JPH02257424A - Magnetic recording medium having excellent electromagnetic conversion characteristics with little sliding noise and d/o - Google Patents

Abstract

PURPOSE:To obtain excellent electromagnetic conversion characteristics and to reduce sliding noise and dropout by providing a nonmagnetic layer adjacent to a nonmagnetic supporting body and incorporating a filler of >=50mum average particle size into the nonmagnetic layer. CONSTITUTION:The nonmagnetic layer is provided adjacent to the nonmagnetic supporting body and at least one magnetic layer is provided thereon. The filer of >=50mum average particle size is incorporated into the nonmagnetic layer. By incorporating the filler of specific particle size into the nonmagnetic layer adjacent to the nonmagnetic supporting body, the amt. of filler to be contained in the magnetic layer can be reduced and thus, the density of magnetic material in the magnetic layer can be increased. The obtd. medium has high electromagnetic conversion characteristics with little sliding noise and dropout.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to magnetic recording media such as magnetic tapes, magnetic disks, and magnetic 70 disks, which have particularly excellent electromagnetic conversion characteristics and other characteristics, and are suitable as video tapes. The present invention relates to magnetic recording media used for.

[Background of the invention]

In recent years, there has been an increasing demand for higher densities in magnetic recording media, and in particular, with the demand for higher recording frequencies in video tapes, extremely high-density recording is required and support is increasing. Various types of devices have been proposed in which a magnetic layer is provided on the magnetic body with a two-layer structure consisting of an upper layer and a lower layer, or a structure with three or more layers (hereinafter, these may be collectively referred to as a multilayer structure).

As is well known, magnetic recording media usually contain ferromagnetic powder, carbon black, abrasives, etc. in various synthetic or natural polymer materials (so-called resin materials) called binders. A suitable solvent is added as necessary to a uniformly dispersed mixture of lubricants, matting agents, dispersants, hardeners, and other components, and the magnetic coating thus obtained is applied onto a support. It is manufactured by forming a magnetic layer, orienting the magnetic layer in a magnetic field, and then drying it.

There are various factors that affect the electromagnetic change characteristics and other characteristics of magnetic recording media. Typical examples include the layer structure, the type and amount of components used in each layer, etc. are correlated with each other and influence the characteristics of the magnetic recording medium.

Incidentally, in order to improve the magnetic recording characteristics of magnetic recording media, many methods have been proposed in which the layer structure, the types of components used, and their ratios are variously changed, but none of them still have sufficiently satisfactory characteristics. The current situation is that nothing can be found.

[Purpose of the invention]

In view of these circumstances, the present inventors have developed a magnetic recording medium that has excellent electromagnetic conversion characteristics, has low both sliding noise and dropout (Dlo), and is particularly suitable for use as a videotape. As a result of various studies in an attempt to develop a magnetic recording medium, the following magnetic recording medium was found to be suitable for the purpose, and the present invention was achieved.

[Structure of the invention]

The present invention provides a magnetic recording medium comprising multiple layers on a non-magnetic support, wherein the layer adjacent to the non-magnetic support is a non-magnetic layer, and the non-magnetic layer contains a filler having an average particle size of 50+sμ or more. The present invention relates to a magnetic recording medium characterized by containing.

The magnetic recording medium of the present invention comprises a nonmagnetic layer provided on a nonmagnetic support, and at least one magnetic layer provided on the nonmagnetic layer.

Here, the non-magnetic layer is, needless to say, a layer that does not contain a magnetic substance, and in the present invention, in this non-magnetic layer,
A filler having an average particle diameter of 50 mμ or more is contained.

The filler in the present invention is a so-called filler,
For example, in this type of magnetic recording medium, carbon black, which is commonly used as a light shielding agent and antistatic agent, and Al2203 (alumina) and 5iC (silicon), which are used as abrasives and matting agents, etc. carbide) or CrO! Refers to inorganic fine particles such as (chromium oxide) and other insoluble organic fine powders.

