WO2008015999A1

WO2008015999A1 - Composite material and optical element

Info

Publication number: WO2008015999A1
Application number: PCT/JP2007/064869
Authority: WO
Inventors: Hiroaki Ando; Shinichi Kurakata
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2006-08-04
Filing date: 2007-07-30
Publication date: 2008-02-07
Also published as: JPWO2008015999A1

Abstract

Provided is an optical element which suppresses deterioration of a refractive index while maintaining light transmittance constant and has excellent heat resistance. An objective lens as the optical element is provided by molding a composite material. The composite material is composed of a resin and inorganic particles, and the inorganic particles are surface-modified with a compound having an adamantyl group.

Description

Specification

Composite material and optical element

Technical field

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

Background art

[0002] MO, CD, DVD, HD—Information equipment such as players, recorders and drives for reading and recording information on optical information recording media such as DVDs and Blu-ray discs is equipped with an optical pickup device. It has been. An optical pickup device includes an optical element unit that irradiates an optical information recording medium with light having a predetermined wavelength emitted from a light source and receives reflected light by a light receiving element. The optical element unit includes these optical element units. It has an optical element such as a lens for condensing light by a light receiving element or a reflection layer of an optical information recording medium.

[0003] It is preferable to apply a plastic material to the optical element of the optical pickup device described above in that it can be manufactured at low cost by means such as injection molding. As plastics that can be applied to optical elements, copolymers of cyclic olefin and α-olefin are known (see Patent Document 1). Substances containing cyclic olefin have a stable refractive index due to changes in humidity. Although the properties are excellent, it is difficult to obtain the desired effect due to the stability of the refractive index due to temperature changes.

[0004] It can be expected that the stability of the refractive index can be improved by suppressing linear expansion with a composite material in which a resin and inorganic particles are mixed (see Patent Document 2). In the technology disclosed in Patent Document 2, it has been proposed to use it as fine particles of composite oxides with other metals in order to compensate for the low refractive index, which is a drawback of silica particles that can be achieved only by suppressing the linear expansion coefficient. . However, in this method, the use of an oxide having a high hygroscopic property may significantly reduce the moisture resistance as a composite material, that is, the refractive index, depending on the humidity.

Patent Document 1: JP 2002-105131 A

Patent Document 2: Japanese Patent Laid-Open No. 2005-146042

Disclosure of the invention Problems to be solved by the invention

[0005] Therefore, as a technique for reducing the hygroscopicity of the inorganic particles, it is conceivable to treat the surface of the inorganic particles with a silane coupling agent or various organic substances. However, if the particle size of the inorganic particles is reduced in order to improve the light transmittance of the composite material, the surface area of the inorganic particles increases, so that the amount of treatment material required for the surface treatment increases and the amount of diffusion into the resin. Often increases. Silicon oil as a by-product of the coupling agent and fatty acids frequently used as organic substances as the surface treatment agent lower the refractive index and impair the heat resistance of the resin.

[0006] An object of the present invention is to provide a composite material and an optical element that suppress a decrease in refractive index while maintaining a constant light transmittance and are excellent in heat resistance.

Means for solving the problem

[0007] In order to achieve the above object, the first aspect of the present invention provides:

A composite material of resin and inorganic particles,

The inorganic particles are surface-modified with a compound having an adamantyl group.

[0008] In the composite material,

The compound having an adamantyl group may be a compound in which an adamantyl group and a carboxyl group or a hydroxyl group are combined, and a monomer having an adamantyl group and an adamantyl group are not included! /, A monomer. It may be a copolymerized compound! /, Or a compound in which an adamantyl group is introduced into a functional group of a silane coupling agent.

[0009] In the composite material,

The resin is preferably a cycloolefin resin.

[0010] The second aspect of the present invention is:

An optical element molded using the composite material of the first form.

The invention's effect

[0011] According to the present invention, it is possible to provide a composite material and an optical element that suppress a decrease in refractive index while maintaining a constant light transmittance and are excellent in heat resistance (see Examples below). Brief Description of Drawings

1] A schematic diagram showing the internal structure of the optical pickup device.

Explanation of symbols

1 Optical pickup device

2 Semiconductor laser oscillator

3 Collimator

4 Beam splitter

5 1/4 wave plate

6 Aperture

7 Objective lens (optical element)

8 Sensor lens group

9 Sensor

10 Two-dimensional actuator

D Optical disc

D1 Protection board

D2 Information recording surface

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. However, the embodiment described below has various technically preferable limitations S for carrying out the present invention, and the scope of the invention is not limited to the following embodiment and illustrated examples. .

