JP2007070564A - Thermoplastic resin composition and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element having a small rate of refractive index change caused by temperature and a small coefficient of thermal expansion. <P>SOLUTION: An object lens 7 as the optical element is formed by using a thermoplastic resin composition, the thermoplastic resin composition is a melt-moldable thermoplastic resin composition obtained by dispersing inorganic particulates in a thermoplastic resin having a refractive index n0, and, when the refractive index of the inorganic particulates is np and the rate of thermal change of the refractive index of the inorganic particulates is dnp/dT, the dnp/dT and volume fraction Φ of the inorganic particulates in the thermoplastic resin composition at 23°C satisfy (A): dnp/dT≥0.00012×(np-n0+0.25)<SP>2</SP>-0.000025, and (B): 0.25≤Φ≤0.5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is suitably used as a lens, a filter, a grating, an optical fiber, a flat optical waveguide, etc., has a small change in refractive index due to temperature, and has excellent transparency and an optical element using the same About.

  Information equipment such as a player, a recorder, and a drive for reading and recording information on an optical information recording medium (hereinafter also simply referred to as a medium) such as MO, CD, and DVD is provided with an optical pickup device. The optical pickup device includes an optical element unit that irradiates a medium with light having a predetermined wavelength emitted from a light source, and receives the reflected light with a light receiving element. The optical element unit receives the light from a reflection layer or a light receiving medium of the medium. An optical element such as a lens for condensing light by the element is included.

  The optical element of the optical pickup device is preferably made of plastic as a material in that it can be manufactured at low cost by means such as injection molding. As a plastic applicable to an optical element, a copolymer of a cyclic olefin and an α-olefin (for example, Patent Document 1) is known.

  An optical element unit using plastic as a material is required to be a substance having optical stability such as a glass lens. For example, an optical plastic material such as a cyclic olefin has an extremely low water absorption as compared with PMMA that has been used as a conventional plastic for lenses, and the change in refractive index due to water absorption is greatly improved. However, the temperature dependence of the optical properties has not yet been solved, and the temperature dependence of the refractive index is currently one order of magnitude greater than that of inorganic glass.

As one method for improving the disadvantages of the optical plastic material as described above, a method using a fine particle filler has been proposed. For example, in Patent Documents 2 to 8, as a method for reducing the temperature dependency of refractive index | dn / dT |, fine particles having dn / dT> 0 are contained in a polymeric host material having dn / dT <0. Dispersed optical products have been proposed. In Patent Documents 2 to 8, the mass% of fine particles required to reduce the dn / dT of the composite in which fine particles are dispersed by 50% compared to the host resin is based on the following formula (1). It is described that it can be calculated (for example, Formula 2 of Patent Document 2).
ν ₅₀ = 0.5 (γ _p / γ _p −γ _n ) (1)

Here, the mass% of fine particles required to reduce dn / dT by 50% is ν ₅₀ × 100%, and γ _p and γ _n represent dn / dT of the host resin and fine particles, respectively.

  However, in recent years, it has been confirmed that the dielectric constant of a composite in which inorganic fine particles are dispersed in a polymer agrees well with the value calculated by the following equation (2) derived by Maxwell-Garnett (for example, non- Patent Document 1).

  According to the above formula (2), it is the volume fraction of the inorganic fine particles that dominates the optical properties of the composite. The dn / dT of the substance is closely related to the linear expansion coefficient α, and as far as the polymer is concerned, it is said that the following formula (3) derived from the Lorentz-Lorentz formula holds (Non-patent Document 2). .

Here, n represents the refractive index of the polymer, and ρ represents the density of the polymer. It is known that the thermal expansion coefficient of the composite also changes depending on the volume fraction of the inorganic fine particles (for example, Non-Patent Document 3).
JP 2002-105131 A (page 4) JP 2002-207101 A (Claims) JP 2002-240901 A (Claims) JP 2002-241560 A (Claims) Japanese Patent Laid-Open No. 2002-241469 (Claims) Japanese Patent Laid-Open No. 2002-241592 (Claims) JP 2002-241612 A (Claims) JP 2002-303701 A (Claims) H. Mataki, et al., Jpn. J. Appl. Phys. 43 (8B), 5819 (2004) Koike Yasuhiro, edited by the Society of Polymer Science, Polymer Science OnePoint “Polymer Optical Properties”, Kyoritsu Shuppan, p. 10 LENielsen, “Mechanical properties of polymers and composites”, Kagaku Dojin, P267-268

From these facts, it is the volume fraction of the inorganic fine particles that controls the dn / dT of the composite, and the inventor of the present invention has obtained the mass% of inorganic determined by the formula (4) described in Patent Documents 2 to 8. Even if the fine particles are added to the host resin by the methods described in Patent Documents 2 to 8, not only dn / dT can be reduced by 50%, but also the dn / dT reduction effect necessary for practical use can be obtained. Confirmed that there is no.
This invention is made | formed in view of the said subject, The objective is to provide the thermoplastic resin composition and optical element with a small rate of change of the refractive index by temperature, and a small thermal expansion coefficient.

In order to solve the above problems, the first invention
A thermoplastic resin composition capable of melt molding in which inorganic fine particles are dispersed in a thermoplastic resin having a refractive index of n0,
Condition where the refractive index temperature change rate dnp / dT of the inorganic fine particles is defined by the following formula (A), where np is the refractive index of the inorganic fine particles and dnp / dT is the temperature change rate of the refractive index of the inorganic fine particles. And the volume fraction Φ of the inorganic fine particles in the thermoplastic resin composition satisfies the condition defined by the following formula (B) at 23 ° C.
dnp / dT ≧ 0.00012 × (np−n0 + 0.25) ² −0.000025 (A)
0.25 ≦ Φ ≦ 0.5 (B)

In the thermoplastic resin composition according to the first invention,
It is preferable that the temperature change rate dnp / dT of the refractive index of the inorganic fine particles satisfies the condition defined by the following formula (C).
dnp / dT ≧ 0.00031 × (np−n0 + 0.25) ² −0.000025 (C)

In the thermoplastic resin composition according to the first invention,
The primary particle diameter of the inorganic fine particles is preferably 30 nm or less.

The second invention is
An optical element formed by using the thermoplastic resin composition according to the first invention.

  According to the first and second inventions, it is possible to provide a thermoplastic resin composition and an optical element that have a small refractive index change rate due to temperature and a small coefficient of thermal expansion (see Examples below).

Hereinafter, the best mode for carrying out the present invention will be described in detail.
As a result of intensive studies in view of the above problems, the present inventor has found that the refractive index of the inorganic fine particles is np in the thermoplastic resin composition in which the inorganic fine particles are dispersed in the thermoplastic resin, and the refractive index of the thermoplastic resin. Is n0, and the temperature change rate of the refractive index of the inorganic fine particles is dnp / dT, when the condition defined by the following formula (A) or (C) is satisfied, the | dn of the thermoplastic resin composition It has been found that / dT | can be reduced, and has reached the present invention. If the thermoplastic resin composition does not satisfy the following formulas (A) and (C), unless the amount of inorganic fine particles added is greater than the upper limit (0.5 in terms of volume fraction) that could be practically added. It has been found that the object of the present invention cannot be achieved.

dnp / dT ≧ 0.00012 × (np−n0 + 0.25) ² −0.000025 (A)
dnp / dT ≧ 0.00031 × (np−n0 + 0.25) ² −0.000025 (C)

In addition, in the thermoplastic resin composition that satisfies the conditions specified by the above formula (A) or (C), the inventor satisfies the conditions specified by the following formula (B) when the volume fraction Φ of the inorganic fine particles is satisfied. Further, it has been found that a dn / dT reduction effect that is more effective in practical use can be obtained.
0.25 ≦ Φ ≦ 0.5 (B)

  The dn / dT of the thermoplastic resin composition in which the inorganic fine particles are dispersed in the thermoplastic resin is, as can be seen from the above formula (2), the refractive index and dn / dT of the inorganic fine particles, the refractive index and dn of the matrix resin. / DT, which is considered to change depending on the volume fraction of the inorganic fine particles, but further changes in the coefficient of thermal expansion of the matrix resin due to the dispersion of the inorganic fine particles (nanofiller effect), and the coefficient of thermal expansion between the inorganic fine particles and the matrix resin The behavior of the volume fraction due to the difference of the temperature is complicated, and the behavior is complicated. The present inventor examines in detail the effect of such nanofiller effect and temperature change of the volume fraction, clarifies conditions for achieving the object of the present invention, and as soon as the present invention has been achieved.

Details of the present invention will be described below.
In the thermoplastic resin composition of the present invention in which inorganic fine particles are dispersed in a thermoplastic resin, the refractive index np of the inorganic fine particles, the refractive index n0 of the thermoplastic resin, and the temperature change rate dnp / dT of the refractive index of the inorganic fine particles are: It means the refractive index and its temperature dependence for light with a wavelength of 588 nm. The refractive index of the thermoplastic resin with respect to light having a wavelength of 588 nm can be measured using a known refractometer, for example, Abbe refractometer (manufactured by Atago Co., Ltd .: DR-M2), automatic refractometer (manufactured by Kalnew Optical Industrial Co., Ltd.) : KPR-200), etc. Further, the refractive index of 588 nm of inorganic fine particles and the temperature dependence of the refractive index can be measured by the Becke line method, but can be obtained by referring to literature values. For example, “Handbook of Thermo-Optic Coefficients of Optical Materials with Applications” by Gorachand Ghosh (Academic Press) describes the refractive index of various materials and the temperature dependence of the refractive index, which can be used as a reference. .

Further, in the thermoplastic resin composition of the present invention, the volume fraction Φ of the inorganic fine particles in the thermoplastic resin composition is given by the following formula (D), and means the volume fraction at 23 ° C. unless otherwise specified. To do.
Φ = (volume occupied by inorganic fine particles) / (volume of thermoplastic resin composition) (D)

Next, details of the thermoplastic resin composition according to the present invention will be described.
The thermoplastic resin composition according to the present invention can be melt-molded in which inorganic fine particles are contained and dispersed in a thermoplastic resin. In the following, first, (1) a thermoplastic resin, (2) inorganic fine particles, and ( 3) Details of the additives that can be added will be described, and then (4) production method and (5) application examples of the thermoplastic resin composition will be described.

(1) Thermoplastic resin The thermoplastic resin is not particularly limited as long as it is a transparent thermoplastic resin generally used as an optical material. From the viewpoint of workability as an optical element, an acrylic resin is used. A cyclic olefin resin, a polycarbonate resin, a polyester resin, a polyether resin, a polyamide resin or a polyimide resin is preferable, and a cyclic olefin is particularly preferable. Specific examples include compounds described in JP-A-2003-73559, and preferred compounds are shown in Table 1 below.

The above-mentioned thermoplastic resin desirably has a moisture absorption rate of 0.2% or less from the viewpoint of dimensional stability as an optical material. Therefore, polyolefin resin (polyethylene, polypropylene), fluororesin (polytetrafluoroethylene) , Teflon (registered trademark) AF: manufactured by DuPont), cyclic olefin resin (manufactured by Nippon Zeon: ZEONEX, manufactured by Mitsui Chemicals: APEL, manufactured by JSR: Arton, manufactured by Ticona: TOPAS), indene / styrene resin, polycarbonate resin, etc. Preferably used.
In the case of using two or more kinds of resins as described above, the water absorption is considered to be substantially the same as the average value of the water absorption in each resin, and the average water absorption is 0.2% or less. It only has to be.

(2) Inorganic fine particles The inorganic fine particles can be arbitrarily selected from inorganic fine particles that satisfy the conditions defined by the above formula (A) or (C). Specifically, oxide fine particles, metal salt fine particles, semiconductor fine particles, and the like are preferably used. Of these, those that do not generate absorption, light emission, fluorescence, etc. in the wavelength region used as an optical element are appropriately selected and used. Is preferred.

As oxide fine particles, the metal constituting the metal oxide is Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb. 1 selected from the group consisting of Sr, Y, Nb, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ta, Hf, W, Ir, Tl, Pb, Bi and rare earth metals A metal oxide that is a seed or two or more metals can be used. Specifically, for example, silicon oxide, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide, hafnium oxide, niobium oxide, tantalum oxide, oxide Magnesium, calcium oxide, strontium oxide, barium oxide, indium oxide, tin oxide, lead oxide, double oxides composed of these oxides, lithium niobate and potassium niobate , Lithium tantalate, the aluminum magnesium oxide (MgAl ₂ O _4), and the like.

  Rare earth oxide can also be used as other oxide fine particles, specifically scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, oxide Examples also include dysprosium, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide. Examples of the metal salt fine particles include carbonates, phosphates, sulfates, and the like, specifically, calcium carbonate, aluminum phosphate, and the like.

