JP5835046B2 - Method for producing polyimide film - Google Patents

Description

  The present invention relates to a method for producing a polyimide film used for a circuit board, a solar cell board, and the like.

  The polyimide film has high heat resistance and high electrical insulation, and even a thin film satisfies the rigidity, heat resistance, and electrical insulation necessary for handling. For this reason, it is widely used in industrial fields, such as an electrical insulation film, a heat insulation film, a base film of a flexible circuit board, and a solar cell substrate.

  The polyimide film is formed by casting a polyimide precursor solution containing a polyamic acid obtained from a tetracarboxylic dianhydride component and a diamine component onto a support to form a thin film. Next, the thin film is dried to form a self-supporting film having self-supporting properties. Then, the self-supporting film is peeled off from the support, and imidized by heat treatment. In order to reduce the linear expansion coefficient of the polyimide film, the self-supporting film is stretched and then imidized.

  In Patent Document 1, a polyimide self-supporting film is stretched 1.1 to 2 times in the running direction while regulating the running direction at a temperature of less than 150 ° C. with a rotating roll to form a stretched film. It is disclosed that a part is held by a tenter clip, stretched at a magnification of 0.8 to 1.3 times in the width direction, and heated to a temperature of 150 to 500 ° C. to produce a polyimide film. And in Example 4 of patent document 1, it extends | stretches in a running direction (MD direction) at the temperature of 63 degreeC, then introduce | transduces into a tenter apparatus, and is each in the width direction (TD direction) at the temperature of 200 degreeC and 400 degreeC. After stretching, heat treatment is performed at 450 ° C. to produce a polyimide film.

  Patent Document 2 discloses that a polyimide self-supporting film is heated at a rate of 18 to 50 ° C./min in a temperature range of 150 to 300 ° C., and at the same time in the temperature range of 200 to 370 ° C. It is possible to produce a polyimide film by stretching 10% to 70% in the take-up direction (MD direction) of the self-supporting film and the direction perpendicular to this (TD direction) and imidizing at a temperature of 300 to 500 ° C. It is disclosed. And in Example 1 of patent document 2, a film is extended | stretched from 270 degreeC to the biaxial direction orthogonal, and extending | stretching is stopped at 335 degreeC, Then, it anneals and manufactures a polyimide film.

JP 2003-176370 A JP-A-1-315428

  Conventionally, when a polyimide self-supporting film is stretched in the MD direction, it is stretched at a constant temperature. Also in patent document 1, it extends | stretches at fixed temperature.

  On the other hand, in Patent Document 2, the self-supporting film is heated at a rate of 18 to 50 ° C./min in a temperature range of 150 to 300 ° C. and simultaneously stretched in the MD direction and the TD direction in a temperature range of 200 to 370 ° C., respectively. doing. That is, in Patent Document 2, the self-supporting film is stretched in the MD direction and the TD direction while being heat-treated in a curing furnace.

  However, if stretching in the MD direction and the TD direction is performed in a curing furnace, there is a problem that the apparatus becomes large and equipment costs increase.

  Therefore, the objective of this invention is providing the manufacturing method of the polyimide film which can manufacture the stretched polyimide film with sufficient productivity.

  The present inventors have found that when a self-supporting film is stretched at a constant temperature, the film may be deformed or broken depending on the tension applied to the film. Thus, as a result of intensive studies on the stretching conditions of the self-supporting film, the present inventors have found that the above problems can be solved by stretching the self-supporting film while raising the temperature, and completed the invention.

  The method for producing a polyimide film of the present invention includes a casting step in which a polyimide precursor solution is cast on a support and dried to form a self-supporting film having self-supporting property, and the self-supporting film is used as the support. A stretching process for obtaining a stretched film by stretching the self-supporting film in the transport direction while raising the temperature so as to reach 100 to 150 ° C. at a temperature rise rate of 50 to 300 ° C./min, and the stretched film. And a curing step of imidization by heat treatment while holding both ends in the width direction.

  As for the manufacturing method of the polyimide film of this invention, it is preferable to heat up the said self-supporting film so that it may become 100-150 degreeC from the state of 20-50 degreeC in the said extending process.

  In the method for producing a polyimide film of the present invention, in the stretching step, the self-supporting film is preferably stretched beyond 0 in the transport direction by 20%.

  In the method for producing a polyimide film of the present invention, in the stretching step, the self-supporting film is preferably stretched at a stretching speed exceeding 40% / min in the transport direction.

According to the method for producing a polyimide film of the present invention, in the stretching step, the self-supporting film is heated to a temperature of 100 to 150 ° C. at a temperature increase rate of 50 to 300 ° C./min. Since a film is extended | stretched in a conveyance direction, it can be extended | stretched in a conveyance direction, reducing the tension | tensile_strength which concerns on a film. For this reason, it can extend | stretch, suppressing the deformation | transformation and cutting | disconnection of a film.
For this reason, according to the present invention, it is possible to suppress the occurrence of defects such as deformation and cracking of the film and to produce a polyimide film stretched at least in the transport direction with high productivity.

It is a figure which shows the relationship between the extending | stretching rate and tension | tensile_strength of the film in Example 1-1. It is a figure which shows the relationship between the draw ratio and tension | tensile_strength of the film in Comparative Example 1-1.

  The method for producing a polyimide film of the present invention is a method of casting a polyimide precursor solution obtained from a tetracarboxylic dianhydride component and a diamine component on a support and drying to form a self-supporting film having self-supporting properties. A casting step, a self-supporting film is peeled from the support, a stretching step in which the self-supporting film is stretched in the conveying direction to obtain a stretched film, and a cured step in which the stretched film is heat-treated and imidized. Including. Hereinafter, each step will be described in detail.

(Casting process)
In the casting step, first, a polyamic acid and an organic solvent are cast onto a support with a polyimide precursor solution to form a casting. Then, the cast is dried to form a self-supporting film having self-supporting properties. Here, having self-supporting means a state having a strength that can be peeled off from the support.

  The polyamic acid can be produced by reacting a tetracarboxylic dianhydride component and a diamine component by a known method. For example, it can be produced by polymerizing a tetracarboxylic dianhydride component and a diamine component in an organic solvent usually used for production of polyimide.

  Examples of the tetracarboxylic dianhydride component include aromatic tetracarboxylic dianhydrides, aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, and the like. Specific examples include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-oxydiphthalic dianhydride, diphenylsulfone-3. , 4,3 ′, 4′-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) sulfide dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1, 1,3,3,3-hexafluoropropane dianhydride and the like.

  Examples of the diamine component include aromatic diamines, aliphatic diamines, and alicyclic diamines. Specific examples include p-phenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, m-tolidine, p-tolidine, 5-amino-2- (p-aminophenyl) benzoxazole, 4 , 4′-diaminobenzanilide, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 3,3 '-Bis (3-aminophenoxy) biphenyl, 3,3'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) ) Biphenyl, bis [3- (3-aminophenoxy) phenyl] ether, bis [3- (4-aminophenoxy) phene Ether], bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [3- (3-aminophenoxy) phenyl] propane, 2,2-bis [3- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) Phenyl] propane and the like.

  Examples of the combination of the tetracarboxylic dianhydride component and the diamine component include the following (1) to (6). These combinations are preferable from the viewpoints of mechanical properties and heat resistance.

(1) A combination of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine.
(2) A combination of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, p-phenylenediamine and 4,4-diaminodiphenyl ether.
(3) A combination of pyromellitic dianhydride and p-phenylenediamine.
(4) A combination of pyromellitic dianhydride, p-phenylenediamine, and 4,4-diaminodiphenyl ether.
(5) A combination of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and p-phenylenediamine.
(6) A combination of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, p-phenylenediamine, and 4,4-diaminodiphenyl ether.

  Any organic solvent may be used as long as it can dissolve the polyamic acid. A known organic solvent can be used. For example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide and the like can be mentioned. These solvents may be used alone or in combination of two or more.

  When imidation is completed by thermal imidation of the polyimide precursor solution, an imidization catalyst or the like may be added to the polyimide precursor solution as necessary. Moreover, when completing imidation by chemical imidation of a polyimide precursor solution, you may add a cyclization catalyst, a dehydrating agent, etc. to a polyimide precursor solution as needed. Here, “completion” for completing imidization includes, for example, that the imidization rate is 100%, and that the desired imidization rate is less than 100%, for example.

  Examples of the imidization catalyst include a substituted or unsubstituted nitrogen-containing heterocyclic compound, an N-oxide compound of the nitrogen-containing heterocyclic compound, a substituted or unsubstituted amino acid compound, an aromatic hydrocarbon compound having a hydroxyl group, or an aromatic Heterocyclic compounds are mentioned.

  Examples of the cyclization catalyst include aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines.

  Examples of the dehydrating agent include aliphatic carboxylic acid anhydrides and aromatic carboxylic acid anhydrides.

  The solid content concentration (polymer component) of the polyimide precursor solution is not particularly limited as long as the concentration is within a viscosity range suitable for film production by casting. 10-30 mass% is preferable, 15-27 mass% is more preferable, and 16-24 mass% is further more preferable.

  For example, the casting of the polyimide precursor solution may be dried by introducing the casting into a casting furnace and drying by heating.

