JPS62212925A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To substantially obviate instantaneous clogging and to provide the titled medium having excellent reproduction output and stability by incorporating at least one kind of silicon nitride, zirconium oxide and diamond respectively having <=0.1mum grain size into a magnetic layer. CONSTITUTION:The magnetic layer of the magnetic recording medium formed with the magnetic layer dispersed with pulverized ferromagnetic powder in a binder to <=1.0mum thickness on a nonmagnetic substrate contains at least one kind of the silicon nitride, zirconium oxide and diamond respectively having <=0.1mum grain size. More specifically, the silicon nitride, zirconium or diamond having <=0.1mum average grain size is used as a polishing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media. In particular, the present invention relates to magnetic recording media having relatively thin magnetic coating layers.

[Conventional technology]

Conventionally, ferromagnetic powders such as ferromagnetic iron oxide, cobalt-containing iron oxide, chromium dioxide, and ferromagnetic alloy powder are used as binders for tape-shaped or disk-shaped magnetic recording media for audio, video, information recording, etc. A magnetic recording medium in which a magnetic layer dispersed therein is coated on a non-magnetic support is mainly used.

In such magnetic recording media, alumina (α-A1203) and chromium oxide (
Particle size α of Cr203), titanium dioxide (T10□), etc.
An abrasive with a diameter of 5 μm to 1.0 μm is used in a dispersed manner.

[Problem that the invention seeks to solve]

However, recently, there has been a trend to reduce the thickness of the magnetic layer to 1.0 μm or less, for example, about 0.7 to 0.8 μm, in order to increase the density and reduce costs of such magnetic recording media. In a thin layer region with a thickness of 1.0 μm or less,
This tends to cause head warping defects due to a decrease in the durability of the magnetic layer and a decrease in Young's modulus, resulting in problems such as instantaneous clogging of the head and occurrence of head scratches. Here, instantaneous clogging does not mean that magnetic layer debris adheres to the head and permanently clogs the head, but that it occurs momentarily when magnetic layer debris passes through the head gap while the tape is running. This is a phenomenon in which a swiss loss occurs, resulting in a momentary lack of playback output.

In addition, even a slight head scratch tends to cause a reduction in reproduction output, and this tendency is particularly noticeable in magnetic recording media using ferromagnetic alloy powder. Therefore, countermeasures against such problems are desired! It is.

[Means for solving problems]

As a result of repeated studies to solve the various problems associated with the thinning of the layer, the present invention found that the cause of the above-mentioned drawbacks was mainly due to the use of conventional abrasives, and Silicon nitride (Si304), zirconium oxide (Zr
It has been found that the above problem can be solved by using O□) or diamond.

As mentioned above, alumina, chromium oxide, etc. with a particle size of 0.5 μm have been used as abrasives in the past, but as magnetic layers have become thinner, the thickness of these abrasives has become a problem.
A conventional content deteriorates the magnetic properties of the magnetic layer and causes scratches on the head, while a lower content reduces the durability of the magnetic layer.

Furthermore, these abrasives have some problems in heat resistance and acid resistance, and this tendency increases as the layer becomes thinner, causing instantaneous clogging of the head. The present inventors solved the above problem by using silicon nitride, zirconium oxide, or diamond with a particle size of 0.1 μm or less, which has a high Mohs hardness and excellent heat resistance and acid resistance, instead of these abrasives. We were able to solve the problem and achieve the present invention.

That is, the present invention provides a magnetic recording medium in which a magnetic layer in which fine ferromagnetic powder is dispersed in a binder is formed on a non-magnetic support to a thickness of 10 μm or less, in which each of the magnetic layers has a particle size of α1 μm.
The magnetic recording medium is characterized in that it contains at least one of silicon nitride, zirconium oxide, and diamond.

The present invention will be explained in detail below.

The present invention can also be applied to magnetic recording media using conventionally commonly used iron oxide-based ferromagnetic powders, CO-containing iron oxide-based ferromagnetic powders, and chromium dioxide (CrO2)-based ferromagnetic powders. Powder, [especially with a specific surface area of 25m27I]
It is particularly effective when using the above ferromagnetic alloy powder. In other words, ferromagnetic alloy powder has lower hardness and smaller particle size than other ferromagnetic powders, and magnetic recording media using this powder tend to have particularly poor durability and polishability. can effectively solve these problems.

The nonmagnetic support used in the present invention is not particularly limited, and any commonly used nonmagnetic support can be used. Examples of materials forming the non-magnetic support include various synthetic resin films such as polyethylene terephthalate (PET), polypro♂, polycarbonate, polyethylene naphthalate, polyamide 9-imide, polyimide, aluminum foil, and stainless steel. Examples include metal foils such as foil. There is also no particular limit to the thickness of the non-magnetic support, but it is generally 3 to 50 pm, preferably 5 to 50 pm.
~30 μm.

The nonmagnetic support may be provided with a backing layer on the side on which the magnetic layer described below is not provided.

The magnetic recording medium of the present invention is one in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support as described above.

The ferromagnetic powder used in the magnetic layer of the present invention includes fine ferromagnetic alloy powder containing iron as a main component, γ-Fe2O3, Fe3O
4. In addition to CO-modified ferromagnetic iron oxide CrO
This is particularly effective when a ferromagnetic alloy powder of I or higher is used as the ferromagnetic powder.

As an example of this ferromagnetic alloy powder, the metal content in the ferromagnetic alloy powder is 75% by weight or more, and 80% by weight or more of the metal content is at least one type of ferromagnetic metal or alloy, and the metal content is Mention may be made of alloys which may contain other components within a range of up to 29% by weight. Further, the ferromagnetic metal may contain a small amount of water, hydroxide, or oxide. Methods for producing these ferromagnetic metal powders are already known, and ferromagnetic alloy powder, which is a typical example of the ferromagnetic powder used in the present invention, can also be produced according to these known methods.

When using ferromagnetic alloy powder, there are no particular restrictions on its shape, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used.

The specific surface area (S BET) of this ferromagnetic alloy powder is 42 m
It is preferably 27I or more, and more preferably 457FL2
It is preferable to use 71 or more.

As the binder used to form the magnetic layer of the present invention, commonly used thermoplastic resins, thermosetting resins, reactive resins, and the like can be used.

These resins can be used alone or in combination.

Thermoplastic resins generally have an average molecular weight of 10,000 to 2.
00,000 and a polymerization degree of about 200 to 2,000. Examples of such thermoplastic resins include vinyl chloride/vinyl acetate copolymer resins, vinyl chloride/vinylidene chloride copolymers, acrylic resins, cellulose derivatives, various synthetic rubber thermoplastic resins, urethane elastomers,
Examples include polyvinyl fluoride, polyamide resin, polyvinyl butyrate, styrene/butadiene copolymer, polystyrene resin, and resins into which hydroxyl groups, carboxyl groups, sulfonic acid groups, phosphoric acid groups, or metal salt groups thereof are introduced. , these can be used alone or in combination.

Thermosetting resins or reactive resins are generally resins with an average molecular weight of 200,000 or less in the coating liquid state, and resins whose molecular weight becomes almost infinite due to condensation reaction or addition reaction after coating. . However, when these resins are thermosetting resins, it is preferable that the resins do not soften or dissolve due to heating during the process leading to curing. Examples of such resins include phenol/
Formalin/novolac resin, phenol/formalin/resol resin, phenol/furfural resin, xylene/formaldehyde resin, urea resin, melamine resin, drying oil-modified alkyd resin, phenolic resin-modified alkyd resin, maleic acid resin-modified alkyd resin, unsaturated polyester A combination of resin, nipoxy resin and curing agent,
Examples include moisture-curable resins having terminal incyanate polyethers, polyisocyanate prepolymers, and combinations of polyisocyanate prepolymers and resins having active hydrogen, and these may be used alone or in combination.

