JP2013028767A - Insulative black polyimide film, cover-lay film and flexible printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulative polyimide film excellent in light blocking performance and insulation performance and having excellent design performance, a cover-lay film obtained by using the insulative polyimide film, and a flexible printed wiring board.SOLUTION: The problem can be solved by providing the polyimide film which is characterized in that: the film contains (A) a perylene black pigment having a benzimidazole skeleton and (B) silica; the totalized gross weight of the pigment (A) and (B) with respect to the whole of the polyimide film is 1 to 20%; and a weight ratio of (A) and (B) is fallen into a range of 0.1 to 5.0.

Description

  The present invention relates to a polyimide film, a coverlay film, and a flexible printed wiring board.

  2. Description of the Related Art In recent years, electronic devices have been rapidly improved in performance, function, and size, and accordingly, there is an increasing demand for downsizing and weight reduction of electronic components used in electronic devices. In response to the above request, the flexible printed wiring board is flexible and can withstand repeated bending, so it can be mounted three-dimensionally and densely in a narrow space, and functions as a wiring, cable, or connector for electronic devices. Its use as a given composite part is expanding. In recent years, in particular, they are frequently used in electronic and optical devices such as cameras, video cameras, and optical pickups of CD-ROM drives, and accordingly, light shielding properties for flexible printed wiring boards have become important. This light shielding property is a characteristic required for flexible printed wiring boards used in light-absorbing parts of optical equipment. Light that tries to enter the light-absorbing parts from the outside is blocked by the wiring board, and light blocked by the wiring board is blocked. It is necessary to diffuse the reflected light so that it does not enter the aphobic part again.

  In addition, the flexible printed wiring board is an electronic component that is indispensable for mobile phones and personal computers, and its demand is increasing year by year. In mobile phones and personal computers, design as well as function has become important, and attempts have been made to make the housing transparent. From the viewpoint of such design properties, a flexible printed wiring board having a low gloss, so-called matte texture is also demanded.

  Furthermore, with the reduction in size and weight of electronic devices, the thickness of flexible printed wiring boards has been reduced, and accordingly, the thickness of coverlay films used for flexible printed wiring boards has also been reduced.

  In order to impart light-shielding properties, conventionally, black ink was printed directly on the electrically insulating film on the coverlay film side of the flexible printed wiring board by a screen printing method or the like. However, in this method, screen printing is performed on a flexible printed wiring board having unevenness, so that workability is poor, and the printing process is increased during the circuit processing process, so that work efficiency is also deteriorated. In addition, when the circuit is processed and bent, the black ink is broken or peeled off to lose the light shielding property, or the inside of the device is contaminated by the black ink.

  In order to solve this problem, a method of blackening the coverlay film has been proposed (see, for example, Patent Document 1). In addition, a technique using a perylene black pigment having a benzimidazole skeleton from the viewpoint of coloring power and insulating properties is also disclosed (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 9-135067 Japanese Patent No. 4709326

  However, as described in Patent Document 1, when carbon black is used as a black pigment, there is a problem in that the insulation properties of the original polyimide film tend to be reduced. In addition, when a perylene black pigment is used as disclosed in Patent Document 2, the possibility of impairing the insulation is reduced, but there is a limit to the design for design such as adjusting the surface property and hue. The present invention has been made in view of the above problems, and its purpose is to provide a polyimide film having excellent light shielding properties, insulating properties, and excellent design properties, and a coverlay film obtained by using the polyimide film and a flexible film. It is to provide a printed wiring board.

  As a result of intensive studies to solve the above problems, the present inventors have obtained excellent light-shielding properties by using a perylene black pigment having a benzimidazole skeleton and a polyimide film containing silica, which is another type of pigment. The present invention has been completed by finding that a cover lay film having both a good matte texture and high insulation reliability can be obtained.

  That is, the present invention includes (A) a perylene black pigment having a benzimidazole skeleton and (B) silica, and the total total weight of the pigments (A) and (B) with respect to the entire polyimide film is 1 to 20 parts, and (A ) And (B) in a weight ratio (A) / (B) in the range of 0.1 to 5.0.

  The polyimide film according to the present invention, as well as the coverlay film and flexible printed wiring board obtained by using the polyimide film, have both excellent light-shielding properties and insulation reliability, and also have low glossiness and good design properties. Excellent.

  Embodiments of the present invention will be described below.

