JP2022064422A - Production method of polyimide film - Google Patents

Abstract

To provide a production method of a polyimide film capable of controlling orientation anisotropic property of a film, even when a rigid monomer is used as a raw material of a polyimide film, or a raw material by which an elastic modulus at a high temperature of a film is low, is selected.SOLUTION: There is provided a production method of a polyimide film, in a tenter heating step, heat treatment is performed by at least three heating furnaces which are coupled in a longitudinal direction of the film, the heating furnaces comprise: a hot wind heating zone in which two or more hot wind furnaces are arranged; and a radiant heat ray heating zone in which one or more radiant heat ray heater furnaces are arranged. In the production method of the polyimide film, a temperature of the first hot wind furnace through which a gel film passes first in the tenter heating step, is 270-360°C, the lowest temperature in the tenter heating step is 270°C or greater, and the highest temperature is 330-420°C.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a polyimide film.

The polyimide film is obtained by applying an organic solvent solution of polyamic acid, which is a precursor of polyimide, on a rotating support such as a metal drum, and drying and curing the film until it has self-supporting property to obtain a gel film. The gel film is continuously manufactured by peeling it off, fixing both ends thereof, transporting the gel film to a heating furnace to heat it while maintaining or widening the width of the gel film, and further drying and curing the gel film.

The tenter method as described above is a known technique suitable for maintaining or stretching the width while resisting the curing shrinkage of the gel film in the drying and curing steps in the heating furnace, but the lateral physical characteristics of the product film can be obtained. It was difficult to make it uniform. The reason for this is that in the tenter, both ends of the film are gripped by clips and pin sheets, so that stretching stress and contraction stress in the vertical direction are constrained, whereas the central part of the film is less affected by the gripping means. This is because the binding force is weakened, and the film is easily affected by stretching stress and contraction stress in the vertical direction. As a result, the directions of stress received at both ends and the center of the film are different, and uneven deformation remains. This phenomenon is called the Boeing phenomenon, and this Boeing phenomenon causes the lateral physical characteristics of the film to become non-uniform.

Anisotropy in the width direction of the polyimide film has been a problem for many years, and various attempts have been made to improve the anisotropy. For example, an organic solvent solution of polyamic acid is cast and applied onto a rotating support, dried and cured until it has self-supporting properties to obtain a gel film, which is peeled off, and both ends thereof are fixed to fix the gel film. In the method for producing a polyimide film, which includes a step of transporting the film to a heating furnace to heat it while maintaining or widening the width, a shrinkage phenomenon on the support of the gel film, the amount of residual volatile components of the gel film, and the start of heating in the heating furnace. There is a method of controlling the orientation by paying attention to the temperature (Patent Document 1). In the tenter heating step in which the end of the gel film is fixed and heated, the elastic modulus of the gel film and the first zone of the tenter heating furnace are focused on the shrinkage stress caused by the volatilization of the solvent in the first zone of the heating furnace. The orientation is determined by determining the tension applied to the gel film, the maximum firing temperature in the heating furnace, and the amount of residual volatile components in the gel film, based on the relationship between the elastic modulus in and the elastic modulus in the second zone in the tenter heating furnace. It is known that it can be controlled (Patent Document 2). Further, in the tenter heating step of the above-mentioned polyimide film manufacturing method, the initial heating temperature is set to 180 ° C. or higher, and in a certain temperature range at the initial stage of heating, orientation is performed by heating without changing the distance between the gripping members at both ends. A method of forming a film having a small anisotropy strength and stretching in the width direction in a temperature range exceeding 220 ° C. to control the linear expansion coefficient within a desired range is known (Patent Document 3).

Japanese Patent Application Laid-Open No. 2003-165850 Japanese Unexamined Patent Publication No. 2008-12776 WO2011 / 145696

A certain effect is also exhibited in controlling the anisotropy by the conventional method for producing a polyimide that controls the orientation anisotropy. However, in order to meet the high performance required for FPC in recent years, the polyimide film is also required to have higher characteristics, and along with this, the choice of the raw material of the polyimide to be used is expanding. If a rigid monomer is used as the raw material to be used, or if a raw material having a low elastic modulus at high temperature is selected, the orientation may not be sufficiently controlled by the conventional method, and there is room for improvement. was there.
Therefore, the problem to be solved by the present invention is that even when a rigid monomer is used as a raw material used for a polyimide film or a raw material having a low elastic modulus at a high temperature of the film is selected, the film has a problem. It is an object of the present invention to provide a method for producing a polyimide film capable of controlling orientation anisotropy.

The present invention can solve the above problems by the following novel method for producing a polyimide film.

1). At a minimum, a polyamic acid organic solvent solution is cast or applied onto the support and dried to form a gel film that is a polyamic acid film that is partially imidized and / or partially dried until it is self-supporting. In the method for producing a polyimide film, which includes a step of peeling the gel film from the support, and a tenter heating step of fixing the end portion of the gel film and performing a heat treatment.
In the tenter heating step, heat treatment is performed by a heating furnace in which a plurality of furnaces of at least 3 connected in the longitudinal direction of the film are arranged.
The heating furnace is composed of a hot air heating zone in which two or more hot air furnaces are arranged and a radiant heat ray heating zone in which one or more radiant heat ray heater furnaces are arranged following the hot air heating zone.
The temperature of the first hot air furnace through which the gel film first passes in the tenter heating step is set in the range of 270 to 360 ° C., and the minimum temperature in the tenter heating step is 270 ° C. or higher.
A method for producing a polyimide film, wherein the temperature of the furnace set to the maximum temperature is in the range of 330 to 420 ° C.

2). The method for producing a polyimide film according to 1), wherein the temperature difference between the hot air furnaces arranged in the hot air heating zone and adjacent to each other is 100 ° C. or less.

3). The method for producing a polyimide film according to 1) or 2), wherein the furnace set to the maximum temperature is a radiant heat ray heater furnace.

4). The hot air heating zone is characterized by having the first hot air heating furnace, the second hot air heating furnace adjacent to the first hot air heating furnace, and the third hot air heating furnace adjacent to the second hot air heating furnace. The method for producing a polyimide film according to any one of 1) to 3).

5). The temperature of the first hot air heating furnace is 290 to 310 ° C, the temperature of the second hot air heating furnace is 340 to 360 ° C, and the temperature of the third hot air heating furnace is 340 to 360 ° C. The method for producing a polyimide film according to 4), wherein the temperature is high.

6). The temperature of the first hot air heating furnace is 270 to 290 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 340 to 360 ° C. The method for producing a polyimide film according to 4), wherein the temperature is high.

7). The temperature of the first hot air heating furnace is 270 to 290 ° C., the temperature of the second hot air heating furnace is 290 to 310 ° C., and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to 4), wherein the temperature is high.

8). The temperature of the first hot air heating furnace is 290 to 310 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to 4), wherein the temperature is high.

9). The temperature of the first hot air heating furnace is 310 to 330 ° C., the temperature of the second hot air heating furnace is 290 to 310 ° C., and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to 4), wherein the temperature is high.

10). The temperature of the first hot air heating furnace is 340 to 360 ° C., the temperature of the second hot air heating furnace is 290 to 310 ° C., and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to 4), wherein the temperature is high.

11). The temperature of the first hot air heating furnace is 270 to 310 ° C., the temperature of the second hot air heating furnace is 370 to 390 ° C., and the temperature of the third hot air heating furnace is 350 to 370 ° C. The method for producing a polyimide film according to 4), wherein the temperature is high.

