Laser recording medium

A laser recording medium in which the metal recording layer is completely encapsulated between an intermediate layer of solvent resistant plastic material formed on a substrate and a protective layer of solvent-based plastic material formed on the recording layer. In some examples the solvent resistant plastic material is a cross-linked polymeric material formed in a solvent coating process and in other examples the solvent resistant plastic material is a vapor deposited polymeric material.

This invention relates generally to binary data information storage systems 
and, in particular, to a data recording medium responsive to energy from a 
focused laser beam. 
The data processing industry has made rapid strides in providing computers 
systems and related peripheral equipment for manipulating binary encoded 
numeric and alphabetic data at faster speeds and storing such data at 
higher densities and lower costs. Large corporations and government 
bureaus have placed increasing reliance on data processing equipment in 
automating data collection, storage and processing to improve the 
efficiency of handling business transactions, accounting information, etc. 
Increases in computer operating speeds are largely the result of 
improvements in semiconductor technology which have produced large scale 
integrated (LSI) circuits involving higher densities of binary logic 
elements or gates operating at faster speeds. Substantial increases in 
memory densities have also been achieved. In the semiconductor memory 
area, bit density increases have resulted both from improved LSI 
technology which enables a shrinking of the size of memory cell elements 
and from new LSI technology such as magnetic bubble domain memories. In 
the magnetic memory area, density improvements in hard and flexible disc 
systems have been achieved by improvements in magnetic recording media and 
reading and writing heads associated therewith. 
Despite the substantial increases in semiconductor and magnetic memory 
system densities, the cost per bit of such storage media together with 
encoding costs does not justify the use of such technology for storing, on 
a routine basis, large volumes of traditional business records, such as 
correspondence, reports, forms, legal documents, etc. The storage and 
maintenance of both current working files of these documents and archives 
of selected documents which must be retained securely for long periods of 
time is still largely a manual operation involving increasingly costly 
personnel and storage space. 
Digital laser recording technology has been developed in recent years to 
provide high density binary data storage which is readily integratable 
with both computer data processing equipment and facsimile document 
scanning and printing apparatus. This technology enables real time optical 
recording of image data in a highly compressed format and rapid 
opto-electronic access to recorded image data and can thus provide the 
basic framework for computer based document storage and retrieval and an 
overall record management system. At the heart of this technology is a 
laser beam writing and reading system which is capable of storing binary 
digital information in the form of the presence or absence of minute holes 
created in a thin film recording medium as a highly focused, modulated 
laser beam is scanned across the recording medium. 
The basic principles of laser image recording are set forth in Becker U.S. 
Pat. No. 3,474,457. Becker et al. U.S. Pat. No. 3,654,624 and McFarland et 
al. U.S. Pat. No. 3,657,707 show a laser recording system utilizing a 
rotating drum carrying a laser recording medium comprising flexible strips 
of plastic materials (such as Mylar) with a layer of energy absorbing 
material thereon. Such a laser recording medium is more fully described in 
Becker et al. U.S. Pat. No. 3,665,483. However, the use of a rotating drum 
or other mechanical scanning of the recording medium limits the record 
scanning speed during both recording and retrieval of data and thus 
artificially constrains the overall system to data writing and reading 
speeds substantially less than those dictated by available laser beam 
energies and recording media sensitivities. In addition, the use of 
flexible recording media limits the alignment precision which can be 
reproducibly achieved between data tracks and the laser beam path and, 
correspondingly, constrains the system to data bit densities substantially 
lower than the minimum cell size dictated by the system optics. Moreover, 
flexible recording media are highly subject to contamination by dust 
particles which may cause data writing and/or reading errors and thus 
require special handling and storage in dust-free compartments within the 
system. It is thus apparent that different approaches to scanning the 
laser beam across the recording medium and different structures for the 
recording medium itself are required to provide a system that fully 
utilizes the write/read speed and bit densities of which laser beam 
recording technology is inherently capable and also simplifies the 
recording media storage and handling requirements. 
