JP5069583B2 - Optical disk substrate and optical disk including the same - Google Patents

Description

  The present invention relates to an optical disk substrate and an optical disk including the optical disk substrate, and in particular, an optical disk substrate made of a low specific gravity polymer having excellent heat resistance, light resistance, low moisture absorption, and good optical properties, and uses the same. This is related to the optical disc.

  Conventionally, cycloolefin polymers obtained by ring-opening metathesis polymerization methods of polystyrene (see Patent Document 1), polymethyl methacrylate (see Patent Document 2), polycarbonate (see Patent Documents 3 to 5), dicyclopentadiene and norbornene derivatives, Cycloolefin copolymers obtained by addition copolymerization of norbornene derivatives and ethylene (see Patent Documents 6 to 9) are excellent in transparency and have a high refractive index, and can be applied to optical disk substrates, optical fibers, or plastic lenses. It has been studied, and in part, its practical application has been made.

  However, among them, polystyrene has a heat distortion temperature of about 90 ° C. and has poor heat resistance and low solvent resistance. Therefore, it is difficult to advance into the optical material field among the plastics described above. is there. On the other hand, polymethyl methacrylate, which has good moldability and high transparency, is a plastic that has greatly advanced in the optical material field because its heat resistance is slightly superior to polystyrene, but acetone, ethyl acetate, etc. Solvent cracks are likely to occur, and the hygroscopic property is high, so that there is a problem that moisture absorption deformation is likely to occur. Polycarbonate also has a problem that its birefringence and shrinkage ratio are larger than those of the two plastics described above, in addition to insufficient water resistance and light resistance.

  Therefore, when considering the application of these three types of plastics to a substrate of an optical disc such as a compact disc (CD), there is a high possibility that it will be exposed to a high-temperature and high-humidity atmosphere, considering the use environment of the optical disc. There is a concern that troubles due to the heat resistance and water resistance of these plastics may occur in the optical disc. Furthermore, since there is a problem with solvent resistance and chemical resistance, the place of use and the handling method are limited (see Non-Patent Document 1).

  Under such circumstances, cycloolefin polymers and cycloolefin copolymers of alicyclic saturated hydrocarbon polymers have been found. However, these plastics are excellent in heat resistance, chemical resistance, solvent resistance, and water resistance. Although they have performances suitable for optical materials compared to the plastics described above, they are heavy due to their high specific gravity. Light resistance was lower than that of polymethyl methacrylate, which was not sufficient.

  Moreover, as disclosed in Non-Patent Document 2, with the increase in capacity due to the increase in the size of the disk, its rotational accuracy has been demanded. However, since the specific gravity of conventional plastics is large and heavy, However, the load on the motor that rotates the disk is increased, and therefore, the rotation of the disk becomes unstable and the reading of data becomes unstable.

  In addition, environmental concerns such as depletion of fossil resources and global warming are feared, and materials with lower environmental impact are being demanded. In particular, in the optical disc, in addition to effective use of resources, further reduction in weight of the substrate resin is required from the viewpoints of reduction of physical distribution energy, reduction of waste, and the like.

JP 2002-60572 A JP-A-7-25949 Japanese Patent No. 2621871 Japanese Patent Publication No. 7-27662 JP 2004-51773 A Japanese Patent No. 2619856 Japanese Patent No. 2729317 JP 61-292601 A Japanese Patent Laid-Open No. 3-12835 Fumio Ide, “Optoelectronics and Polymer Materials”, Kyoritsu Shuppan, 1995, p. 111-153 Naoki Tsuda, “Intuitive Optical Disc”, Optronics, published in 1985, p. 34-35

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is excellent in heat resistance, light resistance, low moisture absorption, and good optical properties. Another object of the present invention is to provide a light-weight optical disc substrate made of a polymer having a low specific gravity and an optical disc using the same.

  As a result of intensive studies to solve such problems, the present inventors have advantageously obtained a target optical disk substrate and an optical disk having the same by using a predetermined β-pinene polymer. As a result, the present invention has been completed.

  That is, the present invention is an optical disc comprising a β-pinene polymer having a specific gravity of 0.85 or more and less than 1.0 and a transmittance of light having a wavelength of 400 to 850 nm of 90% or more. The substrate is the gist thereof.

  According to one of the desirable embodiments of the optical disk substrate according to the present invention, the β-pinene polymer is accelerated for 100 hours according to ASTM-G53 on a plate having a thickness of 1.0 mm. In the exposure test, the yellowing degree (ΔYI) before and after the YI (yellow index) test is 1.0 or less.

  Further, according to one of the other desirable embodiments of the optical disk substrate according to the present invention, the β-pinene polymer is hydrogenated and ([hydrogenated olefinic The number of double bonds] / [number of olefinic double bonds in the polymer before hydrogenation]) × 100 is 95% or more.

  Furthermore, the gist of the present invention is also an optical disc including the optical disc substrate as described above and having a signal recording surface formed on at least one side.

  As described above, the optical disk substrate according to the present invention uses a predetermined β-pinene polymer as a material for forming the optical disk substrate. Due to the excellent characteristics of the β-pinene polymer, the following effects are obtained. Can be played.

(1) Since the β-pinene polymer used as the substrate material of the optical disk is a polymer having a small specific gravity, it is possible to effectively reduce the weight of the target substrate, and thus the optical disk, This can stabilize the rotation of the disk and contribute to the improvement of the data reading accuracy.
(2) Since such β-pinene polymer has high heat resistance and low water absorption, it effectively prevents the optical disk substrate and the optical disk from being deformed by heat, and from being deformed by water adsorption / desorption. Therefore, it is possible to improve the data reading accuracy.
(3) The optical disk substrate according to the present invention and the optical disk using the same can be advantageously thinned because the elastic modulus and impact resistance are highly balanced.
(4) The optical disk substrate according to the present invention and the optical disk using the same have a feature that no harmful gas is generated even if discarded after being discarded.
(5) Since the β-pinene polymer used in the present invention has a low melt viscosity with respect to the molecular weight, it is possible to obtain an optical disk substrate or optical disk with a finer surface pattern.
(6) Since the optical disk substrate according to the present invention and the optical disk using the same are highly transparent, it is possible to improve data reading accuracy.
(7) Since the optical disk substrate according to the present invention and the optical disk using the same have high light resistance, it has an advantage that the performance is not deteriorated when used for a long time.
(8) Since the optical disc substrate according to the present invention and the optical disc using the same have low birefringence, it is possible to improve the data reading accuracy.
(9) Since the β-pinene polymer used in the present invention can be obtained from a raw material derived from a natural product, it is a carbon neutral material and has environmentally friendly characteristics.

