JP2008015199A - Resin composition for optical material, and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition for optical materials containing a thermoplastic transparent resin having excellent transparency, low birefringence and excellent light resistance suitable for optical materials, an optical element used in application where laser light particularly of 405 nm waveband is transmitted, and an optical element which is a member of an optical pick-up apparatus. <P>SOLUTION: The resin composition for optical materials contains the thermoplastic transparent resin obtained by filtering a thermoplastic resin at least once in a state of a solution in an organic solvent with a filter having a pore diameter of ≤0.5 μm, wherein the thermoplastic resin is obtained by hydrogenating ≥90% of aromatic double bonds in a copolymer comprising a specific constitutional unit composition obtained by polymerizing a monomer composition containing a (meth)acrylic ester monomer and an aromatic vinyl monomer. The optical element uses the resin composition for optical materials. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical element using a resin composition for an optical material containing a thermoplastic transparent resin.

  Transparent thermoplastic resins are widely used for optical elements due to their high moldability, light weight, and mass productivity. Especially for various devices such as cameras, digital cameras, film-integrated cameras (film with lens), video cameras, mobile phone cameras, optical pickup devices such as CD, DVD, MO, OA equipment such as copying machines and printers. For the lenses used, transparent thermoplastic resins such as polymethyl methacrylate (PMMA), polycarbonate (PC), and cyclic polyolefin (COP) have been used so far.

  However, the performance required for resin compositions for optical materials using transparent thermoplastic resins is extremely severe due to the recent demand for high density information recording and high color reproducibility of high-performance optical lenses for imaging. It has become. In a small lens, since optical distortion at the time of molding becomes a major factor that determines the performance as a lens, a material that hardly causes optical anisotropy (birefringence) is required. Further, under long-time laser light irradiation or other light energy irradiation conditions, white turbidity may occur in the lens and optical characteristics may be deteriorated.

  Especially for next-generation high-density optical discs, a blue-violet laser with a wavelength of 405 nm is used. However, even if there is a resin composition for optical materials that can withstand irradiation with low-energy laser light at the time of reading, it is as high as at high-speed writing. The present condition is that the resin composition for optical materials which resists irradiation of the energy laser beam is not known.

  A vinyl alicyclic hydrocarbon resin (see Patent Document 1) is disclosed as a resin that can be used for a blue-violet laser having a wavelength of 405 nm, but it may be insufficient in terms of light resistance. In the accelerated light resistance test under high temperature (for example, at 80 ° C. air), the amount of transmitted light is significantly reduced. In addition, the present inventors obtained a polymer composition containing at least one (meth) acrylic acid ester monomer and at least one aromatic vinyl monomer, and are structural units derived from the aromatic vinyl monomer. The aromatic double bond of the copolymer whose molar ratio (A / B) of the structural unit (A mole) derived from the (meth) acrylate monomer to (B mole) is 1 to 4 is hydrogenated by 70% or more. Although it discloses that the thermoplastic transparent resin obtained shows favorable light resistance (refer patent document 2), higher light resistance was calculated | required practically.

The technology for hydrogenating aromatic rings of styrene resins (hydrogenation of aromatic double bonds) has been known for a long time. Polyvinylcyclohexane obtained from polystyrene has the disadvantage of being inferior in mechanical strength. It is a resin with excellent heat distortion resistance. Due to its excellent transparency and heat distortion resistance, application to optical disk substrates has been studied (see Patent Document 3). In addition, examples in which a resin having a specific monomer composition obtained by hydrogenating an aromatic double bond of an MS resin obtained by copolymerization of methyl methacrylate and styrene is applied to optical disc use and plastic lens use are also disclosed (patents). Reference 4 and Patent Document 5). However, a resin obtained by hydrogenating an aromatic double bond of an MS resin (MMA constituent unit / styrene constituent unit = 0.92 or less) having a low MMA copolymerization rate disclosed in them does not necessarily have sufficient mechanical strength. In the case of plastic lenses, etc., there are cases where the practical performance is not satisfied in terms of mechanical properties. In addition, since it contains 50% or more of the vinylcyclohexane repeating units, it contains a lot of tertiary carbon that is easily deteriorated by light and heat, so it deteriorates under irradiation of a blue-violet laser with a wavelength of 405 nm at high temperatures. Could happen.
JP 2001-272501 A JP 2006-89713 A Japanese Patent Laid-Open No. 63-43910 JP-A-6-25326 JP-A-4-75001

  An object of the present invention is to provide a resin composition for an optical material containing a thermoplastic transparent resin excellent in transparency, low birefringence and light resistance required for the resin composition for an optical material described above. To do. Another object of the present invention is to provide an optical element used for transmitting a laser having a wavelength of 405 nm band to a molded body made of this optical material resin composition, and further an optical element which is a member of an optical pickup device.

