JP2000351891A - Aromatic polycarbonate resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition, which is excellent in transferability of signals from a stamper, is small in warpage when molded as a substrate and has a small refractive index in a vertical direction of a molded substrate, by compounding a specified amount of polystyrene glycol having a specified molecular weight in an aromatic polycarbonate resin having a specified molecular weight. SOLUTION: 0.2 to 50 pts.wt. of polystyrene glycol having a molecular weight of 300 to 10,000 is compounded in 100 pts.wt. of an aromatic polycarbonate resin having a viscosity-average molecular weight of 10,000 to 23,000. The aromatic polycarbonate resin should preferably be composed of structural units of formula I, and should more preferably be composed of a polycarbonate resin prepared from 2,2-bis(4-hydroxyphenyl)propane(bisphenol A). In the formula, R1 and R2 independently represent H, 1-6C alkyl or phenyl; and R3 and R4 independently represent H, 1-6C alkyl or halogen. The composition is used as a substrate for optical disk and particularly, as a substrate for high density optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aromatic polycarbonate resin composition, and more particularly, to an aromatic polycarbonate resin for an optical disk substrate and an optical disk substrate comprising the aromatic polycarbonate resin.

[0002]

2. Description of the Related Art Conventionally, aromatic polycarbonate resins have been widely used as resins for optical disc substrates because of their excellent transparency, impact resistance, heat resistance, etc., and the resulting molded articles also have excellent dimensional stability. Have been.

However, in recent years, as the signal density of the optical disk has increased, various performances have been required for the substrate, but it has become difficult to cope with the performance. For example, in order to increase the signal density, the intervals between the guide grooves (grooves) and pits are reduced, and at the same time, the depth is also increased, so that it is difficult to faithfully transfer the signal imprinted on the stamper to the substrate. In addition, if the warp (tilt) of the substrate is large, it becomes difficult to accurately reproduce a signal. Therefore, the higher the density is, the lower the warpage is required. Furthermore, in the case of a high-density magneto-optical disk, unlike a conventional optical disk, the C / N ratio of the signal characteristic is high unless the difference in the vertical refractive index of the substrate is particularly small.
There is a problem that the ratio decreases.

[0004] Conventional polycarbonate resins for optical disk substrates have been reduced in viscosity average molecular weight to about 15,000 to 18,000 in order to improve fluidity. Does not necessarily improve. In order to improve the transferability, there is a method of increasing the mold temperature at the time of molding the substrate. However, when the mold temperature is increased, the thickness of the substrate becomes 0.6 mm like a high-density DVD substrate.
And the substrate is easily warped. In order to reduce the warpage of the substrate, it is conceivable to increase the rigidity by adding glass fibers or inorganic fillers.However, additives such as glass fibers or inorganic fillers often emerge on the substrate surface, and signal It causes transfer failure and the like. Furthermore, fibrous additives such as glass fibers have a high anisotropy and are oriented in the flow direction during injection molding, so that there is a disadvantage that warpage is likely to occur particularly in the case of a thin molded product such as an optical disk substrate. .

[0005] In order to improve the appearance of a molded article containing a fibrous additive, for example, a method of adding a plasticizer such as a phthalic acid compound, or a method of adding a low molecular weight (oligomer) of an aromatic polycarbonate resin. A method and a method of blending polycaprolactone have been proposed, but all have the problem of reduced heat resistance.

On the other hand, in the case of a high-density magneto-optical disk, the numerical aperture of the laser lens increases, the oblique incidence component of the laser increases, and the vertical refractive index difference (refraction between one axis in the substrate plane and the substrate thickness axis). (Ratio difference) is desirable. Various methods have been tried to reduce the vertical refractive index difference, such as improving the molecular structure to lower the photoelastic coefficient, and blending or copolymerizing positive and negative intrinsic birefringence. However, since a special molecular structure is required, the cost of the monomer is high, moldability is poor, and there is a problem in productivity.
Therefore, it has been difficult to obtain a resin for an optical disk substrate that satisfies all of the high transferability, the low warpage, and the low vertical refractive index difference.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high transfer property for faithfully transferring a signal of a stamper to a substrate, a low warp property in which the warp of the substrate is reduced, and a low vertical refractive index of an optical disc substrate to be formed. An object of the present invention is to provide an aromatic polycarbonate resin composition excellent in the difference and an optical disc substrate formed using the aromatic polycarbonate resin composition.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist of the invention is that the molecular weight is 300 to 10,000 based on 100 parts by weight of an aromatic polycarbonate resin. A polystyrene glycol is blended in an amount of 0.2 to 50 parts by weight, and the aromatic polycarbonate resin has a viscosity average molecular weight of 10,000 to 23.0.
The aromatic polycarbonate resin composition is characterized by being 00.

