JP2010201889A - Method of manufacturing polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To favorably maintaining separability between a support base material and a polyimide film, irrespective of a factor such as a kind and a thickness of the support base material, and an outside environment, and to cope with formation of a thin film, in manufacture of the polyimide film by a cast method. <P>SOLUTION: This method of manufacturing the polyimide film includes (a) a process for heat-treating the support base material having a polyimide resin surface at the first temperature within a range of 300°C or more to 500°C or less, (b) a process for applying a polyamide acid solution on the polyimide resin surface of the support base material after heat-treated, followed to be dried to form a polyamide acid layer, (c) a process for imidizing the polyamide acid layer by heat-treating the polyamide acid layer at the second temperature, to lamination-form the polyimide film on the support base material, and (d) a process for separating the polyimide film from the support base material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a polyimide film used for a circuit wiring board or the like.

  A polyimide resin is a resin having excellent heat resistance, mechanical properties, and electrical properties. Use of the polyimide film using the polyimide resin has been expanded to applications such as a substrate of a circuit wiring board represented by a flexible printed wiring board.

  A typical method for producing a polyimide film includes a tenter method and a casting method. The tenter method is a method in which a polyamic acid solution is cast on a rotating drum, peeled off from the rotating drum in the form of a polyamic acid gel film, and heated and cured in a tenter furnace to form a polyimide film (for example, Patent Document 1). ). The casting method is a method in which a polyamic acid solution is applied to an arbitrary supporting substrate, cured by heat treatment, and then a polyimide resin layer is peeled from the supporting substrate to form a polyimide film (for example, Patent Document 2).

  In recent years, electronic devices have been miniaturized, and polyimide films used for electronic components are also strongly required to be thin. In the conventional tenter method, when the film thickness of the produced polyimide film is reduced, the self-supporting property is lowered. Therefore, the polyamic acid gel film is peeled off from the rotating drum or stretched and cured in a tenter furnace. The probability of doing is increased. For this reason, the limit of the thickness of the polyimide film that can be industrially produced by the tenter method is considered to be about 7.5 μm.

  On the other hand, in the casting method, since the polyamic acid solution is applied on the supporting substrate and cured and then peeled off, it can be reinforced with the supporting substrate at the precursor stage with low self-supporting properties, and the film thickness can be reduced. It is considered that this method is more advantageous than the tenter method. As a supporting substrate in the casting method, for example, a metal foil such as copper foil or SUS foil, a metal foil-resin laminate such as a copper clad laminate (CCL), or a resin film such as polyimide has been used. In addition to the necessity of high heat resistance and solvent resistance, the supporting base material is required to have properties such as easy removal of the cured polyimide film (peelability) and low cost. As the polyimide film to be manufactured becomes thinner, the peelability becomes particularly important among the above characteristics. This is because if the polyimide film and the supporting substrate are adhered more strongly than necessary, the polyimide film will be wrinkled, cracked, cracked, etc. during peeling, resulting in a loss of product value and a significant decrease in yield. .

  In the said patent document 2, CCL is used as a support base material in the casting method, and at least one layer of the polyimide film to be produced and the polyimide layer of CCL is 4,4′-diamino-2,2′-. It has been proposed that the releasability of a polyimide film from a support substrate can be improved by using a polyimide resin obtained by reacting a diamine compound containing 40 mol% or more of dimethylbiphenyl with a tetracarboxylic acid.

  Further, Patent Document 3 proposes a method in which a thermoplastic polyimide varnish is directly cast-coated on a release film such as a non-thermoplastic polyimide film and dried to obtain a thermoplastic polyimide film with a release film. Yes. However, in the technique of Patent Document 3, it is assumed that the manufactured thermoplastic polyimide film with a release film is thermocompression bonded to another adherend, and then the release film is mechanically removed. The thermoplastic polyimide film is transferred by peeling. That is, when separating the thermoplastic polyimide film and the release film, the thermoplastic polyimide film is in a state of being supported by being adhered to the adherend, and the process of peeling the thermoplastic polyimide film alone is It is not assumed. Therefore, in Patent Document 3, no attention is paid to the problem when peeling the thermoplastic polyimide film.

JP 2000-191806 A JP 2004-322441 A Japanese Patent Laid-Open No. 11-10664

  As described above, in the film formation by the casting method, it is required that the peelability between the polyimide film and the supporting substrate is better as the polyimide film becomes thinner. However, the peelability between the polyimide film and the support substrate is determined by factors such as the surface free energy on the support substrate side, the water vapor transmission rate of both the polyimide film and the support substrate, and the environmental temperature and humidity. Since it fluctuates depending on external factors, it is difficult to perform stable peeling with a constant peel strength, which causes wrinkles, cracks, tears, etc. in the polyimide film of the product. In particular, when a thin polyimide film having a thickness of about several μm is manufactured, the influence of the above-mentioned factors tends to be remarkably manifested, and a solution has been demanded.

  Therefore, in the production of the polyimide film by the casting method, the present invention maintains good peelability between the support substrate and the polyimide film without being influenced by factors such as the type and thickness of the support substrate and the external environment, Furthermore, it aims at responding to thin film formation.

  As a result of diligent research in view of the above circumstances, the present inventors have used a polyimide resin substrate as a support substrate on which a polyamic acid solution is applied in a casting method, and heat-treating the polyimide resin substrate. The inventors have found that the peelability of the product from the polyimide film can be remarkably improved, thereby completing the present invention.

That is, the manufacturing method of the polyimide film according to the first aspect of the present invention is as follows.
a) heat-treating a supporting substrate having a polyimide resin surface at a first temperature within a range of 300 ° C. or more and 500 ° C. or less;
b) A step of applying a polyamic acid solution on the surface of the polyimide resin of the supporting substrate after the heat treatment and drying to form a polyamic acid layer;
c) imidization by heat-treating the polyamic acid layer at a second temperature, and laminating a polyimide film on the support substrate; and
d) peeling the polyimide film from the support substrate;
It has.

  In the method for producing a polyimide film according to the first aspect of the present invention, after the step d, the support base material is reused, and the steps a to d are performed as one cycle, and one cycle or more is further performed. preferable.

