JP2019214642A - Polyimide film for coverlay film, and manufacturing method therefor - Google Patents

Abstract

To provide a polyimide film for coverlay film having low cost and excellent in mechanical properties.SOLUTION: There are provided a polyimide film for coverlay film, containing a polyimide resin containing a repeating unit represented by the following general formula (1) of 70 mol% or more, and an amide-based solvent of 3 wt.% or more, and a manufacturing method therefor.SELECTED DRAWING: None

Description

  The present invention relates to a polyimide film for a coverlay film and a method for producing the same, and a coverlay film using the polyimide film and a method for producing the same.

  BACKGROUND ART Aromatic polyimide films have excellent heat resistance, mechanical properties, and electrical properties, and have been widely used in various fields such as medical, aerospace materials, and structural materials in recent years, in addition to the fields of electric and electronics. However, in general, these aromatic polyimide films are hardly good in moldability because of their insoluble and infusible properties. Polyimide film is often used for electronic circuit boards, but when manufacturing a polyimide film, the precursor polyamic acid is cast on a metal foil or metal roll in a solution state, dried, and then imidized. It is common to peel off from the surface and then perform heat treatment sequentially. In particular, in order to realize good mechanical properties of the film, it is necessary to perform heat treatment at a high temperature, and it is necessary to extremely reduce the amount of the remaining solvent. In order to enable the production of such a polyimide film, an expensive film forming apparatus is required, and the heat treatment at a high temperature for a long time has made the production cost of the film extremely high.

  On the other hand, as seen in recent smartphones, there is a remarkable demand for higher performance, lighter, thinner and smaller electronic devices, and polyimide films used for electronic circuit boards are also becoming thinner and more sophisticated. It has been demanded. However, it is technically difficult to form a film having a thickness of 10 μm or less uniformly with good productivity in the above-described film forming apparatus, and there has been a problem that the film is often broken during manufacturing.

  A coverlay film manufactured by applying an adhesive on such a polyimide film is used to secure the insulation of the circuit of the flexible printed circuit board and to enhance the bending resistance of the circuit by a reinforcing effect. You.

  In recent years, along with the thinning of the polyimide film and the copper foil layer of the copper-clad laminate, the demand for thinning the film used for the cover lay film has been increasing in recent years. That is, there is a demand for a coverlay film having excellent mechanical strength even when the polyimide film is thin. In particular, an ultra-thin flexible printed circuit board is folded and mounted around a display as seen in a smartphone, and its durability is strongly demanded. In order to solve such a problem, it has been proposed to apply a solvent-soluble polyimide having an extremely low Tg on a release film (for example, see Patent Document 1). It was expected to accompany.

JP 2017-126735 A

  As described above, in the conventional polyimide film formed by casting, it is difficult to make the film thinner, and heat treatment is required to a high temperature to secure mechanical strength. An object of the present invention is to provide a polyimide film for a coverlay film, which can be easily thinned, does not require heat treatment at a high temperature, and exhibits sufficient mechanical properties and sufficient heat resistance.

As a result of repeated studies to solve the above problems, the present inventors have found that a polyimide film made of a polyimide resin containing a repeating unit represented by the general formula (1) in a specific ratio is easily thinned, and No heat treatment at a high temperature was required, and sufficient mechanical properties were exhibited even in a state containing a large amount of an amide-based solvent, and it was found that it was useful as a polyimide film for a coverlay film, and the present invention was completed.
That is, the present invention is as follows.

[1] A polyimide film for a coverlay film, comprising a polyimide resin containing a repeating unit represented by the following general formula (1) in an amount of 70 mol% or more and an amide-based solvent in an amount of 3 wt% or more.

[2] The polyimide film for a coverlay film according to [1], wherein the film has a tensile elongation of 20% or more and a heat deformation temperature of 200 ° C or more.
[3] The polyimide film for a coverlay film according to the above [1] or [2], wherein the polyimide film contains 3 to 15 parts by weight of carbon having a particle size of 1 μm or less based on 100 parts by weight of the polyimide film.
[4] The polyimide film for a coverlay film according to any one of [1] to [3], which is laminated on at least one surface of the support film.

