JPS58158033A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility, surface smoothness, etc. of magnetic powder by incorporating a specific aluminum coupling agent in a magnetic layer. CONSTITUTION:An aluminum coupling agent wherein at least one group which is readily hydrolyzed and at least one group which is hardly hydrolyzed and exhibits lipophilic property are bound to aluminum, as expressed by the general formula on the right (where R is a hydrocarbon group having 2-5 carbon atoms, R' is a hydrocarbon group having 8-22 carbon atoms) is incorporated in a magnetic layer for magnetic recording consisting essentially of magnetic powder and a binder resin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium in which magnetic powder has good dispersibility and magnetic properties and surface smoothness of a magnetic layer are excellent. be.

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating.
It is required to have excellent magnetic properties and surface smoothness, as well as excellent durability.

Therefore, attempts have been made to improve the dispersibility of magnetic powder by treating it with various dispersants, etc., thereby improving its magnetic properties and surface smoothness, as well as improving its wear resistance. However, we have not yet obtained anything that is fully satisfactory.

The inventors have conducted various studies in view of the current situation, and have found that at least one group that is easily hydrolyzed and at least one group that is hydrolyzable and exhibits lipophilicity are contained in the magnetic layer. It has been discovered that the dispersibility of magnetic powder is sufficiently improved by containing an aluminum coupling agent bonded to aluminum, and the magnetic properties and surface smoothness of the magnetic layer are further improved, as well as the abrasion resistance is improved.
This invention has been made.

At least one hydrolyzable compound used in this invention
An aluminum coupling agent in which two groups and at least one group that is difficult to be hydrolyzed and exhibits lipophilicity are bonded to aluminum is / \ / RO0=C-OR' (where k has 2 to 2 carbon atoms) The hydrocarbon group (R/ is a hydrocarbon group having 8 to 22 carbon atoms) is an aluminum compound that acts as a bridge between organic matter and inorganic matter through a strong chemical bond, and can be used as a bridge between magnetic powder and When they come into contact with each other, they strongly react with the water groups on the surface of the powder particles, breaking the bond between the aluminum atoms and -OR, which is easily hydrolyzed, and the aluminum atoms are firmly bonded to the surface of the magnetic powder via oxygen.

Therefore, when this type of aluminum coupling agent is contained in the magnetic layer, it adheres firmly to the surface of the magnetic powder particles, forms a film, and sufficiently improves the dispersibility of the magnetic powder, improving the magnetic properties and improving the magnetic layer. Further improves surface smoothness. Furthermore, the affinity between the magnetic powder and the binder resin is improved, and the wear resistance is also improved.

Specific examples of such aluminum coupling agents include those represented by the following structural formula, and specific examples of commercially available products include AL-
Examples include M.

CH I.

Hs (stearylacetoacetate aluminum diisopropylate) C1 (.

CHl (myristyl acetoacetate aluminum diisopropylene)) CH.

CH.

(Caprylacediacetate aluminum diisopropylene)) These aluminum coupling agents can be prepared by dissolving them in a suitable solvent and adding the solution obtained by this dissolution when preparing a magnetic coating, or by adding this solution when preparing a magnetic coating. The surface of the magnetic powder is treated in advance by immersing the magnetic powder in it.
This magnetic powder is used by being contained in a magnetic layer in a method such as preparing a magnetic paint. At this time, when using a binder resin having a hydroxyl group, if you try to incorporate the aluminum coupling agent into the magnetic layer using the former method, the aluminum coupling agent and the binder resin will react and the magnetic powder will be dispersed. Since the properties are not improved, it is preferable to incorporate an aluminum coupling agent into the magnetic layer by treating the magnetic powder in a solution in which the aluminum coupling agent is dissolved in advance, as in the latter method. If the amount used is less than 0.1% by weight based on the magnetic powder in the magnetic layer, the desired effect will not be obtained, and if it exceeds 10% by weight, there is a risk of bleed-out. It is preferably used within the range, and more preferably within the range of 0.5 to 5 weight units.

Examples of the magnetic powder used in this invention include r-F
e, OB powder, Fe3O4 powder, Co-containing r-FelO
1 powder, Co-containing Fe104 powder, Fe powder, Co
A wide variety of conventionally known magnetic powders are included, such as powder and metal powder such as Fe-Ni powder.

In addition, as the binder resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, cellulose resin,
Any binder resin that has been widely used in the past, such as a urethane resin or an isocyanate compound, can be used.

