JP2021139946A - Lighting control device and driving method of lighting control sheet - Google Patents

Abstract

To provide a lighting control device capable of suppressing a flicker and enabling a reduction of power consumption, and a driving method of a lighting control sheet.SOLUTION: A lighting control device includes: a lighting control sheet 20 having a first transparent electrode 21, a second transparent electrode 22 and a lighting control layer 23 containing liquid crystal molecules interposed between the first transparent electrode 21 and the second transparent electrode 22; and a drive part 32 configured to maintain a luminous transmittance of the lighting control sheet 20 within a prescribed range through applying a direct current voltage between the first transparent electrode 21 and the second transparent electrode 22. If a first reference voltage is defined as a direct current voltage that saturates a transmittance of the lighting control layer 23 through being applied between the first transparent electrode 21 and the second transparent electrode 22 when a residual direct current voltage of the lighting control sheet 20 is zero, the drive part 32 applies a direct current voltage higher than the first reference voltage as a direct current voltage for changing the luminous transmittance.SELECTED DRAWING: Figure 1

Description

The present invention relates to a dimming device that changes the light transmittance of a dimming layer by applying a voltage to liquid crystal molecules, and a method of driving a dimming sheet.

A liquid crystal display device is known as a display device that uses the polarization action of liquid crystal molecules for display. Since it is necessary to suppress uneven distribution of impurity-charged particles in the liquid crystal composition, maintain the chemical structure of the liquid crystal molecules themselves, and periodically rewrite the display data at a frequency higher than the critical fusion frequency, the liquid crystal display is used. The display device applies an AC voltage to the liquid crystal molecules.

In recent years, a new sheet has been proposed as a dimming device that uses the polarization action of liquid crystal molecules to switch between transparent and opaque. The dimming sheet, which is applied to the window glass of buildings and vehicles, the screen on which images are projected, etc., gives the object to which the sheet is attached the function of switching between transparent and opaque, protecting privacy and visualizing the space. Enables expansion.

The dimming device includes a dimming sheet and a driving device. The light control sheet includes a light control layer and a pair of transparent electrodes sandwiching the light control layer. The dimming layer includes a liquid crystal composition and a polymer layer having voids filled with the liquid crystal composition. As the liquid crystal molecules contained in the liquid crystal composition, liquid crystal molecules developed with the spread of liquid crystal display devices are adopted. The drive device applies an AC voltage, which is indispensable in a liquid crystal display device, between a pair of transparent electrodes included in the light control sheet, thereby driving the light control sheet. When the light control sheet is a normal type, the light control sheet is cloudy when no AC voltage is applied between the transparent electrodes, while the light control sheet is cloudy while the AC voltage is applied. Is transparent. On the other hand, when the dimming sheet is a reverse type, the dimming sheet is transparent while the AC voltage is applied while the AC voltage is not applied between the transparent electrodes. , The dimming sheet is cloudy (see, for example, Patent Document 1).

Japanese Patent No. 6610845

By the way, when the dimming sheet is driven by applying an AC voltage, a current corresponding to the frequency of the AC voltage applied to the dimming sheet flows through the dimming sheet. Therefore, the higher the frequency of the AC voltage applied to the dimming sheet, the greater the power consumed by the dimming sheet. Therefore, by applying an AC voltage having a lower frequency to the dimming sheet, dimming is performed. It has been proposed to drive the seat. However, when the light control sheet is driven by applying an AC voltage having a frequency lower than the critical fusion frequency, the observer of the light control sheet visually recognizes flicker, which is a flicker that occurs in the light control sheet.

An object of the present invention is to provide a dimming device capable of suppressing flicker and reducing power consumption, and a method of driving a dimming sheet.

A dimming device for solving the above problems includes a first transparent electrode, a second transparent electrode, and a dimming layer sandwiched between the first transparent electrode and the second transparent electrode and containing liquid crystal molecules. A drive unit that keeps the light transmittance of the light control sheet within a predetermined range by continuously applying a DC voltage between the first transparent electrode and the second transparent electrode. To be equipped. When the residual DC voltage of the dimming sheet is zero, the DC voltage applied between the first transparent electrode and the second transparent electrode to saturate the transmittance of the dimming layer is defined as the first reference voltage. By definition, the drive unit applies a DC voltage higher than the first reference voltage as a DC voltage for changing the light transmission coefficient.

A method for driving the light control sheet for solving the above problems is a light control layer containing a liquid crystal molecule sandwiched between a first transparent electrode, a second transparent electrode, the first transparent electrode, and the second transparent electrode. It is a driving method of a dimming sheet including. When the residual DC voltage of the dimming sheet is zero, the DC voltage applied between the first transparent electrode and the second transparent electrode to saturate the transmittance of the dimming layer is the first reference voltage. When an operation for changing the light transmittance of the dimming sheet is input from the operation unit, the first transparent electrode and the second transparent electrode are used until an operation different from the operation is input from the operation unit. In between, it is included that a DC voltage higher than the first reference voltage for changing the light transmission rate of the dimming sheet is continuously applied.

According to each of the above configurations, since the DC voltage is continuously applied between the transparent electrodes, it is possible to suppress the occurrence of flicker and reduce the power consumed by the dimming sheet as compared with the case where the AC voltage is applied. .. At this time, even if a residual DC voltage is generated in the dimming layer due to the continuous application of the DC voltage, the DC voltage higher than the first reference voltage is applied, so that the change in the transmittance in the dimming layer should be suppressed. Is possible.

In the dimming device, when the residual DC voltage of the dimming sheet is saturated, a direct current applied between the first transparent electrode and the second transparent electrode is applied to saturate the transmittance of the dimming layer. The voltage is the second reference voltage, and the drive unit may use a DC voltage equal to or higher than the second reference voltage as a DC voltage for changing the light transmission coefficient. According to this configuration, it is possible to enhance the effectiveness of suppressing the change in the transmittance due to the residual DC voltage generated in the dimming layer in the dimming layer.

The dimming device further includes an operation unit for inputting an operation for changing the light transmittance of the dimming sheet, and the drive unit is different from the operation when the operation is input to the operation unit. A DC voltage for changing the light transmittance of the light control sheet may be continuously applied between the first transparent electrode and the second transparent electrode until the operation is input.

According to the above configuration, when an operation for changing the light transmittance of the light control sheet is input, a DC voltage is continuously applied between the transparent electrodes until an operation different from this operation is input, so that flicker occurs. It is possible to reduce the power consumed by the dimming sheet as compared with the case where the AC voltage is applied while suppressing the light.

In the dimming device, among the operations input to the operation unit, the operation of applying a voltage between the first transparent electrode and the second transparent electrode is a drive operation, and the drive unit is the drive. The polarity of the DC voltage may be reversed each time an operation is input.