In the present invention, if the particle size of the filler is too small, it is not preferable from the viewpoint of effectiveness, so it is usually
Particles having a particle size of 0μ or more are contained in the nonmagnetic layer adjacent to the nonmagnetic support.

The upper limit of the particle size of the filler varies depending on the type used, so it cannot be generally specified, but for example, when carbon black is used as the filler, the upper limit of the particle size is about 300 to 500 μm. It is.

In this way, by incorporating a filler with a specific particle size into the non-magnetic layer adjacent to the non-magnetic layer, the content of the filler in the magnetic layer can be reduced, and thereby the magnetic material in the magnetic layer can be reduced. It is advantageous to be able to increase the density of

In the present invention, at least one magnetic layer is provided on the nonmagnetic layer, and examples of the magnetic material used for this magnetic layer include γ-FelOs and C.

Containing γ-Fe, O, or Co deposited-Fe20. Co-γ-Fe! 03, Fe50i Co-containing Fe5
Oa or Co coated Fe, Co-γ-Fe such as 04
,Ocry, and other oxide magnetic materials, such as F
e5Ni, Fe-Ni alloy, Fe-Co alloy, Fe-
N1-P alloy, Fe-Ni-Co alloy, Fe-Mn-Z
n alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-C
r alloy, Fe-Co-N1-P alloy, Co-P alloy, C
Examples include various ferromagnetic materials (powders) such as metal magnetic powders mainly composed of Fe, Ni, and Co such as o-Cr alloys.

As an additive to these metal magnetic materials, 5i1Cu
, Zn, Al2, P, Mn, Cr, or a compound thereof.

Hexagonal ferrite such as barium ferrite, iron nitride, etc. are also used.

In the present invention, it is preferable to include a resin containing a functional group as a binder in the nonmagnetic layer adjacent to the nonmagnetic support.

There are various resins containing functional groups that can be used, and a suitable example thereof is a polyester resin containing sodium sulfonate.

Conventionally, various natural or synthetic resins have been proposed as binders for use in this type of magnetic recording medium.
In the present invention, the nonmagnetic layer containing the filler may contain any known binder together with the functional group-containing resin, as long as it does not impair the effects of the present invention.

Suitable such binders include, for example, abrasion-resistant polyurethanes.

It has strong adhesion to other materials, is mechanically strong to withstand repeated applied forces or bending, and has good abrasion and weather resistance.

Furthermore, if a cellulose resin and a vinyl chloride copolymer are used in combination with polyurethane, the dispersibility of the magnetic powder in the magnetic layer will be improved and its mechanical strength will be increased.

However, if only the cellulose resin and the vinyl chloride copolymer are used, the layer becomes too hard, but this can be prevented by the presence of the above-mentioned polyurethane.

Usable cellulose resins include cellulose ether, cellulose inorganic acid ester, cellulose organic acid ester, and the like.

The polyurethane and vinyl chloride copolymers mentioned above may be partially hydrolyzed, and copolymers and polymer blends with polyester resins can also be used.

Preferable examples of the vinyl chloride copolymer include a copolymer containing vinyl chloride-vinyl acetate or a copolymer containing vinyl chloride-vinyl acetate-vinyl alcohol.

Phenoxy resins can also be used.

Phenoxy resin has advantages such as high mechanical strength, excellent dimensional stability, good heat resistance, water resistance, chemical resistance, and good adhesiveness.

These advantages are complementary to those of the polyurethane described above, and the stability of the physical properties of the magnetic recording medium over time can be significantly improved.

Furthermore, in addition to the binders described above, mixtures of thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used.

In order to improve the durability of the magnetic layer of the magnetic recording medium of the present invention, the magnetic paint can contain various curing agents,
For example, isocyanates can be included. Examples of aromatic incyanates include tolylene diisocyanate (TDI) and adducts of these isocyanates with active hydrogen compounds, with an average molecular weight of 10
A value in the range of 0 to 3.000 is preferred.

