JP2011148955A - Method for producing polyimide film, and the resultant polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a transparent polyimide film with markedly reduced discoloration by making a specific aromatic acid dianhydride and a diamine by a specific method, further, to provide a polyimide film composition useful as a film material for forming a product or one member for which transparency, heat resistance and dimensional stability are demanded using the polyimide film, and in addition, to provide a highly heat-resistant product or one member made using the composition. <P>SOLUTION: The polyimide film having high dimensional stability and a coefficient of linear expansion about the same as those of various inorganic materials and markedly reduced in discoloration, is obtained by mixing a specific polyamic acid solution with a dehydrating catalyst and an imidizing agent of 180°C or lower in boiling point followed by conducting a reaction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a polymer compound that is low in color and excellent in dimensional stability. Preferably, it relates to polyimide having excellent heat resistance, and in particular, a polyimide film that can be suitably used as a material (for example, a substitute for display device glass) for forming a product or member that is highly colored with heat resistance and requires high dimensional stability. The manufacturing method of this and the polyimide film obtained by the manufacturing method of the said polyimide film are related.

  In recent years, with the rapid progress of displays such as liquid crystal, organic EL, and electronic paper, and electronics such as solar cells and touch panels, devices have been required to be thinner and lighter, and more flexible. . In these devices, various electronic elements such as thin transistors and transparent electrodes are formed on a glass plate. By changing this glass material to a film material, the panel itself becomes flexible, thin and lightweight. Can be achieved. However, there has been no film material that can withstand the high temperature of the formation process of electronic devices.

  In addition, when an electronic element made of an inorganic material is formed on a film, the linear expansion coefficient of the inorganic material and the film may be greatly different, the film on which the inorganic element is formed may be bent, and further, the inorganic element may be peeled off from the film. There was a case. For this reason, a film material that has transparency and heat resistance and does not have these problems has been desired.

  Since polyimide has high insulation performance as well as heat resistance, it has been applied to semiconductors and electronic components. Electronic parts are often laminated with a metal such as single crystal silicon or copper, and attempts have been made to reduce the linear thermal expansion coefficient of polyimide to the same level as single crystal silicon or metal.

  The chemical structure is a factor that greatly affects the linear thermal expansion coefficient of polyimide. Generally, it is said that the higher the rigidity and linearity of the polyimide polymer chain, the lower the expansion coefficient. In order to reduce the expansion coefficient, various structures have been proposed for both acid dianhydrides and diamines, which are polyimide raw materials. It was.

  For example, Patent Document 1 is obtained by casting a polyamic acid solution obtained from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine. A polyimide film is obtained by immersing the film in a dehydration catalyst and imidizing agent solution. It is described that the linear expansion coefficient of the film was improved by dipping.

  Patent Document 2 was obtained by reacting 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine in m-cresol. Although it is described that the polyimide was obtained by gradually heating the polyamic acid to 300 ° C., it was not satisfactory in terms of linear expansion coefficient and heat resistance (Tg).

  As described above, there has been a demand for the development of a polyimide film that is transparent and has a smaller linear expansion coefficient while maintaining the heat resistance of the polyimide.

JP2007-46054 U.S. Pat.

  The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to obtain a polyimide film having excellent heat resistance, linear expansion coefficient, and the like. In addition, an object is to obtain a polyimide film in which coloring is greatly reduced.

  The configuration of the present invention is as follows.

  1). This is a method for producing a polyimide containing a repeating unit represented by the following formula (1), and a solution obtained by mixing a polyamic acid solution with a solution containing a dehydration catalyst and an imidizing agent having a boiling point of 180 ° C. or lower is flowed on a support. It produces by extending, The manufacturing method of the polyimide film characterized by the above-mentioned.

In the formula, R ¹ represents a tetravalent organic group selected from the following general formula (2), R ² represents a divalent organic group selected from the following general formula (3),

In the formula, R ³ represents hydrogen, halogen, alkyl halide, or a C1-C16 alkyl group.

