JPH0723921B2 - Optical disc substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical disk substrate. More specifically, it relates to a molded product having excellent transparency and small optical distortion.

Molded products used for optical applications, such as plate-shaped products, sheet-shaped products, box-shaped products, block-shaped products, and other molded products of various shapes, are transparent and have a small optical distortion. It is necessary, in particular, a so-called optical disc that optically records and reproduces a signal using a laser beam or the like, for example,
The substrate used to construct digital audio discs, digital video discs, or signal recording discs for electronic computers has excellent transparency and optical distortion.
A retardation with a thickness of 1.2 mm of 60 mμ or less and a small warpage is required.

In order to industrially produce such a molded product, it is advantageous to use a polycarbonate resin having excellent transparency and perform the molding by an injection molding method, but a molded product having a small optical distortion can be obtained. In order to obtain the above, it is necessary to improve the flow of the resin during injection molding to avoid generation of optical nonuniformity due to the flow of the molten resin.

As a method of improving the flow of the molten resin, a method of selecting a high resin temperature during injection molding can be considered, but when the resin temperature is raised, decomposition such as yellowing occurs due to decomposition of the resin, and the transparency of the resulting molded article is improved. There is a risk of damage. Further, it is also possible to use a polycarbonate resin having a low average molecular weight, but a polycarbonate resin having a low average molecular weight, for example, a polycarbonate resin having a number average molecular weight of less than 12000, has a remarkable decrease in molecular weight during injection molding, and mechanical properties. Is greatly reduced, and there is an inconvenience such as damage at the time of mold release during injection molding.

The present inventors have conducted extensive studies to obtain a molded article having excellent transparency and small optical distortion, and as a result, a polycarbonate resin having a specific average molecular weight, that is, an average molecular weight of 12000.
-18,000 bis (hydroxyphenyl) alkane-based polycarbonate resin as the main constituent material, injection molded products have good transparency, small optical distortion, and little warpage, and are suitable for optical disc substrates. And completed the present invention.

That is, an object of the present invention is to provide a molded product of an optical disc substrate having excellent optical characteristics.

The gist of the present invention is to use a bis (hydroxyphenyl) alkane-based polycarbonate resin having an average molecular weight of 12000 to 18000 as a main constituent material, and have an optical distortion of 1.2 mm.
The optical disc substrate is characterized by having a thickness retardation of 60 mμ or less.

Hereinafter, the present invention will be described in detail.

The bis (hydroxyphenyl) alkane-based polycarbonate resin having an average molecular weight of 12000 to 18000 used in the present invention is produced by reacting a bis (hydroxyphenyl) alkane with a carbonic acid ester such as phosgene or diphenyl carbonate. The average molecular weight is calculated from ηsp measured at 20 ° C. using a 6.0 g / methylene chloride solution of a polycarbonate resin, And expression It is the value calculated by. The average molecular weight is usually controlled by adding an end terminating agent such as phenol or p-tert-butylphenol during the production of the polycarbonate resin.

Examples of bis (hydroxyaryl) alkanes include bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, and 2,2-bis (4-
Hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) octane, etc. may be mentioned, but within a range that does not impair the physical properties of the resulting disc, 1, Bis (hydroxyaryl) cycloalkanes such as 1-bis (4-hydroxyphenyl) cyclohexane, dihydroxydiphenyl ethers such as 4,4'-dihydroxyphenyl ether, such as 4,4'-dihydroxydiphenylsulfide Dihydroxydiphenyl sulfides, 4,
It is also possible to use a mixture of dihydroxydiphenyl sulfoxides such as 4'-dihydroxydiphenyl sulfoxide and dihydroxydiphenyl sulfones such as 4,4'-dihydroxydiphenyl sulfone.

Among these polycarbonate resins, the polycarbonate resin produced from 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is preferable.

The average molecular weight of polycarbonate resin is 12,000 to 18,000.
And preferably about 13,000 to 17,500. If the average molecular weight is too high, it is necessary to perform molding at a resin temperature exceeding 400 ° C in order to produce a molded product with low optical strain, and at such high temperatures, decomposition of the resin cannot be avoided and molding There are inconveniences such as the occurrence of silver streaks on the surface of objects and coloring. If the average molecular weight is too low, it is possible to produce a molded product with less optical distortion, but the molecular weight of the resin is significantly reduced during molding, the physical properties of the resin deteriorate, and when releasing from the mold during molding. Even if it comes to break and a molded product is obtained, its mechanical strength is low.

Therefore, when producing the injection-molded article of the present invention, it is preferable to use a phosphite ester in order to prevent coloring and deterioration due to decomposition of the resin during production. Phosphorous acid ester is a diester or triester of phosphorous acid and alcohols or phenols, and as R ¹ and R ² in the general formula shown above, a butyl group, a hexyl group, an octyl group, and a 2-ethylhexyl group. , Alkyl groups such as nonyl group, decyl group, dodecyl group, octadecyl group, pentaerythrityl group and cyclohexyl group, and aryl groups such as phenyl group, toluyl group and nonylphenyl group. Alternatively, R ³ is a hydrogen atom or the above-described alkyl group or aryl group.

Specific examples of the phosphite include tributyl phosphite, tris (2-ethylhexyl) phosphite,
Tridecyl phosphite, tristearyl phosphite, triphenyl phosphite, tricresyl phosphite, tris (nonylphenyl) phosphite, 2-ethylhexyl diphenyl phosphite, decyl diphenyl phosphite, phenyl di-2-ethylhexyl phosphite, phenyl Examples thereof include didecyl phosphite, tricyclohexyl phosphite, distearyl pentaerythrityl diphosphite, diphenyl pentaerythrityl diphosphite, and the like, and phosphite ester having at least one alkyl group is particularly preferable.

The amount of phosphite ester is 0.005 to 0.5% by weight, preferably 0.01 to 0.2% by weight, based on the polycarbonate resin. If the amount of phosphite is too small, it is not possible to suppress coloring and deterioration of transparency due to decomposition of the resin. On the other hand, if the amount is too large, decomposition of the phosphite itself becomes visible, which causes inconvenience such as silver streak.

In order to contain the phosphite ester in the polycarbonate resin, as in the ordinary method for preparing the resin composition, a method of dry blending the two, a method of melt mixing the blend using an extruder or the like, or a phosphorus phosphite It can be carried out by a method of preparing master pellets having a high acid ester content and mixing them with polycarbonate resin pellets.

In the present invention, preferably a polycarbonate resin containing a phosphite, a resin temperature of 330 ~ 400 ℃,
Injection molding is performed at a mold temperature of 50 to 110 ° C.

In this molding, if the resin temperature is too high, the decomposition of the resin becomes unavoidable, which causes coloring and silver streaks, resulting in poor transparency. On the other hand, if the resin temperature is too low, melt flowability will not be sufficient even if the polycarbonate resin of the present invention is used, and a molded product with small optical distortion cannot be obtained. The preferable resin temperature is about 335 to 390 ° C.

The mold temperature is 50 to 110 ° C, preferably about 60 to 105 ° C. If the mold temperature is too high, the deformation during mold release will increase,
A molded product with a small warp cannot be obtained. On the contrary, if it is too low, it becomes impossible to obtain a molded product having a small optical distortion.

The molded product according to the present invention is a molded product having excellent transparency and small optical distortion, and particularly in applications such as digital signal recording disks, it is possible to manufacture a disk having the above characteristics and a small warpage. , Industrially very advantageous.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist.

In the following examples, "part" and "%" indicate "part by weight" and "% by weight", respectively.

Moreover, the measured values of the physical properties are the values measured by the following methods.

Retardation The center portion of the molded disc having a thickness of 1.2 mm and a diameter of 120 mm was measured by attaching a calcite compensator to a polarizing microscope manufactured by Carl Zeiss Co., Ltd. and shown in mμ.

Warp amount The same disc as above was placed on a flat plate, and the floating height of the highest end lifted by the warp was measured by Mitoyo Co., Ltd.
It was measured by using a three-dimensional dimension measuring device manufactured by and manufactured, and indicated in mm.

Total light transmittance 3.5 ounce injection molding machine (TOSHIBA MACHINE CO., LTD IS75S), resin temperature 355 ℃, mold temperature 80 ℃, thickness 3.2mm, diameter 50
mm test piece was prepared and manufactured by Tokyo Denshoku Co., Ltd.
Transmittance was expressed in%, measured according to ASTM D 1003 using TC-5D.

