JP2007254681A - Thermoplastic composite material and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic composite material having a suitable refractive index and transparency as an optical element and an extremely small change by temperature in refractive index, and an optical element using the thermoplastic composite material. <P>SOLUTION: The thermoplastic composite material comprises a transparent thermoplastic resin comprising an organic polymer, and inorganic fine particles dispersed in the thermoplastic resin and containing a metal oxide crystal in amorphous silica. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermoplastic composite material and an optical element, and more particularly to a thermoplastic composite material and an optical element that are suitably used as a lens, a filter, a grating, an optical fiber, a flat optical waveguide, and the like.

  Information devices 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 are 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 a thermoplastic resin-olefin (see, for example, Patent Document 1) is known.

  By the way, in the case of an information device capable of reading and writing information on a plurality of types of media such as a CD / DVD player, for example, the optical pickup device responds to differences in the shape of both media and the wavelength of light to be applied. It is necessary to make it the structure. In this case, it is preferable from the viewpoint of cost and pickup characteristics that the optical element unit is common to all the media.

  On the other hand, 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, optical plastic materials such as cyclic olefins have significantly improved refractive index stability with respect to humidity, whereas the improvement in refractive index stability with temperature is not yet sufficient. .

  As one of methods for correcting the optical refractive index of the plastic lens as described above, various methods using a fine particle filler have been proposed. For example, a fine synthetic optical product composed of a polymeric thermoplastic resin having temperature sensitivity and a dispersed fine particle substance and having reduced temperature sensitivity has been proposed (for example, see Patent Documents 2 and 3). ). However, a resin material obtained by mixing such existing oxide fine particles with a resin has a large decrease in light transmittance, and has only been able to provide a resin material that is not suitable for practical use as an optical element.

For the purpose of increasing the refractive index, many proposals have been made for materials in which inorganic fine particles are dispersed and mixed in a resin (see, for example, Patent Documents 4 and 5). This patent document describes an organic polymer having a high refractive index and a high Abbe number in which inorganic fine particles having a high refractive index and a high Abbe number are dispersed in a transparent base polymer. Furthermore, Patent Document 6 proposes a high refractive index resin composition containing fine particles having a refractive index distribution and a transparent thermoplastic resin.
JP 2002-105131 A JP 2002-207101 A Japanese Patent Laid-Open No. 2002-240901 JP 2001-183501 A JP 2003-73563 A JP-A-2005-213410

However, in the methods of Patent Documents 4 and 5, since the aggregation of fine particles is likely to occur and light scattering is likely to occur, the transparency is not sufficient.
Also, the method of Patent Document 6 cannot prevent aggregation of fine particles, and since light scattering caused by the difference in refractive index between the inorganic fine particles and the resin and the difference in refractive index inside the particles is large, it is sufficiently transparent as an optical material. I can't get sex.

  Accordingly, the present invention has been made in view of the above problems, a thermoplastic composite material having a refractive index and transparency suitable as an optical element, and an extremely small change in refractive index with respect to temperature, and an optical device using the same. It is to provide an element.

The invention described in claim 1
A transparent thermoplastic composite material in which fine particles are dispersed in a thermoplastic resin made of an organic polymer, wherein the fine particles are inorganic fine particles containing metal oxide crystals in amorphous silica. To do.

The invention according to claim 2 is the thermoplastic composite material according to claim 1,
The inorganic fine particles have an average particle diameter of 1 nm or more and 50 nm or less.

The invention according to claim 3 is the thermoplastic composite material according to claim 1 or 2,
The inorganic fine particles have a substantially uniform composition.

The invention according to claim 4 is the thermoplastic composite material according to any one of claims 1 to 3,
The content of the metal oxide crystal in the inorganic fine particles is 20% by mass or more and 80% by mass or less.

Invention of Claim 5 in the thermoplastic composite material of any one of Claims 1-4,
The metal oxide crystal has a refractive index of 1.6 or more and 2.1 or less.

The invention according to claim 6 is the thermoplastic composite material according to any one of claims 1 to 5,
The surface of the inorganic fine particles is modified with an organosilane compound.

The invention according to claim 7 is the thermoplastic composite material according to any one of claims 1 to 6,
When the refractive index of the inorganic fine particles is np, the following formula (A) is satisfied.
1.50 ≦ np <1.75 Formula (A)

The invention according to claim 8 is the thermoplastic composite material according to any one of claims 1 to 7,
When the refractive index of the thermoplastic resin is nh and the refractive index of the inorganic fine particles is np, the following formula (B) is satisfied.
0 ≦ | np−nh | ≦ 0.15 Formula (B)

The invention according to claim 9 is the thermoplastic composite material according to any one of claims 1 to 8,
The refractive index nd25 measured at 25 ° C. using a sodium D line as a light source is 1.5 or more and 1.7 or less.

The invention according to claim 10 is an optical element,
It shape | molds using the thermoplastic composite material of any one of Claims 1-9.

  According to the present invention, by dispersing inorganic fine particles containing metal oxide crystals in amorphous silica in a transparent thermoplastic resin, the refractive index change with respect to temperature change is extremely small and the light transmittance is high. A thermoplastic composite material can be obtained. Along with this, the optical element formed by molding this thermoplastic composite material has a low temperature dependency of the refractive index and a high light transmittance, and is transparent even if stored for a long time in a high temperature and high humidity environment. It is possible to prevent deterioration of the property and refractive index.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the thermoplastic composite material according to the present invention will be described.
The thermoplastic composite material in this embodiment contains a thermoplastic resin and inorganic fine particles, and is molded into a molded product such as an optical element such as an optical resin lens. Hereinafter, (1) inorganic fine particles, (2) a thermoplastic resin, (3) a method for producing a thermoplastic composite material, and (4) a molded product will be described.

