JP2000163806A - Optical polycarbonate resin forming material and optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively control production of white dots on a substrate and to maintain high reliability for a long time by using a polycarbonate resin which has a specified content of sulfur or sulfur compds. calculated as sulfur atoms and which has a specified range of viscosity average mol.wt. to produce a substrate. SOLUTION: The viscosity average mol.wt. of the polycarbonate resin is 10000 to 22000, especially preferably 13000 to 18000. The polycarbonate resin contains <=200 ppb sulfur or sulfur compd. calculated as sulfur atoms, and preferably <=100 ppb. The resin is produced by the normal reaction of divalent phenols and a carbonate precursor by a soln. method or melting method. Pure water of high purity treated by ultrafiltration is used as a means to prevent elution or mixing of sulfur or sulfur compds. During injection molding, the cylinder temp. is preferably controlled to 300 to 400 deg.C, and the die temp. is preferably 50 to 140 deg.C. The number of white dots having >=20 μm size produced in an accelerated deterioration test is <=2 per disk type substrate having 120 mm diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical polycarbonate resin molding material and an optical disk substrate capable of maintaining high reliability for a long period of time, and more particularly to an optical polycarbonate resin molding material having a reduced content of sulfur or a sulfur compound. The present invention relates to an optical disk substrate made of the material.

2. Description of the Related Art An optical disk substrate used for an optical information recording medium that reproduces information by using laser light, such as an audio disk, a laser disk, an optical disk memory, or a magneto-optical disk, and performs additional writing and rewriting includes:
Polycarbonate resins excellent in moldability, strength, light transmittance, moisture resistance and the like are often used. However, the polycarbonate resin having such excellent properties also has a drawback that it is easily hydrolyzed at high temperature and high humidity, and is liable to decrease in molecular weight and impact strength.

On the other hand, one of the characteristics required for an optical disk substrate and an optical information recording medium using the substrate is that high reliability can be maintained for a long period of time. However, as described above, the polycarbonate resin is rapidly deteriorated by hydrolysis under high temperature and high humidity, and it has been difficult to satisfy this requirement. Also, various studies have been made to improve the corrosion resistance of optical information recording media made of polycarbonate resin.
No. 7978 discloses that N in an optical disc substrate
It has been proposed that the content of a and Fe be 1 ppm or less, respectively, and the residual amount of chlorine-based solvent be 10 ppm or less. Further, in Japanese Patent No. 2662049,
Na 1 ppm or less, terminal hydroxyl group content 0.3 mol%
It has been proposed to:

[0003] However, the above prior art focuses on the optical disk substrate, and there is no specific definition of the molding material. Japanese Patent Publication No. 8-27978 does not disclose white spots generated by wet heat treatment.
No. 049 discloses 50 μm generated by wet heat treatment.
A large white point of m or more is described, but a finer white point is not mentioned.

[0004]

SUMMARY OF THE INVENTION The present inventor has found that when a polycarbonate resin optical disk (or its substrate) is held for a long time under high temperature and high humidity conditions, minute white spots are generated inside the optical disk. White spots may grow and expand over time, affecting the reliability of the recording medium,
Research was conducted to find out the cause. The effect of the generation of such minute white spots is that the information carrying density is much higher than that of a normal compact disc (CD), such as DVD-ROM, DV,
Digital versatile discs (DVD) such as D-video, DVD-R, and DVD-RAM are more prominent.

[0005] In order to investigate the cause of the generation of minute white spots in the disk substrate, further studies have been made with a focus on the trace components contained in the polycarbonate resin. Polycarbonate resins are manufactured industrially using several types of raw materials and additives and many devices and equipment. In other words, although slightly different depending on the production process, many trace components are eluted or mixed into the polycarbonate resin produced industrially from the raw materials or additives and the material of the equipment in the production process. ing.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the relationship between trace components in a polycarbonate resin and the generation of minute white spots. 200p as sulfur atom
The inventors have found that the use of pb makes it possible to extremely effectively control the generation of white spots on the polycarbonate resin substrate and to provide an optical disk capable of maintaining high reliability for a long period of time, and reached the present invention.

That is, the present invention relates to an optical polycarbonate resin molding material having a sulfur or sulfur compound content of not more than 200 ppb as a sulfur atom, and an optical disk substrate therefrom. Hereinafter, the present invention will be described in more detail.

