JP2006348132A - Polycarbonate resin composition and optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polycarbonate suitable for an information recording medium such as an optical disk and a near-field recording medium, which is excellent in continuous formability without occurrence of stringing or cracking at the time of molding, excellent in optical characteristics, and information signals are accurately transferred. A resin composition is provided.
A loss angle δ and a complex viscosity η ^* (Pa · s) measured under the conditions of a viscosity average molecular weight of 10,000 to 20,000, a temperature of 250 ° C., and an angular velocity of 10 rad / s are expressed by the following relational expression (1 (A) 100 parts by weight of the aromatic polycarbonate resin (a), a branched aromatic polycarbonate resin (b) in which the loss angle δ and complex viscosity η ^* (Pa · s) measured under the same conditions satisfy the following relational expression (2) ) In an amount of 1 to 10 parts by weight.
5500 < ^Tanδ / η ^{* −0.87} ≦ 9000 (1)
3000 ≦ ^Tanδ / η ^{* −0.87} ≦ 5500 (2)
[Selection figure] None

Description

  The present invention relates to an aromatic polycarbonate resin composition. In particular, the present invention relates to an aromatic polycarbonate resin composition suitable as an optical information recording medium produced by an injection molding method or a material for the substrate.

Aromatic polycarbonate resin is used for compact discs, laser discs, magneto-optical discs, digital video discs, and other optical discs, as well as near-field recording information media characterized by reading and writing signals from the information surface or their substrates. Widely used as a raw material. Such an optical information recording medium is melted by using a mold cavity in which an information signal of a submicron order depth and interval such as pits and grooves is exposed in an injection mold called a stamper. It is manufactured by a method in which a polycarbonate resin is injected and an information signal is transferred to the surface of the molded product. (In the present specification, such a molded product is referred to as “information recording medium” or “substrate for information recording medium (or simply substrate)”).
Aromatic polycarbonate resins have been used for the production of optical information recording media because they are excellent in transparency, optical properties, strength, heat resistance, dimensional stability, impact resistance, etc. Therefore, when a substrate is manufactured by the injection molding method, the fine uneven pattern (information signal) engraved on the stamper is accurately transferred to the surface of the substrate (molded product) (transferability is good), and the warp This is because a high-quality information recording medium substrate having excellent flatness can be obtained.

  However, in recent years, information recording media have become deeper in the pits and grooves of information signals, and the distance (pitches) between pits and grooves has been further reduced to increase the information recording density. The temperature is getting higher. For the purpose of reducing birefringence, the resin temperature is increased to improve the fluidity. Further, for the purpose of increasing productivity, the molding cycle tends to be shortened, and sag and stringing due to resin leakage generated at the tip of the nozzle during injection molding cause troubles in continuous molding and poor appearance.

  Ordinary polycarbonate resins exhibit Newtonian flow behavior under melt processing conditions, and therefore cause a haunting phenomenon or stringing during injection molding. Therefore, for example, Patent Document 1 proposes a method of mixing an ultrahigh molecular weight polycarbonate resin in order to impart non-Newtonian behavior under melt processing conditions. However, the polycarbonate resin generally used for optical discs has a large molecular weight difference from the ultrahigh molecular weight polycarbonate resin to be mixed, so mixing the ultrahigh molecular weight polycarbonate makes it optically non-uniform, resulting in minute white streaks and molding At times, silver and delamination phenomena occur, and mechanical strength is uneven.

Patent Document 2 proposes the use of a branched polycarbonate resin as an optical molding material such as an optical disk, which prevents stringing during molding, and has birefringence, strength, and continuous moldability. It is described that it is improved.
In general, a branched polycarbonate resin is polymerized by adding, for example, a trifunctional phenol, a trifunctional carboxylic acid, or isatin bisphenol as a branching agent when a difunctional phenol is treated with phosgene or a carbonic acid diester or immediately after the treatment. It is manufactured by. However, it is difficult to control the degree of branching, and in order to obtain a resin with a branching amount according to the purpose and necessity, a large amount of product loss occurs, or it is difficult to purify unreacted substances and impurities. There was a problem of causing coloring.

Japanese Patent Laid-Open No. 04-342760 Japanese Patent Laid-Open No. 60-215019

  The present invention provides: Excellent optical characteristics such as birefringence, information signals such as high density grooves and pits engraved on the stamper are accurately transferred, flatness, rigidity, less warpage, optical discs and proximity with less vibration during vibration 1. providing an optical information recording medium such as a field recording medium; The object of the present invention is to provide a polycarbonate resin that is suitable for the production of such an information recording medium and that is excellent in continuous formability without occurrence of stringing or cracking.

The present inventors have repeatedly studied for the above-mentioned purpose, and are two kinds of resins having the physical property value obtained from the measurement of dynamic melt viscoelasticity as an index, and an aromatic having a viscosity average molecular weight of 10,000 to 20,000. It has been found that the above problem can be achieved by using a resin composition in which a small amount of a branched polycarbonate resin is blended with a polycarbonate resin. That is, the gist of the present invention is that the viscosity average molecular weight is 10,000 to 20,000, the loss angle δ and the complex viscosity η ^* (Pa · s) measured under the conditions of a temperature of 250 ° C. and an angular velocity of 10 rad / s. For 100 parts by weight of the aromatic polycarbonate resin (a) satisfying the following relational expression (1), the loss angle δ and complex viscosity η ^* (Pa · s) measured under the same conditions satisfy the following relational expression (2). An aromatic polycarbonate resin composition containing 1 to 10 parts by weight of a branched aromatic polycarbonate resin (b), and an optical information recording medium formed from the composition.
5500 < ^Tanδ / η ^{* −0.87} ≦ 9000 (1)
3000 ≦ ^Tanδ / η ^{* −0.87} ≦ 5500 (2)

  The polycarbonate resin composition of the present invention is excellent in continuous formability without the occurrence of stringing and hunting when producing an optical information recording medium, and the obtained optical information recording medium is excellent in optical properties such as birefringence. Information signals such as high-density grooves and pits carved on the stamper are accurately transferred, and there is little flatness, rigidity and warp, and there is little surface vibration during vibration.

Hereinafter, the present invention will be described in detail.
The aromatic polycarbonate resin (a) used in the present invention is produced by polymerizing an aromatic dihydroxy compound and phosgene by an interfacial method or using an ester exchange reaction with bisaryl carbonate.

  As the raw material aromatic dihydroxy compound, bisphenol A is usually used, but is not particularly limited thereto. For example, 1,1-bis (4-hydroxyphenyl) methane, 1,1-bis (4 -Hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) butane, bis (4-Hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) oxide and the like are used alone or in combination.

The viscosity average molecular weight of the aromatic polycarbonate resin (a) is 10,000 to 20,000. When the viscosity average molecular weight is less than 10,000, the recording medium with low rigidity and practicality (
Alternatively, it is not preferable because the substrate cannot be obtained, and if it exceeds 20,000, the fluidity is inferior, and a thin recording medium in which fine irregularities are accurately transferred to the substrate surface cannot be obtained. The viscosity average molecular weight is preferably 13,000 to 19,000, and particularly preferably 15,000 to 18,000. The viscosity average molecular weight (Mv) in the present invention is an intrinsic viscosity (η) obtained from a solution viscosity measured using a Ostwald viscometer using a solution containing methylene chloride as a solvent, and the following Schnell viscosity formula The value calculated from
[Η] = 1.23 × 10 ⁻⁴ Mv ^0.83

The aromatic polycarbonate resin (a) has a loss angle δ and complex viscosity η ^* (Pa · s) measured under conditions of a temperature of 250 ° C. and an angular velocity of 10 rad / s satisfy the following relational expression (1). .
5500 < ^Tanδ / η ^{* −0.87} ≦ 9000 (1)

