JP2006199740A - Polyimide film and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film having a higher level of heat resistance, mechanical strength and flexibility, and having no metal layer wrinkles or peeling when laminated with a metal layer, and a method for producing the same.
SOLUTION: The average value of the linear expansion coefficient at 100 to 350 ° C. of the film is in the range of 6 to 25 ppm / ° C., and the differential coefficient of the linear expansion coefficient at 100 to 350 ° C. is −0.20 ppm / ° C. ² or more. A certain polyimide film. Also obtained by reaction of polyamic acid solution obtained by reaction of aromatic diamine having benzoxazole structure and aromatic tetracarboxylic acid, and reaction of aromatic diamine having no benzoxazole structure and aromatic tetracarboxylic acid. A mixed solution obtained by mixing a polyamic acid solution is coated and cast on a support, dried to obtain a green film, and then heat-treated at 150 to 500 ° C. to produce a ring-closing imidized polyimide film. .
[Selection figure] None

Description

  The present invention is given a specific linear expansion coefficient (also referred to as CTE or CTE value) that is suitable as a base material for electronic components such as flexible printed wiring boards (flexible printed circuits) and its specificity, particularly at high temperatures. The present invention relates to a polyimide film having excellent heat-resistant adhesion in lamination with a metal thin film layer with less warping and curling.

  Conventionally, ceramic has been used as a base material for electronic components such as information communication equipment (broadcast equipment, mobile radio equipment, portable communication equipment, etc.), radar, high-speed information processing devices, and the like. A base material made of ceramic has heat resistance, and can cope with an increase in the frequency band (reaching the GHz band) of information communication equipment in recent years. However, ceramics are not flexible and cannot be thinned, so the fields that can be used are limited.

  For this reason, studies have been made to use a film made of an organic material as a base material for an electronic component, and a film made of polyimide and a film made of polytetrafluoroethylene have been proposed. A film made of polyimide is excellent in heat resistance and has the advantage that the film can be thin because it is tough, but there are concerns about problems such as a decrease in signal strength and a delay in signal transmission in application to high-frequency signals. . A film made of polytetrafluoroethylene can handle high frequencies, but it has a low elastic modulus, so the film cannot be made thin, the adhesion to metal conductors and resistors on the surface is poor, and the linear expansion coefficient is low. The problem is that it is not suitable for the production of a circuit having a fine wiring due to a large dimensional change due to a temperature change, and the usable fields are limited. As described above, a film for a substrate having both heat resistance, high frequency compatibility and flexibility has not been obtained.

Moreover, the polyimide benzoxazole film which consists of a polyimide which has a benzoxazole ring in the principal chain is proposed as a polyimide film which raised the elasticity modulus (refer patent document 1). A printed wiring board using the polyimide benzoxazole film as a dielectric layer has also been proposed (see Patent Document 2 and Patent Document 3).
JP-A-6-56992 Japanese National Patent Publication No. 11-504369 Japanese National Patent Publication No. 11-505184

However, as represented by a flexible printed wiring board, these electronic components have such a form that a thin film layer of a conductive metal such as copper is placed on a polyimide film as a dielectric layer and an insulating layer. The use of a substrate made of a conventionally known polyimide film or polyimide benzoxazole film has been widely adopted because of its light weight and flexibility.
The lamination of the metal foil or the metal thin film layer on the polyimide film is often exposed to a high temperature, for example, about 300 ° C., and the adhesion between the metal layer and the polyimide film tends to improve as the treatment is performed at a high temperature. However, even if adhesion at high temperature with metal is obtained, if the difference between the linear expansion coefficient of the polyimide film and metal as a substrate film is large, the change from high temperature to low temperature, that is, from the time of lamination, Between the metal and the substrate in a state exposed to a temperature change from high to low temperature or low to high temperature, such as when cooling to room temperature from high temperature processing in subsequent circuit creation and insulation processing, etc. Differences in expansion and contraction behavior occur, and fatal defects such as peeling and wrinkling occur. Therefore, efforts have been made to bring the linear expansion coefficient of the polyimide film as the substrate close to that of the metal.
However, even when a film whose linear expansion coefficient as a mean value of the linear expansion coefficient in a predetermined temperature range known as a linear expansion coefficient is not greatly different from the metal as described above, each temperature of the film is selected. In the plot of each CTE value with respect to, there was a deviation from the metal plot. That is, in the plot of each CTE value with respect to each temperature of the polyimide film, it has a large bending point unlike metal. That is, a film having a CTE value differential coefficient of −0.20 (ppm / ° C. ² ) or less with respect to the temperature at 100 to 350 ° C., in the temperature change from the low temperature to the high temperature and the temperature change from the high temperature to the low temperature. Differences in expansion / contraction behavior with metals resulted in the occurrence of fatal defects as circuits such as peeling and wrinkling.

  The present invention achieves both heat resistance and flexibility at a higher level, and has excellent adhesion from high temperature to low temperature in adhesion to metal that can cope with temperature changes in the process of lamination with metal. It aims at providing a property polyimide film.

