JP2007154026A - Method for producing optical resin material and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical resin material satisfying both of the high transparency (light transmittance) and the high refractive index. <P>SOLUTION: An objective lens 7 according to the present invention is obtained by molding an optical resin material obtained by kneading a thermoplastic resin with inorganic fine particles having 1-100 nm volume average particle diameter. The method for producing the optical resin material comprises a dispersing step for dispersing the inorganic particles into a solution of a first silane coupling agent and a dispersing agent, a surface treatment step for surface-treating the inorganic fine particles with a second silane coupling agent after carrying out dispersing step and a kneading step for kneading the inorganic fine particles with the thermoplastic resin after carrying out surface treatment step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  As shown in Patent Document 1, it has been proposed to obtain an optical resin material in which fine particles are dispersed in an optical resin to suppress the temperature change of the refractive index and the thermal expansion coefficient of the resin. The above physical properties are improved by actually containing fine particles in the resin. However, in order to use an optical resin material in which fine particles are dispersed for use in an optical resin for a lens or the like, high transparency and a high refractive index are required.

  The following proposals have been made as optical resin materials having transparency. In Patent Document 2, the silica surface is made hydrophobic by using a surface treatment agent such as a silane coupling agent to a certain level or more, and mixed with an acrylic polymer, a polycarbonate polymer, or a polystyrene polymer so that the surface is transparent. It has been shown that a thermoplastic resin excellent in properties and rigidity can be obtained. Similarly, Patent Document 3 shows that fine silica having a diameter of not more than a visible light wavelength is blended with a transparent amorphous polymer. However, the refractive index of silica is lower than that of a resin for general optical use. Therefore, even if a transparent optical resin material can be obtained to some extent, the refractive index of the optical resin material is low, which is unsuitable for applications such as lenses.

  On the other hand, the following has been proposed as an optical resin material containing particles having a high refractive index in a resin and having a high refraction.

Patent Document 4 shows that such a material can be obtained by mixing titanium oxide, zinc oxide, or the like in a fine state as an optical resin imparted with high refraction and heat resistance. However, when particles other than silica are used in this way, the transparency of the optical resin material actually deteriorates and is difficult to use for optical applications. This is because a silane coupling agent is very effective for mixing inorganic particles with a hydrophobic resin, but the effect of particles other than silica is reduced. Therefore, an attempt was made to coat the surface of the inorganic fine particles with silica and further hydrophobize it. This treatment significantly increases the hydrophobicity of the particles. However, in order to produce an optical resin material exhibiting high transparency, it is necessary to use fine particles of 100 nm or less in order to prevent light scattering, and the transparency of the optical resin material is reduced due to aggregation of particles during the process. Is a problem.
Japanese Patent Application Laid-Open No. 2002-241592 JP 2003-201114 A Japanese Patent Laid-Open No. 11-343349 JP 2003-73563 A

By carrying out the hydrophobization process with the silane coupling agent to the particle | grains which formed the silica layer on the surface of an inorganic fine particle, the particle | grains with high hydrophobicity can be produced. The treatment for forming the silica layer is mainly performed by a wet method. However, at this time, when the particle diameter becomes ultrafine particles of 100 nm or less, aggregation due to an increase in the surface area of the particles becomes severe. This aggregation causes a decrease in light transmittance when a composite resin of inorganic particles and resin is produced.
An object of the present invention is to obtain an optical resin material that can achieve both high transparency (light transmittance) and high refractive index even when inorganic fine particles having a particle diameter of 100 nm or less are used.

In order to solve the above problems, the first invention
A method for producing an optical resin material obtained by kneading inorganic fine particles in a thermoplastic resin,
A dispersion step of dispersing inorganic fine particles having a volume average particle diameter of 1 to 100 nm in a solution of a first silane coupling agent and a dispersant;
A surface treatment step of subjecting the inorganic fine particles to a surface treatment using a second silane coupling agent after the dispersion step;
A kneading step of kneading the inorganic fine particles into the thermoplastic resin after the surface treatment step;
It is characterized by having.

  The first silane coupling agent is preferably selected from tetraethoxysilane, tetramethoxysilane, and polysilazane.

  The second silane coupling agent is preferably selected from hexamethyldisilazane, trimethylethoxysilane, trimethylmethoxysilane, and trimethylsilyl chloride.

In the first invention,
You may provide the 2nd surface treatment process which surface-treats using a 3rd silane coupling agent after the said surface treatment process and before the said kneading | mixing process.

  The third silane coupling agent is preferably selected from hexamethyldisilazane, trimethylethoxysilane, trimethylmethoxysilane, and trimethylsilyl chloride.

In the first invention,
The inorganic fine particles are preferably oxides or phosphates.

The second invention is
An optical element obtained by molding an optical resin material obtained by the method for manufacturing an optical resin material according to the first invention.

  According to the present invention, in the dispersion step, the surface silica layer is formed using the first silane coupling agent in a state where the inorganic fine particles having not been surface-treated are dispersed using the dispersant. In the surface treatment step 2, the inorganic fine particles can be hydrophobized using the second and third silane coupling agents, and even if the volume average particle diameter of the inorganic fine particles is 100 nm or less, high transparency ( It is possible to obtain an optical resin material capable of satisfying both (light transmittance) and a high refractive index (see Examples below).

The best mode for carrying out the present invention will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.
In the method for producing an optical resin material according to the present invention, the optical resin material is obtained by kneading inorganic fine particles with a thermoplastic resin. The optical element according to the present invention is obtained by molding the optical resin material.
In the following, (1) thermoplastic resin and (2) inorganic fine particles will be described, respectively, and then (3) a method for producing an optical resin material and (4) a method for producing an optical element obtained by the method and its application. Each example will be described.

(1) Thermoplastic resin 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, an acrylic resin or a cyclic olefin is used. A resin, a polycarbonate resin, a polyester resin, a polyether resin, a polyamide resin, or a polyimide resin is preferable, and a cyclic olefin resin is particularly preferable, and examples thereof include compounds described in JP-A-2003-73559. Table 1 shows preferable compounds.

  In the optical resin material, the thermoplastic resin preferably has a water absorption of 0.2% by mass or less. Examples of the resin having a water absorption of 0.2% by mass or less include polyolefin resin (for example, polyethylene, polypropylene, etc.), fluororesin (for example, polytetrafluoroethylene, Teflon (registered trademark) AF (manufactured by DuPont), Top (made by Asahi Glass Co., Ltd.), cyclic olefin resin (for example, ZEONEX (made by Nippon Zeon), Arton (made by JSR), Apel (made by Mitsui Chemicals), TOPAS (made by Polyplastics), etc.), inden / Styrenic resins, polycarbonates and the like are suitable, but not limited to these.

  It is also preferable to use other resins compatible with these resins. When two or more kinds of resins are used, the water absorption rate is considered to be approximately equal to the average value of the water absorption rates of the individual resins, and the average water absorption rate only needs to be 0.2% or less.

(2) Inorganic fine particles The inorganic fine particles are not particularly limited, and it is possible to achieve the object of the present invention that the rate of change in refractive index with temperature of the obtained optical resin material (hereinafter referred to as | dn / dT |) is small. It can be arbitrarily selected from the inorganic fine particles. Specifically, oxide fine particles, metal salt fine particles, semiconductor fine particles, and the like are preferably used. Of these, those that do not generate absorption, light emission, fluorescence, etc. in the wavelength region used as an optical element are appropriately selected and used. Is preferred.

As oxide fine particles, the metal constituting the metal oxide is Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb. 1 selected from the group consisting of Sr, Y, Nb, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ta, Hf, W, Ir, Tl, Pb, Bi and rare earth metals A metal oxide that is a seed or two or more metals can be used. Specifically, for example, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide, hafnium oxide, niobium oxide, tantalum oxide, magnesium oxide, oxidation Calcium, strontium oxide, barium oxide, indium oxide, tin oxide, lead oxide, double oxides composed of these oxides, lithium niobate, potassium niobate, tanta Lithium acid, magnesium aluminum oxide (MgAl ₂ O _4), and the like. In addition, rare earth oxides can also be used as oxide fine particles used in the present invention, specifically, scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide. Terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide and the like. Examples of the metal salt fine particles include carbonates, phosphates, sulfates, and the like, specifically, calcium carbonate, aluminum phosphate, and the like. Among these, the surface of the phosphate is preferably aluminum phosphate because silica is densified by phosphate ions.

Generally, dn / dT of a thermoplastic resin has a negative value, that is, the refractive index decreases as the temperature increases. Therefore, in order to efficiently reduce | dn / dT | of the optical resin material, it is preferable to disperse inorganic fine particles having a large dn / dT. When using inorganic fine particles having the same sign value as dn / dT of the thermoplastic resin, the absolute value of dn / dT of the inorganic fine particles is preferably smaller than dn / dT of the thermoplastic resin as the base material. . Furthermore, inorganic fine particles having a dn / dT opposite in sign to dn / dT of the thermoplastic resin as a base material, that is, inorganic fine particles having a positive value of dn / dT are preferably used. By dispersing such inorganic fine particles in the thermoplastic resin, | dn / dT | of the optical resin material can be effectively reduced with a small amount. The dn / dT of the inorganic fine particles to be dispersed can be appropriately selected depending on the value of dn / dT of the thermoplastic resin as a base material. In general, the inorganic fine particles are dispersed in a thermoplastic resin preferably used for an optical element. When the inorganic fine particles are used, the dn / dT of the inorganic fine particles is preferably larger than −20 × 10 ^{−6, and} more preferably larger than −10 × 10 ⁻⁶ .

  On the other hand, when the inorganic fine particles are dispersed in the thermoplastic resin, it is desirable that the difference in refractive index between the thermoplastic resin as the base material and the inorganic fine particles is small. As a result of the study by the inventors, it has been found that if the difference in refractive index between the thermoplastic resin and the dispersed inorganic fine particles is small, it is difficult to cause scattering when light is transmitted. When the inorganic fine particles are dispersed in the thermoplastic resin, the larger the particles, the easier it is to cause scattering when light is transmitted, but the difference in refractive index between the thermoplastic resin and the dispersed inorganic fine particles is relatively small. It was discovered that even when large inorganic fine particles were used, the degree of light scattering was small. The difference in refractive index between the thermoplastic resin and the dispersed inorganic fine particles is preferably in the range of 0 to 0.3, and more preferably in the range of 0 to 0.15. It was also discovered that the degree of light scattering can be reduced by covering the surface of the inorganic fine particles dispersed simultaneously with an inorganic substance having a small difference from the refractive index of the thermoplastic resin. The difference in refractive index between the thermoplastic resin and the inorganic substance on the surface of the dispersed inorganic fine particles is preferably in the range of 0 to 0.3, and more preferably in the range of 0 to 0.15.

