JPH0547890B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks, and particularly to ferromagnetic metal thin film type magnetic recording media with excellent high recording density. Conventional Structure and Problems There has been remarkable technological development in magnetic recording media in recent years, as seen in the improvement in magnetic recording density. Examples of conventional magnetic recording media include r-Fe ₂ O ₃ powder and CrO ₂ for audio and video tapes.
There is a so-called coating type magnetic recording medium in which powder, pure iron powder, etc. is coated on a polymer film together with a binder such as a resin. However, in order to improve coercive force, recording density, and electromagnetic conversion properties compared to conventional coating-type magnetic recording media, methods such as vacuum evaporation, plating, ion plating, and sputtering have been used to improve Fe,
Metal thin film type magnetic recording media in which magnetic metals such as Ni, Co, and Cr are deposited singly or as an alloy on a polymer film substrate have been studied. Further, as a ferromagnetic metal thin film type magnetic recording medium, a microcassette tape using an oblique incidence deposition method has already been put into practical use. A major problem with ferromagnetic metal thin film magnetic recording media is that when used as a video tape, for example, there is no change in output when repeatedly running on a deck, there is no clogging, and it can be used in any environment. must be capable. Furthermore, the video tape has extremely superior surface properties compared to conventional coating-type tapes, as seen in vacuum evaporation methods, and can maintain surface properties of several hundred Å or less, reducing noise. High image quality with less color output can be obtained. However, although improving the surface quality improves the image quality, the coefficient of friction between the head and the tape increases during recording and playback, making the running performance unstable and causing the tape to become unable to run during repeated runs, resulting in poor running durability. It had Furthermore, since the surface layer of a ferromagnetic metal thin film type magnetic recording medium is covered with metal, it has a drawback of poor storage characteristics compared to a coated type magnetic recording medium. Purpose of the Invention In view of the above-mentioned drawbacks, the inventors of the present invention have conducted various investigations to provide a magnetic recording medium that has excellent running durability and good storage characteristics. Structure of the Invention The present invention provides a magnetic recording medium having a hydroxide between at least a ferromagnetic metal thin film layer and a fluorine compound, and carrying the fluorine compound and the hydroxide at an OH/F ratio in the range of 0.2 to 5.0. It is a medium with excellent running durability and improved storage characteristics under all environments. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. The figure is a sectional view showing the basic configuration of a magnetic recording medium in an embodiment of the present invention. In the figure, 1 is a polymer film, 2 is a ferromagnetic metal thin film layer formed on the polymer film 1, and further on the ferromagnetic metal thin film layer 2 is an upper surface layer 3 made of a fluorine compound.
is formed. Although not shown here, hydroxide is present at least between the ferromagnetic metal thin film layer 2 and the fluorine compound. Here, the polymer film 1 is appropriately selected from polyethylene terephthalate, polyamide, polyimide, polyvinyl chloride, polyethylene naphthalate, polycarbonate, cellulose triacetate, and the like. The ferromagnetic metal thin film layer 2 is made of Co,
Fe, Ni, Cr, or various alloys based on these, such as Co-Ni, Co-Fe, Co-Cr,
Co−Cu, Co−Pt, Co−Cd, Co−Sn, Co−Ni
- Cr and these metal oxides, and can be made into in-plane magnetization films, perpendicular magnetization films, etc. depending on the magnetization method.The formation method of the ferromagnetic metal thin film layer is vapor deposition, ion plating, sputtering, vapor phase growth, etc. Appropriately selected from. Further, the fluorine compounds 3 used in the present invention are roughly classified into fluorine-based organic compounds and fluorine-based inorganic compounds. Here, as the fluorine-based organic compound, -COOH, -COOMe is added to the perfluoroalkyl group of the fluorine-based surfactant.
(Me: metal), −COONH ₄ , −SO ₃ H, −SO ₃ Me
(Me: metal), those with active groups such as -SO ₃ NH ₄ , and fluorine-based plastics. It is appropriately selected from polyfluoro compounds such as tetrafluoroethylene resin, Teflon, hexafluoropropene, perfluoro-α-olefins, vinyl fluoride, vinylidene fluoride, and fluorinated elastomers and copolymers. It is also possible to use partially fluoro compounds of hydrocarbon compounds. In addition, the fluorine-based inorganic compounds used in the present invention include Li, Na, K, Rb, Cs, Be, Mg, Ca,
Sr, Ba, B, Al, Ga, In, Tl, C, Si, N,
It is appropriately selected from compounds consisting of two or more of P, O, S, Cl, Br, I, and fluorine. The method for forming the fluorine compound may be a conventionally known wet method or a dry method such as a vapor deposition method, a sputtering method, an ion plating method, a vapor phase growth method, or a plasma polymerization method. The present invention has a hydroxide at least between a ferromagnetic metal thin film layer and a top layer made of a fluorine compound. The intervening method is to chemically or physically adsorb hydroxide into the ferromagnetic metal thin film layer after forming the ferromagnetic metal thin film layer, or to use hydroxide as a solvent in the fluorine compound.
