JPH0677984B2 - Polyimide film for recording medium and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a highly slipping layer containing a first inorganic filler having an average particle size of 400 to 2000Å in an amount of 0.5 to 5% by weight based on a polyimide resin. And a second inorganic filler having an average particle size smaller than that of the first inorganic filler, a two-layer extruded polyimide film consisting of a low slipping layer containing a ratio lower than the content ratio of the first inorganic filler. And a polyimide film for a recording medium, in which the surface properties of the high-slidable layer and the low-slidable layer of the film are significantly different from each other, which are important for the film for the recording medium, and a method for producing the film. Is.

The polyimide film for a recording medium of the present invention can be preferably used as a heat resistant base film for providing a magnetic layer and the like.

[Description of Prior Art]

Conventionally, aromatic polyimide films have a magnetic layer such as a Co-Cr alloy because they have high mechanical properties and heat resistance.
It is used as a base film that can be provided by a vacuum deposition method, a sputtering method, or the like.

However, the aromatic polyimide film is not always sufficient in terms of slipperiness (lubricity), and in order to impart slipperiness, an inorganic filler (lubricant) is incorporated and fine irregularities are formed on the surface of the film. A slippery film having is proposed.

However, since the above-mentioned slippery film is generally roughened (slippery) by fine irregularities on both sides by the built-in inorganic filler, the surface of one of the films is magnetic. Even if a magnetic recording medium was manufactured by providing layers, the obtained magnetic recording medium could not stably have sufficient output in magnetic recording.

Further, as a method for producing a polyimide film having another polymer coating layer on one side of an aromatic polyimide film, described in Japanese Patent Publication No. 55-2193, "two layers of polyamic acid film coated with another polymer solution. A method for producing a polyimide film "is known, and the applicant of the present invention utilizes the known method as" a method for imparting slipperiness to one surface of a film ",
"In the manufacturing process of the polyimide film, an aromatic polyimide film in which a polymer solution containing a slippery agent is applied to only one side, dried, and heat-treated to provide a coating layer having slipperiness on only one side. The method of manufacturing "is applied for as Japanese Patent Application No. 62-136365.
In the film-forming method by this coating method, the chance of mixing foreign matter into the film increases in the film-forming step, and
Generally, in a very thin coating layer, surface protrusion due to slipperiness that is filled may not be solved and may not be smoothed, and the obtained film may be curled. However, the polyimide film having a smooth surface and a slippery surface may not be produced with good reproducibility, which is not always satisfactory.

[Problems to be Solved by the Present Invention]

The object of the present invention is to solve all of the various problems that the above-mentioned known polyimide films for recording media have, "a low-slidability layer and a high-easy-slip layer that can be preferably used as a film for a recording medium. To provide an aromatic polyimide film "by a novel two-layer extrusion molding having and a new production method by the two-layer extrusion molding capable of easily and reproducibly producing the two-layer extrusion polyimide film. It is to be.

[Means for solving problems]

A first invention of this application is a highly slipping layer containing a first inorganic filler having an average particle diameter of 400 to 2000Å in a proportion of 0.5 to 5% by weight with respect to a polyimide resin, and the first inorganic filler. A second inorganic filler having an average particle size of 0.05 to 0.7 times the average particle size, a low slipping layer containing a ratio of 0.1 to 0.8 times the content of the first inorganic filler with respect to the polyimide resin. A two-layer extruded polyimide film consisting of, wherein the surface A _{0 of the} highly slippery layer A has an average surface roughness (A / Ra) of 20 to 100.
Å, and, microprojection average height (A / Ha) 100~500Å and having a surface B ₀ of TeiekiNameraso B has an average surface roughness of the surface A ₀ of KoekiNamera layer (A / Ra) 0.2-0.8 times the average surface roughness (B / Ra), 0.2-0.8 of the fine projection average height (A / Ha) of the surface A ₀ of the highly slippery layer A.
The present invention relates to a polyimide film for a recording medium, which has double the average height of fine protrusions (B / Ha).

