JPS6228931A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium with excellent adhesion of the undercoat layer to the carrier by forming an undercoat layer contg. a prescribed amts. of carbon black and a photopolymerization initiator on one surface of a carrier consisting of a specified plastic film and irradiating UV rays to cure the layer. CONSTITUTION:An undercoat layer contg. 100pts.wt. binder, 0.1-50pts.wt. carbon black (various additives can be incorporated) and 1-20pts.wt. photopolymerization initiator is formed on one surface of a nonmagnetic carrier consisting of the film of a plastic selected from cellulose derivatives, polyolefin, polyvinyl chloride, polyesters, polycarbonate, polystyrene, polyimide, polyamide-imide and polyether sulfone, and UV rays are irradiated from both surfaces to cure the layer. A magnetic layer is formed thereon. Consequently, a magnetic recording medium with excellent adhesion of the undercoat layer to the carrier can be obtained.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a method for manufacturing a magnetic recording medium having a non-magnetic support and a magnetic layer or an under layer between the non-magnetic support and a back coat layer, Learn more about the history of the undercoat layer! This invention relates to improvements in manufacturing methods.

``Technical background of the invention and its problems 1 Magnetic recording media such as magnetic tapes and magnetic disks usually have a magnetic layer made of fine powder of magnetic material and a binder (binding resin) on a non-magnetic support such as polyester. At this time, as the tape runs and the disk rotates, charge accumulates, resulting in various undesirable phenomena such as reduced running performance and dropouts due to adhesion of foreign matter.

As a solution to this problem, it is common to add conductive fine powder such as carbon black to the magnetic layer to impart antistatic properties to the magnetic layer itself, but this reduces the filling rate of the magnetic material and reduces the electromagnetic conversion characteristics. There was a problem with the loss of .

For this reason, it is necessary to provide an undercoat layer between the nonmagnetic support and the magnetic layer or between the nonmagnetic support and the back coat layer to provide antistatic properties.
Techniques have been devised to prevent the entire tape from becoming static.

However, one layer of underyaw using a conventional thermosetting/thermoplastic type binder has the disadvantage that it takes a long time to dry and harden the resin and requires large-scale equipment, so radiation-curable resin is used as the binder. Under 71-1-an was devised by applying radiation curing methods such as radiation (gamma ray) curing, electron beam curing, and violet radiation curing as a curing means.

``11! So, if we compare this, radiation (gamma rays)
lal! Chemical and electron beam curing methods have many disadvantages, such as extremely expensive irradiation equipment, the need for protection against radiation and X-rays, and the need to perform irradiation in an inert atmosphere to prevent ozone generation. There is.

On the other hand, the violet A-ray curing method has various advantages such as relatively inexpensive irradiation equipment, easy protection from ultraviolet rays, and no inert atmosphere in the irradiation area, but on the other hand, the under Conductive fine powder such as carbon black, which is added to the binder to impart antistatic properties, is
Since the light shielding property is high and the photocuring reaction is significantly inhibited, the portion of the undercoat layer close to the nonmagnetic support is not sufficiently cured, resulting in poor adhesion between the undercoat layer 71-1 and the nonmagnetic support. However, applying this to the under TI-1 layer was a revolution.

As a result of intensive studies aimed at solving these problems, the inventors of the present invention have discovered a magnetic recording medium having radiation-curable underto layers 1 to 1, which are manufactured by irradiating radiation 1 from a specific direction. (Yu) We discovered that the above-mentioned drawbacks could be overcome, and we proceeded to complete the present invention.

[Object of the Invention] The object of the present invention is to provide a magnetic recording medium with excellent magnetic adhesion between the undercoat and the non-magnetic support in the production and removal of a magnetic recording medium having a single layer of radiation-curable undercoat 5. The object of the present invention is to provide a method for manufacturing a recording medium.

