JPH03241518A - Flexible magnetic recording disk - Google Patents

Abstract

PURPOSE:To extend the applicable range of environmental temp. and humidity for a disk by controlling the expansion coefft. against temp. and humidity of a biaxially oriented film comprising poly-1,4-cyclohexylene dimethylene terephthalate to specified ranges. CONSTITUTION:The magnetic recording flexible disk consists of a biaxially oriented film comprising poly-1,4-cyclohexylene dimethylene terephthalate polyester as the base material and a magnetic layer formed on this film. This biaxially oriented film is prepared so that, in the plane including the longitudinal and width directions, it has the maximum temp. expansion coefft. of (9 - 35) x 10<-6> deg.C-1, the maximum humidity expansion coefft. of (0 - 8.0) x 10<-6> % RH<-1>, with the difference between the maximum and minimum temp. expansion coefft. of (0 - 8.0) x 10<-6> deg.C<-1> and the difference between the maximum and minimum humidity expansion coefft. of (0 - 3.0) x 10<-6>%RH<-1>. Thereby, the obtd. flexible magnetic recording disk can be used in an environment of high temp. and humidity ranges for high density magnetic recording.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording flexible disk that can avoid tracking errors. More specifically, the present invention relates to a magnetic recording flexible disk capable of high track density recording.

It has long been known that tracking errors can be prevented by providing a magnetic flexible disk recording/reproducing device itself with a mechanism to suppress temperature changes and a special track detection circuit (track servo, etc.). These methods complicate the recording/reproducing device and are not general-purpose.In practice, magnetic Measures are taken to prevent tracking errors by creating flexible disks.

However, even with such magnetic flexible disks, high temperatures (40 to 50 degrees Celsius) and/or high humidity (approximately 80% RH)
If used in , tracking errors will occur. In particular, magnetic flexible disks recorded under conditions of low temperature (approximately 10°C) or low humidity (approximately 20% RH) are
There is a drawback that tracking errors occur when played back in an atmosphere with normal humidity (about 60%R). This tracking error causes a decrease in the output envelope, resulting in a poor S/N ratio, which remains an unsolved problem.

Purpose of the Invention As a result of repeated research in order to eliminate the above-mentioned drawbacks, the present inventor has determined that the temperature and humidity expansion coefficient of a biaxially oriented film made of poly-1,4-cyclohexylene (dimethylene terephthalate) polyester can be controlled within a specific range. The present inventors have discovered that tracking errors can be avoided by obtaining a film with high dimensional stability and manufacturing a magnetic recording flexible disk using this as a base material, and have arrived at the present invention.

The object of the present invention is to provide usable atmospheric conditions and temperatures.

It is an object of the present invention to provide a magnetic recording flexible disk which has an expanded humidity range and is improved so that no track errors occur even under high temperature and high humidity conditions.

Furthermore, such a magnetic recording flexible disk with high dimensional stability under temperature and humidity makes it possible to increase the density of magnetic recording, especially to improve the track density, and the present invention provides such a disk. This is also another object of the present invention.

Mitome and Yutaka 1 - The present invention uses a biaxially oriented film as a base material made of poly-1,4-cyclohexylene dimethylene terephthalate polyester in which 80 mol% or more of the acid component is composed of terephthalic acid. The maximum coefficient of thermal expansion in the plane including the longitudinal direction and width direction of the film is 9 to 35 x 10'℃-1
．． The maximum humidity expansion rate is 0~8,0XIO'℃%Rlow 1
．． The difference in temperature expansion coefficient between the maximum and minimum is 0 to 8.0X10'
℃-1, and the difference between the maximum and minimum humidity expansion coefficients is 0 to 3. O
This is a magnetic recording flexible disk made by coating a magnetic layer on a material having a 10'%R row of 1 and smoothing the surface by applying a calender roll treatment.

This magnetic recording flexible disk includes the poly-1,
It is obtained by coating a magnetic layer on a biaxially oriented film made of 4-cyclohexylene dimethylene terephthalate polyester, drying it, and then calendering it to smooth the surface. In addition, a biaxially oriented film made of poly-1,4-cyclohexylene dimethylene terephthalate polyester can be manufactured by appropriately controlling the film forming conditions so as to satisfy the above-mentioned temperature and humidity expansion coefficient conditions. Can be done.

The magnetic recording flexible disk of the present invention is composed of a magnetic layer and a base film.

The magnetic layer is made of magnetic powder or metal. The ferromagnetic powder or metal used in the present invention is γ-Fezes.

Co-containing T-Fe 203. Fe 304. Co
Contains Fe30s, CrOp, Co-Ni
-P alloy, C0-Ni-Fe alloy, Go-Cr alloy, C
Known ferromagnetic materials such as o-Ni alloy and barium ferrite can be used.

