JP5277457B2 - Method for producing composite metal oxide fine particle-containing resin material, and optical element using the same - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is suitably used as a lens, filter, grating, optical fiber, flat optical waveguide, etc., and in particular, a method for producing an excellent composite metal oxide fine particle-containing resin material having a low hygroscopic property and a high transmittance and the use thereof The present invention relates to an optical element.

  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 is known (for example, see Patent Document 1).

  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 low water absorption and significantly improved refractive index stability with respect to humidity changes, while still improving the refractive index stability with temperature changes. The current situation is not.

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

  For the purpose of increasing the refractive index, many proposals have been made for materials in which inorganic fine particles are dispersed and mixed in a resin (see, for example, Patent Documents 4 and 5). This patent document describes an organic polymer having a high refractive index and a high Abbe number in which inorganic fine particles having a high refractive index and a high Abbe number are dispersed in a transparent base polymer. However, in the methods of Patent Documents 4 and 5, since the aggregation of fine particles is likely to occur and light scattering is likely to occur, the transparency is not sufficient.

  Further, Patent Document 6 discloses that a resin material having a high light transmittance can be obtained by dispersing inorganic fine particles having a small refractive index difference with a host resin material at a high concentration. However, even in this method, aggregation of fine particles cannot be prevented, and when aggregated, light scattering caused by a difference in refractive index between the voids in the aggregated particles and the resin is large, so that sufficient transparency as an optical material is obtained. I can't.

  Moreover, as a resin material for optical elements, it is required to simultaneously achieve various optical characteristics. For example, the refractive index suitable for the application, the magnitude of the refractive index change due to the temperature change, the magnitude of the refractive index change due to the humidity change, the transmittance, etc. may be mentioned. It is difficult to improve these characteristics by adding a single fine particle, and it is conceivable to add multiple types of fine particles. However, when multiple types of fine particles are added, the size of the fine particles depends on the type of particles. Problems such as unevenness of the thickness and aggregation of particles between different particles have occurred, and a material with stable performance has not been obtained.

In order to reduce the aggregation of fine particles in the resin, it is known to modify the surface of the fine particles. In particular, as a technique for stably performing surface modification, a method for forming metal oxide fine particles in which metal oxide fine particles are surface-modified using a supercritical state or a subcritical state as a reaction field has been proposed (see, for example, Patent Documents 7 and 8). ). Patent Documents 7 and 8 describe a critical state of water suitable for a reaction field, a subcritical state, or a pressure-temperature condition exceeding the critical state. FIG. 1 shows the density-temperature / pressure dependency of water and the dielectric constant-pressure dependency of water. As is clear from this, a unique reaction environment can be provided in the supercritical state. FIG. 2 shows the phase behavior of the water-gas binary system and the water-organic solvent system in the vicinity of the critical point of water, and there is also a characteristic homogeneous phase formation region. This is applied to the surface modification reaction. However, even when a resin material containing such surface-modified fine particles is used, as an optical element for an optical pickup device that requires high accuracy, a decrease in transmittance that occurs when fine particles are added Turned out to be a problem.
JP 2002-105131 A JP 2002-207101 A Japanese Patent Laid-Open No. 2002-240901 JP 2001-183501 A JP 2003-73563 A JP-A-2005-213410 JP 2005-193237 A JP 2005-194148 A

  The present invention has been made in view of the above problems, and its purpose is to adjust the refractive index to a suitable range as an optical element by adding metal oxide fine particles, while having low water absorption, The present invention provides a method for producing a resin material containing composite metal oxide fine particles having high transparency and an optical element using the same.

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

1. (1) A composite metal oxide fine particle is synthesized using a solution containing at least two or more kinds of metal elements (excluding La ) using a supercritical state or a subcritical state as a reaction field, and the composite a step of surface-modified metal oxide fine particles, and (2) the step of mixing with the fine composite metal oxide particles curable resin or a thermoplastic resin, a city seen <br/> including,
Method of producing a composite metal oxide fine particle-containing resin material the curable resin or thermoplastic resin is characterized by containing Mukoto at least cyclic olefin resin.

2. (1) At least one metal different from the metal oxide fine particles on the metal oxide fine particles having at least one metal element (excluding La ) using the supercritical state or the subcritical state as a reaction field A step of synthesizing composite metal oxide fine particles by providing a metal oxide layer using a solution containing an element and surface-modifying the composite metal oxide fine particles; and (2) the composite metal oxide fine particles. mixing with a curable resin or a thermoplastic resin, a city seen including,
Method of producing a composite metal oxide fine particle-containing resin material the curable resin or thermoplastic resin is characterized by containing Mukoto at least cyclic olefin resin.

