CA1070261A - Process for producing a stamper for videodisc purposes - Google Patents

Abstract

Abstract of the Disclosure A stamper for producing replicas of a video disc master formed of a glass substrate containing surface irregularities in the form of an information pattern of raised protrusions is formed by applying a strike coating of a conductive metal such as silver and then electroplating copper and nickel to form a self-supporting negative replica member, termed as "mother", which can be stripped from the surface of the master. The interior of the mother is cleaned and passivated preparatory to use as a mandrel in the electroforming of a positive replica submaster. The submaster may function as a stamper or be utilized after passivation as a mandrel in the electroforming of a submother from which a stamper or a plurality of stampers are formed.

Description

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B~ck~roulltl of the tnv~ntlo 1. Field of the Invention The present invention relates generally to the repli-cation of original records and, more particularly, to a method of converting a video disc master which contains information in the form of microscopic "holes" in a metal surface into a master suitable Eor use in producing repllcas.

2. Description of the Prior ~rt Over the years, there has be~n a contlnuin~ attempt to achieve a low-cost, mass-produced disc which contains video information that can be retrieved with an inexpensive home in-strument for playback through a conventional television set.
Early attempts at providing video information ha-~e generally involved the use of video tape recorders of various sorts as well as photographic techniques. Still other approaches have attempted to utilize thermoplastic recording or the surface alteration of a thin metallic film.
In the copending Canadian application of John S. Winslow, Serial No. 188,420, filed December 18, 1973, and assigned to the assignee of the present invention, a method and apparatus was shown for producing a video disc master which utilized a high power laser in conjunction with a glass disc having a thin film of a relatively low melting point material, such as bismuth, coated thereon. The laser beam was intensity modulated with the video information, and at the point of impingement upon the bismuth film surface, the laser beam, at relatively greater intensities, contained sufficient energy to melt the bismuth film.

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The preEerred ~hy~,ical ~operties of a low melting point mat~rial, such as bismuth, are that the surface tension of the melted material should cause the molten material to immediately coalesce into small, submicroscopic nodules, thereby leaving an area substantially free of the opaque metal coating.
According to the Winslow application, typical "holes" repre-senting video information were on t}le order of 1 micron~
The single master thus produced cannot, in and oÇ
i~selE, under prlor art methods and t~chniques, be easlly utilized to procluce hundreds o~ thousands o~ replicas rapidly and at low C05t. Accordingly, it has been deemed desirable to somehow modify the recorded master so that replication can be easily accomplished.
In the prior art, it has been known to create "masks"
with a predetermined pattern which, in turn, could be used in connection with photoetching techniques to create a plurality of duplicate surfaces, each with a similar predetermined pattern in the surface. For example, such a mask could be utilized to selectively expose discs having a very thin metal surface coating to a laser beam, and a plurality of discs having a similar "hole" pattern in the surface could be produced.
Alternatively, a photoengraving process may be employed utilizing a master mask which, through chemical etching techni-ques, can result in a patterned disc.
Such techniques would not be directly applicable to the needs of the video disc system as presently envisaged because of ,he costs involved and the time required to create the duplicates or replicas. Since the pattern dimensions closely ljr:-~

approximate the ~ velength of visible radiation, normal, high-speed photographic duplication techniques would be seriously affected by diffraction effects.
One of the principal advantages in the use of a video disc for recording and reproduction of audio-visual material through a conventional television set over magnetic tape i5 the opportunity for rapid, mass production of cluE)licate cli~cs.
The relative ease o producing duplicate audio di~cs ver~us the methods of ~roducing audio tapes ~luickly illustrat~s tha~
discs can be stamped at relatively high speeds in large numbers of presses while each tape record requires the serial recordation on a length of tape oE the information to be recorded.
Consequently the relative costs that must be considered as between video tape and video disc are the cost of the material itself, the cost of equipment for transferring the information and the time required for the information transfer. In the audio field, the cost factors clearly favor the disc approach and it has been determined that similar consideration would obtain when providing recorded video information.
In Canadian Patent 918,292, issued January 2, 1973 and assigned to the assignee of the present invention, apparatus was disclosed for embossing information on a sheet vinyl disc.
The creation of the stamper was assumed without any detail as to how the stamper might be created. In the video disc system which has been disclosed in the several related patent appli-cations and patents listed, supra, an original master is created through the use of a high-powered laser and a flat disc having a thin film of reasonably low melting point, high surface