The method for producing a polyimide film according to the second aspect of the present invention,
a) a step of heat-treating a support substrate having a polyimide resin surface on both the front side and the back side at a first temperature within a range of 300 ° C. or more and 500 ° C. or less;
b) a step of applying a polyamic acid solution to one side of the support substrate after the heat treatment and drying to form a polyamic acid layer;
c) imidization by heat-treating the polyamic acid layer at a second temperature, and laminating a polyimide film on the support substrate; and
d) peeling the polyimide film from the support substrate;
With
After the step d, the step b to step d are performed as one cycle, and further one cycle or more is performed, and the support base on the side opposite to the surface on which the polyimide film is peeled off in the step d of the immediately preceding cycle is performed. The step b of the next cycle is performed using the surface of the material.

  Moreover, in the manufacturing method of the polyimide film of this invention, the said support base material is formed in the elongate film form, You may perform each said process by a roll-to-roll system.

  According to the method for producing a polyimide film of the present invention, by providing a support substrate having a polyimide resin surface at a first temperature within a range of 300 ° C. or more and 500 ° C. or less (step a), The peelability between the support substrate and the polyimide film can be greatly improved. As a result, in step d, since the polyimide film and the support substrate can be stably peeled with a constant force without being substantially affected by factors such as the type and thickness of the support substrate and the external environment, It is easy to deal with thinning, and can be manufactured at a high yield in continuous production such as a roll-toe-roll system, and has high industrial utility value.

  Moreover, in the manufacturing method of the polyimide film of this invention, the used support base material can be reused repeatedly and the cost of a support base material can be reduced significantly. In particular, when heat treatment is performed alternately on each side of the support substrate using the heat of the imidization process, the equipment, time, cost and energy consumption required for the heat treatment are hardly increased, and the process efficiency is excellent. ing.

It is process drawing which shows the outline | summary of the manufacturing method of the polyimide film of the 1st Embodiment of this invention. It is process drawing which shows the outline | summary of the manufacturing method of the polyimide film of the 2nd Embodiment of this invention. It is a graph which shows the relationship between the conditions of the heat processing at the time of reuse of a support base material, and peeling strength. It is a graph which shows the relationship between the temperature of the heat processing at the time of reuse of a support base material, and peeling strength.

[First Embodiment]
Hereinafter, the manufacturing method of the polyimide film concerning the 1st Embodiment of this invention is demonstrated. First, an outline of the polyimide resin that is a material of the polyimide film produced by the method of the present invention will be described. In the method of the present invention, the manufacturing object is a polyimide film, and a polyimide resin is also used for the support base material. Therefore, the following description of the polyimide resin is also applied to the support base material as appropriate.

  The polyimide resin includes a so-called polyimide, heat-resistant resin comprising a polymer having an imide group in its structure, as represented by polyamideimide, polybenzimidazole, polyimide ester, polyetherimide, polysiloxaneimide and the like. Is mentioned.

  The polyimide resin can be produced by reacting a known diamine and an acid anhydride in the presence of a solvent. Examples of the diamine used include 4,4′-diaminodiphenyl ether, 2′-methoxy-4,4′-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, and 1,3-bis (4 -Aminophenoxy) benzene, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4 Examples include '-diaminobiphenyl and 4,4'-diaminobenzanilide.

  Examples of diamines other than those described above include 2,2-bis- [4- (3-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, and bis [4- (3- Aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy)] biphenyl, bis [4- (3-aminophenoxy) biphenyl, bis [1- (4-aminophenoxy)] biphenyl, bis [1- ( 3-aminophenoxy)] biphenyl, bis [4- (4-aminophenoxy) phenyl] methane, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] ether, Bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy)] benzophenone, bi [4- (3-Aminophenoxy)] benzophenone, bis [4,4 ′-(4-aminophenoxy)] benzanilide, bis [4,4 ′-(3-aminophenoxy)] benzanilide, 9,9-bis [4- (4-aminophenoxy) phenyl] fluorene, 9,9-bis [4- (3-aminophenoxy) phenyl] fluorene, 2,2-bis- [4- (4-aminophenoxy) phenyl] hexafluoro Propane, 2,2-bis- [4- (3-aminophenoxy) phenyl] hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4 '-Methylene-2,6-diethylaniline, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'- Aminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylsulfone, 3,3 '-Diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4' -Diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4 "-diamino-p-terphenyl, 3,3" -diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine, 2, 6-diaminopyridine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-amino) Phenoxy) benzene, 4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bisaniline, 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisaniline, bis (p- Aminocyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-amino-t-butyl) toluene, 2,4 -Diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-dia Nopirijin, 2,5-diamino-1,3,4-oxadiazole, it can also be used piperazine.

  Examples of the acid anhydride include pyromellitic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride. Products, 4,4′-oxydiphthalic anhydride and the like.

  Moreover, as an acid anhydride other than the above, for example, 2,2 ′, 3,3′-, 2,3,3 ′, 4′- or 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride 2,3 ', 3,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 2,3 ', 3,4'-diphenyl ether tetra Preferred examples include carboxylic dianhydride and bis (2,3-dicarboxyphenyl) ether dianhydride. Also, 3,3 ", 4,4"-, 2,3,3 ", 4"-or 2,2 ", 3,3" -p-terphenyltetracarboxylic dianhydride 2,2-bis (2,3- or 3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3- or 3.4-dicarboxyphenyl) methane dianhydride, bis (2, 3- or 3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3- or 3,4-dicarboxyphenyl) ethane dianhydride, 1,2,7,8-1, , 2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 2,2-bis (3,4 -Dicarboxyphenyl) tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalene Tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5 , 6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7- (or 1,4 , 5,8-) tetrachloronaphthalene-1,4,5,8- (or 2,3,6,7-) tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9 , 10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine- 2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4 , 4'-bis (2,3-dicarboxyphenoxy) diphenylmethane dianhydride and the like can also be used.

  Each diamine and acid anhydride may be used alone or in combination of two or more. In addition, a polyimide resin is not limited to what is obtained from the said diamine and an acid anhydride.

  The reaction between the diamine and the acid anhydride is preferably carried out in an organic solvent. Such an organic solvent is not particularly limited, and specific examples thereof include dimethyl sulfoxide, N, N-dimethylformamide. , N, N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, phenol, cresol, γ-butyrolactone, and the like can be used alone or in combination. Further, the amount of such organic solvent used is not particularly limited, but it should be adjusted so that the concentration of the polyamic acid obtained by the polymerization reaction is about 5 to 30% by weight. preferable.