Becker et al. U.S. Pat. No. 4,001,840 discloses a laser recording system 
which utilizes a mirror assembly rotatable on two orthogonal axes to 
deflect a laser beam in two directions for writing data on a recording 
layer formed on a rigid glass substrate. This mirror-beam deflection 
system is capable of achieving faster beam scanning, and the rigid glass 
substrate supporting the recording layer enables more precise, 
reproducible alignment between the recording medium and the scanned laser 
beam. However, it has been found that the use of a layer of recording 
material directly on a glass substrate results in a laser recording medium 
of substantially less sensitivity than a corresponding laser recording 
medium comprising a recording layer formed on a plastic substrate. In 
addition, the affinity between the metal recording layer and a glass 
substrate may produce irregularities in the shapes and sizes of holes 
burned into the recording layer. Use of a glass substrate thus 
necessitates the forming of a more complex recording medium in order to 
maintain overall sensitivity of the laser recording system and to achieve 
high writing speeds with low error rates. 
A copending and commonly assigned application of Kaczorowski and Shen, Ser. 
No. 950,066, filed Oct. 10, 1978 (now abandoned in favor of continuation 
application Ser. No. 122,613, filed Feb. 19, 1980 now abandoned), 
discloses the use of a layer of common, solvent-based plastic material 
between a glass substrate and the layer of recording material to produce a 
recording medium of substantially improved sensitivity and hole forming 
characteristics. This copending application further discloses the use of 
an additional protective layer of material over the thin recording layer. 
Artisans in this field have generally recognized the benefits of combining 
a layer of plastic material intermediate the substrate and the recording 
layer with a protective coating over the recording layer. However, while 
plastics have been suggested for use as the protective layer, in practice 
artisans have typically employed inorganic materials such as silicon 
dioxide in the protective coating, because the solvent-based plastic 
materials of the intermediate layer are dissolved or attacked when a 
protective layer of the same or similar solvent-based plastic material is 
attempted to be applied as the solvent utilized readily penetrates the 
thin layer of laser recording material. 
In a copending and commonly assigned application of A. Forster and M. 
Ockers, Ser. No. 080,516, filed Oct. 1, 1979, now U.S. Pat. No. 4,360,820 
the use of a vapor deposited plastic layer as a protective coating for a 
laser recording medium is disclosed. In this application the method of 
depositing the protective plastic layer on top of the recording layer of 
the medium precludes any attacking of the intermediate layer between the 
substrate and the recording layer, since no solvent is present in the 
vapor deposition process. Accordingly, the intermediate layer between the 
recording layer and the substrate may be a layer of solvent-based plastic 
material. Alternatively, Forster and Ockers disclose the use of a vapor 
deposited layer of plastic material as the intermediate layer between the 
substrate and the recording layer. While the Forster and Ockers approach 
provides a recording medium in which the recording layer is encased 
between two plastic layers, it requires the use of special vapor 
deposition apparatus to form the parylene layers utilized in the recording 
medium. 
A laser recording medium in accordance with this invention comprises a 
substrate, a first layer of plastic material formed on the substrate, a 
layer of optical energy absorbing material (i.e. a recording layer) formed 
on the first layer of plastic material, and a second layer of plastic 
material formed on the recording layer to provide a protective coating 
therefore, with the plastic material of the first layer being 
characterized by substantial solvent resistance and the plastic material 
of the second layer being a solvent-based plastic material. In accordance 
with a further aspect of this invention, the plastic material of the first 
layer formed on the substrate is a crosslinked polymeric material formed 
by reacting one or more components of a class of materials comprising 
active polymers with one or more components of a class of materials 
comprising cross-linking organic moieties. Preferably the reaction forming 
the crosslinked polymeric material is carried out at elevated temperature 
and in the presence of a selected catalyst to speed the formation of the 
crosslinked material. Alternatively, certain components of crosslinking 
organic moieties may be reacted together in the presence of a selected 
catalyst to form self-condensation, crosslinked polymers. By appropriate 
selection, solvent-resistant plastic layers which have all the necessary 
characteristics for serving as an intermediate layer are formed. 
