JP6091417B2 - Colored film and coloration method using metal nanoparticles - Google Patents

Description

  The present invention relates to a coloring film and a coloring method using metal nanoparticles.

  For example, in the painting of vehicles, there is a desire to paint in a color having a metallic luster. Non-Patent Document 1 proposes that a base coating including a glittering material is applied on a base material, a clear including a gold nanoparticle paste is applied on the base coating, and a coating having a metallic luster is applied. Yes.

TECHNO-COSMOS 2008 Vol. 21 p. 32-38 Japanese Patent No. 4415083

  By the way, in the coating method as described above, a plurality of types of metal particles are required depending on the color to be painted, and it is necessary to synthesize the metal particles respectively.

  Therefore, an object of the present invention is to provide a coloring film and a coloring method using metal nanoparticles that can be colored in many colors even with one kind of metal.

The colored film using the metal nanoparticles of the present invention capable of solving the above problems is
An underlayer having a metal reflecting surface;
And at least one metal nanoparticle layer formed on the metal reflecting surface, the metal nanoparticles having a substantially uniform particle size regularly arranged in a plane, and
The metal nanoparticle layer is colored in a color different from the original color of the metal nanoparticles.

In the colored film of the present invention,
The metal nanoparticles may be covered with an insulator.
Furthermore, the insulator may be any one of an organic fatty acid, an organic amine, and an alkanethiol substitute.
The metal reflecting surface may be hydrophobic.

The coloration method using the metal nanoparticles of the present invention that can solve the above problems is as follows.
A metal nanoparticle layer having a desired color different from the original color of the metal nanoparticles is formed by regularly arranging metal nanoparticles having a substantially uniform particle size on the metal reflection surface in a planar shape. It is characterized by doing.

In the coloration method of the present invention,
The metal nanoparticles may be covered with an insulator.
Furthermore, the insulator may be an organic fatty acid, an organic amine, or an alkanethiol-substituted product.
The metal reflection surface may be subjected to a hydrophobic treatment.

In the coloring method of the present invention,
Dispersing the metal nanoparticles in an organic solvent;
The organic solvent containing the metal nanoparticles is spread on the water surface,
Volatilizing the organic solvent, self-organizing the metal nanoparticles in a two-dimensional direction to form a two-dimensional crystal film,
The metal nanoparticle layer may be formed on the metal reflection surface by transferring the metal reflection surface to the two-dimensional crystal film of the metal nanoparticles formed on the water surface.

  According to the coloring film and the coloring method using the metal nanoparticles according to the present invention, even if a single metal species is used, it can be colored in different colors depending on the number of metal nanoparticle layers. For this reason, even when coating is performed using a plurality of colors, it is only necessary to prepare one kind of metal nanoparticles, so that the coating cost can be reduced.

It is a schematic sectional drawing of the colored film which concerns on embodiment of this invention. It is a schematic diagram which expands and shows a metal nanoparticle. It is a schematic diagram which shows the formation process of a metal nanoparticle layer. It is the SEM photograph which image | photographed the upper surface of the metal nanoparticle layer. It is a schematic diagram explaining the mechanism of coloring. It is a figure which shows the absorption spectrum of a colored film. It is a figure which shows the absorption spectrum of a colored film. It is a figure which shows the absorption spectrum of a colored film. It is a figure which shows the absorption spectrum of a colored film. It is a figure which shows the absorption spectrum of a colored film. It is a figure which shows the calculation result of the absorption spectrum of a colored film.

  Hereinafter, an example of an embodiment of a coloring film and a coloring method using metal nanoparticles according to the present invention will be described with reference to the drawings.

<Structure of colored film>
FIG. 1 is a schematic cross-sectional view showing a colored film 2 according to an embodiment of the present invention. The colored film 2 is provided on the object 1 to be colored. Examples of the object 1 include resin products and metal products, and any material is not particularly selected. The colored film 2 includes a metal base layer 3 provided on the object 1 and a metal nanoparticle layer 4.

  The underlayer 3 includes a reflection surface (metal reflection surface) 3a that reflects incident light toward the metal nanoparticle layer. The reflection surface 3 a is provided on the surface (upper surface) opposite to the surface in contact with the object 1. Examples of the metal of the underlayer 3 include copper, gold, silver, palladium, rhodium, iridium, ruthenium, osnium, and alloys thereof. Of these, metals having high reflectivity in the visible light region, and noble metals such as gold, silver, palladium, rhodium, iridium, ruthenium, and osnium are particularly preferable.

  The metal nanoparticle layer 4 is a layer composed of a plurality of metal nanoparticles 5. Each of the metal nanoparticles 5 has a substantially uniform particle size, and is regularly arranged in a plane to form a layer structure. In the illustrated example, the metal nanoparticle layer 4 has a two-layer structure. As will be described later, the color of the colored film can be changed by changing the number of the metal nanoparticle layers 4. The particle size of the metal nanoparticles 5 is preferably 1 nm to 50 nm, and more preferably 1 nm to 20 nm. Moreover, it is preferable that the mutual distance D of the metal nanoparticles 5 is not more than 5 times the particle size of the metal core 51 described later.

  As the metal nanoparticles 5, metal species capable of forming localized plasmons can be employed. Examples of such metal species include gold, silver, copper, aluminum, platinum, palladium, rhodium, iridium, ruthenium, and osnium. Of these, noble metals such as gold, silver, copper, aluminum, and palladium, which have large localized plasmon absorption, are particularly preferable. Moreover, you may comprise the metal nanoparticle layer 4 by mixing many types of metal seed | species.

  FIG. 2 is an enlarged view showing the metal nanoparticles 5. As shown in FIG. 2, the metal nanoparticle 5 includes a metal nucleus 51 and an insulator 52 that covers the metal nucleus 51. The insulator 52 prevents electrical conduction between adjacent metal nanoparticles 5. For example, as the insulator 52, an insulating organic substance (organic fatty acid, organic amine, alkanethiol substitute, or polymer resin), glass, or the like can be used.

<Coloring method>
The colored film 2 as described above can be formed as follows.
First, the base layer 3 is formed on the object 1 to be colored. In order to form the metal base layer 3, known techniques such as vapor deposition, sputtering, and plating can be used. Further, a reflective surface is formed by applying a reflective surface treatment to the upper surface of the base layer 3. In addition, when the target object 1 itself has a metal reflecting surface, it is not necessary to separately provide the base layer 3 on the target object 1.

Next, a solution having metal nanoparticles 5 is prepared. For example, when a mixture of an organic metal compound containing a metal (for example, silver) serving as the metal nucleus 51 and an organic acid (for example, myristic acid) is thermally decomposed in a non-oxidizing atmosphere, the metal nanoparticle having a uniform particle size in which the organic acid is bonded to the outer periphery. Particles are obtained. In this case, the organic acid becomes the insulator 52.
Further, by substituting the organic acid portion of the organic acid metal salt with an alkanethiol compound, metal nanoparticles having a uniform particle diameter in which alkanethiol is bonded to the outer periphery can be obtained. In this case, the thiol substitution product becomes the insulator 52 (see Patent Document 1 as an example in which the metal core 51 is made of silver).

  At this time, by adjusting the carbon number of the organic fatty acid, organic amine, or alkanethiol-substituted product, the metal nanoparticle 5 in which a compound having a desired carbon chain is bonded to the surface of the metal core 51 can be formed. Thereby, the interparticle distance D of the metal nanoparticle 5 can be adjusted with the length of a carbon chain.

  FIG. 3 is a schematic diagram showing a process of forming the metal nanoparticle layer 4. The solution containing the metal nanoparticles 5 obtained as described above is dispersed in the organic solvent 11, and the organic solvent 11 is spread on the water surface of the water 10. Then, this organic solvent 11 floats on the water surface and forms a thin layer. As the organic solvent volatilizes, the metal nanoparticles 5 self-assemble in the plane direction to form a plurality of small two-dimensional crystal films.

  In this state, the metal nanoparticles 5 forming the two-dimensional crystal film are collected by moving the bar 12 in the horizontal direction near the water surface of the water 10 to form a two-dimensional crystal film having a large particle size (see FIG. 3). (A)). The bar 12 is preferably moved so that the surface pressure applied to the water surface is 5 mN / m or more and 25 mN / m or less. If the surface pressure is lower than this range, the metal nanoparticles 5 are not sufficiently collected, and the crystal lump of the metal nanoparticles 5 does not increase. On the other hand, if the surface pressure is higher than this range, the metal nanoparticles 5 overlap and a three-dimensional crystal is generated.

  Further, the metal reflecting surface 3a is brought into contact with the two-dimensional crystal film including the metal nanoparticles 5 collected in this way ((b) of FIG. 3). Then, the metal nanoparticles 5 having a two-dimensional crystal structure are transferred as a monomolecular film, and one metal nanoparticle layer 4 is formed on the metal reflecting surface 3a. By repeating this contact step, the desired number of metal nanoparticle layers 4 are formed.

  In addition, when the metal nanoparticles 5 are transferred to the reflection surface 3, it is preferable that the metal reflection surface 3 is subjected to a hydrophobic treatment. When the reflective surface 3 is hydrophobic, the organic portion of the insulator 52 (organic fatty acid, organic amine, thiol-substituted product, polymer resin) of the metal nanoparticles 5 is easily fixed to the reflective surface 3a, and transfer is facilitated.

  As the insulator 52 that constitutes the metal nanoparticles 5 together with the metal nuclei 51, an insulator that does not leave the metal nuclei 51 when the organic solvent 11 in which the metal nanoparticles 5 are dispersed is spread on the water surface of the water 10 is adopted. can do. At this time, the bonding mode of the insulator 52 with the metal core 51 is not particularly limited.

  For example, when silver particles are used as the metal nucleus 51 and a thiol substitute is used as the insulator 52, the thiol substitute is chemically bonded to the metal nucleus 51. Further, when silver particles are used as the metal nucleus 51 and a carboxylic acid (organic acid) is used as the insulator 52, the carboxylic acid (organic acid) is bonded to the metal nucleus 51 by an ionic bond. When silver particles are used as the metal nucleus 51 and an organic amine is used as the insulator 52, the organic amine is bonded to the metal nucleus 51 by a physical bond. In the case where gold particles are used as the metal nucleus 51, when carboxylic acid is used as the insulator 52, the carboxylic acid is bonded to the metal nucleus 51 by a covalent bond. Further, when a polymer resin is used as the insulator 52, the insulator 52 can be configured not to be detached from the surface of the metal core 51 even when the polymer resin does not have a functional group.

  FIG. 4 is an SEM photograph obtained by photographing the upper surface of the actually produced metal nanoparticle layer 4. The colored film 2 photographed in FIG. 4 is obtained by forming one metal nanoparticle layer 4 on a silicon wafer. The metal nanoparticle layer 4 was composed of metal nanoparticles 5 made of silver as the metal core 51 and myristic acid as the insulator 52.

  As shown in FIG. 4, the metal nanoparticles 5 have a two-dimensional crystal structure that is self-organized regularly in two dimensions. The crystal structure is a hexagonal close-packed structure in which six metal nanoparticles 5 surround one metal nanoparticle 5 on a plane. The metal nanoparticle layer 4 is polycrystalline with different crystal orientations, and the diameter of one crystal grain is preferably 200 nm or more.

<Coloring mechanism>
The colored film 2 configured as described above is considered to be colored as follows, although there are some points that are not known at present.

(Near Field effect)
FIG. 5 is a schematic cross-sectional view of the colored film 2. When the color L 2 is irradiated with light L <b> 1 from the outside, localized plasmons 10 are excited around the metal nanoparticles 5. In the metal nanoparticle layer 4 of the colored film 2, the metal nanoparticles 5 are regularly arranged in a planar shape. As a result, the localized plasmons 10 excited by the individual metal nanoparticles 5 adjacent in the two-dimensional direction are coupled to each other in the plane direction (left-right direction in FIG. 5), and are longer than the single metal nanoparticles 5. Absorbs light of wavelength.

  A part of the light transmitted through the metal nanoparticle layer 4 is reflected by the metal reflecting surface 3a of the underlayer 3 and enters the metal nanoparticle layer 4 from the back side again. Thereby, the direct light L1 from the outside and the reflected light L2 on the metal reflecting surface 3a enter the metal nanoparticle layer 4 with a slight time difference. Then, a complicated interaction is generated between the localized plasmons 10 excited in the individual metal nanoparticle layers 3. Thereby, the resonance absorption peak exhibits a longer wavelength shift according to the number of layers of the metal nanoparticle layer 4.

(Far Field effect)
The metal nucleus layer A composed of the metal nuclei 51 of the metal nanoparticles 5 has a very large effective dielectric constant only at the wavelength at which the localized plasmon 10 is excited. That is, the metal core layer A has a metamaterial property in which the refractive index greatly changes depending on the wavelength in a narrow wavelength region. On the other hand, the space B between the metal reflecting surface 3a and the metal core layer A and the space C between the metal core layers A adjacent in the vertical direction are the insulator 52 having a small refractive index (and the metal reflection in the space B). It is occupied by a hydrophobic layer formed when the surface 3a is subjected to a hydrophobic treatment.

  Due to the metamaterial nature of the metal core layer A, when the reflected light L2 from the metal reflecting surface 3a is incident on the back surface of the metal nanoparticle layer 4, the light of a specific wavelength depends on the number of layers. It is strongly confined in the layer structure of layer 4.

  As described above, the near field effect in which the localized plasmon 10 is excited by both the direct light L1 and the reflected light L2 from the metal reflecting surface 3a, and the far field of light confinement in the layers A and B of the metal nanoparticle layer 4. Due to the effect, the metal nanoparticle layer 4 is colored in a color different from the original color of the metal nanoparticles 5 according to the number of layers.

  The absorption spectrum of the metal nanoparticle layer 4 will be specifically described with reference to FIG. As a reference example, FIG. 6A shows an absorption spectrum of a metal nanoparticle layer provided on a quartz substrate as an object without passing through the reflective surface 3a. FIG. 6B shows the absorption of the metal nanoparticle layer 4 composed of the silver metal nanoparticles 5 provided on the base layer 3 on the quartz substrate as the object 1 and further provided with the gold base layer 3. The spectrum is shown.

  In FIG. 6, (i) is one layer, (ii) is two layers, (iii) is three layers, (iv) is four layers, (v) is five layers, and the absorption spectrum of the metal nanoparticle layer 4 is laminated. (This also applies to FIGS. 7 to 11 described later). In both (a) and (b) of FIG. 6, a base layer having a thickness of 200 nm was used. In addition, dodecanethiol was allowed to act on the gold base layer 3 as a hydrophobic treatment for hydrophobizing the metal reflecting surface 3a. Hexamethyltridisilazane was also applied to the surface of the quartz substrate as a hydrophobic treatment. In addition, as the metal nanoparticle layer 4, a metal nanoparticle 5 having a particle diameter of 5 nm arranged with an interparticle distance D of 2 nm was used. As the silver metal nanoparticles 5, particles having a particle diameter of 5 nm and having an absorption spectrum peak at a wavelength of 426 nm when dispersed in a toluene solvent were used.

  As shown in FIG. 6A, when a metal nanoparticle layer is provided directly on a quartz substrate without an underlayer, local plasmons are bonded to each other in a plane in the metal nanoparticle layer. Although it shifts to about 50 nm red due to the effect, the absorption peak shape and intensity show the same absorption spectrum as the original metal nanoparticles.

  However, as shown in FIG. 6B, in the case of the colored film 2 according to this embodiment in which the metal nanoparticle layer 4 is provided on the base layer 3 having the reflective surface 3a, the shape is also large. A changed absorption spectrum was observed around 500 nm.

  Furthermore, as shown in FIG. 6 (a), when metal nanoparticles are directly provided on a quartz substrate without an underlayer, the peak of the absorption spectrum moves even if the number of layers of metal nanoparticles changes. do not do. However, as shown in FIG. 6B, when the metal nanoparticle layer 4 is provided on the underlayer 3, the peak of the absorption spectrum is red depending on the number of layers of the metal nanoparticle layer 4. It has shifted. Thereby, it can be confirmed that the color of the colored film 2 can be changed by changing the number of the metal nanoparticle layers 4.

  In addition, the colored film 2 having the absorption spectrum of FIG. 6B has a color having a bright metallic luster of orange to red to pink to purple to blue as the number of the metal nanoparticle layers 4 increases. Presented. This is a color different from the light yellow color of the silver metal nanoparticles 5 dispersed in toluene.

  Thus, according to the coloring film 2 and the coloring method according to the present embodiment, it is possible to cause different colors by changing the number of the metal nanoparticle layers 4. Therefore, the colored film 2 can be colored in a plurality of different colors using a single metal species, and there is no need to prepare different types of metals for different colors as in the prior art. Moreover, since the surface of the color film 2 obtained in this way is colored in a vivid color having a metallic luster, the design of the surface of various articles can be enhanced.

  In the technique of Non-Patent Document 1, unless the silver nanoparticle coating layer is formed to be thick to some extent, the color development is weak or the desired color cannot be developed. However, according to the coloring film 2 and the coloring method according to the present embodiment, the metal nanoparticle layer 4 is colored in a desired color when the required number of metal nanoparticles 5 are stacked. That is, it is not necessary to form the metal nanoparticle layer 4 thick in order to vividly color. Further, even when a plurality of metal nanoparticle layers 4 are formed in order to develop a desired color, each layer is composed of a single layer of metal nanoparticles 5, and therefore the metal nanoparticle layer 4 It will not be thick.

  Moreover, since the thickness of the metal nanoparticle layer 4 is sufficiently small as described above, the number of metal nanoparticles 5 required for coloration can be reduced. Thereby, since it can be made to color vividly at low cost, the design property of the target object 1 can be improved significantly.

  Moreover, the metal nanoparticle layer 4 can be formed by a simple method of transferring the metal nanoparticles 5 of the two-dimensional crystal film that is self-organized into a planar shape on the water surface as described above to the metal reflecting surface 3a. For this reason, the colored film 2 can be provided at low cost. Furthermore, the thickness of the two-dimensional crystal film formed by the metal nanoparticles 5 on the water surface is nano-order and flexible. For this reason, no matter what shape the surface of the underlayer 3 is, when it is brought into contact with the metal reflecting surface 3a, the metal nanoparticles 5 adhere along the surface shape, and the metal nanoparticle layer 4 is easily formed. can do. Therefore, the colored film 2 can be formed on a complicated surface such as a three-dimensional shape. At this time, it is preferable that the metal reflecting surface 3a is subjected to a hydrophobic treatment because the metal nanoparticles 5 are easily attached.

<Color adjustment method>
In FIG. 6, it was confirmed that the color of the colored film 2 can be changed by changing the number of the metal nanoparticle layers 4, but the color of the colored film 2 can be adjusted by other methods. it can. For example, by appropriately selecting the material of the underlayer 3, the particle size of the metal nanoparticles 5, the interparticle distance D of the metal nanoparticles 5, the metal species of the metal core 51 of the metal nanoparticles 5, and the like, the desired color can be obtained. Can be obtained. Alternatively, a plurality of different metals may be adopted as the metal core 51 of the metal nanoparticle 5 to form the metal nanoparticle layer 4 in which different metals are mixed. Furthermore, the color of the colored film 2 can also be changed by changing the combination of the material of the underlayer 3 and the metal species of the metal core 51 of the metal nanoparticles 5. Thereby, the color variation of the coloring film | membrane 2 can be expanded.

  FIG. 7A shows an absorption spectrum of the metal nanoparticle layer 4 in which the metal core 51 is made of silver according to a comparative example in which the base layer 3 is not provided. FIG. 7B shows an absorption spectrum of the metal nanoparticle layer 4 when the base layer 3 is silver and the metal core 51 is silver. As illustrated, also in this example, the metal nanoparticle layer 4 is colored in a color different from the original color of the silver nanoparticles. Moreover, the peak position of the absorption spectrum changes depending on the number of layers.

  Further, comparing FIG. 7B and FIG. 6B, it can be confirmed that the absorption spectrum is changed only by the material of the underlayer 3 being different. Thereby, it can be confirmed that the coloring film 2 can be colored in a desired color by selecting the material of the base layer 3.

  FIG. 8 shows an absorption spectrum of the metal nanoparticle layer 4 when the base layer 3 is gold and the metal core 51 is gold. As illustrated, also in this example, the metal nanoparticle layer 4 is colored in a color different from the original color of the gold nanoparticles. Moreover, the peak position of the absorption spectrum changes depending on the number of layers.

  Moreover, when FIG. 8 and FIG. 6B are compared, it can be confirmed that the absorption spectrum is changed only by the material of the metal core 51 of the metal nanoparticle 5 being different. Thereby, it can be confirmed that the color film 2 can be colored in a desired color by selecting the material of the metal core 51.

  FIG. 9 shows an absorption spectrum of the metal nanoparticle layer 4 when the base layer 3 is gold, the first layer metal nucleus 51 is gold, and the second and subsequent layer metal nuclei 51 are silver. As illustrated, also in this example, the metal nanoparticle layer 4 is colored in a color different from the original color of the metal nanoparticles. Moreover, the peak position of the absorption spectrum changes depending on the number of layers. Moreover, even when the metal nucleus 51 and a plurality of types were mixed, a change in the peak position of the absorption spectrum was confirmed.

  Further, comparing FIG. 9 with FIG. 6B, it can be confirmed that the absorption spectrum is changed only by the material of the metal core 51 of the first metal nanoparticle layer 4 being different. Thereby, it can be confirmed that the colored film 2 can be colored in a desired color by combining different kinds of metal nuclei 51.

  FIG. 10 shows an absorption spectrum of the metal nanoparticle layer 4 when the base layer 3 is gold, the first, second, fourth, and fifth metal nuclei 51 are silver, and the third metal nuclei 51 is gold. As illustrated, also in this example, the metal nanoparticle layer 4 is colored in a color different from the original color of the metal nanoparticles. Moreover, the peak position of the absorption spectrum changes depending on the number of layers. Moreover, even when the metal nucleus 51 and a plurality of types were mixed, a change in peak position of the absorption spectrum was confirmed.

  When FIG. 9 and FIG. 10 are compared, it can be confirmed that the colored film 2 can be colored in different colors only by changing the arrangement position of the gold nanoparticles.

  FIG. 11 shows a result of calculating an absorption spectrum when 1 to 5 metal nanoparticle layers 4 are laminated using the FDTD (Finite-difference time-domain) method. In this calculation, the particle size of the metal nanoparticles 5, the inter-particle distance D, the metal species of the metal nuclei 51, the metal species of the underlayer 3, and the layer A composed of the metal reflection surface 3 and the metal nuclei 51 of the metal nanoparticles 5 Electromagnetic calculation is performed using the thickness and refractive index of the space B between the layers and the space C between the layers A as parameters. 11A shows a case where a metal nanoparticle layer made of silver is formed on a quartz substrate as an object without providing a base layer. FIG. 11B shows a base layer 3 made of silver on the quartz substrate. The case where the metal nanoparticle layer 4 which consists of silver is formed is shown. As shown in FIG. 11, the displacement of the peak of the absorption spectrum of the colored film 2 according to the present embodiment could be confirmed. This makes it possible to predict in advance the conditions for obtaining a desired color by calculation (such as the metal species of the metal nanoparticles 5 and the material of the underlying layer 3), and the colored film 2 can be freely colored in a desired color.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  For example, in the above description, an example in which the colored film 2 is directly formed on the object to be colored has been described. For example, the base layer 3 and the metal nanoparticle layer 4 are laminated on the transfer sheet, You may affix on the target object 1. FIG.

  Further, when the object 1 itself is an object having a reflecting surface, for example, a metal product, the underlayer 3 can be identified with the object 1, so that it is not necessary to separately provide the underlayer 3. In this case, the metal nanoparticle layer 4 is formed directly on the reflecting surface of the object.

  This application is based on a US provisional patent application (61 / 533,903) filed on September 13, 2011, the contents of which are incorporated herein by reference.

  According to the coloring film and the coloring method using the metal nanoparticles according to the present invention, even if a single metal species is used, it can be colored in different colors depending on the number of metal nanoparticle layers. For this reason, even when coating is performed using a plurality of colors, it is only necessary to prepare one kind of metal nanoparticles, so that the coating cost can be reduced.

1: target object, 2: colored film, 3: base reflective surface, 3a: metal reflective surface, 4: metal nanoparticle layer, 5: metal nanoparticle, 51: metal core, 52: insulator, 10: water, 11: Organic solvent, 12: Compression bar

Claims (7)

An underlayer having a metal reflecting surface;
And at least one metal nanoparticle layer formed on the metal reflection surface, the metal nanoparticles having a uniform particle size and covered with an insulator regularly arranged in a plane,
The metal nanoparticle layer formed on the metal reflective surface has an absorption wavelength peak different from the absorption wavelength peak of the metal nanoparticle layer provided on the quartz substrate without the underlayer. A colored film characterized by being colored.   The colored film according to claim 1, wherein the insulator is any one of an organic fatty acid, an organic amine, and an alkanethiol-substituted product.   The colored film according to claim 1, wherein the metal reflecting surface is hydrophobic.   The metal nanoparticle layer formed on the metal reflection surface is formed by regularly arranging metal nanoparticles covered with an insulator having a uniform particle diameter on the metal reflection surface in a planar shape. Forming a metal nanoparticle layer that is colored so that the absorption wavelength peak is different from the absorption wavelength peak of the metal nanoparticle layer provided on the quartz substrate without the underlayer interposed therebetween. Method.   The coloration method according to claim 4, wherein the insulator is any one of an organic acid, an organic amine, and an alkanethiol-substituted product.   The coloration method according to claim 4, wherein the metal reflection surface is subjected to a hydrophobic treatment. Disperse metal nanoparticles in an organic solvent,
The organic solvent containing the metal nanoparticles is spread on the water surface,
Volatilizing the organic solvent, self-organizing the metal nanoparticles in a two-dimensional direction to form a two-dimensional crystal film,
The metal nanoparticle layer is formed on the metal reflective surface by transferring the metal reflective surface in contact with the two-dimensional crystal film of the metal nanoparticles formed on the water surface. The coloration method according to any one of 4 to 6 .

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