JP2015209487A - Polyimide, laminated film, phase difference film, and method of producing laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide that is useful as raw material for the production of a film with high birefringence and is excellent in transparency, mechanical characteristics and solubility in organic solvent, a laminated film and a phase difference film obtained by using the polyimide, and a method of producing the laminated film.SOLUTION: A polyimide comprises a repeating unit having a specific rigid structure, and a repeating unit having a specific fluorene ring structure, at a specific rate. There are also provided a laminated film and a phase difference film obtained by using the polyimide, and a method of producing the laminated film.

Description

  The present invention is useful as a raw material for producing a film having high birefringence, a polyimide excellent in transparency, mechanical properties and solubility in an organic solvent, a laminated film and a retardation film obtained using the polyimide, and the laminated film The present invention relates to a film manufacturing method.

  Conventionally, in a liquid crystal display (LCD), for the purpose of improving viewing angle characteristics and contrast, it is known to use a stretched film obtained by stretching a polymer film as a retardation film. However, in order to develop a large birefringence in order to apply the polymer film to the retardation film, it is usually necessary to mechanically stretch the resin film at a high magnification.

In recent years, as a technique for obtaining a film having a certain birefringence without requiring such mechanical operation, by applying a self-orienting polyimide varnish on a substrate and drying the obtained coating film A method for obtaining a resin film having birefringence has been proposed.
For example, in Patent Document 1, a polyimide copolymer obtained from a diamine compound having a fluorenyl group and the like and an alicyclic tetracarboxylic dianhydride, and a varnish containing the polyimide copolymer are coated on a substrate. An optical compensation film obtained by drying is described.

JP 2010-180350 A

Although the optical compensation film described in Patent Document 1 has transparency and birefringence, a film having excellent transparency and high birefringence has been demanded as LCDs have been further improved in performance and thinned in recent years. ing.
Therefore, there is a need for a polyimide that is useful as a raw material for producing such a film and has excellent transparency, mechanical properties, and solubility in organic solvents.

  The present invention has been made in view of the above-described conventional technology, and is useful as a raw material for producing a film having high birefringence. A polyimide having excellent transparency, mechanical properties, and solubility in an organic solvent, and using this polyimide. It aims at providing the manufacturing method of the laminated film and retardation film which are obtained, and the said laminated film.

  In order to solve the above-mentioned problems, the present inventors diligently studied about polyimide and a film obtained using the polyimide. As a result, it has been found that a polyimide having a repeating unit having a specific rigid structure and a repeating unit having a specific fluorene ring structure is excellent in transparency, mechanical properties and solubility in organic solvents, and to complete the present invention. It came.

Thus, according to the present invention, the following [1] to [3] polyimide, [4] to [6] laminated film, [7] to [8] retardation film, and [9] to [10] laminated film A method of manufacturing a film is provided.
[1] having a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2),
The molar ratio of the repeating unit represented by the formula (1) and the repeating unit represented by the formula (2) [the repeating unit represented by the formula (1): the repeating unit represented by the formula (2)] is 20:80. ~ 70: 30,
The polyimide characterized by the total amount of the repeating unit represented by the formula (1) and the repeating unit represented by the formula (2) being 80 to 100 mol% in all repeating units.

[Wherein, R ¹ and R ² each independently represent a halogen atom, a hydroxyl group, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxyl group having 1 to 6 carbon atoms, Or represents a trifluoromethyl group. A ¹ represents the following formula (3a) or (3b)

(In the formula, * represents a bond.)
Represents a group represented by a and b each independently represents an integer of 0 to 4; When a and b are each 2 or more, a plurality of R ^{1 s} and R ^{2 s} may be the same or different. ]

(In the formula, R ^{3 to} R ⁶ are each independently a halogen atom, a hydroxyl group, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxyl group having 1 to 6 carbon atoms, Or A ¹ represents a group represented by the formula (3a) or (3b), and cf each independently represents an integer of 0 to 4. c, d, e, When f is 2 or more, a plurality of R ^{3 s} , R ^{4 s} , R ^{5 s,} and R ^{6 s} may be the same or different.
[2] The polyimide according to [1], wherein when the film is formed into a film having a thickness of 10 μm, the light transmittance of light having a wavelength of 400 nm is 90% or more.
[3] The polyimide according to [1] or [2], wherein when a saturated solution is prepared by dissolving in cyclopentanone at 25 ° C., the concentration of the saturated solution becomes 5% by weight or more.
[4] A polyimide formed by applying a varnish containing the polyimide according to any one of [1] to [3] on a stretched film and the stretched film, and drying the resulting coating film A laminated film having a film.
[5] The laminated film according to [4], wherein the stretched film is a film obtained by stretching an unstretched cycloolefin polymer film.
[6] The laminated film according to [4] or [5], further having an adhesive layer.
[7] A retardation film obtained by peeling and removing a stretched film from the laminated film according to any one of [4] to [6].
[8] The retardation film according to [7], further having an adhesive layer.
[9] A method for producing a laminated film comprising a step of coating the varnish containing the polyimide according to any one of [1] to [3] on a stretched film and drying the obtained coating film.
[10] The method for producing a laminated film according to [9], wherein the stretched film is a film obtained by stretching an unstretched cycloolefin polymer film.

