JP2007178915A - Fine metal particle-dispersed material and infrared ray shielding filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared ray shielding filter excellent in a visible light transmitting property and an infrared ray shielding property, and a fine metal particle-dispersed material suitable for forming the infrared ray shielding filter. <P>SOLUTION: The fine metal particle-dispersed material has a spectral absorption spectrum satisfying general expression X: X=Amax/Bmax≤0.25 (wherein Amax is the maximum value of the spectral absorption spectrum of 450-650 nm; and Bmax is the maximum value of the spectral absorption spectrum of 700-1,200 nm). The infrared ray shielding filter formed from the fine metal particle-dispersed material is excellent in the visible light transmitting property and the infrared ray shielding property. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a metal fine particle dispersion and an infrared shielding filter formed using the metal particles.
Further, the present invention shields infrared rays or near infrared rays generated from the front of a display such as CRT (cathode ray tube), PDP (plasma display panel), liquid crystal, EL (electroluminescence), FED (field emission display), and the like, The present invention relates to an infrared shielding filter having transparency, and also relates to an optical filter and a plasma display panel provided with the infrared shielding filter.

In general, light having a wavelength of about 380 nm or less is called ultraviolet light, and light having a wavelength of about 700 nm or more is called infrared light.
The light emitted from sunlight has a wide wavelength range of about 200 nm to 5 μm, and includes light other than visible light such as ultraviolet rays and infrared rays. A large amount of ultraviolet rays and infrared rays are also emitted from a high-intensity light source such as a halogen lamp or a metal halide lamp.

Ultraviolet rays tend to cause sunburn, discoloration, deterioration, etc. on the human body and various objects, while infrared rays become thermal energy.
Generally, glass used for window glass or the like cannot completely absorb ultraviolet rays of about 320 nm or more and infrared rays of 5 μm or less, and therefore easily transmits ultraviolet rays and infrared rays from sunlight. Also, the glass and plastic used for the front lens of the lamp cannot completely cut out ultraviolet rays and infrared rays.

  In relation to the above, there is a disclosure relating to ultraviolet and infrared cut glass having an infrared reflection film or an infrared absorption film on the surface of the ultraviolet cut glass on which CuCl and / or CuBr fine particles are deposited (see, for example, Patent Document 1).

  Further, as the infrared absorbing component, fine metal oxide selected from metal group such as indium oxide, tin oxide and ITO, ATO, lanthanum compound, iron, manganese, etc. is 0.01% with respect to polyvinyl acetal resin. There is a disclosure related to a transparent composition for infrared rays cutting contained in a ratio of ˜5 mass% (see, for example, Patent Document 2).

  However, in the former ultraviolet and infrared cut glass, it is necessary to form a multilayer film for infrared cut, and there are problems in cost and heat resistance (reflection wavelength change caused by film thickness change accompanying thermal expansion).

In addition, a method of preparing a compound having a spectral spectrum in the infrared region by controlling the shape of silver fine particles is known (for example, see Reference 3). However, when an optical filter is produced using these silver fine particles, there is a problem that the visible part (400 to 700 nm) has low transparency, and when an infrared light shielding film is produced, the performance satisfactory for practical use cannot be exhibited. .
In the PDP, near-infrared cut performance is an important required characteristic for the purpose of preventing malfunction of the remote control. In particular, with the recent increase in the brightness of PDPs, the amount of near infrared rays generated has increased, so that even higher near infrared ray cutting performance is required.
However, the durability of dyes that absorb near infrared rays is not sufficient, and improvements in this respect are required.

JP 7-61835 A JP 2005-126650 A Jin et al. Nature 425, 487 (2003)

The present invention has been made in view of the above, and an object of the present invention is to provide an infrared shielding filter excellent in visible part permeability and excellent in infrared shielding properties, and a metal fine particle dispersion suitable for forming the filter. An object is to achieve the object.
Still another object of the present invention is to provide an infrared shielding filter for PDP having high near-infrared cutting performance, to provide an optical filter for PDP, and to provide a plasma display panel. .
A further object of the present invention is to provide an infrared shielding filter, an optical filter for PDP, and a plasma display having high near-infrared cut performance and high durability.

Specific means for achieving the above object are as follows.
<1> A metal fine particle dispersion in which a spectral absorption spectrum of a dispersion containing metal fine particles satisfies the following general formula X.
X = Amax / Bmax ≦ 0.25
Amax = maximum value of spectral absorption spectrum from 450nm to 650nm
The maximum value of spectral absorption spectrum of Bmax = 700 nm to 1200 nm <2> The metal fine particle dispersion according to <1>, wherein the metal fine particles have a flat plate shape.
<3> The metal fine particle dispersion according to <1> or <2>, wherein the metal fine particles are silver fine particles or silver-containing alloy fine particles.
<4> The metal fine particle dispersion according to any one of <1> to <3>, wherein the metal fine particles have a sphere equivalent diameter of 50 nm or less.
<5> The metal fine particle dispersion according to any one of <1> to <4>, which contains a dispersion polymer having at least one sulfur atom and / or nitrogen atom.
<6> The main plane shape of the metal fine particles contained in the dispersion containing the metal fine particles is a disc shape having no substantial angle, and the aspect ratio thereof is 3.0 or more. <5> The fine metal particle dispersion according to any one of <5>.
<7> The metal fine particle dispersion according to any one of <1> to <6>, wherein the solid content weight ratio of the metal in the dispersion containing the metal fine particles is 40% or more. .
<8> The metal fine particle dispersion according to any one of <1> to <7>, wherein the dispersion containing the metal fine particles is purified and concentrated by an ultrafiltration method.
<9> The <1> to <1>, wherein the metal fine particles contain a metal obtained by irradiating two or more lights having different wavelengths, at least one of which is irradiated with a wavelength of 700 nm or less. 8> The fine metal particle dispersion described in any one of 8>.
<10> The metal fine particle dispersion according to <9>, wherein the metal particles are prepared by laser light irradiation.
<11> An infrared ray shielding filter formed using the metal fine particle dispersion according to any one of <1> to <10>.
<12> The infrared light shielding filter according to <11>, which is used for a plasma display panel.
<13> An optical filter for a plasma display panel, comprising the infrared ray shielding filter according to <11>.
<14> The plasma display optical filter according to <13>, wherein the plasma display optical filter has at least two functions of antireflection, electromagnetic wave shielding, infrared shielding, color tone adjustment, and ultraviolet absorption. It is.
<15> A plasma display panel comprising the infrared light shielding filter according to <11>.

ADVANTAGE OF THE INVENTION According to this invention, it is excellent in visible part transparency and can provide the infrared shielding filter excellent in infrared shielding property.
In addition, a filter having high durability and excellent infrared shielding properties can be provided and can be suitably used for PDP applications.

The metal fine particle dispersion of the present invention is suitably used for an infrared shielding filter.
Hereinafter, the infrared ray shielding filter of the present invention will be described in detail.
The infrared shielding filter of the present invention contains flat metal fine particles in a dispersed state. For example, the flat metal fine particles are dispersed in the form of a film (for example, provided on a substrate such as a glass substrate). can do. By disposing the infrared shielding filter at an arbitrary position on the optical path in the light emission direction of the infrared (and ultraviolet) light emitting unit, the infrared (and ultraviolet) can be absorbed and cut to be shielded.