In accordance with another aspect of this invention, the plastic material 
of the first layer is a polymeric material formed in a vapor deposition 
process wherein a hot reactive monomer vapor is condensed as a polymeric 
coating on the substrate. The polymeric material formed in this fashion 
may comprise a parylene material. 
By first forming a layer of solvent-resistant plastic material on the 
substrate, a multi-layer laser recording medium can be readily completed 
by next forming the thin recording layer on the solvent-resistant 
intermediate layer and then promptly coating the recording layer with a 
layer of common, solvent-based plastic material to seal the recording 
layer against any deterioration which may otherwise be caused by abrasion 
or reaction with the ambient environment to form metal oxides or 
contamination from the ambient atmosphere. Thus, in accordance with this 
invention solvent-resistant coating is formed on the substrate at a less 
critical time in the process of forming a laser recording medium, so that 
final protection of the recording layer formed thereon can be simply and 
promptly provided by a solvent-based plastic layer.

FIG. 1 illustrates the apparatus utilized in a typical laser beam recording 
system. This type of laser recording system is now generally well known in 
the art and need not be discussed in detail herein. Reference is made to 
the above mentioned Becker U.S. Pat. No. 3,474,457 and Becker et al. U.S. 
Pat. No. 4,001,840 for a more detailed discussion of the principles of 
laser recording and exemplary apparatus embodying these principles. 
Generally laser beam recording involves the use of a laser 10 with its 
output coupled to a beam modulator 20 which is driven by an input signal 
means 50 to produce a modulated laser beam output. In a binary data 
writing mode the input signals means supplies a stream of binary digits 
such that the modulator produces a binary amplitude modulation of the 
laser beam. Focusing and scanning apparatus 30 receives the modulated 
laser beam, focuses it to a very small spot on recording medium 40 and 
scans it in a predetermined pattern across recording medium 40. As the 
modulated laser beam strikes various sequential cell locations of the 
recording layer in laser recording medium 40, it burns a very small hole ( 
0.5-1.0 microns in diameter) therein if the modulated laser beam is on at 
that time or leaves the recording layer undisturbed if the modulated laser 
beam is off. The term "burn" is typically used in the art to describe the 
hole formation in the recording layer even though the recording layer is 
actually melted or vaporized to create a hole rather than being burned in 
the ordinary sense of the word. Accordingly, the binary data input to the 
modulator 20 is reproduced on recording medium 40 as the presence or 
absence of a hole at each cell location in the recording medium. The bit 
pattern written into recording medium 40 can be later read by again 
scanning the recording medium with an unmodulated laser beam and detecting 
the presence or absence of a hole in each cell location in terms of the 
amount of light reflected at each cell location. 
As generally discussed above, laser data recording apparatus is inherently 
capable of recording binary data at very high densities on the order of 
about 10.sup.9 bits per square inch. As previously noted to provide 
apparatus which enables a laser recording system to achieve bit densities 
approaching the inherent capability of the technology it places heavy 
demands on all aspects of the laser recording system and especially the 
laser recording medium. Since data is recorded in the form of the presence 
or absence of minute holes burned into the recording layer by highly 
focused laser beam, the overall stability and durability of the laser 
recording medium both during the recording process and for a long time 
period thereafter is critical in determining the ultimate bit density 
which can be utilized and still achieve data writing and reading at low 
error rates over long periods of time. Stability and durability are 
especially critical if the laser recording system is to be utilized for 
archival storage of image data from documents which are thereafter 
destroyed. 
To provide a recording medium which can accurately and reproducably be 
aligned with the scanning laser beam in a laser recording system requires 
that the recording medium utilize a dimensionally stable inflexible 
substrate such as a thin glass slide of the type generally used by the 
semiconductor industry in forming highly accurate photomasks used in the 
production of large scale integrated circuits. Such glass slides form the 
basis for a recording medium which has excellent dimensional stability and 
can easily be integrated into an overall data slide handling system for 
reproducibly positioning the recording medium with reference to the 
scanning path of the laser beam. Further, it is necessary to form on the 
glass substrate a recording layer of material which is sensitive to 
optical energy of the wavelength of the laser beam in a manner which will 
provide overall long term stability for the recording medium. 
FIG. 2 illustrates the structure of a laser recording medium in accordance 
with this invention as comprising a transparent substrate 41 having formed 
thereon a first layer of plastic material 42, a recording layer 43 and a 
second layer of plastic material 44. Transparent substrate 41 is 
preferably a glass slide. Conveniently, the glass slide may be about four 
inches square and 60 mils thick. On one surface of glass substrate 41 a 
first layer of plastic material 42 is formed. Preferably the laser beam is 
incident on recording layer 43 through the glass substrate 41 and 
intermediate layer 42 since any dust particles which might accumulate on 
the exposed substrate surface are then out-of-focus during reading and 
writing of data in recording layer 43. In accordance with this invention 
the material of this first layer is characterized by substantial 
solvent-resistance. This characteristic may be achieved by utilizing a 
crosslinked polymeric material which, although utilizing solvent-based 
plastic materials in its formation, achieves substantial 
solvent-resistance due to the cross-linking of the polymers comprising the 
final material of the layer. 
Alternatively, solvent-resistant plastic layer 42 can be provided by 
utilizing a polymeric material such as parylene which also has a high 
solvent resistance and is formed in a vapor deposition process wherein a 
hot reactive monomer vapor is condensed on substrate 41 as a polymeric 
coating. This condensed polymeric coating is optionally formed only on one 
surface of the glass substrate 41 if suitable masking techniques are 
utilized on the other surface or may be formed on all surfaces of 
substrate 41. Depending on the process utilized in forming 
solvent-resistant plastic layer 42 it may be formed to a thickness in the 
range of 0.05 microns to 10 microns. Thickness values throughout this 
range are readily attainable utilizing a parylene vapor deposition 
process. When utilizing a coating process involving plastic material 
initially dissolved in a solvent, thicknesses in the range from 0.5 to 
about 2 microns are readily achievable. 
The optical and other characteristics of the materials of an intermediate 
layer 42 of solvent-resistant plastic materials are suited to a laser 
recording medium for use in a system in which the recording layer is 
burned by a laser beam transmitted through both the substrate and the 
intermediate layer. Intermediate layers which have high optical clarity 
are produced. The solvent resistant materials have an index of refraction 
in the range of 1.3-1.7 and are thus sufficiently closely matched to that 
of glass to minimize reflections. These materials also have a much lower 
thermal conductivity than the glass substrate to provide a laser recording 
medium of high sensitivity to laser beam energy. The materials adhere well 
to the glass substrate and bond well to a metal recording layer to produce 
a stable recording medium. 
A number of well-known materials may be utilized as the data recording 
layer 43. Preferably, recording layer 43 is formed with relatively low 
melting point metals such as bismuth or tellurium. Recording layer 43 is 
preferably formed to a thickness of about 50-200 Angstroms in order to 
provide a high sensitivity to laser energy incident thereon. 
Layer 44 of plastic material has the principal function to protect the 
recording layer 43 from abrasion and contamination by chemicals or other 
materials existing in the ambient environment in which recording medium 40 
will be employed. Since intermediate layer 42 is formed of a 
solvent-resistant plastic material, protective layer 44 can be formed in a 
solvent-plastic coating process using any of the common plastics, 
including acrylic, polystyrene, polyurethane, polyethylene, epoxy, 
cellulose acetate materials or mixtures thereof dissolved in a solvent 
such as toluene, ketone or aromatic hydrocarbons. The solvents will not 
themselves adversely affect the thin recording layer and the 
solvent-resistance of the intermediate layer 42 maintains the integrity of 
the bond of both recording layer 43 to intermediate layer 42 and 
intermediate layer 42 with substrate 41. To provide sufficient protection 
for recording layer 43, the protective layer 44 is preferably formed to a 
thickness of at least 0.5 microns. 
In general the formation of a crosslinked polymeric material to serve as 
intermediate layer 42 involves the selection of one or more polymeric 
materials with active hydroxyl, carboxylic or hydrogen (amide) groups to 
react with organic moieties that condense on such active groups in the 
presence of a catalyst and at an elevated temperature to speed the 
crosslinking. Alternatively, certain components of organic moieties can be 
reacted together with certain catalysts to form self-condensation 
polymers. Some general examples of active polymers which may be utilized 
are cellulose esters, polyvinyl acetals, polyester resins, acrylic resins, 
epoxy resins, polyvinyl alcohol, polyvinyl acetate, and alkyd resins. Some 
examples of crosslinking moieties are melamine resins, isocyanates, acid 
anhydrides and formaldehyde resins. Useful catalysts include a number of 
acids, bases and organometallics. 
The following specific examples are given to illustrate the present 
invention in greater detail but are not to be construed to limit the scope 
of the invention. 
EXAMPLE 1 
A clean glass slide was coated with a plastoic having the following 
formulation of components: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
Polyester 4900 (DUPONT) 5 
Methylene Chloride 86.75 
Flow Control Agent 0.16 
Methyl Oxitol 7.8 
Isocyanate Prepolymer (RC 803-DUPONT) 
0.25 
______________________________________ 
The slide coated with this formulation was baked for four hours at a 
temperature of 150.degree. C. to produce crosslinking of the polyester 
resin and isocyanate prepolymer. This resulted in a clear plastic coating 
about 0.5 microns thick with excellent adhesion to the glass slide and 
good solvent resistance. Adhesion was tested by cellophane tape on the 
layer and pulling it off at right angles to the substrate. Solvent 
resistance was tested by dropping methyl ethyl ketone on the surface and 
rubbing the surface with a swab having MEK thereon. Thereafter a layer of 
tellurium approximately 200 Angstroms thick was applied to the crosslinked 
plastic layer by vacuum deposition. Next, a protective coating of 
polymeric material was applied to the tellurium recording layer utilizing 
the following components: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
Cellulose Acetate Butyrate 
7.5 
(CAB 381-20 - EASTMAN CHEMICALS) 
Methyl Ethyl Ketone 89.5 
Flow Control Agent 0.06 
Methyl Oxitol 2.94 
______________________________________ 
The protective coating was baked for about fifteen minutes at a temperature 
of 110.degree. C. Thereafter inspection of the three-layer structure 
showed that no dissolution of the underlying crosslinked polymer layer had 
occurred and an integral encapsulated metal recording layer was produced. 
EXAMPLE 2 
A clean glass slide was coated with a plastic formulation having the 
following components: 
______________________________________ 
Parts 
Components by Weight 
______________________________________ 
Oil-Free Polyester Alkyd Resin 
58 
(Aroplaz 6755-A1-80 - ASHLAND CHEMICALS) 
Methyl Ethyl Ketone 274 
Hexamethoxy Methyl Melamine 
22.5 
(CYMEL 303 - AMERICAN CYANAMID) 
Flow Control Agent 0.6 
Cellulose Acetate Butyrate 1.6 
(CAB 551-0.2 - EASTMAN CHEMICALS) 
Methyl Oxitol 235 
P-Toluene Sulfonic Acid as a catalyst 
0.7 
(CYCAT 4040 - AMERICAN CYANAMID) 
Isopropanol 15.4 
______________________________________ 
The plastic coating with the above formulation was baked for fifteen 
minutes at a temperature of 150.degree. C. to produce a crosslinked 
melamine-polyester film. This plastic film was the optically clear coating 
with excellent adhesion and solvent resistance. The coating thickness was 
approximately 0.5 microns. 
The next step was to apply a thin layer of tellurium to serve as the 
recording layer. This was done by vacuum deposition of a thin film about 
200 Angstroms thick. Thereafter the same protective coating as described 
in Example 1 was applied. The resulting structure was an integral 
encapsulated metal recording layer having no damage to the intermediate 
layer caused during the formation of the protective coating. 
EXAMPLE 3 
A clean glass slide was coated with a plastic material having the following 
formulation: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
Hexamethoxy Methyl Melamine 
17 
(CYMEL 303 - AMERICAN CYANAMID) 
Methyl Ethyl Ketone 423 
Flow Control Agent 0.34 
P-Toluene Sulfonic Acid as a catalyst 
0.8 
(CYCAT 4040 - AMERICAN CYANAMID) 
Methyl Oxitol 16.7 
Isopropanol 17.2 
Cellulose Acetate Butyrate 
25 
(CAB 381-0.5 - EASTMAN CHEMICALS) 
______________________________________ 
The plastic coating with this formulation was baked for fifteen minutes at 
150.degree. C. to achieve crosslinking of the constituent materials. The 
resulting clear coating had excellent adhesion and good solvent 
resistance. The coating thickness was approximately 0.5 microns. 
Thereafter a recording layer of tellurium was deposited in a vacuum 
deposition process to a thickness of approximately 200 Angstroms followed 
by application of a protective coating as described above in Example 1. 
This resulted in an integral encapsulated metal recording layer in which 
the intermediate coating was not affected by the application of the 
protective coating. 
EXAMPLE 4 
A clean glass slide was coated with a plastic material having the following 
formulation: 
______________________________________ 
Parts 
Components by Weight 
______________________________________ 
Oil-free Polyester Alkyd Resin 
49.2 
(Aroplaz 6755-A1-80 - ASHLAND CHEMICALS) 
Methyl Ethyl Ketone 232.6 
Hexamethoxy Methyl Melamine 
19.2 
(CYMEL 303 - ASHLAND CHEMICALS) 
Flow Control Agent 0.5 
Cellulose Acetate Butyrate 1.4 
(CAB 551-0.2 - EASTMAN CHEMICALS) 
Methyl Oxitol 199.4 
Isopropanol 13.1 
Xylene 105 
P-Toluene Sulfonic Acid as a catalyst 
0.6 
(CYCAT 4040 - AMERICAN CYANAMID) 
______________________________________ 
The plastic coating with this information was then baked for fifteen 
minutes at a temperature of 150.degree. C. to produce crosslinking of the 
plastic constituents. An optically clear coating with excellent adhesion 
and solvent resistance in accordance with standard tests was obtained. The 
plastic layer had a thickness of about 0.5 microns. 
Thereafter a layer of tellurium about 200 Angstroms thick was deposited on 
the intermediate plastic coating in a vacuum depositing process. 
Thereafter a second plastic layer was formed by applying a plastic 
material of the following composition on the layer of tellurium: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
Hexamethoxy Methyl Melamine 
8.5 
(CYMEL 303 - AMERICAN CYANAMID) 
Methyl Ethyl Ketone 423 
Flow Control Agent 0.17 
Cellulose Acetate Butyrate 
12.5 
(CAB 381-0.5 - EASTMAN CHEMICALS) 
Methyl Oxitol 0.8 
Isopropanol 8.6 
P-Toluene Sulfonic Acid as a catalyst 
0.4 
(CYCAT 4040 - AMERICAN CYANAMID) 
______________________________________ 
This second plastic coating was baked for fifteen minutes at a temperature 
of 150.degree. C. to produce crosslinking of the plastic constituents. 
This resulted in a protective layer over the tellurium recording layer 
with no disturbance of either the tellurium layer or the underlying 
plastic layer. 
Thereafter a layer of aluminum was applied to the second plastic layer by 
vacuum deposition to a thickness of approximately 750 Angstroms. Finally, 
a protective coating of polymeric material was applied over the aluminum 
film utilizing the protective layer composition set forth above in Example 
1. 
The laser recording medium produced in accordance with this example 
utilizes the tellurium layer as the recording layer with the aluminum 
layer acting as a reflective layer for laser beam energy transmitted 
through the thin tellurium layer. The resulting laser recording medium was 
characterized by excellent durability and stability of the constituents 
layers. 
EXAMPLE 5 
A clean glass slide was coated with a plastic material having the following 
formulation: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
Polyvinyl Butyral 11.2 
(BUTVAR B-73 - MONSANTO) 
Methyl Oxitol 924 
Hexamethoxy Methyl Melamine 
7.4 
(CYMEL 303 - AMERICAN CYANAMID) 
Flow Control Agent 0.14 
Isopropanol 10.7 
P-Toluene Sulfonic Acid 0.49 
(CYCAT 4040 - AMERICAN CYANAMID) 
______________________________________ 
The plastic coating with this formulation was baked for fifteen minutes at 
a temperature of 150.degree. C. to produce cross-linking of the 
constituent plastic material. An optically clear coating with excellent 
adhesion and solvent resistance was achieved. Formation of a complete 
recording medium utilizing this intermediate layer can then be achieved 
using any of the additional steps set forth in previous examples. 
EXAMPLE 6 
In this example a catalyzed one component plastic layer was formed by 
coating a clean glass slide with a plastic material of the following 
formulation: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
Hexamethoxy Methyl Melamine 
25 
(CYMEL 303 - AMERICAN CYANAMID) 
Methyl Ethyl Ketone 200 
Flow Control Agent 0.2 
Methyl Oxitol 9.8 
Isopropanol 14.3 
P-Toluene Sulfonic Acid as a catalyst 
0.7 
(CYCAT 4040 - AMERICAN CYANAMID) 
______________________________________ 
The coating with this formulation was baked for fifteen minutes at a 
temperature of 150.degree. C. to produce a self-condensation type 
crosslinking of the plastic material. The result was an optically clear 
coating with excellent adhesion and solvent resistance. Completion of a 
laser recording medium can be achieved as in any of the Examples 1-4 set 
forth above. 
EXAMPLE 7 
A clean glass slide was provided with a layer of parylene C deposited on 
both sides of the glass slide with a thickness of about 10 microns. 
Thereafter a layer of tellurium was vacuum deposited on the parylene layer 
to a thickness of approximately 200 Angstroms. Next, a protective coating 
of a plastic material having the following composition was applied: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
Cellulose Acetate Butyrate 
7.5 
(CAB 381-20 - EASTMAN CHEMICALS) 
Methyl Ethyl Ketone 89.5 
Flow Control Agent 0.06 
Methyl Oxitol 2.94 
______________________________________ 
This coating was baked for about fifteen minutes at a temperature of 
110.degree. C. The protective layer thusly formed was approximately two 
microns thick. The solvent-based protective coating produced no damage to 
the recording layer or the intermediate layer of parylene and, 
accordingly, an integral encapsulated recording layer was produced. 
In each of the above examples the Flow Control Agent may comprise one of 
the Union Carbide silicones marketed under the trade names L4500, L5310, 
and L6202. It will be appreciated by those skilled in this art that other 
permutations and combinations of the various examples set forth above 
could be employed to achieve the same or similar results. 
It will be apparent to those skilled in the art that the structure of this 
invention could be adapted to form a more complex laser recording medium 
involving one or more additional recording layers by utilizing successive 
layers of solvent-resistant material with a final solvent-based material 
utilized as the protective coating over the medium. Furthermore, the 
invention is readily adaptable to recording media structures involving a 
reflecting layer (not shown) formed on top of protective layer 44 shown in 
FIG. 2 with the thickness of the protective layer being selected in 
conjunction with the optical characteristics of the reflecting layer 
formed thereon to maximize the reflection of optical energy transmitted 
through recording layer 43 back to that recording layer, thereby to 
further increase the sensitivity of the recording medium to laser beam 
energy. Example 4 above comprises a recording medium structure having such 
a reflecting layer and including a final protective coating formed over 
the aluminum reflecting layer to completely encapsulate it.