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1~70~61 tension, opaque matexial. The resulting master, however, has information representecl as transparent are~s in an opaque surface with the -transparent areas arranged in an interrupted generally circular path which, in a preferred embodiment, is arranged in a concentric spiral.
Since the thickness of the heat sensitive opactue layer may be as littl~ as several hundred Angstrom units, ~he m~ter thus produced cannot be directly used in the stamping, compression moldin~, injection molding or embossin~ of a duplicate or re~lica record. In the above-identiEied patent application~ -to Jarsen, and Avanzado, et al, methods were disclosed which resulted in -the production o~ a substantially three-dimensional matrix, wherein the relatively opaque and clear areas are converted into surface discontinuities or bumps which can be preferably 0.7 micron in height. These bumps are of a photoresist material overlying the original master plate. It would be desirable to utilize this photoresist matrix in the creation of a stamper which can be used to emboss, mold or stamp replica discs at relatively low cost in mass production quantities.

Summary of the Invention According to the present invention, the photoresist matrix is converted into self-supporting, rigid, high resolution, negative and positive replicas capable of mass production of replicas by embossing or stamping thermoplastic discs as described in Canadian Patent 918,292 by rendering the surface of the photoresist matrix conductive, suitably by electroless application of a thin layer of silver and then utilizing the conductive matrix as a mandrel in a process for electroforming

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02~1 a ne~ative replic~ "mother" of substantial thickness ancl stren~th. The bismuth layer on the c31ass disc may be removed before application of the conductive layer.
The mother in turn may be utili~ed to form a series of positive replica submothers by pretrèating the silver surface so as to release an electrodeposited layer ~nd then utilizing the treated surEace as a mandr~l for ~lectro~orming the submothers. The pretreatment is suitably a passlv~tlon treatment such as b~ o~idation or sulfurization to ~o~m a thin surEace silver ~xide or silver sulfide which pY~vents the formation o~ a strongly adheren-t bond with the thick metal deposit.
A plurality of submasters may be electroEormed from the mother and utilized as a stamper or embossing member, or the submasters after passivation may be utilized as mandrels for forming a next generation of submothers which in turn can be utilized to form a series of stampers.
The stamper produces replicas by stamping or embossing a thermoplastic material such as vinyl. The stamper and a sheet of vinyl are supported on platens in a chamber. The chamber is depressurized to remove air from between the sheet and the stamper. The sheet is heated to softening temperature and pressure applied to emboss the protrusion pattern into the surface of the sheet. The assembly is cooled and separated to provide an embossed disc. In a preferred embodiment, the embossed disc is "read" through the plastic, so that the depres-sions produced by the positive stamper appear to the playback ; equipment as bumps. The replica can then be provided with a

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reflective metal l~y~r such as by a vapor depo~ition pr~cess.
If desired, an outer ~ear layer of clear plastic can be applièd to the reflective layer.
The same stamper is also used for compressio~ and injection molding or replicas, In this process the stamper (2 stampers if replication is done on ~oth sides of the record) are attached to a suitable moldinc3 di~ which has internal heatin~ and cooling channels, In the compression molding process these chanllQls are heated and cooled alternately b~ the application oE s-team and cooling water. The pre-heated and pre~softened plastic material, like vinyl, PVC or the like is then placed within the pressing die equipped with a stamper or 2 stampers and the die is sub-jected to a high pressing force, for instance in a hydraulic press. The squeezed and formed video disc is then cooled by the application of cooling water in the die channels while under pressure. The press is opened and the finished product is removed. The excess material is then trimmed from the video record.
Injection molding uses a similar process, except the channels in the die are kept at a constant temperature with a circulating luke warm cooling media like water. After the closure of the die, the pre-melted, plastic-like vinyl, poly-styrene, acetal resins, or the like are injected in a fluid stage into the mold cavity. The plastic hardens i~mediately, and after a few seconds curing time, the mold is opened and the finished video disc is removed. In the injection molding ljr: S~