((A) Perylene black pigment having a benzimidazole skeleton)
The perylene black pigment having a benzimidazole skeleton is not particularly limited, and examples thereof include lumogen black FK4280 manufactured by BASF. The perylene black pigment is a black pigment exhibiting a purple color, and can generally effectively appear black when a yellow resin is colored like a polyimide film.

((B) Silica)
As the silica, any of fused silica, fumed silica, synthetic silica and the like may be used. Examples include various HPS series manufactured by Cima Electronics, SQ series manufactured by Hayashi Kasei Co., Ltd., and the like.

(Polyimide film)
The polyimide film according to the present invention will be described.

  A polyimide film is obtained from the polyamic-acid heavy solution which is the precursor. This polyamic acid polymer solution can be produced by a method commonly used by those skilled in the art. That is, one or more tetracarboxylic dianhydride components and one or more diamine components are used in substantially equimolar amounts and polymerized in an organic polar solvent to obtain a polyamic acid polymer solution.

  Typical tetracarboxylic dianhydride components used in the production of polyimide films include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,4 ′ -Oxydiphthalic anhydride, 3,3 ', 4,4'-dimethyldiphenylsilane tetracarboxylic dianhydride, 3,3', 4,4'-tetraphenylsilane tetracarboxylic dianhydride, 1,2, 3,4-furantetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 4,4′-hexafluoroisopropylide Diphthalic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, p-phenylenebis (trimellitic acid mono Ester anhydrides), aromatic tetracarboxylic dianhydrides such as p-phenylenediphthalic anhydride, and the like.

  On the other hand, as the diamine component, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 2,2-bis (4-aminophenoxyphenyl) propane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, bis (4- (4-aminophenoxy) phenyl) sulfone, bis (4- (3-aminophenoxy) Phenyl) sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 2,2-bis (4-aminophenoxyphenyl) hexafluoropropane, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenyl Sulfone, 9,9-bis (4-aminophenyl) fluorene, bisaminophen Xyloketone, 4,4 ′-(1,4-phenylenebis (1-methylethylidene)) bisaniline, 4,4 ′-(1,3-phenylenebis (1-methylethylidene)) bisaniline, metaphenylenediamine, paraphenylene Aromatic diamines such as diamine, 4,4'-diaminobenzanilide, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, or other fats Group diamines can be mentioned.

  As for the polyimide film of this invention, it is desirable that the polyamic acid polymer which is the precursor has a weight average molecular weight of 10,000 to 1,000,000. If the weight average molecular weight is less than 10,000, the resulting film may become brittle. On the other hand, if the weight average molecular weight exceeds 1,000,000, the viscosity of the polyamic acid varnish, which is a polyimide precursor, becomes too high and handling may be difficult.

  Examples of the organic polar solvent used in the reaction for forming the polyamic acid polymer include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N , N-dimethylacetamide, N, N-diethylacetamide, and other acetamide solvents; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, and other pyrrolidone solvents; phenol, o-, m-, or p- Phenol solvents such as cresol, xylenol, halogenated phenol and catechol; or hexamethylphosphoramide, γ-butyrolactone and the like can be mentioned. These are preferably used alone or as a mixture. Furthermore, aromatic hydrocarbons such as xylene and toluene may be partially mixed in the solvent. Further, it is desirable from the viewpoint of handling that this polyamic acid polymer is dissolved in the organic polar solvent in an amount of 5 to 40% by weight, preferably 10 to 30% by weight.

  The method for adding (A) and (B) to the polyimide film in the present invention is a method in which the above polyamic acid is added to a solvent in advance, and a dispersion of (A) and (B) is prepared in advance. In addition, there is a method of adding this after the polyamic acid solution polymerization, but it is not particularly limited. A method in which (A) and (B) are previously dispersed in a solvent and a polyamic acid is further added to prepare a high-concentration dispersion, which is used while being diluted with a polyamic acid solution, is preferable from the viewpoint of handling.

  As a dispersion method, a known dispersion technique such as a ball mill, a bead mill, a three roll, a homogenizer, ultrasonic waves, stirring using a stirring blade, or the like can be applied. In addition, (A) and (B) may produce a dispersion liquid separately, and are good also as one dispersion liquid.

  In order to obtain a polyimide film from the polyamic acid polymer dispersion of (A) and (B), either a thermal method of thermally dehydrating or a chemical method using a dehydrating agent and an imidization catalyst can be used. Although good, it is preferable to use a chemical method because the polyimide film produced has excellent mechanical properties such as elongation and tensile strength.

