JP2011056825A - Method for manufacturing polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the peelability between a supporting base material and a thin polyimide film in the manufacture of the polyimide film by a casting method. <P>SOLUTION: A polyimide film manufacturing method includes the process in which a polyamic acid solution is applied on the supporting base material made of a polyimide resin and dried to form a polyamic acid layer, the process in which the polyamic acid layer is imidated by heat treatment to laminate/form a polyimide film layer on the supporting base material, and the process in which the polyimide film layer is peeled off from the base material to form the polyimide film, and the relationship between the glass transition temperature Tg<SB>1</SB>of the base material and the glass transition temperature Tg<SB>2</SB>of the polyimide film is made to be expressed by: Tg<SB>1</SB>>Tg<SB>2</SB>≥300°C, and the upper limit T<SB>max</SB>of a heat treatment temperature in the imidation is made to be expressed by: Tg<SB>2</SB>≤T<SB>max</SB>≤Tg<SB>2</SB>+30°C. <P>COPYRIGHT: (C)2011,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, the technique of Patent Document 3 is based on the premise that the manufactured thermoplastic polyimide film with a release film is heat-bonded to another adherend, and then the release film is mechanically peeled off. Thus, the transfer of the thermoplastic polyimide film is performed. In other words, 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 thermoplastic polyimide film is separated from the release film by itself. The process of peeling is not assumed. Therefore, in Patent Document 3, no attention is paid to problems such as wrinkles, cracks, and tears 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 base material is better as the polyimide film becomes thinner. However, the peelability between the polyimide film and the supporting substrate is determined by factors such as the surface free energy on the supporting substrate side, the water vapor permeability of both the polyimide film and the supporting substrate, and the environmental temperature and humidity. Since it fluctuates depending on external factors, it is difficult to stably peel at a constant peel strength, which causes wrinkles, cracks, tears, etc. in the polyimide film of the product. In particular, when a polyimide resin support base material is used to produce a thin polyimide film having a thickness of about several μm, the influence of the above factors tends to be remarkably manifested, and a solution has been demanded.

  Accordingly, an object of the present invention is to improve the peelability between a polyimide resin support substrate and a polyimide film in the production of a thin film polyimide film by a casting method.

As a result of intensive studies in view of the above circumstances, the present inventors have found that the glass transition temperature Tg _{1 of} the polyimide resin support substrate on which the polyamic acid solution is applied in the casting method, and the glass transition temperature of the polyimide film to be formed focusing on the relationship between Tg _2. When the glass transition temperature Tg ₁ of the supporting substrate is higher than the glass transition temperature Tg ₂ of the polyimide film on which the film is formed, the releasability is remarkably improved by controlling the imidization temperature within a specific range. The present invention was completed.

That is, the manufacturing method of the polyimide film of the present invention is:
a) a step of applying and drying a polyamic acid solution on a support substrate made of polyimide resin to form a polyamic acid layer;
b) imidization by heat-treating the polyamic acid layer, and laminating and forming a polyimide film layer on the support substrate; and
c) a step of peeling the polyimide film layer from the support substrate to form a polyimide film;
With
The glass transition temperature Tg ₁ of the supporting substrate, the relation between the glass transition temperature Tg ₂ of the polyimide film and _{Tg 1> Tg 2 ≧ 300 ℃} , and the upper limit _{T max} of the heat treatment temperature in the imidization tg ₂ ≦ _T and _max ≦ _Tg 2 + 30 ℃.

In the method for producing a polyimide film of the present invention, it is preferable that the thickness of the film formation film is in the range of 1 μm to 5 μm. Moreover, it is preferable that the moisture permeability of the said support base material is 0.5 g / m < ² > * 24hr or more and 30 g / m < ² > * 24hr or less.

