KR20010056148A - Magnetic recording media - Google Patents

Abstract

PURPOSE: A magnetic recording medium is provided to record at a high density through including a magnetic layer formed by magnetic bodies having inherent characteristic. CONSTITUTION: A magnetic body having a specific characteristic, and inorganic material such as carbon block and abrasive are distributed in a bond solution. Then, additional material such as bond, lubricant, and hardening agent is added for being distributed. Therefore, a coating material is produced. Moreover, a hardening promoting agent is used for reducing activating energy required in hardening. The magnetic coating material is sprayed on a non-magnetic supporter for being dried. Before hardening, a surface leveling process is performed under a high temperature and high pressure condition.

Description

Magnetic recording media {Magnetic recording media}

The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic card or a magnetic disk. Specifically, the present invention relates to a magnetic recording medium capable of high density recording by including a magnetic layer made of magnetic material having a specific range of inherent characteristics.

Conventional magnetic recording media such as magnetic tapes and floppy disks are formed by applying a magnetic coating solution on a nonmagnetic support having a larger area than a conventional product to form a magnetic layer, and performing an orientation treatment or the like to dry the magnetic layer, and then surface smoothing the magnetic layer. The disc is manufactured, and then hardened and slitted to complete the process. The cassette may then be subjected to a casing process to make the cassette as a final product.

The characteristics of the magnetic recording medium produced by the above general method are determined by the magnetic material used as the raw material. That is, the electron conversion characteristics and the physical characteristics, which are the quality characteristics of the magnetic recording medium, are almost determined depending on the kind of the magnetic substance used.

Therefore, various methods are used to supplement the characteristics of the magnetic material. Among them, a method of using a single magnetic material when manufacturing a magnetic recording medium and a method of using a magnetic material in order to eliminate the problems of using a single magnetic material. Etc. In the case of using a single magnetic material, in order to improve the characteristics of the magnetic recording medium, the magnetic properties such as coercivity, saturation magnetization, and specific particle size are measured by measuring specific surface area. By improving some properties, other properties tend to be degraded. In addition, when using a mixed magnetic material, it is managed in a similar manner to a single magnetic material, where synergistic effects may occur with each other, or may be less than expected.

In addition, by forming each magnetic recording layer on the nonmagnetic support using two magnetic materials, there is a middle layer coating method for solving a problem of a single magnetic body and manufacturing a high quality magnetic recording medium. However, in the case of simultaneous layer formation in the middle layer coating method, high level coating technique is required due to the viscoelastic behavior of the magnetic coating during layer formation, and a second paint manufacturing process is required due to the dualization of the paint manufacturing process. Cost increases are inevitable. In the case of sequential middle layer formation, there is a problem in that the interface formation is very poor due to the difference in concentration between the two magnetic layers. Therefore, the deterioration of the properties of the magnetic material appears a lot during the middle layer coating.

Accordingly, the present inventors have conducted studies to improve the recording and reproducing characteristics of the magnetic recording medium, and as a result, the magnetic material having a specific range of specific characteristics, that is, specific surface area, coercivity, saturation magnetization value and coercivity, and Fe ²⁺ content In the case of using a raw material, the inventors have found that a magnetic recording layer capable of high-density recording can be produced.

In the present invention, a magnetic body having a specific surface area of 25 to 36 m ² / g, a coercive force of 600 to 800 Oe, and a ratio (δs / Hc) of saturation magnetization value (δs) and coercive force (Hc) of 0.11 to 0.14 emu / Oe · g It relates to a magnetic recording medium, characterized in that the magnetic layer comprising a formed on a nonmagnetic support.

The magnetic material used in the present invention is preferably Co-containing γ-Fe ₂ O ₃ or Co-containing Fe ₃ O ₄ .

The Fe ²⁺ content of the magnetic body used in the present invention is preferably 11 to 18% by weight based on the total weight of the magnetic body.

Hereinafter, the characteristics of the magnetic body of the present invention will be described in detail.