[0015] First, the composite material according to the present invention will be described.

[0016] The composite material contains (1) a resin and (2) inorganic particles. (1) Resin and

(2) Inorganic particles will be described, followed by (3) Composite material manufacturing methods, (4) Composite material properties, and (5) Optical element manufacturing methods and application examples.

(1) Resin

As the resin, thermoplastic resin, thermosetting resin, photo-curing resin, etc. are applicable. The Although it is not particularly limited as long as it is a transparent resin that is generally used as an optical material, it is preferable that the resin is a thermoplastic resin in terms of workability as an optical element and molding cycle time. It is more preferably a cyclic olefin resin from the viewpoint of low hygroscopicity, which is more preferably an acrylic resin, a cyclic olefin resin, a polycarbonate resin, a polyester resin, a polyether resin, a polyamide resin or a polyimide resin. Examples of the resin include compounds described in JP-A-2003-73559 and the like, and preferred compounds are shown in Table 1 below. Of these resins, those having a moisture absorption rate of 0.5% or less are preferred, and those having a moisture absorption rate of 0.2% or less are more preferred.

[table 1]

(2) Inorganic particles

(2.1) Inorganic particles

The inorganic * insulator is not particularly limited, and it is possible to achieve the objective of having a small rate of change in the refractive index with temperature of the resulting composite material (hereinafter referred to as I dn / dT I). Medium power of particles can be selected arbitrarily.

Specifically, oxide fine particles, metal salt fine particles, semiconductor fine particles, and the like are preferably used. From these, those that do not cause absorption, light emission, fluorescence, or the like in the wavelength region used as an optical element are appropriately selected. It's preferable to use it.

[0020] 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, 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 which is one or more metals selected from the above can be used. Specifically, for example, silicon dioxide (silica), titanium oxide, zinc oxide, aluminum oxide (alumina), zirconium oxide , Hafnium oxide, niobium oxide, tantalum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, indium oxide, tin oxide, lead oxide, and the double oxides of these oxides, lithium niobate and niobium Potassium acid, lithium tantalate, aluminum '' Magnesium oxide (MgAl O), etc.

2 4

[0021] In addition, rare earth oxides can also be used as the oxide fine particles. Specifically, scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, and sulfur oxide. Examples also include pium, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide.

[0022] Furthermore, examples of the metal salt fine particles include carbonates, phosphates, sulfates, and the like, specifically, calcium carbonate, aluminum phosphate, and the like.

[0023] As the inorganic particles described above, one kind of inorganic particles may be used, or a plurality of kinds of inorganic particles may be used in combination. By using a plurality of types of inorganic particles having different properties, the required extraordinary life can be further improved.

[0024] The average particle size of the inorganic particles is preferably lnm or more and lOOnm or less, more preferably lnm or more and 40nm or less. This is because when the average particle size is less than 1 nm, it is difficult to disperse the inorganic particles and the desired performance may not be obtained. Therefore, the average particle size is preferably 1 nm or more. On the other hand, if the average particle size exceeds lOOnm, The average particle diameter is preferably lOOnm or less, because the composite material is turbid and the transparency is lowered and the light transmittance may be less than 70%.

[0025] Here, the average particle diameter refers to a volume average value of diameters (sphere converted particle diameters) when each particle is converted into a sphere having the same volume.

(2.2) Compound having adamantyl group

The inorganic particles are surface-modified with a compound having an adamantyl group!

[0026] A compound having an adamantyl group has, as one property, a high melting point and a high glass transition temperature, and is difficult to lower the glass transition temperature of the composite material when mixed with a resin. As another property, a compound having an adamantyl group has advantages such as low moisture absorption and low heat absorption from the short wavelength region to the ultraviolet region, and is excellent in heat resistance. Sometimes, the physical properties of an optical element molded with the composite material are hardly deteriorated. As another property, a compound having an adamantyl group has a weak intermolecular force when it exists on the surface of inorganic particles, and is particularly easily dispersed in a cycloolefin resin. As another property, a compound having an adamantyl group is difficult to lower the refractive index of the composite material when mixed with a resin having a relatively high refractive index.

