JPH06250236A - Light control device - Google Patents

Abstract

PURPOSE:To provide the light control device which is shortened in response time, can control transmittance over a wide range and can maintain its perfor mance over a long period by using fine particles being mixture of two kinds of fine particles having a different average volumetric sizes as the particle constituting a dielectric substance. CONSTITUTION:The particules constituting the dielectric substance consist of the particles 4 obtained by mixing particules S having a small average grain size and particules L having a large average grain size. The average grain sizes of the respective particules 4 are in a <=0.20mum range, more preferably 0.42 to 0.85mum range of the average diameter (average volumetric size) when the average grain size is converted to the volume of a spherical body having the same volume as the volume of the particules S. Any liquid dielectric substances are usable as the liquid dielectric substance 3 to be dispersed and incorporated with the anisotropic particles, insofar as these substances have a high insulation characteristic and high weatherability, have the viscosity to the extent of allowing the particles 4 to make adequate Brownian movement and have the effect of controlling the settlement of the particules 4 in the liquid dielectric substance 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control device. More specifically, the present invention relates to a light control device having excellent light transmittance control performance.

[0002]

2. Description of the Related Art In recent years, office buildings have become taller and windows have become larger, and at least 25% of energy consumption in the office buildings comes in or out of the windows as light or heat. Therefore, from the viewpoint of effective use of energy, development of a large-area dimmer is desired. Also, with the increase in the number of passenger cars due to the rise of motorization and the increasing number of passenger cars, along with the fact that most cars are equipped with coolers, from the perspective of effective use of energy, a dimmer suitable for passenger car windows. It is also desired to develop.

In order to meet such a demand, a dimmer for the purpose of reducing the heating and cooling load by electrically controlling the transmittance or reflectance of sunlight has been developed. A number of electro-magnetic optical devices have been developed for application to dimmers.

As such a light control device, an electric element (hereinafter referred to as "EC element") using an electrochemical coloring material such as tungsten oxide, molybdenum oxide or nickel oxide has been attracting attention for a long time, and is energetically used in various fields. Research has been continued. And recently, the technology has been improved until it is put to practical use in small glass products such as eyeglasses and automobile mirrors.

However, since these are current-driven types, a voltage drop occurs, the response speed remarkably decreases when a large area is used, and the quality of the constituent materials changes due to electrochemical changes or the like during long-time energization. Inevitably, it has been found that it is extremely difficult to realize a large-area EC device by extending the technology of a small-area EC device.

Therefore, as a substitute for such a current drive type EC element, a voltage drive type light control device has been attracting attention. As a voltage drive type light control device, one using a suspension in which anisotropic dipole fine particles are dispersed in a liquid dielectric (hereinafter referred to as "DPS element") is known (for example, Japanese Patent Application Laid-Open No. S60-18753). 63-303325, JP-A-64-3
8732). This DPS element is basically needle-shaped,
A suspension of fine particles with shape anisotropy, such as a plate, in a liquid dielectric is sandwiched between glass substrates with a transparent conductive film. It utilizes the rate change. This DPS
The device has been known since the mid-1960s, and several patents relating to the device have been issued [for example, US Pat.
No. 1-69038 (B Dee Bostwick)
etc〕.

Further, when a dispersion in which fine particles form a rod-shaped fine particle aggregate (hereinafter referred to as "chain-like body") is formed in the direction parallel to the electric field direction, the fine particles involved in light absorption are significantly reduced. It is possible to obtain a larger change in transmittance than that obtained by only the orientation of
14625).

A factor important in improving the dimming performance of a DPS device using this dispersion is the formation of fine particle chains. That is, the faster and more uniformly the fine particles are formed in the gap direction, the better the response speed and the larger the range of change in transmittance can be obtained. The formation of a chain of fine particles was discovered by Winslo of the United States in the 1940's, and it is believed that an induced dipole moment is formed in the fine particles when an electric field is applied, and is caused by an interaction between dipole moments. It is known by electromagnetics that the magnitude of the induced dipole moment is proportional to the volume of fine particles.
Therefore, by using fine particles having a large particle diameter, chain formation can be promoted, a wide range of transmittance change can be obtained, and a light control device having a good response speed can be obtained.

[0009]

However, when the particle size of the particles is increased, the sedimentation speed of the particles increases according to Stokes' law, and the particles become entangled with each other, which causes color unevenness and transmittance change in the vertical direction. There is a problem that the width is reduced and the switching action is deteriorated.
The stable dimming performance cannot be obtained for a long time.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a dimmer capable of shortening the response time and controlling the transmittance in a wide range. .

