JPH03147540A - Production of substrate for optical recording medium - Google Patents

Abstract

PURPOSE:To easily and continuously produce a substrate for an optical recording medium having small double refraction and good molding property by molding a specified bis-(hydroxyphenyl) alkane polycarbonate resin into substrates by extrusion method. CONSTITUTION:Bis-(hydroxyphenyl) alkane polycarbonate resin having 18,000 - 50,000 number average mol.wt. is molded by extrusion method. The number average mol. wt. of the polycarbonate resin is preferably 25,000 - 50,000. It is also preferable that the substrate is produced by extrusion molding at the resin temp. of 200 - 400 deg.C and roll temp. of 100 - 200 deg.C and that the produced substrate shows the degree of double refraction to <=100nm for recording or reproducing light through a double pass in the effective area for recording/ reproducing. Thereby, a substrate for an optical recording medium can be easily produced, and the obtd. substrate has small double refraction and good molding property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of manufacturing a substrate for an optical recording medium, and more particularly to a method of manufacturing a substrate for an optical recording medium that optically records and reproduces information.

[Prior Art] Conventionally, magnetic materials such as magnetic tapes and magnetic disks, various semiconductor memories, and the like have been mainly used to record various types of information. Does such a magnetic memory semiconductor memory have the advantage of being able to easily write and read information?

On the other hand, there were problems in that the information content could be easily tampered with and that high-density recording was not possible. In order to solve these problems, an optical information recording method using an optical recording medium has been proposed as a means of efficiently handling a wide variety of information, and optical information recording carriers, recording/reproducing methods, recording/reproducing devices, etc. for this purpose have been proposed. is proposed.

Such an optical recording medium as an information recording carrier is generally prepared by using a laser beam to evaporate a part of the optical recording layer on the optical recording medium, to cause a change in reflectance, or to cause deformation. Information is recorded or reproduced based on differences in optical reflectance and transmittance. In this case, the optical recording layer does not require any development treatment after information is written.
So-called DRA that allows you to “read directly after writing”
W (direct read after write; dir
It is an effective medium for recording and storing information because it is capable of high-density recording and additional writing is possible.

FIG. 2 is a schematic cross-sectional view of a conventional optical recording medium. In FIG. 2, 11 is a transparent resin substrate, 12 is a track groove, 13 is an optical recording layer, 14 is a spacer/adhesive layer, and 15 is a protective layer. In FIG. 2, information is recorded and read out optically through the transparent resin substrate 11 and the track groove 12. At this time, the minute unevenness of the track groove 12 is used to generate the phase difference of the laser beam. It is configured so that it can be tracked.

[Problem 8 to be solved by the invention] As a conventional method for manufacturing the transparent resin substrate 11 of the optical recording medium shown in FIG. -There is a problem that only one sheet can be manufactured.

On the other hand, the present inventor found that the method of manufacturing a transparent resin substrate by the extrusion molding method shown in FIG. 1 is preferable. This method is a continuous manufacturing method and has high productivity. In this method, polycarbonate, which has good transparency and moldability, is often used as the material for the transparent resin substrate.

However, in the above molding method, the main causes are thermal stress generated during the cooling and flow process of the resin during molding, molecular orientation, and residual stress due to volume changes near the glass transition point, resulting in birefringence. There are some problems. Birefringence can be expressed as a square of residual stress and photoelastic constant, so in order to obtain molded products with small optical distortions such as these birefringences, it is necessary to improve the fluidity of the resin during molding and melt it. There is a method to avoid optical non-uniformity caused by resin flow.

To solve this problem, in conventional injection molding, one way to improve the fluidity of the resin is to select a high resin temperature during injection. There is a problem in that decomposition causes discoloration such as yellowing, impairing the transparency of the resulting molded product. Another method is to improve the fluidity of the resin by using a resin with a low number average molecular weight as the polycarbonate resin used for molding. For example, if the average molecular weight is 1
Injection molding is performed using polycarbonate resin of 0,000 to 20,000. However, for some reason, Japanese Patent Application Publication No. 55-
Polycarbonate resins with a number average molecular weight of 12,000 to 1 aooo, such as those used in No. 81893 and JP-A-58-126119, lack mechanical strength when extruded, resulting in cracks during molding or uneven patterns. Another problem has arisen in that the transferability of the paper is not good.

