JP2008203377A - High refractive index thin film and composition for formation of high refractive index thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high refractive index thin film having a sufficiently high refractive index by using a wet process and to provide a composition for formation of a thin film to form a high refractive index thin film. <P>SOLUTION: The thin film contains metal nanoparticles that generate localized surface plasmon resonance in a transparent matrix and is formed by coating. The metal nanoparticles are preferably included by 60 to 600 pts.wt. in 100 pts.wt. of the transparent matrix. The composition contains metal nanoparticles that generate localized surface plasmon resonance, a transparent matrix source material and a solvent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high refractive index thin film and a composition for forming a high refractive index thin film.

  In recent years, various functional thin films have been used in various fields. For example, in the optical field, an optical thin film having a relatively high refractive index is used for applications such as an optical filter and an antireflection film.

  Conventionally, this type of optical thin film has been mainly formed by a dry process such as vacuum deposition or sputtering.

  However, the dry process basically requires film formation under a vacuum, so that there are drawbacks such as high cost and poor productivity.

  Therefore, recently, proposals have been made to form a thin film by utilizing a wet process, which is a simple process capable of forming a film in the atmosphere.

  For example, Patent Document 1 discloses that a thin film-forming composition containing an organotitanium compound and a β-diketone is applied and dried, and then the applied film is irradiated with ultraviolet rays and cured to obtain a refractive index. A technique for forming a titanium oxide thin film of about 1.9 is disclosed.

JP-A-2005-353656

  However, the prior art has room for improvement in the following points.

  That is, in general, it is difficult for the wet process to form a dense thin film as compared with the dry process. Therefore, it is difficult to obtain a high refractive index, and some ingenuity is required to further increase the refractive index.

  For example, in Patent Document 1, a specific additive such as β-diketone is added when a coating film formed by a sol-gel method is cured with ultraviolet rays to form a thin film having a high refractive index. However, even with such a device, it has been difficult to achieve a higher refractive index.

  As described above, although there is a high demand for a high refractive index of a coating thin film that can be formed relatively easily, there is a problem that an effective means cannot be found.

  The present invention has been made in view of the above problems, and a problem to be solved by the present invention is to provide a high refractive index thin film having a sufficiently high refractive index using a wet process. Moreover, it is providing the composition for thin film formation for forming the said high refractive index thin film.

  In order to solve the above-described problems, the high refractive index thin film according to the present invention includes metal nanoparticles that cause localized surface plasmon resonance in a transparent matrix and is formed by coating.

  Here, the high refractive index thin film may contain 60 to 600 parts by weight of the metal nanoparticles with respect to 100 parts by weight of the transparent matrix.

  In addition, the refractive index in a wavelength region where there is no absorption due to localized surface plasmon resonance of the metal nanoparticles is preferably 1.95 or more.

  The high refractive index thin film preferably contains an organic component.

  The film thickness is preferably in the range of 10 nm to 300 nm.

  On the other hand, the composition for forming a high refractive index thin film according to the present invention includes metal nanoparticles that cause localized surface plasmon resonance, a transparent matrix material, and a solvent.

  The high refractive index thin film according to the present invention includes metal nanoparticles that cause localized surface plasmon resonance in a transparent matrix. Therefore, even if it is a coating thin film, it has a sufficiently high refractive index compared with the case where it is not included. This is presumably due to the following reasons.

  That is, the incident light incident on the thin film interacts with the locally enhanced electric field generated by the localized surface plasmon resonance of the metal nanoparticles, thereby slowing its traveling speed. Therefore, it is considered that the refractive index is increased.

  Here, when the content of the metal nanoparticles in the transparent matrix is within the specific range, the effect of increasing the refractive index is large, and it is easy to obtain a strong and homogeneous thin film. There are advantages.

  Moreover, when an organic component is contained in the film, there are advantages such as an improvement in the flexibility of the film.

  On the other hand, the composition for forming a high refractive index thin film according to the present invention includes metal nanoparticles that cause localized surface plasmon resonance, a transparent matrix material, and a solvent.