(1) Inorganic fine particles The inorganic fine particles used in the present invention are inorganic fine particles containing metal oxide crystals in amorphous silica (SiO ₂ ) which is an oxide. That is, when infrared spectroscopic analysis is performed on the fine particles of the present invention, absorption is recognized in the vicinity of 1070 to 1120 cm ⁻¹ , and the presence of silica becomes clear. The term “amorphous” as used herein refers to a state in which a clear crystal structure cannot be confirmed by structural analysis means such as X-ray diffraction or electron beam diffraction. That is, the inorganic fine particle of the present invention is a mixed composition of silica and metal oxide in the composition analysis, and is an inorganic fine particle in which only the crystal structure of the metal oxide is detected in the structural analysis.

  As the composition analysis method of the inorganic fine particles, various conventionally known methods can be used, and for example, measurement can be performed by fluorescent X-ray analysis, electron beam microanalyzer, or the like.

Further, the metal oxide contained in the inorganic fine particles is not particularly limited as long as it can be detected as a metal oxide crystal in amorphous silica, and the metal constituting the metal oxide is Li, Na. Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Y, Nb, Zr, Mo, Ag, Cd, In, Sn, Sb , Cs, Ba, La, Ta, Hf, W, Ir, Tl, Pb, Bi, and the like. In the present invention, all of the metal oxides present in the amorphous silica may exist as metal oxide crystals, or a part thereof may exist as amorphous metal oxides.
Further, if the crystal structure is confirmed, the composition may be a metal oxide crystal composed of one kind of metal atom or a composite metal oxide crystal containing several kinds of metal atoms, such as sodium silicate crystal or magnesium silicate crystal. A crystal made of silicon and other metal atoms may be used.

  Moreover, it is preferable that the inorganic fine particles have a substantially uniform composition. The substantially uniform composition mentioned here indicates that the metal oxide crystals in the amorphous silica are almost uniformly dispersed inside the particles. For example, TEM-EDX is measured at 10 or more measurement points on the particle cross section. The compositional analysis is carried out at a measurement point, and the fluctuation range of the composition at each measurement point is within 10%, preferably within 5%. The inorganic fine particles having a substantially uniform composition are preferable because light scattering due to the composition distribution inside the particles does not occur, and thus the transparency is high and the refractive index becomes uniform. Further, the metal oxide crystal is preferably dispersed as fine crystal particles in amorphous silica, and can be detected as fine particles of 5 nm or less, or a crystal lattice composed of several to several tens of atoms. It preferably exists as a cluster.

  Further, in the inorganic fine particles, the content of the metal oxide contained in the amorphous silica can be arbitrarily determined depending on the kind of the metal oxide and the refractive index value of the inorganic fine particles to be produced. In order to disperse the metal oxide substantially uniformly in the crystalline silica, the content of the metal oxide in the inorganic fine particles is preferably 20% by mass or more and 80% by mass or less, and 20% by mass or more and 60% by mass. More preferably, it is at most mass%.

  The inorganic fine particles desirably have a small difference in refractive index from the thermoplastic resin. As a result of the study by the present inventors, if the difference in refractive index between the thermoplastic resin and the inorganic fine particles dispersed in the resin is small, the thermoplastic composite material that can hardly cause scattering when transmitting light Was found to be obtained. In addition, the larger the fine particles dispersed in the thermoplastic resin, the easier the light is scattered when light is transmitted. However, if the difference in the refractive index between the thermoplastic resin and the dispersed fine particles is small, relatively large fine particles It has been found that the frequency of light scattering is reduced even when using, and the transparency can be maintained even when the content of fine particles is increased.

  The inorganic fine particles are desirably fine particles having a relatively low refractive index. As a result of the study by the present inventors, it is possible to effectively reduce dn / dT, which is the rate of change of the refractive index n of the thermoplastic resin composition with respect to the temperature T, by dispersing fine particles having a relatively low refractive index. I knew it was possible. Although the details of the reason why | dn / dT | of the thermoplastic resin composition in which fine particles having a low refractive index are dispersed are small, the temperature change in the volume fraction of inorganic fine particles in the resin composition is It is considered that the lower the refractive index, the smaller the | dn / dT | of the resin composition.

  It is difficult to improve the dn / dT reduction effect, light transmittance, desired refractive index, etc. of the thermoplastic composite material at the same time. The size may be appropriately selected in consideration of the size of dn / dT, the difference between the dn / dT of the fine particles and the dn / dT of the thermoplastic resin as the base material, the refractive index of the fine particles, and the like. In addition, it is preferable to select and use fine particles that are compatible with the thermoplastic resin as a base material, that is, dispersibility with respect to the thermoplastic resin and hardly cause scattering, to maintain light transmittance.

  As described above, the refractive index difference between the inorganic fine particles and the thermoplastic resin is preferably 0.15 or less, more preferably the refractive index difference is 0.1 or less, more preferably the refractive index difference is 0.05 or less. . And although the refractive index of the inorganic fine particles satisfying such a refractive index difference varies depending on the resin composition of the thermoplastic resin, the refractive index of the thermoplastic resin is usually in the range of 1.5 to 1.6. It is preferably 5 to 1.75, and more preferably 1.54 to 1.70.

  Furthermore, in order to achieve the above preferable refractive index with inorganic fine particles containing metal oxide crystals in amorphous silica, a metal oxide having a refractive index of 1.6 or more and 2.1 or less is used for amorphous silica. It is preferable to disperse it uniformly. Specifically, for example, metal oxides such as zinc oxide, aluminum oxide, zirconium oxide, tantalum oxide, magnesium oxide, calcium oxide, yttrium oxide, barium oxide, and indium oxide are preferable. Among these, those that do not generate absorption, light emission, fluorescence, or the like in the wavelength region used as an optical element are preferably selected and used.

  In particular, in the present invention, the thermoplastic composite material in which the inorganic fine particles are dispersed has a light transmittance that can be used as an optical element, and a refractive index nd25 measured by using a sodium D ray as a light source at 25 ° C. is 1. It is preferable to adjust the refractive index of the inorganic fine particles so as to be not less than .5 and not more than 1.7.

  In addition, the said refractive index corresponds to what is measured with an Abbe refractometer etc. according to ASTMD542 standard, for example, and can use the value described in various literature. Also, the inorganic fine particles are dispersed in various solvents with adjusted refractive index, the absorbance of the dispersion is measured, and the refractive index of the solvent that minimizes the value is measured, thereby confirming the refractive index of the inorganic fine particles. it can.

  In addition, the points that should be taken into consideration when selecting the inorganic fine particles will be described below.

  As long as the inorganic fine particles are in a range that does not deteriorate the light transmittance, 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 50 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 size 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 size is preferably 1 nm or more, and the average particle size exceeds 50 nm. Then, the resulting thermoplastic material composition may become turbid, resulting in a decrease in transparency, and the light transmittance may be less than 80%. Therefore, the average particle diameter is preferably 50 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. In particular, if even a small number of particles having a particle diameter of 100 nm or more are present, the light transmittance is remarkably deteriorated. Therefore, the coefficient of variation (the value obtained by dividing the standard deviation by the average as an index of variation in measured values, the dimensionless number) is ± 30 It is preferable that it is, and it is especially preferable that it becomes ± 10.

(1.1) Method for producing inorganic fine particles and surface modification The method for producing inorganic fine particles according to the present invention is not particularly limited, and inorganic fine particles in which metal oxide crystals are present in the amorphous silica of the present invention. Any known method can be used as long as the method can form the film. In general, composite oxide particles are produced by a thermal decomposition method (a method in which raw materials are thermally decomposed to obtain fine particles. A spray drying method, a flame spray method, a plasma method, a gas phase reaction method, a freeze drying method, a heating method) Kerosene method, heated petroleum method), precipitation method (coprecipitation method), hydrolysis method (salt aqueous solution method, alkoxide method, sol-gel method), hydrothermal method (precipitation method, crystallization method, hydrothermal decomposition method, hydrothermal oxidation) Law). Among these methods, the method of producing a composite oxide in a liquid such as a hydrolysis method can form fine particles having a small particle size and a uniform composition. Since it is difficult to form metal oxide crystals, it is necessary to form particles in the presence of fine metal oxide crystals prepared in advance. Further, the hydrothermal method has problems in terms of composition control of composite oxide particles and reduction in particle size.

Therefore, the method for producing the inorganic fine particles of the present invention is preferably a pyrolysis method in a gas phase, but it is difficult to control the composition and particle size of the composite oxide by the ordinary pyrolysis method. In particular, the raw material gas flow containing the raw material of fine particles and the reaction gas flow covering the raw material gas flow described in JP-A-2005-218937, JP-A-2005-305202 and the like flow into the reaction space in a high-temperature atmosphere. A fine particle production method is preferred in which particles are produced by heat treatment at the outer periphery of the raw material gas flow, and fine particles are produced by cooling the produced particles with the reaction gas flow. In this method, particles are generated by a chemical reaction between the raw material gas flow and the reaction gas flow, and the generated particles are cooled by the reaction gas flow to produce fine particles, thereby forming a reaction gas flow. By changing the kind of the reaction gas, the composition of the fine particles to be produced can be changed.
Furthermore, in the present invention, since the inorganic fine particles are required to have a small particle size and a narrow particle size distribution, it is preferable to produce the raw material gas flow as dilute as much as possible without reducing productivity. . In addition, when large particles are inevitably mixed depending on the production conditions, the large particles can be removed using a known classifier at the time of particle production or after collection. As classification methods, there are a method of removing specific gravity difference or electrically large particles from particles in aerosol state, a method of removing large particles by filtering particles dispersed in a solvent, etc. A method of processing by an electric mobility classifier (DMA: Differential Mobility Analyzer) is preferably used.

One feature is that the surface of the inorganic fine particles is modified with an organic compound.
The method for modifying the surface is not particularly limited, and any known method can be used. For example, there is a method of modifying the surface of the fine particles by hydrolysis under conditions where water is present. In this method, a catalyst such as an acid or an alkali is preferably used, and it is generally considered that a hydroxyl group on the surface of fine particles and a hydroxyl group generated by hydrolysis of a surface modifier dehydrate to form a bond.

  In addition, examples of the method for modifying the surface of 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 modifying the surface of the inorganic fine particles include silane coupling agents, silicone oil, titanate, aluminate and zirconate coupling agents. These are not particularly limited, and can be appropriately selected depending on the kind of the 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.

Specifically, for example, as a silane-based surface treatment agent, vinylsilazane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, hexamethyldisilazane and the like can be mentioned. Trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, hexamethyldisilazane and the like are preferably used.
Silicone oil treatment agents include straight silicone oil 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, and methacryl-modified. Silicone oil, mercapto modified silicone oil, phenol modified silicone oil, one-end reactive modified silicone oil, different 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 specially modified silicone oil, higher alkoxy modified silicone oil, higher fat Acid-containing modified silicone oil, modified silicone oil and fluorine-modified silicone oil can be used.

  These treatment agents may be 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. In the case of modifying the surface of fine particles of 50 nm or less, 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, and the properties of the surface-modified fine particles obtained may vary depending on the surface modifier used, and are used for obtaining a resin composition. Affinity with the thermoplastic resin can also be achieved by selecting a surface modifier. The ratio of the surface modification is not particularly limited, but the ratio of the surface modifier is preferably 10 to 99% by mass and more preferably 30 to 98% by mass with respect to the fine particles after the surface modification. preferable.

(2) Thermoplastic resin Next, a thermoplastic resin composed of an organic polymer constituting the thermoplastic composite material will be described.
The thermoplastic resin is not particularly limited as long as it is a transparent thermoplastic resin material generally used as an optical material. However, in consideration of processability as an optical element, acrylic resin, cyclic olefin resin, polycarbonate resin, polyester A resin, a polyether resin, a polyamide resin, or a polyimide resin is preferable. For example, compounds described in JP-A-2003-73559 can be given, and the preferable compounds are shown in Table 1.

  In a thermoplastic composite material, a thermoplastic resin made of an organic polymer has a cyclic structure obtained by hydrogenating a copolymer of a thermoplastic resin-olefin having 2 to 20 carbon atoms and a cyclic olefin. An olefin polymer having an alicyclic hydrocarbon comprising a compound shown in paragraphs [0032] to [0054] of JP-A-7-145213 or a repeating unit having an alicyclic structure A copolymer is preferred. Examples of the cyclic olefin resin preferably used in the present invention include, but are not limited to, ZEONEX (Nippon Zeon), APEL (Mitsui Chemicals), Arton (JSR), TOPAS (Chicona) and the like.

