JP2608868B2 - Magnetic recording media - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a non-binder type magnetic recording medium in which a magnetic layer is formed of a ferromagnetic thin film and does not contain a binder, an additive or the like. Is applied to magnetic recording devices such as audio tape decks, video tape recorders, and PCM recorders, and terminal data processing devices such as large computers and personal computers.

Structure of conventional example and its problems The magnetic layer is formed on a polymer film such as a polyester film or a polyimide film, or a non-magnetic substrate such as a non-magnetic metal thin plate by using thin film forming means such as vacuum deposition, sputtering, and ion plating. Therefore, a non-binder type magnetic recording medium composed of only a magnetic thin film and containing no binder or additives is said to be a high-density magnetic recording medium because of its excellent electromagnetic conversion characteristics at short wavelengths. I have.

In order to realize this high density, it is necessary to reduce the gap of the magnetic head and also to smooth the surface of the magnetic recording medium to reduce the spacing loss as much as possible.

However, if the surface is excessively flattened, it will cause problems in head touch and running performance. Therefore, it is necessary to solve this by controlling the fine shape of the surface.

The surface properties of a non-binder type magnetic recording medium are highly dependent on the surface shape of a plastic film or the like as a substrate, since the thickness of the magnetic layer is as small as about 0.01 to 0.5 μm. Therefore, conventionally, many proposals have been made regarding the surface properties of the film. Examples thereof are JP-A-52-18770, JP-A-52-84264, JP-A-54-40883,
JP-A-53-116115, JP-A-53-128685, JP-A-54-94574, JP-A-56-10455, JP-A-56-10455
No. 56-16937.

In each of these examples, the surface shape is relatively finely and uniformly roughened, for example, wrinkle-like projections are formed, thereby making it possible to improve head touch and running performance at once. The surface condition shown in the above-mentioned example is very effective in terms of head touch and head running at room temperature and normal humidity.

However, it has a disadvantage that squeal is likely to occur in the cylinder part of the rotary head in high humidity such as 30 ° C. and 80 to 90% RH. As a means to solve this, a polyester film is used for the substrate, and the polyester oligomer contained therein is deposited as fine crystals on the substrate surface when forming a magnetic layer in a vacuum, and a magnetic metal thin film layer is formed thereon. Proposals have already been made to form the crystals, but in this case, the frequency of deposition of the oligomer crystals is highly dependent on the location, and it is difficult to deposit the oligomer crystals uniformly over the entire surface, resulting in uneven distribution depending on the location. Cheap. For this reason, there is a disadvantage that the envelope characteristics of the obtained magnetic recording medium are easily disturbed.

Further, it is known that a magnetic thin film formed on a polyester film in which thermoplastic fine particles are projected on the surface as described in JP-A-53-107314 has good running properties and good image quality. . However, in this case, even if an attempt is made to improve the surface properties of the magnetic recording medium in order to increase the recording density, if the surface roughness becomes 0.03 μm or less, stick-slip occurs, resulting in poor runnability.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-binder type magnetic recording medium which improves squeal in high humidity, improves reproduction image quality, and has excellent running stability and durability.

Configuration of the Invention A magnetic recording medium according to the present invention is provided on a plastic surface,
A first particulate projection having fine particles as a nucleus and an average height of 30 to 200 ° and a second particulate projection having a fine particle as a nucleus and having an average height of 100 to 600 ° and larger than the first particulate projection, 1 is formed so that the density of the particulate projections is higher than the density of the second particulate projections, and a ferromagnetic thin film is formed on the first and second particulate projections and the film surface.

FIG. 1 is a plan view of a magnetic recording medium according to the present invention. FIGS. 2 and 3 are cross-sectional views taken along the line AA 'of FIG. In the figure, 1,1 'is a plastic film substrate, and 21,22 and 21', 22 'are nuclei of fine particles of a thermoplastic resin, for example, fine particles of carbon fine particles, silica fine particles, fine particles composed of a hydrolysis product of metal alkoxide, etc. A nucleus or a nucleus of a mixture of a plurality of types selected from the fine particles; 3 'a binding resin for fixing the nuclei 21' and 22 'on the plastic film substrate 1';
Is a ferromagnetic thin film, and 5,5 'is a lubricant.

