JP5594110B2 - Lens for imaging apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a lens for an imaging device having a near-infrared shielding effect, and an imaging device using the same.

  The sensitivity of solid-state image sensors (CCD, CMOS, etc.) used in digital still cameras, digital video cameras, etc. extends from the visible region to the near infrared region of the wavelength of light. On the other hand, human visibility is only in the visible region of the wavelength of light. Therefore, for example, in a digital still camera, light in the visible wavelength region (wavelength 420 to 630 nm) is transmitted and light in the near infrared wavelength region (wavelength 700 to 1200 nm) is transmitted between the imaging lens and the solid-state imaging device. By providing a near-infrared cut filter that absorbs or reflects, the sensitivity of the solid-state imaging device is corrected so as to approach human visibility.

  However, the arrangement of the near-infrared cut filter hinders downsizing and thinning of the image pickup apparatus, and increases the number of parts, resulting in a problem that the product price increases.

  Therefore, in order to solve the above problems, a dielectric multilayer film having an effect of blocking light in the near-infrared region is provided on the surface of the lens, or light in the near-infrared region is selectively absorbed. For example, lenses having a near-infrared cut filter function have been developed, such as molding a lens using a glass material (see, for example, Patent Documents 1 and 2).

  However, the former dielectric multilayer film has a so-called reflective interference filter function that reflects and blocks light in the near-infrared region by light interference, so that the blocking characteristic varies depending on the incident angle of light. There is a problem that the color characteristics change between the central portion and the peripheral portion of the image. Another problem is that multiple images called ghosts are likely to occur due to the reflected light becoming stray light and entering the solid-state imaging device. On the other hand, in the latter lens, the material itself is expensive, and a glass material having a high softening point is press-molded. Therefore, the manufacturing cost is high, and the cost cannot be reduced. Further, the near-infrared cut filter of the imaging device has a sharp change in transmittance between wavelengths of 630 to 700 nm in order to capture dark areas more brightly, in addition to the effect of simply blocking light of wavelengths in the near-infrared region. However, all of the above lenses have insufficient characteristics.

JP-A-5-207350 JP 2002-139605 A

  The present invention uses a lens for an imaging device that has good near-infrared shielding characteristics and can sufficiently reduce the size, thickness, and cost of the imaging device, and such an imaging device lens. An object is to provide an imaging device.

An imaging device lens according to an aspect of the present invention is a lens used in an imaging device including a solid-state imaging device, and is made of an oxide crystallite containing at least Cu and / or P, and has a number average aggregate particle diameter. Contains near-infrared absorbing particles having a diameter of 5 to 200 nm , or a layer containing the near-infrared absorbing particles .

In the imaging device lens, the layer containing the near-infrared absorbing particles may be a layer formed on at least one surface of the lens body.

In the imaging device lens, the oxide may be a compound represented by the following formula (1) _(e.g., LiCuPO _4, Mg 1/2 CuPO _4, etc.).
A _{1 / n} CuPO ₄ (1)
(In the formula, A is at least one selected from the group consisting of alkali metals (Li, Na, K, Rb, Cs), alkaline earth metals (Mg, Ca, Sr, Ba) and NH ₄ ; Is 1 when A is an alkali metal or NH ₄ and is 2 when A is an alkaline earth metal.)

  In the imaging device lens, the near-infrared absorbing particles may have a crystallite size of 5 to 80 nm determined from X-ray diffraction.

In the imaging device lens, the near-infrared absorbing particles may have a reflectance change amount D represented by the following formula (2) of −0.41% / nm or less.
D (% / nm) = [R ₇₀₀ (%) − R ₆₀₀ (%)] / [700 (nm) −600 (nm)] (2)
(In the formula, R ₇₀₀ is a reflectance at a wavelength of 700 nm in the diffuse reflection spectrum of the near-infrared absorbing particles, and R ₆₀₀ is a reflectance at a wavelength of 600 nm in the diffuse reflection spectrum of the near-infrared absorbing particles.)

  In the imaging device lens, the near-infrared absorbing particles may have a reflectance at a wavelength of 715 nm in a diffuse reflection spectrum of 19% or less and a reflectance at a wavelength of 500 nm of 85% or more.

In the imaging device lens, the near-infrared absorbing particles are attributed to water in a microscopic IR spectrum when the absorption intensity of a peak near 1000 cm ⁻¹ attributed to a phosphate group is used as a reference (100%). The peak absorption intensity near 1600 cm ⁻¹ may be 8% or less, and the peak absorption intensity near 3750 cm ⁻¹ attributed to a hydroxyl group may be 26% or less.

The said lens for imaging devices WHEREIN: Content of the said near-infrared absorption particle in the layer containing the said near-infrared absorption particle may be 20-60 mass%.

In the lens for an imaging device, the layer containing the near-infrared absorbing particles may further contain a near-infrared absorbing material free from oxide crystallites containing at least Cu and / or P.

In the lens for an imaging device , the content of the near-infrared absorbing material having no crystallites of an oxide containing at least Cu and / or P in the layer containing the near-infrared absorbing particles is 0.5 to 30% by mass. It may be.

In the imaging device lens, ITO particles may be included as a near-infrared absorbing material having no crystallites of oxide containing at least Cu and / or P.

In the lens for an imaging device, the layer containing the near-infrared absorbing particles may have a transmittance change amount D ′ represented by the following formula (3) of −0.36% / nm or less.
D ′ (% / nm) = [T ₇₀₀ (%) − T ₆₃₀ (%)] / [700 (nm) −630 (nm)] (3)
(Where T ₇₀₀ is the transmittance at a wavelength of 700 nm in the transmission spectrum of the layer containing near-infrared absorbing particles, and T ₆₃₀ is the transmittance at a wavelength of 630 nm in the transmission spectrum of the layer containing near-infrared absorbing particles. is there.)

  An imaging device according to an aspect of the present invention includes the imaging device lens and a solid-state imaging device that receives light incident through the lens and converts the light into an electrical signal.

  According to the lens for an imaging device according to one embodiment of the present invention, the imaging device has favorable near-infrared shielding characteristics, and the imaging device can be sufficiently reduced in size, thickness, and cost. In addition, according to the imaging device of one embodiment of the present invention, it is possible to improve the quality of a captured image and reduce the size, thickness, and cost of the device.

It is sectional drawing which shows an example of the lens for imaging devices by the 1st Embodiment of this invention. It is sectional drawing which shows the modification of the lens for imaging devices by the 1st Embodiment of this invention. It is sectional drawing which shows the other modification of the lens for imaging devices by the 1st Embodiment of this invention. It is sectional drawing which shows the further another modification of the lens for imaging devices by the 1st Embodiment of this invention. It is a figure which shows an example of the X-ray diffraction of the near-infrared absorption particle used in this invention. It is sectional drawing which shows an example of the lens for imaging devices by the 2nd Embodiment of this invention. It is sectional drawing which shows the modification of the lens for imaging devices by the 2nd Embodiment of this invention. It is sectional drawing which shows the other modification of the lens for imaging devices by the 2nd Embodiment of this invention. It is sectional drawing which shows roughly the principal part structure of an example of the imaging device by the 3rd Embodiment of this invention. It is sectional drawing which shows roughly the principal part structure of an example of the imaging device by the 3rd Embodiment of this invention. It is a figure which shows the transmission spectrum of the near-infrared absorption layer of the Example of this invention. It is a figure which shows the transmission spectrum of the near-infrared absorption layer of the other Example of this invention. It is a figure which shows the transmission spectrum of the near-infrared absorption layer of the other Example of this invention. It is a figure which shows the transmission spectrum of the near-infrared absorption layer of the other Example of this invention.

  Hereinafter, modes for carrying out the present invention will be described. Although the description will be made based on the drawings, the drawings are provided for illustration only, and the present invention is not limited to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a lens for an imaging device according to the present embodiment. The lens for the image pickup apparatus of the present embodiment is a solid-state image pickup element of an image pickup apparatus such as a small camera incorporated in an information device such as a digital still camera, a digital video camera, a mobile phone, a notebook personal computer, or a PDA (Personal Digital Assistant). This lens constitutes all or part of a lens system that forms an image.