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prQcess none or velAy Little excess El~sh is produced, so trimming is usually unnec~ssaxy.
In an alternate replicati~n pr~cess, the photoresist matrix is first replicated by casting or molding a negative replica of the matrix surface by means of a releasable, curable resin. The negative replicated mother surface of the mold so produced is then rendered conductive and utilized as a ~andrel in the electroforming process for proctucincl a ~,ubmaster ~Iccordin~
to the invention. A suitable castincl process is disclosed in copendin~ Canadian application Serial N~. 210,3S6, f:i1ecl September 30, 197'1.
In the video disc syste~ described in the rela-ted patents and applications, one systems approach permits the use of either a thin, flexible disc, or a heavier, rigid disc, both of which can be produced from stampers made by the present method.
Such discs can be read on appropriate playback equipment as has been heretofore disclosed.
It is obvious that the present method could be modified to produce replicas in which the surface deformations ~0 are depressions rather than elevated portions, should that type of replica better lend itself to the playback equipment. Further, the requirements of the playback equipment would also determine the size and shape of the surface deformations which represent the video information.
For example, in one system heing developed by the assignee, a reading technique is employed which utilizes light scattering and light reflection to generate electrical signals of different significance. In such a system, the "bumps" or - ljr:S~
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i~;)'7V2~1 "depressions~ serve to scat-ter rather than reflect light applied from the player device. The surface bekween adjacent bumps Ol depressions, however, serves as a plane reflector, and returns substantially all o the light to the player optical system.
In alternative schemes, phase constrast optics are employed in which case it is desirable that roflectin~ planes spaced apart by ~ twllere ~ is the wav~leng~h oE th~ pl~yback radiation and "n" is an odd integer) are employed so that light is reflected from the plane sur~ac~s buk light ~rom the sur~ace discontinuity destructively inte~Eeres with the liyht from ~he plane surface and therefore provides a distinctive signal to the reading optics.
Given an original matrix having such characteristics, the present process is admirably suited to produce replicas utilizing the stamper of the present invention that is created from the matrix.
The novel features which are believed to be character-istic o the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description con-sidered in connection with the accompanying drawings in which -~
several of the preferred embodiments o the invention are illustrated by way o example. It is to be expressly understood, however, that the drawings are for the purpose of i:llustration and description only and are not intended as a deinition o~
the limits of the invention.
Speciically, the invention relates to a process for producing a video disc member from which a plurality of replica 29 video liscs can be formed, and for producing a video disc member -4~ , ' .
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or us~ ~5 ~n int~xmedla~ product ~rom which additional stamper and dia memb~rs can be formed. The process comprises the steps of:
providing a body having an upper surface carrying indicia of the video information to be reproduced, the upper surface being sub-stantially flat for establishing a substantially planar surface in the resulting replica member suitable for reflectiny li~Jh-~ incident thereupon, each of the discontinuiti~s being s~parat~d by a Elat portion of the upper surface, the discontinuities and flat surface portions being arranged in a video information track, each discon-tinuity havin~ a constant dimension in the radial direction and aconstant maximum dimension in the direction perpendicular to the surface, the length of each discontinuity in the direction of the track and the distance between adjacent discontinuities in the direction of the track representing the video information to be - reproduced; forming a first conductive layer upon the upper surface and the discontinuities to a thickness sufficient to support elec-troconductivity in an electroplating bath; electroplating a second layer upon the exposed surface of the first conductive layer to a thickness sufficient to support the first and second layers when -separated from the body; and separating the combined first andsecond layers from the body for providing a first yideo disc mother member having an interface surface carrying the video information in a form complementary to the form of the yideo in- ~
formation carried by the upper surface of the body and suitable ~ .:
for use in reproducing replica video discs having video infor-maticn in a form identical to the form carried by the body.
In another aspect, the inven~ion relates to a stamper and die member for forming video replica discs comprising: a 8a : -, . - . - :
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:10702~ii pod~ having an upper surface ca~ying indicia o~ the video infor-mation to be r~produc~d, tha upper ~urEac~ be.incJ substantiall~
flat for establishing a substantially planar surface in the ~esult-ing replica membex suitable for reflecting light incident thereupon, the upper surface having discontinuities out of the plane of the surface for scattering light incident thereupon, each of the dis-continuities being separated by a flat protion of the upper surface.
the discontinuities and flat surEace portlons being arranycd in a video information track, each discontinuity having a constant di-mension in the radial direction and a con~tant m~ximum dimen~i~nin the direction perpendicular to the surface, the length o~ each di~continuit~ in the circumferential direction and the distance between adjacent discontinuities in the circum~erential direction representing the video in~ormation to be reproduced; and the boay comprising a plurality of metal layers.

