JPS629530A - 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 ester 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 ester 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]

In general, magnetic recording media such as magnetic tapes and flexible magnetic disks are made of magnetic powder, a binder, a solvent, a dispersant, a lubricant, etc. on a non-magnetic support such as a polyester film.
It is obtained by applying and drying a magnetic paint containing various additives such as antistatic agents and abrasives.

However, in recent years, magnetic recording media are required to have even higher densities, and in order to obtain better magnetic properties and electromagnetic conversion properties, magnetic powders with finer particles and higher coercive force are used, and the magnetic layer is also There is a tendency for films to become thinner and thinner.

On the other hand, regarding 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. For this reason, there is a need for magnetic recording media that have greater durability than conventional magnetic recording media.

In order to meet the above requirements, K in the magnetic layer has conventionally been used.

Higher aliphatic compounds such as higher fatty acids, higher fatty acid amides, higher aliphatic alcohols, and higher fatty acid esters, or lubricants such as silicone oil and fluorine oil are contained singly or in combination.

[Problem that the invention seeks to solve]

However, the magnetic recording medium made thin as described above has not been able to sufficiently ensure the required durability. For example, if an attempt is made to ensure durability by adding too much lubricant, magnetic recording media may be exposed to high temperatures for long periods of time.
When used in a high-humidity environment, so-called bluff 9 mink occurs where the lubricant seeps onto the surface of the magnetic layer, resulting in decreased output due to tape sticking, stem slip, or head contamination.

Furthermore, problems such as mechanical deformation (drop-in-out) of the magnetic layer due to head contamination occur.

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.

[Means for Solving the Problems] The present invention provides at least a magnetic layer formed by coating and drying a magnetic paint containing carbon black with an oil absorption of 300 m1/100 F on a non-magnetic support. Furthermore, higher fatty acid ester and general formula.

It is characterized by containing a polysiloxane-prioxyalkylene copolymer represented by:

[Effect]

By further containing two types of specific lubricants on the magnetic layer containing specific carbon black, and using both of them together,
Excellent magnetic properties even in thin magnetic recording media,
While maintaining electromagnetic conversion characteristics, there is no blueing, no output reduction due to tape sticking, step-slip, or head clogging, and no mechanical deformation due to head dirt. A magnetic recording medium having high durability can be provided.

〔Example〕

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

Commercially available carbon blacks used in this example include Ketjen Black EC and Ketjen Black ECX manufactured by Lion Akzo.

There are Ketjen Black ECDJ-600, Ketjen Black ECDJ-500, etc.

1) Prototype example First, Co-coated iron oxide (oil absorption 105ml/100g
.

BET particle size 40 m/jj, coercive force (He) =
6700e), 12.5 parts by weight of vinyl chloride-vinyl acetate-vinyl alcohol copolymer, 12.5 parts by weight of polyurethane resin, carbon black (Ketjen Black ECDJ-600, rp, oil amount 480 m
17100g), 2.3 parts by weight of α-At203 (average particle size 0.5 μm), and 0.8 parts by weight of lecithin.
60 parts by weight each of methyl ethyl ketone (MEK), ) toluene, and hiscycloheximanone were kneaded in a Solcourt 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 terephthalate support having a thickness of 75 μm so that the thickness after drying would be 2 μm to form a magnetic layer.

This magnetic layer contains 5 parts by weight of n-butyl stearate, which is a type of higher fatty acid ester. A surface treatment solution was prepared by dissolving 95 parts by weight of lysiloxane-polyoxyalkylene copolymer in 2000 parts by weight of n-hexane.

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 cm. Sample 1 was prepared by punching.

2) Comparative Example 1 Next, carbon black (Ketjen Black ECDJ-600, oil absorption 480 d/10
Sample 2 was prepared in the same manner as in the prototype example except that carbon black (3.5 parts by weight) with an intake amount of 80 m 17100 I was used instead of 0.1.

3) Comparative Example 2 Polydimethylsiloxane (viscosity 300
Sample 3 was prepared in the same manner as the prototype example except that 95 parts by weight of the sample was used.

These samples 1, 2. and 3 were used to conduct the following various tests.

(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 is 40℃ and the humidity is 80%RH.
While contacting the magnetic head with a magnetic head at a circumferential speed of 17 ml/second in an atmosphere of

(11) Friction coefficient test Samples 1, 2, and 3 were each inserted into a jacket covered with a nonwoven fabric, and friction was applied while contacting with a magnetic head at a circumferential speed of 1.7 m/sec in an atmosphere of a temperature of 40°C and a humidity of 80% RH. The coefficient was measured.

01D Seepage 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) seepage.

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 embodiments, the carbon black used in the present invention has an oil absorption of 300 m1/1.
100# or more is sufficient, and the ratio of the added amount of stellate to the polysiloxane-polyoxyalkylene copolymer is 1/99 to 10/90 in terms of weight ratio. Preferably from 3/97 to 5/
It is sufficient that the lubricant solid content is in the range of 0.5 to 2.0 parts by weight, preferably 1.0 to 1.5 parts by weight based on the magnetic powder. Just add it.

In addition, the higher fatty acid ester has 12 to 40 carbon atoms.
As long as it is within the range of , as a specific example.

In addition to the above-mentioned n-butyl stearate, examples include isopropyl laurate, n-butyl thucrumitate, etc. [Effects of the Invention] As explained above, according to the method for 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 other 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 ester and a general Formulas include ▲mathematical formulas, chemical formulas, tables, etc.▼ (However, m is 5 to 40, n is 1 to 5, a is 0 to 4, and b is 5.
~20, (a/b) < 0.2, R is an alkyl group having 1 to 4 carbon atoms) .