3. The composite metal oxide fine particles have an average particle diameter measured by a TEM method of 5 nm or more and 50 nm or less, and contain at least two metal oxides containing a metal element selected from the group consisting of the following metals M: 3. The method for producing a composite metal oxide fine particle-containing resin material as described in 1 or 2 above.
Metal M: Si, Mg, Al, Ca, Ti, Zr, Mn
4). 4. The method for producing a composite metal oxide fine particle-containing resin material according to any one of 1 to 3, wherein the composite metal oxide fine particles have a refractive index of 1.5 or more and 1.75 or less.

  5. 5. The composite metal oxide according to any one of 1 to 4, wherein the content of the composite metal oxide fine particles in the composite metal oxide fine particle-containing resin material is 10% by volume or more and 40% by volume or less. Of manufacturing fine particle-containing resin material.

  6). Any one of the above 1-4, wherein the refractive index of the curable resin or the thermoplastic resin is nh and the refractive index of the composite metal oxide fine particles is np, the following formula (A) is satisfied: A method for producing the composite metal oxide fine particle-containing resin material according to Item.

Formula (A) 0 ≦ | np−nh | ≦ 0.1 5

7 . 7. An optical element produced using the composite metal oxide fine particle-containing resin material obtained by the method for producing a composite metal oxide fine particle-containing resin material according to any one of 1 to 6 above.

  According to the configuration of the above item 1, the composite metal oxide fine particles capable of improving the characteristics required as an optical element by containing the composite metal oxide fine particles in which at least two kinds of metal oxides are uniformly dispersed. Provided is a production method capable of obtaining a resin material containing composite metal oxide fine particles and a resin material containing composite metal oxide particles having a higher light transmittance and lower water absorption than in the past, and an optical element using the same. be able to.

  According to the structure of said 2nd term | claim, it is required as an optical element by including the composite metal oxide fine particle of what is called a core shell structure which has a layer of a different metal oxide fine particle on at least 1 type of metal oxide particle. Production method capable of obtaining composite metal oxide fine particle-containing resin material capable of improving characteristics, and further obtaining composite metal oxide fine particle-containing resin material having higher light transmittance and lower water absorption than conventional ones And an optical element using the same.

  According to the configuration of the third item, at least, among the characteristics that the transmittance more suitable as the optical element can be obtained, the refractive index change due to the temperature change is small, and the refractive index is suitable as the optical element. An optical element showing one of them can be obtained.

  According to the structure of the said 4th term, the composite metal oxide fine particle containing resin material which has a suitable refractive index as an optical element for optical pick-up apparatuses can be obtained.

  According to the configuration of the fifth aspect, the composite metal oxide fine particles can improve the resin material to have desired characteristics as an optical element, and can suppress a reduction in transmittance.

  According to the structure of the said 6th term | claim, the composite metal oxide fine particle containing resin material for optical elements which has the especially outstanding transmittance | permeability can be obtained.

According to the configuration of the seventh aspect, it is possible to obtain an optical element having low water absorption and high light transmittance while improving desired optical characteristics.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

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

  First, the composite metal oxide fine particle-containing resin material (hereinafter simply referred to as composite material) according to the present invention will be described.

  The composite material in the present embodiment contains a curable resin or a thermoplastic resin and composite metal oxide fine particles, and is molded into a molded product such as an optical element such as an optical resin lens. Yes. Hereinafter, (1) composite metal oxide fine particles, (2) resin, (3) a method for producing a composite material, and (4) a molded product will be described.

  The term “fine particles” in the present specification refers to those having an average particle diameter of 1 μm (1,000 nm) or less, preferably nanoparticles. The nanoparticles generally mean those having an average particle size of 200 nm or less, preferably 100 nm or less, and more preferably those having an average particle size of 5 nm or more and 50 nm or less. . In addition, the nanoparticles preferably have a uniform particle size, but in some cases, a mixture of particles having different particle sizes at a certain ratio may be preferable.

The particle diameter can be measured by a method known in the art, and can be measured by, for example, TEM, adsorption method, light scattering method, SAXS or the like. In TEM, observation is performed with an electron microscope. When the particle size distribution is wide, it is necessary to pay attention to whether or not the particles entering the field of view represent all particles. In the adsorption method, the BET surface area is evaluated by N ₂ adsorption or the like.

(1) Composite Metal Oxide Fine Particles The present invention is characterized in that the composite metal oxide fine particles are synthesized by using a supercritical state or a subcritical state as a reaction field and further surface-modified. In the reaction field in the supercritical state, the mass change due to dehydration from the inside of the crystal at the time of temperature rise is small compared to the metal oxide synthesized at low temperature, and it has a sharp peak by X-ray diffraction. Fine particles with high crystallinity can be obtained, and in-situ surface modification is possible in a reaction field in a supercritical state, so that the fine particle formation and surface modification can be performed in the same reaction field, and the reaction solution in a state without aggregation Fine particles can be collected from inside. Specific reaction conditions are 250 ° C. or more and 500 ° C. or less as the temperature condition, and preferably 10 MPa or more and 30 MPa or less as the pressure condition. However, as long as the reaction field is a critical point or a pressure and / or temperature condition exceeding the critical point. is not.

  Further, monodisperse particles having a narrow particle size distribution can be obtained by controlling the reaction conditions.

  The metal oxide fine particles are required to synthesize composite fine particles composed of at least two kinds of elements in order to achieve various desired optical properties as an optical element. The element distribution in the fine particles is preferably uniform or has a core-shell structure.

  The constituent elements are preferably metal oxides containing at least two selected from Si, Mg, Al, Ca, Ti, Zr, and Mn. Specific examples include composite oxides containing at least two of titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide, calcium oxide, and silica, but are not limited thereto.

  By adding only one kind of metal oxide particles, it is difficult to simultaneously improve the refractive index change, light transmittance, desired refractive index, etc. with respect to the environmental change of the resin material. Depending on the properties required for the resin composition, a plurality of types can be appropriately selected in consideration of properties such as the refractive index of the fine particles. Furthermore, compatibility with a resin as a base material (hereinafter sometimes referred to as a host material), that is, appropriately selecting and using fine particles that are difficult to cause dispersibility and scattering in the resin is necessary for maintaining light transmittance. Is preferable. Therefore, it is preferable that the refractive index difference between the composite metal oxide fine particles of the present invention and the host material is as small as possible, the refractive index of the host material is nh, and the refractive index of the composite metal oxide fine particles is np. It is preferable that the resin satisfies the following formula (A).

Formula (A) 0 ≦ | np−nh | ≦ 0.15
Moreover, as an optical element for optical pick-up apparatuses, those with a refractive index in the range of 1.5 to 1.75 are preferably used. The preferable refractive index of the composite metal oxide fine particles to be added differs depending on the refractive index of the host material, but it is preferable from the viewpoint of obtaining a high transmittance closer to the refractive index of the conventionally used resin. The refractive index of the fine particles is It is preferably 1.5 to 1.75, and more preferably 1.54 to 1.70.

  Examples of the surface modifier used for the surface treatment of the composite metal oxide 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 composite metal oxide fine particles and the type of resin in which the composite metal oxide fine particles are dispersed. Further, two or more surface treatments may be performed simultaneously or at different times.

  Specifically, for example, as a silane-based surface treatment agent, vinylsilazane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, hexamethyldisilazane and the like can be mentioned. Trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, hexamethyldisilazane and the like are preferably used.

  Silicone oil treatment agents include straight silicone oils such as dimethyl silicone oil, methylphenyl silicone oil, and methylhydrogen silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, and methacryl-modified. Silicone oil, mercapto modified silicone oil, phenol modified silicone oil, one-end reactive modified silicone oil, different functional group modified silicone oil, polyether modified silicone oil, methylstyryl modified silicone oil, alkyl modified silicone oil, higher fatty acid ester modified silicone Oil, hydrophilic specially modified silicone oil, higher alkoxy modified silicone oil, higher fat Acid-containing modified silicone oil, modified silicone oil and fluorine-modified silicone oil can be used.

  These surface modifiers may be used alone or in combination, and the properties of the surface modified fine particles obtained may differ depending on the surface modifier used. Affinity with the host material used in obtaining the material can also be achieved by selecting a surface modifier. The ratio of the surface modification is not particularly limited, but the ratio of the surface modifier is preferably 10 to 99% by mass and more preferably 30 to 98% by mass with respect to the fine particles after the surface modification. preferable.

  Further, in the supercritical reaction field, a solvent that promotes the homogenous phase of the organic modifier and water may be present as a coexisting substance. Specific solvents include methanol, ethanol, propanol, i-propanol, butanol, i -Butanol, t-butanol, ethylene glycol, etc. are mentioned.

(2) Resin In the present invention, a curable resin or a thermoplastic resin is used as the resin that becomes the base material of the composite metal oxide fine particle-containing resin material.

