Mehod of forming indicia on compact disks and indicia-bearing compact disks

A new compact disk ("CD") is formed providing a bright, metallic presentation of indicia such as trademarks, promotion and advertising copy and other alphanumeric information around the circumference of the disk with recorded digital data in the disk's central portion. Such a CD may be a 120 mm CD including a central portion recorded in the 80 mm format of a single CD, with the desired indicia formed by a bright metal indicia-bearing substrate in the 20 mm, radially-extending, circumferential portion of the CD that surrounds the recorded digital data. Such CD's are manufactured by recording the digital data in the central 80 mm of a 120 mm master, leaving the remaining unrecorded circumferential portion of the master with a smooth surface and applying the desired indicia onto the unrecorded outer peripheral portion of a disk used to form production stampers.

FIELD OF THE INVENTION 
This invention relates to the production of plastic articles and optical 
storage devices such as compact disks and, more particularly, relates to 
the formation of indicia on compact disks and to novel indicia-bearing 
compact disks. 
BACKGROUND OF THE INVENTION 
Compact disks (CDs) are formed by an optically transparent plastic, such as 
a polycarbonate, like General Electric's Lexan, which is an easily molded 
plastic material capable of transmitting a light beam, such as a thin 
laser beam, without scattering, refracting or distorting the light beam. 
CDs are generally manufactured in a 120 mm format, although an 80 mm 
"single" format is available. With such 120 mm CDs, approximately 74 
minutes of a digital signal, which is generally either music or an audio 
presentation, may be stored in the outer circumferential portion of one 
side of the disk having a radial extent of approximately 58.5 mm. In the 
production of such CDs, the trademarks and alphanumeric information 
identifying the disk content are normally silk-screened onto the side of 
the CD opposite the side to be read by the laser of the CD player. 
The manufacture of CDs begins with a glass plate which has one surface 
highly polished to provide a smooth flat surface which is cleaned to be 
free of dirt. A photoresistive material is applied to the polished and 
clean surface of the glass plate to form a uniform thin film with a 
constant thickness which can only vary about .+-.50 angstroms. After the 
photoresistive coating on the surface of the glass plate has been cured 
and inspected, the digital data representing music or visual images is 
formed in the photoresistive coating by modulation of a high energy laser 
beam. The photoresistive material is then developed in the pattern of the 
digital data and the photoresistive material forming the pattern of the 
digital data is removed from the glass plate, leaving a photoresistive 
coating on the surface of the glass including a pattern of "pits" which 
represent the digital data and the music or audio information. A silver 
coating is formed over the photoresistive coating with its pattern of pits 
representing the digital data, preferably by sputtering, to provide a 
"master" for use in the formation of CDs. The master is then electroplated 
with nickel at a variable plating rate to provide a mating form for molds 
to replicate the digital data by injection molding. This mating form is 
referred to as a "stamper", and/or the "master stamper" and/or the "father 
stamper". 
Rather than use this form in production tooling, the father stamper is 
replicated to provide the production molds actually used in the production 
of CDs. In a manner known in the art, the nickel stamper is oxidized using 
an oxidizing agent. After oxidation, the oxidized nickel stamper is washed 
with water and isopropyl alcohol and is placed into a plating bath to be 
plated with nickel to build a negative image in the form of the original 
master, referred to as a "mother" disk. The nickel mother disk is stripped 
from its father stamper and oxidized with an oxidizing agent and washed 
with water and isopropyl alcohol. The resulting mother is used to form 
production stampers for use in injection molding of the CDs by the same 
process described above in the production of the father stamper from the 
master. 
The production stampers provide a mold surface to form the digital signal 
pits in the polycarbonate CDs formed by injection molding. That is, 
polycarbonate plastic material is injection molded against the production 
stampers and, when removed from the injection molding machine, provides a 
CD substrate including on one surface pits in the pattern of the digital 
data representing the recorded music or audio information. The surface of 
the polycarbonate CD with the recorded information is then coated with a 
reflective aluminum coating by sputtering and after inspection, the 
aluminum-coated recorded surface on the recorded side of the CD is 
protected by a coating of lacquer, or other such protective coating. 