  By the way, the β-pinene polymer used as the optical disk substrate material in the present invention has a specific gravity of 0.85 or more and less than 1.0, and a transmittance of light having a wavelength of 400 to 850 nm is 90% or more. It is a β-pinene polymer. Here, the β-pinene polymer in the present specification and claims refers to a polymer (polymer) having a β-pinene content of 50% by mass or more. In the plastic lens according to the present invention, a β-pinene polymer having a β-pinene content of 60% by mass or more is advantageously used, and more preferably a β-pinene content of 70% by mass or more. -A pinene polymer is used.

  As the β-pinene used as a raw material for producing such β-pinene polymer, any conventionally known one can be used. For example, it is possible to use a terpene such as α-pinene collected from a plant or a petroleum-derived compound, as well as it can be directly used after purification from a plant such as pine or citrus. Β-pinene and the like produced according to a more known technique (for example, the technique disclosed in US Pat. No. 3,278,623) can also be used. The β-pinene polymer obtained by using such plant-derived β-pinene is a carbon neutral material. In this respect, the optical disk substrate according to the present invention is capable of forming a recycling society and global warming. It can contribute to prevention.

  Further, the β-pinene polymer used in the present invention may be a homopolymer of the above-described β-pinene, or at least one kind of other copolymerizable monomers with β-pinene. There is no problem even if it is a copolymer of. Examples of monomers copolymerizable with β-pinene include cationic polymerizable monomers, radical polymerizable monomers, coordination polymerizable monomers, and plant-derived terpenes.

  In the present invention, the cationically polymerizable monomer, radically polymerizable monomer, and coordination polymerizable monomer that are used when producing the β-pinene polymer are generally used conventionally. It is possible to use what is. Plant-derived terpenes can also be used as the polymerizable monomer in any of the cationic polymerization method, radical polymerization method and coordination polymerization method. Specifically, as the cationic polymerizable monomer, isobutylene, isoprene, butadiene, styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, pt-butoxystyrene, indene, alkyl vinyl ether, norbornene Further, as the radical polymerizable monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate (Meth) acrylates such as 2-hydroxypropyl (meth) acrylate and glycidyl (meth) acrylate; nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; amide group-containing vinyl monomers such as acrylamide and methacrylamide Chromatography; vinyl acetate, vinyl pivalate, vinyl esters such as vinyl benzoate, vinyl chloride, vinylidene chloride, maleic anhydride, maleic acid, fumaric acid, fumaric acid esters, may be mentioned maleimide. Examples of coordination polymerizable monomers include ethylene, propylene, 1-hexene, cyclopentene, norbornene, and plant-derived terpenes include myrcene, alloocimene, omesin, α-pinene. , Dipentene, limonene, α-ferrandrene, α-terpinene, γ-terpinene, 2-carene, 3-carene and the like. Among these, one or more types are appropriately selected and used according to the amount of β-pinene used. Since the β-pinene polymer is advantageously obtained by the cationic polymerization method, among the polymerizable monomers as described above, the cationic polymerizable monomer is particularly advantageously used.

  In the case where the copolymerizable monomer is copolymerized with β-pinene, the amount of copolymerization is preferably 0.001 to 50% by mass in the polymer, and more preferably 0.01 to 20% by mass. Particularly preferred is 0.05 to 10% by mass. If the amount of copolymerization is too large, problems such as increased water absorption and reduced heat resistance are undesirable.

  On the other hand, a small amount of bifunctional or higher crosslinkable monomer (hereinafter referred to as a crosslinkable monomer) is copolymerized together with or in place of the above copolymerizable monomer. I can do it. Such a crosslinkable monomer is generally used as a branching agent or a crosslinking agent in the production of a polymer, but has a so-called long chain branching structure by reducing the amount used. A β-pinene polymer having a molecular weight that does not cause an insoluble part in an organic solvent is advantageously obtained. Specific examples of the crosslinkable monomer that can be used in the present invention include m-diisopropenylbenzene, p-diisopropenylbenzene, m-divinylbenzene, p-divinylbenzene, and 1,4-cyclohexanedimethanoldi. Bifunctional vinyl compounds such as vinyl ether and ethylene glycol divinyl ether can be mentioned, and among them, m-diisopropenylbenzene is preferably used from the viewpoints of economy and reactivity.

  When such a crosslinkable monomer is copolymerized with β-pinene (and a monomer copolymerizable with β-pinene), the copolymerization amount is 0.001 to 7% by mass in the polymer. Among them, 0.01 to 5% by mass is more preferable, and 0.05 to 4% by mass is most preferable. If the amount of copolymerization is too large, the resulting β-pinene polymer becomes gel and loses thermoplasticity, which is not preferable.

  By the way, the polymerization method of the β-pinene polymer used in the present invention is not particularly limited, and a known polymerization method suitable for each polymerizable monomer used can be appropriately selected. For example, any one of an anionic polymerization method, a cationic polymerization method, a radical polymerization method and a coordination polymerization method can be selected and used, but in general, a cationic polymerization method is adopted.

In addition, when obtaining the beta-pinene polymer used by this invention according to this cationic polymerization method, a well-known cationic polymerization catalyst will be used suitably as the polymerization catalyst. Specifically, BF ₃ , BF ₃ OEt ₂ , BBr ₃ , BBr ₃ OEt ₂ , AlCl ₃ , AlBr ₃ , AlI ₃ , TiCl ₄ , TiBr ₄ , TiI ₄ , FeCl ₃ , FeCl ₂ , SnCl ₂ , SnCl ₄ , WCl ₆ , MoCl ₅ , SbCl ₅ , TeCl _2, etc., Group 3-16 group metal halogen compounds; HF, HCl, HBr, etc. hydrogen acids; H ₂ SO ₄ , H ₃ BO ₃ , HClO ₄ , oxo acids such as CH ₃ COOH, CH ₂ ClCOOH, CHCl ₂ COOH, CCl ₃ COOH, CF ₃ COOH, p-toluenesulfonic acid, CF ₃ SO ₃ H, H ₃ PO ₄ , P ₂ O ₅ , and these Polymer compounds such as ion exchange resins having a group; heteropolyacids such as phosphomolybdic acid and phosphotungstic acid; SiO ₂ , Al ₂ O ₃ , SiO ₂ -Al ₂ O ₃ , MgO-SiO ₂ , B ₂ O ₃ —Al ₂ O ₃ , WO ₃ —Al ₂ O ₃ , Zr ₂ O ₃ —SiO ₂ , sulfated zirconia, tungstate zirconia, zeolite exchanged with H ⁺ or rare earth elements, activated clay, acidic Examples thereof include solid acids such as solid phosphoric acid in which clay, γ-Al ₂ O ₃ , and P ₂ O ₅ are supported on diatomaceous earth.

