JPH0366023A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium excellent in durability, output and S/N by using two kinds of powders each having the specific center particle size for an abrasive powder in a magnetic layer which contains ferromagnetic metal powder, abrasive powder and binder. CONSTITUTION:The magnetic layer contains ferromagnetic metal powder, abrasive powder and binder, and the abrasive powder consists of two kinds of powders A, B. The powder ..A has the center particle size of 0.01 - 0.3mum, which is smaller than the minimum recording wavelength for general recording so that it gives little noise with improved packing density. The powder B has the center particle size of 0.4 - 1.0mum, which is a little larger than the ferromagnetic powder so that it gives good head touch and proper abrasing property for a head. Thereby, durability of the medium can be improved. Moreover, by controlling the particle size distribution of the powder B, dropout can be reduced and the surface of a heat can be protected from scratching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic disks and magnetic tapes used for image recording, audio recording, data recording, and the like.

[Conventional technology]

Recently, with the spread of home video, the demand for videotapes has increased significantly. On the other hand, the video format ranges from VHS to 5-VH3, 8mm5 high band 8mm5
As a result, magnetic recording media are required to have even greater characteristics and durability than ever before. In addition, recently, electronic still cameras have appeared in parallel with video cameras, and these have also become high-band cameras. Unlike videos, electronic still cameras are devices whose purpose is to record and play back still images, so the magnetic recording medium used for them, or video floppy disks, must have greater durability than video tapes. be done. In addition, in order to correspond to high band,
Characteristics equivalent to or better than 8mm video tape (high output, high S/
H) is also required.

By the way, ferromagnetic metal powder is generally used in video floppy disks and 8mm video tapes in order to obtain sufficient output at short wavelengths. Because it is significantly softer than the ferromagnetic iron oxide powder used, the same amount of abrasive powder as for VHS tapes is used for video floppy disks and
When used in 1.5 mm video tapes, it causes major problems in durability, specifically causing clogging of the spatula gap and loss of the magnetic layer on the media. If the amount is doubled, this durability problem will be solved, but the output and S/H will decrease, which will have a negative effect on high image quality.

These improvements in durability and properties are essentially contradictory, and can occur even when non-metallic magnetic powders such as ferromagnetic iron oxide are used, but in magnetic recording media that use ferromagnetic metal powders, This is a particularly big problem because, in addition to the originally high required properties, ferromagnetic metal powder is soft.

From the above viewpoints, various proposals have been made to balance durability and properties, but none of them have reached a satisfactory level.

[Problem to be solved by the invention] Problems with the prior art will be described below.

The first prior art method is to increase the central particle size (50% value of weight distribution) of the abrasive powder to 0.5 to 2.0 μm. When this method is used, the durability is satisfied and the output is almost satisfied, but there is a decrease in S/N and an increase in dropout, and the head may be damaged.

The second prior art method uses abrasive powder with a central particle size of 0.
．． A medium size of 3 to 0.5 μm is used.

When this method is used, the output and S/N are almost satisfactory, but the durability is still insufficient.

A third method of prior art is that the center particle size of the abrasive powder is 0.
．． O1~0.3μm small ones and center particle size 0.5~2
．． Mix and use large ones with a size of 0 μm. Using this method, durability, output, and S/N can be achieved at quite satisfactory levels, but 1, which is present in the abrasive powder with a large center particle size,
Coarse particles of 0 μm or more, particularly 2.0 μm or more, may cause dropouts or damage to the head.

The conventional examples have been described above, but in all examples, durability,
There is no one that satisfies all aspects such as output, S/N, occurrence of dropouts, and damage to the head.

An object of the present invention is to provide a magnetic recording medium that has excellent durability, output, and S/N, and does not cause dropouts or head damage.

[Means for Solving the Problems] As a means for achieving the above object, the present invention provides a magnetic recording medium having a magnetic layer containing a ferromagnetic metal powder, an abrasive powder, and a binder, in which the abrasive powder is 0. O
The center particle size (50% value of weight distribution) exists between 1 and 0.3 μm and between 0.4 and 1.0 μm2.
It is characterized by being a type of abrasive powder.

