JPH10222837A - Heat resisting synthetic resin film for high density recording magnetic tape and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the magnetic tape, which has a superior short wavelength recording characteristic, by specifying the average thickness of the heat resisting resin film, the shapes and the combination percentage of the particles which are inactive against dispersion acids and alkalis, the shapes of the flocculated particles, the roughness of the surface to form a magnetic layer, the eight of a maximum protrusion and the average roughness of the center surface. SOLUTION: The average thickness of the heat resisting synthetic resin film is 2 to 8μm and the particles having average particles size of 5 to 50nm are distributed at 0.001 to 1.0 weight percentage with an average flocculate rate of 1 to 100 range. The shapes of the flocculated particles included in the film are represented by equations 1 and 2. Note that the average roughness of the center surface to form the magnetic layers measured by an optical surface roughness meter is 0.1 to 3nm, the maximum protrusion height measured by an atomic force microscope is 5 to 50nm and the enter surface square average roughness is 0.1 to 10nm. In the equations, L1 is the length of the flocculated particles in the flow spread direction of the film, L1 stands for the length of the flocculated particles in the direction perpendicular to the flow spread direction, 'A' is the degree of the floccuration and 'a' indicates an average primary particle diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base film for a magnetic tape, and more particularly to a heat-resistant base film for a high-density recording magnetic tape having a signal wavelength of 0.5 .mu.m or less. The present invention relates to a conductive synthetic resin film.

[0002]

2. Description of the Related Art It has been pointed out that the surface property of a base film of a magnetic tape is important for the characteristics of the magnetic tape. In particular, to increase the capacity of the magnetic tape per cassette, use a highly crystalline film with a high elastic modulus such as aramid as the base film, and reduce the tape thickness to increase the tape length per cassette. ,
Also, the signal wavelength has been shortened, and even with a coating type magnetic tape, the fineness of the magnetic powder and the coating thickness have been reduced, and a metal thin film type magnetic tape in which metal has been deposited or sputtered has been used. Since it has been used, the surface of the base film has been required to be even smoother.

On the other hand, a film having a completely smooth surface is used in a film manufacturing process, a magnetic tape processing process, and the like.
It is known that there are problems such as poor sliding with each equipment, wrinkling, high running resistance, and cutting, and usually, fine particles (hereinafter referred to as “lubricants”) are added. The production of a film provided with fine projections and imparted with slipperiness has been performed.

Conventionally, in order to meet these demands, for example, in Japanese Patent Application Laid-Open No. 60-127523, the height of individual fine projections is not accurate, but the height measured by a stylus type surface roughness meter. For example, an aramid film having fine protrusions having a size of 3 to 50 nm of 10 ⁴ to 10 ⁸ / mm ² has been proposed. In Japanese Patent Application Laid-Open No. 4-149452, an aramid film is added to adjust fine protrusions on the surface. An aramid film in which the obtained lubricant particles are in a specific agglomerated state is proposed. Japanese Patent Application Laid-Open No. 8-55328 proposes a magnetic tape using an aramid film having fine protrusions having a height of 50 nm or more measured by an electron microscope of 2 × 10 ³ to 2 × 10 ⁷ / mm ² . .

Japanese Patent Application Laid-Open No. 60-127523 discloses a magnetic tape of a type in which a metal thin film whose surface shape is directly reflected on the surface of the magnetic layer is formed on the base film as compared with a type in which a magnetic layer is coated. , But none of these proposals
At the recording density of video recording at that time, the fine protrusions of the above height were sufficient, but in recent data recording applications, digital signals are recorded and the recording wavelength is also short, so the protrusions In the case of the height, the head is lifted from the surface of the magnetic tape by that much, so-called spacing loss increases, and there has been a problem that signal writing and reading errors occur.

[0006] The reason why a film having fine projections, which have a lower height but are effective for slipperiness, corresponding to recent advances in magnetic tapes, has not been realized by the prior art is disclosed in
As can be seen in Examples and Comparative Examples of -149245, the lubricant particles are not sufficiently dispersed and exist in the film in a state where several to several tens of particles are aggregated,
As for the method of mechanically dispersing the lubricant particles, there is a proposal (eg, Japanese Patent Publication No. 5-36849) in which high energy is intensively added by an ultrasonic disperser or the like (for example, Japanese Patent Publication No. 5-36849). I can't get the status. When aluminum oxide (alumina) is used as the lubricant particles, a relatively good dispersion state may be obtained. However, the solvent system of the present invention cannot be used because alumina is unstable.

