JPH0428015A - Production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the generation of roughening and orientation return on the surfaces of coating films by drying and curing undried magnetic layers while applying perpendicular orientation to magnetic particles between the connected pairs of different pole opposition magnets formed by connecting the magnetic poles and magnetic pole groups with high permeability material plates. CONSTITUTION:In the traveling direction arrow A of a web 10, a magnetic pole 2a is disposed opposite to the magnetic poles 1a of the different pole opposition type and plural 2b1 to 2bn opposite to 1b as the magnetic poles 2a, 2b1 to 2bn on the undried magnetic layer side at suitable intervals. The magnetic poles 1a, 2a have the magnetic field intensity sufficient for orienting the magnetic particles in the undried magnetic layers in a perpendicular direction and 1b to 2bn have the magnetic field intensity to the extent of not generating the orientation return or above. Drying wind, the magnetic fields or electron beam or UV devices 5 are disposed between the magnetic poles 2a, 2b1 to 2bn to dry or cure the undried magnetic layers and to stop the movement of the particles to the extent that the orientation return of the magnetic particles does not arise any more. The perpendicular orientation is stabilized in this way and the high-density recording is assured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media, and particularly to an apparatus for manufacturing perpendicular magnetic recording media using a coating method.

[Conventional technology]

In recent years, there has been a desire to develop high-density magnetic recording media that are superior in recording and reproducing at short wavelengths.
Conventional coated magnetic recording media perform recording and reproduction in the longitudinal direction, so they are approaching their limits and are becoming difficult to cope with. Therefore, the perpendicular magnetic recording system, which in principle has excellent recording and reproducing characteristics at short wavelengths, has attracted attention, and active research and development is being carried out.

One of these is a metal thin film type perpendicular magnetic recording medium that uses vacuum evaporation technology, but this has a significantly different structure than conventional magnetic recording media, and has various problems such as durability and different manufacturing methods. ing.

Under these circumstances, a perpendicular magnetic recording medium using a coating method, which is a conventional magnetic recording medium, is attracting attention.

This perpendicular magnetic recording medium requires orientation treatment using a perpendicular magnetic field when the coating layer is not dried, and is disclosed in Japanese Patent Application Laid-Open No. 57-5824.
No. 1 to No. 58246, No. 58-203631 and No. 6
No. 4-46224 and the like propose vertical alignment, drying in a magnetic field, and arranging two or more pairs of magnets with opposite polarities and passing drying air between the magnets to increase the alignment efficiency.

[Problem to be solved by the invention]

However, in these cases, the magnetic field between the opposing magnets becomes weak or a magnetic field strength wave is generated, and alignment returns are likely to occur, resulting in instability and insufficiency. In order to industrially process the web continuously and at high speed, there are problems such as the need for a long pair of magnets.

The object of the present invention is to provide a perpendicular magnetic recording medium with stable and sufficient perpendicular alignment, guaranteed high density recording, and high productivity at a low cost.

(Means for solving tJB) The formation of magnetic particles in said layer by a perpendicular magnetic field penetrating a wet magnetic layer further coated on a non-magnetic support or a support already coated with magnetic paint thereon. In the direct distribution method, a long N in the running direction is placed on the support side of the undried magnetic layer.
(S) pole and a plurality of short S (N) poles on the undried magnetic layer side, and each pole is connected with a high i3 magnetic material plate between a connected pair of opposite polarity magnets. Perpendicular orientation is given to the magnetic particles, and the magnetic particles are dried or hardened in a magnetic field to such an extent that the magnetic particles do not reorient due to drying air, electron beam irradiation, ultraviolet ray irradiation, etc. from the spacing between the magnets on the side of the undried magnetic layer, and then removed from the magnetic field. This is achieved by a method of manufacturing a magnetic recording medium in which the final desired coating film is obtained by sufficiently drying or curing the film.