The polyimide of the present invention is excellent in transparency, mechanical properties, and solubility in organic solvents.
The laminated film and retardation film of the present invention have high birefringence and are excellent in transparency, mechanical properties, and solubility in organic solvents.
According to the production method of the present invention, the laminated film of the present invention can be produced efficiently.

  Hereinafter, the present invention will be described in detail by dividing it into 1) polyimide, and 2) a method for producing a laminated film, a retardation film and a laminated film.

1) Polyimide The polyimide of the present invention has a repeating unit represented by the above formula (1) (hereinafter sometimes referred to as “repeating unit (1)”) and a repeating unit represented by the above formula (2) (hereinafter referred to as “repeating unit”). The ratio of the repeating unit (1) to the repeating unit (2) [repeating unit (1): repeating unit (2)] molar ratio is 20: 80 to 70:30, and the total amount of the repeating unit (1) and the repeating unit (2) is 80 to 100 mol% in all repeating units.

<Repeating unit (1)>
In the repeating unit (1), R ¹ and R ² are each independently a halogen atom, a hydroxyl group, a linear or branched alkyl group having 1 to 6 carbon atoms, or a linear or branched structure having 1 to 6 carbon atoms. An alkoxyl group or a trifluoromethyl group is represented.

Examples of the halogen atom for R ¹ and R ² include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
R ^1, the number of carbon atoms of the linear or branched alkyl group having 1 to 6 carbon atoms ^{R 2} is 1-3 are preferable. Examples of the linear or branched alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, isopropyl group, isobutyl group, Examples thereof include s-butyl group and t-butyl group.
R ^1, the number of carbon atoms of the linear or branched alkoxyl group having 1 to 6 carbon atoms ^{R 2} is 1-3 are preferable. Examples of the linear or branched alkoxyl group having 1 to 6 carbon atoms include methoxy group, ethoxy group, n-propoxy group, n-butoxy group, n-pentyloxy group, n-hexyloxy group, isopropoxy group, isobutoxy group. Group, t-butoxy group and the like.

a and b each independently represents an integer of 0 to 4; When a and b are integers of 2 to 4, the plurality of R ¹ may be the same or different from each other, and the plurality of R ² may be the same or different from each other. It may be.
A ¹ represents a group represented by the formula (3a) or (3b).

The repeating unit (1) has a structure obtained by reacting a tetracarboxylic dianhydride represented by the following formula (4a) or (4b) with a diamine represented by the following formula (5).
The part derived from tetracarboxylic dianhydride [compound represented by the following formula (4a) or (4b)] has an alicyclic structure.

  For this reason, the polyimide of this invention is excellent in transparency. Moreover, the polyimide of this invention is excellent in the solubility with respect to an organic solvent by having this alicyclic structure. Therefore, by using the polyimide of the present invention, a retardation film can be efficiently produced by a casting method.

  The portion derived from the diamine [compound represented by the following formula (5)] in the repeating unit (1) has a rigid structure in which a π bond is expanded.

  Since the polyimide of the present invention has this rigid structure, the molecular chains are easily aligned. As will be described later, when a polyimide film is formed by a casting method using a stretched film as a base material, this action of the rigid structure causes the fluorene ring in the repeating unit (2) to be perpendicular to the film plane. It becomes easy to stand up and the birefringence of the film is enhanced.

<Repeating unit (2)>
In the repeating unit (2), R ^{3 to} R ⁶ are each independently a halogen atom, a hydroxyl group, a linear or branched alkyl group having 1 to 6 carbon atoms, or a linear or branched structure having 1 to 6 carbon atoms. An alkoxyl group or a trifluoromethyl group is represented.
Specific examples of these groups include the same groups as those exemplified as R ¹ and R ² .
In the repeating unit (2), c to f each independently represents an integer of 0 to 4. When c is an integer of 2 to 4, a plurality of R ³ may be the same as or different from each other. The same applies to R ^{4 to} R ⁶ when e to f are integers of 2 to 4.
In the repeating unit (2), A ¹ represents a group represented by the formula (3a) or (3b).

  The part derived from the tetracarboxylic dianhydride [compound represented by the above formula (4a) or (4b)] in the repeating unit (2) is the tetracarboxylic dianhydride of the repeating unit represented by the formula (1). It is the same thing as a thing. Therefore, the polyimide of the present invention is excellent in transparency and solubility in organic solvents.

The repeating unit (2) has a structure obtained by reacting the tetracarboxylic dianhydride represented by the formula (4a) or (4b) with the diamine represented by the following formula (6).
The part derived from diamine [compound shown by following formula (6)] has a fluorene ring.

  The polyimide of the present invention has a repeating unit having a fluorene ring (repeating unit represented by (2) above) and a repeating unit having the rigid structure (repeating unit represented by the formula (1)). By this combination, the polyimide of the present invention exhibits higher birefringence. Moreover, the polyimide of this invention is excellent in the solubility with respect to an organic solvent by having this fluorene ring structure. Therefore, by using the polyimide of the present invention, a retardation film can be efficiently produced by a casting method.