As a result of intensive studies, the present inventors have determined that a polyimide from a mixed solution obtained by mixing a specific polyamic acid solution obtained by reacting an aromatic diamine having a specific structure with an aromatic tetracarboxylic acid and another polyamic acid solution within a predetermined range. A self-supporting green film that is a precursor film is obtained and imidized, thereby having an average value of linear expansion coefficient within a predetermined range at 100 to 350 ° C., and plotting each linear expansion coefficient value with respect to each temperature. The film was found to have no inflection point, that is, the differential coefficient (dCTE / dT) of the linear expansion coefficient at 100 to 350 ° C. was −0.20 ppm / ° C. ² or more, thereby completing the present invention.
That is, the present invention is a polyimide film obtained by reacting diamines and tetracarboxylic anhydrides, and the average linear expansion coefficient of the film at 100 to 350 ° C. is 6 to 25 ppm / ° C. All of the differential coefficients of the linear expansion coefficient measured and calculated at intervals of 10 ° C. in the plot of the linear expansion coefficient against the respective temperatures in the linear expansion coefficient at 100 to 350 ° C. are −0.20 to +0.70 ppm / ℃ a polyimide film is ^2, also polyimide film aromatic diamine having a benzoxazole structure is diamines and polyimide obtained by the tetracarboxylic acid is reacted in the range of 10～90Mol% of the total diamine It is the said polyimide film which is a film.
Further, a polyamic acid solution (A) obtained by reacting an aromatic diamine having a benzoxazole structure with an aromatic tetracarboxylic acid, an aromatic diamine having no benzoxazole structure and an aromatic tetracarboxylic acid, Is mixed with a polyamic acid solution (B) obtained by reacting A and B at a molar ratio of 10 to 90:90 to 10 (mol ratio in terms of diamine), and the mixed solution is applied onto a support. It is a method for producing a polyimide film as described above, wherein the film is cast and dried to obtain a self-supporting film (green film), and the green film is heat-treated in a range of 150 to 500 ° C. to form a ring-closure imidation to form a polyimide film. .

The film of the present invention has higher rigidity, strength, and heat resistance than the conventionally known polyimide film, and has an average value of linear expansion coefficient close to the average value of linear expansion coefficient of metals such as copper. In addition, in the plot of each linear expansion coefficient value with respect to each temperature, the differential coefficient of the linear expansion coefficient at 100 to 350 ° C. is −0.20 ppm / ° C. ² or more, and there is no large bending, and from high temperature to low temperature in lamination with metal Since the adhesiveness is not impaired with respect to the temperature change, it is suitable for use in electronic devices and other electronic devices. It is particularly useful as a base material for flexible electronic circuit boards.

In the polyimide film of the present invention, the average values of the linear expansion coefficients in the flow direction (MD direction) and the width direction (TD direction) at 100 to 350 ° C are all in the range of 6 to 25 ppm / ° C, and 100 to 350 is polyimide film derivative of the linear expansion coefficient measurement and the flow direction calculated (MD direction) and width direction (TD direction) are all -0.20~ + 0.70ppm / ℃ ² at 10 ° C. intervals in ° C. . It is essential that the average value of the linear expansion coefficient at 100 to 350 ° C. is in the range of 6 to 25 ppm / ° C., and the average value of the linear expansion coefficient at 100 to 350 ° C. is present in this range, so that the polyimide film It becomes the same value as the linear expansion coefficient of laminated copper, etc., and there is no extreme difference in expansion / contraction behavior with respect to temperature change. As a result, it is considered that metal peeling or wrinkles due to lamination is less likely to occur. .
The average value of the linear expansion coefficient at 100 to 350 ° C. is preferably in the range of 11 to 21 ppm / ° C.

The polyimide film of the present invention has a linear expansion coefficient with respect to each temperature in the linear expansion coefficient at 100 to 350 ° C. in addition to the average value of the linear expansion coefficient at 100 to 350 ° C. being in the range of 6 to 25 ppm / ° C. The polyimide film of the present invention is characterized by not having a large inflection point in the plot of (i.e., the flow direction (MD direction) and the width direction (TD) measured and calculated at intervals of 10 ° C at 100 to 350 ° C. Direction) is a polyimide film in which all of the differential coefficients of the linear expansion coefficient are −0.20 to +0.70 ppm / ° C. ² . As a result, adhesion in the metal thin film stack that could not be obtained by simply having an average value of the linear expansion coefficient at 100 to 350 ° C. in the range of 6 to 25 ppm / ° C. is obtained, and peeling of the metal thin film layer and generation of wrinkles are caused. It can be extremely suppressed.
Like the metal, the polyimide film of the present invention basically has no inflection point in the plot of each linear expansion coefficient against each temperature in the linear expansion coefficient. For example, the plots of the linear expansion coefficient in Comparative Example 1 and Comparative Example 2 in FIG. 1 have peaks and valleys, and the inflection points constituting the peaks and valleys do not exist in the plot of linear expansion coefficient with respect to temperature. . The polyimide film of the present invention draws a so-called increasing plot in which the differential coefficient of the linear expansion coefficient at 100 to 350 ° C. basically exists slightly on the plus side from 0, but the linear expansion coefficient at 100 to 350 ° C. May have a slight negative value. In the polyimide film of the present invention, the differential coefficients of the linear expansion coefficient in the flow direction (MD direction) and the width direction (TD direction) measured and calculated at intervals of 10 ° C. at 100 to 350 ° C. are all −0.20 ppm / ° C. ² or more, more preferably −0.15 ppm / ° C. ² or more (see FIG. 2). When the differential coefficient of the linear expansion coefficient is larger than +0.70 ppm / ° C. ² , the adhesiveness with the metal thin film stack is lowered, leading to peeling of the metal thin film layer and generation of wrinkles.