  The drying conditions (heating conditions) for forming the self-supporting film are not particularly limited, but are preferably formed by heating at a temperature of 100 to 180 ° C. for about 2 to 60 minutes, more preferably 120 to Heat at 160 ° C. for 4-30 minutes. In addition, the temperature here means the atmospheric temperature measured with the thermocouple installed in the furnace.

(Stretching process)
In the stretching step, first, the self-supporting film formed in the casting step is peeled from the support. The method for peeling the self-supporting film from the support is not particularly limited, and examples include a method in which the self-supporting film is cooled and peeled by applying a tension via a rotating roll. Then, the self-supporting film peeled off from the support is stretched in the transport direction (MD direction) using a rotating roll or the like while regulating the traveling speed, or both ends of the self-supporting film are held with a holder such as a clip The film is stretched in the conveying direction to obtain a stretched film.

  In the present invention, in the stretching step, the self-supporting film is stretched in the transport direction (MD direction) while being heated to 100 to 150 ° C. at a heating rate of 50 to 300 ° C./min. To do. In addition, the temperature here means the surface temperature of a film measured with the thermocouple affixed on the film.

  By stretching the self-supporting film while raising the temperature, it can be stretched in the transport direction (MD direction) while reducing the tension associated with the film, as shown in the examples described later. For this reason, generation | occurrence | production of a deformation | transformation and a piece of a film can be suppressed, and it can extend | stretch in a conveyance direction (MD direction). In addition, if the solvent content of the film is small, it becomes difficult to stretch further in the curing step, which is the next step. In the present invention, the stretching step is performed at a temperature of 100 to 150 ° C. The solvent is hardly removed from the film, and the obtained stretched film contains a solvent to some extent. For this reason, in the curing step, the stretched film can be further stretched in the width direction (TD direction) or the like.

  In the stretching step, the temperature of the self-supporting film is preferably raised from 20 to 50 ° C. to 100 to 150 ° C. More preferably, the temperature is raised from 30 to 40 ° C. to 130 to 140 ° C. When the stretching start temperature is less than 20 ° C., the stress applied to the film tends to increase at the initial stage of stretching, and when it exceeds 50 ° C., the effect of lowering the stress due to stretching while increasing the temperature tends to decrease. Further, if the stretching end temperature is less than 100 ° C, the stress during stretching tends to be high and the occurrence of film deformation and breakage tends to be large and the apparatus for stretching tends to be large. In this case, it may be difficult to stretch further in the curing step, which is the next step.

  In the stretching step, the rate of temperature rise is 50 to 300 ° C./min, preferably 60 to 270 ° C./min, more preferably 60 to 260 ° C./min, and still more preferably 70 to 250 ° C./min. When the rate of temperature increase is less than 50 ° C./min, the time until the stretching end temperature becomes long and the solvent is easily removed, and it may be difficult to further stretch in the subsequent curing step. When the rate of temperature rise exceeds 300 ° C./min, the amount of heat applied per unit time increases, and the apparatus tends to become large.

  In the stretching step, the self-supporting film is preferably stretched at a stretch ratio of more than 0 and 20% or less in the transport direction, more preferably more than 0 and 15% or less. If the draw ratio is within the above range, the deformation and breakage of the film can be more effectively suppressed.

  In the stretching step, the stretching speed of the self-supporting film is preferably stretched at a stretching speed exceeding 0 and not more than 40% / min in the transport direction, more preferably exceeding 0 and not more than 30% / min. If the stretching speed is within the above range, the deformation and breakage of the film can be more effectively suppressed.

(Cure process)
In the curing step, both ends in the width direction of the stretched film obtained in the stretching step are held with a holder such as a pin tenter, clip, frame, etc., and heat-treated to imidize. If necessary, the holder may be heat-treated by enlarging / reducing in the width direction and / or the conveying direction.

  As described above, in the stretching step, stretching is performed at a relatively low temperature, and thus the stretched film obtained in the stretching step contains a relatively solvent. In the curing process, both ends of the stretched film in the width direction are held, and if necessary, the holder is expanded and contracted in the width direction and / or the transport direction, and heat treatment is performed. Is low and can be easily stretched.

  There is no limitation in particular as a heat processing of a stretched film, A well-known method can be used. For example, a method of gradually heating at a temperature of 100 ° C. to 400 ° C. for 0.05 to 5 hours, more preferably 0.1 to 3 hours can be mentioned. As a specific example, primary heat treatment is performed at a relatively low temperature of 100 ° C. to 170 ° C. for 0.5 to 30 minutes, and then secondary heat treatment is performed at a temperature of 170 ° C. to 220 ° C. for 0.5 to 30 minutes. Thereafter, a third heat treatment is performed at a high temperature of 220 ° C. to 400 ° C. for 0.5 to 30 minutes. If necessary, the fourth high-temperature heat treatment may be performed at a high temperature of 400 ° C. to 550 ° C., preferably 450 to 520 ° C. In addition, the temperature here means the surface temperature of a film measured with the thermocouple affixed on the film.

