JPH04172614A - Magnetic disk - Google Patents

Abstract

PURPOSE:To improve the recording/outputting intensity and the S/N ratio of signals in a wide frequency region by providing on each surface of a non- magnetic supporting body a double magnetic layer including metallic magnetic powders having different magnetic force resistances and/or specific surface areas. CONSTITUTION:A first magnetic layer 1 and a second magnetic layer 2 are sequentially layered on each surface of a non-magnetic supporting body 3 in this order. The first and second magnetic layers 1, 2 include metallic magnetic powders. The metallic magnetic powders in the second magnetic layer 2 have a larger magnetic force resistance and/or a larger specific surface area than those in the first magnetic layer 1. Therefore, the electromagnetic conversion characteristic can be improved independently in a high frequency region and a low frequency region. Both the recording/outputting intensity and the S/N ratio of the signals in a wide frequency region from color signals to luminance signals in the F characteristic can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk, and more particularly to a magnetic disk with excellent electromagnetic conversion characteristics and durability.

[Prior Art and Problems to be Solved by the Invention] Conventionally, magnetic disks such as video floppy disks for electronic still cameras have been manufactured by bonding metal magnetic powder on both sides of a non-magnetic support with binder resin. It has been proposed that layers are formed.

Attempts have also been made to incorporate various additive components into the magnetic layer to improve its properties.

For example, this type of magnetic layer generally has a relatively large TL resistance and is easily charged, so it generates noise when the charged charge is discharged, and there are often problems with dust adhering to it and causing dropouts. In such a case, conductive powder (carbon black, carbon black, etc.) is added to the magnetic layer.
By adding graphite, silver powder, nickel powder, etc.) and surfactants (natural, nonionic, anionic, cationic, amphoteric),
It has been proposed to lower the surface electrical resistance of the magnetic layer (
Japanese Patent Publication No. 45-22726, Japanese Patent Publication No. 47-24881, Japanese Patent Publication No. 47-26882, Japanese Patent Publication No. 48-15440
No. 48-26761, U.S. Patent Specification No. 2,271,623, U.S. Patent No. 2,240,472, U.S. Patent No. 2.288,226, U.S. Patent No. 2,676.122,
No. 2,676.924, No. 2,675,975, No. 2,691,556, No. 2,727,850
No. 1, No. 2,730. '198, same No. 2,742,3
No. 79, No. 2, 7:19,891, No.::, 06
No. 8.101, No. 3,158,484, No. 8.101, No. 3,158,484, No. 8.
No. 201,253, No. 3,210,191, No. 3
．． No. 294,540, No. 3,415,649, No. 3.44], No. 413, No. 3,442,554,
3,475,174, 3,545,974, etc.).

By the way, the most basic characteristics of such a magnetic disk are the electromagnetic conversion characteristics (recording/output intensity, S/N ratio, etc.) of the recording medium (magnetic layer) during signal recording/output and its frequency dependence. In other words, there is a frequency characteristic (F characteristic).

In general, analog signals such as sine waves, digital signals,
IF type signal, 2Fj3. In any case, it is desirable that the recording/output F characteristics of a magnetic disk be as flat as possible over the entire desired frequency range. signal) output is kept well-balanced.

However, conventional magnetic TiSFs have a fundamental drawback in that their F-characteristics are unbalanced, and the output in the high frequency range (luminance signal) is generally significantly lower than that in the low frequency range (chrominance signal). ing.

Therefore, when reproducing the recorded signal, it is necessary to apply an equalizer to forcefully increase the output of the high frequency range (luminance signal) to improve the balance.In this case, it may cause distortion in the entire signal, or This may cause problems such as a decrease in the N ratio.

Therefore, it is desirable to improve this balance by improving the electromagnetic conversion characteristics (F characteristics) of the magnetic layer itself as much as possible.

By the way, in general, if a magnetic material with a low coercive force (Hc) is used in the magnetic layer, the recording/output intensity of signals in the low frequency range (chrominance signal side) will improve, or that in the high frequency range (luminance signal side) will be significantly lower. As a result, as described above, the balance between the luminance signal and the color signal deteriorates significantly.

On the other hand, it is known that the recording and output strength of signals in the high frequency range (luminance signal side) can be improved by using a magnet with a large coercive force (Hc).

