JPS6087436A - Flexible disc for magnetic recording - Google Patents

Abstract

PURPOSE:To improve dimensional stability by adjusting the coefft. of expansion with temp. and humidity of a biaxially oriented film consisting of poly-p-phenylene sulfide in a specific range. CONSTITUTION:A biaxially oriented film of which >=90mol% consists of poly-p- phenylene sulfide is used as a base in this invention. This film is provided with the expansion characteristics in which the max. coeffts. of expansion with the temp. and humidity at the longitudinal and transverse planes are respectively 9- 35X10<-6> deg.C<-1> and 0-5.0X10<-6>%RH<-1> and the difference between the max. value and min. value of the coefft. of expansion with temp. and humidity are respectively 0-8.0X10<-6> deg.C<-1> and 0-2.0X10<-6>%RH<-1>. The coeffts. of expansion are obtd. by setting adequately film forming conditions. The essential requirement for this film is that >=90mol% thereof consists of the constituting unit of the formula I . Para-halobenzene and alkali sulfide are brought into reaction in a polar solvent as a general method for polymerizing such poly-p-phenylene sulfide.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a magnetically recording flexible disk having a magnetic recording layer made of a thin metal film that can avoid tracking errors.

PRIOR ART It has been known to prevent tracking errors by means of suppressing temperature changes in the magnetic flexible disk recording and reproducing apparatus itself, and by providing a special track detection circuit (such as a track servo) in the recording and reproducing apparatus. However, these methods require a complicated recording/reproducing device.

Therefore, in general, tracking errors are prevented by improving the magnetic disk by improving the support film and magnetic material to materials with low coefficients of thermal expansion and humidity expansion, or by manufacturing selected magnetic flexible disks. things are being done.

However, even with improved magnetic flexible disks, dragging errors occur when used at high temperatures (40 to 50° C.) and high humidity (approximately 80% RH). Especially in low humidity (
A magnetic flexible disk recorded at low humidity (about 10℃) and low humidity (about 20%RH) may cause tracking errors when played back at room temperature (about 25℃) and normal humidity (about 60%R - 1). There was a drawback that it occurred. The problem of a decrease in the output envelope due to this tracking error and poor S/N ratio remains unsolved.

In recent years, in particular, high-density magnetic recording media have been developed by forming metal thin films as magnetic recording layers on non-magnetic support thermoplastics by vacuum evaporation, sputtering, or vacuum deposition methods without using binders. This metal thin film is called a magnetic recording material, and by electroless plating method,
Many methods for obtaining metal thin films have been proposed.

In most cases, magnetic flexible disks equipped with a magnetic recording layer made of a thin metal film are classified into so-called perpendicular magnetic recording, in which recording is performed by magnetization in the direction of the thickness of the magnetic recording medium. Improvement alone is not sufficient to increase the density of magnetic recording, and high-density magnetic recording can be achieved by simultaneously satisfying the improvement of track density due to the temperature and humidity expansion coefficient of the base film. It is.

A magnetic recording flexible disk made of a metal thin film capable of such high track density recording has not yet been obtained.

Purpose of the Invention As a result of repeated research in order to eliminate the above-mentioned drawbacks, the present inventor has developed a biaxially oriented film substantially made of poly-p-phenylene sulfide by adjusting the temperature/humidity expansion coefficient to a specific range. The inventors have discovered that tracking errors can be avoided by obtaining a film with excellent dimensional stability and using this film as a support to produce a magnetic recording flexible disk made of a thin metal film, and have thus arrived at the present invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording flexible disk made of a metal thin film that can be used in an improved manner by expanding the usable atmospheric conditions (temperature and humidity range) so that no tracking errors occur even at high temperatures and high humidity.

Furthermore, such a magnetic recording flexible disk made of a metal thin film with high dimensional stability under temperature and humidity also enables high-density magnetic recording, and it is an object of the present invention to provide such a magnetic disk. It is.

The present invention is a magnetic disk in which a support is a biaxially oriented film containing 90 mol% or more of poly-P-phenylene sulfide. The maximum coefficient of thermal expansion of this film in a plane including the longitudinal direction and the width direction is 9 to 35 x 10'
℃-1, maximum humidity expansion rate is O ~ 5.0 x 10''6%R
H-', the difference between the maximum value and the minimum value of the coefficient of thermal expansion is 0 to 8
．． OX 10'C-1 and the difference between the maximum and minimum humidity expansion coefficients is 0 to 2. A biaxially oriented poly-〇-phenylene sulfide film with an expansion characteristic of This is a magnetic recording flexible disk provided with a recording layer.

