JPS5930238A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium while improving wear resistance antistatic characteristic, running characteristics, etc., by adding Al2O3 powder to which carbon black of less than specific means grain size and greater than specific surface area is adsorbed to magnetic powder at a specific rate. CONSTITUTION:The carbon black with <=100mum mean grain size and >=30m<2>/g specific surface area is adsorbed to the Al2O3 powder and a magnetic layer which contains >=about 0.5wt% product on the basis of the powder is formed on a base. The carbon black is adsorbed to Al2O3 by >=about 0.5wt%. When the carbon black and Al2O3 are mixed merely with the magnetic layer, no effect is obtained. Consequently, the magnetic tape etc. superior in electromagnetic conversion characteristic, wear resistance, antistatic characteristic, light shielding characteristic, etc., and never causes a tape end detecting mechanism which uses a photosensor, etc., to malfunction are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and by including carbon black-adsorbed alumina in the magnetic layer, the magnetic layer has excellent wear resistance and durability, and has low reproduction demagnetization. It is also an object of the present invention to provide a magnetic recording medium that has an excellent antistatic effect, is resistant to dirt and dust, has excellent running properties, has excellent light shielding properties, and has a good squareness ratio. purpose.

Conventionally, in the magnetic layer of magnetic recording media such as magnetic tape for video tape recorders or floppy disks,
C1203 or IJ, 20 to improve the wear resistance of the magnetic layer.
Powder No. 3 is added thereto, and carbon black and the like are added to prevent static electricity and improve the 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, but the more they are added, the smaller the packing density of the magnetic powder in the magnetic layer becomes. As a result, the magnetic properties are degraded, and in reality, these properties are used only in an attempt to harmonize them.

Therefore, from the viewpoint of improving ventilation characteristics such as recording density, M
The smaller the amount of addition of 2O3, carbon black, etc., the better, and it is desired to develop a substance that improves properties such as antistatic properties, light shielding properties, and abrasion resistance even with a small amount.

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

Example 420 parts of γ-Fe2O, 65 parts of vinyl chloride-vinyl acetate copolymer, 110 parts of polyurethane distomer, 5 parts of egg yolk cytin, 600 parts of methyl ethyl ketone, 600 parts of toluene, average particle size of 100 m1j or less, specific surface area of 30
A mixture of 3 parts or more of carbon black adsorbed aluminum oxide powder, in which carbon black of 0.5 m2/g or more is adsorbed to aluminum oxide powder, is mixed and dispersed in a sand mill for about 20 hours, and incyanate is added to this mixture. A magnetic paint is made by adding a hardening agent, this magnetic paint is applied to a support such as a polyester film, and after drying, it is calendered and then heated to perform a curing reaction.
Then, the tape is slit into a predetermined length (1) to obtain, for example, a video magnetic tape.

Comparative Example A magnetic tape was obtained in the same manner as in the previous example except that 0.6 parts of the carbon black-adsorbed aluminum oxide powder was used, or a carbon blank and aluminum oxide were used in place of the carbon black-adsorbed aluminum oxide powder.

The properties of the thus obtained magnetic tape, such as reproduction demagnetization, surface electrical resistance, light transmittance, and squareness ratio, were measured as shown in the table.

- In the regenerative demagnetization column, those within -1.5 dB after 200 repeated running tests are marked ○, and those greater than -1,5 dB are marked x.

- In the surface electrical resistance column, those with a resistance of 109Ω1071" or less are marked with an ○, and those with a resistance greater than this are marked with an X.

- In the column for light transmittance, those with a transmittance of 0.5% or less are marked with an ○, and those with a transmittance greater than this are marked with an X.

- In the square ratio column, those with a squareness ratio of 080 or higher are marked with an ○, and those smaller than this are marked with an X.

As can be seen from the above results, carbon black in the magnetic layer has an effect on surface electrical resistance and light shielding properties.
The magnetic layer contains more than 0.08 weight percent of hyaluronan, which has an effect on regenerative demagnetization. If we try to improve the properties of surface electrical resistance, light shielding properties, and regenerative demagnetization, the content of non-magnetic powder such as carbon black and aluminum oxide will increase, the packing density of magnetic powder will decrease, and the electromagnetic conversion properties will decrease. is reduced accordingly, and the magnetic properties such as squareness ratio are deteriorated.On the other hand, as shown in the results of this example, when 7-luminium oxide and carbon black are included in the magnetic layer. Rather, by including carbon black in the adsorbed alumina magnetic layer, especially in the magnetic layer, by incorporating 05 weight coefficient or more, the characteristics of surface electrical resistance, light shielding property, and regenerative demagnetization can be improved even with a small amount. The packing density can be increased accordingly, the deterioration of electromagnetic conversion characteristics is small, and, for example, the squareness ratio characteristics are also excellent.

As described above, the magnetic recording medium according to the present invention has an average grain size of 100 mμ or less and a specific surface area of 3 orr? in the magnetic layer. Since the magnetic layer contains about 0.5 g or more of carbon black adsorbed to aluminum oxide powder, the magnetic layer has excellent wear resistance and durability, and the regenerative demagnetization is small.
Excellent anti-static effect, prevents dirt and dust from adhering to it.
It has excellent running properties and light blocking properties, and the tape end detection mechanism using optical sensors etc. does not malfunction, and even small amounts of additives added to improve these properties are effective. Therefore, it has features such as a relatively high packing density of magnetic powder, good electromagnetic conversion characteristics, and a large squareness ratio.

Patent Applicant: Japan Victor Co., Ltd. Attorney: Utaka Mizutoshi
Continuing amendment (self-motivated) September 1980/Representation of the Commissioner of the Japan Patent Office 1 Case Japanese Patent Application No. 137892/1982 2 Title of the invention Magnetic recording medium 3 Relationship with the case of person making an amendment Patent applicant Nissui Victor Co., Ltd. 4, Agent 1-14, Kanda Sakuma-cho, Chiyoda-ku, Tokyo (7900) Katsu Utaka Self-imposed subject matter (1) Claims (2) Detailed description of the invention 6, Amendments Contents (1) Amend the claims as shown in the attached sheet.

(2) Page 6, line 13 of the specification, “...” and “
Between approximately 0.5 and 10.05, the claims that feature "with respect to magnetic powder" are amended as follows.

Claims (1)

[Claims] In the magnetic layer, the average grain size is 100 mμ or less and the specific surface area is 30
1. A magnetic recording medium comprising about 0.5 weight percent or more of carton black of nv 7 g or more adsorbed to aluminum oxide powder.