According to the above configuration, the polarity of the DC voltage applied between the pair of transparent electrodes is inverted for each drive operation input, so that the haze in the dimming layer is caused by the continuous application of the residual DC voltage to the dimming layer. It is possible to suppress deterioration of optical quality such as value.

In the dimming device, the operation input to the operation unit includes a transparent operation for making the dimming sheet transparent and an opaque operation for making the dimming sheet opaque, and the transparent operation and the opaque operation. One of the operations is an operation of changing the light transmittance of the dimming sheet, and the other of the transparent operation and the opaque operation is an operation different from the operation of changing the light transmittance of the dimming sheet. good.

According to the above configuration, when the operation of making the light control sheet transparent is input, the DC voltage is continuously applied between the transparent electrodes until the operation of making the light control sheet opaque is input. Alternatively, when an operation for making the light control sheet opaque is input, a DC voltage is continuously applied between the transparent electrodes until an operation for making the light control sheet transparent is input. Therefore, it is possible to suppress the occurrence of flicker and reduce the power consumed by the dimming sheet as compared with the case where an AC voltage is applied.

In the dimming device, the dimming layer may include a transparent polymer layer having voids filled with the liquid crystal composition and a liquid crystal composition filled in the voids. According to this configuration, as compared with the configuration without the transparent polymer layer, not only the scattering due to the refractive index anisotropy of the liquid crystal composition but also the three dimensions at the interface between the liquid crystal composition and the transparent polymer layer It is possible to realize an opaque state having a high haze value including general scattering. In addition, the presence of the transparent polymer layer makes it possible to realize a dimming layer having a stronger and more stable structure.

According to the present invention, it is possible to suppress flicker and reduce power consumption.

A cross-sectional view showing the structure of a normal type dimming sheet together with a drive unit. The cross-sectional view which shows the structure in the reverse type dimming sheet together with the drive part. Equivalent circuit of dimmer. The figure which shows an example of the AC voltage applied between a pair of transparent electrodes. The figure which shows an example of the DC voltage applied between a pair of transparent electrodes. The schematic diagram for demonstrating that the residual DC voltage is generated in the dimming layer to which the DC voltage is applied. The schematic diagram for demonstrating that the residual DC voltage is generated in the dimming layer to which the DC voltage is applied. The schematic diagram for demonstrating that the residual DC voltage is generated in the dimming layer to which the DC voltage is applied. The schematic diagram for demonstrating that the residual DC voltage is generated in the dimming layer to which the DC voltage is applied. The schematic diagram for demonstrating that the residual DC voltage is generated in the dimming layer to which the DC voltage is applied. The graph which shows the VH characteristic in a reverse type dimming sheet. The graph which shows the relationship between the shift amount of a saturated drive voltage and the application time of a drive voltage. A graph showing the relationship between the magnitude of the residual DC voltage and the elapsed time since the application of the drive voltage was stopped. A timing chart showing a first example of DC drive. A timing chart showing a second example of DC drive.

An embodiment of a dimming device and a method of driving a dimming sheet will be described with reference to FIGS. 1 to 15. Hereinafter, the structure of the dimming device and the driving method of the dimming sheet will be described in order.

[Structure of dimmer]
The structure of the dimmer will be described with reference to FIGS. 1 to 3. The type of the dimming sheet provided in the dimming device may be a normal type or a reverse type. FIG. 1, which is referred to below, shows a cross-sectional structure of a normal type dimming sheet. On the other hand, FIG. 2 shows the cross-sectional structure of the reverse type dimming sheet.

As shown in FIG. 1, the dimming device 10 includes a dimming sheet 20, an operation unit 31, and a drive unit 32. The light control sheet 20 includes a first transparent electrode 21, a second transparent electrode 22, and a light control layer 23. The dimming layer 23 is sandwiched between the first transparent electrode 21 and the second transparent electrode 22. The first transparent electrode 21 is connected to the drive unit 32. The second transparent electrode 22 is connected to, for example, a reference voltage V0 such as a ground voltage. The reference voltage V0 may be a reference voltage in the drive unit 32.

The first transparent electrode 21 and the second transparent electrode 22 have light transmission through which visible light is transmitted. The light transmission of the first transparent electrode 21 enables visual recognition of an object through the light control sheet 20. The light transmission of the second transparent electrode 22 enables visual recognition of an object through the light control sheet 20 as well as the light transmission of the first transparent electrode 21.

The material for forming each of the transparent electrodes 21 and 22 is composed of, for example, indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, and poly (3,4-ethylenedioxythiophene). Any one selected from the group.

The dimming layer 23 includes a transparent polymer layer and a liquid crystal composition. The transparent polymer layer has voids in which the liquid crystal composition is filled. The liquid crystal composition is filled in the voids of the transparent polymer layer. The liquid crystal composition contains liquid crystal molecules. An example of a liquid crystal molecule is composed of Schiff base type, azo type, azoxy type, biphenyl type, terphenyl type, benzoic acid ester type, trans type, pyrimidine type, cyclohexanecarboxylic acid ester type, phenylcyclohexane type, and dioxane type. It is one of the groups to be selected.

The holding type of the liquid crystal composition is any one selected from the group consisting of a polymer network type, a polymer dispersion type, and a capsule type. The polymer network type has a transparent polymer network having a three-dimensional network, and holds the liquid crystal composition in the network-like voids communicating with each other. The polymer network is an example of a transparent polymer layer. The polymer-dispersed type has a large number of isolated voids in the transparent polymer layer, and holds the liquid crystal composition in the voids dispersed in the polymer layer. In the capsule type, the liquid crystal composition having a capsule shape is held in the transparent polymer layer. In addition to the liquid crystal molecules described above, the liquid crystal composition may contain a monomer for forming a transparent polymer layer, a dichroic dye, and the like.

The dimming layer 23 changes the orientation of the liquid crystal molecules in response to the change in voltage generated between the two transparent electrodes 21 and 22. The change in the orientation of the liquid crystal molecules changes the degree of scattering, the degree of absorption, and the degree of transmission of visible light entering the light control layer 23. The voltage between the two transparent electrodes 21 and 22 is the voltage between the transparent electrodes.

When the voltage between the transparent electrodes is 0 V, the orientation of the liquid crystal molecules on the normal type dimming sheet 20 is disordered. For example, when the two transparent electrodes 21 and 22 both have a reference voltage V0, the orientation direction of the liquid crystal molecules on the normal type dimming sheet 20 is disordered. When the orientation direction of the liquid crystal molecules is disordered, the light transmittance of the normal type light control sheet 20 is relatively low.

When the voltage between the transparent electrodes is equal to or higher than a predetermined value, the liquid crystal molecules are aligned so that the dimming layer 23 transmits visible light in the dimming sheet 20. That is, when the voltage between the two transparent electrodes 21 and 22 is equal to or higher than a predetermined value, the orientation of the liquid crystal molecules is aligned on the light control sheet 20. When the liquid crystal molecules are aligned, the light transmittance on the light control sheet 20 is relatively high.

As described above, the normal type dimming sheet 20 has a relatively high light transmittance when the dimming sheet 20 is energized. The normal type dimming sheet 20 has a relatively low light transmittance when the dimming sheet 20 is not energized. For example, the normal type dimming sheet 20 has a transparent state when the dimming sheet 20 is energized, and has an opaque state when the dimming sheet 20 is not energized.

Transparency is a state in which the presence or absence of an object can be visually recognized through the dimming sheet 20. Opaque is a state in which the presence or absence of an object cannot be visually recognized through the dimming sheet 20. Alternatively, transparency is a state in which the shape and type of an object can be visually recognized through the dimming sheet 20. Opaque is a state in which the shape and type of an object cannot be visually recognized through the dimming sheet 20.

The dimming sheet 20 is attached to a window provided in a moving body such as a vehicle or an aircraft, for example. Further, the dimming sheet 20 is attached to, for example, windows provided in various buildings such as houses, stations, and airports, partitions installed in offices, show windows installed in stores, screens for projecting images, and the like. .. The shape of the light control sheet 20 may be flat or curved.

An operation for changing the light transmittance of the dimming sheet 20 is input to the operation unit 31. Among the operations input to the operation unit 31, the operation of applying a voltage between the first transparent electrode 21 and the second transparent electrode 22 is the drive operation. Further, the operation input to the operation unit 31 includes a transparent operation for making the dimming sheet 20 transparent and an opaque operation for making the dimming sheet 20 opaque. One of the transparent operation and the opaque operation is an operation of changing the light transmittance of the light control sheet 20. The other of the transparent operation and the opaque operation is an operation different from the operation of changing the light transmittance of the light control sheet 20. When the dimming device 10 includes a normal type dimming sheet 20, the transparent operation is an operation of changing the light transmittance of the dimming sheet 20 and a driving operation. When the dimming device 10 includes the normal type dimming sheet 20, the opaque operation is different from the operation of changing the light transmittance of the dimming sheet 20. The operation unit 31 is, for example, a human interface such as a switch and a touch panel included in the dimming device 10.

When an operation for changing the light transmittance of the dimming sheet 20 is input to the operation unit 31, the drive unit 32 has the first transparent electrode 21 and the first transparent electrode 21 until an operation different from the operation is input to the operation unit 31. 2 A DC voltage for changing the light transmittance of the light control sheet 20 is continuously applied between the transparent electrode 22 and the light control sheet 20. In the dimming device 10 including the normal type dimming sheet 20, when the transparent operation is input to the operation unit 31, the drive unit 32 applies a DC voltage to the transparent electrode 21 until the opaque operation is input to the operation unit 31. , Continue to apply between 22. In the present embodiment, the drive unit 32 electrically connected to the light control sheet 20 is oriented by applying a DC voltage between the pair of transparent electrodes 21 and 22 so that the light control layer 23 orients the liquid crystal molecules. Fix it so that it remains transparent.

As shown in FIG. 2, the reverse type light control sheet 20 includes a first transparent electrode 21, a second transparent electrode 22, a first alignment film 24, a second alignment film 25, and a light control layer 23. .. The dimming layer 23 is located between the first alignment film 24 and the second alignment film 25. The first alignment film 24 is located between the dimming layer 23 and the first transparent electrode 21 and is in contact with the dimming layer 23. The second alignment film 25 is located between the light control layer 23 and the second transparent electrode 22, and is in contact with the light control layer 23.

The materials for forming the first alignment film 24 and the second alignment film 25 are, for example, organic compounds such as polyimide, polyamide, polyvinyl alcohol and cyanide compounds, and inorganic compounds such as silicone, silicon oxide and zirconium oxide. , Or a mixture of these.

The first alignment film 24 and the second alignment film 25 are, for example, a vertical alignment film or a horizontal alignment film. The long axis of the liquid crystal molecule is such that the vertically aligned film is perpendicular to the surface opposite to the surface in contact with the first transparent electrode 21 and the surface opposite to the surface in contact with the second transparent electrode 22. Orient the direction. The length of the liquid crystal molecules of the horizontal alignment film is substantially parallel to the surface opposite to the surface in contact with the first transparent electrode 21 and the surface opposite to the surface in contact with the second transparent electrode 22. Orient the axial direction. As described above, regardless of which of the alignment films 24 and 25 is, the alignment films 24 and 25 regulate the orientation of the plurality of liquid crystal molecules included in the dimming layer 23.

When the voltage between the transparent electrodes is 0V, the alignment of the liquid crystal molecules is aligned by the alignment films 24 and 25 so that the dimming layer 23 transmits visible light in the dimming sheet 20. That is, when the voltage between the transparent electrodes is 0 V, the orientation of the liquid crystal molecules on the light control sheet 20 follows the actions of the alignment films 24 and 25. When the orientation of the liquid crystal molecules follows the alignment films 24 and 25, the light transmittance of the light control sheet 20 is relatively high.

When the voltage between the transparent electrodes is equal to or higher than a predetermined value, the liquid crystal molecules are aligned in the light control sheet 20 so as not to follow the actions of the alignment films 24 and 25. When the orientation of the liquid crystal molecules does not follow the action of the alignment films 24 and 25, the light transmittance of the reverse type dimming sheet 20 is relatively low.

As described above, the reverse type dimming sheet 20 has a relatively low light transmittance when the dimming sheet 20 is energized. The reverse type dimming sheet 20 has a relatively high light transmittance when the dimming sheet 20 is not energized. For example, the reverse type light control sheet 20 has an opaque state when the light control sheet 20 is energized, and has a transparent state when the light control sheet 20 is not energized.

An operation for changing the light transmittance of the dimming sheet 20 is input to the operation unit 31 as in the operation unit 31 included in the dimming device 10 provided with the normal type dimming sheet 20. When the dimming device 10 includes the reverse type dimming sheet 20, the opaque operation is an operation of changing the light transmittance of the dimming sheet 20 and a driving operation. When the dimming device 10 includes the reverse type dimming sheet 20, the transparent operation is different from the operation of changing the light transmittance of the dimming sheet 20.

