JP2006299183A - Non-aqueous fine particle dispersion and thermoplastic composite material and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent thermoplastic resin material having remarkably small refractive index variation by temperature, and also to provide a non-aqueous fine particle dispersion suitably used in the dispersion of inorganic fine particles in a resin, and further to provide a thermoplastic composite material and an optical element which are formed by the use of the dispersion, and have improved optical properties. <P>SOLUTION: The non-aqueous fine particle dispersion is formed in a solvent and comprises noncrystalline inorganic fine particles having a modified surface are dispersed in a non-polar solvent in a state where the particles have an average particle diameter of 1 nm to 30 nm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-aqueous fine particle dispersion that is preferably used when fine particles are dispersed in a resin, and a thermoplastic composite material and an optical element that are formed using the non-aqueous fine particle dispersion and have improved optical properties.

  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 (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.

  This fine particle filler is used to modify the refractive index of optical plastics, and by using a filler whose particle size is sufficiently small, light scattering by the filler does not occur. As a result, sufficient transparency can be maintained. For example, technical literature describing the addition of fine particles to increase the refractive index of plastic includes C.I. Becker and P.M. Mueller and H.M. Schmidt, “Optical and Thermodynamic Investigations in Thermoplastic Microsynthetic Materials Having Surfaces Modified with Silica Fine Particles”, SPI Proceedings Volume 3469, July 1998, pages 88-98; Braune and P.M. Mueller and H.M. Schmidt, “Tantalum Oxide Nanomers for Optical Applications”, SPIE Proceedings Vol. 3469, July 1998, pages 124-132 and the like.

  As described above, transparent plastic materials are lighter and less expensive than glass, and are therefore used in various applications in optical systems. However, since the refractive index stability with respect to temperature and humidity is inferior to that of glass, improvement is desired.

With almost no exception, the refractive index of the organic polymer decreases with increasing temperature (that is, the temperature dependence of refractive index dn / dT <0). For example, as shown below, dn / dT of organic polymer materials generally used for optical applications is approximately equal to −10 ⁻⁴ / K.

  A method of reducing the absolute value of dn / dT by mixing a substance having dn / dT> 0 in such a host material having dn / dT <0 can be considered. Since some inorganic materials are known to have dn / dT> 0 as a result of temperature-dependent changes in intramolecular coordination, a host material comprising an organic polymer with dn / dT <0. It is considered that the absolute value of dn / dT can be reduced by mixing inorganic fine particles satisfying dn / dT> 0, and a temperature-sensitive polymeric host material and dispersed fine particle substance A fine synthetic optical product having a reduced temperature sensitivity has been proposed (for example, see Patent Documents 2 and 3). However, for example, as shown by Formula 2 described in Patent Document 3, in order to reduce the dn / dT of the host material by 50%, it is necessary to mix 40 mass% or more of aluminum oxide or magnesium oxide fine particles. It has been shown. However, in such a resin material in which a large amount of inorganic fine particles having a high refractive index is mixed, the light transmittance is greatly reduced, and the inorganic fine particles dispersed in the resin are aggregated, and the performance changes when stored for a long time. Therefore, it has been only possible to provide a resin material that is not suitable for practical use as an optical element.

In order to use it as an optical element, it is essential that the light transmittance is high. For this purpose, it is necessary that the fine particles dispersed in the resin are dispersed with a particle size with extremely small light scattering. In the conventional method, a dispersion of crystalline fine particles such as titanium oxide formed in a gas phase by a flame method, a plasma method, or the like in a solvent is mixed with a resin (see, for example, Patent Documents 4 and 5). . In this case, although a method such as crushing with a disperser has been tried, it is technically very difficult to disperse the particles by breaking the agglomerated state generated during the formation of the particles. On the other hand, the amorphous fine particles formed in the solution have good dispersibility in the solution and can exist with the primary particle size. In addition, since the amorphous fine particles formed in the solution have lower light scattering than the crystalline fine particles, it can be expected that the transparency when dispersed in the resin is increased. However, there has never been an example of dispersing amorphous particles in a resin with such an idea, and a method of dispersing amorphous particles in a resin while maintaining a dispersion state in a solvent is known. There wasn't.
JP 2002-105131 A JP 2002-207101 A Japanese Patent Application Laid-Open No. 2002-241592 JP-A-11-278844 JP 2004-203999 A

  The present invention has been made in view of the above problems, and its purpose is to provide a thermoplastic resin material that is transparent and has a very small refractive index change with respect to temperature, and is required in that case. It is an object of the present invention to provide a non-aqueous fine particle dispersion suitably used for inorganic fine particle dispersion, and a thermoplastic composite material and an optical element which are formed using the non-aqueous fine particle dispersion and have improved optical characteristics.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
Non-aqueous fine particle dispersion, wherein non-crystalline inorganic fine particles formed in a solvent and having a modified surface are dispersed in a non-polar solvent with an average particle size of 1 nm or more and 30 nm or less .