  As shown in FIG. 1, this imaging device lens 10A has one surface (refractive surface) 11a as a flat surface and the other surface (refractive surface) 11b as a convex surface. The surface 11a is provided with a layer (near infrared absorbing layer) 12 containing near infrared absorbing particles as described later, and the antireflection film 13 is provided on the other surface 11b.

  If the lens used for the lens main body 11 is a lens conventionally used for this kind of use, a shape, a material, etc. will not be specifically limited. 2 and 3 show other examples used as the lens body 11. That is, in the imaging apparatus lens 10B shown in FIG. 2, a glass plano-convex lens having a flat plate portion 14 on the outer peripheral portion is used as the lens body 11, and the near-infrared absorbing layer 12 is provided on one surface 11a made of a plane. An antireflection film 13 is provided on the other convex surface 11b. Further, in the imaging device lens 10C shown in FIG. 3, as the lens body 11, one surface 11a has a concave surface, the other surface 11b has a convex surface, and further has a flat plate portion 14 on the outer peripheral portion. A lens is used, a near-infrared absorbing layer 12 is provided on the concave surface 11a of the glass concave-convex lens, and an antireflection film 13 is provided on the other convex surface 11b. In the concavo-convex lens as shown in FIG. 3, a lens having a convex lens function is called a convex meniscus, and a lens having a concave lens function is called a concave meniscus.

  Examples of the material constituting the lens body 11 include crystals such as quartz, lithium niobate, and sapphire; glasses such as BK7, quartz, and low-melting glass for precision press molding; polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Polyester resin such as polyethylene, polypropylene, ethylene vinyl acetate copolymer, etc., acrylic resin such as norbornene resin, polyacrylate, polymethyl methacrylate, urethane resin, vinyl chloride resin, fluorine resin, polycarbonate resin, polyvinyl butyral resin And plastics such as polyvinyl alcohol resin. These materials may have an absorption characteristic for light having a wavelength in the ultraviolet region and / or near infrared region. The lens body 11 may be made of, for example, colored glass obtained by adding CuO or the like to fluorophosphate glass or phosphate glass. The drawings are examples of refractive lenses, but may be a diffractive lens using diffraction such as a Fresnel lens, a hybrid lens using both refraction and diffraction, or the like.

  Although not shown, for example, the antireflection film 13 may be provided on one surface 11a of the lens body 11, and the near-infrared absorbing layer 12 may be provided on the other surface 11b, and the other surface 11b. Furthermore, instead of the antireflection film 13, a near infrared absorption layer 12 similar to the one surface 11a may be formed. That is, you may make it provide the near-infrared absorption layer 12 in both surfaces 11a and 11b of the lens main body 11. FIG.

  Further, a dielectric multilayer film or a moth-eye structure may be provided on the surface close to the near-infrared absorbing layer and air. Thereby, interface reflection can be reduced and the utilization efficiency of light can be improved. Dielectric multilayer film is made by laminating films made of transparent materials such as metal oxides such as silicon oxide, titanium oxide, niobium oxide, tantalum oxide and alumina, metal fluorides such as magnesium fluoride, fluororesin, etc. For example, a vacuum film formation process such as a CVD method, a sputtering method, or a vacuum deposition method, or a wet film formation process such as a spray method or a dip method, etc. Can be used. In addition, the moth-eye structure is a structure in which a regular protrusion array is formed with a period smaller than 400 nm, for example, and the effective refractive index continuously changes in the thickness direction. It has a function of suppressing reflectivity. The moth-eye structure can be formed by molding or the like.

  The lens body 11 may have a structure in which a plurality of lenses are bonded with an adhesive, and in this case, a near-infrared absorbing layer can be provided on the bonding surface. FIG. 4 shows an example of such a lens for an imaging device. In this imaging device lens 10D, a lens body 11 is composed of two lenses 11A and 11B, and a near-infrared absorbing layer 12 is formed on a joint surface thereof. And an antireflection film 13 is provided on the surface opposite to the bonding surface. Such an imaging device lens 10D is formed by providing the near-infrared absorbing layer 12 on one of the two lenses 11A and 11B (for example, the lens 11A) and bonding them together with the other (for example, the lens 11B) with an adhesive. Alternatively, the two lenses 11A and 11B may be bonded together using the near-infrared absorbing layer 12 as an adhesive.

  The type of lens used in the lens body 11 and the presence or absence of the antireflection film 13 are appropriately determined in consideration of the purpose of use, the type of lens used in combination, the arrangement location, and the like.

  In addition, when using the lens which consists of glass as the lens main body 11, in order to improve the adhesiveness with the near-infrared absorption layer 12 and the anti-reflective film 13, the surface treatment by the silane coupling agent is given to the surface. Also good. Examples of the silane coupling agent include γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -N′-β- (amino Ethyl) -γ-aminopropyltriethoxysilane, aminosilanes such as γ-anilinopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Epoxy silanes such as, vinyltrimethoxysilane, vinyl silanes such as N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-chloro Propyltrimethoxysilane, γ-mercaptopropyltrimethoxy Silane or the like can be used.

  Moreover, when using the lens which consists of plastics as the lens main body 11, before forming the near-infrared absorption particle content layer 12 and the anti-reflective film 13, it is preferable to give a corona treatment and an easily bonding process to the lens surface.

Next, the near infrared absorption layer 12 will be described.
The near-infrared absorbing particles contained in the near-infrared absorbing layer 12 are composed of crystallites of the compound represented by the formula (1) described above, and have a number average aggregate particle diameter of 5 to 200 nm. In the present invention, the near-infrared absorbing particles are not particularly limited to such particles, and are composed of oxide crystallites containing at least Cu and / or P, and have a number average aggregate particle diameter of 5 to 5. What is necessary is just 200 nm. By using the crystallite as an absorbing substance, it is possible to maintain near-infrared absorption characteristics resulting from the crystal structure. Further, since the crystallite is a fine particle, it is possible to contain an absorbing substance at a high concentration in the near-infrared absorbing layer 12, and the absorption capacity per unit length can be increased.

Here, “crystallite” means a unit crystal that can be regarded as a single crystal, and “particle” is composed of a plurality of crystallites. By "represented by consisting crystallites of the compound with formula (1)", for example, as shown in FIG. 5, can confirm the crystal structure of A _{1 / n} CuPO ₄ by X-ray diffraction, essentially A _{1 / It} means that the crystallite of _n CuPO ₄ is identified by X-ray diffraction, and “substantially consists of crystallite of A _{1 / n} CuPO ₄ ” means that the crystallite is A _{1 / n} CuPO 4. ₄ may contain impurities within a range where the crystal structure of ₄ can be sufficiently maintained (the crystal structure of A _{1 / n} CuPO ₄ can be confirmed by X-ray diffraction). In addition, X-ray diffraction is measured about the near-infrared absorption particle | grains of a powder state using an X-ray-diffraction apparatus.

The number average aggregated particle diameter of the near infrared absorbing particles is 200 nm or less, preferably 100 nm or less, and more preferably 70 nm or less. Moreover, the number average aggregate particle diameter of the near-infrared absorbing particles is 5 nm or more, preferably 10 nm or more, and more preferably 30 nm or more. If the number average agglomerated particle diameter is 5 nm or more, excessive pulverization treatment is not required for the formation of fine particles, and the crystallite can maintain the crystal structure of A _{1 / n} CuPO _4. As a result, near infrared absorption characteristics are exhibited. it can. Further, when the number average aggregate particle diameter exceeds 200 nm, it is greatly affected by scattering including Mie scattering, so that the transmittance of light in the visible wavelength band is greatly reduced, and the contrast and haze of the near infrared absorption layer 12 are reduced. Performance decreases. If the number average agglomerated particle diameter is 100 nm or less, the influence of scattering is reduced, and if it is 70 nm or less, the influence of scattered light due to Rayleigh scattering is less likely to be affected, so that the transparency is increased. If the number average aggregate particle diameter is 30 to 70 nm, the haze of the near-infrared absorbing layer is reduced (that is, the transmittance is increased), and the near-infrared absorbing characteristics are further improved. Here, the number average agglomerated particle diameter is a value measured using a dynamic light scattering particle size distribution measuring device for a particle diameter measurement dispersion in which near-infrared absorbing particles are dispersed in a dispersion medium.