  Therefore, if this is coated using an appropriate coating method and a transparent matrix is generated from the transparent matrix raw material according to the type of the transparent matrix raw material in the coating film (precursor film), the above high refractive index thin film Can be obtained.

  Hereinafter, the high refractive index thin film according to the present embodiment (hereinafter sometimes referred to as “the present thin film”) and the high refractive index thin film forming composition according to the present embodiment (hereinafter referred to as “the present composition”). .) Will be described in detail.

1. This thin film is a coating thin film formed by coating. The thin film contains metal nanoparticles in a transparent matrix.

  In this thin film, the transparent matrix should just have transparency in the wavelength range which uses this thin film. For example, if this thin film is used in the infrared region, it should be transparent in the infrared region. If this thin film is used in the visible light region, it should be transparent in the visible light region.

  The material of the transparent matrix may be any of inorganic materials, organic materials, and composites thereof.

  Specific examples of the inorganic material include silicon oxide, titanium oxide, zinc oxide, indium oxide, tin oxide, indium and tin oxide, and magnesium oxide. And metal oxides such as aluminum oxide, zirconium oxide, niobium oxide, and cerium oxide. These may be contained alone or in combination of two or more. Note that silicon is called a so-called semi-metal because it belongs to an intermediate between a metal and a non-metal due to its nature. However, in the present invention, silicon is included in the metal component for convenience.

  On the other hand, specific examples of the organic material include (meth) acrylic resins, polycarbonate resins, olefin resins, urethane resins, silicone resins, polyester resins, epoxy resins, polystyrene resins, and the like. Can be illustrated. These may be contained alone or in combination of two or more.

  The thin film contains metal nanoparticles. Here, the metal nanoparticles need to generate localized surface plasmon resonance. This is to increase the refractive index using localized surface plasmon resonance.

  Whether the metal nanoparticles cause localized surface plasmon resonance depends on, for example, the particle size, the particle morphology, and the like. In this thin film, as long as localized surface plasmon resonance occurs, the particle size, particle morphology, metal species, and the like of the metal nanoparticles are not particularly limited. The particle size of the metal nanoparticles is usually about several nm to several tens of nm.

  Specific examples of the metal constituting the metal nanoparticles include noble metals such as gold (Au), silver (Ag), and white metals (Pt, Pd, Ru, Rh, Ir, Os), copper, and indium. And base metals such as iron, germanium, tin, bismuth, nickel, and cobalt. These may be contained alone or in combination of two or more. Further, core-shell structured metal nanoparticles in which a shell layer made of one or more kinds selected from the above metal is coated around a core made of one or more kinds selected from the above metals. There may be.

  The metal nanoparticles are preferably noble metal nanoparticles from the viewpoints of stability in the atmosphere, availability, and the like. Among the noble metal nanoparticles, silver nanoparticles and gold nanoparticles are preferable.

  From the viewpoint of increasing the effect of increasing the refractive index, the present thin film is preferably 60 parts by weight or more, more preferably 100 parts by weight or more, with respect to 100 parts by weight of the transparent matrix. It should be included.

  On the other hand, the present thin film is made into a strong and homogeneous thin film. From the viewpoint of cost and the like, the metal nanoparticles are preferably 600 parts by weight or less, more preferably 400 parts by weight with respect to 100 parts by weight of the transparent matrix. It is good if it contains less than parts by weight.

  The thin film may contain an organic component. As said organic content, the organic content etc. which originate in a transparent matrix raw material can be illustrated, for example. More specifically, for example, organometallic compounds such as metal alkoxides, metal acylates and metal chelates (including decomposition products thereof) can be exemplified. These may be contained alone or in combination of two or more. When this kind of organic component is contained, there is an advantage that flexibility can be imparted.

  Examples of other organic components include organic components covering the surface of metal nanoparticles.

  Whether or not the organic component is contained can be examined using infrared spectroscopy (IR) (infrared absorption analysis) X-ray photoelectron spectroscopy (XPS) or the like.

  In addition to the above, the present thin film may contain a dispersant, a crosslinking agent, a polymerization initiator, a catalyst, and the like used in forming the thin film as long as the effects of the present invention are not impaired.