2). R ² is a divalent organic group selected from the following general formula (4): 1) The method for producing a polyimide film according to 1).

In the formula, R ³ represents hydrogen, halogen, alkyl halide, or a C1-C16 alkyl group.

3). The method for producing a polyimide film according to 1) or 2), wherein R ³ is halogen or alkyl halide.

4). The process for producing a polyimide film as described in any of 1) to 3) wherein R ³ is a trifluoromethyl group.

5). As one of the repeating units represented by the formula (1), the structure of R ¹ is a tetravalent organic group selected from the following general formula (5): The manufacturing method of the polyimide film of description.

  6). The method for producing a polyimide film according to any one of claims 1 to 5, wherein the dehydration catalyst is selected from acid anhydrides.

  7). The polyimide according to any one of 1) to 6), wherein the amount of the imidizing agent used is 0.01 mole equivalent or more and 2.0 mole equivalent or less with respect to the carboxylic acid of the polyamic acid. A method for producing a film.

  8). The polyimide film manufactured by the method according to any one of 1) to 7), wherein the YI of the film is 20 or less.

  9). The polyimide film as described in 8) obtained by imidizing the polyamic acid whose weight average molecular weight is 3,000 or more.

  In addition to transparency, heat resistance, and low linear expansion, the polyimide film obtained by the method according to the present invention has greatly improved colorability and requires heat resistance and low expansion (dimensional stability). It is suitable as a film for members. Specifically, for example, printed materials, color filters, flexible displays, semiconductor parts, interlayer insulating films, wiring coating films, optical circuits, optical circuit parts, antireflection films, holograms, optical members, or use as building materials or structures There is expected.

The present invention is described in detail below.
The polyimide manufactured by this invention is a polyimide containing the repeating unit represented by Formula (1). R ¹ in the formula (1) is a tetravalent organic group having a specific structure listed in the formula (2).

  Specific examples thereof include a structure in which a tetravalent organic group corresponding to each acid dianhydride component described later, that is, an acid anhydride group involved in the formation of a polyimide chain is removed from the acid dianhydride component. Two or more kinds of acid dianhydrides having a tetravalent organic group listed in formula (2) can be used in combination. Of the tetravalent organic groups listed in formula (2), benzene or biphenyl represented by formula (5) is particularly preferable.

  Specific compounds having benzene or biphenyl may include pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, respectively. Among them, 3,3 ′ 4,4′-biphenyltetracarboxylic dianhydride is preferred.

  The polyimide film of the present invention is preferably produced using an acid dianhydride in which all of the acid components have the structure of the formula (2), but not only the structure of the above formula (2) but also one or more formulas An acid dianhydride having no structure of (2) can be used in combination. Other acid dianhydrides that can be used in combination without having the structure of (2) may be used within a range not exceeding 70 mol%, preferably 50 mol%, and further not exceeding 25 mol% of the entire acid dianhydride. When using 2 or more types of acid dianhydrides, they may be regularly arranged or may be present in the polyimide randomly.

  Other acid dianhydrides that can be used in combination include, for example, ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 3, 3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether Dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicar Xylphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexa Fluoropropane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4 -Dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) ) Phenoxy] phenyl} propane dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2- Dicarboxy) phenoxy] phenyl} keto Dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride 4,4′-bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis { 4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-Zika Boxy) phenoxy] phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexafulpropane Dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6 , 7-Naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4 Benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrene And tetracarboxylic dianhydride That.

On the other hand, R ² in the formula (1) is a divalent organic group having a structure represented by the formula (3). Specifically, the polyimide which has a structure of Formula (1) can be obtained using the diamine which has a structure of Formula (3). These diamines can be used in combination of two or more. Of the formula (3), benzene or biphenyl represented by the formula (4) is preferable.

R ³ in the formulas (3) and (4) is a monovalent organic group representing hydrogen, halogen, alkyl halide, or a C1-C16 alkyl group. From the transparency, heat resistance, and dimensional stability of the resulting polyimide, electron withdrawing groups such as halogen and alkyl halides are preferred. As halogens of halogen and halogenated alkyls, fluorine is preferred, among which fluorine atoms or trifluoromethyl groups. In particular, a trifluoromethyl group is preferred. R ² is most preferably a 2,2′-bis (trifluoromethyl) benzidine residue.

  It is preferable to use a diamine having the structure of the formula (3) as the diamine component for the polyimide film of the present invention. However, the diamine having the structure represented by the formula (3) and one or more other diamines are used in combination. Can be used. As other diamines that can be used in combination, 70 mol%, preferably 50 mol%, more preferably 25 mol% of the whole diamine is used within the range in which the transparency of the polyimide can be ensured. It doesn't matter. Moreover, when using 2 or more types of diamine, they may be arranged regularly and may exist in a polyimide at random.

  Examples of other diamines that can be used in combination with the diamine having the structure represented by formula (3) include 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, and 3,3 ′. -Diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 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- (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-aminophenoxy) benzene, 1,4-bis (3-amino Enoxy) 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-ditrifluoromethylbenzyl) 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) Cis) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-amino) Phenoxy) 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, -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] diphenylsulfone, 3,3'-diamino-4,4'-diph Noxybenzophenone, 3,3′-diamino-4,4′-dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′- Bis (3-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3 ′ -Tetramethyl-1,1'-spirobiindane, 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis (3 -Aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, (3-aminopropyl) ether, bis (2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether, 1 , 2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2- Aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1 , 4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1, -Diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diamino Cyclohexane, 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2-aminoethyl) cyclohexane, bis ( 4-aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane.

  The polyimide film in the present invention is characterized by having a structure represented by the formula (1), but it is preferable that the entire polyimide film has a structure substantially represented by the above formula. As the amine component, those having an alkyl halide chain, particularly a trifluoromethyl group are preferred.

  Specifically, as the amine component particularly preferably used, 2,2′-bis (trifluoromethyl) benzidine is preferable. Examples of tetracarboxylic dianhydride include pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, among which 3,3 ′, 4,4 ′. -Biphenyltetracarboxylic dianhydride is preferred.

  As a method for producing the polyimide of the present invention, a polyamic acid which is a precursor is synthesized from an acid dianhydride and a diamine, and a polyimide film is obtained by adding a dehydration catalyst or an imidizing agent thereto. In the method of molding in the state of polyamic acid and then imidizing by heating without using a dehydration catalyst or imidizing agent, the resulting film has poor linear expansion and hysteresis, and is not suitable for the purpose.

  The imidizing agent used may be an imidizing agent having a boiling point of 40 ° C. or higher and 180 ° C. or lower, and examples thereof include amine compounds having a boiling point of 180 ° C. or lower. When an imidizing agent having a boiling point exceeding 180 ° C is used, the film is colored when dried at a high temperature, and the appearance of the film is liable to be damaged. Particularly, an amine compound having a boiling point exceeding 180 ° C is colored when dried at a high temperature, The appearance of the film is easily damaged. Further, if the boiling point is less than 40 ° C., there is a possibility of volatilization before imidization proceeds sufficiently. Preferable amine compounds include pyridine and picoline.

  An acid anhydride and carbodiimide are used as the dehydration catalyst. Examples of the acid anhydride include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride. An example of carbodiimide is dicyclohexylcarbodiimide.

  The addition amount of the imidizing agent is preferably 0.01 to 2.0 times molar equivalent, and particularly preferably 0.05 to 2.0 times molar equivalent, relative to the carboxylic acid group of the polyamic acid. When an imidizing agent exceeding 2.0 times molar equivalent is used, the imidizing agent remains after drying at a high temperature and the film is highly colored. When the amount used is less than 0.01 times molar equivalent, the effect of chemical imidization Does not appear, and the physical properties of the film such as the coefficient of linear expansion tend to decrease.

