JPH0630141B2 - Magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to improvement of a magnetic recording medium.

[Technical Background of the Invention and Problems Thereof] The magnetic layer of a magnetic recording medium, for example, a magnetic tape is usually a magnetic material, a binder resin, a dispersant, an abrasive, an antistatic agent, a lubricant, a curing agent, and other additives. Consists of. When such a magnetic tape is used in a recording / reproducing device such as a cassette deck or a VTR, it travels in contact with a magnetic head, tape guide, cylinder, etc., so the tape has a small friction coefficient and runs smoothly and stably. It is required to have sex. That is, the prevention of "nag" of a music tape and the prevention of "jitter" of a video tape. When the magnetic tape runs, if the friction coefficient becomes large at the contact part between the magnetic layer and the magnetic head or tape guide, cylinder, etc. due to the tension of the tape or the running speed, the vibration of the tape will occur. This causes an inconvenient phenomenon.

Furthermore, the recent development of VTR has been remarkable and has become multifunctional, and a model having all the user's requirements such as a still mechanism, slow, speed, and double speed reproduction has been developed.
Along with this, many items are required from the device side for magnetic tapes. That is, for slow speed, speed, and reproduction, stable running properties of the magnetic tape from low speed to high speed are required.

Therefore, conventionally, a magnetic coating containing a lubricant such as higher fatty acids, their esters, liquid paraffin, fluorinated oil, silicon oil, graphite powder, etc. is applied on the support to form a magnetic layer. The formed magnetic tape is known. However, even with these lubricants, sufficient lubricity cannot be imparted to the magnetic layer of the magnetic tape, and particularly in an environment of high temperature and high humidity (for example, 30 ° C. to 60 ° C.).
It was difficult to secure stable running properties at 70 ° C. and 70% to 90% RH.

[Object of the Invention]

The present invention is intended to provide a magnetic recording medium having stable running performance from low speed to high speed even under high temperature and high humidity.

[Outline of Invention]

The present invention provides a magnetic recording medium comprising a magnetic recording layer provided on a non-magnetic support, wherein the magnetic recording layer comprises a fatty acid, a fatty acid ester and a general formula. [Wherein R is a C ₁ -C ₅ alkyl group, a phenyl group or a substituted phenyl group, R'is a C ₁ -C ₅ alkyl group, m
= 1 to 3 and n = 0 to 2 and m + n = 1 to 3]. The main point is to obtain the above-described magnetic recording medium having excellent running performance. Is.

Examples of the non-magnetic support include a polyester film and the like.

The magnetic recording layer is a ferromagnetic powder, a binder resin, a dispersant,
It is formed of a magnetic paint containing an abrasive and an antistatic agent and containing the above-mentioned three components. Examples of the ferromagnetic powder used here include magnetic iron oxide powder obtained by depositing Co on Fe ₂ O ₃ · FeO _x (x = 1.3 to 1.5), CrO ₂ powder, Fe-Co powder, Ba-ferrite powder and substitution. Examples include type Ba-ferrite powder and other magnetic powders that can be generally used for magnetic tapes. As the binder resin, for example, vinyl chloride-vinyl acetate copolymer, nitrocellulose, cellulose-based derivative, polyurethane, polyester and the like are used. Examples of abrasives include Cr
₂ O ₃ , Al ₂ O _3, etc. are used.

The fatty acids have a relatively slow lubricating effect. Such fatty acid may be saturated or unsaturated, and specific examples thereof include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and oleic acid. The amount of these fatty acids added is 1/1 to 1 of the fatty acid ester used in combination.
It is desirable that the amount is / 10, preferably 1/3 to 1/5. The reason for this is that if the amount of fatty acid added is less than 1/10 of the fatty acid ester, the magnetic recording medium tends to stick to the head when the magnetic head or the like rotates at low speed. If it exceeds, the fatty acid is likely to precipitate in the form of a fatty acid salt, which may lead to deterioration in image quality.

