JP2008238705A - Injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method which can suppress the occurrence of distortion and a deterioration in configuration transferabilities. <P>SOLUTION: The method for injection-molding an organic, inorganic composite material in which fine inorganic particles 100 nm or below in particle size are dispersed in a thermoplastic resin includes the process for packing the composite material in the cavity 26 of a die 1 and the process for taking out a molding made of the composite material from the cavity 26 of the die 1. When the glass transition temperature of the thermoplastic resin is Tg, in the process for packing the composite material, the surface temperature of the cavity 26 of the die 1 is adjusted to be Tg+15C° to Tg+70°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection molding method, and more particularly to an injection molding method for injecting and molding an organic-inorganic composite material in which inorganic fine particles having a particle diameter of 100 nm or less are dispersed in a thermoplastic resin.

  An organic-inorganic composite material is developed in which optical performance is adjusted without impairing transparency as an optical material by dispersing inorganic fine particles sufficiently smaller than the wavelength used in an optical material such as a thermoplastic resin. (See Patent Documents 1 and 2). In particular, in order to obtain sufficient transparency as an optical material, an organic-inorganic composite material in which inorganic fine particles having a particle diameter of 100 nm or less are dispersed has been developed. However, there is a problem that the expected optical performance cannot be obtained when the optical element is actually molded as an imaging element or an optical element for an optical pickup device that requires high optical accuracy.

As a result of the study by the present inventors, when very fine inorganic fine particles having a particle diameter of 100 nm or less are dispersed in the optical material, the surface area of the interface between the thermoplastic resin and the inorganic fine particles is remarkably increased. It has been found that when the inorganic fine particles are dispersed, the thermal conductivity is higher than that of the conventional thermoplastic resin. Therefore, when an organic / inorganic composite material is molded by a conventional thermoplastic resin molding method, the molded optical element is distorted due to low fluidity or molded due to high thermal conductivity. It was found that the surface property (shape transfer property) deteriorates rapidly upon contact with the surface, resulting in a problem that the optical performance deteriorates.
JP 2002-207101 A Japanese Patent Laid-Open No. 2002-240901

  Accordingly, the main object of the present invention is an injection molding method for injecting and molding an organic-inorganic composite material in which inorganic fine particles having a particle diameter of 100 nm or less are dispersed in a thermoplastic resin, and the generation of distortion and shape transferability. An object of the present invention is to provide an injection molding method capable of suppressing the deterioration of the above.

In order to solve the above problems, according to the present invention,
An injection molding method for injecting and molding an organic-inorganic composite material in which inorganic fine particles having a particle diameter of 100 nm or less are dispersed in a thermoplastic resin,
Filling the cavity of the mold with the organic-inorganic composite material;
A step of taking out a molded article composed of the organic-inorganic composite material from the cavity of the mold;
Have
When the glass transition temperature of the thermoplastic resin is Tg, the cavity surface temperature of the mold is set to a temperature of Tg + 15 ° C. or more and Tg + 70 ° C. or less in the step of filling the organic-inorganic composite material. An injection molding method is provided.

Preferably, in the step of taking out the molded product of the organic-inorganic composite material, the temperature of the cavity surface of the mold is set to a temperature of Tg-30 ° C. or higher and Tg or lower.
More preferably, a fine structure is provided on the cavity surface of the mold.

  According to the present invention, since the temperature of the cavity surface of the mold is set to a certain range of Tg + 15 ° C. or more and Tg + 70 ° C. or less in the step of filling the organic-inorganic composite material, the occurrence of distortion and the deterioration of shape transferability are suppressed. (See the examples below).

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

The present embodiment provides a method for producing an optical element by injecting and molding an organic-inorganic composite material in which inorganic fine particles are dispersed in a thermoplastic resin using a mold for injection molding. The optical element that can be manufactured by the injection molding method of the present invention is not particularly limited. However, as an optical element for an optical pickup device and an optical element for an imaging device that are particularly required to have optical stability and precision. Particularly preferred.
In the following, (1) the structure of the mold will be described first, then (2) the thermoplastic resin and (3) inorganic fine particles constituting the organic-inorganic composite material will be described, and finally (4) the mold will be described. A method (including an injection molding method) for producing an optical element using the above will be described.

