JP2021018375A - Liquid crystal lighting control apparatus, power-supply unit and driving method of liquid crystal lighting control film - Google Patents

Abstract

To provide a liquid crystal lighting control apparatus capable of suppressing a sharp rise of a cost of manufacture while sufficiently controlling a transmittance of a liquid crystal lighting control film.SOLUTION: A liquid crystal lighting control apparatus 100 changes a transmittance of a liquid crystal to perform a lighting control, and includes a liquid crystal lighting control film 120 and a power-supply unit 110 for driving thereof. The liquid crystal lighting control apparatus is capable of taking an ON state in which a rectangular wave AC voltage, having a first peak voltage Vp higher than a threshold voltage Vth of the liquid crystal lighting control film 120 and a prescribed first frequency, is supplied from the power-supply unit 110 to the liquid crystal lighting control film 120; and a stand-by state in which an AC voltage, having a second peak voltage Vps equal to or lower than the threshold voltage Vth and a second frequency higher than the first frequency, is supplied from the power-supply unit 110 to the liquid crystal lighting control film 120.SELECTED DRAWING: Figure 12

Description

The present invention relates to a liquid crystal dimming device, a power supply device, and a method for driving a liquid crystal dimming film, and in particular, a liquid crystal dimming film used by being attached to a transparent member having a large area such as a window of a building or an automobile and driving the liquid crystal dimming film. The present invention relates to a liquid crystal dimming device provided with a power supply device for the purpose and a method for driving the liquid crystal dimmer.

Liquid crystals have the property of being able to electrically control their optical characteristics, and are used in various technical fields such as display devices. The liquid crystal dimming cell is also one of such products, and the light transmitting state can be changed by electrically controlling the transmittance of the liquid crystal. Recently, a product called a liquid crystal light control film has been proposed by expanding the area of the liquid crystal light control cell and processing it into a film, as an electronic shade that can gradually switch from a transparent state to a light-shielding state. It has been put to practical use.

For example, in Patent Document 1 below, by providing a resistance member having a variable resistance value between the electrode layers provided on both sides of the liquid crystal layer, the transmittance can be changed depending on the location to perform gradation expression. Possible liquid crystal light control films are disclosed. Further, Patent Document 2 discloses a liquid crystal light control film that avoids a decrease in transmittance by providing a spacer that holds the thickness of the liquid crystal layer, and Patent Document 3 discloses a light distribution that sandwiches the liquid crystal layer. A technique for firmly adhering a sealing agent by permeating a part of a sealing material on a film is disclosed.

Japanese Patent No. 6128269 JP-A-2017-09739 Japanese Patent No. 6120196

In order to drive the liquid crystal light control film, it is necessary to supply electric power from the power supply device, and it is necessary to provide the liquid crystal light control film as a liquid crystal light control device in which the liquid crystal light control film and the power supply device for driving the liquid crystal light control film are combined. In general, a small liquid crystal dimming cell has a large DC resistance and a small electric capacity, so that it can be driven by a relatively small current. Further, in the liquid crystal dimming cell, since a pair of transparent electrodes are arranged at intervals of about several μm with the liquid crystal layer interposed therebetween, it is necessary to take protective measures for the power supply device in consideration of a short circuit accident. Therefore, in general, the output impedance | Z0 | of the power supply device used for the small liquid crystal dimming cell is set high, and usually | Z0 | = several kΩ to 100 kΩ in many cases.

However, the DC resistance of the liquid crystal dimming cell decreases in inverse proportion to the area of the cell, and the electric capacity increases in proportion to the area of the cell. Therefore, in the case of a liquid crystal light control film having a structure in which the area of the liquid crystal light control cell is expanded to form a film, the DC resistance is small and the electric capacity is large as compared with a small liquid crystal light control cell. For this reason, if a general power supply device for a small liquid crystal dimming cell is used as it is as a power source for driving a liquid crystal dimming film, sufficient power is not supplied to the liquid crystal layer even if a normal voltage is applied. Is likely to occur.

In particular, in the case of a liquid crystal light control film used by being attached to a transparent member having a relatively large area such as a window used for the exterior or interior of a building, a window of a vehicle, or glass for a showcase, a conventional general small liquid crystal tone is used. When driven by a power supply device for an optical cell, the transmittance cannot be sufficiently controlled. Therefore, in the past, in order to drive a large liquid crystal light control film without any trouble, measures were taken such as increasing the voltage of the power supply device and providing terminals for applying voltage to the liquid crystal light control film at many locations. Was there. However, if such measures are taken, there will be a problem that the manufacturing cost will increase.

In a conventional liquid crystal dimmer, it is generally driven by an AC signal having a frequency of 30 to 200 Hz. If the frequency of the drive signal is lowered, sufficient power can be supplied even to the liquid crystal light control film having a large area, but if the frequency of the drive signal is lowered to less than 30 Hz, the liquid crystal light control film surface This is not preferable because a flicker phenomenon called "flicker" occurs. Of course, if the DC signal is used instead of the AC signal, the flicker problem does not occur, but the DC drive causes another problem of liquid crystal burn-in.

Therefore, an object of the present invention is to provide a liquid crystal dimming device capable of sufficiently controlling the transmittance of a liquid crystal dimming film while suppressing an increase in manufacturing cost, and such a liquid crystal dimming. It is an object of the present invention to provide a power supply device used for the device and a method for driving a liquid crystal light control film.

In order to solve the above problems, the liquid crystal dimming device of the present invention is a liquid crystal dimming device that performs dimming by changing the transmission rate of the liquid crystal, and is a liquid crystal dimming film and a power source for driving the liquid crystal dimming device. A rectangular wave AC voltage having a first peak voltage higher than the threshold voltage of the liquid crystal dimming film and a predetermined first frequency is supplied from the power supply device to the liquid crystal dimming film. An ON state and a standby state in which an AC voltage having a second peak voltage equal to or lower than the threshold voltage and a second frequency higher than the first frequency is supplied from the power supply device to the liquid crystal dimming film. Can be taken.

The first frequency may be 0.1 Hz or less, which is equal to or more than the lower limit of the frequency at which the liquid crystal light control film does not burn, and the second frequency may be 10 Hz or more and 100 Hz or less. The second peak voltage may be 0.3 times or more and 1.0 times or less the threshold voltage of the liquid crystal light control film. In the liquid crystal dimming device, the AC voltage supplied from the power supply device to the liquid crystal dimming film in the standby state may be a square wave AC voltage.

The liquid crystal light control film has an area suitable for being attached to a transparent plate constituting a window used for the exterior or interior of a building, a window of a vehicle, a transparent partition used as an interior partition, or a case of a showcase. Or, it may have an area suitable for being sandwiched between two transparent plates constituting them. The liquid crystal dimming film is attached to the image display for dimming the external light or the backlight from the front surface or the back surface of the image display, or is arranged before and after the image display. It may have an area suitable for use. The liquid crystal light control film may have an area of 0.1 square m or more.

The power supply device of the present invention is a power supply device for driving a liquid crystal light control film in order to perform dimming by changing the transmission rate of the liquid crystal, and the liquid crystal light control film has a threshold of the liquid crystal light control film. An AC having a rectangular wave AC voltage having a first peak voltage higher than the voltage, a predetermined first frequency, a second peak voltage equal to or lower than the threshold voltage, and a second frequency higher than the first frequency. It has the function of supplying voltage. The first frequency may be 0.1 Hz or less, which is equal to or more than the lower limit of the frequency at which the liquid crystal light control film does not burn, and the second frequency may be 10 Hz or more and 100 Hz or less.

The method for driving the liquid crystal light control film of the present invention is a drive method for driving the liquid crystal light control film in order to perform dimming by changing the transmission rate of the liquid crystal, and the liquid crystal light control film is combined with the liquid crystal. An ON state in which a rectangular wave AC voltage having a first peak voltage higher than the threshold voltage of the dimming film and a predetermined first frequency is supplied, and a second peak voltage equal to or lower than the threshold voltage to the liquid crystal dimming film. And a second frequency higher than the first frequency, and a standby state for supplying an AC voltage having the first frequency can be taken. The first frequency may be 0.1 Hz or less, which is equal to or higher than the lower limit of the frequency at which seizure does not occur on the liquid crystal light control film, and the second frequency may be 10 Hz or higher and 100 Hz or lower.

According to the present invention, it is possible to provide a liquid crystal dimming device, a power supply device, and a method for driving a liquid crystal dimming film, which can suppress an increase in manufacturing cost and sufficiently control the transmittance of the liquid crystal dimming film. Is possible.

It is a block diagram and the perspective view which show the basic structure of the general liquid crystal dimmer 100 including this embodiment. It is a side sectional view of the liquid crystal light control film 120 shown in FIG. It is a circuit diagram which shows the equivalent circuit of the liquid crystal light control film 120 shown in FIG. 2A. It is a graph which shows the alternating current (square wave) drive characteristic of the liquid crystal light control film of 10 mm square. It is a graph which shows the alternating current (sine wave) drive characteristic of the liquid crystal light control film of 10 mm square. It is a graph which shows the alternating current (square wave) drive characteristic of the liquid crystal light control film of 1 m square. It is a graph which shows the alternating current (sine wave) drive characteristic of the liquid crystal light control film of 1 m square. It is a graph which shows the "transmittance-voltage characteristic" of the liquid crystal light control film 120 (normally duck type) shown in FIG. It is a graph which shows the "transmittance-voltage characteristic" of the liquid crystal light control film 120 (normally clear type) shown in FIG. It is a waveform diagram of the square wave AC signal used for the liquid crystal dimming apparatus 100 of this embodiment. It is a graph which shows the characteristic of each frequency band of the AC signal used for driving a liquid crystal light control film 120. It is a graph which shows the characteristic of each frequency band of the AC signal used for driving a liquid crystal light control film 120. It is a front view of the influence measuring apparatus 200 which shows the degree of influence of the occurrence of flicker by a driving frequency. FIG. 5 is a side view (partly a side sectional view) showing a specific measurement method using the influence measuring device 200 shown in FIG. It is a graph which shows the result of the flicker sensation test (the type of normality duck). It is a graph which shows the result of the flicker sensation test (normally clear type). It is a graph which shows the transmittance-frequency characteristic which shows the result of the seizure state test. It is a waveform diagram of the AC signal used for the liquid crystal dimming apparatus 100 of this embodiment, and shows the waveform when the liquid crystal dimming apparatus 100 is sequentially switched from an ON state to a standby state and an ON state. It is a vertical cross-sectional view which shows typically the state of the liquid crystal in the OFF state and the ON state of the liquid crystal dimmer 100 which has the characteristic of the conventional general normally clear. It is a vertical cross-sectional view which shows typically the state of the liquid crystal in the standby state and the ON state of the liquid crystal dimmer 100 which has the characteristic of normal clear of this embodiment. It is a graph which shows the "transmittance-voltage characteristic" and "haze-voltage characteristic" of the liquid crystal light control film 120 (normally clear type) of this embodiment. It is a graph which shows the transmittance fluctuation which occurs at the time of polarity reversal of a driving AC signal. It is a graph which shows the modification which supplies the initial voltage Vpp which is larger than the peak voltage Vp at the time of polarity reversal in order to suppress the transmittance fluctuation shown in FIG.

Hereinafter, one of the embodiments of the present invention (hereinafter, referred to as “the present embodiment”) will be described with reference to the drawings.

<<< §1. Basic configuration of general liquid crystal dimmer >>>
First, in this §1, the basic configuration of a general liquid crystal dimmer will be briefly described. The liquid crystal dimming device according to the present embodiment also has the basic configuration described here. FIG. 1 is a block diagram and a perspective view showing a basic configuration of a general liquid crystal dimming device 100 including the present embodiment. The liquid crystal dimming device 100 has a function of dimming by changing the transmittance of the liquid crystal, and as shown in the figure, the power supply device 110 (shown in the block diagram) and the liquid crystal dimming film 120 (shown in the perspective view). ) And.

