Process for making a reflective data storage medium

• US 4,278,758 A
• Filed: 09/06/1979
• Issued: 07/14/1981
• Est. Priority Date: 07/06/1979
• Status: Expired due to Term

• Current Assignee: LaserCard Corp. (Assa Abloy AB)
• Original Assignee: Drexler Technology Corporation (Assa Abloy AB)
• Inventors: Drexler, Jerome, Bouldin, Eric W.
• Primary Examiner(s): Schilling, Richard L.
• Application Number:
  US06/072,908
• Time in Patent Office: 677 Days
• Field of Search: 430/346, 430/616, 430/416, 430/414, 430/495, 430/350, 430/246, 346/1.1, 346/76 L, 346/135.1
• US Class Current: 430/616
• CPC Class Codes: G03C 5/40 Chemically transforming developed images G03C5/50 takes precedence
• CPC Class Codes: G03C 8/06 Silver salt diffusion transfer
• CPC Class Codes: G11B 7/0045 Recording G11B7/006, G11B7/0065 take precedence
• CPC Class Codes: G11B 7/013 for discrete information, i.e. where each information unit is stored in a distinct discrete location , e.g. digital information formats within a data block or sector
• 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 7/251 comprising inorganic materials dispersed in an organic matrix
• CPC Class Codes: G11B 7/261 Preparing a master, e.g. exposing photoresist, electroforming
• CPC Class Codes: G11B 7/28 Re-recording, i.e. transcribing information from one optical record carrier on to one or more similar or dissimilar record carriers
• CPC Class Codes: G11C 13/048 using other optical storage elements

Abstract

A method for making a reflective data storage medium by creating a volume concentration gradient of silver precipitating nuclei on one surface of a silver halide emulsion coated photoplate. This volume concentration is then built up by a silver diffusion transfer negative development using primarily solution physical development until the surface becomes reflective. Lastly, a thermal annealing step is used to increase reflectivity, recording sensitivity and produce a more uniform contrast ratio.

Claims

1. A method of making a reflective electrically non-conducting data storage medium comprising,

forming an areawise, latent image exposure in a photosensitive silver-halide emulsion layer disposed on a substrate, thereby defining an area for data storage, said exposure creating an areawise layer of silver precipitating nuclei having a volume concentration gradient through the depth of the emulsion, said emulsion having unexposed photosensitive silver-halide remaining therein in concentrations inversely related to said nuclei concentration,

contacting said unexposed photosensitive silver-halide emulsion layer with an aqueous monobath comprising a weak silver-halide developing agent for developing said latent image and a rapid-acting silver-halide solvent for reacting with unexposed and undeveloped silver halide to form soluble silver ion complexes which are transported by chemical diffusion transfer to said silver-precipitating nuclei of said latent image where silver of said silver ion complexes is precipitated and adsorbed on said nuclei in the presence of said developer acting as a reducing agent, thereby forming a reflective electrically non-conducting silver negative of said latent image in said area for data storage, and

heating said reflective electrically non-conducting data storage medium at least to 250°

C. until the reflectivity of the surface increases by at least 5% of the initial reflectivity percentage.

2. The method of claim 1 wherein said heating is carried out in air.

3. The method of claim 1 wherein heating is carried out in an oxygen containing atmosphere.

4. The method of claim 1 wherein said heating is carried out in an oxygen atmosphere.

5. The method of claim 1 wherein said heating is carried out at a temperature of at least 280°

C.

6. The method of claim 1 wherein said heating is by means of radiant heating.

7. The method of claim 1 wherein said heating is carried out for a time of between one-half minute and 20 minutes.

8. The method of claim 1 wherein said heating is carried out for a time of between one and five minutes.

9. A method of making a reflective electrically non-conducting data storage medium of the type wherein information is recorded by laser writing at a specified wavelength comprising,

forming an areawise, latent image exposure in a photo-sensitive silver-halide emulsion layer disposed on a substrate, thereby defining an area for data storage, said exposure creating an areawise layer of silver precipitating nuclei having a volume concentration gradient through the depth of the emulsion, said emulsion having unexposed photosensitive silver-halide remaining therein in concentrations inversely related to said nuclei concentration,

contacting said unexposed photosensitive silver-halide emulsion layer with an aqueous monobath comprising a weak silver-halide developing agent for developing said latent image and a rapid-acting silver-halide solvent for reacting with unexposed and undeveloped silver halide to form soluble silver ion complexes which are transported by chemical diffusion transfer to said silver-precipitating nuclei of said latent image where silver of said silver ion complexes is precipitated and adsorbed on said nuclei in the presence of said developer acting as a reducing agent, thereby forming a reflective electrically non-conducting silver negative of said latent image in said area for data storage, and

heating said reflective electrically non-conducting data storage medium at least to 250°

C. until the absorptivity of the emulsion layer rises to at least 20% at the wavelength of a laser to be used for recording.

10. The method of claim 9 wherein said heating is carried out in air.

11. The method of claim 9 wherein heating is carried out in an oxygen containing atmosphere.

12. The method of claim 9 wherein said heating is carried out in an oxygen atmosphere.

13. The method of claim 9 wherein said heating is carried out at a temperature of at least 280°

C.

14. The method of claim 9 wherein said heating is by means of radiant heating.

15. The method of claim 9 wherein said heating is carried out for a time of between one-half minute and 20 minutes.

16. The method of claim 9 wherein said heating is carried out for a time of between one and five minutes.