JPH0620784B2 - Method for manufacturing optical disk substrate made of polycarbonate resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a material used for producing an optical disc substrate having excellent optical characteristics, in particular, a molded article having excellent transparency and small optical distortion. It is about how to do it.

[Conventional technology]

A molded product used for the optical disk substrate, for example, a plate-shaped or sheet-shaped molded product is required to be transparent and have a small optical distortion. Especially when it is used as an optical information material using digital signals, for example, in the case of digital audio discs, digital video discs, and further discs for reading and writing information, the transparency requirement is extremely strict. Is a single pass ± 2 for the phase difference in the actual molded product
It is required to be within the range of 0 nm.

In addition, such a disk is also required to have no warp and excellent heat resistance.

In order to industrially produce such a molded product, it is advantageous to carry out molding by an injection molding method using a polycarbonate resin excellent in transparency, dimensional stability, heat resistance and the like.

[Problems to be solved by the invention]

However, since the polycarbonate resin has a high melt viscosity, it has a drawback that birefringence becomes large under normal molding conditions. Therefore, in order to lower the melt viscosity, lower the molecular weight,
Studies have been made to reduce the birefringence by raising the temperature of the molten resin at the time of molding, but it has not been fully solved yet. Further, the birefringence of a substrate made of a polycarbonate resin is easily affected by a change with time, which is likely to cause a trouble in a product continuously used for a long time.

[Means for solving problems]

As a result of intensive studies to solve the above-mentioned drawbacks of the optical disk substrate made of polycarbonate, the present inventors have shown that the birefringence is extremely small by performing heat treatment under specific conditions after molding under specific injection molding conditions, Further, they have found that an optical disk substrate that does not change with time can be obtained, and thus reached the present invention.

That is, the present invention aims to produce a substrate having a small birefringence and no change over time. The purpose of this is to manufacture the optical disk substrate made of polycarbonate resin in the first step at a resin temperature of 300-400.
Injection molding at a mold temperature of 50 to 150 ° C. In the second step, the glass transition temperature of the resin measured by a differential scanning calorimeter is T
It is achieved by subjecting the substrate obtained in the first step to heat treatment in the temperature range of (T-90) ° C. to (T-5) ° C. for 1 minute or longer when the temperature is set to 0 ° C.

The present invention will be specifically described below.

The polycarbonate resin used in the present invention is produced by reacting one or more bisphenols with a carbonic acid ester such as phosgene or diphenyl carbonate.

Here, as the bisphenols, specifically, bis (4
-Hydroxyphenyl) meta, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 2,2-
Bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) octane, bis (4-hydroxyphenyl) phenyl methane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane 1,1-bis (4-hydroxyphenyl) -1-phenylpropane, bis (4-hydroxyphenyl) diphenylmethane, bis (4-hydroxyphenyl) dibenzylmethane, 1,1-bis (4- Hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxy-3-chlorophenyl) propane, 2,2-bis (4-hydroxy-3)
-Bromophenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3-isopropylphenyl) propane, 2,2-bis (4-hydroxy-3) -Secondary butylphenyl) propane, 4,4'-dihydroxyphenyl ether, 4,4'-hydroxydiphenyl sulfide, 4,4'-dividoxydiphenyl sulfone and the like.

The method for producing a polycarbonate resin from such bisphenols and phosgene is specifically methylene chloride, 1,
In the presence of an inert solvent such as 2-dichloromethane, an alkaline aqueous solution, pyridine or the like is added as an acid acceptor to one or more kinds of bisphenols, and the reaction is carried out while introducing phosgene. When an aqueous alkaline solution is used as the acid acceptor, the reaction rate is increased by using a tertiary amine such as trimethylamine or triethylamine or a quaternary ammonium compound such as etrabutylammonium chloride or benzyltributylammonium bromide as a catalyst. If necessary, phenol as a molecular weight regulator,
A monovalent phenol such as p-tertiary butylphenol is allowed to coexist. The reaction temperature is 0 to 100 ° C. The catalyst may be added from the beginning, or may be added after the oligomer is produced and then added to have a high molecular weight. When a copolymer is produced from two or more kinds of bisphenol compounds, (a) first, they are simultaneously reacted with phosgene to polymerize.

(B) First, one is reacted with phosgene, and after a certain amount of reaction, the other is put in and polymerized.

(C) Separately reacting with phosgene to form each oligomer, and reacting them to polymerize.

Etc. Any method can be adopted.

Further, the polycarbonate resin used in the present invention may be a mixture of two or more kinds of resins having different structures, which are composed of two or more kinds of separately polymerized bisphenols. As this method, after mixing each powder or granules,
Any method such as a method of mixing in a molten state with an extruder, a kneader, a kneading roll, or the like, a solution blending method, or the like can be used.