The molar ratio of the repeating unit (1) to the repeating unit (2) [repeating unit (1): repeating unit (2)] of the polyimide of the present invention is 20:80 to 70:30, preferably 30. : 70-70: 30.
When the ratio of the repeating unit (1) is too small, it becomes difficult to develop a retardation in a film described later. Moreover, when there are too many ratios of a repeating unit (1), it will become difficult to melt | dissolve a polyimide in an organic solvent, and it will become difficult to manufacture a cast film.

The total amount of the repeating unit (1) and the repeating unit (2) in the polyimide of the present invention is 80 to 100 mol%, preferably 90 to 100 mol%, more preferably 95 to 100 mol in all repeating units. %.
A polyimide having excellent transparency, mechanical properties, and solubility in an organic solvent, which is useful as a raw material for producing a film having high birefringence because the total of the repeating unit (1) and the repeating unit (2) is within the above range. Can be obtained.

  The polyimide of the present invention may have any repeating unit other than the repeating units (1) and (2). Examples of such repeating units include tetracarboxylic dianhydrides other than the tetracarboxylic dianhydrides represented by the formulas (4a) and (4b) described later, and the formulas (5) and (6). And repeating units formed using a diamine other than the diamine.

  The method for synthesizing the polyimide of the present invention is not particularly limited. For example, the tetracarboxylic dianhydride represented by the above formula (4a) or (4b), the diamine represented by the above formula (5), the diamine represented by the above formula (6), etc. Reaction is performed using a tetracarboxylic dianhydride other than the tetracarboxylic dianhydrides represented by the formulas (4a) and (4b) and a diamine other than the diamines represented by the formulas (5) and (6) as raw materials. Thus, the polyimide of the present invention can be synthesized.

  Examples of tetracarboxylic dianhydrides other than the tetracarboxylic dianhydrides represented by the formulas (4a) and (4b) include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and pyromellitic anhydride. 1,2,3,4-benzenetetracarboxylic anhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, 2,3,6,7-naphthalenetetracarboxylic anhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride 2,3,3 ′, 4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride, 2,3,3 ′, 4′-diphenyl ether tetracarbo Acid dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 2,3,3 ′, 4′-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3 , 3 ′, 4,4′-tetracarboxyphenyl) tetrafluoropropane dianhydride, 2,2′-bis (3,4-dicarboxyphenoxyphenyl) sulfone dianhydride, 2,2-bis (2,3 -Dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride and the like.

  Examples of diamines other than the diamines represented by formulas (5) and (6) include 4,4′-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 3,3′-diaminodiphenyl ether, and 3,4′-diamino. Diphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4 '-Diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4' -Diaminodiphenylmethane, 2 2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2-di (3 -Aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2 -(3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis (3-aminophenoxy) ) Benzene, 1,3-bis (4-amino) Phenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4 -Aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α) , Α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoromethyl) Benzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6- Bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl Bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4- Aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) Phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] Benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4 (4-Aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α , Α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α -Dimethylbenzyl] benzene, 4,4′-bis [4- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy Di] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4,4′-dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3, , 3′-diamino-4-biphenoxybenzophenone, 5-amino-2- (p-aminophenyl) benzoxazole, 2,2′-di (p-aminophenyl) -6,6′-bisbenzoxazole, 2 -(4-aminophenyl) -6-aminobenzoxazole, N- (4-aminophenyl) -4-aminobenzamide, N, N'-bis (4-aminophenyl) terephthalamide, 4-aminophenyl-4- Examples thereof include aminobenzoate and 2,2′-dimethylbiphenyl-4,4′-diamine.

  As a method for synthesizing the polyimide of the present invention, tetracarboxylic dianhydride and diamine (hereinafter, these compounds may be referred to as monomers) are reacted to obtain a polyimide precursor, and then the obtained polyimide precursor is obtained. Examples thereof include a method of synthesizing a polyimide by imidizing a body (method 1), a method of synthesizing a polyimide directly from tetracarboxylic dianhydride and diamine (method 2), and the like.

In Method 1 (method of imidizing a polyimide precursor), the method for synthesizing the polyimide precursor is not particularly limited, and a known method can be adopted.
For example, first, a diamine represented by the above formula (5), a diamine represented by the above formula (6), and other diamines used as needed are dissolved in a solvent to obtain a solution. To the solution, gradually add the tetracarboxylic dianhydride represented by the above formula (4a) or (4b) and other tetracarboxylic dianhydrides used as necessary, which are substantially equivalent to the diamine used. The solution of a polyimide precursor can be obtained by adding to and making it react by continuing stirring.
The monomer concentration at this time is not particularly limited, but is usually 5 to 50% by weight, preferably 10 to 40% by weight.

  The solvent used when synthesizing the polyimide precursor is not particularly limited as long as it sufficiently dissolves the monomer and the polyimide precursor. For example, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, hexamethylphosphate triamide; sulfolane, dimethyl sulfoxide, dimethyl sulfone, tetramethylene Sulfur-containing solvents such as sulfone and dimethyltetramethylenesulfone; phenolic solvents such as cresol, phenol and xylenol; diglyme-based solvents such as diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme) and tetraglyme; γ-butyrolactone, Lactone solvents such as γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone; isophorone, cyclohexanone, 3,3,5-trimethylcyclo Examples include ketone solvents such as hexanone; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; other solvents such as pyridine, ethylene glycol, dioxane, and tetramethylurea. These solvents can be used alone or in combination of two or more.

