CA1143475A - Laser pyrographic reflective recording medium - Google Patents
Laser pyrographic reflective recording mediumInfo
- Publication number
- CA1143475A CA1143475A CA000344824A CA344824A CA1143475A CA 1143475 A CA1143475 A CA 1143475A CA 000344824 A CA000344824 A CA 000344824A CA 344824 A CA344824 A CA 344824A CA 1143475 A CA1143475 A CA 1143475A
- Authority
- CA
- Canada
- Prior art keywords
- silver
- reflective
- recording
- coating
- laser
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2407—Tracks or pits; Shape, structure or physical properties thereof
- G11B7/24085—Pits
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
- G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
- G03C5/26—Processes using silver-salt-containing photosensitive materials or agents therefor
- G03C5/40—Chemically transforming developed images
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/0045—Recording
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/251—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials dispersed in an organic matrix
Abstract
Abstract A recording medium for laser writing and a method of making same wherein a silver-halide emulsion coating disposed on a substrate is strongly exposed to actinic radiation and then developed, or otherwise processed for maximum black-ness. The black opaque emulsion is converted to a reflective recording medium by heating at least to 250° C in an oxygen containing environment until the emulsion coating assumes a shiny reflective appearance. Prior to developing, patterns may be photographically imposed on the medium to provide control indicia for the recording system or data base information to a playback system or to provide a means of replicating master recordings.
Description
~ : ' ` ,~
` ~43~75 1LASER PYROGRAP~IlC REFLEGllIVE l'.EC~ORDIN(~ MEDIUM
3_oss Refe~ ence to Related Application 4This is a continuation-in-part of application S.N. 921,723 filed August 17, 51978, now abandoned 6Background of the Invention 7 a. Field of the Invention. The inventicn relates to dat~ storage media, 8 and more particularly to a storage medium useflll for directly reading laser writing 9 immediately after laser writing.
b. Prior Art. Previously, many t~Tpes of opticnl recording media have 11 been developed for laser writin~. For example, an article in Optical En~neerin~, 12 Vol. 15, No. 2, Mnrch-April, 1976, p. ~9 discusses properties of a large.number of 13 media. Some of these media require post write processing before they can be read, 14 ¦ and some can be read immediately after laser writing. The media of interest herein 15 ¦ are for "direct read after write" capability, commonl~7 known as "DRAW" media~
16 ¦ Presently l~nown laser D~AW media are thin metal films in which holes may be ~7 melted~ composite shiny films whose reflectivity at a spot may be reduced by 18 evaporation, thin films of dyes or other coatings which can be ablated at a spot, 19 and dielectric materials whose refractive-index may be changed at a point~ causing ~O a scattering of light when scanned with fl read laser.
21 Today, these media are generally manufactured by means of vacuurn 22 deposition on a batch basis rather than cortimlous-flow basis and are therefore 23 expensive ancl it is difficult to achieve a uniformity of quality for large production 24 quantities of the product since many batches would be involved. Refractive-iadeY.-change materials which have been proposed for futllre manufacture on a continuous ~e6 basis have the disadvantage that in order for these media to be read by reflection, 27 a metal ùndercoating must be applied, thereby introducing a batch type production 28 process with the above ment;oned disadvantages.
~0 ,' 31 ~ '? ~
(~
~ 3475 1 Tlle most commoll VRAW media are thin metal films, usually on a glass
` ~43~75 1LASER PYROGRAP~IlC REFLEGllIVE l'.EC~ORDIN(~ MEDIUM
3_oss Refe~ ence to Related Application 4This is a continuation-in-part of application S.N. 921,723 filed August 17, 51978, now abandoned 6Background of the Invention 7 a. Field of the Invention. The inventicn relates to dat~ storage media, 8 and more particularly to a storage medium useflll for directly reading laser writing 9 immediately after laser writing.
b. Prior Art. Previously, many t~Tpes of opticnl recording media have 11 been developed for laser writin~. For example, an article in Optical En~neerin~, 12 Vol. 15, No. 2, Mnrch-April, 1976, p. ~9 discusses properties of a large.number of 13 media. Some of these media require post write processing before they can be read, 14 ¦ and some can be read immediately after laser writing. The media of interest herein 15 ¦ are for "direct read after write" capability, commonl~7 known as "DRAW" media~
16 ¦ Presently l~nown laser D~AW media are thin metal films in which holes may be ~7 melted~ composite shiny films whose reflectivity at a spot may be reduced by 18 evaporation, thin films of dyes or other coatings which can be ablated at a spot, 19 and dielectric materials whose refractive-index may be changed at a point~ causing ~O a scattering of light when scanned with fl read laser.
21 Today, these media are generally manufactured by means of vacuurn 22 deposition on a batch basis rather than cortimlous-flow basis and are therefore 23 expensive ancl it is difficult to achieve a uniformity of quality for large production 24 quantities of the product since many batches would be involved. Refractive-iadeY.-change materials which have been proposed for futllre manufacture on a continuous ~e6 basis have the disadvantage that in order for these media to be read by reflection, 27 a metal ùndercoating must be applied, thereby introducing a batch type production 28 process with the above ment;oned disadvantages.
~0 ,' 31 ~ '? ~
(~
~ 3475 1 Tlle most commoll VRAW media are thin metal films, usually on a glass
2 substrate. Thin metal films have several advantages: Pirst, they can be producec1
3 easily in small quantities with commerciaUy available sputtering equipment. Second,
4 they can be read either by reflection or by transmission. Third, films of tellurium and bismuth have relatively high recording sensitivities.
6 Ii ortunately, for all of these reasons, metal films have enabled a large 7 amount of research to be conducted and progress to be made in the design of optical 8 data storage systems. To date, tellurium has evolved as the most widely used of~
9 the metal films. However, tellurium must be mam~factured by an expensive, batch-type, vacuum sputtering technique; it does not form a tenacious coating; and ~11 it introduces manufacturing and environmental complications because of its toxicity.
12 In ll.S. patent 3,911,444 I,ou, Watson, and Willens disclose a vacuum-13 deposited metal film recording media ~or laser writing incorporating a separately 14 deposited plnstic film undercoat between the rnetal film and a flexible transparent substrate in order to re~uire less energy to write with a laser and to prevent impurity transfer between the substrate and the radiation absorbing film.
17 In Example I of U.S. patent 3,567,447 Chand diseloses that upon heating 18 a processed silver-halide emulsion coated photoplate, the non-image areas, clear 19 gelatin, darkened to a transparent reddish color and the image areas assumed a reflective metallic sheen. Chand used the reddish color to delineate nonimage areas 21 to be removed chemically, therehy leaving hardened opaque image areas7 with clear non-image areas.
23 In U.S. patent 3,893,~ 29 Endo discloses exposed and partially developed 24 film for recording laser writing hy means of heating the film to cause local deformation which scatter light.
26 In U.S. patent 3,fi89,894 1,a~lra and Eng disclose exposed and developed 27 microfilm to record data by optically writing transparent bits of data with black 28 areas of the microfilm by burning holes through the black silver-halide emulsion.