[0027] The compound having an adamantyl group includes (2.2.1) a compound in which an adamantyl group and a carboxy group or a hydroxyl group are bonded, (2.2.2) a monomer having an adamantyl group, and other monomers. And (2.2.3) compounds in which an adamantyl group is introduced into a functional group of a silane coupling agent.

(2. 2. 1) Compound in which adamantyl group and carboxyl group or hydroxyl group are bonded

The compound is a compound in which an adamantane ring represented by the following formula (1) is bonded to a carboxyl group or a hydroxyl group.

[0028] [Chemical 1]

(1)

(2. 2. 2) A compound obtained by copolymerizing a monomer having an adamantyl group and another monomer (not having an adamantyl group! /, Monomer) Examples of the monomer having an adamantyl group include compounds represented by the following formulas (2) to (; 11). In addition to these functional groups containing a double bond, polymers obtained from epoxies, isocyanates, compounds having an amino group and an adamantyl group, and the like are applicable.

[Chemical 2]

(7) (8)

(2. 2. 3) Adamantyl group 'A compound introduced into the functional group of the agent

The compound can be obtained, for example, by copolymerizing the compounds of the above formulas (2) to (; 11) with a silane coupling agent having a reactive group. Examples include a coupling agent having a polymerizable group and mercaptopropyldimethoxysilane.

(3) Manufacturing method of composite material

The manufacturing method of the composite material includes (3.1) a surface modification step of surface-modifying the inorganic particles with the compound having an adamantyl group described in each item of the above “(2. 2. 1 2. 2. 3)”. (3.2) A dispersion step of dispersing the inorganic particles in the resin after the surface modification step. (3.1) Surface modification process

In the surface modification step, a method of adding a surface modifier (compound having an adamantyl group) to the inorganic particle dispersion and heating and drying, or a solution of the surface modifier on the dried inorganic particle powder The method of spraying and heating, drying and processing is mentioned. In the above method, various dispersers and mixers are used to perform uniform surface treatment. It is preferable.

(3.2) Dispersion process

In the dispersion step, inorganic particles surface-modified with a compound having an adamantyl group (hereinafter referred to as “surface-modified particles”) and a resin (particularly a thermoplastic resin) are mixed to disperse the surface-modified particles in the resin. As a method for mixing the surface-modified particles and the resin, it is preferable to use a melt-kneading method from the viewpoint of reducing the amount of volatile substances used.

[0032] When the melt-kneading method is used in the dispersion step, the surface-modified particles and the resin may be added together and kneaded together! /, Or may be added in stages and kneaded. Les.

[0033] As a method of dividing addition, a method in which one component is added in several times, a method in which one component is added at a time and other components are added stepwise, or a method in which these are combined is used. be able to. The addition of the surface-modified particles can be performed in a powder or agglomerated state. It is possible to add the surface-modified particles in a state of being dispersed in the liquid, but in this case, it is necessary to perform a devolatilization treatment after kneading, and the aggregated particles are dispersed into primary particles in advance. It is preferable to add after making it. In addition, after kneading the surface-modified particles and the resin in advance, when adding components other than the resin (thermoplastic resin) that were not previously added and further melt-kneading them, they are added all at once and kneaded. Alternatively, it may be added in stages and kneaded.

[0034] When the melt-kneading method is used in the dispersion step, one kind of gas selected from the inert gases nitrogen, helium, neon, argon, krypton, and xenon, or a mixture of two or more kinds of gases is used. It is preferable to perform mixing in an atmosphere. However, even general gases such as carbon dioxide, ethylene gas, and hydrogen gas are not reactive to the material to be kneaded! /, If mixed with the inert gas described above, the gas is used. Anyway!

[0035] When the melt-kneading method is used in the dispersion step, it is preferable to eliminate residual oxygen as much as possible in the reaction system in the melt-kneading apparatus. Specifically, in the reaction system The oxygen content is preferably 1% or less, and more preferably 0.2% or less. This is because the resin is deteriorated by the oxidation reaction with oxygen and coloration is likely to occur.

[0036] Examples of apparatuses applicable to the melt-kneading method include Laboplast Mill, Brabender, and Banbury. It is possible to cite closed kneaders or batch kneaders such as a mixer, kneader and roll. As an apparatus used for the melt kneading method, a continuous melt kneading apparatus such as a single screw extruder or a twin screw extruder can be used. When using a continuous melt-kneading apparatus such as an extruder, it is possible to add the components to be added step by step from the middle of the cylinder.

