JPS5868235A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To manufacture a magnetic recording medium having coated layers contg. a ferromagnetic body at both sides and free from dropout and a fluctuation in output in a single stage by utilizing a polymn. reaction under electron beams. CONSTITUTION:By means of a stride extrusion type feeder 3A a coating liq. 2 for a magnetic layer contg. a compound polymerizable under electron beams is coated on one side of a web 1 which is continuously running while being supported by a backing roll 7. A gas is sprayed on the unhardened 1st coated side from a gas spouting device 4 to support the web 1 in a noncontact state, and the coating liq. 2 is coated on the other side of the web 1 by means of a coating device 5. After carrying out the orientation 8 of the magnetic body as required, electron beams are irradiated on the coated layers in a chamber 9 sealed with gaseous nitrogen to harden the layers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium in which ferromagnetic particles are coated on both sides of a support. A. More specifically, the present invention relates to a method for manufacturing the above-mentioned magnetic recording medium in a one-pass process.

In recent years, flexible disks have been developed as information storage devices for computers and the like, on which information is recorded and played back as digital signals in a format similar to recording and playback on vinyl records. The flexible disk is generally made of a sheet of flexible, non-magnetic support such as polyethylene terephthalate, polyester, AB8 resin, etc., and ferromagnetic powder such as r-Fe, 03, Co-containing r-P e 20 on both sides of the sheet. s, F e s 04, Co-containing r@, o4, etc. as a binder, dispersant, abrasive, and 4I
Apply a desired amount of coating liquid mixed with I & solvent etc. using coating methods such as gravure coating, blade coating, air knife coating, etc., and then punch out a circular shape and at the same time punch out the center hole and sector holes to form a donut shape. This is what I did.

The purpose of coating on both sides is to control curl and to record signals on both sides.

To produce a magnetic recording medium containing ferromagnetic particles on both sides of such a support, one side is coated and dried, and then the other side is coated and dried, that is, two passes are applied.
This requires a lot of time to obtain the final product, and the same operations have to be repeated using separate equipment, which not only causes problems such as increased equipment costs and space. , repeated coating and drying may cause wrinkles, web cuts and damage,
In addition to manufacturing defects such as easy contamination during the process, there were also the following quality problems.

■ When the first coated magnetic layer is next coated with the back coating layer, it is easily scratched because it is in contact with the roll in the coater, and this is highly likely to cause dropouts, output fluctuations, and other errors. It was big.

■ It is necessary to take countermeasures such as urgently increasing the scratch strength of the pre-coated magnetic layer, eliminating poor rotation of the contact roll, eliminating all scratches on the roll, or eliminating contact. is extremely difficult. In particular, when using a nip roll or the like, the magnetic layer on the previously coated surface is easily scratched.

Therefore, the inventors of the present invention aimed to provide a magnetic recording medium having magnetic recording layers on both sides of a support, which does not have the above-mentioned drawbacks, that is, has fewer scratches on the surface and fewer dropouts of the pre-coated magnetic layer. As a result of extensive research, it was found that after coating both sides of a support with a coating solution in which ferromagnetic particles were dispersed in a solution of a compound that can be polymerized by electron beams, both l- were simultaneously cured by electron beam irradiation. The above solution solved Zhao.

The first object of the present invention is to obtain a magnetic recording medium that has a coating layer containing a ferromagnetic material on both sides and is free from dropouts and output fluctuations. The 20th purpose is
It is an object of the present invention to provide an advantageous manufacturing method capable of manufacturing the above magnetic recording medium in one pass.

The purpose of the present invention is to coat both sides of a support with a coating solution in which a ferromagnetic material is dispersed in a solution of a compound that can be polymerized by electron beams, and then to simultaneously cure both layers by irradiating electron beams. achieved.