  In the reaction using such a solvent, it is preferable that the mixing ratio of diamine and acid anhydride is such that the molar ratio of acid anhydride to total diamine is 0.95 to 1.05. .

  The diamine and the acid anhydride are preferably reacted for 1 to 24 hours under temperature conditions in the range of 0 ° C to 60 ° C. When the temperature condition is less than the lower limit (0 ° C.), the reaction rate tends to be slow and the molecular weight does not increase. On the other hand, when the upper limit (60 ° C.) is exceeded, imidization proceeds and the reaction solution Tends to gel. By making it react on such temperature conditions, the resin solution of the polyamic acid which is a precursor of a polyimide resin can be obtained efficiently.

  The synthesized polyamic acid is used as a solution. Usually, it is advantageous to use as a reaction solvent solution, but if necessary, it can be concentrated, diluted or replaced with another organic solvent. Moreover, since polyamic acid is generally excellent in solvent solubility, it can be easily used as a solution.

  In FIG. 1, the outline | summary of the manufacturing method of the polyimide film of this Embodiment was shown. The manufacturing method of the polyimide film of this Embodiment is provided with the following process a-process d. The contents of each process will be described in order.

Process a) The process of heat-processing the support base material 1 which has a polyimide resin surface at the 1st temperature in the range of 300 to 500 degreeC:
The support substrate 1 used in the present invention has a function as a support when the polyamic acid solution is applied by a casting method and a function of reinforcing the polyamic acid layer 3. The support substrate 1 can be used in various shapes such as a cut sheet shape, a roll shape, or an endless belt shape. In order to obtain productivity, it is efficient to use a roll-like or endless belt-like film form and a form capable of continuous production. In particular, the supporting substrate 1 is preferably a long roll-shaped film, and it is preferable to perform the steps a to d continuously by a roll-to-roll method.

The support substrate 1 is a substrate having a front surface and a back surface, and at least one of which has a polyimide resin surface formed of a polyimide resin. Although it is possible to use a metal foil-polyimide resin laminate such as a copper clad laminate (CCL) as such a support substrate 1, it is difficult to use both sides and the polyimide resin is economical. It is preferable to use a polyimide film made of In this case, the polyimide film may have a structure in which a plurality of polyimide resin layers are laminated, but a single layer is more advantageous. As the polyimide resin, a non-thermoplastic polyimide resin is preferably used. Among non-thermoplastic polyimide resins, those composed of a low-expansion polyimide resin having low adhesiveness can be suitably used in the present invention. Specifically, the coefficient of linear thermal expansion (CTE) is 1 × 10 ⁻⁶ to 30 × 10 ⁻⁶ (1 / K), preferably 10 × 10 ^{−6 to} 25 × 10 ⁻⁶ (1 / K). It is a low thermal expansion polyimide resin. By applying such a polyimide resin, it is possible to suppress dimensional changes due to heat treatment during the production of the polyimide film. Moreover, the glass transition temperature (Tg) of the polyimide resin applied to the support substrate 1 is preferably 300 ° C. or higher, more preferably 320 ° C. or higher. By using such a polyimide resin, high heat resistance can be maintained. The glass transition temperature can be measured by the method specified in the examples described later.

As the support substrate 1, a commercially available polyimide film can be suitably used. For example, Kapton EN, Kapton H, Kapton V (all trade names) manufactured by Toray DuPont Co., Ltd., Apical manufactured by Kaneka Chemical Co., Ltd. NPI (trade name), Upilex S (trade name) manufactured by Ube Industries, Ltd., etc. can be used. In addition, when metal foils, such as copper foil and SUS foil, are used as the support base material 1, the adhesiveness with the polyimide film 7 becomes too strong, and good peelability cannot be obtained.

  Considering the rigid surface, when the material of the support base 1 is made of polyimide resin, the thickness is preferably in the range of 10 μm to 250 μm, and more preferably in the range of 25 μm to 75 μm. If the thickness of the support substrate 1 is less than 10 μm, sufficient rigidity cannot be obtained and the function as a support is insufficient, and if it exceeds 250 μm, separation (peeling) from the polyimide film 7 (see FIG. 1) of the product occurs. It can be difficult. The thickness of the support substrate 1 has a close correlation with the moisture permeability described later, and the moisture permeability tends to decrease as the thickness increases.

  Moreover, it is thought that the water vapor transmission rate of the support base material 1 has a correlation with the degree of orientation which the polyimide resin which comprises the support base material 1 has other than thickness. That is, when a polyimide resin having a highly oriented polyimide resin and a dense structure is applied to the support substrate 1, the moisture permeability of the support substrate 1 is small, so that the organic solvent in the polyimide film production drying / imidization step Further, the moisture accompanying the progress of imidization concentrates on the interface between the support substrate 1 and the polyimide film layer 5 (see FIG. 1), and hinders the adhesion between the two, thereby facilitating the release of the polyimide film 7 of the product. It is thought that.

From the above viewpoint, it is preferable that the upper limit of the moisture permeability of the support base material 1 is 30 g / m ² · 24 hr or less. When the moisture permeability of the support substrate 1 exceeds 30 g / m ² · 24 hr, the peelability between the support substrate 1 and the polyimide film 7 is deteriorated, but if the moisture permeability is 30 g / m ² · 24 hr or less, the above reason As a result, it is possible to maintain good peelability, to easily maintain the surface state of the back surface side of the support substrate 1, and to easily reduce the peelability of the back surface side. On the other hand, the moisture permeability of the support substrate 1 is preferably 0.5 g / m ² · 24 hr or more. When the moisture permeability is less than 0.5 g / m ² · 24 hr, the organic solvent in the drying / imidization process of polyimide film production and moisture accompanying the imidization process cannot be removed, and the polyimide film layer 5 floats at the stage of the production process. (Partial peeling of the polyimide film layer 5) tends to occur. Therefore, it is desirable to control the upper limit of the thickness of the support substrate 1 to a thickness that does not fall below the lower limit value of the moisture permeability of the support substrate 1 (0.5 g / m ² · 24 hr). Note that the moisture permeability can be measured by a method defined in Examples described later.