The semiconductor fine particles mean fine particles having a semiconductor crystal composition. Specific examples of the semiconductor crystal composition include simple elements of Group 14 elements of the periodic table such as carbon, silicon, germanium, tin, and phosphorus (black phosphorus). A group consisting of a group 15 element such as selenium and tellurium, a compound composed of a group 14 element such as silicon carbide (SiC), tin oxide (IV) ( SnO ₂ ), tin sulfide (II, IV) (Sn (II) Sn (IV) S ₃ ), tin sulfide (IV) (SnS ₂ ), tin sulfide (II) (SnS), tin selenide (II) ( SnSe), tin telluride (II) (SnTe), lead (II) sulfide (PbS), lead selenide (II) (PbSe), lead telluride (II) (PbTe) group 14 elements Compounds with Group 16 elements of the periodic table, boron nitride (BN), boron phosphide (BP), phosphorous arsenide Elemental (BAs), aluminum nitride (AlN), aluminum phosphide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), Compound of periodic table group 13 element and periodic table group 15 element such as gallium antimonide (GaSb), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), indium antimonide (InSb) (Or III-V group compound semiconductor), aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), gallium sulfide (Ga ₂ S ₃ ), gallium selenide (Ga ₂ Se ₃ ), telluride gallium _(Ga 2 _Te 3), indium oxide _{(In 2 O} 3), Indium _{(In 2 S} 3), indium selenide _(In 2 _Se 3), compounds of tellurium indium _(In 2 Te ₃₎ periodic table group 13 elements and the periodic table group 16 element such as, thallium chloride ( I) (TlCl), thallium bromide (I) (TlBr), thallium iodide (I) (TlI) and other group 13 elements and periodic table group 17 elements, zinc oxide (ZnO), Zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), cadmium oxide (CdO), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), mercury sulfide (HgS) ), Mercury selenide (HgSe), mercury telluride (HgTe), etc., a compound of a periodic table group 12 element and a periodic table group 16 element (or II-VI group compound semiconductor) ), Arsenic sulfide _{(III) (As 2 S 3} ), selenium arsenic _{(III) (As 2 Se 3} ), telluride arsenic _{(III) (As 2 Te 3} ), antimony sulfide (III) _(Sb 2 _{S 3} ), Antimony selenide (III) (Sb ₂ Se ₃ ), antimony telluride (III) (Sb ₂ Te ₃ ), bismuth sulfide (III) (Bi ₂ S ₃ ), bismuth selenide (III) (Bi ₂ Se) ₃ ), compounds of periodic table group 15 element and periodic table group 16 element such as bismuth (III) telluride (Bi ₂ Te ₃ ), copper oxide (I) (Cu ₂ O), copper selenide (I ) (Cu ₂ Se) and other compounds of Group 11 elements of the periodic table and Group 16 elements of the periodic table, copper chloride (I) (CuCl), copper bromide (I) (CuBr), copper iodide (I) (CuI), silver chloride (AgCl), silver bromide (AgBr), etc. And compounds of group 17 elements of the periodic table, compounds of group 10 elements of the periodic table such as nickel oxide (II) (NiO), and group 16 elements of the periodic table, cobalt (II) oxide (CoO), cobalt sulfide ( II) Group 8 elements of the periodic table such as (CoS) and Group 16 elements of the periodic table, Group 8 of the periodic table such as triiron tetroxide (Fe ₃ O ₄ ), iron (II) sulfide (FeS), etc. Compound of element and periodic table group 16 element, compound of periodic table group 7 element and periodic table group 16 element such as manganese (II) (MnO), molybdenum sulfide (IV) (MoS ₂ ), oxidation Compounds of Group 6 elements of the periodic table and Group 16 elements of the periodic table such as tungsten (IV) (WO ₂ ), vanadium (II) oxide (VO), vanadium oxide (IV) (VO ₂ ), tantalum oxide (V ) _(Ta 2 _{O 5)} of the periodic table of the group 5 element and the periodic table group 16 elements such as Things, titanium oxide _{(TiO 2, Ti 2 O 5} , Ti 2 O 3, Ti 5 O 9 , etc.) compounds of the periodic table Group 4 element and Periodic Table Group 16 element such as, magnesium sulfide (MgS), selenium Compounds of Group 2 elements of the Periodic Table and Group 16 elements of the Periodic Table such as magnesium halide (MgSe), cadmium (II) chromium (III) (CdCr ₂ O ₄ ), cadmium selenide (II) chromium (III) Chalcogen spinels such as (CdCr ₂ Se ₄ ), copper sulfide (II) chromium (III) (CuCr ₂ S ₄ ), mercury selenide (II) chromium (III) (HgCr ₂ Se ₄ ), barium titanate (BaTiO ₃₎ ) And the like. In addition, G. Schmid et al .; Adv. Mater. 4, 494 (1991) (BN) 75 (BF2) 15F15 and D.C. Fenske et al .; Angew. Chem. Int. Ed. Engl. 29, page 1452 (1990), a semiconductor cluster having a fixed structure such as Cu ₁₄₆ Se ₇₃ (triethylphosphine) ₂₂ reported in the same manner is also exemplified.

Particularly preferable inorganic fine particles satisfying the condition defined by the above formula (A) when using a cyclic olefin resin particularly preferably used as the thermoplastic resin include, for example, silica (silicon oxide), aluminum oxide, aluminum Examples thereof include magnesium oxide (MgAl ₂ O ₄ ), calcium carbonate, and aluminum phosphate. Similarly, particularly preferable inorganic fine particles satisfying the condition defined by the above formula (C) include, for example, silicon oxide, calcium carbonate, aluminum phosphate and the like.

  As the fine particles, one kind of inorganic fine particles may be used, or a plurality of kinds of inorganic fine particles may be used in combination. By using a plurality of types of fine particles having different properties, the required characteristics can be improved more efficiently.

  The inorganic fine particles have an average particle diameter of preferably 1 nm or more and 30 nm or less, more preferably 1 nm or more and 20 nm or less, and further preferably 1 nm or more and 10 nm or less. When the average particle diameter is less than 1 nm, it is difficult to disperse the inorganic fine particles and the desired performance may not be obtained. Therefore, the average particle diameter is preferably 1 nm or more, and the average particle diameter exceeds 30 nm. In addition, the resulting thermoplastic resin composition may become turbid, resulting in a decrease in transparency and a light transmittance of less than 80%. Therefore, the average particle diameter is preferably 30 nm or less. The average particle diameter here refers to the volume average value of the diameter (sphere converted particle diameter) when each particle is converted into a sphere having the same volume.

