WO1984004824A1

WO1984004824A1 - Optical recording structure involving in situ chemical reaction in the active structure

Info

Publication number: WO1984004824A1
Application number: PCT/US1984/000842
Authority: WO
Inventors: Boris J Muchnik; Franklin D Kalk; Fred W Spong
Original assignee: Storage Technology Corp
Priority date: 1983-05-31
Filing date: 1984-05-30
Publication date: 1984-12-06
Also published as: EP0145757A1

Abstract

An optical recording structure (1) comprised of: an optically smooth and light reflecting substrate (2); the lower portion of a matrix material (3), selected from the group consisting of halocarbon polymers; a discontinuous stratum of light absorbing material (5), selected from the group consisting of low melting point semi-conductors, high melting point semi-conductors, high melting point refractory metals and common metals; the upper portion of the matrix material (4), selected from the same group as the lower matrix, and; if desired, a separate protective and hermetic sealing layer (17), and a dust defocusing overcoat (18). In operation, the stratum of light absorbing material (5), though discontinuous, is of sufficient density as to create an anti-reflective condition when the stratum (5) and the matrices (3 and 4) are tuned to the appropriate thicknesses. Upon irradiation by a focused laser beam of sufficient power, the stratum material (5) chemically reacts with the matrix material (3 and 4), destroying the interface (6) which allowed the anti-reflective condition to exist, thereby creating an optically transparent opening (9) which allows a read beam to reflect off the light reflecting substrate (2). Data is therefore recorded in the changes in the reflective condition of the recording structure (1).

Description

OPTICAL RECORDING STRUCTURE INVOLVING IN SITU CHEMICAL REACTION IN THE ACTIVE STRUCTURE

BACKGROUND OF THE INVENTION

The present invention, an optical recording structure, relates to the field of high density information storage devices, and in particular to optical media recording structures for use in high density information storage devices.

In recent years, there have been many attempts to use low power radiation beams, particularly laser beams, to record and store digital information. The prior art has taught various methods for recording data by optical means. However, the method receiving the most attention involves the physical process of ablating a hole or bit in a film that is part of the recording structure. Data are recorded as changes in reflectivity between the written areas and unwritten areas with the written area represented as a succession of pits or holes, with a hole, for example, representing a "1" and the absence of a hole, representing a "0". The recording structure, in its most basic form, is usually disk-shaped and has a substrate upon which the film is deposited containing one relatively thin, energy absorbing coating, into which holes or pits are ablated to record the data. This coating will hereafter be referred to as an active layer.

In the basic ablative process, the active layer is selectively perforated or vaporized by a focussed radiation beam, said beam usually provided by a laser. See, e.g. U.S. Pat. No. 3,774,457 issued to Becker on October 21, 1969, wherein the physical displacement of the active layer is taught. See also, U.S. Pat. No.

3,971,874, issued to Spong on July 27, 1976, and U.S. Pat. No. 4,097,895, issued to Spong on June 27, 1978, wherein the laser burns a pit in the active layer of a two layer anti-reflective structure, thereby exposing a reflective layer.

For readout of data, a lower energy read beam, having a power level insufficient to write on, the medium is focussed onto the active structure of the recording structure so that the changes in reflectivity between the written and unwritten areas modulate the reflected reading beam. Improvements in prior art recording structures have included both the introduction of phase layers as thermal and optical" spacers to maximize the write efficiency and playback contrast, and overcoats for dust defocusing and protection.

In the prior art, the energy absorbing active layer has generally been comprised of either a continuous layer of an organic-dye-impregnated polymer, or a continuous layer of a metal or semi-metal. Examples of organic dye layers are taught in U.S. Pat. Nos. 4,241,355, issued to Bloom et al. on December 21, 1980,; 4,097,895, issued to Spong on June 27, 1978, and; 4,023,185, issued to Bloom et al. on May 10, 1977. Examples of continuous metal active layers can be found in U.S. Pat. Nos. 3,990,084, issued to Ohta et al. on November 2, 1976, and; 3,474,457, issued to Becker on October 21, 1969.