[0011]

That is, the present invention is a dimming device comprising a dielectric containing fine particles dispersed therein, and a pair of electrodes for applying an electric field to the dielectric. The constituent fine particles are fine particles in which fine particles S having a small average particle diameter and fine particles L having a large average particle diameter are mixed, which is a light control device.

The average particle diameter of each of the fine particles is in the range of 0.20 μm or less when converted into a true sphere having the same volume as the volume of the fine particles S (hereinafter referred to as “average volume diameter”). The average volume diameter of the fine particles L is 0.42 to 0.
It is preferably in the range of 85 μm. In the present invention, the average volume diameter of the fine particles means a particle diameter when the average volume of the fine particles obtained from an electron micrograph is converted on the assumption that the fine particles are true spheres.

The dimmer of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a light transmission state of the light control device of the present invention when the action of the electric field is released (hereinafter referred to as “open state”), and FIG. FIG. 3 is a diagram showing a light transmission state of the light control device of the present invention in a “state”). In FIGS. 1 and 2, 1 is a substrate, 2 is a transparent conductive film, 3 is a liquid dielectric, and 4 is fine particles.

Any substrate can be used as the substrate 1 as long as it has been conventionally used as a light control device, and is not particularly limited. As a specific example, a glass substrate such as soda lime glass, or a polymer such as polyethylene terephthalate can be applied. Also,
The shape, size, etc. of the substrate 1 are appropriately determined as needed.

As the transparent conductive film 2, any material can be used as long as it has been conventionally used in a light control device, and is not particularly limited. Specific examples thereof include an ITO film and a SnO ₂ film. The film thickness is also not particularly limited, but a film thickness that is optically adjusted so as to minimize the reflectance of the light control device is preferable. For example, the SnO ₂ film has a thickness of 180 nm.

The liquid dielectric 3 in which the anisotropic fine particles are dispersedly contained has a high insulation property and a high weather resistance, and has a viscosity such that the Brownian motion of the fine particles can be moderately performed, and the fine particles 4 are contained. Any material can be used as long as it has the effect of suppressing sedimentation in the liquid dielectric 3, and is not particularly limited. The specific range of viscosity that can achieve this is 0.65 to 1000 CSt. Among those having such viscosity, the organodimethylsiloxane-based liquid polymer is preferable considering that the temperature range of use of the light control device is -40 to 80 ° C.

The fine particles 4 are those in which the fine particles in the liquid dielectric material 3 form chains by the action of an electric field and have different average volume diameters, and the average volume diameter is 0.20 μm. The following fine particles S and 0.42 to 0.
The fine particles L are in the range of 85 μm.

The reason why the fine particles 4 are composed of fine particles having different average volume diameters is that mixing fine particles having different average volume diameters suppresses sedimentation and promotes chain formation. That is, since the fine particles S having a small average volume diameter suppress sedimentation of the fine particles, and the induced dipole moment of the fine particles L having a large average volume diameter is large, the formation of the chain-like body is promoted by attracting the small particles S. Therefore, the response speed becomes faster, and the range of change in transmittance is large, and excellent light control performance can be maintained for a long time.

When the average volume diameter of the fine particles S is larger than the above range, the effect of suppressing the sedimentation of the fine particles 4 becomes small and it is difficult to obtain the switching life of 1 × 10 ⁵ times or more required for the light control device. Therefore, it is not preferable. Also,
When the average volume diameter of the fine particles L is smaller than the above range, the induced dipole moment is small and it is difficult to obtain the effect of promoting chain formation, and when it is larger than the above range, the respective fine particles are entangled with each other. This tends to hinder the formation of a chain, which is not preferable.

The weight ratio of the fine particles 4 to the total fine particles (S + L) is preferably in the range of 0.01 to 0.3. The weight ratio of the fine particles L is limited as described above. When the ratio of the fine particles L is less than 0.01, the effect of promoting chain formation is not exerted on all the fine particles, and when it is more than 0.3, each fine particle L is This is because the formation of chain-like bodies is hindered by being entangled with each other.

Any substance can be used as the substance constituting the fine particles 4 as long as the suspension forms a chain of fine particles 4 by applying an electric field.
The larger the absorption coefficient of the fine particles, the more preferable it is because the transmittance of sunlight can be controlled in a wider range. Further, the shape of the fine particles is preferably one having shape anisotropy.

Examples of such shape anisotropic fine particles include graphite, TiO _x , TiO _x N _y , TiO _x coated mica, TiO _x N _y coated mica, and metal coated mica.

