JPS63100612A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the resistance of a magnetic layer to rubbing and flawing and to suppress an increase in the wear of a head by incorporating alpha-alumina having 0.1-0.3mum and 0.4-0.6mum average particle sizes into the magnetic layer and specifying the intensities at the 116 faces in X-ray diffraction of both to the values within a specific range. CONSTITUTION:The alpha-alumina of 0.1-0.3mum average particle size and the alpha-alumina of 0.4-0.6mum average particle size with which the ratio between the intensity I1 at the 116 face in the X-ray diffraction of the alpha-alumina having 0.1-0.3mum average particle size and the intensity I2 at the 116 face in the X-ray diffraction of the alpha-alumina having 0.4-0.6mum average particle size is as expressed by the equation are used in combination as a grinding agent. The resistance of the magnetic layer to rubbing and flawing is thereby improved to a greater extent and the increase in the abrasion loss of the magnetic head is suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, and particularly relates to a magnetic recording medium in which a magnetic layer contains an abrasive on a non-magnetic support. The present invention relates to a magnetic recording medium provided on a body.

[Conventional technology]

Magnetic recording media are desired to have high sensitivity, high density, high reliability, and a good balance of various characteristics.

High sensitivity can be achieved by improving the ferromagnetic material, and high density can be achieved by modifying or improving the ferromagnetic material. Also, these characteristics are
This can also be achieved by an improved combination of other composite materials (binders, lubricants, additives, etc.).

However, if the reliability and balance of various characteristics of these magnetic recording media are impaired, the commercial value will decrease, so how to improve reliability and the balance of various characteristics has been a major problem.

One of the additives for magnetic recording media is an abrasive that improves reliability and various characteristics.

Abrasives have various effects on magnetic recording media, and various abrasive particles have been used to improve the scratch resistance of magnetic layers. Specific examples of abrasive particles include chromium oxide, fused alumina, silicon carbide, corundum, diamond, emery (main components: corundum and magnetite), silica, silicon nitride, boron nitride, tungsten carbide, titanium oxide, etc. .

[Problem that the invention seeks to solve]

Currently, in order to achieve higher recording density and higher output, efforts are being made to reduce the gap between the VTR head and the tape.
, has been advanced from both tapes. As a result, tapes are being used under harsher conditions than ever before. By the way, if the amount of abrasive particles is increased or the particle size of the abrasive is increased in order to further improve the scratch resistance of the magnetic layer, the scratch resistance will be significantly improved, but head wear will increase. . In extreme cases, the guide or audio head inside the VTR may be polished to a mirror surface while the vehicle is running, resulting in running abnormalities such as sticking.

An object of the present invention is to suppress an increase in head wear while improving the scratch resistance of the magnetic layer.

[Means for solving problems]

However, the problem of increased head wear when improving the scratch resistance mentioned above can be solved by using α-alumina as an abrasive with an 11 and an average particle size of 0.4-0.
The intensity factor of 116 planes in the X-ray diffraction of 6 μ α-alumina, which ratio is I, / I, = 0
．． Average particle size 0.890/1-1.200/1.
α-Alumina of 1~0.3μ and average particle size of 0.4~
It has been found that a significant improvement can be achieved by using α-alumina of 0.6μ in combination, and the present invention has been achieved. This effect cannot be obtained even by combining two types of α-alumina with average particle sizes of only 0.1-0.3μ and 0.4-0.6μ, and the X-ray diffraction intensity of the 116 plane of both It is necessary that the ratio is between 0.890 and 1,200.

The reason for this is thought to be due to the crystal structure of α-alumina, but it is not certain. This refers to the ratio of the heights of 116 planes.

Thus, in order to achieve the intended purpose of the present invention, it is necessary to use α-alumina X
Intensity I of 116 plane in line diffraction and 1 in X-ray diffraction of α-alumina with average particle size 0.4-0.6μ
It is necessary that the ratio with the strength I2 of the 16 planes is as follows: I, / I, = 0.890/1 to 1.200/1
However, the preferred range is 0.944/1 to 1.05
It is 9/1. Note that it is desirable that the two aluminas have different X-ray diffraction intensity ratios.

The amount of α-alumina used in the magnetic layer is closely related to the effect of the abrasive, and if it is too small, the intended purpose will not be achieved, but if it is too large, other drawbacks may occur. However, the average particle size used in this invention is 0.
α-alumina with a particle size of 1 to 0.3 μ and an average particle size of 0.4 to 0.
The total amount of α-alumina of 6μ is 2 to 1 of the ferromagnetic fine powder.
2%+1%, preferably 4 to 10 wt%.

Further, the ratio of α-alumina with an average particle size of O01 to 0.3 μ and α-alumina with an average particle size of 0.4 to 0.6 μ is 110.25 to 1, preferably 11
It is 0.3 to 110.67, and it is better to have fewer coarse particles.

The α-alumina used is one obtained by the Bayer method, modified Bayer method, organic aluminum method, or the like. In the organoaluminum method, aluminum alkoxide can be used as a raw material, for example. When alumina is obtained by the Bayer method etc., α-
Conditions must be set so that alumina can be obtained, or the alumina obtained by firing must be transformed into the α-form.

Further, a back layer is provided on the opposite side of the non-magnetic support to the side on which the magnetic layer is provided.The back layer reduces the friction coefficient, improves running durability, and improves curl resistance. The back layer is formed by bonding carbon black or the like with a binder.

In order to produce the magnetic recording medium of the present invention, the above-mentioned α-alumina is added to the magnetic paint when making a magnetic paint consisting of fine ferromagnetic powder, a binder, and a solvent, and the magnetic paint is added as necessary. Dispersants, lubricants, antistatic agents, carbon black, etc. can be added to the coating, and these are appropriately mixed and dispersed to create a magnetic paint, which is applied to a non-magnetic support.
A magnetic recording medium can be manufactured by drying and orienting.

As the ferromagnetic fine powder, γ-Fe, O,, Co-containing γ-Fe, O,, Fe50. , Co-containing Fa, 0y-FeOx, G.

Containing “1-FeOx, Cry, Fe-Mn-Zn
alloy, Fe-Go-Ni-P alloy, Co-N1-P alloy, Co-N1-Fe-B alloy, Fe-Ni-Zn alloy,
Known ferromagnetic fine powder such as Ni-Co alloy and Go-Ni-Fe alloy can be used. The particle size of 0 ferromagnetic fine powder is o, oos ~ 1 μm in length, and the axis length/axis The width ratio is about 1/1 to 50/1.

Dispersants include fatty acids with 10 to 22 carbon atoms (R Engineering C0OH
, R is an alkyl group having 9 to 21 carbon atoms), alkali metals (Li, Na, K, etc.) or alkaline earth metals (Mg, Ca, Ba, etc.) of the above fatty acids, Cu, Pb
Metallic soap consisting of etc.; Lecithin etc. are used.

In addition, higher alcohols having 10 or more carbon atoms, sulfuric esters and phosphoric esters thereof, and the like can also be used. These dispersants are used in an amount of 0.05 parts by weight per 100 parts by weight of the ferromagnetic material.
It is added in a range of 20 parts by weight.

Lubricants include silicone oil, graphite, molybdenum disulfide, boron nitride, and graphite fluoride.

Fluorinated alcohol, polyolefin (polyethylene wax, etc.), polyglycol (polyethylene oxide wax, etc.), alkyl phosphate ester, polyphenyl ether, tungsten disulfide, monobasic fatty acid with 10 to 20 carbon atoms, and monobasic fatty acid with 3 to 12 carbon atoms. Fatty acid esters consisting of one or more of monohydric alcohol, dihydric alcohol, trihydric alcohol, tetrahydric alcohol, hexahydric alcohol, monobasic fatty acids with 10 or more carbon atoms and the total number of carbon atoms of the fatty acid is 11
Fatty acid esters consisting of ~28 monovalent to hexavalent alcohols, etc. can be used. Furthermore, fatty acids or fatty acid amides and aliphatic alcohols having 8 to 22 carbon atoms can also be used. These lubricants contain 0.0 parts by weight per 100 parts by weight of binder.
It is added in a range of 5 to 20 parts.

Graphite, carbon black,
Conductive powder such as carbon black graft polymer; Natural surfactant such as saponin; Alkylene oxide type,
Nonionic surfactants such as glycerin series, glycidol series, polyhydric alcohols, polyhydric alcohol esters, alkylphenol EO adducts; higher alkylamines, cyclic amines, hydantoin derivatives, amidoamines, ester amides, quaternary ammonium salts, pyridine, etc. heterocycles, phosphoniums or sulfoniums.

Cationic surfactants such as carboxylic acids, sulfonic acids, phosphoric acids, sulfuric acid ester groups, anionic surfactants containing acidic groups such as phosphoric ester groups; amino acids; amino sulfonic acids, sulfuric or phosphoric esters of amino alcohols, alkyl Amphoteric surfactants such as betaine type are used.

