JP2799616B2 - 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 configuration of the medium having a laminated magnetic layer.

(Prior art)

Magnetic recording media in information processing equipment are extremely useful as recording / reproducing elements and are in great demand, but at the same time, as recording media, the electromagnetic conversion characteristics are high and precise, and the recording capacity is rich and high density. In addition, it is required that the composition be suitable for ensuring runnability, durability, and durability, that it be inexpensive, and that production be free of any problems in production technology. Technical efforts have been made.

Generally, in order to obtain good electric conversion characteristics, the magnetic powder in the magnetic layer is packed at a high density, and it is preferable that the magnetic layer is a thin layer. However, the cost is high and it is difficult to secure the production volume.

In order to obtain good electromagnetic conversion characteristics, it is necessary to smooth the surface of the constituent layer on the magnetic layer side, and the particle size of the magnetic powder and fillers is selected and calendered.

However, if the surface is too smooth, the friction coefficient is increased and running performance is poor. On the other hand, if the surface is too rough, spacing loss, powder drop and head wear become severe.

Therefore, the smoothness or roughness of the surface of the magnetic layer is a matter to be sufficiently examined, but the surface of the non-magnetic support used in the conventional magnetic recording medium (hereinafter collectively referred to as a magnetic tape) is generally the surface of the magnetic tape. It has a surface roughness that derives irregularities to the extent that it has a problem on electromagnetic characteristics, and coupled with the fact that many magnetic tapes that have been put to practical use are composed of a single magnetic layer, The provision of a small amount of undercoat layer does not reach the point where the surface roughness can be absorbed, and causes a high frequency of dropout and the like.

This trouble came to relief by thickening the magnetic layer,
The low level of electromagnetic conversion characteristics due to the thick film is inevitable.

On the other hand, it is possible to considerably analyze the contact behavior with microprojections and damage to the friction surface from the viewpoint of tribology (tribology), but the deformation received by the microprojections is two types of elastic deformation and plastic deformation depending on the shape. The plasticity index の defined below is given as an index of which one is considered and which is received.

ψ = (E ′ / H) (σa / γm) ^1/2 1 / E ′ = (1−ν ₁ ² ) / E ₁ + (1−ν ₂ ² ) / E ₂ where E ₁ and E ₂ are The longitudinal elastic modulus of the contact surface material, H is hardness, ν ₁ and ν ₂ are Poisson's ratio, σa is the standard deviation of the height of the projection apex, and γm is the average radius of the tip of the projection.

E '/ H is a term depending on the physical properties of the surface material, and σ
a / γm is a term derived from the projection shape.

In the above equation, when ψ <0.6, elastic deformation occurs, and ψ
When> 3, it undergoes plastic deformation.

E ′ / H is almost constant depending on the material used, while σa> γm is common in the art and σa / γm fluctuates considerably as a numerical value. The surface damage condition comes different.

The protrusion shape (surface roughness) directly affects the runnability, surface friction, and sparing of the magnetic tape, and is a problem that cannot be overlooked. I can't.

[Object of the invention]

An object of the present invention is to provide an electromagnetic tape which has good electromagnetic conversion characteristics without performance deterioration due to the surface roughness of a non-magnetic support, and has good recording reproducibility in both high and low frequency regions.

[Configuration of the invention]

An object of the present invention described above, the first magnetic layer having a thickness of d ₁ on the non-magnetic support provided a magnetic recording medium having a laminated magnetic layer further superposed a second magnetic layer having a thickness of d _2, wherein The thickness d ₁ of the first magnetic layer is set to 4 × 10 ⁻³ ≦ (Ra / d ₁ ) ≦ 1.8 × with respect to the center line average roughness Ra and the maximum roughness Rmax of the magnetic layer side surface of the non-magnetic support. A magnetic recording medium characterized in that 10 ⁻² 4 × 10 ⁻² ≦ (Rmax / d ₁ ) ≦ 4.5 × 10 ⁻¹ and the thickness d ₂ of the second magnetic layer is d ₂ ≦ 10 μm. Achieved by

In the embodiment of the present invention, a preferable range of Ra and Rmax is 4.5 × 10 ⁻³ ≦ (Ra / d ₁ ) ≦ 1.0 × 10 ⁻² 7.0 × 10 ⁻² ≦ (Rmax / d ₁ ) ≦ 3.0 × 10 ^-1 as the range of the thickness d ₂ of the second magnetic layer is _{0.1 ≦ d 2 ≦ 1.0 (μm} ). Still thickness range d ₁ of the first magnetic _{layer, 1.0 ≦ d 1 ≦ 3.0 (} μm) are preferred.

