JPH06100682A - Polycarbonate for disk base - Google Patents

Abstract

PURPOSE:To provide a high-quality polycarbonate which gives a disk base, such as one for an optical or magnetic disk, excellent in adhesion to a recording film formed on the base. CONSTITUTION:A polycarbonate for a disk base has a content of low-mol.-wt. impurities of up to 3wt.%, or it has, in addition to the content of impurities of the above amt., content of an unreacted bisphenol of up to 20 ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycarbonate for a disc substrate, and more particularly to a high-purity polycarbonate having a very low content of low molecular weight components as impurities and useful as a material for a disc substrate.

[0002]

2. Description of the Related Art Polycarbonate is generally used as a material for disk substrates such as optical disks and magnetic disks. However, this polycarbonate has a problem that the adhesion between the substrate and the recording film is insufficient when used as a disk substrate. Therefore, the present inventors have made various studies to solve the above problems in using polycarbonate as a disk substrate, and a conventional polycarbonate, particularly a polycarbonate obtained by the phosgene method, has a low molecular weight component. Since it is contained as an impurity, it has been found that such an impurity is a major cause of the above problems.

[0003]

Means for Solving the Problems The inventors of the present invention continued their research on the basis of such findings. When a polycarbonate containing these impurities was treated with an organic solvent such as acetone, a low molecular weight impurity was obtained. It has been found that high-purity polycarbonate having a very small content of components solves the above-mentioned problem of adhesiveness between the recording film and the substrate and exhibits very excellent performance as a disk substrate. The present invention has been completed through these processes,
The gist thereof is a polycarbonate for a disk substrate, characterized in that the content of a low molecular weight component as an impurity is 3% by weight or less. Further, the gist of the present invention is a polycarbonate for a disk substrate, which further contains a low molecular weight component as an impurity of 3% by weight or less and an unreacted bisphenol content of 20 ppm or less.

The polycarbonate of the present invention contains less impurities (particularly low molecular weight components) than conventional polycarbonates and has a high degree of purity. Generally, conventional polycarbonates contain various impurities. In particular, low molecular weight components such as polycarbonate oligomers or unreacted bisphenols (bisphenol A, etc.) and methylene chloride used as a solvent are many, and these impurities, Particularly, the low molecular weight component causes the above-mentioned problems when polycarbonate is used for the disk substrate.

In the polycarbonate of the present invention, the content of the low molecular weight component which is the above-mentioned impurity is 3% by weight or less, preferably 2% by weight or less. Further, more preferable polycarbonate has a low molecular weight component content of 3% by weight or less (preferably 2% by weight or less) and an unreacted bisphenol content of 20 ppm or less, preferably 10 ppm.
It is the following. Here, when the low molecular weight component exceeds 3% by weight, the adhesiveness between the recording film and the substrate deteriorates. If the amount of unreacted bisphenols exceeds 20 ppm, the adhesion between the disk substrate and the recording film may be insufficient.

The polycarbonate of the present invention can be obtained by various methods, but it is usually obtained by subjecting a powdery polycarbonate containing impurities obtained by various methods to an extraction treatment with an organic solvent. The method for producing a powdery polycarbonate containing the impurities is not particularly limited, but is usually a phosgene method, particularly an interfacial polycondensation method using bisphenols such as bisphenol A and phosgene as raw materials and methylene chloride as a solvent, In particular, the continuous interfacial polycondensation method can be mentioned. In addition, a so-called pyridine polymerization method using pyridine as a solvent among the transesterification method and the phosgene method can be mentioned. The above-mentioned powdery polycarbonate is not limited to a powdery one in a strict sense, and includes a flake-like one and the like. That is, it includes all powdery, granular, and flake-shaped polycarbonates obtained by the phosgene method or the transesterification method and before being pelletized. For example, the powdery polycarbonate obtained by the above-mentioned continuous interfacial polycondensation is usually in a flake form, and contains 4 to 8% by weight of low molecular weight components such as oligomers of polycarbonate and unreacted bisphenols such as bisphenol A as impurities. It contains 70 to 150 ppm and about 50 to 150 ppm of methylene chloride used as a solvent.

The polycarbonate of the present invention is considered to have a weak precipitation effect on powdery polycarbonate containing such impurities against ketones such as hexane, methanol, acetone and methyl ethyl ketone, and polycarbonate such as toluene and xylene. It is obtained by an extraction treatment with an organic solvent. In the extraction process, 0.5% of powdered polycarbonate was added to the above organic solvent.
It is preferable to use in an amount of 20 to 20 times, and to set the temperature in the range of 40 ° C. or higher and the boiling point of the organic solvent used or lower.
The extraction process is usually carried out under normal pressure, but it may be carried out under pressure.

[0008]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 Low-molecular-weight component 1.5% by weight, unreacted bisphenol A10
After adding 4 ppm (based on phosphorus) of a phosphorus-based antioxidant and 200 ppm of an aliphatic ester to a flaky polycarbonate containing ppm and 40 ppm of methylene chloride,
It was pelletized by an extruder and a disk substrate having a diameter of 13 cm was molded by an injection molding machine. At this time, 5 by injection molding of the disk
The cloudiness of the mirror surface of the mold after 000 shots was visually observed and evaluated as the stamper life. The results are shown in Table 1. 800 Å thick silicon oxide (SiO _x ) layer /
1000 Å thick metal (Tb, Fe, Co) layer / 800 Å thickness
A magneto-optical film having a three-layer structure of a silicon oxide (Si O _x ) layer was formed on the disk substrate by a sputtering method. The performance of the obtained optical disk was evaluated by conducting an adhesion test (adhesion between the magneto-optical film and the substrate) as described below. The results are shown in Table 1.

Adhesion test After the optical disc was left in an atmosphere of 90 ° C. and 90% relative humidity for 100 hours, a pinhole pinhole test was performed using cellophane tape, and the adhesion was displayed based on the following formula. Adhesiveness = (area of remaining portion) / (test area) × 10
0 (%)

Example 2 The same operation as in Example 1 except that a flake polycarbonate containing 1.5% by weight of a low molecular weight component, 30 ppm of unreacted bisphenol A and 10 ppm of methylene chloride was used as the polycarbonate. I went. The results are shown in Table 1.

Example 3 The same operation as in Example 1 was carried out except that a flaky polycarbonate containing 2% by weight of a low molecular weight component, 100 ppm of unreacted bisphenol A and 100 ppm of methylene chloride was used as the polycarbonate. It was The results are shown in Table 1.

Example 4 The same operation as in Example 1 was carried out except that a flaky polycarbonate containing 2% by weight of a low molecular weight component, 10 ppm of unreacted bisphenol A and 100 ppm of methylene chloride was used as the polycarbonate. It was The results are shown in Table 1.

Example 5 Except that in Example 1, a flaky polycarbonate containing 2% by weight of a low molecular weight component, 100 ppm of unreacted bisphenol A and 100 ppm of methylene chloride was used as the polycarbonate, and extraction treatment with methyl ethyl ketone was performed. The same operation as in Example 1 was performed. The results are shown in Table 1.

Example 6 Except that in Example 1, a flaky polycarbonate containing 2% by weight of a low molecular weight component, 200 ppm of unreacted bisphenol A and 100 ppm of methylene chloride was used as the polycarbonate, and extraction treatment with methyl ethyl ketone was performed. The same operation as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was carried out except that a flaky polycarbonate containing 8% by weight of a low molecular weight component, 10 ppm of unreacted bisphenol A and 10 ppm of methylene chloride was used as the polycarbonate. It was The results are shown in Table 1.

Comparative Example 2 The same operation as in Example 1 was carried out except that a flaky polycarbonate containing 4% by weight of a low molecular weight component, 100 ppm of unreacted bisphenol A and 100 ppm of methylene chloride was used as the polycarbonate. It was The results are shown in Table 1.

[0017]

[Table 1]

[0018]

[Table 2]

* In Table 1, the content of impurities in the obtained polycarbonate was analyzed and quantified as follows. Soxhlet extracted with low molecular weight acetone as a solvent. That is, the sample polycarbonate is crushed to 10
Cylindrical filter paper No. 15g that passed through 0 mesh wire mesh
A sample of 84 (28 × 100 mm) was collected, and this was extracted with 300 ml of acetone by refluxing once every 3 to 4 minutes (20 ml / cycle) for 8 hours. After that, the residue after evaporating 300 ml of acetone was weighed and used as a low molecular weight component. Unreacted bisphenol A The above-mentioned low molecular weight component was quantified by liquid chromatography after Soxhlet extraction using acetone as a solvent. Polycarbonate as a sample was dissolved in methylene chloride 1,2-dichloroethane and quantified by gas chromatography (FID).

[0020]

INDUSTRIAL APPLICABILITY The polycarbonate of the present invention has a very low content of low molecular weight components as impurities and is of high quality, and when used for a disk substrate such as an optical disk or a magnetic disk, the substrate and the substrate Adhesiveness to the recording film is good. Therefore, the polycarbonate of the present invention is extremely valuable in practice as a material for a disk substrate having excellent performance, and its wide use is expected.

Claims (2)

[Claims] 1. A polycarbonate for a disk substrate, wherein the content of a low molecular weight component as an impurity is 3% by weight or less. 2. The content of low molecular weight components as impurities is 3
2. The polycarbonate for a disk substrate according to claim 1, wherein the content of unreacted bisphenols is 20 ppm or less and the content of unreacted bisphenols is 20 ppm or less.