Further, the shape of the inorganic fine particles is not particularly limited, but spherical fine particles are preferably used. Specifically, the minimum diameter of the particle (minimum value of the distance between the tangents when drawing two tangents in contact with the outer periphery of the fine particle) / maximum diameter (the value in drawing two tangents in contact with the outer periphery of the fine particle) The maximum value of the distance between tangents) is preferably 0.5 to 1.0, and more preferably 0.7 to 1.0.
Further, the particle size distribution is not particularly limited, but in order to achieve the effect of the present invention more efficiently, a particle having a relatively narrow distribution is preferably used rather than a particle having a wide distribution. Used.

  Furthermore, the inorganic fine particles are preferably subjected to a surface treatment. Examples of the surface treatment method for the inorganic fine particles include surface treatment with a surface modifier such as a coupling agent, polymer graft, and surface treatment with mechanochemical.

  Examples of the surface modifier used for the surface treatment of the inorganic fine particles include silane coupling agents, silicone oil, titanate, aluminate and zirconate coupling agents. These are not particularly limited, but can be appropriately selected depending on the type of inorganic fine particles and the thermoplastic resin in which the inorganic fine particles are dispersed. Further, two or more surface treatments may be performed simultaneously or at different times.

  Examples of silane-based surface treatment agents include vinylsilazane trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, and hexamethyldisilazane. For covering, hexamethyldisilazane or the like is preferably used.

  Examples of silicone oil processing agents include straight silicone oils such as dimethyl silicone oil, methylphenyl silicone oil, and methylhydrogen silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, Methacryl-modified silicone oil, mercapto-modified silicone oil, phenol-modified silicone oil, one-end reactive modified silicone oil, heterogeneous functional group-modified silicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, alkyl-modified silicone oil, higher fatty acid ester Modified silicone oil, hydrophilic special modified silicone oil, higher alkoxy modified silicone oil, higher fat It is possible to use the content-modified silicone oil and modified silicone oil and fluorine-modified silicone oil.

  These treatment agents may be used after appropriately diluted with hexane, toluene, methanol, ethanol, acetone water or the like.

  Examples of the surface treatment method using the surface modifier include a wet heating method, a wet filtration method, a dry stirring method, an integral blend method, and a granulation method. When surface modification of 100 nm or less is performed, the dry stirring method is preferably used from the viewpoint of suppressing particle aggregation, but is not limited thereto.

  These surface modifiers may be used alone or in combination. In addition, the properties of the surface-modified fine particles obtained may differ depending on the surface modifier used, and the affinity with the thermoplastic resin used in obtaining the thermoplastic resin composition can be achieved by selecting the surface modifier. is there. The ratio of the surface modification is not particularly limited, but the ratio of the surface modifier is preferably in the range of 10 to 99% by mass with respect to the inorganic fine particles after the surface modification, and is preferably 30 to 98% by mass. A range is more preferable.

(3) Additives In the production process and molding process of the thermoplastic resin composition, various additives (hereinafter also referred to as compounding agents) can be added as necessary. The additives are not particularly limited, but mainly include plasticizers, antioxidants, light stabilizers, etc. Other than these, heat stabilizers, weather stabilizers, ultraviolet absorbers, near infrared absorption Stabilizers such as agents; resin modifiers such as lubricants; anti-clouding agents such as soft polymers and alcoholic compounds; colorants such as dyes and pigments; antistatic agents, flame retardants and fillers. These compounding agents can be used alone or in combination of two or more thereof, and the compounding amount is appropriately selected within a range not impairing the effects described in the present invention. In particular, the polymer preferably contains at least a plasticizer or an antioxidant.

(3.1) Plasticizer The plasticizer is not particularly limited, but is a phosphate ester plasticizer, a phthalate ester plasticizer, a trimellitic ester plasticizer, a pyromellitic acid plasticizer, Examples include glycolate plasticizers, citrate ester plasticizers, and polyester plasticizers.

  As the phosphate ester plasticizer, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc., phthalate ester plasticizer, diethyl phthalate, Dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, diphenyl phthalate, dicyclohexyl phthalate, etc. For pyromellitic acid ester plasticizers such as triethyl trimellitate, tetrabutyl pyromellitate, tetra Examples of glycolate plasticizers such as phenyl pyromellitate and tetraethyl pyromellitate include triacetin, tributyrin, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate, and citrate plasticizers. Examples thereof include triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, and acetyl tri-n- (2-ethylhexyl) citrate.

(3.2) Antioxidants Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic compounds. Antioxidants are preferred. By blending these antioxidants, it is possible to prevent lens coloring and strength reduction due to oxidative degradation during molding without reducing transparency, heat resistance and the like. The antioxidants can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention, but with respect to 100 parts by mass of the polymer. And it is preferable that it is the range of 0.001-5 mass parts, and it is more preferable that it is the range of 0.01-1 mass part.

  A conventionally well-known thing is applicable as a phenolic antioxidant, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2 , 4-di-t-amyl-6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate and the like, and JP-A Nos. 63-179953 and 1-168643. Acrylate compounds described in Japanese Patent Publication No. 1; octadecyl-3- (3,5-di-tert-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-trimethyl-2,4,6-tris (3,5-di) t-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenylpropionate)) methane [i.e. pentaerythrimethyl-tetrakis ( 3- (3,5-di-t-butyl-4-hydroxyphenylpropionate))], triethylene glycol bis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate) and the like Alkyl substituted phenol compounds; 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-oxyanilino) -1,3,5-triazine, etc. Triazine group-containing phenol compounds, and the like.

  Phosphorous antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t -Butylphenyl) phosphite, monophosphites such as 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide 4,4'-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis (phenyl-di-alkyl (C12-C15) And diphosphite compounds such as) phosphite). 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.

  Sulfur-based antioxidants include dilauryl 3,3-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3-thiodipropionate Pentaerythritol-tetrakis- (β-lauryl-thio-propionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane and the like. .