  As a result of intensive studies in view of the above circumstances, the present inventors have obtained a copolymer comprising a specific constituent unit composition obtained by polymerizing a monomer composition containing a (meth) acrylic acid ester monomer and an aromatic vinyl monomer. Thermoplastic transparent resin produced by filtering a thermoplastic resin obtained by hydrogenating 90% or more of aromatic double bonds at least once with a filter having a pore size of 0.5 μm or less in a state dissolved in an organic solvent. By using a resin composition for an optical material containing an optical element, it was found that an optical element having good light resistance to a laser having a wavelength of 405 nm band can be obtained, and the present invention has been achieved.

  That is, the present invention is obtained by polymerizing a monomer composition containing at least one (meth) acrylic acid ester monomer and at least one aromatic vinyl monomer, and is a structural unit derived from an aromatic vinyl monomer (B Obtained by hydrogenating 90% or more of the aromatic double bond of the copolymer whose molar ratio (A / B) of the structural unit (A mole) derived from the (meth) acrylic acid ester monomer to (mol) is 1 to 4. A resin composition for an optical material comprising a thermoplastic transparent resin, wherein the thermoplastic transparent resin is at least once filtered by a filter having a pore size of 0.5 μm or less in a state dissolved in an organic solvent. It relates to a resin composition for optical materials.

  Moreover, this invention is an optical element used for the use which permeate | transmits the laser of wavelength 405nm band to the molded object obtained from this resin composition for optical materials. Furthermore, an optical element which is a member of an optical pickup device using a laser having a wavelength of 405 nm band is provided.

  The thermoplastic transparent resin obtained by the present invention is particularly excellent in light resistance and low birefringence. In addition, it is resistant to oxidative degradation, and when molding an optical material resin composition containing the thermoplastic transparent resin, it is possible to produce a molded body such as an optical element with few molding defects and excellent color tone. Furthermore, since the balance of transparency, heat distortion resistance, mechanical properties, low water absorption, etc. is excellent, a high-quality optical element can be manufactured.

  Specific examples of (meth) acrylate monomers used in the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate, and (meth) acrylic. (Meth) acrylate alkyls such as stearyl acid, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate; (meth) acrylic acid (2-hydroxyethyl) and (meth) acrylic acid (2-hydroxypropyl), (Meth) acrylic acid hydroxyalkyls such as (meth) acrylic acid (2-hydroxy-2-methylpropyl); (meth) acrylic acid (2-methoxyethyl), (meth) acrylic acid (2-ethoxyethyl), etc. (Meth) acrylic acid alkoxyalkyls; benzyl (meth) acrylate and (meth) acrylic (Meth) acrylic acid esters having an aromatic ring such as phenyl acid; and (meth) acrylic acid esters having a phospholipid-like functional group such as 2- (meth) acryloyloxyethyl phosphorylcholine, etc. From the balance of physical properties, it is preferable to use alkyl methacrylate alone or to use alkyl methacrylate and alkyl acrylate together. Furthermore, it is preferable to use methyl methacrylate 80-100 mol% and alkyl acrylate 0-20 mol%. Of the alkyl acrylates, methyl acrylate or ethyl acrylate is particularly preferred. In the present invention, (meth) acrylic acid refers to methacrylic acid and / or acrylic acid. These may be used alone or in combination of two or more.

  Specific examples of the aromatic vinyl monomer used in the present invention include aromatic vinyl compounds such as styrene, α-methylstyrene, p-hydroxystyrene, alkoxystyrene, and chlorostyrene, and styrene is preferably used. . These may be used alone or in combination of two or more.

  A known method can be used for the polymerization of the (meth) acrylic acid ester monomer and the aromatic vinyl monomer, but industrially, a method based on radical polymerization may be simple. For the radical polymerization, a known method such as a bulk polymerization method, a solution polymerization method, an emulsion polymerization method or a suspension polymerization method can be appropriately selected. For example, the bulk polymerization method and the solution polymerization are performed by a continuous polymerization method in which a monomer composition containing a monomer, a chain transfer agent, and a polymerization initiator is continuously fed to a complete mixing tank and polymerized at 100 to 180 ° C. . In the solution polymerization method, hydrocarbon solvents such as toluene, xylene, cyclohexane and methylcyclohexane; ester solvents such as ethyl acetate; ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as tetrahydrofuran and dioxane; methanol and isopropanol A solvent such as an alcohol solvent is fed to the polymerization tank together with the monomer composition. After the polymerization, the reaction solution can be extracted from the polymerization tank, and the volatile matter can be removed with an extruder or a vacuum tank to obtain a copolymer.