As the binder, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 2,000 to 300,000, and a degree of polymerization of about 10 to 20.
For example, vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic ester acrylonitrile copolymer, acrylic ester vinylidene chloride copolymer, acrylic ester Styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane distomer, nylon-silicon resin, nitrocellulose-polyamide resin, polyfukkavinyl, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer,
Polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin.

Various synthetic rubber-based thermoplastic resins and mixtures thereof are used.

A combination of these binders may be used,
The mixing ratio of the ferromagnetic fine powder to which other additives are added and the binder is in the range of 5 to 300 parts by weight of the binder to 100 parts by weight of the ferromagnetic fine powder.

Organic solvents used during dispersion, kneading, and coating include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran; methanol, ethanol,
Alcohols such as propatool, butanol, isobutyl alcohol, isopropyl alcohol, methylcyclohexanol; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate, monoethyl ether; ether, Glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, and dioxane; benzene, toluene.

Tar-based (aromatic hydrocarbons) such as xylene, cresol, chlorobenzene, and styrene; methylene chloride,
Chlorinated hydrocarbons such as ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene, N,N-dimethylformaldehyde, and hexane can be used.

There are no particular restrictions on the kneading method, and the order of addition of each component can be set as appropriate. For the preparation of magnetic coatings, conventional kneading machines are used, such as two-roll mills, three-roll mills, ball mills, pebble mills, thoron mills, sand grinders, Szs4vari attritors, high-speed impellers, dispersing machines, high-speed stall mills, high-speed impact mills. Mill, disper, kneader-1 high speed mixer, ribbon blender, co-kneader, intensive mixer,
A tumbler, a blender, a disperser, a homogenizer, a spindle screw extruder, a twin screw extruder, an ultrasonic disperser, and the like can be used.

To form the magnetic recording layer, the above compositions are arbitrarily combined and dissolved in an organic solvent, and a coating solution is coated on the support and dried. When used as a tape, the thickness of the support 2.
The thickness is about 5 to 100 microns, preferably about 3 to 70 microns, and in the case of a disk or card, the thickness is about 0.5 to io+m.

In the case of a drum, it can also be used in a cylindrical shape. Materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, and plastics such as polycarbonate, polyamide, and polysulfone. Metals such as aluminum and copper, and ceramics such as glass can also be used. Prior to coating, these supports are subjected to corona discharge treatment, plasma treatment, undercoat treatment, heat treatment, and dust removal treatment.

Metal vapor deposition treatment and alkali treatment may also be performed.

Methods for coating the magnetic recording layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, IJ A-roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, and spray coating. Coating etc. can be used, and other methods are also possible, and detailed explanations of these can be found in "Coating Engineering" published by Asakai Shoten, pp. 253-2.
It is described in detail on page 77 (published on March 20, 1972).

By such a method, the magnetic layer coated on the support is subjected to a treatment to orient the magnetic powder in the layer while immediately drying, if necessary, and then the formed magnetic layer is dried. The conveying speed of the support at this time is usually 10 cm/min to 500 cm/min.
m/min and the drying temperature is controlled between 20°C and 120°C. If necessary, the magnetic recording medium of the present invention is manufactured by subjecting it to a surface smoothing process or cutting it into a desired shape.

〔Example〕

Next, Examples will be described to specifically explain this invention, but this invention is not limited to these Examples. Comparative examples are also shown, 1 part on each side indicates ``parts by weight''.

Example A magnetic paint prepared by the composition and method described below was applied to the surface of a 20 μm thick polyethylene terephthalate base (non-magnetic support) so that the thickness after drying was 6.0 μm, and dried. Ta.

Next, a back layer coating solution prepared according to the composition and method described below was applied to the polyethylene terephthalate surface to which the magnetic paint was not applied so that the thickness after drying was 2.0 μm.

After coating, a drying process and surface smoothing treatment were performed, and the film was immediately wound up.

The rolled original fabric was heat-cured in that state at a temperature of 40''C for 48 hours, and then this original fabric was slit into 1-inch widths to obtain 1-inch video tapes.

