JPS6256574B2 - - Google Patents

Description

[Detailed description of the invention]

(1) Technical Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium, and in particular to a lubricant applied to the surface of a magnetic layer in which perfluoroalkyl polyether is diluted in a high fluoride solution with a boiling point of 90°C or higher. Regarding the method. (2) Background of technology Recently, magnetic media has been
Efforts were made to reduce the flying height of the magnetic head, and the so-called contact start-stop method (CSS method), in which the magnetic head and the medium slide in contact with each other when starting and stopping, was adopted. For the purpose of improving the durability against abrasion, perfluoroalkyl polyether [commercially available under the trade name Krytxx by DuPont, whose molecular formula is

A lubricant such as [Formula] is applied to the surface of the magnetic layer of the medium. Various methods have been proposed for applying the above-mentioned Klytux, including a spin coating method (rotary coating method), a dipping method in which a medium is placed in the Klytux, and a spray method using an appropriate spray gun. Stock solution (100%)
It is rarely used as is, but instead a suspension obtained by diluting Krytx in a solvent such as trichlorotrifluoroethane (trade name Freon TF) or a mixture of Freon TF and isopropyl alcohol is used. (3) Prior art and problems The Krytox mentioned above completely dissolves in Freon TF, so it is convenient for delicately controlling the amount of application. It is difficult to maintain the concentration of the solution. For example, when using the above-described dipping method for coating Krytox, maintaining concentration becomes a more serious problem because of the large volume of solution and the wide opening of the container. In addition, in the spin coating method, Freon TF evaporates quickly, so even if the solution is dropped onto the medium, it is difficult to spread and coat it uniformly over the entire surface.In most cases, spinning is used to achieve uniformity. A buffing or thermal diffusion step is required after coating. All of these circumstances result in an increase in the number of manufacturing steps for magnetic media, which in turn becomes a factor in lowering the yield. (4) Purpose of the Invention In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a method for manufacturing a magnetic medium in which the concentration of a solution of Krytox is easily maintained and the uniform coating property is excellent. (5) Structure of the Invention According to the present invention, a magnetic paint made by dispersing magnetic iron powder in a binder is applied to a non-magnetic substrate to form a magnetic layer, and then a lubricant is applied to the surface of the magnetic layer. A method for manufacturing a magnetic recording medium comprising coating a perfluoroalkyl polyether with a molecular formula of C ₇ F ₁₆ or C ₈ F ₁₆ O alone or a mixture thereof. Provided is a method for producing a magnetic recording medium, characterized in that the magnetic recording medium is coated in a diluted state in a high-fluoride diluent. The diluted concentration of perfluoroalkyl polyether in this solution is 0.2 to 5%. (6) Examples of the invention Examples of the invention will be described in detail below with reference to the drawings. The inventor of this application determined that the problems experienced when using currently commercially available Freon TF were caused by the rapid evaporation rate of Freon, and conducted experiments using various solvents with different boiling points in order to solve the above-mentioned problems. Overlapping,
The relationship between the boiling point and the change in the concentration of Krytox solution over time shown in FIG. 1 was established. In the figure, the horizontal axis shows the boiling point temperature (°C) of the solution, and the vertical axis shows the concentration change rate per day in %. The range indicated by the arrow in the figure is an acceptable range, but when making this determination, a concentration change rate of 3%/day or more was determined to be practically difficult to manage, and a concentration change rate of less than 3%/day was determined to be acceptable. The area with an arrow attached to the circle in the upper left of the coordinates in the figure indicates the case where Freon TF is used, and the concentration change rate is 50%/day or more. In this experiment, a 50 cm cubic container was filled with 5% Krytx dissolved in each solvent, and the changes in concentration were measured when the solvents were left at 25°C for one day. The three points within the arrow range are data based on the method of the present invention. Next, the evaluation results of the coating properties are shown in FIG. This evaluation was performed using both the spin coating method and the dipping method. Regarding the applicability, which is indicated by a score on the vertical axis of the figure, a score of 9 or less is judged to be unsuitable because the quality lacks stability or the next process requires a buffing process or a thermal diffusion process, and a score above 9 is judged to be unsuitable. The item was passed. Specifically, after the solvent evaporates, if the Krytox appears as a continuous film and has good uniformity, it is 10
