in the treatment space becomes 1.0% by volume or less, the illuminance is 300 mW / cm ² and the irradiation amount is 0.3 J / cm ² using an ultraviolet lamp. The coating layer was cured. Further, in the heat treatment zone, heat treatment was performed at 130 ° C. for 5 minutes at a transport force of 300 N / m to form a hard coat layer having a dry film thickness of 7 μm on the polyimide film.

(Preparation of Fluorine-siloxane Graft Polymer I)
Hereinafter, commercially available product names of the materials used for preparing the fluorine-siloxane graft polymer I are shown.

Radical Polymerizable Fluororesin (FA): Cefral Coat (Registered Trademark) CF-803 (Hydroxy (hydroxyl) value 60, number average molecular weight 15000; manufactured by Central Glass Co., Ltd.)
One-end radically polymerizable polysiloxane (B): Silaplane (registered trademark) FM-0721 (number average molecular weight 5000; manufactured by JNC Co., Ltd.)
Radical polymerization initiator: Perbutyl (registered trademark) O (t-butylperoxy-2-ethylhexanoate; manufactured by NOF CORPORATION)
Curing agent: Sumijour (registered trademark) N3200 (biuret-type prepolymer of hexamethylene diisocyanate; manufactured by Sumika Bayer Urethane Co., Ltd.)
First, a radically polymerizable fluororesin (FA) was prepared as follows. Cefral Coat® CF-803 (1554 parts by mass), xylene (233 parts by mass), and 2-isocyanato in a glass reactor equipped with a mechanical stirrer, thermometer, condenser and dry nitrogen gas inlet. Ethyl methacrylate (6.3 parts by mass) was added and heated to 80 ° C. under a dry nitrogen atmosphere. After reacting at 80 ° C. for 2 hours and confirming that the absorption of isocyanate disappeared from the infrared absorption spectrum of the sample, the reaction mixture was taken out and 50% by mass of radically polymerizable fluororesin (FA) was taken out via a urethane bond. Got

Next, in a glass reactor equipped with a mechanical stirrer, a thermometer, a condenser and a dry nitrogen gas inlet, the synthesized radical polymerizable fluororesin (FA) (26.1 parts by mass) and xylene (19.5 parts by mass) were added. By mass), n-butyl acetate (16.3 parts by mass), methyl methacrylate (2.4 parts by mass), n-butyl methacrylate (1.8 parts by mass), lauryl methacrylate (1.8 parts by mass), 2- Add hydroxyethyl methacrylate (1.8 parts by mass), silaplane (registered trademark) FM-0721 (5.2 parts by mass), and perbutyl (registered trademark) O (0.1 parts by mass), and add 90 in a nitrogen atmosphere. After heating to ° C., the mixture was kept at 90 ° C. for 2 hours. Perbutyl® O (0.1 parts by weight) was added and held at 90 ° C. for 5 hours to obtain a solution of 35% by weight fluorine-siloxane graft polymer I having a weight average molecular weight of 171,000.

(2) Preparation of Circular Polarizing Plate A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature 110 ° C., stretching ratio 5 times). This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

Next, a λ / 4 retardation film was produced in the same manner as described in paragraphs [0277]-[0287] of JP2013-101229A.

Next, according to the following steps 1 to 5, the polarizer, the λ / 4 retardation film, and the protective film (Konica Minolta Tack KC4UY (manufactured by Konica Minolta Co., Ltd.)) are bonded together by a roll-to-roll method to form a circular polarizing plate. Made. The protective film was attached so as to be arranged on the back surface side (visual side) of the polarizer.

Step 1: The λ / 4 retardation film and the stretched protective film are immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, washed with water, dried, and bonded to the polarizer. The surface was ken.

Step 2: The above-prepared polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

Step 3: The excess adhesive adhering to the polarizer in step 2 was lightly wiped off, and this was placed on the λ / 4 retardation film treated in step 1.

Step 4: The λ / 4 retardation film and the polarizer laminated in Step 3 and the protective film were bonded together at a pressure of 20 to 30 N / cm ² and a transport speed of about 2 m / min.