  In the case of a methacrylic copolymer, the constituent unit ratio of the copolymer does not necessarily coincide with the charged monomer ratio, and is determined by the amount of monomer actually incorporated into the copolymer by the polymerization reaction. The constitutional unit ratio of the copolymer is the same as the charged monomer ratio when the polymerization conversion rate of the monomer is 100%, but in fact, it is often produced at a polymerization conversion rate of 50 to 80% and is highly reactive. Since the monomer is more easily incorporated into the polymer, there is a difference between the monomer charging ratio and the constituent unit ratio of the copolymer. For this reason, it is necessary to appropriately adjust the charged monomer ratio to obtain a desired constituent unit ratio.

  The constituent unit molar ratio ((meth) acrylic acid ester monomer unit / aromatic vinyl monomer unit = A / B) of the copolymer used for the hydrogenation reaction in the present invention is 1 to 4. If it is less than 1, the mechanical strength is inferior and may not be practically used. If it exceeds 4, warpage and dimensional change of the molded article due to water absorption cannot be ignored, which is not preferable as a resin composition for optical materials. The structural unit molar ratio (A / B) is preferably from 1 to 2.5, more preferably from 1 to 2, from the viewpoint of balance of physical properties.

  The copolymer is dissolved in a suitable solvent to perform a hydrogenation reaction. The hydrogenation reaction solvent and the polymerization solvent may be the same or different. As the hydrogenation reaction solvent, a solvent that has a high solubility in the copolymer and hydrogen before and after the hydrogenation reaction and is inert to the hydrogenation reaction is preferable. For example, hydrocarbon solvents such as cyclohexane and methylcyclohexane; ester solvents such as ethyl acetate; ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as tetrahydrofuran and dioxane; alcohol solvents such as methanol and isopropanol are used. . These may be used alone or in combination.

  The hydrogenation reaction is preferably performed at a hydrogen pressure of 3 to 30 MPa and a reaction temperature of 60 to 250 ° C. using a known method such as a batch reaction or a continuous flow reaction. If the reaction temperature is too low, the reaction does not proceed easily. If the reaction temperature is too high, the molecular weight may be reduced due to cleavage of the molecular chain, or the ester moiety may be hydrogenated. In order to prevent molecular weight reduction due to molecular chain scission and allow the reaction to proceed smoothly, the temperature, hydrogen pressure, etc., depend on the type of catalyst used, the concentration in the reaction system, the concentration of the copolymer in the reaction system, the molecular weight, etc. Is preferably selected as appropriate.

  A known hydrogenation catalyst can be used for the hydrogenation reaction. Specifically, metals such as nickel, palladium, platinum, cobalt, ruthenium and rhodium, or compounds such as oxides, salts and complexes of such metals are used as porous carriers such as carbon, alumina, silica, silica / alumina, and diatomaceous earth. Examples include a supported solid catalyst. Among these, a catalyst in which nickel, palladium, or platinum is supported on carbon, alumina, silica, silica / alumina, or diatomaceous earth is preferably used. The supported amount is preferably 0.1 to 30 wt% of the carrier.

  The hydrogenation rate is 90% or more of the total aromatic double bonds, preferably 95% or more, more preferably 98% or more (including 100%). If it is less than 90%, light resistance may be insufficient, for example, whitening is observed when a laser having a wavelength of 405 nm is irradiated.

  In the thermoplastic transparent resin described above, a known additive is blended within a range that does not impair the characteristics to obtain a resin composition for optical materials. Examples of additives include antioxidants such as phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, benzophenone UV absorbers, benzotriazole UV absorbers, benzoate UV absorbers, and salicylic acid UV absorbers such as UV absorbers, acrylate UV absorbers, metal complex UV absorbers, light stabilizers such as hindered amine light stabilizers, antistatic agents such as alkyl sulfonates and glycerol esters of stearic acid, fats Release agents or lubricants such as aromatic alcohols, aliphatic esters, aromatic esters, triglycerides, fluorine surfactants, higher fatty acid metal salts, phosphate triester compounds, phthalate esters, fatty acid monobasic esters Compounds, dihydric alcohol ester compounds, oxyacid esters Compounds, paraffinic compounds, and the like plasticizers such liquid polymer compound. Moreover, you may add the soft polymer, alcoholic compound, etc. which are known to be effective in whitening prevention. These additives may be used alone or in combination with one another, and may be used in combination of two or more.