Another method is to use polycarbonate that has low viscosity when melted and has good fluidity (Japanese Patent Application Laid-Open No. 61-47
26, JP-A No. 61-16962), or reducing birefringence by heat treatment (annealing) after molding the resin (JP-A-62-140317). However, the methods used in these previous proposals are not effective when molding resin by injection molding, or are they effective when molding resin by injection molding? However, in terms of mechanical strength and resin fluidity, there are problems such as cracks on the end surface of the resin sheet and poor fluidity that may result in residual birefringence. In addition, the method of reducing birefringence by heat treatment (annealing) has the problem of poor productivity, and the problem that when molding an object with a complicated shape, the shape changes due to heat.

The present invention was made in order to solve the above problems, and an object of the present invention is to provide a method for easily and continuously manufacturing a substrate for an optical recording medium with low birefringence and good moldability by extrusion molding. That is.

[Means for Solving the Problems] That is, the present invention provides an optical recording medium for recording and reproducing information by changing optical properties such as reflectance and refractive index by irradiation with a light beam such as a laser beam. In the method for manufacturing a substrate, the number average molecular weight is 18,000 to 5,000.
This method of manufacturing a substrate for an optical recording medium is characterized in that the substrate is continuously manufactured by extrusion molding a 0.0 bis(hydroxyphenyl)alkane-based polycarbonate resin.

The present invention will be explained in detail below.

The present invention provides an optical recording medium that performs recording and reproduction by changing optical properties such as reflectance and transmittance by irradiation with a light beam such as a laser beam.
Using a bis(hydroxyphenyl)alkane polycarbonate resin of 00 to 50,000, the resin temperature is 200
Under conditions of ~400℃ and roll temperature of 100~200℃, a substrate whose birefringence in the effective area through which the recording/reproducing light passes is 100 ns or less in a double pass with respect to the recording/reproducing light is continuously extruded. 1 is a method of manufacturing a substrate for an optical recording medium.

In a preferred embodiment of the present invention, as the bis(hydroxyphenyl)alkane polycarbonate resin, a dihydric phenol compound and a compound represented by the following general formula (1) or (2) as a terminal capper are used. A method for manufacturing a substrate for an optical recording medium using a polycarbonate made of the obtained terminal long-chain alkyl polycarbonate resin is mentioned.

General formula (1): CoH2n-IX (in the formula,
X represents -COCI or -G 0011, Y represents a simple bond or -C00-, and n represents an integer from 8 to 30. ) In addition, as the bis(hydroxyphenyl)alkane-based polycarbonate resin, a dihydric phenol-based compound and a trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group as a branching agent are added to the bis(hydroxyphenyl)alkane-based polycarbonate resin at zero A branched polycarbonate resin obtained by using .01 to 3 mol%, and a terminal long chain alkyl compound obtained by using a dihydric phenol compound and a compound represented by the general formula (1) or (2) above as a terminal stopper. A method using polycarbonate made of a mixture with a polycarbonate resin can be mentioned.

First, the branched polycarbonate resin of the present invention preferably has the following general formula (3) as a dihydric phenol compound.
It is a homo- or copolymer of aromatic polycarbonate resin, which is obtained by reacting a compound represented by the following as a main component with a small amount of a branching agent and a diester of phosgene or carbonic acid.

Furthermore, the terminal long chain alkyl polycarbonate resin of the present invention preferably has a compound represented by the following general formula (3) as a main component as a dihydric phenol compound, and a small amount of the above general formula (1) or It is a homo- or copolymer of aromatic polycarbonate resin made by using a monofunctional terminal capping compound represented by (2) and reacting it with phosgene or carbonic acid diester.

General formula (3): (In the formula, R is a divalent aliphatic having 1 to 15 carbon atoms.

alicyclic or phenyl-substituted alkyl group, or -o-
, -s-, -5o-, -3O2-, -CO-te. x
is an alkyl group, an aryl group or a halogen atom, and p and q are O6l or an integer of 2. ) Monofunctional organic compounds used as the terminal capping agent represented by the above general formula (1) include capric acid chloride, lauric acid chloride, myristic acid chloride, palmitic acid chloride, suderic acid chloride, cerotic acid chloride, capric acid, Examples include aliphatic compounds such as lauric acid, myristic acid, palmitic acid, stearic acid, and cerotic acid.

In addition, the monofunctional organic compounds used as the terminal capping agent represented by the general formula (2) include long-chain alkyl-substituted phenols such as octylphenol, norylphenol, laurylphenol, palmitylphenol, and stearylphenol; octyl hydroxybenzoate; Examples include hydroxybenzoic acid long-chain alkyl esters such as lauryl hydroxybenzoate, noryl hydroxybenzoate, and stearyl hydroxybenzoate.

Further, as the dihydric phenol compound represented by the general formula (3), bis(4-hydroxyphenyl)methane,
1.1-bis(4-hydroxyphenyl)ethane, 2.
2-bis(4-hydroxyphenyl)propane, 2.2
-bis(4-hydroxyphenyl)butane, 1.1-bis(4-hydroxyphenyl)cyclohexane, 2.2
-bis(4-hydroxy-3,5-dichlorophenyl)
Propane, 2,2-bis(4-hydroxy-3-dibromophenyl)propane, 2,2-bis(4-hydroxy-3-dichlorophenyl)propane, 2,2-bis(
4-hydroxyco,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)ether, bis(4
-hydroxyphenyl) sulfone, bis(4-hydroxyphenyl) sulfide, bis(4-hydroxyphenyl) sulfoxide, bis(4-hydroxyphenyl) ketone, 1. l-bis(4-hydroxyphenyl)-1-
Examples include phenylethane and bis(4-hydroxyphenyl)diphenylmethane.

In addition, as a branching agent, a trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group is used, such as phloroglycine, 2,6-dimethyl-2,4,6-tri(
4-Hydroxyphenyl)heptene, 1,:l,5-tri(2-hydroxyphenyl)penzole 1.1.1-
Tri(4-hydroxyphenyl)ethane.

2.6-bis(2-hydroxy-5-methylbenzyl)
-4-methylphenol, α, α', αζ tri(4-hydroxyphenyl) - Polyhydroxy compounds exemplified by 1,3,5-triisopropylbenzene, and 3,3-bis(4-hydroxyaryl) Examples thereof include oxindole (=isatin bisphenol), 5-chloroisatin, 5,7-dichloroisatin, 5-bromiisatin, and the like.

In the present invention, the above general formula (1) or (2) for the dihydric phenol compound represented by the above general formula (3) in the production of terminal long chain alkyl polycarbonate resin
The amount of monofunctional compound used is usually 3 to IO.
mol%, preferably in the range of 4.4 to 7 mol%, and 3
If it is less than mol%, the improvement in fluidity will be insufficient, and if it exceeds 10 mol%, the molecular weight will be low, and there will be a tendency to use it as a plasticizer rather than as a resin composition, so it is preferable. do not have.

Further, in the production of branched polycarbonate resin, the amount of polyfunctional phenol used as a branching agent for the dihydric phenol compound of general formula (3) is 1,000. O1～
A range of 3 mol%, preferably 0.1 to 1.0 mol% is preferred. If it is less than 0.01 mol%, a sufficient branched structure will not be produced, and if it exceeds 3 mol%, high molecular weight substances will be partially produced, which may cause problems such as deterioration of the transparency of the molded product. I don't like it.

In the present invention, the composition ratio of branched polycarbonate resin A and terminal long chain alkyl polycarbonate resin B is A
:B=1:99 to 99:1, and A:B=3:97 to 97:3, especially 5 :95~95:
It is good to have a composition within the range of 5.

