KR940006849B1 - Magnetic recording medium - Google Patents

Abstract

The medium reducing the drop out and enhancing the durability uses CF3(CF2)m(CH2)nCOOH as a lubricant. The medium has a magnetic layer containing the powder of the magnetic material, the binding material and the lubricant material on the non magnetic base layer. The weight ratio of the lubricant is 0.3-3.0 % to the magnetic material.

Description

Magnetic recording medium

The present invention relates to a magnetic recording medium, and more particularly, to a magnetic recording medium having excellent runability and durability, and low dropout.

Magnetic recording media, such as for audio, video, and computers, need to smoothen the surface of the magnetic layer of the magnetic recording media in order to improve recording density and output in the high frequency region. However, the smoother the surface of the magnetic layer is, the higher the coefficient of friction is, the poorer the driveability of the magnetic recording medium is, the more the wear and tear of the surface is caused. It is easy to cause jitter and the like, and also causes particles to fall from the edges, resulting in a decrease in output and dropout.

In order to solve such a problem, the method of conventionally including a lubricant etc. in a magnetic layer is proposed. That is, a method of containing a higher fatty acid, a higher fatty acid ester, a paraffinic hydrocarbon, a mineral oil, a wax and the like in the magnetic layer has been proposed. However, in these methods, when the amount of the lubricant included in the magnetic layer is small, the lubricating effect is low, and the runability is improved. When the amount of addition is increased to increase the lubricating effect, the adhesion-slip phenomenon occurs during the running of the magnetic recording medium, or the lubricant softens and melts due to the heat generated during the running of the magnetic recording medium. There is a problem of deteriorating the mechanical properties in the magnetic layer, such as causing softening of the magnetic layer.

On the other hand, Japanese Patent Publication No. 49-14249, Japanese Patent Publication No. 60-28051, US Patent No. 3,490,946, US Patent No. 3,778,308, US Patent No. 3,954,637, etc. add a small amount of fluorine and silicon-based compound to provide high lubrication effect. A way to get is proposed. However, the fluorine and silicone compounds used as lubricants in these methods have low solubility parameters, so they are poorly compatible with high polarity magnetic powders and binders. If the amount of lubricant added or the type of solvent used is not appropriate, magnetic paints are used. It is difficult to form a smooth magnetic layer in the application of the magnetic coating due to the aggregation of magnetic particles or microspheres of fluorine and silicon compounds, and in some cases pinholes are formed, resulting in an increase in dropout. In addition to causing an increase in the noise level, due to the rapid blooming phenomenon of the material has been the same problem as conventional lubricants for long running.

According to the present invention, in order to solve all the conventional problems as described above, when the fluorinated higher fatty acid compound represented by the following general formula (I) is added as a lubricant, the driving stability is improved even when the magnetic recording medium is used for a long time. It has been found that the remarkable improvement is completed to complete the present invention.

That is, an object of the present invention is to provide a magnetic recording medium having excellent running and running durability and low dropout. To achieve this object, the present invention includes a ferromagnetic powder, a binder, and a lubricant on a nonmagnetic support. A magnetic recording medium comprising a magnetic coating applied and then dried to form a magnetic layer, wherein the fluorinated higher fatty acid represented by the following general formula (I) is used as the lubricant.

(Wherein m is an integer of 4 to 20, n is an integer of 2 to 10, and 8≤m + n≤)

Specific examples of the general formula (I) include the following compounds.

In the above general formula, when the " m + n " value indicating the carbon number is less than 8, good lubricity is not obtained, and when it exceeds 24, it is not preferable because the surface bleeding phenomenon easily occurs. Among these carbon number ranges, the range of 10-20 is particularly preferable.

On the other hand, it is preferable to contain the fluorinated higher fatty acid represented by the said general formula (I) used by this invention in 0.3-3.0 weight part with respect to 100 weight part of ferromagnetic powder. If the content of the fluorinated higher fatty acid is less than 0.3 part by weight, good lubricity is hardly obtained. If the content of the fluorinated higher fatty acid is less than 3.0 part by weight, the lubricant flows to the surface of the magnetic layer to contaminate the head or cause deterioration. It becomes impossible.

In the present invention, the fluorinated higher fatty acids represented by the general formulas (I-1) to (I to 6) described above may be used alone or in combination of two or more.

