KR19990030650A - Video tape for magnetic head cleaning - Google Patents

Abstract

The present invention relates to a magnetic head cleaning tape having a coating layer for magnetic head cleaning formed on a base film. The coating layer comprises α-Fe magnetic body and 7-15% by weight of α-alumina based on the α-Fe magnetic body, and the α-Fe magnetic body has a specific surface area (BET) of 47-55m ² / g and a coercive force of 1500 The magnetic head cleaning tape of the present invention is characterized by -70000e, α-alumina having an average particle diameter of 0.3-0.5 탆, specific surface area of 5.5-12 m ² / g and Mohs hardness of 8.5-9.5. In addition, it has very good electronic properties and reduces the amount of wear on the head.

Description

Video tape for magnetic head cleaning

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape, and more particularly, to a video tape for magnetic head cleaning that can perform the function of recording and reproducing image information in the same way as a general video tape and can also remove contamination of the magnetic head.

When the magnetic tape is used for a long time, part of the coating layer is gradually dropped due to friction with the magnetic head, etc., and adheres to the surface of the head. So-called head contamination occurs which becomes impossible.

As described above, in order to remove the foreign matter attached to the head, a dry method of removing the contamination of the magnetic head by the polishing force of the cleaning tape is generally used.

Conventional dry cleaning tapes have a coating layer containing a large amount of non-magnetic, high hardness abrasives such as Al ₂ O ₃ , α-Fe ₂ O ₃ , Cr ₂ O ₃ , TiO _2, and the like. It is formed by apply | coating and drying a dispersion liquid containing to a predetermined thickness on a base film.

In other words, the dry cleaning tape is designed to remove foreign substances on the surface of the head by mechanical action caused by the pressure of the abrasive particles during friction with the magnetic head rotating at high speed. The amount, type, size, hardness, Conditions such as shape and surface roughness of the tape surface need to be optimized in such a state that the cleaning effect can be sufficiently exhibited.

In addition, such cleaning tapes are generally manufactured in a rough state with enhanced abrasiveness and surface roughness of the coating layer compared with general magnetic tapes in order to improve the cleaning effect. Therefore, the lifespan of the heads is reduced due to scratch damage and abrasion loss of the magnetic heads. It is accompanied by a problem.

Accordingly, an object of the present invention is to improve the cleaning performance by optimizing the conditions of the abrasive used in the cleaning tape in order to solve the above-mentioned problems, and at the same time, it is possible to greatly reduce the head damage generated during head decontamination. It is to provide a head cleaning tape.

In order to achieve the above object, in the present invention, in the magnetic head cleaning tape in which a coating layer for magnetic head cleaning is formed on a base film, the coating layer is based on the α-Fe magnetic material and the α-Fe magnetic material. 15 wt% of α-alumina, the α-Fe magnetic material has a specific surface area (BET) of 47-55 m ² / g, coercive force of 1500-1700Oe, and the α-alumina has an average particle diameter of 0.3-0.5 μm A magnetic head cleaning tape is provided which has a specific surface area of 7.5-12 m ² / g and a Mohs hardness of 8.5-9.5.

In the cleaning tape according to the present invention, the α-Fe magnetic body preferably has a specific surface area and coercive force within the ranges described above. In this case, the polishing force is required to record and reproduce the image program information with a slight improvement. This is because excellent magnetic properties can be obtained.

In the magnetic head cleaning tape of the present invention, the α-alumina is combined with the numerical values related to the average particle diameter, specific surface area and Mohs hardness in the above-mentioned range, and the ratio with the α-Fe magnetic body is also limited to the above range. This results in a tape having excellent magnetic characteristics as well as magnetic head cleaning effect.

In addition to the magnetic material and the abrasive, conventionally used additives such as binders, lubricants, antistatic agents and dispersants may be appropriately added to the coating layer of the magnetic head cleaning tape of the present invention as necessary.

Hereinafter, the manufacturing method of the cleaning tape of the present invention will be described in more detail.

First, a dispersion is prepared by dispersing an α-Fe magnetic body and an α-alumina as an abrasive, a polyurethane as a resin binder, a fatty acid such as myristic acid and stearic acid as a lubricant in a solvent such as methyl ethyl ketone, toluene and cyclohexanone. Polyisocyanate is again dispersed in this dispersion to form a final coating solution. This coating liquid is applied to a thickness of 1.5-2.3 mu m on a nonmagnetic base film such as polyethylene terephthalate having a thickness of about 7.5-9.0 mu m and a surface roughness of 6-8 nm. Immediately after application, the magnetic field is oriented in the longitudinal direction under a magnetic field and dried, followed by a calendering process at a linear pressure of 300 kg / cm to form a surface roughness in the range of 8-10 nm, and then through the slitting process to prepare a tape. Subsequently, a video and / or audio signal in the form of a color bar pattern is recorded on the tape to complete the magnetic head cleaning tape of the present invention.

