Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2000-02-01
2002-05-07
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064500, C428S064600, C430S270110
Reexamination Certificate
active
06383595
ABSTRACT:
TECHNICAL FIELD
The invention relates to an information recording medium which is used as an optical disk.
BACKGROUND ART
Various principles for recording information onto a thin film (recording film) by irradiating a laser beam are known. Among them, since the principle using an atomic arrangement change due to the irradiation of a laser beam such as phase transition (also called a phase change) of a film material, photodarkening, or the like is hardly accompanied with deformation of a thin film, it has a merit such that an information recording medium of a double-sided disk structure is obtained by directly adhering two disk materials. A recording film of a GeSbTe system or the like has an advantage such that information can be rewritten.
According to such a kind of recording film, however, if a mark edge recording or the like to realize a high density is performed, since erasing characteristics are insufficient, a film thickness of the recording film changes due to a flow of the recording film because of a deterioration of jitter due to the rewriting or the rewriting of a number of times exceeding 10
4
, so that a distortion occurs in a reproduction signal waveform. The flow of the recording film occurs by the reason that the recording film flows by the laser irradiation upon recording and the recording film is pressed little by little due to a deformation of a protection layer or an intermediate layer by a thermal expansion. The mark edge recording is a recording system such that an edge portion of a recording mark is made correspond to “1” of a signal and a portion between the marks and a portion in the mark are made correspond to “0”.
For example, a method whereby a heat capacity is reduced by thinning the recording film and a flow of the recording film is prevented by using a principle such that an influence by an adhesion between the recording film and an adjacent layer increases has been disclosed in a literature 1, “T. Ohta et al., “Optical Data Storage”, '89 Proc. SPIE, 1078, 27 (1989)”. A method whereby a component of a high melting point is added into a recording film and a flow of the recording film is prevented has been disclosed in a literature 2, “Hirotsune, Terao, Miyauchi, Minemura, and Fushimi, the Record, p1000, of the 41st Meeting of Applied Physics Concerned Association”. Thus, the large flow of the recording film could be suppressed. However, if the rewriting of a number of times is further repeated, a fluctuation in reflectance level occurs.
To improve overwrite jitter characteristics in the mark edge recording, a disk in which transmitted light is increased has been proposed in a literature 3, “Okubo, Murabatake, Ide, Okada, and Iwanaga, the Record, p98, of the 5th Meeting of the Society of Research of Phase Change Recording”. The disk is constructed by a PC substrate/ZnS−SiO
2
(250 nm)/Ge
2
Sb
2
Te
5
(15 nm)/ZnS−SiO
2
(18 nm)/Si (65 nm).
In JP-A-8-329525, the applicant of the present invention has already disclosed the invention in which a reflection layer is constructed by two layers, a material of the reflection layer is a combination of Al and Si, and a refractive index and an attenuation coefficient of the reflection layer are specified.
Although not become prior art yet, in Japanese Patent Application No. 8-328183 (1996), the applicant of the present invention has already disclosed that Al and the like are used as main components of a first metal layer and a second metal layer and a content of Al and the like of the second metal layer is set to be larger than that of Al and the like of the first metal layer provided near a recording film.
In the specification, a term of “phase change,” is used as a word including not only the phase change between crystal—amorphous but also a phase change between a fusion (change to a liquid phase) and a recrystallization and a phase change between a crystal state—a crystal state.
DISCLOSURE OF INVENTION
Any of the conventional information recording media has a problem such that in case of using it as a rewritable information recording medium of a phase transition type of a high density using the mark edge recording, an increase in jitter due to the rewriting, an increase in jitter at the time of rewriting of a number of times, and a fluctuation in reflectance level occur because erasing characteristics are insufficient.
It is, therefore, an object of the invention to provide an information recording medium in which even if the rewriting is executed or the rewriting is executed a number of times, preferable recording and reproducing characteristics are held, an increase in jitter is smaller, and a fluctuation of a reflectance level is smaller than those of a conventional medium.
(1) The medium of the invention is characterized in that it has a structure such that an information recording thin film which is formed on a substrate and records and/or reproduces information by an atomic arrangement change which occurs by receiving an irradiation of light is provided as a recording layer, at least one protection layer is provided, the protection layer and recording layer are laminated in order from the light incident side, and at least one reflection layer is subsequently laminated through at least one intermediate layer, the recording layer satisfies
Ge
x−w
Sb
y
Te
z
M
w
and lies within a range which satisfies
0.13≦x≦0.22, 0.20 ≦y≦0.32,
0.53≦z≦0.60, w≦0.06, and x+y+z=1
and M consists of any one of
Na, Mg, Al, P, S, Cl, K, Ca, Sc, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nb, Ru, Rh, Cd, In, Sn, I, Cs, Ba, La, Hf, Ta, Re, Os, Ir, Hg, Tl, Pb, Th, U, Ag, Cr, W, Mo, Pt, Co, Ni, Pd, Si, Au, Cu, V, Mn, Fe, Ti, and Bi.
(2) The information recording medium according to (1) is characterized in that the reflection layer comprises a first reflection layer and a second reflection layer which are made of materials of different compositions.
(3) The information recording medium according to (1) is characterized in that the reflection layer comprises a first reflection layer and a second reflection layer which are made of materials in which at least ones of refractive indices or attenuation coefficients are different.
(4) The information recording medium according to any one of (1) to (3) is characterized in that the M is at least one element selected from a group including Ag, Cr, W, and Mo.
(5) The information recording medium according to any one of (1) to (3) is characterized in that the M is at least one element selected from a group including Pd, Pt, and Co.
(6) The information recording medium according to any one of (1) to (5) is characterized in that the protection layer includes a layer containing ZnS of 70 mol % or ore.
(7) The information recording medium according to any one of (1) to (5) is characterized in that the protection layer has a layer of a composition in which at least 90% or more of the total number of atoms is close to any one of (ZnS)—(SiO
2
), (ZnS)—(Al
2
O
3
), (ZnS)—(Al
2
O
3
)—(SiO
2
), and (ZnS)—(Ta
2
O
5
) or a mixture composition thereof.
(8) The information recording medium according to any one of (1) to (5) is characterized in that the protection layer has a layer made of a material containing Al—O of 70 mol % or more.
(9) The information recording medium according to any one of (1) to (5) is characterized in that the protection layer includes two layers made of materials of different compositions.
(10) The information recording medium according to any one of (1) to (5) is characterized in that the protection layer includes at least two layers of a film containing ZnS of 70 mol % or more and a film containing Al—O or Si—O of 70 mol % or more.
(11) The information recording medium according to any one of (1) to (5) is characterized in that the protection layer includes a film containing at least one of Al—O and Si—O of 70 mol % or more is provided between the film containing ZnS of 70 mol % or more and the recording film.
(12) The information recording medium according to (2) or (3) is characterized in that a component of 95% or more of the
Ando Keikichi
Fukui Yukio
Hirotsune Akemi
Ikari Yoshihiro
Miyamoto Makoto
Antonelli Terry Stout & Kraus LLP
Evans Elizabeth
Hitachi , Ltd.
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