  The addition amount of the additive is not particularly limited, but is usually 0.0001 to 5.0 parts by weight, preferably 0.001 to 1.0 parts by weight, more preferably 0.01 to 0.00 parts by weight per 100 parts by weight of the polymer. It is in the range of 5 parts by weight and may be appropriately selected according to the purpose. The method of adding the additive is not particularly limited. For example, in the process of producing a polymer using an organic solvent, the additive is added to a solution in which the polymer is dissolved in the organic solvent, and the solvent is removed by blending in the liquid. The method of doing is mentioned. It may be added before the filtration step described later, or may be passed on after filtration. A method of dry blending the polymer after the solvent has been removed is also preferred because it is convenient.

The resin composition for an optical material containing the thermoplastic transparent resin of the present invention preferably contains as few foreign particles as possible. The foreign substances are substances that are not compatible with the resin, such as impurities mixed from the outside, catalyst residues, gelled products, side reaction products, and the like mixed in the polymer production process. Except for the case where a light diffusing agent is added and the transmitted light is intentionally scattered to be used, in applications that do not use scattered light, a large number of foreign particles is not preferable because the loss of transmitted light increases. Moreover, the deterioration with respect to light is suppressed, so that the quantity of a foreign material particle is small. The particle size of the foreign material can be measured using a light scattering fine particle detector or the like, but it is preferable that the thermoplastic transparent resin does not substantially contain foreign material particles having a particle size of 1 μm or more. The content of foreign particles having a particle size of 0.5 μm or more and less than 1 μm is preferably 3 × 10 ⁴ particles / g or less, and more preferably 2 × 10 ⁴ particles / g or less. In particular, when high transparency is required, the content of foreign particles having a particle size of 0.5 μm or more and less than 1 μm is preferably 5 × 10 ³ particles / g or less. In the present invention, as a method for reducing the content of foreign particles, in the thermoplastic transparent resin production process, a solution containing a polymer is at least 1 with a filter having a pore size of 0.5 μm or less, preferably 0.2 μm or less. Use a method of filtering more than once.

  Filters used include PTFE membrane filters (PTI Proflow, Nippon Pole Enflon, etc.), polypropylene depth filters (PTI Polyflow, etc.), polyethersulfone membrane filters (PTI Clariflow, etc.) ), Sintered metal filters, SUS random fiber type filters, cellulose potential adsorption filters, etc., all of which have a pore diameter of 0.5 μm or less, and at least once with a membrane filter. Can effectively eliminate foreign particles. In order to reduce the load applied to the filter, it is preferable to install a coarse filter having a size of about 1 μm to 10 μm upstream of the filter.

  The step of performing filtration may be performed at any timing, but it is preferable to perform the step in the step before concentrating the reaction liquid from which the catalyst has been removed after the hydrogenation reaction because the viscosity is low and the processing amount increases. Moreover, when pelletizing by devolatilization extrusion, it is also effective to install a heat resistant filter immediately before the extruder.

  In addition, the content of foreign particles is reduced by performing the process exposed to the atmosphere in a clean environment as much as possible, such as the process of cooling the strand melted and discharged from the extruder, the pelletizing process, and the process of introducing pellets into the injection molding machine. be able to. It is preferable to perform at least one of these steps in an environment having a cleanliness of class 5 or higher as defined by ISO 14644-1.

