JP2017090530A - Dispersion for electromagnetic wave adjustment and electromagnetic wave adjustment element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion for wave adjustment and a wave adjustment element which can adjust the absorption wavelength of electromagnetic waves.SOLUTION: The present invention provides a dispersion for wave adjustment that has metal particles with a major axis length of 10 nm-200 nm and a minor axis length of 50 nm or less, and an aspect ratio (major axis length/minor axis length) of 2 or more, and a dispersion medium.SELECTED DRAWING: None

Description

  The present invention relates to an electromagnetic wave adjusting dispersion and an electromagnetic wave adjusting element.

  From the viewpoints of energy saving, privacy protection, anti-glare and the like, there is an increasing interest in electromagnetic wave adjusting elements that can electrically control the transmittance or scattering intensity of electromagnetic waves such as visible light and near infrared rays. So far, electromagnetic wave adjusting elements of the type using electrochromic, liquid crystal, particle dispersion, etc. have been studied and put into practical use.

  Among the above, the type using the particle dispersion liquid allows transmission of electromagnetic waves by changing the state of the particles in the dispersion liquid between a randomly dispersed state and a state oriented along the electric field by applying a voltage. It is what controls the rate. For example, Patent Document 1 discloses a method of controlling the visible light transmission state by applying a voltage to a dispersion liquid containing needle-like particles containing iodine to change the state of particle orientation.

JP 2002-189123 A

  In the method described in Patent Document 1, the electromagnetic wave adjusting element in a light-shielded state exhibits blue, but since particles containing iodine are used as means for electromagnetic wave adjustment, it is difficult to change to a color tone other than blue. For this reason, in responding to diversification of uses of the electromagnetic wave adjusting element, it is useful to develop a technology capable of controlling the color tone in a light-shielded state. In addition, it is useful to develop a technique capable of controlling the absorption of electromagnetic waves having a desired wavelength as well as visible light.

  In view of the above circumstances, an object of the present invention is to provide a dispersion for electromagnetic wave adjustment and an electromagnetic wave adjustment element capable of controlling the absorption wavelength of electromagnetic waves.

Means for solving the above problems include the following embodiments.
<1> a metal particle having a major axis length of 10 nm to 200 nm, a minor axis length of 50 nm or less, and an aspect ratio (major axis length / minor axis length) of 2 or more; A dispersion for electromagnetic wave adjustment, comprising a dispersion medium.
<2> The electromagnetic wave dispersion according to <1>, wherein the metal particles include at least one selected from the group consisting of Ag, Au, and Cu.
<3> The electromagnetic wave dispersion according to <1> or <2>, wherein the metal particles have an insulating film on at least a part of a surface thereof.
<4> The dispersion medium for electromagnetic wave adjustment according to any one of <1> to <3>, wherein the dispersion medium has a viscosity at 25 ° C. of 1 mPa · s to 5000 mPa · s.
<5> The dispersion medium for electromagnetic wave adjustment according to any one of <1> to <4>, wherein the dispersion medium has a refractive index at 25 ° C. of 1.33 to 1.58.
<6> The electromagnetic wave adjusting device according to any one of <1> to <5>, further including a matrix resin, wherein the dispersion medium including the metal particles is present in the matrix resin in the form of droplets. Dispersion.
<7> An electromagnetic wave adjustment comprising: a pair of conductive base materials; and the electromagnetic wave adjustment dispersion according to any one of <1> to <6> disposed between the pair of conductive base materials. element.
<8> The electromagnetic wave adjusting element according to <7>, having an insulating layer between the conductive substrate and the electromagnetic wave adjusting dispersion.

  ADVANTAGE OF THE INVENTION According to this invention, the dispersion | distribution for electromagnetic waves adjustment and electromagnetic wave adjustment element which can control the absorption wavelength of electromagnetic waves are provided.

It is a figure which shows notionally an example of the spectral distribution by the surface plasmon absorption of a metal particle. It is a figure which shows notionally an example of the structure of an electromagnetic wave adjustment element. ₂ is an example of a STEM photograph (bright field image) of the SiO ₂ nanotube obtained in Example 1. FIG. ₂ is an example of a STEM photograph (dark field image) of a SiO ₂ nanotube having an Au nucleus inside obtained in Example 1. FIG. ₂ is an example of a STEM photograph (bright field image) of Ag particles having an SiO ₂ layer obtained in Example 1. FIG. It is a graph showing evaluation results of the electromagnetic adjusting characteristics was performed using the Ag particles having an SiO ₂ layer obtained in Example 1. It is a graph showing evaluation results of the electromagnetic adjusting characteristics was performed using the Ag particles having an SiO ₂ layer obtained in Example 2.

Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless explicitly specified, unless otherwise clearly considered essential in principle. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.
In this specification, the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.
In the present specification, the numerical ranges indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. Good. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In the present specification, the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. It means the content rate of.
In the present specification, the particle diameter of each component in the composition is a mixture of the plurality of types of particles present in the composition unless there is a specific indication when there are a plurality of types of particles corresponding to each component in the composition. Means the value of.
In this specification, the term “layer” or “film” refers to a part of the region in addition to the case where the layer or the film is formed when the region where the layer or film exists is observed. It is also included when it is formed only.

<Dispersion for electromagnetic wave adjustment>
The electromagnetic wave adjusting dispersion of the present embodiment (hereinafter also simply referred to as a dispersion) has a major axis length of 10 nm to 200 nm, a minor axis length of 50 nm or less, and an aspect ratio (major axis length). Metal particles having a length / length of a short axis of 2 or more and a dispersion medium.
The metal particles used in this embodiment exhibit electromagnetic wave absorption by surface plasmons by having a size on the order of nanometers. In this embodiment, this phenomenon is used to control the transmittance of electromagnetic waves incident on the dispersion. Furthermore, by setting the aspect ratio of the metal particles to 2 or more, the degree of electromagnetic wave absorption by the metal particles can be reduced between the state in which the metal particles are randomly dispersed in the dispersion medium and the state in which the metal particles are oriented in a certain direction. It is changing.

  In the present embodiment, the metal particles in a state where no voltage is applied to the dispersion are randomly dispersed in the suspension (the direction of the metal particles is not oriented in a certain direction). Whether the absorption of electromagnetic waves by the metal particles is performed on the major axis surface or the minor axis of the metal particles depends on the orientation of the individual metal particles in the dispersion. On the other hand, when a voltage is applied to the dispersion, the individual metal particles are oriented so that the major axis is along the direction of the electric field, and electromagnetic waves are absorbed mainly on the surface of the minor axis of the metal particles. Utilizing such movement of metal particles, the transmittance of electromagnetic waves is changed or the absorption wavelength is changed depending on the presence or absence of voltage application.

(Metal particles)
The metal particles used in the present embodiment have a major axis length of 10 nm to 200 nm, a minor axis length of 50 nm or less, and an aspect ratio of 2 or more.
In this specification, the major axis of a metal particle and its length are the distance from an arbitrary point a on the surface of the metal particle to an arbitrary point b on the surface of the metal particle different from the point a when a captured image of the metal particle is observed. Is the longest line segment and its length. The short axis and the length of the metal particle are the line segment that is perpendicular to the long axis and connects two points on the surface of the metal particle and has the shortest length and the length thereof. The major axis length and minor axis length of the metal particles can be measured, for example, by observation with a transmission electron microscope (TEM / STEM), a scanning electron microscope (SEM), or the like.

  The major axis length of the metal particles is 10 nm to 200 nm, preferably 20 nm to 100 nm, and more preferably 25 nm to 90 nm. When the length of the major axis of the metal particles is 10 nm or more, the electromagnetic waves are sufficiently absorbed by the dispersed metal particles, and the electromagnetic wave transmittance can be effectively reduced. When the major axis of the metal particles is 200 nm or less, scattering of electromagnetic waves by the dispersed metal particles is suppressed, haze increase is suppressed, and responsiveness (orientation) to voltage application is maintained well. . In addition, since the specific gravity of the metal particles is usually larger than that of the dispersion medium described later, by setting the major axis to 100 nm or less, precipitation of the metal particles in the dispersion is suppressed and the dispersion state is stably maintained. In addition, the longer the length of the major axis of the metal particles, the more the peak of the electromagnetic wave absorption wavelength by the dispersed metal particles tends to shift to the longer wavelength side. Therefore, the absorption wavelength can be shifted to a desired position by adjusting the length of the major axis of the metal particles. In addition, by using metal particles with different major axis lengths, the absorption spectral distribution of the electromagnetic wave adjustment element in the light-shielding state can be adjusted by setting the absorption wavelength to multiple peaks or broadening the peak shape. It becomes possible to do. A desired color tone can be obtained by adjusting the spectral distribution of absorption of the electromagnetic wave adjusting element in a light-shielding state.

