JPS6369023A - Increase of wear resistance of ferromagnetic recording medium - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to surface treatment of magnetic recording materials, in particular electroless plated ferromagnetic recording layer (electroless plated ferromagnetic recording layer).
ferromagnetic recording
The present invention relates to a method of treating the surface of a recording layer to improve the abrasion resistance of the recording layer.

Video tapes, i.e. tapes with a magnetic recording medium layer for recording and reproducing electromagnetic signals used to operate television sets and TV monitors, are such that the tapes are not damaged during use. In order to be able to do this, abrasion resistance of kanashi is required. In use, the tape is held opposite a rapidly rotating recording head and therefore, if the abrasion resistance is inadequate, parts of the recording layer will be rubbed away very rapidly by the head. removed. Wear damage is believed to occur particularly during stationary frame rewinding, where the tape is stationary and the head is therefore rotating facing the same location on the tape that is being rewound.

It has been proposed to provide a protective layer on the recording layer. However, for efficient recording, it is important that the distance between the head and the recording medium be minimal, and because of this importance, the above-mentioned protective layer is necessarily attached to the recording medium. Since the recording medium will be interposed between the head and
No overlying substantial protective layer is available.

The present invention relates to another method for improving the abrasion resistance of recording media by chemical treatment, and the present invention relates to an alternative method for improving the abrasion resistance of recording media by chemical treatment. Can be used for videotapes. The process of the present invention is not limited by the type of substrate supporting the recording layer;
The present invention is equally applicable regardless of whether the recording medium is on tape or other support material that is inert to the chemicals used in processing.

Currently, most commercial videotapes have recording layers made of metal oxides, but more recently recording layers have been made from ferromagnetic metals, such as cobalt, deposited on one surface of a pre-stretched polymer tape. Tapes are now being used which often have an adhesion promoting layer between the polymeric tape and the recording layer. Metals can be deposited on the tape by methods other than vapor deposition, but the nature of the metal particles in the recording layer and their structure are primarily determined by the method of deposition, and metals formed by different methods The physical and chemical properties of the layers are significantly different. A recent, particularly economical metal deposition method for forming layers of high magnetic performance is electroless plating
EP), in which the metal is chemically precipitated from a solution (usually an aqueous solution) of a precursor compound. However, the deposited layer obtained in this way is susceptible to damage due to abrasion, especially if no suitable treatment is carried out.

The particles deposited (by the EP method) exhibit different chemical properties than one deposited metal layer, as shown, for example, by their behavior towards solutions containing hydrogen peroxide.

As a method to improve the corrosion resistance of vapor-deposited cobalt films,
The film is oxidized with EDTA, hydrogen peroxide and hydroxide)
A method of treatment with a dilute aqueous solution of IJum for several minutes, for example 10 to 20 minutes, has been proposed. The inventor has found that when such a solution is applied to an EP metal layer under similar conditions, the metal layer is rapidly destroyed by this treatment. The cause was hydrogen peroxide. When the EP tape is immersed in a hot hydrogen peroxide solution, the cobalt film is destroyed within seconds. After a very short time, the cobalt layer begins to color and turn brown, and then rapidly breaks down. When observed under a microscope, it was observed with the naked eye that many small pores appeared in the cobalt layer at the beginning of the coloration, and these pores rapidly expanded and the layer began to break down. The rapid destruction of this layer can be caused by very dilute hydrogen peroxide solutions, e.g. the ED described above.
It was also observed in a 5% aqueous hydrogen peroxide solution containing TA and sodium hydroxide.

The inventors have found that the hydrogen peroxide solution described above, which causes rapid partitioning of the EP metal layer, initially produces a metal layer that is significantly more #F abrasive than the untreated layer.

According to the present invention, there is no need for ferromagnetic recording media to be easily decomposed by hydrogen peroxide! #? Having a layer of deplated ferromagnetic material and treating this layer with hydrogen peroxide and terminating this treatment before significant decomposition of the recording layer begins? A method of increasing the wear resistance of a ferromagnetic recording medium is provided.

A preferred method for treating the surface of an electrolessly plated ferromagnetic recording layer is to apply a hydrogen peroxide solution to the surface of the recording layer and remove hydrogen peroxide from the treated surface before significant decomposition of the recording layer begins. Consists of removing.

The maximum time that hydrogen peroxide can be kept in contact with the recording layer button depends on the temperature of the hydrogen peroxide solution, and generally the higher the solution temperature, the shorter it is, but it is usually 30 seconds or less, preferably 30 seconds or less. Within about 10 seconds.

