KR19990074242A - Method of manufacturing magnetic recording medium - Google Patents

Abstract

The present invention relates to a method of manufacturing a magnetic recording medium which forms a magnetic layer and a binder layer on a nonmagnetic support.

Description

Method of manufacturing magnetic recording medium

The present invention relates to a method of manufacturing a magnetic recording medium which forms a magnetic layer and a binder layer on a nonmagnetic support.

Conventionally, a method of manufacturing a magnetic recording medium made of a magnetic tape such as an audio tape or a video tape and a magnetic disk such as a floppy disk is applied to form a magnetic layer by applying a magnetic coating liquid onto a nonmagnetic support having a larger area than a conventional product. After drying by performing an orientation treatment or the like, the magnetic layer is subjected to surface smoothing to make an original of a magnetic recording medium. Thereafter, the final product is finished through a slitting process in order to cut to a certain width suitable for the purpose of use after the curing process. As a final process, the cassette, which is the final product of the next step, may be made by a process such as casing.

The magnetic coating liquid is prepared by dispersing other inorganic materials such as ferromagnetic powder, alumina carbon black, lubricants, hardeners, and dispersants in a binder solution, and the surface smoothing treatment improves the smoothing and filling density of the surface of the magnetic layer. , Uniformity of coating thickness can be achieved. Smoothing of the surface of the magnetic material is very effective for improving the reproduction output of the magnetic recording medium and reducing the noise.

Recently, due to the development of technology such as magnetic recording system and high density recording, it is required to manufacture a recording medium having a large storage capacity of the magnetic recording medium. Therefore, it is necessary to increase the information memory per unit area of the 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 the information in a small area, so that the magnetic head becomes smaller and the amount of magnetic flux generated is reduced. Therefore, in order to locally invert the magnetization direction of the magnetic body in the magnetic flux to be reduced as described above, it is necessary to reduce the magnetic layer because the complete magnetization reversal is possible by reducing the magnetic layer volume, that is, reducing the thickness of the magnetic body. However, when the volume of the magnetic layer is reduced, the light shielding effect may be reduced, the surface property may be degraded due to the formation of a thin film, the property may be degraded due to the surface property, the durability may be deteriorated, and the surface may be damaged by foreign materials. In addition, the surface irregularities formed on the non-magnetic support to improve the runability affects the surface of the magnetic layer during the application and during various processes, or the particles contained on the non-magnetic support are eliminated, which causes a fatal magnetic layer destruction and loss of the recording signal. Degradation can occur and cause dropouts.

Accordingly, an object of the present invention is to solve the above problems and to form a magnetic layer having a high filling rate requiring short wavelength recording and local magnetization reversal, as well as high density recording by avoiding recording loss and surface damage due to the influence of nonmagnetic support. The present invention provides a method for producing a high quality magnetic recording medium having excellent magnetic properties and the like, and particularly excellent electron conversion characteristics.

1 is a cross-sectional view of a magnetic recording medium of a laminated structure according to the present invention.

2 is a cross-sectional view of a conventional magnetic recording medium in which only a magnetic layer is laminated on a nonmagnetic support.

* Description of the main parts of the drawings

1 nonmagnetic support 2 binder layer 3 magnetic layer

The present invention is a method of manufacturing a magnetic recording medium by applying a magnetic paint on a nonmagnetic support to form a magnetic layer (3) and forming a binder layer (2) on the opposite side of the magnetic layer (3) on a nonmagnetic support (1). WHEREIN: The glass transition temperature of the binder used for a binder layer is 60 degreeC or more, the glass transition temperature of the binder layer after completion | finish of hardening reaction after addition of a hardening agent is 80 degreeC, and the thickness of the formed binder layer becomes 1 micrometer or less Provided is a method of manufacturing a recording medium.

When the thickness of the binder layer is more than 1㎛, because the glass transition temperature of the binder layer is low, there may be a change in the binder layer, which may cause defects such as running property and may also cause adhesion.

The present invention is described in more detail as follows.