Compounds that can be polymerized by electronic edges include compounds that have one or more carbon-carbon unsaturated bonds, such as acryloyl groups, acrylamide groups, allyl groups, vinyl ether groups, vinyl thioether groups, and unsaturated polyesters. Specifically, unsaturated fatty acids such as acrylic acid and λ-butenoic acid, unsaturated polybasic acids such as maleic acid, fumaric acid, copten-1, dicarboxylic acid, and muconic acid, acrylamide, crotonamide, Unsaturated fatty acid amides such as λ-pente/amide, maleamide,
Examples include acrylic alkyl esters such as methyl acrylate and its homologs, styrene and its homologs α-methylstyrene/β-chlorostyrene, acrylonitrile, vinyl acetate, vinyl propionate, and the like. There may be two or more unsaturated bonds in the molecule. Examples of this compound 1/) include compounds listed in ``Photosensitive Resin Data Collection'' ■ Sogo Kagaku Kenkyusho 14/14/1939, Ko 3j to Ko 3. In particular, unsaturated esters of polyols, such as ethylene diacrylate,
Diethylene glycol diacrylate, glycerol triacrylate, ethylene diacrylate, taerythritol tetraacrylate, etc. and epoxy JJl
Grindyl acrylate having the following is preferred. A compound having one unsaturated bond in the molecule and a compound having two or more unsaturated bonds may be used as a mixture.

Moreover, these compounds may be of high molecular weight. Sometimes preferred are compounds having an acrylate group in the main chain or @ chain of the polymer chain, and these include A,
Vranken l;'atipecCongres
s” // /ri(/ri7λ)K Not cited.For example, the following compounds are shown, and the polyester electric potential of the exemplified compound is a polyurethane skeleton, an epoxy resin skeleton, a polyether skeleton, a polyester skeleton. There may be a skeleton or a mixture of these skeletons.The molecular weight is /, 000.-ko,
ooo is preferred, but is not particularly limited. Further, the above monomers and polymers may be mixed and used as a compound that can be combined with an electron beam.

In addition, vinyl chloride-vinyl chloride-based copolymers, woven edge fiber resins, acetal-based resins, vinyl chloride-vinyl chloride lyso/based resins, urethane resins,
7 of thermoplastic resins such as acrylonitrisitadiene resin
If necessary, more than one species may be added to the magnetic coating liquid of the present invention.

The proportion of compounds that can be polymerized by electron beams in the binder component (organic substances obtained by removing organic solvents from magnetic coating liquid) is 7.
Wt% is preferably 4 or more, and more preferably rwt% or more. If it is less than this, the increase in viscosity and/or gelation of the coating liquid due to electron beam irradiation will be small and the orientation of the magnetic particles will be sufficiently fixed. Binder component contained in magnetic coating liquid (
The total amount of the organic matter obtained by removing the organic solvent from the magnetic coating liquid is preferably O6l to 7 in Ji amount relative to the magnetic particles, and more preferably O, CO to O0S. .

As the magnetic particles, ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide imitation powder, ferromagnetic alloy powder, etc. can be used. The acicular ratio of ferromagnetic iron oxide and chromium dioxide is λ//~λθ/l
degree, preferably z/i or more, average length Oo, 2 to ko,
A range of approximately 0 μm is effective. The metal content of the ferromagnetic alloy powder is 7. twt% or more, and 10wt% or more of the gold component is a ferromagnetic metal (i.e., k″e, Co, Ni% Fe-C
o, pc-Ni, Go-Ni, Fa-Co-Ni) and have a major axis of about 2.2 μm or less.

Examples of organic solvents include ketones such as acetone, methylethylketone, methylinobutylketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate,
Ester systems such as acetic acid glycol monoethyl ether; glycol ether systems such as ether, glycol dimethyl ether, glycol monoethyl ether, and dioxane; aromatic hydrogen ash such as benzene, toluene, and xylene;
Methylene chloride, ethylene chloride, four groups (IL
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene can be selected and used.

Additionally, additives such as lubricants, abrasives, rust preventives, and antistatic agents may be added to the coating composition of the present invention. In particular, lubricants include saturated and unsaturated higher fatty acids, fatty acid esters, higher These include fatty acid amides, higher alcohols, silicone oils, mineral oils, food oils, and fluorine-based compounds. It may be added at the time of manufacturing the magnetic layer, or it may be dissolved in an organic solvent after drying or smoothing treatment, or it may be wrapped or sprayed directly onto the surface of the magnetic layer.