  The emission spectrum from the infrared (and ultraviolet) light emission part can be detected and measured using a spectral radiance meter SR-3 (manufactured by Topcon Corporation).

Hereinafter, the metal fine particle dispersion according to the present invention will be described in detail.
In the fine metal particle dispersion of the present invention, the value of X = Amax / Bmax is 0.25 or less, preferably 0.2 or less, and more preferably 0.1 or less. In the present invention, the value of X = Amax / Bmax is obtained by measuring the maximum value Amax of the absorption spectrum in the visible region (450 nm to 650 nm) and the maximum value Bmax of the absorption spectrum in the long wave region (700 nm to 1200 nm) from the spectral absorption measurement. , Defined as the ratio (Amax / Bmax) of the maximum values of the respective absorption spectra obtained. If the said formula is in the said range, the visible region transmittance | permeability will increase and the effect which suppresses the color tone of a visible region as an infrared cut filter will be acquired. Here, for spectral absorption measurement, “U-3410 type self-recording spectrophotometric type” manufactured by Hitachi, Ltd. can be used.

<Metallic fine particles>
The metal in the metal fine particles is not particularly limited, and any metal may be used. The metal fine particles include composite particles in which two or more kinds of metals are combined, and can be used as alloy fine particles.

In particular, the metal preferably contains a metal selected from the group consisting of the fourth period, the fifth period, and the sixth period of the long periodic table (IUPAC 1991) as a main component. Moreover, it is preferable to contain the metal chosen from the group which consists of 2-14 groups, 2nd group, 8th group, 9th group, 10th group, 11th group, 12th group, 13th group, and More preferably, a metal selected from the group consisting of Group 14 is included as a main component. Among these metals, the metal fine particle is a metal of the fourth period, the fifth period, or the sixth period, and is of Group 2, Group 10, Group 11, Group 12, or Group 14. Metal particles are more preferred.

  Preferred examples of the metal fine particles include copper, silver, gold, platinum, palladium, nickel, tin, cobalt, rhodium, iridium, iron, ruthenium, osmium, manganese, molybdenum, tungsten, niobium, tantel, titanium, bismuth, antimony, Mention may be made of at least one selected from lead and alloys thereof. More preferable metals are copper, silver, gold, platinum, palladium, nickel, tin, cobalt, rhodium, iridium and alloys thereof, and more preferable metals are selected from copper, silver, gold, platinum, tin and alloys thereof. At least one. In particular, silver (silver fine particles) is preferable, and colloidal silver is most preferable as silver.

<Metal compound fine particles>
The “metal compound” is a compound of the metal and an element other than the metal. Examples of the compound of metal and other elements include metal oxides, sulfides, sulfates, carbonates, and the like, and composite particles containing these, and these particles are suitable as the metal compound fine particles.

  Examples of metal compounds include copper oxide (II), iron sulfide, silver sulfide, copper sulfide (II), titanium black, etc., but sulfide particles are preferred because of their color tone and ease of fine particle formation. Silver sulfide is particularly preferable from the viewpoint of ease of fine particle formation and stability.

<Composite particle>
Composite particles are particles in which metals, metal compounds, and metal and metal compounds are combined to form one particle. For example, particles having different compositions between the inside and the surface of the particle, two types of particles are combined. (Including alloys) and the like. Moreover, 1 type or 2 types or more may be sufficient as a metal compound and a metal, respectively.

  The metal fine particles include composite particles of metal and metal, and the metal compound fine particles include composite particles of metal and metal compound, and composite particles of metal compound and metal compound.

  Among the composite particles, an alloy fine particle having silver is preferable, and an alloy fine particle having silver includes an alloy of silver and another metal, an alloy of silver and a silver compound or a metal compound other than the silver compound, and a silver compound and a silver compound. Alloys with other metal compounds are included and can be used as alloy fine particles.

  Specific examples of the composite particles of metal and metal compound preferably include composite particles of silver and silver sulfide, composite particles of silver and copper (II) oxide, and the like.

<Core shell particles>
The fine particles according to the present invention may be core-shell type composite particles (core-shell particles). Core-shell type composite particles (core-shell particles) are obtained by coating the surface of a core material with a shell material.
Examples of the shell material constituting the core-shell type composite particles include Si, Ge, AlSb, InP, Ga, As, GaP, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, PbS, PbSe, PbTe, and Se. , Te, CuCl, CuBr, CuI, TlCl, TlBr, TlI and their solid solutions and at least one semiconductor selected from 90 mol% or more of these, or copper, silver, gold, platinum, palladium, nickel, tin, Examples include at least one metal selected from cobalt, rhodium, iridium, iron, ruthenium, osmium, manganese, molybdenum, tungsten, niobium, tantel, titanium, bismuth, antimony, lead, and alloys thereof.
The shell material is also preferably used as a refractive index adjusting agent for the purpose of reducing the reflectance.

  Moreover, as a preferable core material, at least 1 sort (s) chosen from copper, silver, gold | metal | money, palladium, nickel, tin, bismuth, anmotine, lead, and these alloys can be mentioned.

There is no restriction | limiting in particular in the preparation methods of the composite particle which has a core shell structure, The following are mentioned as a typical method.
(1) A method of forming a metal compound shell on the surface of metal fine particles produced by a known method by oxidation, sulfurization, etc. For example, metal fine particles are dispersed in a dispersion medium such as water, and sodium sulfide or This is a method of adding a sulfide such as ammonium sulfide. By this method, the surface of the particles can be sulfided to form core-shell particles.
In this case, the metal fine particles to be used can be produced by a known method such as a gas phase method or a liquid phase method. The method for producing metal fine particles is described in, for example, “Latest Trends in Technology and Application of Ultrafine Particles II” (Sumibe Techno Research Co., Ltd., issued in 2002).
(2) A method of continuously forming a metal compound shell on the surface in the process of producing metal fine particles. For example, a reducing agent is added to a metal salt solution to reduce a part of metal ions to form metal fine particles. And then adding a sulfide to form a metal sulfide around the produced metal fine particles.

-Shape of metal fine particles-
Advanced Materials 2002, 14, 80-82 and J. Org. Phys. Chem. B. As described in 2003.107, 2466-2470, etc., it is known that the color of metal particles changes depending on the particle shape. The metal fine particles in the present invention can be obtained by combining various types of particles in order to improve infrared light shielding properties. Higher transmission density is obtained by changing the particles from spherical or cubic to flat. In addition, circular tabular grains having substantially no corners in the main planar shape of the tabular grains have better visible part transmittance and better infrared shielding properties.

[Disk-shaped flat particles]
The disk-shaped tabular fine particles are disk-shaped fine particles whose main plane shape has substantially no corners. As a specific example, the shape of the main plane of the tabular grains is rounded, for example, in the shape of a disk or a triangle. Examples thereof include particles having a shape or the like. Among these, disk-shaped metal fine particles, particularly disk-shaped metal fine particles are preferable.

  Here, “disk-shaped” means a tabular grain form having no substantial angle when the grains are regarded as a triaxial cuboid composed of the X axis, the Y axis, and the Z axis by the following method. I will be. In other words, when viewed as a cuboid with a three-axis diameter, the area of a triangle formed from three lines by drawing three straight lines that have a thickness in one uniaxial direction and minimize the extra area around the plane formed by the remaining two axes. This refers to particles having a ratio RA of the excess area to 0.03 or more. Here, RA means (triangular area−particle area) / triangular area.

[Hexagonal flat particle]
The hexagonal tabular fine particles are fine particles having a hexagonal tabular shape. As a specific example, the shape of the main plane of the tabular grains is, for example, a regular hexagon or a hexagonal shape in which four congruent isosceles triangles are stacked. Among them, metal fine particles having a regular hexagonal shape, particularly regular hexagonal metal fine particles are preferable.

  Here, “hexagonal shape” means a tabular grain form having six corners when the particles are regarded as a cuboid having a triaxial diameter composed of the X, Y, and Z axes by the following method. I'll tell you. That is, when it is regarded as a cuboid with a triaxial diameter, it means a particle having a thickness in one uniaxial direction and six corners in a plane formed by the remaining two axes.

[Disc Degree]
The disk degree is a ratio of the disk-like tabular grains to the total number of tabular grains including a triangular flat plate, a hexagonal flat plate, and a disc-like flat plate having a main plane.

  Examples of the metal-based fine particles include hexagonal tabular fine particles and disc-shaped tabular fine particles, and the degree of disc is preferably 50% or more, and more preferably 70% or more.

In the present invention, the “aspect ratio” of the metal fine particles means a value obtained by dividing the major axis length of the metal fine particles defined as described later by the minor axis length, and an average value of values measured for 100 metal fine particles; Define.
The projected area of the particles can be obtained by measuring the area on the electron micrograph and correcting the photographing magnification.

  The diameter (major axis length, minor axis length) of the metal fine particles is a box (cuboid) in which the metal fine particles are triaxial diameters so that one metal fine particle can be exactly (contained). The dimension of the metal fine particle is defined by the length L, the width b, the height, or the thickness t.

  Among the above-mentioned metal-based fine particles, fine particles having an aspect ratio (ratio of major axis length of particles / minor axis length of particles) of 3 or more increase the light absorption effect on the long wavelength side and improve the infrared shielding effect. Is preferable. Among them, the aspect ratio is preferably 4 to 80, and particularly preferably 10 to 60, in that the absorption spectrum can be controlled, the absorption of infrared rays or infrared rays and ultraviolet rays is high, and the shielding effect is excellent.

  The size of the fine particles according to the present invention is preferably 50 nm or less, more preferably 30 nm or less, in terms of a sphere equivalent diameter. The lower limit of the sphere equivalent diameter is 5 nm. When the equivalent sphere diameter is within the above range, the ability to absorb light in the infrared (and ultraviolet) wavelength range is good, and the shielding effect is effectively enhanced.

In the present invention, the sphere equivalent diameter is a diameter (2r) calculated from a volume (= (4/3) πr ³ ) obtained by taking a photograph with an electron microscope and obtaining a volume from fine particles (cross section, thickness). is there. Here, an electron microscope [JEM2010 manufactured by JEOL Ltd. (for example, measured at an acceleration voltage of 200 kV)] or an atomic force microscope [AFM; SPA-400 manufactured by Seiko Instruments Inc.] can be used as the electron microscope.

  In the present invention, tabular grains or discoid grains having an aspect ratio of 3 or more are preferred. When it is a tabular grain or a disk-like grain, it has excellent visibility transparency and good absorption of light in the infrared region (and ultraviolet region). Particularly, acicular particles have excellent absorption in both infrared and ultraviolet regions, and infrared rays. It is effective for obtaining both the shielding effect and the ultraviolet shielding effect.

(Method for producing metal fine particle dispersion of the present invention)
Hereinafter, the preparation of the metal fine particle dispersion of the present invention will be described.
The metal fine particles of the present invention can be prepared by a chemical reduction method of metal ions, an electroless plating method, a metal evaporation method, or the like. Moreover, from the viewpoint of monodispersity of the prepared metal fine particle shape, a method of controlling the shape by irradiating the metal fine particles with light is preferable.
Science 294, 1901-1903 (2001) and Nature 425, 487-490 (2003) can be referred to for the method of controlling the particle shape by irradiating metal fine particles with light.

  Although any reducing agent may be used for the method of forming seed crystal particles before irradiation with light, the standard reduction potential is preferably 0.9 or less. In addition, any method can be used for mixing the metal ion and the reducing agent. However, in order to enhance the effect of the present invention, it is preferable that the metal ion and the reducing agent are added simultaneously under temperature control. . The seed crystal particles are preferably spherical particles having a diameter of 5 to 30 nm.

  In the present invention, when preparing particles having a maximum value of the absorption peak of the spectral spectrum at 800 nm or more by irradiating the metal fine particles with light, at least one of them is irradiated with light of two or more wavelengths, at least one of which is 700 nm or less. The remaining light with different wavelengths is preferably 700 nm or more, and more preferably a combination of 700 nm light and 300 to 450 nm light.

When irradiating two wavelengths of light, the ratio of the light beam incident on the short wavelength light selection filter to the light beam incident on the long wavelength light selection filter is preferably 0.1 or less, and 0.05 or less. More preferably. More preferably, it is preferable to use a laser as the light source and increase the wavelength selectivity rather than selecting long wavelength light with a filter.
By setting the ratio of the luminous flux incident on each filter to the above conditions, the maximum value Amax of the absorption spectrum in the visible region (450 nm to 650 nm) is reduced, and the visible region transmittance is increased. The effect of reducing the visible color is enhanced.
Preferably, Na citrate is preferably added to the fine particle dispersion, and the molar ratio with the metal is preferably 1 or more and 20 or less, and more preferably 3 or more and 12 or less.

-Purification and concentration of fine metal particles-
The metal fine particle dispersion of the present invention can be refined by removing impurities other than the coexisting metal fine particles and impurities such as a residual reducing agent after the metal fine particle preparation, and at the same time concentrate the metal fine particles.
The above purification / concentration method can be any of centrifugal separation, decantation, suction filtration, etc., but it is limited from the viewpoint of the moisture resistance and heat resistance of the filter when an infrared shading filter is produced. An outer filtration method is preferred. Regarding the ultrafiltration method, the method used in “The latest membrane treatment technology and its application” published by Fuji Techno System Co., Ltd. can be referred to.

    Although it does not specifically limit as a filtration membrane used when wash | cleaning and concentrating a dispersion liquid by ultrafiltration, For example, resin-made things, such as polyacrylonitrile, a vinyl chloride / acrylonitrile copolymer, polysulfone, a polyimide, polyamide, are usually used. Things are used. Of these, polyacrylonitrile and polysulfone are preferable, and polysulfone is more preferable. The ultrafiltration filtration membrane is preferably a filtration membrane that can be backwashed from the viewpoint of efficiently washing the filtration membrane that is usually performed after the ultrafiltration is completed.

    By the above purification / concentration method, the ratio of the metal weight in the total solid content contained in the fine metal particle dispersion, that is, the solid weight ratio of the metal can be concentrated to 40% or more. Further, in order to improve stability and durability in the production of an infrared light shielding filter, the solid content weight ratio of the metal is preferably 40% or more, more preferably 60% or more, and most preferably 80% or more.

  Further, the metal fine particle dispersion of the present invention can be subjected to solvent substitution after the preparation of the metal fine particles. Solvent replacement can be performed by adding the target solvent to the purified and concentrated dispersion by centrifugation, decantation, suction filtration, or ultrafiltration. For example, when a decantation method is combined, a non-aqueous solvent can be substituted by gradually adding a non-polar solvent from water and sequentially replacing the solvent. When redispersion is performed after solvent replacement, it is preferable to perform mechanical dispersion using ultrasonic waves, a bead mill disperser, or the like. By performing such redispersion, impurities such as the remaining reducing agent can be removed and solvent replacement can be performed.

The solvent used for the solvent substitution is not particularly limited, and among them, those having an SP value of 9.0 or more are preferable. The “SP value” is also called a solubility parameter, and is expressed by the square root of the cohesive energy density. In the present invention, the SP value means that described in page 838 of “Adhesion Handbook” (edited by the Japan Adhesive Society, published by Nikkan Kogyo Shimbun, first published in 1971).
For example, n-hexane / 7.3, toluene / 8.9, ethyl acetate / 9.1, methyl ethyl ketone / 9.3, acetone / 10.0, ethyl alcohol / 12.7, methyl alcohol / 14.5, water /23.4. Here, the unit of the SP value is “(cal / cm ³ ) ^1/2 ”.
When the solvent redispersion has an SP value of 9.0 or more, the dispersibility is particularly good, and methyl ethyl ketone, 2-propanol, 1-propanol, 1-methoxy-2-propyl acetate, cyclohexanone, acetone, N -Methylpyrrolidone or a mixture thereof is preferably raised.

~ Dispersed polymer ~
In the present invention, metal fine particles can be further formed using a dispersed polymer, and a form in which the metal fine particles are dispersed in the dispersed polymer is preferable. The state of the presence of the fine particles at the time of dispersion is not particularly limited, but the fine particles are preferably present in a stable dispersed state, for example, more preferably in a colloidal state.
In the step of adding the dispersion polymer, it may be added before preparing the particles and may be added in the presence of the dispersion polymer, or may be added for controlling the dispersion state after adjusting the particles.

  Examples of the dispersion polymer include thiol group-containing compounds, amino acids or derivatives thereof, peptide compounds, polysaccharides and natural polymers derived from polysaccharides, synthetic polymers, and polymers such as gels derived therefrom, and the like. Can be used as

The polymers include protective colloid polymers such as gelatin, polyvinyl alcohol (P-3), methylcellulose, hydroxypropyl cellulose, polyalkyleneamine, polyacrylic acid partial alkyl ester, polyvinylpyrrolidone (P-1). , And polyvinylpyrrolidone copolymer.
For the polymer that can be used as the dispersant, for example, the description of “Encyclopedia of Pigments” (edited by Seijiro Ito, published by Asakura Shoin Co., Ltd., 2000) can be referred to.

  In addition to the above, a polymer having a carboxylic acid group in the side chain as a binder, for example, JP-A-59-44615, JP-B-54-34327, JP-B-58-12777, JP-B-54-25957 Methacrylic acid copolymer, acrylic acid copolymer, itaconic acid copolymer, crotonic acid copolymer, maleic acid copolymer described in JP-A-59-53836 and JP-A-59-71048. Examples thereof include a polymer and a partially esterified maleic acid copolymer. Moreover, the cellulose derivative which has a carboxylic acid group in a side chain can also be mentioned. In addition, those obtained by adding a cyclic acid anhydride to a polymer having a hydroxyl group can be preferably used. In particular, a copolymer of benzyl (meth) acrylate and (meth) acrylic acid or a multicomponent copolymer of benzyl (meth) acrylate, (meth) acrylic acid and other monomers described in US Pat. No. 4,139,391 is also available. Can be mentioned.

  Among the binders, those having a dielectric constant in the range of 2 to 2.5 are preferable from the viewpoint of the stability of the dispersion. Particularly preferably, the dielectric constant is in the range of 2.1 to 2.4. The dielectric constant here is a physical quantity indicating how much the atoms in the substance respond when an electric field is applied to the substance.

  The content of the fine metal particles in the fine metal particle dispersion of the present invention is such that the solid metal mass in the dispersion is 40% by mass or more based on the total solid content from the viewpoint of more effectively exerting the effects of the present invention. It is preferable that it is 70 mass% or more.

(Dispersion polymer having one or more sulfur atoms and / or nitrogen atoms)
Next, the dispersion polymer having one or more sulfur atoms and / or nitrogen atoms in the present invention will be described. The dispersion stability of the metal fine particles can be further improved by preparing the metal fine particles in the presence of these dispersion polymers.

The dispersion polymer in the present invention may be a polymer containing both a sulfur atom and a nitrogen atom, or may be a polymer having either a sulfur atom or a nitrogen atom, both of which obtain the effects of the present invention. be able to.
As the polymer having a sulfur atom, those having a thioether group, a mercapto group, a sulfide group or a thioxo group are preferable. As the polymer having a nitrogen atom, those having an amino group or an imino group or a nitrogen-containing heterocyclic compound can be used. preferable.
Examples of the nitrogen-containing heterocycle include 2-mercaptobenzimidazole, pyrrole, pyrrolidine, oxazole, thiazole, imidazole, pyrazole, pyridine, piperidine, pyridazine, pyrimidine, pyrazine, indole, quinoline, and benzimidazole. The group may be unsubstituted or substituted.

  The dispersion polymer in the present invention may have the above-described group containing a sulfur atom or a nitrogen atom as a side chain terminal group of a polymer (including a copolymer) described later or a polymerizable compound. Although it may have other than that, what has as a side chain terminal group is preferable. Hereinafter, a polymer (including a copolymer) or a polymerizable compound is also simply referred to as a polymer.

  As a dispersion polymer in this invention, what has an acidic group is mentioned suitably, for example. There is no restriction | limiting in particular as said acidic group, According to the objective, it can select suitably. Examples of the acidic group include a carboxyl group, a sulfonic acid group, a phosphoric acid group, a boronic acid, a phenol, and a sulfoamide. Among these, a carboxyl group is preferable.

  There is no restriction | limiting in particular as an acid value of the dispersion polymer in this invention, Although it can select suitably according to the objective, For example, 70-300 (mgKOH / g) is preferable, and 90-250 (mgKOH / g) is preferable. More preferably, 100 to 200 (mgKOH / g) is particularly preferable from the viewpoint of dispersion stability.

  Examples of the polymer having a carboxyl group as the acidic group include a vinyl copolymer having a carboxyl group, a polyurethane resin, a polyamic acid resin, a modified epoxy resin, and the like. Among these, solubility in a coating solvent, A vinyl copolymer having a carboxyl group is preferred from the viewpoint of solubility in an alkali developer, suitability for synthesis, ease of adjustment of film properties, and the like. A copolymer of at least one of styrene and a styrene derivative is also preferable.

The vinyl copolymer having a carboxyl group can be obtained by copolymerization of at least (1) a vinyl monomer having a carboxyl group and (2) a monomer copolymerizable with the vinyl monomer of (1).
Examples of the vinyl monomer having a carboxyl group include (meth) acrylic acid, vinyl benzoic acid, maleic acid, maleic acid monoalkyl ester, fumaric acid, itaconic acid, crotonic acid, cinnamic acid, acrylic acid dimer, and hydroxyl group. An addition reaction product of a monomer (for example, 2-hydroxyethyl (meth) acrylate) and a cyclic anhydride (for example, maleic anhydride, phthalic anhydride, cyclohexanedicarboxylic anhydride), ω-carboxy-polycaprolactone mono Examples include (meth) acrylate. Among these, (meth) acrylic acid is particularly preferable from the viewpoints of copolymerizability, cost, solubility, and the like. In the present specification, “(meth) acrylic acid” is a generic term for acrylic acid and methacrylic acid, and the same applies to derivatives thereof.
Moreover, you may use the monomer which has anhydrides, such as maleic anhydride, itaconic anhydride, and citraconic anhydride, as a precursor of a carboxyl group.

  The monomer copolymerizable with the vinyl monomer (1) is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include (meth) acrylic acid esters, crotonic acid esters, and vinyl esters. , Maleic acid diesters, fumaric acid diesters, itaconic acid diesters, (meth) acrylamides, vinyl ethers, vinyl alcohol esters, styrenes (eg, styrene, styrene derivatives, etc.), (meth) acrylonitrile, vinyl groups Substituted heterocyclic groups (for example, vinylpyridine, vinylpyrrolidone, vinylcarbazole, etc.), N-vinylformamide, N-vinylacetamide, N-vinylimidazole, vinylcaprolactone, 2-acrylamido-2-methylpropanesulfonic acid, Monophosphate (2- (Acryloyloxyethyl ester), mono (1-methyl-acryloyloxyethyl ester) phosphate, vinyl monomers having functional groups (for example, urethane group, urea group, sulfonamide group, phenol group, imide group) and the like. Of these, styrenes are preferred.

  Examples of the (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) ) Acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, 2-ethyl (meth) acrylate, tert-octyl (meth) acrylate, Dodecyl (meth) acrylate, octadecyl (meth) acrylate, acetoxyethyl (meth) acrylate, phenyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-methoxyethyl (meth) ) Acrylate, 2-ethoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, 3-phenoxy-2-hydroxypropyl (meth) acrylate, benzyl (meth) acrylate, diethylene glycol monomethyl ether (meta ) Acrylate, diethylene glycol monoethyl ether (meth) acrylate, diethylene glycol monophenyl ether (meth) acrylate, triethylene glycol monomethyl ether (meth) acrylate, triethylene glycol monoethyl ether (meth) acrylate, polyethylene glycol monomethyl ether (meth) acrylate , Polyethylene glycol monoethyl ether (meth) acrylate, β-phenoxyethoxyethyl (meth ) Acrylate, nonylphenoxypolyethylene glycol (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, trifluoroethyl (meth) acrylate, octafluoropentyl (Meth) acrylate, perfluorooctylethyl (meth) acrylate, tribromophenyl (meth) acrylate, tribromophenyloxyethyl (meth) acrylate and the like can be mentioned.

Examples of the crotonic acid esters include butyl crotonate and hexyl crotonate.
Examples of the vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl methoxyacetate, vinyl benzoate, and the like.
Examples of the maleic acid diesters include dimethyl maleate, diethyl maleate, and dibutyl maleate.
Examples of the fumaric acid diesters include dimethyl fumarate, diethyl fumarate, dibutyl fumarate and the like.
Examples of the itaconic acid diesters include dimethyl itaconate, diethyl itaconate, and dibutyl itaconate.

  Examples of the (meth) acrylamides include (meth) acrylylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butylacryl (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-cyclohexyl (meth) acrylamide, N- (2-methoxyethyl) (meth) acrylamide, N, N-dimethyl (meth) Examples include acrylamide, N, N-diethyl (meth) acrylamide, N-phenyl (meth) acrylamide, N-benzyl (meth) acrylamide, (meth) acryloylmorpholine, diacetone acrylamide, and the like.

Examples of the vinyl ethers include methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, and methoxyethyl vinyl ether.
Examples of the vinyl alcohol esters include vinyl versatoate, vinyl acetate, vinyl formate, vinyl propionate, and vinyl butyrate.
Examples of the styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, butyl styrene, hydroxy styrene, methoxy styrene, butoxy styrene, acetoxy styrene, chlorostyrene, dichlorostyrene, bromostyrene, chloro Examples include methylstyrene, hydroxystyrene protected with a group that can be deprotected by an acidic substance (for example, tert-butyloxycarbonyl group), methyl vinylbenzoate, α-methylstyrene, and the like.

  The molecular weight of the dispersion polymer in the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. From the viewpoint of the dispersion stability of the metal fine particles, for example, the weight average molecular weight is 2,000 to 300,000. Is preferable, 4,000 to 150,000 is more preferable, and 6000 to 100,000 is particularly preferable.

Further, the organic / inorganic ratio (I / O value) in the organic conceptual diagram of the dispersed polymer in the present invention is preferably 0.44 or more and 1.90 or less, and more preferably 0.5 or more and 1.65 or less.
When the dispersion polymer in this invention has a sulfur atom, 0.5 mass%-20 mass% are preferable from a viewpoint of the dispersion stability of a metal microparticle, and, as for content of the sulfur atom in a polymer, 1.0 mass%- 10.0 mass% is still more preferable. Moreover, when the dispersible polymer in this invention has a nitrogen atom, 0.5 mass%-20 mass% are preferable from a viewpoint of the dispersion stability of a metal microparticle, and the content of the nitrogen atom in a polymer is 1.0. More preferably, the content is from mass% to 10.0 mass%. Furthermore, when the dispersion polymer in this invention has both a sulfur atom and a nitrogen atom, mass ratio (s / n) of a sulfur atom (s) and a nitrogen atom (n) is from a viewpoint of the dispersion stability of a metal microparticle. 0.01 to 200 is preferable, and 0.1 to 20 is more preferable.

  Specific examples of the case where the dispersion polymer in the invention contains a sulfur atom include a polymer compound having at least one repeating unit represented by the following general formula (1).

In the general formula (1), R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms in total. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, a sec butyl group, an isobutyl group, and a tert-butyl group. Groups are preferred.

In the general formula (1), R ² represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an aralkyl group having 7 to 16 carbon atoms. The group, the aryl group, and the aralkyl group may each independently be unsubstituted or substituted, and may form a saturated or unsaturated cyclic structure.

The alkyl group having 1 to 18 carbon atoms represented by R ² may be unsubstituted or substituted, for example, a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, Examples thereof include alkyl groups such as secbutyl group, isobutyl group, tert-butyl group, hexyl group, octyl group, dodecyl group, stearyl group. As the substituent in the case of having a substituent, for example, a halogen atom, a hydroxyl group, an amino group, an amide group, a carboxyl group, an ester group, a sulfonyl group and the like are preferable.

  Among the above, an alkyl group having 1 to 12 carbon atoms is preferable, an alkyl group having 1 to 8 carbon atoms is more preferable, and a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, and a tert-butyl group are Particularly preferred.

The aryl group represented by R ² may be unsubstituted or substituted, and is preferably an aryl group having 6 to 14 carbon atoms, such as a phenyl group, a toluyl group, a xylyl group, a naphthyl group, And aryl groups such as anthracenyl. As the substituent in the case of having a substituent, for example, a halogen atom, a hydroxyl group, an amino group, an amide group, a carboxyl group, an ester group, a sulfonyl group and the like are preferable.

  Among the above, an aryl group having 6 to 10 carbon atoms is preferable, and a phenyl group is particularly preferable.

The aralkyl group represented by R ² may be unsubstituted or substituted, and is preferably an aralkyl group having 7 to 16 carbon atoms, for example, a benzyl group, a phenethyl group, a naphthylmethyl group, an anthracene group. Examples include aralkyl groups such as a nylmethyl group. As the substituent in the case of having a substituent, for example, a halogen atom, a hydroxyl group, an amino group, an amide group, a carboxyl group, an ester group, a sulfonyl group and the like are preferable.

  Among the above, an aralkyl group having 7 to 11 carbon atoms is preferable, and a benzyl group is particularly preferable.

In the general formula (1), Z represents —O— or NH—. Y represents a divalent linking group having 1 to 8 carbon atoms in total. The divalent linking group having 1 to 8 carbon atoms represented by Y is an alkylene group (eg, methylene, ethylene, propylene, butylene, pentylene), an alkenylene group (eg, ethenylene, propenylene), an alkynylene group ( Examples, ethynylene, propynylene), arylene groups (eg, phenylene), divalent heterocyclic groups (eg, 6-chloro-1,3,5-triazine-2,4-diyl group, pyrimidine 2,4-diyl group) , Quinoxaline-2,3-diyl group, pyridazine-3,6-diyl), -O-, -CO-, -NR- (R is a hydrogen atom, an alkyl group or an aryl group), or a combination thereof (for example,- NHCH2CH2NH-, -NHCONH- and the like are preferable.
Among the above, the alkylene group, alkenylene group, alkynylene group, arylene group, divalent heterocyclic group, R alkyl group or aryl group may have a substituent. Examples of the substituent are the same as those of the aryl group. The alkyl group and aryl group of R are as defined above.

Of the divalent linking groups having 1 to 8 carbon atoms represented by Y, divalent linking groups having 1 to 6 carbon atoms are preferred, and among them, an ethylene group, a propylene group, a butylene group, a hexylene group,- CH ₂ —CH (OH) —CH ₂ — and —C ₂ H ₄ —O—C ₂ H ₄ — are particularly preferred.

The polymer dispersant may be a polymer compound containing two or more sulfur atoms by copolymerizing two or more of the repeating units represented by the general formula (1). Also, thioether structure constituting the side chains, not only one sulfur atom, the Z, the R ^2, by configuring a group having a sulfur atom, a side chain having two or more sulfur atoms be able to.

  The polymer dispersant introduces a thioether structure into a desired polymer compound (preferably as a side chain), homopolymerization of a monomer having a thioether group (preferably in a side chain), or a thioether group (preferably Can be obtained by copolymerization of a monomer having a side chain) with another monomer. Preferably, a thioether structure is introduced into the side chain of the ethylenically unsaturated monomer, or homopolymerization of an ethylenically unsaturated monomer containing a thioether structure in the side chain, or an ethylenically unsaturated group containing a thioether structure in the side chain. It can be obtained by copolymerization of a saturated monomer and another copolymer component.

  Specific examples of the repeating unit represented by the general formula (1) are shown below. However, the present invention is not limited to these.

Among the above, in particular, R ¹ is a hydrogen atom or a methyl group, R ² is a methyl group, an ethyl group, a normal propyl group, a normal butyl group, a tert-butyl group, a phenyl group, and Z is —O—. A compound in which Y is an ethylene group is preferred.

  Specific examples of the case where the dispersion polymer in the present invention contains a nitrogen atom include, for example, a polymer compound having at least one repeating unit represented by the following.

  Specific examples of the dispersion polymer containing a sulfur atom or a nitrogen atom in the present invention will be given below, but the invention is not limited thereto. The following compounds P-2 and 4 to 17 are copolymers having repeating units represented by A, B and C. Moreover, a, b, and c represent the ratio of mass% of each of the repeating units A, B, and C.

  In addition, a surfactant, an antiseptic, a dispersion stabilizer, or the like may be appropriately added to the metal fine particle dispersion of the present invention.

  As the surfactant, any of anionic, cationic, nonionic, and betaine surfactants can be used, and anionic and nonionic surfactants are particularly preferable. Since the solvent of the coating solution is a nonpolar solvent, the HLB value of the surfactant is preferably about 3 to 6.

  The HLB value is described in, for example, “Surfactant Handbook” (Tokiyuki Yoshida, Shinichi Shindo, Yoshiyoshi Yamanaka, published in Engineering Book Co., Ltd. 1987). Specific examples of the surfactant include propylene glycol monostearate, propylene glycol monolaurate, diethylene glycol monostearate, sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, and the like. Examples of the surfactant are also described in the aforementioned “Surfactant Handbook”.

  As the dispersion stabilizer, for example, those described in “Pigment Dispersion Technology (issued by Technical Information Association, Inc. 1999)” can be used.

In addition, a hydrophilic polymer, a surfactant, a preservative, a stabilizer, and the like may be appropriately added to the dispersion liquid in which the fine particles are dispersed.
Any hydrophilic polymer may be used as long as it is soluble in water and can substantially maintain a solution state in a diluted state. For example, proteins and protein-derived substances such as gelatin, collagen, casein, fibronectin, laminin, and elastin; derived from polysaccharides and polysaccharides such as cellulose, starch, agarose, carrageenan, dextran, dextrin, chitin, chitosan, pectin, mannan Natural polymers such as substances; synthetic polymers such as poval (polyvinyl alcohol), polyacrylamide, poly (vinyl pyrrolidone acrylate), polyethylene glycol, polystyrene sulfonic acid, polyallylamine; or gels derived therefrom can be used. When gelatin is used, the type of gelatin is not particularly limited. For example, beef bone alkali-treated gelatin, pig skin alkali-treated gelatin, beef bone acid-treated gelatin, cow bone phthalated gelatin, pig skin acid-treated gelatin, etc. Can be used.

  As the surfactant, any of anionic, cationic, nonionic, and betaine surfactants can be used, and anionic and nonionic surfactants are particularly preferable. The HLB value of the surfactant cannot be generally specified depending on whether the solvent of the coating solution is aqueous or organic solvent, but is preferably about 8 to 18 when the solvent is aqueous, and 3 to 6 in the case of organic solvent. A degree is preferred.

  In addition, about the said HLB value, the description of "surfactant handbook" (Tokiyuki Yoshida, Shinichi Shindo, Yoshiyoshi Yamanaka edition, engineering book Co., Ltd. publication, 1987) can be referred, for example.

Specific examples of the surfactant include propylene glycol monostearate, propylene glycol monolaurate, diethylene glycol monostearate, sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, and the like.
Examples of surfactants are also described in the “Surfactant Handbook”.

The infrared shielding filter of the present invention is suitable as a shielding filter that cuts infrared rays or infrared rays and ultraviolet rays in an image display unit of an image display device such as a plasma display device, an EL display device, a CRT display device, or a liquid crystal display device. Further, it is also suitable as a shielding filter that cuts out ultraviolet rays by being arranged on the light emitting surface of a device equipped with a light source that emits ultraviolet rays such as a fluorescent lamp (including a cathode ray tube) such as a sharksten or an image display backlight.
The liquid crystal display element can be configured, for example, by providing at least two substrates including a color filter, a liquid crystal provided between the substrates, and two electrodes for applying an electric field to the liquid crystal.

(Optical filter for PDP)
The infrared shielding filter for PDP may be provided with a functional layer having functionality separately as necessary. This functional layer can have various specifications for each application. For example, a layer having an electromagnetic wave shielding function, an antireflection layer with an antireflection function with an adjusted refractive index or film thickness, a non-glare layer or an antiglare layer (both have an antiglare function), and visible in a specific wavelength range A layer with a color tone adjustment function that absorbs light, an antifouling layer with a function that easily removes dirt such as fingerprints, a hard coat layer that is difficult to scratch, a layer that has an impact absorption function, and prevents glass scattering when the glass breaks A layer having a function or the like can be provided. These functional layers may be provided on the surface opposite to the layer having an infrared shielding function, or may be provided on the same surface side.
These functional films having infrared shielding ability may be directly bonded to the PDP, or may be bonded to a transparent substrate such as a glass plate or an acrylic resin plate separately from the plasma display panel main body. These functional films are called optical filters (or simply filters).

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
[Example 1]
<Preparation of silver nanoparticle dispersion: A-1>
Polymer P-1 was added to sodium citrate aqueous solution 6.2 × 10 ⁻³ mol / L 800 mL so as to be 7.0 × 10 ⁻² % (W / W), and 1.0 × 10 ⁻² mol / L. 100 cc of silver nitrate aqueous solution and 100 mL of 5.0 × 10 ⁻² mol / L NaBH ₄ aqueous solution were added simultaneously. Stirring was further continued at room temperature for 45 minutes to prepare a liquid containing yellow spherical silver nanoparticles. The obtained spherical silver nanoparticles were spherical particles having a diameter of about 10 nm.
A filter with a transmission wavelength of 440 ± 50 nm and a filter with a transmission limit wavelength of 700 nm are respectively installed in front of the light source, and the above prepared spherical shape on the opposite side of the lamp from the filter so that light of two wavelengths is irradiated on the sample. Silver nanoparticles were placed and the sample temperature was kept at 30 ° C. by a temperature control device. The ratio of luminous flux incident on each filter (filter with a specific transmission wavelength of 440 ± 50 nm / filter with a transmission limit wavelength of 700 nm) was 0.1, and spherical particles were converted into tabular grains by irradiation with xenon light for 30 hours. .
(Polymer P-1)
The following polyvinylpyrrolidone degree of polymerization: 40,000

The obtained metal-containing dispersion having an Ag concentration of 1.0 × 10 ⁻³ mol / L was diluted 0.4 times, and “U-3410 self-recording spectrophotometric form” manufactured by Hitachi, Ltd. was used, and the spectral absorption was obtained. Was measured. The ratio of the maximum value A of absorbance at 450 nm to 650 nm and the maximum value B of absorbance at 700 nm to 1200 nm was 0.17. As a result of TEM observation of this particle dispersion, the aspect ratio was 6.0 and the disk degree was 82%. By the photodynamic scattering method, the equivalent sphere diameter was 24.6 nm.

The ultrafiltration module AHP1010 (manufactured by Asahi Kasei Corporation; molecular weight cut off 50000) and the pump were connected with a silicon tube to obtain an ultrafiltration apparatus. The reaction solution 10L obtained by light irradiation was subjected to ultrafiltration by operating a pump. When the filtrate from the module reached 2 liters, 2 liters of ion exchange water was added. This operation was repeated 4 times. Thereafter, the filtrate was confirmed to have a conductivity of 300 μS / cm or less, and concentrated until the amount of the mother liquor was 100 ml.
Subsequently, an ultrafiltration device comprising a 500 ml stainless steel cup containing mother liquor, an ultrafiltration module AIP1013 (manufactured by Asahi Kasei Corporation; molecular weight cut off 6000), a tube pump, and an aspirator was assembled. The mother liquor obtained previously was put into this stainless steel cup and concentrated to increase the solid content concentration. When the mother liquor reached about 100 ml, the pump was stopped and the concentration was terminated to obtain a silver colloid solution having a solid content of 43%. The average particle size of the silver colloid particles in this solution was about 22.6 nm. This silver nanoparticle dispersion is designated as Particle Dispersion A-1.

[Example 2]
<Preparation of silver nanoparticle dispersion: A-2>
In preparation of the silver nanoparticle dispersion using A-1, except that the polymer P-1 was replaced with a nitrogen-containing polymer P-2, the same procedure as in the preparation of the silver nanoparticle dispersion using A-1 was performed. Silver nanoparticle dispersion liquid A-2 was prepared.

[Example 3]
<Preparation of silver nanoparticle dispersion: A-3>
Silver nanoparticles were prepared in the same manner as the silver nanoparticle dispersion using A-2 except that the xenon light irradiation time was changed from 30 h to 50 h in preparation of the silver nanoparticle dispersion using A-2. Dispersion A-3 was prepared.

[Example 4]
<Preparation of silver nanoparticle dispersion: A-4>
In preparation of the silver nanoparticle dispersion using A-3, the ratio of the luminous flux incident on the filter having a transmission wavelength of 440 ± 50 nm and the filter having a transmission limit wavelength of 700 nm is set to 0.05, and the xenon light irradiation time is changed from 50 h to 70 h. A silver nanoparticle dispersion liquid A-4 was prepared in the same manner as in the preparation of the silver nanoparticle dispersion liquid using A-3, except for the above.

[Example 5]
<Preparation of silver nanoparticle dispersion: A-5>
In the silver nanoparticle dispersion using A-4, instead of concentrating by ultrafiltration, the silver nanoparticle dispersion using A-1 was used except that the following decantation was used. Similarly, silver nanoparticle dispersion liquid A-5 was prepared.
A silver nanopigment dispersion 10L converted from spherical particles to tabular grains by light irradiation was adjusted to pH 7 with 1N nitric acid and allowed to stand for 1 day to agglomerate and settle the silver nanoparticles to obtain an aggregated silver nanoparticle liquid. .
The supernatant of the aggregated silver nanoparticle solution was removed, and 900 ml of distilled water and 1N nitric acid were added to adjust the pH to 2.5. The liquid was stirred with a stirrer to disperse the aggregated silver nanoparticles, and then allowed to stand for 1 hour to precipitate the aggregated silver nanoparticles again. The supernatant liquid was removed to obtain an aggregated silver nanoparticle liquid. This was repeated two more times.
Add 900 ml of methanol to the above-mentioned aggregated silver nanoparticle liquid and stir with a stirrer to disperse the aggregated silver nanoparticles, then let stand for 1 hour, settle the aggregated silver nanoparticles, remove the supernatant liquid, and aggregate the silver nanoparticles A liquid was obtained. This was repeated two more times.
Add 100 ml of acetone to the above aggregated silver nanoparticle liquid and stir with a stirrer to disperse the aggregated silver nanoparticles, then let stand for 1 hour to settle the aggregated silver nanoparticles, remove the supernatant liquid and remove the aggregated silver nanoparticles A liquid was obtained. This was repeated once more to prepare a silver nanoparticle dispersion liquid A-5.

[Example 6]
<Preparation of silver nanoparticle dispersion: A-6>
In the silver nanoparticle dispersion preparation using the A-1, except that the polymer P-1 was replaced with a nitrogen-containing polymer P-3, the same procedure as in the silver nanoparticle dispersion preparation using the A-1, Silver nanoparticle dispersion liquid A-6 was prepared.
(Polymer P-3)
The following degree of polymerization of polyvinyl alcohol: 500
Saponification degree: 85% or more

[Example 7]
<Preparation of silver nanoparticle dispersion: A-7>
In the silver nanoparticle dispersion liquid preparation using A-1, the light is irradiated with two types of laser light of 450 nm and 700 nm, instead of irradiating two wavelengths of light to Ag particles through two types of filters. Prepared a silver nanoparticle dispersion A-7 in the same manner as in the preparation of the silver nanoparticle dispersion using A-1.

