CA1116752A - Photsensitive material for optical digital recording and high density information storage - Google Patents
Photsensitive material for optical digital recording and high density information storageInfo
- Publication number
- CA1116752A CA1116752A CA000290955A CA290955A CA1116752A CA 1116752 A CA1116752 A CA 1116752A CA 000290955 A CA000290955 A CA 000290955A CA 290955 A CA290955 A CA 290955A CA 1116752 A CA1116752 A CA 1116752A
- Authority
- CA
- Canada
- Prior art keywords
- medium
- radiant energy
- organic substance
- level
- intensity
- 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.)
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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
- G11B7/241—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
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- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Mathematical Physics (AREA)
- Thermal Transfer Or Thermal Recording In General (AREA)
- Optical Record Carriers And Manufacture Thereof (AREA)
Abstract
Abstract A synthetic plastic recording medium containing a dispersion of exothermally reactive particles is disclosed. High intensity pulses of laser light cause particles in the light path to react exothermally and thereby char the plastic of the medium to leave a permanent record of the laser pulse.
Description
RJP/jlb 67~92 PHOTOSENSITIVE ~ATERIAL FOR
OPTICAL DIGITAL RECORDING AND
~IGH DENSITY INFORMATION STORAGE
The present invention relates to an improved laser data recording medium and specifically to a photo-sensitive plastic material for optical digital recording.
Data storage systems, e.g. the storage system shown in United States patent No. 3,501,586 dated March 17, 1970 to James T. Russell, have been developed to permanently ` -store data on an optically sensitive recording material ~-by an intensity modulated laser beam. While laser re-cording equipment for this process has been developed to an advanced state, a convenient recording medium has not heretofore been found. Conventional photographic plates have been used, but are disadvantageous because they require special handling and must be "developed"
before the data can be retrieved. Other media have included complex and costly chemical dyes which change color in response to heat or light. Still other media consist of thin layers of energy absorbing material which are perforated by the pulses of laser light. Once perfor-ated, such media tend to wear out with continued use, however.
United States patent No. 3,715,734, dated Fsbruary 6, 1973, to Jack Fajans describes a three dimensional recording medium which is a block of poly- -methyl methacrylate. In this system a laser beam is ex-panded through a system of lenses then steeply converged ,~:
'.
,:, . . . .
~W~ 1 6f~6//~ J
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to 2 focal point inside the block to form opaque spots by carbon-i7ing the block itself at ~he beam's focal point. ~n exceedingly laxge amount of radiant energy is required to carbonize poly-methal methacrylate so that an exceedingly powerful laser is S required. The power requirement of the laser is further expanded because light intensity is reduced as the beam passes through Fajan's several optical components. ~y his own estimate, Fa;an~5 system optics reduce light intensity by 50%.
Summary of the Invention It nas no~i been discovered that the problems of the prior axt may be eliminated by providing a synthetic plastic recording medium matri~ inters~erse~ with sub-micron particles of reactant substances. When a pulse of moderate intensity lasex light strikes such a recording medium, that volume of the medium ~hich is iIl the path of the puisa absorbs li~ht ener~y and is heated, This increase in hea~ causes the reactant substances of particles in the hea~ed volu~.e to react exothermally liberating additional neat energy sufficient to char theplastic in the he~ted vol~ne.
Because suc~ particles of reactant sLbstances are inter-spersed in therecording medium~ the intensity o~ laser light needed to char the plastic and thus the size and ene.rgy require-ments of the laser are greatly reduced. By providing the particles in a thin plastic matrix material which chars readily, complex lens systems which waste excessive amounts of light energy may be eliminated ~rom the laser recording apparatus.
It is an object of this invention to provide a laser-sensitive recording medium which produces a permanent record and which is w~ar-resistant.
-- 2 ~
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1L67~
A further object is to provide a recording medium which may be made easily from inexpensive materials.
An addi.tional object is to provide a recording medium which is sensitive to moderate or low intensity laser radiation so that small, low power lasers can be used as recording instru-ments.
Another object of the invention is to provide a record-ing medium including a thin layer of plastic which chars readily when heated by a pulse beam of laser light.
According to a first aspect of the present invention, there is provided a recording medium for permanently storing an intelligence pattern from which information can be read by ex-posing the medium to radiant energy at a first level of intensity and on which information is recorded by exposing the medium to radiant energy at a second level of intensity which is higher than said first level, comprising a body of solid recording material made of an organic substance and particles of a re-actant substance dispersed in the organic substance, the material being of such a composition that when the body is exposed to radiant energy at said first level of intensity the reactant substance is non-reactive and when the body is exposed to radiant energy at said second level of intensity the material absorbs an amount of radiant energy that, although insufficient alone to provide the minimum amount of heat energy needed to carbonize the organic substance,is sufficient to initiate an exothermal chemical reaction involving the reactant substance, the addition-al energy needed to exceed the minimum amount for carbonization being provided from within the material by the exothermal re action.
