阅读说明：本技术 调光片、调光装置及调光片的管理方法 (Dimming sheet, dimming device and management method of dimming sheet ) 是由 驹津基靖 于 2020-03-18 设计创作，主要内容包括：调光片具备调光层及夹着调光层的一对透明电极层。调光片在一个以上的对象变化率的绝对值中具有0.7以上的最大值,各对象变化率是遮光率[％]相对于对象范围内的施加电压[V]的变化率,对象范围是调光片的遮光率变化10％的施加电压的范围,遮光率由JIS L 1055：2009规定。(The light control sheet includes a light control layer and a pair of transparent electrode layers sandwiching the light control layer. The dimming sheet has a maximum value of 0.7 or more among absolute values of one or more target change rates, each target change rate being a change rate of a light-shielding rate [% ] with respect to an applied voltage [ V ] within a target range, the target range being a range of the applied voltage in which the light-shielding rate of the dimming sheet changes by 10%, the light-shielding rate being defined by JIS L1055: 2009 specifies.)

1. A light control sheet comprising a light control layer and a pair of transparent electrode layers sandwiching the light control layer,

the absolute value of one or more target change rates has a maximum value of 0.7 or more, each target change rate being a change rate of a light-shielding rate [% ] with respect to an applied voltage [ V ] within a target range, the target range being a range of the applied voltage in which the light-shielding rate of the dimming sheet changes by 10%, the light-shielding rate being defined by JIS L1055: 2009 specifies.

2. The dimmer as claimed in claim 1,

the maximum value of the absolute values of the target change rates is 6.0 or less.

3. The dimmer according to claim 1 or 2,

the maximum value of the light-shielding rate is 30% or more.

4. The dimmer according to any one of claims 1 to 3,

the light shielding rate can be changed by 50% or more by applying a voltage to the transparent electrode layer.

5. The dimmer according to any one of claims 1 to 4,

the light control layer contains a polymer network liquid crystal or a polymer dispersed liquid crystal.

6. A light control device is provided with:

the dimming sheet of any one of claims 1 to 5; and

and a control unit for controlling the application of voltage to the transparent electrode layer.

7. The dimming apparatus of claim 6,

the control unit switches the light control sheet to a plurality of states in which the light shielding rates are different from each other by 10% or more by switching the voltage.

8. A method for managing a light control sheet, the light control sheet comprising a light control layer and a pair of transparent electrode layers sandwiching the light control layer, wherein the application of a voltage to the pair of transparent electrode layers enables the light control sheet to be controlled in accordance with JIS L1055: 2009, in the method for controlling a dimming sheet,

comprises the step of judging whether the dimming sheet is normal or not,

the condition for determining that the light control sheet is normal is that, when the voltage applied to the transparent electrode layer is changed, the maximum value of 0.7 or more is included in the absolute values of one or more target change rates, each target change rate is a change rate of a light-shielding rate [% ] with respect to an applied voltage [ V ] within a target range, and the target range is a range of the applied voltage in which the light-shielding rate of the light control sheet changes by 10%.

Technical Field

The invention relates to a dimming sheet, a dimming device with the dimming sheet and a management method of the dimming sheet.

Background

The light control sheet includes a light control layer and a pair of transparent electrode layers sandwiching the light control layer (see, for example, patent document 1). The light control device includes the light control sheet and a control unit for controlling application of a driving voltage to the pair of transparent electrode layers. For example, the alignment state of liquid crystal molecules included in the light modulation layer changes according to the potential difference between the pair of transparent electrode layers, and thus the transparency of the light modulation sheet changes. The control section changes the state of application of the driving voltage, thereby switching between a transparent state and an opaque state of the dimming sheet.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-187775

Disclosure of Invention

Problems to be solved by the invention

The light control sheet is attached to, for example, a window glass of a building or an automobile, and functions as a spacer for partitioning 2 spaces. For the purpose of protecting privacy and the like, it is required that a person or an object in one space cannot be seen from an observer in the other space when the light modulation sheet is in an opaque state.

On the other hand, there are also properties desired for the light control sheet functioning as the separator from the viewpoint of transparency different from that of the light control sheet itself. Specifically, the light modulator is required to be capable of adjusting the brightness in the second space by changing the amount of light entering the second space from the first space. In order to clearly show to an observer in the second space that the light control sheet has a function of adjusting the brightness, the timing at which the brightness is switched is preferably easily recognizable to the observer, that is, the brightness is preferably changed in a short time.

The invention aims to provide a dimming sheet capable of adjusting brightness in a space, a dimming device and a management method of the dimming sheet.

Means for solving the problems

A light control sheet for solving the above problems is provided with a light control layer and a pair of transparent electrode layers sandwiching the light control layer. The absolute value of one or more target change rates has a maximum value of 0.7 or more, each target change rate being a change rate of a light-shielding rate [% ] with respect to an applied voltage [ V ] within a target range, the target range being a range of the applied voltage in which the light-shielding rate of the dimming sheet changes by 10%, the light-shielding rate being defined by JIS L1055: 2009 specifies.

