JPS5954036A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability, antistatic property, light shielding property, surface gloss, etc. of a magnetic layer by incorporating titanium dioxide adsorbed with carbon black or chromic oxide adsorbed with carbon black in the magnetic layer. CONSTITUTION:Magnetic powder such as Co-contg. iron oxide and a binder such as PVC or polyurethane elastomer are mixed. Titanium dioxide adsorbed with carbon black is further mixed with the magnetic powder at about 0.5-30wt% based on the weight of said powder and chromic oxide powder adsorbed with carbon black is mixed therewith at about <=15wt% in such a way that the total added weight of the titanium dioxide adsorbed with carbon black and the chromic oxide adsorbed with carbon black attains about 0.5-30wt%. The resulting magnetic coating is coated on a substrate such as polyester film and is dried, whereby the intended magnetic recording medium is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, in which the durability of the magnetic layer is improved by containing at least carbon black-adsorbed titanium dioxide or carbon black-adsorbed dichromium oxide in the magnetic layer. It also has excellent antistatic effect and light shielding properties, and with improved surface gloss, S/
It is an object of the present invention to provide a magnetic recording medium in which N is also significantly improved.

Conventionally, in the magnetic layer of magnetic recording media such as magnetic tape for video tape recorders or floppy disks,
In order to improve the abrasion resistance of the magnetic layer, Dangerous SOS, 5in2, B
Powders such as eC are added, and carbon black and the like are added to prevent static electricity and improve light-shielding properties of the magnetic layer.

However, in order to obtain the desired effect with these additives, it is necessary to add them in a certain amount, and the more they are added, the smaller the packing density of the magnetic powder in the magnetic layer becomes. Since the surface becomes rough, the magnetic properties deteriorate, and therefore, in reality, these properties are only used in an attempt to harmonize them.

Therefore, from the perspective of improving magnetic properties such as recording density, A
j! It is desirable that the amount of carbon black, etc. added be as small as possible, and it is desired to develop a substance that can improve properties such as antistatic properties, light shielding properties, and durability even with a small amount added.

The present invention has been made in response to the above-mentioned demands, and examples of the magnetic recording medium according to the present invention will be described below.

Example 500 parts by weight of Co-containing iron oxide magnetic powder, 70 parts by weight of vinyl chloride resin, 80 parts by weight of polyurethane elastomer, 5 parts by weight of egg yolk lecithin, 700 parts by weight of methyl ethyl ketone, 700 parts by weight of toluene, specific surface area with an average particle size of 100 mμ or less Tie2 carbon black with 30d11 or more
The carbon black adsorbed titanium dioxide is 150 parts by weight or less, adsorbed at least 0.5% by weight, for example about 10% by weight, based on the powder, the average particle size is 100 mμ or less, and the specific surface area is 30 dl!
! Carbon black of Cr2O, 0 for powder
A mixture of 100 parts by weight or less of dichromium oxide adsorbed with carbon black of 5% by weight or more, for example about 10% by weight, is mixed and dispersed in a sand mill for about 20 hours, and an incyanate curing agent is added thereto to make a magnetic paint. This magnetic paint is coated to a thickness of about 5μ on a support such as a polyester film, dried, calendered, heated to cause a curing reaction, and then slit to a predetermined width to form, for example, a magnetic tape for video. obtain.

In the production of magnetic paint, after mixing the magnetic powder and binder, carbon black-adsorbed titanium dioxide, etc. may be added, or magnetic powder, binder, carbon black-adsorbed titanium dioxide, carbon black-adsorbed oxidation After mixing dichromium, additives such as various hardening agents may be added.

