JPH0832776B2 - Optical disk - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polycarbonate copolymer used in an optical information recording disk for recording a signal with a laser beam or reading a recorded signal by reflecting or transmitting a laser beam. It relates to an optical disc composed of a united body.

(Prior Art) A DRAW (direct recording) is performed by applying a spot beam of a laser beam to a disc and recording a signal in the disc with fine pits or reading a signal recorded by such a pit by detecting the amount of reflected or transmitted light of the laser beam. Read After Write), Erasable-DRAW
The (erasable-direct read-after-write) type optical information recording / reproducing system can remarkably increase the recording density, and in particular, the Erasable-DRAW type allows erasing / writing of recording, and images reproduced from them. It is expected to be widely used for recording or recording / reproducing images and sound quality, recording / reproducing a large amount of information, etc. The disk used in this recording / reproducing system is required to have high optical homogeneity in order to reduce reading errors as well as being transparent because a laser beam passes through the disk body. Thermal stress, molecular orientation, and residual stress due to volume change near the glass transition point generated during the cooling and flowing processes of the resin during formation of the disk main body mainly cause birefringence when the laser beam passes through the disk main body. The large optical non-uniformity caused by the birefringence is a fatal defect for an optical disc.

(Problems to be solved by the invention) Thus, the birefringence mainly caused by the thermal stress, the molecular orientation, and the residual stress generated in the cooling and flowing processes of the resin at the time of forming the disk can be obtained by selecting the forming conditions. The birefringence of the disk can be made quite small, but it is largely dependent on the intrinsic birefringence of the molding resin itself, that is, the photoelastic constant.

(Means for solving the problem) The birefringence is expressed as the product of the photoelastic constant and the residual stress as follows (1)
It can be represented by a formula.

n ₁ −n ₂ = C (σ ₁ −σ ₂ ) (1) n ₁ −n ₂ : Birefringence σ ₁ −σ ₂ : Residual stress C: Photoelastic constant If the photoelastic constant is reduced from Eq. (1), It is obvious that the birefringence of the obtained disk is small even under the same molding conditions. Thus, the inventors have determined that 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol and 2,2'
It was found that a resin having a small photoelastic constant can be obtained by copolymerizing -bis- (4-hydroxy-3-tert-butylphenyl) propane with a carbonate bond without impairing the mechanical properties of the aromatic polycarbonate. It was the invention.

(Structure of the Invention) The present invention relates to 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisphenol (I) in an amount of 95 to 5 mol% and 2,
The present invention relates to an optical disc composed of an aromatic polycarbonate copolymer obtained by carbonate-bonding 2-bis- (4-hydroxy-3-tert-butylphenyl) propane (II) with 5 to 95 mol%. Thus, according to the present invention, there is provided an aromatic polycarbonate copolymer obtained by copolymerizing bisphenols represented by the following formulas (I) and (II) by a carbonate bond.

Further, the content of the structural unit of the formula (II) is preferably from 10 to 90 mol%.
The photoelastic constant of the aromatic polycarbonate obtained when the constituent unit of the formula (II) is less than 10 mol% is not much different from that of the homopolycarbonate of the formula (I). Further, when the constituent unit of the formula (II) exceeds 90 mol%, it becomes brittle as compared with the homopolycarbonate of the formula (I). The viscosity average molecular weight of the copolymer of the present invention is 13,0
00 to 50,000 is preferable. If it is less than 13,000, the copolymer becomes brittle, and if it exceeds 50,000, the flow of the copolymer becomes poor and the moldability is poor.

Further, it is possible to copolymerize the third component. There are the following two methods for producing the polycarbonate copolymer of the present invention.