The range of x in the TiO _x is 1 ≦
x ≦ 2 is preferable, but it is 1.4 when the absorption coefficient is taken into consideration.
It is more desirable that the range of 0 ≦ x ≦ 1.80.
Expressed this in absorption coefficient, 5 × 10 ³ cm ^-1, is preferably more than 1 × 10 ⁴ cm ^-1 or more.

In TiO _x N _y , the range of x + y is 1.37 ≦ x + y ≦ 1.95, and the range of y is 0.15.
It is preferable that ≦ y ≦ 0.92 from the viewpoint of absorption coefficient.
In this composition range, the absorption coefficient reaches 5 × 10 ³ cm ^-1 or more.

These fine particles are not necessarily required to have shape anisotropy, and if the suspension forms a chain of fine particles even if there is little or no anisotropy, it is used. be able to. Further, when the fine particles have shape anisotropy, the chain of fine particles becomes thin, so that the transmittance can be controlled in a wide range.

Further, even when the fine particles 4 exhibit magnetism and form a chain shape of fine particles in the magnetic field direction when dispersed in a liquid, by mixing fine particles having different average volume diameters, the preparation of the present invention can be performed. Similar to the optical device, it is easily inferred that fine particles having a large average volume diameter serve as nuclei to promote the formation of a chain and improve the light control performance. In this case, a chain of fine particles is formed by applying a magnetic field.

When the fine particles 4 are dispersed in the liquid dielectric 3, the fine particle concentration is preferably in the range of 0.5 to 10% by weight.

As means for applying an electric field to the fine particles 4, any means conventionally used in this type of light control device can be used and is not particularly limited. Since the strength of the electric field is inversely proportional to the electrode spacing, the smaller the electrode spacing, the lower the voltage required to obtain the same electric field strength. From this point of view, the electrode interval is preferably in the range of 5 to 100 μm. The applied voltage varies depending on the viscosity of the liquid dielectric 3 and the rod-shaped aggregate forming ability of the fine particles 4, but an electric field of 10 ⁴ Vcm ^-1 or more is usually sufficient.

As a method for manufacturing the light control device of the present invention, a known method which has been conventionally used for manufacturing this type of light control device can be adopted. For example, fine particles are added to a dispersion medium and stirred to prepare a fine particle suspension, and bead-shaped fine particles are added to this fine particle suspension as a spacer,
It can be prepared by dropping on the transparent conductive film of the substrate and sandwiching it with another substrate with the transparent conductive film. In this case, the distance between the substrates is determined by the diameter of the spacer.

[0030]

The light control device of the present invention is composed of a mixture of fine particles having different average volume diameters. The fine particles S having a small average volume diameter suppress the sedimentation speed, and the fine particles L having a large average volume diameter serve as the core. To promote chain formation,
It is possible to improve the response speed and maintain excellent light control performance with a large transmittance variation range for a long period of time.

[0031]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

(Examples 1 to 4 and Comparative Examples 1 and 2) The TiO _x N _y fine particles S and the TiO _x N _y fine particles L shown in Table 1 had a weight ratio (L / (S + L)) of 0.1. After mixing at a ratio, the mixture was dispersed in polydimethylsiloxane (viscosity 20 CSt) using a paint shaker to obtain a suspension having a fine particle concentration of 3%. A bead-shaped spacer (average particle size: 25 μm) was added to this suspension, and a well-mixed mixture was dropped onto a glass substrate with a transparent conductive film (area resistance 200 Ω / mouth),
A dimming device (cell) was produced by sandwiching this between opposing glass substrates.

With respect to the cell thus obtained, the visible light transmittance change width (hereinafter referred to as “ΔT”) in the open state and the closed state (when an electric field of AC 40 V × 60 Hz is applied).
Was measured. The results are shown in Table 1.

The obtained result was ΔT = 49.9%. Further, when RT is a response time required to obtain a transmittance change corresponding to 90% of ΔT after applying an electric field, RT was 3.8 seconds.

The behavior of the fine particles in the cell was observed. First, the fine particles L were oriented in the direction of the electric field, and the fine particles S were aggregated around the fine particles L to form a chain.
It was confirmed that the nuclei promoted chain formation. When a voltage was applied for 2 seconds and a non-application time was 20 seconds, the electric field was repeatedly applied, and good switching life could be confirmed up to 1 × 10 ⁵ times without aggregation or sedimentation.

On the other hand, in the fine particles of Comparative Examples 1 and 2 shown in Table 1, ΔT was 26.5% and 35.5%, respectively. With the fine particles of Comparative Example 2, it was confirmed by a microscope that the chain-like body formed was short and the average volume diameter was small, so that it was difficult to form the chain-like body. Also, RT
= 5.4 seconds. In the fine particles of Comparative Example 1, it was confirmed that the fine particles were settled downward and the fine particles were entangled with each other, so that it was difficult to form a chain.

Also, when the fine particles of Comparative Example 2 are mixed with fine particles having an average volume diameter of 0.82 μm, 0.85 μm and 0.69 μm, as in Examples 2 to 4, ΔT is different. 50.2, 48.0 and 4
It was confirmed that both were improved to 5.4.

[0038]

[Table 1]

(Examples 5 and 6 and Comparative Examples 3 and 4) Dimming was performed in the same manner as in Example 1 using the TiO _x N _y fine particles of Examples 5 and 6 and Comparative Examples 3 and 4 shown in Table 2. Make the device △ T
Was measured.

As in Comparative Example 3, the average volume diameter is 0.13.
Whereas ΔT was 20.3% when the fine particles of μm were used alone, the fine particles of Comparative Example 3 and the fine particles having an average volume diameter of 0.42 μm were mixed as in Example 5. As a result, it was confirmed that ΔT was improved to 42.1%. Further, from Example 6 and Comparative Example 4, by mixing the fine particles S having an average volume diameter of 0.20 μm and the fine particles L having an average volume diameter of 0.42 μm, the ΔT was smaller than that obtained by using the fine particles S of 0.20 μm alone. Was also confirmed to improve.

From the above results, the average volume diameter is 0.20 μm.
It was confirmed that ΔT is improved by mixing the fine particles S of m or less and the fine particles L in the range of 0.42 to 0.85 μm.

[0042]

[Table 2]

(Embodiment 7) The weight ratio (L / (S + L)) of the fine particles S and the fine particles L shown in the first embodiment is 0.01 to 0.
A dimmer was manufactured in the same manner as in Example 1 except that the range was changed to 3, and ΔT was measured. The result is shown in FIG.

As is clear from FIG. 3, the weight ratio (L / (S
+ L)) was in the range of about 0.01 to 0.3, an increase in ΔT was observed.

[0045]

As described above, since the light control device of the present invention uses a mixture of two kinds of fine particles having different average volume diameters, the response time is shortened and the transmittance is wide. It can be controlled and its performance can be maintained for a long time.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a light transmission state in a closed state of a light control device of the present invention.

FIG. 2 is an explanatory diagram showing a light transmission state in an open state of the light control device of the present invention.

FIG. 3 is an explanatory diagram showing the relationship between the weight ratio and ΔT in Example 7 of the present invention.

[Explanation of symbols]

 1 substrate 2 transparent conductive film 3 liquid dielectric 4 fine particles

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masato Hyodo, 3-5-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka Prefecture Nippon Sheet Glass Co., Ltd. (72) Haruo Okuda, 1 Ishihara-cho, Yokkaichi-shi, Mie Ishihara Sangyo Incorporated company Yokkaichi office (72) Inventor Hideo Takahashi 1 Ishihara-cho, Yokkaichi-shi, Mie Ishihara Industrial Co., Ltd. Yokkaichi office

Claims (5)

[Claims] 1. A light control device comprising a dielectric containing fine particles dispersed therein and a pair of electrodes for applying an electric field to the dielectric, wherein the fine particles constituting the dielectric are fine particles S having a small average particle size. And a fine particle L having a large average particle diameter. 2. The average particle size of the fine particles S is
The average diameter when converted into a true sphere having the same volume as that of 0.20 μm or less, and the average particle diameter of the fine particles L is converted into a true sphere having the same volume as the volume of the fine particles L. The dimmer according to claim 1, wherein the average diameter is 0.42 to 0.85 µm. 3. The light control device according to claim 1, wherein a ratio of the fine particles L to all the fine particles is 0.01 to 0.3 weight ratio. 4. At least fine particles S among the fine particles
4. The light control device according to claim 1, wherein is a light-absorbing fine particle. 5. The fine particles are graphite or TiO.
_x (1 ≦ x ≦ 2), TiO _x N _y (1.37 ≦ x + y ≦
1.95, 0.15 ≦ y ≦ 0.92), TiO _x coated mica (1 ≦ x ≦ 2), TiO _x N _y coated mica (1.37)
≦ x + y ≦ 1.95, 0.15 ≦ y ≦ 0.92), and at least one kind of fine particles selected from the group consisting of metal-coated mica, The light control device according to any one of claims 1 to 4.