JPS6029932A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the wear resistance of a magnetic layer, the wear resistance of a magnetic head and the smoothness of a tape surface by providing a magnetic layer consisting of contg. inorg. powder of <=2mum average grain size and >=5 Mchs hardness obtd. by mixing by a dry process under the condition of >=1G impact value and magnetic powder in the presence of an arom. carboxylic acid and/or silicone dispersant. CONSTITUTION:The particle size of inorg. powder is essentially <=2mum and more preferably <=1.5mum average grain size. The reinforcing material has good dispersibility as a dispersant having affinity to a toluene solvent is thickly and securely press-adhered to the surface of the inorg. powder. The reinforcing material having excellent dispersibility into an org. solvent, above all, toluene or a polymer is thus obtd. The reinforcing material is added to the magnetic powder at generally 0.1-15wt%, more preferably 0.5-10wt%. If the reinforcing material is added at 0.1wt% or below, the wear resistance of the magnetic layer decreases and if said material is added at >=15wt%, the wear of the magnetic head increases and therefore the addition at such a rate is undesirable.

Description

[Detailed description of the invention] The present invention relates to magnetic recording media.

More specifically, the present invention relates to an f1 recording medium that has excellent abrasion resistance of the magnetic layer by using a reinforcing material with excellent dispersibility, improved abrasion suppression effect of the magnetic head, and excellent surface flatness. The magnetic head for audio, video, and computers Q11i, + body comes into violent sliding contact with the magnetic head during recording and reproduction, so the magnetic layer wears out and it cannot be said that it has sufficient durability.

Conventionally, in order to improve this drawback, Cr20hA52
0. , A method has been proposed in which non-magnetic powder such as SiC is mixed into the magnetic layer as a reinforcing material.

However, it is not easy to uniformly disperse the reinforcing material in the magnetic layer, and uneven distribution often occurs.As a result, the wear resistance of the magnetic layer decreases, and the magnetic head becomes excessively worn. This causes problems such as a decrease in the smoothness of the tape surface.

In order to improve this inconvenience, a coating liquid for forming a magnetic layer is prepared using a wet method using n-butyl stearate and adding a dispersant such as liquid paraffin or sodium alkylbenzenesulfonate. Those who want to improve the dispersibility of reinforcing materials by mixing / jζ
is known, but it has the drawback that it cannot achieve sufficient dispersibility for the purpose.

The present inventors previously filed a patent application filed in 1983. -192904, obtained by dry mixing in the presence of a dispersant having a lipophilic group under conditions where the 5y value is IG or more. It was proposed to use powder.

However, when toluene or a toluene-containing solvent is used as a solvent for a coating solution for forming a coating film, the dispersant disclosed in ITiI Patent Application Sho may not necessarily be sufficient.

As a result of various studies to overcome the above-mentioned disadvantages, the present invention has found that when dispersibility is imparted to a reinforcing agent using a specific dispersant and by a specific method, toluene or toluene-containing It has been found that dispersibility in solvents can be significantly improved, and by using such a reinforcing agent, the wear resistance of the magnetic layer and the magnetic head can be improved, and the smoothness of the tape surface can be improved. They discovered that this can be done and completed the present invention.

That is, the present invention provides an inorganic material having an average particle diameter of 2 μm or less and a Mohs hardness of 5 or more obtained by dry mixing in the presence of an aromatic carboxylic acid and/or a silicone dispersion force of 1 under conditions of an impact value of 10 or more. The present invention provides a magnetic recording medium having a magnetic layer containing powder and magnetic powder.

Examples of inorganic powders to which a dispersant having a lipophilic group is firmly attached are used in carrying out the present invention, such as benzoic acid, toluic acid, diethylbenzenecarboxylic acid, ethylbenzenecarboxylic acid, diethylbenzenecarboxylic acid, phthalic acid,
Aromatic carboxylic acids such as inphthalic acid, terephthalic acid, naphthoic acid, and cinnamic acid, methyl silicone oil, methylhydrodiene silicone oil, methylphenyl silicone oil, fatty acid-modified silicone oil, alkyl-modified silicone oil, polyoxyalkylene-modified silicone oil A dispersant such as silicone oil and an inorganic powder are converted into an inorganic powder of 0.0, O1 to 20 per part of 100 weight of powder.
It is produced by mixing a mixture in proportions of 0.02 to 1 O@tRx parts under grinding or milling conditions of less than IG, preferably 3 to 15 G.

Particularly preferred are aromatic carboxylic acids such as benzoic acid and toluic acid, and silicone oils such as methyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, and 11811/j acid-modified silicone oil.

When the dispersant is sodium dodecanoate or nrubitan monododecanate other than aromatic carboxylic acid and/or silicone, the effect of improving dispersibility in toluene or a toluene-containing solvent is small and is not preferred.

If the proportion of the dispersant used is less than 0.011 parts by weight, the effect of changing the dispersibility will be small, which is not preferable. On the other hand, the upper limit is determined in consideration of economic efficiency.

An example of the inorganic powder is r-alumina.

α-Alumina, silica, iron oxide, chromium oxide, titanium oxide, zirconium oxide, cerium oxide, tin oxide, silicon carbide, spinel, etc. with a Mohs hardness of 5 or more are used, and if the Mohs hardness is smaller than this, reinforcement is applied. It becomes undesirable as an agent.

