JPH1120019A - Heat-resistant film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant film, which has excellent electromagnetic conversion characteristics and traveling characteristics, for a base film of a magnetic recording media. SOLUTION: A heat-resistant film has average thickness of 2-10 μm, having 0.03-0.4 μm height (H), and 100-2000 μm main pitch (L) on at least one surface, and waviness of 500<=L/H<=15000 randomly. The ratio of thickness dispersion with respect to the average thickness is 1-8%, and the ratio of long-direction thickness dispersion with respect to width-direction thickness dispersion is 0.25-4. Therefore, the film has unique surface configuration and uneven pattern of thickness, which enables providing of a base film for magnetic recording media having good electromagnetic conversion characteristics and traveling characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant film useful for a base film of a magnetic recording medium, and more particularly, to a film having a special shape on its surface and a unique thickness. The present invention relates to a heat-resistant film having excellent electromagnetic conversion characteristics and running properties when used as a base film for a magnetic recording medium because of forming a variation pattern.

[0002]

2. Description of the Related Art Aramid films and polyimide films are known as films having excellent heat resistance.
1247, JP-A-51-81854, JP-A-51-81880, JP-A-52-82953, JP-A-52-84245, and JP-A-52-8
No. 5,251, JP-A-58-42649, JP-A-59-45124, JP-A-61-246918.
JP, JP-A-62-70421, JP-A-60-70421
No. 15,436, JP-A-60-15437, JP-A-62-48726, and the like.

[0003] Particularly, as a base film for a magnetic recording medium, Japanese Patent Application Laid-Open Nos.
JP-A-97038, JP-A-2-1741, JP-A-2-133434, JP-A-3-119512, JP-A-3-114830, JP-A-4-347
No. 16, JP-A-4-149245, JP-A-6-149
-195679, JP-A-8-235568, JP-B5-36849, JP-B5-6459.
No. 4 discloses a technique for adjusting surface smoothness and surface roughness.

[0004] However, despite such ingenuity,
When used as a base film for magnetic recording media,
It has not been possible to achieve both excellent levels of electromagnetic conversion characteristics that require surface smoothness and runnability that requires surface roughness, so to speak.

[0005]

An object of the present invention is to provide a heat-resistant film suitable for use as a base film for a magnetic recording medium for high-density recording.

[0006]

SUMMARY OF THE INVENTION The inventor of the present invention has sought to solve a technical problem which could not be overcome in the past, namely, to obtain a heat-resistant film having both excellent slipperiness (running property) and surface smoothness at an excellent level. As a result of studying from an angle, it was surprisingly surprising that the introduction of random waviness with a specific size and gradient on the film surface, and the unique setting of the film thickness variation pattern The inventors have found that the present invention provides an improvement, and as a result of further studies, the present invention has been achieved.

That is, the present invention relates to a heat-resistant film having an average thickness of 2 to 10 μm, wherein at least one of the surfaces has a thickness of 0.1 μm.
03-0.4 μm height (H), 100-2000 μm
m with a main pitch (L) and 500 ≦ L / H ≦ 15
The heat resistance has a undulation of 000 at random and the ratio of the thickness variation to the average thickness is 1 to 8%, and the ratio of the thickness variation in the length direction to the thickness variation in the width direction is 0.25 to 4. Film.
An aramid film or a polyimide film is used as the heat-resistant film of the present invention.

The aramid used in the present invention is substantially composed of units selected from the group consisting of the following structural units. —NH—Ar ₁ —NH— (1) —CO—Ar ₂ —CO— (2) —NH—Ar ₃ —CO— (3) where Ar ₁ , Ar ₂ and Ar ₃ are at least one aromatic ring Which may be the same or different, and typical examples thereof include the following chemical formula (1), wherein a part of hydrogen on the ring of these aromatic rings is a halogen group, a nitro group, an alkyl group And those substituted with an alkoxy group and the like.

[0009]

Embedded image Here, X is -O-, -CH2-, -SO2-, -S
-, -CO- and the like.

In particular, an aramid in which at least 80 mol% of all aromatic rings are bonded at the para position is preferred. The polyimide used in the present invention has at least one aromatic ring and at least one imide group in the repeating unit of the polymer, and is represented by the following general formula (2) or (3).

[0011]

Embedded image

[0012]

Embedded image Here, Ar ₄ and Ar ₆ contain at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring. This Ar ₄ is derived from an aromatic tetracarboxylic acid or its anhydride. A typical example is Chemical Formula 4.