[5] A cover lay film laminate obtained by laminating an adhesive layer on the polyimide film for a cover lay film according to any one of the above [1] to [4].

[6] a step of applying a polyimide resin containing a repeating unit represented by the following general formula (1) of 70 mol% or more and a polyimide varnish containing an amide solvent on at least one surface of a support film, and Drying the varnish applied on the film at a temperature of 220 ° C. or less to form a polyimide film containing 3% by weight or more of an amide solvent;
A method for producing a polyimide film for a coverlay film, comprising:

[7] a step of coating a polyimide resin containing a repeating unit represented by the following general formula (1) by 70 mol% or more and a polyimide varnish containing an amide-based solvent on at least one surface of a support film;
Drying the varnish applied on the support film at 220 ° C. or lower to form a polyimide film containing 3% by weight or more of the amide-based solvent;
A step of applying an adhesive varnish on the polyimide film, and a step of drying the adhesive varnish applied on the polyimide film at 220 ° C. or lower to form an adhesive layer, producing a coverlay film laminate Method.

According to the present invention, a polyimide film for a coverlay film, which could only be produced by a conventional expensive film deposition apparatus, is formed by depositing a polyimide resin containing a specific repeating unit at a specific ratio and drying at a relatively low temperature. By itself, a polyimide film for coverlay having sufficient mechanical properties and heat resistance can be obtained in a state containing a large amount of the amide-based solvent.
Further, according to the present invention, not only an inexpensive polyimide film can be obtained, but also an extremely thin polyimide film can be easily obtained.
Further, the cover lay film coated with an adhesive can be processed with good productivity without wrinkling because it can be worked with the support film attached when it is attached to a printed circuit board.

で表される繰り返し単位を７０モル％以上含む可溶性ポリイミド樹脂と、アミド系溶媒３重量％以上とを含有する。 The polyimide film for a coverlay film of the present invention has the following general formula (1):

And a soluble polyimide resin containing 70 mol% or more of the repeating unit represented by the formula and 3% by weight or more of the amide solvent.

  The polyimide resin containing a repeating unit represented by the general formula (1) of the present invention comprises 4,4′-oxydiphthalic dianhydride (abbreviation: ODPA) and 2,2′-bis (trifluoromethyl) -4, By reacting 4′-diaminobiphenyl (abbreviation: TFMB) in an amide solvent to obtain a polyamic acid solution as a precursor thereof, and then performing an imidation reaction by an arbitrary method to obtain a polyimide varnish. Can be.

  The polyamic acid solution can be produced by polymerizing a tetracarboxylic dianhydride and a diamine compound by a known method. Usually, the polymerization reaction is carried out in a solvent at 0 to 100 ° C, preferably 10 to 50 ° C, for 10 minutes to 24 hours, preferably for 30 minutes to 12 hours. The solute concentration in the polymerization reaction is 5 to 80% by mass, and preferably 10 to 50% by mass.

Solvents that can be used in the production of the polyamic acid solution are not particularly limited as long as they are inert to the reaction. For example, sulfoxide solvents such as dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, An amide solvent such as N-methyl-2-pyrrolidone and tetramethylurea; an ester solvent such as γ-butyrolactone and γ-valerolactone; More than one kind can be mixed and used. Further, aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, chlorobenzene, dichlorobenzene, and trichlorobenzene can be mixed at an arbitrary ratio.
In the present invention, a solvent that can be used for producing a polyamic acid solution may be used as it is as a solvent for a solvent-soluble polyimide varnish, and N, N-dimethylformamide, N, N-dimethylacetamide, N An amide solvent such as -methyl-2-pyrrolidone is preferably used as a main solvent, and more preferably N-methyl-2-pyrrolidone is used as a main solvent.