According to another aspect of the invention, there is provided a process for permanently storing an intelligence pattern comprising: converting said intelligence pattern into i7S2 a sequence of pulses of radiant energy, each pulse extending over a predetermined period; applying each pulse to a body of solid recording material, said material including an organic substance which chars upon exposure to sufficient amount of heat energy; adjusting said radiant energy to an intensity sufficient to initiate an exothermic -3a-RJP/jlb 67~2 reaction of one or more reactant substances contained in said material; using heat energy from said exo-thermic reaction in com~ination with heat energy produced by radiant energy absorption to exceed said sufficient amount and thereby char said organic subtance; and moving said body in relation to the path of said radiant energy between pulses thereof.
The invention will now be described in greater detail with reference to the accompanying drawlngs, in which:
Fig. l is a block diagram of an analog digital to optical recording system capable of producing a perm-anent record on the recording medium of the present invention; and Fig. 2 is a side cross section view of a record-ing medium according to the present invention.
Referring to Fig. 1, a typical device is shown for recording an intelligence pattern by means o~
a pulsed laser. The system includes a recorder unit 10 having its input connected to an audio visual analog signal source 12, such as a microphone or television camera. This analo~ input signal 23 is applied to the input of an analog-to-digital signal converter 24 pro-vided in the recorder unit 10 and which produces a digitally encoded electrical output signal 26. The output of the analog-to-digital signal converter 24 may ~e directly connected to an electrical optical digital signal recorder 28 through an amplifier 29 i it is desired to record the dîgital signal in real time simultaneously -3~-.
as it is generated. ~Iowever, it may be desirable to temporarily stor~ the digital signal 26 on the magnetic ta~e or other memory device of a digital computer 30 and to reeord sueh signals later at a more convenient time.
The electrieal optieal digital signal recorder 28 converts the digital electrical signal into a digital light sig-nal and records suc~ light signal bv seanning a pulsed laser light,beam ~0 of small spot si2e on a photosensitive reeording medium to produce a traek of digitally encoded spots of less than about lO mierons in diameter. The spots are light opaque to provide 0 or l bits of a binary code. The reeording medium is s--pported, in a fashion whieh may be eonventional, fo'r move-ment in a path perpendicular to the optieal axis and is meeh-anieally coupled to a recording medium positioning meehanism 44 adapted for moving the medium to procluee the traek of digitally eneoded spots. The reeordins medi~m positioning mechanism 44 may includc a drive motor (not sho~n) which is energized selectively in response to sicJnals transmitted by the optical digital signal reeo,-der 28, ~he recording medium 42 or the present invention ineludes a ma~rix of plastie material whieh readily ehars when supplied ~ith a sufficient amount o~ heat energy. Interspersed in this matrix material are particles of one or more reactant substanees which are stable when exposed to laser light of rirst level of intensity1 but whieh reaet exothermally when exposed to laser licJht at a seeond level at a seeond, higher level of intensity.
In Fig. 2, sueh a reeording medium is shown as an active la~er 50 coated on a smooth, optieally refleetive upper surface 52 of a metal substra~e 54. A substantially transparen~ protec-tive layer 56 of plastic material is eoated over the aetive layer .. . . ... .
~ ~JP/ms Cl 6~7/77 18763 ;'7S2 50 so that the protective layer 56 and substrate 54 seal oppo-site sides of the active layer from the atmosphere.
Matrix Material The plastic selected for use as the matrix material of the active layer should be of the type which undergoes a "charring" reaction when heated, e.g. polymers based on furfuryl alcohol or vinylchloride. ~f furfuryl alcohol polymers are used, suitable material for the active layer may be formed by dispers-ing su~-micron particles or the reactant substanc~s in furfuryl alcohol prior to the addition of a catalyst to accelerate poly-merization.
l'ne size and sp~cing of reactant particles in active layers will effect the quality of the recording material. For example, if Saran (vinylindene chloride) is selected as the plastic matrix material and reactant particles of 0.3 to 0.6 microns in diameter are dispersed therein, a spacing of one particle per -cubic micron of Saran lS suitable for most types of reactant substances. By experimentation, it is easy to determine which particle size and spacing will be the most advantageous for any siven combination of matrix and reactant materials.
