JPH062827B2 - Roughened polyimide film and method for producing the same - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a roughened polyimide film. More specifically, the present invention relates to a roughened polyimide film which is particularly useful as a base film for high density recording media.

BACKGROUND OF THE INVENTION A film made of polyester such as polyethylene terephthalate has been generally used as a non-magnetic support (base film) for a magnetic recording medium such as a magnetic tape, but recently, heat resistance, strength, etc. It has been proposed to use an aromatic polyimide film.

As described above, heat resistance and strength are very important properties of the non-magnetic support, but at the same time, the surface condition of the support is also appropriate in order to obtain an excellent magnetic recording medium. Is a serious requirement. That is, a metal thin film type magnetic recording medium in which a magnetic substance layer is formed on the surface of a base film by vapor deposition or the like is capable of high-density recording, but the magnetic layer formed in this way has an extremely thin thickness.
The surface morphology of the base film used tends to appear as the surface morphology of the magnetic layer. Therefore, if the surface of the base film is too rough, there is a problem that the electromagnetic conversion characteristics are deteriorated, and for example, the output is decreased and the dropout is increased. On the other hand, when the film surface is made into a highly smooth state such as a mirror surface for the purpose of improving electromagnetic conversion characteristics, the slipperiness is remarkably lowered, and there is a problem that the running property and durability of the tape are deteriorated.

For the reasons described above, various methods have been proposed for imparting appropriate irregularities to the tape surface in order to improve the running property, abrasion resistance and durability of the tape. For example, a method of coating a tape surface with a coating liquid containing fine particles, a method of adding fine particles to a base film to give fine projections to the film surface, a polymer solution is coated on the base film surface, and then the film is stretched. Therefore, a method for forming a discontinuous film has been proposed. However, in these proposed methods, it is necessary to incorporate a fine particle dispersion, classification, filtration step, or a coating step or a stretching step into a conventional film forming step, and these steps have strict accuracy requirements, and the equipment Is expensive, and the operation control of film production is often difficult.

Further, with these conventional methods, it is not possible to obtain a base film having preferable unevenness like the polyimide film of the present invention shown below.

[Structure of the Invention] The main object of the present invention is to provide a film having excellent strength and heat resistance, and having an appropriate degree of unevenness which is particularly suitable for use as a base film of a high density recording medium such as a magnetic recording medium. And

The present invention provides a total aromatic tetracarboxylic acid component of 15
85 to 85 mol% of biphenyl tetracarboxylic acids
Aromatic tetracarboxylic acid component consisting of 15 mol% of pyromellitic acid, and 30 with respect to wholly aromatic diamine component
An aromatic polyimide film obtained from an aromatic diamine component consisting of -100 mol% of phenylenediamines and 70-0 mol% of diaminodiphenyl ethers, wherein fine projections having a diameter of 0.02 to 2 µm are formed on the film surface. The roughened polyimide film is characterized by being present in a number in the range of 10 ⁴ to 10 ⁸ pieces / mm ² .

The above-mentioned roughened polyimide film is an aromatic tetracarboxylic acid component composed of 15 to 85 mol% of biphenyltetracarboxylic acid and 85 to 15 mol% of pyromellitic acid relative to the wholly aromatic tetracarboxylic acid component. Aroma by heating a polyamic acid obtained from an aromatic diamine component comprising 30 to 100 mol% of phenylenediamines and 70 to 0 mol% of diaminodiphenyleethers with respect to the wholly aromatic diamine component. In producing the group-polyimide film, the maximum heating temperature in the above heating step can be easily produced by making it higher than the glass transition temperature of the obtained aromatic polyimide film.

Hereinafter, the method for producing the roughened polyimide of the present invention will be described in detail with reference to typical embodiments.