''" ' . ~ ' ~3~ S
Many other patents reveal light absorptive media for recording laser writing. My objactive was to devise a moderate-ly reflective DRAW laser recording material which may be manu-factured without the use of a vacuum system and on a continuous basis and which may be used to record non-reflective spots in a reflective field with relatively low energy laser pulses.
Another objective was to devise a laser recording medium which permits the pre-recording of control indicia and certain data base data by normal photographic means to facilitate the use of discs or plates in both the recording apparatus and the playback apparatus.
Temperatures between 280C and 340C are preferred to produce the reflective coating during a time cycle on the order of one-half minute to 20 minutes. Heating methods include the use of a convection oven, a contacting hot source, or radiant heating. A resulting shiny reflective emulsion coated trans-parent or absorptive substrate is a DRAW laser pyrographic reflective recording medium.
An advantage of the recording medium of the present invention is that it may be made on a continuous flow basis.
The emulsion coating is tenacious with respect to its substrate and is not toxic when laser writing ablates portions of the coating. Another advantage is that the emulsion coating may be previously exposed to desired patterns by normal photographic means to provide control indicia for the recording apparatus and/or playback apparatus and for replication of master disc recordings.
According to a broad aspect, the present invention provides an information storage medium for pyrographically recording laser writing comprising a sheet substrate and a refle~tive surface coating disposed on the sheet substrate, the reflective coating comprising reflective silver particles which _ ~347~5 are characterized by a gold color and are distributed within a gelatin matrix.
The information storage medium may be made by photo-graphically processing a silver-halide emuls.ion coating on a substrate to blackness, and thermally converting said black photographically processed silver-halide emulsion coating by heating at least to 250C in an atmosphere having a substantial percentage of oxygen at least until a gold colored reflective component appears on the emulsion coating surface.
-3a-,~
2 Brief Descril-tion of the D~@
Figure 1 is a top plan view of the recording medium of the present invention.
6 Figure 2 is a side sectional view of l:he recording medium of 7 Figure 1.
8 Figures 3-7 are detail views of the recordmg medium of Figure 1 showi~g--9 sequential processing steps for making the finished recording medium.
~igure 8 is a side sectional view of the recording medium of Figure 1 11 showing laser writing.
` ~ ~2 .
13 Description of the Preferred Embodiment . . .
Fi,gllre 1 shows a d-sc lt having an inner periphery 13 and an outer 16 periphery 15. The interior of the inner periphery 13 is ~oid so that a centering collar may be used to hold dise 11 on a splndle for high spee~ rotntion. Wbile the - ~ ~ 18 recordm~ medlum o~ the present invention is described as a disc, a disc configur~tion ;~ ~ is not essential for operating of the recording medium. l~or exarnple, the recording medium may be a flat sheet-lilce material which could be squa~re and with a central 21 hub rather than a hole. It could also be a non rotating rectangulal plate. However, 22 rotating discs are preferred for fnst random access to medium amounts of data and 23 non-rotating rectangular plates in stacks are preferred to provide intermediate speed 29 random access to large amounls of data by mechanically selecting a plate and scanning it by rnechanical and eleetro-optical means.
~6 The disc of ~igure 1 is photographically partitioned into reeording and 27 non-recording arefls. For example~ a first annular recording zone 17 could be spaced 28 ~ ~ from r sec d annular recordin zone 13 by an nnnular guard zone 2l. The function : -~-/' :
" ~ 3~
1 OI the guar(l 7.0ne may be to separ ate different recording fields, to carry control 2 information, such as timing signals and to provide space for data read-write trans-3 ducers to reside when not over recording areas. While such guard bands are preferable, 4 they are not essential to the operation of the present invention. It should be noted ~ that the recording fields are for data and control signal recording, while the guard 6 band is not for data recording, but may have control signal recording thereon. The 7 recording field l9 is shown to have a plurality of concentric, circumferentially-spaced 8 servo tracks 23 thereon. Such servo tracks are thin lines which define the spaces 9 between circular paths wherein data are written. The pattern for such lines is 10 applied photographicRlly as explainecl below with reference to Figures 3--7.
11 ~igure 2 shows a side sectional view of the recording medium of Figure 12 1. The medium consists of a substrate 27 which is a sheet-like layer which is transparent, translucent, or opaque; preferably a high temperature, dimensionally 14 stable material, like glass, ceramic, and thermoset and thermoplastic polyimide ~15 plastics. One of the requirements of the substrate material is that it withstand :L6 temperatures to at least 280C and most likely 320C but up to 34ûC, without 17 thermal deformation. Transparency or absorptivity of the substrate is desired so :L8 that when the light beam of the reflective playback apparatus impinges upon a 19 recorded spot, It either paæes through the substrate or is absorbed by it with 20 minimum reflection. If the substrate is absorptive, it may be absorptive at the 2~ wavelengths of the recording beam or the reading beam, or both. Thus, not all common photographic substrates may be used. For example, the most common 23 photo~,rraphic film bases are polyester polyterephfllate, polycarbonate, or eellulose 2a, triacetate--which normally have maximum continuous operating temperatures of ~6 145C, 132C, and 205C, respectively. Further, in order to coat a photographic emulsion on a substrate, it must be etchable, dimensionally stable, non-destructible 28 by slmlight, h~ve ~ood mechanical strength, and should also be relatively inexpensive 29 and currently available in adequate quantities. Further, when lata recordings are to be read only in reflection rather than transmission, the substrate may be a non-reflectirlg, opaque material. There is one plastic--polymide--that meets 32 ~ _5_ ' ~ 3~75 ( .
1 nll of these conditions. It is available as a thermo-plastic and a thermoset plastic, 2 can operate at 320C for mimltes7 an-l is etchable with alkalines.
3 E~or the case where the substrate is transparent, the recording medium 4 may be read in a transmissive mode, for example as in U. S. patent application serial No. ~45,332, entitled Error Checking Method and Apparatus for Digital Data 6 in Optical Recording Systems, assigned to the assignee of the present invention.
7 The thickness of the substrate is not critical when the lnser beam is B directed onto the surface as shown in Figure 8, but it should have sufficient thickness 9 to provide strength for resistance against breakage. If the laser beam is directed through a transparent substrate, then in order to maintain focus of the beam the11 thickness of the transparent substrate would have to be very uniform (for example, 12 as obtainable from float glass or selected high quality drawn glass). Also, the 13 thicknes~s of the sul~strate may depend on the overall size of the recording medium 14 being used. ~or a 1~-inch disc, a thickness of 1/8 inch may be suitable.lS The purpose of substrate 27 is to support a sîlver-halide emulsion coating 16 29, which is uniformly applied to the substrate in a conventional manner and which 1~ i9 converted subsequently to layers 32 and 33 in Figure 8. Currently availaMe 18 silver-halide emulsions from 3 to B microns thick are adequate, provided they are characterized by very fine silver-halide grain size, i.e., only a small percentage of the grains are larger than 0.07 microns. This grain size ap~ears to be important21 because when grain sizes becorne larger than approximately 0.06 microns the con-22 version from Maclc to reddish coloration, which subsequently becomes metallic, appears 23 to be less complete. Emulsion coated glass plates having these characteristics are 2a~ commercially available and are Icnown as photoplates which are used to make photomasks for the manufacture of semiconductor integrated circuits. ~or example, ~!6 emulsion coated photoplates suitable for use herein are manufactured by Ag~a-27 Gaevaert of Belgium, Konishiroku Photo Industries of Japan and the Eastman Kodak 28 Company.