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nri~~ ;cription o~ ~h~ l)ra~/incJ~.
Figure l is a p~rspectiv~ view of ~ portion oE a matrix member for replication in accordance with th~ invention;
Fiyure 2 is a cross-sectional view of an assembly for forming a first negative elastomeric mold replication of the matrix of Figure l;
Figure 3 is a side sect.ionc~l vi~w of the elclsl:ome~ic mold;
Figure ~ is a side sectional v.iew o:E a cas~ replicat.ion of the mold oE FicJure 3;
Fi~ure 5 is a side sectional view of a metal replication of the cast replication of Fi~ure 4;
Figure 6 is a sectional view of the completed mother member;
Figure 7 is a sectional view of a metal replication submaster of the mother member;
Figure 8 is a sectional view of the separated submaster;
Figure 9 is a sectional view of a portion of a stamper member;
Figure lO is a schematic view of a stamping apparatus;
and, Figure 11 is a perspective view partly in section of a finished replica disc.
Description of the Preferred Emhodiments Referring now to Figure l, the matrix member 10 to be replicated according to the present invention is shown. The matrix member 10 has an upp~r, smooth planar surface 12 on which are mounted a plurality of rounded protuberances 14 generally ' _ g _ ljr:$~

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arran~d in ~ concen~ri~ ~pir~l txack 16. Although the indiv.idual prot~berallc~ are arran~ed in a ~enerally circular pattern, the track 16 is a discontinuous one and includes a flat surface area 18 between adjacent protuberances 14. The preferred embodiment o~ -the present invention contemplates an information track 16 arranged in a spiral, but alternative embodiments contemplating information arranged in circular tracks (not shown) as well.
It is to be further noted that while the pre~erred embodiment illustrated in Figure 1 shows each tr~ck 16 to include protuber-ances 14, it is equally fea~ibl~ to supply d~px~ions in place of the protub~rances 14. The surEace fea~ures provided in the playback replica are intended to scatter radiation rather than reflect it; the choice of one or the other is dictated primarily by the considerations of producing the final stamper or embosser or a casting or molding replica in negative or positive form with respect to the original matrix member 10.
Referring now to Figure 2, in the preferred embodiment of the replication process, the matrix to be replicated is pre-pared as disclosed in copending Canadian application Serial No.
210,354, filed September 30, 1974. As taught in that application, the matrix 10 includes a polished, glass disc on which the video information is arranged as a series of non-conductive photoresist protuberances 14 approximately 0.7 microns high and generally 1 micron in the radial direction. The bumps are generally arranged in a concentric spiral track with a spacing of approximately 2 microns between the centers of adjacent tracks.