  The thin film preferably has a refractive index of 1.95 or more, more preferably 2.0 or more, in a wavelength region where there is no absorption due to localized surface plasmon resonance of the metal nanoparticles.

  In addition, since the said refractive index is so preferable that it is high, the upper limit is not specifically limited.

  The wavelength of the refractive index is defined as the wavelength region because the wavelength region before and after the absorption peak due to the localized surface plasmon resonance of the metal nanoparticles has a low transmittance and is used as an optical film. It is difficult.

  For example, when silver nanoparticles are used as the metal nanoparticles, the wavelength region affected by absorption due to the localized surface plasmon resonance is a region smaller than approximately 1200 nm. Therefore, the refractive index in the wavelength region of 1200 nm or more is preferably 1.95 or more.

  Here, the refractive index can be obtained as follows. With respect to a single transparent support substrate (such as a transparent polymer film or a glass substrate) for supporting this thin film, the transmittance and reflectance in the measurement wavelength region are measured using a spectrophotometer. Further, the thickness of the transparent support substrate is measured with a micrometer or the like.

  Next, using the “Film Tek” series manufactured by Scientific Computing International, or an optical thin film measuring device having the same function, the refractive index of the transparent support substrate is determined from the transmittance, reflectance, and thickness. Obtain the chromatic dispersion of the absorption coefficient.

  Next, with respect to the sample in which the thin film is formed on one side of the transparent support base, incident light having the above measurement wavelength is incident from the thin film side using a spectrophotometer, and the transmittance and reflectance of the sample are measured. Moreover, the thickness of this thin film is measured with a stylus type surface roughness meter or the like.

  Then, using the above apparatus, the refractive index and absorption coefficient of the thin film can be obtained from the refractive index, absorption coefficient, and thickness measured for the transparent support substrate alone and the transmittance, reflectance, and thickness measured for the sample. it can.

  The film thickness of the thin film can be variously adjusted according to its use. The upper limit of the thickness of the thin film is preferably 300 nm or less, more preferably 200 nm or less, from the viewpoint of use as an optical film.

  On the other hand, the lower limit of the thickness of the thin film is preferably 10 nm or more, and more preferably 20 nm or more.

  The thin film may be formed at a time, or may be divided and formed by coating a plurality of times. In this case, the said film thickness is the thickness of the thin film which combined the some division layer.

  In addition, this thin film can be laminated | stacked on the at least one surface side of a transparent support base material. The transparent support substrate may be either an inorganic material or an organic material, as long as it does not easily impair the optical properties of the thin film and can form a thin film on the surface without hindrance. You can choose. In addition, the present thin film may be directly formed on the surface of the transparent support substrate, or one or more other thin films may be interposed between the transparent support substrate and the present thin film.

  Specific examples of the inorganic material include glass. Specific examples of the organic material include polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, polyimide, polyamide, polybutylene terephthalate, polyethylene naphthalate, and polysulfone. , Polymer materials such as polyethersulfone, polyetheretherketone, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, triacetylcellulose, polyurethane, and cycloolefin polymer. Preferably, polyethylene terephthalate, polycarbonate, polymethyl methacrylate, cycloolefin polymer, and the like can be suitably used.

  Specific examples of the use of the thin film include an optical filter and an antireflection film.

2. The present composition The present composition contains metal nanoparticles that cause localized surface plasmon resonance, a transparent matrix material, and a solvent.

  In the present composition, the metal nanoparticles are basically the same as described above in “1. But as a metal nanoparticle contained in this composition, the thing by which the metal surface was surface-modified with the organic component from a viewpoint of improving dispersibility etc. can be used conveniently.

  In the present composition, the raw material of the transparent matrix includes a material capable of forming a transparent matrix by irradiation with heat or active energy rays (ultraviolet rays, electron beams, etc.), polymerization, crosslinking, etc., and “1. The above-described transparent matrix material itself can be used.