[0007] Further, as the lubricant particles, it is preferable to use colloidal particles in which each particle is independently dispersed in a liquid.
JP-A-61-246919, JP-A-3-1195
No. 12, JP-A-4-34716, etc., but it is pointed out that lubricant particles are agglomerated during film production, as is clear from these examples. .

[0008] The reason that the colloidal particles are aggregated is that in the formation of a hardly soluble resin such as aramid or polyimide, an inorganic salt such as lithium chloride or calcium chloride is added as a solvent to an amide type solvent as a solvent. It is necessary to use solvents having high polarity such as strong acids such as concentrated sulfuric acid and the like, and a resin solution containing a lubricant (hereinafter referred to as “dope”) is prepared by adding a colloidal fine particle dispersion to these solvents having high polarity. It is well known that lubricant particles that are finely dispersed in a colloidal form in an organic solvent containing highly polar, especially concentrated sulfuric acid as a solvent or an ionic inorganic salt are aggregated by ions. is there.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-resistant synthetic resin film having preferable mechanical properties and capable of reducing the thickness of a magnetic tape. It is to provide a film with a surface roughness that makes it possible.

[0010]

In mixing the colloidal lubricant dispersion with the above-mentioned solvent, the present inventors have surprisingly found that under certain conditions, it is difficult for the lubricant to agglomerate, and if the agglomeration occurs. As a result, the inventors have found that the shape of the aggregated particles can be controlled, and have completed the present invention.

That is, an object of the present invention is to provide a heat-resistant resin having an average thickness of 2 to 8 μm and an average particle size of 5 nm to 5 μm.
Fine particles of 0 nm which are inactive against acid or alkali are used.
001-1.0% by weight is dispersed in an average cohesion of 1-100, and the shape of the coagulated particles contained in the film is represented by the following formulas (1) and (2). The center plane average roughness (SRa) of the surface to be formed with a resolution of an optical surface roughness meter is 0.1 to 3 nm, and the maximum projection height (Zmax) measured by an atomic force microscope is 5 nm. ~
50 nm, center plane root mean square (RMS) roughness of 0.1 to
Signal wavelength of 0.5 μm
The problem can be solved by the following heat-resistant synthetic resin film suitable for a base of a magnetic tape for high-density recording.

0.01 ≦ L ₂ / L ₁ ≦ 1 (1) A ≦ 2500 × a ⁻² (2) [where L _{1 is} the length of agglomerated particles in the film casting direction] L ₂ : length of agglomerated particles in a direction perpendicular to the casting direction of the film, A: degree of agglomeration, a: average primary particle diameter. ]
In carrying out the present invention, the surface of the film on the side on which the magnetic layer is to be provided has a cut-off wavelength by a method in which the field of view of an interference phase contrast microscope is subjected to photoelectric conversion with a horizontal resolution of 1 μ or less, data processing and measurement of surface roughness. The center plane average roughness (SRa) measured at 80 µm is 0.1 to 3 nm, preferably 0.3 to 3
If the surface roughness is 2 nm and the SRa exceeds 3 nm, the object of the present invention cannot be achieved.

In order to achieve the object of the present invention, in addition to the roughness observed in the unit of optical resolution, substantial irregularities on the film surface forming the magnetic layer are also important. The substantial roughness of the film surface can be accurately measured by an atomic force microscope (AFM). To achieve the object of the present invention, AF
According to M, the maximum projection height (Zmax) is 5 to 50 nm, preferably 10 to 30 nm, and more preferably 10 to 20 nm when used for a magnetic tape of a metal thin film type. The measured center plane root mean square (RMS) is 0.1 to 10 nm,
Preferably, it is 0.3 to 5 nm. Zm
If ax exceeds 50 nm and RMS exceeds 10 nm, the output of the magnetic tape cannot be obtained sufficiently,
The error rate is undesirably high.

In the film of the present invention, in order to control the surface roughness and the like, fine particles as a so-called lubricant are contained in the film in an amount of 0.001 to 1% by weight, preferably 0.01 to 1% by weight.
It must be contained at 0.5% by weight. When the amount of fine particles is 0.0
If the content is less than 01% by weight, the film may not slide smoothly in the film production process or the magnetic tape production process, causing problems such as impairment of stable running and generation of wrinkles, and should be avoided.

Although the fine particles should originally exist independently, it is known that ultrafine particles are likely to be associated and agglutinated. Is required to be in a low coagulation state having an average cohesion degree of 1 to 100, more preferably about 1 to 10. When the average agglomeration degree exceeds 100, there arises a problem that an error is likely to occur in using the magnetic tape for high density recording as an object of the present invention.