A conventional magnetic recording medium is produced by forming a magnetic layer 3 coated with a magnetic coating solution prepared by dispersing ferromagnetic powder in a binder solution on a nonmagnetic support 1 as shown in FIG. The thickness of the medium is 17 µm or more in the VHS standard. Therefore, the conventional tape uses a polymer material such as polyethylene terephthalate having a nonmagnetic support having a thickness of 13 to 16 μm, and a magnetic layer having a thickness of about 2 to 4 μm is applied or deposited thereon to prepare a magnetic recording medium. In the magnetic recording medium according to the present invention, a binder solution prepared by dissolving a binder and a curing agent in an organic solvent on a nonmagnetic support 1 composed of a polymer material such as polyethylene terephthalate, as shown in FIG. The ratio is adjusted to the ratio and applied to the opposite side of the magnetic layer 3 to form a binder layer 2 containing no particles. The main components are ferromagnetic powder and carbon black, and inorganic materials such as abrasives, lubricants, curing agents, and dispersants are used as binders. The magnetic coating solution prepared by dispersing the solution through a high dispersion process was applied onto the nonmagnetic support 1 to obtain a high density group. After the lockable magnetic layer 3 is formed, it is oriented, dried, surface smoothed, cured, and sliced to produce a recording loss, a property deterioration, and a magnetic layer damage caused by the nonmagnetic support. In this case, the magnetic recording medium prepared according to the present invention is designed so that the magnetic layer is capable of high-density magnetic recording, and the binder layer is formed so as to prevent the loss of the magnetic layer due to coarse particles and detachment of particles on the nonmagnetic support. Magnetic recording media originating from the support are manufactured to prevent the occurrence of lethal dropouts.

In the magnetic recording medium according to the present invention, the binder layer does not contain particles in the coating liquid forming the binder layer, and the unevenness of the surface is designed to reduce the contact surface area to improve the running property in the nonmagnetic support. To prevent direct desorption of particles of the nonmagnetic support that may occur while passing through the guide pins, tape guides and deck guides inside the cassette, and to maintain the unevenness of the surface while driving. In addition, the magnetic layer is formed to be made to enable high-density recording on the nonmagnetic support on the opposite side of the binder layer, thereby preventing recording loss and degradation, which are important characteristics of the magnetic recording medium. In manufacturing the magnetic recording medium, it is also possible to produce a back-coated magnetic recording medium coated on a non-magnetic support by dispersing carbon black in a binder solution on the opposite side of the magnetic layer, but in this case, the carbon contained in the back coating material Since the black particles are highly cohesive and are likely to exist as large particles, the particles are dislodged during various processes, resulting in a loss of recording, and in the case of carbon black, it is difficult to disperse due to strong cohesion and small particle size. Since the dispersion is required to have a higher strength than when using the above, the cost of the disperser and the maintenance cost are added, and the cost of manufacturing the magnetic recording medium is at the same time. In addition, since the surface irregularities formed on the nonmagnetic support must be redesigned when forming the carbon black layer, it is considered that the magnetic recording medium has a small improvement in characteristics compared to the cost and time required for development. On the other hand, the present invention for forming a binder layer can be used to form a binder layer exhibiting the antistatic effect of carbon black because it is possible to use a conductive antistatic binder rather than particles, so as to remove particles from the nonmagnetic support as well as particles It is possible to manufacture a high quality magnetic recording medium having good running performance by preventing damage to the magnetic layer due to detachment to prevent recording loss and degradation and to maintain the surface property formed on the nonmagnetic support. In addition, the decrease in the light transmittance, which is another characteristic of the carbon black layer, is not enough to cause a problem in the magnetic recording medium according to the present invention because the light transmittance can be achieved by applying the magnetic layer due to the change of JVC standard. . In forming the binder layer, the coating layer may be applied by various coating methods. However, in order to prevent a poor coating property from being formed due to the uneven coating thickness or the uneven coating thickness formed by a roll coating method or the like, By using an extrusion type coating method that does not come into contact with the sex support, the magnetic recording medium can be manufactured without coating problems by applying it.

As the nonmagnetic support of the present invention, known films such as polyethylene terephthalate, polyethylene naphthalate, polyaramid, polycarbonate, polyamide, polyimide, polyamideimide and aramid can be used.

The non-magnetic support has a centerline average surface roughness of 0.1 m or less, preferably 0.05 m or less. In addition, such nonmagnetic supports not only have to have a low center line average surface roughness but also have no coarseness of 1.0 µm or more. In addition, the shape of the surface roughness can be freely controlled by a filler to be added as needed, and such a filler may be an oxide such as Ca, Si, Ti, and organic fine powder such as carbonate or acrylic.

The ferromagnetic powder that can be used in the magnetic layer is not particularly limited. For example, γ-Fe ₂ O ₃ , Co containing γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co containing Fe ₃ O ₄ , CrO ₂ , Co-Ni-P alloy, Fe-Co-Ni alloy, barium ferrite, Known ferromagnetic powders such as strontium ferrite can be used.

As the abrasive, inorganic materials such as alpha ferrite, SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , Cr ₂ O _3, and Al ₂ O ₃ may be used.

Types of carbon black that can be used include special blacks or rubber blacks. Specifically, pellets (beads) having a particle size of 40 nm or less or powder type carbon blacks include Black Pearl Co., Ltd. and Regal 660. Series, Vulcan 9A32, Vulcan P, Monarch 880, Monarch 800, Black Pearl 880, Black Pearl 800, Vulcan XC-72, Regal 330R, Regal 99R and Degussa's Princedex series, the Princedex 85, 75, L, 55, 45, 40, 35, and Columbian's Raven 2000, Conducttex 900, Raven 1250, 1170, 1020, 850 and Mitsubishi's # 850, MCF 88, MA600, # 3150, # 45, # 47, # 44, # 33, CF9 and others 600L, 50L, 50LB, 40B1, 40B2, 45LB, 40L, 30L, 30LB, 20L, 5L, 40, 30, 30B, 20, 20B, 10, 10B, etc. As a kind of pellet (bead) or powder type carbon black which can be mixed and has a particle size of 40 nm or more, Black Pearl 280 manufactured by Cabot , 130, Monarch 120, Degusa's Printex A, G Colombian's Raven 14, 430 Mitsubishi's # 20, # 10 Lucky's High Black 150B, 160B, etc. can be used alone or in combination.

Examples of the lubricant include ester fatty acids and fatty acids, and specifically, lauric acid, myristic acid, stearic acid, butyl stearate, oleic acid, oleyl alcohol, lauryl alcohol and the like can be used alone or in combination.

Available dispersants include, for titanium, isopropyl triisostearolyl titanate, isopropyl tri (dodecyl) benzenesulfonyl titanate, isopropyl tri (dioctyl) phosphato titanate, isopropyl tri (di Octyl) pyrophosphate titanate, isopropyl triethyl titanate, etc. can be used, and as the aluminum system, diisobutyl (oleyl) aceto acetyl aluminate, diisopropyl (oleyl) acetoacetyl aluminate, acetoalkoxy Aluminum diisopropylate etc. can be used.

As the binder of the present invention, a mixed system including at least one selected from polyester-based polyurethane resins, vinyl chloride-based resins, urethane-based resins, and polyisocyanate-based resins may be used, and each binder may include -COOM, -OSO _3. M, -SO ₃ M, PO (OM ₁ ) (OM ₂ ), -OPO (OM ₁ ) (OM ₂ ), NR ₄ X (where M, M ₁ , M ₂ are Li, Na, K, H,- NR ₄ or HNR ₃ , R represents an alkyl group or H, and X represents a halogen atom. Specifically, Union Carbide's UCAR-527, UCAR-569, VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYES, VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC, PKFE and MPR- TA, MPR-TA5, MPR-TAL, MPR-TSN, MPR-TMF, MPR-TS, MPR-TM, MPR-TAO MR-110 and Nipporan N2301, N2302, N2304 from Nippon Polyurethane Co., Ltd., Pantex T-5105, T-R3080, T-5201 from Nippon Ink and CA-271, CA-237, CA-2237, CA- 236, CA-239, CA-397, CA-398, CA-399, 84847, CA-151HT, CA-152, and TI series of TI-9200, TI-1331, TI-8222, TI-8202, TI-8321, TI-8405, TI-8550, TI-8800, TI-8860, TI-8870, TI-8890, TI-8900, TI-8911, TI-8912, etc. and 5714F1, 5703P, 5701F1P, 5788P, 5719P, 5715P, 5706P, 5755P, 5778P, 5799P and the like can be used.

As a hardening | curing agent, the isocyanate type hardening | curing agent etc. containing a suitable amount of NCO group can be used. Specifically, triylene diisocyanate, 4-4 'diphenylmethane diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, naphthylene-1, 5- diisocyanate, triphenylmethane triisocyanate, etc. can be used.

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

Inorganic materials such as magnetic materials, carbon black, and abrasives, which are usable above, are properly dispersed in the binder solution in an appropriate amount suitable for the purpose, and after the addition of subsidiary materials such as binders, lubricants, and hardeners, the paint is prepared or known again through a dispersion process. Using the technique of to prepare a paint for the above purpose.