.
.
1~3475 1 The shiny reflective component 32 in Figure 8 results from the thermal 2 processing describe-3 herein and reflectivity does not initially exist in the emulsion.
3 At the inception the material of reflective component 32 is mostly, excepting oxygen, 4 all found in the photographic emulsion ~,which is ImiIorm in its composition. A
~ subbing layer, not shown, is usual]y used to attnch the substrate 27 to the emulsion 6 29. Fo~lowing the thermal conversion of the present invention the emulsion 29 of 7 Figure 2 produces a reflective component 32 at the emulsion surface shown in Figure 8 8, with a non-reflective underlayer 33 beneath it~ The reflective component 32 is 9 not well defined in thickness, but exhibits a silver concentration gradient, with most 10 of the silver near the surface, and less extending downwardly. Thus, althou~h ~iguré
11 8 depicts a sharp boundary for refleetive component 32, actually such is not the 12 case and is only pictured in this manner to explain the contrast which exists between 13 the surface of the material and the urlderlying emulsion. The presence of more 14 silver particles at the surface and less below after heating is surprising and not 15 completely understood. It is believed that heat causes breakup of filamentary silver 16 particles into much more mobile, smaller particles which, in the presence of oxygen 17 at the surface concentrate and become reflective.
18 Underlayer 33, while not completely depleted of silver, contains less silver 19 than reflective component 32. Optically, underlayer 33 is pflrtially transmissive to 20 red light having wavelengths of 630 nanometers and longer, so that once craters are 2~ created penetrating reflective component 32, the craters may be detected by trans-22 mission of red light through the underlayer 33, provided that the opacity of the 23 reflective layer is sufficiently great at the selected wavelength to permit detection 24 of the craters through differences in light transmission. The data contained in the 25 craters may nlso be read by changes in reflectivity of the shiny reflective component ~6 throughout the visible spectrum and into the near infrared where it is ultimately limited in its usability &lS it becomes more and more transparent and therefore less 28 reflective in the non-data areas.
' .
~9L3~L~5 ~
1 It should be noted that both the recording areas 17, l 9 and the non-2 recording guard band 21 of Figure l have silver-halide emulsion covering a glass 3 substrate. Thus, the designation of recording and non-recording areas is arbitrary 4 and the entire surface could be used for recording if desired. However, as a matter
6 Ii ortunately, for all of these reasons, metal films have enabled a large 7 amount of research to be conducted and progress to be made in the design of optical 8 data storage systems. To date, tellurium has evolved as the most widely used of~
9 the metal films. However, tellurium must be mam~factured by an expensive, batch-type, vacuum sputtering technique; it does not form a tenacious coating; and ~11 it introduces manufacturing and environmental complications because of its toxicity.
12 In ll.S. patent 3,911,444 I,ou, Watson, and Willens disclose a vacuum-13 deposited metal film recording media ~or laser writing incorporating a separately 14 deposited plnstic film undercoat between the rnetal film and a flexible transparent substrate in order to re~uire less energy to write with a laser and to prevent impurity transfer between the substrate and the radiation absorbing film.
17 In Example I of U.S. patent 3,567,447 Chand diseloses that upon heating 18 a processed silver-halide emulsion coated photoplate, the non-image areas, clear 19 gelatin, darkened to a transparent reddish color and the image areas assumed a reflective metallic sheen. Chand used the reddish color to delineate nonimage areas 21 to be removed chemically, therehy leaving hardened opaque image areas7 with clear non-image areas.
23 In U.S. patent 3,893,~ 29 Endo discloses exposed and partially developed 24 film for recording laser writing hy means of heating the film to cause local deformation which scatter light.
26 In U.S. patent 3,fi89,894 1,a~lra and Eng disclose exposed and developed 27 microfilm to record data by optically writing transparent bits of data with black 28 areas of the microfilm by burning holes through the black silver-halide emulsion.
''" ' . ~ ' ~3~ S
Many other patents reveal light absorptive media for recording laser writing. My objactive was to devise a moderate-ly reflective DRAW laser recording material which may be manu-factured without the use of a vacuum system and on a continuous basis and which may be used to record non-reflective spots in a reflective field with relatively low energy laser pulses.
Another objective was to devise a laser recording medium which permits the pre-recording of control indicia and certain data base data by normal photographic means to facilitate the use of discs or plates in both the recording apparatus and the playback apparatus.
Temperatures between 280C and 340C are preferred to produce the reflective coating during a time cycle on the order of one-half minute to 20 minutes. Heating methods include the use of a convection oven, a contacting hot source, or radiant heating. A resulting shiny reflective emulsion coated trans-parent or absorptive substrate is a DRAW laser pyrographic reflective recording medium.
An advantage of the recording medium of the present invention is that it may be made on a continuous flow basis.
The emulsion coating is tenacious with respect to its substrate and is not toxic when laser writing ablates portions of the coating. Another advantage is that the emulsion coating may be previously exposed to desired patterns by normal photographic means to provide control indicia for the recording apparatus and/or playback apparatus and for replication of master disc recordings.
According to a broad aspect, the present invention provides an information storage medium for pyrographically recording laser writing comprising a sheet substrate and a refle~tive surface coating disposed on the sheet substrate, the reflective coating comprising reflective silver particles which _ ~347~5 are characterized by a gold color and are distributed within a gelatin matrix.
The information storage medium may be made by photo-graphically processing a silver-halide emuls.ion coating on a substrate to blackness, and thermally converting said black photographically processed silver-halide emulsion coating by heating at least to 250C in an atmosphere having a substantial percentage of oxygen at least until a gold colored reflective component appears on the emulsion coating surface.
-3a-,~
2 Brief Descril-tion of the D~@
Figure 1 is a top plan view of the recording medium of the present invention.
6 Figure 2 is a side sectional view of l:he recording medium of 7 Figure 1.
8 Figures 3-7 are detail views of the recordmg medium of Figure 1 showi~g--9 sequential processing steps for making the finished recording medium.
~igure 8 is a side sectional view of the recording medium of Figure 1 11 showing laser writing.
` ~ ~2 .
13 Description of the Preferred Embodiment . . .
Fi,gllre 1 shows a d-sc lt having an inner periphery 13 and an outer 16 periphery 15. The interior of the inner periphery 13 is ~oid so that a centering collar may be used to hold dise 11 on a splndle for high spee~ rotntion. Wbile the - ~ ~ 18 recordm~ medlum o~ the present invention is described as a disc, a disc configur~tion ;~ ~ is not essential for operating of the recording medium. l~or exarnple, the recording medium may be a flat sheet-lilce material which could be squa~re and with a central 21 hub rather than a hole. It could also be a non rotating rectangulal plate. However, 22 rotating discs are preferred for fnst random access to medium amounts of data and 23 non-rotating rectangular plates in stacks are preferred to provide intermediate speed 29 random access to large amounls of data by mechanically selecting a plate and scanning it by rnechanical and eleetro-optical means.