  The polyimide resin containing a repeating unit represented by the general formula (1) of the present invention contains a diamine component other than TFMB and ODPA, a tetracarboxylic dianhydride component other than TFMB and ODPA as long as the solubility of the polyimide is not impaired, and And / or may contain a repeating unit derived from a diamine component other than TFMB and a tetracarboxylic dianhydride component other than ODPA, but the repeating unit represented by the general formula (1) is added to all the repeating units. 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. The polyimide resin containing a repeating unit represented by the general formula (1) of the present invention is particularly preferably a polyimide resin substantially consisting of only the repeating unit represented by the general formula (1).

  That is, TFMB is used as the diamine component of the polyimide resin containing a repeating unit represented by the general formula (1) of the present invention, but a diamine other than TFMB may be used in combination. In addition to TFMB, examples of the diamine used for copolymerization include, for example, 2,2′-dimethyl-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl, 4,4 ′ -Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4'-methylenedi-o- Toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4 ' -Diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3 ' -Diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4'-diaminodiphenylsulfide, 3, 3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,3-bis (3-amino Phenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-diaminobiphenyl, 3,3′-diaminobiphenyl, 3,3 ′ -Dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4 4′-diaminobiphenyl, 4,4′-diamino-p-terphenyl, 3,3′-diamino-p-terphenyl, 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, , 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-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine Etc., and the like.

  Among these diamines, a combination of 2,2′-dimethyl-4,4′-diaminobiphenyl and 3,3′-dimethyl-4,4′-diaminobiphenyl is exemplified as a preferable one in terms of film elongation. Is done.

  When these diamine components other than TFMB are used in combination, the use ratio thereof is preferably 0 to 30 mol%, more preferably 0 to 15 mol%, based on all diamines.

  Similarly, ODPA is used as the tetracarboxylic dianhydride of the polyimide resin containing a repeating unit represented by the general formula (1) of the present invention, but a tetracarboxylic dianhydride other than ODPA is used in combination. You may.

  In addition to ODPA, the tetracarboxylic dianhydride used for copolymerization includes 3,4′-oxydiphthalic dianhydride, 3,3′-oxydiphthalic dianhydride, 2,2-bis [4- ( 3,4-Dicarboxyphenoxy) phenyl] propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 1,2,4,5-benzenetetracarboxylic dianhydride , 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, etc., in a range that does not impair the effects of the present invention. In this case, one kind or a combination of two or more kinds can be used. In particular, from the viewpoint of imparting solvent solubility, 3,4′-oxydiphthalic dianhydride, 3,3′-oxydiphthalic dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl ] Propane dianhydride and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride may be used in combination.

  When these tetracarboxylic dianhydride components other than ODPA are used in combination, the use ratio thereof is preferably 0 to 30 mol%, more preferably 0 to 15 mol%, based on all tetracarboxylic dianhydrides. .

  The polyimide precursor (polyamic acid) is produced by a known method in which a diamine and a tetracarboxylic dianhydride are used in a molar ratio of 0.9 to 1.1 (substantially equimolar) and polymerized in an organic polar solvent. can do. Specifically, after dissolving a diamine in an amide-based solvent such as N, N-dimethylacetamide, N-methyl-2-pyrrolidone under a nitrogen stream, tetracarboxylic dianhydride is added, and the mixture is heated at room temperature for 3 to 3 hours. It is obtained by reacting for about 20 hours. At this time, the molecular terminal may be sealed with an aromatic monoamine or an aromatic monocarboxylic anhydride.

  The polyimide precursor thus obtained is dehydrated and ring-closed by a thermal imidization method or a chemical imidization method to obtain a solvent-soluble polyimide resin represented by the general formula (1) of the present invention. In the thermal imidization, in the case of the present invention, the precursor polyamic acid solution is heated to reflux at a high temperature of about 150 to 250 ° C. At this time, since water generated by the imidization reaction interferes with the ring closure reaction, an aromatic hydrocarbon-based solvent such as toluene or xylene that is incompatible with water is added to the system and azeotroped, and a device such as a Dean-Stark tube is used. Can be discharged out of the system. In chemical imidization, a dehydrating agent and a catalyst are added to a solution of a polyimide precursor (also referred to as “polyamic acid”) as an imidization reaction assistant, and the solution is chemically dehydrated at 30 to 60 ° C. Acetic anhydride is exemplified as a typical dehydrating agent, and pyridine is exemplified as a catalyst. These imidization reaction assistants can be removed by distillation or the like, if necessary.