The poly-p-phenylene sulfide biaxially oriented film that serves as the support for the magnetic disk of the present invention can be prepared at the above-mentioned temperature and temperature range.
This can be achieved by appropriately controlling the film forming conditions so as to satisfy the humidity expansion coefficient conditions.

The magnetic recording flexible disk of the present invention is composed of the support and a magnetic layer. The magnetic layer is vacuum deposited,
Sputtering, ion blating, C, D, V (C
chemical vapor deposition
) or electroless plating, but all conventionally known methods can be used to form these metal thin films.

In the case of vacuum evaporation method, 10'''4~10''GTOrr
The evaporated metal in the tungsten boat or alumina hearth is evaporated under a vacuum by resistance heating, high frequency heating, electron beam heating, etc., and deposited on the support. Fe, Ni, Co, and alloys thereof are commonly used as the deposited metal. Further, the present invention can also be applied to a reactive vapor deposition method in which Fe is vapor-deposited in an 02 atmosphere to obtain an iron oxide thin film. In the ion blating method, DC glow discharge is performed in an atmosphere mainly composed of an inert gas of 10'''4 to TO-31-orr.
An RF glow discharge is generated and the metal is evaporated during the discharge. Ar is usually used as the inert gas. In the sputtering method, a gas discharge is generated in an atmosphere containing 10' to 10-IT Orr (7) Ar as a main component, and the generated Ar ions knock out atoms on the target surface. Methods for generating glow discharge include direct current two-pole and three-pole sputtering methods and high-frequency sputtering methods. There is also a magnetron sputtering method that uses magnetron discharge.

The thickness of the magnetic thin film must be such that it provides sufficient signal output as a high density magnetic recording medium.

Therefore, the thickness of the magnetic thin film varies depending on the thin film forming method and application, but is generally 0.02 to 1. ! iμmrL(200~1
between sooo people).

Methods for forming magnetic thin films for longitudinal recording include evaporation@(thermal evaporation,
Examples include methods such as electron beam evaporation (electron beam evaporation, etc.), sputtering (dipolar direct current sputtering, high frequency sputtering, etc.). In the case of vapor deposition, ferromagnetic metal such as CO is continuously obliquely vapor-deposited onto a non-magnetic plastic support so that the axis of magnetization is expressed in the horizontal direction of the tape, and by repeating the V4 layer, crystal magnetic The tape exhibits anisotropy and shape anisotropy in the horizontal direction of the tape. Therefore, the total thickness of the metal thin film is 0.02 to 0.5 μm (20
0~5000A).

In addition to the method of forming a magnetic thin film for longitudinal recording as described above,
As a method that enables high-density digital recording, for example, an appropriate amount of Cr is mixed into CO (10 to 2
0%), the generated demagnetizing field is suppressed, and an axis of easy magnetization is developed in the perpendicular direction.A perpendicular magnetic recording method in which recording is performed in the perpendicular direction to the substrate surface can also be applied.

In the normal sputtering method, the thickness of CO is 0.2 to 1.5 μm.
A Cr alloy is used. At this time, permalloy (
A magnetic flux concentrator thin film made of a high magnetic permeability material such as Fe-Ni) or supermalloy can be provided. The high permeability material as the magnetic flux concentrator is formed by sputtering, and the film thickness is 0.1 to 1 μTrL (1000 to 100 μTrL).
It is a thin film layer with a low coercive force (less than 500 e). The Co-Cr film thickness of the magnetic recording layer at this time is 0.2 to 1
．． Form to about 5 μm (2,000 to 15,000 people).

The magnetic recording layer made of a metal thin film only needs to have at least one magnetic recording layer on the front and back sides of the base film, but as disclosed in Japanese Patent Publication No. 5B-91, magnetic recording layers made of a thin metal film may have a soft magnetic layer such as a NiFe alloy thin film. Alternatively, there may be a suitable adhesive layer between the base film and the metal thin film, or a protective layer may be provided on the metal thin film.

