KR100252027B1 - Magnetic record medium - Google Patents

Abstract

PURPOSE: A magnetic recording medium is provided to thinly form a magnetic layer, and to reduce contents of a conductive substance like a carbon black and an abrasive. And the magnetic recording medium enables excellent electronic conversion characteristic, traffic ability and transitivity. CONSTITUTION: A base film is included. A magnetic layer formed in one surface of the base film includes a magnetic substance, a binder and an abrasive. An essential component of the abrasive is a non-magnetic black ferric oxide. In the non-magnetic black ferric oxide, an average particle diameter is 0.1 to 1.0 micrometer, a nitrogen absorption specific surface is 1 to 30 m.sup.2/g, the contents of Fe.sup.+2 is 1 to 25%.

Description

Magnetic recording 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 having excellent electron conversion characteristics, running characteristics, durability, and light transmittance characteristics.

Magnetic recording media such as magnetic tapes and magnetic disks are widely used in audio, video and computer fields. Such a magnetic recording medium uses a coating type magnetic recording medium which disperses a magnetic material, a resin, a curing agent, a solvent, a dispersant, and other additives to form a coating, and then applies and dries the nonmagnetic substrate to form a magnetic coating film.

With the advancement of science and technology, information and communication media are becoming smaller, and recording density is required for magnetic recording media. In addition, since the magnetic recording medium is used in contact with the magnetic head, surface smoothness is required to improve not only the magnetic characteristics but also the running performance, and durability is required for repetitive recording and reproducing. In response to these demands, a method of adding carbon black, an abrasive having an Mohs hardness of 8 or more, etc. to the layer has been proposed.

By the way, according to the above method, the running characteristics and the durability can be improved by forming the charging characteristics and the protrusions on the surface of the magnetic layer, but there is a problem in that head wear and drop out are caused and the electron conversion characteristics are degraded.

Meanwhile, V in the video. H. In the case of employing a VHS system, a method of detecting the start and end of a cassette tape by light transmission of the tape is used. At the beginning and the end of the tape, a leader tape having no magnetic layer applied thereto is connected so that light passes through when the leader tape passes. In VHS systems, video tapes are automatically grounded in response to signals output by these light-sensitive sensors. Therefore, the video tape must maintain the light transmittance below a predetermined range. This is because if the light transmittance is too large, the sensor may stop working due to the leader tape. This malfunction can occur if the tape is defective. For example, when a part of the magnetic layer is peeled off or the thickness of the magnetic layer is thin, a light over a predetermined range passes through the tape, and a malfunction may occur in which the sensor detects the light and stops the video deck in operation.

In order to solve the problem that the sensor detects light, a method of using a black magnetic material such as chromium dioxide or magnetite when forming a magnetic layer of a video tape, a method of using a colorant such as carbon black mixed with a magnetic material, or a thickness of the magnetic layer 2 A method of adjusting to -4 탆 is proposed.

According to the method, since the black magnetic material is expensive and the addition of carbon black having a low specific gravity, the filling rate of the magnetic material should be lowered and the thickness of the magnetic layer should be thick, which is not preferable in terms of cost reduction. In addition, there is a problem that it is difficult to increase the density and the capacity of the recording.

The technical problem to be achieved by the present invention is to solve the above problems to provide a magnetic recording medium excellent in electron conversion characteristics, running properties, durability and light transmittance characteristics.

In the present invention, to achieve the above technical problem, the base film; And a magnetic layer formed on one surface of the base film, the magnetic layer comprising a magnetic material, a binder, and an abrasive, wherein the essential component of the abrasive is an average particle diameter of 0.1 to 1.0 탆 and a nitrogen adsorption specific surface area. Provided is a magnetic recording medium having a nonmagnetic black iron oxide (? -Fe ₂ O ₃ ) having a content of 1 to 30 m ² / g and a Fe ⁺² content of 1 to 25% by weight.