These cationic polymerization catalysts may be used in combination, and other compounds may be added to the polymerization system. Such other compounds are compounds that can improve the activity of the catalyst, for example, by adding them. Examples of compounds that improve the activity of metal halide compounds as acidic compounds include MeLi, EtLi, BuLi, Et ₂ Mg, EtMgBr, Et ₃ Al, Et ₂ AlCl, EtAlCl ₂ , Et ₃ Al ₂ Cl ₃ , (I-Bu) ₃ Al, Et ₂ Al (OEt), metal alkyl compounds such as Me ₄ Sn, Et ₄ Sn, Bu ₄ Sn, Bu ₃ SnCl; 2-methoxy-2-phenylpropane, t-butanol, 1 , 4-bis (2-methoxy-2-propyl) benzene, 2-phenyl-2-propanol, and the like are exemplified as compounds used as a polymerization initiator in living cationic polymerization.

  Further, as a polymerization method of the β-pinene polymer used in the present invention, a solution polymerization method using a solvent may be used. The solvent that can be used varies depending on the polymerization method employed, and thus it is difficult to define it uniquely. For example, aromatic hydrocarbon solvents such as benzene, toluene, xylene, etc .; pentane, hexane, heptane, Aliphatic hydrocarbon solvents such as octane, cyclopentane, cyclohexane, methylcyclohexane, decalin; halogenated hydrocarbon solvents such as methyl chloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethylene; esters, Examples thereof include oxygen-containing solvents such as ether. In view of reactivity, it is preferable to use an aromatic hydrocarbon solvent, an aliphatic hydrocarbon solvent, a halogenated hydrocarbon solvent, or the like. These solvents may be used alone or in combination of two or more.

  Although the usage-amount of such a solvent is not specifically limited, About 100-10000 mass parts normally with respect to 100 mass parts of monomers, such as (beta) -pinene, Preferably it is 150-5000 mass parts, More preferably, it is 200-3000. Part by mass. When the amount of the solvent is small, uniform mixing of the polymerization catalyst becomes difficult, so that the reaction becomes non-uniform, and a uniform polymer cannot be obtained, or the control of the reaction becomes difficult. On the other hand, when the amount of solvent is large, there is a problem that productivity is lowered.

  And when performing a polymerization reaction, -80 degreeC-100 degreeC is preferable normally, -40 degreeC-80 degreeC is more preferable especially, -20 degreeC-80 degreeC is the most preferable especially. If this reaction temperature is too low, the progress of the reaction is slow, and if it is too high, it becomes difficult to control the reaction and it is difficult to obtain reproducibility.

  Moreover, the reaction pressure for performing the polymerization reaction is not particularly limited, but is preferably 0.5 to 50 atm, and more preferably 0.7 to 10 atm. Usually, the polymerization reaction is performed at around 1 atm.

  Furthermore, the reaction time for conducting the polymerization reaction is not particularly limited, and the reaction time may be appropriately determined so that a β-pinene polymer is obtained in good yield according to conditions such as reaction temperature and reaction pressure. Good. Usually, it is about 0.01 to 24 hours, preferably 0.2 to 10 hours.

  By the way, the β-pinene polymer after the polymerization reaction is a polymer solution such as reprecipitation, solvent removal under heating, solvent removal under reduced pressure, solvent removal with steam (steam stripping), and the like. It can be separated and obtained from the reaction mixture by the usual operation for isolation from the reaction mixture.

The β-pinene polymer used in the present invention preferably has hydrogenated olefinic double bonds from the viewpoints of light resistance, impact resistance, heat resistance and the like. In general, the hydrogenation rate is preferably 90% or more, more preferably 95% or more, and most preferably 99% or more. In the present invention, the β-pinene polymer is hydrogenated and shows the hydrogenation rate ([number of hydrogenated olefinic double bonds] / [before hydrogenation]). The number of olefinic double bonds in the polymer]]) × 100 is desirably 95% or more. The hydrogenation rate of the unsaturated double bond (carbon-carbon double bond) in the hydrogenated polymer is determined by iodine titration method, infrared spectroscopic spectrum measurement, nuclear magnetic resonance spectrum ( ¹ H-NMR spectrum). It can be calculated using an analysis means such as measurement.

  Here, the method for hydrogenating the β-pinene polymer used in the present invention is not particularly limited, and a known method can be used. For example, homogeneous catalysts such as Wilkinson complex, cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, diatomaceous earth, magnesia, alumina, silica, alumina-magnesia, silica-magnesia, silica-alumina, synthetic zeolite, etc. A known method using a heterogeneous catalyst or the like in which a catalyst metal such as nickel, palladium, or platinum is supported on a support can be used.

  As a solvent that can be used for hydrogenation, any organic solvent that dissolves the polymer and is inert to the hydrogenation catalyst can be used. Specifically, aromatic hydrocarbon solvents such as benzene, toluene, xylene; aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclopentane, cyclohexane, methylcyclohexane, decalin; methyl chloride, methylene chloride Halogenated hydrocarbon solvents such as 1,2-dichloroethane, 1,1,2-trichloroethylene; oxygen-containing solvents such as esters and ethers. In view of reactivity, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents and the like are preferable. These solvents may be used alone or in combination of two or more.

Furthermore, although the reaction temperature of the hydrogenation reaction depends on the hydrogenation catalyst used and the hydrogen pressure, it is generally preferably about 20 ° C to 250 ° C, more preferably 25 ° C to 150 ° C, and even more preferably 40 ° C to 100 ° C. Is most preferred. If the reaction temperature is too low, the reaction will not proceed smoothly, and if the reaction temperature is too high, side reactions and molecular weight will tend to occur. The hydrogen pressure is preferably about normal pressure to about 200 kgf / cm ² , more preferably 5 to 100 kgf / cm ² . If the hydrogen pressure is too low, the reaction does not proceed smoothly, and if the hydrogen pressure is too high, there are restrictions on the apparatus.