Therefore, in conventional magnetic disks of this kind, the output of the luminance signal is sufficiently improved by using a magnetic material with high coercive force (Hc) or a large magnetic material (for example, metal magnetic powder) in the magnetic layer, and the output of the luminance signal and the color signal are Attempts have been made to improve the balance.

However, even if such a method improves the balance to some extent, it will significantly reduce the output of the important color signal and cause the serious problem of lowering the S/N ratio. Ru.

In other words, in conventional magnetic disks of this type, the magnetic layer is a single layer, and the high frequency range (luminance signal) and low frequency range (color signal) are differentiated by selecting the coercive force (Hc) of the magnetic powder. It is difficult to control the electromagnetic conversion characteristics of each independently, and as a result, the output of the luminance signal and color signal and the S/
There was a problem in that it was only possible to improve the balance while maintaining both the N ratios at a high level.

In addition, magnetic disks with multilayered magnetic layers have also been proposed, but in either case, no effective measures have been taken to improve the above problems, and they have the same problems as above. Ta.

The present invention has been made in view of the above circumstances.

An object of the present invention is to solve the above-mentioned problems and independently improve electromagnetic conversion characteristics in a high frequency range (luminance signal) and a low frequency range (chrominance signal). To provide a magnetic disk which has advantages such as improved recording/output intensity and S/N ratio of signals in a frequency range, and also improves the balance between color signals and luminance signals. There is a particular thing.

[Means for Solving the Problems] The present invention for achieving the above object includes laminating a first magnetic layer and a second magnetic layer containing metal magnetic powder in this order on both sides of a non-magnetic support. and in the second magnetic layer,
The coercive force (Hc
) and/or a metal magnetic powder having a large specific surface area (BET value).

In the magnetic disk of the present invention, a first magnetic layer and a second magnetic layer are laminated in this order on both sides of the nonmagnetic support.

- Non-magnetic support - Materials forming the non-magnetic support include, for example, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, and cellulose derivatives such as cellulose triacetate and cellulose tiacetate. ,polyamide,
Plastics such as polycarbonate, Cu, AQ,
Metals such as Zn, glass, boron nitride, Sl carbide,
You can also mention things like ceramics. The form of the non-magnetic support is not particularly limited, and main forms include tape, film, sheet, cart, disk, and drum.

There are no particular restrictions on the thickness of the non-magnetic support; for example, if it is in the form of a film or sheet, it is usually 3 to 1100K, preferably 5 to 50μm, and if it is in the form of a disk or cart, it is about 30gm to IOm, or about 30gm to IOm, or a drum. In the case of the following, it is selected appropriately depending on the recorder, etc.

Note that this nonmagnetic support may have a single layer structure or a multilayer structure. Further, this nonmagnetic support may be subjected to a surface treatment such as a corona discharge treatment.

Each of the first magnetic layer and the second magnetic layer is formed by dispersing metal magnetic powder and various additives blended as necessary in a binder resin.

The metal magnetic powder includes Fe, Ni, and C.

, Fe-AM system, Fe-AM-Ni system, Fe
-A l -Co system, Fe-An-Ni system, Fe-N
i-S i system, Fe-An-Zn system, Fe-Ni-C
o series, Fe-Mn-Zn series, Fe-Ni series, Fe-N1
-A liberal arts, Fe-Ni-Zn, Fe-Ni-Mn,
Fe-Co-N i-P system, Co-Ni system, Fe, Ni
, ferromagnetic powder such as metal magnetic powder containing Co''J as a main component.

Among these, especially considering the corrosion resistance and dispersibility, Fe-An, Fe-An-Ni, Fe-
Al-Zn, Fe-A-Co, Fe-Ni, Fe-N
i-AM, Fe-Ni-Zn, Fe-Ni-Au-5i
-Zn, Fe-Ni-A! Metal magnetic powder of the Q-S i -M n system is preferred.

These metal magnetic powders have saturation magnetization, coercive force [coercive force]
Hc)] and is excellent in high-density recording. Furthermore, if metal magnetic powder with a large specific surface area (for example, 40 m2/g or more) is used, high-density recording is possible and a medium with excellent S/N ratio etc. can be easily realized.

In the present invention, as the metal magnetic powder contained in the second magnetic layer (upper layer, that is, the layer on the outer surface side), the first
Coercive force (Hc) or BET
It is important to use a material with a large specific surface area or both.