(1) Configuration of mold The mold 1 according to the present embodiment includes a fixed mold 10 and a movable mold 20 as shown in the upper part of FIG. 1, and the fixed mold 10 and the movable mold 20 overlap each other. It has a configuration.

  The fixed mold 10 and the movable mold 20 are separated from each other. When a molding material such as a resin (organic-inorganic composite material in the present embodiment) is injected and molded (filled), the fixed mold 10 and the movable mold 20 are closed in close contact with each other. When the molding material (molded product) is taken out, the movable mold 20 is moved and opened so as to be separated from the fixed mold 10.

  As shown in the lower part of FIG. 1, the movable mold 20 is provided with a sprue 22, a runner 23, a gate 24 and a cavity 26. The sprue 22 serves as an inlet for the material to be molded, and is disposed substantially at the center of the movable mold 20. The runner 23 extends radially from the sprue 22 and communicates with the gate 24. The gate 24 is a portion that receives an inflow of the molding material from the runner 23 and injects the molding material into the cavity 26.

  The cavity 26 is a part where a molded product is formed. The molded product is formed from the molding material by receiving injection (filling) of the molding material from the gate 26. In the present embodiment, an optical element for an optical pickup device in which a diffractive structure that is a fine structure is provided on a molding surface (optical surface) is taken as an example of a molded product. As the fine structure, a fine structure which can be provided with various functions by being provided on the optical surface is known, and is not particularly limited in the present invention. For example, a phase structure (including a diffraction structure) constituted by a concentric fine step structure centered on an optical axis having a sawtooth cross section, a fine structure for providing an antireflection function, and the like are known. However, since these structures are known, details are omitted. The cavity 26 is formed with a microstructure 28 (concentric stepped structure) for imparting a microstructure to the molded product, and the microstructure is transferred to the molding material filled in the cavity 26. It has become.

  Circular flow paths 32 and 42 are formed on the periphery of the mold 1 so as to surround the sprue 22, the runner 23, the gate 24 and the cavity 26. An inflow / outflow port (not shown) is connected to the flow paths 32, 42, and the medium can be circulated through the flow paths 32, 42 by flowing in / out the medium (fluid) from the inflow / outflow ports. It can be done. By using a high temperature medium or a low temperature medium (refrigerant) as the medium, the mold 1 (particularly the surface of the cavity 26) can be heated or cooled. As the “medium” to be circulated in the flow paths 32 and 42, a liquid such as oil or a gas such as air can be used.

  On the other hand, in the fixed mold 10, parts having a complementary relationship with the sprue 22, the runner 23, the gate 24, the cavity 26 and the like of the movable mold 20 are formed. The fixed mold 10 is substantially the same as the movable mold 20. It has a configuration.

(2) Thermoplastic resin From the viewpoint of processability as an optical element, the thermoplastic resin 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. A cyclic olefin is particularly preferred. Specific examples include compounds described in JP-A-2003-73559, and preferred compounds are shown in Table 1 below.

  The above-mentioned thermoplastic resin desirably has a moisture absorption rate of 0.2% or less from the viewpoint of dimensional stability as an optical material. Therefore, polyolefin resin (polyethylene, polypropylene), fluororesin (polytetrafluoroethylene) , Teflon (registered trademark) AF: manufactured by DuPont), cyclic olefin resin (manufactured by Nippon Zeon: ZEONEX, manufactured by Mitsui Chemicals: APEL, manufactured by JSR: Arton, manufactured by Chicona: TOPAS), indene / styrene resin, polycarbonate resin, etc. Preferably used.

(3) Inorganic fine particles Examples of inorganic fine particles include oxide fine particles, metal salt fine particles, and semiconductor fine particles. Among these, those that do not generate absorption, light emission, fluorescence, etc. in the wavelength region used as an optical element are appropriately selected. Can be used.

As oxide fine particles, the metal constituting the metal oxide is Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb. 1 selected from the group consisting of Sr, Y, Nb, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ta, Hf, W, Ir, Tl, Pb, Bi and rare earth metals A metal oxide that is a seed or two or more metals can be used. Specifically, for example, silicon oxide, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide, hafnium oxide, niobium oxide, tantalum oxide, oxide Magnesium, calcium oxide, strontium oxide, barium oxide, indium oxide, tin oxide, lead oxide, double oxides composed of these oxides, lithium niobate and potassium niobate , Lithium tantalate, the aluminum magnesium oxide (MgAl ₂ O _4), and the like.

  Rare earth oxides can also be used as other oxide fine particles, specifically scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, oxide Examples also include dysprosium, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide. Examples of the metal salt fine particles include carbonates, phosphates, sulfates, and the like, specifically, calcium carbonate, aluminum phosphate, and the like.

The semiconductor fine particles mean fine particles having a semiconductor crystal composition. Specific examples of the semiconductor crystal composition include simple elements of Group 14 elements of the periodic table such as carbon, silicon, germanium, tin, and phosphorus (black phosphorus). A group consisting of a group 15 element such as selenium and tellurium, a compound composed of a group 14 element such as silicon carbide (SiC), tin oxide (IV) ( SnO ₂ ), tin sulfide (II, IV) (Sn (II) Sn (IV) S ₃ ), tin sulfide (IV) (SnS ₂ ), tin sulfide (II) (SnS), tin selenide (II) ( SnSe), tin telluride (II) (SnTe), lead (II) sulfide (PbS), lead selenide (II) (PbSe), lead telluride (II) (PbTe) group 14 elements Compounds with Group 16 elements of the periodic table, boron nitride (BN), boron phosphide (BP), boron arsenide BAs), aluminum nitride (AlN), aluminum phosphide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), antimony Compound of periodic table group 13 element and periodic table group 15 element such as gallium (GaSb), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), indium antimonide (InSb) (or the like) III-V group compound semiconductor), aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), gallium sulfide (Ga ₂ S ₃ ), gallium selenide (Ga ₂ Se ₃ ), gallium telluride ( Ga ₂ Te ₃ ), indium oxide (In ₂ O ₃ ), indium sulfide (In ₂ S ₃ ), indium selenide (In ₂ Se ₃ ), indium telluride (In ₂ Te ₃ ) and other compounds of group 13 elements of the periodic table and group 16 elements of the periodic table, thallium chloride (I) (TlCl) , Thallium bromide (I) (TlBr), thallium iodide (I) (TlI) compounds such as Group 13 elements and Periodic Table Group 17 elements, zinc oxide (ZnO), zinc sulfide (ZnS) , Zinc selenide (ZnSe), zinc telluride (ZnTe), cadmium oxide (CdO), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), mercury sulfide (HgS), mercury selenide (HgSe), mercury telluride (HgTe) periodic table group 12 element and the periodic table compound of group 16 element such as (or II-VI compound semiconductor), arsenic sulfide (III) (as _{2 3),} selenium arsenic _{(III) (As 2 Se 3} ), telluride arsenic _{(III) (As 2 Te 3} ), antimony sulfide _{(III) (Sb 2 S 3} ), selenium antimony (III) (Sb ₂ Se ₃ ), antimony telluride (III) (Sb ₂ Te ₃ ), bismuth sulfide (III) (Bi ₂ S ₃ ), bismuth selenide (III) (Bi ₂ Se ₃ ), bismuth telluride (III) (Bi) ₂ Te ₃ ) periodic table group 15 element and periodic group 16 element compound, copper oxide (I) (Cu ₂ O), copper selenide (Cu ₂ Se) periodic table Compounds of Group 11 elements and Group 16 elements of the periodic table, copper chloride (I) (CuCl), copper bromide (I) (CuBr), copper iodide (I) (CuI), silver chloride (AgCl), odor Compounds of Group 11 elements of the periodic table and elements of Group 17 of the periodic table, such as silver halide (AgBr), nickel oxide (II) (N O) and other periodic table group 10 elements and periodic table group 16 elements, cobalt oxide (II) (CoO), cobalt sulfide (II) (CoS) and other periodic table group 9 elements and periodic table Compounds with Group 16 elements, compounds of Group 8 elements of the periodic table such as triiron tetroxide (Fe ₃ O ₄ ), iron sulfide (II) (FeS), and Group 16 elements of the periodic table, manganese (II) oxide A compound of a periodic table group 7 element such as (MnO) and a periodic table group 16 element, a periodic table group 6 element such as molybdenum sulfide (IV) (MoS ₂ ), tungsten oxide (IV) (WO ₂ ), etc. Periodic table Group 15 elements such as compounds with Group 16 elements of the periodic table, vanadium oxide (II) (VO), vanadium oxide (IV) (VO ₂ ), tantalum oxide (V) (Ta ₂ O ₅ ), etc. Table compound of group 16 element, titanium oxide _{(TiO 2, Ti 2 O 5} , Ti 2 O 3, Ti 5 O 9 , etc. A compound of a periodic table group 4 element such as a periodic table group 16 element, a compound of a periodic table group 2 element such as magnesium sulfide (MgS) and magnesium selenide (MgSe), and a periodic table group 16 element, Cadmium oxide (II) chromium (III) (CdCr ₂ O ₄ ), cadmium selenide (II) chromium (III) (CdCr ₂ Se ₄ ), copper sulfide (II) chromium (III) (CuCr ₂ S ₄ ), selenium Examples thereof include chalcogen spinels such as mercury (II) chromium (III) (HgCr ₂ Se ₄ ), barium titanate (BaTiO ₃ ), and the like. In addition, G. Schmid et al .; Adv. Mater. 4, 494 (1991) (BN) ₇₅ (BF ₂ ) ₁₅ F ₁₅ and D. Fenske et al .; Angew. Chem. Int. Ed. Engl. 29, page 1452 (1990), a semiconductor cluster having a fixed structure such as Cu ₁₄₆ Se ₇₃ (triethylphosphine) ₂₂ reported in the same manner is also exemplified.