(Claim 2)
The non-aqueous fine particle dispersion according to claim 1, wherein the non-crystalline inorganic fine particles are a metal double oxide or a phosphate.

(Claim 3)
The non-aqueous fine particle dispersion according to claim 1 or 2, wherein the non-crystalline inorganic fine particles have a particle surface modified with an organosilane compound.

(Claim 4)
The non-aqueous fine particle dispersion according to claim 1 or 2, wherein the non-crystalline inorganic fine particles are modified on the surface of the particles with a compound having a carboxylic acid group or a carboxylic anhydride group.

(Claim 5)
A thermoplastic composite material comprising the non-aqueous fine particle dispersion according to any one of claims 1 to 4 and a thermoplastic resin having compatibility with the non-aqueous fine particle dispersion.

(Claim 6)
An optical element formed by using the thermoplastic composite material according to claim 5.

  According to the present invention, a non-aqueous fine particle dispersion of non-crystalline inorganic fine particles having an extremely small average particle diameter, which is stably dispersed in a non-polar solvent, and a refractive index change with respect to temperature using the non-aqueous fine particle dispersion is reduced. A thermoplastic resin material and an optical element with high transmittance can be provided.

  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 inventors have found that amorphous inorganic fine particles formed in a solvent and having a modified surface have an average particle diameter of 1 nm or more and 30 nm in a nonpolar solvent. It has been found that a non-aqueous dispersion of amorphous inorganic fine particles having an extremely small average particle diameter and stably dispersed in a non-polar solvent can be obtained by dispersing in the following.

  First, details of the amorphous inorganic fine particles according to the present invention will be described.

《Amorphous inorganic fine particles》
The amorphous inorganic fine particles according to the present invention (hereinafter also simply referred to as inorganic fine particles) are characterized in that the average particle diameter is dispersed in the range of 1 nm to 30 nm, more preferably 1 nm to 20 nm, and still more preferably 1 nm. The thickness is 10 nm or less. If the average particle size is 1 nm or more, the inorganic fine particles themselves can be stably dispersed and desired performance can be obtained. If the average particle size is 30 nm or less, the resulting thermoplastic material composition can be obtained. Sufficient transparency can be obtained, and the light transmittance can be 70% or more. The average particle diameter here refers to the diameter when converted to a sphere having the same volume as the inorganic fine particles.

  The shape of the inorganic fine particles used in the present invention is not particularly limited, but preferably spherical fine particles are used. 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. Specifically, the coefficient of variation (a value obtained by dividing the standard deviation by the average as an index of variation in the measured value, the dimensionless number) is preferably ± 30, more preferably ± 10.

  The inorganic fine particles used in the present invention are amorphous inorganic fine particles formed in a solution. In particular, the fine inorganic particles are formed by reaction of two or three kinds of soluble salt solutions in water or alcohol. It is preferable. The term “noncrystalline” as used herein refers to a state in which a clear crystal structure cannot be confirmed in X-ray diffraction or electron beam diffraction.

  The inorganic fine particles used in the present invention may have any composition as long as it exhibits non-crystallinity, and examples thereof include oxide fine particles, such as silicon oxide, zinc oxide, aluminum oxide, hafnium oxide, and oxide. Niobium, tantalum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, yttrium oxide, lanthanum oxide, cerium oxide, indium oxide, tin oxide, lead oxide, lithium niobate which is a double oxide composed of these oxides , Potassium niobate, lithium tantalate, titanium barium and the like. Further, phosphates, carbonates, sulfates and the like formed in combination with these oxides are also preferably used, and aluminum phosphate, tantalum phosphate, magnesium carbonate, calcium carbonate, strontium carbonate, zinc sulfate, copper sulfate, Etc.

Furthermore, the temperature-dependent dn / dT value of the refractive index of the inorganic fine particles is preferably 0 or more, and the dn / dT value of the inorganic fine particles is preferably 0 or more and 0.01 or less, particularly preferably 5 ×. 10 ⁻⁵ or more and 5 × 10 ⁻³ or less.