  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 production method of the polyimide film of the present invention, the glass transition temperature Tg ₁ of the supporting substrate, the relation between the glass transition temperature Tg ₂ of the polyimide film and _{Tg 1> Tg 2 ≧ 300 ℃} , and the imidization When the upper limit T _max of the heat treatment temperature is Tg ₂ ≦ T _max ≦ Tg ₂ + 30 ° C., the peelability between the polyimide resin support substrate and the polyimide film can be greatly improved. As a result, in step c, the polyimide resin support substrate and the polyimide film can be stably peeled with a constant force. In particular, even when the thickness of the polyimide film is 4 μm or less, it is possible to maintain good peelability, so the polyimide film can be peeled off alone, and the appearance is also good without causing defects such as wrinkles, cracks, and tears. An ultra-thin polyimide film can be manufactured. Therefore, according to the method of the present invention, for example, a polyimide film can be produced with a high yield in continuous production such as a roll-to-roll method, and the industrial utility value is high.

It is process drawing which shows the outline | summary of the manufacturing method of the polyimide film of embodiment of this invention.

  Hereinafter, the manufacturing method of the polyimide film concerning 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 film is also used for the supporting base material. Therefore, the following description of the polyimide resin is also appropriately applied to the supporting base material.

  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 of the 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. 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. If 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, if the temperature exceeds the upper limit (60 ° C.), imidization proceeds and the reaction solution gels. It tends to be easier.

  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. In FIG. 1, reference numeral 1 denotes a polyimide resin support base (hereinafter sometimes simply referred to as “support base material”), reference numeral 3 denotes a polyamic acid layer, reference numeral 5 denotes a polyimide film layer, and reference numeral 7 denotes a target polyimide film. It is. The manufacturing method of the polyimide film 7 of this Embodiment is provided with the following process a-process c. The contents of each process will be described in order.

Step a) Step of forming a polyamic acid layer 3 by applying and drying a polyamic acid solution on the support substrate 1:
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 film in the form of a roll or endless belt, and a form that can be continuously produced. In particular, the supporting substrate 1 is preferably a long roll-shaped film, and it is preferable to perform the steps a to c continuously by a roll-to-roll method.

The support substrate 1 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 thermoplastic or non-thermoplastic polyimide resin can be used, but it is preferable to use a non-thermoplastic polyimide resin. Among non-thermoplastic polyimide resins, those composed of a low-expansion polyimide resin having low adhesiveness can be suitably used. 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. The glass transition temperature Tg ₁ of the polyimide resin to be applied to the supporting substrate 1 is 300 ° C. or higher, more preferably 320 ° C. or higher. By using such a polyimide resin for the support substrate 1, 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 NPI (trade names) manufactured by Kaneka Chemical Co., Ltd., Upilex S (trade names) 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. In addition, it is not preferable to use a laminated body in which a metal foil and a polyimide film are laminated as the support base material 1 because a plurality of manufacturing steps for forming the laminated body are required and the production cost increases. Moreover, when using a polyimide film as a support base material, since both surfaces of this film can be used as a peeling surface and it can be used several times, it is especially advantageous.

  Considering the rigid surface, the thickness of the support substrate 1 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 becomes insufficient, and if it exceeds 250 μm, it may be difficult to separate (peel) the product from the polyimide film 7. is there. 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. 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.

  It is considered that the moisture permeability of the support substrate 1 has a correlation with the degree of orientation of the polyimide resin constituting the support substrate 1 in addition to the 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 And the water | moisture content accompanying progress of imidation concentrates on the interface of the support base material 1 and the polyimide film layer 5, and inhibits both adhesion | attachment. This is considered to be a factor that facilitates peeling of the polyimide film 7 of the product.

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 Can maintain good peelability. 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 polyimide film production / imidation process and moisture accompanying imidization cannot be removed, and the polyimide film layer 5 floats in the production stage (polyimide). There is a tendency that partial peeling of the film layer 5 occurs. Note that the moisture permeability can be measured by a method defined in Examples described later.

In step a, the polyamic acid layer 3 is formed by directly applying a polyamic acid solution, which is a precursor of the polyimide resin, onto the support substrate 1 and then drying. The polyamic acid may be a precursor of either thermoplastic polyimide or non-thermoplastic polyimide. The solvent in the drying / imidization process of the polyimide film production and the moisture accompanying the progress of imidization are involved in the peelability between the support substrate 1 and the polyimide film 7. The present inventors have found that the glass transition temperature Tg 1 of the supporting substrate _1, focusing on the heat treatment temperature in the glass transition temperature Tg ₂ and imidization of the polyimide film 7 after imidization, to properly control these factors As a result, it has been found that the solvent and imidized water are appropriately retained at the interface between the support substrate 1 and the polyimide film layer 5, and as a result, good releasability of the polyimide film 7 can be maintained. In this embodiment, as a reference for selecting the polyamic acid used, the glass transition temperature Tg ₂ of the polyimide film 7 after imidization, between the glass transition temperature Tg ₁ of the polyimide film which constitutes the supporting substrate 1 , Tg ₁ > Tg ₂ ≧ 300 ° C., preferably Tg ₁ > Tg ₂ ≧ 320 ° C. That is, the glass transition temperature Tg ₁ of the polyimide film of the supporting substrate 1 is higher than the glass transition temperature Tg ₂ of the polyimide film 7 to be deposited, and Tg ₂ is set to be above 300 ° C.. In order to properly control the above three factors involved in peelability, first, the heat treatment temperature in imidization can be easily made based on Tg ₂ by setting the relationship between Tg ₁ and Tg ₂ in the above range. Will be able to control. The heat treatment temperature in imidization will be described later. When Tg ₁ is Tg ₂ or less or 300 ° C. or less, the effect of improving peelability by controlling the imidization temperature described later cannot be sufficiently obtained.

  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.

  Commercially available products can be suitably used as the polyamic acid solution. For example, U-Varnish-A (trade name), which is a non-thermoplastic polyamic acid varnish manufactured by Ube Industries, Ltd., Rika Coat PN manufactured by Shin Nippon Rika Co., Ltd. -20 (trade name) and the like.

  In addition to the polyamic acid and the solvent, the polyamic acid solution includes, for example, fillers such as silica, alumina, boron nitride, titanium oxide, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, magnesium oxide, and calcium oxide, and clay minerals. Etc. 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 such that the thickness of the polyimide film layer 5 after imidation is, for example, 5 μm or less, preferably 1 μm or more and 5 μm or less, more preferably 1 μm or more and 4 μm or less. Adjust to. 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 at the time of peeling are less likely to occur. However, in the method of the present invention, it is possible to cope with a thin film by improving the peelability, and the polyimide film layer 5 can be formed thinly to 5 μm or less.

  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 b) Step of imidizing the polyamic acid layer 3 by heat treatment to form a polyimide film layer 5 on the support base material 1:
The imidization is a step of forming polyimide by proceeding with dehydration and ring closure of polyamic acid by heat treatment. In the heat treatment for imidization, the upper limit T _{max of the} heat treatment temperature is set to Tg ₂ ≦ T _max ≦ Tg ₂ + 30 ° C. Here, the reason of Tg ₂ ≦ T _max is that the imidized water generated when imidizing the solvent of the polyamic acid solution and the polyimide acid is excessively retained at the interface between the polyimide film layer 5 and the support substrate 1. This is in order not to let them. This is because if the solvent or imidized water is excessively retained at the interface between the polyimide film layer 5 and the support substrate 1, foaming and floating may be caused in the production stage of the polyimide film. By setting Tg ₂ ≦ T _max , it is considered that the solvent and imidized water are appropriately discharged out of the system through the polyimide film layer 5.

The reason why T _max ≦ Tg ₂ + 30 ° C. is that the imidized water generated at the time of imidation of the solvent of the polyamic acid solution and the polyamic acid is appropriate at the interface between the support substrate 1 and the polyimide film layer 5. This is because the amount is retained. When the liquid (solvent or moisture) at the interface between the support substrate 1 and the polyimide film layer 5 is completely removed, the adhesion between the support substrate 1 and the polyimide film layer 5 becomes strong, which causes a peeling failure. It is considered to be. By _setting T _max ≦ Tg ₂ + 30 ° C., preferably T _max ≦ Tg ₂ + 25 ° C., more preferably T _max ≦ Tg ₂ + 10 ° C., the solvent and imidized water can pass out of the system via the polyimide film layer 5. It is possible to prevent a small amount of solvent and / or moisture from staying at the interface between the support substrate 1 and the polyimide film layer 5, and to support the support substrate 1 and the polyimide film layer 5. The peeling strength can be reduced and peeling can be facilitated. Here, when T _max exceeds 400 ° C., the liquid component at the interface between the support substrate 1 and the polyimide film layer 5 tends to stay less. Therefore, T _max is preferably 400 ° C. or less, and preferably 370 ° C. or less. More preferably.