The average molecular weight of the polycarbonate resin used in the present invention is
Must be 9,000-22,000, preferably 9,500-1
It is about 8,000.

The average molecular weight as used herein means the following formula from ηsp measured at 20 ° C. using a 6.0 g / methylene solution of polymer.
It is a value obtained from 1 and Equation-2.

ηsp / c = [η] (1 + K'ηsp) ………… 1) [η] ＝ KM ^α …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… fabric stand yet [2] C: polymer concentration (g /) η]: Intrinsic viscosity K ′: 028 K: 1.23 × 10 ⁻⁵ α: 0.83 M: average molecular weight That is, if the average molecular weight is too high, 400 to produce a molded product with little optical distortion. It is necessary to carry out molding at a resin temperature exceeding 0 ° C., and at such a high temperature, decomposition of the resin cannot be avoided, and there are disadvantages such as silver streaks occurring on the surface of the molded product and coloring.

On the other hand, if the average molecular weight is too low, it is possible to obtain a molded product with less optical strain, but the resin strength is low and the resin is easily damaged when released from the mold during molding, and a molded product is obtained. However, the mechanical strength is small.

When the polycarbonate resin used in the present invention is injection-molded, phosphite ester is added to the resin in an amount of 0.0
It is preferable to add 1 to 2.0% by weight in order to suppress coloring and deterioration of transparency due to decomposition of the resin.

Specific examples of such phosphite include tributyl phosphite, tris- (2-ethylhexyl) phosphite, tridecyl phosphite, tristearyl phosphite, triphenyl phosphite, tricresyl phosphite, tris (nonyl phenyl) phosphite. ,
2-ethylhexyldiphenylphosphite, decyldiphenylphenylphosphite, phenyldi-2-ethylhexylphosphite, phenyldidecylphosphite, tricyclohexylphosphite, distearylpentaerythritylphosphite, diphenylpentaerythritylphosphite, etc. Is mentioned.

In the present invention, the polycarbonate resin obtained as described above is used at a resin temperature of 300 to 400 in the first step.
Injection molding at a mold temperature of 50 to 150 ° C.

In this molding, if the resin temperature is too high, the decomposition of the resin is unavoidable, which causes coloration and silver streak, resulting in poor transparency. On the other hand, if the resin temperature is too low, it becomes impossible to obtain a molded product having a small optical strain even if the polycarbonate resin of the present invention in which an optical strain is hard to occur is used. Preferred resin temperature is 30
It is about 0 to 400 ° C.

Further, in this molding, the mold temperature is 50 to 150 ° C, preferably about 60 to 145 ° C. If the mold temperature is too high, the deformation at the time of mold release becomes large, and it becomes impossible to obtain a molded product with small warpage. On the contrary, if it is too low, it becomes impossible to obtain a molded product having a small optical distortion.

In this first step, the birefringence value is preferably in the range of -40 nm to +20 nm.

Next, in the second step of the present invention, the substrate obtained in the first step is heat-treated.

Here, the heat treatment temperature is from (T-90) ° C. to (T-90) when the glass transition temperature of the resin measured by a differential scanning calorimeter is T ° C.
-5) ° C, more preferably from (T-85) ° C to (T-1
5) Within the range of ° C. That is, when the heat treatment is performed at a temperature lower than (T-90) ° C, it is not possible to solve the change in birefringence with time. On the other hand, heat treatment at a temperature higher than (T-5) ° C. is not preferable because the shapes of the groups and pits transferred from the stan bars change during injection molding. The heat treatment time should be 1 minute or longer, preferably 3 minutes or longer. That is, it is impossible to solve the birefringence change with time in a too short time.

Such heat treatment is achieved by setting a hot air dryer, a hot air tunnel, a vacuum dryer or the like at a predetermined temperature and allowing the substrate to stay for a predetermined time. Practically, the birefringence after this heat treatment is preferably in the range of -20 nm to +20 nm.

The polycarbonate resin according to the present invention is useful as a material for optical discs. Here, the optical disk includes a read-only type such as a compact disk and a laser disk; a write-once type used as a document file, a still image file, a moving image file; and an erasable type such as a magneto-optical disk. Of these fields, where heat resistance is especially required,
For example, it is suitable for an erasable optical disc.

〔Example〕

 This will be described in detail below with reference to examples.

In the following examples, all "parts" indicate "parts by weight".

The measured values of the physical properties were those measured by the following methods.

(B) Birefringence (Δn) 1. From the center of a disk with a thickness of 1.2 mm and a diameter of 130 mm.
The birefringence at a position of 8 mm was measured using an ellipsometer manufactured by Mizojiri Optical Co., Ltd.

(B) Glass transition temperature (T) It was measured using a differential scanning calorimeter manufactured by Perkin Elmer.