Reactant Substanccs The reactant substances may be of several types includ-ing thermite type mixtures, match compositions, del~y fuse mix-tures, flara coAmpositions, and simple explosives.
Thermite type mixtures usually contain a reducing ele-rnent which is a metal or an easily oxidized non-metal. In the present invention, the reducing agent could be the charable plastic of the recording material. An oxidizing agent is also included which is typically a metal oxide or salt rich in oxygen.
- : ;
r~Iatch composition li~ewise contaln oxidizing and r~ducing ayents. Suitable e~amples include red phosphorus or phospholus sesquisulfid~ (P4S3) as reducing agent with potas-sium chlorate (KC103) as the oxidizin~ asent.
In delay use compositions zirconium and amorphous boron are typical reducing agents and barium c~romate (BaCr04) a suitable oxidizing agent. ~eactant particles of delay fuse materials could, lor example, include any of the fuel-oxidizer combinations shown in Table I.
TABL
Compo~-ition Reducing ~gent ~wt. %) Oxidizinq ~gent (wt. ~) 1 Zr 22 BaCrO~ 78
OPTICAL DIGITAL RECORDING AND
~IGH DENSITY INFORMATION STORAGE
The present invention relates to an improved laser data recording medium and specifically to a photo-sensitive plastic material for optical digital recording.
Data storage systems, e.g. the storage system shown in United States patent No. 3,501,586 dated March 17, 1970 to James T. Russell, have been developed to permanently ` -store data on an optically sensitive recording material ~-by an intensity modulated laser beam. While laser re-cording equipment for this process has been developed to an advanced state, a convenient recording medium has not heretofore been found. Conventional photographic plates have been used, but are disadvantageous because they require special handling and must be "developed"
before the data can be retrieved. Other media have included complex and costly chemical dyes which change color in response to heat or light. Still other media consist of thin layers of energy absorbing material which are perforated by the pulses of laser light. Once perfor-ated, such media tend to wear out with continued use, however.
United States patent No. 3,715,734, dated Fsbruary 6, 1973, to Jack Fajans describes a three dimensional recording medium which is a block of poly- -methyl methacrylate. In this system a laser beam is ex-panded through a system of lenses then steeply converged ,~:
'.
,:, . . . .
~W~ 1 6f~6//~ J
i75Z
to 2 focal point inside the block to form opaque spots by carbon-i7ing the block itself at ~he beam's focal point. ~n exceedingly laxge amount of radiant energy is required to carbonize poly-methal methacrylate so that an exceedingly powerful laser is S required. The power requirement of the laser is further expanded because light intensity is reduced as the beam passes through Fajan's several optical components. ~y his own estimate, Fa;an~5 system optics reduce light intensity by 50%.
Summary of the Invention It nas no~i been discovered that the problems of the prior axt may be eliminated by providing a synthetic plastic recording medium matri~ inters~erse~ with sub-micron particles of reactant substances. When a pulse of moderate intensity lasex light strikes such a recording medium, that volume of the medium ~hich is iIl the path of the puisa absorbs li~ht ener~y and is heated, This increase in hea~ causes the reactant substances of particles in the hea~ed volu~.e to react exothermally liberating additional neat energy sufficient to char theplastic in the he~ted vol~ne.
Because suc~ particles of reactant sLbstances are inter-spersed in therecording medium~ the intensity o~ laser light needed to char the plastic and thus the size and ene.rgy require-ments of the laser are greatly reduced. By providing the particles in a thin plastic matrix material which chars readily, complex lens systems which waste excessive amounts of light energy may be eliminated ~rom the laser recording apparatus.
It is an object of this invention to provide a laser-sensitive recording medium which produces a permanent record and which is w~ar-resistant.
-- 2 ~
~ : , : ,`
1L67~
A further object is to provide a recording medium which may be made easily from inexpensive materials.
An addi.tional object is to provide a recording medium which is sensitive to moderate or low intensity laser radiation so that small, low power lasers can be used as recording instru-ments.
Another object of the invention is to provide a record-ing medium including a thin layer of plastic which chars readily when heated by a pulse beam of laser light.
According to a first aspect of the present invention, there is provided a recording medium for permanently storing an intelligence pattern from which information can be read by ex-posing the medium to radiant energy at a first level of intensity and on which information is recorded by exposing the medium to radiant energy at a second level of intensity which is higher than said first level, comprising a body of solid recording material made of an organic substance and particles of a re-actant substance dispersed in the organic substance, the material being of such a composition that when the body is exposed to radiant energy at said first level of intensity the reactant substance is non-reactive and when the body is exposed to radiant energy at said second level of intensity the material absorbs an amount of radiant energy that, although insufficient alone to provide the minimum amount of heat energy needed to carbonize the organic substance,is sufficient to initiate an exothermal chemical reaction involving the reactant substance, the addition-al energy needed to exceed the minimum amount for carbonization being provided from within the material by the exothermal re action.
