JP2010270246A - Polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide film which has good slidability and surface characteristic and is suitable for use in high density wiring boards. <P>SOLUTION: The polyimide film includes 0.01-0.08 wt.% of spherical silica particles having an average particle size of 0.2-0.7 μm per the weight of the resin and a particle size distribution of within ±15% of the average particle size and has a number of protrusions originated from silica particles on the surface of 0.1-1.5×10<SP>6</SP>per 1 cm<SP>2</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyimide film that can be suitably used for high-density wiring board applications such as FPC, COF, and TAB requiring high definition.

  Since polyimide film is excellent in heat resistance, electrical insulation, and mechanical strength, it is used as a base film for metal laminates such as Flexible Printed Circuits (FPC), Chip On Film (COF), and Tape Automated Bonding (TAB). It's being used.

  In recent years, as electronic devices have become smaller and thinner and lighter, flexible wiring boards have been increased in density, and the demand for film surface properties has become stricter. Therefore, if projections of several um to several tens of um are present on the film surface, problems such as peeling or disconnection of wiring occur after pattern formation, resulting in NG during appearance inspection and lowering the yield.

  On the other hand, although inorganic particles are added as a lubricant to the film, it is necessary to achieve both a surface property suitable for increasing the density of FPC and a sufficient slip property. If the slipperiness is not sufficient, wrinkles and scratches will occur during roll-to-roll film transport, and winding misalignment processing will fail on the film roll.

  Attempts have been made to obtain a surface property of a film suitable as a base film for a high-density wiring board by reducing the average particle diameter of the filler (see Patent Documents 1 and 2).

JP 2004-217907 A JP 2007-90770 A

  An object of the present invention is to obtain a polyimide film having good surface properties and slipperiness by controlling the silica particle diameter and distribution density.

  As a result of intensive studies, the present inventors have found that a polyimide film containing a specific amount of spherical silica particles having a specific particle size and particle size distribution, and the number of protrusions derived from silica particles on the film surface is in a specific range, The present inventors have found that the surface property, the slipperiness, the film appearance, and the roll shape of the film roll are good, and have reached the present invention.

That is, the present invention includes 0.01 to 0.08 wt% of spherical silica particles having an average particle diameter of 0.2 to 0.7 μm and a particle size distribution within ± 15% of the average particle diameter, The present invention relates to a polyimide film characterized in that the number of protrusions derived from filler on the surface is 0.1 to 1.5 × 10 ⁶ per cm ² . Moreover, it is preferable that the average surface roughness (Ra) of a film is 1 to 5 nm, the root mean square surface roughness (RMS) is 1 to 10 nm, and the 10-point average roughness (Rz) is 50 to 300 nm. The static friction coefficient is preferably 0.5 to 2.0 and the dynamic friction coefficient is preferably 0.4 to 1.0. Moreover, it is preferable that film thickness is 5-75 micrometers.

  According to the present invention, it is possible to obtain a polyimide film having good sliding properties and surface properties and suitable for high-density wiring board applications.

The polyimide film of the present invention contains 0.01 to 0.08 wt% of spherical silica particles having an average particle diameter of 0.2 to 0.7 μm and a particle size distribution within ± 15% of the average particle diameter, The number of protrusions derived from silica particles on the film surface is 0.1 to 1.5 × 10 ⁶ per 1 cm ² .

  In the present invention, the silica particles added to the polyimide film are spherical, the average particle diameter is 0.2 to 0.7 μm, and the particle size distribution is within ± 15% of the average particle diameter. By defining the amount as 0.01 to 0.08 wt%, the resulting film has a static friction coefficient of 0.5 to 2.0, a dynamic friction coefficient of 0.4 to 1.0, and an average surface roughness (Ra). A polyimide film having a thickness of 1 to 5 nm is obtained. As a result, it is possible to obtain a polyimide film for a high-density wiring board with favorable workability.

  The average particle diameter of the silica particles used in the present invention is 0.2 to 0.7 μm, preferably 0.3 to 0.5 μm. By setting the particle diameter within this range, the projection diameter on the film surface can be suppressed to 1 μm or less. Further, the stability, dispersibility, and redispersibility in a dispersion after mixing silica with a solvent are good. That is, the silica particles are unlikely to settle in the slurry, and even if they are settled, they can be easily redispersed. As a result, film surface properties suitable for high density wiring board applications can be obtained, and at the same time, handling of silica particles can be facilitated. As a result, it is possible to obtain transportability in the production process and slipperiness that does not cause winding deviation in the film roll. The above-mentioned winding deviation means that the film of the outermost layer several times is displaced at the time of roll handling after the film roll has been wound.