  Specific examples of the transparent matrix material include organic compounds of metals such as silicon, titanium, zinc, indium, tin, magnesium, aluminum, zirconium, niobium, and cerium; ) Organic materials such as acrylic resins, polycarbonate resins, olefin resins, urethane resins, silicone resins, polyester resins, epoxy resins, polystyrene resins; examples of monomers and oligomers that can produce these organic materials can do. These may be contained alone or in combination of two or more.

  Specific examples of the organometallic compound include metal alkoxides, metal acylates, and metal chelates of the above metals.

  Preferably, an organic silicon compound or the like can be suitably used from the viewpoint of easy curing at a relatively low temperature.

Specific examples of the organic silicon compound include R _n SiX _(4-n) (wherein R is an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, and X is 1 to 4 carbon atoms). Alkoxide group, silanol group, halogen or hydrogen, n is an integer of 0 to 3), and hydrolysates thereof.

  More specifically, as the organic silicon compound, for example, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, Dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, 3,3,3-trifluoropropyltrimethoxysilane , Methyl-3,3,3-trifluoropropyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxytripropyltri Toxisilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane , Γ-methacryloxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-amino Propyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, Examples include titrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, vinyltrichlorosilane, trimethylbromosilane, diethylsilane, and multimers thereof. These may be used alone or in combination.

  In the present composition, an appropriate solvent may be selected according to the type of transparent matrix raw material, the dispersibility of the metal nanoparticles, and the like.

  Specific examples of the solvent include alcohols such as ethanol, methanol, propanol, butanol, heptanol, and isopropyl alcohol, organic acid esters such as ethyl acetate, ketones such as acetonitrile, acetone, and methyl ethyl ketone, tetrahydrofuran, and dioxane. And the like, cycloamides such as formamide, acid amides such as N, N-dimethylformamide, hydrocarbons such as hexane, aromatics such as toluene, water and the like. These may be used alone or in combination.

  In addition to the above, the composition may contain one or more various additives such as a dispersant, a crosslinking agent, and a polymerization initiator, as necessary.

  In the present composition, the content of the transparent matrix raw material in the composition is preferably in the range of 0.1 to 50% by weight.

  When the content of the transparent matrix raw material in the composition is less than 0.1% by weight, the film thickness that can be formed by one coating becomes thin, and a large number of coatings are required to obtain a desired thickness. There is a tendency to become. On the other hand, when it exceeds 50% by weight, the fluidity of the coating solution is lowered, and it tends to be difficult to obtain a uniform film thickness. Therefore, it is good to pay attention to these when selecting the content.

  The content of the transparent matrix raw material in the composition is more preferably in the range of 0.5 to 30% by weight, and still more preferably in the range of 1 to 20% by weight.

  Further, when the content of the transparent matrix raw material in the composition is in the above range, the transparent matrix generated when the transparent matrix is generated from the transparent matrix raw material (for example, silicon oxide is generated from the organic silicon compound). The metal nanoparticles are preferably contained in an amount of 60 to 600 parts by weight with respect to the transparent matrix raw material corresponding to 100 parts by weight of the matrix. The remainder is the above solvent and the like.

  On the other hand, when the content of the transparent matrix raw material in the composition is in the above range, when the transparent matrix raw material becomes a transparent matrix as it is (for example, the transparent polymer itself is used as the transparent matrix raw material), the transparent matrix raw material The metal nanoparticles are preferably contained in an amount of 60 to 600 parts by weight with respect to 100 parts by weight. The remainder is the above solvent and the like.

  The lower limit of the metal nanoparticles is more preferably 100 parts by weight or more, and still more preferably 150 parts by weight or more. On the other hand, the upper limit of the metal nanoparticles is more preferably 500 parts by weight or less, and still more preferably 400 parts by weight or less.

  This composition is, for example, stirring means such as a stirrer for transparent matrix raw materials weighed so as to have a predetermined ratio, metal nanoparticles, an appropriate amount of solvent, and other components added as necessary. Can be prepared by a method such as stirring and mixing for a predetermined time. In this case, the components may be mixed at a time or may be mixed in a plurality of times. Moreover, you may make it mix the metal nanoparticle previously disperse | distributed to the suitable solvent.

  In order to form this thin film using this composition, the following method can be illustrated, for example. That is, a thin film precursor is formed using various coating methods (can be dried if necessary), and the obtained thin film precursor is heated according to the type of the transparent matrix raw material or active energy rays ( The thin film can be formed, for example, by irradiation with ultraviolet rays or electron beams.

  As the coating method of the above coating liquid, from the viewpoint of easy uniform coating, etc., micro gravure method, gravure method, reverse roll coating method, die coating method, knife coating method, dip coating method, spin coating method, bar coating method Various wet coating methods can be exemplified as suitable. These may be appropriately selected and used, and one or more may be used in combination.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

Hereinafter, the present invention will be described in detail using Examples and Comparative Examples.
1. Preparation of thin film forming compositions according to Examples and Comparative Examples (Example 1)
The composition for forming a high refractive index thin film according to Example 1 was prepared by the following procedure. That is, 0.2 g of tetrabutoxy titanium tetramer (manufactured by Nippon Soda Co., Ltd., “B4”) as a polymerization catalyst was added to 20 g of methyltrimethoxysilane, and stirred for 10 minutes to prepare Solution A.

  Next, 5 g of 0.1N nitric acid and 40 g of 2 methoxyethanol were mixed and added dropwise to the solution A, and stirred for 10 minutes to prepare a solution B.

  Next, 6.5 g of silver nanoparticles (Nippon Paint Co., Ltd., “Finesphere SVE102”, particle size 20-30 nm, composition: Ag 30% by weight, dispersion resin 2% by weight, ethanol 68% by weight) and 1 butanol 10 g And stirred for 10 minutes to prepare solution C.

  Next, 6.5 g of the solution B was weighed, mixed with the solution C, and stirred for 10 minutes to prepare a thin film forming composition according to Example 1.

(Example 2)
A thin film forming composition according to Example 2 was prepared in the same manner as the preparation of the high refractive index thin film forming composition according to Example 1, except that 6.5 g of silver nanoparticles were changed to 13 g.

(Comparative Example 1)
A thin film forming composition according to Comparative Example 1 was prepared in the same manner as the preparation of the high refractive index thin film forming composition according to Example 1, except that 6.5 g of silver nanoparticles were changed to 6 g of ethanol.

2. Production of Thin Films According to Examples and Comparative Examples Next, using the obtained thin film forming compositions according to Examples 1 and 2 and Comparative Example 1, Examples 1 and 2 and Comparative Example 1 were performed as follows. The thin film which concerns on was produced.

  Each said composition was apply | coated to one side of the glass substrate (Fibrabo Co., Ltd. product, "BK-7") of diameter 50mm and thickness 1mm with the spin coater, and each thin film precursor was obtained. The spin coating conditions were a solution dripping amount of 0.3 cc, a preliminary rotation of 500 rpm × 3 seconds, and a main rotation of 2100 rpm × 30 seconds.

  Subsequently, each said thin film precursor was dried for 1 minute at 100 degreeC with the glass substrate. Thus, thin films according to Examples 1 and 2 and Comparative Example 1 were produced. FIG. 1 shows a TEM image of a thin film cross section according to Example 1. FIG.

In the thin films according to Example 1 and Example 2, the silver nanoparticles are dispersed in a transparent matrix (main component SiO ₂ ) as shown in FIG. The thin film according to Example 1 contains 170 parts by weight of silver nanoparticles with respect to 100 parts by weight of the transparent matrix. The thin film according to Example 2 contains 340 parts by weight of silver nanoparticles with respect to 100 parts by weight of the transparent matrix.

3. Evaluation of Thin Films Next, the obtained thin films according to Examples 1 and 2 and Comparative Example 1 were evaluated. At this time, the evaluation was performed by obtaining the refractive index and the wavelength dispersion of the absorption coefficient of each thin film according to the following procedure. The reason why the absorption coefficient is obtained is that the wavelength region before and after the absorption peak has a large absorption and the utility value as an optical thin film is low, so that the region is determined.

