JP2015230480A - Image capturing lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image capturing lens that offers minimized back focus variation and improved resin strength without using a method that relies on increased addition of nanoparticles.SOLUTION: Mixing nanotubular aluminum silicate with resin of first and second array lenses 10, 20 allows for suppressing back focus variation of an image sensor using a less amount of aluminum silicate compared with a case of mixing nanoparticles. Self-organization of aluminum silicate produces an expansion suppressing effect that is more than what is expected from the added amount, which resolves the brittleness problem and improves strength of the resin. When each of the first and second array lenses 10, 20 is integrally formed with the resin, aluminum silicate is dispersed in directions along surfaces of the first and second array lenses 10, 20, which allows for suppressing pitch variation due to linear expansion in the directions along the surfaces by adding only a small amount of aluminum silicate.

Description

  The present invention relates to an imaging lens that enables acquisition of a subject image with a single eye or a compound eye.

  If the camera function of a mobile communication terminal or the like in which the imaging optical system is incorporated is continuously used, the temperature of the sensor of the imaging element rises. When the imaging lens is made of resin, unlike glass, it is greatly expanded by heat. For this reason, the focus position moves due to a change in the shape of the lens and a change in the temperature coefficient (dn / dT) of the refractive index. This problem becomes significant with respect to the largest lens when the imaging lens is composed of a plurality of lenses, for example. Further, when the imaging lens is, for example, an array lens, there is a problem that pitch variation between the lenses occurs in addition to the above-described variation in the focus position.

  In order to solve the problem related to the refractive index among the above-mentioned problems, an optical element in which nanoparticles are added to a resin has been proposed (see Patent Document 1). However, in the optical element described in Patent Document 1, the resin becomes brittle due to the mixing of the nanoparticles, and the environmental test may be inferior. In addition, when the optical element is a lens, it is necessary to relatively increase the amount of nanoparticles added in order to suppress back focus fluctuation, and the brittleness of the resin becomes significant. Further, the problem of back focus fluctuation and pitch fluctuation of the array lens is not always solved even by adding nanoparticles.

International Publication No. 2004/113963

  An object of the present invention is to provide an imaging lens that suppresses back focus fluctuation and the like and improves the strength of a resin without using a method of increasing the amount of addition as in the case of nanoparticles.

  In order to solve the above-described problems, the imaging lens according to the present invention is manufactured by molding a resin in which nanotube-shaped aluminum silicate is dispersed.

  According to the imaging lens, by mixing nanotube-shaped aluminum silicate with resin, the refractive index fluctuation can be suppressed with a smaller amount of addition than when mixing nanoparticles, and the back focus fluctuation of the imaging element can be suppressed. Can do. In addition, since the aluminum silicate is self-organized, it has an expansion suppressing effect that is greater than or equal to the addition amount, so that not only can the brittleness of the resin be improved and the strength can be improved, but also the occurrence of warpage due to expansion can be suppressed.

  In a specific aspect or viewpoint of the present invention, in the imaging lens, the aluminum silicate is imogolite. By using imogolite, the network structure or skeletal structure of aluminum silicate is strengthened, and the effect of suppressing changes in refractive index and the like is enhanced.

  In another aspect of the present invention, the resin is any one of a thermoplastic resin, a thermosetting resin, and a photocurable resin. In the case of a thermoplastic resin, it is possible to mass-produce imaging lenses that suppress back focus fluctuation and improve the strength of the resin. Moreover, in the case of a thermosetting resin and a photocurable resin, mixing of aluminum silicate is easy and the shape freedom degree of an imaging lens is high.

  In still another embodiment of the present invention, the amount of aluminum silicate added to the resin is 3% by volume or more and 50% by volume or less.

  In still another aspect of the present invention, an array lens having a plurality of lens elements arranged two-dimensionally. In this case, the back focus fluctuation of each lens element can be suppressed.

  In still another aspect of the present invention, the plurality of lens elements and the support portion that supports the plurality of lens elements from the periphery are integrally formed of resin. In this case, since the aluminum silicate is dispersed in the direction along the surface of the array lens, it is possible to suppress pitch fluctuation due to linear expansion in the direction along the surface with a small amount of addition. In addition, by improving the strength of the resin, better results can be obtained for environmental tests such as a drop test than when no aluminum silicate is added.

(A) is a cross section of an imaging device provided with the array lens of 1st Embodiment, (B) is a top view of the array lens shown to (A). It is a figure which shows typically the state of a nanotube-like aluminum silicate. It is a figure explaining the procedure of preparation of an aluminum silicate, and shaping | molding of an array lens. It is a figure explaining a camera module provided with the imaging lens of a 2nd embodiment.

[First Embodiment]
The array lens and the like according to the first embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1A and 1B, the stacked array lens unit 100 is incorporated in the imaging device 1000.