The polyimide film of the present invention comprises a polyimide obtained by reacting a diamine and a tetracarboxylic acid anhydride, and an aromatic diamine having a specific ratio of an aromatic diamine having a specific structure; It is a polyimide film obtained by reacting with tetracarboxylic acid anhydrides.
The above “reaction” is not particularly limited, but preferably a diamine and a tetracarboxylic acid anhydride are subjected to a ring-opening polyaddition reaction in a solvent to obtain a polyamic acid solution, and then the polyamic acid solution After forming a green film from the film, dehydration condensation (imidation) is performed.
In the present invention, a polyamic acid solution (A) obtained by reacting an aromatic diamine having a benzoxazole structure with an aromatic tetracarboxylic acid, an aromatic diamine having no benzoxazole structure, and an aromatic tetra A polyamic acid solution (B) obtained by reacting with carboxylic acids is mixed at a molar ratio of A: B of 10-90: 90-10, and the mixed solution is applied and cast onto a support, followed by drying. Thus, a method of obtaining a self-supporting film (green film) and heat-treating the green film in a range of 150 to 500 ° C. to form a ring-closing imidized to form a polyimide film is preferably employed.

A polyamic acid solution (A) obtained by reacting an aromatic diamine having a benzoxazole structure with an aromatic tetracarboxylic acid, and a reaction between an aromatic diamine having no benzoxazole structure and an aromatic tetracarboxylic acid The resulting polyamic acid solution (B) is mixed at a molar ratio of A: B of 10-90: 90-10, and the mixed solution is coated and cast on a support, dried and self-supporting. In a method of obtaining a film (green film) and heat-treating the green film in a range of 150 ° C. to 500 ° C. to form a ring-closure imidation to obtain a polyimide film, the mixing ratio of A: B is preferably 25:25 of A: B. The molar ratio is 90: 75-10, and more preferably, the mixing ratio of A: B is such that A: B is 50-90: 50-10.
By using the above-mentioned specific diamine within a predetermined range, a polyimide film having specific linear expansion coefficient characteristics of the present invention can be easily obtained, and when outside the predetermined range, these specific linear expansion coefficient characteristics and mechanical properties are obtained. It becomes difficult to produce a polyimide film having strength, high rigidity, and strength.
In the present invention, aromatic diamines having a benzoxazole structure are preferably used at a predetermined ratio.

  Specific examples of aromatic diamines having a benzoxazole structure that are preferably used at a predetermined ratio in the present invention include the following.

  Among these, amino (aminophenyl) benzoxazole isomers are preferable from the viewpoint of ease of synthesis. Here, “each isomer” refers to each isomer in which two amino groups of amino (aminophenyl) benzoxazole are determined according to the coordination position (eg, the above “formula 1” to “formula 4”). Each compound described in the above. These diamines may be used alone or in combination of two or more.

In the present invention, the following aromatic diamine may be used in addition to the diamine.
Examples of such diamines include 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, and bis [4- (3-aminophenoxy) phenyl]. Sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine,

3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfoxide, 3,4′-diaminodiphenyl sulfoxide 4,4′-diaminodiphenyl sulfoxide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminobenzophenone, 3,4′- Diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [4- (4-aminophenoxy) phenyl] methane, 1 , 1-Bis [4- (4-aminophen Enoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane,

1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) Phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4- (4-aminophenoxy) Phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphenyl] propane, 2- [4- ( 4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphen Le] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane,

  1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) ) Biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- ( 4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) ) Benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3- Aminophenoxy) benzoyl] benzene, 4,4′-bis [4- (3-aminophenoxy) benzoyl] biphenyl, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [ 4- (3-aminophenoxy) phenyl] propane, 3,4'-diaminodiphenyl sulfide,

2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1 -Bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4 '-Bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [3- (3-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, bis [4- 4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4- Aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [ 4- (4-amino-6-fluorophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy) -α, α-dimethylbenzyl] benzene,

3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4′-diamino-4,5′-diphenoxybenzophenone, 3, 3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3 '-Diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'- Diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4′-diamino-4-bipheno Cibenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino-4-phenoxybenzoyl) benzene 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3-bis (3-amino-4-biphenoxybenzoyl) ) Benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5) -Biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzonitrile and Some or all of the hydrogen atoms on the aromatic ring in the aromatic diamine are halogen atoms, alkyl groups having 1 to 3 carbon atoms or alkoxyl groups, cyano groups, or some or all hydrogen atoms of alkyl groups or alkoxyl groups are halogens. Examples thereof include aromatic diamines substituted with C1-C3 halogenated alkyl groups or alkoxyl groups substituted with atoms.

  The tetracarboxylic acid anhydrides used in the present invention are preferably aromatic tetracarboxylic acid anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are less than 30 mol% of the total tetracarboxylic dianhydrides. Examples of such tetracarboxylic acid anhydrides include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3 5,6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3 -(1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride,

Bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1 , 3-Dipropylcyclohexane-1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and the like. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  The solvent used when polymerizing diamines and tetracarboxylic acid anhydrides to obtain polyamic acid is not particularly limited as long as it dissolves both the raw material monomer and the polyamic acid to be produced. Organic solvents are preferred, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphos Examples include hollic amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and halogenated phenols. These solvents can be used alone or in combination. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material. As a specific amount used, the mass of the monomer in the solution in which the monomer is dissolved is usually 5 to 40% by mass, The amount is preferably 10 to 30% by mass.