Examples of aliphatic incyanates include hexamethylene diisocyanate (HMDI) and adducts of these incyanates and active hydrogen compounds. Among these aliphatic incyanates and adducts of these incyanates and active hydrogen compounds, those having a molecular weight in the range of 100 to 3,000 are preferred. Among the aliphatic isocyanates, non-alicyclic incyanates and adducts of these compounds with active hydrogen compounds are preferred.

The magnetic paint used to form the above-mentioned magnetic layer usually contains additives such as a lubricant, an abrasive, a matting agent, and an antistatic agent, and a dispersant is used if necessary.

Examples of lubricants include silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, lauric acid, myristic acid, monobasic fatty acids having 12 to 16 carbon atoms, and the total number of carbon atoms in the fatty acids. Fatty acid esters (so-called waxes) made of monohydric alcohols having 21 to 23 carbon atoms can also be used.

These lubricants are usually added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.

As abrasives, commonly used materials include fused alumina, various aluminas such as σ alumina, silicon carbide, chromium oxide, corundum, artificial corundum, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. be done.

The abrasive used usually has an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm.

These abrasives are usually added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder.

As the matting agent, organic powder or inorganic powder may be used individually or in combination.

As the organic powder used in the present invention, acrylic styrene resin, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment are preferable, but polyolefin resin powder, polyester resin powder, polyamide resin powder, and polyimide resin are preferred. Powder, polyfluoroethylene resin powder, etc. can also be used, and inorganic powders include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate,
barium sulfate, zinc oxide, tin oxide, aluminum oxide,
Chromium oxide, silicon carbide, calcium carbide, σ-Fe@O
s, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, and molybdenum dioxide.

The matting agent usually has an average particle size of 50 .mu.m, preferably 50 to 200 .mu.I. Antistatic agents include carbon black, graphite, conductive powders such as tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds; natural surfactants such as saponin; alkylene oxides, and glycerin. nonionic surfactants such as glycidol-based, higher alkylamines, quaternary ammonium salts, pyridine, other heterocycles, cationic surfactants such as phosphomolam or sulfonium, carboxylic acids, sulfonic acids, phosphoric acids, sulfuric acids. Examples include anionic surfactants containing acidic groups such as ester groups and phosphoric ester groups; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric or phosphoric esters of amino alcohols.

Dispersants used in the present invention include phosphoric acid esters, amine compounds, alkyl sals, fatty acid amides, higher alcohols, polyethylene oxides, sulfosuccinic acids, sulfosuccinic esters, known surfactants, etc. It is also possible to use salts of polymeric dispersants having negative organic groups (e.g. -〇〇〇〇).

These dispersants may be used alone or in combination of two or more.

Solvents blended into the magnetic paint or diluting solvents used during application of this paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohols such as methanol, ethanol, globanol, and butanol, methyl acetate, ethyl acetate, butyl acetate,
Esters such as ethyl lactate and ethylene glycol monoacetate, ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, and tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene, and xylene, methylene chloride, ethylene chloride, carbon tetrachloride, Halogenated hydrocarbons such as chloroform and dichlorobenzene can be used.

In addition, as a support, polyethylene terephthalate,
Examples include polyesters such as polyethylene-2,6-7-talate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarbonate. metals, glass, boron nitride, ceramics such as Si carbide, etc. can also be used.

The thickness of these supports is about 3 to 100 μm in the case of a film or sheet, preferably 5 to 50 μm,
In the case of a disk or card shape, it is about 30 urx-10+am, and in the case of a drum shape, it is used in a cylindrical shape, and the type is determined depending on the recorder used.

Coating methods for forming the magnetic layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, Sober roll coating, transfer roll coating, gravure coating, kiss coating, and casting. Coat, spray coat, extrusion coat, etc. can be used, but are not limited to these.

When constructing a magnetic layer on a support using these coating methods, there are two methods: one method involves stacking the coating and drying steps layer by layer (so-called wet-on-dry coating method), and the other method involves stacking the coating and drying steps layer by layer (so-called wet-on-dry coating method). There is a method in which layers are coated simultaneously or sequentially (so-called wet-on-wet coating method), and either method can be used in manufacturing the magnetic recording medium of the present invention.

