JPH07108938B2 - Disc substrate made of polycarbonate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a disk substrate made of polycarbonate, and more particularly to a useful disk substrate made of high-purity polycarbonate having an extremely low content of impurities.

[Problems to be Solved by Prior Art and Invention]

In general, polycarbonate is used as a material for disk substrates such as optical disks and magnetic disks.

However, when this polycarbonate is molded and used as a disk substrate, the adhesion between the substrate and the recording film is insufficient, and metals such as iron, gallium, and terbium present in the recording film are gradually corroded. Alternatively, since the mold is corroded during molding, there have been various problems such as shortening the stamper life.

Therefore, the present inventors have made various investigations to solve the above problems in using polycarbonate as a disk substrate, and the conventional polycarbonate, particularly the polycarbonate obtained by the phosgene method, has unreacted raw materials and It was found that the used solvent or low molecular weight component was contained as an impurity, and such an impurity was a major cause of the above-mentioned various problems.

[Means for solving problems]

The present inventors continued their research based on such findings, and when a polycarbonate containing these impurities was treated with an organic solvent such as acetone, a highly pure polycarbonate with an extremely small amount of impurities was obtained. We have found that it solves all the problems and exhibits excellent performance as a disk substrate.

The present invention has been completed through such processes, and the gist thereof is that the content of impurities is 2 wt% or less of low molecular weight components extracted by Soxhlet in acetone solvent, and 20 pp of unreacted bisphenols.
A disk substrate made of polycarbonate, characterized by using polycarbonate having m or less and methylene chloride of 15 ppm or less.

The polycarbonate used in the present invention has a smaller content of impurities and a higher purity than conventional polycarbonates. In general, conventional polycarbonates contain various impurities, but especially a lot of low molecular weight components such as acetone solvent Soxhlet extraction (polycarbonate oligomers), unreacted bisphenols (bisphenol A etc.) or methylene chloride used as a solvent, Further, these impurities cause various problems as described above when polycarbonate is used for the disk substrate.

The polycarbonate used in the present invention has a low content of any of the above-mentioned impurities, an acetone solvent Soxhlet extraction low molecular weight component is 2% by weight or less, unreacted bisphenols is 20 ppm or less, preferably 10 ppm or less,
Methylene chloride content is 15 ppm or less.

Here, if the low molecular weight component extracted with Soxhlet in acetone solvent exceeds 2% by weight or the amount of unreacted bisphenols exceeds 20 ppm, the adhesiveness between the disk substrate and the recording film deteriorates. Further, when the content of methylene chloride exceeds 15 ppm, the recording film is easily corroded, and the die is corroded at the time of molding, which shortens the stamper life. In addition,
The content of the low-molecular-weight component extracted by Soxhlet in acetone solvent means the ratio of the component extracted by Soxhlet using acetone as a solvent for the target polycarbonate, as described below.

The polycarbonate used in the present invention can be obtained by various methods, but it is usually obtained by subjecting powdered polycarbonate containing impurities obtained by various methods to extraction treatment with an organic solvent such as acetone.

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-like 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 used in the present invention is a powdered polycarbonate containing such impurities in an organic solvent which is said to have a weak precipitation effect on ketones such as acetone and methyl ethyl ketone, and polycarbonate such as toluene and xylene. It is obtained by extraction processing. In the extraction treatment, the above organic solvent was used in an amount in the range of 0.5 to 20 times that of the powdered polycarbonate, and the temperature was adjusted to 4
It is preferably set in the range of 0 ° C. or higher and the boiling point of the organic solvent used or less. The extraction process is usually performed under normal pressure, but it may be performed under pressure. Acetone is particularly suitable as the organic solvent used in the extraction treatment.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 Soxhlet extraction with acetone solvent Low molecular weight component (hereinafter referred to as low molecular weight component) 4% by weight, unreacted bisphenol A1
To 100 kg of flaky polycarbonate containing 00 ppm and 100 ppm of methylene chloride, 225 kg of acetone was added to obtain 50
Contact treatment (extraction treatment) was carried out by stirring at 1 ° C for 1 hour.

Then, acetone was removed, and the product was dried at 120 ° C. under a reduced pressure of 30 to 1 mmHg for 20 hours. The content of impurities in the obtained flaky polycarbonate was as shown in Table 1.

Next, 4 ppm of phosphorus-based antioxidant (phosphorus equivalent) and 200 ppm of aliphatic ester were added to the flaky polycarbonate, and then pelletized by an extruder, and a disk substrate having a diameter of 13 cm was molded by an injection molding machine. At this time, the degree of haze on the mirror surface of the die after 5000 shots in disk injection molding 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 (T
A magneto-optical film having a three-layer structure of (b, Fe, Co) layer / 800 Å thick silicon oxide (SiO _x ) layer was formed on the disk substrate by a sputtering method. The performance of the obtained optical disk was evaluated by conducting the adhesion (adhesion between the magneto-optical film and the substrate) and corrosiveness tests as described below. The results are shown in Table 1.

Adhesion test After the optical disc was left in an atmosphere of temperature 90 ° C and relative humidity 90% for 100 hours, a pinhole test using a sethan tape was performed, and the adhesion was displayed based on the following formula.

Corrosion test After leaving the above optical disc for 300 hours in an atmosphere of temperature 60 ° C and relative humidity 90%, it is 250μm × 20 at 1000 times with an optical microscope.
The number of pinhole corrosions in the 0 μm field of view was measured.

Example 2 The same operation as in Example 1 was performed, except that the extraction treatment with acetone was performed at the boiling point of acetone (about 56.5 ° C.). The results are shown in Table 1.

Example 3 The same operation as in Example 1 was performed, except that the extraction treatment with acetone was performed at the boiling point of acetone (about 56.5 ° C.) for 30 minutes. The results are shown in Table 1.

Example 4 The same operation as in Example 1 except that the extraction treatment was carried out twice using toluene instead of acetone in the same manner as in Example 1 and the toluene was removed, followed by drying under reduced pressure for 40 hours. I went. The results are shown in Table 1.

Example 5 The same operation as in Example 1 was carried out except that the extraction treatment was carried out by using methyl ethyl ketone instead of acetone in Example 1 and the methyl ethyl ketone was removed, followed by drying under reduced pressure for 40 hours. It was The results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed except that the extraction treatment with acetone was not performed in Example 1. The results are shown in Table 1.

Comparative Example 2 In Example 1, the extraction treatment with acetone was performed using acetone.
The same operation as in Example 1 was performed except that 100 kg was used at 25 ° C. The results are shown in Table 1.

Comparative Example 3 Example 1 was repeated 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, and that extraction treatment with acetone was not performed. The same operation as in 1 was performed. The results are shown in Table 1.

Comparative Example 4 Example 1 was repeated 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, and the extraction treatment with acetone was not performed. The same operation as in 1 was performed. The results are shown in Table 1.

Comparative Example 5 Example 1 was repeated 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, and the extraction treatment with acetone was not performed. The same operation as in 1 was performed. The results are shown in Table 1.

Comparative Example 6 The same operation as in Example 1 was carried out except that in Example 1, hexane was used instead of acetone in the extraction treatment, and the treatment temperature was 40 ° C. The results are shown in Table 1.

Comparative Example 7 The same operation as in Example 1 was carried out except that in Example 1, the extraction process was performed using methanol instead of acetone, and the processing temperature was 40 ° C. The results are shown in Table 1.

Comparative Example 8 Example 1 was repeated except that a flaky polycarbonate containing 4% 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, and the extraction treatment with acetone was not performed. The same operation as in 1 was performed. The results are shown in Table 1.

Comparative Example 9 Example 1 was repeated except that a flaky polycarbonate containing 1.5% by weight of a low molecular weight component, 10 ppm of unreacted bisphenol A and 40 ppm of methylene chloride was used as the polycarbonate, and the extraction treatment with acetone was not performed. The same operation as in 1 was performed. The results are shown in Table 1.

Comparative Example 10 Example 1 was repeated except that a flaky 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, and the extraction treatment with acetone was not performed. The same operation as in 1 was performed. The results are shown in Table 1.

* In Table 1, the content of impurities in the obtained polycarbonate was analyzed and quantified as follows.

Soxhlet extraction with acetone solvent Low molecular weight component (low molecular weight component) It is a component that was Soxhlet extracted with acetone as a solvent. That is, the sample polycarbonate is crushed to 100
15g (all samples) that passed through the mesh of wire mesh was sampled on cylindrical filter paper No.84 (28 x 100mm), and this was returned once every 3 to 4 minutes (20ml / time) using 300ml of acetone. 8 at flow rate
It was refluxed for an hour and extracted. After that, the residue after evaporating 300 ml of acetone was weighed, and this was designated as a low molecular weight component, and shown as a ratio to all samples.

Unreacted bisphenol A Soxhlet extraction of the above-mentioned low molecular weight components using acetone as a solvent, and then the extract was quantified by liquid chromatography.

Polycarbonate as a sample was dissolved in methylene chloride 1,2-dichloroethane and quantified by gas chromatography (FID).

〔The invention's effect〕

Since the disc substrate according to the present invention is made of high-quality polycarbonate with extremely low content of impurities, the disc substrate such as an optical disc or a magnetic disc has good adhesion to the recording film formed on the substrate, and There is no risk of corroding the recording film, and the stamper life is long because the mold is not corroded during molding.

Therefore, the disk substrate made of the polycarbonate according to the present invention is extremely valuable in practical use for manufacturing an optical disk or a magnetic disk having excellent performance, and its wide use is expected.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-77932 (JP, A) JP-A-63-97627 (JP, A) JP-B 38-16347 (JP, B1) JP-B 41- 8475 (JP, B1) JPB 55-21773 (JP, B2)

Claims (4)

[Claims] 1. A disc made of a polycarbonate characterized in that the content of impurities is 2% by weight or less of a low molecular weight component extracted with Soxhlet in acetone, 20 ppm or less of unreacted bisphenols and 15 ppm or less of methylene chloride. substrate. 2. Obtained by subjecting powdered polycarbonate to an extraction treatment with an organic solvent, and the content of impurities is
A disk substrate made of polycarbonate, which is characterized by using a polycarbonate having a low-molecular-weight component of 2% by weight or less of Soxhlet extraction with an acetone solvent, 20 ppm or less of unreacted bisphenols and 15 ppm or less of methylene chloride. 3. The disk substrate according to claim 2, wherein the organic solvent for the extraction treatment is any one selected from acetone, methyl ethyl ketone, toluene and xylene. 4. The disk substrate according to claim 3, wherein the organic solvent for the extraction treatment is acetone.