WO2008090438A2

WO2008090438A2 - Apparatus for light control and method for light control

Info

Publication number: WO2008090438A2
Application number: PCT/IB2008/000129
Authority: WO
Inventors: Ho Keung Tse
Original assignee: Ho Keung Tse
Priority date: 2007-01-22
Filing date: 2008-01-22
Publication date: 2008-07-31
Also published as: GB0701077D0; WO2008090438A3; WO2008090438B1

Abstract

An apparatus for controlling a plurality of light cells comprises a microcomputer responsive to user commands. The user commands are used to adjust the electric field applied to the light cells containing light control fluid therein and to control the amount of light control fluid inside the light cells, wherein the transparent degree of the light control fluid is dependent on the applied electric field.

Description

SMART GLASS

Field of the invention

The present invention relates to controlling transparency of glasses, and particularly, to glasses with transparency thereof being electrically controllable.

Background of the invention

Nowadays, smart glass which transparency can be controllable by applying an electric field are well known, such as electrochromic type, suspended particle devices (SPD) type, liquid crystal type etc.

Both SPD or liquid crystal type can be in film form, generally formed of two sheets of plastic having a liquid medium containing suspended particles/liquid crystals in between (herein after referred to as "light control fluid"). Each plastic sheet has a transparent electrically conductive coating on the surface of the sheet. The plastic is usually a material called polyethylene terephthalate(PET), and the conductive coating material is usually indium tin oxide (ITO).

In the absence of an applied electrical field (OFF state), the suspended particles/liquid crystals in the liquid medium exhibit random Brownian movement or in a non-aligned manner, and hence a beam of light passing there through is reflected, transmitted or absorbed, depending upon the nature of the suspended particles/liquid crystals. When an electric field is applied (ON state) on light control fluid by applying a voltage difference between the two ITO electrically conductive coatings, the suspended particles/liquid crystals become aligned and most of the light can pass through the cell.

To enhance the contrast of liquid crystal material, pleochroic dyes have been mixed with the liquid crystal material to form a solution therewith. The molecules of pleochroic material generally align with the molecules of the liquid crystal material. Therefore, such pleochroic dyes will tend to function optically in a manner similar to that of the liquid crystal material in response to a changing parameter, such as application or non-application of an electric field. Examples of pleochroic dyes with liquid crystal material are described in U.S. Pat. Nos. 3,499,702 and 3,551,026.

One of the disadvantages of such liquid based light control device is that the suspended particles/liquid crystal may agglomerate.

Another disadvantage of such a light control device is that optical characteristics thereof may vary from sample to sample when in mass production. It is therefore an object of the present invention to eliminate the above-mentioned problems in mass production of light control device.

Brief Description of the Drawings

FIG.1 is a block diagram of a light control device comprising 4 light cells, and a motor for driving light control fluid into/out of the light cells.

FIG.2A is a cross section diagram of a light cell, in "ON" state, in accordance with another embodiment.

FIG.2B is a cross section diagram of a light cell, in "OFF" state, in accordance with another embodiment.

FIG.3 is an alternative design for ITO layer 11.

Detailed description of the preferred embodiments

As shown in FIG. 1, there is a light control device connected to a hydraulic chamber containing light control fluid, that is, "suspended particles or liquid crystals or the like" in a liquid medium. Note that this is merely an example given for the sake of simplicity; other light control fluid well known to those in the art may be used.

Each side wall of the light cells therein is formed of elastic plastic with a conductive coating or electrode.

The hydraulic chamber's internal pressure is under control of a movable pistol, which can be moved upward and downward by an electric motor.

Thus, the hydraulic chamber is under the control of the electric motor to supply "light control fluid" to or withdraw "light control fluid" from the 4 light cells of the light control device, through a network of passageways.

It should be noted that the network of passageways are formed of non-elastic plastic, such that when the pressure of the "light control fluid" from the hydraulic chamber increases or decreases, the "light control fluid" can be driven into/out of the 4 light cells.

Although not shown in FIG.1 , there is a microcomputer MC for receiving user commands and in response thereto, controlling the degree of transparency of the light control device.

The light control device is capable of providing different levels of transparency. For the sake of simplicity, only the "ONTOFF" operation of the light control device are explained herein, as follows :

When receiving a "ON" command from a user, the microcomputer MC will cause opposite voltages be respectively applied to the 2 electrodes of the 2 side walls of the light control device, so as to create an electric field for causing the suspended particles/liquid crystals to become aligned and to permit light passing through.