The liquid crystal light control film 120 has a first transparent electrode layer 121, a liquid crystal layer 122, and a second transparent electrode 123 from top to bottom. The first transparent electrode layer 121 is arranged on one surface (upper surface in the case of the figure) of the liquid crystal layer 122, and the second transparent electrode layer 123 is the other surface (lower surface in the case of the figure) of the liquid crystal layer 122. It is located in. Further, a film-side first connection terminal a is provided at a predetermined position of the first transparent electrode layer 121 (in the case of the figure, the left edge of the upper surface), and a predetermined position of the second transparent electrode layer 123 (in the case of the figure). , The left edge of the lower surface) is provided with a second connection terminal b on the film side.

The liquid crystal layer 122 is composed of, for example, a layer containing field effect liquid crystal molecules, and the first transparent electrode layer 121 and the second transparent electrode layer 123 are composed of, for example, a layer made of ITO (Indium Tin Oxide). There is. Actually, in addition to these three layers, a transparent film layer or a filter layer that functions as a protective layer may be used, but in the present application, the description of these additional layers will be omitted.

On the other hand, the power supply device 110 is a component for driving the liquid crystal dimming film 120, and is a power supply side first connection terminal A connected to the film side first connection terminal a and a film side second connection terminal b. It has a function of supplying a predetermined AC voltage between the second connection terminal B on the power supply side connected to the above. The figure shows the conceptual internal configuration of the power supply device 110 as a combination of the ideal power supply 111 and the output impedance 112. The ideal power supply 111 is a theoretical signal source that generates an ideal AC signal (square wave or sine wave), and the output impedance 112 is a resistance element inside a circuit constituting the power supply device 110. The output impedance 112 is the sum of the original impedance of the power supply itself and the impedance intentionally added to protect the power supply and the connection circuit from damage, heat generation, ignition, etc. due to overcurrent. In FIG. 1, the value of the output impedance 112 of the power supply device 110 is indicated by the symbol | Z0 |.

In this way, an AC signal is supplied from the power supply device 110 between the connection terminals a and b on the liquid crystal light control film 120 side, and the liquid crystal layer sandwiched between the first transparent electrode layer 121 and the second transparent electrode layer 123. An AC voltage is applied to the 122 in the thickness direction thereof. The liquid crystal layer 122 contains liquid crystal molecules whose orientation is changed by an electric field, and its translucency is changed by applying a voltage. The term "liquid crystal dimming film" in the present application is basically synonymous with "liquid crystal dimming cell", but in the following examples, a sheet having a relatively large area of each constituent layer is used. None, refers to those used by attaching a film to a transparent member with a large area, such as a building or automobile window.

The liquid crystal light control film 120 is classified into two types of products, normal reddish and normally clear, according to the type of liquid crystal molecules constituting the liquid crystal layer 122. In normal maryak type products, the light transmittance of the liquid crystal layer 122 is low when no voltage is applied, and the film is observed as an "opaque" film by the observer, but when a voltage is applied, the liquid crystal is displayed. The light transmittance of the layer 122 is increased, and the observer observes it as a "transparent" film. On the other hand, the normally clear type product has a high light transmittance of the liquid crystal layer 122 when no voltage is applied, and is observed as a "transparent" film by the observer, but a voltage is applied. In this state, the light transmittance of the liquid crystal layer 122 becomes low, and the film is observed as an "opaque" film by the observer. The present invention is applicable to any type of product.

FIG. 2A is a side sectional view of the liquid crystal light control film 120 shown in FIG. As described above, the liquid crystal layer 122 is a layer sandwiched between the first transparent electrode layer 121 and the second transparent electrode layer 123, and usually has a thickness of about several μm. As described above, the AC voltage generated by the power supply device 110 is applied between the film-side first connection terminal a and the film-side second connection terminal b. The first transparent electrode layer 121 and the second transparent electrode layer 123 are made of a transparent and conductive material such as ITO (Indium Tin Oxside), and an AC voltage is applied to the entire liquid crystal layer 122. .. Therefore, if the liquid crystal layer 122 is transparent, the entire liquid crystal light control film 120 becomes transparent, and if the liquid crystal layer 122 is opaque, the entire liquid crystal light control film 120 becomes opaque.

Here, as shown on the right side of the figure, the film-side first far point c and the film-side second far point d are defined. These distant points c and d are defined points for convenience of explanation, and there is no physical structure. The film-side first far point c is a point defined on the upper surface of the first transparent electrode layer 121, and the film-side second far point d is a point defined on the lower surface of the second transparent electrode layer 123.

An electric signal from the power supply device 110 is directly supplied to the film side first connection terminal a and the film side second connection terminal b, but the film side first far point c and the film side second far point d are supplied with electric signals. The electric signal from the power supply device 110 is indirectly supplied via the first transparent electrode layer 121 and the second transparent electrode layer 123, respectively. Since the first transparent electrode layer 121 and the second transparent electrode layer 123 have some electrical resistance, they are applied between the far points c and d as compared with the voltage applied between the connection terminals a and b. The voltage drops slightly.

FIG. 2B is a circuit diagram showing an equivalent circuit of the liquid crystal light control film 120 shown in FIG. 2A. In the figure, the line from the point a to the point c corresponds to the first transparent electrode layer 121, and the first electrode layer resistance R1 is the resistance between the points a and c of the first transparent electrode layer 121. Similarly, the line from the point b to the point d corresponds to the second transparent electrode layer 123, and the second electrode layer resistor R2 is the resistance between the points b and d of the second transparent electrode layer 123. When considering the resistance of the wiring between the power supply device 110 and the connection terminals a and b, these wiring resistances may be included in the resistors R1 and R2. On the other hand, the RL and CL connected in parallel in the figure are the resistance of the liquid crystal layer 122 (including the resistance when the light distribution film is present) and the electric capacity (the capacitance when the light distribution film is present), respectively. Including).

When the voltage Vin is supplied between the connection terminals a and b, for example, when the connection terminal a side is positive, a current flows in the path along the arrow in the figure. RF is a DC resistance between the connection terminals a and b along such a path, and is referred to here as a DC resistance of the liquid crystal light control film. The value of this RF is as shown at the bottom of the figure.
RF = R1 + R2 + RL
It is expressed by the formula.

As described above, since the resistors R1 and R2 are present in the first transparent electrode layer 121 and the second transparent electrode layer 123, as described above, they are farther than the voltage Vin applied between the connection terminals a and b. The voltage Vend applied between points c and d drops slightly. In the case of a small liquid crystal dimming cell, this voltage drop is slight, so that there is no major problem in operation. However, in the case of a liquid crystal dimming film having a large area, this voltage drop affects the light transmittance. It is a factor that makes a significant difference.

Further, as the area of the liquid crystal light control film 120 increases, the distance between the two points a and c and the distance between the two points b and d also increase, so that the values of the first electrode layer resistance R1 and the second electrode layer resistance R2 Is large, but the liquid crystal layer resistance RL is conversely small. However, since the values of the resistors R1 and R2 are smaller than the values of the resistors RL, the value of the DC resistance RF of the liquid crystal light control film is largely dominated by the value of the resistance RL, and the area of the liquid crystal light control film 120 is large. Then, the value of the resistance RF becomes small. Further, since the resistor RL and the capacitance CL are connected in parallel, when the area of the liquid crystal light control film 120 becomes large and the value of the resistor RL becomes small, more current flows in the resistor RL, and the capacitance CL becomes The electric charge supplied is reduced, and the original power supplied to the capacitance CL to drive the liquid crystal is reduced. Therefore, the larger the area of the liquid crystal light control film 120, the more power needs to be supplied from the power supply device 110.

<<< §2. AC drive characteristics of liquid crystal light control film >>>
The liquid crystal dimming film 120 can also be driven by direct current, and the light transmittance of the liquid crystal layer 122 can be controlled by applying a direct current voltage between the connection terminals a and b shown in FIG. 2A. Is. However, when DC drive is performed, the orientation of the liquid crystal molecules is always fixed in the same direction, so that so-called "liquid crystal burn-in" occurs, and even if the voltage supply is stopped, the original state cannot be restored. There is a problem. For this reason, AC driving (generally, driving by an AC signal having a frequency of 30 to 200 Hz) is often performed.

The liquid crystal dimming device 100 of the present embodiment is also a device on the premise that the liquid crystal dimming film 120 is AC-driven, and the power supply device 110 has a function of supplying AC power. However, in the present invention, the drive is performed by a square wave AC signal having a frequency much lower than that of the conventional general drive frequency band of 30 to 200 Hz. This point will be described in detail in §3.

Here, the AC drive characteristics of the liquid crystal light control film 120 described in §1 will be described. FIG. 3 is a graph showing the AC drive characteristics of the 10 mm square liquid crystal light control film 120. The liquid crystal light control film 120 has a distance between the two points a and c shown in FIG. 2A of about 10 mm at most, and should be called a "liquid crystal light control cell" rather than a "liquid crystal light control film". However, here, for convenience of comparison, it will be referred to as a "liquid crystal dimming film".

FIG. 3A shows a connection terminal supply voltage Vin (voltage between two points a and b in FIG. 2A: voltage when a power supply device 110 that generates a 60 Hz square wave used in a conventional general liquid crystal dimming cell is used. It is a graph which shows the result of having measured the remote terminal supply voltage Vend (voltage between two points c and d of FIG. 2A: a broken line graph) with an oscilloscope (solid line graph). Although only the solid line graph Vin appears in the figure, the broken line graph Vend is a graph that overlaps with the solid line graph Vin. FIG. 3B is a similar graph when the power supply device 110 that generates a 60 Hz sine wave is used, and the broken line graph Vend is also a graph that overlaps with the solid line graph Vin. After all, both the rectangular wave and the sine wave completely match the waveform of the AC voltage Vin and the waveform of the AC voltage Vend, and the thickness of each part of the liquid crystal dimming film 120 shown in FIG. 2A. A uniform voltage will be applied in the direction.

As described above, the graphs shown in FIGS. 3A and 3B are graphs when a 10 mm square liquid crystal light control film 120 (liquid crystal light control cell) is driven by a conventional general power supply for a liquid crystal light control cell. .. According to this graph, it can be seen that a substantially uniform voltage is applied over the entire surface of the liquid crystal light control film 120. That is, if the peak voltage (instantaneous peak voltage of the AC signal) generated by the power supply device 110 is Vp, a peak voltage substantially the same as the peak voltage Vp is applied over the entire surface of the liquid crystal dimming film 120, and the liquid crystal It can be estimated that a substantially uniform light transmittance is obtained over the entire surface of the light control film 120. Therefore, in the case of the liquid crystal light control film 120 (liquid crystal light control cell) of this size, there is no problem even if it is driven by the conventional power supply device 110 for driving the liquid crystal light control cell. ..

On the other hand, FIGS. 4A and 4B are graphs showing the AC drive characteristics of the 1 m square liquid crystal light control film 120. The liquid crystal light control film 120 is a square film having a side of 1 m, and is used by being attached to a transparent member having a large area such as a window of a building or an automobile. Therefore, the distance between the two points a and c shown in FIG. 2A extends to about 1 m, and the values of the first electrode layer resistor R1 and the second electrode layer resistor R2 are not negligible. On the contrary, the value of the liquid crystal layer resistance RL becomes small, the ratio of the current flowing on the resistance RL side increases, and the original power supplied to the capacitance CL for driving the liquid crystal decreases.

4A and 4B show the same power supply device 110 (power supply device used in a conventional general liquid crystal dimming cell) as the power supply device used when the graphs shown in FIGS. 3A and 3B are obtained, respectively. It is a graph which shows the connection terminal supply voltage Vin (solid line graph) and the remote terminal supply voltage Vend (dashed line graph) when it is used. The waveform of the supply voltage Vin shown in the solid line graph is close to the original rectangular wave or sine wave generated by the ideal power supply 111, whereas the waveform of the supply voltage Vend shown in the broken line graph is the original peak. The voltage Vp has dropped considerably, and the waveform has become dull.

That is, the supply voltage Vend (broken line graph) between the two points c and d is lower than the supply voltage Vin (solid line graph) between the two points a and b shown in FIG. 2B, and each part of the liquid crystal dimming film 120 There will be a difference in the applied voltage, and the light transmittance will be uneven. Of course, in some cases, the supply voltage between the two points a and b may also be lower than the voltage originally supplied by the power supply device 110, and the liquid crystal dimming film 120 as a whole cannot perform the original dimming function. Become in a state. That is, in the case of a normal-leading type product, even if an AC signal having a peak voltage Vp is supplied and driven, the original completely transparent state is not obtained and a turbid state is generated. Further, in the case of a normally clear type product, even if an AC signal having a peak voltage Vp is supplied and driven, the original completely opaque state is not obtained, but a semi-transparent portion is formed.

