JPS6288141A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a surface layer in which smoothness and slipperiness are made compatible and to improve electromagnetic characteristics and running durability by bringing the surface of a transfer member adjusted to prescribed roughenss on the surface of a magnetic layer of a magnetic recording medium after coating of the magnetic layer. CONSTITUTION:The surface of the magnetic member having the surface of which the center line average height at 0.25mm coutoff and 80mm measured length is adjusted to 0.05-0.020mum is brought into tight contact with the surface on of the magnetic recording medium on the side where the magnetic layer is coated. A radiation polymerizable compd. is sued as a binder for he magnetic material used in the above-mentioned stage for coating the magnetic layer and the radiation is irradiated thereon after the tight contact of the transfer member. The transfer member is made into a roll- or belt-like material and the surface layer where the smoothness and slipperiness are made compatible is provided to the magnetic layer. The electrical characteristics and running durability are thus improved.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to video tapes and audio tapes.

The present invention relates to a method for manufacturing magnetic recording media such as floppy disks.

(Prior art) In high-density magnetic recording media, which have been developed in recent years, it is necessary to improve the surface properties of the magnetic layer in order to reduce the so-called gap loss between the magnetic head and the magnetic tape. is required.

In this case, a higher surface quality refers to a surface that is smoother and maintains slipperiness, that is, a surface that is densely formed with minute protrusions of uniform height. The conventional method for achieving this high quality magnetic layer surface is to improve the surface properties of the support used in the magnetic recording medium. However, when a magnetic layer is applied to such a support, the proportion of the surface shape of the support remaining on the surface of the magnetic layer decreases as the surface roughness of the support increases. Further, there are limits to increasing the surface properties of the support due to the following points. In other words, 'I
In the step of forming a film and winding it up, if the surface properties of the magnetic recording medium (film) are too good, the frictional resistance against the conveyance roller will be large, often causing meandering or wrinkles. Furthermore, the abrasion resistance between the films increases, and the shape of the winding roll may become distorted.

(Problems to be Solved by the Invention) There are limits to the method of improving the surface properties of the magnetic layer of a magnetic recording medium by improving the surface properties of the support used as described above, and there are limitations to this method in the future. It is expected that this method will not be able to meet the needs for increasing the density of magnetic recording.

Therefore, it has become important to establish a technology that can create a magnetic layer with a high quality surface without relying on the surface properties of the support.

(Objective of the Invention) The present invention was made in view of the above circumstances, and it provides smoothness and ease of slippage on the surface of the magnetic layer coated on the support, regardless of the surface properties of the support. N the roughness that makes it possible to have both sexes! A method for manufacturing magnetic recording media that can be done every time! i! The purpose is to provide

(Structure of the Invention) The method for manufacturing a magnetic recording medium according to the present invention involves closely adhering the surface of a transfer member adjusted to a predetermined roughness instead of a mirror finish to the surface of the magnetic layer of the magnetic recording medium after the magnetic layer has been applied. The surface properties are both smooth and slippery for transfer formation.

The above-mentioned "predetermined roughness" means 7J cutoff 0.25 rt
m, the center line average roughness (Ra) at a measurement length of 80 m is 0.
It means that it is within the range of 0.005 to 0.020 μm.

Although a transfer plate or the like may be used as the transfer member, in order to continuously manufacture magnetic recording media, it is preferable to use a roll or a strip-shaped member.

Note that the rolls also include hollow drum-shaped rolls.

In order to make the above transfer formation more effective, a radiation polymerizable compound is used as a binder for the magnetic material used in the magnetic layer coating process, and the magnetic recording medium is irradiated with radiation after the transfer member is in close contact with the magnetic recording medium. It is preferable to apply The timing of irradiating the radiation may be when the transfer member and the magnetic recording medium are in close contact with each other, or after the transfer member is separated from the magnetic recording medium.

Furthermore, in the case where the transfer member is a hollow drum-shaped roll, radiation irradiation can be performed from inside the drum.

Note that after the transfer member is brought into close contact with the magnetic recording medium, a release agent such as silicone oil is applied to the surface of the transfer member so that the transfer member can be easily removed from the magnetic recording medium. You can also leave it there.