  The curable resin used in the present invention can be cured by any of ultraviolet and electron beam irradiation or heat treatment, and is mixed with the thermoplastic resin in an uncured state and then cured. As long as it forms a transparent resin composition, it can be used without particular limitation, and epoxy resins, vinyl ester resins, silicone resins, and the like are preferably used. For example, when an epoxy resin is used as the curable resin, any epoxy resin having at least two epoxy groups in one molecule can be used. Specifically, bisphenol A type epoxy resin, phenol novolac Examples thereof include halogenated epoxy resins such as type epoxy resins, o-cresol novolac type epoxy resins, triphenylmethane type epoxy resins and bromine-containing epoxy resins, and epoxy resins having a naphthalene ring. The aromatic epoxy resin may be a hydrogenated epoxy resin in which an aromatic ring is hydrogenated to cyclohexane. These epoxy resins can be used alone or in combination of two or more. Moreover, it is although it does not specifically limit as a hardening | curing agent of an epoxy resin, An acid anhydride hardening agent, a phenol hardening agent, etc. can be illustrated. Specific examples of the acid anhydride curing agent include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, 3-methyl-hexahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride. Examples thereof include an acid, a mixture of 3-methyl-hexahydrophthalic anhydride and 4-methyl-hexahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic anhydride, methyl nadic anhydride and the like. Moreover, a hardening accelerator is contained as needed. The curing accelerator is not particularly limited as long as it has good curability, is not colored, and does not impair the transparency of the curable resin. For example, 2-ethyl-4-methylimidazole ( 2E4MZ) and other imidazoles, tertiary amines, quaternary ammonium salts, bicyclic amidines such as diazabicycloundecene and derivatives thereof, phosphines, phosphonium salts, and the like. You may mix and use a seed | species or more.

  As a method for curing the composite metal oxide fine particle-containing resin material, when the curable resin is an ultraviolet ray and electron beam curable resin, a resin composition is filled in a mold having a predetermined shape with translucency, or on a substrate. After the coating, it may be cured by irradiating with ultraviolet rays and electron beams. On the other hand, when the curable resin is a thermosetting resin, it can be cured by compression molding, transfer molding, injection molding or the like.

  Next, the thermoplastic resin will be described.

  The thermoplastic resin in which the composite metal oxide fine particles that can be used in the present invention are dispersed is not particularly limited as long as it is a transparent thermoplastic resin material generally used as an optical material, but it is processed as an optical element. In view of the properties, it is preferably an acrylic resin, a cyclic olefin resin, a polycarbonate resin, a polyester resin, a polyether resin, a polyamide resin, or a polyimide resin, and particularly preferably a cyclic olefin resin, for example, JP-A-2003-73559. The compounds described in Japanese Laid-open Patent Publication No., etc. can be mentioned, and preferred compounds are shown in Table 1.

  Moreover, in the thermoplastic resin material which concerns on this invention, it is preferable that a water absorption is 0.2 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 (manufactured by Nippon Zeon), Arton (manufactured by JSR), Apel (manufactured by Mitsui Chemicals), TOPAS (manufactured 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 is considered to be substantially equal to the average value of the water absorption of each resin, and the average water absorption may be 0.2% or less.

(3-1) Manufacturing method of composite metal oxide fine particle-containing resin material Here, the composite metal oxide fine particle-containing resin material having a thermoplastic resin as a base material will be described as an example. It is not limited, and a curable resin may be used.

  The thermoplastic composite material is obtained by dispersing composite metal oxide fine particles in a thermoplastic resin as a host material. That is, a method in which a thermoplastic resin and composite metal oxide fine particles are prepared independently and then both are mixed, a method in which a thermoplastic resin is prepared in a condition in which pre-made composite metal oxide fine particles exist, Any method can be employed, such as a method of producing composite metal oxide fine particles under the condition in which the thermoplastic resin is present, or a method of producing both thermoplastic resin and composite metal oxide fine particles simultaneously. Specifically, for example, two solutions of a solution in which the thermoplastic resin is dissolved and a dispersion in which the composite metal oxide fine particles are uniformly dispersed are uniformly mixed, and the solution is poorly soluble in the thermoplastic resin. The method for obtaining the desired composite metal oxide fine particle-containing resin material by meeting can be preferably mentioned, but is not limited thereto.