As described above, in the present invention, in a magnetic recording medium in which a magnetic layer comprising ferromagnetic powder, a binder and a lubricant is applied and dried on a nonmagnetic support to form a magnetic layer, the fluorinated high-grade represented by general formula (I) as the lubricant By using the fatty acid, the carboxylic acid group contained in the compound of general formula (I) improves the affinity between the magnetic powder and the binder to suppress the surface bruising phenomenon of the lubricant, and the lubricant is evenly dispersed on the surface of the magnetic layer to provide excellent lubricity. This makes it possible to completely solve the problems in the prior art.

In addition, the compound of general formula (I) contains a fluorine component having a low surface energy, thereby lowering the coefficient of friction, thereby exhibiting stable running performance not only for short time travel but also for long-term use of the magnetic recording medium. It is possible to provide a magnetic recording medium having runability and durability.

The method for producing fluorinated higher fatty acids represented by the general formula (I) of the present invention is well-known and known as "fluorinated carbon derivatives of R. Lichtenberger; Industrial Preparation and Use", "Chemistry and Industry, 104 (7), P 815-825 (1971 edition) [R. Lichtenberger, "Fluorocarbons Derivatives; Industrial Manufacture and Their Uses "Chemie et Industrie, 104 (7) P.815-825 (1971).

The magnetic recording medium of the present invention can be prepared by applying and drying a ferromagnetic powder, a binder, and a magnetic coating obtained by mixing and dispersing a ferromagnetic higher fatty acid represented by the general formula (I) on a nonmagnetic support to form a coated magnetic layer. have. The manufacturing method of the magnetic coating used for the said coating type magnetic layer is explained in detail in Japanese Patent Publication No. 35-15, 39-26794, 43-186, 47-28043, 48-21381, etc. You may use that method as it is. In addition, as described above, the magnetic recording medium of the present invention contains ferromagnetic powder, a binder, and fluorinated higher fatty acids represented by the general formula (I), and further includes additives such as an abrasive, a dispersant, and a dispersion inhibitor. You may use it.

Examples of the ferromagnetic powder include γ-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, CrO ₂ powder, cobalt ferrite powder, barium ferrite powder, iron powder, cobalt powder, and Fe-Co Various conventionally well-known magnetic powders, such as ferromagnetic alloy powders, such as Fe-Ni and Co-Ni, are mentioned, These can be used as it is.

Further, the binder of the present invention may be a fibrous resin such as nitrocellulose, acetyl cellulose or acetyl butyl cellulose, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, Polyvinyl chloride copolymers such as vinyl chloride-vinyl acetate-propanoic acid copolymer, polyester polyurethanes, polyether polyurethanes, polycarbonate polyurethanes such as polyurethane resins, phenoxy resins, epoxy resins, and the like can be used. Can be. These binders may be used alone or in combination of two or more thereof. The ratio of the ferromagnetic powder to the binder is 5 to 100 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the ferromagnetic powder. Additional is used.

Moreover, in this invention, a trifunctional isocyanate compound can be used as a crosslinking agent using the reactivity with the functional group contained in a binder, in order to improve the durability of a magnetic layer. As the dispersant, lecithin, fatty acid amide, polyalkylene oxide alkyl phosphate ester and the like can be used. As the abrasive, α'-Al ₂ O ₃ , α-Fe ₂ O ₃ , Cr ₂ O _3, etc. can be used. Carbon black, carbon black grit, or the like may be used as the inhibitor.

Organic solvents usable in the present invention include ketone solvents such as cyclohexanone, acetone, methyl ethyl ketone, methyl isobutyl ketone, alcohol solvents such as methanol, ethanol, propanol, butanol, methyl acetate, ethyl acetate, butyl acetate Ester solvents such as ethyl lactate, glycol acetate and monoethyl ether, glycol ester solvents such as ether, glycol-dimethyl ether and glycol monoether dioxane, aromatic hydrocarbon solvents such as benzene, toluene and krylsen, methylene Chlorinated hydrocarbon solvents such as chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylenechlorohydrin, dichlorobenzene and the like, and the like, and these may be used alone or in combination of two or more thereof.

Next, a preferred embodiment of the present invention is described. However, these examples are provided only to further illustrate the present invention, and the present invention is not limited to these examples.