Although reaction temperature is not specifically limited, Usually, it is -10-80 degreeC, Preferably it is 0-40 degreeC.
Although reaction time is not specifically limited, Usually, it is 0.5 to 150 hours, Preferably it is 3 to 24 hours.

  The obtained polyimide precursor solution can be subjected to the next imidation reaction as it is or after adjusting the concentration without isolating the polyimide precursor. Alternatively, the polyimide precursor can be isolated by dropping the polyimide precursor solution into a large amount of poor solvent such as water or methanol to precipitate the polyimide precursor, which is filtered, washed and dried. .

  The method for imidizing the polyimide precursor is not particularly limited, and for example, a known chemical imidization method or thermal imidization method can be employed. Especially, since it is not necessary to heat too much and the molecular weight fall of a polyimide can be suppressed, a chemical imidation method is used more suitably.

The chemical imidization method can be performed, for example, by dropping an organic acid anhydride and an organic base into this solution while stirring the solution of the polyimide precursor.
Examples of the solvent for the polyimide precursor solution include the same solvents as those shown as the solvent for the synthesis of the polyimide precursor.
Examples of the organic acid anhydride include acetic anhydride, propionic anhydride, maleic anhydride, and phthalic anhydride. Among these, acetic anhydride is preferably used from the viewpoint of easy removal after the reaction and cost.
Although the usage-amount of an organic acid anhydride is not specifically limited, 1-10 equivalent of the theoretical dehydration amount of a polyimide precursor is preferable, and 2-5 equivalent is more preferable.

Examples of the organic base include heterocyclic compounds such as pyridine and picoline; tertiary amines such as triethylamine and N, N-dimethylaniline;
Although the usage-amount of an organic base is not specifically limited, 0.1-2 equivalent is preferable with respect to an organic acid anhydride, and 0.2-1.5 equivalent is more preferable.

  In the chemical imidization method, the reaction temperature is not particularly limited, but is usually 0 to 130 ° C, preferably 20 to 110 ° C. Although reaction time is not specifically limited, Usually, it is 0.5 to 48 hours, Preferably it is 1 to 24 hours.

  The thermal imidization method can be performed, for example, by heating a solution of the polyimide precursor to a temperature at which a dehydration ring-closing reaction occurs. When heating, either a method of raising the temperature up to the maximum temperature in one step or a method of raising the temperature in multiple steps may be used.

Examples of the solvent for the polyimide precursor solution include the same solvents as those shown as the solvent for the synthesis of the polyimide precursor.
In the thermal imidization method, the reaction temperature is not particularly limited, but is usually 130 to 450 ° C, preferably 300 to 400 ° C. Although reaction time is not specifically limited, Usually, it is 0.1 to 24 hours, Preferably it is 0.5 to 5 hours.
The reaction can be carried out in vacuum, in an inert gas such as nitrogen or argon, or in the air. In the reaction system, an organic base such as γ-picoline or water as a by-product is azeotroped. To distill off, toluene, xylene or the like may be added.

Moreover, the isolated polyimide precursor can also be heat-imidized by heating as it is.
Although reaction temperature is not specifically limited, Usually, it is 200-400 degreeC, Preferably it is 250-300 degreeC.
Although reaction time is not specifically limited, Usually, it is 0.5 to 48 hours, Preferably it is 1 to 24 hours.
The reaction can be performed in a vacuum, in an inert gas such as nitrogen or argon, or in the air. However, since the coloring can be prevented, the reaction is preferably performed in a vacuum or an inert gas.

  When a polyimide is synthesized by Method 2 (a method of directly synthesizing polyimide from tetracarboxylic dianhydride and diamine), for example, by changing reaction conditions of a method for synthesizing a polyimide precursor in Method 1, tetracarboxylic acid is obtained. Polyimide can be synthesized directly from dianhydride and diamine.

Examples of the solvent used for the reaction include the same solvents as those shown for the synthesis of the polyimide precursor. Of these, amide solvents and phenol solvents are preferable.
Although reaction temperature is not specifically limited, Usually, 130-250 degreeC, Preferably it is 150-200 degreeC.
Although reaction time is not specifically limited, Usually, it is 0.5 to 48 hours, Preferably it is 1 to 24 hours.
To the reaction system, toluene, xylene or the like may be added in order to azeotropically distill off an organic base such as γ-picoline or water as a by-product as a catalyst.