~6 The disc of ~igure 1 is photographically partitioned into reeording and 27 non-recording arefls. For example~ a first annular recording zone 17 could be spaced 28 ~ ~ from r sec d annular recordin zone 13 by an nnnular guard zone 2l. The function : -~-/' :
" ~ 3~
1 OI the guar(l 7.0ne may be to separ ate different recording fields, to carry control 2 information, such as timing signals and to provide space for data read-write trans-3 ducers to reside when not over recording areas. While such guard bands are preferable, 4 they are not essential to the operation of the present invention. It should be noted ~ that the recording fields are for data and control signal recording, while the guard 6 band is not for data recording, but may have control signal recording thereon. The 7 recording field l9 is shown to have a plurality of concentric, circumferentially-spaced 8 servo tracks 23 thereon. Such servo tracks are thin lines which define the spaces 9 between circular paths wherein data are written. The pattern for such lines is 10 applied photographicRlly as explainecl below with reference to Figures 3--7.
11 ~igure 2 shows a side sectional view of the recording medium of Figure 12 1. The medium consists of a substrate 27 which is a sheet-like layer which is transparent, translucent, or opaque; preferably a high temperature, dimensionally 14 stable material, like glass, ceramic, and thermoset and thermoplastic polyimide ~15 plastics. One of the requirements of the substrate material is that it withstand :L6 temperatures to at least 280C and most likely 320C but up to 34ûC, without 17 thermal deformation. Transparency or absorptivity of the substrate is desired so :L8 that when the light beam of the reflective playback apparatus impinges upon a 19 recorded spot, It either paæes through the substrate or is absorbed by it with 20 minimum reflection. If the substrate is absorptive, it may be absorptive at the 2~ wavelengths of the recording beam or the reading beam, or both. Thus, not all common photographic substrates may be used. For example, the most common 23 photo~,rraphic film bases are polyester polyterephfllate, polycarbonate, or eellulose 2a, triacetate--which normally have maximum continuous operating temperatures of ~6 145C, 132C, and 205C, respectively. Further, in order to coat a photographic emulsion on a substrate, it must be etchable, dimensionally stable, non-destructible 28 by slmlight, h~ve ~ood mechanical strength, and should also be relatively inexpensive 29 and currently available in adequate quantities. Further, when lata recordings are to be read only in reflection rather than transmission, the substrate may be a non-reflectirlg, opaque material. There is one plastic--polymide--that meets 32 ~ _5_ ' ~ 3~75 ( .
1 nll of these conditions. It is available as a thermo-plastic and a thermoset plastic, 2 can operate at 320C for mimltes7 an-l is etchable with alkalines.
3 E~or the case where the substrate is transparent, the recording medium 4 may be read in a transmissive mode, for example as in U. S. patent application serial No. ~45,332, entitled Error Checking Method and Apparatus for Digital Data 6 in Optical Recording Systems, assigned to the assignee of the present invention.
7 The thickness of the substrate is not critical when the lnser beam is B directed onto the surface as shown in Figure 8, but it should have sufficient thickness 9 to provide strength for resistance against breakage. If the laser beam is directed through a transparent substrate, then in order to maintain focus of the beam the11 thickness of the transparent substrate would have to be very uniform (for example, 12 as obtainable from float glass or selected high quality drawn glass). Also, the 13 thicknes~s of the sul~strate may depend on the overall size of the recording medium 14 being used. ~or a 1~-inch disc, a thickness of 1/8 inch may be suitable.lS The purpose of substrate 27 is to support a sîlver-halide emulsion coating 16 29, which is uniformly applied to the substrate in a conventional manner and which 1~ i9 converted subsequently to layers 32 and 33 in Figure 8. Currently availaMe 18 silver-halide emulsions from 3 to B microns thick are adequate, provided they are characterized by very fine silver-halide grain size, i.e., only a small percentage of the grains are larger than 0.07 microns. This grain size ap~ears to be important21 because when grain sizes becorne larger than approximately 0.06 microns the con-22 version from Maclc to reddish coloration, which subsequently becomes metallic, appears 23 to be less complete. Emulsion coated glass plates having these characteristics are 2a~ commercially available and are Icnown as photoplates which are used to make photomasks for the manufacture of semiconductor integrated circuits. ~or example, ~!6 emulsion coated photoplates suitable for use herein are manufactured by Ag~a-27 Gaevaert of Belgium, Konishiroku Photo Industries of Japan and the Eastman Kodak 28 Company.
.
.
1~3475 1 The shiny reflective component 32 in Figure 8 results from the thermal 2 processing describe-3 herein and reflectivity does not initially exist in the emulsion.
3 At the inception the material of reflective component 32 is mostly, excepting oxygen, 4 all found in the photographic emulsion ~,which is ImiIorm in its composition. A
~ subbing layer, not shown, is usual]y used to attnch the substrate 27 to the emulsion 6 29. Fo~lowing the thermal conversion of the present invention the emulsion 29 of 7 Figure 2 produces a reflective component 32 at the emulsion surface shown in Figure 8 8, with a non-reflective underlayer 33 beneath it~ The reflective component 32 is 9 not well defined in thickness, but exhibits a silver concentration gradient, with most 10 of the silver near the surface, and less extending downwardly. Thus, althou~h ~iguré
11 8 depicts a sharp boundary for refleetive component 32, actually such is not the 12 case and is only pictured in this manner to explain the contrast which exists between 13 the surface of the material and the urlderlying emulsion. The presence of more 14 silver particles at the surface and less below after heating is surprising and not 15 completely understood. It is believed that heat causes breakup of filamentary silver 16 particles into much more mobile, smaller particles which, in the presence of oxygen 17 at the surface concentrate and become reflective.
18 Underlayer 33, while not completely depleted of silver, contains less silver 19 than reflective component 32. Optically, underlayer 33 is pflrtially transmissive to 20 red light having wavelengths of 630 nanometers and longer, so that once craters are 2~ created penetrating reflective component 32, the craters may be detected by trans-22 mission of red light through the underlayer 33, provided that the opacity of the 23 reflective layer is sufficiently great at the selected wavelength to permit detection 24 of the craters through differences in light transmission. The data contained in the 25 craters may nlso be read by changes in reflectivity of the shiny reflective component ~6 throughout the visible spectrum and into the near infrared where it is ultimately limited in its usability &lS it becomes more and more transparent and therefore less 28 reflective in the non-data areas.
' .
~9L3~L~5 ~
1 It should be noted that both the recording areas 17, l 9 and the non-2 recording guard band 21 of Figure l have silver-halide emulsion covering a glass 3 substrate. Thus, the designation of recording and non-recording areas is arbitrary 4 and the entire surface could be used for recording if desired. However, as a matter
5 of convenience, it is preferable to designate areas as non-recording areas. The
6 boundaries between recording and non-recording areas may be defined by concentric
7 lines, just as the servo trac1cs 23 of Figure l, wl ich have been greatly enlarged in-
8 the Figure, may be defined by lines. Typically, servo traclcs are closely spaced
9 concentric circles or adjacent lines of a spiral, with data bein~ written on or between
10 the lines. Such servo track lines, as well as line boundaries for non-recording areas,
11 may be photographically recorded on the recording medium prior to any data recording.