  Various additives (also referred to as compounding agents) can be added as necessary during the preparation of the thermoplastic composite material or in the molding process of the thermoplastic composite material. There are no particular restrictions on the additives, but stabilizers such as antioxidants, heat stabilizers, light stabilizers, weather stabilizers, UV absorbers and near infrared absorbers; resin modifiers such as lubricants and plasticizers An anti-clouding agent such as a soft polymer or an alcohol compound; a colorant such as a dye or a pigment; an antistatic agent, a flame retardant, or a filler. These compounding agents can be used alone or in combination of two or more, and the compounding amount is appropriately selected within a range not impairing the effects described in the present invention. In the present invention, it is particularly preferable that the polymer contains at least a plasticizer or an antioxidant.

[Plasticizer]
The plasticizer is not particularly limited, however, phosphate ester plasticizer, phthalate ester plasticizer, trimellitic ester plasticizer, pyromellitic acid plasticizer, glycolate plasticizer, citrate ester A plasticizer, a polyester plasticizer, etc. can be mentioned.

  In the phosphate ester plasticizer, for example, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Trimellitic plasticizers such as 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 phenyl trimellitate, triethyl trimellitate, etc. Examples of glycolate plasticizers such as tilpyromelitate, tetraphenylpyromellitate, and tetraethylpyromellitate include triacetin, tributyrin, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, and butylphthalylbutyl glycolate. In the citrate plasticizer, for example, triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2-ethylhexyl) citrate, etc. Can be mentioned.

〔Antioxidant〕
Examples of the antioxidant include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic antioxidants are preferable. By blending these antioxidants, it is possible to prevent lens coloring and strength reduction due to oxidative degradation during molding without lowering transparency, heat resistance and the like. These 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 the polymer 100 according to the present invention. Preferably it is 0.001-5 mass parts with respect to a mass part, More preferably, it is 0.01-1 mass part.

  A conventionally well-known thing can be used as a phenolic antioxidant, for example, 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-t-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. pentaerythrmethyl- Tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenylpropionate))], triethylene glycol bis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate) Alkyl-substituted phenolic compounds such as 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-tria Triazine group-containing phenol compounds such emissions; and the like.

  The phosphorus antioxidant is not particularly limited as long as it is usually used in the general resin industry. For example, triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) Phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10 Monophosphite compounds such as -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) phosphite) Like diphosphite compounds such as. 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.

  Examples of the sulfur-based antioxidant include dilauryl 3,3-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3-thiodiprote. Pionate, pentaerythritol-tetrakis- (β-lauryl-thio-propionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, etc. Can be mentioned.

(Light stabilizer)
Examples of the light-resistant stabilizer include benzophenone-based light-resistant stabilizer, benzotriazole-based light-resistant stabilizer, hindered amine-based light-resistant stabilizer, etc., but in the present invention, from the viewpoint of lens transparency, color resistance, etc., hindered amine-based It is preferable to use a light-resistant stabilizer. Among hindered amine light-resistant stabilizers (hereinafter also referred to as HALS), those having a polystyrene-equivalent Mn of 1,000 to 10,000 as measured by GPC using tetrahydrofuran (THF) as a solvent are preferable, and 2,000 to What is 5,000 is more preferable, and what is 2,800-3,800 is especially preferable. If Mn is too small, when HALS is blended by heat-melting and kneading into a block copolymer, a predetermined amount cannot be blended due to volatilization, foaming or silver streak occurs during heat-melt molding such as injection molding, etc. Processing stability decreases. 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. Conversely, if Mn is too large, the dispersibility in the block copolymer is lowered, the transparency of the lens is lowered, and the effect of improving light resistance is reduced. Therefore, in the present invention, a lens having excellent processing stability, low gas generation and transparency can be obtained by setting the HALS Mn within the above range.

  Specific examples of such HALS include N, N ′, N ″, N ′ ″-tetrakis- [4,6-bis- {butyl- (N-methyl-2,2,6,6-tetramethylpiperidine. -4-yl) amino} -triazin-2-yl] -4,7-diazadecane-1,10-diamine, dibutylamine and 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}], 1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl- Polypiperidyl) 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 triazine skeleton. High molecular weight HALS; polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, 1,2,3,4-butanetetracarboxylic acid and 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 Such engagement ester, piperidine ring linked to a high molecular weight HALS, and the like via an ester bond.

  Among these, polycondensates 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}], a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol and the like. 5,000 to 5,000 are preferred.

  The blending amount of the light-resistant stabilizer with respect to the thermoplastic composite material is preferably 0.01 to 20 parts by mass, more preferably 0.02 to 15 parts by mass, and particularly preferably 0.05 to 100 parts by mass of the polymer. -10 parts by mass. If the amount added is too small, the effect of improving light resistance cannot be obtained sufficiently, and coloring occurs when used outdoors for a long time. On the other hand, when the blending amount of HALS is too large, a part of the HALS is generated as a gas, or the dispersibility in the resin is lowered, and the transparency of the lens is lowered.

  In addition, by blending a thermoplastic composite material with a compound having the lowest glass transition temperature of 30 ° C. or less, it can be used for a long period of time without deteriorating various properties such as transparency, heat resistance, and mechanical strength. Can prevent white turbidity in high humidity environment.

(3) Production method of thermoplastic composite material The thermoplastic composite material is obtained by dispersing inorganic fine particles in a thermoplastic resin as a host material, but the production method is not particularly limited. That is, a method in which a thermoplastic resin and inorganic fine particles are separately produced and then mixed together, a method in which a thermoplastic resin is produced under conditions in which pre-made inorganic fine particles exist, and a pre-made thermoplastic resin exists. Any method can be employed, such as a method for producing inorganic fine particles under the conditions to be prepared, a method for producing both thermoplastic resin and inorganic fine particles simultaneously. Specifically, for example, two solutions of a solution in which a thermoplastic resin is dissolved and a dispersion in which inorganic fine particles are uniformly dispersed are uniformly mixed, and the resulting solution is arranged in a solution having poor solubility in the thermoplastic resin. Thus, a method for obtaining a target material composition can be preferably mentioned, but the method is not limited thereto.

