JPH10176046A - Polycarbonate copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject copolymer capable of expressing excellent optical characteristics and sufficient heat resistance and mechanical strength by copolymerizing specific several kinds of bisphenols. SOLUTION: This polycarbonate copolymer comprises 5-95mol.% of repeating units of formula I (R<1> , R<2> are each methyl, ethyl; R<3> is a 1-6C alkyl) and 95-5mol.% of repeating units selected form repeating units of formula II (R<4> , R<5> are each H, a 1-6C alkyl, etc.; X is a group of formula III, etc.; A is a single bond, a 2-4C alkylene) and repeating units of formula IV (R<7> , R<8> are each a 1-6C alkyl, a 6-10C aryl; Y is a group of formula V, etc.). The copolymer has a reducing viscosity (ηsp/c) of at least 0.3dl/g in a 0.5g/dl concentration solution at 20 deg.C, a photoelastic coefficient of <=70×10<-13> cm<2> /dyne, and a glass transition temperature of at least 95 deg.C. The copolymer is obtained by melt-polycondensing a bisphenol compound with a diaryl carbonate in a specific ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polycarbonate copolymer containing a bisphenol having a specific structure. More specifically, it relates to a novel polycarbonate copolymer having excellent optical properties.

[0002]

2. Description of the Related Art Polycarbonate resins produced by reacting 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A) with phosgene or a carbonate-forming compound such as diphenyl carbonate are known for their transparency and heat resistance. And because of its excellent mechanical strength, it is used for a wide range of applications.

[0003] However, with the expansion of various applications, the required properties of polycarbonate resins have become strict, and the appearance of polycarbonate resins having better performance has been demanded. In particular, when a molded product is obtained by injection molding using a conventional polycarbonate resin, the molded product tends to have a large stress optical distortion, that is, the birefringence tends to be large, and such optical distortion becomes a problem. There is a problem that it is not preferable as a material for optical devices.

A homopolymer comprising a repeating unit represented by the following formula (I) has been known for a long time, and USP3
510507, EP 1308521, USP 36557
18, USP369132, USP3737486, U
SP3773812, JP-A-52-15538,
JP-A-52-43847, JP-A-52-5874
7, JP-A-52-128359, and JP-A-5-128359.
It is disclosed in JP-A-3-92864, JP-A-53-110842 and JP-A-54-29358, but has low mechanical strength and is mainly used as a stabilizer.

[0005]

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Japanese Patent Application Laid-Open No. 52-148594 discloses the use of a carbonate oligo copolymer having a total (total polymerization number) of the repeating units represented by the formula (I) of not more than 20 as a stabilizer. Have been. JP-A-59-120206 discloses a selective separation membrane represented by the formula (I) and comprising a repeating unit and a repeating unit derived from bizphenol A.

As described above, at present, no technique has been established for a copolymer containing the repeating unit represented by the formula (I) and having excellent optical properties.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel polycarbonate copolymer having excellent optical properties. Another object of the present invention is to provide a polycarbonate copolymer having excellent transparency and a small photoelastic coefficient. Still another object of the present invention is to provide a polycarbonate copolymer having excellent optical properties as described above and also excellent moldability, heat resistance and mechanical strength. Still another object of the present invention is to provide a method for industrially and efficiently producing the polycarbonate copolymer of the present invention having the above-mentioned excellent properties. Still another object of the present invention is to provide use of the above-mentioned polycarbonate copolymer of the present invention as a material for an information transmission medium or an information recording medium. Still other objects and advantages of the present invention will become apparent from the following description.

[0009]

According to the present invention, the above objects and advantages of the present invention are as follows:

[0010]

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[Here, R ¹ and R ² are the same or different and are a methyl group or an ethyl group, and R ³ is an alkyl group having 1 to 6 carbon atoms. A first repeating unit represented by the formula (II) -a and (II) -b, and a second repeating unit selected from the following formulas (II) -a and (II) -b:

[0012]

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[0013]

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0.5 g / dl using methylene chloride as a solvent
The reduced solution at 20 ° C. has a reduced viscosity (η _sp / c) of at least 0.3 dl / g and a photoelastic coefficient of 70 × 1.
Achieved by a polycarbonate copolymer, characterized in that it is less than or equal to 0 ^-13 cm ² / dyne and has a glass transition temperature of at least 95 ° C.