That is, the coercive force (Hc) and specific surface area (BET value) of the metal magnetic powder used in the first magnetic layer are respectively [Hc
-1] and [SA-1], and the coercive force (Hc) and specific surface area (BE
T value) respectively [Hc-11] and [5A-Ill
To explain the above relationship more specifically by expressing it as follows, 5. In the magnetic disk of the present invention,
lc-11] (Case-■), ■[5
A-1] < [5A-Ill (Cas
e-■).

■[Hc-1] < [Hc-411, and [5A-I
] < [5A-Ill (Case-■
).

Here, in the case of (Case-■), [5A-1] is changed to [
If it is too large compared to 5A-Ill, the object of the present invention may not be fully achieved. Also, (Case
-■), if [Hc-1] is made much larger than [Hc-11], the object of the present invention may not be fully achieved.

The above (Case-+1+) or (Case-+3)
), [tlc-1] and [t
1-limit and lower limit of [l1c-1]
< [As long as the Hc-III relationship is maintained, it can be selected as appropriate depending on the purpose. In addition, the above (Case-(
2)) or (Case-■), [
The upper and lower limits of SA-+] and [5A-1[] are
[5A-1] As long as the relationship of [5A-III is maintained, it can be selected as appropriate depending on the purpose.

The metal magnetic powder used for the first magnetic layer and the second magnetic layer that satisfies these relationships may be appropriately selected from the various metal magnetic powders exemplified above.

By doing this, the electromagnetic conversion characteristics between the low frequency range (color signal) and the high frequency range (luminance signal) can be improved independently, and the electromagnetic conversion characteristics from the low frequency range (color signal) to the high frequency range (luminance signal) can be improved independently.
It is possible to greatly improve characteristics such as signal recording/output intensity and S/N ratio in the entire frequency range covering the luminance signal. Further, by appropriately adjusting the coercive force (Hc) and/or specific surface area (BET value) of each metal magnetic powder used for the first magnetic layer and the second magnetic layer while maintaining the above predetermined relationship, It is possible to flatten the F characteristic while improving characteristics such as signal recording/output intensity and S/N ratio over the entire frequency range, and it is possible to flatten the F characteristic in the low frequency range (color signal) and high frequency range (luminance signal). Is it possible to improve the balance sufficiently?

In the magnetic disk of the present invention, in addition to the metal magnetic powder, the first magnetic layer and/or the second magnetic layer may contain, for example, a lubricant, nonmagnetic abrasive particles, conductive material, etc. Various additive components such as powders and surfactants can be included.

Examples of the lubricant used include silicone oil, graphite, serifidene disulfide, monobasic fatty acids having about 12 to 20 carbon atoms (for example, stearin #), and lubricants having about 3 to 26 carbon atoms. Examples include fatty acid esters made of monohydric alcohols.

The non-magnetic abrasive particles to be used include, for example, alumina [α-Ai20:l (corundum), etc.] 1
Artificial corantum, fused alumina, silicon carbide, chromium oxide, tire cent, synthetic tire cent, garnet, and emery (main constituents corantum and magnetite) may be mentioned. The content of the abrasive particles is preferably 20 parts of heavy acid or less based on the magnetic powder, and the average particle diameter thereof is preferably 0.5 gm or less, more preferably 0.4 gm or less.

Note that the lubricant and non-magnetic abrasive particles are
By including it in the magnetic layer (surface layer), it is possible to significantly improve the contact characteristics with the head (slipping performance, wear resistance, etc.).

Examples of the conductive powder and surfactant include:
Examples may be given in the section of the prior art (including those exemplified in each of the above-mentioned publications and specifications).

Appropriate inclusion of these conductive powders and surfactants, especially in the second magnetic layer, can effectively lower the surface electrical resistance, thereby reducing the occurrence of noise due to the discharge of electrical charges and dropouts due to the adhesion of dust. It is possible to prevent this.

The magnetic layer used in the magnetic disk of the present invention may be obtained by binding the metal magnetic powder with the predetermined properties or the various additive components used as desired with a binder such as a suitable binder resin. It comes.

Binders that can be used typically have an average molecular weight of about 10
,000 to 200,000 binder resins are preferably used.

For example, hinyl chloride-vinyl acetate copolymer, vinyl chloride-hinyritene chloride copolymer, vinyl chloride-acrylonitrile copolymer, urethane resin.

Butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose tiacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, various Synthetic rubber, phenolic resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin, acrylic reaction resin, urethane resin, mixture of high molecular weight polynisder resin and incyanate prepolymer, mixture of polyester polyol and polyisocyanate , urea formaldehyde resin, a mixture of low molecular weight glycol/high molecular weight diol/isocyanate, and mixtures thereof.

It is preferable that these binder resins have a hydrophilic polar group.

The hydrophilic polar groups include -303M, -C00M,
PO(OM')2 (M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium; Ml represents an alkali metal such as hydrogen, lithium, potassium, or sodium, or a hydrocarbon residue, etc.), etc. I can list the following.

When the above-mentioned wood-philic polar group is contained, the wood-philic polar group improves the compatibility between the binder resin and the metal magnetic powder, thereby further improving the dispersibility of the magnetic powder and reducing the aggregation of the magnetic powder. The stability of the coating solution can be further improved by preventing this, and the durability of the medium can also be improved.

In addition, when using between magnetic layers, between a magnetic layer and a non-magnetic support, or when using a subbing layer, an intermediate layer, a surface protective layer, etc., it also improves the adhesion between the layers provided above and below the magnetic layer. This can sufficiently prevent surface roughening of the second Bi layer.

Among the above binder resins, a combination of a urethane resin containing a wood-philic polar group and a vinyl chloride resin is preferred.

Such a vinyl chloride copolymer can be obtained by copolymerizing a copolymerizable copolymer containing a hinyl monochloride monomer, an alkali salt of sulfonic acid or phosphoric acid, and, if necessary, other copolymerizable supermers. Something comes up.

Since this copolymer is produced by vinyl synthesis, it is easy to synthesize, and various copolymer components can be selected, allowing the properties of the copolymer to be optimally adjusted.

Among the metal salts of sulfonic acid or phosphoric acid mentioned above, potassium is particularly preferred in terms of solubility, reactivity, yield, etc.

The blending amount of the metal magnetic powder and the binder resin in the magnetic layer is based on 100 parts by weight of the metal magnetic powder,
Usually, it is 1 to 200 parts by weight, preferably 1 to 50 parts by weight.

If the amount of binder resin blended is too high, the amount of metal magnetic powder blended will be reduced, which may reduce the recording density of the magnetic recording medium. If the amount blended is too small, the strength of the magnetic layer will decrease. , the running durability of the magnetic recording medium may be reduced.

In the present invention, there is no particular restriction on the thickness of each of the first magnetic layer and the second magnetic layer, or the thickness of the first magnetic layer and the second magnetic layer are usually
The dry thickness of the magnetic layer (lower layer) is within the range of approximately 0.5 to 4 pm, and the dry thickness of the second magnetic layer (upper layer) is within the range of approximately 0.1 to 0.5 pm.
It is appropriate to set it within a range of about 5 pm.

Here, if the thickness of the first magnetic layer is too thin or the thickness of the second magnetic layer is too thick, the low frequency range (
Characteristics such as signal recording/output intensity and S/N ratio of color signals may become insufficient. On the other hand, if the second magnetic layer is too thin, the recording/output intensity of signals in a high frequency range (luminance signal) and characteristics such as S/N ratio may become insufficient. Note that the balance between the luminance signal and the color signal can also be improved by appropriately adjusting the film thickness of these magnetic layers.

1. Manufacture of magnetic disk - The method of manufacturing the magnetic disk of the present invention is not particularly limited, and may be manufactured according to a method used in manufacturing a known multilayer magnetic recording medium, or It can also be manufactured by various other methods.

For example, as a method for forming the first magnetic layer and the second magnetic layer on the surface of the non-magnetic support, a magnetic paint is usually prepared by cross-dispersing magnetic layer forming components such as metal magnetic powder and binder resin in a solvent. After that, this magnetic paint is applied to the surface of the non-magnetic support.

Examples of the above solvent include acetone, methyl ethyl ketone (MEK), and methyl isophyl ketone (MI8K).
, ketone dimethanol such as cyclohexanone, ethanol, alcohols such as propatool, methyl acetate,
Ethyl acetate, butyl acetate, propyl acetate, ethyl lactate,
Ester types such as ethylene glycol monoacetate Ether types such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, dioxane, etc. Aromatic hydrocarbons such as henzhen, toluene, xylene, etc. Methylene chloride, ethylene chloride, tetranomized carbon chloroform, ethylene chlorohydrin , halogenated hydrocarbons such as dichlorobenzene can be used.