  In this step a, the support substrate 1 is heat-treated at a first temperature in the range of 300 ° C. or more and 500 ° C. or less. This heat treatment has the meaning of relaxing the adhesive force with the formed polyimide film 7 and improving the peelability by changing the surface state of the support substrate 1 and reducing the wettability. At the molecular level, in the heat treatment, the cleaved imide bond existing on the surface of the polyimide resin constituting the support substrate 1 is closed to modify the surface state to have a large contact angle with pure water, thereby improving the peelability. It is thought that there is an effect. For this purpose, the first temperature is preferably in the range of 320 ° C. or higher and 450 ° C. or lower, more preferably 350 ° C. or higher and 420 ° C. or lower. Further, the glass transition temperature (Tg) of the polyimide resin constituting the support substrate 1 ) Or more. When the heat treatment temperature is lower than 300 ° C., the effect of improving the peelability by the heat treatment cannot be sufficiently obtained. When the heat treatment temperature is higher than 500 ° C., further improvement in the effect cannot be expected, and the support substrate is warped or distorted. There is a possibility that the mechanical properties are deteriorated due to deformation of the resin or modification of the polyimide resin.

  There is no particular limitation on the heating device used for this heat treatment, for example, a non-contact type heating method using electromagnetic waves such as far-infrared rays, ultraviolet rays, microwaves, or a contact type heating method such as a temperature-controllable jacket roll. It is possible to carry out using the adopted heating device or the like. The heat treatment can be performed, for example, by passing the support substrate 1 through a heating furnace over a predetermined time. The heat treatment time is not as important as the temperature, but for example, when the heat treatment is performed at a temperature equal to or higher than the Tg of the support substrate 1, it is preferably 30 seconds to 15 minutes, more preferably 1 to 15 minutes, still more preferably. 5-10 minutes is good. In this case, if the heat treatment time is shorter than 30 seconds, the effect of the heat treatment cannot be sufficiently obtained, and even if it is longer than 15 minutes, no further increase in the effect can be expected, so that the throughput and energy efficiency are lowered.

  In consideration of the peelability from the polyimide film 7, it is preferable that the contact angle of the surface of the support substrate 1 on which the polyimide film 7 is formed (the coated surface on which the polyamic acid solution is applied) is sufficiently large after the heat treatment. . That is, when water droplets are placed on the coated surface of the support substrate 1 after the heat treatment, the contact angle between the support substrate 1 and water is preferably 75 ° or more and 90 ° or less, and 75 ° or more and 85 ° or less. It is more preferable. If the contact angle of the coated surface is 75 ° or more, it is possible to reduce the peel strength between the polyimide film 7 of the product and the support substrate 1, and the occurrence of cracks and tears during peeling or after peeling Generation | occurrence | production of a wrinkle can be prevented and the external appearance of the polyimide film 7 can be made favorable. The appropriate range of the peel strength when peeling the support substrate 1 and the polyimide film 7 varies depending on the thickness of the polyimide film 7. For example, when peeling the polyimide film 7 having a thickness of 2 to 25 μm, 15 N / m. The following (for example, 5 N / m or more and 15 N / m or less) is preferable, and 10 N / m or less (for example, 5 N / m or more and 10 N / m or less) is more preferable. In addition, the measuring method of peeling strength can be performed by the method prescribed | regulated by a postscript Example.

  After the heat treatment, the support substrate 1 is cooled to a temperature at which dew condensation does not occur before proceeding to the next step b. Specifically, it is preferable to cool the support substrate 1 to a temperature within the range of 23 ° C to 40 ° C. The cooling may be natural cooling to near normal temperature, or forcibly cooling by air blowing or the like for the purpose of improving the throughput.

Step b) Step of forming a polyamic acid layer 3 by applying and drying a polyamic acid solution on the surface of the polyimide resin of the support substrate 1 after the heat treatment:
In this step, the polyamic acid layer 3 is formed by applying a solution of the polyamic acid, which is a polyimide resin precursor, directly on the support substrate 1 and then drying. The polyamic acid may be a precursor of either thermoplastic polyimide or non-thermoplastic polyimide. The method for applying the polyamic acid solution to the support substrate 1 is not particularly limited, and for example, it can be applied by a coater such as a comma, a die, a knife, or a lip.

  As the polyamic acid solution, commercially available products can be suitably used. For example, U-Varnish-A (trade name) and U-Varnish-S (trade name) which are non-thermoplastic polyamic acid varnishes manufactured by Ube Industries, Ltd. ), Thermoplastic Polyamic Acid Varnish SPI-200N (trade name), SPI-300N (trade name), SPI-1000G (trade name) manufactured by Nippon Steel Chemical Co., Ltd., Toray Nice # 3000 (trade name) manufactured by Toray Industries, Inc. Product name).

  In addition to the polyamic acid and the solvent, the polyamic acid solution is a filler such as silica, alumina, boron nitride, titanium oxide, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, magnesium oxide, calcium oxide, or clay mineral Can be contained.

When the polyamic acid layer 3 applied to the support substrate 1 is dried, the temperature is controlled so that imidization due to the progress of dehydration and ring closure of the polyamic acid is not completed. The method for drying the polyamic acid layer 3 is not particularly limited. For example, the polyamic acid layer 3 may be dried over a temperature range of 60 ° C. to 200 ° C. over a period of 1 to 60 minutes. Preferably, drying is performed under a temperature condition within a range of 60 ° C to 150 ° C. In the polyamic acid layer 3 after drying, a part of the structure of the precursor may be imidized, but the imidization rate is 50% or less, more preferably 20% or less, and the structure of the precursor is left 50% or more. It is preferable. In addition, the imidation ratio of the precursor is 1 by measuring the infrared absorption spectrum of the polyimide thin film by a transmission method using a Fourier transform infrared spectrophotometer (commercially available product, for example, FT / IR620 manufactured by JASCO Corporation). , relative to the benzene ring carbon hydrogen bonds of 000cm ^-1, are calculated from the absorbance from the imide groups of 1,710cm ^-1.