[Summary of the Invention] The present invention provides a method for producing a magnetic recording medium having a radiation-curable under layer between a non-magnetic support and a magnetic layer, or between a non-magnetic support and a back-yaw layer. −
(Production of one layer of underyo is a non-tf! Step of forming an undercoat layer on one side of the bamboo support and the contact method of this step)-1 Formation surface of one layer and the undercoat layer] - The non-magnetic support is a plastic film, and the non-magnetic support is a plastic film, and the radiation rays used for curing are The type of the film is ultraviolet rays, and the plastic film is selected from the following group A. Polycarbonate 1~ Polystyrene Polyimide Polyamide Imide Polyether Sulfone Underlow 1~ Layer contains carbon black in the range of 0.1 part or more and 50 parts or less per 100 parts (overlapping part, same below) of binder joint name t. It is characterized in that the layer to the undercoat 1 contains a photoinitiator in a range of 1 part IX lx 2 ('1 part J2) per 4100 parts total binder. be.

[Embodiments of the Invention] The characteristics of the present invention are that in the process of irradiating and curing the width qi-ray curable undercoat layer, the underyaw layer is formed on a non-magnetic support. By irradiating the undercoat layer with radiation from both sides of the surface and the opposite surface, in other words, in addition to the radiation irradiated by a normal curing method, the undercoat layer is cured by radiation transmitted through the non-magnetic support. , the hardening of the deep part of the undercoat layer, which had conventionally been insufficient for the surfaces of the undercoat 1 to M, has become sufficient, and as a result, the hardening of the undercoat layer 1 and the non-magnetic support has been improved. The point is that the adhesion is excellent.

The method for manufacturing a magnetic recording medium of the present invention includes a nonmagnetic support and a q
In the method for producing a magnetic recording medium having a radiation-curable undercoat layer between the magnetic layers or between the nonmagnetic support and the backcoat layer, the production of the single layer of the underlow 1 comprises:
A step of forming an undercoat layer on one surface of a non-magnetic support, and a step of curing by irradiating with radiation both the surface on which the undercoat 1 to layers are formed and the surface opposite to the surface on which they are formed. More specifically, coatings constituting underlay 1 to layers are applied on one side of a non-magnetic support, and if a solvent is used together, the solvent is dried and removed, and then the layer is formed. Magnetic paint is applied to the upper layer of the undercoat layer obtained by irradiating radiation from both sides of the surface and the surface opposite to the forming surface, and curing the layer by adding radiation transmitted through the non-magnetic support to normal radiation. This is a method in which a one-part coating is formed by coating and curing the coating, and if a back coat paint is used in place of the coating, it can be applied to the formation of the Barafco-1 (back coating) layer. is also possible.

The method for curing the radiation-curable undercoat layer of the present invention includes:
Various known radiation curing methods can be used.

Examples include a radiation (gamma ray) curing method, an electron beam curing method, an ultraviolet curing method, etc., but the ultraviolet curing method is the most suitable from the process point of view as mentioned in the previous 2.

The irradiation method may be one in which radiation is irradiated from both sides of the undercoat layer forming surface of the nonmagnetic support and the surface opposite to the forming surface, and the irradiation output, the number of irradiation devices, the distance from the irradiation source, The angle etc. are not limited in any way.

Various known ultraviolet light generating devices can be used as curing equipment when applying the ultraviolet curing method.

−〇− Examples include low-pressure mercury lamps, chemical lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, arc lights, xenon lamps, etc. However, in general, lamps are A high-pressure mercury lamp or a metal halide lamp with an output of 30 to 200 W per ann is suitable.

In addition, in order to moderately suppress the temperature rise of the irradiated object due to light irradiation, the wavelength involved in curing (200~=15Or+n
Unnecessary wavelength ranges other than +) may be cut off with a filter or the like, and the object to be irradiated may be cooled by an appropriate method.

The radiation-curable undercoat layer of the present invention consists of a radiation-curable resin as a main component, and a binder made by adding a thermoplastic resin, a thermosetting resin, etc. as necessary, or a binder containing various fillers and additives. This is a cured coating material mixed with appropriate solvents and the like.

As the radiation curable resin of the present invention, various known radiation curable resins can be used.

