JPH0347831A - Aromatic polycarbonate for optical disk - Google Patents

Abstract

PURPOSE:To obtain the subject polycarbonate useful as base material of optical disk, etc., having improved long-term reliability by reacting specific dihydroxy diaryl compound with diaryl carbonate. CONSTITUTION:(A) Dihydroxy diaryl compound composed of >=85mol% dihydroxy diaryl alkene expressed by the formula [Ar<1> and Ar<2> are respectively arylene; Y is (substituted) alkylene] and <=15mol% dihydroxy diaryl compound other than said aryl alkane not containing chlorine atom is reacted with (B) diaryl carbonate not containing chlorine atom to afford the aimed polycarbonate containing 0-0.1ppm chlorine and 0-5mol% hydroxyl group in total end groups.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to aromatic polycarbonate as a substrate material for optical discs such as compact discs, write-once optical discs, and magneto-optical discs.

(Conventional technology) Aromatic polycarbonate is a resin that has excellent physical properties such as heat resistance, transparency, and precision moldability, and is less deformed or deteriorated after molding, and is used as a substrate material for optical disks. It is useful as a.

Optical discs mainly use laser light to read, record, and erase signals, and are highly required to have long-term reliability as a recording material.

However, conventional optical disks using aromatic polycarbonate as a substrate material are still insufficient in terms of long-term reliability, and several methods of improvement have been proposed.

For example, in order to improve the corrosion resistance of the recording layer of an optical disk, a method of reducing the amount of residual chlorine contained in a polycarbonate substrate to 1.0 ppm or less (Japanese Patent Laid-Open No. 63-9762
7), a method for reducing the amount of free chlorine contained in the aromatic polycarbonate resin obtained by the reaction of bisphenol and phosgene to 0.2 ppm (JP-A-64-2)
No. 4829) and the like have been proposed. in this way,
It is clear that residual chlorine compounds and free chlorine corrode the recording layer of optical discs, causing a loss of their long-term reliability.

However, it has been revealed that a considerable amount of chlorine remains in commercially available polycarbonate resin, and the amount of residual chlorine is about 1.3 to 1.6 ppm at the time it is molded into a substrate (Japanese Patent Laid-Open No. 6397627). Publication No.). The reason why chlorine compounds remain in ordinary polycarbonate resins is because of the manufacturing method.

That is, ordinary polycarbonate resins are manufactured by the so-called phosgene method, in which bisphenol A and phosgene are subjected to interfacial polycondensation in a reaction system consisting of methylene chloride and an aqueous sodium hydroxide solution, and the sodium chloride produced as a by-product at this time and the terminal This is thought to be because it was virtually impossible to completely remove chlorine based on chloroformate groups and chlorine compounds such as methylene chloride, which is a solvent, from polycarbonate.

This is clear from the fact that even polycarbonate resins purified through complicated processing steps contain 0.29 Pm of free chlorine (Japanese Patent Application Laid-open No. 24829/1982).

(Problem to be Solved by the Invention) As described above, reducing the chlorine content is an effective method for increasing the long-term reliability of optical discs.
The current level of long-term reliability was not necessarily sufficient.

(Means for Solving the Problems) Therefore, the present inventors conducted extensive research to obtain aromatic polycarbonate for optical disks with further improved long-term reliability. The present inventors have discovered that the long-term reliability of optical discs can be improved by reducing the amount of hydroxyl groups attributable to the polymer terminals of the polycarbonate itself, and have completed the present invention.

That is, the present invention is: An aromatic polycarbonate for optical discs having a chlorine content of O to O, ippm, and a proportion of hydroxyl groups in all terminal groups of 0 to 5 mol %.

The chlorine content in the present invention refers to parts by weight of chlorine atoms relative to the aromatic polycarbonate when a compound containing chlorine, whether inorganic or organic, is contained in the aromatic polycarbonate. be.

Such aromatic polycarbonate may be produced by any method, but in the phosgene method using bisphenols, phosgene, and methylene chloride, the chlorine content should be 0 to 0.1 ppm. However, it is also very difficult to reduce the proportion of terminal hydroxyl groups to 0 to 5% of all terminal groups.