12 Moreover, other nlphanumeric information or data base information which is to be
13 a permanent parl: of the recording medium also may be applied to the recording medium at an earIy time in the processing cycle since it becomes a permanent part 15 of the recording medium.
1 6 One of the advanta~es of the present invention is that the permanent 17 information to be recorded on the recording medium of the present invention may 18 be applied by photographic techniques since the starting material for the recording 19 medium is an unexposed commercially available photoplate used in the manufacture of semiconductor integrated circl1its. After thermal conversion this information may 2~ be read in reflection since the blaclc image areas will become highly reflective and 22 the clear non-image areas will be onl~ slightly reflective.
23 The photographic techniques whic}) may be used to pre-record data base 2a~ and control information are well known in the semi-conductor industry. Lines having a thiclcness of one micron thiclcness may be made. The typical procedure for creating ~G a line pattern is illustrated in Figures 3-6. With reference to Figure 3, the medium 27 ll is exposed to a line pattern consisting of the circular lines 23a, 23b and 23c.
28 ï`he line pattern exists as a latent image in the silver-halide emulsion, the remainc3er 29 of which is unexposed to light.
3() ~3~
1 Figure 4 illustrntes the processing of the plate 11 through a well known 2 commercially available developer which c~luses the image pattern of lines 23a, 23b, 3 23c to become black, characteristic of black silver, the remainder of the material 4 being transparent.
In Figure 5, the developed silver areas 23a~ 23b, 23c are bleached out so 6 that they are clear. The bleach does not afPect the unexposed æones of the recording 7 material 11.
8 In Figure 6, the entire rec~rding medium is now strongly exposed to~
9 actinic radiation, such as by a mercury arc lamp, incandescent lamp or xenon flash lamp, and developed for maximum blackness (fixing is optional). The object OI this 11 step is ta provide black zones for conversion into the reflective data recording ~ields.
12 Of course, the guard zone 21 in ~igure 1 between recording fields will also have 13 the same black char~cter~ only its use is different. This exposure, development and
1 6 One of the advanta~es of the present invention is that the permanent 17 information to be recorded on the recording medium of the present invention may 18 be applied by photographic techniques since the starting material for the recording 19 medium is an unexposed commercially available photoplate used in the manufacture of semiconductor integrated circl1its. After thermal conversion this information may 2~ be read in reflection since the blaclc image areas will become highly reflective and 22 the clear non-image areas will be onl~ slightly reflective.
23 The photographic techniques whic}) may be used to pre-record data base 2a~ and control information are well known in the semi-conductor industry. Lines having a thiclcness of one micron thiclcness may be made. The typical procedure for creating ~G a line pattern is illustrated in Figures 3-6. With reference to Figure 3, the medium 27 ll is exposed to a line pattern consisting of the circular lines 23a, 23b and 23c.
28 ï`he line pattern exists as a latent image in the silver-halide emulsion, the remainc3er 29 of which is unexposed to light.
3() ~3~
1 Figure 4 illustrntes the processing of the plate 11 through a well known 2 commercially available developer which c~luses the image pattern of lines 23a, 23b, 3 23c to become black, characteristic of black silver, the remainder of the material 4 being transparent.
In Figure 5, the developed silver areas 23a~ 23b, 23c are bleached out so 6 that they are clear. The bleach does not afPect the unexposed æones of the recording 7 material 11.
8 In Figure 6, the entire rec~rding medium is now strongly exposed to~
9 actinic radiation, such as by a mercury arc lamp, incandescent lamp or xenon flash lamp, and developed for maximum blackness (fixing is optional). The object OI this 11 step is ta provide black zones for conversion into the reflective data recording ~ields.
12 Of course, the guard zone 21 in ~igure 1 between recording fields will also have 13 the same black char~cter~ only its use is different. This exposure, development and
14 fixing step would be the only processirig procedure taken, prior to heating, if there were no information to be pre-recorded, such as the servo tracks 23a, 23b, 23c and 16 there were no other pre-recorded alphanumeric or control indicia. In fact if no 17 images are to be photog~raphically recorded a fogging developer could be used in 18 some eases to avoid the need for the exposure step. Fogging developers are known 19 for use in reversal processing where it is desired to develop all remaining silver in a silver-halide emulsion. See "The Theory of the Photographic Processl', 4th Ed., ~IcMillan (1977~ p. 4~2. The min~mum extent of blackness opacity must be such 22 that the reflective component 32 subsequently produced by thermal conversion is 23 adequately reflective to the wavelength o light used in reflective playhack. A thin 24 reflective component with adequate reflectivity, less than 0.5 micron thick is preferred in order to minimize energy needed to punch through the coating for laser pyrographic 26 writing.
27 As an alternative to wet chemical development for creating blacl~ emulsion, 28 dry thermal developmenl may also be used. In thermal development, a latent image 29 is developed by henting an e~posed photosensitive thermographic material. Various types of materials exist, but in each case very miid heating causes development.
32 Eleating to about 11 5C lor five seconds causes development in typionl : ' t~`~
~34~75 1 thermographic materials. One type of material which may he thermally developed 2 contains a developer composition together Witll silver-halide grains. Heating causes 3 the developer to become activated, sometimes using moisture derived from the 4 emulsion carrier. In either instance, whether a chemical developer or a dry developer is used~ the photographic emulsion is processed for maximum blackness.
6 Once the recording medium has achieved the described level of blackness, ~ with or without pre-recorded indicia thereon, thermal conversion into a reflectiYe 8 medium may commence by heating the emulsion coating to a temperature of-9 approximately 280C to 340C in air, or 250C to 340C in oxygen, until a shiny reflective component 32 in Figure 8 appears. The coating initially is first converted 11 to a dark eherry red transmissive medium. This conversion, indicated in Figure 7, 12 begins to occur at temperatures as low as 200C. At higher temperatures, specifically 13 at about 3û0C the coating starts to becom0 reflective in less than a minute. After 14 further heating, reflectivity is clearly evident at the upper surface and the material 1S 11 has a characteristic gold color. Electrlcal resistance measurements on the shiny 16 component 32 in Figure 8 indicate no measureable conductivity. Heating methods 17 include the use of a convection oven, contacting hot source or radiant heating.
18 R;adiant heating is preferred because it heats the emulsion fast and uniformly and 19 ean be progr~mmed easily to minimize thermal shock to the substrate.
The shiny component 32 also has low thermal conductivity. It is be]ieved 2' that silver grains which form the Siliny component .,2 are indlvidually separated from 22 each other by gelatin. In other words, the rmild temperatures used in thermally 23 converting the emulsion coating into a shiny component 32 are low enough to preserve 2~ the insulative properties of the ~elatin. Higher temperatures would char or burn the gelatin, perhaps removing it by ablation. It appears that the mild temperatures 26 used herein are adequate to stimulate silver grain brealcup, and cause a dispersion 27 of the grains which appears to be necessary for the creation of the reflective layer.
~8 The oXvgen component of the heating atmosphere is preferably maximized 29 because it lowers both the temperature and tlle time required for processing. Although heating in air will work, fl pure oxygen environment is better. A minimum percentage .' "
~3~75 1 of oxygen, at lcast a few percent and preferably much more, such as the substantial 2 percent of oxygen found in air, is necessary to create the shiny silver component 3 32 by thermal conversion.