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~, -The matr:ix 10 may or m~y not have remaining on the surface a very tllin layer of low melting point, op~que material such as a thin film of bismuth. The bismuth film has perforations below each protuberance 14. If desirable, the bismuth may be removed utilizing a suitable chemical solvent or etchant before metalizing the matrix.
The matl^ix 10 may be ut;.li~ecl as the form.i.ng me~ber or the first .replication by metal platillcJ. ~he m~trix 10 may alternatively be first repl.icated ut;il.ixing curable res.ins ~o Eorm a two-step positive replica thereo:E having the protuberances of an insulative material provided on a planar substrate. Refer-ring now to Flgures 2 and 3, an elastome.ric mold negative replica of the matrix member 10 is produced by coating the surface of the matrix with a mold release agent such as polyvinyl alcohol and coating the opposing surface of a flat, rigid suhstrate 32 such as glass with a primer and then forming a laminate assembly with the surfaces separated by end spacers 34 and central spacer 36. A curable liquid elastomer material such as a silicone rubber elastomer is mixed with catalyst, filtered and degassed and then poured over the surface of the matrix 10. The glass plate 32 with the primed surface down is placed on the spacers 34 and 36. Pressure and heat are applied to effect cure to form a molding member 38 typically 14 mils thick having elastomeric negative replica mold surface 39 which readily separates from ~.
the matrix 10 after cure.
In the next stage of the process for forming an alter- ~
native matrix in accordance with the invention, a cast positive - -replica of the mold surface 39 is formed by casting a curable ljr:S~
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orcJ~nic liquid re~`in such as a polyurethane, acrylic ~r an epoxy into the mold and polymerlæin~ the resin by heat, radiation or catalyst. The layer of resin 40 is suitably supported on a substrate such as a sheet 42 of Mylar polyester filmr The cast layer is generally 3-7 microns thick, suitably about 5 microns.
After the liquid resin is poured into the mold, pressure is applied to the substrate sheet 42 suitably from a roller member to minimize occurrence of trapped bubbles and to assure that the resin fills the depressions 44 completely. The cast positive replica 46 as shown ln Figure 4 includes a ~lat substrate 42 on which is supported a pattern o~ a multiplicity of raised insulator protuberances 47. This replica 46 can also function as the matrix 10 in the plating replication process of the invention to be now further described. Further details of the molding/casting replication steps are disclosed in copending Canadian application Serial No. 210,356.
Referring now to Figure 5, the first step in the metal plating replication process of the invention is the metali~ing of the surface of the matrix member to render it conductive.
The term "matrix" will be understood to include either the master with the developed photoresist pattern or a replica which may have been made from such a master. The metal layer is suitably applied by vapor bombardment, vapor deposition or deposition from electroless plating solution. Suitably the surface is silverplated with an electroless process similar to that used for producing mirror surfaces. The initial sllver film 48 is deposited only to a thickness sufficient to support electroconductivity, suitably from about 0.01 to about 2 mils, .

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- iL0'70261 SQ that the next electroplating step c~n ~e undertakqn.
The silv~rplated matrix member is now in conclition to act as a mandrel for the electroforming of the first negative replica mother member 52 of Figure 6. The mother 52 is formed by connecting the silver layer 48 as the cathode in an electro-plating bath in which is dissolved a salt of the metal to be plated, suitably copper or nickel so that a sufEicit?~tly thick and hard, self-supporting structural member is formecl. In a particular embodiment of the invention the s~lver layer ~ i8 first connected ~s the c~thode in a copper electroplating bath and copper 4~ to a thickness of ~-10 mils, suitably about 6 mils, is plated onto the silver layer -to provide a copper layer ~9 having substantial mass which provides support for the silver surface. The copper plated member is then immersed in a nickel-plating bath and a layer of nickel 50 having a thickness from 1-10 mils, suitably about 5 mils, is electroplated over the copper layer 49 for even greater strength and support.
The nickel/copper/silver composite member is then stripped from the master matrix to form the mother disc 52 shown in Figure 6. Any of the cured photoresist resin or casting ~ resin which may have adhered to the silver surface 48 is cleaned - away. The glass polished surface of the master disc 10 (if a master 10 is the matrix) can then be cleaned, polished and then ~-recoated with bismuth for use as a new master according to the process disclosed and claimed in previous applications. The mother member 52 may also serve as the mold member 30 as des-cribed above for forming cast replicas suitable for use in the process disclosed in previous Canadian application Serial No.

