JP2621871B2 - Polycarbonate molding material for optical disks - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polycarbonate molding material for an optical disk which records and reads a signal by reflection and transmission of a laser beam. This is a significant improvement.

[Conventional technology]

Glass, epoxy resin, and the like were initially used as the substrate material of the optical disk, but a thermoplastic resin from which a substrate can be easily obtained by injection molding has been demanded.

Examples of the optical thermoplastic resin satisfying this requirement include a methyl methacrylate resin, a polycarbonate resin, a polycarbonate polystyrene copolymer, a polymethylpentene resin, and a polynobornene resin.

Among these, polycarbonate resin has been developed and improved as the most possible material from the results of compact discs, etc., but aluminum, platinum,
The long-term reliability of a recording film formed by vapor deposition or sputtering of tellurium, terbinium, iron, cobalt, antimony, selenium, gadolinium and their alloys on a polycarbonate substrate has not always been satisfactory.

[Problems to be solved by the invention]

The present inventors vapor-deposited a metal for a recording film on a molded article for an optical disk made of a polycarbonate resin and conducted a test in a high-temperature and high-humidity environment to analyze and study the destruction of the recording film in order to improve long-term reliability. As a result, it was found that free chlorine was present on the substrate in contact with the vicinity of the recording film destroyed by pitting or general corrosion. Also, in this corroded part,
Sodium was detected together with chlorine, and it was assumed that free chlorine was present in the form of salt or hydrogen chloride.

Therefore, the above-mentioned problem is largely solved by removing salt or hydrogen chloride which is a by-product contained in a halogenated hydrocarbon solution of an aromatic polycarbonate resin usually obtained by an interfacial polymerization reaction of bisphenol and phosgene. It is thought that it is done.

As a conventional method for purifying an aromatic polycarbonate resin obtained by an interfacial polymerization reaction of bisphenol and phosgene, a batch washing operation is repeated using pure water, and when the aqueous layer becomes neutral, the aqueous layer and the resin are removed. Separation from the solution layer by standing or centrifugation, contacting the polycarbonate resin solution with activated carbon to remove monomers and oligomers (Japanese Patent Publication No. 41-8475), mixing of the polycarbonate resin solution with water The contact angle of the solution with water
A method in which an aqueous solution layer and a resin solution layer are phase-separated through a hydrophilic filter material layer (cotton, filter paper, diatomaceous earth, glass cloth, etc.) of 40 degrees or less to remove water-soluble impurities (Japanese Patent Publication No. 46-4222). ).

However, it is difficult to completely remove free chlorine only by washing with pure water, and therefore, it is necessary to reduce the amount of water contained in the resin solution. However, separating the washing water and the resin solution by centrifugation, and reducing the water content in the resin solution to 0.2% or less requires an extremely large centrifugal force and processing time, and the apparatus becomes large,
Industrial implementation is difficult. In addition, it is difficult to reduce the water content in the resin solution to 1% or less by the method of passing through the filter medium layer. Therefore, the conventional method inevitably contains about 0.5 ppm of free chlorine, and as a result, it was difficult to prevent damage due to pitting or corrosion of the recording film under high temperature and high humidity.

In order to solve this, instead of removing free chlorine, a method of taking free chlorine and converting it into a stable and harmless one can be considered.
As a typical method, there is a method of blending existing stabilizers for polycarbonate, but no effective stabilizer has been found yet.

[Means for solving the problem]

The present inventors have intensively studied a method for solving this problem by removing free chlorine, regardless of the stabilizer, and as a result, the water content of the polycarbonate solution can be industrially used by combining centrifugation and filtration. It has been found that it is possible to greatly reduce by a method having properties. As a result, they found that long-term reliability of the recording film was obtained only when the free chlorine content was 0.2 ppm or less, and completed the present invention.

That is, the present invention is an aromatic polycarbonate resin obtained by a reaction between bisphenol and phosgene, and a polycarbonate molding material for an optical disc, wherein free polycarbonate contained in the polycarbonate resin is 0.2 ppm or less.

In the present invention, the free chlorine exceeds 0.2 ppm, for example,
At 0.8 ppm, the number of defects after the environmental test increases to about 10 to 100 times the number of defects in the initial recording film, and this increase is due to the stability of existing phosphite-based materials. It is not solved by some agents.

The method for producing the aromatic polycarbonate of the present invention is the same as the conventional method for producing an aromatic polycarbonate for optical use except that the separation between the washed and purified polycarbonate resin solution and the washing water is performed by using centrifugation and filtration in combination. .

After the aqueous alkali solution is separated from the resin solution after the polymerization reaction, at least three steps of neutralization and purification are performed: water washing / phosphoric acid aqueous solution washing / water washing. 500G layer separation after each washing step
The above-mentioned centrifugal force is applied, and the final stage of water washing is performed until the conductivity of the centrifuged water becomes 10 μs / cm or less, preferably 9 μs / cm or less, and the water content in the resin solution is 0.5%.
The following is assumed.

Next, this resin solution is passed through a 0.5 to 10 μm pore filter, and a part of water in the resin solution is aggregated on the filter filtration surface, and separated from the resin solution as water droplets having a diameter of 1 mm or more. The water content of the resin solution is set to 0.2% or less, preferably 0.15% or less.

The water used for the final washing of the resin solution is ion-exchanged water containing substantially no free chlorine, and the water passes through a mixed phase of the same amount of a strongly basic ion-exchange resin and a strongly acidic ion-exchange resin. It is the lower limit of quantitative analysis of C1 ion by current colorimetry and potentiometric titration.
Those having a concentration of 0.1 ppm or less are preferred. The amount used for the resin solution is in the range of 0.05 to 2.0 times the volume of the resin solution 1, and particularly preferably the amount in which water is dispersed in the resin solution in an emulsified state. In addition, centrifugation is 500G or more, preferably 3000G
The above is the centrifugal force. If the centrifugal force is small here,
The water content in the resin solution increases, and the washing / centrifugation operation is repeated many times, or even if it is repeated, it is difficult for the water washing to have a conductivity of the centrifuged water of 10 μs / cm or less. It is not preferable because the amount of chlorine cannot be reduced to 0.2 ppm or less.

Further, the filter is preferable in terms of separation of water content because the smaller the pore size, the better the separation efficiency is, but from the practical point of view such as pressure loss, those having pores of 0.5 to 10 μm are preferable, and the material is Poly-perfluoroethylene,
Fluororesins such as poly-perfluoroethylene-perfluoropropylene, poly-vinylidene fluoride, polyester,
Hydrophobic materials such as polypropylene are preferable, and relatively hydrophilic materials such as polyamide, cellulose, and stainless steel can also be used.However, filter materials such as glass fiber, activated carbon, and diatomaceous earth cause dust contamination. This is not preferred in the present invention. The type of the filter is a fiber, a continuous porous film, a sintered body of a granular material, or the like made of the above-described material, and is used in one stage or in multiple stages depending on the material or the desired moisture content.

The polycarbonate is separated from the aromatic polycarbonate resin solution obtained by the above method, and usually, desired additives are appropriately blended and extruded into pellets to obtain a polycarbonate molding material for an optical disk of the present invention.

Incidentally, as the polycarbonate resin of the present invention, a homo-, co-polycarbonate resin using ordinary bisphenols, further branched, those having a long-chain alkyl group introduced into the terminal, styrene or the like in the polycarbonate resin. Any of those obtained by grafting or those obtained by graft-polymerizing a polycarbonate resin to polystyrene can be used.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples and the like.

The percentages and parts in the examples and the like are on a weight basis unless otherwise specified.

Example 1 and Comparative Example 1 Polymerization of aromatic polycarbonate resin. A reaction vessel having a capacity of 5 m ³ was charged with 300 kg of bisphenol A, 1,400 of 10% caustic soda, 650 of methylene chloride, and 0.5 kg of hydrosulfite and stirred. 12.3 kg of p-tert-butylphenol was added thereto, and 147 kg of phosgene was added to about 45 kg.
Infused in minutes.

After completion of the phosgene blowing, 0.2 kg of triethylamine was added, and polymerization was carried out for 60 minutes while maintaining the temperature at 30 ° C. under strong stirring.

Washing and centrifugation of resin solution. After completion of the polymerization, the reaction solution was sent to a continuous centrifuge,
The aqueous layer was separated by centrifugal force of 000G. The resin solution was sent to a stirring tank, 300 parts of pure water was added thereto, and the mixture was stirred for 30 minutes. After completion of the stirring, the aqueous layer was centrifuged in the same manner as described above, and the obtained resin solution was sent to a phosphoric acid neutralization tank. % Phosphoric acid aqueous solution 300 was added and stirred, and after completion of the stirring, the phosphoric acid aqueous solution layer was centrifuged in the same manner as described above.

Subsequently, the resin solution separated as described above was sent to a final washing tank, and pure water 300 was added thereto, followed by stirring and centrifugation.

At this time, the conductivity of the separated aqueous layer was 8.6 μs / cm, and the water content of the resin solution was 0.35%.

Filtration of the resin solution. This resin solution was filtered through a poly-perfluoroethylene membrane filter having a pore size of 1.2 μm. Water droplets aggregated on the filter filtration surface to form large droplets and collected on the upper part of the filter housing. As a result, the water content in the resin solution after filtration was 0.12%.

Separation of polycarbonate. This resin solution was mixed with 200 of n-heptane and dropped into water under strong stirring at a temperature of 55 ° C under normal pressure, and after completion of dropping, the temperature was raised to 95 ° C or higher, and the solvent was distilled off. The water slurry of the obtained polycarbonate resin is filtered, the resin powder is taken out, and the powder is pulverized to have an average particle diameter of 1-1.
It was set to 5 mm and dried at 140 ° C. for 3 hours.

 The free chlorine in the dry powder was 0.2 ppm.

Preparation of molding material. The additives shown in Table 1 were added to the above-obtained polycarbonate powder, mixed, and then extruded at 270 ° C. with a vented extruder to obtain a pellet, thereby obtaining a molding material for an optical disk.

Optical disk manufacturing and reliability evaluation. The above pellets were injection molded to obtain a 1.2 mm thick optical disk substrate for data files having a spiral groove on one side.

A Te / Fe / Co alloy, which is a photomagnetic film, was deposited on the substrate by sputtering, and a photocurable acrylic resin was coated on the recording film and cured with ultraviolet light.

The number of defects of 30 μm or less along the circumference of this optical disk was measured on the entire disk surface, and the disk was left at 80 ° C., 90% RH for 300 hrs. The results are shown in Table 1.

Further, for comparison, the same result was shown as Comparative Example 1 by using a polycarbonate molding material obtained by centrifugal purification alone without performing water separation by a membrane filter.

The measurement of free chlorine in the pellets in Table 1
5 g is precisely weighed and dissolved in 150 ml of methylene chloride, and acetone 5
0 ml was added, and it was determined by potentiometric titration using a 0.0005 M silver nitrate / acetone solution as a titration reagent.

The inspection of the number of eaves defects on the disk was performed using an automatic eaves inspection apparatus I, manufactured by JEOL Ltd.

Example 2 and Comparative Example 2 Beeswax 0.1 was added to the polycarbonate resin powder obtained in Example 1.
%, And pelletized in a vented extruder in the same manner. The free chlorine in the pellet was 0.2 ppm.

Using the pellets as a raw material, a compact disk having a thickness of 1.2 mm was molded, an aluminum vapor-deposited film was formed on the substrate, coated with a photocurable acrylic resin, and cured with ultraviolet light.

Defects of more than 50 μm for this compact disc
Table 2 shows the results of an environmental test at 80 ° C. and 90% RH.

Also, for comparison, an alkaline aqueous layer was allowed to stand still from the polycarbonate resin solution after the polymerization reaction, and then pure water was added to the resin solution at 1.5 times the volume of the resin solution and mixed. Was removed. The material of the filter cloth was cotton.

This pure water mixing and filter press separation were performed a total of 5 times to obtain a purified resin solution.

At this time, the conductivity of the final washing water is 60 μs / cm, and the water content is 1.2.
%Met.

Solidification and drying of the polycarbonate from the purified resin solution described above were performed in the same manner as in Example 1, pelletized in the same manner as described above, and production and testing of a compact disk were performed in the same manner. Table 2 shows the results. The free chlorine in the pellets used for molding was 1.2 ppm.

[Functions and Effects of the Invention] As described above, it is clear that the optical disk made of the polycarbonate resin molding material of the present invention has excellent long-term reliability regardless of the material of the recording film. It can be used with confidence even when forced to do so, and its industrial significance is extremely high.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-138097 (JP, A) JP-A-52-96697 (JP, A)

Claims (1)

(57) [Claims] An aromatic polycarbonate resin obtained by the reaction of bisphenol and phosgene, wherein the polycarbonate resin contains 0.2 ppm or less of free chlorine in the polycarbonate resin.