Examples include resins having unsaturated double bonds such as vinyl groups, allyl groups, acryloyl groups, methacryloyl groups, ■=10-poxy groups, etc.; Radical polymerization type resins, such as those based on Gek No. 1, radical addition types such as polyoxygen-polythiol, and cationic polymerization types, such as epoxy resins, are commonly used. Among them, acrylic resins containing (meth)acryloyl groups 1-based resin has an excellent physical property balance of hard 11-bamboo and a cured product, so it is most suitable for the use of the present invention.

This acrylate resin has a (meth)acryloyl group in its molecule, and has a molecular weight of 20%.
Oligomers in the range of 0 to 50,000 are preferred.

Examples include urethane (meth)acrylate 1, epoxy (meth)acrylate], polyester (meth)acrylate, polyol (meth)acrylate, polybutadiene (meth)acrylate, melamine (meth)acrylate, and polyacetal (meth)acrylate. Acrylate, silicone (meth)acrylate-1-, polyamide (meth)acrylate, heterocycle-containing (meth)acrylate, etc.In addition to these, various coating resins are modified to have (meth)acrylate in the molecule.
Resins into which acrylic [lyl groups have been introduced can also be used, and kneaded resins may be used alone or in combination.

As the non-magnetic support of the present invention, various known non-IT supports for magnetic recording media can be used.

Examples include plastic film, paper, non-magnetic metal foil, etc.
Among them, various plastic films are particularly suitable from the viewpoint of transparency of curing radiation and physical properties required as a support.

Examples include regenerated cellulose, ethyl cellulose, cellulose acetate-1 to butylene-1, cellulose derivatives such as cellulose diacetate, cellulose triacetate-1, etc.; poly-1-nophine such as poly-1-ethylene, polypropylene, and poly-1-ethylene; polychloride; Polyesters such as polyethylene terephthalate 1-, polyethylene 2,6-Natsuta l note; Polycarbonate; Polystyrene; Polyaryl 1
Go to No. 1; Polyether-terketone; Polyamide;
Polyimide; Polyamideimide; Polyetherimide;
Polyparabanic acid; polyether sulfone: fluorine-based films such as polyvinyl fluoride and polyvinylidene fluoride are available, and both stretched and unstretched films can be used, and they may be surface-treated.

In addition, when using ultraviolet rays as curing radiation, from the viewpoint of transparency, it is necessary to use cellulose derivatives, polyolefins, polyvinyl chloride, polyvinylidene chloride, polyester J, polycarbonate 1, polystyrene, polyimide, polyamideimide, polyether sal. It is particularly preferred to use Fung's films.

When ultraviolet light is used as the curing radiation for the underrow 8 layer of the present invention, it is necessary to add various known photoinitiators.

Examples include acetophenone, acetophenone diethyl ketal, diacetyl, benzyl, benzyl dimethyl ketal, 1-hydroxycyclohegysylphenylketal,
Phenylketones such as 2-human 1]xy-2-methylphenylpropanone; benzophenone, bis-4,4
′ -dialkylaminobenzophenone, 3,3′
-Benzophenones such as dimethyl-4-methoxybenzophenone; Benzoins such as benzoin and benzoin alkyl ether;
Other examples include anI-laquinones, sulfides, and phenyloximes, which may be used singly or in combination.

If the amount added to the binder is small, the curing speed will be slow and the curing will be insufficient, while if it is too large, problems such as bleeding from the coating film after curing will occur.
It is particularly preferred that the amount be less than 1 part to 20 parts per 00 parts.

When curing the 8 underlay layers of the present invention in the air or an atmosphere containing oxygen, various known curing accelerators are added to the photoinitiator in order to prevent curing damage caused by oxygen. It is suitable to use them together.

Examples include N-Mejirujitanolamine, N,N
- Aliphatic amines such as dimethylethanolamine; bis-4,4'-dialkylaminobenzophenone,
Aromatic amines such as alkyl N,N-dimethylaminobenzoate; and polyamine compounds, which are polymerized products of these, may be used alone or in combination.

The amount added to the binder is preferably in the range of 1 part or more and 20 parts or less per 100 parts of the binder, similar to the photoinitiator.