12). The radiant heat ray heating zone is characterized by having a first radiant heat ray heater furnace and a second radiant heat ray heater furnace adjacent to the first radiant heat ray heater furnace 1) to 11). The method for manufacturing a polyimide film according to the above.

13). The polyimide according to 12), wherein the temperature difference between the first radiant heat ray heater furnace and the second radiant heat ray heater furnace adjacent to the first radiant heat ray heater furnace is 0 to 70 ° C. How to make a film.

14). The polyimide film according to 12), wherein the temperature of the first radiant heat ray heater furnace is 340 to 390 ° C, and the temperature of the second radiant heat ray heater furnace is 340 to 390 ° C.12). Manufacturing method.

15). The polyimide film according to 12), wherein the temperature of the first radiant heat ray heater furnace is 330 to 380 ° C., and the temperature of the second radiant heat ray heater furnace is 370 to 420 ° C.12). Manufacturing method.

16). The polyimide film according to 12), wherein the temperature of the first radiant heat ray heater furnace is 370 to 420 ° C., and the temperature of the second radiant heat ray heater furnace is 330 to 380 ° C.12). Manufacturing method.

17). The method for producing a polyimide film according to any one of 1) to 16), wherein the radiant heat ray heater furnace is a far infrared heater furnace.

18). The method for producing a polyimide film according to any one of 2) to 17), wherein the temperature difference between the hot air furnaces arranged in the hot air heating zone and adjacent to each other is 70 ° C. or less.

19). The method for producing a polyimide film according to any one of 1) to 18), wherein the storage elastic modulus at 350 ° C. when the dynamic viscoelasticity of the polyimide film is measured is 0.5 GPa or less.

20). The method for producing a polyimide film according to any one of 1) to 19), wherein the polyimide film has a polyimide resin having a biphenyl skeleton or a terphenyl skeleton structure.

21). The item according to any one of 1) to 20), further comprising a step of mixing a curing agent containing an imidization catalyst and a dehydrating agent prior to casting or applying the polyamic acid organic solvent solution onto the support. Method for manufacturing polyimide film.

22). A gel film which is a polyamic acid film which is at least partially imidized and / or partially dried until it has self-supporting property by casting or applying a polyamic acid organic solvent solution on the support and drying the gel film. The step of forming is described in any one of 1) to 21), wherein a plurality of polyamic acid organic solvent solutions are cast and / or applied onto a support by a coextrusion method and dried. Method for manufacturing polyimide film.

Embodiments of the present invention will be described below. First, the case of the polyimide film according to the present invention will be described based on an example of the embodiment thereof, but the present invention is not limited thereto. Unless otherwise specified in the present specification, "A to B" representing a numerical range means "A or more (including A and larger than A) and B or less (including B and smaller than B)", respectively.

INDUSTRIAL APPLICABILITY The present invention is a polyimide film obtained by casting or coating a polyimide organic solvent solution on a support, drying the film, and partially imidizing and / or partially drying the film until it has self-supporting property. In a method for producing a polyimide film including a step of forming a gel film, a step of peeling the gel film from a support, and a tenter heating step of fixing an end portion of the gel film and performing a heat treatment, the tenter heating step of the film Heat treatment is performed by a heating furnace in which a plurality of furnaces composed of at least 3 connected in the longitudinal direction are arranged, and the heating furnace is followed by a hot air heating zone in which two or more hot air furnaces are arranged and a hot air heating zone. It is composed of a radiant heat ray heating zone in which one or more radiant heat ray heater furnaces are arranged, and the temperature of the first hot air furnace through which the gel film first passes in the tenter heating step is in the range of 270 to 360 ° C. This is a method for producing a polyimide film, characterized in that the minimum temperature in the tenter heating step is 270 ° C. or higher, and the furnace temperature set to the maximum temperature is in the range of 330 to 420 ° C. In the present specification, the expression "set" such as "the temperature is set in the range of 270 to 360 ° C." is used, but it means "controlled" or "controlled".

In the present invention, in the tenter heating step, heating in the hot air heating zone and heating in the radiant heat ray heating zone are performed, and the temperature of the first hot air furnace through which the gel film first passes is a relatively high temperature of 270 to 360 ° C. Is set to. The temperature of a plurality of existing furnaces following the first hot air furnace is preferably not increased significantly, and the temperature difference between adjacent furnaces is preferably in the range of 100 ° C. or less. Further, among the plurality of furnaces, the maximum temperature is set to a relatively low temperature of 330 to 420 ° C. This was verified and set by the present inventors based on the following hypothesis.

Generally, a film formed by a tenter is considered to have a positive Boeing strain. When the orientation of the polyimide film in the width direction is measured, especially if it is confirmed whether the orientation angle of the edge is negative or positive with respect to the traveling direction, whether the polyimide film has a positive Boeing strain or a negative one. Whether or not it has Boeing strain can be seen along with its degree. Then, when checking the orientation angle of the edges of various polyimide films manufactured through the tenter heating process, including the existing long polyimide film, all the films have positive Boeing. Was confirmed. Since the film finally produced in this way has a positive Boeing strain, the present inventors set the temperature of the above-mentioned plurality of furnaces by assuming the Boeing phenomenon that occurs in each firing furnace. It is.

That is, the present inventors describe the Boeing phenomenon that occurs in each firing furnace in the direction in which the central portion is delayed with respect to the end portion (hereinafter, also referred to as positive Boeing) and the end portion in the direction in which the end portion is delayed with respect to the central portion. First, I caught it by distinguishing it from the Boeing phenomenon (hereinafter also referred to as negative Boeing).

Negative Boeing considered that the dominant factors were the shrinkage stress due to the volatilization of the solvent contained in the gel film and the hardening shrinkage due to the chemical reaction from the precursor polyamic acid to the polyimide. That is, it is considered that negative Boeing occurs especially in the first half of the continuous firing furnace such as the first zone of the tenter heating furnace. It was also considered that positive Boeing is closely related to the decrease in elastic modulus when the film is exposed to high temperature, and is caused by the difference in elastic modulus in the tenter. That is, it is considered that it is particularly likely to occur in the latter half of the continuous firing furnace that reaches the maximum firing temperature, and then it is likely to occur in a relatively high temperature firing furnace in which the residual solvent is sufficiently volatilized. Therefore, it was considered that the anisotropy of the finally produced polyimide film could be improved by balancing (cancelling) the strain caused by positive Boeing and the strain caused by negative Boeing. Based on this idea, the temperature of the first hot air furnace through which the gel film first passes in the tenter heating process, the temperature difference between adjacent furnaces arranged in the heating furnace, and the maximum temperature are set. When the temperature was set in a specific range, a surprising effect of suppressing orientation anisotropy was confirmed. Such an effect is exhibited even in the case of a general-purpose polyimide film which originally has a property of being difficult to orient. However, in recent years, the raw material monomers selected to meet the various film characteristics required for FPC and the film forming conditions of the film have become complicated, and even if a film that meets these characteristics is obtained, the result is In some cases, the film tends to develop orientation. A polyimide film having such a property of being easily oriented exhibits a particularly excellent effect. Hereinafter, a polyamic acid organic solvent solution is cast or applied onto a support and dried to form a gel film which is a polyamic acid film partially imidized and / or partially dried until it has self-supporting property. A step of peeling the gel film from the support, and a tenter heating step of fixing the end portion of the gel film and performing a heat treatment will be described in this order.

<A polyamic acid organic solvent solution is cast or applied onto a support and dried to form a gel film that is a polyamic acid film that is partially imidized and / or partially dried until it has self-supporting properties. Process>
In the method for producing a polyimide film of the present invention, an organic solvent solution of polyamic acid, which is a polyimide precursor, is cast-coated and partially dried and / or imidized to have self-supporting property, which is used in the present invention. As the raw material monomer, diamines and acid polyimides usually used for the synthesis of polyamic acid can be used.

The aromatic diamine is not particularly limited as long as the effects of the present invention can be exhibited, but is 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 4,4'-diaminodiphenyl propane, 4,4'-. Diaminodiphenylmethane, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-oxydianiline, 3,3'-oxydianiline, 3, 4'-oxydianiline, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenylN-methylamine, 4 , 4'-Diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), bis {4- (4-aminophenoxy) phenyl} sulfone, bis {4- (3-aminophenoxy) phenyl} Pulmonate, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (3) -Aminophenoxy) benzene, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 2,2-bis (4-aminophenoxyphenyl) propane, 1,3-bis (4-aminophenoxy) benzene, 4 , 4'-diamino-2,2'-dimethylbiphenyl and the like, and these can be used alone or in combination of two or more.

The acid dianhydride compound that can be used as a raw material monomer for polyamic acid is not particularly limited as long as the effects of the present invention can be exhibited, but pyromellitic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid. Dianoxide, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetra Carboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride, 4,4'-oxyphthalic acid dianhydride Anhydrous, 3,4'-oxyphthalic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, Bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane Dianoxide, bis (2,3-dicarboxyphenyl) methanic acid dianhydride, bis (3,4-dicarboxyphenyl) ethaneic acid dianhydride, oxydiphthalic acid dianhydride, bis (3,4-dicarboxyphenyl) Phenyl) Carboxylic acid dianhydride, p-phenylene bis (trimellitic acid monoesteric acid anhydride), ethylene bis (trimellitic acid monoesteric acid anhydride), bisphenol A bis (trimellitic acid monoesteric acid anhydride) and Examples thereof include similar substances.

In the present invention, a film that is easily in-plane oriented exhibits a better effect, and examples of such a polyimide film include a film having a polyimide resin having a biphenyl skeleton or a terphenyl skeleton structure. Among them, acid dianhydrides including 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and / or 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride and 4,4. A polyimide resin made from a diamine containing'-diaminobenzophenone, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and / or 2,2', 3,3'-biphenyltetracarboxylic acid. An excellent effect is exhibited when a film having a polyimide resin made from an acid dianhydride containing dianhydride and 4,4'-diamino-2,2'-dimethylbiphenyl as raw materials is produced.

As the method for producing a polyamic acid in the present invention, any known method can be used. For example, it can be produced by the following steps (Aa) to (Ac).
(AA) Step: A step of reacting an aromatic diamine and an aromatic acid dianhydride in an organic polar solvent with an excess of the aromatic diamine to obtain a prepolymer having amino groups at both ends.
(A-b) Step: A step of additionally adding an aromatic diamine having a structure different from that used in (A-a).
Step (Ac): Further, the aromatic acid dianhydride having a structure different from that used in the step (Aa) is substantially equal to that of the aromatic diamine and the aromatic acid dianhydride in all the steps. A process of adding and polymerizing in molar form.

Alternatively, the polyamic acid can be obtained by going through the following steps (B-a) to (B-c).
(BA) Step: An aromatic diamine and an aromatic acid dianhydride are reacted in an organic polar solvent with an excess of the aromatic acid dianhydride, and a pre-acid anhydride group is provided at both ends. The process of obtaining a polymer,
(B-b) Step: A step of additionally adding an aromatic acid dianhydride having a structure different from that used in (B-a).
Step (B-c): Further, the aromatic diamine having a structure different from that used in the step (BA) is substantially equimolarized with the aromatic diamine and the aromatic acid dianhydride in all the steps. The process of adding and polymerizing.

Synthetic methods that determine the order of addition such that a particular diamine or acid dianhydride is selectively bound to any diamine or acid dianhydride (eg, steps (AA)-(Ac), and (. Ba) to (Bc)) are referred to as sequence polymerization in the present invention. On the other hand, a synthetic method in which the diamine and acid dianhydride to be bonded are not selected in the order of input is called random polymerization in the present invention.

The solid content concentration of the polyamic acid of the present invention is not particularly limited, and is usually obtained at a concentration of 5 to 35 wt%, preferably 10 to 30 wt%. When the concentration is in this range, an appropriate molecular weight and solution viscosity are obtained.

Various additives such as fillers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, pigments, dyes, fatty acid esters, and organic lubricants (for example, waxes) are added to the polyamic acid of the present invention. be able to.
Further, a thermosetting resin such as an epoxy resin or a phenoxy resin, or a thermoplastic resin such as polyetherketone or polyetheretherketone may be mixed as long as the characteristics of the obtained polyimide film are not impaired. Examples of the method for adding these resins include a method of adding these resins to polyamic acid, which is a precursor of polyimide, if they are soluble in a solvent. If the polyimide is also soluble, it may be added to the polyimide solution. If it is insoluble in a solvent, a method of first imidizing the polyamic acid, which is a precursor of the non-liimide, and then compositing by melt-kneading can be mentioned. However, it is desirable not to use a meltable polyimide in the present invention because the solder heat resistance and the heat shrinkage of the obtained flexible metal-clad laminate may deteriorate. Therefore, it is desirable to use a soluble resin to be mixed with polyimide.

As the organic solvent used in the production of the polyamic acid, any solvent that dissolves the polyamic acid can be used. For example, an amide-based solvent, that is, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like are preferable, and N, N-dimethylformamide and N, N-dimethylacetamide can be more preferably used. .. The solid content concentration of the polyamic acid is not particularly limited, and if it is in the range of 5% by weight to 35% by weight, the polyamic acid having sufficient mechanical strength when made into a polyimide film can be obtained.

The order of addition of the aromatic diamine and the aromatic acid dianhydride, which are the raw materials, is not particularly limited, but the characteristics of the obtained polyimide can be controlled not only by controlling the chemical structure of the raw materials but also by controlling the order of addition. It is possible.

A filler can be added to the polyamic acid for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, and preferred examples thereof include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

Thermosetting resins such as epoxy resin and phenoxy resin, and thermoplastic resins such as polyetherketone and polyetheretherketone may be mixed as long as the characteristics of the obtained polyimide film are not impaired. Examples of the method for adding these resins include a method of adding these resins to polyamic acid, which is a precursor of polyimide, if they are soluble in a solvent. If the polyimide is also soluble, it may be added to the polyimide solution. If it is insoluble in a solvent, a method of first imidizing the polyamic acid, which is a precursor of the polyimide, and then compositing by melt-kneading can be mentioned. However, it is desirable not to use a meltable polyimide in the present invention because the solder heat resistance and the heat shrinkage of the obtained flexible metal-clad laminate may deteriorate. Therefore, it is desirable to use a soluble resin to be mixed with polyimide.

The polyamic acid organic solvent solution thus obtained was cast or applied onto a support and dried, with a partially imidized and / or partially dried polyamic acid film until self-supporting. Form a gel film.

There are two known methods for producing a polyimide film, a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyamic acid organic solvent solution is cast on a support as a film-forming dope without using a dehydration ring closure agent or the like, and imidization is promoted only by heating. On the other hand, the chemical imidization method is a method of promoting imidization by using a polyamic acid organic solvent solution to which at least one of a dehydration ring-closing agent and a catalyst is added as an imidization accelerator as a film-forming dope. Either method may be used, but the chemical imidization method is more productive. In addition, in the present invention, since a film that easily orients in-plane exhibits a better effect, a polyamic acid organic solvent solution to which at least one of a dehydration ring-closing agent and a catalyst is added as an imidization accelerator is deposited. When the chemical imidization method used as is used, a more remarkable effect is exhibited. This is because the polyimide film produced by the chemical imidization method is more likely to be in-plane oriented.

As the dehydration ring closure agent, an acid anhydride typified by acetic anhydride can be preferably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines can be preferably used.

As the support for casting the polyamic acid organic solvent solution, a glass plate, aluminum foil, an endless stainless belt, a stainless drum, or the like can be preferably used.

The method of the present invention is not limited to the case of producing a single-layer polyimide film by casting or applying one polyamic acid organic solvent solution on a support and drying it to obtain a gel film, as well as a plurality of methods. It can also be applied to a method of producing a multilayer polyimide film by casting and / or applying a polyamic acid organic solvent solution on a support by a coextrusion method and drying the film to obtain a multilayer gel film.

<Step of peeling the gel film from the support>
In the process of heating the resin layer on the support to form a self-supporting gel film and then peeling the gel film from the support, the heating conditions are set according to the thickness of the finally obtained film and the production rate. After setting and performing at least one of partial imidization or drying, the film is peeled off from the support to obtain a polyamic acid film (hereinafter referred to as gel film).

The gel film thus obtained is partially dried and contains a solvent, but the residual solvent ratio is (AB) × 100 / B (%).
(A and B in the formula represent the following.)
A: Weight of gel film B: Calculated from the weight of the gel film after heating at 350 ° C. for 10 minutes.

In the present invention, in order to positively generate a negative Boeing phenomenon as described in detail later, the temperature of the first hot air furnace through which the gel film first passes in the tenter heating step is set to a relatively high temperature. ing. However, as one of the means for increasing the negative Boeing strain, it is also effective to increase the amount of residual volatile components in the gel film, and from this viewpoint, the lower limit of the amount of residual volatile components in the gel film is preferable. It is 60%, more preferably 70%, and particularly preferably 80%. This is because the more solvent contained in the gel film, the more the shrinkage stress acting in the negative direction due to the rapid volatilization of the solvent can be increased.

On the other hand, the upper limit is 110%, more preferably 100%, and particularly preferably 90%. If the amount of residual volatile components in the gel film exceeds 110%, the self-supporting property of the gel film is poor, and the gel film may be stretched or broken as soon as it is transferred to the tenter heating furnace, and stable production may not be possible.

<Tenter heating process in which the end of the gel film is fixed and heat treated>
Subsequently, the gel film peeled off from the support is conveyed to the tenter heating step by grasping both ends of the gel film with a pin sheet or a clip laid on the tenter rail while applying an appropriate tension to the gel film. In the tenter heating step of the present invention, heat treatment is performed by a heating furnace in which a plurality of furnaces consisting of at least three or more connected in the longitudinal direction of the film are arranged. The heating furnace is composed of a hot air heating zone in which two or more hot air furnaces are arranged and a radiant heat ray heating zone in which one or more radiant heat ray heater furnaces are arranged following the hot air heating zone. In this step, the volatilization and imidization reaction of the residual volatile components in the gel film is completed by heating stepwise in a plurality of furnaces.

In the tenter heating step, shrinkage due to volatilization of the residual solvent, increase in rigidity due to imidization reaction, and decrease in rigidity due to exposure to high temperature act synergistically, and it is considered that various expansion and contraction behaviors occur in each heating zone. Be done. After hypothesis and verification of various factors that can affect the orientation of the film in the tenter heating step, in the present invention, the temperature of the first hot air furnace through which the gel film first passes in the tenter heating step. Was set in the range of 270 to 360 ° C.

Conventionally, it has been known that the so-called Boeing phenomenon that occurs in the manufacturing process of a polyimide film is related to the orientation anisotropy in the width direction of the polyimide film, and in particular, the orientation in the diagonal direction of about 45 ° at the end becomes a problem. Was there. Then, in order to suppress the Boeing phenomenon as much as possible, a polyamic acid organic solvent solution is cast or applied on the support and dried to obtain a gel film, and then both ends of the gel film in the width direction are grasped and heated. The mainstream idea is that the initial heating when transporting to the furnace and heating should be gradual, that is, the difference between the heating on the support and the initial heating temperature in the heating furnace should not be too large. there were. Therefore, for example, in Patent Document 1, the initial heating temperature when transported to the heating furnace is controlled to be the atmospheric temperature + 100 ° C. or less on the support and 150 to 250 ° C. It is considered that this is an attempt to suppress the rapid shrinkage of the gel film containing the residual volatile components in the tenter heating furnace.

However, in the present invention, on the contrary, the temperature of the first hot air furnace through which the gel film first passes in the tenter heating step is set high. According to the conventional idea, if the gel film is suddenly exposed to a high temperature, the orientation will be further advanced, so this is a means to avoid. Negative Boeing strain and positive under the assumption that the negative Boeing phenomenon occurs in the first half of the process and the positive Boeing phenomenon occurs in the second half of the tenter heating process where the film is exposed to higher temperatures to complete the imidization. Since the temperature pattern of each furnace of the heating furnace is set so as to offset the Boeing strain of the above, the positive Boeing phenomenon that occurs later is taken into consideration in advance, and rather the negative Boeing strain is positively applied in the first furnace. This is because it is based on the technical idea of generating it. Therefore, in the present invention, rather, the initial heating in the tenter heating step is set to a high temperature in order to generate shrinkage stress due to the volatilization of the solvent and hardening shrinkage due to the chemical reaction from the polyamic acid to the polyimide.

Further, it has been clarified in Patent Document 2, for example, that the storage elastic modulus decreases when the film is exposed to a high temperature in the tenter heating step, but this is considered in relation to the cause of the positive Boeing phenomenon. The technical idea of offsetting this with the negative Boeing phenomenon that occurs in the first half of the tenter heating process has not existed in the past and was originally discovered by the present inventors.

As a specific means for increasing negative Boeing, as described in the above-mentioned step of peeling the gel film from the support, in addition to the method of increasing the amount of residual volatile components remaining in the gel film, the first method is described above. Although it is effective to raise the temperature of the hot air furnace in the above, it is particularly effective to raise the temperature of the first hot air furnace to a high temperature in consideration of the influence on other physical properties. The reason why it is effective to raise the temperature of the first hot air furnace is that the solvent contained in the gel film volatilizes rapidly, which can increase the shrinkage stress associated with the volatilization that acts in the negative direction. be.

In the first heating zone, the shrinkage of the film due to the volatilization of the residual solvent and the hardening of the film due to the progress of imidization, that is, the increase in rigidity, are considered to be dominant, and negative Boeing occurs in which the central part of the film is pulled toward the latter half. It is thought that it is.

The negative boeing generated by the shrinkage of the film is insufficient, and if the temperature exceeds 360 ° C., the residual solvent volatilizes while the progress of imidization is insufficient, so that the imidization rate of the obtained film is insufficient and sufficient. There is a tendency that the mechanical strength cannot be guaranteed. Further, the minimum temperature in the tenter heating step of the present invention is 270 ° C. or higher. In the present invention, the temperature of the furnace installed in the heating furnace means the ambient temperature regardless of whether it is a hot air furnace or a radiant heat ray heater furnace.