In the embodiment of the present invention, although it depends on the viscosity of the magnetic paint and the characteristics of the magnetic particles, the interval width of the magnet on the undried magnetic layer side/N-5 between opposing magnets is set to 1 or less, and the position where the support passes is set to N-3
A ratio of 1:2 or less between the opposing magnets compared to the magnet on the support side is preferable because a stable magnetic field region can be obtained.If each magnet or connected pair of magnets is provided with a yoke made of a high magnetic permeability material, the orientation efficiency can be further increased and the magnetic field strength can be increased. can be made uniform.

As the high magnetic permeability material, any material such as permalloy or mild steel can be used.

The strength of the magnetic field of the orientation device is appropriately determined depending on the magnetic properties of the particles of the magnetic paint, the viscosity of the paint, and the like.

〔Example〕

The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the apparatus of the present invention, in which a web 1
Opposed to the magnetic pole 1a of different polarity and the same type in the advancing direction arrow A of 0, 2
a, a plurality of 2b facing 1b, 2b z, 2b
x, ---2b a as the magnetic pole 2a2b on the undried magnetic layer side
r, 2 bz, ---2b, an appropriate interval Sl,
S.R.

S s, -5, and the stable region in the strong magnetic field between each of the different magnetic poles is such that the undried web 10 coated with magnetic paint is placed from 1/3 of the spacing between the different magnetic poles to the support side magnetic pole 1a, l
It is preferable to run in the direction of arrow A near point b.

The magnetic poles 1a, 2a have a magnetic field strength sufficient to orient the magnetic particles in the wet magnetic layer in the vertical direction, and the magnetic poles 1b, 2
br, 2bz, -2b- are magnetic field strengths that are at least as high as not causing orientation return. In a magnetic field of 2 a,
2 b I+ 2 bz, -2b, + magnetic pole s l+
s, -87 to dry or harden the magnetic particles in the undried magnetic layer by disposing a drying air beam or an ultraviolet ray device to stop the movement of the particles.

In this process, the features of the present invention are Ib, 2b, and so on.

In the range of the magnetic field strength above which no reorientation occurs between 2b, . This results in a uniform and stable magnetic field for the magnetic particles in the undried magnetic layer, which prevents unnecessary movement of the magnetic particles during the initial drying and curing process, minimizing the surface roughness of the dried film. I can do it. This reduces the spacing loss between the magnetic layer and the magnetic head during recording and reproduction, and provides an excellent magnetic recording medium as a perpendicular magnetic recording system featuring short wavelength recording.

The binder solution for producing the magnetic paint used in the present invention is a binder solution containing a magnetic material, a resin component, a solvent, and further contains a lubricant, an abrasive, an antistatic agent, etc. as necessary. .

Examples of magnetic materials include hexagonal ferrite such as barium ferrite, iron nitride, and r- containing γ-FezOs+Go.
Fe, O, , Co deposited p'e30. , ferromagnetic materials such as oxide magnetic materials such as crO□ and metal magnetic powders containing Fe, Ni, and Co as main components.

Additives to these metal magnetic materials include St, C
Elements such as u, Zn, Af, P, Mn, and Cr, or compounds thereof may be included.

The barium ferrite is preferably applied to a perpendicular magnetic recording system, and has Ba p' e , 0. , etc. Barium ferrite and a part of barium ferrite are converted to Ca, Sr, pb, etc.
, Co, Ni, Ti, Cr, Zn, In.

Examples include those substituted with metals such as Mn, Cu, Ge, Nb, Zr, and Sn. A combination of these may also be used.

Methods for producing barium weight include coprecipitation-calcination method,
Ceramic method, Franks method, hydrothermal synthesis method, alkoxide method, glass crystallization method, plasma jet method, etc.
In order to obtain the plate-like shape and magnetic properties of the magnetic powder used in the present invention, it is preferable to manufacture it by a glass crystallization method.

As the binder used in the magnetic layer of the present invention, a thermoplastic resin, a thermosetting resin two-reaction type resin, a radiation curing resin, or a mixture thereof is used.

Examples include vinyl chloride-vinyl acetate copolymer and vinyl chloride-vinyl acetate-maleic acid copolymer.

Vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, vinylidene chloride - Acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-metatalic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenolic resin, epoxy resin, thermosetting resin, polyurethane resin , melamine resin, alkyd resin, or a mixture thereof.

Examples of lubricants include higher fatty acids, metal soaps, higher fatty acid esters, higher fatty acid amides, mineral oils, oil-based organic compounds, inorganic fine powders, α-olefin polymers, unsaturated aliphatic hydrocarbons, and/or mixtures thereof. However, it is preferable to use fatty acids and fatty acid esters.

Examples of fatty acids include gabric acid, undecylic acid, lauric acid, tridecylic acid, and myristic acid.

Pentadecylic acid, palmitic acid, heptadecylic acid.

stearic acid, nonadecanoic acid, arachidic acid, behenic acid,
Lignoceric acid, cerotic acid, heptaconic acid, montanic acid, mellisic acid, lactacic acid, cetoleic acid, erucic acid, brassic acid, linoleic acid.

Examples include lyrinic acid, arachidonic acid, and stearolic acid.

As abrasives - for example Cr, 0. , α-At'
, O,, γ-Aj, 0. ．． S i C, MgO, α-F
Examples include e, O, BN, silicon nitride, iron nitride, corundum, artificial corundum, diamond, garnet, etc., and α-AJzOz is preferred.

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, glycerin, etc. Nonionic surfactants, quaternary ammonium salts such as higher alkylamines, cationic surfactants such as pyridine, anionic surfactants containing acidic groups such as carbonic acid, sulfonic acid, phosphoric acid, amino acids, amino sulfonic acids Examples include amphoteric activators such as . Examples of solvents for magnetic paints include ketones such as acetone, methyl ethyl ketone, and cyclohexanone, esters such as methyl acetate, ethyl acetate, and butyl acetate, glycol ethers such as ether dioxane, and aromatic carbons such as benzene, toluene, and xylene. Hydrogens, chloroform, chlorinated hydrocarbons such as carbon tetrachloride can be mentioned. Note that these solvents can be used alone or in combination.

Preferred are polar solvents such as ketones or solvents containing polar solvents.

Furthermore, various hardening agents can be included in the magnetic paint in order to improve the durability of the magnetic layer of the magnetic recording medium.

As an example, incyanate can be included. Isocyanates that can be used include aromatic or aliphatic isocyanates. Isocyanates that can be used include, for example, tolylene diisocyanate (TDI) and adducts of these isocyanates with active hydrogen compounds, and preferably those having an average molecular weight of 1
It is in the range of 00 to 3000.

Among aliphatic isocyanates, such as hexamethylene diisocyanate (HMDI) and adducts of these isocyanates and active hydrogen compounds, preferred are those having a molecular weight in the range of 100 to 3,000. Further, when performing curing treatment by electron beam irradiation, a compound having a reactive double bond (urethane acrylate, etc.) can be used.

Further, curing treatment by ultraviolet irradiation can also be performed.

Embodiments of the apparatus of the present invention will be specifically described.

A magnetic paint was prepared at the following mixing ratio.

Paint formulation: Barium ferrite (Hc-6000s) 100 parts by weight α-A7
! zos 10” carbon black
5r Stearic acid 5 ~ Butyl stearate 2 # Vinyl chloride acid copolymer 10 # Polyurethane 10 - Solvent (MHK/) En=50150) 2 5
0 # After mixing the above composition, use a ball mill to 48
After treatment for 5 hours, apply a urethane curing agent (TDI type).
Part by weight was added, filtered through a filter, coated on lOμ pect film with a gravure coating machine to a dry film thickness of about 3μ, smoothed, passed through this orientation device, and completely dried.
After surface treatment, it was made into a tape.

In the orientation device, the thickness of the magnet in the running direction on the undried magnetic layer side is 150 m, and the arrangement sections s and -s.

is 20fl, the spacing between different poles is 30wM, and the magnetic pole is 1a.