[0008] The polycarbonate resin used in the present invention is usually obtained by reacting a dihydric phenol with a carbonate precursor by a solution method or a melting method. Representative examples of the dihydric phenol used here include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) Phenyl @ methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl)
-1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A), 2,2
-Bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis} (3,5-dibromo- 4-hydroxy) phenyl} propane, 2,2
-Bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis} (4-hydroxy-3-
Phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4
-Hydroxyphenyl) -3,3-dimethylbutane, 2,
4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis ( 4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-
Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4-hydroxy-
3-methyl) phenyl} fluorene, α, α′-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m
-Diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -p-diisopropylbenzene,
3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxydiphenyl ester; Alternatively, two or more kinds can be used in combination.

Bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane,
2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,
3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and α, α′-bis ( 4-hydroxyphenyl)
Homopolymers or copolymers obtained from at least one bisphenol selected from the group consisting of -m-diisopropylbenzene are preferred, and bisphenol A is particularly preferred.
And 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane or α, α'-bis (4-
A copolymer with (hydroxyphenyl) -m-diisopropylbenzene is preferably used.

As the carbonate precursor, carbonyl halide, carbonate ester or haloformate is used, and specific examples include phosgene, diphenyl carbonate and dihaloformate of dihydric phenol.

In producing the polycarbonate resin by reacting the dihydric phenol with the carbonate precursor by a solution method or a melting method, a catalyst, a terminal stopper, an antioxidant for the dihydric phenol, and the like may be used, if necessary. May be used. Further, the polycarbonate resin may be a branched polycarbonate resin obtained by copolymerizing a trifunctional or higher polyfunctional aromatic compound, or a polyester carbonate resin obtained by copolymerizing an aromatic or aliphatic bifunctional carboxylic acid, Further, a mixture of two or more of the obtained polycarbonate resins may be used.

The reaction by the solution method is usually a reaction between dihydric phenol and phosgene, and is carried out in the presence of an acid binder and an organic solvent. As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine is used. As the organic solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. Further, for promoting the reaction, for example, a catalyst such as a tertiary amine such as triethylamine, tetra-n-butylammonium bromide, or tetra-n-butylphosphonium bromide, a quaternary ammonium compound, or a quaternary phosphonium compound may be used. it can. At that time, the reaction temperature is usually 0 to 40 ° C., the reaction time is preferably about 10 minutes to 5 hours, and the pH during the reaction is preferably maintained at 9 or more.

In such a polymerization reaction, a terminal stopper is usually used. Monofunctional phenols can be used as such a terminal stopper. Monofunctional phenols are commonly used as molecular terminators for molecular weight control, and the resulting polycarbonate resins are capped by groups based on monofunctional phenols, so that Excellent heat stability. Such a monofunctional phenol is generally a phenol or a lower alkyl-substituted phenol, and may be a monofunctional phenol represented by the following general formula (1).

[0014]

Embedded image [Wherein, A is a hydrogen atom or a linear or branched alkyl group having 1 to 9 carbon atoms, or a phenyl-substituted alkyl group, and r is an integer of 1 to 5, preferably 1 to 3].

Specific examples of the above monofunctional phenols include phenol, p-tert-butylphenol, p-cumylphenol and isooctylphenol.

Other monofunctional phenols include:
Phenols or benzoic acid chlorides having a long-chain alkyl group or an aliphatic polyester group as a substituent, or long-chain alkyl carboxylic acid chlorides can be used. When blocked, these not only function as a terminal terminator or a molecular weight regulator, but also improve the melt flowability of the resin, not only facilitate the molding process, but also reduce the physical properties as a substrate, especially the water absorption of the resin. And the effect of reducing the birefringence of the substrate is preferably used. Among them, phenols having a long-chain alkyl group represented by the following general formulas (2) and (3) as a substituent are preferably used.

[0017]

Embedded image

[0018]

Embedded image [Wherein, X represents -R-O-, -R-CO-O- or -R
—O—CO—, wherein R is a single bond or 1 carbon atom
Represents a divalent aliphatic hydrocarbon group of 10 to 10, preferably 1 to 5, and n represents an integer of 10 to 50. ]

As the substituted phenols of the formula (2), those wherein n is 10 to 30, especially 10 to 26 are preferred.
Specific examples thereof include decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol, and tricontylphenol.