The polycarbonate copolymer of the present invention consists essentially of a first repeating unit of the above formula (I) and a second repeating unit selected from the above formulas (II) -a and (II) -b. .

In the above (I), R ¹ and R ² are the same or different and are a methyl group or an ethyl group. R ³ , R ⁴ ,
R ⁵ is an alkyl group having 1 to 6 carbon atoms. Carbon number 1-6
The alkyl group may be linear or branched, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, and an iso-butyl group. , Sec-butyl group, tert-butyl group, n-
Examples include a pentyl group and an n-hexyl group.

The repeating unit represented by the above formula (I) includes, for example,

[0018]

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[0019]

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[0020] Particularly,

[0021]

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Is preferred.

In the above formula (II) -a, R ⁴ and R ⁵
Is the same or different and is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

The alkyl group having 1 to 6 carbon atoms may be linear or branched, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group,
n-butyl group, iso-butyl group, sec-butyl group,
Examples thereof include a tert-butyl group, an n-pentyl group, and an n-hexyl group.

Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a cumyl group and a naphthyl group.

In the group -A-O-, A is a single bond and represents an oxy group (-O-) as a whole or a -O- (alkyl group having 2 to 4 carbon atoms) -O- group. Examples of the alkylene group having 2 to 4 carbon atoms in the latter group include, for example,
Examples thereof include 1,2-ethylene, 1,1-ethylene, 1,3-trimethylene, 1,2-propylene, and 1,4-tetramethylene.

The group represented by X is

[0028]

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Is as follows.

The alkyl group having 1 to ⁶ carbon atoms for R ⁶ and the aryl group having 6 to 10 carbon atoms for Ar can be the same as those exemplified for the above group R ⁴ .

In the above formula (II) -b, R ⁷ and R
⁸ is the same or different and is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. Carbon number 1-6
As the alkyl group and the aryl group having 6 to 10 carbon atoms,
Can be exemplified the same as those exemplified in the above groups R ^4.

The group represented by Y is

[0033]

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Is as follows.

R⁹And R^TenAre the same or different, water
An elemental atom or an alkyl group having 1 to 6 carbon atoms or 6 carbon atoms
10 to 10 aryl groups.
Group R ^FourAnd the same ones as
You.

As the second repeating unit, for example,

[0037]

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[0038]

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[0039]

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[0040]

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Are preferred.

These second repeating units (A) to (K) represented by the formulas (II) -a and (II) -b are present in the polycarbonate copolymer of the present invention in one or more kinds. can do.

The polycarbonate copolymer of the present invention comprises 5 to 95 mol% of the first repeating unit represented by the above formula (I) and the second repeating unit 9 represented by the above formula (II).
Consists of 5-5 mol%. 5 mol% of the first repeating unit
If it is smaller than the above, desired optical properties cannot be obtained, and if it exceeds 95 mol%, the mechanical strength and the polymerizability become insufficient. The first repeating unit is preferably from 7 to 93 mol%, more preferably from 10 to 80 mol%, particularly preferably from 15 to 75 mol%.
It is particularly advantageous that the mol% and the second repeating unit preferably comprise 93 to 7 mol%, more preferably 90 to 20 mol%, particularly preferably 85 to 25 mol%.

In the present invention, the following third repeating unit can be present in the copolymer. In particular, a combination of the second repeating unit selected from the group consisting of (A) to (K) and the third repeating unit selected from the group consisting of (L) to (N) is particularly preferable. . The polycarbonate copolymer has a total of the first repeating range and the second repeating unit of at least 50.
The third repeating unit is occupied by 50% by mole or less, and the ratio of the first repeating unit to the second repeating unit is represented by the following formula.

[0045]

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[0046]

## EQU2 ## Second repeating unit (mol%) / first repeating unit = 5/95 to 95/5 Particularly preferably, the ratio is 25/75 to 85/15.

The polycarbonate copolymer of the present invention has a reduced viscosity (η _sp / c) of at least 0.3 dl / g measured at 20 ° C. as a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent. It is. The preferred reduced viscosity is 0.1.
It is in the range of 3 dl / g to 1.0 dl / g.

The polycarbonate copolymer of the present invention has a photoelastic coefficient of 70 × 10 ⁻¹³ cm ² / dyne or less. 1 × 10 ^-13 cm ² / dyne is 1 Brews
70x10 because it is known as ters (B)
^-13 cm ² / dyne or less can be described as 70 B or less.

The photoelastic coefficient is determined by applying a tensile stress of different magnitude to a test piece (10 mm × 100 mm × 1 mm) of a polycarbonate copolymer in the length direction, measuring the generated birefringence, and

[0050]

C = (n ₁ −n ₂ ) / (σ ₁ −σ ₂ ) [where c is the photoelastic coefficient, and n ₁ and n ₂ are multiples at the first and second tensile stresses, respectively. the refractive index and sigma ₁ and sigma ₂ are calculated from the first and second tensile stress, respectively (dyne / cm ²⁾ represents the. The photoelastic coefficient is preferably 60B or less, more preferably 50B or less.

Further, the polycarbonate copolymer of the present invention has a glass transition temperature of at least 95 ° C. The glass transition temperature is preferably at least 110 ° C, more preferably at least 120 ° C.

The polycarbonate copolymer of the present invention can be industrially advantageously produced by the following production method of the present invention.

That is, the following formula (IV)

[0054]

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[Wherein the definitions of R ¹ , R ² and R ³ are the same as in formula (I). ] The following formula (V)

[0056]

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[Wherein the definitions of R ¹ , R ² , R ³ , X and A are the same as in formula (II). A bisphenol represented by the following formula (VI):

[0058]

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[Where Ar ¹ and Ar ² are the same or different and are phenyl or naphthyl, and these groups are selected from the group consisting of a chlorine atom, an alkyl group having 1 to 6 carbon atoms, a methoxycarbonyl group and an ethoxycarbonyl group. It may be substituted by at least one selected. With the compound of the above formula (IV) and the compound of the above formula (V), based on the sum of the compound of the above formula (IV) and the compound of the above formula (V). To 5 mol% and the above formula (IV)
The compound of the formula (VI) is melt-polycondensed with the compound of the formula (VI) at a ratio of 1.0 to 1.3 mol per 1 mol of the total of the compound of the formula (IV) and the compound of the formula (IV), so that the reduced viscosity is at least 0. 3
By producing a dl / g polycarbonate, a polycarbonate copolymer can be produced.

The compound represented by the above formula (IV) includes, for example, 1,1-bis (3-tert-butyl-4-
(Hydroxycy-6-methylphenyl) -n-butane,
1,1-bis (3-tert-butyl-4-hydroxy-6-methylphenyl) -2-methylpropane, 1,1
-Bis (3-tert-butyl-4-hydroxy-6-
Methylphenyl) -2-methylbutane, 1,1-bis (3-tert-butyl-4-hydroxy-6-methylphenyl) ethane and 1,1-bis (3-tert-
Butyl-4-hydroxy-6-methylphenyl) propane, especially 1,1-bis (3-ter).
t-butyl-4-hydroxy-6-methylphenyl)-
n-Butane is preferred.

The compounds represented by the above formula (V) include, for example, 1-phenyl, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl, 3,3,5- Trimethylcyclohexane, 1,
1-bis (4-hydroxyphenyl) fluorene, 1,
1-bis (4-hydroxy-3-methylphenyl) cyclohexane, 1,4-bis [2- (4-hydroxyphenyl) propyl] benzene, 1,3-bis [2- (4-
Hydroxyphenyl) propyl] benzene, 2,2-bis (3-tert-butyl-4-hydroxyphenyl)
Propane, 2,2-bis (4-hydroxy-3-phenyl) propane, 1,1-bis [4- (2-hydroxyethyloxy) phenyl] fluorene, 2,2-bis (4
-Hydroxyphenyl) propane, bis (4-hydroxyphenyl) ether and bis (4-hydroxyphenyl) sulfone.

In the above formula (VI), Ar ¹ and Ar
² is the same or different and is a phenyl group or a naphthyl group. These groups may be substituted with a chlorine atom, an alkyl group having 1 to 6 carbon atoms, a methoxycarbonyl group or an ethoxycarbonyl group. These substituents may be one kind or two or more kinds.

Examples of the alkyl group having 1 to 6 carbon atoms are the same as those described above for R ^{1 in} formula (I).

The compound represented by the formula (VI) includes, for example, diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-
Chlorophenyl carbonate, di (2-methoxycarbonylphenyl) carbonate, phenyl-2-methoxycarbonylphenyl carbonate, di (2-ethoxycarbonylphenyl) carbonate, and dimethyl-p
-Carbonates may be mentioned as preferred.

The method of the present invention is characterized in that the diaryl carbonate of the above formula (VI) is added in a ratio of 1.0 to 1.3 mol per 1 mol of the compound of the above formula (IV) and the compound of the above formula (V) in total. It is carried out using. The preferred ratio within this range is 1,
005 to 1.10 mol.

The compound of the formula (IV) and the compound of the formula (V), which are diol components, are based on the sum of the compound and the compound of the formula (IV) in an amount of 5 to 95 mol% and the compound of the formula (V)
Is used at 95 to 5 mol%. A preferred ratio is 10 to 90 mol% of the compound of the formula (IV) and 90 to 10 mol% of the compound of the formula (VI).

The melt polycondensation of these compounds is preferably carried out in the presence of a catalyst. As such a catalyst, a catalyst usually used for an esterification reaction or a transesterification reaction can be used. Such compounds include alkali metal compounds, alkaline earth metal compounds, nitrogen-containing basic compounds, zinc compounds, boron compounds, aluminum compounds, silicon compounds, germanium compounds, organotin compounds, dull compounds. , Titanium compounds, osmium compounds, antimony compounds, zirconium compounds and the like. Among them, alkali metal compounds, alkaline earth metal compounds and nitrogen-containing basic compounds are particularly preferably used.

The alkali metal compound and alkaline earth metal compound include, for example, hydroxides, hydrogen carbonates, carbonates, acetates, borohydrides, stearates, benzoates and bisphenols of these metals. Salts and the like can be mentioned.

Specific examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, sodium acetate, Potassium acetate, lithium acetate, sodium stearate, potassium stearate, lithium stearate, sodium benzoate, potassium benzoate, lithium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, dilithium hydrogen phosphate, bisphenol A Disodium salt, dipotassium salt, dilithium salt, phenol sodium salt, potassium salt and lithium salt.

Specific examples of the alkaline earth metal compound include calcium hydroxide, barium hydroxide, magnesium hydroxide, strontium carbonate, calcium hydrogen carbonate, barium hydrogen carbonate, magnesium hydrogen carbonate, strontium hydrogen carbonate, Examples include calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, calcium acetate, barium acetate, magnesium acetate, strontium acetate, calcium stearate, barium stearate, magnesium stearate, and strontium stearate.

Further, as the nitrogen-containing basic compound, for example, tetramethylammonium hydroxide (Me ₄ N
OH), tetraethylammonium hydroxide (Et
₄ NOH), tetrabutylammonium hydroxide alkyl, aryl, ammonium hydroxide oxides having like Aruariru group such as (Bu ₄ NOH), trimethylbenzylammonium hydroxide (phenyl _{-CH 2 (Me) 3 NOH)} , trimethylamine, triethylamine Tertiary amines such as dimethylbenzylamine and triphenylamine; secondary amines represented by the formula R ₂ NH (where R is an alkyl group such as methyl and ethyl, and an aryl group such as phenyl and toluyl); Formula R
Primary amines represented by NH ₂ (where R is the same as above); imidazoles such as 2-methylimidazole, 2-phenylimidazole; ammonium carboxylates such as tetramethylammonium acetate (Me ₄ NOCOCH ₃ ) Or tetramethyl ammonium borohydride (Me ₄ NBH ₄ ), tetrabutyl ammonium tetraphenyl borate (Me ₄ NB)
And basic salts such as Ph ₄ ). These compounds may be used alone or in combination of two or more.

In the case of an alkali metal compound and / or an alkaline earth metal compound, these catalysts are used in an amount of 1 × 10 ^-7 to 1 × 10 ^-4 equivalents, preferably 1 × 10 ^-7 to 1 mol of the diol component. ^{-6 to} 5 × 10 ^-5 equivalents.

The melt polycondensation reaction is carried out by distilling the monohydroxy compound produced by stirring under heating in an inert gas atmosphere as is conventionally known. The reaction temperature is usually in the range of 120 to 350 ° C., and in the late stage of the reaction, the degree of reduced pressure of the system is increased to 10 to 0.1 Torr to facilitate the distillation of the monohydroxy compound produced and complete the reaction.

According to the above method, the novel polymer of the present invention can be obtained. Antioxidants, if necessary
Additives such as an ultraviolet absorber and a release agent can be blended.

The novel polycarbonate polymer of the present invention can be advantageously used as a material for an information transmission medium such as an optical fiber or a material for an information recording medium such as an optical disk because of its excellent transparency.

[0076]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 As a diol component, 1,1-
306 parts (0.8 mol) of bis (3-tert-butyl-4-hydroxy-6-methylphenyl) -n-butane and 2,2-bis (3-tert-butyl-4-hydroxyphenyl) propane 68 Parts by weight (0.2 mol)
225 parts by weight (1.05 mol) of diphenyl carbonate as a carbonate-forming compound and 9.1 × 10 ⁻³ of tetramethylammonium hydroxide as a catalyst.
Parts by weight and 4 × 10 ⁻⁴ parts by weight of sodium hydroxide were charged into a reaction vessel equipped with a stirrer, a rectification tower and a decompression device, and the mixture was purged with nitrogen and then melted by heating. After stirring for 30 minutes, the internal temperature is reduced to 1
The pressure was gradually reduced while the temperature was raised to 80 ° C., and the reaction was carried out at 100 mmHg for 30 minutes while distilling off the phenol produced.

Next, after the temperature was raised to 200 ° C., the pressure was gradually reduced, and the reaction was carried out at 50 mmHg for 20 minutes while distilling off phenol. Further, the temperature was gradually raised and reduced to 220 ° C./30 mmHg, and the same temperature and pressure were applied for 20 minutes.
The temperature was repeatedly increased and reduced by the same procedure as described above until the temperature was reduced to 10 mmHg or less and 280 ° C / 1 mmHg or less, and the reaction was continued.

The polymer obtained had a reduced viscosity [η _sp / c] at 20 ° C. of a solution using methylene chloride as a solvent of 0.1.
It was 35 dl / g. The glass transition temperature of the obtained polymer was 150 ° C. as measured with a thermal analyzer (2000 type DSC) manufactured by DuPont. In addition, the polymer is
The film was formed into a 00 μm film and measured with a photoelastic coefficient measuring device (PA-150) manufactured by Riken Keiki. The photoelastic coefficient was as low as 46 × 10 ⁻¹³ cm ² / dyne.
(Similar measurements were made for the following examples and comparative examples.) [Example 2] 1,1-bis (3-t as a diol component
153 parts by weight (0.4 mol) of tert-butyl-4-hydroxy-6-methylphenyl) -n-butane and 2,2
-Bis (3-tert-butyl-4-hydroxyphenyl) propane 34 parts by weight (0.1 mol), bisphenol A 114 parts by weight (0.50 mol), and diphenyl carbonate 225 parts by weight (1. And 9.1 × 10 ⁻³ parts by weight of tetramethylammonium hydroxide and 4 × 10 ⁻⁴ parts by weight of sodium hydroxide as a catalyst in a reaction vessel equipped with a stirrer, a rectification column and a decompression device. After the replacement with nitrogen, the mixture was heated and melted. After stirring for 30 minutes, the internal temperature was gradually raised to 180 ° C. and the pressure was gradually reduced.
The reaction was performed at 00 mmHg for 30 minutes.

Next, after the temperature was raised to 200 ° C., the pressure was gradually reduced, and the reaction was carried out at 50 mmHg for 20 minutes while distilling off phenol. Further, the temperature was gradually raised and reduced to 220 ° C./30 mmHg, and the same temperature and pressure were applied for 20 minutes.
The temperature was repeatedly increased and reduced by the same procedure as described above until the temperature was reduced to 10 mmHg or less and 280 ° C / 1 mmHg or less, and the reaction was continued.

The obtained polymer had a reduced viscosity [η _sp / c] at 20 ° C. of a solution using methylene chloride as a solvent of 0.1.
It was 41 dl / g. The glass transition temperature of the obtained polymer was 150 ° C. as measured with a thermal analyzer (2000 type DSC) manufactured by DuPont. In addition, the polymer is
The film was formed into a 00 μm film and measured with a photoelastic coefficient measuring device (PA-150) manufactured by Riken Keiki. As a result, the photoelastic coefficient was as low as 48 × 10 ⁻¹³ cm ² / dyne.
(Similar measurements were also performed for the following Examples and Comparative Examples.) [Examples 3 to 16] The materials shown in Tables 1 to 5 were used, and the materials shown in Tables 1 to 5 were shown in the same manner as in Example 1. A polycarbonate polymer having properties was obtained.

