CA1069213A - Mold for use in making a video disc - Google Patents

Abstract

ABSTRACT

A mold for use in forming at least the video information layer of a video disc is disclosed. The mold includes a body having a substantially flat upper surface with discontinuities out of the plane of the surface, the discontinuities being separated by a flat portion of the surface. The discontinuities and the flat portions are arranged in a video information track, which track is substantially circular. Each discontinuity has a constant radial dimension and a constant maximum dimension in the direction perpendicular to the flat surface. The length of each discontinuity in the circumferential direction and the corresponding separation between adjacent discontinuities represents the stored information. The discontinuities may take the form of depressions in the surface or protrusions above the surface.

Description

1~69'~3 BACKGROVND OF THE INVENTION
Field of the Invention The present invention relates to information handling systems and more particularly to a mold for producing replicas from a master matrix and to the mold.
This application is a division of copending Canadian application Serial No. 210,356 filed September 30, 1974, directed to the process for producing the replicas and the replicas produced thereby.
Description of the Prior Art Over the years, there has been a continuing attempt to achieve a low cost, mass produced disc which contains video informa-tion that can be retrieved with an inexpensive home instrument for playback for a conventional television set.
Early attempts at providing video information have ~ generally involved the use of video tape recorders of various ; sorts as well as photographic techniquesL ~till other approaches have attempted to utilize thermoplastic records or the surface alteraeion of à thin metallic film.
In the co-pending Canadian application of Manfred H.
Jsrsen, Serial No. 210,354, filed September 30, 1974, entitled "Methot of Creating A Replicating Matrix and the Matrix Created Thereby", assignet to the assignee of the present invention, methods .
were taught which led from a master video recording, such as in the Canadian Patent 1,013,854 and the co-pending t~visional Canatian ~1 application of John S. ~inslow, Serial NQ. 266,802, filed November 1 26, 1976, and as9igned eo the assignee of the present invention, to a three-time~sional matrix from which replicas can be createt.;
i :~` In the co-pending Jarsen applicatlon, supra, the present~

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casting process was disclosed for producing a replica OD a disc which includes a Mylar* polyeAter fllm sub~trate and a polymer layer, into which is molded the information contained in the matrix, ,~ . .

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~ ~06g2~3 1 According to the parent invention, the casting process

2 includes the production of a principal mold which can be usod to

3 produce submatrices which, in turn, would produc~ submolds.

4 Both the Molds and the submolds can be used to "cast" replicas.
In the prefe~red embodiment of the process, a ~ylar substrate of 6 thickness from 4-10 mils is uniformly coated with a very thin 7 (approximately 3-7 microns) layer of a polymerizable resin to 8 which a catalyst has been added.
9 The resin is then brought into contact with the mold and subjected to pressure to assure that the resin fills all of the 11 depressions and/or cavities of the mold. The resin is then 12 permitted to cure. The bond between the .~ylar substrate and the 13 resin is perfected. Afte~ curing; the Mylar and polymerized 14 resin are a unitary structure and, as such, can be peeled from the mold. The same mold can then be used again in the casting 16 of subsequent replicas using substantially the same techniques.
17 The replica, thus cast, is then provided with a reflectiva, 18 metal layer, for example, through a vapor d~position process.
19 If desired, an outer, wear layer of clear plastic can be applied.

21 ¦ In the video disc systems described in the related patents and applications, one systems approach permits the use 22 of a thin, flexible disc, such as is produced by the present 23 method. Such a disc can be read on appro~riate playback 24 e~uipment as has been heretofore disclosed.
If, the exigencies of mass production are such that 2 insufficient molds can be derived from a single matrix, it is 7 feasible, according to the pa~enc invention, to cast a number 28 ¦ of polymer, replioas in the first mold which can function as 29 ¦ submatrices, as well.