  The haze value of the near-infrared absorbing layer 12 is preferably controlled to 1% or less. If the haze value exceeds 1%, the image becomes unclear. The haze value is more preferably controlled to 0.2% or less.

The crystallite size in the near-infrared absorbing particles is preferably 5 to 80 nm, and more preferably 10 to 80 nm. If the crystallite size is 5 nm or more, the crystallite can sufficiently maintain the crystal structure of A _{1 / n} CuPO ₄ , and as a result, sufficient near-infrared absorption characteristics can be exhibited. If the crystallite size is 80 nm or less, the number-average aggregated particle diameter of the near-infrared absorbing particles can be kept small, and the haze of the near-infrared absorbing layer can be kept low. The crystallite size is a value obtained by performing X-ray diffraction on near-infrared absorbing particles and calculating by Scherrer's method.

The reason for adopting alkali metal (Li, Na, K, Rb, Cs), alkaline earth metal (Mg, Ca, Sr, Ba), or NH ₄ as A in formula (1) is as follows (i ) To (iii).
(I) The crystal structure of the crystallite in the near-infrared absorbing particle is a network-like three-dimensional skeleton composed of alternating bonds of PO ₄ ³⁻ and Cu ^2+, and has a space inside the skeleton. The size of the space is alkali metal ion (Li ⁺ : 0.090 nm, Na ⁺ : 0.116 nm, K ⁺ : 0.152 nm, Rb ⁺ : 0.166 nm, Cs ⁺ : 0.181 nm), alkaline earth metal In order to match the ionic radius of ions (Mg ²⁺ : 0.086 nm, Ca ²⁺ : 0.114 nm, Sr ²⁺ : 0.132 nm, Ba ²⁺ : 0.149 nm) and NH ₄ ⁺ (0.166 nm) Sufficiently maintain.
(Ii) Alkali metal ions, alkaline earth metal ions, and NH ₄ ⁺ can stably exist as monovalent or divalent cations in the solution, so that a precursor is generated in the process of producing near-infrared absorbing particles. At this time, cations are easily incorporated into the crystal structure.
(Iii) A cation having strong coordination bond with PO ₄ ^3- (for example, a transition metal ion or the like) may give a crystal structure different from the crystal structure in the present invention that exhibits sufficient near-infrared absorption characteristics. .

As A in the formula (1), K is particularly preferable because it has the most suitable cation size as an ion taken into the skeleton composed of PO ₄ ³⁻ and Cu ²⁺ and takes a thermodynamically stable structure.

The near-infrared absorbing particles preferably have a reflectance change amount D represented by the following formula (2) of −0.41% / nm or less, and more preferably −0.45% / nm or less. .
D (% / nm) = [R ₇₀₀ (%) − R ₆₀₀ (%)] / [700 (nm) −600 (nm)] (2)
In the formula, R ₇₀₀ is a reflectance at a wavelength of 700 nm in the diffuse reflection spectrum of the near-infrared absorbing particles, and R ₆₀₀ is a reflectance at a wavelength of 600 nm in the diffuse reflection spectrum of the near-infrared absorbing particles.

  In the diffuse reflection spectrum measurement in which the powder absorbs light, the intensity of light absorption varies depending on the optical path length at the light absorption wavelength, so that a weak absorption band in the transmission spectrum is observed relatively strongly. Therefore, the reflectance change rate calculation in this specification uses a reflectance value of 600 to 700 nm, which is a range in which the reflectance changes in the same manner as the transmittance change in the transmission spectrum.

  High reflectivity of near infrared absorbing particles means that light absorption by near infrared absorbing particles is low, and low reflectivity of near infrared absorbing particles means that light absorption by near infrared absorbing particles is high. ing. That is, the reflectance of the near infrared absorbing particles is a measure of the transmittance of the near infrared absorbing particles.

  Therefore, if the reflectance change amount D is −0.41% / nm or less, the transmittance change between wavelengths of 630 to 700 nm is sufficiently steep, and the near-infrared absorbing layer containing this has an imaging function. Suitable for apparatus lens.

  The near-infrared absorbing particles preferably have a reflectance at a wavelength of 715 nm in the diffuse reflection spectrum of 19% or less, and more preferably 18% or less. Further, the near-infrared absorbing particles preferably have a reflectance at a wavelength of 500 nm in the diffuse reflection spectrum of 85% or more, and more preferably 86% or more. In addition, a diffuse reflection spectrum is measured about the near-infrared absorption particle of a powder state using an ultraviolet visible spectrophotometer.

The near-infrared absorbing particles can exhibit sufficient near-infrared absorption characteristics when the crystallites sufficiently maintain the crystal structure of A _{1 / n} CuPO ₄ . Therefore, when water or a hydroxyl group adheres to the surface of the crystallite, the crystal structure of A _{1 / n} CuPO ₄ cannot be maintained, so that the difference in light transmittance between the visible light region and the near infrared wavelength region is reduced. A near-infrared absorbing layer containing this is not suitable for a lens for an imaging device.

Therefore, the near-infrared absorbing particles have a peak of about 1600 cm ⁻¹ attributed to water when the absorption intensity of the peak near 1000 cm ⁻¹ attributed to the phosphate group is used as a reference (100%) in the microscopic IR spectrum. It is preferable that the peak absorption intensity is 8% or less, and the peak absorption intensity near 3750 cm ⁻¹ attributed to a hydroxyl group is 26% or less, and the peak absorption intensity near 1600 cm ⁻¹ attributed to water. Is 5% or less, and the absorption intensity of the peak near 3750 cm ⁻¹ attributed to the hydroxyl group is more preferably 15% or less. The microscopic IR spectrum is measured with a Fourier transform infrared spectrophotometer for powdered near-infrared absorbing particles. Specifically, for example, using a Fourier transform infrared spectrophotometer Magna 760 manufactured by Thermo Fisher Scientific, a piece of near-infrared absorbing particles is placed on the diamond plate, flattened with a roller, and microscopic FT-IR method Measure with

Further, in the near-infrared absorbing particles, when the crystal structure other than A _{1 / n} CuPO ₄ , for example, A _{1 / n} Cu ₄ (PO ₄ ) ₃ increases, the change in transmittance between wavelengths of 630 to 700 nm is slow. It becomes. Therefore, it is preferable that it has been identified by X-ray diffraction that it is substantially composed of A _{1 / n} CuPO ₄ crystallites.

The near-infrared absorbing particles used in the present embodiment described above are composed of crystallites of a compound represented by A _{1 / n} CuPO ₄ and have a number average aggregated particle diameter of 5 to 200 nm. The transmittance of light is high, the transmittance of light in the near infrared wavelength region is low, and the transmittance sharply changes between wavelengths of 630 to 700 nm.

The near-infrared absorbing particles can be produced, for example, by a method having the following steps (a) to (c).
(A) a salt containing ^{Cu 2+,} a salt or an organic material containing _PO ^{4 3-,} proportions as _PO ^{4 3-} molar ratio with respect to _{^{Cu 2+ (PO 4 3- / Cu}} 2+) is 10 to 20 And (b) a step of mixing in the presence of ^{An +} (b) a step of baking the product obtained in step (a) at 560 to 760 ° C. (c) several baking products obtained in step (b) Step of crushing so that the average aggregated particle diameter is 5 to 200 nm

[Step (a)]
^Examples of salts containing Cu ²⁺ include copper (II) sulfate pentahydrate, copper (II) chloride dihydrate, copper (II) acetate monohydrate, copper (II) bromide, and copper (II) nitrate. And trihydrate.

Examples of the salt or organic substance containing PO ₄ ^3- include alkali metal phosphates, ammonium phosphates, alkaline earth metal phosphates, phosphoric acid, and the like.