On the other hand, the microcomputer MC will also cause the electric motor to move the pistol of the hydraulic chamber downward, to withdraw the "light control fluid" from the cells. Note that the positive and negative voltage at the 2 side walls will also create an attractive force between the 2 side walls which will further deflate the cells.

It should be noted that, in order for the light control device to become transparent, it is not necessary to have the "light control fluid" be 100% withdrawn from the light control device as this is not possible in practice and also that the suspended particles/liquid crystals in the remaining "light control fluid" is aligned by the applied electric field and their light blocking capability is very low.

When receiving a "OFF" command from a user, the microcomputer MC will cause a same voltage or no voltage be applied to the 2 electrodes of the 2 walls of the cells, so that no net electric field will be formed and the suspended particles/liquid crystals will be in random Brownian movement or in a non-aligned manner and become light blocking.

On the other hand, the microcomputer MC will also cause the electric motor to move the pistol of the hydraulic chamber upward, to drive the "light control fluid" into the light control device. Note that applying the same voltage at the two electrodes of 2 side walls will also induce them with the same charges and repulsive force will drive the 2 elastic plastic walls apart and further inflate the light cells, enhancing the light blocking capability.

The movements of the "light control fluid" within the light control device when "ON" or "OFF" eliminate the problem of "agglomeration" as mentioned above.

Another Embodiment

In this embodiment, the hydraulic chamber may be replaced with a container of light control fluid without the electric motor, and the intake or push out of the light control fluid in a cell is driven by the attractive or repulsive force between the two electrodes, as mentioned above.

Referring to Fig 2A, there is shown a cross section diagram of such a cell in ON state. As shown, in one of the two cell walls, comprising a transparent plate 5, a first ITO layer 10, a thin layer of nonelastic transparent insulation layer 6, ITO layer 11 and another insulation transparent layer 7. This cell wall may be formed by adhering the two surfaces of the nonelastic transparent insulation sheet 6 with 2 separate glass plates each covered with an ITO layer.

In the another cell wall, comprising a glass plate 9, ITO layer 13, an elastic transparent plastic material 8, and another ITO layer 12. Batteries B1 and B2 are two independent voltage sources. This cell wall may be formed by adhering the two surfaces of the elastic transparent plastic sheet 8 with 2 separate glass plates each covered with an ITO layer.

When in ON state, ITO layers 11 ,12 are applied by 2 opposite polarity voltages from voltage source B2, inducing opposite polarity charges in them, thereby creating an electrostatic field which attracts the two ITO layer towards each other. ITO layer 12 will be moved, by this attractive force, towards ITO layer 11 , as ITO layer 12 is coated on elastic layer 8 which is stretchable.

The field on one hand closes the two cell walls and drives the light control fluid out of the cell, and on the other hand causes the light control fluid remained in the cell to have a higher degree of transparency.

No voltages are applied to ITO layers 10,13 and voltage source B1 is standby.

Referring to Fig 2B, it is a cross section diagram of the same cell in OFF state. As seen, ITO layers 11 ,12 of the 2 different cell walls are now applied by 2 same polarity voltages, inducing same polarity charges in them, thereby creating a repulsive force between the 2 ITO layers and ITO layer 12 compresses elastic layer 8 to move away from ITO layer 11.

On the other hand, ITO layers 12,13 are now applied by 2 opposite polarity voltages, inducing opposite polarity charges in them, thereby creating an electrostatic field pushing ITO layer 12 to further compress elastic layer 8.

Thus, more fluid is drawn into the cell. The fluid is light blocking as the electric field so created cannot stop the suspended particles/liquid crystals therein from random Brownian movement or in a non-aligned manner.

Note that voltage sources B1, B2 may provide DC or AC voltages, dependent on the nature of the light control fluid.

Note that it may not be necessary to continue to apply voltages to the ITO layers of the cells. Once the fluid inside the cell reached a certain amount, to provide the desired level of transparency, the fluid may be locked inside the cell by an electrical controllable bi-directional valve disposed at the fluid passageway which being capable of being used to stop/allow the fluid to get into/out of the cell, under the control of the microcomputer MC.

Although it is given by example herein above to use electrostatic field and force to control the transparency and amount of the light control fluid in the cell respectively, other approaches such as electromagnetic field and force generated by current flowing through a number of solenoids may also be used as an alternative.

To design a cell with large area cell wails, it is more desirable to have ITO layer 11 to be divided into several small sub ITO regions, instead of a single large ITO region. As seen in Fig. 3, sub ITO regions A-E are being disposed. When fluid is to be driven out of the cell, sub ITO regions A-E is applied with progressively decreasing voltage so that the "driving out" force exerted on the fluid is greater in lower region A and progressively decreases upward to region E, so as to facilitate upward movement of the fluid.

On the other hand, when fluid is to be driven into the cell, sub ITO regions A-E is applied with progressively increasing voltages so that the "pushing apart" force between the two cell walls is greater in uppermost region E and progressively decreases when downward to region A, this facilitates fluid intake at region E and the hydraulic pressure of the fluid will compensate the lower "pushing apart" force in the lower regions.

An simple alternative to achieve similar effects is to have a single, large ITO layer 11 covering layer 6 entirely, but the thickness of layer 7, which covers ITO layer 11 , has a progressively decreasing thickness from its lowest part to uppermost part.

Other Alternatives

The light control fluid may be a gas which is light blocking.

The term "light" may include visible and non-visible light, "smart glass" may be made of "glass" or other transparent material such as plastic.

A ultrasonic vibrator may be disposed in such a light film/window to generate ultrasonic sound wave, so as to ensure even distribution of the suspended particles/liquid crystals in the liquid.

As "light control fluid" generally exhibits a nonlinear light blocking characteristic with respect to applied electric field, it is desirable to dispose a light detecting mean such as a photocell to detect the intensity of light passing through the light control device. The microcomputer MC can be responsive to the detection output signal to adjust the electric field applied to the light control device as well as the pressure of the hydraulic chamber which in turn controls the thickness of the light cells, thereby achieving the desired light blocking effect of the light cell.

Finally, as normal operation of the light control film/window of different types, different materials and different working principles depend on the environmental temperature, or in other words, the light control film/window may not be controllable when out of a required operation temperature range, it is therefore desirable to have an electronic thermometer to monitor the environmental temperature, and if environmental temperature is higher than or lower than a predetermined safety value, then the light control film/window will be set automatically to "transparent" or "opaque" state, dependent on its application. For instance, if the light control film is used on the windshield of an automobile, it should be set to "transparent" state so as to enable a driver to continue to be able to drive the automobile at extremely low/high temperature.

It should be noted that the above embodiments are given by way of example only, and it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit of the present invention.

Claims

What is claimed is :

1. An apparatus for light control, comprising : means for containing fluid actively controlling the amount of light passing through said apparatus; means for altering the degree of transparency of said fluid; means for altering the amount of said fluid in said means for containing.

2. An apparatus for light control as claimed by claim 1 , wherein said fluid being a liquid medium containing minute elements, further comprising : means for generating ultrasonic sound wave, so as to ensure even distribution of said minute elements in said liquid medium.

3. A method for controlling transparency of a light cell containing light control fluid, comprising the steps of: altering the degree of transparency of said fluid; altering the amount of said fluid in said light cell.

4. A method for controlling transparency of a light cell containing light control fluid, as claimed by claim 3, further comprising the steps of: detecting the light intensity passing through said light cell; wherein the control of the light blocking capability of said light cell is basing on said detection.

5. A method for controlling transparency of a light cell containing light control fluid, as claimed by claim 3, further comprising the steps of: detecting environmental temperature; controlling transparency of said light cell to a predetermined level if said environmental temperature detected reaches a predetermined value.

6. A light cell, containing fluid for controlling light passing through, comprising : a first cell wall with a first conductive layer; a second cell wall with a second conductive layer; means for applying charges separately to said first and second conductive layers, for creating an electrostatic force between said first and second conductive layers, thereby controlling the spacing between said first and second cell walls and also the thickness of said fluid confined within said spacing; Wherein the degree of transparency of said fluid being dependent on said electrostatic field.

7. A light cell, containing fluid for controlling light passing through, comprising : a first cell wall with a first means for creating a field upon activated by a voltage source ; a second cell wall with a second means for creating a field upon activated by a voltage source; means for applying two voltages separately to said first and second means for creating, so as to create a field between said first and second means for creating; pumping means for driving said fluid into or fluid out of said cell;

Wherein the degree of transparency of said fluid being dependent on said field between said first and second means for creating.

8. A light cell, containing fluid for controlling light passing through, further comprising : a first cell wall with a first means for creating a field upon activated by a voltage source; a second cell wall with a second means for creating a field upon activated by a voltage source; means for applying two voltages separately to said first and second means for creating, so as to create a field force between said first and second means for creating, thereby controlling the spacing between said first and second cell walls and also the thickness of said fluid confined within said spacing;

Wherein the degree of transparency of said fluid being dependent on the field being created between said first and second means for creating.