[0037] As a dispersion apparatus for the mixture, various dispersion treatment machines such as a bead mill disperser, an ultrasonic disperser, a high-speed stirring disperser, and a high-pressure disperser are applicable. it can. As the beads used in the bead mill disperser, force S, such as dinoreconia beads and glass beads, and zirconia beads are preferably used. Further, it is more preferable that the diameter of the beads to be used is smaller, and the preferred diameter is in the range of 0.001 to 0.1 mm.

[0038] In the composite material production process, various additives may be added alone or in combination as required.

[0039] Examples of additives include antioxidants, light stabilizers, heat stabilizers, weathering stabilizers, stabilizers such as ultraviolet absorbers and near infrared absorbers, resin modifiers such as lubricants and plasticizers, and soft polymers. And anti-clouding agents such as alcoholic compounds, coloring agents such as dyes and pigments, other antistatic agents, flame retardants and the like.

[0040] Among these additives, examples of the antioxidant include phenolic antioxidants, phosphorus antioxidants, and phenolic antioxidants. By blending these antioxidants, it is possible to prevent the coloring and strength of the lens from being deteriorated due to oxidative deterioration during molding without reducing transparency and heat resistance.

[0041] Further, these antioxidants can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention. However, it is preferably within a range of 0.00;! To 20 parts by mass with respect to 100 parts by mass of the composite material, more preferably within a range of 0.01 to 10 parts by mass.

[0042] As the phenolic antioxidant, conventionally known ones can be applied. For example, 2-t-butyl-6- (3-t-butyl-2-hydroxyl-5 described in JP-B 63-179953 Methylbenzyl) 4 methylphenyl acrylate, 2, 4 di-t-amino -6-(1-(3,5-di-amino-amino-2-hydroxyphenenole) ethenole) phenyl acrylate, etc., and octadecinole described in JP-A-1-168643 3- (3, 5 Di-tert-butyl-4-hydroxyphenyl) propionate and other compounds such as 2,2'-methylene bis (4-methyl-6-tert-butylphenol), 1, 1, 3 tris (2 methyl 4-hydroxyl 5-t-butylphenolino) butane, 1, 3, 5 Trimethylolene 2, 4, 6 tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene 3- (3 ', 5' — Di-butynol-mono-hydroxyphenyl propionate)) methane, ie, pentaerythrimethyl-tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl propionate)), triethylene glycol Alkyl-substituted phenolic compounds such as bis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate) and 6- (4-hydroxy-3,5-di-tert-butylanilino) 2,4 bis-octylthio 1, 3, 5 Triazine group-containing phenolic compounds such as triazine, 4 bisoctylthio 1, 3, 5 triazine, 2 octylthio-1,4,6-bis- (3,5-di-tert-butyl-4-oxyanilino) -1,3,5-5-triazine Etc.

[0043] The phosphorus antioxidant is not particularly limited as long as it is a substance that is usually used in the general resin industry. For example, triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite. , Tris (Noyulfeninore) phosphite, Tris (Dinoyurfeninole) phosphite, Tris (2,4 di-tert-butylphenol) phosphite, 10— (3,5 Di-tert-butyl-4-hydroxybenzyl) 9 , 10 Dihydro-9 oxa 10-phosphaphenanthrene 10-oxide and other monophosphite compounds, 4, A'-butylidenebis (3-methyl-6-t butylphenol tridecyl phosphite), 4, A '— Diphosphite systems such as isopropylidene monobis (phenyl didialkyl (C 12-C 15 phosphite)) Compounds, and the like. Of these, tris (noyulphenyl) phosphite, tris (dinoylphenyl) phosphite, and tris (2,4 di-tert-butylphenyl) phosphite are particularly preferred.

[0044] Examples of iow antioxidants include dilauryl 3,3 thiodipropionate, dimyristinole 3,3'-thiodipropionate, distearyl 3,3-thiodipropionate. , Lauryl stearyl 3, 3—thiodipropionate, pentaerythritol tetrakisto (/ 3 lauryl thiopropionate), 3, 9 bis (2 dodecylthioethyl) 2, 4, 8, 10—tetraoxaspiro [5, 5] Undecane.

[0045] Further, in addition to the above-mentioned phenol-based, phosphoric acid-based and xio-based antioxidants, amine-based antioxidants such as diphenylamine derivatives, nickel or zinc thiocarbamate, etc. can also be applied as antioxidants. It is.