As the fine particles, when a highly acidic inorganic acid is used for dissolving the heat-resistant synthetic resin used in the present invention, or when the polymerization reaction product is directly used for a film forming solution, hydrochloric acid is added during polymerization. Therefore, it is necessary to be inert to acid, and aluminum oxide (alumina) is not preferable. From the viewpoint of the dispersibility of the fine particles, those dispersed in a colloidal form are preferred. As a material that satisfies these conditions, colloidal silica (SiO ₂ ) is commercially available and can be preferably used. May be used.

The colloidal silica usually has a pH of 8 to 1.
Although those stabilized in the range of 1 are used, there are also acidic types which are stabilized at pH 2 to 4, and are preferably used when the solvent shows acidity. The average particle size of the lubricant particles is 5 to 5
0 nm, preferably 10 to 30 nm. If the particle size is too small, it tends to aggregate, and even if the particle size is large, it is difficult to obtain a stable colloidal dispersion. This is out of the range intended by the present invention, which is not preferable.

In carrying out the present invention, the back surface of the film on which the magnetic layer is to be formed is not particularly limited. In many cases, the effect of the present invention is not impaired. In carrying out the present invention, it is important to reduce the thickness of the magnetic tape in order to increase the recording capacity per magnetic tape cassette, and a film suitable for the purpose of the present invention has a thickness of 2 μm.
m and 8 μm or less.

In making the base film thin, it is preferable that the base film has high strength and elastic modulus in view of workability in a magnetic tape manufacturing process, running properties of the magnetic tape, and electromagnetic conversion characteristics. For example, the strength in any direction of the film needs to be 20 kg / mm ² or more, and more preferably 30 kg / mm ² or more. Although there is no particular limitation on the upper limit of the strength for carrying out the present invention, even an aramid film having excellent mechanical properties is usually 60 kg as a achievable strength.
/ Mm ² . Similarly, the elastic modulus is 1000k.
g / mm ² or more, and more preferably 1300 kg / mm ² or more.
The upper limit of the elastic modulus is not particularly limited, but the achievable elastic modulus of the aramid film having excellent mechanical properties is about 2500 kg / mm ² .

The properties of these films should be satisfied in both the longitudinal direction and the width direction, but they do not necessarily have to be the same, and any of the properties can be enhanced according to the purpose. This may be performed by any of a so-called balance type in which the characteristics in the longitudinal direction and the width direction are almost equal, and a uniaxial tension type in which the tension is applied in either direction.

The magnetic tape for high-density recording, which is the object of the present invention, includes a magnetic tape coated with a magnetic metal powder with a binder, and a magnetic metal thin film formed by vapor deposition such as vapor deposition or sputtering. Although it is also preferable to use, the film is required to be heat-resistant in performing the vapor deposit method,
As a measure of heat resistance, it is necessary that the heat shrinkage at 200 ° C. be 2% or less, and more preferably 1% or less, in any direction of the film. If the heat resistance of the base film is lower than this, the film is undesirably deformed when the metal thin film is installed. In particular, due to a demand for a higher performance of the magnetic layer in the future, an increase in the energy density at the time of manufacturing the metal thin film is considered, and the heat energy received by the film is increasing, and the heat resistance of the film is important.

The weather resistance of the film of the present invention is set at 0.1 ° C. or less before and after the treatment for 72 hours in an environment of 50 ° C. and 80% RH, so that the most severe environment is reduced. Thus, it is possible to provide a magnetic tape for high-density recording that has very little reduction in reproduction output even after passing through and has good durability. As the heat-resistant film satisfying these characteristics, a part of a film made of an aramid resin or a polyimide resin can be used.

The aramid resin 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 And may be the same or different. Representative examples of these include the following chemical formula 1.

[0024]

Embedded image In addition, those 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 are also included. Also, X is -O -, - CH ₂ -,
_{-SO 2 -, - S -,} - CO- is a group such as.

In particular, an aramid resin in which at least 80 mol% of all aromatic rings are bonded at the para position is preferred for producing a film used in the present invention. The polyimide resin used in the present invention contains 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).

[0026]

Embedded image

[0027]

Embedded image Here, Ar ₄ and Ar _{6 each} include 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. As a representative example, the following chemical formula 4
One.

Embedded image Wherein Y is, -O -, - CO -, - CH 2 -, - S-,
—SO ₂ — and the like.

Ar ₆ is derived from tricarboxylic anhydride or its halide. As a representative example,
One.