Examples of organic solvents include ketone solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as henzene, toluene, and decathylene, and isopropyl alcohol. Alcohol-based solvents, acid amide-based solvents such as dimethylformamide, sulfonate-based solvents such as dimethyl sulfoxide, ether-based solvents such as tetrahydrochloride, dioxane, etc. to dissolve the aluminum coupling agent and binder resin used. Solvents suitable for these may be used alone or in a mixture of two or more without particular limitation.

In addition, various additives commonly used in magnetic paints,
For example, dispersants, lubricants, abrasives, antistatic agents, etc. may be added as appropriate.

Next, embodiments of the invention will be described.

Example 1 Structural formula゛ C.I.

CH.

10 parts by weight of an aluminum coupling agent represented by is dissolved in 990 parts by weight of F-luene, and 200 parts by weight of Co-containing -Fe203 magnetic powder is dispersed in this solution, washed, and dried to coat 3 parts by weight on the surface of the powder particles. % of the aluminum coupling agent was deposited on the magnetic powder. Using this magnetic powder, Co-containing -Fe 203 magnetic powder
82.5 parts by weight (aluminum coupling agent coverage: 3% by weight) Nitrocellulose H1 (manufactured by Asahi Kasei Corporation,
9 parts by weight of nitrocellulose) Bandex T-5250 (manufactured by Dainippon 81 Ink Co., Ltd., urethane elastomer) Coronate Shikoku Nippon Polyurethane Industries 11, trifunctional low molecular weight isocyanate F compound) Carbon black 3.2# stearic acid-n -Butyl 7' myristic acid
41 cyclohexanone
100 l toluene 10
A magnetic paint was prepared by mixing and dispersing a mixture having a composition of 0 r in a ball mill for about 76 hours. This magnetic paint is applied to a diester paste film with a dry thickness of approximately 4 μm.
A magnetic tape was prepared by applying the material to a thickness of μ, drying it, surface treating it, and cutting it to a predetermined width.

Example 2 In the composition of the magnetic paint in Example 1, C was surface-treated with an aluminum coupling agent.

In place of the containing r-Fe1O and 82.5 parts by weight of magnetic powder, untreated Co-containing r-Fe, 0. 80 parts by weight of magnetic powder was used, and VY was used in place of 1.9 parts by weight of nitrocellulose H.
Using 10 parts by weight of HH (vinyl chloride-vinyl acetate copolymer manufactured by U, C, C, USA), Pandex T-5250
, 8 parts by weight, 10 parts by weight of trTMV-2 (urethane elastomer manufactured by Dainippon Ink Co., Ltd.), and 2.5 parts by weight of an aluminum coupling agent represented by the same structural formula as used in Example 1. Example 1 except for the new additions
I made magnetic tape in the same way.

Example 3 The same procedure as in Example 1 was repeated except that α-Fe magnetic powder was used in place of the co-containing r-Fe20B magnetic powder in Example 1. A magnetic tape was produced in the same manner as in Example 1.

Example 4 In the composition of the magnetic paint in Example 2, c.

A magnetic tape was produced in the same manner as in Example 2, except that the same amount of α-Fe magnetic powder was used in place of the r-Fe, 03-containing magnetic powder.

Comparative Example 1 In the composition of the magnetic paint in Example 1, C was surface-treated with an aluminum coupling agent.

A magnetic tape was produced in the same manner as in Example 1 except that 80 parts by weight of untreated Co-containing r-FelOB magnetic powder was used in place of 82.5 parts by weight of the γ-FezOB-containing magnetic powder.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 3, except that the surface treatment of the 'Fe magnetic powder with the Al4=U coupling agent was omitted. .

The video S/N ratio and the color S/N ratio were measured for the magnetic tapes obtained in each Example and each Comparative Example. Video S
The N ratio and the color S/N ratio were measured by loading the obtained magnetic tape into a video deck modified to change the recording current value, performing recording and reproducing, and measuring it with a color video noise meter 925C manufactured by Sibaku Corporation. For Examples 3 and 4, the video SN ratio and color SN ratio of the magnetic tape obtained in Comparative Example 2 are set to 0. It is expressed as the difference.

The table below shows the results.

As is clear from the table above, the magnetic tapes obtained according to the present invention (Examples 1 to 4) have both a video SN ratio and a color SN ratio, compared to conventional magnetic tapes (Comparative Examples 1 and 2). This indicates that the magnetic recording medium obtained by the present invention has excellent dispersibility of magnetic powder, good smoothness and gloss of the surface of the magnetic layer, and further improved magnetic properties.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

[Claims] 1. A magnetic paint containing an aluminum coupling agent in which at least one group that is easily hydrolyzed and at least one group that is difficult to hydrolyze and exhibits lipophilicity is bonded to aluminum, and magnetic powder is applied onto a substrate. Magnetic recording media made by coating