Example 1

After mixing and dispersing the composition, 5 parts by weight of trifunctional isocyanate compound ("Clonate L" of Japan Polyurethane Co., Ltd.) was further added and mixed again to prepare a magnetic coating. Then, a 15 micron thick polyethylene terephthalate film was prepared. It was apply | coated to the thickness of 4 micrometers on top, and it oriented, dried, calendared, and hardened. This was slit to 1/2 inch wide to make a videotape.

EXAMPLES 2-6

Instead of CF ₃ (CF ₂ ) ₆ (CH) ₄ COOH which is the compound of the above (I-1) as a lubricant in the composition of Example 1, the formulas (I-2), (I-3), (I A video tape was prepared in the same manner as in Example 1, except that the compounds of -4), (I-5) and (I-6) were used.

Comparative Examples 1-3

Example 1 except that stearic acid, liquid paraffin, or silicone compound was used as a lubricant in the composition of Example 1 in place of CF ₃ (CF ₂ ) ₆ (CH) ₄ COOH, which is the compound of (I-1). The videotape was prepared in the same manner as the above.

Dropouts, friction coefficients, durability, surface brimming, and the like of the video tapes obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated and shown in Table 1 below.

Dropouts, friction coefficients, durability, surface brewing, and the like before and after running on these video tapes were evaluated by the following method.

1) Dropout before and after running

Record the five-step difference signal on the video tape with the optimum current, and the attenuation of the video amplifier output during playback is 20dB and the duration is 15 microseconds or more. Represented as an out. In addition, the dropout after 100 times of repeated running was measured and shown as the dropout after running.

2) coefficient of friction

A video tape was contacted with a stainless steel drum of 4 inches in diameter at 180 degrees (π), and the tension (T ₂ ) was measured when the drum was rotated at a speed of 1.8 m / min by applying a tension of 50 g (T ₁ ). Then, the dynamic friction coefficient was calculated by the following equation.

3) durable

Using a durability measuring device (MDT-2000) manufactured by Steinberg, the magnetic tape surface of the video tape was brought into contact with the head, and the time until the magnetic layer was lost was measured. At this time, the traveling speed of the head was measured as 13m / second, the head height of the projected height of 2.5mil, the load 100g.

4) Surface Blooming

Each video tape was wound with 500 g of tension, which was allowed to stand for 48 hours in an atmosphere of 60 ° C. and 80% RH, then cooled to room temperature, and the surface of the magnetic layer was observed to investigate the presence of lubrication of the lubricant.

TABLE 1

EXAMPLES 7-9

A video tape was prepared in the same manner as in Example 1, except that the addition amount in the composition of Example 1 was changed to 0.5, 1.5, and 2.5 parts by weight, respectively.

[Comparative Examples 4 to 5]

A video tape was prepared in the same manner as in Example 1, except that the amount of the lubricant added in the composition of Example 1 was changed to 0.1 and 5.0 parts by weight, respectively.

[Comparative Examples 6-7]

CF ₃ (CF ₂ ) ₄ (CH) ₂ COOH (Comparative Example 6) having a “m + n” value of 6 in the formula (I) instead of the lubricant in the composition of Example 1 described above, and “m + n A video tape was prepared in the same manner as in Example 1, except that CF ₃ (CF ₂ ) ₂₀ (CH) ₈ COOH (Comparative Example 7) having a value of 28 was used.

Dropouts before and after running of the video tapes obtained in Examples 7 to 9 and Comparative Examples 4 to 7, coefficient of friction, durability, surface boring and the like were also evaluated and shown in Table 2 below.

TABLE 2

As can be seen from the results of Tables 1 and 2 showing the results of Examples and Comparative Examples of the present invention, the video tape according to the present invention containing a fluorinated higher fatty acid compound as a lubricant has a low coefficient of friction and is excellent in running performance. In addition, the lubricant is excellent in compatibility with the ferromagnetic powder and the binder, and shows excellent durability even after repeated use, thereby providing an excellent magnetic recording medium with little increase in dropout.

Claims (2)

A magnetic recording medium having a magnetic layer containing ferromagnetic powder, a binder and a lubricant formed on a nonmagnetic support, wherein the fluorinated higher fatty acid compound represented by the following general formula (I) is used as the lubricant. Record carrier.

(Wherein m is an integer of 4 to 20, n is an integer of 2 to 10, and 8 ≦ m + n ≦ 24). The magnetic recording medium of claim 1, wherein the lubricant is added in an amount of 0.3 to 3.0 parts by weight based on 100 parts by weight of the ferromagnetic powder.