  Examples of alkali metal phosphate or alkaline earth metal phosphate include dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, disodium hydrogen phosphate dodecahydrate, sodium dihydrogen phosphate Examples thereof include dihydrate, trisodium phosphate dodecahydrate, lithium phosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate trihydrate, and magnesium phosphate octahydrate. Examples of the ammonium salt of phosphoric acid include diammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium ammonium hydrogen phosphate tetrahydrate, and ammonium phosphate trihydrate.

As a method for allowing ^{An +} to exist, a method using an alkali metal phosphate, an ammonium phosphate, an alkaline earth metal phosphate, or the like as a salt containing PO ₄ ^3- ; a salt containing Cu ²⁺ and PO _{4 When} a salt containing ^3- or an organic substance is mixed, a method of adding a salt containing ^{An +} is exemplified.

Salts containing ^{An +} include alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal chlorides, alkaline earth metal chlorides, alkali metal bromides, alkaline earth metal bromides, Examples thereof include alkali metal nitrates, alkaline earth metal nitrates, alkali metal carbonates, alkaline earth metal carbonates, alkali metal sulfates, alkaline earth metal sulfates, and the like.

Mixing a salt containing Cu ²⁺ with a salt containing PO ₄ ³⁻ or an organic substance is carried out in a solvent capable of dissolving a salt containing Cu ²⁺ , a salt containing PO ₄ ^3−, and a salt containing ^{An +} as required. Preferably it is done. As the solvent, water is preferable.

Ratio of the salt or organic containing salt and _PO ^{4 3-} and containing Cu ²⁺ is, _PO ^{4 3-} molar ratio with respect to ^{_{Cu 2+ (PO 4 3- / Cu}} 2+) 10-20, preferably 12-18 and The ratio is as follows. If PO ₄ ³⁻ / Cu ²⁺ is 10 or more, even if A _{1 / n} Cu ₄ (PO ₄ ) ₃ is not by-produced or by-produced, the amount of the crystallite is A _{1 / n} CuPO ₄ . Since the crystal structure is sufficiently maintained, near-infrared absorbing particles in which the change in transmittance between wavelengths of 630 to 700 nm is sufficiently steep can be obtained. If PO ₄ ³⁻ / Cu ²⁺ is 20 or less, impurities other than A _{1 / n} CuPO ₄ are not by-produced, or even if they are by-produced, the amount of the crystal structure is A _{1 / n} CuPO ₄ . Therefore, near-infrared absorbing particles in which the change in transmittance between wavelengths of 630 to 700 nm is sufficiently steep can be obtained.

Temperature at the time of mixing the salt or organic containing salt and _PO ^{4 3-} and containing Cu ²⁺ is preferably 10 to 95 ° C., and more preferably from 15 to 40 ° C.. If the temperature is too high, the solute is concentrated by evaporation of the solvent, and impurities other than the target product may be mixed. If the temperature is too low, the reaction rate becomes slow and the reaction time becomes long, which is not preferable in terms of the process.

  The product is separated by filtration or the like, and then washed, dried, and dry pulverized as necessary. In the firing in the step (b), it is preferable to remove the moisture contained in the product by washing the product with an organic solvent from the viewpoint of suppressing the adhesion of the particles via water and suppressing the growth of the particles.

[Step (b)]
The firing temperature is preferably 560 to 760 ° C, more preferably 580 to 750 ° C. If the firing temperature is 560 ° C. or higher, the crystal structure changes due to the structural phase transition, and the crystal structure after the structural phase transition is maintained even after cooling to room temperature. If the firing temperature is 760 ° C. or lower, thermal decomposition can be suppressed. If the firing temperature is too low, the crystal structure is different from the case of firing in the above temperature range, and sufficient spectral characteristics may not be obtained.

  In firing, it is preferable to flow the product to be fired (the product obtained in the step (a)) from the viewpoint of suppressing particle growth. A rotary kiln furnace etc. are mentioned as an apparatus which can be baked, making a to-be-baked material flow.

[Step (c)]
Examples of the pulverization method include a known dry pulverization method or wet pulverization method, and the wet pulverization method is preferable from the viewpoint that the number average aggregated particle diameter is easily set to 200 nm or less. Examples of the dry pulverization method include a method using a ball mill, a jet mill, a mill pulverizer, a mixer pulverizer, and the like. Examples of the wet pulverization method include a method using a wet mill (ball mill, planetary mill, etc.), a crusher, a mortar, an impact pulverizer (nanomizer, etc.), a wet micronizer, etc., and a method using a wet micronizer is preferable. .

In the case of the wet pulverization method, it is necessary to disperse the fired product obtained in step (b) in a dispersion medium to obtain a dispersion for crushing. Examples of the dispersion medium include water, alcohol, ketone, ether, ester, aldehyde and the like. A dispersion medium may be used individually by 1 type, and may use 2 or more types together. As the dispersion medium, water or alcohol is preferable from the viewpoint of the working environment, and water is particularly preferable when a high pressure is applied to the dispersion liquid for crushing. The amount of the dispersion medium is preferably 50 to 95% by mass in the disintegrating dispersion (100% by mass) from the viewpoint of maintaining the dispersibility of the fired product. Among them, distilled water is preferable, and water having an electric conductivity of 1.0 × 10 ⁻⁴ S / m or less is particularly preferable. Moreover, as alcohol, especially ethanol and isopropyl alcohol are preferable.

  The pulverized product is separated from the dispersion liquid by centrifugation or the like, if necessary, and then washed, dried, and dry pulverized. Examples of the drying method include a heat drying method, a spray drying method, a freeze drying method, and a vacuum drying method.

  The near-infrared absorbing particles obtained as described above are subjected to surface treatment by a known method for the purpose of improving the weather resistance, acid resistance, water resistance, etc. and improving the compatibility with the binder resin by surface modification. Also good.

  As a surface treatment method, a surface treatment agent or a surface treatment agent diluted with a solvent is added to a dispersion containing near-infrared absorbing particles, the mixture is stirred and treated, and then the solvent is removed and dried (wet method). ); A method (dry method) in which a surface treatment agent diluted with a surface treatment agent or a solvent is jetted with dry air or nitrogen gas and then dried while stirring the near infrared absorbing particles (dry method). Examples of the surface treatment agent include a surfactant and a coupling agent.

  The content of the near-infrared absorbing particles in the near-infrared absorbing layer 12 is preferably 20 to 60% by mass, and more preferably 20 to 50% by mass. When the content of the near-infrared absorbing particles is 20% by mass or more, sufficient near-infrared absorbing characteristics for the near-infrared absorbing layer 12 can be obtained. Moreover, if the content of near-infrared absorbing particles is 60% by mass or less, the light transmittance in the visible wavelength region can be maintained high.

  The near infrared absorbing layer 12 can contain a near infrared ray or an infrared absorbing material other than the near infrared absorbing particles. In this case, the near-infrared absorbing layer 12 may have a multilayer structure including a layer containing near-infrared absorbing particles and / or a near-infrared absorbing material other than the near-infrared absorbing particles.

As the near infrared ray or infrared ray absorbing material other than the near infrared ray absorbing particles, a near infrared ray absorbing material having no crystallites of oxide containing at least Cu and / or P, for example, ITO (In ₂ O ₃ -TiO ₂ system), Examples thereof include inorganic fine particles such as ATO (ZnO—TiO ₂ system) and lanthanum boride, and organic dyes. In particular, ITO particles have a high light transmittance in the visible wavelength region and have a wide range of light absorption properties including an infrared wavelength region exceeding 1200 nm, and therefore need to shield light in the infrared wavelength region. This is particularly preferable. It is preferable to contain 0.5-30 mass% of ITO particles in the near-infrared absorption layer 12, and it is more preferable to contain 1-30 mass%. When the content of the ITO particles is 0.5% by mass or more, a certain effect is obtained with respect to the light shielding property in the infrared wavelength region. Moreover, if content of ITO particle | grains is 30 mass% or less, it does not show absorption to the light of visible wavelength region, but can maintain transparency.

