KR20090023982A - Color filter and display apparatus using the same - Google Patents

Abstract

A color filter and a display device using the same are provided to improve a color characteristic of the color filter by dispersing a metal nano particle into a dispersing medium. A display device includes an image panel(100), an illumination unit(150) and a filter region(F). The image panel includes a liquid crystal layer(130) sealed between two substrates(110,120). The liquid crystal layer is classified into a plurality of pixels individually on/off controlled by the pixel electrode or the TFT(Thin Film Transistor). Each pixel includes red, green, blue subpixels. A plurality of filter regions corresponding to the pixel is formed on the substrate of the pixel panel. The sub filter region corresponding to the sub pixel is prepared in each filter region. The illumination unit includes an optical source(151) and a light guide plate(152). The light guide plate includes an incident surface, a front surface(154), and a rear surface(155) of the light emitted from the optical source. A light guide unit(156) guides the light inputted to at least one surface among the front side and the rear side of the light guide plate to the front side.

Description

Color filter and display apparatus using the same

The present invention relates to a color filter and a display device employing the same, and more particularly, to a color filter capable of reducing a decrease in transmittance and improving color purity and a display device employing the same.

Display apparatuses employing image panels such as liquid crystal displays (LCDs) have been developed. Color filters are employed to implement color images in these display devices. The color filter passes only light of a specific color among white light, and a plurality of filter areas corresponding to pixels of an image panel are arranged on a substrate. Each of the plurality of filter regions includes, for example, sub-filter regions of red (R: red), green (G: green), and blue (B: blue).

In order to realize high quality image quality in display devices, a color filter having high color purity and high light transmittance is required. In the case of a display device employing a transmissive image panel, in order to increase the color purity of the image, the light quality of the backlight device used as the light source may be increased. That is, the color spectrum of the light irradiated from the backlight device may be improved. Therefore, in the display apparatus employing the transmissive image panel, the color purity of the image is less affected by the color specification of the color filter. However, in the case of a display device employing a reflective image panel using external light as a light source, the color characteristics of the color filter greatly affect the color purity of the image. On the other hand, color purity is proportional to the thickness of the filter region, and light transmittance is inversely proportional to the thickness of the filter region. Therefore, increasing the thickness of the filter region to increase the color purity reduces the light transmittance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a color filter and a display apparatus employing the same, which can reduce a decrease in light transmittance while improving color purity.

In order to achieve the above object, the color filter according to the present invention, the substrate; Metal nanoparticles arranged on the substrate to correspond to the pixels of the image panel to selectively transmit only light of a specific color, and are dispersed in the dispersion medium and the pigment dispersed in the dispersion medium to absorb light of a specific wavelength band by plasmon resonance It includes; a plurality of filter region including a.

In one embodiment, the metal nanoparticles are core-shell structured metal nanoparticles with a metal thin film coated on the surface of the dielectric core.

In one embodiment, the metal nanoparticles have one or more of spherical, rod, wire, and polyhedron.

In one embodiment, the core may include one or more materials selected from dielectric materials such as metal oxides and semiconductor oxides. In one embodiment, the metal thin film may include at least one material selected from Au, Pt, Ag, Al, Cu, Ni, Mo, Cr, or an alloy of these metal particles.

In order to achieve the above object, the display device according to the present invention, a plurality of pixels that can be controlled individually; A color filter having a plurality of filter regions arranged to correspond to the plurality of pixels and selectively transmitting only light of a specific color, wherein the filter regions include a dispersion medium in which pigments are dispersed and a plasmon dispersed in the dispersion medium. It includes metal nanoparticles that absorb light in a specific wavelength band by resonance.

In one embodiment, the metal nanoparticles are core-shell structured metal nanoparticles with a metal thin film coated on the surface of the dielectric core.

In one embodiment, the metal nanoparticles have one or more of spherical, rod, wire, and polyhedron.

In one embodiment, the core may include one or more materials selected from dielectric materials such as metal oxides and semiconductor oxides. In one embodiment, the metal thin film may include at least one material selected from Au, Pt, Ag, Al, Cu, Ni, Mo, Cr, or an alloy of these metal particles.

In one embodiment, the plurality of pixels includes reflective pixels.

In example embodiments, the plurality of pixels may include reflection pixels and transmission pixels that are paired with each other.

As described above, according to the color filter and the display device employing the same according to the present invention, the following effects can be obtained.

First, by dispersing a small amount of metal nanoparticles in a dispersion medium to improve the color characteristics of the color filter to improve the color purity of the light passing through the color filter.

Second, since there is little change in the thickness of the filter region, it is possible to minimize the decrease in the light transmittance.

Third, since the concentration of metal nanoparticles dispersed in the dispersion medium is very small, it is possible to manufacture color filters using metal nanoparticles using conventional color filter manufacturing methods such as pigment dispersion method, printing method and inkjet system. .

Fourth, when the color filter according to the present invention is applied to a reflective display device or a transflective display device, color purity can be improved while minimizing a decrease in brightness. Furthermore, it may not be necessary to provide a structure such as a light hole for improving brightness and white balance in the filter area through which external light passes, thereby simplifying the manufacturing process of the color filter.

Fifth, when the color filter according to the present invention is applied to a transmissive display device, the color characteristic condition required for the light source of the lighting unit is alleviated due to the color purity improvement effect, thereby widening the selection range of the light source and reducing the manufacturing cost. You can get it.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a transmissive display device as an embodiment of a display device according to the present invention. Referring to FIG. 1, the display apparatus includes an image panel 100, an illumination unit 150, and a filter region F. As shown in FIG.

The image panel 100 of this embodiment is a transmissive image panel using liquid crystal. The image panel 100 includes a liquid crystal layer 130 enclosed between two substrates 110 and 120. The liquid crystal layer 130 is divided into a plurality of pixels P that can be individually turned on and off by a pixel electrode, a thin film transistor (TFT), and the like, which are not illustrated in the drawing. The plurality of pixels P pass or block light by the pixel electrode or the TFT. Each pixel P includes, for example, a subpixel P _R (P _G ) P _{B of} red (R), green (G), and blue (B) to implement a color image. The substrate 120 of the image panel 100 is provided with a plurality of filter regions F arranged to correspond to the plurality of pixels P. Each of the plurality of filter regions F has a subfilter region F _R (F _R ) corresponding to the subpixels P _R (P _G ) (P _B ) of red (R), green (G), and blue (B). _G ) (F _B ) is provided.

The lighting unit 150 includes a light source 150 and a light guide plate 152. The light guide plate 152 is a flat member made of a light transmissive material such as PMMA and PC. The light guide plate 152 includes a side surface 153 on which light emitted from the light source 151 is incident, and a front surface 154 and a rear surface 155 that cross the side surface 153. The front 154 and back 155 are positioned to face each other. At least one of the front surface 154 and the rear surface 155 of the light guide plate 152 is provided in the light guide means 156 for guiding the light incident through the side surface 153 to the front surface 154. As the light guide means 156, for example, a scattering pattern, a diffraction pattern, or the like can be employed. The lighting unit 150 is located on the back 101 side of the image panel 100. As the light source 151, a point light source such as an LED light or a line light source such as a cold cathode ray light may be employed. The lighting unit 150 of this type is particularly called a backlight unit.

When the illumination light L1 of the illumination unit 150 enters the filter region F, light of a wavelength band corresponding to each sub filter region F _R (F _G ) (F _B ) is transmitted and the rest is absorbed. Red (R), green (G), and blue (B) lights are formed, respectively. Red (R), green (G), and blue (B) light may or may not pass through the liquid crystal layer 130 because the liquid crystal layer 130 is turned on / off by electrical control. Light transmitted through the liquid crystal layer 130 is emitted through the front surface 102 of the image panel 100. A color image is displayed by this transmitted light.

2 is a cross-sectional view of the reflective display device as one embodiment of the display device according to the present invention. Referring to FIG. 2, the display apparatus of this embodiment does not have the lighting unit 150 shown in FIG. 1, and uses external light L2 as a light source. The image panel 100a of this embodiment is a reflective image panel using liquid crystal. The image panel 100a is the same as the image panel 100 illustrated in FIG. 1 except that the reflective film 140 reflecting light is provided below the liquid crystal layer 130.

When the external light L2 is incident on the filter region F, the light of the wavelength band corresponding to each of the sub filter regions F _R (F _G ) (F _B ) is transmitted and the rest is absorbed, respectively, to red (R). , Green (G) and blue (B) light is formed. Red (R), green (G), and blue (B) light may or may not pass through the liquid crystal layer 130 because the liquid crystal layer 130 is turned on / off by electrical control. Light transmitted through the liquid crystal layer 130 is reflected by the reflective film 140. The reflected light passes through the liquid crystal layer 130 and the filter area F again and exits the front surface 102 of the image panel 100a. A color image is displayed by this reflected light.

3 is a cross-sectional view of the transflective display device as one embodiment of the display device according to the present invention. 3, the image panel 100b of this embodiment is a transflective image panel using liquid crystal. The display device of the present embodiment uses the illumination light (L1) and the external light (L2) by the illumination unit 150 as a light source. The image panel 100b is provided with a reflection area 131 provided with a reflective film 140 for reflecting the external light L1 and a transmission area 132 for transmitting the illumination light L1. The reflection area 131 and the transmission area 132 together with the liquid crystal layer 130 constitute a reflection pixel P1 and a transmission pixel P2. The reflective pixels P1 and the transparent pixels P2 are arranged to be paired with each other. In order to implement a color image, each of the reflective pixel P1 and the transparent pixel P2 is, for example, a subpixel P _R (P _G ) (P _{B of} red (R), green (G), and blue (B). ). The filter region F is provided in the substrate 120. The filter area F includes a reflection filter area F1 corresponding to the reflection area 131 and a transmission filter area F2 corresponding to the transmission area P2. Each sub-filter area corresponding to the red (R), green (G), and blue (B) sub-pixels (P _R ) (P _G ) (P _B ) has a reflection filter area (F1) and a transmission filter area (F2), respectively. (F _R ) (F _G ) (F _B ) is provided.

The illumination light L1 may or may not transmit through the liquid crystal layer 130 because the liquid crystal layer 130 of the transmission region 131 is turned on / off by electrical control. Light transmitted through the liquid crystal layer 130 is incident on the transmission filter region P2. Then, light in the wavelength band corresponding to each of the sub filter regions F _R (F _G ) (F _B ) is transmitted and the rest are absorbed to form red (R), green (G), and blue (B) light, respectively. do. Red (R), green (G), and blue (B) light is emitted through the front surface 102 of the image panel 100b. A color image is displayed by this transmitted light.

The external light L2 incident on the reflective filter area F1 is transmitted through the light of the wavelength band corresponding to each of the sub-filter areas F _R (F _G ) (F _B ), and the rest of the external light L 2 is absorbed and red (R). , Green (G) and blue (B) light is formed. Red (R), green (G), and blue (B) light may or may not pass through the liquid crystal layer 130 because the liquid crystal layer 130 is turned on / off by electrical control. Light transmitted through the liquid crystal layer 130 is reflected by the reflective film 140. The reflected light passes through the liquid crystal layer 130 and the transmission filter region F1 and exits the front surface 102 of the image panel 100b. A color image is displayed by this reflected light.

In the display device employing the color filter, the color characteristics of the color filter are very important for realizing high quality color images. The color filter is referred to as including a substrate and a filter region F arranged on the substrate. The substrate may be the substrates 110 and 120 employed in the image panels 100, 100a and 1100b, and may be separate substrates from those of the substrates 110 and 120. In the color filter, a dispersion medium in which pigments are dispersed is arranged on a substrate so as to correspond to a plurality of pixels of an image panel. The dispersion medium depends on the manufacturing method of the color filter.

For example, the pigment dispersion method or the photolithography method is a method of forming the photosensitive resin layer in which the pigment was disperse | distributed on the board | substrate, and patterning it in a monochrome pattern. By repeating this process three times, a color filter layer of red (R), green (G) and blue (B) is obtained. In this case, a photosensitive dispersion medium such as a photoresist is used as the dispersion medium. Further, by dispersing the pigment in the thermosetting resin and printing the substrate three times, a color filter layer of red (R), green (G), and blue (B) is formed, respectively, and the resin is thermally cured to produce a color filter. In the case of the printing method to manufacture, a thermosetting resin is used as a dispersion medium. Moreover, in the case of the method of manufacturing a color filter using the inkjet system currently developed, the ink of the form which mixed a pigment with binders, such as wax, and disperse | distributed to carriers, such as water or an organic solvent, is used. In this case, the dispersion medium refers to a binder such as wax.

In the case of the reflective display device using the external light L1, the color characteristics of the color filter greatly affect the quality of the color image of the display device. In addition, in the case of a semi-transmissive display device that can display an image by reflection and transmission by using the external light L2 and the illumination light L1 provided from the illumination unit 150, the color characteristics of the color filter are reflected on the reflection. This greatly affects the quality of the displayed image. Because, when natural light is used as the external light L2, since natural light has a very broad spectrum distribution in the visible light region as shown in FIG. 4, the spectrum of the reflected light reflected by the reflective film 140 and passing through the color filter is It depends greatly on the color characteristics of the color filter. Therefore, there is a great need to improve the color characteristics of the color filter. In the case of the transmissive display device, since the light L1 having a very sharp R, G, and B spectrum as shown in FIG. 5 is generally supplied from the illumination unit 150, the influence of the color characteristics of the color filter itself is relatively low. little.

The color purity of the light passing through the color filter is improved as the thickness of the filter region F is increased. 6 is a graph showing a change in light intensity and color purity according to the thickness of the filter region F. FIG. Referring to FIG. 6, when the thickness of the filter region F is increased twice from about 1.47 μm to 2.94 μm, the color purity is increased by about 30%.

However, the light transmittance is inversely proportional to the thickness of the filter region F. FIG. 7 is a graph illustrating a change in light transmittance according to a change in thickness of the filter region F. As shown in FIG. Green light (G) was used for the measurement. In the graph of FIG. 7, the area of the lower area of the measurement line is the total light transmittance. According to the experiment, when the thickness of the filter region F is doubled from about 1.47 μm to 2.94 μm, the total light transmittance is reduced by about 30%.

The decrease in the light transmittance in the display device means that the brightness of the displayed image is reduced. Therefore, it is necessary to improve the color purity without reducing the light transmittance or to minimize the decrease in the light transmittance. In general, in the case of the existing pigment type color filter in which only the pigment is dispersed in the base resin, since the color purity of the color filter is determined by the specification of the pigment, there is no method of adjusting the color purity other than the method of changing the concentration of the pigment. In addition, in the case of the pigment-type color filter, since the color characteristics of the pigments change relatively slowly with respect to the wavelength, there is a limit in improving the color purity only by adjusting the concentration of the pigments. In particular, in the case of the reflective or semi-transmissive display device, the image by reflection is formed by passing the external light L2 twice through the color filter, so when the light transmittance is reduced, the illumination light L1 is transmitted through the color filter only once. The brightness of the image is further lowered as compared with the transmissive display device which forms the device. In the case of the transflective display device, the white balance is not matched because the spectra of the external light L2 and the illumination light L1 are different from each other. In order to compensate for this, a light hole is provided in the reflection filter area F1 through which the reflected light passes, so that the external light L2 is transmitted without being filtered, thereby improving brightness of the image and matching white balance. However, in this case, since the light passing through the light-transmitting region remains the external light L2, the color characteristic of the image formed by reflection becomes worse.

As described above, in order to adjust the concentration of the pigment dispersed in the dispersion medium or to change the thickness of the filter region (F), it is difficult to obtain two effects at the same time: improving color purity and preventing lowering of light transmittance. The color filter according to the present invention is characterized by dispersing metal nanoparticles together with a pigment in a dispersion medium. By using plasmon resonance, which is inherent in metal nanoparticles, only light having a specific wavelength can be absorbed, thereby improving color purity of the color filter without substantially changing the thickness of the filter region F, and reducing light transmittance. .

Light absorption by metal nanoparticles is due to absorption of electromagnetic waves by polarization of metal nanoparticles. When light of a specific wavelength is incident on the surface of the metal nanoparticles, most of the light energy is transferred to free electrons on the surface of the metal to cause resonance, which is called plasmon resonance. The plasmon resonance condition of the metal nanoparticles is obtained from the electrical polarizability of the metal nanoparticles. The following formula applies to spherical metal nanoparticles.

The electrical polarization (α) of the spherical metal nanoparticles is

로 표시된다.

Is displayed.

을 만족하는 파장영역에서 광흡수가 일어나게 된다. Where ε is the dielectric constant of the metal nanoparticles and ε _m is the dielectric constant of the medium surrounding the metal nanoparticles. Since the dielectric constant is a function of wavelength,

The absorption of light occurs in the wavelength region satisfying.

Metal particles that can be used to improve the color purity of color filters should have absorption characteristics in the vicinity of visible light. Such metal nanoparticles include, for example, Au, Pt, Ag, Al, Cu, Ni, Mo, Cr, or alloys of these metal particles.

As shown in FIG. 8, silver (Ag) nanoparticles having a particle diameter of about 10 nm have absorption characteristics in an ultraviolet region having a wavelength of about 350 nm, so that silver nanoparticles may be absorbed in order to improve color purity of a color filter. You need to shift the band slightly. As shown in FIG. 9, a thin film of silver is coated on the surface of the dielectric core 21 to form metal nanoparticles having a core-shell structure in which a shell 22 is formed. The plasmon resonance condition of the metal nanoparticles of the core-shell structure is obtained from the electrical ploarizability of the metal nanoparticles of the core-shell structure. The following formula applies to spherical metal nanoparticles.

Here, the resonance condition is

)인 경우에는

,Thick shell (

)

,

가 된다.For thin shells (p << 1)

Becomes

r ₁ is the radius of the core 21, r ₂ is the radius of the metal nanoparticles including the shell 22, ε ₁ is the dielectric constant of the core 21, ε ₂ is the dielectric constant of the shell 22, ε ₃ silver metal The dielectric constant of the medium surrounding the nanoparticles.

10 shows absorption characteristics of metal nanoparticles having a core-shell structure of SiO ₂ -Ag. Referring to Figure 10, the absorption at about 635nm wavelength range of the visible light range in the case of the metal nano-particles coated with Ag to 2nm thick SiO ₂ cores coated with Ag to a 1nm thick metal nanoparticles and 20nm in diameter on SiO ₂ core of 10nm diameter It can be seen that it has characteristics. Therefore, metal nanoparticles having a core-shell structure may be used to improve color purity of the color filter.

As another example, FIG. 11 shows about 50 metal nanoparticles of SiO ₂ -Ag core-shell structure coated with silver having a thickness of about 2 to 5 nm on a 10 nm SiO ₂ spherical core in the filter regions F _G and F _B. It is a graph which shows the light transmittance at the time of disperse | distributing about / micrometer <^3> . In FIG. 11, the solid line indicates the light transmittance of the conventional pigment type color filter, and the dotted line indicates the light transmittance when the metal nanoparticles of the core-shell structure are dispersed. Fig. 12 is a graph showing the color gamut in this case. Referring to FIG. 11, it can be seen that the bandwidths of the green light G and the blue light B are narrowed by the light absorption of the metal nanoparticles. In FIG. 12, S _NTSC denotes NTSC standard color coordinate, S ₁ denotes color coordinate when a conventional pigment-type color filter is adopted, and S ₂ denotes about 50 nanoparticles of SiO ₂ -Ag core-shell structured metal nanoparticles. The color coordinates at the time of dispersing to about ³ are displayed. The color purity may be expressed as the ratio of the inner area of the color coordinates S ₁ (S ₂ ) to the inner area of the color coordinates S _NTSC . According to the experiment of FIG. 12, S ₁ / S _NTSC is about 44.7%, and S ₂ / S _NTSC is about 59.2%. Therefore, it can be seen that the color purity is improved by about 30% or more. The total light transmittance can be seen by comparing the area of the bottom area of the solid line and the area of the bottom area of the dotted line in FIG. 11, which is reduced by about 10%. Accordingly, the color purity can be improved by about 30% without increasing the thickness of the filter region F of the color filter. Considering that the light transmittance is reduced by about 30% when the thickness of the filter area F is doubled to improve the color purity by about 30%, the color purity improvement effect of the present experiment is very satisfactory.

In the present experiment, the effect of improving color purity was confirmed using SiO ₂ -Ag core-shell metal nanoparticles, but the scope of the present invention is not limited thereto. In addition to silver (Ag), for example, Au, Pt, Ag, Al, Cu, Ni, Mo, Cr, or an alloy of these metal particles may be used as the metal forming the shell. As the core, various dielectric materials such as metal oxides such as Si and TiO ₂ and semiconductor oxides can be used. In addition, the light absorption band of the metal nanoparticles depends on the type, size, shape, concentration, etc. of the metal particles. Therefore, in order to adjust the color purity and the light transmittance of the color filter within a desired range, It will be understood by those skilled in the art that various changes in size, shape, and concentration can be made. In addition, it will be understood by those skilled in the art that not only spherical but also various types of metal nanoparticles such as rod, wire, and polyhedron may be employed.

The above embodiments are merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the invention described in the claims below.

1 is a cross-sectional view showing the structure of a transmissive display device as one embodiment of a display device according to the present invention;

2 is a cross-sectional view showing the structure of a reflective display device as one embodiment of the display device according to the present invention;

3 is a cross-sectional view showing the structure of a transflective display device as one embodiment of the display device according to the present invention;

4 is a graph showing a relationship between illumination light and color characteristics of a color filter.

5 is a graph showing a relationship between natural light and color characteristics of a color filter;

6 is a graph showing a change in light intensity and color purity according to the change in the thickness of the filter region.

7 is a graph showing the change in light transmittance according to the change in the thickness of the filter region.

8 is a graph showing the light absorption characteristics of silver nanoparticles.

9 illustrates metal nanoparticles having a core-shell structure.

10 is a graph showing light absorption characteristics of silver nanoparticles having a core-shell structure.

FIG. 11 is a graph showing the light transmittance of a color filter when silver nanoparticles having a core-shell structure are employed. FIG.

12 is a color coordinate graph showing color purity of a color filter when silver nanoparticles having a core-shell structure are employed.

<Explanation of symbols for the main parts of the drawings>

21 ...... Core 22 ...... Shell

100, 100a, 100b ...... Image Panel 101 ...... Front of Image Panel

102 ...... Back of image panel 110.120 ...... Substrate

130 ...... Liquid crystal layer 131 ...... Reflection zone

132 ...... Transmission area 140 ...... Reflective film

150 ...... Lighting unit 151 ...... Light source

152 ... light guide plate 153 ... side of the light guide plate

154 ...... The front of the light guide plate 155 ...... The back of the light guide plate

156 ...... Light guide P ...... pixel

P1 ...... reflective pixel P2 ...... transmissive pixel

P _R , P _G , P _B ... Subpixel F ... Filter Area

F1 ...... reflection filter area F2 ...... transmission filter area

F _R , F _G , F _B ... sub filter area

Claims (12)

Board; Metal nano-arrays arranged on the substrate to correspond to the pixels of the image panel to selectively transmit only light having a specific color, and are dispersed in the dispersion medium and metal nano-particles dispersed in the dispersion medium to absorb light of a specific wavelength band by plasmon resonance. And a plurality of filter regions including particles. The method of claim 1, The metal nanoparticle is a color filter, characterized in that the metal nanoparticles of the core-shell structure is coated with a metal thin film on the surface of the dielectric core. The method of claim 2, The core is a color filter, characterized in that it comprises one or more materials selected from dielectric materials, such as metal oxide, semiconductor oxide. The method of claim 2, The metal thin film is a color filter, characterized in that it comprises at least one material selected from Au, Pt, Ag, Al, Cu, Ni, Mo, Cr, or alloy of these metal particles (alloy). The method according to any one of claims 1 to 4, The metal nanoparticle is a color filter, characterized in that it has a form of one or more of spherical, rod, wire, polyhedron. A plurality of pixels that can be individually controlled; And a color filter arranged to correspond to the plurality of pixels and having a plurality of filter regions for selectively transmitting only light of a specific color. The filter area, A display device comprising a dispersion medium in which a pigment is dispersed and metal nanoparticles dispersed in the dispersion medium and absorbing light of a specific wavelength band by plasmon resonance. The method of claim 6, And the metal nanoparticles are core-shell structured metal nanoparticles with a metal thin film coated on a surface of the dielectric core. The method of claim 7, wherein And the core comprises at least one material selected from dielectric materials such as metal oxide and semiconductor oxide. The method of claim 7, wherein The metal thin film includes at least one material selected from Au, Pt, Ag, Al, Cu, Ni, Mo, Cr, or an alloy of these metal particles. The method according to any one of claims 6 to 9, The metal nanoparticle is a display device, characterized in that it has a form of one or more of spherical, rod-shaped, wire-like, polyhedron. The method according to any one of claims 6 to 9, And the plurality of pixels include reflective pixels. The method according to any one of claims 6 to 9, And the plurality of pixels includes a reflective pixel and a transparent pixel that are paired with each other.

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