FR2493020A1 - INFORMATION DISC, ESPECIALLY HIGH DENSITY VIDEO DISC - Google Patents

Abstract

HIGH DENSITY INFORMATION DISK 22 CONSTITUTED OF ELECTRICALLY CONDUCTIVE POLYVINYL CHLORIDE CONTAINING CONDUCTIVE PARTICLES AND COMPOSITE ADDTITS, AND IN WHICH THE INFORMATION IS CONTAINED AS A RELIEF CONFIGURATION OF SURFACE IN A SPIRFACE 30 MENAGE THE SURFACE OF THIS DISC, THIS DISC BEING CHARACTERIZED IN THAT Furrow 32 EXTENDS BEYOND ZONE 30 WHERE INFORMATION IS RECORDED, SUCH AS COMPOSITE ADDITIVE MATERIALS 34, INCOMPATIBLE WITH OTHER COMPONENTS , WHICH ARE COLLECTED ON THE SURFACE OF THE DISC 22, ACCUMULATES OUTSIDE OF ZONE 30 CONTAINING THE RECORDED PROGRAM.

Description

The present invention relates to the manufacture of discs containing

  high density information. More particularly, the invention relates to the fa-

  brication of such discs having reduced defects,

  High density information discs, including an information track

  mation in the form of a raised surface configuration made on the surface of a conductive plastic material, are described, for example, in

  US Patent No. 4,228,050. These discs can be played capa-

  citive using the general system described in US Patent No. 3,842,194.

  The configuration of information, in this last American patent, is presented

  in the form of a spiral groove in the surfaces of the disc.

  The material of the disc is made by mixing a re-

  polyvinyl chloride, for example a polymer or a copolymer, having a relatively high glass transition temperature (T),

  with a conductive material, for example carbon black or other materials

  conductive cells very finely divided, in an amount sufficient to

  hold a capacitive reading (playback of the recording). Since the presence of large amounts of inorganic fillers makes polyvinyl chloride resins hard and shiny, it is necessary to also add relatively large amounts of additives such as lubricants,

  both internal and external, as well as processing enhancers

  and plasticizers. The amounts of such additions vary depending on the amount and type of conductive filler added to the resin and the molecular weight, as well as the content of the copolymer of the polyvinyl chloride resin. A composition suitable for the production of high density information discs, for example video discs as described above, and

  having the necessary properties with regard to the ability to process

  dimensional stability, is described in US Pat. No. 4,228,050. The composition thus described comprises a resin based on polyvinyl chloride containing, based on the total composition, of the order of 1.5 to 4%. by weight of stabilizers, from 1 to 3% by weight approximately of at least two lubricants, a sufficient quantity of conductive particles of carbon black finely divided, so as to obtain the desired conductivity, and up to approximately 10% by weight additional modifiers, with z 2493020 provided that less than 5% by weight of liquid additives are present in

the composition.

  However, such a composition, when used for molding

  by compressing a high density information disc,

  spots or discoloration in the surface of the disc. These stains or colors result from the presence of certain additives, in particular processing improvement adjuvants and lubricants which are incompatible with the

  resin, and which resurface on the surface of the disc during the molding operation

  age. The present licensee noted that these spots and colors tended

  to gather more particularly at the end of the program area, that is

  that is to say at the location of the surface of the disc where the configuration ends

  surface relief and groove areas of the disc. These spots and accumulations

  matter lations have a number of disadvantages, among them

  which we can mention in particular: they are unpredictable; when the style or stylus passes over or through this material, debris can strike the style, which can contribute to the creation of noise and / or a drop in level or disappearance of information, and, finally, the accumulation on the surface of the disc of incompatible materials entailed a modification of the chemical composition of this disc in the zones thus polluted. The pollution caused by the presence of these stains can cause problems during treatments following pressing of the disc, for example during cleaning operations, as described in detail in US patent application No. 091 878, filed on November 7 1979 by Nyman and Huck, and during the lubrication of the disc, as described in the

U.S. Patent No. 4,275,101.

  The Applicant has discovered that by extending the groove of the disc inward, beyond the area containing the recorded program, incompatible additives on the surface of the disc tend to accumulate in the area of the unrecorded groove. , thus avoiding the area containing the recorded program, and therefore reducing optical defects and improving the signal-to-noise ratio of the ray most in the interior of the disc area

containing the program.

  Other characteristics and advantages of this invention stand out

  from the description given below with reference to the accompanying drawing, which

3 2493020

  illustrates an exemplary embodiment devoid of any limiting character. In the drawing: - Figure 1 is a plan view of an information disc obtained by molding, according to the prior art; - Figure 2 is a plan view of a molded information disc according to the present invention; and,

  - Figure 3 is a sectional view of the disc shown in Figure

  gure 2, this section being made along the lines and arrows 3-3 in Figure 2.

  Referring to the drawings, and more particularly to Figure 1, there is shown a disk 2 containing information, this having been molded, during the production of the disk, in the form of a configuration.

  in surface relief in a substantially V-shaped spiral groove.