Conventionally known conditions may be applied for the polymerization reaction for obtaining the polyamic acid (hereinafter also simply referred to as “polymerization reaction”). As a specific example, in a temperature range of 0 to 80 ° C., 10 Stirring and / or mixing continuously for min-70 hours. If necessary, the polymerization reaction may be divided or the temperature may be increased or decreased. In this case, the order of adding both monomers is not particularly limited. For example, it is preferable to add aromatic tetracarboxylic acid anhydrides to a solution of aromatic diamines. The mass of the polyamic acid in the polyamic acid solution obtained by the polymerization reaction is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and the viscosity of the solution is measured with a Brookfield viscometer (25 ° C.). From the viewpoint of the stability of liquid feeding, it is preferably 10 to 2000 Pa · s, and more preferably 100 to 1000 Pa · s.
The reduced viscosity (ηsp / C) of the polyamic acid in the present invention is not particularly limited, but is preferably 2.0 or more, more preferably 3.0 or more, and still more preferably 4.0 dl / g or more.

Vacuum defoaming during the polymerization reaction is effective for producing a high-quality polyamic acid organic solvent solution. Moreover, you may perform superposition | polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction. Examples of the end capping agent include compounds having a carbon-carbon double bond such as maleic anhydride. The amount of maleic anhydride used is preferably 0.001 to 1.0 mol per mol of aromatic diamine.
In order to form a polyimide film from the polyamic acid solution obtained by the polymerization reaction, a green film is obtained by coating the polyamic acid solution on a support and drying, and then subjecting the green film to a heat treatment. A method of imidization reaction may be mentioned.

  The support on which the polyamic acid solution is applied is only required to have smoothness and rigidity sufficient to form the polyamic acid solution into a film, and a drum or belt whose surface is made of metal, plastic, glass, porcelain, etc. And the like. Among them, the surface of the support is preferably a metal, more preferably stainless steel that does not rust and has excellent corrosion resistance. The surface of the support may be plated with metal such as Cr, Ni, or Sn. The surface of the support can be mirror-finished or processed into a satin finish as required. Application of the polyamic acid solution to the support includes, but is not limited to, casting from a slit base, extrusion through an extruder, squeegee coating, reverse coating, die coating, applicator coating, wire bar coating, etc. Conventionally known solution coating means can be appropriately used.

  The support on which the polyamic acid solution is applied is only required to have smoothness and rigidity sufficient to form the polyamic acid solution into a film, and a drum or belt whose surface is made of metal, plastic, glass, porcelain, etc. And the like. A method using a polymer film having moderate rigidity and high smoothness is also a preferred embodiment. Among them, the surface of the support is preferably a metal, more preferably stainless steel that does not rust and has excellent corrosion resistance. The surface of the support may be plated with metal such as Cr, Ni, or Sn. The surface of the support can be mirror-finished or processed into a satin finish as required. Application of the polyamic acid solution to the support includes, but is not limited to, casting from a slit base, extrusion through an extruder, squeegee coating, reverse coating, die coating, applicator coating, wire bar coating, etc. Conventionally known solution coating means can be appropriately used.

  When the green film is dried to such an extent that self-supporting properties can be obtained, a green film can be obtained in which the imidation ratio of the front and back surfaces and the difference thereof are within a predetermined range by controlling the amount of residual solvent relative to the total mass after drying. . Specifically, the amount of residual solvent with respect to the total mass after drying is preferably 25 to 50% by mass, and more preferably 35 to 50% by mass. When the residual solvent amount is lower than 25% by mass, the imidization rate on one side of the green film becomes relatively high, and it becomes difficult to obtain a green film with a small difference in imidization rate between the front and back surfaces. In addition, the green film tends to become brittle due to a decrease in molecular weight. Moreover, when it exceeds 50 mass%, self-supporting property becomes inadequate and conveyance of a film becomes difficult in many cases.

  As drying conditions for obtaining a green film in which the amount of residual solvent relative to the total mass after drying is within a predetermined range, for example, when N-methylpyrrolidone is used as a solvent, the drying temperature is preferably 70 to 130 ° C., More preferably, it is 75-125 degreeC, More preferably, it is 80-120 degreeC. When the drying temperature is higher than 130 ° C., the molecular weight is lowered and the green film tends to be brittle. In addition, imidization partially proceeds during the production of the green film, and it becomes difficult to obtain desired physical properties during the imidization process. On the other hand, when the temperature is lower than 70 ° C., the drying time becomes long, the molecular weight tends to decrease, and the handling property tends to be poor due to insufficient drying. The drying time is preferably 10 to 90 minutes, more preferably 15 to 80 minutes, although it depends on the drying temperature. When the drying time is longer than 90 minutes, the molecular weight is lowered and the film tends to be brittle. When the drying time is shorter than 10 minutes, the drying property is insufficient and the handling property tends to be poor. Further, in order to improve the drying efficiency or suppress the generation of bubbles at the time of drying, the temperature may be raised stepwise in the range of 70 to 130 ° C. for drying.

A conventionally known drying apparatus that achieves such conditions can be applied, and examples thereof include hot air, hot nitrogen, far infrared rays, and high frequency induction heating.
In the case of performing hot air drying, when the green film is dried to such an extent that self-supporting property is obtained, the range of the imidization ratio on the front and back surfaces of the green film and the difference thereof are set within a predetermined range. It is preferable to control the temperature difference to 10 ° C. or less, preferably 5 ° C. or less, and it is necessary to control the temperature difference by individually controlling the hot air temperature on the upper surface / lower surface.

As a method for imidizing the green film, a conventionally known imidization reaction can be appropriately used. For example, using a polyamic acid solution that does not contain a ring-closing catalyst or a dehydrating agent, the imidization reaction proceeds by subjecting it to a heat treatment (so-called thermal ring-closing method), or a polycyclic acid solution containing a ring-closing catalyst and a dehydrating agent. In order to obtain a polyimide film in which the difference in surface orientation between the front and back surfaces of the polyimide film is small, a chemical ring closing method can be mentioned in which an imidization reaction is performed by the action of the above ring closing catalyst and dehydrating agent. The thermal ring closure method is preferred.
The maximum heating temperature of the thermal ring closure method is about 100 to 500 ° C, preferably 200 to 480 ° C. When the maximum heating temperature is lower than this range, it is difficult to close the ring sufficiently, and when it is higher than this range, deterioration proceeds and the film tends to become brittle. A more preferable embodiment includes a two-stage heat treatment in which treatment is performed at 150 to 250 ° C. for 3 to 20 minutes and then treatment is performed at 350 to 500 ° C. for 3 to 20 minutes.
In the chemical ring closure method, after the polyamic acid solution is applied to a support, the imidization reaction is partially advanced to form a self-supporting film, and then imidization can be performed completely by heating. In this case, the condition for partially proceeding with the imidization reaction is preferably a heat treatment for 3 to 20 minutes at 100 to 200 ° C., and the condition for allowing the imidization reaction to be completely performed is preferably 200 to 400 ° C. For 3 to 20 minutes.

The timing for adding the ring-closing catalyst to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine, and betapicoline. Among them, heterocyclic tertiary amines are mentioned. At least one amine selected from is preferred. Although the usage-amount of a ring-closing catalyst with respect to 1 mol of polyamic acids does not have limitation in particular, Preferably it is 0.5-8 mol.
The timing of adding the dehydrating agent to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride. Among them, acetic anhydride, benzoic anhydride, etc. Acids or mixtures thereof are preferred. Moreover, the usage-amount of the dehydrating agent with respect to 1 mol of polyamic acids is not particularly limited, but is preferably 0.1 to 4 mol. When a dehydrating agent is used, a gelation retarder such as acetylacetone may be used in combination.

Whether it is a thermal cyclization reaction or a chemical cyclization method, the polyimide film precursor (green sheet, film) formed on the support may be peeled off from the support before it is completely imidized. The film may be peeled after imidization.
Although the thickness of a polyimide film is not specifically limited, When considering using it for the base substrate for printed wiring boards mentioned later, it is 1-150 micrometers normally, Preferably it is 3-50 micrometers. This thickness can be easily controlled by the amount of the polyamic acid solution applied to the support and the concentration of the polyamic acid solution.
The thermal ring closure method is a method in which polyamic acid is imidized by heating. The polyamic acid solution may contain a ring closing catalyst and a dehydrating agent, and the imidization reaction may be promoted by the action of the ring closing catalyst and the dehydrating agent. In this method, after the polyamic acid solution is applied to the support, the imidization reaction is partially advanced to form a film having self-supporting property, and then imidization can be performed completely by heating.
The timing for adding the ring-closing catalyst to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine, and betapicoline. Among them, heterocyclic tertiary amines are mentioned. At least one amine selected from is preferred. Although the usage-amount of a ring-closing catalyst with respect to 1 mol of polyamic acids does not have limitation in particular, Preferably it is 0.5-8 mol.

The timing of adding the dehydrating agent to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride. Among them, acetic anhydride, benzoic anhydride, etc. Acids or mixtures thereof are preferred. Moreover, the usage-amount of the dehydrating agent with respect to 1 mol of polyamic acids is not particularly limited, but is preferably 0.1 to 4 mol. When a dehydrating agent is used, a gelation retarder such as acetylacetone may be used in combination.
The polyimide film precursor (green sheet, film) formed on the support may be peeled off from the support before complete imidization, or may be peeled off after imidization.

The polyimide film of the present invention is preferably provided with a lubricant in the polyimide to give fine irregularities on the film surface to improve the slipping property of the film.
As the lubricant, inorganic or organic fine particles having an average particle diameter of about 0.03 μm to 3 μm can be used. Specific examples include titanium oxide, alumina, silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, Examples include magnesium oxide, calcium oxide, and clay minerals.
The polyimide film of the present invention is usually an unstretched film, but may be stretched uniaxially or biaxially. Here, the unstretched film refers to a film obtained without intentionally applying a mechanical external force in the surface expansion direction of the film by tenter stretching, roll stretching, inflation stretching, or the like.

A printed wiring board base substrate will be described as an example using the polyimide film of the present invention.
Here, the “base substrate for a printed wiring board” is a substantially flat substrate having a structure in which a metal layer is laminated on at least one surface of an insulating plate. The metal layer to be laminated may be a metal layer for a circuit that is intended to form a circuit by processing such as etching or the like. It may be a metal layer used for the purpose.
As the use of “base substrate for printed wiring board”, FPC, TAB carrier tape, COF base material, CSP base material, etc. can make use of the characteristics of the polyimide film of the present invention that the degree of curl is small. preferable.

