Polycarbonate resin composition

A polycarbonate resin composition comprising a blended mixture of PA0 (A) 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight of from about 13,000 to about 18,000, PA0 (B) 0.01 to 0.1 part by weight of a partial ester of a monobasic fatty acid having 10 to 22 carbon atoms with a polyhydric alcohol having 2 to 10 carbon atoms, PA0 (C) 0.001 to 0.01 part by weight of trimethyl phosphate, and PA0 (D) 0.00001 to 0.002 part by weight, calculated as phosphorus atoms, of a phosphite ester having 9 to 60 carbon atoms.

This invention relates to a polycarbonate resin composition, and 
specifically, to a polycarbonate resin composition having various 
excellent properties such as excellent flowability, thermal stability, 
moldability and hydrolysis resistance and pinhole formation resistance on 
a thin coated layer on the surface of a molded article prepared from the 
resin composition. The polycarbonate resin composition of this invention 
is useful in many applications, especially in optical applications. 
More specifically, this invention relates to a polycarbonate resin 
composition comprising a blended mixture of 
(A) 100 parts by weight of a polycarbonate resin having a viscosity average 
molecular weight of from about 13,000 to about 18,000, 
(B) 0.01 to 0.1 part by weight of a partial ester of a monobasic fatty acid 
having 10 to 22 carbon atoms with a polyhydric alcohol having 2 to 10 
carbon atoms, 
(C) 0.001 to 0.01 part by weight of trimethyl phosphate and 
(D) 0.00001 to 0.002 part by weight, calculated as phosphorus atoms, of a 
phosphite ester having 9 to 60 carbon atoms. 
Polycarbonate resins have been used in a wide range of applications, and 
recently attracted attention as resins which give substrates for 
information recording articles such as digital signal recording discs, 
optical articles such as lenses, prisms and Fresnel lenses and excellent 
molded articles for use in other optical applications. 
In such optical uses, one important property required of the polycarbonate 
resin is that a molded article of the polycarbonate resin has a reduced 
optical distortion (retardation). Generally, such a resin article is 
essentially required to have a birefringence of not more than 100 nm. To 
obtain such low-birefringence molded articles, it is the usual practice to 
use a polycarbonate resin having a viscosity average molecular weight of 
not more than about 20,000. Since the molding temperature for such a 
polycarbonate resin reaches about 300.degree. to about 400.degree. C., it 
is desired to use a polycarbonate resin composition having high thermal 
stability and excellent mold releasability. 
In optical applications, for example as a substrate for information 
recording devices, it is frequently the practice to provide a thin coated 
layer of a metal or a metal compound or a thin coated layer containing a 
dye on the surface of the substrate. Furthermore, in using the 
polycarbonate resin as a lens, a thin coated layer of a metal, a metal 
compound, an organosiloxane-type paint or a melamine-type paint is 
frequently applied to the lens surface for prevention of scratching, or 
for antihaze and antiglare purposes. In such optical applications, it is 
desired to use a polycarbonate resin composition having excellent 
hydrolysis resistance, excellent resistance to pinhole formation on the 
thin coated layer, and therefore a satisfactory life or durability. 
It is extremely difficult, however, to provide a polycarbonate resin 
composition having excellent properties that meet the aforesaid various 
requirements, and it has been desired to develop such a composition. 
Japanese Patent Publication No. 41092/1972 (published on Oct. 17, 1972), 
for example, discloses a polycarbonate resin composition comprising a 
polycarbonate resin and as a lubricant for improving the releasability of 
a molded product from a mold, 0.05 to 5% by weight, preferably 0.1 to 0.5% 
by weight, of an ester or partial ester of a monobasic saturated aliphatic 
carboxylic acid having 12 to 30 carbon atoms with a monohydric saturated 
aliphatic alcohol or a polyhydric alcohol. The lubricant in this patent 
document includes partial esters which can overlap component (B) of the 
composition of the present invention. This patent document, however, 
neither describes nor suggests a composition comprising a combination of 
essential components (A) to (D) in the present invention. It quite fails 
to describe the utilization of the polycarbonate resin composition in 
optical applications, the technical problems in such applications and an 
idea of solving such problems. Furthermore, this patent document 
illustrates only the use of polycarbonate resins having a molecular weight 
exceeding about 20,000, for example 24,000 and 25,000. 
Japanese Laid-Open Patent Publication No. 81245/1985 (laid open on May 9, 
1985) discloses a polycarbonate resin composition comprising a 
polycarbonate resin having a viscosity average molecular weight of 15,000 
to 35,000 and containing 15 to 150 ppm, calculated as chlorine atoms, of a 
chlorine compound such as methylene chloride and 0.001 to 0.5% by weight, 
preferably 0.03 to 0.1% by weight, of a partial ester, preferably a 
monoester, of a monobasic saturated aliphatic carboxylic acid having 
preferably 10 to 24, more preferably 12 to 20, carbon atoms, with a 
polyhydric alcohol in order to prevent the corrosion of a mold which 
adversely affect the appearance of a molded article prepared from it, the 
releasability of the molded aricle from the mold, the dimensional accuracy 
of the molded article, and the life of the mold, etc. The partial ester in 
this patent document can overlap the component (B) in the composition of 
this invention. However, this patent document totally fails to describe or 
suggest a composition comprising a combination of essential components (A) 
to (D) in the present invention. Furthermore, it does not touch upon the 
utilization of the composition in optical applications, the technical 
problems in such utility, and an idea of solving these problems. 
Japanese Laid-Open Patent Publication No. 50348/1977 (laid open on April 
22, 1977) discloses the stabilization of a molten polycarbonate resin 
against discoloration by chlorine. Specifically, this patent document 
describes a process for producing a polycarbonate resin molded article 
having improved color, which comprises mixing 100 parts by weight of a 
polycarbonate resin containing 0.005 to 0.2% by weight of chlorine with 
0.005 to 0.1 part by weight of a methyl phosphate ester, preferably 
trimethyl phosphate, and melt-molding the mixture. Trimethyl phosphate in 
this patent document corresponds to component (C) of the composition of 
the present invention. However, this patent document neither describes nor 
suggests a composition comprising a combination of essential components 
(A) to (D) in the present invention. The patent document totally fails to 
disclose the utilization of the composition in optical applications, the 
technical problems in such utility, and guidelines for solving the 
problems. 
Japanese Laid-Open Patent Publication No. 126119/1983 (laid open on July 
27, 1983) describes a process for producing a polycarbonate resin molded 
article having excellent optical properties, particularly high 
transparency and reduced optical distortion. According to this process, a 
polycarbonate resin derived from a bis(hydroxyphenyl)alkane having an 
average molecular weight of 12,000 to 18,000 containing 0.005 to 0.5% by 
weight, preferably 0.01 to 0.2% by weight, of a phosphite ester of the 
following formula 
##STR1## 
wherein R.sup.1 and R.sup.2 each represent an alkyl 
or aryl group, and R.sup.3 represents a hydrogen 
atom or an alkyl or aryl group, is injection-molded at a resin temperature 
of 330 to 400.degree. C. and a mold temperature of 50.degree. to 
110.degree. C. The phosphite ester in this patent document can overlap 
component (D) in the composition of the present invention. However, this 
patent document also fails to describe or suggest a composition comprising 
a combination of essential components (A) to (D) in the present invention. 
It is directed to the improvement of transparency and optical distortion, 
but the patent document quite fails to touch upon an idea of 
simultaneously solving the technical problems of hydrolysis resistance and 
pinhole formation resistance described hereinabove. 
Japanese Laid-Open Patent Publication No. 180553/1983 (laid open on October 
22, 1983) proposes a polycarbonate resin molding material for use in 
making optical devices and appliances. It specifically discloses that the 
occurrence of burn marks or decomposition and degeneration of a 
polycarbonate resin having a viscosity average molecular weight of from 
15,000 to 18,000 during molding at high temperatures can be inhibited by 
incorporating 100 to 300 ppm, preferably 150 to 200 ppm, of an antioxidant 
in the polycarbonate resin. This patent document gives 
tris(nonylphenyl)phosphite, 2-hexylbenzylphenyl phosphite and triphenyl 
phosphite as examples of the antioxidant. The above-illustrated 
antioxidants in this patent document can overlap component (D) of the 
composition of the present invention. However, it also fails to describe 
or suggest a composition comprising a combination of essential components 
(A) to (D) in the present invention. The invention disclosed in this 
patent document is directed to the prevention of the occurrence of burn 
marks and decomposition and degradation having regard to optical 
applications, but the patent document neither describes nor suggest 
guidelines for simultaneously solving the technical problems of hydrolysis 
resistance and pinhole formation resistance stated hereinabove. 
