JPH0673175B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium such as a magnetic tape or a magnetic disk.

[Outline of Invention]

The present invention provides a magnetic recording medium in which a magnetic layer mainly composed of a ferromagnetic powder and a binder is formed on a non-magnetic support, and a Cr layer having a particle size of 0.5 to 0.8 μm is used as an abrasive in the magnetic layer.
It was added and Cr ₂ O ₃ having a particle size of ₂ O ₃ and 1.0 to 1.5 [mu] m, less the head abrasion is intended to provide a magnetic recording medium excellent in still characteristics.

[Conventional technology]

In the field of magnetic recording, higher density recording and shorter wavelength of recording signals are being promoted. In response to this, for example, a coating type in which a magnetic coating is applied on a non-magnetic support to form a magnetic layer In the magnetic recording medium (1), the magnetic powder dispersed in the magnetic layer is made finer and highly packed, and as a result, the smoothness of the magnetic layer tends to be improved.

When the surface of the magnetic layer is smoothed in this way, it is advantageous in terms of, for example, spacing loss, but the contact area with the magnetic head, the guide post, the rotary head cylinder, and the like is substantially increased, There is a possibility that the friction coefficient may increase and the running performance and durability may be hindered. Especially in video tape, it is contacted with the magnetic head at high speed,
This tendency is remarkable because the use conditions are severe such as continuous contact at the same place to obtain a still image.

Under these circumstances, in this type of magnetic recording medium, abrasives such as Cr ₂ O ₃ , Al ₂ O ₃ , TiO ₂ and SiO ₂ are added to the magnetic layer.

However, when adding such an abrasive,
It is difficult to select the addition amount and particle size. For example, if the addition amount of the abrasive is too large, the electromagnetic conversion characteristics deteriorate, and if the addition amount is too small, the predetermined durability cannot be obtained.

Also, regarding the particle size of the abrasive, if the particle size is small, the head wear amount is small, but the still characteristics deteriorate. On the other hand, if the particle size is large, the still characteristics are improved but the head wear amount is increased.

Therefore, in the conventional magnetic recording medium, an abrasive having an appropriate particle size was used to obtain a balance between the head wear amount and the still characteristics, but in this case, both the head wear amount and the still characteristics are obtained. We couldn't fully satisfy both.

[Problems to be solved by the invention]

As described above, it is difficult to simultaneously satisfy both the head wear amount and the still characteristics by using one type of abrasive. Further, as described in, for example, JP-A-57-162129, it has been proposed to use two kinds of abrasives, but even in this case, it is difficult to select the particle size of the abrasives, and the above-mentioned publications are used. It was found that the effect cannot be said to be sufficient particularly in the still characteristics when the one having the particle size as described in 1) is used.

Therefore, the present invention has been proposed in order to eliminate the drawbacks of the conventional ones, and provides a magnetic recording medium excellent in durability (still characteristics) without abrading the magnetic head. The purpose is to

[Means for solving problems]

The inventors of the present invention have made extensive studies on the particle size of abrasives and those that do not achieve the above-mentioned object, and have completed the present invention, in which a ferromagnetic powder and a binder are provided on a non-magnetic support. In a magnetic recording medium having a magnetic layer mainly composed of Cr, the magnetic layer comprises Cr ₂ O ₃ having a grain size of 0.5 to 0.8 μm.
It is characterized by containing Cr ₂ O ₃ having a particle size of 1.0 to 1.5 μm.

That is, in the present invention, Cr ₂ O having a particle size of 0.5 to 0.8 μm is used.
_3, the addition of the Cr ₂ O ₃ having a particle size 1.0~1.5μm as an abrasive.

It was confirmed by experiments that Cr ₂ O ₃ exhibits the most excellent effect as the abrasive.

As the Cr ₂ O ₃ to be added, but those two kinds of different particle sizes are used, where, Cr ₂ O of smaller particle size
No. ₃ needs to have a particle size within the range of 0.5 to 0.8 μm. If the particle size is less than 0.5 μm, it is difficult to secure still characteristics. On the contrary, when the particle size exceeds 0.8 μm, the head wear amount becomes too large.

On the other hand, the larger particle size Cr ₂ O ₃ has a particle size of 1.0 to 1.5.
It must be in the μm range. If the particle size is less than 1.0 μm, it is difficult to improve the still characteristics, and conversely 1.
If it exceeds 5 μm, the head may be damaged.

By using these two types of Cr ₂ O ₃ as abrasives, durability is improved without impairing electromagnetic conversion characteristics,
The amount of head wear can be suppressed.

In the magnetic recording medium of the present invention, the magnetic layer is, for example, a ferromagnetic coating and a magnetic coating prepared by dissolving the above-mentioned two kinds of Cr ₂ O ₃ in a binder and dissolving it in an organic solvent on the surface of the non-magnetic support. It is formed by applying to.

Here, as the material of the non-magnetic support, any material can be used as long as it is usually used for this kind of magnetic recording medium, for example, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene. , Cellulose derivatives such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, holimide, polyamide and polyamideimide,
Examples thereof include paper, metals such as aluminum and copper, light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon. The form of this non-magnetic support may be any of film, tape, sheet, disk, card, drum and the like.

As the ferromagnetic powder used in the magnetic layer, any ordinary powder can be used. Therefore, examples of the ferromagnetic powder that can be used include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite fine particles, and iron nitride.

As the above-mentioned ferromagnetic iron oxide particles, when represented by the general formula FeOx, those having an X value in the range of 1.33 ≦ X ≦ 1.50, that is, maghemite (γ-Fe ₂ O ₃ , X = 1.50), magnetite (Fe ₃
O ₄ , X = 1.33) and their solid solutions (FeOx, 1.33 <X <1.5
0). Further, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. Cobalt-containing iron oxide is roughly classified into two types: a doped type and an adhered type.

As the above-mentioned ferromagnetic chromium dioxide, it is possible to use CrO ₂ or those to which at least one kind of Ru, Sn, Te, Sb, Fe, Ti, V, Mn or the like is added for the purpose of improving coercive force.

As the ferromagnetic alloy powder, Fe, Co, Ni, Fe-Co, Fe-Ni, Fe
-Co-Ni, Co-Ni, Fe-Co-B, Fe-Co-Cr-B, Mn-Bi, Mn
-Al, Fe-Co-V and the like can be used, and metal components such as Al, Si, Ti, Cr, Mn, Cu and Zn may be added to these for the purpose of improving various characteristics.

Further, as the resin used as the binder, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-
Vinyl alcohol copolymer, vinyl chloride-vinyl acetate-
Maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer Coal, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl Butyral, cellulose derivative,
Examples thereof include styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin, urea-formaldehyde resin, or a mixture thereof.

In addition to the binder and the ferromagnetic powder, a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive, etc. may be added to the magnetic layer.

The above-mentioned constituent materials of the magnetic layer are dissolved in an organic solvent to prepare a magnetic paint, and the magnetic paint is applied onto a non-magnetic support. The solvent of the magnetic paint is acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or the like. Ketone type, ester type such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol monoethyl ether acetate, glycol ether type such as glycol dimethyl ether, glycol monoethyl ether and dioxane,
Aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane and heptane, chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene. Can be mentioned.

