JPS5945348A - Polyethylene terephthalate film for metallic thin film magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the titled film giving a magnetic recording medium free from the deposition of oligomer even at a high temperature in the application of the metallic thin film by evaporation, etc., and having smooth surface, by adding a sorbitan ester to polyethylene terephthalate. CONSTITUTION:A polyethylene terephthalate containing 0.001-0.2wt%, preferably 0.004-0.02wt% of a sorbitan ester is used as the base resin of the objective film. The sorbitan ester is preferably a triester composed of sorbitan and a 8- 22C fatty acid. Both components are extruded under the condition of the polymer melting temperature of 260-320 deg.C and a residence time in the extruder of 2- 20min. When a polymer is used in the form of pellets, it should be dried to a water-content of <=0.005% before use. The thickness of the film is 3-100mum, preferably 5-75mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention i1 high-density magnetic recording, ν11. The present invention relates to a polyethylene terephthalate film for use in bodies, especially metal thin film magnetic recording media.

In recent years, as a high-density magnetic recording medium, a thin film of Mt gold has been deposited as a magnetic recording layer without using a binder by vacuum deposition or sputtering. A thin film magnetic recording material made of this ferromagnetic metal is used as a refractive index material. When forming a metal thin film using thin film forming means such as vapor deposition, sputtering, or ion grating, the polyethylene terephthalate film, which is a non-magnetic support, is likely to be thermally deformed due to exposure to high heat. A method has been adopted in which heat is absorbed by bringing the cooling doshim into close contact with the cooling doshim. And, for example, 7j=
Ion heat generated during k (kinetic energy, ■ latent heat of condensation and ■ radiation heat; ion heat generated during sputtering; ionic heat generated during ion plating, ■
Condensation latent heat and radiant heat are cooling functions. However, when metal condenses on the surface of a polyethylene terephthalate film under vacuum, the surface of the film is exposed to high temperatures for a very short time, and polyethylene terephthalate oligomer crystals diffuse and precipitate from inside the polyethylene terephthalate film, causing magnetic properties. ? Formation of fine protrusions on the surface of the W film cannot be avoided.

Surface protrusions caused by the oligomer crystals cause unfavorable electromagnetic conversion characteristics and dropouts. Therefore, the surface of the magnetic recording medium is required to be smooth, and a film free of such oligomer precipitation is required.

The present inventor has arrived at the present invention as a result of intensive studies on polyethylene terephthalate films free of oligomer precipitation from this viewpoint.

That is, the present invention provides: (1) sorbitan ester in an amount of 0.001% to 0.2%;
This is a polyethylene terephthalate film for metal thin film magnetic recording media containing %.

The polyethylene terephthalate referred to in the present invention includes not only a homopolymer but also a copolymerized polyethylene terephthalate in which 85 or more of the repeating units are ethylene terephthalate units, and the remainder is other components.

In the present invention, sorbitan ester is an ester consisting of sorbitan and a fatty acid having 8 to 22 carbon atoms, and is mono-ester based on the number of bonds of the fatty acid.

It refers to something that is accomplished by a group of people. Among these, triesters are most preferred as sorbitan esters because they have good heat resistance.

Methods for gradually adding sorbitan ester to polyethylene terephthalate include tri-blending it with polyethylene terephthalate, feeding it into an extruder, and extruding it to form a film. There is a method of blending the sorbitan ester with a pellet of polyethylene terephthalate containing no sorbitan ester to form a film by extrusion, but the method is not limited to these methods.

The content of sorbitan ester is o, oo1% to 0.2
It is in the range of ti%. The sorbitan ester-containing polyethylene terephthalate is extruded, for example, at a polymer melting temperature of 260 DEG to 320 DEG C. and a residence time in the extruder of 2 to 20 minutes using the method described above. In JQ, when polyethylene terephthalate is extruded and solidified into chips, the polymer is solidified into chips.
Dry lamp crystallization is carried out at a temperature of 20℃ or higher, generally 160 to 170℃ for at least about 2 hours, until the moisture content of the chips reaches Ojl.
It is preferable to carry out complete melt extrusion with an O57jj f% of 1% or less.