4 At a minimum, the shiny reflective component must be visible on the surface OI the material to be usefall for reading the data by differential reflectivity.
6 How&ver, in some instances it may be desirable to have a thicker coatîng of tlle 7 shiny material; in this instance longer heating would be required. For example, in~
13 the instance of therma~ly converting the entire thiclcness of the coating~ heating for above 2û mim~tes is needed. Conversion may oceur at temperatures between 280 C
:LO and 340C. The higher the conversion temperature, the faster the reaction and the 11 more complete conversion; however, 320C is selected as a preEerred maximum~
12 temperature so as to minimize the charring of the gelatin in the emulsion coating 13 and to minimize possible thermal damage to the substrate. Charring in gelatin is 14 noted by an amber color in the material. Note that the shiny component 32 only occurs where black silver previously existed. The shiny component is thus derived 16 from the silver in the developed silver -halidc emulsion. While the silver appears 17 at the surface and is concentrated there, the thickness of the shiny component is 18 not well defined because of a silver concentration gradient diminishing toward the 19 direction away from tlle exposed surface. It was shown above that certain black :~0 ¦ silver areas could be removed by bleaching in order to leave control indicia Ol line 21 boundaries. Clear indicia markings c e simple types can also be introduced by a 22 negative processing procedure in which a mask or an intermittent beam is used to 23 create the black images Y~hich outline the clear indicia.
24 While a silver-halide emulsion is the~ starting material for the recording medium of the present invention, the finished product is considered to be a silver 26 gelatin complex, the halides being substantially removed in the exposure and develop-2q ment process. The finished product is characterized by a reflective silver component 28 at the surface thereof having a silver g~adient with more silver at the surface and 29 less below, but with some silver throughout the gelatin.
To use the recording medium of the present invention laser light is focused 31 on a spot at the surface of the coating of the recording medium. Enou~h laser 32 energy is delivered to the spot to remove the shiny reflective material. The shiny ~ ~ ( ~:
~3~7Si 1 mnterial is plimarily at the surace and since a re~lective read proeedure is usecl, 2 for example as described in U.S. patent 3,657,707, the recorclin~ laser beam need 3 only penetrate and remove the shiny coating--not tlle fu11 depth of the emulsion 4 coating. Transmissive type reading can be nccomplished to a limited extent i~ a 5 red or very near infrared laser beam is used such that the opas~ity o~ the coatin~
6 blocks 90% of the light and the recor ded craters permit transmission of at least q 50% of the light. -Figure 8 shows emulsion coating 29 on substrate 27 covered by shiny 9 component 32 having a crater 30 damaging the shiny component created by means 10 OI laser light indicated by the rays 31. The size of the craters is kept at a minimum~
ïl preferably slightly under one micron in diameter but no larger than a few microns 12 in diameter to achieve high data densities. Data written by means of lflser light 13 are recorded in the recording areas 17, 19 shown in Figure 1, designated by the 14 letter R. As mentioned previously, these recording areas may also contain pre-
27 As an alternative to wet chemical development for creating blacl~ emulsion, 28 dry thermal developmenl may also be used. In thermal development, a latent image 29 is developed by henting an e~posed photosensitive thermographic material. Various types of materials exist, but in each case very miid heating causes development.
32 Eleating to about 11 5C lor five seconds causes development in typionl : ' t~`~
~34~75 1 thermographic materials. One type of material which may he thermally developed 2 contains a developer composition together Witll silver-halide grains. Heating causes 3 the developer to become activated, sometimes using moisture derived from the 4 emulsion carrier. In either instance, whether a chemical developer or a dry developer is used~ the photographic emulsion is processed for maximum blackness.
6 Once the recording medium has achieved the described level of blackness, ~ with or without pre-recorded indicia thereon, thermal conversion into a reflectiYe 8 medium may commence by heating the emulsion coating to a temperature of-9 approximately 280C to 340C in air, or 250C to 340C in oxygen, until a shiny reflective component 32 in Figure 8 appears. The coating initially is first converted 11 to a dark eherry red transmissive medium. This conversion, indicated in Figure 7, 12 begins to occur at temperatures as low as 200C. At higher temperatures, specifically 13 at about 3û0C the coating starts to becom0 reflective in less than a minute. After 14 further heating, reflectivity is clearly evident at the upper surface and the material 1S 11 has a characteristic gold color. Electrlcal resistance measurements on the shiny 16 component 32 in Figure 8 indicate no measureable conductivity. Heating methods 17 include the use of a convection oven, contacting hot source or radiant heating.
18 R;adiant heating is preferred because it heats the emulsion fast and uniformly and 19 ean be progr~mmed easily to minimize thermal shock to the substrate.
The shiny component 32 also has low thermal conductivity. It is be]ieved 2' that silver grains which form the Siliny component .,2 are indlvidually separated from 22 each other by gelatin. In other words, the rmild temperatures used in thermally 23 converting the emulsion coating into a shiny component 32 are low enough to preserve 2~ the insulative properties of the ~elatin. Higher temperatures would char or burn the gelatin, perhaps removing it by ablation. It appears that the mild temperatures 26 used herein are adequate to stimulate silver grain brealcup, and cause a dispersion 27 of the grains which appears to be necessary for the creation of the reflective layer.
~8 The oXvgen component of the heating atmosphere is preferably maximized 29 because it lowers both the temperature and tlle time required for processing. Although heating in air will work, fl pure oxygen environment is better. A minimum percentage .' "
~3~75 1 of oxygen, at lcast a few percent and preferably much more, such as the substantial 2 percent of oxygen found in air, is necessary to create the shiny silver component 3 32 by thermal conversion.
4 At a minimum, the shiny reflective component must be visible on the surface OI the material to be usefall for reading the data by differential reflectivity.
6 How&ver, in some instances it may be desirable to have a thicker coatîng of tlle 7 shiny material; in this instance longer heating would be required. For example, in~
13 the instance of therma~ly converting the entire thiclcness of the coating~ heating for above 2û mim~tes is needed. Conversion may oceur at temperatures between 280 C
:LO and 340C. The higher the conversion temperature, the faster the reaction and the 11 more complete conversion; however, 320C is selected as a preEerred maximum~
12 temperature so as to minimize the charring of the gelatin in the emulsion coating 13 and to minimize possible thermal damage to the substrate. Charring in gelatin is 14 noted by an amber color in the material. Note that the shiny component 32 only occurs where black silver previously existed. The shiny component is thus derived 16 from the silver in the developed silver -halidc emulsion. While the silver appears 17 at the surface and is concentrated there, the thickness of the shiny component is 18 not well defined because of a silver concentration gradient diminishing toward the 19 direction away from tlle exposed surface. It was shown above that certain black :~0 ¦ silver areas could be removed by bleaching in order to leave control indicia Ol line 21 boundaries. Clear indicia markings c e simple types can also be introduced by a 22 negative processing procedure in which a mask or an intermittent beam is used to 23 create the black images Y~hich outline the clear indicia.
24 While a silver-halide emulsion is the~ starting material for the recording medium of the present invention, the finished product is considered to be a silver 26 gelatin complex, the halides being substantially removed in the exposure and develop-2q ment process. The finished product is characterized by a reflective silver component 28 at the surface thereof having a silver g~adient with more silver at the surface and 29 less below, but with some silver throughout the gelatin.
To use the recording medium of the present invention laser light is focused 31 on a spot at the surface of the coating of the recording medium. Enou~h laser 32 energy is delivered to the spot to remove the shiny reflective material. The shiny ~ ~ ( ~:
~3~7Si 1 mnterial is plimarily at the surace and since a re~lective read proeedure is usecl, 2 for example as described in U.S. patent 3,657,707, the recorclin~ laser beam need 3 only penetrate and remove the shiny coating--not tlle fu11 depth of the emulsion 4 coating. Transmissive type reading can be nccomplished to a limited extent i~ a 5 red or very near infrared laser beam is used such that the opas~ity o~ the coatin~
6 blocks 90% of the light and the recor ded craters permit transmission of at least q 50% of the light. -Figure 8 shows emulsion coating 29 on substrate 27 covered by shiny 9 component 32 having a crater 30 damaging the shiny component created by means 10 OI laser light indicated by the rays 31. The size of the craters is kept at a minimum~
ïl preferably slightly under one micron in diameter but no larger than a few microns 12 in diameter to achieve high data densities. Data written by means of lflser light 13 are recorded in the recording areas 17, 19 shown in Figure 1, designated by the 14 letter R. As mentioned previously, these recording areas may also contain pre-
15 recorded data base data and control indicia whieh may be disposed over essentially
16 the entire area OI the medium. No data is recorded in the guard band 2l, designated
17 by the letter G, although this region may have control indicia written therein.
18 Control indicia in either of the areas may be written by means of photographic
19 techniques or by pyrographic methods such as laser writing.
20 ` Thus, the recording medium of the present inve11tion may contain R mix 2~ of pre-recorded data and control indicia which has been applied to the recording~
22 medium by photogrAphic techniques, as well as subseguently ~vritten data applied to 23 the recolc1ing medium by laser pyrographic writing. There is no data storage 2~ distinction between pre-recorded non-reElective spots and non-reflective spots made 25 by laser writing. In the read mode, data base data and control inormation are 26 accessible on the same disc as data, while in the record mode the control information 27 is used.
;~!8 The table below lists the relative contrast measurements obtained from 29 1aser writing and reading as shown in Figure 8 on a sample of this laser pyrographic 3V reflective recording mediurn on a glass substrate. Measurements were made by ~ 5 1 recording and reading 32 spots at each of L6 power levels, or a total of 512 spots, 2 with an argon laser generating the green 5l4 nanometer line~ Electron micro~raphs 3 ancl optical microscope photographs were taken of the holes created. These photos 4 confirmed that the depth of the holes at rated power levels is considerably le~ss 5 than the 0.8 micron hole diameter itsel~; also, that at the lower power levels the 6 holes are reduced in size. The ta~le illustrates that the contrast is almost unchanged 7 from power levels oE 28 milliwatts down to 6.9 milliwatts, indicating that as long 8 ¦ as the power is above the required level, the material performs well. There is no-g ¦ apparent "overpower" effect. Note that there is little further degrac3ation in contrast 10 ¦ down to 4.6 milliwatts. Finally note that the usable contrast (when the median :ll ¦ contrast is much larger than the 1 Sigma distribution value) is as low as 2.2 milliwatts.
12 Frorn these data it can be concluded that the medium could be rated at 5 milliwatts 13 for 0.8 micron beam recording with 100 nanosecond pulses. This is sligrhtly less than 14 that required to record on a thin layer o~ vacuum-deposited tellurium--fl metal which ~5 is one of the more popular lase.r recording ma-terials.
16 The above clescribed reflective recording medium reqllires much less laser lr~ energy and creates considerably less recording debris than prior media in which holes 18 were burned through an entire 6 microns thick black silver-halide emulsion.
19 The method herein described results in melting and removal o~ less than O.S micron of the thermally converted emulsion. Thus, the laser energy required and the debris gen~rated are reduced by more than one order Oe magnitude ~ my 22 proposed recordin~ method and medium.
23 Note that the thermally converted processed silver-halicle emlllsion Imder 24 the reflective coating, 33, plays a thermal insulating role in improving recording sensitivity similar to what is accomplished by the plastic film undercoat of the prior 26 art. However, the present coating metilod does not require the added step OI a 27 batch-type vacllum cleposition procedure. A continuous flow manufacturing process 28 may be used to produce the reflective coating.
7S ~-TA~LE
LASEl~ Wl~ITING AND READING ON
PYROGRAPIlIC REE~LECTIVE RECORDING MEDIUM
Laser Beam: 514 Nanometers Wavelengtl 0.8 Micron Diameter 100 Nanosecond Pulses Statistical Distribution Pulsed Power at SurfaceRelative Contrastof Contrast Ratios of Recording Medium Ratio Avera~edof the 32 Spots (in Milliwat~s) Over 32 Spots (+ 1 Si~ma) 2~ 2~L~7 + 276 24.3 2361 ~ 442 - -
22 medium by photogrAphic techniques, as well as subseguently ~vritten data applied to 23 the recolc1ing medium by laser pyrographic writing. There is no data storage 2~ distinction between pre-recorded non-reElective spots and non-reflective spots made 25 by laser writing. In the read mode, data base data and control inormation are 26 accessible on the same disc as data, while in the record mode the control information 27 is used.
;~!8 The table below lists the relative contrast measurements obtained from 29 1aser writing and reading as shown in Figure 8 on a sample of this laser pyrographic 3V reflective recording mediurn on a glass substrate. Measurements were made by ~ 5 1 recording and reading 32 spots at each of L6 power levels, or a total of 512 spots, 2 with an argon laser generating the green 5l4 nanometer line~ Electron micro~raphs 3 ancl optical microscope photographs were taken of the holes created. These photos 4 confirmed that the depth of the holes at rated power levels is considerably le~ss 5 than the 0.8 micron hole diameter itsel~; also, that at the lower power levels the 6 holes are reduced in size. The ta~le illustrates that the contrast is almost unchanged 7 from power levels oE 28 milliwatts down to 6.9 milliwatts, indicating that as long 8 ¦ as the power is above the required level, the material performs well. There is no-g ¦ apparent "overpower" effect. Note that there is little further degrac3ation in contrast 10 ¦ down to 4.6 milliwatts. Finally note that the usable contrast (when the median :ll ¦ contrast is much larger than the 1 Sigma distribution value) is as low as 2.2 milliwatts.
12 Frorn these data it can be concluded that the medium could be rated at 5 milliwatts 13 for 0.8 micron beam recording with 100 nanosecond pulses. This is sligrhtly less than 14 that required to record on a thin layer o~ vacuum-deposited tellurium--fl metal which ~5 is one of the more popular lase.r recording ma-terials.
16 The above clescribed reflective recording medium reqllires much less laser lr~ energy and creates considerably less recording debris than prior media in which holes 18 were burned through an entire 6 microns thick black silver-halide emulsion.