Embedded image Here, Ar ₅ and Ar ₇ contain at least one aromatic ring and are derived from aromatic diamines and aromatic isocyanates. Representative examples of Ar ₅ or Ar ₇ include the following chemical formula 6.

[0030]

Embedded image

Here, those in which a part of hydrogen on the ring of these aromatic rings is substituted by a halogen group, a nitro group, an alkyl group, an alkoxy group, or the like are also included. Z is -O-, -CH
_{2 -, - S -, -} SO 2 -, - CO- is a group such as.
In particular, a polyimide resin in which 80% or more of Ar ₅ and Ar ₇ are aromatic rings bonded to the para position is preferable for producing the film of the present invention.

In practicing the present invention, an aramid resin or a polyimide resin used for producing a film may be used in addition to the above-mentioned lubricant, unless the properties of the film are impaired or the object of the present invention is not adversely affected. , An antioxidant, other additives, and other polymers may be contained.
The film may also contain a colorant such as a dye or a pigment, a flame retardant, an antistatic agent, an antioxidant, and other modifiers, as long as they do not contradict the purpose of the present invention.

The method for producing the film of the present invention is not particularly limited, and a production method suitable for each resin is employed. First, as for the aramid resin, in the case of those soluble in an organic solvent, it is polymerized directly in a solvent, or once isolated and redissolved to form a solution, and then formed into a film by a dry method or a wet method, Further, those which are hardly soluble in organic solvents such as polyparaphenylene terephthalamide (PPTA) are dissolved in concentrated sulfuric acid or the like to form a solution, and then formed into a film by a wet method.

On the other hand, as for the polyimide resin, a tetracarboxylic anhydride is reacted with an aromatic diamine in an organic solvent to obtain a polyamic acid, and this solution is directly or once subjected to a ring-closing treatment to obtain a polyimide. The solution is obtained by dissolving, and they are formed into a film by a dry method or a wet method. In the dry method, a 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 as in the dry method, and then guided into the coagulating liquid and coagulated. In order to produce the film of the present invention, the discharge shear rate at the time of casting from a die in any of a dry method and a wet method is 5 × 10 ^{4 to} 5 × 10 ⁵ s.
It is indispensable that the ec ^-1 and the draft are cast on the support in the range of 1 to 5, and if the casting is performed under these conditions, the relatively agglomerated particles also have a flat shape elongated in the casting direction. And does not contribute to the deterioration of the film surface properties. If the discharge shear rate is 5 × 10 ⁴ sec ⁻¹ or less, the aggregated particles do not become flat in the casting direction, and the film surface property is impaired. In addition, film formation cannot be performed stably at 5 × 10 ⁵ sec ⁻¹ or more.

Next, these films are washed with solvents and inorganic salts in the films, and then subjected to processes such as stretching, drying and heat treatment. The surface smoothness film of the present invention is prepared by mixing lubricant particles adjusted to a specific agglomerated state in a solution of aramid resin or a polyamic acid which is a polyimide or a precursor of polyimide, and forming the solution to form a film. To manufacture.

In order to obtain a film having a surface roughness of the present invention,
The state of dispersion of the fine particles is important. In carrying out the present invention, it is important that the fine particles are dispersed in the resin solution to have an average agglomeration degree of 1 to 100, more preferably about 1.1 to 10. In realizing such a dispersion state of the fine particles, in the method of dispersing the fine particles of the powder in water or various organic solvents, even if a strong homogenizer is used, complete separation and dispersion of the aggregated fine particles cannot be realized. However, it is not preferable, and it is necessary to use particles in which fine particles are dispersed alone in a colloidal state. Commercially available colloidal fine particle dispersions are usually sold at a concentration of about 20% by weight to 50% by weight. However, even if these commercially available colloidal fine particle dispersions are used, the inorganic acid or inorganic salt can be used. When mixed with the contained solvent, agglomeration of fine particles occurs, and it is difficult to achieve a desired dispersion state.

As a specific method for realizing the resin solution in a dispersed state of the fine particles of the present invention, for example, a colloidal dispersion liquid of the fine particles is used in a solvent or a dispersion liquid containing no inorganic acid or inorganic salt in advance. Fine particle concentration of 0.1 to 10% by weight, more preferably 0.1 to 5% by weight
After diluting so as to become, this diluted dispersion is mixed with a solvent containing an inorganic acid or an inorganic salt, the average degree of aggregation is 1 to
This can be realized by using a solvent in which fine particles are dispersed in 100 and adjusting the heat-resistant synthetic resin solution using the solvent.
When a dispersion having a fine particle concentration of more than 10% by weight is mixed with a solvent containing an inorganic acid or an inorganic salt, the degree of aggregation of the colloidal fine particles is undesirably increased.

