KR910003453B1 - Magnetic recording medium for vtr - Google Patents

Abstract

A magnetic recording medium is manufactured by (a) adding monoisocyanates of R-NCO [R= C6-30 aliphatic gp. as a coupling agent to ketones as an organic solvent, (b) stirring the mixt. and then adding magnetic powders to the mixt. to produce a first magnetic pigment, (c) adding a bonding agent i.e. vinyl resin and urethane resin to the first pigment, (d) dispersing the mixt. by the sandgrinder to produce a second magnetic pigment, and (e) coating a base film with the second pigment. The medium has a good dispersiveness of the magnetic powders and durability of the magnetic tapes.

Description

Magnetic recording media for video

The present invention relates to a magnetic recording medium for video. More particularly, the present invention relates to a magnetic recording medium for video in which magnetic dispersibility and durability of a tape are enhanced by using a magnetic paint containing a monoisocyanate coupling agent.

Recently, the demand for magnetic recording media, especially video tapes, is increasing rapidly, and users' demand for high-quality products is increasing day by day. Accordingly, in the video tape manufacturing industry, in order to meet the needs of users, New technologies are being developed in various ways. In particular, the research aims to improve the uniformity of the magnetic coating applied to the base film and the dispersibility of the magnetic components contained in the magnetic coating and to improve the durability of the tape. I have tried.

That is, in the past, various methods have been proposed to improve the dispersibility of the magnetic components contained in the magnetic paint during the manufacture of the video tape. As an example, a method of using a surfactant such as lecithin as a dispersant in the magnetic paint may be used. Japanese Unexamined Patent Publications 48-15001 and 48-15002, 60-47650 and 60-48047. However, in the case of manufacturing a video tape using this method, for example, when an additional binder or solvent is added to the magnetic paint after the primary injection process of the magnetic component, the surfactant is released from the magnetic component surface and the magnetic component is aggregated. The phenomenon occurred.

In addition, as a method for supplementing and improving the phenomenon of agglomeration of the magnetic components as described above, US Pat. Nos. 4,076,890, 4,397,751 and 4,444,850 use an actual phosphorus or titanate-based compound as a coupling agent to provide extra A method of coupling a binder or solvent to a hydroxyl group or adsorbed water on the magnetic surface by chemical bonding has been proposed. The use of this method improves the dispersibility of the magnetic component and prevents coagulation. In the coupling reaction, alcohol, which acts as an empty solvent with respect to a general binder, is produced as a side reaction product. As a result, the fluidity of the binder contained in the magnetic paint is reduced, resulting in a decrease in the uniformity of the magnetic paint. There was also a problem that the surface properties of the tape were also worsened and the electron change characteristic of the tape was also degraded.

In addition, in recent years, in order to improve the durability of video tapes, a binder having excellent durability is selected and used, and in particular, a binder having a high molecular weight benzene ring structure is preferred. Although somewhat improved, such binders have a high stiffness, resulting in lower solubility compared to binders with low stiffness, causing another problem.

Therefore, the present invention is to solve the conventional problems as described above, the monoisocyanate-based compound using a magnetic paint added as a coupling agent to improve the dispersibility of the magnetic component, and also to enhance the durability of the tape The purpose is to provide a magnetic recording medium.

Hereinafter, the present invention will be described in detail.

The present invention relates to a magnetic recording medium for a video coated with a magnetic coating containing a magnetic component on a base film, wherein the monoisocyanate coupling agent represented by the following general formula (I) contains 0.01 to 1% by weight, based on the magnetic component. The magnetic coating is applied.

R-NCO

Wherein R represents an aliphatic group having 6 to 30 carbon atoms.

Hereinafter, the present invention will be described in more detail.

In the magnetic recording medium for video according to the present invention, after adding a monoisocyanate compound as a coupling agent to an organic solvent of ketones, which is a dominant dispersion medium, the primary magnetic material is subjected to a pre-dispersion step of slowly adding a magnetic component with stirring. After the paint is prepared, a vinyl-based resin and a conventional binder such as a urethane-based resin are added thereto, dispersed by sand grinder, etc. to prepare a secondary stable magnetic paint, and then coated on a base film for a magnetic recording medium. do.