[0046] In addition, among the additives described above, a compound group having a minimum temperature at the glass transition temperature of 30 ° C or less may be blended as an anti-turbidity agent. As a result, it is possible to prevent the occurrence of white turbidity in an environment of high temperature and high humidity for a long time by suppressing deterioration of various properties such as transparency, heat resistance and mechanical strength.

[0047] Among the additives described above, examples of the light resistance stabilizer include benzophenone light resistance stabilizer, benzotriazole light resistance stabilizer, hindered amine light resistance stabilizer, and the like. From the viewpoint of properties and the like, it is preferable to use a hindered amine light-resistant stabilizer (hereinafter referred to as “HALS”). As such HALS, those having a low molecular weight, medium molecular weight and high molecular weight can be appropriately selected. However, it is preferable to use low molecular weight or medium molecular weight HALS when forming a molded body from a composite material. Particularly when preparing a film-shaped molded body, high molecular weight HALS may be used. preferable.

[0048] HALS with a relatively low molecular weight includes LA-77 (Asahi Denka), Tinuvin765 (CSC), Tinuvinl23 (CSC), Tinuvin440 (CSC), Tinuvinl44 (CSC), HostavinN20 (Hoechst) Manufactured) and the like.

[0049] Examples of medium molecular weight HALS include LA-57 (Asahi Denka), LA-52 (Asahi Denka), LA-67 (Asahi Denka), LA-62 (Asahi Denka), and the like. It is done.

[0050] HALS with a high molecular weight includes LA-68 (Asahi Denka), LA-63 (Asahi Denka), Ho stavinN30 (Hoechst), Chimassorb944 (CSC), Chimassorb2020 (CSC), Chimassorbl l9 (CSC), Tinuvin622 (CSC), CyasorbUV-3346 (Cytec), CyasorbUV-3529 (Cytec), Uvasil299 (GLC), etc. [0051] Further, it is also preferable to slightly combine various lubricants and fluorine elastomer as processing aids during molding and extrusion.

(4) Properties of composite materials

The light transmittance of the composite material produced as described above is preferably 50% or more, more preferably 70% or more, with respect to 405 nm light when the thickness is 3 mm. More preferably, it is 85% or more.

[0052] Although various values can be selected for the Abbe number of the composite material by selecting the surface-modified particles and the resin, it is preferable to use particles that can obtain anomalous dispersion. In this case, the composite material can be effectively used for achromatization, and its value may increase.

[0053] The water absorption rate of the composite material is preferably 2% or less, more preferably 1% or less in an environment of a temperature of 80 ° C and a relative humidity of 90%, more preferably 0.5%. It is most preferable that

[0054] In the present embodiment, the water absorption is expressed in mass% unless otherwise specified. In addition, the water absorption rate can be measured from a change in mass when a pre-dried composite material is stored for a certain period of time under specific high temperature and high humidity conditions. In the present embodiment, the water absorption rate is calculated more accurately by measuring the amount of water contained when dried by the Karl Fischer method and measuring the mass change after the subsequent water absorption.

[0055] The composite material is preferably negative in the AMES test! /. This is because a positive result in the AMES test may impair the user's health, increase the environmental burden, and reduce the material stability.

(5) Optical element manufacturing methods and application examples

(5.1) Optical element manufacturing method

By molding the composite material obtained as described above, it is possible to manufacture the optical element according to the present invention. The molding method is not particularly limited, but the melt molding method is preferable from the viewpoint of characteristics such as low birefringence, mechanical strength and dimensional accuracy in the molded product. Examples of the melt molding method include press molding, extrusion molding, and injection molding. From the viewpoint of productivity, it is preferable to apply injection molding as the melt molding method. In addition, in the case of forming a molded product with a photocurable resin, cast polymerization or the like can be used. [0056] The molding condition is a force that is appropriately selected according to the purpose of use or molding method. For example, as the temperature of the composite material in injection molding, an appropriate fluidity is imparted to the resin at the time of molding to reduce the distortion of the molded product. It is preferable that the temperature is in the range of 150 ° C to 400 ° C from the viewpoints of preventing silver streaks due to thermal decomposition of the resin and effectively preventing yellowing of the molded product. More preferably, it is within the range of 200 ° C to 350 ° C, and particularly preferably within the range of 200 ° C to 330 ° C.

[0057] When injection molding is used as a molding method, all general methods such as a molding method using carbon dioxide gas as a plasticizer and a method of improving transferability by induction heating of a mold can be applied. is there.

