JPH058492B2 - - Google Patents

Description

[Detailed description of the invention]

Field of the Invention The present invention relates to a magnetic recording medium in which a magnetic layer is formed on a non-magnetic support, which is used for audio, video, magnetic tape for computers, floppy disks, disks for electronic cameras, and magnetic cards. In particular, it concerns the incorporation of non-magnetic solid particles surface-treated with organic titanate compounds into a magnetic layer to improve its durability and abrasion resistance. Background of the Invention In magnetic recording media, it is basically required that the magnetic coating film has good durability and wear resistance. If the abrasion resistance is poor, a large amount of magnetic powder falls off from the coating surface, and the falling powder tends to cause output reduction, head clogging, dropout, etc. In recent years, as the demand for higher recording densities has increased, there has been an increasing demand for smoother coating film surfaces in order to suppress spacing loss, which accounts for a large proportion of reproduction loss. At the same time, the ferromagnetic powder used in magnetic coatings has shifted from γ-iron oxide and Co-coated iron oxide to metal or alloy particles with large saturation magnetization. In this case, the friction coefficient of the coating surface is high and the coating film becomes brittle, so there is a tendency for more magnetic powder to fall off from the coating surface, and further durability and wear resistance of the magnetic coating is required. Ru. In any case, in order to run a magnetic recording medium with high reliability for as long as possible, it is necessary to enhance its durability and wear resistance. Prior Art As a countermeasure to this problem, various lubricants have been added to magnetic paint to form a lubricant-containing magnetic coating.
Efforts have been made to reduce friction and improve durability by applying lubricants to the surface of the coating film, but the current level is still not satisfactory. In addition, efforts have been made to improve durability and abrasion resistance by incorporating non-magnetic solid particles for reinforcement into the magnetic coating, but the dispersibility and binding properties with the coating binder were poor, resulting in less than the desired It has not yet been effective. Summary of the Invention The present inventor has discovered that the method of including the above reinforcing non-magnetic solid particles in a magnetic coating film is basically a very effective method for improving the durability and abrasion resistance of a magnetic coating film. With this in mind, we conducted various studies on the coexistence of magnetic coatings and reinforcing non-magnetic solid particles. the result,
It has been found that the durability and abrasion resistance of a magnetic coating can be significantly improved by incorporating non-magnetic solid particles whose surface has been treated with an organic titanate compound into the magnetic coating. Non-magnetic solid particles surface-treated with an organic titanate compound have a Mohs hardness of 6.
Abrasive particles with a particle size of 1 μm or less are desirable, such as α-Al ₂ O ₃ , Cr ₂ O ₃ , SiC, TiO ₂ ,
SiO ₂ etc. are typical. These inorganic solid particles have a reinforcing effect on the paint film and are very effective in improving durability and abrasion resistance. However, by surface treating these inorganic solid particles with an organic titanate compound, coupling As a result, the surface of the inorganic substance and the polymeric binder, which is a magnetic coating film binder, are organically bonded, so that the reinforcing effect appears significantly and the dispersibility of the inorganic solid particles is also improved. Although many types of organic compounds were tried, organic titanate compounds gave particularly good results. This is thought to be the result of the effective action of the hydrocarbon groups in the molecule in addition to the coupling effect, an effect not seen in other compounds that do not contain such relatively long-chain hydrocarbon groups. It is. It is a known method to add an organic titanate compound to a magnetic paint for the treatment of magnetic powder. It is not known that a magnetic coating film that is highly durable and wear-resistant can be obtained. Preliminary surface treatment of the nonmagnetic solid particles with an organic titanate compound is advantageous in that a film can be reliably formed on the surface of the nonmagnetic solid particles with a small amount of the organic titanate compound. DETAILED DESCRIPTION OF THE INVENTION The present invention provides γ
-Fe ₂ O ₃ , magnetite, Co-deposited iron oxide, Fe,
Ferromagnetic metals such as Ni and Co, alloys of two or more thereof, or those with a small amount of additional elements added, Ba
It is useful for all magnetic recording media using ferrite and the like. Also, a binder combined with these ferromagnetic powders,
That is, examples of the polymer binder include vinyl chloride-vinyl acetate copolymer, vinyl chloride acetate-vinyl alcohol copolymer, vinyl chloride-vinyl propionate copolymer, vinyl chloride-vinyl propionate-vinyl alcohol copolymer, and vinyl acetate-vinyl alcohol copolymer. Maleic acid copolymer, vinyl acetate salt, maleic acid,
Vinyl alcohol copolymers, vinyl chloride resins such as vinyl chloride-terminated OH side chain alkyl group copolymers, vinyl chloride/vinylidene, vinyl chloride/vinylidene-
Vinylidene chloride resins such as maleic acid copolymers,
Cellulose resins such as nitrocellulose and cellulose acetobutyrate, acrylic resins, saturated polyester resins, and butyral resins. Epoxy resins, phenoxy resins, polyether resins, polyurethane prepolymers, polyurethane elastomers, acrylonitrile butadiene rubber, butadiene rubber, etc. are commonly used. As a non-magnetic support pair to which magnetic paint is applied,
Polyester film is generally used, but films of higher strength and heat resistance such as polyimide, aromatic polyamide, polysulfone, etc. can also be used. As the non-magnetic solid particles used in the present invention, any material that can have a reinforcing effect can be used, but particularly preferred are various ceramics, particularly hard abrasives with a Mohs hardness of 6 or more. For example, α-Al ₂ O ₃ , Cr ₂ O ₃ , SiC,
Examples include TiO ₂ and SiO ₂ . Preferably, the particle size is as fine as 1 μm or less. According to the invention, these non-magnetic solid particles are pre-surface treated with an organic titanate compound before addition to the magnetic paint. The organic titanate compound used here is a substance represented by the general formula (R′O−) _n Ti−(OXR″) _o , where R′ is a hydrocarbon group, and X is carboxy, phosphate pyrophosphate, or sulfonyl. etc.,
R'' is a hydrocarbon group, m, n=1-4.
As a specific example, Kenritsuchi Petrochemicals
KR-TTS (isopropyl tristearoyl titanate) and KR38S (isopropyl tridioctyl pyrophosphate titanate) are famous. Methods for surface treating inorganic solid particles with such organic titanate compounds include direct stirring and mixing, stirring and mixing in an organic solvent or emulsified state in water, and then removing the solvent or water. be. By performing the surface treatment in advance in this way, a film of the organic titanate compound can be formed on the entire surface of the solid particles by using a small amount of the organic titanate compound, which is extremely convenient. These surface-treated inorganic solid particles are put into a ball mill, sand grind mill, etc. together with ferromagnetic powder, binder, solvent, and other additives.
After being dispersed for a certain period of time, it is applied as a magnetic paint onto a non-magnetic support. Examples of additives include conventional abrasives, dispersants, lubricants, antistatic agents, etc., and any known additives may be used. Furthermore, when an isocyanate compound is used as a substance for crosslinking the above-mentioned magnetic coating film binder, an organic titanate compound containing a functional group capable of reacting with isocyanate, such as -OH, _-NH2, etc. is used. When surface treatment is performed, the organic titanate compound is chemically bonded to the -OH and _-NH2 groups in the binder via the isocyanate group, so the coating reinforcement effect of the inorganic solid particles is further enhanced.
Very effective. The above-mentioned isocyanate compound includes 2. or 2.6 tolylene diisocyanate,
Aromatic diisocyanates such as diphenylmethane diisocyanate, isophorone diisocyanate,
Alicyclic diisocyanates such as xylylene diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate, and polymers thereof, or adducts of diisocyanates with polyols such as trimethylolpropane are used. Example 1 α-Al ₂ O ₃ (particle size 0.5 μm) 100 parts Organic titanate compound KR-38S 5 parts Methyl ethyl ketone 300 parts The above composition was placed in a mixer and mixed for about 3 hours. The resulting paste was centrifuged to remove the solvent and then dried at 70°C for 24 hours to adsorb the organic titanate compound onto the α-Al ₂ O ₃ surface. The following magnetic paint was created using this surface-treated α-Al ₂ O ₃ . Co-coated iron oxide 100 parts Above α-Al ₂ O ₃ 2.5 parts Nitrocellulose impregnated with salt vinyl acetate resin 16 parts Polyurethane resin 12 parts Myristic acid 1.4 parts Butyl stearate 0.7 parts Methyl ethyl ketone 150 parts Methyl isibutyl ketone 150 parts Above composition The material was placed in a ball mill and mixed for 48 hours. Add 5 parts of an isocyanate compound (Coronate L: Nippon Polyurethane) to the resulting paint,
Sample tape A was coated on a polyester film to a dry thickness of 6 μm, subjected to surface treatment, heat treated, and then cut into 1/2 inch width samples.
It was created. Example 2 In place of α-Al ₂ O ₃ in Example 1, Cr ₂ O ₃ (particle size
Sample tape B was prepared using the same composition. Example 3 In place of α-Al ₂ O ₃ in Example 1, 50 parts each of α-Al ₂ O ₃ (particle size 0.5 μm) and TiO ₂ (particle size 0.3 μm) were used for surface treatment. Sample tape C was prepared with the same composition. Comparative Example 1 A magnetic paint was created in the same manner as in Example 1 except that untreated α-Al ₂ O ₃ (particle size 0.5 μm) was used instead of the surface-treated α-Al ₂ O ₃ in Example 1. Then, sample tape D was prepared. Comparative Example 2 An organic titanate compound was added to the paint of Comparative Example 1.
Sample tape E was prepared by adding 3 parts of KR38S. Evaluation of Examples and Comparative Examples The clogging frequency and still performance were evaluated using a VHS deck. These are the results of one hour of recording and playback on a VHS deck. The results are shown in the table below.

