Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-04-05
2004-09-14
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C264S176100, C264S219000, C359S107000, C359S642000, C369S275200, C369S275100, C428S064200, C528S198000
Reexamination Certificate
active
06790927
ABSTRACT:
The present application is a U.S. non-provisional application based upon and claiming priority from Japanese Application No. 2001-159441, with a filing date of May 28, 2001, which is hereby incorporated by reference.
DETAILED DESCRIPTION OF THE INVENTION
TECHNOLOGICAL FIELD OF THE INVENTION
The present invention relates to an optical polycarbonate, and more specifically relates to an optical polycarbonate that has excellent color stability and moldability, and is particularly well suited to use in optical disk substrates.
TECHNOLOGICAL BACKGROUND TO THE INVENTION
Polycarbonates have excellent impact resistance and other mechanical properties, and furthermore have excellent heat resistance, transparency, and so on, and are therefore widely used in various applications such as mechanical parts, optical disks, and automobile parts. They hold particularly great promise in optical applications such as optical memory disks, optical fibers, and lenses, and considerable research has been conducted in this area.
Known methods for manufacturing a polycarbonate include a method in which a bisphenol such as bisphenol A is directly reacted with phosgene (interfacial method), and a method in which a bisphenol such as bisphenol A is subjected to a melt polycondensation reaction (ester interchange reaction) with a carbonic diester such as diphenyl carbonate.
Of these, the interfacial method using phosgene entails the use of a large quantity of a solvent such as methylene chloride, and the removal of the chlorine is extremely difficult, so the product is not necessarily favorable for use as an optical polycarbonate.
Meanwhile, a melt polycondensation reaction method has the advantage of allowing a polycarbonate to be manufactured at a lower cost than an interfacial method. Also, no phosgene or other such toxic substances are used, nor is any solvent such as methylene chloride required, so this method is very promising as a way to manufacture optical polycarbonates.
It is considered very important, though, that a polycarbonate used in optical disk materials have a low molecular weight and that [this molecular weight] be adjusted to within a narrow range in order to maintain the strength of the molded disk and to transfer fine pits, crepe, and so forth to the surface during injection molding.
However, even when a polycarbonate with a low molecular weight is used, as discussed in Japanese Laid-Open Patent Application H11-300842, for instance, the molding has to be conducted under extremely limited conditions, in which the difference between the glass transition temperature of the polycarbonate resin and the mold temperature setting on the side where the stamper is installed is between 0 and 7° C., and this is unsatisfactory in terms of being suited to mass production.
Japanese Laid-Open Patent Application H11-35671 discloses an attempt at improving transfer during injection molding, in which a low molecular weight compound expressed by the following formula is added in an amount of 3.5 to 8 wt % to an optical polycarbonate. Copolymerizing a polycarbonate with a polysiloxane compound or the like has also been proposed, as discussed in Japanese Laid-Open Patent Application H10-158499.
(In the formula, X is a C
1
to C
4
alkylene group, C
2
or C
3
alkylidene group, oxygen atom, sulfur atom, carbonyl group, sulfinyl group, or sulfone group, and n is an integer from 1 to 4.)
Nevertheless, problems encountered with a method in which a low molecular weight polycarbonate is combined with another compound are that there is an increase in gas generation during molding, more mold fouling occurs during continuous production, and productivity is too low. When a polysiloxane compound is copolymerized, the manufacture of the polycarbonate itself requires a tremendous investment outlay, and because of differences in the optical characteristics and moldability of the resulting copolymerized polycarbonate, conventional disk manufacturing equipment cannot be used, among the many other practical problems.
In light of this situation, the inventors conducted research aimed at solving the above problems, whereupon they arrived at the present invention upon discovering that an optical polycarbonate that has excellent moldability and color stability, and that also affords excellent transfer in the injection molding of an optical disk can be obtained by adding a low molecular weight component (molecular weight of 1000 or less) in an amount of 1 wt % or less to a polycarbonate obtained by melt polycondensation, and adding a specific carbonate oligomer in a specific amount.
OBJECT OF THE INVENTION
The present invention was conceived in light of the above prior art, and it is an object thereof to provide an optical polycarbonate that has excellent moldability and color stability at high temperature as well as applications for this optical polycarbonate.
SUMMARY OF THE INVENTION
The optical polycarbonate (resin composition) pertaining to the present invention is:
an optical polycarbonate obtained by the melt polycondensation of a bisphenol and a carbonic diester in the presence of an alkaline compound catalyst, wherein in that:
(i) a compound expressed by the following Formula [A] is contained in an amount of 30 to 2000 ppm;
(ii) a compound expressed by the following Formula [B] is contained in an amount of 30 to 4000 ppm;
(iii) a compound expressed by the following Formula [C] is contained in an amount of 80 to 8000 ppm;
(iv) the viscosity average molecular weight is between 12,000 and 18,000; and
(v) the portion with a molecular weight (as measured by GPC) of 1000 or less accounts for 0.5 to 1.5 wt %.
The glass transition temperature of the optical polycarbonate should be 147° C. or lower.
It is preferable if the bisphenol is substantially composed of bisphenol A.
The optical disk pertaining to the present invention is formed from the above-mentioned optical polycarbonate.
Specific Description of the Invention
The optical polycarbonate pertaining to the present invention will now be described in specific terms.
Optical Polycarbonate
The optical polycarbonate resin pertaining to the present invention is an optical polycarbonate obtained by the melt polycondensation of a bisphenol and a carbonic diester in the presence of an alkaline compound catalyst.
The optical polycarbonate pertaining to the present invention usually has a viscosity average molecular weight (iv) between 12,000 and 18,000, and preferably between 13,000 and 17,000. The viscosity average molecular weight is calculated from the following equation after using an Ostwald viscometer to measure the intrinsic viscosity (IV) of a solution in which methylene chloride is used as a solvent.
Viscosity average molecular weight=(IV×10,000/1.23)
1/0.83
An optical polycarbonate having this viscosity average molecular weight will have little optical distortion, and will also have excellent strength. There will be a sharp drop in strength if the viscosity average molecular weight is less than 12,000. If the viscosity average molecular weight is over 18,000, though, the transfer of fine pits, crepe, and so forth to the surface will be inadequate during optical disk injection molding.
The optical polycarbonate pertaining to the present invention contains (i) a compound expressed by the following Formula [A] in an amount of 30 to 2000 ppm, and preferably in an amount of 50 to 2000 ppm.
The optical polycarbonate pertaining to the present invention contains (ii) a compound expressed by the following Formula [B] in an amount of 30 to 4000 ppm, and preferably in an amount of 50 to 3000 ppm.
The optical polycarbonate pertaining to the present invention contains (iii) a compound expressed by the following Formula [C] in an amount of 80 to 8000 ppm, and preferably in an amount of 100 to 5000 ppm.
The low molecular weight oligomer components expressed by [A] to [C] are quantified by liquid chromatography or the like.
If, as in the present invention, an optical polycarbonate
Inoue Kazushige
Shimoda Tomoaki
Boykin Terressa
General Electric Company
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