JPS63124217A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility and orientational property of magnetic powder even if said powder is pulverized and to prevent degradation in magnetic characteristics and electromagnetic conversion characteristic by incorporating the magnetic powder treated by a specific compd. contg. a hydrocarbon group into a magnetic layer. CONSTITUTION:The characteristics such as max. residual magnetic flux density and squareness ratio of the magnetic powder begin to degrade if the magnetic powder treated with a compd. A having an alkyl group of many carbon atoms is used for a magnetic recording medium contg. the magnetic powder treated with the compd. expressed by formula A in the magnetic layer. It is, therefore, important that R1 be the hydrocarbon group of <=6C and that R2 be the hydrocarbon group of <=14C. Aggregation hardly rises with such magnetic powder and the dispersibility of the magnetic powder is good. The coated film strength of the magnetic layer obtd. by coating the magnetic coating compd. of said magnetic powder is high and further, the magnetic characteristics and electromagnetic conversion characteristic are excellent as well. This recording medium is suitable for high-density recording.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

[Prior art and its problems]

Magnetic recording media such as magnetic tapes are made by mixing and dispersing magnetic powder, which is fine ferromagnetic powder, a binder, various additives, and organic solvents on a non-magnetic support such as polyester. It is usually obtained by applying a predetermined thickness and then drying, calendering, and other predetermined steps. Even with such coating-type magnetic recording media, the demand for higher density recording has recently increased with the progress of high-density recording in recording and reproducing devices, and from this perspective, magnetic recording media The magnetic powder used is required to be made into fine particles. However, when magnetic powder is made into fine particles for high-density recording,
Micronized magnetic powder is more likely to agglomerate, and
Poor affinity with binders, etc., resulting in decreased dispersibility of magnetic powder in the magnetic paint and decreased orientation in the magnetic layer, leading to decreased magnetic properties and electromagnetic conversion characteristics of the magnetic recording medium. Therefore, it is insufficient to simply make the magnetic powder into fine particles. For this reason, attempts have been made to use a large amount of a dispersant when making magnetic powder into fine particles, but using a large amount of a dispersant lowers the packing density of the magnetic powder in the magnetic layer. , the strength of the magnetic layer coating is greatly reduced, and further disadvantages such as oozing of the dispersant occur.

[Disclosure of the invention]

While conducting research on the drawbacks that occur when magnetic powder is made into fine particles for high-density recording, the present inventor found that due to the agglomeration of the fine magnetic powder, In order to prevent the magnetic powder from deteriorating, it was discovered that it would be best to apply a surface treatment to the magnetic powder itself to make it difficult for the magnetic powder to agglomerate. As we experimented with various compounds for surface treatment, we found that magnetic powder treated with the following compound [A] did not cause agglomeration and had good dispersibility in magnetic paint.
In addition, the coating strength of the magnetic layer of a magnetic recording medium obtained by applying a magnetic paint containing magnetic powder treated with this compound [A] is high, and furthermore, the magnetic properties and electromagnetic conversion properties are excellent.
We found that it is suitable for high-density recording. ○ Here, if the number of carbon atoms in R, R, of the compound represented by the above general formula [A] is too large, that is, the magnetic powder treated with the compound [A] having an alkyl group with a large number of carbon atoms. A magnetic recording medium whose magnetic layer is constructed using
Since its characteristics such as maximum residual magnetic flux density B and squareness ratio 11s begin to decrease, R1 is a hydrocarbon group with a carbon number of 6 or less, and R2 has a carbon number of 14
It is important that the hydrocarbon group is one of the following. In addition, it is more desirable that R1 is an alkyl group having 2 to 5 carbon atoms, and it is even more desirable that R2 is an alkyl group having 4 to 12 carbon atoms. The magnetic powder treated with the compound of the general formula [A] can be prepared by adding about 0.5 to 3.5 parts by weight of the compound represented by the formula [A] to 100 parts by weight of the magnetic powder in a predetermined solvent. It is obtained by mixing and dispersing.