  Since the polyimide film manufactured in this way has at least a stretch control range in the transport direction (MD direction), a polyimide film having a desired linear expansion coefficient can be efficiently manufactured. For this reason, it can be preferably used for a substrate or an insulating material of an electric / electronic component. For example, it can be used as a printed circuit board, a flexible printed circuit board, a TAB tape, a COF tape, a cover substrate such as a chip member such as an IC chip, a substrate such as a liquid crystal display, an organic electroluminescence display, electronic paper, or a solar cell. it can.

[Production example] (Production of self-supporting film)
To 100 parts by mass of N, N-dimethylacetamide (hereinafter referred to as “DMAc”), 5.7 parts by mass of paraphenylenediamine (hereinafter referred to as “PPD”) was added and dissolved by stirring. 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter referred to as “s-BPDA”) was gradually added to the obtained solution to obtain a polyimide precursor solution. The solid content concentration was 18% by mass.
The obtained polyimide precursor solution was cast on a glass plate so that the thickness after final drying was 35 μm, dried at 120 ° C. for 15 minutes, peeled from the glass plate, and the solvent content was 35.5 mass. % Self-supporting film was produced.

[Test Example 1]
(Example 1-1)
The self-supporting film produced in the production example was adjusted to a size of 2 × 12 cm and used as a sample cell.
The sample cell is clamped at 1 cm from both ends in the longitudinal direction, and the sample cell longitudinal direction (MD) is increased from 30 ° C. to 120 ° C. at a heating rate of 180 ° C./min. Direction) was stretched 10% in the MD direction at a stretching rate of 20% / min. The film tension after 10% stretching was 5 N / cm. The relationship between the stretch ratio of the film and the tension is shown in FIG.

(Comparative Example 1-1)
In Example 1-1, a portion of 1 cm from the both ends in the longitudinal direction of the sample cell is gripped with a clip, and the stretching rate is 20% / min in the longitudinal direction (MD direction) of the sample cell at a constant temperature of 120 ° C. The film was stretched 10% in the MD direction. The film tension after 10% stretching was 11 N / cm. FIG. 2 shows the relationship between the stretching ratio of the film and the tension.

  As shown in FIGS. 1 and 2, by stretching the self-supporting film while raising the temperature, the tension related to the film could be reduced.

[Test Example 2]
(Example 2-1)
The self-supporting film produced in the production example was adjusted to a size of 2 × 12 cm and used as a sample cell.
While holding a 1 cm portion from both ends of the sample cell in the longitudinal direction with a pin sheet and raising the temperature from 30 ° C. to 130 ° C. at a temperature increase rate of 190 ° C./min, the sample cell longitudinal direction ( The film was stretched 5 to 15% in the MD direction at a stretching speed of 9.4 to 28.1% / min in the MD direction).

(Comparative Example 2-1)
In Example 2-1, a portion 1 cm from both ends in the longitudinal direction of the sample cell was held with a pin sheet, and 9.4 to 37.5 in the longitudinal direction (MD direction) of the sample cell at a constant temperature of 130 ° C. The film was stretched 5 to 15% in the MD direction at a stretching rate of% / min.

  Observe the appearance of the hole in the pin sheet of the film after stretching, ◎ if there is no deformation in the pin sheet hole, ○ if the pin sheet hole deformation is small, △ if the pin sheet hole deformation is large The case where the cut occurred was defined as x. The results are shown in Table 1.

Claims (4)

A casting step of casting a polyimide precursor solution on a support and drying to form a self-supporting film having a self-supporting property;
The self-supporting film is peeled from the support and stretched by stretching the self-supporting film in the conveying direction while raising the temperature to 100 to 150 ° C. at a temperature increase rate of 50 to 300 ° C./min. A stretching step to obtain a film;
And a curing step of imidization by heat treatment while holding both ends in the width direction of the stretched film.   The manufacturing method of the polyimide film of Claim 1 which heats up the said self-supporting film so that it may become 100-150 degreeC from the state of 20-50 degreeC in the said extending process.   The method for producing a polyimide film according to claim 1 or 2, wherein in the stretching step, the self-supporting film is stretched by more than 0 and 20% in the transport direction.   The method for producing a polyimide film according to any one of claims 1 to 3, wherein in the stretching step, the self-supporting film is stretched at a stretching speed exceeding 40% / min in the transport direction.