Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-05-09
2004-05-11
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C264S219000, C264S330000, C264S340000, C359S107000, C369S047360, C369S059110, C369S059240, C428S064200, C528S198000
Reexamination Certificate
active
06734277
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of enhancing pit replication in the molding of optical disks. More particularly the method relates to chemical modification of polycarbonate endgroups which results in improved molding properties and in particular improved pit replication.
Polycarbonates, especially aromatic polycarbonates, are routinely used in the manufacture of optical disks and are prized for their transparency, toughness, and processability. Bisphenol A polycarbonate is widely used in the fabrication of optical data recording media, including optical disks as exemplified by compact audio disks, CD-ROM disks, and digital versatile disks (DVD).
As data storage densities are increased, physical features of the optical disks are compressed. Thus, as data storage density is increased, features of the disk such as tracks or grooves must be decreased in size in order to accommodate an increased number of these features per unit area of the disk. As the size a physical feature of the disk, for example the tracks, is decreased, the controlled reproduction of this physical feature, referred to generally as pit replication, becomes increasingly difficult. In DVD-R disks, for example, information is encoded in a recordable dye at the bottom of a track which has been molded into a polycarbonate substrate. A laser reading or writing to a DVD-R disk which encounters a defective portion of the track (a portion of the track which does not conform specified track dimensions) will skip to a properly dimensioned portion of the track thereby decreasing the data storage capacity of the disk. This “laser skipping” results in “block error” and a corresponding “block error rate”. There is a direct relationship between “percent replication” of a molded-in physical feature such as the disk track and the block error rate. The higher the percent replication value (the closer the pit replication value is to 100 percent) the lower will be the block error rate. Thus, the ability to reproducibly mold a feature such as a disk track of specified dimensions into an optical data storage device such as a DVD-R disk is keenly sought after by commercial manufacturers of optical data storage devices.
Although polycarbonate is widely employed in the manufacture of optical devices such as optical disks, discovery of methods for further improving the utility of polycarbonates by enhancing pit replication in optical disks molded from polycarbonates represents an attractive goal from both technical and commercial perspectives. It is of interest, therefore, to develop methods for enhancing pit replication in the molding of optical disks comprising polycarbonate.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a method for enhancing pit replication in the molding of optical data storage devices comprising polycarbonate. This and further objects of the invention will be more readily appreciated when considering the following disclosure and appended claims.
In one aspect the present invention relates to a method of enhancing pit replication in the molding of optical data storage devices comprising one or more polycarbonates, said method comprising capping at least one of said polycarbonates with end groups having structure I
wherein R
1
is a C
14
-C
30
alkyl group, R
2
is a C
1
-C
30
alkyl group, n is an integer from 1 to 5 and m is an integer from 0 to 4.
In another aspect the present invention provides a method for the enhancement of pit replication in the molding of optical data storage devices comprising two or more constituent polycarbonates by capping at least one of the constituent polycarbonates with endgroups having structure I in a polymerization step or in a post polymerization step.
DETAILED DESCRIPTION OF THE INVENTION
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included herein. In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.
The term “polycarbonate” as used herein includes copolycarbonates, homopolycarbonates and (co)polyestercarbonates.
The terms “endcapping agent” and “chainstopping agent” are used interchangeably.
The term “short chain alkylphenol” as used herein refers to an alkylphenol in which the total number of alkyl group carbon atoms attached to the phenolic ring is less than 14. The total number of alkyl group carbon atoms attached to the phenolic ring is referred to as the “carbon count”. Short chain alkylphenols are exemplified by p-cresol and o-cresol (carbon count=1); 2,6-dimethylphenol (carbon count=2); 4-octylphenol (carbon count=8); 4-nonylphenol (carbon count=9), 4-dodecylphenol (carbon count=12); 2-methyl-4-decylphenol (carbon count=11); 2,6-dimthehyl-3-undecylphenol (carbon count=13).
The term “long chain alkylphenol” as used herein refers to an alkylphenol in which the total number of alkyl group carbon atoms attached to the phenolic ring is greater than 14. The total number of alkyl group carbon atoms attached to the phenolic ring is referred to as the “carbon count”. Long chain alkyl phenols are exemplified by 4-pentdecylphenol and 3-pentadecylphenol (carbon count=15); 2,6-dimethyl-4-tetradecylphenol (carbon count=16); 2,4-dioctylphenol (carbon count=16); and 2,4-dinonylphenol (carbon count=18).
As used herein the terms 3-pentadecylphenol, meta-pentadecylphenol, and cardanol are used interchangeably.
As used herein the term “pit replication” refers to the process wherein the features of a mold stamper are transferred to a thermoplastic material comprising at least one polycarbonate during the molding of an optical data storage device, such as an optical disk. Thus, the term refers to the replication of molded in features such as grooves or tracks as well as pits, and includes instances in which the feature being molded into the thermoplastic does not include pits. With reference to optical disks, the term pit replication as defined herein encompasses the replication of disk features generally.
As used herein the term “pit replication” encompasses the terms “groove replication” and “track replication” when used in reference to the molding of an optical disk.
As used herein the term “percent replication” is a comparison of the difference in dimensions between the features replicated in a thermoplastic by a stamper during molding, and the physical features of the stamper itself, wherein both the dimensions of the replicated features in the thermoplastic and those of the stamper are determined by Atomic Force Microscopy (AFM). For example, in a molded optical disk comprising polycarbonate one may measure the dimensions of a disk track located 55 mm from the disk center using AFM and compare said dimensions with the corresponding physical feature on the stamper. The measured depth of the molded track is divided by the value of the analogous physical feature on the stamper and is multiplied by 100 to give the percent replication value.
As used herein the terms “percent pit replication” and “percent replication” are used interchangeably.
As used herein the terms “capping” and “endcapping” are used interchangeably.
The present invention provides a method for enhancing pit replication in the molding of optical data storage devices, such as optical disks, comprising one or more polycarbonates, said method comprising a step of capping at least one of the constituent polycarbonates with end groups having structure I. The one or more polycarbonates used in the molding of the optical disks comprise at least one repeat unit corresponding to structure II
wherein R
3
-R
10
are independently a hydrogen atom, halogen atom, nitro group, cyano group, C
1
-C
20
alkyl radical C
4
-C
20
cycloalkyl radical, or C
6
-C
20
aryl radical; W is a bond, an oxygen atom, a sulfur atom, a SO
2
group, a C
1
-C
20
aliphatic radical, a C
6
-C
20
aromatic radical, a C
6
Brack Hans-Peter
Dris Irene
Goewey Christopher David
Lens Jan-Pleun
Whitney John Morgan
Boykin Terressa
Caruso Andrew J.
General Electric Company
Patnode Patrick K.
LandOfFree
Method of enhancing pit replication in optical disks does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of enhancing pit replication in optical disks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of enhancing pit replication in optical disks will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3208243