Further, as the substituted phenols of the formula (3), a compound in which X is -R-CO-O- and R is a single bond is suitable, and n is 10 to 30, especially 10 to 26. Those are preferable, and specific examples thereof include decyl hydroxybenzoate, dodecyl hydroxybenzoate, tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate and tricontyl hydroxybenzoate. .

It is desirable that these terminal stoppers be introduced at least at 5 mol%, preferably at least 10 mol%, based on all terminals of the obtained polycarbonate resin. Or a mixture of two or more. The reaction by the melting method is usually a transesterification reaction between a dihydric phenol and a carbonate ester. It is done by the method of letting out. The reaction temperature varies depending on the boiling point of the produced alcohol or phenol, but is usually in the range of 120 to 350 ° C. In the latter half of the reaction, the pressure of the system is reduced to about 10 to 0.1 Torr to facilitate the distillation of the alcohol or phenol produced. The reaction time is usually about 1 to 4 hours.

Examples of the carbonate ester include an optionally substituted ester such as an aryl group having 6 to 10 carbon atoms, an aralkyl group or an alkyl group having 1 to 4 carbon atoms. Specific examples include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, and the like. Is preferred.

A polymerization catalyst may be used to increase the polymerization rate. Examples of the polymerization catalyst include sodium hydroxide, potassium hydroxide, alkali metal compounds such as sodium and potassium salts of dihydric phenol, and water. Alkaline earth metal compounds such as calcium oxide, barium hydroxide and magnesium hydroxide; nitrogen-containing basic compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylamine and triethylamine; alkoxides of alkali metals and alkaline earth metals Manganese, organic acid salts of alkali metals and alkaline earth metals, zinc compounds, boron compounds, aluminum compounds, silicon compounds, germanium compounds, organic tin compounds, lead compounds, osmium compounds, antimony compounds Compounds, titanium compounds, usually the esterification reaction, such as zirconium compounds, there can be used a catalyst used in the transesterification reaction. The catalyst may be used alone or in combination of two or more. The amount of the polymerization catalyst to be used is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁸ per 1 mol of the starting dihydric phenol.
^-3 equivalents, more preferably 1 × 10 ^{−7 to} 5 × 10 ⁻⁴ equivalents.

The polycarbonate resin has a viscosity average molecular weight (M) of preferably 10,000 to 22,000, more preferably 12,000 to 20,000, and more preferably 13,000 to 20,000.
000 to 18,000 is particularly preferred. A polycarbonate resin having such a viscosity average molecular weight is preferable because sufficient strength is obtained as an optical material, and the melt fluidity during molding is good, and molding distortion is not generated. The viscosity average molecular weight referred to in the present invention is obtained by inserting the specific viscosity (η _sp ) obtained from a solution obtained by dissolving 0.7 g of a polycarbonate resin in 100 mL of methylene chloride at 20 ° C. into the following equation. η _sp /c=[η]+0.45×[η] ² c (where [η] is the intrinsic viscosity) [η] = 1.23 × 10 ^-4 M ^0.83 c = 0.7

The raw material polycarbonate resin is manufactured by a conventionally known method (solution polymerization method, melt polymerization method, etc.), and then subjected to precision purification and microfiltration treatment in a solution state, or to granulation after granulation (desolvation). It is preferable to remove impurities and foreign matters such as low molecular weight components and unreacted components by washing the raw material with a poor solvent such as acetone under heating conditions. Further, in the extrusion step (pelletizing step) of obtaining a pellet-like polycarbonate resin for use in injection molding, it is preferable to remove foreign matter by passing through a sintered metal filter having a filtration accuracy of 10 μm in a molten state. If necessary, it is also preferable to add an additive such as a phosphorus-based antioxidant. In any case, it is necessary to minimize the content of foreign materials, impurities, solvents and the like in the raw material resin before injection molding.