Polycarbonate resins tend to be more susceptible to degradation than other 
resins because of their relatively high temperatures used in injection 
molding or extrusion. This tendency leads to a decrease in molecular 
weight or to coloration due to thermal degradation. In an attempt to 
overcome such troubles, Japanese Laid-Open Patent Publication No. 
111959/1974 (laid open on October 24, 1974) proposes a polycarbonate resin 
composition comprising a polycarbonate resin, a component which can 
overlap component (B) of the composition of this invention and a component 
which can overlap component (D) of the composition of this invention. This 
patent document states that the use of the component corresponding to 
component (B) alone produces only a small effect of imparting thermal 
stability and the use of the component corresponding to component (D) 
alone in an amount sufficient to impart thermal stability results in the 
occurrence of foams or silver streaks in a molded article prepared from 
the resin composition. It specifically proposes a thermally stable 
polycarbonate resin composition which can embrace a composition comprising 
a polycarbonate resin, 0.01 to 2% by weight of a glycerin ester of a 
monobasic saturated aliphatic carboxylic acid having 10 to 30 carbon atoms 
and 0.001 to 0.1% by weight, calculated as phosphorus atoms, of 
phosphorous acid or a phosphite ester. However, this patent document 
neither describes nor suggests a composition comprising a combination of 
essential components (A) to (D) in the present invention which corresponds 
to the composition proposed in this prior patent document plus the 
component (C) in the composition of the present invention. Furthermore, 
this patent document totally fails to disclose the utilization of the 
composition in optical applications, the technical problems in such 
utility and guidelines for solving the problems. It is also silent on an 
idea of solving the technical problems of hydrolysis resistance and 
pinhole formation resistance stated hereinabove, and only illustrates the 
use of polycarbonate resin having a viscosity average molecular weight in 
the range of 25,000 to 29,400 which quite falls outside the range of not 
more than about 20,000. 
The present inventors have made investigations in order to provide a 
polycarbonate resin composition having a combination of excellent 
properties, and particularly a polycarbonate resin composition in which 
the polycarbonate resin has a viscosity average molecular weight of from 
about 13,000 to about 18,000, and which can give a molded article having 
excellent quality. 
These investigations have led to the discovery that a polycarbonate resin 
composition comprising essential components (A) to (D) has properties 
required of optical applications including flowability, thermal stability, 
moldability, hydrolysis resistance and pinhole formation resistance. 
Investigations of the present inventors have shown that by incorporating 
the following components (B), (C) and (D) in the above specified amounts 
into a polycarbonate resin component (A) having a viscosity average 
molecular weight of from about 13,000 to about 18,000, a polycarbonate 
resin composition of high quality having the various excellent properties 
described above can be obtained. 
Component (B) 
This component can overlap the components which when used alone, are useful 
for inhibiting the corrosion of a mold that exerts adverse effects on the 
releasability of a polycarbonate resin molded article from the mold, the 
appearance of the molded article, etc. (for example, the above-cited 
Japanese Laid-Open Patent Publication No. 81245/1985), and which the 
above-cited Japanese Laid-Open Patent Publication points out, produce only 
a small effect of imparting thermal stability when used alone. 
Component (C) 
This component includes trimethyl phosphate known to be utilized alone for 
the inhibition of discoloration of a molten polycarbonate resin by 
chlorine (the above cited Japanese Laid-Open Patent Publication No. 
50348/1977). 
Component (D) 
This component can overlap the phosphite ester which singly is useful for 
increasing the thermal stability of a polycarbonate resin and imparting 
oxidation resistance to it in optical applications (the above-cited 
Japanese Laid-Open Patent Publications Nos. 126119/1983 and 180553/1983) 
and which, the above-cited Japanese Laid-Open Patent Publication points 
out, cause foaming or the occurrence of silver streaks in molded articles 
of the polycarbonate when used singly in amounts useful for increasing 
thermal stability. 
Investigations of the present inventors have shown that the aforesaid 
component (D) singly may cause troubles of hydrolysis or pinhole formation 
when used in smaller amounts, but when it is used in combination with the 
component (C) in accordance with this invention, it can, in reduced 
amounts, effectively increase the thermal stability of the polycarbonate 
resin composition in which the polycarbonate resin has a viscosity average 
molecular weight of about 13,000 to about 18,000, and also can effectively 
avoid the troubles of hydrolysis and pinhole formation as a result of 
using it in the presence of component (B). 
