JPH02203442A - Optical disk substrate - Google Patents

Abstract

PURPOSE:To provide excellent heat resistance, transparency and low hygroscopicity and to allow exact recording and reproducing by using specific thermoplastic arom. polyester as an essential component and confining the double refractions of a perpendicular incident single bus to <60nm. CONSTITUTION:The thermoplastic arom. polyester contg. the constitutional unit expressed by formula I is used as the essential component and the double refractions of the perpendicular incident single bus is <60nm. This polyester resin is obtd. by polycondensation of resorcinol or the reactive deriv. thereof and at least one selected from phthalic acid, telephthalic acid and isophthalic acid or the reactive deriv. thereof and contains the resorcinol as the essential component of diol. The ordinary excellent heat resistance, transparency and low hygroscopicity are obtd. in this way and the exact recording and reproducing are possible as the double refractions are <60nm and the glass transition temp. is above the prescribed temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polyester optical disk substrate that has low birefringence and excellent heat resistance.

[Prior Art] Conventionally, polyester resins that are transparent and have excellent heat resistance have mainly been composed of dicarboxylic acid units such as terephthalic acid and isophthalic acid, and bisphenol A units. It has been well known for a long time in publications such as No.

[Problems to be Solved by the Invention] However, when such a polyester resin is used as an optical disk substrate, it is not suitable for precise processing by injection molding due to the poor melt flowability of the resin.
It has a problem of high birefringence, and as an optical disk substrate, it has the disadvantage of making accurate recording and reproduction difficult.

The present invention aims to eliminate the drawbacks of such conventional techniques, and in addition to the advantages of conventional non-grade polyester resins such as excellent heat resistance, transparency, and low moisture absorption,
It is an object of the present invention to provide an optical disc substrate that has excellent melt flowability and extremely low birefringence, so that accurate recording and reproduction can be performed.

[Means for Solving the Problems] The present invention has the following configuration to achieve the above object.

``An optical disk substrate characterized in that the main component is a thermoplastic aromatic polyester containing a structural unit represented by the following general formula [A], and the birefringence in a single pass of normal incidence is less than 60 nm.

The polyester resin of the present invention is obtained by polycondensing resorcinol or a reactive derivative thereof with at least one selected from phthalic acid, terephthalic acid, and isophthalic acid, or a reactive derivative thereof. It is characterized by containing it as a main component.

In general, aromatic rings such as phenyl rings have a large difference in electron distribution between the horizontal and vertical directions of the ring, and in polymers such as polycarbonate in which aromatic rings are oriented,
This is the cause of birefringence. In the present invention, the phenyl ring of resorcinol is difficult to align on the same plane as the phenyl rings of adjacent phthalic acid, terephthalic acid, and isophthalic acid due to steric hindrance. The optical anisotropy of the phenyl ring is canceled out within the molecule, resulting in extremely low birefringence.Furthermore, the polymer chain itself has a rigid but highly curved structure, so it maintains high heat resistance (glass transition temperature). Excellent melt fluidity can be achieved while maintaining the temperature.

Reactive derivatives of resorcinol include diacetylated products, and reactive derivatives of phthalic acid, terephthalic acid, and isophthalic acid include dichlorides, dialkyl esters, diaryl esters, etc. of these dicarboxylic acids.

In the present invention, in order to enhance the melt flowability and strength of the polymer, and also for the purpose of improving moldability, ethylene glycol, propylene glycol, cyclohexane-1,4-dimetatool, etc. It is possible to use one type or two or more types of aliphatic glycols having 2 to 10 carbon atoms in combination, or to copolymerize bisphenols represented by the following general formula.

(However, X is selected from the group consisting of o, S, SO2, Co, alkylene group and alkylidene group, and Y is O
selected from H and its reactive derivative groups. AI,
A 2 is selected from the group consisting of halogen and hydrocarbon groups. m and n represent integers of 0 to 4. ) Here, preferred halogens include chlorine, bromine, etc., and preferred examples of hydrocarbon groups include methyl group,
Examples include ethyl group and n-propyl group. Also, Y
is selected from OH and its reactive derivative groups, and reactive derivative groups include CH3CO2 groups and the like. Specific examples of bisphenol include 4,4'-dihydroxy-diphenyl ether, bis(4-hydroxy-
2-methylphenyl)-ether, bis(4-hydroxy-3-chlorophenyl)-ether, bis(4-hydroxyphenyl)-sulfide, bis(4-hydroxyphenyl)-sulfone, bis(4-hydroxyphenyl)-ketone , bis(4-hydroxyphenyl)-methane, bis(4-hydroxy-3-methylphenyl)-methane, bis(4-hydroxy-3,5-dichlorophenyl)-methane, bis(4-hydroxy-3,5- dibromophenyl)-methane, bis(4-hydroxy-3,5-
difluorophenyl)-methane, 1.1-bis(4-hydroxyphenyl)-ethane, 2.2-bis(4-hydroxy-3-methylphenyl)-propane, 2.2-bis(4-hydroxy-3- chlorophenyl)-propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 1,1-bis(4-hydroxyphenyl)-n-butane, 2,2-bis(4-hydroxy-
3,5-dibromophenyl)propane, bis(4-hydroxyphenyl)-phenylmethane, bis(4-hydroxyphenyl)-cyphelmethane, bis(4-hydroxyphenyl)-4'-methylphenylmethane, 1゜1-
Bis(4-hydroxyphenyl)-2,2,21lichloroethane, bis(4-hydroxyphenyl)-4'
-chlorophenylmethane, 1,1-bis(4-hydroxyphenyl)-cyclohexane, bis(4-hydroxyphenyl)-cyclohexylmethane, 2,2-bis(4
-Hydroxynaphthyl)-propane, etc., but the most typical ones manufactured for boat fishing are 2
．． 2-bis(4-hydroxyphenyl)propane or bisphenol A is mentioned. These bisphenols may be used as a mixture of two or more types, or may be used as derivatives by acetylation or the like. Also, if necessary, small amounts of other divalent compounds, e.g.
．． Dihydroxynaphthalenes such as 6-dihydroxynaphthalene, hydroquinone, 2,6-dihydroxytoluene, 2,6-dihydroxychlorobenzene, 3,6-dihydroxytoluene, and the like can be used.

In addition, within the range of less than 30 mol% of the dicarboxylic acid component, such as malonic acid, succinic acid, and adipic acid, which have 2 to 1 carbon atoms,
It is also preferable to use one or more types of aliphatic dicarboxylic acids or reactive derivatives thereof in combination.

When the proportion of resorcinol in the diol component is less than 70 mol%, birefringence increases, and when the total proportion of phthalic acid, terephthalic acid and isophthalic acid in the dicarboxylic acid component is less than 70 mol%, heat resistance decreases.

Various methods can be employed for producing the polyester of the present invention without particular limitations.

For example, an interfacial polymerization method in which an aromatic dicarboxylic acid chloride dissolved in an organic solvent incompatible with water and a dihydroxy compound dissolved in an alkaline aqueous solution are mixed and reacted (see Japanese Patent Publication No. 40-1959), aromatic dicarboxylic acid A solution polymerization method in which a chloride and a dihydroxy compound are reacted in an organic solvent (see Japanese Patent Publication No. 37-5599), a method in which an aromatic dicarboxylic acid phenyl ester and a dihydroxy compound are polymerized in a molten state (Japanese Patent Publication No. 37-5599)
No. 8-115247, No. 43-28119), a method of polymerizing an aromatic dicarboxylic acid and an acetate of a dihydroxy compound in a molten state [1ndust
real and Engineering Chemi
A method such as that described in Str7 Vol 51 P47 (1959) can be applied.

At this time, conventional catalysts, stabilizers such as phosphorous acid, phosphoric acid or derivatives thereof, phenol derivatives, etc. may be used as necessary.

Furthermore, in the present invention, injection molding, which has excellent productivity, can be preferably applied as a method for molding the optical disc.

Further, the optical disc substrate of the present invention contains the above-mentioned polyester as a main component, and the term "main component" means that it contains 95% by weight or more of the substrate. Additives that impair transparency must be avoided in polymers for optical disk substrates, but additives such as mold release agents, antistatic agents, ultraviolet absorbers, and antioxidants, as well as organic compound additives, may be added as necessary. can be used.

For optical discs that perform recording and playback using a laser, the glass transition temperature, which is a measure of the heat resistance of the resin used for the substrate, is 100%.
The temperature must be above ℃.

In the present invention, by using monomers constituting rigid polymer chains, the glass transition temperature can be increased to 100°C or higher.
Preferably, the temperature can be set to 120°C or higher. The glass transition temperature of a polymer can be measured by differential scanning calorimetry (D SC).

Although the polyester resin of the present invention exhibits a high glass transition temperature, it melts at a relatively low temperature and the molten polymer has good fluidity, so it can be molded at a relatively low temperature.

The birefringence of the optical disk substrate obtained from the polyester resin of the present invention needs to be less than 60 nm at single-pass normal incidence, preferably 30 nm or less,
More preferably, the thickness can be kept to 10 nm or less. In the present invention, the birefringence can be suppressed to less than 60 nm without strictly controlling the molding conditions, and the molding yield is high. Moreover, birefringence can be measured with an ellipsometer. Moreover, transparency can be measured by the ASTM D-1003 method.

Further, the polyester of the present invention can be hydrolyzed to analyze its constituent units according to a conventional method.

In addition to the conventional properties of excellent heat resistance, transparency, and low moisture absorption, the polyester optical disk substrate obtained by the present invention also has birefringence of less than 60 nm and a glass transition point of 100°C or higher. In addition to optical disk substrates, its uses include optical lenses,
It can be used as a film for optical cards, etc.

[Example] The present invention will be described below with reference to Examples. The glass transition temperature in the examples was determined using Dupont-990DSC.
It is a value measured by heating at a temperature increase rate of 0° C./min, and the intrinsic viscosity is a value measured as an orthochlorophenol solution at 25° C. Saturated water absorption rate is 75℃
The weight change was calculated after being left in warm water for 24 hours.

Birefringence was measured at 830 nm using an ellipsometer.

Example 1 5.5 g (0.05 mol) resorcinol, 4.2
g of sodium hydroxide, 0.06 g of triethylbenzylammonium chloride were dissolved in 300 ml of water. On the other hand, 5.08 g (0,025 mol) of terephthalic acid chloride and 5.08 g (0,025 mol) of isophthalic acid chloride (0,025 mol) were added to 15
It was dissolved in 0 cc of methylene chloride and charged into a dropping funnel. The alkaline aqueous solution of resorcinol was cooled to 10° C., and a methylene chloride solution of terephthalic acid and isophthalic acid chloride was added dropwise thereto over 5 minutes while vigorously stirring with a homomixer. The reaction mixture was heated at 25°C for an additional 1
After stirring for an hour, the polymer precipitated out as a viscous substance. The upper aqueous layer was removed and the residue was stirred vigorously for 500 m
The polymer solution was then diluted with 150 ml of methylene chloride and filtered. This solution was poured into methanol to separate the polymer, which was vacuum dried at 120° C. for 12 hours.

This polyester was injection molded at 280°C to a thickness of 1.
A disk with a diameter of 2 mm and a diameter of 130 mm was obtained.

Regarding performance, the results are shown in Table 1.

The glass transition temperature was 134° C., which is high enough to be used as an optical disk substrate, and the birefringence was as good as that of PMMA. The saturated water absorption rate was equivalent to that of polycarbonate, and the dimensional change upon water absorption was within the measurement error. Furthermore, it had a strength sufficient for practical use, and a light transmittance of 90% or more.

Example 2 A polyester optical disk substrate was obtained in the same manner as in Example 1, except that 20 mol% of bisphenol A was used and the proportion of resorcinol was 80 mol%.

The results are shown in Table 1.

Comparative Example A polyester optical disk substrate was obtained in the same manner as in Example 1, except that bisphenol A was used instead of lusorcinol.

The results are shown in Table 1. Although it has extremely good heat resistance and excellent light transmittance of 87%, it requires a high molding temperature of 350°C and has the fatal disadvantage of high birefringence.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 using hydroquinone without using resorcinol, and the polymer was separated. The obtained polymer was crystalline and opaque, and even when heated to 500° C., it did not melt and could not be injection molded.

[Effects of the Invention] Since the optical disc substrate of the present invention has a birefringence of less than 60 nm, accurate recording and reproduction can be performed as a disc substrate material.

In addition, it has particularly excellent heat resistance and low moisture absorption, so it has excellent dimensional and morphological stability.

Furthermore, although the polyester resin of the present invention exhibits a high glass transition temperature, it melts at a relatively low temperature,
Since the molten polymer has good fluidity, it is easy to process and mold.

Claims (1)

[Claims] (1) An optical disk substrate characterized in that the main component is a thermoplastic aromatic polyester containing a structural unit represented by the following general formula [A], and the birefringence at normal incidence single pass is less than 60 nm. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [A]