  The resin composition for an optical material containing the thermoplastic transparent resin of the present invention can be processed into a desired shape by heating and melting. The molding can be performed by a known injection molding method, extrusion molding method, hot press molding method, or the like. Among them, injection molding is more commonly used for optical elements because of its productivity. The cylinder temperature at the time of injection molding is preferably 220 to 320 ° C, more preferably 230 to 300 ° C. More preferably, it is 240 degreeC-290 degreeC. If the cylinder temperature is too high, the resin may be decomposed or deteriorated, resulting in reduced strength characteristics or coloring. If it is too low, residual stress will be generated in the molded product, resulting in increased birefringence, cavity shape, etc. The transferability of the ink may deteriorate. The mold temperature is preferably 50 to 180 ° C, more preferably 80 to 150 ° C. If the mold temperature is too high, mold release failure occurs, and the molding cycle becomes longer, resulting in poor productivity. If it is too low, the birefringence becomes large or the transferability becomes poor. The injection pressure is preferably 30 to 200 MPa, more preferably 60 to 150 MPa. The pressure holding time is preferably 1 to 300 seconds, more preferably 5 to 150 seconds. If the pressure holding time is too long, decomposition or deterioration of the resin occurs, and if it is too short, molding shrinkage increases. The cooling time is preferably 5 to 300 seconds, more preferably 10 to 150 seconds. If the cooling time is too long, the productivity decreases, and if it is too short, the birefringence increases or the transferability deteriorates. When the molding conditions are in the above range, the mechanical strength, birefringence, releasability, transferability, productivity, etc. of the optical element are balanced. Since the thermoplastic transparent resin of the present invention is excellent in thermal decomposition resistance, it is possible to produce a molded article having excellent color tone with few molding defects due to thermal degradation or the like by any method.

  Specific applications of the molded product include various light guide plates, various light guides, optical fibers, lenses, prisms, optical filters, optical films, and other optical elements that transmit light, particularly wavelengths. Since the light resistance of the 405 nm band laser light is also good, it is most suitable for use in which it is transmitted. In the injection molding, an arbitrary shape can be formed depending on the shape in the cavity of the mold, but a functional surface such as a diffraction grating, a prism, or a low reflection processing can be formed on the surface of the optical element. Specific examples of applications include pickup objective lenses, collimating lenses, cylindrical lenses, achromatic lenses, beam expanders, receiver lenses, and optical elements such as optical filters, beam splitters, half mirrors, optical fibers, and diffraction gratings. And is useful as a member of an optical pickup device using these optical elements.

  Generally, birefringence occurs in an optical element manufactured by injection molding because stress during molding remains. If a plastic lens or the like having a large birefringence is used in an optical pickup device, the spot shape is deformed into an elliptical shape, and recording and reproduction of the optical information recording medium cannot be performed satisfactorily. Since the molded body obtained from the resin composition for optical materials containing the thermoplastic transparent resin used in the present invention has a small birefringence, the optical element is used for applications that need to transmit polarized light regardless of the molding means and shape. Is optimal. There are a liquid crystal display member, an optical information recording member, and the like as a member for the purpose of transmitting polarized light, and it can be particularly preferably used as a member of an optical pickup device.

  An optical pickup device using a laser with a wavelength of 405 nm band is used for next-generation high-density optical discs. There are various types, and all optical pickup devices are required to be compatible with conventional DVDs and CDs. In order to solve this, a method of using two objective lenses by switching at the used wavelength, or a method of correcting aberrations by utilizing the action of refraction and diffraction by shaping a sawtooth diffraction structure on the lens surface. A method using a movable collimator lens is disclosed. The fine structure exhibiting the diffractive action may be applied to the objective lens or may be applied to the collimator lens. That is, glass is often used as a material for optical elements used in optical pickup devices that use lasers having a wavelength of 405 nm band because of the problem of light resistance, but has such a complicated shape and fine surface structure. It is practically meaningful to produce an optical material resin composition containing the thermoplastic transparent resin used in the present invention by injection molding.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples. In addition, the evaluation method of the resin composition for optical materials containing a thermoplastic transparent resin and a fat thermoplastic transparent resin is as follows.