Below, the present invention will be used for Mr. M who is implementing the present invention.

The roll or strip used in the present invention is suitably made of iron polished to a mirror finish with gold sides and hidden chrome plating. It is possible to impart the required roughness to the surface of the roll or strip by applying an electric shock (N flow reversal) during plating.

As the ferromagnetic powder used in the present invention, ferromagnetic iron oxide fine powder, Co-doped ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, ferromagnetic alloy powder, barium ferrite, etc. can be used. It is effective that the acicular ratio of ferromagnetic iron oxide and chromium dioxide is about 2/1 to 20/1, preferably 5/1 or more, and the average length is about 0.2 to 2.0 μm. The ferromagnetic alloy powder has a metal content of 75 wt% or more, and 80 wt% or more of the metal content is ferromagnetic metal powder (i.e., l”e, Go,
Ni, Fe-Co, Fe-Ni, Go
-Ni, Fe-Co-N1) with a major axis of approximately 1.0
It is a particle smaller than μ side.

The binders used in the present invention include thermoplastic resins such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-acrylic acid copolymer, and vinyl chloride-vinyl acetate copolymer. Vinyl propionate
Maleic acid copolymer, vinyl chloride-vinyl propionate-butenoic acid copolymer, vinylidene chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-propionic acid Vinyl chloride/vinyl acetate copolymers such as vinyl-vinyl alcohol copolymers, cellulose resins such as cellulose nitrate, cellulose acetate butyrate, cellulose diacetate, and cellulose propionate, polyvinyl formal,
Acetal resins such as polyvinyl acetal and polyvinyl butyral, phenoxy resins, urethane resins, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylic acid ester-acrylonitrile copolymers, vinylidene chloride-acrylonitrile copolymers , butadiene acrylonitrile copolymer, polyester resin, polyisocyanate compound, etc. are suitable.

When using radiation polymerizable compounds, polyester type urethane acrylate, polyether type urethane acrylate, polyester ether type urethane acrylate,
These are acrylate oligomers and methacrylate oligomers such as epoxy acrylate, polyester acrylate, and polyether acrylate, and specific examples of these are A.

Vranken “Fafipec Congr.
ess” 1119 (1972).

For example. Other radiation polymerizable compounds include ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexaacrylate, bis -2-acryloyloxyethyl-hydroxyethyl isocyanurate, tris(β-acryoyloxyethyl)isocyanurate and other polyfunctional acrylate compounds, and polyfunctional methacrylate compounds thereof, as well as acrylic acid, methyl acrylate and these Homologous acrylic acid alkyl esters, methacrylic acid alkyl esters, styrene, α-methylstyrene,
Acrylonitrile, acrylamide, vinyl acetate, vinyl propionate, etc. have one carbon-carbon unsaturated bond in the molecule.
It is a compound having more than one.

Two or more of the above binders can be used in combination.

It is also possible to add a thermoplastic resin to the radiation polymerizable compound.

Particularly preferable binders among the above are three components: a cellulose resin or a vinyl chloride/vinyl acetate copolymer, a urethane resin, and a polyisocyanate, a cellulose resin or a vinyl chloride/vinyl acetate copolymer, a urethane acrylate, and a polyfunctional It is a three-component system of acrylate compounds.

More preferably, it is a three-component system of a cellulose resin or a vinyl chloride/vinyl acetate copolymer, a urethane acrylate, and a polyfunctional acrylate compound. In this case, the preferred ratio of the cellulose resin or vinyl chloride/vinyl acetate copolymer to the urethane acrylate is 4/1 to 1/2, and the ratio of the total of these to the polyfunctional acrylate is 872 to 1/1.

