JPS629533A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent running property and durability by coating a mixture composed of a higher fatty acid anhydride and specific copolymer on a magnetic layer formed by coating a magnetic paint contg. carbon black having a prescribed oil absorption on a non-magnetic substrate and drying the coating. CONSTITUTION:The magnetic layer is formed by coating the magnetic paint contg. 1-15wt% carbon black having >=300ml/100g oil absorption on the non- magnetic substrate and drying the coating. The surface coating liquid prepd. by dissolving 5pts.wt. higher fatty acid anhydride and 95pts.wt. the polysiloxane/ polyoxy alkylene copolymer expressed by formula I (where m is 5-40, n is 1-5, a is 0-4, b is 5-20, a/b<0.2, R is an alkyl group of 1-4C) in 2,000pts.wt. n-hexane is coated on the magnetic layer at 1.2pts.wt. by the weight of the magnetic powder in the magnetic layer and is dried. The magnetic recording medium having the excellent running property and durability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a magnetic recording medium that has excellent running properties and excellent durability.

[Prior art]

Generally, magnetic recording media such as magnetic tapes and flexible magnetic disks are made by depositing magnetic powder, binder, and solvent on a non-magnetic support such as polyester film.

It can be obtained by applying and drying a magnetic paint consisting of various additives such as a dispersant, a lubricant, an antistatic agent, and an abrasive.

By the way, in recent years, magnetic recording media have been required to have even higher density, and even better magnetic properties.

In order to obtain electromagnetic conversion characteristics, magnetic powder with fine particles and high coercive force is used, and the magnetic layer is also becoming increasingly thin.

On the other hand, in terms of durability, this reduction in film thickness causes a decrease in the mechanical strength of the magnetic recording medium, and therefore, reduction in film thickness is extremely difficult. Therefore, there is a need for a magnetic recording medium that has superior durability compared to conventional magnetic recording media.

In order to meet the above requirements, higher aliphatic compounds such as higher fatty acids, higher fatty acid amides, higher fatty alcohols, higher fatty acid esters, etc. have been conventionally used in the magnetic layer.

Alternatively, a lubricant such as silicone oil or fluorine oil may be contained alone or in combination.

[Problem that the invention seeks to solve]

However, as described above, thin magnetic recording media can sufficiently ensure the required durability.

I hadn't gotten to the point where I did. For example, if you try to ensure durability by adding too much lubricant,
When used in a high-temperature, high-humidity environment, so-called pluming occurs in which the lubricant seeps onto the surface of the magnetic layer, resulting in tape sticking, step-slip, or a decrease in output due to head dirt, and furthermore, magnetic properties caused by head dirt. Problems such as mechanical deformation of the layers (drolage in-out) arise.

The object of the present invention is to eliminate such conventional drawbacks.

An object of the present invention is to provide a magnetic recording medium with excellent running properties and excellent durability.

[Failure to solve the problem]

The present invention is applied to a magnetic layer formed by coating and drying a magnetic paint containing at least carbine black with an oil absorption of 300 ml on a non-magnetic support.

It is further characterized in that it contains a higher fatty acid anhydride and a polysiloxane-polyoxyalkylene copolymer having the general formula C3H6(OC2H4)a(oC3H6), OR.

[Effect]

By further containing two types of specific lubricants on the magnetic layer containing specific carbon black, and by using both in combination, excellent magnetic properties and electromagnetic conversion properties can be maintained even in thin magnetic recording media. So, without causing pluming,
Tape sticking phenomenon.

It is possible to provide a magnetic recording medium that has excellent durability and does not suffer from slippage, output reduction due to head clogging, or mechanical deformation due to head dirt.

〔Example〕

The present invention will be explained below with reference to Examples.

Commercially available carbine blacks used in this example include Ketjen Black EC, Ketjen Black ECX, Ketjen Black ECDJ-600, and Ketjen Black ECDJ manufactured by Lion Akzo.
-500 etc.

1) Prototype example: Co-coated iron oxide (oil absorption 105mA'/100
．． ! li+.

BET particle size 40 m2/fl *Coercive force (He) = 6
700e) to 7e heavy i part, vinyl chloride-vinyl acetate-
12.5 parts by weight of vinyl alcohol copolymer, 12.5 parts by weight of polyurethane resin, Carbin Black (Ketjen Black KCDJ-600, oil absorption 480 mA!
/100#), 2.3 parts by weight of α-At203 (average particle size 0.5 μm), 0.8 parts by weight of lecithin, methyl ethyl ketone (MEK), ) toluene, and hiscyclohexanone, respectively. 60 parts by weight were kneaded in a ball mill for 50 hours. Thereafter, 5 parts by weight of an incyanate compound was added and mixed and dispersed for 1 hour to prepare a magnetic paint. Next, this magnetic paint was applied onto a polyethylene terebutyrate support having a thickness of 75 μm so that the thickness after drying would be 2 μm to form a magnetic layer.