The other side of the base film is further provided with a back coating layer (back coating layer) containing a conductive powder, a binder and an abrasive. At this time, the essential constituents of the abrasive are non-magnetic black iron oxide (α-Fe ₂ O ₃ ) having an average particle diameter of 0.1 to 1.0 µm, a nitrogen adsorption specific surface area of 1 to 30 m ² / g, and a Fe ⁺² content of 1 to 25% by weight. Is preferably.

The present invention has a feature of using a black iron oxide that can simultaneously perform the role of light shielding and polishing when forming a magnetic layer. The black iron oxide is manufactured by the following process as a nonmagnetic material.

Needle-shaped magnetic α-iron oxide (Fe ₂ O ₃ ) is reduced to coat Fe ^{+ 2} on its surface. Subsequently, a spherical black iron oxide may be obtained by coating a nonmagnetic material such as manganese or cobalt on the resultant surface.

The magnetic layer of this invention consists of a composition containing a magnetic body, a binder, and an abrasive. As the magnetic material, a magnetic material having a particle diameter of 0.005 to 1 μm, an axial ratio of 1 to 50, and a specific surface area of 1 to 30 m 2 / g is used. Specific examples thereof include γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co containing (deposition, modified, dope) γ-Fe ₂ O ₃ , Co containing (deposition, modified, dope) Fe ₃ O ₄ , FeO _x , Co containing (deposition, modified, dope) FeO _x , CrO ₂ and the like.

The binder has an average molecular weight of 1 × 10⁴3 × 10⁵, Thermoplastic resins, thermosetting resins, reactive resins or mixtures thereof having a degree of polymerization of about 250 to 2000 are used.

The abrasive has an average particle diameter of 0.1 to 1.0 µm, an essential component, a nitrogen adsorption specific surface area of 1 to 30 m ² / g, and black iron oxide having a Fe ⁺² content of 1 to 25% by weight, a Mohs hardness of 6 or more, and an average particle diameter. It consists of at least one selected from alumina and titanium dioxide which are 0.05-5 micrometers. The content of black iron oxide is preferably 0.1 to 100% by weight based on the total weight of the abrasive.

The magnetic layer includes a solvent and an additive for forming a conventional magnetic layer, in addition to the above-described magnetic body, binder, and abrasive. Such additives include antistatic agents, surfactants, dispersants, curing agents, lubricants and the like, the content of which is at a conventional level.

Conductive powder is used as the antistatic agent, and specific examples thereof include carbon black. Preferably, the carbon black has an average particle diameter of 5 to 1000 nm and a nitrogen adsorption specific surface area of 1 to 1500 m 2 / g.

As the surfactant, fatty acids, alcohols, esters, alkali metals, and the like are used. As lubricants, inorganic powders, resin powders, fatty acids having 10 to 20 carbon atoms, alcohols having 3 to 12 carbon atoms, fatty acid esters, and the like are used. use. Ketones, alcohols, esters, aromatic hydrocarbons, chlorinated hydrocarbons and the like are used as solvents, and polyisocyanates having a molecular weight of 100 to 20000 are used as the curing agent.

The back coating layer of the present invention is formed on the other side of the base film, and consists of a composition comprising a conductive powder, a binder and an abrasive.

As described above, the abrasive has an average particle diameter of 0.1 to 1.0 µm as an essential component, a nitrogen adsorption specific surface area of 1 to 30 m ² / g, a black iron oxide having a Fe ⁺² content of 1 to 25% by weight, and a Mohs hardness of 6 or more. And at least one selected from alumina and titanium dioxide having an average particle diameter of 0.05 to 5 µm. The content of black iron oxide is the same as that of the magnetic layer.

Hereinafter, a method of manufacturing a magnetic recording medium according to the present invention will be described.

A magnetic material, a binder, an abrasive, a solvent, and other additives are sufficiently mixed to prepare a composition for forming a magnetic layer.

The composition is applied on the flat surface of the base film, then self-aligned and dried. After the drying is completed, the magnetic recording medium is completed by sequentially performing the calendering, curing and slitting processes.