[Action]

By adding two kinds of Cr ₂ O ₃ having different average particle sizes of 0.5 to 0.8 μm and 1.0 to 1.5 μm to the magnetic layer, the amount of head wear is suppressed and at the same time the still characteristics are improved.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

Example 1. Co-deposited γ-Fe ₂ O ₃ 100 parts by weight Polyurethane resin 15 parts by weight (Nippon Polyurethane Co., # 3113) Nitrocellulose 5 parts by weight (Asahi Kasei Co., H1 / 2) Carbon black (average particle size) 50 μm) 7 parts by weight Lubricant 4 parts by weight Abrasive Cr ₂ O ₃ : Average particle size 0.5 μm 3 parts by weight Cr ₂ O ₃ : Average particle size 1.5 μm 3 parts by weight Dispersant 1 part by weight (Armor and Chemical Co.) Diomine T) Methyl ethyl ketone 150 parts by weight Toluene 150 parts by weight The above composition was mixed in a ball mill for 24 hours, 5 parts by weight of a curing agent (Nippon Polyurethane Co., Coronate L) was added, and the mixture was filtered with an average pore size of 1 μm. After filtering, 15
It was coated and dried on a polyethylene terephthalate film having a thickness of μm.

After that, calendering was performed to adjust the surface properties to obtain a magnetic film having a coating thickness of 5 μm. This film was cut into a 1/2 inch width to prepare a sample tape.

Example 2 A sample tape was prepared in the same manner as in Example 1 except that Cr ₂ O ₃ 3 parts by weight having an average particle size of 0.5 μm and Cr ₂ O ₃ 3 parts by weight having an average particle size of 1.0 μm were used as abrasives. Created.

Example 3 A sample tape was prepared in the same manner as in Example 1, except that 3 parts by weight of Cr ₂ O ₃ having an average particle size of 0.8 μm and 3 parts by weight of Cr ₂ O _{3 having an} average particle size of 1.0 μm were used as abrasives. Created.

Example 4 A sample tape was prepared in the same manner as in Example 1 except that Cr ₂ O ₃ 3 parts by weight having an average particle size of 0.8 μm and Cr ₂ O ₃ 3 parts by weight having an average particle size of 1.5 μm were used as abrasives. Created.

Comparative Example 1. Using 6 parts by weight of Cr ₂ O _{3 having} an average particle size of 1.5 μm as an abrasive,
A sample tape was prepared in the same manner as in Example 1 except for the above.

Comparative Example 2. Using 6 parts by weight of Cr ₂ O _{3 having} an average particle size of 1.0 μm as an abrasive,
A sample tape was prepared in the same manner as in Example 1 except for the above.

Comparative Example 3. Using 6 parts by weight of Cr ₂ O _{3 having} an average particle size of 0.8 μm as an abrasive,
A sample tape was prepared in the same manner as in Example 1 except for the above.

Comparative Example 4. Using 6 parts by weight of Cr ₂ O _{3 having} an average particle size of 0.5 μm as an abrasive,
A sample tape was prepared in the same manner as in Example 1 except for the above.

The head wear amount and the still characteristics of the sample tapes prepared in each of the above-mentioned Examples and Comparative Examples were measured. The results are shown in the table below. Here, the head wear amount was measured under the conditions of a temperature of 23 ° C. and a relative humidity of 60% for 200 hours in a reproducing mode using a video tape recorder, and the decrease amount of the head protrusion amount was measured. For the still time, use a video tape recorder to play back a still image that was previously recorded under the condition of 5 ° C.
It is shown by the time until it falls to 6 dB.

As is clear from this table, in each of the examples using two types of Cr ₂ O ₃ having different average particle diameters, compared with the comparative example,
It can be seen that both still characteristics and head wear amount show excellent characteristics.

〔The invention's effect〕

As is clear from the above description, in the present invention,
Since two kinds of Cr ₂ O ₃ having different average particle diameters of 0.5 to 0.8 μm and 1.0 to 1.5 μm are added to the magnetic layer as abrasives,
It is possible to obtain a magnetic recording medium that is excellent in durability and has a small amount of head wear without impairing electromagnetic conversion characteristics.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer mainly composed of a ferromagnetic powder and a binder, wherein the magnetic layer is Cr ₂ O having a grain size of 0.5 to 0.8 μm. ₃ and 1.0 ~
A magnetic recording medium containing Cr ₂ O ₃ having a particle size of 1.5 μm.