  The length of the minor axis of the metal particles is 50 nm or less, preferably 30 nm or less, and more preferably 20 nm or less. When the length of the minor axis of the metal particles is 50 nm or less, absorption of electromagnetic waves by the metal particles in the oriented state is suppressed, and high transmittance can be maintained. Moreover, scattering of electromagnetic waves is suppressed and haze is kept low. The lower limit of the length of the minor axis of the metal particles is not particularly limited, but is preferably 3 nm or more from the viewpoint of shape controllability when producing the metal particles, stability after production, and the like. It is more preferable.

  There are no particular restrictions on the material of the metal particles, and the length of the major and minor axes of the metal particles, the absorption wavelength according to the nature of the dispersion medium (kind, dielectric constant, refractive index, etc.), etc., are taken into account. It can be appropriately selected according to the color tone of the adjusting element. The metal particles may be at least one selected from the group consisting of Ag, Au, Cu, Pt, Pd, Co, Fe, Mo, and Bi, for example. The metal particles may contain a substance other than metal as long as the effects of the present invention are achieved.

  An example of a spectral distribution due to surface plasmon absorption of metal particles is conceptually shown in FIG. As shown in FIG. 1, the spectral distribution due to surface plasmon absorption of metal particles is usually located on the longer wavelength side of the absorption peak a mainly due to the type of metal and the minor axis of the metal particles, and the absorption peak a. And an absorption peak b due to the long axis. The wavelength range of the absorption peak b varies depending on the length and aspect ratio of the metal particles.

When the electromagnetic wave to be adjusted is visible light, the absorption peak b is preferably present between the visible range and the near infrared range, and is present between 400 nm and 1200 nm (range indicated by (i) in FIG. 1). It is more preferable that it exists between 400 nm and 800 nm (a range indicated by (ii) in FIG. 1).
When the absorption peak b exists between 400 nm and 1200 nm (for example, in the case of a metal particle having an absorption peak such as b3 in FIG. 1), by adjusting the metal particle concentration in the dispersion, only in the visible region In addition, it is possible to control the spectral distribution of a wide wavelength range in the near infrared region by the orientation operation of the metal particles.
Moreover, when the absorption peak b exists between 400 nm and 800 nm, the metal particle concentration in the dispersion tends to be kept lower than when the absorption peak b exists between 400 nm and 1200 nm. For this reason, it exists in the tendency which can suppress the driving failure by aggregation of metal particles more effectively.
Furthermore, in order to obtain sufficient absorption in the visible region and sufficient change in color tone due to the absorption peak b, the absorption peak a having a small absorption change with respect to the orientation operation of the metal particles is within the range of 600 nm or less in the visible region. It is preferable that it exists in. Furthermore, in order to make the color displayed on the electromagnetic wave adjusting element by the orientation of the metal particles an achromatic color or a color close to an achromatic color, it is more preferable that the absorption peak a is present at a wavelength of 400 nm or less, shorter than the visible range. .

  From the viewpoint of suppressing the absorption of visible light by the metal particles in the oriented state and increasing the transmittance, it is preferable to select a metal having an absorption peak a on the shorter wavelength side. From this point of view, the metal particles preferably contain at least one selected from the group consisting of Ag, Au and Cu, and more preferably contain Ag having an absorption peak a on the shorter wavelength side than the visible range. .

  The spectral distribution of the entire metal particle may be adjusted so that a plurality of absorption peaks b exist (b1 to b3 in FIG. 1), or may be adjusted so that the shape of the absorption peak b is broad. Specific methods for adjusting the spectral distribution of the entire metal particles include a method of combining metal particles having different shapes (particularly, the length and aspect ratio of the long axis), a method of combining metal particles having different materials, and the like. . By adjusting the spectral distribution (position, shape, number, etc. of absorption peaks) of the metal particles as a whole, it is possible to absorb electromagnetic waves having a desired wavelength and to adjust a desired color tone.