In FIG. 2, the cores 21 and 22 are fixed on the plastic film substrate by themselves, and in FIG.
Particulate protrusions are formed from 1 ', 22' and the binding resin 3 '.

The lubricant 5 exists on the entire surface of the ferromagnetic thin film 4, but the lubricant 5 'exists only on a specific portion on the ferromagnetic thin film 4'.

The height of the particulate resin protrusion is measured by a high-accuracy stylus-type surface roughness measuring device (TALYSTEP-1, manufactured by TAYLOR-HOBSON), and the maximum surface roughness specified in JISBO601,
If expressed as the distance from the peak to the valley bottom of the irregularities according to Rmax, the height suitable for the present invention is 30 to 2 in the particulate projections 21 and 21 ′ constituted by smaller nuclei.
00Å, the large nuclei composed particulate protrusions 22,2
In 2 ′, it is in the range of 100 to 600 °, and the height of the former is h
_1, the relationship between them the height of the latter and h ₂ is h ₁ <h _2, who when h ₁ is smaller near 30Å is h ₁ ≦ h _2/3 are preferable. In general, it is difficult to obtain the effect of preventing squeal in high humidity when the particle projections are composed only of nuclei of 30 mm or less, and when the particle projections are formed only of nuclei of 500 mm or more, the output and the envelope are easily disturbed. Become. As in the present invention, using the particulate protrusions composed of the two types of particle heights h ₁ and h ₂ ,
The density of protrusions height h ₁ which determines the reproduction output characteristics, when'll consider to be greater than the density of the height h ₂ which acts on the running property may squeak preventing effect in a high humidity, yet the amount of decrease in the output is very It is possible to obtain a magnetic recording medium with little envelope disturbance and excellent running stability and durability.

In contact with the magnetic head, (is called spacing) for the density particulate protrusions 21, 21 'is large, the average height h ₁ with the the particulate projections, the distance between the magnetic tape head It mainly contributes. Thus the average height h ₁ with particle-like projections 21, 21 'in order to maintain the reproduction output due to the generation of the spacing in good condition who very small is desirable, in practice, the particle-like projections 21 , 2
The average height h ₁ of 1 ′ is preferably 30 to 200 °. Generally 30
構成 さ れ る If the projections are smaller than 200 mm, the cylinder inside the rotary head will squeal in high humidity, and the reproduction output will be less stable. Degradation of reproduction image quality is remarkable when recording / reproducing on a tape.

Particulate protrusions with large average height and low density
2 ′ has a function added to the running property of the magnetic tape, and has an average height of 100 ° or less (also referred to as surface roughness).
In the coefficient of friction becomes extremely high, in order to wear to the magnetic head becomes more pronounced wear phenomena above 600 Å, average height h ₂ of the particulate protrusions 22 and 22 'are, 100～600A is desirable.

Incidentally, especially when selecting small average height h ₁ near 30 Å, average height h ₂ is preferably greater than or equal to about 3 times the average height h _1,
In this case, h ₂ may be set to 100 ° or more. As the density of the particulate resin protrusion particulate protrusions have a height h ₁ 21,2
It is preferable that the number 1 ′ is 100,000 / mm ² or more, and the number of the particulate protrusions 22 and 22 ′ having a height h ₂ is 100,000 / mm ² or less.

In addition, this density was observed in a minimum of 10 visual fields with a differential interference optical microscope with a magnification of 400 or a minimum of 10 visual fields with a scanning electron microscope at a magnification of 3000, and the number of particulate protrusions existing in those visual fields was determined. determined, in which converted per 1 mm ^2.

The planar extent of the particulate resin projections is suitably 1 to 20 times, more preferably 2 to 10 times, their height. If it is 20 times or more, the effect of preventing squeal in high humidity is reduced.

As a plastic film used as a substrate, polyethylene terephthalate or a copolymer thereof,
Polyester film made of a mixture, polyethylene naphthalate or a copolymer thereof, a mixture thereof, a polyimide film such as polyester imide or polyimide, an aromatic polyamide film, etc., particularly those having excellent surface smoothness, polyester film For example, there are few fine protrusions composed of the residue of the polymerization catalyst, or the fine protrusions have a size of several hundred mm or less and have good smoothness, wrinkles, earthworm powder, granules and the like described above. It is suitable to form uniform fine projections on the surface and have a surface roughness of several hundreds of square meters or less.

