Method for making a broadband reflective laser recording and data storage medium with absorptive underlayer

• US 4,312,938 A
• Filed: 10/17/1980
• Issued: 01/26/1982
• 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): Louie, Jr., Won H.
• Application Number:
  US06/198,242
• Time in Patent Office: 466 Days
• Field of Search: 430/246, 430/394, 430/414, 430/496, 430/415, 430/11, 430/416, 430/502, 430/407, 430/401, 430/409, 430/410, 430/616, 430/16, 430/346, 430/231, 430/229, 430/964, 430/945 , 430/510, 430/523, 430/539, 346/76 L, 346/135.1
• US Class Current: 430/496
• 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

Abstract

A broadband laser recording and data storage medium for direct read after writing, formed from a photosensitive silver-halide emulsion in four steps. First, a non-saturating actinic radiation exposure is used to create latent images. A normal photographic development is used to produce a medium of gray neutral density. The surface of the remaining silver halide is fogged in a water or alcohol based solution to create a very thin layer of silver precipitating nuclei on the surface. Finally, a single-step, negative silver diffusion transfer process is used to dissolve the unexposed and undeveloped silver halide, forming silver ion complexes. These complexes are transported by diffusion transfer to the sites of the silver precipitating nuclei and the filamentary silver on the surface, where the silver complexes are reduced to metallic silver on both the nuclei and the filamentary silver to form a high concentration of non-filamentary silver particles at the surface of a low melting temperature colloid matrix which is highly reflective of light and electrically non-conducting.

Claims

1. A negative photographic process for making a reflective optical data storage medium comprising

areawise exposing a silver-halide emulsion photosensitive medium to a uniform non-saturating level of actinic radiation,

developing said emulsion to a gray color having an optical density to red light of between 0.05 and 2.0, the optical density being directly related to the exposure, while leaving both exposed, developed silver and unexposed, undeveloped silver halide in place,

forming an areawise layer of silver precipitating nuclei on the surface of said developed emulsion at sites of undeveloped silver halide,

contacting said developed and nucleated emulsion with a monobath comprising a silver-halide solvent and a silver reducing agent, whereby unexposed and undeveloped silver halide forms soluble silver complexes and is transported by diffusion transfer to said precipitating nuclei where said silver complexes are reduced to metallic silver, leaving exposed developed silver in place, thereby producing a layer of reflective metallic primarily non-filamentary silver over a gray layer of primarily filamentary silver.

2. The method of claim 1 wherein said exposure of said photosensitive medium is carried out by directing uniform intensity actinic radiation over the surface of said photosensitive medium.

3. The method of claim 1 wherein said exposure of said photosensitive medium comprises creating a pattern of two or more levels of non-saturating actinic radiation over the surface of said photosensitive medium.

4. The method of claim 1 wherein said forming of an areawise layer of silver precipitating nuclei is carried out by contacting a surface of said photosensitive silver-halide emulsion with a fogging agent.

5. The method of claim 4 wherein said fogging agent comprises a solution of borohydride anion.

6. The method of claim 1 wherein said developing of said gray color is to an optical density between 0.1 and 0.8.

7. The method of claim 1 wherein said areawise layer of silver precipitating nuclei is formed by providing a silver precipitating layer at the air-emulsion interface of said silver-halide emulsion.

8. A negative photographic process for making a reflective optical data storage medium comprising

areawise exposing a silver-halide emulsion photosensitive medium to a uniform non-saturating level of actinic radiation,

developing the exposed silver halide of said exposed medium to low-reflective, filamentary gray silver, while leaving both exposed, developed gray silver and unexposed, undeveloped silver halide in place,

forming a layer of silver precipitating nuclei at sites of undeveloped silver halide at the surface of the gray medium,

dissolving unexposed silver halide in said medium to form soluble silver ion complexes, while leaving developed gray silver in place,

transporting by silver diffusion transfer soluble silver ion complexes to said precipitating nuclei and said developed filamentary silver and

reducing and precipitating said soluble silver complexes to reflective metallic silver at said nuclei and said developed filamentary silver in a reflective metallic layer of primarily non-filamentary silver less than one micron thick over a low-reflective gray layer of primarily filamentary silver.

9. The method of claim 8 wherein said exposure of said photosensitive medium is carried out by directing uniform intensity actinic radiation over the surface of said photosensitive medium.

10. The method of claim 8 wherein said exposure of said photosensitive medium comprises creating alternating patterns of higher and lower non-saturating levels of actinic radiation over the surface of said photosensitive medium.

11. The method of claim 8 wherein said silver precipitating nuclei is formed by creating a depthwise decreasing concentration in said reduced medium.

12. The method of claim 8 wherein said silver precipitating nuclei are formed by contacting said reduced medium with a solution of borohydride anion.

13. A negative photographic process for making a reflective optical data storage medium comprising

areawise exposing a silver-halide emulsion photosensitive medium to a moderate exposure of actinic radiation through a mask having at least two levels of optical density to the actinic radiation, where said mask is disposed between the source of said actinic radiation and said photosensitive medium,

exposing the entire silver-halide photosensitive emulsion to a weak to moderate exposure of actinic radiation,

developing said exposed emulsion to create low-reflective, gray filamentary silver, while leaving both exposed, developed gray silver and unexposed, undeveloped silver halide in place,

nucleating a surface layer of unexposed silver halide in said developed medium, whereby silver precipitating nuclei are created in said surface layer, and

contacting said nucleated emulsion with a monobath comprising a silverhalide solvent and a silver reducing agent, leaving developed gray silver in place, whereby unexposed and undeveloped silver halide forms soluble silver ion complexes and is transported by diffusion transfer to said nuclei where silver is reduced to reflective metallic silver on said nuclei and to said filamentary silver where silver is reduced to metallic silver on said filamentary silver thereby forming a reflective metallic layer of primarily non-filamentary silver over a low-reflective gray layer of primarily filamentary silver.

14. The method of claim 13 wherein said nucleating step comprises forming silver precipitating nuclei at the surface of said developed medium.

15. The method of claim 13 wherein said nucleating step comprises contacting said developed medium with a solution of a borohydride anion.