The aromatic polyamic acid used in the method for producing a roughened polyimide of the present invention is 15 to 85 mol% of biphenyltetracarboxylic acid and 85 to 15 mol% of pyromellitic acid with respect to the wholly aromatic tetracarboxylic acid component. An aromatic tetracarboxylic acid component consisting of, and an aromatic diamine component consisting of 30 to 100 mol% of phenylenediamines and 70 to 0 mol% of diaminodiphenyl ethers relative to the wholly aromatic diamine component, Use equimolar,
It is an aromatic polyamic acid obtained by polymerization in an organic polar solvent.

Examples of the biphenyltetracarboxylic acids include biphenyltetracarboxylic acid, a dianhydride thereof, a lower alkyl ester thereof, and a mixture thereof. As the biphenyl tetracarboxylic acids, 2,
Preferable examples include 3 ', 3,4'-biphenyltetracarboxylic acids and 3,3', 4,4'-biphenyltetracarboxylic acids.

Examples of the pyromellitic acid include pyromellitic acid, a dianhydride thereof, a lower alkyl ester thereof, and a mixture thereof.

The aromatic tetracarboxylic acid component contains other aromatic compounds in an amount of 70 mol% or less, preferably 50 mol% or less, more preferably 30 mol% or less based on the total aromatic tetracarboxylic acid component. Tetracarboxylic acids may be used. Examples of such other aromatic tetracarboxylic acids include 3,3 ′, 4,4′-benzophenone tetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane,
Bis (3,4-dicarboxyphenyl) methane, bis (3,4-
Examples thereof include dicarboxyphenyl) ether, bis (3,4-dicarboxyphenyl) phosphine, and anhydrides of these carboxylic acids and lower alkyl esters.

In the present invention, phenylenediamines include 1,4-
Examples thereof include diaminobenzene (paraphenylenediamine), 1,3-diaminobenzene and 1,2-diaminobenzene.

In the present invention, the aromatic diamine component is 70 mol% or less, preferably 50 mol% or less, more preferably 30 mol% or less, and preferably 1 mol% or more, more preferably 5 mol, based on the total aromatic diamine component. Diaminodiphenyl ethers can also be used together in an amount of at least%. Preferable examples of such diaminodiphenyl ethers include 4,4′-diaminophenyl ether, 3,4-diaminodiphenyl ether, and 3,3′-diaminodiphenyl ether.

Note that the aromatic diamine component contains other aromatic diamines in an amount of 70 mol% or less, preferably 50 mol% or less, and more preferably 30 mol% or less with respect to the total aromatic diamine component. You may. Examples of such other aromatic diamine components include diphenylthioether-based diamis such as 4,4′-diaminodiphenylthioether, 3,
3'-diaminobenzophenone, benzophenone diamines such as 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylphosphine, diphenylphosphine diamines such as 4,4'-diaminodiphenylphosphine, 3,3'-
Examples thereof include diphenylmethane-based diamines such as diaminodiphenylmethane and 4,4′-diaminophenylmethane.

As the organic polar solvent used in the polymerization reaction, a solution that uniformly dissolves each monomer component, and / or an oligomer produced by both monomer components, or a low molecular weight polyamic acid is used. Examples of such organic polar solvents include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, amide solvents such as N-methylcaprolactam, dimethyl sulfoxide, and hexamethylfosformamide. , Dimethyl sulfone, tetramethylene sulfone, dimethyl tetramethylene sulfone, pyridine, ethylene glycol and the like. These organic polar solvents can also be used in admixture with other organic solubilizers such as benzene, toluene, benzonitrile, xylene, solvent naphtha, and dioxane.

When carrying out the polymerization reaction, the concentration of all the monomers in the organic polar solvent is 5 to 40% by weight, preferably 6 to 35% by weight, particularly preferably 10 to 30% by weight.

The polymerization reaction of the above-mentioned aromatic tetracarboxylic acid component and aromatic diamine component is carried out, for example, by practically mixing them in equimolar amounts, and at a reaction temperature of 100 ° C or lower, preferably 80 ° C.
It is carried out by carrying out the reaction for about 0.2 to 60 hours at a temperature of not more than 0 ° C.