According to another aspect of the invention, there is provided a process for permanently storing an intelligence pattern comprising: converting said intelligence pattern into i7S2 a sequence of pulses of radiant energy, each pulse extending over a predetermined period; applying each pulse to a body of solid recording material, said material including an organic substance which chars upon exposure to sufficient amount of heat energy; adjusting said radiant energy to an intensity sufficient to initiate an exothermic -3a-RJP/jlb 67~2 reaction of one or more reactant substances contained in said material; using heat energy from said exo-thermic reaction in com~ination with heat energy produced by radiant energy absorption to exceed said sufficient amount and thereby char said organic subtance; and moving said body in relation to the path of said radiant energy between pulses thereof.
The invention will now be described in greater detail with reference to the accompanying drawlngs, in which:
Fig. l is a block diagram of an analog digital to optical recording system capable of producing a perm-anent record on the recording medium of the present invention; and Fig. 2 is a side cross section view of a record-ing medium according to the present invention.
Referring to Fig. 1, a typical device is shown for recording an intelligence pattern by means o~
a pulsed laser. The system includes a recorder unit 10 having its input connected to an audio visual analog signal source 12, such as a microphone or television camera. This analo~ input signal 23 is applied to the input of an analog-to-digital signal converter 24 pro-vided in the recorder unit 10 and which produces a digitally encoded electrical output signal 26. The output of the analog-to-digital signal converter 24 may ~e directly connected to an electrical optical digital signal recorder 28 through an amplifier 29 i it is desired to record the dîgital signal in real time simultaneously -3~-.
as it is generated. ~Iowever, it may be desirable to temporarily stor~ the digital signal 26 on the magnetic ta~e or other memory device of a digital computer 30 and to reeord sueh signals later at a more convenient time.
The electrieal optieal digital signal recorder 28 converts the digital electrical signal into a digital light sig-nal and records suc~ light signal bv seanning a pulsed laser light,beam ~0 of small spot si2e on a photosensitive reeording medium to produce a traek of digitally encoded spots of less than about lO mierons in diameter. The spots are light opaque to provide 0 or l bits of a binary code. The reeording medium is s--pported, in a fashion whieh may be eonventional, fo'r move-ment in a path perpendicular to the optieal axis and is meeh-anieally coupled to a recording medium positioning meehanism 44 adapted for moving the medium to procluee the traek of digitally eneoded spots. The reeordins medi~m positioning mechanism 44 may includc a drive motor (not sho~n) which is energized selectively in response to sicJnals transmitted by the optical digital signal reeo,-der 28, ~he recording medium 42 or the present invention ineludes a ma~rix of plastie material whieh readily ehars when supplied ~ith a sufficient amount o~ heat energy. Interspersed in this matrix material are particles of one or more reactant substanees which are stable when exposed to laser light of rirst level of intensity1 but whieh reaet exothermally when exposed to laser licJht at a seeond level at a seeond, higher level of intensity.
In Fig. 2, sueh a reeording medium is shown as an active la~er 50 coated on a smooth, optieally refleetive upper surface 52 of a metal substra~e 54. A substantially transparen~ protec-tive layer 56 of plastic material is eoated over the aetive layer .. . . ... .
~ ~JP/ms Cl 6~7/77 18763 ;'7S2 50 so that the protective layer 56 and substrate 54 seal oppo-site sides of the active layer from the atmosphere.
Matrix Material The plastic selected for use as the matrix material of the active layer should be of the type which undergoes a "charring" reaction when heated, e.g. polymers based on furfuryl alcohol or vinylchloride. ~f furfuryl alcohol polymers are used, suitable material for the active layer may be formed by dispers-ing su~-micron particles or the reactant substanc~s in furfuryl alcohol prior to the addition of a catalyst to accelerate poly-merization.
l'ne size and sp~cing of reactant particles in active layers will effect the quality of the recording material. For example, if Saran (vinylindene chloride) is selected as the plastic matrix material and reactant particles of 0.3 to 0.6 microns in diameter are dispersed therein, a spacing of one particle per -cubic micron of Saran lS suitable for most types of reactant substances. By experimentation, it is easy to determine which particle size and spacing will be the most advantageous for any siven combination of matrix and reactant materials.
Reactant Substanccs The reactant substances may be of several types includ-ing thermite type mixtures, match compositions, del~y fuse mix-tures, flara coAmpositions, and simple explosives.
Thermite type mixtures usually contain a reducing ele-rnent which is a metal or an easily oxidized non-metal. In the present invention, the reducing agent could be the charable plastic of the recording material. An oxidizing agent is also included which is typically a metal oxide or salt rich in oxygen.
- : ;
r~Iatch composition li~ewise contaln oxidizing and r~ducing ayents. Suitable e~amples include red phosphorus or phospholus sesquisulfid~ (P4S3) as reducing agent with potas-sium chlorate (KC103) as the oxidizin~ asent.
In delay use compositions zirconium and amorphous boron are typical reducing agents and barium c~romate (BaCr04) a suitable oxidizing agent. ~eactant particles of delay fuse materials could, lor example, include any of the fuel-oxidizer combinations shown in Table I.
TABL
Compo~-ition Reducing ~gent ~wt. %) Oxidizinq ~gent (wt. ~) 1 Zr 22 BaCrO~ 78
2 " 28 " 72
3 " 35 " 65
4 " 40 " 60 B 5 " 95 6 " 10 " 90 7 " 15 " 85 Flare compositions contain magnesium or aluminum metal as a reducing agent. These metals are suscep~ible to laser ignition for oxidation by a wide variety of oxidizing agents.
Explosive compositions include compounds with excess resonance ener~y or which contain the fuel-oxidizer combination within a single molecule such as lead styphnate.
Substrzte and Protective Layers The substrate 52 should comprise a material which can be treated to form an optically reflective surface. ~letals such as low carbon steel, aluminum, ~lnd brass, may be polished to provide a suita~le surface Other materials such as metalized RJP;srd ~1 6/~ 1/ 18763 ~
ceramic, or metalized plastic can be-used in some circum-stances. The protective layer 56 may be made of any material which is substantially transparent to laser light when bonded to the matrix material.
Operation To record on the medium of the present inver,tion a pulse of laser light 40a is beamed normally toward the pro-tective layer 56 of the medium 42a. The pulse passes through the transparent protective layer 56 and enters the active layer 50 where it is partially absorbed heating a spot in the layer. Light not absorbed by the active layer 50 is reflected from the surface 52 back through the heated spot so that an additional fraction of the light energy may be absorbed.
If laser light having an intensity of 100 milli-joules per pulse and a wave length of about 5300A is focused into a one cubic micron spot in a matrix material with a specific heat of about 0.5 calories per gram, a cubic micron of the medium would rise almost 500C. in temperature assum-ing total absorbance. Total absorbance is not possible, however, and a realistic absorbance of about 50~ would create a temperature rise insufficient to char the plastic matrix material.
A 50% absorbance would, ho~ever, be sufficient to initiate an exothermic reaction between reactant substances in~erspersed in the matrix material. For example, interspersed reactant mixtures would ignite at temperatures in the order of 200-300C. depending on the size, spacing and environment of the reactive particles. Thusj such reactive particles can easily be ignited by a laser having the above-described characteristics.
Once ignited, thermite particles produce heat pulses of 300-950 calories per gram which raise temperatures in the active layer R~ SL~ ~.L o/28//l 1876~
~6~S;~
to between 3,000 and 5,000C. at the spot of laser e~citation.
~hen raised to this elevated temperature, the matrix material chars leaving a darkened spot as a permanent record of the laser light pulse.
Combustion does not propagate from the spot of laser e~citation because the reactant particles comprise a dis-continuous phase in a matrix of a plastic material which will not sustain combustion in the absence of a source of ignition.
After ignition, heat in the active layer rapidly diffuses into 10 the surrounding environment, but is insufficient to ignite reactant particles outside the area of laser excitation. The presence of a metal substrate furtr.er aids in preventing the uncontrolled propagation of the exothermic reaction by acting as a heat sink to draw off excess heat from the reaction.
Data recorded as charred spots on the recording medium is read by directing a beam of low intensity laser light toward the protective layer of the recording mediu~.
Tl~is playbac~ light beam must be of lower intensity than the recording beam so that the active layer a~sorbs insu~ficient energy to initiate an exothermic reaction between the remain-ing particles of reactive substances. If the playback light be~m encounters a charred spot in the active layer, it is ab-sorbed or scattered. If, however, the playback beam does not encounter a charred spot, it is reflected from the reflective surface of the substrate to a photosensitive detector ap-paratus (not shown) which converts the reflected light into an electrical digital signal. Alternatively, after the data are recorded, the reflective metal substrate might be stripped off the active layer and protective layer. For playback, the light would be transmitted thxough the record to the detector, I~J L; S L ~ Dl r~ / 6 ~ ~
7~i2 which is on the opposite side of the record from the scanner.