[0013]

Embedded image Here, Y is, -O -, - CO -, - CH 2 -, - S
—, —SO ₂ — and the like. Ar ₆ is derived from tricarboxylic anhydride or its halide. Ar
_As a representative example of _6, the following chemical formula 5 is given.

[0014]

Embedded image Ar ₅ and Ar ₇ contain at least one aromatic ring and are derived from aromatic diamines and aromatic isocyanates. Ar
_{As a} typical example of ₅ or Ar _7, the following chemical formula 6 can be mentioned, in which a part of hydrogen on the ring of these aromatic rings is substituted with a halogen group, a nitro group, an alkyl group, an alkoxy group, or the like. Is also included.

[0015]

Embedded image Here, Z _{is, -O -, - CH 2 -} , - S -, - SO 2
-, -CO- and the like.

In particular, polyimides in which 80% or more of Ar ₅ and Ar ₇ are aromatic rings bonded to the para position are preferred. Also, the aramid film or polyimide film of the present invention, or impair the physical properties of the film, as long as it does not contradict the purpose of the present invention, an antioxidant, a delustering agent, an ultraviolet light stabilizer,
Other additives and the like, and other polymers may be contained.

A feature of the present invention is that at least one of the film surfaces has a height (H) of 0.03 to 0.4 μm,
It has a main pitch (L) of ２０００2000 μm and 500 ≦ L /
That is, it has a swell with a gradient of H ≦ 15000. Height less than 0.03 μm or / and 2000 μm
And / or a swell with a gradient (L / H) of more than 15000 has poor slipperiness and makes film processing difficult. In this case, the idea of ensuring the slipperiness by adding a large amount of fine particles is not preferable because the surface smoothness of the film is insufficient. On the other hand, 0.4 μm
A height greater than or equal to and / or a main pitch of less than 100 μm,
If / and / or waviness having a gradient of less than 500 is introduced on the film surface, when it is used as a base film of a magnetic recording medium, the electromagnetic conversion characteristics become inferior.
The swell preferably has a height of 0.05 to 0.3 μm,
It has a main pitch of 200 to 1500 μm. Also, 100
An L / H swell of 0-10000 is more preferred.

As described above, by introducing a undulation having a long period of 100 μm or more and a specific gentle gradient to the film surface, the running property of the film can be drastically improved without any adverse effect on the electromagnetic conversion characteristics. The fact that the present inventors have found is surprising. The present invention
Although it can be applied to a thin film having an average thickness of about 2 to 10 μm, it is also characterized by a pattern of thickness variation. That is, the ratio of the thickness variation to the average thickness, and the ratio of the thickness variation in the width direction to that in the length direction are set to specific ranges.

The ratio of the thickness variation to the average thickness is 1 to
8%, preferably this ratio is 1-5
% Range. If this ratio exceeds 8%, the rolled film will have a poor winding appearance, not only will the release from the roll itself or the workability of the film after the release be poor, but also the appearance of the film will be surprising. It was found that the coefficient of friction of the rubber increased and the running performance became poor. In other words, the running property of the film can be improved by setting the ratio to 8% or less, preferably 5% or less. Further, it has been found that when the ratio is less than 1%, static electricity is easily generated when the roll film is released.

It is important that the ratio of the thickness variation in the length direction to the thickness variation in the width direction is between 0.25 and 4, preferably 0.33-3. If this ratio exceeds 4, the electromagnetic conversion characteristics when the film is taped may be poor, whereas if it is less than 0.25, the running properties of the film may be reduced or the rolled form may be poor.

Further, it has been found that a main pitch of the thickness variation in the width direction of 10 to 200 mm is effective and preferable in improving the handleability of the film of the present invention. Although the detailed mechanism is unknown, it is considered to be related to the ability to hold air when the film is wound into a roll and the difficulty of electrostatic charging. The main pitch of the thickness variation can be determined by, for example, measuring the thickness distribution and performing Fourier analysis on the thickness distribution to specify the pitch having the largest contribution.

The thickness variation of the film is generally determined by the conditions under which the film undergoes plastic deformation in the film forming process, for example,
Variations in widthwise clearance, temperature, stress, concentration, etc. in processes such as discharge from die, delivery from die to metal roll / endless belt, drafting, delivery between rolls or from belt to roll, stretching, heat treatment, etc. Results in thickness variations in the width direction, and temporal variations produce thickness variations in the length direction. Therefore, the specified thickness variation pattern can be obtained by controlling these film formation factors and their variations.