The above fatty acid ester exhibits a lubricating action at a relatively medium speed to a high speed. Such fatty acid ester may be saturated or unsaturated, and specific examples thereof include methyl stearate, ethyl stearate, butyl stearate, methyl myristate, butyl laurate, methyl oleate, and butyl palmitate. The amount of the fatty acid ester added is 0.5 to 10 parts by weight, preferably 4 to 6 parts by weight, based on 100 parts by weight of the binder resin constituting the magnetic recording layer. The reason is that the amount of fatty acid ester added is
If it is less than 0.5 part by weight, the lubricating effect at medium to high speed cannot be sufficiently achieved. However, if the amount added exceeds 10 parts by weight, running property becomes unstable due to bleeding of the fatty acid ester itself, As a result, image fluctuations are likely to occur.

The alkoxysilane represented by the above general formula has the function of enhancing the water repellency of the magnetic recording layer and of stably exerting the lubricating properties of the fatty acid and the fatty acid ester at low speed, medium speed to high speed under high temperature and high humidity. . Examples of such alkoxysilanes include methylhydroxydimethoxysilane, ethyldihydroxymonoethoxysilane, methyltrihydroxysilane, and methyldihydroxymonoisopyroxysilane. The amount of the alkoxysilane added is set to the binder resin 10 that constitutes the magnetic recording layer.
It should be in the range of 0.2 to 3 parts by weight with respect to 0 parts by weight. The reason for this is that if the amount of alkoxysilane added is less than 0.2 parts by weight, it is difficult to sufficiently exert the effect of improving water repellency (moisture resistance). However, if the amount exceeds the range, magnetic recording There is bleeding on the layer surface, which deteriorates runnability.

Next, one manufacturing method for obtaining the magnetic recording medium of the present invention will be briefly described.

First, a ferromagnetic powder, a binder resin, a dispersant, an abrasive, an antistatic agent, etc. are sufficiently kneaded with, for example, a three-roll mill, a ball mill, a sand grinder, a kneader, etc., and then a curing agent is added to the kneaded product, and A fatty acid, a fatty acid ester and an alkoxysilane are added and mixed to prepare a magnetic paint. Then, this magnetic coating is applied on a non-magnetic support such as a polyester film by air doctor coating, plate coating, nice edge coating, reverse roll coating, transfer roll coating, gravure coating, etc., and after drying, a surface forming treatment ( A magnetic recording layer is formed by carrying out a calendar treatment) to manufacture a magnetic recording medium.

Therefore, according to the present invention, a fatty acid highly effective for relatively low-speed lubrication, a fatty acid ester highly effective for relatively medium to high-speed lubrication, and a general formula alkoxysilane highly effective for water repellency are contained. Due to the fact that it has a smooth and stable running property from low speed to high speed, especially under high temperature and high humidity,
It is possible to obtain a magnetic recording medium with improved "nag" and "jitter" during running.

Example of Invention

 Next, examples of the present invention will be described.

Examples 1 to 6, Comparative Examples 1 to 4, Reference Examples 1 to 3 First, 100 parts by weight of Ba-ferrite powder substituted with Ti and Co (average particle size 0.1 μm, coercive force; 800 [Oe]), chlorinated. 5 parts by weight of vinyl-vinyl acetate copolymer, 10 parts by weight of polyurethane resin, 4 parts by weight of carbon black, Cr ₂ O ₃ 2.5
Parts by weight and lecithin 2 parts by weight, methyl ethyl ketone 12
The dispersion treatment was carried out with a disperser (sand grinder) in the presence of 0 part by weight and 60 parts by weight of toluene. Subsequently, after passing through to remove dust and particles of the dispersion medium during the dispersion treatment, 20% by weight of polyisocyanate was added to the resin. Subsequently, the fatty acids, fatty acid esters and silane coupling agents shown in Table 1 below were added and sufficiently stirred and mixed to prepare 11 kinds of magnetic paints.

Then, each of the magnetic paints was applied onto a polyethylene terephthalate film, dried, and subjected to surface treatment with a super calendar, followed by curing the coating film at 60 ° C. for 2 days,
Further, 10 kinds of magnetic tape samples were cut into 1/2 inch width (Examples 1 to 6, Comparative Examples 1 to 4 and Reference Examples 1 to 3).
Was manufactured. The magnetic tape samples obtained in Examples 1 to 6, Comparative Examples 1 to 4 and Reference Examples 1 to 3 were run at 25 ° C. and 40% RH at a running speed of 5 mm / sec, a running speed of 20 mm / sec and running. Surface friction coefficient (μK ₁ ), (μK ₂ ), (μK ₃ ) at speed 300 mm / sec, and running speed 5 mm / sec, running speed 20 mm / sec and running speed 300 mm / sec at 35 ° C, 88% Surface friction coefficient (μK ₁ ),
(ΜK ₂ ) and (μK ₃ ) were measured. The result is the second
Shown in the table. The friction coefficient (μK) was measured by T / T ₀ = exp μKQ [where T _{0 is the} measured tension (30 g), T is the running tension, and Q is the constant].

