JPH08279142A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium adaptable to the attainment of high recording density and provided with considerably improved electromagnetic transducing characteristics by using Fe-Co alloy powder as ferromagnetic powder and specifying the major axis size of the ferromagnetic powder. CONSTITUTION: Ferromagnetic powder hard to sinter and having surface properties fit for dispersion is obtd. by using an Fe-Co alloy contg. 6-30at.% Co basing on the amt. of Fe. The number of the ferromagnetic powder filled per unit volume is increased by regulating the average major axis size of the ferromagnetic powder to 0.06-0.20μm. The surface of a medium is made moderately porous by imparting a proper compsn. to a binder forming a magnetic layer to form a structure by which an added lubricant is efficiently fed to the surface of the medium. When a proper amt. of a lubricant such as fatty acid ester is added, the lubricant is sufficiently fed to the surface of a magnetic coating film without plasticizing the coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium containing an alloy powder as a ferromagnetic powder, and further to a method for producing the same.

[0002]

2. Description of the Related Art In magnetic recording media such as video tapes, electromagnetic conversion characteristics have been actively studied for the purpose of high recording density and high image quality.

Regarding the improvement of electromagnetic change characteristics, a metal thin film type magnetic recording medium such as a so-called vapor deposition tape has been proposed in recent years, and has been put to practical use in some formats such as a high quality video tape recorder. In terms of price and the like, a coating type magnetic recording medium in which a magnetic coating is applied to form a magnetic layer is currently the mainstream.

In the coating type magnetic recording medium, in order to improve the electromagnetic conversion characteristics, it is necessary to examine the details. Up to now, the magnetic characteristics have been improved, and the spacing loss due to the mirror surface of the tape surface has been reduced. Is being investigated.

For example, from the viewpoint of raw materials, studies have been made on finer ferromagnetic powders having excellent magnetic properties, and binders and dispersants which can disperse the ferromagnetic powders more uniformly.
In particular, regarding ferromagnetic powders, it is necessary to improve coercive force, saturation magnetization, and finer particles, and to prevent oxidation of iron oxide or Al compounds on the surface of metallic iron magnetic powders. What is deposited as a layer is used. Further, the Al compound is also important for ensuring the adsorption with the binder in forming the coating material.

On the other hand, in terms of process, the kneading and mixing method for dispersing the ferromagnetic powder more uniformly, the compounding method for obtaining higher magnetic characteristics, the higher magnetic characteristics for further magnetic Studies have been conducted on a calendering method for finishing the surface of the recording medium to a more mirror surface.

[0007]

As described above, various improvements have been made in the coating type magnetic recording medium, but in the magnetic recording medium used in the format having a short recording wavelength, the characteristics and dispersibility are improved. In this respect, further improvement is desired. However, it is difficult to greatly improve the electromagnetic conversion characteristics of the coating type magnetic recording medium for the following reasons.

For example, in order to obtain sufficient magnetic properties with conventional metallic iron magnetic powder, it is necessary to reduce the thickness of the antioxidant layer or raise the reduction temperature. This leads to deterioration of rust property and, in the case of Al compound, deterioration of dispersibility. If the reduction temperature is raised, the ferromagnetic powders will sinter with each other and the particle distribution will increase, resulting in deterioration of electromagnetic conversion characteristics when formed into a tape.

[0009] Further, if it is attempted to make fine particles while maintaining the rust preventive property, as a result, the metallic iron portion is reduced and the magnetic properties are deteriorated. Furthermore, even if fine particles are achieved, the problem of deterioration of the dispersibility of the ferromagnetic powder during the preparation of the coating remains.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and achieves compatibility between magnetic characteristics and dispersibility, and makes it possible to greatly improve electromagnetic conversion characteristics in short wavelength recording. It is intended to provide a medium, and further to provide a method for producing the medium.

[0011]

The magnetic recording medium of the present invention is a magnetic recording medium comprising a non-magnetic support and a coating film containing ferromagnetic powder formed as a magnetic layer.

In order to achieve the above-mentioned object, the ferromagnetic powder used is mainly Fe, with 6 to 30 atomic% of Co, 1 to 6 atomic% of Y, and 10 to 15% of Al relative to Fe.
The alloy powder contains atomic%, and the major axis length of the ferromagnetic powder is 0.06 to 0.20 μm.

In the magnetic recording medium of the present invention, when the ferromagnetic powder used is an alloy containing 6 to 30 atom% of Co, it is possible to obtain magnetic characteristics higher than that of Fe alone. At this time, even if the Co content is less than 6 atomic% or more than 30 atomic%, the magnetic characteristics cannot exceed the characteristics of Fe alone.

Further, Y is 1 to 6 atomic%, Al is 10 to 1
By adding 5 atomic%, it becomes difficult for the ferromagnetic powders to sinter with each other even if the reduction temperature is raised, and it becomes possible to obtain high saturation magnetization and coercive force at the same time. If the addition amount of Y is less than 1 atom%, sintering cannot be prevented, and if it exceeds 6 atom%, the magnetic properties are deteriorated. If the added amount of Al is less than 10 atomic%, the surface state of the ferromagnetic powder changes, and the dispersibility decreases when it is made into a paint. On the other hand, if it exceeds 15 atom%, the magnetic properties also deteriorate.

By adding these elements and setting the major axis length of the ferromagnetic powder to 0.06 to 0.20 μm, it is possible to sufficiently cope with high density recording. Here, the major axis length is 0.
If it is less than 06 μm, the dispersibility becomes poor when it is made into a paint, and the electromagnetic change characteristics deteriorate. The major axis length is 0.2
If it exceeds 0 μm, short wavelength recording cannot be supported, and the electromagnetic conversion characteristics are also deteriorated.

