JP2002187945A - Optical polycarbonate resin molding material and information recording medium comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical polycarbonate resin molding material which is suitable for producing an optical member, e.g. an optical recording medium for recording various information signals, such as sound signals or image signals; and an information recording medium comprising the same. SOLUTION: The resin molding material contains 1.5% or lower substance represented by formula (1) and 50 ppm or lower substance represented by formula (2). An optical disk substrate comprising the molding material is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molding material suitable for manufacturing an optical material, for example, an optical recording medium for recording various information signals such as audio signals and image signals, and information comprising the same. It relates to a recording medium.

[0002]

2. Description of the Related Art Optical disks for recording and reproducing information by irradiating a laser beam include digital audio disks (so-called compact disks), optical video disks (so-called laser disks), various write-once disks, magneto-optical disks, and phase-change disks. Changeable disks and the like have been put to practical use. Of these, compact discs and laser discs are read-only (Read Only Memory:
ROM) type optical disk. In these optical disks, generally, pits corresponding to information signals are formed in an uneven shape on a transparent substrate, and an Al reflective layer is formed thereon with a thickness of 40 nm or more. In such an optical disc, an information signal is reproduced by detecting a change in reflectance caused by optical interference generated in the pit.

On the other hand, a write-once optical disc has an R (Recordable) on which arbitrary information can be written by a user.
e) type optical disk, a magneto-optical disk and a phase change type disk are RAMs (Random Access Memory) in which arbitrary information can be repeatedly written.
y) type optical disc. That is, the R-type optical disc is constituted by a write-once type recording layer on which an optical characteristic is irreversibly changed or an uneven shape is formed by irradiation of a laser beam on a transparent substrate. As the recording layer, for example, a cyanine-based, phthalocyanine-based, or azo-based organic dye that is decomposed by heating by laser beam irradiation, changes its optical constant, and causes deformation of the substrate due to a change in volume is used. Magneto-optical disks allow users to repeatedly write and erase information,
This is a rewritable optical disk that has a T
A perpendicular magnetization film having a magneto-optical effect (for example, the Kerr effect) such as a b-Fe-Co amorphous alloy thin film is formed. In this magneto-optical disk, recording pits are formed by magnetizing a micro area of a perpendicular magnetization film upward or downward in response to an information signal. The information signal is reproduced by utilizing that the rotation angle θk (Kerr rotation angle) of the linearly polarized light in the reflected light differs depending on the direction of magnetization of the perpendicular magnetization film. A phase change disk is a rewritable disk like a magneto-optical disk. For example, a Ge-Sb-Te phase change material that exhibits a crystalline state in an initial state and changes to an amorphous state when irradiated with a laser beam. Are used. In this recording layer, recording pits are formed by changing the phase of a minute area corresponding to an information signal, and the information signal is detected by detecting a change in the reflectance between an amorphous portion corresponding to the pit and another crystal area. Will be played. In such magneto-optical disks and phase change disks,
For the purpose of preventing the oxidation of the recording layer and increasing the signal modulation degree due to multiple interference, a four-layer structure is often adopted in which both sides of the recording layer are sandwiched between transparent dielectric layers and an Al reflective layer is further laminated thereon. . In addition, as the dielectric layer, a silicon nitride film, a Zn—SiO ₂ mixed film, or the like is used.

Recently, studies on using such an optical disk for digital video recording have been actively conducted, and a digital versatile disk (DVD) has been developed as such an optical disk. This DVD has a diameter of 120 mm, which is the same as a CD, and records video information equivalent to one movie, so that it can be reproduced with image quality comparable to that of a current television. Here, recording such video information on an optical disk requires, for example, a recording capacity 6 to 8 times that of a CD. For this reason, in DVD, the laser wavelength is set to 78 for CD.
By shortening the wavelength to 635-650 nm with respect to 0 nm and increasing the numerical aperture NA of the objective lens to 0.52 or 0.6 with respect to 0.45 in CD, the shortest recording mark of the track pitch or pit is obtained. The length is shortened and the recording density is increased.