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I ' j ' ' ~ ' I ~ :' , ~06~Z13 1 ~n altcrnatc replica can be madc ~rom an acrylic-polyestcr 2 combination. Thc acrylic rcplicas whcn plated, can be dis-3 tributed as such. The acrylic replicas could also be utilized 4 ¦ as a starting element in the scries of plating steps that

5 ¦ ultimately result in a stamper for use in the alternative,

6¦ stamping process of producing replicas.

7 In yet other, alternative casting methods, replicas can

8 1 be produced by first flowing the resin-catalyst mixture into

9 I the mold. The Mylar polyester film substrate is applied later,

10 ¦ and becomes bonded to the cured resin.

11 ¦ The replica is then "peeled" off the mold. In the

12 ¦ preferred embodiment, the cast replica is then subjected to a

13 ¦ metallizing step in which a suitably reflective metal such as

14 aluminu~ is applied to the surface. Vapor deposition of

15 ¦ alu~inum has been found to be satisfactory. The reflective

16 ¦ -coating enhances the optical contrast between the deformed

17 ¦ areas representing information and the plane areas adjacent

18 I thereto. ~n additional coating of a clear plastic, wear layer

19 ¦ can be applied to protect the metal fil~ from scratches or

20¦ abrasions.

21¦ It is obvious that the present method could be modified 2~ to produce replicas in which the surface deformations are de-23 pressions rather than elevated portions, should that type of 24 replica better lend itself to the playback equipment. Further, 25 I the requirements of the playback equipment would also determine 26¦ the size and shape of the surface deformations which represent 271 the video information.
28¦ For example, in the system being developed by the assignee, a reading technique is employed which utilizes light -31 ~ -5~

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1~692~3 ~catter~ng and light reflection to generate electrical signal~
of different ~lgnificance. In such a system, the "bumps" or "depressions" serve to scatter rather than reflect light applied from the player device. The surface between ad~acent bumps or depresslons, however, serves as a plane reflector, and returns substantially all of the light to the player optical system.
In the alternative schemes, phase contrast optics are employed in ~hich case it is de!3irable that reflecting planes be spaced apart by n4 (where~ is the wavelength of the playback radiation and "n" is an odd integer~ be employed so that light reflected from a one of the surfaces is constructively interfered with, and light from the other of the surfaces is destruc~ively interfered with.
Given an original matrix ha~ing such characteristics, the present process is admirably suited to produce repllcas utilizing the mold of the present invention, that is created from the ~atrix.
The invention accordlng to tke parent application may be defined as a disc-shaped record carrying video information ~n a form suitable of being sensed by an impin~ing light beam, and the video information is arranged in a track li~e fashion; an information bearing layer having a ~irst surface and a second .
surface; the first surface of t~e in~ormation bearing layer carry-I ing the video information as a line of discontinuities positioned out of the plane of tbe first surface; each di~continuity having 8 constant dimenslon in the radlal direction and a con~tant maximum~
tlmenslon in the direction perpendlcular to the surface; the :
; length of each di~ccntlnuity in the clrcumferentlal direction~and th~ di~tance between ad~acent discontinuitle8 in the circumferenelal .
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direction representing the stored ~nformation, and each dls-continuity reflects the impinging light beam differently than the planar surface portions of the first surface.
The parent application is also seen to define a process for producing a disc-shaped record which comprises providing a master matrix carrying information represented as a series of surface dis-continuities arranged in a track l.ike fashion; forming an elastomeric negative mold having an upper surface carrying the video information in a form complementary to the information bearing surface of the matrix; the upper surface of the mold being formed with a pattern of surface deformities separated by flat surface portions of the upper surface; making a replica disc in the elastomeric mold; and removing the replica disc having a planar surface exhibiting a pattern of discontinuities arranged identical to the information track carried by the master matrix.
To go along with the process and the product defined in ; the parent applicaeion, the invention of the present divisional ` application may be defined as a mold for use in forming at least the video information layer of a video disc comprising a body of .
elastomeric material having an upper surface, the upper surface being substantially flat for establishing a substantially planar surface in the resulting video disc suitable for reflecting light incident thereto, and the upper surface having discontinuities out of the plane of the surface, and each of the discontinuities being separated by a flat portion of the upper surface, and the dis-continu~ties and flat surface portions being arranged as an image of a video information track, the video information track being generally disposed in a substantially circular path, each dis- ~
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continuity hsvinl~ a constant dimen~ion in the radial direction and - 6a - ;~
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1~69Z~3 a constant maximum dimension in the direction perpendicular to the surface, the length of each discontinuity in the circumfe~ential direction and the di~tance between ad~acent discontinuities in the circumferential direction representing the stored in~ormation.
The present invention also is characterized by a process for producing a mold for replicating a disc-shaped record, comprising the steps of: forming a master matrix carrying information represented as a series of surface discontinuities positioned out of the plane of a planar surface of the matrix and arranged in a track-like fashion, each discontinuity having a constant dimension in the radial direction and a constant maximum dimension in the direction perpendicular to the planar surface, the length of each discontinuity in the circumferential direction and the distance between ad~acent discontinuities in the clrcumferential direction representing stored information, and flowing an elastomeric compound against the matrix and allowing the elastomeric compound to cure -to form a negative mold having an upper surface carrying the video information in a form complementary to the information carrying surface of the matrix, the upper surface of the mold thereby being formed with a pattern of surface discontinuities separated by flat surface portions of the upper surface.
The novel features which are believed to be characteristic of the invention, both as to organization and method of operation, - together with further ob~ects and advantages thereof, will be better understood from the following description considered in connection witb the accompanying drawings in which several of the preferred embodlment9 of the invention are illustrated by way of example. It to be express].y understood, however, that the drawings are for .
the purpose of illustration and description only and are not inte~ded - - 6b -;~ ~ dap/ ~