  A central hole 4 is molded in the disc 2, so that this disc can be positioned on a spindle. The disc has a thicker raised part 6, adjacent to the central hole 4, and a part forming a thick bead 8 around the outer edge of the disc 2. These thick parts 6 and 8 serve as supports, and they prevent the zone 10 from the disc. , containing the recorded program, to come into contact with the reading table or deck, which minimizes the risk of scratching or otherwise damaging the surface where this area containing the information is located. 1Z spots have been represented on the internal part of zone 10 which covers several of the

  the most interior furrows in this area.

  Figure 2 is a plan view of the disc 22 containing information according to an exemplary implementation of this invention. This disc contains a

  central hole 24, a raised portion 26, a bead 28 and a registered area

  containing the program 30, these various parts corresponding respectively

  tively to parts 4, 6, 8 and 10 of the disc 2 shown in Figure 1. This

  during, the disc represented in this Figure 2 includes an extension zone

  furrow or extension 32 which extends well beyond zone 30 con-

  holding the recorded program. The spots 34, in this example of realization

  tion, accumulate on the innermost edge of the extension 32

  of the groove, well beyond the zone where the program is recorded, which

  prime any problem when reading this zone 30.

  Figure 3 is a sectional view of the disc 22 according to the invention, the

4 249302O

  references of identical or similar elements being the same.

  In order to produce a disc according to the present invention, etching in a V-shaped groove, in a smooth copper recording substrate, according to US Pat. "Re-issue" no. 29 113, a raised surface configuration containing audio, video and color information. At the end of the recorded program which must be played back when the disc is played, a signal to raise the

  reading tip is engraved in the substrate, this signal indicating the end of the pro-.

  recorded gram. The engraving of the V-shaped groove continues beyond

  of the zone receiving the recorded program, by extending the under signal

  lifting for several furrows, for example so as to extend the furrows over a distance of about 0.6 to 1.3 cm inwards, from

  of the area containing the recorded information. The recorded substrate is

  continuation reproduced, to obtain a replica, in a nickel plating bath in order to

  form a stamp or matrix, and discs are produced by molding and

  pressure at a temperature of the order of 176.70C, using a 36-second cycle and using the modified nickel matrix or stamp,

  with the extended groove described above.

  The example who knows, which of course has no limiting character,

illustrates the invention.

Example:

  A suitable molding composition was produced by mixing the following constituents: - 78% by weight of a polyvinyl chloride resin "lGeon 110 x 346", Z5 marketed by the American company BF Goodrich Company - 13.0 % by weight of conductive carbon black "Ketjenblack EC", from the firm Akzo Chemie;

  - 1.5% by weight of a tin stabilizer, "Thermolite T35", commercially

  read by the American firm M & T Chemical Co. Inc .; - 2.0% by weight of treatment improvement additives, "Acryloid K-147", from the company Rohm and Haas Co .; - 0.75% by weight of treatment improvement additives "Acryloid K-175" from the company Rohm and Haas Co., - 0.5% by weight of lubricant "Loxiol G-30" from the Company German Henkel International GmbH; - 1.0% by weight of calcium stearate - 3.0% by weight of diundecyl phthalate; and, - 1.0% by weight of stabilizer "Mark 275", from the company Argus Chemical Co. From this molding composition, a disc was produced which had a diameter of 30.28 cm, a central hole of 3.3 cm in diameter, a raised central part extending over 4.2 cm beyond the central hole, a bead having a diameter of 0.97 cm, and an area of grooves extending over 8.69 cm beyond the bead area. An area of the disc groove of the order of 0.64 cm, adjacent to the raised central part, did not contain

video information.

  Inspection of the disc showed that stains accumulated in

  the area of the disc with grooves containing no information.

  It remains to be understood that this invention is not limited to the examples of embodiment or implementation described here, but that it

includes all variants.

24930O0

Claims (4)

  1 - High density information disc (22) made of electrically conductive polyvinyl chloride containing conductive particles and composite additives, and in which the information is contained in the form of a relief configuration of surface (30) provided in a spiral groove in the surface of this disc, this disc being characterized in that the groove (32) extends beyond the area (30) where the information is recorded, so that the materials d '' composite additives (34), incompatible with   the other constituents, which are collected on the surface of the disc (22), become   accumulate outside the zone (30) containing the recorded program.   2 - Disc according to claim 1, characterized in that the parts   conductive cells are made of carbon black.   3 - Method for reducing the defects of an electrically conductive disc containing high density information, which consists in making a disc from a molded polyvinyl chloride resin loaded with conductive particles, in which the information is realized in the form of a surface relief configuration in a spiral groove engraved on the   surface of the disc, this process being characterized in that said groove in spi-   rale extends beyond the configuration containing the recorded information,   so that incompatible surface materials collect together beyond the registered area.   4 - Method according to claim 3, characterized in that the   conductive particles are made of carbon black.   - Original nickel model to make, by molding and compression, discs containing high density information, comprising a spiral groove in which the recorded information is contained under the   form of a raised surface configuration which constitutes a negative of the in-   formation to be molded in the discs, this original model being characteristic   terized in that the spiral groove extends beyond the configuration of in-   recorded formations, so that surface materials incompa-   Targets collect beyond the surface configuration containing the information mation.