The binder solution and the coating material are coated on a non-magnetic support that runs at high speed in a series of steps to produce a magnetic recording medium by drying, smoothing, curing and cutting.

Therefore, according to the present invention, it is possible not only to provide a high-quality magnetic recording medium having excellent driving characteristics, driving durability, light shielding effect, surface properties, and electron conversion characteristics, but also to bring about economical savings.

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]

1. Composition of magnetic layer

Composition of the magnetic layer

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

Carbon Black: Mitsubishi's MA7B 6 parts by weight

Lucky's High Black 150B 3 parts by weight

Abrasive: α-Fe ₂ O ₃ 3 parts by weight

Al ₂ O ₃ 3 parts by weight

Binder: 12 parts by weight of polyester polyurethane resin

13 parts by weight of polyvinyl chloride resin

Fatty acid: 2 parts by weight

Fatty acid ester: 2 parts by weight

Curing agent: 6 parts by weight of triphenylmethane triisocyanate

Organic solvent: 140 parts by weight of cyclohexanone

Methyl ethyl ketone 140 parts by weight

Toluene 120 parts by weight

2. Composition of binder layer

Binder: 9 parts by weight of polyester polyurethane resin

1 part by weight of polyvinyl chloride resin

Curing agent: 6 parts by weight of triphenylmethane triisocyanate

Organic solvent: 100 parts by weight of cyclohexanone

100 parts by weight of methyl ethyl ketone

Toluene 100 parts by weight

The magnetic layer was applied onto the nonmagnetic support (polyester film) with the above composition to prepare a magnetic recording medium. The physical properties of the binder used and the thickness of the binder layer of the prepared magnetic recording medium are shown in Table 1.

Binder layer Glass transition temperature (Tg ℃) Binder layer thickness (㎛) Binder Tg Tg after curing Example 1 U 60 80 0.05 Example 2 U 70 85 0.05 Example 3 U 80 95 0.05 Example 4 U 70 85 0.1 Comparative Example 1 radish Comparative Example 2 U 40 50 0.05 Comparative Example 3 U 70 85 2 Comparative Example 4 Carbon black layer 1.5

The characteristics such as electron conversion characteristics, tape torque, durability, and dropout of the video tapes produced by the methods of Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 2.

Assessment Methods

1) RF output

A video tape (BR-7000) manufactured by Victor Japan Inc. was used to record a 100% white signal, and then measured the output during playback. The RF-output of the video tape obtained in Comparative Example 1 was set to 0 dB. The difference is shown as a reference.

2) Dropout

After recording the 5-step difference signal on the video tape with the optimal recording current, the dropout is regarded as the dropout of the video amplifier attenuation of 20dB and the duration of 15μsec or more during playback. It is shown.

3) running durability

Using a durability meter manufactured by Bergman, USA, the magnetic layer of the video tape was contacted with the head, and the time until the magnetic layer was damaged was measured and evaluated in four steps as follows.

A: 60 minutes or more

B: 50 minutes or more-less than 60 minutes

C: 40 minutes or more-less than 50 minutes

D: 30 minutes or more-less than 40 minutes

4) Tape torque when driving

The torque during tape travel was measured by G / cm using the VT-500D of the Yokohama Systems Research Institute.

RF output Drop Out Tape torque durability Example 1 +1.0 4 260 A Example 2 +0.9 3 210 A Example 3 +0.7 3 180 A Example 4 +0.8 4 240 A Comparative Example 1 +0.5 20 250 C Comparative Example 2 +0.6 6 400 B Comparative Example 3 +0.9 5 370 B Comparative Example 4 +0.9 15 260 A

As can be seen from the above table, the magnetic recording medium manufactured by the method of the present invention has better electronic conversion characteristics, durability and runability compared with the magnetic recording medium of Comparative Example, which is a magnetic device produced by a conventional method. It was found that the dropout characteristics, which are excellent and important characteristics of the magnetic recording medium, were very excellent.

Claims (1)

In a method of manufacturing a magnetic recording medium by applying a magnetic paint on a nonmagnetic support to form a magnetic layer (3) and forming a binder layer (2) on a surface opposite to the magnetic layer (3) on a nonmagnetic support (1), The glass transition temperature of the binder used for the binder layer is 60 ° C or higher, the glass transition temperature of the binder layer after completion of the curing reaction after the addition of the curing agent is 80 ° C, and the thickness of the formed binder layer is 1 μm or less. Manufacturing method.