In this magnetic layer, 5 parts by weight of stearic anhydride, which is a type of higher fatty acid anhydride, and 95 parts by weight of a polysiloxane-polyoxyalkylene copolymer expressed by F9 were dissolved in 2000 parts by weight of n-hexane. A surface treatment solution was prepared.

This surface treatment liquid was applied to the magnetic layer so that the solid content of the surface treatment liquid was 1.2 parts by weight based on the magnetic powder in the magnetic layer, and after drying, it was applied to a disk-like sheet with an outer diameter of 133 mm. Sample 1 was prepared by removing the sample.

2) Comparative Example 1 Next, carbon black (Ketjen Black ECDJ-600, oil absorption amount 4801 rLl) used in the above-mentioned prototype example was used.
/loo, F), the inhalation amount is 80rLl/10
Sample 2 was prepared using 0p carbon black (3.5 parts by weight) and in the same manner as the prototype example.

3) Comparative Example 2 95 parts by weight of polymethylsiloxane (viscosity 300 centistokes) was used in place of the polysiloxane-polyoxyalkylene copolymer represented by C3H6(OC3H6)2oOC2H5 used in the prototype example, and the rest were the same as the prototype. Sample 3 was prepared in the same manner as in the example.

The following various tests were conducted using these samples 1, 2, and 3.

(i) Durability Test Samples 1, 2, and 3 were each inserted into a jacket covered with a nonwoven fabric, and a 125 kHz signal was recorded using a magnetic recording/reproducing tester. After that, the temperature was 40℃ and the humidity was 804R.
While contacting with a magnetic head at a circumferential speed of 1.7 V seconds in an atmosphere of
The time required for the initial reproduction output signal to reach 80 degrees was measured.

(11) Friction coefficient test Samples 1, 2, and 3 were each inserted into a jacket covered with a nonwoven fabric, and brought into contact with a magnetic head at a circumferential speed of 1.7 mA'JJ in an atmosphere with a temperature of 40°C and a humidity of 804 RH. The friction coefficient was measured while

G11) L extrusion test Samples 1, 2, and 3 were left in an atmosphere with a temperature of 40° C. and a humidity of 80% RH for 7 days, and then taken out at room temperature and visually observed for oil (lubricating oil) exudation.

The results of these durability tests, friction coefficient tests, and seepage tests are shown in the table below.

As is clear from this table, Sample 1 prepared according to the present invention has a small coefficient of friction, excellent long-term running performance even in high temperature and high humidity, and excellent durability.

In order to obtain the same characteristics (effects) as in the above embodiment, the carden plastic used in the present invention has an oil absorption of 300 mJ/
It is sufficient that it is 100ff or more, and the amount added is in the range of 1 to 1"5% by weight, preferably 3 to 7% by weight based on the magnetic powder. On the other hand, higher fatty acid anhydride and polysiloxane-polyoxy The proportion of the alkylene copolymer is 1/99 to 10/90 by weight.

It is preferably within the range of 3/97 to 5/95.

In addition, the lubricant solid content is 0.5 to 0.5 to the magnetic powder.
It may be added in an amount of 2.0 parts by weight, preferably in a range of 1.0 to 1.5 parts by weight.

Note that the higher fatty acid anhydride may have carbon atoms in the range of 24 to 44, and specific examples include lauric anhydride in addition to the above-mentioned stearic anhydride.

Examples include myristic anhydride, palmitic anhydride, and the like.

〔Effect of the invention〕

As explained above, according to the method of manufacturing a magnetic recording medium according to the present invention, it is possible to provide a magnetic recording medium that has better running properties and is more durable than conventional magnetic recording media.

Claims (1)

[Claims] 1. On a magnetic layer formed by coating and drying a magnetic paint containing at least carbon black with an oil absorption of 300 ml/100 g, a higher fatty acid anhydride and a higher fatty acid anhydride are further applied. The general formula is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, m is 5 to 40, n is 1 to 5, a is 0 to 4, b is 5
~20, (a/b) < 0.2, R is an alkyl group having 1 to 4 carbon atoms) .