When the magnetic properties of the magnetic tape obtained as described above, such as the squareness ratio, are measured, as shown in Figure 1, the sum of carbon black-adsorbed titanium dioxide and carbon black-adsorbed dichromium oxide is the magnetic powder. On the other hand, when the content is less than about 30% by weight, the squareness ratio is as large as about 08 or more, and the magnetic properties are excellent. Incidentally, regardless of the addition ratio of carbon black adsorbed titanium dioxide and carbon black adsorbed dichromium oxide, the total addition amount of carbon black adsorbed titanium dioxide and carbon black adsorbed dichromium oxide is approximately 30% by weight based on the magnetic powder. In the following cases, the squareness ratio is excellent.

In addition, in order to investigate whether the tape end detection mechanism malfunctions in a recording/playback device equipped with a tape end detection mechanism using an optical sensor, etc., we measured the light transmittance at a wavelength of 9000A, and found that carbon black adsorbed titanium dioxide and If the sum of carbon black adsorbed dichromium oxide and carbon black adsorbed titanium dioxide is about 0.5% by weight or more based on the magnetic powder, the light transmittance will be about 0.5% or less. The end detection mechanism is less likely to malfunction.

In addition, in order to examine the durability of the magnetic layer, when we measured the relationship between the number of repeated regenerations and the regeneration demagnetization, we found that the sum of carbon black adsorbed dichromium oxide and carbon black adsorbed titanium dioxide was measured as shown in Figure 3. is 20% by weight based on the magnetic powder.
And those in which carbon black adsorbed dichromium oxide is varied within the range of 0 to 20% by weight based on the magnetic powder are different from those containing no carbon black adsorbed dichromium oxide or carbon black adsorbed titanium dioxide. It can be seen that the reproduction demagnetization is extremely small and the magnetic layer is highly durable. That is, the durability of the magnetic layer is improved by adding dichromium oxide adsorbed to carbon black.

Furthermore, as shown in Fig. 4, when examining the relationship with color S/N, we find that the amount of carbon black adsorbed dichromium oxide added to the magnetic powder is 0% by weight, 05% by weight, and 10% by weight.
, 20% by weight, and the sum of carbon black adsorbed dichromium oxide and carbon black adsorbed titanium dioxide is 30% by weight relative to the magnetic powder.Color S/N
When measured, the color S/N is improved by adding carbon black-adsorbed titanium dioxide and carbon black-adsorbed dichromium oxide.

Judging comprehensively from these results, titanium dioxide powder adsorbing carbon black with an average particle size of 100 mμ or less and a specific surface area of 30 d/P or more is about 0.5 to 30% by weight of the magnetic powder. , Nichromium oxide adsorbed with carbon black similar to the above has a ratio of about 1 to the magnetic powder.
5% by weight or less, and the total added weight of the carbon black-adsorbed titanium dioxide and the carbon black-adsorbed dichromium oxide is more than about 0.5% by weight and less than about 30% by weight based on the magnetic powder. By including adsorbed titanium dioxide and carbon black adsorbed dichromium oxide in the magnetic layer, an extremely excellent magnetic recording medium can be obtained.

The present invention is characterized by the use of titanium dioxide adsorbed on carbon black and dichromium oxide adsorbed on carbon black. However, the advantages of the present invention cannot be obtained in this form.

As mentioned above, since the magnetic recording medium according to the present invention contains carbon black-adsorbed titanium dioxide or carbon black-adsorbed dichromium oxide in the magnetic layer, it exhibits a high squareness ratio, and also has a high squareness ratio. The tape end detection mechanism must have a high light-shielding property that prevents malfunctions, and even after repeated playback tests, the playback demagnetization is small, and the magnetic layer has high durability. has features such as improved surface gloss and excellent color S/N.

[Brief explanation of drawings]

1, 2, 3, and 4 show the squareness ratio, light transmittance, reproduction area a and U color of the magnetic recording medium according to the present invention.
It is a graph showing S/N characteristics. Figure 1 Figure 2 Capo 7 Bunok 1 Defeat 9 No Mu! 171rl Kano (Wt UJ Fig. 3)

Claims (1)

[Claims] A magnetic recording medium characterized in that the magnetic layer contains carbon black-adsorbed titanium dioxide or carbon black-adsorbed dichromium oxide.