Further, the specific surface area SSA of the ferromagnetic powder is
Is preferably set in the range of SSA ≦ 7 / (ρ × d). Here, ρ represents the specific gravity of the ferromagnetic powder, and d
Represents the minor axis length of the ferromagnetic powder. Specific surface area SSA is 7 / (ρ
If it is larger than xd), there arises a problem that rust resistance is deteriorated.

Further, the ten-point average roughness of the coating side surface of the non-magnetic support coated with the magnetic coating material containing the ferromagnetic powder is Rz.
(Nm), the thickness Tc (nm) of the magnetic layer is 15 ×
It is preferable that Rz ≦ Tc. By setting the thickness Tc of the magnetic layer to be thicker than 15 × Rz, stable running performance can be obtained without being affected by the surface property of the non-magnetic support.

The durability and running property are greatly affected by the roughness of the back surface of the magnetic recording medium, and the back surface roughness is the center line average roughness Ra.
If it is less than 10 nm, the friction of the back surface itself becomes high, and the running property of the medium is deteriorated to induce damage to the medium. Further, when the back surface roughness exceeds 20 nm, the surface property of the back surface is transferred to the medium surface in the process of curing the magnetic coating film, and as a result, the surface roughness of the medium is also lowered and electromagnetic conversion characteristics are deteriorated.

The magnetic paint is prepared by dispersing the above-mentioned ferromagnetic powder in a binder. As the binder, any resin material usually used in magnetic recording media of this type can be used. However, the type is not particularly limited. Typical binder resins are, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer. Polymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, polyester polyurethane, polyether polyurethane, polycarbonate polyurethane, Polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, polyvinyl acetal, cellulose derivative, styrene- Formaldehyde resin - Tajien copolymer, polyester resin, phenol resin, phenoxy resin, epoxy resin, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea.

In order to obtain good dispersibility, the polar group shown below may be introduced into a part or all of the binder used.

--COOM, --SO ₃ M, --OSO ₃ M,-
_{P = O (OM) 2 -O} -P = O (OM) 2, -NR 4 X, -NR 2, -SH ( although, M is H, Li, Na, K, NR 4, R is an alkyl group or H and X each represent a halogen atom.) The amount of these polar groups is 0.03 to 0.
It is preferably 3 mmol. The amount of polar groups is binder 1
When it is less than 0.03 mmol per g, the effect on the dispersibility is small, while when it is more than 0.3 mmol, not only the hygroscopicity becomes high and the weather resistance deteriorates, but also the dispersibility deteriorates. It may end up.

Further, in order to form a crosslinked structure of the binder, polyisocyanate may be added as a curing agent. As the polyisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, isophorone diisocyanate and other isocyanates, and adducts of these isocyanates with polyhydric alcohols such as trimethylolpropane, Condensation products of isocyanates and the like can be used.

The above-mentioned binder is preferably mixed in a proportion of 16 to 20 parts by weight with respect to 100 parts by weight of the ferromagnetic powder. When the amount of the binder is less than 16 parts by weight, it becomes difficult to disperse the ferromagnetic powder at the time of producing the magnetic coating material, so that the magnetic characteristics are deteriorated and the required electromagnetic conversion characteristics cannot be obtained. If it exceeds, the pores on the surface of the magnetic recording medium are blocked by the binder, so that when a lubricant such as that described later is added, it becomes difficult for the lubricant to appear on the surface and the durability is reduced.

A lubricant may be added to the magnetic paint. As the lubricant used in the present invention, myristic acid,
Representative examples include higher fatty acids such as palmitic acid, stearic acid and oleic acid, salts thereof with metals and amines, and ester compounds of fatty acids and monohydric alcohols. The fatty acid ester compound has 10 to 2 carbon atoms.
4 monobasic fatty acids (which may be branched or may contain an unsaturated bond), monohydric alcohols having 1 to 18 carbon atoms (which may be branched or may contain an unsaturated bond) and alkylenes. An ester compound consisting of an oxide monoalkyl ether is used. Examples of these are methyl stearate, ethyl stearate, propyl stearate, butyl stearate, sec-butyl stearate, tert-butyl stearate, isobutyl stearate, pentyl stearate, heptyl stearate, octyl stearate, stearin. Examples thereof include butoxyethyl acid salt, butyl palmitate, pentyl palmitate, heptyl palmitate, octyl palmitate, isooctyl palmitate, octyl myristate, and oleyl oleate.

Furthermore, ester compounds of fatty acids and dihydric to hexahydric alcohols, silicone oils containing those modified with fatty acids and the like, alkyl phosphates and the like are also mentioned, and these include ether bonds by addition of ethylene oxide and the like. Other substituents may be contained, or fluorine may be partially contained.

Alternatively, perfluoropolyether and its modified products, solid lubricants such as molybdenum disulfide and graphite can be used.

These are the initial stage of mixing and dispersing the magnetic paint,
It may be added on the way or at the end, and may be top-coated after the magnetic layer is formed.

Although the amount of the above lubricant added is arbitrary,
In particular, the amount of the fatty acid ester added is preferably 1.5 to 3.0 parts by weight with respect to 100 parts by weight of the ferromagnetic powder. If the amount of the fatty acid ester added is less than 1.5 parts by weight, the lubricant will be insufficient and the durability will be reduced even if there are sufficient pores on the surface of the magnetic coating film. When the amount of the lubricant exceeds 3.0 parts by weight, the magnetic coating film is plasticized, so that the durability also deteriorates.

Further, by adding 1 to 5 parts by weight of a polyvalent (divalent or higher) carboxylic acid having a molecular weight of 300 or less or an anhydride thereof to 100 parts by weight of the ferromagnetic powder in the magnetic coating material,
The dispersibility of the ferromagnetic powder is improved, whereby a magnetic recording medium having good electromagnetic conversion characteristics can be obtained.

