JPH0584576B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an optical disk made of a polycarbonate copolymer used in an optical information recording disk that records a signal using a laser beam or reads out the recorded signal by reflecting or transmitting the laser beam. (Prior art) A spot beam of a laser beam is applied to a disk, and signals are recorded on the disk using minute pits, or signals recorded by such pits are read out by detecting the amount of reflected or transmitted light of the laser beam. DRAW (Direct Read After Write), Erasable-DRAW (Erasable-Direct Read After Write)
The optical information recording and reproducing method can significantly increase the recording density, especially with the Erasable-DRAW type, which allows erasure of records. Since it is possible to write on it, and the images and sound quality reproduced from them have excellent characteristics, it is expected that it will be widely put to practical use in recording and 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, molecular orientation, and residual stress due to volume changes near the glass transition point. This large optical non-uniformity caused by birefringence is a fatal defect for optical disks. (Problems to be Solved by the Invention) As described above, birefringence mainly caused by thermal stress, molecular orientation, and residual stress generated during the cooling and flow process of the resin during disk molding can be controlled by selecting the forming conditions. Although the birefringence of the resulting disk can be considerably reduced, it is highly dependent on the inherent birefringence of the molded resin itself, that is, the photoelastic constant. (Means to solve the problem) Birefringence is expressed as the product of photoelastic constant and residual stress as follows:
It can be expressed by equation (1). n ₁ - n ₂ = C (σ ₁ - σ ₂ ) (1) n ₁ - n ₂ : Birefringence σ ₁ - σ ₂ : Residual stress C: Photoelastic constant From equation (1), if the photoelastic constant is made smaller, It is clear that the birefringence of the disc obtained is smaller even if the molding conditions are the same. Therefore, the inventors 2,2-
bis-(4-hydroxyphenyl)propane and 2,
By copolymerizing 2-bis-(4-hydroxy-3-tertiarybutylphenyl)propane through carbonate bonds, a resin with a small photoelastic constant can be obtained without impairing the mechanical properties of aromatic polycarbonate. The present invention was developed based on the discovery of the fact that (Structure of the Invention) The present invention comprises 95 to 5 mol% of 2,2-bis-(4-hydroxyphenyl)propane (I) and 2,2-bis-(4-hydroxy-3-tert-butylphenyl). This invention relates to an optical disc made of an aromatic polycarbonate copolymer obtained by carbonate bonding with 5 to 95 mol% of propane (). Thus, according to the invention, the following formula (I),
An aromatic polycarbonate copolymer obtained by copolymerizing bisphenols represented by () through carbonate bonds is provided.

[ka]