The specific surface area of the magnetic body of this invention is 25-36 m <^2> / g. At this time, if the specific surface area is less than 25m ² / g, there is a problem such as deterioration characteristics, if the specific surface area exceeds 36m ² / g, it is difficult to disperse the magnetic paint, so that the signal omission due to undispersed or long color signal Recording and reproducing becomes disadvantageous.

In addition, the coercive force of the magnetic body of this invention is 600-800Oe. At this time, if the coercive force is less than 600Oe, there is a problem such as deterioration of the physical properties of the tape. If the coercive force exceeds 800Oe, the coercive force of the magnetic material is greater than the force required for recording and reproducing, so that the erase rate is lowered and the color signal having the electronic change characteristic. Will have an adverse effect on the playback output.

Moreover, the recording efficiency characteristic which is the ratio of the saturation magnetization value (delta) s and the coercive force (Hc) of a magnetic body is 0.11-0.14 emu / Oe * g. If the recording efficiency characteristic is less than 0.11 emu / Oe · g, the relatively high coercivity increases the energy cost used for dispersion and the cobalt content used to increase efficiency and coercivity, resulting in low efficiency and high raw material cost. do. In addition, when a magnetic material having a recording efficiency characteristic of more than 0.14 emu / Oe · g is used, the recording efficiency is very advantageous, but the coercive force is relatively low, and the overall recording balance becomes somewhat disadvantageous.

In addition, the magnetic body of the present invention preferably contains 11 to 18% by weight of Fe ^{2+ based} on the total weight of the magnetic body. At this time, if the content of Fe ²⁺ is less than 11% by weight, when the initial and the end of the recording medium by using the light transmittance, the consumption of the magnetic paint is large, the productivity is lowered, excessive car to compensate for this problem In the case of using the black, signal dispersion occurs due to the influence of undispersed products. In addition, in order to increase the saturation magnetization value, when the Fe ²⁺ content in the magnetic material exceeds 18% by weight, the change over time may be severe, resulting in deterioration of the characteristics of the magnetic recording medium for a long time and storage of the magnetic material.

There is no particular limitation on the magnetic material that can be used in the magnetic layer of the present invention. Examples thereof include 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- Known ferromagnetic powders such as Ni-P alloys, Fe-Co-Ni alloys, barium ferrite and strontium ferrite can be used, and Co-containing γ-Fe ₂ O ₃ and Co-containing Fe ₃ O ₄ are particularly preferable.

Next, the method of manufacturing the magnetic recording medium of the present invention is as follows.

In the present invention, after the initial dispersion of the magnetic body having the intrinsic properties of the specific range described above, inorganic materials such as carbon black and abrasives in the binder solution in an appropriate amount appropriate for the purpose, and added to the auxiliary materials such as binders, lubricants and curing agents Then, the paint is produced again through a dispersion process or the paint is manufactured for the above purpose using a known technique. In the present invention, a curing accelerator may be used to lower the activation energy required for curing. Examples of the curing accelerator include dibutyltin dilaurylate, dibutyltin-2-ethylhexylate, 2-ethylhexyl cobalt, and triethylamine. Commercially available materials can be used. The magnetic coating prepared using the raw material is coated on the nonmagnetic support, and then subjected to a drying process, and then surface smoothing is performed under conditions of high temperature and high pressure in the surface smoothing process before curing is performed.

As the nonmagnetic support used in the present invention, known films such as polyethylene terephthalate, polyethylene naphthalate, polyaramid, polycarbonate, polyamide, polyimide, polyamideimide and aramid can be used. The nonmagnetic support has a centerline average surface roughness of 0.1 μm or less, more preferably 0.05 μm or less, and not only the centerline average surface roughness needs to be small, but also no coarseness of 1.0 μm or more are better. In addition, the shape of the surface roughness can be freely adjusted with a filler (filler) added as needed, and as such a filler, oxides such as Ca, Si, Ti, and organic fine powder such as carbonate and acrylic may be used.

As the abrasive used in the present invention, 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 can be used.