In the present invention, the heating furnace is a radiant heat in which a hot air heating zone in which two or more hot air furnaces including the first hot air furnace are arranged and one or more radiant heat ray heater furnaces arranged following the hot air heating zone are arranged. It is composed of a linear heating zone, and heating is performed step by step by a plurality of furnaces. Further, the temperature difference between adjacent hot air furnaces arranged in the hot air heating zone is 100 ° C. or less. It is desirable because it enhances the effect. The temperature difference is preferably 70 ° C. or lower, more preferably 50 ° C. or lower, still more preferably 30 ° C. or lower. After the negative Boeing strain is generated in the first hot air furnace, it is considered that the decrease in rigidity due to the exposure of the film to high temperature is dominant after the second hot air furnace, and the central part is at the end. On the other hand, it is considered that positive Boeing (a phenomenon in which the central part of the film is pulled toward the furnace in front of which the rigidity is considered to be relatively maintained) is occurring. Since this positive Boeing strain is unavoidable, the positive Boeing is controlled to be balanced with the negative Boeing strain by reducing the temperature difference between adjacent furnaces after the second hot air furnace. That is, it suppresses the extreme increase in positive Boeing.

Further, in order to reduce positive Boeing, it is effective to set the temperature in the latter half to a relatively low temperature in a plurality of furnaces arranged in the heating furnace. Further, the present invention is also characterized in that the maximum temperature at the time of stepwise heating is set to 330 to 420 ° C. In the method for producing a polyimide film of the present invention, heating at the maximum temperature can be performed by the radiant heat ray heating zone in which one or more radiant heat ray heater furnaces arranged following the hot air heating zone are arranged. Therefore, the maximum temperature of the radiant heat ray heater is preferably 330 to 420 ° C. The reason why it is most effective to set the maximum temperature as low as 330 to 420 ° C. is that the film can be conveyed without the elastic modulus being lowered too much. The maximum temperature is preferably 330 to 390 ° C, more preferably 330 to 360 ° C.

After being heated stepwise in this way and finally heated to the maximum temperature, the tenter heating step is completed through the slow cooling zone to finally obtain a polyimide film. Although the conversion to polyimide is almost completed by heating at this maximum temperature, it is considered that the film is no longer elastic and exhibits viscoelastic behavior because it is exposed to high temperature.

A more preferable example of the heating furnace used in the tenter heating step of the present invention is shown below. First, the number of hot air furnaces in the hot air heating zone needs to be at least 2 or more from the viewpoint of efficient heating, but it is preferably composed of three hot air furnaces. Of course, it does not prevent it from being composed of four or more hot air furnaces. Further, the number of radiant heat ray heater furnaces in the radiant heat ray heating zone needs to be at least 1 or more, but it is preferably composed of two radiant heat ray heater furnaces. Of course, it does not prevent it from being composed of three or more radiant heat ray heater furnaces. The radiant heat ray heater furnace is preferably a far infrared heater furnace.

From the viewpoint of suppressing the orientation anisotropy, it is preferable to reduce the temperature difference between adjacent furnaces in all of the hot air furnace and the radiant heat ray heater furnace arranged in the heating furnace, but the film. From the viewpoint of satisfying the basic characteristics of the above, a certain temperature difference may be provided between the hot air heating zone and the radiant heat ray heating zone. However, when two or more radiant heat ray heater furnaces are arranged in the radiant heat ray heating zone, it is preferable that the temperature difference between the radiant heat ray heater furnaces adjacent to each other is 70 ° C. or less.

In the following, a case where a hot air zone consisting of three hot air furnaces and a radiant heat ray heating zone consisting of two radiant heat ray heater furnaces, which is the most preferable configuration of the heating furnace in the tenter heating step, is arranged as an example, is more preferable heating method. Will be described in detail.

The hot air heating zone consisting of three hot air furnaces includes a first hot air heating furnace, a second hot air heating furnace adjacent to the first hot air heating furnace, and a third hot air heating furnace adjacent to the second hot air heating furnace. Express.

As an example of one preferable hot air zone, the temperature of the first hot air heating furnace is 290 to 310 ° C, the temperature of the second hot air heating furnace is 340 to 360 ° C, and the temperature of the third hot air heating furnace is 340 to 360 ° C. The temperature of the heating furnace is 340 to 360 ° C. Further, in this example, the temperature difference between the first hot air furnace and the second hot air furnace is preferably 50 ° C. or less, and the temperature difference between the second hot air furnace and the third hot air furnace is 30 ° C. or less. It is preferable to have.

Another preferred example is that the temperature of the first hot air heating furnace is 270 to 290 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 290 to 310 ° C. The temperature is 340 to 360 ° C. Further, in this example, the temperature difference between the first hot air furnace and the second hot air furnace is preferably 50 ° C. or less, and the temperature difference between the second hot air furnace and the third hot air furnace is 30 ° C. or less. It is preferable to have.

Another preferred example is that the temperature of the first hot air heating furnace is 270 to 290 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 290 to 310 ° C. The temperature is 290 to 310 ° C. Further, in this example, the temperature difference between the first hot air furnace and the second hot air furnace is preferably 50 ° C. or less, and the temperature difference between the second hot air furnace and the third hot air furnace is 30 ° C. or less. It is preferable to have.

Another preferred example is that the temperature of the first hot air heating furnace is 290 to 310 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 290 to 310 ° C. The temperature is 290 to 310 ° C. Further, in this example, the temperature difference between the first hot air furnace and the second hot air furnace is preferably 50 ° C. or less, and the temperature difference between the second hot air furnace and the third hot air furnace is 30 ° C. or less. It is preferable to have.

In another preferred example, the temperature of the first hot air heating furnace is 310 to 330 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is The temperature is 290 to 310 ° C. Further, in this example, the temperature difference between the first hot air furnace and the second hot air furnace is preferably 50 ° C. or less, and the temperature difference between the second hot air furnace and the third hot air furnace is 30 ° C. or less. It is preferable to have.

Yet another preferred example is that the temperature of the first hot air heating furnace is 340 to 360 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 290 to 310 ° C. The temperature is 290 to 310 ° C. Further, in this example, the temperature difference between the first hot air furnace and the second hot air furnace is preferably 50 ° C. or less, and the temperature difference between the second hot air furnace and the third hot air furnace is 30 ° C. or less. It is preferable to have.

In another preferable example, the temperature of the first hot air heating furnace is 270 to 310 ° C, the temperature of the second hot air heating furnace is 370 to 390 ° C, and the temperature of the third hot air heating furnace is 370 to 390 ° C. The temperature is 250 to 370 ° C. Further, in this example, the temperature difference between the first hot air furnace and the second hot air furnace is preferably 50 ° C. or less, and the temperature difference between the second hot air furnace and the third hot air furnace is 30 ° C. or less. It is preferable to have.

The radiant heat ray heating zone composed of two radiant heat ray heater furnaces is expressed as a first radiant heat ray heater furnace and a second radiant heat ray heater furnace adjacent to the first radiant heat ray heater furnace.

Next, as an example of one preferable radiant heat ray heating zone, the temperature of the first radiant heat ray heater furnace is 340 to 390 ° C., and the temperature of the second radiant heat ray heater furnace is 340 to 390 ° C. There is. Further, in this example, the temperature difference between the first radiant heat ray heater furnace and the second radiant heat ray heater furnace is preferably 30 ° C. or less.

In another preferred example of the radiant heat ray heating zone, the temperature of the first radiant heat ray heater furnace is 330 to 380 ° C., and the temperature of the second radiant heat ray heater furnace is 370 to 420 ° C. Further, in this example, the temperature difference between the first radiant heat ray heater furnace and the second radiant heat ray heater furnace is preferably 30 ° C. or less.