(Effects)

By providing the constituent requirements of the present invention, the surface roughness Ra of the finished magnetic layer: 0.001 to 0.018 μm, Rmax; 0.030 to 0.150
μm, the thickness of the magnetic layer can be reduced to 4.0 μm or less, and the high electromagnetic conversion characteristics can be given by suppressing the thickness to 3.0 μm or less.
It is possible to provide a magnetic tape suitable for recording and reproduction in both frequency bands optimally applied to recording in a low frequency range.

In the present invention, the apparatus and the material technology conventionally used for manufacturing magnetic tapes are used.

As the magnetic material used in the present invention, for example, γ-Fe
₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , Co-coated γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe
₃ O ₄ , Co-coated Fe ₃ O ₄ , oxide magnetic material such as CrO ₂ such as Fe, Ni,
Fe-Ni alloy, Fe-Co alloy, Fe-Ni-P alloy, Fe-Ni-Co alloy, Fe-Mn-Zn alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-Cr alloy, Fe-Co -Ni-P alloy, Co-P alloy, Co-Cr alloy, etc.Fe, N
Various ferromagnetic substances such as metal magnetic powder containing i, Co as a main component are exemplified. As an additive to these metal magnetic materials,
Elements such as Si, Cu, Zn, Al, P, Mn, and Cr or compounds thereof may be contained. Further, hexagonal ferrites such as barium ferrite, iron nitride and the like are also used.

Examples of the binder used in the present invention include polyurethane having abrasion resistance. It has a strong adhesive force to other substances, is mechanically tough against repeated stress or bending, and has good wear resistance and weather resistance.

Also, when a cellulose resin and a vinyl chloride copolymer are used in combination with the polyurethane, the dispersibility of the magnetic powder in the magnetic layer is improved, and the mechanical strength is increased. However, the layer becomes too hard with only the cellulose resin and the vinyl chloride copolymer, but this can be prevented by the presence of the above-mentioned polyurethane.

Cellulose ether,
Cellulose inorganic acid esters and cellulose organic acid esters can be used. The above-mentioned vinyl chloride copolymer may be partially hydrolyzed. As the vinyl chloride copolymer, preferably, a copolymer containing vinyl chloride-vinyl acetate is used.

Phenoxy resins can also be used. Phenoxy resin has high mechanical strength, excellent dimensional stability,
It has advantages such as good heat resistance, water resistance, chemical resistance and good adhesiveness.

These advantages are complementary to the above-mentioned polyurethane, and can significantly enhance the temporal stability of the physical properties of the tape.

Further, in addition to the binder described above, a mixture of a thermoplastic resin, a thermosetting resin, a reactive resin, or an electron beam irradiation-curable resin may be used.

In order to improve the durability of the magnetic layer of the magnetic tape of the present invention, various hardeners can be contained in the magnetic paint, for example, isocyanate can be contained.

Examples of the aromatic isocyanate include tolylene diisocyanate (TDI) and the adduct thereof with an isocyanate active hydrogen compound.
Those in the range of 100 to 3,000 are preferred.

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

A dispersant is used in the magnetic paint used to form the magnetic layer, and if necessary, additives such as a lubricant, an abrasive, a matting agent, and an antistatic agent may be contained. As the dispersant used in the present invention, in addition to the phosphate according to the present invention, amine compounds, alkyl sulfates, fatty acid amides, higher alcohols, polyethylene oxide, sulfosuccinic acid, sulfosuccinates, known surfactants And salts thereof, and a salt of a polymer dispersant having a negative organic group (for example, -COOH) can also be used. These dispersants may be used alone or in combination of two or more. In addition, as a lubricant,
Silicon 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 of the fatty acids are combined with the number of carbon atoms. Fatty acid esters (so-called waxes) composed of 21 to 23 monohydric alcohols can also be used. These lubricants are added in the range of 0.2 to 20 parts by weight based on 100 parts by weight of the binder.

