Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
1999-03-11
2001-03-06
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064400, C428S064500, C428S064600, C428S913000, C430S270130, C430S270140, C430S322000, C430S945000, C369S283000, C369S288000
Reexamination Certificate
active
06197399
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a recording medium which is capable of realizing a high-density recording by means of light irradiation or electric charge injection, and to a method of manufacturing the recording medium.
It is desired in the latest information-oriented society to develop a recording and reproducing method and an apparatus which enable to achieve, in conformity with an increasing quantity of information, an extremely high recording density as compared with the conventional methods and apparatuses.
There are two kinds of technique for realizing optical recording, i.e., heat mode recording in which light is employed as heat, and photon mode recording in which light is employed as it is without being converted into heat. The heat mode recording is put into practical use in magneto-optical recording or in phase-change recording.
In order to improve the recording density by means of the heat mode recording, a technique employing a near-field scanning optical microscope (NSOM) which enables to form a microspot smaller than the wavelength of light has been proposed. For example, Betzig et al have succeeded to form recording spots having a size of 60 nm in an attempt to realize magneto-optical recording and reproducing of information by irradiating a Co/Pt multilayered film with an output of Ar ion laser through an NSOM probe (Appl. Phys. Lett., 61, 142 (1992)). Further, Hosaka et al have succeeded to form recording spots having a size of 50 nm by irradiating a 30 nm-thick Ge
2
Sb
2
Te
5
film with an output of a semiconductor laser through an NSOM probe so as to cause phase change in the film (Thin Solid Film, 273, 122 (1996); J. Appl. Phys., 79, 8092 (1996)). However, these methods are accompanied with problems that the recording spots are enlarged due to heat diffusion and that they require a large energy. Therefore, it is expected that these methods are not applicable to the realization of a recording density in the order of terabits/cm
2
where a recording spot size is required to be reduced to as small as about 10 nm.
Under the circumstances, the present inventors disclosed a recording medium which is capable of reading fluorescence by utilizing phase change in an organic dye molecule (Japanese Patent Unexamined Publication H7-254153). According to the recording medium, if an organic dye molecule having a low heat conductivity is employed, it is possible to greatly reduce the recording spot size. However, even with this method, it is still difficult to realize a recording density in the order of terabits/cm
2
where a spot size is required to be reduced to about 10 nm. Further, this recording medium is accompanied with problems that, since amorphous regions are brought into contact with a crystal region, the amorphous regions are likely to be crystallized, thus destroying the recorded data. Furthermore, since the phase change medium is constituted by a uniform medium, a difference in signal level between the crystal region and the amorphous region is relatively small, thus leading to increase in noise.
Likewise, a uniform medium for the photon mode recording employing a photochromic compound is also accompanied with the problem of noise.
On the other hand, Japanese Patent Unexamined Publication H8-45122 discloses a recording medium provided with dot-like recording domains having a size of 10 to 100 nm and comprising an organic dye molecule in which recording is performed by injecting an electric charge into the recording domains. Since a single dot constitutes a recording unit in the recording medium, it is possible to improve a recording density. However, this recording medium is accompanied with the problems that it is difficult to form recording dots, each constituting a recording unit, uniformly in size and position, and that the size and the position of the dot thus formed are likely altered with time. In addition, it is difficult to entirely flatten the recording medium.
As described above, no one has succeeded as yet to realize a practical recording medium capable of recording with a very high density in the order of terabits/cm
2
.
BRIEF SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a recording medium and a manufacturing method thereof, which make it possible to ensure the stability of the recording domains, to reduce a noise level, and to easily flatten the entire surface of the recording medium.
According to the present invention, there is provided a recording medium, comprising a hydrophilic film formed on a substrate; recording domains formed directly on the hydrophilic film so as to make a predetermined pattern, each recording domain being made of an organic dye molecule and having a size of 50 nm or less; and an isolation region surrounding the recording domains, the isolation region being make of an organic molecular film.
According to the present invention, there is provided another recording medium, comprising an inorganic material film formed on a substrate; and recording domains buried in the inorganic material film so as to make a predetermined pattern, each recording domain being formed of a recording material selected from an organic dye molecule and an inorganic phase-change material and having a size of 50 nm or less.
The aforementioned recording media according to the present invention can be manufactured by various methods as explained below.
A first method comprises the steps of: forming a hydrophilic film on a substrate; forming an isolation region so as to expose regions having a size of 50 nm or less in the surface of the hydrophilic film with arranging the exposed regions into a predetermined pattern; and self-aggregating organic dye molecules selectively on the exposed regions of the hydrophilic film thereby forming recording domains.
A second method comprises the steps of: forming a hydrogen-terminated atomic film on a substrate; forming regions of a hydrophilic film on the hydrogen-terminated atomic film so as to form a predetermined pattern, each region having a size of 50 nm or less; self-aggregating organic dye molecules selectively on the regions of the hydrophilic film, thereby forming recording domains; forming another hydrophilic film in the region surrounding the recording domains; and forming an isolation region on the hydrophilic film in the region surrounding the recording domains, the isolation region being made of an organic molecular film.
A third method comprises the steps of: forming a hydrophilic film on a substrate; forming an organic dye molecular film on the hydrophilic film; patterning the organic dye molecular film so as to form a predetermined pattern, thereby forming recording domains having a size of 50 nm or less; and forming an isolation region on a region between the patterned recording domains made of the organic dye molecular film.
A fourth method comprises the steps of: forming an inorganic material film on a substrate; forming pits in the inorganic material film so as to form a predetermined pattern; filling the pits with a recording material selected from an organic dye molecule and an inorganic phase-change material; and removing an excessive recording material out of the pits.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5591501 (1997-01-01), Ovshinsky
patent: 5904969 (1999-05-01), Kamezaki et al.
patent: 7-254153 (1995-07-01), None
patent: 8-45122 (1996-08-01), None
E. Betzig et al., “Near field magneto-optics and high density data storage,” Appl. Phys. Lett. 61 (2), Jul. 13, 1992, pp. 142-144.
S. Hosaka et al., “Scanning near-field optical microscope with a laser diode and nanometer-sized bit recording,” Thin Solid Films 273, 1996, pp. 122-127.
L.C. Lenchyshyn et al., “Voltage-tuning in multi
Hieda Hiroyuki
Ishino Takashi
Naito Katsuyuki
Evans Elizabeth
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
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