The method and conditions for diluting the colloidal dispersion of fine particles are not particularly limited. The method for mixing the diluted dispersion of fine particles with a solvent containing an inorganic acid or an inorganic salt is not particularly limited, and a stirring type homogenizer, an ultrasonic homogenizer, or the like may be used in addition to a normal mixing device. Further, when the fine particle concentration is 0.1 to 10
In mixing the diluted dispersion diluted to have a weight% with a solvent containing an inorganic acid or an inorganic salt, the addition of the diluted dispersion is performed while the solvent flows at a speed of 50 to 1000 m / min. Addition of the amount to the solvent at a rate not exceeding 0.1% by volume of the solvent amount per minute is a preferred embodiment because it can achieve good dispersibility.

In addition, when a dispersion containing more than 10% by weight of colloidal fine particles is directly added to a solvent containing an inorganic acid or an inorganic salt, the dispersion is dispersed in a solvent stirred with an ultrasonic homogenizer. The addition amount of the solution was set at 0.
Fine particles can be dispersed to an average degree of aggregation of 1 to 100 even by adding to the solvent at a rate not exceeding 1% by volume. It is also a preferred embodiment that the solvent in which the fine particles are dispersed by the above method is filtered in order to remove foreign substances other than aggregated particles and lubricant fine particles generated before the solvent is used for polymerization or dissolution of the resin. The fine particles once dispersed in the solvent are relatively stable, and the fine particles hardly aggregate with time, but it is preferable to use the fine particles immediately after the adjustment.

The method for producing a magnetic tape using the film of the present invention is not particularly limited, and a conventional method of applying a magnetic powder onto a film with a binder may also be used. A method of forming a thin film may be used. In manufacturing the coating type magnetic tape, any type and size of the magnetic material, the type and blend of the binder, the coating method, and the like may be arbitrarily selected.
A known method may be used for forming the metal thin film of the magnetic layer. For example, Co, Ni, Cr, Fe
Alternatively, these alloys are directly deposited on a base film by a vapor deposition method, for example, a vacuum evaporation method, an ion plating method, a sputtering method, or the like, or Al, T
After forming a pre-coat layer of i, Cr, etc., it is grown as a crystal in the form of a thin film. In the horizontal magnetization method, the crystal axis of the magnetic layer may be obliquely inclined to the base film, and in the vertical magnetization method, the crystal axis may be grown vertically, if necessary. For the purpose of improving the abrasion resistance of the surface of the metal thin film magnetic layer, oxidizing or nitriding the surface, or providing an amorphous carbon layer or a crystalline diamond thin film phase by means such as a vapor phase growth method. Is also a preferred embodiment.

[Method of Measuring Characteristics] The method of measuring characteristic values according to the present invention is as follows. (1) Method for Measuring Film Thickness, Strength, Elongation, and Elastic Modulus The film thickness was measured using a dial gauge having a measurement surface with a diameter of 2 mm. The strength, elongation, and elastic modulus are values measured using a constant-speed elongation type high-elongation measuring instrument at a measurement length of 100 mm and a pulling speed of 50 mm / min.

(2) Method of Measuring Heat Shrinkage A 2 cm × 5 cm sample piece was cut out from the film, and 4 c
The mark is made by making a mark with a knife at intervals of m.
After leaving for 72 hours in an atmosphere of 5% RH, the distance between the labels was read and measured with a microscope. Then, in the case of thermal shrinkage, it was placed in a 200 ° C. hot air oven for 2 hours, and in the case of a weather resistance test, , 50 ° C., 85% RH in a thermo-hygrostat for 72 hours without any restraint.
After leaving for 72 hours in an atmosphere of 55% RH, the distance between the labels was read and measured with a microscope.

(3) Measurement method of center plane average roughness (SRa) by optical microscopy The definition of SRa is shown, for example, in Jiro Nara, "Method of Measuring and Evaluating Surface Roughness" (Sogo Gijutsu Center, 1983). In this case, a method was used in which an interference image of an interference phase contrast microscope was calculated and processed. That is, New V manufactured by ZYGO
Using an item 100 type surface roughness measuring device, the objective lens magnification was 40 times, the camera resolution was 550 μm, and the cutoff was 25.
In μm, SRa was measured at any three points of the film and expressed as an average.