Evaluation method (1) Molar ratio of structural units in copolymer
^It calculated from the measured value of ¹ H-NMR (400 MHz: CDCl ₃ ).
(2) Hydrogenation rate It calculated | required by the decreasing rate of absorption of wavelength 260nm in the UV spectrum measurement before and behind hydrogenation reaction. From the absorbance A _{1 at} the concentration C ₁ of the resin before the hydrogenation reaction and the absorbance A _{2 at} the concentration C ₂ of the resin after the hydrogenation reaction, it was calculated from the following equation.
Hydrogenation rate = 100 × [1- (A ₂ × C ₁ ) / (A ₁ × C ₂ )]
(3) Glass transition temperature (Tg)
Using a DSC220 type differential scanning calorimetry (DSC) apparatus manufactured by Seiko Denshi Kogyo Co., Ltd., the resin amount was 10 mg, 10 ° C./min. The measurement was performed under the conditions described above, and the midpoint method was used.
(4) Bending test (bending strength, flexural modulus)
A 126 × 12 × 3.2 (mm) rectangular parallelepiped test piece obtained by injection molding was annealed for 16 hours at a temperature 20 ° C. lower than Tg, respectively, and conditioned at 23 ° C. and 50 RH for 88 hours or more. went. The bending strength and flexural modulus were measured according to JIS K7203.
(5) Measurement of the amount of minute foreign matter The sample prepared by the following method was measured with a HIAC ROYCO SYSTEM 8011 manufactured by Particle Scientific Instruments, and the amount of minute foreign matter of 0.5 μm or more and less than 1.0 μm was counted. . As a method for preparing the measurement sample, the obtained pellet of the resin composition for optical material was filtered in advance with ultrasonic cleaning with isopropyl alcohol from which foreign matters had been removed, the surface deposits were removed, and the resulting washed pellets were preliminarily foreign matter. A 5 wt% solution was prepared by dissolving in toluene from which the water was removed.
(6) Measurement of birefringence A disk-shaped flat plate having a thickness of 50 mmφ and a thickness of 3.2 mm was molded using an AUTOSHOT 100B manufactured by FANUC, an injection molding machine. The cylinder temperature is 230 ° C. The mold temperature was set to 20 ° C. lower than Tg, and the cooling time was 15 seconds. The phase difference of the central part of the disc-shaped flat plate obtained by appropriately determining the measurement value, the holding pressure, and the holding time so that there is no sink on the molded piece was measured with an ellipsometer M-220 manufactured by JASCO. The measurement wavelengths used were three wavelengths of 405 nm, 650 nm, and 780 nm.
(7) Initial light transmittance at a wavelength of 405 nm A 3.2 mm thick flat plate was measured by a transmission method using an ultraviolet-visible spectrophotometer UV-3100PC manufactured by Shimadzu Corporation.
(8) Light resistance of 405 nm wavelength laser A 3.2 mm-thick thermoplastic resin plate obtained by injection molding is placed in an oven at 80 ° C. under air, a beam diameter of 4.8 mmφ, and an energy density of 500 mW / cm ^2. A laser beam having a wavelength of 405 nm band adjusted to become was irradiated. Measure the light transmittance of the laser light irradiated part with an ultraviolet-visible spectrophotometer with a modified beam stop so that the measurement can be focused on a site of about 2 mmφ, and the time-dependent change in the light transmittance at a wavelength of 405 nm Tracked. The irradiation time when the transmittance of light having a wavelength of 405 nm was reduced by 0.5% was recorded, and light resistance was evaluated. Irradiation time showing light resistance was evaluated as ◯ for 300 hours or more, less than 300 hours, Δ for 150 hours or more, and x for less than 150 hours.
(9) Transferability of plastic lens The injection-molded plastic lens was observed with an optical microscope, and defectives such as sink marks, surface dents, and roughness were regarded as defective. Of the 100 plastic lenses produced, A was assigned when there was no defective product, B was assigned when there were 1 to 10 defective products, and C was assigned when there were 11 or more defective products.
(10) Light resistance of a 405 nm wavelength laser of a plastic lens An injection molded plastic lens is placed in an oven at 80 ° C. in the air, and a laser beam having a wavelength of 405 nm is adjusted for an energy density of 500 mW / cm ² for 300 hours. Irradiated. After a predetermined time, the sample was observed visually and with an optical microscope. A sample without whitening or roughening of the surface of the irradiated portion was indicated by ◯, a symbol showing a change was indicated by Δ, and a change was confirmed by ×.

Example 1
A monomer composition comprising 59.9 mol% methyl methacrylate and 39.9 mol% styrene as monomer components and 2.1 × 10 ⁻³ mol% t-amylperoxy 2-ethylhexanoate as a polymerization initiator Then, the mixture was continuously fed at a rate of 1 kg / hour to a 10 liter complete mixing tank with a helical ribbon blade, and continuous polymerization was carried out at an average residence time of 2.5 hours and a polymerization temperature of 150 ° C.

The polymerization liquid is drawn out from the bottom with a gear pump so that the polymerization tank liquid level is constant, and while maintaining at 150 ° C., it is introduced into an extruder equipped with a vent port to devolatilize and extrude into a strand, Cutting into pellets (resin A). At this time, the molar ratio (A / B) of the structural units in the copolymer was 1.5.
In addition, 16.4 mg of Resin A was dissolved in 15 mL of chloroform, and the measured absorbance at a wavelength of 260 nm was 1.093.