The poly-p-phenylene sulfide that is the support film in the present invention has a structural unit of -C-
It is essential that the polymer be composed of S, and if it is less than 90 mol %, the crystallinity of the polymer will decrease and the coefficient of thermal expansion will increase, which is not preferable.

The method for polymerizing such poly-phenylene sulfide is generally to react para-halobenzene with an alkali sulfide in a polar solvent.

As the polymerization conditions, a temperature of 250 to 350° C. is selected, and the polymerization time can be appropriately determined depending on the type of catalyst used, the pressure within the polymerization system, and the degree of polymerization. In the poly-p-phenylene sulfide film, for example, deterioration inhibitors, particulate silica,
A matting agent, lubricant, etc. such as kaolin, calcium carbonate, and calcium phosphate can also be contained or dispersed therein.

In the biaxially oriented film made of poly-p-phenylene sulfide used in the present invention, the maximum thermal expansion coefficient in the plane including the longitudinal direction and width direction of the C1 film is 9 to 3.
5X 10'℃-1, preferably 9~25X10''G
'G-1, maximum humidity expansion rate is O ~ 5.0 x 10''G%
RH-' (preferably O~2.5X10-G%RH-'
) The difference between the maximum value and the minimum value of the humidity expansion coefficient is 0 to 8. OX
10'G℃-' (preferably 0-5.OX 10'
C-') The difference between the maximum value and the minimum value of the humidity expansion coefficient is O ~ 2,
OX 10'% R1-1-1 preferably O~1.5X
When the condition of 10'% RH-1) is satisfied, tracking errors can be avoided and the magnetic disk can be used in a wide temperature and humidity range. If the temperature expansion coefficient or humidity expansion coefficient exceeds the above range, if the magnetic recording flexible disk is reproduced at a different temperature than when recording, the difference in temperature expansion coefficient and humidity expansion coefficient will cause the magnetic recording flexible disk to lose its center. As a result, the magnetic head and recording track are often misaligned, resulting in tracking errors. As a result, the output changes and a drop error 1- occurs.

Currently, polyethylene terephthalate-based polyester film, which is most commonly used for magnetic recording flexible disks, has a maximum thermal expansion coefficient of approximately 17×1.
0'6℃-1, the difference between the maximum and minimum coefficient of thermal expansion is 8 x 10
``6℃-1, which roughly matches the thermal expansion coefficient of the recording/reproducing device in terms of thermal expansion coefficient, but due to the difference in the direction of thermal expansion coefficient, that is, anisotropy, track misalignment occurs. There is.

Also, the humidity expansion coefficient is approximately 1ix1o-c%It J
Since the humidity expansion coefficient of the recording/reproducing apparatus can be considered to be O, a 1-rack deviation corresponding to a change in humidity is quite large, about -1.

On the other hand, by using the biaxially oriented film made of poly-p-71 nylene sulfide of the present invention as a support, track deviation due to temperature expansion and humidity expansion is reduced compared to the commonly used biaxially oriented film made of polyethylene terephthalate polyester. By reducing the difference between the maximum and minimum coefficients of thermal expansion and the difference between the maximum and minimum coefficients of humidity expansion, trunk displacement can be further suppressed.

As a result, it is possible to obtain a magnetic recording flexible disk that can be used in an atmosphere with a wide range of temperature and humidity, and that can perform high-density magnetic recording.

The poly-p-phenylene sulfide film for obtaining the above-mentioned properties can be produced in accordance with the method for forming polyester films such as polyethylene terephthalate and polybutylene terephthalate-I.

For example, an unstretched film can be cast by melt extrusion at 300 to 350° C. depending on the melting point by the ①-die method, inflation method, or the like. The film is then biaxially stretched to form a biaxially oriented film, and the stretching temperature at this time can be approximately the same to high temperature as in the case of polyethylene terephthalate film.

The stretching temperature is preferably about 80 to 140°C. The stretching ratio is 3.0 to 5.0 times (preferably 3.0 times) in the longitudinal direction.
．． 5 to 4.5 times), and 3.0 to 5.048 in the lateral direction (preferably 3.5 to 4.5 times). The obtained biaxially oriented film is heated at 150 to 280°C (preferably 180 to 280°C).
By heat setting at 270 DEG C. for 1 to 100 seconds, a film with a small deviation of 1 to 100 degrees can be obtained even with changes in temperature and humidity according to the present invention. However, the biaxially oriented film made of poly(0-phenylene sulfide) of the present invention can be produced using this method. ? It is not limited to only what is given. For example, by performing the above heat setting process twice with different running directions and making the second heat setting temperature higher than the first heat setting, the difference between the maximum and minimum temperature and humidity expansion coefficients can be minimized to the full width of the film. It can be held for a long time.