The larger the maximum value of the absolute value of the target change rate is, the more quickly the light-shielding rate changes by 10% at any time from the instruction of switching the applied voltage to the end of the change of the light-shielding rate. That is, at the above timing, the light shielding rate changes more quickly by the amount of change in which the change in brightness in the space can be recognized. Then, if the maximum value of the absolute value of the object change rate is 0.7 or more, the rate of change of the light shielding rate at the time becomes good, and the timing of the brightness switching becomes easily recognizable by the observer. As a result, a light modulation sheet having a function of adjusting brightness and capable of clearly showing the function to the observer can be realized.

In the method for managing a light control sheet for solving the above problems, the light control sheet is provided with a light control layer and a pair of transparent electrode layers sandwiching the light control layer, and a voltage can be applied to the pair of transparent electrode layers so that a voltage of JIS L1055: 2009 specified light-shielding rate. The management method includes a step of determining whether the light control sheet is normal, and the condition for determining that the light control sheet is normal is that, when the applied voltage to the transparent electrode layer is changed, the absolute value of one or more target change rates has a maximum value of 0.7 or more, each target change rate is a change rate of a light-shielding rate [% ] with respect to an applied voltage [ V ] within a target range, and the target range is a range of the applied voltage in which the light-shielding rate of the light control sheet changes by 10%.

According to the above-described management method, quality management relating to the light-shielding property of the light control sheet can be performed, and by using the management method, it is possible to realize manufacturing of the light control sheet or the like having a function of adjusting brightness in a space and in which the timing of switching of the brightness is easily recognized by an observer.

Drawings

Fig. 1 is a diagram showing a configuration of a light control device including a general-type light control sheet in one embodiment of the light control device.

Fig. 2 is a diagram showing a configuration of a light control device including a reverse type light control sheet in one embodiment of the light control device.

Fig. 3 is a graph showing a standard relationship between an applied voltage and a light-shielding ratio in a dimming sheet.

Fig. 4 is a graph showing the relationship between the applied voltage and the light shielding rate in the light control sheet of each test example.

Fig. 5 is a graph showing the relationship between the applied voltage and each parameter in the light modulation sheet of test example 1.

Fig. 6 is a graph showing the relationship between the applied voltage and each parameter in the light modulation sheet of test example 2.

Fig. 7 is a graph showing the relationship between the applied voltage and each parameter in the light modulating sheet of test example 3.

Fig. 8 is a graph showing the relationship between the applied voltage and each parameter in the light modulating sheet of test example 4.

Fig. 9 is a graph showing the relationship between the applied voltage and each parameter in the light modulating sheet of test example 5.

Detailed Description

An embodiment of a dimming sheet, a dimming device, and a method for managing a dimming sheet will be described below with reference to the drawings.

[ basic Structure of light control device ]

With reference to fig. 1 and 2, the basic configuration of the light control device will be described centering on the configuration of the light control sheet included in the light control device.

As shown in fig. 1, the light control device 100 includes a light control sheet 10 and a control unit 20 that controls application of a driving voltage to the light control sheet 10. The dimming sheet 10 has any one of a general type and an inverted type. Fig. 1 shows a cross-sectional configuration of a general type dimming sheet 10N.

The light control sheet 10N of the conventional type includes a light control layer 11, a first transparent electrode layer 12A and a second transparent electrode layer 12B which are a pair of transparent electrode layers, and a first transparent support layer 13A and a second transparent support layer 13B which are a pair of transparent support layers. The first transparent electrode layer 12A and the second transparent electrode layer 12B sandwich the light modulation layer 11, and the first transparent support layer 13A and the second transparent support layer 13B sandwich the light modulation layer 11 and the transparent electrode layers 12A and 12B. First transparent supporting layer 13A supports first transparent electrode layer 12A, and second transparent supporting layer 13B supports second transparent electrode layer 12B.

The first terminal portion 15A is connected to the surface of the first transparent electrode layer 12A. The first transparent electrode layer 12A is connected to the control unit 20 via a wiring extending from the first terminal portion 15A. A second terminal portion 15B is connected to the surface of the second transparent electrode layer 12B. The second transparent electrode layer 12B is connected to the control unit 20 via a wiring extending from the second terminal portion 15B. At the end of the light control sheet 10N, the first transparent electrode layer 12A is exposed from the light control layer 11, the second transparent electrode layer 12B, and the second transparent supporting layer 13B. The first terminal portion 15A is disposed in the exposed region of the first transparent electrode layer 12A. The second transparent electrode layer 12B is exposed from the light control layer 11, the first transparent electrode layer 12A, and the first transparent supporting layer 13A at the end of the light control sheet 10N. The second terminal portion 15B is disposed in the exposed region of the second transparent electrode layer 12B. The terminal portions 15A and 15B constitute a part of the dimming sheet 10N.

The control unit 20 generates a driving voltage as an ac voltage and applies the driving voltage to the first transparent electrode layer 12A and the second transparent electrode layer 12B.

The light modulation layer 11 includes a liquid crystal composition. The liquid crystal composition contains liquid crystal molecules. The light modulation layer 11 is composed of, for example, a Polymer Network Liquid Crystal (PNLC), a Polymer Dispersed Liquid Crystal (PDLC), a capsule Nematic Liquid Crystal (NCAP), or the like. For example, a polymer network type liquid crystal includes a polymer network having a three-dimensional network, and liquid crystal molecules are held in voids of the polymer network. In the liquid crystal molecules contained in the light control layer 11, for example, the dielectric anisotropy is positive, and the dielectric constant in the long axis direction of the liquid crystal molecules is larger than the dielectric constant in the short axis direction of the liquid crystal molecules. The light control layer 11 may have a predetermined color and contain a dye that does not interfere with the movement of liquid crystal molecules. With this configuration, the light control sheet 10 having a predetermined primary color can be realized.

The first transparent electrode layer 12A and the second transparent electrode layer 12B are transparent layers having conductivity. Examples of the material constituting the transparent electrode layers 12A and 12B include Indium Tin Oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide, zinc oxide, Carbon Nanotubes (CNT), and a polymer containing poly (3, 4-ethylenedioxythiophene) (PEDOT). The transparent electrode layers 12A and 12B may be a multilayer film including an Ag alloy thin film.

The first transparent supporting layer 13A and the second transparent supporting layer 13B are transparent substrates, respectively. The transparent support layers 13A and 13B may be, for example, a glass substrate, a silicon substrate, a polymer film, or the like. The material for forming the polymer film may be, for example, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl alcohol, polycarbonate, polyvinyl chloride, polyimide, polysulfone, cycloolefin polymer, triacetyl cellulose, or the like.

The first terminal portion 15A and the second terminal portion 15B are each formed of, for example, a conductive adhesive layer, a wiring board, a lead wire, and the like. The conductive adhesive layer may be, for example, a metal tape, a conductive film, a conductive paste, or the like. The wiring substrate may be, for example, fpc (flexible printed circuits).

Fig. 2 shows a sectional configuration of the inverted type dimming sheet 10R. The reverse type light control sheet 10R includes a first alignment layer 14A and a second alignment layer 14B, which are a pair of alignment layers sandwiching the light control layer 11, in addition to the light control layer 11, the transparent electrode layers 12A and 12B, and the transparent support layers 13A and 13B. The first alignment layer 14A is located between the light modulation layer 11 and the first transparent electrode layer 12A, and the second alignment layer 14B is located between the light modulation layer 11 and the second transparent electrode layer 12B. That is, the first transparent electrode layer 12A and the second transparent electrode layer 12B sandwich the light modulation layer 11 and the alignment layers 14A and 14B.

The alignment layers 14A and 14B are, for example, vertical alignment films. The alignment layers 14A and 14B are configured to align the liquid crystal molecules contained in the light control layer 11 such that the long axis direction of the liquid crystal molecules is along a normal direction along a surface on which the alignment layers 14A and 14B extend when the first transparent electrode layer 12A and the second transparent electrode layer 12B are at the same potential. On the other hand, when a potential difference is generated between the transparent electrode layers 12A and 12B, the alignment layers 14A and 14B can change the long axis direction of the liquid crystal molecules contained in the light control layer 11 to a direction other than the normal direction.

The material constituting the alignment layers 14A and 14B may be, for example, polyamide, polyimide, polycarbonate, polystyrene, polysiloxane, polyester, polyacrylate, or the like. The polyester may be, for example, polyethylene terephthalate, polyethylene naphthalate, or the like. The polyacrylate may be, for example, polymethyl methacrylate or the like. The alignment layers 14A and 14B are processed to function as vertical alignment films, for example, polishing, polarized light irradiation, and microfabrication.

In the normal type, when no driving voltage is applied to the transparent electrode layers 12A and 12B, that is, when the first transparent electrode layer 12A and the second transparent electrode layer 12B are at the same potential, the long axis direction of the liquid crystal molecules contained in the light control layer 11 is irregular. Therefore, light incident on the light control layer 11 is scattered, and the light control sheet 10 becomes opaque. On the other hand, when a drive voltage is applied to the transparent electrode layers 12A and 12B to generate a potential difference between the first transparent electrode layer 12A and the second transparent electrode layer 12B, the liquid crystal molecules are aligned by the potential difference, and the long axis direction of the liquid crystal molecules is along the electric field direction between the transparent electrode layers 12A and 12B. As a result, light easily transmits through the light modulation layer 11. As the applied driving voltage becomes larger within a predetermined range, the transparency of the dimming sheet 10 becomes higher.

In the reverse type, when no driving voltage is applied to the transparent electrode layers 12A, 12B, the liquid crystal molecules are aligned by the alignment layers 14A, 14B, and the long axis direction of the liquid crystal molecules is along the normal direction along the surfaces of the alignment layers 14A, 14B. As a result, the dimming sheet 10 becomes transparent. On the other hand, when a drive voltage is applied to the transparent electrode layers 12A and 12B, the long axis direction of the liquid crystal molecules differs from the normal direction due to the potential difference between the first transparent electrode layer 12A and the second transparent electrode layer 12B, and light is less likely to transmit through the light modulation layer 11. As the applied driving voltage becomes larger within a prescribed range, the transparency of the dimming sheet 10 becomes lower.

[ light-shielding rate ]

The dimming sheet 10 is attached to a transparent member located at the boundary of two spaces. Thus, the light adjusting sheet 10 functions as a spacer that can adjust the light shielding properties of the two spaces. The surface on which the dimming sheet 10 is stuck may be a flat surface or a curved surface. For example, the dimming sheet 10 is attached to a building material or a vehicle member. The building material is, for example, a window glass, a partition, a glass wall, or the like. The vehicle member is, for example, a window glass of an automobile.

The light modulation sheet 10 may be configured such that the light shielding property of the light modulation sheet 10 can be switched between the first state and the second state by controlling the driving voltage so that the brightness in the space partitioned by the light modulation sheet 10 can be arbitrarily adjusted. The second state is a state that is significantly different from the first state.

In general, the transparency of the light control sheet 10 is evaluated by the haze representing the degree of diffusion of light in the light control sheet 10. In contrast, the light shielding property of the light control sheet 10 depends on how much light passes through the light control sheet 10 from one space to illuminate the other space, and is not limited to parallel light or diffused light. This problem is difficult to accurately evaluate in terms of haze. For example, in a diffusion state of a certain level or more, the sensitivity of the light-shielding property of the haze is low, and therefore, the change in the haze of the light control sheet with respect to the change in the drive voltage does not completely coincide with the change in the light-shielding rate. Thus, the inventors of the present application found that: by using a method represented by JISL 1055: 2009(a method) can evaluate the light-shielding performance of the light-modulating sheet 10 by a light-shielding ratio, and evaluate the brightness adjusting function of the light-modulating sheet 10.

The inventors of the present application found, through the verification of the test example using the light control sheet 10: if the light-shielding rates differ by 10% or more, the difference in light-shielding performance of the light control sheet 10 can be recognized by a person. That is, if the light-shielding rate in the first state and the light-shielding rate in the second state of the light modulator 10 differ by 10% or more, the change in brightness in the space caused by the switching between the first state and the second state can be perceived by a person present in the space.

The first state is a state in which the light shielding rate of the light modulating sheet 10 is highest within a predetermined range of the driving voltage, and the second state is a state in which the light shielding rate of the light modulating sheet 10 is lowest within the range of the driving voltage. The control unit 20 may switch the state of the light control sheet 10 to two states, i.e., the first state and the second state, or may switch the state to 3 or more states including a state having a light shielding rate between the light shielding rate in the first state and the light shielding rate in the second state. In the dimming sheet 10, the transparency in the second state is higher than the transparency in the first state.

Further, the inventors of the present application evaluated the speed of change in the light blocking ratio, that is, the speed of change in the brightness by the light control sheet 10, by analyzing the relationship between the driving voltage and the light blocking ratio. This will be described in detail below.

Fig. 3 shows a tendency of standardization of the relationship between the drive voltage and the light shielding rate in the light control sheet 10N of the general type obtained as a result of the above analysis. As shown in fig. 3, the light blocking ratio S is maximized when the applied voltage Vo, which is the driving voltage applied to the transparent electrode layers 12A and 12B, is 0V. When the applied voltage Vo is increased from 0V, the light-shielding rate S gradually decreases as the applied voltage Vo increases while the applied voltage Vo is small. When the applied voltage Vo becomes a medium level, the light-shielding rate S decreases rapidly with the increase of the applied voltage Vo. As the applied voltage Vo becomes larger, the light-shielding rate S is slowly decreased with the rise of the applied voltage Vo. When the applied voltage Vo is greater than or equal to the predetermined value, the change in the light-shielding rate S is reduced, and the light-shielding rate S hardly changes.

Here, a range of the applied voltage Vo in which the light-shielding rate S changes by 10% is defined as a target range VR, and a change rate of the applied voltage Vo [ V ] with respect to the light-shielding rate S [% ] in the target range VR, that is, a change amount of the light-shielding rate S per 1V rise of the applied voltage Vo is defined as a target change rate RC. That is, when the lower limit value of the applied voltage Vo in the target range VR is V1 and the upper limit value of the applied voltage Vo in the target range VR is V2, | RC | which is the absolute value of the target rate of change RC is obtained by the following calculation formula in the normal mode.

|RC|＝|-10|/(V2-V1)

Fig. 3 shows one object range VR as an example.

As described above, when the light shielding rate S changes by 10% or more, the change in brightness in the space can be recognized by the observer present in the space. The object change rate RC represents a change rate of the light shielding rate S with respect to the applied voltage Vo in a case where the light shielding rate S of the light adjusting sheet 10 changes to such an extent that a change in brightness can be recognized.

The inventors of the present application found through the verification of the test example using the dimming sheet 10: in the range of the driving voltage applied to the transparent electrode layers 12A and 12B, if the maximum value of the absolute value of the object change rate RC is 0.7 or more, the speed of the change in the light shielding rate is good, and the timing of the change in brightness is recognized. For example, when the first state is realized when the drive voltage is 0V and the second state is realized when the drive voltage is 50V, the maximum value of the absolute value of the target rate of change RC among the target rates of change RC in each target range VR included in the range of 0V to 50V may be 0.7 or more.

In addition, in the inverted type dimmer strip 10R, the increase and decrease of the light-shielding rate S is opposite to the increase and decrease of the applied voltage Vo, compared to the normal type. That is, when the applied voltage Vo is 0V, the light-shielding rate S is minimum, and when the applied voltage Vo is increased from 0V, the light-shielding rate S gradually increases as the applied voltage Vo increases while the applied voltage Vo is small. When the applied voltage Vo is of a medium magnitude, the light-shielding rate S rises abruptly with the rise of the applied voltage Vo. When the applied voltage Vo further increases, the light-shielding rate S gradually increases with the increase of the applied voltage Vo. When the applied voltage Vo is greater than or equal to the predetermined value, the change in the light-shielding rate S is reduced, and the light-shielding rate S hardly changes.

In the reverse type, too, a range of the applied voltage Vo in which the light-shielding rate S is changed by 10% is defined as a target range VR, and a rate of change of the applied voltage Vo [ V ] with respect to the light-shielding rate S [% ] within the target range VR is defined as a target rate of change RC. When the lower limit value of the applied voltage Vo in the target range VR is V1 and the upper limit value of the applied voltage Vo in the target range VR is V2, the absolute value of the target rate of change RC is obtained by the following calculation formula.

|RC|＝|10|/(V2-V1)

In the reverse type, too, in the range of the driving voltage applied to the transparent electrode layers 12A and 12B, if the maximum value of the absolute value of the object change rate RC is 0.7 or more, the change speed of the light shielding rate is good.

The following describes test examples and verification results in detail.

By changing the total thickness of the light control sheet 10 and the configuration of the light control layer 11, 5 test examples having different maximum values of the absolute values of the target change rates RC were obtained. The configuration of the light control layer 11, which is the target of change in the test example, includes: the kind and composition of the liquid crystal constituting the light modulation layer 11; the density of the polymer in the case where the light control layer 11 contains the polymer; and the void size of the polymer network in the case where the light modulation layer 11 is formed of PNLC. Each test example is a general-type light control sheet 10N.

The light shielding ratio tends to be smaller in the maximum value as the total thickness of the dimming sheet 10 is smaller, and tends to be larger in the minimum value as the total thickness of the dimming sheet 10 is larger. In order to sufficiently secure the difference between the maximum value and the minimum value of the light-shielding rate, that is, the difference between the light-shielding rate in the first state and the light-shielding rate in the second state, the total thickness of the light control sheet 10 is preferably 40 μm to 400 μm. The thickness of the transparent support layers 13A and 13B used in this case is preferably 20 μm to 200 μm, and the thickness of the light modulation layer 11 is preferably 5 μm to 50 μm.

The light control sheet of test example 1 includes a light control layer 11 made of PNLC, transparent electrode layers 12A and 12B made of ITO, and transparent support layers 13A and 13B made of polyethylene terephthalate. The total thickness of the light control sheet of test example 1 was 120 μm, and the thickness of each of the first transparent support layer 13A and the second transparent support layer 13B was 50 μm.

In the light control sheet of test example 2, the total thickness of the light control layer 11 and the structure of the light control layer 11 were different from those of test example 1. The total thickness of the dimmer of experimental example 2 was 270 μm, and the thicknesses of the first transparent support layer 13A and the second transparent support layer 13B were 125 μm, respectively.

In the light control sheet of test example 3, the total thickness of the light control layer 11 and the structure of the light control layer 11 were different from those of test example 1. The total thickness of the light control sheet of test example 3 was 400 μm, and the thickness of each of the first transparent support layer 13A and the second transparent support layer 13B was 188 μm.

In the light control sheet of test example 4, the total thickness of the light control layer 11 and the structure of the light control layer 11 were different from those of test example 1. The total thickness of the dimmer of experimental example 4 was 400 μm, and the thicknesses of the first transparent support layer 13A and the second transparent support layer 13B were 188 μm, respectively.

In the light control sheet of test example 5, the total thickness of the light control layer 11 and the structure of the light control layer 11 were different from those of test example 1. The total thickness of the light control sheet of test example 5 was 400 μm, and the thickness of each of the first transparent support layer 13A and the second transparent support layer 13B was 188 μm.

The light control sheet of test example 1 was disposed at the boundary between two spaces, and a white light source was disposed in one space. Then, when the light shielding rate was changed by changing the driving voltage applied between the transparent electrode layers 12A and 12B, the change in brightness in the other space was evaluated by sensory evaluation. As a result, it was confirmed that when the light shielding rate was changed by 10%, the change in brightness was recognized. Further, when the light-shielding rate is changed by 50%, the change in brightness can be recognized more clearly.

Thus, it was confirmed that if the difference between the light shielding rate in the first state and the light shielding rate in the second state of the light modulation sheet 10 is 10% or more, the brightness in the space can be adjusted by switching between the first state and the second state. It was also confirmed that, in order to make the difference between the light-shielding properties of the light control sheet 10 in the first state and the second state significant and to improve the adjustment function of the brightness in the space, the difference between the light-shielding rate in the first state and the light-shielding rate in the second state is preferably 50% or more.

When the light shielding rate is 30% or more, it can be recognized that light is shielded by the light control sheet 10. Therefore, the light shielding rate in the first state is preferably 30% or more.

Fig. 4 shows the results of measuring the relationship between the drive voltage applied between the transparent electrode layers 12A and 12B and the light shielding rate for each test example. In each test example, the light shielding rate S was shifted by 1% to set a plurality of target ranges VR. Then, the upper limit value and the lower limit value of the applied voltage Vo are read from the graph for each target range VR, thereby calculating the target rate of change RC. Then, the maximum value of the absolute value of the target rate of change RC is obtained.

In test example 1, it was confirmed that the absolute value of the target change rate RC becomes the maximum in the vicinity of the target range VR in which the light shielding rate S was changed from 44% to 34% and the target range VR in which the light shielding rate S was changed from 43% to 33%, that is, in the vicinity of the applied voltage Vo of 12V. It was confirmed that the maximum value of the absolute value of the object change rate RC was about 5.3.

In test example 2, it was confirmed that the absolute value of the target rate of change RC was the largest in the vicinity of each target range VR included in the range of the light shielding rate S of 47% to 30%, that is, in the vicinity of the applied voltage Vo of 7V to 8V. It was confirmed that the maximum value of the absolute value of the target rate of change RC was about 7.1.

In test example 3, it was confirmed that the absolute value of the target rate of change RC was the largest in the vicinity of each target range VR included in the range of the light shielding rate S of 51% to 34%, that is, in the vicinity of the applied voltage Vo of 15V to 25V. It was confirmed that the maximum value of the absolute value of the target rate of change RC was about 1.0.

In test example 4, it was confirmed that the absolute value of the target rate of change RC was the largest in the vicinity of each target range VR included in the range of the light shielding rate S of 41% to 28%, that is, in the vicinity of the applied voltage Vo of 15V to 20V. It was confirmed that the maximum value of the absolute value of the target rate of change RC was about 1.8.

In test example 5, it was confirmed that the absolute value of the target rate of change RC was the largest in the vicinity of each target range VR included in the range of the light shielding rate S of 36% to 24%, that is, in the vicinity of the applied voltage Vo of 10V to 25V. It was confirmed that the maximum value of the absolute value of the target rate of change RC was about 0.6.

When the applied voltage Vo was gradually changed, it was confirmed that the light-shielding rate S of the dimming sheet of each test example changed along the curve of each test example shown in fig. 4. This situation implies that: when a predetermined drive voltage is applied to switch between the first state and the second state, the light blocking rate S of the light control sheet of each test example changes with time in the same manner as the curve of each test example shown in fig. 4. It implies that: as the absolute value of the target change rate RC is larger, the change speed of the light shielding rate within the range of the change rate having the target change rate RC is faster, that is, the time required for the light shielding rate to change by 10% within the range is shorter. In other words, the larger the absolute value of the object change rate RC, the shorter the time required for the brightness to change so as to be recognizable.

Therefore, the greater the maximum value of the absolute value of the target rate of change RC, the more quickly the light-shielding rate changes by 10% at any time from when the control unit 20 instructs switching of the drive voltage for switching between the first state and the second state to when the change of the light-shielding rate is completed. That is, at the above timing, the light shielding rate changes more quickly by the amount of change that can be recognized as a change in brightness. As a result, the timing of switching the brightness of the light control sheet 10 is easily recognized by the observer.

In each test example, the light control sheet was disposed at the boundary between two spaces, and the white light source was disposed in one space. Then, the driving voltage applied between the transparent electrode layers 12A and 12B was switched from 0V to 50V, and the change in brightness in the other space was evaluated sensorially. As a result, in test example 5, it was difficult to recognize the timing of switching the brightness. In contrast, in test examples 1 to 4, switching of the brightness was recognized. In particular, in test example 1 and test example 2, the brightness was perceived to change instantaneously.

Therefore, it was confirmed that if the maximum value of the absolute value of the object change rate RC is 0.7 or more, the change speed of the light shielding rate is good. Further, it was confirmed that if the maximum value of the absolute value of the subject change rate RC is 3.0 or more, the change speed of the light shielding rate is particularly improved.

The maximum value of the absolute value of the target rate of change RC is preferably 6.0 or less. In the light control sheet 10, the effective voltage applied to the light control layer 11 decreases as the distance from the terminal portions 15A and 15B increases. Therefore, if the light blocking ratio is largely changed in a narrow voltage range, the light blocking ratio is poor in the plane of the light control sheet 10, and the light control sheet 10 may be visually recognized as having unevenness in the in-plane transparency. In particular, the problem becomes more significant as the area of the dimming sheet 10 is larger. If the maximum value of the absolute value of the subject change rate RC is 6.0 or less, the change in the light shielding rate is suppressed to an extent not excessively steep in each subject range VR. That is, the voltage range of each target range VR can be suppressed from becoming too narrow. Therefore, even when the light modulation sheet 10 is driven by using an applied voltage in the vicinity of the target range VR having the maximum target change rate RC, it is possible to suppress the occurrence of unevenness due to the difference in light shielding rate.

Next, the results of verifying the difference between the light-shielding rate and other parameters will be described. Fig. 5 to 9 show the results of measuring the relationship between the driving voltage and each of the light blocking ratio, the total light transmittance, the parallel light transmittance, the diffusion transmittance, and the haze for each test example. Total light transmittance, parallel light transmittance, diffuse transmittance and haze, as measured in JISK 7361-1: 1997 and JIS K7136: 2000 as a standard. Fig. 5 shows the measurement results of test example 1, fig. 6 shows the measurement results of test example 2, fig. 7 shows the measurement results of test example 3, fig. 8 shows the measurement results of test example 4, and fig. 9 shows the measurement results of test example 5. In fig. 5 to 9, S represents a light-shielding rate, T.T represents a total light transmittance, P.T represents a parallel light transmittance, DIF represents a diffuse transmittance, and HZ represents a haze.

Referring to fig. 5 to 9, it can be seen that: the change pattern of the light-shielding rate with respect to the applied voltage Vo is different from the change pattern of each parameter of the total light transmittance, the parallel light transmittance, the diffuse transmittance, and the haze. Specifically, the total light transmittance and the diffuse transmittance are parameters used for calculating the haze, and the parallel light transmittance and the diffuse transmittance are components of the total light transmittance, and therefore, changes in these parameters are linked. On the other hand, when these parameters are compared with the light shielding rate, the magnitude of the applied voltage Vo whose change rate is changed and the range of the applied voltage Vo whose change rate is large are different. For example, both the light-shielding rate and the haze decrease with an increase in applied voltage, but the amount of change in the light-shielding rate in the low-voltage region is larger than the amount of change in the haze in the low-voltage region. In other words, even in a low voltage region where the haze hardly changes from the maximum value, the light-shielding rate starts to decrease.

Therefore, in the evaluation of the function of adjusting the brightness of the light control sheet 10, that is, the evaluation of the light blocking property of the light control sheet 10, it is significant to use the light blocking rate, which is a parameter measured by a method suitable for the evaluation target, without using the haze or the like that has been conventionally used in the evaluation of the transparency of the light control sheet 10.

In addition, for each test example, the resolution was measured when the driving voltage was 0V. The clarity is a parameter for evaluating the state of the light control sheet 10 using narrow-angle scattered light, and is measured using the integrating sphere type light transmittance measuring device similar to the device used for the measurement of the haze. In the image of the subject transmitted through the light control sheet 10, how clear a very small portion of the subject is can be evaluated by the sharpness. The smaller the value of sharpness of the light modulation sheet 10, the lower the sharpness of the subject across the light modulation sheet 10.

The sharpness is calculated by the following equation (1) where, of light passing through a test piece of a light control sheet disposed between a light source and an integrating sphere, the light quantity of straight light that advances straight with respect to the optical axis of parallel light entering the light control sheet is represented by lC, and the light quantity of narrow-angle scattered light that has an angle within ± 2.5 ° with respect to the optical axis of the parallel light is represented by lR.

100×(lC-lR)/(lC+lR)···(1)

As a result of the measurement of the resolution, it was confirmed that 46.0% in test example 1, 51.8% in test example 2, 7.4% in test example 3, 39.9% in test example 4, and 9.7% in test example 5.

From these results, it is understood that the light modulation sheet of test example 1 is excellent in the brightness adjustment function and also excellent in the shielding function of the object through the light modulation sheet. Therefore, the light control sheet of test example 1 was highly useful as a separator.

[ method for managing dimming sheet ]

The method of managing a light control sheet is used, for example, in the manufacture of light control sheets. In the method for managing a dimming sheet, whether the dimming sheet is normal or not is determined. In the condition for determining that the dimming sheet is normal, the maximum value including the absolute value of the target rate of change RC is 0.7 or more as condition 1.

In the case where the method for managing a dimming sheet is used for the manufacture of a dimming sheet, the method for manufacturing a dimming sheet includes: measuring a light shielding rate of the light control sheet while changing a magnitude of the driving voltage after the light control sheet is formed, and calculating a maximum value of an absolute value of the target change rate RC; and determining that the dimming slice in which the maximum value of the absolute value of the target rate of change RC satisfies the condition 1 is normal.

According to such a manufacturing method, the light control sheet 10 having a function of adjusting brightness in a space and having a timing of switching brightness easily recognizable by an observer can be manufactured.

The condition for determining that the light control sheet is normal may include, in addition to the condition 1, an upper limit value of a maximum value of an absolute value of the target change rate RC and a lower limit value of a difference between the light blocking rate in the first state and the light blocking rate in the second state.

As described above, according to the above embodiment, the following effects can be obtained.

(1) Since the maximum value of the absolute value of the target change rate RC is 0.7 or more, the timing at which the brightness is switched by the light modulation sheet 10 is easily recognized by the observer. As a result, the light control sheet 10 having a function of adjusting brightness and clearly showing the function to the observer can be realized.

(2) Since the maximum value of the absolute value of the target rate of change RC is 6.0 or less, the range of the voltage in which the light-shielding rate can be suppressed from changing by 10% is too narrow. Therefore, even when a voltage drop occurs according to the extension of the light control sheet 10, it is possible to suppress the occurrence of a recognizable difference in the in-plane light shielding rate of the light control sheet 10. As a result, it is possible to prevent the unevenness generated in the light control sheet 10 from being visually recognized.

(3) Since the light-shielding rate of the light-modulating sheet 10 in the first state, that is, the maximum value of the light-shielding rate of the light-modulating sheet 10 when the driving voltage in the predetermined range is applied is 30% or more, the light-shielding property of the light-modulating sheet 10 in the first state can be sufficiently ensured. This enables the light control sheet 10 to have excellent light shielding properties.

(4) The difference between the light-shielding rate of the light modulating sheet 10 in the first state and the light-shielding rate of the light modulating sheet in the second state is 50% or more. In other words, the light control sheet 10 is configured to be capable of changing the light shielding rate by 50% or more by applying the driving voltage. With this configuration, the brightness in the space can be changed more by switching between the first state and the second state. This can improve the brightness adjustment function of the light adjuster 10.

(5) If the light modulation layer 11 is configured to include a polymer network liquid crystal or a polymer dispersed liquid crystal, it is easy to realize a light modulation sheet having a large difference between the maximum value and the minimum value of the light shielding rate and a large maximum value of the absolute value of the target change rate RC.

(6) According to the management method of the light control sheet using the condition 1 as the condition for determining that the light control sheet 10 is normal, quality management related to the light-shielding property of the light control sheet 10 can be performed. By using this management method, it is possible to manufacture the light modulation sheet 10 which has a function of adjusting brightness in a space and in which the timing of switching the brightness is easily recognized by an observer.

[ modification example ]

The above embodiment can be modified and implemented as follows.

As described above, the control unit 20 of the light control device 100 may switch the state of the light control sheet 10 to two states, i.e., the first state and the second state, or may switch to 3 or more states including a state having a light shielding rate between the first state and the second state. By applying a drive voltage equal to or higher than the upper limit of the target range VR at which the absolute value of the target rate of change RC becomes maximum, the control unit 20 can realize the light control device 100 including the light control sheet 10 which has a function of adjusting the brightness in the space and in which the timing of the brightness switching is easily recognized by the observer.

When the state of the light modulation sheet 10 is switched to 3 or more states, the control unit 20 applies a drive voltage corresponding to a light shielding rate designated by an external operation device or the like to the light modulation sheet 10, for example, by including information such as a table for converting light shielding rates different from each other into the drive voltage.

Here, it is preferable that, among the plurality of states of the light control sheet 10, the light blocking ratio in each state differs from the light blocking ratio in the other state by 10% or more. With this configuration, the observer can recognize the change in brightness every time the state of the light modulator 10 is switched. Thus, the brightness in the space can be switched to a plurality of stages by the light control device 100, and the brightness adjustment function can be improved.

The light control sheet 10 may also be used as a screen for projecting an image in the first state. The higher the light shielding rate in the first state, the more the light-modulating sheet 10 can suppress light transmission for projection, and thus can function as a screen on which an image is more clearly displayed.