Melt fluidity Using a 3.5 oz injection molding machine (same as above) and a 2 mm thick mold for spiral flow measurement, injection molding is performed at a resin temperature of 355 ° C, a mold temperature of 80 ° C, and an injection pressure of 850 kg / cm ² . The flow length is shown in mm.

Melt index (MI) A value (g / 10 minutes) measured at a temperature of 230 ° C and a load of 5 kgf according to the ISO R-1133 test method.

Production Example A of Polycarbonate Resin A 100 parts aqueous solution of 13% bisphenol A sodium salt prepared by dissolving bisphenol A in 5% aqueous sodium hydroxide solution, p-tert-butylphenol 0.298 parts,
2.44 parts of 2% triethylamine aqueous solution and methylene chloride
539 parts were mixed and stirred, and interfacial polymerization was carried out while introducing 56.8 parts of phosgene.

The reaction mixture was separated, 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 obtain a polycarbonate resin having an average molecular weight of 17800.

Tridecyl phosphite on this polycarbonate resin,
The resin compositions containing 0.05% of 2-ethylhexyldiphenylphosphite or trisnonylphenylphosphite have total light transmittances of 91%, 90% and 87%, respectively.
%, Melt flowability was 550 mm, 540 mm and 540 mm.
If it does not contain phosphite, the total light transmittance is 81
%, Melt fluidity was 530 mm.

Production Example B of Polycarbonate Resin A polycarbonate resin having an average molecular weight of 15500 was obtained in the same manner as in Production Example A except that 0.347 parts of p-tert-butylphenol was used.

Tridecyl phosphite 0.
The resin composition containing 02% or 0.15% has a total light transmittance of 91% and a melt fluidity of 850 mm.
And was 900 mm.

Production Example C of Polycarbonate Resin A polycarbonate resin having an average molecular weight of 21800 was obtained in the same manner as in Production Example A except that 0.237 parts of p-tert-butylphenol was used.

Tridecyl phosphite 0.
The resin composition containing 05% had a total light transmittance of 90% and a melt fluidity of 340 mm.

Examples 1 to 8 and Comparative Example 1 The polycarbonate resin flakes having an average molecular weight of 17800 produced in Production Example A were mixed with the phosphite ester shown in Table 1 below and melt-kneaded at 270 ° C. using a 40 mmφ extruder. It was extruded and pelletized to obtain a phosphite-containing polycarbonate resin pellet having an average molecular weight shown in Table 1 below.

Using a 4 ounce injection molding machine (J150S manufactured by Japan Steel Works, Ltd.), these pellets are molded into a digital audio disk substrate with a thickness of 1.2 mm and a diameter of 120 mm at the resin temperature and mold temperature shown in Table 1 below. did.

The retardation and the amount of warpage of the obtained disk were as shown in Table 1 below.

For comparison, as a polycarbonate resin, Production Example C was used.
The results of using the polycarbonate resin having an average molecular weight of 21800 manufactured in 1. are also shown.

Examples 9 to 10 Polycarbonate resin having an average molecular weight of 15500 produced in Production Example B was mixed with tridecyl phosphite in the amounts shown in Table 2 below, and a digital audio disc was molded in the same manner as in Example 1. .

The retardation and the amount of warpage of the obtained disk were as shown in Table 2 below.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Plastic material course “Polycarbonate resin” 100-102 September 30, 1969, Published by Nikkan Kogyo Shimbun, Textbook of Optical Industrial Technology Staff Training “Optical Technology”, 1981 edition, Vol. 15 P. 11 ~ 15, 44 ~ 46

Claims (2)

[Claims] 1. A bis (hydroxyphenyl) alkane-based polycarbonate resin having an average molecular weight of 12000 to 18000 as a main constituent material, and an optical strain of 60 mm or less in terms of retardation of 1.2 mm thickness. Optical disc substrate to be used. 2. An optical disk substrate having an average molecular weight of 12000.
A bis (hydroxyphenyl) alkane-based polycarbonate resin of 18,000 to 0.008 and a phosphorous acid ester represented by the following general formula in an amount of 0.005 to 0.5% by weight are injection-molded to obtain a composition. The optical disk substrate according to item 1. General formula