(4) Maximum protrusion height (Zmax) and center plane root mean square (R) measured by an atomic force microscope (AFM)
MS) Measurement Method A film was fixed on a silicon wafer with a carbon paste, and TMX2010 manufactured by Topometrix was used.
Using a Discoverer-type AFM, a range of 5 μm × 5 μm was observed at a scanning speed of 2 Hz in a non-contact mode. In the image processing, a three-dimensional leveling process was performed. In addition, both Zmax and RMS are 10
Expressed as the average of the measured values of the visual field.

(5) Method for Measuring Average Aggregation Degree of Fine Particles A thin sample having a thickness of about 100 nm was cut out from a film by a conventional method, and observed at a magnification of 50,000 times with a JEOL JEM200FX transmission microscope. 50 of fine particle aggregates (including those that exist alone)
The number of the fine particles constituting each of them or each of them which are aggregated and dispersed is counted and expressed as an average value.

(6) Measuring method of magnetic properties The magnetic properties were measured according to JIS X 6129-1993.
In order to evaluate the characteristics of the present invention at a short wavelength, the output measurement was performed at 4499.8 ftpmm, and the missing pulse zone measurement was performed at a recording frequency of 9 MHz and 12 MHz with the JIS standard changed.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples and the like. In the examples,% not particularly indicated is% by weight. (Reference Example) A DDS-2 standard magnetic tape for data recording manufactured by Company S was identified as a chlorine-containing aramid resin film by elemental analysis and infrared spectroscopic analysis, and the film was subjected to transmission electron microscopy. As a result, it was found that fine particles of 10 to 20 nm were contained at an average agglomeration degree of about 150. As a result of analyzing the fine particles by the SEM-EDX method, they were found to be silica. The commercially available magnetic tape of DDS-2 standard manufactured by T Company is also based on an aramid resin film although chlorine is not detected, and about 40 nm of silica fine particles have an average cohesion degree of 15 on the film. Was included.

(Example 1, Comparative Example 1) A dispersion containing 20% of 20 nm colloidal silica particles was mixed with distilled water to prepare a diluent having a silica concentration of 5%, and 100.6%
The concentrated sulfuric acid was circulated at a speed of 100 m / min, and a silica diluent was fed and mixed at a rate of 0.06% by volume / min with respect to the total concentrated sulfuric acid. PPT is performed using concentrated sulfuric acid containing 0.01% of silica thus prepared.
A is dissolved so that the polymer concentration becomes 12.5%, and P
PTA dope was adjusted. The dope irregularly reflected light during stirring, and was observed under an optical microscope, and was found to be in a liquid crystal state, such as exhibiting optical anisotropy that makes the dark field of a crossed Nicol of a polarizing microscope a bright field.

The PPTA dope was filtered through a 5 μm-cut filter made of a sintered nonwoven fabric of stainless steel, and then discharged from a die onto an endless belt at a shear rate of 5 × 10 ^5.
sec ^-1, was cast as the draft ratio is 1.2. Then, the dope is subjected to a moisture absorption treatment simultaneously with heating on the belt to convert the dope from a liquid crystal phase to an isotropic phase.
Solidified in 0.1% sulfuric acid, neutralized, washed with water,
After being stretched by a factor of 1, the paper was stretched in the transverse direction by a clip tenter.
The film was stretched by one time, dried with hot air while maintaining a constant length state, then heat-treated at 430 ° C. while holding the film with a tenter, and then wound up.

The obtained PPTA film has a thickness of 4.
The physical properties of the film are strength of 42 and 43 kg / mm ² and elongation of 1 in the longitudinal direction and the width direction, respectively.
4, 12%, elastic modulus 1510, 1510 kg / mm ² ,
200 ° C heat shrinkage 0.2, 0.2%, 50 ° C, 80%
The dimensional changes after the RH treatment were 0.06 and 0.07%, and the aggregation state of the silica particles and the film surface data were as shown in Table 1.

For comparison, the PPTA dope prepared in the same manner was filtered through a filter made of a sintered nonwoven fabric of stainless steel cut at 5 μm, and then discharged from the die onto an endless belt at a shear rate of 5 × 10 ³ sec ^-1 and a draft rate of Is 1.2
Cast to become. Next, the dope is subjected to a moisture absorption treatment simultaneously with heating on a belt to convert the dope from a liquid crystal phase to an isotropic phase. Thereafter, the dope is coagulated in 30% sulfuric acid at 10 ° C., and neutralized.
After washing with water and stretching 1.1 times in the longitudinal direction, the film is stretched 1.1 times in the transverse direction by a clip tenter, dried with hot air while maintaining a fixed length, and then at 430 ° C. while holding the film with the tenter. And then wound up.

