JP2006110808A - Radio-wave transmissible wavelength selection plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio-wave transmissible wavelength selection plate suitable as window glass for an automobile and window glass for a building, which is constituted so as to reduce the reflectivity against the radio wave of the frequency band of TV broadcasting, satellite broadcasting and a portable telephone and as a sufficient solar radiation shielding capacity and a visible light transmissivity reduced in irregular reflection and excellent in perspective properties. <P>SOLUTION: The radio-wave transmissible wavelength selection plate is constituted by forming a transparent dielectric layer on a transparent substrate and forming Ag fine particles 1 on the transparent dielectric layer and characterized in that each of the Ag fine particles has apex parts at least at two places, the height of the apex parts is 8-150 nm, the diameter of the circumcircle of the Ag fine particles is 100-600 nm and the ratio of the coating area of the Ag fine particles to the surface area of the transparent substrate is 0.2-0.8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention is a radio wave transmission wavelength selection plate that can efficiently transmit radio waves and visible light arriving on a window glass of a building, an automobile, etc., and exhibit sufficient heat insulation by reflecting solar heat rays. It relates to a manufacturing method.

  In recent years, for the purpose of shielding solar radiation, a window glass coated with a conductive thin film or a window glass attached with a film coated with a conductive thin film has begun to spread.

  If such a window glass is constructed in a high-rise building, it will cause radio waves in the TV frequency band to be reflected and cause ghosts on the TV screen. Furthermore, it becomes difficult to receive satellite broadcasts using an antenna provided indoors.

  Further, when used as a window glass for a house or a window glass for an automobile, communication by a mobile phone may be difficult. Moreover, it became the cause of reducing the gain of the glass antenna provided in the indoor antenna and the window glass of the vehicle.

  Under such circumstances, at present, a transparent heat ray reflective film having a relatively high electrical resistance is coated on a glass substrate to transmit a part of visible light and reduce radio wave reflection to prevent radio interference. Has been done.

  For example, in the case of glass with a conductive film, the length of the conductive film parallel to the direction of the electric field of the incident radio wave is 1/20 times or less the wavelength of the radio wave. It is known to divide into two to prevent radio interference (Patent Document 1).

  However, the method of coating a transparent heat ray reflective film having a relatively high electrical resistance can reduce radio wave reflection and prevent radio wave interference, but the heat ray shielding performance is not sufficient, and the comfort of life. There was a problem.

  Patent Document 1 discloses a method of dividing a conductive film. The splitting length is much larger than the wavelengths of visible light and near-infrared light that occupy most of the sunlight, so all of this light is reflected, preventing radio interference and having sufficient solar radiation shielding performance. Although a transmissive wavelength selective screen glass can be obtained, there is a problem in that visible light transparency cannot be secured. Furthermore, in a large window such as the size of the opening of 2 m × 3 m, for example, in order to transmit satellite broadcast waves, 1/20 of the wavelength of satellite broadcast is about 1/20, at least the conductive film is 1.25 mm square, Preferably it must be cut to 0.5 mm square. In order to cut a large-area conductive film into such small segments with, for example, an yttrium-aluminum-garnet laser, there is a problem that it takes a long time and is not practical.

  Therefore, the present inventors have proposed a radio wave transmission wavelength selection plate in which fine particles made of Ag are formed on a transparent substrate (Patent Document 2).

  In the radio wave transmission wavelength selection glass formed by forming granular Ag on a transparent substrate as shown in Patent Document 2, in order to increase the near-infrared shielding coefficient (Es) defined by the equation (1), the spectral reflectance is increased. When the maximum wavelength (hereinafter abbreviated as the resonance wavelength) is shifted to a range of 600 nm to 1500 nm, there is a problem that the spectral reflectance is lowered in the entire wavelength region.