  The illustrated laminated array lens unit 100 is a laminated body in which a plurality (specifically, two) of array lenses 10 and 20 are stacked, and is used as an imaging lens of a compound eye optical system. The first and second array lenses 10 and 20 are square plate-like members extending in parallel to the XY plane, and are stacked in the Z-axis direction perpendicular to the XY plane and joined to each other.

  In addition to the array lens unit 100 described above, the imaging apparatus 1000 includes a sensor array 60 having a plurality of detection units (sensor elements) 61 provided corresponding to the individual composite lenses 1a constituting the array lens unit 100. And an image processing unit 65 that performs image processing conforming to the visual field division method or the super-resolution method on the image signals detected by the sensor array 60. Here, the array lens unit 100 is bonded to the sensor array 60 and accommodated in a rectangular frame-like case 50.

  In the array lens unit 100, the first array lens 10 on the object side is an integrally molded product made of resin and has a substantially square outline when viewed from the central axis AX direction or the Z-axis direction. The first array lens 10 includes a plurality of lens elements 10a, each of which is an optical element, and a support portion 10b that supports the plurality of lens elements 10a from the periphery. The plurality of lens elements 10a constituting the first array lens 10 are two-dimensionally arranged on square lattice points (16 × 4 × 4 in the illustrated example) arranged in parallel to the XY plane. Each lens element 10a has a first optical surface 11a that is convex on the first main surface 10p on the object side, and a second optical surface 11b that is concave on the second main surface 10q on the object side. Both optical surfaces 11a and 11b are aspherical surfaces, for example. The support portion 10b is a flat plate-like portion, and includes a plurality of peripheral portions 10c so as to surround each lens element 10a.

  The second array lens 20 on the image side is an integrally molded product made of resin and has a substantially square outline when viewed from the central axis AX direction. The second array lens 20 includes a plurality of lens elements 20a, each of which is an optical element, and a support portion 20b that supports the plurality of lens elements 20a from the periphery. The plurality of lens elements 20a are two-dimensionally arranged on square lattice points (16 × 4 × 4 in the illustrated example) arranged in parallel to the XY plane. Each lens element 20a has a first optical surface 21a that is concave on the first main surface 20p on the object side, and a second optical surface 21b that is convex on the second main surface 20q on the image side. Both optical surfaces 21a and 21b are aspherical surfaces, for example. The support portion 20b is a flat plate-like portion and includes a plurality of peripheral portions 20c so as to surround each lens element 20a.

  The first and second array lenses 10 and 20 are formed using any one of a thermoplastic resin, a thermosetting resin, and a photocurable resin as a base material. The thermoplastic resin is a transparent resin in an optical system such as COP, PMMA, PC, and PET. Examples of the thermosetting resin include acrylic resin, allyl ester resin, silicone resin, vinyl resin, and epoxy resin. Examples of the photocurable resin include an acrylic resin, an allyl ester resin, a vinyl resin, and an epoxy resin. Since the first and second array lenses 10 and 20 have the same configuration, the first array lens 10 will be mainly described below.

  The first array lens 10 is manufactured by molding a thermoplastic or other resin in which nanotube-shaped aluminum silicate is dispersed. Here, the nanotube-like aluminum silicate is a compound having a ratio of a to b (b / a) of 10 or more, where a is an average outer diameter and b is an average length. The ratio (b / a) between a and b is preferably 1000 or less. Moreover, it is preferable that the average length of nanotube-shaped aluminum silicate is 20-3000 nm, More preferably, it is 20-1500 nm. When the length of the nanotube-like aluminum silicate is relatively long, the nanotube-like aluminum silicate AS forms a network structure in the first array lens 10 as shown in FIG. Therefore, even when subjected to an impact, the nanotube-shaped aluminum silicate AS easily disperses the force applied to the first array lens 10, and the first array lens 10 does not easily crack. Note that even when the nanotube-like aluminum silicate AS is added to the resin, the resin is sufficiently light-transmitting in the optical system.

Nanotube-like aluminum silicate is a compound whose main constituent elements are silicon (Si), aluminum (Al), oxygen (O), and hydrogen (H), and is represented by ≡Si—O—Al≡. This is a Japanese hydrated aluminum silicate having a structure. The composition of the nanotube-like aluminum silicate is typically represented by SiO ₂ .Al ₂ O ₃ .2H ₂ O or (OH) ₃ Al ₂ O ₃ SiOH.

  The nanotube-like aluminum silicate is preferably imogolite. Imogolite is a kind of natural clay component that appears in soils based on descending volcanic products such as volcanic ash and pumice, but artificially produced products also fall under this category. Imogolite is preferably particles having an average outer diameter of 2.0 to 3.0 nm, an average inner diameter of 0.5 to 1.5 nm, and an average length of several tens of nm to several μm.

  The concentration of the nanotube-like aluminum silicate (including imogolite) contained in the resin forming the first array lens 10 is preferably 3% by volume or more and less than 50% by volume after molding. Further, it is more preferably 5% by volume or more and 10% by volume or less. In this case, the effect of improving the brittleness of the first array lens 10 is optimized, and the first array lens 10 is extremely resistant to dropping impact. In addition, the density | concentration of nanotube-like aluminum silicate can be measured using the differential thermothermal weight simultaneous measuring apparatus (TG / DTA6200 by SII nanotechnology company), for example. Specifically, the temperature of the molded first array lens 10 is raised to 600 ° C., and the nanotube-like aluminum silicate that is a residue left after all the resin components are burned is measured to calculate the concentration.

[Method for preparing nanotube-shaped aluminum silicate]
The nanotube-like aluminum silicate can be obtained from a natural mineral, but can also be prepared, for example, through the following two steps (step S1 in FIG. 3).
(I) First step of treating an inorganic silicon compound solution with an ion exchanger to prepare an orthosilicate solution having an electrical conductivity of 5 to 500 μS / cm and a pH of 3.5 to 7.5 as described above (ii) Orthosilicate Second step of heating after mixing solution, inorganic aluminum compound solution and urea or ammonia, adjusting to pH 2.8-7.5

(I) 1st process In the said (i) 1st process, the inorganic silicon compound in an inorganic silicon compound solution is ion-exchange-processed with an ion exchanger, and electrical conductivity 5-500 microsiemens / cm, pH 3.5-7. 5 is prepared (step S11 in FIG. 3). Nanotube-like aluminum silicates are usually prepared from orthosilicate. However, orthosilicic acid is generally not distributed and is difficult to obtain. Therefore, it is preferable to prepare orthosilicic acid by subjecting the inorganic silicon compound to ion exchange treatment with an ion exchanger.

(Inorganic silicon compound solution)
The inorganic silicon compound solution for preparing orthosilicate includes an inorganic silicon compound and a solvent. The inorganic silicon compound is not particularly limited as long as silicate ions are generated when solvated, and examples of the inorganic silicon compound include sodium orthosilicate, sodium metasilicate, potassium metasilicate, water glass and the like. .

  On the other hand, the solvent contained in the inorganic silicon compound solution is not particularly limited as long as it is easily miscible with the inorganic silicon compound. Examples of the solvent include water, alcohols and the like. From the viewpoint of the solubility of the resulting nanotube-shaped aluminum silicate and the handleability of the solution during heating, the solvent is preferably water. Moreover, it is preferable that the silicon concentration in an inorganic silicon compound solution is 20 mM or less from a viewpoint of suppressing that a silicic acid superpose | polymerizes at the time of ion exchange and a polysilicic acid produces | generates.

(Ion exchanger)
Either an anion exchanger or a cation exchanger may be used as the ion exchanger used for the ion exchange treatment of the inorganic silicon compound. The ion exchanger is such that the orthosilicate solution obtained after ion exchange of the inorganic silicon compound solution has an electric conductivity of 5 to 500 μS / cm as described above and a pH of 3.5 to 7.5 as described above. It is selected appropriately.

  The electrical conductivity of theoretical pure water is an insulator of about 0.055 μS / cm. Therefore, when the solvent of the orthosilicic acid solution is water, the electric conductivity can be said to be an index indicating the total amount of ions in the solution. The electrical conductivity of the orthosilicate solution is measured by a common electrical conductivity meter. An example of an electric conductivity meter is ES-51 (Horiba, Ltd.), which is measured at room temperature (25 ° C.).

(Ii) Second Step After the second step, the orthosilicic acid solution obtained in the first step described above is mixed with an inorganic aluminum compound solution and urea or ammonium, and adjusted to pH 2.8 to 7.5. This is a heating process (step S12 in FIG. 3). In the second step, the element molar ratio (Si / Al) of Si and Al in the mixed solution obtained by mixing the orthosilicic acid solution, the inorganic aluminum compound solution, and urea or ammonium is 0.3 to 1.0. It is preferable. When the element molar ratio (Si / Al) of the mixed solution is within the above range, the target nanotube-like aluminum silicate (imogolite) is obtained with high purity, and by-products such as boehmite, gibbsite, amorphous silica, and allophane are obtained. The production of objects is suppressed.

(Inorganic aluminum compound solution)
The inorganic aluminum compound solution mixed with the orthosilicate solution contains an inorganic aluminum compound and a solvent. The inorganic aluminum compound is not particularly limited as long as aluminum ions are produced when solvated, and examples thereof include aluminum chloride, aluminum perchlorate, aluminum nitrate, and aluminum sec-butoxide. The solvent contained in the inorganic aluminum compound solution is not particularly limited as long as it is easily miscible with the inorganic aluminum compound. The solvent may be water, alcohols, and the like, but water is preferable from the viewpoint of the solubility of the resulting nanotube-shaped aluminum silicate and ease of handling during heating.