  The addition amount of the dehydration catalyst is preferably 0.05 to 15.0 times molar equivalent, and particularly preferably 2.0 to 10 times molar equivalent, relative to the carboxylic acid group of the polyamic acid. In a method using a dehydration catalyst, for example, Patent Document 2 discloses a method of obtaining a polyimide film by immersing the obtained polyamic acid film in a dehydration catalyst and an imidizing agent. In this method, the linear expansion coefficient of the resulting polyimide film and the dimensional stability before and after heating are not sufficient, and the resulting inorganic laminated film is bent and the inorganic film formed on the film is destroyed. Is difficult to solve.

  Moreover, as a use ratio of the imidizing agent and the dehydration catalyst, it is preferable to use the dehydration catalyst in a ratio of 2 to 10 mol, more preferably 3 to 7 times mol per mol of the imidizing agent.

  Next, the method for synthesizing the polyimide according to the present invention will be illustrated more specifically, but the present invention is not limited thereto. An example will be described in which polyimide is synthesized using 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride as an acid component and 2,2′-bis (trifluoromethyl) benzidine as an amine component.

  First, substantially equimolar 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was gradually added while stirring dimethylacetamide in which 2,2′-bis (trifluoromethyl) benzidine was dissolved. Thus, polyamic acid can be obtained. The temperature at the time of mixing may be room temperature as long as attention is paid to heat generation, but it can be carried out at 10 ° C. or lower, further 5 ° C. or lower. The stirring time can be 10 hours or longer, and further 20 hours or longer. After the obtained polyamic acid is brought to a low temperature of 0 ° C. or lower, an imidizing agent having a boiling point of 180 ° C. or lower and a dehydration catalyst are added, and the dimethylacetamide solution can be obtained by vigorously stirring.

  After defoaming under vacuum or using a centrifugal precipitator, etc., it is applied onto a substrate such as glass, film or belt, dried, and a coating film is formed. A polyimide can be obtained.

  The polyimide of the present invention synthesized as described above has good heat resistance and dimensional stability because it uses a component having an aromatic group. Specifically, the proportion of the acid component having an aromatic group in the acid component constituting the repeating unit of the imide structure is preferably 50 mol% or more, particularly preferably 70 mol% or more, and the repeating unit of the imide structure is constituted. The proportion of the amine component having an aromatic group in the amine component is preferably 40 mol% or more, particularly preferably 60 mol% or more, and in particular, both the acid and amine components may be components having an aromatic group. Particularly preferred.

  The dimensional stability here means the dimensional change rate of the film before and after the film is heated and cooled. When this rate of dimensional change is large, the smoothness of the film may be lost, or when an inorganic thin film is formed on the film, the inorganic thin film may be damaged. Specifically, the dimensional change rate is preferably within ± 0.03%, more preferably within ± 0.01%, and particularly preferably within ± 0.004.

  The polyimide film of the present invention synthesized in this way is also characterized by low colorability (lighter color tone than conventional polyimide) and transparency. For example, the YI (yellow index) of a 50 μm-thick film is A polyimide film of 20 or less, or 18 or less can be obtained. In addition, it is possible to obtain a film having a total light transmittance of 80% or more, more preferably 83% or more, particularly 84% or more, and a haze of 2.5% or less, further 2.3% or less. is there.

  The weight average molecular weight of the polyamic acid of the present invention is preferably in the range of 3,000 to 1,000,000, more preferably in the range of 5,000 to 500,000, although it depends on its use. More preferably, it is in the range of 10,000 to 500,000. When the weight average molecular weight is 3,000 or less, it is difficult to obtain sufficient strength when a coating film or film is used. Further, if it is less than 10,000, coloring may occur because the number of polymer ends that cause coloring becomes relatively large. On the other hand, when it exceeds 1,000,000, the viscosity increases and the solubility also decreases, so that it is difficult to obtain a coating film or film having a smooth surface and a uniform film thickness. The molecular weight used here refers to a value in terms of polystyrene by gel permeation chromatography (GPC).

  The polyimide of the present invention is characterized by particularly excellent low colorability and dimensional stability, but is also excellent in other properties such as heat resistance and insulation. For example, the glass transition temperature is preferably as high as possible from the viewpoint of heat resistance, but in the differential scanning calorimeter, the glass transition temperature when measured at a temperature rising rate of 10 ° C./min is 200 ° C. or higher, Furthermore, it is possible to obtain polyimide at 300 ° C. or higher.

