JPS61236021A - 3-methylbutene-1 polymer film for magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk consisting of a base material having an excellent surface characteristic and having excellent heat resistance by specifying the thermal shrinkage percentage and humidity expansion coefficient in all directions in the plane. CONSTITUTION:A 3-methylbutene-1 polymer film for a magnetic disk having <=4% thermal shrinkage percentage in all directions in the plane at 180 deg.C and <=0.6X10<-6>/% RH humidity expansion coefficient and having excellent heat resistance is used. The poly-3-methylbutene-1 is the homopolymer of 3- methylbutene-1 or a copolymer of 3-methylbutene-1 and a 2-18C alpha-olefin and/or polyene. Ethylene, propylene, etc., are exemplified as the 2-18C alpha-olefin which is copolymerized with 3-methylbutene-1 and butadiene, hexadiene, etc., are exemplified as the polyene. Consequently, a magnetic disk having low humidity expansion coefficient and thermal shrinkage percentage, having an excellent surface characteristic and with less change in the output can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-resistant magnetic disk having a small coefficient of humidity expansion and a small coefficient of thermal contraction, and improved surface characteristics.

[Prior art and its problems]

Conventionally, magnetic disks are made by laminating a magnetic layer on a polyester film as a base material, by coating the surface with magnetic particles together with a binder, or by fixing magnetic metal using methods such as vacuum deposition, sputtering, or plating. things are known.

However, in recent years, efforts have been made to make magnetic disks more compact and to increase their density, but conventional disks have had the disadvantage of having a large humidity expansion coefficient.

In other words, since the coefficient of humidity expansion is large, dimensional changes occur in an atmosphere of high temperature and high humidity, and problems such as track misalignment, output reduction, and output fluctuation, which are not so common with magnetic recording tapes, are likely to occur. In order to eliminate the above drawbacks, it has been considered to use a material with excellent heat resistance and a low humidity expansion coefficient as the base material of the disk, such as polyolefin, but conventional polyolefins have poor heat resistance and shrinkage height decreases. Unfortunately, it has not been applied because surface defects caused by foreign matter and poor surface roughness tend to cause dropouts when made into disks. (JP-A-39-1-993 [OBJECTS OF THE INVENTION] An object of the present invention is to have a low humidity expansion coefficient of less than 5% of the thermal contraction rate of IGO° C. in all directions within the text.

The present invention provides a magnetic disk with excellent heat resistance and made of a base material with good surface characteristics.

[Structure of the invention]

As a result of intensive studies to achieve the above object, the inventors have
Among polyolefins, it has been discovered that only a polymer film made of 3-methylbutene-1 achieves the above object.

In other words, the gist of the present invention is that 1
The thermal shrinkage rate at 80°C is 4I% or less, and the humidity expansion coefficient is 0. The present invention provides a 3-methylbutene-1 polymer film for magnetic disks which has excellent heat resistance and has an A X /0-6/% RH or less.

The present invention will be explained in more detail below.

Poly-3-methylbutene-l used in the present invention
is a homopolymer of 3-methylbutene-1 or a copolymer of 3-methylbutene and an α-olefin and/or polyene having 2 to no grams of carbon atoms. Examples of α-olefins having a carbon number of λ to l that are copolymerized with 3-methylbutene-1 include ethylene, propylene, and butene! , hexene-
Examples of polyenes include butadiene, hexadiene, methylhexadiene, ethylidene norbornene, and the like.

The copolymerization method may be so-called random copolymerization or block copolymerization. Among these, preferred are homopolymers of 3-methylbutene-1, random copolymers and block copolymers of 3-methylbutene-1 and ethylene, propylene, or butene, and 3-methylbutene-1 with a small amount of diene. It is a copolymer with The amount of these copolymerized components in the polymer is preferably at most 10% by weight, more preferably at most -0% by weight.