A polyvalent carboxylic acid having a molecular weight of 300 or less or an anhydride thereof is adsorbed by a carboxyl group at a basic point on the surface of the ferromagnetic powder, and further another carboxyl group is directed to the outside so that the surface of the ferromagnetic powder is acidified. It is thought that it creates dots and further strengthens the affinity with the binder.

Higher fatty acids such as stearic acid generally used as a lubricant have only one carboxyl group in the molecule, and when this is adsorbed on the ferromagnetic powder, the activity of the surface of the ferromagnetic powder decreases, Adsorption of the binder to the ferromagnetic powder is hindered and the dispersibility cannot be improved.

In addition, when the binder has a large molecular weight such as a binder having a carboxyl group in the molecule, some molecules cannot be adsorbed, and the viscosity of the coating material is significantly increased.

As the polycarboxylic acid having a molecular weight of 300 or less and their anhydrides, any compound may be used as long as it is a compound containing a plurality of carboxyl groups in one molecule.

Specifically, tartaric acid, citric acid, acetylcitric acid, malic acid, succinic acid, fumaric acid, benzenetricarboxylic acid, maleic acid, phthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexenedicarboxylic acid, adipic acid. , Azelaic acid, sebacic acid, trimellitic acid, pyromellitic acid, nitrilotriacetic acid, iminodiacetic acid, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, phthalic anhydride and the like.

The amount of addition is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the ferromagnetic powder. If the addition amount is 1 part by weight or less, the effect is difficult to be exhibited, and even if it exceeds 5 parts by weight, the effect is not improved so much and the dispersibility may be deteriorated.

In addition to the above-mentioned components, various additives such as abrasives may be added to the magnetic paint. As an abrasive,
Alumina, chromium oxide, titanium oxide, α-iron oxide, silicon carbide, corundum, (artificial) diamond and the like can be mentioned.

These may be added to the magnetic coating material in the form of powder, or may be added in the state of a slurry dispersed separately from the ferromagnetic powder at any of the initial stage, the middle stage, and the final stage of the mixing / dispersion of the magnetic coating material. Good.

As other additives, various known raw materials are used for the purpose of antistatic effect such as carbon black, light shielding effect, friction reducing effect, dispersion effect, crosslinking promotion effect, plasticizing effect, and the like. It can also be used.

Solvents used for forming paints include ketones such as methyl ethyl ketone and cyclohexanone, alcohols such as methanol and isopropyl alcohol, esters such as ethyl acetate and butyl acetate, aromatic hydrocarbons such as toluene and benzene, and tetrachloride. Examples thereof include chlorinated hydrocarbons such as carbon and chloroform, ethers such as dioxane and diethylene glycol monoethyl ether, and the like.

As the non-magnetic support coated with a magnetic coating composed of these, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyamides or imides such as aramid, polyolefins such as polypropylene, celluloses such as cellulose triacetate, , Other plastic films such as polycarbonate, metals such as aluminum, glass, ceramics and the like.

Further, in the magnetic recording medium of the present invention, the magnetic layer may be a single layer or a multilayer of two or more layers. Furthermore, on the same side as the magnetic layer on the non-magnetic support,
An undercoat layer containing a binder and a non-magnetic or very small magnetic powder such as α-iron oxide, carbon black, titanium oxide, calcium carbonate, and alumina may be provided.

The above is the basic constitution of the magnetic recording medium of the present invention, but the constitution of the magnetic recording medium is not limited to this, and for example, the non-magnetic support may be provided on the side opposite to the side on which the magnetic layer is formed. A back coat layer mainly composed of magnetic or magnetic powder and a binder may be formed.

As the non-magnetic powder used in the back coat layer, those mainly composed of carbon black are generally used, but calcium carbonate, alumina, titanium oxide, α-iron oxide and the like can also be used. As the magnetic powder, any known ferromagnetic powder that can be used in the magnetic layer can be used.

As the binder and the additive used for the back coat layer, any of those exemplified above for the magnetic layer can be used. You may use them individually or in combination.

In order to manufacture the above-mentioned magnetic recording medium, an ordinary coating type magnetic recording medium manufacturing process may be followed. In particular, in the kneading process, the ferromagnetic powder and the binder have a solid content of 73. ˜80 wt%, the binder weight ratio to the ferromagnetic powder 100 is set to a range of 14 to 18 and kneaded and mixed by a biaxial continuous kneading mixer to obtain a coating having good dispersibility, A magnetic recording medium having excellent electromagnetic conversion characteristics can be obtained. At this time, the molecular weight of 3
By adding a polyvalent carboxylic acid of not more than 00 or an anhydride thereof, the dispersibility is further improved and the electromagnetic conversion characteristics are further improved.

If the weight ratio of the binder to the solid content or the ferromagnetic powder is outside the above range, good kneading cannot be performed. That is,
If the solid content is less than 73% by weight, the kneaded product will be too soft, and if it exceeds 80% by weight, it will be too hard. Ferromagnetic powder 1
When the amount of the binder is less than 14 parts by weight with respect to 00 parts by weight,
The kneaded product becomes powdery, and when it exceeds 18 parts by weight, it becomes too soft. In the kneading in such a state, it is difficult to loosen the aggregation of the ferromagnetic powder and the "wetting" of the ferromagnetic powder by the binder is insufficient, so that a coating having good dispersibility cannot be obtained. The solid content is preferably 75 to 78% by weight, and the binder is 15 to 16.5 parts by weight with respect to 100 parts by weight of the ferromagnetic powder.

When kneading and mixing with a twin-screw continuous kneading mixer, 50 to 70% by weight of the organic solvent contained in the raw material mixture is composed of a solvent having a boiling point of 100 ° C. or higher, and the rest is boiling point 90. It is preferable to use a solvent having a temperature of not higher than 0 ° C. to knead and mix.