  There is no particular limitation on the heating device used for the heat treatment during the imidization, for example, a non-contact type heating method using electromagnetic waves such as far infrared rays, ultraviolet rays, microwaves, contact with a temperature-controllable jacket roll, etc. It is possible to use a heating apparatus that employs a mold heating method. The heat treatment can be performed, for example, by passing a laminated body of the support substrate 1 and the polyimide film layer 5 over a predetermined time in a heating furnace.

Step c) Step of peeling the polyimide film layer 5 from the support substrate 1 to form the polyimide film 7:
The method of peeling the polyimide film layer 5 from the support substrate 1 to form the polyimide film 7 is not particularly limited. For example, the method of transferring the polyimide film 7 to an adherend also supports the polyimide film 7 as a single unit. A method of peeling from the material 1 may be used. However, in this embodiment, since the peelability between the support base material 1 and the polyimide film 7 is improved, the polyimide film 7 is used alone as a support base material regardless of the method of transferring the polyimide film 7 to the adherend. 1 can be easily peeled off. Therefore, for example, a method of peeling the long support substrate 1 and the long polyimide film 7 by winding them on a roll, such as a roll-to-roll method, is preferably employed.

As described above, in the method of the present invention, Tg ₁ > Tg ₂ ≧ 300 ° C. and Tg ₂ ≦ T _max ≦ Tg ₂ + 30 ° C., whereby the polyimide film 7 and the support substrate 1 are separated in step c. The polyimide film 7 alone can be stably peeled from the support substrate 1 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. In addition, it is possible to manufacture a thin film, for example, an ultrathin film having a thickness of 5 μm or less, which is difficult to manufacture by the conventional tenter method.

  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.

  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.

[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.

[Evaluation of peel strength]
The peel strength was evaluated by measuring the peel strength by a T-shaped peel test method 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 5 N / m or less, the peelability is “very good”, and when the peel strength is more than 5 N / m and 15 N / m or less, the peelability is “good” (practical range), and more than 15 N / m. The peelability was evaluated as “bad”.

[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 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.

Synthesis example 1
In a 500 ml separable flask, 29.4 g of 2,2′-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) (0.072 mol) was stirred with 255 g of N, N— Dissolved in dimethylacetamide (DMAc). Next, 15.8 g of pyromellitic anhydride (PMDA) (0.072 mol) was added to the solution in a nitrogen stream. Thereafter, polymerization reaction was continued for about 3 hours of stirring, solid concentration 15 wt%, the solution viscosity to obtain a polyamic acid solution _{S 1} of 100 poise [10Pa · s]. In addition, Tg of the polyimide resin obtained by imidating this resin solution was 315 degreeC. This resin is thermoplastic.

Synthesis example 2
In a 500 ml separable flask, with stirring, 20 g 4,4′-diamino-2,2′-dimethylbiphenyl (DADMB) (0.094 mol) and 2 g 1,3-bis (4-aminophenoxy) ) Benzene (1,3-BAB) (0.007 mol) was dissolved in 255 g N, N-dimethylacetamide (DMAc). Next, 5 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) (0.017 mol) and 18 g of pyromellitic anhydride (PMDA) (0 0.083 mol) was added. Thereafter, polymerization reaction was continued for about 3 hours of stirring, solid concentration 15 wt%, the solution viscosity to obtain a polyamic acid solution _{S 2} of 200 poise [20Pa · s]. In addition, Tg of the polyimide resin obtained by imidating this resin solution was 364 degreeC. This resin is non-thermoplastic.