It is an object of this invention therefore to provide a polycarbonate 
resin composition having various improved properties which is especially 
useful in optical applications.

The above and other objects of this invention along with its advantages 
will become apparent from the following description. 
The polycarbonate resin (A) in the composition of this invention and the 
method of its production are known. Commercially available polycarbonate 
resins can also be used in this invention. 
The polycarbonate resin component (A) may be produced by techniques known 
per se by reacting dihydric phenols with carbonate-precursors such as 
phosgene and diphenyl carbonate. Examples of the dihydric phenols are 
hydroquinone, dihydroxydiphenyl, bis(hydroxyphenyl)alkanes, 
bis(hydroxyphenyl)cycloalkanes, bis(hydroxyphenyl)ethers, bis 
(hydroxyphenyl)ketones, bis(hydroxyphenyl)sulfides, 
bis(hydroxyphenyl)sulfones and halogenated or lower alkylated products 
thereof. A polycarbonate resin derived from a bis(hydroxyphenyl)alkane and 
a carbonate precursor is preferred. The bis(hydroxyphenyl)alkane may, for 
example, be at least one member selected from the group consisting of 
2,2-bis(4-hydroxyphenyl)-propane (bisphenol A), 
1,1-bis(4-hydroxyphenyl)ethane and 
2,2-bis(4-hydroxyphenyl)hexafluoropropane. The dihydric phenols may be 
used singly or in combination. Polycarbonate resins obtained by 
copolymerizing a small amount of an aromatic dicarboxylic acid further as 
a comonomer, and polycarbonate resins having a branched structure can also 
be used. The polycarbonates may be used singly or in combination. 
In the present invention, the polycarbonate resin (A) has a viscosity 
average molecular weight (M) of from about 13,000 to about 18,000. If the 
molecular weight (M) is lower than the lower limit specified, the strength 
of a molded article from the polycarbonate resin is unsatisfactory for 
practical applications. If it is higher than the specified upper limit, 
molding strains tend to occur during molding, and the molded articles 
become unsuitable for optical applications. Accordingly, in the present 
invention, the polycarbonate resin (A) used has a viscosity average 
molecular weight (M) of from about 13,000 to about 18,000. 
The molecular weight (M) of the polycarbonate in this invention is 
calculated in accordance with the following equation from the intrinsic 
viscosity [.eta.] (dl/g) of the polycarbonate resin determined at 
20.degree. C. for a methylene chloride solution of the resin. 
EQU [.eta.]=1.23.times.10.sup.-4 M.sup.0.83 
The partial fatty acid ester (B) used in the composition of this invention 
is a partial ester of a monobasic fatty acid having 10 to 22 carbon atoms 
with a polyhydric alcohol having 2 to 10 carbon atoms. The partial ester 
can be produced by esterifying the monobasic fatty acid with the 
polyhydric alcohol by techniques known per se, and is also available 
commercially. Such commercially available partial esters can also be used 
in this invention. The partial esters may be used singly or in 
combination, and are also available in such forms on the market. 
Examples of the partial fatty acid ester (B) are partial esters formed 
between at least one monobasic fatty acid having 10 to 22 carbon atoms 
selected from the group consisting of myristic acid, palmitic acid, 
stearic acid, oleic acid and fatty acids of hardened fish oils and at 
least one polyhydric alcohol having 2 to 10 carbon atoms selected from the 
group consisting of ethylene glycol, glycerin and pentaerythritol. 
Preferred among these partial esters are those formed between glycerol and 
at least one fatty acid having 18 to 22 carbon atoms such as stearic acid, 
oleic acid and fatty acids (e.g., C.sub.18 -C.sup.22) of hardened fish 
oils. 
Trimethyl phosphate, are used as the component (C) of the polycarbonate 
resin composition of this invention. 
The component (D) used in the polycarbonate resin composition of this 
invention is a phosphite ester having 9 to 60 carbon atoms. It is as 
mono-, di- or tri-ester. The tri-ester and a mixture of a major amount of 
the tri-ester with a minor amount of the mono- and/or di-ester are 
preferably used. Examples of the triester include tributyl phosphite, 
tris(2-ethylhexyl) phosphite, tridecyl phosphite, tristearyl phosphite, 
triphenyl phosphite, tricresyl phosphite, tris(nonylphenyl) phosphite, 
2-ethylhexyl diphenyl phosphite, phenyl di-2-ethylhexyl phosphite, phenyl 
didecyl phosphite, tricyclohexyl phosphite, distearyl pentaerythrityl 
diphosphite, diphenyl pentaerythrityl diphosphite, didecyl diphenyl 
phosphite, and tris(2,4-di-t-butylphenyl) phosphite. These phosphite 
esters as component (D) may be used singly or in combination. Among them, 
preferred are triphenyl phosphite, tris(nonylphenyl) phosphite, 
2-ethylhexyl diphenyl phosphite and tris(2,4-ditert.butylphenyl) 
phosphite. 
The individual components of the polycarbonate resin composition of this 
invention must meet the specific quantitative requirements. Specifically, 
0.01 to 0.1 part by weight of component (B), 0.001 to 0.01 part by weight 
of component (C) and 0.00001 to 0.002 part by weight, calculated as 
phosphorus atoms, of component (D) are used per 100 parts by weight of 
component (A). 
Details of the operation mechanism of the components (B), (C) and (D) on 
the polycarbonate resin component (A) having a viscosity average molecular 
weight of from about 13,000 to about 18,000 have not been elucidated 
fully. It is presumed however that as shown in Examples and Comparative 
Examples given hereinafter, these components affect one another complexly 
to give a polycarbonate resin composition having the aforesaid excellent 
properties particularly suitable for optical applications. It is difficult 
therefore to describe in a generalized manner the functions and effects of 
the individual components used in the specified quantitative proportions 
which contribute to the properties of the polycarbonate resin composition 
of this invention, but their main functions and effects will be described 
below. 
In the specific combination of components (A) to (D) in the polycarbonate 
resin composition of this invention, component (B) not only improves the 
releasability of a molded article of the composition from a mold, but also 
in combination with components (C) and (D), serves to produce a 
synergistic effect that is conducive to a further improvement in the color 
of the molded article. Moreover, it has been unexpectedly found that 
component (B) markedly improves the life and durability of a coated thin 
layer on the surface of a molded article of the composition in the 
aforesaid optical applications. If the amount of component (B) is too 
small outside the specified range of 0.01 to 0.1 part by weight per 100 
parts by weight of component (A), the effect of improving the mold 
releasability is reduced and the resulting molded articles tend to develop 
optical distortions. Furthermore, the effect of improving the color of the 
molded article is greatly reduced, and it is difficult to achieve an 
unexpected and marked improvement in the life and durability of the thin 
coated layer. If the amount of component (B) is too large outside the 
above-specified range, silver streaks are liable to form in the molded 
article, and the formation of a thin coated layer on it becomes difficult. 
In the combination of essential components (A) to (D) of the polycarbonate 
resin composition of this invention, component (C) serves to decrease the 
amount of component (D) which may induce the hydrolysis or pinhole 
formation stated hereinabove, and has a thermal stability improving action 
synergistically with component (D) so as to increase the thermal stability 
of the resin component (A) effectively. Phosphorus contained in component 
(C) is pentavalent phosphorus, and the component (C) intrinsically cannot 
be expected to have an antioxidation effect by its reducing action. 
Furthermore, trimethyl phosphate has a boiling point of 197.degree. C. and 
triethyl phosphate has a boiling point of 215.degree. C. It is natural to 
consider such compounds to be unsuitable for incorporation in a 
polycarbonate resin which is molded at temperatures of about 300.degree. 
to 400.degree. C. It has been found unexpectedly that component (C) 
cooperatively acts with component (D) in the copresence of component (B) 
to impart an excellent heat stabilizing effect to the polycarbonate resin 
composition of this invention without involving undesirable hydrolysis or 
pinhole formation. If the amount of component (C) is too small beyond the 
range of 0.001 0.01 to 0.01 part by weight per 100 parts by weight of 
component (A), it is difficult to obviate the coloration of the molded 
article, and it is impossible to overcome the difficulty of the use of 
component (D) which may cause hydrolysis or pinhole formation. If it is 
too large outside the specified range, silver streaks are liable to form 
in the molded article. 
In the combination of the essential components (A) to (D) in the 
polycarbonate resin composition of this invention, the component (D), in 
cooperation with component (C), exhibits a hitherto unexpected and unknown 
action of imparting an excellent thermal stabilization effect to the 
polycarbonate resin composition of this invention without involving the 
undesirable hydrolysis or pinhole formation. If the amount of component 
(D) used is too small beyond the range of 0.00001 to 0.002 part by weight, 
calculated as phosphorus atoms, per 100 parts by weight of the component 
(A), the aforesaid unexpected action cannot be achieved. If it is too 
large beyond the specified range, the color of the molded aricle is 
deteriorated, and silver streaks are liable to form in the molded article. 
Moreover, hydrolysis or pinhole formation occurs. 
The components (B) to (D) in the polycarbonate resin composition complexly 
affect each other and subtly contribute to the quality of the 
polycarbonate resin composition of this invention. Acordingly, in the 
practice of this invention, it is desirable to determine the suitable 
amounts of these components experimentally depending upon the types and 
combinations of these components with reference to their actions and 
amounts described hereinabove. It will be easily understood by those 
skilled in the art that after they read the present specification and know 
that the high quality polycarbonate composition can be provided by the 
specific combination of the components described herein, they can 
exprimentally select and determine such suitable amounts of the individual 
components of the composition. 
In addition to the essential components (A), (B), (C) and (D) of the 
composition of this invention described in detail hereinabove, the 
composition may contain other various additives customarily used in the 
art. Examples of the additives are ultraviolet absorbers, coloring agents, 
phenolic antioxidants and fluorescent bleaching agents. The amounts of the 
additives may be those customarily used, and as required, those skilled in 
the art can easily select and determine them experimentally. 
The composition of this invention can be easily prepared by mixing the 
essential components (A) to (D) and, if required, other additives to form 
a blended mixture. 
The mixing may be carried out by any known method, and the sequence of 
mixing the components is optional. Most preferably, these ingredients are 
meltmixed by an extruder. The mixing may be carried out at a temperature 
at which the component (A) is in the molten state, for example at about 
240.degree. to about 330.degree. C. 
Articles for use in optical applications may be produced by injection 
molding or injection-compression molding the polycarbonate resin 
composition at a resin temperature of, for example, about 300.degree. to 
400.degree. C. mold temperature of, for example, about 70.degree. to 
120.degree. C. 
Even when the polycarbonate resin composition of this invention is molded 
at 300.degree. to 400.degree. C., it rapidly and completely fills a mold 
for thin-walled articles, and the molded articles can be released very 
smoothly from the mold, without decomposition or the occurrence of burn 
marks and silver streaks. 
The optical articles obtained from the resin composition of this invention 
accurately duplicate the mold. They have a transparency represented by a 
light transmittance of about 90%, and are free from any optical distortion 
that is detrimental to practical application. Furthermore, a thin film of 
a metal or a metal compound formed on the surface of such a molded 
article, or a thin film formed thereon for preventing scratching and for 
antihaze and antiglare purposes, together with the polycarbonate resin 
substrate, has excellent wet heat resistance and can endure long-term use. 
Since the polycarbonate resin composition of the invention has all the 
properties required of optical applications, it can be used fully for 
practical applications as substrates for information recording, and 
various lenses, prisms and Fresnel lenses. 
The following Examples and Comparative Examples illustrate the present 
invention more specifically. 
The birefringence, appearance, pinhole formation, thermal stability and 
hydrolysis resistance of the molded articles and the viscosity average 
molecular weight of the polycarbonate resin in these examples were 
determined or measured by the following methods 
Measurement of birefringence 
The birefringence of a molded plate of the composition was measured by a 
polarized microscope (a product of Karl-Zeiss) equipped with a 
compensator, and expressed in nm. 
Evaluation of a molded article having a vacuum-deposited coating 
A molded circular plate was put into a bell jar of a vacuum depositing 
device, and aluminum was vapor-deposited only on one surface of the plate 
at 10.sup.-5 torr. A polyurethane resin was coated on the plate, and the 
plate was left to stand for 72 hours in a constant-temperature 
constant-humidity machine in an atmosphere kept at a relative humidity of 
95% and a temperature of 85.degree. C. Then, the number of pinholes was 
counted. Pinholes are undesirable since they prevent accurate recording of 
information. 
Appearance 
Visually observed during and after the molding. The appearance was rated 
"good" when the mold releasability was good and there was no burn mark, 
silver streak nor coloration. 
Evaluation of thermal stability 
A sample plate, 2 mm thick, 50 mm wide and 70 mm long, was produced by 
injection molding of pellets in a 3-ounce injection molding machine (made 
by The Japan Steel Works, Ltd.) at a resin temperature of 380.degree. C. 
To test its heat stability, the sample plate was caused to reside for 10 
minutes in the cylinder of the molding machine. Then, the color of the 
sample plate and the color of another sample plate without the aforesaid 
residence in the cylinder were measured by a color difference meter (made 
by Color Machine Company). The color was expressed by b value. The smaller 
the b value, the lower the degree of coloration. 
Evaluation of hydrolysis resistance 
The sample plate obtained without residence in regard to the evaluation of 
thermal stability was treated in a steam sterilizer at 120.degree. C. for 
11 hours, and then the viscosity average molecular weight of the treated 
sample plate was measured. 
Determination of viscosity average molecular weight 
The resin (0.7 g) was dissolved in 100 ml of methylene chloride and the 
specific viscosity .eta..sub.sp of the solution was measured at 20.degree. 
C. by an Ostwald viscometer. The viscosity average molecular weight M was 
calculated from the following expression. 
EQU .eta..sub.sp /0.7=[.eta.]+0.45.times.0.7.times.[.eta.].sup.2 
EQU [.eta.]=1.23.times.10.sup.-4 M.sup.0.83 
EXAMPLES 1-9 and COMATIVE EXAMPLES 1-10 
An alkaline aqueous solution of bisphenol A and methylene chloride were 
stirred at 25.degree. C., and phosgene was introduced. Then, a molecular 
weight controller and triethylamine were added, and the reaction was 
carried out for about 3 hours. The methylene chloride layer of the 
reaction mixture was repeatedly washed with water. The solvent was 
removed, and the slurry-like polycarbonate was dried under reduced 
pressure at 110.degree. C. for 4 hours to give a polycarbonate powder 
having an average molecular weight of 15,000. 
One hundred parts by weight of the polycarbonate powder were mixed with the 
additives indicated in Table 1, and the mixture was extruded at a 
temperature of 250.degree. to 270.degree. C. using a 30 mm extruder. The 
extruded thread was pelletized by a cutter. The pellets were molded by an 
injection molding machine (Neomat 150/75, made by Sumitomo Heavy Machinery 
Industry Co., Ltd.) at a resin temperature of 350.degree. C. and a mold 
temperature of 90.degree. C. to produce a circular plate having a diameter 
of 155 mm and a thickness of 2.0 mm. The plate was evaluated by the 
methods described hereinabove. The birefringence of the plate was measured 
at a position 45 mm away circumferentially from the center of the circular 
plate. The results are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Component (D) 
Component (B) 
Component (C) Parts by 
Parts by weight 
Type 
Parts by weight 
Type Parts by weight 
Type 
weight 
of phosphorus 
__________________________________________________________________________ 
Example 
1 B1 0.03 trimethyl 
0.004 D1 0.001 
0.0001 
phosphate 
2 " 0.04 trimethyl 
0.005 D2 0.005 
0.0002 
phosphate 
3 " 0.04 trimethyl 
0.010 " 0.005 
0.0002 
phosphate 
4 " 0.05 trimethyl 
0.006 D1 0.004 
0.0004 
phosphate 
5 " 0.04 trimethyl 
0.005 " 0.010 
0.0010 
phosphate 
6 " 0.04 trimethyl 
0.005 " 0.020 
0.0020 
phosphate 
7 " 0.04 trimethyl 
0.005 D2 0.030 
0.0013 
