DE2837601A1 - RECORDING MEDIA, IN PARTICULAR DISC - Google Patents

Description

Drv-lng. Reitman König ■ OipJ.-Ing. Klaus Bergen Cecilienallee 76 A Düsseldorf 3O Telephone 452QQS Patentanwälte

August 25, 1978 32 437 B

RCA Corporation, 30 Rockefeller Plaza,
New York, MY 10020 (V.St.A.)

"Recording media, in particular optical disk"

The invention relates to a laser-compatible recording medium, in particular an optical disc, on a substrate layer made of plastic, a layer that reflects the laser light and on top of it a layer that absorbs the laser light Layer lie. In particular, it is about an information carrier or a record for example in an image recording apparatus and for playing back recorded information on an image reproducing apparatus (Video record player).

In FR-OS 2 344 920 such an information or recording medium is described on which the recording of the respective signal to be recorded is carried out by removing or melting a layer which absorbs laser light of a predetermined frequency in sections or points or lines. The recording medium can be a flat, coated with a reflective layer made of highly reflective material such as aluminum
Be a glass plate in which on the reflective layer a thin, from one of the light of the recording frequency
highly absorbent material layer. Penetrates when recording or when recording
Both incident and reflected, modulated laser light cover the thin absorption layer and increase its temperature to such an extent that it

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nend information representing pattern of holes is peeled off, peeled off or melted. The layer thickness of the absorption layer was chosen so that an anti-reflection condition on the coated information carrier at the frequency of the recording light or the plate is set.

This known record carrier is a very effective one Heating to the melting or peeling temperature the absorption layer possible. Bs becomes a sequence of regularly shaped holes of micrometer or Submicron dimension formed along a recording track. The length and pitch of these holes contain the Information to be stored, e.g. that of frequency-modulated video signals. This results in excellent Recordings or video disks or tapes with a signal-to-noise ratio of up to 50 decibels (dB) with a very high packing density of the stored information. For example, requires a single television picture only the area of about 1 mm. The known recording medium therefore allows a high quality Playback of recorded television signals of broadcast quality.

The recording medium described in the above-mentioned FR-OS, however, is very expensive to manufacture. Namely, the substrate carrying the reflective and absorbent layers must have a high degree of surface perfection exhibit, because surface defects of micrometer dimension or even smaller size Signal dropouts or interference in the video signal being played.

There are various arrangements for compensating for certain ones Signal failures known, but only then

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are effective when the disruptions reach an amount the level above the normal size of the image information to be stored or reproduced of the respective video signal. Unevenness in the substrate of the recording medium can also be compensated for will. For this purpose, sharpness controls are used that ensure a fixed distance or exact compliance the focal length of the objective lens from the recording plane.

Up to now, however, microscopic defects in the substrate of the recording medium have only been detected by careful mechanical operation Polishing the surface of the glass in question can be eliminated. This procedure leads Although it produces good results, it is very time-consuming. The costly surface treatment is a disadvantage Previous image disk substrates added that these substrates consist of glass, which is known is very fragile. It can therefore especially when rotating at high speeds of normally 1800 revolutions per minute when recording and when playing, break easily occur. If necessary, will this not only destroys the image plate, but the break also means a certain danger for the operator. Less fragile materials, e.g. polyester panes suitable for photography Quality, acrylic or pressed vinyl, but not that required for optical disc substrates Surface quality and are completely unsuitable in this context.

The invention is based on the object of providing an unbreakable substrate for the recording medium mentioned at the beginning.

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To create a carrier, the surface of which is free from macroscopic with less effort than with previous glass plates and microscopic defects and which are suitable for recording image signals in broadcast quality is. The inventive solution to this problem is characterized by a thin, flat, smooth, hard, inert cover layer between the substrate layer, free of macroscopic and microscopic surface defects and the reflective layer.

According to the invention, substrates made of plastic can be used thus free from macroscopic and microscopic surface defects be made that the plastic substrate with a thin layer of a flowable and when Flowing material that fills every surface defect and creates a very smooth layer is coated, which hardens or dries quickly at lower temperatures to make it smooth, even, inert, hard and durable To form cover layer on which the reflective layer can be deposited. Preferably there is the top layer according to the invention made of acrylic resin latex, Epoxy paint, bichromated gelatin, polyurethane paint, alkyd paint or light-curable polymers.

According to the invention, numerous commercially available Coatings and finishes can be used as a top layer. Surprisingly, it has been found that by applying commercially available paints, varnishes, epoxy paints, polyurethane floor and furniture polishes or acrylic resin dispersion floor finishes, as well as curable gelatins and photo-curable polymers on plastic substrates having very imperfect surfaces and by drying and / or hardening the

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Respective cover layer substrates with microscopically flat surfaces are created, which are used for recording and for Reproduction of picture signals with broadcast quality are suitable.

In the following, further details of the invention are explained in part with reference to the schematic drawing. Show it:

1 shows a cross section through an embodiment of the recording medium according to the invention;

Fig. 2 shows a cross section through another embodiment of the record carrier;

3 shows a cross section through a further exemplary embodiment of the recording medium; and

4 shows a block diagram of a system for recording and playing back information with the record carrier.