Also, for each magnetic tape sample, 35 ° C, 88%
The jitter was measured and the results are shown in Table 2 above. The jitter was measured at a β-III mode speed of 35 ° C. and 88%.

Further, when the humidity dependency of the friction coefficient was examined for Examples 3 and 7 and Comparative Materials 1 and 2, the characteristic diagram shown in FIG. 1 was obtained. In the figure, A ₃ is a characteristic line of the magnetic tape sample of Example 3, A ₇ is a characteristic line of the same sample of Example 7, B ₁ is a characteristic line of the same sample of Comparative Example 1, and B ₂ is a comparative example. 2 is a characteristic line of the same sample of No. 2. Further, when the speed dependence was examined, the characteristic diagram shown in FIG. 2 was obtained. In addition, A _{3 in} FIG.
Is the characteristic line of the magnetic tape sample of Example 3, and B ₂ is the characteristic line of the same sample of Comparative Example 2.

As is clear from Table 2 and FIGS. 1 and 2, Comparative Examples 1 and 2 show a remarkable decrease in running property at high humidity and high speed. On the other hand, the magnetic tape samples of Examples 1 to 6 have small speed dependence even under high humidity, and have excellent running properties.

Further, in the magnetic tape sample of Reference Example 1, since the amount of alkoxysilane added was large relative to the binder resin, Examples 1 to 1
It can be seen that the running property is inferior to the magnetic tape sample of No. 6. The magnetic tape sample of Reference Example 2 is shown in Table 2. Although the data are not much different from those of the magnetic tape samples of Examples 1 to 6, the fatty acids were precipitated in the form of salt after being left for about 1 week, and the image quality was improved. It has caused a decline. Further, in the magnetic tape sample of Reference Example 3, since the other silane coupling agent was used, the magnetic head adhered to the surface of the magnetic recording layer particularly under the environment of 35 ° C. and 88% RH.
Even the measurement has become a difficult situation.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to provide a magnetic recording medium which has stable running performance from low speed to high speed even under high temperature and high humidity, and which improves "nagi" and "jitter" during running. .

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing humidity dependence of friction coefficient of magnetic tape samples in Examples 3 and 7 and Comparative Examples 1 and 2.
FIG. 2 is a characteristic diagram showing the speed dependence of the friction coefficient of the magnetic tape samples in Example 3 and Comparative Example 2.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuya Kumagai, Komukai-shi, Kawasaki-shi, Kanagawa 1 Komu Toshiba-shi, Higashi Koshibaura Electric Co., Ltd. (72) Inventor Ryo Takeya Komukai, Kawasaki-shi, Kanagawa TOSHIBA-Cho, No. 1 Higashi Koshibaura Electric Co., Ltd. (56) References JP-A-58-177526 (JP, A)

Claims (3)

[Claims] 1. A magnetic recording medium comprising a magnetic recording layer provided on a non-magnetic support, wherein the magnetic layer comprises a binder resin,
0.5-10 with respect to 100 parts by weight of the binder resin
Part by weight of fatty acid ester, fatty acid in an amount not more than the amount of the fatty acid ester added, and 0.2 to 3 parts by weight of the general formula based on 100 parts by weight of the binder resin. [Wherein R is a C ₁ -C ₅ alkyl group, a phenyl group, or a substituted phenyl group, R'is a C ₁ -C ₅ alkyl group, m = 1 to 3, n = 0 to 2 and m + n = 1 to 3]
A magnetic recording medium characterized by containing an alkoxysilane represented by. 2. The magnetic recording medium according to claim 1, wherein the fatty acid is selected from C _{7 to} C ₁₈ acids. 3. The magnetic recording medium according to claim 1, wherein the magnetic powder is Ba-ferrite or substitutional Ba-ferrite.