Where λ is the wavelength of the electromagnetic wave incident on the film surface
Rdp: reflectance of film surface at wavelength λ
JP-A-6-40752 JP 2000-281388 A

In order to increase the area ratio, the present inventors have found that the above-mentioned problem is caused by the small proportion of the area occupied by the bottom surface of the fine particles (hereinafter abbreviated as area ratio) of about 0.25. Japanese Patent Application No. 2003-107752 proposes a method in which an Ag layer is laminated on Ag fine particles on the surface of a transparent substrate and then heat treatment is performed to form fine particles made of only Ag around Ag fine particles.

  In the proposal of Japanese Patent Application No. 2003-107752, in a radio wave transmission wavelength selection glass formed by forming Ag fine particles on a transparent substrate, a wavelength (maximum spectral reflectance) in order to increase the near-infrared shielding coefficient (Es) ( In the following, the abbreviated resonance wavelength is required to be in the range of 600 nm to 1500 nm, and the particle size of the Ag fine particles has been increased. There was a problem of becoming.

  The radio wave transmission wavelength selection plate of the present invention is a radio wave transmission wavelength selection plate in which a layer of Ag fine particles is formed on a transparent substrate. A dielectric layer is formed on the transparent substrate, and Ag is formed on the transparent dielectric layer. Fine particles are formed, the Ag fine particles have at least two vertex portions, the height of the vertex portions is in the range of 8 to 150 nm, and the diameter of the circumscribed circle of the Ag fine particles is in the range of 100 nm to 600 nm. In the radio wave transmission wavelength selection plate, the ratio of the coated area of the Ag fine particles to the surface area of the transparent substrate is in the range of 0.2 to 0.8.

  Further, in the radio wave transmission wavelength selection plate of the present invention, when the Ag fine particle has three or more apex portions in the radio wave transmission wavelength selection plate, one apex portion of the Ag fine particle is adjacent to the apex portion. The radio wave transmission wavelength selection plate is characterized in that an angle formed by two straight lines connecting two vertex portions is 60 degrees or more.

  The radio wave transmission wavelength selection plate of the present invention is characterized in that, in the radio wave transmission wavelength selection plate, the diffuse reflection ratio (Hr) defined by the equation (2) is 0.1 or less. It is a selection board.

Here, Rn is a regular reflectance on the Ag fine particle layer side at a wavelength of 550 nm, Rt is a reflectance including irregular reflection on the Ag fine particle layer side at a wavelength of 550 nm, and the radio wave transmission wavelength selection plate of the present invention is the radio wave transmission plate. An electromagnetic wave wavelength selective plate, wherein the electromagnetic wave is incident on the surface of the layer made of Ag fine particles, and the near infrared ray shielding coefficient (Es) is set to 0.3 or more.

  The radio wave transmission wavelength selection plate according to the present invention reduces the reflectivity with respect to radio waves in the frequency bands of TV broadcast, satellite broadcast, and mobile phone, and has a sufficient solar shading performance and a low visibility and excellent visibility. Provided is a radio wave transmissive wavelength selection plate having light transmittance and suitable as a window glass for automobiles and window glass for buildings.

  As the transparent substrate used in the present invention, a glass substrate, a transparent ceramic substrate, a heat-resistant transparent plastic substrate or the like can be used, and when the radio wave transmitting wavelength selection plate of the present invention is used for a building or a vehicle opening, Although a glass substrate is desirable, it is preferable to select a glass substrate, a transparent ceramic substrate, a heat-resistant transparent plastic substrate, or the like according to the place of use.

  FIG. 1 is a cross-sectional view showing a configuration of a radio wave transmission wavelength selection plate of the present invention. The transparent dielectric layer 2 is formed on the transparent substrate 5, and the Ag fine particle layer 3 is formed on the transparent dielectric layer 2.

  As the transparent dielectric layer 2, Al, Si, Ti, Ta, Ge, In, W, V, Mn, Cr, Ni, nitride of any metal of stainless steel, Al, Si, Zn, Sn, Ti , Ta, Ge, In, W, V, Mn, Cr, Ni, an oxide of any metal of stainless steel, or a laminate of these in multiple layers can be used.

  In particular, Al and Si metal nitrides and Al, Si, Zn, Sn, Ti, Ta, and In metal oxides are colorless and transparent, so a radio wave transmission wavelength selection plate with high visible light transmittance is required. It is suitable for architectural and vehicle window glass.

  When the transparent dielectric layer 4 is further coated on the Ag fine particles, the visible light transmittance is increased by the interaction with the transparent dielectric layer 4 formed on the transparent substrate, and the Ag granular layer is prevented from being altered. The transparent dielectric layer 4 used in this case is preferably an Al, Si nitride, Al, Si, Zn, Sn, Ti, Ta, In oxide, or these It is desirable to laminate a plurality of layers.

  As a method for forming the transparent dielectric layer 4, a film forming method such as sputtering, vacuum deposition, CVD, or ion plating is used. In particular, the DC magnetron sputtering method is preferable from the viewpoint of the uniformity and productivity of the generated layer.

  Ag fine particles are formed by heating the Ag film formed on the transparent dielectric layer 2 so that at least two Ag fine particles having a shape obtained by cutting out a sphere or an ellipsoid by a plane overlap each other. Ag fine particles having the shape they have are formed. 2A is a schematic diagram when Ag fine particles are observed from the normal direction of the transparent substrate, and FIG. 1B shows a vertical section taken along the line aa ′ of FIG. In FIG. 1B, P1 and P2 indicate the apex portions of the Ag fine particles, and h1 and h2 indicate the height of the Ag fine particles.

  The shape of the Ag fine particles is a combination of fine particles of a shape obtained by cutting out a sphere as shown in FIG. 2 in a plane, and a combination of dome-shaped, flat, scale-like, and needle-shaped fine particles. From the viewpoint of excellent performance, Ag fine particles having a shape obtained by cutting off a sphere in a plane, a dome shape, a flat shape, or a scale-like Ag particle are preferable.

  FIG. 3 schematically shows an example of Ag fine particles having three or more apexes. The vertex portions adjacent to the vertex portion of P5 are P4 and P6, and the angle formed by two straight lines connecting the two vertex portions adjacent to the vertex portion P5 is θ.

  In order that the Ag fine particles of the present invention have radio wave transmission performance, it is desirable that θ be 60 degrees or more.

  In the present invention, the shape control of the Ag fine particles shown in FIG. 2 is facilitated. As a result, the radio wave transmission wavelength selection plate of the present invention allows the resonance wavelength to be reduced without increasing the irregular reflection ratio defined by Equation (1). It is possible to set the infrared shielding coefficient in the range of 600 nm to 1500 nm, and a radio wave transmitting wavelength selection plate having excellent heat insulation can be obtained.

  The radio wave transmitting wavelength selection plate of the present invention is composed of Ag fine particles having a large number of Ag fine particle surfaces parallel to the transparent substrate, and the height of the vertex of the particles is smaller than the diameter of the circumscribed circle. As a result, the radio wave transmission wavelength selection plate of the present invention is designed so that the resonance wavelength falls within the range of 600 nm to 1500 nm having a large near-infrared shielding coefficient without increasing the irregular reflection ratio defined by the equation (1). Thus, a radio wave transmissive wavelength selection plate having excellent heat insulation can be obtained.

  When an Ag continuous film directly formed on a transparent substrate is heated, Ag atoms in the film move to a site where the surface energy per unit volume is small. As a result, a defect site is generated in the continuous film, and changes to a mesh-like layer. Further, when the heating is continued, it changes to Ag fine particles having at least two apexes, and finally independent grains are generated. Since this particle shape change is completed within a very short time, it was very difficult to form Ag fine particles having two or more apexes.

  The radio wave transmission wavelength selection plate of the present invention is formed by laminating an Ag film on a dielectric film having a higher affinity with an Ag film than a transparent substrate, for example, a titanium oxide film, so that Ag atoms in the Ag film are heated. It is found that the speed of movement to a site with low energy is reduced, and it is possible to obtain Ag fine particles having two or more apexes relatively easily.

  The number of granular Ag per unit area can be controlled by the film thickness of the transparent dielectric film, and the particle diameter of the Ag fine particles can be controlled by the film thickness of the Ag film laminated on the transparent dielectric film. Therefore, the number of granular Ag per unit area is preferably controlled by the film thickness of the transparent dielectric film. Furthermore, the particle diameter of the Ag fine particles is preferably controlled by the film thickness of the Ag film laminated on the transparent dielectric film.

    In addition, although the preferable particle height of Ag microparticles | fine-particles is 8 nm-150 nm, it is not limited to these. The diameter of the circumscribed circle of the Ag fine particles is preferably 100 nm to 600 nm. The particle height is the height of the apex portion of the Ag fine particles in FIG.

  The Ag film preferably has a thickness in the range of 5 nm to 1 μm. If the thickness is less than 5 nm, the Ag film becomes island-like and is not uniformly formed. This is not preferable, and if it exceeds 1 μm, it is difficult to form in a granular form at a heating temperature below the softening point of the transparent substrate.

  A method for forming the Ag film is not particularly limited, and a film forming method such as a sputtering method, a vacuum evaporation method, a CVD method, or an ion plating method can be used. In particular, the DC magnetron sputtering method is preferable from the viewpoint of the uniformity and productivity of the generated layer.

  The Ag film can be heated by resistance heating, gas combustion heating, irradiation with a beam such as a laser or an electron beam, or induction heating.

  When a heat-resistant transparent plastic is used as a transparent substrate, heating with a laser beam that is hardly absorbed by the transparent substrate, or induction heating that can selectively heat only a conductive substance are suitable heating methods.

  In addition, about heating conditions, it is preferable that heating temperature shall be 150 degreeC or more and below the temperature which a transparent substrate does not soften.

  When the transparent substrate on which the Ag film is formed is heated in, for example, a heating furnace, it is desirable to set the temperature to 150 ° C. or higher in order to form granular Ag alloy or Ag fine particles in several hours.

  When the temperature of the transparent substrate exceeds the softening point, particularly when oxide glass is used for the transparent substrate, Ag atoms diffuse into the transparent substrate, and the wavelength selectivity due to the reflection of electromagnetic waves is significantly reduced.

  Note that when the Ag film is irradiated by laser or electron beam irradiation or induction heating, the Ag film can be selectively heated without heating the transparent substrate. Therefore, the upper limit of the heating temperature is set to the boiling point 2212 of Ag. It can be set to ° C.

  In addition, the heating time is preferably several seconds to several hours in the case of resistance heating or gas combustion heating, and is preferably from microseconds to several seconds in the case of irradiation with a beam such as a laser or an electron beam or induction heating. In addition, you may cool by forced cooling, such as cooling by natural cooling or blowing air after heating.

  Further, the radio wave transmission wavelength selection plate of the present invention selectively reflects near infrared rays by controlling the particle size, number, distribution, etc. of Ag fine particles according to the thickness of the Ag film, the thickness of the transparent dielectric film, and the heating conditions. To do. The number may be grasped as a ratio of the occupied area of the substrate surface to the particle diameter.

  In order to selectively reflect near-infrared rays, the near-infrared shielding coefficient (Es) defined by equation (2) is preferably 0.3 or more. In order to set the near-infrared shielding coefficient to 0.3 or more, the wavelength at which the spectral reflectance of the radio wave transmission wavelength selection plate is maximized is preferably in the wavelength range of 600 nm to 1500 nm. The diameter is controlled, and the diameter of the circumcircle of the Ag fine particles is preferably in the range of 100 nm to 600 nm. Furthermore, the occupation area ratio is preferably in the range of 0.2 to 0.8.

  When the occupied area ratio of Ag fine particles is less than 0.2, the average distance between the granular Ags is more than twice the particle size, the mutual interference between the particles is reduced, and the radio wave transmission wavelength having an effective near-infrared shielding coefficient The selection board cannot be obtained.

  Further, when the diameter of the circumscribed circle of the Ag fine particles is less than 100 nm, the maximum value of the spectral reflectance becomes 600 nm or less. When it exceeds 600 nm, the maximum value of the spectral reflectance becomes 1500 nm or more, and the near-infrared shielding efficiency is drastically reduced.

  When the occupied area ratio exceeds 0.8, most of the Ag fine particles are in a chain, and the wavelength selection function of transmitting radio waves is lost.

  The occupied area ratio of the Ag fine particles is obtained, for example, by obtaining a photograph (hereinafter referred to as SEM image) observed with a field emission scanning electron microscope (FE-SEM) from the normal direction of the transparent substrate, and the Ag fine particles and the Ag fine particles are not present. The SEM image can be binarized by image processing with respect to the surface of the substrate, and the total area of the Ag fine particles can be divided by the area of the entire SEM image.

  Further, the particle diameter of the Ag fine particles is obtained by obtaining the number of Ag fine particles from an image obtained by binarizing the SEM image, dividing the total area of the Ag fine particles by the number, and obtaining the obtained area as a circle having the same area. The diameter of the circle may be the particle diameter of the Ag fine particles.

  Therefore, for example, when the shape of the Ag fine particles is a dome shape, the particle size corresponds to the diameter of the bottom surface of the dome.

  In the radio wave transmission wavelength selection plate of the present invention, it is preferable to provide a transparent dielectric layer on the upper layer of the Ag fine particles.

  When a transparent dielectric layer is provided on the upper layer of the Ag fine particles, after forming the Ag fine particles, the transparent dielectric layer is laminated on the Ag fine particles.

Example 1
The radio wave transmission wavelength selection plate of the present invention was manufactured by the following procedure. A float glass plate was used as the transparent substrate.

(1) First, the washed 3 mm thick float glass plate was put in a DC magnetron sputtering apparatus and evacuated until the degree of vacuum in the tank reached 2-4 × 10 ⁻⁴ Pa. The distance between the target and the glass substrate was 90 mm.

    (2) Next, a Ti target (diameter: 152 mm, thickness: 5 mm) was applied with a power of DC 200 W and discharged to form a 100 nm-thick titanium oxide film. During the film formation, the pressure of the mixed gas of Ar and oxygen was controlled to 1 Pa.

    (3) Next, an Ag target (diameter: 152 mm, thickness: 5 mm) was applied with a power of DC 30 W and discharged to form an Ag film having a thickness of 12.7 nm. During the film formation, the Ar gas pressure was controlled to 1 Pa.

    (4) Next, the transparent substrate on which the titanium oxide film and the Ag film are laminated is heated in a constant temperature oven at 550 ° C. for 5 minutes, and then taken out of the furnace and allowed to cool. Formed.

  The spectral reflectance and the spectral transmittance of the radio wave transmission wavelength selection plate obtained in the wavelength range of 300 to 2500 nm were measured using a Hitachi U-4000 type self-recording spectrophotometer. Furthermore, the measured value was substituted into Formula (2), and the near-infrared shielding coefficient was calculated.

  As a result, a favorable wavelength selection plate having a resonance wavelength of 875 nm, a near-infrared shielding coefficient as large as 0.45, an irregular reflection ratio of 0.01, and a visible light transmittance of 55% was obtained.

  Furthermore, the form of Ag fine particles produced | generated on the titanium oxide film | membrane was observed using Hitachi S-4500 type | mold FE-SEM.

  As a result, the Ag fine particles were Ag fine particles having two or more apexes, and the area ratio of the fine particles was 0.48. The height of the particles was 20 nm to 80 nm, and the path length of the induced current was in the range of 100 nm to 350 nm.

Comparative Example 1
The radio wave transmission wavelength selection plate of the present invention was manufactured by the following procedure. A float glass plate was used as the transparent substrate.

(1) First, the washed 3 mm thick float glass plate was put in a DC magnetron sputtering apparatus and evacuated until the degree of vacuum in the tank reached 2-4 × 10 ⁻⁴ Pa. The distance between the target and the glass substrate was 90 mm.

  (2) Next, four Pd chips (10 mm × 10 mm × 1 mm rectangular parallelepiped) were placed at equal intervals in the erosion region of the Ag target (diameter 152 mm, thickness 5 mm). The target was applied with a power of DC 30 W and discharged to form an Ag—Pd mixed film having a thickness of 13 nm. During the film formation, the Ar gas pressure was controlled to 1 Pa.

  (3) Next, the transparent substrate on which the Ag mixed film is formed is heated in a constant temperature oven with an atmospheric temperature of 500 ° C. for 5 minutes, and then taken out of the furnace and allowed to cool, whereby a granular Ag alloy is formed on the surface of the transparent substrate. Formed.

  (4) Next, an Ag target (diameter: 152 mm, thickness: 5 mm) was applied with electric power of DC 30 W and discharged, and an Ag film having a thickness of 13 nm was laminated on the granular Ag alloy. The atmosphere during film formation was Ar gas having a pressure of 1 Pa.

  (5) Next, the laminated Ag film was heated for 5 minutes in a constant temperature furnace having an atmospheric temperature of 450 ° C., then taken out of the furnace and allowed to cool to produce Ag fine particles on the surface of the substrate glass.

  (6) Next, the steps (4) and (5) were repeated two more times to increase the particle size L and height of the Ag fine particles.

  As a result, Ag fine particles composed of hemispherical isolated particles were generated, and the resonance wavelength was 720 nm and the near-infrared shielding coefficient was as high as 0.51. However, the irregular reflection ratio was as high as 0.63, and a good wavelength selection plate could not be obtained.

  In Example 1, the wavelength selection plate having a low haze value and a high near-infrared shielding coefficient was obtained by shifting the resonance wavelength to a range of 600 nm to 1500 nm while suppressing the irregular reflection ratio to 0.1 or less. However, in the case of Comparative Example 1, a wavelength selection plate having a high near-infrared shielding coefficient could be produced, but a plate having a low haze value was not obtained.

It is sectional drawing which shows the structure of a radio wave transmissive wavelength selection board typically. It is a schematic diagram which shows the shape of Ag fine particle with two vertex parts. It is a top view which shows typically the shape of Ag microparticles | fine-particles of three or more vertex parts.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ag fine particle 2 Transparent dielectric material layer 3 Ag fine particle layer 4 Transparent dielectric material layer 5, 5 'Transparent substrate

Claims (4)

In a radio wave transmission wavelength selection plate in which a layer of Ag fine particles is formed on a transparent substrate, a dielectric layer is formed on the transparent substrate, Ag fine particles are formed on the transparent dielectric layer, and the Ag fine particles are It has at least two apex portions, the apex height is in the range of 8 to 150 nm, the diameter of the circumscribed circle of the Ag microparticles is in the range of 100 to 600 nm, and the Ag microparticles have a surface area of the transparent substrate. A radio wave transmission wavelength selection plate, wherein the ratio of the covering area is in the range of 0.2 to 0.8. 2. The radio wave transmission property according to claim 1, wherein when the Ag fine particle has three or more apexes, an angle of a straight line connecting the three nearest apexes of the Ag fine particle is 60 degrees or more. Wavelength selection plate. 3. The radio wave transmissive wavelength selective plate according to claim 1, wherein an irregular reflection ratio (Hr) defined by the equation (2) is 0.1 or less. 4.

Here, Rn is a regular reflectance on the Ag fine particle layer side at a wavelength of 550 nm, and Rt is a reflectance including irregular reflection on the Ag fine particle layer side at a wavelength of 550 nm. The radio wave transmissive wavelength selection plate according to any one of claims 1 to 3, wherein a near-infrared shielding coefficient (Es) is 0.3 or more.

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