JP2515993B2 - 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 method can increase the recording density equally, and especially the Erasable-DRAW type erases the recording. Since it is writable and has excellent characteristics in images and sound quality reproduced from them, it is expected to be widely used for recording or recording / reproducing images and sound quality, and recording / reproducing a large amount of information. 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. The thermal stress, the molecular orientation, and the residual stress due to the volume change near the glass transition point generated during the cooling and flowing processes of the resin during the formation of the disk body are the main causes, and birefringence occurs when the laser beam passes through the disk body. The large optical nonuniformity due to this 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 the equation (1), molding conditions It is clear that even with the same, the birefringence of the obtained disk will be small. Therefore, the inventors have found that 4,4 '[1,4-phenylenebis (1-methylethylidene)] bisphenol and 1,1'
The present invention was found to be the fact that a resin having a small photoelastic constant can be obtained by copolymerizing -bis- (4-hydroxyphenyl) cyclohexane with a carbonate bond without impairing the mechanical properties of an aromatic polycarbonate. is there.

(Structure of the Invention) The present invention relates to 4,4 ′ [1,4-phenylenebis (1-methylethylidene)] bisphenol (I) 97-3 mol% and 1,1
It relates to an optical disc comprising an aromatic polycarbonate copolymer obtained by carbonate-bonding with 3 to 97 mol% of -bis- (4-hydroxyphenyl) cyclohexane (II). Thus, according to the present invention, there is provided an aromatic polycarbonate copolymer obtained by copolymerizing bisphenoles 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). On the other hand, when the content of the structural unit of the formula (II) exceeds 90 mol%, the fluidity of the obtained aromatic polycarbonate is remarkably lowered as compared with the homopolycarbonate of the formula (I). The viscosity average molecular weight of the copolymer of the present invention is 1
3,000-50,000 are preferred. 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, the third component can be copolymerized. There are the following two methods for producing the polycarbonate copolymer of the present invention.

Transesterification method Stoichiometric excess over stoichiometric equivalent to a mixture of 4,4 '-[1,4-phenylenebis (1-methylethylidene)] bisphenol and 1,1-bis- (4-hydroxyphenyl) cyclohexane The diphenyl carbonate of 1. is reacted in the presence of an ordinary carbonation catalyst at a temperature of about 160 to 180 ° C. under atmospheric pressure and an inert gas for about 30 minutes to react for about 2 minutes.
The precondensation is finally completed under a temperature of 180 to 220 ° C. and 10 Torr and 220 ° C. while gradually reducing the pressure over a period of 3 hours. Thereafter, the reaction is carried out at 10 Torr and 270 ° C. for 30 minutes, and at 5 Torr and 270 ° C. for 20 minutes, and then the condensation is advanced after 1.5 hours to 2.0 hours at 270 ° C. under a reduced pressure of 0.5 Torr or less, preferably 0.3 Torr to 0.1 Torr. .
Incidentally, as the carbonate-forming catalyst for the carbonate bond, an alkali metal such as a lithium-based catalyst, a potassium-based catalyst, a sodium-based catalyst, a calcium-based catalyst, a tin-based catalyst, or an alkaline earth metal catalyst is suitable. Lithium, potassium borohydride, potassium hydrogen phosphate, sodium hydroxide, sodium borohydride, calcium hydride, dibutyltin oxide, first oxide
Tin. Of these, it is preferable to use an allium catalyst.

Phosgene method Stirrer, thermometer, gas inlet tube,
Turn on the exhaust pipe. 4,4 '-[1,4-phenylenebis (1-
Methyl ethylidene)] bisphenol and 1,1-bis-
A mixture of (4-vidroxyphenyl) cyclohexane is dissolved in pyridine and phosgene gas is introduced while vigorously stirring the mixture. However, phosgene is a deadly poison, and therefore it is operated 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. With the introduction of gas, pyridine hydrochloride precipitates and the content becomes cloudy. Water-cool the reaction humidity 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 thus obtained records a signal with a laser beam, or reads out the recorded signal by reflection or transmission of a laser beam, DRAW, Erasable-D.
It is useful for RAW optical information recording discs. The present invention is described below with reference to examples, but the present invention is not limited to these examples.

Example 1 250 parts by weight of 4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bisphenol (60 mol%) and 129 parts by weight of 1,1-bis- (4-hydroxyphenyl) cyclohexane (40 mol%) ) And 265 parts by weight of diphenyl carbonate were placed in a three-necked three-neck flask, degassed, and N ₂ persive was repeated 5 times, and then melted in a silicon bath at 180 ° C. while introducing nitrogen. After melting, add a solution of potassium phosphine hydride, which is a carbonation catalyst, in phenol in advance (10 ^-3 mol% based on the total amount of bisphenol charged), and stir at 180 ° C under N ₂ for 30 minutes. I cultivated it. Next, after stirring at 100 Torr for 30 minutes at the same temperature, the mixture is further stirred at the same temperature for 5 minutes.
The pressure was reduced to 0 Torr and the reaction was performed for 60 minutes. Then gradually increase the temperature to 220 ° C
The reaction was carried out for 60 minutes, and 80% of the theoretical amount of phenol distilled was distilled by the reaction so far. After that, 10 at the same temperature
Reduce the pressure to Torr, react for 30 minutes and gradually raise the temperature to 270 ° C.
The reaction was performed for 0 minutes. Further, at the same temperature, the pressure was reduced to 5 Torr and the reaction was carried out for 30 minutes to distill almost all the theoretical amount of phenol distilled to complete the precondensation. Next, post-condensation was performed at the same temperature for 2 hours at 0.1 to 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 = 19,200.

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
Dissolve 250 parts by weight of 4 '-[1,4-phenylenebis (1-methylethylden)] bisphenol and 129 parts by weight of 1,1-bis- (4-hydroxyphenyl) cyclohexane, add dichloromethane, and stir it vigorously. While introducing phosgene gas. Phosgene was introduced from the bomb into the flask through an empty flush bottle, a flush bottle containing water, and an empty flush bottle. The reaction temperature during the introduction of phosgene gas is
It was water-cooled to 25 ° C or lower. The solution becomes viscous as the condensation proceeds. Further, phosgene was passed until the yellow color of the phosgene-hydrogen chloride complex did not disappear. After completion of the reaction, the reaction solution was poured into methanol, filtered and washed repeatedly with water. Further, the produced polycarbonate was reprecipitated and purified from methanol solution. After purification and drying well, use dichloromethane as a solvent at 20 ℃.
The solution viscosity was measured at. The viscosity calculated from this value was measured. The viscosity average molecular weight calculated from this value is v = 2
It was 0,500.

(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
The polycarbonate copolymer described in 1 and 2 was used with an injection molding machine (manufactured by Taiki Seisakusho, Dynamelter) to obtain a diameter of 130 m.
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.

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 also has excellent durability.

Claims (1)

(57) [Claims] 1. 97-4 mol% of 4,4 '-[1,4-phenylenebis (1-methylethylidene)] bisphenol and 1,1-
Bis- (4-hydroxyphenyl) cyclohexane 3 to
Optical disc made of aromatic polycarbonate copolymer obtained by carbonate-bonding with 97 mol%