The obtained PPTA film has a thickness of 4.
The physical properties of the film are strength of 43 and 43 kg / mm ² and elongation of 1 in the longitudinal direction and the width direction, respectively.
4, 13%, elasticity 1500, 1510 kg / mm ² ,
200 ° C heat shrinkage 0.2, 0.2%, 50 ° C, 80%
The dimensional changes after the RH treatment were 0.08 and 0.07%, and the aggregation state of the silica particles and the film surface data 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 its magnetic properties were measured. The output of the magnetic tape of Comparative Example 1 was 90%, the missing pulse zone was 160% at 9 MHz, and 33% at 12 MHz.
It was 0%.

Example 2, Comparative Example 2 A dispersion containing 40% of colloidal silica particles having a particle size of 40 nm was mixed with distilled water to prepare a diluent having a silica concentration of 5%. The doping of PPTA was adjusted under the same conditions as described above. This P
The PTA dope was filtered through a 5 μm-cut filter made of sintered stainless steel non-woven fabric, and then cast from a die onto an endless belt at a discharge shear rate of 3 × 10 ⁵ sec ⁻¹ and a draft rate of 1.2. Example 1
The same operation as described above was performed to obtain a film.

The obtained PPTA film has a thickness of 4.
The physical properties of the film are strength of 43 and 43 kg / mm ² and elongation of 1 in the longitudinal direction and the width direction, respectively.
4, 13%, elasticity 1500, 1510 kg / mm ² ,
200 ° C heat shrinkage 0.2, 0.2%, 50 ° C, 80%
The dimensional changes after the RH treatment were 0.06 and 0.05%, and the aggregation state of the silica particles and the film surface data were as shown in Table 1.

For comparison, a film was prepared in the same manner except that the colloidal silica dispersion was used without dilution, and the resulting PPTA film had a thickness of 4.5.
μm, and the physical properties of the film were 42 and 41 kg / mm ² in elongation and width, respectively,
2, 13%, elasticity 1520, 1500 kg / mm ² ,
200 ° C heat shrinkage 0.2, 0.2%, 50 ° C, 80%
The dimensional changes after the RH treatment were 0.06 and 0.05%, and the aggregation state of the silica particles and the film surface data were as shown in Table 1.

Using the obtained film, a magnetic tape having a magnetic layer made of metal powder was produced as a trial, assembled into a DDS-2 standard cartridge, and its magnetic properties were measured. The output of the comparative example 2 is 91%, the missing pulse zone is 150% at 9 MHz, and 35% at 12 MHz.
It was 0%.

Example 3 A colloidal silica dispersion containing 20% of spherical silica having an average particle size of about 20 nm in water was added to 100.5% sulfuric acid at a rate of 2 ml / min with stirring by an ultrasonic homogenizer. And the silica concentration is 0.01
% Concentrated sulfuric acid was adjusted. PPTA was dissolved using concentrated sulfuric acid containing 0.01% of silica thus adjusted so that the polymer concentration became 12.5%, and the dope of PPTA was adjusted.

After the PPTA dope was filtered through a 5 μm-cut filter made of a sintered nonwoven fabric of stainless steel, the discharge shear rate was 5 × 10 ⁴ from the die onto an endless belt.
sec ^-1, was cast as the draft ratio is 1.2. Then, the dope is subjected to a moisture absorption treatment simultaneously with heating on the belt to convert the dope from a liquid crystal phase to an isotropic phase.
Solidified in 0.1% sulfuric acid, neutralized, washed with water,
After being stretched by a factor of 1, the paper was stretched in the transverse direction by a clip tenter.
The film was stretched by one time, dried with hot air while maintaining a constant length state, then heat-treated at 430 ° C. while holding the film with a tenter, and then wound up.

The obtained PPTA film has a thickness of 4.
The physical properties of the film are strength of 44 and 43 kg / mm ² and elongation of 1 in the longitudinal direction and the width direction, respectively.
5, 13%, elastic modulus 1510, 1510 kg / mm ² ,
200 ° C heat shrinkage 0.2, 0.2%, 50 ° C, 80%
The dimensional changes after the RH treatment were 0.06 and 0.05%, and the aggregation state of the silica particles and the film surface data 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 its magnetic properties were measured. Compared with the magnetic tape of Comparative Example 1, the output was 92%, the missing pulse zone was 140% at 9 MHz, and 32% at 12 MHz.
It was 0%.