The polycarbonate resin used in the present invention has a sulfur or sulfur compound of 200 pp as a sulfur atom.
b, preferably 100 ppb or less. For this reason, it is desirable to employ a means that minimizes elution or contamination of sulfur or sulfur compounds in the production process. As one of them, a method of removing a sulfur compound can be adopted. Examples of such means include microfiltration and washing with high-purity pure water that does not contain sulfur or sulfur compound ions or water-soluble impurities. Further, it is recommended to use a packing material having a low sulfur content as a material or to select a material having a small amount of sulfur eluted. Also, when carbon monoxide is generated from coke as a raw material and phosgene is produced from this carbon monoxide and chlorine, the sulfur component in the coke is mixed into the phosgene. It is also recommended to treat the carbon oxide with an alkali to remove the generated sulfur component. When an optical disk substrate is manufactured from the above polycarbonate resin, an injection molding machine (including an injection compression molding machine) is used. As this injection molding machine, a commonly used one may be used, but from the viewpoint of suppressing the generation of carbides and increasing the reliability of the disk substrate, the adhesion to the resin as a cylinder or a screw is low, and the corrosion resistance and abrasion resistance are low. It is preferable to use a material made of a material having properties.
Injection molding conditions are cylinder temperature 300-400.
C. and a mold temperature of 50 to 140 ° C. are preferred, whereby an optically excellent optical disc substrate can be obtained. The environment in the molding step is preferably as clean as possible from the viewpoint of the present invention. It is also important to sufficiently dry the material to be subjected to molding to remove moisture, and to take care not to cause stagnation that may cause decomposition of the molten resin.

The optical disk substrate made of the optical polycarbonate resin molding material according to the present invention has a very small generation of minute white spots even when held for a long time under high temperature and high humidity conditions, and is excellent as an optical disk substrate, especially a DVD substrate. ing. The characteristics under this high temperature and high humidity condition are as follows.
It is confirmed by examining the number of white spots generated after holding in a thermo-hygrostat controlled at a relative humidity of 85% for 1000 hours.
The number of white spots generated on a disk obtained from the aromatic polycarbonate resin molding material according to the present invention is 2 or less per substrate having a diameter of 120 mm, and preferably 1 or less.

[0028]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The evaluation was performed according to the following method. (A) Amount of trace components contained Analysis method: ICP (Inductively Coupled)
(led Plasma) emission spectroscopy (b) Number of white spots after wet heat treatment In order to reproduce the increase in white spots when left in a severe atmosphere for a long time, the disk was controlled at a temperature of 80 ° C. and a relative humidity of 85%. It was kept in a thermo-hygrostat for 1000 hours, and then the number of white spots of 20 μm or more was counted using a polarizing microscope. This was performed for 25 optical disk substrates (120 mm in diameter), and the average value was obtained, and this was defined as the number of white spots.

Example 1 In a reactor equipped with a thermometer, a stirrer and a reflux condenser, 219.4 parts of ion-exchanged water and 40.2% of a 48% aqueous sodium hydroxide solution were used.
After dissolving 57.5 parts (0.252 mol) of 2,2-bis (4-hydroxyphenyl) propane and 0.12 parts of hydrosulfite, 181 parts of methylene chloride was added thereto, and the mixture was stirred. Phosgene 2 at 15-25 ° C
8.3 parts were blown in for 40 minutes. After completion of the phosgene blowing, 7.2 parts of a 48% aqueous sodium hydroxide solution and p
2.42 parts of -tert-butylphenol was added, stirring was started, 0.06 parts of triethylamine was added after emulsification, and the mixture was further stirred at 28 to 33 ° C for 1 hour to complete the reaction. After the completion of the reaction, the product was diluted with methylene chloride, washed with water, acidified with hydrochloric acid, and washed with water.When the conductivity of the aqueous phase became almost the same as that of ion-exchanged water, an isolation chamber having a foreign substance take-out port in the bearing was formed. The methylene chloride was evaporated by the provided kneader to obtain a powder having a viscosity average molecular weight of 15,000. To this powder was added 0.01% by weight of tris (2,4-di-tert-butylphenyl) phosphite and 0.08% by weight of monoglyceride stearate. Next, the powder was used as a vent-type twin screw extruder [KTX manufactured by Kobe Steel Ltd.]
-46] and melt-kneaded while degassing at a cylinder temperature of 240 ° C to obtain pellets.

The sulfur atoms contained in the pellet are converted to ICP
(Inductively Coupled Plas
ma) Analyzed by emission spectroscopy. As a result, the sulfur atom was 70 ppb. An optical disk substrate (120 mm in diameter and 0.6 m in thickness) was formed using a disk molding machine [DISK3M III manufactured by Sumitomo Heavy Industries, Ltd.] using the pellets.
m), and the 25 substrates were heated at a temperature of 80 ° C. and a humidity of 85
%, The white spots on the substrate were counted using an optical microscope. This was performed for 25 optical disk substrates, the average value was determined, and this was defined as the number of white spots.

