KR19990074243A - Method for manufacturing magnetic recording medium - Google Patents

Abstract

The present invention relates to a method of manufacturing a magnetic recording medium on which a magnetic layer is formed on a nonmagnetic support. More particularly, the present invention relates to a method for producing a high-quality magnetic recording medium having excellent durability, running property, dispersion stability of a magnetic paint, and coatability.

Description

Method for manufacturing magnetic recording medium

The present invention relates to a method of manufacturing a magnetic recording medium on which a magnetic layer is formed on a nonmagnetic support.

Magnetic recording mediums such as magnetic tapes such as audio tapes and video tapes and magnetic disks such as floppy discs are formed by applying a magnetic coating liquid onto a nonmagnetic support having a wider area than ordinary products to form magnetic layers, And then the magnetic layer is subjected to a surface smoothing treatment to form a disk of a magnetic recording medium, followed by a hardening step to complete the final product. In the final step, the final product of the next step, such as a cassette, can be made through processes such as car setting.

The magnetic coating liquid is prepared by dispersing ferromagnetic powder, other inorganic substances such as alumina carbon black, a lubricant, a curing agent, a dispersant, etc. in a binder solution. The surface smoothing treatment improves the surface smoothness and filling density of the magnetic layer, Uniformity of coating thickness, and the like can be achieved. Smoothing of the surface of the magnetic body is very effective for improvement of reproduction output and reduction of noise of the magnetic recording medium.

It is necessary to increase the information storage capacity per unit area of the recording medium because the recent development of magnetic recording systems and high density recording and the like requires the manufacture of a recording medium having a large storage capacity of the magnetic recording medium.

Therefore, in order to increase the density of the information recording, it is necessary to concentrate the recording magnetic flux generated from the magnetic head for recording and reproducing information on a minute area, so that the magnetic head is miniaturized and the amount of generated magnetic flux is reduced. Therefore, in order to invert the magnetization direction of the magnetic body locally in the reduced magnetic flux, it is possible to completely invert the magnetization by decreasing the thickness of the magnetic layer, that is, by reducing the thickness of the magnetic body. However, if the volume of the magnetic layer is reduced, the effect of the light shielding effect may be deteriorated, the surface property may be deteriorated due to the formation of the thin film layer, the property may be deteriorated due to the decrease of the surface property, and the durability may be lowered. Particularly, the decrease in durability of the magnetic recording medium is fatal to the magnetic recording medium and may cause an increase in the dropout.

It is therefore an object of the present invention to solve the above problems and to provide a magnetic recording medium having a high filling rate which requires recording of a short wavelength and inversion of magnetization in a local portion, And a method for producing a high-quality magnetic recording medium which is excellent in magnetic characteristics and particularly excellent in electronic conversion characteristics and excellent in durability, running property, dispersion stability of a magnetic paint and coating property.

The present invention relates to a method of manufacturing a magnetic recording medium.

The magnetic recording medium of the present invention comprises a magnetic layer formed by dispersing a ferromagnetic powder, carbon black and an abrasive in a binder solution on a nonmagnetic support, and forming a magnetic layer, followed by drying, surface smoothing, Wherein the binder is a polyester polyurethane resin having a mass average molecular weight of 60,000 or more, a viscosity of 30 wt% to 900 cps or less, and a glass transition temperature of 30 ° C or more.

The binder of the present invention may be used alone or in combination with at least one material selected from the group consisting of a vinyl chloride resin, a urethane resin and a polyisocyanate based on a polyester-based polyurethane resin.

The polyester-based polyurethane used as the binder of the present invention is used not only to improve the dispersibility and dispersion stability of the coating material but also to improve the physical properties such as durability, flexibility, strength and running property, In order to lower the viscosity of the polyester-based polyurethane, if a low molecular weight material is used, the dispersibility and coatability of the coating material can be ensured. However, since the durability and physical properties of the thinned magnetic layer deteriorate, an ester-based polyurethane resin Is more than 60,000, it is important to secure the durability and physical properties of the magnetic layer after crosslinking between the binders.

When the glass transition temperature of the polyester-based polyurethane resin is lower than 30 ° C, the surface of the magnetic layer changes during curing and adversely affects the running property. In the magnetic recording medium after the curing process has been completed, Which causes many problems in the cassette winding process and the like.

In addition, since the viscosity characteristics of the coating material greatly affects the dispersibility and dispersion stability of the magnetic paint and the coating ability, it is very important to set appropriate viscosity conditions of the polyester-based polyurethane resin which greatly affects the viscosity characteristics of the magnetic paint. That is, in order to increase the coating speed or to improve the coating ability for improving the productivity, it is advantageous to lower the viscosity of the coating material so that the dispersion stability does not deteriorate. For this purpose, the viscosity condition of the polyester- Preferably 30 wt% to 900 cps or less.

Hereinafter, the present invention will be described in detail.

A binder solution is applied on a nonmagnetic support composed of a polymeric material such as polyethylene terephthalate on a surface of the magnetic layer on which a magnetic layer is not formed to form a binder layer, and an inorganic material such as a ferromagnetic powder, an abrasive, or carbon black, a lubricant, A magnetic coating liquid prepared by dispersing a binder solution in a high dispersion process is coated on a nonmagnetic support to form a magnetic layer and then subjected to orientation, drying, surface smoothing, hardening, and alarization to obtain a recording loss And to a method of manufacturing a magnetic recording medium without magnetic layer damage.

The nonmagnetic support of the present invention may be a known film such as polyethylene terephthalate, polyethylene naphthalate, polyaramid, polycarbonate, polyamide, polyimide, polyamideimide, and aramid.

The nonmagnetic support has a centerline average surface roughness of 0.1 占 퐉 or less, preferably 0.05 占 퐉 or less. Such a non-magnetic support should not only have a small centerline average surface roughness but also have no coarse projections of 1.0 탆 or more. Further, the shape of the surface roughness can be freely controlled by a pillar which is added as the need arises. As the pillar, oxides such as Ca, Si, Ti, organic carbonate such as carbonate and acrylic can be used.

The ferromagnetic powder usable in the magnetic layer is not particularly limited. Examples of the ferromagnetic material include γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , Co-containing Fe ₃ O ₄ , CrO ₂ , Co-Ni-P alloy, Fe-Co-Ni alloy, barium ferrite and strontium ferrite A known ferromagnetic powder can be used.

Abrasives may be used as an inorganic material such as alpha-ferrite _{(α-Fe 2 O 3)} , SiO 2, TiO 2, ZrO 2, SnO 2, Sb 2 O 3, Cr 2 O 3 and Al ₂ O _3.

Specific examples of usable carbon black include special black or black for rubber, and specifically, pellets (beads) having a particle size of 40 nm or less or carbon blacks of the powder type include Blackfowler, 75, L, 55, and 55, which are the printers of the Degussa printers, series, Vulcan 9A32, Vulcan P, Monarch 880, Monarch 800, Blackpulse 880, Blackpulse 800, Vulcan XC-72, Regal 330R, Regal 99R, MCV 88, MA600, # 3150, # 45, # 47, # 44, # 33, and CF9 of Mitsubishi, 50L, 50LB, 40B1, 40B2, 45LB, 40L, 30L, 30LB, 20L, 5L, 40, 30, 30B, 20, 20B, 10 and 10B of Lucky's high black series, As a kind of pellet (bead) or powder type carbon black having a particle size of 40 nm or more, Black Pearls 28 0, 130, Monarch 120 and the like, and Printte A of Degussa, Raven 14 of G Colombian, 430 # 20 of # Mitsubishi, # 10 MA7B Lucky, HighBlack 150B, and 160B.

Examples of the lubricant include ester fatty acids and fatty acids. Specific examples thereof include lauric acid, myristic acid, stearic acid, butyl stearate, oleic acid, oleyl alcohol and lauryl alcohol.

Examples of usable dispersing agents include isopropyltriisostearoyltitanate, isopropyltri (dodecyl) benzenesulfonyltitanate, isopropyltri (dioctyl) phosphatotitanate, isopropyltri (di (Oleyl) acetoacetyl aluminate, diisopropyl (oleyl) acetoacetyl aluminate, acetoalkoxy (allyloxy) acetylacetyl aluminate, and the like can be used. Aluminum diisopropylate and the like can be used.

(M, M1 and M2 represent Li, Na, K, H, -NR4 or HNR3, and R represents an alkyl group or an alkenyl group) Or H, and X represents a halogen atom). More specifically, UCAR-527, UCAR-569, VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYES, VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC, and PKFE manufactured by Union Carbide Co., DX80, DX82, DX83, and 100FD of electrochemical company and MR105, MR100 of Japan Xion and the like of electrochemical company and the like of TAXI, MPR-TA5, MPR-TAL, MPR-TSN, MPR-TMF, MPR- T-52080, T-5287, and T-5282 manufactured by Nippon Polyurethane Industry Co., Ltd., Nippon N2301, N2302 and N2304 manufactured by Nippon Polyurethane Industry Co., TI-9200, TI-1331, TI-1322, CA-2337, CA-239, CA-397, CA-398, CA-399, 8212, TI-8202, TI-8321, TI-8405, TI-8550, TI-8800, TI-8860, TI-8870, TI-8880, TI-8890, TI-8900, TI- 5714F1, 5703P, 5701F1P, 5788P, 5719P, 5715P, 5706P, 5755P, 5778P, 5799P, etc. of BF Goodrich Co. can be used.

As the curing agent, an isocyanate-based curing agent containing an appropriate amount of NCO groups may be used. Specific examples thereof include tolylene diisocyanate, 4-4'diphenylmethane diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane triisocyanate and the like.

The organic solvent that can be used as the solvent may be any organic solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, ketones such as cyclohexanone, methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol , Methylcyclohexanone and the like, esters such as methyl acetate, butyl acetate and isobutyl acetate, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether and dioxane, aromatics such as benzene, toluene and chlorobenzene Chlorinated hydrocarbons such as hydrocarbons, methylene chloride, ethylene chloride, and carbon tetrachloride can be used. Such an organic solvent need not necessarily be 100% pure, and may contain impurities of 10 to 30% or less, preferably 10% or less, of isomers, side reactants, decomposition products, etc. in addition to the main component.

It is possible to appropriately initial disperse the inorganic substance such as the magnetic substance, carbon black and abrasive which are usable in the binder solution in an appropriate amount suitable for the application and then to add a binder such as a binder, lubricant, hardener and the like, The coating material is prepared in accordance with the above-mentioned purpose.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited by the following Examples.

Examples and Comparative Examples

The composition of the magnetic layer

Ferromagnetic powder: Co-containing γ-Fe ₂ O ₃ 100 parts by weight

Carbon black: 6 parts by weight of MA7B manufactured by Mitsubishi

3 parts by weight of Lucky's High Black 150B

Polishing agent:? -Fe ₂ O ₃ 3 parts by weight

Al ₂ O ₃ 3 parts by weight

Binder: Polyester-based polyurethane resin 12 parts by weight

Polyvinyl chloride resin 13 parts by weight

Fatty acid: 2 parts by weight

Fatty acid ester: 2 parts by weight

Curing agent: Triphenylmethane triisocyanate 6 parts by weight

Organic solvent: cyclohexanone 140 parts by weight

Methyl ethyl ketone 140 parts by weight

120 parts by weight of toluene

- A magnetic layer was coated on a nonmagnetic support (polyester film) with the above composition to prepare a magnetic recording medium. The physical properties of the polyester-based polyurethane resin used in Examples and Comparative Examples are shown in Table 1

.