  The inorganic fine particles preferably used in the present invention are non-crystalline and have a dn / dT value of 0 or more, and at the same time, in a process such as heating when used for mixing with a resin, It is preferable that decomposition does not occur and the characteristics do not change.

  In view of the above points, examples of the inorganic fine particles preferably used in the present invention include metal double oxides and phosphates.

《Formation method of amorphous inorganic fine particles, surface modification method》
The method for forming inorganic fine particles according to the present invention is characterized in that it is formed in a solvent such as water or alcohol in order to form monodisperse non-crystalline particles having a small particle size. Any known method can be used as the particle forming method. For example, desired oxide fine particles can be obtained by using a metal halide or an alkoxy metal as a raw material and hydrolyzing in a reaction system containing water. At this time, a method of using an organic acid, an organic amine or the like in combination is also used for stabilizing the fine particles. Further, a reaction crystallization method in which particles are precipitated by mixing two or more kinds of solutions, a uniform precipitation method (urea method) using precipitation due to pH change, and the like can be preferably used.
In the present invention, after forming non-crystalline inorganic fine particles by forming particles by these methods in water or alcohol, the average particle size is 1 to 3 in a nonpolar solvent by further modifying the particle surface. It is characterized by being dispersed as fine particles of 30 nm.

  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. Examples of the surface modifier used for the surface treatment of 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 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. 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 the present invention, an organic silane compound generally called a silane coupling agent is preferably used as the surface modifier used for surface modification of the inorganic fine particles. Examples of the organic silane compound include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetraphenoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, methyltriethoxysilane, methyltriphenoxysilane, Ethyltriethoxysilane, phenyltrimethoxysilane, 3-methylphenyltrimethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiphenoxysilane, trimethylmethoxysilane, triethylethoxysilane, triphenylmethoxysilane, tri Examples include phenylphenoxysilane.

  Further, for example, a method of modifying the particle surface by adsorbing the dispersant to an acidic group or a basic group present on the particle surface is also effective. In particular, a compound having a carboxylic acid group and / or a carboxylic anhydride group adsorbed on a basic group is preferably used. The compound having a carboxylic acid group is not particularly limited, and examples thereof include linear carboxylic acids such as stearic acid, dicarboxylic acids such as cyclohexane carboxylic acid and maleic acid having a cyclic structure, and mercapto groups and amide groups. A compound suitable for the type of resin to be mixed can be selected from those having a relatively small molecular weight, such as those having a substituent, and those having a carboxyl group in the main chain or side chain of the polymer compound. In addition, carboxylic acid anhydrides such as succinic anhydride and maleic anhydride, and acid-modified products obtained by reacting maleic anhydride with polymer chains are also preferably used.

  These compounds have different characteristics such as reaction rate, and compounds suitable for surface modification conditions can be used. Further, only one type may be used or a plurality of types may be used in combination. Furthermore, the properties of the surface-modified fine particles obtained may vary depending on the compound used, and the affinity with the thermoplastic resin used to obtain the material composition can be achieved by selecting the compound used for the surface modification. is there.

  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.

  The non-aqueous fine particle dispersion of the present invention is characterized in that inorganic fine particles are surface-modified as described above and then dispersed as fine particles having an average particle diameter of 1 to 30 nm in a nonpolar solvent. A nonpolar solvent here refers to the solvent whose content rate of solvents which have polar groups, such as water and alcohol, is 20% or less, Preferably it is 0 to 10%. The kind of the nonpolar solvent is preferably selected from those suitable for mixing with the resin which is the subsequent process, and for example, toluene, xylene, hexane, cyclohexane, tetrahydrofuran and the like capable of dissolving the resin can be preferably used.

  The dispersion method in the nonpolar solvent is not particularly limited, but the method of performing solvent replacement after surface modification of the fine particles in the solution, the method of adding the fine particles dried by removing the solvent to the nonpolar solvent, etc. Is mentioned. In addition, it is one of preferred embodiments to control to a desired particle size by mixing inorganic fine particles and a nonpolar solvent and then dispersing using an ultrasonic treatment or a bead mill disperser.