Since the terminal long-chain alkyl polycarbonate resin used in the present invention has a long-chain alkyl group at the molecular end, its fluidity "Q value" is greatly improved. However, the "Q value" is the melt viscosity measured with an elevated flow tester, and is 28
0℃, 160kg/cm2 pressure, 1mm+φx
The amount of molten resin flowing out from a 10m5L nozzle is cc/s.
It is expressed in units of ec, and the flow value "Q value" increases as the melt viscosity decreases.

Further, the flow characteristic "Q value" of the branched polycarbonate resin is improved by branching.

That is, a branched normal end (e.g., a terminal p-
Polycarbonate resins containing tert-butylphenol exhibit superior fluidity compared to unbranched polycarbonate resins. Therefore, the fluidity of a resin composition obtained by mixing a branched polycarbonate resin with a normal polycarbonate resin is slightly increased compared to that of a normal polycarbonate.

In the polycarbonate resin composition used in the present invention, there is a correlation between the "Q value" of one composition and the birefringence of a molded article. That is, the "Q value" of the composition is 20x
to' cc/see or more, preferably 30x to'
cc/sec or more, the average molecular weight and composition ratio of the composition of polycarbonate resin and terminal long-chain alkyl polycarbonate, which has been conventionally used as an optical material, has a "Q ratio" indicating fluidity of 20 x 10' cc/s
It may be set to be equal to or greater than ec, preferably equal to or greater than: lOx lO'cc/sec. For this purpose, the number average molecular weight of the polycarbonate resin used in the manufacture of optical recording medium substrates using extrusion molding must be taooo to 5.
0000 is suitable, more preferably 25000-5
It is 0000. If the number average molecular weight is higher than 50,000, the melt viscosity of the resin will be high, so the melting and molding temperatures will be high, which will easily cause yellowing due to thermal decomposition of the resin, and furthermore, the transferability of the uneven pattern will be poor. Deteriorate. On the other hand, if the number average molecular weight of the resin is less than 18,000, 1
Mechanical strength decreases, making cracks more likely to occur during molding, and the durability and solvent resistance of the resin deteriorate.

In addition, in extrusion molding, the resin temperature is 200 to 400℃.
In order to mold the resin by heating it to a high temperature, it is desirable that the glass transition point of the resin is 125° C. or higher.

In the extrusion molding method used in the present invention, the flow rate of molten resin during molding is lower than in conventional injection molding methods, so it is possible to manufacture transparent resin substrates with low birefringence even with resins having a high average molecular weight. It is possible, but on the other hand,
Because tension is applied to wind up the extruded resin,
a Mechanical strength is necessary. The optimum average molecular weight of the polycarbonate resin used for this purpose is that even if the same resin is used, a resin with a slightly higher average molecular weight is preferable.

In addition, the polycarbonate resin may include, if necessary,
Phosphite esters such as diesters or triesters of phosphorous acid and alcohols or phenols may be added, and if necessary, the necessary amount of ultraviolet absorption may be added to improve durability and light resistance. The agent can be mixed into the polycarbonate resin. As the ultraviolet absorber, salicylic acid type, benzophenone type, benzotriazole type, cyanoacturate type, etc. can be used. A melting method or the like can be used for mixing the resin into the resin.

In the present invention, the polycarbonate resin prepared as described above is extruded to produce an optical recording medium substrate. FIG. 1 is an explanatory diagram showing an example of the method for manufacturing an optical recording medium substrate of the present invention. In FIG. 1, l is a resin substrate, 2 is a forming roll, 3 is a pressure roll, and 4
is a T-die, 5 is a ruler, 16 is a hopper, and 7 is a take-up roll. The distance between the forming roll 2 and the pressure roll 3 can be adjusted so that the unevenness of the stamper provided on the forming roll 2 can be sufficiently transferred to the surface of the resin substrate 1.