When an operation for changing the light transmittance of the dimming sheet 20 is input to the operation unit 31, the drive unit 32 has the first transparent electrode 21 and the first transparent electrode 21 until an operation different from the operation is input to the operation unit 31. 2 A DC voltage for changing the light transmittance of the light control sheet 20 is continuously applied between the transparent electrode 22 and the light control sheet 20. In the dimming device 10 including the reverse type dimming sheet 20, when the opaque operation is input to the operation unit 31, the drive unit 32 applies a DC voltage to the transparent electrode 21 until the transparent operation is input to the operation unit 31. , Continue to apply between 22. In the present embodiment, the drive unit 32 electrically connected to the light control sheet 20 is oriented by applying a DC voltage between the pair of transparent electrodes 21 and 22 so that the light control layer 23 orients the liquid crystal molecules. Fix to maintain opacity.

FIG. 3 is an equivalent circuit of the dimming device 10.
As shown in FIG. 3, in the equivalent circuit of the dimming device 10, the first transparent electrode 21 is regarded as the resistance component R21, and the second transparent electrode 22 is regarded as the resistance component R22. The dimming layer 23 is regarded as a parallel circuit of the capacitance component C23 and the resistance component R23. The resistance component R23 of the dimming layer 23 is significantly larger than the resistance components R21 and R22.

[How to drive the dimming sheet]
A method of driving the dimming sheet 20 will be described with reference to FIGS. 4 to 15. As described above, the drive unit 32 drives the dimming sheet 20 by applying a DC voltage between the pair of transparent electrodes 21 and 22. In the following, first, referring to FIGS. 4 and 5, a driving method using an AC voltage, which is a driving method of a dimming sheet required in a liquid crystal display device, and a driving method using a DC voltage in the present disclosure. The difference from the above will be explained. In the following, for convenience of simplifying the examination, both the resistance component R21 of the first transparent electrode 21 and the resistance component R22 of the second transparent electrode are regarded as zero.

FIG. 4 shows an example of the waveform of the AC voltage applied between the pair of transparent electrodes 21 and 22 in the driving method using the AC voltage.
As shown in FIG. 4, in the AC drive using the AC voltage, the AC voltage of the frequency f is applied between the pair of transparent electrodes 21 and 22. In the AC voltage, since one period P includes a rise and a fall of the voltage, a current flows through the capacitance component C23 of the dimming layer 23 at the rise and fall. Therefore, when the light control sheet 20 is driven for 1 second, a current flows 4 f times through the capacitance component C23 of the light control layer 23. In the AC drive, the current Ic flowing through the capacitance component C23 of the dimming layer 23 in one second can be expressed by the following equation (1). In the formula (1), C is a capacitance value in the capacitance component C23 of the dimming layer 23, and V is a voltage value applied by the drive unit 32 between the pair of transparent electrodes 21 and 22.
Ic = 4fCV ... Equation (1)

Further, in the AC drive, the current flowing through the dimming layer 23 while a constant voltage is applied between the pair of transparent electrodes 21 and 22 is the leak current in the dimming layer 23. The leak current Ir can be expressed by the following equation (2). In the formula (2), R is a resistance value in the resistance component R23 of the dimming layer 23.
Ir = V / R ... Equation (2)

FIG. 5 shows an example of the waveform of the DC voltage applied between the pair of transparent electrodes 21 and 22 in the driving method using the DC voltage.
As shown in FIG. 5, in the DC drive using the DC voltage, when the DC voltage is continuously applied for 1 second, the adjustment is performed only twice at the rise of the DC voltage and at the fall of the DC voltage. A current flows through the capacitance component C23 of the optical layer 23. Therefore, in the DC drive, the current Ic flowing through the capacitance component C23 of the dimming layer 23 in one second can be expressed by the following equation (3).
Ic = 2CV ... Equation (3)

In the DC drive, the current flowing through the dimming layer 23 while a constant voltage is applied between the pair of transparent electrodes 21 and 22 is a leak current in the dimming layer 23 as in the AC drive. The leak current Ir can be expressed by the equation (2) as described above.

Hereinafter, in the equivalent circuit described above with reference to FIG. 3, the power consumed during AC drive and the power consumed during DC drive will be described. As described above, the resistance of each of the transparent electrodes 21 and 22 is significantly smaller than the resistance of the dimming layer 23, so even if the resistance components R21 and R22 are considered to be zero, the following It does not significantly affect the results of a comparative study of AC drive and DC drive explained in.

Strictly speaking, it is possible to ignore such resistance component R21 and resistance component R22 when the area of the light control sheet 20 is up to about ^{1 m 2.} Since the resistance component R23 decreases as the area of the light control sheet 20 increases, the sizes of the resistance component R21 and the resistance component R22 cannot be ignored from the relative relationship with the resistance component R23. However, since the current value flowing through the resistor follows Ohm's law regardless of whether it is DC drive or AC drive, even if the series resistance value changes due to an increase in the area of the dimming sheet 20, DC drive and AC drive It does not affect the result of the comparison with. Therefore, in the following description for discussing the difference in power consumption depending on the driving method, the resistance component R21 and the resistance component R22 are ignored for the sake of simplicity.

First, the power consumption W can be expressed by the following equation (4).
W = VI = V (Ir + Ic) ... Equation (4)
Power _{W A} of the AC driving, the formula (1), equation (2), and, based on the equation (4) can be expressed by the following equation (5). In contrast, the power consumption W _D of the DC drive, on the basis of equation (2) into equation (4) can be expressed by the following equation (6).
_{W A = V A (Ir +} Ic) = V A 2 (1 / R + 4Cf) ... formula (5)
_{W D = V D (Ir +} Ic) = V D 2 (1 / R + 2C) ... (6)

Here, equal to the voltage V _D is the voltage V _A, the assuming either a voltage V, the difference between the power consumption of the AC drive and the DC drive (W A _{-W D)} has the following formula ( It can be represented by 7).
^{_{(W A -W D) = 2CV}} 2 (2f-1) ... (7)

For example, the capacitance value C is 0.1ĩF, resistance R is 100 K.OMEGA, while a voltage V 30 V, when the frequency f is 50Hz, the power consumption _{W A} of the AC drive is 27mW in power consumption _{W D} of the DC driving is 9 mW. As described above, even when the dimming sheet 20 is driven for only one second, the power consumption W can be reduced by 65% or more with respect to the AC drive if the DC drive is used. Further, when the time for driving the light control sheet 20 in a continuous and a T, the difference in power consumption between the AC drive and the DC drive (W A _{-W D)} is 8MWT.

As described later, when considering the power consumption W _D of the DC drive, it is necessary to considering the residual DC voltage generated in the light-modulating layer 23 by application of a DC voltage. For example, when the above specific values are applied and the residual DC voltage is assumed to be 10 V, the voltage V _{A in} AC drive is 30 V and the voltage V _{D in} DC drive is 40 V. Therefore, the power consumption _{W A} of the AC drive while it is 27 mW, the power consumption _{W D} of the DC driving is 16 mW. Even when the residual DC voltage is added in this way, the power consumption W can be reduced by about 40% with respect to the AC drive if the DC drive is used. In this way, according to the DC drive, when an operation for changing the light transmittance of the light control sheet is input, a DC voltage is applied between the transparent electrodes 21 and 22 until an operation different from this operation is input. Therefore, the power consumed by the dimming sheet 20 can be reduced as compared with the AC drive.

