JPS629528A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent running property and durability by coating a sodium alkyl sulfonate 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. the carbon black (1-15wt%) having 300ml/10g oil absorption on the non-magnetic substrate and drying the coating. The surface coating liquid prepd. by dissolving 5pts.wt. sodium alkylsulfonate and 95pts.wt. the polysiloxane/ polyoxy alkyl 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 from various additives such as magnetic powder, binders, solvents and dispersants, lubricants, antistatic agents, and abrasives on a non-magnetic support such as a polyester film. It is obtained by applying and drying a magnetic paint.

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, 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, conventionally, in the magnetic layer.

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, as described above, it has not been possible to sufficiently ensure the required durability with thin magnetic recording media. For example, if you try to ensure durability by adding too much lubricant.

When magnetic recording media are used in high temperature and high humidity environments for long periods of time, so-called blooming occurs in which the lubricant seeps onto the surface of the magnetic layer, resulting in tape sticking, step-slip, or decreased output due to head dirt. 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 to try to solve problems]

The present invention has an oil absorption amount of at least 3001 nl/100,
On a magnetic layer formed by coating and drying a magnetic paint containing Cargan black No. 9 on a non-magnetic support, sodium alkyl sulfonate and a polysiloxane represented by the general formula %) are further applied. It is characterized by containing a polyoxyalkylene copolymer.

[Effect]

on a magnetic layer containing specific I carbon black.

Furthermore, by containing two types of specific lubricants and using both in combination, it maintains excellent magnetic properties and electromagnetic conversion properties even in thin magnetic recording media, and does not cause blooming. It is possible to provide a magnetic recording medium that has excellent durability and does not suffer from tape sticking, step-slip, or a decrease in output due to head clogging, as well as mechanical deformation due to head dirt.

〔Example〕

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

There are two commercially available carbon blacks used in this example, such as 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-adhered iron oxide (oil absorption 105ml/100g).

BET particle size 40m/g, coercive force (Hc) = 6700e
), 75 parts by weight, chloride? 12.5 parts by weight of "vinyl acetate-vinyl alcohol copolymer", 12.5 parts by weight of polyurethane resin, carbon black (Ketjen 7'7y ECDJ-600# oil absorption 480 m)
l/10011)'t3.5 parts by weight, α-At203
2.3 parts by weight of (average particle size: 0.5 pm), 0.8 parts by weight of lecithin, and 60 parts by weight each of methyl ethyl ketone (MEK), toluene, and hiscyclohexanone are 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 the entire magnetic layer.

In this magnetic layer, 5 parts by weight of sodium 1-octadecanesulfonate, which is a type of sodium alkylsulfonate, and 195 parts by weight of a polysiloxane-polyoxyalkylene copolymer, expressed as the following, were added in 2000 parts by weight of n-hexane. Prepare a surface treatment solution by dissolving it in

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 punching.

2) Comparative Example 1 Next, carbon black C Ketjenblack ECDJ-600 used in the above-mentioned prototype example, oil absorption amount 480ml/1
0Qg), the inhalation amount is 80ral/100.
! Sample 2t was prepared using carbon black (3.5 parts by weight) of i' and in the same manner as in the prototype example.

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

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 1 and 1 ml second in an atmosphere of

(11) Friction coefficient test Samples 1, 2, and 3 were each inserted into a wire rope to which a nonwoven fabric was pasted, and the friction coefficient was measured while making contact with a magnetic head at a circumferential speed of L7 m/sec in an atmosphere of a temperature of 40°C and a humidity of 80% RH. was measured.

(Surface oozing 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) oozing out.

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, has good running performance over a long period of time even at high temperatures and high humidity, and has excellent durability.6 In order to obtain the same characteristics (effects) as in the example, the carbon black used in the present invention must have an oil absorption of 300 ml.
/100,! i' or more, and the weight ratio of the added sodium sulfonate to the polysiloxane-2-lioxyalkylene copolymer is 1/99 to 10/90. Preferably, the lubricant solid content is in the range of 3/97 to 5/95, and the lubricant solid content is 0.5 to 2.0 to the magnetic powder.
It may be added in an amount of 1.0 to 1.5 parts by weight, preferably 1.0 to 1.5 parts by weight.

In addition, specific examples of sodium alkylsulfonate include sodium 1-hexadecanesulfonate, sodium 1-tetradecanesulfonate, etc. in addition to the above-mentioned sodium 1-octadecanesulfonate. [Effects of the Invention] As explained above. As described 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 conventional magnetic recording media.

Agent (7783) Attorney Noriyasu Ikeda 1'.

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, sodium alkyl sulfonate is further added. , 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). Production method