  Among the above inorganic fine particles, a resin used as an optical material often has a refractive index of about 1.4 to 1.7, and therefore oxide fine particles having a refractive index close to this are preferably used. Specific examples include silica (silicon oxide), calcium carbonate, aluminum phosphate, aluminum oxide, magnesium oxide, and aluminum / magnesium oxide. From the viewpoint that the refractive index can be arbitrarily adjusted, composite oxide fine particles containing Si and a metal element other than Si are more preferably used. As for the form of the composite particle, even if it is a composite structure in which the components are almost uniform in the same particle, it is a composite structure called a so-called core-shell structure in which the component of the inner layer and the component of the outer layer constituting the particle are different. Also good.

  In the present embodiment, the inorganic fine particles dispersed in the thermoplastic resin may be one kind of inorganic fine particles or a combination of plural kinds of inorganic fine particles as long as the light transmittance is not deteriorated. . By using a plurality of types of fine particles having different properties, the required characteristics can be improved more efficiently.

  The average primary particle diameter of the inorganic fine particles is preferably 1 to 100 nm, more preferably 1 to 50 nm, and particularly preferably 1 to 15 nm. The average primary particle diameter of the inorganic fine particles indicates an average value of the diameters when the inorganic fine particles are converted into spheres having the same volume, and this value can be evaluated from a transmission electron micrograph.

  The shape of the inorganic fine particles is not particularly limited, but spherical fine particles are preferably used. Specifically, the minimum diameter of the particle (minimum value of the distance between the tangents when drawing two tangents in contact with the outer periphery of the fine particle) / maximum diameter (the value in drawing two tangents in contact with the outer periphery of the fine particle) The maximum value of the distance between tangents) is preferably 0.5 to 1.0, and more preferably 0.7 to 1.0.

  Moreover, in the state made into the organic-inorganic composite material (the state dispersed in the thermoplastic resin), the lower limit of the mixing ratio of the inorganic fine particles to the whole organic-inorganic composite material is 5% by volume or more, preferably 10 volumes. %, More preferably 20% by volume or more, and the upper limit is 50% by volume or less, preferably 40% by volume or less.

(4) Optical Element Manufacturing Method First, an organic-inorganic composite material in which inorganic fine particles are dispersed in a resin plastic resin is manufactured. Specifically, a method of forming a composite by polymerizing a thermoplastic resin in the presence of inorganic fine particles, a method of forming and combining inorganic fine particles in the presence of a thermoplastic resin, and the inorganic fine particles as a solvent for the thermoplastic resin A method of making a dispersion in a liquid and then compounding by removing the solvent, a method of preparing inorganic fine particles and a thermoplastic resin separately, and compounding by melt kneading, melt kneading in a state containing a solvent, etc. It can be produced by any method.

