JPS5868227A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the wear resistance and running stability, by forming a ferromagnetic thin film on a plastic film having granular, wrinkly or vermicular protrusions contg. fine particles allowed to locally exist therein on the surface. CONSTITUTION:Granular, wrinkly or vermicular protrusions 2, 2' having 50- 300Angstrom height and about 0.1-10mum intervals and contg. fine particles 3, 3' having 0.01-0.2mum diameter allowed to locally exist therein are formed on a substrate film 1, 1', and a ferromagnetic thin film 4, 4' is laid on the surfaces of the protrusions 2, 2' by vacuum deposition or other means.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferromagnetic thin film magnetic recording medium particularly suitable for a magnetic tape for a rotary head type videotape recorder, which satisfies both abrasion resistance due to the magnetic head and running stability. This is something that we are trying to encourage.

Iron, cobalt, nickel, alloys mainly composed of these, or thin films of their oxides are deposited by double evaporation,
Polyester film is produced using vacuum deposition methods such as sputtering and ion blasting.

A ferromagnetic thin-film magnetic recording medium formed on a polymer film base such as a polyimide film can be coated with conventional coating, but in order to increase the density, it is necessary to coat the surface of the magnetic recording medium. It is necessary to smooth it out and reduce the spacing loss as much as possible.

However, if the surface is made too flat, it will cause problems in head touch and running surface. In order to further improve the magnetic tape recording density in rotating head video tape recorder systems that have become popular in the general market in recent years, it is necessary to apply ferromagnetic thin film magnetic recording media. Practical performance requirements for magnetic recording media include good head touch and head abrasion resistance, resistance to head clogging, and good contact with rotating head cylinders, tape guide posts, audio fixed heads, etc. Stable running performance (low friction,
Good abrasion resistance) can be obtained. The surface properties of the ferromagnetic thin film magnetic recording medium are such that the magnetic layer thickness is 0.1 to 0.
Since it is very small at about 5 μm, it almost entirely depends on the surface shape of the plastic film that is the substrate. Therefore, traditionally. An example of this is JP-A-53-116
No. 115, JP-A-53-128683,
JP-A-64-94574, JP-A-56-1045
Publication No. 5.

It is described in JP-A No. 56-16937, etc.

In all of these examples, the head touch and running performance are improved at once by roughening the surface shape relatively finely and uniformly, for example by forming wrinkle-like protrusions, earthworm-like or granular protrusions. This is an attempt to improve.

However, the video rotary head has a narrow contact width of several hundred microns or less, and the relative speed change with the magnetic tape is as fast as several meters and seven seconds, whereas the friction in the magnetic tape running system is slow (several meters or seven seconds). centimeter 7 seconds) Because of the large-area contact, it is thought that the optimal magnetic tape surface properties for these are not uniform. Furthermore, as a measure to prevent head clogging, a surface that has some abrasive effect on the head is required. From this point of view, the present inventors investigated the optimal surface properties for these requirements and decided to
Granular with localized fine particles of 1 to 0.2 μm.

Wrinkled, -! The present invention relates to a magnetic recording medium characterized in that a ferromagnetic thin film is formed on a plastic film having a worm-like film on its surface.

Fine particles with a diameter of 0.01 to 0.2 μm are commonly known as colloid particles, such as At20
3. SIO29MqO9TiO2, Zno, Fe2O3
゜CdO, N i O, CaWO4, B a T f
Metal oxides such as O3, CaCo3. B a Co
3. Carbonates such as Co Co a, Au, Ag.

Fine metal particles such as Cu, Ni, Fe, etc., or protective colloids and resin particles obtained using these particles as cores, which can be decomposed by acid-alkali, hydrolysis of organometallic compounds, hydrolysis of halides, hydrothermal reaction, thermal decomposition,
Reduction of salt solutions, evaporation method in gas.

It is obtained by polymer orientation, adsorption, etc.