The polyamic acid solution used for producing the polyimide film of the present invention has a rotational viscosity measured at 30 ° C.
About 0.1-50000 poise, especially 0.5-30000
Poise, more preferably about 1 to 20,000 poise, is preferable from the viewpoint of workability of handling this polyamic acid solution. Therefore, the above polymerization reaction is
It is desirable to carry out the polyamic acid produced to such an extent that it exhibits the above viscosity.

In the production of the polyimide film of the present invention, for example, first the solution of the aromatic polyamic acid described above is first prepared by using a suitable support (for example, a metal, ceramic or plastic roll, or a metal belt, or a metal thin film tape). On the surface of the roll (or belt) being fed, about 10-2000 μm, in particular 20-100
A polyamic acid solution having a uniform thickness of about 0 μm is formed into a film state, and then 60 using a heat source such as hot air or infrared rays.
By heating to ˜160 ° C. and gradually removing the solvent, pre-drying is performed until it becomes self-supporting, and the self-supporting film is peeled from the support. The self-supporting film to be peeled off preferably has a weight loss upon heating in the range of 10 to 65% by weight, and particularly preferably in the range of 15 to 60% by weight.

The heating loss of the self-supporting film is a value calculated by the following equation from the weight W ₁ before drying and the weight W ₂ after drying after drying the symmetrical film for 20 minutes at 420 ° C. .

Heat loss (% by weight) = {(W ₁ -W ₂ ) / W ₁ } × 100 Next, the solvent contained in the self-supporting film was removed and the amide / acid bond was converted to an imide bond. To do so, heating at a temperature of about 100 ° C. or higher, thereby producing an aromatic polyimide film.

The maximum heating temperature for producing the aromatic polyimide film is not lower than the glass transition temperature (Tg) of the aromatic polyimide, preferably 20 ° C or higher than Tg, more preferably 30 to 200 ° C, and particularly preferably 50 to 160. By setting the temperature to ℃, it is possible to form fine projections under the desired conditions on the surface of the aromatic polyimide film to be formed.

Most of the size of the fine protrusions formed on the surface of the aromatic polyimide film produced under the above heating conditions is 0.
It is in the range of 02 to 2 μm. The size of the fine projections referred to here means the length of the maximum diameter portion of the fine projections observed when the film surface is magnified 10,000 times with an electron microscope.

The number of fine projections having a diameter of 0.02 to 2 μm formed on the surface of the aromatic polyimide film of the present invention is 10 ⁴ to 1
0 a ⁸ / mm ^2, preferably ¹⁰ 5 to 10 ⁸ /
It is in the range of mm ² , and more preferably in the range of 10 ⁶ to 10 ⁸ pieces / mm ² . The number of fine protrusions is a numerical value obtained by counting the number of protrusions having a maximum diameter of 0.02 μm or more observed when the film surface is magnified 10,000 times with an electron microscope.

The size and number of fine projections formed on the surface of the aromatic polyimide film of the present invention by the above method vary depending on the composition of the aromatic polyimide film, the glass transition temperature and the maximum heating temperature. As a general tendency, the larger the difference between the glass transition temperature and the maximum heating temperature, the larger the size of the fine projections formed on the film surface within the above range, and the larger the number thereof. Furthermore, when the 4,4'-diaminodiphenyl ether component is used as the aromatic diamine component, and the larger the amount used,
The size and number of fine protrusions formed on the surface of the film tend to increase. Further, even when the maximum heating temperature when converting the polyamic acid film into the polyimide film is the same, the appearance of the fine protrusions on the surface may be different due to the difference in the heating rate. Further, generally speaking, as the film thickness decreases, the size and number of fine protrusions tend to decrease.

The thickness of the roughened polyimide film in the present invention is usually in the range of 1 to 100 μm, preferably 2 to 50 μm.
It is in the range of m.