Further, according to the DC drive, the polarity is not reversed at the DC voltage after the operation for changing the light transmittance is input until an operation different from this operation is input. Therefore, in AC drive, flicker does not occur in the dimming sheet, unlike the case where an AC voltage having a frequency lower than the critical fusion frequency is applied. As a result, according to the DC drive, it is possible to suppress the occurrence of flicker and reduce the power consumption as compared with the case where the AC voltage is applied.

As described above, conventionally, the uneven distribution of impurity-charged particles in the liquid crystal composition is suppressed, the chemical structure of the liquid crystal molecules themselves is maintained, and the display data is displayed at a frequency higher than the critical fusion frequency. Since it is necessary to rewrite the liquid crystal display periodically, the liquid crystal display device has no choice but to apply an AC voltage to the liquid crystal molecules. On the other hand, from the results of driving the dimming sheet 20 by the above-mentioned DC drive, the stability of the chemical structure of the liquid crystal molecules themselves is recognized. It can be said that it has made it possible to stabilize the chemical structure of the molecule itself under AC drive.

On the other hand, just as a liquid crystal display device can display innumerable colors, each of a plurality of pixels included in the liquid crystal display device is required to be able to accurately display 256 gradations in terms of brightness. Therefore, although the stability of the chemical structure of the liquid crystal molecules is enhanced as described above, in the liquid crystal display device that requires such gradation expression, a shift in the voltage-haze characteristic described later is allowed. Therefore, the liquid crystal display device has no choice but to apply an AC voltage to the liquid crystal molecules.

The shift in the voltage-haze characteristic is due to the impurity charged particles inevitably contained in the liquid crystal composition. Further, considering that it is a common technical knowledge that the liquid crystal composition inevitably contains impurity-charged particles, the liquid crystal display device applies an AC voltage to the liquid crystal molecules from the viewpoint of suppressing the above-mentioned shift in the liquid crystal composition. It can be said that doing is also a common technical knowledge.

Further, when the dimming sheet 20 is used indoors or in the vehicle and the dimming sheet 20 is AC-driven, the light radiated from the lighting equipment installed indoors or in the vehicle and the dimming sheet 20 are used. It may interfere with the light. Specifically, since both the lighting equipment and the dimming sheet 20 are AC-driven, the frequency of the AC voltage applied to the lighting equipment and the frequency of the AC voltage applied to the dimming sheet 20 have a specific relationship. If the above conditions are satisfied, the optical characteristics of the light control sheet 20 may be affected by the AC voltage applied to the lighting equipment. On the other hand, when the dimming sheet 20 is driven by direct current, such interference does not occur.

Further, according to the DC drive, it is possible to simplify the apparatus and the equipment required for applying the voltage to the dimming sheet 20 as compared with the AC drive. This makes it possible to expand the environment in which the dimming sheet 20 can be mounted.

Next, with reference to FIGS. 6 to 13, the residual DC voltage generated in the dimming layer 23 when the dimming sheet 20 is DC-driven will be described. 6 to 10 schematically show the direction of the electric field generated by the residual DC voltage generated in the dimming layer 23 and the direction of the electric field generated by the DC voltage applied to the dimming sheet 20. 6 to 10 illustrate a normal type dimming sheet 20.

The liquid crystal composition contained in the light control layer 23 contains charged particles, which are unavoidable impurities, in addition to the plurality of liquid crystal molecules. The mass, or density, of charged particles per unit volume of the liquid crystal composition decreases as the purity of the liquid crystal molecules increases. With the development and widespread use of technology in liquid crystal display devices, the purification of liquid crystal molecules is progressing, but it is difficult to completely eliminate charged particles contained in the liquid crystal composition. When the DC voltage is continuously applied between the pair of transparent electrodes 21 and 22, the distribution of charged particles in the dimming layer 23 is biased as compared with before the application of the DC voltage. For example, in the normal type light control sheet 20, impurity charged particles are adsorbed between the light control layer 23 and the transparent electrodes 21 and 22. On the other hand, in the reverse type light control sheet 20, charged particles are adsorbed on the surfaces of the alignment films 24 and 25.

As shown in FIG. 6, when the DC drive is started in a state where the potential of the first transparent electrode 21 is higher than the potential of the second transparent electrode 22, positively charged particles and negatively charged particles are charged in the dimming layer 23. And are present irregularly. Then, as shown in FIG. 7, when the DC drive in a state where the potential of the first transparent electrode 21 is higher than the potential of the second transparent electrode 22 is continuously performed for a predetermined period, the dimming layer 23 and the second are Negatively charged particles are adsorbed between the 1 transparent electrode 21 and positively charged particles are adsorbed between the dimming layer 23 and the second transparent electrode 22. Therefore, a residual DC voltage is generated in the dimming layer 23, and as a result, an electric field E23 is generated in the dimming layer 23 along the direction from the second transparent electrode 22 to the first transparent electrode 21.

On the other hand, since the drive unit 32 applies a DC voltage so that the potential of the first transparent electrode 21 is higher than the potential of the second transparent electrode 22, the drive unit 32 has a pair of transparent electrodes 21. The DC voltage applied between the 22s creates an electric potential E30 along the direction from the first transparent electrode 21 to the second transparent electrode 22. In the following, when a DC voltage is applied so that the potential of the first transparent electrode 21 is higher than the potential of the second transparent electrode 22, a voltage having a positive polarity is applied. 2 When a DC voltage is applied so that the potential of the transparent electrode 22 is higher than the potential of the first transparent electrode 21, a voltage having a negative polarity is applied.

Then, as shown in FIG. 8, a DC voltage having a positive polarity is continuously applied, and then a DC voltage having a negative polarity is continuously applied to obtain a DC voltage having a positive polarity. The bias in the distribution of charged particles caused by the application of

At this time, for example, in the normal type dimming sheet 20, the charged particles adsorbed between the dimming layer 23 and the transparent electrodes 21 and 22 adsorbed the charged particles on the transparent electrodes 21 and 22. It moves toward the transparent electrodes 22 and 21 different from the above. Further, in the reverse type light control sheet 20, the charged particles adsorbed on the alignment films 24 and 25 move toward the alignment films 25 and 24 different from the alignment films 24 and 25 adsorbing the charged particles. do. As a result, the strength of the electric field E23 generated by the application of the DC voltage having a positive polarity gradually decreases. Since the direction of the electric field E23 is the same as the direction of the electric field E30, the magnitude of the effective electric field is the sum of the magnitude of the electric field E30 and the magnitude of the electric field E23 immediately after a DC voltage having a negative polarity is applied. Become.