Transesterification method Stoichiometry for a mixture of 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol and 2,2-bis- (4-hydroxy-3-tert-butylphenyl) propane To about 160 to 1 in the presence of a conventional carbonation catalyst in diphenyl carbonate in a slight excess over the equivalent amount.
The reaction is carried out at a temperature of 80 ° C under atmospheric pressure for about 30 minutes under the condition of introducing an inert gas, and the pressure is gradually reduced over a period of about 2 hours to 3 hours, and finally at a temperature of 180-220 ° C, 10 Torr, 220 The precondensation is completed at ℃. Then, at 10 Torr, 270 ° C for 30 minutes, 5 Tor
r, react at 270 ° C for 20 minutes, then 0.5 Torr or less, preferably
The post-condensation is allowed to proceed for 1.5 to 2.0 hours at 270 ° C. under a reduced pressure of 0.3 Torr to 0.1 Torr. In addition, as a carbonate conversion catalyst for the carbonate bond, an alkali metal or alkaline earth metal catalyst such as a lithium catalyst, a potassium catalyst, a sodium catalyst, a calcium catalyst, and a tin catalyst is suitable. Examples include lithium, potassium borohydride, potassium hydrogen phosphate, sodium hydroxide, sodium borohydride, calcium hydride, dibutyltin oxide, and stannous oxide. Of these, it is preferable to use a potassium-based catalyst.

Phosgene method Stirrer, thermometer, gas inlet tube,
Turn on the exhaust pipe. 4,4 '-[1,3-phenylenebis (1-
Methyl ethylidene)] bisphenol and 2,2-bis-
(4-hydroxy-3-tert-butylphenyl)
The mixture of propane is dissolved in pyridine, and phosgene gas is introduced with vigorous stirring. However, phosgene is a deadly poison, so operate in a strong draft. In addition, a unit that decomposes and detoxifies excess phosgene with a 10% aqueous solution of sodium hydroxide is installed at the exhaust end. Phosgene is introduced into the flask through a bubble bottle from a cylinder, a bubble bottle containing paraffin (counting the number of bubbles), and an empty bubble bottle. The glass inlet tube should be inserted over the stirrer and the tip should be funneled out so as not to be picked up by the precipitated pyridine salt. As the gas is introduced, the hydrochloride of pyridine precipitates and the content becomes cloudy. The reaction temperature is
Water-cool to 30 ° C or less. It becomes viscous as the condensation progresses. Pass phosgene until the yellow color of the phosgene-hydrogen chloride complex no longer disappears. After the reaction is completed, methanol is added to precipitate a polymer, which is separated by filtration and dried. 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 manner is useful for recording a signal by a laser beam, or for reading a recorded signal by reflection or transmission of a laser beam, an Erasable-DRAW optical information recording disk. . The present invention is described below with reference to examples, but the present invention is not limited to these examples. The viscosity average molecular weight shown in the following examples was obtained as a relational expression between the intrinsic viscosity [η] and the molecular weight M by measuring with a methylene chloride solution of bisphenol A / polycarbonate at 20 ° C. [η] = 1.11 × 10 ⁻⁴ M ^0.82 is the molecular weight in terms of bisphenol A / polycarbonate calculated from the intrinsic viscosity using the formula of [E. Miiller & O. Bayer; USP 2,999,844 (1961)].