  In the thermoplastic composite material, the degree of mixing of the thermoplastic resin and the composite metal oxide fine particles is not particularly limited, but in order to achieve the effect of the present invention more efficiently, it is mixed uniformly. 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 influenced by the production method, and it is important to select a method in consideration of the characteristics of the thermoplastic resin and the composite metal oxide fine particles to be used. In order to mix both the thermoplastic resin and the composite metal oxide fine particles more uniformly, a method of directly bonding the thermoplastic resin and the composite metal oxide fine particles can be suitably used in the present invention.

  The content of the composite metal oxide fine particles according to the present invention is not particularly limited as long as the effects of the present invention can be exhibited, and can be arbitrarily determined depending on the types of the thermoplastic resin and the composite metal oxide fine particles. The content of the composite metal oxide fine particles according to the present invention is preferably such that the volume fraction of the composite metal oxide fine particles with respect to the total volume of the composite material to be produced is 5% or more and 80% or less, 10% or more, 60 % Is more preferable, and 10% or more and 40% or less is more preferable. The volume fraction of inorganic fine particles here is expressed by the formula (x / a) / Y when the specific gravity of the composite metal oxide fine particles is a, the content is x grams, and the total volume of the composite material produced is Y milliliters. It is calculated | required by x100.

  Quantification of the content of composite metal oxide fine particles is observed with a transmission electron microscope (TEM). Observation of composite metal oxide fine particle images (information on composite metal oxide fine particle composition can be obtained by local elemental analysis such as EDX) Alternatively, it can be calculated from the contained mass of a predetermined composition obtained by elemental analysis of ash contained in a given resin composition and the specific gravity of crystals of the composition.

(3-2) Characteristics of Composite Material The composite material of the present invention produced as described above preferably has a small temperature change rate (dn / dT) of refractive index. In order to obtain such a composite material, the absolute value of dn / dT of at least one of the metal oxides used in the composite metal oxide fine particles is smaller than the dn / dT of the base resin, It is preferable that the codes of dn / dT are opposite to each other.

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

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

In the composite material, | dn / dT |, which is the absolute value of dn / dT, is preferably 0 or more and 9.0 × 10 ⁻⁵ or less, and | dn / dT | is 0 or more and 5.0 or less. × 10 ⁻⁵ or less is preferable. 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 composite material preferably has transparency in the visible region wavelength. The transparency of the composite material is preferably 70% or more, more preferably 80% or more, and most preferably 90% or more when the light transmittance in the visible region wavelength is 3 mm. Such measurement is performed, for example, by a test according to ASTM D-1003 (3 mm thickness) standard. The visible region here means a wavelength region of 400 to 650 nm.

  The refractive index of the composite material is determined by the combination of the thermoplastic resin and the composite metal oxide fine particles. Usually, the composite metal oxide fine particles having a refractive index higher than that of the thermoplastic resin can be selected to be higher than that of the thermoplastic resin. preferable.

  By selecting the metal oxide to be used as described above, the composite material can be made to be an optically excellent material having a small temperature dependency of the refractive index and high transparency. When a thermoplastic material is used as a base material, it has thermoplasticity and / or injection moldability, so that it can be made a material that is much better in molding processability than a glass material. This material that has both excellent optical properties and moldability is a property that has not been achieved with the materials disclosed so far, and has been described above with specific thermoplastic resins and specific multi-metal oxides. These characteristics can be obtained by comprising fine particles.

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

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

  For example, as an optical resin lens, an imaging lens of a camera; a lens such as a microscope, an endoscope, a telescope lens; an all-light transmission lens such as a spectacle lens; a CD, a CD-ROM, 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 beam printer fθ lens, laser scanning lens such as sensor lens; camera Finder type prism lenses.

  Examples of optical disc applications include CD, CD-ROM, WORM (recordable optical disc), MO (rewritable optical disc; magneto-optical disc), MD (mini disc), DVD (digital video disc), and the like. Other optical applications include light guide plates such as liquid crystal displays; optical films such as polarizing films, retardation films and light 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.

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

  The optical resin lens is prepared by first preparing a composite material (may be a mixture of resin and composite metal oxide fine particles, or a mixture of resin, composite metal oxide fine particles and additives), It is produced through a step of molding the obtained composite material.

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

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

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

  Hereinafter, an optical pickup device 1 in which an optical element is used as an objective lens will be described with reference to FIG. Here, FIG. 3 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. 3, the optical pickup device 1 in this embodiment includes a semiconductor laser oscillator 2 that is a light source. On the optical axis of the blue light emitted from the semiconductor laser oscillator 2, a collimator 3, a beam splitter 4, a quarter wavelength plate 5, a diaphragm 6, and an objective lens 7 are arranged in a direction away from the semiconductor laser oscillator 2. Are sequentially arranged.

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

  Here, the objective lens 7 is a single-lens optical lens using the composite material of the present invention. The objective lens 7 is disposed at a position facing the optical disk D, and transmits blue light emitted from the semiconductor laser oscillator 2 to one surface of the optical disk D. It is designed to concentrate on the top. The objective lens 7 is provided with a two-dimensional actuator 10, and the objective lens 7 is movable on the optical axis by the operation of the two-dimensional actuator 10. In the diaphragm 6, the incident light beam is narrowed to a diameter of 3 mm.

  Next, the operation of the optical pickup device 1 will be described.

  The optical pickup device 1 in the present embodiment emits blue light from the semiconductor laser oscillator 2 at the time of recording information on the optical disc D or at the time of reproducing information recorded on the optical disc D. As shown in FIG. 1, the emitted blue light becomes a light beam L1, is collimated to infinite parallel light through the collimator 3, and then passes through the beam splitter 4 to pass through the quarter-wave plate 5. To Penetrate. Further, after sequentially passing through the aperture 6 and the objective lens 7, a condensing spot is formed on the information recording surface D2 via the protective substrate D1 of the optical disc D.

  The light that forms the condensed spot is modulated by the information pits on the information recording surface D2 of the optical disc D and reflected by the information recording surface D2. 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.

  Note that the numerical aperture required for the objective lens 7 varies depending on the thickness dimension of the protective substrate D1 and the size of the information pit in the optical disk D. In the present embodiment, the optical disc D is a high density, and its numerical aperture is set to 0.85.

  Moreover, you may employ | adopt suitably the used wavelength of a light source in the range which is 390 nm-420 nm.

  Therefore, an optical path in which the composite material manufactured by the above method is applied to an optical pickup device, and a predetermined optical path difference is given to at least one optical surface with respect to a specific wavelength light passing through the optical surface. By applying to an optical element (objective lens) having a difference providing structure, even when light having a short wavelength near 400 nm is used for recording and reproducing information on a so-called next-generation optical disc such as Blu-Ray Disc. It is possible to provide optical characteristics with good accuracy. In addition, the optical pickup device using the element can have good pickup characteristics when information is reproduced or recorded on the optical information recording medium.

  The optical element for the optical pickup device referred to in the present invention refers to an optical system of the optical pickup device, for example, an objective lens, an objective lens unit, a coupling lens (collimator), a beam expander, a beam shaper, and a correction plate. The thing which can be used as members, such as.

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

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

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

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

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

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

Example 1
[Synthesis and surface modification of composite metal oxide fine particles]
In an autoclave, a predetermined amount of 0.01 [mol / L] aqueous Zr (NO ₃ ) solution, 0.01 [mol / L] tetraethoxysilane (TEOS) with hydrogen peroxide of 0.05 [mol / L]. In addition, a charge and a predetermined amount of hexamethyldisilazane (HMDS) were charged. In advance, the reaction tube was placed in a heating furnace set at 400 ° C. and heated. The pressure when assuming pure water is 390 [bar]. After a reaction time of 10 [min], the product was recovered. 200 particles were extracted from a TEM photograph of the collected fine particles, and an average particle diameter (D50) and a 90% diameter (D90) were calculated.

[Production of resin material containing composite metal oxide fine particles]
As preparations before kneading the composite metal oxide fine particles in the resin, each resin was dried at 80 ° C. for 8 hours, and the composite metal oxide fine particles were dried at 200 ° C. for 4 hours.

  The collected fine particles were subjected to solid-liquid separation and washing with a centrifuge, and dried at 90 ° C. and 10 [h] to obtain white powdered composite metal oxide fine particles.

  The obtained composite metal oxide fine particles were added to a molten cyclic olefin resin (APEL5014DP manufactured by Mitsui Chemicals), and a composite metal oxide fine particle-containing resin material in which the composite metal oxide fine particles were dispersed by melt kneading was produced. The kneading conditions were kneading for 5 minutes after the addition of the powder was completed at a set temperature of 200 ° C. and 30 rpm using a kneader manufactured by HAAKE.

  The composite metal oxide fine particle-containing resin material was melted and heat-molded to prepare a test plate having a thickness of 3 mm.