As described above, the power supply device designed to drive the 10 mm square liquid crystal light control film can normally drive the liquid crystal light control film, but can normally drive the 1 m square liquid crystal light control film. Can't be done. The present invention has an area suitable for being attached to a window used for the exterior or interior of a building, a window of a vehicle, a transparent partition used as an interior partition, or a transparent plate such as glass constituting a showcase case. The main purpose is a liquid crystal dimming device having a liquid crystal dimming film having the above, and the present invention relates to a device used as an electronic shade, for example. The liquid crystal light control device is not limited to the one in which the liquid crystal light control film is attached to the transparent plate. For example, in a window, a transparent partition, or a case composed of two transparent plates, the liquid crystal light control film can be used. It may be sandwiched between two transparent plates via an interlayer film or the like. Further, in the image display, the present invention is used by being attached to the image display or arranged before and after the image display in order to dimm the external light or the backlight from the front surface or the back surface. It also focuses on a liquid crystal dimming device having a liquid crystal dimming film having an area suitable for the above. The power supply device used in such a liquid crystal dimming device needs to have a function suitable for driving a liquid crystal dimming film having a large area.

According to an experiment conducted by the inventor of the present application, a general power supply device designed for driving a liquid crystal dimming cell of about 10 mm square has a large liquid crystal dimming having an area of 0.1 square m or more. The film could not be driven normally. Specifically, when the general power supply device is used to drive the liquid crystal light control film by applying an AC voltage of 60 Hz to one of the edges of the liquid crystal light control film, the area of the liquid crystal light control film is 0.1 square m. When the above is reached, the phenomenon that the actual voltage applied to the liquid crystal light control film decreases begins to appear. The present invention has been made mainly for a liquid crystal dimming device having a large liquid crystal dimming film having an area of 0.1 square m or more, and normally drives such a large liquid crystal dimming film. It proposes the optimum drive frequency for the power supply device that can be used.

<<< §3. Features of the liquid crystal dimming device of this embodiment >>>
<3.1 Driving method of the liquid crystal dimmer of the present embodiment>
As a method for supplying sufficient electric power to drive the large-sized liquid crystal light control film 120 without any trouble, there is a method of increasing the voltage of the power supply device 110. 5A and 5B are graphs showing the "transmittance-voltage characteristics" of the liquid crystal light control film 120 shown in FIG. This graph shows the peak voltage of the square wave AC signal (unit: V: hereinafter simply referred to as applied voltage) on the premise that a 60 Hz square wave AC signal is applied between both connection terminals a and b of the liquid crystal light control film 120. The light transmission rate (unit%: average value over the entire surface) of the liquid crystal light control film 120 at that time is shown.

The liquid crystal dimming film 120 used as the measurement target of the “transmittance-voltage characteristic” shown in the graph of FIG. 5A uses a normal mary duck type liquid crystal layer 122, and the transmittance is 0 when the applied voltage is 0 V. Although the state of complete shading of% is maintained, the transmittance gradually increases when the applied voltage exceeds about 3 V, and when the applied voltage reaches 10 V, the transmittance becomes about 33%, like frosted glass. It becomes a translucent state.

As described above, the example shown in FIG. 5A is an example of the liquid crystal dimming device 100 having a function of performing dimming in which the transmittance is controlled in the range of 0% to 33%, and the applied voltage is in the range of 0 to 10V. By adjusting with, the transmittance can be controlled in the range of 0% to 33%. However, looking at this characteristic, it has the characteristic that the transmittance changes abruptly when the applied voltage is around 4 to 5 V, and in the section where the applied voltage is 0 to 3 V or the section where the applied voltage is 6 to 10 V, the transmittance becomes high. Not much change has occurred. That is, it has a characteristic that the transmittance changes abruptly in the region where the applied voltage takes an intermediate value, and the change in the transmittance becomes slow in the portion where the applied voltage is low or high.

The liquid crystal light control film 120 used as the measurement target of the "transmittance-voltage characteristic" shown in the graph of FIG. 5B uses a normally clear type liquid crystal layer 122, and has a transmittance of 70 when the applied voltage is 0 V. The transparent state of% is maintained, but when the applied voltage exceeds about 1 V, the transmittance gradually decreases, and when the applied voltage reaches 10 V, the transmittance becomes about 20% and the light-shielded state is established.

As described above, the example shown in FIG. 5B is an example of the liquid crystal dimming device 100 having a function of performing dimming in which the transmittance is controlled in the range of 70% to 20%, and the applied voltage is in the range of 0 to 10V. By adjusting with, the transmittance can be controlled in the range of 70% to 20%. However, looking at this characteristic, it has the characteristic that the transmittance changes sharply when the applied voltage is around 1.5 to 4 V, and in the section where the applied voltage is 0 to 1.5 V or 4 to 10 V. , The transmittance has not changed so much. That is, it has a characteristic that the transmittance changes abruptly in the region where the applied voltage takes an intermediate value, and the change in the transmittance becomes slow in the portion where the applied voltage is low or high.

The voltage Vp of the AC drive signal shown in FIGS. 3A and 3 and 4A and 4B is the peak voltage of the AC signal output by the power supply device 110, and FIG. 5A of the liquid crystal light control film 120 to be supplied with power. A predetermined voltage value is set as the peak voltage Vp in consideration of the characteristics shown in FIG. 5B.

For example, when using a liquid crystal dimming film 120 having the characteristics of normality as shown in FIG. 5A and performing dimming in which the transmittance is controlled in the range of 0% to 33% for the purpose of use, the minimum transmittance is obtained. Is set to 0% and the maximum transmittance is set to 33%. In this case, when the power supply device 110 does not supply a voltage, the liquid crystal light control film 120 exhibits a minimum transmittance of 0%, and the power supply device 110 supplies an AC voltage having a peak voltage Vp = 10V. If so, the liquid crystal light control film 120 will exhibit a maximum transmittance of 33%. Therefore, in this case, the peak voltage Vp = 10V may be set.

Further, when the liquid crystal light control film 120 having the characteristic of normally clear as shown in FIG. 5B is used and the light control is performed in which the transmittance is controlled in the range of 70% to 20% for the purpose of its application, the maximum transmittance is obtained. Is set to 70% and the minimum transmittance is set to 20%. In this case, when the power supply device 110 does not supply the voltage, the liquid crystal light control film 120 exhibits a maximum transmittance of 70%, and the power supply device 110 supplies an AC voltage having a peak voltage Vp = 10V. If so, the liquid crystal light control film 120 will exhibit a minimum transmittance of 20%. Therefore, in this case, the peak voltage Vp = 10V may be set.

In short, the liquid crystal dimming film 120 has a minimum transmittance and a maximum transmittance defined for its use, and when the power supply device 110 does not supply voltage, the liquid crystal dimming film 120 has a minimum transmittance. The liquid crystal light control film 120 exhibits the minimum transmittance and the maximum transmittance when either the transmittance or the maximum transmittance is shown and the power supply device 110 supplies an AC voltage having a peak voltage Vp. It will show the other transmittance of the rate.

Therefore, one of the methods for supplying sufficient power for driving the large-sized liquid crystal light control film 120 without any trouble is a method for increasing the voltage of the power supply device 110. For example, in order to drive a liquid crystal dimming film having "transmission-voltage characteristics" shown in the graphs of FIGS. 5A and 5B, basically, an AC voltage having a peak voltage Vp = 10V should be supplied. However, as shown in the broken line graphs of FIGS. 4A and 4B, when the AC waveform becomes dull and the voltage actually applied to the liquid crystal dimming film 120 drops, allow a margin, for example, peak voltage Vp = A power supply device 110 having a function of supplying an AC voltage having 15 V may be prepared. Then, even if the actual applied voltage is slightly lowered, the desired transmittance set in advance can be obtained. However, increasing the output voltage of the power supply device 110 causes a problem that the cost rises.

As another method of supplying sufficient power to drive the large-sized liquid crystal light control film 120 without any trouble, there is also a method of providing connection terminals for applying a voltage to the liquid crystal light control film 120 at a large number of places. However, this method also has a problem that the cost rises. For example, in the case of the example shown in FIG. 1, film-side connection terminals a and b are provided on the left edge of the liquid crystal light control film 120, and these connection terminals are provided along the edge of the liquid crystal light control film 120. If it is provided at many locations, it is possible to suppress a partial voltage drop. However, since the number of electrical connection points with the power supply device 110 increases, the manufacturing cost has to rise.

In order to reduce the manufacturing cost, as shown in the example shown in FIG. 1, the first connection terminal a on the film side is provided at a predetermined position on the edge of the liquid crystal dimming film 120 (in the case of the illustrated example, the left edge). It is preferable that the second connection terminal b on the film side is provided at a position facing the predetermined position of the liquid crystal light control film 120, and the wiring from the power supply device 110 is provided at only one place.

On the other hand, as yet another method of supplying sufficient power, a method of using a low resistance transparent electrode as a pair of transparent electrode layers can be considered, but the low resistance transparent electrode has a low light transmittance and a poor appearance. It is not suitable for windows used for the exterior or interior of buildings, windows for vehicles, or large liquid crystal dimmers used by attaching to glass for showcases.

Therefore, the inventor of the present application specifies the frequency of the AC drive signal supplied from the power supply device 110 in order to sufficiently control the transmittance of the liquid crystal light control film 120 by the power supply device 110 while suppressing the increase in manufacturing cost. I focused on setting the value. As described above, in the conventional liquid crystal dimmer, it is common to drive with an AC signal having a frequency of 30 to 200 Hz. In general, when driven in a high frequency range exceeding 200 Hz, the applied voltage drops sharply due to the blunting of the waveform as shown by the broken line graph in FIG. 4, and sufficient charge cannot be supplied, and the low frequency range of less than 30 Hz. This is because a flicker phenomenon called flicker occurs on the surface of the liquid crystal light control film when driven by.

As described above, it has been common knowledge to use a frequency in the middle frequency range of 30 to 200 Hz as the drive frequency of the liquid crystal light control film 120. Contrary to this common sense, the feature of the present invention is that a drive frequency lower than the low frequency range in which flicker occurs is used. FIG. 6 is a waveform diagram of a square wave AC signal used in the liquid crystal dimming device 100 of the present embodiment. For example, if the frequency of this square wave AC signal is set to a very low frequency of 0.01 Hz, the period T is a very long time of 100 sec. In FIG. 6, the waveform of the section of the half-period T / 2 of this rectangular wave AC signal is drawn, but when the frequency is set to 0.01 Hz, the half-period T / 2 = 50 sec is a long time.

As described above, even if the voltage Vin (solid line graph) is supplied from the power supply device 110 between the connection terminals a and b, the voltage Vend (broken line graph) applied between the distant points c and d has a slight waveform bluntness. It will occur. However, if the half cycle T / 2 is set to a long time of 50 sec, the voltage drops due to the influence of the waveform blunt immediately after the polarity reversal every half cycle, but after that, the voltage becomes the peak voltage Vp. Reach and stabilize. That is, if the period T is set to such a length, the difference between the broken line graph and the straight line graph shown in FIG. 6 is only a short period immediately after the polarity reversal every half period. Therefore, the peak voltage Vp is supplied to the entire liquid crystal light control film 120 over almost the entire time zone, and sufficient power is sufficient to drive the large liquid crystal light control film 120 without any trouble. You will be able to supply.

However, the longer the period T is set, the closer the drive signal is to direct current, which causes another problem of liquid crystal burn-in. This liquid crystal seizure phenomenon is a problem that when a DC voltage is continuously applied for a long time, the orientation of the liquid crystal molecules is always fixed in the same direction, and even if the voltage supply is stopped, the original state cannot be restored. In order to avoid this seizure phenomenon, the conventional general liquid crystal dimmer is driven by an AC signal instead of being driven by a DC signal. Therefore, in carrying out the present invention, a lower limit value is set for the drive frequency in order to avoid this burn-in phenomenon.