The binder used with the magnetic powder in the present invention includes known thermoplastic resins and thermosetting resins.

It is a reactive resin or a mixture thereof. in particular,
Vinyl chloride vinyl acetate copolymer 1MA vinyl chloride nylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrol copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer , methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, polyvinyl fluoride.

(vinylidene chloride acriminitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives, cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.).

Styrene-butadiene copolymer, polyester resin.

Chlorovinyl ether acrylic acid ester copolymers, amino resins, various base rubber thermoplastic resins, and mixtures thereof are used.

Methods for coating the magnetic layer on the support film include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, and kiss coating.

Cast coat, spray coat, etc. can be used.

A magnetic layer is applied to the base film to a thickness of 0.1 to 20 μm. Poly-1,4 which is the base film in the present invention
- As for the cyclohexylene dimethylene terephthalate polyester, 80 mol% or more of the dibasic acid component is composed of terephthalic acid, and the glycol bottom valve is a glycol selected from the cis or trans isomer of 1,4-cyclohexane dimetatool. It is. Dibasic acid components other than terephthalic acid include isophthalic acid, phthalic acid, and adipic acid.

Examples include dibasic acids such as sepatic acid, succinic acid, and oxalic acid. Preferably it is isophthalic.

The 1,4-cyclohexane dimetatool used in the present invention may be produced by catalytic reduction of dimethyl terephthalate or terephthalic acid, but there is no problem in producing it by either method.

Although the ratio of the cis isomer to the trans isomer of 1.4-cyclohexanedimetatool is not particularly limited, it is preferably in the range of cis isomer/trans isomer = 4/6 to 0/10.

In the poly-1,4-cyclohexylene dimethylene terephthalate polyester, for example, stabilizers such as phosphoric acid, phosphorous acid and their esters, titanium dioxide,
Particulate silica, kaolin.

Matting agents such as calcium carbonate and calcium phosphate.

A lubricant or the like may be included.

The biaxially oriented film made of poly-1,4-cyclohexylene dimethylene terephthalate polyester used in the present invention has a maximum thermal expansion coefficient of 9 to 35 x 10''6 in a plane including the longitudinal direction and width direction of the film. ℃−1
, preferably 9-25X10-6°C-1 maximum humidity expansion coefficient of 0-8. OX 10'%RH-1, preferably 0~
5. OX 10'%Rday-1, and the difference in temperature expansion coefficient between maximum and minimum is 0 to 8. OX 10'C-1, preferably 0 to s, OX 10"6C-1. Also, the difference in humidity expansion coefficient between the maximum and minimum is 0 to 3. Ox 10"6% R low richness, preferably 0 to 2.5×10−6% RH−1. When the temperature/humidity expansion coefficient of the film base material satisfies this range, tracking errors of the flexible disk can be prevented and it can be used in a wide temperature/humidity range. If the temperature or humidity expansion coefficient exceeds the range specified above, the magnetic recording flexible disc may expand from the center due to the difference in temperature expansion coefficient and humidity expansion coefficient when played back at a temperature different from the atmosphere recorded on the magnetic recording flexible disc. This difference causes the magnetic head and recording track to deviate, causing tracking errors. As a result, the output changes,
Causes dropout.

With current technology, the maximum thermal expansion rate of polyethylene terephthalate polyester film, which is most commonly used for magnetic recording flexible disks, is approximately 17X.
10-'℃-1, the difference between the maximum and minimum coefficient of thermal expansion is 8 x 1
Although the thermal expansion coefficient is about 0''6° C.-1, which is almost the same as the thermal expansion coefficient of the recording/reproducing device, it is not possible to completely prevent tram slippage due to the difference in the thermal expansion coefficient in the in-plane direction.

In addition, the humidity expansion coefficient is quite large, about 11 x 10''6%R days, and the track deviation corresponding to humidity changes is quite large since the humidity expansion coefficient of the recording and reproducing device can be regarded as O.On the other hand, the 1. By using a biaxially oriented film made of 4-cyclohexylene dimethylene terephthalate-based polyester, - Tracks due to temperature expansion and humidity expansion are better than the biaxially oriented film made of polyethylene terephthalate-based polyester used for the crotch. By reducing the deviation and the difference between the maximum value and the minimum value of the temperature expansion coefficient and the difference between the maximum value and the minimum value of the humidity expansion coefficient, the track deviation can be further suppressed, and it can be used over a wide range of temperatures and humidity. This basic film can be used in a wide range of atmospheres without any problem.Furthermore, this basic film can be used to produce magnetic recording flexible disks with high density magnetic recording.

As a method for forming a poly-1,4-cyclohexylene dimethylene terephthalate-based polyester film to obtain the above-mentioned expansion characteristics, a method similar to that for forming a normal polyester film such as polyethylene terephthalate can be applied. For example, a melt-extruded unstretched film can be produced by a T-die method, an inflation method, or the like. Furthermore, it can be stretched in the 2@ direction to form a biaxially oriented film.

The stretching temperature at this time can be carried out under almost the same conditions as in the case of polyethylene terephthalate film, but
, 4-cyclohexylene dimethylene terephthalate type polyester, the glass transition temperature and melting point change depending on the terephthalic acid content, so it is necessary to appropriately select the melting temperature and the temperature of the casting drum accordingly.

The stretching temperature is usually 80 to 140°C, and the stretching ratio is 3.0 to 5.0 times in the machine direction, preferably 3.
．． Select 5 to 4.5 times, 3.0 to 5.0 times in the lateral direction, preferably about 3.5 to 4.5 times. The obtained biaxially oriented film is heated at 150-260°C (preferably 180-260°C).
By heat setting at 50° C. for 1 to 100 seconds, the film of the present invention with small track deviation due to temperature/humidity expansion can be obtained. However, the biaxially oriented film made of poly-1,4-cyclohexylene dimethylene terephthalate polyester of the present invention is not limited to that obtained by such a method. The biaxially oriented film of the present invention can have an appropriate thickness depending on its use, but usually has a thickness of 25 to 1
It is selected from a range of about 25μ. However, the thickness is not limited to this range. The method for measuring characteristic values in the present invention is as follows.

(1) Temperature expansion coefficient Constant load elongation test 11 manufactured by Japan Automatic Control Co., Ltd. (ITL2 type)
Place it in a constant temperature and humidity chamber and take measurements. The measurement sample is heat-treated in advance under predetermined conditions (for example, 70°C for 30 minutes), and the sample is installed in the test machine at a temperature of 20°C and a humidity of 60% R.
The coefficient of thermal expansion is measured by reading the dimensional change between the mouth (relative humidity) and the temperature 40°C/60% R)-1. The original sample length at this time was 505 aw+, and the sample width was 174 inches. The weight added during measurement is 5
It was fixed at a width of 9/1/4 inch. If a long sample cannot be obtained, use a thermomechanical analyzer @TM made by Shinku Riko Co., Ltd.
-3000 can also be used for measurement. When determining the difference between the maximum value and the minimum value of the coefficient of thermal expansion, T M −
Use 3000. Sample dimensions are 15m long and 5m wide.
1M1, temperature 10℃, humidity 0%RH and temperature 40
By reading the dimensional change at °C and relative humidity 0%, the difference between the maximum and minimum thermal expansion coefficients can be determined. Since the values obtained by both measurement methods completely match, either measurement method may be used.

(3 Humidity Expansion Rate As in the case of determining the temperature expansion coefficient, a constant load elongation tester manufactured by Japan Automatic Control Co., Ltd. was used, and a sample that had been pretreated at a temperature of 40°C and a relative humidity of 90% was mounted. ℃
- Determine the humidity expansion coefficient by reading the dimensional change between 30% relative humidity and 20°C/70% relative humidity. If the sample could not be taken for a long time, the thermomechanical analyzer manufactured by Shinku Riko Co., Ltd. was placed in a constant temperature constant room machine and the measurement was performed under the above conditions as in the case of measuring thermal expansion. In this case as well, the values obtained by either method are completely consistent.

(3) Tracking deviation test (1 degree change) The following method is used for the tracking deviation test. A magnetic recording flexible disk coated with a magnetic layer, calendered and punched into a disk shape is heated at a temperature of 15°C and a humidity of 60%.
The recording is made on day R, and the maximum output and output envelope of the magnetic sheet at that time are measured. Next, maintain the ambient temperature at 40℃ and humidity 60%R day, and check the maximum output and output envelope at that temperature.
Output envelope at R mouth and temperature 40℃ humidity 60%R
The tracking state is determined by comparing the output envelopes for the eyes. The smaller this difference is, the better the tracking characteristics are. If this difference is 3 db or more, the tracking is poor and the evaluation is ×, and the 3 dl
) were evaluated as ○.

(4) Tracking deviation test (humidity change) As in the previous section, record in an atmosphere with a temperature of 25°C and relative humidity of 20%, and further maintain the atmospheric conditions at a temperature of 25°C and relative humidity of 70%. Compare the output envelope when the temperature is 25° C. and the relative humidity is 70%. Evaluate the tracking quality in the same way 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 6 and Comparative Examples 1 to 3 85 mol% of terephthalic acid as a dibasic acid component.