  In addition, the density | concentration of (beta) -pinene polymer in such a hydrogenation reaction system is about 2 mass%-40 mass% normally, Preferably it is 3 mass%-30 mass%, More preferably, it is 5 mass%-20 % By mass. If the concentration of β-pinene polymer is low, productivity is likely to decrease, which is not preferable. Moreover, when the density | concentration of (beta) -pinene polymer is too high, the hydrogenated polymer may precipitate or the viscosity of a reaction mixture may become high and it may become difficult to perform stirring smoothly, and is unpreferable.

  The reaction time of the hydrogenation reaction depends on the hydrogenation catalyst used, the hydrogen pressure, and the reaction temperature, but is usually about 0.1 to 50 hours, preferably 0.2 to 20 hours, more preferably 0.5 hours to 10 hours will be employed.

  Furthermore, the β-pinene polymer after the hydrogenation reaction may be polymerized by, for example, reprecipitation, solvent removal under heating, solvent removal under reduced pressure, or solvent removal with steam (steam stripping). The product is separated and obtained from the reaction mixture by a normal operation for isolation from the solution.

  By the way, the molecular weight of the β-pinene polymer used in the present invention is about 30,000 to 1,000,000 in terms of weight average molecular weight from the viewpoints of the viscosity and melt viscosity of the polymerization solution, moldability, strength of the optical disk, and heat resistance. It is preferably 40,000 to 500,000, more preferably 60,000 to 250,000, and most preferably 90,000 to 200,000. The weight average molecular weight of the polymer can be calculated using a known analysis method such as gel permeation chromatography (GPC) obtained in terms of polystyrene or static light scattering measurement (SLS).

  In addition, the glass transition temperature (Tg) of the β-pinene polymer used in the present invention is preferably higher from the usage environment of the optical disk substrate, and is generally preferably 80 ° C. or higher. In order to avoid this, it is desirable that the temperature is 100 ° C. or higher, and more preferable is 110 ° C. or higher. The upper limit of the glass transition temperature is not particularly defined, but is preferably about 200 ° C. This is because, in an amorphous polymer such as the β-pinene polymer used in the present invention, if the glass transition temperature is too high, the entanglement of the polymer is reduced and the molded product may become brittle.

  Further, the light transmittance of the β-pinene polymer used in the present invention is 90% or more in the transmittance of light having a wavelength of 400 to 850 nm in order to exhibit an excellent function as an optical disk substrate. There is a need. When this light transmittance is lowered, problems such as deterioration of data reading accuracy are caused.

  Furthermore, the β-pinene polymer used in the present invention preferably has a lower water absorption rate from the viewpoint of dimensional stability. The water absorption of the β-pinene polymer is preferably 0.2% or less as a saturated water absorption when placed in an atmosphere of 60 ° C. and 90% RH (relative humidity), more preferably 0.1% or less. In particular, 0.05% or less is most preferable. A β-pinene polymer giving such a water absorption rate is advantageously selected.

  Such a β-pinene polymer used in the present invention is characterized by a low specific gravity. This is because a lighter substrate, and thus an optical disc, can be obtained because the specific gravity is small. Accordingly, the specific gravity of the β-pinene polymer used in the present invention needs to be 0.85 or more and less than 1.0, and more preferably 0.85 to 0.98. This is because it is difficult to obtain a polymer having a specific gravity smaller than 0.85, and when the specific gravity is 1.0 or more, the object of weight reduction cannot be sufficiently achieved.

In addition, the β-pinene polymer used in the present invention is characterized by a small photoelastic coefficient. In particular, it has a feature that the photoelastic coefficient at a temperature equal to or higher than Tg is small. In addition, when the photoelastic coefficient at a temperature equal to or higher than Tg is large, there is a problem that optical distortion of a generally obtained molded product increases. In addition, when trying to obtain a molded product with a small optical distortion, there is a problem that a range in which molding conditions can be selected is narrow and productivity is lowered. Therefore, the photoelastic coefficient at a preferable temperature equal to or higher than Tg (for example, Tg + 20 ° C.) cannot be generally specified depending on the application, but is −3.0 × 10 ^{−10 to} 3.0 × 10 ⁻¹⁰ cm ² / dyn. It is preferable that −1.0 × 10 ^{−10 to} 1.0 × 10 ⁻¹⁰ cm ² / dyn is more preferable. By having a photoelastic coefficient in this range, a molded product having a small optical distortion can be obtained with high productivity.

  Furthermore, since the β-pinene polymer used in the present invention has a large flexural modulus and hardly undergoes deformation due to bending, the optical disk substrate made of such β-pinene polymer can be made thinner. Have. In general, the flexural modulus of the β-pinene polymer is preferably 2500 MPa or more, more preferably 2700 MPa or more.

  In addition, the β-pinene polymer for forming the optical disk substrate according to the present invention may contain various known compounding agents alone or in accordance with necessity within a range not impairing the object of the present invention. More than one species can be combined and mixed.

  Specific examples of such various compounding agents are not particularly limited as long as they are usually used in the resin industry. For example, antioxidants, ultraviolet absorbers, light stabilizers, near infrared absorption And compounding agents such as a colorant such as a colorant, a dye and a pigment, a lubricant, a plasticizer (softening agent), an antistatic agent, a fluorescent brightening agent, and a filler.

  Among them, examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, phenolic antioxidants are preferable, and alkyl-substituted phenolic oxidations. Inhibitors are particularly preferred.

  As the phenolic antioxidant used here, specifically, conventionally known ones can be used. For example, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methyl Benzyl) -4-methylphenyl acrylate, 2,4-di-t-amyl-6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate, etc. Acrylate compounds such as those described in JP-A-179953 and JP-A-1-168463; octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2′-methylene -Bis (4-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5- Limethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxy) Phenylpropionate) methane [i.e. pentaerythrimethyl-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenylpropionate)], triethylene glycol bis (3- (3-t-butyl- Alkyl-substituted phenolic compounds such as 4-hydroxy-5-methylphenyl) propionate); 6- (4-hydroxy-3,5-di-t-butylanilino) -2,4-bisoctylthio-1,3,5 -Triazine, 4-bisoctylthio-1,3,5-triazine, 2-octylthio-4,6-bis- (3,5-di-t-butyl-4-oxyani Roh) triazine group-containing phenol compounds such as 1,3,5-triazine.

