JPS58158035A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the surface smoothness, abrasion resistance, etc. of a back coating layer by incorporating a specific aluminum coupling agent together with carbon black in said layer. CONSTITUTION:A layer wherein carbon black and 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 and R' is a hydrocarbon group having 8- 22 carbon atoms) are incorporated in a resin binder is provided on the opposite surface of a substrate having a magnetic recording layer on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium such as a magnetic tape having a barafcoat layer with excellent surface smoothness and wear resistance.

Generally, in magnetic recording media such as magnetic tapes, a substrate having a magnetic layer on one side is used to effectively prevent winding irregularities and base film scraping during high-speed winding, and to improve running stability and durability. A back coat layer is provided on the opposite side of the film, and for example, a back coat layer with carbon black dispersed in a binder resin is provided as a film with relatively good running stability and durability. There is.

However, the carbon black that has been commonly used has relatively poor dispersibility in the binder resin, so the surface smoothness of the backcoat layer is far inferior to that of the magnetic layer, and when the tape is wound, There are drawbacks such as the rough surface of this pack two floor forming traces on the surface of the magnetic layer and deteriorating the electrical properties.Also, carbon black may fall off during tape running, which may affect running stability and durability. There are drawbacks such as a decline in

The inventors conducted various studies in view of the current situation.

As a result, in the back coat layer, an aluminum coupling agent in which at least one group that is easily hydrolyzed and at least one group that is difficult to be hydrolyzed and exhibits lipophilicity are bonded to an aluminum compound is added to carbon black. When the carbon black is added to the binder resin, the dispersibility of carbon black in the binder resin is improved, and the surface smoothness of the back coat layer is sufficiently improved, and the running stability and durability are improved without causing any drop-off of the carbon black, etc. It was discovered that the abrasion resistance was also sufficiently improved, and the present invention was completed.

At least one hydrolyzable compound used in this invention
and at least one group that is difficult to be hydrolyzed and exhibits lipophilicity are bonded to aluminum. ' represents a hydrocarbon group having 8 to 22 carbon atoms.) It is an aluminum compound that acts as a bridge between organic matter and inorganic matter through a strong chemical bond, and when it comes into contact with carbon black, it forms carbon black. reacts strongly with the surface of the powder particles of carbon black, the bond between the aluminum atom and -OR which is easily hydrolyzed is broken, and the aluminum atom is firmly bonded to the surface of the powder particle of carbon black via oxygen. Therefore, when this type of aluminum coupling agent is contained in the back coat layer, it adheres firmly to the surface of the carbon black powder particles, forming a film and improving the dispersibility in the binder resin. As a result, the surface smoothness of the back coat layer is sufficiently improved, and there is no drop-off of carbon black, etc., and running stability and durability are 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, for example, AL manufactured by Ajinomoto Co., Ltd.
-M etc. are mentioned.

CH3 CH3 (steryl acetoacetate/aluminum diisopropylate) CH3 CH3 (myristyl acetoacetate/aluminum diisopropylate) CH.

CH8 (Cabryla heptoacetate aluminum diimpropylate) These aluminum coupling agents can be prepared by combining them with a suitable solvent such as toluene, methyl isobutyl ketone,
Either dissolve the carbon black in tetrahydrofuran or the like and add the solution obtained by this dissolution when preparing the paint, or immerse the carbon black in this solution and perform a surface treatment on the carbon black powder in advance. It is contained in the backfoot layer and used in methods such as preparing puncture coat layer paints using. At this time, when used together with a binder resin having a hydroxyl group, in order to incorporate the aluminum coupling agent into the back coat layer using the former method, the surdo aluminum coupling agent and the binder resin react to form carbon black. Since the dispersibility of the aluminum coupling agent is not improved, it is preferable to incorporate the aluminum coupling agent into the back coat layer by treating carbon black in a solution in which the aluminum coupling agent is dissolved in advance, as in the latter method. The amount used is 0 relative to the carbon black in the back coat layer.
．． If it is less than 1 weight percent, the desired effect cannot be obtained, and if it exceeds 10 weight percent, it is excessive aluminum.

0.0 because the ram coupling agent bleeds out.
It is preferably within the range of 1 to 10% by weight, and 0.5% by weight.
It is more preferable to use it within the range of 5% by weight.