(3.3) Light Stabilizer Examples of the light stabilizer include a benzophenone light stabilizer, a benzotriazole light stabilizer, a hindered amine light stabilizer, etc. From the viewpoint of properties and the like, it is preferable to use a hindered amine light-resistant stabilizer. Among hindered amine light-resistant stabilizers (hereinafter referred to as HALS), those having a molecular weight Mn in terms of polystyrene by liquid chromatography using tetrahydrofuran as a solvent are preferably 1,000 to 10,000, and preferably 2,000 to 5,000. Some are more preferred, with 2,800-3,800 being particularly preferred. When Mn is too small, when HALS is blended by heating and kneading into a block copolymer, a predetermined amount cannot be blended due to volatilization, or foaming or silver streak occurs during heat melting molding such as injection molding. This is because there arises a problem that the stability is lowered.

  Further, when the lens is used for a long time with the lamp turned on, a volatile component is generated as a gas from the lens. For this reason, when Mn is too large, the dispersibility to a block copolymer will fall, the transparency of a lens will fall, and the effect of light resistance improvement will reduce. Therefore, by setting the HALS Mn within the above-described range, a lens excellent in processing stability, low gas generation property, and transparency can be obtained.

  The HALS mentioned above includes N, N ′, N ″, N ′ ″-tetrakis- [4,6-bis- {butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl]. ) Amino} -triazin-2-yl] -4,7-diazadecane-1,10-diamine, dibutylamine and 1,3,5-triazine, N, N'-bis (2,2,6,6- Polycondensate with tetramethyl-4-piperidyl) butylamine, poly [{(1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2, 2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], 1,6-hexanediamine-N, N′- Bis (2,2,6,6-tetramethyl-4-pipe Di) and morpholine-2,4,6-trichloro-1,3,5-triazine, poly [(6-morpholino-s-triazine-2,4-diyl) (2,2, 6,6, -tetramethyl-4-piperidyl) imino] -hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl) imino] and other piperidine rings are bonded via a lyazine skeleton. Molecular weight HALS; polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, 1,2,3,4-butanetetracarboxylic acid, 1,2,2 , 6,6-pentamethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane S Piperidine ring, such as Le compound is bound high molecular weight HALS, and the like via an ester bond.

  Among these, a polycondensate of dibutylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1 , 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {( 2,2,6,6-tetramethyl-4-piperidyl) imino}], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, etc. Is preferably in the range of 2,000 to 5,000.

(3.4) Compounding Amount The compounding amount of the various additives described above with respect to the thermoplastic resin composition is preferably in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the polymer. A range of 02 to 15 parts by mass is more preferable, and a range of 0.05 to 10 parts by mass is particularly preferable. This is because if the addition amount is too small, the effect of improving the light resistance cannot be sufficiently obtained. Therefore, when used as an optical element such as a lens, coloring occurs due to irradiation with a laser or the like, and the HALS content is too large. This is because a part of the gas is generated as a gas and the dispersibility in the resin is lowered, so that the transparency of the lens is lowered.

  Moreover, it is preferable to mix | blend the compound whose lowest glass transition temperature is 30 degrees C or less in addition to a thermoplastic resin composition. This is because white turbidity in a high temperature and high humidity environment for a long time can be prevented without degrading various properties such as transparency, heat resistance and mechanical strength.

(4) Manufacturing method Although the thermoplastic resin composition which concerns on this invention consists of a thermoplastic resin and inorganic fine particles as mentioned above, the manufacturing method is not specifically limited. Therefore, a method of forming a composite by polymerizing a thermoplastic resin in the presence of inorganic fine particles, a method of forming and combining inorganic fine particles in the presence of a thermoplastic resin, and a solution in which the inorganic fine particles are used as a solvent for the thermoplastic resin. Any method including a dispersion and then compounding by removing the solvent, a method of preparing inorganic fine particles and a thermoplastic resin separately, and compounding by melt kneading, melt kneading in a state containing a solvent, etc. It can also be produced by a method. Various additives may be added at any step of the compounding process, but the addition timing that does not hinder the compounding can be selected.

  Although the manufacturing method of a thermoplastic resin composition is not specifically limited, It is preferable that a thermoplastic resin composition is manufactured by the melt-kneading method. As an apparatus which can be used for melt kneading, a closed kneading apparatus or a batch kneading apparatus such as a lab plast mill, a Brabender, a Banbury mixer, a kneader, a roll, and the like can be given. Moreover, it can also manufacture using a continuous melt-kneading apparatus like a single screw extruder, a twin screw extruder, etc.

  In the method for producing a thermoplastic resin composition, when melt kneading is used, the thermoplastic resin and the inorganic fine particles may be added and kneaded all at once, or may be divided and added stepwise. In this case, in a melt-kneading apparatus such as an extruder, it is possible to add the components to be added step by step from the middle of the cylinder. In addition, after kneading in advance, when components other than thermoplastic resin that have not been added in advance are added and further melt-kneaded, these may be added all at once and kneaded, or added in stages. And may be kneaded. The method of adding in a divided manner or the method of adding one component in several batches can be adopted, the method of adding one component at a time and the method of adding different components in stages can also be adopted, both of which are combined The method is fine.

  In the case of compounding by melt kneading, the inorganic fine particles can be added in a powder or agglomerated state. Or it is also possible to add in the state disperse | distributed in the liquid. When adding in the state disperse | distributed in the liquid, it is preferable to perform devolatilization after kneading | mixing.

  When adding in the state disperse | distributed in a liquid, it is preferable to disperse | distribute aggregated particles to a primary particle beforehand, and to add. Various dispersing machines can be used for dispersion, but a bead mill is particularly preferable. There are various kinds of beads, but those having a small size are preferable, and those having a diameter of 0.1 mm or less and 0.001 mm or more are particularly preferable.

  In the present invention, since the water absorption rate of the thermoplastic resin greatly affects the physical properties of the inorganic-organic composite thermoplastic resin composition, the water absorption rate of the thermoplastic resin is preferably 0.2% by mass or less. By setting the water absorption rate of the thermoplastic resin to the conditions specified above, when a composite material is used as the optical material, the change in the refractive index due to a change in the environment falls within an allowable range. Furthermore, it is preferable that it is 0.1 mass% or less.

  Regarding the content of the inorganic fine particles in the thermoplastic resin composition of the present invention, the volume fraction Φ of the inorganic fine particles in the thermoplastic resin composition is preferably 0.25 ≦ Φ ≦ 0.5. When the volume fraction Φ is smaller than 0.25, there is a concern that the effect of the present invention cannot be exhibited. When the volume fraction Φ is larger than 0.5, the fluidity of the thermoplastic resin melt in which inorganic fine particles are dispersed is low. There is a concern that it will be lowered and molding will be difficult. It is more preferable that 0.3 ≦ Φ ≦ 0.4 as the volume fraction at which the effects of the present invention can be further exerted and molding can be easily performed.