The melt viscosity was measured using a conical disc rotary rheometer, and was measured at 330°C and a shear rate of Q, /// seconds, i.e., an angular velocity of Q, /radian/second.
It is necessary that it is X/Q4 poise or more. If it is less than this, it is unsuitable because stretching, especially breakage, occurs frequently. A high melt viscosity is preferable in terms of stretchability and mechanical properties, but if it is too high, the melt extrusion moldability of the polymer deteriorates, which is not preferable. The melt viscosity is usually expressed by the above measurement method as follows: /X/Q4~/X/, 7? Selected from Poise range.

There are no particular restrictions on the method for producing poly-3-methylbutene having such a melt viscosity, but the following method is suitable.

That is, in an aliphatic, alicyclic, or aromatic hydrocarbon such as hexane, heptane, cyclohexane, benzene, etc., in a liquid olefinic state or in the absence of a solvent, the aluminum content is less than or equal to the atomic ratio of aluminum to titanium. - a catalyst comprising a solid titanium trichloride catalyst complex containing a complexing agent and aluminum cyinobutyl monochloride; 3-methylbutene-1 is polymerized alone or 3-methylbutene-1 is copolymerized with an α-olefin and/or polyene having a carbon number of y to ig in the presence of a polymerization temperature of 0-/kO ℃. Either 3-methylbutene-1 is polymerized alone in the presence of a catalyst, or 3-methylbutene-1 and carbon atoms
There is also a method in which a polymer obtained by copolymerizing Nog with an α-olefin and/or a polyene is crosslinked.

Furthermore, in order to impart slipperiness to the film, it is also preferable to add organic particles, inorganic particles, etc. to the film, or to blend other polymers into the film.

As the additive for adjusting the surface roughness and the mass coefficient, an organic or inorganic compound having an average particle size of about Qmμ to IOμ is usually used, although it varies depending on the type and purpose of the additive. The amount added depends on the particle size distribution, particle size, etc., and is generally selected from the range of 0.001-10% by weight, preferably from 0.001 to 11% by weight, although it cannot be determined generally.

Examples of organic additives include high melting point polyethylene terephthalate, polyorganosiloxane, crosslinked polymer compounds, fluorine-based compounds such as polytetrafluoroethylene, and salts of organic carboxylic acids such as calcium terephthalate. It can be added as fine particles with a controlled diameter.

-1. Examples of inorganic additives include LiF, Li01
, Li, CO,, Li3PO4, Na1F, Na
1l, NA2003, MgO5Mg0o3, Mg80
4, Oa OO,, CaSO4,0a(H,PO4)2
, ○aHPO4, Oa, (PO4)2, Br003, B
rBO4, B a 003, Ba5O,, A1. o,,
Sin,,Tie□,zrO2,l1le3(Ton)
Inert inorganic particles that are insoluble and non-reactive with the resin, such as kaolin, celite, talc, zeolite, boron nitride, and metal powders such as Sb, Go, and Bi, can be added.

The surface roughness can also be changed by blending other polymers such as polyethylene, polystyrene, and polycarbonate. Other compounds such as dyes, pigments, antistatic agents, conductive substances, antioxidants, antifoaming agents, etc. may be added as necessary.

The thus obtained high molecular weight polymer containing inorganic particles is extruded from a die through a filter and taken to a cooling drum to prepare an unstretched film. The unstretched film is stretched, if necessary, at a stretching temperature of 3O<0>C to 10<0>C, both vertically and horizontally by -IQ times, to produce a biaxially oriented film. Materials with large in-plane anisotropy are also unsuitable for l-axis stretching and biaxial stretching. The unstretched film and biaxially oriented film thus obtained are obtained by heat-setting at a temperature of 750° C. or higher and a melting temperature of 750° C. or higher. Biaxial orientation is simultaneous biaxial,
Sequential two axes and combinations of them are also effective.