(C) Group groove depth It was measured using a Talisstep manufactured by Rank Taylor Hobson.

<Production Example A of Polycarbonate Resin> Bisphenol A was dissolved in a 5% aqueous sodium hydroxide solution.

Aqueous solution of bisphenol A sodium salt 13% 100 parts p-tert-butyl phenol 0.35 part 2% triethylamine aqueous solution 2.44 parts Methylene chloride 539 parts are mixed and stirred, and 56.8 parts of phosgene is introduced into this to carry out interfacial polymerization. Natsuta.

The reaction mixture was separated, and the methylene chloride solution containing the polycarbonate resin was washed with water, an aqueous hydrochloric acid solution and then water, and the methylene chloride was evaporated to give an average molecular weight of 15.
500 polycarbonate resins were obtained.

<Production Example B of Polycarbonate Resin> (a) Production of Oligomer 1,1-Bis (4-hydroxyphenyl) -1-phenylethane 100 parts Sodium hydroxide 40 parts Water 600 parts Methylene chloride 375 parts The above mixture is agitated. The reactor was charged and stirred at 800 rpm. 57 parts of phosgene was blown into this for 1 hour to carry out interfacial polymerization. After completion of the reaction, only the methylene chloride solution containing the polycarbonate oligomer was collected. The analysis results of the methylene chloride solution of the obtained oligomer are as follows.

Oligomer concentration 22.5% by weight (Note 1) Terminal chloroformate group concentration 0.42N (Note 2) Terminal phenolic hydroxyl group concentration 0.020N (Note 3) The oligomer solution obtained by the above method is abbreviated as "oligomer solution-a" below. To do.

Note 1) Measured after evaporation to dryness.

Note 2) Neutralization titration of aniline hydrochloride obtained by reacting with aniline with 0.2N aqueous sodium hydroxide solution.

Note 3) Colorimetric determination at 546 nm of color development when dissolved in titanium tetrachloride and acetic acid solution.

(B) Production of Polycarbonate Polycarbonate oligomer solution-a 140 parts p-tert-butyl phenol 1.9 parts Methylene chloride 80 parts The above mixture was charged into a reactor equipped with a stirrer and stirred at 550 rpm. Further, an aqueous solution having the following composition, that is, a 7.3% aqueous solution of sodium hydroxide 80 parts and a 2% aqueous solution of triethylamine 1 part were added, and interfacial polymerization was performed for 3 hours to separate the reaction mixture,
Methylene chloride solution containing polycarbonate resin, water,
The resin was removed by washing with aqueous hydrochloric acid and then with water and finally evaporating the methylene chloride. The average molecular weight of this resin was 11,200.

<Production Example C of Polycarbonate Resin> (a) Production of Oligomer 16.6% aqueous solution of bisphenol A sodium salt prepared by dissolving bisphenol A in aqueous sodium hydroxide solution 100 parts p-tertiary butylphenol 0.1. 23 parts Methylene chloride 40 parts Phosgene 7 parts The mixture having the above composition was quantitatively supplied to the pipe reactor for interfacial polymerization.

The reaction mixture was separated and only the ethylene chloride solution containing the polycarbonate oligomer was collected.

The analysis results of the methylene chloride solution of the obtained oligomer are as follows.

Oligomer concentration 24.5% by weight Terminal chloroformate group concentration 1.3N Terminal phenolic hydroxyl group concentration 0.3N The oligomer solution obtained by the above method is abbreviated as oligomer solution-b below.

(B) Production of Polycarbonate Polycarbonate oligomer solution-b 370 parts p-tertiary butylphenol 1.0 part Methylene chloride 300 parts The above mixture was charged into a reactor equipped with a stirrer and stirred at 550 rpm. Further, an aqueous solution having the following composition, that is, 17% aqueous solution of sodium salt of 2,2-bis- (4-hydroxy-3-methylphenyl) propane 200 parts 25% aqueous solution of sodium hydroxide 20 parts 2% aqueous solution of triethylamine 2 parts Was added, and the interfacial polymerization was carried out for about 1.5 hours to separate the reaction mixture, and the methylene chloride solution containing the polycarbonate resin was washed with water, an aqueous hydrochloric acid solution and then water, and finally the methylene chloride was evaporated. The resin was removed.

The average molecular weight of this resin was 17,000, and the amount of 2,2-bis (4-hydroxy-3-methylphenyl) propane copolymerized from the results of NMR analysis was 30.5% by weight.
It was.