Whether the active layer is comprised of an organic dye or a metal, or semi-metal, the prior art has generally taught data recording by hole formation via the physical displacement of the active layer. However, in the physical displacement of the active layer, debris is often produced which litters both written and unwritten areas, thereby increasing media noise. The surface tension of the melted material causes the formation of a rim on the perimeter of the hole. The formation of this rim decreases the

O PI

signal to noise ratio of the playback signal by introducing random phase shifts in the playback signal zero crossings as the read beam passes from an unwritten area of the active layer, to the built up rim, and then onto the pit. Finally, ablation can cause a thin coating of material to be deposited on the focussing lens. This build-up gradually reduces the amount of light able to pass through the lens, reducing the efficiency of the system.

The prior art has addressed this problem by placing a protective transparent coating over the active layer. This has reduced the amount of debris which could escape to contaminate adjacent areas or coat the objective lens. See e.g., U.S. Pat. Nos. 4,315,269, issued to Bloom et al. on February 9, 1982; 4,300,143, issued to Bell et al. on November 10, 1981, and; 3,990,084, issued to Hamisch et al. on November 2, 1976. In Bell, for example, the overcoat is an optically transparent layer of silicon dioxide, which in conjunction with the thicknesses of the active and phase layers, is tuned for the wavelength of the laser beam in order to establish an anti-reflection condition. However, Bell, Hamisch, and Booth all teach having an overcoat layer of material which is chemically unreactive with respect to the active layer. As will be discussed below, the present invention avoids hole formation and the attendant rim and debris problems of the prior art by the use of chemical reaction between the components of an active layer structure.

Another problem faced in the prior art has been the relatively high power needed to write data by the ablative process. There has been a need to heat the active layer to a temperature sufficient to cause melting, and to provide sufficient energy to physically displace the heated active layer material_.. The prior art has addressed this problem by developing new active layer materials which, on the one hand, are more sensitive to the laser beam, thus

ablating at a lower temperature, and yet still able to develop adequate signal to noise ratios. See, for example, U.S. Pat. No. 4,222,071, issued to Bell et al. on September 9, 1980, wherein an active layer of tellurium is disclosed.

To address the energy problems, the prior art has also taught the use of a transparent phase layer between the active layer and the reflecting surface. This phase layer optically tunes the structure such that absorption in the active layer is optimized. The phase layer also thermally isolates the active layer. See e.g. U.S. Pat. Nos. 4,222,071, issued to Bell et al. on September 9, 1980, and; 4,216,501, issued to Bell on August 5, 1980. Generally, Bell has taught the use of a dielectric phase layer, that is inert so that it does not react with the active layer, other than to physically capture the ejected debris and to deform to allow the displacement of the heated active layer material. See also the above-mentioned organic dye active layer disclosures wherein more sensitive active layers are taught.

The problems described in the prior art became particularly acute when relatively wide bands, are written such as when 4-10 micrometer wide coarse seek bands are written. Writing such wide bands, using the ablative process, results in excessively noisy coarse seek signals due to debris in the coarse seek bands. It is to avoiding specific problems of this nature that the present invention is particularly well suited. The present invention provides a new and unique recording method and structure that addresses the problems discussed above in a novel manner. The present invention discloses the use of a discontinuous layer of a light absorbing material, such as a tellurium alloy, encapsulated between an upper and lower layer of a transparent matrix material, such as a halocarbon polymer, together forming a composite material

OMPI

which forms an "active structure". This active structure can be incorporated into either optically tuned or untuned recording structures. When the active structure is irradiated by a focussed radiation beam of sufficient intensity, the absorbing material chemically reacts with the matrix material, while some of the absorbing material becomes locally dispersed within the matrix material. The resultant written active structure has different optical properties from the unwritten active structure.

While the chemical reactions that occur are not completely understood, using the preferred embodiment as an example, it is believed that upon irradiation, the tellurium and the loosely bound halogen atoms in the polymer are provided sufficient energy to react to form a tellurium-halogen compound, such as tellurium tetrafluoride. This tellurium halide is light transmissive, and thereby changes the reflectivity of the irradiated spot relative to that of the surrounding unwritten area. The present invention is distinguished from the prior art in that upon irradiation with the laser beam, a chemical transformation of the active structure materials is accomplished, the transformation changing the optical constants of the irradiated active structure. This makes it unnecessary to physically displace the active structure material in order to alter the reflectivity of the recording structure.

The present invention is also distinguished from the prior art wherein continuous layers of active material are taught. In the present invention the active structure is formed by a discontinuous stratum of light absorbing globules encapsulated in matrix material. The encapsulation of the globules is important to the efficient operation of the disclosed invention in that encapsulated globules present a greater surface-to-volume ratio than a continous film, thereby increasing the rate at which the globule material

reacts with the matrix material. This in turn provides for a more thorough reaction as well as decreasing the power level needed to write data. Thus, prior art teachings that the protective layer can be deposited onto an active layer after the data is written in the active layer, failed to take into account the advantages of encapsulating globules of light absorbing material in a light transparent matrix that chemically reacts with the globules. However, in the present invention, complete encapsulation is necessary for the efficient operation of the invention.

As noted above, in the prior art recording structures, rim formation causes playback noise problems. In the present invention, rim formation is not an issue because the light absorbing material of the absorbing stratum is not physically displaced out of a pit to pile up on the rim. Rather, the absorbing material reacts essentially in-situ with the matrix material to form a more transparent reaction product. This therefore provides for greater sensitivity and cleaner playback transitions, thus- achieving higher signal-to-noise ratios. By not requiring the physical displacement or vaporization of the absorbing stratum material, lower power levels for writing can be used.

In U. S. Patent No. 4,214,249, issued to Kasai on July 22, 1980, the creation of a light trans issive condition is disclosed wherein a metal layer diffuses into a non-metal layer. However, Kasai teaches only the physical diffusion of a metal into a member of a non-metallic group consisting of sulfur, selenium and tellurium, with the resultant formation of chalcogenide alloy. The present invention is to be differentiated from Kasai in that the reflective change comes not from a physical diffusion between layers, but rather from a chemical reaction between the light absorbing material and the encapsulating matrix.

OMH

In the present invention, the significant reaction product is believed to be an optically semi-transparent compound formed between a strong oxidizer and a metallic or semi-metallic material. For example, with a tellurium alloy as the absorbing stratum and a fluorine-rich polymer as the matrix material, the reaction product is a tellurium fluoride.

It is an object of this invention to provide a means for optically recording and storing information.

It is another object of this invention to provide a means for storing data at a high rate.

It is still another object of this invention^' to provide a means for storing digital data at high density.

It is still another object of this invention to provide a means for storing data with a high signal to noise ratio.

It is still another object of this invention to provide a means for recording data on an optical recording structure with a long archival lifetime.

It is still another object of this invention to provide a high sensitivity optical recording structure.

It is still another further object of this invention to provide a means for recording data on an optical recording structure without ablating the surface of the optical structure.

It is still another object of this invention to provide an optical recording structure upon which patterns of any format can be written, such as wide, coarse seek, servo bands.

It is yet a further object of this invention to provide a chemically reactive active structure for recording data in an optical recording structure.

OMPI

BRIEF SUMMARY OF THE INVENTION

In the preferred embodiment, the recording structure is contemplated for use in an optical recording device employing a relatively higher power writing laser beam and a relatively lower power reading laser beam. In the recording device, the recording structure moves relative to the beams. When the recording structure is in the form of a rotating disk, the write and read beams translate radially over the rotating disk, so that data can be recorded in either concentric circles or in a single continuous spiral as desired. Information is recorded by intensity modulating the write beam and directing it onto the recording structure, the beam selectively causing a chemical reaction in the recording structure, and thereby creating a data mark.

In the preferred embodiment, the recording structure is comprised of an optically smooth and light reflective substrate, or alternatively, separate planarizing and light reflective layers overlying the substrate. Deposited over the reflecting surface is the lower portion of the matrix. The matrix material is selected from the group of halocarbon polymers. The discontinuous absorbing stratum is then deposited over the lower matrix, the absorbing stratum globules being distributed over the lower matrix surface. In the preferred embodiment, the absorbing stratum material is selected from a group consisting of low melting point semi-conductors, high melting point semi-conductors, high melting point refractory metals, and common metals. The upper portion of the matrix, selected from the same group as the lower matrix, is then deposited over the globules, thereby completely encapsulating the globules in the matrix material. If desired, separate protective and hermetic sealing and dust defocusing overcoats may

_ OMPI _,

then be applied.

Using well known thin-film deposition techniques, the absorbing stratum, though discontinuous, is deposited in sufficient density so as to create an anti-reflection condition when the matrices and the absorbing stratum are properly tuned to appropriate thicknesses. In the preferred embodiment, a lower matrix is deposited using plasma polymerization techniques to a depth of approximately 700 angstroms. The absorbing stratum is deposited to a mass equivalent thickness of approximately 80-100 angstroms. Care was taken to deposit this stratum to a thickness sufficient to establish a relatively high optical extinction index k_, i.e. greater than unity in the stratum, but riot so thick as to establish an essentially connected, continuous layer having bulk electrical and optical properties. After the absorbing stratum is deposited, the upper matrix is deposited. The upper matrix is deposited to a thickness of approximately 3000 angstroms. Note that in this preferred embodiment both the upper and lower matrix thicknesses are designed for purposes of establishing the ant-i-reflective condition. Recording is achieved by applying the modulated write laser beam to the recording structure, causing the selective reaction between the halocarbon polymer matrix material and the encapsulated absorbing stratum material. The chemical reaction product is more optically transparent than the unreacted absorbing stratum. Thus, where the initial absorbing stratum is unchanged, the read beam is effectively absorbed. However, where the reaction product is present and the stratum is light transmissive the an i-reflective condition is destroyed and the read beam is reflected by the reflecting surface. The modulated read beam is then directed to sensing circuitry which converts the reflection/anti-reflection pattern into an electrical information signal.

OMPI Z°* >

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the preferred embodiment of the basic elements of the disclosed invention, showing a reflective substrate, and an absorbing stratum encapsulated between an upper and a lower matrix, the lower matrix overlying the reflecting surface.

FIG. 2 is a schematic representation of the preferred embodiment of the disclosed invention showing an optically more transparent area in the absorbing stratum created by the chemical reaction between the absorbing stratum and the upper and lower matrices.

FIGS. 3a, b and c, are detailed pictorial representations, serially depicting the encapsulation of the absorbing stratum between the lower and the upper matrices. These drawings more accurately portray, at the sub-microscopic level, the matrix/absorbing-stratum interface, and the complete encapsulation of the discontinuous absorbing stratum globules.

FIG. 4a is a detailed pictorial representation of a single globule after complete encapsulation, but prior ^"to irradiation by a write laser beam. FIG. 4b is a detailed pictorial representation of the same area featured in FIG. 4a, after irradiation by a write laser beam, showing the chemical reaction product.

FIG. 5 is a schematic representation of the preferred embodiment of the disclosed invention incorporated into a reflective optical recording structure.

FIG. 6 is a schematic representation of an alternative embodiment of the disclosed invention incorporated into a radiation transmissive optical recording structure.

O PI \VI?0

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, the disclosed invention, an optical recording structure 1, in its basic form, is comprised of an optically smooth reflecting substrate 2 over which is deposited a lower matrix 3, and an upper matrix 4. Encapsulated at the interface 6 between the upper and the lower matrices is an absorbing stratum 5. The matrices 3 and 4, and the absorbing stratum together form the active structure 7.

The substrate 2 consists of a support material, such as glass, aluminum, or plastic. It is necessary that the substrate 2 have an optically smooth and reflecting surface. In the preferred embodiment, the matrix materials are selected from the group of halocarbon polymers. While the preferred embodiment contemplates both the lower 3 and the upper 4 matrix to be of the same material, it should be understood that both matrices need not be of the same material.

The absorbing stratum 5 is selected from a group consisting of low melting point semi-conductors, high melting point semi-conductors, high melting point refractory metals, and common metals. As shown in FIG. 2, upon reaction with the matrices 3 and 4, the absorbing stratum 5 becomes an optically more transparent reaction product 8. In the preferred embodiment, a tellurium-rich alloy comprised of tellurium, selenium and arsenic is used. Using well known thin-film deposition techniques, matrices 3 and 4, and the absorbing stratum 5 are deposited in such a relationship as to create an anti-reflection condition.

While the illustrative examples discussed herein disclose the reactions of a tellurium alloy absorbing stratum 5 and fluorocarbon polymer matrices 3 and 4, it is understood that the present invention contemplates all combinations of the groupings selected

for the matrices 3 and 4, and the absorbing stratum 5, which form optically more transparent reaction products 8. However, the tellurium-alloy/ fluorocarbon-polymer combination is of particular interest due to the low thermal conductivities of the fluoropolymers and the relatively low melting points of the tellurium alloys. This results in a relatively sharply defined reaction volume because the chemical reaction can occur at a temperature that is low relative to temperatures required for ablative^' processes. In the preferred embodiment, the tellurium alloy composition by atomic fraction was 80% tellurium, 19% selenui , and 1% arsenic. This allows for smaller marks and therefore denser data patterns.

FIG.2 is a schematic representation of the active structure 7 after irradiation by a write laser beam. The tellurium-alloy absorbing stratum 5 has reacted with the fluorocarbon polymer matrices 3 and 4 to form the tellurium fluoride reaction products 8. These reaction products 8 are optically more transparent, at least at the wavelength of the read laser beam, and form an optical opening 9. This allows a read beam (not shown) to pass through the optical opening 9 to reflect off the reflecting surface 10 of the substrate 2.

While the previous drawings have shown the matrices interface 6 as relatively flat and have shown the absorbing stratum 5 as a thin continuous film, FIGS. 3a, b and c, more accurately present the interface as it appears at the sub-microscopic level. As shown in FIG. 3a, the lower matrix 3, formed from polymers, presents a rather craggy, non-uniform, surface. Using thin film deposition techniques, such as sputtering, the discontinuous stratum 5 of a tellurium alloy is deposited on the lower matrix 3 surface. Depending upon the materials selected from the matrix group and the absorbing stratum group, the amount of material used for the

O PI

absorbing stratum 5 varies, but the stratum 5 is deposited in sufficient quantity to establish the anti-reflective condition in cooperation with the matrices 3 and 4. However, as shown in FIG. 3b, in the preferred embodiment, the amount of material for the absorbing stratum 5 that is deposited must be such that deposited globules 11 of the absorbing stratum material remain separate and disconnected so as to form a discontinuous film. If deposition is continued to the point where the absorbing stratum 5 becomes continuous, the effectiveness of the invention is diminished, because the surface-to- volume ratio will be significantly reduced, thereby reducing, the surface available for reaction. As shown in FIG. 3c, once the upper matrix 4 is deposited, the encapsulation of each globule 11 is complete, thereby completing formation of the active structure 7.

In FIGS. 4a and 4b, a schematic representation of a single encapsulated globule 11 is shown in order to better explain what is believed to be the chemical reaction that occurs. For example, when the matrices 3 and 4 consist of a plasma polymerized fluorocarbon, loosely bound fluorine atoms are available, and when a globule 11, consisting of a tellurium alloy is encapsulated, a portion of the tellurium atoms are believed to react spontaneously with the fluorine atoms in the area immediately adjacent to the globule 11. This is believed to form a reaction product shell 8 of tellurium fluoride, and a fluorine-deficient shell 12, which cooperate to inhibit further spontaneous tellurium-fluorine reactions. Thus, as shown in FIG. 4a, the active structure 7 is established, which consists of an unreacted tellurium alloy globule 11, a reaction product shell 8 of tellurium fluoride, a fluorine-deficient polymer shell 12, and the unreacted lower and upper matrices 3 and 4.

FIG. 4b shows the same area after irradiation by a write laser

beam. It is believed that the heat energy imparted to the tellurium alloy, and in turn, to the adjacent matrices areas 3 and 4, is sufficient to overcome the shells 8 and 12. This allows the tellurium globule 11 to react completely with the matrices 3 and 4. The tellurium globule 11 is thus replaced with a tellurium fluoride reaction product 8. The reaction product 8, like the surrounding matrices 3 and 4, is light transmissive, at least at the read laser wavelengths. This creates, as shown in FIG. 2, the optical opening 9 through which a read beam can pass to be reflected by the reflecting substrate 2. Thus, while the above described reaction will occur with a continuous absorbing layer, those skilled in the art will appreciate the desirability of encapsulating the discontinuous absorbing stratum 5 in the matrices 3 and 4, in that encapsulation allows for the rapid and complete reaction of the stratum 5 with the matrices 3 and 4.

While it is understood the invention will function in its basic form, FIG. 5 shows the disclosed invention 1 incorporated into a fully developed optical structure 13, comprising a support substrate 14; a planarizing layer 15 for providing an optically smooth surface; a reflecting layer 16 overlying the planarizing layer 15; an active structure comprised of lower and upper matrices 3 and 4, having encapsulated therein an absorbing stratum 5; an hermetic sealing layer 17; and a defocusing and protective layer 18. If the substrate 14 is of a material which can be made suitably optically smooth and reflective, then the planarizing 15 and reflecting 16 layers may be omitted. The lower matrix 3 can serve as a phase layer to optimize write sensitivity and playback contrast as taught in the prior art.

While the disclosed invention has been discussed in reference to a reflecting substrate and tuned anti-reflecting structures, it will

O Pl

be obvious to those skilled in the art that the invention can be used in other forms such as the "Philips Air Sandwich" configuration, or in a simple radiation transmissive mode of signal readout, as shown in FIG. 6, wherein the active structure 7 underlies the transmissive support structure 19.

Claims

CLAIMS We claim:

1. A radiation recording structure for use in an information storage device having a write and a read focussed radiation beam, said recording structure comprised of: a substrate, said substrate providing support for the recording structure, and; an active structure, said active structure having a radiation transmissive matrix material, said material deposited on the substrate and an energy absorbing stratum, said stratum encapsulated in the matrix material, wherein the active structure becomes radiation transmissive upon irradiation by a focussed radiation beam.

2. A radiation recording structure of claim 1 wherein the absorbing stratum consists of energy absorbing material globules encapsulated in a matrix material.

3. A radiation recording structure of claim 2, wherein upon irradiation by a focussed radiation beam, the absorbing stratum material chemically reacts with the matrix material to form a reaction product which is read beam transmissive.

4. A radiation recording structure of claim 1 wherein the lower part of the matrix is a phase layer.

5. A radiation recording structure of claim 1 wherein the upper and the lower parts of the matrix and the absorbing stratum are of such thicknesses as to provide a substantially

O PI

anti-reflective structure prior to irradiation and a highly reflective structure after irradiation, and wherein the substrate has a reflecting surface or a reflecting coating.

6. An optical recording structure for use in an information storage device having a write and a read focussed laser beam, said recording structure comprised of: a substrate, said substrate providing support for the recording structure, and; an active structure, said active structure having a light transmissive matrix material, said material deposited on the substrate, and an energy absorbing stratum, said stratum encapsulated in the matrix material, wherein the active structure becomes radiation transmissive upon irradiation by a focussed radiation beam.

7. An optical recording structure of claim 6 wherein the absorbing stratum consists of absorbing material globules discontinuously encapsulated in the matrix material.

8. An optical recording structure of claim 7 wherein, upon irradiation by a focussed laser beam, the absorbing stratum material chemically reacts with the matrix material to form a reaction product which is read beam transmissive.

9. An optical recording structure of claim 8 wherein the absorbing stratum is selected from a group consisting of low melting point semi-conductors, high melting point semi-conductors, high melting point refractory metals, and common metals.

10. An optical recording structure of claim 9 wherein the absorbing reactive stratum is comprised of a semi-conductor alloy.

11. An optical recording structure of claim 10 wherein the semi-conductor alloy is comprised of a tellurium alloy.

12. An optical recording structure of claim 11 wherein the tellurium alloy is comprised of tellurium, selenium and arsenic.

13. An optical recording structure of claim 12, wherein the tellurium alloy composition is comprised of 80% tellurium, 19% selenium and 1% arsenic, by atomic fraction.

14. An optical recording structure of claim 13 wherein the matrix material is a halocarbon polymer.

15. An optical recording structure of claim 14 wherein the matrix material is comprised of plasma polymerized tetrafluoroethylene.

16. An optical recording structure of claim 15 wherein the irradiation of the active structure with a write laser beam initiates a chemical reaction between the tellurium alloy and the plasma polymerized tetrafluoroethylene matrix forming a tellurium fluoride compound, said compound being more transparent to light at least at the wavelength of the read beam.

17. An optical recording structure of claim 6 wherein the lower part of the matrix is a phase layer.

OMPI

18. A optical recording structure of claim 6 wherein the upper and lower parts of the matrix and the absorbing stratum are of such thicknesses as to provide a substantially anti-reflective structure prior to irradiation and a highly reflective structure after irradiation, and wherein the substrate has a reflective surface or a reflective coating.

19. A method for preparing an optical recording structure comprising the steps of: depositing a lower matrix of light transmissive material on a reflective substrate, said material deposited to a depth of approximately 700 angstroms, depositing a discontinuous stratum of energy absorbing material over the lower matrix, said material deposited to^' a mass equivalent depth of approximately 80 Angstroms, and; depositing an upper matrix of light transmissive material over the energy absorbing stratum, said material deposited to a thickness of approximately 3,000 angstroms, thereby encapsulating the absorbing stratum material between the upper and the lower matrix material.

20. An optical recording structure of claim 19 wherein the absorbing stratum is selected from a group consisting of low melting point semi-conductors, high melting point semi-conductors, high melting point refractory metals, and common metals.

21. An optical recording structure of claim 20 wherein the absorbing stratum is comprised of a semi-conductor alloy.

22. An optical recording structure of claim 21 wherein the absorbtive stratum is comprised of a tellurium alloy.

23. A optical recording structure of claim 22 wherein the matrix materials are chosen from the group of halocarbon polymers.

24. An optical recording media of claim 23 wherein the upper and the lower matrices each consist of the same selected material.

25. An optical recording media of claim 19 wherein the lower matrix is deposited to thickness sufficient to act as a phase layer.

26. An optical recording structure of claim 19, wherein the upper and lower matrices and the absorbing stratum are of such thicknesses as to establish a substantially anti-reflective structure prior to irradiation and a highly reflective structure after irradiation.

OMPI ..O