The biaxially oriented film can have an appropriate thickness depending on its use, but it can usually be selected from a range of about 25 to 125 μm.
It is not limited to this range.

The method for measuring characteristic values in the present invention is as follows.

(1) Temperature expansion coefficient A constant load elongation tester (IT L2 type) manufactured by Japan Automatic Control Co., Ltd. is placed in a constant temperature and humidity chamber, and the measurement is carried out there. The measurement sample is heat-treated in advance under predetermined conditions (for example, 70°C for 30 minutes), and the sample is placed in a testing machine at 20°C and humidity of 60°C.
The coefficient of thermal expansion is determined by reading the dimensional change between %R)-1 (relative humidity) and 40°C and 60% relative humidity.

The sample length at this time was 505#, and the sample width was 1/4 inch. The load applied during measurement is constant at 5 g (in 1/4 inch). If a long sample cannot be obtained, use the thermomechanical analyzer TM-3000 manufactured by Shinku Riko Co., Ltd.
It can be measured using This method may be used when calculating the difference between the maximum value and the minimum value of the coefficient of thermal expansion. One size of the sample has a length of 15 g and rlJ of 5 mm, and is kept at 20°C and humidity O.
Determine the difference between the maximum and minimum thermal expansion coefficients by reading the dimensional changes in %Rl-1 and O%RH at 40°C.

Of course, the values obtained by both measuring instruments are completely consistent.

(2) Humidity expansion rate As in the case of measuring the temperature expansion coefficient, use a constant load elongation tester manufactured by Japan Automatic Control Co., Ltd., and pre-process it under the conditions of 40°C and humidity 90%RH. Attach the sample to
The humidity expansion rate is determined by reading the dimensional change between 20° C. humidity 30% R1-1 and 20° C. humidity 70% RH.

A thermomechanical analyzer made by Shinku Riko Co., Ltd. was placed in a constant dry/humidity machine on the zero-temperature lifting platform, and measurements were taken under the same conditions as in the case of temperature expansion measurements.

(3) Tracking deviation test (temperature change) The following method was used for the tracking deviation test. Magnetic recording layers were formed on both sides of the base film by sputtering a metal thin film, and magnetic recording was performed on the magnetic recording flexible disk that was scooped out into a disk shape using a ring head at 15° C. and humidity of 60% R1-1. Examine the maximum output and output envelope of the magnetic sheet. Next, maintain the ambient temperature at 4()℃ humidity 60% RH, measure the maximum output and output envelope at that temperature, and measure the maximum output and output envelope at 15℃ humidity 60%RH.
Output envelope at %RH and 40℃ humidity 60%R
The output envelopes at H are compared to determine whether 1 to racking is good. The smaller this difference is, the better the tracking characteristics are.

If this difference is 3 dB or more, tracking is poor and the evaluation is ``x'', and if it is within 3 dB, it is evaluated as ``O''.

(4) Tracking deviation test (humidity change) Record at 25℃, humidity 20%R)-1 as in the previous section, and further maintain the atmospheric conditions at 25℃, humidity 70%RH, and 25℃ humidity 20%
The output envelopes at R)-1 and 25° C. and 70% R)-1 are compared to evaluate the quality of tracking as in the previous section. The evaluation method is the same as in Section 3.

Example Next, the present invention will be specifically explained with reference to Examples.

Examples 1 to 4 and Comparative Examples 1 to 2 1 mol of Na2S/9-day 20, 0.05 mol of NaOH, 0.6 mol of sodium benzoate, and 3.5 mol of N-methylpyrrolidone were placed in an autoclave and heated to 210°C. After dehydration, the system was cooled to 160°C, 1 mol of p-dichlorobenpine was added, and the system was heated to 280°C.
Polymerization was carried out under stirring.

After the polymerization was completed, the temperature was lowered to room temperature, and washing was repeated with water and acetone to obtain Poly-Roof 1 nylene fluoride polymer.