<Mixing of resin and amorphous inorganic fine particles>
The thermoplastic composite material of the present invention comprises a thermoplastic resin as a host material and inorganic fine particles, but the preparation method is not particularly limited. That is, in the present invention, a dispersion of inorganic fine particles in a nonpolar solvent is used. However, the resin is directly dissolved in the dispersion, and the solvent of the dispersion is removed and mixed with the resin. Any method such as a method and a method of mixing a dispersion of fine particles and a resin solution can be employed. Specifically, for example, by mixing two solutions of a solution in which a host material is dissolved and a dispersion in which inorganic fine particles are uniformly dispersed, and meeting in a solution having poor solubility with respect to the host material, Preferred examples include a method for obtaining a target material composition and a method for obtaining a target material composition by dissolving and mixing a resin in a fine particle dispersion and then distilling off the solvent. Furthermore, although the method of using the resin composition produced by these methods as a masterbatch, and also melt-kneading with resin is preferable, it is not limited to this.

  In the thermoplastic material composition according to the present invention, the degree of mixing of the host material and the inorganic fine particles is not particularly limited, but in order to express the effect of the present invention more efficiently, they are uniformly mixed. It is desirable. 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 host material and inorganic fine particles used.

  The content of the inorganic fine particles according to the present invention is not particularly limited as long as the effect of the present invention can be exhibited, and can be arbitrarily determined depending on the type of the host material and the inorganic fine particles. The total content of the inorganic fine particles according to the present invention is preferably 20% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 60% by mass or less, based on the mass of the host material. More preferably, it is at least 50% by mass. The content of inorganic fine particles can be determined by observing particle images with a transmission electron microscope (TEM) (information on the composition can also be obtained by local elemental analysis such as EDX), or the ash content contained in a given resin composition It can be calculated from the content weight of the predetermined particle composition obtained by the elemental analysis and the specific gravity of the particle composition.

  Furthermore, in the present invention, amorphous inorganic fine particles are used as the inorganic fine particles, and it is preferable to carry out under the condition that the inorganic fine particles are not crystallized when mixed with the resin.

《Host material made of organic polymer》
Next, a host material made of an organic polymer constituting the thermoplastic composite material of the present invention will be described.

  The organic polymer host material according to the present invention 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, an acrylic resin, a cyclic olefin A resin, a polycarbonate resin, a polyester 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 preferable compounds are shown in Table 1.

  In the thermoplastic resin material according to the present invention, the host material made of an organic polymer is a cyclic structure obtained by hydrogenating a copolymer of an α-olefin having 2 to 20 carbon atoms and a cyclic olefin. And alicyclic hydrocarbons composed of repeating units having an alicyclic structure or compounds shown in paragraphs [0032] to [0054] of JP-A-7-145213 It is preferable that it is a copolymer. 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.

<Other ingredients>
In preparing the thermoplastic resin material according to the present invention or in the molding process of the resin composition, various additives (also referred to as compounding agents) can be added as necessary. 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 or a flame retardant; 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, coloring resistance, etc. 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 excellent in processing stability, low gas generation and transparency can be obtained by setting the HALS Mn in 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 thermoplastic resin material according to the present invention 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, so that the transparency of the lens is lowered.

  Further, by blending the thermoplastic resin material according to the present invention with a compound having the lowest glass transition temperature of 30 ° C. or less, without reducing various properties such as transparency, heat resistance, and mechanical strength, It can prevent cloudiness in long-term high temperature and high humidity environment.

<< Characteristics of Thermoplastic Composite Material of the Present Invention >>
The thermoplastic composite material in which inorganic fine particles are dispersed in the thermoplastic resin material according to the present invention is characterized in that the temperature change rate (dn / dT) of the refractive index is small.

  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, a preferable method can be selected according to the form of the thermoplastic composite material, for example, ellipsometry, spectral reflectance method, optical waveguide method, Abbe method, minimum deviation method, and the like.

In the thermoplastic composite material of the present invention, it is preferable that | dn / dT | which is the absolute value of dn / dT is 0 or more and 9.0 × 10 ⁻⁵ or less, and | dn / dT | As described above, it is preferably 5.0 × 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 of the present invention preferably has transparency in the visible region wavelength. The transparency of the thermoplastic composite material of the present invention is such that the light transmittance in the visible region wavelength is usually 50% or more, preferably 60% or more, more preferably 70% or more, most preferably 85% or more when the optical path length is 3 mm. It is desirable that Such measurement is performed, for example, by a test according to the ASTM D-1003 (3 mm thickness) standard. The visible region here means a wavelength region of 400 to 650 nm.

  Further, the refractive index of the thermoplastic composite material of the present invention can be adjusted depending on the use, but is usually preferably in the range of about 1.4 to 2.7, more preferably 1.5 to 2.4, and most preferably 1. .5 to 2.0.

  The thermoplastic material according to the present invention is a material composition that has a low temperature dependence of the refractive index, has high transparency, is optically excellent, and has thermoplasticity and / or injection moldability. It is a thermoplastic material with excellent processability. 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 composed of a specific thermoplastic resin and specific inorganic fine particles. It is thought that it contributes to this characteristic.

<< Method for producing optical element (resin lens for optics) >>
Next, a method for producing an optical resin lens that is one of the optical elements of the present invention will be described.

  The optical resin lens according to the present invention is prepared by first preparing a resin composition (a resin alone or a mixture of a resin and an additive), and then molding the obtained resin composition. The process of carrying out is included.

  The molded product of the thermoplastic composite material of the present invention is obtained by molding a molding material comprising the resin composition. 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.

  The molded product according to the present invention 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 and a transparent property. It is used as an optical resin lens, which is one of the optical elements of the present invention, because of its excellent properties, mechanical strength, heat resistance, and low water absorption, but is also suitable as other optical components.

《Optical resin lens》
The optical resin lens according to the present invention can be obtained by the above-described manufacturing method, and specific examples of application to optical components are as follows.

  For 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, a CD-ROM, or a 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; Examples include prism lenses for camera viewfinder systems.

  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 diffusing films; light diffusing plates; optical cards;

  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.

  As an example of the use of the optical resin lens according to the present invention, an example used as an objective lens used in a pickup device for an optical disk will be described with reference to FIG.

  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. This optical disk has a protective substrate thickness of 0.1 mm and a storage capacity of about 30 GB.

  FIG. 1 is a schematic diagram showing an example of an optical pickup device used in the present invention.

  In the optical pickup device 1, the laser diode (LD) 2 is a light source, and a blue-violet laser having a wavelength λ of 405 nm is used, but a laser having a wavelength in the range of 390 nm to 420 nm can be appropriately employed.

  The beam splitter (BS) 3 transmits the light source incident from the LD 2 in the direction of the objective optical element (OBL) 4, but with respect to the reflected light (returned light) from the optical disk (optical information recording medium) 5, the sensor lens (SL). 6 to collect light on the light receiving sensor (PD) 7.

  The light beam emitted from the LD 2 is incident on the collimator (COL) 8, collimated into infinite parallel light, and then incident on the objective lens OBL 4 via the beam splitter (BS) 3. Then, a condensing spot is formed on the information recording surface 5 b via the protective substrate 5 a of the optical disc (optical information recording medium) 5. Then, after reflecting on the information recording surface 5b, the direction of polarization is changed by the quarter wave plate (Q) 9 along the same path, the path is bent by the BS 3, and the sensor (SL) 6 is passed through the sensor ( Condensed on PD) 7. This sensor photoelectrically converts it into an electrical signal.

  The objective optical element OBL4 is a single lens optical resin lens that is injection-molded with resin. An aperture (AP) 10 is provided on the incident surface side to determine the beam diameter. Here, the incident light beam is reduced to a diameter of 3 mm. The actuator (AC) 11 performs focusing and tracking.

  The numerical aperture required for the objective optical element OBL4 varies depending on the thickness of the protective substrate of the optical information recording medium and the size of the pits. Here, the numerical aperture of the high-density optical disk (optical information recording medium) 5 is 0.85.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Preparation of fine particle dispersion>
[Preparation of Nonaqueous Fine Particle Dispersion 1: Present Invention]
Under a nitrogen atmosphere, a solution in which 20 g of pentaethoxyniobium was added to 165.9 g of ethanol was prepared. To this solution, a mixed solution of 2.6 g of lithium hydroxide monohydrate and 183.2 g of ethanol was added dropwise with stirring. After stirring at room temperature for 16 hours, the mixture was concentrated to an oxide concentration of 5% to obtain a LiNbO ₃ dispersion. To 100 g of this LiNbO ₃ 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 heated to 100 ° C. and further stirred for 2 hours. The obtained transparent dispersion was concentrated using a rotary evaporator, and further cyclohexane was added to replace the solvent, followed by sonication for 30 minutes, and LiNbO ₃ whose surface was modified with cyclopentyltrimethoxysilane. A cyclohexane dispersion containing 10% was obtained. When the particle size distribution of the obtained cyclohexane dispersion was measured by a dynamic scattering method, the average particle size was 11 nm, and this was designated as non-aqueous fine particle dispersion 1. Further, when X-ray diffraction of a powder obtained by drying a part of the non-aqueous fine particle dispersion 1 was measured, it was confirmed that the particles were amorphous particles in which no clear diffraction pattern was observed.