2a to 5000G, lb, 2b1.2b2, 2b, also 3
A permanent magnet of 000G was used, and mild steel was used as the high magnetic permeability material.

Further, hot air was used for drying and solidification, and the wind speed at the tip of the nozzle was set to 5 ml sec. The processing speed at this time is 50■/w
I ran in.

Example-1 uses a barium ferrite plate ratio of 5°, Example-2 uses a barium ferrite plate ratio of 71, and Comparative Example 1 uses a barium ferrite plate ratio of 71.
5, No orientation, Comparative Example-2 has a barium ferrite plate ratio of -5, N-3 opposing pair type.

Table 1 shows the comparison results of the above contents.

Table SQ: Vertical squareness ratio D50 after demagnetizing field correction:
In the case of the orientation device of the present invention, as shown in the comparison between the recording density in Figs. 3 and 4 when the output is reduced to 1/2, the change in the magnetic field strength between the N-3 counter value stones is similar to that of the N pole (Fig. In the imaginary line V near the center), the strength and weakness waves are the smallest and the effect of the support side magnet having a single-piece structure is seen. In the case of a plurality of magnetic poles of the same type on both sides as shown in FIG. 4, the place where the strong and weak waves are small is located at the center of the N-3 counter value stone, and the strong and weak waves are still large. From the above, it can be seen that the uniformity of the magnetic field is good and a wide stable range can be obtained. Furthermore, as shown in Table 1, the surface roughness and squareness ratio in the vertical direction are high.

〔Effect of the invention〕

As described above, the method for manufacturing a magnetic recording medium according to the present invention can prevent the surface roughness of the coating film of the magnetic recording medium and the occurrence of orientation return, and can also obtain a high vertical alignment squareness. I can do it. By arranging one or all of the orientation holding parts using permanent magnets, it is possible to use inexpensive manufacturing equipment with low power consumption and small space.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view of an orientation device according to the present invention. FIG. 2 is a schematic vertical cross-sectional view. FIG. 3 is a partial cross-sectional view and a curve of change in magnetic field strength depending on the distance between the N and S opposing poles. Figure 4 is a partial cross-sectional view of multiple magnetic poles of the same type on both sides and its N
-3 is a magnetic field strength change curve depending on the distance between opposing poles. 1a...High magnetic field generating magnet (or electromagnet) 1b...Low magnetic field generating magnet 2a...High magnetic field generating magnet (or electromagnet) 2b+~2b
,...Low magnetic field generating magnet group 3...High magnetic permeability material plate 4...Surface high magnetic permeability material plate 5...Drying air supply device or electron beam or ultraviolet ray irradiation device 1
0...Magnetic paint coated support, 11...Guide roll 12...Chamber. Figure ■ Figure 3 @l

Claims (2)

[Claims] (1) On a non-magnetic support or a support already coated with a magnetic coating, the wet magnetic layer is applied in an apparatus for perpendicularly aligning the magnetic particles in said layer by means of a perpendicular magnetic field penetrating the coated wet magnetic layer. On the opposite side, there is a plurality of N(S) magnetic poles that are long in the running direction, and on the other side of the undried magnetic layer, there are multiple S(N) magnetic poles that are short in the running direction. different poles (N-S), in which a dry air, electron beam irradiation, or ultraviolet ray irradiation device is arranged in the section between the short magnetic poles, and each magnetic pole and magnetic pole group are connected with a high magnetic permeability material plate. A manufacturing apparatus for a magnetic recording medium, characterized in that drying air, electron beams, or ultraviolet rays are sent to an undried magnetic layer to dry and harden the undried magnetic layer while giving perpendicular orientation to magnetic particles between a pair of opposing magnets. (2) A claim characterized in that the magnetic field near the entrance of the opposite polarity opposing magnet through which the undried magnetic layer is passed is strengthened to achieve sufficient forced orientation, and thereafter a magnetic field is applied to an extent that no reorientation occurs. (1) Magnetic recording medium manufacturing apparatus.