JPH01176320A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling stability and to prevent flawing of the surface of a back coat layer and chipping, etc., of a tape guide by incorporating the powder of a composite oxide of lithium and aluminum and carbon black into the back coat layer. CONSTITUTION:The powder of the composite oxide of the lithium and aluminum and the carbon black are incorporated into the back coat layer. The powder of the composite oxide of the lithium and aluminum to be used as the reinforcing material of the back coat layer not only functions as the reinforcing material but also provides the effect of improving the traveling stability, preventing powder dislodgement, improving the flawing property (durability) of the back coat layer and decreasing the chipping property of the tape guide in contact with the sliding contact face of the back coat layer for its own properties and the particle size, content, etc. The traveling stability is thereby improved and the surface flawing of the back coat layer and the chipping of the tape guide are prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium in which a magnetic layer is formed on one side of a non-magnetic support and a back coat layer is formed on the other side. In particular, the present invention relates to a magnetic recording medium with improved characteristics of a back coat layer.

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer is formed on one side of a non-magnetic support and a back coat layer is formed on the other side, in which lithium-aluminum composite oxide powder and carbon black are contained in the back coat layer. The present invention aims to provide a magnetic recording medium which has excellent running stability and can prevent scratches on the surface of the back coat layer, scraping of the tape guide, etc. by containing the following.

[Conventional technology]

In general, for magnetic recording media such as audio tapes and video tapes, the purpose is to effectively prevent winding irregularities and scratches on the bank surface of the non-magnetic support during high-speed winding, and to improve running stability and durability. Conventionally, a back coat layer is provided on the back surface of a nonmagnetic support having a magnetic layer on the surface.

The back coat layer provided for the above-mentioned purpose is made by coating non-magnetic inorganic material powder such as carbon black, alumina, titanium oxide, α-iron oxide, calcium carbonate, baryram sulfate, zinc oxide, silica, etc. in a binder resin. It is formed by coating the back side of a non-magnetic support with a coating material dispersed in .

[Problem that the invention seeks to solve] [However,
If a large amount of the non-magnetic inorganic material powder is added to the back coat layer in an attempt to strengthen the reinforcing function of Bafukuko Jl, the durability of the back coat 71 will improve, but
Problem 1: Due to the running of the magnetic recording medium, powder falls off from the back coat layer and the tape guide that comes into direct contact with the back coat layer becomes extremely abraded.
Occur.

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and it is possible to improve the running stability of a magnetic recording medium, and prevent powder falling off, scratches on the surface of the back coat layer, etc.
The object of the present invention is to provide a magnetic recording medium that does not suffer from scratching of the tape guide.

[Means for solving problems]

In order to achieve the above-mentioned objects, the present invention has conducted intensive research and found that a new lithium-aluminum composite oxide is very effective as a non-magnetic inorganic material powder to be added to the magnetic layer. It has been found that adding oxides improves running stability and prevents powder falling, scratches on the surface of the back coat layer, and scraping of the tape guide.

The present invention has been made based on the above findings, and provides a magnetic recording medium in which a magnetic layer is formed on one side of a non-magnetic support and a back coat layer is formed on the other side. It is characterized by containing lithium/aluminum composite oxide powder and carbon black.

The lithium-aluminum composite oxide powder used in this invention is a new material and is a salt formed from aluminum oxide and lithium oxide, which is more basic than aluminum oxide. In the above formula, X represents an integer of 2 or less, and y represents an integer of 5 or less,
). Specifically, for example, x=1. y
-1, L i A j! 02%X! 1 *
When y=5, LiA! An example of this is represented by the formula Sol.

Above L iAj! The average particle diameter of the lithium/aluminum composite oxide powder expressed as Ox + L 1AZsos is preferably within the range of 0.1 to 0.8 μm, and if it is less than 0.1 μm, the lithium/aluminum composite oxide powder The effect of adding powder cannot be obtained,
Because the particles are so fine, they aggregate and cause powder to fall off, causing deterioration in running stability, scratches on the surface of the back coat layer, and an increase in the coefficient of friction.

Furthermore, if the average particle diameter is larger than 0.8 μm, the sliding portion with the back coat layer of the magnetic recording medium will be scraped, resulting in a large amount of wear on the tape guide, for example.

Note that the effect remains excellent regardless of the particle shape of the lithium-aluminum composite oxide powder, such as spherical, prismatic, or distorted.

Therefore, by containing a predetermined amount of lithium-aluminum composite oxide powder with a predetermined particle size in the back coat layer, the excellent back coat surface reinforcing function is fully exhibited, and the running stability of the magnetic recording medium is improved. In addition, it is possible to prevent dust from falling off and scratches on the surface of the back coat layer, and it also satisfies the effects of preventing the tape guide from being scraped in contact with the magnetic recording medium.