7A and 7B are graphs showing the characteristics of each frequency band of the AC signal used to drive the liquid crystal light control film 120. FIG. 7A shows the characteristics of each frequency band, with the frequency of the AC voltage supplied from the power supply device 110 to the liquid crystal light control film 120 on the horizontal axis. As described above, in the high frequency range exceeding 200 Hz, the voltage drop due to the waveform blunting becomes severe, and sufficient charge cannot be supplied. In particular, in a liquid crystal light control film having a large liquid crystal light control cell, it is difficult to supply sufficient charges in this high frequency range.

On the other hand, in the low frequency range of less than 30 Hz, the occurrence of flicker causes an unpleasant flicker to be noticed by the observer. Therefore, conventionally, it has been generally driven by an AC voltage having a frequency in the middle frequency range of 30 to 200 Hz. However, even if the frequency is within this medium frequency range, if the liquid crystal dimming cell becomes large, there is a possibility that sufficient charge cannot be supplied.

The inventor of the present application has found that even in the frequency range of 30 Hz or less, the unpleasant flicker caused by flicker becomes less noticeable when the frequency is further lowered. That is, it was found that when the frequency is equal to or lower than the upper limit frequency fH shown on the frequency axis of FIG. 7A, even if flicker occurs, the flicker does not feel unpleasant. Therefore, contrary to the conventional technical common sense that "a frequency range of 30 Hz or less cannot be used because flicker occurs", it is possible to use a frequency band even lower than this low frequency range. all right.

On the other hand, at a frequency of 0 Hz (that is, direct current), the above-mentioned problem of liquid crystal burn-in occurs. Further, the problem of burn-in also occurs in the vicinity of direct current having a frequency close to 0 Hz. Therefore, as shown in the figure, the lower limit frequency fL is set as the lowest frequency at which the problem of seizure does not occur, and the range above the lower limit frequency fL and below the upper limit frequency fH is defined as the specific frequency band. In the present invention, this specific frequency is defined. We decided to use a rectangular wave AC signal with a frequency within the band to drive the liquid crystal light control film.

FIG. 7B is an enlarged view of the vicinity of the specific frequency band, which is the drive range of the present embodiment. As shown in the figure, if the upper limit frequency fH is exceeded, an unpleasant flicker occurs in a low frequency region, which is not preferable. If the frequency is equal to or lower than the upper limit frequency fH, even if flicker occurs, the flicker will not be unpleasant. The value of this upper limit frequency fH means the upper limit value of the frequency at which unpleasant flicker does not occur for the observer, and as described in 3.2, it can be confirmed that fH = 0.1 Hz (period TH = 10 sec). It was.

For example, in the example shown in FIG. 6, when the frequency of the rectangular wave AC signal is set to 0.1 Hz (upper limit frequency fH), the period T becomes 10 sec, and the polarity is inverted every half cycle T / 2 = 5 sec. At the time of this polarity reversal, flicker occurs for a moment (in the present application, such "flicker" is also referred to as "flicker" for convenience), but such "flicker" is driven at a frequency of about 20 Hz. It does not cause the unpleasant "flicker" that occurs when you do. As described above, when the upper limit frequency fH = 0.1 Hz or less, unpleasant "flickering" does not occur.

On the other hand, as shown in FIG. 7B, when the frequency of the driving AC signal is less than the lower limit frequency fL, it falls into the DC vicinity region where burn-in occurs, which is not preferable. The value of this lower limit frequency fL differs depending on the configuration of the liquid crystal layer 122 used, but in the case of the specific liquid crystal dimming film 120 used in the experiment described in §3.2, fL = 1.9 × ^10-6 Hz ( It was confirmed that the cycle TL = 6 days). In other words, in the case of the specific liquid crystal light control film 120 used in the experiment, seizure does not occur even if a voltage of the same polarity is applied for a period of half cycle TL / 2 = 3 days (72 hours). It will be.

After all, the feature of the present invention is that the power supply device 110 supplies the liquid crystal dimming film 120 with a square wave AC voltage having a predetermined driving frequency to drive the liquid crystal light control film 120, and the liquid crystal is used as the predetermined driving frequency. The point is that the dimming film 120 uses a frequency higher than the frequency at which seizure occurs, and the liquid crystal dimming film 120 uses a frequency lower than the frequency at which flicker that is unpleasant for the observer occurs. Specifically, as described in detail in §3.2, the lower limit of the frequency at which seizure does not occur on the liquid crystal light control film is set to the lower limit frequency fL, 0.1 Hz is set to the upper limit frequency fH, and the lower limit frequency fL is changed to the upper limit frequency fH. When the range is defined as a specific frequency band, the power supply device 110 may supply a rectangular wave AC voltage having a frequency within the specific frequency band.

As described above, in the liquid crystal dimming device of the present embodiment, the liquid crystal dimming film is formed by a rectangular wave AC signal having a frequency in a frequency band far lower than the conventional general driving frequency band of 30 to 200 Hz. Therefore, it becomes possible to supply sufficient power even to a liquid crystal light control film having a large area, and it becomes possible to sufficiently control the transmittance. Further, since the drive frequency of the present embodiment is set to a frequency lower than the frequency at which the flicker that is unpleasant for the observer occurs, the occurrence of the flicker that is unpleasant can be suppressed. Moreover, since the drive is performed at a frequency higher than the frequency at which the liquid crystal light control film is burned, it is possible to prevent the liquid crystal light control film from being burned.

As described above, in the present embodiment, since the liquid crystal dimming film is driven by the AC signal having a frequency within the specific frequency band, the supply voltage of the power supply device 110 can be increased or the voltage can be applied to the liquid crystal dimming film 120. It is not necessary to adopt a method of providing connection terminals for application at a large number of places, and as a result, there is no problem that the manufacturing cost rises. Therefore, according to the present embodiment, it is possible to sufficiently control the transmittance of the liquid crystal light control film by the power supply device while suppressing the increase in the manufacturing cost.

<3.2 Experiment for determining upper limit frequency fH and lower limit frequency fL>
Here, the experiments performed to determine the upper limit frequency fH and the lower limit frequency fL shown in FIGS. 7A and 7B and the results thereof will be described.

First, an experiment performed to determine the upper limit frequency fH will be described. As shown in FIGS. 7A and 7B, the upper limit frequency fH is a frequency indicating a boundary between a low frequency region where unpleasant flicker occurs and a drive region (specific frequency band) of the present embodiment in which such flicker does not occur. Is. Therefore, the inventor of the present application investigated the relationship between the drive frequency and the occurrence of flicker by using an influence measuring device that indicates the degree of influence of the occurrence of flicker depending on the drive frequency.

FIG. 8 is a front view of the influence measuring device 200. As shown in the figure, the effect measuring device 200 has a rectangular opening 211 opened in the center of a rectangular A4 size black drawing paper 210, and a liquid crystal dimming device 220 (in FIG. 8, the outline thereof is represented by a chain line). (Indicating) is attached. Actually, the backlight 230 is arranged on the back side of the liquid crystal dimming device 220. The diagonal line hatching in FIG. 8 indicates the surface area of the black drawing paper 210, and does not indicate the cross section.

The opening 211 provided in the black drawing paper 210 is a square having a side of 50 mm, and serves to expose the surface portion of the liquid crystal dimming film of the liquid crystal dimming device 220. The liquid crystal dimming device 220 is a device provided with a normal-leading type liquid crystal dimming film having "transmittance-voltage characteristics" shown in FIG. 5A, and has a light transmittance (on the back surface) when no voltage is applied. It has a light-shielding property that makes the transmittance of light from the installed backlight 230) 0%. As the voltage applied to the liquid crystal light control film is increased, the transmittance gradually increases as shown in the graph of FIG. 5, and when the applied voltage reaches 10 V, the transmittance reaches 33%. Reach.

The liquid crystal light control film (liquid crystal light control cell) used in the liquid crystal light control device 220 has an area (about 50 mm square) substantially equal to the area of the opening 211, and is the main object of the present invention. It is not a large film. Therefore, basically, the connection terminal supply voltage Vin supplied from the power supply device is applied to the entire surface of the liquid crystal dimming cell as it is, and the voltage does not drop. The purpose of the experiment performed here is to change the drive frequency using a conventional small liquid crystal dimming cell and determine whether or not an unpleasant flicker is recognized by the observer due to the effect.

The backlight 230 (not shown in FIG. 8) that illuminates from the back surface of the liquid crystal light control film is a lighting device equipped with an LED and a resin diffuser, and is white with a brightness of 2000 cd / m ^2. It has a function of illuminating with an illumination light close to that of. Therefore, when the observer observes the influence measuring device 200 from the front, the liquid crystal dimming film of the liquid crystal dimming device 220 can be recognized in the opening 211, and the voltage applied to the liquid crystal dimming film is increased. By doing so, it is possible to recognize how the white illumination light is transmitted from the inside of the opening 211.

FIG. 9 is a side view showing a specific measurement method using the influence measuring device 200 shown in FIG. 8 (the portion of the black drawing paper 210 is a side sectional view). As described above, the black drawing paper 210 has an opening 211, and a liquid crystal dimming device 220 is attached to the back side thereof. A backlight 230 is arranged on the back surface of the liquid crystal dimmer 220.

The following experiment was conducted in an environment in which the impact measuring device 200 was installed in a room with a white wallpaper attached to the inside, and the subject 400 was seated at a position 3 m away from the front of the impact measuring device 200 as shown in the figure. I was broken. The influence measuring device 200 and the subject 400 are illuminated by a daylight fluorescent lamp 300 installed on the ceiling of the room with an illuminance of 1000 lpx. Further, when observed from the subject 400, the fluorescent lamp 300 is adjusted so as not to be reflected on the liquid crystal dimming film surface of the liquid crystal dimming device 220.

An experiment using this effect measuring device 200 (hereinafter referred to as a flicker sensation test) was carried out in the following procedure. First, the liquid crystal dimming device 220 of the influence measuring device 200 is driven by using a rectangular wave AC voltage having a peak voltage Vp = 10V and a driving frequency of 100Hz (frequency in the middle frequency range shown in FIG. 7A), and the subject 400 Ask the following two questions.
Question 1: Did you feel any flickering in the display inside the opening?
Question 2: If you feel flicker, did you feel flicker unpleasant?
Then, while gradually reducing the drive frequency from 100 Hz in a predetermined step, the same question was repeated until the drive frequency reached 0.01 Hz. Such a flicker sensation test was performed on 400 subjects of 10 subjects, and the number of people who obtained positive answers to the two questions was counted.

FIG. 10A is a graph showing the result of this flicker sensation test. The horizontal axis of the graph is the drive frequency (Hz) of the logarithmic scale, and the vertical axis of the graph is the subject who gave a positive answer to the above two questions when the liquid crystal dimmer 220 was driven at each drive frequency. The number of people (people). The black square plot is the number of subjects who answered affirmatively in Question 1 above (that is, the number of subjects who felt flicker), and the white circle plot is the number of subjects who answered affirmatively in Question 2 above. The number of people (ie, the number of people who felt uncomfortable with flicker) (black squares and white circles overlap in some frequency sections).

After all, in FIG. 10A, the graph connecting the black square plots shown by the alternate long and short dash lines shows the change with respect to the frequency of the number of people who felt the flicker, and the graph connecting the white circle plots shown by the broken line felt the flicker unpleasant. It shows the change of the number of people with respect to the frequency. As shown in the figure, in the frequency range of 30 Hz or higher, the number of people who felt flicker was almost 0, and the number of people who felt flicker unpleasant was also 0. When the frequency is less than 30 Hz, the number of people who feel the flicker and the number of people who feel it unpleasant rise sharply. Conventionally, the lower limit of the drive frequency of a general liquid crystal dimming cell is set to 30 Hz because driving at a frequency lower than 30 Hz causes unpleasant flicker for humans.

As shown in the graph of FIG. 10A, when the frequency is set to 10 Hz or less, it can be seen that all 10 subjects feel uncomfortable with flicker. However, when the frequency reaches 0.1 Hz, it can be seen that although many subjects feel flicker, the number of people who feel it unpleasant decreases extremely. When the frequency is further lowered and reaches 0.01 Hz, the number of people who feel flicker decreases significantly, and the number of people who feel flicker unpleasant becomes zero.

In general applications such as electronic shades, even if flicker is felt, there is no practical problem as long as the flicker is not unpleasant. Therefore, the value of the upper limit value fH of the drive frequency may be determined based on the graph shown by the broken line in FIG. Specifically, as shown in the figure, it can be seen that when the frequency becomes 0.1 Hz or less, the number of people who feel uncomfortable with flicker sharply decreases. That is, the drive frequency of 0.1 Hz is a numerical value having a critical significance, and is an upper limit value of the drive frequency at which unpleasant flicker does not occur.

FIG. 10B is a graph showing the results of performing the same flicker sensation test on a device provided with a normally clear type liquid crystal dimming film 120 having the “transmittance-voltage characteristic” shown in FIG. 5B. Even with a device equipped with a normally clear type liquid crystal dimming film 120 having "transmittance-voltage characteristics" shown in FIG. 5B, a normal-leading type having "transmittance-voltage characteristics" shown in FIG. 5A. The same result as the device equipped with the liquid crystal light control film of No. 1 was obtained.

From the result of this flicker sensation test, it can be seen that the upper limit frequency shown in FIGS. 7A and 7B may be set to fH = 0.1 Hz. The result of this flicker sensory test shows the physiological effect of flicker (rapid change in brightness) on the display surface of the liquid crystal dimmer 220 on humans, and shows the human sensory characteristics for the change in brightness. It shows. Therefore, regardless of the liquid crystal dimming device 220 used in the influence measuring device 200 and the area of the opening 211, the drive has an upper limit frequency fH = 0.1 Hz or less. It is shown that if the liquid crystal light control cell (liquid crystal light control film) is driven by the frequency, unpleasant flicker is not recognized as a human sense.

In other words, the critical value of 0.1 Hz is a value that has universality as the upper limit frequency fH in which unpleasant flicker is not recognized in the inherent sensory characteristics of human beings, and has the configuration described in §1. It can be said that the frequency value is widely applicable to a general liquid crystal light control cell (liquid crystal light control film).

Subsequently, an experiment performed to determine the lower limit frequency fL will be described. As shown in FIGS. 7A and 7B, the lower limit frequency fL is a frequency indicating the boundary between the DC vicinity region where burn-in occurs and the drive region (specific frequency band) of the present embodiment where burn-in does not occur. Therefore, the inventor of the present application has driven a liquid crystal dimming cell using a square wave AC voltage of various frequencies, and investigated the relationship between the drive frequency and the occurrence of burn-in by an experiment. Here, this experiment will be referred to as a seizure condition test. This seizure condition test was performed in the following procedure.

First, the liquid crystal dimming device 100 used in the experiment was prepared. The liquid crystal dimming device 100 is a device having the configuration shown in FIG. 1, and the liquid crystal dimming film 120 used in this device has the transmittance-voltage characteristics shown in FIG. 5 (normally). Dark characteristics). Specifically, in the liquid crystal light control film 120, the liquid crystal layer 122 is composed of a layer having a thickness of 7 μm containing field effect type liquid crystal molecules (guest host type), and the first transparent electrode layer 121 and the second transparent are transparent. The electrode layer 123 is composed of a layer made of ITO and having a thickness of 30 nm. The value of the DC resistance RF is 800 kΩ. Further, as shown in the example shown in FIG. 1, the connection with the power supply device 110 is made to the film-side first connection terminal a and the film-side first connection terminal b provided at the edge portion.

First, the liquid crystal dimmer 100 for this experiment is used in 2000 using a square wave AC voltage having a peak voltage of Vp = 10 V and a drive frequency of 3 × 10 ^-3 Hz (frequency in a specific frequency band shown in FIG. 7 (b)). It is continuously driven for an hour (about 83 days). Then, during this 2000-hour continuous driving period, the transmittance of the liquid crystal light control film 120 is appropriately measured. After the continuous drive period of 2000 hours is completed, a drive pause period in which the supply voltage to the liquid crystal light control film 120 is set to 0 V is provided for 1 minute, and then the transmittance of the liquid crystal light control film 120 is measured again.

In short, the liquid crystal light control film 120 is supplied with a square wave AC voltage having a peak voltage of Vp = 10 V and 3 × 10 ^-3 Hz, and the transmittance is measured while continuously driving for 2000 hours, and then the voltage is supplied. After stopping and leaving it for 1 minute, an experiment to measure the transmittance again will be performed. In the seizure condition test, the drive frequency is 3 × 10 ^-7 Hz (period: about 926) while the drive frequency is gradually reduced from 3 × 10 ^-3 Hz (period: about 5 minutes) in a predetermined step. It was repeated until the time was reached.

FIG. 11 shows the result of this baking state test. The horizontal axis of each graph G1 and G2 is the drive frequency (Hz) of the logarithmic scale, and the vertical axis is the transmittance of the liquid crystal dimming film 120. is there. Here, the graph G1 (graph in which the plots of the black squares are connected by the alternate long and short dash lines) in FIG. 11 is a graph showing the average transmittance during the continuous driving period of 2000 hours, and the graph G2 (the plots of the white circles are connected by the broken line). The graph) is a graph showing the transmittance measured 1 minute after the power supply is stopped after the continuous driving period of 2000 hours is completed.

Since the graph G1 is the average transmittance during the continuous driving period of 2000 hours when a square wave AC voltage having a peak voltage Vp is applied, it almost shows the maximum transmittance by design. However, when the drive frequency becomes 3 × ^10-6 Hz or less, the transmittance slightly decreases. It is presumed that the reason is that ionic impurities in the liquid crystal adhere to the transparent electrode and the voltage applied to the liquid crystal decreases.

On the other hand, the graph G2 shows the transmittance one minute after the voltage supply is stopped, and the transmittance in a state where no voltage is applied to the liquid crystal dimming film 120 having the characteristic of normal dryk. Since it is a rate, the transmittance should be 0%. However, it can be seen that when the drive frequency is lower than 3 × ^10-5 Hz, the transmittance slightly increases, and when the drive frequency is lower than 1.9 × ^10-6 Hz, the transmittance increases sharply. Looking at the specific measured values, the transmittance is 4% when the drive frequency is 1.9 x ^10-6 Hz, while the transmittance is 4% when the drive frequency is 1.8 x ^10-6 Hz. The transmittance of is rapidly increasing to 13%.

In particular, as shown at the left end of the graph of FIG. 11, when the drive frequency is 3 × 10 ^-7 Hz, the transmittance exceeds 20%, and the plot value of the white circle (voltage is not applied). The state) has risen to a value that is not much different from the plot value of the black square (state in which the peak voltage Vp is applied). This indicates that the liquid crystal light control film 120 is completely in the burn-in state.

In this way, when the drive frequency is 1.9 × ^10-6 Hz or higher, the transmittance is at most 4% or less, so that a general observer does not recognize the occurrence of the burn-in phenomenon, and practically, it is practical. The burn-in phenomenon does not matter. However, when the drive frequency is less than 1.9 × ^10-6 Hz, the transmittance rapidly increases to a value exceeding 10%, and the occurrence of the burn-in phenomenon becomes conspicuous. Therefore, the drive frequency of 1.9 x ^10-6 Hz (period: about 6 days) is a numerical value with critical significance, and burn-in (burn-in to the extent recognized by a general observer) does not occur. This is the lower limit of the drive frequency.

From the result of this baking state test, when a voltage was applied to the liquid crystal light control film 120 used in the experiment under the driving conditions used in the experiment, the value of the lower limit frequency fL shown in FIG. 7B was set to fL = 1. It can be seen that it should be set to .9 × ^10-6 Hz. However, as a result of this seizure state test, as described above, the liquid crystal layer 122 is composed of a layer containing electric field effect type liquid crystal molecules (guest host type) having a predetermined thickness, and the first transparent electrode layer 121. And the unique liquid crystal dimming film 120 obtained when the second transparent electrode layer 123 is composed of a layer made of ITO having a predetermined thickness and is driven by a driving voltage of a peak voltage Vp = 10V. This is the measurement result. Therefore, the lower limit frequency value of fL = 1.9 × ^10-6 Hz is not a universal value commonly used when the arbitrary liquid crystal dimming film 120 is driven by an arbitrary drive voltage.

As described above, the upper limit frequency fH is a value having a universal significance as an upper limit value in which unpleasant flicker is not recognized in the unique sensory characteristics of human beings, whereas the lower limit frequency fL is a value. , When a specific liquid crystal light control film is driven under specific conditions, it is the lower limit of the drive frequency at which seizure does not occur. Therefore, each liquid crystal light control film and each drive condition has a unique value. Need to be set. In other words, the value of the lower limit frequency fL depends on the dimensions of each part of the liquid crystal light control film 120 to be used, the types of liquid crystals constituting the liquid crystal layer 122 and impurities contained therein, the peak voltage of the driving signal, and the like. , Each will be different.

Therefore, in order to strictly determine the value of the lower limit frequency fL when the specific liquid crystal light control film 120 is driven under the specific conditions, it is necessary to carry out an individual baking condition test. However, when the inventor of the present application carried out this seizure state test on some examples in which the dimensions of each part, the types of liquid crystals and impurities, the peak voltage of the drive signal, etc. were changed, the lower limit frequency fL was generally fL =. It was confirmed that the frequency was within the range of 1.1 × ^10-6 Hz (cycle TL = 10 days) to 2.8 × ^10-5 Hz (cycle TL = 10 hours). Therefore, if the lower limit frequency fL is set to fL = 2.8 × ^10-5 Hz (period TL = 10 hours), the liquid crystal dimming film 120 having an arbitrary configuration can be driven under arbitrary driving conditions. Even if it does, it is possible to prevent seizure.

After all, in carrying out the present invention, a universal value of fH = 0.1 Hz is set as the upper limit value fH of the drive frequency at which unpleasant flicker is not recognized by humans, and the lower limit value fL of the drive frequency at which seizure does not occur is set. Appropriateness within the range of fL = 1.1 × ^10-6 Hz (period TL = 10 days) to 2.8 × ^10-5 Hz (period TL = 10 hours), depending on the liquid crystal light control film 120 actually used. A value is set, the range from the lower limit value fL to the upper limit value fH is defined as a specific frequency band, and the power supply device 110 supplies the liquid crystal dimming film 120 with a rectangular wave AC voltage having a frequency within this specific frequency band. You can do it. As described above, since the degree of the unpleasant flicker phenomenon and the burn-in phenomenon suddenly changes with the upper limit value fH and the lower limit value fL as boundaries, all of these values are said to be universal values having a critical significance. be able to.

As described above, the feature of the liquid crystal dimming device 100 of the present embodiment is that the frequency of the drive signal supplied from the power supply device 110 to the liquid crystal dimming film 120 is set to a frequency within a specific frequency band. That is, the power supply device 110 of the present embodiment includes a liquid crystal layer 122 and a first transparent electrode layer 121 arranged on one surface of the liquid crystal layer 122 in order to perform dimming by changing the transmittance of the liquid crystal. A device for driving a liquid crystal light control film 120 having a second transparent electrode layer 123 arranged on the other surface of the liquid crystal layer 122, the first transparent electrode layer 121 and the second transparent electrode layer 123. It has a function of supplying a rectangular wave AC voltage having a predetermined drive frequency to drive the light, and the predetermined drive frequency is higher than the frequency at which the liquid crystal dimming film 120 is seized, and the liquid crystal is displayed. A feature of the light control film 120 is that a frequency lower than the frequency at which flicker that is unpleasant for the observer occurs is used.

From the results of the flicker sensation test and the burn-in state test described above, the specific frequency band indicating the frequency range of the drive signal supplied by the power supply device 110 is the lower limit of the frequency at which the liquid crystal dimming film 120 does not burn. It was found that a range of the lower limit frequency fL (in the case of the above example, fL = 1.9 × ^10-6 Hz) or more and 0.1 Hz or less is preferable.

As described above, in the conventional liquid crystal dimmer, it is common to drive with an AC signal having a frequency of 30 to 200 Hz (a frequency higher than the frequency at which flicker occurs), but in the present embodiment, this is performed. Since the drive is performed at a frequency much lower than the general drive frequency, sufficient power can be supplied even to the liquid crystal light control film 120 having a large area, and the transmittance can be sufficiently controlled. It will be possible to do. Further, since the drive frequency in the present embodiment is set to a frequency lower than the frequency at which the flicker that is unpleasant for the observer occurs, the occurrence of the flicker that is unpleasant can be suppressed. Moreover, since the liquid crystal light control film 120 is driven at a frequency higher than the frequency at which the burn-in occurs, it is possible to prevent the liquid crystal light control film 120 from being burned.