Example 2
Fine particles were prepared in the same manner as in Example 1 except that a 0.01 [mol / L] Al (NO ₃ ) ₃ aqueous solution was used instead of the 0.01 [mol / L] Zr (NO ₃ ) aqueous solution. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Example 3
Example except that 0.1 [mol / L] Al (NO ₃ ) ₃ aqueous solution was used instead of 0.01 [mol / L] Zr (NO ₃ ) aqueous solution and the reaction time was 3 [min]. Fine particles were prepared as in 1. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Example 4
Fine particles were prepared in the same manner as in Example 1 except that Al ₂ O ₃ fine particles (10 nm) were used instead of the 0.01 [mol / L] aqueous Zr (NO ₃ ) solution. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Example 5
Fine particles were produced in the same manner as in Example 1 except that Al ₂ O ₃ fine particles (22 nm) were used instead of the 0.01 [mol / L] aqueous Zr (NO ₃ ) solution. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Example 6
Fine particles were prepared in the same manner as in Example 1 except that Al ₂ O ₃ fine particles (55 nm) were used instead of the 0.01 [mol / L] aqueous Zr (NO ₃ ) solution. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Example 7
SiO ₂ fine particles (10 nm) were used in place of 0.01 [mol / L] Zr (NO ₃ ) aqueous solution, and 0.01 [mol / l] Al (NO ₃ ) ₃ aqueous solution was used in place of TEOS. Except that, fine particles were prepared in the same manner as in Example 1. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Example 8
Fine particles produced in the same manner as in Example 2 were added with 10 g of 1,6-hexanediol diacrylate in methyl ethyl ketone, the solvent was removed by a rotary evaporator, and the mixture was stirred on a hot plate at 80 ° C. for 5 hours. When the viscosity increased, 0.1 g of a photopolymerization initiator composed of a mixture of 1-hydroxycyclohexyl phenyl ketone and benzophenone was added and defoamed to obtain a resin composition. This resin composition was molded and irradiated with ultraviolet rays to produce a test plate having a thickness of 3 mm. The integrated light quantity of the irradiated ultraviolet rays was about 4000 mJ / cm ² .

Example 9
Using the fine particles produced in the same manner as in Example 4, a composite metal oxide fine particle-containing resin material was produced in the same manner as in Example 1 so that the particle filling rate shown in Table 2 was obtained, and the thickness was 3 mm by melting and thermoforming. A test plate was prepared.

Example 10
Using the fine particles produced in the same manner as in Example 4, a composite metal oxide fine particle-containing resin material was produced in the same manner as in Example 1 so that the particle filling rate shown in Table 2 was obtained, and the thickness was 3 mm by melting and thermoforming. A test plate was prepared.

Example 11
Using the fine particles produced in the same manner as in Example 4, a composite metal oxide fine particle-containing resin material was produced in the same manner as in Example 1 so that the particle filling rate shown in Table 2 was obtained, and the thickness was 3 mm by melting and thermoforming. A test plate was prepared.

Example 12
Using the fine particles produced in the same manner as in Example 4, a composite metal oxide fine particle-containing resin material was produced in the same manner as in Example 1 so that the particle filling rate shown in Table 2 was obtained, and the thickness was 3 mm by melting and thermoforming. A test plate was prepared.

Example 13
Fine particles were prepared in the same manner as in Example 1 except that MgO fine particles (40 nm) were used instead of the 0.01 [mol / L] aqueous Zr (NO ₃ ) solution. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Comparative Example 1
4 g of HMDS is added to 30 g of alumina silicate fine particles (50% Al ₂ O ₃ /50% SiO ₂ mixture, particle size 40 nm) prepared by the plasma method while stirring under argon. Subsequently, the mixture was heated at 200 ° C. for 30 minutes and then cooled to room temperature to obtain surface-modified oxide fine particles. Fine particles were produced in the same manner as in Example 1. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

Comparative Example 2
A mixed liquid of 4.6 g of pure water, 1.0 g of 26% ammonia water and 43 g of methanol, a mixed liquid of 14 g of tetramethoxysilane (TMOS) and 2.3 g of methanol, and 6.4 g of pure water and 1.0 g of 26% ammonia water. Was added dropwise over 15 minutes while maintaining the liquid temperature at 25 ° C., and then a mixed solution of 60 g of aluminum tetraisopropoxide and 1.5 g of isopropanol was added over 10 minutes to obtain a silica / alumina mixed sol. It was.

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

  To 5 g of the fine particles, 300 g of methanol and a 1 mol% nitric acid aqueous solution were added. While this liquid was stirred at 50 ° C., a mixed liquid of 100 g of methanol and 6 g of cyclopentyltrimethoxysilane was added over 60 minutes, and then further stirred for 24 hours. The obtained transparent dispersion was suspended in ethyl acetate and centrifuged to obtain fine particles. A composite metal oxide fine particle-containing resin material was produced from these fine particles in the same manner as in Example 1, and a test plate having a thickness of 3 mm was produced by melting and thermoforming.