When preparing a propagated cloth composition, the magnetic particles and each of the above-mentioned components are fed into a kneading machine either all at the same time or one after the other. At this time, the dispersant may be first dispersed together with the magnetic particles, and then the compound or thermoplastic resin which can be dispersed by electron beams may be added.

Various kneaders are used to mix and disperse the composition. For example, two roll mills, ball mills, su/doctor tinders,
These include dispersers, high-speed impeller dispersers, and high-speed mixer homogenizers. As a method for applying magnetism onto the support, doctor coating, flade coating, air knife coating, Swiss coating, reverse roll coating, Clavia coating, etc. can be used.

The thickness of the magnetic layer is approximately 0.0 mm in dry thickness. Coat so that it has a circumference of j-/j μm. This dry thickness is determined by the use, shape, specifications, etc. of the magnetic recording medium.

Materials for the support include polyesters such as polyethylene terephthalate and polyethylene-1,≦-su7talate; polyolefins such as polyethylene and polypropylene; cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate. Cellulose derivatives such as nate;
Vinyl resins such as polyvinyl chloride and polyvinylidene chloride; In addition to plastics such as polycarbonate, polyimide, and polyamideimide, non-magnetic metals such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these, depending on the application; Paper , baryta, or paper coated or laminated with α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, and ethylene-butylene/copolymer can also be used. These non-magnetic supports may be transparent or opaque depending on the purpose of use.

The thickness of these non-magnetic supports is approximately 3 to 3
It is about 700 μm, preferably 0 μm from j-/, and more preferably from θ to 110 μm.

Further, the support may be in any form such as a tape, sheet, card, or disk, and various materials are selected as necessary depending on the form.

Methods for coating the magnetic layer on the support include extrusion coating, air doctor coating, blade coating, air knife coating, curtain coating, squeeze coating), f! Coating, linozo roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, spray coating, spin coating, etc. can be used, and other methods are also possible, and detailed explanations of these can be found in "Coding Engineering", page 2j3. It is described in detail on page 77 (Showa≠ published by Asakura Homare Store on March 20, 2017).

Among these coating methods, the most preferred are extrusion coating, flade coating, air doctor coating, and curtain coating.

In the present invention, it is undesirable for the web to come into contact with pass rolls or the like during the curing process after the coating liquid is applied to the support. The side with the cured coating is supported by a gas (air cushion) during the application of the other side.

FIG. 1 is a schematic diagram of a magnetic recording medium manufacturing apparatus according to embodiment 1i3i of the present invention. In FIG. 1, a coating liquid for a magnetic layer containing a compound that can be polymerized by an electronic edge is applied to one side of a web l that is continuously running while being supported by a batten/darol 7 by slide extrusion. The liquid is applied by the mold liquid supply device 3A, and the liquid is sent to the No. 1 coating section.

In the second application section, gas is blown from a 4L gas blowing device f1 onto the uncured first coating surface, and the web 1 is supported with the gas without contact. Equipment for dispersing magnetic layer coating fi, λ containing #'@ compounds that can be polymerized by electron beams! to the top surface of the support. If necessary, the web that has been subjected to inspection on both sides is subjected to orientation treatment of the magnetic material at t.
The coating liquid is sent to a chamber sealed with Ii1'Jg gas and cured by electron beam irradiation.

In Figure 2, 3B is an extrusion type liquid supply device;
IO is the bus roll for supporting the web.

A treatment for orienting the magnetic powder may be performed as necessary before electron beam irradiation.

In this case, the orienting magnetic field is approximately SOO~NO0 with alternating current or direct current.
00 Gauss, and the drying temperature is approximately to-/117 (
The temperature is about 7'C, and the drying time is about 3~)θ minutes.

The method for orienting magnetic powder is also described in the following patents.

For example, rice 1. l! Ll patent/, Rihiro, t≠θ issue; same λ
.

72 Otsu, 31 De issue; same J, 001.19/ issue; same 3,
/7 no, 77; same! , +t/4. Hari; 3.1
No. 173,760; J, tt/, lJ1; Special Publication Show 3
Co-3≠27; Same 3ter 2136t-q, Same 4cO-
No. 231, 24A; No. 110-231.25; Same! /
-/3/II No.; same pi-i3o4t3; four pieces 1-3
97 Coco No. Specification Jin etc.