  The thickness (after drying) of the polyamic acid layer 3 is preferably in the range of 25 to 50 μm, for example, and more preferably in the range of 35 to 45 μm. If the polyamic acid layer 3 is formed thick, the polyimide film 7 of the product is also thickened, so that wrinkles, cracks, tears and the like are less likely to occur at the time of peeling, but the method of the present invention can be applied to a thin film. For this reason, the polyamic acid layer 3 can be thinly formed, for example, in the range of 15 to 25 μm.

  In addition, although it is industrially advantageous that the polyamic acid layer 3 is a single layer, the polyamic acid solution is repeatedly applied and dried on the support substrate 1, and a plurality of layers made of polyamic acids having different types and properties are laminated. It is also possible to form a polyamic acid layer having the structure described above.

Step c) Step of imidizing the polyamic acid layer 3 by heat treatment at a second temperature and laminating the polyimide film layer 5 on the support substrate 1:
The imidization is a step of forming polyimide by proceeding with dehydration and ring closure of polyamic acid by heat treatment. In the present embodiment, the heat treatment for imidization may be performed at a temperature and time that can complete the imidization of the polyamic acid, for example, within a range of 60 ° C to 450 ° C, preferably 80 ° C to 420 ° C. This can be done by heating at the second temperature for a time in the range of 1 to 60 minutes. The polyimide film layer 5 can be laminated on the support substrate 1 by heat treatment. In addition, there is no restriction | limiting in particular in the heating apparatus used in the imidation of the process c, The thing of the structure similar to the process a can be used.

Step d) Step of peeling the polyimide film 7 from the support substrate 1:
The method of peeling the polyimide film 7 from the support substrate 1 is not particularly limited. For example, in the roll-to-roll method, the long support substrate 1 and the long polyimide film 7 are wound on rolls, respectively. A method of peeling by taking is preferably employed. In this Embodiment, since the process b and the process c are performed in the state which made wettability of the coating surface of the support base material 1 small enough by the heat processing of the process a, the support base material 1 and the polyimide film 7 are easily carried out. Can be peeled off.

  In the manufacturing method of the polyimide film of this Embodiment, after the process d, the used support base material 1 can be reused and the process a-process d can be made into one cycle, and at least 1 cycle or more can be performed. . It is considered that the polyimide film forming surface (coating surface) of the supporting substrate 1 is hydrolyzed during imidization, and the imide ring is partially opened. Therefore, when the support substrate 1 once used is reused as it is, the wettability of the surface is increased, so that the adhesiveness with the polyimide film 7 is increased and the peelability is lowered. However, the surface state of the support substrate 1 can be recovered by performing the heat treatment in the step a again on the used support substrate 1 from which the polyimide film 7 has been peeled off. By performing the heat treatment in step a, it is considered that the ring-opened imide ring can be closed and thereby the contact state can be recovered to a large surface state. Therefore, by performing the heat treatment of step a for each cycle and reusing the support substrate 1, the cost for the support substrate 1 can be greatly reduced, and an efficient process with excellent economic efficiency. Is realized.

  In both the second and subsequent cycles, either one of both surfaces of the support substrate 1 may be used. From the viewpoint of extracting the number of times the support substrate 1 is used to the maximum, one surface of the support substrate 1 is provided for each cycle. It is preferable to use them alternately.

  As described above, in the method of the present invention, it is possible to improve the peelability between the polyimide film 7 and the support substrate 1 in the step d by performing the heat treatment of the support substrate 1 in the step a. The influence of factors such as the type and thickness of the material 1 and the external environment is eliminated as much as possible, and the polyimide film 7 and the support substrate 1 can be stably peeled with a constant force. Therefore, it is possible to prevent the polyimide film 7 of the product from being cracked, torn, wrinkled, etc., and improve the yield. In particular, it is possible to manufacture with a high yield in continuous production such as a roll-to-roll method, and industrial utility value is high. Also, it is possible to produce an ultrathin film having a thickness of, for example, 2 to 7 μm, which has been difficult to produce by the conventional tenter method. Furthermore, when reusing the support base material 1, the cost concerning the support base material 1 can be reduced significantly.

  In the above description, only the characteristic steps of the method of the present invention have been described, but this does not prevent inclusion of steps other than those described above, and any step can be included, and these can be performed according to a conventional method. it can.

[Second Embodiment]
Next, the manufacturing method of the polyimide film which concerns on the 2nd Embodiment of this invention is demonstrated. Similar to the first embodiment, the present embodiment also includes the steps a to d, and therefore, the following description will focus on differences from the first embodiment. In the present embodiment, a supporting substrate having a polyimide resin surface on both the front side and the back side is used as the supporting substrate 1. Although it is possible to use a double-sided resin laminate in which a polyimide resin layer is laminated on both sides of a metal foil as such a support substrate 1, it is possible to use a polyimide film made of a polyimide resin in terms of economy. preferable. In this case, the polyimide film may have a structure in which a plurality of polyimide resin layers are laminated, but a single layer is more advantageous.

  In this embodiment, after performing steps a to d as in the first embodiment, one cycle or more is further performed with steps b to d as one cycle. In this case, the step b of the next cycle is performed using the surface of the support substrate 1 opposite to the surface from which the polyimide film 7 was peeled off in the step d of the immediately preceding cycle. In the first embodiment, when the support base material 1 is reused, the surface state of the support base material 1 is recovered by performing step a. However, in this embodiment, the polyamide is used in step c. The surface state of the support substrate 1 is recovered by utilizing the heat generated when the acid layer 3 is imidized at the second temperature. In the present embodiment, steps a to d can be performed in the same manner as in the first embodiment except for the temperature setting at the time of imidization in step c, so that the description of the contents of each step is omitted. To do.

  An outline of the steps in this embodiment is shown in FIG. The contents of each process are basically the same as those in the first embodiment. First, since the A surface and B surface of the support base material 1 are exposed in the process a, both surfaces are heat-processed and the surface state is adjusted. Next, in step b, the polyamic acid solution is applied to the A surface of the supporting substrate 1 to form the polyamic acid layer 3. Next, in step c, the polyamic acid layer 3 is imidized by heat treatment at a second temperature, and the polyimide film layer 5 is laminated on the support substrate 1. At this time, since the B surface (the surface that is not the coated surface) of the support substrate 1 is an open surface, the surface state is adjusted by the heat of imidization (although in the first cycle, B surface Since the surface is already in a good surface state in terms of peelability from the polyimide film 7 by the heat treatment in step a, there may be no substantial change). On the other hand, at the time of imidization, on the A surface in contact with the polyamic acid layer 3, hydrolysis causes partial cleavage of the imide ring, and wettability increases (contact angle decreases).