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

<Example 1>

The first composition was 100 g of Fe-containing Fe ₃ O ₄ (nitrogen adsorption specific surface area 30 m 2 / g, powder Hc 700 Oe, Fe ⁺² content 18 wt%), 10 g of vinyl chloride resin (MR110. Japan Zeon), alumina (AKP50) , Japan Sumitomo Co., Ltd. 7.0g, Iron Oxide (Bayferrox, Germany Bayer Co., Ltd.) 5.0g, Carbon Black (MA100, Mitsubishi Co., Ltd.) 5.0g, Black Iron Oxide (particle diameter 0.2㎛, Nitrogen adsorption specific surface area 15㎡ / g, α-Fe ₂ O ₃ , Fe ⁺² content 15% by weight) 10.0g, methyl ethyl ketone 53.5g and 61.8g cyclohexanone was sufficiently mixed to prepare.

The second composition was prepared by thoroughly mixing 6.7 g of polyurethane resin (KU2010, Dongyang Spinning Co., Ltd.), 2.0 g of myristic acid, 1.0 g of butyl stearate, 37.8 g of cyclohexanone, 29.5 g of methyl ethyl ketone, and 29.5 g of toluene. .

The third composition was prepared by mixing 3.0 g of polyisocyanate (D103H, Takeda Japan), 1.67 g of methyl ethyl ketone, and 1.67 g of toluene.

The fourth composition is prepared by mixing 100.0 g of carbon black, 50.0 g of black iron oxide, 62.5 g of nitrocellulose resin, 62.5 g of polyurethane resin, 25.0 g of polyisocyanate, 567.0 g of methyl ethyl ketone, 567.0 g of toluene and 567.0 g of cyclohexanone. It was.

The first composition, the second composition, and the third composition were sufficiently mixed and uniformly applied to the flat surface of the base film with a thickness of 2.0 μm.

The resultant was self-oriented at 5000 gauss and then hot air dried at 115 ° C. for at least 10 seconds. Then, calendaring was performed on conditions of 110 degreeC and 300 kg / cm of linear pressures.

The fourth composition was uniformly applied to the other side of the base film to a thickness of 0.8㎛, and then cured at 60 ℃ for 24 hours to form a back coating layer.

The resultant was slit to 1/2 inch width to complete the magnetic tape.

<Example 2>

The same process as in Example 1 was conducted except that the back coating layer was not formed on the base film.

<Example 3>

The same procedure was followed as in Example 1, except that 2g and 3g of carbon black and alumina were used in the first composition, and that black iron oxide was not used in the fourth composition.

<Example 4>

The same process as in Example 3 was conducted except that the back coating layer was not formed on the base film.

Comparative Example 1

The same procedure as in Example 1 was conducted except that black iron oxide was not used in the first composition.

Comparative Example 2

The same procedure as in Example 1 was carried out except that black iron oxide was not used in the first composition and no back coating layer was formed on the base film.

Comparative Example 3

The same procedure was followed as in Example 1, except that 2g and 3g of carbon black and alumina were used in the first composition, that black iron oxide was not used, and that black iron oxide was not used in the fourth composition. .

<Comparative Example 4>

The composition was carried out in the same manner as in Example 1, except that carbon black and alumina were used in 2g and 3g, black iron oxide was not used, and no back coating layer was formed on the base film. .

The characteristics of the magnetic recording media prepared according to Example 1-4 and Comparative Example 1-4 were evaluated according to the following methods.

(1) electronic characteristics

JVC's VHS reference tape, VRT-2, is used to evaluate the relative RF output of 4.2MHz in VHS normal mode.

(2) light transmittance

Evaluate using JVC's standard light transmission device.

(3) Runability and durability

Environmental treatment is carried out for 72 hours using a tape running tester (TBT-3000) manufactured by Yokohama Systems, Japan under conditions of a temperature of 60 ° C and a relative humidity of 80%. Subsequently, the tape was subjected to a running speed of 3.3 cm / s, a pulling force of 30 g, and a contact angle of 180 degrees at room temperature. The burnishing tape coated with alumina particles uniformly was wound on a head drum for VHS having a diameter of 62 Φ, and then rotated back at 40 rpm. The driving performance was evaluated by observing the degree of change in winding tension by traveling for a time. The durability of the burnishing tape is evaluated after grasping.