Example 1 4,4 ′-[1,3-Phenylenebis (1-methylethylidene)] bisphenol 208 parts by weight (50 mol%) and 2,2-bis- (4-hydroxy-3-tert-butylphenyl) propane 204 parts by weight (50 mol%) and 264 parts by weight of diphenyl carbonate were placed in a 3 l three-necked flask, and after degassing and N ₂ purging were repeated 5 times, they were melted in a silicon bath at 160 ° C. while introducing nitrogen. Once melted, a solution of potassium borohydride, which is a carbonation catalyst, in phenol beforehand (10 ^-3 relative to the total amount of bisphenol charged).
mol% amount) was added, and the mixture was stirred at 160 ° C. under N ₂ for 30 minutes.
Next, after stirring at 100 Torr at the same temperature for 30 minutes, the pressure was further reduced to 50 Torr at the same temperature and the reaction was performed for 60 minutes. Next, the temperature was gradually raised to 220 ° C. and the reaction was carried out for 60 minutes, and 80% of the theoretical amount of phenol distilled was distilled by the reaction so far. Then, the pressure was reduced to 10 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. 5To under the same temperature
The pressure was reduced to rr and the reaction was carried out for 30 minutes to distill almost all the theoretical amount of phenol distilled, and the precondensation was completed. Next, at the same temperature, 0.1 ~
Post-condensation was performed for 2 hours at 0.3 Torr. The product polymer was taken out under nitrogen and cooled, and then the solution viscosity was measured at 20 ° C. using dichloromethane as a solvent. The viscosity average molecular weight calculated from this value was v = 19,800. Also, DSC
(Differential scanning calorimeter; Perkin-Elmer2C type) glass transition point is Tg = 111 ° C.
It turned out to be. Furthermore, when measuring the photoelastic constant C = 38 Brewster ^{(Brewsters, 10- 12 m 2 /} N) to be found. The instrument used for the measurement is DSC; Differential Scanning Calorimeter Perkin
-Elmer2C type, the photoelastic constant was measured using a self-made one, but the calculation method of the photoelastic constant is the test piece (50 mm × 10 mm × 1 m
Different tensile stresses were added to m) in the length direction, and the respective values were substituted into the formula (1), and the photoelastic constant was determined from the slope. The photoelastic constant of 2,2-bis- (4-hydroxyphenyl) propane polycarbonate is C = 82.
Brewster ^{(Brewsters, 10- 12 m 2 /} N) was.

Example 2 A three-necked flask was equipped with a stirrer, a thermometer, a gas inlet pipe, and an exhaust pipe. 4, in a 10% by weight aqueous solution of sodium hydroxide
208 parts by weight of 4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol and 2,2-bis- (4-hydroxy-3-tert-butylphenyl) propane
204 parts by weight was melted, dichloromethane was added, and phosgene gas was introduced with vigorous stirring. Phosgene was introduced from the bomb into the flask through an empty flush bottle, a flush bottle containing water, and an empty flush bottle. Water cooling was performed so that the reaction temperature during the introduction of the phosgene gas was 25 ° C. or less. The solution becomes viscous as the condensation progresses. After completion of the reaction, the reaction solution was poured into methanol, separated by filtration, and washed with water repeatedly. Further, the produced polycarbonate was reprecipitated and purified from methanol 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 v = 21,800
Met. The glass transition point Tg = 111 ° C., the photoelastic constant was ^{C = 38Brewsters (10- 12 m 2} / N).

(Evaluation of recording characteristics) A recording film was attached to the polycarbonate copolymer produced as described above, and optical recording characteristics were evaluated. That is, the embodiment
130 m diameter of the polycarbonate copolymer described in 1, 2 using an injection molding machine (manufactured by Meiki Seisakusho, Dynamelter)
m, a 1.2 mm thick disc-shaped substrate, and Tb
Using an alloy target of _23.5 Fe _64.2 Co _12.3 (atomic%), a magneto-optical recording film was formed in a thickness of 1,000 mm in a sputtering apparatus (RF sputtering apparatus, manufactured by Japan Vacuum Corporation). An inorganic glass protective film of 1,000 liters described in JP-A-60-177449 by the applicant of the present invention was formed on this recording film using the same sputtering apparatus as described above. The performance of the obtained magneto-optical disk was evaluated based on the CN ratio, the BER, and the CN ratio change rate under the conditions of 60 ° C. and 90 RH%. The results were as shown in Table 1.

Claims (1)

[Claims] 1. 95% to 5 mol% of 4,4 '-[1,3-phenylenebis (1-methylethylidene) bisphenol and 2,2-bis- (4-hydroxy-3-tert-butylphenyl) propane 5 Optical disc comprising an aromatic polycarbonate copolymer obtained by carbonate-coupling with .about.95 mol%.