Among these particles, the average diameter when localized in a granular, wrinkled or vermiform film is 0.01 to 0.
A thickness in the range of 2 μm is applicable to the present invention. For example, it is possible to use Au particles of 0.005 μm for nucleation and locally grow them into particles of 0.01 μm.

As a method for forming wrinkle-like protrusions on a polyester film, which is a type of plastic film, for example, a linear saturated polyester such as polyethylene terephthalate, polybutylene terephthalate, polyoxyethylene-P-oxybenzoate, etc. is mixed with dichloroacetic acid or ornchlor. There is a method in which a solution dissolved in a solvent such as a mixture of phenol and tetrachloroethane is applied thinly onto a polyester film and dried, but in this case, a certain amount of the above-mentioned fine particles is added to the solution in advance. By this, a polyester substrate suitable for the present invention can be obtained. Another method is to apply a resin liquid mainly composed of an aqueous emulsion of silicone resin to the surface of the film during stretching in the polyester film forming process, and then continue to stretch it with a dry-hardening sickle to form particles, or even worm-like shapes. There is a method for obtaining an entrance surface having a film structure, and even in this case, a film can be obtained by adding a certain amount of the above-mentioned fine particles to an aqueous emulsion. The amount of fine particles added is 0.1 υt% of the resin solid content in the resin liquid.
~50tvt% range, more preferably 0.6~1o
A range of wt% is appropriate.

If the amount of fine particles is less than 0.1 tcrt%, it is difficult to improve the runnability under high humidity, and if it is more than 60 tcrt%, the noise of the magnetic recording medium increases and the output decreases.

1 and 2 are cross-sectional views in the thickness direction of a magnetic recording medium that is an embodiment of the present invention. Figure 1.

In Fig. 2, 1 and 1' are the substrate films, 2 and 2' are the wrinkles and worm-like protrusions formed on the substrate films 1 and 1', and 3 and 3' are the wrinkles and inside the worm-like protrusions. 4.4' is a ferromagnetic thin film layer formed on the surface, 5 and 6' are substrate films, and wrinkle-like and earthworm-like protrusions a and e formed on the back surface of the lumen 1°1'. , 6/ are fine particles localized in the wrinkle-like and earthworm-like protrusions 5, 5'. Note that FIG. 1 shows the case where the height of the layer of wrinkle-like projections is equal to or less than the diameter of the fine particles, and FIG. 2 shows the case where the height of the layer of earthworm-like projections is larger than the diameter of the fine particles. All of them are characterized by the fact that fine particles protrude locally in the wrinkle-like and earthworm-like protrusions, as typified by the fine particle protrusions 7 and 7'. In addition, Fig. 1.

In Figure 42, there are wrinkles and wrinkles on both surfaces of the substrate film.
However, there is no need to worry about making the back side of the magnetic recording medium the same shape as the front side, and a thin polymer film containing a lubricant with good lubricity may be formed on the back side. , other known methods such as var.

The magnetic recording medium according to the present invention preferably has a surface dimension within the range described below, and the measured value of the protrusion flatness is determined according to the maximum surface roughness, Rmax, specified in JIS BO601. The distance from the top of the mountain to the bottom of the valley on uneven surfaces is measured using a tactile type surface roughness measuring device (TALYSTMP-1゜TAY) for sieve fine dust.
L (manufactured by JR-HUBSIJN). In addition, the number of granular, wrinkled, or earthworm-like protrusions per unit surface area, and the number of protrusions due to fine particles can be determined by differential interference using an optical microscope (OPTI PH0T).

XP-NR type, manufactured by Nippon Kogaku Kogyo Co., Ltd.) 50 times to 40 times
Observe at least 10 fields of view or more at a specific magnification between 0x and measure the number of protrusions present in those fields,
It is determined as the average value per ++lII+2.

In the present invention, the size of the granular, wrinkled, or earthworm-like protrusions is 60 to 300A in height and 0.1 to 0.1 to 300A in height.
A range of 10 μm is appropriate, and if the height is smaller than 5 OA, it becomes difficult to obtain the effect of roughening the surface, increasing wear due to the rotating head, and shortening the life of the still. Moreover, when the height is 3008 or more, the output decreases, and furthermore, when the distance is 1 μm or more, noise occurs. Thin-film magnetic recording media with granular, wrinkled, or worm-like protrusions in the above-mentioned size range on the surface have good runnability on a video recorder in normal humidity (1) (at 80% R0H). In this case, running delays and stick-slips are likely to occur in the fixed cylinder part of the rotary head or in the tape guide post part, causing noise and squealing, and in extreme cases, it becomes impossible to run.

To prevent and improve this phenomenon, the above, granular.

It is preferable that microprotrusions based on solid particles coexist with the wrinkle-like or earthworm-like protrusions. This microprotrusion is at least 5OA smaller than the tip of the granular, wrinkled or worm-like protrusion.
More preferably, it is effective to have 100 or more protruding pieces, and the requirement is that at least 100 pieces or more, and more preferably 1000 pieces or more, are effective.

To form a ferromagnetic thin film on a substrate film, for example, a ferromagnetic thin film of iron, cobalt-nickel, or an alloy thereof is directly deposited on the substrate by vacuum evaporation, ion blasting, sputtering, etc.

Alternatively, it is formed through a base thin film such as aluminum, titanium, chromium, etc. Further, it can also be inserted as a separator between these nonmagnetic thin films. In these cases, by incorporating oxygen into the ferromagnetic thin film and the underlying thin film (partially oxidizing the metal), it is possible to further improve the adhesion strength with the substrate film and improve the still life. 10,-. If necessary, it is possible to apply an overcoat made of various non-magnetic materials to the surface of the ferromagnetic thin film, and it is also desirable to apply various known measures to improve runnability on the back side of the substrate film. .

Next, the present invention will be specifically explained in detail.

On a uniaxially stretched film made of polyethylene terephthalate that contains almost no particulates due to polymerization catalyst residue, the following colloidal solution was added to an aqueous emulsion containing an epoxidized polydimethylsiloxane emulsion, a magnesium chloride emulsion, and methylcellulose with alkali added to the solution separately). An emulsion coating solution obtained by adding the above was applied to both sides and dried, followed by cross-rolling and heat-setting to obtain a polyester film having a thickness of 12 μm and having a worm-like structure with localized protruding fine particles on both rkJ. Cobalt-nickel alloy (N i 20
wt%) to form a ferromagnetic thin film layer with a thickness of 0.1 μm, a graphite-containing epoxy resin lubricant thin film was formed on the back side in the air, and then the magnetic layer surface shape was determined by slitting the tape width. Nine types of magnetic tape samples with different values were obtained. The surface shapes of these samples are shown in the table. These shredded samples were assembled into a cassette, and an image quality test was conducted using a commercially available home video recorder at 25° C., 65% R, 1-1, and the stell life was also measured. Also, 2
Image quality test was carried out again at 6℃85%H, 66%R
, H. We investigated the deterioration in image quality due to jitter and other factors under high humidity compared to the case in . The results are also listed in the same table. Note that Sample 1 in the same table is outside the scope of the present invention and is listed as a comparative example.

(iT aperture 1lIhi-bazdo/L4) 1 has a long skeleton life and shows no deterioration in image quality under high humidity.

As described above, the magnetic recording medium according to the present invention has both the head abrasion resistance and the running stability as a video magnetic tape, and has very high practical value.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views of a magnetic recording medium that is an embodiment of the present invention. 1.1'...Substrate film, 2. 2',
6. 5'...protrusion, 3.3', 6. 6'
...Fine particles, 4゜4'...Ferromagnetic layer. Name of agent: Patent attorney Toshio Nakao and one other person Is
Figure 1 WS2 Figure 7'

Claims (1)

[Claims] A magnetic recording medium characterized in that a ferromagnetic thin film is formed on a plastic film having a granular or vermiform film on the surface of which fine particles with a diameter of 0.01 to 0.2 μm are localized.