Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1999-12-09
2003-02-11
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
Reexamination Certificate
active
06518572
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an infrared microscopic/FT-IR (Fourier transform infrared spectrometer) apparatus based on an attenuated total reflection method, in which a surface portion of a sample is analyzed by bringing a prism into press-contact with the surface of the sample, making an infrared light ray incident on the prism at an arbitrary angle, and analyzing the spectrum of the infrared light ray totally reflected from the surface of the sample by the FT-IR apparatus, and a method for analysis of high density recording media using the apparatus.
Magnetic recording media are widely utilized as an audio tape, a video tape, a back-up data cartridge, a floppy disk, and a hard disk. In particular, recently, examination has been actively made to shorten a recording wavelength or realize high density recording by adopting a digital recording method or the like, and it has been required to develop magnetic recording media excellent in electromagnetic transformation characteristic.
With respect to a coating type magnetic recording medium having been mainly used at present, it has been examined to make a magnetic layer thin for reducing a self-demagnetization loss upon recording, thereby improving the electromagnetic transformation characteristic. In recent years, various coating methods have been proposed from the viewpoint of thinning of the magnetic layer.
In general, the surface of a recording medium is smoothened to minimize a spacing loss upon recording/reproducing. In high density recording, since a recording wavelength used is short, recording tends to be affected by the surface roughness, and therefore, the control of the surface roughness is particularly important.
In this way, with increased output of a magnetic tape, it is required to significantly enhance the smoothness of the surface of a magnetic layer, and correspondingly the substantial contact area of the magnetic layer with a sliding member such as a magnetic head or a guide roller becomes large. As a result, the friction coefficient between the magnetic layer and the sliding member becomes large, and thereby an adhesion phenomenon (so-called sticking) therebetween is easy to occur. This causes a problem such as the lack of running characteristic and durability of the magnetic tape.
To solve the above problem, it has been examined to use various organic lubricants. For example, attempts have been made to add higher fatty acid or its ester in or on the magnetic layer of the magnetic recording medium for reducing the friction coefficient between the magnetic layer and the sliding member.
At the present time, however, as a method of quantitatively measuring the amount of lubricant adhering on the surface of the magnetic recording medium or contained in the medium, there has been known only a method of analyzing the amount of the lubricant by extracting the lubricant by. using solvent. According to such an extraction method, only a lubricant dissolved in a solvent (hexane or toluene) can be measured, and it takes a lot of time to measure the amount of the lubricant. For this reason, it has been very difficult to control the added amount of a lubricant in the production process for a magnetic recording medium.
On the other hand, in a magnetic recording apparatus, typically a hard disk, mainly including a recording/reproducing magnetic head and a magnetic recording medium, a friction force occurs between the magnetic head and the magnetic recording medium, thereby causing wear of the magnetic head and the magnetic recording medium. If the wear reaches a magnetic layer of the magnetic recording medium, there occurs a so-called head crush phenomenon in which information recorded in the recording layer is crushed, and accordingly, to ensure the reliability of the magnetic recording apparatus, it is important to prevent the above-mentioned head crush phenomenon.
To prevent the head crush phenomenon, it is required to improve the wear resistance of a magnetic recording medium itself. In general, to achieve such a purpose, a magnetic layer is covered with a protective layer made from carbon, an oxide, a carbide, or a nitride and further a lubricating film is formed on the protective layer. The lubricating film generally requires characteristics such as a low surface energy, heat resistance, chemical stability and lubricity. At present, a perfluoroalkylpolyether or a perfluoroalkyl compound disclosed in U.S. Pat. No. 3,778,308 has been most extensively used as a compound for forming the lubricating film.
In a magnetic recording apparatus having been mainly used at present, recording/reproducing is performed in a state in which a specific gap is kept between a magnetic head and the surface of a magnetic recording medium. Such a specific gap is called a floating amount. To enhance the recording density to the magnetic recording medium, it is required to make small the floating amount of the magnetic head. In recent years, as the recording density of a magnetic recording apparatus becomes significantly higher, the floating amount becomes smaller. Further, as the ultimate recording method, in recent years, there has been proposed a so-called contact recording method in which recording/reproducing is performed with the floating amount set to zero, that is, in a state in which a magnetic head is usually in contact with the surface of a magnetic recording medium.
In this way, as the floating amount of a magnetic head becomes smaller, a period of time in which the magnetic head is slid in contact with the surface of a magnetic recording medium becomes necessarily larger, and therefore, it is required to reduce the dynamic friction coefficient and wear by enhancing the continuously sliding durability of a lubricating film. Further, in a magnetic recording apparatus.operated in accordance with the extremely low floating method or contact recording method, since the surface roughness and waviness of a magnetic recording medium becomes smaller, a higher maximum static friction force (adhesion) is easy to occur between the magnetic head and the magnetic recording medium. The adhesion may cause the impossible starting of the magnetic recording medium or damage of the magnetic head.
The thickness of a lubricating film present on the surface of the magnetic recording medium is one major cause of occurrence of adhesion. The amount of the lubricant present on the magnetic recording medium is quantitatively measured, for example, by using an ellipsometer or in accordance with XPS (X-ray photoelectron spectroscopy). In the case of the method using the ellipsometer, since the measured result is largely affected by the surface roughness of the magnetic recording medium, it is difficult to accurately measure the amount of the lubricant. In the case of XPS, since the measurement is performed in vacuum, the lubricant on the surface of the magnetic recording medium is lost, and since the measurement is performed by using fluorine atoms, it is impossible to suitably measure a hydrocarbon based lubricant.
With respect to an optical disk (phase change type or magneto-optical type), a spacing between a conventional disk and the optical head is in a range of several hundred nm to several &mgr;m, which spacing is considerably larger than the spacing adopted for other magnetic recording methods. Accordingly, a protective film having about several hundred &mgr;m is formed on a recording layer of the optical disk. In this way, since the conventional optical disk has a large spacing, a protective film having a large thickness can be formed on the recording layer, with a result that there is a sufficient margin to take a tribological characteristic into account.
In the case of optical recording performed in a near field, which is being studied and developed at present, however, a spacing between a recording layer and an optical head may be considered to be 100 &mgr;m or less, and therefore, the thickness of a protective layer must be several ten nm or less. In this case, the tribological characteristic required for optical rec
Kamei Takahiro
Kishii Noriyuki
Kobayashi Ken
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