  After the completion of such imidization (dehydration ring closure) reaction, polyimide is isolated from the obtained reaction solution, and then redissolved in an amide solvent or the like at a predetermined concentration to obtain a polyimide film for a coverlay film as a polyimide varnish. May be used. Alternatively, the reaction solution may be used as it is, or the reaction solution may be appropriately diluted / concentrated to a desired concentration and used as a polyimide varnish in the method for producing a polyimide film for a coverlay film of the present invention.

  A preferable polymerization degree of the polyimide is 1,000 to 100,000 cP as a viscosity measured by a B-type or E-type viscometer in a polyimide solution of 10% by weight to 20% by weight, and preferably 5,000 to 50,000. 000 cP. The molecular weight of the polyimide can be determined by the GPC method. The preferred molecular weight range (polystyrene equivalent) of the polyimide is 15,000 to 250,000 in number average molecular weight, 30,000 to 800,000 in weight average molecular weight, and preferably 50,000 to 300,000. Although desirable, these are indicative and not all polyimides outside this range cannot be used.

  In the present invention, any components other than polyimide, such as any resin, various fillers and additives, can be added to the polyimide film as needed, as long as the object of the present invention is not impaired. For example, inorganic fine particles such as silica, alumina, boron nitride, and aluminum nitride may be blended for the purpose of improving the slipperiness and the thermal conductivity. Such an optional component may be added to the polyimide varnish, but is preferably 30% by weight or less, more preferably 10% by weight or less, based on the total weight of the obtained polyimide film.

  In recent years, particularly in the case of a polyimide film for a coverlay film, 3 to 15 parts by weight of carbon having a particle size of 1 μm or less is often added to 100 parts by weight of the polyimide film to achieve blackening. The purpose is to increase the light-shielding property to conceal the internal electronic circuit. Generally, the greater the amount of addition, the higher the concealment property, but conversely, the film elongation tends to decrease. In particular, carbon having a particle size of more than 1 μm is not preferable because it significantly lowers the film elongation.

  The polyimide varnish containing the polyimide resin containing the repeating unit represented by the general formula (1) and the amide-based solvent thus obtained is subjected to the production (method) of the polyimide film for a coverlay film of the present invention. be able to. Such a production method is, specifically, a step of applying the varnish on at least one surface of a support film, and drying the varnish applied on the support film at 220 ° C. or lower to form a polyimide film. Process. According to this production method, a polyimide resin for a coverlay film containing a polyimide resin containing the repeating unit represented by the general formula (1) in an amount of 70 mol% and an amide-based solvent in an amount of 3% by weight or more is obtained. The resulting polyimide film for the coverlay film is laminated on at least one side of the support film, but the support film may be peeled off, if necessary, for example, at the time of laminating the polyimide film to a flexible printed board. it can.

  The support film is not particularly limited as long as it is a film having releasability and is stable through the method for producing a polyimide film for a coverlay film. For example, as the support film, a thermoplastic film resin or a thermosetting film having a releasing property may be mentioned, but a thermosetting film is preferably used because it is generally expensive as seen in a polyimide film. Is a thermosetting film, more preferably a biaxially stretched film having a Tg of 70 ° C. or more, such as polyethylene terephthalate, polyethylene naphthalate, and polyphenylene sulfide. A biaxially stretched film can minimize shrinkage and deformation when dried at 150 to 220 ° C. due to its heat resistance. However, a thermoplastic biaxially stretched film having a Tg of less than 70 ° C. It is not preferable because it sometimes deforms greatly.

  These support films may be subjected to a release treatment in advance, if necessary, so that the polyimide film can be easily peeled off later. As the release treatment, for example, a release agent such as silicone is previously applied to the polyimide varnish coating surface of the support film.