Hereinafter, the present invention will be described in detail. As the aromatic polycarbonate resin in the present invention, a polymer or copolymer obtained by a phosgene method of reacting a dihydroxydiaryl compound with phosgene, or a transesterification method of reacting a dihydroxydiaryl compound with a carbonate such as diphenyl carbonate is used. No.

As the dihydroxydiaryl compound,
In addition to bisphenol A, bis (4-hydroxydiphenyl) methane, 1,1-bis (4-hydroxyphenyl)
Ethane, 2,2-bis (4-hydroxydiphenyl) butane, 2,2-bis (4-hydroxyphenyl) octane, bis (4-hydroxyphenyl) phenylmethane,
2,2-bis (4-hydroxy-3-methylphenyl)
Propane, 1,1-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4
-Hydroxy-3,5-dibromophenyl) propane,
Bis (hydroxyaryl) alkanes such as 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, bis (hydroxyaryl) cycloalkanes such as 1,1-bis (4-hydroxyphenyl) cyclohexane Dihydroxydiaryl ethers such as 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxy-3,3′-dimethyldiphenyl ether, 4,4′-dihydroxyphenyl sulfide,
Dihydroxydiaryl sulfides such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; 4,4'-dihydroxydiphenyl sulphoxide; and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulphoxide. And dihydroxydiarylsulfoxides such as 4,4'-dihydroxydiphenylsulfone and 4,4'-dihydroxy-3,3'-dimethyldiphenylsulfone. These may be used alone or as a mixture of two or more. In addition to these, biperazine, dipiperidyl, hydroquinone, resorcinol,
4,4′-dihydroxydiphenyl and the like may be used as a mixture.

The aromatic polycarbonate resin preferably includes an aromatic polycarbonate resin having a structural unit represented by the following general formula (1). Where R
¹ and R ² each represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms and a phenyl group, preferably a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, and R ³ and R ⁴ each represent a hydrogen atom And an alkyl group having 1 to 6 carbon atoms and a halogen atom, preferably a hydrogen atom and an alkyl group having 1 to 6 carbon atoms.

[0012]

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More preferably, the aromatic polycarbonate resin is a polycarbonate resin produced from 2,2-bis (4-hydroxyphenyl) propane (bisphenol A).

The viscosity average molecular weight of the aromatic polycarbonate resin is from 10,000 to 23,000. If the viscosity average molecular weight is less than 10,000, it is difficult to obtain a molded article having low rigidity and practicality. If it exceeds 23,000, molding fluid is inferior and molding distortion increases, and the birefringence of the substrate increases. I do. The viscosity average molecular weight is preferably 12,000.
0 to 20,000. , More preferably 14,00
0 to 18,000. In the present invention, the viscosity average molecular weight (M) is defined as the intrinsic viscosity (η) obtained using an Ostwald viscometer using methylene chloride as a solvent,
ell viscosity equation, that is, (η) = 1.23 × 10 ⁻⁵
M means a value calculated from ^0.85 .

The aromatic polycarbonate resin in the present invention can be obtained by using the phosgene method (interfacial polycondensation method), the transesterification method (melting method), etc., which are used in the production of ordinary polycarbonate.

The polystyrene glycol of the present invention has a structural unit represented by the following general formula (2).

[0017]

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The molecular weight of polystyrene glycol is 30
0 to 10,000. If the molecular weight is less than 300, it tends to volatilize as a gas during molding, and the molecular weight is 10,
If it exceeds 000, the effect of reducing the glass transition temperature is small.
The molecular weight of the polystyrene glycol is preferably 400
~ 8,000, more preferably 500 ~ 5,000.
0. The molecular weight of polystyrene glycol is GPC
(Gel permeation chromatography).

The amount of polystyrene glycol is 0.2 parts by weight based on 100 parts by weight of the aromatic polycarbonate resin.
５０50 parts by weight. If the amount is less than 0.3 parts by weight, the effects of lowering the glass transition temperature, improving the rigidity, and reducing the low vertical birefringence are small. If the amount exceeds 50 parts by weight, the transparency of the substrate is easily impaired. The blending amount of polystyrene glycol is preferably 0.3 to 30 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the aromatic polycarbonate resin.
5 parts by weight.

By adding polystyrene glycol to the aromatic polycarbonate, the glass transition temperature of the resin composition is reduced, and at the same time, the rigidity is increased. Lowering the glass transition temperature has the same effect as increasing the mold temperature during molding, improving transferability without increasing the mold temperature, and increasing rigidity reduces the warpage of the substrate. Therefore, high transfer and low warpage can be achieved. The reason why the glass transition temperature is reduced by adding polystyrene glycol to the aromatic polycarbonate is that the styrene structure is arranged between the molecular chains, thereby improving the slipperiness between the molecular chains and increasing the plasticizing effect. Presumed.