As the abrasive, generally used materials such as fused alumina, silicon carbide, chlorinated oxide, corundum, artificial corundum, artificial diamond, garnet, emery (main components: corundum and magnetite) and the like are used. These abrasives have an average particle size of 0.05 to 5 μm, and particularly preferably 0.1 to 2 μm. These abrasives are added in the range of 1 to 20 parts by weight based on 100 parts by weight of the binder.

As the matting agent, an organic powder or an inorganic powder is used individually or in combination.

As the organic powder used in the present invention, acrylic styrene-based resin, benzoguanamine-based resin powder, melamine-based resin powder, and phthalocyanine-based pigment are preferable, but polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, and polyimide-based resin are preferable. Powders, polyfluorinated ethylene resin powders and the like can also be used. As inorganic powders, silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide, α-Fe ₂ O
₃ , talc, kaolin, calcium sulfate, boron oxide, zinc fluoride, molybdenum dioxide.

Examples of antistatic agents include conductive powders such as carbon black, graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds; natural surfactants such as saponin; alkylene oxides; glycerin And glycidol-based nonionic surfactants; higher alkylamines, quaternary ammonium salts, pyridine, other heterocycles, cationic surfactants such as phosphonium or sulfoniums; carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid Anionic surfactants containing an acidic group such as an ester group or a phosphoric ester group; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphoric esters of amino alcohol;

Examples of the solvent to be blended in the paint or a diluting solvent at the time of applying the paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone;
Alcohols such as methanol, ethanol, propanol and butanol; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and ethylene glycol cenoacetate; ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane and tetrahydrofuran; benzene , Toluene and xylene; and halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform and dichlorobenzene.

Examples of the support include polyethylene terephthalate, polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarbonate. Metals such as Cu, Al and Zn, glass, ceramics such as boron nitride BN and Si carbide can also be used.

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

An intermediate layer for improving adhesion may be provided between the support and the magnetic layer.

As a coating method for forming the above-mentioned laminated magnetic layer on the support, in the case of wet on wet, simultaneous and sequential application of extrusion, river scroll + extrusion, gravure roll + exclusion, and the like can be considered.

Further, it is also conceivable to combine any one of air doctor coat, blade coat, air knife coat, squeeze coat impregnated coat, transfer roll coat, kiss coat, cast coat and spray coat.

In the case of wet on dry, any combination of the above coating methods may be used.

Next, FIG. 2 shows an example of the above-described magnetic tape manufacturing apparatus.

In this manufacturing apparatus, in manufacturing the magnetic tape shown in FIG. 1, first, the film-like support 1 pulled out from the supply roll 32 is coated with the respective coating materials for the magnetic layers 2 and 4 by the extrusion coaters 10 and 11. After applying, for example, 2000Gaus
s is oriented by the pre-orientation magnet 33, and further, for example, 2000G
The auss is introduced into a drier 34 in which a later-staged magnet 35 is disposed, where hot air is blown from nozzles disposed above and below for drying. Next, the dried support 1 with each coating layer is led to a super calendar device 37 composed of a combination of calendar rolls 38, where it is calendered and then wound up on a winding roll.
Winded up at 39. Each paint may be supplied to the extrusion coaters 10 and 11 through an inline mixer (not shown). Note that, in the figure, the arrow D indicates the transport direction of the non-magnetic base film. Extrusion coaters 10 and 11 are provided with liquid reservoirs 13 and 14, respectively, so that the paint from each coater is wet on wet.
Layer by method.

FIG. 3 shows an example of an extrusion coater. Figure (A)
Are the same as those shown in FIG.
(B) is for one head (for sequential wet on wet coating), and (C) is a single head where both magnetic paints 2 'and 4' intersect inside the head. It discharges in the same direction (for simultaneous wet-on-wet multilayer coating).

Since the above method is a wet-on-wet coating method, the uppermost layer can be easily applied on the lower layer, and particularly the uppermost layer having a small thickness can be uniformly applied, and a plurality of layers can be applied with high reproducibility.

In addition, the apparatus used for the above-mentioned multilayer coating does not necessarily need to be an extrusion coater, and other known coating apparatuses can be used.

〔Example〕

 The present invention will be specifically described with reference to examples.

Examples 1-4 and Comparative Examples (1)-(5) The following magnetic paint formulations A and B, and undercoat paint formulation C
A magnetic tape sample was prepared in accordance with the above and the characteristics were measured.