The surface roughness of the coating layer may vary depending on the amount of abrasive and the calendering conditions, which will be described in detail with reference to RF-output characteristics and cleaning characteristics, which are video electron conversion characteristics.

When the average surface roughness of the coating layer is low, the RF-power is generally around -2 dB, which is a satisfactory range, but the removal of foreign matter from the head is not sufficient, resulting in a poor cleaning effect. Gradually increasing the amount of abrasive reduces the magnetic flux density of the tape and decreases the signal output, but improves the cleaning effect by increasing the abrasive fraction on the surface. However, when the abrasive, which is a nonmagnetic material, increases by more than a certain amount based on the magnetic material, the RF power is decreased and the surface roughness is increased due to the surface roughness of the abrasive.

On the other hand, in the case where the average surface roughness of the coating layer is adjusted to be rough, the cleaning effect is very excellent due to the abrasion effect such as coarse protrusions, and the effect is not highly dependent on the abrasive content. However, the rough surface causes a drastic reduction in RF output, making it unsuitable for recording and playing back video program information. In other words, increasing the content of the abrasive while maintaining a constant surface roughness gradually increases the cleaning effect and head wear, but gradually decreases the output, and if the surface roughness is changed while maintaining the constant abrasive content, the surface roughness may increase. The cleaning effect and head wear are improved, but the output is greatly reduced.

The magnetic head cleaning tape of the present invention is characterized in that the conditions and general conditions relating to the abrasive and the magnetic material are optimized in order to reproduce the video signal clearly and to improve the cleaning performance and to avoid excessive head wear. This optimization can only be done through a number of experiments, the present invention has achieved an outstanding effect that was not previously predicted.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples, and the scope of the present invention is not limited to Examples and Comparative Examples.

In Examples and Comparative Examples of the present invention, the performance evaluation of the cleaning tape was performed by the following method.

(1) head cleaning property

Sony's 8mm video recorder (EV-S35) was used as the video recorder. The cotton swab was moistened with a certain concentration (10%) of sugar water, rubbed on a common 8mm tape magnetic layer of the same lot according to the number of times and the sequence, and the head was contaminated with this tape. In this contaminated head, the color bar was recorded on the head cleaning tapes prepared in Examples and Comparative Examples, followed by measuring the decontamination time required for the color bar to be reproduced cleanly. (Circle) and the case of 40-70 second (circle) and the case of 40-70 second (triangle | delta) and the case of 1 minute 30 second or more were shown by (circle) for the case where contamination is removed completely within 15 second.

(2) Head wear

Wind the cleaning tape in 2 hours (106m), and repeat the playback for 100 hours, and use the optical microscope and gauge to measure the difference in head height (head height is defined as the distance from the rotating drum to the protruding surface) using the optical microscope and gauge. Measured. The degree of head wear seen in the conventional dry cleaning tape is indicated by × (20 μm or more) and relatively expressed by Δ (12-20 μm), ○ (6-12 μm) and ◎ (within 5 μm). .

(3) RF output

As the electronic conversion characteristic, RF-output is shown by comparing the RF-output of 5.4MHz relative to Sony's tape (RSE5001).

(4) Center line average surface roughness (RA)

Measurements were made using an optical non-contact three-dimensional surface roughness meter (set the cut-off value to 0.08) from WYKD.

<Example 1>

α-Fe magnetic material (BET: 53m ² / g, coercive force: 1600Oe): 100g

α-alumina (average particle size: 0.4 μm, BET: 8 m ² / g, Mohs hardness: 9): 12 g

Polyurethane: 8.3g

Polyvinyl chloride: 8.3 g

Myristic acid: 1 g

Stearic acid: 1 g

Butyl Stearate: 1g

Polyisocyanate: 7 g

Carbon Black: 1.5g

Toluene: 100 g

Methyl ethyl ketone: 100 g

Cyclohexanone: 100 g

The coating liquid comprising the above components was applied on a nonmagnetic base film (polyethylene terephthalate) by a conventional method, dried and subjected to a calendering process at a linear pressure of 300 kg / cm to prepare a cleaning tape, and then a color bar image signal. Recorded. The performance was evaluated according to the method described above for this tape and the results are shown in Table 1 below.