  Among these, the method of preparing the inorganic fine particles and the thermoplastic resin separately and combining them by melt-kneading is preferably used because it is simple and can suppress the manufacturing cost. As an apparatus which can be used for melt kneading, a closed kneading apparatus or a batch kneading apparatus such as a lab plast mill, a Brabender, a Banbury mixer, a kneader, a roll, and the like can be given. Moreover, it can also manufacture using a continuous melt-kneading apparatus like a single screw extruder, a twin screw extruder, etc.

  When melt kneading is used in the method for producing an organic-inorganic composite material, the thermoplastic resin and the inorganic fine particles may be added and kneaded all at once, or may be added in stages and kneaded. In this case, in a 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. In addition, after kneading in advance, when components other than thermoplastic resin that have not been added in advance are added and further melt-kneaded, these may be added all at once and kneaded, or added in stages. And may be kneaded. The method of adding in a divided manner or the method of adding one component in several batches can be adopted, the method of adding one component at a time and the method of adding different components in stages can also be adopted, both of which are combined The method is fine.

  In the case of compounding by melt kneading, the inorganic fine particles can be added as a powder, or can be added in a dispersed state in the liquid, but the inorganic fine particles can be added in advance at a predetermined mixing ratio. A method is preferred in which a master batch in which fine particles and a resin are premixed is prepared, and then the master batch and the resin are combined by melt-kneading. In this case, as a method for producing a masterbatch, it is preferable to apply a wet mixing method from the viewpoint that the organic-inorganic composite material is less damaged and can be uniformly mixed. The wet mixing method is a method of preparing a masterbatch by dissolving a resin in an appropriately selected solvent and mixing the solvent in which the resin is dissolved and inorganic fine particles, and finally by volatilizing the solvent. A master batch can be obtained.

  Solvents applicable to the production of the masterbatch include, for example, aromatic hydrocarbons such as benzene, toluene, xylene, ketones such as acetone, methyl ethyl ketone, cyclohexanone, heptanone, ethyl acetate, acetic acid-t-butyl, acetic acid- Esters such as n-butyl and acetic acid-n-hexyl, halogenated hydrocarbons such as 1,2-dichloroethane, chloroform and chlorobenzene, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, Ethers such as tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, Aprotic polar solvents such as Holland can be mentioned. These solvents can be used alone or in combination of two or more.

  When the production of the organic-inorganic composite material is completed, the organic-inorganic composite material is injected and molded using the mold 1 to produce an optical element.

  Specifically, in a state where the fixed mold 10 and the movable mold 20 are closed, a high-temperature medium such as oil is circulated through the flow paths 32 and 42 of the mold 1, and the thermoplastic resin in the organic-inorganic composite material is circulated. When the glass transition temperature is Tg, the temperature of the surface of the cavity 26 is Tg + 15 ° C. or more and Tg + 70 ° C. or less, and when the surface temperature of the cavity 26 reaches a desired temperature, the prepared organic-inorganic composite material from the sprue 22 is removed. The organic / inorganic composite material is injected and filled into the cavity 26 from the runner 23 and the gate 24. In the present invention, the glass transition temperature (Tg) means a temperature measured at a heating rate of 10 ° C./min by differential scanning calorimetry based on JIS K7121.

  Thereafter, a low-temperature medium such as oil is circulated in the flow paths 32 and 42 instead of the above-mentioned high-temperature medium, and the mold 1 is cooled until the surface temperature of the cavity 26 becomes Tg-30 ° C. or higher and Tg or lower. When the surface temperature of the cavity 26 reaches a desired temperature, the movable mold 20 is moved so as to be separated from the fixed mold 10, and a molded product made of the organic-inorganic composite material is taken out from the cavity 26. As a result, the shape of the fine structure portion 28 of the cavity 26 is transferred, and an optical element having a fine structure can be manufactured.