  The number average aggregate particle diameter of the ITO particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, and more preferably 5 to 60 nm from the viewpoint of suppressing scattering and maintaining transparency. Even more preferred. Examples of organic dyes include cyanine compounds, phthalocyanine compounds, naphthalocyanine compounds, dithiol metal complex compounds, diimonium compounds, polymethine compounds, phthalide compounds, naphthoquinone compounds, anthraquinone compounds, indophenols. Series compounds and the like can be used.

  The near-infrared absorbing layer 12 can also contain other light absorbing materials such as ultraviolet absorbing materials. Examples of the ultraviolet absorber include particles of zinc oxide, titanium oxide, cerium oxide, zirconium oxide, mica, kaolin, sericite, and the like. The number average aggregate particle diameter of the other light absorbing material is preferably 5 to 200 nm, more preferably 5 to 100 nm, and even more preferably 5 to 60 nm from the viewpoint of transparency.

  The near-infrared absorbing layer 12 can further contain a transparent resin. By including the transparent resin, the near-infrared absorbing layer 12 can be easily formed, and the durability of the near-infrared absorbing layer 12 and thus the imaging device lenses 10A to 10C can be enhanced.

  Transparent resins include polyester resins, acrylic resins, polyolefin resins, polycarbonate resins, polyamide resins, alkyd resins, and other thermoplastic resins, epoxy resins, thermosetting acrylic resins, and thermosetting resins such as silsesquioxane resins. Is mentioned. Of these, acrylic resins or polyester resins are preferred from the viewpoint of transparency. The content of the transparent resin in the near-infrared absorbing layer 12 is preferably 40 to 80% by mass, and more preferably 50 to 80% by mass. If the content of the transparent resin is 40% by mass or more, the effect of use is sufficiently obtained, and if it is 80% by mass or less, sufficient near infrared absorption characteristics can be maintained.

  In addition to the above components, the near-infrared absorbing layer 12 further includes a color tone correction dye, a leveling agent, an antistatic agent, a heat stabilizer, an antioxidant, a dispersant, a flame retardant, as long as the effects of the present invention are not impaired. Further, a lubricant, a plasticizer and the like may be contained.

  The near-infrared absorbing layer 12 is prepared by, for example, preparing a coating liquid by dispersing or dissolving the above-described near-infrared absorbing particles and other components blended as necessary in a dispersion medium. It can be formed by coating on the main body 11 and drying. The coating and drying can be performed in a plurality of times. In this case, a plurality of coating liquids having different components may be prepared, and these may be sequentially coated and dried. Specifically, for example, a coating liquid containing near-infrared absorbing particles and a coating liquid containing ITO particles are individually prepared, and these are sequentially coated on the lens body 11 and dried. The absorption layer 12 can be formed.

  Examples of the dispersion medium include water, alcohol, ketone, ether, ester, aldehyde, amine, aliphatic hydrocarbon, alicyclic hydrocarbon, and aromatic hydrocarbon. A dispersion medium may be used individually by 1 type, and 2 or more types may be mixed and used for it. The dispersion medium is preferably water or alcohol from the viewpoint of the working environment. The amount of the dispersion medium is preferably 50 to 95% by mass in the dispersion (100% by mass) from the viewpoint of maintaining the dispersibility of the near-infrared absorbing particles.

  A dispersing agent can be mix | blended with a coating liquid as needed. Examples of the dispersant include those having a modification effect on the surface of the near-infrared absorbing particles, such as surfactants, silane compounds, silicone resins, titanate coupling agents, aluminum coupling agents, zircoaluminate cups. A ring agent or the like is used.

  Surfactants include anionic surfactants (special polycarboxylic acid type polymer surfactants, alkyl phosphate esters, etc.), nonionic surfactants (polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxy Ethylene carboxylic acid esters, sorbitan higher carboxylic acid esters, etc.), cationic surfactants (polyoxyethylene alkylamine carboxylic acid esters, alkylamines, alkylammonium salts, etc.), and amphoteric surfactants (higher alkylbetaines, etc.). .

  Examples of the silane compound include a silane coupling agent, chlorosilane, alkoxysilane, and silazane. Examples of the silane coupling agent include alkoxysilanes having a functional group (glycidoxy group, vinyl group, amino group, alkenyl group, epoxy group, mercapto group, chloro group, ammonium group, acryloxy group, methacryloxy group, etc.).

  Examples of the silicone resin include methyl silicone resin and methylphenyl silicone resin.

  Examples of titanate coupling agents include those having an acyloxy group, phosphoxy group, pyrophosphoxy group, sulfoxy group, aryloxy group, and the like.

  Examples of the aluminum coupling agent include acetoalkoxyaluminum diisopropylate.

  Examples of the zircoaluminate coupling agent include those having an amino group, a mercapto group, an alkyl group, an alkenyl group, and the like.

  Although the quantity of a dispersing agent is based also on the kind of dispersing agent, 0.5-10 mass% is preferable among dispersion liquids (100 mass%). If the amount of the dispersant is within the above range, the dispersibility of the near-infrared absorbing particles becomes good, the transparency is not impaired, and the sedimentation of the near-infrared absorbing particles over time can be suppressed.

  In addition, a stirrer such as a rotation / revolution mixer, a bead mill, a planetary mill, or an ultrasonic homogenizer can be used for preparing the coating liquid. In order to ensure high transparency, it is preferable to sufficiently stir. Stirring may be performed continuously or intermittently.

  For coating the coating liquid, a coating method such as a dip coating method, a spray coating method, a spin coating method, a bead coating method, a gravure coater method, a micro gravure method, or the like can be used. In addition, a screen printing method, a flexographic printing method, etc. can also be used.

  The thickness of the near-infrared absorbing layer 12 is preferably in the range of 1 to 200 μm, more preferably in the range of 4 to 100 μm, and still more preferably in the range of 20 to 50 μm. By setting it as 1 micrometer or more, near-infrared absorptivity can fully be expressed, and the residual of the dispersion medium at the time of layer formation can be suppressed by setting it as 200 micrometers or less. Further, when the thickness is 4 μm or more, it becomes easier to obtain the flatness of the film thickness, and it is possible to make it difficult for the variation in the absorption rate to occur. When the thickness is 100 μm or less, the flatness of the film thickness is further easily obtained. It is advantageous for thinning.

The near-infrared absorbing layer 12 has a transmittance change amount D ′ represented by the following formula (3) of preferably −0.36% / nm or less, and more preferably −0.45% / nm or less.
D ′ (% / nm) = [T ₇₀₀ (%) − T ₆₃₀ (%)] / [700 (nm) −630 (nm)] (3).
In the formula, T ₇₀₀ is a transmittance at a wavelength of 700 nm in the transmission spectrum of the near-infrared absorbing layer, and T ₆₃₀ is a transmittance at a wavelength of 630 nm in the transmission spectrum of the near-infrared absorbing layer.

  When the transmittance change amount D ′ is −0.36% / nm or less, the transmittance change between wavelengths of 630 to 700 nm is sufficiently steep, which is suitable for a lens for an imaging device. If it is −0.45% / nm or less, the utilization efficiency of light in the visible wavelength region is further improved while blocking light in the near infrared wavelength region, which is advantageous in terms of noise suppression in dark area imaging.

  Further, the transmittance of the near-infrared absorbing layer 12 at a wavelength of 715 nm is preferably 10% or less, and more preferably 5% or less. Further, the transmittance of the near-infrared absorbing layer 12 at a wavelength of 500 nm is preferably 80% or more, and more preferably 85% or more. In addition, the transmittance | permeability of a near-infrared absorption layer is measured using an ultraviolet visible spectrophotometer.

  The antireflection film 13 is made of a metal oxide such as zirconium oxide, cesium oxide, tantalum oxide, alumina, magnesium oxide, yttrium oxide, tin oxide or tungsten oxide, a metal fluoride such as magnesium fluoride, or a transparent material such as fluororesin. In order to form a reflection suppression effect by using light interference, for example, a vacuum film forming process such as a CVD method, a sputtering method, a vacuum evaporation method, a spray method, a dip method, etc. A wet film forming process such as a method can be used.

  The imaging device lenses 10 </ b> A to 10 </ b> C of the present embodiment include the near-infrared absorbing layer 12 on at least one surface of the lens body 11, so that the near-infrared cut filter that has been conventionally arranged separately may be omitted. Thus, the imaging apparatus can be reduced in size, thickness, and cost.

Moreover, the near-infrared absorbing layer 12 is made of a crystallite of a compound represented by A _{1 / n} CuPO ₄ and has a number average aggregate particle diameter of 5 to 200 nm. Since near-infrared absorbing particles having a low light transmittance in the infrared wavelength region and a sharp change in transmittance between wavelengths of 630 to 700 nm are contained, it is possible to have good near-infrared shielding characteristics.

  Moreover, since the near-infrared absorption layer 12 can be formed by coating and drying a coating liquid prepared by dispersing near-infrared absorbing particles in a dispersion medium on one main surface of the lens body 11, it is easy. And can be manufactured at low cost.

(Second Embodiment)
FIG. 6 is a cross-sectional view showing the imaging apparatus lens according to the present embodiment. The imaging device lens of the present embodiment is also a small camera incorporated in information equipment such as a digital still camera, a digital video camera, a mobile phone, a notebook personal computer, and a PDA, like the imaging device lens of the first embodiment. The lens which comprises all or one part of the lens system imaged on a solid-state image sensor of imaging devices, such as. In the present embodiment, in order to avoid overlapping description, description of points that are common to the first embodiment will be omitted, and differences will be mainly described.

  As shown in FIG. 6, this imaging device lens 50A is a so-called plano-convex lens in which one surface 51a is a flat surface and the other surface 51b is a convex surface. It is composed of particles and other components blended as necessary.

  The lens shape is not particularly limited. For example, it may be a plano-convex lens having a flat plate portion 52 on the outer periphery, such as an imaging device lens 50B shown in FIG. 7, and also shown in FIG. Like the imaging device lens 50 </ b> C, one surface 51 a may be a concave surface, the other surface 51 b may be a convex surface, and a concavo-convex lens having a flat plate portion 52 on the outer periphery. Furthermore, although illustration is omitted, an antireflection film may be provided on one surface 51a (or 51b) or both surfaces 51a (or 51b) of these imaging device lenses 50A to 50C. The shape of the lens, the presence / absence of an antireflection film, and the like are appropriately determined in consideration of the application, the type of lens used in combination, the arrangement location, and the like.

  The imaging device lenses 50 </ b> A to 50 </ b> C of the present embodiment include a fixed mold and a movable mold movable with respect to the fixed mold, and an injection mold having a lens-shaped cavity to be formed therebetween. For example, the mold can be used as follows.

  First, the above-described near-infrared absorbing particles and other components blended as necessary are mixed. The molding die is provided with a gate portion for supplying such a mixture to the cavity, and the mixture is supplied from the gate portion to the cavity to be cooled and solidified. Thereafter, the movable mold is moved, the molded product is peeled off from the fixed mold, and taken out to the outside.

  The imaging device lenses 50 </ b> A to 50 </ b> C can be molded not only by such injection molding but also by transfer molding, cast molding, or the like. Further, as a molding die, a multi-cavity die can be used. In this case, after molding, an antireflection film 13 is formed as necessary, and then cut into individual lenses by a dicing apparatus. As a result, individual imaging device lenses 50A to 50C as shown in FIGS. 6 to 8 are obtained.

The transmittance change amount D ′ represented by the following expression (3) of the imaging device lenses 50 </ b> A to 50 </ b> C of the present embodiment is preferably −0.36% / nm or less, and more preferably −0.45% / nm or less. preferable.
D ′ (% / nm) = [T ₇₀₀ (%) − T ₆₃₀ (%)] / [700 (nm) −630 (nm)] (3).
In the equation, T ₇₀₀ is a transmittance at a wavelength of 700 nm in the transmission spectrum of the lens for the imaging device, and T ₆₃₀ is a transmittance at a wavelength of 630 nm in the transmission spectrum of the lens for the imaging device.

  When the transmittance change amount D ′ is −0.36% / nm or less, the transmittance change between wavelengths of 630 to 700 nm is sufficiently steep, which is suitable for a lens for an imaging device. If it is −0.45% / nm or less, the utilization efficiency of light in the visible wavelength region is further improved while blocking light in the near infrared wavelength region, which is advantageous in terms of noise suppression in dark area imaging.

  Further, the transmittance of the imaging device lenses 50A to 50C at a wavelength of 715 nm is preferably 10% or less, and more preferably 5% or less. Further, the transmittance of the imaging device lenses 50A to 50C at a wavelength of 500 nm is preferably 80% or more, and more preferably 85% or more. The transmittance of the imaging device lens is measured using an ultraviolet-visible spectrophotometer.

  Also in the second embodiment, the same effect as in the first embodiment can be obtained. Further, in the present embodiment, since the near infrared absorbing particles are included in the lens itself, the imaging device can be further reduced in size and thickness as compared with the first embodiment. Moreover, since the lens shaping | molding process and the near-infrared absorption layer 12 formation process in 1st Embodiment can be performed by one process, further cost reduction and productivity improvement can be aimed at.

  In addition, since the lens thickness difference is caused by the optical path of the transmitted light, the transmission spectral characteristics may vary. In such a case, for example, a meniscus lens with a small thickness difference between the lenses is used, and the density and the near-infrared absorbing particle density is changed depending on the lens location to cancel the thickness difference. It is preferable to take a countermeasure such as canceling the wall thickness difference by combining a plurality of near-infrared absorbing lenses having different densities of infrared absorbing particles, and variation in transmission spectral characteristics due to the lens wall thickness difference can be reduced.

(Third embodiment)
FIG. 9 is a cross-sectional view schematically showing a main configuration of the imaging apparatus according to the present embodiment. As shown in FIG. 9, the imaging device 80A of the present embodiment includes a substrate 81, a solid-state imaging device 82 mounted on the substrate 81, a cover glass 83, and an imaging device lens of the present invention (in the example of the drawings). , The imaging apparatus lens 10 </ b> A) shown in FIG. 1 and an aperture stop 84. The solid-state image sensor 82, the imaging device lens 10A, and the aperture stop 84 are disposed along the optical axis x.

  The solid-state imaging element 82 is an electronic component that converts light that has passed through the imaging device lens 10A into an electrical signal, and specifically, a CCD, CMOS, or the like is used. The cover glass 83 is disposed on the surface of the solid-state image sensor 82 on the imaging device lens 10A side, and has a function of protecting the solid-state image sensor 82 from the external environment. In the imaging apparatus lens 10A, the plane side on which the near-infrared absorbing layer 12 is provided faces the aperture stop 84 side, that is, the light incident side, and the convex side on which the antireflection film 13 is provided faces the solid-state imaging element 82 side. Has been placed. On the other hand, the convex side provided with the antireflection film 13 is directed to the aperture stop 84 side, that is, the light incident side, and the plane side provided with the near infrared absorption layer 12 is directed to the solid-state image sensor 82 side. May be arranged.

  In the imaging device 80A configured as described above, light incident from the aperture of the aperture stop 84 is received by the solid-state imaging device 82 through the imaging device lens 10A, and the received light is electrically converted by the solid-state imaging device 82. It is converted into a signal and output as an image signal. The imaging device lens 10 </ b> A is provided with a near-infrared absorbing layer 12, and light from which the near-infrared light is blocked is received by the solid-state imaging device 82.

  As described above, the imaging apparatus lens 10A has both a lens function and a function of blocking near infrared rays. Therefore, the imaging apparatus 80A can omit a conventionally required near infrared cut filter. The device can be reduced in size and thickness.

Moreover, the near-infrared absorbing layer 12 is made of a crystallite of a compound represented by A _{1 / n} CuPO ₄ and has a number average aggregate particle diameter of 5 to 200 nm. Since it contains near-infrared absorbing particles having a low light transmittance in the infrared wavelength region and a sharp change in transmittance between wavelengths of 630 to 700 nm, the central portion of the image such as a near-infrared blocking dielectric multilayer film Thus, there is no problem that color characteristics change in the peripheral portion or a multiple image called a ghost is likely to occur, and a high quality photographed image can be obtained.