[0005] Among them, the increase in the numerical aperture NA of the objective lens decreases the allowable amount of warpage of the disk substrate. For this reason, in the case of DVD, the thickness of the substrate is reduced to 0.6 mm from 1.2 mm of the CD, whereby
The distance that the laser light passes through the disk substrate is shortened to compensate for the allowable amount of warpage. Then, as described in JP-A-6-274940, in order to compensate for a decrease in disk strength due to further thinning of the substrate, the substrate is further laminated on a recording layer formed on the substrate, so-called, Adhered structure is adopted.
As the recording layer of the bonded optical disk, any of the ROM-type recording layer, the R-type recording layer, and the RAM-type recording layer used in the above-described single-plate configuration can be adopted. Further, the bonded optical disks include a single-sided bonded optical disk using only one surface thereof and a double-sided bonded optical disk using both surfaces thereof. For the optical disk substrates as described above, polycarbonate resins excellent in moldability, strength, light transmittance, moisture resistance, and the like are often used.

[0006] In recent years, with the spread of optical disk substrates, there is an increasing demand for improved substrate productivity. Resins contain various volatile components, and if molding is performed for a long period of time, various components accumulate on a mold, a stamper, and the like, leading to deterioration of substrate characteristics such as optical and mechanical characteristics. Further, there is also a problem that the above various substrate characteristics are deteriorated by long-time molding. For this reason, continuous molding must be temporarily stopped in order to clean the mold and the stamper, which has had an adverse effect on the improvement in productivity.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and as a result of intensive studies on the problems, the present invention has been made to reduce the content of a specific substance in a polycarbonate resin. We have found that it is possible to obtain optical discs that can control the deterioration of polycarbonate resin substrates very effectively and maintain high reliability over a long period of time. It has also been found that an optical polycarbonate resin molding material and an optical disk substrate capable of improving the properties can be obtained.

[0008]

According to the present invention, the content of the substance represented by the following formula (1) is 1.5% or less and the content of the substance represented by the following formula (2) is 50 pp:
The present invention provides an optical polycarbonate resin molding material made of a polycarbonate resin of m or less and an optical disk substrate formed from the material.

[0009]

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[0010]

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Wherein A is a hydrogen atom, an alkyl group, a phenylalkyl group or an aliphatic ester group, and r is an integer of 1-5. ]

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, CD-R, C
D-RW, MO, DVD-ROM, DVD-Audi
o, sufficient reliability as a substrate of an optical disk of a digital versatile disk (DVD) represented by a DVD-R, a DVD-RAM, etc., particularly a disk substrate used for a high-density optical disk such as a substrate of a DVD; In order to improve the substrate productivity, the content of the substance represented by the above formula (1) in the molding material (aromatic polycarbonate resin) provided for molding the substrate is 1.5% or less, and When the content of the substance represented by the above formula (2) is 50
It is necessary to be below ppm. These are those added as terminal stoppers during the polymerization reaction of the polycarbonate resin and remaining in the resin and those formed by the reaction of the polymerized material during the polymerization reaction of the polycarbonate resin.

When the content of the substance represented by the formula (1) is 1.
When the content of the substance represented by the formula (2) is 5 ppm or less and 50 ppm or less, generation of minute white spots on the substrate and the number of times of cleaning the mold and the stamper can be minimized. When materials having a content of the substance represented by the formula (1) exceeding 1.5% and a content of the substance represented by the formula (2) exceeding 50 ppm are used, these materials have sufficient reliability and substrate production. Sex is not obtained. The content of the substance represented by the formula (1) is 1.5% or less, preferably 1.0% or less, and more preferably 0.5% or less, whereby a more reliable effect can be obtained. Most preferably, it is 0.3% or less. The content of the substance represented by the formula (2) is 50 ppm or less,
Preferably not more than 40 ppm, more preferably 30 pp
When it is less than m, a certain effect can be obtained. Most preferred is 15 ppm or less.