After the lacquer coating is cured, desired indicia are silk-screened onto 
the lacquer coating in a manner well known in the art. Such indicia 
frequently include the trademarks of the record company, the name of the 
performer, the names of the recorded songs, the number and running time of 
the various tracks and other such information. 
In reproducing the recorded information on the CD, the CD player directs a 
laser beam through the polycarbonate material forming the uncoated side of 
the disk and senses the variations in reflection of the laser beam from 
the pits and the reflective aluminum coating to reproduce the recorded 
music and audio information and the like. 
SUMMARY OF THE INVENTION 
In the invention, a novel CD is formed providing a bright, metallic 
presentation of indicia such as trademarks, promotion and advertising copy 
and other alphanumeric information around the circumference of the disk 
with recorded digital data in the disk's central portion. It should be 
understood that in the remainder of the description of this invention, we 
will refer to "desired indicia" which will mean any readable indicia, such 
as pictures and other images, trademarks, symbols, words and numbers. 
Preferably, a CD of the invention may be a 120 mm CD including a central 
portion recorded in the 80 mm format of a single CD with the desired 
indicia formed by a bright metal indicia-bearing substrate in the 20 mm, 
radially-extending, circumferential portion of the CD that surrounds the 
recorded digital data. 
In the preferred method of the invention, such CDs are manufactured by 
recording the digital data in the central 80 mm of a 120 mm master, 
leaving the remaining unrecorded circumferential portion of the master 
with a smooth surface. A father stamper is formed as described above 
including an unrecorded peripheral portion. A mother to be used in 
producing production stampers is then produced by electroforming the 
mother on the father stamper, as set forth above, including an unrecorded 
peripheral portion. After stripping the nickel mother from the father 
stamper, desired indicia is silk-screened onto the unrecorded outer 
peripheral portion of the mother with silver ink of high purity. After the 
silver ink has cured on the periphery of the mother disk in the pattern of 
the desired indicia, the nickel on the mother disk is oxidized with an 
oxidizing agent, as set forth above, washed only with water and placed 
while water-wet in the nickel electroforming bath where a nickel 
production stamper is formed, including a central portion with the 
recorded digital data and a 20 mm wide peripheral portion adapted to form 
the desired indicia. 
Such production stampers are used to form, by injection molding, CDs 
including a central portion with pits in the pattern of the recorded 
digital data and an outer peripheral portion with the surface adapted to 
present the desired indicia in a bright reflective metal when the 
injection-molded CD is provided with its reflective aluminum coating 
through sputtering. 
Thus, the invention provides a novel CD particularly adapted for 
promotional use or for a new CD-single with digitally recorded music, 
audio or visual information in the central portion of the disk, and a 
bright, eye-catching presentation of desired indicia in a large area 
surrounding the recorded digital information. Furthermore, the invention 
can supplement information which may be silk-screened onto the lacquer 
side of the disk and, in some cases, may entirely eliminate the 
silk-screening operation.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
FIG. 1 is a process diagram to illustrate the steps taken to produce a CD. 
It should be understood that FIG. 1 is diagrammatic and is not intended to 
depict actual structures or scales. FIG. 1 shows a series of 
cross-sections of elements used in the production of a CD. Element sizes 
and thicknesses and pit size are all substantially enlarged and out of 
scale in order to help indicate the manufacturing process, which is well 
known in the art. 
As indicated at A of FIG. 1, the manufacture of CDs begins with a glass 
plate 10 which has one surface 11 highly polished to provide a smooth flat 
surface which is cleaned to be free of dirt. As indicated at B of FIG. 1, 
a photoresistive material 12 is applied to the polished and clean surface 
11 of the glass plate 10 to form a uniform thin film with a constant 
thickness which can only vary about .+-.50 angstroms. After the 
photoresistive coating on the surface of the glass plate has been cured 
and inspected, the glass plate is rotated and the digital data 
representing music or other digital information is formed in the 
photoresistive coating by modulation of a high energy laser beam 13, as 
indicated at C of FIG. 1. The photoresistive material is then developed in 
the pattern of the digital data, and the photoresistive material forming 
the pattern of the digital data is removed from the glass plate, as 
indicated at D of FIG. 1, leaving a photoresistive coating on the surface 
of the glass including a pattern of "pits" 14 which represent the digital 
data and the music or audio information. As indicated at E of FIG. 1, a 
silver coating 15 is formed over the photoresistive coating 12 with its 
pattern of pits 14 representing the digital data, preferably by sputtering 
to provide a "master" 16 for use in the formation of CDs. 
The master is then electroplated with nickel, as indicated at F of FIG. 1, 
at a variable plating rate to provide a mating form for molds to replicate 
the digital data by injection molding. This mating form 18 is referred to 
as a "stamper" and/or a "master stamper" or "father stamper". 
Rather than use this form in production tooling, the stamper 18 is 
replicated, as indicated at G-K of FIG. 1, to provide the production molds 
actually used in the production of CDs. In a manner known in the art, the 
stamper 18 is oxidized using an oxidizing agent. After oxidization, the 
oxidized stamper 18 is washed with water and isopropyl alcohol. As 
indicated at H of FIG. 11, stamper 18 is placed into a plating bath to be 
plated with nickel to build a negative image in the form of the original 
master, referred to as a "mother" disk 17. The nickel mother disk 17 is 
stripped from its father stamper 18, as indicated at I of FIG. 1, and 
oxidized with an oxidizing agent and washed with water and isopropyl 
alcohol. 
The resulting mother 17 is used to form production stampers for use in 
injection molding of the CDs by the process described above to produce the 
father stamper 18 from the master 16. That is, the mother 17 is 
electroplated with nickel, as indicated at J of FIG. 1, to provide a 
production stamper 19, which is used to mold the CDs. 
The production stampers 19 provide a mold surface to form pits 14 in a 
polycarbonate CD 20 formed by injection molding. As indicated at L of FIG. 
1, polycarbonate plastic material is injection-molded against the 
production stampers 19 and, when removed from the injection molding 
machine, provide a CD substrate 20, including in one surface, pits 14 in 
the pattern of the digital data representing the recorded music or digital 
information. As indicated at M of FIG. 1, the recorded surface 21 of the 
polycarbonate CD substrate 20 is then coated with a reflective aluminum 
coating 22 by sputtering and after inspection, the aluminum-coated 
recorded surface on said one side 21 of the CD is protected by a coating 
of lacquer 23 or other such protective coating. 
After the lacquer coating is cured, desired indicia may be silk-screened 
onto the lacquer coating in a manner well known in the art. Such indicia 
frequently include the trademarks of the record company, the name of the 
performer, the names of the recorded songs, the number and running time of 
the various tracks and other such information. 
In reproducing the recorded information on the CD, the CD player directs a 
laser beam through the polycarbonate forming the uncoated side 25 of the 
disk and senses the variations in reflection of the laser beam from the 
pits 14 and the reflective aluminum coating to reproduce the recorded 
music and audio information and the like. 
In the invention, a novel CD is formed providing a bright, metallic 
presentation of desired indicia, such as trademarks, promotion and 
advertising copy and other alphanumeric information around the 
circumference of the disk with recorded digital data in the disk's central 
portion. It should be understood that in the remainder of the description 
of this invention, we will refer to desired indicia which will mean any 
readable indicia, such as pictures and other images, trademarks, symbols, 
words and numbers. 
Preferably, as shown in FIG. 2, a CD 30 of the invention may be a 120 mm CD 
including a central portion 31 recorded in the 80 mm format of a single CD 
and an unrecorded peripheral portion 32 with the desired indicia 33 formed 
by a bright metal indicia-bearing surface in the 20 mm radially extending 
circumferential portion 32 of the CD surrounding the recorded digital 
data, as more fully described below. 
FIG. 3 is a process diagram to illustrate the steps used in the invention. 
FIG. 3 is a series of cross-sections of one-half of the elements used in 
the invention to produce CDs, such as those shown in FIG. 2. Like FIG. 1, 
the elements shown in FIG. 1 and their sizes and shapes are enlarged and 
out of proportion to help indicate the process steps used in the 
invention. 
In the preferred method of the invention, such CDs are manufactured by 
recording the digital data in the central 80 mm (see portion 31 of FIG. 2) 
of a 120 mm master, leaving the remaining circumferential portion (see 
portion 32 of FIG. 2) of the master with a smooth surface. A 
father-stamper is formed as described above including an unrecorded 
peripheral portion. A mother 40 (FIG. 3), to be used in producing 
production stampers, is then produced by electroforming the mother on the 
father stamper, as set forth above. 
