JPS629531A - 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 amide 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 amide 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 [Field of Industrial 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 coating magnetic powder, binder, solvent, etc. 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.

Incidentally, in recent years, there has been a demand for higher densities in magnetic recording media, and in order to obtain better magnetic properties and electromagnetic conversion properties, finer particles and higher coercive force magnetic powders are used, and the magnetic layer There is also a tendency for films to become thinner and thinner.

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. 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, 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, magnetic recording media made thin as described above have not yet achieved sufficient durability. For example, if an attempt is made to ensure durability by containing an excessive amount of lubricant, if used for a long time in a high temperature and high humidity environment, so-called blooming will occur, where the lubricant seeps onto the surface of the magnetic layer.

Problems such as 7t' tape sticking phenomenon, stellar l-slip, decrease in output due to aluminum or head contamination, and 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 problems]

The present invention has an oil absorption amount of at least 30 (3ml/100
A magnetic coating containing fi carbon black is applied onto a non-magnetic support and dried to form a magnetic layer.

It is further characterized in that it contains higher fatty acid amide and polysiloxane-polyoxyalkylene copolymer gold having the general formula C3H6(OC2H4)a(OC3H6)bOR.

[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. .

Does not cause blooming, reduces output due to tape sticking phenomenon, stellar slip, or head clogging.
Furthermore, it is possible to provide a magnetic recording medium that has excellent durability and is free from mechanical deformation caused by head contamination.

〔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.

l) Prototype example First, Co-coated iron oxide (oil absorption 105mA'/100g
.

BET particle size 40m2/i Coercive force (He) = 6700
s), 12.5 parts by weight of vinyl chloride-vinyl acetate-vinyl alcohol copolymer, 12.5 parts by weight of polyurethane resin, carbon black (Ketjenblack ECDJ-600, oil absorption 48 QmA') ,/1
00 g), 2.3 parts by weight of α-At203 (average particle size 0.S μm), lecithin'i 0
．． 8 parts by weight, 60 parts by weight each of methyl ethyl ketone (MEK), ) toluene, and synlohexanone 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 terephthalate 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, 125 parts by weight of amide stearate, which is a type of higher fatty acid amide, and 95 parts by weight of polysiloxane-polyoxyalkylene copolymer X' expressed by A 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 toner based on the magnetic powder in the magnetic layer mentioned above, and after drying, a disk with an outer diameter of 133+m++ (7) was coated. Sample 1 was prepared by punching.

2) Comparative Example 1 Next, carbon black (Ketjen Black ECDJ-600, oil absorption 480 ml/lO) used in the above-mentioned prototype example was used.
Sample 2 was prepared in the same manner as the prototype example except that carbon black (3.5 parts by weight) f with an inhalation amount of 80 ml/L OOg was used instead of OOg).

3) Comparative Example 2 Sample 3 was prepared in the same manner as in the prototype example except for the polysiloxane-polyoxyalkylene resin represented by the formula used in the prototype 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 nonwoven fabric, and a magnetic recording/reproducing tester was used to A kHz signal was recorded. After that, the temperature is 40℃ and the humidity is 80%RH.
While contacting the magnetic bed at a circumferential speed of 1.7 m/sec in an atmosphere of
The time required for the signal to reach 80% of the initial reproduction output signal was measured.

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

(iiD L exudation 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.

Table 2 As is clear from this table, Sample 1 prepared according to the present invention has a small coefficient of friction, has good running performance over a long period of time even under high temperature and high humidity, and has excellent durability.

In order to obtain the same characteristics (effects) as in the above embodiment, the carbon black used in the present invention has an oil absorption of 300 m/Z.
oo! ! The amount added may be in the range of 1 to 15% by weight, preferably 3 to 7% by weight based on the magnetic powder. On the other hand, the weight ratio of higher fatty acid amide and polysiloxane-polyoxyalkylene copolymer is 1/1.
The solid content of the lubricant should be in the range of 99 to 10/90, preferably 3/97 to 5/95, and the lubricant solid content is 0.5 to 2.01 parts, preferably 1.0 parts to the magnetic powder. 0~
It may be added in an amount of 1.5 parts by weight.

The higher fatty acid amide may have carbon atoms in the range of 12 to 22, and specific examples thereof include lauric acid amide, myristic acid amide, palmitic acid amide, etc. in addition to the above-mentioned stearic acid amide.

〔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. A magnetic coating containing at least carbon black with an oil absorption of 300 ml/100 g is coated on a non-magnetic support and dried to form a magnetic layer. The 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) .