Example 1 Polycarbonate resin flake 10 produced in Production Example A
0.05 part of trisnonylphenyl phosphite was mixed with 0 part, melt-kneaded at 260 ° C. using an extruder with a 40 mmφ vent, and then extruded into pellets. Using an injection molding machine (M-140A manufactured by Meiki Co., Ltd.), this pellet was attached with a grooved stamper on the movable side of the mold, and a disk having a thickness of 1.2 mm and a diameter of 130 mm at a resin temperature of 370 ° C and a mold temperature of 110 ° C. It was molded into a shape.

The substrate (A) had a birefringence of -20 nm and a groove groove depth of 720Å.

The birefringence of the substrate (B) obtained by heat-treating the substrate (A) for 60 minutes in a constant temperature hot air dryer at 80 ° C. was extremely small as 2 nm, and the groove groove depth was 720 Å.

Further, the substrate (B) is placed in a constant temperature and humidity chamber at 50 ° C to 90 ° C RH for 48 hours.
The birefringence of the substrate (C) retained for 0 hours was 2 nm and the groove groove depth was 720 Å, showing no change with time.

Comparative Example 1 Example 1 without heat treating the substrate (A) obtained in Example 1
When kept for 480 hours under the same conditions as above, the birefringence is -5 nm.
It has changed significantly over time.

Comparative Example 2 The substrate (A) obtained in Example 1 was heated to 3 ° C. from the glass transition temperature.
When heat treatment was performed at a low temperature of 145 ° C. for 60 minutes in the same manner as in Example 1, the groove groove was 200 Å.

Comparative Example 3 The glass transition temperature of the substrate (A) obtained in Example 1 was 98.
Substrate heat-treated in the same manner as in Example 1 at 50 ° C. lower for 50 minutes
The birefringence of (B) was -19 nm, which was almost unchanged before and after the heat treatment.

When this substrate (B) was held under the same conditions as in Example 1 for 480 hours, the birefringence changed significantly with time to -4 nm.

Comparative Example 4 The substrate (A) obtained in Example 1 was heat-treated at 80 ° C. for 30 seconds in the same manner as in Example 1, and the birefringence of the substrate (B) was −15 nm.
It was.

When this substrate (B) was held under the same conditions as in Example 1 for 480 hours, the birefringence changed significantly to -4 nm with time.

Examples 2 and 3 The birefringence of the substrate (B) obtained by subjecting the substrate (A) obtained in Example 1 to the heat treatment under the temperature and time conditions shown in Table 2 is extremely small, and in the substrate (C), there is a change with time. Monakatsu.

Example 4 100 parts of the polycarbonate resin produced in Production Example B was mixed with 0.04 part of trisnonylphenyl phosphite,
The mixture was melt-kneaded at 270 ° C. using an extruder with a 40 mmφ vent and extruded into pellets.

This pellet was subjected to the same operation as in Example 1 to obtain a resin temperature of 385.
Molded at a mold temperature of 135 ° C.

The substrate (A) had a birefringence of -8 nm and a groove groove depth of 680Å.

This substrate (A) was heat-treated at 110 ° C. for 60 minutes in the same manner as in Example 1, and the birefringence of the substrate (B) was 3 nm, which was extremely small, and the groove groove depth was 680 Å.

Furthermore, when the substrate (B) was kept under the same conditions as in Example 1 for 480 hours, there was no change in birefringence with time.

Example 5 2 parts per 100 parts of the polycarbonate resin produced in Production Example C
-Ethylhexyl diphenyl phosphite (0.05 parts) was mixed and melt-kneaded at 260 ° C using an extruder with a 40 mmφ vent, and then extruded into pellets. This pellet was operated in the same manner as in Example 1 with a resin temperature of 350 ° C. and a mold temperature of 1
Molded at 00 ° C.

The substrate (A) had a birefringence of -30 nm and a groove groove depth of 730Å.

This substrate (A) was heat treated at 80 ° C. for 60 minutes in the same manner as in Example 1, and the birefringence of the substrate (B) was extremely small at 1 nm, and the groove groove depth was 730Å.

Furthermore, when the substrate (B) was kept under the same conditions as in Example 1 for 480 hours, there was no change in birefringence with time.

〔The invention's effect〕

As described above, the molded article obtained by the production method of the present invention has extremely small birefringence and has no change in birefringence over time, and is suitable for use as an optical disk substrate.

Claims (2)

[Claims] 1. When manufacturing an optical disk substrate made of a polycarbonate resin, a resin temperature of 300 to 4 is used in the first step.
Injection molding was performed at 00 ° C and a mold temperature of 50 to 150 ° C. In the second step, when the glass transition temperature of the resin measured by a differential scanning calorimeter was T ° C, (T-90) ° C to (T-5) ) ° C. temperature range, heat treatment for 1 minute or more, optical disk substrate manufacturing method 2. A method for producing an optical disk substrate according to claim 1, wherein a polycarbonate resin having an average molecular weight of 9,000 to 22,000 is used.