Alternatively, there is a method in which the surface of the ferromagnetic metal thin film layer is coated with the fluorine compound in a hydroxide atmosphere during coating with the fluorine compound by a dry method. In this case, the appropriate ratio of fluorine compound to hydroxide on the surface of the ferromagnetic metal thin film layer is in the range of OH/F0.2 to 5, and a photoelectron analyzer is used to quantify the OH amount of the magnetic recording medium. The F and OH spectra were quantified using ESCA (hereinafter referred to as ESCA), and the optimal amount of OH was estimated from the OH/F ratio, taking into account the sensitivity correction of the spectrum. The magnetic recording medium constructed as described above has a structure in which the ferromagnetic metal thin film layer and the fluorine compound adhere to each other by interposing hydroxide at least between the ferromagnetic metal thin film layer and the upper surface layer made of the fluorine compound. It has improved strength and dispersion, has excellent durability against repeated running on a deck, and has excellent storage properties such as corrosion resistance and weather resistance. More specific examples of the present invention will be described below. Example 1 A ferromagnetic metal thin film layer with a thickness of 1500 Å was formed on a polyethylene terephthalate film by electron beam melting a Co80-Ni20% alloy in an oxygen gas atmosphere by oblique evaporation. The angle of incidence of the vapor flow during deposition is
The deposition was carried out at an average deposition rate of 1000 Å/sec with 40°R to 90°R components. In this case, an oil diffusion pump is used to exhaust the vacuum equipment, and CO−Ni is heated under a vacuum degree of 10 ^-4 to ^{10 -5} torr.
The alloy was deposited. On the formed ferromagnetic metal thin film layer, a 0.1 wt% ethanol solution of perfluoroalkylcarboxylic acid having 9 carbon atoms in a perfluoroalkyl group was applied, and the concentration of the coating solution was adjusted to 10 mg/m ² by a reverse roll method. Coated. in this case
The OH/F value by ESCA is 1.2. Example 2 A cryopump was used in the vacuum evacuation system of Example 1, and the vacuum pump was used in an oxygen gas-steam atmosphere (water content 10 vol%).
Vacuum deposition was performed in the same manner as in Example 1, and the same amount of a material having a perfluoroalkyl group and an active group of -COOCo was applied. In this case, the OH/F value by ESCA is 2.0. Example 3 On a ferromagnetic metal thin film layer vacuum-deposited in the same manner as in Example 1, in the same vacuum apparatus, tetrafluoroethylene resin, which is a fluorine plastic, was organically deposited to a thickness of 100 Å using a dry method in a water vapor atmosphere. Coated with. In this case, the OH/F value by ESCA is 0.8. Example 4 Oxygen-water vapor (5 vol) was added to the vacuum atmosphere of Example 1.
%) mixed gas was introduced to form a ferromagnetic metal thin film layer with a thickness of 1300 Å on the polyethylene terephthalate film. A 0.3 wt % solution of a partially fluorinated hydrocarbon compound in isopropyl alcohol was applied onto the ferromagnetic metal thin film layer at a coating solution concentration of 30 mg/m ² . in this case
The OH/F value by ESCA is 0.5. Example 5 The ferromagnetic metal thin film layer obtained in Example 2 was coated with boron fluoride, which is a fluorine-based inorganic compound, to a thickness of 50 Å using a sputtering method. In this case, the OH/F value by ESCA is 3.0. Example 6 In the same manner as in Example 1, perfluoroalkyl carbon acid is dissolved in ethanol solvent and applied at a high concentration so that the OH/F value by ESCA is 0.2. Example 7 In the same manner as in Example 1, perfluoroalkylcarboxylic acid is dissolved in ethanol solvent and applied at a low concentration so that the OH/F value of the substrate by ESCA is 5. The magnetic recording medium obtained in the above example was cut into tapes with a width of 8 mm, and the tapes were evaluated for environmental preservation characteristics. The evaluation method was to create a prototype for an 8 mm width deck testing machine that has a running system equivalent to that of a commercially available VHS deck (for example, Matsushita Electric's Matsuku Road 88: NV-8800 model), and test the running durability of repeated runs for a tape length of 50 m. The characteristics were investigated before and after storage at 50°C and 90% environment. In addition, in order to quantify the hydroxide on the ferromagnetic metal thin film layer, we used ESCA to quantify the spectra of Co metal and hydroxide. The amount of oxide was estimated. Tape used as prototype deck for running durability
It was run for 100 passes, and the ratio before and after running 100 passes/initial friction coefficient value, the output fluctuation after 100 passes, and the clogging state were observed. Environmental storage characteristics are determined by leaving it in a 90% atmosphere at 50℃ for one month, changing magnetic properties before and after storage, and ESCA.
Evaluation was made based on the increase in OH groups and the change in output due to repeated running using a prototype deck. Those with a small amount of change before and after the test were marked with a circle, those with a slight change that could be seen as practically unacceptable were marked with a triangle, and those with a large amount of change that were practically unusable were marked with an x. To summarize the evaluation results of the examples of the present invention, as shown in Table 1, a ferromagnetic metal thin film layer is formed on a polymer film, and an upper surface layer consisting of a fluorine compound is formed on the surface, and fluorine and hydroxide are formed. By optimizing the ratio of materials, the running durability of the tape is improved and the storage characteristics under various environments are significantly improved. In the present invention, the optimum amount of hydroxide compound is the OH/F ratio

[Table] In the present invention, the optimum amount of hydroxide is OH/F ratio 0.2~
In the range of 5.0, if the OH/F ratio is less than 0.2, the running durability will be poor and the storage properties will not be affected, and if it is more than 5.0, the hydroxide will cause clogging and adversely affect the running properties. Preferably 0.3-3.0
The reason why there is an appropriate amount of hydroxide within this range is probably related to the reactivity of the hydroxide, magnetic metal, and fluorine-based compound, and the hydroxide has a strong adhesion strength between the fluorine-based compound and the magnetic metal. This is thought to be because it is involved in the degree of dispersion of the fluorine compound. In this example, the effects were specifically shown for several types of samples, but it was confirmed that the combinations of the other materials mentioned above constituting the present invention also had similar effects. Further, in the above embodiments, a magnetic tape was used as an example of the magnetic recording medium, but it is also possible to take the form of a magnetic disk, a magnetic sheet, etc. without departing from the gist of the present invention. Effects of the Invention As described above, the present invention includes a ferromagnetic metal thin film layer formed on a polymer film, and an upper surface layer made of a fluorine compound formed on the ferromagnetic metal thin film layer. Hydroxide is present at least between the metal thin film layer and the fluorine compound, and by optimizing the amount of hydroxide, it is possible to improve running durability and environmental preservation characteristics, making it practical. The effect is great.

[Brief explanation of the drawing]

The figure is a sectional view showing a magnetic recording medium in an example of the present invention. 1...Polymer film, 2...Ferromagnetic metal thin film layer, 3...Top layer.

Claims (1)

[Claims] 1 A ferromagnetic metal thin film layer formed on a polymer film, and an upper surface layer made of a fluorine compound formed on the ferromagnetic metal thin film layer, wherein the ferromagnetic metal thin film layer and the fluorine compound 1. A magnetic recording medium characterized in that the fluorine compound and the hydroxide are supported at an OH/F ratio in the range of 0.2 to 5.0.