The orientation direction of the magnetic material is determined by its use.

In other words, while disks do not require orientation treatment, sound tapes, small video tapes, and memory tapes require orientation treatment parallel to the length of the tape, and broadcast videotapes require orientation treatment in the length direction. On the other hand, it is oriented with an inclination of 30° to Oo.

After curing, calendering is performed to increase the smoothness of the sprayed surface.

The electron beam may be irradiated in two stages.The first stage is irradiated to such an extent that complete curing does not occur, and after a smoothing process such as a calendar is applied, the second stage is irradiated, which is more powerful than the first stage. It is more advantageous to do this in order to obtain smoothness.

As the electron beam accelerator, a scanning method, a double scanning method, a linear cathode method, or a curtain beam method can be adopted.

In the present invention, the electron beam must have sufficient intensity and irradiation amount to pass through the copying fabric layer and the support on one side, reach the coating layer on the other side, and sufficiently cure this coating layer. . Therefore, as for the electron beam characteristics, the accelerating voltage is ioo ~
1000 to ■, preferably 110 to 7ookV,
The absorbed dose is /-JO megarads, preferably 3 to 10 megarads. If the accelerating voltage is less than 700 V, there will be insufficient energy transmission cap, and if it exceeds too much V, the energy efficiency used for polymerization will decrease, making it uneconomical. If the absorbed dose is less than O0j megarad, the curing reaction will be insufficient and the strength of the magnetic layer will not be obtained, and if it exceeds 20 megarad, the energy efficiency used for curing will decrease and the irradiated object will become overheated, especially for pull sticks. This is not preferable because the support is deformed.

The present invention will be explained in more detail below using Examples and Comparative Examples. It will be readily understood by those skilled in the art that the components, proportions, order of operations, etc. shown herein may be modified without departing from the spirit of the invention.

Therefore, the invention should not be limited to the examples below. Similarly, in the following Examples and Comparative Examples, "1 part" refers to "IL lid part".

Example Magnetic 1-* Blood rp @ x Q s / 00 parts Nitrocellulose (R8//, 2Hl 10 parts Urethane resin (adipic acid, butanediol, tolylenediyne 7 Anate condensate 3 10 parts Acrylic acid 0.5 parts Ester acrylate oligomer (Takuyasei Aloex MAloo) 2 parts Sameethylene diacrylate 2 parts Methyl ethyl ketone
KojObu Stearinjo
1 part butyl stearate
Apply the above magnetic layer coating solution to a dry thickness on both sides of a polyethylene terephthalate support of 1 part jllsj Oμ! After applying the coating so that it becomes μ, the acceleration voltage is tyskV.

Electron beam irradiation was performed at a beam current/jmk. Next, the solvent was dried and a smoothing process was performed using a carrier/dar, followed by irradiation with an electron beam at an accelerating voltage of 3θOk and a beam current of jmA to obtain a magnetic recording medium.

The above processing was performed at a line speed of 700 m/7 min.

The magnetic recording medium thus obtained was punched into a donut shape to produce a flexible/pull disk. Let this be the sample.

COMPARATIVE EXAMPLE Blood in Example was coated on one side of a support, cured by electron beam irradiation, and rolled up. The coating amount and curing conditions at this time were the same as in the final example.

Magnetic NIi was coated on the remaining side of the web coated on one side under the same conditions as described above, and a magnetic recording medium was obtained by applying magnetic layers on both sides of the support once. Let the magnetic recording medium thus obtained be sample λ.

The S/N ratio and dropout were measured for each sample and sample λ, and Table 1 was obtained. The S/N ratio was based on sample A/.

Table-1

[Brief explanation of the drawing]

@ Figure 1 and Figure 2 are explanatory diagrams showing embodiments of the present invention, l is a web (support), JA, JB and j are liquid injection devices,
? indicates a chamber for electron beam irradiation.

Claims (1)

[Claims] A coating solution obtained by dispersing ferromagnetic particles in a solution of a compound that can be polymerized by electron beams is applied to both sides of the support,
A method for producing a magnetic recording medium, characterized in that both layers are simultaneously cured by electron beam irradiation.