The metal laminated on at least one surface of the polyimide film is not particularly limited, and is preferably copper, aluminum, nickel, chromium or the like. The lamination means is not particularly limited, and the following means are exemplified.
・ Means for attaching a metal plate to a polyimide film using an adhesive,
-Means for forming a metal thin film layer on a polyimide film using vacuum coating techniques such as vapor deposition, sputtering, ion plating, etc.
A means for forming a metal layer on a polyimide film by a wet plating method such as electroless plating or electroplating.
A metal layer can be laminated on at least one side of a polyimide film by combining these means alone or in combination.

Especially, as a method of laminating a metal layer, a method of forming a base metal layer by sputtering and thickening by electroplating is preferable.
In this case, the base metal may be a simple substance or an alloy such as Cu, Ni, Cr, Mo, Zn, Ti, Ag, Au, and Fe. Further, a good conductor such as Cu may be further deposited as a conductive layer on the base metal by sputtering.
The thickness of the underlayer and the conductive layer is preferably 100 to 5000 mm.
Cu is preferable as the metal to be electroplated.

  The thickness of the metal layer is not particularly limited, but when the metal layer is used for a circuit (conductive), the thickness of the metal layer is preferably 1 to 175 μm, more preferably 3 to 105 μm. is there. When using the polyimide film which bonded the metal layer as a thermal radiation board, the thickness of a metal layer becomes like this. Preferably it is 50-3000 micrometers. The surface roughness of the surface of the metal layer bonded to the polyimide is not particularly limited, but the centerline average roughness (hereinafter referred to as Ra) and ten points in JIS B 0601 (definition and display of surface roughness). A value represented by average roughness (hereinafter referred to as Rz) is preferably 0.1 μm or less for Ra and 1.00 μm or less for Rz because the effect of improving the adhesion between the film and the metal layer is great. . Of these, those satisfying these conditions are preferred. In addition, although Ra and Rz are so preferable that they are small, the minimum of Ra is 0.0001 micrometer and the minimum of Rz is 0.001 micrometer from the ease of acquisition and processing.

  An inorganic coating film such as a single metal or a metal oxide may be formed on the surface of the metal layer used in the present invention. Further, the surface of the metal layer may be subjected to treatment with a coupling agent (aminosilane, epoxysilane, etc.), sand plast treatment, hole treatment, corona treatment, plasma treatment, etching treatment, and the like. Similarly, the surface of the polyimide film may be subjected to honing treatment, corona treatment, plasma treatment, etching treatment, and the like.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by a following example. In addition, the evaluation method of the physical property in the following examples is as follows.
1. Reduced viscosity of polyamic acid (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g / dl was measured at 25 ° C. with an Ubbelohde type viscosity tube.
(When the solvent used for preparing the polyamic acid solution was DMAc, the polymer was dissolved and measured using DMAc.)

2. The thickness of the polyimide film was measured using a micrometer (Finereuf, Millitron (registered trademark) 1245D).

3. Test specimens obtained by cutting a polyimide film to be measured into strips of 100 mm × 10 mm in the flow direction (MD direction) and the width direction (TD direction), respectively. It was. Using a tensile tester (manufactured by Shimadzu Corp., Autograph (registered trademark) model name AG-5000A) under the conditions of a tensile speed of 50 mm / min and a distance between chucks of 40 mm, the tensile modulus and tension in each of the MD and TD directions. The breaking strength and tensile breaking elongation were measured.

4). Average value of linear expansion coefficient of polyimide film About the polyimide film to be measured, the expansion / contraction rate in the flow direction (MD direction) and the width direction (TD direction) was measured under the following conditions, and 30 ° C to 40 ° C, 40 ° C to 50 ° C. Measure the stretch rate / temperature at intervals of ℃, ... and 10 ℃, perform this measurement up to 400 ℃, and calculate the average value of all measured values from 100 ℃ to 350 ℃ as the average value of linear expansion coefficient did. The meanings of the MD direction and the TD direction are the same as in the measurement of “3.” above.

5). Differential coefficient of linear expansion coefficient of polyimide film For the polyimide film to be measured, the expansion / contraction rate in the flow direction (MD direction) and the width direction (TD direction) is measured under the following conditions, and 30 ° C to 40 ° C, 40 ° C to 50 ° C. Measure the stretch rate / temperature at intervals of ℃, ... and 10 ℃, perform this measurement up to 400 ℃, subject each measured value from 100 ℃ to 350 ℃ to the differential operation with respect to the temperature, 100 A differential coefficient of a linear expansion coefficient at a temperature at intervals of 10 ° C. from ℃ to 350 ° C. was calculated. The outline is shown in FIG.1 and FIG.2. The minimum value and the maximum value of the differential coefficient of the linear expansion coefficient in Examples and Comparative Examples are the minimum value and the maximum differential coefficient of the linear expansion coefficient in the MD direction and the TD direction measured and calculated at intervals of 10 ° C. in this temperature range. Value.
Device name: TMA4000S manufactured by MAC Science
Sample length; 10mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rising end temperature: 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

6). The warp (curl degree) of the warp film of the polyimide film means the degree of deformation in the thickness direction with respect to the surface direction of the film after performing a predetermined heat treatment. Specifically, as shown in FIG. X50 mm test piece was treated with hot air at 400 ° C. for 10 minutes, and then the test piece was allowed to stand on a plane, and distances from the four corner planes (h ₁ , h ₂ , h ₃ , h ₄ : unit mm) The average value is warp (curl amount) (mm), and is a value expressed as a percentage (%) of the warp (curl amount) with respect to the distance (35.36 mm) from each vertex to the center of the test piece.
Specifically, it is calculated by the following formula.
Warpage (mm) = (h ₁ + h ₂ + h ₃ + h ₄ ) / 4

7). Twist and swell Take at least 1 m of the resulting polyimide film and place it on a horizontal surface. Visually observe the twist and swell in the width direction in particular. When the swell was slightly observable, it was judged as Δ, and when the twist and swell were many, it was judged as x.

8). Peeling of the laminated metal thin film and wrinkle At least 0.3 m of the obtained metal thin film layer laminated polyimide film was collected and allowed to stand on a horizontal surface, and the peeling of the metal thin film layer and wrinkles were visually observed. The case where no wrinkles were observed was judged as ◎, the case where peeling and wrinkles could be observed slightly, Δ, and the case where peeling and wrinkles could be observed were judged as x.

[Reference Example 1]
(Polyamide acid polymerization-1)
The inside of a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod was purged with nitrogen, and then 500 parts by mass of 5-amino-2- (p-aminophenyl) benzoxazole was charged. Next, after 8000 parts by mass of N, N-dimethylacetamide was added and completely dissolved, 485 parts by mass of pyromellitic dianhydride was added and stirred at a reaction temperature of 25 ° C. for 48 hours. A polyamic acid solution (A) was obtained. The solution obtained had a ηsp / C of 4.0 dl / g.

[Reference Example 2]
(Polyamide acid polymerization-2)
545 parts by weight of pyromellitic anhydride and 500 parts by weight of 4,4′diaminodiphenyl ether were dissolved in 5000 parts by weight of N, N-dimethylacetamide and reacted in the same manner while maintaining the temperature at 20 ° C. or lower to obtain a polyamic acid solution ( B-1) was obtained. The solution obtained had a ηsp / C of 2.2 dl / g.

[Reference Example 3]
(Polyamide acid polymerization-3)
As a tetracarboxylic dianhydride, 398 parts by mass of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 147 parts by mass of paraphenylenediamine are dissolved in 4600 parts by mass of N, N-dimethylacetamide, and the temperature is increased. Was kept in a temperature of 20 ° C. or lower in the same manner to obtain a polyamic acid solution (B-2). The obtained solution had a ηsp / C of 3.0 dl / g.

[Examples 1-4, Comparative Examples 1-3]
The polyamic acid solution obtained in each reference example was mixed in the ratio shown in Tables 1 and 2, and the polyamic acid solution was coated on one side of a copper foil having a width of 600 mm and a thickness of 12 μm using a comma coater. The film was coated to 24 μm and dried at 110 ° C. for 60 minutes to obtain a green film as each polyimide precursor film. The green film was passed through a continuous heat treatment furnace purged with nitrogen, and the first stage, Two-stage high temperature heating of two stages was performed to advance the imidization reaction. Then, the polyimide film of each example which exhibits brown was obtained by cooling to room temperature in 5 minutes. The measurement results of the obtained polyimide film are shown in Tables 1 and 2.
Using each polyimide film, the polyimide film is loaded into a vacuum sputtering apparatus, the polyimide film running speed is 4.5 m / min, the atmosphere during vacuum thin film formation sputtering is 2.7 × 10 ⁻¹ Pa under argon gas, argon / When the water abundance ratio was 96 / 0.5 (mass ratio), the input power was 4.5 W / cm ² and the Cu thin film layer was formed with a thickness of 110 nm to obtain a copper thin film laminate of each polyimide film. The obtained core copper thin film laminate had a surface resistance value of 0.29Ω / □. The peeling and wrinkle of the copper thin film layer in the copper thin film laminate of each polyimide film were evaluated. The results are shown in Tables 1 and 2.

In the column of tensile breaking strength to linear expansion coefficient (average value), the upper row shows values in the flow direction (MD direction) and the lower row shows values in the width direction (TD direction).

In the column of tensile breaking strength to linear expansion coefficient (average value), the upper row shows values in the flow direction (MD direction) and the lower row shows values in the width direction (TD direction).