  Resin A was dissolved in dioxane to prepare a 10 wt% dioxane solution. A 1000 mL autoclave was charged with 500 parts by weight of a 10 wt% dioxane solution and 1 part by weight of 10 wt% Pd / C (manufactured by NE Chemcat), and the hydrogenation reaction was carried out by maintaining the hydrogen pressure at 10 MPa at 200 ° C. for 15 hours. After removing the catalyst with a filter, dioxane was distilled off by heating to concentrate the reaction solution to 50 wt%. Dilution to 10 wt% with toluene was repeated to replace the solvent to obtain a 50 wt% toluene solution.

  Absorbance at a wavelength of 260 nm measured by dissolving 62.5 mg of the resin obtained by precipitation purification in methanol from a part of the obtained resin liquid and 5 mL of chloroform was 0.521. From the absorbance of the resin A at a wavelength of 260 nm and the concentration of the measurement sample, the hydrogenation rate was calculated to be 96%.

  The 50 wt% toluene solution was again diluted with toluene to 10 wt%, and octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate was added in an amount of 0.05 parts by weight to 100 parts by weight of resin. -(2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol in an amount of 0.01 parts by weight, bis (1,2,2, 6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate is added in an amount of 0.02 parts by weight based on 100 parts by weight of the resin. did.

  The composition was filtered through two cartridge-type filter housings connected in series with a gear pump. A PP depth filter (PTI Polyflow pore diameter 5 μm) was used as the first prefilter, and a PTFE membrane filter (PTI Proflow II pore diameter 0.45 μm) was used as the second finish filter. The filtered resin solution was heated in a tank, and further introduced into an extruder equipped with a vent port by a gear pump to devolatilize volatile components and extruded into a strand shape. This was cut with a pelletizer installed in a clean booth to obtain pellets of a resin composition for an optical material containing a thermoplastic transparent resin (Composition A1).

  Various test pieces were produced at a cylinder temperature of 260 ° C. by using an injection molding machine (FANUC AUTOSHOT 100B) using the composition A1, and the glass transition temperature, bending strength, bending elastic modulus, minute foreign matter amount, wavelength 405 nm, 650 nm, The amount of birefringence (phase difference) at 780 nm, the initial light transmittance at a wavelength of 405 nm, and the light resistance of a laser with a wavelength of 405 nm were evaluated. The results are shown in Table 1.

Example 2
A copolymer was synthesized in the same manner as in Production Example 1 except that 80.0 mol% methyl methacrylate and 19.8 mol% styrene were used as monomer components (Resin B). The molar ratio (A / B) of the structural units in the copolymer was 4.0.

  A resin composition for an optical material containing a thermoplastic transparent resin was obtained by a hydrogenation reaction in the same manner as in Example 1 except that the resin B was used (composition B1). The hydrogenation rate was 100%. Using composition B, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of fine foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 1.

Example 3
A copolymer was synthesized in the same manner as in Example 1 except that 50.7 mol% methyl methacrylate, 9.3 mol% methyl acrylate, and 39.8 mol% styrene were used as the monomer components (Resin C). The molar ratio (A / B) of the structural units in the copolymer was 1.6.

A resin composition for an optical material containing a thermoplastic transparent resin was obtained by a hydrogenation reaction in the same manner as in Example 1 except that the resin C was used (composition C1). The hydrogenation rate was 97%. Using composition C1, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of fine foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 1.
Example 4
A copolymer was synthesized in the same manner as in Example 1 except that 51.3 mol% methyl methacrylate and 48.7 mol% styrene were used as monomer components (Resin D). The molar ratio (A / B) of the structural units in the copolymer was 1.1.

  A resin composition for an optical material containing a thermoplastic transparent resin was obtained by a hydrogenation reaction in the same manner as in Example 1 except that the resin D was used (composition D1). The hydrogenation rate was 98%. Using composition D1, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of fine foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 1.

Comparative Example 1
A resin composition for an optical material containing a thermoplastic transparent resin having a different hydrogenation rate (72% hydrogenation rate, composition A2) in the same manner as in Example 1 except that the hydrogenation reaction time of the resin A was reduced to 10 hours. ) Using composition A2, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of fine foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 2.

Comparative Example 2
Resin composition for optical materials containing a thermoplastic transparent resin having a different hydrogenation rate (hydrogenation rate: 76%, composition) in the same manner as in Example 1 except that the time for the hydrogenation reaction of resin B was shortened to 3 hours B2) was obtained. Using composition B2, in the same manner as in Production Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of fine foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 2.