In yet another preferred example of the radiant heat ray heating zone, the temperature of the first radiant heat ray heater furnace is 370 to 420 ° C., and the temperature of the second radiant heat ray heater furnace is 330 to 380 ° C. Further, in this example, the temperature difference between the first radiant heat ray heater furnace and the second radiant heat ray heater furnace is preferably 30 ° C. or less.

As described in detail above, in the process of manufacturing a polyimide film, the polyimide film receives various thermal histories, so that the deformation due to Boeing changes from moment to moment in each zone.

In the present invention, it has been found that controlling the direction and magnitude of Boeing strain in each heating furnace is essential for suppressing the orientation anisotropy, and in order to finally cancel each of these, it is necessary to control each heating furnace. It has been found that by controlling the temperature, the strong orientation anisotropy that occurs at the edges can be improved.

Based on the above idea, since the temperature of each furnace placed in the heating furnace in the tenter heating process is set, the effect of the present invention is that the polyimide film is assumed to have a large positive Boeing strain. It exerts a better effect on production. The elastic modulus in the first half of the heating furnace at a relatively low temperature is high, and the elastic modulus tends to decrease as the temperature rises as the temperature rises in the latter half of the heating furnace. Due to such a difference in elastic modulus generated in the transport direction, a force is applied so that the film on the downstream side having a reduced elastic modulus is pulled by the film on the upstream side in which the elastic modulus is maintained high, so that the central portion is an end portion. This is because the Boeing phenomenon, which is delayed with respect to the above, occurs. An example of such a film is a polyimide film having a storage elastic modulus of 0.5 GPa or less at 350 ° C. when the dynamic viscoelasticity of the finally obtained polyimide film is measured, and is 0.3 GPa or less. A certain polyimide film exhibits a more excellent effect, and a polyimide film of 0.2 GPa or less exhibits a further excellent effect. For films where the positive Boeing strain is expected to be large, the negative Boeing can be increased to offset this, and the positive Boeing can be suppressed as much as possible to suppress the orientation anisotropy of the resulting film. It will be possible.

Further, in the production method of the present invention, a film having an in-plane orientation easily exhibits a better effect, and examples of such a polyimide film include a film having a polyimide resin having a biphenyl skeleton or a terphenyl skeleton structure.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

The evaluation method of MOR-c of the polyimide film in the synthesis example, the example and the comparative example is as follows.

(Evaluation method of MOR-c of polyimide film)
The polyimide films obtained in Examples and Comparative Examples were cut out from the central portion, a position 70 mm from the left end and a position 70 mm from the right end to a size of 50 mm × 50 mm, and the molecular orientation state was evaluated. MOR-c was determined using a microwave molecular orientation meter MOA-6015A manufactured by Oji Measuring Instruments Co., Ltd. as the measuring device. Here, MOR-c is a value obtained by converting the obtained molecular orientation degree MOR into the thickness of the test piece. The results obtained are shown in Table 1.

(Measurement of storage elastic modulus)
Using the obtained single-layer film of the adhesive layer, dynamic viscoelasticity was measured in an air atmosphere by DDMS6100 manufactured by SII Nanotechnology, and a graph plotting the storage elastic modulus and loss elastic modulus with respect to the measured temperature. It was prepared, and the storage elastic modulus and the loss elastic modulus at 350 ° C. were read from the graph.
-Sample measurement range; width 9 mm, distance between grippers 20 mm
-Measurement temperature range; 0 ° C to 440 ° C
・ Temperature rise rate: 3 ° C / min ・ Strain amplitude: 10 μm
・ Measurement frequency: 5Hz
-Minimum tension / compressive force; 100 mN
-Tension / compression gain; 1.5
-Initial force amplitude; 100 mN

(Synthesis Example 1)
N, N-dimethylformamide (hereinafter, also referred to as DMF) 1785.0 kg, p-phenylenediamine (hereinafter, also referred to as PDA) 72.1 kg, and 1,3-bis (4-aminophenoxy) benzene (hereinafter, also referred to as PDA). After adding 26.5 kg of TPE-R and stirring for 5 minutes, while stirring in a nitrogen atmosphere, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter, also referred to as BPDA). 176.4 kg was added gradually. After visually confirming that BPDA was dissolved, 30.8 kg of pyromellitic dianhydride (hereinafter, also referred to as PMDA) was gradually added and stirred for 30 minutes. Finally, a solution prepared by dissolving 3.8 kg of PMDA in DMF so as to have a solid content concentration of 7.2% was prepared, and this solution was gradually added to the above reaction solution while paying attention to the increase in viscosity. When the viscosity at 23 ° C. reached 2000 poise, the addition and stirring were stopped to obtain a polyamic acid solution.

(Synthesis Example 2)
To 1892.0 kg of DMF, 120.0 kg of TPE-R and 37.4 kg of 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter, also referred to as m-TB) were added, and BPDA86 was stirred under a nitrogen atmosphere. .4 kg was added gradually. After visually confirming that BPDA was dissolved, 41.0 kg of PMDA was added and the mixture was stirred for 30 minutes. A solution prepared by dissolving 3.8 g of PMDA in DMF so as to have a solid content concentration of 7.2% was gradually added to the above reaction solution while paying attention to the increase in viscosity, and the viscosity became 800 poise. When it reached the point, the polymerization was completed.

(Comparative Example 1)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 62% was formed by applying the solution on an endless belt at 120 ° C. and heating and drying for 180 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 200 ° C. is used for 23 seconds, and the second hot air furnace at 350 ° C. is used for 22 seconds. , Heated in a third hot air oven at 350 ° C. for 18 seconds. After that, it was heated in a first far-infrared heater furnace at 390 ° C for 23 seconds and then in a second far-infrared heater furnace at 390 ° C for 22 seconds. A 4 μm / 17 μm / 4 μm multilayer polyimide film was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end. The storage elastic modulus of the multilayer polyimide film was 0.2 GPa.

(Comparative Example 2)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm was obtained by the same method as in Comparative Example 1 except that the temperature of the first hot air furnace was 230 ° C. However, the amount of residual volatile components in the gel film was 63% in this comparative example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 1)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm was obtained by the same method as in Comparative Example 1 except that the temperature of the first heat wind furnace was 280 ° C. However, the amount of residual volatile components in the gel film was 63% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end. The storage elastic modulus of the multilayer polyimide film was 0.2 GPa.

(Example 2)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm was obtained by the same method as in Comparative Example 1 except that the temperature of the first hot air furnace was 300 ° C. However, the amount of residual volatile components in the gel film was 63% in this comparative example. Table 1 shows MOR-c at the center, 70 mm from the left end and 70 mm from the right end of the obtained multilayer polyimide film.

(Example 3)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 98% was formed by applying the solution on an endless belt at 100 ° C. and heating and drying for 180 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 300 ° C. is used for 23 seconds, and the second hot air furnace at 300 ° C. is used for 22 seconds. , Heated in a third hot air furnace at 300 ° C. for 18 seconds. After that, it was heated in a first far-infrared heater furnace at 400 ° C. for 23 seconds and in a second far-infrared heater furnace at 380 ° C. for 22 seconds. A 4 μm / 17 μm / 4 μm multilayer polyimide film was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 4)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm was obtained by the same method as in Example 3 except that the temperature of the second hot air furnace was 350 ° C. and that of the third hot air furnace was 380 ° C. However, the amount of residual volatile components in the gel film was 99% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 5)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 62% was formed by applying the solution on an endless belt at 120 ° C. and heating and drying for 180 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 280 ° C. is used for 23 seconds, and the second hot air furnace at 350 ° C. is used for 22 seconds. , Heated in a third hot air oven at 350 ° C. for 18 seconds. After that, it was heated in a first far-infrared heater furnace at 390 ° C for 23 seconds and then in a second far-infrared heater furnace at 390 ° C for 22 seconds. A 4 μm / 17 μm / 4 μm multilayer polyimide film was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 6)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm was obtained by the same method as in Example 5 except that the temperature of the second hot air furnace was 380 ° C. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end. However, the amount of residual volatile components in the gel film was 61% in this example.