As a comparative example, 0.8 mol of p-dichlorobenzene was used in the same manner as in the example (however, 0.8 mol of p-dichlorobenzene was used instead of 1 mol of p-dichlorobenzene).
5 mol, using 0.15 mol of m-dichlorobenzene)
Polymerization was carried out at 280°C with stirring to obtain a copolymer of bo-p-phenylene sulfide and poly-11-phenylene sulfide.

Furthermore, as a comparative example, polyethylene terephthalate was polymerized by a conventional method.

These polymers were melt extruded at 300°C and 1050μ
An unstretched film was obtained. Next, it is stretched 3.3 to 3.7 times in the machine direction at 90 to 120°C, 3.4 to 3.8 times in the transverse direction at 100 to 130°C, and further stretched 1 time at 200 to 270°C.
The mold was fixed for 0 to 30 seconds to obtain films with a thickness of 75 μm under different film forming conditions. Both sides of the biaxially oriented film thus obtained were sputtered to a thickness of 0 by a sputtering method using facing targets as disclosed in Japanese Patent Application Laid-Open No. 57-158380.
．． A 5 μm Ni-Fe alloy film and a 0.4 μm Co-C alloy film were sequentially formed to form a double-sided two-layer medium.

That is, N+ Fe alloy film NiFe alloy target (
Ni: 81wt%, 330gX 150m) 2
Using a sputtering device of the type 1 to 1 type, in which the targets were placed facing each other at an interval of 120 m, the targets were placed at a temperature of 23°C on the sides of both targets.
Argon gas pressure i, op a (
Pascal) and sputtering was performed at an average deposition rate of 0.2 μ/min to sequentially form 0.5 μm NiFe alloy films on both surfaces.

Then, the Go Or alloy film is formed using a COCr alloy target (C
r: 17 wt%) using the same apparatus as above.
While running the sheet on which the Ni-Fe alloy film was formed on a rotating drum kept at 0°C, the average deposition rate was 0.2μ/min.
Perform sputtering at 0.4. cz C0Cr alloy films were sequentially formed on both sides to create a double-sided two-layer medium. Thereafter, a magnetic recording flexible disk having an outer diameter of 20 cm and an inner diameter of 3.8 cm was cut out and tested using a recording/reproducing apparatus.

The sheet recorder rotated at 3BOr, p, m, and the magnetic head was positioned 8 cm from the center of the disk. Track 111 was 300μ, and head +A Fj was ferrite. 1M for magnetic recording flexible disk
The l-1z signal was recorded under predetermined conditions, reproduced under predetermined conditions, and evaluated based on the difference in output envelope.

15℃, 60%R of this magnetic recording flexible disk
1-1 and 25°C, 20% R)l) was less than 10.2 dB.

Films made of poly-p-phenylene sulfide under various film-forming conditions were subjected to temperature, humidity expansion coefficient, and track deviation tests, and the results are shown in Table 1.

From the results in Table 1, it was found that tracking errors were improved in Examples 1 to 4, and the magnetic disks could be used in a high temperature and high humidity atmosphere. On the other hand, it was found that Comparative Examples 1 and 2 could not be used in a high temperature and high humidity atmosphere.

Effects of the Invention By applying a poly-p-phenylene sulfide biaxially oriented film having a specific temperature and humidity expansion coefficient to the support of the magnetic recording disk, a magnetic recording disk without tracking errors can be obtained. Furthermore, high-density recording is also possible by increasing the track density. Since the magnetic recording disk of the present invention has a small change in expansion coefficient due to temperature and humidity,
It has the advantage of being adaptable to a wide range of atmospheric conditions.

Claims (1)

[Claims] In a magnetic recording disk in which a plastic film is used as a support and a magnetic recording layer made of a metal thin film is provided on the support, the plastic film accounts for 90 mol% or more of poly-p.
- A biaxially oriented film made of phenylene sulfide, which has a maximum thermal expansion coefficient of 9 to 35X 1.0' in a plane including the longitudinal direction and the l' direction.
℃-', the maximum humidity expansion coefficient is 0 to 5. Ox 10'%
RH-1, the difference between the maximum and minimum coefficient of thermal expansion is 0 to g
, ox io"c" and the difference between the maximum value and the minimum value of the humidity expansion coefficient is O~2.0X10-6%R) (-1).