The film of the present invention should have a humidity expansion coefficient of 0. A
I, and it does not meet the purpose. Therefore, it was decided to use a polyolefin, and as a result of intensive studies, it was found that among polyolefins, a poly-3-methylbutene-1 film was particularly suitable. Biaxial stretching is highly preferred in order to obtain a film with a particularly low humidity expansion coefficient. However, for magnetic disks, it is necessary that the thermal shrinkage rate at 180° C. in all in-plane directions be 4'% or less. If it is greater than 4%, it is unsuitable for use as a magnetic disk because of large dimensional changes due to environmental changes.

For this purpose, it is necessary to have a film with excellent heat resistance, and conventional polyolefins are not suitable.

Further, the film of the present invention has a surface roughness g (Ra) of o
, oos to 060 S μm is preferable from the viewpoint of disk runnability and trope-out.

These values can be changed by changing the type, particle size, particle size distribution, etc. of the particles to be added. However, even if the Ra is the same, the running performance will be different and the amount of coarse material will change, so they are almost the same.
For Ra, a system with good runnability and few coarse particles should be selected.

As a result of intensive studies on this point, it was found that poly-3-methylbutene is the most suitable, whereas other polyolefins contain coarse materials as raw materials. In addition to the method described above, the surface roughness can also be adjusted by changing the stretching conditions. In any case, Ra is adjusted depending on the use of the magnetic disk. However, for high-density magnetic disk applications, Ra is required to be 0.003 or less.
In the case of a film having an Ra of 0,000 oz or less, it is also a suitable method to impart running properties and adhesion to the magnetic layer by, for example, in-line or off-line coating treatment on one or both sides.

By applying a magnetic layer to the film with various surface roughness obtained in this way, it is possible to form a magnetic disk using a conventional method. The sizes include the standard type with a diameter of 5 inches, the mini floppy with a diameter of 3 inches, and the micro floppy with a diameter of 3 inches and 3 inches.
We were able to obtain a film that is suitable for use in magnetic disks and has excellent heat resistance, low shrinkage, and surface properties.

The characteristic values of the present invention are determined by the following measurement method.

(1) Humidity expansion coefficient (β) A sample with sample length/kOB and sample width 1O1iK is set in a constant temperature and humidity layer, and a constant load (109) is applied. Find the original length L (I Cm) at a constant temperature of 20°C and relative humidity of 33% RE,
Dimensional change caused by changing humidity gs%RE [ΔL
)Cynm) is measured. Dimensional changes are determined by converting them into electrical quantities using a differential transformer and recording them.

β=ΔL/Lo/ΔH Here, ΔH is the amount of change in relative humidity, i.e., t, t-
3! =RiOchiRH.

(2) Average surface roughness, cL) From the film roughness curve in the direction of its center value, measure the length L (
When a part with a standard length of 2 mm is extracted, the center line of this extracted part is the X axis, the vertical magnification direction is the Y axis, and the roughness curve is expressed as Y = f (X), the following formula is used. The given value is expressed in μm.

',, fL Ra= 1f(X)ldX Note that the effects of the present invention were evaluated based on the following criteria.

(1) After recording a signal on the output outermost track of the disk using a floppy disk drive under the conditions of temperature jO ℃ and relative humidity 33%RH, store it for 3 hours at t3%RH condition, take it out, and measure the disk outer diameter. The dimensional changes and the output changes in the outermost track were measured. The average output is the average value of the maximum output and minimum output of the test track, and the average output of 3A; ToRTl is ioo
Calculated as %.

(2) Dropouts The RF signal was subjected to envelope detection, waveform shaping was performed using a selection circuit, and the number of dropouts per unit time was measured.

〔Example〕

Next, an example of an embodiment of the present invention will be described based on Examples.

