Erasable optical data storage medium

• US 4,719,615 A
• Filed: 03/04/1986
• Issued: 01/12/1988
• Est. Priority Date: 08/22/1983
• Status: Expired due to Term

• Current Assignee: Optical Data Corp (S&P Global Inc.)
• Original Assignee: Optical Data Corp (S&P Global Inc.)
• Inventors: Skiens, W. Eugene, Gordon, N. Ross, Feyrer, Clyde D.
• Primary Examiner(s): Faber, Alan
• Application Number:
  US06/835,960
• Time in Patent Office: 679 Days
• Field of Search: 369/100, 369/111, 369/275, 369/284, 369/286, 369/288, 346/76 L, 346/135.1, 346/137, 346/77 E, 365/126, 365/120, 365/127, 365/124, 358/344
• US Class Current: 369/284
• CPC Class Codes: G11B 7/00452 involving bubble or bump forming
• CPC Class Codes: G11B 7/0055 Erasing G11B7/006, G11B7/0065 take precedence
• CPC Class Codes: G11B 7/24 Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the arrangement of information on the carrier G11B7/007
• CPC Class Codes: G11B 7/244 comprising organic materials only
• CPC Class Codes: G11B 7/245 containing a polymeric component
• CPC Class Codes: G11B 7/246 containing dyes
• CPC Class Codes: G11B 7/2467 azo-dyes
• CPC Class Codes: G11B 7/248 porphines; azaporphines, e.g. phthalocyanines
• CPC Class Codes: G11B 7/2532 comprising metals

Abstract

An erasable optical data storage medium including a substrate and a dual layer of a first material and a second material on the substrate. The dual layer is susceptible to expansion and contraction, to writing data thermally, to erasing data thermally and mechanically, and to reading data optically, the first material and the second material, respectively, being bonded together and remaining in the same physical state upon the expansion and relaxation of the dual layer. Methods and apparatus are also disclosed for recording data bits on the medium.

Claims

1. An optical recording medium comprising:

(a) a first layer of a first material;

(b) a second layer of a second material adjacent to said first material;

(c) said first and second layers cooperating as a medium for forming an optically detectable deformation therein by thermal expansion of said first material without liquefaction or gasification of said first or second materials when said first layer is locally heated with light radiation of a first preselected wavelength;

(d) said first material and said second material being sufficiently bonded to each other to enable said second layer to hold said first material in stretched, expanded condition upon cessation of said light radiation and cooling of said first material, retaining said optically detectable deformation, said second layer being sufficiently strong and rigid to hold said first material in stretched, expanded condition.

2. The medium of claim 1, said first and second layers further cooperating as an erasable optical recording medium for relaxing said optically-detectable deformation, without liquefaction or gasification of said first or second materials, when said second material is locally heated with light radiation of a second preselected wavelength.

3. The medium of claim 1 wherein said second material is adapted to substantially transmit light of said first preselected wavelength.

4. An optical recording medium comprising:

(a) a first layer of a first material having a glass transition temperature ("T_g 1");

(b) a second layer of a second material bonded to said first material, said second material having a glass transition temperature ("T_g 2") above ambient temperature and also above T_g 1;

(c) said first and second layers comprising a dual layer recording medium;

(d) said first material having a high coefficient of thermal expansion;

(e) said second material being adapted to permit localized thermal expansion of said first material when said second material is above T_g 2 and adapted to retain said first material bonded thereto in an expanded configuration when said second material is cooled below T_g 2; and

(f) said dual layer recording medium being adapted to form and retain an optically-detectable deformation therein by localized thermal expansion of said first material, without liquefaction or gasification of said first or second materials, when locally heated with light radiation of a first preselected wavelength.

5. The medium of claim 4 wherein said dual layer recording medium is adapted to permit contraction of said first material from its expanded configuration when said second material is locally heated above Tg2 by light radiation of a second preselected wavelength.

6. The medium of claim 5 wherein said second material includes second light-sensitive means for absorbing energy from light radiation of said second preselected wavelength while substantially transmitting light radiation of said first preselected wavelength.

7. The medium of claim 6 wherein said second light-sensitive means includes a dye.

8. The medium of claim 5 wherein said expanded first material, upon contraction, assists said second material to relax said optically-detectable deformation in said dual layer recording medium.

9. The medium of claim 5 wherein said first material includes elastic means for relaxing said optically-detectable deformation by pulling upon said second material bonded thereto.

10. The medium of claim 4 wherein said first and second materials are polymers.

11. The medium of claim 4 wherein said first and second materials have relatively low thermal conductivity.

12. The medium of claim 4 wherein said first material includes first light-sensitive means for absorbing energy from light radiation of said first preselected wavelength.

13. The medium of claim 12 wherein said first light-sensitive means includes a dye.

14. The medium of claim 4 wherein said second material is adapted to substantially transmit light of said first preselected wavelength.

15. The medium of claim 4 wherein said first and second materials are not metals or metal oxides.

16. The medium of claim 4 wherein said first material is elastic, having a relatively high yield strain.

17. The medium of claim 4 wherein said second material is thermoplastic or thermoset with a relatively low yield strain.

18. The medium of claim 4 wherein said second material is glassy at ambient temperature but becomes rubbery when heated above Tg2.

19. An optical recording medium comprising:

(a) a first polymer layer;

(b) a second polymer layer bonded to said first layer;

(c) said first layer having a high coefficient of thermal expansion and a first glass transition temperature ("Tg1"), said first layer adapted to produce a deformation due to localized thermal expansion upon heating;

(d) said second layer having a glass transition temperature (Tg2) which is above ambient temperature and above Tg1, said second layer being adapted to permit localized thermal expansion of said first layer when said second layer is heated above Tg2 and adapted to retain said first layer in expanded configuration when said second layer is cooled below Tg2; and

(e) said first and second layers cooperating as a medium for forming and retaining therein an optically-detectable deformation when locally heated with light radiation of a first preselected wavelength.

20. The medium of claim 19 wherein said second layer is adapted to local heating above Tg2 when exposed to light radiation of a second preselected wavelength, said first and second layers cooperating as a medium for permitting contraction of said first material from its expanded state and relaxing said optically-detectable deformation when said second material is locally heated by light radiation of said second preselected wavelength.

21. The medium of claim 19 wherein said first and second layers are adapted to cooperate to form and retain an optically-detectable deformation without liquefaction or gasification of said first or second layers.