  First, the transmittance | permeability and reflectance in a wavelength range 250-2500 nm were measured using the spectrophotometer about the glass substrate single-piece | unit used at the time of thin film formation.

  Next, using “Film Tek 3000” manufactured by Scientific Computing International, the wavelength dispersion of the refractive index and absorption coefficient of the glass substrate was determined from the transmittance, reflectance, and thickness.

Then, 2. Using a spectrophotometer, the incident light of the above wavelength is incident from the thin film side, and the transmittance and reflectance of each glass substrate with a thin film are measured. did. Moreover, the thickness of each thin film was measured with a stylus meter.
The thickness of the thin film according to Example 1 was 190 nm, the thickness of the thin film according to Example 2 was 200 nm, and the thickness of the thin film according to Comparative Example 1 was 164 nm.

  Then, using the above Film Tek 3000, from the refractive index, absorption coefficient, thickness obtained for the glass substrate alone, and the transmittance, reflectance, thickness measured for each thin film-attached glass substrate, the refractive index, absorption coefficient of each thin film Chromatic dispersion was determined.

4). Results FIG. 2 shows the relationship between the wavelength and refractive index of thin films according to Examples and Comparative Examples. In FIG. 3, the relationship between the wavelength and absorption coefficient of the thin film which concerns on an Example and a comparative example is shown.

  2 and 3, the following can be understood. That is, according to FIG. 3, the thin film according to Comparative Example 1 has no change in the absorption coefficient with respect to the measurement wavelength. On the other hand, the thin film according to Example 1 and Example 2 has an absorption peak of measurement light in the vicinity of a wavelength of 400 nm. This is a peak due to localized surface plasmon resonance of the silver nanoparticles used.

  And according to FIG. 2, the thin film which concerns on Example 1 and 2 which contains the silver nanoparticle which produces localized surface plasmon resonance in a transparent matrix is sufficient compared with the thin film which concerns on Comparative Example 1 which does not contain this It can be seen that it has a high refractive index (Example 1 has a wavelength region of 600 nm or more and a refractive index of 2.0 or more, and Example 2 has a wavelength region of 600 nm or more and a refractive index of 2.3 or more).

  This shows that it is possible to increase the refractive index of the thin film by adding metal nanoparticles that cause localized surface plasmon resonance in the transparent matrix.

  Although the details of this mechanism are not clear, the progress of the incident light incident on the thin film interacts with a locally enhanced electric field generated by localized surface plasmon resonance of the metal nanoparticles. It is presumed that the speed becomes slow and therefore the refractive index is increased.

  Further, comparing the thin films according to Example 1 and Example 2, it can be seen that the higher the silver nanoparticle content, the higher the refractive index.

  Further, it can be seen that the thin films according to Examples 1 and 2 are suitable mainly as an optical filter or an antireflection film used in the infrared region where the influence of the refractive index due to plasmon absorption is small.

2 is a TEM photograph showing a cross section of a thin film according to Example 1; It is the figure which showed the relationship between the wavelength and refractive index of the thin film which concern on an Example and a comparative example. It is the figure which showed the relationship between the wavelength and absorption coefficient of the thin film which concerns on an Example and a comparative example.

Claims (6)

  A high-refractive-index thin film comprising metal nanoparticles that cause localized surface plasmon resonance in a transparent matrix and formed by coating.   The high refractive index thin film according to claim 1, wherein the metal nanoparticles are included in an amount of 60 to 600 parts by weight with respect to 100 parts by weight of the transparent matrix.   3. The high refractive index thin film according to claim 1, wherein a refractive index in a wavelength region where there is no absorption due to localized surface plasmon resonance of the metal nanoparticles is 1.95 or more.   The high refractive index thin film according to any one of claims 1 to 3, comprising an organic component.   The high refractive index thin film according to any one of claims 1 to 4, wherein the film thickness is in the range of 10 nm to 300 nm.   A composition for forming a high refractive index thin film, comprising metal nanoparticles that cause localized surface plasmon resonance, a transparent matrix material, and a solvent.