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210,3S6 or for Çorming a cast repl.i.~a s~lita~le ~ox actin~ as amatrix in the process of the invention, The negative replica mo-ther 52 may be further replicated utilizing it as a mandrel in a further electroforming process to create a submaster, Generally the silver surface 48 is pretreated to render it more readily separable from the following replication. The surEace is suitably pass:i.vatecl by oxidation such as by oxygen gas, ozonc or a weak llquid ox.i.cl.i7,ing agent such as nitric ~cid or potas9ium p~xm~ncJanclte, I~e~rring now to Figure 7, the mother member 52 .is connec-ted a~ a ca~hode in a nickel-plating bath and a layer 54 of nickel is electro-plated onto the passivated silver surface 48. The nickel layer 54 is suitably 2-10 mils thick, generally about 5 mils, and a further layer of copper 56 and an additional layer of nickel 58 may be similarly electroplated onto the previous layers to provide a self-supporting positive replica submaster member 60 as shown in Figure 8, The process may be repeated using the submaster 60 as a mandrel to produce a submother.
A plurality of stamper members 70 as shown in Figure 9 are similarly produced by utilizing either the submaster 60 or the submother member as a mandrel in the electroforming process to form a composite member having a plurality of layers 64, 66, 68 suitably formed respectively of nickel, copper, and nickel on either a "positive" or "negative" of the original matrix. The stamper member 70 is stripped from the passivated surface of the submother mother member.
The finished stamper includes a positive replica 72 of the protrusions 14 of the matrix member 10. This positive i ljr: sf . . : - - - ~ .:

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r~plica i5 a h~ clelled 3urEace suit~bly for actinc~ ~s a f~rming member for replicatlon oE numerous copies from thermopl~stic members such as vin~l resins, for example, polyvinylchloride through molding, stamping or embossing processes.
Referring now to Figure 10, a shee-t or disc 80 of vinyl is placed between a metal diaphragm 82 which is backed by a first platen member 83 and the Eorming surEacc oE ~hc stamper 70 supported on ~ second platen memb~r 84. rl~he assembly is placed within an enclosure 86 which is depressuri%ed through vent 88 to remove air ~rom between the di~c oE therm~plastic 80 and the stamper 70. The assembly '30 is heated to the softening temperature of the thermoplastic disc 80 while pressure is applied to the diaphragm 82 and the platens 83, 84. The softened thermoplastic resin is embossed by the protrusion of the positive replica to form depressions.
The preferred replica disc 96 produced is shown in Figure 11. This disc is read through the plastic, so that the depressions produced by the positive stamper 70 appear to the reading apparatus as bumps. The preferred replica disc 96 could alternatively be produced by use of a sub-mother as the stamper. The sub-mother, having indentations, would produce a pattern of protruding bumps on the replica disc produced, which disc would be read from the convex side of the bumps.
~ The final replica disc 96 includes, in a preferred embodiment, a surface pattern of discontinuous bumps 94 separated by planar surface areas 98. A reflective metal coating 100, such as aluminum, is applied by a process such as vapor deposition to enhance the reflectivity of the planar ljr:SI

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If desired, an additional clear plastic coating 102 can be applied to the disc 96 to protect the metalllc surface 100 from scratches, abrasion and wear. Further, such a layer would keep scratches, fingerprints and the like out oE the plane of focus of the reading beam which acquires the information r~presented by th~ bumps ~.
Thus, there has been disclosed a complete process for converting the information pattern of a matrix containiny an information pattern in the form of relatively fragile pro-tuberances from a planar surface relatively fragile into a strong, self-supporting stamper for forming replica discs by a stamping embossing process. The invention also includes a process for forming mold or casting members also suitable for use in mass production of plastic replicas of the matrix member utilizing molding or casting processes.
It is to be understood that only preferred embodiments of the invention have been described and that numerous sub-stitutions, alterations and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