As the monoisocyanate compound used as the coupling agent in the present invention, it is preferable to use a monocyanate compound having 6 to 30 carbon atoms prepared by a general method such as treating an amine compound with phosgene. If the number of carbon atoms is less than 6, the compound itself is unstable, whereas if the number of carbon atoms is more than 30, the chemical bond with the magnetic surface becomes difficult due to steric hindrance.

In addition, when the monoisocyanate-based coupling agent is used less than 0.01% by weight relative to the magnetic component, it does not exhibit a sufficient coupling effect, whereas when a large amount of the monoisocyanate is used in an amount of 1% by weight or more, It remains undesired because it hinders the formation of the net structure of the magnetic coating by causing the curing reaction with the binder as it will eventually reduce the durability of the final tape.

On the other hand, the magnetic coating prepared according to the present invention is given a good dispersibility to the magnetic component by the coupling agent added through the pre-dispersion process as described above, monoisocyanate system having a structure of the general formula (I) Since the coupling agent spontaneously rearranges and chemically bonds with the hydroxyl group or the adsorbed water on the surface of the magnetic component to form a urethane group in the coupling agent chain, the compatibility with the urethane binder introduced during the manufacture of the secondary magnetic paint is also greatly improved. As a result, the durability of the tape is also improved.

The present invention will be described in detail based on Examples and Comparative Examples as follows, and the numerical evaluation of the tape produced accordingly is based on the following method.

1. Magnetic characteristics (square ratio): Measured using the Toei Vibration Specimen field, the closer the value is to 1, the better the magnetic characteristics.

2. Weathering and durability measurement (dropout): After 200 hours running in a thermostat with a temperature of 40 ° C. and a relative humidity of 85%, the measurement is performed using a drop out measuring device manufactured by Shivaso company.

3. Glossiness change (60 ℃): Compare the gloss after dispersing the magnetic paint with sand grinder and before applying it to the base film. At this time, the less the change in glossiness, the better the dispersibility and the stability paint is evaluated.

4. R / F output: It depends on the surface property of the magnetic recording tape according to the uniformity of the magnetic paint. It is recorded by comparing with the existing tape measured with an oscilloscope.

Example 1

Magnetic component (Co-γ-Fe ₂ O ₃ ) 100 (weight ratio)

Coupling Agent (CH ₃ (CH ₂ ) ₁₇ NCO, Tokyo KASEI) 0.5

Vinyl binder (VAGH) 6

Urethane binders (5703 Estane 14

Curing Agent (Coronate El) 4

Ketones Solvent 300

According to the composition as described above, first put the coupling agent in the ketone solvent and stir it while slowly adding the magnetic component to prepare the primary magnetic paint, and then the solution dissolved in the solvent in the solvent to the paint and 60 minutes with sand grinder. After dispersing, the curing agent was added again, restirred at high speed and applied to the base film, oriented and dried to prepare a magnetic recording tape.

Comparative Example 1

Magnetic ingredient 100 (weight ratio)

Dispersants (Lecithin) 3

Vinyl binder (VAGH) 6

Urethane Binder (5703) 14

Curing Agent (Coronate El) 4

Solvent 300

According to the composition as described above was carried out in the same manner as in Example 1, but using a dispersant instead of a coupling agent to prepare a magnetic recording tape.

Comparative Example 2

Magnetic ingredient 100

Coupling Agent (KR-138S, Titanate) 0.5

Vinyl binder (VAGH) 6

Urethane Binder (5703) 14

Curing Agent (Coronate El) 4

Solvent 300

A magnetic recording tape was produced in the same manner as in Example 1 according to the above composition.

TABLE 1

Claims (1)

A magnetic recording medium for video coated with a magnetic coating containing a magnetic component on a base film, wherein the monoisocyanate coupling agent represented by the following general formula (I) contains 0.01 to 1% by weight of the magnetic component. A magnetic recording medium for video, characterized by being coated with a magnetic paint. R-NCO Wherein R represents an aliphatic group having 6 to 30 carbon atoms.