[Effect of the Invention] The roughened aromatic polyimide film of the present invention is obtained by using a specific amount of biphenyltetracarboxylic acid and pyromellitic acid in combination as an aromatic carboxylic acid component for the production thereof. Such an aromatic polyimide film has excellent mechanical properties, for example, high tensile strength (usually about 20 kg / mm ² or more, 25 k
g / mm ² or more), a suitable elastic modulus (usually about 300 to 900 kg / mm ² ), and excellent thermal properties such as a high second-order transition temperature (usually about 300).
Since it has a high thermal decomposition temperature (usually about 400 ° C. or higher), it exhibits excellent properties especially as a support for magnetic recording media such as magnetic tapes.

Further, the roughened polyimide film of the present invention has an appropriate amount of fine projections on the surface thereof, and therefore, when the magnetic recording layer is formed thereon, the surface of the recording layer has a substantially equal amount. To have fine protrusions. Therefore, when used as a base film for a magnetic recording medium, particularly as a base film for a metal thin film magnetic recording medium, the resulting magnetic recording medium has good electromagnetic conversion characteristics and excellent running properties and durability.

Next, examples and comparative examples of the present invention will be described.

Each physical property value and evaluation method are as follows.

(1) Glass transition temperature: Determined by a tensile method using a TMA apparatus manufactured by Rigaku Denki Co., Ltd.

(2) Number of fine protrusions: The film surface was observed with an electron microscope at a magnification of 10,000, and the number of protrusions having a maximum diameter of 0.02 μm or more was counted.

(3) Electromagnetic conversion characteristics: recorded at a center frequency of 4.5 MHz,
The S / N ratio (relative value) in the case of reproduction was measured using Comparative Example 14 as a reference (0 dB).

A: The output is larger than -3 dB.

B: The output is smaller than -3 dB.

(4) Runnability: We observed screen drooping due to irregular running of the tape.

A: The running performance was good and there was no droop on the playback screen.

B: Running performance is poor and playback screen is distorted.

(5) Durability: Scratches on the magnetic surface and a decrease in output were observed after running 100 times.

A: Almost no scratches or weak scratches. The output drop is less than -3 dB.

B: Strong abrasion is observed. The output drop is greater than -3 dB.

[Example 1] N, N-dimethylacetamide 448 g, p-phenylenediamine (PPD) 22.
709 g (0.21 mol), 4,4'-diaminodiphenyl ether (4,4'-DADE) 18.022 g (0.09)
Mol) and stirred at room temperature (about 30 ° C.) in nitrogen. To this solution, 44.133 g (0.15 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 32.718 g of pyromellitic dianhydride (PMDA) were added.
(0.15 mol) was added and stirred for 6 hours to obtain a solution of polyamic acid. Logarithmic viscosity of this solution (30 ° C, 0.
5 g / 100 m, N, N-dimethylacetamide)
2.54, rotational viscosity 2400 poise (30 ° C)
Met. The viscosity was measured using an E viscometer manufactured by Tokyo Keiki Co., Ltd.

The polyamic acid solution was cast on a glass plate to form a film of the polyamic acid solution, the film was dried with hot air at 120 ° C. for 20 minutes, and the solvent was distilled off to form a polyamic acid film.

Next, the polyamic acid film was peeled off from the glass plate. The weight loss on heating of this film was 34.1% by weight.

This polyamic acid film was attached to a metal frame, and the temperature was raised from 200 ° C. to 400 ° C. in a hot air dryer for 20 minutes to prepare an aromatic polyimide film having a thickness of 35 μm. The glass transition temperature of this aromatic polyimide film was 360 ° C.

The number of fine protrusions on the surface of this aromatic polyimide film is 5.
It was 0 × 10 ⁶ mm ² .

Example 2 The maximum heating temperature of polyamic acid was 450 ° C. (Tg of polyimide = 360 ° C.), and 200 ° C. to 450 ° C.
An aromatic polyimide film having a thickness of 35 μm was prepared in the same manner as in Example 1 except that the temperature was raised for 5 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 2.
It was 6 × 10 ⁷ pieces / mm ² .