(Urea or ammonia)
In the second step, either urea or ammonia may be mixed with the above-described orthosilicate solution or the like. When mixing with the orthosilicate solution, urea or ammonia may be mixed with a solvent and adjusted to a predetermined concentration. As the solvent, the same solvent as the solvent contained in the inorganic aluminum compound solution may be used.

(Heat treatment)
After the pH adjustment, the mixture is heated. The heating temperature at this time is not particularly limited, but the heating temperature is preferably 80 to 120 ° C. from the viewpoint of obtaining a higher-purity nanotube-shaped aluminum silicate. Nanotube-like aluminum silicate is neutral to weakly acidic, but when the heating temperature is too high, urea rapidly undergoes thermal decomposition. As a result, the ammonia concentration in the mixed solution rapidly rises and the pH tends to shift to the alkaline side, making it difficult to obtain a nanotube-like aluminum silicate. Moreover, if heating temperature is 120 degrees C or less, precipitation of the boehmite (monohydric aluminum oxide) which is a by-product will be suppressed. On the other hand, when the heating temperature is 80 ° C. or more, the synthesis rate of the nanotube-shaped aluminum silicate is increased, and the nanotube-shaped aluminum silicate is prepared with high productivity. The heating time of the mixed solution is not particularly limited, but is preferably 12 hours or more and 100 hours or less from the viewpoint of efficiently obtaining the nanotube-like aluminum silicate.

  In the mixed solution after heating, the nanotube-shaped aluminum silicate is dispersed in the above-mentioned solvent, and the mixed solution exhibits a gel shape. Here, when the solvent is water, the water may be replaced with a solvent such as alcohol.

  In solvent replacement, an organic solvent is added to the heated mixture (gel), and the mixture is stirred and centrifuged to remove the supernatant. The organic solvent is added again, stirred and dispersed, and then centrifuged. The above operation is repeated an appropriate number of times to replace the aqueous phase of the gel with the organic solvent phase. Further, the solvent can be replaced by a semipermeable membrane, a membrane filter or the like.

  Examples of the solvent for replacing water, that is, the solvent for dispersing the nanotube-like aluminum silicate include alcohols such as methanol, ethanol, propanol, and butanol, and organic solvents such as acetone, methyl ethyl ketone, and acetonitrile.

  Whether or not a desired nanotube-like aluminum silicate has been prepared by the above method can be confirmed by measurement by X-ray diffraction and measurement by a scanning electron microscope (SEM).

(Iii) Other steps In addition to the first step and the second step, the method for producing a nanotube-shaped aluminum silicate further includes a recovery step for solid separation and desalting of the product obtained in the second step. May be. In the recovery step, the desalting method is not particularly limited. For example, the desalting can be performed by a dialysis membrane or ultrafiltration. In preparing the nanotube-shaped aluminum silicate, other steps such as solvent replacement and powder drying may be included as necessary.

[Preparation of imogolite (nanotube-like aluminum silicate)]
Hereinafter, an example of a method for preparing imogolite (nanotube-like aluminum silicate) by performing the first and second steps described above under more restricted conditions will be described.

(First step)
Sodium orthosilicate is dissolved in ion exchange water to prepare 10 L of 3.0 mM sodium orthosilicate aqueous solution. The sodium orthosilicate aqueous solution is allowed to flow into a column packed with a cation exchange resin to obtain a 3.0 mM orthosilicate aqueous solution. The flow rate in the column is set so that the resulting orthosilicate aqueous solution has an electric conductivity of 500 μS / cm or less.

(Second step)
2 L of the obtained 3.0 mM orthosilicate aqueous solution, 1 L of 30 mM aluminum nitrate aqueous solution, 1 L of 28 mM urea aqueous solution, 1 L of 3.8 mM sodium hydroxide aqueous solution, and 2 L of ion-exchanged water are mixed. Then, a mixed solution is prepared so that the molar concentration of Si and Al is 1: 2. It adjusts by addition of the said sodium hydroxide aqueous solution so that the pH of the said liquid mixture may become the range of pH 4.0-7.0.

  After sufficiently stirring the mixed solution, the mixed solution is heated in an autoclave at 100 ° C. for 72 hours. After returning the mixed solution to room temperature, 1/10 volume of 5M sodium chloride aqueous solution is added to the mixed solution to gelate, and centrifuged to obtain a transparent nanotube-shaped aluminum silicate gel. The salt (NaCl) contained in the obtained gel is removed by a dialysis membrane to obtain an aqueous dispersion of nanotube-shaped aluminum silicate.

  The average length of imogolite obtained by the above method is 150 nm, the average outer diameter is 2.2 nm, and the average inner diameter is 1.0 nm.

[Surface Treatment Method for Nanotube Aluminum Silicate]
The surface of the nanotube-shaped aluminum silicate obtained by the above method is preferably subjected to surface treatment (step S2 in FIG. 3). By performing the surface treatment, the miscibility with the matrix resin can be increased and the dispersibility can be increased. The method for performing the surface treatment is not particularly limited, and any known method can be used.

