JPH04103019A - magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve coating film strength and durability without causing deterioration in electromagnetic conversion characteristics by incorporating a metal magnetic powder having specified BET surface area as a ferromagnetic material into a magnetic layer and specifying the surface gloss. CONSTITUTION:A metal powder having <= 46 m<2>/g BET surface area is used to improve the film strength. Further, the 45 deg. - 45 deg. surface gloss which largely relates to surfaces smoothness of the coating film is specified to >= 250 % in order to increase the head output. By decreasing the surface area of the magnetic powder, the amt. of binder required to cover the magnetic powder particles can be decreased. Thereby, the packing rate of the magnetic powder in the coating film can be increased, which improves electromagnetic conversion characteristics and durability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention applies a magnetic paint containing metal magnetic powder as a ferromagnetic material to a substrate such as a polyester film to form a magnetic layer, thereby producing a video floppy disk. The present invention relates to magnetic recording media used for.

Conventional technology In recent years, floppy disks have been used as external storage media for computers, etc.

Bee disks are widely used. Additionally, VideoFLO and B-Disk are also used as image recording media. This video floppy disk is made by coating magnetic paint on a base material such as polyester, and then hardening and treating the surface.
It is punched out into a disk shape, the surface polished, and placed in a designated case.

Problems to be Solved by the Invention A video floppy disk that achieves high recording density contains metal magnetic powder as a ferromagnetic material. Conventional video tapes using iron oxide-based magnetic powder use magnetic powder with a BET surface area of approximately 45n(/g).
Attempts have been made to increase the T surface area. Furthermore, the metal magnetic powder used to achieve even higher recording densities has a BET surface area of approximately 48n(/g), and here too, an even higher BET surface area is being sought. Floppy disks using metal magnetic powder can easily obtain surface smoothness and improve head output, and also reduce noise from the medium and have high S/S.
It is easy to obtain N, and the frequency characteristics are also improved, making it suitable for high-density recording. However, on the other hand, magnetic powder with a large surface area causes the demagnetic powder to become fine particles, making it difficult to improve the coating strength. However, using magnetic powder with a low BET surface area increases noise and lowers the S/N. There was a problem.

Means for Solving the Problems In order to solve the above problems, BE is used as a metal magnetic powder.
Improve the strength of the coating film by using a T surface area of 46nf/g or less, and further increase the 45°-45° surface gloss of 250% or more in accordance with the JIS standard (28741), which has a high correlation with the surface smoothness of the coating film. This improves head output. In addition, since the surface area of the magnetic powder is reduced, the amount of binder resin required to envelop the magnetic powder is reduced, which improves the packing ratio of the magnetic powder in the coating film and further improves the magnetic conversion characteristics. be able to. Since the S/N is improved by increasing the number of magnetic powders per unit volume of coating film,
A video floppy disk with a value of 0 or more that can compensate for the decrease in S/N due to the large particle size of the magnetic powder, improves coating strength without deteriorating electromagnetic characteristics, and has excellent durability in various environments. can be obtained.

Function: In the present invention, by using magnetic powder with a BET surface area of 46 nf/g or less, the strength of the coating film is improved, and the 45°-45° surface gloss, which is highly correlated with surface smoothness, is improved to 250°.
% or more, it is possible to obtain a video floppy disk with improved durability under various environmental conditions and excellent t-magnetic conversion characteristics such as head output.

Example Examples of the present invention will be described below.

A magnetic layer is provided on a substrate such as polyester by applying magnetic paint. Regarding the packing ratio of magnetic powder in this magnetic layer,
It was set at <70.4 wL%, which is slightly higher than before.

As Example 1, the surface of a polyester film with a thickness of 33 μm was activated by corona discharge, etc., and then a magnetic paint having the composition shown in Table 1 using metal magnetic powder with a BET surface area of 42 nf/g was applied and dried. and then further heat to 90°C
Calendering was carried out at 30 m/min, so that the final magnetic layer thickness was approximately 3.5 μm.

Floppy disks were prepared under the same conditions as in Example 1 except that magnetic powders having different ET surface areas were used as shown in Tables 1 and 2, and their durability and electromagnetic conversion characteristics were measured. The 45°-45° surface gloss at that time was in the range of 266-273%. The equipment used to measure the surface gloss was J.
This is a VC-ID manufactured by Nippon Denshoku Kogyo ■ that complies with IS standards.

(Margin below) Thereafter, after the coating film was cured, it was punched out into a disc shape, the surface was polished, a center hub was attached, the disc was placed in a predetermined case, and the tM1 conversion characteristics and durability were measured.

