KR100625051B1 - Magnetic media - Google Patents

Abstract

The present invention relates to a magnetic recording medium prepared by applying a magnetic coating composed of a magnetic material, an abrasive, a binder, a lubricant, a curing agent, and an organic solvent, on which a carbon black is deposited on a ferromagnetic powder, onto a nonmagnetic support. Carbon black is pre-deposited on the ferromagnetic powder, rather than simple mixing, to improve the blackness and dispersibility of the magnetic coating, so that the electron conversion characteristics are excellent, the durability is excellent, and the drop-out characteristic is one of the important characteristics of the magnetic recording medium. Do.

Carbon Black, Magnetic Materials, Ferromagnetic Powder, Carbon Coating, Video Tape

Description

Magnetic recording medium {Magnetic media}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly, to a magnetic recording medium including a magnetic material having carbon black deposited on a ferromagnetic powder.

Magnetic tapes and floppy discs, such as conventional audio tapes and video tapes. In a method of manufacturing a magnetic recording medium made of a magnetic disk, such as a magnetic disk, a magnetic layer is usually coated on a nonmagnetic support having a wider area than a product to form a magnetic layer, dried by orientation treatment, and the like, and then the surface of the magnetic layer surface layer is dried. The smoothing process is used to make the disc of the magnetic recording medium. Then, the final product is completed through a slitting process in order to go through a curing process and cut to a certain width suitable for the purpose of use. Finally, the cassette, which is the final product of the next step, may be made by a process such as casing.

The magnetic paint is prepared by dispersing other inorganic materials such as ferromagnetic powder, alumina or carbon black, and a lubricant, a hardening agent, and a dispersant in a binder solution, and the coating smoothing treatment improves the smoothing and filling density of the surface of the magnetic layer, thereby making uniform coating thickness. And the like 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 a 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 storage capacity per unit area of the magnetic recording medium. 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, thereby miniaturizing the magnetic head and reducing the amount of magnetic flux generated.

As the amount of magnetic flux decreases, in order to locally reverse the magnetization direction of the magnetic body, it is necessary to reduce the magnetic layer volume, that is, reduce the thickness of the magnetic layer.

However, when the volume of the magnetic layer is reduced, the light shielding effect may be lowered, the surface properties may be lowered due to the formation of a thin film, the characteristics may be lowered due to the lowered surface properties, durability may be reduced, and surface damage may be caused by foreign substances.

On the other hand, the surface irregularities are formed on the non-magnetic support to improve the runability, which affects the surface of the magnetic layer during the coating process or various processes, or the particles contained on the non-magnetic support are eliminated to destroy the deadly magnetic layer as a magnetic recording medium, Loss or degradation of the recording signal may appear, causing drop-out.

The object of the present invention is to supplement the above problems and to improve the blackness and dispersibility of the magnetic coating by using the ferromagnetic powder deposited carbon black as a magnetic material to minimize the recording loss and surface damage due to the influence of the non-magnetic support The present invention provides a magnetic recording medium capable of high density recording, excellent electron conversion characteristics, and an ultra-thin coating layer.

In order to achieve the above object, the magnetic recording medium of the present invention is manufactured by applying a magnetic coating made of ferromagnetic powder, an abrasive, a binder, a lubricant, a curing agent, and an organic solvent coated with carbon black on a nonmagnetic support. do.

In the present invention, the carbon black is formed on the ferromagnetic powder, unlike the conventional magnetic layer formed by mixing a magnetic coating composed of carbon black, ferromagnetic powder, an abrasive, a binder, a lubricant, a curing agent, and an organic solvent and applying the same on a nonmagnetic support. It is deposited directly and mixed with the raw materials and applied onto a nonmagnetic support to form a magnetic layer.

The raw materials of magnetic recording media are made of magnetic coating by mixing and dispersing ferromagnetic powder, that is, general magnetic materials, with carbon black. In this case, Hc value of magnetic coating liquid of magnetic recording media is 600-800 Oe (powder characteristic). Level.

The carbon-deposited ferromagnetic powder, which is a raw material of the magnetic recording medium according to the present invention, is a carbon black deposited on a ferromagnetic powder that is currently used in the manufacture of the magnetic recording medium, and facilitates blackness, dispersibility and antistatic effect, and other inorganic substances. When it is added, it is formed of a paint which is not disadvantageous as a magnetic paint, and is then manufactured to have properties superior to conventional magnetic paint levels through an orientation, drying, surface smoothing, curing, and annealing process.

Here, the carbon black used for carbon deposition has a specific surface area value of about 25-40 m <2> / g, and it is good in dispersibility. The viscosity of the magnetic paint should be adjusted appropriately for the application and coating process.

The properties of the carbon deposited ferromagnetic powder are in the range of conventional ferromagnetic powders, and Hc is advantageously in the range of 600 to 800 Oe (powder properties).