The second invention of this application is a first aromatic polyamic acid solution containing a first inorganic filler having an average particle size of 400 to 2000Å in a proportion of 0.5 to 5% by weight with respect to the aromatic polyamic acid. The second inorganic filler having an average particle diameter of 0.1 to 0.7 times the average particle diameter of the first inorganic filler, 0.1 to 0.8 of the content ratio of the first inorganic filler with respect to the aromatic polyamic acid. A second aromatic polyamic acid solution containing in a proportion that is double the amount is simultaneously supplied to an extruder having a two-layer extrusion molding die, and a two-layer thin film of both solutions is discharged from the discharge port of the die. The body is continuously extruded onto a smooth support, and the thin film on the support is dried to form a self-supporting film, then
Peel off the self-supporting film from the support, and finally,
The present invention relates to a method for producing a polyimide film for a recording medium, which comprises heat-treating the self-supporting film.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a drawing schematically showing a micrograph of a cross section of the polyimide film for recording medium of the present invention.

FIG. 2 is a sectional view showing an example of the outline of a film forming apparatus used in the method for producing a polyimide film for a recording medium of the present invention, and FIGS. 3 and 4 are installed in the film forming apparatus. FIG. 3 is a cross-sectional view schematically showing an example of a two-layer extrusion die.

The polyimide film of the present invention, as shown in FIG. 1, has a highly slipping layer A containing a slippery lubricant consisting of a specific fine first inorganic filler along one side of the film, and on the other side thereof. Along with this, the low-slidability layer B containing the specific second inorganic filler in an appropriately small amount is continuously and integrally formed in the thickness direction of the film. It is composed of a two-layer extruded aromatic polyimide film obtained by a solution casting film forming method.

The two-layer extruded polyimide film of the present invention, the aromatic polyimide matrix forming the film, even when observed by an electron micrograph, does not find a particularly clear boundary surface in any of the thickness directions, and There is no definite interface that allows the film to be separated into two layers, and the polyimide matrix forms a substantially continuous phase.

The aromatic polyimide may be a heat-resistant high molecular weight polymer obtained by polymerization and imidization from an aromatic tetracarboxylic acid component and an aromatic diamine component.

The aromatic tetracarboxylic acid component, for example, 3,
Biphenyltetracarboxylic acids such as 3 ', 4,4'-biphenyltetracarboxylic acid or its acid dianhydride, 2,3,3', 4'-biphenyltetracarboxylic acid or its acid dianhydride, pyromet acid or its Pyromellitic acids such as acid dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid or acid dianhydride thereof can be mentioned.

Further, as the aromatic diamine, diphenyl ether type diamine compounds such as 4,4′-diaminodiphenyl ether and 3,4′-diaminodiphenyl ether, 4,
Examples thereof include diphenyl sulfone-based diamine compounds such as 4'-diaminodiphenyl sulfone and 3,4'-diaminodiphenyl sulfone, and phenylene diamine compounds such as o-, m- or p-phenylenediamine.

In the present invention, as the aromatic polyimide, (a) an aromatic tetracarboxylic acid component containing 50% by mole or more, particularly 60% by mole or more of biphenyltetracarboxylic acids with respect to the total acid component, and phenylenediamine as a total diamine component Or 50% by mole or more, particularly 60% by mole or more of an aromatic diamine component, or (b) biphenyltetracarboxylic acids (50% by mole or more,
55-90 mol%) and pyromellitic acids (less than 50 mol%, especially 10-45 mol%) as the main components, aromatic tetracarboxylic acid component, and phenylenediamine (50 mol% or more, especially 55- 95 mol%) and diaminodiphenyl ether (containing less than 50 mol%, especially 5 to 45 mol%) as the main components, and an aromatic diamine component in both components in equimolar amounts in an organic solvent to polymerize the polyamic acid. An aromatic polyimide obtained by generating an acid and imidizing it when molding a polyimide film from the polyamic acid is particularly preferable in terms of mechanical properties, heat resistance, dimensional stability, and the like.

