JP2003020332A - Optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk substrate which comprises an aromatic polycarbonate resin and is a high-precision recording medium with a high transfer ratio. SOLUTION: This optical disk substrate is prepared by molding an aromatic polycarbonate resin prepared by using 2,2-bis(4-hydroxyphenyl)-4-methylpentane as the dihydric phenol component. The distance between groove lines or pit lines formed on the substrate is 0.17 μm-0.8 μm and is in the range of λ/8n-λ/2n (wherein λ is the wavelength of laser light used for recording and reproduction; and n is the refractive index of the substrate).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium formed by molding a specific aromatic polycarbonate resin, and more particularly to a high-density recording medium, which is an optical disk substrate molded from a polycarbonate resin excellent in precision transferability to a stamper shape. And an optical recording medium.

[0002]

2. Description of the Related Art Conventionally, polycarbonate resins have been widely used in many fields as engineering plastics because of their excellent transparency, heat resistance, mechanical properties and dimensional stability. In particular, a polycarbonate resin obtained by using bisphenol A as a dihydric phenol component is excellent in transparency and is therefore suitably used as an optical material, especially as a material for an optical disk substrate. However, in recent years, optical discs have been rapidly increased in recording density and thinning. As a method of increasing the recording density, an interval between grooves or pits, that is, a track pitch is narrowed to increase the recording density in the track direction. Is. Specifically, in order to increase the recording density from a compact disc (CD) to a digital versatile disc (DVD), the recording pitch in the track direction is reduced by narrowing the track pitch from 1.6 μm to 0.74 μm. It's doubled. On the other hand, because of the fact that the molding is performed at a high speed cycle, the conventional polycarbonate resin has not always been sufficiently satisfactory in terms of moldability, especially transfer accuracy, in the optical disc having a high recording density.

Therefore, in order to improve the transfer accuracy, the cylinder temperature of the molding machine is about 380 ° C. and the mold temperature is 130.
It was necessary to raise it to about ℃. However, if the molding temperature is increased and the molding cycle is accelerated, there is a problem that when the mold is taken out of the mold, a mold release defect occurs, the shape of pits and grooves is deformed, and the transfer accuracy is lowered.

Further, a method of adding a large amount of a low molecular weight substance to a polycarbonate resin in order to impart high fluidity (JP-A-9-208684, JP-A-11-1551, etc.) or a specific long-chain alkylphenol Is used as a terminal stopper (JP-A-11-2692).
No. 60 bulletin) has been proposed. However, the method of increasing the content of this low molecular weight product or the method of modifying the end group with a long-chain alkylphenol generally causes a large decrease in thermal stability, and therefore accelerates thermal decomposition at the time of molding, resulting in disc substrate The mechanical strength is remarkably reduced, and the substrate may crack due to the protruding force from the mold.
Also, the substrate will be damaged during handling of the optical disc substrate.

Further, a polycarbonate resin composed of a dihydric phenol represented by the following formula [I] is proposed to be applied to an optical disk substrate by utilizing its excellent optical characteristics and low hygroscopicity (International Publication No. WO07 /). 22649). According to the example, it is disclosed that when a stamper having a pit depth of 112 nm is used to mold a substrate having a thickness of 1.2 mm and a diameter of 120 mm, pits and grooves can be accurately transferred.

However, the injection molding conditions described in the above publication were adopted for this polycarbonate resin, a stamper having a pit depth of 145 nm, an interval of 0.5 μm and a width of 0.2 μm was used, and the thickness was 0.6 mm and the diameter was 120 mm. When the substrate of No. 1 is molded, there is a problem that pits and grooves cannot be accurately transferred, that is, the transfer rate is low due to the increase in flow resistance due to the thin substrate thickness and the deep pit depth. No substrate was obtained.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk substrate having a stamper shape accurately transferred, that is, a high transfer rate, in molding an optical recording medium, especially a high density recording medium.

As a result of intensive studies aimed at achieving the above object, the present inventors have found that in order to accurately transfer the stamper shape when an optical disk substrate is to be molded by an injection molding method, etc. It is necessary that the resin easily deforms into a stamper shape due to pressure and mold clamping pressure during injection compression molding, that is, the resin surface when holding pressure and mold clamping pressure are applied in the temperature dependence curve of elastic modulus. It was found that a material having a low elastic modulus in the transition to glass region, which is considered to be temperature, is excellent in high precision transferability. That is, it was found that the above objects can be achieved for the first time by using an aromatic polycarbonate resin (PC-MIBK) obtained by using a compound represented by the following formula as a dihydric phenol component and employing specific injection molding conditions. The present invention has been reached.

[0009]

According to the present invention, a dihydric phenol component is represented by the following formula (I)

[0010]

[Chemical 2]

Aromatic polycarbonate resin (PC
-MIBK), which is an optical disk substrate molded with a groove row or pit row spacing of 0.1 μm to 0.8
The optical depth of the groove or pit is in the range of λ / 8n to λ / 2n with respect to the wavelength λ of the laser light used for recording and reproduction and the refractive index n of the substrate. An optical disk substrate is provided. According to the present invention, there is provided an optical disc substrate which achieves high precision transfer to a stamper shape, and particularly an optical disc substrate having a transfer rate of 95% or more.

The term "high precision transfer" in the present invention means that when an optical disk substrate is manufactured by injection molding using a transparent thermoplastic resin molding material, the fine uneven shape stamped on the stamper is faithfully transferred. It is a property that can be done. In the present invention, the following formula (I) is used as the dihydric phenol component constituting the polycarbonate.

[0013]

[Chemical 3]

The compound represented by In addition to this dihydric phenol, another dihydric phenol may be copolymerized at a ratio that does not impair the purpose and properties, for example, 10 mol% or less, preferably 5 mol% or less.

Here, as typical examples of other dihydric phenols, 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 (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-
Methyl butane, 2,2-bis (4-hydroxyphenyl) pentane, 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, 1,1′-bis-
(4-Hydroxyphenyl) -ortho-diisopropylbenzene, 1,1'-bis- (4-hydroxyphenyl)
-Meta-diisopropylbenzene, 1,1'-bis- (4
-Hydroxyphenyl) -para-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-
Dimethyl adamantane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide,
4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ester and the like can be mentioned.

Examples of the carbonate precursor used in producing a polycarbonate using the above dihydric phenol include carbonyl halide, carbonate ester, haloformate, and the like. Specifically, phosgene,
Examples thereof include diphenyl carbonate or dihaloformate of dihydric phenol, and phosgene or diphenyl carbonate is preferable. In the case of producing a polycarbonate resin by reacting the above dihydric phenol with a carbonate precursor by, for example, a solution polymerization method or a melt polymerization method, a catalyst, a terminal stopper, an antioxidant of a dihydric phenol, etc. May be used.

The reaction by the solution polymerization method is usually a reaction between a dihydric phenol and phosgene, which 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, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. It is also possible to use 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 for accelerating the reaction. it can. At that time, the reaction temperature is usually 0 to 40 ° C., the reaction time is preferably 10 minutes to 5 hours, and the pH during the reaction is preferably 9 or more.

Further, in such a polymerization reaction, a terminal stopper is usually used. Monofunctional phenols can be used as such an end terminator. Monofunctional phenols are commonly used as molecular terminating agents for molecular weight control, and the resulting polycarbonate resins are compared to those that do not because the ends are blocked by groups based on monofunctional phenols. Excellent thermal stability. Such monofunctional phenols are generally phenols or lower alkyl-substituted phenols represented by the following formula [II]

[0019]

[Chemical 4]

[In the formula, A is a hydrogen atom or 1 to 9 carbon atoms.
Is a linear or branched alkyl group or a phenyl-substituted alkyl group, and r is an integer of 1 to 5, preferably 1 to 3. ] Monofunctional phenols represented by can be shown.

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

As other monofunctional phenols,
Phenols or benzoic acid chlorides having a long-chain alkyl group or aliphatic polyester group as a substituent, or long-chain alkylcarboxylic acid chlorides can be used, and the end of the polycarbonate polymer is blocked with these. Then, these not only function as a terminal terminating agent or a molecular weight modifier, but not only the melt fluidity of the resin is improved and the molding process is facilitated,
It is preferably used because it has the effect of lowering the physical properties of the substrate, especially the water absorption of the resin, and the effect of reducing the birefringence of the substrate. Among them, the following formulas [III] and [I
V]

[0023]

[Chemical 5]

[0024]

[Chemical 6]

[Wherein, X is -R-CO-O- or -R
-O-CO-, where R is a single bond or 1 carbon atom
-10, preferably 1-5 divalent aliphatic hydrocarbon group is shown, and n shows the integer of 10-50. ] Phenols having a long-chain alkyl group represented by the formula as a substituent are preferably used.