Example 3 The maximum heating temperature of polyamic acid was 450 ° C. (Tg of polyimide = 360 ° C.), and 200 ° C. to 450 ° C.
An aromatic polyimide film having a thickness of 21 μm was prepared in the same manner as in Example 1 except that the temperature was raised for 5 minutes and then heating was performed at 450 ° C. for 5 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 2.
It was 3 × 10 ⁷ pieces / mm ² .

Example 4 The maximum heating temperature of polyamic acid was 450 ° C. (Tg of polyimide = 360 ° C.), and 200 ° C. to 450 ° C.
An aromatic polyimide film having a thickness of 10 μm was prepared in the same manner as in Example 1 except that the temperature was raised for 5 minutes and then heating was performed at 450 ° C. for 5 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 1.
It was 0 × 10 ⁷ pieces / mm ² .

Example 5 The maximum heating temperature of polyamic acid was 450 ° C. (polyimide Tg = 360 ° C.), and 200 ° C. to 450 ° C. was used.
An aromatic polyimide film having a thickness of 56 μm was prepared in the same manner as in Example 1 except that the temperature was raised for 1 minute and then heating was performed at 450 ° C. for 5 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 1.
It was 8 × 10 ⁷ pieces / mm ² .

Example 6 The maximum heating temperature of polyamic acid was 450 ° C. (Tg of polyimide = 360 ° C.), and 200 ° C. to 450 ° C.
An aromatic polyimide film having a thickness of 12 μm was prepared in the same manner as in Example 1 except that the temperature was raised for 0 minutes and the heating was performed at 450 ° C. for 5 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 5.
It was 0 × 10 ⁶ pieces / mm ² .

[Comparative Example 1] The maximum heating temperature of the polyamic acid was set to 300 ° C (Tg of polyimide = 360 ° C), and 200 ° C to 300 ° C was set to 1
An aromatic polyimide film having a thickness of 35 μm was prepared in the same manner as in Example 1 except that the temperature was raised for 0 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Comparative Example 2] The maximum heating temperature of polyamic acid was set to 350 ° C (Tg of polyimide = 360 ° C), and 200 ° C to 350 ° C was set to 1
An aromatic polyimide film having a thickness of 35 μm was prepared in the same manner as in Example 1 except that the temperature was raised for 5 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Evaluation as Magnetic Tape Support] On the surface of the polyimide film obtained in each example, a Co—Cr alloy bath having a thickness of 0.2 μm was formed by vacuum vapor deposition to form a magnetic tape, and the electromagnetic conversion characteristics of the magnetic tape, The running property and durability were evaluated by the method of the previous term. The result is first
Shown in the table.

[Example 7] The amount of p-phenylenediamine (PPD) used was 0.15.
Mol, and 4,4'-diaminodiphenyl ether (4,4'-
A polyamic acid was obtained in the same manner as in Example 1 except that the amount of DADE) used was changed to 0.15 mol. The logarithmic viscosity (30 ° C., 0.5 g / 100 m, N, N-dimethylacetamide) of this solution was 2.61, and the rotational viscosity was 43.
It was 00 poise (30 ° C.).

The polyamic acid solution was cast on a glass plate to form a film of the polyamic acid solution, the film was dried with hot air at 120 ° C. for 20 minutes, and the solvent was distilled off to form a polyamic acid film.

Next, the polyamic acid film was peeled off from the glass plate. The weight loss on heating of this film was 37.6% by weight.

This polyamic acid film was attached to a metal frame, and the temperature was raised from 200 ° C. to 400 ° C. in a hot air dryer for 20 minutes to prepare an aromatic polyimide film having a thickness of 39 μm. The glass transition temperature of this aromatic polyimide film was 330 ° C.

The number of fine protrusions on the surface of this aromatic polyimide film is 2.
It was 8 × 10 ⁷ pieces / mm ² .

