Optical information recording medium
First Claim
1. An optical information recording medium comprising on a substrate:
- a recording layer which reversibly transforms between optically detectable crystalline and amorphous states by the irradiation of a laser beam; and
a first dielectric layer and a second dielectric layer formed on a bottom and a top surface of said recording layer;
said optical information recording medium further comprising a third dielectric layer on an outside surface of at least one layer selected from the group consisting of said first dielectric layer and second dielectric layer;
said third dielectric layer having a coefficient of thermal expansion smaller than coefficients of thermal expansion of said first dielectric layer and said second dielectric layer; and
wherein said optical information recording medium comprises no metallic reflection layer, whereina difference of reflectances (Δ
R=Rcry-Ramo) is 15% or more where Rcry is a reflectance of the light beam reflected by said recording layer which is in a crystalline state, and Ramo is the reflectance of said recording layer in an amorphous state; and
wherein a difference of absorptivities (Δ
A=Acry-Aamo) is 5% or more where Acry is an absorption coefficient of the light beam absorbed by said recording layer which is in the crystalline state, and Aamo is the absorption coefficient of said recording layer in the amorphous state.
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Accused Products
Abstract
On a substrate, a recording layer which reversibly transforms between two states with different optical properties--a crystalline phase and an amorphous phase--by the irradiation of a laser beam, a first and a second dielectric layer on the bottom and the top surfaces of the recording layer, and a third dielectric layer on one surface of the first or the second dielectric layers and on the opposite side with respect to the recording layer are successively laminated, thus preparing an optical information recording medium. The third dielectric layer has a smaller coefficient of thermal expansion than the first and the second dielectric layers, so that the thermal deformation of the first and the second dielectric layers is reduced and the mass transfer of the recording layer is controlled. As a result, the overwrite cycle characteristics of the optical information recording medium are excellent.
35 Citations
19 Claims
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1. An optical information recording medium comprising on a substrate:
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a recording layer which reversibly transforms between optically detectable crystalline and amorphous states by the irradiation of a laser beam; and a first dielectric layer and a second dielectric layer formed on a bottom and a top surface of said recording layer;
said optical information recording medium further comprising a third dielectric layer on an outside surface of at least one layer selected from the group consisting of said first dielectric layer and second dielectric layer;
said third dielectric layer having a coefficient of thermal expansion smaller than coefficients of thermal expansion of said first dielectric layer and said second dielectric layer; and
wherein said optical information recording medium comprises no metallic reflection layer, whereina difference of reflectances (Δ
R=Rcry-Ramo) is 15% or more where Rcry is a reflectance of the light beam reflected by said recording layer which is in a crystalline state, and Ramo is the reflectance of said recording layer in an amorphous state; and
wherein a difference of absorptivities (Δ
A=Acry-Aamo) is 5% or more where Acry is an absorption coefficient of the light beam absorbed by said recording layer which is in the crystalline state, and Aamo is the absorption coefficient of said recording layer in the amorphous state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification