Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-05-12
2001-09-11
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S196000
Reexamination Certificate
active
06288205
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polycarbonate resin, more particularly, a polycarbonate resin suitable for use as a substrate for transfer type optical information recording media such as optical disks. The present invention further relates to a substrate for optical information recording media which is formed from the polycarbonate resin and to an optical information recording medium employing the substrate.
BACKGROUND ART
Compared to conventional magnetic recording, optical recording, which is capable of noncontact recording and reproducing, is characterized by being less influenced by marring or fouling and is contributing greatly to an increase in storage capacity.
Recording media for use in this technique are constituted by forming an information recording layer on a transparent substrate made of, e.g., a polycarbonate resin. Polycarbonate resins are suitable for use as the material of substrates for the information recording media because they have satisfactory heat resistance in melt molding, reduced dimensional changes after molding, and excellent mechanical properties. In recent years, with the increasing storage capacity in this field where polycarbonate resins are used, the distance between pit tracks transferred to a transparent substrate is becoming shorter and the depth of the pits are becoming larger. As a result, it has become usual to mold polycarbonate resins at higher molding temperatures and higher mold temperatures. However, because of the insufficient heat resistance of the resins, molding at higher temperatures tends to yield low-molecular volatiles, which deposit on the stamper and replicas to cause bit errors, leading to serious problems. The higher-temperature molding further causes scorching due to resin deterioration, resulting in an increased error frequency in the final products. Because of such various problems, there has been a desire for a material which can be molded at a lower temperature. On the other hand, the mold temperature also is becoming higher so as to cope with the shorter distance between bit tracks and the larger depth of pits. However, as the mold temperature increases, the problem of warpage of molded substrates becomes severer. There has hence been a desire for a lower mold temperature as in the case of molding temperature.
Under these circumstances, polycarbonate resins have been strongly required to be a material which can be molded at a lower molding temperature and a lower mold temperature without impairing important properties possessed by disk substrates (birefringence, suitability for transfer, and warpage).
It has been well known in this respect that a polycarbonate resin which itself has improved flowability is obtained by using an alkylphenol in which the alkyl chain is longer than in the alkylphenols conventionally used as chain terminators for polycarbonate resins. For example, British Patent 965,457 discloses a technique of lowering melt viscosity by using a long-chain monohydric alcohol as a chain terminator, while U.S. Pat. No. 3,240,756 discloses the use of an alkylphenol as a terminator. In Unexamined Published Japanese Patent Application No. 51-34992 are given examples in which a phenol, acid chloride, acid, or alcohol having an alkyl group having 8 to 20 carbon atoms is used as a chain terminator to produce a polycarbonate having improved flowability. Recently, examples in which a polycarbonate resin having a long-chain alkyl group at each terminal is used as an optical molded article are given in Unexamined Published Japanese Patent Application No. 60-203632 The above references each states that an improvement in flowability is possible due to the long-chain alkyl groups present at molecular ends of the polycarbonate.
However, it has been found that such a polycarbonate obtained with a long-chain alkylphenol gives products having a far more yellowish hue as compared with those obtained from the polycarbonates produced with t-butylphenol, which has been conventionally employed, and that the polycarbonate is colored to such a degree that the molded products are unsuitable for use in optical recording media.
DISCLOSURE OF THE INVENTION
The present inventors have made intensive studies in order to eliminate the problems of the prior art techniques described above. As a result, the present invention has been achieved.
One essential aspect of the present invention resides in a polycarbonate resin obtained by reacting starting materials comprising a dihydric phenol, a carbonate material, and a chain terminator comprising a p-substituted phenol (hereinafter referred to as a para isomer) represented by the following general formula (I), characterized in that the amount of an o-substituted phenol (hereinafter referred to as an ortho isomer) contained as an impurity in the chain terminator used satisfies the following relationship (i):
(wherein R is an organic group having 6 to 30 carbon atoms)
(
ortho
isomer
amount
)
(
para
isomer
amount
)
+
(
ortho
isomer
amount
)
×
10
6
≤
10
(
0.31
×
(
number
of
C
'
s
)
+
0.8
)
(
i
)
(wherein “number of C's” represents the number of carbon atoms in the substituent organic group of the substituted phenols).
Another essential aspect of the present invention resides in a polycarbonate resin obtained by reacting starting materials comprising a dihydric phenol, a carbonate material, and a chain terminator comprising a p-substituted phenol represented by the following general formula (I), characterized in that the polycarbonate resin, when molded at 360° C. and a cycle time of 180 seconds, gives molded objects (3.2 mm thick) having a YI of 2.5 or lower and a difference in YI between the first shot and the tenth shot (hereinafter referred to as &Dgr;YI) of 0.8 or smaller:
(wherein R is an organic group having 6 to 30 carbon atoms).
Still another essential aspect of the present invention resides in a substrate for optical information recording media which comprises the polycarbonate resin, and in an optical information recording medium employing the substrate.
BEST MODES FOR CARRYING OUT THE INVENTION
The polycarbonate resin of the present invention is produced by reacting starting materials comprising a dihydric phenol, a carbonate material, and a specific chain terminator.
The dihydric phenol used in the present invention is a compound having two phenolic hydroxyl groups. This phenol is preferably a compound represented by the general formula HO-Z-OH, wherein Z is an organic group comprising one or more aromatic nuclei, and one or more of the hydrogen atoms bonded to the carbon atoms of the aromatic nuclei each may be replaced with a chlorine atom, bromine atom, aliphatic group, or alicyclic group. The aromatic nuclei may differ from each other in substituent. The aromatic nuclei may be bonded to each other with a crosslinking member. Examples of this crosslinking member include aliphatic groups, alicyclic groups, heteroatoms, and combinations of these.
Specific examples of the dihydric phenol include hydroquinone, resorcinol, dihydroxydiphenyl, bis(hydroxyphenyl)alkanes, bis(hydroxyphenyl)cycloalkanes, bis(hydroxyphenyl)sulfides, bis(hydroxyphenyl) ethers, bis(hydroxyphenyl)ketones, bis(hydroxyphenyl) sulfones, bis(hydroxyphenyl)sulfoxides, bis(hydroxyphenyl)di-alkylbenzenes, and derivatives thereof in which one or more of the aromatic nuclei have one or more alkyl or halogen substituents. Two or more of these dihydric phenols can be used in combination.
These dihydric phenols and other appropriate dihydric phenols are given in, e.g., U.S. Pat. Nos. 4,982,014, 3,028,365, 2,999,835, 3,148,172, 3,275,601, 2,991,273, 3,271,367, 3,062,781, 2,970,131, and 2,999,846, German Offenlegungschrifts 1,570,703, 2,063,050, 2,063,052, and2,211,956, and French Patent 1,561,518.
Preferred dihydric phenols include bisphenol s containing two phenol residues in the skeleton, such as 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,
Inoue Toshimitsu
Kuma Kiyoji
Miyamoto Masaaki
Shiraishi Yoshitaka
Uchimura Ryuji
Boykin Terressa M.
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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