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US 5,620,792 AGranted
Magneto-optic recording medium having constant reflectance over a range of wavelengths
AssigneeImation Corp.
InventorWilliam A. Challener, IV
Life of this patent
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Abstract
A multilayer medium comprising a substrate, a composite dielectric layer, a magneto-optic recording layer, another dielectric layer, and a reflective layer. The composite dielectric layer has two sublayers made of different materials with distinct refractive indices, or alternatively has a single layer with a refractive index gradient. The refractive index of the portion of the composite dielectric layer adjacent the substrate is about 0.3 to 1.0 greater than the refractive index of the portion of the composite dielectric layer adjacent the recording layer.
Claims22
A magneto-optic recording medium, comprising, in order:
- a substrate;
- a first dielectric layer, comprised of at least one layer;
- a magneto-optic recording layer;
- a second dielectric layer;
- and
- a reflective layer;
- wherein the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, wherein n.sub.1 -n.sub.2, .DELTA.n, is within the range of from about 0.3 to 1.0, and wherein the medium is optically tuned over a range of wavelengths so that the medium has a specular reflectance at normal incidence within the range of about 18% to 30% over a range of wavelengths from 400 nm to 850 nm.
4 more elements
A magneto-optic recording medium, comprising, in order:
- a substrate;
- a first dielectric layer, comprised of at least one layer;
- a magneto-optic recording layer;
- a second dielectric layer;
- and
- a reflective layer;
- wherein the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, wherein n.sub.1 - n.sub.2, .DELTA.n, is within the range of from about 0.3 to 1.0, and wherein the medium is optically tuned over a range of wavelengths so that the medium has a specular reflectance at normal incidence having maximum and minimum values over a range of wavelengths from 400 nm to 850 nm, wherein the maximum value is less than 1.25 times as great as the minimum value.
4 more elements
A magneto-optic recording medium, comprising, in order:
- a substrate;
- a first dielectric layer comprised of at least one layer;
- a magneto-optic recording layer for creating a magneto-optical rotation effect;
- a second dielectric layer;
- and
- a reflective layer;
- wherein:
- the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, wherein n.sub.1 - n.sub.2, .DELTA.n, is within the range of from about 0.3 to 1.0;
- wherein the medium has a specular reflectance at normal incidence which varies over a range of wavelengths from 400 nm to 850 nm;
- and
- values of n.sub.1 and n.sub.2, and the thicknesses of the layers are such that the specular reflectance is within the range from 18% to 30% over said wavelength range while the magneto-optical rotation effect is retained.
8 more elements
A magneto-optic recording medium, comprising, in order:
- a substrate;
- a first dielectric layer comprised of at least one layer;
- a magneto-optic recording layer for creating a magneto-optical rotation effect;
- a second dielectric layer;
- and
- a reflective layer;
- wherein:
- the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, and wherein n.sub.1 - n.sub.2, .DELTA.n, is within the range of from about 0.3 to 1.0;
- wherein the medium has a specular reflectance at normal incidence which varies over a range of wavelengths from 400 nm to 850 nm;
- and
- values for n.sub.1 and n.sub.2 and the thicknesses of the layers are selected to optimize the specular reflectance, R, and ellipticity, .epsilon., of the medium, while retaining the magneto-optical rotation effect, for a range of wavelengths so that the specular reflectance over the range from 400 to 850 nm is within the range from 18-30%.
8 more elements
A magneto-optic recording medium, comprising, in order:
- a substrate;
- a first dielectric layer comprised of at least one layer;
- a magneto-optic recording layer for creating a magneto-optical rotation effect;
- a second dielectric layer;
- and
- a reflective layer;
- wherein:.
- the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, and wherein n.sub.1 - n.sub.2, .DELTA.n, is within the range of from about 0.3 to 1.0;
- wherein the medium has a specular reflectance, R, at normal incidence having maximum and minimum values over a range of wavelengths from 400 nm to 850 nm;
- and
- values for n.sub.1 and n.sub.2 and the thicknesses of the layers are selected to optimize the specular reflectance, R, and ellipticity, .epsilon., of the medium, while retaining the magneto-optical rotation effect, for a range of wavelengths so that the maximum value of the specular reflectance is less than 1.25 times as great as the minimum value over the range from 400 to 850 nm.