The ferromagnetic powder coated with carbon can bring about the same performance as the uncoated magnetic paint even if a small amount of carbon black is added on the antistatic surface, and the viscosity of the finished magnetic paint can be easily controlled and exhibit low light transmission. Can be.

In the prior art, it is possible to exhibit high light transmittance under the influence of undispersed carbon black. Therefore, the ferromagnetic powder deposited with carbon can supplement the above problems and facilitate the manufacture of magnetic coating.

The ferromagnetic powder that can be used for carbon deposition is not particularly limited, such as γ-Fe ₂ O ₃ , Co-γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-Fe ₃ O ₄ , CrO ₂ , Co-Ni Known ferromagnetic powders such as -P alloy and Fe-Co-Ni alloy can be used.

Carbon blacks used for carbon deposition include special blacks or rubber blacks. Specifically, pellets or powder type carbon blacks having a particle size of 40 nm or less include BlackPearls, Regal 660 series, Vulcan 9A32 and Vulcan from Cabot. P, Monarch 880, Monarch 800, Black Pearls 880, Black Pearls 800, Vulcan XC-72, Regal 330R, Regal 99R and Degussa's printex series, Printex 85, 75, L, 55, 45, 40, 35, etc. Columbian's Raven 2000, Conductex 900, Riven 1250, 1170, 1020, 850 and Mitsubishi's # 850, MCF 88, MA 600, # 3150, # 45, # 47, # 44, # 33, CF9, etc. Alternatively, a pellet or powder carbon black having a particle size of 40 nm or more may be used as BlackPearls 280, 130, Monarch 120, etc. of CABOT, and Detex's Printex A, G, and Columbian's Raven 14, 430 Mitsubishi Corporation. 20, # 10 etc. can be used alone or mixed There.

The carbon black is deposited on the ferromagnetic powder. Specifically, carbon black is added to Co-Fe ₂ O ₃ , which is a ferromagnetic powder, and dispersed by applying heat, followed by drying by washing.

When the ferromagnetic powder deposited with carbon is blended with a conventional magnetic paint raw material, the magnetic paint will be described in detail;

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

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.

In the dispersant that can be used, the titanium-based 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 type, diisobutyl (oleyl) aceto acetyl aluminate, diisopropyl (oleyl) acetoacetyl aluminate, acetoalkoxy Aluminum diisopropylate and the like can be used.

As the binder, a vinyl chloride-based resin, a urethane-based resin, or a mixed system separated from a polyisocyanate-based compound may be used. For each binder, -COOH, -OSO ₃ M, -SO ₃ M, PO (OM ₁ ) (OM ₂ ) , -PO (OM ₁ ) (OM ₂ ), NR ₄ X, wherein M, M ₁ , M ₂ are Li, Na, K, H, -NR ₄ or HNR ₃ , R is an alkyl group or H, and X Is a halogen atom) at least one functional group.

Specifically, Union Carbide's UCAR-527, UCAR-569, VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYES, VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC, PKFE, etc. TA, MPR-TA5, MPR-TAL, MPR-TSN, MPR-TMF, MPR-TS, MPR-TM, MPR-TAO, etc., 100OW, DX80, DX82, DX83, 100FD from Electrochemistry, etc., MR105, MR100, MR-110, Nipponran N2301, N2302, N2304 from Nippon Polyurethane Co., Ltd., Pantex T-5105, T-R3080, T-5201 from Nippon Ink, etc., CA-271, CA-237, CA-2237, CA from Nippon Ink. -236, CA-239, CA-397, CA-398, CA-399, 84847, CA-151HT, CA-152, etc., TI-9200, TI-1331, TI-8222, TI- 8202, TI-8321, TI-8405, TI-8550, TI-8800, TI-8860, TI-8870, TI-8890, TI-8890, TI-8900, TI-8911, TI-8912 and BF Goodrich's 5714F1 , 5703P, 5701F1P, 5788P, 5719P, 5715P, 5706P, 5755P, 5778P, 5799P and the like can be used.

As the curing agent, an isocyanate-based curing agent or the like containing an appropriate amount of NCO group can be used. 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 in arbitrary ratios. Alcohols such as alcohols and methylcyclohexanone, 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. The organic solvent does not necessarily need to be 100% pure, and in addition to the main component, impurities of 10 to 30% or less, preferably 10% or less, such as isomers, side reactions, and decomposition products may be used.

After dispersing such ferromagnetic powders and inorganic materials such as abrasives in the binder solution at an appropriate content for the purpose, adding auxiliary materials such as binders, lubricants, and curing agents, and then preparing paints through dispersion process or using known techniques. To prepare a paint.

The magnetic coating prepared in this way is coated on a non-magnetic support that travels at high speed in a predetermined volume in a sequence or in a sequence, and then dried, smoothed, cured, and cut to manufacture a magnetic recording medium.

Magnetic recording media made of ferromagnetic powder are coated on a nonmagnetic support, that is, a film. The film is polyethylene terephthalate, polyethylene naphthalate, polyamide, polycarbonate, polyimide, polyamideimide, aramid, etc. Film can be used.

The nonmagnetic support to which the magnetic paint is applied has a center line average surface roughness of 0.1 μm or less. In addition, such a nonmagnetic support is so good that there are no coarseness of 1.0 micrometer or more. In addition, the shape of the surface roughness can be freely adjusted with a filler (filler) to be added as needed, and as such a filler, oxides such as Ca, Si, Ti, organic fine powder such as carbonate, acrylic, and the like can be used.

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

Examples 1-4 and Comparative Examples 1-4

Ferromagnetic powder 100 parts by weight, abrasive 5 parts by weight, binder 25 parts by weight, lubricant 4 parts by weight, curing agent 8 parts by weight, cyclohexanone 120 parts by weight, methyl ethyl ketone 120 parts by weight, toluene 120 parts by weight of polyester film A magnetic recording medium was prepared by coating onto a film.

At this time, the carbon deposition on the ferromagnetic powder was carried out in each of the carbon black having a specific surface area as shown in Table 1, as shown in Table 1, specifically, the content ratio per specific surface area of the carbon black and the specific surface area of the magnetic body By using differently to determine the favorable conditions in the characteristics of the magnetic recording medium.

In Comparative Examples 1 and 2, carbon black was mixed with the magnetic coating itself without carbon deposition, and then coated on a polyester film in the same manner as above to prepare a magnetic recording medium.

In addition, the specific surface area of the carbon deposited ferromagnetic powder magnetic body was measured and the results are shown in Table 1 below.

Carbon black Specific surface area of magnetic material (㎡ / g) Specific surface area (㎡ / g) Content (parts by weight) Example 1 33 9 33.4 Example 2 33 7 33.4 Example 3 33 7 34.6 Example 4 31 7 33.4 Comparative Example 1 Unprocessed goods 7 33.4 Comparative Example 2 Unprocessed goods                                              9 33.4 Comparative Example 3 33 3 24 Comparative Example 4 23 4 33.4

The RF output, drop-out, and driving durability of the video tapes prepared according to the above Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 2 below.

Assessment Methods

(1) RF output

Mount a reference video tape on a video deck (BR-7000) from Victor Japan, record a 100% white signal, measure the output during playback, set the RF-output of the video tape obtained from the reference tape to 0 dB, and set this value. The difference is shown as a reference.

(2) drop-out

After recording the five-step difference signal on the video tape with the optimal recording current, it is regarded as drop-out that the attenuation of the video amplifier during playback is 20 dB and the duration is 15 μsec or more, and the measurement is continued for 10 minutes, and then the number per minute Averaged.

(3) Driving durability

The magnetic layer of the video tape was brought into contact with the head using a durability meter manufactured by Bergman, USA, 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-60 minutes or more, C-40 minutes or more-50 minutes or more, D-30 minutes or more-40 minutes or more

RF output Drop-out Driving durability Example 1 +1.3 2 A Example 2 +1.5 3 A Example 3 +1.2 3 A Example 4 +1.6 One A Comparative Example 1 +0.0 19 B Comparative Example 2 -0.5 20 B Comparative Example 3 +0.1 21 B Comparative Example 4 -0.2 17 C

In the magnetic recording medium prepared using the ferromagnetic powder magnetic material deposited with carbon from the results of Table 2, the carbon black and the ferromagnetic powder were mixed with each other (Comparative Examples 1 and 2), or the specific surface area of the added carbon black was measured. Compared with those outside the range of (Comparative Examples 3 and 4), the electron conversion characteristics are good, the durability is excellent, and the draw-out characteristic is one of the important characteristics of the magnetic recording medium.

As described in detail above, the magnetic recording medium prepared by applying a magnetic paint prepared by the conventional magnetic coating composition on a nonmagnetic support, including a magnetic material in which carbon black is deposited on the ferromagnetic powder according to the present invention, Compared with the simple mixing with ferromagnetic powder, the black paint and dispersibility of magnetic coating are improved, so the electron conversion characteristics are excellent, the durability is excellent, and the drop-out characteristic, which is one of the important characteristics of the magnetic recording medium, is excellent.

Claims (2)

In a magnetic recording medium prepared by applying a magnetic paint on a nonmagnetic support, The magnetic recording medium of the magnetic coating is characterized in that the carbon black is deposited on the ferromagnetic powder. The method of claim 1, Carbon black has a specific surface area of 25 to 40 m 2 / g, a magnetic surface of 25 to 40 m 2 / g, and the content of carbon black is 3 to 10 parts by weight based on 100 parts by weight of ferromagnetic powder. Magnetic recording media.