As the type of the first and second inorganic fillers, fine particle-shaped inorganic fillers generally used as a slip agent can be used, and examples thereof include silica, colloidal silica, titanium oxide, and calcium carbonate. Inorganic fillers made of magnesium oxide, alumina, or the like can be preferably used, and the materials of the first inorganic filler and the second inorganic filler may be the same or different.

In this invention, the average particle size of the first inorganic filler is
400 ~ 2000 Å, preferably about 400 ~ 1000 Å, the average particle size of the second inorganic filler is 0.05 ~ 0.7 times the average particle size of the first inorganic filler, preferably about 0.1 ~ 0.6 times. An inorganic filler having an average particle size.

The average particle diameter of the second inorganic filler is 500 Å or less, particularly about 100 ~ 450 Å, more preferably about 200 ~ 400 Å, formed by two-layer extrusion using the second inorganic filler. When a magnetic layer is provided on the surface of the low-slip layer of the two-layer extruded polyimide film, it is possible to form a magnetic recording medium having excellent electromagnetic conversion characteristics of the magnetic recording medium and the durability of the magnetic layer. Optimal.

In the two-layer extruded polyimide film of the present invention, the compounding density of the first inorganic filler contained in the high-slidability layer, and the compounding density of the second filler contained in the low-slidability layer are both in each layer. Approximately 1 × 10 ^{4 to} 5 observed from the surface with an electron microscope
× 10 ⁷ cells / mm ^2, that is a ratio such particularly from 5 × 10 ⁴ to 1 × 10 ⁷ cells / mm ² about the particle density is preferred from the viewpoint of handling properties of the film.

As shown in FIG. 1, the polyimide film has a highly slippery layer A containing a first inorganic filler and a low slippery layer B containing a second inorganic filler. The thickness ratio of each layer (A part / B part) is 0.1-1.
It is preferably 0, particularly 0.2 to 8, and more preferably about 0.3 to 5. Further, the total thickness of the aromatic polyimide film of the present invention (A portion + B portion) is about 2 to 200 μm.
m, especially about 3 to 150 μm, more preferably 5 to 60 μm
m is preferable from the viewpoint of flexibility of the film.

The polyimide film of the present invention, the surface A ₀ of the highly easy-slipping layer side in which the first inorganic filler is incorporated has a large number of minute projections based on the first inorganic filler, and,
Surface of the low-slidability layer side in which the second inorganic filler is incorporated
A large number of fine projections based on the second inorganic filler are projected on B ₀ .

The surface A ₀ of the highly easy-slipping layer side has an average surface roughness (A / Ra) of 20 to 100Å, preferably about 20 to 50Å, and a fine projection average height (A / Ha). Is 100-500Å,
It has preferably about 110 to 300Å, and the surface B ₀ of the low-slip layer B is 0.2 to 0.8 times the average surface roughness (A / Ra) of the surface A ₀ of the high-slip layer A, preferably 0.2 to 0.6 times the average surface roughness (B / Ra), 0.2 to 0.8 times the average fine projection average height (A / Ha) on the surface A ₀ of the highly slippery layer A, preferably 0.2 to 0.6 times the average fine projection height. (B / Ha).

In the present invention, the surface B ₀ of the low slip layer B of the two-layer extruded polyimide film has an average surface roughness (B / Ra) of 25 Å or less,
Especially 10 to 23Å, and the average height of fine protrusions (A / Ha)
Is 150 Å or less, especially about 20 to 120 Å, because an excellent magnetic layer can be formed on the surface of the low-slidability layer, which is most suitable.

Bilayer extruded polyimide film of the above is the surface A ₀ of KoekiNamera layer side, the "friction coefficient between films" when measured in contact by overlapping and surface B ₀ of TeiekiNamera layer, static friction A coefficient of about 0.1 to 0.7, preferably about 0.2 to 0.6 is suitable from the viewpoint of handling (handling property) in a processing step such as forming a magnetic recording medium of a film.

In the two-layer extruded polyimide film of the present invention, as described above, the surface A ₀ of the high easy-slip layer and the surface B ₀ of the low easy-slip layer of the film are preferably easily slipped, and their friction coefficients are Within a small range, the film is excellent in running property, processability and the like, and the surface B ₀ of the low-slidability layer of the film is a magnetic metal layer exhibiting excellent magnetic properties and durability. The point that it has a suitable surface property to form,
Most distinctive.

In the manufacturing method of the present invention, as shown in FIG.
For example, the first and second aromatic polyamic acid solutions a and b containing the first and second inorganic fillers are fed from the polymer solution supply ports 9a and 9b to an extruder having a two-layer extrusion molding die 1. , A simultaneous support, and then a two-layer thin film material of both solutions is wound around the pair of drive wheels 2 from the discharge port of the die 1 and rotated to rotate a smooth support (metal belt). 3) is continuously extruded onto the upper surface of the support 3, and in the casting furnace 6, the thin film body 4 on the upper surface of the support 3 is appropriately dried on the support 3 by a heater or a hot air blowing device 5. A self-supporting film 4'is formed, then the self-supporting film 4'is peeled from the support, and finally, the self-supporting film 4'is provided inside a plurality of heaters 11. The curing furnace 13 is passed through to add Processed to form an aromatic polyimide film 4 'of the present invention, further, it is cooled in the cooling chamber 20 to a room temperature (about 0 to 50 ° C.),
It is wound on a winding roll 30 of a winding machine 31 (not shown in its entirety).

The two-layer extrusion molding die has, for example, as shown in FIG. 3, polymer solution supply ports 46 and 47, and a polymer solution passage is provided from each supply port to each manifold 42.
Are formed towards the respective manifold
The flow path at the bottom of 42 is in an alternating current at a confluence point 43, and the passage (lip portion) of the polymer solution after the confluence is in communication with a slit-shaped discharge port 44, and the polymer solution is discharged from this discharge port 44. A thin film-like structure (multi-manifold type two-layer die 41) for discharging onto the support 48 is preferable.

In the die shown in FIG. 3, the distance between the lip portions can be adjusted by a lip adjusting bolt, and the bottom portion of each manifold 42 (a portion near the confluence) has a choke bar 45. The spacing of the voids in the flow path is adjusted by the method.

Further, each of the above-mentioned manifolds preferably has a hanger coat type shape.

Further, as the two-layer extrusion molding die, as shown in FIG. 4, polymer solution supply ports 56 and 57 are provided on the left and right of the upper part of the die, and the passage of the polymer solution is provided with a partition plate 59. At 53, the polymer solution is joined immediately, and the manifold 52 is connected to the flow path of the polymer solution from the joining point, and the passage (lip portion) of the polymer solution at the bottom of the manifold 52 is a slit-shaped outlet 54. The polymer solution in a thin film form from the discharge port 54 to the support 58.
It may have a structure for discharging on top (feed block type two-layer die or single manifold type two-layer die 51).

The above-mentioned first and second polymer solutions a and b are the above-mentioned first and second inorganic fillers having a performance as a lubricant.
What is necessary is just to consist of an aromatic polyamic acid (aromatic polyimide precursor) obtained from the above-mentioned aromatic tetracarboxylic acid component and aromatic diamine component and an organic solvent.

In the first and second polymer solutions, the content of each inorganic filler is 0.1 to 5% by weight, particularly about 0.3 to 3% by weight, and the content of aromatic polyamic acid is 5 to 40% by weight. It is particularly preferable that the amount is about 10 to 30% by weight.

The aromatic polyamic acid in the first and second polymer solutions is preferably composed of the same monomer components.

The above-mentioned first and second polymer solutions have a "solution viscosity (rotational viscosity)" at the temperature of discharge from the two-layer extrusion die in the above two-layer extrusion molding, about 50 to 10,000 poise, particularly 100 It is preferably about 6000 poise.

The aromatic polyamic acid used in the first and second polymer solutions has an inherent viscosity (measurement temperature; 30 ° C., concentration;
0.5 g / 100 ml solvent and solvent; N-methyl-2-pyrrolidone) is about 0.5-6, especially 1.0-5, more preferably 1.
It is preferable that it is about 5 to 4.

The organic solvent used in the first and second polymer solutions is, for example, N-methyl-2-pyrrolidone, N,
Examples thereof include amide-based organic solvents such as N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, and mixed solvents containing them as a main component.

The temperature of the aromatic polyamic acid solution at the time of discharging from the two-layer extrusion die in the above two-layer extrusion molding is 0 to 150.
℃, particularly 5 ~ 100 ℃, more preferably 10 ~ 60 ℃, the temperature for drying the thin film after the polymer solution is discharged (casting temperature) is 100 ~ 180
C., especially about 120 to 150.degree.

In the polyimide film produced by the production method of the present invention, the ratio of the thickness of the “highly easy sliding layer portion A containing the first inorganic filler and the low easily sliding layer portion B containing the second inorganic filler”. Can be adjusted by adjusting the discharge amount of each polymer solution from the two-layer extrusion die.

The drying of the thin film of the polymer solution on the support should be performed at a drying temperature of 100 to 180 ° C, particularly about 120 to 160 ° C, and a drying time of 1 to 60 minutes, especially 5 to 30 minutes. Is preferred.

Further, the heat treatment of the self-supporting polymer film peeled from the support, the heat treatment temperature is about 250 ~ 600 ℃, especially about 300 ~ 550 ℃, the heat treatment time is about 1 to 60 minutes, especially 2 ~. About 30 minutes is preferable for imidization of the polymer and removal of the solvent in the film.

In the film production method of the present invention, the film formation rate is 0.1
The aromatic polyimide film having the above-mentioned performance can be continuously produced at a rate of -10 m / min, particularly 0.2-5 m / min.

〔Example〕

Hereinafter, the present invention will be described in more detail by showing Examples and Comparative Examples of the present invention.

In the examples and comparative examples, each measurement test was performed by the following method.

The average surface roughness (Ra) is 0.2μ with a tally step surface roughness meter (Rank Taylor Hobson).
Using a 2.5μx stylus, the load is 2 mg, the roughness direction magnification is 200,000 to 500,000 times, and the measurement length is 1 mm.
The center line average roughness was measured.

The number of fine protrusions is 5000 times or more (preferably
The number of fine projections due to each added inorganic filler (slippery) was measured by counting the number of fine projections with a diameter of 100 Å or more by observing the photograph of the film surface taken at 10000 times or more) .

The average height of the fine protrusions is determined by shadowing with the observation of the electron microscope used in the measurement of the number of fine protrusions.
The "length of the shadow of the fine protrusion" was measured by image processing, and the height of the fine protrusion was calculated from the length of the shadow of the fine protrusion and the irradiation angle of light at that time.

Regarding the friction coefficient between the films showing the handling property, the static friction coefficient μ _S and the dynamic friction coefficient μ _K when the front and back sides of two films were rubbed were measured according to the standard of ASTM D1894.

As for the post friction coefficient μ indicating practical handling property (running property), as shown in FIG. 5, a sample film 61 having a width of 12.5 mm is used, and a weight 64 is attached to the tip of the film to load ( T ₀ ) With 27 g applied, wrap the film around a free roll 62 with a diameter of 20 mm that rotates freely,
Next, wrap the friction pin 63 so that the contact angle (θ) with the friction pin 63 (fixed circular friction pin) with a circular cross section of 8 mm is 180 °, and run at a pulling speed of 100 mm / min. The force (T
i) was measured, and the post friction coefficient was calculated by the following calculation formula.

The electromagnetic conversion characteristics, which show the characteristics as a magnetic recording medium, are obtained by applying an appropriate recording current to a magnetic recording medium (VTR tape) obtained by forming a magnetic layer made of a Co-Cr alloy on a tape-shaped film by sputtering. After recording, the signal S containing the video demodulated signal at the time of reproduction and the noise N are measured using a video noise meter, the S / N ratio is calculated from the measured values of the S and N, and the ratio is calculated. The value (dB) further calculated from the value is shown.

In addition, manufactured by the conventional single-layer film forming method,
The "electromagnetic conversion characteristics" of the "VTR tape with recording medium having the same magnetic layer", which uses a polyimide film with both sides equally slippery as the base film, was designated as "OdB".

The path durability of the magnetic recording medium is VHS or 8 mm.
Of magnetic recording media made in tape using a VTR for
After running under conditions of high temperature and high humidity of ℃ and 80% RH, the number of times (runs) is shown as the number of times when scratches or missing parts occur on the magnetic surface.

Reference Examples 1 to 5 Aromatic tetracarboxylic acid component consisting of equimolar amounts of 3,3,4,4'-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and 70% by mole of paraphenylenediamine
The aromatic diamine component consisting of 4,4'-diaminodiphenyl ether 30 mol%, N, N-dimethylacetamide, and colloidal silica in the types and proportions shown in Table 1 are mixed to prepare the above-mentioned monomer. Aromatic polyamic solution consisting of N, N-dimethylacetamide solution of aromatic polyamic acid (polymer concentration; 18% by weight) (solution viscosity (rotary viscosity) at 30 ° C) About 4000-6000 poise) was prepared.

Examples 1-2 and Comparative Examples 1-2 Using the film forming apparatus as shown in FIG. 2 provided with the two-layer extrusion molding die (multi-manifold type two-layer die) shown in FIG. The aromatic polyamic acid solutions selected from the aromatic polyamic acid solutions and having the combinations shown in Table 2 were simultaneously supplied from the polymer solution supply ports 9a and 9b to the extrusion molding mechanism having the two-layer extrusion molding die 1. Then, a two-layer thin film material of both solutions is discharged from the discharge port of the die 1 at a discharge temperature of 30 ° C. around a pair of driving wheels 2 and is rotated by a smooth support (metal support). Belt 3) is continuously extruded onto the upper surface of the support body 3 and the thin film-like body 4 on the upper surface of the support body 3 is heated on the support body 3 at a temperature of about 140 ° C. by a hot air blowing device 5. Allow to dry for 6 minutes at temperature Lifting of the film 4 '(solvent content: 40 wt%
The following) is formed, then the self-supporting film 4'is peeled off from the support, and finally, the self-supporting film 4'is passed through a curing oven 13 in which an infrared heater 11 is installed. About 150
To 450 ° C. for 4 minutes in a temperature range of which the aromatic polyimide film 4 ″ is formed, and the film 4 ″ is cooled in the cooling chamber 20 to room temperature. The aromatic polyimide film having a thickness of 10 μm was manufactured by winding the film on a winding roll 30 of a winding machine 31 (the whole is not shown).

The film forming speed was 0.6 m / min.

As a result of observing the cross section of each of the two-layer molded aromatic polyimide films produced as described above with an electron microscope, as shown in FIG. 1, the highly slipping layer portion A in which large colloidal silica is present is The thickness of the low-slidability layer portion B (Example) having a small colloidal silica therein or the layer portion B not containing the inorganic filler (Comparative example, not shown) is about 5 μm. Was about 5 μm.

Further, the two-layer molded aromatic polyimide film obtained in Example 1 was subjected to a tensile test and the like,
The tensile strength was 35 kg / mm ² and the elongation was 50%.

Further, various performance tests of the above aromatic polyimide film were conducted, and the results are shown in Table 2.

Comparative Examples 3 to 4 Using the aromatic polyamic acid solutions prepared in Reference Examples 1 and 3 and using an extruder equipped with a single-layer molding nozzle, the same procedure as in Example 1 was repeated. A single-layer molded aromatic polyimide film (thickness 10 μm) was molded.

Various performance tests of the above aromatic polyimide film were conducted, and the results are shown in Table 2.

[Operation and Effect of the Present Invention] In the aromatic polyimide film of the present invention, as described above, the surface of the highly slippery layer of the film is easily slipped to a high level and the friction coefficient is in a small range, and as a result, , A magnetic recording medium (metal) having a high level of performance (especially durability) while the film has excellent running property and the surface of the other low-slidability layer has appropriate smoothness. It is suitable for formation and can be suitably used as a heat resistant base film for a magnetic recording medium for forming a magnetic layer by a sputtering method, an evaporation method or the like.

The method for producing a two-layer extruded polyimide film of the present invention is a two-layer film having different front and back surfaces by simultaneously extruding two kinds of aromatic polyamic acid solutions from a two-layer extrusion molding die and casting the polymer solution. The double-layered extruded aromatic polyimide film having the above-mentioned properties can be continuously produced with good industrial reproducibility by the production method of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drawing based on a micrograph of a cross section of a polyimide film for a recording medium of the present invention. FIG. 2 is a cross-sectional view showing an outline of a film forming apparatus used in the method for producing a polyimide film for recording medium of the present invention,
FIG. 3 and FIG. 4 are cross-sectional views each showing an outline of an example of a two-layer extrusion die arranged in the film forming apparatus. FIG. 5 is a sectional view showing the outline of an apparatus for measuring the post friction coefficient of a film. A: Highly easy sliding layer, B: Low easily sliding layer 1; Two-layer extrusion molding die, 2; Pair of drive wheels, 3; Support,
4; thin film, 4 '; self-supporting film, 4 "; aromatic polyimide film, 5; hot air blowing device, 6; casting furnace, 7; exhaust port, 8, 21, 31, etc .; guide roll,
13; Cure furnace, 20; Cooling chamber, 30; Take-up roll, 41; Multi-manihole type die, 51; Feed block type die, 46, 47, 56, and 57; Feed port, 42 and 52; Manifold, 43 And 53; confluence, 44 and 54; outlet.

Claims (2)

[Claims] 1. A highly slippery layer containing a first inorganic filler having an average particle diameter of 400 to 2000Å in a proportion of 0.5 to 5% by weight based on a polyimide resin, and an average particle diameter of the first inorganic filler. 0.
The second inorganic filler having an average particle size of 05 to 0.7 times the content of the first inorganic filler with respect to the polyimide resin.
A two-layer extruded polyimide film comprising a low-slidability layer contained in a ratio of 0.1 to 0.8 times, wherein the surface A _{0 of the high-} slidability layer A has an average surface roughness (A / Ra) of 20 to 100.
Å, and which has a fine protrusions average height (A / Ha) 100~500Å, surface B ₀ of TeiekiNameraso B has an average surface roughness of the surface A ₀ of KoekiNameraso A (A / Ra ) Of 0.1 to 0.8 times the average surface roughness (B / Ra), 0.2 to the average height of fine protrusions (A / Ha) of the surface A ₀ of the highly slippery layer A.
A polyimide film for a recording medium, which has an average height (B / Ha) of 0.8 times the fine protrusions. 2. A first aromatic polyamic acid solution containing a first inorganic filler having an average particle diameter of 400 to 2000Å in a proportion of 0.5 to 5% by weight based on the aromatic polyamic acid, and the first inorganic. A second inorganic filler having an average particle size of 0.1 to 0.7 times the average particle size of the filler, containing at a ratio that is 0.1 to 0.8 times the content ratio of the first inorganic filler with respect to the aromatic polyamic acid. And a second aromatic polyamic acid solution,
Simultaneously supplying to an extruder having a two-layer extrusion molding die, a two-layer thin film of both solutions is continuously extruded from a discharge port of the die onto a smooth support, and the support is The above thin film is dried to form a self-supporting film, the self-supporting film is peeled off from the support, and finally the self-supporting film is heat-treated. Manufacturing method of polyimide film for recording medium.