Example 1 (Preparation of homogeneous titanium trichloride solution) 1!rOytl of purified toluene and 90 mm of titanium tetrachloride were placed in a dry argon-substituted 500-capacity four-bottle flask.
ol and then di-n-butyl ether? Omm
ol was added. Titanium tetrachloride and di-
It reacted with n-butyl ether and was uniformly dissolved in toluene to obtain an orange-yellow homogeneous solution. While stirring the solution and keeping it at 2S°C, a solution containing 20rdtlC of diethylalheminium monochloride (4'3mmol'k) toluene was gradually added, and a dark orange homogeneous solution of titanium trichloride was obtained. Ta.

(Titanium trichloride precipitate formation and catalyst cracking) When the homogeneous solution of titanium trichloride obtained in step (A) above was heated to ?!r'C, purple titanium trichloride appeared during the temperature rise. Precipitate formation was observed.

After stirring at 91°C for 6Q minutes, the precipitate was separated and poured into 100 ml of n-hebutane.
The mixture was washed three times with orrtl to obtain a finely divided purple titanium trichloride catalyst complex. Elemental analysis revealed that this catalyst complex has the formula 'r
io13(A1013) 0.00μ((n○4H*)
20] 0.0! It had a composition of r.

(Production of polymer) 3-Methylbutene-
Polymerization of No. 1 was carried out as follows. Thoroughly vacuum dry
In an autoclave purged with nitrogen, the solid titanium trichloride catalyst complex obtained in Example No. 4 was mixed with O, Lycium pg, and diisobutylaluminum monochloride. / A mmo
I prepared l. Then liquefy 3-methylbutene-1 & 3
After charging 0/i, polymerization was carried out at 0° C. for 3.3 hours.

Next is isobutyl alcohol 2! Rml was charged to stop the polymerization, and excess unreacted monomer was expelled. Next, 1,000 grains of beef sun was introduced into the normal reactor, and after stirring for 30 minutes at SO°C, the supernatant liquid was extracted and the catalyst component in the polymer was washed and removed.

Irganox IQIQ was added to the obtained poly-3-methylbutene as an additive in an amount of 0. Part 2, Irgafos P-KP
Q, is 0. After adding two parts (both manufactured by Nippon Ciba Geigy), pelletization was carried out using an extruder at 320°C. The melting point of this product was 3 ott°C, and the melt viscosity of the press-molded product under the conditions of 330°C and a shear rate Q of /l/sec was 7x/θS poise.

(Manufacture of film) The pellets have an average particle diameter of o and rμ of T10! A polymer containing 0.3 weight:1% of the film was added to 13
The extrusion was extruded through a UOOQ mesh filter using a T-die at 0° C., and then taken to a cooling drum using a contact method to obtain an unstretched film.

The unstretched film was stretched at 100° C. by a factor of e, a, a, o in the vertical direction and in the horizontal direction by a simultaneous biaxial stretching method to obtain a biaxial film. The U-axis oriented film was heat-set at 2-0°C to obtain a 75μ film. Heat yield H of the obtained film at ltO ℃
TA is 1. vertically and horizontally. ! r%,/, 14%. Using this film as a base material, magnetic layers with a thickness of 3 μm were formed on both sides by a conventional method, and then a disk shape was punched out to produce a magnetic disk with a diameter of 200×m.

Comparative example! Example 1 using a commercially available biaxially distributed polypropylene film
I made a magnetic disk in the same way.

Table 1 shows the humidity expansion coefficient, surface characteristics, output change, and dropout characteristics of the base material and magnetic disk.

It can be seen from Table 1 that the film of the present invention is extremely suitable for use as a magnetic disk.

Table 2 [Effects of the Invention] According to the present invention, a magnetic disk having a small coefficient of humidity expansion and a small coefficient of thermal contraction, excellent surface characteristics, and little change in output can be obtained.

Claims (1)

[Claims] (1) Thermal contraction rate at 180°C in all in-plane directions is 4% or less, and the humidity expansion coefficient is 0.6 x 10^
- 3-Methylbutene-1 polymer film for magnetic disks with excellent heat resistance of 6/% RH or less