So far, the solvent used for coating has been
Various things are known. The raw material temperature at the time of kneading depends on the specifications of the kneading machine, but becomes a considerably high temperature of about 20 to 90 ° C. due to the shearing force for loosening the aggregation of the ferromagnetic powder. When an organic solvent having a boiling point within this temperature range or below this temperature is used as the main solvent during kneading, the concentration of solids in the kneading mixture deviates due to evaporation of the solvent, and stable kneading is performed. Absent. Even if the cooling equipment of the kneading machine tries to cope with it, the temperature rises above the above temperature momentarily, and it is difficult to follow the cooling in the equipment. Therefore, it is effective to use a solvent having a relatively high boiling point as the main solvent. If the composition ratio of the high boiling point solvent is outside the above range, good kneading cannot be performed. That is, when the ratio of the high boiling point solvent is less than 50% by weight, the solvent evaporation in the kneaded material is remarkable and the kneaded material becomes brittle, while when it exceeds 70% by weight, it is too soft and the shearing force for loosening the agglomeration is produced. Hard to join.

Therefore, when kneading and mixing the raw materials, it is preferable to select and use a solvent that meets the above conditions from the above solvents. The solvents used for kneading and mixing and for forming the paint may be different or the same.

[0050]

The magnetic characteristics of the ferromagnetic powder can be enhanced by using a Fe-Co alloy containing 6 to 30 atomic% of Co with respect to Fe. Further, by containing 1 to 6 atom% of Y and 10 to 15 atom% of Al, it is difficult to sinter and a surface property suitable for dispersion can be obtained. Furthermore, by setting the average major axis length of the ferromagnetic powder to be 0.06 to 0.20 μm, the number of ferromagnetic powders filled per unit volume is increased.

Further, by appropriately adjusting the composition of the binder constituting the magnetic layer, appropriate pores are formed on the medium surface, and the internally added lubricant is efficiently supplied to the medium surface. . Therefore, by adding an appropriate amount of a lubricant, for example, a fatty acid ester, a sufficient supply amount of the lubricant can be obtained without plasticizing the magnetic coating film.

On the other hand, a polyvalent (divalent or higher) carboxylic acid having a molecular weight of 300 or less or an anhydride thereof is adsorbed by a carboxyl group at a basic point on the surface of the ferromagnetic powder, and further another carboxyl group is directed to the outside to make it ferromagnetic. By forming acid points on the powder surface, the affinity with the binder is strengthened, and the ferromagnetic powder is more easily dispersed.

In particular, the ferromagnetic powder and the binder are mixed in a solid content of 7
Kneading with a biaxial continuous kneading mixer together with a polyvalent carboxylic acid having a molecular weight of 300 or less or an anhydride thereof within a range of 3 to 80% by weight and a binder weight ratio to the ferromagnetic powder 100 of 14 to 18. Thus, the shearing force works efficiently against the strong aggregation between the ferromagnetic powders, and the wetting of the binder on the surface of the ferromagnetic powders also progresses. For this reason, strong aggregation between the ferromagnetic powders is easily released, and the ferromagnetic powders are more easily dispersed.

When kneading and mixing the raw materials, 50 to 70% by weight of the organic solvent composition contained in the raw material mixture is composed of a solvent having a boiling point of 100 ° C. or higher, and the rest is composed of a solvent having a boiling point of 90 ° C. or lower. As a result, the change in the state of the solvent during the kneading step can be suppressed. Therefore, the solvent distribution in the mixture can be kept uniform, and the ferromagnetic powder can be dispersed more uniformly.

[0055]

EXAMPLES Some specific examples to which the present invention is applied will be described below, but the present invention is not limited to these examples.

Experiment 1 A magnetic tape was produced with the following contents.

Magnetic powder: 100 parts by weight See Table 1 for details Binder: Polyester-based polyurethane resin 6 parts by weight Polyester main component; isiphthalic acid-ethylene glycol urethanized isocyanate; diphenylmethane diisocyanate polar group; sulfonic acid sodium salt 0.12 mmol / g-containing molecular weight; about 21000 vinyl chloride-based copolymer 12 parts by weight polar group; potassium sulfate salt 0.08 mmol / g-containing degree of polymerization; about 305 abrasive: alumina (Al ₂ O ₃ ) α conversion of 85%, average particle size Diameter 0.5 μm 8 parts by weight Lubricant: Stearic acid 1.5 parts by weight Butyl stearate 2 parts by weight Solvent: Methyl ethyl ketone / toluene / cyclohexane = 100/100/50 parts by weight After the above materials are dispersed in a sand mill, a curing agent Add 20 parts by weight of (Cornate L) After stirring, it was applied to a polyethylene terephthalate base film.

Then, magnetic field orientation treatment was performed, and the film was appropriately dried and wound. A calendering treatment was performed and a curing treatment was performed. Then, 20 parts by weight of a curing agent (Cornate L) was added to the coating composition for the backcoat layer having the following composition, and the coating was applied to the film surface opposite to the magnetic layer to form a backcoat layer having a thickness of 0.5 μm. .

Coating composition for back coat layer Pigment: Carbon black 100 parts by weight Average particle size 0.02 μm, DBP oil absorption 105 cc / 100 g Binder: Polyester polyurethane resin 30 parts by weight Polyester main component; Isiphthalic acid-ethylene glycol Urethane isocyanate Diphenylmethane diisocyanate polar group; sulfonic acid sodium salt 0.1 mmol / g-containing molecular weight; about 20,000 phenoxy resin U.S.S. C. "PKHH" manufactured by Company C 70 parts by weight Solvent: methyl ethyl ketone 500 parts by weight The magnetic tape prepared as described above was cut into 8 mm width and the tape electromagnetic conversion characteristics were measured. The results are also shown in Table 1 below.

[0060]

[Table 1]

Evaluation Results Examples 1-1, 1-2, 1-3, Comparative Examples 1-1, 1-2
As a result, the magnetic properties were improved from the Co content of 6 atom%, and good values were obtained for both video output and color output. 10
Further improvement is seen up to about atomic percent, and the same effect is seen up to about 30 atomic percent. On the other hand, if it exceeds 30 atom%, both the video output and the color output will decrease.