phosphate 
8 B2 0.05 trimethyl 
0.005 " 0.010 
0.0004 
phosphate 
9 " 0.04 trimethyl 
0.005 " 0.030 
0.0013 
phosphate 
Comparative 
Example 
1 B1 0.001 trimethyl 
0.005 D2 0.030 
0.0013 
phosphate 
2 " 0.50 trimethyl 
0.005 " 0.030 
0.0013 
phosphate 
3 " 0.04 trimethyl 
-- " 0.030 
0.0013 
phosphate 
4 " 0.04 trimethyl 
0.050 " 0.030 
0.0013 
phosphate 
5 " 0.04 trimethyl 
0.005 " -- -- 
phosphate 
6 " 0.04 trimethyl 
0.001 " 0.050 
0.0022 
phosphate 
7 " 0.04 trimethyl 
0.005 " 0.300 
0.0130 
phosphate 
8 " 0.04 trimethyl 
-- " 0.053 
0.0024 
phosphate 
9 " 0.04 trimethyl 
0.011 -- -- -- 
phosphate 
10 " 0.04 trimethyl 
-- -- -- -- 
phosphate 
__________________________________________________________________________ 
Number of pinholes 
Thermal 
of the circular 
stability 
Circular plate vacuum deposited 
(b value) 
Bire- coating No After 
Hydrolysis 
fringence Before 
After 
resi- 
resi- 
resistance 
(nm) Appearance treatment 
treatment 
dence 
dence 
(--M) 
__________________________________________________________________________ 
Example 
1 78 Good 0 0 3.3 4.5 14,800 
2 52 " 0 0 3.7 4.5 14,700 
3 67 " 0 0 3.6 4.3 14,700 
4 56 " 0 0 3.6 4.2 14,600 
5 64 " 0 0 3.5 4.1 14,500 
6 53 " 0 0 3.3 3.7 14,100 
7 41 " 0 0 3.5 4.0 14,400 
8 45 " 0 0 3.7 4.4 14,600 
9 53 " 0 0 3.5 4.0 14,300 
Comparative 
Example 
1 153 Poor releasability 
0 23 4.0 5.0 14,400 
2 -- Silver streaks formed, 
-- -- -- -- -- 
surface had a tacky feel 
3 -- Yellowish 0 0 4.4 5.6 14,300 
4 -- Silver streaks formed 
-- -- -- -- -- 
5 -- Burn marks occured 
-- -- -- -- -- 
6 58 Good 0 7 3.5 3.9 13,800 
7 -- Blackish 0 45 -- -- -- 
8 56 Good 0 12 3.6 4.1 13,500 
9 -- Orangish 0 0 5.2 7.2 14,500 
10 -- Burn marks occured 
-- -- -- -- -- 
__________________________________________________________________________ 
Note 
B1: Resistat AF101 (tradename, Daiichi Kogyo Seiyaku K. K.; containing a 
partial ester of C.sub.18 -C.sub.22 monobasic fatty acids and glycerol as 
a main component) 
B2: Rickemal S100A (tradename, Riken Vitamin Co., Ltd.; containing a 
stearyl monoglyceride as a main component) 
D1: triphenyl phosphite 
D2: tris(mixed mono/dinonylphenyl)phosphite 
EXAMPLES 10-14 
The pellets used in Examples 1 and 4 to 7 were respectively molded by an 
injection molding machine (Neomat 1575/300, made by Sumitomo Heavy 
Machinery Industrial Co., Ltd.) at a resin temperature of 360.degree. C. 
and a mold temperature of 120.degree. C. to produce a circular plate 
having a diameter of 300 mm and a thickness of 1.2 mm. The plate was 
evaluated by the methods descriped above. The birefringence was measured 
at positons 65, 85, 105, 125, and 145 mm, respectively, away 
circumferentially from the center of the circular plate. The results are 
shown in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Component (B) 
Component (C) 
Component (D) 
Circular plate 
Parts Parts Parts 
Parts by 
Birefringence (nm) 
by by by weight of 
65 85 105 
125 
145 
Appear- 
Example 
Type 
weight 
Type weight 
Type 
weight 
phosphorus 
mm mm mm mm mm ance 
__________________________________________________________________________ 
10 B1 0.03 
Trimethyl 
0.004 
D1 0.001 
0.0001 
38 25 21 19 52 Good 
phosphate 
11 " 0.05 
Trimethyl 
0.006 
" 0.004 
0.0004 
21 17 18 16 43 " 
phosphate 
12 " 0.04 
Trimethyl 
0.005 
" 0.01 
0.001 19 15 17 11 39 " 
phosphate 
13 " 0.04 
Trimethyl 
0.005 
" 0.02 
0.002 13 10 11 9 23 " 
phosphate 
14 " 0.04 
Trimethyl 
0.005 
D2 0.03 
0.0013 
10 9 10 7 18 " 
phosphate 
__________________________________________________________________________