Synthesis example 3
In a 500 ml separable flask, 21.5 g of 4,4′-diamino-2,2′-dimethylbiphenyl (DADMB) (0.107 mol) was added to 255 g of N, N-dimethylacetamide (DMAc) with stirring. ). Next, 23.5 g of pyromellitic anhydride (PMDA) (0.107 mol) was added to the solution in a nitrogen stream. Thereafter, polymerization reaction was continued for about 3 hours of stirring, solid concentration 15 wt%, the solution viscosity to obtain a polyamic acid solution _{S 3} of 100 poise [10Pa · s]. In addition, Tg of the polyimide resin obtained by imidating this resin solution was 393 degreeC. This resin is non-thermoplastic.

Example 1
A long polyimide film having a thickness of 25 μm (Upilex S; trade name, manufactured by Ube Industries, CTE 12 × 10 ⁻⁶ / K, Tg 336 ° C., moisture permeability 1.7 g / m ² · 24 hr) was used as a supporting substrate. .

Next, on one surface of the supporting substrate, a polyamic acid solution S ₁ obtained in Synthesis Example 1 was uniformly applied to remove excess solvent component was dried by heating at 100 ° C. or lower. Next, heat treatment is performed for 10 minutes in a continuous heating furnace with a maximum temperature of 320 ° C., and after imidization is completed, the polyimide film (film formation film) having a thickness of 4 μm is formed by cooling to room temperature and peeling from the support substrate. Obtained. At this time, the peel strength of the film formed from the supporting substrate was 3.7 N / m or less, and peeling was easy. No defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

Example 2
As a supporting substrate, a 25 μm-thick long polyimide film (Upilex S; trade name, manufactured by Ube Industries, CTE12 × 10 ⁻⁶ / K, Tg 336 ° C., moisture permeability 1.7 g / m ² · 24 hr) is used. In Example 1, a polyimide film having a thickness of 4 μm was formed in the same manner as in Example 1 except that heat treatment was performed at a maximum temperature of 335 ° C. for 10 minutes instead of the heat treatment at a maximum temperature of 320 ° C. for 10 minutes. Film). At this time, the peel strength of the film formed from the supporting substrate was 9.5 N / m or less, and peeling was easy. No defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

Example 3
As the supporting substrate, a long polyimide film having a thickness of 75 [mu] m; but using (Kapton H trade name, manufactured by Du Pont-Toray ^{Co., CTE16 × 10 -6 / K,} Tg411 ℃, moisture permeability ^27g / m 2 · 24hr) Obtained a polyimide film (film formation film) having a thickness of 4 μm in the same manner as in Example 1. At this time, the peel strength of the film formed from the supporting substrate was 8.2 N / m or less, and peeling was easy. No defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

Example 4
A long polyimide film (Kapton H; trade name, manufactured by Toray DuPont, CTE 16 × 10 ⁻⁶ / K, Tg 411 ° C., moisture permeability 27 g / m ² · 24 hr) was used as a supporting substrate.

Next, on one surface of the supporting substrate, a polyamic acid solution S ₂ obtained in Synthesis Example 2 was uniformly applied to remove excess solvent component was dried by heating at 100 ° C. or lower. Next, heat treatment is performed for 10 minutes in a continuous heating furnace having a maximum temperature of 370 ° C., and after imidization is completed, the polyimide film (deposition film) having a thickness of 4 μm is formed by cooling to room temperature and peeling from the support substrate. Obtained. At this time, the peel strength of the film formed from the support substrate was 3.6 N / m or less, and the peel was easy. No defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

Example 5
As a support substrate, a 75 μm thick polyimide film (Kapton H; trade name, manufactured by Toray DuPont, CTE 16 × 10 ⁻⁶ / K, Tg 411 ° C., moisture permeability 27 g / m ² · 24 hr) is used. In Example 4, a polyimide film (film-forming film) having a thickness of 4 μm was formed in the same manner as in Example 4 except that heat treatment was performed at a maximum temperature of 384 ° C. for 10 minutes instead of the heat treatment at a maximum temperature of 370 ° C. for 10 minutes. ) At this time, the peel strength of the film formed from the supporting substrate was 14.4 N / m or less, and peeling was easy. No defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

Example 6
A long polyimide film (Kapton H; trade name, manufactured by Toray DuPont, CTE 16 × 10 ⁻⁶ / K, Tg 411 ° C., moisture permeability 27 g / m ² · 24 hr) was used as a supporting substrate.