After stripping the nickel mother 40 from the father stamper, as indicated 
at N of FIG. 3, the steps described above result in the mother 40, 
including an unrecorded, generally smooth outer peripheral portion 42, 20 
mm wide that corresponds to portion 32 of the FIG. 2 disk and a recorded 
central portion 41 in the central 80 mm of the disk that corresponds to 
portion 31 of the FIG. 2 disk. Before the preferred indicia is 
silk-screened onto mother, a temporary protective cover, coating or 
laminate 46 is applied to the center 80 mm of digital data. This protects 
the digital data from physical damage while the desired indicia is being 
applied. This protective coating 46 is removed before cure of silver ink, 
as described below. As indicated at O of FIG. 3, a silk-screen 43 is 
provided with openings 44 in the form of the desired indicia, and a silver 
ink 45 of high purity is applied through the openings 44 by silk-screening 
to the unrecorded peripheral portion 42 of the mother 40. A preferred 
silver ink is Flexible Silver Coating No. A-3617 sold by Inglehard Corp., 
Specialty Chemicals Division, Menlo Park, Conn. 28, Edison, N.J. 00818. A 
non-preferred but usable silver ink is Inglehard Corp.'s Flexible Silver 
Coating SC 4004 (No. 16). After the desired indicia, the temporary 
protective coating 46 is removed. 
As indicated at P of FIG. 3, after the silver ink has cured, which with the 
preferred inks is preferably overnight, the mother 40 has been provided 
with a print of the desired indicia 44 in its unrecorded outer peripheral 
portion 42. 
After the silver ink has cured on the periphery of the mother disk in the 
pattern of the desired indicia, the nickel on the mother disk is oxidized 
with an oxidizing agent, indicated at Q of FIG. 3, and then washed only 
with water, as indicated at R of FIG. 3. The washed mother 40 is then 
placed while water-wet in the nickel electroforming bath where a nickel 
production stamper 50 is formed, as indicated at S of FIG. 3, including a 
central portion 51 with the recorded digital data and a 20 mm wide 
peripheral portion 52 adapted to form the desired indicia, as indicated at 
T of FIG. 3. 
Such production stampers 50 are used to provide a mold surface and to form, 
by injection molding, CD substrate 30 of clear polycarbonate material, as 
indicated at U of FIG. 3, including a central portion 31 with pits in the 
pattern of the recorded digital data and an outer peripheral portion 32 
with the surface adapted to present the desired indicia 33 in a bright 
reflective metal when the injection-molded CD is provided with its 
reflective aluminum coating through sputtering. As indicated at W of FIG. 
3, the recorded surface 34 of CD substrate 30 is provided with an aluminum 
coating 35 and then with a protective lacquer coating 36. 
By the process indicated in FIG. 3 and described above, a CD, like that 
shown in FIG. 2, can be made with digitally recorded music, audio or 
digital information in the central portion 31 of the disk, and a bright, 
eye-catching presentation of desired indicia 33 in the large area of the 
peripheral portion 32 surrounding the recorded digital information. The 
desired indicia 33 may supplement the information which may be 
silk-screened onto the lacquer side 34 of the disk and, in some cases, may 
entirely eliminate the silk-screening operation. 
While we have described a preferred embodiment and the best mode currently 
known to us to practice the invention, other embodiments of the invention 
will be apparent to those skilled in the art and the invention is to be 
limited only by the scope of the following claims and the prior art. While 
the invention was described in the manufacture of audio compact disks, 
CD-ROM, CD-I and other optical storage devices may also be manufactured 
with the invention. In addition, although the above description describes 
the application of the desired indicia to a mother disk by silk-screening, 
it will be apparent that the desired indicia may be applied to the master 
or to the father stamper, and, furthermore, that the desired indicia be 
applied to any of the generations of forms used to produce production 
stampers by processes other than silk-screening, such as by etching, 
adhering or otherwise producing the desired indicia on an unrecorded 
surface portion of a disk. It is a feature of the invention that the 
desired indicia is molded into the transparent plastic surface of the 
resulting article.