  Next, the polyimide film 7 of a product is peeled from the support base material 1 at the process d. The first cycle is completed as described above, but the used support base material 1 is in terms of releasability between the polyimide film 7 and the A surface that has been hydrolyzed during imidization and has increased wettability. It has B surface which has a favorable surface state. In the present embodiment, attention is paid to the unused B side in the first cycle, and in the next second cycle, it is possible to omit the step a by applying the polyamic acid solution to this B side. Become.

  In the second cycle, the polyamic acid solution is applied to the B surface of the support substrate 1 in step b to form the polyamic acid layer 3 and imidization is performed in step c. Contrary to the first cycle, the B surface in contact with the polyamic acid layer 3 undergoes hydrolysis during imidization, resulting in partial cleavage of the imide ring and increased wettability (small contact angle). Become). However, since the A surface is an open surface, a ring closing reaction of the imide ring occurs due to heat during imidization, and the surface state is adjusted. That is, the wettability of the A surface of the support substrate 1 is small, the contact angle is large, and the surface state is recovered to be excellent in terms of peelability from the polyimide film 7. Thus, in order to recover the surface state of the A surface of the supporting substrate 1 by the heat treatment for imidization in step c, the temperature for heat treatment for imidization (second temperature) is set to the temperature for heat treatment in step a (first step). 1 temperature) or higher. That is, in this Embodiment, 2nd temperature is set to the temperature in the range which can complete the imidation reaction of a polyamic acid, and can recover the surface state of the support base material 1. FIG. Further, when both the A surface and the B surface of the support substrate 1 are used alternately and the imidization heat treatment is used as the heat treatment in the step a, the imidation heat treatment temperature (second temperature) is If the temperature is too high, the support substrate 1 and the polyimide film 7 tend to adhere to each other. Therefore, the upper limit of the second temperature is preferably set to 420 ° C. From such a viewpoint, in the present embodiment, the second temperature is preferably in the range of 300 ° C. to 420 ° C., for example, and more preferably in the range of 320 ° C. to 380 ° C.

  Next, the polyimide film 7 of a product is peeled from the support base material 1 at the process d. The second cycle is completed as described above, but the used support base material 1 has a B surface that has been wetted by hydrolysis during imidization, and a polyimide film 7 by heat treatment during imidization. In other words, it has a surface A that has been recovered to a good surface state in terms of releasability.

  In the third cycle, the polyamic acid solution is applied in step b by using the A surface of the support substrate 1 whose surface state has been recovered. Thereafter, the third cycle is completed by performing steps c and d in the same manner as described above. Next, in the fourth cycle, steps b to d are performed using the B surface of the support base material 1. Thus, the peelability of the support base material 1 and the polyimide film 7 is maintained in a good state by repeating the steps b to d by alternately using the A surface and the B surface of the support base material 1 one by one. Thus, a polyimide film can be efficiently produced while stably performing the separation in step d with a constant peeling force.

  As described above, in the present embodiment, the second temperature during the heat treatment at the time of imidation in step c is used to complete the imidization reaction of the polyamic acid and recover the surface state of the support substrate 1. By setting the temperature within a range that can be allowed to be performed, the surface A and the surface B of the support substrate 1 are alternately used / recovered without performing step a except for the first cycle, and the coated surface is always maintained. It can be used in a state excellent in releasability from the polyimide film 7. Therefore, in the step d, it is possible to stably peel the polyimide film 7 and the support substrate 1 with a constant force, and the polyimide film 7 of the product is cracked, torn, wrinkled, etc. at the time of peeling. It is possible to prevent and improve the yield, and it is also possible to produce an ultrathin film having a thickness of 2 to 7 μm, for example. In particular, the cost of the support substrate 1 can be greatly reduced by reusing the support substrate 1. Furthermore, in the present embodiment, after the second cycle, step a is not necessary, and heat at the time of imidization in step c can be effectively used, so that energy efficiency is also excellent.

  Other configurations and effects in the present embodiment are the same as those in the first embodiment.

EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. Unless otherwise specified in the examples of the present invention, various measurements and evaluations are as follows. Moreover, the symbol used for the Example has the following meaning.
DMAc: N, N-dimethylacetamide DADMB: 4,4′-diamino-2,2′-dimethylbiphenyl 1,3-BAB: 1,3-bis (4-aminophenoxy) benzene BPDA: 3,3 ′, 4 , 4'-biphenyltetracarboxylic dianhydride PMDA: pyromellitic dianhydride

[Evaluation of peel strength]
The peel strength was evaluated by measuring 90 °, 10 mm peel strength at room temperature for a sample cut into a strip shape having a width of 10 mm using a STRograph R-1 manufactured by Toyo Seiki Seisakusho. When the peel strength is 10 N / m or less, the peelability is “very good”, and when the peel strength is more than 10 N / m and 15 N / m or less, the peelability is “good” (practical range), and 15 N / m. The super peelability was evaluated as “poor”.

[Measurement of contact angle]
The contact angle of pure water was measured with a fully automatic contact angle meter (Kyowa Interface Science Co., Ltd., CA-W type, analysis software FAMAS) using ultra pure water, and calculated by the θ / 2θ method.

[Measurement of linear thermal expansion coefficient]
The coefficient of linear thermal expansion was determined by using a thermomechanical analyzer (manufactured by Seiko Instruments Inc.), raising the temperature of the sample to 250 ° C., holding the sample at that temperature for 10 minutes, and then cooling at a rate of 5 ° C./min. To an average linear thermal expansion coefficient (CTE) from 100 ° C to 100 ° C.

[Measurement of glass transition temperature (Tg)]
The glass transition temperature was measured at a rate of 10 ° C./min from room temperature to 400 ° C. while applying a 1 Hz vibration using a 10 mm wide sample using a viscoelasticity analyzer (RSA-II manufactured by Rheometric Science Effy Co., Ltd.). It was determined from the maximum loss tangent (Tan δ) when the temperature was raised at.