As a guideline, particularly when using a high temperature hydrogen peroxide solution of, for example, 20 to 30 volumes, contact between the solution and the recording layer is preferably terminated within about 10 seconds after application of the solution.

Another parameter that influences the treatment of the recording layer with hydrogen peroxide is the amount of hydrogen peroxide, ie the layer thickness of the hydrogen peroxide solution applied to the recording layer. Removal of the solution is conveniently carried out by evaporation, so that thicker layers of solution take longer to remove than thinner layers. It is preferred to use a very thin layer of solution, which, in addition to allowing rapid removal of the hydrogen peroxide, also reduces the amount of hydrogen peroxide that would otherwise cause significant coloration/decomposition of the recording layer. It also has the advantage of being able to be limited to a sufficiently low level.

In this case, since the hydrogen peroxide is removed by reacting with the recording medium, there is little need for rapid drying of the recording medium. However, in practice it is preferred to use a very thin coating of hydrogen peroxide solution and to dry the recording layer rapidly, for example within about 10 seconds.

In a preferred method, the thickness of the layer of hydrogen peroxide solution applied onto the recording layer is a few μm, for example 2 or 3 μm, and such a thin layer (which itself is typically 0.1 μm thick)
(thickness)] by wiping the surface with a tissue or sponge impregnated with a hydrogen peroxide solution. Alternatively, very thin layers of solution can be applied by a variety of well-known techniques such as spraying, brushing, doctoring, kissing and roller coating. These methods can also be used to apply thick layers of the solution, for example up to about 10βm, and can also be simple dipping techniques.

In many cases, especially when using very thin layers of hydrogen peroxide solution, this solution can be evaporated from the recording layer at ambient temperature without blowing air or other fluids onto the surface. Blowing, optionally with heated dry air, is a useful means for rapid removal of thick layers of hydrogen peroxide solution, and the recording tape may be directly heated if necessary. Any temperature, for example about 80'C1, can be used as long as the recording layer and its support are not damaged.

Hydrogen peroxide solutions are usually aqueous solutions and generally have a Fi20
~30 volumes or more of concentrated hydrogen peroxide solution. Although a very dilute solution can be used, a solution at a temperature of 1 volume:1 t% or higher, particularly 5 volume:1% or higher is preferred. This solution may contain additives dissolved, dispersed, or emulsified in the solution, which can precipitate and remain on the recording layer when the solution is removed by evaporation. An example of a useful additive is EDT
A. A peroxide activator and a lubricant such as a long chain fatty acid, such as stearic acid.

Instead of applying hydrogen peroxide as a solution, the abrasion resistance can also be improved by treating the EP-film with hydrogen peroxide vapor. This method can be carried out simply by suspending the tape over a concentrated hydrogen peroxide solution held at an elevated temperature. When using a 30 vy% solution at 80°C, it may be necessary to process the film for a longer period of time, e.g. up to at least 10 minutes, than would be comfortable if the solution were applied directly. However, it has been observed that there is a lower risk of film failure when using this method if the surface is kept dry and no condensate is present. Thus, a preferred steam treatment is one in which the EP-process film is heated to a temperature at least as high as the temperature of the steam before contacting with the hydrogen peroxide vapor.

The method of the invention can be applied to recording layers consisting of any ferromagnetic material, but especially consisting essentially of cobalt (
It is thus possible to apply layers consisting of cobalt (which may contain up to a few percent of other elements, for example phosphorus), alloys of cobalt or mixtures of cobalt and other metals, for example nickel.

Next, the present invention will be explained with reference to examples.

Example 1 A coated polyester consisting of a polyester support tape suitable for processing into videotape and EP-coated with a cobalt recording layer was coated with 10-
It was placed on a flat glass plate with dimensions of X15X0.4crIK and fixed with adhesive tape.

The surface of the sample was wiped with a pad of tissue paper soaked in a 30 W/y hydrogen peroxide solution to form a solution layer approximately 2 microns thick.

The solution was immediately evaporated from the surface of the sample tape at ambient temperature.

The abrasion resistance of the surface, ie of the cobalt recording layer, was determined by a friction test on a REL abrasion test apparatus commonly used for evaluating paint films. This device has six arms that move back and forth over the tape surface. Each arm l'cU500. A pad of tissue paper is attached which is loaded with a % load and is in contact with the surface of the recording layer.

