FR2471714A1 - ABLATION OPTICAL RECORDING MEDIUM FOR USE WITH A RECORDING LASER BEAM AND FOR USE IN A RESTITUTION DEVICE EMPLOYING A REFLECTIVE LIGHT BEAM AT A FREQUENCY GIVEN - Google Patents

Abstract

THE INVENTION RELATES TO A RECORDING MEDIA WHICH INCLUDES A SUBSTRATE COATED WITH A LIGHT-REFLECTING LAYER, WHICH, IN TURN, IS COATED WITH A LIGHT-ABSORBING LAYER. ACCORDING TO THE INVENTION, THE LIGHT ABSORBING LAYER 114 IS CHOSEN FROM THE GROUP CONSISTING OF BIS- (DITHIO-A-DICETONE) COMPLEXES IN PLATINUM, HAVING THE FORMULA (CF DRAWING IN BOPI) OR R IS A PHENYL OR PHENYL GROUP SUBSTITUTE; DURING RECORDING, PARTS 116 OF LAYER 114 ARE REMOVED BY ABLATION, BY A FOCUSED LIGHT BEAM THE INTENSITY OF WHICH IS MODULATED TO THUS EXPOSE PARTS OF REFLECTIVE LAYER 112 AND RECORD THE VIDEO INFORMATION AS SHAPED AS A REFLECTIVE-ANTI-REFLECTIVE PATTERN. THE INVENTION APPLIES IN PARTICULAR TO VIDEODISKS.

Description

The present invention relates to a new recording medium

  optical. More particularly, it relates to an optical recording medium for use with a solid state injection laser of the AlSaAs type. Spong, U.S. Patent 4,097,895, June 27, 1978, discloses a recording medium which comprises a light reflecting material, such as aluminum or gold, coated with a light absorbing layer. , such as fluorescein operating with a light source of an argon laser. The thickness of the light absorbing layer is choidie so that

  the structure has minimal reflectivity.

  An incident light beam ablates, vaporizes, or melts the light absorbing layer, leaving a hole and exposing the light reflecting layer. After recording, at the wavelength of the recording light, there will be a maximum contrast between the light reflection layer and the light-absorbing layer and the light reflective layer. On the other hand, when the light-reflecting material itself is a thin layer than a non-conductive substrate, little energy is lost either by reflection by the thin and absorbing layer or by transmission through the reflective layer, thus, the energy absorbed light beam is concentrated into a very thin film and the sensitivity

  at the registration is very high.

  Because of its low need for input power, its small size and its ability to directly modulate its output optical power by modulation of the driving electric current, a solid-state injection laser, in particular a laser AlGa.s, which operates in the wavelength range of the order of 750 to 850 nanometers, is a preferred light source for an optical recording system. Thus, materials undergoing ablation, vaporizing or melting at low temperatures upon absorption of optical energy in this wavelength range would be

  very useful in an optical recording system.

  In order to be useful as a light absorbing layer for the. recording medium described above, the materials must be able to be applied to a substrate in the form of a thin and smooth film of very good optical quality and to a predetermined thickness; they must be absorbent at the frequency of the optical source employee; and they must be able to be removed by ablation,

  spray or melt to form uniform holes.

  Bloom et al., U.S. patent application

  No. 837,853 filed September 29, 1977, there is described a -

  ablative optical recording medium, operating with an AlGaAs laser, which comprises a substrate coated with a light reflecting layer which, in turn, is coated with a light absorbing layer selected from the group consisting of lead phthalocyanine , chloroaluminum phthalocyanine, vanadyl phthalocyanine], phthalocyanine

  stannic and chloroaluminum chlorophthalocyanine.

  These materials, however, have the disadvantage that their ablation temperature is of the order of 300 to 400 C. Materials having a lower ablation temperature would require less energy to reach this temperature and would thus be more sensitive. Thus, light-absorbing materials between 750 nm and 850 nm form amorphous and specular films with

  low melting temperature would represent an improvement

  considerable influence in the art.

  The present invention relates to an optical recording medium which consists of a light reflecting layer and a light absorbing layer at a wavelength in the range of 750 nm to about 850 nm, comprising a complex in platinum, bis (dithio-CO-diketones); the substituents on the ethylenic group are phenyl or substituted phenyl groups. The invention will be better understood and other purposes,

  characteristics, details and advantages of it

  more clearly in the explanatory description

  which will follow made with reference to the accompanying schematic drawings given solely by way of example illustrating an embodiment of the invention and in which - Figure 1 is a cross-sectional view of a recording medium according to the invention , lover

recording; -

  FIG. 2 is a cross-sectional view of a recording medium according to the invention, after recording; and FIG. 3 is a schematic view of a recording and playback system in which the recording medium according to the invention can be used. The light reflecting layer should reflect the light used for recording. Suitable light reflective materials include aluminum, rhodium, gold and the like. The material reflecting light to a thickness such that it

  substantially reflects all the recording light.