The phosphorus antioxidant is not particularly limited as long as it is usually used in the general resin industry. For example, triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris ( Nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl)- Monophosphite compounds such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tri Decylphosphite), 4,4′-isopropylidene-bis (phenyl-di-alkyl (C ₁₂ -C ₁₅ ) phosphite) And diphosphite-based compounds. Among these, monophosphite compounds are preferable, and tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite and the like are particularly preferable.

  Furthermore, examples of the sulfur antioxidant include dilauryl 3,3-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3. -Thiodipropionate, pentaerythritol-tetrakis- (β-lauryl-thiopropionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5 ] Undecane etc. can be mentioned.

  And these antioxidant can be used individually or in combination of 2 or more types, respectively. The amount of such an antioxidant is appropriately determined within a range that does not impair the purpose of the present invention, but is usually 0.001 with respect to 100 parts by mass of the β-pinene polymer. It is about -5 mass parts, Preferably it is the range of 0.01-1 mass part.

  Examples of the ultraviolet absorber include 2- (2-hydroxy-5-methylphenyl) 2H-benzotriazole, 2- (3-t-butyl-2-hydroxy-5-methylphenyl) -5-chloro- 2H-benzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) ) -2H-benzotriazole, 5-chloro-2- (3,5-di-t-butyl-2-hydroxyphenyl) -2H-benzotriazole, 2- (3,5-di-t-amyl-2-) Benzotriazole ultraviolet absorbers such as hydroxyphenyl) -2H-benzotriazole; 4-t-butylphenyl-2-hydroxybenzoate, phenyl-2-hydroxy Zoate, 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2H- Benzotriazol-2-yl) -4-methyl-6- (3,4,5,6-tetrahydrophthalimidylmethyl) phenol, 2- (2-hydroxy-5-t-octylphenyl) -2H-benzotriazole Benzoate ultraviolet absorbers such as 2- (2-hydroxy-4-octylphenyl) -2H-benzotriazole; 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone -5-sulfonic acid trihydrate, 2-hydroxy-4-octyloxybenzophenone, 4 Benzophenone series such as dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone UV absorbers; acrylate UV absorbers such as ethyl-2-cyano-3,3-diphenyl acrylate, 2′-ethylhexyl-2-cyano-3,3-diphenyl acrylate; [2,2′-thiobis (4- t-octylphenolate)]-2-ethylhexylamine nickel and other metal complex ultraviolet absorbers and the like can be used.

  Furthermore, examples of the light stabilizer include 2,2,6,6-tetramethyl-4-piperidylbenzoate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, and bis (1,2 , 2,6,6-pentamethyl-4-piperidyl) -2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate, 4- (3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionyloxy) -1- (2- (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) ethyl) -2,2, Examples thereof include hindered amine light stabilizers such as 6,6-tetramethylpiperidine.

  In addition, as the near-infrared absorber, for example, cyanine-based near-infrared absorber; pyrylium-based near-infrared absorber; squarylium-based near-infrared absorber; croconium-based near-infrared absorber; Infrared absorbers; dithiol metal complex-based near infrared absorbers; naphthoquinone near infrared absorbers; anthraquinone near infrared absorbers; indophenol near infrared absorbers; As commercially available near infrared absorbers, SIR-103, SIR-114, SIR-128, SIR-130, SIR-132, SIR-152, SIR-159, SIR-162 (above, Mitsui Toatsu Dye Co., Ltd.) Company-made), Kayasorb IR-750, Kayasorb IRG-002, Kayasorb IRG-003, Kayasorb IR-820B, Kayasorb IRG-022, Kayasorb IRG-023, Kayasorb CY9, Kayasorb CY9, , Manufactured by Nippon Kayaku Co., Ltd.).

  The dye is not particularly limited as long as it is uniformly dispersed / dissolved in the β-pinene polymer to be used, but has excellent compatibility with the β-pinene polymer used in the present invention. Therefore, oil-soluble dyes (various CI solvent dyes) are widely used. Specific examples of the oil-soluble dye include “Color Index” published in The Society of Dyers and Colorists, Vol. 3. Various C.I. I. Solvent dyes may be mentioned.

  Further, among the pigments, organic pigments include, for example, diarylide pigments such as Pigment Red 38; azo lake pigments such as Pigment Red 48: 2, Pigment Red 53, Pigment Red 57: 1; Pigment Red 144, Pigment Red 166, Pigment Red 220, Pigment Red 221, Pigment Red 248, and other condensed azo pigments; Pigment Red 171, Pigment Red 175, Pigment Red 176, Pigment Red 185, Pigment Red 208, and other benzimidazolone pigments; Quinacridone pigments such as Pigment Red 149, Pigment Red 178, and Pigment Red 179; and anthraquinone pigments such as Pigment Red 177. Examples of inorganic pigments include titanium oxide, carbon black, red pepper, chrome red, molybdenum red, resurge, and iron oxide.

  When coloring is required for the optical disk substrate of the present invention, any of the dyes and pigments described above can be used within the scope of the object of the present invention and is not particularly limited. In the case of an optical disk in which such optical characteristics are problematic, coloring with a dye is preferable. In addition, the ultraviolet absorber may show a yellow to red color visually, and the near infrared absorber may show a black color visually, so there is no need to use these and dyes strictly, Moreover, there is no problem even if they are used in combination.

  As the lubricant, organic compounds such as aliphatic alcohol esters, polyhydric alcohol esters or partial esters, inorganic fine particles, and the like can be used. Here, examples of the organic compound include glycerol monostearate, glycerol monolaurate, glycerol distearate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, and the like.

  Further, as other lubricants, generally inorganic fine particles can be used. Here, the inorganic fine particles include oxides, sulfides, hydroxides, nitrides, halides, carbonates, sulfates, acetic acids of the elements of Groups 1, 2, 4, and 6-14 of the periodic table. Examples thereof include fine particles of salts, phosphates, phosphites, organic carboxylates, silicates, titanates, borates and their hydrates, composite compounds centered on them, natural compounds, and the like.

  Examples of the plasticizer include tricresyl phosphate, trixylenyl phosphate, triphenyl phosphate, triethylphenyl phosphate, diphenyl cresyl phosphate, monophenyl dicresyl phosphate, diphenyl monoxylenyl phosphate. Phosphate triester plasticizers such as phosphate, monophenyldixylenyl phosphate, tributyl phosphate, triethyl phosphate; dimethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-phthalate Phthalate plasticizers such as 2-ethylhexyl, diisononyl phthalate, octyldecyl phthalate, and butylbenzyl phthalate; fatty acid monobasic acids such as butyl oleate and glycerol monooleate Plasticizers; dihydric alcohol ester plasticizers; oxyester plasticizers and the like can be used. Of these, phosphate triester plasticizers are preferred, and tricresyl phosphate and trixylenyl phosphate are preferred. Particularly preferred.