There is yet another alternative. If there is sufficient laser energy, or the active layer is sufficiently sensitive, a transparent substrate without reflector could be used.
Again, for playback, the light would be transmitted to the detector rather than reflected.
~ hile we have sho~n and described preferred embodi-ments of our invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects.
_ g _
Explosive compositions include compounds with excess resonance ener~y or which contain the fuel-oxidizer combination within a single molecule such as lead styphnate.
Substrzte and Protective Layers The substrate 52 should comprise a material which can be treated to form an optically reflective surface. ~letals such as low carbon steel, aluminum, ~lnd brass, may be polished to provide a suita~le surface Other materials such as metalized RJP;srd ~1 6/~ 1/ 18763 ~
ceramic, or metalized plastic can be-used in some circum-stances. The protective layer 56 may be made of any material which is substantially transparent to laser light when bonded to the matrix material.
Operation To record on the medium of the present inver,tion a pulse of laser light 40a is beamed normally toward the pro-tective layer 56 of the medium 42a. The pulse passes through the transparent protective layer 56 and enters the active layer 50 where it is partially absorbed heating a spot in the layer. Light not absorbed by the active layer 50 is reflected from the surface 52 back through the heated spot so that an additional fraction of the light energy may be absorbed.
If laser light having an intensity of 100 milli-joules per pulse and a wave length of about 5300A is focused into a one cubic micron spot in a matrix material with a specific heat of about 0.5 calories per gram, a cubic micron of the medium would rise almost 500C. in temperature assum-ing total absorbance. Total absorbance is not possible, however, and a realistic absorbance of about 50~ would create a temperature rise insufficient to char the plastic matrix material.
A 50% absorbance would, ho~ever, be sufficient to initiate an exothermic reaction between reactant substances in~erspersed in the matrix material. For example, interspersed reactant mixtures would ignite at temperatures in the order of 200-300C. depending on the size, spacing and environment of the reactive particles. Thusj such reactive particles can easily be ignited by a laser having the above-described characteristics.
Once ignited, thermite particles produce heat pulses of 300-950 calories per gram which raise temperatures in the active layer R~ SL~ ~.L o/28//l 1876~
~6~S;~
to between 3,000 and 5,000C. at the spot of laser e~citation.
~hen raised to this elevated temperature, the matrix material chars leaving a darkened spot as a permanent record of the laser light pulse.
Combustion does not propagate from the spot of laser e~citation because the reactant particles comprise a dis-continuous phase in a matrix of a plastic material which will not sustain combustion in the absence of a source of ignition.
After ignition, heat in the active layer rapidly diffuses into 10 the surrounding environment, but is insufficient to ignite reactant particles outside the area of laser excitation. The presence of a metal substrate furtr.er aids in preventing the uncontrolled propagation of the exothermic reaction by acting as a heat sink to draw off excess heat from the reaction.
Data recorded as charred spots on the recording medium is read by directing a beam of low intensity laser light toward the protective layer of the recording mediu~.
Tl~is playbac~ light beam must be of lower intensity than the recording beam so that the active layer a~sorbs insu~ficient energy to initiate an exothermic reaction between the remain-ing particles of reactive substances. If the playback light be~m encounters a charred spot in the active layer, it is ab-sorbed or scattered. If, however, the playback beam does not encounter a charred spot, it is reflected from the reflective surface of the substrate to a photosensitive detector ap-paratus (not shown) which converts the reflected light into an electrical digital signal. Alternatively, after the data are recorded, the reflective metal substrate might be stripped off the active layer and protective layer. For playback, the light would be transmitted thxough the record to the detector, I~J L; S L ~ Dl r~ / 6 ~ ~
7~i2 which is on the opposite side of the record from the scanner.
There is yet another alternative. If there is sufficient laser energy, or the active layer is sufficiently sensitive, a transparent substrate without reflector could be used.
Again, for playback, the light would be transmitted to the detector rather than reflected.
~ hile we have sho~n and described preferred embodi-ments of our invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects.