Example 2 An optical disk substrate was molded and evaluated in the same manner as in Example 1 except that a polycarbonate resin having a sulfur atom content of 160 ppb was used as a raw material pellet.
Table 1 shows the results.

Example 3 Raw material pellets were produced in the same manner as in Example 1 except that 2.72 parts of p-tert-butylphenol was added to obtain a powder having a viscosity average molecular weight of 14,000. The pellets thus obtained had a sulfur atom content of 80 ppb. Thereafter, an optical disk substrate was formed in the same manner as in Example 1, and this was evaluated. Table 1 shows the results.

Example 4 In a reactor equipped with a stirrer and a distillation column, 2,2-bis (4-
228 parts (about 1 mol) of (hydroxyphenyl) propane,
220 parts (about 1.03 mol) of diphenyl carbonate (manufactured by Bayer) and sodium hydroxide 0.00 as a catalyst.
0024 parts (about 6 × 10 ^-7 mol / bisphenol A 1 mol) and tetramethylammonium hydroxide 0.00
73 parts (about 8 × 10 ^-5 mol / bisphenol A 1 mol)
And the atmosphere was replaced with nitrogen. This mixture was heated to 200 ° C. and dissolved with stirring. Then, the degree of decompression is set to 30
Most of the phenol was distilled off in 1 hour while heating as Torr, and the temperature was further raised to 270 ° C.
When the polymerization reaction was performed for 2 hours at orr, 2.3 parts of 2-methoxycarbonylphenylphenyl carbonate was added as a terminal stopper. Then 270 ° C, 1T
The terminal blocking reaction was performed at orr or lower for 5 minutes. Next, in the molten state, 0.0008 parts (about 4 × 10 ⁻⁶ mol / 1 mol of bisphenol A) of diphenyl acid phosphate as a catalyst neutralizing agent was added, and the reaction was continued at 270 ° C. and 10 Torr or less for 10 minutes, Viscosity average molecular weight 15,000
Was obtained. The polymer was sent to the extruder by a gear pump. In the middle of the extruder, 0.01% by weight of tris (2,4-di-tert-butylphenyl) phosphite and 0.08% by weight of monoglyceride stearate were added to obtain polycarbonate pellets.

The sulfur atom contained in the pellet is converted to ICP
Analysis was performed by emission spectroscopy. As a result, the sulfur atom is 5
It was 0 ppb or less. Hereinafter, an optical disk substrate was formed in the same manner as in Example 1, and this was evaluated. Table 1 shows the results.

Comparative Example 1 An optical disk substrate was formed in the same manner as in Example 1 except that a polycarbonate resin having 360 ppb sulfur atoms was used as a raw material pellet, and this was evaluated. Table 1 shows the results.

Comparative Example 2 An optical disk substrate was molded and evaluated in the same manner as in Example 1 except that a polycarbonate resin having 600 ppb of sulfur atoms was used as a raw material pellet. Table 1 shows the results.

From these results, in order to obtain a highly reliable high-density optical disk substrate, the aromatic polycarbonate resin molding material used for molding the substrate is reduced by reducing sulfur or sulfur compounds, which have not been a problem in the past. It has been found that a reliable disk substrate has been provided.

[0038]

[Table 1]

[0039]

According to the molding material of the present invention, the amount of sulfur atoms contained in the material is as small as 200 ppb or less, and the deterioration of the polycarbonate resin can be effectively controlled to obtain an extremely reliable optical disk substrate. In particular, even in a high-density optical disk such as a digital versatile disk (DVD), the effect exerted is remarkable.

Claims (5)

[Claims] An optical polycarbonate resin molding material characterized in that the content of sulfur or a sulfur compound is 200 ppb or less as a sulfur atom. 2. A viscosity average molecular weight of 10,000 to 2,200.
2. The optical polycarbonate resin molding material according to claim 1, wherein the value is 0. 3. An optical disk substrate made of the optical polycarbonate resin molding material according to claim 1. 4. An optical disk substrate for DVD comprising the optical polycarbonate resin molding material according to claim 1. 5. An accelerated deterioration test (80 ° C. × 85%) made of the optical polycarbonate resin molding material according to claim 1.
An optical disk in which the number of white spots having a size of 20 μm or more after RH × 1000 hours) is 2 or less per disk-shaped substrate having a diameter of 120 mm.