A method for forming particulate resin protrusions on these films will be described.

When the fine particles of the thermoplastic resin are used as the core, for example, a method of adding a solvent that does not easily dissolve the resin to the thermoplastic resin solution, coating the film on the film surface, and drying it, There is a method in which a resin to which another soluble resin is added is applied on the film surface and dried. Examples of the thermoplastic resin include various polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolymers based on them, nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, and copolymers thereof. The most suitable are various polyamides, polycarbonates, polyarylates, polysulfones, polyethersulfones, polyphenylene oxides, phenoxys and the like, but other resins such as polystyrene, polyacrylate and polyvinyl chloride can also be used.

As the binding resin, besides various thermoplastic resins, a crosslinkable resin such as epoxy, phenol, and silicone can also be used.

When using carbon fine particles as a core, for example, a particle size of 10 to 50
There is a method of dissolving 20 to 10,000 ppm of a resin serving as a binder in a carbon colloid solution in which 5% of fine carbon particles are dispersed in 5 to 5000 ppm, and then coating and drying on a plastic film. In this case, the carbon fine particles are prepared by converting carbon black, acetylene black, or the like produced by an oil furnace method, a gas furnace method, a channel method, a thermal method, or the like into an organic solvent such as a ketone, ester, alcohol, aliphatic or aromatic hydrocarbon. It is dispersed as fine particles, and coarse particles are excessively removed as necessary.

Examples of the resin serving as a binder include saturated polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, nylon 6, nylon 6
6, polyamide such as nylon 610, nylon 11, nylon 12, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, polyacrylate, polyvinyl chloride, polyvinyl butyral,
Various resins such as polyphenylene oxide and phenoxy resin can be used alone, copolymers or mixtures thereof.
Further, a cross-linked resin such as an epoxy resin, a urethane resin, a silicone resin, a phenol resin, a melamine resin or a modified resin thereof can also be used.

When silica fine particles are used as a nucleus, for example, a particle size of 10 to 50
There is a method in which a resin serving as a binder is dissolved in a silica colloid solution in which 0 to 100 ppm of silica fine particles are dispersed in a volume of 10 to 10,000 ppm, and then applied to a plastic film and dried. As the silica fine particles, for example, fine powder silica obtained by a dry method comprising silicon tetrachloride (eg, Aeros
il: Nippon Aerosil Co., Ltd., finely divided silica obtained by decomposition of sodium silicate with acid or alkali (eg, Syloi
d: Fuji Devison Chemical Co., Ltd.), silica sol obtained by ion exchange of sodium silicate (for example, Snowtex: Nissan Chemical Industries, Ltd.), etc., which are mainly composed of water, alcohol, ketone, ester, etc. The solution is dispersed in a solution to be used, and if necessary, coarse particles are excessively removed. Examples of the resin serving as a binder include saturated polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, nylon 6, and nylon.
Polyamides such as 66, nylon 610, nylon 11, nylon 12, etc., polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, polyacrylate, polyvinyl chloride, polyvinyl butyne,
Various resins such as polyphenylene oxide and phenoxy resin can be used alone, copolymers or mixtures thereof.
Further, a crosslinkable resin such as an epoxy resin, a urethane resin, a silicone resin, a phenol resin, a melamine resin or a modified resin thereof can also be used.

When the core is composed of fine particles composed of a hydrolysis product of a metal alkoxide, a diluted solution of a metal alkoxide (10 to 10) is used.
00 ppm) of an organic solution containing 10 to 10,000 ppm of water.
% To hydrolyze the metal alkoxide to a particle size of 10 to 50.
There is a method of dissolving 20 to 5000 ppm of a resin serving as a binder in a solution in which 0% fine particles are precipitated and dispersed, and then coating and drying the solution on a substrate.