When kneading the magnetic layer-forming components, the metal magnetic powder and other magnetic layer-forming components are fed simultaneously or individually into a mixer.

For example, the metal magnetic powder is added to a solution containing a dispersant, and after kneading for a predetermined period of time, the remaining components are added and further Rls are added to form a magnetic paint. Various types of kneading machines can be used to cross-disperse the components forming the magnetic layer.

Examples of this kneading machine include a two-roll mill, a three-roll mill, a two-hole mill, a beflu mill, a cytoclinter, an Sq+4vari attritor, a high-speed impeller disperser, a high-speed stone mill, a high-speed #strike mill, a tisper niter, a high-speed mixer, and a homogenizer. -5 ultrasonic disperser etc.

Examples of coating methods include wet-on-wet, wet-on-dry, and dry-on. -wet) method, try-on-try (dry-on-dry) method, etc.

Among these, the wet-on-wet method and the wet-on-try method are preferred, and the wet-on-wet method is particularly preferred.

Compared to other coating methods, the wet-on-uniform coating method coats the upper layer while the lower layer is wet, so the surface of the lower layer (i.e., the interface with the upper layer) is smooth and the surface of the upper layer is smooth. There is one point: the adhesiveness between the upper and lower layers is good, and there is no peeling of the film.

Application methods for magnetic paint include, for example, the Krahia coat ink method, knife coach ink method, wire bar coach ink method, doctor freight coach ink method, reverse roll coach ink method, dip coating method, air knife coating method, and calendar coach ink method. The methods include the Skies Coach Ink Method, the Kiss Coach Ink Method, and the Fantin Coating Method.

In this way, the first magnetic layer and the second magnetic layer are formed on the non-magnetic support.
Form a magnetic layer.

After applying the magnetic layer forming component, it is generally subjected to a magnetic field orientation treatment if necessary in an undried state, and then subjected to a surface smoothing treatment using a super calender roll, etc., and then cut into a desired shape. A magnetic recording medium can be obtained by

In the manner described above, the magnetic disk of the present invention, in which the first magnetic layer 1 and the second magnetic layer 2 are provided in this order on both surfaces of the non-magnetic support 3, as illustrated in FIG. 1, is manufactured. Something comes up.

Incidentally, in the magnetic disk of the present invention, an overcoat layer (not shown) can be provided on the surface of the second magnetic layer 2, if necessary. Further, the magnetic disk of the present invention may not be shown in FIG. 1, or may have an undercoat layer provided between the nonmagnetic support 3 and the first magnetic layer l, or It is also possible to have an undercoat layer or not.

Further, if necessary, an appropriate intermediate layer (for example, an adhesive layer, etc.) may be provided between the first magnetic layer 1 and the second magnetic layer 2.

The magnetic disk of the present invention has a wide range of electromagnetic conversion characteristics (especially recording/output intensity and S/N ratio in F characteristics) in recording and outputting signals, ranging from a low frequency range (color signal) to a high frequency range (luminance signal). In addition, it is possible to improve characteristics such as signal recording/output strength and S/N ratio over the wide frequency range, flatten the F characteristic, and improve the performance in the low frequency range ( color signal)
This magnetic disk has the advantage of being able to sufficiently modify the balance between the high frequency range (luminance signal) and the high frequency range (luminance signal), and is extremely superior in practical use. It can be advantageously used in fields where magnetic disks are used.

The reason why the magnetic disk of the present invention has such excellent features may or may not be definitively determined at this stage, and may be due to the following reasons.

First, in the case of the magnetic disk of the present invention, unlike the conventional one having a single magnetic layer, the magnetic disk has a first magnetic layer on both sides of a non-magnetic support.
Two magnetic layers, a magnetic layer and a second magnetic layer, containing metal magnetic powder with different properties are provided, and as described above, this allows the low frequency range (color signal) and the high frequency range (luminance signal) to be separated. ) can be independently improved. In other words, it is possible to improve the recording/output intensity and S/N ratio of signals in the low frequency range (color signal side), or mainly to improve the coercive force (Hc) and /
This is effectively achieved by the first magnetic layer containing metal magnetic powder with a relatively small specific surface area (BET value). The second magnetic layer contains metal magnetic powder that has a relatively large coercive force (Hc) and/or specific surface 1 (BET value), which is advantageous mainly for high frequency ranges (luminance signals), or improves the N ratio, etc. It is believed that this can be effectively achieved by

Furthermore, in the magnetic disk of the present invention, the second &aqueous layer, which is advantageous for the high frequency range (luminance signal), is disposed on the upper N (outer layer or outer layer side), and is advantageous for the low frequency range (color signal). It should also be noted that the first magnetic layer, which is advantageous in contrast, is arranged in the lower layer (inner layer) thereof.