Examples 1-4 and 1-5, Comparative examples 1-3 and 1
From -4, when the Y content exceeds 1 atom%, the effect of preventing sintering between magnetic powders appears, and up to 6 atom%, it is possible to obtain good video output and color output due to the improvement of magnetic properties due to this effect. Becomes If it is not added, both the video output and color output will decrease due to sintering between the magnetic powders. If it exceeds 6 atomic%, the magnetic properties are deteriorated and the output is also decreased.

Examples 1-6, 1-7, Comparative Examples 1-5, 1
From -6, by containing 10 atomic% or more of Al, the magnetic powder surface condition is improved, the dispersibility is improved, and a high output is obtained. When the content is less than 10 atom%, the dispersibility is significantly deteriorated and both video output and color output are reduced. If it exceeds 15 atom%, the magnetic properties are deteriorated and a good output cannot be obtained.

Examples 1-8 and 1-9, Comparative Examples 1-7 and 1
From -8, good electromagnetic characteristics can be obtained when the major axis length of the magnetic powder is in the range of 0.06 to 0.20 μm. If the major axis length is shorter than 0.06 μm, the dispersibility is reduced and a sufficient output cannot be obtained. If it is larger than 0.20 μm, color output can be obtained, but video output for short-wavelength recording is lowered.

Experiment 2 A magnetic tape was produced with the following contents.

Magnetic powder: The content of each element is the magnetic powder A of Experiment 1.
Follow See Table 2 for details Binder content, process, backcoat paint follow Experiment 1.

[0067]

[Table 2]

Evaluation Results Table 2 above, Examples 1-1 to 1-4, Comparative Examples 1-1 and 1-
Video and color output can be obtained from 2, but the specific surface area is 7 /
If it is (ρ × minor axis length) or less, rust resistance is good, but 7
If / (ρ × minor axis length) is exceeded, the amount of voids on the surface of the magnetic powder increases, and the area in which the magnetic powder is exposed to the air increases, and the rust prevention property deteriorates.

Experiment 3 A magnetic tape was produced with the following contents.

Magnetic powder: The content of each element is the magnetic powder A of Experiment 1.
Follow

The binder content, process and backcoat paint are in accordance with Experiment 1.

However, in the coating process, two types of polyethylene terephthalate base films (PET) having different 10-point average roughness Rz on the coating side were used, and the thickness of the magnetic layer was further changed. Details are shown in Table 3 below.

[0073]

[Table 3]

Evaluation Results Examples 1-13 and 1-14, Comparative Examples 1-11 and 1-12
Therefore, when the magnetic layer thickness is Rz × 15 or more, the influence of the protrusions represented by Rz on the base film is eliminated, and stable running property can be obtained. When Rz × 15 or less, the output is good, but the effect of the protrusions on the base film appears on the magnetic surface, and the running property becomes unstable.

Experiment 4 The materials shown in Table 4 below were dispersed in a sand mill, 20 parts by weight of a curing agent (Cornate L) was added, and the mixture was stirred and then coated on a polyethylene terephthalate base film. Then, magnetic field orientation treatment was performed, and the material was appropriately dried and wound. A calendering treatment was performed and a curing treatment was performed.

[0076]

[Table 4]

Then, 20 parts by weight of a curing agent (Cornate L) was added to the coating composition for back coat layer having the composition shown in Table 5 below, and the coating was applied to the film surface opposite to the magnetic layer to give 0.5 μm.
The back coat layer was formed to have a thickness of m.

[0078]

[Table 5]

The wide tape produced as described above was cut into 8 mm width to prepare a sample tape, which was incorporated into a Hi-8 video cassette.

The electromagnetic conversion characteristics of the produced sample tape were evaluated by the method described below.

(1) Video Output Using a 8 mm VTR EV-S900, a 7 MHz sine wave was recorded on a tape, and the reproduced output was read by a spectrum analyzer, and the result of Comparative Example 2-1 was 0 dB.
The relative values are shown in Table 6.

(2) Color output 750 kHz using 8 mm VTR EV-S900
The sine wave of is recorded on the tape, the reproduction output is read by the spectrum analyzer, and the result of the comparative example 2-1 is 0.
The relative values in dB are shown in Table 6.

Evaluation Results The results of the video output and color output of each sample tape measured as described above are shown in Table 6 below.

[0084]

[Table 6]

Examples 2-1, 2-2, 2-3, Comparative Example 2
From -1 and 2-2, the magnetic properties were improved from a Co content of 6 atomic%, and good values were obtained for both video output and color output. Further improvement is seen up to about 10 atom%, 30
Similar effects are seen up to atomic%. On the other hand, if it exceeds 30 atom%, both the video output and the color output will decrease.

Examples 2-4 and 2-5, Comparative examples 2-3 and 2
From -4, when the Y content exceeds 1 atom%, the effect of preventing sintering between magnetic powders appears, and up to 6 atom%, it is possible to obtain good video output and color output due to the improvement of magnetic properties due to this effect. Becomes If it is not added, both the video output and color output will decrease due to sintering between the magnetic powders. If it exceeds 6 atomic%, the magnetic properties are deteriorated and the output is also decreased.

Examples 2-6 and 2-7, Comparative examples 2-5 and 2
From -6, by containing 10 atomic% or more of Al, the magnetic powder surface condition is improved, the dispersibility is improved, and a high output is obtained. When the content is less than 10 atom%, the dispersibility is significantly deteriorated and both video output and color output are reduced. If it exceeds 15 atom%, the magnetic properties are deteriorated and a good output cannot be obtained.