[Measurement of moisture permeability]
The moisture permeability was measured by a cup method based on JIS Z0208. Hygroscopic agent / calcium chloride (anhydrous) was enclosed in a moisture-permeable cup made of aluminum with a permeation area of 2.826 × 10 ⁻³ m ² and repeated weighing operations every 24 hours under the test conditions of 40 ° C. and 90 RH%. The mass increase of the cup was evaluated as the amount of water vapor permeated.

Production Example 1
In 255 g of DMAc, 19.11 g (0.090 mol) of DADMB and 2.92 g of 1,3-BAB (0.010 mol) were dissolved in a vessel with stirring. Next, 5.79 g BPDA (0.020 mol) and 17.17 g PMDA (0.079 mol) were added. Thereafter, the polymerization reaction was continued for about 3 hours to obtain a polyamic acid solution having a solid concentration of 15% by weight and a solution viscosity of 200 poise [20 Pa · s].

Example 1
As a supporting substrate, a polyimide film having a thickness of 25 μm (Upilex S; trade name, manufactured by Ube Industries, Ltd., pure water contact angle 74.8 °, CTE 12 × 10 ⁻⁶ / K, Tg 336 ° C., moisture permeability 1.7 g / m ² · 24 hr) and heat-treated at a temperature of 360 ° C. for 5 minutes in a heating furnace. At this time, the contact angle of pure water on the surface of the support substrate was 80 ° or more.

  Next, the polyamic acid solution obtained in Production Example 1 was uniformly applied to one side of the support substrate, and was dried by heating at a temperature of 100 ° C. or lower to remove excess solvent. Next, heat treatment was performed for 10 minutes in a heating furnace having a maximum temperature of 360 ° C. to complete imidization, followed by cooling to room temperature and peeling from the support substrate to obtain a polyimide film having a thickness of 4 μm. In this first cycle, the peel strength of the polyimide film from the supporting substrate was 10 N / m or less, and peeling was easy. In the obtained film, no defects in appearance such as wrinkles, cracks and tears were observed.

  The contact angle of pure water on the surface of the support substrate after peeling the polyimide film was reduced to 69.9 °. When this used support base material was heat-treated at 360 ° C. for 5 minutes in a heating furnace, the contact angle of pure water recovered to 82.5 °. Using this support substrate, the second cycle polyimide film was formed under the same conditions as described above, and the peelability between the polyimide film and the support substrate was the same as during the first cycle film formation. A polyimide film having a thickness of 4 μm was able to be produced while maintaining a good temperature. The peeling strength of the polyimide film from the supporting substrate at this time was 10 N / m or less as in the first cycle, and peeling was easy. No defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

  Furthermore, by repeating the above procedure, it is possible to reuse the support substrate for 10 cycles or more while maintaining the peel strength of the polyimide film from the support substrate at 10 N / m or less and maintaining the appearance of the film. there were. The above results are shown in Table 1.

Example 2
As a supporting base material, a polyimide film having a thickness of 75 μm (Upilex S; trade name, manufactured by Ube Industries, Ltd., pure water contact angle 74.8 °, CTE 12 × 10 ⁻⁶ / K, Tg 336 ° C., moisture permeability 0.9 g / A polyimide film was formed only for one cycle in the same manner as in Example 1 except that m ² · 24 hr) was used. The results are shown in Table 1.

Example 3
As a supporting substrate, a polyimide film with a thickness of 38 μm (Kapton EN; trade name, manufactured by Toray DuPont, pure water contact angle 70.4 °, CTE 16 × 10 ⁻⁶ / K, Tg 364 ° C., moisture permeability 17 g / m ^The film formation of the polyimide film was carried out for only one cycle in the same manner as in Example 1 except that ² · 24 hr) was used. The results are shown in Table 1.

Example 4
A polyimide film (Kapton EN; trade name, manufactured by Toray DuPont Co., Ltd., pure water contact angle 74.0 °, CTE 16 × 10 ⁻⁶ / K, Tg 364 ° C., moisture permeability 22 g / m) ² · 24 hr), and a polyimide film was formed in the same manner as in Example 1 except that the heat treatment for reusing the support substrate was performed at 420 ° C. for 10 minutes after the end of the first cycle. went. The results are shown in Table 1.

Example 5
As a supporting substrate, a polyimide film having a thickness of 75 μm (Kapton H; trade name, manufactured by Toray DuPont, pure water contact angle 76.6 °, CTE 16 × 10 ⁻⁶ / K, Tg 411 ° C., moisture permeability 27 g / m) ² · 24 hr), and a polyimide film was formed in the same manner as in Example 1 except that the heat treatment for reusing the support substrate was performed at 420 ° C. for 10 minutes after the end of the first cycle. went. The results are shown in Table 1.

Example 6
As a supporting substrate, a 25 μm-thick polyimide film (Kapton V; trade name, manufactured by Toray DuPont, pure water contact angle 45 °, CTE 16 × 10 ⁻⁶ / K, Tg 410 ° C., moisture permeability 84 g / m ^2. 24 hr), and a polyimide film was formed in the same manner as in Example 1 except that the heat treatment for reusing the supporting substrate after completion of the first cycle was performed at 420 ° C. for 10 minutes. . The results are shown in Table 1.

Example 7
As a supporting substrate, a polyimide film having a thickness of 25 μm (Apical NPI; trade name, manufactured by Kaneka Corporation, contact angle of pure water 63.2 °, CTE 18 × 10 ⁻⁶ / K, Tg 400 ° C. or less, moisture permeability 66 g / m ² -24 hr) and after the first cycle, a polyimide film was formed in the same manner as in Example 1 except that the heat treatment for reusing the support substrate was performed at 420 ° C for 10 minutes. It was. The results are shown in Table 1.

Comparative Example 1
Except that the support substrate was not heat-treated before application of the polyamic acid solution, the first cycle was carried out in the same manner as in Example 6 to obtain a polyimide film having a thickness of 4 μm. The peel strength when peeling the polyimide film from the support substrate exceeded 15 N / m, and defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

Comparative Example 2
The first cycle was carried out in the same manner as in Example 7 except that the supporting substrate was not heat-treated before application of the polyamic acid solution, thereby obtaining a polyimide film having a thickness of 4 μm. The peel strength when peeling the polyimide film from the support substrate exceeded 15 N / m, and defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

  From the results in Table 1, in Examples 1 to 7 in which the support substrate was subjected to heat treatment (step a) before application of the polyamic acid solution, both were excellent regardless of the thickness of the support substrate and the initial contact angle. Showed good peelability. On the other hand, in Comparative Examples 1 and 2 where the support substrate was not subjected to the heat treatment in step a, the peel strength exceeded 15 N / m, which was unsuitable for practical use.