Further, other specific examples of the plasticizer include squalane (C ₃₀ H ₆₂ , Mw = 422.8), liquid paraffin (white oil, ISO VG10, ISO VG15, ISO VG32, ISO stipulated in JIS-K-2231). VG68, ISO VG100, ISO VG8 and ISO VG21), polyisobutene, hydrogenated polybutadiene, hydrogenated polyisoprene, and the like. Among these, squalane, liquid paraffin, and polyisobutene are preferably used.

  Furthermore, examples of the antistatic agent include long-chain alkyl alcohols such as stearyl alcohol and behenyl alcohol, fatty acid esters of polyhydric alcohols such as glycerol monostearate and pentaerythritol monostearate, and stearyl alcohol and behenyl alcohol. Particularly preferred.

  These compounding agents can be used alone or in admixture of two or more, and the mixing ratio is appropriately selected within a range not impairing the object of the present invention. Moreover, even if it exists in each compounding quantity of an above-described compounding agent, although suitably selected in the range which does not impair the objective of this invention, with respect to 100 mass parts of (beta) -pinene polymer about each compounding agent. Usually, it is about 0.001 to 5 parts by mass, preferably 0.01 to 1 part by mass.

  The β-pinene polymer for molding the optical disk substrate according to the present invention as described above can be blended with other polymer components as necessary within a range not impairing the object of the present invention. . Examples of the other polymer include rubbery polymers, specifically, diene rubbers such as natural rubber, polybutadiene rubber, polyisoprene rubber, acrylonitrile / butadiene copolymer rubber; styrene / butadiene copolymer. Rubber, styrene / isoprene copolymer rubber, styrene / butadiene / isoprene terpolymer rubber; hydrogenated diene rubber; ethylene / α-olefin copolymer such as ethylene / propylene copolymer, propylene / other Saturated polyolefin rubbers such as α-olefin copolymers; α-olefins such as ethylene / propylene / diene copolymers, α-olefin / diene copolymers, isobutylene / isoprene copolymers, and isobutylene / diene copolymers・ Diene polymer rubber; urethane rubber, silicone rubber, polyester Special rubbers such as tellurium rubber, acrylic rubber, propylene oxide rubber and ethylene / acrylic rubber; thermoplastic elastomers such as styrene / butadiene / styrene block copolymer rubber and styrene / isoprene / styrene block copolymer rubber; heat of hydrogenation Mention may be made of plastic elastomers; urethane thermoplastic elastomers; polyamide thermoplastic elastomers; 1,2-polybutadiene thermoplastic elastomers. The blending amount is appropriately selected within a range not impairing the object of the present invention, but is usually about 3 to 30 parts by mass, preferably 5 with respect to 100 parts by mass of the β-pinene polymer. It is the range of -20 mass parts.

  As a method for forming an optical disk substrate according to the present invention, known methods such as an injection molding method, a hot press molding method, an extrusion molding method, and a cutting method are appropriately employed. Among these, from the viewpoint of productivity, an injection molding method or an extrusion molding method is preferably used. The thickness of the optical disk substrate thus obtained is generally about 30 to 300 μm, preferably 70 to 200 μm.

  As described above, according to the present invention, when a predetermined β-pinene polymer is used as a resin for an optical disk substrate, there are problems of heat resistance and water resistance in a conventional polymethyl methacrylate resin, and birefringence and dimensions in a polycarbonate resin. The problems of stability and water resistance are solved at once, and a disk substrate having excellent characteristics is provided. Accordingly, the disk substrate according to the present invention having the recording layer laminated by various known methods is advantageously used as an optical disk such as a compact disk, a video disk, a write-once optical disk, a rewritable optical disk, and a magneto-optical disk. It can be done. It can also be used as an optical card using a similar recording method.

  Here, if the manufacturing method of the optical disk concerning this invention is demonstrated more concretely, first, uneven | corrugated pit is formed in the disk board | substrate according to this invention which consists of an above-mentioned (beta) -pinene polymer. The concave / convex pits are coated on such a disk substrate with, for example, an ultraviolet curable resin or a thermosetting resin, and then a stamper having concave / convex pits storing predetermined information is pressed. Thereafter, it can be formed by a method of curing the resin by ultraviolet rays or heat, or a method of forming a concavo-convex pit on the substrate by hot pressing a stamper directly on the disk substrate. Therefore, as the ultraviolet curable resin, a known acrylic resin or the like is used, and as the thermosetting resin, a phenol resin or an epoxy resin is used.

Next, a functional film such as a reflective film, a recording film, and a dielectric film is formed on such uneven pits. This functional film may be formed of an inorganic compound or an organic compound. Examples of the inorganic compound that can be used as the functional film include a reflective film such as Ni, Al, Au, and Pt, and a recording film that includes a Tb—Fe alloy, a Dy—Fe alloy, and a Cd—Tb. In addition to rare earth-transition metal amorphous alloys such as Al alloys, Cd—Tb—Dy—Fe alloys, Cd—C alloys, Tb—Fe—Co alloys, Ge—Te, Sb—Te alloys, In—Sb In a dielectric film, such as phase change type recording materials such as Te-CS ₂ , Pb—Te—Se, Te—C, TeO ₂ , Sb—Se, Bi—Te, etc., CdS, ZnS _{, ZnSe, SiO 2, Si,} Si 3 N 4, AlN, can be mentioned TiO _2, TaO _2, MgF compounds such _2. Examples of organic compounds include methine / polymethine, quinones, naphthoquinones, anthraquinones, phthalocyanines, dithiols, tetrahydrocholines, dioxanes, dithiazines, thiabililiums, porphyrins, etc. . For the formation of the target functional film, a known method such as a vapor deposition method, a sputtering method, an ion plating method, a dipping method, or a spin coating method is used.

  The optical disk substrate according to the present invention formed with a functional coating in this way is used as a so-called single-plate type optical disk with one side serving as a signal recording surface. Is used as a so-called double-sided type optical disc in which both sides of the optical disc substrate are bonded to each other through an adhesive layer with their signal recording surfaces facing each other to form a signal recording surface. To get. In both the single-plate type optical disc and the double-sided type optical disc, the optical disc substrate according to the present invention is irradiated with a reading light such as a laser beam and transmitted therethrough, and a signal recording surface formed on the opposite surface. However, the ratio of one or two optical disk substrates in such an optical disk is configured to occupy 5 to 95% by mass of the entire optical disk, thereby effectively functioning as a substrate. You will be harassed.

  Hereinafter, some examples of the present invention will be shown and the present invention will be more specifically clarified, but the present invention is not limited by the description of such examples. It goes without saying. In addition to the following examples, the present invention can be subjected to various changes, corrections, improvements and the like based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Should be understood.

  First, as a material for forming an optical disk substrate according to the present invention, a hydrogenated β-pinene polymer was synthesized as follows.

  About the fully dried glass flask with a cock, after the inside was sufficiently substituted with nitrogen, dehydrated N-hexane: 184 parts by mass, dehydrated methylene chloride: 210 parts by mass, and dehydrated diethyl ether : 0.5 part by mass was added and cooled to -78 ° C. While stirring the mixture at -78 ° C, hexane solution of ethylaluminum dichloride (concentration: 1.0 mol / L): 7.2 parts by mass was further added. Next, in a state where the inside of the flask was kept at −78 ° C., when 3.0 parts by mass of a hexane solution of p-dicumulyl chloride (concentration: 0.1 mol / L) was added, the color changed to red amber. Thereafter, 60 parts by mass of β-pinene that was immediately purified by distillation was added to the flask over 1 hour. The solution gradually became dark blue and the viscosity of the solution increased. After the addition of β-pinene, 30 parts by mass of methanol was added to terminate the reaction. In the flask, an aqueous solution obtained by adding 5 parts by mass of citric acid to 100 parts by mass of distilled water is added and stirred for 5 minutes. Then, the aqueous layer is extracted, and the aqueous layer becomes neutral by adding distilled water. Until the aluminum compound was removed. The obtained organic layer was reprecipitated in a mixed solvent of methanol / acetone (50/50 vol%): 5000 parts by mass and then sufficiently dried to obtain 60 parts by mass of β-pinene polymer (A1). . The obtained β-pinene polymer (A1) had a weight average molecular weight of 116,000, a number average molecular weight of 51,000, and a glass transition temperature of 95 ° C.

By adding 70 parts by mass of cyclohexane and 30 parts by mass of the β-pinene polymer (A1) obtained as described above to a pressure vessel equipped with a stirrer substituted with nitrogen, and stirring the mixture, a β-pinene polymer ( A1) was completely dissolved. Next, 5% palladium-supported alumina (manufactured by NE ChemCat) as a hydrogenation catalyst: 30 parts by mass was added and sufficiently dispersed by stirring, and then the inside of the pressure vessel was sufficiently replaced with hydrogen. While stirring at 1000 rpm, the mixture was reacted at 100 ° C. and hydrogen pressure of 40 kgf / cm ² for 6 hours, and then returned to normal pressure. The reaction solution was diluted by adding 200 parts by mass of cyclohexane, filtered through a 0.5 μm Teflon (registered trademark) filter to separate and remove the catalyst, and then a mixed solvent of methanol / acetone (50/50 vol%): 5000 After re-precipitation in parts by mass, it was sufficiently dried to obtain 29 parts by mass of β-pinene polymer hydrogenated product (H1). When the hydrogenation rate of the obtained β-pinene polymer hydrogenated product (H1) was determined from ¹ H-NMR, it was 99.9%, the weight average molecular weight was 112,000, and the number average molecular weight was 50,800. The glass transition temperature was 130 ° C. and the specific gravity was 0.930.

  Thereafter, 0.1 part of 2- (5-methyl-2hydroxyphenyl) benzotriazole, which is an ultraviolet absorber, is added to 100 parts by mass of the thus obtained high molecular weight β-pinene polymer hydrogenated product (H1). After mixing a mass part and 0.1 mass part of Irganox 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd.) which is a phenolic antioxidant, using a Henschel mixer, melt-kneading using an extruder, A pellet-like β-pinene polymer hydrogenated composition (M1) was obtained.

  In addition, about the material obtained at each above-mentioned process, and the material manufactured at the following process, the physical-property measurement was performed as follows.

-Molecular weight-
The number average molecular weight and the weight average molecular weight are both determined in terms of polystyrene based on measurement by gel permeation chromatography (GPC). Here, HLC-8020 (product number) manufactured by Tosoh Co., Ltd. is used as the GPC device, and TSKgel / GMH-M manufactured by Tosoh Co., Ltd. and one G2000H are connected in series as the column. Using.

-Hydrogenation rate-
^{From the 1} H-NMR spectrum, the hydrogenation rate {([number of hydrogenated olefinic double bonds] / [hydrogen] is determined by the reduction rate (%) of olefinic double bond protons (4 to 6 ppm) of the raw material resin. The number of olefinic double bonds in the polymer before addition]) × 100 (%)} was determined.

-Glass transition temperature (Tg)-
It measured by the differential scanning calorimetry (DSC) using the sample which fully dried and removed the solvent. First, a sample is heated from 25 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min under a stream of nitrogen of 100 ml / min to obtain a DSC curve. Next, using the obtained DSC curve, as shown in FIG. 1, a parallel line E passing through the intersection of the center tangent B and the base line C before the transition and parallel to the temperature axis, and the center tangent B A parallel line F passing through the intersection of the base line D after the transition and parallel to the temperature axis is drawn. In this specification, the temperature A at the intersection of the parallel line G that bisects the two parallel lines E and F and the DSC curve is defined as the glass transition temperature (Tg). In addition, here, DSC30 (product number) manufactured by METTLER TOLEDO Co., Ltd. was used as a measuring device.

-Light transmittance-
The light transmittance at wavelengths of 400 nm and 850 nm was measured using a spectrophotometer (U4000 (product number) manufactured by Hitachi, Ltd.). The criteria for determination are as follows.
○: 90% or more ×: less than 90%

-Water absorption rate-
A press-molded plate having a length of 140 mm, a width of 60 mm, and a thickness of 0.8 mm was placed in an atmosphere of 60 ° C. and 90% RH for 10 days, and the ratio of the weight increased from the initial weight was determined. The water absorption rate. The arithmetic expression is as follows.
Water absorption (%) = Weight increase x 100 / initial weight

-Refractive index (nD)-
It measured at 25 degreeC based on JIS-K-7142 using RX-2000 (product number) made from Atago Co., Ltd ..