- ~()6~2~3 as a definition of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a portion of the surface of a mold made in accordance with the present invention;

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I 16~69~3 1 ¦ FIG. 2 is a sidc section view of the apparatus used ~o 2 produce the mold of lIG. l;
3 FIG. 3 is a sidc section view of the mold of FIG. 2 taken 4 along line 3-3 in the direction of the appended arrows prior to the castin~J of a replica;
6 FIG. 4 is a side section view of apparatus for providing 7 a polymerizable resin and substrate combination;
8 FIG. 5 including FIGS. 5a and 5b are side section views 9 of the ~old of FIG. 1 with a resin and substrate co~biantion being applied in alternative pro~esses;
11 FIG. 6 is a side section view of the mold during the 12 casting step;
13 FIG. 7 is a side section view of the polymerized resin 14 and substrate being removed from the mold;
15 I FIG. 8 is a side section view of a cast acrylic replica 16 ¦ in the mold; and . - .
17 ¦ FIG. 9 is a perspective view of a portion of a replica 18¦ disc partly broken away to show the metal and plastic protective .
19¦ coatings. - -20¦ DESCRIPTIO~ OF THE PREFERR~D EMBODIMENTS
21 In FIG. 1, there is shown in perspectiva view a portion

22¦ f a mold 10 made in accordance with the present 231 invention. As will be noted, the mold 10 has an upper surface 12 24I in which is formed a plurality of depressions 14 generally 25¦ arranged in a concentric spiral track 16.
26¦ Although the individual depressions are arranged in a 271 generally circular pattern, the track 16 is a discontinuous one, 28¦ and includes a flat surface area 18 between adjacent depxessions . .

330 ¦ 14. The pref~rr d embodi-~4t o~ the present invo-tion contempla tl 32~ _7_ ' , , ' ' .:

1 an information trac~ 16 arrangcd in a spir~l, but altcrnative 2 embodiments contcmplate information arra~gcd in circular 3 tracks, not shown, as well.
4 It is to be furthcr notcd that while thc preferred e~bodiment illustrat~d in FIG. :L shows each track 16 to include 6 depressions 14, it is equally feasible to supply protuberances 7 ¦ or "bumps" in place of the depressions 14. If the surface 81 features p~ovided in the playback replica are intended to scatter ¦ radiation rather than reflect it, the choice of one or the other is dictated primarily by considerations of fahrication of 11 the mold 10, or the replica to be cast in the mold 10.
12 ¦ ~he process of producing the mold 10 can be éxplained 13 ¦ in connection with FIG. 2. The starting material should be a 141 matrix 20, such as is disclosed in the copending Jarsen ~5¦ application. As taught in that application, the matrix 20 includes a 16¦ glass disc 22 on which the video information is arranged as a 17 series of photoresist "bumps" 24 approximately.7 micron high 18 ¦ and generally 1 micron in the radial direction. The bumps are 19 ¦ generally arranged in a concentric, spiral track with a spacing 20 i of approximately two microns between the centers of adjacent 21¦ tracks. , ~.
2 ¦ The matrix 20 may or may not have remaining on the surface, 31 a very thin layer of a low melting point opaque material 26 such 251 as is disclosed in the copending Winslow application. A thin bismuth film has been found to be suitable for this purpose.
26 If desirable, the bismuth film 26 may be removed utilizing a 27 suitable chemical solvent. Such a step is generally not under-28 taken in that it may jeopardiza the integrity of the in~ormat~n 29 pattern.

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~ 1~692~3 1 I To prcparc the matrix 20 for the present procoss, a mold 2 ¦ release compound (not sho~n) is spun on to the matrix 20 and 3 ¦ permittcd to dry, after which it is bak2d. In one satisfactory 4 ¦ procoss, a commercial release, identified as Fitzgerald Polyvinyl 5 ¦ Alcohol ;~lold Release, is diluted with three parts of water to 6 ¦ each part of mold r~lease.
7 ¦ With a matrix 20 such as is disclosed by Jarsen supra, 8 ¦ approximately 25 cc. of mold release is diluted to a total 9 ¦ quantity of 100 cc., filtered and then applied to the matrix 20.
10 ¦ The mold release is dried in air for approximately 10 minutes, 11 ¦ and the matrix is then baked at a temperature of 300 F.
12 ¦ for approximately 30 minutes.
13 ¦ As seen in FIG. 2, apparatus is shown which is suitable 14 ¦ for use in the production of the mold 10. A heater unit 30 has, i~ ¦ placed on its upper surface, a block of aluminum 32 which is a 16 ¦ good thermal conductor.- The glass-based matrix 20 is securea 17 I to the aluminum platQ 32 using a wax 34 which acts as both an 181 adhesive and a cushion.
19¦ Spacers 36 are provided to create a volume in which the 2Q¦ mola 10 can be made. In the preferred em~odiment, first 21¦ spacers 36, approximately 14 mils high, are placed around the 22¦ periphery of the matrix 20, and a second spacer-38 approximately 231 7 mils in thickness is placed at the center of the matrix disc.
24¦ A glass plate 40 is coated with a primer compound 42 to 251 which the elastomeric material comprising the mold will adhere.
26¦ One such primer material is sold under the designation 271 Primer SS4120 by the General Electric Company. The primer 28¦ coating 42 is permitted to air dry for approximately 30 minutes.
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_9_ ` ~ 1069Z~3 ¦ In the prefcrr~d cmbodiment, the mold 10 1~ made ~f a 2¦ silicon~ rubber elastomer, such as is sold by the General 3¦ Electric Company und~r the designation nTv 615~ silicone rubber.
4¦ In the proccss, being d~scribcd herein, it has been found that 5 ¦ approximately 200 grams of the silicone rubber, with 20 grams of 6I the proper catalyst for that compound, are su~ficient to make a 7 ¦ roughly 15 inch diameter mold that is approximately 14 mils thick.
8I The mixture of silicone rubber and catalyst is mix d for - 9 ¦ approximately 15 minutes, fil~ered and deaassed, until all lO~ bubbles have disappeared. The compound is then poured over the 11 I surface of the matrix 20 which has been treated with the mold 12 ¦ release. The glass plate 40 with the applied primer layer 42 is 13 I placed, primer layer down, on the spacers 36, 38 and 14 ¦ immediately overlies the rubber catalyst mixture.
15 j ~ A rubber platen 44 is then placed on the glass disc 40, 16 ¦ and a mass 46 is placed on the platen 44 to apply a uniform 17 I pressure over the surface of the glass 22.
18 I The rubber mixture is then cured. The temperatures and 19 ¦ cure times are, of course, related. For lower temperatures, 20 j ranging from 160 to 200 F., a curing time of approximately 21 1 12 hours can be used. At the higher curing temperatures, 22¦ shorter curing times can be used. For example, a 14 mil thick,