Mass average molecular weight Viscosity (30% by weight) Glass transition temperature (캜) Example 1 70,000 840 40 Example 2 90,000 880 33 Example 3 85,000 800 68 Example 4 67,000 890 42 Example 5 65,000 750 41 Comparative Example 1 40,000 700 40 Comparative Example 2 90,000 1300 45 Comparative Example 3 90,000 890 11 Comparative Example 4 45,000 700 23 Comparative Example 5 55,000 1,000 45

The properties such as electronic conversion characteristics, durability, dynamic friction coefficient, dispersion stability, and coating properties of videotapes of Examples and Comparative Examples respectively prepared using the polyester polyurethane resin having the physical properties shown in Table 1 in the above composition, And the results are shown in Table 2. < tb > < TABLE >

Assessment Methods

1) RF-output

The reference video tape was mounted on a VIDEO TECH (BR-7000) manufactured by Victor Company of Japan and a 100% white signal was recorded. The output at the time of reproduction was measured. The RF output of the video tape obtained in Comparative Example 1 was set to 0 dB, The difference is shown as a standard.

2) Running durability

Using a durability meter manufactured by Steinberg, USA, the magnetic layer of the videotape was brought into contact with the head, and the time until the magnetic layer was damaged was measured and evaluated in the following four stages.

A: more than 60 minutes, B: more than 50 minutes to less than 60 minutes, C: less than 40 minutes to less than 50 minutes

D: Less than 30 minutes to less than 40 minutes

3) Coefficient of friction (running)

A video tape is brought into contact with a drum made of stainless steel having a diameter of 4 inches at an angle of 180 ° and a tension T2 applied to the videotape when the drum is rotated at a speed of 1.8 m / And the coefficient of dynamic friction was calculated by the following equation.

4) Dispersion stability

The magnetic paint was left at room temperature for 1 day, and then the gloss before and after leaving for one day was compared with that after one day, and classified into four grades based on the degree of gloss decrease.

A: less than 10%, B: 10 to 19%, C: 20 to 29%, D: 30%

5) Coating property

The magnetic paint was applied to a non-magnetic support and classified into four grades by checking the coated surface and winding state.

A: Good coating surface and winding condition, B: Good coating surface, poor winding condition

C: poor coating condition, good winding condition, D: bad coating condition, poor winding condition

RF output durability Coefficient of friction Dispersion stability Application property Example 1 +0.7 B 0.197 A A Example 2 +1.6 A 0.231 A B Example 3 +0.6 A 0.180 A A Example 4 +0.8 B 0.247 A B Example 5 +1.2 B 0.226 B A Comparative Example 1 +1.7 D 0.498 D A Comparative Example 2 -0.5 A 0.237 A D Comparative Example 3 +2.0 B 0.597 B B Comparative Example 4 +1.7 C 0.478 C A Comparative Example 5 +0.2 C 0.227 A D

As can be seen from the above table, the magnetic recording medium manufactured by the method of the present invention has a good electron conversion characteristic and is excellent in durability, The dispersion stability of the magnetic paint and the coatability were excellent.

Therefore, it can be seen that when a magnetic recording medium is manufactured using the polyester-based polyurethane resin according to the present invention as a binder, a high-quality magnetic recording medium is provided.

Claims (2)

A magnetic recording medium produced by coating a magnetic paint prepared by dispersing ferromagnetic powder, carbon black and an abrasive agent in a binder solution on a non-magnetic support to form a magnetic layer, followed by drying, surface smoothing, hardening, And a polyester polyurethane resin having a mass average molecular weight of 60,000 or more, a viscosity of 30 wt% to 900cps and a glass transition temperature of 30 DEG C or more as the binder. The production method according to claim 1, wherein the polyester-based polyurethane resin is used alone as the binder, or the polyester-based polyurethane resin is mixed with at least one material selected from vinyl chloride resin, urethane resin and polyisocyanate .