_ g _
Claims (24)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A recording medium for permanently storing an intelli-gence pattern from which information can be read by exposing the medium to radiant energy at a first level of intensity and on which information is recorded by exposing the medium to radiant energy at a second level of intensity which is higher than said first level, comprising a body of solid recording material made of an organic substance and particles of a reactant substance dispersed in the organic substance, the material being of such a composition that when the body is exposed to radiant energy at said first level of intensity the reactant substance is non-reactive and when the body is exposed to radiant energy at said second level of intensity the material absorbs an amount of radiant energy that, although insufficient alone to provide the minimum amount of heat energy needed to carbonize the organic substance, is sufficient to initiate an exothermal chemical re-action involving the reactant substance, the additional energy needed to exceed the minimum amount for carbonization being provided from within the material by the exothermal reaction.
2. The medium of claim 1 wherein said body comprises an active layer.
3. The medium of claim 2 further comprising a substrate layer having a smooth, optically reflective upper surface positioned against said active layer.
4. The medium of claim 3 wherein said active layer is no more than six (6) microns thick.
RJP:dl Al 4/10/80 20703
RJP:dl Al 4/10/80 20703
5. The medium of claim 3 further comprising a substantially transparent protective plastics layer posi-tioned against said active layer opposite said substrate layer.
6. The medium of claim 3 wherein said substrate layer comprises a metal composition selected from the class consisting of low carbon steel, aluminum and brass.
7. The medium of claim 3 further comprising a substantially transparent protective plastics layer posi-tioned against a face of said active layer which is opposite said substrate layer.
8. The medium of claim 1 wherein said reactant substance comprises sub-micron particles dispersed within said recording material.
9. The medium of claim 8 wherein: said particles are between 0.3 and 0.6 microns in diameter; and about one said particle is included per cubic micron of said organic substance.
10. The medium of claim 1 wherein said reactant substance comprises substances which react exothermally when heated to 300°C.
11. The medium of claim 1 wherein said reactant substance comprises: a reducing agent; and an oxidizing agent exothermally reactive with said reducing agent when ignited.
12. The medium of claim 11 wherein said reducing agent comprises said organic substance.
RJP:dl Al 4/10/80 20703
RJP:dl Al 4/10/80 20703
13. The medium of claim 11 wherein said oxidizing agent is selected from the class consisting of metal oxides, oxygen-containing salts and mixtures thereof.
14. The medium of claim 11 wherein: said reducing agent is selected from the class consisting of red phospho-rus, phosphorus sesquisulfide (P4S3) and mixtures thereof;
and said oxidizing agent comprises potassium chlorate.
and said oxidizing agent comprises potassium chlorate.
15. The medium of claim 11 wherein: said reducing agent is selected from the group consisting of amorphous boron, zirconium, and mixtures thereof; and said oxidizing agent comprises barium chromate.
16. The medium of claim 11 wherein said reducing agent is selected from the class of metals consisting of magnesium, aluminum, and mixtures thereof.
17. The medium of claim 1 wherein said reactant substance comprises a single explosive substance.
18. The medium of claim 17 wherein said explosive substance comprises lead styphnate.
19. The medium of claim 1 wherein said organic substance is selected from the class of plastics consisting of polymers containing furfuryl alcohol and polymers con-taining vinyl chloride.
20. The medium of claim 1 wherein said reactant substance comprises a substance which chemically reacts exothermally when exposed to laser light of a predetermined level of intensity.
21. A recording medium for permanently storing an intelligence pattern, from which information is read by RJP:dl Al 4/10/80 20703 exposure to radiant energy at a first level of intensity and on which information is recorded by exposure to radiant energy at a second level of intensity which is higher than said first level, comprising: a metallic substrate having a smooth, optically reflective upper surface; a uniform layer of recording material over said substrate, said material being made of an organic substance selected from the class of plastics consisting of polymers containing furfuryl alcohol and polymers containing vinyl chloride which. (a) carbonize to the extent that said organic sub-stance becomes substantially opaque to radiant energy upon exposure to a predetermined minimum amount of heat energy, and (b) partially absorb said radiant energy in an amount insufficient to produce heat energy of said predetermined minimum amount when exposed to radiant energy at said second level of intensity; dispersed in said organic substance, particles of reducing and inorganic oxidizing agents which (a) are nonreactive when exposed to the amount of heat energy produced in said organic substance when said body is exposed to radiant energy at said first level of in-tensity, during the reading of information from said record-ing medium, and (b) chemically react exothermally when exposed to the amount of energy produced in said organic substance when said body is exposed to radiant energy at said second level of intensity, during the recording of information on said recording medium and, due to the exo-thermic reaction, liberate sufficient heat energy that the total amount of heat energy in said layer, at the location of radiant energy contact, exceeds said predetermined mini-mum amount so that said organic substance carbonizes and, due to carbonization, becomes substantially opaque to radiant energy at said location; and a substantially RJP:dl Al 4/10/80 20703 transparent protective layer of plastics material over said layer of recording material, said protective layer and substrate formed to seal each side of said layer of record-ing material.