The unstretched polyethylene prephthalate film thus prepared is 2.5 times or more in at least one direction.
Stretch to 6.041″7 or more.Stretching method u: For example, the glass transition point (Tg) of polyethylene terephthalate
) to (Tg-1-s O) One step of stretching is carried out at ℃, followed by Tg~(Tg-4-
50) Perform the second stage of stretching at a temperature of 1::.

Furthermore, if necessary, a third-stage stretching can be performed in the direction of the first stage. Stretching deviation in one direction is good so that N-small is 2.5 to 6.0 times.

Obtained film l-J: Heat set at a temperature of 150 to 250°C for 1 to 60 seconds. Film thickness is 3-100 μn
L % Preferably e is 5 to 75 μm, which is suitable as a support for magnetic recording media.

The sorbitan ester-containing polyethylene terephthalate film obtained by the above method is a total disaster! The reason is not clear, but surprisingly, no oligomer precipitation is observed when metal thin films are formed using thin film forming methods such as evaporation, sputtering, and ion blating, even though they are exposed to high heat. This has the advantage that a metal thin film magnetic recording medium with a smooth surface can be obtained.

If the amount of sorbitan ester added is less than 0.001 if-Q, precipitation of oligomers cannot be suppressed. If the amount of sorbitan ester added exceeds 0.2 mm, it is possible to suppress the precipitation of oligomers, but depending on the manner of crosstalk, dents that are thought to be traces of sorbitan ester often appear on the film surface. Its size is +b
], O~100 ptrH depth 0.05~0.211
It is about m, but in rare cases it is 100μ in width? I+, depth 0.2p
A book larger than m appears.

A gold pf4 thin film was formed on the surface of such a film to create a metal magnetic recording body. It's not right. Sorbitan-“Spru addition h1σ>or-+
11iI), box e, l, 0.004 to L1. f+
2 71i 11i % Te:k・ru.

<yh'+? 'h De-M Narinote p, l; &J,
A sky 7j: it't method, Su': y termets,
Or, there are gracing fj, etc., but these forces θ, since τ, all the known forces are -1 IJll will come.

A 5-1b /fl: Law field r', v(-+yo, I
(1'-I 0-67 art vacuum-1) Tongues in the boat or aluminum nano-base
', the system is emitted by heating the sub-beam, etc., and the layer is deposited on the 14 supports. As an intermittent attachment, l;i', Fe,
Nl, G.

and their alloys are commonly used. In addition, the present invention can also be applied to a reactive vapor deposition method in which a film of 10 (c foot 3; 0-3 Torr
1) C glow emission in an atmosphere that generates an inert gas of
:, generates RF glow discharge, Group 1. Evaporate the metal inside.

Ar is usually used as the inert gas. A glow discharge is generated in a spa atmosphere, and the generated Ar ions knock out atoms on the target surface. Methods for generating glow discharge include direct current two-pole, three-pole snowdrop method, and high-frequency sputtering θ. There is also a magnetron sensor method that uses magnetron discharge.

The thickness of the magnetic thin film is 48 mm, which is sufficient for high-density magnetic recording media.
It must be something that provides signal output. Therefore, the thickness of the magnetic thin film c) varies depending on the thin film formation method and application.
Generally 0.02~1,511m (200~1sooo
It is between X).

Methods for forming magnetic thin films for longitudinal recording such as audio, video, and computers include V, evaporation (thermal evaporation, electron beam evaporation, etc.), sputtering (dipolar DC sputtering,
Examples include methods such as high frequency sputtering, etc.). In the case of vapor deposition, CO is used so that the axis of easy magnetization appears in the horizontal direction of the tape.
By continuously obliquely depositing ferromagnetic metals such as ferromagnetic metals on a non-magnetic plastic support and repeatedly laminating them, magnetocrystalline anisotropy and shape anisotropy are developed in the horizontal direction of the tape. be. Total follow-up and ten-no-gold N!
,? llr membrane 1v ld:, 0.02-0.5 μm (
In addition to long-distance recording such as audio, video, and computers, PCs are also a method that enables high-density digital recording.
M. For flexible disks, for example, Cr is added to CO so that the axis of easy magnetization is developed in the perpendicular direction of the non-magnetic support.
It is also possible to apply a perpendicular magnetic recording method in which recording is performed in the direction perpendicular to the base plane by appropriately mixing (10 to 20%) the demagnetizing field to suppress the generated demagnetizing field and to develop an axis of easy magnetization in the perpendicular direction.

Usually, a CO to Cr alloy with a thickness of 0.2 to 1 and a depth of 571 m is used by sputtering. At this time, a magnetic flux concentrator thin film made of a high magnetic permeability material such as permalloy (Fe-Ni) or supermalloy can be disposed between the nonmagnetic support and the magnetic recording layer having an axis of easy magnetization in the perpendicular direction. . The high magnetic permeability wheel as a magnetic flux concentrator is formed by sputtering, and the film thickness is 0.1~xpm (too~5O
OOOX) (7) Low coercive force (500 (l or less)) 1 ton of thin film.The Co''-Cr film H of the magnetic recording layer at this time is
It is formed to have a thickness of about 0.2 to 1.5 μr++ (2000 to 15000 λ).

In this way, the metal thin film formed by means such as steam sputtering is as thin as 1.511 m at maximum, and the unrestricted surface state of the non-magnetic plastic support remains as it is, or the oligomers precipitated from inside the film become magnetic. The film forms irregularities, disturbs the surface condition, and causes the electric (J3 conversion characteristic Rζ) of the magnetic recording medium.

From the viewpoint of electromagnetic conversion characteristics, it is necessary that the surface of the nonmagnetic plastic support is smooth and that the film does not precipitate oligomers when heated.

In this sense, the film 7j1 of the present jM invention is formed by exposing it to high temperature using a metal thin film forming method such as a vacuum evaporation method, a sputtering method, or an ion grating method.
i! It has the advantage that it is possible to produce a metal film magnetic recording medium material without oligomer precipitation even when it is formed.

The Firno f4°a11 method of the present invention is shown below.

Observation of oligomer precipitation status l) Vapor deposition tape: Deposited iN+ with C, o-N1 ferromagnetic metal obliquely deposited using a scanning electron microscope. do.

2) Sputter dove: Co-Cr ferromagnetic metal is sputtered on the sputter L and fr sputter surfaces with a ★゛ type 1 grain and enlarged to 50 QO 1 S in the same manner. .

71- The situation of lycomer precipitation is classified as L- and L-lower: ×: Oligomer is precipitated on the entire surface 1, and 11 is not present for Aφ.

◯: A slight amount of sesame precipitation is observed, but it can be used.

◎: There is almost no precipitation of niolibomer and it can be used without any problem.

(11) Overall evaluation: Excellent: There is almost no precipitation of oligomers, the number of dropouts is small, and there is no problem at the level O. Good: Some precipitation of oligomers is observed, and the number of dropouts is a little high, but the usable RIJ ability is good.

Bad: There is a lot of oligomer precipitation and a large number of dropouts, making it unsuitable for toilet use.

Examples will be described below, but the method is not limited to these methods.

Examples 1 to 3 and Comparative Examples 1 to 2 In each of Examples 1 to 3 and Comparative Examples 1 to 2, 0.023 parts (0,020 mol) of zinc acetate was added to 100 parts of diethyl terephthalate and 70 parts of ethylene glycol as a catalyst. Add dimethyl terebutanate) and heat to 150-240℃
The transesterification reaction was carried out while distilling methanol off for 4 hours, and once... : (After cooling in a hot trench, the agent (glycol solution of compound 05) was added to A7 with trimethyl phosphate)
-co, 014 section added. Next, using a small condensation catalyst,
Added 0.04 parts of antimony trioxide j+IJ L,,1
One condensation reaction was carried out for 4 hours in a high vacuum of 8 g or less, and the intrinsic viscosity was 1.65 (o-chlorophenol soluble).

Polyethylene terephthalate (measured at 25°C) was used live.

Examples 1, 2.3 and Comparative Example 1 are Sorbitan Tristea l Note Yusonoshi-Pi1(], o 01 Jukuma Chi.

0.02 weight, mixed mixture, 0.2% eastern polyethylene derephthalate, 3 weight polyethylene derephthalate were charged into the Triblend L extruder. Do not add solpitan tristearate, j 4
011m unstretched fill J, fτ! M,i'hi
L % 3.5 times at 90℃ in the digit direction, 1()5 in the horizontal direction
4.0 iZ' at ℃.

Successive biaxial stretching was performed, and heat setting was further performed at 210° C. for 30 seconds to produce a film with a thickness of 10111H.

In addition, before the biaxially stretched film was heat-set, nine coats of a coating liquid having the following composition were applied to one side of the film.

Composition of the coating liquid: The coating amount is approximately 2.2 l/- in wet form, and the solid content is approximately 0.0126? / m'.

The film obtained in the above manner had good slipperiness, no blocking occurred, and could be easily rolled up.

While running the polyethylene terephthalate film obtained in this way, 3.5
1Co, N1 in oxygen atmosphere at X 10' Torr
(80% Co, 10% Nl) was deposited (thickness 0.1
μnr + substrate moving speed 1 on/m) I, ta. The magnetic recording medium thus blunted and ejaculated was slit into 1/2〃P and the tape (7) was slit at a speed of 14.3 msr+/l+ec (relative speed 3. 75 m/sec), recording/reproduction is performed at a center recording wavelength of 0.83 μm, and dropout (
40 μs 716 dB) was measured.

The results are shown in Table 1.

From the above results, Comparative Examples 1 and 2 have a large amount of oligomer precipitation, a large number of dropouts, and inferior properties, whereas Examples 1 and 3 of the present invention have almost no oligomer precipitation. It is understood that the number of dropouts is small and the performance is significantly superior.

Examples 4-6. and Comparative Examples 1 to 3 Examples 4 to 6 and Comparative Examples 3 to 4 were applied to the polyethylene terephthalate film obtained in Examples 1 to 3 and Comparative Examples 1 to 2, respectively, on the opposite side of the coating solution. A thin metal layer was formed in the following order.

(2) MO-low O-force vermalloy layer, then (2) Co--Cr perpendicular magnetization film was formed on the permalloy layer by the following method to form a thin WA.

■ λ-0-permalloy layer: 1 ml f' MO-permalloy target (N178%, Fe18%, M.

4φ) using the DC magnetron sputtering method.
10” 5 in T’orr’s person r (qq, 9g%)
A 0.57 oys thick film was produced at a deposition rate of 0 OA/min. The obtained film had a coercive force in the in-plane direction of about 20e (nisgurdead).

@Co-Cr Jm: 4 mm thick Co-Cr
Using an alloy target (Crl 7 wtφ), DC
A Co--Cr alloy film with a thickness of 0.5 μm was obtained by magnetron sputtering in Ar (99.99%) at I×10 Torr at a deposition rate of 5ooX/min.

The magnetic recording medium thus obtained is 174'It]
Slit it and use it as a tape, 0.3μ? Recording and reproduction were performed at a speed of 9.5 cm/see using a ring head with a gap length of Fl, and the magnetic conversion characteristics (digital recording density characteristics) were evaluated.

The evaluation criteria is 10 KBPI, 8 during recording and playback.
/N (dB) ratio and the reduction rate of the output during 50 KDPI recording and reproducing with respect to the output during 10 KBPI recording and reproducing, the high density recording characteristics and the noise level were evaluated.

The results are shown in Table 2.

From the above results, Comparative Example 3. In contrast to Examples 4 to 4 of the present invention, the reduction in playback output was large and the noise level was inferior.
The S/N (dl'l) ratio of the magnetic recording medium No. 6 is large;
Moreover, it is believed that the nozzle level is significantly superior.

Claims (2)

[Claims] (1) A polyethylene terephthalate film for metal thin film magnetic recording media containing 0.001% to 0.2% by weight of norbitane ester. (2) Sorbitan ester 0. (+ (14~0
, 02 (including knowledge and knowledge)
The polyethylene terephthalate film described in μJ1 item 1.