[Preparation of Nonaqueous Fine Particle Dispersion 2: Present Invention]
Under a nitrogen atmosphere, a solution was prepared by adding 20 g of pentaethoxyniobium to 165.9 g of 2-methoxyethanol. To this solution, a mixed solution of 2.6 g of lithium hydroxide monohydrate and 183.2 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% to obtain a LiNbO ₃ dispersion. To 100 g of this LiNbO ₃ dispersion, 20 g of cyclohexanecarboxylic acid was added and stirred at 100 ° C. for 1 hour. This liquid was concentrated using a rotary evaporator, and further cyclohexane was added to replace the solvent, followed by sonication for 30 minutes, and cyclohexane dispersion containing 10% of LiNbO ₃ whose surface was modified with cyclohexanecarboxylic acid. A liquid was obtained. When the particle size distribution of the obtained cyclohexane dispersion was measured by a dynamic scattering method, the average particle size was 5 nm, and this was designated as non-aqueous fine particle dispersion 2. Further, when X-ray diffraction of a powder obtained by drying a part of the non-aqueous fine particle dispersion 2 was measured, it was confirmed that the particles were amorphous particles in which no clear diffraction pattern was observed.

[Preparation of Nonaqueous Fine Particle Dispersion 3: Present Invention]
Under a nitrogen atmosphere, a solution was prepared by adding 25 g of pentaethoxyniobium to 323 g of 2-methoxyethanol. To this solution, a mixed solution of 3.5 g of water and 344.5 g of 2-methoxyethanol was added dropwise with stirring. After stirring at room temperature for 16 hours, the solution was concentrated to an oxide concentration of 5% to obtain a Nb ₂ O ₅ dispersion. To 100 g of this Nb ₂ O ₅ dispersion, 20 g of cyclohexanecarboxylic acid was added and stirred at 100 ° C. for 1 hour. This liquid was concentrated using a rotary evaporator, and further cyclohexane was added to replace the solvent, followed by sonication for 30 minutes, containing 10% of Nb ₂ O ₅ whose surface was modified with cyclohexanecarboxylic acid. A cyclohexane dispersion was obtained. When the particle size distribution of the obtained cyclohexane dispersion was measured by a dynamic scattering method, the average particle size was 8 nm, and this was designated as non-aqueous fine particle dispersion 3. Moreover, when X-ray diffraction of the powder obtained by drying a part of this dispersion liquid was measured, it was confirmed that the particles were amorphous particles in which no clear diffraction pattern was observed.

[Preparation of Nonaqueous Fine Particle Dispersion 4: Present Invention]
To 3 liters of an aqueous solution containing 0.027 mol of disodium hydrogen phosphate, 2 liters of an aqueous solution of 3.53 mol of aluminum sulfate and 2 liters of 7.06 mol of an aqueous solution of disodium hydrogen phosphate were added by a double jet method. Added over a minute. During the formation of inorganic fine particles, the pH was controlled at 3.0 using sulfuric acid, and the temperature was controlled at 30 ° C. After the addition was completed, soluble salts were desalted and removed by ultrafiltration to obtain a 10% aluminum phosphate dispersion. After 100 g of this aluminum phosphate dispersion was centrifuged to remove the supernatant, 100 g of methanol and a 1 mol% nitric acid aqueous solution were added. While stirring this solution at 50 ° C., 5 g of cyclohexylmethyldimethoxysilane was added, and then stirred for 2 hours. Furthermore, after adding 200 g of cyclohexane, it heated at 80-110 degreeC, and methanol and water were distilled off over 10 hours. The obtained slurry was dispersed for 1 hour using 50 μm beads with Ultra Apex Mill UAM-015 manufactured by Kotobuki Industry Co., Ltd., and a transparent dispersion of aluminum phosphate particles surface-modified with cyclohexylmethyldimethoxysilane was obtained. Obtained. When the particle size distribution of this dispersion was measured by a dynamic scattering method, the average particle size was 20 nm, and this was designated as non-aqueous fine particle dispersion 4. Further, when X-ray diffraction of a powder obtained by drying a part of the non-aqueous fine particle dispersion 4 was measured, it was confirmed that the particles were amorphous particles in which no clear diffraction pattern was observed.