  Each process from the filling step to the removal step (from filling of the organic-inorganic composite material into the cavity 26 to the next filling) is set as one cycle, and these cycles are repeated a plurality of times, so that the number of cycles is met. A plurality of molded articles (that is, optical elements) can be mass-produced. In the present embodiment, since four cavities 26 are provided in the mold 1, four optical elements can be manufactured by one cycle molding.

  In the above embodiment, since the temperature of the surface of the cavity 26 of the mold 1 is set to a certain range of Tg + 15 ° C. or more and Tg + 70 ° C. or less in the step of filling the organic-inorganic composite material, distortion occurs and shape transferability deteriorates. (See Examples below).

(1) Preparation of sample (1.1) Synthesis of inorganic fine particles Silica sol (manufactured by Catalyst Kasei Kogyo Co., Ltd .: Cataloid, particle size 5 nm, SiO ₂ concentration 20% by weight) 460 g and 176 kg of water were mixed, and the concentration was 5 6500 g of a weight% NaOH aqueous solution was added to adjust the pH of the dispersion to 10.5, and then the temperature of the dispersion was raised to 95 ° C. and maintained at 95 ° C. for 30 minutes to prepare a particle dispersion.

An aqueous alkali silicate solution obtained by mixing 17744 g of water glass (manufactured by Dokai Chemical Co., Ltd .: JIS No. 3 water glass, SiO ₂ concentration 24 wt%) and 54320 g of water in a particle dispersion maintained at a temperature of 95 ° C. A sodium aluminate aqueous solution obtained by mixing 5440 g of an aqueous sodium aluminate solution (Al ₂ O ₃ concentration 22 wt%, Na ₂ O concentration 17 wt%) and 102880 g of water, 2280 g of ammonium sulfate, and 57360 g of water were mixed. The obtained electrolyte aqueous solution was added in 11 hours. At this time, the addition rate is 1.2 (SiO ₂ + Al ₂ O ₃ ) g / nuclear particle unit surface area (m ² ) time, alkali (sum of alkali silicate and sodium aluminate) and electrolyte equivalent ratio E _a / _{E E} was 2.18. Next, after aging for 1 hour, washing was performed with an ultrafiltration membrane until the pH of the growth core particle dispersion reached 10.

  Further, 15.4 g of methyltrimethoxysilane was added, stirred at room temperature for 1 hour, and then refluxed for 2 hours. Thereafter, methyl ethyl ketone was added dropwise while maintaining the volume at a constant pressure while heating and distilling under normal pressure, and when the tower top temperature reached 79 ° C. and the water content was 1.0% or less, the process was terminated. After cooling to room temperature, microfiltration was performed using a 3 μ membrane filter to obtain a methyl ethyl ketone dispersion sol. As a result of TEM observation, the average particle diameter in terms of volume was 10 nm. These operations were repeated several times to ensure the amount of particles necessary for composite preparation (kneading).

(1.2) Preparation of organic / inorganic composite material The particle dispersion was mixed with Apel 5014 manufactured by Mitsui Chemicals, Inc. (glass transition point Tg = 135 ° C .; differential scanning calorimetry (DSC) of JIS K7121 at a rate of temperature increase of 10 ° C. / The mixture was melt kneaded while devolatilizing to a value measured in min) to prepare an organic-inorganic composite material. The content of inorganic fine particles in the organic-inorganic composite material was set to 50% by weight. Surface treatment of inorganic fine particles was performed by adding cyclohexylmethyldimethoxysilane during melt kneading. For melt-kneading, Laboplast mill KF-6V was used under nitrogen. The mixture was kneaded at 100 rpm for 10 minutes, and degassed under reduced pressure at 20 Torr for 2 minutes before the end. After repeating these operations several times, the obtained solid was pulverized to obtain an organic-inorganic composite material for injection molding.

(1.3) Production of molded product An in-line injection molding machine having a clamping force of 30 tons was used for molding. The cylinder temperature was set to 280 ° C., and the organic-inorganic composite material plasticized in the cylinder was injection molded. At the time of the injection molding, while changing the temperature of the cavity at the time of filling the resin and the temperature of the cavity at the time of taking out the molded product, there are nine kinds according to the combination of the temperature at the time of filling and the temperature at the time of taking out. Molded products were produced (see Table 2), and these molded products were designated as “Samples 1 to 9”.