The results of Example 2, Example 3, Comparative Example 1, and Comparative Example 2 and the durability test are shown in Table 2, and the durability of 3°C, 8o% R) (as an example) is shown in Figure 1. Here, the durability test was terminated when the output decreased to 70% of the initial output.The durability decreased rapidly when the BET surface area of the magnetic powder was 48 rrr/g or more.

Also, these disks have 9MHz and 1.25MHz
Figure 2 shows the playback output when the signal is recorded.

The reproduction output decreases as the BET surface area of the magnetic powder increases, but the extent of this decrease is more remarkable for the 25 MHz signal. This is probably because the recording wavelength of the 1.25 MHz signal is larger, so the difference in magnetic flux density of the magnetic coating appears rather than the surface smoothness.

That is, as mentioned above, the nonmagnetic film on the surface of the magnetic powder has a high BE.
The larger the T surface area, the smaller the magnetic flux density of the coating film. On the other hand, the effect of the magnetic flux density of the coating film also appears for the 9 MHz signal, but because the recording wavelength is short, the effect of the surface smoothness has a greater influence than the magnetic flux density, and the 1.25 MHz signal
There was no noticeable difference in the z signal.

This durability test was conducted using Sony's PDDloo.
Still durability was measured on 5 tracks. To measure electromagnetic conversion characteristics, R5000H manufactured by Fuji Photo Film ■ was modified to record RF multiplied signals, and measurements were taken with 25 trunks.

Next, by changing the calender temperature and speed using the same paint composition as in Example 1 and Example 2, coating films with different surface gloss levels of 45°-45° were prepared, and the t-magnetic conversion characteristics such as head output were adjusted. It was measured. The surface gloss here was measured using the above-mentioned surface gloss meter. ! The electromagnetic conversion evaluation device described above was used to measure the magnetic conversion characteristics. FIG. 3 shows the relationship between the output power of a 9 MHz signal and the surface glossiness of a floppy disk (same composition as in Example 1) using metal magnetic powder with a BET surface area of 42+12/g. The head output exceeds the reference when the surface gloss is 250% or more. The reference disk used here is “Electronic Still Camera 9V
This is a disc with characteristics approved by the Association.

FIG. 4 shows the relationship between the surface glossiness of a video floppy disk (same composition as in Example 2) and Y-3/N when metal magnetic powder with a BET surface area of 46 n2/g was used. In this case as well, the surface glossiness is 250% or more, which is higher than the reference value.

The frequency characteristics are also shown in Table 2.

4 compared to magnetic powder with a BET surface area of 48r+2/g or more.
Those below 6 rrr/g are slightly inferior, but the surface gloss is 2
For values above 50%, the values are equivalent to the reference, and there are no particular problems.The frequency characteristics here are 12MH
It was measured by the ratio of the reproduction output of 9MHz and 9MHz, and the relationship with the reference was shown.

Comparative Example 1 is a case where conventional magnetic powder is used, and the durability at 3°C is extremely poor compared to the Example, and Comparative Example 2
However, its durability has deteriorated further.

The reason why the durability is good when the BET surface area is 46r+2/g or less is probably because the smaller the BET surface area of the magnetic powder, the larger the magnetic powder and the improved magnetic 11111 strength.Furthermore, if the BET surface area is 48n2/g or more, the coating film Not only could no improvement in strength be expected, but also the binder resin was highly adsorbed to the surface of the magnetic powder (probably because its role as a binder was rapidly reduced).

As described in detail, according to the present invention, it is possible to produce a video floppy disk that has improved electromagnetic characteristics such as head output, and has excellent durability in various environments.

[Brief explanation of drawings]

Figure 1 shows the BET surface area value of metal magnetic powder and 3℃80%R.
Figure 2 shows the relationship between durability of H and B of metal magnetic powder.
FIG. 3 is a diagram showing the relationship between ET surface area value and head output, FIG. 3 is a diagram showing the relationship between surface glossiness and head output, and FIG. 4 is a diagram showing the relationship between surface glossiness and Y-3/N. Name of agent: Patent attorney Haruaki Ogata and 2 others Tsuru 1 Adoring Powder βET% face attack (“1/l”)

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer is provided by coating a magnetic paint on a substrate such as a polyester film, the magnetic layer is a ferromagnetic material and has a BET surface area of 46 m^2/
g or less of metal magnetic powder, and the magnetic layer has a 45°-
A magnetic recording medium characterized in that the surface glossiness at 45° is 250% or more.