  Examples of the surface treatment agent used for the surface treatment of nanotube-shaped aluminum silicate powder (inorganic particles) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetraphenoxysilane, methyltrimethoxysilane, and ethyltrimethoxy. Silane, propyltrimethoxysilane, methyltriethoxysilane, methyltriphenoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane, 3-methylphenyltrimethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldi Phenoxysilane, trimethylmethoxysilane, triethylethoxysilane, triphenylmethoxysilane, triphenylphenoxysilane, cyclopentyltrimethoxy , Cyclohexyltriethoxysilane, benzyldimethylethoxysilane, octyltriethoxysilane, vinyltriacetoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldichlorosilane, γ-chloro Propylmethyldimethoxysilane, γ-chloropropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ- Aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethyl Toxisilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ- (2-aminoethyl) Aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane / hydrochloride, aminosilane compound and the like It is done. Moreover, in the said compound, it can replace with silane and can use what has aluminum, titanium, a zirconia, etc. In that case, examples of the surface treatment agent include aluminum triethoxide, aluminum triisoproxyd, and the like.

  As surface treatment agents, isostearic acid, stearic acid, cyclopropanecarboxylic acid, cyclohexanecarboxylic acid, cyclopentanecarboxylic acid, cyclohexanepropionic acid, octylic acid, palmitic acid, behenic acid, undecylenic acid, oleic acid, hexahydrophthalic acid Any of the surface treatment agents such as fatty acids such as these, metal salts thereof, and organic phosphate surface treatment agents can be used. Moreover, these can be used individually or in mixture of 2 or more types.

  The compounds exemplified above have different characteristics such as reaction rate, and compounds suitable for surface treatment conditions can be used. Further, only one type may be used or a plurality of types may be used in combination. Furthermore, the properties of the surface-treated fine particles obtained may vary depending on the compound used. For example, by selecting the compound to be used for the surface treatment, it is possible to achieve affinity with the photo-curable resin used to obtain the composite material. It is.

  Although the ratio of a surface treating agent is not specifically limited, Preferably it is 10-99 mass% with respect to the inorganic particle after surface treatment, More preferably, it is 30-98 mass%.

[Method for producing nanotube-shaped aluminum silicate-containing resin (organic-inorganic composite material)]
Aluminum silicate-containing resins (including imogolite-containing resins) can be obtained by mixing aluminum silicate with the resin (step S3 in FIG. 3). The aluminum silicate-containing resin may be prepared by adding and kneading aluminum silicate to the molten resin, or after mixing the resin dissolved in the solvent with aluminum silicate. You may produce by removing an organic solvent. The resin mixed with the aluminum silicate can be selected from a thermoplastic resin, a thermosetting resin, and a photocurable resin.

  In this embodiment, the organic-inorganic composite material is produced by a melt kneading method. In the melt-kneading method, an organic-inorganic composite material can be prepared by mixing a resin or aluminum silicate prepared by an existing method, so that an inexpensive organic-inorganic composite material can be usually produced. In the melt kneading, an organic solvent can also be used. By using an organic solvent, the temperature of melt kneading can be lowered, and the deterioration of the resin can be easily suppressed. In this case, it is preferable to devolatilize after melt-kneading to remove the organic solvent from the organic-inorganic composite material.

  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 mentioned. Further, a continuous melt kneader such as a single screw extruder or a twin screw extruder can be used.

  Specific kneaders used in the method of mixing the treated aluminum silicate and resin include KRC kneader (manufactured by Kurimoto Iron Works), polylab system (manufactured by HAAKE), and nanocon mixer (Toyo Seiki Seisakusho). Co., Ltd.), Nauta Mixer Bus Co. Kneader (Buss), TEM extruder (Toshiba Machine Co., Ltd.), TEX twin-screw kneader (Nihon Steel Works), PCM kneader (Ikegai Iron Works) Manufactured), three roll mill, mixing roll mill, kneader (manufactured by Inoue Mfg. Co., Ltd.), kneedex (manufactured by Mitsui Mining Co., Ltd.), MS pressure kneader, nider ruder (manufactured by Moriyama Mfg. Co., Ltd.), Banbury mixer (manufactured by Kobe Steel Ltd.) ).

  In the method for producing an organic-inorganic composite material, when melt kneading is used, the resin and aluminum silicate 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, components to be added stepwise can be added from the middle of the cylinder.

  When compounding by melt kneading, the aluminum silicate can be added in a powdered or agglomerated state, or can be added in a dispersed state in the liquid. When adding in the state disperse | distributed in the liquid, it is preferable to perform devolatilization after kneading | mixing.

  The first and second array lenses 10 and 20 are molded by, for example, injection molding using a mold, press molding using a mold or a resin mold, or cast molding (step S4 in FIG. 3). The aluminum silicate resin obtained by the above steps is processed into a lens or an array lens having a desired shape by injection molding using a mold, thermosetting treatment, or photocuring treatment. Specifically, the first and second array lenses 10 and 20 shown in FIG.

  The first and second array lenses 10 and 20 are aligned in a stacked state, and are bonded or bonded to each other by an adhesive such as a photo-curable resin. By such joining or adhesion, an array lens unit 100 including a large number of synthetic lenses 1a arranged two-dimensionally in a matrix is obtained. The array lens unit 100 and the sensor array 60 shown in FIG. 1A and the like are housed in a case 50, and an imaging device 1000 is obtained. The optical axis OA of each synthetic lens 1a is parallel to the entire central axis AX. The plurality of synthetic lenses 1a arranged two-dimensionally on the lattice points corresponds to a single-eye lens of a field division method or a super-resolution method. Here, the field division method is a method of obtaining one image by joining images of different fields of view formed by the respective composite lenses 1a, which are individual compound optical systems, with images of different fields of view by image processing. is there. The super-resolution method is a method of obtaining one high-resolution image by image processing from images of the same field of view formed by the respective composite lenses 1a that are individual compound optical systems.

  On the object side of the case 50 that houses the array lens unit 100, an entrance diaphragm plate 45 fixed by adhesion to the case 50 or the like is disposed. Although a detailed description is omitted in the case 50 and the entrance diaphragm plate 45, a large number of openings are formed corresponding to the lens elements 10a and the like. A thin light-shielding diaphragm plate may be provided between the first array lens 10 and the second array lens 20 or on the image side of the second array lens 20.

  According to the imaging lens described above, the back focus fluctuation of the imaging element can be suppressed by mixing the nano-sized aluminum silicate with the resin with a smaller amount of addition than when the nanoparticles are mixed. In addition, since the aluminum silicate is self-organized, it has an expansion suppressing effect that is greater than or equal to the addition amount, so that the brittleness of the resin can be eliminated and the strength can be improved. In particular, in the first and second array lenses 10 and 20 having a plurality of lens elements 10a and 20a arranged two-dimensionally, back focus fluctuations of the lens elements 10a and 20a can be suppressed. Further, when the first and second array lenses 10 and 20 are integrally formed of resin, aluminum silicate is dispersed in the direction along the surfaces of the first and second array lenses 10 and 20, Pitch fluctuation due to linear expansion in the direction along the surface can be suppressed with a small addition amount. In addition, by improving the strength of the resin, better results can be obtained for environmental tests such as a drop test than when no aluminum silicate is added.

  In addition, since sensors, such as an image pick-up element, are the products made from silicon, a pitch fluctuation is small. Therefore, if there is a difference between the pitch fluctuation of the image sensor and the pitch fluctuation of the lens element, an error occurs in image capture.

[Example 1]
Hereinafter, Example 1 of the present embodiment will be described.
In Example 1, an array lens was molded by injection molding using a thermoplastic resin as a sample. APL5514ML (made by Mitsui Chemicals) was used as the thermoplastic resin. A desired amount of imogolite-containing resin was produced by melt kneading. Using this imogolite-containing resin, an array lens shown in FIG. 1A and the like was molded by injection molding. In the first array lens 10 shown in FIG. 1B, among the lens elements 10a in the right column, the center of the lens element 10a in the first row (optical axis OA) and the center of the lens element 10a in the fourth row (light The distance d between the axes OA) was measured using a microscope. Specifically, the distance d at the reference temperature of 20 ° C. was set to 10 mm, and the distance d at the maximum temperature of 60 ° C. at the actual use of the array lens was measured. Further, a free drop test was performed in which the array lens was dropped from a height of 1.5 m.

表１に示すように、イモゴライトの含有量が３〜５０体積％の場合、レンズ要素間の距離ｄが１０．０２ｍｍ未満であり、アレイレンズの面に沿った方向の線膨張を抑えることができた。また、イモゴライトの含有量が３〜５０体積％（より好ましくは５〜１０体積％）の場合、落下試験においても破損が生じず、アレイレンズの強度が高いことがわかる。一方、イモゴライトを含有しない場合、レンズ要素間の距離ｄが１０．０２ｍｍ以上となり、アレイレンズの面に沿った方向の線膨張が大きくなった。また、イモゴライトを含有しない場合、落下試験において、破損が生じ、アレイレンズが脆いことがわかる。 Table 1 shows the performance of the array lens of Example 1. In Table 1, “Distance between lens elements (d)”, a case where the distance d at 60 ° C. was less than 10.02 mm was judged as “good”, and a case where it was 10.02 mm or more was judged as “bad”. In Table 1 “Brittleness (drop test)”, the case where the array lens is not damaged (destructed or cracked) even if the drop test is performed 400 times is rated “「 ”and the drop test is performed 300 times. Even when the array lens was not damaged (broken or cracked), it was judged as “good”, and when the array lens was broken less than 300 times, it was judged as “bad”.
[Table 1]

As shown in Table 1, when the imogolite content is 3 to 50% by volume, the distance d between the lens elements is less than 10.02 mm, and linear expansion in the direction along the surface of the array lens can be suppressed. It was. In addition, when the content of imogolite is 3 to 50% by volume (more preferably 5 to 10% by volume), it is found that no damage occurs in the drop test and the strength of the array lens is high. On the other hand, when no imogolite was contained, the distance d between the lens elements was 10.02 mm or more, and the linear expansion in the direction along the surface of the array lens increased. Moreover, when it does not contain imogolite, it turns out in a drop test that damage occurs and the array lens is brittle.

[Comparative Example 1]
In Comparative Example 1, as the resin forming the sample, a thermoplastic resin (specifically APL5514ML) kneaded with nanoparticles (specifically, silica RX-300 (manufactured by Aerosil Japan)) was used. Silica RX-300 has a particle size of 7 nm. In Comparative Example 1, the array lens molding method, evaluation method, and the like are the same as in Example 1.

表２に示すように、シリカの含有量が実施例１で良好な濃度であった１０体積％であっても、アレイレンズの線膨張変化が大きく、かつ脆いことがわかる。以上のことにより、ナノチューブ状のアルミニウムケイ酸塩であるイモゴライトは、ナノ微粒子であるシリカよりも少ない添加量で、アレイレンズの線膨張変化を抑え、かつ強度を向上させることができることがわかる。 Table 2 shows the performance of the array lens of Comparative Example 1.
[Table 2]

As shown in Table 2, it can be seen that even when the silica content was 10% by volume which was a good concentration in Example 1, the change in linear expansion of the array lens was large and fragile. From the above, it can be seen that imogolite, which is a nanotube-shaped aluminum silicate, can suppress the change in linear expansion of the array lens and improve the strength with a smaller addition amount than silica, which is a nanoparticle.

[Example 2]
Hereinafter, Example 2 of the present embodiment will be described.
In this example, an array lens was molded using a thermosetting resin among curable resins as a sample. A thermosetting acrylic resin was used as the thermoplastic resin. Specifically, 2-alkyl-2-adamantyl- (meth) -acrylate was used. As a thermal polymerization initiator, 1% by volume of Parroyl L (1 hour half-life 79.5 ° C.) was added. In addition, any of the radical thermal polymerization initiators (for example, organic peroxide) can be used as the thermal polymerization initiator. A desired amount of imogolite-containing resin was produced by melt kneading. In Example 2, the array lens molding method, evaluation method, and the like are the same as in Example 1.

表３に示すように、アレイレンズの樹脂がアクリル樹脂であっても、イモゴライトの含有量が３〜５０体積％の場合、アレイレンズの面に沿った方向の線膨張を抑えることができた。また、イモゴライトの含有量が３〜５０体積％（より好ましくは５〜１０体積％）の場合、落下試験においても破損が生じなかった。一方、イモゴライトを含有しない場合、アレイレンズの面に沿った方向の線膨張が大きくなった。また、イモゴライトを含有しない場合、落下試験において、破損が生じた。 Table 3 shows the performance of the array lens of Example 2.
[Table 3]

As shown in Table 3, even when the resin of the array lens was an acrylic resin, the linear expansion in the direction along the surface of the array lens could be suppressed when the imogolite content was 3 to 50% by volume. Moreover, when the content of imogolite was 3 to 50% by volume (more preferably 5 to 10% by volume), no breakage occurred in the drop test. On the other hand, when imogolite was not contained, the linear expansion in the direction along the surface of the array lens increased. Further, when no imogolite was contained, breakage occurred in the drop test.

[Comparative Example 2]
In Comparative Example 2, the resin forming the sample was a thermosetting resin (specifically, 2-alkyl-2-adamantyl- (meth) -acrylate) and a nanoparticulate (specifically, silica RX-300 (Nippon Aerosil). Kneaded) was used. In Comparative Example 2, the molding method and evaluation method of the array lens are the same as in Example 1.

表４に示すように、シリカの含有量が実施例２で良好な濃度であった１０体積％であっても、アレイレンズの線膨張変化が大きく、かつ脆いことがわかる。以上のことにより、ナノチューブ状のアルミニウムケイ酸塩であるイモゴライトは、硬化性樹脂に混錬させた場合でも、実施例１と同様に、ナノ微粒子であるシリカよりも少ない添加量で、アレイレンズの線膨張変化を抑え、かつ強度を向上させることができることがわかる。 Table 4 shows the performance of the array lens of Comparative Example 2.
[Table 4]

As shown in Table 4, it can be seen that even when the silica content was 10% by volume which was a good concentration in Example 2, the linear expansion change of the array lens was large and fragile. As described above, even when imogolite, which is a nanotube-shaped aluminum silicate, is kneaded into a curable resin, as in Example 1, it can be added in an amount smaller than that of silica, which is a nanoparticulate. It can be seen that the linear expansion change can be suppressed and the strength can be improved.