The dynamic melt viscoelasticity of the polycarbonate resin used in the present invention means a value measured by the method described below.
First, the polycarbonate resin was dried at 120 ° C. for 5 hours, and then press molded at 250 ° C. into a shape having a diameter of 25 mm and a thickness of 1.5 mm to obtain a measurement sample. Before the measurement, the sample was dried under reduced pressure at 120 ° C. for 4 hours and subjected to measurement. Using a viscoelasticity measuring instrument RDA-700 (manufactured by Rheometrix Co., Ltd.), a parallel plate type jig with a diameter of 25 mm is mounted, and the measurement temperature is 250 ° C. in a nitrogen stream that satisfies the appropriate conditions of this instrument. Set to. The measurement temperature was set by measuring the temperature in the oven. Thereafter, the dried measurement sample was set in an apparatus, and after setting the sample so that the entire sample was sufficiently set temperature, the measurement was performed by rotating at an angular velocity of 10 rad / s and a strain of 10%. By this measurement, loss tangent Tan δ and complex viscosity η ^* (Pa · s) were determined.

The loss angle δ represents a delay in strain phase with respect to stress, which is obtained from measurement of dynamic melt viscoelasticity, and is generally known as one of indices indicating dynamic viscoelasticity. When δ (Tan δ) is large, it indicates that the viscous property of viscoelasticity is strong, and when it is small, it indicates that the elastic property is strong. Factors that determine this value are complex, for example, the molecular structure including the type of monomer including copolymerization, copolymerization composition, copolymerization structure, branching structure such as the number of branch points and the length of the branch chain, etc. , Molecular weight, molecular weight distribution and the like. According to Japanese Patent Laid-Open No. 2002-308975, the linear polycarbonate produced by the interface method is obtained by dividing the value of δ (Tan δ) by the complex viscosity (η ^* (Pa · s)) that is an index such as molecular weight. ^Tanδ / η ^{* −0.87} = approximately 8000 linearly aligned (where −0.87, which is an index of η ^* , represents the slope of the straight line, and ^Tanδ / η ^{* −0.87} is This represents the value of Tan δ when the above straight line is extrapolated to η ^* = 1 (Pa · s), that is, the value of Tan δ / η ^{* −0.87} is used as a parameter, and the loss angle depends on the molecular weight (viscosity). Sex can be excluded.) On the other hand, it has been found that polycarbonates produced by the melt process generally do not ride on this straight line. Further, the branched polycarbonate resin produced by the interface method does not ride on the straight line.

The branched aromatic polycarbonate resin (b) used in the present invention is a polycarbonate resin having a branch, and may be produced by either the interface method or the melting method (transesterification method).
The branched resin (b) must have a loss angle δ and complex viscosity η ^* (Pa · s) measured under the conditions of a temperature of 250 ° C. and an angular velocity of 10 rad / s satisfy the following relational expression (2): Preferably, the following relational expression (2-1) is satisfied.

3000 ≦ ^Tanδ / η ^{* −0.87} ≦ 5500 (2)
3500 ≦ ^Tanδ / η ^{* −0.87} ≦ 5000 (2-1)

To obtain a branched aromatic polycarbonate resin, as part of the aromatic dihydroxy compound, a branching agent such as phloroglucin, 4,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptene-2, 4,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptane, 2,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptene-3, 4,6-dimethyl- 2,4,6-tris (4-hydroxyphenyl) heptane, 1,3,5-tris (4-hydroxyphenyl) heptane, 1,3,5-tris (4-hydroxyphenyl) benzene, 1,1,1 -Polyhydroxy compounds exemplified by tris (4-hydroxyphenyl) ethane and 3,3-bis (4-hydroxyaryl) oxindole = Isatin bisphenol), 5-chloro isatin bisphenol, may be used 5,7-dichloro-isatin bisphenol, polyhydroxy compounds such as 5-bromo-isatin bisphenol. The usage-amount of a polyhydroxy compound is 0.1-2 mol% of a dihydroxy compound, for example.
The viscosity average molecular weight of the branched resin (b) is preferably about 20,000 to 28,000.

The amount of the branched aromatic polycarbonate resin (b) in the resin composition of the present invention is in the range of 1 to 10 parts by weight with respect to 100 parts by weight of the aromatic polycarbonate resin (a). If the amount is too much or less than the above range, the object of the present invention is not achieved.
The method for mixing the aromatic polycarbonate resin (a) and the branched aromatic polycarbonate resin (b) is not particularly limited, and any method can be adopted, for example, mixing with a super mixer, a tumbler, a nauter mixer or the like. Then, a method of melt extrusion with a vented extruder or a twin screw ruder or the like and pelletizing is applied.
At this time, additives such as a heat stabilizer, an antioxidant, a light stabilizer, a colorant, an antistatic agent, a lubricant, and a release agent can be added as necessary.

  The information recording medium according to the present invention can be produced by an injection molding method using the resin composition as a raw material. At that time, the cylinder temperature and mold temperature of the injection molding machine can be appropriately selected according to the density of the information signal, the warp, and the required degree of surface runout. The injection mold is placed with one or both surfaces of the mold cavity exposed with a stamper with information signals such as pits and grooves on the depth and interval of submicron order, and the cylinder temperature of the injection molding machine is set. A molded body (information recording medium or substrate) to which an information signal is transferred is manufactured by injecting molten resin into a mold cavity with a mold temperature set in a range of 250 to 400 ° C. and a mold temperature in a range of 50 to 140 ° C. can do. At this time, if an injection compression molding technique is employed, further improvement in transferability can be expected.

  The optical information recording medium of the present invention may be transparent or opaque. When recording / reproducing laser light passes through the inside of the recording medium as in the current optical disk substrate, it needs to be transparent, and when the laser reads (reproduces) or records directly from the information surface as in near-field recording May be opaque. That is, information is read or written (recorded) from the information surface or the surface opposite to the information surface in a transparent substrate, and information is read or written from the information surface in an opaque substrate. Although the thickness of the substrate is further reduced as the information signal density is increased, the substrate according to the present invention is preferably a single substrate having a thickness of 0.3 to 1.5 mm.

An optical information recording medium according to the present invention is an optical information recording medium such as a compact disk, a laser disk, a magneto-optical disk, a digital video disk, or a near-field recording medium that reads and writes information signals from the information surface side ( Substrate).
In the case of an optical disc, an information layer that can be recorded and / or reproduced by a laser beam having a wavelength of 300 nm to 800 nm is provided on the substrate directly or via another layer, and if necessary, further on the information layer. It can be manufactured by laminating an arbitrary layer. Alternatively, two substrates can be used, and an information layer that can be recorded and / or reproduced by a laser beam having a wavelength of 300 nm to 800 nm is provided between the substrates, and the two substrates are bonded together.
In the case of a near-field recording medium, the same configuration as described above can be used. However, when the recording / reproducing laser beam is not irradiated through the substrate, the substrate may be opaque.
The information recording medium according to the present invention can read or write information signals using a laser having a wavelength of 300 nm to 800 nm, particularly preferably a laser having a wavelength of 385 to 780 nm.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.
In the following examples, the following aromatic polycarbonate resins were used.

* Polycarbonate resin (a): "Iupilon H-4000" manufactured by Mitsubishi Engineering Plastics, polycarbonate for optical disks having a viscosity average molecular weight of 16,000,
^Tanδ / η ^{* −0.87} = about 8,000.
* Polycarbonate resin (b): “Novarex M7027B” manufactured by Mitsubishi Engineering Plastics, branched polycarbonate having a viscosity average molecular weight of 26,000,
^Tanδ / η ^{* −0.87} = about 3,500.
* Polycarbonate resin (c): “Iupilon H-3000” manufactured by Mitsubishi Engineering Plastics Co., Ltd., viscosity average molecular weight 18,000, Tan δ / η ^{* −0.87} = about 8,000.

[Examples 1-4, Comparative Examples 1-3]
Aromatic polycarbonate resins were weighed and blended in the proportions (parts by weight) listed in Table 1 and mixed by a tumbler. The resulting mixture was used at a cylinder temperature of 270 ° C. using a 40 mmφ vented extruder. It was melted and kneaded under conditions to form pellets.
The obtained pellets were subjected to a cylinder temperature of 380 ° C. using an injection molding machine (manufactured by Sumitomo Heavy Industries, model: SD40α) equipped with a stamper (mold for optical disc production) having a groove depth of 150 nm and a pitch of 0.74 μm. A transparent optical disk substrate having a thickness of 0.6 mm and a diameter of 120 mm was obtained under conditions of a mold temperature of 128 ° C. and a molding cycle of 6.0 sec. An evaluation test was performed on the following items on the optical disk substrate obtained while checking the presence or absence of sprue stringing during molding, and the results are shown in Table 1.

(1) Evaluation of transferability of information signal (groove depth nm): The groove depth was measured at four locations along the circumference of the radial direction 57 mm of the optical disk substrate obtained in the example or the comparative example. A larger value means better transferability of the information signal. The measurement was performed using an atomic force microscope (Olympus, model: NV2100) under the conditions of cantilever: conical, load value: 30 nN, number of scanning lines: 128, scanning speed: 5 sec / line.

(2) Measurement of substrate warpage and surface deflection: radius of optical disk substrate while rotating optical disk substrate obtained in Example or Comparative Example at 60 rpm using disk warpage angle automatic measuring device (Admon Science) Irradiation with a laser beam having a wavelength of 780 nm from a semiconductor laser at four locations along the circumference at positions 25 mm, 37 mm, 49 mm, and 57 mm in the direction of the radial direction (degree), tangential direction (angle) degree) and the amount of surface runout (μm) were measured, and the maximum value of the measured values was adopted. The smaller these values, the better.

(3) Measurement of birefringence of substrate: Using the birefringence automatic measuring device (Oak Corp., model: ADR-130N) obtained in the examples or comparative examples, the number of measurement points is 4 at a radial position of 25 mm, and the wavelength is at nm. The phase difference was measured with a normal incidence single pass.

From Table 1, the following is clear.
1) The optical information recording medium substrates of Examples 1 to 3 according to the present invention do not show sprue stringing at the time of molding, and are formed only from a conventional aromatic polycarbonate resin (a) (Comparison) Compared with Example 1), it is excellent in high cycle formability. Further, the warpage angle in the radial direction, the warpage angle in the tangential direction, and the surface runout are small.
2) The effect of the present invention cannot be obtained if the blended amount of the branched polycarbonate resin (b) is too large or too small.
3) Polycarbonate with a simply increased viscosity average molecular weight (Comparative Example 4) does not cause sprue stringing, but is not suitable for an optical information recording medium because the phase difference deteriorates.

An optical information recording medium manufactured from the aromatic polycarbonate resin composition according to the present invention has less warpage and surface vibration of the substrate, and an optical disk or near-field recording medium with less surface vibration even when vibration occurs when rotated at high speed. It is suitable for.

Claims (2)

The loss angle δ and complex viscosity η ^* (Pa · s) measured under the conditions of a viscosity average molecular weight of 10,000 to 20,000, a temperature of 250 ° C., and an angular velocity of 10 rad / s are expressed by the following relational expression (1): A branched aromatic polycarbonate resin in which the loss angle δ and complex viscosity η ^* (Pa · s) measured under the same conditions satisfy the following relational expression (2) with respect to 100 parts by weight of the aromatic polycarbonate resin (a) to be satisfied ( An aromatic polycarbonate resin composition containing 1 to 10 parts by weight of b).
5500 < ^Tanδ / η ^{* −0.87} ≦ 9000 (1)
3000 ≦ ^Tanδ / η ^{* −0.87} ≦ 5500 (2)   An optical information recording medium obtained by injection molding the aromatic polycarbonate resin composition according to claim 1.