  The lens mold used for injection molding is a CD / DVD compatible optical pickup lens, has a diffractive structure on the entire surface of the optical functional surface, and has a CD numerical aperture (NA) of 0.45. The numerical aperture (NA) of DVD was 0.65. Both molded articles have a lens part and a flange part surrounding the lens part, and the maximum length in the optical axis direction (maximum thickness of the lens part) is 2.00 mm, which is perpendicular to the optical axis direction. The maximum length in the direction (the maximum length connecting the ends of the flange portion) was 5.00 mm.

(2) Sample evaluation (2.1) Aberration measurement For each sample 1-9, coma aberration is measured with an interferometer that can be numerically analyzed using a known method (use wavelength is 100 nm). did. The measurement results are shown in Table 2 below. In sample 4, the inorganic fine particles are lifted by rapid solidification on the cavity surface, and in sample 5, the interference fringes are disturbed due to the surface roughness that seems to be caused by the bleed out of the additive, and the aberration cannot be measured. It was.

(2.2) Observation of appearance The lens surface of each sample 1 to 9 was observed with an optical microscope, and the presence or absence of shape change such as distortion was confirmed. The observation results are shown in Table 2 below.

(2.3) Observation of shape transferability When the molding was automatically operated, the molded product was automatically taken out by an automatic take-out machine, and the shape transferability (release property) of the molded product was observed. The observation results are shown in Table 2 below.

(3) Results and Discussion As shown in Table 2, in the measurement of coma aberration, good values were obtained for Samples 1 to 3 and 6 to 9. In the observation of the appearance of the molded product, optical surfaces having a glossy surface were obtained in Samples 1 to 3 and 6 to 9, but in Sample 4, a transfer failure that was thought to be the appearance of inorganic fine particles was observed (Table 2). "× ^(1)" reference), the rough surface in sample 5 was observed respectively in the reference (in Table 2 "× ^(2)"). In the observation of the shape transferability of the molded product, any of the samples 1 to 9 has a shape transferability within the allowable range as the lens performance, and no trouble due to automatic removal occurred. Part deformation occurred (see “Δ ⁽³⁾ ” in Table 2 ⁾ , and the runner chipped in Sample 8 ⁽ see “Δ ⁽⁴⁾ ” in Table 2).

  As described above, when the mold temperature at the time of resin filling is set to the glass transition temperature Tg + 15 ° C. to Tg + 70 ° C. of the base resin of the organic / inorganic composite material, the appearance of the molded product is good, the shape transferability is excellent, and It was found that a lens molded product with small aberration can be obtained. From the above, it can be seen that setting the mold temperature at the time of resin filling to the glass transition temperature Tg + 15 ° C. or more and Tg + 70 ° C. or less of the base resin is useful for suppressing the occurrence of distortion and the deterioration of shape transferability. .

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic of the metal mold | die which concerns on preferable embodiment of this invention, an upper stage is the front view of the said metal mold | die, and the lower stage is drawing (plan view of a female mold) which looked at the AA line in the upper stage from the upper direction. .

Explanation of symbols

1 Mold 10 Fixed mold 20 Movable mold 22 Sprue 24 Gate 26 Cavity 28 Fine structure 32, 42 Flow path

Claims (3)

An injection molding method for injecting and molding an organic-inorganic composite material in which inorganic fine particles having a particle diameter of 100 nm or less are dispersed in a thermoplastic resin,
Filling the cavity of the mold with the organic-inorganic composite material;
A step of taking out a molded article composed of the organic-inorganic composite material from the cavity of the mold;
Have
When the glass transition temperature of the thermoplastic resin is Tg, the cavity surface temperature of the mold is set to a temperature of Tg + 15 ° C. or more and Tg + 70 ° C. or less in the step of filling the organic-inorganic composite material. Injection molding method. The injection molding method according to claim 1,
In the step of taking out the molded product of the organic-inorganic composite material, the temperature of the cavity surface of the mold is set to a temperature not lower than Tg-30 ° C. and not higher than Tg. In the injection molding method according to claim 1 or 2,
An injection molding method, wherein a microstructure is provided on a cavity surface of the mold.

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