[0058] 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 shape or a sheet shape, and has a low birefringence, Since it is excellent in transparency, mechanical strength, heat resistance, low water absorption, etc., it can be applied to various optical components.

(5.2) Application examples of optical elements

Examples of application of the optical element according to the present invention to an optical component include an optical lens and an optical prism, and specific examples thereof include an imaging system lens of a camera; a lens such as a microscope, an endoscope, and a telescope lens; Optically transmissive lenses such as eyeglass lenses; CD, CD-ROM, WORM (write-once optical disc), MO (rewritable optical disc; magneto-optical disc), MD (mini-beam printer fΘ lens, sensor lens, etc. A laser scanning system lens; a prism lens of a camera lens system, and the like.

[0059] 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.

In addition, the optical element according to the present invention is also suitably used as various filters, gratings, optical fibers, flat optical waveguides, and the like.

[0061] Among the above-described molded products, it is suitably used as an optical element such as a pickup lens or a laser scanning lens that requires low birefringence. Hereinafter, the optical pickup device 1 in which the optical element according to the present invention is used as the objective lens 7 will be described with reference to FIG.

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

As shown in FIG. 1, the optical pickup device 1 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, the collimator 3, the beam splitter 4, the quarter-wave plate 5, the diaphragm 6, and the objective lens are directed in a direction away from the semiconductor laser oscillator 2. 7 are sequentially arranged.

[0065] A sensor lens group 8 and a sensor 9 each including two sets of lenses are sequentially disposed in a position close to the beam splitter 4 and in a direction perpendicular to the optical axis of the blue light described above.

[0066] The objective lens 7 as 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. It is summer. 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 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, which is transmitted through the collimator 3 and collimated into infinite parallel light. Transparent. Further, after 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.

[0069] The light that forms the focused 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-wave plate 5, and is reflected by the beam splitter 4. After that, astigmatism is given through the sensor lens group 8 and received by the sensor 9, and finally converted into an electric signal by being photoelectrically converted by the sensor 9.

[0070] Thereafter, such an operation is repeatedly performed to record information on the optical disc D, The reproduction operation of the information recorded on the optical disc D is completed.

Note that the numerical aperture NA 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 disc D. In this embodiment, it is a high-density optical disc D, and its numerical aperture is set to 0.85.

Example

[0072] (1) Preparation of sample

(1. 1) Preparation of surface modifier

(1. 1. 1) Preparation of surface modifier 1

0. A dropping device, thermometer, nitrogen gas inlet tube, stirring device and reflux condenser were installed in a three-liter four-separable flask, and dehydrated isopropyl alcohol 2 Og was charged in the flask to about 80. C heated with C. Mix uniformly with 10 g of methacrylolic acid, 50 g of methinoremethacrylate, 2 g of 2-methyl-2-adamantyl methacrylate, 2 g of N, N'-azobisisovaleronitryl and 20 g of isopropyl alcohol. The obtained solution was dropped into the flask over 2 hours and reacted at the same temperature for 5 hours. Thereafter, 60 g of isopropyl alcohol was added and cooled to obtain a 50% by mass dispersant solution. This dispersant solution was designated as “Surface modifier 1”.

(1. 1. 2) Preparation of surface modifier 2

0. A dripping device, thermometer, nitrogen gas inlet tube, stirring device and reflux condenser were installed in a three-liter four-separable flask, charged with 20 g of dehydrated methyl ethyl ketone and heated at about 80 ° C. did. Silane coupling agent (Shin-Etsu Chemical KBE-502) 20g, methyl methacrylate 40g, 2-methyl 2-adamantyl methacrylate 40g, N, N'-azobisisovaleronitrile 2g, isopropyl alcohol 20g The homogenized solution was dropped into the flask over 2 hours and reacted at the same temperature for 5 hours. Thereafter, the solvent was removed by vacuum drying to obtain a white powder. The white powder was designated as “Surface modifier 2”.

(1.2) Preparation of composite materials and samples

(1.2.1) Preparation of composite material 1 and sample 1

For 100g of aqueous dispersion of ZrO particles (Sumitomo Osaka Cement, primary particle size 3nm, 10% by mass)

2

Then, 100 g of acetic acid was added and stirred well. In addition, anion exchange resin (organo amber Light IRA402BL OH AG) was treated with an appropriate amount to remove only chloride ions, and then 100 g of 2 methoxyethanol was added and further stirred.