  A polyimide varnish is applied on at least one side of these support films. It is possible to select an arbitrary coating method such as a gravure coat, a die coat, and a bar coat.

  If the polyimide varnish is dried rapidly after application, a skin layer may be formed on the surface layer of the polyimide film. Therefore, it is preferable to dry the polyimide film in multiple stages from a low temperature to a maximum drying temperature. The amide solvent and the imidization reaction assistant are almost dried at 120 ° C to 220 ° C, preferably 130 ° C to 200 ° C. Is not preferred.

  The amide solvent remains in the polyimide film after drying at 220 ° C. or less at 3% by weight or more (based on the total weight of the polyimide film), but preferably does not exceed 15% by weight in terms of mechanical properties, More preferably, it does not exceed 10% by weight.

  The tensile elongation of the obtained polyimide film is preferably 20% or more, and if it is smaller than that, the folding properties as a coverlay film are unfavorably deteriorated. The heat deformation temperature is preferably 200 ° C. or more, and if it is lower than that, a problem such as swelling during solder immersion may occur, which is not preferable. In the case of a polyimide film having a tensile elongation of more than 50%, a thin film having a low elastic modulus is generally not preferable since it is assumed that a thin film is likely to be deformed during lamination.

  Although the thickness of the polyimide film after drying is arbitrary, it is required to be 3 μm or more in order to sufficiently secure the insulation of the circuit, and is 50 μm or less in consideration of the bendability.

  A coverlay adhesive may be applied on the polyimide film surface of the thus obtained two-layer film of the support film and the polyimide film, if necessary, to produce a coverlay film laminate. Therefore, the method for producing a coverlay film laminate of the present invention comprises a polyimide resin containing a repeating unit represented by the general formula (1) in an amount of 70 mol% or more and a polyimide varnish containing an amide-based solvent, at least for a support film. A step of coating on one side, a step of drying the varnish applied on the support film at 220 ° C. or lower to form a polyimide film containing at least 3% by weight of the amide solvent, and an adhesive varnish on the polyimide film And a step of drying the adhesive varnish applied on the polyimide film at 220 ° C. or lower to form an adhesive layer. As an adhesive for the cover lay film for a flexible printed board, an arbitrary adhesive such as an acrylic adhesive, a butadiene adhesive, or an epoxy adhesive can be selected. The adhesive varnish is applied to the surface of the polyimide film and dried to form an adhesive layer. Recently, polyphenylene ether-based or polyimide-based adhesives have been actively studied to improve high-frequency transmission characteristics, but it is naturally possible to apply these low-dielectric adhesives. Generally, since these adhesives have tackiness at room temperature, it is general to attach a protective film to the surface thereof.

The thus obtained cover lay film laminate having a four-layer structure of a support film / polyimide film / adhesive / protective film is punched according to the shape of the flexible printed circuit board, and then protected. The film and the support film are peeled off and bonded to a flexible printed circuit board.
In the case of an extremely thin coverlay film, it can be bonded to a flexible printed circuit board with the support film attached, resulting in extremely excellent workability. Finally, the support film is easily peeled off from the flexible printed circuit board. be able to.

  Hereinafter, the present invention will be described with reference to examples. However, the present invention is not limited to the following examples. In the following Examples, Comparative Examples, and Test Examples, evaluation methods of the obtained products are shown below.

(1) Measurement of Residual Solvent Amount (wt%) Using TGA-DTA (manufactured by Shimadzu Corporation: DTG-60), the polyimide film was measured under a nitrogen atmosphere at a temperature rise of 10 ° C./min. And the weight difference of 300 ° C. was used as the residual solvent amount.

(2) Tensile test Using Shimadzu Autograph AGS-J at room temperature at a tensile speed of 0.5 cm / min, tensile modulus, breaking strength, and breaking elongation were calculated by analysis software. The test piece shape was a film having a measurement length of 10 cm and a width of 1 cm, and five tensile tests were performed, and the tensile strength and tensile elongation were calculated by averaging the values of three intermediate pieces excluding the upper and lower two pieces.