23 ¦ 15 inch diameter mold will cure in approximately 2 hours at

24 1 400~ F.

25 ~ At the conclusion of the curing period, the upper plate 40

26 is separated from the matrix 20. The presence of the mold .

27 ¦ release on the matrix 20 and the primer 42 on the upper glass

28 I disc 40 causes the mold thus created to adhere to the upper 291 disc 40 and not to the matrix 20. .

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~ 69Z13 1 The comploted rubber mold 10, shown in FIG. 3, can then 2 be trimme~d to cut a~lay the cxtru~ed exccss ~nd should be cleaned 3 and vacuumed for use in replication. If tho mold reloase has 4 worked ~ell, the original matrix may be used to produce yet additional molds. However, because the surface features on the 6 matrix 20 are mer~ly hardened photoresist material adhering to the glass disc 22, it is not generally expected that more than 8 a very limited number of molds can be made from the original 9 matrix 20. A mold 10 once made, however, can be used to cast either replicas, to be used for playback, or submatrices, which 11 ¦ may or may not be used for playbac~.
12 I Turning next to PIG. 4, the process of producing a replica 13 j is partially illustrated. In a preferred embodiment, a Mylar 14 I polyester film substrate 50 is cut into a 15 inch disc and placed 15¦ on a glass support plate 52. Both are then placed on a 16 turntable 54. The substrate 50 is washed with acetone and Xylene 17 ¦ and is spun dry.
18 I A polyurethane resin mixture is then prepared. In the 19 i preferred e~bodiment, a polyurethane resin is employed which is 20 ¦ sold by Hughson Chemical Company under the designation 21 ! Chemglaze z051. Alternatively, a similar resin, Chemglaze Z052, i 22 j may also be used. A resin thinner, sold under the designation ~3 Chemglaze 9951 is also used in the preferred embodiment. The 241¦ resin and thinner are generally used in a ratio of 3 parts resin to 2 parts of thinner.
26 A catalyst sold by the Hughson Chemical Company as ~ast 27 Catalyst 9984 or 9986 is also employed to speed the polymerization 28 process. In the preferred embodiment, 10 cc. of catalyst is

29 ¦ diluted to 75 cc., using the thinner, prior to use.