[Example 8] The thickness was the same as in Example 7 except that the maximum heating temperature of the polyamic acid was 410 ° C (Tg of polyimide = 330 ° C) and the temperature was raised from 200 ° C to 410 ° C for 20 minutes. A 39 μm aromatic polyimide film was prepared.

The number of fine protrusions on the surface of this aromatic polyimide film is 2.
It was 5 × 10 ⁷ pieces / mm ² .

Example 9 The maximum heating temperature of polyamic acid was 450 ° C. (Tg of polyimide = 330 ° C.), and 200 ° C. to 450 ° C.
An aromatic polyimide film having a thickness of 39 μm was prepared in the same manner as in Example 7 except that the temperature was raised for 5 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 4.
It was 1 × 10 ⁷ pieces / mm ² .

[Comparative Example 3] The maximum heating temperature of polyamic acid was set to 300 ° C (Tg of polyimide = 330 ° C), and 200 ° C to 300 ° C was set to 1
An aromatic polyimide film having a thickness of 39 μm was prepared in the same manner as in Example 7 except that the temperature was raised for 0 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Comparative Example 4] The maximum heating temperature of the polyamic acid was set to 340 ° C (Tg of polyimide = 350 ° C), and 200 ° C to 350 ° C was set to 1
An aromatic polyimide film having a thickness of 39 μm was prepared in the same manner as in Example 7 except that the temperature was raised for 5 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Evaluation as Magnetic Tape Support] On the surface of the polyimide film obtained in each example, a Co—Cr alloy layer having a thickness of 0.2 μm was formed by vacuum vapor deposition to form a magnetic tape. The runnability and durability were evaluated by the above methods. The result is the second
Shown in the table.

[Example 10] The amount of p-phenylenediamine (PPD) used was 0.12.
Mol and 4,4'-diaminodiphenyl ether (4,4'-
The amount of DADE) was changed to 0.15 mol, and 3,3 ', 4,4'-
Other than changing the amount of biphenyltetracarboxylic dianhydride (s-BPDA) used to 0.12 mol and the amount of pyromellitic dianhydride (PMDA) to 0.18 mol,
A polyamic acid was obtained in the same manner as in Example 1. The logarithmic viscosity (30 ° C., 0.5 g / 100 m, N, N-dimethylacetamide) of this solution is 2.01, and the rotational viscosity is 1
It was 500 poise (30 ° C.).

The polyamic acid solution was cast on a glass plate to form a film of the polyamic acid solution, the film was dried with hot air at 120 ° C. for 20 minutes, and the solvent was distilled off to form a polyamic acid film.

Next, the polyamic acid film was peeled off from the glass plate. The weight loss on heating of this film was 36.2% by weight.

This polyamic acid film was attached to a metal frame, and the temperature was raised from 200 ° C. to 400 ° C. in a hot air dryer for 20 minutes to prepare an aromatic polyimide film having a thickness of 43 μm. The glass transition temperature of this aromatic polyimide film was 350 ° C.

The number of fine protrusions on the surface of this aromatic polyimide film is 9.
It was 0 × 10 ⁶ pieces / mm ² .

Example 11 The maximum heating temperature of polyamic acid was 410 ° C. (Tg of polyimide = 350 ° C.), and 200 ° C. to 410 ° C.
An aromatic polyimide film having a thickness of 43 μm was prepared in the same manner as in Example 10 except that the temperature was raised for 0 minutes.

The number of fine protrusions on the surface of the aromatic polyimide film is 3.
It was 4 × 10 ⁷ pieces / mm ² .

Example 12 The maximum heating temperature of polyamic acid was 450 ° C. (Tg of polyimide = 350 ° C.), and 200 ° C. to 450 ° C.
An aromatic polyimide film having a thickness of 43 μm was prepared in the same manner as in Example 10 except that the temperature was raised for 5 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 2.
It was 3 × 10 ⁷ pieces / mm ² .

