FR2466830A1 - LASER RECORDING MEDIUM - Google Patents

Abstract

Disclosed is a laser recording medium. The structure of this recording medium comprises a substrate 41 on which are applied a first layer 42 of plastic material, a layer 43 of optical energy absorbing material, and a second layer 44 of plastic material constituting a protective coating. The plastic of the first layer 42 is characterized by high resistance to solvents, and the plastic of the second layer 44 is a solvent-based material. Field of application: memorization and storage of documents and other information. (CF DRAWING IN BOPI)

Description

The invention relates generally to storage systems

information in data

  binaries, and more particularly a recording medium

  data that reacts to the energy of a focused laser beam. The data processing industry has made rapid progress in developing computer systems and associated peripheral equipment for handling alphabetic and digital data in binary code at higher speeds, and for storing these data. data at higher densities and at lower cost. The administrative departments of large corporations and governments are increasingly relying on data processing equipment to automate the collection, storage and processing of data to improve the efficiency of business transaction manipulation. accounting information, etc. Increases in computer work rates are due in large part to advances in semiconductor technology that has enabled the production of large-scale integrated circuits (LSIs) with higher densities of binary logic elements or gates that operate at higher speeds. higher speeds. The densities of the memories have also been substantially increased. In the field of semiconductor memories, bit-density increases have resulted in both advances in large-scale integrated circuit technology, allowing a decrease in the size of elementary memory cells, and new technologies applied to circuits. integrated on a large scale such as magnetic bubble memories. In the field of magnetic memories, density improvements have been achieved in rigid and flexible disk systems by improvements in magnetic recording media and read heads and

  associated with them.

  Despite the significant increases in the density of semiconductor memory and magnetic memory systems, the cost per bit of these storage media,

2466830.

  as well as coding costs, do not justify the use of such a technology for program-based storage of large volumes of traditional business records such as correspondence, reports, forms , official documents, etc. The memorization and maintenance of both the current working files constituted by these documents, and archives consisting of selected documents, which must be kept safe for long periods, still largely rely on manual operations requiring personnel and ever more expensive storage spaces. The technology of digital laser recording, which has developed over the last few years, allows for high density storage of binary data, which can be easily integrated with computer data processing equipment and printing and printing equipment. exploration of facsimile documents. This technology enables real-time optical data logging

  image in a highly compressed format and opto-

  fast electronic to the stored image data, and thus is the basis for memorizing and retrieving documents by means of a computer and a global record management system. A laser beam writing and reading system, constituting the core of this technology, makes it possible to memorize binary digital information in the form of the presence or absence of very small holes formed in a recording medium, consisting of a thin film, when a modulated and highly focused laser beam is shifted to

  explore the recording medium.

  The basic principles of registration

  laser images are shown in the United States patent.

  United States of America NI 3,474,457. United States Patent Nos. 3,654,624 and 3,657,707 disclose a laser recording system using a rotating drum which carries a laser recording medium comprising flexible strips of plastic material (eg "Mylar") coated with a layer of energy absorbing material. Such a laser recording medium is described in more detail in U.S. Patent No. 3,665,483. However, the use of a rotating drum or any other mechanical means recording limits the scanning speed both during recording and during data extraction, which artificially limits the entire system to significantly lower write and read speeds than those imposed by the energies that the laser beam offers and the sensitivities of the recording media. In addition, the use of flexible recording media limits the alignment accuracy that can be obtained repeatedly between the data tracks and the laser beam path and, therefore, limits the system to bit densities. of data substantially less than the minimum dimension of a cell imposed by the optics of the system. In addition, flexible recording media are very prone to contamination by dust particles, which can lead to errors in writing and / or reading of data and thus require special handling and storage precautions. dust-free compartments inside the system. It therefore appears necessary to use different means to control the movement

  the laser beam on the recording medium

  and the various structures for the recording medium itself so that the resulting system makes full use of the read / write speed and bit densities that laser beam recording technology allows and which also simplifies the recording requirements.

  handling and storage of recording media.

  U.S. Patent No. 4,001,840 discloses a laser recording system that utilizes a mirror assembly that is rotatable on two orthogonal axes to deflect a laser beam in two directions to write data to a laser layer. recording formed on a rigid glass substrate. This mirror beam deflection system increases the scanning speed of the beam and the rigid glass substrate supporting the recording layer allows alignment

  more precise and reproducible between the recording medium

  ment and the laser beam moved. However, it has been found that the use of a recording material layer applied directly to a glass substrate constitutes a laser recording medium having a significantly lower sensitivity than that of a recording medium.

  corresponding laser comprising a recording layer

  formed on a plastic substrate. In addition, the affinity between the recording metal layer and a glass substrate may result in irregularities in the shape and size of the holes made by burning in the recording layer. The use of a glass substrate therefore requires the realization of a more complex recording medium to maintain the overall sensitivity of the laser recording system and to achieve

  high write speeds with low error rates.

  U.S. Patent Application No. 950,066, filed October 10, 1978 by Kaczorowski and Shen, discloses the use of a common solvent-based plastics material layer between a glass substrate and the substrate. recording material layer to produce a recording medium having substantially improved sensitivity and hole-forming characteristics. This application also describes the use of an additional layer of protection applied to the thin recording layer. Specialists in this field generally recognize. advantages obtained by combining a layer of plastic material placed between the substrate and the recording layer and a coating

  protector applied to the recording layer.

  However, although plastics have been suggested for the protective layer, in practice, specialists generally use inorganic materials such as silicon dioxide for the protective layer, because the solvent-based plastics of the intermediate layer are dissolved or etched when a protective layer made of the same solvent-based plastics material or the like is applied, since the solvent used readily passes through the thin layer of laser recording material. U.S. Patent Application No. 80,516, filed October 1, 1979 by A. Forster and M. Ockers, discloses the use of a vapor deposited plastic layer to form a coating.

  protector for a laser recording medium.

  In this application, the method for depositing the protective plastic layer on the top of the recording layer of the support prevents any attack of the intermediate layer between the substrate and the recording layer, since no solvent is used. in the vapor deposition process. Therefore, the intermediate layer between the recording layer and the substrate may be a solvent-based plastic layer. Alternatively, the aforementioned NI 80 516 application describes the use of a vapor deposited plastic layer as an intermediate layer between the substrate and the recording layer. Although this method provides a recording medium in which the recording layer is held between two plastic layers, this process requires the use of a special spray apparatus to form the parylene layers.

  used in the recording medium.

  A laser recording medium comprising a substrate, a first plastic layer 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 form a protective coating of this recording layer, the plastic material of the first layer being characterized by high resistance to solvents and the plastic material of the second layer being a solvent-based material. According to another characteristic of the invention, the plastics material of the first layer formed on the substrate is a crosslinked polymeric material formed by reaction of one or more components of a class of materials comprising active polymers with one or more components of a class of

  materials comprising organic crosslinking moieties.

  The reaction forming the crosslinked polymeric material is preferably conducted at elevated temperature and in the presence of a catalyst selected to accelerate the formation of the crosslinked material. Alternatively, some components of the organic crosslinking moieties may be reacted with one another in the presence of a catalyst selected to form cross-linked, self-condensing polymers. By a suitable choice, layers of solvent-resistant plastic are formed, having all the characteristics

  necessary to form an intermediate layer.

  According to another characteristic of the invention, the plastics material of the first layer is a polymeric material formed by a vapor deposition process in which a monomer vapor that reacts with heat is condensed forming a polymeric coating on the substrate. The polymeric material formed in this way can

understand a parylene.

  By first forming a solvent-resistant plastic layer on the substrate, it is possible to

  easily complete the production of a recording medium

  multi-layer laser then forming the thin recording layer on the solvent-resistant intermediate layer and then rapidly coating the recording layer with a common solvent-based plastic layer to protect the recording layer against any deterioration that may otherwise result from abrasion or reaction with the environment to form metal oxides, or contamination by the ambient atmosphere. Thus, according to the invention, a solvent-resistant coating is formed on the substrate at the least critical moment of the process of producing the laser recording medium, so that the final protection of the recording layer formed on the substrate can be obtained simply and quickly at

  means of a solvent-based plastic layer.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting example and in which: FIG. 1 is a simplified diagram of an example of a laser recording apparatus using the recording medium by laser according to the invention; and Fig. 2 is a partial cross section showing the structure of the laser recording medium

according to the invention.

  Figure 1 shows the apparatus used in a conventional laser beam recording system. This type of laser recording system is generally well known to those skilled in the art and therefore it is not necessary to describe it in detail, but reference can be made to US Pat. Nos. 3,474,457 and US Pat. No. 4,001,840, which describes in detail the principles of laser recording and examples of apparatus embodying these principles. In general, laser beam recording consists in using a laser whose output is connected to a beam modulator 20 which is driven by an input signal producing element 50 to produce a laser modulated laser beam. exit. In binary data writing mode, the element producing the input signals provides a stream of binary digits so that the modulator realizes a binary amplitude modulation of the laser beam. A focusing and scanning device receives the modulated laser beam, concentrates or focuses it at a very small point on the recording medium and moves it in a predetermined scanning motion across the recording medium 40. . When the modulated laser beam reaches various successive positions of cells of the recording layer of the support 40, it burns a very small hole (0.5-1.0 micrometer diameter) in the film layer. recording whether the modulated laser beam is in the "working" state at this time, or it does not produce any effect on the recording layer if the modulated laser beam is in the "idle" state. The term "burning" is generally used to describe the formation of a hole in the recording layer, although the latter is actually melted or vaporized for hole formation rather than burned in the common sense. Therefore, the binary data provided to the modulator 20 is reproduced on the recording medium 40 in the form of the presence or absence of a hole in each cell position of the recording medium. The bit network written on the recording medium 40 can then be read by re-scanning the recording medium by means of a non-modulated laser beam and by detecting the presence or absence of a hole. in each cell position, this detection relating to the quantity of

  light reflected at each cell position.

  As described generally above, the laser data recording apparatus is, by its nature, capable of recording binary data at very high densities, of the order of about 155 × 10 bits. / cm2. As stated previously, the realization of an apparatus enabling a laser recording system to reach bit densities approaching the inherent possibilities of the technology places very large loads on all the characteristics of the laser recording system, and in particular on the laser recording medium. Since the data are recorded in the form of the presence or absence of

  small holes made by burning in the recording layer

  With the aid of a highly concentrated laser beam, the overall stability and longevity of the laser recording medium, both during the recording process and for a long consecutive time, are critical for the determination of the final density. of bits that can be used while allowing the writing and reading of data with low error rates for long periods of time. Stability and longevity are particularly critical if the laser recording system is to be used for archiving image data from documents that are subsequently destroyed. To produce a recording medium that can be precisely and repeatedly aligned with the

  laser beam for exploration in a recording system

  By laser means, the recording medium must have a non-flexible, dimensionally stable substrate, for example a thin glass slide of the type generally used in the semiconductor industry to form very precise photographic masks employed in the semiconductor industry. in the production of large-scale integrated circuits. Such glass slides form the basis of a recording medium having excellent dimensional stability and which can be easily integrated into a data slide handling assembly for repeatedly positioning the recording medium with respect to the recording medium. exploration trajectory followed by the laser beam. In addition, it is necessary to form on the glass substrate a layer of recording material that is sensitive to the optical energy of the wavelength of the laser beam, in a manner that confers on the medium

  long-term overall stability.

  Figure 2 shows the structure of the laser recording medium according to the invention. This support comprises a transparent substrate 41 on which are formed a first layer 42 of plastic, a recording layer 43 and a second layer 44 of plastics material. The transparent substrate 41 is preferably a glass slide. The glass slide may advantageously have the

  form of a square of 10 cm of side and 1,5 mm of thickness.

  A first layer 42 of plastic material is formed on a first surface of the glass substrate 41. The laser beam preferably arrives on the recording layer 43 through the glass substrate 41 and the intermediate layer 42, because the dust particles which may have accumulated on the exposed surface of the substrate are thus off-center during the reading and the writing data into the recording layer 43. According to the invention, the material of this first layer is characterized by a high resistance to solvents. This characteristic can be. obtained by the use of a cross-linked polymeric material which, although using solvent-based plastics for its production, achieves a high resistance to solvents as a result of the crosslinking of the constituent polymers;

final layer.

  Alternatively, the layer 42 of solvent resistant plastics material can be obtained by the use of a polymeric material such as parylene which is also highly resistant to solvents and which is formed by a vapor deposition process in which a monomer vapor reacts to heat is condensed

  on the substrate 41 in the form of a polymeric coating.

  The condensed polymeric coating may be formed only on one surface of the glass substrate 41 if suitable masking techniques are used on the other surface, or it may be formed on all surfaces of the substrate 41. Depending on the process used for forming the solvent-resistant plastic layer 42, this layer may be formed to a thickness of 0.05 to 10 microns. Thickness values within this range can be easily obtained by using a parylene deposition process by

  vaporization. When implementing a coating process

  using a plastic material initially dissolved in a solvent, thicknesses of the order of 0.5 to about

  2 microns can be easily obtained.

  The optical and other characteristics of the materials of an intermediate layer 42 made of solvent resistant plastics are adapted to a laser recording medium to be used in a system in which the recording layer is burned by a transmitted laser beam. through the substrate and the intermediate layer. Intermediate layers having a high optical transparency are produced. Resistant materials

  solvents have a refractive index of about

  1.7 and these indices are therefore sufficiently close to those of glass to minimize reflections. These materials also have a much lower thermal conductivity than the glass substrate, so that the laser recording medium has a high sensitivity to the energy of the laser beam. The materials adhere well to the glass substrate and bond well to a recording metal layer, thereby providing support

stable recording.

  A number of well known materials can be used for the realization of the data recording layer 43. The recording layer 43 is preferably made of relatively low melting point metals, for example bismuth or tellurium. The recording layer 43 is preferably formed to a thickness of about 5 to 20 nanometers in order to provide a high sensitivity to the energy of the laser beam it receives. The main function of the plastic layer 44 is to protect the recording layer 43 against abrasion and contamination by chemicals or other materials present in the environment in which the recording medium 40 is used. Since the intermediate layer 42 is made of a solvent-resistant plastic material, the protective layer 44 can be obtained by carrying out a method of applying a plastics material containing a solvent, for example any of a number of common plastics such as

  acrylics, polystyrene, polyurethane, poly-

  ethylene, epoxy, cellulose acetate or mixtures thereof, dissolved in a solvent such as toluene, a ketone or aromatic hydrocarbons. The solvents do not affect, by themselves, the thin recording layer and the solvent resistance of the intermediate layer 42 maintains the integrity of the bonds of the recording layer 43 with the intermediate layer 42 and the intermediate layer 42 with the substrate 41.

  to obtain sufficient protection for layer 43 of

  the protective layer 44 is preferably formed

  at a thickness of at least 0.5 micrometer.

  In general, the production of a crosslinked polymeric material which can serve as an intermediate layer 42 involves the selection of one or more polymeric materials with hydroxyl, carboxylic or hydrogen (amide) groups active to react with organic moieties that condense on such active groups in the presence of a catalyst and at elevated temperature to accelerate the crosslinking. Alternatively, some organic portion components can be reacted with one another

  with certain catalysts to form polymers of

  condensation. Some general examples of active polymers that can be used include cellulosic esters, polyvinyl acetals, polyester resins,

  acrylic resins, epoxy resins, polyalcohol

  vinyl, polyvinyl acetate and alkyd resins. Examples of crosslinking moieties include melamine resins, isocyanates, acid anhydrides, and formaldehyde resins. Useful catalysts include a

  number of acids, bases and organo-

  metal. The following examples describe in more detail and for illustrative purposes, but in no way limiting, the support

recording device according to the invention.

EXAMPLE 1

  A clean glass slide is coated with a plastic material having the following component formulation: Components Parts by Weight Polyester "4900" (DUPONT) 5 Methylene Chloride 86.75 Flow Agent 0.16 "Methyl Oxitol" 7, Isocyanate (prepolymer) "RC 803" from Dupont 0.25 The slide coated with this composition is baked for 4 hours at a temperature of 150WC causing crosslinking of the polyester resin and the isocyanate of the prepolymer. This gives a clear plastic coating, about 0.5 micron thick, with excellent adhesion to the glass slide and good solvent resistance. The adhesion is tested using a "Cellophane" tape applied to the layer and pulled outward, perpendicular to the substrate. Solvent resistance is tested by the application of methyl ethyl ketone dropwise on the surface and by friction

  of the latter with a buffer carrying methyl-

  ethyl ketone. Then, a layer of tellurium about nanometers thick is applied to the layer of plastics crosslinked by vacuum deposition. A protective layer of polymeric material is then applied to the recording layer consisting of tellurium, which polymeric material comprises the following components: Components Parts by weight Cellulose acetate butyrate

  ("CAB381-20" - EASTMAN CHEMICALS) 7.5

  Methyl Ethyl Ketone 89.5 Flow Agent 0.06 "Methyl Oxitol" 2.94 The protective coating is baked for about 15 minutes at a temperature of 110 ° C. Then, an examination of the three-layer structure thus obtained shows that no dissolution of the underlying layer of cross-linked polymer has occurred and that a

  fully coated recording metal layer.

EXAMPLE 2

  A clean glass slide is coated with a plastic composition comprising the following components Components Oil-Free Alkyd Polyester Resin ("Aroplaz 6755-Al-80" ASHLAND CHEMICALS) Methyl Ethyl Ketone Hexamethoxymethyl Melamine

("CYMEL 303" AMERICAN CYANAMID)

  Flow Agent Cellulose Acetate Butyrate

("CAB 551-0,2" - EASTMAN CHEMICALS)

  Methylated "oxitol" p-toluenesulfonic acid (catalyst Parts by weight 22.5 0.6 1.6 "CYCAT 4040" from AMERICAN CYANAMID) 0.7 Isopropanol 15.4 Plastic coating having the composition indicated above is baked for 15 minutes at a temperature of 150 ° C to produce a cross-linked melamine-polyester film. This plastic film constitutes the optically transparent coating which has excellent adhesion and excellent solvent resistance. The thickness of the coating is

about 0.5 micrometer.

  The next step is to apply a thin

  layer of tellurium which assumes the function of a layer of

  tration. This operation is performed by vacuum deposition

  a thin film of about 20 nanometers thick.

  Then, the same protective layer as that described in Example 1 is applied. The resulting structure has a fully coated recording metal layer, and an intermediate layer exhibiting no deterioration

  resulting from the formation of the protective coating.

EXAMPLE 3

  A clean glass slide is coated with a plastic material having the following composition: Components Parts by weight Hexamethoxymethylmelamine

  ("CYMEL 303" - AMERICAN CYANAMID) 17

  Methyl Ethyl Ketone 423 Flow Agent 0.34 p-Toluene Sulfonic Acid ("CYCAT 4040" Catalyst)

AMERICAN CYANAMID) 0.8

  Methylated "Oxitol" 16.7 Isopropanol 17.2 Cellulose acetate butyrate

  (CAB 381-0.5 - EASTMAN CHEMICALS) 25

  The plastic coating having this formulation is baked for 15 minutes at 150 ° C. in order to cause the crosslinking of the constituent materials. The clear coating thus obtained has excellent adhesion and good solvent resistance. Its thickness

is about 0.5 micrometer.

  Then, a tellurium recording layer is vacuum deposited to a thickness of about 20 nanometers, and then a protective coating is applied as described in Example 1. This results in a fully recording metal layer. coated and an intermediate coating which is unaffected

  by the application of the protective coating.

EXAMPLE 4

  A clean glass slide is coated with a plastic material having the following formulation: Components Parts by weight Oil-free alkyd polyester resin ("Aroplaz 6755-Al-80" - ASHLAND CHEMICALS) 49.2 Methyl ethyl ketone 232.6 Hexamethoxymethyl melamine

  ("CYMEL 303" - ASHLAND CHEMICALS) 19.2

  Flow Agent 0.5 Cellulose Acetate Butyrate

  ("CAB 551-0.2 - EASTMAN CHEMICALS) 1.4

  "Oxitol" Methylated 199.4 Isopropanol 13.1 Xylene 105 p-Toluenesulfonic acid (Catalyst "CYCAT 4040" from the firm AMERICAN CYANAMID) 0.6 Then, the coating of material is baked for 15 minutes and at a temperature of 150 ° C. plastic to cause crosslinking of the components of the material

  plastic. This gives an optically transparent coating

  parent exhibiting excellent adhesion and solvent resistance, as demonstrated by standardized assays. The plastic layer has a thickness

about 0.5 micrometer.

  A layer of tellurium about 20 nanometers thick is then deposited under vacuum on the intermediate layer of plastic. A second layer is then formed on the tellurium layer by applying a plastics material having the following composition. Components Parts by weight Hexamethoxymethylmelamine

  ("CYMEL 303" - AMERICAN CYANAMID) 8.5

  Methyl Ethyl Ketone 423 Flow Agent 0.17 Cellulose Acetate Butyrate

  ("CAB 381-0.5" - EASTMAN CHEMICALS) 12.5

  "Oxitol" methylated 0.8 isopropanol 8.6 p-toluenesulphonic acid (catalyst "CYCAT 4040" from the firm AMERICAN CYANAMID) 0.4 - This second plastic layer is baked for 15 minutes at a temperature of 1500C. produce a crosslinking of the components of the plastic material. This gives a protective layer covering the recording layer in tellurium without the latter or the

  underlying layer of plastic material are affected.

  An aluminum layer is then vacuum-applied to the second plastic layer to a thickness of about 75 nanometers. Finally, a protective coating of polymeric material is applied to the aluminum film, this coating having the composition

  previously indicated in Example 1.

  The laser recording medium produced in accordance with this example uses the tellurium layer as the recording layer, the aluminum layer assuming the function of a reflective layer for the energy of the laser beam transmitted through the thin layer of tellurium. The laser recording medium thus obtained is characterized by excellent durability and stability of the constituent layers.

EXAMPLE 5

  A clean glass slide is coated with a plastic material having the following formulation Components Parts by Weight Polyvinylbutyral

("BUTVAR B-73" - MONSANTO) 11.2

  "Oxitol" methylated 924 Hexamethoxymethylmelamine

  ("CYMEL 303" - AMERICAN CYANAMID) 7.4

  Flow Agent 0.14 Isopropanol 10.7 p-Toluenesulfonic acid

  ("CYCAT 4040" - AMERICAN CYANAMID) 0.49

  Cook for 15 minutes at a temperature of

  1500C the plastic coating having this formulation to cause crosslinking of the constituent plastic material. An optically transparent coating is thus obtained with excellent adhesion and excellent solvent resistance. It is then possible to form a complete recording medium with the aid of this intermediate layer and by carrying out the additional steps indicated in the preceding examples.

EXAMPLE 6

  In this example, a single-component catalyzed plastic layer is formed by coating a clean glass slide with a plastics material having the following formulation: Components Parts by weight Hexamethoxymethylmelamine

  ("CYMEL 303" - AMERICAN CYANAMID) 25

  Methyl Ethyl Ketone 200 Flow Agent 0.2 "Oxitol" methyl 9.8 Isopropanol 14.3 p-Toluenesulfonic acid (catalyst "CYCAT 4040" from AMERICAN CYANAMID) 0.7

  Cook for 15 minutes at a temperature of

  The coating having this formulation is capped at 150 C to produce a self-condensation type cross-linking of the plastic. An optically transparent coating is thus obtained which exhibits excellent adhesion and excellent solvent resistance. A laser recording medium can be completed by carrying out the operations described in any of Examples 1 to 4 above.

EXAMPLE 7

  A layer of parylene C deposited on both sides of the slide, to a thickness of about 10 microns, is applied to a clean glass slide. Then, a layer of tellurium is deposited under vacuum on the parylene layer, to a thickness of about 20 nanometers. A protective coating is then applied, this coating consisting of a plastics material having the following composition: Components Parts by weight Cellulose acetate butyrate

  ("CAB 381-20" - EASTMAN CHEMICALS) 7.5

  Methyl Ethyl Ketone 89.5 Flow Agent 0.06 "Methyl Oxitol" 2.94 This coating is baked for about 15 minutes at a temperature of 110 ° C. The protective layer thus formed has a thickness of about 2 microns. The solvent-based protective coating so produced does not

  deteriorates neither the recording layer nor the

  medium of parylene and, consequently, we obtain a

  fully coated recording layer.

  In each of the examples described above, the flow agent may comprise one of the silicones marketed by Union Carbide Corporation under the references "L4500", "L5310" and "L6202". It also appears to those skilled in the art that other permutations and combinations of the various examples described above are possible to obtain the same results or similar results. It is also obvious to those skilled in the art that the structure according to the invention can be adapted for producing a laser recording medium more

  complex, with one or more layers of

  This is achieved by the use of successive layers of solvent-resistant material with a solvent-based final material used as a protective coating on the substrate. Furthermore, the invention can be easily adapted to recording medium structures having a reflective layer (not shown) formed on the top of the protective layer 44 shown in FIG. 2, the thickness of the protective layer being chosen according to the optical characteristics of the reflective layer formed thereon to maximize the reflection of the optical energy reflected back through the recording layer 43 to the same recording layer, thereby further increasing the sensitivity of the

  recording medium at the energy of the laser beam.

  Example 4 above describes a recording medium structure comprising such a reflective layer and a final protective coating formed on the aluminum reflective layer to completely coat the latter. It goes without saying that many modifications can be made to the recording medium described and

  shown without departing from the scope of the invention.

Claims (7)

  Laser recording medium, characterized in that it comprises a substrate (41), a first layer (42) of plastic material formed on said substrate, a layer (43) of optical energy absorbing material, formed on the first layer of plastic material, and a second layer (44) of plastic material formed on said layer of energy absorbing material to provide a protective coating for said layer, the plastic material of the first layer being characterized by resistance solvent and the plastic of the second layer being a plastic material to solvent base.   Recording medium according to claim 1, characterized in that the plastic material of the first layer is a crosslinked polymeric material formed by reacting at least one component selected from a group of materials comprising active polymers, with least one component chosen in. a group of subjects   comprising organic crosslinking moieties.   3. Support. recording apparatus according to claim 2, characterized in that the reaction is carried out at an elevated temperature and in the presence of a selected component in a group of materials comprising catalysts for accelerating the formation of the material crosslinked polymer.   Record carrier according to claim 1, characterized in that the plastics material of the first layer is a crosslinked polymeric material formed by reacting at least two components selected from a group of materials comprising organic crosslinking moieties, presence of a selected component in a group of materials comprising catalysts to form a   polymeric self-condensation material.   A recording medium according to claim 1, characterized in that the plastics material of the first layer is a polymeric material formed during a vapor deposition process in which a hot reaction monomer vapor is condensed on   the substrate to form a polymeric coating.   Recording medium according to claim 4, characterized in that the plastic material of the first layer comprises a parylene. 7. Recording medium according to one   any of claims 1, 2, 3, 4, 5 and 6, characterized   in that the second plastic layer is characterized by a high resistance to solvents, this support also comprising a layer of reflective material formed on the second layer of plastic material, and a third layer of plastic material formed on said layer of reflective material and   comprising a solvent-based plastic material.