[Second Embodiment]
Hereinafter, an imaging lens according to the second embodiment will be described. The imaging lens according to the second embodiment is a partial modification of the imaging lens of the first embodiment, and items that are not particularly described are the same as those of the first embodiment.

As shown in FIG. 4, the imaging lens 200 is incorporated in the camera module 70.
The camera module 70 includes an imaging lens 200 that is an imaging optical system that forms a subject image, an imaging element 71 that detects a subject image formed by the imaging lens 200, and holds the imaging element 71 from behind and wiring and the like. And a lens barrel portion 74 having an opening OP for holding the imaging lens 200 and the like and allowing a light beam from the object side to enter. The imaging lens 200 has a function of forming a subject image on the image plane of the imaging element 71 or the imaging plane (projected plane) I. The camera module 70 is used by being incorporated in an imaging device (not shown), but may be used alone.

  The imaging lens 200 forms a subject image on the imaging surface (projection surface) I of the imaging element 71, and in order from the object side, the first lens L1, the second lens L2, and the third lens L3. And a fourth lens L4. The aperture stop S is disposed on the object side surface side of the first lens L1.

  The image sensor 71 is a sensor chip made of a solid-state image sensor. The wiring board 72 has a role of aligning and fixing the image sensor 71 to other members (for example, the lens barrel portion 74). On the imaging lens 200 side of the imaging element 71, a parallel plate F is arranged and fixed so as to cover the imaging element 71 and the like by a holder member (not shown). The lens barrel 74 houses and holds the imaging lens 200. The lens barrel portion 74 enables the focusing operation of the imaging lens 200 by moving any one or more of the lenses L1 to L3 constituting the imaging lens 200 along the optical axis AX2. For example, it has a drive mechanism 75a. Between the light exit surface of the fourth lens L4 and the imaging surface (image surface) I, a parallel plate F having an appropriate thickness is disposed.

  The first to fourth lenses L1 to L4 constituting the imaging lens 200 are formed of any one of a thermoplastic resin, a thermosetting resin, and a photocurable resin. The first to fourth lenses L1 to L4 have a substantially circular outline when viewed from the direction of the central axis AX.

  In the present embodiment, the first to fourth lenses L1 to L4 are formed of a resin obtained by kneading nanotube-shaped aluminum silicate, as in the first embodiment.

  According to the imaging lens of the present embodiment, by mixing nano-particles by mixing nanotube-shaped aluminum silicate with the resin forming the first to fourth lenses L1 to L4 constituting the imaging lens 200. The back focus fluctuation of the image sensor can be suppressed with a small addition amount. In addition, since the aluminum silicate is self-organized, it has an expansion suppressing effect that is greater than or equal to the addition amount, so that the brittleness of the resin can be eliminated and the strength can be improved.

  In addition, it is not necessary that all the lenses of the first to fourth lenses L1 to L4 are formed of a resin containing a nanotube-like aluminum silicate, and one or more lenses contain a nanotube-like aluminum silicate. It only has to be done.

  The array lens according to the present embodiment has been described above, but the array lens according to the present invention is not limited to the above. For example, in the above-described embodiment, the shapes and sizes of the first and second optical surfaces 11a, 11b, 21a, and 21b can be appropriately changed according to applications and functions. Further, although the outer shape of the first and second array lenses 10 and 20 is a quadrangle, it may be other shapes such as a circle.

  In the above-described embodiment, two array lenses are stacked. However, only one single layer may be used without stacking. Further, three or more array lenses may be laminated.

  Moreover, in the said embodiment, although the array lens was integrally molded with resin, you may form several resin-made lens parts, for example on a glass-made board | substrate.

DESCRIPTION OF SYMBOLS 10,20 ... Array lens, 10a, 20a ... Lens element, 11a, 11b, 21a, 21b ... Optical surface, 50 ... Case, 70 ... Camera module, 71 ... Image sensor, 60 ... Sensor array, 100 ... Array lens unit, DESCRIPTION OF SYMBOLS 100 ... Imaging device 200 ... Imaging lens 1000 ... Imaging device

Claims (6)

  An imaging lens produced by molding a resin in which nanotube-shaped aluminum silicate is dispersed.   The imaging lens according to claim 1, wherein the aluminum silicate is imogolite.   The imaging lens according to claim 1, wherein the resin is any one of a thermoplastic resin, a thermosetting resin, and a photocurable resin.   The imaging lens according to any one of claims 1 to 3, wherein an amount of the aluminum silicate added to the resin is 3% by volume or more and 50% by volume or less.   The imaging lens according to any one of claims 1 to 4, wherein the imaging lens is an array lens having a plurality of lens elements arranged two-dimensionally.   The imaging lens according to claim 5, wherein the plurality of lens elements and a support portion that supports the plurality of lens elements from the periphery are integrally formed of the resin.

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