Therefore, one of the preferred methods for producing the aromatic polycarbonate of the present invention is a method of reacting a dihydroxydiaryl compound that does not contain a chlorine atom with a diaryl carbonate that does not contain a chlorine atom.

Particularly preferable is JP-A No.
The method is to use a part of the method described in Japanese Patent No. 158033.

That is, the dihydroxydiaryl compound and the diaryl carbonate are prepolymerized under heating and melting to obtain a weight average molecular weight (Mw) of 2,000 to 20,000, preferably 4,000 to 156,000, and even more preferably 5. ,000~12゜00
0 and in which the proportion of hydroxyl groups in the total end groups is less than 50 mol%, preferably less than 40 mol%, even more preferably less than 35 mol%; This is a method in which a polymer is crystallized and then the crystallized prepolymer is subjected to solid phase polymerization. By this method, the aromatic polycarbonate of the present invention can be easily obtained.

The dihydroxydiaryl compound mentioned here has the general formula (I): HO-Ar'-Y-Ar"-0H-... (1) HO
-Ar1-Y-Ar'' consists of 85 mol% or more of dihydroxydiarylalkane represented by arylene group and Y is alkylene or substituted alkylene group, respectively, and 15 mol% or less of a dihydroxydiaryl compound other than the dihydroxydiarylalkane. is preferably used.

Ar1-Y-Ar2 in the general formula (1) of 1111 is each an arylene group, such as phenylene,
Represents a group such as naphthylene, biphenylene, pyrylidine, etc., and Y represents an alkylene or substituted alkylene group (here, R
I, R2, Rv and R4 are each a hydrogen atom, a lower alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group, and may optionally be substituted with an alkoxy group, and k is an integer of 3 to 11. ).

Further, in addition to the dihydroxydiaryl alkane represented by the general formula (1), the dihydroxydiaryl compound in the raw material may be added to the general formula % formula % () [Ar1- Y-Ar" has the same meaning as above, Z is a simple bond or -〇--CO3Sow
A divalent group such as CO2CON (R') (R' has the same meaning as above)] may contain a dihydroxydiaryl compound represented by the following.

Furthermore, such an arylene group (A r 'Ar"
), one or more hydrogen atoms are substituted with other substituents, such as lower alkyl groups, lower alkoxy groups, phenyl groups, phenoxy groups, vinyl groups, cyano groups, ester groups, amide groups, nitro groups, etc. It may be something.

As the dihydroxydiarylalkane represented by the general formula (1), for example, HO-R5 and R6 are a hydrogen atom, a halogen atom, a lower alkyl group having 1 to 4 carbon atoms, and a lower alkoxy group having 1 to 4 carbon atoms, respectively. , a cycloalkyl group or a phenyl group, which may be the same or different, m and n are integers of 1 to 4, and when m is 2 or more, R5 may be different from each other, and when n is 2 or more, R6 may be different from each other), etc. are preferably used.

Among these compounds, bisphenol A, which is 2,2-bis(4-hydroxyphenyl)propane, and substituted bisphenol A@ are particularly preferred.

Further, these dihydroxydiarylalkane may be used alone or in combination of two or more. When two or more types of dihydroxydiarylalkane are used, the aromatic polycarbonate is usually a copolymer having skeletons of two or more of these types.

Further, as the dihydroxydiaryl compound represented by the general formula (If), for example, dihydroxybiphenyls represented by; 1 HO-R5, R6, m and n have the same meanings as above)
Examples include.

In addition, diaryl carbonate used as another raw material has the general formula (■): Ar'-0CO-Ar'... (II
I) A carbonate ester of an aromatic monohydroxy compound represented by 1, in which Ar3 and Ar' are aryl groups, which may be the same or different. good. In addition, in the Ar3 and Ar', 1
When two or more hydrogen atoms are substituted for other substituents, such as a lower alkyl group, a lower alkoxy group, a phenyl group, a phenoxy group,
It may be substituted with a vinyl group, a cyano group, an ester group, an amide group, a nitro group, or the like.

Examples of such diaryl carbonates include,
General formula (■): 2 HO-R7 and R8 are each a hydrogen atom and a carbon number of 1 to
4 lower alkyl group, lower alkoxy group having 1 to 4 carbon atoms, cycloalkyl group, or phenyl group, p and q are integers of 1 to 5, and when p is 2 or more, R7 is different from each other. There may be, and if q is 2 or more,
R1+ may be different. ) Substituted or unsubstituted diphenyl carbonates represented by:

Among these diphenyl carbonates, diphenyl carbonate and contrast diaryl carbonates such as lower alkyl-substituted diphenyl carbonates such as ditolyl carbonate and di-t-butylphenyl carbonate are preferred, and diaryl carbonates with the simplest structure are particularly preferred. Diphenyl carbonate is preferred.

These diaryl carbonates may be used alone or in combination of two or more types, but the reaction system becomes complicated and there is not much advantage, so it is preferable to use one type of symmetrical diaryl carbonate. Good.

It is necessary to use these dihydroxydiaryl compounds and diaryl compounds that do not contain chlorine as a substituent, and furthermore, inorganic chlorine compounds such as sodium chloride, organic solvents containing chlorine (for example, methylene chloride), etc. , chloroform, chlorobenzene, etc.).

Furthermore, as a method for producing the aromatic polycarbonate of the present invention, the method previously applied by the present inventors (Japanese Patent Application No. 6
3-308802) can also be used.

This method can be carried out, for example, by prepolymerizing the dihydroxydiaryl compound and diphenyl carbonate of the general formula (■) under heating and melting to obtain a compound having a weight average molecular weight (Mw) of 2,000 to 20,000, preferably 4,000. ~15,000. Even more preferably 5,
000 to 12,000 and the proportion of hydroxyl groups in the total terminal groups is less than 50%, preferably less than 40%, even more preferably 35%.
This method involves preparing a smaller amount of prepolymer, crystallizing the prepolymer, and then solid-state polymerizing the crystallized prepolymer. According to this method, an alkyl-substituted phenyl carbonate group (■) at the terminal: (R represents a linear or branched alkyl group having 1 to 20 carbon atoms, and l represents an integer of 1 to 5. Note that l is 2 to 5, R may be the same or different.) It is possible to produce an aromatic polycarbonate having R in the coexistence of an alkyl-substituted phenol represented by .

The reason why the aromatic polycarbonate of the present invention with a chlorine content of 0 to 0.1 ppm and a proportion of hydroxyl groups in all end groups of 0 to 5% improves the long-term reliability of optical discs is probably due to the following reasons: In addition to the absence of corrosion of the recording layer due to almost no or no presence of salt 5-chlorine, the generation of crazes and whitening when the disk substrate is heated is almost eliminated by reducing the amount of terminal hydroxyl groups. This is probably due to the fact that this phenomenon no longer occurs, and furthermore, it is believed that these effects are acting synergistically.

In this sense, it is preferable that the amount of terminal hydroxyl groups present is as small as possible, but if the proportion of the terminal hydroxyl groups is 5% or less, sufficient long-term reliability can be obtained, but it is more preferable. is 4% or less, particularly preferably 3%
% or less.

(Examples) Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

In addition, ■ Molecular weight is expressed as the weight average molecular weight (Mw) measured by gel permeation chromatography (GPC). ■ The proportion of hydroxyl groups in all terminal groups is determined by high performance liquid chromatography. A.

Horbach et al.'s method (method for quantifying phenolic -OH groups, Makromol, Cheml, ■8.215
(1965)).

■ To determine the chlorine content in polycarbonate, dissolve 10 g of dry polymer in 90 g of methylene chloride and add 50 g of acetone.
This value was measured by adding Id and performing potentiometric titration using an automatic titrator using a 0.0005M nitric acid tI7 acetone solution as a titration reagent.

Example 1 45.6 kg of bisphenol A containing no chlorine compounds and 48 kg of diphenyl carbonate were placed in a 1001 glass-lined glue reactor, and after repeating vacuum degassing and dry nitrogen introduction several times, the reactor was heated to a temperature of 180 to 190°.
After heating to C to melt the contents, degassing under reduced pressure and introducing dry nitrogen were repeated several times. Next, the temperature inside the reactor was reduced to 2
Raise the temperature to 30-235°C, stir, and add dry nitrogen for 2 hours.
After introducing at 00N 42/hr for 2 hours, the reaction system was reduced in pressure and the reaction was carried out at 5 to 10 txmKg for 2 hours, thereby distilling phenol partially containing diphenyl carbonate. Thereafter, by pressurizing the inside of the reactor with dry nitrogen to 2 to 3 kg/c4, the prepolymer was extracted through a perforated plate provided at the bottom of the reactor and introduced into an acetone bath to obtain a crystalline prepolymer. .

The Mw of the white powdery prepolymer obtained by distilling off acetone was 6,400, and the proportion of terminal hydroxyl groups was 12 mol %.

This crystalline prepolymer was placed in a tumbler type dryer,
Solid phase polymerization was carried out by rotary stirring at a temperature of 190 to 220 °C for 4 hours under a reduced pressure of 2 to 5 mmHg while introducing a small amount of nitrogen. As a result, the proportion of terminal hydroxyl groups at Mw = 15,000 was was less than 2%. In addition, the chlorine content was 0.1 ppm or less.

After adding and mixing 50 ppm of trisnonylphenyl phosphite to the aromatic polycarbonate powder obtained above, the mixture was extruded at 270°C using an extruder to form pellets.

This pellet was injection molded to produce an optical disk substrate having a thickness of 1.2 mm and having a spiral group on one side.

On this substrate, as a magneto-optical recording film, T b / Fe
A magneto-optical disk was fabricated by depositing /Co alloy by sputtering, then coating with a photo-curable acrylic resin, and curing with ultraviolet light.

Long-term reliability was evaluated by storing this magneto-optical disk under conditions of 90° C. and 85% relative humidity, and expressing the increase in error rate over time as a ratio to the initial error rate. The results are shown in FIG. 1(a).

Comparative Example 1 A magneto-optical disk was prepared in the same manner as in Example 1 using an aromatic polycarbonate with Mw = 14,800 (chlorine content 0.6 ppm, proportion of terminal hydroxyl groups 8 mol%) produced by the phosgene method. 9- Manufacture and long-term reliability evaluation were conducted. The results are shown in Figure 1 (b).

Comparative Example 2 Chlorine content is 0. A magneto-optical disk was prepared and its long-term reliability was evaluated in the same manner as in Example 1 using an aromatic polycarbonate having a terminal hydroxyl group ratio of ippm of 10 mol %; Mw = 15,200.

The results are shown in FIG. 1(c).

Comparative Example 3 An aromatic polycarbonate (manufactured by the phosgene method) with a chlorine content of 1.0 ppm and a terminal hydroxyl group ratio of 4 mol %; Mw = 15,000 was used in the same manner as in Example 1. We fabricated magneto-optical disks and evaluated their long-term reliability.

The results are shown in FIG. 1(d).

Aromatic polycarbonates having a proportion of 0-hydroxyl groups of 0 to 5 mol % are excellent as substrate materials for optical discs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing changes over time in the error rate ratio of magneto-optical disks whose substrate materials are aromatic polycarbonates having different chlorine contents and terminal hydroxyl group ratios. (1 other person) (Effects of the invention)

Claims (2)

[Claims] (1) An aromatic polycarbonate for optical discs having a chlorine content of 0 to 0.1 ppm and a proportion of hydroxyl groups in all terminal groups of 0 to 5 mol%. (2) The aromatic polycarbonate for optical discs according to claim (1), which is obtained by reacting a dihydroxydiaryl compound that does not contain a chlorine atom and a diaryl carbonate that does not contain a chlorine atom. [However, the dihydroxydiaryl compound has the general formula: HO-Ar^1-Y-Ar^2-OH...(I)(
85 mol% or more of dihydroxydiarylalkane (wherein Ar^1 and Ar^2 are each an arylene group, and Y is an alkylene or substituted alkylene group) and 15 mol% of a dihydroxydiaryl compound other than the dihydroxydiarylalkane. It consists of the following: ]