  The particle size distribution of the silica particles used in the present invention is within ± 15%, preferably within ± 10%. By making the particle size distribution of the silica particles in this range, the variation in the number of particles per unit weight can be minimized. As a result, it is possible to uniformly reproduce the surface characteristics such as the number of protrusions derived from silica particles, protrusion height and distribution density. Further, no slippage occurs, and slipperiness with good film transportability is obtained.

In the method of calculating the average particle size and particle size distribution of silica particles in the present invention, silica particles are photographed with an electron microscope, and 300 particle sizes are measured from the photographed image. Of the 300 measured silica particles, 10 upper and lower limits are excluded, and the average particle size and particle size distribution are calculated from the remaining 280 particle sizes. The average particle size (S _ave ) is the number average, and the particle size distribution is the difference between the maximum particle size (S _max ) and the minimum particle size (S _min ) from the average particle size. The upper limit (Sd _max ) and lower limit (Sd _min ) of the particle size distribution are obtained by the following equations.

  The silica particles used in the present invention are characterized by being spherical silica. By using spherical particles, uniform protrusions can be formed no matter where the particles appear as protrusions on the film surface. When pulverized particles that are not spherical are used, it is difficult to form protrusions uniformly on the film surface, and the amount of added particles and slipperiness tend to vary greatly. Further, since the projection height / projection diameter and slipperiness of the film surface are not uniform, the film surface is likely to be damaged.

  The addition amount of the silica particles used in the present invention is 0.01 to 0.80% by weight, preferably 0.02 to 0.60% by weight, based on the polyimide resin or polyamic acid. The desired surface properties and slipperiness cannot be obtained only by making the addition amount of the silica particles within the aforementioned range. For the first time by satisfying all of the particle size, particle size distribution, and particle shape of silica, protrusions are uniformly formed on the surface of the film without agglomeration of the particles, and it has suitable slipperiness for film transport by roll-to-roll. A polyimide film can be obtained.

The number of projections on the film surface of the present invention is 0.1 to 1.5 × 10 ⁶ , preferably 0.5 to 1.2 × 10 ⁶ per 1 cm ² . When the number of protrusions is within the above range, a smooth film surface property can be obtained without aggregation of silica particles, and it can be suitably used as a base film for a high-density wiring board.

  As a method for preparing a silica particle dispersion used in the present invention, silica particles are dispersed in a solvent used for polymerization, and a silica particle dispersion having a silica particle content of 1 to 25% by weight, preferably 5 to 15% by weight. Get. For dispersion, any known method such as an ordinary stirrer, ultrasonic wave, or bead mill may be used.

  The polyimide film of the present invention is produced using polyamic acid as a precursor. As the polymerization method of the polyamic acid, any known method and a combination thereof can be used, and the polyamic acid is designed by selecting a monomer so that various physical properties of the final polyimide can be achieved.

  In the present invention, any monomer addition method may be used for the polymerization of the polyamic acid, and examples of the monomer include the following monomers.

  As the acid dianhydride component, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride 3,3 ′, 4,4′-dimethyldiphenylsilanetetracarboxylic dianhydride, 3,3 ′, 4,4′-tetraphenylsilanetetracarboxylic dianhydride, 1,2,3,4- Furantetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4 ' -Bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3 ', 4,4'-hexafluoroisopropylidenediphthalic dianhydride, 3,3', 4,4'-biphenyltetra Carboxylic dianhydride or 2,3 ′, 3,4′-biphenyltetracarboxylic dianhydride is preferably used. Not only one type of the above may be used, but a plurality of types may be mixed and used.

  As the diamine component, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4, 4'-oxydianiline, 3,3'-oxydianiline, 3,4'-oxydianiline, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diamino Diphenylethylphosphine oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), bis {4- (4-amino Phenoxy) phenyl} sulfone, bis {4- (3-aminophenoxy) fe Sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, Preferably, 2,2-bis (4-aminophenoxyphenyl) propane or paraphenylenediamine is used. Not only one type of the above may be used, but a plurality of types may be mixed and used.

  In the present invention, the viscosity of the polyamic acid solution is 100 poises or less, preferably 50 poises or less, particularly preferably 30 poises or less. Moreover, the solid content concentration of the polyamic acid in the polyamic acid solution is preferably 5 to 40 wt%, preferably 10 to 30 wt%, and more preferably 12 to 25 wt%.

  After adding a dispersion of silica particles to the prepolymer solution, the polymerization is completed to obtain a polyamic acid solution of 1000 to 6000 poise, preferably 1500 to 3500 poise. When the final solution viscosity is within this range, it becomes easy to realize good film forming properties and productivity.