[Application Example 1]
<Example of manufacturing carrier tape and semiconductor circuit element package>
A TAB carrier tape was prepared using each polyimide film obtained in Examples and Comparative Examples.
First, RV50 manufactured by Toyobo Co., Ltd. was applied as an adhesive on the surface of each polyimide film slit to a width of 140 mm so as to have a coating thickness of 35 μm, and dried in a dry oven at 80 ° C. for 15 minutes. Then, the sprocket holes for transport and the device holes were punched out.
Next, the rolled surface of Japan Energy rolled copper foil, BHY-22-T (18 μm) adhesion-treated surface and the adhesive-coated surface of the film were combined, and a roll temperature of 120 ° C. and a feed rate of 60 cm / min were obtained using a silicon rubber roller laminator. After laminating and winding, the adhesive was cured by treatment at 150 ° C. for 5 hours in a vacuum dryer.
Next, an etching resist ink was screen-printed at a portion corresponding to the back side of the device hole and cured with ultraviolet rays. Further, a photoresist was applied to the surface of the rolled copper foil, and a predetermined pattern was exposed and developed. Then, using the patterned resist as a mask, etching was performed using a ferric chloride aqueous solution. Finally, tin plating with a thickness of 1.5 μm was applied to the inner lead portion and the outer lead portion to prepare 50 TAB carrier tapes. The thinnest part of the obtained tape has a line width / line spacing = 60/60 μm.
A semiconductor chip was mounted on the obtained carrier tape, subjected to a bonding process using gang bonding, and then sealed with a resin by a potting method to manufacture a semiconductor circuit element package. The number of contacts on the inner bonding side of the obtained semiconductor circuit element package is 256.
The package from each polyimide film obtained as described above was loaded into an Etak temperature cycle test apparatus, and a heating / cooling test was performed. The test was performed by repeatedly heating and cooling between a low temperature of −50 ° C. and a high temperature of 150 ° C. every 30 minutes. The test time was 3000 hours. A continuity test was conducted after the test to determine the defect rate at the connection point. Examples From each example were zero. The main cause of the defect rate of 0 is considered to be that the characteristic in the linear expansion coefficient of the film due to repeated heating and cooling contributed to the fact that the film is less warped and curled.
On the other hand, a semiconductor circuit element package was produced in the same manner as described above except that the polyimide film of the comparative example was used in the same manner, and the defect rate of the connection points was determined in the same manner as 20 to 7000 ppm.

[Application 2]
<Production method of metallized film>
Each polyimide film obtained by the Example and the comparative example was cut into a 25 cm × 25 cm square, and fixed by being sandwiched between stainless steel frames having a direct 24 cm opening. Next, plasma treatment of the film surface was performed. The plasma treatment conditions were a xenon gas, a frequency of 13.56 MHz, an output of 100 W, a gas pressure of 0.8 Pa, a treatment temperature of 25 ° C., and a treatment time of 5 minutes.
Next, using a nickel-chromium (3%) alloy target under conditions of a frequency of 13.56 MHz, an output of 400 W, a gas pressure of 0.8 Pa, and a thickness of 50 mm at a rate of 10 mm / second by RF sputtering in a xenon atmosphere. Then, the temperature of the substrate is raised to 250 ° C. and copper is deposited at a rate of 100 Å / second to form a copper thin film (conductive layer) having a thickness of 0.5 μm. Formed.
Each obtained metallized film is fixed to a plastic frame, and a copper sulfate plating bath is used to form a thick copper plating layer (thickening layer) having a thickness of 5 μm, followed by heat treatment at 300 ° C. for 10 minutes. And the metallized polyimide film was obtained from the polyimide film of each target example.
The obtained metallized film in each example of the example was free from peeling of the metal layer and generation of wrinkles and cracks.
On the other hand, a metallized film was obtained in the same manner except that the film of the comparative example was used, but peeling of the metal layer and generation of cracks were observed. The difference in the occurrence of peeling, wrinkles and cracking of these metal layers is considered to be due to the characteristics of the linear expansion coefficient of the polyimide film as the base film and the magnitude of the occurrence of warping and twisting.

The polyimide film of the present invention has a value similar to that of a metal such as copper as an average value of linear expansion coefficient, and the linear expansion coefficient does not change extremely in a wide temperature range, that is, the differential linear expansion coefficient is In addition to the heat resistance of the polyimide film, it exhibits stable expansion / contraction behavior over a wide temperature range, and is exposed from low to high temperatures such as metal thin film lamination processes. It can be widely used in applications such as processes that are exposed to low to high temperatures.
It is excellent in the quality of the metal thin film laminated with the polyimide film and the adhesion to the film, and can be widely used as a member of electric / electronic materials such as a flexible printed wiring board.

Plot of temperature and linear expansion coefficient of polyimide film at 100-350 ° C

Plot diagram of differential coefficient of linear expansion coefficient with respect to each temperature at 100 ° C. to 350 ° C. of polyimide film

It is the schematic diagram which showed the measuring method of the curl degree of a polyimide film. (A) is a top view, (b) is a sectional view indicated by aa in (a) before hot air treatment, and (c) is indicated by aa in (a) after hot air treatment. It is sectional drawing.

Explanation of symbols

1: Polyimide film specimen 2: Alumina ceramic plate

Claims (3)

A polyimide film obtained by reacting a diamine with a tetracarboxylic acid anhydride, and the average value of linear expansion coefficients at 100 to 350 ° C. of the film is 6 to 25 ppm / ° C., and A polyimide film characterized in that all differential coefficients of linear expansion coefficient measured and calculated at intervals of 10 ° C. at 100 to 350 ° C. are −0.20 to +0.70 ppm / ° C. ² .   The polyimide film according to claim 1, wherein the polyimide is a polyimide obtained by reacting diamines having a benzoxazole structure in a range of 10 to 90 mol% with respect to the total diamine and tetracarboxylic acids.   A polyamic acid solution (A) obtained by reacting an aromatic diamine having a benzoxazole structure with an aromatic tetracarboxylic acid, and a reaction between an aromatic diamine having no benzoxazole structure and an aromatic tetracarboxylic acid The polyamic acid solution (B) obtained by mixing is mixed at a molar ratio of A: B of 10 to 90:90 to 10 (mol ratio in terms of diamine), and the mixed solution is applied and cast on a support. 3. A self-supporting film (green film) is obtained by drying, and the green film is heat-treated in a range of 150 to 500 ° C. to form a ring-closure imidation to form a polyimide film. The manufacturing method of the polyimide film.