Almost no change in winding tension: ◎

The change in winding tension is within 3% of the total size: ○

Variation in winding tension of 3 to 10% of the total size: △

The amount of change in winding tension is more than 10% of the total size: ×

Not traveling: ××

No contamination of burnishing tate: A

There is some contamination: B

Contaminated: C

High pollution: D

Very heavy pollution: F

The electronic properties, light transmittance, runability and durability of the magnetic tapes prepared according to Examples 1-4 and Comparative Examples 1-4 were measured and shown in Table 1 below.

division RF-OUT (dB) Light transmittance (%) Run durability Example 1 1.5 0.1 ◎ A Example 2 1.4 0.6 ◎ A Example 3 1.8 0.25 ◎ A Example 4 1.7 0.9 ◎ B Comparative Example 1 1.7 0.2 ○ B Comparative Example 2 1.5 0.9 △-○ C Comparative Example 3 1.9 0.3 ○ C Comparative Example 4 1.8 1.4 △ D

From Table 1, when the blackness of the magnetic layer is improved by using black iron oxide as an abrasive (Example 1-4), only magnetic material (Co-containing Fe ₃ O ₄ ) is used under the same conditions (Comparative Example 1-4). Compared with the above, light transmittance, runability and durability were improved. In addition, when using black iron oxide as an abrasive and using 2 g of antistatic carbon black (Examples 3 and 4), the effect of suppressing light transmittance is slightly lower than when using 5 g of carbon black (Examples 1 and 2). However, the electronic properties were found to be more improved.

In addition, in the case of having a back coating layer, when carbon black and black iron oxide are mixed and used together (Example 1), runability, durability and light transmittance are compared with those using only carbon black alone (Comparative Example 3). It was found that the properties were the same level and the electronic properties were slightly degraded.

In summary, in the case where black iron oxide is added to the magnetic layer, only carbon black may be used in an amount sufficient to obtain an antistatic effect, thereby improving the electron conversion characteristics of the magnetic recording medium. In addition, when black iron oxide is added to the back coating layer, the viscosity characteristic of the composition for forming the back coating layer is improved, thereby improving productivity as well as improving runability and durability.

According to the present invention, it is possible to obtain a magnetic recording medium having excellent electron conversion characteristics, running properties and durability. In particular, in the case of further comprising a back coating layer in addition to the magnetic layer, a magnetic recording medium having improved characteristics can be obtained.

The magnetic recording medium of the present invention can form the thickness of the magnetic layer as thin as possible, can reduce the content of the conductive material, such as carbon black, abrasives, etc. can not only reduce the cost but also can be increased in capacity.

Claims (6)

Base film; And a magnetic layer formed on one surface of the base film, the magnetic layer including a magnetic material, a binder, and an abrasive, the magnetic recording medium comprising: An essential component of the abrasive is a magnetic recording medium having a nonmagnetic black iron oxide having an average particle diameter of 0.1 to 1.0 µm, a nitrogen adsorption specific surface area of 1 to 30 m ² / g, and a Fe ⁺² content of 1 to 25% by weight. The magnetic recording medium of claim 1, wherein the iron oxide is α-Fe ₂ O ₃ . 2. The magnetic recording medium of claim 1, further comprising a back coating layer comprising a conductive powder, a binder, and an abrasive on the other side of the base film. The essential component of the abrasive is nonmagnetic black iron oxide having an average particle diameter of 0.1 to 1.0 µm, a nitrogen adsorption specific surface area of 1 to 30 m ² / g, and a Fe ⁺² content of 1 to 25% by weight. Magnetic recording medium. The magnetic recording medium of claim 4, wherein the iron oxide is α-Fe ₂ O ₃ . The magnetic recording medium according to claim 1 or 4, wherein the content of the iron oxide is 0.1 to 100% by weight based on the total weight of the abrasive.