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3a ¦ * Trademark I . ' ' ' ' ' . ~ . ~. ;., ~ ' ' '; , 1¦ ~pproximatcly 5 cc. of the dilutcd catalyst i5 thcn mi~ed ~¦ with 100 cc. of the dilutcd r~sin solution. The combination is 31 mixed well for approximatcly 3 minutcs and is then "spun" onto the substrate disc 50. With the turntable 54 operating at 5 i approximately 400 rpm, a polymer 56 coating is spun on for 61 approximately 5 seconds, to result in an approximately 5 micron 71l layer in the preferred embodiment. The thicXness can range from 8l~ 3 to 7 microns.
g l! The methods of ap~lying the coated substrate to the 10¦1 mold 10 are shown in FIG. 5. As shown in FIG. 5~, the preferred 11 , technique is to partially wrap the substrate 50 around a rather 12 i large roller 58 and then to roll the combination onto the mold 10.
13 ¦ This method provides a gradual application of the resin coated 14 ¦ substrate 50 and, at the same time, provides an opportunity to 15 I assure an even and uniform application of pressure to the resin 16 , layer 56, while minimizing the occurrence of trapped bubbles of 17 ~ air or gas in the mold 10.
18 ~hile the resin layer 56 is setting up, the combination 19 I can be rolled again with a heavier roller. The set-up time runs for from 15 to 45 minutes depending upon the resin-catalyst 21 i combination and the thicXness of the resin layer 56.
22 i Other materials can be used in addition to the polyurethane 23 ¦ resin. For example, acrylics and epoxies can also be employed as 24 j well as monomers which can be polymerized by radiation such as 251 ultraviolet light or radio freguency energy as taught in the 261 related ~roadbent patents, supra. Similarly, substrates other 27¦, than Mylar polyester film could be employed, including metal 28 1 ~oils, which can be thin and flexible.
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I ~69Z~3 1 ¦ It has also bcen found that an al~crna~ivo ca3ting proc~ss 2 j can be employed, as illustrated in FIG. 5B. The rc~in is 3 ! thinne~ and mixed with the ca~alyst and applicd directly to the 4 I mold 10. The substrate 50' is then rolled onto the resin layer 56' 51 which is then permitted to cure and to adhere the substrate 50' 6 I as illustrated in FIG. 6. The f.i~ishcd replica will then be 71 substantially the same, no matter which process is employed.
8 In FIG. 7, there is shown a method of removing a replica 60 9¦ from the mold 10. The roller 58 which was used to apply the 10 I polymer-substrate combination ca~ be used to remove the cast and 11!. cured replica 60. One surface of the replica 60 adheres to the 12 i roller 58, which, when rotated! removes the cured replica 60 13 I from the mold 10.
14 ~ Alternatively, an acrylic material may be cast in the 1~ mold 10 as shown in FIG. 8. The acrylic replica 62 may be used 16 with a polyester film substrate 63. The acrylic replica can be 17 used interchang`eably with the polyurethane replicas. .
1~ ' It has also been noted that, inasmuch as the acrylic .
lg i replicas 62 can be plated, the plated acrylic replica 62 can also be utilized as an interim element in the process of 21 , producing stampers for making replicas utilizing embossing 22¦ techniques. .
23 ~ile the methods of producing the mold and the replicas . -.
24 ' have been described in terms of a system which utili~es "bumps".
26 j to represent information, it is equally feasible to employ thé
26 ! same process to create a mold whose surface resembles the matrix .~.
27 ! and from which alternative replicas can be cast. In the 28 !~ alternative replicas, information is represented as depressions 291 in the replica sur ace.
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~ " .-13- . ~ ~ :' . ` ~ ~ " . ' ' ' ' ~ ~ , ,' ' ;, , , , , , , , , , . ' ! ' ' . ~ ' . ' ' S ~ larly, while the present invention has been described in terms of a video disc system that employs light scattering for the reco~nition of information, the process steps are equally applicable to phase contrast recording and playback systems. In such systems, a mold can be created from the original master. The reflecting planes are separated by a vertical distance of n~ (where ~ is the ~avelen~th of the illuminating radiati~n and "n" is an odd inte~er) and can be easily replicated.
- It would seem that a relatively rigid replica would be preferable for this type of playback.
Turning finally to FIG. 9, a replica disc 60 is shown in some greater detail. The disc 60 includes, in the preferred embodiment, a surface pattern of discontinuous bumps 64 separated by planar areas 66. A reflective metal coating 68, such as aluminum, is applied by a process such as vapor deposition to enhance the reflectivity of the planar portions 66 and to enhance the light scattering capability of the individual sur~ace deformations 64 representing information.
If desired, an additional, clear plastic coating 70 can be applied to the disc 60 to protect the metallic surface 68 from scratches, abrasion, and wear. However, with the "non-; contact" playback systems, as well as the vacu~ playback trans-- ducqr and fluid cushion turntables disclosed by Jarsen, supra, t~le chances of abrasive wear, at least with respect to the playback mechanism, is m:inimized.
Thus there has been disclosed a complete process for converting a matrix derived from a master disc into a replica disc for playback. The process includes, first, a process for ywl/~ - 14 -; . : . .
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~. . ~ . ~ - . . .-~ 1~692~3 1 I ereating molds from a matrix. The replicas from the fir~t mold 2 I eould bc employed to mak~ additional submolds without any 105s 3 ¦ in fidelity.
4 ¦ Seeond, a process is taught for the easting of replicas 5 ¦ from the molds thus taught. The replicas include a surface 6 ¦ layer which is a polymerizable co~pound that has been cast in 7 ¦ the mold and` a polyester substrate, which is bonded to the 8 ¦ surface layer to give it struetural integrity. Additional 9 ¦ surface coatings of reflective metal and clear plastie are added 10¦ to protee~ ~he di e fr~ wear and abrasioDs. ¦