  The refractive index of a thermoplastic resin preferably used as an optical resin material is often about 1.4 to 1.6. Examples of inorganic fine particles dispersed in these thermoplastic resins include calcium carbonate and aluminum phosphate. Aluminum oxide, magnesium oxide, aluminum / magnesium oxide and the like are preferably used.

  Further, the inventors' research has revealed that the dn / dT of the optical resin material can be effectively reduced by dispersing inorganic fine particles having a relatively low refractive index. Although the details of the reason why | dn / dT | of the optical resin material in which inorganic fine particles having a low refractive index are dispersed are small, the change in the volume fraction of the inorganic fine particles in the optical resin material is caused by the temperature change of the inorganic fine particles. It is considered that the lower the refractive index, the smaller the | dn / dT | of the optical resin material. As inorganic fine particles having a relatively low refractive index, for example, calcium carbonate and aluminum phosphate are preferably used.

  It is difficult to simultaneously improve the dn / dT reduction effect, optical transparency, desired refractive index, etc. of the optical resin material, and the inorganic fine particles dispersed in the thermoplastic resin have characteristics required for the optical resin material. Depending on the size of dn / dT of the inorganic fine particles themselves, the difference between the dn / dT of the inorganic fine particles and the dn / dT of the thermoplastic resin as the base material, the refractive index of the inorganic fine particles, etc. be able to. Furthermore, it is preferable to appropriately select and use inorganic 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.

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

  The volume average particle diameter of the inorganic fine particles is preferably 1 to 100 nm, more preferably 1 to 30 nm, and further preferably 1 to 10 nm. When the volume average particle diameter is less than 1 nm, it may be difficult to disperse the inorganic fine particles and the desired performance may not be obtained. When the volume average particle diameter exceeds 100 nm, the obtained optical resin material becomes turbid and transparent. May decrease.

  Here, the volume average particle diameter is an average particle diameter obtained by the X-ray small angle scattering measurement method. When the inorganic fine particles are aggregated to form aggregated particles, the average particle diameter is calculated by converting the aggregated particles as one particle.

  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 (the 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 or less, and more preferably ± 10 or less.

  The refractive index of the inorganic fine particles is preferably in the range of 1.3 to 2.3, and more preferably in the range of 1.5 to 1.8. Further, it is preferable that the inorganic fine particles have a small linear expansion coefficient. This is because the linear expansion coefficient of the optical resin material after the inorganic fine particles are dispersed is affected.

(3) Method for Producing Optical Resin Material The method for producing an optical resin material according to the present invention is a method of kneading inorganic fine particles with a thermoplastic resin, specifically, (3.1) inorganic fine particles. And (3.2) a surface treatment step of performing a surface treatment on the inorganic fine particles using the second silane coupling agent after the dispersion step; (3.3) A kneading step of kneading the inorganic fine particles into the thermoplastic resin after the surface treatment step.

(3.1) Dispersion step The dispersion step is based on a dispersion method in wet processing. In this dispersion method, a dispersion apparatus in wet processing is applied. As the dispersing device, a medium stirring mill such as an ultrasonic disperser or a bead mill can be applied. Of these, a bead mill is preferred. The bead mill is filled with beads as a medium in a container, and the surface-treated inorganic fine particles and solvent are poured while stirring the beads, and these are further stirred in the container to pulverize the aggregated particles of the inorganic fine particles with the beads. And disperse in a solvent. Specific examples of the bead mill include Star Mill ZRS (manufactured by Ashizawa Finetech Co., Ltd.), Ultra Apex Mill (manufactured by Kotobuki Industries Co., Ltd.), and the like.

  Such an apparatus can obtain a slurry by sufficiently dispersing inorganic fine particles in a solvent and then centrifuging only the beads. Since only the beads are separated by centrifugation, finer beads can be used, and the inorganic fine particles are pulverized to a volume average particle diameter closer to the primary particles. Here, as the beads, glass, alumina, steel, diamond, flint stone and the like can be used, and zirconia powder (for example, TZ series (manufactured by Tosoh Corporation)) is preferable. The particle diameter of the beads is preferably about 0.03 to 0.3 mm.

  As the first silane coupling agent applicable to the dispersion step, any reagent that can form a silica film can be preferably used, and any of polysilazane, tetramethoxysilane, and tetraethoxysilane is preferably used. Can do. As polysilazane, NL110 and NP110 (manufactured by AZ Electromaterials), which are solution-type reagents containing a catalyst for accelerating curing, are also commercially available and can be preferably used. Among these, from the viewpoint that a dense silica film can be formed, a tetraethoxysilane coupling agent can be preferably used. In the present invention, the treatment is performed in a liquid. In general, it is desirable to adjust the basicity of the slurry in which the particles are dispersed using ammonia and to add the first coupling agent. It is desirable that the inorganic fine particles in the slurry are well dispersed. It is desirable to perform dispersion using an ultrasonic wave or a bead mill.

  Commercially available products such as fatty acid amides can be used as the dispersant applicable to the dispersion step. Among these, a polymer dispersant is desirable in view of stably dispersing particles in a solvent with a smaller particle size. The polymer dispersant is preferably an acid-modified product of a resin to be mixed, an acid-modified product of a resin having the same composition with a lower molecular weight, an acid-modified product of a resin having a similar structure to the resin, or a basic modified product. More preferably, an acid-modified resin or a basic modified product compatible with the resin to be mixed is desirable. The term “compatible” in the present invention means that when the modified product and the thermoplastic resin are mixed, it is transparent and free from dust. Various acid-modified products such as maleic acid-modified and acrylic acid-modified are preferably used. In addition, amide modification can also be used. There are various types of commercially available ones, which can be selected and used depending on the application. Examples of polyethylene-based modified resins include the sun wax series (manufactured by Sanyo Chemical Industries), and examples of polypropylene-based resin modified products include the biscol series (manufactured by Sanyo Chemical Industries). Taking an optical resin as an example, TOPAS TMG MAH 2050 (maleic acid modified) is commercially available as an acid modified product for optical resin grade TOPAS5017 (manufactured by TiCoNa). For example, this acid-modified product is transparent even when mixed with APEL (Mitsui Chemicals). The amount of the polymer dispersant is desirably an arbitrary amount less than or equal to the maximum value equivalent to the acidic group and / or basic group present on the particle surface. The addition amount of the dispersant is preferably 20 wt% or less, more preferably 10 wt% or less with respect to the particles. When a dispersant of 20 wt% or more is used, it is difficult to form a silica film densely.

(3.2) Surface treatment process As the 2nd silane coupling agent in a surface treatment process, the silane coupling agent which can hydrophobize the surface is applicable. Commercially available silane coupling agents include hexamethyldisilazane, trimethylethoxysilane, trimethylmethoxysilane, trimethylsilyl chloride, methyltriethoxysilane, dimethyldiethoxysilane, decyltrimethoxysilane, vinyltrichlorosilane, vinyltrimethoxy. Silane, vinyltriethoxysilane, N-2 (aminoethyl) 3aminopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, SZ6187 made by Toray Dow Silicone, etc. can be preferably used, but are not limited thereto. .

  Among these, a monofunctional silane coupling agent is preferable because the aggregation of particles in the case of treatment in a dispersion is small. Furthermore, as the particle size is reduced, the surface area relative to the weight increases, and when a surface treatment is performed using a surface treatment agent having a large molecular weight, a large amount of the surface treatment agent is required. The physical properties of an optical resin material produced using particles containing a large amount of surface treatment deteriorate. Therefore, a silane coupling agent having a small molecular weight and high hydrophobicity is desirable, and hexamethyldisilazane, trimethylethoxysilane, trimethylmethoxysilane, and trimethylsilyl chloride can be more preferably used.

  The addition amount of the second silane coupling agent is desirably 5 to 20% by weight, more desirably 10 to 15% by weight, based on the total inorganic fine particles. If added in an amount of 20% by weight or more, an aggregate of the second coupling agent is formed, which causes a decrease in the transmittance of the optical resin material, and if it is less than 5% by weight, sufficient hydrophobicity is imparted to the particles. difficult.

(3.3) Kneading Step After the dispersion step, the inorganic fine particles after surface treatment and the thermoplastic resin are kneaded. Specific kneaders include KRC kneader (manufactured by Kurimoto Iron Works); polylab system (manufactured by HAAKE); nanocon mixer (manufactured by Toyo Seiki Seisakusho); Nauter mixer bus co-kneader (manufactured by Buss) ); TEM type extruder (manufactured by Toshiba Machine Co., Ltd.); TEX twin-screw kneader (manufactured by Nippon Steel Works); PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.); ); Needex (manufactured by Mitsui Mining); MS pressure kneader, nider ruder (manufactured by Moriyama Seisakusho); Banbury mixer (manufactured by Kobe Steel).
The resin material for optics can be manufactured by performing each process of a kneading | mixing process through the surface treatment process from the above dispersion | distribution process.

(3.4) Second surface treatment step In the present embodiment, the inorganic fine particles may be subjected to a surface treatment using a third silane coupling agent after the surface treatment step and before the kneading step. Good (second surface treatment step). As a 3rd silane coupling agent in a 2nd surface treatment process, the thing similar to the said 2nd silane coupling agent can be used, The addition amount is 5-20 weight with respect to all the inorganic fine particles. % Is desirable, more desirably 10 to 15% by weight. If added in an amount of 20% by weight or more, aggregates of the third coupling agent are formed, which causes a decrease in the transmittance of the optical resin material. If the amount is 5% by weight or less, sufficient hydrophobicity is imparted to the particles. difficult.

(4) Optical Element Manufacturing Method and Application Examples (4.1) Optical Element Manufacturing Method Next, a method for manufacturing an optical element (for example, an optical resin lens) according to the present invention will be described.
In the production of the optical element, the optical resin material obtained as described above is molded. The molding method is not particularly limited, but melt molding is preferable in order to obtain a molded product excellent in 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 optical resin material in injection molding prevents the sink and distortion of the molded product by imparting appropriate fluidity to the resin during molding. From the viewpoint of preventing the occurrence of silver streak due to thermal decomposition of the resin, and effectively preventing yellowing of the molded product, a range of 150 ° C to 400 ° C is preferable, and a range of 200 ° C to 350 ° C is more preferable. Yes, particularly preferably in the range of 200 ° C to 330 ° C.

  The 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 or a sheet shape, and has a low birefringence, transparency, mechanical Since it is excellent in strength, heat resistance and low water absorption, it is suitably used as an optical resin lens that is one of the optical elements of the present invention, but may be used as other optical components.

(4.2) Application Example of Optical Element The optical element according to the present invention can be obtained by the manufacturing method described above, and a specific application example to an optical component is 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 diffusion films; light diffusion plates; optical cards; liquid crystal display element substrates.

  Among these, the optical element according to the present invention is suitably used as a pickup lens or a laser scanning lens that requires low birefringence, and is most preferably used as a pickup lens.

Hereinafter, an optical pickup device 1 using an optical element molded from an optical resin material will be described with reference to FIG.
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.

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

Next, the operation of the optical pickup device 1 will be described.
The optical pickup device 1 in the present embodiment emits blue light from the semiconductor laser oscillator 2 at the time of recording information on the optical disc D or at the time of reproducing information recorded on the optical disc D. As shown in FIG. 1, the emitted blue light becomes a light beam 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, also the numerical aperture NA required for the objective lens 7 different. In the present embodiment, the optical disc D is a high density, and its numerical aperture is set to 0.85.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

(1) Preparation of sample (1.1) Preparation of inorganic fine particles First, nanoparticles of aluminum phosphate were prepared by reaction crystallization using a double jet method. Hereinafter, a manufacturing method thereof will be described.
3 liters of an aqueous solution containing 0.027 moles of triammonium phosphate each of 3.53 moles of aluminum sulfate aqueous solution (first solution) and 10.59 moles of aqueous solution of triammonium phosphate (second solution) 2 liters was added over 10 minutes by the double jet method. During the formation of inorganic fine particles, the pH was controlled to 6.5 with sulfuric acid, and the temperature was controlled to 25 ° C. After the addition, soluble salts were desalted and removed by ultrafiltration to obtain a 10% by mass aluminum phosphate dispersion.

This solution was spray-dried by spray drying to obtain an aluminum phosphate powder having a volume average particle size of 20 nm.
Next, by increasing the concentration of the first solution and the second solution by a factor of 2, an aluminum phosphate powder having a volume average particle diameter of 65 nm was obtained by the same production method.
Further, by increasing the concentration of the first solution and the second solution by a factor of 3, an aluminum phosphate powder having a volume average particle size of 110 nm was obtained.

  The “volume average particle diameter of the aluminum phosphate powder” herein is an average particle diameter determined by the X-ray small angle scattering measurement method, and the aluminum phosphate powder aggregates to form aggregated particles. If it is, the average particle diameter is calculated by converting the aggregated particles as one particle.

(1.1.1) Preparation of inorganic fine particles 1 The study was performed using aluminum phosphate having a volume average particle diameter of 65 nm prepared by chemical crystallization. As solution 1, a mixed solution of pure water 40 cc, ethanol 140 cc, ammonia water 7.5 cc, polycarboxylic acid ammonium salt (A-6114 manufactured by Toa Gosei Co., Ltd., molecular weight 10,000) 0.35 g is prepared, and the mixed solution 7.5 g of aluminum phosphate was added. Next, the aluminum phosphate was dispersed using an ultra apex mill (Sakai Industry Co., Ltd.).

  Next, a solution of 20 cc of tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.), 4 cc of water, and 14 cc of ethanol was prepared as Solution 2. Solution 2 was added dropwise to solution 1 over 8 hours at room temperature using a pump. When stirring was further continued for 1 hour, the pH of the solution was raised to 10.4 using aqueous ammonia. Further, the mixture was stirred at room temperature for 15 hours (dispersing step).

  Next, 100 ml of ethanol was added to the solution and centrifuged to remove unreacted tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.). Next, the aluminum phosphate was ultrasonically redispersed in 140 cc of ethanol, 40 cc of pure water, and 7.5 cc of aqueous ammonia. To this, 1 g of trimethylethoxysilane (LS-875 manufactured by Shin-Etsu Chemical Co., Ltd.) was added and further stirred for 15 hours (surface treatment step). After completion of stirring, centrifugation was performed. Drying was performed at 100 ° C. for 10 hours to obtain a white powder. By this operation, a surface-treated aluminum phosphate powder having a hydrophobicity of 42% could be obtained. The aluminum phosphate powder was designated as “inorganic fine particle 1”.

(1.1.2) Preparation of inorganic fine particles 2 The study was performed using aluminum phosphate having a volume average particle diameter of 65 nm prepared by chemical crystallization. As a solution 1, a mixed solution of pure water 40 cc, ethanol 140 cc, ammonia water 7.5 cc, polycarboxylic acid ammonium salt (Toa Gosei Co., Ltd. A-6114, molecular weight 10,000) 0.35 g is prepared. 7.5 g of aluminum phosphate was added. Next, the aluminum phosphate was dispersed using an ultra apex mill (Sakai Industry Co., Ltd.).