As the carbon black used in this invention, any conventionally used carbon black can be used, such as Black Pearl L1 Black Pearl 1300 manufactured by Cabot Corporation and Mitsubishi $2400B manufactured by Mitsubishi Chemical Corporation.
, Mitsubishi #2200B, Mitsubishi $1000, Mitsubishi MA-10
0, Sanya MA-8, Royal Spectra, Neo Spectra AG, Rapen 5250 manufactured by Columbia Carbon, Asahi Thermal H5-500 manufactured by Asahi Carbon, Geast 5 H manufactured by Tokai Carbon, Ketjen Black manufactured by Lion Akzo, etc. can be lost.

In addition, as a binder resin, vinyl chloride-vinyl acetate 4
copolymer, polyvinyl butyral resin, cellulose resin,
Any conventionally widely used binder resin such as polyurethane resin or incyanate 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 benzene, toluene, and xylene, and alcohol solvents such as isopropyl alcohol. There are particular restrictions on the solvents suitable for dissolving the aluminum coupling agent and binder resin used, such as acid amide solvents such as dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, and ether solvents such as tetrahydrofuran and dioxane. They can be used alone or in a mixture of two or more.

In addition, various commonly used additives such as dispersants, It8iIIv agents, abrasives, etc. may be appropriately added to the puncture coat layer.

Next, embodiments of the invention will be described.

Example 1 5 parts of an aluminum coupling agent represented by the structural formula were dissolved in 995 parts by weight of toluene, and 100 parts of Black Pearl-L (carbon black manufactured by Cabot Corporation) was uniformly dispersed in this solution. , washed, and dried to obtain Black Pearl-L in which 3% by weight of the aluminum coupling agent was deposited on the surface of the powder particles. Using Black Pearl-L obtained by surface treatment in this way, Nitrocellulose H1 (manufactured by Asahi Kasei Co., Ltd., 18 parts by weight, nitrocellulose), Bandex TMV-2 (manufactured by Dainippon 16 N Ink Co., Ltd., urethane elastomer), Coronate. A mixture consisting of 100 l of cyclohexanone, 100 l of toluene, and 100 l of cyclohexanone was mixed and dispersed in a ball mill. A back coat layer paint was prepared. This back-to-back layer paint was applied to the opposite side of the 11μ thick Daryester base film on which the approximately 4μ thick normal magnetic layer had been formed, to a dry thickness of approximately 2μ, and dried to form a pack foot layer. , and cut it to a predetermined width to make magnetic tape.

Actual Example 2 In the composition of the back coat layer paint in Example 1,
60 parts by weight of untreated Black Pearl-L was used in place of the heavy wax part of Black Pearl-L62, which had been surface-treated with an aluminum coupling agent.

Example 1 except that the same amount of vinyl chloride-vinyl acetate copolymer (manufactured by C0C Co., Ltd.) was used, and a new portion of double aluminum coupling agent represented by the same structural formula as used in Example 1 was added. A magnetic tape was made in the same manner as in 1.

Comparative Example 1 In the composition of the back coat layer paint in Example 1,
A magnetic tape was prepared in the same manner as in Example 1 except that 60 parts by weight of untreated Black Pearl-L was used in place of 62 parts by weight of Black Pearl-L whose surface had been treated with an aluminum coupling agent.

Comparative Example 2 In the composition of the back coat layer paint in Example 2,
A magnetic tape was made in the same manner as Actual Bar Example 2 except that the aluminum coupling agent was omitted.

Regarding the magnetic tapes obtained in each Example and each Comparative Example, 60. The video SN was measured before and after storage in 'C for 100 hours, and the difference is shown in the table below. In addition, to examine durability, the obtained magnetic tape was run once at 3.3 Qll/g e (at 40°C and 80% RH) and played back. The number of rows was measured.

The table below shows the results.

As is clear from the table above, the magnetic tapes obtained by the present invention (Examples 1 and 2) are different from the conventional magnetic tapes (Comparative Examples 1 and 2).
and 2), both have good durability and the video SN does not deteriorate even when stored in a wound state. Therefore, the magnetic recording medium obtained by this invention has excellent wear resistance and surface smoothness. It can be seen that the durability and electrical properties are further improved.

Patent source: Hitachi Maxell, Ltd.

Claims (1)

[Claims] 1. An aluminum coupling agent in which at least one group that is easily hydrolyzed and at least one group that is difficult to be hydrolyzed and exhibits lipophilicity are bonded to aluminum on the opposite side of a substrate having a magnetic layer on one side. A magnetic recording medium characterized by having a back coat layer containing carbon black.