  Furthermore, the imaging device lens including the near-infrared absorbing layer 12 can be easily and inexpensively manufactured, so that the cost can be reduced.

  Note that the lens system of the imaging device 80A illustrated in FIG. 9 includes only one lens, but a plurality of lenses may be incorporated. In this case, at least one lens may be an imaging device lens according to the present invention, and the other lenses may be conventional lenses. Further, the arrangement position of the lens for an imaging device of the present invention is not particularly limited.

  FIG. 10 shows an example of an imaging device 80B in which the lens system includes a plurality of lenses. The imaging device 80B includes a substrate 81, a solid-state imaging device 82 mounted on the substrate 81, a cover glass 83, a plurality of lens groups 85, and an aperture stop 84. In the example of FIG. 10, the plurality of lens groups 85 includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens from the aperture stop 84 side toward the imaging surface of the solid-state imaging device 82. The lens L4 is arranged in order, and the imaging device lens 10C shown in FIG. 3 is used for the fourth lens L4 arranged closest to the solid-state imaging element 82.

  Also in the imaging device 80B configured as described above, the imaging device lens 10C has both a lens function and a function of blocking near infrared rays, and thus the imaging device 80A omits the conventionally required near infrared cut filter. Accordingly, the image pickup apparatus can be reduced in size and thickness.

Moreover, the near-infrared absorbing layer 12 is made of a crystallite of a compound represented by A _{1 / n} CuPO ₄ and has a number average aggregate particle diameter of 5 to 200 nm. Since it contains near-infrared absorbing particles having a low light transmittance in the infrared wavelength region and a sharp change in transmittance between wavelengths of 630 to 700 nm, the central portion of the image such as a near-infrared blocking dielectric multilayer film Thus, there is no problem that color characteristics change in the peripheral portion or a multiple image called a ghost is likely to occur, and a high quality photographed image can be obtained.

  Furthermore, the imaging device lens including the near-infrared absorbing layer 12 can be easily and inexpensively manufactured, so that the cost can be reduced.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all. In addition, the various physical-property values in an Example and a comparative example were measured by the method shown below.

[X-ray diffraction]
About the near-infrared absorption particle | grains of a powder state, the X-ray-diffraction measurement was performed using the X-ray-diffraction apparatus (the RIGAKU company make, RINT-TTR-III), and the crystal structure was identified. Further, the size of the crystallite was obtained by calculation according to Scherrer's method for reflection at 2θ = 14 °.

[Number average agglomerated particle size]
About a dispersion for particle size measurement (solid content concentration: 5% by mass) in which near-infrared absorbing particles are dispersed in water, a dynamic light scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac Ultrafine Particle Size Analyzer UPA-) 150) was used to measure the number average aggregate particle size.

[Change D in reflectance]
About the near-infrared absorption particle | grains of a powder state, the diffuse reflection spectrum (reflectance) was measured and calculated using the ultraviolet visible spectrophotometer (the Hitachi High-Technologies company make, U-4100 type). Note that barium sulfate was used as a baseline.

[Transmittance and transmittance change D ′]
The near-infrared absorption layer was measured by calculating a transmission spectrum (transmittance) using an ultraviolet-visible spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corporation).

[Production of near-infrared absorbing particles]
(Production Example 1)
To 500 g of an aqueous solution of 52% by mass dipotassium hydrogen phosphate (manufactured by Junsei Kagaku), 500 g of an aqueous solution of 5% by mass copper sulfate pentahydrate (manufactured by Junsei Kagaku) is added and stirred at room temperature for 5 hours or more A solution (PO ₄ ³⁻ / Cu ²⁺ (molar ratio) = 15) was obtained.

  The product was separated from the resulting light blue solution by suction filtration and washed with water and acetone to give a light blue product. The product was transferred to a crucible and vacuum-dried at 100 ° C. for 4 hours, and then dry pulverization for 30 seconds was performed twice using a wonder blender (manufactured by Osaka Chemical Co., Ltd., hereinafter the same).

  The powdered product was transferred to a crucible and fired at 600 ° C. for 8 hours in the air to obtain a yellow-green fired product. The fired product was subjected to dry grinding for 30 seconds twice using a wonder blender. The obtained yellowish green fired product was 15.4 g, and the yield based on the number of moles of copper sulfate pentahydrate was 78%.

X-ray diffraction was measured for the fired product. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ could be confirmed, and the fired product was identified as particles substantially consisting of crystallites of KCuPO ₄ .

  The fired product was dispersed in water to obtain a dispersion having a solid content of 10% by mass, treated with an ultrasonic homogenizer, and then wet pulverized using a wet micronizer (Starburst Mini, manufactured by Sugino Machine Co., Ltd.). . The number of times the dispersion passes through the orifice diameter is defined as the number of wet pulverization treatments. In this example, the number of wet pulverization treatments was 20.

  The crushed material was centrifuged from the dispersion after wet pulverization, transferred to a crucible, and dried at 150 ° C. to obtain a yellow-green crushed material. About the crushed material, 30 seconds of dry-type grinding | pulverization was performed twice using the wonder blender.

X-ray diffraction of the crushed material was measured. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ could be confirmed, and the crushed material was identified to be near-infrared absorbing particles substantially consisting of KCuPO ₄ crystallites. The crystallite size was 27 nm. In addition, a dispersion for measuring the particle size of near-infrared absorbing particles was prepared, and the number average aggregated particle size was measured and found to be 89 nm. Furthermore, the diffuse reflection spectrum (reflectance) of the near-infrared absorbing particles was measured, and the change D in reflectivity was determined to be -0.46% / nm.

[Manufacture of lenses for imaging devices]
Example 1
The near-infrared absorbing particles obtained in Production Example 1 and a methacrylic resin (manufactured by ADELL, trade name HV153; refractive index 1.63) have a solid content of 37% by mass of near-infrared absorbing particles and 63% by mass of methacrylic resin. After mixing at such a ratio, zirconia beads having a diameter of 0.5 mm were added to this mixed solution and pulverized using a ball mill to obtain a dispersion. The obtained dispersion was applied to one surface (flat surface) of a glass plano-convex lens using a spin coater (Spin Coater MS-A200, manufactured by Mikasa), heated at 120 ° C. for 1 minute, and a near-infrared absorbing layer having a thickness of 100 μm. (Absorbed layer (I)) is formed. Separately from this, a film similar to the absorption layer (I) was formed on a glass plate (soda glass) having a thickness of 1.3 mm in the same manner, and the transmittance was measured. The results are shown in Table 1 and FIG. 11 (transmission spectrum).

(Example 2)
ITO particles (manufactured by Fuji Titanium Co., Ltd., crystallite size 38 nm) were mixed with ethanol together with a dispersant to obtain a dispersion having a solid content of 20% by weight.

  This ITO particle-containing dispersion was applied to one surface (flat surface) of a glass plano-convex lens using a spin coater (spin coater MS-A200), dried by heating at 150 ° C. for 15 minutes, and a near-infrared absorbing layer having a thickness of 4 μm ( Absorbing layer (II)). Separately from this, a film similar to the absorption layer (II) was formed on a 3.5 mm thick glass plate (Float plate glass manufactured by Asahi Glass Co., Ltd., clear FL 3.5), and the transmittance was measured. . The results are shown in Table 1 and FIG. 12 (transmission spectrum).

  The near-infrared absorbing particles obtained in Production Example 1 and a 30% by mass cyclohexanone solution of a polyester resin (trade name Byron 103, manufactured by Toyobo Co., Ltd .; refractive index: 1.60 to 1.61) have a solid content of near-infrared. The mixture was mixed in such a ratio as to be 44% by mass of absorbent particles and 56% by mass of the polyester resin, and stirred with a rotation / revolution mixer to obtain a dispersion. The obtained dispersion was applied onto the absorption layer (II) using a spin coater (Spin Coater MS-A200 manufactured by Mikasa Co., Ltd.), heated at 150 ° C. for 15 minutes, and a near infrared absorption layer (absorption layer (absorption layer ( III). Separately, the same as the absorbing layer (III) on the above-mentioned film formed in the same manner as the absorbing layer (II) on a 3.5 mm thick glass plate (Float plate glass manufactured by Asahi Glass Co., Ltd., clear FL 3.5) This film was formed in the same manner, and the transmittance was measured. The results are shown in Table 1 and FIG. 13 (transmission spectrum).

(Example 3)
The near-infrared absorbing particles obtained in Production Example 1, the ITO particles used in Example 2 (manufactured by Fuji Titanium Co., Ltd.), and a 30% by mass cyclohexanone solution of a polyester resin (trade name: Byron 103) have a solid content of near-infrared. The mixture was mixed in such a ratio that 50% by mass of absorbing particles, 3% by mass of ITO particles and 46% by mass of polyester resin were mixed, and stirred with a rotation / revolution mixer to obtain a dispersion. The obtained dispersion was applied to one surface (flat surface) of a glass plano-convex lens using a spin coater (Spin Coater MS-A200, manufactured by Mikasa), heated at 150 ° C. for 15 minutes, and a near-infrared absorbing layer having a thickness of 50 μm. (Absorbed layer (IV)) is formed. Separately from this, a film similar to the absorption layer (IV) was formed on a slide glass having a thickness of 1.3 mm (manufactured by Muto Chemical Co., Ltd., material: soda glass) by the same method, and the transmittance was measured. The results are shown in Table 1 and FIG. 14 (transmission spectrum).

Example 4
Near-infrared absorbing particles (number average agglomerated particle diameter 65 nm) obtained by sizing from the near-infrared absorbing particles obtained in Production Example 1 and epoxy resin (trade name EX1011 manufactured by Nagase Sangyo Co., Ltd .; refractive index 1.62) Were mixed in such a ratio that the solid content was 37% by mass of the near-infrared absorbing particles and 73% by mass of the epoxy resin. To this mixed solution, zirconia beads having a diameter of 0.5 mm were added and pulverized using a ball mill to obtain a dispersion. The obtained dispersion was applied to one surface (flat surface) of a glass plano-convex lens using a spin coater (spin coater MS-A200), heated at 100 ° C. for 1 hour, and further heated at 180 ° C. for 4 hours to obtain a thickness. A near-infrared absorption layer (denoted as absorption layer (V)) of 100 μm is formed. Separately, a film similar to the absorbing layer (V) was formed on a glass plate (soda glass) having a thickness of 1.3 mm in the same manner, and the transmittance was measured. The results are shown in Table 1.

  The lens for an image pickup apparatus of the present invention has a good infrared shielding function, and can sufficiently reduce the size, thickness, and cost of the image pickup apparatus. Therefore, a digital still camera, a digital video camera, and a mobile phone It can be suitably used for an imaging apparatus using a solid-state imaging device, such as a small camera incorporated in an information device such as a notebook personal computer or PDA.

  10A, 10B, 10C, 50A, 50B, 50C ... Lens for imaging device, 11 ... Lens body, 12 ... Near-infrared absorbing layer, 80A, 80B ... Imaging device, 82 ... Solid-state imaging device, L1-L4 ... First to second 4 lenses.

Claims (19)

A lens used in an imaging device including a solid-state imaging device,
Imaging comprising an oxide crystallite containing at least Cu and / or P and containing near-infrared absorbing particles having a number average aggregated particle diameter of 5 to 200 nm , or comprising a layer containing the near-infrared absorbing particles Lens for device. The imaging device lens according to claim 1, wherein the layer containing the near-infrared absorbing particles is a layer formed on at least one surface of the lens body. The imaging device lens according to claim 1 or 2 , wherein a content of the near-infrared absorbing particles in a layer containing the near-infrared absorbing particles is 20 to 60% by mass. The imaging device according to any one of claims 1 to 3 , wherein the layer containing the near-infrared absorbing particles further contains a near-infrared absorbing material having no crystallites of an oxide containing at least Cu and / or P. Lens. The content of the at least Cu and / or near-infrared-absorbing material with no crystallites oxide containing P in the layer containing the near infrared absorbing particles of claim 4 wherein 0.5 to 30 wt% Lens for imaging device. The lens for an imaging device according to claim 4 or 5 , comprising ITO particles as the near-infrared absorbing material having no crystallites of an oxide containing at least Cu and / or P. Layer containing the near infrared absorbing particles, the change amount D of transmittance 'represented by the following formula, is not more than -0.36% / nm, an imaging according to any one of claims 1 to 6 Lens for device.
D ′ (% / nm) = [T ₇₀₀ (%) − T ₆₃₀ (%)] / [700 (nm) −630 (nm) ]
(Where T ₇₀₀ is the transmittance at a wavelength of 700 nm in the transmission spectrum of the layer containing near-infrared absorbing particles, and T ₆₃₀ is the transmittance at a wavelength of 630 nm in the transmission spectrum of the layer containing near-infrared absorbing particles. is there.) The imaging device lens according to claim 1, wherein the imaging device lens is a lens containing the near-infrared absorbing particles. The lens for an imaging device according to claim 8, wherein the content of the near-infrared absorbing particles is 20 to 60% by mass. The lens for an imaging device according to claim 8 or 9, further comprising a near-infrared absorbing material free from oxide crystallites containing at least Cu and / or P. The imaging device lens according to claim 10, wherein a content of the near-infrared absorbing material having no crystallites of oxide containing at least Cu and / or P is 0.5 to 30% by mass.   The lens for an imaging device according to claim 10 or 11, comprising ITO particles as a near-infrared absorbing material having no crystallites of an oxide containing at least Cu and / or P. The lens for an imaging device according to claim 8, wherein a transmittance change amount D ′ represented by the following formula is −0.36% / nm or less.
  D ′ (% / nm) = [T ₇₀₀ (%)-T ₆₃₀ (%)] / [700 (nm) -630 (nm)]
(Where T ₇₀₀ Is the transmittance at a wavelength of 700 nm in the transmission spectrum of the lens for the imaging device, and T ₆₃₀ Is the transmittance at a wavelength of 630 nm in the transmission spectrum of the imaging device lens. ) The oxide is a compound represented by the following formula (1), the imaging device lens according to any one of claims 1 to 13.
A _{1 / n} CuPO ₄ (1)
(In the formula, A is at least one selected from the group consisting of alkali metals (Li, Na, K, Rb, Cs), alkaline earth metals (Mg, Ca, Sr, Ba) and NH ₄ ; Is 1 when A is an alkali metal or NH ₄ and is 2 when A is an alkaline earth metal.) The lens for an imaging device according to any one of claims 1 to 14 , wherein the near-infrared absorbing particles have a crystallite size of 5 to 80 nm determined from X-ray diffraction. The near-infrared-absorbing particles, the change amount D of reflectivity represented by the following formula (2) is not more than -0.41% / nm, for imaging apparatus according to any one of claims 1 to 15 lens.
D (% / nm) = [R ₇₀₀ (%) − R ₆₀₀ (%)] / [700 (nm) −600 (nm)] (2)
(In the formula, R ₇₀₀ is a reflectance at a wavelength of 700 nm in the diffuse reflection spectrum of the near-infrared absorbing particles, and R ₆₀₀ is a reflectance at a wavelength of 600 nm in the diffuse reflection spectrum of the near-infrared absorbing particles.) The near-infrared absorbing particles according to any one of claims 1 to 16 , wherein a reflectance at a wavelength of 715 nm in a diffuse reflectance spectrum is 19% or less, and a reflectance at a wavelength of 500 nm is 85% or more. Lens for imaging devices. The near-infrared absorbing particle has a peak near 1600 cm ⁻¹ attributed to water when the absorption intensity of a peak near 1000 cm ⁻¹ attributed to a phosphate group is defined as a reference (100%) in a microscopic IR spectrum. the absorption intensity is 8% or less, and the absorption intensity of a peak in the vicinity of 3750cm ^-1, which is attributed to hydroxyl groups is less than 26%, the imaging device lens according to any one of claims 1 to 17. Comprising an imaging device lens according, and a solid-state image sensor that converts light incident through the lens to the light receiving electrical signals to any one of claims 1 to 18 imaging device.

Images