[Comparative Example 5] The maximum heating temperature of polyamic acid was set to 300 ° C (Tg of polyimide = 350 ° C), and 200 ° C to 300 ° C was set to 1
An aromatic polyimide film having a thickness of 43 μm was prepared in the same manner as in Example 10 except that the temperature was raised for 0 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Comparative Example 6] The maximum heating temperature of the polyamic acid was set to 340 ° C (Tg of polyimide = 350 ° C), and 200 ° C to 350 ° C was set to 1
An aromatic polyimide film having a thickness of 43 μm was prepared in the same manner as in Example 10 except that the temperature was raised for 5 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Evaluation as Magnetic Tape Support] On the surface of the polyimide film obtained in each example, a Co—Cr alloy layer having a thickness of 0.2 μm was formed by vacuum vapor deposition to form a magnetic tape. The runnability and durability were evaluated by the above methods. The result is the third
Shown in the table.

[Example 13] The amount of p-phenylenediamine (PPD) used was 0.12.
Mol and 4,4'-diaminodiphenyl ether (4,4'-
Change the amount of DADE) to 0.18 mol, and change to 3,3 ', 4,4'-
Except that the amount of biphenyltetracarboxylic dianhydride (s-BPDA) used was changed to 0.09 mol and the amount of pyromellitic dianhydride (PMDA) used was changed to 0.21 mol,
A polyamic acid was obtained in the same manner as in Example 1. The logarithmic viscosity (30 ° C., 0.5 g / 100 m, N, N-dimethylacetamide) of this solution is 1.90, and the rotational viscosity is 1.
It was 200 poise (30 ° C.).

The polyamic acid solution was cast on a glass plate to form a film of the polyamic acid solution, the film was dried with hot air at 120 ° C. for 20 minutes, and the solvent was distilled off to form a polyamic acid film.

Next, the polyamic acid film was peeled off from the glass plate. The weight loss on heating of this film was 34.7% by weight.

This polyamic acid film was attached to a metal frame, and the temperature was raised from 200 ° C. to 400 ° C. in a hot air drier for 20 minutes to prepare an aromatic polyimide film having a thickness of 37 μm. The glass transition temperature of this aromatic polyimide film was 350 ° C.

The number of fine protrusions on the surface of this aromatic polyimide film is 1.
It was 2 × 10 ⁷ pieces / mm ² .

Example 14 The maximum heating temperature of polyamic acid was 410 ° C. (Tg of polyimide = 350 ° C.), and 200 ° C. to 410 ° C.
An aromatic polyimide film having a thickness of 37 μm was prepared in the same manner as in Example 10 except that the temperature was raised for 0 minutes.

The number of fine protrusions on the surface of this aromatic polyimide film is 4.
It was 2 × 10 ⁷ pieces / mm ² .

Example 15 The maximum heating temperature of polyamic acid is 450 ° C. (Tg of polyimide = 350 ° C.), and 200 ° C. to 450 ° C.
An aromatic polyimide film having a thickness of 37 μm was prepared in the same manner as in Example 10 except that the temperature was raised for 5 minutes.

The number of fine protrusions on the surface of the aromatic polyimide film is 3.
It was 6 × 10 ⁷ pieces / mm ² .

[Comparative Example 7] The maximum heating temperature of polyamic acid was set to 300 ° C (Tg of polyimide = 350 ° C), and 200 ° C to 300 ° C was set to 1
An aromatic polyimide film having a thickness of 37 μm was prepared in the same manner as in Example 13 except that the temperature was raised for 0 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Comparative Example 8] The maximum heating temperature of polyamic acid was set to 340 ° C (Tg of polyimide = 350 ° C), and 200 ° C to 350 ° C was set to 1
An aromatic polyimide film having a thickness of 43 μm was prepared in the same manner as in Example 13 except that the temperature was raised for 5 minutes.

No fine projections were formed on the surface of this aromatic polyimide film.