In the present invention, the film contains preferably 0 to 10% by weight, more preferably 0 to 3% by weight of fine particles. If it exceeds 10% by weight, the film has good slipperiness, but the surface protrusions of the film increase, and the smoothness is impaired. It is surprising that the technique of the present invention can be applied to those containing no fine particles at all. This is because conventionally, generally, the slipperiness of a film has been ensured by adding fine particles.

The characteristics of the present invention are remarkably exhibited when the added amount of the fine particles is small. The fine particles may be contained uniformly in the thickness direction of the film, or may be contained non-uniformly, for example, on at least one surface and in the vicinity thereof. In the film of the present invention, preferably, at least one surface has 0 to 5 protrusions / cm ² having a height of 0.27 μm or more and less than 0.54 μm, and a height of 0.54 μm or more and less than 0.81 μm. The number of the projections is 0 to 2/10 cm ² , and the number of the projections having a height of 0.81 μm or more is 0 to 0.5 / 100 cm ² , and more preferably the number of the projections of 0.54 μm or more is 0.
Individual. If the protrusions having the above heights are present in excess of the above number, in the case of a magnetic tape, undesired phenomena such as a decrease in output, an increase in dropout, and an increase in noise are caused.

The film of the present invention desirably has fine moderate irregularities on the surface. When this unevenness is represented by a center plane average roughness (SRa), it is 0.0002 to 0.01 μm.
It is. The technique of the present invention is preferably applied to a film having a coefficient of hygroscopic expansion of 100 ppm /% RH or less. A film having a coefficient of hygroscopic expansion of more than 100 ppm /% RH has a humidity dimensional stability at a level that cannot be practically used, and is more preferably applied to a film having 50 ppm /% RH or less.

The film of the present invention has a Young's modulus (Mi) of 7
It is preferably from 00 to 2500 kg / mm ² . A film having a Young's modulus of less than 700 kg / mm ² is no longer a film in the range of a high-rigidity film, and the average thickness of the film claimed in the present invention deteriorates the handling of a roll-shaped film. On the other hand, 2500kg
Aramid or polyimide films in excess of / mm ² tend to tear and become brittle, and are no longer useful as films. High Young's modulus film
It can be realized by increasing the number of para-oriented components in the molecular structure and by applying a relatively high stretching ratio at the time of production to highly orient the molecular chains.

The present invention can be applied not only to a so-called balance type in which the physical properties of the film are constant in all directions in the film plane, but also to a tensile type in which the film is reinforced in the length direction or the width direction. . The films of the present invention also preferably have an elongation in the range of 5-100%. This is because films with an elongation of less than 5% are often found to be brittle. On the other hand, it is generally desirable that the elongation is large, but practically, the upper limit is about 100%.
The elongation can be achieved by adjusting the type of polymer, the degree of polymerization, the degree of stretching orientation, the degree of crystallization, and the like.

The film of the present invention preferably has a heat shrinkage at 200 ° C. in the range of 0 to 0.5%. This is because, if the heat shrinkage is large, when the film is subjected to a high temperature history in a film processing step or the like, the flatness of the film may be reduced. The reduction of the heat shrinkage can be achieved by selecting a polymer type, heat setting, and the like. A film having a small heat shrinkage is one of the evidences that the film has heat resistance.

The film of the present invention preferably has a coefficient of kinetic friction with a metal mirror surface in the range of 0.02 to 0.4, more preferably in the range of 0.02 to 0.3. If the coefficient of friction is too small, handling in the processing step becomes unstable, and if it is too large, wrinkling, distortion and damage are increased in the processing step. In the present invention, it has been found that the presence of the specific undulations described above has helped to reduce the friction coefficient. Adjustment of the coefficient of friction can also be achieved by introducing a specific thickness variation into the film, or by selecting the amount, type, particle size, degree of dispersion and the like of the fine particles.

In the present invention, even when the surface smoothness of the film is improved by reducing the addition amount of the fine particles, for example, to 0 to 0.1% by weight, the friction coefficient can be easily processed. There is a feature. In the method of producing the film of the present invention, it is necessary to devise a portion necessary to generate a unique surface waviness and a specific thickness variation pattern, but basically, a production method suitable for each polymer is used. it can.