  As long as the effect of the present invention is sufficiently achieved, the dispersion has a condition that the major axis is 10 nm to 200 nm, the minor axis is 50 nm or less, and the aspect ratio is 2 or more. It may include only metal particles that satisfy all, or may further include metal particles that do not satisfy all or any of the above conditions. From the viewpoint of sufficiently obtaining the effects of the present invention, the metal particles satisfying all the conditions that the major axis length is 10 nm to 200 nm, the minor axis length is 50 nm or less, and the aspect ratio is 2 or more. The ratio of the entire metal particles is preferably 60% or more, and more preferably 75% or more. The said ratio can be made into the ratio of the metal particle which satisfy | fills the said conditions in 100 metal particles arbitrarily selected when observing an electron microscope image etc., for example.

  The content of the metal particles in the dispersion is preferably 0.1% by mass to 30% by mass, more preferably 0.2% by mass to 25% by mass in the total amount of the dispersion. More preferably, it is 3 mass%-20 mass%. If the content of the metal particles in the dispersion is 0.1% by mass or more, there is a tendency to sufficiently absorb electromagnetic waves in a state where no voltage is applied. If the content is 30% by mass or less, the voltage is applied. There is a tendency that the electromagnetic wave transmittance can be sufficiently maintained in such a state. Moreover, it is in the tendency which can suppress the drive malfunction and the raise of power consumption by the short circuit between the electrodes in an electromagnetic wave adjustment element, the orientation operation | movement defect of the metal particle by the resistance fall of a dispersion, etc.

  The method for producing the metal particles is not particularly limited. Specific examples include a soft template synthesis method and a hard template synthesis method. From the viewpoint of easy control of the shape (especially the short axis) of the metal particles, it is preferable to produce the particles by a soft template synthesis method. Examples of the soft template synthesis method include (1) a step of producing a tube made of silicon dioxide and (2) a step of depositing a metal in the produced tube. For details of the method, see, for example, J. Org. Am. Chem. Soc. The description of 2011, 133, 19706-19709 can be referred to.

  The metal particles may have an insulating film on at least a part of the surface. By having an insulating film, it tends to be able to effectively prevent a short circuit when a voltage is applied. Further, it tends to be able to effectively prevent alteration of metal particles due to oxidation, deformation due to heat, and the like. Furthermore, the affinity with the dispersion medium can be improved depending on the material of the insulating film. Further, by forming the insulating film using a surfactant or the like, effects such as prevention of aggregation and improvement of dispersion stability can be expected.

  The material of the insulating film is not particularly limited, and may be an inorganic material, an organic material, or a hybrid material of an inorganic material and an organic material. Examples of the inorganic substance include oxides such as silicon dioxide. Examples of organic substances include surfactants and modified silicone compounds. As a hybrid material of an inorganic substance and an organic substance, a silane coupling agent, a titanium coupling agent, and the like can be given. These materials may be used alone or in combination of two or more.

The method for forming the insulating film on at least a part of the surface of the metal particles is not particularly limited. For example, J. et al. Am. Chem. Soc. In the method described in 2011, 133, 19706-19709, since SiO ₂ exists on the surface of the metal particles to be produced, it is conceivable to use it as an insulating film without removing it.

(Dispersion medium)
The type of the dispersion medium used in the present embodiment is not particularly limited, and can be selected according to the type of metal particles, the use environment of the electromagnetic wave adjusting element, and the like. For example, when the material of the metal particles is easily oxidized, it is preferable to select an acrylic resin, a silicone resin, or the like as the dispersion medium. When the electromagnetic wave adjusting element is used in an environment with a large temperature change, it is preferable to select a dispersion medium having a small temperature dependency of viscosity from the viewpoint of reducing a difference in response speed due to a temperature change. Examples of such a dispersion medium include silicone resins, modified silicone resins, and resins having a polysiloxane structure such as a graft copolymer made of an acrylic resin and a silicone resin. A dispersion medium may be used individually by 1 type, or may use 2 or more types together. Since the silicone resin is generally hydrophobic, it is also preferable in that it can suppress deterioration in performance due to moisture absorption.

  The silicone resin may be a linear type or a branched type. Moreover, any of a dialkyl silicone resin, an alkylaryl silicone resin, a diaryl silicone resin, and the like may be used. Among them, dimethyldiphenyl silicone resin is preferable from the viewpoint of low gas permeability, low water content, and refractive index control when combined with a matrix resin described later.