As the non-magnetic support, polyethylene terephthalate,
Polyesters such as polyethylene-2,6-naphthalate: Polyolefins such as polyethylene and polypropylene: Cellulose derivatives such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate: polyvinyl chloride, polyvinylidene chloride, etc. Vinyl wood WI: Polycarbonate, polyimide, polyamideimide, etc. Depending on the application, aluminum, copper, tin, etc.
Non-magnetic metals such as zinc or non-magnetic alloys containing zinc or non-magnetic alloys of these metals can be used, or a support in which eight layers of these non-magnetic metals are provided on a plastic support by a method such as vacuum deposition can be used. These supports are preferably coated with a lower layer or subjected to physical treatment such as corona treatment before being coated with a magnetic layer. Yet before these supports are used,
A back coat layer may be provided. Further, a back coat layer may be provided on the side opposite to the retractable layer on which the magnetic layer is applied.

Radiation irradiation in the present invention includes ultraviolet rays, electron beams, γ-rays, β-rays, X-rays, etc., but electron beams are more preferable. As the N beam irradiation device, a scanning method, a double scanning method, a curtain beam method, a broad beam curtain method, etc. can be adopted.

As for the electron beam characteristics, the accelerating voltage is 100 to 1000 kV.
, preferably 150 to 300 kV, and the absorbed dose is 1.0 to 20 megarads, preferably 2 to 10 megarads. If the accelerating voltage is 100kV or less,
If the amount of energy transmitted is insufficient and exceeds 1000 kV, the energy efficiency used for polymerization decreases and is not economical.

If the absorbed dose is less than 1.0 megarads, the curing reaction will be insufficient and the strength of the magnetic layer will not be obtained; if it exceeds 20 megarads, the energy efficiency used for curing will decrease, the irradiated object will generate heat, and especially This is not preferable because the nonmagnetic support is deformed.

When using a three-component binder consisting of cellulose or vinyl chloride-vinyl acetate copolymer, 1-notane resin, and polyisocyanate, that is, a binder that does not contain radiation polymerizable compounds, after peeling from the roll or strip. ,40~100℃
It is preferable to heat the stool at IIflt. In addition, if a system containing a radiation-polymerizable compound is selected, the metal roll or strip, the magnetic layer, and the non-magnetic support are in a sandwich structure state (process) or after peeling from the roll or strip, the radiation is irradiate. Particularly preferably, the irradiation is performed while the magnetic layer is in the above-mentioned sandwich structure, and it is easiest to peel off the magnetic layer from the metal roll or strip. When irradiating fJ4 in a sandwich structure, irradiation is performed from the non-magnetic support side, but when irradiation is performed after peeling from the roll or strip, it may be irradiated from the magnetic layer side.

Solvents used include acetone, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl acetate;
Glycol ethers such as ether, glycol dimethyl ether, glycol monoethyl ether, and dioxane; Aromatic hydrocarbons such as benzene, toluene, and xylene; Methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. chlorinated hydrocarbons such as tetrahydrofuran can be selected and used. The ratio of the ferromagnetic support, binder, and solvent of the magnetic coating liquid can be arbitrarily adjusted within the range of 2/1/6 to 6/1/15 by weight.

In the present invention, coating methods on the non-magnetic support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, and spray coating. , spin code, etc. can be used, and other methods are also possible, and detailed explanations of these are described in "Coating Engineering", pages 253 to 277 (published by Asakura Shoten on March 20, 1981). ing.

The thickness of the magnetic layer is applied so that the dry thickness is in the range of 1 to 10 μm.

Drying after coating the magnetic layer is preferably carried out when the amount of residual solvent reaches 0.05 to 10vt% of the magnetic layer using hot air.
．． When the amount is 5 to 5 wt%, more preferably 1.5 to 5 wt%, it comes into contact with a mirror-finished roll or strip. The contact pressure at this time is 1 to 50 匈/α, preferably 5 to 3
(Hg/cm. The magnetic layer is peeled off from the support in about 0.1 to 5 seconds after contact. If necessary, the mirror roll or strip may be heated to about 40°C to 100°C. When using radiation irradiation, it is easier to peel off the magnetic layer by irradiating it while the magnetic layer has not yet peeled off after contact, and the smoothness of the magnetic layer can be maintained.
It is also possible to provide a drying zone once after 1 liter.

Further, after drying, heat curing or radiation irradiation may be performed if necessary.