A score of 5 was given if the Krytox appeared uniformly granular (because wiping or heat diffusion treatment was required in a subsequent step), and a score of 3 was given if the Krytox was not uniformly applied. Note that the intermediate value of these score distributions was determined as appropriate. In the figure, the horizontal axis indicates the boiling point temperature of the solution (° C.), the range indicated by the arrow indicates a pass, square marks indicate those obtained by the dipping method, and circles indicate those obtained by the spin coating method. The diameter is approximately 36cm for both spin coating and dipping methods.
The solution concentration and coating conditions (for example, rotation speed in spin coating, disk pulling speed in dipping method) were optimized to coat 30 mg per 14-inch disk, and the coating was evaluated. Next, the concentration and winchiesta type head when using the solvent with a boiling point of about 100°C according to the present invention are determined.
Figure 3 shows the relationship between the number of CSS (contact start and stop) durability cycles. Krytx was applied to the disk by both a spin coating method and a dipping method, and coating conditions determined to be optimal were selected for each method. Therefore, wiping and heat diffusion treatments are not performed. In the figure, the horizontal axis shows the concentration of Krytox solution (%), the vertical axis shows the number of durability in tens of thousands, and the range shown by the arrow is the pass.
Square marks indicate the dipping method, and circle marks indicate the spin coating method. The passing line for durability was set at 10,000 times or more. Furthermore, apply a pressure of about 10g on the disk mentioned above.
A winchiesta-type head was left for 24 hours at 24°C and 70% humidity, and the adsorption force (head stay (sticking between the head and disk)) generated between the head and disk was measured. The results are shown in Figure 4. In the figure, the horizontal axis is the Krytox solution concentration (%), the vertical axis is the adsorption force (g), and the range indicated by the arrow indicates a passing grade with an adsorption force of 5 g or less. The square marks and round marks are the same as in Fig. 3. Regarding the pass line, since no scratches were observed on either the head or the disk when the suction force was 5 g or less, a value of 5 g or less was considered acceptable. From the results explained above, it was determined that the practical concentration at which stable quality can be obtained when coating Krytox using the solvent according to the present invention is 0.2 to 0.5%. That is, if the degree of dilution is less than this range, coating conditions that provide sufficient durability cannot be obtained, whereas if it is diluted more than this range, the adsorption force becomes too large and is not suitable for practical use. (7) Effects of the Invention As explained above, when the method of the present invention is used, a Klytox solution with a low concentration change rate can be obtained, and when this solution is used, it is possible to obtain a solution of high quality, high durability, and adsorption power. A small lubricant layer can be obtained, which greatly contributes to improving the reliability of the magnetic medium.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the boiling point and the change in concentration of the Krytox solution over time, Fig. 2 is a diagram showing the coatability of the solution, and Fig. 3 is a diagram showing the relationship between the concentration and the time when the solvent of the present invention is used. FIG. 4 is a diagram showing the relationship between the durability of the CSS head and the adsorption power of the CSS head.

Claims (1)

[Claims] 1. Manufacture of a magnetic recording medium by applying a magnetic paint made by dispersing magnetic iron powder in a binder to a non-magnetic substrate to form a magnetic layer, and then applying a lubricant to the surface of the magnetic layer. In the method, the lubricant is prepared by diluting perfluoroalkyl polyether in a highly fluorinated diluted solution having a molecular formula of either C ₇ F ₁₆ or C ₈ F ₁₆ O alone or a mixture thereof. A method for manufacturing a magnetic recording medium, characterized in that the magnetic recording medium is coated in a state in which the magnetic recording medium is coated. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the diluted concentration of perfluoroalkyl polyether in the high fluoride diluent is 0.2% to 5%.