[Image Omitted] Furthermore, the structural unit of formula () is preferably 10 to 90 mol%. This is because when the structural unit of formula () is less than 10 mol %, the photoelastic constant of the resulting aromatic polycarbonate is not much different from that of the homopolycarbonate of formula (I). Moreover, when the structural unit of formula () exceeds 90 mol %, the glass transition point of the aromatic polycarbonate obtained is significantly lower than that of the homopolycarbonate of formula (I). In addition, the viscosity average molecular weight of the copolymer of the present invention is preferably 13,000 to 50,000. 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. There are the following two methods for producing the polycarbonate copolymer of the present invention. Transesterification method 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-(4-hydroxy-3-
An inert gas is introduced into a slightly stoichiometrically equivalent excess of diphenyl carbonate to a mixture of tert-butylphenyl (tertiary butyl phenyl) propane at a temperature of about 160 to 180° C. under normal pressure in the presence of a conventional carbonation catalyst. React for about 30 minutes under the same conditions for about 2 to 3 hours.
The precondensation is completed at a temperature of 180 to 220°C while gradually reducing the pressure over time, and finally at 10 Torr and 220°C. After that, 10 Torr, 30 minutes at 270℃, 5 Torr,
The reaction is carried out at 270° C. for 20 minutes, and the condensation is continued at 270° C. for 1.5 to 2.0 hours under reduced pressure of less than 0.5 Torr, preferably 0.3 Torr to 0.1 Torr. For carbonate bonding, alkali metal or alkaline earth metal catalysts such as lithium-based catalysts, potassium-based catalysts, sodium-based catalysts, calcium-based catalysts, and tin-based catalysts are suitable as carbonation catalysts, such as lithium hydroxide, carbonate, etc. Lithium, potassium borohydride,
Examples include potassium hydrogen phosphate, sodium hydroxide, sodium borohydride, calcium hydride, dibutyltin oxide, and stannous oxide. Among these, it is preferable to use a potassium catalyst. Phosgene method Attach a stirrer, thermometer, gas inlet pipe, and exhaust pipe to a three-necked flask. 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-
A mixture of (4-hydroxy-3-tertiarybutylphenyl)propane is dissolved in pyridine, and the mixture is vigorously stirred while phosgene gas is introduced. Since phosgene is extremely poisonous, 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 using 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 bubbles), 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 out and the mixture becomes cloudy. Cool with water so that the reaction temperature is 30°C or less. As condensation progresses, it becomes sticky. Phosgene is passed through the mixture until the yellow color of the phosgene-hydrogen chloride complex no longer disappears. After the reaction is completed, methanol is added to precipitate the polymer, which is then filtered and dried. The polycarbonate produced is methylene chloride,
Since it is soluble in pyridine, chloroform, tetrahydrofuran, etc., it is purified by reprecipitation from these solutions with methanol. The polycarbonate copolymer thus obtained is useful for DRAW and Erasable-DRAW optical information recording disks that record signals using laser beams or read out recorded signals by reflection or transmission of laser beams. . EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. Example 1 192 parts by weight (50 mol%) of 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-
122 parts by weight (50 mol%) of (4-hydroxy-3-tert-butylphenyl)propane and 264 parts by weight of diphenyl carbonate were placed in a three-necked flask, and degassing _{and N2} purging were repeated five times.
It was melted in a silicon bath at 160°C while introducing nitrogen. Once melted, add a solution of potassium borohydride, which is a carbonation catalyst, dissolved in phenol (10 ^-3 based on the total amount of bisphenol charged).
(mol% amount) was added and stirred and incubated at 160°C under N ₂ for 30 minutes. Next, at the same temperature, the pressure was increased to 100 Torr, and after stirring for 30 minutes, the pressure was further reduced to 50 Torr at the same temperature, and the pressure was reduced to 60 Torr.
It was allowed to react for a minute. Then gradually increase the temperature to 220℃
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 10 Torr at the same temperature, and the reaction was allowed to proceed for 30 minutes, and the temperature was gradually increased to 270°C.
The mixture was raised to ℃ and allowed to react for 30 minutes. Furthermore, 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 for 2 hours at 0.1 to 0.3 Toor.
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 v=23000. Example 2 A three-necked flask is equipped with a stirrer, a thermometer, a gas inlet pipe, and an exhaust pipe. 2,2- in dichloromethane
Dissolve 192 parts by weight of bis-(4-hydroxyphenyl)propane and 122 parts by weight of 2,2-bis-(4-hydroxy-3-tert-butylphenyl)propane, add a 10% by weight aqueous solution of sodium hydroxide, and dissolve. Phosgene gas was introduced while stirring vigorously. 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 water-cooled so as to be below 25°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 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, dry thoroughly and heat at 20℃ using dichloromethane as a solvent.
The solution viscosity was measured. The viscosity calculated from this value was measured. The viscosity average molecular weight calculated from this value was v=26,000. (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, the polycarbonate copolymers described in Examples 1 and 2 were molded into a disc-shaped substrate with a diameter of 130 mm and a thickness of 1.2 mm using an injection molding machine (manufactured by Meiki Seisakusho, Dynamelter), and Tb was applied onto this substrate. Sputtering equipment (RF sputtering equipment, manufactured by Japan Vacuum Co., Ltd.) using an alloy target of _23.5 Fe _64.2 Co _12.3 (atomic%)
A magneto-optical recording film with a thickness of 1000 Å was formed inside. On this recording film, a protective film of 1000 Å of inorganic glass as described in Japanese Patent Application Laid-open No. 177449/1983 by the present applicant was formed using the same sputtering apparatus as above. The performance of the obtained magneto-optical disk was measured by CN ratio, BER and 60℃90RH%.
It was evaluated by the rate of change in CN ratio under the following conditions. The results were as shown in Table 1.

[Table] As is clear from the results in Table 1, the polycarbonate copolymer according to the present invention has a lower birefringence value.
It can be seen that the CN ratio has been significantly improved and the durability is also excellent.

Claims (1)

[Claims] 1 2,2-bis-(4-hydroxyphenyl)
An optical formula consisting of an aromatic polycarbonate copolymer obtained by carbonate bonding of 95 to 5 mol% of propane and 5 to 95 mol% of 2,2-bis-(4-hydroxy-3-tert-butylphenyl)propane. disc.