Moreover, if necessary, coating and eroding orientation can be easily applied. In this case, solenoids, electromagnets, and permanent magnets can be used.

The magnetic coating liquid of the present invention also has lubricating properties, abrasives, dispersants,
Additives such as antistatic agents and rust preventive agents may be added. In particular, lubricants include saturated and unsaturated higher fatty acids, fatty acid esters, higher fatty acid amides, higher alcohols, silicone oils, mineral oils, food oils, fluorine compounds, etc., and these may be added when preparing the coating solution. Further, after being peeled off from the roll or strip, it may be dissolved in an organic solvent, or it may be directly applied or sprayed onto the surface of the magnetic layer.

The present invention will be explained in more detail below using Examples and Comparative Examples. In the following Examples and Comparative Examples, "1 part" refers to "part by weight."

[Example] Examples 1 and 2, Comparative Example 1.2 Lecithin 4 parts Stearin M 4 parts Butyl stearate 4 parts Carbon black
10 parts Methyl ethyl ketone/toluene = 5/5 800 parts The above ingredients were kneaded in a ball mill for 50 hours, and the coating obtained was coated on a 10μ milky polyethylene terephthalate film 1 with a thickness of coating liquid 2. It was applied to the skin with a thickness of 20μ. After magnetic field orientation with a co magnet, 1
Dry at 00℃ and nip pressure 20 to metal roll 7.
9/an) was irradiated with an electron beam. The electron beam has an accelerating voltage of 16
It was irradiated with 100M rad at 5kV. Thereafter, it was peeled off and a second drying process was performed.

For each of the Examples and Comparative Examples, the metal roll used for this removal has a surface property as shown in Attached Table 1.

Note that the roll used in Comparative Example 1 is a general mirror finish roll.

For each experiment, we investigated the following:

Metal roll surface properties: Surface roughness: The roll surface was measured using a surface roughness meter manufactured by Koita Research Institute, and is expressed as center line average roughness defined in Section 5 of JIS-BO601. (Cutoff 0.25#l) Video S/N: Record gray signal with 50% setup using Matsushita Electric Co., Ltd.'s NV8200 video tape recorder, and remove noise with a Sivac model 925C S/N meter. It was measured. Video S/N is shown as a relative comparative value when Comparative Example 1 is set to OdB.

C/N: Carrier liquid (carrier) at 3 MHz and 3.5 MHz was recorded and the carrier to noise ratio was measured based on Comparative Example 1 (±OdB>).

Running durability: After running 100 times, the decrease in output was measured.

(Effects of the Invention) As described in detail above, the method for manufacturing a magnetic recording medium according to the present invention has the following advantages:
By bringing the surface of the transfer member adjusted to a predetermined roughness into close contact, the magnetic layer is given a surface property that is both smooth and easy to slide, resulting in a magnetic layer with excellent electromagnetic properties and running durability. A recording medium can be obtained.

The surface roughness of the magnetic layer of the magnetic recording medium produced according to the present invention is particularly suitable for applications such as audio tapes and 1/2'' video tapes.

[Brief explanation of drawings]

FIG. 1 is a side view of a detailed illustration of the invention. 1... Polyethylene terephthalate film 2...
Coating liquid 3...Coating part 4...Magnetic layer 5...First drying part 6...Nib part 7...Metal roll for roughness transfer

Claims (1)

[Claims] 1) In the subsequent step of the magnetic layer coating step in the coating type magnetic recording medium manufacturing process, a cutoff of 0.25 mm is applied to at least the surface of the magnetic recording medium on which the magnetic layer is coated. A method for manufacturing a magnetic recording medium, comprising: bringing a surface of a transfer member having a surface having a center line average roughness of 0.005 to 0.020 μm at a measurement length of 80 mm into close contact with each other. 2) A radiation polymerizable compound is employed as a binder for the magnetic material used in the magnetic layer coating step, and the magnetic recording medium is irradiated with radiation after the transfer member is brought into close contact with the magnetic recording medium. A method for manufacturing a magnetic recording medium according to scope 1. 3) The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the transfer member is a roll or a strip.