  As a method for forming a polyimide film of the present invention, a polyamic acid solution is cast into a film and thermally cyclized and desolvated to obtain a polyimide film, and a cyclization catalyst and a dehydrating agent are mixed in the polyamic acid solution. A method of obtaining a polyimide film by chemically cyclizing to prepare a gel film and desolvating it by heating may be used, and any method may be used or may be used in combination.

  Examples of the dehydrating agent used in the chemical ring closure method include acetic anhydride, propionic anhydride, butyric anhydride, formic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, picolinic anhydride Etc. As the catalyst, organic tertiary amines are often used, and examples thereof include trimethylamine, triethylamine, dimethylaniline, pyridine, β-picoline, isoquinoline, quinoline and the like.

  In the present invention, the film preferably has an average surface roughness (Ra) of 1 to 5 nm, a root mean square surface roughness (RMS) of 1 to 10 nm, and a 10-point average roughness (Rz) of 50 to 300 nm, more preferably. The average surface roughness (Ra) is 1.5 to 4.5 nm, the root mean square surface roughness (RMS) is 3 to 8.5 nm, and the 10-point average roughness (Rz) is 150 to 250 nm. In order to set the average surface roughness, the square average surface roughness, and the 10-point average roughness within the above ranges, the average particle diameter is 0.2 to 0.7 μm, and the particle size distribution is within ± 15% of the average particle diameter. It develops by adding 0.01 to 0.08 wt% of spherical silica per resin weight. By adjusting to this range, the protrusions derived from the filler can be minimized, and the slipperiness can be made suitable for film processing and conveyance.

  In the present invention, the static friction coefficient between films is preferably 0.5 to 2.0, the dynamic friction coefficient is 0.4 to 1.0, more preferably the static friction coefficient 0.6 to 1.5, and the dynamic friction coefficient 0.5. ~ 0.6. In order to make the static friction coefficient and the dynamic friction coefficient within the above ranges, spherical silica having an average particle size of 0.2 to 0.7 μm and a particle size distribution within ± 15% of the average particle size is 0.01 to 0 per resin weight. This can be achieved by adding 0.08 wt%. By achieving slipperiness within this range, it is possible to obtain suitable transportability in roll-to-roll, and to suppress the occurrence of winding deviation in the film roll.

  The film thickness in this invention becomes like this. Preferably it is 5-75 micrometers, More preferably, it is 30-40 micrometers, More preferably, it is 33-37 micrometers. By setting the thickness within the above range, the film can be stably conveyed by roll-to-roll, and the hardness and strain of the film suitable for processing the base film for a high-density wiring board can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. Each characteristic of the polyimide film was implemented by the following methods.

(Average particle size / size distribution)
Silica particles were photographed with an electron microscope, and 300 particle sizes were measured from the photographed images. From 300 measured silica particles, 10 upper and lower limits were excluded, and the average particle size and particle size distribution were calculated from the remaining 280 particle sizes. The average particle diameter was the number average, and the particle size distribution was calculated as the difference between the maximum and minimum particle diameters from the average particle diameter.

(Measurement of friction coefficient)
Measured according to ASTM D1894.

(Measurement of surface roughness)
In accordance with JIS standard (JISB0601-1982), surface roughness using a scanning probe microscope (SP-400 manufactured by SII NanoTechnology Co., Ltd.) and a data analysis device (NanoNavi station manufactured by SII NanoTechnology Co., Ltd.) Was measured. The measurement mode was a dynamic force mode (DFM), the scanner used SPA400-PZTFS150N, and the cantilever used SI-DF40. A measurement sample is cut out to 5 × 5 mm, and is fixed to a sample table with double-sided tape. The measurement area was 50 × 50 μm. After the measurement, using a data analysis device, average surface roughness (Ra), root mean square surface roughness (RMS), and 10-point average roughness (Rz) were determined, and an average value of N = 3 was taken as a measured value.

Average surface roughness (Ra), root mean square surface roughness (RMS), and 10-point average roughness (Rz) are defined as follows.
When the range of (X, Y) is (X _L , Y _B ) to (X _R , Y _T ), the surface area (S ₀ ) of the measurement surface is given by

If the average value of the height data (Z) in the measurement surface is Z ₀ ,

It becomes a plane parallel to the XY plane represented by Z ₀ is obtained by the following equation.

The average surface roughness (Ra) is a value obtained by averaging the absolute values of deviations from the reference surface to the designated surface, and is given by the following equation.