  In general, the light reflecting layer is applied to a substrate. The substrate must have a flat and optically even surface, to which the subsequent light reflective layer can adhere. A glass plate or disc or a plastic disc is suitable. If the light reflecting material can be formed to be a self-contained layer being optically recible, the substrate can be removed. Materials that have been found useful as a light absorbing layer in the recording medium are platinum complexes of bis- (dithio-CO-diketones) having the formula:

R, S

C l 0 g X Pt. C

S

  o in each case R 1 is a phenyl group or a phenyl group substituted with an alkyl or alkoxy group such as p-isopropylphenyl or p-methoxyphenyl]. The preparation of these compounds has been described by Schranzer and Mayweg in

  J. Amer. Chem. Soc., Vols 87, pages 1483-1489 (1965).

  These materials absorb at the wavelengths of the solid-state injection laser between 750 and 850 nm, and they can all be evaporated on a light reflective layer to provide optical and regular light absorbing layers. o information

  can be recorded at high signal-to-noise ratios.

  The materials according to the invention can be applied to the light reflecting layer by traditional evaporation under vacuum. The material is introduced into a suitable container pumrvu a resistance heater and placed in a vacuum chamber. The

  The heater is then connected to a source of electric power.

  A substrate is placed above the dye on a support

  rotary. The substrate is then rotated at about 50 rpm.

  The vacuum chamber is evacuated to about 106 torr and current is applied to the heater for

  raise the temperature of the material to its evaporating temperature

  tion. The evaporation is continued until an absorbent layer is deposited, at the required thickness, on the light reflecting layer, and at this point the

  electric is interrupted and the room is stale.

  The thickness of the evaporated layer is controlled using an optical system that measures the reflectivity

  the reflective surface coated with the material. The evaporation

  is stopped when the reflectivity reaches its minimum value. The present invention will be better explained

  with reference to the accompanying drawings.

  Fig. 1 shows a recording medium according to the invention, prior to exposure to a recording light beam, and comprises a glass substrate 110, a light reflecting layer 112 formed of a gold layer of 600 A order of thickness or other metal to a suitable thickness, and an absorbent layer 114

  light in one of the two above mentioned materials.

  Fig. 2 shows a recording medium according to the invention after exposure to a recording light beam, and the absorbing layer 114 has been removed by ablation to leave a hole 116, exposing the light reflecting layer 112, It will be appreciated that a recording medium, after recording, contains a number of holes 116 rather than the single hole

shown in Figure 2.

  The use of the recording medium according to the invention will be explained in more detail with reference to FIG. 3. For recording, the light emitted by a LaGaAs injection laser 10 is modulated directly in response to an electrical signal. received 14. The modulated light beam is enlarged by a recording optical system 16 to increase the diameter of the laser beam whose intensity is modulated, so that it fills the aperture of an objective 18 in the parallel planes and perpendicular to the laser planes 10. The modulated and enlarged laser beam is totally reflected. by a polarizing beam splitter, and it goes through a plate

  quarter-wave 22 towards the objective 180 The recording beam

  modulated mode then impacts on a recording medium

  24, as described in Figure 1, and ablates or evaporates a portion of the light absorbing layer to expose a portion of the light reflecting layer. The recording medium 24 is rotated by the drive 26 of the platen at about 1800 rpm. A servo-focuser 28 maintains a constant distance between the objective 18 and

  the surface of the recording medium 24.

  For reading, an unmodulated and less intense laser beam, that is to say not able to cause the ablation of the recording medium, follows the same path as the recording beam towards the support

  24. The registered motive for reflection-

  anti-reflection, modulates the light reflected through the objective 18 of the quarter-wave plate 22. The light, now turned 900 in polarization by the two passages through the quarter-wave plate 22, passes through the the photodetector 32 converts the reflected light beam into an electrical output signal at the terminal 34, which corresponds to the signal received from the source 14 A slaving 26 controls the light reflected through the optical rendering system 30, and it deflects the radially incident light beam for

  ensure that this beam remains centered on the recording track.

interesting record.

  The present invention will be better illustrated by the following examples, which should in no case be

limit the frame.

Example 1

  A substrate of a vinyl disc was coated, by evaporation, with a. layer of gold of the order of 600 A thick. The coated substrate was placed in a vacuum chamber above an evaporation cup containing the bis (diphenyl-dithio-C1-diketone complex) in the

  platinum and rotated at 50 rpm.

  The vacuum chamber was evacuated to about 10-6 torr and a source of electric power was connected to the

  cup. The cup was heated to about 225-275oC.

  and at this temperature the shutter was opened and the material evaporated at about 4 A per second. Evaporation was continued until an absorption layer about 600 A thick was deposited on the gold layer. A specular and continuous layer was deposited, smooth and amorphous. The real (n) and imaginary (k) parts

  of the dielectric constant of the bis (diphenyl-

  dithio-CC-diketone) platinum at 800 nm are respectively

of 2.08 and 0.5.

  The resulting recording medium was exposed to a series of 50 nanosecond light pulses having a wavelength of 800 nm from an AlGaAs injection laser in an apparatus such as that shown in FIG. absorbent was removed by ablation of the disc by multiple exposure with

milliwatts on the disk.

Example 2

  Following the general procedure of Example 1, a substrate coated with gold was coated, as in Example 1,

  one layer of the bis (di-p-isopropylphenyl-dithio) complex

O

  CO adicetone) in platinum having 1324 A thickness.

  The real (n) and imaginary (k) parts of the constant

  dielectric layer of bis (di-p-isopropylphenyl)

  dithio-β-diketone) platinum at 800 nm are respectively

of 1.75 and 0.78.

  He deposited a specular and continuous layer,

amorphous and smooth.

Example 3

  Following the general procedure of Example 1, a gold-coated substrate as in Example 1 was coated

  one layer of the bis (ei-p-methoxyphenyl-dithio) complex

  CX-diketone) in platinum with a thickness of 1900 A. The real (n) and imaginary (k) parts of the constant

  dielectric layer of bis (di-p-methoxyphenyl dithio-

  cz-diketone) -platinum at 800 nm are respectively 1.61

and 0.76.

  A specular and continuous layer was deposited, amorphous and smooth. The film reduced the reflectivity of the recording medium to about 7% with respect to about 95% reflectivity of the gold layer prior to addition of the absorbent layer. Comparison Examples Following the general procedure of Example 1, gold-coated vinyl discs were coated with bis (dithio-O-diketone) complexes in platinum, palladium or nickel, with aryl groups or identical or different substituted alkyls. Complexes belong to the class having formula

R J /

R1

L / LCLT

R S

  M may be Pt, Pd or Ni and R1 and R2 may be alkyl, phenyl, or phenyl substituted with alkyl or alkoxy. These materials produced either nonspecific films or films with a bad anti-reflection condition during evaporation. In almost all cases, the films initially formed a veil and became crystalline in the presence of water. None of these dyes proved appropriate in this case. The data are summarized in Table I.

Table I

COMMENTS

  p-CH3O-C6H4p-C3H7-C6H4 C6H5C6H5p-CH30-C6H4p-C3H7-C6H4p-CH30-C6H4 n-C3H7 3H7 C2H5C6H5p-C3H7-C6H4C6H5C6H5C6H5p-C3H7-C6H4 p4CH3OC6H4 n-C3H7 C2H5 Crystalline film Cloudy film Cloudy film, no absorption Cloudy film Light film, weak absorption and strong reflectivity Cloudy film Cloudy film Film immediately forms a film Film immediately forms a web M R1 R2 Pt Pd Pd Ni Ni Ni Ni Ni Ni ra "-J -à

247171 4 '

  Of course, the invention is not limited to the embodiment described and shown which has been given as an example. In particular, it includes all the means constituting technical equivalents of the means described and their combinations if they are executed according to its spirit and implemented in

  the scope of the following claims.

Claims (11)

R E V E N D I C A T I 0 N S _ _________ __ _M__________   An optical ablation recording medium for use with a recording laser producing light at a given frequency, of the type comprising a light reflecting layer coated with a light absorbing layer, characterized in that it consists of use, as a light absorbing layer, a platinum bis (dithio-OC-diketone) complex having the formula   R is phenyl or substituted phenyl.   2. Recording medium according to the claim   1, characterized in that R is a phenyl group.   3. Recording medium according to the claim   1, characterized in that R is a p-isopropylphenyl group.   2QI 4. Recording medium according to the claim   1, characterized in that R is a p-methoxyphenyl group.   5. Recording medium according to claim 1, characterized in that the thickness of the abovementioned absorbent layer is chosen to reduce the reflectivity to a source of light emitting Ane wavelength of order from 750 to 850 nm.   An information carrier for use in a rendering apparatus employing a rendering light beam at a given frequency, of the type comprising a light reflecting layer coated with a light absorbing layer, with an information track formed in said absorbent layer, characterized in that   light absorbing layer, a complex bis (dithio-C -   diketone) -platin having for fommula 2471714 I   R is a phenyl or substituted phenyl group.   7. Information carrier according to claim 6, characterized in that the aforementioned track consists of a succession of spaced holes in the absorbent layer   above, which represent the recorded information.   8. Information medium according to the claim   6, characterized in that R is a phenyl group.   9. Information carrier according to the claim   6, characterized in that R is a p-isopropylphenyl group.   10. Information carrier according to the claim   6, characterized in that R is a p-methoxyphenyl group.   11. An information carrier according to claim 6, characterized in that the thickness of the abovementioned absorbent layer is chosen to reduce the reflectivity to a source of light emitted by a wavelength of the wave. from 750 to 850 ni.