JPS6093625A - Polyether ether ketone film for vertical magnetization - Google Patents

Abstract

PURPOSE:To improve surface smoothness, heat resistance, low hygroscopicity and linear expandability by subjecting a polyether ether ketone film to molecular orientation and heat setting and regulating the max. surface roughness to below a specific value. CONSTITUTION:A base film for vertical magnetization which is formed by subjecting polyether ether ketone to molecular orientation and heat setting and had <=500Angstrom max. surface roughness is obtd. At least >=80kg/cm<2> backward tension is applied to the polyether ether keton film and is subjected to rolling to 1.5-4 times under at least >=100kg/cm linear pressure by a pair of pressurizing rolls kept in a temp. range of >=80 deg.C and <=140 deg.C as the 1st stage and the film is heat-set at >=250 deg.C and below the m.p. as the 2nd stage. The 3rd stage in which the film is stretched 1.5-4 times at >=120 deg.C and <=200 deg.C in the transverse direction of the film is added beteen the above-mentioned stages. The film is stretched 1.5-4 times in the transverse direction and 1.1-2 times in the longitudinal direction at >=120 deg.C and <=200 deg.C after the 1st stage and thereafter the film is subjected to the 2nd stage. The film is stretched 1.5-4 times in the longitudinal and/or transverse direction at >=120 deg.C and thereafter the film is subjected to the above-described 2nd stage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a base film for perpendicular magnetization having a maximum surface roughness of 500A or less, which is made by molecularly orienting and heat-setting polyetheretherketone. The maximum surface roughness here is the surface roughness specified in JIS BO601, and can be measured by the stylus method.

Furthermore, polyetheretherketone is a thermoplastic resin having the following structural units repeatedly and exhibits extremely excellent heat resistance.

Currently, magnetic recording plays a major role as external memory in tape recorders, VTRs, and other computers, and floppy disks are becoming increasingly important for office automation machines and personal computers. In this way, magnetic recording is used in the form of tape or disk, and polyester film is the mainstream as the base film. On the other hand, recently, a perpendicular magnetization method has been proposed to increase recording density, and development is progressing in the industry toward practical use. However, base films for vertical i and other applications are required to have surface smoothness, heat resistance, low moisture absorption, and a small coefficient of linear expansion, and existing commercially available films all have problems and are not practical. For example, polyester film lacks heat resistance when forming a magnetic film, resulting in extremely poor productivity and is not practical. In addition, in the case of a polyimide film with good heat resistance, it is not practical due to the influence of absorbed moisture, which makes it impossible to create a high vacuum during the formation of the magnetic film, the adhesion strength between the film and the magnetic film is insufficient, and the surface is rough.

On the other hand, the molecularly oriented and heat-set polyetheretherketone film of the present invention solves all of these problems, and has a high heat resistance with a melting point of 334°C, a hygroscopicity lower than that of polyester, and a linear expansion coefficient. small,
Moreover, as the maximum surface roughness becomes 500A or less due to molecular orientation, it has all the characteristics necessary as a base film for perpendicular magnetization.

Note that if the maximum surface roughness exceeds 500X, the surface smoothness after forming the magnetic film will be insufficient, causing troubles due to contact with the main magnetic pole during recording and reproduction.

Therefore, the maximum surface roughness must be 500% or less.

As a result of intensive studies on base films for perpendicular magnetization, the inventors of the present invention found that, as mentioned above, a film with a maximum surface roughness of 500X or less and made of molecularly oriented and heat-set polyetheretherketone has extremely excellent suitability. This is what led to the present invention.

Stretching and roll rolling can be cited as molecular orientation means for the polyetheretherketone film of the present invention.

Further, the present inventors further investigated the improvement of surface smoothness, which is particularly important for a base film for perpendicular magnetization, and found that the roll rolling method is an extremely excellent method. That is, it has been found that in the case of stretching, the surface of the film is free, whereas in roll rolling, the surface is regulated by the application rolls, so that a film with better surface smoothness can be produced. Note that it would be more effective if a liquid lubricant was used during rolling, but this is not a necessary condition. However, since roll rolling is basically a means of orienting molecules in the length direction of the film, it can be used as is for tape applications, but in cases where isotropy is required, such as in floppy disks, it is necessary to orient the molecules in the film width direction. It is preferable to also carry out molecular orientation, and stretching is necessary as a means for this purpose.

Furthermore, in tape applications, in addition to roll rolling, if the film is stretched in the direction of the film and also in the length direction, a film with extremely high molecular orientation can be obtained and the film can be made thinner. In any case, the order of rolling and stretching may be carried out first. When rolling, a rear tension of at least 80#/cm2 or more must be applied on the entry side of the pressure roll.

Here, the backward tension, also called the extending force, is a force that acts in the opposite direction to the direction in which the film travels, and is 80V.
/cs+2 If it is lower than the neutral point on the pressure roll (
The highest pressure point) shifts to the roll entry side, making it more likely that defects will occur, making stable machining difficult. Therefore, it is necessary to apply a rear tension of 80/Ca12 or more.

Next, regarding the rolling temperature, the pressure roll was heated to 80°C or higher for 1
It can be arbitrarily set within a temperature range of 40°C or higher. If the temperature is lower than this range, a large number of pressure rolls will be required to obtain the desired rolling ratio, and a very large force will be required to apply pressure between the rolls, which will cause equipment problems and be expensive in terms of equipment. This is inappropriate as a rolling condition. On the other hand, if the temperature is higher than this range, there is no problem in rolling workability, but surface smoothness, which is important for perpendicular magnetization, deteriorates somewhat, which is not preferable.

