Data storage medium having reflective particulate silver layer

• US 4,269,917 A
• Filed: 07/14/1980
• Issued: 05/26/1981
• 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 C.
• Application Number:
  US06/168,335
• Time in Patent Office: 316 Days
• Field of Search: 430/16, 430/616, 430/9, 430/346, 430/246, 430/251, 430/416, 430/414, 430/229, 430/231, 430/964, 430/945, 346/1.1, 346/76 L, 346/135.1, 428/457, 428/459
• US Class Current: 430/16
• 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
• CPC Class Codes: Y10S 430/146 Laser beam
• CPC Class Codes: Y10S 430/165 Thermal imaging composition
• CPC Class Codes: Y10T 428/31678 Of metal
• CPC Class Codes: Y10T 428/31685 Natural source polyamide [e.g., casein, gelatin, etc.]

Abstract

A reflective laser recording and data storage medium, for direct reading after writing, formed from a photosensitive silver-halide emulsion wherein a surface latent image exposure on the recording area forms a depthwise gradient of silver nuclei. A single step negative silver diffusion transfer process is used to develop silver nuclei of the latent image and dissolve unexposed silver halide elsewhere, forming silver ion complexes. These complexes are transported by diffusion transfer to the developing silver nuclei sites where silver is precipitated and adsorbed to form a high concentration of non-filamentary particles at a surface of a low melting temperature dielectric colloid matrix which is highly reflective of light and electrically non-conducting.

Claims

1. A reflective data storage medium comprising,

a low melting temperature colloid matrix supported on a substrate, and

a surface layer of non-filamentary individual silver particles, disposed in said matrix, having maximum particle dimensions primarily under 0.05 microns, some of which are aggregated with similar particles, and having a volume concentration of silver particles greater at said surface than in the interior of said matrix, said surface having an areawise substantially uniform reflectivity to visible light, said uniform reflectivity being between 15% and 75% and being electrically non-conductive.

2. The data storage medium of claim 1 wherein the volume concentration at said reflective surface layer exceeds the lowest silver volume concentration within the interior of said colloid matrix layer by a ratio of at least 5:

1.

3. The data storage medium of claim 1 wherein said reflective surface layer is less than one micron thick.

4. The data storage medium of claim 1 wherein said volume concentration of silver particles in said reflective layer is a minimum of 20% and a maximum of 70%.

5. The data storage medium of claim 1 wherein said colloid matrix layer is photographic gelatin used in the manufacture of silver-halide emulsions.

6. The data storage medium of claim 1 wherein said reflective surface layer is derived from a photographic emulsion.

7. The data storage medium of claim 6 wherein said reflective surface layer contains pre-recorded information indicia therein.

8. The data storage medium of claim 7 wherein said pre-recorded information indicia comprises a photographic image.

9. The data storage medium of claim 7 wherein said pre-recorded information indicia comprises a pattern of laser writing.

10. The data storage medium of claim 7 wherein said pre-recorded information indicia comprises a photographic image and a pattern of laser writing.

11. The data storage medium of claim 1 wherein the colloid matrix forms an underlayer component beneath said reflective layer which is transmissive of visible light.

12. The data storage medium of claim 1 wherein the colloid matrix forms an underlayer component beneath said reflective layer which is absorptive of green and blue light.

13. The data storage medium of claim 1 wherein said reflective layer of said matrix layer is distal to said substrate.

14. The data storage medium of claim 1 wherein said reflective surface layer of said matrix layer is proximate to said substrate.

15. The data storage medium of claim 1 wherein said reflective surface layer includes interspersed regions of essentially clear colloid matrix material.

16. The data storage medium of claim 1 wherein said reflective surface layer includes interspersed black regions consisting of black filamentary silver particles.

17. The data storage medium of claim 1 wherein the thickness of the colloid matrix layer is less than 15 microns.