As described above, in the present embodiment, since the liquid crystal dimming film 120 is driven by the AC signal having a frequency within the specific frequency band, the liquid crystal dimming film 120 is driven by the power supply device while suppressing the increase in the manufacturing cost. It becomes possible to sufficiently control the transmittance.

<3.3 Control in standby state of the liquid crystal dimmer of the present embodiment>
The liquid crystal dimming device 100 of the present embodiment has the above-mentioned characteristics, but the inventor of the present application further states that the following new problems arise in such a liquid crystal dimming device 100. I found it.

Before explaining the new problem, first, in the liquid crystal dimming device 100, a state in which the above-mentioned liquid crystal dimming film 120 is supplied with a square wave AC voltage having a peak voltage Vp and a frequency within a specific frequency band. , The ON state is defined, and the state in which no voltage is applied to the liquid crystal light control film 120 (that is, the state in which the applied voltage is 0V) is defined as the OFF state.

In the liquid crystal dimming device 100 of the present embodiment, when switching between the ON state and the OFF state in a short time is repeated for a long time (for example, when switching at 1-second intervals is repeated several tens of times), the ON state is repeated. In the OFF state, it was observed that display unevenness (that is, non-uniformity of transmittance) of the liquid crystal light control film 120 occurred. As a result of research by the inventor of the present application, the cause of this display unevenness is mainly due to the delay in the response of the liquid crystal molecule 122a and the occurrence of the uneven distribution of charged particles in the liquid crystal dimming film 120. I found that.

In order to cope with this new problem, the liquid crystal dimming device 100 of the present embodiment can take a standby state described below in addition to the OFF state and the ON state. In this standby state, the liquid crystal dimming film 120 has a peak voltage Vps lower than the ON state (more specifically, a peak voltage Vps equal to or lower than the threshold voltage Vth of the liquid crystal dimming film 120 described later) and the ON state. It is a state in which a rectangular wave AC voltage having a high frequency is supplied.

FIG. 12 is a waveform diagram of an AC signal used in the liquid crystal dimming device 100 of the present embodiment, showing a waveform when the liquid crystal dimming device 100 is sequentially switched from the ON state to the standby state and the ON state. Is.

In the conventional general liquid crystal dimming device, there is no distinction between the OFF state and the standby state with respect to the voltage applied to the liquid crystal dimming cell, and the voltage is applied to the liquid crystal dimming cell except in the ON state. It was not in a state. On the other hand, the liquid crystal dimming device 100 of the present embodiment basically takes a standby state except when it is in the ON state. In the standby state, a square wave AC voltage having a peak voltage of Vps is applied to the liquid crystal light control film 120 so that the observer does not recognize the change in the transmittance from the OFF state. By applying the square wave AC voltage having the peak voltage Vps, the liquid crystal in the liquid crystal light control film 120 in the standby state is in a state of being tilted to some extent from the OFF state.

FIG. 13A is a vertical cross-sectional view schematically showing the states of the liquid crystal molecules 122a in the OFF state and the ON state of the conventional liquid crystal dimming device having the characteristics of general normally clear. FIG. 13B is a vertical cross-sectional view schematically showing a state of the liquid crystal molecule 122a in the standby state and the ON state of the liquid crystal dimming device 100 having the characteristic of normally clear of the present embodiment.

In a conventional liquid crystal dimming device having a general normal clear characteristic, as shown in FIG. 13A, when switching from the OFF state to the ON state, the liquid crystal molecules 122a are arranged in the ON state only when they are tilted from the state in the OFF state. Will move to. On the other hand, in the liquid crystal dimming device 100 having the characteristic of normally clear of the present embodiment, as shown in FIG. 13B, when the standby state is switched to the ON state, the liquid crystal molecules 122a are tilted to some extent from the OFF state. It will be further tilted to shift to the arrangement in the ON state.

Therefore, the transition of the liquid crystal molecule 122a from the standby state to the ON state in the liquid crystal dimming device 100 of the present embodiment is compared with the transition of the liquid crystal molecule 122a from the OFF state to the ON state in the conventional general liquid crystal dimming device. And it will be fast. That is, in the liquid crystal dimming device 100 of the present embodiment, the liquid crystal molecule 122a is in a state of being tilted to some extent in the standby state, and the response is started from the state of being tilted to some extent, so that the response speed is increased. As a result, in the liquid crystal dimming device 100 of the present embodiment, the delay in the response of the liquid crystal molecules 122a at a location away from the film-side first connection terminal a and the film-side second connection terminal b is suppressed. .. That is, in the liquid crystal dimming device 100 of the present embodiment, the occurrence of display unevenness of the liquid crystal dimming film 120 due to the delay in the response of the liquid crystal molecules 122a is suppressed.

Further, when the liquid crystal dimming device 100 of the present embodiment is maintained in the ON state for a long period of time, the voltage applied to the liquid crystal dimming film 120 repeats plus and minus at regular intervals. Therefore, the polarity of the voltage applied to the liquid crystal light control film 120 is not biased. However, in the liquid crystal dimming device 100 of the present embodiment, if the switching between the ON state and the OFF state is repeated for a long time, the polarity of the voltage applied to the liquid crystal dimming film 120 is biased. There is a risk. For example, if the voltage applied to the liquid crystal dimming film 120 is always positive after switching from the OFF state to the ON state and then repeating the process of turning the applied voltage from positive to negative before changing to negative, the voltage applied to the liquid crystal dimming film 120 is always positive. The polarity of the voltage will be biased.

If the polarity of the voltage applied to the liquid crystal light control film 120 is biased, the distribution of charged particles in the liquid crystal light control film 120 will be biased. The liquid crystal molecules 122a in the liquid crystal light control film 120 are affected by the electric field generated by the bias of the distribution of the charged particles. This is also one of the causes of display unevenness of the liquid crystal dimming film 120 that occurs when switching between the ON state and the OFF state in a short time is repeated for a long time in the liquid crystal dimming device 100 of the present embodiment. It has become.

The inventor of the present application eliminates the bias in the distribution of charged particles generated in the liquid crystal dimming film 120 by applying a square wave AC voltage having a frequency higher than that in the ON state to the liquid crystal dimming film 120 in the standby state. Found to be done. From this point of view, in the liquid crystal dimming device 100 of the present embodiment, a square wave AC voltage having a frequency higher than that in the ON state is applied to the liquid crystal dimming film 120 in the standby state. Also, the period of this square wave AC voltage shall be sufficiently shorter than the average duration of the standby state in order to repeat the application of positive and negative voltages a sufficient number of times during the continuation of the standby state. It has become.

Next, the peak voltage Vps and frequency of the rectangular wave AC voltage in the standby state will be described in more detail.

FIG. 14 is a graph showing "transmittance-voltage characteristics" and "haze-voltage characteristics" of the liquid crystal light control film 120 (normally clear type) of the present embodiment.

The peak voltage Vps of the square wave AC voltage in the standby state is set to 0.3 times or more and 1.0 times or less the threshold voltage Vth of the liquid crystal light control film 120. On the other hand, the peak voltage Vp of the square wave AC voltage applied to the liquid crystal light control film 120 in the ON state is set to be higher than the threshold voltage Vth.

The threshold voltage Vth is an applied voltage that serves as a threshold when the transmission state of the liquid crystal light control film 120 changes. That is, the threshold voltage Vth of the liquid crystal light control film 120 having the characteristic of normal dryk is an applied voltage that becomes a threshold value when the liquid crystal light control film 120 changes from the non-transmissive state to the transmissive state. Further, the threshold voltage Vth of the liquid crystal dimming film 120 having the characteristic of normally clear is an applied voltage that becomes a threshold value when the liquid crystal dimming film 120 changes from the transmissive state to the non-transmissive state. The threshold voltage Vth may be appropriately set according to the type of the liquid crystal dimming film 120, the application of the liquid crystal dimming device 100, and the like.

For example, the threshold voltage Vth may be the applied voltage when the transmittance of the liquid crystal light control film 120 changes by 2% from the transmittance (that is, the minimum transmittance or the maximum transmittance) when no voltage is applied. Conceivable. In this case, the threshold voltage Vth of the liquid crystal light control film 120 having the characteristic of normality duck is the applied voltage when the transmittance is increased by 2% from the transmittance when no voltage is applied (that is, the minimum transmittance). Is. Further, the threshold voltage Vth of the liquid crystal light control film 120 having the characteristic of normally clear is the applied voltage when the transmittance is 2% lower than the transmittance when no voltage is applied (that is, the maximum transmittance). is there. If the change in the transmittance of the liquid crystal light control film 120 is within 2%, a normal observer cannot recognize the change in the transmittance. The transmittance of the liquid crystal light control film 120 is the total light transmittance and can be measured according to JIS K 7361.

The peak voltage Vps of the square wave AC voltage in the standby state is equal to or higher than the applied voltage at which the liquid crystal in the liquid crystal light control film 120 is tilted to some extent from the OFF state, and is usually the transmittance of the liquid crystal light control film 120. The change from the OFF state is set to the maximum applied voltage or less that is not recognized by the observer.

According to the research of the inventor of the present application, when the peak voltage Vps is 0.3 times or more the threshold voltage Vth, display unevenness due to the delay in the response of the liquid crystal molecule 122a can be suppressed to some extent, and the peak voltage Vps is set to 0. It has been found that when the value is 5 times or more, display unevenness due to a delay in the response of the liquid crystal molecule 122a can be suppressed more effectively. Further, by setting the peak voltage Vps to 0.8 times or less the threshold voltage Vth, it is possible to prevent the observer from recognizing a change in the transmittance of the liquid crystal dimming film 120 due to the influence of disturbance or the like. Therefore, the peak voltage Vps of the square wave AC voltage in the standby state is preferably 0.3 times or more and 1.0 times or less the threshold voltage Vth of the liquid crystal dimming film 120, and is 0.5 times the threshold voltage Vth. As mentioned above, it is more preferably 0.8 times or less.

As shown in FIG. 14, the liquid crystal light control film 120 usually has a voltage band Bh in which the haze has a maximum value and becomes high. The voltage band Bh in which the haze has a maximum value and becomes high usually overlaps with the voltage band in which the transmittance of the liquid crystal dimming film 120 changes abruptly, and exists in a region higher than the threshold voltage Vth. However, depending on the type of the liquid crystal light control film 120, it is conceivable that the voltage in the voltage band Bh, which has a maximum haze and becomes high, becomes lower than the threshold voltage Vth. In that case, the peak voltage Vps of the square wave AC voltage in the standby state is preferably a voltage lower than the voltage in the voltage band Bh where the haze has a maximum value and becomes high. The haze of the liquid crystal light control film 120 can be measured according to JIS K 7136.

The frequency of the square wave AC voltage in the standby state is set to 30 Hz or more and 100 Hz or less.

According to the research of the inventor of the present application, it has been found that when the frequency is 10 Hz or higher, the bias of the distribution of charged particles in the liquid crystal light control film 120 can be eliminated to some extent quickly. However, by setting the frequency in the standby state to 30 Hz or higher, which does not cause the observer to feel flicker even in the ON state, it is possible to suppress the possibility of causing the observer to feel flicker even in the standby state. Further, by setting the frequency to 30 Hz or higher, the bias of the distribution of charged particles in the liquid crystal light control film 120 can be eliminated more quickly and effectively. Further, by setting the frequency to 30 Hz or higher, the application of positive and negative voltages can be repeated a sufficient number of times during the average duration of the standby state. Therefore, the frequency of the rectangular wave AC voltage in the standby state may be 10 Hz or higher, but is preferably 30 Hz or higher.

Further, according to the research of the inventor of the present application, in the case of a large liquid crystal light control film 120 having an area of 0.1 square m or more, when the frequency becomes higher than 100 Hz, the voltage distribution in the plane of the liquid crystal light control film 120 and It has been found that the variation of the actual voltage waveform becomes large enough to be recognized by the observer. Therefore, the frequency of the rectangular wave AC voltage in the standby state is preferably 100 Hz or less.

The liquid crystal dimming device 100 of the present embodiment takes a standby state use mode that takes a standby state and an ON state, and a standby state non-use mode that takes an OFF state and an ON state without taking a standby state. Can be done. As a result, in a situation where switching between the OFF state and the ON state of the liquid crystal dimming device 100 is not expected for a short time, the power consumption of the liquid crystal dimming device 100 can be suppressed by taking the standby state non-use mode.

As described above, further features of the liquid crystal dimming device 100 of the present embodiment are an OFF state in which a voltage is not applied to the liquid crystal dimming film 120 and a peak higher than the threshold voltage Vth of the liquid crystal dimming film 120. In addition to the ON state in which a square wave AC voltage having a voltage Vp (first peak voltage) and a frequency within a specific frequency band (first frequency) is supplied, the threshold voltage of the liquid crystal dimming film 120 The point is that it takes a standby state in which a square wave AC voltage having a peak voltage Vps (second peak voltage) of Vth or less and a frequency higher than the ON state (second frequency) is supplied. is there. That is, the power supply device 110 of the present embodiment includes a liquid crystal layer 122 and a first transparent electrode layer 121 arranged on one surface of the liquid crystal layer 122 in order to perform dimming by changing the transmittance of the liquid crystal. A device for driving a liquid crystal dimming film 120 having a second transparent electrode layer 123 arranged on the other surface of the liquid crystal layer 122, which is in an OFF state, an ON state, and a standby state. In the standby state, a rectangular wave AC voltage having a peak voltage Vps equal to or lower than the threshold voltage Vth of the liquid crystal dimming film 120 and a frequency higher than the ON state between the first transparent electrode layer 121 and the second transparent electrode layer 123. It is further characterized in that it has a function of supplying and driving.

Due to such a feature, the liquid crystal dimming device 100 of the present embodiment has a high response speed of the liquid crystal molecules 122a when switching between the standby state and the ON state, and as a result, the standby state and the ON state can be switched in a short time. In the case of switching, the occurrence of display unevenness due to the influence of the difference in the response speed of the liquid crystal molecule 122a at the location is suppressed. Further, in the liquid crystal dimming device 100 of the present embodiment, in the standby state, a square wave AC voltage having a frequency higher than that in the ON state is applied to the liquid crystal dimming film 120, so that the standby state and the ON state are short-time. It is possible to eliminate the bias of the distribution of charged particles that occurs when switching with.

In the liquid crystal dimming device 100 of the present embodiment, a square wave AC voltage is supplied to the liquid crystal dimming film 120 in the standby state, but the supplied AC voltage is not limited to that of the rectangular wave. The liquid crystal dimming device 100 of the present invention may supply another AC voltage such as a sinusoidal AC voltage or a triangular wave AC voltage to the liquid crystal dimming film 120 in the standby state. However, from the viewpoint of the stability of the arrangement of the liquid crystal molecules 122a in the standby state, the liquid crystal dimming device 100 of the present invention is such that the liquid crystal dimming film 120 is supplied with a square wave AC voltage in the standby state. preferable. Further, from the viewpoint of effectively eliminating the bias of the distribution of charged particles, the liquid crystal dimming device 100 of the present invention supplies the liquid crystal dimming film 120 with positive and negative symmetric AC voltage in the standby state. Is preferable.

Further, the liquid crystal light control film 120 of the present embodiment has a guest-host type liquid crystal, but is not limited thereto. The liquid crystal light control film 120 of the present invention may have other types of liquid crystals such as TN type, VA type, STN type or IPS type. However, the present invention can be suitably used for a liquid crystal dimming film 120 having a guest-host type liquid crystal, which contains a constituent material other than the liquid crystal and tends to cause a bias in the distribution of charged particles.

<<< §4. Modifications of the present invention >>>
Although the basic embodiment of the present invention has been described so far, some modifications of the present invention will be described here.

<4.1 Deformation example in which the initial voltage Vpp is applied at the time of polarity reversal>
In the liquid crystal dimming device 100 according to the present invention, a square wave AC voltage of 0.1 Hz or less (an AC signal having a frequency lower than the frequency at which unpleasant flicker occurs) is supplied to the liquid crystal dimming film 120. Since the drive is performed, as described above, even if the observer recognizes the flicker, it does not feel unpleasant. However, even if it does not give an unpleasant feeling, it is preferable to reduce the occurrence of flicker as much as possible. Therefore, here, a modified example in which the occurrence of flicker is further reduced will be described.

FIG. 15 is a graph showing the transmittance fluctuation that occurs in the liquid crystal light control film 120 when the polarity of the drive AC signal supplied from the power supply device 110 is reversed. Here, the voltage graph (lower graph) of FIG. 15 shows the waveform (period T) of the rectangular wave AC voltage applied to the liquid crystal dimming film 120, the horizontal axis is time t, and the vertical axis is the applied voltage (period T). The unit V) is shown. The Vin shown by the solid line in the voltage graph of FIG. 15 shows the voltage waveform applied between the film-side first connection terminal a and the film-side second connection terminal b shown in FIG. 2A, and is the voltage graph of FIG. The Vend shown by the broken line in the above indicates the voltage waveform applied between the film-side first far point c and the film-side second far point d shown in FIG. 2A. The transmittance graph (upper graph) of FIG. 15 is a graph showing the optical response (transmittance) of the cell, and the horizontal axis is synchronized with the time axis t of the voltage graph.

The voltage waveform Vin shown by the solid line in the voltage graph of FIG. 15 is a square wave substantially equal to the rectangular wave AC voltage generated by the power supply device 110, while the voltage waveform Vend shown by the broken line is the resistance of the transparent electrode layers 121 and 123. Due to the influence of R1, R2, etc., the waveform becomes rounded. This has already been explained in §2. Looking at the liquid crystal light control film 120 as a whole, the farther away from the film side connection terminals a and b, the more severe the waveform bluntness becomes. Further, as can be seen by comparing the graphs of FIGS. 3A and 3B and FIGS. 4A and 4B, the bluntness of this waveform becomes more remarkable as the liquid crystal dimming cell (liquid crystal dimming film) becomes larger.

In the case of the voltage waveform Vin shown by the solid line in the voltage graph of FIG. 15, the supply voltage instantly switches from the peak voltage −Vp to + Vp or from + Vp to −Vp when the polarity of the driving AC signal is reversed. Therefore, the absolute value of the supply voltage remains substantially maintained at the peak voltage Vp, and flicker hardly occurs. However, in the case of the voltage waveform Vend shown by the broken line in the voltage graph of FIG. 15, the supply voltage gently changes from the peak voltage −Vp to + Vp or from + Vp to −Vp when the polarity of the driving AC signal is reversed. Since it will change, the absolute value of the supply voltage will drop from the peak voltage Vp, causing flicker.

For example, as shown in the voltage graph of FIG. 15, when the absolute value of the voltage waveform Vend decreases from the peak voltage Vp, as shown in the transmittance graph, at time t1 where a slight time lag has elapsed (the length of the time lag). Is determined according to the responsiveness of the liquid crystal used in the liquid crystal layer 122), and the optical response (transmittance) of the cell begins to decrease slightly (in the case of a liquid crystal dimming film having a normal-like characteristic). Eventually, at time t2, the absolute value of the voltage waveform Vend recovers to some extent, so that the optical response of the cell starts to rise. Therefore, before and after the time t2, a phenomenon occurs in which the transmittance is slightly lowered, which is observed as flicker.

Similarly, at time t3, when the absolute value of the voltage waveform Vend drops to some extent from the peak voltage Vp, as shown in the voltage graph of FIG. 15, the optical response (transparency) of the cell begins to drop slightly due to the influence. Eventually, at time t4, the absolute value of the voltage waveform Vend recovers to some extent, so that the optical response of the cell starts to rise. Therefore, before and after the time t4, a phenomenon that the transmittance slightly decreases occurs, and this is observed as flicker.

Eventually, cell transmittance fluctuations H1, H2, and H3 occur for each half-cycle Ta and Tb in which polarity inversion occurs in the driving AC signal, and these transmittance fluctuations H1, H2, and H3 are observed as flicker. Will be done.

As a method for further reducing such transmittance fluctuations H1, H2, and H3, the inventor of the present application has an initial voltage Vpp whose absolute value is higher than the peak voltage Vp at the initial portion of each half cycle Ta and Tb where polarity reversal occurs. I came up with the idea of supplying. FIG. 16 is a graph showing a modified example in which an initial voltage Vpp larger than the peak voltage Vp is supplied at the time of polarity reversal in order to suppress the transmittance fluctuations H1, H2, and H3 shown in FIG.

Here, the voltage graph of FIG. 16 shows the waveform of the rectangular wave AC voltage applied to the liquid crystal dimming film 120, the horizontal axis represents the time t, and the vertical axis represents the applied voltage (unit V). The Vin shown by the solid line in the voltage graph of FIG. 16 is the voltage waveform applied between the film side first connection terminal a and the film side second connection terminal b, similarly to the solid line Vin of the voltage graph of FIG. Is shown. However, in the Vin shown by the solid line in the voltage graph of FIG. 16, the first half initial voltage + Vpp higher than the positive peak voltage + Vp is supplied in the first half early period P1 immediately after the polarity reversal from negative to positive occurs. A positive peak voltage + Vp is supplied to the following first half subsequent period P2. Further, in the latter half early period P3 immediately after the polarity reversal from positive to negative occurs, the latter half initial voltage −Vpp lower than the negative peak voltage −Vp is supplied, and in the subsequent latter half subsequent period P4, the negative peak voltage − Vp is supplied.

The Vend shown by the alternate long and short dash line in the voltage graph of FIG. 16 is between the first far point c on the film side and the second far point d on the film side, similarly to the Vend shown by the broken line in the voltage graph of FIG. The applied voltage waveform is shown. Note that the graph Vend 0 shown by the broken line in the voltage graph of FIG. 16 is a graph having the same waveform as the Vend shown by the broken line in the voltage graph of FIG. 15 drawn for comparison.

Vend 0 shown by the broken line in the voltage graph of FIG. 16 (same as Vend shown by the broken line in the voltage graph of FIG. 15) is the rectangular wave alternating current of Vin shown by the solid line of the voltage graph of FIG. While the potential difference that occurs between terminals c and d when a voltage is applied between terminals a and b is shown, the Vend shown by the single point chain line in the voltage graph of FIG. 16 is the voltage of FIG. It shows the potential difference that occurs between terminals c and d when the rectangular wave AC voltage of Vin shown by the solid line in the graph is applied between terminals a and b.

As described above, the difference between Vend 0 shown by the broken line in the voltage graph of FIG. 16 and Vend shown by the alternate long and short dash line is the difference between Vin shown by the solid line in the voltage graph of FIG. This is due to the difference from Vin shown by the solid line in the voltage graph of. That is, by increasing the absolute value of the applied voltage from Vp to Vpp in the first half early period P1 and the second half early period P3, the Vend shown by the alternate long and short dash line in the voltage graph of FIG. 16 has a steeper rise or rise. It means that it is showing a fall. As a result, as shown in the transmittance graph of FIG. 16, the effect of further reducing the transmittance fluctuations H1, H2, and H3 is obtained.

The solid line of the transmittance graph of FIG. 16 shows the optical response (transmittance) of the cell when Vin shown by the solid line of the voltage graph of FIG. 16 is supplied, and the horizontal axis is the voltage graph of FIG. Is synchronized with the time axis t of. The broken line of the transmittance graph of FIG. 16 is drawn with the same waveform as the solid line of the transmittance graph of FIG. 15 for comparison reference. In the solid line of the transmittance graph of FIG. 16, the cell transmittance fluctuations H1, H2, and H3 occur after the polarity inversion occurs in the driving AC signal, but the fluctuation is compared with the broken line. It can be seen that the amount has been greatly reduced. This is because, in the first half early period P1 and the second half early period P3, the initial voltage Vpp whose overall value is larger than the peak voltage Vp is applied.

In short, in the modified example described here, the power supply device 110 applies a positive voltage to the first transparent electrode layer 121 side with the second transparent electrode layer 123 side as a reference potential, and the first half cycle Ta and the first transparent electrode layer. In the case of supplying the latter half cycle Ta that applies a negative voltage to the 121 side and the AC voltage with one cycle T as one cycle T, the first half early period P1 and the first half subsequent period P2 are set in the first half cycle Ta, and the latter half cycle Tb. The latter half early period P3 and the latter half subsequent period P4 are set, and the first half initial period P1 is supplied with the first half initial voltage + Vpp higher than the positive peak voltage + Vp on the first transparent electrode layer 121 side, and the first half subsequent period P1. A positive peak voltage + Vp is supplied to the first transparent electrode layer 121 side to P2, and a latter half initial voltage-Vpp lower than the negative peak voltage -Vp to the first transparent electrode layer 121 side during the latter half early period P3. In the latter half subsequent period P4, a negative peak voltage −Vp may be supplied to the first transparent electrode layer 121 side.

When driving is performed using a square wave AC voltage having such unique characteristics, the amount of fluctuation of the transmittance H1, H2, and H3 can be reduced as shown by the solid line in the transmittance graph of FIG. , It becomes possible to suppress that the transmittance fluctuations H1, H2, and H3 are observed as flicker. In the case of the embodiment shown here, P1 = P2 = 0.05 sec is set for the half cycle Ta = Tb = 500 sec, but the lengths of the initial periods P1 and P3 reduce the amount of transmittance fluctuation. It may be set appropriately while observing the effect of.

<4.2 Modification example of adjusting the responsiveness of the liquid crystal>
As described above, the transmittance fluctuations H1, H2, and H3 shown by the solid line in the transmittance graph of FIG. 15 are brought about by the temporary decrease in the applied voltage to the liquid crystal. Therefore, as another approach to reduce the transmittance fluctuations H1, H2, and H3, it is also effective to adjust the responsiveness of the liquid crystal (the responsiveness when the orientation of the liquid crystal molecules changes according to the applied voltage). .. Specifically, if measures are taken such that the liquid crystal layer 122 is composed of a liquid crystal having a relatively slow response (for example, a liquid crystal having a high viscosity), the optical response of the cell shown in the transmittance graph of FIG. 15 becomes higher. Since it becomes slow, the transmittance fluctuations H1, H2, and H3 can be reduced.

After all, if the above approach is adopted, the power supply device 110 applies a positive voltage to the first transparent electrode layer 121 side with the second transparent electrode layer 123 side as a reference potential, and the first half cycle Ta and the first transparent. Immediately after switching from the first half cycle Ta to the second half cycle Tb, and from the second half cycle Tb to the first half, on the premise that the second half cycle Tb that applies a negative voltage to the electrode layer 121 side and the AC voltage with one cycle T are supplied. Immediately after switching to the period Ta, the liquid crystal layer 122 having a responsiveness that does not cause flicker that can be recognized by the observer (for example, sufficient to show a slow responsiveness that does not cause flicker that can be recognized by the observer). The liquid crystal light control film 120 may be formed by using a liquid crystal layer made of a liquid crystal having a high viscosity.

<4.3 Modification example regarding duty ratio of AC drive signal>
The power supply device 110 used in the liquid crystal dimming device 100 according to the present invention is like the square wave AC signal Vin shown in the solid line of the voltage graph of FIG. 15 and the square wave AC signal Vin shown in the solid line of the voltage graph of FIG. It has a function of supplying an AC drive signal to the liquid crystal light control film 120. In these examples, an example in which the length ratio (duty ratio) of the first half cycle Ta and the second half cycle Tb is 1: 1 is shown.

However, in carrying out the present invention, the duty ratio of the rectangular wave AC signal does not necessarily have to be 1: 1 and may be set to other than 1: 1 such as 2: 1 or 3: 1. It doesn't matter. That is, the power supply device 110 applies a positive voltage to the first transparent electrode layer 121 side as a reference potential in the first half period Ta and a negative voltage to the first transparent electrode layer 121 side. An AC voltage with the applied second half cycle Ta and one cycle T is supplied, but the duty ratio indicating the ratio between the length of the first half cycle Ta and the length of the second half cycle Tb is set to 1: 1. Alternatively, it may be set to other than 1: 1.

However, since the period T of the square wave AC signal needs to be a value corresponding to the drive frequency of the specific frequency band described in §3.2, the drive of the specific frequency band is also performed for the half periods Ta and Tb. It must be a half-cycle value corresponding to the frequency. Further, in order to suppress seizure, it is preferable that "positive voltage x application time" and "negative voltage x application time" are the same so that the integrated value of the applied voltage becomes 0 as much as possible. Considering these points, the duty ratio does not necessarily have to be set to 1: 1, but it is not preferable to set the duty ratio too large from the viewpoint of preventing seizure.

Further, in the examples described so far, the frequency (period) of the AC drive signal is fixed to a specific value for driving, but the frequency of the AC drive signal is specified in §3.2. As long as the frequency is within the frequency band, it may be changed over time. That is, the power supply device 110 may switch a plurality of frequencies within the specific frequency band and supply an AC voltage having a drive frequency that fluctuates with time to drive the device.

<4.4 Understanding as a driving method for liquid crystal light control film>
So far, the present invention has been described as an invention of a liquid crystal dimming device for dimming by changing the transmittance of a liquid crystal and a power supply device used for the same, but the present invention is a method for driving a liquid crystal dimming film. It is also possible to grasp.

That is, in the present invention, in order to perform dimming by changing the transmittance of the liquid crystal, the liquid crystal layer 122, the first transparent electrode layer 121 arranged on one surface of the liquid crystal layer 122, and the liquid crystal layer 122. It is possible to grasp as a driving method of the liquid crystal light control film for driving the liquid crystal light control film 120 having the second transparent electrode layer 123 arranged on the other surface of the above. In this driving method, in the ON state, a rectangular wave AC voltage having a predetermined driving frequency is supplied between the first transparent electrode layer 121 and the second transparent electrode layer 123 to drive the device, and the predetermined driving method is performed. As the frequency, a frequency higher than the frequency at which the liquid crystal light control film 120 causes seizure and lower than the frequency at which the liquid crystal light control film 120 causes unpleasant flicker for the observer may be used.

More specifically, in the method for driving the liquid crystal light control film, the lower limit frequency fL, which is the lower limit of the frequency at which the liquid crystal light control film does not seize, and the upper limit frequency fH = 0.1 Hz are defined, and the lower limit frequency fL. The range from to the upper limit frequency fH may be set as a specific frequency band, and a rectangular wave AC voltage having a frequency within this specific frequency band may be supplied for driving.

Further, in this driving method, an OFF state, a standby state, and an ON state are taken, and in the standby state, the liquid crystal light control film 120 is placed between the first transparent electrode layer 121 and the second transparent electrode layer 123. A square wave AC voltage having a peak voltage Vps equal to or lower than the threshold voltage Vth and a frequency higher than the ON state may be supplied for driving. The peak voltage Vps at this time is preferably 0.3 times or more and 1.0 times or less of the threshold voltage Vth of the liquid crystal light control film 120, and is 0.5 times or more and 0.8 times or less of the threshold voltage Vth. Is more preferable. The frequency is preferably 10 Hz or higher and 100 Hz or lower, and more preferably 30 Hz or higher and 100 Hz or lower.

100: Liquid crystal dimming device 110: Power supply device 111: Ideal power supply 112: Output impedance 120: Liquid crystal dimming film 121: First transparent electrode layer 122: Liquid crystal layer 122a: Liquid crystal molecule 123: Second transparent electrode layer 200: Impact measurement Device 210: Black drawing paper 211: Opening 220: Liquid crystal dimming device 230: Backlight 300: Fluorescent lamp 400: Subject A: Power supply side first connection terminal a: Film side first connection terminal B: Power supply side second connection terminal b: Second connection terminal on the film side CL: Liquid crystal layer capacity c: First far point on the film side d: Second far point on the film side fH: Upper limit frequency (0.1H) of a specific frequency band
fL: Lower limit frequency of a specific frequency band (for example, 1.9 × ^10-6 Hz)
G1: Graph showing the transmittance during continuous driving G2: Graph showing the degree of seizure H1, H2, H3: Transmittance fluctuation P1: First half early period P2: First half succeeding period P3: Second half early period P4: Second half succeeding period R1: 1st electrode layer resistance R2: 2nd electrode layer resistance RL: Liquid crystal layer resistance RF: DC resistance of liquid crystal light control film t: Time t1 to t4: Time T: Drive AC signal cycle Ta: First half cycle Tb: Second half cycle TH: Period corresponding to the upper limit frequency fH (10 sec)
TL: Period corresponding to the lower limit frequency fL (3days)
Vend, Vend0: Far terminal supply voltage Vin: Connection terminal supply voltage Vp: Peak voltage in the ON state (first peak voltage)
Vpp: Initial voltage Vps: Peak voltage in standby state (second peak voltage)
Bh: Voltage band

Claims (11)

A liquid crystal dimming device that performs dimming by changing the transmittance of the liquid crystal.
It is equipped with a liquid crystal dimming film and a power supply device for driving it.
An ON state in which a square wave AC voltage having a first peak voltage higher than the threshold voltage of the liquid crystal light control film and a predetermined first frequency is supplied from the power supply device to the liquid crystal light control film.
It is possible to take a standby state in which an AC voltage having a second peak voltage equal to or lower than the threshold voltage and a second frequency higher than the first frequency is supplied from the power supply device to the liquid crystal light control film. A liquid crystal dimmer that can be used. The liquid crystal dimming device according to claim 1.
The first frequency is 0.1 Hz or less, which is equal to or higher than the lower limit of the frequency at which seizure does not occur on the liquid crystal light control film.
The second frequency is 10 Hz or more and 100 Hz or less. The liquid crystal dimming device according to claim 1 or 2.
A liquid crystal dimming device in which the second peak voltage is 0.3 times or more and 1.0 times or less the threshold voltage of the liquid crystal dimming film. The liquid crystal dimming device according to any one of claims 1 to 3.
A liquid crystal dimming device in which the AC voltage supplied from the power supply device to the liquid crystal dimming film in the standby state is a square wave AC voltage. The liquid crystal dimming device according to any one of claims 1 to 4.
An area suitable for the liquid crystal light control film to be attached to a transparent plate constituting a window used for the exterior or interior of a building, a window of a vehicle, a transparent partition used as an interior partition, or a case of a showcase. Or, a liquid crystal dimming device having an area suitable for being sandwiched between two transparent plates constituting them. The liquid crystal dimming device according to any one of claims 1 to 4.
The liquid crystal light control film is attached to the image display display or arranged before and after the image display display in order to dimm the external light or the backlight from the front surface or the back surface of the image display display. A liquid crystal dimming device having an area suitable for use. The liquid crystal dimming device according to any one of claims 1 to 6.
A liquid crystal dimming device in which the liquid crystal dimming film has an area of 0.1 square m or more. It is a power supply device for driving a liquid crystal dimming film in order to perform dimming by changing the transmittance of the liquid crystal.
A square wave AC voltage having a first peak voltage higher than the threshold voltage of the liquid crystal light control film and a predetermined first frequency on the liquid crystal light control film.
A power supply device having a function of supplying an AC voltage having a second peak voltage equal to or lower than the threshold voltage and a second frequency higher than the first frequency. The power supply device according to claim 8.
The first frequency is 0.1 Hz or less, which is equal to or higher than the lower limit of the frequency at which seizure does not occur on the liquid crystal light control film.
The second frequency is 10 Hz or more and 100 Hz or less. It is a driving method for driving a liquid crystal dimming film in order to perform dimming by changing the transmittance of the liquid crystal.
An ON state in which a square wave AC voltage having a first peak voltage higher than the threshold voltage of the liquid crystal light control film and a predetermined first frequency is supplied to the liquid crystal light control film.
The liquid crystal light control film can be in a standby state in which an AC voltage having a second peak voltage equal to or lower than the threshold voltage and a second frequency higher than the first frequency is supplied to the liquid crystal light control film. Driving method. The method for driving a liquid crystal light control film according to claim 10.
The first frequency is 0.1 Hz or less, which is equal to or higher than the lower limit of the frequency at which seizure does not occur on the liquid crystal light control film.
The method for driving a liquid crystal light control film, wherein the second frequency is 10 Hz or more and 100 Hz or less.