  The polyimide according to the present invention may be subjected to a coating or molding process for producing a product or member as it is, but the polyimide is dissolved or dispersed in a solvent as necessary, and further, a light or thermosetting component, A polyimide resin composition may be prepared by blending a non-polymerizable binder resin other than polyimide according to the present invention and other components.

  In order to impart processing characteristics and various functionalities to the resin composition according to the present invention, various organic or inorganic low-molecular or high-molecular compounds may be blended. For example, dyes, surfactants, leveling agents, plasticizers, fine particles, sensitizers, and the like can be used. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicate, and these may have a porous or hollow structure. The function or form includes pigments, fillers, fibers, and the like.

  In the polyimide resin composition according to the present invention, the polyimide having the structure represented by the formula (1) is usually contained within a range of 40 to 99.9% by weight with respect to the entire solid content of the resin composition. Can be made. In addition, the blending ratio of other optional components is preferably in the range of 0.1% by weight to 60% by weight with respect to the entire solid content of the polyimide resin composition. When the amount is less than 0.1% by weight, the effect of adding the additive is hardly exhibited, and when the amount exceeds 60% by weight, the characteristics of the resin composition are hardly reflected in the final product. In addition, solid content of a polyimide resin composition is all components other than a solvent.

  The polyimide film according to the present invention can be used by forming various inorganic thin films such as metal oxides and transparent electrodes on the surface thereof. The method for forming these inorganic thin films is not particularly limited, and may be, for example, a PVD method such as a CVD method, a sputtering method, a vacuum deposition method, or an ion plating method.

  Since the polyimide resin composition according to the present invention has high dimensional stability in addition to the original characteristics of polyimide such as heat resistance and insulation, fields and products in which these characteristics are effective, for example, printed matter, Suitable for forming color filters, flexible displays, semiconductor parts, interlayer insulating films, wiring coating films, optical circuits, optical circuit parts, antireflection films, holograms, optical members or building materials. Specifically, the polyimide film of the present invention can be used as a so-called optical film and used as a polarizing plate in combination with a deflector.

  Moreover, the optical member which consists of a polarizing plate using the polyimide film of this invention or the polyimide film of this invention is provided in the at least one surface of a liquid crystal cell, and it can use also as a liquid crystal panel. Furthermore, it can also be used as a liquid crystal display device using the liquid crystal panel.

(Synthesis of precursor solution)
2,2'-bis (trifluoromethyl) benzidine (21.8 g, 68 mmol) was charged into a 300 ml three-necked flask, dissolved in 167 g of dehydrated dimethylacetamide (DMAc), and cooled in an ice bath under a nitrogen stream. While stirring. Thereto was added 20 g (68 mmol) of the above 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and after completion of the addition, the mixture was stirred for 40 hours to obtain a viscous liquid (precursor solution). Moreover, as a result of measuring the molecular weight of this precursor solution, the weight average molecular weight was 94000.

(Example)
The synthesized precursor solution (20 g) was cooled to around 0 ° C., then 0.91 g (9.7 mmol) of β-picoline (boiling point 144 ° C.) as an imidizing agent, and 4.98 g (48. 48 g) of acetic anhydride as a dehydration catalyst. 8 mmol) and 1.11 g of DMAc were added and stirred vigorously. Then, after defoaming with a centrifugal settling machine, it flowed on aluminum foil, and it apply | coated on aluminum foil with the comma coater which set the slit space | interval to 0.77 mm. Thereafter, the temperature was raised from 100 ° C. to 350 ° C. over 20 minutes and heated at 350 ° C. for 8 minutes to obtain a transparent polyimide film having a thickness of 50 μm and YI of 15.6.