In FIG. 1, the polycarbonate resin sheet extruded from the T-die 4 of the Ruder 5 is inserted between the forming roll 2 and the pressure roll 3 in a softened state, and the uneven surface of the forming roll 2 and the pressure roll 3, the uneven signals of the stamper are sequentially transferred onto the surface of the resin substrate l.

The preferred extrusion molding conditions are a Ruder temperature of 250
~35G”C1T die temperature is 250~350'C1
The temperature of the forming roll is 100 to 200°C. In this molding, it is not preferable to raise the temperature of the ruler or T-die to more than 350''C because the resin will thermally decompose and turn black or yellow.

On the other hand, if the temperature of the Ruder or T-die is lower than 250 DEG C., the fluidity of the molten resin will deteriorate, resulting in non-uniform substrate thickness and birefringence. If the resin used does not cause the above-mentioned problems, melting can be achieved even when the temperature of the Ruder or T-die is in the range of 200 to 400°C.

The extrusion speed is at least 211 minutes, preferably at least 101 minutes. The preferred temperature of the forming roll is the forming roll,
The temperature of both pressure rolls is 100 to 200°C.

If the roll temperature exceeds 200°C, the resin to be molded will stick to the roll and peel off, or the end face of the resin will crack during JI molding. On the other hand, if the roll temperature is lower than 100, it becomes impossible to transfer the uneven pattern formed on the roll.

The substrate manufactured by the method for manufacturing a substrate for an optical recording medium of the present invention is provided with an optical recording layer or a reflective layer, and other protective layers as necessary to produce an optical recording medium. These methods and materials can be freely selected from those commonly used in optical recording media.

The optical recording medium substrate of the present invention can be used for all optical recording media such as optical discs, optical cards, optical tapes, and optical coins.

[Example] Hereinafter, the present invention will be explained in more detail by showing examples.

Example 1 3.7 kg of sodium hydroxide was dissolved in 42 Jl of water,
7.3 kg of 2.2-bis(4-hydroxyphenyl)propane (BPA) and 8 g of hydrosulfide were dissolved while maintaining the temperature at 0°C. Add methylene chloride 2
745 g of hydroxybenzoic stearyl was added with stirring, and 1.5 kg of phosgene was blown into the mixture over 60 minutes. After blowing in phosgene, the reaction solution was emulsified by stirring vigorously. The mixture was added and stirred for about 1 hour to continue polymerization. The polymerization solution was separated into an aqueous layer and an organic layer, and the organic layer was neutralized with phosphoric acid. After washing with water was repeated until the pH of the washing solution became neutral, 35 grams of isopropanol was added to the polymerization solution. was precipitated. The precipitate was filtered and then dried to obtain a white powdery polycarbonate resin. The number average molecular weight of this product was measured in methylene chloride and found to be 30,000. The "Q value" is 72 x 10' cc no sec, and the photoelastic constant is 78 BrewsLers (10-
From the OSC measurement, the glass turning point was 7g=1:10°C.

This resin has a pitch of 1.61Lm, a width of 0.6μ, and a depth of 7
Extrusion molding A (Hitachi Zosen Shipbuilding Co., Ltd.) to which a nickel stamper of φ86m5+ with continuous grooves of 0.00 mm is attached to a steel roll with a roll diameter of 300I attached with an adhesive (W-bond; A (1 Nikka Seiko)) , 5IIT90-32
DVG), the ruder temperature was 270°C, the T die temperature was 265°C, and the forming and pressure roll temperatures were each 120°C.
Molding the above polycarbonate resin under the conditions of 2.
: Extruded at a speed of 1 m7 to a thickness of 1.2 m.

When the extruded substrate was measured, the birefringence was 10 nm or less in a double pass (measured with a birefringence measuring machine manufactured by Nippon Denshi Kogaku Co., Ltd., input = 830 nm).

In addition, the light transmittance was 89% and it was sufficiently transparent (Hitachi U
-: 1400, measured at input = 830 nm). The amount of surface runout was sufficiently small at 50 μm or less in pp (measured with a three-dimensional measuring machine manufactured by Carl Zeiss). Furthermore, no stringiness was observed.

Next, this substrate was cut into 86 layers -φ, and the following structural formula (
The optical recording material shown in 4) was solvent coated.

(Mountain C) 2Niγ Flea N (Mountain C) 2cpo,'
(4) For the protective board, cut 0.31-thick polycarbonate (Ondai Kasei, Panlight 251) into 86 mm diameter.
It was glued so that there was an air gap of 1 mm.

When recording and playing back, the disc rotation speed was 1800 rpm.
m, writing frequency 3MHz, writing power 61w
, readout ratio r7-0.5+aWte, C/N ratio 4;t
57 dB, and the pit error rate was I x 10-'. Even when this value was stored for 1,000 hours under the conditions of 60°C, 190% Old 1, there was no change in either the read or write characteristics.

Example 2 Similarly to Example 1, 3.7 kg of sodium hydroxide was mixed with 4 kg of water.
2.2-bis(4) dissolved in 2fL and kept at 20℃
-Hydroxyphenyl)propane (BPA) 71kg
, 325 g of 2,6-dimethyl-2.4.6-)-ly(4-hydroxyphenyl)heptene, and 8 g of hydrosulfide were dissolved. Add to this methylene chloride 28
While stirring carefully, 455 g of lauric acid chloride was added, and 3.5 kg of phosgene was blown in over 60 minutes. After blowing in phosgene, the reaction mixture was vigorously stirred to emulsify it. After emulsification, 8 g of triethylamine was added and the mixture was stirred for about 1 hour to allow polymerization. The polymerization solution was separated into an aqueous layer and an organic layer, and the organic layer was neutralized with phosphoric acid. After repeating washing with water until the p++ of the washing solution became neutral, 35 grams of isopropanol was added to the polymer. was precipitated. The precipitate was filtered and then dried to obtain a white powdery polycarbonate resin.

The number average molecular weight of this product was measured in methylene chloride and found to be 30,000. "Q value" is 76X 10'cc
/sec. When the photoelastic constant was measured, it was 79 Brewsters (12.2/N).
)Met.

From DSC measurements, the glass transition point is 7g=t:+o℃
There was.

Next, an optical recording medium substrate was produced in the same manner as in Example 1. When the produced substrate was measured in the same manner as in Example 1, the birefringence was sufficiently small at less than lot++s. In addition, the light transmittance was 91% and it was sufficiently transparent. The amount of surface runout is pp
It was small enough at 30 ru. Furthermore, no stringiness was observed.

An optical recording layer was formed on this substrate in the same manner as in Example 1, and recording was performed.
When reproduced, the C/N ratio was 55 dB and the pit error rate was 1 x 10-6. When stored in the same manner as in Example 1, neither CAM nor pit error rate changed.

Example 3 Similarly to Example 1, 3.7 kg of sodium hydroxide was mixed with 4 kg of water.
2.2-Bis(4-
Hydroxyphenyl)propane (BPA) 71kg,
325 g of 2,6-dimethyl-2,4.6-tri(4-hydroxyphenyl)heptene and 8 g of hydrosulfide were dissolved. To this was added 28 g of methylene chloride, 504 g of stearic acid chloride was added while stirring, and 3.5 kg of phosgene was blown into the mixture over 60 minutes. After blowing in phosgene, stir vigorously to emulsify the reaction solution.
After emulsification, add 8 g of triethylamine and stir for about 1 hour. Separate the polymerized solution into an aqueous layer and an organic layer, neutralize the organic layer with phosphoric acid, and adjust the pH of the washing solution to neutral. After repeated washing with water until the mixture was completely dissolved, 35 portions of Improper Tool was added to precipitate the polymer. The precipitate was filtered 7 times and then dried to obtain a white powdery polycarbonate resin.

The number average molecular weight of this product in methylene chloride was determined to be 30,000. "Q value" is 51X 10'c
It was c/see. When the photoelastic constant was measured, it was 89 Brewsters (10-”m2/N
) was there.

According to DSC measurement, the glass transition point was Tg=128°C.

Next, an optical recording medium substrate was prepared in the same manner as in Example 1. When the prepared substrate was measured in the same manner as in Example 1, the birefringence was 10 nm or less, which was sufficiently small. In addition, the light transmittance was 90% and was sufficiently transparent. The amount of surface runout is 3 in p-p
It was small enough at 0 ru■. Furthermore, no stringiness was observed.

An optical recording layer was formed on this substrate in the same manner as in Example 1, and recording was performed.
When I played it back, the C/N ratio was 55dB.

The pit error rate was t x to-'. When stored in the same manner as in Example 1, neither the C/N nor the pit error rate changed.

Comparative Example 1 A substrate for an optical recording medium was prepared using commercially available polycarbonate (Ondai Kasei, HachiD5503) in the same manner as in Example 1. When the prepared substrate was measured in the same manner as in Example 1, the birefringence was was sufficiently small, less than 1 Onm. Further, although the light transmittance was 90% and it was sufficiently transparent, the end face of the substrate was cracked and the substrate was not suitable for practical use. Due to the lack of strength of the substrate, one or more layers of the substrate are curved and wavy. Therefore, it was impossible to manufacture optical recording media.

[Effects of the Invention] As explained above, according to the present invention, by molding a specific bis(hydroxyphenyl)alkane-based polycarbonate resin by extrusion molding, an optical recording medium with low birefringence and good moldability can be produced. This provides the advantage that substrates can be manufactured easily and continuously.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing an example of the method for manufacturing an optical recording medium substrate of the present invention, and FIG. 2 is a cross-sectional view showing a conventional optical recording medium. l... Resin substrate 2... Forming roll 3... Pressure roll 4... T-tie 5/Axis J radar 6... Hopper 7... Pick-up roll 11... Transparent resin substrate 12... ...Track groove portion 13...Optical recording layer 14-...Spacer/adhesive layer 15...Protective layer Fig. 1 Fig. 2

Claims (4)

[Claims] (1) Recording and recording of information by changing optical properties such as reflectance and refractive index by irradiation with a light beam such as a laser beam.
A method for manufacturing a substrate for an optical recording medium for reproduction, characterized in that the substrate is continuously manufactured by extrusion molding a bis(hydroxyphenyl)alkane-based polycarbonate resin having a number average molecular weight of 18,000 to 50,000. A method for manufacturing a substrate for optical recording media. (2) Resin temperature 200~400℃, roll temperature 100~
2. The method for manufacturing an optical recording medium substrate according to claim 1, wherein the extrusion molding is carried out at 200°C. (3) Manufacturing a substrate for an optical recording medium according to claim 1, wherein the birefringence of the effective portion of the substrate formed by extrusion through which the recording/reproducing light passes is 100 nm or less in a double pass with respect to the recording/reproducing light. Method. (4) As the bis(hydroxyphenyl)alkane-based polycarbonate resin, a terminal long-chain alkyl polycarbonate obtained using a dihydric phenol-based compound and a compound represented by the following general formula (1) or (2) as a terminal stopper. Claim 1: Polycarbonate made of resin is used.
The method for manufacturing the optical recording medium substrate described above. General formula (1): C_nH_2_n_+_1-X general formula (
2): ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, X represents -COCI or -COOH, Y represents a simple bond or -COO-, and n represents an integer from 8 to 30.) (5) As the bis(hydroxyphenyl)alkane polycarbonate resin, a dihydric phenol compound and a trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group as a branching agent are added in an amount of 0.01 to 0.01 to the dihydric phenol compound. A branched polycarbonate resin obtained by using 3 mol%, and a terminal long chain alkyl polycarbonate resin obtained by using a compound represented by the following general formula (1) or (2) as a dihydric phenol compound and a terminal capping agent. 2. The method for manufacturing an optical recording medium substrate according to claim 1, wherein a polycarbonate comprising a mixture of is used. General formula (1): C_nH_2_n_+_1-X general formula (
2): ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, X represents -COCl or -COOH, Y represents a simple bond or -COO-, and n represents an integer from 8 to 30.)