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Claims (15)

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

1. A process for producing a video disc member from which a plurality of replica video discs can be formed, and for pro-ducing a video disc member for use as an intermediate product from which additional stamper and die members can be formed, said process comprising the steps of:
providing a body having an upper surface carrying indicia of the video information to be reproduced, the upper surface being substantially flat for establishing a substantially planar surface in the resulting replica member suitable for reflecting light incident thereupon, this body having discontin-uities separated by a flat portion of said upper surface, the discontinuities and flat surface portions being arranged in a video information track, each discontinuity having a constant dimension in the radial direction and a constant maximum dimen-sion in the direction perpendicular to said surface, the length of each discontinuity in the direction of the track and the distance between adjacent discontinuities in the direction of the track representing the video information to be reproduced;
forming a first conductive layer upon said upper sur-face and said discontinuities to a thickness sufficient to support electroconductivity in an electroplating bath;
electroplating a second layer upon said exposed surface of said first conductive layer to a thickness sufficient to sup-port said first and second layers when separated from said body;
and separating said combined first and second layers from said body for providing a first video disc mother member having an interface surface carrying said video information in a form complementary to the form of said video information carried by said upper surface of said body and suitable for use in reproduc-ing replica video discs having video information in a form identical to the form carried by said body.

2. A process according to Claim 1 further including the steps of electroforming metal onto the surface of the mother member in sufficient thickness to form a self-supporting positive replica submaster and separating the submaster from the mother.

3. A process according to Claim 2 further comprising the step of pretreating the surface of the mother member to render said submaster readily separable from the mother member.

4. A process according to Claim 3 in which the pretreatment is effected by passivating said surface.

5. A process according to Claim 3 further including the subsequent step of forming a negative replica of said body by electroforming a separable submother utilizing said submaster as an electroforming mandrel.

6. A process according to Claim 5 further including the subsequent step of forming a stamper which is a positive replica of the body by electroforming a separable stamper utilizing said submother as an electroforming mandrel.

7. A process according to Claim 1 in which the thin conductive layer is applied to the surface of the matrix member by means of an electroless silverplating process.

8. A process according to Claim 1 in which the strong, self-supporting layer is formed by electroplating, at least one member selected from the group consisting of copper and nickel onto said thin conductive surface to a thickness of from 2 to 20 mils.

9. A process according to Claim 1 in which said discon-tinuities are arranged in a spiral path, each discontinuity having a predetermined width in the radial direction and having a height of the same order of magnitude as said pre-determined width.

10. A process according to Claim 1 in which the discontinu-ities and protuberances have an arcuate, rounded exterior shape.

11. A process according to Claim 12, in which the height and width of the protuberances is approximately 1 micron.

12. A process according to Claim 11 in which the height of the protuberances above the surface is equal to approximately an odd multiple of 1/4 the wavelength of the radiation to be used in reading the information represented by the multiplicity of protuberances.

13. A stamper and die member for forming video replica discs comprising:
a body having an upper surface carrying indicia of the video information to be reproduced, said upper surface being sub-stantially flat for establishing a substantially planar surface in the resulting replica member suitable for reflecting light incident thereupon, said upper surface having discontinuities out of the plane of the surface for scattering light incident thereupon, each of said discontinuities being separated by a flat portion of said upper surface, and said discontinuities and flat surface portions being arranged in a video information track, each discontinuity having a constant dimension in the radial direction and a constant maximum dimension in the direct-ion perpendicular to said surface, the length of each discontin-uity in the circumferential direction and the distance between adjacent discontinuities in the circumferential direction repres-enting the video information to be reproduced; and said body comprising a plurality of metal layers.

14. A stamper according to Claim 13 in which the discontin-uities project outwardly from said planar surface and are rounded bumps approximately 1 micron in width in a radial direction.

15. A stamper according to Claim 13 in which the length of the discontinuities in a circumferential direction is of the order of magnitude of 1 micron.