[Evaluation of linear thermal expansion coefficient and dimensional change rate before and after heating]
Using a thermomechanical analyzer (trade name: TMA120C, manufactured by Seiko Instruments Inc.), pulling at one end in the longitudinal direction of the film under a nitrogen stream, temperature increase rate 10 ° C / min, temperature decrease rate 10 ° C / min, film size 10 mm x 3 mm Measurement was performed with a load of 6 g. As a result, the linear thermal expansion coefficient at 100 ° C. to 200 ° C. was 1.7 ppm / K. When the film was heated from 50 ° C. to 210 ° C. and returned to 50 ° C., the dimensional change rate of the film was + 0.001%. In addition, the dimensional change rate was described as − (minus) when contracted from the original dimension, and + (plus) when expanded.

[Evaluation of YI]
YI of the obtained film was measured using HANDY COLORIMTER NR-3000 manufactured by Nippon Denshoku Industries Co., Ltd.

[Evaluation of glass transition temperature]
The Tg (glass transition temperature) of the polymer was determined by DSC-50 (Shimadzu heat flux differential scanning calorimeter) measured at a rate of temperature increase of 10 ° C./min. As a result, no clear Tg was observed up to 400 ° C.

[Evaluation of haze and total light transmittance]
This was carried out using a haze meter 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. The measurement was performed three times, and the average value was taken as the measured value of the film. As a result, haze was 2.0% and total light transmittance was 86%.

(Comparative example)
50 μm thickness according to Example 1 except that the dehydration catalyst was 0.45 g (3.3 mmol) of 3,5-diethylpyridine (boiling point 203 ° C.), 4.89 g (22.2 mmol) of acetic anhydride and 1.58 g of DMAc. A polyimide film was prepared. The obtained polyimide film had a linear expansion coefficient of -2.1 ppm / K, a dimensional change rate of + 0.005%, a haze of 2.9%, a total light transmittance of 85%, and a yellow color index of 25.7. Was a strong polyimide film. As a result of measuring Tg, no clear Tg was observed up to 400 ° C.

  From these results, the polyimide film of the present invention prepared by adding a low boiling point imidizing agent to polyamic acid has good heat resistance and dimensional stability, and can produce a low color film. Fields and products in which these characteristics are effective, such as paints, printing inks, color filters, films for flexible displays, semiconductor devices, electronic parts, interlayer insulation films, wiring coating films, optical circuits, optical circuit parts, Suitable for forming antireflection films, holograms, other optical members or building materials.

Claims (9)

This is a method for producing a polyimide containing a repeating unit represented by the following formula (1), and a solution obtained by mixing a polyamic acid solution with a solution containing a dehydration catalyst and an imidizing agent having a boiling point of 180 ° C. or lower is flowed on a support. It produces by extending, The manufacturing method of the polyimide film characterized by the above-mentioned.

In the formula, R ¹ represents a tetravalent organic group selected from the following general formula (2), R ² represents a divalent organic group selected from the following general formula (3),

In the formula, R ³ represents hydrogen, halogen, alkyl halide, or a C1-C16 alkyl group. The method for producing a polyimide film according to claim 1, wherein R ² is a divalent organic group selected from the following general formula (4).

In the formula, R ³ represents hydrogen, halogen, alkyl halide, or a C1-C16 alkyl group. The method for producing a polyimide film according to claim 1 or 2, wherein R ³ is halogen or alkyl halide. The method for producing a polyimide film according to any one of claims 1 to ^{3, wherein} R ³ is a trifluoromethyl group. 5. The method for producing a polyimide film according to claim 1, wherein R ¹ is a tetravalent organic group selected from the following general formula (5).

The method for producing a polyimide film according to any one of claims 1 to 5, wherein the dehydration catalyst is selected from acid anhydrides. The polyimide according to any one of claims 1 to 6, wherein an addition amount of the imidizing agent is 0.01 mole equivalent or more and 2.0 mole equivalent or less with respect to the carboxylic acid of the polyamic acid. A method for producing a film. The polyimide film manufactured by the method according to claim 1, wherein the film has a YI of 20 or less. The polyimide film according to claim 8, which is obtained by imidizing a polyamic acid having a weight average molecular weight of 3,000 or more.