[Table] As is clear from the table above, Samples A, B, and C containing inorganic solid particles whose surface was treated with an organic titanate compound had fewer clogging events than Sample D, which was not surface-treated. ing. or,
E added to the paint was not very effective, and it seems that the organic titanate was not working effectively. In addition, regarding stills, each sample showed a time of 60 minutes or more, and there was no significant difference between the samples. Effects of the Present Invention As explained above, the present invention has succeeded in sufficiently exhibiting the reinforcing effect of non-magnetic solid particles by including magnetic solid particles surface-treated with an organic titanate compound in a magnetic coating film. Therefore, the amount of organic titanate compound required for surface treatment can be minimized. This contributes to improving the durability and wear resistance of magnetic recording media, which will be increasingly required in the future.

Claims (1)

[Scope of Claims] 1. A magnetic recording medium characterized by containing magnetic solid particles surface-treated with an organic titanate compound in a magnetic coating film. 2 Magnetized solid particles have a Mohs hardness of 6 or more and a particle size of
Claim 1, which is an abrasive particle of 1 μm or less
Magnetic recording medium described in Section 1. 3 Magnetized solid particles are α-Al ₂ O ₃ , Cr ₂ O ₃ , SiC,
2. A magnetic recording medium according to claim 1, wherein the magnetic recording medium is selected from TiO ₂ and SiO ₂ .