Optical disk assembly retaining rings

An optical disk assembly includes a web assembly having a flexible disk-shaped support web carrying a record layer. The support web has an information storage region. A pair of annular retaining ring members engage opposite sides of an annular peripheral region of the web assembly to clamp the support therebetween. The peripheral region of the support is wrapped about an annular reference surface of one ring member and is pushed into an annular recess with undercut area in that ring member. The other ring member is formed from a malleable ring, such as an annular tube, which is deformed into the recess undercut to provide a locking interfit therebetween. The peripheral region of the web assembly is interleaved between the ring members.

CROSS-REFERENCE TO RELATED APPLICATION 
Reference is made herein to commonly-assigned, copending U.S. Pat. 
application Ser. No. 438,565, filed Nov. 3, 1982 in the names of K. G. 
Budinski and K. F. Brandon entitled OPTICAL DISK ASSEMBLY RETAINING RINGS. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to record medium assemblies useful in high 
density storage of information by optical writing and/or reading, and more 
particularly to improved configurations for optical disk assembly 
retaining rings. 
2. Description of the Prior Art 
The currently preferred optical disk technology employs disk elements with 
spiral or concentric tracks of minute (e.g., on the order of a micron or 
less in size), optically-detectable marks. One real-time mode of recording 
(writing) such marks is by scanning tracks on the disk with an 
equivalently small beam of radiation (e.g., from a laser) which is 
modulated "off or on" according to an electrical signal representative of 
the information to be written. Information is recovered (read) by scanning 
the tracks with the same size or only slightly larger, but still very 
tightly focused, radiation (e.g. light) spot. The recovered information is 
in the form of a fluctuating electrical signal obtained from a 
photodetector that senses the read-out light reflected from the recorded 
disk. 
In order to write and read information in the form of such minute markings, 
optical systems of high numerical aperture are used to focus light to 
equivalently minute spots. Such optical systems have extremely small 
depths of focus and the proper positional relation between the writing or 
reading optical system, and the optical disk record surface must be 
stringently maintained both smooth and flat. 
One approach to achieve requisite smoothness, flatness and protective 
requirements for high density storage of information is disclosed in 
commonly-assigned U.S. Pat. No. 4,365,258, issued Dec. 21, 1982 to F. F. 
Geyer and E. M. Leonard. In that approach an improved optical disk 
assembly adapted for high density storage of information comprises (i) a 
flexible, disk-shaped support carrying a record layer; (ii) a transparent 
disk-shaped cover sheet opposing the record layer, and (iii) an annular 
retaining ring for holding the support and cover sheet in 
circumferentially-symmetric tension. 
Commonly-assigned, copending U.S. patent application Ser. No, 438,565, 
filed Nov. 3 1982 in the names of K. G. Budinski and K. F. Brandon 
discloses an optical disk assembly having a pair of formed metal ring 
members which close together upon opposite sides of the support web. 
Cooperative surfaces on the ring members provide a locking interfit to 
inhibit separation of the ring members. Although the formed metal ring 
members have proven to be highly successful, they do require close 
manufacturing tolerances to ensure a proper locking interfit. By the 
present invention, these tolerances can be relaxed somewhat to enhance 
manufacturability. 
SUMMARY OF THE INVENTION 
An optical disk assembly in accordance with the invention includes a web 
assembly including a flexible disk-shaped support web and preferably an 
opposed cover sheet. The support carries a record layer with an 
information storage region. 
A pair of annular retaining ring members engage opposite sides of an 
annular peripheral region of the support to clamp the support 
therebetween. One of the ring members has a recess with an undercut area. 
The peripheral region of the web assembly is wrapped about an annular 
reference surface on that ring member and is pushed into the recess. The 
other ring member is formed from a malleable ring, such as an annular 
tube, which is deformed into the recess undercut area to provide a locking 
interfit therebetween. The peripheral region of the web assembly is 
interleaved between the ring members. 
The invention and its objects and advantages, will become more apparent in 
the detailed description of the preferred embodiments presented below.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2, an optical disk assembly 10 includes a web 
assembly having a flexible, disk-shaped support web 12 carrying a record 
layer (and other appropriate layers) on one major surface of the support 
web. The web assembly also includes a continuous, flexible, disk-shaped 
cover sheet 14 which is substantially transparent with respect to the 
write and/or read wavelength suitable for use with the record layer. The 
diameter of cover sheet 14 corresponds generally to the diameter of 
support web 12. 
The support web and cover sheet are held in spaced relation by an annular 
composite retaining ring 16 and spacer 18. The retaining ring engages 
support web 12 and cover sheet 14 substantially continuously at respective 
annular peripheral portions thereof. The web assembly has a predetermined 
information storage region radially inwardly of retaining ring 16 and 
spacer 18. Reference is made to aforementioned U.S. Pat. No. 4,365,258 for 
a description of useful and preferred materials and characteristics for 
the disk-shaped support web and the cover sheet. 
The web assembly is retained in circumferentially-symmetric tension by 
cooperating first and second annular ring members 20 and 22, respectively, 
of composite retaining ring 16 engaging opposed sides of the peripheral 
region of the web assembly. Retaining ring member 20 has an annular 
reference surface 24 against which support web 12 is positioned to locate 
the recording layer in a predetermined plane. Ring member 20 also has an 
annular recess with a generally U-shaped cross-sectional shape open at the 
side facing support 12. Each radial end of the recess has a profile 
sloping inwardly towards the open side of the recess to form undercut 
areas. Second ring member 22 extends into the undercut regions to clamp 
the web assembly and to provide a locking interfit. 
It is preferred that the cooperative engagement between disk-shaped support 
web 12, cover sheet 14, and spacer 18 significantly seal the space between 
the record layer on support web 12 and the opposed surface of cover sheet 
14. Although not included in the illustrated embodiments, the optical disk 
assembly may have a central rigid hub including spacing means for 
maintaining proper spacing between the record layer and the cover sheet. 
Preferred tensions for the disk-shaped support and cover sheet materials 
are from substantially zero to just below the elastic limit, or yield 
point, of those materials. More specifically, the preferred tensions 
depend upon the desired degree of planarity for the particular member 
(i.e. size, composition, etc.). It is preferred that support web material 
tension be below the elastic limit of the particular material; however, in 
certain applications some yield can be acceptable as long as surface 
planarity remains in the desired tolerance. In general, the tension should 
be selected with respect to the support web material so that the stressed 
material's continuous relaxation over time (i.e. material creep) is slow 
enough to insure adequate spacing and planarizing tension throughout the 
expected product life period. 
During the assembly operation, support web 12 and cover sheet 14 are placed 
under circumferentially-symmetric radial tension with ring members 20 and 
22 on opposed sides thereof (Fig. 3). The ring parts are aligned with 
annular spacer 18, and brought together (FIG. 4) by an anvil and press 26 
and 28, respectively to begin pressing the web assembly around reference 
surface 24. As ring member 22 moves into the recess in ring member 20, it 
begins to deform and fill the recess (FIG. 4). When ring member 22 extends 
into the undercut areas of the recess (FIG. 5), the assembly is locked 
together. Now the web can be cut free of the tensioning mechanism, not 
shown. 
In the illustrated embodiment, ring member 22 is preferably made of metal 
such as by spin forming, roll forming, stamping or other suitable 
technique, although molded plastic may be used. Ring member 22 is 
preferably formed from an annular tube of malleable material, although a 
solid ring could indeed be used. 
The invention has been described in detail with particular reference to 
certain preferred embodiments thereof, but it will be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention.