JPS63154733A - Optical disc - Google Patents

Abstract

PURPOSE:To make it possible to reduce the double refraction of an optical disc by decreasing the photoelastic constant of an aromatic polycarbonate, by forming the disc from an aromatic polycarbonate copolymer obtained by copolymerizing two specified bisphenols through carbonate bonds. CONSTITUTION:This optical disc is formed from an aromatic polycarbonate copolymer obtained by copolymerizing 97-3mol% at least one member selected from among 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)-4- methylpentane and 2,2-bis(4-hydroxyphenyl)octane with 3-97mol% 2,2-bis(4- hydroxy-3-tert-butylphenyl)propane through carbonate bonds. It is preferable that the viscosity-averge MW of said copolymer is 13,000-50,000.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a polycarbonate copolymer used in optical information recording disks that record signals using laser beams or read out recorded signals by reflection or transmission of laser beams. Concerning an optical disc consisting of a combination.

(Prior art) A DRAW (direct) method in which a spot beam of a laser beam is applied to a disk and signals are recorded on the disk using minute pits, or the signals recorded by such pits are read out by detecting the amount of reflected or transmitted light of the laser beam.

Read, After Write), Erasable-DR
AW (Erasable, Direct Read After)
The write) type optical information recording and reproducing method can significantly increase the recording density, and the Erasable-DRAW type in particular allows erasing and writing of records, and the images and sound quality reproduced from them have excellent characteristics. Therefore, it is expected that it will be widely put to practical use in recording or reproducing images and sound quality, recording and reproducing large amounts of information, etc. The disks used in this recording/reproducing system are required not only to be transparent because the laser beam passes through the disk body, but also to have optical homogeneity to reduce reading errors. Birefringence occurs when the laser beam passes through the disk body, mainly due to thermal stress generated during the cooling and flow process of the resin during disk body formation, residual stress due to bimolecular orientation and volume change near the glass transition point. This large optical non-uniformity caused by birefringence is a fatal defect for optical discs.

(Problem to be solved by the invention) As described above, birefringence, which is mainly caused by the thermal stress bimolecular orientation and residual stress generated during the cooling and flow process of the resin during disk molding, can be obtained by selecting the forming conditions. Although the birefringence of the disk can be made considerably small, it is highly dependent on the inherent birefringence of the molding resin itself, that is, the photoelastic constant.

(Means for solving the problem) Birefringence can be expressed by the following equation (1) as a product of a photoelastic constant and a residual stress.

nl-n2=C(al-a2) (1)
nx-n2: Birefringence σ1-0□: Residual stress C: Photoelastic constant It is clear from equation (1) that if the photoelastic constant is made smaller, the birefringence of the disc obtained will be smaller even if the molding conditions are the same. Therefore, the inventors developed 2,2-bis, (4-hydroxyphenyl)butane, and 2,2-bis.

(4-hydroxyphenyl)-4-methylpentane, 2
．． One selected from 2-bis-(4-hydroxyphenyl)octane and 2,2-bis-(4-hydroxy-
The present invention was based on the discovery that a resin with a small photoelastic constant can be obtained without impairing the mechanical properties of aromatic polycarbonate by copolymerizing it with 3-tert,-butylphenyl)propane through a carbonate bond. be.

(Structure of the Invention) The present invention provides 2,2-bis-(4-hydroxyphenyl)butane (I), 2.2-bis-(4-hydroxyphenyl)-4-methylpentane (II), 2.2- Bis-(4
-Hydroxyphenyl)octane (III) 97 to 3 mol% and 2,2-bis, (4-hydroxy-3-tert, -butylphenyl)propane (■) 3 to 97 mol%. This invention relates to an optical disc made of an aromatic polycarbonate copolymer obtained by carbonate bonding. Thus, according to the present invention, there is provided an aromatic polycarbonate copolymer obtained by copolymerizing bisphenols represented by the following formulas (I), (II), (III), and (IV) through carbonate bonds.

Moreover, the structural unit of formula (IV) is preferably 10 to 90 mol%. This is because the structural unit of formula (IV) is 10 mol%
The photoelastic constant of the resulting aromatic polycarbonate is not much different from that of the homopolycarbonate formed by formulas (I), (II), and (III). Furthermore, aromatic polycarbonates obtained when the structural unit of formula (IV) exceeds 90 mol% are of formulas (I), (II), (
It is more brittle than the homopolycarbonate consisting of III). In addition, the viscosity average molecular weight of the copolymer of the present invention is 13,
000 to 50,000 is preferred. If it is less than 13,000, the copolymer will become brittle, and if it exceeds 50,000, the copolymer will have poor flow and poor moldability.

Furthermore, it is also possible to copolymerize the third component.

The method for producing the polycarbonate copolymer of the present invention includes:
There are two methods:

■Transesterification method 2.2-bis-(4-hydroxyphenyl)butane,
2.2-bis-(4-hydroxyphenyl)-4-methylpentane.

2. one selected from 2-bis-(4-hydroxyphenyl)octane; A slight excess of the stoichiometric equivalent of diphenyl power to the mixture of bis-(4-hydroxy-3-tert,-butylphenyl)propane.
carbonate in the presence of a conventional carbonation catalyst.
React for about 30 minutes at a temperature of ~180°C under normal pressure and with inert gas introduced, and finally at a temperature of 180 to 220°C while gradually reducing the pressure over a period of about 2 to 3 hours. Precondensation is completed under 10 Torr and 2208C. Then, 30 minutes at 10 Torr, 270°C, 5 Torr
.

React for 20 minutes at 270°C, then reduce the temperature to 0.5 Torr or less, preferably 0.3 Torr to 0.5 Torr. The condensation is carried out after 1°5 hours to 2.0 hours at 2700 C under a vacuum of ITorr. In addition, carbonation catalysts for carbonate bonding include alkali metals such as lithium-based catalysts, potassium-based catalysts, sodium-based catalysts, calcium-based catalysts, and tin-based catalysts;
Alkaline earth metal catalysts are suitable, such as lithium hydroxide, lithium carbonate, potassium borohydride, potassium hydrogen phosphate, sodium hydroxide, sodium borohydride, calcium hydride, dibutyltin oxide, stannous oxide. It will be done. Among these, it is preferable to use a potassium catalyst.

■Phosgene method Attach a stirrer, thermometer, gas inlet pipe, and exhaust pipe to the three-bottle flask. selected from 2,2-bis-(4-hydroxyphenyl)butane, 2,2-bis-(4-hydroxyphenyl)-4-methylpentane, 2,2-bis-(4-hydroxyphenyl)octane one and two, two
A mixture of -bis-(4-hydroxy-3-tert,-butylphenyl)propane is dissolved in pyridine, and while vigorously stirring, phosgene gas is introduced, but since phosgene is highly toxic, the process is carried out in a strong fume hood. Additionally, a unit is installed at the exhaust end to decompose and detoxify excess phosgene with a 10% sodium hydroxide aqueous solution. Phosgene is introduced into the flask through the air wash bottle from the cylinder, the air wash bottle containing paraffin (count the number of ponds), and the empty air wash bottle. The glass introduction tube should be inserted into the top of the stirrer, and the tip should be widened into a funnel shape to prevent it from becoming clogged by precipitated pyridine salt. As gas is introduced, pyridine hydrochloride precipitates and the contents become cloudy. Cool with water so that the reaction temperature is 30°C or less. As condensation progresses, it becomes viscous. Phosgene is passed through the mixture until the yellow color of the phosgene-hydrogen chloride complex no longer disappears.

After the reaction is complete, methanol is added to precipitate the polymer,
Filter and dry. Since the polycarbonate produced is soluble in methylene chloride, pyridine, chloroform, tetrahydrofuran, etc., it is purified by reprecipitation from these solutions with methanol. The polycarbonate copolymer obtained in this way can be used for DRAW, Erasable-D, etc., which record signals using laser beams or read out signals recorded by reflection or transmission of laser beams.
This is useful for RAW optical information recording discs. EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 2.2-bis-(4-hydroxyphenyl)butane 14
5 (50 mo 1%), 204 parts by weight (50 mo 1%) of 2,2-bis-(4-hydroxy-3-tert,-butylphenyl)propane, and 264 parts by weight of diphenyl carbonate were placed in a three-bottle flask and desorbed. Qi, N2
After repeating the purge 5 times, silicone bath at 160°C''
'c It was melted while introducing nitrogen. Once melted, add a solution of potassium borohydride, which is a carbonation catalyst, dissolved in phenol (10-3 mo1% amount based on the total amount of bisphenol charged), and heat at 160°C with N2.
Next, the mixture was incubated for 30 minutes. Next, under the same temperature, 100T
The pressure was reduced to 500 m Torr and the mixture was incubated for 30 minutes, and then the pressure was further reduced to 5 Q Torr and reacted for 60 minutes at the same temperature. Next, the temperature was gradually raised to 220° C. and the reaction was continued for 60 minutes, and 80% of the theoretical amount of phenol was distilled out through the reaction up to this point. Thereafter, the pressure was reduced to 1 Q Torr at the same temperature, and the reaction was carried out for 40 minutes.The temperature was gradually raised to 270°C, and the reaction was carried out for 30 minutes. Furthermore, the pressure was reduced to 5 Torr at the same temperature, and the reaction was allowed to proceed for 30 minutes, and almost the entire amount of phenol, theoretically calculated, was distilled out to complete the precondensation. Next, condensation was carried out at the same temperature at 0.1 to Q and 3 Torr for 2 hours. After the product polymer was taken out and cooled under nitrogen, the solution viscosity was measured at 20°C using dichloromethane as a solvent. The viscosity average molecular weight calculated from this value was Mv=19,500.