The number of frictions, ie, the number of times the pad moved over the surface, was counted with a counter. The test was stopped after 5,000 rubs.

In the series of abrasion tests described above, several light surface scratches were observed on the sample tape after 5,000 rubs. In all samples, the removal of cobalt from the surface of the recording layer was slight.

Example 2 Using the method described in Example 1, each sample of EP-coated polyester tape was coated with a 30 VV% hydrogen peroxide solution by wiping the solution to form a 2 μm thick solution layer. Ta. This solution layer was immediately evaporated from the surface at ambient temperature. The sample was then wiped with a 0.2 VV% solution of lauroyl oxide in isopropyl alcohol to form a 2 micron thick solution layer. Isopropyl alcohol was allowed to evaporate at ambient temperature.

As a result of performing an abrasion test on the obtained sample, the surface of the cobalt recording layer after 7,000 times of friction showed only slight damage, and almost no cobalt was removed.

Example 3 Another sample of the same EP-coated tape was treated by exposure to hydrogen peroxide vapor, ie, vapor over a heated hydrogen peroxide solution. This solution is a 30 W/y% aqueous hydrogen peroxide solution held at a temperature of approximately 8°C, and the tape samples are suspended above the solution for various times, typically 2-10 minutes. The samples were then tested as described in Example IK. To prevent condensation from forming on these coated surfaces during processing, all samples were suspended 80" before hanging above the solution.
CK was heated in advance.

Although the treatment time was much longer than in the case of coating under the conditions of Example 1, no significant decomposition occurred and the wear resistance obtained especially for the samples suspended for 1 hour was The degree of improvement in performance is very different from that obtained in Example 1.
It was similar. A sample of EP-coated tape treated as described above for about 10 minutes withstood 5,000 rubs on an abrasion tester with very little cobalt removed.

Comparative Example Abrasion tests were conducted on samples of untreated EP-coated polyester tape for comparative purposes. The test in this case is 20
It was stopped after 0 frictions. It was observed that the cobalt recording layer was removed rapidly, leaving a bare batch and after 200 rubs (in some cases after only 100 rubs), in fact the cobalt of the clasp had been removed.

Additionally, for comparison purposes, samples of FJP-coated polyester tape were treated with a previously proposed treatment method for vapor-deposited cobalt tapes, i.e., containing EDTA and sodium hydroxide.
The specimens were immersed in a hydrogen peroxide solution for 20 minutes. As a result, the cobalt recording layer was observed to become rapidly colored and completely destroyed within a few minutes.

Claims (1)

[Claims] 1. The ferromagnetic recording medium has a layer made of an electrolessly plated ferromagnetic material that is easily decomposed by hydrogen peroxide, and the layer is treated with hydrogen peroxide, and this treatment is applied to the recording medium as described above. A method for increasing the wear resistance of a ferromagnetic recording medium, characterized in that the wear resistance of a ferromagnetic recording medium is terminated before significant decomposition of the layer begins. 2. The method of claim 1, wherein a solution of hydrogen peroxide is applied to the surface of the ferromagnetic material and the hydrogen peroxide is removed from the treated surface before significant decomposition of the recording layer begins. 3. The method according to claim 2, wherein the solution is an aqueous solution containing 1% by weight or more of hydrogen peroxide. 4. The method according to claim 3, wherein the solution contains 20 to 30% by volume of hydrogen peroxide. 5. The method according to any one of claims 2 to 4, wherein the contact between the ferromagnetic material and the solution is terminated within 10 seconds after application of the solution. 6. A method according to claim 5, wherein the contacting is carried out by blowing warm dry air onto the surface of the layer of ferromagnetic material, while maintaining the layer at a similarly high temperature. 7. Apply hydrogen peroxide solution to the surface of the ferromagnetic material with a thickness of 2 to 10 μm.
A method according to any one of claims 2 to 4, wherein the method is applied as a thin layer having a thickness of . 8. The method according to claim 1, wherein the ferromagnetic material is treated with hydrogen peroxide vapor. 9. Suspending the recording medium over a concentrated aqueous solution of hydrogen peroxide held at an elevated temperature, thereby bringing it into contact with the hydrogen peroxide, and reducing the temperature of the recording medium to a level of vapor before contacting the hydrogen peroxide. 10. The method of claim 9, wherein the method is heated to a temperature at least as high as the temperature. 10. A method according to any one of the preceding claims, wherein the ferromagnetic material is essentially cobalt, an alloy of cobalt, or a mixture of cobalt and other metals.