  A film obtained by casting or coating a solution obtained by adding a stoichiometric or higher amount of a dehydrating agent and a catalytic amount of a tertiary amine to the polyamic acid polymer dispersion of the above (A) and (B) on a drum or an endless belt. The film is dried at a temperature of 200 ° C. or lower for about 10 to 10,000 seconds to obtain a self-supporting polyamic acid polymer film. Next, this is peeled off from the support and the end is fixed. Thereafter, it is imidized by heating at a predetermined temperature, and after cooling, fixing of the end portion is released to obtain an insulating polyimide film.

  Examples of the dehydrating agent herein include aliphatic acid anhydrides such as acetic anhydride and aromatic acid anhydrides such as benzoic anhydride. Examples of the imidization catalyst include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline, and isoquinoline. .

  In addition, the polyimide film is a method of applying various organic substances such as a thermosetting resin, a thermoplastic resin, an organic monomer, and a coupling agent as a primer for the purpose of improving the adhesion to different materials such as an adhesive, Various surface treatments such as a surface treatment with an oxide, an organic alkali, etc., a plasma treatment, a corona treatment, and a surface grafting method can be performed.

(Weight of pigment contained in film)
The weight of the pigment contained in the film can be measured as follows. That is, it can be measured by dissolving a black polyimide film using a hydrazine solution, filtering, washing, and drying and then measuring the weight and comparing it with the weight of the film before treatment. The total weight of the films (A) and (B) needs to be in the range of 1% to 20%, preferably in the range of 5% to 15%, and in the range of 5% to 10%. Further preferred. When the total weight of the pigment is below these ranges, the effect of the added pigment is reduced, and when it exceeds these ranges, the insulating properties and film strength tend to decrease.

  The weight ratio (A) / (B) between (A) and (B) must be in the range of 0.1 to 5.0, preferably in the range of 0.5 to 3.0, and More preferably, it is in the range of 8 to 2.0. When the value of (A) / (B) is below these ranges, the film cannot be colored, and when it exceeds these ranges, the film strength tends to decrease.

(Coverlay film)
The polyimide film according to the present invention can be suitably used for a cover lay film which is an insulating film used for covering the conductor pattern on the outer surface of the printed board completely or partially. A coverlay film is formed by applying and drying an adhesive on one side of the polyimide film, or by bonding an adhesive film, and a separator is attached to protect the adhesive surface as necessary. Can be obtained at

  Since the polyimide film of the present invention has a sufficient light-shielding property and a matte texture by itself, it is not necessary to add a black pigment to the adhesive, and therefore there is no possibility of causing poor insulation.

  Moreover, since the polyimide film of this invention has also ensured sufficient insulation, the coverlay film excellent in the insulation function and the protection function can be obtained without causing a failure of insulation due to contact with the outside.

(Flexible printed wiring board)
As described above, after obtaining a coverlay film from the polyimide film according to the present invention, the flexible printed wiring board obtained using the coverlay film is excellent in light shielding properties and insulation reliability. It is suitably used for electronic / optical devices such as an optical pickup section of a CD-ROM drive. Moreover, since it has a matte texture, it can be suitably used for applications that require design and design.

  The flexible printed wiring board according to the present invention is a printed wiring board obtained by patterning a flexible copper-clad laminate, punched with a coverlay film obtained from the insulating polyimide film according to the present invention, and subjected to pressing and laminating. Bonding and terminal plating can be performed, and a reinforcing plate can be bonded as necessary.

  Moreover, since the insulation polyimide film which concerns on this invention has high insulation reliability, it can be used not only as a coverlay film but as a base film of a flexible printed copper clad laminated board.

  Needless to say, the application of the present invention is not limited to this, and the insulating resin material of the present invention can be used for various applications.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to these. In addition, the characteristic of the film in an Example and a comparative example was evaluated as follows.

[Total light transmittance]
It calculated | required by measuring a total light transmittance (%) according to ASTMD1003 using the Nippon Denshoku Industries Co., Ltd. haze meter and NDH5000 using a 50 mm square polyimide film.

[Glossiness]
It calculated | required by measuring the glossiness (%) in incident angle 20 degrees, 60 degrees, and 85 degrees using the Nippon Denshoku Industries Co., Ltd. gloss meter and V-7000 using a 100 mm square polyimide film. .