Examples 2-8 and 2-9, Comparative Examples 2-7 and 2
From -8, good electromagnetic characteristics can be obtained when the major axis length of the magnetic powder is in the range of 0.06 to 0.20 μm. If the major axis length is shorter than 0.06 μm, the dispersibility is reduced and a sufficient output cannot be obtained. If it is larger than 0.20 μm, color output can be obtained, but video output for short-wavelength recording is lowered.

Experiment 5 Magnetic paints were prepared from the materials shown in Tables 7 and 8 below, and coated on base films having different back surface roughnesses to prepare Hi8 video tapes. The method for producing the sample tape and the composition of the back coat layer are in accordance with Experiment 4.

[0090]

[Table 7]

[0091]

[Table 8]

Electromagnetic conversion characteristics, durability of sample tape,
And the back surface roughness of the medium was evaluated by the following methods.

(1) Video output, color output Same as Experiment 4.

(2) Durability Still: Using an EV-S900, 8 mm VTR modified for still driving for a long time, the time from the initial stage until the RF output attenuates by 3 dB under the environment of temperature -5 ° C. Was measured. At this time, the sample tape exceeding 120 minutes was marked with ◯, the sample tape of 60 to 120 minutes was marked with Δ, and the sample tape of 60 minutes or less was marked with x.

Damage: The final portion of each sample tape was recorded for 10 minutes in an environment of temperature 40 ° C. and humidity 80% using an EV-S35 of 8 mm VTR, and the reproduction of the recorded portion was repeated 100 times in the same environment. The subsequent sample tape (especially the edge portion) was observed for damage. At this time, the sample tape in which no damage was found was marked, the sample tape in which damage was found but did not cause noise on the playback screen was marked with Δ, and the sample tape which became noise on the playing screen due to damage was marked with x. .

(3) Medium Back Surface Roughness The average protrusion height Ra was measured with a three-dimensional roughness measuring device at a cutoff of 25 μm.

Evaluation Results Table 9 shows the evaluation results of the sample tapes measured as described above.

[0098]

[Table 9]

As shown in Examples 3-2, 3-3, 3-5 and Comparative Examples 3-1, 3-4, by setting the binder in the range of 16 to 20 parts by weight, good electromagnetic conversion can be obtained. The characteristics and durability are obtained. When the amount of the binder was less than 16 parts by weight as in Comparative Example 3-1, the dispersibility of the magnetic powder was lowered during the preparation of the magnetic coating material, and thus the electromagnetic conversion characteristics were lowered. Further, as in Comparative Example 3-4, when the amount of the binder was more than 20 parts by weight, the pores on the magnetic surface were closed and it was difficult to supply the lubricant to the magnetic surface, so that the durability was lowered.

Further, it is necessary that the internal addition amount of the fatty acid ester as the lubricant is within the range of 1.5 to 3.0 parts by weight.
As in Comparative Example 3-2, the internal addition amount of the fatty acid ester was 1.
If it is less than 5 parts by weight, the absolute amount of lubricant will be insufficient,
Durability decreases. Further, as in Comparative Example 3-3, when the internal addition amount of the lubricant exceeds 3.0 parts by weight, the magnetic coating film is plasticized and the durability is lowered.

On the other hand, the medium back surface roughness has a great influence on the electromagnetic conversion characteristics and durability, and as in Examples 3-2 and 3-3 and Comparative Examples 3-5 and 3-6, Ra is 10 to 20 nm. Within the range, good electromagnetic conversion characteristics and durability can be obtained.

Here, as in Comparative Example 3-5, when the medium back surface roughness became rougher than 20 nm, the magnetic surface roughness deteriorated due to the transfer of the back surface, and the electromagnetic conversion characteristics deteriorated. Further, as in Comparative Example 3-6, when the medium back surface roughness is 10 nm or less, the running property is deteriorated, and thus the sample tape is damaged.

Experiment 6 The materials shown in Table 11 below were sand mill dispersed,
20 parts by weight of a curing agent (Cornate L) was added and stirred, and then coated on a polyethylene terephthalate base film. Then, magnetic field orientation treatment was performed, and the material was appropriately dried and wound. A calendering treatment was performed and a curing treatment was performed.

[0104]

[Table 10]

Then, 20 parts by weight of a curing agent (Cornate L) was added to the coating composition for back coat layer having the composition shown in Table 9 above, and the coating was applied to the film surface opposite to the magnetic layer to give 0.5 μm.
The back coat layer was formed to have a thickness of m.

[0106]

[Table 11]

The wide tape produced as described above was cut into 8 mm width to prepare a sample tape, which was incorporated in a Hi-8 video cassette.

The electromagnetic conversion characteristics of the produced sample tape were evaluated by the methods described below.

(1) Video Output Using an 8 mm VTR EV-S900, a 7 MHz sine wave was recorded on a tape, and the reproduced output was read by a spectrum analyzer, and the result of Comparative Example 4-1 was 0 dB.
The relative values of are shown in Table 12.

(2) Color output 750 kHz using 8 mm VTR EV-S900
The sine wave of is recorded on the tape, the reproduction output is read by the spectrum analyzer, and the result of the comparative example 2-1 is 0.
The relative values in dB are shown in Table 12.

Evaluation Results The results of video output and color output of each sample tape measured as described above are shown in Table 12 below.

[0112]

[Table 12]

Examples 4-1, 4-2, 4-3 and Comparative Example 4
From -1 and 4-2, the magnetic properties were improved from a Co content of 6 atomic%, and good values were obtained for both video output and color output. Further improvement is seen up to about 10 atom%, 30
Similar effects are seen up to atomic%. On the other hand, if it exceeds 30 atom%, both the video output and the color output will decrease.

Examples 4-4 and 4-5, Comparative Examples 4-3 and 4
From -4, when the Y content exceeds 1 atom%, the effect of preventing sintering between magnetic powders appears, and up to 6 atom%, it is possible to obtain good video output and color output due to the improvement of magnetic properties due to this effect. Becomes If it is not added, both the video output and color output will decrease due to sintering between the magnetic powders. If it exceeds 6 atomic%, the magnetic properties are deteriorated and the output is also decreased.

