JPS5924433A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To avert effectively the camber of a magnetic disc, to prevent unstable rotation and to improve the druability of a back layer by determining the thickness of a magnetic layer and the thickness of the back layer at a limited relation and maintaining the average surface roughness of the back layer at <=0.1mum. CONSTITUTION:If the ratio between the thickness A of a magnetic layer and the thickness A' of a back layer and the rate of curling, that is, camber of a magnetic disc is at 0.8A<=A'<=1.2A, the generation of the curling can be minimized. If the average surface roughness of the back layer is maintained at <=0.1mum, durability is improved. Carbon black, graphite, tungsten disulfide, and molybdenum disulfide are used as the back layer. A coating for the back layer is applied on the rear of a raw magnetic tape, which is then subjected to a supercalendering treatment. This treatment is accomplished by a calender treatment means disposed alternately with seven stages of elastic rolls 2 each consisting of a metallic core 2a applied with an elastic urethane coating 2a on the circumferential surface thereof and metallic rolls 1.

Description

[Detailed description of the invention] Industrial applications The present invention relates to magnetic recording media, particularly magnetic disks.

BACKGROUND TECHNOLOGY AND PROBLEMS In conventional magnetic disks, the disk is rotated at high speed and its centrifugal force is used to make the disk rigid and flat, thereby making it possible to press the magnetic head against the magnetic disk and reducing separation loss. I have to. Therefore, the purpose of the antistatic layer in conventional magnetic disks was to take into consideration the generation of static electricity caused by the high speed rotation of the disk.

With recent technological advances in high-density and short-wavelength recording of magnetic disks, there has been a trend toward smaller disk diameters and lower rotational speeds.

The decrease in centrifugal force due to the miniaturization of the disk and the slow rotation of the disk increases separation loss, so at the same time there is a demand for flattening the disk itself, and in order to improve the so-called contact characteristics, pressure bonding to the grip layer is required. It becomes necessary to press the rad firmly. For this purpose, crimping is used to press the disk against the magnetic head. The durability of the back layer against rad is required.

OBJECTS OF THE INVENTION In view of the above-mentioned points, the present invention provides a method for effectively avoiding warping of a magnetic disk and preventing unstable rotation thereof by paying special consideration to the back layer of the magnetic disk, for example. This improves the durability of this glue layer.

Summary of the Invention In the present invention, a magnetic layer is deposited on one side of a flexible non-magnetic support, and a notched layer is formed on the other side. In particular, the thickness of the non-magnetic support is The thickness is 20 to 100 μm, and the thickness A of the magnetic layer and the thickness N of the back layer are
The relationship is 0.8A≦61.2 people, and the average surface roughness is 0.1 μm or less.

That is, in the present invention, the magnetic disk, etc. provided with such an fz notch layer can be used as a magnetic disk. Focusing on the fact that warpage in self-recording media occurs due to differences in the amount of substantial thermal contraction of the magnetic layer and non-magnetic layer formed on both sides of the non-magnetic support, In other words, in the present invention, the amount of heat shrinkage is largely dependent on the thickness of the magnetic layer and the back layer. Focusing on that,
Special consideration is given to the thickness of the magnetic layer and backing layer.

In the back layer of a magnetic disk, especially the antistatic layer,
So-called long length! Unlike tape-shaped magnetic recording media, their structure does not require special winding characteristics or a reduction in the coefficient of friction, and their durability against pressure pads, which can cause dropouts, is extremely high. .

In the present invention, the average surface roughness of the back layer is
As mentioned above, the thickness is set to 01 μm or less. This is because it was recognized that the durability of the navel was improved when the average surface roughness was set to 0.1 μm.The back layer was made of carbon black, graphite, tungsten disulfide, and molybdenum disulfide.

Or A/? 203. Cr2O5,5102,TlO2
High hardness reinforcement materials such as

Containing relatively soft inorganic particles such as CaCO3+CaO+MgO+MnO, or r-Fe205.
It may also be filled with magnetic side slopes such as Fe3O4+CrO2. In any case, the average particle size is approximately 1
The average particle size is preferably about 500 μm or less, but the particle size varies depending on the type of particles. For example, when carbon black is used, it is preferable that the average particle size is about 500 μm or less.

Furthermore, the blending ratio (P/11 ratio) between the weight P of the inorganic filler and the weight in of the inorganic filler described above (P/11 ratio) can be adjusted over a wide range depending on the inorganic pigment used, but for example, when carbon black is used, P/B is preferably in the range of 0.1 to 20.

In addition, the thickness of the flexible nonmagnetic film is 20 to 100 μm.
The reason why this is selected is that if it is too thin, it will be difficult to secure sufficient contact with the magnetic head, and if it is too thick, the l17# loss will be significant.

FIG. 1 shows the results of measuring the ratio of the thickness A of the magnetic layer to the thickness A' of the f-layer and the amount of curl, or warpage, of the magnetic disk. When 8A≦A'≦1.2A, the occurrence of the curl could be kept sufficiently small, and the occurrence of unstable rotation and idle lag-out during rotation of the magnetic disk due to this curl could be avoided.

The surface roughness can be reduced to 0.1/jm or less by selecting the particle size or composition of the pigment contained in the backing layer, by dispersing these pigments, by calendering, or by calendering. Selection can be made by a combination of any of the methods. As shown in Figure 2, during the calendering process, a wide tape-shaped original magnetic chinier' (3) is placed between the metal roll (1) and the elastic roll (2) to be later cut out as a disk.
In this case, the metal roll temperature is preferably 60 to 120° C., and the linear pressure is preferably 150 to 30 g/nn.

Example Example 1 Prepare a mixture with the following composition.

Ferromagnetic acicular alloy (retention crab 11800e, BET specific surface area: 4 en'Az)...9119000.・、
100 layers of vinyl chloride-vinyl acetate copolymer (trade name: VYIIH+-=, manufactured by 4-Incano 2-ite Co., Ltd.)
・・・・・・・・・・・・ 10-layer thermoplastic polyurethane resin (Product name: Nissan 5701.B°F Gutdrich Co., Ltd. #) ・・
・・・・・・・・・ 6 parts by weight Cr2O3・・・・
・・・・・・・10 parts lecithin
・・・・・・・・・・・・ 2 parts by weight Fatty acid ester ・・・・・・・・・ 1 part by weight Toluene ・・・・・・・・・・・・ 50
Heavy beast methyl ethyl ketone ・・・・・・・・・
・・・ 50 heavy acid parts cyclohexanone ・・・
・・・・・・・・・ 50 parts by weight A mixture having the above composition was kneaded in a peel mill for 24 hours, and then 5 parts by weight of an isocyanate compound (trade name: Coronate, manufactured by Nippon Polyurethane Industries, Ltd.) was added and subjected to high-speed shearing for 1 hour. A magnetic paint was created by dispersing it.

This magnetic paint was applied onto a non-magnetic support made of polyethylene terephthalate film with a thickness of 36 μm at a coater speed of 20 μm so that the thickness after drying was 4 μm, and the coating film became fluid. During a certain period of time, a non-orientation treatment was performed by passing through an alternating current solenoid (frequency 50 Hz, 5 A) to produce an original magnetic chive.

Next, in order to form a back layer, a paint having the following composition was first prepared.

Carbine Black (Asahi Carpin Co., Ltd. Asahi Tsu7-Mn4F
55+furnace system: average particle size is approximately 100 μm)...
50 heavy acid part polyurethane resin (Nistan 5702 manufactured by Gutdrich, % plasticity 1? urethane)
・・・・・・・・・・・・ 70 Electrical part epoxy resin (trade name: Ebicuron 35I, manufactured by Dainippon Ink Co., Ltd.)
・・・・・・・・・・・・ 30 heavy heavy toluene
・・・・・・・・・・・・ 150 Heavy R part methyl ethyl ketone ・・・・・・・・・・・・ 15
0 Seiharu 1 Cyclohexanone ・・・・・・・・・・・・
...100■M parts of each of these raw materials (?-lumil)
After mixing for 5 hours, 10 stacked portions of an isocyanate compound (trade name: Coronate L, manufactured by Nikkizu Urethane Kogyo Co., Ltd.) were added and pressed for 30 minutes in a tank stirrer to form a paint with a packed layer ratio. This pack layer side paint was applied to the back side of the original anti-magnetic desolation film at a coater speed of 2 so that the thickness after drying was 3.5 μm.
It was coated at a ratio of 0 m/+ and subjected to sous and f-calender treatments. As shown in FIG. 2, this supercalendaring process involves coating the peripheral surface of the metal core (2A) with elastic urethane.
! The elastic rolls (2) and metal rolls (1) coated with (2a) are alternately arranged in seven stages. Pressing is carried out by running the original antimagnetic tube (3) in a meandering manner so that the layer side is the side to be pressed onto the metal roll.

In this case, the temperature applied to the metal roll (1) was 100° C., IEE 300k17/z, and the calender speed was 40 m/min.

Next, this chip (3) was punched out to a diameter of 47 mm to create a magnetic disk.

Examples 2 to 4 Magnetic disks were prepared in the same manner as in Example 1, but the thicknesses A and A' and surface roughness of the magnetic layer and back layer were varied. Those numerical values are as described for each implementation side temperature in the table of FIG.

The results of measuring the number of curls 1, back layer powder falling off, and mud lag out on each of these magnetic disks are shown in the table of FIG. In the same table, Comparative Examples 1 to 4 are magnetic disks prepared by the same method as in Example 1, but the respective thicknesses A and A' of the magnetic layer and the back layer, and the surface When selecting roughness, these values are as entered in each column of the same table. Here, the surface roughness was measured using a Kosaka Kensha Tai, stylus type roughness meter. When measuring powder falling off, a mark of 0 means that there was very little powder falling off.
The mark indicates that there is little powder falling off, the Δ mark indicates that it is slightly observed, and the
Although there were many marks, the XX marks were most noticeable.

As mentioned above, it can be seen that the product according to the present invention has the following effects: a small curl number, less powder falling, and less muddy lag out.

In each of the Examples according to the present invention, scratches on the surface of the pack layer were visually evaluated after running on a rotating sheet record with the pad applied from the side of the pack layer. In the case where the roughness was selected to be 01 μm or less, these scratches were not visible at all, but in the case where the surface roughness of the back layer was set to 02 to 0.3/1 m, numerous concentric scratches were visible. .

Effects of the Invention According to the magnetic recording medium of the present invention, it is possible to obtain a magnetic recording medium with less curling, so that the magnetic disk formed thereby has no disadvantages such as unstable rotation during its rotation. It can be avoided, the occurrence of muddy lag out is sufficiently minimized, and a back layer with excellent durability can be constructed. Rad pressure can be sufficiently increased, and excellent characteristics can be obtained in small, low-speed rotating magnetic disks.

[Brief explanation of drawings]

FIG. 1 is a measurement curve diagram of curl time used to explain the present invention;
FIG. 2 is a diagram for explaining calendering of a magnetic head according to the present invention, and FIG. 3 is a front page showing measurement results of each characteristic on each side. (1) is a metal roll, (2) is an elastic roll, and (3) is a raw magnetic chive. Bar sy4's number A' A 192-

Claims (1)

[Scope of Claims] A magnetic recording medium having a surface pressure magnetic layer on one side of a flexible nonmagnetic support and a back layer formed on the other side, wherein the thickness of the nonmagnetic support is 20 to 100 μm, and , a magnetic recording characterized in that the thickness A of the magnetic layer and the thickness A' of the back layer satisfy 0.8A≦A′≦1.2A, and the average surface roughness thereof is 0.1 μm or less. Medium.