(3) Measurement of heat deformation temperature A polyimide film having a size of 3 mm × 15 mm was heated from 30 ° C. at a constant heating rate (5 ° C./min) while applying a load of 5.0 g using a thermomechanical analysis (TMA) device. The temperature was raised to 330 ° C., and the temperature at which thermal deformation occurred was determined.

Abbreviations of chemical products used in the examples are shown below.
ODPA: 4,4'-oxydiphthalic dianhydride BISDA: 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride BPDA: 3,3 ', 4,4'-biphenyl Tetracarboxylic dianhydride TFMB: 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl FDA: 9,9 -Bis (4-aminophenyl) fluorene NMP: N-methyl-2-pyrrolidone

[Example 1]
357.2 g of NMP and 32.02 g (0.1 mol) of NMP were charged into a four-necked flask equipped with a nitrogen gas inlet tube, a thermometer, a cooler, a stirrer, and a Dean-Stark tube, and after dissolution, 31.02 g of ODPA (0. 1 mol) and stirred at room temperature for 24 hours. Thereafter, 57 g of xylene was charged, the temperature was gradually raised to the xylene reflux temperature, water generated by the imidization dehydration reaction was removed from the system, and the mixture was stirred at 210 ° C. for 5 hours. When the varnish obtained after cooling was confirmed by infrared spectroscopy (IR), the presence of an imide group was confirmed. This varnish was applied to a 25 μm-thick biaxially stretched PPS film (Torelina, manufactured by Toray Industries, Inc.) using a 30 mmφ glass tube applicator, and the conditions were 130 ° C. for 5 minutes, 150 ° C. for 5 minutes, and 180 ° C. for 5 minutes. And dried with a hot air dryer. The polyimide film was peeled off from the PPS to obtain a transparent film having a thickness of 18 μm. When measured by TGA-DTA, the amount of residual solvent was 9.0%. When a tensile test was performed, the tensile strength was 120 MPa and the tensile elongation was 31.6%. The heat distortion temperature was 297.8 ° C.

[Example 2]
As in Example 1, TFMB (0.1 mol) and ODPA (0.1 mol) were reacted at room temperature for 24 hours. After the reaction, 30.6 g of acetic anhydride and 7.9 g of pyridine were added, and the imidization reaction was further performed for 6 hours. When the obtained varnish was confirmed by IR, the presence of an imide group was confirmed. When a film having a thickness of 18 μm was obtained and evaluated in the same manner as in Example 1, when a tensile test was performed with a residual solvent amount of 8.5%, the tensile strength was 125 MPa and the tensile elongation was 31.0%. The heat distortion temperature was 296.8 ° C.

[Example 3]
As in Example 2, TFMB (0.09 mol) and m-TB (0.01 mol) were reacted with ODPA (0.1 mol) at room temperature for 24 hours. After the reaction, 30.6 g of acetic anhydride and 7.9 g of pyridine were added, and the imidization reaction was further performed for 6 hours. When the obtained varnish was confirmed by IR, the presence of an imide group was confirmed. When a film having a thickness of 18 μm was obtained and evaluated in the same manner as in Example 1, when a tensile test was performed with a residual solvent amount of 8.5%, the tensile strength was 126 MPa and the tensile elongation was 22.2%. The heat distortion temperature was 287.5 ° C.

[Example 4]
As in Example 2, TFMB (0.1 mol) was reacted with ODPA (0.09 mol) and BISDA at room temperature for 24 hours. After the reaction, 30.6 g of acetic anhydride and 7.9 g of pyridine were added, and the imidization reaction was further performed for 6 hours. When the obtained varnish was confirmed by IR, the presence of an imide group was confirmed. When a film having a thickness of 18 μm was obtained and evaluated in the same manner as in Example 1, when a tensile test was performed with a residual solvent amount of 8.0%, the tensile strength was 120 MPa and the tensile elongation was 21.2%. The heat distortion temperature was 257.4 ° C.

[Comparative Example 1]
As in Example 2, TFMB (0.04 mol) and m-TB (0.06 mol) were reacted with ODPA (0.1 mol) at room temperature for 24 hours. After the reaction, 30.6 g of acetic anhydride and 7.9 g of pyridine were added, and the imidization reaction was further performed for 6 hours. When the obtained varnish was confirmed by IR, the presence of an imide group was confirmed. This varnish hardened into a gel after storage for one day and could not be applied.

[Comparative Example 2]
As in Example 2, TFMB (0.1 mol) was reacted with ODPA (0.05 mol) and BISDA (0.05 mol) at room temperature for 24 hours. After the reaction, 30.6 g of acetic anhydride and 7.9 g of pyridine were added, and the imidization reaction was further performed for 6 hours. When the obtained varnish was confirmed by IR, the presence of an imide group was confirmed. When a film having a thickness of 18 μm was obtained and evaluated in the same manner as in Example 1, when a tensile test was performed with a residual solvent amount of 8.0%, the tensile strength was 115 MPa and the tensile elongation was 11.2%. It was a brittle film. The heat distortion temperature was 257.3 ° C.

[Comparative Example 3]
As in Example 2, TFMB (0.1 mol) was reacted with ODPA (0.05 mol) and BPDA (0.05 mol) at room temperature for 24 hours. After the reaction, 30.6 g of acetic anhydride and 7.9 g of pyridine were added, and the imidization reaction was further performed for 6 hours. When the obtained varnish was confirmed by IR, the presence of an imide group was confirmed. The varnish solidified in a gel during the reaction and could not be applied.

[Comparative Example 4]
As in Example 2, TFMB (0.05 mol) and FDA (0.05 mol) were reacted with ODPA (0.1 mol) at room temperature for 24 hours. After the reaction, 30.6 g of acetic anhydride and 7.9 g of pyridine were added, and the imidization reaction was further performed for 6 hours. When the obtained varnish was confirmed by IR, the presence of an imide group was confirmed. When a film having a thickness of 18 μm was obtained and evaluated in the same manner as in Example 1, when a tensile test was performed with a residual solvent amount of 7.0%, the tensile strength was 105 MPa and the tensile elongation was 5.5%. It was a brittle film. The heat distortion temperature was 295.0 ° C.

Claims (7)

A polyimide film for a coverlay film, comprising a polyimide resin containing a repeating unit represented by the following general formula (1) in an amount of 70 mol% or more and an amide-based solvent in an amount of 3 wt% or more.

  The polyimide film for a coverlay film according to claim 1, wherein the film has a tensile elongation of 20% or more and a heat deformation temperature of 200C or more.   3. The polyimide film for a coverlay film according to claim 1, wherein the polyimide film contains 3 to 15 parts by weight of carbon having a particle size of 1 μm or less based on 100 parts by weight of the polyimide film.   The polyimide film for a coverlay film according to any one of claims 1 to 3, wherein the polyimide film is laminated on at least one surface of the support film.   A coverlay film laminate comprising an adhesive layer laminated on the polyimide film for a coverlay film according to any one of claims 1 to 4. A step of applying a polyimide resin containing a repeating unit represented by the following general formula (1) of 70 mol% or more and a polyimide varnish containing an amide-based solvent on at least one surface of the support film; Drying the coated varnish at a temperature of 220 ° C. or less to form a polyimide film containing 3% by weight or more of an amide solvent,
A method for producing a polyimide film for a coverlay film, comprising:

A step of coating a polyimide resin containing a repeating unit represented by the following general formula (1) by 70 mol% or more and a polyimide varnish containing an amide-based solvent on at least one surface of a support film;
Drying the varnish applied on the support film at 220 ° C. or lower to form a polyimide film containing 3% by weight or more of an amide solvent, and applying an adhesive varnish on the polyimide film; and A method for producing a coverlay film laminate, comprising a step of drying an adhesive varnish applied on a polyimide film at 220 ° C. or lower to form an adhesive layer.