JPS6389533A - Optical disc - Google Patents

Abstract

PURPOSE:To obtain a low-photoelastic constant aromatic polycarbonate copolymer for optical discs, by bonding 1,1'-bis(4-hydroxyphenyl)-p-diisopropylbenzene to 4,4-dihydroxy-2,2,2-triphenylethane through a carbonate bond. CONSTITUTION:This optical disc is formed from an aromatic polycarbonate copolymer obtained by bonding 97-3mol% 1,1'-bis(4-hydroxyphenyl)-p- diisopropylbenzene to 3-97mol% 4,4-dihydroxy-2,2,2-triphenylethane through a carbonate bond. The viscosity-average MW of said copolymer is preferably 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) DRAW (Direct RAW) is a 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 signals recorded by such pits are read out by detecting the amount of reflected or transmitted light of the laser beam. Read After Write), Erasab
le-DRAW (Erasable Direct Read)
The after-write (after-write) type optical information recording and reproducing system can significantly increase the recording density, especially in Erasable-D.
The RAW type allows erasing and writing of records, and the images and sound quality reproduced from them have excellent characteristics, so it is widely used for recording and reproducing images and sound quality, recording and reproducing large amounts of information, etc. It is expected that. 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 proposed that 1,1'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene and 4
, 4-dihydroxy-2,2,2-triphenylethane through carbonate bonding, it was discovered that a resin with a small photoelastic constant can be obtained without impairing the mechanical properties of aromatic polycarbonate, and the present invention is based on this discovery. This is what we have come to.

(Structure of the Invention) The present invention relates to 1.1'-bis, (4-hydroxyphenyl)
- Aromatic polycarbonate obtained by carbonate bonding of 97 to 3 mol% of p-diisopropylbenzene (I) and 3 to 97 mol% of 4,4'-dihydroxy-2,2,2-)liphenylethane (II) This invention relates to an optical disc made of a copolymer. Thus, according to this invention,
An aromatic polycarbonate copolymer obtained by copolymerizing bisphenols represented by the following formulas (I) and (II) through carbonate bonds is provided.

(I) (II) Moreover, the structural unit of formula (II) is preferably 10 to 90 mol%. This is because when 10 mol% of the structural units of formula (II) are ungrooved, the photoelastic constant of the resulting aromatic polycarbonate is not much different from that of the homopolycarbonate of formula (I). Furthermore, when the content of the structural unit of formula (II) exceeds 90 mol %, the fluidity 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. 1
If it is less than 3,000, the copolymer becomes brittle and 50,000
If it exceeds this amount, the flow of the copolymer will be poor and the moldability will be poor.

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 1.1 cobis-(4-hydroxyphenyl)-p-diisopropylbenzene and 4,4-dihydroxy-2,2,
Conditions in which an inert gas is introduced into a slightly excess stoichiometrically equivalent amount of diphenyl carbonate to a mixture of 2-triphenylethane in the presence of a conventional carbonation catalyst at a temperature of 160 to 180°C and under normal pressure. The reaction is carried out for about 30 minutes at a temperature of 180 to 220°C while gradually reducing the pressure over a period of about 2 to 3 hours, and the precondensation is finally completed at 10 Torr and 220°C. Then, 5T for 30 minutes at 10 Torr and 270°C.
orr.

React at 270°C for 20 minutes, then add 0.5TorI-
The following is preferably 0.3 Torr to 0. Edge alignment is allowed to proceed for 1°5 to 2.0 hours at 2708C under a vacuum of ITorr. 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, potassium hydrogen phosphate, sodium hydroxide, sodium borohydride, calcium hydride, dibutyltin oxide, styl oxide
An example is tin. 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. A mixture of 1,1'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene and 4,4-dihydroxy-2,2,2-)riphenylethane is dissolved in pyridine, and phosgene gas is introduced while stirring vigorously. However, since phosgene is extremely poisonous, it must be operated 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 the condensation progresses, it becomes viscous. Phosgene is passed through it until the yellow color of the phosgene-hydrogen chloride complex does not disappear. After the reaction is complete, methanol is added to precipitate the polymer, which is then filtered and dried. Since it 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 is
DRAW records signals using a laser beam, or reads out recorded signals by reflecting or transmitting the laser beam.

It is useful for erasable-DRAW 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 1.1: 208 parts by weight (50 mo1%) of bis, (4-hydroxyphenyl), p, diisopropylbenzene and 4
, 174 parts by weight (50 mo1%) of 4-dihydroxy-2,2,2-triphenylethane and 264 parts by weight of diphenyl carbonate were placed in a 31-hole flask and degassed with N2.
After repeating purging five times, it was melted in a silicon bath at 180°C while nitrogen was introduced. Once melted, a solution of potassium borohydride, which is a carbonation catalyst, dissolved in phenol in advance (10-3 mo1% amount based on the total amount of bisphenol charged) was added, and at 180°C2N2,
The mixture was stirred and brewed for 30 minutes. Next, under the same temperature, 1QQTor
After stirring for 30 minutes at r, further 5QTo at the same temperature.
The pressure was reduced to rr and the reaction was carried out for 30 minutes. Then gradually increase the temperature to 22
The temperature was raised to 0°C and the reaction was carried out for 60 minutes, so that 80% of the theoretical amount of phenol was distilled out. Thereafter, the pressure was reduced to 1 Q Torr at the same temperature, and the reaction was carried out for 30 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, it was tightened after 1.5 hours at the same temperature at 0.1 to Q and 3 Torr. 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 is M
v=19,600.

Example 2 A three-hole flask is equipped with a stirrer, a thermometer, a gas inlet pipe, and an exhaust pipe. 1,1 bis-(4-hydroxyphenyl)-p-diisopropylbenzene in dichloromethane 20
8 parts by weight and 4 parts by weight of 4,4-dihydroxy-2,2,2-)diphenyleph 21F were dissolved, a 10% by weight aqueous solution of sodium hydroxide was added, and while stirring the mixture vigorously, 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 is ~1v=20,800
Met.

(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
, 2, using an injection molding machine (
Diameter: 130m using Dynamelter (manufactured by Taiki Seisakusho)
m, formed into a disk-shaped substrate with a thickness of 1.2 mm, and sputtering equipment (RF sputtering equipment, manufactured by Japan Vacuum Co., Ltd.) using an alloy target of Tb23.5Fe64°2CO12,3 (atomic%) on this substrate. Among them, 1,000 people formed magneto-optical recording films. On this recording film, a protective film of 1,000 inorganic glasses as described in JP-A-60-177449 by the present applicant was 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 reading power 1mW, carrier frequency IMHz, 30KHz in resolution band (Note 2) CN change rate (%) = 60 relative to initial CN ratio
Comparative example of reduction in CN ratio after 30 days under 990°C 990 RH% condition (Note 3) = A magneto-optical disk was prepared using the same procedure as above using a conventionally known polycarbonate (AD-5503 from Ondai Kasei Co., Ltd.) substrate. It's something I made.

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] 97 to 3 mol% of 1,1'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene and 3 to 97 mol% of 4,4-dihydroxy-2,2,2-triphenylethane are bonded with carbonate. Optical disc made of the resulting aromatic polycarbonate copolymer