Erasable optical data storage medium and method for recording data on the medium

Claim 1

An erasable optical data storage medium, comprising: a) a substrate; and b) a dual layer of a first material and a second material on said substrate, said dual layer being susceptible to expansion and relaxation, to writing data thermally, to erasing data thermally and mechanically, and to reading data optically, said first material and said second material being bonded together, and said first material and said second material, respectively, remaining in the same physical state upon said expansion and said relaxation of said dual layer.

Claim 58

A method of writing data on an erasable optical data storage medium having a substrate and a dual layer on the substrate of a first material and a second material bonded together, said first material being elastic and said second material having a glass transition temperature, comprising: a) heating the first material to elastically expand the first material within the elastic limit of the first layer, a small amount of heat also heating the second material above the glass transition temperature to make the second material rubbery; b) allowing the heated first material to expand and push up the heated second material as the heated first material expands elastically; and c) cooling the expanded second material to below the glass transition temperature while the first material is in a stretched, expanded condition, the cooled second material then having a reversibly fixed deformation and holding the first material in the stretched, expanded condition.

Claim 59

A method of writing data on an erasable optical data storage medium having a substrate and a dual layer on the substrate of a first material and a second material bonded together, said first material being elastic and said second material having a glass transition temperature, comprising: a) heating the first material to elastically expand the first material within the elastic limit of the first layer, a small amount of heat also heating the second material above the glass transition temperature to make the second material rubbery; b) allowing the heated first material to expand and push up the heated second material as the heated first material expands elastically; and c) cooling the expanded second material to below the glass transition temperature while the first material is in a stretched, expanded condition, the cooled second material then having a reversibly fixed deformation and holding the first material in the stretched, expanded condition.

Claim 63

A method, according to claim - 58, wherein the second material is viscous and lightly cross-linked to prevent viscous flow, and the step of allowing the heated second material to relax includes allowing elastic forces of the expanded first material and forces due to the stretched cross-linking of the expanded second material to pull down the second material to its relaxed state.

Claim 65

A method of writing data on an erasable optical data storage medium having a substrate and a dual layer on the substrate of a first material and a second material bonded together, said first material being elastic and said second material having a glass transition temperature above ambient temperature, comprising: a) heating the second material above the glass transition temperature to cause the second material to become rubbery; b) heating the first material to elastically expand the first material within the elastic limit of the first material; c) allowing the heated first material to expand and push up the heated second material as the heated first material expands elastically; and d) cooling the expanded second material below the glass transition temperature ' while the first material is in a stretched, expanded condition, the cooled second material then having a reversibly fixed deformation and holding the first material in the stretched, expanded condition.

Claim 66

A method of writing data on an erasable optical data storage medium having a substrate and a dual layer on the substrate of a first material and a second material bonded together, said first material being elastic and said second material having a glass transition temperature above ambient temperature, comprising: a) heating the second material above the glass transition temperature to cause the second material to become rubbery; b) heating the first material to elastically expand the first material within the elastic limit of the first material; c) allowing the heated first material to expand and push up the heated second material as the heated first material expands elastically; and d) cooling the expanded second material below the glass transition temperature ' while the first material is in a stretched, expanded condition, the cooled second material then having a reversibly fixed deformation and holding the first material in the stretched, expanded condition.

Claim 71

A method of recording data on an erasable optical data storage medium having a substrate and a dual layer of a first material and a second material on the substrate, said dual layer corresponding to one data bit stored at one location on the erasable optical data storage medium, comprising the steps of: a) erasing the one data bit stored at the one location on the erasable optical data storage medium, including heating the second material; and b) writing another data bit at the one location on the erasable optical data storage medium while the second material has not yet cooled.

Claim 72

A method of recording data on an erasable optical data storage medium having a substrate and a dual layer of a first material and a second material on the substrate, said dual layer corresponding to one data bit stored at one location on the erasable optical data storage medium, comprising the steps of: a) erasing the one data bit stored at the one location on the erasable optical data storage medium, including heating the second material; and b) writing another data bit at the one location on the erasable optical data storage medium while the second material has not yet cooled.