Example 2 A three-hole flask is equipped with a stirrer, a thermometer, a gas inlet pipe, and an exhaust pipe. 2,2 in dichloromethane. Dissolve 145 parts by weight of bis-(4-hydroxyphenyl)butane and 204 parts by weight of 2,2-bis-(4-hydroxy-3-tert,-butylphenyl)propane, and add 1 part by weight of sodium hydroxide.
A 0% by weight aqueous solution was added and the mixture was vigorously stirred while phosgene gas was introduced. Phosgene was introduced from the cylinder into the flask through an empty air wash bottle, a water filled air wash bottle, and an empty air wash bottle. The reaction temperature during the introduction of phosgene gas was 25
It was water-cooled to below °C. As the condensation progresses, the solution becomes viscous. Further, phosgene was passed through the mixture until the yellow color of the phosgene-hydrogen chloride complex no longer disappeared. After the reaction was completed, the reaction solution was poured into methanol, filtered, and washed with water repeatedly. Furthermore, the produced polycarbonate was purified by reprecipitation with methanol from a dichloromethane solution. After purification and drying thoroughly, use dichloromethane as a solvent at 20°
Solution viscosity was measured at C. The viscosity calculated from this value was measured. The viscosity average molecular weight calculated from this value is Mv=
It was 20,000.

Example 3 162 parts by weight (50 mo1%) of 2.2-bis-(4-hydroxyphenyl)-4-methylpentane and 204 parts by weight of 2,2-bis,(4-hydroxy-3-tert,-butylphenyl)propane Fl (50 mo 1%) and 264 parts by weight of diphenyl carbonate were put into a 31 molar flask, degassed and N2 purged 5 times, and then melted while introducing a silicon bath at 160°C'CM. Once melted, add a solution of potassium borohydride, which is a carbonation catalyst, dissolved in phenol (10-3 mo1% amount based on the total amount of bisphenol charged),
The mixture was stirred and incubated at 0°C under 2N2 for 30 minutes. Next, at the same temperature, the mixture was stirred for 30 minutes at 1QQ Torr, and then the pressure was further reduced to 5QTorr at the same temperature, and the mixture was allowed to react for 60 minutes. Next, the temperature was gradually raised to 220° C. and the reaction was continued for 60 minutes, and 80% of the theoretical amount of phenol was distilled out through the reaction up to this point. After that, the pressure was reduced to 1QTo, rr at the same temperature, and 4
After reacting for 0 minutes, the temperature was gradually raised to 270°C and reacting for 30 minutes. Further, at the same temperature, the pressure was reduced to 5 Torr and the reaction was allowed to proceed for 30 minutes, and almost all of the theoretical amount of phenol was distilled out to complete the precondensation. Next, under the same temperature, 0.1~Q, 3 Tor
Condensation was carried out for 2 hours at r. After taking out the product polymer under nitrogen and cooling it, dichloromethane was used as a solvent and 2
Solution viscosity was measured at 0°C. The viscosity average molecular weight calculated from this value was Mv=18,000.

Example 4 A three-hole flask is equipped with a stirrer, a thermometer, a gas inlet pipe, and an exhaust pipe. 162ffi of 2,2-bis-(4-hydroxyphenyl)-4-methylpentane in dichloromethane
Quantity part and 2,2. bis-(4-hydroxy-3-tert
, -butylphenyl)propane (204 parts by weight) was dissolved,
A 10% by weight aqueous solution of sodium hydroxide was added and the mixture was vigorously stirred while phosgene gas was introduced. Phosgene was introduced from the cylinder into the flask through an empty air wash bottle, a water filled air wash bottle, and an empty air wash bottle.

The reaction temperature during introduction of phosgene gas was water-cooled to 25°C or less. As the condensation progresses, the solution becomes viscous. Further, phosgene was passed through the mixture until the yellow color of the phosgene-hydrogen chloride complex no longer disappeared. After the reaction was completed, the reaction solution was poured into methanol, filtered, and washed with water repeatedly. Furthermore, the produced polycarbonate was purified by reprecipitation with methanol from a dichloromethane solution. After purification and thorough drying, the solution viscosity was measured at 20°C using dichloromethane as a solvent. The viscosity calculated from this value was measured. The viscosity average molecular weight calculated from this value was Mv=19,800.

Example 5 2.2-bis-(4-hydroxyphenyl)octane 1
79 parts by weight (50 mo1%), 204 parts by weight of 2,2-bis-(4-hydroxy-3-tert,-butylphenyl)propane (50 mo1%), and 264 parts by weight of diphenyl carbonate were placed in a 31-mole flask. After repeating degassing and N2 purge 5 times, silicon bath 160
It was melted at 0.degree. C. while nitrogen was being introduced. Once melted, add a solution of potassium borohydride, which is a carbonation catalyst, dissolved in phenol (10-3 mo1% amount based on the total amount of bisphenol charged), and heat at 160°C2N.
2, and stirred and brewed for 30 minutes. Next, under the same temperature, 1QQ
After stirring for 30 minutes at Torr, stir for another 5 minutes at the same temperature.
The pressure was reduced to QTorr and the reaction was carried out for 60 minutes. Next, the temperature was gradually raised to 220° C. and the reaction was continued for 60 minutes, and 80% of the theoretical amount of phenol was distilled out through the reaction up to this point. Thereafter, the pressure was reduced to 1 Q Torr at the same temperature, and the reaction was carried out for 40 minutes.The temperature was gradually raised to 270°C, and the reaction was carried out for 30 minutes. Further, at the same temperature, the pressure was reduced to 5 Torr and the reaction was allowed to proceed for 30 minutes, and almost all of the theoretical amount of phenol was distilled out to complete the precondensation. Next, condensation was carried out at the same temperature at 0.1 to Q and 3 Torr for 2 hours. After the product polymer was taken out and cooled under nitrogen, the solution viscosity was measured at 20°C using dichloromethane as a solvent. The viscosity average molecular weight calculated from this value was Mv=18,000.

Example 6 A three-hole flask is equipped with a stirrer, a thermometer, a gas inlet pipe, and an exhaust pipe. Dissolve 179 parts by weight of 2,2-bis-(4-hydroxyphenyl)octane and 204 parts by weight of 2゜2-bis-(4-hydroxy-3-tert,-butylphenyl)propane in dichloromethane, and add 10 parts by weight of sodium hydroxide. % aqueous solution was added and the mixture was vigorously stirred while phosgene gas was introduced. Phosgene was introduced from the cylinder into the flask through an empty air wash bottle, a water filled air wash bottle, and an empty air wash bottle. The reaction temperature during the introduction of phosgene gas is 2
It was water-cooled to 56C or less. As the condensation progresses, the solution becomes viscous. Further, phosgene was passed through the mixture until the yellow color of the phosgene-hydrogen chloride complex no longer disappeared. After the reaction was completed, the reaction solution was poured into methanol, filtered, and washed with water repeatedly. Furthermore, the produced polycarbonate was purified by reprecipitation with methanol from a dichloromethane solution. After purification and thorough drying, dichloromethane was used as a solvent for 20
Solution viscosity was measured at °C. The viscosity calculated from this value was measured. The viscosity average molecular weight calculated from this value is Mv
=19,000.

(Evaluation of recording properties) A recording film was attached to the polycarbonate copolymer produced as described above, and the optical recording properties were evaluated. That is, Example 1
The polycarbonate copolymer described in , 2, 3, 4, and 5.6 was molded into a disc-shaped substrate with a diameter of 130 mm and a thickness of 1° to 2 mm using an injection molding machine (manufactured by Multiki Seisakusho, Dynamelter). Tb23゜5Fe64.2co12 on the substrate
．． Sputtering equipment (RF sputtering equipment, manufactured by Japan Vacuum Co., Ltd.) using an alloy target of 3 (atomic %)
Among them, 1,000 people formed magneto-optical recording films. On this recording film, inorganic glass protective films i and ooo described in Japanese Patent Application Laid-open No. 177449/1983 by the present applicant were formed using the same sputtering apparatus as above. The performance of the obtained magneto-optical disk was evaluated by the CN ratio, BER, and the rate of change of CN ratio under the conditions of 60° C. and 90 RH%. The results are shown in Table 1.

Table 1 (Note 1) CN ratio = writing power 7mW (milliwatt)
.

Measured at read power 1mW, carrier frequency IMHz, 30KHz in resolution band (Note 2) CN change rate (%) = 600 with respect to initial CN ratio
C.

Comparative example of degree of decrease in CN ratio after 30 days under 90RH% condition (Note 3) = conventionally known polycarbonate (Ondaikasei)
A magneto-optical disk was fabricated using a substrate manufactured by AD-5503) manufactured by Co., Ltd. in the same manner as above.

As is clear from the results in Table 1, the polycarbonate copolymer according to the present invention has a significantly improved CN ratio due to a decrease in birefringence value, and is also found to have excellent durability.

Claims (1)

[Claims] 2,2-bis-(4-hydroxyphenyl)butane, 2
, 2-bis-(4-hydroxyphenyl)-4-methylpentane, 2,2-bis-(4-hydroxyphenyl)
97-3 mol% of a type selected from octane and 2,
An optical disc made of an aromatic polycarbonate copolymer obtained by carbonate bonding with 3 to 97% of 2-bis-(4-hydroxy-3-tert.-butylphenyl)propane.