First, for an aramid resin, in the case of a resin soluble in an organic solvent, a solution is prepared by directly polymerizing in a solvent, or once isolating and then re-dissolving the polymer, followed by a dry method or a wet method. A film is formed, and a resin that is hardly soluble in an organic solvent such as polyparaphenylene terephthalamide (PPTA) is dissolved in concentrated sulfuric acid or the like to form a solution, and then the film is formed by a dry method or a wet method.

On the other hand, with respect to the polyimide resin, a tetracarboxylic anhydride is reacted with an aromatic diamine in an organic solvent to obtain a polyamic acid. The solution is obtained by dissolution, and they are formed into a film by a dry method or a wet method. In the dry method, the solution is extruded from a die, cast on a support such as a metal drum or an endless belt, and the drying or imidization reaction proceeds until the cast solution forms a self-supporting film.

In the wet method, the solution is extruded directly from a die into a coagulating liquid, or cast on a metal drum or an endless belt in the same manner as in the dry method, and if necessary, a part of the solvent is removed. And solidify. Next, these films are washed with a solvent or an inorganic salt in the films, and then subjected to treatments such as stretching, drying, and heat treatment.

In any of the film forming methods, the film after the film formation is manufactured so as to have a unique undulation characteristic of the present invention. According to the knowledge of the present inventor, a film having such a unique undulation is realized for the first time under a combination of unknown unknown film forming conditions, and has a relatively wide molecular weight distribution (number average). Using a polymer having a ratio of weight average molecular weight to molecular weight of 2.0 or more) and discharging from a die at a high shear rate of about 1000 sec-1 or more,
That was when the film was formed with a draft of 1.5 or more (ratio of the film take-up speed to the extrusion speed from the die). Here, the draft is a ratio of a film take-up speed to an extrusion speed from a die, that is, a running speed of a metal drum or an endless belt. However, this does not preclude obtaining the film of the present invention by other methods.

In order to improve the slipperiness of the films and prevent the blocking phenomenon, a method of mixing fine particles in the film may be used, and these fine particles are also referred to as a lubricant. Examples of the fine particles include an organic compound and an inorganic compound, and usually, for example, SiO ₂ , TiO ₂ , ZnO,
Inorganic compounds such as Al ₂ O ₃ , CaSO ₄ , BaSO ₄ , CaCO ₃ , carbon black, zeolite, and other metal powders are used. Particle size is 0.001-2 μm,
The addition amount is selected from 0 to 10% by weight. That is, the fine particles are mixed in an aramid resin or a solution of a polyimide or a polyamic acid which is a precursor of the polyimide, and the solution is formed into a film. At this time, in order to improve the dispersion of the fine particles, a homogenizer of an ultrasonic system or a stirring system is preferably used. Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to these Examples and the like.

[0036]

【Example】

<Method of Measuring Characteristics> The method of measuring characteristic values of the present invention is as follows. (1) Method of measuring thickness and thickness variation of film The thickness of the film was measured using a digital electronic micrometer (K351C type manufactured by Anritsu Corporation) using a measuring element with a diameter of 2 mm for each sample of the entire width of the film and the same length as the sample. The thickness is measured in each direction along the line segment divided into five equal parts. The average thickness of the film is represented by the average value of all the measured values, and the variation in thickness is represented by the difference between the maximum value and the minimum value among all the measured values. The thickness variation in the width direction is the difference between the maximum value and the minimum value in all the measured values in the width direction, and the thickness variation in the length direction is represented by the difference between the maximum value and the minimum value in all the measured values in the length direction. The main pitch of the thickness variation is represented by a pitch showing the maximum contribution by performing a Fourier transform analysis of the measured value.

(2) Method of measuring strength, elongation, and Young's modulus of film The strength, elongation, and Young's modulus were measured using a constant-speed elongation type elongation measuring machine at a measuring length of 100 mm and a pulling speed of 50 mm / min. It was done. (3) Method of measuring surface waviness Using ZYGO New View 100 type surface roughness measuring device, objective lens magnification 2.5 times, camera resolution 8.8 μm, cutoff 5 mm
The height (H) is obtained by the PV value measured for each point, and the main pitch (L) is obtained by the main wavelength by the Fourier transform analysis of the undulation of the center line.
Represents

(4) Method of Measuring Center Surface Average Roughness (SRa) SRa is defined, for example, by Jiro Nara, “Measurement of Surface Roughness,
Evaluation method ”(Sogo Gijutsu Center, 1983), and a method of calculating and obtaining an interference image of an interference phase contrast microscope was used. In other words, New View of ZYGO
Using a 100 type surface roughness measuring device, objective lens magnification 4
SRa was measured at any three points of the film at 0 times, with a camera resolution of 550 μm, and a cut-off of 25 μm, and the average was represented.

(5) Method of Measuring Heat Shrinkage A 2 cm × 5 cm sample piece was cut out from a film, and 4 c
m at a distance of 25 m with a blade to make a marker.
After leaving for 72 hours in an atmosphere of 5% relative humidity, the distance between the labels was read and measured with a microscope, and then left in a hot air oven at 200 ° C. for 2 hours without restraint.
After leaving again for 72 hours in an atmosphere of 25 ° C. and 55% relative humidity, the distance between the labels was read and measured with a microscope.

(6) Method of measuring the coefficient of hygroscopic expansion in the direction of the film surface Thermodynamic property measuring device (TMA, TM7 manufactured by Vacuum Riko Co., Ltd.)
000 type), a sample with a width of 5 mm was attached, and a load of 0.
After removing the residual strain of the sample by raising the temperature once to 300 ° C. under 3 g, the sample was cooled under a dry nitrogen stream, and the change in humidity between dry nitrogen and air and the change in the dimensions of the film were measured at 23 ° C. Then, it was calculated. (7) Method of measuring dynamic friction coefficient As a metal mirror surface, a mirror-polished stainless steel fixed roll (diameter 60 mm) is set so that it has an angle of 90 °.
A load of 50 g was applied to one end of the film having a width of 1 cm, and the other end was pulled at a speed of 20 cm / min. The tension was calculated from the tensile tension of the film using Euler's equation.

(8) Method for measuring coarse protrusions on the surface Aluminum was uniformly deposited to a thickness of 20 nm on the surface of the film, and using a monochromatic halogen light having a wavelength of 0.546 μm, magnification of 200 times by an optical multiplex interference microscope. And any 3c
By observing the m square film surface, one interference fringe with respect to the protrusion is 0.27 μm or more and less than 0.54 μm in height, and two interference fringes is 0.54 μm or more with two interference fringes. Projections having a height of less than 0.81 μm and three or more interference fringes are counted as projections having a height of 0.81 μm or more, and are represented by an average value of 10 times. (9) Measuring method of electromagnetic conversion characteristics of magnetic tape According to JIS X 6129-1993, in order to grasp the characteristics at short wavelength, the output measurement is 4499.8 ftpm.
m, the recording frequency is 9M in the missing pulse zone measurement.
The measurement was performed by changing the JIS standard to 12 Hz and 12 MHz, respectively.

Example 1 The ratio of the weight average molecular weight to the number average molecular weight measured by gel permeation chromatography was 3.
Polyparaphenylene terephthalamide (PPT)
A) is dissolved in 99.8% concentrated sulfuric acid so that the polymer concentration becomes 12%, discharged from a die at a shear rate of 21000 sec ⁻¹ , and cast on an endless belt so that a draft of 2.3 is applied. did. 0.04μ in advance for concentrated sulfuric acid
m of colloidal silica particles was dispersed by an ultrasonic stirrer so as to be 0.2% by weight based on PPTA.
After heating and doping on a belt, the dope is converted from a liquid crystal phase to an isotropic phase, then coagulated in 15% sulfuric acid at 0 ° C., neutralized, washed with water, and cut in a length direction of 1.05. After stretching the film, the film is transversely stretched to 1.1 times with a clip tenter, and then dried at 150 ° C. with hot air while maintaining a fixed length.
After a tension heat treatment at 30 ° C., the film was rolled up.

The roll-shaped PPTA film having an average thickness of 4.6 μm and having a width of 600 mm has an equilibrium moisture absorption of 2.7% at 25 ° C. and a relative humidity of 55%. Almost no, and the properties were as shown in Table 1. Using the obtained film, a magnetic tape having a magnetic layer made of metal powder was trial-produced, assembled into a DDS-2 standard cartridge, and measured for magnetic properties.
Output 102%, Missing pulse zone 85% (9MHz), 70% (12MHz) compared to DS-2 standard tape
And it was excellent. Also, there was no trouble in the trial production process of the magnetic tape.

(Comparative Example 1) In Example 1, the draft was changed to 3.8, and the film was wound up without any change except for the conditions related thereto. Table 1 shows the properties of the obtained film.
As shown in the figure, the surface waviness was large and out of the range of the present invention. In the same manner as in Example 1, a DDS-2 standard magnetic tape was prototyped. Although there was no trouble in the trial production process, the missing pulse zone was as large as 120% of the commercial tape.

Comparative Example 2 A film was wound up under the same conditions as in Example 1 except that the coagulating liquid was changed to 52% sulfuric acid. The properties of the obtained film are shown in Table 1, and the pattern of thickness variation was out of the range of the present invention. This is presumed to be due to the fact that coagulation slowed down due to a change in the composition of the coagulation bath, particularly because the thickness unevenness in the length direction became large. The DDS-
Two standard magnetic tapes were prototyped. In the trial production process, there was no major trouble except for the difficulty in running, which was considered to be due to the large coefficient of friction of the film, but the missing pulse zone was as large as 140% of the commercial tape.

[0046]

[Table 1]

Example 2 In Example 1, a polymer having a weight-average molecular weight to number-average molecular weight ratio of 2.5 was used, and the shear rate discharged from the die was set to 3000 sec ^-1 .
Example 1 except that the draft was 2.5 and the amount of colloidal silica particles was 0.01% by weight based on PPTA.
A prototype was produced in the same manner as described above. The average thickness of the obtained roll-shaped film was 5.2 μm, and the film had the properties shown in Table 2. From the obtained film, a prototype of a vapor-deposited tape having excellent magnetic properties was successfully produced.

(Comparative Example 3) A film having the characteristics shown in Table 2 was obtained by repeating Example 2 except that the draft was changed to 1.2. This film was out of the scope of the present invention in terms of L / H, and trial production of a vapor deposition tape was attempted.
The running trouble of the film occurred frequently, and it was difficult to obtain the evaporation tape.

Example 3 Polyparaphenylene-2-chloroterephthalamide (PPClTA) having a weight-average molecular weight to number-average molecular weight ratio of 3.4 was dissolved so that the polymer concentration became 13% by weight, and the solution was poured from a die. 80000 seconds
^It was discharged at a shear rate of ^-1 and cast on an endless belt in draft 2.1. 0.02 to concentrated sulfuric acid
The μm titanium oxide fine particles were dispersed by an ultrasonic disperser so as to be 0.2% by weight with respect to PPClTA. A film was made by performing the same operations as in Example 1,
It was rolled up.

A film having balanced properties in the vertical and horizontal directions was obtained, and the characteristics of the film are shown in Table 2. In the same manner as in Example 1, a magnetic tape compliant with the DDS-2 standard was prototyped from this film. Film and tape are DDS-
Despite being thinner than the two standards, there was no trouble in the prototyping process and it could be performed smoothly and the tape performance was excellent.

[0051]

[Table 2]

[0052]

Since the film of the present invention has a unique surface shape and thickness variation pattern, it is a feature that could not be realized with a conventional heat-resistant film, that is, a magnetic tape using the film of the present invention as a base film. In this case, there is a feature that both excellent electromagnetic conversion characteristics and good running performance are provided. Also, it is excellent in workability and handling when processing into a magnetic tape. Therefore, the film of the present invention is extremely useful as a base film of a magnetic tape regardless of a coating type, a vapor deposition type, or a sputtering type. In addition, it is useful for a base film of an ink ribbon of a sublimation type video printer, an electric insulating substrate, and the like.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 77/00 C08L 77/00 79/08 79/08 G11B 5/704 G11B 5/704 // B29L 7:00

Claims (2)

[Claims] 1. A heat-resistant film having an average thickness of 2 to 10 μm, wherein at least one of the surfaces has a thickness of 0.03 to 0.4 μm.
m has a height (H), a main pitch (L) of 100 to 2000 μm, and has a random undulation satisfying 500 ≦ L / H ≦ 15000, and the ratio of thickness variation to average thickness is 1 to 8 %, And the ratio of the thickness variation in the length direction to the thickness variation in the width direction is 0.1%.
A heat-resistant film of 25 to 4. 2. The composition contains 0 to 10% by weight of fine particles, and has at least one side of 0.27 μm to 0.54 μm.
0-5 protrusions / cm 2, 0.54 μm in height less than m
0 to 2 protrusions having a height of less than 0.81 μm / 10c
m2, 0 to 0.5 protrusions having a height of 0.81 μm or more /
The heat-resistant film according to claim 1, which has a size of 100 cm2.