The undercoat layer of the present invention may be prepared using various known methods as necessary for the purpose of imparting various properties to the undercoat layer, that is, expressing antistatic properties, improving light-shielding properties, and improving coating film vlJ14 as an extender pigment. It is also possible to contain fisi.

Examples include carbon black, Graphi l-1 calcium carbonate, aluminum silicate, magnesium silicate,
Inorganic substances such as barium sulfate, silica, aluminum oxide, titanium oxide, 1trill oxide, kaolin, clay, and various inorganic pigments; organic substances such as polyl'E ethylene terephthalate 1~, phenol resin, benzoguanamine resin, and various organic pigments; These may be used singly or in combination.

In particular, conductive fine powder added for the purpose of preventing static electricity, especially carbon black, has a high light-shielding property, and conventional methods cause a significant decrease in adhesion to a non-fJi support, so this defense cannot be applied. In this case, carbon black should be added in an amount of 0.1 part or more per 100 parts of the binder, since if the amount added to the binder is too small, the anti-static properties will be insufficient. A range of 50 parts or less is particularly preferred.

The paint constituting the under two layers of the present invention may contain various known solvents, if necessary.

Examples and examples include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene, xylene, and naphtha; methylene chloride, 1.1.1-
Chlorinated hydrocarbons such as 1-dichloroethane, chlorobenzene, 0-dichlorobenzene; Alcohols such as methanol, ethanol, isopropanol, butanol, pencil alcohol; dimethyl ether, methyl isoethyl ether, dihydrofuran, dioxane etc.T
Ketones such as ace]-, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; Esters such as ethyl formate, ethyl acetate, and butyl acetate; Others include glycol ethers, N-methylpyrrolidone, dimethylformamide, and diacetone Alcohol, isophorone, etc. are used alone or in combination.

The paint constituting the undercoat layer of the present invention can also contain various known additives, if necessary.

Examples include dispersants, leveling agents, antifoaming agents, surfactants, coating modifiers, adhesion promoters, wetting agents, antisettling agents, viscosity modifiers, stabilizers, and the like.

The method for producing the paint constituting the undercoat layer of the present invention involves blending various fillers and additives (photoinitiator, curing accelerator, etc.) with a mixture of binder components as necessary. If a solvent is used in combination, the binder components can be dissolved in an appropriate solvent to form a binder solution, and then the same blending can be carried out.Alternatively, each component can be blended without a solvent, diluted with a solvent, and the viscosity Adjustments may be made, and various additives may be prepared as a solution in an appropriate solvent and then blended.

Various known coating methods can be used to coat the 8 underyaw layers/magnetic layer of the present invention.

Examples include curtain coat, gravure offset coat, gravure coat, spin coat, spray coat,
There are dip coat, (air) Dr. Yo 1-11-transfer roll coat, (air) knife coat, blade coat, reverse roll coat, etc. The thickness of Anguro L-Decoy at the time of application is 0 after drying and curing. In the range from .1μ to 5.0μm, the magnetic layer thickness is also 0.1μm.
A range of from 1 μm to 15 μm is preferable.

As the composition of the magnetic paint of the present invention, various known compositions can be used.

Examples of magnetic powder in magnetic paint include T-Fe20:l, Ff3304, Co-containing -F
e203. COO Fe: l 04, Cro2
.

co, Fe-Go, Go-Nl, Fe-
There are powders such as Go-Ni, Ha-IJum ferrite, etc.
Examples of binders in magnetic 1131 include vinyl chloride copolymer resin, polyurethane resin, polyester resin, 1=
Examples include ululose resin, polyvinyl acetal resin, and epoxy resin, and may also contain various known fillers, solvents, additives, and the like.

The present invention will be explained below using specific examples.

Example 1 Ubisan #893 (urethane acrylate oligomer,
(manufactured by Thiokol, USA), 60 parts of penta-T Lythritol triacrylate, and 25 parts of carphone black were dissolved in 200 parts of toluene and 200 parts of methyl ethyl ketone.
Dispersion was carried out for 2 hours using a sand grinder to form a paint.

This was combined with 5 parts of benzophenone as a photoinitiator and 23 parts of 4,4'-diethylaminobenzophenone as a curing accelerator.
1.5 parts was added and applied to a 13IIIll thick polyester film using a gravure coating method, and after drying the coating film and removing the solvent, 1. With an energy amount of OJ/cm, 2.2
The coating films were cured by irradiating ultraviolet rays with an energy amount of J/ctl to obtain an undercoat layer with a thickness of 0.5 μm. This was designated as sample A.

This -L layer is coated with magnetic paint (Vinyrite VAGH (vinyl chloride-vinyl acetate-vinyl alcohol copolymer resin, U.S.
(manufactured by CC), 70 parts of CO-containing -Fe20+ powder, 5 parts of dioctyl phthalate, and 1 part of lecithin were dissolved in 80 parts of toluene, 80 parts of methyl ethyl ketone, and 80 parts of cyclohexanone, and mixed using a sand grinder for 2 hours. After the coating film is dried, the surface is smoothed using a super calender, and each portion is coated with 2-inch width and coated with 1 to 100 ml of Surin to a thickness of 6.5 mm. A magnetic recording medium having a magnetic layer of 0 μm was obtained. This was designated as Trial 11B.

Comparative Example 1 A trial production was carried out under the same conditions as in Example 1, except that the undercoat coating film was exposed to ultraviolet light from the same side as the coating film. Tested as an undercoat layer and as a recording medium. lr) was obtained.

Comparative Example 2 A trial production was carried out under the same conditions as in Example 1, except that the 8 underlayer layers were not applied on the polyester film.

Sample F was obtained as a magnetic recording medium.

The following evaluations were made regarding these items, and the following results were obtained.

As shown in Table 1 and Table 2, the underyaw 1 single layer of Example 1 has good adhesion to the non-magnetic support, and the magnetic recording medium having this undercoat layer has a drop resistance after 5000 passes. It can be seen that the increase in outs is suppressed.

(Note) The evaluation method is as follows: Adhesion: Chiban Co., Ltd. GA Cellotape was used for tape adhesion to non-magnetic supports) By Drop Ala 1 to Nitrotube Out Counter (
15μsec, -16dB.

Video S/N: Relative value to Comparative Example 2 [Effect 1 of the invention As described above, according to the present invention, in the method of manufacturing a magnetic recording medium having one radiation-curable underyaw layer,
It becomes possible to easily obtain a high-quality magnetic recording medium with excellent adhesion to the support, good surface smoothness of the magnetic layer, and excellent electromagnetic conversion characteristics with high productivity.

Claims (5)

[Claims] (1) In a method for producing a magnetic recording medium having a radiation-curable undercoat layer between a non-magnetic support and a magnetic layer or between a non-magnetic support and a backcoat layer, the production of the undercoat layer comprises: a non-magnetic support; A step of forming an undercoat layer on one side of the undercoat layer, and after this step, a step of irradiating the undercoat layer with radiation and curing both the surface on which the undercoat layer is formed and the surface opposite to the surface on which the undercoat layer is formed. A method for manufacturing a magnetic recording medium, characterized in that it is made through the following steps. (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the nonmagnetic support is a plastic film, and the type of radiation used for curing is ultraviolet rays. (3) The method for manufacturing a magnetic recording medium according to claim 2, wherein the plastic film is selected from Group A below. [Group A]: Cellulose derivative polyolefin polyvinyl chloride polyvinylidene chloride polyester polycarbonate polystyrene polyimide polyamide imide polyether sulfone (4) Claim 1, characterized in that the undercoat layer contains carbon black in a range of 0.1 part or more and 50 parts or less based on a total of 100 parts (parts by weight, the same applies hereinafter) of the binder. A method of manufacturing the magnetic recording medium described above. (5) The method for producing a magnetic recording medium according to claim 2, wherein the undercoat layer contains a photoinitiator in a range of 1 part to 20 parts based on a total of 100 parts of the binder. .