Optical recording medium, method of producing the same and method of producing the optical recording card

• US 5,217,844 A
• Filed: 11/08/1989
• Issued: 06/08/1993
• Est. Priority Date: 05/08/1987
• Status: Expired due to Fees

• Current Assignee: Kyodo Printing Company Limited
• Original Assignee: Kyodo Printing Company Limited
• Inventors: Fujita, Minoru, Kakinuma, Yuji, Fukushima, Yoichi
• Primary Examiner(s): Schilling, Richard L.
• Application Number:
  US07/439,383
• Time in Patent Office: 1,308 Days
• Field of Search: 430/270, 430/495, 430/945, 430/346, 430/273, 430/616, 430/944, 430/964, 430/508, 430/945, 346/135.1
• US Class Current: 430/270.11
• CPC Class Codes: G06K 19/14 the marking being sensed by radiation
• CPC Class Codes: G11B 2007/24308 transition metal elements of group 11 (Cu, Ag, Au)
• CPC Class Codes: G11B 7/0033 with cards or other card-like flat carriers, e.g. flat sheets of optical film
• 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 7/24085 Pits
• CPC Class Codes: G11B 7/243 comprising inorganic materials only, e.g. ablative layers
• CPC Class Codes: G11B 7/257 of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
• CPC Class Codes: G11B 7/26 Apparatus or processes specially adapted for the manufacture of record carriers
• CPC Class Codes: Y10S 430/145 Infrared
• CPC Class Codes: Y10S 430/146 Laser beam
• CPC Class Codes: Y10S 430/165 Thermal imaging composition

Abstract

An optical recording medium includes a silver grain layer containing a large number of blackened fine silver grains and a coloring matter layer containing coloring matter on a base board and the coloring matter has an ability of absorbing near-infrared ray. When laser beam having a density of optical energy more than a boundary which represents a threshold with respect to the density of optical energy is radiated to the optical recording medium, a part of the latter is deformed to form a plurality of convexities which will be utilized as optical recording pit. The recording pits formed in this way are detected by presence or absence of reflection of radiated light whereby the content of optical recorded informations can be read. The optical recording pits are not deformed further irrespective of how long a reading light comprising laser beam having a density of energy less than the threshold is repeatedly radiated to the optical pits. Accordingly, any reduction of S/N ratio of a signal does not take place as time elapses.

Claims

1. A method of producing an optical recording medium in which an intensity of reading light is below a recording threshold of the medium and in a range of 1/5 to 1/10 of that of recording light, said recording medium consisting essentially of a layer of coloring matter superposed on a photosensitive member,

wherein said method comprises the steps of forming a photosensitive member comprising a photographic emulsion layer containing silver halide grains, said photographic emulsion layer being located on a base board, blackening said photosensitive member to release silver grains by exposing said photosensitive member to light, silver halide grains of said photosensitive member being suspended in said emulsion, developing and fixing said photosensitive member, and forming a coloring matter layer constituted by dyestuff only which has a thickness in the range of 50 to 2000 angstroms and has an ability of absorbing near-infrared radiation, said coloring matter layer being located on the photographic emulsion layer.

2. A method of producing an optical recording card in which an intensity of reading light is below a recording threshold of the medium and in a range of 1/5 to 1/10 of that of recording light,

wherein said method comprises the steps of temporarily adhering to a transparent card front board an optical recording medium including a photographic emulsion layer containing a suspension of fine silver halide grains in said emulsion and a coloring matter layer constituted by dyestuff only, said coloring matter layer having a thickness in the range of 50 to 2000 angstroms and having an ability of absorbing near-infrared radiation, said adhering step placing said photographic emulsion layer and said coloring matter layer on a base board to build a layered structure in such a manner that said coloring matter layer faces said card front board, adhering a first intermediate layer to the coloring matter layer side of said card front board, adhering a second intermediate layer to said first intermediate layer and then adhering a card rear board to said second intermediate layer.

3. An optical recording card in which an intensity of reading light is below a recording threshold of the medium and in a range of 1/5 to 1/10 of that of recording light comprising

a transparent card front board, and an optical recording medium adhered to said card front board;

a first intermediate layer adhered to said optical recording medium, a second intermediate layer adhered to said first intermediate layer, and a card rear board adhered to said second intermediate layer;

wherein said card front board and said optical recording medium and said first intermediate layer and said second intermediate layer and said card rear board are superposed one above another to build a layered structure;

said optical recording medium comprises a base board and a photographic emulsion layer which has a thickness in a range of 0.1-10 microns and which includes a suspension of fine silver halide grains in said emulsion, the photographic emulsion layer being located on the base board; and

said optical recording medium further comprises a coloring matter layer constituted by dyestuff only which has a thickness in the range of 50-2000 angstroms and has an ability of absorbing near-infrared radiation, the coloring matter layer being located on the silver grain layer, the base board and the photographic emulsion layer and the coloring matter layer being superposed one above another to form a layered structure wherein said coloring matter layer faces said card front board.

4. An optical recording medium in which an intensity of reading light is below a recording threshold of the medium and in a range of 1/5 to 1/10 of that of recording light consisting essentially of

a base board, a photographic emulsion layer and a coloring matter layer;

wherein said photographic emulsion layer comprises a suspension of fine silver halide grains, said photographic emulsion layer being located on the base board;

the coloring matter layer constituted by dyestuff only which has a thickness in the range of 50 to 2000 angstroms and has an ability of absorbing near-infrared radiation, the coloring matter layer being located on said photographic emulsion layer;

said photographic emulsion layer and the coloring matter layer are superposed one above another to build a layered structure, at least a part of the photographic emulsion layer being blackened by exposure to light followed by developing and fixing, wherein at least another part of the said photographic emulsion layer is blackened by exposure to light to build an optical recording portion; and

said optical recording medium has a threshold level of light energy density of at least 3 mW/5 μ

mφ

for deformation of said optical recording medium.