Generally, signals in the high frequency range (luminance signals).

It mainly acts effectively on the metal magnetic powder (second magnetic layer) near the surface without reaching the inside too much, while the low frequency range (color signal) can generally reach deep inside.
It can be inferred that this mainly acts effectively on the internal metal magnetic powder (first magnetic layer).

As a comprehensive result of the above, the magnetic disk of the present invention has characteristics such as signal recording/output intensity and S/N ratio in the entire frequency range from the low frequency range (color signal) to the high frequency range (luminance signal). In addition, it is possible to maintain and improve the balance between the low frequency range (chrominance signal) and the high frequency range (luminance signal) while maintaining a high output level.

Of course, it is obvious that even if the magnetic layer is simply made into a multilayer structure such as a two-layer structure, the above-described excellent effects exhibited by the magnetic disk of the present invention cannot be achieved.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

In addition, the ingredients, proportions, operating procedures, etc. shown below.

Various changes may be made without departing from the spirit of the invention.

(Example I) The ingredients shown below are thoroughly kneaded and dispersed using a kneader and a ball mill, and then, immediately before coating, a polyisocyanate compound (Coronate manufactured by Nippon Polyurethane) 5 is added.
Parts by weight were added and mixed to prepare magnetic paint A and magnetic paint B for magnetic layers.

Magnetic paint A Iron-nickel ferromagnetic alloy powder...100 parts by weight [Nickel content: 3%, specific surface area (BET value): 45 m2/g, coercive force (H
c) :13500e] Carbon black...0.5 parts by weight (R-14 manufactured by Columbia Carbon Nippon Co., Ltd., specific surface area 45 m2/
g, particle size 68km) Polyurethane resin...
5 parts by weight [Niraporan 2304: manufactured by Nippon Polyurethane ■] Hinychloride-vinyl acetate-vinyl alcohol copolymer...8 parts by weight (VAGA
(manufactured by U.C., Inc.) α-alumina...
...7 parts by weight myristic acid...2 parts by weight Phthylsdaleate...1 part by weight cyclohexanone...200 parts by weight Toluene...・
・・・・・・・・・ 30 parts by weight methyl ethyl ketone...
...30 parts by weight Magnetic paint iron-nickel ferromagnetic alloy powder ...100 parts by weight [nickel content: 3% by weight, specific surface area (BET value): 45s2/g, coercive force (H
c) : 14500 e] Kakarhon Fluff・
...0.5 parts by weight (R-14 manufactured by Columbia Carbon Nippon Co., Ltd., specific surface area 45 2/g, particle size 68 m) Polyurethane resin ...5 parts by weight [Niraporan 2304: Made by Nippon Polyurethane] Vinyl chloride-hinyl acetate-hinyl alcohol copolymer...8 East part (VAGA
(manufactured by U.C., Inc.) α-alumina...
...7 parts by weight Mysostin leprosy...2 parts by weight Phthyl stearate...1 part by weight Cyclohexanone...200 parts by weight 1-luene...・
・・・・・・・・・ 30 parts by weight methyl ethyl ketone・
...30 parts by weight Next, on a polyethylene terephthalate base film with a thickness of 32 gm, the above magnetic paint A and magnetic paint B were sequentially applied to the film thickness (dry film thickness) shown in Table 1. The coating was applied by a wet-on-wet method using an extrusion extrusion coater, and after drying, a calendar treatment was performed. After that, magnetic paint A and magnetic paint B are similarly applied to the opposite side of the polyethylene terephthalate base film in the same way, and after drying, a calendar treatment is performed to coat the first magnetic layer and the magnetic paint B on both sides of the base film. A magnetic film was prepared in which two magnetic layers were sequentially laminated.

The magnetic film thus obtained was punched out into a disk shape of 2 inches in diameter and placed in cassettes 1 to 1 to produce an electronic still video floppy.