  The modified silicone resin may be a linear type or a branched type. Examples of the modified silicone resin include a side chain type having a modifying group at the side chain of the polysiloxane chain that is the main chain, a double-end type having a modifying group at both ends of the polysiloxane chain that is the main chain, and a polysiloxane that is the main chain. Examples thereof include a single-end type having a modifying group at one end of the chain, and a double-end type of side chain having a modifying group at both the side chain and the terminal of the polysiloxane chain which is the main chain. The modifying group in the modified silicone resin can be appropriately selected depending on the purpose and the like. Examples of modifying groups include amino groups, monoalkylamino groups, dialkylamino groups, monoarylamino groups, diarylamino groups, epoxy groups, alicyclic epoxy groups, hydroxy groups, mercapto groups, carboxy groups, polyether groups, aralkyl groups. , Fluoroalkyl groups, long-chain alkyl groups, higher fatty acid ester groups, higher fatty acid amide groups, silanol groups, and the like. By appropriately selecting the modified silicone resin used as the dispersion medium, the dispersibility of the metal particles can be improved. Further, it is possible to stably form droplets on the matrix resin described later.

  The graft copolymer comprising an acrylic resin and a silicone resin may be a compound having a structure in which the main chain is derived from an acrylic resin or a compound having a structure in which the main chain is derived from a silicone resin.

  The viscosity of the dispersion medium is not particularly limited and can be appropriately selected depending on the purpose and the like. From the viewpoint of the response speed of the electromagnetic wave adjusting element, the viscosity at 25 ° C. is preferably 1 mPa · s to 5000 mPa · s, and more preferably 100 mPa · s to 5000 mPa · s. When two or more kinds of dispersion media are used in combination, the viscosity of the dispersion medium means the viscosity of the mixture of the dispersion media used together.

The refractive index of the dispersion medium is not particularly limited, and can be appropriately selected depending on the target absorption wavelength range, the type of constituent material of the electromagnetic wave adjusting element (metal particles, matrix resin described later, insulating layer, etc.), and the like. From the viewpoint of visible light adjustment in the electromagnetic wave adjusting element, the refractive index at 25 ° C. is preferably 1.33 to 1.58, and more preferably 1.39 to 1.51. When two or more kinds of dispersion media are used in combination, the refractive index of the dispersion medium means the refractive index of the mixture of the dispersion media to be used in the same manner as the viscosity.
The refractive index of the dispersion medium is an Abbe refractometer (for example, DR-A1 (trade name), manufactured by Atago Co., Ltd.), a digital refractometer (for example, RX-9000α (trade name), manufactured by Atago Co., Ltd.), etc. Can be measured at 25 ° C. by a conventional method.

(Matrix resin)
The dispersion may further include a matrix resin, and the dispersion medium including the metal particles may be present in the form of droplets in the matrix resin. The matrix resin can be phase-separated from the dispersion medium, and is not particularly limited as long as the dispersion medium can be present in the form of droplets in the matrix resin when mixed with the dispersion medium. The matrix resin is preferably one that is cured by ultraviolet irradiation or the like. Examples of such a combination of the dispersion medium and the matrix resin include a combination in which the dispersion medium is a (meth) acrylate oligomer and the matrix resin is an ultraviolet curable silicone resin. From the viewpoint of achieving good electromagnetic wave transmittance, the difference in refractive index between the matrix resin and the dispersion medium at 25 ° C. is preferably within 0.01, and more preferably within 0.005. (Meth) acrylic acid ester means either one or both of acrylic acid ester and methacrylic acid ester.

  When the dispersion is in a state in which the dispersion medium containing metal particles is present in the form of droplets in the matrix resin, aggregation, sedimentation, and the like of the metal particles are suppressed when the electromagnetic wave adjusting element is configured, and there is no unevenness. There exists a tendency for the electromagnetic wave adjustment effect to be acquired. Further, by curing the matrix resin, the position of the dispersion medium containing metal particles present in the form of droplets in the matrix resin is fixed, and there is a tendency to obtain a more uniform electromagnetic wave adjusting effect.

  There is no particular limitation on the method of making the dispersion medium exist in the form of droplets in the matrix resin. For example, the method described in [0009] to [0036] of JP-A-2002-189123 (Patent Document 1) can be referred to.

(Other ingredients)
The dispersion may contain components other than the metal particles, the dispersion medium, and the matrix resin as necessary. Examples of such components include dispersion stabilizers such as surfactants, thickeners for viscosity adjustment, pigments for correcting the color tone of the electromagnetic wave adjusting element in a light-shielding and transmitting state, and colorants such as dyes. It is done. When the above pigment is included, the average particle size of the pigment is preferably 500 nm or less, and more preferably 100 nm or less from the viewpoint of haze suppression. The average particle size here is the particle size (D50) when the volume-based cumulative value from the small particle size side is 50% in the particle size distribution curve. For example, SALD-7100 (trade name, Co., Ltd.) It is a value measured using a laser diffraction particle size distribution measuring device such as manufactured by Shimadzu.