  The degree of mixing of the thermoplastic resin and the inorganic fine particles in the thermoplastic resin composition is not particularly limited, but it is desirable that they are mixed uniformly in order to achieve the effect of the present invention more efficiently. . When the degree of mixing is insufficient, there is a concern that the particle size distribution of the inorganic fine particles in the thermoplastic resin composition may become difficult to satisfy the conditions specified in the present invention. Since the particle size distribution of the inorganic fine particles in the thermoplastic resin composition is greatly influenced by the production method, the optimum method should be selected in consideration of the characteristics of the thermoplastic resin and inorganic fine particles used. is important.

  Various molding materials can be obtained by molding the thermoplastic resin composition as described above, and the molding method is not particularly limited, but low birefringence, mechanical strength, dimensional accuracy, etc. In order to obtain a molded product having excellent characteristics, a melt molding method is preferred. Examples of the melt molding method include commercially available press molding, commercially available extrusion molding, and commercially available injection molding. From the viewpoint of moldability and productivity, injection molding is preferred.

  The molding conditions in the molding process are appropriately selected depending on the purpose of use or the molding method, but the temperature of the thermoplastic resin composition in the injection molding is such that an appropriate fluidity is imparted to the thermoplastic resin during molding. From the viewpoint of preventing the occurrence of silver streak due to thermal decomposition of the thermoplastic resin along with the occurrence of sink marks and strain, and further effectively preventing yellowing of the molded product, it should be in the range of 150 ° C to 400 ° C. Is preferable, the range of 200 ° C to 350 ° C is more preferable, and the range of 200 ° C to 330 ° C is particularly preferable.

(5) Application example The thermoplastic resin composition can be applied to an optical element or the like. The molded product can be used in various forms such as spherical, rod-shaped, plate-shaped, cylindrical, cylindrical, tube-shaped, fibrous, film or sheet-shaped, and has low birefringence, transparency, machine Since it is excellent in strength, heat resistance and low water absorption, application to various optical elements is suitable.

  As a specific application example, as an optical lens or an optical prism, an imaging lens of a camera; a lens such as a microscope, an endoscope or a telescope lens; an all-light transmission lens such as a spectacle lens; a CD or a CD-ROM , WORM (recordable optical disc), MO (rewritable optical disc; magneto-optical disc), MD (mini disc), DVD (digital video disc) and other optical disc pickup lens; laser beam printer fθ lens, sensor lens And a laser scanning system lens such as a camera finder system prism lens.

  Other optical applications include light guide plates such as liquid crystal displays; optical films such as polarizing films, retardation films and light diffusion films; light diffusion plates; optical cards; liquid crystal display element substrates.

  Among the above-mentioned molded products, it is preferable to be used as an optical element such as a pickup lens that requires low birefringence or a laser scanning lens.

  Hereinafter, an optical pickup device 1 using an optical element molded from the thermoplastic resin composition in the present embodiment will be described with reference to FIG.

FIG. 1 is a schematic diagram showing the internal structure of the optical pickup device 1.
As shown in FIG. 1, the optical pickup device 1 in this embodiment includes a semiconductor laser oscillator 2 that is a light source. On the optical axis of the blue light emitted from the semiconductor laser oscillator 2, a collimator 3, a beam splitter 4, a quarter wavelength plate 5, a diaphragm 6, and an objective lens 7 are arranged in a direction away from the semiconductor laser oscillator 2. Are sequentially arranged.

  In addition, a sensor lens group 8 and a sensor 9 including two sets of lenses are sequentially disposed in a direction close to the beam splitter 4 and in a direction perpendicular to the optical axis of the blue light described above.

  The objective lens 7 that is an optical element is disposed at a position facing the optical disc D, and condenses the blue light emitted from the semiconductor laser oscillator 2 on one surface of the optical disc D. . Such an objective lens 7 is provided with a two-dimensional actuator 10, and the objective lens 7 is movable on the optical axis by the operation of the two-dimensional actuator 10.

Next, the operation of the optical pickup device 1 will be described.
The optical pickup device 1 in the present embodiment emits blue light from the semiconductor laser oscillator 2 at the time of recording information on the optical disc D or at the time of reproducing information recorded on the optical disc D. As shown in FIG. 1, the emitted blue light becomes a light beam L1, is collimated to infinite parallel light through the collimator 3, and then passes through the beam splitter 4 to pass through the quarter-wave plate 5. To Penetrate. Further, after passing through the diaphragm 6 and the objective lens 7, a condensed spot is formed on the information recording surface D ₂ via the protective substrate D ₁ of the optical disc D.

The light that forms the condensed spot is modulated by the information pits on the information recording surface D ₂ of the optical disc D and reflected by the information recording surface D ₂ . Then, the reflected light is sequentially transmitted through the objective lens 7 and the diaphragm 6, the polarization direction is changed by the quarter wavelength plate 5, and the reflected light is reflected by the beam splitter 4. After that, astigmatism is given through the sensor lens group 8, received by the sensor 9, and finally converted into an electric signal by being photoelectrically converted by the sensor 9.
Thereafter, such an operation is repeatedly performed, and the operation of recording information on the optical disc D and the operation of reproducing information recorded on the optical disc D are completed.

Incidentally, the magnitude of the thickness and the information pits of the protective substrate D ₁ of the optical disc D, also the numerical aperture NA required for the objective lens 7 different. In the present embodiment, the optical disc D is a high density, and its numerical aperture is set to 0.85.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Example 1]
(1) Preparation of sample (1.1) Preparation of thermoplastic resin compositions 1-12 (1.1.1) Preparation of thermoplastic resin composition 1 Aluminum oxide fine particles (alumina C: primary average) manufactured by Nippon Aerosil Co., Ltd. (Particle diameter 13 nm) was placed in an eggplant flask and then dried under reduced pressure at 190 ° C. for 1 hour. Thereafter, the inside of the eggplant flask was replaced with argon, an appropriate amount of hexamethyldisilazane (manufactured by Shin-Etsu Chemical Co., Ltd .: HMDS-3) was added, and the mixture was stirred well at 300 ° C. for 2 hr. The obtained surface-treated aluminum oxide fine particles were designated as inorganic fine particles A.