The central particle size used in the present invention is 0. Powder A at O1~0.3 μm has the shortest recording wavelength (0
, 5 to 1.0 μm), the generation of noise is minimal. Also, the length of the ferromagnetic metal powder particles (
Since it has a particle size equivalent to 0.1 to 0.4 μm), it has good backing performance and improves output. Further, since the particle diameter is relatively small, the polishing performance for the head is not very good, but the high hardness increases the elastic modulus of the magnetic layer and improves the durability to some extent.

On the other hand, the center particle size used in the present invention is 0.4 to 1.0μ.
Powder B in m has a slightly larger particle size than the ferromagnetic metal powder, so it tends to be slightly exposed on the surface of the magnetic layer, thereby exhibiting good head touch and moderate head abrasiveness, and as a result, magnetic recording Greatly improves media durability. Moreover, in the present invention, the center particle size is particularly 0.4~! ,
The particle size distribution of powder B at 0 μm is determined as follows: >1.0 μm is less than 10% by weight per abrasive powder, and >2.0 μm is 1% by weight per abrasive powder.
．． By reducing the amount of coarse particles to less than 0 weight percent compared to conventional examples, it is possible to greatly reduce the occurrence of dropouts due to partial detachment of the magnetic layer, and completely eliminate the phenomenon of damaging the head surface. . In terms of characteristics, since there are few abrasive particles larger than 1.0 μm, the decrease in output and the deterioration in S/N can be made very small. In this way, the abrasive powder is divided into powder A and powder B.
With this configuration, it is possible to obtain a magnetic recording medium that has excellent durability, output, and S/N, and does not cause dropouts or damage to the head.

In order to achieve the above-mentioned effect of using the polishing side powder, the weight ratio of powder A and powder B should be 80:20 to 20:8.
It is preferable to set it to about 0, and thereby the above-mentioned effects can be harmonized and the effects can be maximized.

In addition, as the polishing powder that can be used in the present invention,
Any substance can be used as the abrasive, such as α-Al2203, CrJs, and SIC.

Further, powder A and powder B may be made of the same material or different materials, and powder A and powder B do not need to be made of the same material.

The magnetic recording medium of the present invention has a magnetic layer basically consisting of a ferromagnetic metal powder, an abrasive powder, and a binder provided on a nonmagnetic support. The present invention can be applied regardless of the magnetic layer described above, and can be similarly applied to a medium provided with a lubricating oil or the like in addition to the above-mentioned magnetic layer. In addition to the above components, the magnetic layer may contain, if necessary,
It may contain a lubricant, a dispersant, etc.

The ferromagnetic metal powder that can be used in the present invention may be a known one such as an Fe-Nf alloy, but it is preferable that the particle size is adjusted to the polishing powder according to the present invention. That is, the particle size distribution of powder A and powder B constituting the polishing side powder is similar to the distribution of the ferromagnetic metal powder, and the center particle size is about 0.1 to 0.5 μm larger than that of the ferromagnetic metal powder. It is preferable to adjust the center particle diameters of Powder A and Powder B within the above ranges.

The content of the polishing side powder is 2 to 2 parts per 100 parts by weight of the ferromagnetic metal powder, taking into consideration the durability of the magnetic layer and the S/N ratio.
It is sufficient to increase the amount by 0 parts by weight.

Further, the above-mentioned other configurations of the present invention can be performed using known techniques, and the magnetic recording medium of the present invention can be manufactured.

[Example j Next, an example will be shown to specifically explain the present invention.

Floppy disks were prepared according to Example 1-4 and Comparative Example 1-4 shown below, and the five items of each sample, including output, S/N, dropout, durability, and presence or absence of head damage, were measured in the following manner. The results are summarized in Table 1.

(1) Output, S/Ill: Measured using a luminance signal (7 MHz), and Example 1 was set to OdB.

(2) Number of tracks with dropouts out of the total number of tracks (50).

(3) The time it takes for the output to drop by 3 dB after continuously playing the 25th track.

(4) After 100 hours, the surface of the head was observed using a microscope.

Example 1 (Magnetic paint formulation) 100 parts by weight of ferromagnetic metal powder (Fe-N
i alloy, specific surface area = 50 rn'/g) 10 parts by weight of vinyl chloride copolymer (VAGH manufactured by UCC)
) Polyurethane 10 parts by weight (Nippon Polyurethane #2304) Phosphate ester 1 part by weight (Toho Chemical RE-610) Abrasive (A-B a-Al2zOs) A: Center particle size 0.1 μm 5 parts by weight B : Center particle size 0.
6 μm 5 parts by weight (5% by weight over 1 μm, 2 μm
0.5% by weight) [Other Examples] Methyl ethyl ketone 100 parts by weight Toluene
100 parts by weight Methyl isobutyl ketone 100 parts by weight After stirring and mixing the above composition for 12 hours using a sand grinder, 6 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane) as a hardening agent and 6 parts of fatty acid ester as a lubricant were added. After adding and filtering, a magnetic paint was obtained. This magnetic paint was applied to both the front and back sides of a 33 μm thick polyester film, and after drying,
Calendering was performed to obtain a magnetic film with a total thickness of 40 μm. This magnetic film was punched out into a disk shape of 47 mmφ and mounted in a jacket to produce a video floppy disk.

Example 2 In Example 1, a of the following particle size was used as two types of abrasives.
-Al2zOs A: Center particle size 0.2 μm, 4 parts by weight B: Center particle size 0.5 μm, 6 parts by weight (over 1 μmm weight%, over 2 μm 0.3 weight%) The same procedure as in Example 1 was used. Created a video floppy disk.

Example 3 In Example 1, C with the following particle size was used as two types of abrasives.
r*Os A: Center particle size 0.1 μm 5 parts by weight B: Center particle size 0.5 μm 5 parts by weight (6% by weight of more than 1 μm, 0.7% by weight of more than 2 μm) was used as in Example 1. A video floppy disk was created in the same way.

Example 4 In Example 1, A with the following particle size was used as the two types of abrasives.
! *Os and Cr2bs A:1. O, center particle size 0.05 g m 8 parts by weight B
: Crabs center particle size 0.7 μm 4 parts by weight (1
A video floppy disk was prepared in the same manner as in Example 1, except that 8% by weight of particles larger than 2 μm and 5% by weight of particles larger than 2 μm were used.

Comparative Example 1 In Example 1, one type of abrasive was used and the following particle size ε
A video floppy disk was prepared in the same manner as in Example 1, except that 10 parts by weight of 0.03 with a center particle diameter of 0.2 μm were used.

Comparative Example 2 In Example 1, one type of abrasive was used and l of the following particle size was used.
, except that 10 parts by weight of O3 with a center particle size of 0.6 μm (7% by weight of more than 1 μm, 0.5% by weight of more than 2 μm) was used.
A video floppy disk was prepared in the same manner as in Example 1.

Comparative Example 3 In Example 1, A with the following particle size was used as two types of abrasives.
l2zOs A: 5 parts by weight with a central particle size of 0.1 μm B: 5 parts by weight with a central particle size of 0.6 μm (5% by weight over 1 μm μm, 3% by weight over 2 μm) Example 1
I created a video floppy disk in the same way.

Comparative Example 4 In Example 1, A with the following particle size was used as two types of abrasives.
l220s A: 1.03 center particle size 0. IILm 6 parts by weight B:
Crabs center particle size 0.7 μm 4 parts by weight (1
A video floppy disk was produced in the same manner as in Example 1, except that 0% by weight of particles exceeding 2 μm and 5% by weight of particles exceeding 2 μm were used.

As is clear from Table I, Examples 1-4, in which the abrasive powders had two different particle size distributions, were all excellent on average in each item, and no head damage was observed.

[Effects of the Invention] As explained above, in the present invention, by using abrasive powder with two types of center particle diameters, large and small, characteristics (output, S/N) and durability, which were difficult to achieve in the past, have been achieved. It has become possible to achieve both. Further, significant improvement effects can be obtained with respect to occurrence of dropouts and head damage. This effect becomes more pronounced by regulating the particle size distribution of the larger abrasive powder.

It goes without saying that the gist of the present invention can be applied not only to the video floppy disk described in the above embodiments, but also to other magnetic recording media such as magnetic disks, magnetic tapes, and magnetic sheets.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer comprising a ferromagnetic metal powder, an abrasive powder, and a binder, wherein the abrasive powder has a diameter of between 0.01 and 0.3 μm and a diameter of 0.4 μm. ~1.0
A magnetic recording medium comprising two types of abrasive powder each having a center particle diameter (50% value of weight distribution) between μm. 2. The magnetic recording medium according to claim 1, wherein in the particle size distribution of the abrasive powder, the particle size of more than 1.0 μm is less than 10 weight percent, and the particle size of more than 2.0 μm is less than 1.0 weight percent.