<< Evaluation of composite metal oxide fine particles >>
(Water absorption rate)
Using a high-temperature and high-humidity machine “PR-2PK” (product name, manufactured by Espec Co., Ltd.), the fine particles previously dried at 100 ° C. and 10% RH for 100 hours are stored at 80 ° C. and 90% RH for 500 hours. The water absorption was determined from the increase in mass.

<Evaluation of resin material containing composite metal oxide fine particles>
(Evaluation of refractive index)
The refractive index at a wavelength of 588 nm of the resin composition was measured using an automatic refractometer KPR-200 manufactured by Kalnew Optical Industry Co., Ltd. Further, the refractive index of only the resin was measured, and the composite metal oxide fine particle refractive index was calculated.

(Measurement of transmittance)
The blue light transmittance at a wavelength of 405 nm was measured for the above test plate. The transmittance measurement method was based on ASTM D 1003. The results are shown in the column of “Transmittance” in Table 2 below. From the viewpoint of practicality, the transmittance needs to be 50% or more.

  The above measurement results are shown in Table 2 below.

  From the above table, Examples 1 to 13 of the configuration of the present invention contain a plurality of types of metal oxide fine particles, but the composite metal oxide fine particles have a lower water absorption rate and the composite material has a significantly higher transmittance than the comparative example. Both were high and found to be excellent composite materials.

  Moreover, when the composite materials of Examples 1 to 13 of the present invention were used as molding materials for optical pickup lenses as examples of optical elements, a lens having excellent moldability, refractive index, and light transmittance can be obtained. did it.

It is a figure which shows the density-temperature / pressure dependence of water, and the dielectric constant-pressure dependence of water. It is a figure which shows the phase behavior of the water-gas binary component system in the vicinity of the critical point of water, and the phase behavior of a water-organic solvent system. 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 / 4lambda wavelength plate 6 Aperture 7 Objective lens 8 Sensor lens group 9 Sensor 10 Two-dimensional actuator D Optical disk D1 Protection board D2 Information recording surface

Claims (7)

(1) A composite metal oxide fine particle is synthesized using a solution containing at least two or more kinds of metal elements (excluding La ) using a supercritical state or a subcritical state as a reaction field, and the composite a step of surface-modified metal oxide fine particles, and (2) the step of mixing with the fine composite metal oxide particles curable resin or a thermoplastic resin, a city seen including,
Method of producing a composite metal oxide fine particle-containing resin material the curable resin or thermoplastic resin is characterized by containing Mukoto at least cyclic olefin resin. (1) At least one metal different from the metal oxide fine particles on the metal oxide fine particles having at least one metal element (excluding La ) using the supercritical state or the subcritical state as a reaction field A step of synthesizing composite metal oxide fine particles by providing a metal oxide layer using a solution containing an element and surface-modifying the composite metal oxide fine particles; and (2) the composite metal oxide fine particles. mixing with a curable resin or a thermoplastic resin, a city seen including,
Method of producing a composite metal oxide fine particle-containing resin material the curable resin or thermoplastic resin is characterized by containing Mukoto at least cyclic olefin resin. The composite metal oxide fine particles have an average particle diameter measured by a TEM method of 5 nm or more and 50 nm or less, and contain at least two metal oxides containing a metal element selected from the group consisting of the following metals M: The method for producing a composite metal oxide fine particle-containing resin material according to claim 1 or 2.
Metal M: Si, Mg, Al, Ca, Ti, Zr, Mn The method for producing a composite metal oxide fine particle-containing resin material according to any one of claims 1 to 3, wherein the composite metal oxide fine particles have a refractive index of 1.5 or more and 1.75 or less. The composite metal oxide according to any one of claims 1 to 4, wherein a content of the composite metal oxide fine particles in the composite metal oxide fine particle-containing resin material is 10% by volume or more and 40% by volume or less. A method for producing a resin material containing oxide fine particles. The following formula (A) is satisfied, where nh is the refractive index of the curable resin or thermoplastic resin, and np is the refractive index of the composite metal oxide fine particles. 2. A method for producing a composite metal oxide fine particle-containing resin material according to item 1.
Formula (A) 0 ≦ | np−nh | ≦ 0.15 An optical element produced by using the composite metal oxide fine particle-containing resin material obtained by the method for producing a composite metal oxide fine particle-containing resin material according to any one of claims 1 to 6 .

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