JPH0481457A - Polycarbonate molding material for optical use - Google Patents

Abstract

PURPOSE:To obtain the title molding material capable of producing polycarbonate substrates for optical use excellent in transparency and free from internal defects by pelletizing polycarbonate resin granules incorporated with a specified amount of phosphorous acid in combination with water. CONSTITUTION:(A) A polycarbonate resin 12000-20000 (pref. 13000-18000) in viscosity-average molecular weight is incorporated with (B) 5-50 (pref. 10-40) ppm of phosphorous acid and (C) such an amount water as to come to 500-5000 (pref. 1000-3000) ppm in the moisture content of the component A, and, where needed, (D) a thermal stabilizer (pref. trisnonylphenyl phosphite, tridecyl phosphite), (E) a releasant (pref. stearic monoglyceride, pentaerythritol monoglyceride), etc., and the resulting blend is extruded into pellets, thus obtaining the objective molding material.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical polycarbonate molding material, and more specifically, to a polycarbonate molding material that can be used to produce an optical polycarbonate substrate that has excellent transparency and is free from internal defects. It relates to molding materials.

[Prior Art and its Problems] Polycarbonate resins have excellent transparency, heat resistance, and dimensional stability, and are therefore known to be used as optical substrates for, for example, optical discs, lenses, and prisms. These optical substrates are required to be non-colored, highly transparent, and free from foreign matter and internal defects (scratches) for use in boat fishing.

On the other hand, polycarbonate resin is usually produced by reacting a dihydroxydiaryl compound such as bisphenol A with phosgene in the presence of alkali in a mixed solvent consisting of water and a halogenated hydrocarbon, but in the case of optical polycarbonate In order to improve moldability, the molecular weight of the polymer is adjusted to a relatively low value, and in addition, by avoiding the contamination of foreign substances from the outside, and by thoroughly refining the resulting polymer, solvents and by-product salts are prevented from entering the polymer. It is necessary to suppress contamination as low as possible.

However, when a substrate for an optical desk is manufactured using, for example, an injection molding method using the polycarbonate resin manufactured in this way, there is no problem with the substrate immediately after molding, but
When this substrate is held at high temperature and high humidity for a long time, there is a drawback that fine point defects with a diameter of several tens of microns are generated within the substrate.

Although these point defects are minute and occur in small numbers, they affect the reliability of recorded information on optical discs (for example, signal reading errors), so it is important to suppress their occurrence as much as possible. is important. Although the cause of this point defect is not clear, it is thought to be caused by partial hydrolysis of the polycarbonate resin. Therefore, attempts have been made to add various stabilizers to polycarbonate resin, but so far no method has been found that can sufficiently suppress the above-mentioned point defects without impairing the optical function. do not have.

[Means for Solving the Problems 1] In view of the above circumstances, the present inventors have developed a method that can suppress the occurrence of point defects even if an optical disk substrate made of polycarbonate resin is kept at high temperature and high humidity for a long time. As a result of extensive research, we found that when molding optical disk substrates using a molding material obtained by pelletizing polycarbonate resin powder to which a specific amount of phosphorous acid is added together with water,
It has been found that the obtained substrate is not colored, has good transparency, and has almost no occurrence of the above-mentioned point defects.

That is, the gist of the present invention is to add 5-50 ppm of phosphorous acid to a polycarbonate resin and to add water to reduce the water content of the resin to 50 ppm.
The present invention relates to an optical polycarbonate molding material, which is made by adjusting the content to 0 to 5000 ppm and then pelletizing it by extrusion molding.

The present invention will be explained in detail below.

The production method for the polycarbonate resin targeted by the present invention is not particularly limited, but usually, a dihydroxydiaryl compound and phosgene are mixed in a mixed solvent of water and a halogenated hydrocarbon in the presence of an alkali. Examples include polymers obtained by reaction. Further, as the dihydroxycyatool compound, a compound containing 2,2-bis(4-hydroxyphenyl)propane [bisphenol A] as a main component is typically typical. In some cases, the polycarbonate resin of the present invention may be a copolymer with other components.