The reaction can be performed by the above-described method 1 or method 2, and the resulting polyimide solution can be dropped into a large amount of poor solvent to precipitate the polyimide. Furthermore, polyimide powder can be obtained by filtering, washing, drying, etc. the deposited polyimide.
The poor solvent is not particularly limited as long as it does not dissolve polyimide, but it has high affinity with a reaction solvent and a chemical imidizing agent and can be efficiently removed by drying. An alcohol solvent such as n-propanol and isopropanol; a ketone solvent such as acetone; an ester solvent such as ethyl acetate; a mixed solvent thereof;

The weight average molecular weight of the polyimide of this invention is 5,000-1,000,000 normally, Preferably it is 10,000-500,000.
The molecular weight distribution of the polyimide is usually 1.3 to 3, preferably 1.5 to 2.5.
By using a polyimide having a weight average molecular weight or molecular weight distribution within the above range, a film having excellent transparency and mechanical properties and high birefringence can be easily obtained.
In addition, a weight average molecular weight and molecular weight distribution are the polystyrene conversion values obtained by the gel permeation chromatography method which uses cyclopentanone as a solvent.

  The polyimide of the present invention is excellent in transparency. The polyimide of the present invention preferably has a light transmittance of 90% or more, more preferably 95% or more, when the film is formed into a film having a thickness of 10 μm.

  The polyimide of the present invention has high solubility in organic solvents. When the polyimide of the present invention is dissolved in cyclopentanone at 25 ° C. to prepare a saturated solution, the concentration of the saturated solution is preferably 5% by weight or more, more preferably 10% by weight or more. . There is no particular upper limit for the concentration of the saturated solution, but it is usually 50% by weight or less.

  As described above, the polyimide of the present invention has excellent transparency and high solubility in organic solvents. A polyimide having such characteristics is suitably used as a material for producing an optical film by a casting method.

2) Manufacturing method of laminated film, retardation film and laminated film The laminated film of the present invention is a stretched film, and a coated varnish containing the polyimide of the present invention is coated on the stretched film. And a polyimide film formed by drying.

〔varnish〕
The varnish used for manufacturing the laminated film of the present invention can be prepared by dissolving an appropriate amount of the polyimide of the present invention in a solvent.
The solvent used for preparing the varnish is not particularly limited as long as it dissolves polyimide and does not attack the stretched film. Since the solvent can be efficiently evaporated from the coating film after the varnish is applied, the boiling point of the solvent is preferably 180 ° C. or less, more preferably 150 ° C. or less, and further preferably 130 ° C. or less.

As the solvent to be used, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, hexamethylphosphoric triamide; sulfolane, dimethyl sulfoxide, dimethyl sulfone Sulfur-containing solvents such as tetramethylene sulfone and dimethyltetramethylene sulfone; phenol solvents such as cresol, phenol and xylenol; diglyme solvents such as diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme) and tetraglyme; γ -Lactone solvents such as butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone; diethyl ketone, methyl isobutyl ketone, cyclo Ketone solvents such as pentanone, isophorone, cyclohexanone and 3,3,5-trimethylcyclohexanone; aromatic hydrocarbon solvents such as benzene, toluene and xylene; other solvents such as pyridine, ethylene glycol, dioxane and tetramethylurea; Etc. These solvents can be used alone or in combination of two or more.
Among these, when a cycloolefin polymer film is used as the stretched film, a ketone solvent is preferable, and cyclopentanone is more preferable.

  The polyimide concentration (resin concentration) in the varnish can be appropriately determined according to the coating method of the varnish and the target film thickness. The resin concentration is preferably 5 to 30% by weight, more preferably 5 to 20% by weight.

  The varnish may contain an additive as long as the effects of the present invention are not impaired. Examples of the additive include an oxidation stabilizer, a filler, an adhesion promoter, a silane coupling agent, a photosensitizer, a photopolymerization initiator, a sensitizer, a terminal blocking agent, and a crosslinking agent.

[Stretched film]
The stretched film used in the present invention is not particularly limited as long as birefringence is expressed by stretching.
The stretched film material is not particularly limited as long as it is a thermoplastic resin, but preferably has a glass transition temperature (Tg) of 80 to 200 ° C, more preferably 100 to 180 ° C.
Examples of the thermoplastic resin constituting the stretched film include cycloolefin polymer, polycarbonate, polyarylate, polyethylene terephthalate, polysulfone, polyethersulfone, polyphenylene sulfide, polyimide, polyamideimide, polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyolefin. , Polyvinyl alcohol, polyvinyl chloride polymethyl methacrylate, polyarylate and the like. Among these, cycloolefin polymer and polycarbonate are preferable, and cycloolefin polymer is particularly preferable.

Examples of the cycloolefin polymer include norbornene resins, monocyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.
The norbornene-based resin includes a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, or a monomer having a norbornene structure. An addition copolymer of a monomer, an addition copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, or the like can be given.

  Commercially available cycloolefin polymers include “Topas” (manufactured by Ticona), “Arton” (manufactured by JSR), “Zeonor” and “Zeonex” (manufactured by Nippon Zeon) ”,“ Appel ”(manufactured by Mitsui Chemicals). (All are trade names).

A stretched film used in the present invention can be obtained by forming the thermoplastic resin into a film to obtain a thermoplastic resin film and stretching the film.
When forming a film, a known film forming method such as a solvent casting method or a melt extrusion method can be appropriately used. Further, commercially available thermoplastic resin films such as “Essina”, “SCA40” (manufactured by Sekisui Chemical Co., Ltd.), “Zeonor Film” (manufactured by Nippon Zeon Co., Ltd.), “Arton Film” (manufactured by JSR Corporation), etc. it can.