  In Examples 1 and 4 to 7, the used support base material is recovered to a surface state having good peelability from the polyimide film by performing the heat treatment in step a, and can be used repeatedly for a plurality of cycles. there were.

Reference example 1
In Example 1, the support substrate that had been used in the first cycle was used as it was without heat treatment, and a second cycle of film formation was performed. In addition, the contact angle of the pure water on the surface of the support base material after peeling the polyimide film was reduced to 69.9 °. As a result, the peel strength of the polyimide film from the support substrate increased to 20 N / m or more, and the film was torn during the peeling, and the peeled film was strongly curled due to plastic deformation.

Test example 1
As a support substrate, a polyimide film (UPILEX S; trade name, manufactured by Ube Industries, Ltd., contact angle of pure water 74.8 °, Tg 336 ° C.) with a thickness of 25 μm is used. The polyamic acid solution obtained in Preparation Example 1 was uniformly applied and dried by heating at a temperature of 100 ° C. or lower to remove excess solvent. Next, heat treatment was performed for 10 minutes in a heating furnace having a maximum temperature of 360 ° C. to complete imidization, followed by cooling to room temperature and peeling from the support substrate to obtain a polyimide film having a thickness of 4 μm. Next, the same heat treatment conditions (first temperature of step a) and time for the used support base material are changed, the same film forming operation is repeated, and the heat treatment conditions for reusing the support base material and polyimide The relationship with the peel strength when peeling the film was examined. The heat treatment conditions at the time of reuse were no treatment (no heat treatment was performed), 90 ° C./60 minutes, 250 ° C./30 minutes, and 360 ° C./10 minutes. In addition, the double-sided alternating coating in which the supporting base material was recovered by the heat treatment during imidization without separately providing the heat treatment step (step a) from the second cycle was also evaluated. The above results are shown in FIG.

  From FIG. 3, in the sections of no treatment, 90 ° C./60 minutes and 250 ° C./30 minutes, the peel strength exceeded 15 N / m in the second cycle, and the supporting substrate could not be reused practically. On the other hand, in the heat treatment at 360 ° C. for 10 minutes, the peel strength was 10 N / m or less even in the fifth cycle, and the peelability between the support substrate and the polyimide film was maintained in a good state. Also, even with double-sided alternating coating using heat treatment during imidization, the peel strength increased with the number of cycles, but until about the third cycle, the peelability showed no practical problem. From the above results, it has been found that temperature is a more important factor than time as the heat treatment condition during reuse. In addition, the higher the heat treatment temperature during reuse, the shorter the heat treatment time required to achieve the same effect, and it is important to set the temperature conditions appropriately to improve throughput. I found out.

  Based on the result of FIG. 3, the heat treatment temperature (first temperature of step a) for the used support substrate is changed and the film forming operation similar to the above is repeated, and the heat treatment temperature and peel strength at the time of reuse are determined. More detailed tests were conducted on the relationship. The heat treatment temperature during reuse was 280 ° C., 320 ° C., 360 ° C., and the heat treatment time was 10 minutes. The results are shown in FIG.

  As shown in FIG. 4, when the heat treatment temperature at the time of reuse is 280 ° C., the peel strength exceeded 15 N / m from the second cycle, but at 320 ° C. and 360 ° C., it is 15 N / m or less until the third cycle. It was a practically acceptable peel strength. In particular, when the heat treatment temperature was 360 ° C., the peel strength was about 5 N / m even in the third cycle, and the peelability was excellent.

  From the above results, in order to reuse the supporting substrate, it is effective to perform heat treatment at a temperature of 300 ° C. to 500 ° C., preferably 320 ° C. to 450 ° C., more preferably 350 ° C. to 420 ° C. In particular, it has been found that it is preferable to heat to a temperature equal to or higher than the Tg of the polyimide resin constituting the support substrate. By heating to a temperature equal to or higher than Tg, it was possible to increase the number of cycles in which the support substrate can be reused.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible, and such modifications are included in the scope of the present invention. .

  DESCRIPTION OF SYMBOLS 1 ... Support base material, 3 ... Polyamic acid layer, 5 ... Polyimide film layer, 7 ... Polyimide film

Claims (4)

A method for producing a polyimide film,
a) heat-treating a supporting substrate having a polyimide resin surface at a first temperature within a range of 300 ° C. or more and 500 ° C. or less;
b) A step of applying a polyamic acid solution on the surface of the polyimide resin of the supporting substrate after the heat treatment and drying to form a polyamic acid layer;
c) imidization by heat-treating the polyamic acid layer at a second temperature, and laminating a polyimide film on the support substrate; and
d) peeling the polyimide film from the support substrate;
The manufacturing method of the polyimide film characterized by comprising.   2. The method for producing a polyimide film according to claim 1, wherein after the step d, the support substrate is reused, and the steps a to d are set as one cycle, and one cycle or more is further performed. A method for producing a polyimide film,
a) a step of heat-treating a supporting base material having a polyimide resin surface on both the front side and the back side at a first temperature within a range of 300 ° C. or higher and 500 ° C. or lower;
b) a step of applying a polyamic acid solution to one side of the support substrate after the heat treatment and drying to form a polyamic acid layer;
c) imidization by heat-treating the polyamic acid layer at a second temperature, and laminating a polyimide film on the support substrate; and
d) peeling the polyimide film from the support substrate;
With
After the step d, the step b to step d are performed as one cycle, and further one cycle or more is performed, and the support base on the side opposite to the surface on which the polyimide film is peeled off in the step d of the immediately preceding cycle is performed. The manufacturing method of the polyimide film characterized by performing the process b of the following cycle using the surface of a material.   The said support base material is formed in the elongate film form, The said each process is performed by a roll-to-roll system, The polyimide film of any one of Claims 1-3 characterized by the above-mentioned. Manufacturing method.

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