8 more elements
A magneto-optic recording medium, comprising, in order:
- a substrate;
- a first dielectric layer comprised of at least one layer;
- a magneto-optic recording layer for creating a magneto-optical rotation effect;
- a second dielectric layer;
- and
- a reflective layer;
- wherein:
- the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, and wherein n.sub.1 - n.sub.2, .DELTA.n, is within the range of from about 0.3 to 1.0;
- wherein the medium has a specular reflectance at normal incidence having maximum and minimum values over a range of wavelengths from 400 nm to 850 nm;
- and
- the values of n.sub.1 and n.sub.2 and the thicknesses of the layers are such that the maximum value of the specular reflectance is less than 1.25 times as great as the minimum value over said wavelength range while the magneto-optical rotation effect is retained.
8 more elements
A magneto-optic recording medium comprising, in order:
- a first dielectric layer having a thickness t.sub.1, the first dielectric layer being comprised of at least one layer;
- a magneto-optic recording layer having a thickness t.sub.2 for creating a magneto-optical rotation effect;
- a second dielectric layer having a thickness t.sub.3 ;
- and
- a reflective layer having a thickness t.sub.4 ;
- wherein:
- the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, and wherein n.sub.1 - n.sub.2, .DELTA.n, is within the range of from about 0.3 to 1.0;
- the medium has a specular reflectance, R, at normal incidence having maximum and minimum values over a range of wavelengths from 400 nm to 850 nm;
- and
- values for t.sub.1, t.sub.2, t.sub.3, t.sub.4, n.sub.1, and n.sub.2 are selected to optimize the specular reflectance, R, and ellipticity, .epsilon., of the medium, while retaining the magneto-optical rotation effect, for a range of wavelengths so that the maximum value of the specular reflectance is less than 1.25 times as great as the minimum value over the range from 400 to 850 nm.
7 more elements
A method of making a magneto-optic recording medium, the medium comprising, in order:
- a substrate, a first dielectric layer, a magneto-optic recording layer, a second dielectric layer, and a reflective layer, the method comprising the steps of:
- selecting a first material having a first thickness t.sub.1 for use as the first dielectric layer, the first dielectric layer being comprised of at least one layer;
- selecting a second material having a thickness t.sub.2 for use as a magneto-optic recording layer, the first dielectric layer having a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at the interface with the recording layer, wherein n.sub.1 -n.sub.2, .DELTA.n, is within the range from about 0.3 to 1.0;
- selecting a third material having a thickness t.sub.3 for use as a second dielectric layer;
- selecting a fourth material having a thickness t.sub.4 for use as a reflective layer;
- selecting values for n.sub.1, n.sub.2, t.sub.1, t.sub.2, t.sub.3, and t.sub.4 so that the medium has a specular reflectance at normal incidence having maximum and minimum values over a range of wavelengths from 400 nm to 850 nm;
- and
- optically tuning the medium comprised of the ordered layers by varying the values of n.sub.1, n.sub.2, t.sub.1, t.sub.2, t.sub.3, and t.sub.4 so that the maximum value of the specular reflectance over the range from 400 to 850 nm is less than 1.25 times as great as the minimum value.
5 more elements
A method of making a magneto-optic recording medium, wherein the medium has a specular reflectance at normal incidence within the range of 18% to 30% over a range of wavelengths from 400-850 nm, the medium comprising, in order, a substrate, a first dielectric layer, a magneto-optic recording layer, a second dielectric layer, and a reflective layer, the method comprising the steps of:
- depositing the first dielectric layer on the substrate so that the first dielectric layer has a first index of refraction n.sub.1 at the interface with the substrate and a second index of refraction n.sub.2 at a side of the first dielectric layer opposite the substrate, wherein n.sub.1 -n.sub.2, .DELTA.n, is within the range from about 0.3 to 1.0;
- depositing the recording layer over the first dielectric layer;
- depositing the second dielectric layer over the recording layer;
- and
- depositing the reflective layer over the second dielectric layer.
2 more elements
Dependencies are inferred from the claim text.