In addition, the linear pressure must be 10 (A'/cm or more) or 100K.
F/.

If it is lower, sufficient orientation cannot be achieved.

Under the above conditions, the rolling strength is 1.5 to 4 times, but if it is less than 1.5 times, the orientation effect is insufficient, and if it is rolled more than 4 times, breakage occurs frequently and stable processing becomes difficult. In addition, these things are the same in the case of stretching, and the magnification is 1.5 to 1.5.
4 times better.

Further, the stretching temperature must be in the range of 120'C or higher and 200'C or lower. If the temperature is lower than this range, uniform stretching will not be possible, resulting in a film with extremely poor thickness accuracy.On the other hand, if the temperature is higher than this range, crystallization will proceed and the yield stress will increase, making stretching difficult. In addition, when not only rolling but also stretching is used in the length direction of the film, the appropriate stretching ratio is 1.degree. 1 to 2.times. from the viewpoint of stable processability and orientation effect. Further, heat setting is carried out at a temperature of 250°C or higher and lower than the melting point, but if the temperature is lower than 250°C, sufficient dimensional stability cannot be obtained.

Through the above steps, a base film suitable for perpendicular magnetization can be obtained.
0-Cr alloy, iron oxide, Co-P alloy, CoNi alloy,
A thin film of a magnetic material such as a CoP Ni alloy can be formed. Thin film forming means include sputtering, vacuum evaporation, ion blating, electroplating, etc., and the base film of the present invention can be applied to any of them.

EXAMPLES Hereinafter, the present invention will be specifically illustrated by examples, but the present invention is not limited by these in any way.

Examples 1 to 2, Comparative Examples 1 to 3 Polyether ether ketone (manufactured by ■C■, 45G) was
A raw film with a thickness of 0.2 t was prepared by extruding it from a 1'' die with a width of 400 mm using a 0.00 extruder. This raw film was rolled by a pair of pressure rolls with a diameter of 2600 m and a surface length of 700 m, and was further heat set. ;0, 19F Ya 5tylus tip was attached and measured. Table 1 shows the processing conditions and maximum surface roughness measurement results.

Examples 3 to 4, Comparative Examples 4 to 5 Raw films prepared in the same manner as in Example 1 were rolled or stretched in the longitudinal direction, further stretched in the lateral direction, and then heat set. The maximum surface roughness of the obtained film was measured in the same manner as in Example 1. Table 1 shows the processing conditions and maximum surface roughness measurement results.

Example 5 A raw film prepared in the same manner as in Example 1 was rolled,
Further, after transverse stretching and longitudinal stretching, heat setting was performed. The maximum surface roughness of the obtained film was measured in the same manner as in Example 1. Table 1 shows the processing conditions and maximum surface roughness measurement results.

Permalloy with an average thickness of 3000 A was deposited as a soft magnetic layer on both sides of the film obtained in Example 3 by sputtering, and then 2
0% Cr CO alloy is deposited and the average film thickness is 5oooo
It was possible to form a perpendicularly magnetized film easily and stably.

Comparative Example 6 Permalloy and 2
An attempt was made to fly a 0% Cr-Co alloy, but the film was deformed by sputtering and a good product could not be obtained.

Comparative Examples 7-8 Commercially available polyester film (Toshi, Lumirror ■) 50μ
product and polyimide film (Dupont, Ka
Permalloy and 20% Cr-Co were prepared in the same manner as in Example 4 using 50μ products (pton d type).
Attempts were made to fly the alloy, but Lumirror ■ had low heat resistance, resulting in extremely low productivity and impractical use.

Regarding Kapton (2), a high vacuum could not be obtained due to the absorbed moisture, and the adhesion between the magnetic layer and the film was poor and the film easily peeled off. Moreover, even before peeling, a good product could not be obtained due to poor surface smoothness.

Claims (5)

[Claims] (1) Polyether circle-telketone film is molecularly oriented and heat set, with a maximum surface roughness of 500.
A base film for perpendicular magnetization that is less than or equal to X. (2) Apply a backward tension of at least 80 Kf/ci+' to the polyether ether ketone film, and apply a back tension of at least 6100 Kf/ci+ using a pair of pressure rolls in a temperature range 1 of 80°C to 140°C. 1 at linear pressure
．． Claim No. 1, characterized in that it is rolled 5 to 4 times and heat-set at a temperature of 250°C or higher and lower than the melting point.
Base film for perpendicular magnetization described in ). (3) Apply a rear tension of at least 80 zelkova/cm2 or more to the polyether nee-derketone film and heat it at 80°C.
At least 100? 1.5~ at linear pressure of /3 or more
Roll rolled 4 times, stretched 1.5 to 4 times at a temperature of 120°C or higher and 200°C or lower with the direction in the film, and then flattened ζ.
The base film for perpendicular magnetization according to claim (1), which is heat-set at a temperature of 250° C. or higher and lower than the melting point. (4) Apply a rear tension of at least 680°/am2 to the polyetheretherketone film and heat it at 80°C.
Above 14 (7'
Stretch the film 1.5 to 4 times in the width direction and 1.1 to 2 times in the length direction at the following temperatures, and further stretch to 250
The base film for perpendicular magnetization according to claim 1, wherein the base film is heat-set at a temperature of not less than 0.degree. C. and not more than the melting point. (5) 120% polyetheretherketone film
A special feature characterized by stretching the film by 1.5 to 4 times in the length direction and/or film width direction at a temperature of not less than 200°C and not more than 200°C, and further heat-setting at a temperature of not less than 250°C and not more than the melting point. A base film for perpendicular magnetization according to claim (1).