Step 5: A sample in which the polarizer prepared in Step 4 and the λ / 4 retardation film and the protective film were bonded together was dried in a dryer at 80 ° C. for 2 minutes to prepare a circular polarizing plate.

(3) Fabrication of Organic EL Display Device Polyimide films 1 to 14, 18 to 26 prepared in the above Examples, Reference Examples and Comparative Examples were used as a transparent substrate, and a reflective electrode made of chromium was formed on the polyimide film, and further said. An anode made of ITO (tin-doped indium oxide) was formed on the reflective electrode.

A hole transport layer having a thickness of 80 nm was formed on the anode by a sputtering method using poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS). Next, using a shadow mask, a red light emitting layer R, a green light emitting layer G, and a blue light emitting layer B having a layer thickness of 100 nm were formed on the hole transport layer, respectively. The red light emitting layer R contains tris (8-hydroxyquinolinate) aluminum (Alq ₃ ) as a host and 4- (dicyanomethylene) -2-methyl-6 (p-dimethylaminostylyl) -4H-pyran (DCM) as a luminescent compound. ) And co-deposited (mass ratio 99: 1). The green light emitting layer G was _{formed by co-depositing (mass ratio 99: 1) Alq 3} as a host and coumarin 6 (3- (2-benzothiazolyl) -7- (diethylamino) coumarin) as a luminescent compound. The blue light emitting layer B was formed by co-depositing BAlq as a host and Perylene as a luminescent compound (mass ratio 90:10). In this way, an organic light emitting layer composed of a hole transport layer, a red light emitting layer R, a green light emitting layer G, and a blue light emitting layer B was formed.

Further, calcium was formed on the organic light emitting layer by a vacuum vapor deposition method to a thickness of 4 nm to form a first cathode. Next, aluminum was formed on the first cathode to a thickness of 2 nm to form a second cathode. The aluminum used for the second cathode has a role of preventing the calcium, which is the first cathode, from being chemically altered when the transparent conductive film formed on the transparent conductive film is formed by a sputtering method.

Next, ITO was formed on the first and second cathodes by a sputtering method to a thickness of 80 nm to form a transparent electrode. Further, silicon nitride was formed on the transparent electrode to a thickness of 200 nm by a CVD method to form an insulating film. In this way, the organic EL element was manufactured.

Next, a thermosetting liquid adhesive (epoxy resin) was applied to one side of a polyethylene terephthalate film with a gas barrier layer having a thickness of 20 μm to a thickness of 25 μm to prepare a sealing unit.

Next, under a reduced pressure condition of 0.1 MPa at 90 ° C., the organic EL element formed from the transparent substrate to the insulating film and the sealing unit were pressed together and held for 5 minutes. Subsequently, the laminate was heated at 90 ° C. for 30 minutes in an atmospheric pressure environment to cure the adhesive, and an organic EL display device was produced.

The light emitting area of the organic EL display device produced above was 1296 mm × 784 mm. Further, the front luminance when a DC voltage of 6 V was applied to this organic EL display device was 1200 cd / m ² . To measure the front luminance, use a spectral radiance meter CS-1000 manufactured by Konica Minolta Co., Ltd. so that the 2 degree viewing angle front luminance is aligned with the normal line from the light emitting surface. Then, the visible light wavelength range of 430 to 480 nm was measured, and the integrated intensity was taken.

(4) Manufacture of Organic EL Display Device The manufactured circular polarizing plate is laminated on the manufactured organic EL display device, and the produced polyimide film with a hard coat layer is used as a front member on the hard coat layer. Organic EL display devices 1 to 26 were manufactured by laminating via an adhesive layer so as to be a surface layer.

(5) Evaluation of Organic EL Display Device The manufactured organic EL display device was subjected to sensory evaluation of image quality regarding white color development and black color development. The sensory evaluation was performed according to the following criteria. The results are shown in Table 4 below. The white coloration is acceptable if it is ○ or ◎. In addition, black color development is acceptable if it is ○ or ◎.

From Table 4, the organic EL display device using the films 1 to 4, 10 to 13 and 18 to 24 of the present invention does not satisfy the aspect ratio, average diameter or surface modification of the filler, and the films 5 to 9, 14 and 25 to It can be seen that the film of the present invention is excellent in visibility as compared with the organic EL display device using 26, which is not yellowish (white color development), is not turbid and is excellent in transparency (black color development).

Claims (7)

A film containing a polyimide resin and a metal oxide filler.
It said metal oxide filler is an aspect ratio (long diameter / short diameter) of from 110 to 2000 and an average diameter is 1 to 10 nm, a sulfonic acid group on the surface of the metal oxide filler _(-SO 3 H), carboxyl It has a compound having at least one group selected from the group consisting of; (n = 1 or _{2 -P (= O) (OH} ) 3-n), group (-COOH) and phosphate groups
The polyimide resin has the following formula (A):
In the above formula (A), R consists of an aromatic hydrocarbon ring, an aromatic heterocycle, a tetravalent group derived from an aliphatic hydrocarbon having 4 to 39 carbon atoms or an alicyclic hydrocarbon, or a combination thereof. Represents a tetravalent group, where R is a combination of any two or more of the above, these are -O-, -SO _2- , -CO-, -CH _2- , -C ( CH ₃ ) _2- , -OSi (CH ₃ ) _2- , -C ₂ H ₄ O-, -CF _2- , -C (CF ₃ ) _2- , -OSi (CF ₃ ) _2- , -C ₂ F _{It may be linked via at least one bonding group selected from the group consisting of 4} O- and -S-, and is represented by an aromatic hydrocarbon ring represented by R, an aromatic heterocycle, and a fat having 4 to 39 carbon atoms. At least one hydrogen atom in a group hydrocarbon or an alicyclic hydrocarbon is a fluorine atom, a monofluoromethyl group (-CFH ₂ ), a difluoromethyl group (-CF ₂ H), a trifluoromethyl group (-CF ₃ ). , monofluoroethyl group _{(-CFH-CH 3, -CH 2} -CFH 2), or difluoroethyl group _{(-CF 2 -CH 3, -CFH-} CFH 2, -CH 2 -CF 2 H) substituted with;
A represents a divalent group consisting of a divalent aliphatic hydrocarbon having 2 to 39 carbon atoms, an alicyclic hydrocarbon, a divalent group derived from an aromatic hydrocarbon, or a combination thereof. If is a combination of any two or more of the above, they are -O-, -SO _2- , -CO-, -CH _2- , -C (CH ₃ ) _2- , -OSi (CH ₃ ). Select from the group consisting of _2- , -C ₂ H ₄ O-, -CF _2- , -C (CF ₃ ) _2- , -OSi (CF ₃ ) _2- , -C ₂ F _{4 O- and -S-} It may be linked via at least one bonding group, and is at least one in an aromatic hydrocarbon ring represented by A, an aromatic heterocycle, an aliphatic hydrocarbon having 4 to 39 carbon atoms, or an alicyclic hydrocarbon. One hydrogen atom is a fluorine atom, a monofluoromethyl group (-CFH ₂ ), a difluoromethyl group (-CF ₂ H), a trifluoromethyl group (-CF ₃ ), a monofluoroethyl group (-CFH-CH 3, _{-CFH-CH 3).} Replaced with CH _{2 -CFH 2} ) or a difluoroethyl group (-CF _2- CH ₃ , -CFH-CFH ₂ , -CH _2- CF ₂ H),
A film which is a polyimide resin having a repeating unit represented by. The film according to claim 1, wherein the metal oxide is alumina or boehmite. In the formula (A), R is the following structural formula:
It is a group represented by, and A is the following structural formula:
The film according to claim 1 or 2, which is a group represented by. The film according to any one of claims 1 to 3, wherein the compound has an aryl group. The film according to any one of claims 1 to 4, wherein the content of the metal oxide filler is 0.1 to 30% by mass with respect to the polyimide resin. The film according to any one of claims 1 to 5, wherein the total light transmittance is 80% or more, and at least one of the initial yellowness (initial YI) and the initial haze is 3% or less. A display device having the film according to any one of claims 1 to 6 as a front plate.