The average molecular weight of the polycarbonate resin used in the present invention is usually 12,000-20,000, preferably 13,000, since precise molding is required for optical use.
000-18000. The viscosity average molecular weight is determined by using a methylene chloride solution of polycarbonate resin (concentration 6 g/l) and using an Ubbelohde viscosity tube at 20°C relative viscosity ("
1rel) and calculated from the following formula.

"lsp = rlrel-1"lsp/C= [11] ('rlsp to 1+) (wherein, C is the concentration of the polycarbonate resin solution (g/l),
[r1] is the limiting viscosity, and K' is a constant of 0.28. )
[rl]=KMC (In the formula, K is a constant 1.23 x 10-5, M is a viscosity average molecular weight, and is o, 83.) The average molecular weight of the polycarbonate resin is adjusted according to a conventional method, for example, This can be carried out by adding a known terminal capping agent such as phenol or P-tert-butylphenol to the polymerization system.

In addition, the polycarbonate resin used in the present invention is free from foreign matter,
It is necessary to minimize the content of impurities such as reaction solvents and by-product salts.

The above-mentioned polycarbonate resin is usually obtained in the form of powder or granules, and then pelletized by extrusion molding to obtain an optical molding material.

This pelletizing method is not particularly limited, and according to a conventional method, first, a strand is formed using an extruder, and then, after cooling, it can be pelletized using a pelletizer.

The molding temperature (resin temperature) at this time is usually 250-30
It is 0°C. Further, the size of the pellet is usually about 1-3 mm in diameter and 2-3 mm in length.

In the present invention, when molding the above pellets, it is essential to add phosphorous acid and water to the polycarbonate resin. In short, pellets of polycarbonate resin, which is desirable as an optical molding material, are obtained through the interaction of phosphorous acid and water.

The amount of phosphorous acid added to polycarbonate resin is
5-50 ppm, preferably 10-40 ppm. If the amount added is too small, it will not be possible to sufficiently suppress the occurrence of point defects when the optical substrate manufactured by injection molding the obtained pellets is held at high temperature and high humidity. On the other hand, if the amount is too large, the properties as an optical substrate such as adhesion with the recording film will be impaired, which is not preferable.

In addition, the amount of water added to the polycarbonate resin is such that the water content of the polycarbonate resin when pelletizing is 500%.
-5000 ppm, preferably 1000-3000p
Adjust to within the pm range. If the amount of water added is too small, the occurrence of the above-mentioned point defects cannot be sufficiently suppressed, and if it is too large, hydrolysis of the polycarbonate resin will occur, which is not preferable.

Furthermore, in the present invention, other additives such as a heat stabilizer and a mold release agent may be added to the polycarbonate resin as necessary. However, in the case of the present invention, it is not desirable to use too many additives, and other additives include:
Minimum required amount of material that does not adversely affect the quality of optical molded products.
It is preferable to use Suitable thermal stabilizers include, for example, phosphorous esters such as trisnonylphenyl phosphite, tridecyl phosphite, di(monononylphenyl)-dinonylphenyl phosphite, and the like.

Suitable mold release agents include, for example, stearic acid monoglyceride, behenic acid monoglyceride, pentaerythritol monoglyceride, stearyl stearate, pentaerythritol tetrastearate, and the like. It is preferable to use highly purified additives, and in some cases, it is preferable to use them after purification.

The polycarbonate molding material of the present invention can be used to produce optical molded products such as optical disk masters using a conventional method, for example, an injection molding machine.
Resin temperature) is usually 330-400°C. Also, the injection pressure is usually 1000-2000kg/c
It is m2G.

[Example 1] Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1-3 and Comparative Example 1-2 [Manufacture of polycarbonate] A 13.5% aqueous solution of sodium salt of bisphenol A prepared by dissolving 100 parts by weight of bisphenol A in 640 parts by weight of a 5.6% aqueous sodium hydroxide solution. 340 parts by weight of methylene chloride were mixed uniformly, and 48.
After introducing 7 parts by weight, the reaction was carried out at room temperature to produce an oligomer.