[Example 1] 100 parts by weight of acicular magnetic powder with a BET value of 35+*2/g, 2 parts by weight of a compound represented by the above general formula [A] where R1=C2115, R2・Cs1l+t, and 280 parts by weight of a solvent.
A magnetic paint containing magnetic powder having a compound represented by the general formula [A] adsorbed on the surface thereof is obtained by thoroughly mixing and dispersing 1 part of the magnetic powder. Next, 20 parts by weight of a predetermined binder, 10 parts by weight of an abrasive, and 5 parts by weight of carbon black were added to this magnetic paint, and these were thoroughly mixed and dispersed. The magnetic paint obtained in this way is coated on a non-magnetic support such as polyester, and subjected to ordinary treatments such as orientation, calendering and curing treatment to produce magnetic recording such as magnetic tape. Get medium. (Examples 2 to 4) In Example 1, R,=C,IIs, R2=C5ll
+t instead of the compound represented by the general formula [A], R1
・Cs1l++, R2・C,11, using a compound represented by the general formula [A] (Example 2), R+=C5l
Using a compound represented by the general formula [A] of lz, R2・C+5llz+ (Example 3), R1・Cs1l+8,
R2・C4I1. A magnetic recording medium is obtained in the same manner as in Example 4 using a compound represented by the general formula [A].

Comparative Example 1 A magnetic recording medium was obtained by carrying out the same procedure as in Example 1 using lecithin instead of the compound represented by the general formula [A].

[Comparative Example 2.3] In Example 1, R, = C, Ils, R2 = C5ll
+t instead of the compound represented by the general formula [A], R1
Using a compound represented by -maximum [A] of "C7+115, R2・C,l+," (Comparative Example 2), R+"Cs1
A magnetic recording medium is obtained in the same manner as in Comparative Example 3 using a compound represented by the general formula [A] of lz, R2·C+5llz+.

Comparative Example 4 A magnetic recording medium was obtained by carrying out the same procedure as in Example 1 without using any compound represented by the general formula [A].

【Characteristic】

Regarding the magnetic recording media obtained on each side above, we observed the maximum residual magnetic flux density Bn+, the squareness ratio Rs, and the magnetic head after it was installed in a recording/reproducing device and ran it repeatedly, and examined the head dirt. The results are shown in the table. As shown in the table, when magnetic powder without any surface treatment is used, as shown in Comparative Example 4, agglomeration of the magnetic powder occurs due to atomization of the magnetic powder, resulting in poor magnetic properties due to BII and Rs. On the other hand, when magnetic powder treated with the compound represented by the general formula [A] is used as a recording medium, as shown in Examples 1 to 4, BIll is large, Rs is high, Its magnetic properties and electromagnetic conversion properties are excellent. However, even if magnetic powder is treated with the compound of -ffi formula [A], R+, R2 in the compound of general formula [A]
As the number of carbon atoms increases, as shown in Comparative Examples 2 and 3, Bm
The improvement in the magnetic properties and electromagnetic conversion properties is small, as is shown in FIG. Furthermore, as shown in Comparative Example 2.3, if the number of carbon atoms in R1 and R2 is too large, not only the improvement in magnetic properties and electromagnetic conversion properties is small, but also the drawback of increased head contamination is observed. . In addition, the magnetic recording medium of this example treated the magnetic powder with lecithin, which is well known as a dispersant, and the magnetic recording medium of Comparative Example 1 was made in the same manner using the lecithin-treated magnetic powder. The degree of improvement in magnetic properties and electromagnetic conversion properties is extremely high.

【effect】

The magnetic recording medium according to the present invention has the general formula [A] in the magnetic layer.
Since it contains magnetic powder treated with a compound represented by the following, the dispersibility and orientation of the magnetic powder in this magnetic layer are excellent even if the magnetic powder is made into fine particles.
Therefore, the magnetic properties and electromagnetic conversion properties do not deteriorate even if the magnetic powder is made into fine particles, and it is compatible with high-density recording.Furthermore, the mechanical strength of the magnetic layer is sufficient, and such excellent The manufacturing process of the magnetic recording medium exhibiting this feature does not require any major modification of the conventional process, so it has the advantage of being able to be provided at the same cost as the conventional process.

Claims (1)

[Scope of Claims] A magnetic recording medium characterized in that a magnetic layer contains magnetic powder treated with a compound represented by the following general formula [A]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [A] (However, R_1 is a hydrocarbon group with 6 or less carbon atoms, R_2
is a hydrocarbon group having 14 or less carbon atoms)