JPH079695B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic card, and a magnetic disk.

[Conventional technology]

In general, the magnetic layer of a magnetic recording medium is one in which magnetic powder is bound in a binder component in a dispersed state.However, since the surface of the magnetic layer slides in contact with the magnetic head at a large relative speed during recording and reproduction, the coefficient of friction is reduced. Therefore, it is required to improve running performance.

Therefore, in order to meet the above-mentioned demand, conventionally, by blending higher fatty acids, silicone oil, fluorinated oil, etc. as a lubricant in the magnetic layer, lubricity is imparted to the surface of the magnetic layer to improve the running property. The method is universal. However, there is a problem that the higher fatty acids do not easily bleed out to the surface of the magnetic layer, and therefore the lubricity improving effect is small relative to the blending amount. In addition, silicone oil and fluorinated oil cause excessive bleeding out to the magnetic layer surface, resulting in surface roughness on the magnetic layer surface and poor dispersion of magnetic powder, which tends to deteriorate magnetic properties. It was

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems in conventional general-purpose lubricants such as higher fatty acids and silicone oils, that is, suitable bleed-out in place of conventional general-purpose lubricants. It is an object of the present invention to provide a magnetic recording medium having excellent running properties and good magnetic properties by using a lubricant component having excellent properties and having a great effect of improving lubricity.

[Means for solving problems]

As a result of intensive studies conducted by the present inventors for the above purpose, when a specific silicon-modified higher fatty acid is blended in a magnetic layer as a lubricant component, bleedout of the lubricant component to the magnetic layer surface is appropriate. Therefore, the surface of the magnetic layer is not roughened, high lubricity is imparted to the magnetic layer, the runnability of the magnetic recording medium is greatly improved, and the dispersibility of the magnetic powder is improved and the magnetic characteristics are improved. It was found that the following was achieved and the present invention was accomplished.

That is, the present invention provides a magnetic recording medium having a magnetic layer containing magnetic powder and a binder on a base, wherein a silicon compound is chemically bonded to the alkyl structure portion of a higher fatty acid in the magnetic layer by a Si--O--C bond. As the silicon-modified higher fatty acid formed by binding, the following general formula (I); (Where X and Y are monovalent groups such as an alkyl group, a halogen atom, a hydroxyl group, an alkoxy group, a siloxy group and a silyl group, n is an integer of 0 to 10 and m is an integer of 10 to 18) The present invention relates to a magnetic recording medium containing a modified higher fatty acid.

[Constitution / Operation of Invention]

The silicon-modified higher fatty acid used in the present invention has various silicon compounds in the alkyl structure part of the higher fatty acid.
It has a specific structure chemically bonded by an —O—C bond, and when incorporated into a magnetic layer of a magnetic recording medium, it acts as a lubricant exhibiting an appropriate bleed-out property, and the surface of the magnetic layer The function of improving the magnetic characteristics by making the friction coefficient extremely small to give excellent running properties to the magnetic recording medium and making the dispersibility of the magnetic powder favorable.

Such a silicon-modified higher fatty acid has the following general formula (I); (Where X and Y are monovalent groups such as an alkyl group, a halogen atom, a hydroxyl group, an alkoxy group, a siloxy group and a silyl group, n is an integer of 0 to 10 and m is an integer of 10 to 18) Modified higher fatty acid, especially n
And n = 1 to 8 and both X and Y are trimethylsiloxy groups [(CH ₃ ) ₃ SiO-].

In order to synthesize the silicon-modified higher fatty acid used in the present invention, for example, a functional group capable of forming a Si--O--C bond by the reaction between a silicon compound having a reactive group and the above functional group is treated with an alkyl structural moiety, particularly It can be obtained by reacting with a higher fatty acid introduced into the terminal portion. For example, if one reactive group is a hydroxyl group, an alkoxy group, a halogen atom such as chlorine, etc. may be selected and reacted with the other reactive group, and a suitable catalyst may be used for this reaction if necessary. May be.

By the way, in the above general formula (I), n = 0 and m = 15 silicon-modified higher fatty acid, that is, the structural formula (I-1); The compound represented by is synthesized, for example, as follows. That is, 10 g of 16-hydroxyhexadecanoic acid and 100 g of chloroform were put into a three-necked flask having a capacity of 300 ml equipped with a reflux tube, and after sufficiently stirring, 30 g of dimethylchlorosilane was added and well at about 45 ° C. for about 1 hour. The reaction is carried out by stirring, and then the temperature is raised to about 70 ° C. to evaporate off unreacted dimethylchlorosilane, chloroform and hydrogen chloride to obtain about 10.5 g of the compound of the above structural formula (I-1). To be

The silicon-modified higher fatty acid obtained in the above reaction may be partially mixed with unmodified higher fatty acid, and even this mixture can be used as the lubricant of the present invention. Moreover, the proportion of the unmodified higher fatty acid is preferably 20% by weight or less, and particularly preferably 5% by weight or less, based on the whole.

Incidentally, Japanese Patent Publication No. 52-34923 and Japanese Patent Publication No. 52-34924 disclose compounds which are considered to be one of silicon-modified higher fatty acids as a lubricant component for magnetic recording media. Each of these compounds is a compound in which a silicon compound is ester-bonded to a carboxyl group of a higher fatty acid, and the silicon compound is chemically bonded to an alkyl structure portion of the higher fatty acid in the present invention through a Si-O-C bond. Is completely different in structure.

By including the specific silicon-modified higher fatty acid described above in the magnetic layer in the present invention, the excellent lubricity is exhibited under a proper bleed-out property, and the dispersibility of the magnetic powder is improved. Is not clear, but
It is guessed as follows. That is, since the silicon-modified higher fatty acid has a higher fatty acid structure portion having a high affinity for the binder component of the magnetic layer and a silicon structure portion having a lower affinity on the contrary, it exhibits an appropriate bleed-out property, and Due to the presence of the carboxyl group, which has a strong binding property to the magnetic powder, the individual particles of the magnetic powder having a large frictional resistance are wrapped in the silicon-modified higher fatty acid, and thus excellent lubricity is imparted. At the same time, it is presumed that the dispersibility of the magnetic powder will be improved by the above-mentioned wrapping action.

The silicon-modified higher fatty acid represented by the general formula (I) has a particularly excellent lubricating ability at the trimethylsiloxy group portion at one end and is bulky, that is, structurally large, so that it easily appears on the surface of the magnetic layer. The effect of improving lubricity is particularly excellent.

The amount of such silicon-modified higher fatty acid used is preferably 0.05 to 5 parts by weight, and particularly preferably 0.2 to 2.0 parts by weight, based on 100 parts by weight of the magnetic powder in the magnetic layer. If the amount used is less than 0.05 parts by weight, the effect of improving lubricity becomes insufficient, and conversely, if it exceeds 5 parts by weight, the characteristics may be deteriorated due to the decrease in density of the magnetic powder and the surface of the magnetic layer may be roughened due to excessive bleedout. Is not preferred.

The magnetic recording medium of the present invention may be produced in the same manner as in the prior art. The binder component and the above-mentioned silicon-modified higher fatty acid are dissolved in an organic solvent, and magnetic powder is mixed and dispersed in this solution to form a magnetic coating material. Is prepared, and this magnetic coating material is applied onto a substrate such as a polyester film and dried to form a magnetic layer.

As the binder component, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, fibrin resin,
Various materials such as polyisocyanate compounds and polyurethane, which are conventionally known as binder components for magnetic powders, can be used.

Further, as the magnetic powder, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , intermediate oxides of these, Co-containing γ-Fe ₂ O ₃ , Co-containing Fe ₃ O ₄ , and oxide systems such as Cr ₂ O ₃ are used. Examples thereof include magnetic powder, and metallic magnetic powder made of Fe, Co, Ni or alloys thereof.

Further, the magnetic layer may appropriately contain various additive components such as a dispersant, an antistatic agent, a reinforcing agent, and an abrasive, if necessary.

〔The invention's effect〕

The magnetic recording medium of the present invention is excellent because the specific silicon-modified higher fatty acid contained in the magnetic layer acts as a lubricant having an appropriate bleed-out property, so that the friction coefficient of the magnetic layer surface is extremely small. Since the silicone-modified higher fatty acid contributes to improving the dispersibility of the magnetic powder, it has good magnetic properties.

〔Example〕

Hereinafter, examples of the present invention will be described together with comparative examples. In the following, "parts" means "parts by weight".

Example 1 100 parts of γ-Fe ₂ O ₃ powder, 15 parts of vinyl chloride-vinyl acetate-vinyl alcohol copolymer (product name VAGH manufactured by UCC), polyurethane resin (product name Estan 5701 manufactured by Gutudrichsch)
10 parts and methyl isobutyl ketone-toluene (weight ratio
1: 1) 200 parts of the mixed solvent was mixed and dispersed in a ball mill for 72 hours, 0.5 part of the silicon-modified higher fatty acid represented by the structural formula (I-1) was added, and the mixture was further mixed in the ball mill for 1 hour to obtain a magnetic paint. Prepared. This magnetic coating is applied on a 25 μm thick polyester film so that the thickness after drying is 5 μm, dried, and then calendered according to the usual method, and cut into 1/2 inch width to form a magnetic tape. Obtained.

Example 2 The amount of silicon-modified higher fatty acid used in Example 1 was 1.
A magnetic tape was obtained in the same manner as in Example 1 except that the amount was 0.

