KR19990002981A - Floppy disks for magnetic head cleaning - Google Patents

Abstract

The magnetic head cleaning disk according to the present invention, which is produced by coating a composition including a ferromagnetic substance and an abrasive on both sides of a base film, functions not only as a cleaning disk for removing contamination of a magnetic head but also as a magnetic recording / And is suitable as a cleaning disk used in a dry cleaning method.

Description

Floppy disks for magnetic head cleaning

The present invention relates to a floppy disk, and more particularly, to a floppy disk drive (hereinafter referred to as an FDD) for magnetic head cleaning capable of performing a magnetic recording and reproducing function in the same manner as a floppy disk, Lt; / RTI >

A floppy disk inserted and used in the FDD is a medium to which magnetic recording technology is applied, and has a magnetic film including a ferromagnetic powder and a resin binder on a non-magnetic base film such as polyethylene terephthalate (hereinafter referred to as PET).

On the magnetic film, a track having a constant area for forming a concentric circle is formed, and the magnetic head in the FDD rotates at high speed to record and reproduce information. In this process, friction due to contact between the magnetic head and the floppy disk in the FDD is inevitable, and wear of the disk surface is generally caused.

Therefore, in order to sufficiently perform the function of the floppy disk as a magnetic recording / reproducing medium, there is a need to compensate for a defect that the surface of the floppy disk is worn by contact with the magnetic head rotating at high speed.

According to the prior art, there has been known a method for alleviating or reducing abrasion of a surface of a floppy disk contacting a magnetic head by adding a lubricant such as carbon, a non-magnetic fine particle such as a high-strength abrasive, and a fatty acid ester to the coating layer on the base film .

However, even in the case of a floppy disk manufactured using the above additive, when the magnetic disk is used for a long time, part of the coat layer gradually drops off due to contact with the magnetic head having a relatively high strength or friction, The phenomenon can not be avoided, and the output loss and error of the magnetic head are caused by the foreign substances adhered in this way, resulting in a serious phenomenon in which recording and reproduction become impossible. Therefore, it is necessary to periodically clean the magnetic head in order to remove foreign matter adhering to the magnetic head.

There are two types of magnetic head cleaning methods: a wet type in which a fibrous porous sheet containing a cleaning solution such as alcohol is used to remove contamination of a magnetic head by a dissolving power such as alcohol, and a wet type which removes head contamination by a polishing force on a cleaning disk .

Generally, since a magnetic film is formed on both sides of a base film in order to increase storage capacity of a floppy disk, a double-sided head is used corresponding to a magnetic head used in an FDD. Further, since the magnetic head is structured so as to be finely embedded in the head supporting device in the FDD, a separate cleaning floppy disk is required for dry cleaning.

According to the prior art, there is disclosed a dry cleaning floppy disk in which a mixture of an abrasive, a lubricant and a resin binder having a Mohs hardness of 4 or more is coated on a base film of a floppy disk together with a ferromagnetic material (Japanese Patent Application Laid-Open No. 61-227216) . Here, a mixed composition obtained by adding a lubricant, a vinyl chloride resin, a urethane resin, or the like to a high strength nonmagnetic abrasive such as Cr ₂ O ₃ as a main material is used as a coating layer, and the center line surface roughness of the floppy disk is set to 190 to 390 nm. However, the above-mentioned conventional floppy disk has a problem that the abrasive coating layer has excessive abrasive force, which may cause abrasion and damage of the magnetic head.

Another example of the prior art is a cleaning disc having a center line surface roughness of 4 to 15 nm, which is produced by using barium ferrite having a particle diameter of 0.5 탆 as a magnetic material and adding 3% by weight of alumina as an abrasive on the basis of the weight of magnetic material 5-334634) and a magnetic material is coated on both surfaces of the base film so that one surface of the coating composition is calendered to be used as a recording and reproducing surface and the other surface is coated so as to be used as a cleaning surface And a cleaning disk manufactured by calendering (Japanese Patent Publication No. 63-279414). However, in the case of the above-mentioned cleaning disks, the weight fraction of the abrasive contained therein or the surface roughness of the disk is too low, so that a sufficient cleaning effect can not be obtained as a dry cleaning disk.

As can be seen from the above, the conventional cleaning disk merely performs a function of simply removing the contamination of the magnetic head, and even if it has a magnetic recording and reproducing function, the cleaning function is not sufficient.

In order to record and reproduce data using a cleaning disk, the FDD must be capable of formatting. For this purpose, the cleaning disk must be able to maintain at least 45% of its output with respect to the input current from the magnetic head, and all characteristics must meet the requirements as a magnetic recording and reproducing floppy disk.

Disclosure of Invention Technical Problem [8] The present invention provides a magnetic head cleaning floppy disk capable of performing data recording and reproducing functions and effectively removing foreign matter adhered to a magnetic head.