  Next, a solution of 20 cc of tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.), 4 cc of water, and 14 cc of ethanol was prepared as Solution 2. At room temperature, solution 2 was added dropwise to solution 1 using a pump over 8 hours. When stirring was further continued for 1 hour, the pH of the solution was raised to 10.4 using aqueous ammonia. Further, the mixture was stirred at room temperature for 15 hours (dispersing step).

  Next, 100 ml of ethanol was added to the solution and centrifuged to remove unreacted tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.). Drying was performed at 100 ° C. for 10 hours to obtain a white powder. Next, it heated up to 250 degreeC under nitrogen and dried. Furthermore, 10% by weight of hexamethyldisilazane was added to the powder and stirred at 90 ° C. (surface treatment step). By this operation, a surface-treated aluminum phosphate powder having a hydrophobicity of 56% could be obtained. The aluminum phosphate powder was designated as “inorganic fine particles 2”.

(1.1.3) Preparation of Inorganic Fine Particle 3 A study was performed using aluminum phosphate having a volume average particle diameter of 65 nm prepared by chemical crystallization. As a solution 1, a mixed solution of pure water 40 cc, ethanol 140 cc, ammonia water 7.5 cc, polycarboxylic acid ammonium salt (Toa Gosei Co., Ltd. A-6114, molecular weight 10,000) 0.35 g is prepared. 7.5 g of aluminum phosphate was added. Next, the aluminum phosphate was dispersed using an ultra apex mill (Sakai Industry Co., Ltd.).

  Next, a solution of 20 cc of tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.), 4 cc of water, and 14 cc of ethanol was prepared as Solution 2. At room temperature, solution 2 was added dropwise to solution 1 using a pump over 8 hours. When stirring was further continued for 1 hour, the pH of the solution was raised to 10.4 using aqueous ammonia. Further, the mixture was stirred at room temperature for 15 hours (dispersing step).

  Next, 100 ml of ethanol was added to the solution and centrifuged to remove unreacted tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.). Next, the aluminum phosphate was ultrasonically redispersed in 140 cc of ethanol, 40 cc of pure water, and 7.5 cc of aqueous ammonia. To this, 1.5 g of trimethylethoxysilane (Shin-Etsu Chemical LS-875) was added. Furthermore, stirring was performed for 15 hours (surface treatment process).

  After completion of stirring, centrifugation was performed. Drying was performed at 100 ° C. for 10 hours to obtain a white powder. Next, it heated up to 250 degreeC under nitrogen and dried. Furthermore, 10% by weight of hexamethyldisilazane was added to the powder and stirred at 90 ° C. (second surface treatment step). By this operation, a surface-treated aluminum phosphate powder having a hydrophobicity of 57% could be obtained. The aluminum phosphate powder was designated as “inorganic fine particles 3”.

(1.1.4) Preparation of inorganic fine particles 4 A study was performed using aluminum phosphate having a volume average particle diameter of 20 nm prepared by chemical crystallization. As a solution 1, a mixed solution of pure water 40 cc, ethanol 140 cc, ammonia water (25%) 7.5 cc, polycarboxylic acid ammonium salt (Toa Gosei Co., Ltd. A-6114, molecular weight 10,000) 0.1 g was prepared, 2.5 g of aluminum phosphate was added to the mixed solution. Next, the aluminum phosphate was dispersed using an ultra apex mill (Sakai Industry Co., Ltd.).

  Next, a solution of 20 cc of tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.), 4 cc of water, and 14 cc of ethanol was prepared as Solution 2. At room temperature, solution 2 was added dropwise to solution 1 using a pump over 8 hours. When stirring was further continued for 1 hour, the pH of the solution was raised to 10.4 using aqueous ammonia. Further, the mixture was stirred at room temperature for 15 hours (dispersing step).

  Next, 100 ml of ethanol was added to the solution and centrifuged to remove unreacted tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.). Next, the aluminum phosphate was ultrasonically redispersed in 140 cc of ethanol, 40 cc of pure water, and 7.5 cc of aqueous ammonia (25%). Here, 0.5 g of trimethylethoxysilane (LS-875 manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and stirring was further performed for 15 hours (surface treatment step).

  After completion of stirring, centrifugation was performed. Drying was performed at 100 ° C. for 10 hours to obtain a white powder. Next, it heated up to 250 degreeC under nitrogen and dried. Furthermore, 10% by weight of hexamethyldisilazane was added to the powder and stirred at 90 ° C. (second surface treatment step). By this operation, a surface-treated aluminum phosphate powder having a hydrophobization degree of 58% could be obtained. The aluminum phosphate powder was designated as “inorganic fine particles 4”.

(1.1.5) Preparation of Inorganic Fine Particles 5 Investigation was made using alumina (TM-300 manufactured by Daimei Chemical, volume average particle diameter: 7 nm). As a solution 1, a mixed solution of pure water 40 cc, ethanol 140 cc, ammonia water (25%) 7.5 cc, polycarboxylic acid ammonium salt (Toa Gosei Co., Ltd. A-6114, molecular weight 10,000) 0.4 g was prepared, To the mixed solution, 8 g of alumina (TM-300 manufactured by Daimei Chemical, volume average particle diameter: 7 nm) was added.