 All "parts" in Examples are parts by weight.

Magnetic coating composition A Co-γ-Fe ₂ O ₃ 100 parts Vinyl chloride / vinyl acetate / vinyl alcohol copolymer 15 parts Polyurethane resin 5 parts α-Al ₂ O ₃ 3 parts Carbon black 10 parts Myristic acid 2 parts Stearic acid 2 Part Cyclohexanone 100 parts Methyl ethyl ketone 100 parts Toluene 160 parts Magnetic coating composition B Co-γ-Fe ₂ O ₃ 100 parts Vinyl chloride / vinyl acetate / vinyl alcohol copolymer 13 parts Polyurethane resin 4 parts α-Al ₂ O ₃ 2 parts Carbon Black 13 parts Myristic acid 1 part Stearic acid 1 part Butyl stearate 2 parts Cyclohexanone 200 parts Methyl ethyl ketone 200 parts Toluene 160 parts Subscription formula C Vinylidene chloride / acrylonitrile copolymer 10 parts Cyclohexanone 90 parts On a terephthalate support, coated as shown in Table 1, Examples and Comparative Examples It was.

The performance of the obtained samples was evaluated, and the results are shown in Table 2.

As is clear from Table 2, the video tapes of the examples have excellent electromagnetic conversion characteristics and provide tapes with little dropout.

Also, the RF envelope represents the goodness of the video tape to the head of the deck, and is generally known to be closely related to the coefficient of friction and the stiffness of the tape. However, we have experimentally found that this RF envelope varies greatly with the dry thickness of the magnetic layer. Therefore, the thickness of the magnetic layer may not be too large in order to smooth the surface roughness, and an appropriate film thickness is required. In Examples 1 to 4, the film thickness is appropriate and the RF envelope is good, whereas in Comparative Example 2, the film thickness is too large, and the RF envelope is defective. In Comparative Example-1, the roughness of the non-magnetic support was too large relative to the thickness of the lower layer, resulting in an increase in D / 0 and a decrease in electromagnetic characteristics (particularly, poor chroma output having low frequency characteristics). I have.

Similarly, Comparative Examples 3 and 4, which are an upper layer and a lower single layer, also have extremely poor D / 0 and electromagnetic characteristics, and Comparative Examples using an undercoat layer
5 also shows that this cannot be a means for improving this.

Using a dropout counter VD-5M manufactured by JVC, the output that is longer than 1500 μsec and the output of the RF envelope drops by 20 dB or more is considered as one dropout.
The total length was measured, and the average value per minute was determined.

(4) Lumi S / N Measured with a color video noise meter Shibasoku 925D / 1.

(5) C-Cut Made by NF circuit design block, AC voltmeter M-170
Was measured by (Unit: dB) (6) RF envelope Run each video tape on a VHD deck (J-VC S-7000) and project the RF envelope on an oscilloscope (HITACHI). The oscilloscope screen was photographed, the maximum and minimum values of the envelope were read, and the ratio was examined.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetic tape according to the present invention. Second
FIG. 3 is a schematic view of an example of a magnetic tape manufacturing apparatus, and FIG. 3 is a view showing a shape of a head of an extrusion coater. DESCRIPTION OF SYMBOLS 1 ... Support, 2 ... First magnetic layer, 3 ... Back coat layer, 4 ... Second magnetic layer, 10 and 11 ... Code head, 37 ... Calendar, 2 'and 4' ... Magnetic paint

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/716 G11B 5/704

Claims (1)

(57) [Claims] 1. A first magnetic layer having a thickness of d ₁ provided on a nonmagnetic support, a magnetic recording medium having a laminated magnetic layer further superposed a second magnetic layer having a thickness of d _2, the first magnetic The thickness d ₁ of the layer,
With respect to the center line average roughness Ra and the maximum roughness Rmax of the magnetic layer side surface of the nonmagnetic support, 4 × 10 ⁻³ ≦ (Ra / d ₁ ) ≦ 1.8 × 10 ⁻² 4 × 10 ⁻² ≦ ( Rmax / d ₁ ) ≦ 4.5 × 10 ⁻¹ , and the thickness d ₂ of the second magnetic layer is d ₂ ≦ 10 μm.