Comparative Example 3
A resin composition for an optical material containing a thermoplastic transparent resin having a different hydrogenation rate (hydrogenation rate: 72%, composition C2) in the same manner as in Example 1 except that the hydrogenation reaction time of the resin C was shortened to 3 hours. ) Using composition C2, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of minute foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 2.

Comparative Example 4
Resin composition for optical material containing a thermoplastic transparent resin having a different hydrogenation rate (hydrogenation rate: 70%, composition D2) in the same manner as in Example 1 except that the hydrogenation reaction time of resin D was reduced to 8 hours. ) Using composition D2, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of minute foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 2.

Comparative Example 5
A copolymer was synthesized in the same manner as in Example 1 except that 20.4 mol% of methyl methacrylate and 79.4 mol% of styrene were used as monomer components (Resin E). The molar ratio (A / B) of the structural units in the copolymer was 0.25.

  A resin composition for an optical material containing a thermoplastic transparent resin was obtained by a hydrogenation reaction in the same manner as in Example 1 except that the resin E was used (composition E1). The hydrogenation rate was 95%. Using composition E1, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of fine foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 2.

Comparative Example 6
In Example 1, a resin composition for an optical material containing a thermoplastic transparent resin was produced in the same manner as in Example 1 except that the composition in a solution state was produced without filtration through a filter. (Composition A3). Using composition A3, in the same manner as in Example 1, glass transition temperature, bending strength, bending elastic modulus, amount of minute foreign matter, birefringence amount (phase difference) at wavelengths of 405 nm, 650 nm, and 780 nm, initial ray at wavelength of 405 nm The transmittance and the light resistance of a 405 nm wavelength laser were evaluated. The results are shown in Table 2.

Example 5 Molding of Plastic Lens Using the resin composition for optical materials produced in Example 1, an injection molding machine (manufactured by FANUC, AUTOSHOOT 100B) was used to form a pickup lens at a resin temperature of 260 ° C. and a mold temperature of 100 ° C. Molded. The obtained lens was placed between two orthogonal polarizing plates and observed on a surface light source, but almost no unevenness or light loss due to birefringence was observed. The transferability of the shape inside the cavity was also good, and the light resistance was also good. The results of evaluation of transferability and light resistance are shown in Table 3.

Example 6
A pickup lens was molded in the same manner as in Example 5 by using the optical material resin composition prepared in Example 2. The obtained lens was placed between two orthogonal polarizing plates and observed on a surface light source, but almost no unevenness or light loss due to birefringence was observed. The transferability of the shape inside the cavity was also good, and the light resistance was also good. The results of evaluation of transferability and light resistance are shown in Table 3.

Example 7
A pickup lens was molded in the same manner as in Example 5 by using the optical material resin composition prepared in Example 3. The obtained lens was placed between two orthogonal polarizing plates and observed on a surface light source, but almost no unevenness or light loss due to birefringence was observed. The transferability of the shape inside the cavity was also good, and the light resistance was also good. The results of evaluation of transferability and light resistance are shown in Table 3.

Example 8
A pickup lens was molded in the same manner as in Example 5 using the optical material resin composition prepared in Example 4. The obtained lens was placed between two orthogonal polarizing plates and observed on a surface light source, but almost no unevenness or light loss due to birefringence was observed. The transferability of the shape inside the cavity was also good, and the light resistance was also good. The results of evaluation of transferability and light resistance are shown in Table 3.

Claims (4)

It is obtained by polymerizing a monomer composition containing at least one (meth) acrylic acid ester monomer and at least one aromatic vinyl monomer, and (meth) with respect to the structural unit (B mole) derived from the aromatic vinyl monomer. ) Thermoplastic transparent resin obtained by hydrogenating 90% or more of the aromatic double bond of the copolymer whose molar ratio (A / B) of the structural unit (A mole) derived from the acrylate monomer is 1-4. A resin composition for an optical material comprising the thermoplastic transparent resin that has been filtered at least once with a filter having a pore size of 0.5 μm or less in a state dissolved in an organic solvent. Resin composition. The optical element formed by shape | molding the resin composition for optical materials of Claim 1. The optical element according to claim 2, wherein the optical element is used by transmitting at least a laser beam having a wavelength of 405 nm. The optical element according to claim 3, wherein the optical element is a member incorporated in the optical pickup device.