In order to achieve the above object, the present invention provides a magnetic head cleaning floppy disk having a coating layer formed on both surfaces of a base film, wherein the coating layer comprises a ferromagnetic body made of Co-γ-Fe ₂ O ₃ , To 250% by weight of an abrasive, and the surface roughness of the disk is 15 to 25 nm.

In the magnetic head cleaning disk according to the present invention, the base film may be at least one selected from the group consisting of polyesters including polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate, polyethylene, polypropylene and polyisoprene, Cellulose derivatives including polyolefins, cellulose triacetate and cellulose diacetate, and vinyl resins such as polyvinylidene chloride, among which polyethylene terephthalate (hereinafter referred to as PET) is particularly preferable.

In the cleaning disk according to the present invention, the Co-γ-Fe ₂ O ₃ magnetic material preferably has a needle-like structure with a Mohs hardness of 5 or more, a coercive force of 700 to 750 Oe and a specific surface area of 15 to 20 m ² / g This is because the magnetic properties and the abrasive force can be sufficiently exhibited at this time.

In the cleaning disk according to the present invention, α-Al ₂ O ₃ alumina, Al ₂ O ₃ and α-Fe ₂ O ₃ can be used as the abrasive, and in particular, Mohs hardness is 9 or more, 15 to 20 m ² / g, and a high purity Al ₂ O ₃ having an average particle size of 0.45 μm is preferable.

Lubricants, dispersants, resin binders, hardeners, and the like may be added as needed in addition to the magnetic material and the abrasive.

In the cleaning disk according to the present invention, the lubricant, the dispersant, the resin binder and the curing agent to be added are not particularly limited as long as they are conventional ones used in the art. Among them, a vinyl chloride-acrylic copolymer is particularly preferred as the resin binder, a polyisocyanate .

It is known that the surface characteristics of the disk, particularly the surface roughness, vary depending on the addition ratio of the ferromagnetic material and the abrasive, and this surface roughness has an important influence on the output characteristics and the cleaning performance of the floppy disk. On the other hand, the surface roughness also varies depending on the calendering process conditions such as temperature, line pressure and process speed as well as the content of the abrasive.

In general, if the amount of abrasive is gradually increased while maintaining the surface roughness constant, the magnetic flux density of the coating layer becomes small, the regeneration property is deteriorated, and the damage rate of the head is increased, but the cleaning effect is increased. On the other hand, if the surface roughness is gradually increased while maintaining the abrasive content constant, the reproduction output becomes unstable and errors occur frequently, but the cleaning effect is greatly increased. Therefore, it is possible to improve the cleaning performance of the magnetic head cleaning floppy disk by adjusting the amount of the supplied abrasive and the surface roughness, and to maintain the minimum output power of 45% or more so that a certain amount of data can be recorded and reproduced. In view of such a principle, the present inventors have gone through many experiments and studies to find out the appropriate amount of abrasive powder and the optimum surface roughness of the disc, and have come to the present invention.

In the present invention, a 100 to 250 weight% of the abrasive is added based on the weight of the ferromagnetic material, and in this case, the surface roughness of the floppy disk is 15 to 25 nm.

The method for manufacturing the magnetic head cleaning disk according to the present invention is not particularly limited as long as it is a conventional method known in the art.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the scope of the present invention is not limited to the examples and the comparative examples.

In the Examples and Comparative Examples of the present invention, the performance of the floppy disk was evaluated as follows.

(1) Center line average roughness (RA)

And measured using a WYKD optical non-contact type three-dimensional surface roughness meter.

(2) Average track regeneration voltage (TAA) and other characteristics

The input current of the magnetic head was measured at the outermost track 00 track (1F (250KHZ)), and the innermost track was measured using the ML-5000 (FDD for Sony SOF73W 3.5 2HD manufactured by Media Logic Corporation, USA) The value was expressed as a percentage value based on the PTB reference value built in the evaluator after recording and reproducing at a frequency of 2F (500KHZ) on track 79 track.

(3) Cleaning performance

Cleaning performance was performed in FDD with contaminated magnetic head.

A Samsung 3.5 2HD SFD321D / T type FDD that has been modified to allow continuous driving by power supply. A contaminated disk is inserted into the FDD for more than 3 million times, and the data is not normally reproduced after connection to the PC is regarded as a contaminated magnetic head do. At this time, the FDD was measured by using an FDD Exercise (SK-472, manufactured by Tokyo Engineering Co., Ltd.) and an oscilloscope (VP = 5739A, National) to measure the amplitude envelope of the contaminated magnetic head To 80%. ≪ / RTI >

A floppy disk manufactured as described in the following embodiment was inserted into the FDD with the contaminated magnetic head incorporated therein and the format command was repeatedly performed to compare the number of commands until the disk was normally formatted without a bad sector. In FDD, the format confirmation time is expressed as about 25 seconds for one time, G for 1 to 5 times, M for 6 to 10 times, and B for 10 or more times. It is the abbreviation of Good, Middle, Bad respectively.

For cleaned heads, the amplitude envelope measured using FDD Exacys and an oscilloscope was recovered to more than 80% based on measurements before head contamination.

(4) Head damage degree

A scratch damage degree of the head was observed by an optical microscope after passing the cleaning disk to the above FDD for 1 million times, and when it was good, it was indicated as G and when it was defective, it was indicated as B.

Example 1

Co-γ-Fe ₂ O ₃ : 100 g

(Longer axis average particle diameter 0.35㎛, a specific surface area 17㎡ / g, coercive force of 730 Oe, Mohs hardness _{5.5) Al 2 O 3: 250} g

(Average particle diameter 0.45 mu m, specific surface area 15-20 m < 2 > / g, Mohs hardness 9)

Vinyl chloride: 25.2 g

Polyurethane: 30.8 g

Isocyanate: 14 g

High fatty acid ester: 17.5 g

Methyl ethyl ketone: 186.2 g

Toluene: 93.1 g

Cyclohexanone: 186.2 g

A coating composition prepared by mixing and dispersing the above compounds in the composition ratio was coated on both sides of a PET base film having a thickness of 75 탆 and a surface roughness of 15 nm to a thickness of 1.0 탆 and dried. Then, after calendering under the conditions of a temperature of 70 ° C and a linear pressure of 150 kg / cm ² , a 3.5 2HD (formatted capacity 1.44 MB) floppy disk was produced by cutting and assembling to an outer diameter of 86 mm.

Example 2

A floppy disk was prepared in the same manner as in Example 1, except that the amount of Al ₂ O ₃ added was changed to 100 g.

Example 3

A floppy disk was produced in the same manner as in Example 1, except that the temperature was changed to 90 占 폚 and the linear pressure to 150 kg / cm2 in the calendering step.

Comparative Example 1

A floppy disk was prepared in the same manner as in Example 1, except that Al ₂ O ₃ was not added.

Comparative Example 2

A floppy disk was produced in the same manner as in Example 1, except that the amount of Al ₂ O ₃ added was changed to 350 g.

In order to evaluate the surface characteristics, electronic conversion characteristics, cleaning effect and head damage degree of the floppy disk manufactured in each of the above embodiments, the center line average roughness Ra, the track average reproduction voltage TAA, The results are shown in Table 1, and for the floppy disk according to Example 1, other characteristics required for a floppy disk as a magnetic recording medium were measured and shown in Table 2.

division Ra [nm] TAA (79 tracks) [%, ref] Cleaning performance Head damage Example 1 23 46-49 G G Example 2 19 50-53 G G Example 3 17 47-50 M-G G Comparative Example 1 14 95-105 B G Comparative Example 2 26 34-37 G G

Item track Measure Output [%, Ref] 0 52-53 79 46-49 Resolution 79 95.9 Redundancy characteristics 79 87.7 ANSI modulation 0 2.6-4.7 Peak shift 79 92.0

As shown in Table 1, in the case of Examples 1 and 2 in which the abrasive was added in the range of 100 to 250 wt% based on the weight of the ferromagnetic body in the production of the floppy disk, the cleaning performance of the cleaning disk was excellent, And the track average reproducing voltage TAA was maintained at 46 to 53% level, thereby providing excellent data recording and reproducing functions. On the other hand, in the case of Comparative Example 1 in which no abrasive was added at all, the data recording and regenerating function was excellent, but the driving stability and durability were weak, and the cleaning performance was particularly weak. Also, in the case of Comparative Example 2 in which the addition amount of the abrasive was 350 g, the reproduction output was 34 to 37% and the electronic conversion characteristic was poor.

In the case of Example 4 in which the calendering conditions were different, the surface roughness was 17 nm as compared with Example 1, and the improvement of the output characteristics due to the reduction of the head-media gap was somewhat improved. On the other hand, Did not do it.

On the other hand, as can be seen from Table 2, the magnetic head cleaning floppy disk manufactured according to Example 1 showed values within a range that the magnetic recording medium had to have in terms of output and other electronic characteristics.

As can be seen from the above, the floppy disk according to the present invention has a cleaning function capable of removing the contamination of the magnetic head as well as the magnetic recording and reproducing function.

Claims (4)

A floppy disk having a coating layer formed on both surfaces of a base film, the disk comprising: a ferromagnetic body made of Co-γ-Fe ₂ O ₃ and 100 to 250% by weight of an abrasive based on the ferromagnetic body; Wherein the magnetic head is a magnetic disk. The magnetic head cleaning disk according to claim 1, wherein the base film is at least one selected from the group consisting of polyesters, polyolefins, cellulose derivatives, and vinyl resins. The magnetic head cleaning disk according to claim 1, wherein the abrasive is at least one selected from the group consisting of Al ₂ O ₃ , Cr ₂ O _3, and α-Fe ₂ O ₃ . The magnetic head cleaning disk according to claim 3, wherein the abrasive is high purity Al ₂ O ₃ having a Mohs hardness of 9 or more, an average particle size of 0.45 μm, and a specific surface area of 15 to 20 m ₂ / g.