Next, the reaction mixture containing the oligomer was separated into an aqueous phase and a methylene chloride phase, and the methylene chloride phase was mixed with 270 parts by weight of methylene chloride, 160 parts by weight of a 5% aqueous sodium hydroxide solution, and 3.95 parts by weight of P-tert-butylphenol. and 2.44 parts by weight of a 2% triethylamine aqueous solution were added thereto, and interfacial polymerization was carried out by stirring vigorously at room temperature, and the resulting mixture was separated into an aqueous phase and a methylene chloride phase.

The methylene chloride solution in which the produced polycarbonate obtained here is dissolved is sufficiently washed by repeated washings of ① water, ② aqueous hydrochloric acid solution, and ② water, and then placed in water at 45°C in a stirring device equipped with shear blades. By discharging, methylene chloride was volatilized and polycarbonate resin granules were precipitated. Then, this was separated and dried to recover the polycarbonate resin.

The viscosity average molecular weight of this polycarbonate resin is 1450
0, and the total light transmittance was 93%.

[Preparation of pellets] Stearic acid monoglyceride 1100 is added to the polycarbonate resin granules recovered by the above method as a mold release agent.
PP and ① Phosphorous acid in the amounts shown in Table 1 were mixed uniformly, and water was further sprayed to adjust the water content in the resin to the amount shown in Table 1. The method for measuring water content is as described below.

Thereafter, this was made into
A strand was formed by extrusion at a temperature of 0°C, which was then cooled with water and cut with a pelletizer to obtain pellets (2.3 mm x 2.3 mm) of polycarbonate resin.

[Molding of optical disk substrate] Next, the above pellets were used to mold an optical disk substrate (diameter 130 mm, thickness 1.2 mm) using a disk injection molding machine at a molding resin temperature of 370°C, and then molded from polycarbonate resin. A substrate for an optical disk was obtained. All of the optical disk substrates obtained here had excellent transparency and had no internal defects.

The thus obtained polycarbonate optical disk substrates (5 each) were subjected to a retention test under the conditions shown below, the number of point defects after the test was determined, and the transparency of the substrate was checked. The results are shown in Table 1.

(b) Measurement of the number of point defects Five polycarbonate optical disk substrates obtained by injection molding were heated at a constant temperature and humidity of 85°C and 85% humidity.
After holding for 00 hours, the total number of point-like defects of 20 microns or more generated in all the substrates was counted, and this was divided by 5 to show the average number of defects per substrate.

(b) Transparency Five polycarbonate optical disk substrates after the retention test in (a) above were stacked and the degree of coloring and transparency when observed from the side were determined by the naked eye.

(c) Measurement of water content in resin Collect the resin just before pelletizing it, use it as a sample, put 1 g of the sample in a heating furnace, and add 200 ml of dehumidified nitrogen residue.
The sample was introduced into a heating furnace at a rate of 1/min to heat and vaporize the moisture in the sample. (Moisture vaporizer VA-05
Type: Mitsubishi Kasei Co., Ltd.) The vaporized moisture was measured using a Karl Fischer titrator (trace moisture measuring device CA-05 model 2, made by Mitsubishi Kasei Co., Ltd.). The time required for titration is 5~
It's 10 minutes.

Table 1 [Effects of the Invention] When an optical molded product, such as a substrate for an optical disk, is produced by injection molding using the polycarbonate resin molding material of the present invention, it may be exposed to high temperature and high humidity for a long time. Even if the substrate is maintained for a long time, internal defects will hardly occur in the substrate. Therefore, by forming an information recording film on this substrate, an extremely highly reliable optical disc can be obtained.

Claims (1)

[Claims] (1) It is characterized by adding 5-50 ppm of phosphorous acid to a polycarbonate resin and adjusting the water content of the resin to 500-5000 ppm by adding water, and then pelletizing it by extrusion molding. Optical polycarbonate molding material.