1 to 3 are exemplary embodiments of the invention, shown as a whole with 10 designated recording medium. This one contains one of some Inexpensive plastic substrate 12. The substrate 12 may, for example, be made of polyvinyl chloride (PVC) as well Acrylic or polyethylene terephthalate polymers or the like be made and in the form of a tape or a plate. In the following, however, the recording medium is described as a disk.

Suitable materials for producing the substrate 12 are polyester plates, polymethyl methacrylate or Acrylic panels and usually in the (sound) sound

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The panel industry used panel blanks made of PVC. Even with careful preparation and treatment high-quality materials of the aforementioned types do not have panels made of such materials per se to manufacture of optical disks sufficiently flawless surface.

Regarding the materials for forming the cover layer according to the invention 14 on the plastic substrate 12 include acrylic dispersion (latex) floor finishes as well as epoxy paints without dye, decomposed with known thinners; dichromated gelatin, e.g., a mixture of 2 to 5% by weight gelatin solution and about 2% by weight sodium dichromate; Polyurethane lacquers j Alkyd resin lacquers, e.g. from 35% by weight soy flaxseed alkyd resin modified with ester resin and 65% by weight of an aliphatic hydrocarbon solvent; and crosslinking or hardening when irradiated with ultraviolet light or the like Monomers.

The top layer 14 of the present invention can be applied in any way, e.g., by spraying or the like, to the as Plate formed substrate 12 according to FIGS. 1 to 3 are applied. It is important that when applying the Cover layer 14 prevents the formation of small waves or corrugations and other gross surface defects will. Advantageously, they become paint or varnish compositions a few drops of a leveling or relaxing agent added. That Covering material can be thinned to obtain a cover layer 12 of the desired thickness, which Cover layer 14, however, must be thick enough to remove any imperfection or imperfection of the surface of the panel

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10 to be able to fill out.

After application, the cover layer 14 is solidified by drying or hardening. For example, paints can through Spray applied and dried in the air or "at a slightly elevated temperature of e.g. about 45 ° C. The remaining water can be removed from water-containing top layer materials by drying in an oven circulating hot air. Care should be taken when applying and drying of the cover layer 14, the surrounding atmosphere is dust-free.

A metallic, light-reflecting layer 16, generally by vacuum evaporation. For example, an aluminum layer of about 50 nm Thickness, a rhodium layer about 100 nm thick or a gold layer about 80 nm thick can be used.

A light-absorbing layer 18 is then applied to the light-reflecting layer 16. Such light absorbing, non-reflective layer 18 can be either a single layer of organic dye 1 and 2, as described for example in the above FR-OS, or a double-layer system of an absorbent layer 26 and a non-absorbent spacer or intermediate layer 24 according to FIG.

Suitable materials for making a single layer of organic dye for the absorbent layer are for example fluorescein or 4-phenylazo-1-naphthylamine from about 40 to 50 nm thick. Suitable double

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layer systems can be "for example from a Bismuth or titanium layer about 7.5 nm thick or a rhodium layer about 30 nm thick on a spacer layer 24 made from silicon dioxide.

In either case, the recording on the disk is effected by melting or peeling holes or otherwise altering the absorbent layer 18 or 26. The heat associated with this process also tends to pass through the light reflective layer 16 into the substrate 12. However, since the substrate materials coated according to the invention can be sensitive to heat, it may be desirable to place a thermal insulation layer (not shown) between the cover layer 14 according to the invention and the light-reflecting layer Λ 6. place. A silicon dioxide layer approximately 300 nm thick is suitable for this. However, the thickness of such a layer is not critical.

Alternatively, the optical spacer layer 24 of the double-layer system 24, 26 described above can be used simultaneously can be used as a thermal insulation layer. In this case, however, a certain thickness must be adhered to the spacer layer 24 is important. This layer thickness depends namely because of the structural requirements to achieve it the initially mentioned antireflection condition of the optical constants of the reflective layer 16, the spacer layer 24 and the light-absorbing sub-layer 26.

To the surface of the recording medium 12 in front of the Effects of dust or other contaminants can be protected on the particular light-absorbing

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Layer 18 or 26 according to FIGS. 2 and 3, an outer, coating or protective layer 20 can be applied. Preferably a layer of transparent silicone resin that can be vulcanized at room temperature is used for this purpose.

The use of the recording medium according to the invention is explained in detail with reference to FIG. An argon laser 110 emitted light fed to a modulator 112. There the intensity of the laser light is dependent on an electrical input signal coming from a signal input 116 is modulated. With the help of the optical system (Light pen) 116, the modulated light is amplified by the diameter of the intensity-modulated laser beam so that it fills the desired opening angle of an objective lens 118. To Total reflection of the enlarged modulated laser beam on a polarizing splitter plate 120 is the light passed through a beam-rotating quarter-wave plate (quarter-wave plate) 122 to the objective lens 118. The modulated beam then falls on a recording medium or a recording medium 10 according to FIG 1 to 3 and changes its light-absorbing layer, for example by peeling off a number of Holes, such as the hole 22 according to FIG. 2 or the hole 32 according to FIG. 3, in the absorption layer 18 or 26, respectively. During recording (and also during playback), the recording medium 10 becomes along a spiral track scanned and rotated with the help of a turntable 124 at about 1800 revolutions per minute. With this one In the process, a focus control 126 can be used to maintain a constant distance between the objective lens 118 and the surface of the recording medium 10 to be adjusted or regulated.

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An unmodulated laser beam with a lower intensity than the one recording is used for playback Has laser beam in such a way that the reading laser beam does not cause any changes in the recording medium. The reading laser beam follows the same path as the receiving laser beam on the recording medium 10. The pattern of a sequence of reflection and non-reflection areas generated during the example modulates the light reflected during playback, which passes through the objective lens 118 and the quarter wave plate 122 arrives. This is now done by two passages through the quarter-wave plate 122 in the plane of polarization Light rotated by 90 ° passes through the polarizing splitter plate 120 and is with the help of the Playback optics 128 directed at a photodetector 130. The latter converts the reflected light into an electrical one Output signal that corresponds to the input signal and to be taken off at the signal output 132. A tracking controller 134 is provided for that by the reproduction optics 128 guided light so that the light trail when playing the same path on the recording medium 10 follows as when recording.

The recording medium according to the invention forms a blank, in particular a disk blank, on the image information can be recorded in the manner described above. The intensity of the recording The light can be regulated depending on the information to be recorded. That can be Example by means of frequency-modulated carrier waves with the aid of video signals representative of the respective image happen. The intensity of the recording light beam should be controlled so that it

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between one for creating changes in the absorbent layer changes at a sufficient level and a lower level that does not produce such changes. Simultaneously the frequency of these level changes should correspond to the amplitude changes of the video signal.

Depending on the effect of the modulated light beam, the Plate made of a series of holes or depressions due to thermal change in the absorbent material, e.g. the hole 22 according to Fig. 2 or the hole 32 according to Fig. 3, existing information track is generated. With the recording medium according to the invention can record images with a signal-to-noise ratio be stored by broadcast standard.

The invention is explained in more detail with the aid of the following exemplary embodiments.

example 1

A sheet made of pressed polyvinyl chloride with a diameter of 30.5 cm was sprayed with a Layer of an aqueous solution of acrylic floor polish covered. The applied layer was dried at room temperature. A A silicon dioxide layer with a thickness of about 300 nm is vapor-deposited as a thermal barrier.

Subsequently, an aluminum layer about 50 nm thick was applied to the silicon dioxide layer one after the other, a silicon dioxide layer about 80 nm thick and a titanium layer about 7.5 nm thick are known

Way applied. Finally, the plate was coated with a silicone resin layer which can be vulcanized at room temperature about 75 micrometers thick coated as a protective layer.

With the aid of an apparatus according to FIG. 4, a recording was made while varying the energy of the recording laser made. The characteristic values of the intake are compiled in the table. Counterexample 1 relates to a recording medium without barrier and protective layers, while counterexample 2 is for a recording medium applies without an outer protective layer.

Table 1 I opposite Opposite Laser energy game 1 game 2 XmW.) Signal-to-noise ratio (in dB) 42 45 Example '. 43 44 400 42 40 350 46 * 35 <35 300 48 250 50 Example 2 49

Using the coated with the top layer Plate of Example 1, a plate blank was produced by successively on the coated substrate an approximately 80 nm thick reflective layer made of gold,. an approximately 40 nm thick absorption layer made of 4-phenylazo-1-naphthylamine, a 167 nm thick barrier layer of silicon dioxide and a protective layer approximately 75 micrometers thick made of silicone that can be vulcanized at room temperature.

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The recording was carried out in the same way as in Example 1, with an energy of the recording laser beam of about 300 mW resulted, a signal-to-noise ratio of 47 dB.

Example 5

A filtered solution of 2% bichromated gelatin in water was sprayed onto a groove-free plate blank made of polyvinyl chloride and dried in clean air at 45 ° C. for a period of 24 hours. Otherwise, the recording medium was produced in the same way as in Example 1. There were only 1 to 5 failures per television picture.

A similar recording medium, its polyvinyl chloride substrate but did not have the top layer according to the invention, was recorded. When playing, there were hundreds of failures per television image.

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Claims (2)

RCA Corporation, 30 Rockefeller Plaza, New York , NY 10020 (V.St.A.) Claims; Λ J Laser-compatible recording medium, in particular an image plate, "in which a layer that reflects the laser light lies on a substrate layer made of plastic and a layer that absorbs the laser light lies on top of it, characterized by a thin, flat, smooth, hard, inert, free of macroscopic and microscopic surface defects Cover layer (14) between the substrate layer (12) and the reflective layer (16). 2. Recording medium according to claim 1, characterized in that the cover layer (14) Made of acrylic resin latex, epoxy paint, bichromated Gelatin, polyurethane varnish, alkyd varnish or light-curable polymers. 9 fu 9O98U / O687