As the polycarbonate resin used in the present invention, a resin obtained by reacting a dihydric phenol with a carbonate precursor by an interfacial polymerization method or a melt polymerization method can be used. Among them, a resin obtained by an interfacial polymerization method is preferable. The dihydric phenol used here is 2,2-bis {(4-hydroxyphenyl) propane} (commonly called bisphenol A). Carbonate precursors include phosgene or diphenyl carbonate. In producing the polycarbonate resin by reacting the dihydric phenol with the carbonate precursor by an interfacial polymerization method or a melt polymerization method, a catalyst, a dihydric phenol antioxidant, or the like may be used as necessary.

The reaction by the interfacial polymerization 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 tertiary amine such as triethylamine, tetra-n-butylammonium bromide and tetra-n-butylphosphonium bromide, a quaternary ammonium compound, and 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.

The reaction by the melt polymerization method is usually a transesterification reaction between a dihydric phenol and a carbonate ester, and a simple reaction is carried out by mixing the dihydric phenol with the carbonate ester in the presence of an inert gas while heating. It is carried out by a method of distilling a functional phenol. The reaction temperature varies depending on the boiling point of the monofunctional phenols to be produced and the like, but is usually in the range of 120 to 350 ° C. In the latter stage of the reaction, the pressure of the system is reduced to about 10 to 0.1 Torr to facilitate the distillation of the monofunctional phenols formed. Since the monofunctional phenols generated during the reaction remain in the polycarbonate resin, a sufficient reaction time is required, and the reaction time is about 1 to 4 hours. Diphenyl carbonate is used as the carbonate ester.

A polymerization catalyst can 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.
^-4 equivalents, more preferably 1 × 10 ^{−7 to} 5 × 10 ⁻⁴ equivalents.

In order to reduce the number of phenolic terminal groups in the polymerization reaction, a terminal stopper other than monofunctional phenols such as bis (chlorophenyl) carbonate, bis (bromo) Compounds such as phenyl) carbonate, bis (nitrophenyl) carbonate, bis (phenylphenyl) carbonate, chlorophenylphenylcarbonate, bromophenylphenylcarbonate, nitrophenylphenylcarbonate, phenylphenylcarbonate, methoxycarbonylphenylphenylcarbonate and ethoxycarbonylphenylphenylcarbonate Is preferably added. Among them, 2-chlorophenylphenyl carbonate and 2-methoxycarbonylphenylphenyl are preferable, and 2-methoxycarbonylphenylphenyl is particularly preferably used.

In the polymerization reaction of the polycarbonate resin by the interfacial polymerization method, a terminal stopper is usually used. The terminator is used for controlling the molecular weight, and the obtained polycarbonate resin has a terminal capped,
It has better thermal stability than those not. Examples of such a terminal stopper include monofunctional phenols represented by the following general formulas (3) to (5).

[0020]

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[Wherein B is a hydrogen atom or a carbon number of 1 to 9]
Is an alkyl group or a phenylalkyl group (where the carbon number of the alkyl portion is 1 to 9), and r is 1 to 5, preferably 1
-3. ]

[0022]

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[0023]

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[In these formulas, X is -R-CO-O- or -RO-CO-, wherein R is a single bond or a divalent group having 1 to 10, preferably 1 to 5 carbon atoms. It represents a fatty acid hydrocarbon group, and n represents an integer of 10 to 50. Specific examples of the monofunctional phenol represented by the general formula (3) include, for example, phenol, isopropylphenol, p-tert-butylphenol, p-cresol, p-cumylphenol, and isooctylphenol.

The monofunctional phenols represented by the general formulas (4) and (5) are phenols having a long-chain alkyl group or an aliphatic ester group as a substituent. When the ends of the resin are blocked, they not only function as a terminator or a molecular weight regulator, but also improve the melt flowability of the resin and facilitate molding processing, as well as physical properties as a substrate, particularly of the resin. It has the effect of lowering the water absorption,
It is also preferably used because it has the effect of reducing the birefringence of the substrate.

The substituted phenols of the above general formula (4) are preferably those having n of 10 to 30, especially 10 to 26, and specific examples thereof include decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, Octadecylphenol, eicosylphenol, docosylphenol, triacontylphenol and the like can be mentioned.