Since the intrinsic birefringence of the styrene structure is smaller than the intrinsic birefringence of the aromatic polycarbonate, the intrinsic birefringence of the aromatic polycarbonate is reduced by adding polystyrene glycol to the aromatic polycarbonate. This has the effect of reducing the directional refractive index difference. Furthermore, since polystyrene glycol also acts as a plasticizer, it exists between the molecular chains of the aromatic polycarbonate, so the phenyl group of the polystyrene glycol is located perpendicular to the benzene ring of the aromatic polycarbonate in the main chain. It is considered that the photoelastic coefficient is also reduced, so that there is an effect of reducing the vertical refractive index difference.

The polycarbonate resin composition of the present invention comprises
The rigidity at room temperature is high due to the interaction between the styrene structure existing between the molecular chains and the molecular chains, but at a temperature of 100 ° C. or higher, the glass transition temperature is reduced and the moldability is improved. It is considered that this is because the interaction between the styrene structure and the molecular chain is relaxed and a plasticizer effect is exhibited. For example, an aromatic polycarbonate resin having a viscosity average molecular weight of 16,000 has a flexural modulus of about 22,000 kgf / cm2, but a blending modulus of about 25,500 kgf / cm2 by blending 20 parts by weight of polystyrene glycol. Become higher.

The bisphenol A type aromatic polycarbonate resin has a glass transition temperature of 140 to 150.
Although it is about ° C., the addition of polystyrene glycol lowers the glass transition temperature of the resin composition. For example,
By adding 1 part by weight of polystyrene glycol, the glass transition temperature of the aromatic polycarbonate resin composition decreases by about 10 ° C.

The aromatic polycarbonate resin composition of the present invention may contain, if necessary, a flame retardant, a flame retardant auxiliary, a coloring agent, a plasticizer, a lubricant, a heat stabilizer, a charge stabilizer within a range not to impair the object of the present invention. Inhibitors, release agents, ultraviolet rays, absorbers and the like can be added. The mixing ratio of the release agent is preferably 10 to 20,000 pp with respect to the polycarbonate copolymer.
m, more preferably 50 to 10,000 ppm. The compounding ratio of the heat stabilizer is preferably from 1 to 1000 ppm, more preferably from 2 to 600 ppm, based on the polycarbonate copolymer. As a method for producing the aromatic polycarbonate resin composition of the present invention, various additives are blended in a predetermined amount with the aromatic polycarbonate resin, mixed by a mixer such as a V-type blender, and the obtained mixture is melted by an extruder. A method of kneading and pelletizing.

The optical disk substrate of the present invention is manufactured by injection molding the above-mentioned aromatic polycarbonate resin, specifically by the following injection compression method. In the injection compression method, a thin disk made of nickel called a stamper with the information to be transferred to the magneto-optical disk substrate is engraved on one side of the injection molding die and the mold is closed by closing the die. Injection process of injecting the provided polycarbonate resin, pressure holding process of operating the injection cylinder for a certain period after injection to maintain the pressure, cooling process of stopping the operation of the injection cylinder and cooling without lowering the mold clamping pressure, and mold clamping The operation of the cylinder also includes a mold opening step of opening the stopper mold and taking out the optical disc substrate on which the information of the stamper has been transferred as an injection molded product.

The optical disk substrate taken out of the mold has a magnetic recording layer, a reflective layer, etc. formed on the surface thereof, a protective layer formed thereon, and, if necessary, a plurality of substrates bonded together to form an optical disk. . The optical disk substrate may be annealed before forming the magnetization recording layer, the reflection layer, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

The following components were used in Examples and Comparative Examples. (1) Aromatic polycarbonate resin: Polycarbonate NOVAREX7020AD2 (2,2-bis (4) for optical disc manufactured by Mitsubishi Engineering-Plastics Corporation
-Hydroxyphenyl) aromatic polycarbonate obtained using propane, viscosity average molecular weight 16,000)

(2) Polystyrene glycol: phenylethylene oxide was polymerized by pressurizing and heating in the presence of sodium methylate as a catalyst to obtain a polymer having a molecular weight of 750 and a polymer having a molecular weight of 1500. Evaluation methods in Examples and Comparative Examples are shown below. (3) Glass transition temperature: DSC (manufactured by Seiko, model:
(SSC-5000). 10 ° C / min under a nitrogen stream.

(4) Transferability: The groove depth at a point of R = 58 mm on the molded substrate was measured with an atomic force microscope (Olympus, model NV
2100), cantilever: conical, load value 3
0nN, number of scanning lines: 128, scanning speed: 5 sec /
line. (5) Warpage: Using a disk warpage angle measuring device (manufactured by Admon Science), while rotating the optical disk substrate at 60 rpm, the substrate was measured in the radial direction of 25 mm, 37 mm, and 49 mm.
A semiconductor laser having a wavelength of 780 nm was irradiated at the positions of mm and 57 mm, and the highest warp angle was obtained.

(6) Vertical birefringence measuring method of optical disk substrate: One direction in the radial direction is determined, and the radial directions R25, 36,
At each point of 47 and 58 mm, the vertical birefringence based on the following equation was determined. Vertical birefringence VB = 3.9468 × 10 ⁻⁶ × (radial positive direction 30 ° inclined phase difference + tangential direction positive direction 30 ° inclined phase difference) The maximum value of vertical birefringence is determined from each point, and the circumference is calculated. The average in four directions was defined as the maximum value of vertical birefringence. The device is an oak automatic birefringence measuring device ADR-130N (light source He-NE63)
2.8 nm).

Examples 1 to 3 Polystyrene glycol having a molecular weight of 750 was mixed with 100 parts by weight of an aromatic polycarbonate resin in the amount shown in the table, and pentaerythritol stearate as a release agent was further added to the aromatic polycarbonate resin. And 1000 ppm of phosphorous acid as a heat stabilizer, and 20 ppm of phosphorous acid.
It pelletized at a temperature of 270 ° C. in a φ single screw extruder. The pellets were molded into an optical disk substrate (5 ") under the following conditions, and various evaluations were carried out.
Other conditions are as follows. Molding machine: Sumitomo Heavy Industries DISK5 Mold: Mold for 5.25 inch MO Molded substrate thickness: 1.2 mm Stamper groove depth: 160 nm Stamper groove pitch: 0.70 μm Injection time: 0.3 second Cooling time: 8.0 seconds Screw rotation speed: 360 rpm Screw diameter: 25 mmφ Mold clamping force: Injection, 20T during holding pressure, 25T during cooling

Example 4 In Example 1, the molecular weight was 7
Molecular weight 150 instead of 50 polystyrene glycol
Except that polystyrene glycol 0 was used, pelletization was performed in the same manner as in Example 1, and an optical disk substrate was molded under the same conditions, and various evaluations were performed. Example 5 Pelletization was performed in the same manner as in Example 2 except that polystyrene glycol having a molecular weight of 1500 was used instead of polystyrene glycol having a molecular weight of 750, and an optical disk substrate was molded under the same conditions to perform various evaluations. Was.

Comparative Example 1 Pellets were formed in the same manner as in Example 1 except that polystyrene glycol was not blended, and an optical disk substrate was molded under the same conditions, and various evaluations were performed.

[0034]

[Table 1]

From Table 1, the following becomes clear. Book
Aromatic polycarbonate resin composition according to the present invention (Example
The optical disk substrate obtained from 1) to 5) is an aromatic polycarbonate.
-Carbonate resin alone (Comparative Example 1)
The glass transition temperature is lower than that of shaped products, and the transferability is excellent.
Small warpage and vertical refractive index difference of 400 × 10 ^-6
The following is useful as an optical disk substrate.

[0036]

Industrial Applicability The aromatic polycarbonate resin composition of the present invention has a low glass transition temperature, is excellent in transferability of a signal of a stamper, has a small warp of a substrate, and has a small vertical refractive index difference of a molded substrate. It can be widely used as a raw material resin for manufacturing high density optical disc substrates. Further, the optical disk substrate molded using the aromatic polycarbonate resin composition of the present invention has high transferability, low warpage,
It is excellent in low refractive index difference in the vertical direction and can be suitably used as a high-density optical disk substrate, and its industrial utility value is extremely large.

Continuation of the front page (72) Inventor Hiroyoshi Maruyama 5-6-1 Higashi-Hachiman, Hiratsuka-shi, Kanagawa F-term in the Technology Center of Mitsubishi Engineering-Plastics Corporation (reference) 4J002 CG011 CG021 CG031 CH022 GS02

Claims (3)

[Claims] 1. A polystyrene glycol having a molecular weight of 300 to 10,000 is compounded in an amount of 0.2 to 50 parts by weight based on 100 parts by weight of an aromatic polycarbonate resin, and the viscosity average molecular weight of the aromatic polycarbonate resin is 1
An aromatic polycarbonate resin composition having a molecular weight of from 000 to 23,000. 2. The aromatic polycarbonate resin composition according to claim 1, wherein the aromatic polycarbonate resin is an aromatic polycarbonate resin having a structural unit represented by the following formula (1). Embedded image (Wherein, R ¹ and R ² each represent a hydrogen atom and a carbon atom 1
To 6 represent an alkyl group and a phenyl group, and R ³ and R ⁴
Represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and a halogen atom, respectively. ) 3. An optical disk substrate formed using the aromatic polycarbonate resin composition according to claim 1.