Further, the particle size of the inorganic powder must be 2 μm or less in average particle size, preferably 1.5 μm or less. This is not desirable.

The reinforcing material of the present invention has a thick and firmly bonded dispersant having an affinity for toluene-based solvents on the surface of the inorganic powder, so it has good dispersibility and is particularly resistant to toluene in organic solvents. It has the advantage that it becomes a reinforcing material with excellent dispersibility in polymers.

In general, what is the addition ratio of the reinforcing material of the present invention to the magnetic powder? ,
1 to 41%, preferably 0.5 to 10%. If the proportion of the reinforcing material added is less than 0.1% by weight, the wear resistance of the magnetic layer will decrease, while if it exceeds 15% by weight, the wear of the magnetic head will increase, which is not preferable.

The magnetic material used in the present invention may be a known magnetic material such as I Fe2O3, FegO, Co-containing γ-F.
e,,01, reduced iron powder, and Cr02 are optionally used. The particle size is not particularly limited, but generally 001~
A thickness in the range of 5 μm is used.

The binder used in the present invention is, for example, a thermal iiJ plastic resin, a thermosetting resin, or a γ[i1 compound thereof. Examples of such binders include epoxy resin, polyurethane resin, urea resin, polyamide resin, silicone resin, polyester resin,
Examples include phenol resins, urea formaldehyde resins, vinyl resins, cellulose derivatives, acrylic acid or methacrylic acid polymers or copolymers thereof, alkyd resins, and mixtures thereof.

Examples are shown below to explain the present invention in more detail, but the present invention is not limited to the following examples unless the gist of the invention is exceeded.

Example 1 α-alumina particles toof having an average particle size of 0.6 μm and dispersant P-) Ruylic acid l? was charged into a vibrating mill (impact value = 6G) having an internal volume of 84 mm, and pulverized and mixed for 20 minutes.

The easily dispersible alumina powder thus obtained and
7E Elec・10 rsl and test tube (height 10crn
) and shaken for 5 minutes.

Next, after performing an ultrasonic dispersion treatment, it was allowed to stand still, and the sedimentation height was measured after standing for 24 hours. As a result, the sedimentation height was 8
．． It was 7 cm.

Magnetic paints were produced using the alumina produced as described in 1 above, with the following tunities and compounding ratios.

Ferromagnetic iron oxide 100 weight scale Alumina 5 Vinyrite VYHH15u (trade name manufactured by U, C, C, USA) Polyurethane prepolymer 5 Carbon black 5 n-butyl stearate l Liquid paraffin 0,2 Methyl ethyl I reketone lOθ "Toluene 100 Nt" After dispersing the magnetic paint in a ball mill for 20 hours, it was coated on a 20 μm thick polystyrene base film L to a dry thickness of 6, dried, and coated to a specified thickness. Cut it to the width of t.

Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that the amine in the magnetic coating composition of Example 1 was replaced with unpulverized α-lumina particles together with the dispersant.

The magnetic chip manufactured as described below was loaded into a video tape recorder, and the Soul characteristics were measured. The amount of wear on the magnetic head of the magnetic tape was also measured.

In addition, the tape surface was measured with a surface roughness meter to determine the center line average roughness.

The results are shown in Table 1.

Table 1 Mixing process μm Length Tsuji Example 2 All oxide aluminum 11 having an average granulation J″ diameter of 0.4 μm was mixed with a vibrating mill having an internal volume of 3e (impact value =
6G) and ground and mixed for 20 minutes.

The easily dispersible oxidized chloride thus obtained had a sedimentation height of 9.6 cm.

Using the chromium oxide produced as described above, a porcelain paint was produced with the following Ichi H1 blending ratio.

Ferromagnetic iron oxide ioo parts by weight Chromium oxide 7 Polyurethane prepolymer 5 Carbon black 5 N-butyl stearate 1 # Liquid paraffin 02 Methyl ethyl ketone 100 Toluene 100 20% of the magnetic paint was prepared using a ball mill. After time mixing and dispersion treatment, the mixture was coated on a polyester base film having a thickness of 20 μm and dried to a dry thickness of 6 μm, and cut into a predetermined width.

Comparative Example 2 The magnetic coating composition of Example 2 except that chromium oxide was replaced with unpulverized chromium oxide particles together with a dispersant.
A magnetic tape was made in exactly the same manner as in Example-2.

The steel properties, head wear amount, and centerline average roughness of the magnetic tape manufactured as described above were measured under the same conditions as in Example 1.

The results are shown in Table 2.

From Table 2 onwards, it is clear that the reinforcing material of the present invention has excellent dispersibility, and tapes made using this reinforcing material have excellent abrasion resistance of the magnetic layer and improved wear-suppressing effect on the magnetic head. It is clear that the surface smoothness of the tape is improved.

Claims (1)

[Claims] Contains an inorganic powder and magnetic powder with an average particle diameter of 2 μm or less and a Mohs hardness of 5 or more obtained by dry mixing in the presence of an aromatic carboxylic acid and/or a silicone dispersant under conditions with an impact value of IG or less. A magnetic rhombus 1if having a magnetic layer consisting of
+ν body.