The amount of binder used is, based on 100 parts by weight of ferromagnetic powder,
Generally in the range of 10 to 100 parts by weight, preferably 15 to 100 parts by weight.
The range is 50 parts by weight.

The present invention is characterized in that the magnetic layer as described above contains fine powders of silicon nitride, zirconium oxide, and diamond having a particle size of 1 μm or less as an abrasive.

Such abrasives have high heat resistance and acid resistance, and have a hardness of dog (silicon nitride is about 9, zirconium oxide is about 9, and diamond is about 10 on the Mohs scale), so those with the above particle size can be used in the magnetic layer. When the coating thickness of the magnetic layer is 1μ
When using a thin film type magnetic recording medium with a diameter of 0.1 μm or less, abrasive particles with a diameter of 0.1 μm or less are uniformly dispersed on the surface of the magnetic layer compared to conventional abrasives, so the head surface can be worn evenly and appropriately. It is possible to prevent head scratches and instantaneous clogging, and to prevent a decrease in playback output that would otherwise occur due to thinning of the film. On the other hand, the durability of the magnetic layer is improved and instantaneous clogging can be prevented.

If the particle size of the abrasive is 0.1 μm or more, the above effects cannot be obtained, and head scratches and instantaneous clogging may occur. In addition, the above abrasive is used with a cap of about 3-2 ferromagnetic powder.
It is 0% by weight.

Similarly, other commonly used particulate additives (e.g., carbon black with an average particle size of 0.015 to 0.2 μm as an antistatic agent) may be added to the extent that they do not impede the achievement of the objects of the present invention. It is also possible to do so.

In manufacturing the magnetic layer of the magnetic recording medium of the present invention, first, a magnetic paint is prepared by kneading the above-mentioned abrasive with a ferromagnetic powder such as a ferromagnetic alloy powder, a binder, and, if necessary, other granular fillers with a solvent. It is formed by coating it on a support, subjecting it to magnetic field orientation, etc., and then drying it.

As the solvent used in the crosstalk, a solvent commonly used for preparing magnetic paints can be used.

For the method of cross-talk, a method commonly used as a cross-wire method for magnetic paint can be used. Further, the order of addition of each component can be set as appropriate.

Various techniques are known as techniques for preparing magnetic paints, and any of these known techniques can be used in manufacturing the magnetic recording medium of the present invention.

When preparing a magnetic paint, known additives such as a dispersant, an antistatic agent, and a lubricant may also be used.

Examples of dispersants include fatty acids having 12 to 18 carbon atoms, metal soaps made of the above fatty acids and alkali metals or alkaline earth metals, esters of the above fatty acids, and compounds in which some or all of the hydrogen atoms of the above fatty acids are replaced with fluorine atoms. Substituted compounds, amides of the above fatty acids, aliphatic amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl borates,
Known dispersants such as sarcosine) L alkyl ether esters, trialkyl polyolefin oxy quaternary ammonium salts, and lecithin can be mentioned. When a dispersant is used, it is usually used in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder used.

Examples of antistatic agents include natural surfactants; nonionic surfactants; cationic surfactants; anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate ester groups, and phosphate ester groups; Agents: Examples include amphoteric activators such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like. When a conductive fine powder such as carbon black is used as an antistatic agent, it is used in the range of 0.2 to 20 parts by weight per 100 parts by weight of the binder, and when a surfactant is used, is used in a range of 0.1 to 10 parts by weight.

Examples of lubricants include the above-mentioned fatty acids, higher alcohols, monobasic fatty acids having 12 to 2 carbon atoms such as phthyl stearate and sorbitan oleate, and monohydric or polyhydric alcohols having 3 to 20 carbon atoms. In addition to fatty acid esters, mineral oils, animal and vegetable oils, olefin low polymers, and α-olefin low polymers, known lubricants such as fine graphite powder and lubricants for plastics can be mentioned.