(Example 2) Magnetic paint C and magnetic paint resin consisting of the components shown below were prepared in the same manner as in the preparation method of magnetic paint A in Example 1.

Magnetic paint C Iron-aluminum ferromagnetic alloy powder...100 parts by weight [aluminum content, 3% by weight, specific surface area (BET value): 42127g, coercive force (Hc): 14000 e-cocarbon black...・0.5 parts by weight (R-14 manufactured by Columbia Carbon Nippon Co., Ltd., specific surface area 45 m2/g, particle size 68
7zm) Polyurethane resin・・・・・・5 parts by weight [
Niraporan 2304 Nippon Polyurethane Co-vinyl chloride-vinyl acetate-hinyl alcohol copolymer...8 Heavy Inspector (VAGA)
(manufactured by U.C.C., USA) α~Alumina...
7 parts by weight Myristic acid 2 parts by weight Phthyl stearate 2 parts by weight Cyclohexanone 200 parts by weight Toluene
...30 parts by weight methyl ethyl ketone...
... 30 heavy seam magnetic paint D: Iron-aluminum ferromagnetic alloy powder...100 parts by weight [Aluminum content: 3% by weight, specific surface area (BET value) 47x27g, coercive force (Hc): 14000e) Carbon fluff...0.5 parts by weight (R-14 manufactured by Columbia Carbon Nippon Co., Ltd., specific surface @ 45 m2/
g, particle size 68) Lm) Polyurethane resin...
・5 parts by weight [Nipporan 2304: B polyurethane■
] Vinyl chloride-hinyl acetate-hinyl alcohol copolymer...8 parts by weight (VAGA
: Manufactured by U, C, C, USA) α-Alumina: 7 parts by weight Myristic acid: 2 parts by weight Phthyl stearate
...1 part by weight cyclohexanone...
200 parts by weight Toluene: 30 parts by weight Methyl ethyl ketone: 30 parts by weight Next, magnetic paint C was used instead of magnetic paint A, and magnetic paint C was used instead of magnetic paint B. A magnetic film was produced in the same manner as in Example 1, except that a paint was used and the thicknesses of the first and second magnetic layers were set to the respective values shown in Table 1. Using this magnetic film, An electronic still video floppy was produced in the same manner as in Example 1.

(Example 3) Magnetic paint E and magnetic paint F consisting of the components shown below were prepared in the same manner as in Example 1 for preparing magnetic paint A.

Magnetic paint E Iron-nickel ferromagnetic alloy powder...100 parts by weight [nickel content 3% by weight, specific surface area (BET value): 42s2/g, coercive force (H
c) : I:1500e] Carbon Frauch...
・・・0.51 part (Columbia carphone R manufactured by Nihon Sha Co., Ltd.)
-14, specific surface area 4Ev2/g, particle size 68μm) Polyurethane resin...5 ton i part [Niraporan 23
04: Nippon Polyurethane Co., Ltd.] Hinyl chloride-vinyl acetate-hinyl alcohol copolymer...8 parts (VAGA:
(manufactured by U.C.C., USA) α-Alumina・・・・・・・7 Part myristic acid・・・・・・・・・Type 2 broken part Phthyl stearate・
・・・・・・1 East part cyclohexanone・・・・・・
200 parts by weight Toluene: 30 parts by weight Methyl ethyl ketone: 30 parts by weight Magnetic coating iron-nickel ferromagnetic alloy powder: 100 parts by weight [Nickel content 3% by weight, specific surface area (BET value), 47 2/g, coercive force (Hc
): 14500 e-cocarbon black...
...0.5 part by weight (R- manufactured by Columbia Carbon Japan Co., Ltd.)
14. Specific surface area 45 2 / g, particle size 68 μm) Bowurethane resin 5 parts by weight [Niraporan 2
304: Made by Nippon Polyurethane] Vinyl chloride-vinegar-vinyl-vinyl alcohol copolymer...8 parts by weight (VAGA
: Manufactured by U.C.C., USA) α-Alumina...
・・・7 Heavy parts myristic acid ・・・・・・・・・2
Flfr Flfr
Toluene ・・・ ・ ・ ・ ・ ・ ・ 30
Heavy ψ part Methyl ethyl ketone... 30 Heavy parts Next, magnetic paint E was used in place of magnetic paint A, and magnetic paint B was used instead of magnetic paint A.
A magnetic film was produced in the same manner as in Example 1, except that magnetic coating material F was used instead of , and the film thicknesses of the first and second magnetic layers were set to the respective values shown in Table 1. An electronic still video floppy was manufactured in the same manner as in Example 1.