Nitrocellulose 5 parts Carbon black (average particle size: 20mμ)
Tripartite oleic acid
2 parts Butyl stearate
1 part stearic acid
O, S part fatty acid modified silicone
2 parts oleic acid amide
O, S part Butyl acetate
240 parts methyl ethyl ketone
120 parts of the above composition was placed in a ball mill and cross-dispersed for 48 hours, then 10 parts of a polyisocyanate compound (Coronate L-75, manufactured by Nippon Polyurethane Co., Ltd.) was added and cross-dispersed for another 1 hour.

After dispersing the crosstalk, it was filtered using a filter having an average pore size of 1 μm to obtain a magnetic paint.

Back coating composition carbon black (1) (average particle size: 30-μ) 50
Carbon black (■) (Average particle size: 300
+aμ) 50 parts Vinylidene chloride resin ("1)
30.1 parts polyurethane resin (・2
) 24.3 parts oleic acid
0.5 parts Oleic acid amide 0.5 parts Cyclohexanone 40 parts Methyl ethyl ketone 500 parts The above composition was placed in a ball mill and mixed and dispersed for 70 hours.
, manufactured by Nippon Polyurethane Co., Ltd.) and 19.1 parts,
Crosstalk was further dispersed for 1 hour. After dispersing the crosstalk, it was filtered using a filter having an average pore size of 3μ to obtain a back layer coating solution.

As the vinylidene chloride copolymer (-1), Saran Resin F-216 (copolymer of vinylidene chloride and acrylonitrile 1M manufactured by Dow Co., Ltd.) was used.

Further, as the above-mentioned polyurethane resin (Fist 2), "Nilaboran N-2304J (manufactured by Nippon Polyurethane) was used.

On each side, α-alumina-I and α-alumina-I
Magnetic paints were prepared by changing (1) as shown in Table 1, and samples were prepared by coating. The same back layer coating solution was used.

(Evaluation of video tapes) The head abrasion and scratch resistance of the obtained video tapes were evaluated first.
Shown in the table.

The physical properties were measured as follows.

Amount of wear on the video head when 50 passes of 60 minutes in length are applied to the standing katsuo. Time taken to still out when a load of 500 g is applied in the still state (Measurement method of X-ray diffraction) X-ray made by Rigaku Denki Copper is irradiated with alpha rays using a diffraction device and 116
The height of the peak of the plane (57,5″″) was examined.

〔Effect of the invention〕

According to the present invention, the scratch resistance of the magnetic layer in a magnetic recording medium is significantly improved, and an increase in the amount of wear of the magnetic head can be suppressed. As seen in Table 1 in the above examples, the scratch resistance of the magnetic layer in this invention is as follows:
The time until still-out is 120 seconds or more, which is an excellent value, and at the same time, the amount of head wear is as small as 2.7μ or less, and both properties can be satisfied at the same time. On the other hand, when using only one of the two types of α-alumina, the scratch resistance is extremely poor or the amount of head wear is large, and even when two types of α-alumina are used, the average particle size is Those which are not within the specified range show the same tendency as above, and those whose intensity ratio of 116 planes by X-ray diffraction of both α-aluminas are not within the specified range even if the average particle size range is satisfied are due to head wear. Even if the amount is small, the scratch resistance is not good.

Therefore, by meeting both of the necessary requirements, the present invention can simultaneously obtain both of the effects that were previously unobtainable, and these effects are not available in conventional magnetic recording media.

Procedural amendment 1986 patent application No. 1245571 2. Name of the invention magnetic recording medium

Claims (3)

[Claims] (1) In a magnetic recording medium comprising a magnetic layer on one side of a nonmagnetic support and a back layer on the opposite side, α-alumina with an average particle size of 0.1 to 0.3μ is contained in the magnetic layer. and α-alumina with an average particle size of 0.4 to 0.6μ, the intensity I_1 of the 116 plane in X-ray diffraction of α-alumina with an average particle size of 0.1 to 0.3μ, and the average particle size of 0.4 A magnetic recording medium characterized in that the ratio of the intensity I_2 of the 116 plane in X-ray diffraction of α-alumina of ~0.6μ is as follows: I_1/I_2=0.890/1 to 1.200/1 . (2) A patent claim in which the weight ratio of α-alumina with an average particle size of 0.1 to 0.3μ and α-alumina with an average particle size of 0.4 to 0.6μ is 1/0.25 to 1/1. The magnetic recording medium according to item 1. (3) The total amount of α-alumina with an average particle size of 0.1 to 0.3μ and α-alumina with an average particle size of 0.4 to 0.6μ is 2 to 12 wt% of the ferromagnetic fine powder. The magnetic recording medium according to scope 1.