On the other hand, carbon black, which is added to the back coat layer at the same time as the above-mentioned lithium/aluminum composite oxide powder, is added for the purpose of preventing static electricity on the back coat layer, and its particle size is 0.01 to 0. It is preferable to use particles within the range of 0.1 μm.
If the diameter is less than 0.1 μm, the dispersion in the back coat layer will be rapid, which may adversely affect running performance.
If it is larger, the antistatic effect cannot be obtained.

When adding the above lithium-aluminum composite oxide powder and carbon black to the back coat layer, both
It is preferable to add lithium/aluminum composite oxide powder/carbon black in a ratio of 0.5/99.5 to 25/75 (weight ratio).

1ffl containing the above-mentioned lithium-aluminum composite oxide powder is usually prepared by mixing and dispersing the above-mentioned lithium-aluminum composite oxide powder and carbon black together with a binder component, an organic solvent, and other additives. The coating layer is formed by preparing a coating material, applying it to the back side of a non-magnetic support on which a magnetic layer has been previously formed, and drying it.

Here, as the binder, any conventionally widely used binder resin can be used, such as 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 ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, thermoplastic polyurethane resin, Polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer,
Butadiene-acrylonitrile copolymer, acrylonitrile-cyclodiene-methacrylic acid copolymer, polyvinyl butyral.

Cellulose derivatives, styrene-pukuden copolymers, polyester resins, phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins.

Binder resins such as melamine resins, alkyd resins, urea-formaldehyde resins or mixtures thereof may be mentioned.

In addition, organic solvents used in the back coat layer include:
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl acetate; and glycol ethers 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, methylene chloride, ethylene chloride,
Carbon tetrachloride, chloroform, ethylene chlorohydrin,
Examples include chlorinated hydrocarbons such as dichlorobenzene.

Furthermore, additives commonly used in the past may be used together with the lithium-aluminum composite oxide powder and carbon black (for example, CaC0, powder, 13aS
O4 powder, Zn○ powder, α-Fe103 powder, TiO
Examples include z powder.

Furthermore, various additives commonly used in back coat layers, such as lubricants and dispersants, may be added as appropriate.

On the other hand, in the magnetic recording medium of the present invention, the magnetic layer is made of a magnetic paint prepared by dispersing, for example, ferromagnetic powder in a binder commonly used as a binder for this type of recording medium and dissolving it in an organic solvent. It is formed by coating on the surface of a magnetic support.

Here, any ordinary magnetic powder can be used as the magnetic powder used in the magnetic layer.

Therefore, the magnetic powders that can be used include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, and ferromagnetic iron oxide particles. Examples include J4 magnetic alloy powder, hexagonal barium ferrite fine particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those in which the value of X is in the range of 1.33≦X≦1.50 when expressed by the -i formula FeOx, that is, maghemite (γ-Fe2O3).

X=1.50), Magnephyte (FesOl, X
= 1.33) and their solid solutions (FeOx, 1.
33 < There are two types.

The above-mentioned ferromagnetic chromium dioxide may include CrO, or Ru and Sn for the purpose of improving coercive force thereof.

It is possible to use one with a small amount of Te, Sb, 'Fe, Ti, V, Mn, etc. added thereto.

As the ferromagnetic alloy powder, Fe + Co, N
i.

Fe-Co, Fe-Ni, Fe-Co-Ni, C.

-Ni, Fa-Co-B, Fe-Co-Cr-B.

Mn-Bi, Mn-An, Fe-Co-V, etc. can be used, and Δ1. S
Metal components such as i, Ti, Cr, Mn, Cu, and Zn may be added.

These magnetic materials are mixed with a binder resin and an organic solvent, and a 6≦■ paint is applied onto a non-magnetic support.
The magnetic layer may be formed by drying, or by depositing a ferromagnetic material on a nonmagnetic support by means such as vacuum deposition, ion blasting, sputtering, plating, or the like.

Furthermore, in addition to the commonly used binder and the above-mentioned magnetic powder, the magnetic layer contains a dispersant that is commonly used as an additive.
Lubricants, abrasives, antistatic agents, rust inhibitors, etc. may also be added.

The material for the non-magnetic support forming the FJ and the magnetic layer as described above may be any material that is normally used in this type 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, polycarbonate polyimide, polyamide, and polyamideimide. Plastics such as paper, aluminum, metals such as copper, light alloys such as aluminum alloys, titanium alloys, etc.
Examples include ceramics and single crystal silicon. The nonmagnetic support may be in any form such as a film, tape, sheet, disk, card, or drum.

[Effect]

The lithium-aluminum composite oxide powder used as a reinforcing agent for the back coat layer not only functions as a reinforcing agent, but also improves running stability and powder removal due to its own properties, particle size, content, etc. This has the effect of preventing scratches (durability) of the back coat layer, and reducing the abrasion of the tape guide that is in sliding contact with the back coat a.

〔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.

Additive 10 parts by weight (L
Antistatic agent 90 parts by weight (carbon black, particle size 24 mμ.

Manufactured by Cabosoto, trade name: Black Burls) Binder
30 parts by weight (vinyl chloride-vinyl acetate copolymer) Binder 20 parts by weight (Polyurekun 9 manufactured by Nippon Polyurethane Co., Ltd.)

Product name N-5033) Lubricant (butyl stearate) 1 part by weight Solvent (methyl ethyl ketone) 200ffiff
1 part solvent (methyl isobutyl ketone') 50f
50 parts by weight of solvent (toluene) 100 parts by weight of magnetic powder (specific surface area 40 m/g, Co-Hr iron oxide) binder
8 parts by weight of trocellulose, manufactured by Asahi Kasei Co., Ltd. (trade name: NCI/2H); 12 parts of binder (polyurethane, manufactured by Nippon Polyurethane Co., Ltd.);

Product name N-2304) Lubricant (butyl stearate) Type 2 dish polishing agent 5 parts by weight (α alumina, manufactured by Sumitomo Chemical Co., Ltd., product name AKP-30) Antistatic agent
2 Heavy Industries Department (Carbon, manufactured by Caboft Co., Ltd., trade name Vulcan XC-72) Solvent (methyl ethyl ketone) 120ffi
Part ffi: 60 parts by weight of solvent (methyl isobutyl ketone) 60 parts by weight of solvent (toluene) The above magnetic store composition was mixed in a ball mill for 48 hours, filtered with a filter, and then 2 parts by weight of Coronate L was added. After 30 minutes, this was coated on a 16 μmW polyethylene terephthalate film so that the film thickness after drying would be 6 μm.Then, the film was subjected to magnetic field orientation treatment, dried, and wound up. This was calendered and then further hardened.

Separately from the above magnetic Pj composition, a back coat layer composition was mixed in a ball mill for 48 hours, and 2.5 parts by weight of Coronate L was added thereto to prepare a back coat layer paint. This was coated on the back side of the polyethylene terephthalate film on which the magnetic layer was formed as described above so that the coating thickness after drying was 2 μm.Then, this was rolled up.
After calendering, the tape was slit into 1/2 inch width to prepare a sample tape.

The types of additives, particle size, amount added, and addition of antistatic agent (carbon black) in the back coat layer composition were changed as shown in Table 1, and the other changes were carried out. A sample tape was prepared in the same manner as in Example 1.

Two-stop comparison test in history The types, particle diameters, and amounts of additives in the backcoat layer composition, and the amount of antistatic agent (carbon black) added were changed as shown in Table 1, and the other values were as shown in Example 1. A sample tape was prepared in the same manner as in Example 1.

Examples 1 to 9 and Comparative Examples 1 to 60 Backco) Fi! , & types of additives used in the formulation.

Table 1 shows the particle size, amount added, and amount of antistatic agent (carbon black) added.

(The following is a blank space) Table 1 For each of the sample tapes obtained, the scratch resistance of the back coat surface, the guide abrasion resistance, the friction coefficient, and the powder falling off were measured. The results are shown in Table 2.

In addition, the scratch resistance of the back coat layer, guide abrasion resistance, and powder fall-off were visually observed as ○ for good and Δ for average.
The coefficient of friction was determined by measuring the coefficient of friction between the surface of the back coat layer and IS stainless steel at a low tape speed (0°411/5ec).

(The following is a blank space) Table 2 As is clear from the above Table 2, Example 1 according to the present invention
~For each sample tape of Example 9, there was no scratching on the back coat surface, no scraping of the tape guide, and no powder falling off, and F! ! The friction coefficient is also a very small value.

On the other hand, the sample tapes of Comparative Examples 1 to 6 use additives that have been used conventionally, but the scratch resistance of the back coat layer surface, tape guide scraping, and powder falling have deteriorated, and furthermore, P? ! The friction coefficient also has a large value.

(Effects of the Invention) As is clear from the above explanation, in the present invention, a novel lithium/aluminum composite oxide powder is used as an additive for the back coat layer. Due to these effects, it is possible to improve the running stability of the magnetic recording medium, and to provide a magnetic recording medium that can prevent powder falling off, scratches on the surface of the back coat layer, and even scraping of the tape guide. .

Patent applicant: Sony Corporation Agent Patent Attorney Akira Koba Same mouthpiece Sakae Same as Masaru Sato Procedures from Fu Zheng Lu Cap) March 24, 1986

Claims (1)

[Scope of Claims] A magnetic recording medium in which a magnetic layer is formed on one surface of a non-magnetic support and a back coat layer is formed on the other surface, wherein the back coat layer contains lithium-aluminum composite oxide powder. A magnetic recording medium characterized by containing carbon black.