JP2001172492A - Optical information board and aromatic polycarbonate resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information board having excellent transferability of signal and flatness of the board surface. SOLUTION: The objective optical information board having a track pitch of <=0.8 μm is produced by the injection molding of an aromatic polycarbonate resin composition composed of (A) 100 pts.wt. of an aromatic polycarbonate having a viscosity-average molecular weight of 10,000-20,000 and (B) 1-20 pts.wt. of a compound of formula (1) (R1 and R2 are each a 1-3C alkyl or phenyl; R3 and R4 are each H or a 1-4C alkyl; and (n) is 1-5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical information substrate. More specifically, the present invention relates to an optical information substrate that is excellent in transferability of signals such as pits and grooves of a stamper, is excellent in flatness of a substrate, and can reduce manufacturing cost.

[0002]

2. Description of the Related Art Conventionally, optical information substrates such as CDs (compact disks), MDs (mini disks), MOs (magneto-optical disks), and DVDs (digital versatile disks) have been injection molded from aromatic polycarbonate resins for optics. Is generally obtained by Aromatic polycarbonates have been widely used as materials for optical information substrates because of their excellent transparency, impact resistance, heat resistance, and the like, and the resulting molded articles also have excellent dimensional stability.

In a transparent optical information substrate such as a compact disk (CD) or a digital versatile disk (DVD), fine irregularities such as pits and grooves on the submicron order on the surface of a mold cavity are formed on the surface of a molded product. It must be transferred accurately. The thickness of the substrate itself may be reduced in order to increase the signal density. But,
In order to increase the signal density on the substrate surface, it is necessary to reduce the interval (track pitch) between pits and grooves. In particular, in a write-once DVD-R or the like that uses an organic dye as a signal film, the depth of the groove must be increased in order to ensure signal contrast. As described above, the fine unevenness in which the depth of the pits or grooves is increased and the interval between the pits and grooves is reduced makes it extremely difficult to transfer the pattern to the substrate surface.

[0004]

Recently, high density recording such as DVD has been advanced, and it is difficult to transfer a signal to a substrate of a stamper. Particularly, when a track pitch is 0.8 μm or less, it becomes difficult to transfer a signal suddenly. -R (write-once DV
In the case of D), the groove depth is as deep as 200 nm,
The track pitch is as small as 0.7 μm, and accurate signal transfer and good flatness of the substrate cannot be obtained by using an optical aromatic polycarbonate resin used in conventional CDs and MDs. . Therefore, a signal reading defect or a writing defect has occurred. Techniques for accurately transferring the fine irregularities onto the substrate surface of the molded article (improving the transferability) include (1) a method of setting a high mold temperature at the time of substrate production, and (2) a method of using an aromatic polycarbonate resin. Methods for lowering the glass transition temperature and the like are known. However, if the mold temperature is set high by the method (1), the temperature at the time of removal from the mold becomes high, and the flatness of the substrate deteriorates. A resin having a lower transition temperature tends to have a lower rigidity at the same time, and thus has a drawback that the flatness of the substrate deteriorates. Even if the temperature of the mold is raised, it is possible to improve the flatness to some extent by extending the cooling time in the mold, but this is not desirable in production because the molding cycle becomes longer. Accordingly, as long as the conventional aromatic polycarbonate resin for optical use is used, a substrate satisfying the characteristics has not been obtained even if the molding conditions are changed. Further, resins other than the aromatic polycarbonate resin, for example, polymethyl methacrylate (PMM)
The use of A) or amorphous polyolefin has the advantage of reducing the birefringence of the substrate, but cannot improve transferability and flatness. Therefore, among DVD-R (4.7 GB) substrates, a substrate that simultaneously satisfies the transferability and flatness of the substrate has not been found yet.

[0005]

Under these circumstances, the present inventors have made intensive studies to provide an optical information substrate having excellent signal transferability and at the same time excellent substrate flatness. The resin composition has a viscosity average molecular weight of 10,000
An aromatic polycarbonate of 0 to 20,000 is used as a base resin, and the above formula (1) is used for 100 parts by weight of the base resin.
It has been found that a compound having a composition of 1 to 20 parts by weight has excellent performance for an optical information substrate. In particular,
It has been found that there is a sufficient effect as a high-density optical information substrate having a track pitch of 0.8 μm or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The base resin of the aromatic polycarbonate resin composition forming the optical information substrate of the present invention is an aromatic polycarbonate having a predetermined degree of polymerization. The aromatic polycarbonate is a polymer or a 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. A typical example is a polycarbonate produced from 2,2-bis (4-hydroxyphenyl) propane (bisphenol A).

The dihydroxydiaryl compounds include 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, 2,2-bis (4 Bis (hydroxyaryl) alkanes such as -hydroxy-3,5-dichlorophenyl) propane, bis (hydroxyaryl) cycloalkanes such as 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4′- Of dihydroxydiaryl ethers such as dihydroxydiphenylether, 4,4'-dihydroxy-3,3'-dimethyldiphenylether, 4,4'-dihydroxyphenylsulfide, and 4,4'-dihydroxy-3,3'-dimethyldiphenylsulfide Dihydroxydiaryl sulfides such as 4,4'-dihi Dihydroxydiarylsulfoxides such as droxydiphenylsulfoxide, 4,4′-dihydroxy-3,3′-dimethyldiphenylsulfoxide, 4,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxy-3, 3 '
Dihydroxydiarylsulfones such as -dimethyldiphenylsulfone; These may be used alone or as a mixture of two or more types. In addition, biperazine, dipiperidyl, hydroquinone, resorcin, 4,4′-dihydroxydiphenyl, and the like may be used in combination.

The aromatic polycarbonate constituting the optical information substrate of the present invention has a viscosity average molecular weight of 10,000 to 2
It must be in the range of 0000. When the viscosity average molecular weight is less than 10,000, a substrate having low rigidity and no practical use can not be obtained, and when it exceeds 20,000, a substrate having poor fluidity and excellent signal transfer properties cannot be obtained. The viscosity average molecular weight is preferably 12,000 to 18,000
Of which, particularly preferred are 15,000 to 17,
000. In the present invention, the term "viscosity average molecular weight (M)" refers to the intrinsic viscosity (η) obtained using an Ostwald viscometer using methylene chloride as a solvent, and the following Schnell viscosity equation, that is, (η) = 1. It means a value calculated from 23 × 10 ⁻⁵ M ^0.85 .

It is well known that in the case of a conventional optical polycarbonate resin, the transferability of a substrate is improved by lowering the glass transition temperature of the resin and approaching the mold temperature (for example, Japanese Patent Application No. 11-110). 163516). However, when the glass transition temperature is lowered to approach the mold temperature, the flatness deteriorates. Therefore, a material whose rigidity does not decrease even when the glass transition temperature is lowered exhibits an effect excellent in transferability and flatness. That is, the compound of the following formula (1) is used for 100 parts by weight of the aromatic polycarbonate used in the present invention.

[0010]

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Wherein R ₁ and R ₂ are each an alkyl group having 1 to 3 carbon atoms or a phenyl group, and R ₃ and R ₄ are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. And n is a number from 1 to 5.) The resin composition containing 1 to 20 parts by weight of the resin composition has a low glass transition temperature and at the same time has a high rigidity. It is an excellent material.

Specifically, the compound of the above formula (1)
₁ , when a compound in which R ₂ is a methyl group is blended with, for example, 5 parts by weight based on 100 parts by weight of an aromatic polycarbonate, the glass transition temperature is reduced by about 20 ° C. as compared with the case where it is not blended, Has an increase of about 30%. As long as R ₁ and R ₂ are an alkyl group having 1 to 3 carbon atoms or a phenyl group, the same effect is obtained. However, when the alkyl group has 4 or more carbon atoms, thermal stability is not good. On the other hand, when R ₃ and R ₄ are a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, the effect is found. Also in the case of an alkyl group having 5 or more carbon atoms, thermal stability is not good. The alkyl group may be linear or branched. n
Should be chosen in the range of 1-5. When n is 6 or more, the compatibility with the base resin is reduced, and the transparency is poor. Also, if n is small, the gas during molding increases, so the value of n should desirably be selected from 2 to 4. The compounding amount of the compound of the formula (1) should be selected from 1 to 20 parts by weight. If the amount is less than 1 part by weight, the effect of lowering the glass transition temperature and the effect of improving the rigidity are not seen. Preferably it should be chosen between 3 and 10 parts by weight.

In the present invention, the compound of the formula (1), which is blended with an aromatic polycarbonate, has a high compatibility with the base resin, so that it enters between the molecular chains of the aromatic polycarbonate and acts like a plasticizer. By doing so, it is considered that the glass transition temperature is reduced. Further, it is considered that the elasticity at the mold temperature or room temperature is increased by the interaction of the base resin with the aromatic polycarbonate due to the molecular arrangement. The glass transition temperature of the polycarbonate resin composition in the present invention is preferably 130 ° C. or lower. When the glass transition temperature exceeds 130 ° C., the transferability tends to decrease. The elastic modulus at the mold temperature in injection molding of the polycarbonate resin composition is preferably 2.0 GPa or more. If the elastic modulus at the mold temperature is less than 2.0 GPa, the warpage of the substrate tends to increase.

In order to increase the density of information on an optical disk, it is desirable that the laser wavelength be as short as possible. As the laser wavelength becomes shorter, the depth of the pits and grooves of the signal tends to be shallower, but since the track pitch becomes shorter, it cannot be made too shallow in order to obtain signal contrast. Therefore, it becomes more difficult to transfer signals as the substrate has a shorter wavelength and a smaller track pitch. In particular, when a signal stored on a transparent substrate made of an aromatic polycarbonate resin composition is read by a laser beam having a wavelength of 300 to 700 nm, that is, a signal is written on a high-density optical information substrate having a track pitch of 0.8 μm or less. The effect is found when memorizing. Preferably, the laser light wavelength should be selected from the range of 300 to 650 nm, and the track pitch should be selected in the range of 0.2 to 0.8 μm.

The compound of the formula (1) is obtained by reacting 4,4-dihydroxydiphenylalkane with alkylphenyl chlorocarbonate in the presence of triethylamine and recrystallizing with toluene. Depending on the reaction conditions, n = 1 to 5 and mixtures thereof are obtained.

The aromatic polycarbonate resin composition according to the present invention may contain a flame retardant, a flame retardant auxiliary, a coloring agent, a plasticizer, a lubricant, a heat stabilizer, if necessary, as long as the object of the present invention is not impaired. An antistatic agent, a release agent, an ultraviolet absorber and the like can be added. To prepare the aromatic polycarbonate resin composition according to the present invention, a compound of the formula (1) and, if necessary, the above-mentioned various additives are weighed to a predetermined amount in an aromatic polycarbonate, and a mixer such as a V-type blender is weighed. And the resulting mixture is melted and kneaded with an extruder to form pellets.

The optical information substrate according to the present invention can be suitably used for existing and next-generation high-density optical disk substrates.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following description examples unless it exceeds the gist. In the following Examples and Comparative Examples, the physical properties of the obtained pellets or molded product samples were evaluated according to the following procedures.

(1) Glass transition temperature: Differential scanning calorimetry (DSC) (manufactured by Seiko, Model: SSC-5000)
At 20 ° C./mi under a nitrogen stream.
The inflection point observed when the temperature was raised at the rate of n was defined as the glass transition temperature.

(2) Modulus of elasticity at mold temperature: Apparatus: UBM dynamic viscoelastic apparatus Rheogel
-E4000 Frequency: 11 Hz Specimen: length 20 mm x width 5 mm x thickness 0.6 mm (prepared by cutting a sample molded DVD substrate) Cooling rate: 2 ° C / min Mode: tensile mode Storage modulus at 125 ° C Is the elastic modulus.

(3) Method of measuring flatness of substrate: Measuring device: Automatic disk warp angle measuring device by Admon Science Laser light source: Semiconductor laser 780 nm Rotation speed: 60 rpm Radial direction: R25, 37, 49, 57 mm Circumferential direction : 4 points Measurement direction: The maximum value of the radius and the warp angle in the circumferential direction was defined as flatness.

(4) Method for evaluating transferability of signal of substrate: D
Using a stamper having a groove depth of 200 nm and a pitch of 0.74 μm in a VD-R (4.7 GB) format, an optical disc substrate having a thickness of 0.6 mm and a diameter of 120 mm is formed, and a groove depth of 57 mm in a radial direction of the substrate is formed. The measurement was made at four points in the circumferential direction, and the average value was taken as the transferability. The measurement conditions are as follows. Atomic force microscope: Olympus NV2100 cantilever: conical Load value: 30 nN Number of scanning lines: 128 Scanning speed: 5 sec / line

Examples 1 to 5 and Comparative Examples Polycarbonate for optical disks having a viscosity average molecular weight of 16,000 (manufactured by Mitsubishi Engineering-Plastics Corporation, N
OVAREX7020AD2) 100 parts by weight of the formula (1) having R _{1 to} R ₄ having the number of carbon atoms shown in Table 1 and n = 2
Are weighed and blended in the proportions (parts by weight) shown in Table 1 and mixed by a tumbler, and the obtained mixture is melted and kneaded by a 40 mmφ vent type extruder at a cylinder temperature of 270 ° C. And pelletized. The glass transition temperature of the obtained pellet was measured. The results are shown in Table 1.

The obtained pellets were subjected to an injection molding machine for optical disk substrates (SD40, manufactured by Sumitomo Heavy Industries, Ltd.).
The cylinder temperature was fixed at 360 ° C, the mold temperature was set at 125 ° C, a DVD-R (4.7 GB) substrate was molded, and various physical properties of the obtained molded product were evaluated.
It was shown to.

[0025]

[Table 1]

According to the above table, the optical information substrates (Examples 1 to 5) obtained by blending various compounds of the formula (1) according to the present invention were obtained from the optical information substrates (Formula (1) It can be seen that the transferability is excellent and the flatness is excellent at the same time as compared with the case of the compound of the formula (2).

[0027]

The optical information substrate according to the present invention is different from the conventional optical information substrate in that even if it is a high-density substrate, the transfer property can be improved.
Because of its excellent flatness, it can be widely used as an optical disk substrate, and its industrial utility value is extremely large.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 17:00 B29L 17:00 (72) Inventor Hiroshi Nakano 5-6-1 Higashi-Yawata, Hiratsuka-shi, Kanagawa 3 R-Engineering Plastics Co., Ltd. Technology Center F-term (reference) 4F206 AA28 AH79 JA07 JQ81 4J002 CG001 EH066 GS02 5D029 KA07 KC09 KC11

Claims (4)

[Claims] 1. An optical information substrate obtained by injection molding an aromatic polycarbonate resin composition having the following composition and having a track pitch of 0.8 μm or less. (A) 100 parts by weight of an aromatic polycarbonate having a viscosity average molecular weight of 10,000 to 20,000 (B) 1 to 20 parts by weight of a compound of the following formula (1) (Wherein, R ₁ and R ₂ are each an alkyl group having 1 to 3 carbon atoms or a phenyl group, R ₃ and R ₄ are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,
n is a number from 1 to 5. ) 2. The optical information substrate according to claim 1, wherein the glass transition temperature of the aromatic polycarbonate resin composition is 130 ° C. or lower. 3. The optical information substrate according to claim 1, wherein the aromatic polycarbonate resin composition has an elastic modulus at a mold temperature of 2.0 GPa or more. 4. An aromatic polycarbonate resin composition having the following composition for molding an optical information substrate having a track pitch of 0.8 μm or less. Composition: (A) 100 parts by weight of an aromatic polycarbonate having a viscosity average molecular weight of 10,000 to 20,000 (B) 1 to 20 parts by weight of a compound of the following formula (1) (Wherein, R ₁ and R ₂ are each an alkyl group having 1 to 3 carbon atoms or a phenyl group, R ₃ and R ₄ are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,
n is a number from 1 to 5. )