  Thereafter, a thermoplastic resin (ZEONEX 330R manufactured by Nippon Zeon Co., Ltd.) was melted using a twin screw extruder (manufactured by Toyo Seiki Seisakusho: LAB PLASTMILL), and inorganic fine particles A were added and kneaded to obtain a thermoplastic resin composition. . At this time, the addition amount of the inorganic fine particles A was set so that the volume fraction of the inorganic fine particles A with respect to the thermoplastic resin composition was 0.2. After kneading, it was extruded from a strand die, cut and pelletized, and this was designated as “thermoplastic resin composition 1”.

(1.1.2) Production of thermoplastic resin composition 2 In production of the thermoplastic resin composition 1, the inorganic fine particles A were mixed so that the volume fraction of the inorganic fine particles relative to the thermoplastic resin composition was 0.3. A “thermoplastic resin composition 2” was produced in the same manner as the thermoplastic resin composition 1 except that it was added.

(1.1.3) Production of Thermoplastic Resin Composition 3 Aluminum oxide having an average particle size of about 37 nm obtained from Kemco International Associates was placed in an eggplant flask and then dried under reduced pressure at 190 ° C. for 1 hour. Thereafter, the inside of the eggplant flask was replaced with argon, an appropriate amount of hexamethyldisilazane (manufactured by Shin-Etsu Chemical Co., Ltd .: HMDS-3) was added, and the mixture was stirred well at 300 ° C. for 2 hr. The obtained surface-treated aluminum oxide fine particles were designated as inorganic fine particles B. A “thermoplastic resin composition 3” was prepared in the same manner as the thermoplastic resin composition 1 except that the inorganic fine particles B were used in place of the inorganic fine particles A in the production of the thermoplastic resin composition 1.

(1.1.4) Production of thermoplastic resin composition 4 In production of the thermoplastic resin composition 3, the inorganic fine particles B are adjusted so that the volume fraction of the inorganic fine particles B relative to the thermoplastic resin composition is 0.3. A “thermoplastic resin composition 4” was produced in the same manner as the thermoplastic resin composition 3 except that it was added.

(1.1.5) Preparation of thermoplastic resin composition 5 In the preparation of the thermoplastic resin composition 1, instead of the inorganic fine particles A, inorganic fine particles C (silica fine particles manufactured by Nippon Aerosil Co., Ltd .: RX200, primary particle size 12 nm) were used. A “thermoplastic resin composition 5” was produced in the same manner as the thermoplastic resin composition 1 except that it was used.

(1.1.6) Production of thermoplastic resin composition 6 In production of the thermoplastic resin composition 5, the inorganic fine particles B are adjusted so that the volume fraction of the inorganic fine particles B relative to the thermoplastic resin composition is 0.3. A resin composition 1-6 was produced in the same manner as the resin composition 1-5 except that it was added.

(1.1.7) Preparation of thermoplastic resin composition 7 In the preparation of the thermoplastic resin composition 5, the inorganic fine particles B were adjusted so that the volume fraction of the inorganic fine particles B relative to the thermoplastic resin composition was 0.4. A thermoplastic resin composition 7 was produced in the same manner as the thermoplastic resin composition 5 except that it was added.

(1.1.8) Production of thermoplastic resin composition 8 In production of the thermoplastic resin composition 5, the inorganic fine particles B were adjusted so that the volume fraction of the inorganic fine particles B relative to the thermoplastic resin composition was 0.55. A thermoplastic resin composition 8 was produced in the same manner as the thermoplastic resin composition 5 except that it was added. However, since the torque reached the upper limit during kneading in the twin-screw extruder, kneading was stopped when the upper limit was reached.

(1.1.9) Preparation of thermoplastic resin composition 9 In preparation of thermoplastic resin composition 2, instead of inorganic fine particles A, inorganic fine particles D (calcium carbonate fine particles manufactured by Shiroishi Kogyo Co., Ltd. A “thermoplastic resin composition 9” was prepared in the same manner as the thermoplastic resin composition 2 except that the treatment and the average particle diameter were 30 nm).

(1.1.10) Production of thermoplastic resin composition 10 A solution in which 2.0 g of pentaethoxyniobium was added to 16.59 g of 2-methoxyethanol under a nitrogen atmosphere was produced. To this solution, a mixed solution of 0.26 g of lithium hydroxide monohydrate and 18.32 g of 2-methoxyethanol was added dropwise with stirring. After stirring at room temperature for 16 hours, the mixture was concentrated to an oxide concentration of 5% by weight to obtain a LiNbO ₃ dispersion. To 100 g of this dispersion, 300 g of methanol and a 1 mol% nitric acid aqueous solution were added. While stirring this solution at 50 ° C., a mixed solution of 100 g of methanol and 6 g of cyclopentyltrimethoxysilane was added over 60 minutes, and then the mixture was further stirred for 2 hours. The obtained transparent dispersion was suspended in ethyl acetate and centrifuged to obtain a white fine powder. According to TEM observation, this powder had an average particle diameter of about 6 nm, and this was designated as inorganic fine particles E. Then, in the production of the thermoplastic resin composition 2, a “thermoplastic resin composition 10” was produced in the same manner as the thermoplastic resin composition 2 except that the inorganic fine particles E were used instead of the inorganic fine particles A.

(1.1.11) Production of Thermoplastic Resin Composition 11 Titanium oxide manufactured by Ishihara Sangyo Co., Ltd. (Taipaque ST-01, average particle size of about 7 nm) was placed in an eggplant flask and then reduced in pressure at 190 ° C. for 1 hour. Dried. Thereafter, the inside of the eggplant flask was replaced with argon, an appropriate amount of hexamethyldisilazane (manufactured by Shin-Etsu Chemical Co., Ltd .: HMDS-3) was added, and the mixture was stirred well at 300 ° C. for 2 hr. The obtained surface-treated titanium oxide fine particles were designated as inorganic fine particles F. Then, in the production of the thermoplastic resin composition 2, a “thermoplastic resin composition 11” was produced in the same manner as the thermoplastic resin composition 2 except that the inorganic fine particles F were used instead of the inorganic fine particles A.

(1.1.12) Production of Thermoplastic Resin Composition 12 After putting yttrium oxide fine particles (average particle diameter of about 13 nm) manufactured by Nippon Electric Works Co., Ltd. into an eggplant flask, they were dried under reduced pressure at 190 ° C. for 1 hour. Thereafter, the inside of the eggplant flask was replaced with argon, an appropriate amount of hexamethyldisilazane (manufactured by Shin-Etsu Chemical Co., Ltd .: HMDS-3) was added, and the mixture was stirred well at 300 ° C. for 2 hr. The obtained surface-treated titanium oxide fine particles were designated as inorganic fine particles G. Then, in the production of the thermoplastic resin composition 2, a “thermoplastic resin composition 12” was produced in the same manner as the thermoplastic resin composition 2 except that the inorganic fine particles G were used instead of the inorganic fine particles A.

(1.2) Production of Samples 1 to 12 Each thermoplastic resin composition 1 to 12 produced in the item (1.1) above was melted by heating and molded into a test plate having a thickness of 3 mm. The test plates were designated as “Samples 1 to 12” (the numerical parts of the thermoplastic resin compositions 1 to 12 correspond to the numerical parts of the samples 1 to 12).

(2) Evaluation of each sample Each sample 1-12 was processed as needed, and the propriety of each sample 1-12 was evaluated by two items of "dn / dT change rate" and "linear expansion coefficient change rate". . Hereinafter, details of the measurement or calculation method of each item will be described.

(2.1) Change rate of dn / dT Using an automatic refractometer (Kalnew Optical Industry Co., Ltd .: KPR-200), the temperature of each sample 1-12 was changed from 10 ° C. to 60 ° C., and the refractive index at a wavelength of 588 nm was determined. Measured and calculated dnp / dT in each sample 1-12. In addition, dn / dT in the thermoplastic resin was calculated by the same method for a thermoplastic resin to which inorganic fine particles were not added (manufactured by Nippon Zeon: ZEONEX 330R). Based on these calculation results, the rate of change of dn / dT was calculated by the following formula, and is shown in Table 2 below as “dn / dT rate of change (%)”.

  dn / dT change rate = (dn / dT in the thermoplastic resin−dnp / dT in each sample 1 to 12) / (dn / dT in the thermoplastic resin) × 100

(2.2) Linear expansion coefficient change rate The linear expansion of the molded body of samples 1 to 12 and a thermoplastic resin (manufactured by ZEON: ZEONEX 330R) by thermomechanical analysis (TMA) using CN8098F1 manufactured by Rigaku Corporation. The coefficient was measured. The measurement was performed by measuring the displacement in the thickness direction of the disk. Based on these measurement results, the rate of change of the linear expansion coefficient was calculated by the following formula, and the “linear expansion coefficient change rate (%)” was shown in Table 2 below.

  Linear expansion coefficient change rate = (Linear expansion coefficient in thermoplastic resin−Linear expansion coefficient in samples 1 to 12) / (Linear expansion coefficient in thermoplastic resin) × 100

(3) Summary When samples 1, 3, 5, 8, 10-12 and samples 2, 4, 6, 7, 9 are compared, as shown in Table 2, the above formulas (A), (B), (C Samples 2, 4, 6, 7, and 9 satisfying the conditions specified in (1) are compared with samples 1, 3, 5, 8, and 10-12 that do not satisfy at least one of these conditions. And the linear expansion coefficient change rate result is good. From the above, it can be seen that it is useful that the temperature change rate of the refractive index of the inorganic fine particles and the volume fraction of the inorganic fine particles satisfy the conditions defined by the above formulas (A), (B), and (C).

[Example 2]
(1) Preparation of Samples In the preparation of Samples 1 to 12 in Example 1, thermoplastic resin compositions 21 to 32 were prepared in the same manner as described above except that APEL 5014S manufactured by Mitsui Chemicals, Inc. was applied as the thermoplastic resin. did. Thereafter, the respective thermoplastic resin compositions 21 to 32 were heated and melted and formed into test plates each having a thickness of 3 mm, and these test plates were designated as “Samples 21 to 32”.

(2) Evaluation of sample Each sample 21-32 was processed as needed, and the possibility of each sample 21-32 was evaluated by the total of two items of "dn / dT change rate" and "linear expansion coefficient change rate". The measurement or calculation method for each item is as described in Example 1, and the evaluation results are shown in Table 3 below.

(3) Summary When the samples 21, 23, 25, 28, 30 to 32 and the samples 22, 24, 26, 27, 29 are compared, as shown in Table 3, the above formulas (A), (B), (C The samples 22, 24, 26, 27, and 29 that satisfy the conditions specified in (1) are compared with the samples 21, 23, 25, 28, and 30 to 32 that do not satisfy at least one of these conditions. And the linear expansion coefficient change rate result is good. From the above, as in Example 1, it is useful that the temperature change rate of the refractive index of the inorganic fine particles and the volume fraction of the inorganic fine particles satisfy the conditions defined by the above formulas (A), (B), and (C). It can be seen that it is.

2 is a schematic diagram showing an internal structure of the optical pickup device 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 2 Semiconductor laser oscillator 3 Collimator 4 Beam splitter 5 1/4 wavelength plate 6 Aperture 7 Objective lens (optical element)
8 Sensor lens group 9 Sensor 10 Two-dimensional actuator D Optical disk D ₁ Protective substrate D ₂ Information recording surface

Claims (4)

A thermoplastic resin composition capable of melt molding in which inorganic fine particles are dispersed in a thermoplastic resin having a refractive index of n0,
Condition where the refractive index temperature change rate dnp / dT of the inorganic fine particles is defined by the following formula (A), where np is the refractive index of the inorganic fine particles and dnp / dT is the temperature change rate of the refractive index of the inorganic fine particles. And the volume fraction Φ of the inorganic fine particles occupying in the thermoplastic resin composition satisfies the condition defined by the following formula (B) at 23 ° C.
dnp / dT ≧ 0.00012 × (np−n0 + 0.25) ² −0.000025 (A)
0.25 ≦ Φ ≦ 0.5 (B) In the thermoplastic resin composition according to claim 1,
A thermoplastic resin composition characterized in that a temperature change rate dnp / dT of a refractive index of the inorganic fine particles satisfies a condition defined by the following formula (C).
dnp / dT ≧ 0.00031 × (np−n0 + 0.25) ² −0.000025 (C) In the thermoplastic resin composition according to claim 1 or 2,
A thermoplastic resin composition, wherein the inorganic fine particles have a primary particle diameter of 30 nm or less.   An optical element formed by using the thermoplastic resin composition according to any one of claims 1 to 3.

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