Examples 4-6 and 4-7, Comparative Examples 4-5 and 4
From -6, by containing 10 atomic% or more of Al, the magnetic powder surface condition is improved, the dispersibility is improved, and a high output is obtained. When the content is less than 10 atom%, the dispersibility is significantly deteriorated and both video output and color output are reduced. If it exceeds 15 atom%, the magnetic properties are deteriorated and a good output cannot be obtained.

Examples 4-8 and 4-9, Comparative Examples 4-7 and 4
From -8, good electromagnetic characteristics can be obtained when the major axis length of the magnetic powder is in the range of 0.06 to 0.20 μm. If the major axis length is shorter than 0.06 μm, the dispersibility is reduced and a sufficient output cannot be obtained. If it is larger than 0.20 μm, color output can be obtained, but video output for short-wavelength recording is lowered.

Experiment 7 Predetermined amount of the materials shown in Table 13 below (see Table 14)
Was mixed with a twin-screw continuous kneader, the shortage was added, the dispersion was added, and the mixture was dispersed in a sand mill. After 20 parts by weight of a curing agent (Cornate L) was added and stirred, polyethylene terephthalate base was added. It was applied on a film. Then, magnetic field orientation treatment was performed, and the material was appropriately dried and wound. A calendering treatment was performed and a curing treatment was performed.

[0118]

[Table 13]

After that, a sample tape was prepared in the same manner as in Experiment 6, and the electromagnetic conversion characteristics of the prepared sample tape were evaluated in the same manner as in Experiment 6.

The ratio of the two kinds of binders was the same for the kneaded part and the deficient part. The solvent was kneaded, and methylethylketone: toluene: cyclohexanone = 5: 1: 4 (weight ratio), and the deficiency was added so that the amount shown in Table 13 was obtained.

Evaluation Results The results are shown in Table 14 below.

[0122]

[Table 14]

As can be seen from Table 14, Example 5-
Sample tapes 1 to 5-15 are comparative examples 5-1 and 5-
Electromagnetic conversion characteristics are higher than those of No. 2.

Here, a more detailed comparison will be made with reference to Examples 5-2 and 5- in which 1 to 5 parts by weight of a polycarboxylic acid is added.
The sample tapes 3,5,4,5,6,5-7 have higher electromagnetic conversion characteristics than the sample tapes of Example 5-1 produced under the same conditions except for the above. In addition, the solid content during kneading is 7
The sample tapes of Examples 5-2, 5-8, 5-9 having 3 to 78% by weight have electromagnetic conversion characteristics better than those of the sample tapes of Examples 5-12, 5-13 produced under other conditions. high.

Further, the weight of the binder at the time of kneading was 14 to 18 with respect to 100 parts by weight of the ferromagnetic powder.
The sample tapes of −2, 5-10, and 5-11 have higher electromagnetic conversion characteristics than the sample tapes of Example 5-14 manufactured under other conditions. Further, the sample tapes of Comparative Examples 5-1 and 5-2 in which the ferromagnetic powder does not satisfy the requirements of the present invention have electromagnetic conversion characteristics whether the polyvalent carboxylic acid is added or kneaded and mixed under good conditions. Is low.

Experiment 8 The materials shown in Table 15 below were dispersed in a sand mill,
20 parts by weight of a curing agent (Cornate L) was added and stirred, and then coated on a polyethylene terephthalate base film. Then, magnetic field orientation treatment was performed, and the material was appropriately dried and wound. A calendering treatment was performed and a curing treatment was performed.

[0127]

[Table 15]

Then, 20 parts by weight of a curing agent (Cornate L) was added to the coating composition for back coat layer having the composition shown in Table 16 below, and the coating was applied to the film surface opposite to the magnetic layer, and 0.5
The back coat layer was formed to have a thickness of μm.

[0129]

[Table 16]

The wide tape produced as described above was cut into 8 mm width to prepare a sample tape, which was incorporated into a Hi-8 video cassette.

The electromagnetic conversion characteristics of the produced sample tape were evaluated by the methods described below.

(1) Video output Using a 8 mm VTR EV-S900, a 7 MHz sine wave was recorded on a tape, and the reproduced output was read by a spectrum analyzer, and the result of Comparative Example 6-1 was 0 dB.
The relative values are shown in Table 6.

(2) Color output 750 kHz using 8 mm VTR EV-S900
Was recorded on a tape, and the reproduction output was read by a spectrum analyzer, and the result of Comparative Example 6-1 was 0.
The relative values in dB are shown in Table 17.

Evaluation Results The results of video output and color output of each sample tape measured as described above are shown in Table 17 below.

[0135]

[Table 17]

Examples 6-1, 6-2, 6-3 and Comparative Example 6
From -1, 6-2, the magnetic properties were improved from the Co content of 6 atomic%, and good values were obtained for both video output and color output. Further improvement is seen up to about 10 atom%, 30
Similar effects are seen up to atomic%. On the other hand, if it exceeds 30 atom%, both the video output and the color output will decrease.

Examples 6-4 and 6-5, Comparative Examples 6-3 and 6
From -4, when the Y content exceeds 1 atom%, the effect of preventing sintering between magnetic powders appears, and up to 6 atom%, it is possible to obtain good video output and color output due to the improvement of magnetic properties due to this effect. Becomes If it is not added, both the video output and color output will decrease due to sintering between the magnetic powders. If it exceeds 6 atomic%, the magnetic properties are deteriorated and the output is also decreased.

Examples 6-6, 6-7, Comparative Examples 6-5, 6
From -6, by containing 10 atomic% or more of Al, the magnetic powder surface condition is improved, the dispersibility is improved, and a high output is obtained. When the content is less than 10 atom%, the dispersibility is significantly deteriorated and both video output and color output are reduced. If it exceeds 15 atom%, the magnetic properties are deteriorated and a good output cannot be obtained.

Examples 6-8 and 6-9, Comparative Examples 6-7 and 6
From -8, good electromagnetic characteristics can be obtained when the major axis length of the magnetic powder is in the range of 0.06 to 0.20 μm. If the major axis length is shorter than 0.06 μm, the dispersibility is reduced and a sufficient output cannot be obtained. If it is larger than 0.20 μm, color output can be obtained, but video output for short-wavelength recording is lowered.

Experiment 9 Predetermined amounts of the materials shown in Table 18 below (see Table 19)
Was mixed with a twin-screw continuous kneader, the shortage was added, disperse treatment was performed, and the mixture was dispersed in a sand mill. After 20 parts by weight of a curing agent (Cornate L) was added and stirred, polyethylene was added. It was coated on a terephthalate base film. Then, magnetic field orientation treatment was performed, and the material was appropriately dried and wound. A calendering treatment was performed and a curing treatment was performed.

[0141]

[Table 18]

After that, a sample tape was prepared in the same manner as in Experiment 8, and the electromagnetic conversion characteristics of the prepared sample tape were evaluated in the same manner as in Experiment 8.

Evaluation Results The results are shown in Table 19 below.

[0144]

[Table 19]

As can be seen from Table 19, Example 7-
The sample tapes 1 to 7-6 are comparative examples 7-1 to 7-6.
Electromagnetic conversion characteristics are higher than those of.

A more detailed comparison will be made with reference to Examples 7-1 and 7-, in which the solid content during kneading was 75 to 80% by weight.
The sample tapes of Nos. 2 and 7-3 have higher electromagnetic conversion characteristics than the sample tapes of Comparative Examples 7-1 and 7-2 produced under the same conditions except for the above.

Further, the sample tapes of Examples 7-1, 7-4 and 7-5 in which the weight of the binder at the time of kneading was 15 to 16.5 with respect to 100 parts by weight of the ferromagnetic powder were Has higher electromagnetic conversion characteristics than the sample tapes of Comparative Examples 7-3 and 7-4 produced under the same conditions. In addition, in the kneading solvent composition, high boiling point toluene + cyclohexanone 50-
The sample tapes of Examples 7-1 and 7-6, which were 70%, were prepared under the same conditions as in Comparative Examples 7-5 and 7-6.
Electromagnetic conversion characteristics are higher than those of sample tapes.

[0148]

As is apparent from the above description, according to the present invention, the magnetic properties of the ferromagnetic powder, such as coercive force and saturation magnetization, and atomization, as well as dispersibility, can be achieved at a high level. Thus, it is possible to provide a magnetic recording medium which can be used for high density recording and has dramatically improved electromagnetic conversion characteristics.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Miyazaki 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (9)

[Claims] 1. A magnetic recording medium in which a coating film containing ferromagnetic powder is formed as a magnetic layer on a non-magnetic support, wherein the ferromagnetic powder is mainly Fe, and Co is 6 to 6 with respect to Fe. 30 atomic%, Y 1 to 6 atomic%, Al 10 to 15
This is an alloy powder containing atomic%, and the major axis length of this ferromagnetic powder is 0.06 to 0.20 μm.
A magnetic recording medium characterized by the following. 2. The specific surface area of the ferromagnetic powder by the BET method is S
The magnetic recording medium according to claim 1, wherein SSA ≦ 7 / (ρ × d), where SA is the specific gravity, ρ is the minor axis length, and d is the minor axis length. 3. When the ten-point average roughness of the surface of the non-magnetic support on the side where the magnetic layer is formed is Rz and the thickness of the magnetic layer is Tc, 15 × Rz ≦ Tc is satisfied. The magnetic recording medium according to claim 1. 4. The surface roughness of the surface of the non-magnetic support opposite to the side where the magnetic layer is formed has a center line average roughness Ra of 10 to 10.
The magnetic recording medium according to claim 1, which has a thickness of 20 nm. 5. The magnetic layer contains a binder in an amount of 16 to 20 parts by weight with respect to 100 parts by weight of the ferromagnetic powder, and a lubricant containing a fatty acid ester, and the addition amount of the fatty acid ester is adjusted. 1. 100 parts by weight of ferromagnetic powder
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is contained in a proportion of 5 to 3.0 parts by weight. 6. The magnetic layer contains a polycarboxylic acid having a molecular weight of 300 or less or an anhydride thereof in a ratio of 1 to 5 parts by weight based on 100 parts by weight of the ferromagnetic powder. Magnetic recording medium. 7. Fe is the main component, and Co is added to Fe.
˜30 at%, Y at 1 to 6 at%, Al at 10 to 15 at%, and the major axis length is 0.06 to 0.20 μ.
When the ferromagnetic powder of m and the binder are kneaded and mixed with an organic solvent to form a coating material and applied on a non-magnetic support, the ferromagnetic powder and the binder are kneaded by a biaxial continuous kneading mixer. While mixing, the solid content during kneading and mixing is 73-
80% by weight, and 14 to 18 parts by weight of binder with respect to 100 parts by weight of ferromagnetic powder. 8. The method for producing a magnetic recording medium according to claim 7, wherein a polyvalent carboxylic acid having a molecular weight of 300 or less or an anhydride thereof is added when the ferromagnetic powder and the binder are kneaded and mixed. 9. The solid content at the time of kneading and mixing is 75 to 80% by weight.
And the binder is 15 to 1 with respect to 100 parts by weight of the ferromagnetic powder.
The magnetic material according to claim 7, wherein the amount of the organic solvent is 6.5 parts by weight, 50 to 70% by weight of the organic solvent is a solvent having a boiling point of 100 ° C or higher, and the remaining organic solvent is a solvent having a boiling point of 90 ° C or lower. Recording medium manufacturing method.