[Preparation of Nonaqueous Fine Particle Dispersion 5: Present Invention]
To 3 liters of an aqueous solution containing 0.027 mol of trisodium phosphate, 2 liters of 3.53 mol of aluminum sulfate aqueous solution and 2 liters of 14.1 mol of trisodium phosphate aqueous solution were added for 10 minutes by the double jet method. Added over time. During the fine particle formation, the pH was controlled at 10.0, and the temperature was controlled at 30 ° C. After the addition was completed, soluble salts were desalted and removed by ultrafiltration to obtain a 10% aluminum phosphate dispersion. After 100 g of this aluminum phosphate dispersion was centrifuged to remove the supernatant, 100 g of methanol and a 1 mol% nitric acid aqueous solution were added. While stirring this liquid at 50 ° C., 5 g of TICONA TMG SCH0440 made by Ticona having a maleic anhydride group was added, and then stirred for 2 hours. Furthermore, after adding 200 g of cyclohexane, it heated at 80-110 degreeC and distilled methanol water over 10 hours. The obtained slurry was dispersed for 1 hour using 50 μm beads with Ultra Apex Mill UAM-015 manufactured by Kotobuki Industry Co., Ltd. to obtain a transparent dispersion of aluminum phosphate particles surface-modified with maleic anhydride groups. It was. When the particle size distribution of this dispersion was measured by a dynamic scattering method, the average particle size was 13 nm, and this was designated as non-aqueous fine particle dispersion 5. Further, when X-ray diffraction of a powder obtained by drying a part of this non-aqueous fine particle dispersion 5 was measured, it was confirmed that the powder was an amorphous particle in which no clear diffraction pattern was observed.

[Preparation of fine particle dispersion A: comparative example]
With reference to the contents described in Examples of JP-A-11-278844, titanium oxide fine particles having an average particle diameter of 25 nm were formed by oxidizing and cooling metal titanium vapor by a direct current plasma arc method. Ultrasonic treatment was performed for 30 minutes by adding 10% of the titanium oxide fine particles and 3% of sodium dodecylbenzenesulfonate as a dispersant in a cyclohexane solvent. As a result, the obtained dispersion was a cyclohexane dispersion of titanium oxide fine particles surface-modified with sodium dodecylbenzenesulfonate, and this was used as a comparative fine particle dispersion A. Further, when X-ray diffraction was performed on the powder obtained by drying a part of the fine particle dispersion A, a diffraction pattern showing titanium oxide crystals was observed.

[Preparation of Fine Particle Dispersion B: Comparative Example]
10% of RX300, which is a hydrophobized silica manufactured by Nippon Aerosil Co., was added to a cyclohexane solvent and subjected to ultrasonic treatment for 30 minutes. Further, ultra-apex mill UAM-015 manufactured by Kotobuki Industries Co., Ltd. was used for dispersion for 1 hour using 50 μm beads to obtain a cyclohexane dispersion of silica fine particles whose surface was modified with hexamethyldisilazane. When the particle size distribution of this dispersion was measured by a dynamic scattering method, the average particle size was 15 nm, and this was designated as comparative fine particle dispersion B. Further, when X-ray diffraction was performed on the powder obtained by drying a part of the fine particle dispersion B, a diffraction pattern showing silica crystals was observed.

<Mixing of thermoplastic resin material and inorganic fine particles>
To 100 g of each of the prepared non-aqueous fine particle dispersions 1 to 5 and fine particle dispersions A and B, 10 g of a transparent cycloolefin polymer ZEONEX 330R manufactured by Nippon Zeon Co., Ltd. as a thermoplastic resin material was added, and then 30 ° C. Stir for minutes.

<< Evaluation of transparency >>
The mixed solution of the fine particle dispersion and the thermoplastic resin material was applied on a slide glass, left to dry in a draft for 3 hours, and then visually observed to evaluate transparency according to the following criteria. .

5: Transparent and no turbidity 4: Slight turbidity is observed 3: Some turbidity is observed, but there is no problem in practical use 2: Transparency is low due to white turbidity 1: Opaque And a part of the solvent was distilled off, and further the solvent was distilled off under reduced pressure to obtain a thermoplastic composite material in which fine particles were dispersed. This thermoplastic composite material was molded into a thickness of 5 mm by hot pressing, and the transparency was evaluated according to the same criteria as described above.

  The results obtained as described above are shown in Table 2.

  As is clear from the results shown in Table 2, it can be seen that the thermoplastic composite material using the non-aqueous fine particle dispersion of the present invention is superior in transparency to the comparative example.