  The thermoplastic resin film may contain a compounding agent in addition to the thermoplastic resin. Compounding agents include layered crystalline compounds; inorganic fine particles; antioxidants, heat stabilizers, light stabilizers, weathering stabilizers, UV absorbers, near infrared absorbers and other stabilizers; resin modifiers such as lubricants and plasticizers Agents; coloring agents such as dyes and pigments; antistatic agents and the like. These compounding agents can be used alone or in combination of two or more. The compounding quantity of a compounding agent can be suitably determined in the range which does not impair the objective of this invention.

  When stretching the thermoplastic resin film, a known method such as a uniaxial stretching method, a biaxial stretching method, or an oblique stretching method can be used.

  The stretched film is preferably subjected to a surface treatment such as an atmospheric pressure plasma surface treatment or a silane coupling agent treatment. By forming a polyimide film on the surface of the stretched film that has been subjected to these surface treatments by a casting method, the polyimide film can more strongly reflect the arrangement of molecular chains constituting the stretched film, and is superior in birefringence. A film can be formed.

Although the thickness of a stretched film is not specifically limited, Preferably it is 5-200 micrometers, More preferably, it is 20-100 micrometers.
The in-plane retardation (Re) at a wavelength of 550 nm of the stretched film is not particularly limited, but is preferably 30 to 250 nm, and more preferably 80 to 200 nm.

When the laminated film is used as it is as a retardation film without peeling and removing the stretched film from the laminated film obtained by forming the polyimide film [retarded film (α) or retardation film (β) described later], used The stretched film is preferably excellent in transparency. In this case, the light transmittance of light having a wavelength of 400 to 800 nm of the stretched film is preferably 90% or more, and more preferably 95% or more.
On the other hand, when the stretched film is used as a process sheet and the stretched film is peeled and removed [for example, a retardation film (γ) described later], the stretched film used may be inferior in transparency.

[Laminated film]
The laminated film of the present invention can be produced by forming a polyimide film by coating the varnish on a stretched film and drying the resulting coating film.

  The method for applying the varnish is not particularly limited, and a conventionally known method can be used. Examples of the coating method include spin coating, dip coating, roll coating, curtain coating, die coating, and slit coating.

  The drying temperature is usually 50 to 130 ° C., preferably 60 to 120 ° C., more preferably 70 to 110 ° C., and the drying time is usually 1 to 60 minutes, preferably 1 to 50 minutes, more preferably 1 to 40. Minutes.

  The film thickness of the polyimide film is usually 1 μm or more, preferably 1 to 100 μm, more preferably 5 to 50 μm.

The laminated film of this invention should just have the said polyimide film, and another layer is not specifically limited.
The laminated film of the present invention can be used as it is as a retardation film. Examples of the laminated film of the present invention include a film having the polyimide film on one side of the stretched film [retardation film (α)] and a film having the polyimide film on both sides of the stretched film [retardation film (β)]. It is done.

Examples of the retardation film (α) include a film having a layered structure of a stretched film / polyimide film immediately after a polyimide film is formed on one side of the stretched film.
Examples of the retardation film (β) include a film having a layer structure of polyimide film / stretched film / polyimide film obtained by further forming a polyimide film on the stretched film side of the retardation film (α). Can be mentioned.

[Phase difference film]
A retardation film [retardation film (γ)] can be obtained by peeling and removing the stretched film from the laminated film.
Examples of the retardation film (γ) include a film made only of a polyimide film. The stretched film can be removed by, for example, immersing the retardation film (α) in water.

  The laminated film and retardation film of the present invention (hereinafter sometimes referred to as “laminated film etc.”) may have an adhesive layer. By laminating the laminated film or the like of the present invention having an adhesive layer to another film or the like, a laminated film having birefringence can be efficiently obtained.

When forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive or adhesive usually used in an optical film can be used. For example, hot melt adhesives, thermosetting adhesives, pressure sensitive adhesives, energy ray curable adhesives, hygroscopic adhesives, dry adhesives, UV curable adhesives, polymerization adhesives, two-component reactions A mold adhesive, an anaerobic adhesive, or the like can be used.
When forming an adhesive layer, a commercially available transparent adhesive sheet can also be used. Examples of such a transparent adhesive sheet include LUCIACS (manufactured by Nitto Denko Corporation).

  The laminated film of the present invention is excellent in transparency. The light transmittance of light having a wavelength of 400 nm, such as the laminated film of the present invention, is preferably 90% or more, more preferably 95% or more.

  The polyimide film constituting the laminated film of the present invention has high birefringence. The birefringence of the polyimide film at a wavelength of 400 to 800 nm is usually 0.02 or more, preferably 0.03 or more. There is no particular upper limit value for the birefringence, but it is usually 0.06 or less.

  The polyimide film constituting the laminated film of the present invention is excellent in mechanical properties. When a tensile test was performed at a rate of 100 mm / min using a polyimide film having a thickness of 10 μm and a width of 10 mm, the breaking strength is preferably 60 MPa or more, more preferably 80 MPa or more, and the upper limit is not particularly limited, but 200 MPa Degree. The elongation at break is preferably 5% or more, more preferably 10% or more, and the upper limit is not particularly limited, but is about 50%.