Then, as shown in FIG. 9, positively charged particles and negatively charged particles temporarily exist irregularly in the dimming layer 23, which is caused by the application of a DC voltage having a positive polarity. The bias in the distribution of charged particles is temporarily eliminated. As a result, the electric field E23 disappears temporarily.

As shown in FIG. 10, when a DC voltage having a negative polarity is continuously applied for a predetermined period, positively charged particles are adsorbed between the dimming layer 23 and the first transparent electrode 21. On the other hand, negatively charged particles are adsorbed between the light control layer 23 and the second transparent electrode 22. Therefore, finally, a residual DC voltage having a polarity opposite to that when a DC voltage having a positive polarity is applied is generated in the dimming layer 23. As a result, an electric field E23 is generated in the dimming layer along the direction from the first transparent electrode 21 to the second transparent electrode 22.

On the other hand, in the drive unit 32, since the DC voltage is applied so that the potential of the second transparent electrode 22 is higher than the potential of the first transparent electrode 21, the drive unit 32 is a pair of transparent electrodes 21. The DC voltage applied between the 22s creates an electric field E30 along the direction from the second transparent electrode 22 to the first transparent electrode 21.

The residual DC voltage in the dimming layer 23 is measured by using a measuring method such as a flicker elimination method or a dielectric absorption method.

FIG. 11 shows an example of the voltage-haze characteristic when a DC voltage having a positive polarity is applied to the reverse type dimming sheet 20. The horizontal axis in FIG. 11 indicates the absolute value of the applied voltage. In FIG. 11, the solid line shows the voltage-haze characteristic in the dimming sheet 20 in the reference state, that is, in the state where the residual DC voltage is zero. Further, the broken line indicates the voltage-haze characteristic in a state where the residual DC voltage is saturated by continuously applying the DC voltage having the positive polarity or the DC voltage having the negative polarity described above.

On the other hand, in the alternate long and short dash line, as described above, when the residual DC voltage is saturated by applying the DC voltage having a positive polarity, the polarity of the applied DC voltage is reversed, that is, negative. The initial state of the voltage-haze characteristic in the dimming sheet 20 when a DC voltage having the polarity of is applied is shown. In the alternate long and short dash line, when the residual DC voltage is saturated by applying a DC voltage having a negative polarity and the polarity of the applied DC voltage is reversed, that is, the DC voltage having a positive polarity is The initial state of the voltage-haze characteristic in the dimming sheet 20 when applied is also shown. The voltage-haze characteristic indicated by the alternate long and short dash line corresponds to the state shown in FIG. This characteristic means that the effective electric field applied to the light control sheet 20 is temporarily the sum of the electric field E30 and the electric field E23.

As shown in FIG. 11, in the dimming sheet 20 in the reference state, the haze starts to increase when a DC voltage of 7 V is applied, and the haze rises sharply by increasing the DC voltage from 7 V to 20 V. Since the haze of the light control sheet 20 is maintained constant even when a DC voltage of 28 V or higher is applied, the haze of the light control sheet 20 is saturated by applying a DC voltage of 28 V. That is, the transmittance of the light control sheet 20 is saturated by applying a DC voltage of 28 V. In the example shown in FIG. 11, the DC voltage is applied between the first transparent electrode 21 and the second transparent electrode 22 when the residual DC voltage of the dimming sheet 20 is zero, and the dimming layer 23 This is the first reference voltage that saturates the transmittance.

On the other hand, in the dimming sheet 20 having a positive saturation state or a negative saturation state, haze starts to increase when a DC voltage of 12V is applied, and by increasing the DC voltage from 12V to 25V, Haze rises sharply. Since the haze of the light control sheet 20 is maintained constant even when a DC voltage of 33 V or higher is applied, the haze of the light control sheet 20 is saturated by applying a DC voltage of 33 V. That is, the transmittance of the dimming sheet 20 is saturated by applying a DC voltage of 33V. In the example shown in FIG. 11, the DC voltage is applied between the first transparent electrode 21 and the second transparent electrode 22 when the residual DC voltage of the dimming sheet 20 is saturated, and the dimming layer 23 This is the second reference voltage that saturates the transmittance.

As described above, the amount of electric charge that can be transferred by the electric field is finally constant regardless of the direction of application of the electric field, and more accurately, it is constant unless the liquid crystal molecules are decomposed. Then, when the polarity of the DC voltage applied after the positive saturation state is reversed, the haze starts to rise when a DC voltage of 2V is applied, and by increasing the DC voltage from 2V to 15V, the haze rises sharply. Initial characteristics can be seen. As described above, immediately after the polarity of the DC voltage is reversed, the liquid crystal molecules contained in the dimming layer 23 can apparently operate at a lower voltage. However, if the reversed DC voltage is continuously applied, the haze of the light control sheet 20 is saturated by finally applying the DC voltage of 33V. That is, by applying a DC voltage of 33 V, the transmittance of the light control sheet 20 is finally saturated. That is, the saturation value of the residual DC voltage is a constant value regardless of the direction of the applied DC electric field. Note that FIG. 12, which is referred to below, shows that the saturation value of the residual DC voltage is constant regardless of the direction of the applied DC electric field.

As described above, in the example shown in FIG. 11, when the residual DC voltage of the dimming sheet 20 has a saturated state, the transmittance of the dimming sheet 20 is saturated as compared with the case where the dimming sheet 20 is in the reference state. The voltage to be applied is deviated by 5V in the positive direction. The amount of deviation of the voltage that saturates the transmittance in the state where the residual DC voltage is generated with respect to the voltage that saturates the transmittance in the reference state becomes the residual DC voltage in the DC voltage that saturates the transmittance of the dimming layer 23. The resulting shift amount. The deviation of 5 V in the negative direction shown in FIG. 11 causes the above-mentioned residual DC voltage to act to strengthen the applied electric field due to the reversal of the polarity of the applied DC voltage, and as a result, the operating voltage apparently increases. It shows that the voltage has dropped by 5V. At this time, the electric field direction of the residual DC voltage is the same as the electric field direction of the applied DC voltage after the polarity is reversed.

FIG. 12 shows an example of the relationship between the shift amount of the DC voltage at which the transmittance of the dimming layer 23 is saturated and the elapsed time from the start of application of the DC voltage having a positive polarity. Note that FIG. 12 shows an example in which the DC voltage applied between the pair of transparent electrodes 21 and 22 is 30 V.

As shown in FIG. 12, from the start of application of the DC voltage to the elapse of 100 minutes, the shift amount of the DC voltage at which the transmittance of the dimming layer 23 is saturated increases with the lapse of the application time. It increases almost linearly. On the other hand, after 120 minutes have passed since the application of the DC voltage was started, the shift amount of the DC voltage is kept constant even if the application time is longer than that. As described above, the shift amount of the DC voltage, that is, the residual DC voltage generated in the dimming layer 23 is saturated at a specific application time.

As described above, when the DC voltage having a positive polarity is continuously applied, the saturation voltage in the dimming sheet 20 shifts in the positive direction, so that the drive unit 32 is higher than the first reference voltage. It is preferable to set a high DC voltage to a DC voltage for changing the light transmittance of the light control sheet 20. As a result, even if a residual DC voltage is generated in the dimming layer due to the continuous application of the DC voltage, a DC voltage higher than the first reference voltage is applied, so that the change in the transmittance in the dimming layer can be suppressed. Is possible.

Further, since the dimming layer 23 has the second reference voltage as described above, the drive unit 32 converts the DC voltage equal to or higher than the second reference voltage into a DC voltage for changing the light transmittance of the dimming sheet 20. It is preferable to set it. Thereby, it is possible to enhance the effectiveness of suppressing the change in the transmittance caused by the residual DC voltage generated in the dimming layer 23 in the dimming layer 23 having the driving state. In order to suppress the power consumption W in the light control layer 23, it is preferable that the drive unit 32 sets the second reference voltage to a DC voltage for changing the light transmittance of the light control sheet 20.

The light control sheet 20 is required to show two states, a transparent state in which the transmittance is saturated and an opaque state, while an intermediate state in which the transmittance is located between the transparent state and the opaque state. There are scenes where it is not required to show. Therefore, in the dimming sheet 20, even if the voltage-haze characteristic of the dimming sheet 20 fluctuates, it is sufficient that the change in the transmittance of the dimming sheet 20 in the transparent state or the opaque state is suppressed. In this respect, as described above, the problem is solved by setting the second reference voltage to the DC voltage for changing the light transmittance of the light control sheet 20. As a result, even the dimming sheet 20 including the dimming layer 23 containing the liquid crystal composition can be driven by direct current.

On the other hand, in a liquid crystal display device having a display layer containing a liquid crystal composition, a plurality of liquid crystal display devices are provided so that innumerable colors required to be displayed on the liquid crystal display device can be displayed. Each of the pixels is required to be able to display 256 gradations in terms of brightness. In such a liquid crystal display device, it is essential to suppress the residual DC voltage generated in the display layer, thereby suppressing the fluctuation of the voltage-transmittance characteristic. Since the development and widespread use of technology in liquid crystal display devices is supported by such gradation expression, it is natural that AC driving of liquid crystal display devices is a common general technical knowledge in the field of liquid crystal devices. It can be said that.

FIG. 13 shows an example of the relationship between the value of the residual DC voltage on the light control sheet 20 and the elapsed time after stopping the application of the DC voltage between the pair of transparent electrodes 21 and 22. Note that FIG. 13 shows an example in which the DC voltage applied between the pair of transparent electrodes 21 and 22 is 30 V.

As shown in FIG. 13, the residual DC voltage sharply decreases from the time when the application of the DC voltage is stopped until 15 minutes elapses, and the residual DC voltage decreases from the elapsed time of 15 minutes to 100 minutes. As a result, the residual DC voltage becomes almost zero 100 minutes after the application of the DC voltage is stopped. As described above, it takes at least 15 minutes after the application of the DC voltage is stopped until the residual DC voltage in the dimming layer 23 approaches zero. Therefore, even if the application of the DC voltage is temporarily stopped and then the application of the DC voltage is started again at intervals of several minutes, it is driven in order to suppress the change in the transmittance of the dimming sheet 20 due to the residual DC voltage. It is preferable to set the voltage to be equal to or higher than the saturated drive voltage.

14 and 15 show two examples of DC drive.
As shown in FIG. 14, the drive unit 32 can reverse the polarity of the DC voltage when the total drive period due to the repetition of the drive operation has elapsed a predetermined period. The drive period PD is a period in which the drive unit 32 applies a DC voltage between the pair of transparent electrodes 21 and 22. The total drive period is the sum of the periods in which the DC voltage is applied between the pair of transparent electrodes 21 and 22 by the two or more drive periods PD. In the example shown in FIG. 14, the drive unit 32 first sets a DC voltage having a positive polarity to a DC voltage applied by the drive operation. Then, when the total drive period, which is the sum of the drive period PDs, elapses for a predetermined time, the drive unit 32 applies a DC voltage having a negative polarity between the pair of transparent electrodes 21 and 21. The drive unit 32 reverses the polarity of the DC voltage even when the period of applying the DC voltage having a negative polarity between the pair of transparent electrodes 21 and 22 has elapsed, thereby positive. A DC voltage having the polarity of is applied between the pair of transparent electrodes 21 and 22.

In this way, the polarity of the DC voltage is reversed when the total drive period due to the repetition of the drive operation elapses, so that the dimming layer 23 is caused by the continuous application of the residual DC voltage to the dimming layer 23. It is possible to suppress the deterioration of the optical quality of the.

As shown in FIG. 15, the drive unit 32 can reverse the polarity of the DC voltage each time a drive operation is input. In the example shown in FIG. 15, the drive unit 32 first sets a DC voltage having a positive polarity to a DC voltage applied by the drive operation. Then, when the next drive operation is input, the drive unit 32 sets the DC voltage having a negative polarity to the DC voltage applied by the drive operation. The drive unit 32 alternately applies a DC voltage having a positive polarity and a DC voltage having a negative polarity each time a drive operation is input. As a result, the polarity of the DC voltage applied between the pair of transparent electrodes 21 and 22 is inverted for each drive operation input, so that the dimming layer is caused by the continuous application of the residual DC voltage to the dimming layer 23. It is possible to suppress the deterioration of the optical quality of the.

As is clear from the above description, the present disclosure presupposes that the voltage-haze characteristic shifts within a certain range during the application of a DC voltage. Therefore, the technical idea of the present disclosure is that the haze values in halftones other than the transparent state and the opaque state, that is, the haze values included between the haze value in the transparent state and the haze value in the opaque state are the same. It is a fact that the problem is that it is usually not easy to reproduce with a voltage value.

However, there is no problem in realizing the two states of transparency and opacity, in other words, the binary value of the haze value with good reproducibility. As described above, the main point of view of the present disclosure is that a low power consumption and flickerless dimming device is realized by the DC voltage drive in which the applied voltage is appropriately set.

As described above, according to the embodiment of the dimming device and the driving method of the dimming sheet, the effects described below can be obtained.
(1) When an operation for changing the light transmittance of the dimming sheet 20 is input, a DC voltage is continuously applied between the transparent electrodes 21 and 22 until an operation different from this operation is input, so that flicker occurs. It is possible to reduce the power consumed by the dimming sheet 20 as compared with the case where the AC voltage is applied.

(2) Since the polarity of the DC voltage applied between the pair of transparent electrodes 21 and 22 is inverted for each drive operation input, the dimming layer 23 is caused by the continuous application of the residual DC voltage to the dimming layer 23. It is possible to suppress a decrease in optical quality such as a haze value in.

(3) Haze in the dimming layer 23 due to the continuous application of the residual DC voltage to the dimming layer 23 because the polarity of the DC voltage is inverted when the total driving period due to the repetition of the driving operation elapses. It is possible to suppress deterioration of optical quality such as value.

(4) When the operation of making the light control sheet 20 transparent is input, the DC voltage is continuously applied between the transparent electrodes 21 and 22 until the operation of making the light control sheet 20 opaque is input. Alternatively, when the operation of making the light control sheet 20 opaque is input, the DC voltage is continuously applied between the transparent electrodes 21 and 22 until the operation of making the light control sheet 20 transparent is input. Therefore, it is possible to suppress the occurrence of flicker and reduce the power consumed by the dimming sheet 20 as compared with the case where an AC voltage is applied. Further, it is necessary to realize an opaque state having a high haze value including not only scattering due to refractive index anisotropy of the liquid crystal composition but also three-dimensional scattering at the interface between the liquid crystal composition and the transparent polymer layer. Is possible. In addition, the presence of the transparent polymer layer makes it possible to realize a dimming layer having a stronger and more stable structure.

(5) Even if a residual DC voltage is generated in the dimming layer 23 due to the continuous application of the DC voltage, the DC voltage higher than the first reference voltage is applied, so that the transmittance or haze in the dimming layer 23 is increased. It is possible to suppress changes.

(6) It is possible to enhance the effectiveness of suppressing the change in the transmittance caused by the residual DC voltage generated in the dimming layer 23 in the dimming layer 23.

The above embodiment can be modified and implemented as follows.
[Drive part]
The drive unit 32 may apply a DC voltage having the same polarity each time a drive operation is input. Even in this case, when the drive unit 32 inputs an operation for changing the light transmittance of the dimming sheet 20 to the operation unit 31, an operation different from the operation is input to the operation unit 31. Until then, by continuing to apply a DC voltage for changing the light transmittance of the light control sheet 20, it is possible to obtain an effect according to (1) described above. As shown in FIG. 13, the residual DC voltage in the dimming layer 23 is eliminated according to the period elapsed after the application of the DC voltage is stopped. Therefore, when the application of the DC voltage having the same polarity is repeated, the dimmer 10 measures, for example, the time elapsed from the time when the application of the DC voltage is stopped, and after the predetermined time has elapsed, for example, It is possible to allow the operation input from the operation unit 31. As a result, it is possible to apply the DC voltage to the dimming layer 23 in a state where the residual DC voltage generated in the dimming layer 23 due to the application of the DC voltage is relaxed.

When a switching signal input by a device other than the operation unit such as a communication device and a timer device is input, the drive unit 32 uses the light of the dimming sheet 20 until a switching signal different from the switching signal is input. The configuration may be such that a DC voltage for changing the transmittance is continuously applied. As a result, the drive unit 32 keeps the light transmittance of the light control sheet 20 within a predetermined range by continuing to apply a DC voltage between the first transparent electrode 21 and the second transparent electrode 22. In this case, for example, the first switching signal has the same function as the operation of changing the light transmittance of the dimming sheet 20 input to the operation unit 31, and the second switching signal is the operation unit 31. It has the same function as the operation different from the operation of changing the light transmittance of the light control sheet 20 input to. Even with such a configuration, it is possible to obtain an effect according to (1) described above.

10 ... Dimming device 20 ... Dimming sheet 21 ... 1st transparent electrode 22 ... 2nd transparent electrode 23 ... Dimming layer 24 ... 1st alignment film 25 ... 2nd alignment film 31 ... Operation unit 32 ... Drive unit

Claims (7)

A dimming sheet including a first transparent electrode, a second transparent electrode, and a dimming layer sandwiched between the first transparent electrode and the second transparent electrode and containing liquid crystal molecules.
A drive unit that keeps the light transmittance of the dimming sheet within a predetermined range by continuously applying a DC voltage between the first transparent electrode and the second transparent electrode is provided.
When the residual DC voltage of the dimming sheet is zero, the DC voltage applied between the first transparent electrode and the second transparent electrode to saturate the transmittance of the dimming layer is defined as the first reference voltage. By definition, the drive unit is a dimming device that applies a DC voltage higher than the first reference voltage as a DC voltage for changing the light transmittance. When the residual DC voltage of the light control sheet is saturated, the DC voltage applied between the first transparent electrode and the second transparent electrode to saturate the transmittance of the light control layer is the second reference voltage. And
The dimming device according to claim 1, wherein the drive unit uses a DC voltage equal to or higher than the second reference voltage as a DC voltage for changing the light transmittance. An operation unit for inputting an operation for changing the light transmittance of the dimming sheet is further provided.
When the operation is input to the operation unit, the drive unit holds the dimming sheet between the first transparent electrode and the second transparent electrode until an operation different from the operation is input. The dimming device according to claim 1 or 2, wherein a DC voltage for continuously applying a DC voltage for changing the light transmittance of the light is continuously applied. Among the operations input to the operation unit, the operation of applying a voltage between the first transparent electrode and the second transparent electrode is a drive operation.
The dimming device according to claim 3, wherein the drive unit reverses the polarity of the DC voltage each time the drive operation is input. The operation input to the operation unit includes a transparent operation for making the dimming sheet transparent and an opaque operation for making the dimming sheet opaque.
One of the transparent operation and the opaque operation is an operation of changing the light transmittance of the dimming sheet, and the other of the transparent operation and the opaque operation is an operation of changing the light transmittance of the dimming sheet. The dimming device according to claim 3 or 4, wherein is a different operation. The dimming according to any one of claims 1 to 5, wherein the dimming layer includes a transparent polymer layer having voids filled with the liquid crystal composition and a liquid crystal composition filled in the voids. Device. A method for driving a light control sheet including a first transparent electrode, a second transparent electrode, and a light control layer sandwiched between the first transparent electrode and the second transparent electrode and containing liquid crystal molecules.
When the residual DC voltage of the light control sheet is zero, the DC voltage applied between the first transparent electrode and the second transparent electrode to saturate the transmittance of the light control layer is the first reference voltage. can be,
When an operation for changing the light transmittance of the light control sheet is input from the operation unit, the first transparent electrode and the second transparent electrode are used until an operation different from the operation is input from the operation unit. A method for driving a dimming sheet, which comprises continuously applying a DC voltage higher than the first reference voltage for changing the light transmittance of the dimming sheet.

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