As the metal alkoxide, for example, tetraethoxysilane, aluminum S-butoxide, aluminum t-
Butoxide, aluminum isopropyl borate, trimethyl borate, tri-tert-butyl borate, tetra-i-propoxy titanium, tetra-n-butoxy titanium, tetrakis (2-ethylhexoxy) titanium, tri-n-butoxy titanium monostearate, tetramethyl Titanate, tetraethyl titanate, zirconium tetra-t-butoxide, tetraisopropyl zirconate, indium isopropoxide, etc., and the binder resin is a saturated polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, nylon 6 , Nylon 66, nylon 61
Polyamide such as nylon 11, nylon 12, nylon 12, polystyrene, polycarbonate, polyarylate, polysulfone, polyether sulfone, polyacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyphenylene oxide, phenoxy resin, etc. A simple substance, a mixture, or a copolymer can be used, and a crosslinkable resin such as an epoxy resin, a urethane resin, a silicone resin, and a phenol resin can also be used.

As the ferromagnetic metal thin film, for example, a metal thin film mainly composed of Co, Ni, Fe, etc. formed by oblique evaporation or vertical evaporation, and a metal thin film mainly composed of an alloy thereof (for example, a Co-Cr perpendicular magnetization film) are used. Although it can be used, for the purpose of improving the adhesion strength to a plastic film or the corrosion resistance and abrasion resistance of a ferromagnetic metal thin film itself, an atmosphere containing oxygen obtained when the atmosphere at the time of vapor deposition is an atmosphere in which oxygen gas is dominant is used. It is desirable to use a magnetic metal thin film.

The oxygen content is suitably at least 3% or more, preferably 5% or more in terms of the atomic ratio to the ferromagnetic metal or non-magnetic metal near the substrate film surface. If necessary, prior to the formation of the ferromagnetic metal thin film, a thin film having a mechanical reinforcing effect, for example, an oxygen-containing metal thin film such as Ti, Cr, Ni, etc.
It is also possible to form an oxide thin film such as l ₂ O ₃ and SiO ₂ .

The combination of the above-described ferromagnetic metal thin film containing oxygen or the above-described non-magnetic metal layer formed as necessary underneath and the underlayer having particulate protrusions can greatly improve the still life. Becomes The still life is also related to the thickness of the ferromagnetic metal thin film. When the thickness is less than 400 mm, the still life is sharply reduced.
It is hoped that this is the case.

By allowing the lubricant to be present on the surface of the ferromagnetic metal thin film layer, it is possible to further enhance the running property and the improvement effect based on the shape of the particulate projections. This makes the prevention of squeal in high humidity more complete.

The lubricant on the ferromagnetic metal thin film may be present on the entire surface as shown in FIG. 2, or may be locally present as shown in FIG.

As means for this, other than a method of directly applying or depositing on the front surface of the ferromagnetic metal thin film, a method of applying or depositing on the back surface of the magnetic recording medium and laminating (winding) the magnetic recording medium
Sometimes, a method of transferring the image to the surface of the ferromagnetic metal thin film is also possible.

It is also possible to use a resin binder or the like to firmly fix the lubricant.

As the lubricant, fatty acid, fatty acid ester, fatty acid amide, metal soap, aliphatic alcohol, paraffin, silicone, fluorine-based surfactant, inorganic lubricant and the like can be used. As further preferably 0.5~500mg per surface 1 m ² is the abundance of the lubricant is suitably 5 to 200 mg.

Fatty acids include those having 12 or more carbon atoms, such as lauric acid, myristyl acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, and linolenic acid.

As the fatty acid ester, ethyl stearate, butyl stearate, acyl stearate, monoglyceride stearate, monoglyceride palmitate, monoglyceride oleate, pentaerythritol tetrastearate and the like can be used.

Examples of the fatty acid amide include caproic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, linoleic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, and the like. Can be used.

Metallic soaps include zinc, lead, nickel, cobalt, iron, aluminum, magnesium, strontium, copper, etc., such as lauric acid, myristic acid, balmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, and linolenic acid. Salt, lauryl, palmityl, myristyl,
Salts of sulfonic acids such as stearyl, behenyl, oleyl, linole, and linolene with the above-mentioned various metals can be used.

Cetyl alcohol, stearyl alcohol and the like can be used as the aliphatic alcohol.

As the paraffin, a saturated hydrocarbon such as n-octadecane, n-nonadecane, n-tridecane, n-docosan, and n-dotriacontane can be used.

As the silicone, polysiloxane in which hydrogen is partially substituted with an alkyl group or a phenyl group, and those obtained by modifying these with fatty acids, aliphatic alcohols, acid amides, and the like can be used.

As the fluorosurfactants, perfluoroalkylcarboxylic acid and perfluoroalkylsulfonic acid and sodium, potassium, magnesium, zinc, aluminum,
Salts with iron, cobalt, nickel, etc., perfluoroalkyl phosphates, perfluoroalkyl betaines, perfluoroalkyltrimethylammonium salts, perfluoroethylene oxide, perfluoroalkyl fatty acid esters and the like can be used.

Examples of the inorganic lubricant include graphite powder, molybdenum disulfide powder, tungsten disulfide powder, molybdenum selenide powder, tungsten selenide powder, and calcium fluoride powder.

The surface of the magnetic recording medium of the present invention, the back surface, or the vicinity thereof, the voids in the ferromagnetic metal thin film, the interface between the ferromagnetic metal thin film and the plastic film, the inside of the plastic film, etc. Various additives such as an agent and an antistatic agent can be added as required.

 Next, a specific example will be described.

Example -1 The following composition solutions -1 and 2 were mixed on a smooth biaxially stretched polyethylene terephthalate film having a surface roughness of 30 ° or less by greatly suppressing protrusions caused by the polymerization catalyst residue, and a coating thickness of about 10 µm. Continuous coating and drying so that the surface is about 5000 particles / mm ² with a height of about 550 ° with carbon fine particles as the core and silica fine particles as the core, the height is about 10
A long film sample having an undercoat layer having about 200,000 particulate projections / mm ^{2 of} 0 ° was obtained. This sample is designated as A.

Composition liquid-1 Carbon ……… 0.15phr Ethyl acetate ……… 500 phr Toluene ……… 500 phr Polyester ……… 0.5 phr Composition liquid-2 Methanol silica gel (manufactured by Nissan Chemical Industries, Ltd.) .....
0.08 phr methanol ……… 200 phr ethyl acetate ……… 1000 phr toluene ……… 100 phr polyester ……… 0.5 phr Example 2 The composition liquid-1 in Example-1 was used in the same manner, but the composition liquid-2 was changed to the following composition liquid-3, so that the particulate projections having a height of about 550 ° with carbon fine particles as nuclei were obtained. about 5000 / mm ² and a height of approximately 100Å particulate projections about 2
A film long sample having an undercoat layer having a thickness of 100,000 pieces / mm ² was obtained. This sample is designated as B.

Composition liquid-3 carbon ............ 0.02phr Methylene chloride ……… 500 phr Toluene ……… 300 phr Methyl ethyl ketone ……… 200 phr Polyether sulfone ……… 0.5 phr Example 3 In Example 2, the composition liquid-3 was used in the same manner, but the composition liquid-1 was changed to the following composition liquid-4, whereby the particle-like projections made of nylon 66 and having a particle height of about 550 ° were formed. 50,000 / mm ² and the fine carbon particles to give the core and a film long sample to form an undercoat layer having particulate projections about 2,000,000 / mm ² and a height of about 100 Å. This sample is designated as C.

Composition liquid-4 nylon 66 ……… 0.15phr Phenol: 300 phr Cellosolve acetate: 700 phr Example 4 Composition liquid-2 was used in the same manner as above, except that composition liquid-1 was changed to the following composition liquid-5 to reduce the particle height of polysulfone. particulate protrusions of 400Å to obtain about 10,000 / mm ² and the silica fine particles of the film long sample to form an undercoat layer having about 200,000 / mm ² particulate high protrusions 100Å to the nucleus. This sample is designated as D.

Composition liquid-5 polysulfone 0.1 phr Methylene chloride: 100 phr Benzene: 100 phr Ethyl acetate: 800 phr Comparative Examples-5 to 9 The composition liquids 1 to 5 used in Examples 1 to 4 were used alone to obtain particulate projections. A long film sample having an undercoat layer formed thereon was obtained.

 These samples are E, F, G, H, and I.

Comparative Example-10 A sample of the plastic film itself used in Examples 1-4 and Comparative Examples-1-5 is designated as J.