[Production method of laminated film]
The manufacturing method of the laminated | multilayer film of this invention has the process of coating the varnish containing the polyimide of this invention on a stretched film, and drying the obtained coating film.
Examples of the polyimide, varnish, and stretched film used in the method of the present invention include those described above. Moreover, the said method can be utilized as a coating method of a varnish, and the drying method of the obtained coating film.

  According to the method of the present invention, a laminated film can be efficiently produced by a casting method. In particular, it is preferable to use a cycloolefin polymer film as a stretched film because birefringence can be strongly expressed, and it is more preferable to use a cycloolefin polymer film that has been subjected to an atmospheric pressure plasma surface treatment and a silane coupling agent treatment. preferable.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples. In the following Examples and Comparative Examples, “parts” and “%” are based on weight unless otherwise specified.

The materials used in the examples are as follows.
Cycloolefin film (1): Atmospheric pressure plasma surface treatment and silane coupling agent (manufactured by Chisso Corporation, trade name: Sila Ace S330) for cycloolefin-based stretched film (manufactured by Nippon Zeon, product name: Zeonoa ZM-16) ) Film obtained by treatment Cycloolefin film (2): Cycloolefin unstretched film (manufactured by ZEON Corporation, product name: ZEONOR ZF-16), atmospheric pressure plasma surface treatment and silane coupling agent (Product name: Sila Ace S330, manufactured by Chisso Corporation) Film obtained by processing

[Example 1]
4,4′-diaminobenzanilide (DABA) 3.409 g (0.015 mol), 9,9′-bis (4-aminophenyl) fluorene (BAFL) 5.226 g (0.015 mol), N, N -Dimethylacetamide (DMAc) 107.6g was mixed and it stirred at 25 degreeC for 20 minutes. Subsequently, the obtained solution was ice-cooled, and 18.259 g (0.03 mol) of bis (octahydro-1,3-dioxo-5-isobenzofurancarboxylic acid) 4,4′-sulfonyldianilide (PSHT) was added to this solution. The mixture was stirred for 2 hours under ice-cooling and then for 20 hours at 25 ° C. to obtain a polyimide precursor varnish.
To the obtained polyimide precursor varnish, 12.25 g (0.12 mol) of acetic anhydride and 11.87 g (0.15 mol) of pyridine were added, 1 hour at 25 ° C., 1 hour at 80 ° C., 4 hours at 110 ° C. The chemical imidization reaction was performed by stirring. At this time, the reaction solution did not gel. After the reaction, the reaction solution was diluted with DMAc so that the resin concentration became 7%, and the obtained diluted solution was dropped into 8 L of methanol to precipitate polyimide, which was collected by filtration.
The polyimide was washed twice with methanol and then vacuum-dried at 130 ° C. for 6 hours (yield: 25.12 g, yield 97.1%).
When the solubility of the obtained polyimide in cyclopentanone at 25 ° C. was examined, the concentration of the saturated solution was 20% or more.

Polyimide was dissolved in cyclopentanone to obtain a varnish having a concentration of 20%. Next, this varnish was applied onto the cycloolefin film (1) using a doctor blade so that the film thickness after drying was 10 μm, and the obtained coating film was applied using a nitrogen stream type inert oven. And dried at 80 ° C. for 30 minutes and 150 ° C. for 60 minutes to obtain a laminated film composed of the cycloolefin film (1) and the polyimide film.
After cutting the obtained laminated film to expose the cross section of the film, the polyimide film was peeled off from the cycloolefin film (1) by being immersed in water for 24 hours, and the peeled polyimide film was vacuumed at 130 ° C. for 3 hours. Dried.

[Example 2]
A polyimide film was prepared in the same manner as in Example 1 except that the amount of DABA used was changed to 2.045 g (0.009 mol) and the amount of BAFL used was changed to 7.316 g (0.021 mol). Got.

Example 3
A polyimide film was prepared in the same manner as in Example 1 except that the amount of DABA used was changed to 4.772 g (0.021 mol) and the amount of BAFL used was changed to 3.136 g (0.009 mol). Got.

Example 4
A polyimide film was prepared in the same manner as in Example 1 except that PSHT was changed to bis (octahydro-1,3-dioxo-5-isobenzofurancarboxylic acid) 1,4-phenylenediamide (PPHT) in Example 1. Obtained.

[Comparative Example 1]
A polyimide film was obtained in the same manner as in Example 1 except that the cycloolefin film (1) was changed to the cycloolefin film (2) in Example 1.

[Comparative Example 2]
In Example 1, polyimide was synthesized in the same manner as in Example 1 except that only 6.818 g (0.03 mol) of DABA was used as the diamine. The obtained polyimide was hardly soluble in cyclopentanone at 25 ° C. (saturated solution concentration was 5% or less), and a polyimide film could not be obtained.

[Comparative Example 3]
In Example 1, a polyimide film was obtained in the same manner as in Example 1 except that only BAFL 10.453 g (0.03 mol) was used as the diamine.