Since it is undesirable from the viewpoint of effectiveness to make the thickness of the uppermost magnetic layer of the magnetic recording medium of the present invention too thick, it is generally desirable that the thickness be 1.5 μm or less.

In addition, above and below the magnetic layer or between the magnetic layers,
A nonmagnetic layer may also be provided as long as the effects of the present invention are not impaired.

By such a method, the magnetic layer coated on the support is subjected to a treatment to orient the ferromagnetic metal oxide powder in the layer, if necessary, and then the formed magnetic layer is dried.

In this case, the orientation magnetic field is approximately lθ~500 in alternating current or direct current.
The temperature is about 0 Gauss, the drying temperature is about 30 to 120°C, and the drying time is about 0.1 to 10 minutes. Further, the magnetic recording medium of the present invention is manufactured by subjecting it to surface smoothing treatment or cutting it into a desired shape, if necessary.

Next, the present invention will be explained with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

〔Example〕

After thoroughly kneading the paints with the compositions listed in Table 1 (paints for non-magnetic layers), Table 2 (paints for magnetic layers other than the top layer), and Table 3 (paints for the topmost magnetic layer), Polyisocyanate (manufactured by Nippon Polyurethane Industries Co., Ltd., product name
A coating material for coating was prepared by adding 5 parts by weight of Coronate L].

Next, each coating material was coated in multiple layers on a support according to a conventional method, subjected to magnetic field orientation treatment, and dried to produce a magnetic recording medium.

Electromagnetic conversion characteristics and other characteristics of the magnetic recording medium thus obtained were measured.

The type of filler used and other manufacturing conditions are shown in Table 3.
Table 4 shows the characteristics of the magnetic recording medium.

Table 1: Paint A for non-magnetic layers; Table 2: Paint B for magnetic layers other than the top layer; Table 4: filler type and other manufacturing conditions; Table 5: properties of magnetic recording media; Coating C for the uppermost magnetic layer> As is clear from Table 5, the magnetic recording medium of the present invention (each example) has high electromagnetic conversion characteristics such as lumi S/N and chroma output. It is excellent in that it has low sliding noise and less dropouts, but
Although the magnetic recording media (comparative examples) not according to the present invention have good electromagnetic conversion characteristics, there are many sliding noises and dropouts.

<Method for measuring characteristics in Examples and Comparative Examples> Lumi S/N A 100% white signal is input to the magnetic recording medium at a reference level. The reproduced video signal is input to 925DI (noise meter manufactured by Shibaku), and the Lumi S/N is read from the absolute noise value obtained.

- The output during playback of a chroma output 500 Kllz% RF signal was determined.

Sliding noise> (i) Perform playback without running the tape, and measure system noise with a spectrum analyzer.

(i) Play the sample tape for 1 minute and measure the sliding noise with a spectrum analyzer (1 pass).

(iii) The sample tape is played back 10 times for 1 minute each, and the sliding noise is measured using a spectrum analyzer.

(10 passes) (iv) Read the noise level around 9 MHz (C0 dB based on the system noise) and the noise values of each of the 1 path and 10 path.

All measurements are at room temperature 20±2°C1 relative humidity lO±2
% environmental conditions, with the top cover of the VTR removed.

Dropout> 100% dropout in a certain area (10 to 30m) on the magnetic recording medium
A white signal was input and played back, and the dropout of 10 μs at a -14 dB level was measured in units of 1 minute using a Shibaku Co., Ltd. counter (model VHOIBZ).
The average value of the total length of the measurement part is taken as the measurement value.

〔Effect of the invention〕

The magnetic recording medium of the present invention has excellent electromagnetic conversion characteristics such as lumi S/N and chroma output, and has low sliding noise and low dropout.

Claims (1)

[Claims] (1) In a magnetic recording medium comprising multiple layers on a non-magnetic support, the layer adjacent to the non-magnetic support is a non-magnetic layer, and a filler with an average particle size of 50 mμ or more is contained in the non-magnetic layer. A magnetic recording medium characterized by containing: