JP7468142B2 - Light control device - Google Patents

Description

The present invention relates to a light control device equipped with a light control film.

2. Description of the Related Art Various proposals have been made so far with respect to light control films that are attached to windows to control the transmission of external light, and light control devices using the same.
One such light control film uses liquid crystal (see, for example, Patent Document 1). In light control films using liquid crystal, liquid crystal is sandwiched between two transparent film materials with transparent electrodes, and the amount of external light transmitted is controlled by changing the orientation of the liquid crystal molecules by applying a voltage between the transparent electrodes.

Patent No. 6489272

Such light control devices can control the amount of external light that passes through. However, there is a demand for light control devices that can be used in a wider range of applications and have improved design features, rather than simply changing the amount of light that passes through.

The objective of the embodiment of the present disclosure is to provide a light control device with a more aesthetically pleasing design.

The embodiments of the present disclosure solve the above problems by the following solving means. Note that, for ease of understanding, the embodiments will be described with corresponding reference numerals, but are not limited thereto.
A first disclosed embodiment is a light control device including a first electrode (11), a second electrode (16), and a liquid crystal layer (8) of a guest-host type containing a liquid crystal material and a dichroic dye, the light transmittance of which changes depending on a potential difference between the first electrode and the second electrode, the light control film (1) being in a light-shielding state when the potential difference is a first potential difference and in a light-transmitting state when the potential difference is a second potential difference that is larger than the first potential difference, the light control film being divided into a plurality of segments (SG1 to SG7), and at least one of the first electrode and the second electrode being divided corresponding to the plurality of segments. The light control device (20) is composed of a plurality of partial electrodes (161-167) and includes a control unit (23) that switches the potential difference between the first potential difference and the second potential difference individually for a plurality of the segments, the liquid crystal layer having a maximum haze value immediately after switching the potential difference from the second potential difference to the first potential difference and then gradually decreasing, and the control unit switches the potential difference in the segments from the second potential difference to the first potential difference in sequence at predetermined time intervals T along the arrangement direction of the plurality of the segments when switching the light control film from a light-transmitting state to a light-blocking state.
A second disclosed embodiment is a dimming device (20) of the first disclosed embodiment, in which when the time from when the potential difference in the liquid crystal layer (8) is switched from the second potential difference to the first potential difference to when the change in the haze value is almost eliminated is defined as time T0, the specified time T satisfies T≦T0.
A third disclosed embodiment is a light control device (1) according to the second disclosed embodiment, wherein the time T0 is a time from when the potential difference in the liquid crystal layer (8) is switched from the second potential difference to the first potential difference until the rate of change in the haze value Rh defined by the formula Rh=|(Ha−Hb)/Hb×100| becomes less than 1%, where Ht is a haze value at a certain point in time and Ha is an average value of the haze value for 7 seconds prior to that point in time.
A fourth disclosed embodiment is a dimming device (20) according to any one of the first to third disclosed embodiments, in which the ratio d/p satisfies 2.25≦d/p≦6.0, where d is the thickness of the liquid crystal layer (8) and p is the chiral pitch of the liquid crystal molecules contained in the liquid crystal layer.
A fifth disclosed embodiment is a dimming device (20) in which, in any of the first to fourth disclosed embodiments, when the time Tp is the time from when the potential difference in the liquid crystal layer (8) is switched from the second potential difference to the first potential difference to when the change in the decrease in the light transmittance of the liquid crystal layer is almost eliminated, the specified time T satisfies T≦Tp.
A sixth disclosed embodiment is a light control device (20) according to the fifth disclosed embodiment, wherein the time Tp is a time from when the potential difference in the liquid crystal layer (8) is switched from the second potential difference to the first potential difference until the rate of change Rt of the light transmittance defined by the formula Rt = |(Kt-Ka)/Ka x 100| becomes less than 1%, where Kt is the light transmittance at a certain point in time and Ka is the average light transmittance for 7 seconds prior to that point in time.

According to the embodiment of the present disclosure, it is possible to provide a light control device with a more aesthetically pleasing design.

2 is an enlarged view of a portion of a cross section of a light control film 1 used in a light control device 20 of an embodiment. FIG. FIG. 2 is a diagram showing a plan view of a light control film 1 used in the light control device 20 of the embodiment. 2A to 2C are diagrams illustrating the configurations of a first electrode 11 and a second electrode 16 of a light control film 1 according to an embodiment. FIG. 2 is a diagram illustrating a method for measuring chiral pitch p. FIG. 2 is a block diagram of a light control device 20 according to the embodiment. FIG. 11 is a diagram showing how the light control film 1 changes when the setting unit 22 switches the light control film 1 from a "light-transmitting state" to a "light-blocking state" in the light control device 20 of the embodiment. 1 is a graph showing changes in haze value for Samples 1 to 7. 1 is a graph showing changes in transmittance of Samples 1 to 7.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings etc. Note that each of the drawings shown below, including Fig. 1, is a schematic diagram, and the size and shape of each part are appropriately exaggerated for ease of understanding.
Furthermore, the terms plate, film, etc. are used, but in general usage, they are used in the order of thickness, plate, sheet, film, and so on, and this specification follows suit. However, since such distinction in usage has no technical meaning, these terms can be used interchangeably as appropriate.

In this specification, terms specifying shapes or geometric conditions, such as parallel and orthogonal, are intended to include not only their strict meanings but also states that have a similar optical function and have an error that can be regarded as parallel or orthogonal.
Furthermore, the numerical values such as the dimensions of each component and the names of materials described in this specification are merely examples of embodiments, and are not intended to be limiting, and may be appropriately selected and used.

(Embodiment)
FIG. 1 is an enlarged view of a part of a cross section of a light control film 1 used in a light control device 20 of the present embodiment.
FIG. 2 is a diagram showing a plan view of the light control film 1 used in the light control device 20 of this embodiment.
The light control film 1 is a component that is sandwiched, together with an intermediate film such as PVB, between two glass sheets that form laminated glass in a portion where light control is to be performed, such as a sunroof or window of a vehicle, and controls transmitted light in response to changes in the applied voltage. The light control film 1 may also be used by being attached to a portion where light control is to be performed, such as a window glass of a building, a showcase, an indoor transparent partition, or a sunroof of a vehicle, by an adhesive layer or the like. In this embodiment, an example in which the light control film is sandwiched between laminated glass and provided on a side window of a vehicle will be described.

In addition, the light control film 1 has a plurality of regions (hereinafter, each region is appropriately referred to as a segment) as shown in Fig. 2. In Fig. 2 and other figures, the boundary lines of each region are indicated by dashed lines for ease of understanding.
In this embodiment, as an example, the light control film 1 has seven segments SG1 to SG7 of equal width arranged adjacent to each other along the direction of the arrow d, as shown in Figure 2.

As shown in Figure 1, the light-controlling film 1 is a guest-host type light-controlling film 1 in which a liquid crystal layer 8 is sandwiched between a film-like first laminate 5D and a second laminate 5U, and the transmitted light is controlled by changing the electric field to the liquid crystal layer 8.
The first laminate 5D is formed by arranging a first electrode 11, a first alignment film 13, and a spacer 12 on a first substrate 6 which is a transparent film material. The second laminate 5U is formed by arranging a second electrode 16 and a second alignment film 17 on a second substrate 15 which is a transparent film material.
The strength of the electric field in the liquid crystal layer 8 changes when the first electrodes 11 and the second electrodes 16 provided on the second stack 5U and the first stack 5D are driven.

The first substrate 6 and the second substrate 15 can be made of various transparent film materials that are applicable to this type of film material. In this embodiment, the first substrate 6 and the second substrate 15 are made of polyethylene terephthalate film (PET film). However, the first substrate 6 and the second substrate 15 can be made of various transparent film materials such as COP (cycloolefin polymer) film, TAC film, acrylic film, polycarbonate film (PC film), etc., depending on the environment and purpose in which the light control film 1 is used.

3 is a diagram illustrating the configuration of the first electrode 11 and the second electrode 16 of the light control film 1 of this embodiment. In FIG. 3, in order to facilitate understanding, illustrations other than the first electrode 11 and the second electrode 16 constituting the light control film 1 are omitted.
The first electrode 11 and the second electrode 16 are so-called transparent electrodes, and various electrode materials applicable to this type of film material can be applied. In this embodiment, the first electrode 11 and the second electrode 16 are formed of a transparent electrode material made of ITO (Indium Tin Oxide).
The potential difference between the first electrode 11 and the second electrode 16 becomes the voltage applied to the liquid crystal layer 8 .

3, in this embodiment, the second electrode 16 is divided into seven parts along the direction of the arrow d (see FIG. 2) according to each segment of the light control film 1, and is formed on the second substrate 15 as a plurality of insulated partial electrodes 161 to 167 that can be individually supplied with driving power. In addition, the first electrode 11 facing the second electrode 16 is not divided and is formed over the entire area of the first substrate 6 where the liquid crystal layer 8 is formed.
By arranging the first electrode 11 and the second electrode 16 in this manner, the light-controlling film 1 can adjust the voltage (the potential difference between the first electrode 11 and the second electrode 16) applied independently to each of the segments SG1 to SG7, thereby changing the light transmittance of the segment.
In the following description of the specification, unless otherwise specified, "transmittance" refers to the transmittance of light (particularly visible light) (total light transmittance).

The spacers 12 are provided to define the thickness of the liquid crystal layer 8, and can be made of a wide variety of resin materials. The spacers 12 in this embodiment are bead spacers, as shown in FIG.
The spacer 12 is not limited to this, and may be a columnar spacer or the like produced by applying a photoresist onto the first substrate 6 on which the first electrode 11 is produced using a photoresist, exposing the photoresist to light, and developing the photoresist. In this case, the spacer 12 may be provided on the second stack 5U, or may be provided on both the second stack 5U and the first stack 5D.

The first alignment film 13 and the second alignment film 17 are prepared by subjecting a polyimide resin layer to a rubbing treatment. The first alignment film 13 and the second alignment film 17 may be prepared using a variety of configurations capable of exerting an alignment control force on the liquid crystal material of the liquid crystal layer 8, and may be prepared using a so-called photo-alignment film.
In this case, the photo-alignment material may be any of various materials to which a photo-alignment method can be applied, and may be, for example, a dimerization-type material whose alignment does not change by irradiation with ultraviolet light once aligned. This photo-dimerization-type material is disclosed in "M. Schadt, K. Schmitt, V. Kozinkov and V. Chigrinov: Jpn. J. Appl.Phys., 31, 2155 (1992)" and "M. Schadt, H. Seiberle and A. Schuster: Nature, 381, 212 (1996)" and the like.

In this embodiment, the light-controlling film 1 is shown as an example in which a first alignment film 13 and a second alignment film 17 are rubbed in order to suppress appearance defects due to poor alignment, etc. However, in cases where poor appearance, etc. are not an issue, an alignment film that has not been subjected to rubbing treatment or photo-alignment treatment, etc. may be used.
Furthermore, in the case of the present embodiment where the light control film 1 is divided into a plurality of segments and the segments are driven individually, part or all of the first electrode 11 and the second electrode 16 may be removed to form the segments, and in this case, part or all of the first alignment film 13 and the second alignment film 17 may be removed, and further, part of the first substrate 6 and the second substrate 15 may be removed.

In the light control film 1, a sealant 19 is arranged so as to surround the liquid crystal layer 8, and this sealant 19 holds the second laminate 5U and the first laminate 5D together, preventing leakage of the liquid crystal material.

The liquid crystal layer 8 contains a liquid crystal material and a dichroic dye, and is driven by a guest-host system.
Nematic liquid crystal is used as the liquid crystal material forming the liquid crystal layer 8. The liquid crystal material contains a chiral agent, and the chiral pitch p of the liquid crystal molecules can be adjusted by adjusting the content of the chiral agent. The chiral pitch is the distance when the liquid crystal molecules are twisted by one period (360°) in the thickness direction of the liquid crystal layer 8.
The chiral agent is a low molecular weight compound having an optically active site, and induces a helical structure in the nematic liquid crystal. Examples of the chiral agent include S-811, R811, CB-15, MLC6247, MLC6248, R1011, and S1011 (all manufactured by Merck).

A dichroic dye is a dye whose absorbance in the long axis direction of the molecule is different from that in the short axis direction. When the orientation state of the liquid crystal molecules changes due to a change in the voltage applied to the liquid crystal layer 8 (light control film 1), the orientation state of the dichroic dye also changes in response to the change in the orientation state of the liquid crystal molecules. Examples of dichroic dyes that can be used include LSY-116, LSR-401, LSR-405, LSB-278, LSB-350, and LSB-335 (all manufactured by Mitsubishi Chemical Corporation).

Here, a method for measuring the chiral pitch p will be described. As described above, the chiral pitch is the distance (dimension) in the thickness direction of the liquid crystal layer 8 when the liquid crystal molecules are twisted by one period (360°).
4A and 4B are diagrams for explaining a method for measuring the chiral pitch p. Fig. 4A is a cross-sectional view parallel to the thickness direction of a wedge-shaped cell 30 used in the measurement, and Fig. 4B is a plan view of the wedge-shaped cell 30, showing a striped pattern due to the difference in brightness observed when measuring the chiral pitch p.
The wedge-shaped cell 30 includes two glass plates 31, 32 and a base 33 disposed between the two glass plates 31, 32 to form a wedge shape. A cross section parallel to the thickness direction of the wedge-shaped cell 30 is wedge-shaped, and in this embodiment, is triangular as shown in Fig. 4(a). Here, the wedge shape refers to a shape that is wide at one end and gradually narrows toward the other end, and includes shapes including triangular and trapezoidal shapes.

A horizontal alignment film (not shown) is formed on the liquid crystal side surface 32a of the glass plate 32, which forms the bottom surface of the wedge-shaped cell 30. Therefore, when a guest-host type liquid crystal material is sealed between the two glass plates 31 and 32 of the wedge-shaped cell 30, the liquid crystal molecules are aligned along the alignment direction of this alignment film and rotate according to the height of the cell.

When a guest-host type liquid crystal material is poured into the wedge-shaped cell 30, stripes due to the difference in brightness appear every time the liquid crystal molecules rotate 180 degrees, as shown in Fig. 4(b). These stripes become darker as the cell height H increases. Moreover, these stripes appear at equal pitches every time the liquid crystal rotates 180 degrees.
Therefore, if the width of the stripe is a, the dimension of the wedge-shaped cell 30 in the stripe arrangement direction is L, the maximum cell height of the wedge-shaped cell 30 is H, and the chiral pitch is p, the following equation is obtained from the similarity ratio.
2 x a:L = p:H

From the above, the chiral pitch p is expressed by the following formula.
p = 2 x a x H/L
In this embodiment, the dimension of the stripe width a was measured three times, and the average value was taken as the chiral pitch p. Also, while Fig. 4 shows an example in which the liquid crystal material is filled in the entire space formed by the glass plates 31, 32 and the base 33, the present invention is not limited to this, and it is possible to measure the chiral pitch p as long as an amount of liquid crystal material sufficient to observe two stripes required for measurement is filled.

The chiral pitch p is preferably 0.5 μm or more.
When a liquid crystal material having a helical structure is used in the liquid crystal layer 8, a phenomenon occurs in which light with a wavelength equal to the average refractive index n of the liquid crystal material multiplied by the chiral pitch p is selectively reflected. If the chiral pitch p is less than 0.5 μm, this phenomenon causes light with a specific wavelength in the visible light region to be selectively reflected, which may cause the light control film 1 to appear colored in a specific color or reduce the light transmittance of the light control film 1. Therefore, it is preferable that the chiral pitch p satisfies the above range.

The thickness (cell gap) d of the liquid crystal layer 8 is preferably set to be 2 μm or more and 20 μm or less.
If the thickness d of the liquid crystal layer 8 is less than 2 μm, it is difficult to manufacture the light control film 1 including such a liquid crystal layer 8, and the yield during production of the light control film 1 is significantly reduced, which is undesirable. Also, if the thickness d of the liquid crystal layer 8 is greater than 20 μm, the amount of liquid crystal material used increases, which is undesirable as it increases the material cost of the light control film 1. Therefore, it is preferable that the thickness d of the liquid crystal layer 8 is within the above range.
If a foreign object is mixed into the liquid crystal layer 8 having a small thickness d, and the dimensions of the foreign object are larger than the thickness d of the liquid crystal layer 8, the liquid crystal layer 8 will swell only in the area where the foreign object is mixed in, and this will often deteriorate the appearance of the light control film 1. However, if the thickness d of the liquid crystal layer 8 is sufficiently ensured, it is possible to reduce deterioration of the appearance due to the mixing of the foreign object.

The light control film 1 (liquid crystal layer 8) of this embodiment has a normally dark structure (normally black structure). The normally dark structure is a structure in which the light transmittance is at a minimum and the screen is black (light-shielding state) when no voltage is applied to the liquid crystal. In contrast, the normally clear structure is a structure in which the light transmittance is at a maximum and the screen is transparent (transmitting state) when no voltage is applied to the liquid crystal.
In this embodiment, the liquid crystal of the liquid crystal layer 8 is p (positive) type, and when no voltage is applied to the light-controlling film 1 (liquid crystal layer 8) (when the potential difference between the first electrode 11 and the second electrode 16 is the first potential difference), the liquid crystal molecules rotate with their longitudinal direction tilted toward the surface direction of the light-controlling film 1 (direction perpendicular to the thickness direction), and accordingly, the dichroic dye also rotates with its longitudinal direction tilted toward the surface direction of the light-controlling film 1 (direction perpendicular to the thickness direction). In other words, the liquid crystal molecules and the dichroic dye are horizontally oriented. Therefore, the light-controlling film 1 has a low transmittance of light (visible light) and is in a light-shielding state (dark state) in which it appears black.

On the other hand, when a predetermined voltage is applied to the light-controlling film 1 (liquid crystal layer 8) (when the potential difference between the first electrode 11 and the second electrode 16 is a second potential difference greater than the first potential difference), the liquid crystal molecules have their long axis direction parallel to the thickness direction of the liquid crystal layer 8, and accordingly, the dichroic dye also has its long axis direction parallel to the thickness direction of the liquid crystal layer 8. In other words, the liquid crystal molecules and the dichroic dye are vertically oriented. Therefore, the light-controlling film 1 has a high transmittance of light (visible light) and is in a transparent state (bright state) that allows the view on the other side to be clearly seen through the light-controlling film 1.
Regarding the voltage applied to the liquid crystal layer 8, the voltage in the light-transmitting state is called the light-transmitting voltage, and the voltage in the light-shielding state is called the light-shielding voltage. That is, when the potential difference between the first electrode 11 and the second electrode 16 is the second potential difference, the light-transmitting voltage is applied to the liquid crystal layer 8, and when the potential difference between the first electrode 11 and the second electrode 16 is the first potential difference, the light-shielding voltage is applied to the liquid crystal layer 8. The light-transmitting voltage is greater than the light-shielding voltage.

Here, we further explain the changes in appearance of the light-controlling film 1 when the voltage applied to the liquid crystal layer 8 of the light-controlling film 1 of this embodiment changes from a light-transmitting voltage to a light-blocking voltage, that is, when the potential difference applied to the liquid crystal layer 8 (the potential difference between the first electrode 11 and the second electrode 16) changes from the second potential difference to the first potential difference.
When the potential difference applied to the liquid crystal layer 8 changes from the second potential difference to the first potential difference, the long axis direction of the liquid crystal molecules and the dichroic dye changes from a direction parallel to the thickness direction to a rotated state toward the surface direction of the liquid crystal layer 8 (light-controlling film 1) (a direction perpendicular to the thickness direction).
At this time, the change in the long axis direction of the liquid crystal molecules and the dichroic dye is due to the regulating force of the first alignment film 13 and the second alignment film 17 and the regulating force of the chiral agent, and since it is weaker than the regulating force due to the voltage, it takes several seconds to several tens of seconds for the change to occur.
Therefore, the light transmittance of the liquid crystal layer 8 (light-controlling film 1) drops significantly immediately after the potential difference in the liquid crystal layer 8 is switched from the second potential difference to the first potential difference, and then gradually drops more slowly over time, and after a predetermined time has passed, the liquid crystal layer 8 enters a light-blocking state.

Furthermore, due to the change in the long axis directions of the liquid crystal molecules and the dichroic dye, a cloudy state, i.e., a haze state, is observed in the light control film 1 immediately after switching the potential difference. This occurs because light passing through the liquid crystal layer 8 is scattered in the process in which the long axis directions of the liquid crystal molecules and the dichroic dye change as described above. The haze value in this haze state is characterized by increasing to a maximum value immediately after switching the potential difference in the liquid crystal layer 8 from the second potential difference to the first potential difference, and gradually decreasing over time.
The haze value is the ratio of the diffuse transmittance (diffuse light transmittance) to the total light transmittance. That is, it is an index of the transparency of the light control film 1 and represents the turbidity (cloudiness). If the haze value is large, the light control film 1 will be in a cloudy state (hazy state).

When the potential difference in the liquid crystal layer 8 is switched from the second potential difference to the first potential difference, the light-controlling film 1, which was in a light-transmitting state with a maximum transmittance and a low haze value, changes to an intermediate tone state in which the transmittance is lower than in the light-transmitting state, and the transmittance gradually decreases over time, until it reaches a light-shielding state with a minimum transmittance. In the intermediate tone state, the haze value of the light-controlling film 1 is maximum immediately after the potential difference in the liquid crystal layer is switched, and it appears cloudy, and then decreases over time, reaching a minimum in the light-shielding state.

Next, we will explain the change in appearance of the light-controlling film 1 when the voltage applied to the liquid crystal layer 8 of the light-controlling film 1 of this embodiment changes from a light-blocking voltage to a light-transmitting voltage, that is, when the potential difference across the liquid crystal layer 8 (the potential difference between the first electrode 11 and the second electrode 16) changes from a first potential difference to a second potential difference that is greater than the first potential difference.
When the potential difference applied to the liquid crystal layer 8 changes from the first potential difference to the second potential difference, the long axis direction of the liquid crystal molecules and dichroic dye changes from a state in which they are tilted and rotated toward the surface direction of the liquid crystal layer 8 (light-controlling film 1) (a direction perpendicular to the thickness direction) to a direction parallel to the thickness direction.
At this time, the change in the long axis direction of the liquid crystal molecules and the dichroic dye is due to the regulating force caused by the voltage, which is greater than the regulating forces caused by the first alignment film 13 and the second alignment film 17 and the regulating force of the chiral agent, and the time required for the change is very short, less than one second.

Therefore, due to changes in the long axis directions of the liquid crystal molecules and the dichroic dye, the above-mentioned haze state is observed in the light control film 1. However, as described above, the time required for this change is short, so the time it takes to achieve the haze state is also very short, and it is perceived as momentarily shining bright white.
Furthermore, at this time, the transmittance of the liquid crystal layer 8 (light control film 1) increases rapidly immediately after the potential difference is switched from the first potential difference to the second potential difference, and the liquid crystal layer 8 enters a light-transmitting state.
Therefore, when the potential difference in the liquid crystal layer 8 is switched from the first potential difference to the second potential difference, the light-control film 1, which was in a light-blocking state with the minimum transmittance and low haze value, changes in a short period of time through a haze state in which the haze value is maximized and the film appears bright and white, and then to a light-transmitting state in which the transmittance is maximized and the haze value is small.

FIG. 5 is a block diagram of the light control device 20 of the present embodiment.
The light control device 20 includes the light control film 1 described above, a power supply unit 21, a setting unit 22, and a control unit 23. The power supply unit 21 is a power source for supplying a voltage applied to the light control film 1. The setting unit 22 is, for example, a switch that can be operated by the user, and can set the light control film 1 to a "light-transmitting state" or a "light-blocking state." The control unit 23 is a part that individually controls the voltage applied to each segment SG1 to SG7 of the light control film 1 based on the input from the setting unit 22.

In the dimming device 20 of this embodiment, when the setting unit 22 sets the "light-transmitting state" for the light-controlling film 1, the potential difference between the first electrode 11 and the second electrode 16 is the second potential difference over the entire surface of the light-controlling film 1, and the light-controlling film 1 is in a light-transmitting state in which the light transmittance is maximized. Also, when the setting unit 22 selects the "light-shielding state" for the light-controlling film 1, the potential difference between the first electrode 11 and the second electrode 16 is the first potential difference, which is smaller than the second potential difference, over the entire surface of the light-controlling film 1, and the light-shielding film 1 is in a light-shielding state in which the light transmittance is minimized.

Furthermore, in the light control device 20 of this embodiment, the setting unit 22 can control the voltages applied individually to the segments SG1 to SG7 by using the partial electrodes 161 to 167 (see FIG. 3) corresponding to the seven segments SG1 to SG7 of the light control film 1.
Then, when the setting of the light-controlling film 1 is switched from the "light-transmitting state" to the "light-blocking state" by inputting a setting in the setting unit 22, the control unit 23 switches the potential difference between the first electrode 11 and the second electrode 16 corresponding to each segment from the second potential difference (light-transmitting voltage) to a smaller first potential difference (light-blocking voltage) for each segment SG1 to SG7 in sequence along the arrangement direction (the direction of arrow d shown in Figure 2) every predetermined time T [seconds].

In addition, if the time from when the potential difference between the first electrode 11 and the second electrode 16 in the liquid crystal layer 8 is switched from the second potential difference to the first potential difference until the haze value of the liquid crystal layer 8 (light-controlling film 1) no longer changes is defined as T0 [seconds], then it is preferable that the above-mentioned specified time T satisfies T≦T0.
Furthermore, if the time from when the potential difference in the liquid crystal layer 8 is switched from the second potential difference to the first potential difference until the change in transmittance disappears is defined as time Tp [seconds], it is preferable that the above-mentioned specified time T satisfies T≦Tp.
This produces an effect that the transmittance and haze value are different between adjacent segments, and the transmittance and haze value are visually perceived as changing in a gradational manner in the arrangement direction of the segments SG1 to SG7 (the direction of the arrow d shown in FIG. 2). Note that this time T can be set appropriately according to the size of the light control film 1, the number of segments, the usage environment, etc., as long as T≦T0 and T≦Tp are satisfied as described above.

Here, the state in which the haze value hardly changes refers to a state in which the rate of change in the haze value Rh [%] is less than 1% (Rh<1%) when defined by the following formula.
Rh=|(Ht-Ha)/Ha×100|
In the above formula, Ht is the haze value at a certain point in time, and Ha is the average haze value for the 7 seconds prior to that point in time.
When the rate of change in haze value Rh defined by the above formula is less than 1%, the change in haze value is very small and can be regarded as no change in haze value.
Therefore, time T0 is the time from when the potential difference applied to the liquid crystal layer 8 is switched from the second potential difference to the first potential difference until the rate of change Rh of the haze value calculated by the above formula becomes less than 1%.

The state in which the transmittance hardly changes refers to a state in which the rate of change in transmittance Rt [%] is less than 1% (Rt<1%) when defined by the following formula.
Rt = |(Kt-Ka)/Ka x 100|
In the above formula, Kt [%] is the transmittance at a certain point in time, and Ka [%] is the average transmittance for 7 seconds prior to that point in time.
When the rate of change in transmittance defined by the above formula is less than 1% (Rt<1%), the change in transmittance is very small and can be regarded as no change in transmittance.
Therefore, the time Tp is the time from when the potential difference applied to the liquid crystal layer 8 is switched from the second potential difference to the first potential difference until the rate of change Rt of the transmittance calculated by the above formula becomes less than 1%.

In this embodiment, when the setting unit 22 inputs a switch from the "light-transmitting state" to the "light-blocking state" for the light-controlling film 1 to the control unit 23, the control unit 23 controls the voltage applied to the partial electrodes 161 to 167 for each of the segments SG1 to SG7, and switches the potential difference across the liquid crystal layer 8 of the next segment from the second potential difference to the first potential difference every T seconds, which is within T0 seconds and within Tp seconds after the potential difference across the liquid crystal layer 8 of the previous segment is switched from the second potential difference to the first potential difference, along the arrangement direction of the segments (direction of arrow d).
As a result, in the light control device 20 of this embodiment, the entire surface of the light control film 1 is in a light-transmitting state, and each segment changes sequentially along the arrangement direction of the segments (the direction of the arrow d) through a half-tone state in which the transmittance decreases and the segments gradually become darker, before moving to a light-shielding state. In addition, in each segment, in the half-tone state, the haze value decreases from the maximum value over time.

FIG. 6 is a diagram showing the change in the light control film 1 when the setting unit 22 switches the light control film 1 from a "light-transmitting state" to a "light-blocking state" in the light control device 20 of this embodiment.
When the “light-transmitting state” is selected for the light-controlling film 1 by the setting unit 22, the potential difference between the first electrode 11 and the second electrode 16 over the entire surface of the light-controlling film 1 becomes the second potential difference (light-transmitting voltage), and as shown in Figure 6 (a), the entire surface of the light-controlling film 1 is in a light-transmitting state.

When the setting unit 22 selects the "light-shielding state" for the light-controlling film 1, the control unit 23, based on input from the setting unit 22, switches the voltage applied to each segment SG1 to SG7 of the light-controlling film 1 from the light-transmitting voltage to the light-shielding voltage at predetermined intervals in sequence along the segment arrangement direction (direction of arrow d). In other words, the potential difference between the first electrode 11 and second electrode 16 (partial electrodes 161 to 167) of each segment SG1 to SG7 is switched in sequence from the second potential difference to the first potential difference.

Specifically, the control unit 23 first sets the voltage applied to the segment SG1 to the light-shielded voltage, that is, sets the potential difference between the first electrode 11 and the partial electrode 161 to the first potential difference. At this time, the voltages applied to the other segments SG2 to SG7 remain at the light-transmitted voltage (the potential differences between the first electrode 11 and the partial electrodes 162 to 167 remain at the second potential difference).
Immediately after the potential difference between the first electrode 11 and the partial electrode 161 becomes the first potential difference, as shown in Fig. 6(b) , in the light control film 1, the segment SG1 has the maximum haze value, but the transmittance is lower than in the light-transmitting state, and is in a half-tone state. Also, the segments SG2 to SG7 are in the light-transmitting state.
Thereafter, the haze value of the segment SG1 decreases over time, and after T0 seconds the haze value remains unchanged. The transmittance of the segment SG1 also decreases over time, and after Tp seconds the transmittance remains unchanged. At this time, the segment SG1 is in a light-shielding state.

Next, the control unit 23 sets the potential difference between the first electrode 11 and partial electrode 161 in segment SG1 to the first potential difference, within T0 seconds and within Tp seconds, the potential difference between the first electrode 11 and partial electrode 162 in the adjacent segment SG2 to the first potential difference.
In this embodiment, the potential difference between the first electrode 11 and the partial electrode 162 in the segment SG2 is set to the first potential difference a predetermined time T seconds (here, T1 seconds as an example) after the potential difference between the first electrode 11 and the partial electrode 161 in the segment SG1 is set to the first potential difference. At this time, T1≦T0 and T1≦Tp.

Immediately after the potential difference between the first electrode 11 and the partial electrode 162 becomes the first potential difference, for example, as shown in FIG. 6(c), segments SG3 to SG7 are in the light-transmitting state, and segments SG2 and SG1 are in the halftone state. However, at this time, segment SG2 is in a state where the transmittance is smaller than in the light-transmitting state but the haze value is at its maximum, and segment SG1 is in a state where the transmittance and haze value are smaller than those of segment SG2. In other words, the haze value and transmittance of segment SG2 are greater than those of segment SG1.

Next, a predetermined time T seconds (here, as an example, T2 seconds) after the potential difference between the first electrode and the partial electrode 162 in the segment SG2 is set to the first potential difference, the control unit 23 sets the potential difference between the first electrode 11 and the partial electrode 163 in the segment SG3 to the first potential difference. At this time, T2≦T0 and T2≦Tp. In this embodiment, this time T2 is the same as the above-mentioned time T1, but is not limited to this and may be different.
Immediately after the potential difference between the first electrode 11 and the partial electrode 163 becomes the first potential difference, the haze value of the segment SG3 increases to the maximum value. Therefore, at this time, as shown in Fig. 6D, for example, the segments SG4 to SG7 are in the light-transmitting state, the segments SG3 and SG2 are in the halftone state, and the segment SG1 is in the light-shielding state. At this time, in the segments SG1 to SG3 that are not in the light-transmitting state, the transmittance and haze value are, in order from largest to smallest, the segments SG3, SG2, and SG1. Therefore, it is visually recognized that the transmittance and haze value change in a gradational manner (tone-like manner) from segment SG3 to segment SG1, decreasing.

Similarly, for segments SG4 to SG7, the control unit 23 switches the potential difference between the first electrode 11 and the partial electrodes 164 to 167 corresponding to each segment to the first potential difference every predetermined time T seconds, which is shorter than time T0 and time Tp.
Immediately after the control unit 23 causes the potential difference between the corresponding first electrode 11 and partial electrode 167 of the last segment SG7 to become the first potential difference, the haze value and transmittance are, for example, in descending order, as follows: segment SG7, segment SG6, segment SG5, segment SG4, segment SG3, segment SG2, and segment SG1. Depending on the length of time T for switching the potential difference, for example, segments SG5 to SG1 may all be in a light-shielding state and may have the same transmittance.
As a result, the light control film 1 can be seen to change stepwise from a light transmitting state to a halftone state in which the transmittance and haze value are gradually reduced, and then to a light blocking state along the arrangement direction (direction of arrow d) of the segments SG1 to SG7. Then, over time, the entire surface of the light control film 1 finally becomes light blocking.

In this way, the control unit 23 controls the voltage applied to the partial electrodes corresponding to each segment, and switches the potential difference applied to the liquid crystal layer 8 of each segment from the second potential difference to the first potential difference in sequence along the arrangement direction of the segments SG1 to SG7, so that each segment of the light control film 1 is observed to change in a gradational manner from a light-transmitting state, through a half-tone state, to a light-blocking state in sequence along the arrangement direction.

Therefore, according to this embodiment, the design of the light control device 20 can be further improved. In addition, according to this embodiment, the change from the light-transmitting state to the light-blocking state of the light control film 1 is not a change over the entire surface, but a change along the arrangement direction of the segments SG1 to SG7, and the change from the light-transmitting state to the light-blocking state is not abrupt, but is visually recognized as a gradation having intermediate tones in which the transmittance and haze value gradually decrease. In other words, the appearance of the outside scenery through the light control film 1 does not change from the light-transmitting state to the light-blocking state instantaneously and over the entire surface, but each segment changes from the transmitting state to the light-blocking state through intermediate tones in which the transmittance and haze value gradually decrease, and the change is visually recognized by the observer as occurring in sequence along the arrangement direction of the segments SG1 to SG7. Therefore, it is possible to achieve the effect of softening the impression of the change in the appearance of the outside scenery through the light control film 1 at the time of switching, the effect of improving the sense of luxury as a light control device, the effect of suppressing the visual division between each area at the time of switching, and the like.

Next, a change in the light control film 1 when the setting unit 22 of the light control device 20 sets the light control film 1 from the "light blocking state" to the "light transmitting state" will be described.
When the "light-blocking state" is selected for the light-controlling film 1 by the setting unit 22, the potential difference between the first electrode 11 and the second electrode 16 over the entire surface of the light-controlling film 1 becomes a first potential difference (light-blocking voltage), and the light-control film 1 is in a light-blocking state over the entire surface.

When the setting unit 22 selects the "light-transmitting state" for the light-controlling film 1, the control unit 23 switches the potential difference between the first electrode 11 and the partial electrodes 161-167 corresponding to each segment SG1-SG7 of the light-controlling film 1 from the first potential difference to the second potential difference in the direction of the segment arrangement (the direction of the arrow d shown in FIG. 2) in response to the input from the setting unit 22. That is, the light-transmitting voltage is applied in sequence starting from segment SG1. Note that the order in which the potential difference of each segment is switched may be the reverse of the order in which the "light-transmitting state" is switched to the "light-shielding state" described above, that is, the reverse of the direction of the arrow d shown in FIG. 2. In this case, the light-transmitting voltage is applied first to segment SG7, and then to SG6, SG5, SG4, and so on.

As a result, the light-control film 1 momentarily goes into a hazy state with high transmittance and high haze value, starting from segment SG1 along the arrangement direction, which is visually recognized by the observer as a bright, cloudy white state, and then the haze value drops rapidly and changes to a light-transmitting state in a short time. Note that the time for which the light-transmitting voltage is applied in order from segment SG1 to SG7 is not particularly limited, and may be set appropriately depending on the usage environment, the number of segments, the characteristics of the light-control film 1, etc.

(Regarding Samples 1 to 7)
Here, several samples (samples 1 to 7) having different d/p ratios of the liquid crystal layer 8 were prepared as the light-controlling film 1, and the changes in the haze value and transmittance were investigated when the potential difference between the first electrode 11 and the second electrode 16 was switched from the first potential difference to the second potential difference.
As described above, p is the chiral pitch of the liquid crystal molecules, d is the thickness of the liquid crystal layer (cell gap), and the ratio of these is d/p. Furthermore, Samples 1 to 7 are not segmented.

Fig. 7 is a graph showing the change in haze value of Samples 1 to 7. In the graph of Fig. 7, the vertical axis represents the haze value [%], and the horizontal axis represents time [seconds].
Fig. 8 is a graph showing the change in transmittance of Samples 1 to 7. In the graph of Fig. 8, the vertical axis represents transmittance (total light transmittance) [%], and the horizontal axis represents time [seconds].
7 and 8, the horizontal axis indicates the time when the potential difference between the first electrode 11 and the second electrode 16 in each sample is set to the first potential difference as 0 seconds. Therefore, among the measurement values shown in the graphs in Fig. 7 and 8, the measurement values in the region before 0 seconds on the horizontal axis are the haze value and transmittance of each sample in a light-transmitting state.

Samples 1 to 7 and the measuring equipment used to measure the haze values thereof will be described below.
Samples 1 to 7 have different values of the ratio d/p, etc., as described below. Samples 1 to 7 used in the measurement use a guest-host type liquid crystal material as the liquid crystal material for the liquid crystal layer 8, and have a normally dark structure. Samples 1 to 7 each have a square shape measuring 260 mm x 260 mm in plan view.

An AC voltage of 60 Hz (rectangular wave) was applied to Samples 1 to 7 by an AC power supply (eK-FGJ manufactured by Matsusada Precision Co., Ltd.). As an example, the second potential difference (light-transmitting voltage) which is the potential difference between the first electrode 11 and the second electrode 16 in the light-transmitting state was set to 20 V, and the first potential difference (light-shielding voltage) which is the potential difference between the first electrode 11 and the second electrode 16 in the light-shielding state was set to 0 V.
The haze value and transmittance of Samples 1 to 7 were measured using a haze meter (NDH 7000II, manufactured by Nippon Denshoku Kogyo Co., Ltd.). The haze value was measured in accordance with JIS K 7136. Due to the characteristics of the haze meter used in the measurements, the haze value and transmittance were measured every 7 seconds.

The thickness (cell gap) d of the liquid crystal layer 8 in Samples 1 to 7 corresponds to the height of the spacers 12 in the liquid crystal layer 8 (the dimension of the spacers 12 in the thickness direction of the liquid crystal layer 8) and can be measured by various measuring instruments.
When the spacers 12 are columnar, their height (thickness d of the liquid crystal layer 8) can be measured by an optical interference shape measuring device. When the spacers 12 are spherical bead spacers, their height can be measured by a microscope such as a scanning electron microscope (SEM).
The method for measuring the chiral pitch p is as described above.

The d/p ratio of each sample is as follows:
Sample 1: d/p=3.0 (chiral pitch p=4 μm)
Sample 2: d/p=3.0 (chiral pitch p=3 μm)
Sample 3: d/p=3.75 (chiral pitch p=2.4 μm)
Sample 4: d/p=4.5 (chiral pitch p=2 μm)
Sample 5: d/p=3.0 (chiral pitch p=3 μm)
Sample 6: d/p=6.0 (chiral pitch p=2 μm)
Sample 7: d/p=2.25 (chiral pitch p=4 μm)

As shown in Fig. 7, for each sample, the haze value reaches a maximum value immediately after the potential difference between the first electrode 11 and the second electrode 16 is switched from the second potential difference to the first potential difference, but the haze value decreases over time, and gradually the change is almost constant. Also, as shown in Fig. 8, for each sample, the transmittance decreases significantly immediately after the potential difference between the first electrode 11 and the second electrode 16 is switched from the second potential difference to the first potential difference, and then the transmittance decreases gradually over time, and the change is almost constant.
7, the measurement results for Samples 1 to 7 show that the higher the ratio d/p, the higher the haze value and the longer the state in which the haze value is high (e.g., Samples 4 and 6). This is believed to be because the higher the ratio d/p, the greater the number of rotations of the major axes of the liquid crystal molecules and the dichroic dye.

With regard to the above-mentioned samples 1 to 7, by appropriately selecting according to the usage environment of the dimming device 20, the desired optical performance, the number of segments, etc., any of them can be used as the dimming film 1 of the dimming device 20 such as this embodiment.
For example, when a sample such as sample 5 shown in FIG. 7 is used, in which the slope of the graph when the haze value decreases after reaching a maximum value is gentle, the difference in haze value between adjacent segments becomes small, and a gradation with more tones can be realized.
In the graph shown in FIG. 7 , the maximum haze value of sample 7 is lower than those of the other samples. This is because the haze meter used in the measurement measures the haze value every 7 seconds, and the haze state is clearly visible to the naked eye.

In the above samples 1 to 7, the time T0 until the change in the haze value almost disappears (the time until the change becomes stable) and the time Tp until the change in the transmittance almost disappears (the time until the change becomes stable) are as follows, based on the formula defined using the above-mentioned rate of change Rh of the haze value and the rate of change Rt of the transmittance.
Sample 1: Time T0 is about 35 seconds, time Tp is about 21 seconds. Sample 2: Time T0 is about 42 seconds, time Tp is about 21 seconds. Sample 3: Time T0 is about 49 seconds, time Tp is about 21 seconds. Sample 4: Time T0 is about 63 seconds, time Tp is about 35 seconds. Sample 5: Time T0 is about 28 seconds, time Tp is about 21 seconds. Sample 6: Time T0 is about 98 seconds, time Tp is about 77 seconds. Sample 7: Time T0 is about 21 seconds, time Tp is about 21 seconds.

In the above-described embodiment, the light-control film 1 is applied to the side window of a vehicle, and from the viewpoint of using it like a curtain, it is preferable to use a liquid crystal layer 8 (light-control film 1) in which the ratio d/p satisfies 2.25≦d/p≦6.0. All of the above-described samples 1 to 7 can be suitably used as the light-control film 1 of the light control device 20 of this embodiment. In this case, the time T, which is the interval between switching the voltage applied to each segment, is preferably within 1 second, for example, which is suitable for practical use as a light-control curtain.

(Modifications)
The present disclosure is not limited to the above-described embodiment, and various modifications and variations are possible, and are within the scope of the present disclosure. The above-described embodiment and the following modified embodiments may be used in appropriate combination, but detailed description thereof will be omitted.
(1) In the embodiment, an example has been shown in which the first electrode 11 is formed on the entire surface of the first substrate 6, but this is not limiting, and the first electrode 11 may be divided into seven parts in accordance with the segments SG1 to SG7, and partial electrodes corresponding to each segment may be arranged and formed, similar to the second electrode 16. Furthermore, this is not limiting, and the first electrode 11 may be divided into seven parts in accordance with the segments SG1 to SG7, and partial electrodes corresponding to each segment may be arranged and formed, and the second electrode 16 may be formed on the entire surface of the second substrate 15.

(2) In the embodiment, the dimensions of the segments SG1 to SG7 in the arrangement direction (the direction of arrow d) are shown to be of equal width, but this is not limited thereto. The dimensions may be different or may change in stages or continuously depending on the environment in which the dimmer device 20 is used, etc.
In the embodiment, the segments SG1 to SG7 are arranged in the left-right direction in the figure, but the present invention is not limited to this, and the segments may be arranged in the up-down direction or in an oblique direction. Furthermore, in the light control film 1, a plurality of segments may be arranged in two directions that intersect on a plane parallel to the plane of the film.
In addition, in the embodiment, an example has been shown in which the segments 1SG1 to SG7 have a rectangular shape when viewed from above, but this is not limited to this, and for example, the planar shape may be a square shape, another quadrilateral shape such as a parallelogram shape or a trapezoid shape, or another polygonal shape such as a triangular shape or a hexagonal shape, and the corners of these may be convex curved shapes, or a circular shape or an elliptical shape, or a shape that combines curves and straight lines, and various shapes can be selected.

(3) In the embodiment, the setting unit 22 is an example of a switch or the like that can be operated by the user, but this is not limited thereto. For example, the setting unit 22 may be configured to be operated by input using a touch panel or the like, and the configuration of the setting unit 22 is not particularly limited.

(4) In the embodiment, when the light-controlling film 1 switches from the "light-transmitting state" to the "light-blocking state", the control unit 23 switches the voltage applied to each segment in sequence along the arrangement direction of the segments SG1 to SG7 (the direction of the arrow d shown in FIG. 2). However, this is not limited to the above, and the voltage applied may be changed in sequence, for example, starting from segment SG4, in the opposite direction of the arrow d toward segment SG1, and in the direction of the arrow d toward segment SG7. The control unit 23 may also switch the voltage applied to some of the multiple segments (for example, segments SG1 to SG3) in sequence.

(5) In the embodiment, when the light-controlling film 1 switches from the "light-blocking state" to the "light-transmitting state", the control unit 23 switches the voltage applied to each segment in sequence along the arrangement direction of the segments SG1 to SG7 (the direction of the arrow d). However, this is not limited to the above. For example, the voltage applied to all segments may be switched at the same time, or the voltage applied to each segment may be switched in sequence in the opposite direction to the direction of the arrow d. Also, the voltage applied to some of the multiple segments (for example, segments SG1 to SG3) may be switched in sequence. Also, for example, the voltage applied to the successive segments may change starting from segment SG4, in the opposite direction to the direction of the arrow d toward segment SG1, and in the direction of the arrow d toward segment SG7.

REFERENCE SIGNS LIST 1 light control film 5D first laminate 5U second laminate 6 first substrate 8 liquid crystal layer 11 first electrode (transparent electrode)
12 Spacer 13 First alignment film 15 Second substrate 16 Second electrode (transparent electrode)
17 Second alignment film 19 Sealing material 20 Light control device 21 Power supply unit 22 Setting unit 23 Control unit

Claims (3)

A light control device comprising a first electrode, a second electrode, and a guest-host type liquid crystal layer containing a liquid crystal material and a dichroic dye, the light transmittance of which changes depending on a potential difference between the first electrode and the second electrode, the light control film being in a light-shielding state when the potential difference is a first potential difference and in a light-transmitting state when the potential difference is a second potential difference greater than the first potential difference,
The light management film is divided into a plurality of segments,
At least one of the first electrode and the second electrode is composed of a plurality of partial electrodes divided corresponding to the plurality of segments,
a control unit that switches the potential difference between the first potential difference and the second potential difference for each of the plurality of segments;
the liquid crystal layer has a maximum haze value and then gradually decreases immediately after the potential difference is switched from the second potential difference to the first potential difference,
When switching the light control film from the light transmitting state to the light blocking state, the control unit sequentially switches the potential difference in the segments from the second potential difference to the first potential difference at predetermined time intervals T along the arrangement direction of the plurality of segments ,
The haze value at a certain point in time is Ht, the average haze value for the 7 seconds prior to that point is Ha, and the rate of change in the haze value Rh [%] is expressed as
Rh=|(Ht-Ha)/Ha×100|
The predetermined time T is defined as follows:
T≦T0
Meet your dimmer. The light control device according to claim 1 ,
When the thickness of the liquid crystal layer is d and the chiral pitch of the liquid crystal molecules contained in the liquid crystal layer is p, the ratio d/p is 2.25≦d/p≦6.0.
Meet your dimmer. The light control device according to claim 1 or 2 ,
The light transmittance at a certain point in time is Kt, the average light transmittance for 7 seconds prior to that point is Ka, and the rate of change in the light transmittance Rt [%] is expressed as follows:
Rt = |(Kt-Ka)/Ka x 100|
where Tp is a time from when the potential difference in the liquid crystal layer is switched from the second potential difference to the first potential difference until the rate of change Rt of the light transmittance defined by the above formula becomes less than 1%, then the predetermined time T is
T≦Tp
Meet your dimmer.

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