Example 3 In place of the silicon-modified higher fatty acid used in Example 1, n = 1, m = 11, and 0.5 parts of silicon-modified higher fatty acid in which X and Y are both methyl groups in the general formula (I) were used. A magnetic tape was obtained in the same manner as in Example 1.

Example 4 In place of the silicon-modified higher fatty acid in Example 1, n = 8, m = 15 in the general formula (I), and 0.5 parts of a silicon-modified higher fatty acid in which X and Y are both methyl groups were used. A magnetic tape was obtained in the same manner as in Example 1.

Comparative Example 1 A magnetic tape was obtained in the same manner as in Example 1 except that 1.0 part of palmitic acid was used in place of the silicon-modified higher fatty acid in Example 1.

Comparative Example 2 Instead of the silicon-modified higher fatty acid in Example 1, dimethylpolysiloxane (trade name SH-20 manufactured by Toray Silicone Co., Ltd.
0, viscosity 1,000 centipoise) except that 0.5 parts was used,
A magnetic tape was obtained in the same manner as in Example 1.

Comparative Example 3 Instead of the silicon-modified higher fatty acid in Example 1, a fluorinated oil (trade name: Daiful Oil # 1,00 manufactured by Daikin Co., Ltd.) was used.
0) A magnetic tape was obtained in the same manner as in Example 1 except that 0.5 part was used.

Comparative Example 4 A magnetic tape was obtained in the same manner as in Example 1 except that the silicon-modified higher fatty acid in Example 1 was not used.

Comparative Example 5 Instead of the silicon-modified higher fatty acid in Example 1, the following structural formula described in JP-A-56-13527 (page 6, lower left column); A magnetic tape was obtained in the same manner as in Example 1 except that 0.5 part of the polysiloxane ester represented by

Comparative Example 6 Instead of the silicon-modified higher fatty acid in Example 1, the following structural formula described in JP-A-57-37730 (Example 1); A magnetic tape was obtained in the same manner as in Example 1 except that 0.5 part of the organic silicone compound represented by

Comparative Example 7 Instead of the silicon-modified higher fatty acid in Example 1, the following structural formula described in JP-A-60-5421 (Example 2 thereof); A magnetic tape was obtained in the same manner as in Example 1 except that 0.5 part of myristic acid-modified silicon represented by

Regarding the magnetic tapes obtained in the above Examples and Comparative Examples, when each magnetic tape was wound around a stainless steel cylinder having a surface roughness (Ra) of 0.02 μm and a diameter of 30 mm at a winding angle of 110 ° and a relative speed of 5 mm / sec. The friction coefficient of the tape was measured, and the squareness ratio of the tape was measured using a vibration type magnetic recorder (VSM). The results are shown in the table below.

As is clear from the results in the above table, since the magnetic tapes (Examples 1 to 4) according to the present invention contain the specific silicon-modified higher fatty acid in the magnetic layer, the friction coefficient of the surface of the magnetic layer is extremely small and the running property is improved. It is clear that the magnetic powder exhibits excellent magnetic properties because it is excellent and the dispersibility of the magnetic powder is good. On the other hand, a conventional magnetic tape using a general-purpose lubricant component (Comparative Examples 1 to 3)
In addition, the magnetic tape using the lubricant component composed of an esterified product of a silicon compound and a fatty acid (Comparative Examples 5 to 7) has a smaller friction coefficient than those not using the lubricant component (Comparative Example 4). However, the degree of occurrence is small, especially those using silicone oil or fluorinated oil (Comparative example
It can be seen that the magnetic properties are deteriorated due to the poor dispersibility of the magnetic powder in the case of (2, 3) or the one using an esterified product of a silicon compound and a fatty acid (Comparative Examples 5 to 7). Examples 1 to 4
The surface roughness of the magnetic layer was not recognized in the magnetic tapes of Comparative Examples 1 and 4, but Comparative Examples 2 and 3 and Comparative Examples 5 to 7
The surface of the magnetic tape was slightly rough.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-94233 (JP, A) JP-A-58-64631 (JP, A) JP-A-56-13527 (JP, A) JP-A-57- 37730 (JP, A) JP-A-60-5421 (JP, A)

Claims (1)

[Claims] 1. A magnetic recording medium comprising a base and a magnetic layer containing magnetic powder and a binder, wherein a silicon compound is added to the alkyl structure portion of a higher fatty acid in the magnetic layer to form Si--O.
As a silicon-modified higher fatty acid chemically bonded by a —C bond, the following general formula (I); (Where X and Y are monovalent groups such as an alkyl group, a halogen atom, a hydroxyl group, an alkoxy group, a siloxy group and a silyl group, n is an integer of 0 to 10 and m is an integer of 10 to 18) A magnetic recording medium containing a modified higher fatty acid.