Claim 77

A method of recording data on an erasable optical data storage medium having a substrate and a dual layer of a first material and a second material on the substrate, the dual layer being susceptible to expansion and relaxation, to writing data thermally, to erasing data thermally and mechanically, and to reading data optically, the first material and the second material being bonded together, the first material and the second material, respectively, remaining in the same physical state upon the expansion and relaxation of the dual layer, and the expanded or relaxed condition of the dual layer representing one data bit stored at one location of the erasable optical data storage medium, comprising the steps of: a) first erasing the one data bit stored at the one location on the erasable optical data storage medium, including: i) generating a first laser beam; ii) focusing the first laser beam through an objective lens onto the second material; and iii) heating the second material with the focused first laser beam to a rubbery condition; and b) then writing another data bit stored at the one location on the erasable optical data storage medium, including: i) generating a second laser beam, ii) focusing the second laser beam through the objective lens and the second material onto the first material during the same view by the objective lens of the second material, iii) heating the first material to elastically expand the first material on the second material, with the first material remaining in contact with the substrate; and iv) cooling the second material to form a reversibly fixed deformation in which the second material holds the first material in an expanded condition.

Claim 78

A method of recording data on an erasable optical data storage medium having a substrate and a dual layer of a first material and a second material on the substrate, the dual layer being susceptible to expansion and relaxation, to writing data thermally, to erasing data thermally and mechanically, and to reading data optically, the first material and the second material being bonded together, the first material and the second material, respectively, remaining in the same physical state upon the expansion and relaxation of the dual layer, and the expanded or relaxed condition of the dual layer representing one data bit stored at one location of the erasable optical data storage medium, comprising the steps of: a) first erasing the one data bit stored at the one location on the erasable optical data storage medium, including: i) generating a first laser beam; ii) focusing the first laser beam through an objective lens onto the second material; and iii) heating the second material with the focused first laser beam to a rubbery condition; and b) then writing another data bit stored at the one location on the erasable optical data storage medium, including: i) generating a second laser beam, ii) focusing the second laser beam through the objective lens and the second material onto the first material during the same view by the objective lens of the second material, iii) heating the first material to elastically expand the first material on the second material, with the first material remaining in contact with the substrate; and iv) cooling the second material to form a reversibly fixed deformation in which the second material holds the first material in an expanded condition.

Claim 79

A system for recording a data bit, comprising: a) an erasable optical data storage medium, including i) a substrate having a low coefficient of thermal expansion; and ii) a dual layer of a first material and a second material on said substrate, said dual layer being susceptible to expansion and relaxation, to writing data thermally, to erasing data thermally and mechanically, and to reading data optically, said first material and said second material being bonded together, and said first material and said second material, respectively, remaining in the same physical state upon said expansion-- and said relaxation of said dual layer; b) means for generating a first laser beam and a second laser beam, said first material being absorptive of, and said second material being substantially transparent to, said first laser beam, and said second material being absorptive of said second laser beam; c) means for focusing said first laser beam on said first material to heat and elastically expand said first material onto said second material to write the data bit; d) means for focusing said second laser beam on said second material to heat said second material and to erase the data bit; and e) means for moving said erasable optical data storage medium relative to said first laser beam and said second laser beam.

Claim 80

A system for recording a data bit, comprising: a) an erasable optical data storage medium, including i) a substrate having a low coefficient of thermal expansion; and ii) a dual layer of a first material and a second material on said substrate, said dual layer being susceptible to expansion and relaxation, to writing data thermally, to erasing data thermally and mechanically, and to reading data optically, said first material and said second material being bonded together, and said first material and said second material, respectively, remaining in the same physical state upon said expansion-- and said relaxation of said dual layer; b) means for generating a first laser beam and a second laser beam, said first material being absorptive of, and said second material being substantially transparent to, said first laser beam, and said second material being absorptive of said second laser beam; c) means for focusing said first laser beam on said first material to heat and elastically expand said first material onto said second material to write the data bit; d) means for focusing said second laser beam on said second material to heat said second material and to erase the data bit; and e) means for moving said erasable optical data storage medium relative to said first laser beam and said second laser beam.