(Reference example 1)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 62% was formed by applying the solution on an endless belt at 120 ° C. and heating and drying for 180 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 200 ° C. is used for 23 seconds, and the second hot air furnace at 350 ° C. is used for 22 seconds. , Heated in a third hot air oven at 350 ° C. for 18 seconds. After that, it was heated in a first far-infrared heater furnace at 370 ° C for 23 seconds and then in a second far-infrared heater furnace at 370 ° C for 22 seconds. A 4 μm / 17 μm / 4 μm multilayer polyimide film was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Reference example 2)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm was prepared in the same manner as in Reference Example 1 except that the temperature of the first far-infrared heater furnace was 420 ° C and the temperature of the second far-infrared heater furnace was 420 ° C. Obtained. The amount of residual volatile components in the gel film was 61% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 7)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property with a residual volatile component amount of 81% was formed by applying the solution on an endless belt at 90 ° C. and heating and drying for 240 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, and both ends in the lateral direction are fixed with a tenter for 31 seconds in the first hot air furnace at 300 ° C. and 29 seconds in the second hot air furnace at 300 ° C. , Heated in a third hot air oven at 300 ° C. for 24 seconds. After that, it was heated in a first far-infrared heater furnace at 350 ° C. for 37 seconds and in a second far-infrared heater furnace at 350 ° C. for 36 seconds. A 4 μm / 17 μm / 4 μm multilayer polyimide film was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 8)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm in the same manner as in Example 7 except that the temperature of the first far-infrared heater furnace is 370 ° C and the temperature of the second far-infrared heater furnace is 370 ° C. Got However, the amount of residual volatile components in the gel film was 80% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 9)
A multilayer polyimide film having a thickness of 4 μm / 17 μm / 4 μm in the same manner as in Example 7 except that the temperature of the first far-infrared heater furnace is 390 ° C and the temperature of the second far-infrared heater furnace is 390 ° C. Got However, the amount of residual volatile components in the gel film was 82% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 10)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 60% was formed by applying the solution on an endless belt at 150 ° C. and heating and drying for 320 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 280 ° C. for 41 seconds and the second hot air furnace at 300 ° C. for 39 seconds. , Heated in a third hot air furnace at 300 ° C. for 32 seconds. Then, after heating in a first far-infrared heater furnace at 370 ° C for 48 seconds and in a second far-infrared heater furnace at 370 ° C for 47 seconds, a slow cooling zone and an end slit process were performed to increase the width and thickness to 2150 mm. A multilayer polyimide film of 8 μm / 34 μm / 8 μm was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 11)
A multilayer polyimide film having a thickness of 8 μm / 34 μm / 8 μm was obtained by the same method as in Example 10 except that the temperature of the third hot air furnace was 350 ° C. The amount of residual volatile components in the gel film was 60% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 12)
A multilayer polyimide film having a thickness of 8 μm / 34 μm / 8 μm was obtained by the same method as in Example 10 except that the temperature of the third hot air furnace was 380 ° C. The amount of residual volatile components in the gel film was 60% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 13)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 70% was formed by applying the solution on an endless belt at 120 ° C. and heating and drying for 320 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 280 ° C. for 41 seconds and the second hot air furnace at 300 ° C. for 39 seconds. , Heated in a third hot air furnace at 300 ° C. for 32 seconds. Then, after heating in a first far-infrared heater furnace at 370 ° C for 48 seconds and in a second far-infrared heater furnace at 370 ° C for 47 seconds, a slow cooling zone and an end slit process were performed to increase the width and thickness to 2150 mm. A multilayer polyimide film of 8 μm / 34 μm / 8 μm was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 14)
A multilayer polyimide film having a thickness of 8 μm / 34 μm / 8 μm was obtained by the same method as in Example 13 except that the temperature of the first hot air furnace was 300 ° C. The amount of residual volatile components in the gel film was 70% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 15)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 99% was formed by applying the solution on an endless belt at 90 ° C. and heating and drying for 480 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 300 ° C. for 62 seconds and the second hot air furnace at 300 ° C. for 58 seconds. , Heated in a third hot air furnace at 300 ° C. for 48 seconds. After that, it was heated in a first far-infrared heater furnace at 380 ° C for 73 seconds and in a second far-infrared heater furnace at 350 ° C for 73 seconds, and then passed through a slow cooling zone and an end slit process to increase the width and thickness to 2150 mm. A multilayer polyimide film of 8 μm / 34 μm / 8 μm was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 16)
A multilayer polyimide film having a thickness of 8 μm / 34 μm / 8 μm was obtained by the same method as in Example 15 except that the temperature of the first hot air furnace was 320 ° C. However, the amount of residual volatile components in the gel film was 91% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 17)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 80% was formed by applying the solution on an endless belt at 100 ° C. and heating and drying for 480 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 300 ° C. for 62 seconds and the second hot air furnace at 300 ° C. for 58 seconds. , Heated in a third hot air furnace at 300 ° C. for 48 seconds. After that, it was heated in a first far-infrared heater furnace at 380 ° C for 73 seconds in a second far-infrared heater furnace at 380 ° C for 73 seconds, and then passed through a slow cooling zone and an end slit process to increase the width and thickness to 2150 mm. A multilayer polyimide film of 8 μm / 34 μm / 8 μm was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 18)
A multilayer polyimide film having a thickness of 8 μm / 34 μm / 8 μm was obtained by the same method as in Example 17 except that the temperature of the first hot air furnace was 320 ° C. However, the amount of residual volatile components in the gel film was 81% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 19)
Using a three-layer coextruded three-layer die, the polyamic acid solution obtained in Synthesis Example 2 / the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthesis Example 2 has a three-layer structure in this order. A gel film having a self-supporting property in which the amount of residual volatile components of the gel film was 73% was formed by applying the solution on an endless belt at 90 ° C. and heating and drying for 120 seconds. At this time, the polyamic acid solution obtained in Synthesis Example 1 was cured with acetic anhydride / isoquinolin / DMF (weight ratio 303/153/144) with respect to 100 g of the polyamic acid immediately before being charged into the three-layer die. 40 g of the agent (chemical dehydrating agent and imidization catalyst) was added and mixed with a mixer. After that, the self-supporting gel film is peeled off from the support, both ends in the lateral direction are fixed with a tenter, and the first hot air furnace at 300 ° C. is used for 16 seconds, and the second hot air furnace at 300 ° C. is used for 15 seconds. , Heated in a third hot air oven at 300 ° C. for 12 seconds. After that, it was heated in a first far-infrared heater furnace at 350 ° C. for 19 seconds and in a second far-infrared heater furnace at 350 ° C. for 18 seconds. A multilayer polyimide film of 2 μm / 8.5 μm / 2 μm was obtained. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 20)
The same method as in Example 19 except that the temperature of the first far-infrared heater furnace is 370 ° C and the temperature of the second far-infrared heater furnace is 370 ° C, and the thickness is 2 μm / 8.5 μm / 2 μm. A polyimide film was obtained. The amount of residual volatile components in the gel film was 73% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

(Example 21)
The same method as in Example 19 except that the temperature of the first far-infrared heater furnace is 400 ° C and the temperature of the second far-infrared heater furnace is 380 ° C, and the thickness is 2 μm / 8.5 μm / 2 μm. A polyimide film was obtained. However, the amount of residual volatile components in the gel film was 74% in this example. Table 1 shows MOR-c at the center of the obtained multilayer polyimide film, at a position 70 mm from the left end and at a position 70 mm from the right end.

From the results of Comparative Examples 1 and 2 and Examples 1 to 21 in Table 1, it can be seen that when the temperature of the first hot air furnace is relatively high at 270 to 360 ° C., the molecular orientation of the obtained multilayer polyimide film is excellent. It is considered that this is because the negative Boeing could be increased by raising the temperature of the first hot air furnace, and the positive Boeing could be offset.

Further, from the results of Examples 3 and 4 and the results of Examples 5 and 6 in Table 1, it is found that the temperature difference between the adjacent hot air furnaces is small, especially when the temperature of the second hot air furnace is low. It can be seen that the molecular orientation of the obtained multilayer polyimide film is excellent. It is considered that this is because the positive Boeing generated in the second hot air furnace could be reduced.

Further, from the results of Examples 10, 11 and 12 in Table 1, the molecules of the obtained multilayer polyimide film are obtained when the temperature difference between adjacent hot air furnaces is small, especially when the temperature of the third hot air furnace is low. It can be seen that the orientation is excellent. It is considered that this is because the positive Boeing generated in the third hot air furnace could be reduced.

Further, from the results of Examples 7, 8 and 9 in Table 1, it can be seen that the lower the temperature of the far-infrared heater furnace set to the maximum temperature, the better the molecular orientation of the obtained multilayer polyimide film. The same can be seen from the results of Examples 19 and 20 and the results of Example 21 in Table 1. It is considered that this is because the positive Boeing generated in the furnace could be reduced by lowering the temperature of the far-infrared heater furnace set to the maximum temperature. From the results of Reference Example 1 and Reference Example 2, the effect of improving the orientation anisotropy of the film by lowering the temperature set to the maximum temperature can be clearly confirmed.

Claims (22)

At a minimum, a polyamic acid organic solvent solution is cast or applied onto the support and dried to form a gel film that is a polyamic acid film that is partially imidized and / or partially dried until it is self-supporting. In the method for producing a polyimide film, which includes a step of peeling the gel film from the support, and a tenter heating step of fixing the end portion of the gel film and performing a heat treatment.
In the tenter heating step, heat treatment is performed by a heating furnace in which a plurality of furnaces of at least 3 connected in the longitudinal direction of the film are arranged.
The heating furnace is composed of a hot air heating zone in which two or more hot air furnaces are arranged and a radiant heat ray heating zone in which one or more radiant heat ray heater furnaces are arranged following the hot air heating zone.
The temperature of the first hot air furnace through which the gel film first passes in the tenter heating step is set in the range of 270 to 360 ° C., and the minimum temperature in the tenter heating step is 270 ° C. or higher.
A method for producing a polyimide film, wherein the temperature of the furnace set to the maximum temperature is in the range of 330 to 420 ° C. The method for producing a polyimide film according to claim 1, wherein the temperature difference between the hot air furnaces arranged in the hot air heating zone and adjacent to each other is 100 ° C. or less. The method for producing a polyimide film according to claim 1 or 2, wherein the furnace set to the maximum temperature is a radiant heat ray heater furnace. The hot air heating zone is characterized by having the first hot air heating furnace, the second hot air heating furnace adjacent to the first hot air heating furnace, and the third hot air heating furnace adjacent to the second hot air heating furnace. The method for producing a polyimide film according to any one of claims 1 to 3. The temperature of the first hot air heating furnace is 290 to 310 ° C, the temperature of the second hot air heating furnace is 340 to 360 ° C, and the temperature of the third hot air heating furnace is 340 to 360 ° C. The method for producing a polyimide film according to claim 4, wherein the temperature is set to ℃. The temperature of the first hot air heating furnace is 270 to 290 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 340 to 360 ° C. The method for producing a polyimide film according to claim 4, wherein the temperature is set to ℃. The temperature of the first hot air heating furnace is 270 to 290 ° C., the temperature of the second hot air heating furnace is 290 to 310 ° C., and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to claim 4, wherein the temperature is set to ℃. The temperature of the first hot air heating furnace is 290 to 310 ° C, the temperature of the second hot air heating furnace is 290 to 310 ° C, and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to claim 4, wherein the temperature is set to ℃. The temperature of the first hot air heating furnace is 310 to 330 ° C., the temperature of the second hot air heating furnace is 290 to 310 ° C., and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to claim 4, wherein the temperature is set to ℃. The temperature of the first hot air heating furnace is 340 to 360 ° C., the temperature of the second hot air heating furnace is 290 to 310 ° C., and the temperature of the third hot air heating furnace is 290 to 310 ° C. The method for producing a polyimide film according to claim 4, wherein the temperature is set to ℃. The temperature of the first hot air heating furnace is 270 to 310 ° C., the temperature of the second hot air heating furnace is 370 to 390 ° C., and the temperature of the third hot air heating furnace is 350 to 370 ° C. The method for producing a polyimide film according to claim 4, wherein the temperature is set to ℃. The invention according to any one of claims 1 to 11, wherein the radiant heat ray heating zone has a first radiant heat ray heater furnace and a second radiant heat ray heater furnace adjacent to the first radiant heat ray heater furnace. The method for manufacturing a polyimide film according to the above. The twelfth aspect of claim 12, wherein the temperature difference between the first radiant heat ray heater furnace and the second radiant heat ray heater furnace adjacent to the first radiant heat ray heater furnace is 0 to 70 ° C. Method for manufacturing polyimide film. The polyimide according to claim 12, wherein the temperature of the first radiant heat ray heater furnace is 340 to 390 ° C, and the temperature of the second radiant heat ray heater furnace is 340 to 390 ° C. Film manufacturing method. The polyimide according to claim 12, wherein the temperature of the first radiant heat ray heater furnace is 330 to 380 ° C., and the temperature of the second radiant heat ray heater furnace is 370 to 420 ° C. Film manufacturing method. The polyimide according to claim 12, wherein the temperature of the first radiant heat ray heater furnace is 370 to 420 ° C., and the temperature of the second radiant heat ray heater furnace is 330 to 380 ° C. Film manufacturing method. The method for producing a polyimide film according to any one of claims 1 to 16, wherein the radiant heat ray heater furnace is a far infrared heater furnace. The method for producing a polyimide film according to any one of claims 2 to 17, wherein the temperature difference between the hot air furnaces arranged in the hot air heating zone and adjacent to each other is 70 ° C. or less. The method for producing a polyimide film according to any one of claims 1 to 18, wherein the storage elastic modulus at 350 ° C. when the dynamic viscoelasticity of the polyimide film is measured is 0.5 GPa or less. The method for producing a polyimide film according to any one of claims 1 to 19, wherein the polyimide film has a polyimide resin having a biphenyl skeleton or a terphenyl skeleton structure. The invention according to any one of claims 1 to 20, further comprising a step of mixing a curing agent containing an imidization catalyst and a dehydrating agent prior to casting or applying the polyamic acid organic solvent solution onto the support. Method for manufacturing polyimide film. A gel film which is a polyamic acid film which is at least partially imidized and / or partially dried until it has self-supporting property by casting or applying a polyamic acid organic solvent solution on the support and drying the gel film. The step according to any one of claims 1 to 21, wherein the step of forming is to cast and / or apply a plurality of polyamic acid organic solvent solutions onto the support by a coextrusion method and dry the film. Method for manufacturing polyimide film.