<Electromagnetic wave adjusting element>
The electromagnetic wave adjusting element of the present embodiment has a pair of conductive substrates and an electromagnetic wave adjusting dispersion disposed between the pair of conductive substrates. The electromagnetic wave adjusting dispersion includes metal particles and a dispersion medium, and details and preferred embodiments thereof are as described above.

  An example of the structure of the electromagnetic wave adjusting element will be described with reference to FIG. However, the present invention is not limited to this. Moreover, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this.

The electromagnetic wave adjusting element 1 includes conductive base materials 2 and 3 having base materials 4 and 6 coated with conductive layers 5 and 7, respectively. Between the conductive substrate 2 and the conductive substrate 3, the electromagnetic wave adjusting dispersion 8 is arranged in a layered manner. The electromagnetic wave adjusting dispersion 8 contains metal particles 9 and a dispersion medium 10. If necessary, an insulating layer may be formed between the conductive layers 5 and 7 and the electromagnetic wave adjusting dispersion 8 in order to prevent the conductive layers 5 and 7 from being short-circuited via the metal particles 9.
It is preferable that the insulating layer is highly transparent and can be produced without damaging the conductive substrates 2 and 3. The material of the insulating layer is not particularly limited, and may be an inorganic material, an organic material, or a hybrid material of an inorganic material and an organic material. Examples of inorganic substances include oxides such as SiO ₂ and Al ₂ O ₃ , aluminosilicates such as layered silicate minerals, and nitrides such as silicon nitride. Examples of organic substances include organic resins such as polyimide resins and acrylic resins. The insulating layer is composed of the electromagnetic wave adjusting dispersion 8, the matrix resin, and the materials of the conductive base materials 2 and 3, the affinity and chemical stability for the sealing agent described later, the use environment conditions (temperature, Humidity, solar radiation, etc.).

  A power source 12 is connected to the electromagnetic wave adjusting element 1 via a switch 11. The power source used for operating the electromagnetic wave adjusting element 1 can be, for example, alternating current and a voltage range (effective value) of 5 V to 200 V and a frequency range of 30 Hz to 500 kHz.

  In the state shown in FIG. 2, the switch 11 of the electromagnetic wave adjusting element 1 is turned off and no electric field is applied. Therefore, the metal particles 9 in the electromagnetic wave adjusting dispersion 8 are each directed in a random direction by Brownian motion. Yes. Therefore, the electromagnetic wave incident on the electromagnetic wave adjusting element 1 is absorbed by the metal particles 9 and the transmittance is reduced.

  When the switch 11 of the electromagnetic wave adjusting element 1 is connected and an electric field is applied, the metal particles 9 are oriented so that the long axis is along the electric field. For this reason, the degree of absorption of the incident electromagnetic wave by the metal particles 9 is smaller than that in the state where no electric field is applied to the electromagnetic wave adjusting element 1. As a result, the electromagnetic wave transmittance is maintained higher than that in the state where no electric field is applied to the electromagnetic wave adjusting element 1.

(Method for manufacturing electromagnetic wave adjusting element)
The manufacturing method of the electromagnetic wave adjusting element is not particularly limited. For example, it can be produced by a method including the following steps (1) and (2).

(1) A pair of conductive substrates are arranged to face each other, a sealing agent is applied therebetween, and the pair of conductive substrates are bonded. Thereby, a space corresponding to the thickness of the electromagnetic wave adjusting dispersion is formed between the pair of conductive substrates. The position where the sealing agent is applied can be, for example, an end portion of the conductive base material. Or when a sealing agent contains spacer beads etc., it can be set as the whole or part of the opposing surface of an electroconductive base material. The distance between the conductive substrates is not particularly limited. For example, it can be in the range of 50 μm to 300 μm. If the distance between the conductive substrates is 50 μm or more, the thickness uniformity of the electromagnetic wave adjusting element tends to be easily maintained, and if it is 300 μm or less, the driving voltage tends to be reduced.

(2) Next, the dispersion is filled in the space between the pair of conductive substrates. The dispersion can be prepared, for example, by the dispersion preparation method described above. The method for filling the dispersion is not particularly limited. For example, it can be filled by capillarity from a place not sealed with the sealing agent at the end of the conductive substrate. After the dispersion is filled between the conductive substrates, the portions not sealed with the sealing agent at the end of the conductive substrate are sealed with the sealing agent. This isolates the dispersion from the outside air.

  As another method, for example, a dispersion is applied on the surface of one conductive substrate, and then the other conductive substrate is bonded and bonded to the surface to which the dispersion is applied, followed by sealing. A method is mentioned. Examples of the method for applying the dispersion include a method using a bar coater, an applicator, a doctor blade, a roll coater, a die coater, a comma coater and the like, and a dropping injection method (ODF) under vacuum. When applying a dispersion to an electroconductive base material, you may dilute with a suitable solvent as needed. When a solvent is used, it is preferable to volatilize the solvent after applying the dispersion on the conductive substrate.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
(1) Production of SiO ₂ nanotubes 11 g of polyethylene glycol hexadecyl ether (Croda International PLC, trade name: Brij C10) was mixed with 15 ml of cyclohexane and stirred at 50 ° C. for 10 minutes. Subsequently, 1.9 ml of 0.8 M NiCl ₂ aqueous solution and 0.45 ml of hydrazine monohydrate were added in this order, and the mixture was stirred at 50 ° C. for 3 hours.

Next, 30 μl of a buffer solution (3-aminopropyltriethoxysilane, APS) and 1 ml of diethylamine were added and stirred at 50 ° C. for 1.5 hours. Subsequently, 3 ml of tetraethyl orthosilicate (TEOS) was added and stirred at 50 ° C. for 3 hours. Thereafter, washing with isopropanol, the surface of the _Ni-N 2 _{H 4} is the core was obtained isopropanol dispersion 25ml of nanoparticles coated with SiO _2.

35 ml of 1M HCl aqueous solution was added to 6 ml of the isopropanol dispersion of nanoparticles obtained above, and the mixture was stirred at room temperature (25 ° C.) for 1 hour, and Ni—N ₂ H ₄ was removed by etching. Thereafter, it was washed with water until neutral, and dried to obtain hollow SiO ₂ nanotubes. An example of the STEM photograph (bright field image) of the obtained SiO ₂ nanotube is shown in FIG. Ethanol 34.7ml the SiO ₂ nanotubes obtained by adding 28 wt% ammonium hydroxide 300 [mu] l, to prepare a ethanol dispersion 15ml of SiO ₂ nanotubes.

(2) Production of Au nuclei 2 ml was taken out from the above-mentioned SiO ₂ nanotube ethanol dispersion, washed with water until neutral, and 15 ml of an SiO ₂ nanotube aqueous dispersion was prepared. To 15 ml of the obtained aqueous dispersion of SiO ₂ nanotubes, 30 μl of a 1.25M HAuCl ₄ aqueous solution was added, stirred at room temperature for 15 minutes, and washed with water three times. To 1 ml of this aqueous dispersion, 0.5 ml of 0.1 M NaBH ₄ aqueous solution was added. Further, washing for 10 minutes with 0.01 M HCl aqueous solution was performed twice, and washing with 15 ml of water at 70 ° C. for 1 hour was performed. In this way, SiO ₂ nanotubes having Au nuclei inside were prepared. An example of the STEM photograph (dark field image) of the SiO ₂ nanotube having the Au nucleus inside is shown in FIG.

(3) Ag nucleus growth 1 ml of 0.1M trisodium citrate dihydrate (TSC) aqueous solution, 1 ml of acetonitrile, 200 μl of 0.1M ascorbic acid aqueous solution, and 30 μl of 0.1M AgNO ₃ aqueous solution were added to 1 ml of water. Then, the mixture was stirred until it became colorless and transparent to prepare an Ag growth solution.

To the Ag growth solution, 80 μl of an aqueous dispersion of SiO ₂ nanotubes with Au nuclei inside was added to nucleate Ag from the Au nuclei. The degree of Ag nucleation can be confirmed by observing how the color of the dispersion changes in the order of colorless, yellow, red, blue, gray, and green. When the aqueous dispersion turned green, it was washed while centrifuging with water to obtain Ag particles having a SiO ₂ layer. An example of a STEM photograph (bright field image) of the Ag particles having the obtained SiO ₂ layer is shown in FIG.

When the Ag particles having the obtained SiO ₂ layer were observed with a TEM (100,000 to 400,000 times), the major axis was 10 nm to 200 nm, the minor axis was 50 nm or less, and the aspect ratio was 2 The above Ag particles were present in 60 or more in 100 arbitrarily selected particles.

<Example 2>
In Example 1, Ag particles having a SiO ₂ layer were produced in the same manner as in Example 1 except that the aqueous dispersion changed to a gray color and was washed while being centrifuged with water.

When the Ag particles having the obtained SiO ₂ layer were observed with a TEM (100,000 to 400,000 times), the major axis was 10 nm to 200 nm, the minor axis was 50 nm or less, and the aspect ratio was 2 More than 60 Ag particles were present in 100 arbitrarily selected Ag particles.

<Evaluation of electromagnetic wave adjustment characteristics>
Using Ag particles having the SiO ₂ layer obtained in Example 1 and Example 2, a glass cell for evaluation of electromagnetic wave adjusting characteristics was produced. Specifically, an aqueous dispersion of Ag particles was prepared, and then water was replaced with a solvent (isoamyl acetate) that was compatible with the dispersion medium to be used (a mixture of silicone resin and modified silicone). Subsequently, it was mixed with a dispersion medium (a mixture of silicone resin and modified silicone), and the solvent was distilled off with an evaporator to prepare a dispersion containing Ag particles.

Next, an SiO ₂ colloidal resin dispersion was applied onto a glass substrate (40 mm × 30 mm × 0.7 mm) ITO electrode having an ITO electrode on one side, and an insulating layer was formed by curing the resin component. Two glass substrates were prepared, arranged so that the insulating layer sides face each other, and 1 ml of a dispersion containing Ag particles was injected therebetween, and the periphery was sealed to produce a glass cell.

Using the produced glass cell, the transmitted light intensity (au) in a state where no voltage was applied (OFF), a state where a voltage of 100 V was applied, and a state where a voltage of 50 V was applied was measured. The driving voltage was 50 Hz. The measurement was performed at room temperature (25 ° C.) using a spectrophotometer. The results in the case of using the Ag particles having the SiO ₂ layer obtained in Example 1 and Example 2 are shown in FIGS. 6 and 7, respectively.

  As shown in FIGS. 6 and 7, the glass cell produced using the dispersion containing Ag particles produced in Example 1 and Example 2 has a transmitted light intensity depending on the presence / absence of voltage application and the magnitude of the voltage. However, the electromagnetic wave preparation effect was demonstrated. Further, it was found that the absorption distribution can be changed by changing the production conditions of the Ag particles, and the color tone of the electromagnetic wave preparation element can be controlled using this.

1: Electromagnetic wave adjustment element 2, 3: Conductive base material 4, 6: Base material 5, 7: Conductive layer 8: Dispersion for electromagnetic wave adjustment 9: Metal particle 10: Dispersion medium 11: Switch 12: Power supply

Claims (8)

  Metal particles having a major axis length of 10 nm to 200 nm, a minor axis length of 50 nm or less, and an aspect ratio (major axis length / minor axis length) of 2 or more, a dispersion medium, A dispersion for electromagnetic wave adjustment, comprising:   The dispersion for electromagnetic wave adjustment according to claim 1, wherein the metal particles include at least one selected from the group consisting of Ag, Au, and Cu.   The dispersion for electromagnetic wave adjustment according to claim 1, wherein the metal particles have an insulating film on at least a part of a surface thereof.   The dispersion for electromagnetic waves according to claim 1, wherein the dispersion medium has a viscosity at 25 ° C. of 1 mPa · s to 5000 mPa · s.   The dispersion medium for electromagnetic wave adjustment according to any one of claims 1 to 4, wherein the dispersion medium has a refractive index of 1.33 to 1.58 at 25 ° C.   The dispersion for electromagnetic wave adjustment according to any one of claims 1 to 5, further comprising a matrix resin, wherein the dispersion medium containing the metal particles is present in the matrix resin in the form of droplets.   The electromagnetic wave adjustment element which has a pair of electroconductive base material and the electromagnetic wave adjustment dispersion of any one of Claims 1-6 arrange | positioned between the said pair of electroconductive base materials.   The electromagnetic wave adjusting element according to claim 7, further comprising an insulating layer between the conductive substrate and the electromagnetic wave adjusting dispersion.