(Example 4) A magnetic film was produced in the same manner as in Example 1, except that the thickness of the second magnetic layer formed from magnetic paint B was changed to the value shown in Table 1, and an electronic still video film was produced in the same manner as in Example 1. Manufactured floppies.

(Comparative Example 1) Same as Example 1 except that only the magnetic layer corresponding to the second magnetic layer (formed from magnetic paint B) was directly formed on both sides of the base film without forming the first magnetic layer. A magnetic film having a single magnetic layer on both sides of a base film was prepared using the above methods, and an electronic still video floppy was manufactured in the same manner as in Example 1 using this magnetic film.

(Comparative Example 2) Same as Example 1 except that only the magnetic layer corresponding to the first magnetic layer (formed from magnetic paint A) was directly formed on both sides of the base film without forming the second magnetic layer. A magnetic film having a single magnetic layer on both sides of a base film was prepared using the above methods, and an electronic still video floppy was manufactured in the same manner as in Example 1 using this magnetic film.

(Comparative Example 3) Magnetic paint A and magnetic paint B were replaced (i.e., the first
A magnetic film was prepared in the same manner as in Example 2, except that the magnetic layer was formed from magnetic paint B, and the second magnetic layer was formed from magnetic paint A. Using this magnetic film, Example 1 was prepared.
An electronic still video floppy was manufactured in the same manner.

(Comparative Example 4) By replacing the magnetic paint C and the magnetic paint (i.e., the first
A magnetic film was produced in the same manner as in Example 2, except that the magnetic layer was formed from magnetic paint and the second magnetic layer was formed from magnetic paint C. Using this magnetic film, Example 2
An electronic still video floppy was manufactured in the same manner.

The following performance tests were conducted on each of the electronic still video floppies described above, and the results are shown in Tables 1 and 2.

(1) RF output Sine wave signals of 1.25 and 7.0 MHz were recorded using an MVR-5500 manufactured by Calaney ■, and the reproduced RF output was measured.

The results show that the measured playback RF output of the electronic still video floppy manufactured in Example 1 is 0.0.
The values are shown in Table 1 as relative values when expressed as dfl. RF
The larger the specific output value, the better the electronic still video floppy.

(2) Noise level ■ 6. of each sample where the I'IF output of 7.0 MHz was measured using a spectrum analyzer manufactured by Ahan Test. The OMHz noise level was set at 114.

The measured noise levels are listed in Table 2 as relative values when the noise level of the electronic still video floppy manufactured in Example 1 is set to 0.0 dB. The smaller the noise level value is, the better the electronic still Hideo Frosobee is.

(3) Using F characteristic Sony MVR-5500, 7.0
7.0 MHz, 10.01+! The ratio of the reproduced RF output in Hz, R1+7/RH,o, was measured. The results are RH7/RH of the reference disc (disc determined by the electronic still camera conference). 0. OdB
The relative values are shown in Table 1. 0.0
The closer it is to dB, the better the balance of the F characteristics is.

(Wood page, blank space below) Table 2 (Measurement of 6 layers for 7 frequency signal) Magnetic force (Hc) and/or specific surface area (B
By providing two magnetic layers containing different metal magnetic powders (ET value), the electromagnetic conversion characteristics in the high frequency range (luminance signal) and low frequency range (color signal) are improved independently. Recording, output intensity, and S/N of signals in a wide frequency range from color signals to luminance signals in F-characteristics
Therefore, it is possible to provide a magnetic disk which is extremely useful in practice and has advantages such as improved balance between a single color signal and a luminance signal.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a magnetic disk (magnetic recording medium section) of the present invention. l...First magnetic layer 2...Second magnetic layer 3...Nonmagnetic support

Claims (1)

[Claims] (1) A first magnetic layer containing metal magnetic powder and a second magnetic layer are laminated in this order on both sides of a non-magnetic support, and the second magnetic layer contains the first magnetic layer. Coercive force (Hc) and/or specific surface area (B
A magnetic disk characterized by using metal magnetic powder having a large ET value.