Example-5 Each of the above samples was sequentially connected, and a Co, Ni ferromagnetic metal thin film (Ni = 20 wt%, film thickness 1) was formed on each surface by a connected vacuum oblique deposition method.
000Å) was formed in the presence of trace amounts of oxygen.

The oxygen content of the magnetic layer was 5% in terms of the atomic ratio to the metal. After that, various lubricant solutions were applied to the surface of each sample and slit into a predetermined width to obtain a magnetic tape.

A magnetic tape was prepared for a specific sample among the above A to J without applying a lubricant solution after vapor deposition.

These were subjected to a prototype video recorder in an environment of 30 ° C. and 90% RH, and the squealing state, output, and still life of the rotating head cylinder were measured.

The output in Table 1 is 0 [d
B].

Also, under the same environment, a post with a diameter of 4φ and a material of SUS420J2 is installed, and a magnetic tape is wound around the post, and a constant tension is applied to the magnetic tape, and the magnetic tape is applied at a speed of 18 mm / sec. The dynamic friction coefficient μ was measured using a dynamic friction coefficient measuring machine to which the tape was fed. Table 1 shows the relationship between the number of reciprocations and the dynamic friction coefficient μ after the magnetic tape was reciprocated 100 times and traveled.
The term "presence / absence of stability" refers to "stability" if the fluctuation of the dynamic friction coefficient μ is extremely small when the vehicle is reciprocated 100 times, and "stability" if the fluctuation is extremely large. "None" qualitatively describes the relationship between the number of reciprocations of the magnetic tape and the coefficient of dynamic friction. Also,
`` Presence or absence of flaws '' means that after running back and forth 100 times, there was a flaw on the surface of the ferromagnetic thin film of the magnetic tape,
It shows whether there was nothing.

Although not particularly described in the above Examples and in Table 1, it is made of polyethylene terephthalate containing almost no fine particles resulting from polymerization catalyst residue, and has a surface modified with a thickener during the film-forming stretching. By applying and curing a liquid mainly composed of silicone emulsion, the surface roughness becomes 100 mm.
Using a biaxially stretched polyester film on which a heterogeneous polymer thin layer composed of fine wavy irregularities was formed, the same coating treatment as in Examples -1 to 4 was performed thereon to form a base layer. Table 1 also shows a magnetic tape formed by providing a ferromagnetic thin film layer by the method shown in -5 and then slitting the surface to a predetermined width with various lubricant solutions applied to each sample. The result is almost the same as the result.

Effects of the Invention As is clear from the above embodiments, the magnetic recording medium of the present invention does not generate squeal even in high humidity, has a very small decrease in output, and has a good still life. Moreover, the running stability and durability, that is, the dynamic friction coefficient μ is small,
In addition, there is little variation and no scratches are generated during traveling, and the practical value is extremely high.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a magnetic recording medium according to the present invention, FIG.
FIG. 3 is a sectional view taken along line AA 'of FIG. 1,1 '... Plastic film substrate, 21,22,21', 22 '
… Fine particle nuclei, 3 '... binding resin, 4, 4' ... ferromagnetic thin film, 5, 5 '... lubricant.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kunio Hibino 1006 Kadoma Kadoma Matsushita Electric Industrial Co., Ltd. (72) Inventor Mikio Murai 1006 Odaka Kadoma Kadoma City Matsushita Electric Industrial Co., Ltd. (72) Inventor Person Shigeki Kawase 1006 Kadoma Kadoma, Matsushita Electric Industrial Co., Ltd. (72) Inventor Koichi Shinohara 1006 Kadoma Kadoma, Kadoma City Matsushita Electric Industrial Co., Ltd. (56) References JP-A-56-13515 (JP, A) JP-A-56-13517 (JP, A) JP-A-56-13516 (JP, A) JP-A-56-13518 (JP, A)

Claims (1)

(57) [Claims] 1. A first particulate projection having fine particles as a nucleus and having an average height of 30 to 200 ° on a plastic film surface and an average height of 100 to 600 ° having fine particles as a nucleus. A large second particulate projection is formed such that the first particulate projection density is higher than the second particulate projection density, and is formed on the first and second particulate projections and the film surface. A magnetic recording medium characterized by forming a ferromagnetic thin film.