The carbon black usable in the present invention includes a special black or rubber black, and specifically, a pellet (bead) or powder type carbon black having a particle size of 40 nm or less is black pulsel and regal of Cabot Co. 660 Series, Vulcan 9A32, Vulcan P, Monarch 880, Monarch 800, Black Pearl 880, Black Pulse 800, Vulcan XC-72, Regal 330R, Regal 99R and Degussa Printex series, Printex 85, 75, L, 55 Columbia, Raven 2000, Conducttex 900, Raven 1250, 1170, 1020, 850, and Mitsubishi's # 850, MCF 88, MA600, # 3150, # 45, # 47, # 44, # 33, CF9 Lucky or its own high black series 600L, 50L, 50LB, 40B1, 40B2, 45LB, 40L, 30L, 30LB, 20L, 5L, 40, 30, 30B, 20, 20B, 10, 10B, etc. Black pearl 280, 130 of Kabot company with the carbon black of the pellet (bead) or powder type which can use, and has the particle size more than 40nm , Monarch 120 and the like Degu's Printex A, G Colombian's Raven 14, 430 Mitsubishi's # 20, # 10 Lucky's High Black 150B, 160B and the like can be used alone or in combination.

Lubricants that can be used include ester fatty acids, fatty acids, and the like, 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) benzesulfonyl titanate, isopropyl tri (dioctyl) phosphate titanate, isopropyl tri (dioctyl) Pyrophosphate titanate, isopropyl triethyl titanate, and the like can be used, and as the aluminum type, diisobutyl (oleyl) aceto acetyl aluminate, diisopropyl (oleyl) aceto acetyl aluminate, aceto alkoxy aluminum diiso Propylate and the like can be used.

As the binder, a vinyl chloride-based resin, a urethane-based resin, a mixed system obtained from a polyisocyanate-based compound, or the like can be used, and for each binder, -COOM, -OSO ₃ M, -SO ₃ M, PO (OM ₁ ) (OM ₂ ), -OPO (OM ₁ ) (OM ₂ ), NR ₄ X (wherein M, M ₁ , M ₂ represents Li, Na, K, H, -NR ₄ or HNR ₃ , and R represents an alkyl group or H , 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, 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, Nippon-N2301, N2302, N2304 from Japan Polyurethane Co., Ltd., Pantex T-5105, T-R3080, T-5201, T-5287, T-5282 from Nippon Polyurethane Co., Ltd. 237, CA-2237, CA-236, CA-239, CA-397, CA-398, CA-339, 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-8900, TI-8911, TI-8912 and BF Good Goodrich's 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.

Organic solvents usable as solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohesanone, methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, Alcohols such as methylcyclohexanol, esters such as methyl acetate, butyl acetate and isobutyl acetate, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether and dioxane, aromatic hydrocarbons such as benzene, toluene and chlorobenzene , Chlorinated hydrocarbons such as methylene chloride, ethylene chloride and carbon tetrachloride can be used. Such an organic solvent does not necessarily need to be 100% pure, and in addition to the main component, there may be 10 to 30% or less of impurities such as isomers, side reactions, and decomposition products, and preferably 10% or less of impurities.

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.

Composition of Magnetic Layers in Examples and Comparative Examples

The compositions of the magnetic layers used in Examples 1-5 and Comparative Examples 1-5 were as follows.

100 parts by weight of Co-containing γ-Fe ₂ O ₃ ferromagnetic powder,

Carbon black 10 parts by weight,

20 parts by weight of PVC and PU binder,

4 parts by weight of fatty acid ester lubricant,

1 part by weight of isopropyl triisostearolyl titanate dispersant,

5 parts by weight of a triylene diisocyanate curing agent,

0.5 parts by weight of dibutyl tin dilauryl cure accelerator,

Organic solvent: 130 parts by weight of cyclohexanone,

150 parts by weight of methyl ethyl ketone,

Toluene 150 parts by weight.

Table 1 shows the specific surface area, coercive force, Fe ²⁺ content, and the saturation magnetization value and the coercive force ratio of magnetic materials of Examples 1-5 and Comparative Examples 1-5.

At this time, the coercive force and the saturation magnetization value of the magnetic body were measured as follows. That is, the magnetic properties of the magnetic material and the magnetic recording medium can be evaluated using the VSM, a magnetic property measuring device. The measuring method is that when a magnetic field is added to an object having magnetic properties, it becomes magnetized. Induction power is generated according to Lentz's law. In this case, the induced voltage is proportional to the degree of magnetization, so when converted using the induced voltage, a hysteresis curve representing the intrinsic properties of the magnet can be drawn, and the coercivity and the saturation magnetization can be obtained using the curve.

Examples and Comparative Examples Specific surface area (m ² / g) Coercive force (Oe) Content of Fe ²⁺ (% by weight) Recording Efficiency Characteristics (emu / Oeg) Example 1 34 705 17.5 0.14 Example 2 26 720 12.2 0.11 Example 3 32 680 16.1 0.12 Example 4 34 780 17.4 0.13 Example 5 35 705 17.7 0.14 Comparative Example 1 25 780 11.0 0.10 Comparative Example 2 26 640 19.5 0.15 Comparative Example 3 26 630 10.5 0.10 Comparative Example 4 32 850 17.8 0.10 Comparative Example 5 23 650 12.0 0.12

How to evaluate tape properties

The electron conversion characteristics, hi-fi characteristics, changes over time, and light transmittance of the video tapes prepared by the methods of Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 2.

RF output

A reference video tape was mounted on a video deck (BR-7000) manufactured by Victor Japan, recorded a 100% white signal, and then measured for output during playback.The RF-output of the video tape obtained from the reference tape was set to 0 dB. As a difference, the RF outputs of the video tapes of the examples and the comparative examples were shown.

Audio hi-fi output

A reference video tape was mounted on a video deck (BR-7000) manufactured by Victor Japan, recorded a hi-fi signal, and then measured for output during playback. As a difference, the hi-fi output of the video tape of each Example and a comparative example was shown.

Changes in magnetic material over time

After 5 days at 60 ℃ 90% condition was evaluated based on the rate of reduction of the Fe ²⁺ content compared to the initial value.

A: 10% or less

B: 10% or more and 25% or less

C: 25% or more and 40% or less

D: more than 40%

Light transmittance

The optical transmittance of magnetic recording media of the same thickness was evaluated with the model VT-1M sold by Victor Japan.

RF output Hi-fi output Change over time Light transmittance Example 1 +1.5 +0.9 B 0.4 Example 2 +0.2 +1.5 A 0.8 Example 3 +0.5 +1.0 A 0.6 Example 4 +1.0 +0.8 B 0.4 Example 5 +1.0 +1.0 B 0.3 Comparative Example 1 +1.7 -1.0 A 1.3 Comparative Example 2 -0.5 -0.8 D 0.1 Comparative Example 3 -0.6 -0.8 A 1.4 Comparative Example 4 -1.0 -0.1 D 0.3 Comparative Example 5 +0.5 +0.2 B 1.1

As shown in the above table, it can be seen that the magnetic recording medium prepared according to the present invention has good electron conversion characteristics and excellent change over time, light transmittance, etc. of the magnetic material as compared with that produced by the method of Comparative Example.

Claims (3)

It contains a magnetic material having a specific surface area of 25 to 36 m ² / g, a coercive force of 600 to 800 Oe, and a ratio of saturation magnetization value (δs) and coercive force (Hc) (δs / Hc) of 0.11 to 0.14 emu / Oe · g. A magnetic recording medium, characterized in that the magnetic layer is formed on a nonmagnetic support. The recording medium according to claim 1, wherein the magnetic material is Co-containing γ-Fe ₂ O ₃ or Co-containing Fe ₃ O ₄ printing medium. The magnetic recording medium of claim 1, wherein the Fe ²⁺ content of the magnetic material is 11 to 18 wt% based on the total weight of the magnetic material.