<Example 2>

Except that the use amount of α-alumina was 7g was carried out in the same manner as in Example 1, the performance of the obtained tape was evaluated and the results are shown in Table 1 below.

<Example 3>

Except that the amount of α-alumina was used 10g was carried out in the same manner as in Example 1, the performance of the obtained tape was evaluated and the results are shown in Table 1 below.

<Example 4>

Except that the amount of α-alumina used to 15g was carried out in the same manner as in Example 1, the performance of the obtained tape was evaluated and the results are shown in Table 1 below.

<Example 5>

α-alumina was carried out in the same manner as in Example 1 except that the average particle diameter was 0.5㎛, BET 6m ² / g was used, and the performance of the obtained tape was evaluated by the following Table 1 Shown in

<Comparative Example 1>

Except that the amount of α-alumina was used as 4g was carried out in the same manner as in Example 1, the performance of the obtained tape was evaluated and the results are shown in Table 1 below.

<Comparative Example 2>

Except that did not use a-alumina was carried out in the same manner as in Example 1, the performance of the obtained tape was evaluated and the results are shown in Table 1 below.

<Comparative Example 3>

Except that the use amount of α-alumina was 30g was carried out in the same manner as in Example 1, the performance of the obtained tape was evaluated and the results are shown in Table 1 below.

<Comparative Example 4>

α-alumina was carried out in the same manner as in Example 1 except that the average particle diameter was 0.2㎛, and a spherical one was used. The performance of the obtained tape was evaluated and the results are shown in Table 1 below.

<Comparative Example 5>

α-alumina was carried out in the same manner as in Example 1 except that the average particle diameter of 0.16㎛, BET 15m ² / g was used, the performance of the obtained tape was evaluated in Table 1 Shown in

<Comparative Example 6>

α-alumina was carried out in the same manner as in Example 1 except that the average particle diameter of 0.12㎛, BET 19m ² / g was used, the performance of the obtained tape was evaluated in Table 1 Shown in

division Ra (nm) RF output (dB) Cleaning performance Head wearability Example 1 10.0 -1.8 O ~ ◎ △-○ Example 2 8.7 -0.7 ○ ◎ Example 3 9.3 -1.3 ○ ○ Example 4 11.2 -2.5 ◎ △ Example 5 10.5 -2.0 ◎ △ Comparative Example 1 8.2 -0.5 × ◎ Comparative Example 2 7.6 0.0 × ◎ Comparative Example 3 16.0 -4.5 ◎ × Comparative Example 4 8.8 -1.5 × to △ ○ Comparative Example 5 8.6 -1.5 × to △ ○ Comparative Example 6 7.7 -1.3 × ◎

From the above results, the following points can be seen.

The magnetic head cleaning tape prepared according to Example 1 had a surface roughness of 10.0 nm, a coercive force in the longitudinal direction of 1500Oe or more, and completely removed contaminants accumulated in the head within 30 seconds. Also in Example 2 obtained by slightly reducing the amount of abrasive, it was excellent in terms of head wear and electronic properties, and also good cleaning performance. In the case of Example 4, which slightly increased the amount of abrasive, the cleaning property was excellent, but the head wear property and the electronic property were slightly decreased. However, this value was also satisfactory with the 8 mm head cleaning tape. The cleaning tape obtained according to Example 5, in which the average particle diameter of the abrasive used was slightly smaller and the specific surface area was slightly reduced, also showed satisfactory levels in all respects.

On the other hand, in the case of Comparative Examples 1 to 3 in which the abrasive is not used at all or in a small amount or excessive amount, the cleaning property is improved as the amount of the abrasive is increased, but the head wear is severe and the electronic characteristics are not good. It was not suitable as a tape with regeneration and cleaning. In addition, even in Comparative Example 4 in which the average particle diameter of the abrasive particles was reduced, the cleaning property was not good, and in Comparative Examples 5 and 6 in which the average particle diameter was reduced and the specific surface area was increased, the cleaning property was very poor.

As can be seen from the above, the magnetic head cleaning tape according to the present invention has a magnetic recording / reproducing function as well as a cleaning function for removing contamination of the magnetic head, and its performance is very excellent.

Claims (1)

A magnetic head cleaning tape having a coating layer for magnetic head cleaning formed on a base film, wherein the coating layer contains α-Fe magnetic material and 7-15% by weight of α-alumina based on the α-Fe magnetic body. The α-Fe magnetic body has a specific surface area (BET) of 47-55 m ² / g and a coercive force of 1500-1700Oe, and the α-alumina has an average particle diameter of 0.3-0.5 μm and a specific surface area of 5.5-12 m ² / g and a Mohs hardness of 8.5-9.5.