As the substituted phenols of the above general formula (5), 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 30
26 are preferred, and specific examples thereof include, for example, decyl hydroxybenzoate, dodecyl hydroxybenzoate, tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate and tricontyl hydroxybenzoate. No.

Among these monofunctional phenols, monofunctional phenols represented by the above formula (3) are preferred, more preferably alkyl-substituted or phenylalkyl-substituted phenols, and particularly preferably p-tert.
-Butylphenol or p-cumylphenol. These monofunctional phenolic terminal stoppers are used in at least 5 terminals relative to all terminals of the obtained polycarbonate resin.
Mol%, preferably at least 10 mol%, is introduced at the end, and the terminator is used alone or
You may mix and use more than one kind.

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 limiting viscosity) [η] = 1.23 × 10 ⁻⁴ M ^0.83 c = 0.7 The polycarbonate resin is produced by a conventionally known method (interfacial polymerization method, melt polymerization method, etc.). Perform alkali extraction or filtration in solution state, granulation (desolvation)
The granular material after washing with ketones such as acetone, aliphatic hydrocarbons such as hexane, polycarbonate poor solvents such as aromatic hydrocarbons such as xylene and non-solvents and impurities such as low molecular weight components and unreacted components. It is preferable to remove foreign matter. 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 additives such as a release agent such as a polyhydric alcohol fatty acid ester and an antioxidant such as a phosphorus compound. 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.

As a method for reducing the content of the substances represented by the formulas (1) and (2), for example, after manufacturing by a conventionally known method (solution polymerization method, melt polymerization method, etc.),
The granular resin after granulation (desolvation) is removed by washing with a non-solvent or non-solvent such as a polycarbonate such as ketones such as acetone, aliphatic hydrocarbons such as hexane, and aromatic hydrocarbons such as xylene. Is preferred. Conventionally, the polycarbonate represented by the formula (1) and the formula (2) are adjusted according to the synthesis conditions of the polycarbonate, for example, the adjustment of the catalyst type and the amount of the catalyst, the conditions such as the temperature, the time and the pressure, and the adjustment of the type and the amount of the terminal stopper. Polycarbonates having various contents have been obtained, and from among them, those having specific content of the substances represented by the formulas (1) and (2) are selected and used in the present invention. The effect can also be achieved.

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 water, and to take care not to cause stagnation which may cause decomposition of the molten resin. It is also important to take care not to use a substrate having an abnormality in birefringence, mechanical characteristics, etc. as a product or a test substrate.

The optical disk substrate made of the optical polycarbonate resin molding material according to the present invention has very little white spots even when it is kept under high temperature and high humidity conditions for a long time.
DR, CD-RW, MO, digital video disk,
DVD-ROM, DVD-audio, DVD-R, D
Digital versatile, represented by VD-RAM, etc.
It is excellent as a substrate of an optical disk of a disk (DVD), particularly a substrate of a DVD. The characteristics under the conditions of high temperature and high humidity are as follows: the disk substrate has a size of 20% after standing in a constant temperature and humidity chamber controlled at a temperature of 80 ° C. and a relative humidity of 85% for 1000 hours.
It is confirmed by examining the number of white spots of μm or more. The number of white spots generated on the disk substrate obtained from the 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.

[0034]

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.

(1) Quantitative analysis of the substance represented by Formula 1 Gel Permission Chromatog
The ratio was calculated from the area ratio of the peaks using a graphy (GPC). The measurement was performed under the following conditions. Apparatus: LC-20 manufactured by JASCO Column: JAIGEL2HF x 2 tubes + JA manufactured by JASCO
IGEL3HF x 3 Moving layer: chloroform Detector: UV (254 nm) Set temperature: 40 ° C (2) Quantitative analysis of substance represented by formula (2) Quantification was performed using high performance liquid chromatography (HPLC).

(3) CD productivity test Injection molding machine [DISK 3M III manufactured by Sumitomo Heavy Industries, Ltd.]
Attach a mold for exclusive use of CD to the mold, attach a stamper for pitted nickel CD to this mold, and put the molding material into the hopper of the molding machine by automatic conveyance. The cylinder temperature is 335 ° C, the mold temperature is The molding was continuously performed at 65 ° C. After the start of continuous molding, the number of defective substrates produced increased due to the occurrence of abnormal birefringence and mechanical characteristics, and the number of molded substrates until the number of defective substrates per 100 units exceeded 3% was determined. The criterion for judging the quality of a production board is that the birefringence is ± 100 nm or less in a double pass, and the mechanical properties are ±
Within 1.6 degrees.

(4) DVD productivity test Injection molding machine [DISK 3M III manufactured by Sumitomo Heavy Industries, Ltd.]
A mold for DVD is attached to the mold, a nickel stamper for DVD made of pits is mounted on the mold, and the molding material is automatically fed into a hopper of a molding machine, and a cylinder temperature of 378 ° C. and a mold temperature are set. Molding was performed continuously at 119 ° C., and the number of molded sheets was determined in the same manner as in the CD productivity test. The criteria for judging the quality of the production substrate were as follows: the birefringence was ± 100 nm or less in a double pass, the mechanical characteristics were ± 0.8 degrees in a radial warp angle, and ± 0.3 degrees in a circumferential warp angle.

(5) Long-term reliability test Disk molding machine [DISK 3M manufactured by Sumitomo Heavy Industries, Ltd.]
III] optical disc substrate (diameter 120
mm, thickness 1.2 mm) at a temperature of 80 ° C.
After standing in a thermo-hygrostat controlled at a relative humidity of 85% for 1000 hours, the number of white spots having a size of 20 μm or more in the substrate was counted. This was performed for 25 optical disk substrates, and the average value was determined, and this was defined as the number of white spots.

Example 1 A 2,2-bis (4- (2- (4-phenyl) -tetraphenyl) derivative having a total content of the substance (multiple peaks) represented by the formula (1) of 1.3% and a p-tert-butylphenol content of 35 ppm was used. (Hydroxyphenyl) propane skeleton polycarbonate powder to phosphorus antioxidant [tris (2,4-di-t-butylphenyl) phosphite] 50 ppm and fatty acid ester
[Glycerin monostearate (Liquemar S-100)
A)] and pelletized with an extruder after adding 100 ppm. Using the obtained pellets, a CD productivity test, a DVD productivity test, and a long-term reliability test were performed. Table 1 shows the results.

Example 2 The procedure of Example 1 was repeated except that the total content of the substance (multiple peaks) represented by the formula (1) was 0.2% and the content of p-tert-butylphenol was 8 ppm. 1
The same operation as described above was performed. Table 1 shows the results.

Comparative Example 1 In Example 1, the total content of the substance (multiple peaks) represented by the formula (1) was 2.5%, and p-tert
The same operation as in Example 1 was performed except that the content of -butylphenol was 85 ppm. Table 1 shows the results.

[0042]

[Table 1]

As shown in Table 1, by using the polymer of the present invention, a high-density disk substrate having high moldability and high reliability can be obtained.

[0044]

As described above, a disk substrate can be obtained with good moldability by using the resin molding material of the present invention.

Claims (6)

[Claims] 1. An optical polycarbonate resin molding comprising a polycarbonate resin having a content of the substance represented by the formula (1) of 1.5% or less and a content of the substance represented by the formula (2) of 50 ppm or less. material. Embedded image Embedded image Wherein A is a hydrogen atom, an alkyl group, a phenylalkyl group or an aliphatic ester group, and r is an integer of 1 to 5. ] 2. An optical polycarbonate resin molding material according to claim 1, wherein the polycarbonate resin has a viscosity average molecular weight of 10,000 to 22,000. 3. The optical polycarbonate resin molding material according to claim 1, wherein in the formula (2), A is an alkyl group having 1 to 9 carbon atoms or a phenylalkyl group having 7 to 15 carbon atoms. 4. An optical disk substrate formed from the optical polycarbonate resin molding material according to claim 1. 5. A digital versatile resin formed from the optical polycarbonate resin molding material according to claim 1.
An optical disk substrate for a disk (DVD). 6. An information recording medium using the optical disk substrate according to claim 4.