[0063]

[Table 1]

[0064]

According to the present invention, by controlling the degree of agglomeration of lubricant particles contained in a film and the shape of the agglomerated particles, it is possible to reduce the fineness of fine projections on the film surface formed thereby. It becomes possible, and the slipperiness with each equipment in the film manufacturing process, the magnetic tape manufacturing process, etc. is not impaired, while the magnetic tape manufactured using the film of the present invention hinders the following of the magnetic layer surface of the magnetic head A smooth surface without any problem is obtained, and there is little occurrence of errors when writing and reading short-wavelength signals.

According to the magnetic tape using the film of the present invention, magnetic recording of a high recording capacity can be performed by a short wavelength signal, which is increasingly required in the future, and is used for information recording such as multimedia, and high quality such as digital high vision. It is possible to provide a magnetic tape useful for recording television images, backing up computer information records in an advanced information society, and the like.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 9/02 C08K 9/02 C08L 77/10 C08L 77/10 // B29L 7:00

Claims (5)

[Claims] An average thickness of a heat-resistant resin is 2 to 8 μm.
m, and 0.001 to 1.0% by weight of fine particles inert to acid having an average particle size of 5 to 50 nm having an average cohesion of 1 to 1
And the shape of the aggregated particles contained in the film is represented by the following formulas (1) and (2), and the resolution of the optical surface roughness meter on the surface on which the magnetic layer is to be formed is shown. The average roughness (SRa) of the center plane as seen in the above is 0.1 to 3 nm, and the maximum projection height (Zm) measured by an atomic force microscope.
ax) is 5 to 50 nm, and the root mean square roughness (RM) is
A heat-resistant synthetic resin film suitable for a base of a magnetic tape for high-density recording, wherein S) is 0.1 to 10 nm. 0.01 ≦ L ₂ / L ₁ ≦ 1 (1) A ≦ 2500 × a ⁻² (2) [where L _{1 is} the length of aggregated particles in the film casting direction, L ₂ : The length of the aggregated particles in the direction perpendicular to the casting direction of the film, A: degree of aggregation, a: average primary particle diameter. ] 2. The heat-resistant synthetic resin film has a strength of 20 to 60 kg / mm in any direction of the film.
² , elastic modulus of 1000 to 2500 kg / mm ² , 200
2. The base for a magnetic tape for high-density recording according to claim 1, wherein the heat shrinkage at 2 ° C. is 2% or less, and the dimensional change before and after the treatment for 72 hours in an environment of 50 ° C. and 80% RH is 0.1% or less. Heat-resistant synthetic resin film. 3. A heat-resistant synthetic method using a solvent in which fine particles inactive against colloidal acids having an average particle diameter of 5 to 40 nm are previously mixed with 0.001 to 1.0% by weight based on a resin to be dissolved. Adjusting the resin solution, when producing a film by a wet, dry, or dry-wet method, when adding the colloidal fine particle dispersion to a solvent containing an inorganic acid or an inorganic salt, the dispersion is preliminarily made of an inorganic acid or an inorganic acid. After diluting with a solvent containing no salt or a dispersing agent used in the dispersion so that the fine particle concentration becomes 0.1 to 10% by weight, the mixture is mixed with a solvent containing an inorganic acid or an inorganic salt, and the average agglomeration is performed. Degree 1
A method for producing a heat-resistant synthetic resin film suitable for a base of a high-density magnetic recording tape, characterized in that fine particles are dispersed in a range of 100 to 100. 4. A dispersion of fine particles inactive against a colloidal acid in advance, which is a dispersant used for a solvent or a dispersion containing no inorganic acid or inorganic salt, and having a fine particle concentration of 0.1 to 10%. %, And while the solvent flows at a speed of 10 to 1000 m / min, the amount of the diluted dispersion added to the solvent at a rate not exceeding 0.1% by volume of the solvent amount per minute. The method for producing a heat-resistant synthetic resin film suitable for a base of a high-density magnetic recording tape according to claim 3, wherein the fine particles are dispersed to have an average degree of aggregation of 1 to 100. 5. A heat-resistant synthetic resin solution is prepared by using a solvent in which fine particles inactive against colloidal acids having an average particle diameter of 5 to 50 nm are mixed in a proportion of 0.001 to 1.0% by weight. When producing a film by a wet, dry, or dry-wet method, the discharge shear rate when the heat-resistant resin solution is cast from a slit die is 5 × 10 ^{4 to} 5 × 10 ⁵ sec.
and c ^-1, the draft ratio high-density magnetic containing aggregated particles of claim 1, wherein the casting so that 1 to 5. (take-up speed ratio of the support surface for the discharge rate from the die) A method for producing a heat-resistant synthetic resin film suitable for a base of a recording tape.