JPH04103021A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain high durability by incorporating at least one kind of fatty acid ester having ether bond in fatty acid ester of <= 400 mol. wt. CONSTITUTION:Fatty acid ester of >= 500 mol. wt. and fatty acid ester of <=400 mol. wt. are incorporated into a lubricant to be incorporated into a magnetic layer. As for the fatty acid ester of <=400 mol. wt., at least one kind of fatty acid ester having ether bond is used. To form the magnetic layer, a polyester film is activated in its surface with corona discharge or the like, on which a magnetic coating material is applied and dried, and then subjected to calendering. After the coating film is cured, the medium is punched into a disk, the surface of which is then polished. Thus, the obtd. medium has improved durability at both high temp. and low temp.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-density magnetic layer formed by coating a magnetic paint containing metal or iron oxide magnetic powder as a ferromagnetic material on a substrate such as a polyester film. The present invention relates to recording magnetic recording media.

2. Description of the Related Art In recent years, floppy magnetic disks have been widely used for external storage in personal computers and the like. This floppy disk is made by applying magnetic paint to a base material such as polyester, surface treating it, hardening it, punching it into a disk shape, and polishing the surface.
It is manufactured in a predetermined case.

Problems to be Solved by the Invention Video floppy disks that achieve high recording density contain metal magnetic powder as a ferromagnetic material. Generally, metal magnetic powder having a BET surface area of 4 Brd/g or more is used, and attempts are being made to further increase the BET surface area.

Floppy disks using such fine-grained metal magnetic powder can easily achieve surface smoothness, improve head output, reduce noise from the medium, and easily achieve high S/N ratio. It has improved characteristics and is suitable for high-density recording, but on the other hand, magnetic powder with a large surface area turns the magnetic powder into fine particles, making it difficult to improve the strength of the coating film, making it difficult to satisfy all durability requirements in each environment. is difficult,
Furthermore, improvement in surface smoothness also acts in the direction of deteriorating durability. For these reasons, it has been difficult to achieve high durability in all environments.

Means for Solving the Problems In order to solve the above problems, a fatty acid ester with a molecular weight of 500 or more and a 9-fatty acid ester with a molecular weight of 400 or less is used as a lubricant in the magnetic layer, and the fatty acid ester with a molecular weight of 400 or less has an ether bond. The configuration is such that at least one type of the above is used.

Function: In the structure of the present invention, the magnetic layer contains a fatty acid ester with a molecular weight of 500 or more as a lubricant that is effective for improving durability at low temperatures, and a fatty acid ester with a molecular weight of 400 or less that is effective for improving durability at room temperature and high temperature. and has a molecular weight of 400
Since at least one fatty acid ester having an ether bond is used as the following fatty acid ester, a magnetic recording medium having excellent durability at both high and low temperatures can be obtained.

Example An embodiment of the present invention will be described below.

Magnetic paint is provided on a substrate such as polyester by applying magnetic paint.

[Example] Example 6 As a specific example, after activating the surface of a polyester film with a thickness of 33 μm by corona discharge or the like, the first
A magnetic paint having the composition shown in the table was applied, dried, and then calendered.

The final magnetic layer thickness here is set to 35 μm.
1 (simply written as ester in the table).

Examples 1 to 6 The lubrication law quantities were as shown in Table 2, and all media preparations were as in Example 1 described above.

The amount of lubricant here is expressed as a weight percentage relative to the binder.

(Margins below) Thereafter, after the coating film was cured, it was punched out into a disc shape, the surface was polished, and the disc was placed in a designated case to evaluate its durability.

In Examples 1 to 6, butyl stearate was used as a fatty acid ester with a molecular weight of 400 or less (hereinafter referred to as low molecular weight) without an ether bond, butoxyethyl stearate was used as a fatty acid ester with an ether bond, and oleyl oleate was used as a fatty acid ester (denoted as high molecular weight) (hereinafter referred to as fatty acid ester). Samples of Examples 7 to 9 were created by changing the type of each lubricant as shown in Table 3 while keeping the ratio and amount unchanged.

(Margin below) Comparative Examples 1 to 9 Next, as Comparative Examples 1 to 9, the same lubricant as in Example 1 was fixed, and the ratio and amount were determined as shown in Table 4. I made the changes and created a sample.