[Evaluation as Magnetic Tape Support] On the surface of the polyimide film obtained in each example, a Co—Cr alloy layer having a thickness of 0.2 μm was formed by vacuum vapor deposition to form a magnetic tape. The runnability and durability were evaluated by the above methods. The result is the fourth
Shown in the table.

[Examples 16 to 28] p-Phenylenediamine (PPD), 4,4'-diaminophenyl ether (4,4'-DADE), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride ( s-BPDA) and pyromellitic dianhydride (PMDA) were changed to the amounts shown in Table 5, respectively, to obtain a polyamic acid in the same manner as in Example 1.

The resulting polyamic acid solution is cast on a glass plate to form a film of the polyamic acid solution, and the film is formed at 120 ° C.
After drying for 20 minutes with hot air to evaporate the solvent to form a polyamic acid film, this film was peeled off. This polyamic acid film was attached to a metal frame and heated from 200 ° C to 5 2 to the maximum temperature shown in the table
0 minutes (when the maximum temperature is 400 ° C and 410 ° C),
Alternatively, the temperature was raised for 25 minutes (when the maximum temperature was 450 ° C.) to prepare an aromatic polyimide film having a thickness shown in Table 5.

The number of fine projections on the surface of the obtained aromatic polyimide film is shown in Table 5.

A 0.2 μm-thick Co—Cr alloy layer was formed on the surface of the polyimide film obtained in Examples 16 to 28 to form a magnetic tape, and the electromagnetic conversion characteristics, running property and durability of the magnetic tape were measured. Was evaluated by the above method, the evaluation of A was obtained for all the items.

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Claims (7)

[Claims] 1. A total aromatic tetracarboxylic acid component relative to 1
5-85 mol% biphenyl tetracarboxylic acids and 85
Aromatic tetracarboxylic acid component consisting of ~ 15 mol% of pyromellitic acid, and 3 with respect to wholly aromatic diamine component
An aromatic polyimide film obtained from an aromatic diamine component consisting of 0 to 100 mol% of phenylenediamines and 70 to 0 mol% of diaminodiphenyl ethers, wherein fine projections having a diameter of 0.02 to 2 μm are formed on the film surface. Is present at a number in the range of 10 ⁴ to 10 ⁸ pieces / mm ² , a roughened polyimide film. 2. A diameter of the film surface of 0.02 to 2 μm
^2. The roughened polyimide film according to claim 1, wherein the number of the fine protrusions is in the range of 10 ⁵ to 10 ⁸ pieces / mm ² . 3. The film surface has a diameter of 0.02 to 2 μm.
^2. The roughened polyimide film according to claim 1, wherein the number of fine protrusions is in the range of 10 ⁶ to 10 ⁸ / mm ² . 4. The first to third aspects of the present invention, wherein the fine protrusions are substantially made of polyimide.
The roughened polyimide film according to any one of the items. 5. One for every wholly aromatic tetracarboxylic acid component.
5-85 mol% biphenyl tetracarboxylic acids and 85
Aromatic tetracarboxylic acid component consisting of ~ 15 mol% of pyromellitic acid, and 3 with respect to wholly aromatic diamine component
In producing an aromatic polyimide film by heating a polyamic acid obtained from an aromatic diamine component consisting of 0 to 100 mol% of phenylenediamines and 70 to 0 mol% of diaminodiphenyl ethers, in the above heating step, The maximum heating temperature is set higher than the glass transition temperature of the aromatic polyimide film obtained, and the diameter of the film surface is 0.02 to 2
A method for producing a roughened polyimide film, wherein the number of micron-sized fine protrusions is 10 ⁴ to 10 ⁸ / mm ² . 6. The method for producing a roughened polyimide film according to claim 5, wherein the maximum heating temperature is set to 20 ° C. or more higher than the glass transition temperature of the obtained aromatic polyimide film. . 7. The maximum heating temperature is 30 to 200 ° C. higher than the glass transition temperature of the aromatic polyimide film obtained.
The method for producing a surface-roughened polyimide film according to claim 5, wherein the height is increased.