3 g of 1-adamantanecarboxylic acid was added thereto and stirred well, followed by drying at 100 ° C. for 10 hours under nitrogen to obtain a white powder. The white powder was melt-kneaded with 5 g of cycloolefin resin (Mitsubishi Rayon Ataripet MF) to obtain composite material 1. The composite material 1 was injection molded to produce a 3 mm thick molded body, and the molded body was designated as “Sample 1”.

(1.2.2) Preparation of composite material 2 and sample 2

In preparation of the composite material 1 and sample 1, 0.3 g of oleic acid was used instead of the 1-adamantanecarboxylic acid. Otherwise, composite material 2 was obtained in the same manner as composite material 1 and sample 1. The composite material 2 was injection-molded to produce a 3 mm-thick molded body, and the molded body was designated as “Sample 2”.

(1. 2. 3) Preparation of composite material 3, sample 3

50 g of alumina (Alumina TM-300 manufactured by Daimei Chemical Co., Ltd.) was placed in 1000 g of ethanol. The obtained slurry was mixed with 20 g of a liquid containing 10 g of the surface modifier 1 and dried. The obtained alumina particles were melt-kneaded with a cycloolefin resin (APEL5014 manufactured by Mitsui Chemicals) in the same manner as in preparation of the composite material 1 and sample 1 to obtain composite material 3. The composite material 3 was injection-molded to produce a 3 mm-thick molded body, and the molded body was designated as “Sample 3”.

(1. 2. 4) Preparation of composite material 4, sample 4

In the preparation of Sample 3, 20 g of a xylene solution containing 10 g of a modified cycloolefin resin (TOPAS TMG MAH2050 manufactured by Ticona) was used instead of 20 g of the solution containing 10 g of the surface modifier 1. Otherwise, composite material 4 was obtained in the same manner as in preparation of composite material 3 and sample 3 above. The composite material 4 was injection-molded to produce a 3 mm-thick molded body, and the molded body was designated as “Sample 4”.

(1. 2. 5) Preparation of composite material 5 and sample 5

To a reaction vessel equipped with a stirrer, dropping funnel and thermometer, 40 ml of 2-propanol (IPA) as a solvent and 5% tetramethylammonium hydroxide aqueous solution (TMAH aqueous solution) as a basic catalyst I was charged. In a dropping funnel, 15 ml of IPA and 12. 69 g of 3—Metatali Roxypropyltrimethoxysilane (MTMS: SZ-6300 manufactured by Toray Dow Cowing Silicon Co., Ltd.) was added, and an IPA solution of MTMS was added dropwise at room temperature over 30 minutes while stirring the reaction vessel.

[0074] After completion of the dropwise addition of the MTMS IPA solution, the mixture was stirred for 2 hours without heating. Thereafter, the solvent was removed under reduced pressure, and 50 ml of toluene was dissolved. The reaction solution was washed with saturated brine until neutral, and then dehydrated with anhydrous magnesium sulfate. 8.6 g of hydrolyzed product (silsesquioxane) was obtained by filtering off anhydrous magnesium sulfate and concentrating. This silsesquioxane was a colorless viscous liquid soluble in various organic solvents.

[0075] Next, 20 · 65 g of silsesquioxane obtained by repeating the above operation several times for a reaction vessel equipped with a stirrer, a Din Stark, and a cooling tube, 82 ml of toluene, and 10% TMA H aqueous solution. 3. 0 g was added and heated gradually to distill off the water. The mixture was further heated to 130 ° C and the toluene was recondensed at the reflux temperature. The temperature of the reaction solution at this time was 108 ° C. The mixture was stirred for 2 hours after refluxing toluene, and the time after that was regarded as the end of the reaction. The reaction solution was washed with saturated Japanese brine until neutral, and then dehydrated with anhydrous magnesium sulfate. The anhydrous magnesium sulfate was filtered and concentrated to obtain 18.77 g of the target cage-type silsesquioxane (mixture). The cage-type silsesquioxane obtained was a colorless viscous liquid soluble in various organic solvents.