  In the thermoplastic composite material, the degree of mixing of the thermoplastic resin and the inorganic fine particles is not particularly limited, but it is desirable that they are uniformly mixed in order to achieve the effect of the present invention more efficiently. If the degree of mixing is insufficient, there is a concern that it may affect the optical properties such as refractive index, Abbe number, and light transmittance, and it will also adversely affect resin processability such as thermoplasticity and melt moldability. There is a fear. The degree of mixing is considered to be affected by the production method, and it is important to select a method in consideration of the characteristics of the thermoplastic resin and inorganic fine particles used. In order to more uniformly mix both the thermoplastic resin and the inorganic fine particles, a method of directly bonding the thermoplastic resin and the inorganic fine particles can be suitably used in the present invention.

  The content of the inorganic fine particles according to the present invention is not particularly limited as long as the effects of the present invention can be exhibited, and can be arbitrarily determined depending on the types of the thermoplastic resin and the inorganic fine particles. The content of the inorganic fine particles according to the present invention is such that the volume fraction of the inorganic fine particles relative to the total volume of the organic-inorganic composite material to be produced is preferably 20% or more and 60% or less, and is 20% or more and 50% or less More preferably, it is 30% or more and 50% or less. The volume fraction of inorganic fine particles here is expressed by the formula (x / a) / Y × where the specific gravity of the inorganic fine particles is a, the content is x grams, and the total volume of the produced organic-inorganic composite material is Y milliliters. 100 is required. The content of the inorganic fine particles can be determined by observing the image of the inorganic fine particles with a transmission electron microscope (TEM) (information on the inorganic fine particle composition can also be obtained by local elemental analysis such as EDX), or given resin composition It can be calculated from the content weight of a predetermined composition obtained by elemental analysis of the contained ash and the specific gravity of crystals of the composition.

(3.1) Properties of thermoplastic composite material The thermoplastic composite material of the present invention produced as described above is characterized by a small temperature change rate (dn / dT) of refractive index.

  Here, dn / dT, which is an index of the rate of change of refractive index n with respect to temperature T, indicates that the refractive index (n) of the material changes at a rate of dn / dT with respect to the change in temperature (T). Yes. The value of dn / dT can be obtained by measuring the refractive index of the resin material at each temperature and reading the temperature change rate of the refractive index.

  As a method for measuring the refractive index, for example, a preferred method can be selected according to the form of the thermoplastic resin material from ellipsometry, spectral reflectance method, optical waveguide method, Abbe method, minimum deviation method, and the like.

In the thermoplastic composite material, | dn / dT |, which is the absolute value of dn / dT, is preferably 0 or more and 9.0 × 10 ⁻⁵ or less, and | dn / dT | is 0 or more and 5 or less. It is preferably 0.0 × 10 ⁻⁵ or less. This dn / dT is preferably in the above-mentioned range in all wavelength regions, but if it is in the above-mentioned range in the wavelength region used when used as an optical element, an optical element having superior temperature stability than the conventional one Is preferable.

  The thermoplastic composite material preferably has transparency in the visible region wavelength. The transparency of the organic-inorganic composite material is preferably 70% or more, more preferably 80% or more, and most preferably 90% or more when the light transmittance in the visible region wavelength is 3 mm. Such measurement is performed, for example, by a test according to ASTM D-1003 (3 mm thickness) standard. The visible region here means a wavelength region of 400 to 650 nm.

  The refractive index of the thermoplastic composite material is determined by the combination of the thermoplastic resin and the inorganic fine particles, but it is usually preferable to make the refractive index higher than that of the thermoplastic resin by selecting inorganic fine particles having a higher refractive index than the thermoplastic resin. Specifically, the range of about 1.45 to 2.0 is preferable, and more preferably 1.49 to 1.7.

  Therefore, a thermoplastic composite material is a material composition that has a low refractive index temperature dependency, high transparency, and excellent optical properties, and further has thermoplasticity and / or injection moldability. It is a thermoplastic material with excellent properties. This material having both excellent optical properties and moldability is a property that has not been achieved with the materials disclosed so far, and is based on the specific thermoplastic resin and the specific inorganic fine particles as described above. This is considered to contribute to this characteristic.

(4) Molded Product Next, an optical element will be described as an example of a molded product molded using the thermoplastic composite material of the present invention.

  Examples of the optical element according to the present invention include optical resin lenses applicable to optical lenses and optical prisms. Specific examples of application of optical resin lenses to optical components are as follows.

  For example, as an optical resin lens, an imaging lens for a camera; a lens such as a microscope, an endoscope, a telescope lens; an all-light transmission lens such as a spectacle lens; a CD, CD-ROM, WORM (recordable optical disk), MO (rewritable optical disc; magneto-optical disc), MD (mini disc), optical disc pick-up lens such as DVD (digital video disc); laser scanning system lens such as laser beam printer fθ lens, sensor lens; camera Finder type prism lenses.

  Examples of optical disc applications include CD, CD-ROM, WORM (recordable optical disc), MO (rewritable optical disc: magneto-optical disc), MD (mini disc), DVD (digital video disc), and the like. 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 these, it is suitable as a pickup lens or a laser scanning system lens that requires low birefringence, and is most suitably used for a pickup lens.

  Next, a method for producing an optical resin lens will be described as an example of an optical element molded using the thermoplastic composite material of the present invention.

  The optical resin lens is prepared by first preparing a thermoplastic composite material (which may be a mixture of a resin and inorganic fine particles or a mixture of a resin, inorganic fine particles and an additive), and then the obtained heat. It is produced through a process of molding a plastic composite material.

  The molding method is not particularly limited, but melt molding is preferable in order to obtain a molded product having excellent characteristics such as low birefringence, mechanical strength, and dimensional accuracy. Examples of the melt molding method include commercially available press molding, commercially available extrusion molding, and commercially available injection molding, and injection molding is preferred from the viewpoints of moldability and productivity.

  The molding conditions are appropriately selected depending on the purpose of use or molding method. For example, the temperature of the resin composition in injection molding (in the case of a resin alone or in a mixture of both a resin and an additive) is appropriate at the time of molding. 150 ° C. to 400 ° C. from the viewpoint of imparting fluidity to the resin to prevent sink marks and distortion of the molded product, preventing the occurrence of silver streak due to thermal decomposition of the resin, and effectively preventing yellowing of the molded product. The range of ° C is preferred, more preferably in the range of 200 ° C to 350 ° C, and particularly preferably in the range of 200 ° C to 330 ° C.

  Moreover, the optical element which is a molded product can be used in various forms such as a spherical shape, a rod shape, a plate shape, a cylindrical shape, a tubular shape, a tubular shape, a fibrous shape, a film shape or a sheet shape, and has a low birefringence. Since it is excellent in transparency, mechanical strength, heat resistance and low water absorption, it is used as an optical resin lens which is one of the optical elements of the present invention, but is also suitable as other optical components.

  Hereinafter, an optical pickup device 1 in which an optical resin lens is used as an objective lens will be described with reference to FIG. Here, FIG. 1 is a schematic diagram showing the internal structure of the optical pickup device 1.

  In this embodiment, the target is a “high-density optical disk” using a so-called blue-violet laser light source having a used wavelength of 405 nm, the protective substrate thickness of this optical disk is 0.1 mm, and the storage capacity is about 30 GB.

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.

  Here, the objective lens 7 is a single optical resin lens, 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. It has become. The 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. In the diaphragm 6, the incident light beam is narrowed to a diameter of 3 mm.

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 L ₁ , is collimated to infinite parallel light through the collimator 3, and then is transmitted through the beam splitter 4 to be a quarter wavelength plate 5. Transparent. Furthermore, after sequentially passing through the aperture 6 and the objective lens 7 to form a converged spot on the information recording surface D ₂ through the protective substrate D ₁ of the optical disc D.

Light that formed the concentrated light spot is modulated by the information recording surface D ₂ of the optical disk D by the information pit is reflected by the information recording surface D _2. Then, the reflected light becomes a light beam L ₂ , is sequentially transmitted through the objective lens 7 and the diaphragm 6, is changed in polarization direction by the quarter wavelength plate 5, and 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, even numerical apertures 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.
Moreover, you may employ | adopt suitably the used wavelength of a light source in the range which is 390 nm-420 nm.

  Therefore, the thermoplastic composite material produced by the above method is applied to an optical pickup device, and a predetermined optical path difference is given to at least one optical surface with respect to a specific wavelength light passing through the optical surface. By applying to an optical element (objective lens) having an optical path difference providing structure, a light having a short wavelength of about 400 nm is used for recording and reproducing information on a so-called next-generation optical disc such as a Blu-Ray Disc. However, the optical element itself is not clouded or the refractive index is not changed, the product life is extremely long, and a good optical refractive index and high-precision optical characteristics can be provided. In addition, the optical pickup device using the element can have good pickup characteristics when information is reproduced or recorded on the optical information recording medium.

  The optical element referred to in the present invention is used as a member of an optical system of an optical pickup device, for example, an objective lens, an objective lens unit, a coupling lens (collimator), a beam expander, a beam shaper, a correction plate, etc. Point to what you can do.

  In addition, the objective lens, in a narrow sense, refers to a lens having a condensing function that is disposed so as to face the optical information recording medium at the position closest to the optical information recording medium when the optical information recording medium is loaded in the optical pickup device. In a broad sense, a lens that can be actuated at least in the optical axis direction by an actuator together with the lens.

  The optical information recording medium refers to a general optical disc that reproduces and / or records information using a light beam having a predetermined wavelength, such as CD, DVD, CD-R, MD, MO, and high-density DVD.

  Information reproduction means reproduction of information recorded on the information recording surface of the optical information recording medium, and information recording means recording information on the information recording surface of the optical information recording medium. . Note that reproduction here includes simply reading information.

  The optical element and the optical pickup device of the present invention may be used for only recording or reproducing information, or may be used for both recording and reproduction.

The at least one optical surface refers to the light incident surface or the light exit surface of the front and back surfaces of the lens, and has either an optical path difference providing structure on either the incident surface or the light exit surface. It may be provided on both sides.

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

(1) Preparation of inorganic fine particles Inorganic fine particles 1 to 12 were produced according to the following procedure.

[Preparation of inorganic fine particles 1]
A mixed solution of 463.1 g of pure water, 104.8 g of 26% ammonia water and 4255.0 g of methanol, a mixed solution of 1368 g of tetramethoxysilane (TMOS) and 229.4 g of methanol, 643.2 g of pure water, and 104% 26% ammonia water 104 .8 g of the mixed liquid was dropped over 150 minutes while keeping the liquid temperature at 25 ° C., and then a mixed liquid of 5969 g of titanium tetraisopropoxide and 150 g of isopropanol was added over 100 minutes to obtain a silica / titanium mixed sol. It was.

  The sol was distilled while heating and distilling under normal pressure, and the pure water was added dropwise while keeping the volume constant. When it was confirmed that the tower top temperature reached 100 ° C. and the pH was 8 or less, the addition of pure water was completed. As a result, a fine particle dispersion was obtained.

Further, 15.4 g of methyltrimethoxysilane was added, stirred at room temperature for 1 hour, and then refluxed for 2 hours. Thereafter, methyl ethyl ketone was added dropwise while maintaining the volume at a constant pressure while heating and distilling under normal pressure, and when the tower top temperature reached 79 ° C. and the water content was 1.0% or less, the process was terminated. After cooling to room temperature, microfiltration was performed using a 3 μ membrane filter to obtain a methyl ethyl ketone-dispersed silica sol. As a result of TEM observation, the volume-converted average particle size (particle size) was 13 nm. Further, an absorption peak derived from silica exists at 1098 cm ⁻¹ by IR measurement, and is a composition in which Si and Ti are uniformly dispersed by a TEM / EDX composition analysis result of the particle cross section, and a clear crystal structure is obtained by XRD measurement. It was confirmed to be an amorphous composite oxide particle having no peak to be represented.

[Preparation of inorganic fine particles 2]
Using a nano-creator manufactured by Hosokawa Micron Co., Ltd., a raw material gas flow prepared by making polydimethylsiloxane and tetra (2-ethylhexyl) titanate 3: 1 by weight of SiO ₂ and TiO ₂ , and oxygen gas White fine powdery inorganic fine particles 2 were formed by flowing into a reaction space in a high temperature atmosphere and reacting them. Table 2 shows the particle size measurement result by TEM observation of the obtained particles, the presence or absence of an absorption peak derived from silica by IR measurement, the composition analysis result by TEM / EDX of the particle cross section, and the crystal structure analysis result by XRD measurement. As a result, the inorganic fine particles 2 were particles in which titanium oxide crystals were uniformly dispersed in amorphous silica.

[Preparation of inorganic fine particles 3 to 7]
In [Preparation of Inorganic fine particles 2], as a raw material gas flow and polydimethylsiloxane, and ethylacetoacetate aluminum di-n-butyrate, a mixture of aluminum mono -n- butoxy diethyl acetoacetate is Al ₂ O ₃ described in Table 2 Except using the solution prepared so that it might become a weight ratio, the inorganic fine particle 3-the inorganic fine particle 7 of the white fine powder form was formed by the same method. The results of evaluating the obtained particles are shown in Table 2. As a result, the inorganic fine particles 3 were particles having a core-shell structure having an alumina crystal core in the central portion and surrounding amorphous silica. Inorganic fine particles 4 to 6 were particles in which alumina crystals were uniformly dispersed in amorphous silica. Inorganic fine particles 7 were particles in which the presence of amorphous silica could not be confirmed, and alumina crystals and aluminum silicate crystals were mixed non-uniformly.

[Preparation of inorganic fine particles 8]
In [Preparation of inorganic fine particles 2], a white fine powdery state is obtained in the same manner except that a solution prepared by mixing ZnO with the weight ratio shown in Table 2 is used as a raw material gas flow. Inorganic fine particles 8 were formed. The results of evaluating the obtained particles are shown in Table 2. As a result, the inorganic fine particles 8 were particles in which zinc silicate crystals were uniformly dispersed in amorphous silica.

[Preparation of inorganic fine particles 9, 10]
In [Preparation of Inorganic Fine Particles 2], a white fine powdery state is obtained in the same manner except that a solution prepared by mixing polydimethylsiloxane and a magnesium compound so that the MgO has a weight ratio shown in Table 2 is used as a raw material gas stream. Inorganic fine particles 9 and 10 were formed. The results of evaluating the obtained particles are shown in Table 2. As a result, the inorganic fine particles 9 were particles in which magnesium silicate crystals were uniformly dispersed in amorphous silica. The inorganic fine particles 10 were particles in which the presence of amorphous silica could not be confirmed, and magnesium oxide crystals and magnesium silicate crystals were uniformly mixed.

[Preparation of inorganic fine particles 11]
In [Preparation of inorganic fine particles 1], except that a solution prepared by mixing octamethylcyclotetrasiloxane and zirconium 2-ethylhexanoate so that the weight ratio of SiO ₂ and ZrO ₂ is 2: 1 is used as a raw material gas stream, In the same manner, white fine powdery inorganic fine particles 11 were formed. The results of evaluating the obtained particles are shown in Table 2. As a result, the inorganic fine particles 11 were particles having a core-shell structure having a zirconia crystal core in the central portion and surrounding the amorphous silica.

[Preparation of inorganic fine particles 12]
Table 2 shows the results of a similar evaluation using Aluminum Oxide C manufactured by Nippon Aerosil Co., Ltd. as inorganic fine particles 12.

(Measurement of composition, particle size, metal oxide content)
TEM observation was performed on the inorganic fine particles 1 to 12 and the volume-average particle size (particle size) was determined. Moreover, the content rate of the metal oxide was measured based on the composition analysis by TEM / EDX of a particle cross section. Further, XRD measurement was performed, and the dispersion state of silica and metal oxide was confirmed based on the presence or absence of a peak representing the crystal structure. The results are shown in Table 2.

(Measurement of refractive index)
Refraction of the solvent in which the above-mentioned inorganic fine particles 1 to 12 are dispersed in a solvent having a different refractive index prepared using 1,3-dichloropropane, methyl salicylate, 1-bromonaphthalene, or diiodomethane, and the liquid becomes transparent. The refractive index np of each particle was measured by measuring the rate. The results are shown in Table 2.

(2) Production of thermoplastic composite material Next, the following surface modification was applied to the inorganic fine particles 1 to 12.

(Surface modification of inorganic fine particles)
First, 300 g of methanol and a 1 mol% nitric acid aqueous solution were added to 5 g of each of the inorganic fine particles 1 to 12. 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 further stirred for 24 hours. The obtained transparent dispersion was suspended in ethyl acetate and centrifuged to obtain a white fine powder.

  Next, as a preparation before kneading the inorganic fine particles in the resin with respect to the surface-modified inorganic fine particles 1 to 12, the thermoplastic resin (ZEONEX340R) to be used is dried at 80 ° C. for 8 hours, and the inorganic fine particles are 200 Drying was performed at 4 ° C. for 4 hours. The obtained dried inorganic fine particles 1 to 12 and the thermoplastic resin are used for producing the thermoplastic composite materials 1 to 12 shown below.

[Preparation of thermoplastic composite material 1]
A thermoplastic composite in which two inorganic fine powders that have been dried are added to a molten cyclic olefin resin (ZEONEX340R) made by Nippon Zeon so that the content is 20% by volume, and inorganic fine particles are dispersed by melt-kneading. Material 1 was produced. The kneading conditions were carried out for 5 minutes after the addition of the powder was completed at a set temperature of 200 ° C. and 30 rpm using a HAAKE kneader.

[Production of thermoplastic composite material 2]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material was prepared in the same manner except that the dried inorganic fine particles 3 were used instead of the dried inorganic fine particles 2 and dispersed in the resin. 9 was obtained.

[Preparation of thermoplastic composite material 3]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material is similarly prepared except that the dried inorganic fine particles 4 are used instead of the dried inorganic fine particles 2 and dispersed in a resin. 2 was obtained.

[Production of thermoplastic composite material 4]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material is similarly prepared except that the dried inorganic fine particles 5 are used instead of the dried inorganic fine particles 2 and dispersed in a resin. 3 was obtained.

[Production of thermoplastic composite material 5]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material is similarly prepared except that the dried inorganic fine particles 6 are used in place of the dried inorganic fine particles 2 and dispersed in the resin. 4 was obtained.

[Preparation of thermoplastic composite material 6]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material was prepared in the same manner except that the dried inorganic fine particles 8 were used instead of the dried inorganic fine particles 2 and dispersed in a resin. 5 was obtained.

[Preparation of thermoplastic composite material 7]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material was prepared in the same manner except that the dried inorganic fine particles 9 were used instead of the dried inorganic fine particles 2 and dispersed in the resin. 6 was obtained.

[Preparation of thermoplastic composite material 8]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material was prepared in the same manner except that the dried inorganic fine particles 11 were used instead of the dried inorganic fine particles 2 and dispersed in a resin. 11 was obtained.

[Preparation of thermoplastic composite material 9]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material is similarly prepared except that the dried inorganic fine particles 1 are used in place of the dried inorganic fine particles 2 and dispersed in a resin. 8 was obtained.

[Production of thermoplastic composite material 10]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material is similarly prepared except that the dried inorganic fine particles 7 are used in place of the dried inorganic fine particles 2 and dispersed in a resin. 10 was obtained.

[Production of thermoplastic composite material 11]
In [Preparation of thermoplastic composite material 1], a thermoplastic composite material was prepared in the same manner except that the dried inorganic fine particles 10 were used in place of the dried inorganic fine particles 2 and dispersed in a resin. 7 was obtained.

[Production of thermoplastic composite material 12]
In [Production of thermoplastic composite material 1], a thermoplastic composite material was prepared in the same manner except that the dried inorganic fine particles 12 were used instead of the dried inorganic fine particles 2 and dispersed in a resin. 12 was obtained.

(Evaluation of thermoplastic composite materials)
The physical properties of the obtained thermoplastic composite materials 1 to 12 were evaluated.

(Evaluation of refractive index)
Each of the thermoplastic composite materials 1 to 12 was melted and heat-molded to prepare a test plate having a thickness of 3 mm, and the refraction at a wavelength of 588 nm was performed using an automatic refractometer KPR-200 manufactured by Kalnew Optical Industry Co., Ltd. The rate was measured by changing the sample temperature from 10 ° C to 60 ° C. The refractive index at 25 ° C. is nd 25, the temperature change rate of the refractive index from 10 ° C. to 60 ° C. is dn / dT, and the obtained results are shown in Table 3 below.

(Measurement of transmittance)
Each of the prepared thermoplastic composite materials 1 to 12 was melted and heat-molded to prepare each test plate having a thickness of 3.0 mm. Each of the plates was immediately subjected to a method in accordance with ASTM D1003 by Tokyo Denshoku Co., Ltd. ) The light transmittance was measured using TURBIDITY METER T-2600DA manufactured by this company, and the measured light transmittance was defined as transmittance A (%). Next, each test plate was allowed to stand for 48 hours in an environment of 65 ° C., and then the light transmittance after the forced deterioration treatment was measured by the same method as described above, and this was defined as transmittance B (%). . In addition, when the measured light transmittance was 80% or less, it was determined that the transparency was poor and it was not suitable for an optical element. The obtained results are shown in Table 3 below.

  As is apparent from the results shown in Table 3, the thermoplastic composite materials 1 to 8 of the present invention have a smaller refractive index temperature dependency and transparency than the thermoplastic composite materials 9 to 12 of the comparative example. I understand that it is expensive. Furthermore, even after the forced deterioration treatment is performed, it can be seen that the degree of decrease in transparency is extremely small, and it is extremely useful as a resin material used for optical elements.

  Furthermore, as a result of producing and evaluating a plastic optical element using the thermoplastic composite materials 1 to 8, the optical element of the present invention has good optical characteristics and is used for recording and reproduction of CDs and DVDs. Even when Blue-Ray was irradiated for a long time, it was confirmed that the material was resistant to material alteration such as clouding.

It is a schematic diagram which shows an example of the pick-up apparatus for optical discs where the optical resin lens of this invention is used as an objective lens.

Explanation of symbols

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

Claims (10)

  A transparent thermoplastic composite material in which fine particles are dispersed in a thermoplastic resin made of an organic polymer, wherein the fine particles are inorganic fine particles containing metal oxide crystals in amorphous silica. Thermoplastic composite material.   The thermoplastic composite material according to claim 1, wherein the inorganic fine particles have an average particle size of 1 nm or more and 50 nm or less.   The thermoplastic composite material according to claim 1 or 2, wherein the inorganic fine particles have a substantially uniform composition.   4. The thermoplastic composite material according to claim 1, wherein a content of the metal oxide crystal in the inorganic fine particles is 20% by mass or more and 80% by mass or less.   5. The thermoplastic composite material according to claim 1, wherein a refractive index of the metal oxide crystal is 1.6 or more and 2.1 or less.   The thermoplastic composite material according to claim 1, wherein the surface of the inorganic fine particles is modified with an organosilane compound. The thermoplastic composite material according to claim 1, wherein the following formula (A) is satisfied when a refractive index of the inorganic fine particles is np.
1.50 ≦ np <1.75 Formula (A) The thermoplastic composite according to any one of claims 1 to 7, wherein the following formula (B) is satisfied, where nh is a refractive index of the thermoplastic resin and np is a refractive index of the inorganic fine particles. material.
0 ≦ | np−nh | ≦ 0.15 Formula (B)   The thermoplastic composite material according to any one of claims 1 to 8, wherein a refractive index nd25 measured at 25 ° C using a sodium D line as a light source is 1.5 or more and 1.7 or less.   An optical element formed by using the thermoplastic composite material according to claim 1.

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