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A mold for use in forming at least the video information layer of a video disc comprising:
a body of elastomeric material having an upper surface, said upper surface being substantially flat for establishing a substantially planar surface in the resulting video disc suitable for reflecting light incident thereto, and said upper surface having discontinuities out of the plane of the surface, and each of said discontinuities being separated by a flat portion of said upper surface, and said discontinuities and flat surface portions being arranged as an image of a video information track, said video information track being generally disposed in a substantially circular path, each discontinuity having a constant dimension in the radial direction and a constant maximum dimension in the direction perpendicular to said surface, the length of each discontinuity in the circumferential direction and the distance between adjacent discontinuities in the circumferential direction representing the stored information.

2. The mold of claim 1 above, wherein said surface discontinuities are generally depressions in the surface, whereby video discs produced from said mold have raised surface continuities.

3. The mold of claim 1 above, wherein said surface discontinuities are elevated from the surface whereby video discs produced from said mold have depressed surface discontinuities.

4. The mold of claim 1 above, wherein said body is made of a silicone rubber elastomer.

5. A process for producing a mold for replicating a disc-shaped record, comprising the steps of: forming a master matrix carrying information represented as a series of surface discontinuities positioned out of the plane of a planar surface of the matrix and arranged in a track-like fashion, each discontinuity having a constant dimension in the radial direction and a constant maximum dimension in the direction perpendicular to said planar surface, the length of each discontinuity in the circumferential direction and the distance between adjacent discontinuities in the circumferential direction representing stored information; and flowing an elastomeric compound against said matrix and allowing the elastomeric compound to cure to form a negative mold having an upper surface carrying the video information in a form complementary to the information carrying surface of the matrix, said upper surface of the mold thereby being formed with a pattern of surface discontinuities separated by flat surface portions of said upper surface.

6. The process as claimed in Claim 5, and further including the steps of: applying a mold release compound to the surface of the matrix prior to the forming step; and adhering a backing plate to the mold to facilitate removal thereof from the matrix and to provide additional support to the mold.

7. The process as claimed in Claim 5, including the steps of: prior to said mold forming step, rotating the matrix while applying a mold release compound to the information carrying surface of the matrix, and drying said mold release compound;
providing material ingredients for preparing a mold compound;
mixing said ingredients to form the mold compound; filtering and degassing said mold compound for removing all bubbles, said mold forming step including pouring the filtered and degassed mold compound over the information bearing surface of the matrix, and curing the mold compound and separating the cured mold from the master matrix.

8. The process as claimed in Claim 5, therein said forming step comprises: providing a glass disc substrate having a first disc surface defining said matrix planar surface; and forming said discontinuities in a video information track on said first surface, said information track being in the form of a series of photoresist discontinuities, the dis-continuities generally arranged in a concentric, spiral track.

9. The process as claimed in Claim 7, wherein said forming step includes: providing a silicon rubber compound as the material for making the mold; and applying a uniform pressure over said compound subsequent to said pouring step.

10. The process as claimed in Claim 9, wherein said curing step includes heating said compound until cured while being subjected to said uniform pressure.