JP2889976B2 - Polyimide film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film, and more particularly to a polyimide film having improved adhesion.

[0002]

2. Description of the Related Art Polyimide film has heat resistance, cold resistance,
It is known to have excellent properties such as chemical resistance, electrical insulation, and mechanical strength. It is known as an electrical insulating material for electric wires, a heat insulating material, a base film for a flexible printed wiring board (FPC), and an IC tape auto manufacturer. It is widely used as a base film for carrier tapes for tied bonding (TAB), tapes for fixing lead frames of ICs, and the like. Of these, in applications such as FPC, TAB carrier tape, and lead frame fixing tape,
A polyimide film and a copper foil are used by being bonded via various adhesives. However, polyimide films often have insufficient adhesion to copper foils due to their chemical structure and high chemical resistance (solvent) stability. At present, various surface treatments (for example, Alkali treatment, coupling agent application treatment,
After performing sandblasting, corona discharge treatment, plasma treatment, etc., they are adhered.

[0003]

In the surface treatment of a polyimide film, for example, an alkali treatment, a coupling agent coating treatment, a sand blasting treatment, etc. are performed after the film is formed, and after each treatment such as an alkali treatment, further washing, Since a separate process such as drying is required, problems are involved not only in terms of productivity, stability and cost, but also in terms of environmental conservation. On the other hand, corona discharge treatment and plasma treatment
It has been mainly performed to improve printability on the surface of paper, plastics, and the like. As is well known, the apparatus can be incorporated (in-line) into a film forming apparatus because of the simplicity of the apparatus, which is an advantageous processing as compared with the above-described post-processing.

[0004] Therefore, the present inventors have studied corona discharge treatment to improve the adhesiveness to the polyimide film. As a result, it has been found that the corona discharge treatment slightly improves the adhesiveness of various polyimide films made of different raw materials. Was done. However, when a polyimide-based adhesive was used as the adhesive, no improvement in adhesiveness was observed at all, and it was found that there was a problem as a practical treatment.

Further, the present inventors have studied a plasma treatment to improve the adhesiveness to a polyimide film. As a result, a conventional polyimide film, ie, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were used as raw materials. In the case of the polyimide film described above, and the polyimide film using biphenyltetracarboxylic dianhydride and paraphenylenediamine as raw materials, it was observed that the plasma treatment slightly improved the adhesiveness. However, similarly, when a polyimide-based adhesive was used as the adhesive, no improvement in adhesiveness was observed at all, and it was found that there was a problem as a practical treatment.

Accordingly, the present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, by applying a plasma treatment to a polyimide film having a specific structural unit, a practically sufficient adhesive property is improved. The inventors have found that a polyimide film can be provided, and have reached the present invention.

[0007]

Means for Solving the Problems The gist of the polyimide film according to the present invention is that the polyimide film has the structural units represented by the general formulas (1) and (2) in one molecule. That is, a film formed of polyimide is subjected to plasma processing.

Embedded image

Embedded image (In the formula, R is a tetravalent organic group.)

[0008] In the polyimide film of the present invention, the atmosphere gas in the plasma treatment is a gas selected from tetrafluoromethane, oxygen, nitrogen, argon, carbon dioxide and a mixed gas thereof.

Next, the gist of the method for producing a polyimide film according to the present invention is that a polyamic acid produced from an organic tetracarboxylic dianhydride, 4,4'-diaminodiphenyl ether and paraphenylenediamine is used. After forming into a film and converting it into polyimide to produce a polyimide film, the polyimide film is subjected to a plasma treatment.

In the method for producing a polyimide film, the addition ratio of 4,4'-diaminodiphenyl ether and paraphenylenediamine is 1 to 1 in molar ratio.
0: 1 to 1: 5, more preferably 5: 1 to 1: 1.

[0011]

The present inventors have found that a film having high adhesiveness can be obtained by subjecting the above-mentioned polyimide film having a specific molecular structure to plasma treatment. However, the mechanism is not always clear,
The surface of the polyimide film having a specific molecular structure used in the present invention is easily modified by plasma treatment due to having the special molecular structure as compared with the polyimide film having another molecular structure. It is presumed that the effects of the invention are exhibited.

The polyimide film of the present invention is obtained by converting a polyamic acid formed from an organic tetracarboxylic dianhydride, 4,4'-diaminodiphenyl ether and paraphenylenediamine. here,
The addition ratio of 4,4'-diaminodiphenyl ether and paraphenylenediamine can be arbitrarily set, but is preferably from 10: 1 to 1: 5, more preferably from 5: 1 to 1: 1 in molar ratio. Is preferred. In a flexible printed wiring board or the like which is an example in which the polyimide film according to the present invention is used, when used by bending,
Films that are not too hard and not too soft are preferred. On the other hand, the higher the proportion of paraphenylenediamine, the harder the polyimide film, and the lower the proportion, the softer the polyimide film. Therefore, when the ratio is within the above range, a polyimide film meeting the above conditions can be obtained.

[0013]

Next, examples of the polyimide film according to the present invention will be described in detail. In the present invention, first, the polyimide film to be subjected to the plasma treatment has the general formula (3):

Embedded image (In the formula, R is a tetravalent organic group.) An organic tetracarboxylic dianhydride such as pyromellitic dianhydride, and 4,4′-diaminodiphenyl ether and paraphenylenediamine are represented by the following formula: This is a polyimide film having a structural unit represented by the general formula (1) and the general formula (2) in one molecule obtained by using it as a raw material. That is, such a polyimide film is obtained by dissolving a solution in which organic diamine 4,4'-diaminodiphenyl ether and paraphenylenediamine are dissolved in an organic solvent, and an organic tetracarboxylic dianhydride represented by the general formula (3). An organic solvent solution of a polyamic acid, which is a polyimide precursor obtained by the reaction, is formed into a film by a known film-forming method, and is then dehydrated and closed by a known polyamic acid polymerization method.

Here, the tetravalent organic group R in the general formulas (1), (2) and (3) is an aliphatic group or

Embedded image Wherein R ₁ and R ₂ are each a hydrogen atom or a methyl group.

Specific examples of the organic tetracarboxylic dianhydride represented by the general formula (3) include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, naphthalene-1,2,2
5,6-tetracarboxylic dianhydride, 2,2 ', 3
3'-diphenyltetracarboxylic dianhydride, 2,3
5,6-pyridinetetracarboxylic dianhydride, 2,2-
Bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3 4-dicarboxyphenyl) ether dianhydride, 1,2,4,5-naphthalenetetracarboxylic dianhydride, 1,2,5,8-naphthalenetetracarboxylic dianhydride, 2,2-bis (2 , 3-Dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3
-Dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride,
Bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, benzene-1,2 And 3,3,4-tetracarboxylic dianhydride, 3,4,3 ', 4'-benzophenonetetracarboxylic dianhydride, and a mixture of two or more of these. Among them, pyromellitic dianhydride is particularly preferable.

Among the organic diamines, 4,4'-diaminodiphenyl ether or paraphenylenediamine used in the present invention is used after being dissolved in an organic solvent. 4,
A predetermined amount of each of 4'-diaminodiphenyl ether and paraphenylenediamine is previously dissolved in an organic solvent, and an organic tetracarboxylic dianhydride is added to the solution to obtain a polyamic acid solution having a predetermined viscosity. Alternatively, one of 4,4'-diaminodiphenyl ether and paraphenylenediamine is dissolved in an organic solvent, an organic tetracarboxylic dianhydride is added to this solution, and the mixture is stirred. A diamine may be added to obtain a polyamic acid solution having a predetermined viscosity.

Here, the addition ratio of 4,4'-diaminodiphenyl ether and paraphenylenediamine is not particularly limited, and it is necessary that at least both are added. However, as for the addition ratio of 4,4'-diaminodiphenyl ether and paraphenylenediamine, the polyimide film becomes harder when the addition ratio of paraphenylenediamine increases, and conversely, the polyimide film becomes softer when the addition ratio of paraphenylenediamine decreases. For this reason, it is preferable to set the addition ratio of both depending on the use of the polyimide film. For example, when the obtained polyimide film is used for a flexible printed wiring board or the like, it is preferable that the characteristics of the film be neither too hard nor too soft. To obtain a polyimide film that meets such conditions, it is necessary to use 4,4'-diamino. The addition ratio of diphenyl ether and paraphenylenediamine is 1
It is preferably in the range of 0: 1 to 1: 5, more preferably 5: 1 to 1: 1.

The organic solvent used in the present invention is, for example,
N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphoramide, N-methyl-2 -In addition to pyrrolidone, dimethyl sulfone, and the like, a mixture of two or more of these, or a mixture of these solvents and benzene, toluene, xylene, benzonitrile, dioxane, cyclohexane, or the like as appropriate is exemplified. Among them, 4,4 '
A good solvent for diaminodiphenyl ether and paraphenylenediamine and the above general formula (3)
Since it is necessary that the organic tetracarboxylic acid dianhydride represented by and a generated polyamic acid be a good solvent, particularly, N, N-dimethylformamide,
N, N-dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone or a mixture of two or more thereof is preferred, and an organic polar solvent is more preferred.

Polyamide acid obtained from 4,4'-diaminodiphenyl ether and paraphenylenediamine and the organic tetracarboxylic dianhydride represented by the general formula (3) is polymerized by a known polymerization method to obtain a polyimide. Invert. Methods for converting polyamic acid to polyimide include, for example, heating polyamic acid to effect dehydration ring closure, or adding a dehydration ring closure agent or a dehydration ring closure agent and a catalyst to a polyamic acid solution to chemically dehydrate ring closure, or a combination thereof. A dehydration ring closure method is usually used. In order to further improve the mechanical properties and the like of the obtained polyimide film, various additives may be added to the polyamic acid solution, and there is no particular limitation.

Examples of the dehydrating ring-closing agent include organic carboxylic acid anhydrides, N, N'-dialkylcarbodiimides, lower fatty acid halides, halogenated lower fatty acid halides, halogenated lower fatty acid anhydrides, allylphosphonic acid In addition to dihalides and the like, mixtures thereof can be mentioned. Among them, acetic anhydride is particularly preferable, and other preferable dehydration ring-closing agents include ketene and benzoic anhydride. Examples of the catalyst include pyridine, isoquinoline and tertiary amines.
Specific examples thereof include 3,4-lutidine, 3,5-lutidine, 4-methylpyridine, 4-isopropylpyridine,
N-dimethylbenzylamine, 4-benzylpyridine or 4-dimethyldodecylamine, picolines, triethylamine and the like can be mentioned. Among them, isoquinoline is particularly preferred.

Since the obtained solution of the polyamic acid as the polyimide precursor has a high viscosity, the polyamic acid solution is usually extruded or cast onto a casting drum or an endless belt to form a film. The above is subjected to dehydration ring closure to convert to polyimide. After curing the film converted to polyimide to at least a degree having self-supporting property, the polyimide film is peeled off from a drum or a belt to produce a polyimide film. The manufactured polyimide film is further subjected to a heat treatment or the like, if necessary, to be used as a stable polyimide film.

Next, a known method such as a glow discharge is employed as a plasma processing method in the present invention. The condition of the plasma processing can be arbitrarily selected.
The pressure is preferably 0 to 2000 W · min / m ² and the pressure is 1 Torr or less. The atmosphere gas for the plasma treatment can also be arbitrarily selected, but is preferably tetrafluoromethane CF ₄ ,
A non-reactive gas or a reactive gas such as oxygen, nitrogen, argon, carbon dioxide, or a mixed gas of two or more thereof is employed. The plasma treatment may be performed only on one side of the polyimide film, but may be performed on both sides, and there is no limitation. After the plasma treatment, ions of the opposite polarity to the static electricity may be applied to the film surface so as to remove the static electricity charged on the polyimide film.

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

The viscosity of the polyamic acid in the examples is measured by a B-type viscometer. Further, the adhesive strength in the present invention was measured by bonding a polyimide film and a copper foil with a known thermoplastic polyimide adhesive based on the method of IPC-FC-241A and fixing the film surface on a hard plate.

Example 1 815 g of N, N-dimethylformamide was added to ODA (4,4).
70.28 g of 4'-diaminodiphenyl ether) was dissolved, and PMDA (pyromellitic dianhydride) 10
After adding 2.07 g and stirring for 1 hour, p-PDA was added.
About 12.65 g of (paraphenylenediamine) was added to obtain a polyamic acid solution whose viscosity was adjusted to 2500 poise. The molar ratio of the added organic diamine is ODA: p-PD
A = 3: 1. Using this polyamic acid solution, a 25 μm-thick polyimide film was obtained by a known method.

The obtained polyimide film was subjected to a plasma treatment under a pressure of 10 ^-1 Torr and an argon output in an argon atmosphere.
Glow discharge of 000 W · min / m ² was performed. The adhesive strength of the obtained film was as shown in Table 1.

Example 2 815 g of N, N-dimethylformamide was added to ODA (4,4).
63.70 g of 4'-diaminodiphenyl ether) was dissolved therein, and PMDA (pyromellitic dianhydride) 10
After adding 4.09 g and stirring for 1 hour, p-PDA was added.
Approximately 17.20 g of (paraphenylenediamine) was added to obtain a polyamic acid solution whose viscosity was adjusted to 2500 poise. The molar ratio of the added organic diamine is ODA: p-PD
A = 2: 1. Using this polyamic acid solution, a 25 μm-thick polyimide film was obtained by a known method.

The obtained polyimide film was subjected to a plasma treatment under a pressure of 10 ^-1 Torr under an argon atmosphere with a discharge output of 1.
Glow discharge of 000 W · min / m ² was performed. The adhesive strength of the obtained film was as shown in Table 1.

[Table 1]

Comparative Example 1 A polyimide film having a thickness of 25 μm was obtained in the same manner as in Example 1. However, no plasma treatment was performed. The adhesive strength of the obtained film was as shown in Table 1, and was significantly inferior to Example 1.

Comparative Example 2 In the same manner as in Example 2, a polyimide film having a thickness of 25 μm was obtained. However, no plasma treatment was performed. The adhesive strength of the obtained film was as shown in Table 1, and was significantly inferior to Example 2.

Comparative Example 3 815 g of N, N-dimethylformamide was added to ODA (4,
88.37 g of 4'-diaminodiphenyl ether) was dissolved therein, and PMDA (pyromellitic dianhydride) 9 was added thereto.
4.33 g was added to obtain a polyamic acid solution whose viscosity was adjusted to 2500 poise. Using this polyamic acid solution, a 25 μm-thick polyimide film was obtained by a known method. The adhesive strength of the obtained film was as shown in Table 1.

Comparative Example 4 In the same manner as in Comparative Example 3, a polyimide film having a thickness of 25 μm was obtained. The obtained polyimide film was subjected to a plasma treatment under a pressure of 10 ^-1 Torr and an argon atmosphere in a discharge output of 1.
Glow discharge of 000 W · min / m ² was performed. The adhesive strength of the obtained film was as shown in Table 1. Although the adhesive strength was slightly improved as compared with Comparative Example 3, p-PD
The adhesive strength was significantly inferior to Examples 1 and 2 to which A was added.

Comparative Example 5 p-PDA4 was added to 815 g of N, N-dimethylformamide.
4.58 g was dissolved, and to this was added 129.45 g of biphenyltetracarboxylic dianhydride to increase the viscosity to 2500.
A polyamic acid solution adjusted to poise was obtained. Using this polyamic acid solution, a 25 μm-thick polyimide film was obtained by a known method. The adhesive strength of the obtained film was as shown in Table 1.

Comparative Example 6 In the same manner as in Comparative Example 5, a polyimide film having a thickness of 25 μm was obtained. The obtained polyimide film was subjected to a plasma treatment under a pressure of 10 ^-1 Torr and an argon atmosphere in a discharge output of 1.
Glow discharge of 000 W · min / m ² was performed. The adhesive strength of the obtained film was as shown in Table 1. Although the adhesive strength was slightly improved as compared with Comparative Example 5, the adhesive strength was significantly inferior as compared with Examples 1 and 2 to which ODA was added.

[0035]

As is clear from Table 1, the polyimide film according to the present invention has remarkably improved adhesiveness to a film not subjected to the plasma treatment and a polyimide film having another molecular structure. Therefore, it can be suitably used in a wide range of fields such as applications to flexible printed wiring boards.

Further, such a polyimide film is
The flexible printed wiring board is manufactured by setting the molar ratio of 4'-diaminodiphenyl ether and paraphenylenediamine in the range of 10: 1 to 1: 5, more preferably 5: 1 to 1: 1. It is possible to produce a polyimide film having optimal characteristics that are not too hard and not too soft for the like.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08J 5/00-5/02 C08J 5/12-5/22 C08G 73/10 C08J 7/00

Claims (4)

(57) [Claims] 1. A film formed of a polyimide having a structural unit represented by the general formula (1) and the general formula (2) in a molecule is subjected to a plasma treatment. Polyimide film. Embedded image Embedded image (In the formula, R is a tetravalent organic group.) 2. The polyimide film according to claim 1, wherein an atmosphere gas in the plasma treatment is a gas selected from tetrafluoromethane, oxygen, nitrogen, argon, carbon dioxide, and a mixed gas thereof. 3. An organic tetracarboxylic dianhydride, 4,
Polyimide acid produced from 4'-diaminodiphenyl ether and paraphenylenediamine is formed into a film and converted into polyimide to produce a polyimide film, and then the polyimide film is subjected to plasma treatment. Manufacturing method. 4. The method according to claim 1, wherein the molar ratio of 4,4'-diaminodiphenyl ether to paraphenylenediamine is from 10: 1 to 1: 5, more preferably from 5: 1 to 1: 1. The method for producing a polyimide film according to claim 3.