The root mean square roughness (RMS) is a square root of a value obtained by averaging the squares of deviations from the reference plane to the designated plane, and is given by the following equation.

The 10-point average roughness (Rz) is a value representing the difference between the average value of the height data of the peak from the maximum to the fifth on the measurement surface and the average value of the depth data of the valley from the minimum to the fifth. .

(Number of protrusions derived from silica particles)
Using the data analysis device, the data after analysis was made three-dimensional, the number of protrusions derived from 50 μm square silica particles was counted, and the average value of N = 3 was converted to 1 cm square to obtain the number of protrusions.

(Synthesis Example 1)
20 mol equivalent of 4,4′-oxydianiline (ODA) dissolved in N, N-dimethylformamide (DMF) cooled to 10 ° C., and 30 mol equivalent of 2,2-bis (4-aminophenoxyphenyl) propane (BAPP) did. 20 mol equivalent of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 25 mol equivalent of pyromellitic dianhydride (PMDA) were added thereto and stirred for 30 minutes. Further, 50 mol equivalent of paraphenylenediamine (PDA) was dissolved, and then 51 mol equivalent of PMDA was added and dissolved to obtain a prepolymer. The prepolymer viscosity was 15 poise.
A separately prepared PMDA DMF solution (7% by weight) was gradually added dropwise to this prepolymer solution, and the addition was stopped when the viscosity reached about 2000 poises, followed by uniform stirring for 1 hour. The finally obtained solution had a viscosity at 23 ° C. of 2300 poise and a solid content concentration of 15% by weight.

Example 1
Spherical silica particles (average particle size: 0.55 μm, particle size distribution: −9.1 to + 9.1%) were added so as to be 10% by weight with respect to DMF, and dispersed for 90 minutes using an ultrasonic disperser. It added so that the silica particle content in a film might be 0.02 weight% with respect to the prepolymer solution obtained by the synthesis example 1 here, and it stirred for 30 minutes. Subsequently, a PMDA solution was added in the same manner as in Synthesis Example 1 to finally obtain a polyamic acid solution having a viscosity at 23 ° C. of 2300 poise.
To this solution, a curing agent composed of acetic anhydride / isoquinoline / DMF (weight ratio 20:10:80) was continuously stirred by a mixer at a weight ratio of 50% with respect to the polyamic acid solution, extruded from a T die, and extruded from the die. The bottom 25 mm was cast on a stainless endless belt running at a speed of 10 mm / min. This resin film was dried and imidized at 130 ° C. × 100 seconds, 300 ° C. × 20 seconds, 450 ° C. × 20 seconds, 500 ° C. × 20 seconds to obtain a 35 μm polyimide film. The properties of this polyimide film are shown in Table 1.

(Example 2)
Example 1 except that spherical silica particles (average particle size 0.55 μm, particle size distribution −9.1 to + 9.1%) were added so that the silica particle content in the film was 0.06 wt%. In the same manner, a polyimide film was obtained. The properties of this film are shown in Table 1.

(Example 3)
Example 1 except that spherical silica particles (average particle size: 0.33 μm, particle size distribution: 12.1 to + 9.1%) were added so that the silica particle content in the film was 0.03% by weight. In the same manner, a polyimide film was obtained. The properties of this film are shown in Table 1.

(Comparative Example 1)
Except that spherical silica particles (average particle size 0.25 μm, particle size distribution −60 to + 300%) were added so that the silica particle content in the film was 0.10% by weight, the same procedure as in Example 1 was performed. A polyimide film was obtained. The properties of this film are shown in Table 1.

(Comparative Example 2)
Example 1 except that spherical silica particles (average particle size 0.55 μm, particle size distribution −9.1 to + 9.1%) were added so that the silica particle content in the film was 0.10 wt%. In the same manner, a polyimide film was obtained. The properties of this film are shown in Table 1.

Claims (4)

Contains 0.01 to 0.08 wt% of spherical silica particles having an average particle size of 0.2 to 0.7 μm and a particle size distribution within ± 15% of the average particle size per resin weight, and the silica particle-derived protrusions on the film surface A polyimide film having a number of 0.1 to 1.5 × 10 ⁶ per cm ² .   The average surface roughness (Ra) of the film is 1 to 5 nm, the root mean square surface roughness (RMS) is 1 to 10 nm, and the 10-point average roughness (Rz) is 50 to 300 nm. The polyimide film described in 1.   The polyimide film according to claim 1 or 2, wherein a static friction coefficient between films is 0.5 to 2.0, and a dynamic friction coefficient is 0.4 to 1.0. The polyimide film according to claim 1, wherein the film thickness is 5 to 75 μm.