15 mol% of isophthalic acid and 1.
Using 4-cyclohexane dimetatool, these and 0.05 mol% of titanium oxide as a catalyst were placed in an autoclave, heated under stirring to cause transesterification reaction, and then polycondensation reaction to form 1,4 cyclohexane dimetatool. Poly-1 consisting of metatool, terephthalic acid and isophthalic acid,
A 4-cyclohexylene dimethylene terephthalate polyester was obtained.

On the other hand, polycyclohexylene-1,4-dimethylene terephthalate consisting of 100 mol% of terephthalic acid and 100 mol% of 1,4-cyclohexane dimetatool was also polymerized in the same manner. As a comparative example, polyethylene terephthalate was polymerized by a conventional method.

These three types of polyester were melt extruded at 300°C, and 10
A 50μ unstretched film was obtained. Then 90-120
Stretched 3.3-3.7 times in the machine direction at 100-130°C, 3.4-3.8 times in the transverse direction at 100-130°C, and further stretched 200-240 times.
C. for 10 to 30 seconds to obtain biaxially oriented films having a thickness of 75 microns under different film forming conditions. The biaxially oriented film thus obtained was coated with a magnetic coating liquid having the following composition to a thickness of 5 μm.

(Magnetic coating liquid) T −F e 2 Ch
200 parts by weight, 1 part vinyl chloride-vinyl acetate copolymer resin (VAG port manufactured by UCC), 30 parts by weight polyurethane (PP-88 manufactured by Nippon Polyurethane Industries), 20 parts by weight isocyanate compound (Coronetro, manufactured by Nippon Polyurethane Industries), 40 parts by weight carbon ( Average size: 0.5μφ) 20 parts by weight dimethylsiloxane
2 parts by weight toluene
70 parts by weight methyl ethyl ketone
70 parts by weight cyclohexanone
70 parts by weight of the above coating material was thoroughly mixed and stirred and applied onto the biaxially oriented film, followed by calender roll treatment. 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 recording and reproducing operations were performed using a recording and reproducing device. Seat recorder is 360rph
The position of the magnetic head is 8C from the center of the disk.
It became an IR. The inside of the track was 300μ, and the material of the head was ferrite. A 1MM2O signal was recorded on a magnetic recording flexible disk under predetermined conditions, and reproduced under predetermined conditions to measure the difference in output envelope. Conditions of 15°C, 60% R mouth and 25°C for this magnetic recording flexible disk.

The envelope at 20%R was less than 0.2 dB.

Poly-1,4-cyclohexylene dimethylene terephthalate polyesters under various film forming conditions were subjected to temperature/humidity expansion coefficient and track deviation tests, and the results are shown in Table 1.

As is clear from the above results, when the I humidity expansion coefficient is in an appropriate range, tracking errors are improved as shown in Examples 1 to 6, and magnetic disks can be used for recording and reproducing in high-temperature, high-humidity atmospheres. It turns out that it is possible. On the other hand, tracking errors occur in Comparative Examples 1 to 3. Thus, it has been found that the disk of the present invention has high industrial value as a flexible disk with high track density.

Effects of the Invention The magnetic recording flexible disk of the present invention is made of a specific polyester, namely poly-1,4-cyclohexylene dimethylene terephthalate, which is biaxially stretched so as to be balanced in the longitudinal direction and the width direction. A magnetic layer is provided on the surface of this polyester film. If the base film has a predetermined temperature expansion coefficient and humidity expansion coefficient, tracking errors will not occur even if the track density is increased as a magnetic disk.
& has the advantage of enabling density recording. Furthermore, this magnetic disk has the advantage that there is no tracking error even if the temperature and humidity conditions between recording and reproduction are different. Therefore, the flexible disk of the present invention can withstand changes in atmosphere and has a wide range of applications.

Claims (1)

[Claims] In a magnetic recording disk formed by providing a magnetic layer on a polyester film base material and smoothing the surface, the polyester film is a biaxially oriented film consisting essentially of poly-1,4-cyclohexylene dimethylene terephthalate, The maximum coefficient of thermal expansion of the film in a plane including the longitudinal direction and the width direction is 9 to 35 x 10^-^6 °C^-
^1, Maximum humidity expansion rate is 0 to 8.0 x 10^-^6R
H^-^1, the difference in temperature expansion coefficient between the maximum and minimum is 0 to 8.
0 x 10^-^6℃^-^1, and the difference in humidity expansion coefficient between the maximum and minimum is 0 to 3.0 x 10^-^6%RH^-^1
A magnetic recording flexible disk characterized by: