DE3228584C2 - - Google Patents

Description

In the production of optical video discs, the information to be recorded in one side of a thin transparent substrate made of a thermoplastic Material such as polymethyl methacrylate, thereby pressed or impressed that the temperature of the substrate up to is raised to a softening, whereupon a press or Embossing element that carries the records against the substrate is pressed, then the substrate in contact with the embossing element until a solid state is cooled (DE 30 28 947 A1).

According to the previous procedure, a reflective Coating on the substrate in the vapor deposition or vacuum Metallization process in a second device brings after the substrate is removed from the press had been. According to other known methods, the resulting video plate with its reflective Layer together with another similar plate brings what further recorded information ent held, and combined into a complete video disc, what video information contained on both sides, that can be reproduced optically.

The state of the art practice of removing one thin transparent substrate from the press and time  wise storing the substrate leads to accumulation of dust and oil particles contained in the air on the surface of the substrate with the recorded Video information. Furthermore, the vapor deposition or vacuum Deposition process according to the prior art for bring the reflective layers into microscopic Scale is usually imperfect, especially as regards the relatively large surface area of a typical video disc (which is usually of the order of a diameter of 300 mm). In addition, with ver do not entrain foreign particles according to the state of the art be removed, which already carry the information Surfaces of the disks are present. The result is that in the reflective surfaces of the known Slices or plates of many microscopic defects themselves adjust and that these defects in the plates after full usually ends as visible or audible Disorders in the playback of the on the disks recorded information come to light when this occurs Playback devices can be played.

The object of the invention is therefore a method for Record video information on a plastic creating a substrate that eliminates the need the embossed disks or plates from the press to one second device to transfer there the reflective Apply coatings, and thus to avoid that the Plates while making a build up of alien particles are exposed on them.

The characteristics of the To serve to solve this task saying 1.

It is known per se, a thermoplastic information carrier before embossing the information relief with a reflective, metallic layer to be provided (DE-AS 26 24 017).

By means of fluid organometallic compositions the metal atoms in the molecules of the compound  Settlements or connections caused a thin metallic coating due to foreign deposits to create areas that depend on the decomposition temp Such connections are heated, these Procedure as pyrolysis or chemical vapor deposition is known. Although the deposition of metals by Zer settlement of organometallic compounds, including gas plating is known, is known to be so produced Metals primarily for creating high purity just applied. According to the invention, the method used for organometallic deposition an optical surface of relatively high and uniform Re flexibility over a large area create.

The area of organometallic compositions or Compounds which are used in the method according to the invention can be applied is wide. Although both liquid as well as gaseous compositions used can be, are the examples described by the Type in which a metallic composition, such as Aluminum, in its gaseous form for plating one reflective surface on the substrate of a video plate is used. The gaseous forms of aluminum can e.g. B. alkyls, alkyl halides, alkyl hydrides, hydride Halides and similar alloys are as follows are collectively referred to as aluminum alkyls, though other organometallic compounds such as tellurium tetramethyl and the like. When carrying out the Ver driving can be used.

The invention is based on schematic drawings on an embodiment of a device for through carry out the method according to the invention with further individual explained in more detail. It shows  

Fig. 1 is a schematic representation of a typical device for performing the method according to the invention, where the device is shown in a first operating position, and

Fig. 2 is a schematic representation of the device according to Fig. 1 in a second operating position.

In the drawings, elements 1, 2, 3 and 4 form the basic components of a hydraulic press of the type currently used in the pressing of records and video records. The press comprises a table 1 and a lower mold plate 2 mounted thereon. At the end of a hydraulic piston 4 , an upper mold plate 3 is attached. Suitable heating and cooling agents 16, 28 pass through both mold plates.

Fig. 1 shows the press in its open and raised position. The video plate stamp 5 , the z. B. consists of nickel and contains the information to be drawn on the video plates to be recorded is attached to the lower surface of the mold plate 3 . In the embodiment shown, the mold plate 3 contains egg nen centrally above the die 5 extending channel 6 , which opens into a central hole in the die. The channel 6 runs above it radially to the outer edge of the upper mold plate 3 , and a hose 7 is inserted into a pipe nipple 6 a , which projects from the end of the channel.

The press includes an arm 8 , which is fastened to a bearing 10 , which in turn is rotatable about a mounting column 9 and vertically displaceable thereon. A flat Zy cylinder 11 , which is closed on its underside, is mounted at the end of the arm 8 . A diffusion body 12 is supported in the cylinder 11 so that it has a distance from the Bo to form a plenum chamber 13 . At the peripheral edge of the mold plate 3 , a cross-sectionally circular elastomer seal 14 is provided, which creates a seal between the cylinder 11 and the mold plate 3 when the device according to FIG. 1 is closed.

The sealing pressure is provided by a piston 15 , which plays in a hydraulic cylinder 17 . The upper end of the piston acts on the underside of the arm 8 , and when the piston is extended as shown in FIG. 1, it causes the arm 8 to press the cylinder 11 against the upper die plate 3 and to seal these two parts against each other. The piston 15 is moved into its upper, extended position according to FIG. 1 by introducing a hydraulic pressure medium via a pipe 18 into the lower end of the cylinder 17 .

In the first step of the process according to the invention, the mold plate 3 is heated by steam, fluorocarbon gas or another suitable means to the pyrolysis temperature of, for example, aluminum alkyl via the elements 16 . The heating heat is quickly transferred to the embossing element 5 . A delivery amount of a chemically relatively inactive gas, such as argon, is fed via a flexible hose 19 and a central hole in the bottom of the cylinder 11 to the plenum chamber 13 . This gas is passed through the porous diffusion body 12 to the heated embossing element 5 . The inactive gas then passes through the central hole of the embossing element and reaches the outside of the device via the channel 6 and the hose 7 . The inactive gas is, for example, delivered by a pressure wave 21 via a device which can be controlled with a manually or automatically controllable valve 20 .

In the second step of the method according to the invention, the valve 20 is switched to a position in which the supply of the inactive gas is shut off and the supply of the aluminum alkyl gas is opened from a pressure source 22 . The aluminum alkyl gas flows through the hose 19 to the plenum chamber 13 and via the porous diffusion body 12 to the space between it and the bottom surface of the die 5 , which carries the embossing or pattern to be applied to the video plate. The aluminum alkyl gas also flows through the channel 6 to the hose 7 . While the aluminum alkyl gas flows through the device, it decomposes to form a metal coating, in the present case made of aluminum, on the hot, exposed surface of the die 5 . When the deposited metal layer has reached the desired thickness, the valve 20 is switched to its position according to FIG. 1 in order to feed inactive or inert gas again, to clean the gas flow path of any residues of the aluminum alkyl gas and its gaseous decomposition products and to dispose of a known type via the hose 7 and the valve 23 .

In the next step of the process, hydraulic pressure is guided via the tube 26 into the cylinder 17 to the upper side of the piston 27 in order to lower it. The bearing 10 moves along the column 9 to a stop 27 , and the arm 8 and the cylinder 11 move together with the diffusion body 12 down from the mold plate 3 away. The arm 8 is then pivoted together with the cylinder 11 and the diffusion body 12 by hand or automatically by approximately 90 ° in the horizontal plane into the position shown in FIG. 2.

Coinciding with the first process step described above, an appropriate amount of thermoplastic material 25 is placed in a cavity in the surface of the second mold plate 12 and heating elements 28 are turned on to melt the material. In the next process step, the hydraulic piston 4 drives the heated mold plate 3 and the die 5 with the reflective layer applied thereon in intimate and uniform contact with the molten surface of the thermoplastic substrate 25 , as shown in FIG. 2. At the same time, the seal 24 creates an intimate sealing contact between the mold plates 2 and 3 from an elastomer material, so that after manual or automatic switching of the valve 23 via the flow paths 6, 7 and 23, a vacuum source creates a vacuum in the molding space. After the residual gases between the metal-coated die surface and the substrate surface have been removed, a uniform transfer of the metal coating and a perfect, bubble-free adhesion of the metal coating to the plastic substrate is generated. At this time, a cooling fluid is introduced via the elements 16 of the upper mold plate 3 and the elements 28 of the lower mold plate 2 . When the plastic substrate 25 is sufficiently cooled and cured, the hydraulic Kol ben 4 is raised together with the mold plate 3 and the die 5 back into the position shown in FIG. 1. However, since the reflective metal coating was adhered to the plastic plate 25 with an adhesive force greater than that with which it adhered to the die, the reflective coating is transferred from the die to the plastic plate.

The arm 8 can then be pivoted back into its position according to FIG. 1 and raised again by the piston 15 against the mold plate 3 in order to press the cylinder 11 against the mold plate 3 again and to start the process for producing the next video plate again.

In order to facilitate the transfer of the reflective aluminum coating, the embossing surface of the embossing stamp 5 is provided by means of vapor deposition or in some other way with a thin layer of a material which has little adhesion to aluminum. The temperatures of the upper and lower mold plates 3 and 2 of the press can be varied independently of one another by means of the elements 16 and 28 . For example, the upper mold plate can be heated to about 290 ° C during the pyrolysis, while the plastic material in the lower mold plate is heated to about 220 ° C. In addition, the upper, hotter mold plate 3 and thus also the die 5 is preferably cooled more intensively than the lower mold plate 2 carrying the plastic substrate. In this way, the different thermal expansion coefficients of the metal die 5 and the plastic material in the lower mold plate 2 are compensated to compensate for the radial shear stresses that normally occur in the outer edge zones of the plastic plate 25 . Such claims, which often destroy the outer areas of the embossed video recordings in the production of video plates in the usual way, are thus avoided in the method according to the invention.

Claims (11)

1. A method for recording video information on a plastic substrate, with an embossing element which has embossments or elevations on a surface which represent video information, characterized by coating the surface of the embossing element with a reflective material in the pyrolysis process; Providing a plastic substrate and heating the plastic substrate to the melt state in a mold; Moving the embossing element against a surface of the plastic substrate in order to provide the embossing with impressions corresponding to the video information on the embossing element and at the same time to cause the reflective material to stick to the embossed surface of the plastic substrate; Cooling the embossing element and the plastic substrate while they are still in contact with one another; Retracting the embossing element from the surface of the plastic substrate to cause the reflective coating to be transferred from the embossing element to a plastic plate. 2. The method according to claim 1, characterized records that the temperature of the embossing element is raised to a predetermined temperature and that an organometallic composition in fluid Condition over the surface of the embossing element is performed to the reflective coating To form deposit of the composition. 3. The method according to claim 2, characterized records that the organometallic composition in a gaseous state over the surface of the embossing element is guided. 4. The method according to claim 2 or 3, characterized records that the organometallic composition is formed by an aluminum alkyl. 5. The method according to any one of claims 1 to 4, characterized characterized that the embossing element with a layer of a selected material is drawn, the lower adhesion to the reflective Material than on the plastic substrate. 6. The method according to any one of claims 1 to 5, characterized characterized that the plastic substrate is a thermoplastic material. 7. The method according to any one of claims 1 to 6, characterized characterized that the plastic substrate is transparent. 8. The method according to claim 7, characterized records that the plastic substrate Is polymethyl methacrylate.   9. The method according to claim 1, characterized records that the embossing element and the art substrate are cooled differently. 10. The method according to claim 2, characterized records that the embossing element on a higher temperature than the molten plastic substrate is heated. 11. The method according to any one of claims 1 to 10, characterized characterized in that a vacuum between the embossing element and the plastic substrate ge will create to remove residual gases.