[0082]

[Table 1]

[0083]

[Table 2]

[0084]

[Table 3]

[0085]

[Table 4]

[0086]

[Table 5]

[Comparative Example 1] 2,2-
The reaction was carried out in the same manner as in Example 1 except that 228 parts by weight of bis (4-hydroxyphenyl) propane was used to obtain a polymer.

The resulting polymer had a reduced viscosity [η _sp / c] at 20 ° C. of a solution using methylene chloride as a solvent of 0.1.
It was 49 dl / g.

The glass transition temperature of the obtained polymer is 149 ° C.
The photoelastic coefficient was 79 × 10 ⁻¹³ cm ² / dyne, which was a high value.

Comparative Example 2 As a diol component, 1,1-
The reaction was carried out in the same manner as in Example 1 except that only 383 parts by weight (1.0 mol) of bis (3-tert-butyl-4-hydroxy-6-methylphenyl) -n-butane was used.

The polymer obtained had a reduced viscosity [η _sp / c] at 20 ° C. of a solution using methylene chloride as a solvent of 0.1.
It was 33 dl / g.

The glass transition temperature of the obtained polymer was 160.
° C. In addition, the strength was insufficient, and a film having a strength sufficient to measure the photoelastic coefficient could not be produced.

[0093]

As described above, the polycarbonate copolymer of the present invention has a smaller photoelastic effect and a smaller birefringence due to less molding distortion than conventional polycarbonate resins, and has excellent optical properties. It is.

The polycarbonate synthesized from a bisphenol having a specific substituted structure represented by the formula (I) and a carbonate-forming compound was inferior in mechanical strength. By carrying out copolymerization with a compound, a polycarbonate having excellent optical properties and sufficient heat resistance and mechanical strength can be obtained.

Therefore, the polycarbonate of the present invention can be used for optical devices such as optical discs.
It can be effectively used as a material for various industrial equipment.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Katsushi Sasaki 2-1 Hinodecho, Iwakuni-shi, Yamaguchi Prefecture Teijin Limited Iwakuni Research Center

Claims (8)

[Claims] 1. A compound represented by the following formula (I): [Where R ¹ and R ² are the same or different and are a methyl group or an ethyl group, and R ³ is an alkyl group having 1 to 6 carbon atoms. ]
And 5 to 95 mol% of a first repeating unit represented by the formula: and 95 to 5% of a second repeating unit selected from the following formulas (II) -a and (II) -b. Embedded image The reduced viscosity (η _sp / c) at 20 ° C. of a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent is at least 0.
3 dl / g and a photoelastic coefficient of 70 × 10 ⁻¹³ cm ²
/ Dyne or less and a glass transition temperature of at least 95 ° C. 2. The first repeating unit 15 according to claim 1,
2. The polycarbonate copolymer according to claim 1, comprising about 75 mol% and 85 to 25 mol% of a second repeating unit. (A) a first repeating unit according to claim 1; (b) a second repeating unit according to claim 1; and (c) a small amount selected from the group consisting of the following formula (III): Both are composed of one type of third repeating unit. The sum of the first repeating unit and the second repeating unit accounts for at least 50 mol%, and the third repeating unit accounts for 50 mol%.
The reduced viscosity (η _sp / c) at 20 ° C. of a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent is at least 0.
3 dl / g and a photoelastic coefficient of 70 × 10 ⁻¹³ cm ²
/ Dyne or less and a glass transition temperature of at least 95 ° C. 4. The polycarbonate copolymer according to claim 3, wherein the ratio of the first repeating unit to the second repeating unit is represented by the following formula. ## EQU1 ## Second repeating unit (mol%) / first repeating unit (mol%) = 5/95 to 95/5 5. An information transmission medium comprising the polycarbonate copolymer according to claim 1 as a material. 6. An information recording medium comprising the polycarbonate copolymer according to claim 1 as a material. 7. An information transmission medium comprising the polycarbonate copolymer according to claim 3 as a material. 8. An information recording medium comprising the polycarbonate copolymer according to claim 3 as a material.