Example 2
<< Production of thermoplastic composite material >>
Each thermoplastic resin was dried at 80 ° C. for 8 hours as preparation before kneading inorganic fine particles in the thermoplastic resin material.

[Preparation of thermoplastic composite material 1]
500 g of non-aqueous fine particle dispersion 1 containing 10% of LiNbO ₃ , 20 g of dried cycloolefin polymer APL5014DP (resin 1) manufactured by Mitsui Chemicals, and 5 g of Nippon Oil & Fats amide-based lubricant Alfro S-10 Were stirred and mixed at 60 ° C. for 30 minutes. Then, after heating to 120 degreeC and distilling a solvent off over 3 hours, it pressure-reduced to 1.33 kPa and distilling a solvent off, and the resin composition 1 was obtained. The resin composition 1 was pulverized and added to 30 g of APL5014DP (resin 1) melted in a kneading apparatus manufactured by HAAKE, and kneaded to obtain a thermoplastic composite material 1 containing 50% of LiNbO ₃ particles. . The kneading conditions were kneading for 5 minutes after the addition of the resin composition 1 was completed at a preset temperature of 180 ° C. and 30 rpm.

[Production of thermoplastic composite materials 2 to 7]
In the production of the thermoplastic composite material 1, the non-aqueous fine particle dispersion 1 is similarly changed except that the non-aqueous fine particle dispersions 2 to 5 and the fine particle dispersions A and B are respectively changed. ~ 7 were made.

[Production of thermoplastic composite materials 8 to 14]
In the production of the thermoplastic composite materials 2, 5, and 7, APL5014DP (resin 1) was changed to ZEONEX 340R (resin 2) manufactured by Nippon Zeon Co., Ltd., and the addition amount of fine particles was changed as shown in Table 3. In the same manner as described above, thermoplastic composite materials 8 to 14 were produced. The kneading conditions at this time were set to a preset temperature of 200 ° C. and 30 rpm.

<Evaluation of thermoplastic composite material>
(Measurement of refractive index)
Each of the prepared thermoplastic composite materials 1 to 14 is melted and heat-molded to prepare each test plate having a thickness of 0.5 mm, and an Abbe refractometer (Atago Co., Ltd., DR-M2) is used for each. The refractive index was measured by changing the measurement temperature from 10 ° C. to 50 ° C. at a wavelength of 588 nm, and the refractive index nd25 at 25 ° C. and the temperature change rate dn / dT of the refractive index were obtained.

(Measurement of transmittance)
Each of the prepared thermoplastic composite materials 1 to 14 is melted and heat-molded to prepare each test plate having a thickness of 3.0 mm. Each of the plates is 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 70% or less, it was determined that the transparency was poor and it was not suitable for an optical element.

  The results obtained as described above are shown in Table 3.

  As is clear from the results shown in Table 3, it can be seen that the thermoplastic composite material of the present invention has a lower temperature dependency of the refractive index and a higher transparency than the comparative example. 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 resin composition, the optical element of the present invention has a good optical characteristic and has a Blue-Ray used for recording and reproduction of CDs and DVDs. Even when irradiated for a long time, it was confirmed that the material was excellent in resistance 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 Laser diode 3 Beam splitter 4 Objective optical element (also called objective lens)
DESCRIPTION OF SYMBOLS 5 Optical disk 5a Protective board 5b Information recording surface 6 Sensor lens 7 Sensor 8 Collimator 9 1/4 wavelength plate 10 Aperture 11 Actuator

Claims (6)

Non-aqueous fine particle dispersion, wherein non-crystalline inorganic fine particles formed in a solvent and having a modified surface are dispersed in a non-polar solvent with an average particle size of 1 nm or more and 30 nm or less . The non-aqueous fine particle dispersion according to claim 1, wherein the non-crystalline inorganic fine particles are a metal double oxide or a phosphate. The non-aqueous fine particle dispersion according to claim 1 or 2, wherein the non-crystalline inorganic fine particles have a particle surface modified with an organosilane compound. The non-aqueous fine particle dispersion according to claim 1 or 2, wherein the non-crystalline inorganic fine particles are modified on the surface of the particles with a compound having a carboxylic acid group or a carboxylic anhydride group. A thermoplastic composite material comprising the non-aqueous fine particle dispersion according to any one of claims 1 to 4 and a thermoplastic resin having compatibility with the non-aqueous fine particle dispersion. An optical element formed by using the thermoplastic composite material according to claim 5.

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