JPH0224824A - Magnetic recording medium and production thereof - Google Patents

Abstract

PURPOSE:To enhance the dispersibility of magnetic powder and to improve the traveling durability of a coated film by incorporating a compd. having <=1,000mol.wt. and both functions of an acrylic group and phosphoric acid group into a magnetic layer constituting the magnetic recording medium. CONSTITUTION:The dispersibility of the magnetic powder is improved if the compd. expressed by the general formula is used and is irradiated with electron rays after formation of the coated film. In addition, the bleeding out of the dispersant from the coated film is obviated and the durability of the recording medium is improved. A compd. contg. phosphate group is preferable as such compd. and sticks well to the surface of the magnetic powder which is relatively hydrophilic. On the other hand, the hydrocarbon parts of the ester elongate in a solvent and repulse against each other, thus increasing the dispersion stability of the magnetic powder. This compd. is used preferably at 0.1-20wt.% per 100pts.wt. magnetic powder in case of using said compd. as the dispersant. A vinyl chloride/vinyl acetate resin, butyral resin, etc., are used as the binder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media, and more particularly to improvements in dispersants Vζ.

[Conventional technology]

Conventionally, the dispersibility of magnetic powder in the magnetic layer has greatly increased due to the special order of electromagnetic conversion of magnetic recording media. Dispersants such as acid soda are used.

However, when magnetic powder is dispersed using these substances, one molecule is 11t - 11! Even after being formed into a film, it remains with a low molecular weight. Therefore, there are too many city loans.

A bleed effect from the coating film may impair the customization of the magnetic medium, and the low molecular weight causes the film to deteriorate in mechanical properties, resulting in the durability of the magnetic medium:
make worse.

[Problem that the invention seeks to solve]

The purpose of this invention is to solve the drawback that the dispersant of conventional products (h) remains at a low molecular weight in the magnetic coating film, and thereby provide a magnetic recording medium with excellent dispersibility and durability. shall be.

[Means to solve the problem]

As a result of intensive study t-1 in order to solve the drawbacks mentioned in the following, the present inventors used a compound represented by the following - film surface % formula %) as a dispersant and irradiated it with an electron beam after forming an. The molecular strength of the magnetic powder is good, the 3rd dispersant does not bleed out from the coating film, and the primary carbon
ITfi! It no longer works as an i agent.

It was discovered that the durability of the magnetic medium is the same as above, and the present invention was completed.

The above compound has a relatively hydrophilic phosphate group.
The hydrocarbon part of the magnetic powder is adsorbed on the surface of the magnetic powder, and the hydrocarbon part of the -10,000 ester extends into the melt and explodes with each other, increasing the dispersion stability of the magnetic powder.

Magnetic paint 1 with magnetic powder dispersed in this way: e! After forming a single film, electron beam irradiation is performed.

The 21 bonds of the hydrocarbon moiety open and combine to form a polymer.

Therefore, it is assumed that low molecular weight components are eliminated.

When using the combination compound as a dispersant, the summer dose is 100 ii of magnetic powder (0.1 parts by weight to 20 parts by weight per part
The amount of free space is preferably 0.5 parts to 10 parts. If the amount of dispersant is too small, the effect as a dispersant will be small, and if it is too large, the double bond group S degree will increase, and the degree of 1 will increase due to electron beam irradiation, making the M film hard and brittle.

Further, as the binder used in the present invention, conventionally known resins 9 such as vinyl chloride-vinyl acetate resin, butyl 2-
Le resin, fiber #t! ! Store-based toga resin, polycrethane resin, polyester resin, etc. can be used.

More desirable are resins in which double bonds are introduced and modified.

In addition, in the present invention, magnetic powder, magnetic m! A additive.

Any of the conventionally known agents for magnetic paint can be used.

〔Example〕

An embodiment of the present invention will be described below.

Example 1 a-Fe powder 100i1iJJk part 2
-Acryloyloxyethyl acid phosphate
3-part vinyl chloride-vinyl acetate-vinyl alcohol copolymer (UCC ylv)
A(Jf()?mff1g Polycrethane resin (Niraporan 2301 manufactured by Nippon Polyurethane Co., Ltd.)
5 parts by weight of tristic acid
2il parts n-pudel stearate
111 Part 4-Alumina 511
1 part cyclohexanone 1501 parts Methyl ethyl ketone 1501 parts The above composition was dispersed in a sand kil at a linear speed of 500 m/s for 5 hours, and then a polyfunctional incyanate compound (Coronet L, manufactured by Nippon Polyurethane Co., Ltd.) was dispersed. After blending 31 parts, it was filtered to obtain a magnetic paint. This magnetic coating material was applied onto a polyester film so that the coating thickness after drying was 5 μm. After that, it was irradiated with an electron beam of t:6 Mrad, and then cut into a predetermined width to make magnetic tape.

Example 2 Co-coated γ-Fe was used instead of α-Fe powder in Example 1.
A magnetic tape was obtained in the same manner as in Example 1 except that the same amount of zes f was used.

Example 3 Example 10 minutes The same amount of 2-methacryloyloxyethyl acid phosphate was used instead of the 2-acryloyloxyethyl acid phosphate.
A magnetic tape was obtained in the same manner as in Example 2.

Example 4 A magnetic tape was obtained in the same manner as in Example 3, except that the magnetic powder in Example 3 was replaced with α-F.Os and the same amount of Co-adhered γ-Fa*Os was used.

Comparative Example 1 Example 10 Dispersant 2-1 A magnetic tape was obtained in the same manner as in Example 1 except that chloroyloxyethyl acid phosphate was not used.

Comparative Example 2 A magnetic tape was obtained in the same manner as in Example 2, except that diethyl acid phosphate in the dispersant 2-acryloyl was not used.

The Kadoya ratio of the magnetic tape obtained in each of the above Examples and Comparative Examples and the surface properties of magnetic 1m were measured as indicators of the dispersibility of the magnetic powder. Furthermore, the still life was measured as the durability of the magnetic layer.

Surface quality is -20jog (Ra/Ra (Comparative Example 2))
It was displayed in

Still life is Hitachi VTR recorder VT-80
00E t- is used to continuously reproduce the output of a constant signal in a still image state, and displays the time in minutes until the output reaches 6 dB of the initial output.9.

〔Effect of the invention〕

As explained above, as a precaution, a compound containing both acrylic and phosphoric acid functional groups is used as a dispersant for washing powder, and a magnetic film containing this dispersant is irradiated with an electron beam after the coating film is formed. It is clear that a magnetic recording medium with excellent dispersibility of powder and excellent running durability of the coating film can be obtained.

Claims (2)

[Claims] (1) A magnetic recording medium characterized in that the magnetic layer contains a compound having a molecular weight of 1000 or less and having both an acrylic group and a phosphoric acid group. (2) A method for producing a magnetic recording medium, characterized in that the magnetic layer contains a compound having both acrylic and phosphoric acid functional groups and is irradiated with an electron beam.