The amount of lubricant added can be arbitrarily determined according to known techniques.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly limited to having only the above-mentioned effects; for example, if the dispersant is a lubricant, Alternatively, it may act as an antistatic agent. Therefore, it goes without saying that the effects of compounds etc. exemplified by the above classifications are not limited to those listed in the above classifications, and when using substances that have multiple effects, the amount of is preferably determined by considering the action and effect of the substance.

The magnetic paint thus prepared is coated on the above-mentioned non-magnetic support according to a known method. Coating is usually done directly onto the non-magnetic support. However, it can also be applied onto a non-magnetic support via an adhesive layer or the like.

In the present invention, the magnetic layer is applied as a thin layer with a thickness of 1.0 μm or less. Even if the layer is made thinner in this manner, as described above, in the present invention, there will be no reduction in reproduction output due to instantaneous clogging of the head.

A magnetic layer coated on a non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. Also, if necessary, surface smoothing treatment is performed. A magnetic recording medium that has been subjected to surface smoothing treatment or the like is cut into a desired shape.

〔Example〕

Next, the present invention will be explained by examples. Note that "parts" in Examples (Comparative Examples) are "parts by weight."

Example 1 A magnetic coating liquid having the composition shown below was prepared, coated on a 7 μm thick polyethylene terephthalate nonmagnetic support so that the dry thickness of the magnetic layer was Lopm, and dried to produce a magnetic recording medium. .

Magnetic fabric liquid composition 813N4 (particle size 0.08 μm)
5 parts 400X110A)
12 parts urethane resin (manufactured by Nippon Polyurethane Co., Ltd.:
N-230112 parts Polyisocyanate (manufactured by Nippon Polyurethane Co., Ltd.: Coronate L) 8 parts Carbon plastic (particle size 0.04 μm) 2 parts Stylethyl ketone 300 parts Stearic acid 5 parts Butyl stearate 2 parts Example 2
A sample was prepared in the same manner as in Example 1 except that Zr02 (particle size 0.08 μm) was used instead of 813H2O.

Example 3 A sample was prepared in the same manner as in Example 1 except that diamond (particle size α08 μm) was used instead of 813N4.

Comparative example l α-A12o3 (particle size 0.5 μm) instead of 813N4
A sample was made in the same manner as in Example 1, except that .

Comparative Example 2 α-A1203 (particle size 0.08.c) was used instead of 813N4.
A sample was prepared in the same manner as in Example 1 except that +m) was used.

Comparative Example 3 A sample was prepared using 513N4 with a particle size of 0.5 μm instead of 813N4 with a particle size of 0.08 μm in Example 1.

The above sample was slit into long lengths in 81111,
A test was conducted using an 8 Tsuru VTR (FUJIX8: M8), and instantaneous clogging and reduction in playback output were investigated as follows.

Momentary clogging: Repeated playback after recording (1 pass 90 minutes) 10
It was expressed as the total number of momentary absences of the reproduced image on the monitor screen during the pass.

Output drop: Initial output (aB) of the first playback after recording and 2
It is shown as a difference from the output of the first pass (aB).

The results obtained are shown in the table below.

Instantaneous clogging Output drop (aB) Example 1 2 pieces ±0 1 20 near ±0 13 1 piece ±0 Comparative example 1 40 pieces -5 dB l 2 20 pieces -1aB I 3 5 pieces -5aB [Effects of the invention] As is clear from the above results, the present invention has a particle size of 0.
Compared to comparative examples using other abrasives or abrasives with particle sizes outside the range of the present invention, the samples using a 1 μm abrasive had almost no instantaneous clogging, and had higher playback output and stability. It turns out that it is excellent.

Claims (2)

[Claims] (1) In a magnetic recording medium in which a magnetic layer in which fine ferromagnetic powder is dispersed in a binder is formed on a non-magnetic support to a thickness of 1.0 μm or less, each of the magnetic layers has a particle size of 0.1 μm or less. silicon nitride (Si_3N_4), zirconium oxide (Zr
A magnetic recording medium comprising at least one of O_2) and diamond. (2) The magnetic recording medium according to claim (1), wherein the ferromagnetic fine powder is a ferromagnetic alloy powder.