KR100252028B1 - Magnetic record medium - Google Patents

Abstract

PURPOSE: A magnetic recording medium is provided to appropriately control surface roughness of a base film, so that a drop-out phenomenon can be improved. And the magnetic recording medium enables excellent electronic conversion characteristic, traffic ability and transitivity, though a back coating layer is not additionally formed on the base film. CONSTITUTION: A base film has the first, second and third polyester films. The first polyester film including a carbon black has a light cutoff characteristic. The second polyester film is deposited on one surface of the first polyester film. The third polyester film is deposited on another surface of the first polyester film. A magnetic layer is formed on an upper portion of the second polyester film. The surface roughness of the second polyester film is 0.002 to 0.015 micrometer. And the surface roughness of the third polyester film is 0.010 to 0.040 micrometer.

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 properties 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, to the magnetic 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 having excellent electron conversion characteristics, durability, runability and light transmittance characteristics.

In order to achieve the above object, in the present invention, the first polyester film containing carbon black, the second polyester film laminated on one surface of the first polyester film and the first polyester film A base film including a third polyester film laminated on the other surface; And a magnetic layer formed on the second polyester film of the base film, the magnetic recording medium comprising:

The surface roughness of the second polyester film is 0.002 to 0.015 µm,

A magnetic recording medium is provided, wherein the surface roughness of the third polyester film is 0.010 to 0.040 µm.

The base film of the present invention may further include one or more inner layers between the first polyester film and the second polyester film or between the first polyester film and the third polyester film. At this time, the inner layer is not particularly limited, and serves to improve the overall characteristics of the base film.

The base film of the present invention comprises a first polyester film having light blocking properties by adding carbon black, and having a second polyester film (hereinafter referred to as a flat surface) having different surface roughnesses on both surfaces of the intermediate layer. A third polyester film (hereinafter, referred to as a running surface) is provided. Here, the flat surface is in contact with the magnetic layer, and its surface roughness is preferably 0.002 to 0.015 µm. If the surface roughness of the flat surface is less than 0.02㎛, it is difficult to run on a guide roll that is in contact with the flat surface during the coating and calendering process, and the productivity is lowered. I can't. The running surface is in contact with the traveling system, and its surface roughness is preferably 0.010 to 0.040 µm. If the surface roughness of the running surface is less than 0.010 µm, the running performance is not satisfactory. If the surface roughness is more than 0.040 µm, the drop out phenomenon is caused, which is not preferable.

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 70 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.

As the abrasive, at least one selected from alumina, chromium oxide, iron oxide, and titanium dioxide is used as an inorganic particle having a Mohs hardness of 6 or more and an average particle diameter of 0.05 to 5 µm.

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.

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 made of Co ₃ containing Fe ₃ O ₄ (nitrogen adsorption specific surface area 30㎡ / g, powder Hc 700 Oe, Fe ⁺² content 18% by weight) 100g, vinyl chloride resin (MR110, Japan Zeion) 10g, alumina (AKP50 It was prepared by thoroughly mixing 7.0 g of Sumitomo, Japan, 5.0 g of iron oxide (Bayferrox, Bayer, Germany), 5.0 g of carbon black (MA100, Mitsubishi, Japan), 53.5 g of methyl ethyl ketone, and 61.8 g of cyclohexanone.

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 base film contains carbon black and is formed on one surface of the A layer and the A layer having light blocking properties, and is formed on the B layer having a surface roughness of 0.002 μm and the other surface of the A layer. A polyethylene terephthalate film having a C layer of 0.04 μm and having a total light transmittance of 30% was used.

The first composition, the second composition, and the third composition were sufficiently mixed and uniformly applied to the upper part of the B layer of the base film with a thickness of 2.0 μm, self-aligned at 500 gauss, and then hot air dried at 115 ° C. for at least 10 seconds. . Subsequently, calendering was performed under conditions of 110 ° C. and 300 kg / cm linear pressure, and cured at 60 ° C. for 24 hours, followed by slitting to 1/2 inch width to complete the magnetic tape.

<Example 2>

The surface roughness of the layer B constituting the base film was 0.005 μm, and the surface roughness of the layer C was 0.025 μm, except that the surface roughness was 0.025 μm.

<Example 3>

The surface roughness of the B layer constituting the base film was 0.010 μm, and the surface roughness of the C layer was 0.018 μm, except that the surface roughness was 0.018 μm.

<Example 4>

In the first composition, using a nitrogen adsorption specific surface area 45㎡ / g, powder Hc 8200 Oe, Fe ^{+ 2} content of Co ₃ Fe ₃ O ₄ as a magnetic material, 3g of carbon black and alumina, respectively , It was carried out according to the same method as in Example 1 except that the total light transmittance of the base film is 13%.

Example 5

The surface roughness of the layer B constituting the base film was 0.005 μm, and the surface roughness of the layer C was 0.025 μm, except that the surface roughness was 0.025 μm.

<Example 6>

The surface roughness of the layer B constituting the base film was 0.010 μm, and the surface roughness of the layer C was 0.018 μm, except that the surface roughness was 0.018 μm.

Comparative Example 1

The surface roughness of both the B layer and the C layer constituting the base film was carried out according to the same method as in Example 1, except that the total light transmittance was 86%.

Comparative Example 2

The surface roughness of both the B layer and the C layer constituting the base film was carried out according to the same method as in Example 1, except that the total light transmittance was 86%.

Comparative Example 3

Except that the surface roughness of both the B layer and the C layer constituting the base film was 0.020 µm and the overall light transmittance was 86%, the same procedure as in Example 1 was carried out.

<Comparative Example 4>

In the first composition, using a nitrogen adsorption specific surface area 45㎡ / g, powder Hc 8200 Oe, Fe ^{+ 2} content of Co ₃ Fe ₃ O ₄ as a magnetic material, 3g of carbon black and alumina, respectively The surface roughness of both the B layer and the C layer constituting the base film was 0.002 µm, and the overall light transmittance was 86%.

Comparative Example 5

In the first composition, a nitrogen adsorption specific surface area of 45 m 2 / g, powder Hc 8200 Oe, Fe ^{+ 2} containing Fe ₃ O ₄ containing 10% by weight of Fe, 3g of carbon black and alumina, respectively, The surface roughness of both the B layer and the C layer constituting the film was 0.012 μm, and the light transmittance was 86%.

Comparative Example 6

In the first composition, using a nitrogen adsorption specific surface area 45㎡ / g, powder Hc 8200 Oe, Fe ^{+ 2} content of Co ₃ Fe ₃ O ₄ as a magnetic material, 3g of carbon black and alumina, respectively The surface roughness of both the B layer and the C layer constituting the base film was 0.020 µm, and the overall light transmittance was 86%.

The properties of the magnetic tape prepared according to Example 1-6 and Comparative Example 1-6 were measured according to the following method.

1) Average surface roughness

Average surface roughness refers to the surface roughness of the center line and is measured using an optical non-contact three-dimensional surface roughness meter.

2) Electronic characteristic

The electronic characteristics are evaluated by comparing the RF output of 4.2MHz in VHS normal mode using JVC's VHC reference tape VRT-2.

(2) light transmittance

The light transmittance of the base film was measured in a transmission mode at a wavelength of 920 nm using a UV-VIS spectrometer, and the light transmittance of the magnetic tape was measured using a standard light transmittance of JVC.

(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 brought to a running speed of 3.3 cm / s, a pull-out force of 30 g, and a contact angle of 180 degrees at room temperature. By running for a time and observing the degree of change in the winding tension, the runability is evaluated as follows. 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: ○

The amount of change in winding tension is 3 ~ 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 characteristics of the magnetic recording tapes according to Example 1-6 and Comparative Example 1-6 were measured and shown in Table 1 below.

division RF-OUT (dB) Run durability Light transmittance Example 1 2.0 ◎ A 0.6 Example 2 1.7 ◎ A 0.6 Example 3 1.5 ○ ~ ◎ A 0.6 Example 4 3.2 ◎ B 1.1 Example 5 3.0 ◎ B 1.1 Example 6 2.7 ○ ~ ◎ B 1.1 Comparative Example 1 1.9 ×× F 1.7 Comparative Example 2 1.5 × D 1.7 Comparative Example 3 0.9 ○ C 1.7 Comparative Example 4 2.9 ×× F 7.3 Comparative Example 5 2.5 ×× F 7.3 Comparative Example 6 1.5 △-○ D 7.3

From Table 1, it can be seen that when the magnetic layer is densified, highly packed, and smoothed, the electron conversion characteristics of the magnetic tape are improved, but the running and durability characteristics are significantly reduced. And when forming the magnetic layer using the same composition, it was found that when the light transmittance of the base film is lowered, the light transmittance of the magnetic tape is lowered.

In the magnetic layer base film, the surface roughness of the surface (layer B) in contact with the magnetic layer is 0.002 µm, the surface roughness of the layer (layer C) in contact with the traveling system is 0.040 µm, and the overall light transmittance is about 30%. (Example 1-3) had excellent electron conversion characteristics, running properties, durability, and light transmittance characteristics, so that the reliability and stability as a whole tape were very excellent.

In addition, when the magnetic body in the magnetic layer was made finer, the blackness was lowered, and the contents of the carbon black and the alumina were reduced (Example 4-6) than in the case of Example 1-3, the B layer and the C layer of the base film. By appropriately controlling the surface roughness of and reducing the light transmittance of the base film itself, a magnetic recording medium having the same level of electron conversion characteristics, durability, runability and light transmittance characteristics as in the case of Example 1-3 can be obtained.

On the other hand, when the surface roughness of the B layer and the C layer of the base film is equally small and the light transmittance is high (Comparative Example 1-6), the electron conversion characteristics are excellent, but the driving itself is not possible, and the light transmittance characteristics are very low. .

According to the present invention, the dropout phenomenon can be improved by appropriately controlling the surface roughness of the base film, and a magnetic recording medium excellent in all of the electron conversion characteristics, running properties and durability can be obtained without separately forming a back coating layer on the base film. Can be.

Claims (3)

A first polyester film containing carbon black and having a light blocking property, a second polyester film laminated on one surface of the first polyester film, and a third poly laminated on the other surface of the first polyester film A base film including an ester film; And a magnetic layer formed on the second polyester film of the base film, the magnetic recording medium comprising: The surface roughness of the second polyester film is 0.002 to 0.015 µm, And the surface roughness of said third polyester film is from 0.010 to 0.040 占 퐉. The magnetic recording medium of claim 1, further comprising at least one inner layer between the first polyester film and the second polyester film. The magnetic recording medium of claim 1, further comprising at least one inner layer between the first polyester film and the third polyester film.