Broadband reflective laser recording and data storage medium with absorptive underlayer

• US 4,284,716 A
• Filed: 04/14/1980
• Issued: 08/18/1981
• 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:
  US06/140,136
• Time in Patent Office: 491 Days
• Field of Search: 430/616, 430/16, 430/346, 430/246, 430/416, 430/414, 430/231, 430/229, 430/964, 430/945, 430/523, 430/539, 430/510, 346/76 L, 346/135.1
• US Class Current: 430/510
• 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 7/26 Apparatus or processes specially adapted for the manufacture of record carriers
• 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 430/165 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 reflective data recording medium comprising,

a colloid matrix underlayer disposed on a substrate, said underlayer having primarily filamentary silver particles therein characterized by an optical density to red light between 0.2 and 3.0, and absorptive of visible and infrared light, and

a reflective surface layer primarily of non-filamentary individual silver particles in said colloid matrix, said reflective surface layer disposed atop said underlayer, having maximum silver particle dimensions primarily under 0.05 microns, some of which are aggregated with similar particles, and having a volume concentration of silver particles greater in said surface layer than in said colloid matrix underlayer, said reflective surface layer having at least one area having substantially uniform reflectivity, said uniform reflectivity being between 10% and 75%.

2. The data recording medium of claim 1 wherein the volume concentration of silver in said reflective surface layer exceeds the lowest silver volume concentration within said colloid matrix underlayer by a ratio of at least 3:

1.

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

4. The data recording medium of claim 1 wherein said volume concentration of silver particles in said reflective layer is a minimum of 20% and a maximum of 50%.

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

6. The data recording medium of claim 1 wherein said reflective surface layer comprises primarily non-filamentary silver particles and at least 1% filamentary silver particles of the total silver volume concentration in said reflective layer.

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

8. A data recording medium of claim 1 wherein said reflective surface layer is electrically non-conductive.