[Dielectric breakdown voltage]
Using a 100 mm square polyimide film, a value V / μm obtained by dividing the value of the dielectric breakdown voltage by the thickness of the measurement sample was measured according to JIS C 2110-7.1.

[Mechanical strength of film during film formation]
When the film was formed, it was determined that the film could be formed without any problem, and that the film was broken was determined as x.

(Synthesis Example 1; Synthesis 1 of polyamic acid polymer)
To 620.4 g of N, N-dimethylformamide (DMF) cooled to 10 ° C., 10.1 g of p-phenylenediamine (p-PDA) and 56 of 4,4′-diaminodiphenyl ether (4,4′-ODA) After 2 g was added and dissolved, 79.2 g of pyromellitic dianhydride (PMDA) was added and stirred for 60 minutes to dissolve. Furthermore, a DMF solution of PMDA (PMD 2.45 g / DMF 31.6 g) separately prepared was carefully added to this solution, and the addition was stopped when the viscosity reached about 3000 poise. Stirring was performed for 1 hour to obtain a polyamic acid polymer solution (a) having a solid content concentration of about 18.5% by weight and a rotational viscosity at 23 ° C. of 3200 poise.

Example 1
To 69 g of DMF, 5.0 g of Lumogen Black FK4280 manufactured by BASF as (A) and 5.0 g of spherical silica HPS-2000 as (B) were added, and the mixture was stirred with a homogenizer for 10 minutes. 11 g of the polyamic acid polymer solution (a) was added to this dispersion to obtain 80 g of a master batch. A polyamic acid solution (a) 87.12 was added to 22.9 g of this master batch, and a curing agent comprising acetic anhydride / 3,5-diethylpyridine / DMF (weight ratio 12.90 / 2.96 / 13.14). Was stirred and defoamed at a temperature of 0 ° C. or less, and cast onto an aluminum foil using a comma coater. This resin film is heated at 120 ° C. for 60 seconds, and then the self-supporting gel film is peeled off from the aluminum foil and fixed to the metal frame. At 250 ° C. for 11 seconds, 350 ° C. for 11 seconds, 450 ° C. for 120 seconds Drying and imidization gave a polyimide film with a thickness of 12.5 μm. The properties of the obtained film are shown in Table 1. Moreover, when the obtained film was melt | dissolved using the hydrazine solution and filtered, wash | cleaned and dried and the weight was measured, the pigment of 14% of weight with respect to the film weight was obtained.

(Comparative Example 1)
A polyimide film was obtained in the same manner as in Example 1 except that spherical silica HPS-2000 was not used as the component (B). The properties of the obtained film are shown in Table 1. Moreover, when the obtained film was melt | dissolved using the hydrazine solution and filtered, wash | cleaned and dried and the weight was measured, the pigment of the weight of 7% with respect to the film weight was obtained.

(Comparative Example 2)
10 g of Lumogen Black FK4280 manufactured by BASF as (A) and 10 g of spherical silica HPS-2000 as (B) were added to 69 g of DMF, and the mixture was stirred with a homogenizer for 10 minutes. 11 g of the polyamic acid polymer solution (a) was added to this dispersion to obtain 100 g of a master batch. A polyamic acid solution (a) 87.12 was added to 22.9 g of this master batch, and a curing agent comprising acetic anhydride / 3,5-diethylpyridine / DMF (weight ratio 12.90 / 2.96 / 13.14). Was stirred and defoamed at a temperature of 0 ° C. or less, and cast onto an aluminum foil using a comma coater. The resin film is heated at 120 ° C. for 60 seconds, and then the self-supporting gel film is peeled off from the aluminum foil and fixed to the metal frame. At 250 ° C. for 11 seconds, 350 ° C. for 11 seconds, 450 ° C. for 120 seconds. Although it tried to dry and imidize, the film broke down on the way and the film which was sufficient for evaluation was not able to be obtained. Further, the broken piece of the resin film was dissolved using a hydrazine solution, filtered, washed and dried, and then the weight was measured. As a result, a pigment having a weight of 28% with respect to the weight of the film piece was obtained.

Claims (3)

  (A) a perylene black pigment having a benzimidazole skeleton and (B) silica, the total total weight of the pigments (A) and (B) with respect to the whole polyimide film is 1 to 20%, and (A) and (B) Weight ratio (A) / (B) is contained in the range of 0.1-5.0, The polyimide film characterized by the above-mentioned.   A coverlay film using the polyimide film according to claim 1.   The flexible printed wiring board formed using the polyimide film of Claim 1 or 2.