The substituted phenols of the formula (III) are preferably those in which n is 10 to 30, particularly 10 to 26,
Specific examples thereof include decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol and triacontylphenol.

Suitable substituted phenols of the above formula (IV) are compounds in which X is --R--CO--O-- and R is a single bond, and n is 10 to 30, particularly 10 to 26.
Are preferred, and specific examples thereof include decyl hydroxybenzoate, dodecyl hydroxybenzoate,
Mention may be made of tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate and triacontyl hydroxybenzoate. It is desirable that these terminal terminators are introduced into at least 5 mol%, preferably at least 10 mol% of the terminals of the obtained polycarbonate resin, and the terminator may be used alone or You may use it in mixture of 2 or more types.

The reaction by the melt polymerization method is typically a transesterification reaction between a dihydric phenol and a carbonate ester, and the dihydric phenol and the carbonate ester are mixed while heating in the presence of an inert gas, It is carried out by a method of distilling the produced alcohol or phenol. The reaction temperature varies depending on the boiling point of the alcohol or phenol to be produced, but is usually in the range of 120 to 350 ° C. In the latter half of the reaction, the reaction system is 10-0.1 Tor
The pressure is reduced to about r (1.3 to 0.13 × 103 Pa) 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 aryl group having 6 to 10 carbon atoms, an aralkyl group, an alkyl group having 1 to 4 carbon atoms, and the like. Specifically, diphenyl carbonate,
Examples thereof include ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, and among them, diphenyl carbonate is preferable.

Further, a polymerization catalyst is used to increase the polymerization rate.
As the polymerization catalyst, for example, water can be used.
Sodium oxide, potassium hydroxide, dihydric phenol
Alkali metal compounds such as thorium salt and potassium salt;
Calcium oxide, barium hydroxide, magnesium hydroxide, etc.
Alkaline earth metal compounds of tetramethylammonium
Hydroxide, tetraethylammonium hydroxy
Nitrogen-containing salts such as sodium chloride, trimethylamine and triethylamine
Basic compound; Alcohol of alkali metal or alkaline earth metal
Xides; organic acid salts of alkali metals and alkaline earth metals
Kinds; In addition, zinc compounds, boron compounds, aluminum
Um compounds, silicon compounds, germanium compounds,
Organotin compounds, lead compounds, osmium compounds,
Antimony compounds, manganese compounds, titanium compounds
Esterification reaction of zirconium compounds, zirconium compounds, etc.,
The catalyst used in the transesterification reaction can be used
It The catalysts may be used alone or in combination of two or more.
You may use it. The amount of these polymerization catalysts used depends on the raw materials.
1 mol per 1 mol of the dihydric phenol ^-8
~ 1 x 10^-3Equivalent, more preferably 1 × 10^-7~ 5 x 1
0^-FourIt is selected within the equivalent range.

Further, in the polymerization reaction, in order to reduce the phenolic terminal group, for example, bis (chlorophenyl) carbonate, bis (bromophenyl) carbonate, bis (nitrophenyl) carbonate, at a later stage or after the completion of the polycondensation reaction. , Bis (phenylphenyl)
Carbonate, chlorophenyl phenyl carbonate,
It is preferable to add compounds such as bromophenylphenyl carbonate, nitrophenylphenyl carbonate, phenylphenyl carbonate, methoxycarbonylphenylphenyl carbonate and ethoxycarbonylphenylphenyl carbonate. Of these, 2-chlorophenylphenyl carbonate, 2-methoxycarbonylphenylphenyl carbonate and 2-ethoxycarbonylphenylphenyl carbonate are preferable, and 2-methoxycarbonylphenylphenyl carbonate is particularly preferable.

In the present invention, the viscosity average molecular weight of the aromatic polycarbonate resin optical molding material is not particularly limited, but if the molecular weight is excessively low, the strength of the substrate after molding will be problematic, and conversely, it will be excessive. When it is high, the melt fluidity at the time of molding is poor and the optical distortion unfavorable to the substrate increases. Considering this fact, the viscosity average molecular weight is 1
The range of 1,000 to 20,000 is preferable, and 12,000
0 to 18,000 is particularly preferable. A polycarbonate resin optical molding material having such a viscosity average molecular weight is preferable because sufficient strength as an optical material can be obtained and the melt fluidity at the time of molding is good and molding distortion does not occur.

The raw material polycarbonate resin is preferably produced by a conventionally known conventional method (solution polymerization method, melt polymerization method, etc.) and then filtered in a solution state to remove impurities such as unreacted components and foreign substances. Further, in the extrusion step (pelletizing step) of obtaining a pellet-shaped polycarbonate resin for injection molding, it is preferable to remove foreign matters 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, the raw material resin before injection molding is foreign matter, impurities,
It is necessary to keep the content of the solvent and the like as low as possible.

An injection molding machine (including an injection compression molding machine) is used when an optical disk substrate is manufactured from the above polycarbonate resin optical molding material. This injection molding machine may be one that is generally used, but from the viewpoint of suppressing the generation of carbides and increasing the reliability of the disk substrate, the adhesion between the cylinder and screw and the resin is low, and the corrosion resistance and wear resistance are low. It is preferable to use a material formed of a material exhibiting properties. As conditions for injection molding, it is preferable that the resin temperature, that is, the cylinder set temperature is 325 to 355 ° C., and the mold temperature, that is, the mold temperature control set temperature is 106 to 120 ° C. By adopting such conditions, the transfer rate is 95
% Or more, preferably 100% of the optical disk substrate is obtained.

When the resin temperature is lower than 325 ° C. or the mold temperature is lower than 106 ° C., the surface temperature of the resin at the time of transfer to the stamper shape becomes low, the depth of pits and grooves decreases, and the resin temperature decreases. The flow resistance of
The oblique incidence birefringence phase difference of the obtained substrate becomes large. Further, if the resin temperature is higher than 355 ° C. or the mold temperature is higher than 120 ° C., not only it takes time to cool the obtained substrate, but also the substrate does not solidify sufficiently at the time of mold release, and the substrate warps. Will occur. The environment in the molding process is preferably as clean as possible in view of the purpose of the present invention. In addition, it is important to sufficiently dry the material to be molded to remove water, and to take measures so as not to cause retention that would cause decomposition of the molten resin.

The optical disk substrate molded in this way is
Compact discs (hereinafter sometimes referred to as CDs), CD-Rs, MOs, MD-MOs, etc., as well as digital versatile discs (hereinafter referred to as DVDs),
DVD-ROM, DVD-video, DVD-R, D
VD-RAM, DVR-Blue, HD-DVD-RA
It is used as a substrate for a high density optical disc represented by M and the like.

Since the polycarbonate resin optical molding material of the present invention is excellent in high precision transferability, the gap between groove rows or bit rows is 0.1 μm to 0.8 μm, preferably 0.1 to 0.5 μm, and further Preferably 0.1-0.3
It is possible to easily obtain an optical disk substrate having a thickness of 5 μm by molding. The optical depth of the groove or bit is λ / 8n to λ / 2n, preferably λ / 6n to λ / 2n, with respect to the wavelength λ of the laser light used for recording and reproduction and the refractive index n of the substrate, and further, Preferably λ / 4n to λ /
An optical disk substrate in the range of 2n can be obtained.
Thus, it is possible to easily provide a base material for a high density optical disc recording medium having a recording density of 10 Gbit / inch 2 or more.

[0038]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto. In the examples, "parts" are parts by weight. The evaluation was according to the following method. (1) Viscosity average molecular weight 100 mL of methylene chloride for all polymer species
The specific viscosity (ηsp) obtained by using a 20 ° C. solution in which 0.7 g of a polycarbonate resin was dissolved was obtained by inserting it into the following equation. ηsp / c = [η] + 0.45 × [η] ² c (however, [η]
Is the intrinsic viscosity) [η] = 1.23 × 10 ⁻⁴ M ^0.83 c = 0.7 (2) Transfer injection molding machine (M35B-D manufactured by injection molding machine)
-DM) and cavity thickness 0.6 mmt, mold with diameter 120 mm and depth 145 nm, interval 0.5 μm, width 0.2 μm.
A disk substrate was molded using a stamper having m grooves. Next, atomic force microscope (Seiko Denshi Kogyo S
PI3700), the depth of the groove portion of the disk substrate at r = 55 mm was measured to obtain the groove shape reproduction ratio (= 100 × disk groove depth / stamper groove depth (%)).

Example 1 Production of aromatic polycarbonate resin obtained by using 2,2-bis (4-hydroxyphenyl) -4-methylpentane represented by the above formula (I) as a dihydric phenol component; thermometer, stirring 68.6 parts of 48% sodium hydroxide aqueous solution and 34 parts of ion-exchanged water in a reactor equipped with a heating machine and a reflux condenser.
8 parts, were charged, and after dissolving 74 parts of 2,2-bis (4-hydroxyphenyl) -4-methylpentane and 0.140.35 parts of hydrosulfite therein, 233.3 parts of methylene chloride was added, 34.8 parts of phosgene was blown in under stirring at 15 to 25 ° C. over 40 minutes. After the completion of blowing phosgene, 7.6 parts of 48% sodium hydroxide aqueous solution and 2.47 parts of p-tert-butylphenol were added,
After stirring and emulsification, 0.15 part of triethylamine was added, and the mixture was further stirred at 28 to 33 ° C. for 1 hour to complete the reaction. After completion of the reaction, the product was diluted with methylene chloride, washed with water, acidified with hydrochloric acid, washed with water, and repeatedly washed with water until the conductivity of the aqueous phase was almost the same as that of ion-exchanged water. The viscosity-average molecular weight was 15,200. A methylene chloride solution of polycarbonate resin was obtained.

The methylene chloride solution of the polymer produced was passed through a filter having an opening of 0.3 μm, and then the polycarbonate resin solution was added dropwise to warm water in a kneader provided with an isolation chamber having a foreign matter outlet at the bearing portion, and chlorinated. The polycarbonate resin was made into flakes while distilling off methylene.
Next, the liquid polycarbonate resin was pulverized and dried to obtain a powder. Tris (2,4-di-
tert-butylphenyl) phosphite to 0.002
5% by weight and 0.05% by weight of stearic acid monoglyceride were added. Next, the powder was melt-kneaded with a vent type twin-screw extruder [KTX-46 manufactured by Kobe Steel, Ltd.] at a cylinder temperature of 240 ° C. while being melted and kneaded to obtain pellets having a viscosity average molecular weight of 15,100. These pellets were injected into an injection molding machine (M35B-D-DM manufactured by Meiki Seisakusho) with a mold having a cavity thickness of 0.6 mm and a diameter of 120 mm and a depth of 14.
Using a stamper with grooves of 5 nm, 0.5 μm spacing, and 0.2 μm width, cylinder set temperature 330 ° C., mold temperature 108 ° C., filling time 0.2 sec, cooling time 15 sec, mold clamping force 35 The disk substrate was molded in tons. The molding evaluation results at this time are shown in Table 1.

Comparative Example 1 Molding evaluation was carried out in the same manner as in Example 1 except that the cylinder set temperature during injection molding was 320 ° C. and the mold set temperature was 90 ° C. The molding evaluation results at this time are shown in Table 1.

[0042]

[Table 1]

[0043]

According to the present invention, it is possible to provide an optical disk substrate having a stamper shape transferred with high precision as an optical recording medium formed by molding a specific polycarbonate resin, particularly a high density recording medium. The effect produced is exceptional.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor, Kuniwei Hayashi             1-2-2 Uchisaiwaicho, Chiyoda-ku, Tokyo             Human Kasei Co., Ltd. (72) Inventor Shigeki Fujimaru             1-2-2 Uchisaiwaicho, Chiyoda-ku, Tokyo             Human Kasei Co., Ltd. F-term (reference) 4J029 AA09 AB07 AC01 AE05 BB12A                 5D029 KA07 KB03 WB11 WB17 WC01                       WC04 WC05 WD10                 5D121 AA02 DD05

Claims (4)

[Claims] 1. A dihydric phenol component is represented by the following formula [I]: Aromatic polycarbonate resin (PC-MIBK)
An optical disk substrate molded from, wherein the spacing between the groove rows or pit rows is 0.1 μm to 0.8 μm, and the optical depth of the grooves or pits is the wavelength λ of the laser beam used for recording / reproduction and the substrate. An optical disk substrate having a refractive index n of λ / 8n to λ / 2n. 2. The resin temperature during injection molding is 325 ° C. to 3 ° C.
The optical disk substrate according to claim 1, which is molded at 55 ° C. 3. The mold temperature at the time of injection molding is 106 ° C. to 1 ° C.
The optical disk substrate according to claim 1, which is molded at 20 ° C. 4. A transfer rate of 95% or more, 1 to
3. The optical disc substrate according to any one of 3 above.