  Next, as a solution 2, a solution of 40 cc of tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.), 4 cc of water, and 14 cc of ethanol was prepared. At room temperature, solution 2 was added dropwise to solution 1 using a pump over 8 hours. When stirring was continued for another hour, the pH of the solution was raised to 10.4 using aqueous ammonia. Further, the mixture was stirred at room temperature for 15 hours (dispersing step).

  Next, 100 ml of ethanol was added to the solution and centrifuged to remove unreacted tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.). Next, alumina (volume average particle diameter 7 nm, TM-300 manufactured by Daimei Chemical Co., Ltd.) was ultrasonically redispersed in ethanol 140 cc, pure water 40 cc, and ammonia water (25%) 7.5 cc. To this, 1.5 g of trimethylethoxysilane (LS-875 manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and stirring was further performed for 15 hours (surface treatment step).

  After completion of stirring, centrifugation was performed. Drying was performed at 100 ° C. for 10 hours to obtain a white powder. Next, it heated up to 250 degreeC under nitrogen and dried. Furthermore, 10% by weight of hexamethyldisilazane was added to the powder and stirred at 90 ° C. (second surface treatment step). By this operation, it was possible to obtain surface-treated alumina having a hydrophobization degree of 51%. The alumina was designated as “inorganic fine particle 5”.

(1.1.6) Preparation of inorganic fine particles 6 The study was performed using aluminum phosphate having a volume average particle diameter of 20 nm prepared by chemical crystallization. As a solution 1, a mixed solution of 40 cc of pure water, 140 cc of ethanol, and 7.5 cc of aqueous ammonia was prepared, and 2.5 g of aluminum phosphate was added to the mixed solution. Next, the aluminum phosphate was dispersed using an ultra apex mill (Sakai Industry Co., Ltd.).

  Furthermore, a solution of 20 cc of tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.), 4 cc of water, and 14 cc of ethanol was prepared as Solution 2. At room temperature, solution 2 was added dropwise to solution 1 using a pump over 8 hours. When stirring was continued for another hour, the pH of the solution was raised to 10.4 using aqueous ammonia. Further, the mixture was stirred at room temperature for 15 hours (dispersing step).

  Next, 100 ml of ethanol was added to the solution and centrifuged to remove unreacted tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.). Next, the aluminum phosphate was ultrasonically redispersed in 140 cc of ethanol, 40 cc of pure water, and 7.5 cc of aqueous ammonia. Here, 0.5 g of trimethylethoxysilane (LS-875 manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and stirring was further performed for 15 hours (surface treatment step).

  After completion of stirring, centrifugation was performed. Drying was performed at 100 ° C. for 10 hours to obtain a white powder. Next, it heated up to 250 degreeC under nitrogen and dried. Furthermore, 10% by weight of hexamethyldisilazane was added to the powder and stirred at 90 ° C. (second surface treatment step). By this operation, a surface-treated aluminum phosphate powder having a hydrophobicity of 57% could be obtained. The aluminum phosphate was designated as “inorganic fine particles 6”.

(1.1.7) Preparation of inorganic fine particle 7 It investigated using the aluminum phosphate with the volume average particle diameter produced by the chemical crystallization of 20 nm. Prepare a mixed solution of 40 g of pure water, 140 cc of ethanol, 7.5 cc of ammonia water, 0.1 g of polycarboxylic acid ammonium salt (Toa Gosei Co., Ltd. A-6114, molecular weight 10,000), and add aluminum phosphate to the mixed solution. 2.5 g was added to prepare a slurry. To this, 0.5 g of trimethylethoxysilane (LS-875 manufactured by Shin-Etsu Chemical) was added. Furthermore, stirring was performed for 15 hours (surface treatment process).

  After completion of stirring, centrifugation was performed. Drying was performed at 100 ° C. for 10 hours to obtain a white powder. Next, it heated up to 250 degreeC under nitrogen and dried. Furthermore, 10% by weight of hexamethyldisilazane was added to the powder and stirred at 90 ° C. (second surface treatment step). By this operation, a surface-treated aluminum phosphate powder having a hydrophobization degree of 20% could be obtained. The aluminum phosphate powder was designated as “inorganic fine particles 7”.

(1.1.8) Preparation of inorganic fine particles 8 The study was performed using aluminum phosphate having a volume average particle diameter of 110 nm prepared by chemical crystallization. As a solution 1, a mixed solution of pure water 40 cc, ethanol 140 cc, ammonia water 7.5 cc, polycarboxylic acid ammonium salt (Toa Gosei Co., Ltd. A-6114, molecular weight 10,000) 0.5 g is prepared. 10 g of aluminum phosphate was added. Next, aluminum phosphate was dispersed using an Ultra Apex mill (Kotobuki Giken).

  Next, a solution of 20 cc of tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.), 4 cc of water, and 14 cc of ethanol was prepared as Solution 2. At room temperature, solution 2 was added dropwise to solution 1 using a pump over 8 hours. When stirring was further continued for 1 hour, the pH of the solution was raised to 10.4 using aqueous ammonia. Further, the mixture was stirred at room temperature for 15 hours (dispersing step).