Next, on one surface of the supporting substrate, a polyamic acid solution S ₃ obtained in Synthesis Example 3 was uniformly applied to remove excess solvent component was dried by heating at 100 ° C. or lower. Next, after performing heat treatment for 10 minutes in a continuous heating furnace with a maximum temperature of 400 ° C. to complete imidization, the polyimide film (film formation film) having a thickness of 4 μm is formed by cooling to room temperature and peeling from the support substrate. Obtained. At this time, the peel strength of the film formed from the support substrate was 14.8 N / m or less, and the peel was easy. No defects in appearance such as wrinkles, cracks and tears were observed in the obtained film.

Comparative Example 1
As a supporting substrate, a 25 μm-thick long polyimide film (Upilex S; trade name, manufactured by Ube Industries, CTE12 × 10 ⁻⁶ / K, Tg 336 ° C., moisture permeability 1.7 g / m ² · 24 hr) is used. In Example 1, a polyimide film having a thickness of 4 μm was formed in the same manner as in Example 1 except that heat treatment was performed at a maximum temperature of 360 ° C. for 10 minutes instead of the heat treatment at a maximum temperature of 320 ° C. for 10 minutes. Film), but could not be peeled off from the supporting substrate.

Comparative Example 2
As a support substrate, a 75 μm thick polyimide film (Kapton H; trade name, manufactured by Toray DuPont, CTE 16 × 10 ⁻⁶ / K, Tg 411 ° C., moisture permeability 27 g / m ² · 24 hr) is used. In Example 1, a polyimide film having a thickness of 4 μm (deposited film) was used in the same manner as in Example 1 except that heat treatment was performed at a maximum temperature of 360 ° C. for 10 minutes instead of the heat treatment at a maximum temperature of 320 ° C. for 10 minutes. ), But could not be peeled off from the support substrate.

Comparative Example 3
As a support substrate, a 75 μm thick polyimide film (Kapton H; trade name, manufactured by Toray DuPont, CTE 16 × 10 ⁻⁶ / K, Tg 411 ° C., moisture permeability 27 g / m ² · 24 hr) is used. In Example 4, a polyimide film (film-forming film) having a thickness of 4 μm was formed in the same manner as in Example 4 except that heat treatment was performed at a maximum temperature of 400 ° C. for 10 minutes instead of the heat treatment at a maximum temperature of 370 ° C. for 10 minutes. ), But could not be peeled off from the support substrate.

From the results in Table 1, the glass transition temperature of the supporting substrate and the film formed is in a relationship of Tg ₁ > Tg ₂ ≧ 300 ° C., and the maximum temperature of imidization is Tg ₂ ≦ T _max ≦ Tg ₂ + 30 ° C. The performed Examples 1 to 6 all showed excellent peelability and good appearance. On the other hand, Comparative Examples 1 to 3 that did not satisfy the relationship of Tg ₂ ≦ T _max ≦ Tg ₂ + 30 ° C. were all unpeelable.

  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) a step of applying and drying a polyamic acid solution on a support substrate made of polyimide resin to form a polyamic acid layer;
b) imidization by heat-treating the polyamic acid layer, and laminating and forming a polyimide film layer on the support substrate; and
c) a step of peeling the polyimide film layer from the support substrate to form a polyimide film;
With
The glass transition temperature Tg ₁ of the supporting substrate, the relation between the glass transition temperature Tg ₂ of the polyimide film and _{Tg 1> Tg 2 ≧ 300 ℃} , and the upper limit _{T max} of the heat treatment temperature in the imidization A method for producing a polyimide film, wherein Tg ₂ ≦ T _max ≦ Tg ₂ + 30 ° C.   The method for producing a polyimide film according to claim 1, wherein a thickness of the film formation film is in a range of 1 μm to 5 μm. 3. The method for producing a polyimide film according to claim 1, wherein the moisture permeability of the support substrate is 0.5 g / m ² · 24 hr or more and 30 g / m ² · 24 hr or less.   The said polyimide resin support base material is formed in elongate, The manufacturing method of the polyimide film of any one of Claim 1 to 3 which performs each said process by a roll-to-roll system.

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