19 The method herein described results in melting and removal o~ less than O.S micron of the thermally converted emulsion. Thus, the laser energy required and the debris gen~rated are reduced by more than one order Oe magnitude ~ my 22 proposed recordin~ method and medium.
23 Note that the thermally converted processed silver-halicle emlllsion Imder 24 the reflective coating, 33, plays a thermal insulating role in improving recording sensitivity similar to what is accomplished by the plastic film undercoat of the prior 26 art. However, the present coating metilod does not require the added step OI a 27 batch-type vacllum cleposition procedure. A continuous flow manufacturing process 28 may be used to produce the reflective coating.
7S ~-TA~LE
LASEl~ Wl~ITING AND READING ON
PYROGRAPIlIC REE~LECTIVE RECORDING MEDIUM
Laser Beam: 514 Nanometers Wavelengtl 0.8 Micron Diameter 100 Nanosecond Pulses Statistical Distribution Pulsed Power at SurfaceRelative Contrastof Contrast Ratios of Recording Medium Ratio Avera~edof the 32 Spots (in Milliwat~s) Over 32 Spots (+ 1 Si~ma) 2~ 2~L~7 + 276 24.3 2361 ~ 442 - -
21 : 2518 . + 267 18 2700 ~ 296 15.4 2690 -~ 314 12.8 ~ 2804 + 267 10.4 2634 + 270 8.7 265~ + 325 6.9 249~ ~ + 336 5.7 2221 . + 459 4.6 2156 + 432 3.6 186U + 624 .8 1725 +-380 2.2 ~ 1217 . + 250 : 1 ~7 654 + 188 1.3 279 . + 145 ~ ~ .
.
,~ .
:
.
.
-13 a-' :
.
,~ .
:
.
.
-13 a-' :
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An information storage medium for pyrographically recording laser writing comprising a sheet substrate and a reflective surface coating disposed on the sheet substrate, the reflective coating comprising reflective silver particles which are characterized by a gold color and are distributed within a gelatin matrix.
2. The medium of Claim 1 wherein said reflective surface coating has a silver concentration gradient whereby the silver concentration is greatest at the surface boundary away from said substrate and diminishes in concentration toward said sub-strate.
3. The medium of Claim 1 wherein said reflective surface coating has a reflective silver component extending throughout said coating.
4. A method of making a laser pyrographic information and storage medium comprising, photographically processing a silver-halide emulsion coating on a substrate to blackness, and ther-mally converting said black photographically processed silver-halide emulsion coating by heating at least to 250°C in an atmosphere having a substantial percentage of oxygen at least until a gold colored reflective component appears on the emulsion coating surface.
5. The method of Claim 4 wherein said step of photographic-ally processing said silver-halide emulsion is further defined by the steps of exposing said silver-halide emulsion coating on a substrate to actinic radiation, and developing said silver-halide emulsion coating.
6. The method of Claim 4 wherein said step of photographic processing includes photographically defining in the emulsion areas for recording data by laser pyrographic means and areas set aside for no laser pyrographic recording.
7. The method of Claim 4 wherein said step of photographic processing includes photographically defining in the emulsion lines defining servo tracks.
8. The method of Claim 4 wherein said step of photo-graphic processing includes photographically defining in the emulsion lines defining control indicia.
9. The method of Claim 6 wherein said step of photo-graphic processing includes recording data base data in a photographically defined area set aside for no laser pyrographic recording.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US1223579A | 1979-02-14 | 1979-02-14 | |
| US012,235 | 1979-02-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143475A true CA1143475A (en) | 1983-03-22 |
Family
ID=21753995
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000344824A Expired CA1143475A (en) | 1979-02-14 | 1980-01-31 | Laser pyrographic reflective recording medium |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS55108995A (en) |
| BE (1) | BE881492A (en) |
| CA (1) | CA1143475A (en) |
| DE (1) | DE3002911C2 (en) |
| FR (1) | FR2449322A1 (en) |
| GB (1) | GB2042200B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56132335A (en) * | 1980-02-11 | 1981-10-16 | Fuji Photo Film Co Ltd | Optical recording medium and its manufacture |
| GB2081461B (en) * | 1980-07-21 | 1984-03-07 | Drexler Tech | Double-sided silver halide material |
| US4385372A (en) * | 1981-05-01 | 1983-05-24 | Drexler Technology Corporation | Reflective optical data storage and laser recording media having grooved dielectric encoded prerecorded information |
| EP0080884A3 (en) * | 1981-11-27 | 1984-02-01 | Konishiroku Photo Industry Co. Ltd. | A recording medium and a method for the production thereof |
| JPS58224794A (en) * | 1982-06-25 | 1983-12-27 | Konishiroku Photo Ind Co Ltd | Optical information recording medium |
| JP2553860B2 (en) * | 1987-05-08 | 1996-11-13 | 共同印刷株式会社 | Optical recording member, method of manufacturing the same, and method of manufacturing optical recording card |
| DE102004026819A1 (en) * | 2004-06-02 | 2006-01-26 | Steag Hamatech Ag | Production of a partially reflecting layer of optical data carrier, especially a compact disk or digital versatile disk, comprises applying liquid containing reflecting particles on a surface of a disk-like substrate and drying the liquid |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3314073A (en) * | 1964-10-20 | 1967-04-11 | Prec Instr Company | Laser recorder with vaporizable film |
| NL162215C (en) * | 1967-07-03 | Ibm | ||
| US3567477A (en) * | 1967-11-15 | 1971-03-02 | Du Pont | Molybdate orange pigment |
| US3647456A (en) * | 1968-12-23 | 1972-03-07 | Ibm | Method of making conductive silver images and emulsion therefor |
| US3911444A (en) * | 1974-04-04 | 1975-10-07 | Bell Telephone Labor Inc | Metal film recording media for laser writing |
| JPS5230850B2 (en) * | 1974-10-07 | 1977-08-11 | ||
| JPS51105821A (en) * | 1975-03-14 | 1976-09-20 | Fuji Photo Film Co Ltd | Masukugazono keiseihoho |
| JPS6015055B2 (en) * | 1976-09-06 | 1985-04-17 | 富士写真フイルム株式会社 | How to form a mask image |
-
1980
- 1980-01-22 GB GB8002060A patent/GB2042200B/en not_active Expired
- 1980-01-24 JP JP770880A patent/JPS55108995A/en active Granted
- 1980-01-28 DE DE3002911A patent/DE3002911C2/en not_active Expired
- 1980-01-31 CA CA000344824A patent/CA1143475A/en not_active Expired
- 1980-02-01 FR FR8002270A patent/FR2449322A1/en active Granted
- 1980-02-01 BE BE1/9705A patent/BE881492A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2449322B1 (en) | 1982-10-08 |
| GB2042200A (en) | 1980-09-17 |
| DE3002911A1 (en) | 1980-09-04 |
| JPS6326464B2 (en) | 1988-05-30 |
| FR2449322A1 (en) | 1980-09-12 |
| BE881492A (en) | 1980-08-01 |
| DE3002911C2 (en) | 1983-12-29 |
| GB2042200B (en) | 1983-03-09 |
| JPS55108995A (en) | 1980-08-21 |
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