[0076] Saddle-type silicon resin obtained above (having methacryloyl groups on all the key atoms)

) 24 parts by weight, 10 parts by weight of trimethylolpropane tritalylate, 60 parts by weight of dicyclopentanyldiatalate, 5 parts by weight of urethane acrylate oligomer 1, and 1- A transparent silicone resin composition (composite material) is prepared by mixing 2.5 parts by mass of hydroxycyclohexyl phenyl ketone, 1 part of the above surface modifier 2 and 50 parts of silica powder (A300 from Nippon Aerosil). 5) obtained. The composite material 5 is poured into a mold so as to have a thickness of 3 mm, and cured using a 30 W / cm high-pressure mercury lamp at a cumulative exposure of 20000 mj / cm ² to obtain a sheet-like shape having a predetermined thickness. A silicon resin molding was obtained. The silicon resin molding was designated as “Sample 5”.

(1. 2. 6) Preparation of composite material 6, sample 6

Instead of using 1 part of surface modifier 2 in the preparation of composite material 5 and sample 5, cut One part of a pulling agent (SZ6187 manufactured by Toray Dow Coung) was used. Otherwise, composite material 6 was prepared and molded in the same manner as composite material 5 and sample 5, and the molded product was designated as “sample 6”.

(1. 2. 7) Preparation of composite material 7, sample 7

2

Then, 100 g of acetic acid was added and stirred well. Further, 100 g of 2-methoxyethanol was added and further stirred. After distilling off water at 100 ° C., 5 g of the surface modifier 2 was added, and the mixture was further heated under reflux for 1 hour, followed by drying to remove the solvent and obtain surface-treated ZrO particles.

2

10 g of 1-adamantyl methacrylate prepared according to JP 2002-193883 as a thermosetting monomer, 15 g of the surface-treated ZrO particles as inorganic fine particles, oxidized

2

0.1 lg of phenolic antioxidant (Chino 'Specialty' Chemicals, Irgan oxlOlO) as an inhibitor, and 1, 1 (t-butylperoxy) 3, 3, 5 trimethylcyclohexane (Japan) After mixing with Ogre Co., Ltd., Perhexa 3Μ-95) 0 · 05g, it was dispersed using a desktop type three-roll mill (RM-1, Irie Shokai Co., Ltd.). The obtained dispersion was poured into a 3 mm thick mold and cured in an oven at 120 ° C. for 1 hour to prepare Sample 7.

(1. 2. 8) Preparation of composite material 8 and sample 8

Sample 8 was prepared in the same manner as in the preparation of Sample 7, except that an equivalent amount of a silane coupling agent (KBE-502 manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of the surface modifier 2.

(2) Physical property measurement of samples 1-8

(2.1) Measurement of light transmittance

Using a TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd., the light transmittance with respect to light having a wavelength of 405 nm was measured for each of the samples 1 to 6. The transmittance was measured by a method based on ASTM D 1003. The measurement results are shown in Table 2 below.

(2.2) Refractive index measurement

Using an automatic refractometer (KPR-200, manufactured by Carneux Optical Industry), the refractive index at 23 ° C for light having a wavelength of 588 nm was measured for each of samples 1 to 8. The measurement results are shown in Table 2 below.

(2.3) Measurement of glass transition temperature The glass transition temperature (Tg) of each sample 18 was measured using a differential scanning calorimeter (Seiko Electronics DSC320). The measurement results are shown in Table 2 below.

[0078] Samples 5 and 7 had a Tg of 300 C or more and could not be measured.

[0079] [Table 2]

(3) Summary

As shown in Table 2, when looking at Samples 1, 3, 5, 7 and Samples 2, 4, 6, 8, Samples 1, 3, 5, 7 are compared to Samples 2, 4, 6, 8 In terms of light transmittance, refractive index, and glass transition temperature, it is excellent. From the above, it can be seen that it is useful to modify the surface of inorganic particles with a compound having an adamantyl group.

Claims

The scope of the claims

[1] A composite material of resin and inorganic particles,

A composite material, wherein the inorganic particles are surface-modified with a compound having an adamantyl group.

[2] The composite material according to claim 1, wherein the compound having an adamantyl group is a compound in which an adamantyl group and a carboxyl group or a hydroxyl group are bonded.

[3] The composite material according to claim 1, wherein the compound having an adamantyl group is a compound obtained by copolymerizing a monomer having an adamantyl group and a monomer having no adamantyl group.

[4] The composite material according to claim 1, wherein the compound having an adamantyl group is a compound in which an adamantyl group is introduced into a functional group of a silane coupling agent.

[5] The composite material according to any one of claims 1 to 4, wherein the resin is a cycloolefin resin.

[6] An optical element formed by using the composite material according to any one of claims 1 to 5.