22. The medium of claim 21 wherein said organic substance comprises said reducing agent.
23. A process for permanently storing an intelli-gence pattern comprising: converting said intelligence pattern into a sequence of pulses of radiant energy, each pulse extending over a predetermined period; applying each pulse to a body of solid recording material, said material including an organic substance which chars upon exposure to sufficient amount of heat energy; adjusting said radiant energy to an intensity sufficient to initiate an exothermic reaction of one or more reactant substances contained in said material; using heat energy from said exothermic reaction in combination with heat energy produced by radiant energy absorption to exceed said sufficient amount and thereby char said organic substance; and moving said body in relation to the path of said radiant energy between pulses thereof.
24. The process of claim 23 further comprising backing said recording medium with a metallic material dur-ing said applying, said metallic material acting as a mirror to reflect radiant energy back into said medium and as a heat sink to receive excess heat energy and thereby limit the propagation of said exothermic reaction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US81579877A | 1977-07-15 | 1977-07-15 | |
| US815,798 | 1992-01-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116752A true CA1116752A (en) | 1982-01-19 |
Family
ID=25218862
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000290955A Expired CA1116752A (en) | 1977-07-15 | 1977-11-15 | Photsensitive material for optical digital recording and high density information storage |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5421721A (en) |
| CA (1) | CA1116752A (en) |
| DE (1) | DE2817357A1 (en) |
| FR (1) | FR2397293A1 (en) |
| GB (1) | GB1592390A (en) |
| NL (1) | NL7714152A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4496957A (en) * | 1979-07-02 | 1985-01-29 | Xerox Corporation | Optical disk |
| US4425570A (en) * | 1981-06-12 | 1984-01-10 | Rca Corporation | Reversible recording medium and information record |
| JPS58224794A (en) * | 1982-06-25 | 1983-12-27 | Konishiroku Photo Ind Co Ltd | Optical information recording medium |
| US4622284A (en) * | 1984-03-01 | 1986-11-11 | Digital Recording Corporation | Process of using metal azide recording media with laser |
| ES2028780T3 (en) * | 1985-10-15 | 1992-07-16 | Gao Gesellschaft Fur Automation Und Organisation Mbh | IDENTITY CARD WITH VISUALLY APPRECIABLE AUTHENTICITY MARK AND PROCEDURE FOR ITS MANUFACTURE. |
| GB2379441A (en) * | 2001-09-07 | 2003-03-12 | Polight Tech Ltd | Holographic recording medium |
| US20170252868A1 (en) * | 2016-03-02 | 2017-09-07 | Tong Li | System and method for marking a substrate |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3547629A (en) * | 1962-09-27 | 1970-12-15 | American Screen Process Equip | Photoflash method of transferring information and fabricating printed circuits |
| DE1574687B2 (en) * | 1968-02-06 | 1978-08-10 | Robert Bosch Gmbh, 7000 Stuttgart | Data carriers for information |
| DE2441263A1 (en) * | 1974-08-28 | 1976-03-18 | Philips Patentverwaltung | RECORDING PROCEDURES |
| FR2368779A1 (en) * | 1976-10-22 | 1978-05-19 | Thomson Brandt | THERMOSENSITIVE MEDIA INTENDED FOR RECORDING INFORMATION AND PROCESS FOR RECORDING INFORMATION ON SUCH MEDIA |
-
1977
- 1977-11-15 CA CA000290955A patent/CA1116752A/en not_active Expired
- 1977-11-22 GB GB48672/77A patent/GB1592390A/en not_active Expired
- 1977-12-20 NL NL7714152A patent/NL7714152A/en not_active Application Discontinuation
-
1978
- 1978-01-09 FR FR7800430A patent/FR2397293A1/en active Granted
- 1978-04-20 DE DE19782817357 patent/DE2817357A1/en active Granted
- 1978-04-24 JP JP4916378A patent/JPS5421721A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB1592390A (en) | 1981-07-08 |
| JPS5421721A (en) | 1979-02-19 |
| DE2817357C2 (en) | 1987-06-11 |
| FR2397293A1 (en) | 1979-02-09 |
| NL7714152A (en) | 1979-01-17 |
| FR2397293B1 (en) | 1984-12-07 |
| DE2817357A1 (en) | 1979-01-25 |
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