[Example 8]
<Preparation of silver nanoparticle dispersion: A-8>
In the silver nanoparticle dispersion liquid preparation using A-2, instead of irradiating two wavelengths of light to Ag particles through two types of filters, light irradiation is performed using two types of laser light of 450 nm and 700 nm. No. A silver nanoparticle dispersion A-8 was prepared in the same manner as in the preparation of the silver nanoparticle dispersion using A-2.

[Example 9]
<Preparation of silver nanoparticle dispersion: A-9>
In the silver nanoparticle dispersion using A-6, instead of irradiating two wavelengths of light on Ag particles through two types of filters, light irradiation is performed using two types of laser light of 450 nm and 700 nm. No. A silver nanoparticle dispersion A-9 was prepared in the same manner as in the preparation of the silver nanoparticle dispersion using A-6.

[Example 10]
<Preparation of silver nanoparticle dispersion: A-10>
In preparation of the silver nanoparticle dispersion using A-1, the silver nanoparticle dispersion was prepared in the same manner as in the preparation of the silver nanoparticle dispersion using A-1, except that the light source of irradiation light was changed from an Xe lamp to a fluorescent lamp. A particle dispersion A-10 was prepared.

  Table 1 shows the aspect ratio, the equivalent sphere diameter, the disk degree, the solid metal concentration, the concentration method, and the Amax / Bmax values of the fine particle dispersions of A-1 to A-10.

<Preparation of infrared light shielding filter containing metal fine particle dispersion>
Next, the silver nanoparticle dispersions A-1 to 10 obtained above were applied onto a glass substrate using a spin coater so that the dry film thickness was 1.0 μm, and dried at 100 ° C. for 5 minutes, An infrared shielding filter was produced.

[Example 11]
<Preparation of infrared shading filter containing pigment>
An optical polyester resin (manufactured by Kanebo Co., Ltd., trade name “O-PET”) was dissolved in cyclopentanone so as to have a resin concentration of 10% to prepare a base solution of a near-infrared shielding film. To 100 g of this main agent solution, 5.6 mg of nickel, bis-1,2-diphenyl-1,2-ethenedithiolato (manufactured by Midori Chemical Co., Ltd., trade name “MIR101”), phthalocyanine dye (manufactured by Nippon Kayaku Co., Ltd., 3.2 mg of trade name “EEX Color 801K”), 22.4 mg of diimmonium dye (made by Nippon Kayaku Co., Ltd., trade name “IRG022”), and anthraquinone dye (Dye A made by Dainippon Seika Co., Ltd.) Was dissolved to prepare a pigment dispersion.
This dye dispersion was applied using a spin coater so that the dry film thickness was 1.0 μm, and dried at 100 ° C. for 5 minutes to prepare an infrared shielding filter.
And the produced infrared shielding filter was arrange | positioned on the liquid crystal display part of a liquid crystal display, it inserted in the optical path between an observer and a display part, and the infrared shielding effect was evaluated as follows.

<Evaluation>
The emission spectrum from the liquid crystal display before placing the infrared shielding filter as described above was measured with a spectral radiance meter SR-3 (manufactured by Topcon). Subsequently, when the infrared shielding filter is placed on the liquid crystal display of the liquid crystal display (manufacturer: Samsung Electronics, model: Sync Master 172X), the emission spectrum from the liquid crystal display is measured in the same manner as described above via the infrared shielding filter. did.
(Evaluation of moisture resistance)
Using a constant temperature and humidity tester KCH-1000 manufactured by Tokyo Rika Kikai Co., Ltd., setting the temperature to 60 ° C and relative humidity 90% RH, measuring the spectral transmittance of each sample after a 500 hour test at a wavelength of 850 nm. The ratio of the increase after the test to the value before the test was calculated.

(Evaluation of heat resistance)
Using a constant temperature and temperature chamber manufactured by Isuzu Seisakusho Co., Ltd., set the temperature to 80 ° C, measure the spectral transmittance of each sample after a 500 hour test at a wavelength of 850 nm, and increase after the test with respect to the value before the original test The percentage of was calculated.

Example 12
(Preparation of optical filter for PDP)
The dispersion having infrared shielding properties obtained in the above examples was applied to a polyethylene terephthalate film, and a glass plate was bonded through an acrylic translucent adhesive having a thickness of 25 μm. The acrylic light-transmitting pressure-sensitive adhesive layer contained a toning dye (PS-Red-G, PS-Violet-RC manufactured by Mitsui Chemicals) that adjusts the transmission characteristics of the optical filter. Furthermore, an antireflection film (trade name Realak 8201 manufactured by Nippon Oil & Fats Co., Ltd.) was bonded to the opposite main surface of the glass plate via an adhesive material to produce an optical filter.
The obtained optical filter had excellent transparency and near-infrared cutting ability, and was excellent in visibility due to the antireflection layer. Further, by adding a dye, a color-adjusting function can be imparted, and it can be suitably used as an optical filter such as a plasma display.

Claims (15)

A metal fine particle dispersion wherein the spectral absorption spectrum of the dispersion containing the metal fine particles satisfies the following general formula X:
X = Amax / Bmax ≦ 0.25
Amax = maximum value of spectral absorption spectrum from 450nm to 650nm
Bmax = maximum value of spectral absorption spectrum from 700nm to 1200nm   The metal fine particle dispersion according to claim 1, wherein the metal fine particles have a flat plate shape.   3. The metal fine particle dispersion according to claim 1, wherein the metal fine particles are silver fine particles or alloy fine particles containing silver.   The metal fine particle dispersion according to any one of claims 1 to 3, wherein the metal fine particles have a sphere equivalent diameter of 50 nm or less.   5. The metal fine particle dispersion according to claim 1, comprising a dispersion polymer having at least one sulfur atom and / or nitrogen atom.   The main plane shape of the metal fine particles contained in the dispersion containing the metal fine particles is a disk shape having no substantial angle, and the aspect ratio thereof is 3.0 or more. 2. The metal fine particle dispersion according to item 1.   The metal fine particle dispersion according to any one of claims 1 to 6, wherein a solid content weight ratio of the metal in the dispersion containing the metal fine particles is 40% or more.   The metal fine particle dispersion according to any one of claims 1 to 7, wherein the dispersion containing the metal fine particles is purified and concentrated by an ultrafiltration method.   The metal fine particles contain a metal obtained by irradiating two or more lights having different wavelengths, at least one of which is irradiated with a wavelength of 700 nm or less. The metal fine particle dispersion described in the item.   The metal fine particle dispersion according to claim 9, wherein the metal particles are prepared by laser light irradiation.   An infrared shielding filter formed using the metal fine particle dispersion according to any one of claims 1 to 10.   The infrared light shielding filter according to claim 11, wherein the infrared light shielding filter is for a plasma display panel.   An optical filter for a plasma display panel, comprising the infrared ray shielding filter according to claim 11.   The optical filter for plasma display according to claim 13, having at least two functions of antireflection, electromagnetic wave shielding, infrared shielding, color tone adjustment, and ultraviolet absorption.   A plasma display panel comprising the infrared light shielding filter according to claim 11.