(Left below) Durability tests were conducted on the samples prepared as described above. The floppy disk drive used in the durability test was PDD-100 manufactured by Sony ■, and the end of the durability test was defined as the point in time when the head output decreased to 70% of the initial head output.

The test environment was 40°C and 80% RH.

There were three environments: 3°C, 5% RH, and 3"C, 80% RH.

The results of the durability test are shown in Table 5 together with Examples and Comparative Examples. The results are relative comparisons with the durability of Example 1 set as 100.

(Margins below) Example 1 has a composition located almost in the center of the claimed scope, and the durability of each sample was compared based on this durability.

In Example 2, the low molecular weight ester was 10% and the total amount of lubricant was 20%, and although the amount of lubricant was smaller than in Example 1 and the durability was slightly lower, the decrease was not that large. On the other hand, Comparative Example 4 had the same amount of low molecular weight ester as Example 2, but did not contain any high molecular weight ester, resulting in a decrease in durability, particularly at 3°C.

In Comparative Example 5, the total amount of lubricant was the same as in Example 1, but the low molecular weight ester was particularly low, and the durability at 40°C was particularly low. I think it contains enough ester, but
Durability at 3°C is also low.

Although the reason for this is not clear, it is thought that the low molecular weight ester brings out the effects of the high molecular weight ester through some kind of interaction, and that the low molecular weight ester is present in a small amount.

In Examples 3 and 4, the total amount of lubricant is the same at 45%, but the amount of low molecular weight ester is different.

These had almost the same durability as Example 1, and the effect of the lubricant was seen. In Comparative Example 6, the total amount of lubricant was the same as in Examples 3 and 4, but no high molecular weight ester was contained and the durability, especially at low temperatures, was reduced. Comparative Example 7 has the same amount of low molecular weight ester as Example 3, but contains 50% of the binder in the total amount of lubricant, and although the decrease in durability is small compared to other comparative examples. There was a clear difference compared to the example. Also, Comparative Example 7
However, the surface smoothness is slightly reduced, making it unsuitable for high-density recording.

In Examples 5 and 6, the amount of low molecular weight esters and the total amount of lubricant were the same as in Example 1, but the ratio of esters containing ether bonds to esters not containing ether bonds was changed to 3, respectively.
:1.1:3. The durability is not significantly different from Example 1, but Example 6, which has a higher proportion of ester containing an ether bond, has slightly better durability. Since the ether bond exhibits some inorganic properties, it is thought that it may have some kind of interaction with other lubricants, which may have had some effect on lubricant seepage.

Comparative example 1. Comparative Example 2 and Comparative Example 3 are samples in which no high molecular weight ester, low molecular weight ester containing an ether bond, and no ether bond containing any ester are blended. It was also shown that the durability of these samples was clearly different from that of the examples, and that even if any one of them was missing, the durability would be reduced.

Next, in Examples 7 to 9, other lubricants satisfying the conditions of molecular weight and the presence or absence of an ether bond were investigated. These also exhibited durability similar to other examples.

Furthermore, durability will be further improved if the particle size of the magnetic powder is increased and the strength of the magnetic coating is improved.

As described in detail, according to the present invention, it is possible to create a magnetic recording medium that has high surface smoothness suitable for high-density recording and has excellent durability in various environments.

Claims (2)

[Claims] (1) In a magnetic recording medium, a magnetic layer is formed by coating a magnetic paint consisting of magnetic powder, antistatic agent, abrasive, binder resin, lubricant, solvent, etc. on a substrate such as a polyester film. The lubricant contained is a fatty acid ester with a molecular weight of 500 and a molecular weight of 400.
A magnetic recording medium comprising the following fatty acid esters, and the fatty acid esters having a molecular weight of 400 or less include at least one type of fatty acid ester having an ether bond. (2) a fatty acid ester with a molecular weight of 400 or less, in which the weight ratio of the fatty acid ester without an ether bond to the fatty acid ester with an ether bond is in the range of 3:1 to 1:3;
The fatty acid ester having a molecular weight of 400 or less is contained in an amount of 10 to 40% by weight based on the binder resin, and the total content of the lubricant containing these is based on the binder resin.
The magnetic recording medium according to claim 1, characterized in that the content is in the range of 20 to 45% by weight.