  Next, 100 ml of ethanol was added to the solution and centrifuged to remove unreacted tetraethoxysilane (LS-2430 manufactured by Shin-Etsu Chemical Co., Ltd.). Next, the aluminum phosphate was ultrasonically redispersed in 140 cc of ethanol, 40 cc of pure water, and 7.5 cc of aqueous ammonia. To this, 0.5 g of trimethylethoxysilane (Shin-Etsu Chemical LS-875) was added and further stirred for 15 hours (surface treatment step).

  After completion of stirring, centrifugation was performed. Drying was performed at 100 ° C. for 10 hours to obtain a white powder. Next, it heated up to 250 degreeC under nitrogen and dried. Furthermore, 10% by weight of hexamethyldisilazane was added to the powder and stirred at 90 ° C. (second surface treatment step). By this operation, a surface-treated aluminum phosphate powder having a hydrophobicity of 57% could be obtained. The aluminum phosphate powder was designated as “inorganic fine particles 8”.

The degree of hydrophobicity of the inorganic fine particles 1 to 8 was determined as follows.
1-80.2 g of each inorganic fine particle is added to 50 ml of water, and methanol is added from the burette until the total amount of each inorganic fine particle 1-8 is suspended. Here, the volume of added methanol was set to Vml, and the degree of hydrophobicity of each inorganic fine particle 1 to 8 was determined from the following formula.
Hydrophobicity = V / (50 + V) × 100

(1.2) Preparation of samples 1 to 8 Using a polylab system (manufactured by HAAKE), 20% by volume of the inorganic fine particles 1 to 8 are added to a thermoplastic resin (ZEONEX330R manufactured by Nippon Zeon Co., Ltd.). By melting and kneading this, "Samples 1 to 8 (corresponding to optical resin material)" containing 20% by volume of inorganic fine particles 1 to 8 could be obtained (kneading step). Each sample 1-8 respond | corresponds to the kind of inorganic fine particle 1-8, and the number (numerical part) of a sample and the number (numeric part) of an inorganic fine particle mutually respond | correspond.

  Samples 1 to 8 obtained as a result were stored at 250 ° C. for 2 hours, the weight loss was 2% by weight or less, and deterioration of physical properties due to residual solvent and unreacted silane coupling agent was It is thought that there is nothing.

(2) Measurement of physical properties of sample (2.1) Measurement of transmittance Each sample 1 to 8 is injection-molded to produce a molded body for measurement (thickness 3 mm), and the wavelength of each molded body is 587.5 nm. The transmittance was measured. For the measurement, a spectrophotometer UV-3150 manufactured by Shimadzu Corporation was used. The measurement results are shown in Table 2 below.

(2.2) Measurement of refractive index Each sample 1-18 was melted and heat-molded to prepare a test plate having a thickness of 3 mm. Then, about each sample 1-18, the refractive index of wavelength 587.5nm was measured using the automatic refractometer KPR-200 by a Calnew optical industry company. The measurement results are shown in Table 2 below.

(3) Summary As shown in Table 2, when Samples 1-5 are compared with Samples 6-8, Samples 1-5 are superior to those of Comparative Samples 6-8 in the properties of transmittance and refractive index. . Therefore, even if inorganic fine particles with a volume average particle size of 100 nm or less are used, high transparency and a high refractive index are realized by performing each of the dispersion process, the surface treatment process, and the second surface treatment process. You can see that you can.

It is a schematic diagram which shows the internal structure of an optical pick-up apparatus.

Explanation of symbols

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

Claims (7)

A method for producing an optical resin material obtained by kneading inorganic fine particles in a thermoplastic resin,
A dispersion step of dispersing inorganic fine particles having a volume average particle diameter of 1 to 100 nm in a solution of a first silane coupling agent and a dispersant;
A surface treatment step of subjecting the inorganic fine particles to a surface treatment using a second silane coupling agent after the dispersion step;
A kneading step of kneading the inorganic fine particles into the thermoplastic resin after the surface treatment step;
A method for producing an optical resin material, comprising: In the manufacturing method of the optical resin material of Claim 1,
The method for producing an optical resin material, wherein the first silane coupling agent is selected from tetraethoxysilane, tetramethoxysilane, and polysilazane. In the manufacturing method of the optical resin material of Claim 1 or 2,
The method for producing an optical resin material, wherein the second silane coupling agent is selected from hexamethyldisilazane, trimethylethoxysilane, trimethylmethoxysilane, and trimethylsilyl chloride. In the manufacturing method of the optical resin material as described in any one of Claims 1-3,
A second surface treatment step of performing a surface treatment on the inorganic fine particles using a third silane coupling agent after the surface treatment step and before the kneading step is provided. Method. In the manufacturing method of the optical resin material of Claim 4,
The method for producing an optical resin material, wherein the third silane coupling agent is selected from hexamethyldisilazane, trimethylethoxysilane, trimethylmethoxysilane, and trimethylsilyl chloride. In the manufacturing method of the optical resin material as described in any one of Claims 1-5,
The method for producing an optical resin material, wherein the inorganic fine particles are an oxide or a phosphate.   An optical element obtained by molding an optical resin material obtained by the method for producing an optical resin material according to any one of claims 1 to 6.

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