-Specific gravity-
It measured according to A method of JIS-K-7112: 1999. Judgment criteria are as follows.
○: Specific gravity <1.0
Δ: 1.0 ≦ specific gravity <1.1
×: 1.1 ≦ specific gravity

-Light resistance-
A press-molded plate with a thickness of 1.0 mm was subjected to an accelerated exposure test for 100 hours in accordance with ASTM-G53, and the yellowing degree (ΔYI) before and after the YI (yellow index) test. ) Was measured. Here, an ultraviolet exposure tester (ATLAS-UVCON manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used. YI was measured according to JIS-K-7103. And it evaluated according to the following criteria.
ΔYI = (YI after 100 hours of UV exposure) − (YI before UV exposure)
○: ΔYI ≦ 1 Long-term light resistance is very good ×: 1 <ΔYI Long-term light resistance is poor

-Photoelastic coefficient-
Thickness: A 200 μm film was annealed overnight at a temperature 20 ° C. lower than Tg, and then subjected to a tensile stress in the major axis direction at a temperature 20 ° C. higher than Tg. It was measured with M220 (manufactured by JASCO Corporation), and the photoelastic coefficient was calculated from the amount of change in retardation with respect to stress.

-Flexural modulus-
Using the test piece, the flexural modulus at 23 ° C. was measured using an autograph (manufactured by Shimadzu Corporation) according to JIS-K-7171. In addition, the determination criteria are as follows.
○: Flexural modulus is 2500 MPa or more ×: Flexural modulus is less than 2500 MPa

Example 1
After mounting a pit forming stamper for a CD (compact disk) prepared in advance in a mold, using the previously prepared β-pinene polymer hydrogenated composition (M1), a resin temperature: 250 ° C., Injection molding was performed at a mold temperature of 90 ° C. and an injection pressure of 680 kg / cm ² to obtain a 12 cmφ disk substrate having a thickness of 1.2 mm. The optical disk substrate thus obtained was evaluated, and the evaluation results are shown in Table 1 below.

Subsequently, Al was vapor-deposited on the pit forming surface of the obtained disk substrate to a thickness of 1 μm using a vacuum vapor deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.) under the condition of vacuum degree: 2 × 10 ⁻⁶ Torr. . Thereafter, an ultraviolet curable methyl acrylate monomer was applied on the surface of the Al vapor deposition film to form a 10 μm cured film.

-Comparative Example 1-
After a pit forming stamper for a CD (compact disc) prepared in advance is mounted on the mold, ZEONOR 1060R (alicyclic polyolefin resin) manufactured by Nippon Zeon Co., Ltd., resin temperature: 260 ° C., mold Injection molding was performed at a temperature of 90 ° C. and an injection pressure of 680 kg / cm ² to obtain a 12 cmφ disk substrate having a thickness of 1.2 mm. The optical disk substrate thus obtained was evaluated, and the evaluation results are shown in Table 1 below.

Subsequently, Al was vapor-deposited on the pit forming surface of the obtained disk substrate to a thickness of 1 μm using a vacuum vapor deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.) under the condition of vacuum degree: 2 × 10 ⁻⁶ Torr. . Thereafter, an ultraviolet curable methyl acrylate monomer was applied on the surface of the Al deposited film to form a 10 μm cured film.

-Comparative Example 2-
After a pit forming stamper for CD (compact disc) prepared in advance is mounted on the mold, S3000 (polycarbonate) manufactured by Mitsubishi Engineering Plastics Co., Ltd. is used, resin temperature: 300 ° C., mold temperature: 90 Injection molding was performed at 0 ° C. and an injection pressure of 680 kg / cm ² to obtain a 12 cmφ disk substrate having a thickness of 1.2 mm. The evaluation results for the optical disk substrate thus obtained are shown in Table 1 below.

Subsequently, Al was vapor-deposited on the pit formation surface of the obtained substrate using a vacuum vapor deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.) under a vacuum degree of 2 × 10 ⁻⁶ Torr to a thickness of 1 μm. Thereafter, an ultraviolet curable methyl acrylate monomer was applied on the surface of the Al deposited film to form a 10 μm cured film.

-Comparative Example 3-
After a pit forming stamper for a CD (compact disc) prepared in advance was mounted on the mold, Kuraray Co., Ltd. Parapet GH1000S (polymethyl methacrylate) was used, resin temperature: 260 ° C., mold temperature: 90 Injection molding was performed at 0 ° C. and an injection pressure of 680 kg / cm ² to obtain a 12 cmφ disk substrate having a thickness of 1.2 mm. The evaluation results for the optical disk substrate thus obtained are shown in Table 1 below.

Subsequently, Al was vapor-deposited on the pit formation surface of the obtained substrate using a vacuum vapor deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.) under a vacuum degree of 2 × 10 ⁻⁶ Torr to a thickness of 1 μm. Thereafter, an ultraviolet curable methyl acrylate monomer was applied on the surface of the Al vapor deposition film to form a 10 μm cured film.

  As is apparent from the results of Table 1, the disk substrate (Example 1) manufactured according to the present invention is significantly lighter than the resins shown in Comparative Examples 1 to 3, and thus is suitable for a motor that rotates the disk. Since the load is small and the rotation is stable, it is recognized that the data has a high reading accuracy. In addition, since the photoelastic coefficient is low, an optical disk having a low birefringence is provided, and thus there is a feature that data reading errors are small. In addition, the disk substrate according to the present invention (Example 1) has a high bending strength, so that it is difficult to bend and the rotation is stable.

It is explanatory drawing which shows the method of calculating | requiring the glass transition temperature in an Example from a DSC curve.

Claims (4)

  An optical disk substrate comprising a β-pinene polymer having a specific gravity of 0.85 or more and less than 1.0 and a transmittance of light having a wavelength of 400 to 850 nm of 90% or more.   In the accelerated exposure test for 100 hours in accordance with ASTM-G53 on a plate having a thickness of 1.0 mm, the β-pinene polymer has a yellowing degree (ΔYI) before and after the YI (yellow index) test. The optical disk substrate according to claim 1, wherein the optical disk substrate has a characteristic of 1.0 or less.   The β-pinene polymer is hydrogenated, and ([number of olefinic double bonds hydrogenated] / [number of olefinic double bonds in the polymer before hydrogenation] The optical disk substrate according to claim 1 or 2, wherein a value of) × 100 is 95% or more. An optical disc comprising the optical disc substrate according to any one of claims 1 to 3, wherein a signal recording surface is formed on at least one side.

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