[Comparative Example 4]
In Example 1, 8.826 g (0.03 mol) of 3,3′4,4′-biphenyltetracarboxylic dianhydride (S-BPDA) was used as tetracarboxylic dianhydride, and BAFL10. A polyimide was synthesized in the same manner as in Example 1 except that 453 g (0.03 mol) was used. The obtained polyimide was hardly soluble in cyclopentanone at 25 ° C. (the concentration of the saturated solution was 5% or less), and a polyimide film could not be obtained.

  The following measurements were performed on the polyimides and polyimide films obtained in Examples 1 to 4 and Comparative Examples 1 to 4, and the physical properties were evaluated. The results are shown in Table 1.

[Solubility]
The polyimide was dissolved in cyclopentanone at 25 ° C., and the solubility was evaluated according to the following criteria.
○: A solution having a concentration exceeding 20% is obtained.
Δ: A solution having a concentration exceeding 5% and 20% or less is obtained.
X: A solution having a concentration exceeding 5% cannot be obtained.

(Phase difference measurement)
Using a spectroscopic erythrometer (manufactured by JA WOOLLAM JAPAN, product name: M-2000, polyimide film (thick film about 10 μm), film surface direction (x axis, y axis), film vertical direction ( The refractive index (z-axis) was measured, and the phase difference (Rth) was calculated.

(Measurement of light transmittance)
Using a UV-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, product name: V-570), the light transmittance at a wavelength of 400 nm of the polyimide film (film thickness: 10 μm) was measured, and the light transmittance was 90% or more. The case where is.

(Measurement of thermal expansion coefficient)
Using a thermomechanical analyzer (product name: TMASS7100, manufactured by SII), under a nitrogen atmosphere, temperature range: room temperature to 300 ° C., temperature increase rate: 5 ° C./min, thermal expansion coefficient of polyimide film under conditions of 2 cycles (Ppm / ° C.) was measured, and the measured value of the second cycle was adopted.

[Membrane breaking strength, breaking elongation]
Using a precision universal testing machine (manufactured by Shimadzu Corporation, product name: Autograph AG), a tensile test was performed at a rate of 100 mm / min using a polyimide film having a thickness of 10 μm and a width of 10 mm, and breaking strength (MPa). The elongation at break (%) was measured.

The following can be seen from Table 1.
The polyimides obtained in Examples 1 to 4 exhibit high solubility with respect to cyclopentanone, and can prepare a varnish for a casting method.
On the other hand, the polyimide of Comparative Example 2 using only DABA as the diamine and the polyimide of Comparative Example 4 using S-BPDA as the tetracarboxylic dianhydride are both poor in solubility in cyclopentanone.
In Comparative Example 1, since an unstretched film was used as a base material, birefringence was not sufficiently developed.
In Comparative Example 3, since DABA is not used as a diamine, birefringence is hardly exhibited.

Claims (10)

Having a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2),
The molar ratio of the repeating unit represented by the formula (1) and the repeating unit represented by the formula (2) [the repeating unit represented by the formula (1): the repeating unit represented by the formula (2)] is 20:80. ~ 70: 30,
The polyimide characterized by the total amount of the repeating unit represented by the formula (1) and the repeating unit represented by the formula (2) being 80 to 100 mol% in all repeating units.

[Wherein, R ¹ and R ² each independently represent a halogen atom, a hydroxyl group, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxyl group having 1 to 6 carbon atoms, Or represents a trifluoromethyl group. A ¹ represents the following formula (3a) or (3b)

(In the formula, * represents a bond.)
Represents a group represented by a and b each independently represents an integer of 0 to 4; When a and b are each 2 or more, a plurality of R ^{1 s} and R ^{2 s} may be the same or different. ]

(In the formula, R ^{3 to} R ⁶ are each independently a halogen atom, a hydroxyl group, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxyl group having 1 to 6 carbon atoms, Or A ¹ represents a group represented by the formula (3a) or (3b), and cf each independently represents an integer of 0 to 4. c, d, e, When f is 2 or more, a plurality of R ^{3 s} , R ^{4 s} , R ^{5 s,} and R ^{6 s} may be the same or different.   The polyimide according to claim 1, wherein when formed into a film having a thickness of 10 μm, the light transmittance of light having a wavelength of 400 nm of the film becomes 90% or more.   The polyimide according to claim 1 or 2, wherein when a saturated solution is prepared by dissolving in cyclopentanone at 25 ° C, the concentration of the saturated solution becomes 5% by weight or more.   A laminate having a stretched film and a polyimide film formed by applying the varnish containing the polyimide according to any one of claims 1 to 3 on the stretched film and drying the resulting coating film. the film.   The laminated film according to claim 4, wherein the stretched film is a film obtained by stretching an unstretched cycloolefin polymer film.   Furthermore, the laminated film of Claim 4 or 5 which has an adhesive layer.   A retardation film obtained by peeling and removing a stretched film from the laminated film according to claim 4.   Furthermore, the retardation film of Claim 7 which has an adhesive layer.   The manufacturing method of the laminated | multilayer film which has the process of coating the varnish containing the polyimide in any one of Claims 1-3 on a stretched film, and drying the obtained coating film.   The method for producing a laminated film according to claim 9, wherein the stretched film is a film obtained by stretching an unstretched cycloolefin polymer film.